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Sample records for terahertz reflection spectroscopy

  1. Terahertz reflection spectroscopy for the detection of explosives

    NASA Astrophysics Data System (ADS)

    Leahy-Hoppa, Megan R.; Fitch, Michael J.; Osiander, Robert

    2008-02-01

    Terahertz (THz) technology has been demonstrated as a promising tool for detection of explosives and is being developed for aviation screening and sensing of improvised explosive devices. THz radiation is attractive for many applications due to its ability to penetrate through a wide range of dielectric materials including clothing, paper, cardboard, plastics, and wood. Of course, metals block THz waves as is the case for microwave, IR, and visible light. Our work has involved investigating the reflection spectroscopy of a variety of materials including explosives such as RDX and PETN, plastic explosive taggants such as DMDNB, and other organic materials. We have also investigated the changes of the reflection spectra in varying grades of sucrose. Spectral differences are observed between three grades of crystalline sugar in the region from 0.1 to 1 THz. By exploiting the unique spectral features, the discrimination capabilities of THz reflection spectroscopy points to the broad applicability of identifying a wide variety of materials.

  2. Reflection terahertz time-domain spectroscopy of RDX and HMX explosives

    NASA Astrophysics Data System (ADS)

    Choi, Kyujin; Hong, Taeyoon; Ik Sim, Kyung; Ha, Taewoo; Cheol Park, Byung; Hyuk Chung, Jin; Gyeong Cho, Soo; Hoon Kim, Jae

    2014-01-01

    We report on our study of RDX and HMX, two of the most commonly used explosive materials, in bulk pellets with reflection terahertz time-domain spectroscopy in the frequency range of 0.3-3 THz. The maximum entropy method was utilized to correct our raw reflection data against the phase error due to the relative displacement between the sample and the reference. Both the refractive index n and the extinction coefficient k in the terahertz region were acquired for these two explosives without a Kramers-Kronig analysis. Both RDX and HMX exhibit a series of distinct peaks not quite detectable in the more conventional transmission-type measurements due to their high terahertz absorptivity. Our results are compared with the literature data on powder samples.

  3. Investigating murals with terahertz reflective tomography

    NASA Astrophysics Data System (ADS)

    Yuan, Minjie; Sun, Wenfeng; Wang, Xinke; Wang, Sen; Zhang, Qunxi; Ye, Jiasheng; Zhang, Yan

    2015-08-01

    Terahertz time-domain spectroscopy (THz-TDS) imaging technology has been proposed to be used in the non-invasive detection of murals. THz-TDS images provide structural data of the sample that cannot be obtained with other complementary techniques. In this paper, two types of defects hidden in the plaster used to simulate the cases of defects in the murals, have been investigated by the terahertz reflected time domain spectroscopy imaging system. These preset defects include a leaf slice and a slit built in the plaster. With the terahertz reflective tomography, information about defects has been determined involving the thickness from the surface of sample to the built-in defect, the profile and distribution of the defect. With this THz tomography, different defects with the changes of optical thickness and their relative refractive index have been identified. The application of reflective pulsed terahertz imaging has been extended to the defect detection of the murals.

  4. A quantitative study for determination of sugar concentration using attenuated total reflectance terahertz (ATR-THz) spectroscopy

    NASA Astrophysics Data System (ADS)

    Suhandy, Diding; Suzuki, Tetsuhito; Ogawa, Yuichi; Kondo, Naoshi; Ishihara, Takeshi; Takemoto, Yuichiro

    2011-06-01

    The objective of our research was to use ATR-THz spectroscopy together with chemometric for quantitative study in food analysis. Glucose, fructose and sucrose are main component of sugar both in fresh and processed fruits. The use of spectroscopic-based method for sugar determination is well reported especially using visible, near infrared (NIR) and middle infrared (MIR) spectroscopy. However, the use of terahertz spectroscopy for sugar determination in fruits has not yet been reported. In this work, a quantitative study for sugars determination using attenuated total reflectance terahertz (ATR-THz) spectroscopy was conducted. Each samples of glucose, fructose and sucrose solution with different concentrations were prepared respectively and their absorbance spectra between wavenumber 20 and 450 cm-1 (between 0.6 THz and 13.5 THz) were acquired using a terahertz-based Fourier Transform spectrometer (FARIS-1S, JASCO Co., Japan). This spectrometer was equipped with a high pressure of mercury lamp as light source and a pyroelectric sensor made from deuterated L-alanine triglycine sulfate (DLTGS) as detector. Each spectrum was acquired using 16 cm-1 of resolution and 200 scans for averaging. The spectra of water and sugar solutions were compared and discussed. The results showed that increasing sugar concentration caused decreasing absorbance. The correlation between sugar concentration and its spectra was investigated using multivariate analysis. Calibration models for glucose, fructose and sucrose determination were developed using partial least squares (PLS) regression. The calibration model was evaluated using some parameters such as coefficient of determination (R2), standard error of calibration (SEC), standard error of prediction (SEP), bias between actual and predicted sugar concentration value and ratio prediction to deviation (RPD) parameter. The cross validation method was used to validate each calibration model. It is showed that the use of ATR-THz spectroscopy combined with appropriate chemometric can be a potential for a rapid determination of sugar concentrations.

  5. Terahertz time-domain spectroscopy of biological tissues

    SciTech Connect

    Nazarov, M M; Shkurinov, A P; Kuleshov, E A; Tuchin, V V

    2008-07-31

    Terahertz absorption spectra and dispersion of biologically important substances such as sugar, water, hemoglobin, lipids and tissues are studied. The characteristic absorption lines in the frequency range of a terahertz spectrometer (0.1-3.5 THz) are found. The refraction indices and absorption coefficients of human tooth enamel and dentine are measured. The method of terahertz phase reflection spectroscopy is developed for strongly absorbing substances. Simple and reliable methods of time-resolved terahertz spectroscopy are developed. (biophotonics)

  6. Characterization of burn injuries using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Arbab, M. Hassan; Dickey, Trevor C.; Winebrenner, Dale P.; Chen, Antao; Mourad, Pierre D.

    2011-03-01

    The accuracy rates of the clinical assessment techniques used in grading burn injuries remain significantly low for partial thickness burns. In this paper, we present experimental results from terahertz characterization of 2nd and 3rd degree burn wounds induced on a rat model. Reflection measurements were obtained from the surface of both burned and normal skin using pulsed terahertz spectroscopy. Signal processing techniques are described for interpretation of the acquired terahertz waveform and differentiation of burn wounds. Furthermore, the progression of burn injuries is shown by comparison between acute characterization and 72-hours survival studies. While the water content of healthy and desiccated skin has been considered as a source of terahertz signal contrast, it is demonstrated that other biological effects such as formation of post-burn interstitial edema as well as the density of the discrete scattering structures in the skin (such as hair follicles, sweat glands, etc.) play a significant role in the terahertz response of the burn wounds.

  7. Terahertz spectroscopy of liver cirrhosis: investigating the origin of contrast

    NASA Astrophysics Data System (ADS)

    Sy, Stanley; Huang, Shengyang; Wang, Yi-Xiang J.; Yu, Jun; Ahuja, Anil T.; Zhang, Yuan-ting; Pickwell-MacPherson, Emma

    2010-12-01

    We have previously demonstrated that terahertz pulsed imaging is able to distinguish between rat tissues from different healthy organs. In this paper we report our measurements of healthy and cirrhotic liver tissues using terahertz reflection spectroscopy. The water content of the fresh tissue samples was also measured in order to investigate the correlations between the terahertz properties, water content, structural changes and cirrhosis. Finally, the samples were fixed in formalin to determine whether water was the sole source of image contrast in this study. We found that the cirrhotic tissue had a higher water content and absorption coefficient than the normal tissue and that even after formalin fixing there were significant differences between the normal and cirrhotic tissues' terahertz properties. Our results show that terahertz pulsed imaging can distinguish between healthy and diseased tissue due to differences in absorption originating from both water content and tissue structure.

  8. A Concealed Barcode Identification System Using Terahertz Time-domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Guan, Yu; Yamamoto, Manabu; Kitazawa, Toshiyuki; Tripathi, Saroj R.; Takeya, Kei; Kawase, Kodo

    2015-03-01

    We present a concealed terahertz barcode/chipless tag to achieve remote identification through an obstructing material using terahertz radiation. We show scanned terahertz reflection spectral images of barcodes concealed by a thick obstacle. A concealed and double- side printed terahertz barcode structure is proposed, and we demonstrate that our design has better performance in definition than a single-side printed barcode using terahertz time-domain spectroscopy. This technique combines the benefits of a chipless tag to read encoded information covered by an optically opaque material with low cost and a simple fabrication process. Simulations are also described, along with an explanation of the principle of the terahertz barcode identification system.

  9. FEATURE ARTICLE Terahertz Spectroscopy

    E-print Network

    -resolved THz spectroscopy", are that it implies generation and detection of THz pulses in a synchronous could be generated, propagated through free space, and subsequently detected in the time-domain. Since spectroscopy grew out of efforts to generate and detect ultrashort electrical transients as they propagated

  10. Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures

    SciTech Connect

    Azad, Abul K; Chen, Houtong; Taylor, Antoinette; O' Hara, John F; Han, Jiaguang; Lu, Xinchao; Zhang, Weili

    2009-01-01

    The fascinating properties of plasmonic structures have had significant impact on the development of next generation ultracompact photonic and optoelectronic components. We study two-dimensional plasmonic structures functioning at terahertz frequencies. Resonant terahertz response due to surface plasmons and dipole localized surface plasmons were investigated by the state-of-the-art terahertz time domain spectroscopy (THz-TDS) using both transmission and reflection configurations. Extraordinary terahertz transmission was demonstrated through the subwavelength metallic hole arrays made from good conducting metals as well as poor metals. Metallic arrays m!lde from Pb, generally a poor metal, and having optically thin thicknesses less than one-third of a skin depth also contributed in enhanced THz transmission. A direct transition of a surface plasmon resonance from a photonic crystal minimum was observed in a photo-doped semiconductor array. Electrical controls of the surface plasmon resonances by hybridization of the Schottkey diode between the metallic grating and the semiconductor substrate are investigated as a function of the applied reverse bias. In addition, we have demonstrated photo-induced creation and annihilation of surface plasmons with appropriate semiconductors at room temperature. According to the Fano model, the transmission properties are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Such plasmonic structures may find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, tunable filters, and integrated terahertz devices.

  11. Superconducting microbolometers for time-resolved terahertz spectroscopy

    E-print Network

    Devoret, Michel H.

    Superconducting microbolometers for time-resolved terahertz spectroscopy Daniel F. Santavicca niobium microbolometers designed for time-resolved terahertz spectroscopy on nanosecond to millisecond, superconducting devices, time-resolved spectroscopy 1. INTRODUCTION The superconducting microbolometer has been

  12. Metamaterial-Enhanced Nonlinear Terahertz Spectroscopy

    E-print Network

    Hwang, Harold Young

    We demonstrate large nonlinear terahertz responses in the gaps of metamaterial split ring resonators in several materials and use nonlinear THz transmission and THz-pump/THz-probe spectroscopy to study the nonlinear responses ...

  13. Developments and advances in nonlinear terahertz spectroscopy

    E-print Network

    Brandt, Nathaniel Curran

    2014-01-01

    Nonlinear terahertz (THz) spectroscopy is a rapidly developing field, which is concerned with driving and observing nonlinear material responses in the THz range of the electromagnetic spectrum. In this thesis, I present ...

  14. Nondestructive analysis of structure and components of tablet coated with film by the usage of terahertz time-domain reflection spectroscopy.

    PubMed

    Takeuchi, Issei; Shimakura, Kemmaro; Ohtake, Hideyuki; Takayanagi, Jun; Tomoda, Keishiro; Nakajima, Takehisa; Terada, Hiroshi; Makino, Kimiko

    2014-01-01

    Nondestructive analysis of tablet is of great importance from the aspect of productivity and safety. In terahertz (THz) region, however, the analysis of core of coated tablet has not been progressed. In this study, we have measured a flat-surface push-pull osmotic pump tablet, having no orifice, having bilayer core and a coating film layer. The bilayer core was made from the drug layer and the push layer, and acetaminophen was contained in the drug layer as a model drug. To study its structure and components, we have obtained reflection spectra from the drug layer side and the push layer side measurements using THz time-domain reflection spectroscopy (THz-TDRS). From these results, detection of the peak of acetaminophen in the spectrum from the drug layer side measurements was confirmed. We have made ridges approximated toward the peak using a general method of linear regression analysis in both spectra. Two-sample t-test was applied to their gradients, and significant difference between the drug layer and the push layer was shown. These results suggested that THz-TDRS is applicable to the analysis of structure and component of a coated tablet. PMID:24282048

  15. Investigation of inflammable liquids by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Ikeda, Takeshi; Matsushita, Akira; Tatsuno, Michiaki; Minami, Yukio; Yamaguchi, Mariko; Yamamoto, Kohji; Tani, Masahiko; Hangyo, Masanori

    2005-07-01

    We have examined a nondestructive and contactless screening method for water and inflammable liquids stored in common beverage plastic bottles by the terahertz time-domain spectroscopy. No THz transmission has been observed between 10 and 60cm-1 for 45-mm-thick water in plastic bottles. Part of the THz wave, on the other hand, has been transmitted through the commercially available inflammable liquids in the same bottles. The differences in the absorption intensities and the refractive indices in the THz region, which reflect the ingredients of organic compounds, allow us to distinguish these inflammable liquids. We confirm that the screening method based on the THz transmission can be applied to classifying the commercially available inflammable liquids stored in plastic bottles and to distinguishing these inflammable liquids from water as well.

  16. Extending applicability of terahertz spectroscopy for biosensing

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Ramakrishnan

    Terahertz (THz) vibrational resonance spectroscopy has recently emerged as a promising technique for fingerprinting biological molecules. Absorption spectra in this frequency range (0.1-10 THz) reflect molecular internal vibrations involving the weakest hydrogen bonds and/or non-bonded interactions, which are species specific. Of prime importance is improving detection sensitivity of molecules with low absorption characteristics in the THz gap. Also of importance is the characterization of biological molecules in the THz gap (10-25 cm-1) by physical parameters (refractive index and absorption coefficient) rather than sample dependent parameters (transmission, reflection) and extending spectroscopy to the low THz range where remote sensing is most viable. To address the sensitivity issue, it is shown that periodic arrays of rectangular slots with subwavelength width provide for local electromagnetic field enhancements due to edge effects in the low frequency range of interest, 10-25 cm-1 (300-750 GHz). Periodic structures of Au, doped Si and InSb were studied. InSb is confirmed to offer the highest results with the local power enhancements on the order of 1100 at frequency 14 cm -1. InSb and Si have large skin depths in the frequency range of interest and so the analysis of their structures was done through the Fourier expansion method of field diffracted from gratings. Au however has small skin depths at these frequencies compared to the thickness. Surface impedance boundary conditions were employed to model the Au structure, for which the Fourier expansion method was unsuitable owing to the huge magnitude of Au permittivity. The applications possibly include development of novel bio-sensors, with the strongly enhanced local electromagnetic fields leading to increased detection sensitivity, and monitoring biophysical processes such as DNA denaturation. Transmission and reflection data from parallel, independent experiments are utilized in the Interference Spectroscopy Technique model based on thin film interference to calculate the fine structure of refractive index and absorption coefficient of biological molecules (DNA, proteins) in the THz gap. As to spectroscopy in the low THz range (3-10 cm-1), a noise source was used in free space configuration in the FT-IR set-up to obtain transmission and reflection data of biological molecules that act as fingerprints.

  17. Applications of terahertz spectroscopy to pharmaceutical sciences.

    PubMed

    Taday, Philip F

    2004-02-15

    The application of terahertz pulsed spectroscopy within the US Food and Drug Administration's (FDA's) recent process analytical technology (PAT) initiative is considered. As a case study the potency levels in paracetamol (4-acetamidophenol) and aspirin (acetylsalicylic acid) test tablets have been recovered from the terahertz absorption spectra using a multivariate partial-least-squares (PLS) calibration model. Root-mean-square errors of cross-validation (RMSECVs) of 2.85% and 3.90% were obtained for paracetamol and aspirin, respectively. Information about other excipients can also be obtained; for example, using the strong lactose absorption lines in the tablets, RMSECVs of 3.65% and 4.30% could be recovered from the paracetamol and aspirin samples, respectively. As active ingredients may also change their solid-state form during formulation processing or storage and as this can adversely affect the final dosage performance, monitoring of pharmaceutical ingredients is essential for a 'right-first-time' philosophy within the industry. Terahertz pulse spectroscopy is a high-throughput technique with many areas of potential exploitation in the pharmaceutical industry; these issues are discussed in this paper. PMID:15306525

  18. A promising diagnostic method: Terahertz pulsed imaging and spectroscopy

    PubMed Central

    Sun, Yiwen; Sy, Ming Yiu; Wang, Yi-Xiang J; Ahuja, Anil T; Zhang, Yuan-Ting; Pickwell-MacPherson, Emma

    2011-01-01

    The terahertz band lies between the microwave and infrared regions of the electromagnetic spectrum. This radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. It is strongly attenuated by water and very sensitive to water content. Unique absorption spectra due to intermolecular vibrations in this region have been found in different biological materials. These unique features make terahertz imaging very attractive for medical applications in order to provide complimentary information to existing imaging techniques. There has been an increasing interest in terahertz imaging and spectroscopy of biologically related applications within the last few years and more and more terahertz spectra are being reported. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques, and a number of applications such as molecular spectroscopy, tissue characterization and skin imaging are discussed. PMID:21512652

  19. Terahertz spectroscopy for quantifying refined oil mixtures.

    PubMed

    Li, Yi-nan; Li, Jian; Zeng, Zhou-mo; Li, Jie; Tian, Zhen; Wang, Wei-kui

    2012-08-20

    In this paper, the absorption coefficient spectra of samples prepared as mixtures of gasoline and diesel in different proportions are obtained by terahertz time-domain spectroscopy. To quantify the components of refined oil mixtures, a method is proposed to evaluate the best frequency band for regression analysis. With the data in this frequency band, dualistic linear regression fitting is used to determine the volume fraction of gasoline and diesel in the mixture based on the Beer-Lambert law. The minimum of regression fitting R-Square is 0.99967, and the mean error of fitted volume fraction of 97# gasoline is 4.3%. Results show that refined oil mixtures can be quantitatively analyzed through absorption coefficient spectra in terahertz frequency, which it has bright application prospects in the storage and transportation field for refined oil. PMID:22907017

  20. Terahertz spectroscopy of pigmentary skin nevi in vivo

    NASA Astrophysics Data System (ADS)

    Zaitsev, K. I.; Chernomyrdin, N. V.; Kudrin, K. G.; Reshetov, I. V.; Yurchenko, S. O.

    2015-09-01

    Pigmentary skin nevi are studied in vivo using terahertz pulsed spectroscopy. Dielectric parameters of healthy skin and dysplastic and nondysplastic nevi are reconstructed and analyzed. The fact that complex permittivities of the samples substantially differ in the terahertz spectral range can be used for early noninvasive diagnostics of dysplastic nevi, which are precursors of melanoma (the most dangerous skin cancer). A method is proposed to identify various dysplastic and nondysplastic nevi using the analysis of terahertz dielectric characteristics. It is demonstrated that terahertz pulsed spectroscopy is promising for early noninvasive diagnostics of dysplastic nevi and melanomas of the skin.

  1. High power, high resolution terahertz spectroscopy technologies and its applications

    NASA Astrophysics Data System (ADS)

    Wu, Dong Ho; Graber, Benjamin; Kim, Christopher

    2015-03-01

    Since a large number of molecules' resonance frequencies lie within terahertz frequencies, terahertz spectroscopy is a highly useful tool for scientific investigation of various materials. At the same time one can use the same technology for the identification of hidden materials. Despite these potential applications presently terahertz spectroscopy is largely underutilized, and it is mostly being used in the laboratory environment. This is in part largely due to the fact that no portable, high power, high resolution spectrometer is currently available. So we have been developing a high power, wideband terahertz source. The terahertz source is capable to produce a relatively high power (>2 mW), wideband (0.1 - 3 THz) terahertz beam. In addition to the source we have optimized and calibrated an electro-optic (EO) detector, of which sensitivity is 10-13 W/(Hz)1/2. Recently, by utilizing these terahertz source and detector, we have constructed a high power, high resolution terahertz spectrometer, and carried out various experiments to understand resonance spectra of water vapor, chemicals and ionized air. Also we constructed a modified terahertz spectrometer for a stand-off detection applications. In this presentation I will discuss our experimental achievements and progresses. Supported by DTRA.

  2. Optical characteristics of pesticides measured by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Kyu; Kim, Giyoung; Son, Joo-Hiuk

    2015-07-01

    In this study, we measured the optical characteristics of pesticides by terahertz time-domain spectroscopy. Pesticide samples were prepared as pellets that were mixed with polyethylene powder and placed in the center of the path of a terahertz electromagnetic (EM) wave in the spectroscopy system. The absorbance of each sample showed obvious differences in absorption peaks. From this result, we showed that these pesticide products had resonance modes in the terahertz range, and this method can be used to make a sensor that is able to measure low concentrations of pesticides in farm produce.

  3. Moisture detection in composites by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Malinowski, Pawe?; Pa?ka, Norbert; Opoka, Szymon; Wandowski, Tomasz; Ostachowicz, Wies?aw

    2015-07-01

    The application of Glass Fibre Reinforced Polymers (GFRP) in many branches of industry has been increasing steadily. Many research works focus on damage identification for structures made out of such materials. However, not only delaminations, cracks or other damage can have a negative influence of GFRP parts performance. Previous research proved that fluid absorption influences the mechanical performance of composites. GFRP parts can be contaminated by moisture or release agent during manufacturing, while fuel, hydraulic fluid and moisture ingression into the composite can be the in-service treats. In the reported research authors focus on moisture detection. There are numerous sources of moisture such as post manufacturing NDT inspection with ultrasonics coupled by water or exposition to moisture during transportation and in service. An NDT tool used for the research is a terahertz (THz) spectrometer. The device uses an electromagnetic radiation in the terahertz range (0.1-3 THz) and allows for reflection and transmission measurements. The spectrometer is equipped with moving table that allows for XY scanning of large objects such as GFRP panels. In the conducted research refractive indices were experimentally extracted from the materials of interest (water and GFRP). Time signals as well as C-scans were analysed for samples with moisture contamination. In order to be sure that the observed effects are related to moisture contamination reference measurements were conducted. The obtained results showed that the THz NDT technique can detect moisture hidden under a GFRP with multiple layers.

  4. Selectivity of Terahertz Gas-Phase Spectroscopy.

    PubMed

    Smith, Ryan M; Arnold, Mark A

    2015-11-01

    Analytical potential of terahertz (THz) spectroscopy is assessed by comparing selectivity for a set of eight environmentally important gases over THz and infrared (IR) optical frequencies. Selectivity coefficients are determined over selected spectral regions for acetaldehyde, acetonitrile, ethanol, water, methanol, ammonia, propionaldehyde, and propionitrile. These selectivity coefficients quantify the magnitude of the net analyte signal for each test compound relative to the other seven. In addition to the THz spectral range (2-125 cm(-1)), selectivity coefficients are determined for the following IR regions 600-1300, 1300-2000, 2600-3100, 3100-4000, and 4000-6500 cm(-1). Highest selectivity is afforded over the THz frequencies for six of the eight test compounds and THz selectivity coefficients for the other two gases (water and acetonitrile) are acceptable for environmental measurements. PMID:26436438

  5. Papyrus imaging with terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Labaune, J.; Jackson, J. B.; Pagès-Camagna, S.; Duling, I. N.; Menu, M.; Mourou, G. A.

    2010-09-01

    Terahertz time domain spectroscopic imaging (THz-TDSI) is a non-ionizing, non-contact and non-destructive measurement technique that has been recently utilized to study cultural heritage artifacts. We will present this technique and the results of non-contact measurements of papyrus texts, including images of hidden papyri. Inks for modern papyrus specimens were prepared using the historical binder, Arabic gum, and two common pigments used to write ancient texts, carbon black and red ochre. The samples were scanned in reflection at normal incidence with a pulse with a spectral range between 0.1 and 1.5 THz. Temporal analysis of the signals provides the depths of the layers, and their frequency spectra give information about the inks.

  6. Tissue characterization using terahertz pulsed imaging in reflection geometry

    NASA Astrophysics Data System (ADS)

    Huang, S. Y.; Wang, Y. X. J.; Yeung, D. K. W.; Ahuja, A. T.; Zhang, Y.-T.; Pickwell-MacPherson, E.

    2009-01-01

    Terahertz pulsed imaging (TPI™) is a non-ionizing and non-destructive imaging technique that has been recently used to study a wide range of biological materials. The severe attenuation of terahertz radiation in samples with high water content means that biological samples need to be very thin if they are to be measured in transmission geometry. To overcome this limitation, samples could be measured in reflection geometry and this is the most feasible way in which TPI could be performed in a clinical setting. In this study, we therefore used TPI in reflection geometry to characterize the terahertz properties of several organ samples freshly harvested from laboratory rats. We observed differences in the measured time domain responses and determined the frequency-dependent optical properties to characterize the samples further. We found statistically significant differences between the tissue types. These results show that TPI has the potential to accurately differentiate between tissue types non-invasively.

  7. High-resolution broadband terahertz spectroscopy via electronic heterodyne detection of photonically generated terahertz frequency comb.

    PubMed

    Pavelyev, D G; Skryl, A S; Bakunov, M I

    2014-10-01

    We report an alternative approach to the terahertz frequency-comb spectroscopy (TFCS) based on nonlinear mixing of a photonically generated terahertz pulse train with a continuous wave signal from an electronic synthesizer. A superlattice is used as a nonlinear mixer. Unlike the standard TFCS technique, this approach does not require a complex double-laser system but retains the advantages of TFCS-high spectral resolution and wide bandwidth. PMID:25360955

  8. Terahertz reflection response measurement using a phonon polariton wave

    NASA Astrophysics Data System (ADS)

    Inoue, Hayato; Katayama, Kenji; Shen, Qing; Toyoda, Taro; Nelson, Keith A.

    2009-03-01

    We developed a new technique for the measurement of terahertz reflection responses utilizing a propagating phonon polariton wave. Frequency tunable phonon polariton waves were generated by the recently developed continuously variable spatial frequency transient grating method [K. Katayama, H. Inoue, H. Sugiya, Q. Shen, T. Taro, and K. A. Nelson, Appl. Phys. Lett. 92, 031906 (2008)]. The phonon polariton wave traveled in a ferroelectric crystal in an in-plane direction with an inclined angle of 26°, and the wave reflected at the crystal edge where a sample was positioned. The reflected polariton wave was detected by the same method as that used for the generation of the polariton waves. By comparing the reflection intensities in the presence and absence of the sample, reflectivity of the polariton wave was calculated, and the refractive index and absorption in the terahertz region were obtained.

  9. Terahertz technology for imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Crowe, T. W.; Porterfield, D. W.; Hesler, J. L.; Bishop, W. L.; Kurtz, D. S.; Hui, K.

    2006-05-01

    The terahertz region of the electromagnetic spectrum has unique properties that make it especially useful for imaging and spectroscopic detection of concealed weapons, explosives and chemical and biological materials. However, terahertz energy is difficult to generate and detect, and this has led to a technology gap in this frequency band. Nonlinear diodes can be used to bridge this gap by translating the functionality achieved at microwave frequencies to the terahertz band. Basic building blocks include low-noise mixers, frequency multipliers, sideband generators and direct detectors. These terahertz components rely on planar Schottky diodes and recently developed integrated diode circuits make them easier to assemble and more robust. The new generation of terahertz sources and receivers requires no mechanical tuning, yet achieves high efficiency and broad bandwidth. This paper reviews the basic design of terahertz transmitters and receivers, with special emphasis on the recent development of systems that are compact, easy to use and have excellent performance.

  10. Terahertz quantum well photodetectors with reflection-grating couplers

    SciTech Connect

    Zhang, R.; Fu, Z. L.; Gu, L. L.; Guo, X. G.; Cao, J. C.

    2014-12-08

    The design, fabrication, and characterization of terahertz (THz) quantum well photodetectors with one-dimensional reflection-grating coupler are presented. It is found that the reflection gratings could effectively couple the THz waves normally incident to the device. Compared with the 45-degree facet sample, the peak responsivity of this grating-coupled detector is enhanced by over 20%. The effects of the gratings on the photocurrent spectra are also analyzed.

  11. Measurement and modeling of rough surface effects on terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Henry, S. C.; Schecklman, S.; Kniffin, G. P.; Zurk, L. M.; Chen, A.

    2010-02-01

    Recent improvements in sensing technology have driven new research areas within the terahertz (THz) portion of the electromagnetic (EM) spectrum. While there are several promising THz applications, several outstanding technical challenges need to be addressed before robust systems can be deployed. A particularly compelling application is the potential use of THz reflection spectroscopy for stand-off detection of drugs and explosives. A primary challenge for this application is to have sufficient signal-to-noise ratio (SNR) to allow spectroscopic identification of the target material, and surface roughness can have an impact on identification. However, scattering from a rough surface may be observed at all angles, suggesting diffuse returns can be used in robust imaging of non-cooperative targets. Furthermore, the scattering physics can also distort the reflection spectra, complicating classification algorithms. In this work, rough surface scattering effects were first isolated by measuring diffuse scattering for gold-coated sandpaper of varying roughness. Secondly, we measured scattering returns from a rough sample with a spectral signature, namely ?-lactose monohydrate mixed with Teflon and pressed with sandpaper to introduce controlled roughness. For both the specular and diffuse reflection measurements, the application of traditional spectroscopy techniques provided the ability to resolve the 0.54 THz absorption peak. These results are compared with results from a smooth surface. Implications of the results on the ability to detect explosives with THz reflection spectroscopy are presented and discussed. In addition, the Small Perturbation Method (SPM) is employed to predict backscatter from lactose with a small amount of roughness.

  12. Terahertz vibrational absorption spectroscopy using microstrip-line waveguides

    NASA Astrophysics Data System (ADS)

    Byrne, M. B.; Cunningham, J.; Tych, K.; Burnett, A. D.; Stringer, M. R.; Wood, C. D.; Dazhang, L.; Lachab, M.; Linfield, E. H.; Davies, A. G.

    2008-11-01

    We demonstrate that terahertz microstrip-line waveguides can be used to measure absorption spectra of polycrystalline materials with a high frequency resolution (˜2 GHz) and with a spatial resolution that is determined by the microstrip-line dimensions, rather than the free-space wavelength. The evanescent terahertz-bandwidth electric field extending above the microstrip line interacts with, and is modified by, overlaid dielectric samples, thus enabling the characteristic vibrational absorption resonances in the sample to be probed. As an example, the terahertz absorption spectrum of polycrystalline lactose monohydrate was investigated; the lowest lying mode was observed at 534(±2) GHz, in excellent agreement with free-space measurements. This microstrip technique offers both a higher spatial and frequency resolution than free-space terahertz time-domain spectroscopy and requires no contact between the waveguide and sample.

  13. Continuous wave terahertz reflection imaging of human colorectal tissue

    NASA Astrophysics Data System (ADS)

    Doradla, Pallavi; Alavi, Karim; Joseph, Cecil S.; Giles, Robert H.

    2013-03-01

    Continuous wave terahertz (THz) imaging has the potential to offer a safe, non-ionizing, and nondestructive medical imaging modality for delineating colorectal cancer. Fresh excisions of normal colon tissue were obtained from surgeries performed at the University of Massachusetts Medical School, Worcester. Reflection measurements of thick sections of colorectal tissues, mounted in an aluminum sample holder, were obtained for both fresh and formalin fixed tissues. The two-dimensional reflection images were acquired by using an optically pumped far-infrared molecular gas laser operating at 584 GHz with liquid Helium cooled silicon bolometer detector. Using polarizers in the experiment both co-polarized and cross-polarized remittance form the samples was collected. Analysis of the images showed the importance of understanding the effects of formalin fixation while determining reflectance level of tissue response. The resulting co- and cross-polarized images of both normal and formalin fixed tissues showed uniform terahertz response over the entire sample area. Initial measurements indicated a co-polarized reflectance of 16%, and a cross-polarized reflectance of 0.55% from fresh excisions of normal colonic tissues.

  14. Conformational characteristics of ?-glucan in laminarin probed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Shin, Hee Jun; Oh, Seung Jae; Kim, Sung In; Won Kim, Ha; Son, Joo-Hiuk

    2009-03-01

    We measured the binding-state-dependent power absorptions, refractive indices, and dielectric constants of triple-stranded helices (TSHs) and single-stranded helices (SSHs) ?-glucans in laminarin using terahertz time-domain spectroscopy (TDS). The SSH ?-glucan was obtained from a TSH ?-glucan laminarin by a chemical treatment with NaOH solution. The power absorption of TSH ?-glucan increased more rapidly than that of the SSH ?-glucan with the frequency increment. The refractive index and dielectric constants of TSH ?-glucan were also larger than those of the SSH ?-glucan. This result implies that terahertz-TDS is a very effective method in classifying the conformational state of ?-glucans.

  15. Discrimination of genetically modified sugar beets based on terahertz spectroscopy.

    PubMed

    Chen, Tao; Li, Zhi; Yin, Xianhua; Hu, Fangrong; Hu, Cong

    2016-01-15

    The objective of this paper was to apply terahertz (THz) spectroscopy combined with chemometrics techniques for discrimination of genetically modified (GM) and non-GM sugar beets. In this paper, the THz spectra of 84 sugar beet samples (36 GM sugar beets and 48 non-GM ones) were obtained by using terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.2 to 1.2 THz. Three chemometrics methods, principal component analysis (PCA), discriminant analysis (DA) and discriminant partial least squares (DPLS), were employed to classify sugar beet samples into two groups: genetically modified organisms (GMOs) and non-GMOs. The DPLS method yielded the best classification result, and the percentages of successful classification for GM and non-GM sugar beets were both 100%. Results of the present study demonstrate the usefulness of THz spectroscopy together with chemometrics methods as a powerful tool to distinguish GM and non-GM sugar beets. PMID:26436847

  16. Discrimination of genetically modified sugar beets based on terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Li, Zhi; Yin, Xianhua; Hu, Fangrong; Hu, Cong

    2016-01-01

    The objective of this paper was to apply terahertz (THz) spectroscopy combined with chemometrics techniques for discrimination of genetically modified (GM) and non-GM sugar beets. In this paper, the THz spectra of 84 sugar beet samples (36 GM sugar beets and 48 non-GM ones) were obtained by using terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.2 to 1.2 THz. Three chemometrics methods, principal component analysis (PCA), discriminant analysis (DA) and discriminant partial least squares (DPLS), were employed to classify sugar beet samples into two groups: genetically modified organisms (GMOs) and non-GMOs. The DPLS method yielded the best classification result, and the percentages of successful classification for GM and non-GM sugar beets were both 100%. Results of the present study demonstrate the usefulness of THz spectroscopy together with chemometrics methods as a powerful tool to distinguish GM and non-GM sugar beets.

  17. Terahertz and Infrared Spectroscopy of Gated Large-Area Graphene Zhengzong Sun,

    E-print Network

    Natelson, Douglas

    Terahertz and Infrared Spectroscopy of Gated Large-Area Graphene Lei Ren, Qi Zhang, Jun Yao, Department of Mechanical Engineering and Materials Science, and ¶ Department of Physics and Astronomy, Rice and infrared waves. Using time-domain terahertz spectroscopy and Fourier- transform infrared spectroscopy

  18. Terahertz spectroscopy of a multilayers flake of graphene

    NASA Astrophysics Data System (ADS)

    Clericò, V.; Delgado Notario, J. A.; Campos, N.; Gómez, D.; Diez, E.; Velazquez, J. E.; Meziani, Y. M.

    2015-10-01

    Terahertz Time Domain Spectroscopy (THz-TDS) technique has been used to characterize two graphene based samples produced by exfoliation and CVD methods. In both cases, we find two interesting bands, in both CVD and exfoliated graphene, in the 0.2-2 THz range. Quality information can be extracted with this non-destructive technique. The obtained values of the conductivity are in the same range of those obtained in the literature.

  19. Reflection type of terahertz imaging system using a high-T{sub c} superconducting oscillator

    SciTech Connect

    Kashiwagi, T.; Minami, H.; Kadowaki, K.; Nakade, K.; Saiwai, Y.; Kitamura, T.; Watanabe, C.; Ishida, K.; Sekimoto, S.; Asanuma, K.; Yasui, T.; Shibano, Y.; Markovi?, B.; Mirkovi?, J.; Tsujimoto, M.; Yamamoto, T.

    2014-01-13

    A reflection type of imaging system is shown at sub-terahertz frequencies generated from high-T{sub c} superconducting intrinsic Josephson junction mesa structures fabricated by single crystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+?} to demonstrate how the sub-terahertz imaging technique using monochromatic radiation is powerful and unique for the variety of practical applications. Several examples are discussed in detail and are compared to other terahertz imaging systems.

  20. Terahertz spectroscopy properties of the selected engine oils

    NASA Astrophysics Data System (ADS)

    Zhu, Shouming; Zhao, Kun; Lu, Tian; Zhao, Songqing; Zhou, Qingli; Shi, Yulei; Zhao, Dongmei; Zhang, Cunlin

    2010-11-01

    Engine oil, most of which is extracted from petroleum, consist of complex mixtures of hydrocarbons of molecular weights in the range of 250-1000. Variable amounts of different additives are put into them to inhibit oxidation, improve the viscosity index, decrease the fluidity point and avoid foaming or settling of solid particles among others. Terahertz (THz) spectroscopy contains rich physical, chemical, and structural information of the materials. Most low-frequency vibrational and rotational spectra of many petrochemicals lie in this frequency range. In recent years, much attention has been paid to the THz spectroscopic studies of petroleum products. In this paper, the optical properties and spectroscopy of selected kinds of engine oil consisting of shell HELIX 10W-40, Mobilube GX 80W-90, GEELY ENGINE OIL SG 10W-30, SMA engine oil SG 5W-30, SMA engine oil SG 10W-30, SMA engine oil SG 75W-90 have been studied by the terahertz time-domain spectroscopy (THz-TDS) in the spectral range of 0.6-2.5 THz. Engine oil with different viscosities in the terahertz spectrum has certain regularity. In the THz-TDS, with the increase of viscosity, time delay is greater and with the increase of viscosity, refractive indexes also grow and their rank is extremely regular. The specific kinds of engine oil can be identified according to their different spectral features in the THz range. The THz-TDS technology has potentially significant impact on the engine oil analysis.

  1. Terahertz pulse imaging in reflection geometry of human skin cancer and skin tissue

    NASA Astrophysics Data System (ADS)

    Woodward, Ruth M.; Cole, Bryan E.; Wallace, Vincent P.; Pye, Richard J.; Arnone, Donald D.; Linfield, Edmund H.; Pepper, Michael

    2002-11-01

    We demonstrate the application of terahertz pulse imaging (TPI) in reflection geometry for the study of skin tissue and related cancers both in vitro and in vivo. The sensitivity of terahertz radiation to polar molecules, such as water, makes TPI suitable for studying the hydration levels in the skin and the determination of the lateral spread of skin cancer pre-operatively. By studying the terahertz pulse shape in the time domain we have been able to differentiate between diseased and normal tissue for the study of basal cell carcinoma (BCC). Basal cell carcinoma has shown a positive terahertz contrast, and inflammation and scar tissue a negative terahertz contrast compared to normal tissue. In vivo measurements on the stratum corneum have enabled visualization of the stratum corneum-epidermis interface and the study of skin hydration levels. These results demonstrate the potential of terahertz pulse imaging for the study of skin tissue and its related disorders, both in vitro and in vivo.

  2. Terahertz BWO spectroscopy of conductors and superconductors

    SciTech Connect

    Gorshunov, B P; Volkov, A A; Prokhorov, A S; Spektor, I E; Akimitsu, J; Dressel, M; Nieuwenhuys, G; Tomic, S; Uchida, S

    2007-10-31

    Methods for direct (without the use of the Kramers-Kronig relations) measuring the dielectric response (dynamic conductivity and permittivity) spectra of dielectrics, conductors, and superconductors in the terahertz frequency range (0.03-1.5 THz) are described. The methods are realised by using BWO (backward-wave oscillator) spectrometers developed at the A.M. Prokhorov General Physics Institute, RAS. Dielectric measurements can be performed at temperatures from 2 to 1000 K in magnetic fields up to 8 T. The dielectric response spectra are investigated for a number of materials with properties determined by electron correlation effects: superconductors, one-dimensional conductors, heavy fermion systems, spin-ladder cuprates, and spin glasses. (special issue devoted to the 25th anniversary of the a.m. prokhorov general physics institute)

  3. Hydration state inside HeLa cell monolayer investigated with terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Shiraga, K.; Suzuki, T.; Kondo, N.; Tanaka, K.; Ogawa, Y.

    2015-06-01

    The hydration state in living cells is believed to be associated with various cellular activities. Nevertheless, in vivo characterization of intracellular hydration state under physiological condition has not been well documented to date. In this study, the hydration state of an intact HeLa cell monolayer was investigated by terahertz time-domain attenuated total reflection spectroscopy. Combined with the extended theory of Onsager, we found 23.8 ± 7.4% of HeLa intracellular water was hydrated to biomolecules (corresponding to 1.25 g H2O/g solute); exhibiting slower relaxation dynamics than bulk water.

  4. Non-Destructive Corrosion Detection Using Terahertz Time-Domain Spectroscopy and Imaging

    NASA Astrophysics Data System (ADS)

    Owens, Lindsay; Smith, Stanley; Petkie, Doug; Deibel, Jason

    2008-10-01

    The objective of this project is to detect corrosion of manufactured metal underneath paint. The system used in this research is a commercial terahertz time-domain spectroscopy and imaging system. THz signals are generated and detected using optical excitation of biased semiconductor antennas with 100 femtosecond pulses from an 800 nm laser. Spectral images were of metal samples were taken at frequencies between 100 GHz and 1 THz using a variety of imaging modalities in both transmission and reflection. Prelimiary imaging data shows a clear distinction between corroded and clean metal concealed underneath a coat of paint.

  5. Spectroscopic study of terahertz reflection and transmission properties of carbon-fiber-reinforced plastic composites

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Shi, Changcheng; Ma, Yuting; Han, Xiaohui; Li, Wei; Chang, Tianying; Wei, Dongshan; Du, Chunlei; Cui, Hong-Liang

    2015-05-01

    Carbon-fiber-reinforced plastic (CFRP) composites are widely used in aerospace and concrete structure reinforcement due to their high strength and light weight. Terahertz (THz) time-domain spectroscopy is an attractive tool for defect inspection in CFRP composites. In order to improve THz nondestructive testing of CFRP composites, we have carried out systematic investigations of THz reflection and transmission properties of CFRP. Unidirectional CFRP composites with different thicknesses are measured with polarization directions 0 deg to 90 deg with respect to the fiber direction, in both reflection and transmission modes. As shown in the experiments, CFRP composites are electrically conducting and therefore exhibit a high THz reflectivity. In addition, CFRP composites have polarization-dependent reflectivity and transmissivity for THz radiation. The reflected THz power in the case of parallel polarization is nearly 1.8 times higher than for perpendicular polarization. At the same time, in the transmission of THz wave, a CFRP acts as a Fabry-Pérot cavity resulting from multiple internal reflections from the CFRP-air interfaces. Moreover, from the measured data, we extract the refractive index and absorption coefficient of CFRP composites in the THz frequency range.

  6. Characterization of Wheat Varieties Using Terahertz Time-Domain Spectroscopy

    PubMed Central

    Ge, Hongyi; Jiang, Yuying; Lian, Feiyu; Zhang, Yuan; Xia, Shanhong

    2015-01-01

    Terahertz (THz) spectroscopy and multivariate data analysis were explored to discriminate eight wheat varieties. The absorption spectra were measured using THz time-domain spectroscopy from 0.2 to 2.0 THz. Using partial least squares (PLS), a regression model for discriminating wheat varieties was developed. The coefficient of correlation in cross validation (R) and root-mean-square error of cross validation (RMSECV) were 0.985 and 1.162, respectively. In addition, interval PLS was applied to optimize the models by selecting the most appropriate regions in the spectra, improving the prediction accuracy (R = 0.992 and RMSECV = 0.967). Results demonstrate that THz spectroscopy combined with multivariate analysis can provide rapid, nondestructive discrimination of wheat varieties. PMID:26024421

  7. Two-dimensional Raman-terahertz spectroscopy of water

    PubMed Central

    Savolainen, Janne; Ahmed, Saima; Hamm, Peter

    2013-01-01

    Two-dimensional Raman-terahertz (THz) spectroscopy is presented as a multidimensional spectroscopy directly in the far-IR regime. The method is used to explore the dynamics of the collective intermolecular modes of liquid water at ambient temperatures that emerge from the hydrogen-bond networks water forming. Two-dimensional Raman-THz spectroscopy interrogates these modes twice and as such can elucidate couplings and inhomogeneities of the various degrees of freedoms. An echo in the 2D Raman-THz response is indeed identified, indicating that a heterogeneous distribution of hydrogen-bond networks exists, albeit only on a very short 100-fs timescale. This timescale appears to be too short to be compatible with more extended, persistent structures assumed within a two-state model of water. PMID:24297930

  8. Aeronautics composite material inspection with a terahertz time-domain spectroscopy system

    NASA Astrophysics Data System (ADS)

    Ospald, Frank; Zouaghi, Wissem; Beigang, René; Matheis, Carsten; Jonuscheit, Joachim; Recur, Benoit; Guillet, Jean-Paul; Mounaix, Patrick; Vleugels, Wouter; Bosom, Pablo Venegas; González, Laura Vega; López, Ion; Edo, Rafael Martínez; Sternberg, Yehuda; Vandewal, Marijke

    2014-03-01

    The usability of pulsed broadband terahertz radiation for the inspection of composite materials from the aeronautics industry is investigated, with the goal of developing a mobile time-domain spectroscopy system that operates in reflection geometry. A wide range of samples based on glass and carbon fiber reinforced plastics with various types of defects is examined using an imaging system; the results are evaluated both in time and frequency domain. The conductivity of carbon fibers prevents penetration of the respective samples but also allows analysis of coatings from the reflected THz pulses. Glass fiber composites are, in principle, transparent for THz radiation, but commonly with significant absorption for wavelengths >1 THz. Depending on depth, matrix material, and size, defects like foreign material inserts, delaminations, or moisture contamination can be visualized. If a defect is not too deep in the sample, its location can be correctly identified from the delay between partial reflections at the surface and the defect itself.

  9. Terahertz spectroscopy of methanimine and its isotopologs

    NASA Astrophysics Data System (ADS)

    Motoki, Yuta; Isobe, Fuya; Ozeki, Hiroyuki; Kobayashi, Kaori

    2014-06-01

    Context. Methanimine (CH2NH) is a simple molecule composed of methylene and imine. The molecule has been detected toward the Galactic center, star-forming regions, circumstellar envelopes, and other galaxies since 1973. In previous studies, the rest frequency of methanimine has been measured for normal species up to the 650-GHz region, but its 13CH2NH, CH2 15NH, and CH2ND isotopologs were limited to the 100-GHz region. Aims: If a rotational temperature of 100 K is assumed for methanimine, the highest intensity falls at approximately 1.5 THz. In addition to normal methanimine, the 13CH2NH, CH2 15NH, and CH2ND isotopologs in their ground-vibrational states were observed in the frequency range of 120-1600 GHz to provide accurate rest frequency information. Based on this study, the calculated rest frequencies below 2 THz should be sufficiently precise and support observations using all ALMA and Herschel/HIFI observational bands. Methods: Methanimine was generated by pyrolysis of diaminoethane (DAE) vapor at 850 °C. 13CH2NH and CH2 15NH isotopologs were measured with their natural abundance, and deuterization of DAE was performed by mixing normal DAE with deuterated water, D2O, and then pyrolyzed. This gives the deuterated isotopolog of methanimine, CH2ND. Spectral measurements were performed by using the 23 kHz source-frequency modulated terahertz spectrometer at Toho University. Results: Both a- and b-type transitions up to 1.6 THz for the three isotopologs and the normal species were measured. Rotational and centrifugal distortion constants for the three isotopologs were accurately determined. For normal species (CH2NH), both electric quadrupole and nuclear spin-rotation coupling constants for nitrogen nucleus were determined, while for the 13CH2NH and CH2ND species, only electric quadrupole-coupling constants for nitrogen nucleus were determined. Conclusions: Our spectral line frequencies are suitable for a future astronomical search for these isotopologs of methanimine. The 1? frequency accuracy up to 2 THz is lower than 100 kHz. The full line list is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/A28

  10. Far-infrared signature of animal tissues characterized by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    He, Mingxia; Azad, Abul K.; Ye, Shenghua; Zhang, Weili

    2006-03-01

    We present terahertz time-domain spectroscopy characterization of various animal tissues obtained from pork and rats. As the sensitivity of terahertz radiation to polar molecules of water is very high, biological tissues with high level of hydration show strong absorption at terahertz frequencies. The experimental data indicate that skin, fat and lean pork tissues have different frequency-dependent response to terahertz radiation due to the variation in water content. The same type tissue from different animals, however, is observed to show very similar water absorption.

  11. Effect on influenza hemagglutinin protein binding with neutralizing antibody using terahertz spectroscopy technology

    NASA Astrophysics Data System (ADS)

    Sun, Yiwen; Zhong, Junlan; Zuo, Jian; Zhang, Cunlin

    2014-11-01

    Terahertz spectroscopy is sensitive to probe several aspects of biological systems. We have reported the terahertz dielectric spectrum is able to identify the type of the charges in the hydrogen-bonded antibodies' networks in our previous work. Recently we demonstrate a highly sensitive THz-TDS method to monitor binding interaction of influenza hemagglutinin (HA) against its target antibody F10. The terahertz dielectric properties of HA was strongly affected by the presence of a specific antibody. Protein solution concentration or even molecular binding interaction can also affect the terahertz signal. This enables us to detect the specificity and sensitivity of antibody-antigen binding under THz radiation.

  12. Cartilage analysis by reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Laun, T.; Muenzer, M.; Wenzel, U.; Princz, S.; Hessling, M.

    2015-07-01

    A cartilage bioreactor with analytical functions for cartilage quality monitoring is being developed. For determining cartilage composition, reflection spectroscopy in the visible (VIS) and near infrared (NIR) spectral region is evaluated. Main goal is the determination of the most abundant cartilage compounds water, collagen I and collagen II. Therefore VIS and NIR reflection spectra of different cartilage samples of cow, pig and lamb are recorded. Due to missing analytical instrumentation for identifying the cartilage composition of these samples, typical literature concentration values are used for the development of chemometric models. In spite of these limitations the chemometric models provide good cross correlation results for the prediction of collagen I and II and water concentration based on the visible and the NIR reflection spectra.

  13. Determination of tetracycline hydrochloride by terahertz spectroscopy with PLSR model.

    PubMed

    Qin, Jianyuan; Xie, Lijuan; Ying, Yibin

    2015-03-01

    Antibiotic residues in agricultural and food products are of great concern to legislatures and consumers. Reliable techniques for rapid and sensitive detection of these residues are necessary to ensure food safety. In this study, tetracycline hydrochloride (TC-HCl) in powder and solution form was detected and quantified using terahertz (THz) spectroscopy. Partial least-squares regression (PLSR) was used to build calibration models. The results obtained in this study indicated that the PLSR model for powder samples was excellent and could be used for quality control. However, the PLSR model for solution samples was not robust and needed to be improved. Overall, THz spectroscopy combined with PLSR model had its potential for the rapid and non-destructive prediction of TC-HCl residue without sophisticated methods, although the accuracy was not high for solution samples which should be improved in future study. PMID:25306365

  14. The generation of high field terahertz radiation and its application in terahertz nonlinear spectroscopy

    E-print Network

    Yeh, Ka-Lo

    2009-01-01

    In this thesis research, I implemented a terahertz generation scheme that enables high-field near-single-cycle terahertz (THz) pulse generation via optical rectification in a LiNbO3 (LN) crystal. I also developed a method ...

  15. Surface-enhanced terahertz spectroscopy using gold rod structures resonant with terahertz waves.

    PubMed

    Ueno, Kosei; Nozawa, Sho; Misawa, Hiroaki

    2015-11-01

    Terahertz (THz) spectroscopy is a promising method to measure the spectrum of low-frequency modes of molecules or ensembles, such as crystals and polymers, including proteins. However, the main drawback of THz spectroscopy is its extremely low sensitivity. In the present study, we report on signal enhancement in THz spectroscopy achieved by depositing amino acid molecules or their derivatives on a gold rod structured silicon substrate whose localized surface plasmon resonance is exhibited in the THz frequency region. The distinct peaks derived from the enhancement of the inherent spectrum based on a molecular crystal were clearly observed when a longitudinal plasmon resonance mode of the gold rod structure was excited and the plasmon resonance band overlapped the molecular/intermolecular vibrational mode. We discuss the mechanism by which surface-enhanced THz spectroscopy was induced from the viewpoint of the enhancement of light-matter coupling due to plasmon excitation and the modulation of the plasmon band by dipole coupling between the plasmon dipole and molecular/intermolecular vibrational modes. PMID:26561128

  16. Quantitative measurement of permeabilization of living cells by terahertz attenuated total reflection

    NASA Astrophysics Data System (ADS)

    Grognot, Marianne; Gallot, Guilhem

    2015-09-01

    Using Attenuated Total Reflection imaging technique in the terahertz domain, we demonstrate non-invasive, non-staining real time measurements of cytoplasm leakage during permeabilization of epithelial cells by saponin. The terahertz signal is mostly sensitive to the intracellular protein concentration in the cells, in a very good agreement with standard bicinchoninic acid protein measurements. It opens the way to in situ real time dynamics of protein content and permeabilization in live cells.

  17. Developments in time-resolved ultrafast imaging and spectroscopy at terahertz frequencies

    E-print Network

    Teo, Stephanie M

    2014-01-01

    Prior to the advent of high energy pulsed femtosecond lasers, the field of terahertz (THz) spectroscopy was stagnated by the lack of both high power THz sources and sensitive THz detectors. Over the past few years, it has ...

  18. Adaptive optics instrumentation in submillimeter/terahertz spectroscopy with a flexible polyvinylidene fluoride cladding hollow waveguide

    NASA Astrophysics Data System (ADS)

    Hidaka, Takehiko; Ishikawa, Akihiro; Kojou, Jun-Ichiro; Ikari, Tomofumi; Ishikawa, Yoh-Ichi; Minamide, Hiroaki; Kudoh, Akito; Nishizawa, Jun-Ichi; Ito, Hiromasa

    2007-08-01

    A simple instrument has been developed to carry out temperature dependent submillimeter/terahertz-wave spectroscopy using a polyvinylidene fluoride flexible hollow waveguide and an eggplant-shape launching lens.

  19. Characteristics of Gadolinium Oxide Nanoparticles Using Terahertz Spectroscopy

    SciTech Connect

    Lee, Dongkyu; Maeng, Inhee; Son, Joo-Hiuk; Oh, Seung Jae; Kim, Taekhoon; Cho, Byung Kyu; Lee, Kwangyeol

    2009-04-19

    The penetration property of the terahertz electromagnetic (THz) wave is relevant to its use. We used the THz wave spectroscopy system which easily penetrates some materials that do not contain water, e.g., plastic and ceramics. The system has been developed for several purposes, including measuring the properties of semiconductors and bio-materials, and detecting plastic bombs and ceramic knives at airports. It is also used for medical imaging systems, such as magnetic resonance imaging (MRI), at some research institutes. It can show not only the difference in amplitude, but also the difference of the phase of each point of sample. MRI technology usually uses contrast agents to enhance the quality of the image. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), made with a heavy metal ion, is commonly used as a clinical MRI contrast agent. Gadolinium oxide (Gd{sub 2}O{sub 3}) nanoparticle is a new contrast agent. It serves to equip the core of each particle with antibodies or ligands. It can freely circulate in blood vessels without amassing in the liver or lungs. This study shows the characteristics of gadolinium oxide nanoparticles to further advance terahertz medical imaging.

  20. Investigation of the sol-gel transition of gelatin using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Kawabe, Shunsuke; Seki, Munetoshi; Tabata, Hitoshi

    2014-04-01

    The sol-gel transition temperature of gelatin is determined using viscoelasticity measurement and terahertz time-domain spectroscopy. From the results of the viscoelasticity measurement, the sol-gel transition temperature is determined to be 30-32 °C, and it strongly depended on the concentration. However, terahertz time-domain spectroscopy indicates a particular transition temperature of 36 °C. A distinction of these transition temperatures is attributed to the difference in the structural changes detected by these measurements.

  1. Hydration dynamics of oriented DNA films investigated by time-domain terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Kistner, C.; André, A.; Fischer, T.; Thoma, A.; Janke, C.; Bartels, A.; Gisler, T.; Maret, G.; Dekorsy, T.

    2007-06-01

    The B to A conformational transition of highly oriented DNA films due to a hydration change is observed with time-domain terahertz spectroscopy. Wet-spun films of calf thymus and salmon DNA are investigated for different film thicknesses and for different polarizations of the terahertz radiation relative to the DNA orientation. A clear polarization dependence is observed. Asynchronous optical sampling allows recording of terahertz absorption and background spectra in a few 10s, permitting the tracking of the dehydration dynamics on a time scale of minutes. The observation of a phase transition is corroborated by Raman spectroscopy.

  2. Application of image processing for terahertz time domain spectroscopy imaging quantitative detection

    NASA Astrophysics Data System (ADS)

    Li, Li-juan; Wang, Sheng; Ren, Jiao-jiao; Zhou, Ming-xing; Zhao, Duo

    2015-03-01

    According to nondestructive testing principle for the terahertz time domain spectroscopy Imaging, using digital image processing techniques, through Terahertz time-domain spectroscopy system collected images and two-dimensional datas and using a range of processing methods, including selecting regions of interest, contrast enhancement, edge detection, and defects being detected. In the paper, Matlab programming is been use to defect recognition of Terahertz, by figuring out the pixels to determine defects defect area and border length, roundness, diameter size. Through the experiment of the qualitative analysis and quantitative calculation of Matlab image processing, this method of detection of defects of geometric dimension of the sample to get a better result.

  3. High-speed terahertz reflection three-dimensional imaging for nondestructive

    E-print Network

    .4290) Nondestructive testing. References and links 1. W. Withayachumnankul, G. M. Png, X. Yin, S. Atakaramians, IHigh-speed terahertz reflection three- dimensional imaging for nondestructive evaluation Kyong Hwan of the imaging system to nondestructive evaluation, a THz reflection 3D image of an artificially made sample

  4. Application of wavelet transforms in terahertz spectroscopy of rough surface targets

    NASA Astrophysics Data System (ADS)

    Arbab, M. Hassan; Winebrenner, Dale P.; Thorsos, Eric I.; Chen, Antao

    2010-02-01

    Previously, it has been shown that scattering of terahertz waves by surface roughness of a target can alter the terahertz absorption spectrum and thus obscure the detection of some chemicals in both transmission and reflection geometries. In this paper it is demonstrated that by employing Maximal Overlap Discrete Wavelet Transform (MODWT) coefficients, wavelet-based methods can be used to retrieve spectroscopic information from a broadband terahertz signal reflected from a rough surface target. It is concluded that while the commonly used direct frequency domain deconvolution method fails to accurately characterize and detect the resonance in the dielectric constant of rough surface lactose pellets, wavelet techniques were able to successfully identify such features.

  5. Terahertz spectroscopy of concrete for evaluating the critical hydration level

    NASA Astrophysics Data System (ADS)

    Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Sasmal, Saptarshi; Pesala, Bala

    2014-03-01

    Concrete, a mixture of cement, coarse aggregate, sand and filler material (if any), is widely used in the construction industry. Cement, mainly composed of Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) reacts readily with water, a process known as hydration. The hydration process forms a solid material known as hardened cement paste which is mainly composed of Calcium Silicate Hydrate (C-S-H), Calcium Hydroxide and Calcium Carbonate. To quantify the critical hydration level, an accurate and fast technique is highly desired. However, in conventional XRD technique, the peaks of the constituents of anhydrated and hydrated cement cannot be resolved properly, where as Mid-infrared (MIR) spectroscopy has low penetration depth and hence cannot be used to determine the hydration level of thicker concrete samples easily. Further, MIR spectroscopy cannot be used to effectively track the formation of Calcium Hydroxide, a key by-product during the hydration process. This paper describes a promising approach to quantify the hydration dynamics of cement using Terahertz (THz) spectroscopy. This technique has been employed to track the time dependent reaction mechanism of the key constituents of cement that react with water and form the products in the hydrated cement, viz., C-S-H, Calcium Hydroxide and Calcium Carbonate. This study helps in providing an improved understanding on the hydration kinetics of cement and also to optimise the physio-mechanical characteristics of concrete.

  6. Terahertz pulse imaging in reflection geometry of skin tissue using time-domain analysis techniques

    NASA Astrophysics Data System (ADS)

    Woodward, Ruth M.; Wallace, Vincent P.; Cole, Bryan E.; Pye, Richard J.; Arnone, Donald D.; Linfield, Edmund H.; Pepper, Michael

    2002-06-01

    We demonstrate the application of Terahertz Pulse Imaging (TPI) in reflection geometry for the study of skin tissue and related cancers. The terahertz frequency regime of 0.1-100THz excites the vibrational modes of molecules, allowing for spectroscopic investigation. The sensitivity of terahertz to polar molecules, such as water, makes TPI suitable for studying the hydration levels in the stratum corneum and the determination of the lateral spread of skin cancer pre-operatively. By studying the terahertz pulse shape in the time domain we have been able to differentiate between diseased and normal tissue for the study of basal cell carcinoma (BCC). Measurements on scar tissue, which is known to contain less water than the surrounding skin, and on regions of inflammation, show a clear contrast in the THz image compared to normal skin. We discuss the time domain analysis techniques used to classify the different tissue types. Basal cell carcinoma shows a positive terahertz contrast, and inflammation and scar tissue shows a negative terahertz contrast compared to normal tissue. This demonstrates for the first time the potential of TPI both in the study of skin cancer and inflammatory related disorders.

  7. 3-D Terahertz Synthetic-Aperture Imaging and Spectroscopy

    NASA Astrophysics Data System (ADS)

    Henry, Samuel C.

    Terahertz (THz) wavelengths have attracted recent interest in multiple disciplines within engineering and science. Situated between the infrared and the microwave region of the electromagnetic spectrum, THz energy can propagate through non-polar materials such as clothing or packaging layers. Moreover, many chemical compounds, including explosives and many drugs, reveal strong absorption signatures in the THz range. For these reasons, THz wavelengths have great potential for non-destructive evaluation and explosive detection. Three-dimensional (3-D) reflection imaging with considerable depth resolution is also possible using pulsed THz systems. While THz imaging (especially 3-D) systems typically operate in transmission mode, reflection offers the most practical configuration for standoff detection, especially for objects with high water content (like human tissue) which are opaque at THz frequencies. In this research, reflection-based THz synthetic-aperture (SA) imaging is investigated as a potential imaging solution. THz SA imaging results presented in this dissertation are unique in that a 2-D planar synthetic array was used to generate a 3-D image without relying on a narrow time-window for depth isolation cite [Shen 2005]. Novel THz chemical detection techniques are developed and combined with broadband THz SA capabilities to provide concurrent 3-D spectral imaging. All algorithms are tested with various objects and pressed pellets using a pulsed THz time-domain system in the Northwest Electromagnetics and Acoustics Research Laboratory (NEAR-Lab).

  8. Quantitative analyses of tartaric acid based on terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Cao, Binghua; Fan, Mengbao

    2010-10-01

    Terahertz wave is the electromagnetic spectrum situated between microwave and infrared wave. Quantitative analysis based on terahertz spectroscopy is very important for the application of terahertz techniques. But how to realize it is still under study. L-tartaric acid is widely used as acidulant in beverage, and other food, such as soft drinks, wine, candy, bread and some colloidal sweetmeats. In this paper, terahertz time-domain spectroscopy is applied to quantify the tartaric acid. Two methods are employed to process the terahertz spectra of different samples with different content of tartaric acid. The first one is linear regression combining correlation analysis. The second is partial least square (PLS), in which the absorption spectra in the 0.8-1.4THz region are used to quantify the tartaric acid. To compare the performance of these two principles, the relative error of the two methods is analyzed. For this experiment, the first method does better than the second one. But the first method is suitable for the quantitative analysis of materials which has obvious terahertz absorption peaks, while for material which has no obvious terahertz absorption peaks, the second one is more appropriate.

  9. Ultrafast Terahertz Kerr Effect Spectroscopy of Liquids and Binary Mixtures

    NASA Astrophysics Data System (ADS)

    Allodi, Marco A.; Finneran, Ian A.; Blake, Geoffrey

    2015-06-01

    The ultrafast TeraHertz Kerr effect (TKE) has recently been demonstrated as a nonlinear spectroscopic technique capable of measuring the dielectric relaxation of liquids. The true power of this technique lies in its ability to provide complementary information to measurements taken using heterodyne-detected optical Kerr effect (OKE) spectroscopy. The optical pulses in OKE measurements interact with the sample via the molecular polarizability, a rank-two tensor, in contrast with THz pulses that interact with the molecules via the dipole moment, a rank-one tensor. Given the different light-matter interactions in the two techniques, TKE measurements help complete the physical picture of intermolecular interactions at short timescales. We report here our implementation of heterodyne-detected TKE spectroscopy, along with measurements of pure liquids, and binary mixtures. Some of the liquids presented here were previously believed to be TKE inactive, thus showing that we have achieved a greater sensitivity than the previous implementation in the literature. In addition, we will discuss a variety of binary mixtures and show how the TKE data can be compared with OKE data to deepen our physical understanding of intermolecular interactions in liquids.

  10. Gelatin embedding: a novel way to preserve biological samples for terahertz imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Fan, Shuting; Ung, Benjamin; Parrott, Edward P. J.; Pickwell-MacPherson, Emma

    2015-04-01

    Sample dehydration has traditionally been a challenging problem in ex vivo terahertz biomedical experiments as water content changes significantly affect the terahertz properties and can diminish important contrast features. In this paper, we propose a novel method to prevent sample dehydration using gelatin embedding. By looking at terahertz image data and calculating the optical properties of the gelatin-embedded sample, we find that our method successfully preserves the sample for at least 35?h, both for imaging and spectroscopy. Our novel preservation method demonstrates for the first time the capability to simultaneously maintain sample structural integrity and prevent dehydration at room temperature. This is particularly relevant for terahertz studies of freshly excised tissues but could be beneficial for other imaging and spectroscopy techniques.

  11. Interfacial Electron Transfer and Transient Photoconductivity Studied with Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Milot, Rebecca Lee

    Terahertz spectroscopy is distinguished from other far infrared and millimeter wave spectroscopies by its inherent phase sensitivity and sub-picosecond time resolution making it a versatile technique to study a wide range of physical phenomena. As THz spectroscopy is still a relatively new field, many aspects of THz generation mechanisms have not been fully examined. Using terahertz emission spectroscopy (TES), THz emission from ZnTe(110) was analyzed and found to be limited by two-photon absorption and free-carrier generation at high excitation fluences. Due to concerns about the continued use of fossil fuels, solar energy has been widely investigated as a promising source of renewable energy. Dye-sensitized solar cells (DSSCs) have been developed as a low-cost alternative to conventional photovoltaic solar cells. To solve the issues of the intermittency and inefficient transport associated with solar energy, researchers are attempting to adapt DSSCs for water oxidation and chemical fuel production. Both device designs incorporate sensitizer molecules covalently bound to metal oxide nanoparticles. The sensitizer, which is comprised of a chromophore and anchoring group, absorbs light and transfers an electron from its excited state to the conduction band of the metal oxide, producing an electric current. Using time-resolved THz spectroscopy (TRTS), an optical pump/THz probe technique, the efficiency and dynamics of electron injection from sensitizers to metal oxides was evaluated as a function of the chromophore, its anchoring group, and the metal oxide identity. Experiments for studying fully functioning DSSCs and water oxidation devices are also described. Bio-inspired pentafluorophenyl porphyrin chromophores have been designed and synthesized for use in photoelectrochemical water oxidation cells. Influences on the efficiency and dynamics of electron injection from the chromophores into TiO2 and SnO2 nanoparticles due to changes in both the central substituent to the porphyrin ring and degree of fluorination of ring substituents were analyzed. Due to the high reduction potentials of these sensitizers, injection into TiO2 was generally not observed. Injection timescales from the porphyrins into SnO2 depended strongly on the identity of the central substituent and were affected by competition with excited-state deactivation processes. The carboxylate anchoring group is commonly used to bind DSSC sensitizers to metal oxide surfaces but is typically not stable under the aqueous and oxidative conditions required for water oxidation. Electron injection efficiency and water stability of several alternative anchoring groups, including phosphonic acid, hydroxamic acid, acerylacetone, and boronic acid, were evaluated. While all of the anchoring groups exhibited water stability superior to carboxylate, the hydroxamate anchor had the best combination of ease of handling and electron injection efficiency. The effects on photoconductivity due to metal oxide morphology and the addition of dopants were also analyzed. Mixtures of anatase and rutile TiO 2 nanoparticles are known to exhibit cooperative effects which increase the efficiency of DSSCs and photocatalysis relative to the pure-phase materials. Through analysis of TRTS measurements, the mechanism of this synergistic effect was found to involve electron transfer from the lower-mobility, higher surface area rutile nanoparticles to anatase particles, resulting in a higher charge collection efficiency. In addition to morphology, doping has been investigated as a means of expanding the spectral range of visible absorption of photocatalysts. Doping ZnO nanowires with manganese(II) was found to significantly decrease the electron mobility, and doping with cobalt(II) increased the timescale for electron trapping. These differences can be understood by considering the changes to the band structure of ZnO effected by the dopants. Preliminary analyses of the solvent and electrolyte dependence on the electron injection rate and efficiency suggest that electron injection can be affected by

  12. Non-destructive evaluation of the hidden voids in integrated circuit packages using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Park, Sung-Hyeon; Jang, Jin-Wook; Kim, Hak-Sung

    2015-09-01

    In this work, a terahertz time-domain spectroscopy (THz-TDS) imaging technique was used as a non-destructive inspection method for detecting voids in integrated circuit (IC) packages. Transmission and reflection modes, with an angle of incidence of 30°, were used to detect voids in IC packages. The locations of the detected voids in the IC packages could be calculated by analyzing THz waveforms. Finally, voids that are positioned at the different interfaces in the IC package samples could be successfully detected and imaged. Therefore, this THz-TDS imaging technique is expected to be a promising technique for non-destructive evaluation of IC packages.

  13. Advanced birefringence measurements in standard terahertz time-domain spectroscopy.

    PubMed

    Pfleger, Michael; Roitner, Heinz; Pühringer, Harald; Wiesauer, Karin; Grün, Hubert; Katletz, Stefan

    2014-05-20

    Polarization-sensitive (PS) terahertz (THz) technology can be used for investigating anisotropic materials that are opaque for visible light. A full characterization of an anisotropic material requires the extraction of the birefringence as well as the orientation of the optical axis from the measurement data. We present an approach based on THz time-domain spectroscopy (TDS) that exploits the spectral content of the THz signal for determining these two parameters from only two measurements. In contrast to an earlier approach with a more sophisticated PS-THz system and quasi-circularly polarized THz radiation, now a simple standard THz-TDS system can be employed. After a description of the mathematical model for data analysis we demonstrate the applicability of our method for a lithium niobate crystal and furthermore for a glass-fiber reinforced polymer sample, for which the orientation of the optical axis and birefringence are obtained in a spatially resolved way, showing the potential of the method also for PS-THz imaging. As no specialized setup or components are required, our approach can be easily and extensively applied for the analysis of anisotropic samples at THz frequencies. PMID:24922202

  14. Time-domain terahertz spectroscopy of artificial skin

    NASA Astrophysics Data System (ADS)

    Corridon, Peter M.; Ascázubi, Ricardo; Krest, Courtney; Wilke, Ingrid

    2006-02-01

    Time-domain Terahertz (THz) spectroscopy and imaging is currently evaluated as a novel tool for medical imaging and diagnostics. The application of THz-pulse imaging of human skin tissues and related cancers has been demonstrated recently in-vitro and in-vivo. With this in mind, we present a time-domain THz-transmission study of artificial skin. The skin samples consist of a monolayer of porous matrix of fibers of cross-linked bovine tendon collagen and a glycosaminoglycan (chondroitin-6-sulfate) that is manufactured with a controlled porosity and defined degradation rate. Another set of samples consists of the collagen monolayer covered with a silicone layer. We have measured the THz-transmission and determined the index of refraction and absorption of our samples between 0.1 and 3 THz for various states of hydration in distilled water and saline solutions. The transmission of the THz-radiation through the artificial skin samples is modeled by electromagnetic wave theory. Moreover, the THz-optical properties of the artificial skin layers are compared to the THz-optical properties of freshly excised human skin samples. Based on this comparison the potential use of artificial skin samples as photo-medical phantoms for human skin is discussed.

  15. Terahertz Spectroscopy and Global Analysis of H_3O^+

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.; Pearson, John C.; Pickett, Herbert M.

    2009-06-01

    Eight ground state inversion transitions of H_3O^+ in the 0.9-1.6 THz region have been measured using the frequency multiplier submillimeter spectrometer (FMSS) at JPL. The accuracy of these measurements is estimated to be 300 kHz. The ions were generated in a DC discharge through a gas mixture of a few mTorr of H_2 and 30 mTorr of H_2O. A multistate analysis was carried out for H_3O^+, which includes the lines observed in this work, previous submillimeter and terahertz inversion transitions in the ground state, and previous infrared data on all the four vibrational fundamental bands. Accurate molecular parameters were obtained with taking into account the strong Coriolis interaction between the symmetric OH stretching mode ?_1 and the doubly degenerate asymmetric OH stretching mode ?_3. Frequency predictions, particularly for high-J transitions in the ground state and in the ?_1 and ?_3 fundamental bands, have been greatly improved by including in our analysis 200 more high-J transitions, which were excluded in previous analyses. The more precise measurements and new predictions reported here will support the analysis of astronomical observations by the future high resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA.

  16. Terahertz and Infrared Laboratory Spectroscopy in Support of NASA Missions

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan

    2015-06-01

    The JPL molecular spectroscopy group supports NASA programs encompassing Astrophysics, Atmospheric Science, and Planetary Science. Ongoing activities include measurement and analysis of molecular spectra in the terahertz and infrared regions under conditions akin to the remote environments under study in NASA missions. This presentation will show the implementation of state-of-the-art spectroscopic techniques to fulfill spectroscopic demands of the Herschel Space Observatory and the Orbiting Carbon Observatory re-flight (OCO-2). A demonstrative example of the significantly improved frequency predictions for the H_3O^+ ground state high-J transitions will be given. This work was critical to Herschel's successful identification of highly excited metastable H_3O^+ Terahertz lines with J=K up to 11, one of the Herschel mission's many surprising observational results. The observation and subsequent laboratory work revealed that (1) these highly excited H_3O^+ lines had already been observed by European Southern Observatory's Atacama Pathfinder Experiment telescope a few years before but had been classified as U-lines; (2) the H_3O^+ number density was previously underestimated by an order of magnitude, due to ignorance of the population in the metastable states. A second example focuses on O_2, an important absorber from the microwave through the deep UV. This work is motivated by the challenge of developing an accurate and complete spectroscopic characterization of molecular oxygen across a wide frequency range for current and planned Earth atmospheric observations. Especially, OCO-2 utilizes the O_2 A-band for air mass calibration; extremely accurate O_2 molecular data, i.e., line positions with uncertainty on the order of MHz for the A-band around 13000 wn, are required to fulfill the demand of the proposed 0.25% precision for the carbon dioxide concentration retrievals. G. Pilbratt, J. Riedinger, T. Passvogel, G. Crone, D. Doyle, U. Gageur et al. A&A, 518, L1 (2010). D. Crisp, B.M Fisher, C. O'Dell, C. Frankenberg, R. Basilio, H. Boesch et al., Atmos. Meas. Tech. 5, 687-707 (2012).

  17. Laminated helmet materials characterization by terahertz kinetics spectroscopy

    NASA Astrophysics Data System (ADS)

    Rahman, Anis; Rahman, Aunik K.

    2015-05-01

    High speed acquisition of reflected terahertz energy constitutes a kinetics spectrum that is an effective tool for layered materials' deformation characterization under ballistic impact. Here we describe utilizing the kinetics spectrum for quantifying a deformation event due to impact in material used for Soldier's helmet. The same technique may be utilized for real-time assessment of trauma by measuring the helmet wore by athletes. The deformation of a laminated material (e.g., a helmet) is dependent on the nature of impact and projectile; thus can uniquely characterize the impact condition leading to a diagnostic procedure based on the energy received by an athlete during an impact. We outline the calibration process for a given material under ballistic impact and then utilize the calibration for extracting physical parameters from the measured kinetics spectrum. Measured kinetics spectra are used to outline the method and rationale for extending the concept to a diagnosis tool. In particular, captured kinetics spectra from multilayered plates subjected to ballistic hit under experimental conditions by high speed digital acquisition system. An algorithm was devised to extract deformation and deformation velocity from which the energy received on the skull was estimated via laws of nonrelativistic motion. This energy is assumed to be related to actual injury conditions, thus forming a basis for determining whether the hit would cause concussion, trauma, or stigma. Such quantification may be used for diagnosing a Soldier's trauma condition in the field or that of an athlete's.

  18. Terahertz spectroscopy and imaging for cultural heritage management: state of art and perspectives

    NASA Astrophysics Data System (ADS)

    Catapano, Ilaria; Soldovieri, Francesco

    2014-05-01

    Non-invasive diagnostic tools able to provide information on the materials and preservation state of artworks are crucial to help conservators, archaeologists and anthropologists to plan and carry out their tasks properly. In this frame, technological solutions exploiting Terahertz (THz) radiation, i.e., working at frequencies ranging from 0.1 to 10 THz, are currently deserving huge attention as complementary techniques to classical analysis methodologies based on electromagnetic radiations from X-rays to mid infrared [1]. The main advantage offered by THz spectroscopy and imaging systems is referred to their capability of providing information useful to determine the construction modality, the history life and the conservation state of artworks as well as to identify previous restoration actions [1,2]. In particular, unlike mid- and near-infrared spectroscopy, which provides fingerprint absorption spectra depending on the intramolecular behavior, THz spectroscopy is related to the structure of the molecules of the investigated object. Hence, it can discriminate, for instance, the different materials mixed in a paint [1,2]. Moreover, THz radiation is able to penetrate several materials which are opaque to both visible and infrared materials, such as varnish, paint, plaster, paper, wood, plastic, and so on. Accordingly, it is useful to detect hidden objects and characterize the inner structure of the artwork under test even in the direction of the depth, while avoiding core drillings. In this frame, THz systems allow us to discriminate different layers of materials present in artworks like paints, to obtain images providing information on the construction technique as well as to discover risk factors affecting the preservation state, such as non-visible cracks, hidden molds and air gaps between the paint layer and underlying structure. Furthermore, adopting a no-ionizing radiation, THz systems offer the not trivial benefit of negligible long term risks to the molecular stability of the exposed objects and humans. Recently, the interest on THz technology is also growing up thanks to the development of flexible and compact commercial systems having source and detector probes coupled by means of optical fiber cables and that do not require complex optical alignments. These features allow us to reconfigure the measurement configuration easily; thus transmission, normal reflection and oblique reflection data can be collected according to the constrains and objective of the survey to be performed. Moreover, they open the way to on field applications. An example of last generation THz systems is the Fiber-Coupled Terahertz Time Domain System (FICO) marketed by Z-Omega and available at the Institute of Electromagnetic Sensing of the Environment. Such a system is designed to perform both transmission and reflection spectroscopy and imaging measurements in the range from 60GHz to 3THz; with a waveform acquisition speed up to 500Hz. A review of the literature assessing potentialities and open challenges of THz spectroscopy and imaging in the frame of cultural heritage preservation will be provided at the conferences, with a specific focus on the diagnostic capabilities of last generation systems. REFERENCES [1] K. Fukunaga, I. Hosako, Innovative non-invasive analysis techniques for cultural heritage using terahertz technology, C. R. Physique, vol. 11, pp.519-526, 2010. [2] G.Fillippidis, M. Massaouti, A. Selimis, E.J. Gualda, J.M. Manceau, S. Tzortzakis, Nonlinear imaging and THz diagnostic tools in the service of Cultural Heritage, Appl. Phys. A, vol.106, pp.257-263, 2012.

  19. High-resolution terahertz spectroscopy with a single tunable frequency comb.

    PubMed

    Skryl, A S; Pavelyev, D G; Tretyakov, M Y; Bakunov, M I

    2014-12-29

    We report an improvement of three orders of magnitude in the spectral resolution of a recently proposed single-comb terahertz spectroscopy [Opt. Lett.39, 5669 (2014)]. The improvement is achieved by using a femtosecond optical pulse train with a tunable repetition rate. Terahertz comb with tunable spectral line spacing generated by the train is detected via nonlinear mixing with a harmonic of a CW signal from a microwave frequency synthesizer. By applying this technique to the low-pressure gas spectroscopy, we achieved a 100 kHz spectral resolution in measuring separate absorption lines of the rotational manifold of fluoroform (CF3H). PMID:25607192

  20. Terahertz nano-spectroscopy and imaging of superfluid surface plasmons in conventional and anisotropic superconductors

    NASA Astrophysics Data System (ADS)

    Stinson, H. T.; Wu, J. S.; Jiang, B. Y.; Fei, Z.; Rodin, A. S.; Chapler, B.; McLeod, A. S.; Castro Neto, A.; Lee, Y. S.; Fogler, M. M.; Basov, D. N.

    2015-03-01

    We numerically model near-field spectroscopy and superfluid polariton imaging experiments on conventional and unconventional superconductors in the infrared and terahertz regime. Our modeling shows that near-field spectroscopy can measure the magnitude of the superconducting gap in Bardeen-Cooper-Schrieffer superconductors with nanoscale spatial resolution. We demonstrate how the same technique can measure the c-axis plasma frequency, and thus the c-axis superfluid density, of layered unconventional superconductors such as cuprates and pnictides with identical spatial resolution. We discuss the development of a cryogenic terahertz near-field microscope designed to perform these proposed experiments.

  1. Precise Determination of Thicknesses of Multilayer Polyethylene Composite Materials by Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Palka, Norbert; Krimi, Soufiene; Ospald, Frank; Miedzinska, Danuta; Gieleta, Roman; Malek, Marcin; Beigang, Rene

    2015-06-01

    The multilayer structure of an ultra-high molecular weight polyethylene (UHMWPE) composite material was investigated in the terahertz (THz) spectral range by means of time-domain spectroscopy (TDS) technique. Such structures consist of many alternating layers of fibers, each being perpendicular to the other and each having a thickness of about 50 ?m. Refractive indices of two composite samples and of a sample composed of four single layers (plies) having the same fiber orientation were determined for two orthogonal orientations of the electric field in a transmission TDS system. The birefringence of a single layer was measured, and the origin of this phenomenon is discussed. Using the TDS system in reflection, the formation of many pulses shifted in time was observed originating from reflections from interfaces of successive layers caused by the periodic modulation of the refractive index along the propagation of the THz radiation. This phenomenon is theoretically described and simulated by means of a transfer matrix method (TMM). A time-domain fitting procedure was used to determine thicknesses of all layers of the composite material. The reconstructed waveform based on the optimized thicknesses shows very good agreement with the measured waveform, with typical differences between measurements and simulations between 3 and 7 ?m (depending on the sample). As a result, we were able to determine the thicknesses of all layers of two multilayer (~200 plies) structures by means of the reflection TDS technology with high accuracy.

  2. Terahertz time-domain and Fourier-transform infrared spectroscopy of traditional Korean pigments

    NASA Astrophysics Data System (ADS)

    Hong, Taeyoon; Choi, Kyujin; Ha, Taewoo; Park, Byung Cheol; Sim, Kyung Ik; Kim, Jong Hyeon; Kim, Jae Hoon; Kwon, Jy Eun; Lee, Sanghyun; Kang, Dai Ill; Lee, Han Hyoung

    2014-03-01

    Representative traditional Korean pigments (oyster shell white [hobun], massicot [miltaseung], indigo [jjok], azurite [seokcheong], malachite [seokrok], and red lead [yeondan]) have been studied with terahertz time-domain spectroscopy (THz-TDS) and Fourier-transform infrared spectroscopy (FTIRS) over the spectral region of 0.1-7.5 THz. Both the refractive index n and the extinction coefficient k were simultaneously and independently determined in the terahertz region without a Kramers-Kronig analysis while the absoprtion coefficient spectra were acquired in the infrared region. All pigments studied in the present work exhibited a set of characteristic absorption peaks unique to the pigment species in addition to a background that increased with increasing frequency. Our study demonstrates that terahertz and infrared techniques can be useful identification and diagnostic tools for the traditional Korean pigments used in heritage buildings and artworks.

  3. Indirect Terahertz Spectroscopy of Molecular Ions Using Highly Accurate and Precise Mid-Ir Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mills, Andrew A.; Ford, Kyle B.; Kreckel, Holger; Perera, Manori; Crabtree, Kyle N.; McCall, Benjamin J.

    2009-06-01

    With the advent of Herschel and SOFIA, laboratory methods capable of providing molecular rest frequencies in the terahertz and sub-millimeter regime are increasingly important. As of yet, it has been difficult to perform spectroscopy in this wavelength region due to the limited availability of radiation sources, optics, and detectors. Our goal is to provide accurate THz rest frequencies for molecular ions by combining previously recorded microwave transitions with combination differences obtained from high precision mid-IR spectroscopy. We are constructing a Sensitive Resolved Ion Beam Spectroscopy setup which will harness the benefits of kinematic compression in a molecular ion beam to enable very high resolution spectroscopy. This ion beam is interrogated by continuous-wave cavity ringdown spectroscopy using a home-made widely tunable difference frequency laser that utilizes two near-IR lasers and a periodically-poled lithium niobate crystal. Here, we report our efforts to optimize our ion beam spectrometer and to perform high-precision and high-accuracy frequency measurements using an optical frequency comb. footnote

  4. Terahertz time-domain spectroscopy and quantitative analysis of metal gluconates.

    PubMed

    Li, Shaoxian; Yang, Jingqi; Zhao, Hongwei; Yang, Na; Jing, Dandan; Zhang, Jianbing; Li, Qingnuan; Han, Jiaguang

    2015-01-01

    A series of metal gluconates (Na(+), K(+), Mg(2+), Ca(2+), Fe(2+), Cu(2+), and Zn(2+)) were investigated by terahertz (THz) time-domain spectroscopy. The absorption coefficients and refractive indices of the samples were obtained in the frequency range of 0.5-2.6 THz. The gluconates showed distinct THz characteristic fingerprints, and the dissimilarities reflect their different structures, hydrogen-bond networks, and molecular interactions. In addition, some common features were observed among these gluconates, and the similarities probably come from the similar carbohydrate anion group. The X-ray powder diffraction measurements of these metal gluconates were performed, and the copper(II) gluconate was found to be amorphous, corresponding to the monotonic increase feature in the THz absorption spectrum. The results suggest that THz spectroscopy is sensitive to molecular structure and physical form. Binary and ternary mixtures of different gluconates were quantitatively analyzed based on the Beer-Lambert law. A chemical map of a tablet containing calcium D-gluconate monohydrate and ?-lactose in the polyethylene host was obtained by THz imaging. The study shows that THz technology is a useful tool in pharmaceutical research and quality control applications. PMID:25506686

  5. Application of Terahertz Time-Domain Spectroscopy in nondestructive testing of adhesion quality

    NASA Astrophysics Data System (ADS)

    Zhao, Duo; Ren, Jiaojiao; Qao, Xiaoli; Li, Lijuan

    2015-10-01

    Multilayer composites assembled flexibly with have important effect on the performance and safety of aircrafts. The nondestructive detection on the adhesion layer is an important index to evaluate the quality of aircraft assembly. Terahertz Time-Domain Spectroscopy (THz-TDS) is a newly developed spectroscopy technique based on femtosecond laser technology which currently applied to qualitative analysis as a means of security detection and material identification. Compared with the traditional tensile testing, the detection of defects in the adhesion layer could be nondestructive, visible, positioning and more accurate. The spectral analysis on the material to be assembled was done respectively. The testing model was established in accord with the extracted optical parameters. With the employment of a reflective THz-TDS device, X-Y spot scanning was done to obtain waveforms of every location on an assembled sample. Layered analysis was done by selecting region of interest in time domain waveforms. Conclusions of Time- Frequency spectrum analysis and scanning imaging performance are relatively satisfying through the experiments. The defects could be located and analyzed accurately and efficiently. The research reveals that THz-TDS (0.1THz~5THz) has good testing performance on the adhesion quality of multilayer composites.

  6. Character research on 2.52 terahertz coaxial reflection-mode confocal scanning microscopic imaging

    NASA Astrophysics Data System (ADS)

    Yang, Yong-fa; Li, Qi; Hu, Jia-qi

    2014-12-01

    The technology of terahertz (THz) is a major research area in the 21st century. THz imaging is an important research direction. The single-frequency continuous-wave THz technology is combined with coaxial reflection-mode confocal scanning microscopic imaging in this article. Under the given system parameters, the transverse response character of 2.52THz (118.83?m) coaxial reflection-mode confocal scanning microscopic imaging is emulated and analyzed. The results of emulation show that coaxial reflection-mode confocal scanning microscopic imaging is feasible in THz region.

  7. Time-domain terahertz magneto-spectroscopy of semiconductors

    NASA Astrophysics Data System (ADS)

    Wang, Xiangfend

    The terahertz frequency range, 0.1-10 THz, is one of the richest frequency ranges in condensed matter spectroscopy. Many important excitations and dynamical phenomena occur in this range, including superconducting gaps, protein conformational modes, phonons, and plasmons, just to name a few. Spectroscopic studies in this region provide valuable insights into the quantum states and dynamics of confined, driven, or interacting electrons in solids. In this dissertation research I have developed a time-domain THz magneto-spectroscopy system to investigate various THz magnetic excitations in semiconductors, including a high-mobility two-dimensional electron gas (2DEG) in a GaAs quantum well and lightly-doped InSb. In the 2DEG, I have observed very long-lived (up to ˜ 50 ps) coherent THz oscillations, which correspond to a time-domain observation of cyclotron resonance. From the data both the real and imaginary parts of the conductivity can be simultaneously determined because of the phase-sensitive-detection nature of this technique. Magnetic field and temperature dependent results provide some important information on electron scattering in this system. In InSb, I have found that the THz transmittance of the sample sensitively changes with the temperature and magnetic field, showing a number of non-intuitive spectral features. In particular, I observed a sudden appearance and disappearance of transparency with increasing temperature, which resulted in a transparency window of a narrow temperature region (160-190 K), over a frequency range of 0.1-0.8 THz. Detailed theoretical simulations based on a cold magneto-plasma model demonstrate that this novel phenomenon is a manifestation of coherent interference of the cyclotron-resonance-active and cyclotron-resonance-inactive modes co-propagating through the magneto-plasma along the magnetic field direction. Finally, I have obtained some experimental results on the 1s--2p-- impurity transition at 1.6 K that provide insight on the nature of the magnetic-field-induced metal-to-insulator transition that is known to occur in this system. The materials studied in this research are highly tunable with external fields and doping and thus promising for future THz devices such as tunable THz detectors, filters, and Faraday rotators.

  8. Emulation and design of terahertz reflection-mode confocal scanning microscopy based on virtual pinhole

    NASA Astrophysics Data System (ADS)

    Yang, Yong-fa; Li, Qi

    2014-12-01

    In the practical application of terahertz reflection-mode confocal scanning microscopy, the size of detector pinhole is an important factor that determines the performance of spatial resolution characteristic of the microscopic system. However, the use of physical pinhole brings some inconvenience to the experiment and the adjustment error has a great influence on the experiment result. Through reasonably selecting the parameter of matrix detector virtual pinhole (VPH), it can efficiently approximate the physical pinhole. By using this approach, the difficulty of experimental calibration is reduced significantly. In this article, an imaging scheme of terahertz reflection-mode confocal scanning microscopy that is based on the matrix detector VPH is put forward. The influence of detector pinhole size on the axial resolution of confocal scanning microscopy is emulated and analyzed. Then, the parameter of VPH is emulated when the best axial imaging performance is reached.

  9. Optical Properties of Laminarin Using Terahertz Time-Domain Spectroscopy (abstract)

    NASA Astrophysics Data System (ADS)

    Shin, Hee Jun; Maeng, Inhee; Oh, Seung Jae; Kim, Sung In; Kim, Ha Won; Son, Joo-Hiuk

    2009-04-01

    Terahertz spectroscopy is important in the study of biomolecular structure because the vibration and rotation energy of large molecules such as DNA, proteins, and polysaccharides are laid in terahertz regions. Terahertz time-domain spectroscopy (THz-TDS), using terahertz pulses generated and detected by femto-second pulses laser, has been used in the study of biomolecular dynamics, as well as carrier dynamics of semiconductors. Laminarin is a polysaccharide of glucose in brown algae. It is made up of ?(1-3)-glucan and ?(1-6)-glucan. ?-glucan is an anticancer material that activates the immune reaction of human cells and inhibits proliferation of cancer cells. ?-glucan with a single-strand structure has been reported to activate the immune reaction to a greater extent than ?-glucan with a triple-strand helix structure. We used THz-TDS to characterize the difference between single-strand and triple-strand ?-glucan. We obtained single-strand ?-glucan by chemical treatment of triple-strand ?-glucan. We measured the frequency dependent optical constants of Laminarin using THz-TDS. Power absorption of the triple-strand helix is larger than the single-strand helix in terahertz regions. The refractive index of the triple-strand helix is also larger than that of the single-strand helix.

  10. Terahertz Time Domain Spectroscopy of Phonon-Depopulation Based Quantum Cascade Lasers

    SciTech Connect

    Rungsawang, R.; Dhillon, S. S.; Jukam, N.; Oustinov, D.; Madeo, J.; Tignon, J.; Colombelli, R.; Dean, P.; Salih, M.; Khanna, S. P.; Linfield, E.; Davies, A. G.

    2011-12-23

    A 3.1 THz phonon depopulation-based quantum-cascade-laser is investigated using terahertz time domain spectroscopy. A gain of 25 cm{sup -1} and absorption features due to the lower laser level being populated from a parasitic electronic channel are highlighted.

  11. Laser Original Magneto-Optical Spectroscopy of Semiconductors Using Terahertz Quantum Cascade Lasers

    E-print Network

    Natelson, Douglas

    860 Laser Original Magneto-Optical Spectroscopy of Semiconductors Using Terahertz Quantum Cascade 77005, U.S.A. Received October 7, 2005 We have used quantum-cascade lasers operating at 4.7 THz, 3.5 THz the first spectroscopic application of THz quantum-cascade lasers. Results show that these compact lasers

  12. Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

    E-print Network

    Heinz, Tony F.

    resonances and intraband transitions in low-dimensional systems. Moreover, using a pump-probe schemeCarrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy Ronald Ulbricht Fundamental Research on Matter (FOM) - Institute for Atomic and Molecular Physics (AMOLF), Science

  13. Terahertz spectroscopy of intrinsic biomarkers for non-melanoma skin Cecil S. Joseph1*

    E-print Network

    Massachusetts at Lowell, University of

    to the National Institute of Health (NIH), people with fairer skin have a higher risk of getting skin cancerTerahertz spectroscopy of intrinsic biomarkers for non-melanoma skin cancer. Cecil S. Joseph1 of human cancers. The aim of this study was to identify intrinsic biomarkers for non-melanoma skin cancer

  14. "Developing terahertz spectroscopy to be used for the study of bio-materials."

    E-print Network

    Zhigilei, Leonid V.

    "Developing terahertz spectroscopy to be used for the study of bio-materials." Tatiana Globus or detection and identification of bio-targets. THz radiation interacts with the low-frequency internal these vibrations. The subThz/Thz regions of absorption spectra of bio-molecules and species reveal these low

  15. Direct MD Simulations of Terahertz Absorption and 2D Spectroscopy Applied to Explosive Crystals

    E-print Network

    Goddard III, William A.

    Direct MD Simulations of Terahertz Absorption and 2D Spectroscopy Applied to Explosive Crystals G of crystalline cyclotrimethylenetrinitramine (RDX) and triacetone triperoxide (TATP) were simulated with the Reax crystals8 of sugars, explosives,4,9-13 biosystems,14,15 and slow kinetic phenomena such as evaporation.16

  16. SELECTED ASPECTS OF TERAHERTZ SPECTROSCOPY IN PHARMACEUTICAL SCIENCES.

    PubMed

    Nowak, Kacper; Pli?ski, Edward F; Karolewicz, Bo?ena; Jarz?b, Przemys?aw P; Pli?ska, Stanis?awa; Fuglewicz, Bogus?aw; Walczakowski, Micha? J; Augustyn, ?ukasz; Sterczewsk, ?ukasz A; Grzelczak, Micha? P; Hruszowiec, Mariusz; Beziuk, Grzegorz; Mikulic, Martin; Pa?ka, Norbert; Szustakowskip, Mieczys?aw

    2015-01-01

    THz-TDS techniques are applied to investigate selected pharmaceutical samples. Investigations were performed on selected pharmaceutical samples with active pharmaceutical ingredients (API)--famotidine, ranitidine, fenofibrate, lovastatin, simvastatin, aspirin, ketoconazole, acyclovir (hydrated and non-hydrated), on excipients--lactose, glucose (hydrated and non-hydrated), Pluronic 127, and on mixtures of selected compounds. Pseudo-polymorphism effects are considered as well. Examples of the terahertz imaging technique are also given. APIs and excipients can be easily recognized in the terahertz band by their specific "fingerprints" as individual components and in mixtures. The hydration process as a variety of polymorphism can also be easily monitored using the THz technique. Moreover, terahertz light can be useful for the penetration of tablets, giving clear pictures of possible defects in tablet coatings. PMID:26665391

  17. Terahertz spectroscopy of human skin constituents in suspension

    NASA Astrophysics Data System (ADS)

    Joseph, Cecil; Yaroslavsky, Anna; Al-Arashi, Munir; Gatesman, Andrew; Goyette, Thomas; Giles, Robert

    2008-03-01

    Continuous wave terahertz imaging has the potential to offer a non-invasive medical imaging modality for detecting different types of human cancers. The aim of this study was to identify frequencies of interest for continuous wave terahertz imaging of skin cancer. The absorption characteristics of water, collagen, and elastin were studied in the range between 20 and 100cm-1. In addition, we have recorded and analyzed the teraherz absorption spectra of several substances that are present in human skin (i.e. tryptophan, tyrosine, melanin, urocanic acid, keratin) and their water suspensions with the goal of using them as biomarkers for skin cancer detection.

  18. Crystallization of amorphous lactose at high humidity studied by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    McIntosh, Alexander I.; Yang, Bin; Goldup, Stephen M.; Watkinson, Michael; Donnan, Robert S.

    2013-02-01

    We report the first use of terahertz time-domain spectroscopy (THz-TDS) to study the hydration and crystallization of an amorphous molecular solid at high humidity. Lactose in its amorphous and monohydrate forms exhibits different terahertz spectra due to the lack of long range order in the amorphous material. This difference allowed the transformation of amorphous lactose to its monohydrate form at high humidity to be studied in real time. Spectral fitting of frequency-domain data allowed kinetic data to be obtained and the crystallization was found to obey Avrami kinetics. Bulk changes during the crystallization could also be observed in the time-domain.

  19. Application of terahertz spectroscopy and molecular modeling in isomers investigation: Glucose and fructose

    NASA Astrophysics Data System (ADS)

    Zheng, Zhuan-Ping; Fan, Wen-Hui; Liang, Yu-Qing; Yan, Hui

    2012-04-01

    Terahertz spectra of glucose and fructose have been measured by terahertz time-domain spectroscopy (THz-TDS) at room temperature. Because they have the same molecular formula, the differences of the THz spectra can be attributed to their molecular structures and the arrangement of molecules in unit cell. In this paper, gaseous-state theory has been employed to simulate the isolated molecule of these two isomers. The results indicate that experimental THz spectral features (0.5 - 4.0 THz) of glucose and fructose arise from the mixture of intramolecular and intermolecular modes, involving hydrogen bonds and covalent bonds, and with the intermolecular modes dominating.

  20. Analysis of drugs-of-abuse and explosives using terahertz time-domain and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Burnett, Andrew; Fan, Wenhui; Upadhya, Prashanth; Cunningham, John; Linfield, Edmund; Davies, Giles; Edwards, Howell; Munshi, Tasnim; O'Neil, Andrew

    2006-02-01

    We demonstrate that, through coherent measurement of the transmitted terahertz electric fields, broadband (0.3-8THz) time-domain spectroscopy can be used to measure far-infrared vibrational modes of a range of illegal drugs and high explosives that are of interest to the forensic and security services. Our results show that these absorption features are highly sensitive to the structural and spatial arrangement of the molecules. Terahertz frequency spectra are also compared with high-resolution low-frequency Raman spectra to assist in understanding the low frequency inter- and intra-molecular vibrational modes of the molecules.

  1. Application of femtotechnologies and terahertz spectroscopy methods in cataract diagnostics

    NASA Astrophysics Data System (ADS)

    Sakhnov, S. N.; Leksutkina, E. V.; Smolyanskaya, O. A.; Usov, A. V.; Parakhuda, S. E.; Grachev, Ya. V.; Kozlov, S. A.

    2011-08-01

    We study the destructive action of femtosecond pulses (200 fs) on the human cataractous crystalline lens and the transmission of the cataractous lens in the terahertz spectral range of electromagnetic oscillations (0.2-1 THz) in relation to the density of the nucleus of the lens.

  2. Near-Field Orientation Sensitive Terahertz Micro-Spectroscopy of Single Crystals

    NASA Astrophysics Data System (ADS)

    Acbas, Gheorghe; Singh, Rohit; Snell, Edward; Markelz, Andrea

    2012-02-01

    We present spectroscopic imaging studies of molecular crystals. These measurements examine the anisotropy of the intra and inter-molecular vibrational modes of single crystals at terahertz frequencies. The method is based on the technique developed in [1-2] for sub-wavelength resolution time domain terahertz spectroscopy (THz TDS), with added polarization orientation dependent measurements and hydration control. This method allows us to study the spectroscopic properties of small single crystals with sizes down to 20 micrometers. In addition, mapping the spectroscopic information at such small spatial scales allows us to reduce the water absorption and interference artifacts that usually affect protein THz TDS measurements. We show the polarization sensitive terahertz absorption spectra in the (0.3-3THz) range of sucrose, oxalic acid and lysozyme protein crystals. *M. A. Seo, et. al., Opt. Express, 15(19):11781--11789, 09 (2007) *J. R Knab, et. al., App. Phys. Lett.,97, 031115 (2010)

  3. Leaf water dynamics of Arabidopsis thaliana monitored in-vivo using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Castro-Camus, E.; Palomar, M.; Covarrubias, A. A.

    2013-10-01

    The declining water availability for agriculture is becoming problematic for many countries. Therefore the study of plants under water restriction is acquiring extraordinary importance. Botanists currently follow the dehydration of plants comparing the fresh and dry weight of excised organs, or measuring their osmotic or water potentials; these are destructive methods inappropriate for in-vivo determination of plants' hydration dynamics. Water is opaque in the terahertz band, while dehydrated biological tissues are partially transparent. We used terahertz spectroscopy to study the water dynamics of Arabidopsis thaliana by comparing the dehydration kinetics of leaves from plants under well-irrigated and water deficit conditions. We also present measurements of the effect of dark-light cycles and abscisic acid on its water dynamics. The measurements we present provide a new perspective on the water dynamics of plants under different external stimuli and confirm that terahertz can be an excellent non-contact probe of in-vivo tissue hydration.

  4. Picosecond thermoelectric dynamics in layered cobaltite thin films probed by terahertz emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Takahashi, Kouhei; Kanno, Tsutomu; Sakai, Akihiro; Tamaki, Hiromasa; Yamada, Yuka

    2015-09-01

    The operation speed of thermoelectric devices is generally limited to microsecond or millisecond time scales. This is due to the difficulty in manipulating and measuring the thermoelectric transients at high speeds. Although recent advances in optical characterization techniques have succeeded to detect thermoelectric signals in picosecond time scales in a few special nanomaterials such as graphene, thermoelectric dynamics in most of the standard thermoelectric materials still remain unknown. Here we investigate the picosecond carrier dynamics of standard thermoelectric CaxCoO2 thin films by means of terahertz emission spectroscopy. The terahertz radiation signals generated from the CaxCoO2 films by femtosecond laser absorption are found to be strongly dependent on crystal orientation. We discuss that the terahertz emission properties of CaxCoO2 films can be described well in terms of the unique tensorial properties of the Seebeck coefficient. The unordinary terahertz emission property associated with the tensorial property of a Seebeck coefficient provides convincing evidence of picosecond evolution of the thermoelectric current even in this standard material. Our results not only promote general understanding of the ultrafast charge dynamics in solids but may also pave the way to develop optoelectronic devices including bias-free terahertz sources and high-speed infrared sensors.

  5. Diffuse reflection imaging at terahertz frequencies for security applications

    NASA Astrophysics Data System (ADS)

    Dean, P.; Khanna, S.; Chakraborty, S.; Lachab, M.; Davies, A. G.; Linfield, E. H.

    2007-10-01

    We report diffuse reflection imaging of concealed powdered samples in atmospheric air using a quantum cascade laser operating at 2.83 THz. The imaging system uses a helium-cooled silicon bolometer for mapping radiation diffusely reflected and scattered from samples, and a room-temperature pyroelectric sensor for simultaneously acquiring a specular image. A range of powders concealed within plastic packaging and standard FedEx envelopes was imaged with a resolution of better than 0.5 mm, and it was possible to detect powdered samples concealed within packaging from which there was a strong component of surface reflection. The feasibility of performing dual-wavelength diffuse reflection imaging for identification of illicit drugs and explosives is discussed.

  6. Characteristic responses of biological and nanoscale systems in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Angeluts, A. A.; Balakin, A. V.; Evdokimov, M. G.; Esaulkov, M. N.; Nazarov, M. M.; Ozheredov, I. A.; Sapozhnikov, D. A.; Solyankin, P. M.; Cherkasova, O. P.; Shkurinov, A. P.

    2014-07-01

    This paper briefly examines methods for the generation of pulsed terahertz radiation and principles of pulsed terahertz spectroscopy, an advanced informative method for studies of complex biological and nanostructured systems. Some of its practical applications are described. Using a number of steroid hormones as examples, we demonstrate that terahertz spectroscopy in combination with molecular dynamics methods and computer simulation allows one to gain information about the structure of molecules in crystals. A 'terahertz colour vision' method is proposed for analysis of pulsed terahertz signals reflected from biological tissues and it is shown that this method can be effectively used to analyse the properties of biological tissues and for early skin cancer diagnosis.

  7. Terahertz Spectra of L-Ascorbic Acid and Thiamine Hydrochloride Studied by Terahertz Spectroscopy and Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Jiang, Ling; Li, Miao; Li, Chun; Sun, Haijun; Xu, Li; Jin, Biaobin; Liu, Yunfei

    2014-10-01

    We have investigated the terahertz spectra of L-ascorbic acid and thiamine hydrochloride measured by terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infrared spectroscopy (FTIR). The measured absorption spectra were demonstrated to be in good agreement with the results simulated by Density Functional Theory (DFT) using hybrid functional B3LYP with basis set of 6-31G (d), except with slight frequency shift and few peaks missing. We presented the comparison of measured spectra by the FTIR spectroscopy employing low temperature silicon bolometer as detector and the TDS system. The measured spectra of the L-ascorbic acid showed shoulder bands at 0.25, 1.1, 1.5, 1.82, 2.03, 2.30, 2.44, 2.67, 2.97, 3.12, and 3.40 THz, respectively. The spectra of the thiamine hydrochloride show shoulder bands at 0.48, 1.11, 1.57, 1.75, 1.92, 2.08, 2.31, 2.53, 2.69, 2.85, 3.12, 3.22, and 3.31 THz. Most absorption peaks of the two samples agree with the results simulated by Density Function Theory (DFT) method of Gaussian 09 software. In our work, more spectral peaks based on experimental and theoretical results were found in comparison to that of other groups, since we employed higher sensitive FTIR measurement system and considered the effect of number of molecule unit in simulation. The study suggests that the effect of intermolecular vibration is stronger than intramolecular interaction on the absorption bands in THz region.

  8. Continuous Wave Terahertz Reflection Imaging of Human Colorectal Tissue

    E-print Network

    Massachusetts at Lowell, University of

    -ionizing, and nondestructive medical imaging modality for delineating colorectal cancer. Fresh excisions of normal colon tissue-polarized remittance form the samples was collected. Analysis of the images showed the importance of understanding the effects of formalin fixation while determining reflectance level of tissue response. The resulting co

  9. Biomedical Applications of Terahertz Spectroscopy: A Brief Review

    NASA Astrophysics Data System (ADS)

    Vargas-Luna, M.; Huerta-Franco, R.

    2008-08-01

    The Terahertz (THz) window of the electromagnetic spectrum has been partially explored but almost unexploited commercially. In recent years there has been an increased interest and a technological boost in THz research for detection systems, material characterization and imaging. Among many hot topics the researchers are interested in medical applications, and protein characterization. We present a general overview of the field showing some of the handicaps and promises of this region of the electromagnetic spectrum.

  10. New terahertz dielectric spectroscopy for the study aqueous solutions

    E-print Network

    George, Deepu K; Vinh, N Q

    2015-01-01

    We present a development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As a first application we report on the measurement of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17 to 37.36 cm-1 or 0.268 to 60 mm). The system provides a coherent radiation source with a power up to 20 mW in the gigahertz-to-terahertz region. The power signal-to-noise ratio of our instrument reaches 1015 and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with an error bars of 0.02 oC from above 0 oC to 90 oC. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  11. Investigating the use of terahertz pulsed time domain reflection imaging for the study of fabric layers of an Egyptian mummy

    NASA Astrophysics Data System (ADS)

    Fukunaga, K.; Cortes, E.; Cosentino, A.; Stã¼nkel, I.; Leona, M.; Duling, N.; Mininberg, D. T.

    2011-08-01

    This paper reports the first use of terahertz time domain reflection imaging involving textiles on part of a complete human mummy, still in original wrapping. X-ray technique has been used extensively to investigate anatomical features, since X-ray pass through the wrapping. Terahertz waves, on the other hand, can penetrate into non-metallic materials and its reflection depends on the refractive index of materials at the interface, such as textiles and the air. The mummy of Kharushere (ca. 945-712 B.C.) was examined by using Terahertz time domain reflection imaging in the Egyptian galleries of The Metropolitan Museum of Art. Experimental results suggest that the Terahetz imaging is a promising technique for probing the fabric layers surrounding Egyptian mummies, although it is still very limited in its current state. In the future it could become a useful complement to CT scanning when materials with low radiographic density and contrast are being investigated

  12. A terahertz time-domain spectrometer for simultaneous transmission and reflection measurements at normal incidence.

    PubMed

    Brunner, Fabian D J; Schneider, Arno; Günter, Peter

    2009-11-01

    We present a versatile terahertz time-domain spectrometer which allows reflection measurements at normal incidence and double pass transmission measurements in a single experimental setup. Two different modes for transmission measurements are demonstrated for precise measurements of transparent high or low refractive index materials, respectively. The refractive indices and absorption coefficients of cesium iodide, potassium bromide, sodium chloride, polytetrafluoroethylene (PTFE, Teflon), and silicon have been measured in the frequency range between 1.4 and 4.7 THz. The parameters of the Lorentz oscillator functions describing the phonon polariton dispersions of CsI and KBr have been determined. PMID:19997298

  13. Imaging molecular adsorption and desorption dynamics on graphene using terahertz emission spectroscopy

    PubMed Central

    Sano, Y.; Kawayama, I.; Tabata, M.; Salek, K. A.; Murakami, H.; Wang, M.; Vajtai, R.; Ajayan, P. M.; Kono, J.; Tonouchi, M.

    2014-01-01

    Being an atomically thin material, graphene is known to be extremely susceptible to its environment, including defects and phonons in the substrate on which it is placed as well as gas molecules that surround it. Thus, any device design using graphene has to take into consideration all surrounding components, and device performance needs to be evaluated in terms of environmental influence. However, no methods have been established to date to readily measure the density and distribution of external perturbations in a quantitative and non-destructive manner. Here, we present a rapid and non-contact method for visualizing the distribution of molecular adsorbates on graphene semi-quantitatively using terahertz time-domain spectroscopy and imaging. We found that the waveform of terahertz bursts emitted from graphene-coated InP sensitively changes with the type of atmospheric gas, laser irradiation time, and ultraviolet light illumination. The terahertz waveform change is explained through band structure modifications in the InP surface depletion layer due to the presence of localized electric dipoles induced by adsorbed oxygen. These results demonstrate that terahertz emission serves as a local probe for monitoring adsorption and desorption processes on graphene films and devices, suggesting a novel two-dimensional sensor for detecting local chemical reactions. PMID:25116593

  14. Imaging molecular adsorption and desorption dynamics on graphene using terahertz emission spectroscopy.

    PubMed

    Sano, Y; Kawayama, I; Tabata, M; Salek, K A; Murakami, H; Wang, M; Vajtai, R; Ajayan, P M; Kono, J; Tonouchi, M

    2014-01-01

    Being an atomically thin material, graphene is known to be extremely susceptible to its environment, including defects and phonons in the substrate on which it is placed as well as gas molecules that surround it. Thus, any device design using graphene has to take into consideration all surrounding components, and device performance needs to be evaluated in terms of environmental influence. However, no methods have been established to date to readily measure the density and distribution of external perturbations in a quantitative and non-destructive manner. Here, we present a rapid and non-contact method for visualizing the distribution of molecular adsorbates on graphene semi-quantitatively using terahertz time-domain spectroscopy and imaging. We found that the waveform of terahertz bursts emitted from graphene-coated InP sensitively changes with the type of atmospheric gas, laser irradiation time, and ultraviolet light illumination. The terahertz waveform change is explained through band structure modifications in the InP surface depletion layer due to the presence of localized electric dipoles induced by adsorbed oxygen. These results demonstrate that terahertz emission serves as a local probe for monitoring adsorption and desorption processes on graphene films and devices, suggesting a novel two-dimensional sensor for detecting local chemical reactions. PMID:25116593

  15. Solute-induced retardation of water dynamics probed directly by terahertz spectroscopy

    PubMed Central

    Heugen, U.; Schwaab, G.; Bründermann, E.; Heyden, M.; Yu, X.; Leitner, D. M.; Havenith, M.

    2006-01-01

    The dynamics of water surrounding a solute is of fundamental importance in chemistry and biology. The properties of water molecules near the surface of a bio-molecule have been the subject of numerous, sometimes controversial experimental and theoretical studies, with some suggesting the existence of rather rigid water structures around carbohydrates and proteins [Pal, S. K., Peon, J., Bagchi, B. & Zewail A. H. (2002) J. Phys. Chem. B 106, 12376–12395]. Hydrogen bond rearrangement in water occurs on the picosecond time scale, so relevant experiments must access these times. Here, we show that terahertz spectroscopy can directly investigate hydration layers. By a precise measurement of absorption coefficients between 2.3 THz and 2.9 THz we could determine the size and the characteristics of the hydration shell. The hydration layer around a carbohydrate (lactose) is determined to extend to 5.13 ± 0.24 Å from the surface corresponding to ?123 water molecules beyond the first solvation shell. Accompanying molecular modeling calculations support this result and provide a microscopic visualization. Terahertz spectroscopy is shown to probe the collective modes in the water network. The observed increase of the terahertz absorption of the water in the hydration layer is explained in terms of coherent oscillations of the hydration water and solute. Simulations also reveal a slowing down of the hydrogen bond rearrangement dynamics for water molecules near lactose, which occur on the picosecond time scale. The present study demonstrates that terahertz spectroscopy is a sensitive tool to detect solute-induced changes in the water network. PMID:16895986

  16. Ultrafast multi-terahertz nano-spectroscopy with sub-cycle temporal resolution

    NASA Astrophysics Data System (ADS)

    Eisele, M.; Cocker, T. L.; Huber, M. A.; Plankl, M.; Viti, L.; Ercolani, D.; Sorba, L.; Vitiello, M. S.; Huber, R.

    2014-11-01

    Phase-locked ultrashort pulses in the rich terahertz spectral range have provided key insights into phenomena as diverse as quantum confinement, first-order phase transitions, high-temperature superconductivity and carrier transport in nanomaterials. Ultrabroadband electro-optic sampling of few-cycle field transients can even reveal novel dynamics that occur faster than a single oscillation cycle of light. However, conventional terahertz spectroscopy is intrinsically restricted to ensemble measurements by the diffraction limit. As a result, it measures dielectric functions averaged over the size, structure, orientation and density of nanoparticles, nanocrystals or nanodomains. Here, we extend ultrabroadband time-resolved terahertz spectroscopy to the sub-nanoparticle scale (10?nm) by combining sub-cycle, field-resolved detection (10?fs) with scattering-type near-field scanning optical microscopy (s-NSOM). We trace the time-dependent dielectric function at the surface of a single photoexcited InAs nanowire in all three spatial dimensions and reveal the ultrafast (<50?fs) formation of a local carrier depletion layer.

  17. Characterization of plasma treated surfaces for food safety by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Sulovská, Kate?ina; Lehocký, Marián.

    2014-10-01

    A physico-chemical approach to modify surfaces not only for use in medicine, but also for preservation of food is nowadays widely studied to lower the risks of increased number of bacterial pathogens that are in a direct contact with people. Food safety is very important part of preserving sustainability during crises, especially after the enterohaemorrhagic Escherichia coli outbreak in Europe in 2011. One of the possibility how we can protect food against various pathogens is the modification of packing materials that are directly in contact with preserved food. This contribution deals with the characterization of modified surfaces with antibacterial properties via Terahertz spectroscopy. For the purpose of this paper, three monomers were used for grafting onto air radiofrequency plasma activated low density polyethylene surface, which created a brush-like structure. Next, the antibacterial agents, Irgasan and Chlorhexidine, were anchored to these surfaces. These antibacterial agents were selected for supposed effect on two most frequently occurring bacterial strains - Escherichia coli and Staphylococcus aureus. Materials were further tested for the presence of antibacterial agent molecules, in our case by means of terahertz spectroscopy. Each material was tested on two spectroscopes - the SPECTRA and the OSCAT terahertz instruments.

  18. [Preliminary research on insect damage detection in pecans using terahertz spectroscopy].

    PubMed

    Li, Bin; Wang, Ning; Zhang, Wei-Li; Zhao, Chun-Jiang; Zhang, Bao-Hua

    2014-05-01

    Pecan is an important nut in US, however, the inner insect influences pecan's quality a lot. To realize the nondestructive detection of insect damage in American pecans rapidly and efficiently, preliminary research on insect damage detection in pecans was conducted based on terahertz spectroscopy. Firstly, a set of native pecan nuts were collected and were manually sliced with a thickness of about 1, 2 and 3 mm and with a size of about 2 cm(length) X 1 cm(width) for every pecan nutmeat; Pecan shell and inner separator were also cut into the same size. Secondly, the absorption spectra of the nutmeat slices, shell, and inner separator were collected using THz time-domain spectroscopy (THz-TDS) developed by a group of researchers at Oklahoma State University, and the spectral characteristic of the slices was analyzed. Thirdly, the absorption spectra of the alive manduca sexta and dry pecan weevil were collected, and due to the high contents in the insects, very obvious spectral characteristics were found. Finally, the transmission experiment was conducted with the whole pecans. The results from the preliminary study show a potential application of THz technology for insect damage detection. This research provides a reference for further understanding terahertz and exploring sample preparation methods, test methods, data acquisition and optical parameters calculation methods, and developing nondestructive detection system for insect damage in American pecans based on terahertz technology. PMID:25095406

  19. Study on spectral properties of difenoconazole by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Qian; Liu, Ying; Kou, Kuan; Zhao, Guozhong

    2015-08-01

    The terahertz (THz) and infrared spectra of solid pesticide difenoconazole are studied. The absorption spectra of difenoconazole are obtained at room temperature in the frequency range of 0.2 THz - 2.6 THz by using of terahertz time-domain spectroscopy (THz-TDS) and in the frequency range of 1.8 THz - 10 THz by the Fourier Transform Infrared Spectroscopy (FTIR). The experimental results show five significant absorption peaks in THz frequency range, respectively, 0.66 T, 0.80 T, 1.03 T, 1.31 T and 1.57 T, and those peaks corresponding to the abnormal dispersion. The spectral characteristics between 0.2 THz and 15 THz of difenoconazole are simulated by using of Gaussian03 software based on the single molecular model and the density functional theory (DFT). Both of simulation and experimental results fit well in the terahertz range. Moreover, the quantitative analysis of difenoconazole is studied based on the THz-TDS measurement. The absorption coefficient and refractive index spectra of difenoconazoles at different proportions doped with polyethylene (PE) are obtained. The partial least squares (PLS) model is built. It is possible to predict the concentration of difenoconazole in the mixtures by this method.

  20. Terahertz spectroscopy of deuterated formaldehyde using a frequency multiplication chain

    NASA Astrophysics Data System (ADS)

    Zakharenko, Olena; Motiyenko, Roman A.; Margulès, Laurent; Huet, Thérèse R.

    2015-11-01

    The rotational spectra of deuterated formaldehyde HDCO and D2CO were recorded between 1.1 and 1.52 THz in order to benchmark new terahertz frequency multiplication chain used in the Lille spectrometer. Important spectrometer parameters such as sensitivity, measurement accuracy, and harmonic composition of the radiation source have been tested using the newly measured spectra. For each of the main deuterated isotopic species of formaldehyde the existent datasets from high resolution measurements were augmented by more than 300 new distinct transition frequencies. Most of these frequencies were measured with an accuracy better than 30 kHz. In addition, the high sensitivity of the spectrometer provided by the new frequency multiplication chain allowed observation, assignment and analysis of 13C, 17O, 18O, and 13C18O isotopic species of HDCO and D2CO. For some of these isotopologues the rotational parameters were determined for the first time.

  1. Terahertz spectroscopy of low-dimensional nanomaterials: nonlinear emission and ultrafast electrodynamics

    NASA Astrophysics Data System (ADS)

    Luo, Liang; Wang, Jigang

    2015-08-01

    Nonlinear and non-equilibrium properties of low-dimensional quantum materials are fundamental in nanoscale science yet transformative in nonlinear imaging/photonic technology today. These have been poorly addressed in many nano-materials despite of their well-established equilibrium optical and transport properties. The development of ultrafast terahertz (THz) sources and nonlinear spectroscopy tools facilitates understanding these issues and reveals a wide range of novel nonlinear and quantum phenomena that are not expected in bulk solids or atoms. In this paper, we discuss our recent discoveries in two model photonic and electronic nanostructures to solve two outstanding questions: (1) how to create nonlinear broadband terahertz emitters using deeply subwavelength nanoscale meta-atom resonators? (2) How to access one-dimensional (1D) dark excitons and their non-equilibrium correlated states in single-walled carbon nanotubes (SWMTs)?

  2. Diffuse reflectance spectroscopy of liver tissue

    NASA Astrophysics Data System (ADS)

    Reistad, Nina; Nilsson, Jan; Vilhelmsson Timmermand, Oskar; Sturesson, Christian; Andersson-Engels, Stefan

    2015-06-01

    Diffuse reflectance spectroscopy (DRS) with a fiber-optic contact probe is a cost-effective, rapid, and non-invasive optical method used to extract diagnosis information of tissue. By combining commercially available VIS- and NIR-spectrometers with various fiber-optic contact-probes, we have access to the full wavelength range from around 400 to 1600 nm. Using this flexible and portable spectroscopy system, we have acquired ex-vivo DRS-spectra from murine, porcine, and human liver tissue. For extracting the tissue optical properties from the measured spectra, we have employed and compared predictions from two models for light propagation in tissue, diffusion theory model (DT) and Monte Carlo simulations (MC). The focus in this work is on the capacity of this DRS-technique in discriminating metastatic tumor tissue from normal liver tissue as well as in assessing and characterizing damage to non-malignant liver tissue induced by preoperative chemotherapy for colorectal liver metastases.

  3. Detection of porosity of pharmaceutical compacts by terahertz radiation transmission and light reflection measurement techniques.

    PubMed

    Bawuah, Prince; Pierotic Mendia, Alessandra; Silfsten, Pertti; Pääkkönen, Pertti; Ervasti, Tuomas; Ketolainen, Jarkko; Zeitler, J Axel; Peiponen, Kai-Erik

    2014-04-25

    We report on the non-destructive quantification of the porosity of pharmaceutical compacts (microcrystalline cellulose tablets) by using both optical and terahertz techniques. For the full analysis of the porosity of pharmaceutical tablets, the results obtained in both cases have shown that optical and terahertz techniques are complementary. The intrinsic refractive index of microcrystalline cellulose was estimated using the effective refractive index obtained from the time delay of the THz pulse together with the Bruggeman model for effective media. Once this intrinsic refractive index is known, the unknown porosity of the tablet can be estimated with the aid of the measured effective refractive index as well as the thickness of the pharmaceutical tablet. The method was tested using a set of thirteen tablets having different porosities. It is shown that the error in the estimation of the unknown tablet's porosity is less than 1%. In addition, surface roughness was measured by using an optical interferometer and gloss by using a diffractive-optical-element based glossmeter. The measurement was achieved by scanning the tablets with a probe beam and detecting the reflected light. The surface roughness and gloss data show relatively good correlation with the porosities of the tablets. PMID:24530384

  4. Non-contact quantitative diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Sorgato, Veronica; Berger, Michel; Emain, Charlotte; Koenig, Anne; Roig, Blandine; Vever-Bizet, Christine; Dinten, Jean-Marc; Bourg-Heckly, Geneviève; Planat-Chrétien, Anne

    2015-07-01

    We validate a non-contact Diffuse Reflectance Spectroscopy (DRS) system as a first stage to approach quantitative multi-spectral imaging technique. The non-contact DRS system with separated illumination and detection paths was developed with different progressive set-ups which were all compared to a well-founded contact DRS system. While quantitation of the absorption coefficient is well achieved with the existing method, the calculation of the scattering coefficient is deteriorated by the non-contact architecture measurements. We have therefore developed an adaptive reference-based algorithm to compensate for this effect.

  5. Thermal denaturation of protein studied by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Fu, Xiuhua; Li, Xiangjun; Liu, Jianjun; Du, Yong; Hong, Zhi

    2012-12-01

    In this study, the absorption spectra of native or thermal protein were measured in 0.2-1.4THz using terahertz time-domain spectroscopy (THz-TDS) system at room temperature, their absorption spectra and the refractive spectra were obtained. Experimental results indicate that protein both has strong absorption but their characteristics were not distinct in the THz region, and the absorption decreased during thermal denatured state. In order to prove protein had been denatured, we used Differential scanning calorimeter (DSC) measured their denatured temperature, from their DSC heating traces, collagen Td=101?, Bovine serum albumin Td=97?. While we also combined the Fourier transform infrared spectrometer (FTIR) to investigate their secondary and tertiary structure before and after denatuation, but the results did not have the distinct changes. We turned the absorption spectra and the refractive spectra to the dielectric spectra, and used the one-stage Debye model simulated the terahertz dielectric spectra of protein before and after denaturation. This research proved that the terahertz spectrum technology is feasible in testing protein that were affected by temperature or other factors which can provide theoretical foundation in the further study about the THz spectrum of protein and peptide temperature stability.

  6. Diagnosing breast cancer using diffuse reflectance spectroscopy and intrinsic fluorescence spectroscopy

    E-print Network

    Fitzmaurice, Maryann

    Using diffuse reflectance spectroscopy and intrinsic fluorescence spectroscopy, we have developed an algorithm that successfully classifies normal breast tissue, fibrocystic change, fibroadenoma, and infiltrating ductal ...

  7. In vivo spectroscopy of healthy skin and pathology in terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Kudrin, Konstantin G.; Reshetov, Igor V.; Gavdush, Arseniy A.; Chernomyrdin, Nikita V.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

    2015-01-01

    Biomedical applications of terahertz (THz) technology and, in particular, THz pulsed spectroscopy have attracted considerable interest in the scientific community. A lot of papers have been dedicated to studying the ability for human disease diagnosis, including the diagnosis of human skin cancers. In this paper we have studied the THz material parameters and THz dielectric properties of human skin and pathology in vivo, and THz pulsed spectroscopy has been utilized for this purpose. We have found a contrast between material parameters of basal cell carcinoma and healthy skin, and we have also compared the THz material parameters of dysplastic and non-dysplastic pigmentary nevi in order to study the ability for early melanoma diagnosis. Significant differences between the THz material parameters of healthy skin and pathology have been detected, thus, THz pulsed spectroscopy promises to be become an effective tool for non-invasive diagnosis of skin neoplasms.

  8. Dielectric Relaxation of HCl and NaCl Solutions Investigated by Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Qiao, Wenchao; Yang, Kejian; Thoma, Arne; Dekorsy, Thomas

    2012-10-01

    We have used Terahertz time-domain spectroscopy (THz-TDS) to investigate the complex dielectric function of water solutions containing different ions. Using HCl and NaCl solutions with different concentrations we study the changes of the dielectric response introduced by the ions. We find a linear increase of the real and imaginary part of the dielectric function compared with pure water with increasing ion concentrations. We use an expanded model for fitting the dielectric function based on a combination of a Debye relation and damped harmonic oscillators for the anions and cations. A good agreement between the model and the experimental results is obtained.

  9. Terahertz time-domain spectroscopy study of solid state reaction between ?-naphthol and p-benzoquinone

    NASA Astrophysics Data System (ADS)

    Liu, Guifeng; Ma, Shihua; Ji, Te; Wang, Wenfeng

    2008-12-01

    Terahertz time-domain spectroscopy (THz-TDS) was utilized to study solid state reaction progress between ?-naphthol(NP) and p-benzoquinone(BQ). Density functional theory (DFT) was employed to optimize the structure of the complex. The result shows that the reaction product is associated by hydrogen bonding between one of the oxygen atoms of BQ and one hydrogen atom of the hydroxyl group of NP; and FTIR spectra is presented as supporting evidence. Our work demonstrated that THz-TDS was a promising and complementary method in analyzing solid-state reaction between NP and BQ.

  10. Quantitative analysis of the mixtures of illicit drugs using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Dejun; Zhao, Shusen; Shen, Jingling

    2008-03-01

    A method was proposed to quantitatively inspect the mixtures of illicit drugs with terahertz time-domain spectroscopy technique. The mass percentages of all components in a mixture can be obtained by linear regression analysis, on the assumption that all components in the mixture and their absorption features be known. For illicit drugs were scarce and expensive, firstly we used common chemicals, Benzophenone, Anthraquinone, Pyridoxine hydrochloride and L-Ascorbic acid in the experiment. Then illicit drugs and a common adulterant, methamphetamine and flour, were selected for our experiment. Experimental results were in significant agreement with actual content, which suggested that it could be an effective method for quantitative identification of illicit drugs.

  11. Investigation of thermal denaturation of solid bovine serum albumin by terahertz dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Xiangjun; Fu, Xiuhua; Liu, Jianjun; Du, Yong; Hong, Zhi

    2013-10-01

    We investigate the thermal denaturation of solid bovine serum albumin (BSA) using terahertz time domain spectroscopy (THz-TDS). When the protein is heated up from 25 °C to 107 °C and cooled down to 25 °C again, an irreversible decrease in its THz absorption coefficient and refractive index is observed. The corresponding frequency-dependent permittivity during heating is fitted by the Debye model with single relaxation time. The relaxation times during temperature rising agree very well with Arrhenius equation with the activation energy of 6.52 kJ/(K·mol), which can be an indicator for the stability of BSA during thermal denaturation process.

  12. Label-free monitoring of interaction between DNA and oxaliplatin in aqueous solution by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Wu, Xiaojun; E, Yiwen; Xu, Xinlong; Wang, Li

    2012-07-01

    We demonstrated the feasibility of applying terahertz time-domain spectroscopy (THz-TDS) to monitor the molecular reactions in aqueous solutions of anticancer drug oxaliplatin with ?-DNA and macrophages DNA. The reaction time dependent refractive index and absorption coefficient were extracted and analyzed. The reaction half-decaying time of about 4.0 h for ?-DNA and 12.9 h for M-DNA was established. The results suggest that the THz-TDS detection could be an effective label-free technique to sense the molecular reaction in aqueous solutions and could be very useful in biology, medicine, and pharmacy industry.

  13. Bacillus spores and their relevant chemicals studied by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Tang, Jianhua; Yang, Bin; Llewellyn, Ian; Cutler, Ronald R.; Donnan, Robert S.

    2014-01-01

    Terahertz time domain spectroscopy has been used to investigate 0.2-2.2 THz transmission responses of Bacillus spores and their related chemical components. Whilst no THz signatures could be clearly associated with either sporulated cells or their chief chemical components, differing degrees of signal attenuation and frequency-dependent light scattering were observed depending on spore composition and culture media. The observed monotonic increase in absorption by spores over this THz spectral domain is mainly from Mie scattering and also from remnant water bound to the spores.

  14. Optical Reflection Spectroscopy of GEO Objects

    NASA Technical Reports Server (NTRS)

    Seitzer, Patrick; Cardona, Tammaso; Lederer, Susan M.; Cowardin, Heather; Abercromby, Kira J.; Barker, Edwin S.; Bedard, Donald

    2013-01-01

    We report on optical reflection spectroscopy of geosynchronous (GEO) objects in the US Space Surveillance Network (SSN) catalog. These observations were obtained using imaging spectrographs on the 6.5-m Magellan telescopes at the Las Campanas Observatory in Chile. Our goal is to determine the composition of these objects by comparing these spectral observations with ground-based laboratory measurements of spacecraft materials. The observations are all low resolution (1 nm after smoothing) obtained through a 5 arcsecond wide slit and using a grism as the dispersing element. The spectral range covered was from 450 nm to 800 nm. All spectra were flux calibrated using observations of standard stars with the exact same instrumental setup. An effort was made to obtain all observations within a limited range of topocentric phase angle, although the solar incident angle is unknown due to the lack of any knowledge of the attitude of the observed surface at the time of observation.

  15. Mesoscopic structuring and dynamics of alcohol/water solutions probed by Terahertz Time-Domain Spectroscopy and Pulsed Field Gradient Nuclear Magnetic Resonance

    E-print Network

    Li, Ruoyu; D'Agostino, Carmine; McGregor, James; Mantle, Michael D.; Zeitler, J. Axel; Gladden, Lynn F.

    2014-08-12

    and methanol with water.58,60 The terahertz absorption spectra were calculated using the Beer?Lambert law from the acquired data by truncating the waveforms 20 ps after the main peak which is just before the first etalon reflection from the quartz windows... . ? RESULTS Terahertz Absorption Spectra. The terahertz absorption spectra of the pure liquids are plotted in Figure 2. The absorption spectra of alcohol/water mixtures are typical of those of pure liquids, which increase monotonically with frequency, and...

  16. High spectral resolution reflectance spectroscopy of minerals

    USGS Publications Warehouse

    Clark, R.N.; King, T.V.V.; Klejwa, M.; Swayze, G.A.; Vergo, N.

    1990-01-01

    The reflectance spectra of minerals are studied as a function of spectral resolution in the range from 0.2 to 3.0 ??m. Selected absorption bands were studied at resolving powers (??/????) as high as 2240. At resolving powers of approximately 1000, many OH-bearing minerals show diagnostic sharp absorptions at the resolution limit. At low resolution, some minerals may not be distinguishable, but as the resolution is increased, most can be easily identified. As the resolution is increased, many minerals show fine structure, particularly in the OH-stretching overtone region near 1.4 ??m. The fine structure can enhance the ability to discriminate between minerals, and in some cases the fine structure can be used to determine elemental composition. The study shows that high-resolution reflectance spectroscopy of minerals may prove to be a very important tool in the laboratory, in the field using field-portable spectrometers, from aircraft, and from satellites looking at Earth or other planetary surfaces. -from Authors

  17. Reflectance spectroscopy of organic compounds: 1. Alkanes

    USGS Publications Warehouse

    Clark, R.N.; Curchin, J.M.; Hoefen, T.M.; Swayze, G.A.

    2009-01-01

    Reflectance spectra of the organic compounds comprising the alkane series are presented from the ultraviolet to midinfrared, 0.35 to 15.5 /??m. Alkanes are hydrocarbon molecules containing only single carbon-carbon bonds, and are found naturally on the Earth and in the atmospheres of the giant planets and Saturn's moon, Titan. This paper presents the spectral properties of the alkanes as the first in a series of papers to build a spectral database of organic compounds for use in remote sensing studies. Applications range from mapping the environment on the Earth, to the search for organic molecules and life in the solar system and throughout the. universe. We show that the spectral reflectance properties of organic compounds are rich, with major diagnostic spectral features throughout the spectral range studied. Little to no spectral change was observed as a function of temperature and only small shifts and changes in the width of absorption bands were observed between liquids and solids, making remote detection of spectral properties throughout the solar system simpler. Some high molecular weight organic compounds contain single-bonded carbon chains and have spectra similar to alkanes even ' when they fall into other families. Small spectral differences are often present allowing discrimination among some compounds, further illustrating the need to catalog spectral properties for accurate remote sensing identification with spectroscopy.

  18. Insulin amyloid fibrillation studied by terahertz spectroscopy and other biophysical methods

    SciTech Connect

    Liu, Rui; He, Mingxia; Su, Rongxin; Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072 ; Yu, Yanjun; Qi, Wei; He, Zhimin; Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072

    2010-01-01

    Assembly and fibrillation of amyloid proteins are believed to play a key role in the etiology of various human diseases, including Alzheimer's, Parkinson's, Huntington's and type II diabetes. Insights into conformational changes and formation processes during amyloid fibrillation are essential for the clinical diagnosis and drug discovery. To study the changes in secondary, tertiary, quaternary structures, and the alteration in the collective vibrational mode density of states during the amyloid fibrillation, bovine insulin in 20% acetic acid was incubated at 60 {sup o}C, and its multi-level structures were followed by various biophysical techniques, including circular dichroism (CD), thioflavin T fluorescence (ThT), dynamic light scattering (DLS), electron microscopy, and terahertz (THz) absorption spectroscopy. The experimental data demonstrated a transformation of {alpha}-helix into {beta}-sheet starting at 26 h. This was followed by the aggregation of insulin, as shown by ThT binding, with a transition midpoint at 41 h, and by the bulk formation of mature aggregates after about 71 h. THz is a quick and non-invasive technique, which has the advantage of allowing the study of the conformational state of biomolecules and tissues. We first applied THz spectroscopy to study the amyloid fibrillation. At the terahertz frequency range of 0.2-2.0 THz, there was an apparent increase in both the absorbance and refractive index in THz spectra. Thus, THz is expected to provide a new way of looking into amyloid fibrillation.

  19. Speckle in active millimeter-wave and terahertz imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.

    2007-04-01

    Wideband millimeter-wave imaging techniques and systems have been developed at Pacific Northwest National Laboratory (PNNL) for concealed weapon detection and other applications. These techniques evolved from singlefrequency millimeter-wave holographic imaging methods to wideband three-dimensional planar and cylindrical techniques and systems. The single-frequency holographic method was derived from optical and ultrasonic holography techniques. Speckle is highly significant in this case, and is caused by constructive and destructive interference from multiple scattering locations or depths within a single resolution cell. The wideband three-dimensional techniques developed at PNNL significantly reduce the speckle effect through the use of high depth resolution obtained from the wide bandwidth of the illumination. For these techniques, speckle can still be significant in some cases and affect image quality. In this paper, we explore the situations in which speckle occurs and its relationship to lateral and depth resolution. This will be accomplished through numerical simulation and demonstrated in actual imaging results. Speckle may also play a significant role in altering reflection spectra in wideband terahertz spectra. Reflection from rough surfaces will generate speckle, which will result in significant variation in the reflection spectrum as measured over very wide bandwidths. This effect may make if difficult to interpret spectral absorption features from general reflectance data. In this paper, physical optics numerical simulation techniques will be used to model the reflection from arbitrary random surfaces and explore the effect of the surface on the reflection spectra and reconstructed image. Laboratory imaging and numerical modeling results in the millimeter-wave through the terahertz frequency ranges are presented.

  20. Speckle in Active Millimeter-Wave and Terahertz Imaging and Spectroscopy

    SciTech Connect

    Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.

    2007-04-01

    Wideband millimeter-wave imaging techniques and systems have been developed at PNNL for concealed weapon detection and other applications. These techniques evolved from single-frequency millimeter-wave holographic imaging methods to wideband three-dimensional planar and cylindrical techniques and systems. The single-frequency holographic method was derived from optical and ultrasonic holography techniques. Speckle is highly significant in this case, and is caused by constructive and destructive interference from multiple scattering locations or depths within a single resolution cell. The wideband three-dimensional techniques developed at PNNL significantly reduce the speckle effect through the use of high depth resolution obtained from the wide bandwidth of the illumination. For these techniques, speckle can still be significant in some cases and affect image quality. In this paper, we explore the situations in which speckle occurs and it's relationship to lateral and depth resolution. This will be accomplished through numerical simulation and demonstrated in actual imaging results. Speckle may also play a significant role in altering reflection spectra in wideband terahertz spectra. Reflection from rough surfaces will generate speckle, which will result in significant variation in the reflection spectrum as measured over very wide bandwidths. This effect may make if difficult to interpret spectral absorption features from general reflectance data. In this paper, physical optics numerical simulation techniques will be used to model the reflection from arbitrary random surfaces and explore the effect of the surface on the reflection spectra and reconstructed image. Laboratory imaging and numerical modeling results in the millimeter-wave through the terahertz frequency ranges are presented.

  1. Quantitative characterization of the ,,D2O...3 torsional manifold by terahertz laser spectroscopy and theoretical analysis

    E-print Network

    Cohen, Ronald C.

    of the trimer torsional and hydrogen bond stretch/bend vibrational modes which underlies the torsional model,16 All of these spectra have been observed in the ``torsional band'' or ``bending band'' region of liquidQuantitative characterization of the ,,D2O...3 torsional manifold by terahertz laser spectroscopy

  2. Non-destructive inspections of illicit drugs in envelope using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Ning; Shen, Jingling; Lu, Meihong; Jia, Yan; Sun, Jinhai; Liang, Laishun; Shi, Yanning; Xu, Xiaoyu; Zhang, Cunlin

    2006-09-01

    The absorption spectra of two illicit drugs, methylenedioxyamphetarnine (MDA) and methamphetamine (MA), within and without two conventional envelopes are studied using terahertz time-domain spectroscopy technique. The characteristic absorption spectra of MDA and MA are obtained in the range of 0.2 THz to 2.5 THz. MDA has an obvious absorption peak at 1.41 THz while MA has obvious absorption peaks at 1.23 THz, 1.67 THz, 1.84 THz and 2.43 THz. We find that the absorption peaks of MDA and MA within the envelopes are almost the same as those without the envelopes respectively although the two envelopes have some different absorption in THz waveband. This result indicates that the type of illicit drugs in envelopes can be determined by identifying their characteristic absorption peaks, and THz time-domain spectroscopy is one of the most powerful candidates for illicit drugs inspection.

  3. Terahertz spectroscopy for the study of paraffin-embedded gastric cancer samples

    NASA Astrophysics Data System (ADS)

    Wahaia, Faustino; Kasalynas, Irmantas; Seliuta, Dalius; Molis, Gediminas; Urbanowicz, Andrzej; Carvalho Silva, Catia D.; Carneiro, Fatima; Valusis, Gintaras; Granja, Pedro L.

    2015-01-01

    Terahertz (THz) spectroscopy constitute promising technique for biomedical applications as a complementary and powerful tool for diseases screening specially for early cancer diagnostic. The THz radiation is not harmful to biological tissues. As increased blood supply in cancer-affected tissues and consequent local increase in tissue water content makes THz technology a potentially attractive. In the present work, samples of healthy and adenocarcinoma-affected gastric tissue were analyzed using transmission time-domain THz spectroscopy (THz-TDS). The work shows the capability of the technique to distinguish between normal and cancerous regions in dried and paraffin-embedded samples. Plots of absorption coefficient ? and refractive index n of normal and cancer affected tissues, are presented and the conditions for discrimination between normal and affected tissues are discussed.

  4. Using Terahertz Spectroscopy to Study Systems with Solar Energy Applications

    NASA Astrophysics Data System (ADS)

    Milot, Rebecca L.; Moore, Gary F.; Martini, Lauren A.; Brudvig, Gary W.; Crabtree, Robert H.; Schmuttenmaer, Charles A.

    2013-06-01

    Biomimetic solar water oxidation systems are being developed as renewable alternatives to fossil fuels. One possible design incorporates thin-film dye-sensitized nanoparticle photoanades to capture and convert visible light to charge carriers and catalysts to facilitate water oxidation. The physical properties of the dye are important due to its position as the light absorber and electron transfer initiator. Given the role that porphyrins play in photosynthesis and their synthetic tunability, they are promising components for these photoanodes. Time-Resolved THz Spectroscopy (TRTS), an optical pump/THz probe technique, is a non-contact electrical probe with proven usefulness for studying electron transfer and conductivity on a sub-picosecond timescale. Using TRTS, the efficiency and dynamics of electron injection from porphyrin dyes into metal oxide surfaces was found to be strongly influenced by the structure and photophysical properties of the dye.

  5. Sub-terahertz resonance spectroscopy of biological macromolecules and cells

    NASA Astrophysics Data System (ADS)

    Globus, Tatiana; Moyer, Aaron; Gelmont, Boris; Khromova, Tatyana; Sizov, Igor; Ferrance, Jerome

    2013-05-01

    Recently we introduced a Sub-THz spectroscopic system for characterizing vibrational resonance features from biological materials. This new, continuous-wave, frequency-domain spectroscopic sensor operates at room temperature between 315 and 480 GHz with spectral resolution of at least 1 GHz and utilizes the source and detector components from Virginia Diode, Inc. In this work we present experimental results and interpretation of spectroscopic signatures from bacterial cells and their biological macromolecule structural components. Transmission and absorption spectra of the bacterial protein thioredoxin, DNA and lyophilized cells of Escherichia coli (E. coli), as well as spores of Bacillus subtillis and B. atrophaeus have been characterized. Experimental results for biomolecules are compared with absorption spectra calculated using molecular dynamics simulation, and confirm the underlying physics for resonance spectroscopy based on interactions between THz radiation and vibrational modes or groups of modes of atomic motions. Such interactions result in multiple intense and narrow specific resonances in transmission/absorption spectra from nano-gram samples with spectral line widths as small as 3 GHz. The results of this study indicate diverse relaxation dynamic mechanisms relevant to sub-THz vibrational spectroscopy, including long-lasting processes. We demonstrate that high sensitivity in resolved specific absorption fingerprints provides conditions for reliable detection, identification and discrimination capability, to the level of strains of the same bacteria, and for monitoring interactions between biomaterials and reagents in near real-time. Additionally, it creates the basis for the development of new types of advanced biological sensors through integrating the developed system with a microfluidic platform for biomaterial samples.

  6. Label-free detection and characterization of the binding of hemagglutinin protein and broadly neutralizing monoclonal antibodies using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Yiwen; Zhong, Junlan; Zhang, Cunlin; Zuo, Jian; Pickwell-MacPherson, Emma

    2015-03-01

    Hemagglutinin (HA) is the main surface glycoprotein of the influenza A virus. The H9N2 subtype influenza A virus is recognized as the most possible pandemic strain as it has crossed the species barrier, infecting swine and humans. We use terahertz spectroscopy to study the hydration shell formation around H9 subtype influenza A virus's HA protein (H9 HA) as well as the detection of antigen binding of H9 HA with the broadly neutralizing monoclonal antibody. We observe a remarkable concentration dependent nonlinear response of the H9 HA, which reveals the formation process of the hydration shell around H9 HA molecules. Furthermore, we show that terahertz dielectric properties of the H9 HA are strongly affected by the presence of the monoclonal antibody F10 and that the terahertz dielectric loss tangent can be used to detect the antibody binding at lower concentrations than the standard ELISA test.

  7. Reflectance anisotropy spectroscopy of magnetite (110) surfaces

    NASA Astrophysics Data System (ADS)

    Fleischer, K.; Verre, R.; Mauit, O.; Sofin, R. G. S.; Farrell, L.; Byrne, C.; Smith, C. M.; McGilp, J. F.; Shvets, I. V.

    2014-05-01

    Reflectance anisotropy spectroscopy (RAS) has been used to measure the optical anisotropies of bulk and thin-film Fe3O4(110) surfaces. The spectra indicate that small shifts in energy of the optical transitions, associated with anisotropic strain or electric field gradients caused by the (110) surface termination or a native oxide layer, are responsible for the strong signal observed. The RAS response was then measured as a function of temperature. A distinct change in the RAS line-shape amplitude was observed in the spectral range from 0.8 to 1.6 eV for temperatures below the Verwey transition of the crystal. Finally, thin-film magnetite was grown by molecular beam epitaxy on MgO(110) substrates. Changes in the RAS spectra were found for different film thickness, suggesting that RAS can be used to monitor the growth of magnetite (110) films in situ. The thickness dependence of the RAS is discussed in terms of various models for the origin of the RAS signal.

  8. Parallel-Plate Waveguide Terahertz Time Domain Spectroscopy for Ultrathin Conductive Films

    NASA Astrophysics Data System (ADS)

    Razanoelina, M.; Kinjo, R.; Takayama, K.; Kawayama, I.; Murakami, H.; Mittleman, Daniel M.; Tonouchi, M.

    2015-12-01

    Development of techniques for characterization of extremely thin films is an important challenge in terahertz (THz) science and applications. Spectroscopic measurements of materials on the nanometer scale or of atomic layer thickness (2D materials) require a sufficient terahertz wave-matter interaction length, which is challenging to achieve in conventional transmission geometry. Waveguide-based THz spectroscopy offers an alternative method to overcome this problem. In this paper, we investigate a new parallel-plate waveguide (PPWG) technique for measuring dielectric properties of ultrathin gold films, in which we mount the thin film sample at the center of the waveguide. We discuss a model of THz dielectric parameter extraction based on waveguide theory and analyze the response of thin films for both transverse magnetic (TM) and transverse electric (TE) waveguide modes. In contrast to other waveguide methods, our approach enables comparison of the material response with different electromagnetic field distributions without significantly changing the experimental setup. As a result, we demonstrate that TE modes have a better sensitivity to the properties of the thin film. For prototype test samples, optical parameters extracted using our method are in good agreement with literature values.

  9. Discrimination of Transgenic Rice containing the Cry1Ab Protein using Terahertz Spectroscopy and Chemometrics

    NASA Astrophysics Data System (ADS)

    Xu, Wendao; Xie, Lijuan; Ye, Zunzhong; Gao, Weilu; Yao, Yang; Chen, Min; Qin, Jianyuan; Ying, Yibin

    2015-07-01

    Spectroscopic techniques combined with chemometrics methods have proven to be effective tools for the discrimination of objects with similar properties. In this work, terahertz time-domain spectroscopy (THz-TDS) combined with discriminate analysis (DA) and principal component analysis (PCA) with derivative pretreatments was performed to differentiate transgenic rice (Hua Hui 1, containing the Cry1Ab protein) from its parent (Ming Hui 63). Both rice samples and the Cry1Ab protein were ground and pressed into pellets for terahertz (THz) measurements. The resulting time-domain spectra were transformed into frequency-domain spectra, and then, the transmittances of the rice and Cry1Ab protein were calculated. By applying the first derivative of the THz spectra in conjunction with the DA model, the discrimination of transgenic from non-transgenic rice was possible with accuracies up to 89.4% and 85.0% for the calibration set and validation set, respectively. The results indicated that THz spectroscopic techniques and chemometrics methods could be new feasible ways to differentiate transgenic rice.

  10. Solvation Dynamics of Trimethylamine N-Oxide in Aqueous Solution Probed by Terahertz Spectroscopy.

    PubMed

    Knake, Lukas; Schwaab, Gerhard; Kartaschew, Konstantin; Havenith, Martina

    2015-10-29

    We have studied the hydration dynamics of trimethylamine N-oxide (TMAO) in aqueous solution using a combination of concentration-dependent terahertz/far-infrared (THz/FIR) and Raman spectroscopic techniques. Terahertz/FIR absorption was measured using narrowband (76-93 cm(-1)) p-Ge laser and broad band (30-400 cm(-1)) Fourier transform spectroscopy. We used principal component analysis in combination with a semi-ideal chemical equilibrium model to dissect the spectra into linear and nonlinear contributions of the solvated solute extinction. We attribute the linear part to the average extinction and Raman scattering of TMAO-water aggregates with approximately 3-4 water strongly hydrogen bonded to TMAO. An additional nonlinear concentration dependence indicates a decrease of the number of attached water molecules with increasing TMAO concentrations due to a shift in association equilibria. The Raman spectra reveal a frequency shift of the (narrowband) intramolecular vibrations with decreasing dilution. Based on the results of a detailed analysis and isotopic substitution, the experimentally observed absorption bands at 0, 176, and 388 cm(-1) could be assigned to water relaxation modes, an intermolecular TMAO-H2O stretch, and the C-N-C bending mode, respectively. Our results provide evidence for a local modification of the water structure. PMID:26214376

  11. Discrimination of Transgenic Rice containing the Cry1Ab Protein using Terahertz Spectroscopy and Chemometrics

    PubMed Central

    Xu, Wendao; Xie, Lijuan; Ye, Zunzhong; Gao, Weilu; Yao, Yang; Chen, Min; Qin, Jianyuan; Ying, Yibin

    2015-01-01

    Spectroscopic techniques combined with chemometrics methods have proven to be effective tools for the discrimination of objects with similar properties. In this work, terahertz time-domain spectroscopy (THz-TDS) combined with discriminate analysis (DA) and principal component analysis (PCA) with derivative pretreatments was performed to differentiate transgenic rice (Hua Hui 1, containing the Cry1Ab protein) from its parent (Ming Hui 63). Both rice samples and the Cry1Ab protein were ground and pressed into pellets for terahertz (THz) measurements. The resulting time-domain spectra were transformed into frequency-domain spectra, and then, the transmittances of the rice and Cry1Ab protein were calculated. By applying the first derivative of the THz spectra in conjunction with the DA model, the discrimination of transgenic from non-transgenic rice was possible with accuracies up to 89.4% and 85.0% for the calibration set and validation set, respectively. The results indicated that THz spectroscopic techniques and chemometrics methods could be new feasible ways to differentiate transgenic rice. PMID:26154950

  12. High-speed terahertz reflection three-dimensional imaging using beam steering.

    PubMed

    Yee, Dae-Su; Jin, Kyong Hwan; Yahng, Ji Sang; Yang, Ho-Soon; Kim, Chi Yup; Ye, Jong Chul

    2015-02-23

    High-speed terahertz (THz) reflection three-dimensional (3D) imaging is demonstrated using electronically-controlled optical sampling (ECOPS) and beam steering. ECOPS measurement is used for scanning an axial range of 7.8 mm in free space at 1 kHz scan rate while a transverse range of 100 × 100 mm(2) is scanned using beam steering instead of moving an imaging target. Telecentric f-? lenses with axial and non-axial symmetry have been developed for beam steering. It is experimentally demonstrated that the non-axially symmetric lens has better characteristics than the axially symmetric lens. The total scan time depends on the number of points in a transverse range. For example, it takes 40 s for 200 × 200 points and 10 s for 100 × 100 points. To demonstrate the application of the imaging technique to nondestructive testing, THz 3D tomographic images of a glass fiber reinforced polymer sample with artificial internal defects have been acquired using the lenses for comparison. PMID:25836537

  13. Adaptive sampling dual terahertz comb spectroscopy using free-running dual femtosecond lasers

    E-print Network

    Yasui, Takeshi; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2014-01-01

    Dual terahertz (THz) comb spectroscopy is a promising methods for high accuracy, high resolution, and broadband THz spectroscopy because the mode-resolved THz comb spectrum possesses both characteristics of broadband THz radiation and narrow-linewidth continuous-wave THz radiation and all frequency mode of THz comb can be phase-locked to a microwave frequency standard. However, requirement of stabilized dual femtosecond lasers has often hindered wide use of this method. In this article, we demonstrated the adaptive sampling, dual THz comb spectroscopy, enabling use of free-running dual femtosecond lasers. To correct the non-linearity of time and frequency scale caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing signal in a data acquisition board. The demonstrated results did not only indicate the implementation of dual THz comb spectroscopy with free-running dual lasers but also implied the superiority of its spect...

  14. Specular Reflection and Diffuse Reflectance Spectroscopy of Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Studies on the occurrence and effects of specular reflection in mid-infrared spectra of soils have shown that distortions due to specular reflection occur for both organic (humic acid) and non-organic fractions (carbonates, silica, ashed fraction of soil). The results demonstrated explain why the s...

  15. Reflection Electron Microscopy and Spectroscopy for Surface Analysis

    E-print Network

    Wang, Zhong L.

    1 Reflection Electron Microscopy and Spectroscopy for Surface Analysis by Zhong Lin Wang known as high-resolution analytical electron microscopy, which is becoming an indispensable technique. This book is about the reflection high-energy electron diffraction (RHEED), reflection electron microscopy

  16. Identification of Transgenic Organisms Based on Terahertz Spectroscopy and Hyper Sausage Neuron

    NASA Astrophysics Data System (ADS)

    Liu, J.; Li, Zh.; Hu, F.; Chen, T.; Du, Y.; Xin, H.

    2015-03-01

    This paper presents a novel approach for identifi cation of terahertz (THz) spectra of genetically modifi ed organisms (GMOs) based on hyper sausage neuron (HSN), and THz transmittance spectra of some typical transgenic sugarbeet samples are investigated to demonstrate its feasibility. Principal component analysis (PCA) is applied to extract features of the spectrum data, and instead of the original spectrum data, the feature signals are fed into the HSN pattern recognition, a new multiple weights neural network (MWNN). The experimental result shows that the HSN model not only can correctly classify different types of transgenic sugar-beets, but also can reject nonsimilar samples of the same type. The proposed approach provides a new effective method for detection and identification of genetically modified organisms by using THz spectroscopy.

  17. Hyper sausage neuron: Recognition of transgenic sugar-beet based on terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Li, Zhi; Hu, Fangrong; Chen, Tao; Du, Yong; Xin, Haitao

    2015-01-01

    This paper presents a novel approach for identification of terahertz (THz) spectral of genetically modified organisms (GMOs) based on Hyper Sausage Neuron (HSN), and THz transmittance spectra of some typical transgenic sugar-beet samples are investigated to demonstrate its feasibility. Principal component analysis (PCA) is applied to extract features of the spectrum data, and instead of the original spectrum data, the feature signals are fed into the HSN pattern recognition, a new multiple weights neural network (MWNN). The experimental result shows that the HSN model not only can correctly classify different types of transgenic sugar-beets, but also can reject identity non similar samples in the same type. The proposed approach provides a new effective method for detection and identification of GMOs by using THz spectroscopy.

  18. Continuous Tera-Hertz wave transmission spectroscopy of Nb double superconducting split-ring resonator array

    NASA Astrophysics Data System (ADS)

    Zuo, JunWei; Liu, RuiYuan; Zhou, YuRong; Li, YanRong; Wang, YunPing

    2012-02-01

    Transmission spectroscopy of two Nb double superconducting split-ring samples with different thicknesses on MgO substrates was measured by a continuous Tera-Hertz spectrometer. The transmission curves of two different samples with the thicknesses of 50 and 150 nm at 7.5 K show dips at 480, 545 GHz, respectively, which origin from the different capacities and inductances of the samples. For the sample of 50 nm, the dip shifts to lower frequency, also decreases in depth and increases in width with temperature or field increasing below T c of Nb film, while the sample of 150 nm does not show such a phenomenon. This thickness-dependent transmission behavior is due to the kinetic inductance and conductivity change of superfluid electrons in Nb film and may suggest a practical tunable THz filter based on the thinner samples.

  19. Carrier dynamics of rubrene single-crystals revealed by transient broadband terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Yada, H.; Uchida, R.; Sekine, H.; Terashige, T.; Tao, S.; Matsui, Y.; Kida, N.; Fratini, S.; Ciuchi, S.; Okada, Y.; Uemura, T.; Takeya, J.; Okamoto, H.

    2014-10-01

    Carrier dynamics of an organic molecular semiconductor, rubrene, was investigated by optical-pump terahertz-probe spectroscopy from 1 to 15 THz. At 294 K, a Drude-like response due to photogenerated hole carriers is observed below 8 THz. The real part ? 1 ( ? ) of the optical conductivity is suppressed below 2 THz, indicating the presence of a localization effect. Such a spectral feature was reproduced by a Drude-Anderson model including the effect of dynamical disorder due to intermolecular vibrations. At 50 K, the spectral weight of ? 1 ( ? ) due to photocarriers shifts to lower frequency below 4 THz and the suppression of ? 1 ( ? ) is hardly observed, which we associate with a reduction of thermal molecular motions. The overall photocarrier generation and recombination dynamics is also discussed.

  20. Terahertz magneto-optical spectroscopy of a two-dimensional hole gas

    DOE PAGESBeta

    Kamaraju, N.; Pan, W.; Ekenberg, U.; Gvozdi?, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.; Reno, J.; Taylor, A. J.; Prasankumar, R. P.

    2015-01-21

    Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We then used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also found that impurity scattering dominates cyclotron resonance decay in the 2DHG,more »in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.« less

  1. Terahertz magneto-optical spectroscopy of a two-dimensional hole gas

    SciTech Connect

    Kamaraju, N. Taylor, A. J.; Prasankumar, R. P.; Pan, W.; Reno, J.; Ekenberg, U.; Gvozdi?, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.

    2015-01-19

    Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also find that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.

  2. Terahertz magneto-optical spectroscopy of a two-dimensional hole gas

    SciTech Connect

    Kamaraju, N.; Pan, W.; Ekenberg, U.; Gvozdi?, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.; Reno, J.; Taylor, A. J.; Prasankumar, R. P.

    2015-01-21

    Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We then used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also found that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.

  3. Low-frequency Spectra of a Phospholipid Bilayer Studied by Terahertz Time-domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Andachi, Tomoyo; Yamamoto, Naoki; Tamura, Atsuo; Tominaga, Keisuke

    2013-08-01

    We have investigated the low-frequency spectra of a phospholipid bilayer composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) by terahertz time-domain spectroscopy (THz-TDS). We focused on the temperature and hydration dependence of the low-frequency spectra of a gel-phase sample. The spectra of the dehydrated and hydrated samples showed shoulder bands at 45 and 30 cm-1, respectively. In contrast to the dehydrated sample, in the hydrated sample spectra the slope of the temperature change of the absorption coefficient increased sharply around 240 K. This result suggests that water molecules affect the change in the low-frequency dynamics. We obtained the absorption coefficient difference spectra for different hydration levels to clarify the mechanism of the spectral change.

  4. Degradation diagnosis of ultrahigh-molecular weight polyethylene with terahertz-time-domain spectroscopy

    SciTech Connect

    Yamamoto, Kohji; Yamaguchi, Mariko; Tani, Masahiko; Hangyo, Masanori; Teramura, Satoshi; Isu, Toshiro; Tomita, Naohide

    2004-11-29

    We investigated ultrahigh-molecular-weight-polyethylene (UHMWPE) samples prepared by various conditions with terahertz-time-domain spectroscopy (THz-TDS). Degradation of the virgin UHMWPE samples by {gamma} irradiation induced a drastic increase of the absorption ranging continuously over the THz region. The increase of the absorption continuum is interpreted to originate in the oxidation of the amorphous region within the sample. Only slight THz spectral changes induced by the {gamma} irradiation were, however, observed for the UHMWPE samples doped with 0.1 and 0.3 wt % vitamin E. This result agrees with the earlier indication that vitamin E has an antidegradation effect on UHMWPE. The present result shows that the THz-TDS can be used for the quality control of UHMWPE by monitoring the absorption continuum in the THz region.

  5. Rapid determination of saponification value and polymer content of vegetable and fish oils by terahertz spectroscopy.

    PubMed

    Jiang, Feng Ling; Ikeda, Ikuo; Ogawa, Yuichi; Endo, Yasushi

    2012-01-01

    A rapid method for determining the saponification value (SV) and polymer content of vegetable and fish oils using the terahertz (THz) spectroscopy was developed. When the THz absorption spectra for vegetable and fish oils were measured in the range of 20 to 400 cm?¹, two peaks were seen at 77 and 328 cm?¹. The level of absorbance at 77 cm?¹ correlated well with the SV. When the THz absorption spectra of thermally treated high-oleic safflower oils were measured, the absorbance increased with heating time. The polymer content in thermally treated oil correlated with the absorbance at 77 cm?¹. These results demonstrate that the THz spectrometry is a suitable non-destructive technique for the rapid determination of the SV and polymer content of vegetable and fish oils. PMID:23018850

  6. Charge-carrier dynamics in benzoporphyrin films investigated by time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Ohta, Kaoru; Hiraoka, Sho; Tamura, Yuto; Yamada, Hiroko; Tominaga, Keisuke

    2015-11-01

    We investigated charge-carrier dynamics in benzoporphyrin (BP) and BP-based bulk heterojunction (BHJ) films with optical pump-broadband terahertz (THz) probe spectroscopy. In both samples, we observed instantaneous appearance of transient THz signals, which are attributed to mobile charge carriers that are much lower in transition energy than excitons. These carriers recombine and/or trap at defect sites within a few ps. In the BP-based BHJ films, the decay dynamics of transient THz signals was faster relative to that in the BP films. In contrast to the BP films, approximately 10% of the transient signal does not decay within 35 ps, indicating survival of free charge carriers.

  7. Terahertz time-domain spectroscopy of transient metallic and superconducting states

    NASA Astrophysics Data System (ADS)

    Orenstein, J.; Dodge, J. S.

    2015-10-01

    Time-resolved terahertz time-domain spectroscopy (THz-TDS) is an ideal tool for probing photoinduced nonequilibrium metallic and superconducting states. Here, we focus on the interpretation of the two-dimensional response function ? (? ;t ) that it measures, examining whether it provides an accurate snapshot of the instantaneous optical conductivity ? (? ;t ) . For the Drude model with a time-dependent carrier density, we show that ? (? ;t ) is not simply related to ? (? ;t ) . The difference in the two response functions is most pronounced when the momentum relaxation rate of photocarriers is small, as would be the case in a system that becomes superconducting following pulsed photoexcitation. From the analysis of our model, we identify signatures of photoinduced superconductivity that could be seen by time-resolved THz-TDS.

  8. Doppler-Limited Spectroscopy with a Decade-Spanning Terahertz Frequency Comb

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Good, Jacob T.; Holland, Daniel; Carroll, Brandon; Allodi, Marco A.; Blake, Geoffrey

    2015-06-01

    We report the generation and detection of a decade-spanning TeraHertz (THz) frequency comb (0.15-2.4 THz) using two Ti:Sapphire femtosecond laser oscillators and ASynchronous OPtical Sampling THz Time-Domain Spectroscopy (ASOPS-THz-TDS). The measured linewidth of the comb at 1.5 THz is 3 kHz over a 60 second acquisition. With time-domain detection of the comb, we measure three transitions of water vapor at 10 mTorr between 1-2 THz with an average Doppler-limited fractional uncertainty of 5.9×10-8. Significant improvements in bandwidth, resolution, and sensitivity are possible with existing technologies and will enable future studies of jet-cooled hydrogen-bonded clusters.

  9. Electron density measurement of inductively coupled plasmas by terahertz time-domain spectroscopy (THz-TDS)

    NASA Astrophysics Data System (ADS)

    Ando, Ayumi; Kurose, Tomoko; Reymond, Vivien; Kitano, Katsuhisa; Kitahara, Hideaki; Takano, Keisuke; Tani, Masahiko; Hangyo, Masanori; Hamaguchi, Satoshi

    2011-10-01

    The electron densities of argon inductively coupled plasmas were measured by terahertz time-domain spectroscopy (THz-TDS). At a low pressure, the electron densities were also measured with a Langmuir-type double probe and the validity of THz-TDS electron-density measurement in a plasma has been corroborated. As the input radio-frequency (RF) power increases, the plasma density and gas temperature increase, which makes the probe measurement less reliable or even impossible, due to the large heat load to the probe surface. On the contrary, the THz-TDS measurement is unaffected by the gas temperature and becomes more reliable due to the higher electron density at higher input power for plasma generation.

  10. Electron density measurement for plasmas by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Ando, A.; Kitahara, H.; Kurose, T.; Kitano, K.; Takano, K.; Tani, M.; Hangyo, M.; Hamaguchi, S.

    2010-05-01

    A new plasma diagnostic tool of terahertz time-domain spectroscopy (THz-TDS) has been developed. The THz-TDS system allows one to obtain the electron density and collision frequency of a plasma simultaneously from the phase shift and absorption rate of THz waves that are transmitted through the plasma. The line-averaged electron densities of Ar inductively coupled plasmas (ICPs) and CH4/Ar capacitively coupled plasmas (CCPs) were evaluated by the system and found to be 1017-1018 m-3 for Ar ICPs and 1015-1016 m-3 for CH4/Ar CCPs, depending on the discharge conditions. These results have demonstrated the feasibility of electron density measurements by THz-TDS for reactive plasmas.

  11. Quantitative Analysis for Monitoring Formulation of Lubricating Oil Using Terahertz Time-Domain Transmission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tian, Lu; Zhao, Kun; Zhou, Qing-Li; Shi, Yu-Lei; Zhang, Cun-Lin

    2012-04-01

    The quantitative analysis of zinc isopropyl-isooctyl-dithiophosphate (T204) mixed with lube base oil from Korea with viscosity index 70 (T204-Korea70) is presented by using terahertz time-domain spectroscopy (THz-TDS). Compared with the middle-infrared spectra of zinc n-butyl-isooctyl-dithiophosphate (T202) and T204, THz spectra of T202 and T204 show the weak broad absorption bands. Then, the absorption coefficients of the T204-Korea70 system follow Beer's law at the concentration from 0.124 to 4.024%. The experimental absorption spectra of T204-Korea70 agree with the calculated ones based on the standard absorption coefficients of T204 and Korea70. The quantitative analysis enables a strategy to monitor the formulation of lubricating oil in real time.

  12. Intrinsic carrier multiplication efficiency in bulk Si crystals evaluated by optical-pump/terahertz-probe spectroscopy

    SciTech Connect

    Yamashita, G.; Nagai, M. E-mail: ashida@mp.es.osaka-u.ac.jp; Ashida, M. E-mail: ashida@mp.es.osaka-u.ac.jp; Matsubara, E.; Kanemitsu, Y.

    2014-12-08

    We estimated the carrier multiplication efficiency in the most common solar-cell material, Si, by using optical-pump/terahertz-probe spectroscopy. Through close analysis of time-resolved data, we extracted the exact number of photoexcited carriers from the sheet carrier density 10 ps after photoexcitation, excluding the influences of spatial diffusion and surface recombination in the time domain. For incident photon energies greater than 4.0?eV, we observed enhanced internal quantum efficiency due to carrier multiplication. The evaluated value of internal quantum efficiency agrees well with the results of photocurrent measurements. This optical method allows us to estimate the carrier multiplication and surface recombination of carriers quantitatively, which are crucial for the design of the solar cells.

  13. Fiber-remote reflectance spectroscopy with an optimized diffuse reflectance sensor system

    SciTech Connect

    Driver, R.D.; Grim, K.P.; Dewey, G.; Brubaker, M.L.

    1995-12-31

    A diffuse reflectance spectroscopy system is described which can operate in a contact and non-contact mode on powders, slurries and other diffusely scattering materials. Diffuse reflectance spectra are presented for a number of samples including common household materials. A comparison is made of the probe with a Bio-Rad diffuse reflectance accessory. Second derivative spectra are shown of a calibration mixture of polymer additives. The use of the diffuse reflectance system for non-destructive tablet hardness measurements is discussed. Sensor multiplexing for diffuse reflectance spectroscopy, is reviewed.

  14. Skin cancer detection by oblique-incidence diffuse reflectance spectroscopy 

    E-print Network

    Smith, Elizabeth Brooks

    2009-05-15

    Skin cancer is the most common form of cancer and it is on the rise. If skin cancer is diagnosed early enough, the survival rate is close to 90%. Oblique-incidence diffuse reflectance (OIR) spectroscopy offers a technology ...

  15. Classification of skin abnormalties using oblique incident diffuse reflectance spectroscopy 

    E-print Network

    Garcia Uribe, Alejandro

    2002-01-01

    This thesis describes a study for the classification of skin abnormalities using oblique incident diffuse reflectance spectroscopy as part of the goal to provide a computer-assisted tool to dermatologists for lowering the number of benign biopsies...

  16. Wideband terahertz spectroscopy of explosives M.R. Leahy-Hoppa a,b,*, M.J. Fitch a

    E-print Network

    Hayden, L. Michael

    explosives: RDX (1,3,5-trinitroperhydro-1,3,5-triazine), HMX (1,3,5,7-tetranitroperhydro-1,3,5,7-tetrazocine can be identified. The explosives we investigated are RDX, HMX, TNT, and PETN. These four explosivesWideband terahertz spectroscopy of explosives M.R. Leahy-Hoppa a,b,*, M.J. Fitch a , X. Zheng b , L

  17. Terahertz time domain spectroscopy allows contactless monitoring of grapevine water status

    PubMed Central

    Santesteban, Luis G.; Palacios, Inés; Miranda, Carlos; Iriarte, Juan C.; Royo, José B.; Gonzalo, Ramón

    2015-01-01

    Agriculture is the sector with the greatest water consumption, since food production is frequently based on crop irrigation. Proper irrigation management requires reliable information on plant water status, but all the plant-based methods to determine it suffer from several inconveniences, mainly caused by the necessity of destructive sampling or of alteration of the plant organ due to contact installation. The aim of this work is to test if terahertz (THz) time domain reflectance measurements made on the grapevine trunk allows contactless monitoring of plant status. The experiments were performed on a potted 14-years-old plant, using a general purpose THz emitter receiver head. Trunk THz time-domain reflection signal proved to be very sensitive to changes in plant water availability, as its pattern follows the trend of soil water content and trunk growth variations. Therefore, it could be used to contactless monitor plant water status. Apart from that, THz reflection signal was observed to respond to light conditions which, according to a specifically designed girdling experiment, was caused by changes in the phloem. This latter results opens a promising field of research for contactless monitoring of phloem activity. PMID:26082791

  18. Molecular recognition and interaction between uracil and urea in solid-state studied by terahertz time-domain spectroscopy.

    PubMed

    Yang, Jingqi; Li, Shaoxian; Zhao, Hongwei; Song, Bo; Zhang, Guoxin; Zhang, Jianbing; Zhu, Yiming; Han, Jiaguang

    2014-11-20

    Using terahertz time-domain spectroscopy characterization, we observe that urea is able to recognize and interact with uracil efficiently even in the solid phase without involving water or solvents. A cocrystal configuration linked by a pair of hydrogen bonds between uracil and urea was formed. The terahertz absorption spectrum of the cocrystal shows a distinct new absorption at 0.8 THz (26.7 cm(-1)), which originates from the intermolecular hydrogen bonding. Both mechanical milling and heating can accelerate the reaction efficiently. Density functional theory was adopted to simulate the vibrational modes of the cocrystal, and the results agree well with the experimental observation. Multiple techniques, including powder X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy, were performed to investigate the reaction process, and they presented supportive evidence. This work enables in-depth understanding of recognition and interaction of urea with nucleobases and comprehension of the denaturation related to RNA. We also demonstrate that terahertz spectroscopy is an effective and alternative tool for online measurement and quality control in pharmaceutical and chemical industries. PMID:25386785

  19. High Speed Terahertz Pulse Imaging in the Reflection Geometry and Image Quality Enhancement by Digital Image Processing

    NASA Astrophysics Data System (ADS)

    Shon, Chae-Hwa; Chong, Won-Yong; Jeon, Seok-Gy; Kim, Geun-Ju; Kim, Jung-Il; Jin, Yun-Sik

    2008-01-01

    We describe the formation and enhancement of two dimensional pulsed terahertz (THz) images obtained in the reflection geometry with a high-speed optical delay line. Two test objects are imaged and analyzed with respect to material information and concealed structure. Clear THz images were obtained with various imaging modes and were compared with the X-ray images. The THz image of a sample revealed material features that the X-ray image cannot distinguish. We could enhance the THz image quality using various image processing techniques, such as edge detection, de-noising, high-pass filtering, and wavelet filtering.

  20. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

    PubMed Central

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-01-01

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

  1. Qualitative and quantitative analysis of calcium-based microfillers using terahertz spectroscopy and imaging.

    PubMed

    Abina, Andreja; Puc, Uroš; Jegli?, Anton; Prah, Jana; Venckevi?ius, Rimvydas; Kašalynas, Irmantas; Valušis, Gintaras; Zidanšek, Aleksander

    2015-10-01

    In different industrial applications, several strictly defined parameters of calcium-based microfillers such as average particle size, particle size distribution, morphology, specific surface area, polymorphism and chemical purity, play a key role in the determination of its usefulness and effectiveness. Therefore, an analytical tool is required for rapid and non-destructive characterization of calcium-based microfillers during the synthesis process or before its use in a further manufacturing process. Since spectroscopic techniques are preferred over microscopy and thermogravimetry, particularly due to its non-destructive nature and short analysis time, we applied terahertz (THz) spectroscopy to analyse calcite microfillers concentration in polymer matrix, its granulation and chemical treatment. Based on the analysis of peak absorbance amplitude, peak frequency position, and the appearance of additional spectral features, quantitative and qualitative analysis was successfully achieved. In addition, THz imaging was also applied for both quantitative and qualitative analysis of calcium-based microfillers. By using spatial distribution map, the inhomogeneity in concentration of calcium carbonate in polymer matrix was characterized. Moreover, by THz spectroscopy and imaging different calcium compounds were detected in binary mixtures. Finally, we demonstrated that the applied spectroscopic technique offers valuable results and can be, in combination with other spectroscopic and microscopic techniques, converted to a powerful rapid analytical tool. PMID:26078145

  2. Preliminary study on quality evaluation of pecans with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Bin; Cao, Wei; Mathanker, Sunil; Zhang, Weili; Wang, Ning

    2010-11-01

    This paper reports a preliminary work on a feasibility study of applying terahertz (THz) technology for pecan quality evaluation. A set of native pecan nuts collected in 2009 were used during the experiment. Each pecan nutmeat was manually sliced at a thickness of about 1mm, 2mm, and 3mm and a size of about 2cm (length) ×1cm (width). Pecan shell and inner separator were also cut into the same size. The absorption spectra for the nutmeat slices, shell, and inner separator were collected using a THz time-domain spectroscopy (THz-TDS) developed by a group of researchers at Oklahoma State University. The test results show that nutmeat, shell, and inner separator had different absorption characteristics within the bandwidth of 0.2-2.0 THz. To study the capability of insect damage detection of the THz spectroscopy, the absorption spectra of insects (living manduca sexta and dry pecan weevil) were also collected. Due to high water contents in the insects, very obvious spectral characteristics were found. The results from the preliminary study show a potential of THz technology applied for quality detection of bio-products. However, since bio-products mostly have high water content and are handled under an environment with certain levels of water content, practical issues needs to be further investigated to make the THz technology a feasible tool for quality evaluation.

  3. Feasibility of using terahertz spectroscopy to detect seven different pesticides in wheat flour.

    PubMed

    Maeng, Inhee; Baek, Seung Hyun; Kim, Hwa Yeon; Ok, Gyeong-Sik; Choi, Sung-Wook; Chun, Hyang Sook

    2014-12-01

    This study investigated the feasibility of detecting pesticides using terahertz (THz) spectroscopy in high-density polyethylene and/or wheat flour mixtures. The absorption spectra of seven pesticides (dicofol, chlorpyrifos, chlorpyrifos-methyl, daminozide, imidacloprid, diethyldithiocarbamate, and dimethyldithiocarbamate) were measured in the frequency range 0.1 to 3 THz at room temperature. Five of the seven pesticides exhibited specific absorption peaks in the low-energy THz range. The two remaining pesticides had no specific absorption peaks in this frequency range, but they exhibited different frequency-dependent refractive indices. The absorption coefficients of imidacloprid increased with its increasing weight ratio in high-density polyethylene, and the fitted power absorptions and refractive indices using a Maxwell-Garnett effective medium model were comparable to the measured data. Imidacloprid was also identified from its characteristic absorption peaks in wheat flour mixtures, and a linear relationship between the absorption coefficient and the weight ratio was observed. Our results show the potential of detection of selected pesticides in foods, such as wheat flour, using THz spectroscopy. PMID:25474054

  4. Standoff Detection of Hidden Explosives and Cold and Fire Arms by Terahertz Time-Domain Spectroscopy and Active Spectral Imaging (Review)

    NASA Astrophysics Data System (ADS)

    Skvortsov, L. A.

    2014-11-01

    Terahertz time-domain spectroscopy and standoff spectral imaging for detection of explosives and cold and fire arms hidden, for example, under clothing, were reviewed. Special attention was paid to different schemes for practical implementation of these methods. Progress in this direction and existing problems and the prospects for their solution were discussed. Issues related to sources and receivers of terahertz radiation were briefly discussed. It was noted that interest in quantum-cascade lasers as compact sources of terahertz radiation and the potential of using them at room temperature were increasing.

  5. Does Spectral Format Matter in Diffuse Reflection Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near- and more recently, mid-infrared diffuse reflectance spectroscopy have come to be extensively used to determine the composition of products ranging from forages to drugs. In these methods, spectra are generally collected as (Reflectance or R) and transformed to log (1/R) according to the Beer-...

  6. Monitoring the Polymerization of Two-Component Epoxy Adhesives Using a Terahertz Time Domain Reflection System

    NASA Astrophysics Data System (ADS)

    Probst, T.; Sommer, S.; Soltani, A.; Kraus, E.; Baudrit, B.; Town, G. E.; Koch, M.

    2015-06-01

    We report nondestructive measurements of the properties of two-component epoxy adhesives at THz wavelengths using a reflective time-domain spectroscopy system. We describe a simple method to determine the refractive index, layer thickness, and absorption coefficient using time-domain data applying a Fresnel-equation based approach. The results indicate that the adhesive's curing process may be monitored using a simple parameter extraction technique based on time-domain measurements for systems featuring small bandwidth, showing good agreement with data obtained with from transmission measurements.

  7. In vivo terahertz spectroscopy of pigmentary skin nevi: Pilot study of non-invasive early diagnosis of dysplasia

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Kudrin, Konstantin G.; Karasik, Valeriy E.; Reshetov, Igor V.; Yurchenko, Stanislav O.

    2015-02-01

    In vivo terahertz (THz) spectroscopy of pigmentary skin nevi is performed. The in vivo THz dielectric characteristics of healthy skin and dysplastic and non-dysplastic skin nevi are reconstructed and analyzed. The dielectric permittivity curves of these samples in the THz range exhibit significant differences that could allow non-invasive early diagnosis of dysplastic nevi, which are melanoma precursors. An approach for differentiating dysplastic and non-dysplastic skin nevi using the THz dielectric permittivity is proposed. The results demonstrate that THz pulsed spectroscopy is potentially an effective tool for non-invasive early diagnosis of dysplastic nevi and melanomas of the skin.

  8. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Tonouchi, Masayoshi; Reno, John L.

    2013-05-01

    A useful synergy is being established between terahertz research and nanotechnology. High power sources [1-3] and detectors [4] in what was once considered the terahertz 'frequency gap' [5] in the electromagnetic spectrum have stimulated research with huge potential benefits in a range of industries including food, medicine and security, as well as fundamental physics and astrophysics. This special section, with guest editors Masayoshi Tonouchi and John Reno, gives a glimpse of the new horizons nanotechnology is broaching in terahertz research. While the wavelengths relevant to the terahertz domain range from hundreds of micrometres to millimetres, structures at the nanoscale reveal interesting low energy dynamics in this region. As a result terahertz spectroscopy techniques are becoming increasingly important in nanomaterial characterization, as demonstrated in this special section by colleagues at the University of Oxford in the UK and the Australian National University. They use terahertz spectroscopy to identify the best nanostructure parameters for specific applications [6]. The low energy dynamics in nanostructures also makes them valuable tools for terahertz detection [7]. In addition the much sought after terahertz detection over broadband frequency ranges has been demonstrated, providing versatility that has been greatly in demand, particularly in spectroscopy applications [8, 9]. Also in this special section, researchers in Germany and China tackle some of the coupling issues in terahertz time domain spectroscopy with an emitter specifically well suited for systems operated with an amplified fibre [3]. 'In medical imaging, the advantage of THz radiation is safety, because its energy is much lower than the ionization energy of biological molecules, in contrast to hazardous x-ray radiation,' explains Joo-Hiuk Son from the University of Seoul in Korea in his review [10]. As he also points out, the rotational and vibrational energies of water molecules are within the THz spectral region providing an additional benefit. His review describes the principle, characteristics, and applications of terahertz molecular imaging, where the use of nanoparticle probes allows dramatically enhanced sensitivity. Jiaguang Han and Weili Zhang and colleagues in China, Saudi Arabia, Japan and the US report exciting developments for optoelectronics [11]. They describe work on plasmon-induced transparency (PIT), an analogue of electromagnetically induced transparency (EIT) where interference leads to a sharp transparency window that may be useful for nonlinear and slow-light devices, optical switching, pulse delay, and storage for optical information processing. While PIT has advantages over the cumbersome experimental systems required for EIT, it has so far been constrained to very narrow band operation. Now Zhang and colleagues present the simulation, implementation, and measurement of a broadband PIT metamaterial functioning across a frequency range greater than 0.40 THz in the terahertz regime. 'We can foresee a historic breakthrough for science and technology through terahertz research,' concluded Masayoshi Tonouchi in his review over five years ago as momentum in the field was mounting [12]. He added, 'It is also noteworthy that THz research is built on many areas of science and the coordination of a range of disciplines is giving birth to a new science.' With the inherently multidisciplinary nature of nanotechnology research it is not so strange to see the marriage of the two fields form such a fruitful partnership, as this special section highlights. References [1] Williams B S, Kumar S, Hu Q and Reno J L 2006 High-power terahertz quantum-cascade lasers Electron. Lett. 42 89-91 [2] Köhler R et al 2002 Terahertz semiconductor-heterostructure laser Nature 417 156-9 [3] Mittendorff M, Xu M, Dietz R J B, K¨unzel H, Sartorius B, Schneider H, Helm M and Winnerl S 2013 Large area photoconductive THz emitter for 1.55 ?m excitation based on an InGaAs heterostructure Nanotechnology 24 214007 [4] Chen H-T, Padilla W J, Zide J M O, Gossa

  9. Nondestructive evaluation of crystallized-particle size in lactose-powder by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamauchi, Satoshi; Hatakeyama, Sakura; Imai, Yoh; Tonouchi, Masayoshi

    2014-03-01

    Transmission-type terahertz time-domain spectroscopy is applied to evaluate crystallized lactose particle of size below 30 ?m, which is far too small compared to the wavelength of incident terahertz (THz)-wave. The THz-absorption spectrum of lactose is successfully deconvoluted by Lorentzian to two spectra with peaks at 17.1 cm-1 (0.53 THz) and 45.6 cm-1 (1.37 THz) derived from ?-lactose monohydrate, and a spectrum at 39.7 cm-1 (1.19 THz) from anhydrous ?-lactose after removal of the broad-band spectrum by polynomial cubic function. Lactose is mainly crystallized into ?-lactose monohydrate from the supersaturated solution at room temperature with a small amount of anhydrous ?-lactose below 4%. The absorption feature is dependent on the crystallized particle size and the integrated intensity ratio of the two absorptions due to ?-lactose monohydrate is correlated in linear for the size.

  10. Reflectance spectroscopy for evaluating hair follicle cycle

    NASA Astrophysics Data System (ADS)

    Liu, Caihua; Guan, Yue; Wang, Jianru; Zhu, Dan

    2014-02-01

    Hair follicle, as a mini-organ with perpetually cycling of telogen, anagen and catagen, provides a valuable experimental model for studying hair and organ regeneration. The transition of hair follicle from telogen to anagen is a significant sign for successful regeneration. So far discrimination of the hair follicle stage is mostly based on canonical histological examination and empirical speculation based on skin color. Hardly a method has been proposed to quantitatively evaluate the hair follicle stage. In this work, a commercial optical fiber spectrometer was applied to monitor diffuse reflectance of mouse skin with hair follicle cycling, and then the change of reflectance was obtained. Histological examination was used to verify the hair follicle stage. In comparison with the histological examination, the skin diffuse reflectance was relatively high for mouse with telogen hair follicles; it decreased once hair follicles transited to anagen stage; then it increased reversely at catagen stage. This study provided a new method to quantitatively evaluate the hair follicle stage, and should be valuable for the basic and therapeutic investigations on hair regeneration.

  11. Time-domain terahertz spectroscopy and applications on drugs and explosives

    NASA Astrophysics Data System (ADS)

    Fan, W. H.; Zhao, W.; Cheng, G. H.; Burnett, A. D.; Upadhya, P. C.; Cunningham, J. E.; Linfield, E. H.; Davies, A. G.

    2008-03-01

    Many materials of interest to the forensic and security services, such as explosives, drugs and biological agents, exhibit characteristic spectral features in the terahertz (THz) frequency range. These spectral features originate from inter-molecular interactions, involving collective motions of molecules. Broadband THz time-domain spectroscopy (THz-TDS) system have been used to analyze a number of drugs-of-abuse and explosives that are of interest to the forensic and security services. These samples ranged from crystalline powders, pressed into pellets, to thin sheets of plastic explosives, and all being measured in transmission geometry in the frequency range 0.1 - 8 THz. To well understand the nature of the observed spectral features and the effects of thermal broadening on these far-infrared signatures, temperature-dependent THz-TDS measurements have also been performed at temperatures as low as 4 K, especially for two types of cocaine. Well-resolved low-frequency absorption peaks were observed in the frequency range 0.1 - 3 THz with high resolution. Some of absorption peaks were found clearly to become more intense and shift to higher frequencies as the temperature was reduced. The results confirm that the low-frequency collective modes are highly sensitive to the structural and spatial arrangement of molecules. Furthermore, a number of common postal packaging materials made from paper, cardboard, even several types of plastic, have been tested with drug sample to assess the ability of THz-TDS in a hostile detection environment.

  12. Evidence for bandgap opening in buckled epitaxial graphene from ultrafast time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Mihnev, Momchil T.; Wang, Feng; Liu, Gang; Rothwell, Sara; Cohen, Philip I.; Feldman, Leonard C.; Conrad, Edward H.; Norris, Theodore B.

    2015-10-01

    We utilize ultrafast time-resolved terahertz (THz) spectroscopy as a direct, sensitive, and non-contact all-optical probe to investigate the hot-carrier relaxation and cooling dynamics of buckled epitaxial graphene. This special form of graphene is grown epitaxially on nitrogen-seeded single-crystal silicon carbide (SiC( 000 1 ¯ )) substrates by thermal decomposition of Si atoms. The pre-deposited interfacial nitrogen atoms pin the first graphene layer to the SiC substrate, and cause it and subsequent graphene layers to buckle into nanoscale folds, which opens an energy gap of up to ˜0.7 eV. We observe a remarkable increase of up to two orders of magnitude in the relaxation rate of the THz carrier dynamics of this semiconducting form of epitaxial graphene relative to pristine epitaxial graphene, which we attribute to a large enhancement of the optical-phonon-mediated carrier cooling and recombination over a wide range of electron temperatures due to the finite bandgap. Our results suggest that the introduced bandgap is spatially non-homogenous, with local values close to the optical phonon energy of ˜200 meV, which allows the conduction and the valence band to be bridged by optical phonon emission. We also demonstrate that carrier relaxation times can be modified by orders of magnitude by careful bandgap engineering, which could find application in novel graphene-based devices that incorporate both metallic and semiconducting forms of graphene.

  13. Study on silicon nanostructure based solar cell by ultrafast terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Peng, Longyao; Zhu, Liguo; Tang, Hao; Meng, Kun; Zhong, Sencheng; Li, Zeren; Zhang, Rongzhu

    2013-08-01

    Recently, Silicon nanowires(Si NWs) have been suggested as a promising candidate for solar energy harvesting. The Si NWs have the advantage of enhancing the optical absorption for broadband spectra, which increases the optical absorption significantly. It is of crucial importance for high efficiency solar cell. We applied the transient optical-pump THz emission spectroscopy to research Si NWs fabricated by chemical etching and to analyse the THz radiation mechanism. The experiment datas indicated that Si NWs enhance the optical absorption significantly. And the lifetime and dynamics properties of photoexcited carriers are important to the photovoltaic conversion efficiency of solar cell. Here the optical-pump terahertz-probe system was employed to study the ultrafast dynamics and transport properties of photoexcited carriers in Si NWs. The experiment results shown that carrier lifetime in Si NWs is approximate 0.7ns, and it reduces optical energy-conversion efficiencies of solar cell. However, compared to other silicon nanostructures, Si NWs fabricated by chemical etching have relative high values for both the carrier lifetime and mobility. The detailed analysis of the optical absorption and carriers dynamics would be significant for optimizing configuration of the silicon nanostructures.

  14. Monitoring Plant Drought Stress Response Using Terahertz Time-Domain Spectroscopy[C][W

    PubMed Central

    Born, Norman; Behringer, David; Liepelt, Sascha; Beyer, Sarah; Schwerdtfeger, Michael; Ziegenhagen, Birgit; Koch, Martin

    2014-01-01

    We present a novel measurement setup for monitoring changes in leaf water status using nondestructive terahertz time-domain spectroscopy (THz-TDS). Previous studies on a variety of plants showed the principal applicability of THz-TDS. In such setups, decreasing leaf water content directly correlates with increasing THz transmission. Our new system allows for continuous, nondestructive monitoring of the water status of multiple individual plants each at the same constant leaf position. It overcomes previous drawbacks, which were mainly due to the necessity of relocating the plants. Using needles of silver fir (Abies alba) seedlings as test subjects, we show that the transmission varies along the main axis of a single needle due to a variation in thickness. Therefore, the relocation of plants during the measuring period, which was necessary in the previous THz-TDS setups, should be avoided. Furthermore, we show a highly significant correlation between gravimetric water content and respective THz transmission. By monitoring the relative change in transmission, we were able to narrow down the permanent wilting point of the seedlings. Thus, we established groups of plants with well-defined levels of water stress that could not be detected visually. This opens up the possibility for a broad range of genetic and physiological experiments. PMID:24501000

  15. Investigating the position isomerism effect of dihydroxybenzoic acid compounds by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, Yong; Hao, Guohui; Zhao, Rongjiao; Hong, Zhi

    2011-11-01

    Far-infrared vibrational absorption of a series of dihydroxybenzoic acid (DHBA) compounds with different substituted hydroxy group at different positions have been investigated using terahertz time-domain spectroscopy (THz-TDS) at room temperature. The experimental results show large difference among absorption spectra of different DHBA (2,3-DHBA, 2,4-DHBA, 2,5-DHBA, 2,6-DHBA) compounds in 0.2 ~ 2.0 THz region, which probably originated from the difference of intra-molecular and inter-molecular hydrogen bonds due to the presence of two hydroxyl group in different positions with respect to the carboxylic group in different DHBAs. All the experimental DHBAs vibrational modes showed distinct fingerprint absorption in THz region and theorectical calculation based on density functional theory (DFT) was carried out to assist the analysis and assignment of the vibrational modes. The results indicate that THz-TDS technology can not only give a new experimental method to identify and characterize the position isomerism effect of hydroxyl group between such different kinds of DHBAs from molecule-level, but also provide a useful suggestion for further assessing the possible relationships between the DHBAs vibrational properties and the effects of the substituted hydroxy group position to better know their biochemical activities in food, pharmaceutical and cosmetic fields.

  16. Determination of soluble solids content in apple products by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Hao, Guohui; Liu, Jianjun; Hong, Zhi

    2011-08-01

    Soluble solids content is an important index for fruit quality. One of the traditional methods in determining soluble solids content of fruits is refractometry which measures the refractive index in visible or near infrared. Here we reported the use of terahertz time-domain transmission spectroscopy (THz-TDTS) technique for the determination of soluble solids content in apple products. Not only the refractive index, but also the absorption coefficient is used in regression model. In method one, sucrose solutions were for the calibration set , root mean square of validation set (RMSEP) was 0.168% for absorption coefficient model, 0.741% for refractive index model. In method two, apple products were for the calibration set, RMSEP was 0.143% for absorption coefficient model, 0.648% for refractive index model. Less absolute error of 0.2% between predicted and refractometer value has been both obtained from two methods with absorption coefficient model. This result proved the THz-TDS technique is quite potential for nondestructive detection on food quality.

  17. Investigating the position isomerism effect of dihydroxybenzoic acid compounds by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, Yong; Hao, Guohui; Zhao, Rongjiao; Hong, Zhi

    2012-03-01

    Far-infrared vibrational absorption of a series of dihydroxybenzoic acid (DHBA) compounds with different substituted hydroxy group at different positions have been investigated using terahertz time-domain spectroscopy (THz-TDS) at room temperature. The experimental results show large difference among absorption spectra of different DHBA (2,3-DHBA, 2,4-DHBA, 2,5-DHBA, 2,6-DHBA) compounds in 0.2 ~ 2.0 THz region, which probably originated from the difference of intra-molecular and inter-molecular hydrogen bonds due to the presence of two hydroxyl group in different positions with respect to the carboxylic group in different DHBAs. All the experimental DHBAs vibrational modes showed distinct fingerprint absorption in THz region and theorectical calculation based on density functional theory (DFT) was carried out to assist the analysis and assignment of the vibrational modes. The results indicate that THz-TDS technology can not only give a new experimental method to identify and characterize the position isomerism effect of hydroxyl group between such different kinds of DHBAs from molecule-level, but also provide a useful suggestion for further assessing the possible relationships between the DHBAs vibrational properties and the effects of the substituted hydroxy group position to better know their biochemical activities in food, pharmaceutical and cosmetic fields.

  18. Distinguishing Gasoline Engine Oils of Different Viscosities Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Adbul-Munaim, Ali Mazin; Reuter, Marco; Koch, Martin; Watson, Dennis G.

    2015-07-01

    Terahertz-time-domain spectroscopy (THz-TDS) in the range of 0.5-2.0 THz was evaluated for distinguishing among gasoline engine oils of three different grades (SAE 5W-20, 10W-40, and 20W-50) from the same manufacturer. Absorption coefficient showed limited potential and only distinguished ( p < 0.05) the 20W-50 grade from the other two grades in the 1.7-2.0-THz range. Refractive index data demonstrated relatively flat and consistently spaced curves for the three oil grades. ANOVA results confirmed a highly significant difference ( p < 0.0001) in refractive index among each of the three oils across the 0.5-2.0-THz range. Linear regression was applied to refractive index data at 0.25-THz intervals from 0.5 to 2.0 THz to predict kinematic viscosity. All seven linear regression models, intercepts, and refractive index coefficients were highly significant ( p < 0.0001). All models had a similar fit with R 2 ranging from 0.9773 to 0.9827 and RMSE ranging from 6.33 to 7.75. The refractive indices at 1.25 THz produced the best fit. The refractive indices of these oil samples were promising for identification and distinction of oil grades.

  19. Characteristic responses of biological and nanoscale systems in the terahertz frequency range

    SciTech Connect

    Angeluts, A A; Balakin, A V; Evdokimov, M G; Ozheredov, I A; Sapozhnikov, D A; Solyankin, P M; Shkurinov, A P; Esaulkov, M N; Nazarov, M M; Cherkasova, O P

    2014-07-31

    This paper briefly examines methods for the generation of pulsed terahertz radiation and principles of pulsed terahertz spectroscopy, an advanced informative method for studies of complex biological and nanostructured systems. Some of its practical applications are described. Using a number of steroid hormones as examples, we demonstrate that terahertz spectroscopy in combination with molecular dynamics methods and computer simulation allows one to gain information about the structure of molecules in crystals. A 'terahertz colour vision' method is proposed for analysis of pulsed terahertz signals reflected from biological tissues and it is shown that this method can be effectively used to analyse the properties of biological tissues and for early skin cancer diagnosis. (laser biophotonics)

  20. Combined theory of reflectance and emittance spectroscopy

    NASA Technical Reports Server (NTRS)

    Hapke, Bruce

    1995-01-01

    The theory in which either or both reflected sunlight and thermally emitted radiation contribute to the power received by a detector viewing a particulate medium, such as a powder in the laboratory or a planetary regolith, is considered theoretically. This theory is of considerable interest for the interpretation of data from field or spacecraft instruments that are sensitive to the near-infrared region of the spectrum, such as NIMS (near-infrared mapping spectrometer) and VIMS (visual and infrared mapping spectrometer), as well as thermal infrared detectors.

  1. Accessing deep optical properties of skin using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Koenig, Anne; Roig, Blandine; Le Digabel, Jimmy; Josse, Gwendal; Dinten, Jean-Marc

    2015-07-01

    Diffuse reflectance spectroscopy characterizes composition and structure of tissues by determining their scattering and absorption properties. We have developed in our laboratory a low-cost spatially resolved diffuse reflectance spectroscopy instrument. We present in this study some results showing how to adapt this technology on multi-layered tissues. First of all, a method enabling determination of scattering and absorption properties of multi-layered phantoms is described; the adaptation of the initial methodology to focus on deep layers is especially detailed. Then some preliminary results obtained on a panel of volunteer's redness faces are presented.

  2. Diffuse reflectance spectroscopy of fibrous proteins.

    PubMed

    Millington, Keith R

    2012-09-01

    UV-visible diffuse reflectance (DR) spectra of the fibrous proteins wool and feather keratin, silk fibroin and bovine skin collagen are presented. Natural wool contains much higher levels of visible chromophores across the whole visible range (700-400 nm) than the other proteins and only those above 450 nm are effectively removed by bleaching. Both oxidative and reductive bleaching are inefficient for removing yellow chromophores (450-400 nm absorbers) from wool. The DR spectra of the four UV-absorbing amino acids tryptophan, tyrosine, cystine and phenylalanine were recorded as finely ground powders. In contrast to their UV-visible spectra in aqueous solution where tryptophan and tyrosine are the major UV absorbing species, surprisingly the disulphide chromophore of solid cystine has the strongest UV absorbance measured using the DR remission function F(R)(?). The DR spectra of unpigmented feather and wool keratin appear to be dominated by cystine absorption near 290 nm, whereas silk fibroin appears similar to tyrosine. Because cystine has a flat reflectance spectrum in the visible region from 700 to 400 nm and the powder therefore appears white, cystine absorption does not contribute to the cream colour of wool despite the high concentration of cystine residues near the cuticle surface. The disulphide absorption of solid L: -cystine in the DR spectrum at 290 nm is significantly red shifted by ~40 nm relative to its wavelength in solution, whereas homocystine and lipoic acid showed smaller red shifts of 20 nm. The large red shift observed for cystine and the large difference in intensity of absorption in its UV-visible and DR spectra may be due to differences in the dihedral angle between the crystalline solid and the solvated molecules in solution. PMID:22218994

  3. Application of terahertz time-domain spectroscopy combined with chemometrics to quantitative analysis of imidacloprid in rice samples

    NASA Astrophysics Data System (ADS)

    Chen, Zewei; Zhang, Zhuoyong; Zhu, Ruohua; Xiang, Yuhong; Yang, Yuping; Harrington, Peter B.

    2015-12-01

    Terahertz time-domain spectroscopy (THz-TDS) has been utilized as an effective tool for quantitative analysis of imidacloprid in rice powder samples. Unlike previous studies, our method for sample preparation was mixing imidacloprid with rice powder instead of polyethylene. Then, terahertz time domain transmission spectra of these mixed samples were measured and the absorption coefficient spectra of the samples with frequency range extending from 0.3 to 1.7 THz were obtained. Asymmetric least square (AsLS) method was utilized to correct the slope baselines that are presented in THz absorption coefficient spectra and improve signal-to-noise ratio of THz spectra. Chemometrics methods, including partial least squares (PLS), support vector regression (SVR), interval partial least squares (iPLS), and backward interval partial least squares (biPLS), were used for quantitative model building and prediction. To achieve a reliable and unbiased estimation, bootstrapped Latin partition was chosen as an approach for statistical cross-validation. Results showed that the mean value of root mean square error of prediction (RMSEP) for PLS (0.5%) is smaller than SVR (0.7%), these two methods were based on the whole absorption coefficient spectra. In addition, PLS performed a better performance with a lower RMSEP (0.3%) based on the THz absorption coefficient spectra after AsLS baseline correction. Alternatively, two methods for variable selection, namely iPLS and biPLS, yielded models with improved predictions. Comparing with conventional PLS and SVR, the mean values of RMSEP were 0.4% (iPLS) and 0.3% (biPLS) by selecting the informative frequency ranges. The results demonstrated that an accurate quantitative analysis of imidacloprid in rice powder samples could be achieved by terahertz time-domain transmission spectroscopy combined with chemometrics. Furthermore, these results demonstrate that THz time-domain spectroscopy can be used for quantitative determinations of other pesticides in other agricultural products.

  4. Nonlinear terahertz spectroscopy of electronic and vibrational responses in condensed matter systems

    E-print Network

    Hwang, Harold Young

    2012-01-01

    In this work, I describe experiments utilizing high-field terahertz (THz) pulses to initiate nonlinear responses in several classes of materials. We have developed several methods for interrogating the nonlinear THz response ...

  5. Broadband terahertz time-domain spectroscopy of ferroelectric LiTaO{sub 3}: Phonon-polariton dispersion

    SciTech Connect

    Kojima, Seiji Mori, Tatsuya

    2014-11-05

    The lowest frequency IR active A{sub 1}(z) and E(x) modes of a ferroelectric congruent lithium tantalate crystal were studied by the broadband polarized Terahertz Time-Domain Spectroscopy using the coherent THz radiation from 0.2 to 6.5 THz. The dispersion relations of the real and imaginary parts of a polariton wave vector were determined from the complex extraordinary and ordinary refractive indices for the A{sub 1}(z) and E(x) symmetry phonon-polaritons, respectively. The observed complex dispersion relations of two symmetries are in agreement within the experimental uncertainty with the calculated dispersion curves by the damped harmonic oscillator model.

  6. Terahertz time-domain spectroscopy of atmospheric water vapor from 0.4 to 2.7 THz.

    SciTech Connect

    Allman, Ronald E.; Foltynowicz, Robert J.

    2005-10-01

    We conducted broadband absorption measurements of atmospheric water vapor in the ground state, X {sup 1}A{sub 1} (000), from 0.4 to 2.7 THz with a pressure broadening-limited resolution of 6.2 GHz using pulsed, terahertz time-domain spectroscopy (THz-TDS). We measured a total of seventy-two absorption lines and forty-nine lines were identified as H{sub 2}{sup 16}O resonances. All the H{sub 2}{sup 16}O lines identified were confirmed by comparing their center frequencies to experimental values available in the literature.

  7. Soil phosphorus and potassium estimation by reflectance spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Visible and near infrared (VNIR) diffuse reflectance spectroscopy has potential in site-specific measurement of soil properties. However, previous studies have reported VNIR estimates of plant available soil phosphorus (P) and potassium (K) to be of variable accuracy. In this study, we used a databa...

  8. Analytical study of spacecraft deposition contamination by internal reflection spectroscopy

    NASA Technical Reports Server (NTRS)

    Mookherji, T.

    1972-01-01

    Infrared absorption spectra of ten individual contaminant materials and four binary mixtures of these have been studied using the internal reflection spectroscopy technique. The effect of ultraviolet radiation on these contaminants has also been studied. It has been observed that all siloxanes, silanes, and esters are drastically affected by ultraviolet irradiation. In most cases polymerization and tar formation results.

  9. Inferring sedimentary chlorophyll concentrations with reflectance spectroscopy: a novel approach

    E-print Network

    Wolfe, Alexander P.

    Inferring sedimentary chlorophyll concentrations with reflectance spectroscopy: a novel approach it possible to rapidly and nondestructively assess the chlorophyll content of plants and natural waters. However, to date this approach has not been applied to chlorophyll and chlorophyll deriv- atives preserved

  10. Technical Report: Final project report for Terahertz Spectroscopy of Complex Matter

    SciTech Connect

    R. A. Cheville; D. R. Grischkowsky

    2007-02-08

    This project designed characterization techniques for thin films of complex matter and other materials in the terahertz spectral region extending from approximately 100 GHz to 4000 GHz (4 THz) midway between radio waves and light. THz has traditionally been a difficult region of the spectrum in which to conduct spectroscopic measurements. The “THz gap” arises from the nature of the sources and detectors used in spectroscopy both at the optical (high frequency) side and electronic (low frequency) side of the gap. To deal with the extremely rapid oscillations of the electric field in this frequency region this research project adapted techniques from both the electronics and optics technologies by fabricating microscopic antennas and driving them with short optical pulses. This research technique creates nearly single cycle pulses with extremely broad spectral bandwidth that are able to cover the THz spectral range with a single measurement. The technique of THz time domain spectroscopy (THz-TDS) has seen increasing use and acceptance in laboratories over the past fifteen years. However significant technical challenges remain in order to allow THz-TDS to be applied to measurement of solid materials, particularly thin films and complex matter. This project focused on the development and adaptation of time domain THz measurement techniques to investigate the electronic properties of complex matter in the terahertz frequency region from 25 GHz to beyond 5 THz (<1 inv. cm to >165 inv. cm). This project pursued multiple tracks in adapting THz Time Domain Spectroscopy (THz-TDS) to measurement of complex matter. The first, and most important, is development of a reliable methods to characterize the complex dielectric constant of thin films with high accuracy when the wavelength of the THz radiation is much longer than the thickness of the film. We have pursued several techniques for measurement of thin films. The most promising of these are waveguide spectroscopy and THz interferometry. Since THz spectroscopy measures the changes of the transmitted spectra, any noise on the THz signal contributes to measurement errors. The dynamic range—defined as the RMS noise of the THz detector compared to the peak THz signal—of THz spectroscopy using photoconductive antennas is extremely high, typically over 10,000. However the precision with which spectroscopic data can be measured is limited by the noise on the laser source which is typically 0.1% to 1%. For low values of the sample absorbance and for values of optical thickness less than approximately 0.01, the change in transmission approaches the measurement accuracy. The sample refractive index can be measured with better accuracy since the index causes a temporal shift of the THz pulse by an amount time shift of nd/c where n is the refractive index, d the sample thickness, and c the speed of light. Time shifts of tens of femtoseconds can generally be resolved so that index-thickness values of nd > ten microns can be accurately measured. Waveguide spectroscopy is a way to increase the path length in thin film by several orders of magnitude, and thus have a large interaction length even when the film is much less than a wavelength in thickness. Film thicknesses of 10’s of nm have been measured. THz interferometry cancels out many of the noise sources of THz spectroscopy and can thus result in measurements of films of several hundred nm in thickness and is additionally suitable for optical pump, THz probe spectroscopic techniques. A large amount of additional work was performed in support of the main project direction or to explore promising alternative avenues for research. This report discussed work on the the confinement of low density species for measurement of nanogram or picogram quantities of material. Whispering gallery mode resonators to achieve long path lengths were also investigated as were imaging techniques for sub-wavelength imaging of thin films. The report concludes with a report on investigations of fundamental issues in THz beam propagation and coupli

  11. Apollo 17 Soil Characterization for Reflectance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Taylor, L. A.; Pieters, C.; Patchen, A.; Morris, R. V.; Keller, L. P.; Wentworth, S.; McKay, D. S.

    1999-01-01

    It is the fine fractions that dominate the observed spectral signatures of bulk lunar soil, and the next to the smallest size fractions are the most similar to the overall properties of the bulk soil. Thus, our Lunar Soil Characterization Consortium has concentrated on understanding the inter-relations of compositional, mineralogical, and optical properties of the <45-micron size fraction and its component sizes (20-44 micron, 10-20 micron, and <10 micron size fractions). To be able to generalize our results beyond the particular sample set studied, it is necessary to quantitatively identify the observed effects of space weathering and evaluate the processes involved. For this, it is necessary to know the chemistry of each size fraction, modal abundances of each phase, average compositions of the minerals and glasses, I(sub s)/FeO values, reflectance spectra, and the physical makeup of the individual particles and their patinas. This characterization includes the important dissection of the pyroxene minerals into four separate populations, with data on both modes and average chemical compositions. Armed with such data, it should be possible to effectively isolate spectral effects of space weathering from spectral properties related to mineral and glass chemistry. Four mare soils from the Apollo 17 site were selected for characterization based upon similarities in bulk composition and their contrasting maturities, ranging from immature to submature to mature. The methodology of our characterization has been discussed previously. Results of the Apollo 17 mare soils, outlined herein, are being prepared for publication in MAPS. As shown, with decreasing grain size, the agglutinitic (impact) glass content profoundly increases. This is the most impressive change for the mare soils. In several soils we have examined, there is an over two-fold increase in the agglutinitic glass contents between the 90-150- micron and the 10-20-micron size fractions. Accompanying this increase in agglutinitic glass is a definite decrease in pyroxenes and to lesser extents, the oxides (ilmenite), volcanic glass, and olivine. Unexpectedly, however, the absolute plagioclase abundances stay relatively constant throughout the different grain sizes, although the abundance of plagioclase relative to the mafic minerals increases with decreasing particle size. These soils were chosen for study based upon their similarities in FeO and Ti02 content, allowing for direct comparisons between evolutions of chemistry between size fractions and among different maturities of soils. The bulk chemistry of these fractions was determined by EMP analyses of fused glass beads. In contrast to the systematic variations in bulk chemistry discussed below, the relatively uniform composition of agglutinitic glass with grain size and soil maturity is illustrated. The composition of the bulk fraction of each size fraction becomes more feldspathic with increasing maturity, with the effect being most pronounced for the finest fractions. The composition of the agglutinitic glass, however, is relatively invariant and more feldspathic (i.e., rich in Al2O3) than even the <10-micron fraction. This relation not only strengthens the "fusion of the finest fraction" (F(sup 3)) hypothesis, but also highlights the important role of plagioclase in the formation of agglutinitic glass. With decreasing grain size, FeO, MgO, and TiO2 contents decrease, whereas CaO, Na2O, and Al2O3 (plag components) increase for all soils. These chemical variations would appear to be coupled with the significant increase in agglutinitic glass and decrease in oxide (ilmenite),pyroxene, and volcanic glass. These changes in chemistry do not appear to be due to distinct changes in the compositions of individual phases but to their abundances. Values of I(sub s)/FeO increase with decreasing grain size, even though the bulk FeO contents decrease. That is, the percentage of the total Fe that is present as nanophase Fe(sup O) has increased substantially in the smaller size fraction. Note that the incre

  12. Combination of silicon phase masks with time-domain spectroscopy for single-scan terahertz imaging

    NASA Astrophysics Data System (ADS)

    Jolly, A.; Gokhan, F. S.; Jolly, J.-C.; Hocquet, S.; Chassagne, B.

    2015-09-01

    We demonstrate the effectiveness of silicon phase masks to implement spatially resolved, multispectral imaging capabilities in the range of terahertz frequencies, using a standard setup of basic interest for time-domain spectrometry with a single-cell source and a single-cell detector. Our principle primarily aims at the development of robust and inexpensive systems. It consists of appropriate space-to-time encoding, in order to ensure single-scan triggering and then take advantage of rapid and self-consistent measurements in the two-dimensional space. The process enables very efficient discrimination giving access to a relevant spatial resolution in the analysis of small size, planar assemblies made of inhomogeneous materials. Benchmark results are provided to validate the concept, thanks to prototyping phase masks with 2 × 2 pixels, prior evidencing actual performance limitations in the case of 3 × 3 pixels. Due to the frequency bandwidth of 0.1-1.5 THz in our setup and to the available operating conditions, currently acceptable pixel resolutions lie in the range of 3-4 mm. Numerical modeling by means of finite elements helps to discuss these numbers and to investigate the relevant theoretical issues, figuring the main propagation issues in connection with a sub-picosecond seed pulse throughout various masks. This involves diffraction and trailing edge effects when crossing the mask together with residual, parasitic reflections. Finally, we give a consistent prospective for improved performance, via realistic updates regarding the architecture of the setup and complementary post-processing. Further values for the attainable spatial resolution then range from 5 × 5 to 6 × 6 pixels.

  13. Pancreatic tissue assessment using fluorescence and reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Chandra, Malavika; Heidt, David; Simeone, Diane; McKenna, Barbara; Scheiman, James; Mycek, Mary-Ann

    2007-07-01

    The ability of multi-modal optical spectroscopy to detect signals from pancreatic tissue was demonstrated by studying human pancreatic cancer xenografts in mice and freshly excised human pancreatic tumor tissue. Measured optical spectra and fluorescence decays were correlated with tissue morphological and biochemical properties. The measured spectral features and decay times correlated well with expected pathological differences in normal, pancreatitis and adenocarcinoma tissue states. The observed differences between the fluorescence and reflectance properties of normal, pancreatitis and adenocarcinoma tissue indicate a possible application of multi-modal optical spectroscopy to differentiating between the three tissue classifications.

  14. Optical Fiber Sensing Based on Reflection Laser Spectroscopy

    PubMed Central

    Gagliardi, Gianluca; Salza, Mario; Ferraro, Pietro; Chehura, Edmond; Tatam, Ralph P.; Gangopadhyay, Tarun K.; Ballard, Nicholas; Paz-Soldan, Daniel; Barnes, Jack A.; Loock, Hans-Peter; Lam, Timothy T.-Y.; Chow, Jong H.; De Natale, Paolo

    2010-01-01

    An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given. Fiber Bragg-gratings (FBGs) and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking techniques. Silica fiber-ring cavities are used for chemical sensing based on evanescent-wave spectroscopy. Various arrangements for signal recovery and noise reduction, as an extension of most typical spectroscopic techniques, are illustrated and results on detection performances are presented. PMID:22294902

  15. Gas-Phase Terahertz Spectroscopy and the Study of Complex Interstellar Chemistry

    NASA Astrophysics Data System (ADS)

    Braakman, Rogier

    2010-11-01

    Terahertz spectroscopy holds great promise in the advancement of the field of astrochemistry. The sensitive observation of interstellar THz radiation is expected to lower detection limits and allow the study of larger and more complex species than is currently possible at millimeter wavelengths, which will place further constraints on chemical models and permit a direct comparison to the organic compounds seen in carbonaceous chondrites. With the successful recent launch of the Herschel Space Telescope, which will give high-fidelity access to interstellar THz radiation for the first time, and the completion of the Atacama Large Millimeter Array (ALMA) by 2013, the THz astronomy era is upon us. Unfortunately, laboratory THz spectroscopy presents significant challenges and will be soon be lagging behind the newly available observational platforms. Technologies to extend the capabilities of high-resolution spectroscopic systems into the THz domain are actively being pursued on many fronts, but affordable systems that are broadly tunable, sensitive and achieve the necessary resolution are not yet available. The work in this thesis should therefore be seen as part of the effort in the transition from centimeter-/millimeter-wave to THz spectroscopy that is currently taking place in the astrochemistry community. As part of this thesis, observational searches for the complex organics hydroxyacetone (CH3COCH2OH), 2-cyanoethanol (OHCH 2CH2CN) and methoxyacetonitrile (CH3OCH2 CN) were attempted at millimeter wavelengths. The unsuccessful nature of these searches highlight the current limits of studying interstellar chemistry using pure rotational spectroscopy. The characterization of the laboratory spectra of these molecules is nonetheless important as it will aid in the assignment and description of the rotational substructure and band shapes of their THz torsional spectra, features that may allow their interstellar detection; and this thesis presents methods by which such complex spectra may be rapidly and efficiently collected and fit using automated spectrometers and modern software tools. The description of the spectrum of hydroxyacetone is furthermore of interest due to the presence of the very low barrier to internal rotation in this molecule. Many interstellar compounds, both known and potential future targets, have functional groups capable of internal rotation in their structure; and so the effort in understanding the complex effects of the low barrier rotor in this case will benefit the general effort to further understand internal rotation. In searching for new interstellar molecules, both at millimeter wavelengths and at higher THz frequencies, characterization of the complete spectra of known interstellar molecules is of great importance to allow substraction of their contribution to observational spectra. In this thesis, the ground-state rotational spectrum of methanol, the most important "interstellar weed", is catalogued and described in detail through most of the THz region that will be accessible with Herschel and ALMA. Lastly, as part of the effort to increase the sensitivity of THz spectrometers, the use of Fabry-Perot cavities at these frequencies is explored. Such resonant cavities hold the potential to significantly increase the possible path lengths in spectroscopic system and to allow novel and sensitive detection techniques. Optimal configurations and the limits on achievable path lengths and Q-factors of such cavities are discussed, as are the possible extensions of Fourier Transform MicroWave (FT-MW) techniques to THz frequencies.

  16. Attenuated total reflectance spectroscopy with chirped-pulse upconversion.

    PubMed

    Shirai, Hideto; Duchesne, Constance; Furutani, Yuji; Fuji, Takao

    2014-12-01

    Chirped-pulse upconversion technique has been applied to attenuated total reflectance (ATR) infrared spectroscopy. An extremely broadband infrared pulse was sent to an ATR diamond prism and the reflected pulse was converted to the visible by using four-wave mixing in krypton gas. Absorption spectra of liquids in the range from 200 to 5500 cm(-1) were measured with a visible spectrometer on a single-shot basis. The system was applied to observe the dynamics of exchanging process of two solvents, water and acetone, which give clear vibrational spectral contrast. We observed that the exchange was finished within ? 10 ms. PMID:25606893

  17. Studies of adipocere using attenuated total reflectance infrared spectroscopy.

    PubMed

    Stuart, B H; Craft, L; Forbes, S L; Dent, B B

    2005-09-01

    Attenuated total reflectance (ATR) infrared spectroscopy has been used to characterize pig adipocere formation. The compositions of adipocere samples obtained by burial of pig adipose tissue in soil and in mock coffins were compared with that of the original adipose tissue using this technique. The ART spectra show that bands resulting from triglyceride and fatty acid C=O stretching are particularly useful for monitoring the changes in adipocere formation. The technique is able to be used to investigate how the burial environment affects the rate of adipocere formation and supports the results of earlier gas chromatograph and mass spectrometer and diffuse reflectance infrared studies. ATR spectroscopy has also been demonstrated to have the advantage of convenient sample preparation. PMID:25870046

  18. Submillimeter and millimeter reflection spectroscopy of vacuum compatible absorbing materials

    NASA Astrophysics Data System (ADS)

    Fischer, J.; Benson, J.; Boyd, D. A.

    1983-07-01

    We report on Fourier transform reflection spectroscopy of materials that are candidates for use as absorbers in beam dumps and blackbody calibration sources for submillimeter and millimeter wave plasma diagnostics. The materials have been chosen for vacuum compatibility and resilience to plasma bombardment. Data are presented at 4 and 28 cm-1 on the materials: Avco hot-pressed SiC, Dielectric Communications SiC 9030, Avco hot-pressed B4C, and Corning Macor, a machinable glass ceramic.

  19. Polarization orientation dependence of the far infrared spectra of oriented single crystals of 1,3,5,-trinitro-s-triazine (RDX) using terahertz-time-domain spectroscopy

    SciTech Connect

    Whitley, Von H; Hooks, Dan E; Ramos, Kyle J; O' Hara, John F; Azad, A K; Taylor, A J; Barber, J; Averitt, R D

    2008-01-01

    The far infrared spectra of (100), (010), and (001)-oriented RDX single crystals were measured as the crystal was rotated about the axis perpendicular to the polarization plane of the incident radiation. Absorption measurements were taken at temperatures of both 20 K and 295 K for all rotations using terahertz time-domain spectroscopy. A number of discrete absorptions were found ranging from 10-100 cm(-1) (0.3-3 THz). The absorptions are highly dependent on the orientation of the terahertz polarization with respect to crystallographic axes.

  20. Efficient generation of charges via below-gap photoexcitation of polymer-fullerene blend films investigated by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Parkinson, P.; Lloyd-Hughes, J.; Johnston, M. B.; Herz, L. M.

    2008-09-01

    Using optical-pump terahertz-probe spectroscopy, we have investigated the time-resolved conductivity dynamics of photoexcited polymer-fullerene bulk heterojunction blends for two model polymers: poly[3-hexylthiophene] (P3HT) and poly[2-methoxy-5-( 3,7 -dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) blended with [6,6]-phenyl- C61 butyric acid methyl ester (PCBM). The observed terahertz-frequency conductivity is characteristic of dispersive charge transport for photoexcitation both at the ?-?? absorption peak (560 nm for P3HT) and significantly below it (800 nm). The photoconductivity at 800 nm is unexpectedly high, which we attribute to the presence of a charge-transfer complex. We report the excitation-fluence dependence of the photoconductivity over more than four orders of magnitude, obtained by utilizing a terahertz spectrometer based upon on either a laser oscillator or an amplifier source. The time-averaged photoconductivity of the P3HT:PCBM blend is over 20 times larger than that of P3HT, indicating that long-lived hole polarons are responsible for the high photovoltaic efficiency of polymer:fullerene blends. At early times (˜ps) the linear dependence of photoconductivity upon fluence indicates that interfacial charge transfer dominates as an exciton decay pathway, generating charges with mobility of at least ˜0.1cm2V-1s-1 . At later times, a sublinear relationship shows that carrier-carrier recombination effects influence the conductivity on a longer time scale (>1?s) with a bimolecular charge annihilation constant for the blends that is approximately two to three orders of magnitude smaller than that typical for neat polymer films.

  1. Reflectance spectroscopy for noninvasive evaluation of hair follicle stage

    NASA Astrophysics Data System (ADS)

    Liu, Caihua; Guan, Yue; Wang, Jianru; Zhong, Xiewei; Liu, Xiuli; Zhu, Dan

    2015-05-01

    Hair follicle offers an excellent model for systems biology and regenerative medicine. So far, the stages of hair follicle growth have been evaluated by histological examination. In this work, a noninvasive spectroscopy was proposed by measuring the diffuse reflectance of mouse skin and analyzing the melanin value. Results show that the skin diffuse reflectance was relatively high when hair follicles were at the telogen stage and at the beginning of the anagen stage, and decreased with the progression of the anagen stage. When the hair follicle entered into the catagen stage, the diffuse reflectance gradually increased. The changes in the melanin content of skin had contrary dynamics. Substages of the hair follicle cycle could be distinguished by comparing the changes in melanin value with the histological examination. This study provided a new method for noninvasive evaluation of the hair follicle stage, and should be valuable for basic and therapeutic investigations on hair regeneration.

  2. Reflective mesoscopic spectroscopy for noninvasive detection of reflective index alternations at nano-scale

    NASA Astrophysics Data System (ADS)

    Tao, Yuanhao; Ding, Zhihua

    2011-01-01

    Cancer has been one of the most serious threats to human life. However, there is no substantial improvement in overall treatment of cancer patients. One of the key reasons is the unavailability of convenient method to detect cellular alterations in ultra-early stage of carcinogenesis processes, where genetic aberrations at nano-scale have not yet resulted in histological changes. In this paper, we described an optical method based on reflective mesoscopic spectroscopy for ultra-early cancer detection. According to mesoscopic light transport theory, photons propagating in one dimension (1D) within a weakly disordered medium have the non-self-averaging effect. Reflected signal after 1D propagating is sensitive to any length scale of refractive index fluctuations due to multiple interferences of light waves travelling along 1D trajectory. The principle of mesoscopic spectroscopy for perceiving reflective index fluctuations at length scale of nanometers is introduced. A system for the measurement of reflective mesoscopic spectroscopy based on spatial-incoherence broadband source and spectrometer is established. Simulations on light propagation in cell-emulating model with controlled refractive index distribution are done by finite-difference time-domain (FDTD) approach.

  3. Probing the conformational changes of proteins in liquid water by dielectric terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Charkhesht, Ali; George, Deepu; Vinh, Nguyen

    2015-03-01

    Proteins solvated in their biological milieu are expected to exhibit strong absorption in the terahertz range that contain information on their global and sub-global collective vibrational modes (conformational dynamics) and global dynamical correlations among solvent water molecules and proteins. Measurements in this region, however, are challenging due to the strong absorption of water and often severe interference artifacts. In response, we have developed a highly sensitive dielectric terahertz frequency-domain system and a terahertz-time domain system for probing the collective dynamics in aqueous solution. Using these techniques we explore the complex dielectric response from 5 GHz up to 3 THz that directly probes such questions as the hydration level around proteins and the large scale vibrational modes of biological polymers. We make a direct comparison to the existing molecular dynamic simulations and normal mode calculations and investigate the dependence of the terahertz frequency dynamics on protein concentration. Our measurements shed light on the macromolecular motions in a biologically relevant water environment.

  4. Ultrafast conductivity in a low-band-gap polyphenylene and fullerene blend studied by terahertz spectroscopy

    E-print Network

    Ku?el, Petr

    Ultrafast conductivity in a low-band-gap polyphenylene and fullerene blend studied by terahertz-band-gap polyphenylene copolymer and fullerene derivative. The optical excitation pulse generates free holes delocalized in these systems. The pri- mary excitation in polymer/fullerene bulk heterojunctions is an exciton on the polymer

  5. Collective Dynamics of Lysozyme in Water: Terahertz Absorption Spectroscopy and Comparison with Theory

    E-print Network

    Xu, Jing

    confirm the existence of dense, overlapping normal modes in the terahertz frequency range. Our observed reported regarding the low-frequency normal modes of the monomeric protein hen egg white lysozyme, inviting Materials and Solution Preparation. For this study, we employed chicken hen egg white lysozyme (Sigma, St

  6. Terahertz spectroscopy with a holographic Fourier transform spectrometer plus array detector using coherent synchrotron radiation

    SciTech Connect

    Nikolay I. Agladz, John Klopf, Gwyn Williams, Albert J. Sievers

    2010-06-01

    By use of coherent terahertz synchrotron radiation, we experimentally tested a holographic Fourier transform spectrometer coupled to an array detector to determine its viability as a spectral device. Somewhat surprisingly, the overall performance strongly depends on the absorptivity of the birefringent lithium tantalate pixels in the array detector.

  7. EXPERIMENT #3 REFLECTANCE SPECTROSCOPY We will use the reflectance attachment and fiber optics OceanOptics spectrophotometer to

    E-print Network

    Nazarenko, Alexander

    EXPERIMENT #3 REFLECTANCE SPECTROSCOPY We will use the reflectance attachment and fiber optics OceanOptics spectrophotometer to measure the reflectance spectrum of several paint samples in the special optically flat-bottomed cell so that the bottom is completely covered. Scan the reflectance

  8. Terahertz tomography using quantum-cascade lasers

    E-print Network

    Kao, Tsung-Yu

    The interfaces of a dielectric sample are resolved in reflection geometry using light from a frequency agile array of terahertz quantum-cascade lasers. The terahertz source is a 10-element linear array of third-order ...

  9. Nondestructive monitoring of aircraft composites using terahertz radiation

    NASA Astrophysics Data System (ADS)

    Balbekin, Nikolay S.; Novoselov, Evgenii V.; Pavlov, Pavel V.; Bespalov, Victor G.; Petrov, Nikolay V.

    2015-03-01

    In this paper we consider using the terahertz (THz) time domain spectroscopy (TDS) for non destructive testing and determining the chemical composition of the vanes and rotor-blade spars. A versatile terahertz spectrometer for reflection and transmission has been used for experiments. We consider the features of measured terahertz signal in temporal and spectral domains during propagation through and reflecting from various defects in investigated objects, such as voids and foliation. We discuss requirements are applicable to the setup and are necessary to produce an image of these defects, such as signal-to-noise ratio and a method for registration THz radiation. Obtained results indicated the prospects of the THz TDS method for the inspection of defects and determination of the particularities of chemical composition of aircraft parts.

  10. Investigation of coherent acoustic phonons in terahertz quantum cascade laser structures using femtosecond pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Bruchhausen, Axel; Lloyd-Hughes, James; Hettich, Mike; Gebs, Raphael; Grossmann, Martin; Ristow, Oliver; Bartels, Albrecht; Fischer, Milan; Beck, Mattias; Scalari, Giacomo; Faist, Jérôme; Rudra, Alok; Gallo, Pascal; Kapon, Eli; Dekorsy, Thomas

    2012-08-01

    The dynamics of acoustic vibrations in terahertz quantum cascade laser structures (THz-QCLs) is studied by means of femtosecond pump-probe spectroscopy. The phonon modes are characterized by the folding of the acoustic dispersion into an effective reduced Brillouin zone. An accurate identification of this dispersion allows the sample structure and periodicity to be determined with high precision on the order of 0.1%. By temperature tuning the energy of the electronic levels of the system and performing wavelength dependent measurements, we are able to study the impulsive resonant generation and detection of coherent acoustic phonon modes. These results are supported by simulations of the electronic system that well explain the experimental observations. The effects of interface (IF) roughness on coherent acoustic phonon spectra are clearly observed for equal nominal THz-QCL structures but with different interface qualities.

  11. New insights into the diverse electronic phases of a novel vanadium dioxide polymorph: a terahertz spectroscopy study.

    PubMed

    Lourembam, James; Srivastava, Amar; La-o-vorakiat, Chan; Rotella, H; Venkatesan, T; Chia, Elbert E M

    2015-01-01

    A remarkable feature of vanadium dioxide is that it can be synthesized in a number of polymorphs. The conductivity mechanism in the metastable layered polymorph VO2(B) thin films has been investigated by terahertz time-domain spectroscopy (THz-TDS). In VO2(B), a critical temperature of 240 K marks the appearance of a non-zero Drude term in the observed complex conductivity, indicating the evolution from a pure insulating state towards a metallic state. In contrast, the THz conductivity of the well-known VO2(M1) is well fitted only by a modification of the Drude model to include backscattering. We also identified two different THz conductivity regimes separated by temperature in these two polymorphs. The electronic phase diagram is constructed, revealing that the width and onset of the metal-insulator transition in the B phase develop differently from the M1 phase. PMID:25777320

  12. Investigation of pharmaceutical drugs and caffeine-containing foods using Fourier and terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    KaraliÅ«nas, Mindaugas; Venckevi?ius, Rimvydas; Kašalynas, Irmantas; Puc, Uroš; Abina, Andreja; Jegli?, Anton; Zidanšek, Aleksander; Valušis, Gintaras

    2015-08-01

    Several pharmaceutical drugs, such as alprazolam, ibuprofen, acetaminophen, activated carbon and others, and caffeine-containing foods were tested using terahertz (THz) time domain spectroscopy in the range from 0.3 to 2 THz. The dry powder of pharmaceutical drugs was mixed with HDPE and pressed into the pellets using hydraulic press. The coffee grounds were also pressed into the pellets after ball-milling and mixing with HDPE. The caffeine containing liquid foods were dried out on the paper strips of various stacking. Experiments allow one to determine characteristic spectral signatures of the investigated substances within THz range caused by active pharmaceutical ingredients, like in the case of caffeine, as well as supporting pharmaceutical ingredients. Spectroscopic THz imaging approach is considered as a possible option to identify packaged pharmaceutical drugs. The caffeine spectral features in the tested caffeine containing foods are difficult to observed due to the low caffeine concentration and complex caffeine chemical surrounding.

  13. Focus: Phase-resolved nonlinear terahertz spectroscopy--From charge dynamics in solids to molecular excitations in liquids.

    PubMed

    Elsaesser, Thomas; Reimann, Klaus; Woerner, Michael

    2015-06-01

    Intense terahertz (THz) electric field transients with amplitudes up to several megavolts/centimeter and novel multidimensional techniques are the key ingredients of nonlinear THz spectroscopy, a new area of basic research. Both nonlinear light-matter interactions including the non-perturbative regime and THz driven charge transport give new insight into the character and dynamics of low-energy excitations of condensed matter and into quantum kinetic phenomena. This article provides an overview of recent progress in this field, combining an account of technological developments with selected prototype results for liquids and solids. The potential of nonlinear THz methods for future studies of low-frequency excitations of condensed-phase molecular systems is discussed as well. PMID:26049419

  14. New Insights into the Diverse Electronic Phases of a Novel Vanadium Dioxide Polymorph: A Terahertz Spectroscopy Study

    PubMed Central

    Lourembam, James; Srivastava, Amar; La-o-vorakiat, Chan; Rotella, H.; Venkatesan, T.; Chia, Elbert E. M.

    2015-01-01

    A remarkable feature of vanadium dioxide is that it can be synthesized in a number of polymorphs. The conductivity mechanism in the metastable layered polymorph VO2(B) thin films has been investigated by terahertz time-domain spectroscopy (THz-TDS). In VO2(B), a critical temperature of 240?K marks the appearance of a non-zero Drude term in the observed complex conductivity, indicating the evolution from a pure insulating state towards a metallic state. In contrast, the THz conductivity of the well-known VO2(M1) is well fitted only by a modification of the Drude model to include backscattering. We also identified two different THz conductivity regimes separated by temperature in these two polymorphs. The electronic phase diagram is constructed, revealing that the width and onset of the metal-insulator transition in the B phase develop differently from the M1 phase. PMID:25777320

  15. Softening of infrared-active mode of perovskite BaZrO3 proved by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Helal, M. A.; Mori, T.; Kojima, S.

    2015-05-01

    The low-frequency infrared-active optical modes were studied in a barium zirconate, BaZrO3, single crystal with the perovskite structure using terahertz (THz) time-domain spectroscopy (TDS). The real and imaginary parts of the dielectric constants were accurately determined in the frequency range between 0.2 and 2.7 THz. Upon cooling from room temperature to 8 K, the lowest-frequency TO1 mode at 2.32 THz showed a pronounced softening to 1.94 THz. The real part of the dielectric constant at 0.5 THz determined by THz-TDS obeys Barrett's relation, and the existence of a plateau confirms that the quantum effects lead to saturation of the soft mode frequencies of the TO1 and TO2 modes below ?20 K. This is reminiscent of incipient ferroelectrics with the perovskite structure such as CaTiO3.

  16. Book Review published by Analysis, 1997: Reflection Electron Microscopy and Spectroscopy for Surface Analysis, By Zhong Lin Wang

    E-print Network

    Wang, Zhong L.

    Book Review published by Analysis, 1997: Reflection Electron Microscopy and Spectroscopy. These are RHEED (reflection high energy electron diffraction), REM (reflection electron microscopy), SREM. There are many applications of reflection electron microscopy and spectroscopy scattered throughout the book

  17. Pancreatic tumor margin detection by oblique incidence diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Garcia-Uribe, Alejandro; Chang, Cheng-Chung; Zou, Jun; Banerjee, Bhaskar; Kuczynski, John; Wang, Lihong V.

    2011-03-01

    In surgical treatment of pancreatic cancers, the effectiveness of the procedures largely depends on the ability to completely and precisely remove the malignant tumors. We present the ex-vivo use of oblique incidence diffuse reflectance spectroscopy (OIRDS) to detect and differentiate normal from neoplastic tissue. An OIRDS probe has been constructed to provide scattering and absorption information of the pancreatic tissue. To reveal the physiological origin of the difference in these optical signatures, the optical scattering coefficients were extracted along the pancreatic duct with 1-cm spacing. Experimental results show that OIDRS was able to successfully determinate the tumor margins based on the higher optical scattering on malignant tissue.

  18. Coherent broadband continuous-wave terahertz spectroscopy on solid-state samples

    NASA Astrophysics Data System (ADS)

    Roggenbuck, A.; Schmitz, H.; Deninger, A.; Cámara Mayorga, I.; Hemberger, J.; Güsten, R.; Grüninger, M.

    2010-04-01

    Measuring the complex dielectric function ?(?)=?1+i?2 of solid-state samples in the terahertz frequency range with high spectral resolution remains difficult. Using a continuous-wave terahertz spectrometer based on photomixing in the frequency range from 60 GHz to 1.8 THz, we obtain the most precise data of ?(?) reported to date for the well-studied example of ?-lactose monohydrate. We are able to determine both ?1 and ?2 due to coherent detection and show that the results are Kramers-Kronig consistent. Our analysis is based on scanning an interference pattern in frequency and relies on the high spectral resolution in the MHz range. This enables us to avoid mechanically moving parts such as a delay stage. Moreover, we show that the optical data can be used to determine both ?(?) and the sample thickness d independently.

  19. Analysis of remote reflection spectroscopy to monitor plant health

    NASA Astrophysics Data System (ADS)

    Woodhouse, R.; Heeb, M.; Berry, W.; Hoshizaki, T.; Wood, M.

    1994-11-01

    Remote non-contact reflection spectroscopy is examined as a method for detecting stress in Controlled Ecological Life Support System CELSS type crops. Lettuce (Latuca Sativa L. cv. Waldmans Green) and wheat (Triticum Aestivum L. cv. Yecora Rojo) were grown hydroponically. Copper and zinc treatments provided toxic conditions. Nitrogen, phosphorous, and potassium treatments were used for deficiency conditions. Water stress was also induced in test plants. Reflectance spectra were obtained in the visible and near infrared (400nm to 2600nm) wavebands. Numerous effects of stress conditions can be observed in the collected spectra and this technique appears to have promise as a remote monitor of plant health, but significant research remains to be conducted to realize the promise.

  20. [Evaluation of walnut by terahertz nondestructive technology].

    PubMed

    Qi, Shu-Ye; Zhang, Zhen-Wei; Zhao, Kun; Han, Dong-Hai

    2012-12-01

    The deterioration and shell thickness of walnut were studied using the terahertz time domain spectroscopy. Firstly, the THz spectra of moth-eaten, moldy and normal walnuts were compared, and the bad walnuts were properly rejected due to the differences of absorption peaks. Secondly, the transmission-type and reflection-type terahertz time domain spectroscopy system was used simultaneously, and a new formula to calculate shell thickness of walnut was built in the THz system. Then the authors measured the shell thickness based on the detectable refractive index of walnut, and the relative error was 3.7%. Consequently, the quality of walnut was evaluated nondestructively according to physical and chemical indicators from walnut THz spectra respectively. PMID:23427574

  1. Screening mail for powders using terahertz technology

    NASA Astrophysics Data System (ADS)

    Kemp, Mike

    2011-11-01

    Following the 2001 Anthrax letter attacks in the USA, there has been a continuing interest in techniques that can detect or identify so-called 'white powder' concealed in envelopes. Electromagnetic waves (wavelengths 100-500 ?m) in the terahertz frequency range penetrate paper and have short enough wavelengths to provide good resolution images; some materials also have spectroscopic signatures in the terahertz region. We report on an experimental study into the use of terahertz imaging and spectroscopy for mail screening. Spectroscopic signatures of target powders were measured and, using a specially designed test rig, a number of imaging methods based on reflection, transmission and scattering were investigated. It was found that, contrary to some previous reports, bacterial spores do not appear to have any strong spectroscopic signatures which would enable them to be identified. Imaging techniques based on reflection imaging and scattering are ineffective in this application, due to the similarities in optical properties between powders of interest and paper. However, transmission imaging using time-of-flight of terahertz pulses was found to be a very simple and sensitive method of detecting small quantities (25 mg) of powder, even in quite thick envelopes. An initial feasibility study indicates that this method could be used as the basis of a practical mail screening system.

  2. Inspection of mechanical and electrical properties of silicon wafers using terahertz tomography and spectroscopy

    NASA Astrophysics Data System (ADS)

    Arnold, Thomas; Muehleisen, Wolfgang; Schicker, Johannes; Hirschl, Christina

    2015-05-01

    Two different THz applications in the semiconductor industry were explored and validated against established reference measurement techniques and simulations. The first application investigated the possibility of measuring mechanical deformation behaviour of silicon wafers. Time-domain THz tomography mapping scans were carried out to measure wafer thickness and flatness, both in the native state and under different external mechanical loads. These measurements were carried out for a variety of wafers, and the ensuing deformation maps used to validate newly developed numerical simulation models for wafer deformation, and vice versa. In the second part of this paper, carrier dynamics of optically injected charges were investigated by THz spectroscopy. THz pump/probe measurements were carried out in transmission and reflection arrangements on silicon wafers illuminated by a metal halide light source. The light source generates free charge carriers in the semiconductor material that affect the transmission and reflection properties of the semiconductor material. The results of the THz measurements are compared to established standard techniques, like microwave-detected photo-conductance decay (MWPCD) or quasi-steady-state photo conductance (QSSPC) measurements. The defective areas identified with the THz measurements are in good agreement with the defective areas identified by the reference methods. A common benefit of time-domain THz measurements is that the wafer thickness, which is an important measure for the interaction volume of the THz radiation with the semiconductor material, can be calculated from the time- domain signals. The results indicate that THz spectroscopy and imaging can be valuable tools for defect analysis and quality control of silicon wafers, especially since the measurement is fully contact-free and can determine mechanical and electrical properties within a single modality.

  3. An automatic detection software for differential reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Yuksel, Seniha Esen; Dubroca, Thierry; Hummel, Rolf E.; Gader, Paul D.

    2012-06-01

    Recent terrorist attacks have sprung a need for a large scale explosive detector. Our group has developed differential reflection spectroscopy which can detect explosive residue on surfaces such as parcel, cargo and luggage. In short, broad band ultra-violet and visible light is shone onto a material (such as a parcel) moving on a conveyor belt. Upon reflection off the surface, the light intensity is recorded with a spectrograph (spectrometer in combination with a CCD camera). This reflected light intensity is then subtracted and normalized with the next data point collected, resulting in differential reflection spectra in the 200-500 nm range. Explosives show spectral finger-prints at specific wavelengths, for example, the spectrum of 2,4,6, trinitrotoluene (TNT) shows an absorption edge at 420 nm. Additionally, we have developed an automated software which detects the characteristic features of explosives. One of the biggest challenges for the algorithm is to reach a practical limit of detection. In this study, we introduce our automatic detection software which is a combination of principal component analysis and support vector machines. Finally we present the sensitivity and selectivity response of our algorithm as a function of the amount of explosive detected on a given surface.

  4. Assessing human skin with diffuse reflectance spectroscopy and colorimetry

    NASA Astrophysics Data System (ADS)

    Seo, InSeok; Liu, Yang; Bargo, Paulo R.; Kollias, Nikiforos

    2012-02-01

    Colorimetry has been used as an objective measure of perceived skin color by human eye to document and score physiological responses of the skin from external insults. CIE color space values (L*, a* and b*) are the most commonly used parameters to correlate visually perceived color attributes such as L* for pigment, a* for erythema, and b* for sallowness of the skin. In this study, we investigated the relation of Lab color scale to the amount of major skin chromophores (oxy-, deoxyhemoglobin and melanin) calculated from diffuse reflectance spectroscopy. Thirty two healthy human subjects with ages from 20 to 70 years old, skin types I-VI, were recruited for the study. DRS and colorimetry measurements were taken from the left and right cheeks, and on the right upper inner arm. The melanin content calculated from 630-700 nm range of DRS measurements was shown to correlate with the lightness of skin (L*) for most skin types. For subjects with medium-to-light complexion, melanin measured at the blue part spectrum and hemoglobin interfered on the relation of lightness of the skin color to the melanin content. The sallowness of the skin that is quantified by the melanin contribution at the blue part spectrum of DRS was found to be related to b* scale. This study demonstrates the importance of documenting skin color by assessing individual skin chromophores with diffuse reflectance spectroscopy, in comparison to colorimetry assessment.

  5. Autofluorescence and diffuse reflectance patterns in cervical spectroscopy

    NASA Astrophysics Data System (ADS)

    Marin, Nena Maribel

    Fluorescence and diffuse reflectance spectroscopy are two new optical technologies, which have shown promise to aid in the real time, non-invasive identification of cancers and precancers. Spectral patterns carry a fingerprint of scattering, absorption and fluorescence properties in tissue. Scattering, absorption and fluorescence in tissue are directly affected by biological features that are diagnostically significant, such as nuclear size, micro-vessel density, volume fraction of collagen fibers, tissue oxygenation and cell metabolism. Thus, analysis of spectral patterns can unlock a wealth of information directly related with the onset and progression of disease. Data from a Phase II clinical trial to assess the technical efficacy of fluorescence and diffuse reflectance spectroscopy acquired from 850 women at three clinical locations with two research grade optical devices is calibrated and analyzed. Tools to process and standardize spectra so that data from multiple spectrometers can be combined and analyzed are presented. Methodologies for calibration and quality assurance of optical systems are established to simplify design issues and ensure validity of data for future clinical trials. Empirically based algorithms, using multivariate statistical approaches are applied to spectra and evaluated as a clinical diagnostic tool. Physically based algorithms, using mathematical models of light propagation in tissue are presented. The presented mathematical model combines a diffusion theory in P3 approximation reflectance model and a 2-layer fluorescence model using exponential attenuation and diffusion theory. The resulting adjoint fluorescence and reflectance model extracts twelve optical properties characterizing fluorescence efficiency of cervical epithelium and stroma fluorophores, stromal hemoglobin and collagen absorption, oxygen saturation, and stromal scattering strength and shape. Validations with Monte Carlo simulations show that adjoint model extracted optical properties of the epithelium and the stroma can be estimated accurately. Adjoint model is applied to 926 clinical measurements from 503 patients. Mean values of extracted optical properties have demonstrated to characterize the biological changes associated with dysplastic progression. Finally, penalized logistic regression algorithms are applied to discriminate dysplastic stages in tissue based on extracted optical features. This work provides understandable and interpretable information regarding predictive and generalization ability of optical spectroscopy in neoplastic changes using a minimum subset of optical measurements. Ultimately these methodologies would facilitate the transfer of these optical technologies into clinical practice.

  6. Surface-enhanced, multi-dimensional attenuated total reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Kraack, Jan Philip; Lotti, Davide; Hamm, Peter

    2015-08-01

    Ultrafast two-dimensional infrared spectroscopy (2D IR) spectroscopy is performed in attenuated total reflectance (ATR) geometry with the Kretschmann configuration in order to measure femtosecond to picosecond dynamics of self-assembled monolayers on gold-coated solid-liquid interfaces. In the monolayers low-absorbing (<200 M-1 cm-1) nitrile functional groups are used as local vibrational probes to monitor vibrational relaxation and spectral diffusion in dependence of different environments of the nitrile group. By comparing spectral diffusion dynamics of the vibrational probe in bulk solution and in the monolayer we find that the dynamics are slowed down by more than a factor of 20 upon immobilization of the sample. Moreover, spectral diffusion dynamics are affected by the local environment within the monolayers as evidenced by 2D ATR IR experiments on mixed monolayers with different aliphatic and aromatic co-adsorbates. The results are interpreted in terms of absent excitation energy-transfer as well as solvation dynamics around the nitrile vibrational probe. Our results demonstrate that 2D ATR IR spectroscopy offers the possibility to obtain ultrafast dynamics from sub-monolayer coverages of even low-absorbing vibrational probes such as nitrile functional groups.

  7. Determination of carrier concentration dependent electron effective mass and scattering time of n-ZnO thin film by terahertz time domain spectroscopy

    SciTech Connect

    Tang, J.; Tay, C. B.; Deng, L. Y.; Zhang, X. H.; Chai, J. W.; Qin, H.; Liu, H. W.; Venkatesan, T.; Chua, S. J.

    2014-01-21

    We demonstrated a novel and widely accessible method for determining the electron effective mass and scattering time of ZnO films with different carrier concentrations by combining terahertz time-domain spectroscopy with Hall measurement. The terahertz time domain spectroscopy (THz-TDS) transmission spectra (0.1–2THz) were well described by Drude model. It is found that electron effective mass varied from 0.23m{sub 0} to 0.26m{sub 0} as the electron concentration changes from 5.9?×?10{sup 17}?cm{sup ?3} to 4.0?×?10{sup 19}?cm{sup ?3}. The carrier concentration dependent characteristic is ascribed to the non-parabolicity of conduction band. Free carrier localization mechanism explained the discrepancy in mobilities obtained from THz-TDS and Hall measurements.

  8. Near-Infrared Reflectance Spectroscopy is a Rapid, Cost-Effective Predictor

    E-print Network

    Marsh, Helene

    relationship between the spectrum of near-infrared light reflected by a sample and a set of standard laboratoryNear-Infrared Reflectance Spectroscopy is a Rapid, Cost-Effective Predictor of Seagrass Nutrients + Business Media, Inc. 2006 Abstract Near-infrared reflectance spectroscopy was used to analyze nutrient com

  9. Effect of in-material losses on terahertz absorption, transmission, and reflection in photonic crystals made of polar dielectrics

    NASA Astrophysics Data System (ADS)

    Serebryannikov, Andriy E.; Nojima, S.; Alici, K. B.; Ozbay, Ekmel

    2015-10-01

    The effect of the material absorption factor on terahertz absorption (A), transmittance (T), and reflectance (R) for slabs of PhC that comprise rods made of GaAs, a polar dielectric, is studied. The main goal was to illustrate how critical a choice of the absorption factor for simulations is and to indicate the importance of the possible modification of the absorption ability by using either active or lossy impurities. The spectra of A, T, and R are strongly sensitive to the location of the polaritonic gap with respect to the photonic pass and stop bands connected with periodicity that enables the efficient combination of the effects of material and structural parameters. It will be shown that the spectra can strongly depend on the utilized value of the material absorption factor. In particular, both narrow and wide absorption bands may appear owing to a variation of the material parameters with a frequency in the vicinity of the polaritonic gap. The latter are often achieved at wideband suppression of transmission, so that an ultra-wide stop band can appear as a result of adjustment of the stop bands having different origin. The results obtained at simultaneous variation of the absorption factor and frequency, and angle of incidence and frequency, indicate the possibility of the existence of wide ranges of tolerance, in which the basic features do remain. This allows for mitigating the accuracy requirements for the absorption factor in simulations and promises the efficient absorption of nonmonochromatic waves and beams with a wide angular spectrum. Suppression of narrowband effects in transmission is demonstrated at rather large values of the absorption factor, when they appear due to either the defect modes related to structural defects or dispersion inspired variations of the material parameters in the vicinity of the polaritonic gap. Comparison with auxiliary structures helps one to detect the common features and differences of homogeneous slabs and slabs of a PhC, which are made of GaAs.

  10. Synthesis, structure, terahertz spectroscopy and luminescent properties of copper(I) complexes with mercaptan ligands and triphenylphosphine

    NASA Astrophysics Data System (ADS)

    Qiu, Qi-Ming; Liu, Min; Li, Zhong-Feng; Jin, Qiong-Hua; Huang, Xu; Zhang, Zhen-Wei; Zhang, Cun-Lin; Meng, Qing-Xuan

    2014-03-01

    The reactions of copper(I) halides with triphenylphosphine (PPh3) and mercaptan ligand [2-mercapto-6-nitrobenzothiazole (HMNBT), 2-amino-5-mercapto-1,3,4-thiadiazole (HAMTD) and 2-mercapto-5-methyl-benzimidazole (MMBD)] yielded seven complexes, [CuCl(HMNBT)(PPh3)2] (1), [CuX(HMNBT)(PPh3)]2 (X = Cl, Br) (2-3), [Cu(MNBT)(HMNBT)(PPh3)2] (4), [CuBr(HAMTD)(PPh3)2]·CH3OH (5) and [CuX(MMBD)(PPh3)2]·2CH3OH (X = Br, I) (6-7). These complexes were characterized by elemental analysis, X-ray diffraction, 1H NMR and 31P NMR spectroscopy. In these complexes the mercaptan ligands act as monodentate or bridged ligand with S as the coordination atom. In complexes 1 and 4, hydrogen bonds CH⋯X and weak interactions CH⋯? lead to the formation of chains and 2D network respectively, while complexes 2 and 3 are dinuclear. In 5-7, intramolecular hydrogen bonds link the [CuX(thione)(PPh3)2] molecules and the solvated methanol molecules into centrosymmetric dimers. Complexes 1-5 represent first copper(I) halide complexes of HMNBT and HAMTD. The complexes 1, 5, 6 and 7 exhibit interesting fluorescence in the solid state at room temperature and their terahertz (THz) time-domain spectroscopy was also studied.

  11. Andreev reflection spectroscopy of iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Chien, C. L.

    2009-03-01

    After a reign of over two decades by the cuprate superconductors, several new families of iron-based high-temperature superconductors have recently been discovered. Essential to a superconductor is the nature of the superconducting gap, its value, its structure, and its temperature dependence. Point contact Andreev reflection (PCAR) spectroscopy operating in the ballistic limit is one of few techniques that can quantitatively measure the gap of these new Fe-based superconductors and its temperature dependence. In SmFeAsO1-xFx (0.15 <= x <= 0.30), we have determined a single gap 2?/kBTC 3.5-3.6 close to the BCS s-wave prediction and with a BCS-like temperature dependence.ootnotetextT. Y. Chen, Z. Tesanovic, R. H. Liu, X. H. Chen, and C. L. Chien, Nature, 453, 1224 (2008) These results will be compared with various theoretical possibilities and those obtained by other measurements, such as ARPES and penetration depth. While the principles of the PCAR spectroscopy are well established, poor contact control and ballistic heating might lead to the appearance of spurious gaps and pseudogaps in PCAR measurements. In collaboration with T. Y. Chen, S. X. Huang and Z. Tesanovic at JHU and R. H. Liu and X. H. Chen at USTC.

  12. Total internal reflection photoacoustic spectroscopy for the detection of ?-hematin

    NASA Astrophysics Data System (ADS)

    Goldschmidt, Benjamin S.; Sudduth, Amanda S. M.; Samson, Edward B.; Whiteside, Paul J. D.; Bhattacharyya, Kiran D.; Viator, John A.

    2012-06-01

    Evanescent field sensing methods are currently used to detect many different types of disease markers and biologically important chemicals such as the HER2 breast cancer receptor. Hinoue et al. used Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) as a method of using the evanescent field to detect an optically opaque dye at a sample interface. Although their methods were successful at detecting dyes, the results at that time did not show a very practical spectroscopic technique, which was due to the less than typical sensitivity of TIRPAS as a spectroscopy modality given the low power (~1 to 2 W) lasers being used. Contrarily, we have used an Nd:YAG laser with a five nanosecond pulse that gives peak power of 1 MW coupled with the TIRPAS system to increase the sensitivity of this technique for biological material sensing. All efforts were focused on the eventual detection of the optically absorbing material, hemozoin, which is created as a byproduct of a malarial infection in blood. We used an optically analogous material, ?-hematin, to determine the potential for detection in the TIRPAS system. In addition, four properties which control the sensitivity were investigated to increase understanding about the sensor's function as a biosensing method.

  13. Reduction of effective terahertz focal spot size by means of nested concentric parabolic reflectors

    NASA Astrophysics Data System (ADS)

    Neumann, V. A.; Laurita, N. J.; Pan, LiDong; Armitage, N. P.

    2015-09-01

    An ongoing limitation of terahertz spectroscopy is that the technique is generally limited to the study of relatively large samples of order 4 mm across due to the generally large size of the focal beam spot. We present a nested concentric parabolic reflector design which can reduce the terahertz focal spot size. This parabolic reflector design takes advantage of the feature that reflected rays experience a relative time delay which is the same for all paths. The increase in effective optical path for reflected light is equivalent to the aperture diameter itself. We have shown that the light throughput of an aperture of 2 mm can be increased by a factor 15 as compared to a regular aperture of the same size at low frequencies. This technique can potentially be used to reduce the focal spot size in terahertz spectroscopy and enable the study of smaller samples.

  14. Reduction of Effective Terahertz Focal Spot Size By Means Of Nested Concentric Parabolic Reflectors

    E-print Network

    Neumann, V A; Pan, LiDong; Armitage, N P

    2015-01-01

    An ongoing limitation of terahertz spectroscopy is that the technique is generally limited to the study of relatively large samples of order 4 mm across due to the generally large size of the focal beam spot. We present a nested concentric parabolic reflector design which can reduce the terahertz focal spot size. This parabolic reflector design takes advantage of the feature that reflected rays experience a relative time delay which is the same for all paths. The increase in effective optical path for reflected light is equivalent to the aperture diameter itself. We have shown that the light throughput of an aperture of 2 mm can be increased by a factor 15 as compared to a regular aperture of the same size at low frequencies. This technique can potentially be used to reduce the focal spot size in terahertz spectroscopy and enable the study of smaller samples.

  15. Anatomy-Based Algorithms for Detecting Oral Cancer Using Reflectance and Fluorescence Spectroscopy

    E-print Network

    McGee, Sasha

    OBJECTIVES: We used reflectance and fluorescence spectroscopy to noninvasively and quantitatively distinguish benign from dysplastic/malignant oral lesions. We designed diagnostic algorithms to account for differences in ...

  16. Resonant Reflection Spectroscopy of Biomolecular Arrays in Muscle

    PubMed Central

    Young, Kevin W.; Radic, Stojan; Myslivets, Evgeny; O’Connor, Shawn M.; Lieber, Richard L.

    2014-01-01

    Sarcomeres, the functional units of contraction in striated muscle, are composed of an array of interdigitating protein filaments. Direct interaction between overlapping filaments generates muscular force, which produces animal movement. When filament length is known, sarcomere length successfully predicts potential force, even in whole muscles that contain billions of sarcomere units. Inability to perform in vivo sarcomere measurements with submicrometer resolution is a long-standing challenge in the muscle physiology field and has hampered studies of normal muscle function, adaptation, injury, aging, and disease, particularly in humans. Here, we develop theory and demonstrate the feasibility of to our knowledge a new technique that measures sarcomere length with submicrometer resolution. In this believed novel approach, we examine sarcomere structure by measuring the multiple resonant reflections that are uniquely defined by Fourier decomposition of the sarcomere protein spatial framework. Using a new supercontinuum spectroscopic system, we show close agreement between sarcomere lengths measured by resonant reflection spectroscopy and laser diffraction in an ensemble of 10 distinct muscles. PMID:25418304

  17. FDTD-based computed terahertz wave propagation in multilayer medium structures

    NASA Astrophysics Data System (ADS)

    Tu, Wan-li; Zhong, Shun-cong; Yao, Hai-zi; Shen, Yao-chun

    2013-08-01

    The terahertz region of the electromagnetic spectrum spans the frequency range of 0.1THz~10THz, which means it sandwiches between the mid-infrared (IR) and the millimeter/ microwave. With the development and commercialization of terahertz pulsed spectroscopy (TPS) and terahertz pulsed imaging (TPI) systems, terahertz technologies have been widely used in the sensing and imaging fields. It allows high quality cross-sectional images from within scattering media to be obtained nondestructively. Characterizing the interaction of terahertz radiation with multilayer medium structures is critical for the development of nondestructive testing technology. Currently, there was much experimental investigation of using TPI for the characterization of terahertz radiation in materials (e.g., pharmaceutical tablet coatings), but there were few theoretical researches on propagation of terahertz radiation in multilayer medium structures. Finite Difference Time Domain (FDTD) algorithm is a proven method for electromagnetic scattering theory, which analyzes continuous electromagnetic problems by employing finite difference and obtains electromagnetic field value at the sampling point to approach the actual continuous solutions. In the present work, we investigated the propagation of terahertz radiation in multilayer medium structures based on FDTD method. The model of multilayer medium structures under the THz frequency plane wave incidence was established, and the reflected radiation properties were recorded and analyzed. The terahertz radiation used was broad-band in the frequency up to 2 THz. A batch of single layer coated pharmaceutical tablets, whose coating thickness in the range of 40~100?m, was computed by FDTD method. We found that the simulation results on pharmaceutical tablet coatings were in good agreement with the experimental results obtained using a commercial system (TPI imaga 2000, TeraView, Cambridge, UK) , demonstrating its usefulness in simulating and analyzing terahertz responses from a multilayered sample.

  18. Terahertz Spectroscopy of the Ground State of Methylamine (CH_3NH_2)

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.

    2009-06-01

    Measurements of the torsion-rotation spectrum of methylamine have been extended into the terahertz region. The accuracy of these measurements is estimated to be ranging from 50 kHz to 100 kHz.. About 1000 lines were assigned based on a SPCAT prediction. The Hamiltonian model follows the group-theoretical formalism developed by Ohashi and Hougen. These assigned lines were fitted together with all prior available data (1800 lines) using the SPFIT program, and improved molecular parameters were obtained for CH_3NH_2 by adding the new measurements. New frequency and intensity predictions have been made based on the obtained molecular parameters. This Hamiltonian model may facilitate future studies on protonated methanol (CH_3OH_2^+). N. Ohashi and J. T.Hougen J. Mol. Spectrosco. 121, 474 (1987).

  19. Gain measurements of scattering-assisted terahertz quantum cascade lasers

    E-print Network

    Hu, Qing

    Using terahertz time-domain spectroscopy, the gain of scattering-assisted terahertz quantum cascade lasers is measured. By examining the intersubband gain and absorption over a wide range of bias voltages, we experimentally ...

  20. Terahertz spectroscopy of two-dimensional electron-hole pairs: probing Mott physics of magneto-excitons

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Gao, Weilu; Watson, John; Manfra, Michael; Kono, Junichiro

    2015-03-01

    Density-dependent Coulomb interactions can drive electron-hole (e - h) pairs in semiconductors through an excitonic Mott transition from an excitonic gas into an e - h plasma. Theoretical studies suggest that these interactions can be strongly modified by an external magnetic field, including the absence of inter-exciton interactions in the high magnetic field limit in two dimensions, due to an e - h charge symmetry, which results in ultrastable magneto-excitons. Here, we present a systematic experimental study of e - h pairs in photo-excited undoped GaAs quantum wells in magnetic fields with ultrafast terahertz spectroscopy. We simultaneously monitored the dynamics of the intraexcitonic 1 s-2 p transition (which splits into 1 s-2p+ and 1 s-2p- transitions in a magnetic field) and the cyclotron resonance of unbound electrons and holes up to 10 Tesla. We found that the 1 s-2p- absorption feature is robust at high magnetic fields even under high excitation fluences, indicating magnetically enhanced stability of excitons. We will discuss the Mott physics of magneto-excitons as a function of temperature, e - h pair density, optical pump delay time, as well as magnetic field, and also compare two-dimensional excitons in GaAs quantum wells with three-dimensional excitons in bulk GaAs.

  1. [Application of interval selection methods in quantitative analysis of multicomponent mixtures by terahertz time-domain spectroscopy].

    PubMed

    Chen, Tao; Li, Zhi; Mo, Wei; Hu, Fang-rong

    2014-12-01

    Interval selection methods combined with terahertz time-domain spectroscopy (THz-TDS) technique were used to perform quantitative analysis of component concentrations in multicomponent mixtures. The THz spectra of 100 quaternary pharmaceutical mixtures composed of lactose monohydrate, acetaminophen, microcrystalline cellulose and soluble starch were measured using THz-TDS system. Four spectral interval selection methods, including iPLS, mwPLS, siPLS and biPLS, were employed to select spectral intervals of THz absorbance spectra of multicomponent mixtures and correlate THz absorbance spectra with the concentrations of lactose monohydrate. The mwPLS method yielded the most accurate result as compared with the other three interval selection methods and full-spectrum PLS. The optimal mwPLS model was obtained with lower root mean square error of cross-validation (RMSECV) of 0.9803, lower root mean square error of prediction (RMSEP) of 1.1141, higher correlation coefficient for calibration (Rc) of 0.9960, and higher correlation coefficient for prediction (Rp) of 0.9951. Experimental results demonstrate that spectral interval selection combined with THz-TDS could be successfully applied as an accurate and rapid method to determine component concentrations in multicomponent mixtures. PMID:25881416

  2. Transient terahertz spectroscopy of excitons and unbound carriers in quasi two-dimensional electron-hole gases

    SciTech Connect

    Kaindl, Robert A.; Hagele, D.; Carnahan, M.A.; Chemla, D.S.

    2008-09-11

    We report a comprehensive experimental study and detailed model analysis of the terahertz (THz) dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued THz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the THz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the THz response exhibits both intra-excitonic and Drude features. Utilizing a two-component dielectric function, we derive the underlying exciton and unbound pair densities. In the ionized state, excellent agreement is found with the Saha thermodynamic equilibrium, which provides experimental verification of the two-component analysis and density scaling. During exciton formation, in turn, the pair kinetics is quantitatively described by a Saha equilibrium that follows the carrier cooling dynamics. The THz-derived kinetics is, moreover, consistent with time-resolved luminescence measured for comparison. Our study establishes a basis for tracking pair densities via transient THz spectroscopy of photoexcited quasi-2D electron-hole gases.

  3. Determination of the optical properties of melanin-pigmented human skin equivalents using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Lipscomb, Dawn; Echchgadda, Ibtissam; Peralta, Xomalin G.; Wilmink, Gerald J.

    2013-02-01

    Terahertz time-domain spectroscopy (THz-TDS) methods have been utilized in previous studies in order to characterize the optical properties of skin and its primary constituents (i.e., water, collagen, and keratin). However, similar experiments have not yet been performed to investigate whether melanocytes and the melanin pigment that they synthesize contribute to skin's optical properties. In this study, we used THz-TDS methods operating in transmission geometry to measure the optical properties of in vitro human skin equivalents with or without normal human melanocytes. Skin equivalents were cultured for three weeks to promote gradual melanogenesis, and THz time domain data were collected at various time intervals. Frequency-domain analysis techniques were performed to determine the index of refraction (n) and absorption coefficient (?a) for each skin sample over the frequency range of 0.1-2.0 THz. We found that for all samples as frequency increased, n decreased exponentially and the ?a increased linearly. Additionally, we observed that skin samples with higher levels of melanin exhibited greater n and ?a values than the non-pigmented samples. Our results indicate that melanocytes and the degree of melanin pigmentation contribute in an appreciable manner to the skin's optical properties. Future studies will be performed to examine whether these contributions are observed in human skin in vivo.

  4. Low-frequency vibration study of amino acids using terahertz spectroscopy and solid-state density functional theory

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Tominaga, Keisuke; Hayashi, Michitoshi; Wang, Houng-Wei

    2014-11-01

    Understanding the low-frequency normal modes of amino acids, the building blocks of proteins, is crucial to reveal the vibration-function relationship in the macromolecular system. Recent advances in terahertz spectroscopy (THz) and solid-state density functional theory (DFT) have ensured an accurate description of low-frequency modes of amino acids. New knowledge people have learnt so far is that the inter- and intra-molecular vibrations are strongly mixed with each other in the THz region through the vibrational coordinate mixing. Rich information is believed embedded in this phenomenon. We introduce a generalized mode-analysis method that allows for the accurate decomposition of a normal mode of interest into the three intermolecular translations, three principal librations and various intrinsic intramolecular vibrations. This mode-analysis method will be demonstrated in the crystalline C60 systems and then applied to shed light on the nature of low-frequency phonons of glycine, diglycine and triglycine. This method helps reveal new intramolecular vibrational modes on the first hand, and more importantly, illuminate a new phenomenon of the frequency distribution of intramolecular vibrations (FDIV). FDIV describes the possible broad distributions of important intramolecular vibrations in the low-frequency normal modes. The FDIV concept may indicate an additional mechanism for the intramolecular vibrations to become thermally active and participate in various biological functions.

  5. Charge transport and localization in nanocrystalline CdS films: A time-resolved terahertz spectroscopy study

    NASA Astrophysics Data System (ADS)

    Mics, Z.; N?mec, H.; Rychetský, I.; Kužel, P.; Formánek, P.; Malý, P.; N?mec, P.

    2011-04-01

    Assessment of characteristic length and time scales of the charge localization in nanostructured semiconductors is a key point for understanding the initial stage of carrier transport after photoexcitation. A concerted use of time-resolved terahertz spectroscopy and Monte Carlo simulations of the motion of confined electrons allow us to obtain this information and develop a quantitative microscopic model of the electron transport in a nanocrystalline CdS film. A weak localization is observed inside individual nanocrystals while much stronger localization stems from the existence of nanocrystal clusters partially surrounded by voids. The efficiency of the short-range transport is controlled by the excess energy of electrons: Its increase enhances the conductive coupling between adjacent nanocrystals and clusters. Relaxation of electrons with high excess energy then leads to a decrease of their mobility on a subpicosecond time scale. Filling of conduction-band states by increasing the optical pump fluence allows us to maintain a high level of conductive coupling even at later times.

  6. Near- and Mid-Infrared Reflectance Spectroscopy for the Quantitative and Qualitative Analysis of Agricultural Products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For several decades near-infrared diffuse reflectance spectroscopy (NIRS) has been used to determine the composition of a variety of agricultural products. More recently, diffuse reflectance Fourier transform mid-infrared spectroscopy (DRIFTS) has similarly been shown to be able to determine the co...

  7. Mid- Versus Near-Infrared Reflectance Spectroscopy for On-Site Determination of Soil Carbon

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research has demonstrated that the determination of soil C diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is often more accurate and produces more robust calibrations than near-infrared (NIR) reflectance spectroscopy (NIRS) when analyzing ground, dry soils. DRIFTS is also not ...

  8. Intramyocardial oxygen transport by quantitative diffuse reflectance spectroscopy in calves

    NASA Astrophysics Data System (ADS)

    Lindbergh, Tobias; Larsson, Marcus; Szabó, Zoltán; Casimir-Ahn, Henrik; Strömberg, Tomas

    2010-03-01

    Intramyocardial oxygen transport was assessed during open-chest surgery in calves by diffuse reflectance spectroscopy using a small intramuscular fiber-optic probe. The sum of hemo- and myoglobin tissue fraction and oxygen saturation, the tissue fraction and oxidation of cytochrome aa3, and the tissue fraction of methemoglobin were estimated using a calibrated empirical light transport model. Increasing the oxygen content in the inhaled gas, 21%-50%-100%, in five calves (group A) gave an increasing oxygen saturation of 19+/-4%, 24+/-5%, and 28+/-8% (p<0.001, ANOVA repeated measures design) and mean tissue fractions of 1.6% (cytochrome aa3) and 1.1% (hemo- and myoglobin). Cardiac arrest in two calves gave an oxygen saturation lower than 5%. In two calves (group B), a left ventricular assistive device (LVAD pump) was implanted. Oxygen saturation in group B animals increased with LVAD pump speed (p<0.001, ANOVA) and with oxygen content in inhaled gas (p<0.001, ANOVA). The cytochrome aa3 oxidation level was above 96% in both group A and group B calves, including the two cases involving cardiac arrest. In conclusion, the estimated tissue fractions and oxygenation/oxidation levels of the myocardial chromophores during respiratory and hemodynamic provocations were in agreement with previously presented results, demonstrating the potential of the method.

  9. Probing skin interaction with hydrogen peroxide using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zonios, George; Dimou, Aikaterini; Galaris, Dimitrios

    2008-01-01

    Hydrogen peroxide is an important oxidizing agent in biological systems. In dermatology, it is frequently used as topical antiseptic, it has a haemostatic function, it can cause skin blanching, and it can facilitate skin tanning. In this work, we investigated skin interaction with hydrogen peroxide, non-invasively, using diffuse reflectance spectroscopy. We observed transient changes in the oxyhaemoglobin and deoxyhaemoglobin concentrations as a result of topical application of dilute H2O2 solutions to the skin, with changes in deoxyhaemoglobin concentration being more pronounced. Furthermore, we did not observe any appreciable changes in melanin absorption properties as well as in the skin scattering properties. We also found no evidence for production of oxidized haemoglobin forms. Our observations are consistent with an at least partial decomposition of hydrogen peroxide within the stratum corneum and epidermis, with the resulting oxygen and/or remaining hydrogen peroxide inducing vasoconstriction to dermal blood vessels and increasing haemoglobin oxygen saturation. An assessment of the effects of topical application of hydrogen peroxide to the skin may serve as the basis for the development of non-invasive techniques to measure skin antioxidant capacity and also may shed light onto skin related disorders such as vitiligo.

  10. Noninvasive measurements of carotenoids in bovine udder by reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Klein, Julia; Darvin, Maxim E.; Müller, Kerstin E.; Lademann, Jürgen

    2012-10-01

    For a long time, the antioxidative status in cattle has been discussed as an indicator for stress conditions resulting from disease or exertion. Until now, invasive approaches have been necessary to obtain blood samples or biopsy materials and gain insights into the antioxidative status of cattle. Due to these efforts and the costs of the analyses, serial sampling is feasible in an experimental setting, but not for measurements on a routine basis. The present study focuses on the feasibility of an innovative, noninvasive spectroscopic technique that allows in vivo measurements of carotenoids in the skin by reflection spectroscopy. To this end, in a first trial, repeated measurements of the carotenoid concentration of the udder skin were performed on 25 healthy cattle from different breeds. Carotenoid concentrations showed highly significant differences between individual animals (P<0.001), although they were kept under the same environmental conditions and received the same diet. The carotenoid concentrations in "sensitive" and "robust" cows (evaluated by a temperament test) differed significantly (P<0.005), with higher concentrations observed in robust cows.

  11. Time-resolved terahertz spectroscopy of electrically conductive metal-organic frameworks doped with redox active species

    NASA Astrophysics Data System (ADS)

    Alberding, Brian G.; Heilweil, Edwin J.

    2015-09-01

    Metal-Organic Frameworks (MOFs) are three-dimensional coordination polymers that are well known for large pore surface area and their ability to adsorb molecules from both the gaseous and solution phases. In general, MOFs are electrically insulating, but promising opportunities for tuning the electronic structure exist because MOFs possess synthetic versatility; the metal and organic ligand subunits can be exchanged or dopant molecules can be introduced into the pore space. Two such MOFs with demonstrated electrical conductivity are Cu3(1,3,5-benzenetricarboxylate)2, a.k.a HKUST-1, and Cu[Ni(pyrazine-2,3-dithiolate)2]. Herein, these two MOFs have been infiltrated with the redox active species 7,7,8,8-tetracyanoquinodimethane (TCNQ) and iodine under solution phase conditions and shown to produce redox products within the MOF pore space. Vibrational bands assignable to TCNQ anion and triiodide anion have been observed in the Mid-IR and Terahertz ranges using FTIR Spectroscopy. The MOF samples have been further investigated by Time-Resolved Terehertz Spectroscopy (TRTS). Using this technique, the charge mobility, separation, and recombination dynamics have been followed on the picosecond time scale following photoexcitation with visible radiation. The preliminary results show that the MOF samples have small inherent photoconductivity with charge separation lifetimes on the order of a few picoseconds. In the case of HKUST-1, the MOF can also be supported by a TiO2 film and initial results show that charge injection into the TiO2 layer occurs with a comparable efficiency to the dye sensitizer N3, [cis-Bis(isothiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylato ruthenium(II)], and therefore this MOF has potential as a new light absorbing and charge conducting material in photovoltaic devices.

  12. Terahertz sources and detectors

    NASA Astrophysics Data System (ADS)

    Crowe, Thomas W.; Porterfield, David W.; Hesler, Jeffrey L.; Bishop, William L.; Kurtz, David S.; Hui, Kai

    2005-05-01

    Through the support of the US Army Research Office we are developing terahertz sources and detectors suitable for use in the spectroscopy of chemical and biological materials as well as for use in imaging systems to detect concealed weapons. Our technology relies on nonlinear diodes to translate the functionality achieved at microwave frequencies to the terahertz band. Basic building blocks that have been developed for this application include low-noise mixers, frequency multipliers, sideband generators and direct detectors. These components rely on planar Schottky diodes and integrated diode circuits and are therefore easy to assemble and robust. They require no mechanical tuners to achieve high efficiency and broad bandwidth. This paper will review the range of performance that has been achieved with these terahertz components and briefly discuss preliminary results achieved with a spectroscopy system and the development of sources for imaging systems.

  13. Point contact Andreev reflection spectroscopy for measuring spin polarization

    NASA Astrophysics Data System (ADS)

    Faiz, Muhammad Muzummal

    The Co-Pt systems have been extensively studied because of their potential applications in spintronic devices. We have experimentally measured transport spin polarization (PC) using Point Contact Andreev Reflection (PCAR) spectroscopy and magnetic properties of Co1-xPt x alloys. All films with x varying from 0 to 100% and a thickness of ˜1000 A were grown on Si substrates covered with ˜250 A of SiO 2 by magnetron sputtering (Ref. [1]). We have also performed band-structure calculations of the spin polarization in the same Co-Pt system. We have demonstrated that the experimental and theoretical results are in reasonably good agreement. We have compared the PCAR results with the tunneling spin polarization (TSP) values recently reported by Kaiser et al. (Ref. [1]) and showed that the overall trend of PCAR spin polarization is almost the same as for TSP with Al 2O3 barrier, but it is very different from the TSP with ALN barrier. We have performed X-ray Diffraction (XRD) experiments on these alloys and found that they, in general, exhibited face centered cubic crystallographic structure. Furthermore, our results renounce the idea of a direct relationship between the spin polarization and the magnetic moment for these alloys. We were surprised to find that pure Pt films showed obvious magnetic signatures both from PCAR spectroscopy and magnetization measurements, while TSP was found to be zero for pure Pt electrodes (Ref. [1]). The Co-based Heusler alloys are also of special interest for possible spintronic applications due to their high Curie temperatures and high magnetic moment per unit cell. Co2FeSi is especially promising as a candidate half-metal as it has a Curie temperature of approximately 1100 K and the integer magnetic moment of 6 muB per unit cell (Ref. [2]). The samples have been prepared by arc melting of stoichiometric quantities of pure metals in argon atmosphere followed by annealing in sealed quartz tubes at 1300 K. We have experimentally measured PC in Co2FeSi and Co2Mn0.5Fe0.5Si using PCAR spectroscopy. We found that spin polarization for these two alloys was significantly lower than that predicted by theoretical studies. We have attributed this reduction in spin polarization to the defects and disorder in the crystallographic structure within the Heusler alloys. Moreover, we have also experimentally demonstrated that doping with Mn in Co2FeSi did not improve spin polarization for this alloy. Spin diffusion length (Lsf) is of fundamental importance for spin dependent transport and spintronic devices. So far, most of the measurements of Lsf in nonmagnetic metals have been done in the lateral non-local geometry, with the chemical potential difference characterizing the spin imbalance. We have experimentally demonstrated spin transport studies in Heusler/Au bilayers using PCAR spectroscopy. Variable thickness Au films were deposited on top of the Heusler alloys and the PCAR spectroscopy was then used to probe PC on the Au side. In our approach Lsf was measured directly with PCAR spectroscopy. A spin polarized current was injected from a ferromagnetic electrode, Co2Mn0.5Fe0.5Si Heusler alloy, into Au films of variable thickness. The spin current, which gradually decays with the increased thickness of the film, was measured with a superconducting Nb tip. We developed a phenomenological theory which allowed us to determine Lsf in such a system. We found L sf in Au to be on the order of 312+/-36 nm at 4 K, comparable to the results obtained by other techniques using conventional ferromagnetic spin injectors. Similar results were obtained with a Gd single crystal. One of the potential advantages of this new technique, however, is the ability to do the point contact measurements on the side of the normal electrode, which should allow one to do the complete measurement of spin diffusion length by consequentially measuring the spin polarization in a normal metal as a function of thickness in a single sample. This experimental demonstration may be considered as the first step in this direction. (Abstract shortened b

  14. Terahertz quantum cascade laser based optical coherence tomography

    E-print Network

    Lee, Alan W. M.

    The interfaces of a dielectric sample are resolved in reflection geometry using light from a frequency agile array of terahertz quantum-cascade lasers. The terahertz source is a 10-element linear array of third-order ...

  15. Phase-sensitive time-domain terahertz reflection spectroscopy A. Pashkin,a)

    E-print Network

    Ku?el, Petr

    silicon and for ferroelectric SrBi2Ta2O9 bulk ceramics as well as thin film on sapphire substrates is fully developed and reliable, but it can be applied only to transparent samples. However, in the case with different levels of doping. The next sample was a ferroelectric ceramic, SrBi2Ta2O9 SBT , which is a very

  16. Hydration and hydrogen bond network of water around hydrophobic surface investigated by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Shiraga, K.; Suzuki, T.; Kondo, N.; Ogawa, Y.

    2014-12-01

    Water conformation around hydrophobic side chains of four amino acids (glycine, L-alanine, L-aminobutyric acid, and L-norvaline) was investigated via changes in complex dielectric constant in the terahertz (THz) region. Each of these amino acids has the same hydrophilic backbone, with successive additions of hydrophobic straight methylene groups (-CH2-) to the side chain. Changes in the degree of hydration (number of dynamically retarded water molecules relative to bulk water) and the structural conformation of the water hydrogen bond (HB) network related to the number of methylene groups were quantitatively measured. Since dielectric responses in the THz region represent water relaxations and water HB vibrations at a sub-picosecond and picosecond timescale, these measurements characterized the water relaxations and HB vibrations perturbed by the methylene apolar groups. We found each successive straight -CH2- group on the side chain restrained approximately two hydrophobic hydration water molecules. Additionally, the number of non-hydrogen-bonded (NHB) water molecules increased slightly around these hydrophobic side chains. The latter result seems to contradict the iceberg model proposed by Frank and Evans, where water molecules are said to be more ordered around apolar surfaces. Furthermore, we compared the water-hydrophilic interactions of the hydrophilic amino acid backbone with those with the water-hydrophobic interactions around the side chains. As the hydrophobicity of the side chain increased, the ordering of the surrounding water HB network was altered from that surrounding the hydrophilic amino acid backbone, thereby diminishing the fraction of NHB water and ordering the surrounding tetrahedral water HB network.

  17. Imaging of ex vivo nonmelanoma skin cancers in the optical and terahertz spectral regions optical and terahertz skin cancers imaging.

    PubMed

    Joseph, Cecil S; Patel, Rakesh; Neel, Victor A; Giles, Robert H; Yaroslavsky, Anna N

    2014-05-01

    We tested the hypothesis that polarization sensitive optical and terahertz imaging may be combined for accurate nonmelanoma skin cancer (NMSC) delineation. Nine NMSC specimens were imaged. 513 ?m and 440 nm wavelengths were used for terahertz and optical imaging, respectively. Histopathology was processed for evaluation. Terahertz reflectance of NMSC was quantified. Our results demonstrate that cross-polarized terahertz images correctly identified location of the tumours, whereas cross-polarized and polarization difference optical images accurately presented morphological features. Cross-polarized terahertz images exhibited lower reflectivity values in cancer as compared to normal tissue. Combination of optical and terahertz imaging shows promise for intraoperative delineation of NMSC. PMID:22987857

  18. Reflectance spectroscopy in planetary science: Review and strategy for the future

    NASA Technical Reports Server (NTRS)

    Mccord, Thomas B. (editor)

    1987-01-01

    Reflectance spectroscopy is a remote sensing technique used to study the surfaces and atmospheres of solar system bodies. It provides first-order information on the presence and amounts of certain ions, molecules, and minerals on a surface or in an atmosphere. Reflectance spectroscopy has become one of the most important investigations conducted on most current and planned NASA Solar System Exploration Program space missions. This book reviews the field of reflectance spectroscopy, including information on the scientific technique, contributions, present conditions, and future directions and needs.

  19. Terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong; Taylor, Antoineete J; Azad, Abul K; O' Hara, John F

    2009-01-01

    In this paper we present our recent developments in terahertz (THz) metamaterials and devices. Planar THz metamaterials and their complementary structures fabricated on suitable substrates have shown electric resonant response, which causes the band-pass or band-stop property in THz transmission and reflection. The operational frequency can be further tuned up to 20% upon photoexcitation of an integrated semiconductor region in the splitring resonators as the metamaterial elements. On the other hand, the use of semiconductors as metamaterial substrates enables dynamical control of metamaterial resonances through photoexcitation, and reducing the substrate carrier lifetime further enables an ultrafast switching recovery. The metamaterial resonances can also be actively controlled by application of a voltage bias when they are fabricated on semiconductor substrates with appropriate doping concentration and thickness. Using this electrically driven approach, THz modulation depth up to 80% and modulation speed of 2 MHz at room temperature have been demonstrated, which suggests practical THz applications.

  20. Inter/intra molecular dynamics in gases and liquids studied by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Xin, Xuying

    This thesis presents a description of the low-frequency terahertz (THz) absorption spectrum of a variety of materials that are of interest to many biological and chemical processes. The work described here encompasses the development of time-domain THz spectrometers, based on amplified Ti: Sapphire lasers systems as well as mode-locked Erbium doped fiber lasers as the driving source. These systems were applied to characterize the absorption spectrum of liquid water and water vapor, heavy water vapor, methanol vapor and tryptophan in the 0.2-2.2THz frequency range. The absorption profiles observed are closely related to the intermolecular or intramolecular motions in the materials of interest. In liquid water, the absorption profile shows evidence for modes due to large-scale structure amongst individual water molecules. The effects on the overall absorption profile are further deduced by the addition of various solutes which can enhance or break the formation of molecule networks. Various solutions are examined such as KCl in liquid water. Ions can change the strength of hydrogen bond in liquid water in the similar way as temperature does. Both K+ and Cl- are considered to be strong "structure breakers" in terms of their functions as softening the strength of hydrogen bond in liquid water. Theoretically, this will cause a red shift of some mode frequencies, reducing the absorption intensity at those frequencies and, at the same time, increasing the absorption at non-mode frequencies toward the vicinity of the low frequencies. For liquid water, the vapor phase was also examined, where for varying concentrations (humidity) Beer's Law does not hold to explain the observed absorption profiles. Again the reduced absorption of certain modes is explained by interactions between water monomers and their nature due to hydrogen spins. There are two species of water molecules in terms of the nuclear spin effect of hydrogen atoms in water molecule, ortho-water and para-water. The two types of water molecules present significantly different properties, e.g. different surface adsorption on metals. The effects of para-water and ortho-water on the THz absorption profile are discussed. Finally, I discuss the absorption profile of methanol vapor and tryptophan. In methanol vapor we observe coherent echoes after absorption by a THz transient and attribute it to the relaxation of the molecule due to the regularly spaced rotational manifold. In tryptophan two distinct absorption modes are observed due to torsional modes. These "soft-modes" are calculated and attributed to intramolecular motions between various atoms. The results of this body of work are discussed in the context of applications ranging from medicine, pharmaceuticals and the cosmetics industries.

  1. Determination of plant silicon content with near infrared reflectance spectroscopy

    PubMed Central

    Smis, Adriaan; Ancin Murguzur, Francisco Javier; Struyf, Eric; Soininen, Eeva M.; Herranz Jusdado, Juan G.; Meire, Patrick; Bråthen, Kari Anne

    2014-01-01

    Silicon (Si) is one of the most common elements in the earth bedrock, and its continental cycle is strongly biologically controlled. Yet, research on the biogeochemical cycle of Si in ecosystems is hampered by the time and cost associated with the currently used chemical analysis methods. Here, we assessed the suitability of Near Infrared Reflectance Spectroscopy (NIRS) for measuring Si content in plant tissues. NIR spectra depend on the characteristics of the present bonds between H and N, C and O, which can be calibrated against concentrations of various compounds. Because Si in plants always occurs as hydrated condensates of orthosilicic acid (Si(OH)4), linked to organic biomolecules, we hypothesized that NIRS is suitable for measuring Si content in plants across a range of plant species. We based our testing on 442 samples of 29 plant species belonging to a range of growth forms. We calibrated the NIRS method against a well-established plant Si analysis method by using partial least-squares regression. Si concentrations ranged from detection limit (0.24 ppmSi) to 7.8% Si on dry weight and were well predicted by NIRS. The model fit with validation data was good across all plant species (n = 141, R2 = 0.90, RMSEP = 0.24), but improved when only graminoids were modeled (n = 66, R2 = 0.95, RMSEP = 0.10). A species specific model for the grass Deschampsia cespitosa showed even slightly better results than the model for all graminoids (n = 16, R2 = 0.93, RMSEP = 0.015). We show for the first time that NIRS is applicable for determining plant Si concentration across a range of plant species and growth forms, and represents a time- and cost-effective alternative to the chemical Si analysis methods. As NIRS can be applied concurrently to a range of plant organic constituents, it opens up unprecedented research possibilities for studying interrelations between Si and other plant compounds in vegetation, and for addressing the role of Si in ecosystems across a range of Si research domains. PMID:25309567

  2. Asymmetric planar terahertz metamaterials

    SciTech Connect

    Singh, Ramjan; Al - Naib, Ibraheem A. I.; Koch, Martin; Zhang, Weili

    2010-01-01

    Using terahertz time-domain spectroscopy, we report an experimental observation of three distinct resonances in split ring resonators (SRRs) for both vertical and horizontal electric field polarizations at normal incidence. Breaking the symmetry in SRRs by gradually displacing the capacitive gap from the centre towards the comer of the ring allows for an 85% modulation of the fundamental inductive-capacitive (LC) resonance. Increasing asymmetry leads to the evolution of an otherwise inaccessible high quality factor electric quadrupole resonance that can be exploited for bio-sensing applications in the terahertz region.

  3. Non-invasive detection of oral cancer using reflectance and fluorescence spectroscopy

    E-print Network

    McGee, Sasha Alanda

    2008-01-01

    In vivo reflectance and fluorescence spectra were collected from patients with oral lesions, as well as healthy volunteers, in order to evaluate the potential of spectroscopy to serve as a non-invasive tool for the detection ...

  4. The use of near infrared reflectance spectroscopy to predict protein fractions in free-ranging cattle 

    E-print Network

    Whitley, Evan Micah

    1996-01-01

    Research was conducted to assess the feasibility of using near infrared reflectance spectroscopy (NIRS) technology to predict fractional protein utilization in cattle on forage based diets. Forage samples were obtained from esophageal and ruminal...

  5. Fecal near-infrared reflectance spectroscopy calibrations for predicting diet quality and intake of donkeys 

    E-print Network

    Kidane, Negusse Fessehaye

    2006-08-16

    The objective of these studies was to develop near-infrared reflectance spectroscopy calibration equations from diet-fecal pair datasets to predict the diet quality and intake of donkeys. One hundred-forty diet-fecal pair ...

  6. Highly tunable optical activity in planar achiral terahertz metamaterials

    E-print Network

    Zheludev, Nikolay

    Highly tunable optical activity in planar achiral terahertz metamaterials Ranjan Singh,1,2,* Eric: Using terahertz time domain spectroscopy we demonstrate tunable polarization rotation and circular(5663), 1494­1496 (2004). 12. H. O. Moser, B. D. F. Casse, O. Wilhelmi, and B. T. Saw, "Terahertz response

  7. Reflectance spectroscopy: quantitative analysis techniques for remote sensing applications.

    USGS Publications Warehouse

    Clark, R.N.; Roush, T.L.

    1984-01-01

    Several methods for the analysis of remotely sensed reflectance data are compared, including empirical methods and scattering theories, both of which are important for solving remote sensing problems. The concept of the photon mean path length and the implications for use in modeling reflectance spectra are presented.-from Authors

  8. Direct MD Simulations of Terahertz Absorption and 2D Spectroscopy Applied to Explosive Crystals.

    PubMed

    Katz, G; Zybin, S; Goddard, W A; Zeiri, Y; Kosloff, R

    2014-03-01

    A direct molecular dynamics simulation of the THz spectrum of a molecular crystal is presented. A time-dependent electric field is added to a molecular dynamics simulation of a crystal slab. The absorption spectrum is composed from the energy dissipated calculated from a series of applied pulses characterized by a carrier frequency. The spectrum of crystalline cyclotrimethylenetrinitramine (RDX) and triacetone triperoxide (TATP) were simulated with the ReaxFF force field. The proposed direct method avoids the linear response and harmonic approximations. A multidimensional extension of the spectroscopy is suggested and simulated based on the nonlinear response to a single polarized pulse of radiation in the perpendicular polarization direction. PMID:26274066

  9. Infrared/Terahertz double resonance spectroscopy of CH3F and CH3Cl at atmospheric pressure

    E-print Network

    Dane J. Phillips; Elizabeth A. Tanner; Frank C. De Lucia; Henry O. Everitt

    2012-05-12

    A new method for highly selective remote sensing of atmospheric trace polar molecular gases is described. Based on infrared/terahertz double resonance spectroscopic techniques, the molecule- specific coincidence between the lines of a CO2 laser and rotational-vibrational molecular absorption transitions provide two dimensions of recognition specificity: infrared coincidence frequency and the corresponding terahertz frequency whose absorption strength is modulated by the laser. Atmospheric pressure broadening expands the molecular recognition "specificity matrix" by simultaneously relaxing the infrared coincidence requirement and strengthening the corresponding terahertz signature. Representative double resonance spectra are calculated for prototypical molecules CH3F and CH3Cl and their principal isotopomers, from which a heuristic model is developed to estimate the specificity matrix and double resonance signature strength for any polar molecule.

  10. Terahertz Spectroscopy of Molecules in the Interstellar Medium and around Stars - Sure Bets and Challenges

    NASA Astrophysics Data System (ADS)

    Menten, Karl M.

    2009-06-01

    In the very near future, powerful new observatories willrevolutionize broad band astronomical spectroscopy at THz frequencies. These include the Herschel Space Observatory, the Atacama Large Millimeter Array and, at somewhat lower, GHz, frequencies the Expanded Very Large Array. The latter two, ``radio''-style interferometers will allow sub-arcsecond, high spectral resolution imaging with total instantaneous observing bandwidths up to 100 times larger than present day facilities. This will allow comprehensive multi-transition/multi species studies that offer new approaches to a variety of astrophysical/chemical areas all of which are dependent on the availability of extensive laboratory data. To give a few examples: For many interesting sources it will be possible to get a complete astrochemical ``fingerprint'' in a single observing session with high-quality images of the distributions of the individual species! Targets include the extremely molecule-rich hot molecular cores around protostellar objects and emission from vibrationally excited lines from the innermost circumstellar envelopes of nearby asymptotic branch branch stars which will be imaged with a resolution better than the stellar diameter. Complete, high spectral resolution scans of various keystone objects over the whole 480-1250 and 1410-1920 GHz ranges will be conducted by the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel. These include lines from various important hydride species and, importantly, water vapor that are not observable from the ground. Organic molecules have hundreds of GHz/THz lines. However, due to the generally low abundances and large partition functions of ``new'' (yet to identified) very complex species, all of these are weak and have to be picked out of a thicket of also weak rotational lines from within relatively low energy vibrationally excited levels from various isotopologues of known species. Here, comprehensive model spectra of all the species known to exist in a source have to be constructed to ``weed out'' the contaminants. This requires comprehensive laboratory data, which as of now is far from existing. Moreover, Herschel will allow access to types of transitions, e.g., vibrational ones from carbon chain species, for which spectroscopic data has yet to be obtained. I shall give an overview of the challenges and great opportunities of astronomical molecular spectroscopy in the coming years and the crucial role of laboratory spectroscopy.

  11. The effect of anisotropic reflectance on imaging spectroscopy of snow properties

    E-print Network

    Dozier, Jeff

    The effect of anisotropic reflectance on imaging spectroscopy of snow properties Thomas H. Paintera in revised form 19 September 2003; accepted 30 September 2003 Abstract How does snow's anisotropic directional reflectance affect the mapping of snow properties from imaging spectrometer data? This sensitivity

  12. Reflectance spectroscopy of pigmented cutaneous benign and malignant lesions

    NASA Astrophysics Data System (ADS)

    Borisova, E.; Jeliazkova, Al.; Pavlova, E.; Troyanova, P.; Kundurdjiev, T.; Pavlova, P.; Avramov, L.

    2014-10-01

    For the DRS measurements of skin benign, dysplastic and malignant lesions in vivo we applied halogen lamp (LS-1, OceanOptics Inc, Dunedin, Fl, USA) as a continuous light source in the region of 400-900 nm, optical probe (6+1 fibers) for the delivery of illumination and diffuse reflected light from the skin investigated and microspectrometer USB4000 (OceanOptics Inc., Dunedin, Fl, USA) for a storage and display of the spectra detected. As a diffuse reflectance standard Spectralon® plate was used to calibrate the spectrometer. The reflectance spectra obtained from normal skin in identical anatomic sites of different patients have similar spectral shape features, slightly differ by the reflectance intensity at different wavelengths, depending on the particular patient' skin phototype. One could find diagnostically important spectral features, related to specific intensity changes for a given wavelength due to specific pigments appearance, slope changes by value and sign for the reflectance spectra curves in a specific spectral range, disappearance or manifestation of minima, related to hemoglobin absorption at 410-420 nm, 543, 575 nm. Based on the observed peculiarities multispectral analysis of the reflectance spectra of the different lesions was used and diagnostically specific features are found. Discrimination using the DRS data obtained between benign compound and dermal nevi (45 cases), dysplastic nevi (17 cases) and pigmented malignant melanoma (41 cases) lesions is achieved with a diagnostic accuracy of 96 % for the benign nevi vs. MM, and 90 % for the dysplastic nevi vs. MM.

  13. [Application of near infrared reflectance spectroscopy to predict meat chemical compositions: a review].

    PubMed

    Tao, Lin-Li; Yang, Xiu-Juan; Deng, Jun-Ming; Zhang, Xi

    2013-11-01

    In contrast to conventional methods for the determination of meat chemical composition, near infrared reflectance spectroscopy enables rapid, simple, secure and simultaneous assessment of numerous meat properties. The present review focuses on the use of near infrared reflectance spectroscopy to predict meat chemical compositions. The potential of near infrared reflectance spectroscopy to predict crude protein, intramuscular fat, fatty acid, moisture, ash, myoglobin and collagen of beef, pork, chicken and lamb is reviewed. This paper discusses existing questions and reasons in the current research. According to the published results, although published results vary considerably, they suggest that near-infrared reflectance spectroscopy shows a great potential to replace the expensive and time-consuming chemical analysis of meat composition. In particular, under commercial conditions where simultaneous measurements of different chemical components are required, near infrared reflectance spectroscopy is expected to be the method of choice. The majority of studies selected feature-related wavelengths using principal components regression, developed the calibration model using partial least squares and modified partial least squares, and estimated the prediction accuracy by means of cross-validation using the same sample set previously used for the calibration. Meat fatty acid composition predicted by near-infrared spectroscopy and non-destructive prediction and visualization of chemical composition in meat using near-infrared hyperspectral imaging and multivariate regression are the hot studying field now. On the other hand, near infrared reflectance spectroscopy shows great difference for predicting different attributes of meat quality which are closely related to the selection of calibration sample set, preprocessing of near-infrared spectroscopy and modeling approach. Sample preparation also has an important effect on the reliability of NIR prediction; in particular, lack of homogeneity of the meat samples influenced the accuracy of estimation of chemical components. In general the predicting results of intramuscular fat, fatty acid and moisture are best, the predicting results of crude protein and myoglobin are better, while the predicting results of ash and collagen are less accurate. PMID:24555369

  14. Doppler-shifted reflections of X rays in beamfoil spectroscopy

    NASA Technical Reports Server (NTRS)

    Bernstein, E. M.; Mcintyre, L. C., Jr.

    1976-01-01

    Carbon foils were positioned at roughly 10 deg to the conventional perpendicular position so that the spectrometer would view the beam on emergence from the foil, with no radiation shielded by a bowed or wrinkled foil or by the foil holder. Extraneous peaks due to reflected radiation were detected in the spectrum obtained with the tilted foil. A large satellite appears longward of the spectral line and is attributed to Doppler-shifted radiation reflected from the foil surface. Special tests arranged to validate the origin of the satellites are described. The relative intensity of the reflected radiation compared with the direct radiation observed is at variance with the relative intensities reported for longer wavelengths. The reasons for this, possible effects of spectrometer geometry, and applications in the investigation or generation of polarization remain to be investigated

  15. Midinfrared spectroscopy of synthetic olivines: Thermal emission, specular and diffuse reflectance, and attenuated total reflectance

    E-print Network

    Glotch, Timothy D.

    , and attenuated total reflectance studies of forsterite to fayalite Melissa D. Lane,1 Timothy D. Glotch,2 M. Darby] Synthetic olivine samples ranging in composition from forsterite to fayalite are analyzed in the midinfrared is identified of a specific emissivity maximum/reflectivity minimum (the flection position). From forsterite

  16. Hydration kinetics of cement composites with varying water-cement ratio using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Ray, Shaumik; Dash, Jyotirmayee; Devi, Nirmala; Sasmal, Saptarshi; Pesala, Bala

    2015-03-01

    Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.

  17. Identification of thermal degradation using probabilistic models in reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Criner, A. K.; Cherry, A. J.; Cooney, A. T.; Katter, T. D.; Banks, H. T.; Hu, Shuhua; Catenacci, Jared

    2015-03-01

    Different probabilistic models of molecular vibration modes are considered to model the reflectance spectra of chemical species through the dielectric constant. We discuss probability measure estimators in parametric and nonparametric models. Analyses of ceramic matrix composite samples that have been heat treated for different amounts of times are compared. We finally compare these results with the analysis of vitreous silica using nonparametric models.

  18. Monitoring bruise age using visible diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    McMurdy, John W.; Duffy, Susan; Crawford, Gregory P.

    2007-02-01

    The ability to determine the age of a bruise of unknown age mechanism is important in matters of domestic and child abuse and forensics. While physicians are asked to make clinical judgment on the age of a bruise using color and tenderness, studies have shown that a physicians estimate is highly inaccurate and in cases no better than chance alone. We present here the temporal progression of reflection spectrum collected from accidentally inflicted contusions in adult and child study participants with a synopsis of the observed phenomena. Reflection spectra collected using a portable fiber optic reflection spectrometer can track the increase in extravasated hemoglobin from trauma caused blood vessel rupture and subsequent removal of this hemoglobin occurring concurrent with an increase in the absorption attributed to the breakdown product bilirubin. We hypothesize that this time dependent pattern can be used to determine the age of an unknown bruise in an individual provided rate constant information for the patient can be determined in a controlled calibration bruise. Using reflection spectra to estimate bruise age can provide a rapid and noninvasive method to improve the ability of physicians in dating the age of a contusion.

  19. Probing Photoexcited Carriers in a Few-Layer MoS2 Laminate by Time-Resolved Optical Pump-Terahertz Probe Spectroscopy.

    PubMed

    Kar, Srabani; Su, Y; Nair, R R; Sood, A K

    2015-12-22

    We report the dynamics of photoinduced carriers in a free-standing MoS2 laminate consisting of a few layers (1-6 layers) using time-resolved optical pump-terahertz probe spectroscopy. Upon photoexcitation with the 800 nm pump pulse, the terahertz conductivity increases due to absorption by the photoinduced charge carriers. The relaxation of the non-equilibrium carriers shows fast as well as slow decay channels, analyzed using a rate equation model incorporating defect-assisted Auger scattering of photoexcited electrons, holes, and excitons. The fast relaxation time occurs due to the capture of electrons and holes by defects via Auger processes, resulting in nonradiative recombination. The slower relaxation arises since the excitons are bound to the defects, preventing the defect-assisted Auger recombination of the electrons and the holes. Our results provide a comprehensive understanding of the non-equilibrium carrier kinetics in a system of unscreened Coulomb interactions, where defect-assisted Auger processes dominate and should be applicable to other 2D systems. PMID:26516987

  20. Total reflection X-ray photoelectron spectroscopy as a semiconductor lubricant elemental analysis method

    NASA Astrophysics Data System (ADS)

    Alshehabi, Abbas; Sasaki, Nobuharu; Kawai, Jun

    2015-12-01

    Photoelectron spectra from a typical hard disk storage media device (HDD) were measured at total reflection and non-total reflection at unburnished, acetone-cleaned, and argon-sputtered conditions. F, O, N, and C usually making the upper layer of a typical hard disk medium were detected. Enhancement of the photoelectron emission of the fluorocarbon lubricant was observed at total reflection. Pt and Co were only found by non-total X-ray photoelectron spectroscopy (XPS) because they are constituents of a deeper region than the top and interface regions. Argon-sputtered, ultrasonic acetone-cleaned, and unburnished top layers were compared at total and non-total reflection conditions. Total reflection X-ray photoelectron spectroscopy (TRXPS) is demonstrated to be a powerful tool for storage media lubrication layer chemical state analysis, reliable for industrial quality control application , and reproducible.

  1. ChemCam Passive Reflectance Spectroscopy at Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Johnson, J. R.; Bell, J. F.; Cloutis, E.; Bender, S.; Blaney, D. L.; Ehlmann, B. L.; Gasnault, O.; Kinch, K. M.; Le Mouelic, S.; Rice, M. S.; Wiens, R. C.; DeFlores, L.; Team, M.

    2013-12-01

    The Laser-Induced Breakdown Spectrometer (LIBS) portion of the ChemCam instrument on the Mars Science Laboratory Curiosity rover uses 3 dispersive spectrometers to cover the ultraviolet (240-342 nm), visible (382-469 nm) and visible/near-infrared (474-906 nm) spectral regions at high spectral (<0.5nm) and spatial (0.65mrad) resolution. In active LIBS mode, light emitted from a laser-generated plasma is dispersed onto these spectrometers and used to detect elemental emission lines. Typical observations include 3 msec-exposure 'dark' spectra (acquired with the LIBS laser off) used to remove the background signal from the LIBS measurement. Similar 'passive' observations of the ChemCam calibration target holder can be made at similar times of day and at identical exposure times (to minimize variations from dark current). Because this target exhibits ~95% flat reflectance in the ~400-900 nm region, radiance spectra ratios (surface/calibration target) can be normalized to known calibration target lab spectra to produce relative reflectance spectra (400-900 nm) with an estimated accuracy of 10-20%. Initial results replicated the known spectral shape and overall reflectance values of the ChemCam calibration targets and green color chip on the Mastcam calibration target. Dust contamination was evident, although dust on the ChemCam calibration targets is minimized by their tilted placement on the rover deck. All ChemCam targets that were sunlit during LIBS acquisition (~80% of all measurements) provide 'dark' spectra for which relative reflectance spectra can be obtained. Owing to the dusty nature of the Gale landing sites, passive spectra observed to date exhibit spectral shapes indicative of ferric phases, similar to spectra of palagonitic soils. Most spectra are bracketed in reflectance by typical 'bright' and 'dark' spectra from the OMEGA and CRISM orbital spectrometers. Preliminary Mastcam reflectance spectra are similar, providing additional confidence regarding the first-order calibration of the ChemCam spectra. The spectral similarity to palagonitic soils is consistent with the results from the CheMin instrument for Rocknest sands. Changes in the 535 nm band depth are likely indicative of differences in the relative amount of ferric iron in crystalline phases. More strongly negative spectral slopes > 600 nm are typical of lower-reflectance, less dusty rock surfaces, whereas positive slopes < 600 nm are consistent with higher-reflectance, dustier surfaces. ChemCam elemental detections of Ca- and S-bearing veins correlate to high reflectance targets with some dust contamination. Spectra of the John_Klein and Cumberland drill tailings, as well as brushed and broken rock surfaces in the Yellowknife Bay area, exhibit much less 'red' spectral features, including inflections near 550 nm that are consistent with a number of ferrous and ferric iron-bearing clay mineral phases, similar to CheMin results. Ongoing work with ChemCam passive spectra will include efforts to utilize the UV spectral range (sensitive to iron content), investigate photometric effects of illumination variations on the calibration targets, and dust mitigation efforts. As Curiosity traverses toward Mt. Sharp, passive spectra will be used as an additional tool to remotely track variations in surface chemistry and mineralogy, particularly for iron-bearing sulfate, oxide, and clay minerals.

  2. [Application and prospect of near infrared reflectance spectroscopy in forage analysis].

    PubMed

    Ren, Xiu-Zhen; Guo, Hong-Ru; Jia, Yu-Shan; Ge, Gen-Tu; Wang, Kun

    2009-03-01

    Forage was the material basis of animal husbandry production, and its quality is directly related to the quality of animal products. It was very important to control the forage quality and detect the composition of forage raw materials in forage production. Predication of forage quality was often completed by the traditional and classical methods in the past, which were complex, time consuming and expensive, and could not acquire the nutritional value of forage timely. Near infrared reflectance spectroscopy was a highly efficient and rapid modern analysis technique developed in 1970's. It comprehensively applied the latest research results of computer technique, spectroscopy and chemometrics, and has been widely used in various fields owing to its unique advantages such as being timely, less expensive, non-destructive, and so on. Near infrared reflectance spectroscopy has gained more and more importance though its application to forage analysis was very late. Presently, not only conventional composition (such as moisture, dry matter, crude protein, crude fiber, crude fat, crude ash neutral detergent fiber, acid detergent fiber, etc.), but also non-conventional composition (including minerals, trace elements, enzyme and anti-nutritional factors etc. ) and anti-nutritional factors in forage were determined by means of near infrared reflectance spectroscopy. Testing and analyzing the conventional composition in forage was the traditional applied field of near infrared reflectance spectroscopy, a lot of studies of which were done and it has already been one of the standard methods of testing the conventional composition. Forage bioavaibility was also evaluated by near infrared reflectance spectroscopy, so as to assess the utilization rate and nutritional value of forage. Moreover, near infrared spectroscopy could be used successfully to predict the botanical composition in grassland and leaf/stem ratios. Near infrared spectroscopy technique and its application and prospect in forage analysis were reviewed in the present paper. PMID:19455789

  3. Catheter based mid-infrared reflectance and reflectance generated absorption spectroscopy

    DOEpatents

    Holman, Hoi-Ying N

    2013-10-29

    A method of characterizing conditions in a tissue, by (a) providing a catheter that has a light source that emits light in selected wavenumbers within the range of mid-IR spectrum; (b) directing the light from the catheter to an area of tissue at a location inside a blood vessel of a subject; (c) collecting light reflected from the location and generating a reflectance spectra; and (d) comparing the reflectance spectra to a reference spectra of normal tissue, whereby a location having an increased number of absorbance peaks at said selected wavenumbers indicates a tissue inside the blood vessel containing a physiological marker for atherosclerosis.

  4. Measuring Black Hole Spin Using X-Ray Reflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Reynolds, Christopher S.

    2014-09-01

    I review the current status of X-ray reflection (a.k.a. broad iron line) based black hole spin measurements. This is a powerful technique that allows us to measure robust black hole spins across the mass range, from the stellar-mass black holes in X-ray binaries to the supermassive black holes in active galactic nuclei. After describing the basic assumptions of this approach, I lay out the detailed methodology focusing on "best practices" that have been found necessary to obtain robust results. Reflecting my own biases, this review is slanted towards a discussion of supermassive black hole (SMBH) spin in active galactic nuclei (AGN). Pulling together all of the available XMM-Newton and Suzaku results from the literature that satisfy objective quality control criteria, it is clear that a large fraction of SMBHs are rapidly-spinning, although there are tentative hints of a more slowly spinning population at high ( M>5×107 M ?) and low ( M<2×106 M ?) mass. I also engage in a brief review of the spins of stellar-mass black holes in X-ray binaries. In general, reflection-based and continuum-fitting based spin measures are in agreement, although there remain two objects (GRO J1655-40 and 4U 1543-475) for which that is not true. I end this review by discussing the exciting frontier of relativistic reverberation, particularly the discovery of broad iron line reverberation in XMM-Newton data for the Seyfert galaxies NGC 4151, NGC 7314 and MCG-5-23-16. As well as confirming the basic paradigm of relativistic disk reflection, this detection of reverberation demonstrates that future large-area X-ray observatories such as LOFT will make tremendous progress in studies of strong gravity using relativistic reverberation in AGN.

  5. Study on reflection of human skin with liquid paraffin as the penetration enhancer by spectroscopy.

    PubMed

    Chen, Kun; Liang, Yanmei; Zhang, Yuan

    2013-10-01

    Optical clearing agents can improve tissue optical transmittance by reducing the diffuse reflection. The reflection on in vivo human skin before and after applying anhydrous glycerol and 30 to 50% liquid paraffin glycerol mixed solution are investigated in this paper. From their visible and near-infrared reflection spectroscopy, all of their diffuse reflections are reduced after applying the agents. It is found that the three mixed solutions show stronger effect than that of anhydrous glycerol. These results further prove liquid paraffin can enhance the percutaneous penetration of glycerol and take synergistically optical clearing effect with glycerol over visible and near-infrared wave bands. PMID:24091625

  6. Three-dimensional invisibility cloaks functioning at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Cao, Wei; Zhou, Fan; Liang, Dachuan; Gu, Jianqiang; Han, Jiaguang; Sun, Cheng; Zhang, Weili

    2014-05-01

    Quasi-three-dimensional invisibility cloaks, comprised of either homogeneous or inhomogeneous media, are experimentally demonstrated in the terahertz regime. The inhomogeneous cloak was lithographically fabricated using a scalable Projection Microstereolithography process. The triangular cloaking structure has a total thickness of 4.4 mm, comprised of 220 layers of 20 ?m thickness. The cloak operates at a broad frequency range between 0.3 and 0.6 THz, and is placed over an ?-lactose monohydrate absorber with rectangular shape. Characterized using angular-resolved reflection terahertz time-domain spectroscopy, the results indicate that the terahertz invisibility cloak has successfully concealed both the geometrical and spectroscopic signatures of the absorber, making it undetectable to the observer. The homogeneous cloaking device made from birefringent crystalline sapphire features a large concealed volume, low loss, and broad bandwidth. It is capable of hiding objects with a dimension nearly an order of magnitude larger than that of its lithographic counterpart, but without involving complex and time-consuming cleanroom processing. The cloak device was made from two 20-mm-thick high-purity sapphire prisms. The cloaking region has a maximum height 1.75 mm with a volume of approximately 5% of the whole sample. The reflected TM beam from the cloak shows nearly the same profile as that reflected by a flat mirror.

  7. Low-frequency vibrational properties of crystalline and glassy indomethacin probed by terahertz time-domain spectroscopy and low-frequency Raman scattering.

    PubMed

    Shibata, Tomohiko; Mori, Tatsuya; Kojima, Seiji

    2015-11-01

    In order to clarify the intermolecular vibrations, the low-frequency modes of the glassy and crystalline states of model pharmaceutical indomethacin have been studied using broadband terahertz time-domain spectroscopy and low-frequency Raman scattering. In the crystalline ?-form, the center of symmetry was suggested by the observation of the exclusion principle of the infrared (IR) and Raman selection rules in the frequency range between 0.2 and 6.5 THz. In addition, a boson peak of the glassy state was observed in both IR and Raman spectra and their frequency showed apparent discrepancy. The intermediate correlation length of the glassy structure was estimated to be about 2.5 nm. The existence of hydrogen bonded cyclic dimers in a glassy state was suggested by the observation of the infrared active intermolecular vibrational mode of the hydrogen bonded cyclic dimers as a broad peak at 3.0 THz in the IR spectrum. PMID:26051642

  8. Photoinduced insulator-metal phase transition and the metallic phase propagation in VO2 films investigated by time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Xue, Xin; Jiang, Meng; Li, Gaofang; Lin, Xian; Ma, Guohong; Jin, Ping

    2013-11-01

    The particle size and film thickness dependence of the photoinduced insulator-metal phase transition in VO2 films has been studied systematically by time-resolved terahertz spectroscopy at room temperature. It is found that the dynamical photoinduced phase transition from insulator to metal consists of two processes: a 1.7 ps fast process and a slow process with a typical time constant of 40 ps. Both of the two processes show particle size independence. The 40 ps slow process is revealed to arise from the longitudinal propagation of the metallic phase from the photoexcited surface to the interior of the VO2 film. A phase boundary propagation speed with a magnitude of ˜2400 m/s is obtained, which is close to the velocity of sound in solid materials and coincides with the prediction of diffusionless phase transformation. Our experimental results clearly establish the entire procedure of photoinduced phase change in the VO2 film.

  9. Employing time-resolved terahertz spectroscopy to analyze carrier dynamics in thin-film Cu{sub 2}ZnSn(S,Se){sub 4} absorber layers

    SciTech Connect

    Guglietta, Glenn W.; Baxter, Jason B.; Choudhury, Kaushik Roy; Caspar, Jonathan V.

    2014-06-23

    We report the application of time-resolved terahertz spectroscopy (TRTS) to measure photoexcited carrier lifetimes and mobility, and to determine recombination mechanisms in Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSSe) thin films fabricated from nanocrystal inks. Ultrafast time resolution permits tracking the evolution of carrier density to determine recombination rates and mechanisms. The carrier generation profile was manipulated by varying the photoexcitation wavelength and fluence to distinguish between surface, Shockley-Read-Hall (SRH), radiative, and Auger recombination mechanisms and determine rate constants. Surface and SRH recombination are the dominant mechanisms for the air/CZTSSe/SiO{sub 2}/Si film stack. Diffusion to, and then recombination at, the air-CZTSSe interface occurred on the order of 100 picoseconds, while SRH recombination lifetimes were 1–2 nanoseconds. TRTS measurements can provide information that is complementary to conventional time-resolved photoluminescence measurements and can direct the design of efficient thin film photovoltaics.

  10. Temperature and carrier-density dependence of electron-hole scattering in silicon investigated by optical-pump terahertz-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Terashige, T.; Yada, H.; Matsui, Y.; Miyamoto, T.; Kida, N.; Okamoto, H.

    2015-06-01

    We measured the optical conductivity ? ˜(? ) spectra of photodoped silicon by optical-pump terahertz-probe spectroscopy and analyzed them with a two-carrier Drude model. Taking into account the values of electron (hole)-phonon scattering rates previously reported in chemically doped silicon, we evaluated the electron-hole scattering rates ?e -h. From 293 to 90 K , the magnitudes and temperature dependence of ?e -h were successfully reproduced by a theoretical model including the effects of Rutherford scattering, Coulomb screening, and Pauli exclusion. This suggests that these three factors dominate electron-hole scattering processes in silicon. Below 90 K , ?e -h becomes larger than that of the theoretical curve, which is attributable to a prolongation of the relaxation time of hot carriers.

  11. Diffuse reflectance spectroscopy: a clinical study of tuberculin skin tests reading

    NASA Astrophysics Data System (ADS)

    Koenig, Anne; Grande, Sophie; Dahel, Karima; Planat-Chrétien, Anne; Poher, Vincent; Goujon, Catherine; Dinten, Jean-Marc

    2013-02-01

    Diffuse reflectance spectroscopy is a technique widely used to determine optical properties of tissues: scattering and absorption coefficients. In this study, we present the development of a low-cost optical instrument usable in a clinical environment based upon the spatially resolved diffuse reflectance spectroscopy approach. This instrument has been used in a clinical study to support the diagnosis of tuberculosis. The idea is to establish a new scanning method for an early detection of inflammation due to a reagent injection, before the onset of visual signs. Results comparing the instrumental and classical clinical readings are presented.

  12. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    SciTech Connect

    Bertram, F. Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E.; Zhang, F.; Pan, J.; Carlà, F.; Nilsson, J.-O.

    2014-07-21

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  13. In vivo soft tissue differentiation by diffuse reflectance spectroscopy: preliminary results

    NASA Astrophysics Data System (ADS)

    Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Neukam, Friedrich Wilhelm; Schmidt, Michael; Douplik, Alexandre

    Remote laser surgery does not provide haptic feedback to operate layer by layer and preserve vulnerable anatomical structures like nerve tissue or blood vessels. The aim of this study is identification of soft tissue in vivo by diffuse reflectance spectroscopy to set the base for a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Various soft tissues can be identified by diffuse reflectance spectroscopy in vivo. The results may set the base for a feedback system to prevent nerve damage during oral and maxillofacial laser surgery.

  14. Terahertz pulsed imaging in vivo

    NASA Astrophysics Data System (ADS)

    Pickwell-MacPherson, E.

    2011-03-01

    Terahertz (1012 Hz) pulsed imaging is a totally non-destructive and non-ionising imaging modality and thus potential applications in medicine are being investigated. In this paper we present results using our hand-held terahertz probe that has been designed for in vivo use. In particular, we use the terahertz probe to perform reflection geometry in vivo measurements of human skin. The hand-held terahertz probe gives more flexibility than a typical flat-bed imaging system, but it also results in noisier data and requires existing processing methods to be improved. We describe the requirements and limitations of system geometry, data acquisition rate, image resolution and penetration depth and explain how various factors are dependent on each other. We show how some of the physical limitations can be overcome using novel data processing methods.

  15. Polarization-dependent differential reflectance spectroscopy for real-time monitoring of organic thin film growth.

    PubMed

    Navarro-Quezada, A; Aiglinger, M; Ghanbari, E; Wagner, Th; Zeppenfeld, P

    2015-11-01

    By monitoring the reflectance of a sample surface during deposition of a thin organic film, one can obtain information with submonolayer resolution in real-time. A special kind of optical spectroscopy is Differential Reflectance Spectroscopy (DRS), which compares the reflectance before and during deposition of a thin film or any other change of the surface optical properties. In this work, we present an extended DRS setup that allows monitoring simultaneously both linear polarization states (s and p) of the reflected light. We implement polarization-dependent DRS to monitor the growth of perflouropentacene thin films on a Ag(110) single crystal. The setup allows us to deduce the optical anisotropy of the sample and, in particular, the preferred orientation of the molecules on the surface. PMID:26628122

  16. Investigation of the enzymatic digestion of plant cell walls using reflectance Fourier Transform Infrared spectroscopy.

    PubMed

    Hopkinson, J; Moustou, C; Charlwood, K A; Newbery, J E; Charlwood, B V

    1985-12-01

    A method has been developed to determine the reflectance Fourier Transform Infrared spectra of plant cells grown in vitro and of the protoplasts released from such cells by enzymatic digestion. It is demonstrated that there is a smooth and reproducible transition in spectral detail as enzymatic digestion procedes. Reflectance Fourier Transform Infrared spectroscopy has been used to monitor the progress of protoplast release during enzymatic digestion of cell wall material. PMID:24254073

  17. Terahertz metamaterials

    DOEpatents

    Peralta, Xomalin Guaiuli; Brener, Igal; O'Hara, John; Azad, Abul; Smirnova, Evgenya; Williams, John D.; Averitt, Richard D.

    2014-08-12

    Terahertz metamaterials comprise a periodic array of resonator elements disposed on a dielectric substrate or thin membrane, wherein the resonator elements have a structure that provides a tunable magnetic permeability or a tunable electric permittivity for incident electromagnetic radiation at a frequency greater than about 100 GHz and the periodic array has a lattice constant that is smaller than the wavelength of the incident electromagnetic radiation. Microfabricated metamaterials exhibit lower losses and can be assembled into three-dimensional structures that enable full coupling of incident electromagnetic terahertz radiation in two or three orthogonal directions. Furthermore, polarization sensitive and insensitive metamaterials at terahertz frequencies can enable new devices and applications.

  18. Far infrared (terahertz) spectroscopy of a series of polycyclic aromatic hydrocarbons and application to structure interpretation of asphaltenes and related compounds.

    PubMed

    Cataldo, Franco; Angelini, Giancarlo; García-Hernández, D Aníbal; Manchado, Arturo

    2013-07-01

    A series of 33 different polycyclic aromatic hydrocarbons (PAHs) were studied by far infrared spectroscopy (terahertz spectroscopy) in the spectral range comprised between 600 and 50 cm(-1). In addition to common PAHs like naphthalene, anthracene, phenanthrene, fluoranthene, picene, pyrene, benzo[?]pyrene, and perylene, also quite unusual PAHs were studied like tetracene, pentacene, acenaphtene, acenaphtylene, triphenylene, and decacyclene. A series of alkylated naphthalenes and anthracenes were studied as well as methypyrene. Partially or totally hydrogenated PAHs were also object of the present investigation, ranging from tetrahydronaphthalene (tetralin) to decahydronaphthalene (decalin), 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, hexahydropyrene, and dodecahydrotriphenylene. Finally, the large and quite rare PAHs coronene, quaterrylene, hexabenzocoronene, and dicoronylene were studied by far infrared spectroscopy. The resulting reference spectra were used in the interpretation of the chemical structure of asphaltenes (as extracted from a heavy petroleum fraction and from bitumen), the chemical structures of other petroleum fractions known as DAE (distillate aromatic extract) and RAE (residual aromatic extract), and a possible interpretation of components of the chemical structure of anthracite coal. Asphaltenes, heavy petroleum fractions, and coal were proposed as model compounds for the interpretation of the emission spectra of certain proto-planetary nebulae (PPNe) with a good matching in the mid infrared between the band pattern of the PPNe emission spectra and the spectra of these oil fractions or coal. Although this study was finalized in an astrochemical context, it may find application also in the petroleum and coal chemistry. PMID:23603577

  19. Frequency selective terahertz retroreflectors

    NASA Astrophysics Data System (ADS)

    Williams, Richard James

    The use of novel optical structures operating at terahertz frequencies in industrial and military applications continues to grow. Some of these novel structures include gratings, frequency selective surfaces, metamaterials and metasurfaces, and retroreflectors. A retroreflector is a device that exhibits enhanced backscatter by concentrating the reflected wave in the direction of the source. Retroreflectors have applications in a variety of diverse fields such as aviation, radar systems, antenna technology, communications, navigation, passive identification, and metrology due to their large acceptance angles and frequency bandwidth. This thesis describes the design, fabrication, and characterization of a retroreflector designed for terahertz frequencies and the incorporation of a frequency selective surface in order to endow the retroreflector with narrow-band frequency performance. The radar cross section of several spherical lens reflectors operating at terahertz frequencies was investigated. Spherical lens reflectors with diameters ranging from 2 mm to 8 mm were fabricated from fused silica ball lenses and their radar cross section was measured at 100 GHz, 160 GHz, and 350 GHz. Crossed-dipole frequency selective surfaces exhibiting band-pass characteristics at 350 GHz fabricated from 12 um-thick Nickel screens were applied to the apertures of the spherical lens reflectors. The radar cross section of the frequency selective retroreflectors was measured at 160 GHz and 350 GHz to demonstrate proof-of-concept of narrow-band terahertz performance.

  20. Weathering Grade Classification of Granite Stone Monument Using Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hyun, C.; Roh, T.; Choi, M.; Park, H.

    2009-05-01

    Stone monument has been placed in field and exposed to rain and wind. This outdoor environment and air pollution induced weathering of stone monument. Weathering grade classification is necessary to manage and conserve stone monuments. Visual interpretation by geologist and laboratory experiments using specimens fallen off from the monument to avoid damage on the monument have been applied to classify weathering grade conventionally. Rocks and minerals absorb some particular wavelength ranges of electromagnetic energy by electronic process and vibrational process of composing elements and these phenomena produce intrinsic diagnostic spectral reflectance curve. Non-destructive technique for weathering degree assessment measures those diagnostic absorption features of weathering products and converts the depths of features related to abundance of the materials to relative weathering degree. We selected granite outcrop to apply conventional six folded weathering grade classification method using Schmidt hammer rebound teste. The correlations between Schmidt hammer rebound values and absorption depths of iron oxides such as ferric oxide in the vicinity of 0.9 micrometer wavelength and clay minerals such as illite and kaolinite in the vicinity of 2.2 micrometer wavelength, representative weathering products of granite, were analyzed. The Schmidt hammer rebound value decreased according to increase of absorption depths induced from those weathering products. Weathering grade classification on the granite stone monument was conducted by using absorption depths of weathering products This research is supported from National Research Institute of Cultural Heritage and we appreciate for this.

  1. Reflectance and Thermal Infrared Spectroscopy of Mars: Relationship Between ISM and TES for Compositional Determinations

    NASA Technical Reports Server (NTRS)

    Boyce, Joseph (Technical Monitor); Mustard, John

    2004-01-01

    Reflectance spectroscopy has demonstrated that high albedo surfaces on Mars contain heavily altered materials with some component of hematite, poorly crystalline ferric oxides, and an undefined silicate matrix. The spectral properties of many low albedo regions indicate crystalline basalts containing both low and high calcium pyroxene, a mineralogy consistent with the basaltic SNC meteorites. The Thermal Emission Spectrometer (TES) experiment on the Mars Geochemical Surveyor has acquired critical new data relevant to surface composition and mineralogy, but in a wavelength region that is complementary to reflectance spectroscopy. The essence of the completed research was to analyze TES data in the context of reflectance data obtained by the French ISM imaging spectrometer experiment in 1989. This approach increased our understanding of the complementary nature of these wavelength regions for mineralogic determinations using actual observations of the martian surface. The research effort focused on three regions of scientific importance: Syrtis Major-Isidis Basin, Oxia Palus-Arabia, and Valles Marineris. In each region distinct spatial variations related to reflectance, and in derived mineralogic information and interpreted compositional units were analyzed. In addition, specific science questions related to the composition of volcanics and crustal evolution, soil compositions and pedogenic processes, and the relationship between pristine lithologies and weathering provided an overall science-driven framework for the work. The detailed work plan involved colocation of TES and ISM data, extraction of reflectance and emissivity spectra from areas of known reflectance variability, and quantitative analysis using factor analysis and statistical techniques to determine the degree of correspondence between these different wavelength regions. Identified coherent variations in TES spectroscopy were assessed against known atmospheric effects to validate that the variations are due to surface properties. With this new understanding of reflectance and emission spectroscopy, mineralogic interpretations were derived and applied to the science objectives of the three regions.

  2. Diffuse Reflectance Spectroscopy of Human Skin Using a Commercial Fiber Optic Spectrometer

    NASA Astrophysics Data System (ADS)

    Atencio, J. A. Delgado; Rodríguez, M. Cunill; Montiel, S. Vázquez y.; Gutiérrez, J. L.; Martínez, F.; Gutiérrez, B.; Orozco, E.; Castro, Jorge; Rodríguez, A. Cornejo

    2008-08-01

    Diffuse reflectance spectroscopy is a reliable and easy to implement technique in human tissue characterization. In this work we evaluate the performance of the commercial USB4000 miniature fiber optic spectrometer in the in-vivo measurement of the diffuse reflectance spectra of different healthy skin sites and lesions in a population of 54 volunteers. Results show, that this spectrometer reproduces well the typical signatures of skin spectra over the 400-1000 nm region. Remarkable spectral differences exist between lesions and normal surrounding skin. A diffusion-based model was used to simulate reflectance spectra collected by the optical probe of the system.

  3. Diffuse Reflectance Spectroscopy of Human Skin Using a Commercial Fiber Optic Spectrometer

    SciTech Connect

    Atencio, J. A. Delgado; Rodriguez, M. Cunill; Montiel, S. Vazquez y; Castro, Jorge; Rodriguez, A. Cornejo; Gutierrez, J. L.; Martinez, F.; Gutierrez, B.; Orozco, E.

    2008-08-11

    Diffuse reflectance spectroscopy is a reliable and easy to implement technique in human tissue characterization. In this work we evaluate the performance of the commercial USB4000 miniature fiber optic spectrometer in the in-vivo measurement of the diffuse reflectance spectra of different healthy skin sites and lesions in a population of 54 volunteers. Results show, that this spectrometer reproduces well the typical signatures of skin spectra over the 400-1000 nm region. Remarkable spectral differences exist between lesions and normal surrounding skin. A diffusion-based model was used to simulate reflectance spectra collected by the optical probe of the system.

  4. Measurement of Trans-Fatty Acids in Cereal Products Without Oil Extraction Using NIR Reflectance Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near infrared (NIR) reflectance spectroscopy was evaluated as a rapid technique, to determine the trans-fatty acid content of ground cereal products. NIR spectra were obtained with a dispersive spectrometer and trans-fatty acids determined by modified AOAC Method 996.01. First derivative PLS1 mode...

  5. Prediction of olive quality using FT-NIR spectroscopy in reflectance and transmittance modes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to use FT-NIR spectroscopy to predict the firmness, oil content and color of two olive (Olea europaea L) varieties (‘Ayvalik’ and ‘Gemlik’). Spectral measurements were performed on the intact olives for the wavelengths of 780-2500 nm in reflectance and for 800-1725...

  6. Absorption and Scattering Coefficients: A Biophysical-Chemistry Experiment Using Reflectance Spectroscopy

    ERIC Educational Resources Information Center

    Cordon, Gabriela B.; Lagorio, M. Gabriela

    2007-01-01

    A biophysical-chemistry experiment, based on the reflectance spectroscopy for calculating the absorption and scattering coefficients of leaves is described. The results show that different plants species exhibit different values for both the coefficients because of their different pigment composition.

  7. Optical reflectivity of solid and liquid methane: Application to spectroscopy of Titan's hydrocarbon lakes

    E-print Network

    Jacobsen, Steven D.

    Optical reflectivity of solid and liquid methane: Application to spectroscopy of Titan direct observations for interpreting their surface compositions. At Titan, the Cassini spacecraft and southern latitudes of Titan. Citation: Adams, K. A., S. D. Jacobsen, Z. Liu, S.-M. Thomas, M. Somayazulu

  8. Nondestructive Olive Quality Detection Using FT-NIR Spectroscopy in Reflectance Mode

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quality features (firmness, oil content and color in terms of hue and chroma) of two olive (Olea europaea L) varieties (‘Ayvalik’ and ‘Gemlik’) were predicted using Fourier transform near-infrared (FT-NIR) spectroscopy. Reflectance measurements of intact olives were performed using a bifurcated fibe...

  9. INVESTIGATING ULTRASONIC DIFFRACTION GRATING SPECTROSCOPY AND REFLECTION TECHNIQUES FOR CHARACTERIZING SLURRY PROPERTIES

    EPA Science Inventory

    The objectives of the project are to investigate the use of (1) ultrasonic diffraction grating spectroscopy (UDGS) for measuring the particle size of a slurry and (2) shear wave reflection techniques to measure the viscosity of a slurry. For the first topic, the basic principle...

  10. Real time, in-situ temperature monitoring using diffuse reflectance spectroscopy

    SciTech Connect

    Booth, J.L.; Beard, B.T.; Pearsall, T.P.; Wang, Z.Z.; Stevens, J.E.; Blain, M.G.; Meisenheimer, T.L.

    1996-11-01

    Real time temperature measurements have been performed on both GaAs and silicon substrates during wafer processing using a technique based upon diffuse reflectance spectroscopy (DRS). Good temperature resolution ({+-}O.4 {degrees}C) and rapid updates have enabled the process control potential of the device to be demonstrated.

  11. FAECAL NEAR INFRARED REFLECTANCE SPECTROSCOPY TO PREDICT DIET QUALITY FOR SHEEP

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Faecal near infrared reflectance spectroscopy (NIRS) is a non-invasive method to determine diet quality in herbivores, but has not been reported for sheep (Ovis aries) in the US. A diet reference chemistry:faecal near infrared spectra calibration (n = 78) was developed to determine if faecal NIRS c...

  12. In vivo detection of epileptic brain tissue using static fluorescence and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Yadav, Nitin; Bhatia, Sanjiv; Ragheb, John; Mehta, Rupal; Jayakar, Prasanna; Yong, William; Lin, Wei-Chiang

    2013-02-01

    Diffuse reflectance and fluorescence spectroscopy are used to detect histopathological abnormalities of an epileptic brain in a human subject study. Static diffuse reflectance and fluorescence spectra are acquired from normal and epileptic brain areas, defined by electrocorticography (ECoG), from pediatric patients undergoing epilepsy surgery. Biopsy specimens are taken from the investigated sites within an abnormal brain. Spectral analysis reveals significant differences in diffuse reflectance spectra and the ratio of fluorescence and diffuse reflectance spectra from normal and epileptic brain areas defined by ECoG and histology. Using these spectral differences, tissue classification models with accuracy above 80% are developed based on linear discriminant analysis. The differences between the diffuse reflectance spectra from the normal and epileptic brain areas observed in this study are attributed to alterations in the static hemodynamic characteristics of an epileptic brain, suggesting a unique association between the histopathological and the hemodynamic abnormalities in an epileptic brain.

  13. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.

    1991-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it was used as the major method of identifying possible mineral analogs of the Martian surface. A summary of proposed Martian surface compositions from reflectance spectroscopy before 1979 was presented. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite were suggested as Mars soil analog materials.

  14. Terahertz Spectroscopy and Global Analysis of the Bending Vibrations of ^{12}C_2H_2 and ^{12}C_2D_2

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.; Pearson, John C.; Pickett, Herbert M.; Lattanzi, Valerio; Walters, Adam

    2009-06-01

    Symmetric molecules have no permanent dipole moment and are undetectable by rotational spectroscopy. Their interstellar observations have previously been limited to mid-infrared vibration-rotation spectroscopy. Although relatively weak, vibrational difference bands provide a means for detection of non polar molecules by terahertz techniques with microwave precision. Herschel, SOFIA, and ALMA have the potential to identify a number of difference bands of light symmetric species, e.g., C_2H_2, CH_4 and C_3. This paper reports the results of the laboratory study on ^{12}C_2H_2 and ^{12}C_2D_2. The symmetric isotopomers of acetylene have two bending modes, the trans bending ?_4 (^1{?}_g), and the cis bending ?_5 (^1{?}_u). For ^{12}C_2H_2, the two bending modes occur at 612 and 729 cm^{-1}, respectively. For ^{12}C_2D_2, the two bending modes occur at 511 and 538 cm^{-1}. The ?_5-?_4 difference bands are allowed and occur in the microwave, terahertz, and far-infrared wavelengths, with band origins at 117 cm^{-1} (3500 GHz) for ^{12}C_2H_2 and 27 cm^{-1} (900 GHz) for ^{12}C_2D_2. Two hundred and fifty-one ^{12}C_2D_2 transitions, which are from ?_5-?_4, (?_5+?_4)-2?_4 and 2?_5-(?_5+?_4) bands, have been measured in the 0.2-1.6 THz region, and 202 of them were observed for the first time. The precision of these measurements is estimated to be from 50 kHz to 100 kHz. A multistate analysis was carried out for the bending vibrational modes ?_4 and ?_5 of ^{12}C_2D_2, which includes the lines observed in this work and prior microwave, far-infrared and infrared data on the pure bending levels. Significantly improved molecular parameters were obtained for ^{12}C_2D_2 by adding the new measurements to the old data set which had only 10 lines with microwave measurement precision. The experiments on ^{12}C_2H_2 are in progress and ten P branch lines have been observed. We will present the ^{12}C_2H_2 results to date.

  15. Diagnostics of pigmented skin tumors based on laser-induced autofluorescence and diffuse reflectance spectroscopy

    SciTech Connect

    Borisova, E; Avramov, L; Troyanova, P; Pavlova, P

    2008-06-30

    Results of investigation of cutaneous benign and malignant pigmented lesions by laser-induced autofluorescence spectroscopy (LIAFS) and diffuse reflectance spectroscopy (DRS) are presented. The autofluorescence of human skin was excited by a 337-nm nitrogen laser. A broadband halogen lamp (400-900 nm) was used for diffuse reflectance measurements. A microspectrometer detected in vivo the fluorescence and reflectance signals from human skin. The main spectral features of benign (dermal nevi, compound nevi, dysplastic nevi) and malignant (melanoma) lesions are discussed. The combined usage of the fluorescence and reflectance spectral methods to determine the type of the lesion, which increases the total diagnostic accuracy, is compared with the usage of LIAFS or DRS only. We also applied colorimetric transformation of the reflectance spectra detected and received additional evaluation criteria for determination of type of the lesion under study. Spectra from healthy skin areas near the lesion were detected and changes between healthy and lesion skin spectra were revealed. The influence of the main skin pigments on the detected spectra is discussed and evaluation of possibilities for differentiation between malignant and benign lesions is performed based on their spectral properties. This research shows that the non-invasive and high-sensitive in vivo detection by means of appropriate light sources and detectors should be possible, related to the real-time determination of existing pathological conditions. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  16. Development of techniques for advanced optical contamination measurement with internal reflection spectroscopy, phase 1, volume 1

    NASA Technical Reports Server (NTRS)

    Hayes, J. D.

    1972-01-01

    The feasibility of monitoring volatile contaminants in a large space simulation chamber using techniques of internal reflection spectroscopy was demonstrated analytically and experimentally. The infrared spectral region was selected as the operational spectral range in order to provide unique identification of the contaminants along with sufficient sensitivity to detect trace contaminant concentrations. It was determined theoretically that a monolayer of the contaminants could be detected and identified using optimized experimental procedures. This ability was verified experimentally. Procedures were developed to correct the attenuated total reflectance spectra for thick sample distortion. However, by using two different element designs the need for such correction can be avoided.

  17. Monitoring of (reactive) ion etching (RIE) with reflectance anisotropy spectroscopy (RAS) equipment

    NASA Astrophysics Data System (ADS)

    Barzen, Lars; Richter, Johannes; Fouckhardt, Henning; Wahl, Michael; Kopnarski, Michael

    2015-02-01

    Experimental results on the application of reflectance anisotropy spectroscopy (RAS) to the monitoring of (reactive) ion etching of monocrystalline semiconductor samples are described. To show the potential of this technique RAS signals collected during etching of GaAs/AlxGa1-xAs multilayer samples are compared to RAS data obtained before during molecular-beam epitaxial (MBE) growth of these very samples. A change of the RIE-RAS spectrum can be attributed to a change of material composition. And the current etch depth can be monitored with an accuracy at least down to several tens of nanometers - f. e. by recording the average reflected intensity.

  18. Terahertz spectroscopy in the pseudo-Kagome system Cu3Bi(SeO3)2O2Br

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Schmidt, M.; Goncharov, Y.; Tsurkan, V.; Krug von Nidda, H.-A.; Loidl, A.; Deisenhofer, J.

    2012-11-01

    Terahertz (THz) transmission spectra have been measured as a function of temperature and magnetic field on single crystals of Cu3Bi(SeO3)2O2Br. In time-domain THz spectra without magnetic field, two resonance absorptions are observed below the magnetic ordering temperature TN˜27.4 K. The corresponding resonance frequencies increase with decreasing temperature and reach energies of 1.28 and 1.23 meV at 3.5 K. Multifrequency electron spin resonance transmission spectra as a function of the applied magnetic field show the field dependence of four magnetic resonance modes, which can be modeled as a ferromagnetic resonance including demagnetization and anisotropy effects.

  19. Time-Domain Terahertz Spectroscopy (0.3 - 7.5 THz) of Molecular Ices of Simple Alcohols

    NASA Astrophysics Data System (ADS)

    McGuire, Brett A.; Ioppolo, Sergio; Allodi, Marco A.; de Vries, Xander; Finneran, Ian; Carroll, Brandon; Blake, Geoffrey

    2014-06-01

    We have recently constructed a time-domain TeraHertz (THz) spectrometer for the study of molecular ices in the far-infrared. Here, we present the results of a study of amorphous and crystalline ices of simple alcohols from methanol (CH_3OH) through butanol (CH_3(CH_2)_3OH) in the region of 0.3 - 7.5 THz. We examine the effects of the length and degree of branching of the carbon chain on the observed spectra arising from the bulk, large-amplitude motions which are prominent in this spectral region. We also discuss these results in an astrochemical context: the application of these spectra to astronomical observations of interstellar ices with Herschel PACS/SPIRE and SOFIA.

  20. Monitoring of landfill leachate dispersion using reflectance spectroscopy and ground-penetrating radar.

    PubMed

    Splajt, T; Ferrier, G; Frostick, L E

    2003-09-15

    The utility of ground-penetrating radar and reflectance spectroscopy in the monitoring of landfill sites has been investigated. Strong correlations between red edge inflection position and chlorophyll and heavy metal concentrations have been demonstrated from grassland species affected by leachate contamination of the soil adjacent to the landfill test site. This study demonstrated that reflectance spectroscopy can identify vegetation affected by leachate-contaminated soil at a range of spatial resolutions. To identify the vegetation affected by leachate contamination, the spectroradiometer must have contiguous bands at sufficient spectral resolution over the critical wave range that measures chlorophyll absorption and the red edge (between 650 and 750 nm). The utility of ground-penetrating radar data to identify leachate escaping from breakout points in the contaminant wall has also been demonstrated. An integrated approach using these techniques, combined with field and borehole sampling and contaminant migration modeling, offers a possible cost-effective monitoring approach for landfill sites. PMID:14524467

  1. Terahertz Technology: A Boon to Tablet Analysis

    PubMed Central

    Wagh, M. P.; Sonawane, Y. H.; Joshi, O. U.

    2009-01-01

    The terahertz gap has a frequency ranges from ?0.3 THz to ?10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets. PMID:20490288

  2. Phonon Mode Transformation Across the Orthohombic-Tetragonal Phase Transition in a Lead Iodide Perovskite CH3NH3PbI3: A Terahertz Time-Domain Spectroscopy Approach.

    PubMed

    La-O-Vorakiat, Chan; Xia, Huanxin; Kadro, Jeannette; Salim, Teddy; Zhao, Daming; Ahmed, Towfiq; Lam, Yeng Ming; Zhu, Jian-Xin; Marcus, Rudolph A; Michel-Beyerle, Maria-Elisabeth; Chia, Elbert E M

    2016-01-01

    We study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3 thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition. The carrier mobility values calculated from the low-temperature phonon mode frequencies, via two theoretical approaches, are found to agree reasonably with the experimental value (?2000 cm(2) V(-1) s(-1)) from a previous time-resolved THz spectroscopy work. Thus, we have established a possible link between terahertz phonon modes and the transport properties of perovskite-based solar cells. PMID:26633131

  3. Terahertz optical properties of the cornea

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Quan; Lu, Yuan-Fu; Jiao, Guo-Hua; Chen, Xian-Feng; Li, Jin-Ying; Chen, Si-Hai; Dong, Yu-Ming; Lv, Jian-Cheng

    2016-01-01

    We present a study aimed at developing a terahertz time domain spectroscopy (THz-TDS) system for detection of the optical properties of ex vivo rabbit corneal tissues with different water content at terahertz frequencies (0.1-0.3 THz). The refractive index decreased with frequency while the absorption coefficient increased with frequency. Our experimental results matched the theoretical calculation very well revealing that both the absorption coefficient and the refractive index of a hydrated cornea were much larger than that of a dehydrated cornea and the terahertz properties depended on the hydrate conditions of the biosamples.

  4. Quantitative reflectance spectroscopy of buddingtonite from the Cuprite mining district, Nevada

    SciTech Connect

    Felzer, B.; Hauff, P.; Goetz, A.F.H.

    1994-02-01

    Buddingtonite, an ammonium-bearing feldspar diagnostic of volcanic-hosted alteration, can be identified and, in some cases, quantitatively measured using short-wave infrared (SWIR) reflectance spectroscopy. In this study over 200 samples from Cuprite, Nevada, were evaluated by X ray diffraction, chemical analysis, scanning electron microscopy, and SWIR reflectance spectroscopy with the objective of developing a quantitative remote-sensing technique for rapid determination of the amount of ammonium or buddingtonite present, and its distribution across the site. Based upon the Hapke theory of radiative transfer from particulate surfaces, spectra from quantitative, physical mixtures were compared with computed mixture spectra. We hypothesized that the concentration of ammonium in each sample is related to the size and shape of the ammonium absorption bands and tested this hypothesis for samples of relatively pure buddingtonite. We found that the band depth of the 2.12-micron NH4 feature is linearly related to the NH4 concentration for the Cuprite buddingtonite, and that the relationship is approximately exponential for a larger range of NH4 concentrations. Associated minerals such as smectite and jarosite suppress the depth of the 2.12-micron NH4 absorption band. Quantitative reflectance spectroscopy is possible when the effects of these associated minerals are also considered.

  5. In Situ Diffuse Reflectance IR Spectroscopy and X-ray Absorption Spectroscopy for Fast Catalytic Processes

    SciTech Connect

    N Marinkovic; Q Wang; A Frenkel

    2011-12-31

    A new instrument for synchronous in situ investigations of catalytic materials by IR and X-ray absorption spectroscopies was designed and built at the X18A beamline of the National Synchrotron Light Source of Brookhaven National Laboratory. It provides analytical tools for solving structural, electronic and kinetic problems in catalysis science by two complementary methods. Among the features attractive for catalysis research are the broad range of catalytically active elements that can be investigated (starting with Ni and beyond), the wide range of reaction conditions (temperatures up to 873 K, various reactive gases) and time scales (starting from tens of seconds). The results of several representative experiments that illustrate the attractive capabilities of the new set-up are discussed.

  6. Terahertz traveling-wave microtube

    NASA Astrophysics Data System (ADS)

    Velazco, Jose E.; Ceperley, Peter H.; Foshee, James F.

    2004-09-01

    Microwave Technologies is developing a revolutionary miniature terahertz traveling-wave microtube (TTM) that will provide sub-millimeter wave radiation for many civilian and military applications. This new concept uses a dielectric microtube in conjunction with a microscopic electron beam. The electron beam is produced by a single micron-sized emitter, which lies underneath the microtube to produce high-power terahertz electromagnetic radiation. The TTM should be easily fabricated using state-of-the-art solid-state technology, and will be a pioneering step towards combining vacuum tube technology with solid-state microfabrication technology. Some of the applications for these exciting new devices include terahertz high-resolution radar, THz chemical and biological sensing, commercial THz line-of-sight networking and ultrahigh-speed computers. A key application of the device under development will be as a miniature terahertz source for biological and chemical spectroscopy. We present detailed numerical and computational analysis of this concept. We also present initial experimental testing of a dielectric microtube designed to operate at 0.1 THz. Once successfully developed, TTMs will be the basis for a new generation of high power terahertz sources capable of producing ultrahigh frequency radiation with high efficiency in an amazingly compact and lightweight package.

  7. Measurement of low loss and mirrors' reflectivity using cavity ring down spectroscopy with high accuracy

    NASA Astrophysics Data System (ADS)

    Yang, Dexing; Jiang, Yajun; Zhao, Jianlin; Di, Nan

    2006-02-01

    Differential laser gyro is an ideal equipment to solve the "lock-in" behavior. The ring cavity must be low loss and the reflectivity of mirrors in gyro must be more than 99.99%. But the insertion of a piece of quartz glass and a Faraday cell in the cavity will broaden the "lock-in" area due to additional loss, so it is very important to measure ultra-high reflectivity of mirrors and the loss of transparent glass plate used in gyro. 632.8nm He-Ne laser is the most suitable light to travel around the ring cavity in gyro, so the traditional cavity ring down spectroscopy (CRDS) must be improved by using continuous-wave (CW) He-Ne laser instead of pulsed one. The results show that the single-pass loss through the glass plate can be kept below 3.0×10 -11cm -1. Using combination of linear and folded cavity ring down spectroscopy, the loss such as absorption of gas in the cavity are counteracted due to the equalized length of cavity, so the reflectivity of the mirrors is measured with high accuracy. The ring down time of the cavity with and without a sample is obtained respectively, and then the total loss of the measured sample is calculated. The results show that the improved CRDS is suitable for accurately measuring low loss of medium and reflectivity of mirrors.

  8. Characterization of material degradation in ceramic matrix composites using infrared reflectance spectroscopy

    SciTech Connect

    Cooney, Adam T.; Flattum-Riemers, Richard Y.; Scott, Benjamin J.

    2011-06-23

    Ceramic matrix composite materials for thermal protection systems are required to maintain operational performance in extreme thermal and mechanical environments. In-service inspection of materials capable of assessing the degree and extent of damage and degradation will be required to ensure the safety and readiness of future air vehicles. Infrared reflectance spectroscopy is an established material characterization technique capable of extracting information regarding the chemical composition of substances. The viability of this technique as a potentially powerful nondestructive evaluation method capable of monitoring degradation in thermal protection system materials subjected to extreme mechanical and thermal environments is analyzed. Several oxide-based and non-oxide-based ceramic matrix composite materials were stressed to failure in a high temperature environment and subsequently measured using infrared reflectance spectroscopy. Spectral signatures at locations along the length of the samples were compared resulting in distinct and monotonic reflectance peak changes while approaching the fracture point. The chemical significance of the observed signatures and the feasibility of infrared reflectance nondestructive evaluation techniques are discussed.

  9. Synthesis, structure, terahertz spectroscopy and luminescent properties of copper (I) complexes with bis(diphenylphosphino)methane and N-donor ligands

    NASA Astrophysics Data System (ADS)

    Fan, Wei-Wei; Li, Zhong-Feng; Li, Jiao-Bao; Yang, Yu-Ping; Yuan, Yuan; Tang, Han-Qin; Gao, Ling-Xiao; Jin, Qiong-Hua; Zhang, Zhen-Wei; Zhang, Cun-Lin

    2015-11-01

    The reactions of copper(I) salts CuX [X = Cl, OTf (OTf = CF3SO3) and ClO4] and bis(diphenylphosphino)methane (dppm) with 4,4-bipyridine (4,4-bipy), 2,2-bipyridine (2,2-bipy), isoquinoline (i-C9H7N) and 1,10-phenanthroline (phen) lead to five new copper(I) complexes: [CuCl(dppm)(i-C9H7N)]2 (1), {[CuCl(dppm)(phen)]2•5H2O}n (2), [Cu2Cl2(dppm)2(4,4-bipy)]•4CH3CN (3), [Cu(dppm)(2,2-bipy)]2(OTf)2 (4), {[Cu2Cl(dppm)2(4,4-bipy)](ClO4)}n (5). Complexes 1, 3 and 4 are of dinuclear structure with eight-membered Cu2P4C2 rings. The structure of compound 2 can be simplified as three-dimensional topology. Complex 5 is of infinite chain structure linked by 4,4-bipy. All these complexes are characterized by IR, elemental analyses, single-crystal X-ray diffraction analysis, luminescence, NMR and terahertz time-domain spectroscopy.

  10. Determination of Cellulose Fiber Structure Using IR Reflectance Spectroscopy of Paper

    NASA Astrophysics Data System (ADS)

    Derkacheva, O. Yu.

    2015-01-01

    A rapid and non-destructive method for analyzing the structure of cellulose fibers using IR reflectance spectroscopy from a paper surface was developed and verified for correctness. IR absorption and reflectance spectra of standard paper samples of known composition (sheets made of four fibers of different origin without additives and with additives of kaolin and chalk) were analyzed. Good correlations between these two spectral methods were found for the studied samples. Calibration curves were useful for assessing the structure of cellulose samples from XVIth century historical paper. Data on the degree of cellulose ordering that were obtained from the paper reflectance spectra indicated that the studied sheets consisted mainly of flax fibers with added cotton. This agreed fully with the historical fact that the studied samples were rag papers.

  11. Active terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong; O' Hara, John F; Taylor, Antoinette J

    2009-01-01

    In this paper we present an overview of research in our group in terahertz (THz) metamaterials and their applications. We have developed a series of planar metamaterials operating at THz frequencies, all of which exhibit a strong resonant response. By incorporating natural materials, e.g. semiconductors, as the substrates or as critical regions of metamaterial elements, we are able to effectively control the metamaterial resonance by the application of external stimuli, e.g., photoexcitation and electrical bias. Such actively controllable metamaterials provide novel functionalities for solid-state device applications with unprecedented performance, such as THz spectroscopy, imaging, and many others.

  12. Terahertz radar cross section measurements.

    PubMed

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-12-01

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar on full-size objects. The measurements are performed in a terahertz time-domain system with freely propagating terahertz pulses generated by tilted pulse front excitation of lithium niobate crystals and measured with sub-picosecond time resolution. The application of a time domain system provides ranging information and also allows for identification of scattering points such as weaponry attached to the aircraft. The shapes of the models and positions of reflecting parts are retrieved by the filtered back projection algorithm. PMID:21164990

  13. Highly Sensitive Terahertz Sensing of Glycerol-Water Mixtures with Metamaterials

    NASA Astrophysics Data System (ADS)

    Miyamaru, F.; Hattori, K.; Shiraga, K.; Kawashima, S.; Suga, S.; Nishida, T.; Takeda, M. W.; Ogawa, Y.

    2013-11-01

    We demonstrate the highly sensitive terahertz (THz) sensing of a water-glycerol mixture poured on a metamaterial surface using reflection-based THz time domain spectroscopy. The reflectance at the resonant dip frequency changes significantly with glycerol concentration. The detection sensitivity is about 8 times higher than that compared to the case without a metamaterial structure. We also investigate how sensitivity depends on the Q factor of the metamaterial resonance for highly absorptive media, such as a water solution in the THz region.

  14. Quantitative Analysis of Naturally Colored Cotton and White Cotton Blends by UV-VIS Diffuse Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hu, X.; Zhang, Q.; Yu, H.; Zhao, D.; Dong, S.; Zhou, W.; Tang, Z.

    2015-01-01

    A new method was discussed to quantitatively analyze the blend ratio of naturally colored cotton (NCC) and white cotton (WC) by UV-vis diffuse reflectance spectroscopy (UV-vis DRS). Three kinds of spectroscopy parameters, diffuse reflectance, reflection absorbance, and the K-M function, were used to correlate them with the blend ratio of NCC/ WC fibers. The results showed that diffuse reflectance and blending ratio had the highest correlation coefficients. Therefore this method can be widely used to quantify the blending ratio of NCC/WC fibers as a result of its greater accuracy and simplicity compared to traditional detection methods.

  15. Terahertz polarization imaging for colon cancer detection

    NASA Astrophysics Data System (ADS)

    Doradla, Pallavi; Alavi, Karim; Joseph, Cecil S.; Giles, Robert H.

    2014-03-01

    Continuous wave terahertz (THz) imaging has the potential to offer a safe, noninvasive medical imaging modality for delineating colorectal cancer. The terahertz reflectance measurements of fresh 3 - 5 mm thick human colonic excisions were acquired using a continuous-wave polarization imaging technique. A CO2 optically pumped Far- Infrared molecular gas laser operating at 584 GHz was used to illuminate the colon tissue, while the reflected signals were detected using a liquid Helium cooled silicon bolometer. Both co-polarized and cross-polarized remittance from the samples was collected using wire grid polarizers in the experiment. The experimental analysis of 2D images obtained from THz reflection polarization imaging techniques showed intrinsic contrast between cancerous and normal regions based on increased reflection from the tumor. Also, the study demonstrates that the cross-polarized terahertz images not only correlates better with the histology, but also provide consistent relative reflectance difference values between normal and cancerous regions for all the measured specimens.

  16. Ultra-broadband terahertz time-domain ellipsometric spectroscopy utilizing GaP and GaSe emitters and an epitaxial layer transferred photoconductive detector

    SciTech Connect

    Yamashita, Masatsugu Takahashi, Hideki; Otani, Chiko; Ouchi, Toshihiko

    2014-02-03

    We present a reflection-type ultra-broadband terahertz (THz) time-domain spectroscopic ellipsometry system covering the frequency range of 0.5–30 THz. GaP (110) and z-cut GaSe crystals are used as emitters to generate the THz and mid-infrared pulses, respectively, and a photoconductive antenna switch using a low-temperature grown GaAs epitaxial layer transferred on Si substrate was used as a detector. By changing the emitter between the GaP and GaSe crystals, the measurable frequency range can be easily switched from the 0.5–7.8 THz range to the 7.8–30 THz range without additional optical alignment. We demonstrated the measurement of the dielectric function in a p-type InAs wafer and the optical conductivity of an indium tin oxide (ITO) thin film. The obtained carrier density and the mobility of the ITO thin film show good agreement with that obtained by the Hall measurement.

  17. Ultra-broadband terahertz time-domain ellipsometric spectroscopy utilizing GaP and GaSe emitters and an epitaxial layer transferred photoconductive detector

    NASA Astrophysics Data System (ADS)

    Yamashita, Masatsugu; Takahashi, Hideki; Ouchi, Toshihiko; Otani, Chiko

    2014-02-01

    We present a reflection-type ultra-broadband terahertz (THz) time-domain spectroscopic ellipsometry system covering the frequency range of 0.5-30 THz. GaP (110) and z-cut GaSe crystals are used as emitters to generate the THz and mid-infrared pulses, respectively, and a photoconductive antenna switch using a low-temperature grown GaAs epitaxial layer transferred on Si substrate was used as a detector. By changing the emitter between the GaP and GaSe crystals, the measurable frequency range can be easily switched from the 0.5-7.8 THz range to the 7.8-30 THz range without additional optical alignment. We demonstrated the measurement of the dielectric function in a p-type InAs wafer and the optical conductivity of an indium tin oxide (ITO) thin film. The obtained carrier density and the mobility of the ITO thin film show good agreement with that obtained by the Hall measurement.

  18. Terahertz spectroscopy and solid-state density functional theory calculation of anthracene: Effect of dispersion force on the vibrational modes

    SciTech Connect

    Zhang, Feng; Tominaga, Keisuke E-mail: tominaga@kobe-u.ca.jp; Hayashi, Michitoshi E-mail: tominaga@kobe-u.ca.jp Wang, Houng-Wei; Kambara, Ohki; Sasaki, Tetsuo; Nishizawa, Jun-ichi E-mail: tominaga@kobe-u.ca.jp

    2014-05-07

    The phonon modes of molecular crystals in the terahertz frequency region often feature delicately coupled inter- and intra-molecular vibrations. Recent advances in density functional theory such as DFT-D{sup *} have enabled accurate frequency calculation. However, the nature of normal modes has not been quantitatively discussed against experimental criteria such as isotope shift (IS) and correlation field splitting (CFS). Here, we report an analytical mode-decoupling method that allows for the decomposition of a normal mode of interest into intermolecular translation, libration, and intramolecular vibrational motions. We show an application of this method using the crystalline anthracene system as an example. The relationship between the experimentally obtained IS and the IS obtained by PBE-D{sup *} simulation indicates that two distinctive regions exist. Region I is associated with a pure intermolecular translation, whereas region II features coupled intramolecular vibrations that are further coupled by a weak intermolecular translation. We find that the PBE-D{sup *} data show excellent agreement with the experimental data in terms of IS and CFS in region II; however, PBE-D{sup *} produces significant deviations in IS in region I where strong coupling between inter- and intra-molecular vibrations contributes to normal modes. The result of this analysis is expected to facilitate future improvement of DFT-D{sup *}.

  19. TERAHERTZ SPECTROSCOPY OF THE BENDING VIBRATIONS OF ACETYLENE {sup 12}C{sub 2}H{sub 2}

    SciTech Connect

    Yu Shanshan; Drouin, Brian J.; Pearson, John C.

    2009-11-01

    Twenty P-branch transitions of {sup 12}C{sub 2}H{sub 2} have been measured in the 0.8-1.6 THz region of its bending vibrational difference band. The accuracy of these measurements is estimated to be 100 kHz. The {sup 12}C{sub 2}H{sub 2} molecules were generated under room temperature by passing 150 mTorr H{sub 2}O vapor through calcium carbide (CaC{sub 2}) powder. The observed transitions were modeled together with prior far-infrared data involving the bending levels with SIGMA{sub t}V{sub t} (t = 4,5)<=2. Frequency predictions of {sup 12}C{sub 2}H{sub 2} in the terahertz region have been greatly improved by adding the first data of 'microwave' precision. The new measurements and predictions reported here will facilitate the analyses of astronomical observations by the high spectral resolution telescopes such as Herschel, SOFIA, and ALMA.

  20. Broadband reflectance spectroscopy for establishing a quantitative metric of vascular leak using the Miles assay

    NASA Astrophysics Data System (ADS)

    McMurdy, John; Reichner, Jonathan; Mathews, Zara; Markey, Mary; Intwala, Sunny; Crawford, Gregory

    2009-09-01

    Monitoring the physiological effects of biological mediators on vascular permeability is important for identifying potential targets for antivascular leak therapy. This therapy is relevant to treatments for pulmonary edema and other disorders. Current methods of quantifying vascular leak are in vitro and do not allow repeated measurement of the same animal. Using an in vivo diffuse reflectance optical method allows pharmacokinetic analysis of candidate antileak molecules. Here, vascular leak is assessed in mice and rats by using the Miles assay and introducing irritation both topically using mustard oil and intradermally using vascular endothelial growth factor (VEGF). The severity of the leak is assessed using broadband diffuse reflectance spectroscopy with a fiber reflectance probe. Postprocessing techniques are applied to extract an artificial quantitative metric of leak from reflectance spectra at vascular leak sites on the skin of the animal. This leak metric is calculated with respect to elapsed time from irritation in both mustard oil and VEGF treatments on mice and VEGF treatments on rats, showing a repeatable increase in leak metric with leak severity. Furthermore, effects of pressure on the leak metric are observed to have minimal effect on the reflectance spectra, while spatial positioning showed spatially nonuniform leak sites.

  1. Characterization of atherosclerotic plaque by reflection spectroscopy and thermography: a comparison

    NASA Astrophysics Data System (ADS)

    Lilledahl, Magnus B.; Haugen, Olav A.; Randeberg, Lise L.; Svaasand, Lars O.

    2005-04-01

    Many methods for detecting and measuring vulnerable atherosclerotic plaques have been proposed. These include reflection spectroscopy, thermography, ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI). This paper presents an analysis and a comparison of two of these methods, near-infrared reflection spectroscopy (NIRS) and thermography. Most of the published literature evaluate methods statistically. A more analytic approach will make it easier to compare the different methods and determine if the measured signal will be strong enough in a real measurement situation. This is the approach taken in this article. Eight samples of human aorta were examined by NIRS and subsequently prepared for histology. A total of 28 measurement points were selected. A measure of the lipid content based on reflection spectra is proposed. Comparisons of this lipid measure with histology show that the lipid content in the plaques yields relatively small changes in the value of this lipid-index. Reflectance spectra from models based on the diffusion approximation for total reflectance were simulated. Temperature measurements were performed on three Watanabe heritable hyperlipidemic (WHHL) rabbits and one New Zealand white (NZW) rabbit with a thermistor-type intravascular temperature sensor. The measurements gave no significant signals which correlated with the subsequent histology. A simple analytic model was developed which indicates that a temperature increase of more than 0.01-0.04 °C at the surface of a vessel wall, due to inflammation in a plaque, is unlikely. Such a small temperature difference will probably be obscured by normal variation in the vessel wall temperature.

  2. Portable, Fiber-Based, Diffuse Reflection Spectroscopy (DRS) Systems for Estimating Tissue Optical Properties.

    PubMed

    Vishwanath, Karthik; Chang, Kevin; Klein, Daniel; Deng, Yu Feng; Chang, Vivide; Phelps, Janelle E; Ramanujam, Nimmi

    2011-02-01

    Steady-state diffuse reflection spectroscopy is a well-studied optical technique that can provide a noninvasive and quantitative method for characterizing the absorption and scattering properties of biological tissues. Here, we compare three fiber-based diffuse reflection spectroscopy systems that were assembled to create a light-weight, portable, and robust optical spectrometer that could be easily translated for repeated and reliable use in mobile settings. The three systems were built using a broadband light source and a compact, commercially available spectrograph. We tested two different light sources and two spectrographs (manufactured by two different vendors). The assembled systems were characterized by their signal-to-noise ratios, the source-intensity drifts, and detector linearity. We quantified the performance of these instruments in extracting optical properties from diffuse reflectance spectra in tissue-mimicking liquid phantoms with well-controlled optical absorption and scattering coefficients. We show that all assembled systems were able to extract the optical absorption and scattering properties with errors less than 10%, while providing greater than ten-fold decrease in footprint and cost (relative to a previously well-characterized and widely used commercial system). Finally, we demonstrate the use of these small systems to measure optical biomarkers in vivo in a small-animal model cancer therapy study. We show that optical measurements from the simple portable system provide estimates of tumor oxygen saturation similar to those detected using the commercial system in murine tumor models of head and neck cancer. PMID:21499501

  3. In vivo characterization of myocardial infarction using fluorescence and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ti, Yalin; Chen, Poching; Lin, Wei-Chiang

    2010-05-01

    We explore the feasibility of using combined fluorescence and diffuse reflectance spectroscopy to characterize a myocardial infarct at different developing stages. An animal study is conducted using rats with surgically induced myocaridal infarction (MI). In vivo fluorescence spectra at 337-nm excitation and diffuse reflectance between 400 and 900 nm are measured from the heart. Spectral acquisition is performed: 1. for normal heart tissue; 2. for the area immediately surrounding the infarct; and 3. for the infarcted tissue itself, one, two, three, and four weeks into MI development. Histological and statistical analyses are used to identify unique pathohistological features and spectral alterations associated with the investigated regions. The main alterations (p<0.05) in diffuse reflectance spectra are identified primarily between 450 and 600 nm. The dominant fluorescence alterations are increases in peak fluorescence intensity at 400 and 460 nm. The extent of these spectral alterations is related to the duration of the infarction. The findings of this study support the concept that optical spectroscopy could be useful as a tool to noninvasively determine the in vivo pathophysiological features of a myocardial infarct and its surrounding tissue, thereby providing real-time feedback to surgeons during various surgical interventions for MI.

  4. Use of a coherent fiber bundle for multi-diameter single fiber reflectance spectroscopy

    PubMed Central

    Hoy, C. L.; Gamm, U. A.; Sterenborg, H. J. C. M.; Robinson, D. J.; Amelink, A.

    2012-01-01

    Multi-diameter single fiber reflectance (MDSFR) spectroscopy enables quantitative measurement of tissue optical properties, including the reduced scattering coefficient and the phase function parameter ?. However, the accuracy and speed of the procedure are currently limited by the need for co-localized measurements using multiple fiber optic probes with different fiber diameters. This study demonstrates the use of a coherent fiber bundle acting as a single fiber with a variable diameter for the purposes of MDSFR spectroscopy. Using Intralipid optical phantoms with reduced scattering coefficients between 0.24 and 3 mm?1, we find that the spectral reflectance and effective path lengths measured by the fiber bundle (NA = 0.40) are equivalent to those measured by single solid-core fibers (NA = 0.22) for fiber diameters between 0.4 and 1.0 mm (r ? 0.997). This one-to-one correlation may hold for a 0.2 mm fiber diameter as well (r = 0.816); however, the experimental system used in this study suffers from a low signal-to-noise for small dimensionless reduced scattering coefficients due to spurious back reflections within the experimental system. Based on these results, the coherent fiber bundle is suitable for use as a variable-diameter fiber in clinical MDSFR quantification of tissue optical properties. PMID:23082287

  5. Terahertz spectroscopic investigation of four kinds of vitamins

    NASA Astrophysics Data System (ADS)

    Zhao, Guozhong; Yu, Bin; Zhang, Cunlin

    2009-11-01

    The terahertz spectra of four kinds of vitamins are presented. The refractive index and absorption spectra of these vitamins are obtained by the terahertz time-domain spectroscopy. The full-geometry optimizations and frequency calculations using the density functional theory are applied to obtain the structure and vibration frequencies of these vitamin molecules. The calculated vibration frequencies are compared with the experimental data. The results show that there are terahertz fingerprint absorptions for all of four kinds of vitamins. The terahertz absorbance spectra of vitamins result from not only the intramolecular vibration modes, but also the intermolecular interaction or phonon modes.

  6. Infrared Attenuated Total Reflectance Spectroscopy: An Innovative Strategy for Analyzing Mineral Components in Energy Relevant Systems

    PubMed Central

    Müller, Christian Menno; Pejcic, Bobby; Esteban, Lionel; Piane, Claudio Delle; Raven, Mark; Mizaikoff, Boris

    2014-01-01

    The direct qualitative and quantitative determination of mineral components in shale rocks is a problem that has not been satisfactorily resolved to date. Infrared spectroscopy (IR) is a non-destructive method frequently used in mineral identification, yet challenging due to the similarity of spectral features resulting from quartz, clay, and feldspar minerals. This study reports on a significant improvement of this methodology by combining infrared attenuated total reflection spectroscopy (IR-ATR) with partial least squares (PLS) regression techniques for classifying and quantifying various mineral components present in a number of different shale rocks. The developed multivariate classification model was calibrated using pure component mixtures of the most common shale minerals (i.e., kaolinite, illite, montmorillonite, calcite, and quartz). Using this model, the IR spectra of 11 real-world shale samples were analyzed and evaluated. Finally, the performance of the developed IR-ATR method was compared with results obtained via X-ray diffraction (XRD) analysis. PMID:25358261

  7. Phthalocyanine identification in paintings by reflectance spectroscopy. A laboratory and in situ study

    NASA Astrophysics Data System (ADS)

    Poldi, G.; Caglio, S.

    2013-06-01

    The importance of identifying pigments using non invasive (n.i.) analyses has gained increasing importance in the field of spectroscopy applied to art conservation and art studies. Among the large set of pigments synthesized and marketed during 20th century, surely phthalocyanine blue and green pigments occupy an important role in the field of painting (including restoration) and printing, thanks to their characteristics like brightness and fastness. This research focused on the most used phthalocyanine blue (PB15:1 and PB15:3) and green pigments (PG7), and on the possibility to identify these organic compounds using a methodology like reflectance spectroscopy in the UV, visible and near IR range (UV-vis-NIR RS), performed easily through portable instruments. Laboratory tests and three examples carried out on real paintings are discussed.

  8. Infrared attenuated total reflection spectroscopy for the characterization of gold nanoparticles in solution.

    PubMed

    López-Lorente, Ángela Inmaculada; Sieger, Markus; Valcárcel, Miguel; Mizaikoff, Boris

    2014-01-01

    In situ synthesis of bare gold nanoparticles mediated by stainless steel as reducing agent was monitored via infrared attenuated total reflection (IR-ATR) spectroscopy. Gold nanoparticles were directly synthesized within the liquid cell of the ATR unit taking immediate advantage of the stainless steel walls of the ATR cell. As nanoparticles were formed, a layer of particles was deposited at the SiO2 ATR waveguide surface. Incidentally, the absorption bands of water increased resulting from surface-enhanced infrared absorption (SEIRA) effects arising from the presence of the gold nanoparticles within the evanescent field. Next to the influence of the Au(III) precursor concentration and the temperature, the suitability of IR-ATR spectroscopy as an innovative tool for investigating changes of nanoparticles in solution, including their aggregation promoted by an increase of the ionic strength or via a pH decrease, and for detailing the sedimentation process of gold nanoparticles was confirmed. PMID:24313342

  9. Infrared attenuated total reflectance spectroscopy: an innovative strategy for analyzing mineral components in energy relevant systems.

    PubMed

    Müller, Christian Menno; Pejcic, Bobby; Esteban, Lionel; Delle Piane, Claudio; Raven, Mark; Mizaikoff, Boris

    2014-01-01

    The direct qualitative and quantitative determination of mineral components in shale rocks is a problem that has not been satisfactorily resolved to date. Infrared spectroscopy (IR) is a non-destructive method frequently used in mineral identification, yet challenging due to the similarity of spectral features resulting from quartz, clay, and feldspar minerals. This study reports on a significant improvement of this methodology by combining infrared attenuated total reflection spectroscopy (IR-ATR) with partial least squares (PLS) regression techniques for classifying and quantifying various mineral components present in a number of different shale rocks. The developed multivariate classification model was calibrated using pure component mixtures of the most common shale minerals (i.e., kaolinite, illite, montmorillonite, calcite, and quartz). Using this model, the IR spectra of 11 real-world shale samples were analyzed and evaluated. Finally, the performance of the developed IR-ATR method was compared with results obtained via X-ray diffraction (XRD) analysis. PMID:25358261

  10. Interaction of mineral surfaces with simple organci molecules by diffuse reflectance IR spectroscopy (DRIFT)

    SciTech Connect

    Joan Thomas; Michael Kelley

    2007-06-18

    Diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS) was used to characterize multi-layers of lysine, glutamic acid and salicylic acid on ?-alumina and kaolinite surfaces. The results agreed well with those previously obtained by ATR-IR in aqueous media where available, indicating that DRIFT may be regarded as effectively an in-situ spectroscopy for these materials. In the case of salicylic acid adsorption onto ?-alumina, DRIFTS was used to identify monolayer coverage and to detect molecules down to coverage of 3% of a monolayer. The spectroscopic results as to coverage were confirmed by analysis of the solutions used for treatment. The spectra obtained allowed identification of changes in the bonding environment with increasing surface coverage. DRIFTS, offers several advantages in terms of materials, experimental technique and data treatment, motivating further investigations.

  11. Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

    SciTech Connect

    Lastras-Martínez, A. E-mail: alastras@gmail.com; Ortega-Gallegos, J.; Guevara-Macías, L. E.; Nuñez-Olvera, O.; Balderas-Navarro, R. E.; Lastras-Martínez, L. F.; Lastras-Montaño, L. A.; Lastras-Montaño, M. A.

    2014-03-01

    We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

  12. Hygrothermal degradation of 3-glycidoxypropyltrimethoxysilane films studied by neutron and X-ray reflectivity and attenuated total reflection infrared spectroscopy.

    SciTech Connect

    Tallant, David Robert; Garcia, Manuel Joseph; Majewski, Jaroslaw; Kent, Michael Stuart; Yim, Hyun

    2005-05-01

    Thin films of organosilanes have great technological importance in the areas of adhesion promotion, durability, and corrosion resistance. However, it is well-known that water can degrade organosilane films, particularly at elevated temperatures. In this work, X-ray and neutron reflectivity (XR and NR) were combined with attenuated total reflection infrared (ATR-IR) spectroscopy to study the chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D{sub 2}O or H{sub 2}O at 80 C. For NR and XR, ultrathin ({approx}100 {angstrom}) films were prepared by spin-coating. Both D{sub 2}O and H{sub 2}O provide neutron scattering contrast with GPS. Variations in the neutron scattering length density (SLD) profiles (a function of mass density and atomic composition) with conditioning time were measured after drying the samples out and also swelled with H{sub 2}O or D{sub 2}O vapor at room temperature. For samples that were dried out prior to measurement, little or no change was observed for H{sub 2}O conditioning up to 3.5 days, but large changes were observed after 30 days of conditioning. The range of conditioning time for this structural change was narrowed to between 4 and 10 days with XR. The SLD profiles indicated that the top portion of the GPS film was transformed into a thick low-density layer after conditioning, but the bottom portion showed little structural change. A previous NR study of as-prepared GPS films involving swelling with deuterated nitrobenzene showed that the central portion of the film has much lower cross-link density than the region nearest the substrate. The present data show that the central portion also swells to a much greater extent with water and hydrolyzes more rapidly. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. For ATR-IR, GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples. The IR spectra revealed an increase in vicinal silanol generation over the first 3 days of conditioning followed by geminal silanol generation. Thus, the structural change detected by NR and XR roughly coincided with the onset of geminal silanol generation. Finally, little change in the reflectivity data was observed for films conditioned with D{sub 2}O at 80 C for 1 month. This indicates that hydrolysis of Si-O-Si is much slower with D{sub 2}O than with H{sub 2}O.

  13. Attenuated total reflection surface-enhanced infrared absorption spectroscopy at a cobalt electrode.

    PubMed

    Huo, Sheng-Juan; Wang, Jin-Yi; Sun, Da-Lin; Cai, Wen-Bin

    2009-10-01

    In situ surface-enhanced infrared absorption spectroscopy (SEIRAS) in attenuated total reflection (ATR) configuration has been extended to a Co electrode fabricated by potentiostatic deposition of a 50-nm-thick Co overlayer onto a Au underlayer chemically preformed on the reflecting plane of an ATR Si hemi-cylindrical prism. The as-prepared Co-on-Au film was characterized with atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The AFM images of the films before and after Co coating revealed island structures facilitating the SEIRA effect with Co nanoparticles much smaller than the underlying Au ones. The XPS spectrum did not contain any characteristic peaks related to Au, suggestive of a virtually pinhole-free nature of the Co overlayer. The voltammetric response of the as-prepared films in phosphate buffer solution (PBS, pH 6.9) was characteristic of a polycrystalline bulk Co electrode. Normally directed unipolar bands were found for surface probe CO molecules on Co surfaces in the PBS with their major band (CO(L)) intensity being one order of magnitude higher than that obtained with conventional IR reflection-absorption spectroscopy (IRRAS). By taking advantage of the higher detection sensitivity, the bands for linearly bonded CO (CO(L)) at 1965-2005 cm(-1) and the multi-bonded (CO(M)) band at 1845-1875 cm(-1) were clearly detected with their Stark tuning rates being 59 and 63 cm(-1) x V(-1), respectively, which would be otherwise unobtainable with the conventional IRRAS in the neutral solution. PMID:19843367

  14. Characterization of a variable angle reflection Fourier transform infrared accessory modified for surface plasmon resonance spectroscopy.

    PubMed

    Menegazzo, Nicola; Kegel, Laurel L; Kim, Yoon-Chang; Booksh, Karl S

    2010-10-01

    The Harrick AutoSeagull variable angle reflection accessory for Fourier transform infrared (FT-IR) spectrometers provides access to various spectroscopic techniques in a highly flexible platform. In particular, its ability to perform total internal reflection measurements is of interest because it also forms the basis for surface plasmon resonance (SPR) spectroscopy in prism-based configurations. The work presented here discusses the modification of the AutoSeagull to perform SPR spectroscopy, allowing for easy incorporation of the technique into most common FT-IR spectrometers. The wavelength dependency of the dielectric constant of the plasmon-supporting metal (in our case, gold) is largely responsible for the sensitivity attributed to changes in the sample's refractive index (RI) monitored by SPR spectroscopy. Furthermore, the optical properties of gold are such that when near-infrared (NIR) and/or mid-infrared (mid-IR) wavelengths are used to excite surface plasmons, higher sensitivities to RI changes are experienced compared to surface plasmons excited with visible wavelengths. The result is that in addition to instrumental simplicity, SPR analysis on FT-IR spectrometers, as permitted by the modified AutoSeagull, also benefits from the wavelength ranges accessible. Adaptation of the AutoSeagull to SPR spectroscopy involved the incorporation of slit apertures to minimize the angular spread reaching the detector, resulting in sharper SPR "dips" but at the cost of noisier spectra. In addition, discussion of the system's analytical performance includes comparison of dip quality as a function of slit size, tailoring of the dip minima location with respect to incident angle, and sensitivity to bulk RI changes. PMID:20925990

  15. Sub-terahertz spectroscopy reveals that proteins influence the properties of water at greater distances than previously detected

    SciTech Connect

    Sushko, Oleksandr; Dubrovka, Rostyslav; Donnan, Robert S.

    2015-02-07

    The initial purpose of the study is to systematically investigate the solvation properties of different proteins in water solution by terahertz (THz) radiation absorption. Transmission measurements of protein water solutions have been performed using a vector network analyser-driven quasi-optical bench covering the WR-3 waveguide band (0.220–0.325 THz). The following proteins, ranging from low to high molecular weight, were chosen for this study: lysozyme, myoglobin, and bovine serum albumin (BSA). Absorption properties of solutions were studied at different concentrations of proteins ranging from 2 to 100 mg/ml. The concentration-dependent absorption of protein molecules was determined by treating the solution as a two-component model first; then, based on protein absorptivity, the extent of the hydration shell is estimated. Protein molecules are shown to possess a concentration-dependent absorptivity in water solutions. Absorption curves of all three proteins sharply peak towards a dilution-limit that is attributed to the enhanced flexibility of protein and amino acid side chains. An alternative approach to the determination of hydration shell thickness is thereby suggested, based on protein absorptivity. The proposed approach is independent of the absorption of the hydration shell. The derived estimate of hydration shell thickness for each protein supports previous findings that protein-water interaction dynamics extends beyond 2-3 water solvation-layers as predicted by molecular dynamics simulations and other techniques such as NMR, X-ray scattering, and neutron scattering. According to our estimations, the radius of the dynamic hydration shell is 16, 19, and 25 Å, respectively, for lysozyme, myoglobin, and BSA proteins and correlates with the dipole moment of the protein. It is also seen that THz radiation can serve as an initial estimate of the protein hydrophobicity.

  16. Sub-terahertz spectroscopy reveals that proteins influence the properties of water at greater distances than previously detected

    NASA Astrophysics Data System (ADS)

    Sushko, Oleksandr; Dubrovka, Rostyslav; Donnan, Robert S.

    2015-02-01

    The initial purpose of the study is to systematically investigate the solvation properties of different proteins in water solution by terahertz (THz) radiation absorption. Transmission measurements of protein water solutions have been performed using a vector network analyser-driven quasi-optical bench covering the WR-3 waveguide band (0.220-0.325 THz). The following proteins, ranging from low to high molecular weight, were chosen for this study: lysozyme, myoglobin, and bovine serum albumin (BSA). Absorption properties of solutions were studied at different concentrations of proteins ranging from 2 to 100 mg/ml. The concentration-dependent absorption of protein molecules was determined by treating the solution as a two-component model first; then, based on protein absorptivity, the extent of the hydration shell is estimated. Protein molecules are shown to possess a concentration-dependent absorptivity in water solutions. Absorption curves of all three proteins sharply peak towards a dilution-limit that is attributed to the enhanced flexibility of protein and amino acid side chains. An alternative approach to the determination of hydration shell thickness is thereby suggested, based on protein absorptivity. The proposed approach is independent of the absorption of the hydration shell. The derived estimate of hydration shell thickness for each protein supports previous findings that protein-water interaction dynamics extends beyond 2-3 water solvation-layers as predicted by molecular dynamics simulations and other techniques such as NMR, X-ray scattering, and neutron scattering. According to our estimations, the radius of the dynamic hydration shell is 16, 19, and 25 Å, respectively, for lysozyme, myoglobin, and BSA proteins and correlates with the dipole moment of the protein. It is also seen that THz radiation can serve as an initial estimate of the protein hydrophobicity.

  17. Point-Contact Andreev Reflection Spectroscopy in Pt-Substituted BaFe2As2

    NASA Astrophysics Data System (ADS)

    Ziemak, Steven; Zhang, Xiaohang; Drye, Tyler; Greene, Richard; Paglione, Johnpierre

    2012-02-01

    We have investigated the superconducting order parameter of BaFe2-xPtxAs2 using point-contact Andreev reflection spectroscopy (PCAR). The samples used were large single crystals with measured Pt concentrations consistent with optimal doping (x = 0.15). Junctions were made between gold or lead tips and the c-axis of the superconducting samples. Conductivity spectra were measured over a range of temperatures and fit to curves generated using the Blonder-Tinkham-Klapwijk (BTK) model for two gaps, one isotropic and one angle-dependent gap with nodes.

  18. Selective reflection spectroscopy of a resonant vapor at the interface with a metallic layer

    NASA Astrophysics Data System (ADS)

    Chevrollier, M.; Oriá, M.; de Souza, J. G.; Bloch, D.; Fichet, M.; Ducloy, M.

    2001-04-01

    We discuss the properties of selective reflection spectroscopy at the interface between a resonant vapor and a complex dense medium, such as a metallic film layered on a dielectric substrate. We show that in the approximation of a low-density vapor, the signal mixes up the absorptive and dispersive components of the ``effective resonant susceptibility'' of the vapor, with the mixture amount governed by simple laws of linear optics. Preliminary experiments performed at the interface between Cs vapor (D2, 852-nm line) and a silver-coated glass window are reported, that show qualitatively the effect of the atom-surface van der Waals interaction.

  19. Effect of probe geometry and optical properties on the sampling depth for diffuse reflectance spectroscopy

    PubMed Central

    Hennessy, Ricky; Goth, Will; Sharma, Manu; Markey, Mia K.; Tunnell, James W.

    2014-01-01

    Abstract. The sampling depth of light for diffuse reflectance spectroscopy is analyzed both experimentally and computationally. A Monte Carlo (MC) model was used to investigate the effect of optical properties and probe geometry on sampling depth. MC model estimates of sampling depth show an excellent agreement with experimental measurements over a wide range of optical properties and probe geometries. The MC data are used to define a mathematical expression for sampling depth that is expressed in terms of optical properties and probe geometry parameters. PMID:25349033

  20. Negative Probability Sampling in Study of Reflection Surface Electron Spectroscopy Spectrum

    E-print Network

    Da, Bo; Ding, ZheJun

    2015-01-01

    We propose a sampling method to include the negative contribution to probability density distribution in a sampling procedure. This sampling method is a universal solution for all negative probability problem and shows extraordinarily power in negative cross section problem. A Monte Carlo simulation including negative cross section contribution is developed and successfully preformed to simulate reflection electron energy loss spectroscopy (REELS) spectra for Ag and Au as examples. Excellent agreement is found between simulated spectra and experimental measurements. Notably improved fits to experimental REELS spectra in low energy loss range illustrate the method's strength as well as the necessity of negative cross section contribution.

  1. Mössbauer spectroscopy, magnetic characteristics, and reflection loss analysis of nickel-strontium substituted cobalt ferrite nanoparticles

    SciTech Connect

    Ghasemi, Ali; Paesano, Andrea; Cerqueira Machado, Carla Fabiana; Shirsath, Sagar E.; Liu, Xiaoxi; Morisako, Akimitsu

    2014-05-07

    In current research work, Co{sub 1-x}Ni{sub x/2}Sr{sub x/2}Fe{sub 2}O{sub 4} (x?=?0–1 in a step of 0.2) ferrite nanoparticles were synthesized by a sol-gel method. According to the evolution in the subspectral areas obtained from Mössbauer spectroscopy, it was found that the relaxing iron belongs mostly to the site B, since the Mössbauer fraction of site A does not vary appreciably. With an increase in Ni-Sr substitution contents in cobalt ferrite, the coercivity and saturation of magnetization decrease. Variation of reflection loss versus frequency in microwave X-band demonstrates that the reflection peak shifts to lower frequency by adding substituted cations and the synthesized nanoparticles can be considered for application in electromagnetic wave absorber technology.

  2. Sediment mineralogy based on visible and near-infrared reflectance spectroscopy

    USGS Publications Warehouse

    Jarrard, R.D.; Vanden Berg, M.D.

    2006-01-01

    Visible and near-infrared spectroscopy (VNIS) can be used to measure reflectance spectra (wavelength 350-2500 nm) for sediment cores and samples. A local ground-truth calibration of spectral features to mineral percentages is calculated by measuring reflectance spectra for a suite of samples of known mineralogy. This approach has been tested on powders, core plugs and split cores, and we conclude that it works well on all three, unless pore water is present. Initial VNIS studies have concentrated on determination of relative proportions of carbonate, opal, smectite and illite in equatorial Pacific sediments. Shipboard VNIS-based determination of these four components was demonstrated on Ocean Drilling Program Leg 199. ?? The Geological Society of London 2006.

  3. Classification of the waxy condition of durum wheat by near infrared reflectance spectroscopy using wavelets and a genetic algorithm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near infrared (NIR) reflectance spectroscopy has been applied to the problem of differentiating four genotypes of durum wheat: ‘waxy’, wx-A1 null, wx-B1 null and wild type. The test data consisted of 95 NIR reflectance spectra of wheat samples obtained from a USDA-ARS wheat breeding program. A two...

  4. Modeling changes in the hemoglobin concentration of skin with total diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Glennie, Diana L.; Hayward, Joseph E.; Farrell, Thomas J.

    2015-03-01

    The ability to monitor changes in the concentration of hemoglobin in the blood of the skin in real time is a key component to personalized patient care. Since hemoglobin has a unique absorption spectrum in the visible light range, diffuse reflectance spectroscopy is the most common approach. Although the collection of the diffuse reflectance spectrum with an integrating sphere (IS) has several calibration challenges, this collection method is sufficiently user-friendly that it may be worth overcoming the initial difficulty. Once the spectrum is obtained, it is commonly interpreted with a log-inverse-reflectance (LIR) or "absorbance" analysis that can only accurately monitor changes in the hemoglobin concentration when there are no changes to the nonhemoglobin chromophore concentrations which is not always the case. We address the difficulties associated with collection of the diffuse reflectance spectrum with an IS and propose a model capable of retrieving relative changes in hemoglobin concentration from the visible light spectrum. The model is capable of accounting for concentration changes in the nonhemoglobin chromophores and is first characterized with theoretical spectra and liquid phantoms. The model is then used in comparison with a common LIR analysis on temporal measurements from blanched and reddened human skin.

  5. Optimally designed narrowband guided-mode resonance reflectance filters for mid-infrared spectroscopy

    PubMed Central

    Liu, Jui-Nung; Schulmerich, Matthew V.; Bhargava, Rohit; Cunningham, Brian T.

    2011-01-01

    An alternative to the well-established Fourier transform infrared (FT-IR) spectrometry, termed discrete frequency infrared (DFIR) spectrometry, has recently been proposed. This approach uses narrowband mid-infrared reflectance filters based on guided-mode resonance (GMR) in waveguide gratings, but filters designed and fabricated have not attained the spectral selectivity (? 32 cm?1) commonly employed for measurements of condensed matter using FT-IR spectroscopy. With the incorporation of dispersion and optical absorption of materials, we present here optimal design of double-layer surface-relief silicon nitride-based GMR filters in the mid-IR for various narrow bandwidths below 32 cm?1. Both shift of the filter resonance wavelengths arising from the dispersion effect and reduction of peak reflection efficiency and electric field enhancement due to the absorption effect show that the optical characteristics of materials must be taken into consideration rigorously for accurate design of narrowband GMR filters. By incorporating considerations for background reflections, the optimally designed GMR filters can have bandwidth narrower than the designed filter by the antireflection equivalence method based on the same index modulation magnitude, without sacrificing low sideband reflections near resonance. The reported work will enable use of GMR filters-based instrumentation for common measurements of condensed matter, including tissues and polymer samples. PMID:22109445

  6. Noninvasive blood glucose sensing on human body with near-infrared reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Zhen-hao; Hao, Chang-ning; Zhang, Lin-lin; Huang, Yan-chao; Shi, Yi-qin; Jiang, Geng-ru; Duan, Jun-li

    2011-08-01

    The non-invasive blood glucose sensing method has shown its high impact on the clinic application. This can make the measurement on the clinically relevant concentrations of glucose be free from the pain of patient. The transmission spectrum study indicates that the dependence of glucose concentration on the absorbance is in linear manner for the glucose concentration in the region of 30mg/dL to 4.5×104mg/dL. By the near infrared reflection spectroscopy of fiber spectrometer, the reflection band between 1.2?m and 1.35?m can be used to correlated with the glucose concentration in the range of 30 to 300 mg/dL. This reflection band is finally used to measure the glucose concentration effect in non-invasive manner, which gives the statistical significance of P value 0.02. Our experiment result shows that it is possible to get the glucose concentration by the near infrared reflection spectrum measurement on the human forefinger. This non-invasive blood glucose sensing method may useful in clinic after more experiment for different people.

  7. Development of magnetic system with high-anisotropy localized magnetic field for terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Azbite, Solveyga E.; Denisultanov, Alaudi K.; Khodzitsky, Mikhail K.

    2015-08-01

    In this paper magnetic system with a localized high-intensity magnetic field due to giant magnetic anisotropy magnets was proposed for THz time-domain spectroscopy. The magnetic system consists of two hemispheres which are made from two types of magnets. The both hemispheres will be used for an improvement of THz generation and one hemisphere will be used for investigation of spectral and optical properties of an object at strong magnetic field. The proposed magnetic system was numerically calculated in COMSOL MultiPhysics using AC/DC Module. These results may be used for development of real magnetic THz time-domain spectroscopy system.

  8. Terahertz analysis of an East Asian historical mural painting

    NASA Astrophysics Data System (ADS)

    Fukunaga, K.; Hosako, I.; Kohdzuma, Y.; Koezuka, T.; Kim, M.-J.; Ikari, T.; Du, X.

    2010-05-01

    Terahertz (THz) spectroscopy and THz and imaging techniques are expected to have great potential for the non-invasive analysis of artworks. We have applied THz imaging to analyse the historic mural painting of a Lamaism temple by using a transportable time-domain THz imaging system; such an attempt is the first in the world. The reflection image revealed that there are two orange colours in the painting, although they appear the same to the naked eye. THz imaging can also estimate the depth of cracks. The colours were examined by X-ray fluorescence and Raman spectroscopy, and the results were found to be in good agreement. This work proved that THz imaging can contribute to the non-invasive analysis of cultural heritage.

  9. Single nanowire photoconductive terahertz detectors.

    PubMed

    Peng, Kun; Parkinson, Patrick; Fu, Lan; Gao, Qiang; Jiang, Nian; Guo, Ya-Nan; Wang, Fan; Joyce, Hannah J; Boland, Jessica L; Tan, Hark Hoe; Jagadish, Chennupati; Johnston, Michael B

    2015-01-14

    Spectroscopy and imaging in the terahertz (THz) region of the electromagnetic spectrum has proven to provide important insights in fields as diverse as chemical analysis, materials characterization, security screening, and nondestructive testing. However, compact optoelectronics suited to the most powerful terahertz technique, time-domain spectroscopy, are lacking. Here, we implement single GaAs nanowires as microscopic coherent THz sensors and for the first time incorporated them into the pulsed time-domain technique. We also demonstrate the functionality of the single nanowire THz detector as a spectrometer by using it to measure the transmission spectrum of a 290 GHz low pass filter. Thus, nanowires are shown to be well suited for THz device applications and hold particular promise as near-field THz sensors. PMID:25490548

  10. Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy

    E-print Network

    Tanner, David B.

    (explosive) materials including 1,3,5 trinitro-s- triazine (RDX) have characteristic spectral features to the secondary explosive 1,3,5 trinitro-s-triazine. Samples were also subjected to Fourier transform infrared THz spectroscopy to the detec- tion of concealed explosives, and chemical and biological agents

  11. Electrical and optical characterization of Group III-V heterostructures with emphasis on terahertz devices

    NASA Astrophysics Data System (ADS)

    Weerasekara, Aruna B.

    Electrical and optical characterizations of heterostructures and thin films based on group III-V compound semiconductors are presented. Optical properties of GaMnN thin films grown by Metalorganic Chemical Vapor Deposition (MOCVD) on GaN/Sapphire templates were investigated using IR reflection spectroscopy. Experimental reflection spectra were fitted using a non-linear fitting algorithm, and the high frequency dielectric constant (epsiloninfinity), optical phonon frequencies of E1TO and E1 LO, and their oscillator strengths (S) and broadening constants (Gamma) were obtained for GaMnN thin films with different Mn fraction. The high frequency dielectric constant (epsiloninfinity) of InN thin films grown by the high pressure chemical vapor deposition (HPCVD) method was also investigated by IR reflection spectroscopy and the average was found to vary between 7.0--8.6. The mobility of free carriers in InN thin films was calculated using the damping constant of the plasma oscillator. The terahertz detection capability of n-type GaAs/AlGaAs Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) structures was demonstrated. A threshold frequency (fc) of 3.2 THz (93 mum) with a peak responsivity of 6.5 A/W at 7.1 THz was obtained using a 0.7 mum thick 1x1018 cm-3 n-type doped GaAs emitter layer and a 1 mum thick undoped Al0.04Ga0.96As barrier layer. Using n-type doped GaAs emitter layers, the possibility of obtaining small workfunctions (Delta) required for terahertz detectors has been successfully demonstrated. In addition, the possibility of using GaN (GaMnN) and InN materials for terahertz detection was investigated and a possible GaN base terahertz detector design is presented. The non-linear behavior of the Inter Pulse Time Intervals (IPTI) of neuron-like electric pulses triggered externally in a GaAs/InGaAs Multi Quantum Well (MQW) structure at low temperature (˜ 10 K) was investigated. It was found that a grouping behavior of IPTIs exists at slow triggering pulse rates. Furthermore, the calculated correlation dimension reveals that the dimensionality of the system is higher than the average dimension found in most of the natural systems. Finally, an investigation of terahertz radiation effect on biological system is reported. Index words. Infrared, Detectors, Terahertz, Optical Phonon, Plasmon, Heterojunction, Homojunction, Free carrier absorption, Quantum efficiency, Responsivity, Dark current, Arrhenius, Absorption coefficient, Dielectric function, High frequency dielectric constant, Plasma frequency, Neuron-like pulses, Negative differential resistance, Correlation dimension, Embedding dimension, Return maps, Bifurcation, and Power spectrum.

  12. UV-Vis Reflection-Absorption Spectroscopy at air-liquid interfaces.

    PubMed

    Rubia-Payá, Carlos; de Miguel, Gustavo; Martín-Romero, María T; Giner-Casares, Juan J; Camacho, Luis

    2015-11-01

    UV-Visible Reflection-Absorption Spectroscopy (UVRAS) technique is reviewed with a general perspective on fundamental and applications. UVRAS is formally identical to IR Reflection-Absorption Spectroscopy (IRRAS), and therefore, the methodology developed for this IR technique can be applied in the UV-visible region. UVRAS can be applied to air-solid, air-liquid or liquid-liquid interfaces. This review focuses on the use of UVRAS for studying Langmuir monolayers. We introduce the theoretical framework for a successful understanding of the UVRAS data, and we illustrate the usage of this data treatment to a previous study from our group comprising an amphiphilic porphyrin. For ultrathin films with a thickness of few nm, UVRAS produces positive or negative bands when p-polarized radiation is used, depending on the incidence angle and the orientation of dipole absorption. UVRAS technique provides highly valuable information on tilt of chromophores at the air-liquid interface, and moreover allows the determination of optical parameters. We propose UVRAS as a powerful technique to investigate the in situ optical properties of Langmuir monolayers. PMID:26385430

  13. High pressure sample cell for total internal reflection fluorescence spectroscopy at pressures up to 2500 bar

    NASA Astrophysics Data System (ADS)

    Koo, Juny; Czeslik, Claus

    2012-08-01

    Total internal reflection fluorescence (TIRF) spectroscopy is a surface sensitive technique that is widely used to characterize the structure and dynamics of molecules at planar liquid-solid interfaces. In particular, biomolecular systems, such as protein adsorbates and lipid membranes can easily be studied by TIRF spectroscopy. Applying pressure to molecular systems offers access to all kinds of volume changes occurring during assembly of molecules, phase transitions, and chemical reactions. So far, most of these volume changes have been characterized in bulk solution, only. Here, we describe the design and performance of a high pressure sample cell that allows for TIRF spectroscopy under high pressures up to 2500 bar (2.5 × 108 Pa), in order to expand the understanding of volume effects from the bulk phase to liquid-solid interfaces. The new sample cell is based on a cylindrical body made of Nimonic 90 alloy and incorporates a pressure transmitting sample cuvette. This cuvette is composed of a fused silica prism and a flexible rubber gasket. It contains the sample solution and ensures a complete separation of the sample from the liquid pressure medium. The sample solution is in contact with the inner wall of the prism forming the interface under study, where fluorescent molecules are immobilized. In this way, the new high pressure TIRF sample cell is very useful for studying any biomolecular layer that can be deposited at a planar water-silica interface. As examples, high pressure TIRF data of adsorbed lysozyme and two phospholipid membranes are presented.

  14. A metal-dielectric antenna for terahertz near-field imaging

    NASA Astrophysics Data System (ADS)

    Klein, N.; Lahl, P.; Poppe, U.; Kadlec, F.; Kužel, P.

    2005-07-01

    We present an antenna-based approach to near-field imaging and spectroscopy, which can be used for both continuous-wave and pulsed broadband electromagnetic radiations from microwave to terahertz frequencies. Our near-field antenna consists of a rectangular-shaped block of low-loss dielectric material sharpened to a pyramidal tip which is partially metallized and terminated by a micron-sized plane facet. At this facet the entire energy of the incident wave is concentrated as a very high but strongly localized electric field, which can be used as a sensitive near-field microprobe for electromagnetic radiation. Currently, experiments in reflection geometry with pulsed terahertz radiation and continuous-wave radiation near 80GHz reveal a frequency-independent spatial resolution of about 20?m corresponding to ? /200 at 80GHz, which is only limited by the size of the facet terminating the tip.

  15. Bidirectional reflectance spectroscopy of carbonaceous chondrites: Implications for water quantification and primary composition

    NASA Astrophysics Data System (ADS)

    Garenne, A.; Beck, P.; Montes-Hernandez, G.; Brissaud, O.; Schmitt, B.; Quirico, E.; Bonal, L.; Beck, C.; Howard, K. T.

    2016-01-01

    In this study, we measured bidirectional reflectance spectra (0.5-4.0 ?m) of 24 CMs, five CRs, one CI, one CV, and one C2 carbonaceous chondrites. These meteorites are known to have experienced an important variability in their relative degrees of aqueous alteration degree (Rubin et al. [2007]. Geochim. Cosmochim. Acta 71, 2361-2382; Howard et al. [2009]. Geochim. Cosmochim. Acta 73, 4576-4589; Howard et al. [2011]. Geochim. Cosmochim. Acta 75, 2735-2751; Alexander et al. [2013]. Geochim. Cosmochim. Acta 123, 244-260). These measurements were performed on meteorite powders inside an environmental cell under a primary vacuum and heated at 60 °C in order to minimize adsorbed terrestrial water. This protocol allows controlling of atmospheric conditions (i.e. humidity) in order to avoid contamination by terrestrial water. We discuss various spectral metrics (e.g. reflectance, band depth, single-scattering albedo, …) in the light of recent bulk composition characterization (Howard et al. [2009]. Geochim. Cosmochim. Acta 73, 4576-4589; Howard et al. [2015]. Geochim. Cosmochim. Acta 149, 206-222; Alexander et al. [2012]. Science 337, 721; Beck et al. [2014]. Icarus 229, 263-277; Garenne et al. [2014]. Geochim. Cosmochim. Acta 137, 93-112). This study reveals variability of reflectance among meteorite groups. The reflectance is not correlated with carbon or hydrogen abundance neither with measured grain size distribution. We suggest that it is rather controlled by the nature of accreted components, in particular the initial matrix/chondrule proportion. Band depth, integrated band depth, mean optical path length, normalized optical path length, effective single-particle absorption thickness were calculated on the so called 3-?m band for reflectance spectra and for single scattering albedo spectra. They were compared with hydrated phase proportions from previous study on the same meteorites by thermogravimetric analyses and infrared spectroscopy in transmission. We find that normalized optical path length (NOPL) is the most appropriate to quantify water abundance, with an absolute error of about 5 wt.%. These datasets also reveal a variability of the band shape between 2.8 and 2.9 ?m, which is interpreted as reflecting variation in the chemical composition and structure of phyllosilicates. This chemical variation could also be used to quantify the aqueous alteration degree between meteorite groups. The combination of reflectance at 2 ?m and the depth of 3-?m band can be combined, to classify carbonaceous chondrites in reflectance in term of primary composition (e.g. matrix/chondrule ratio, carbon content) and secondary processes (e.g. aqueous alteration, thermal metamorphism). This could be used to decipher the nature of aqueous alteration in C-complex asteroids.

  16. Evaluation of vitamin C content in kiwifruit by diffuse reflectance FT-NIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Fu, Xiaping; Ying, Yibin; Lu, Huishan; Yu, Haiyan; Liu, Yande

    2005-11-01

    Vitamin C is considered an important nutrition component of fruits, especially of kiwifruit. Traditional destructive method for vitamin C measurement is very complex and fussy. Near Infrared (NIR)spectroscopy is a promising technique for nondestructive measurement of fruit internal qualities, such as soluble solid content (SSC), valid acidity (VA). The objective of this research was to study the potential of NIR diffuse reflectance spectroscopy as a way for nondestructive measurement of vitamin C content in "Qinmei" kiwifruit. NIR spectral data were collected in the spectral range of 800-2500 nm with different combinations of resolution (4 cm-1, 16 cm-1 and 32 cm-1) and scan number (32, 64 and 128). Statistical models were developed using partial least square (PLS) method. The combination with resolution of 4 cm-1 and scan number of 64 gave the best result when all samples were used in calibration sample set. Then two spectral pretreatments multiplicative signal correction (MSC) and standard normal variate (SNV), and three kinds of mathematical treatment of original spectra, first derivative spectra and second derivative spectra were discussed. The PLS model of second derivative spectra using SNV pretreatment turned out better prediction results: correlation coefficient (r) of 0. 93, root mean square error of calibration (RMSEC) of 9.24 mg/100g and root mean square error of prediction (RMSEP) of 10.3 mg/100g. The results of this study showed that NIR diffuse reflectance spectroscopy could be used for kiwifruit vitamin C prediction. The higher the resolution, the better the results, but longer time will be taken, which may not be suitable for on-line use. Therefore, further research still needs to be done.

  17. Porous polymer fibers for low-loss Terahertz guiding

    E-print Network

    Skorobogatiy, Maksim

    Spectroscopy to Quantify Pharmaceutical Polymorphism and Crystallinity," J. Pharmaceutical Sci. 94, 837-destructive terahertz imaging of illicit drugs using spectral fingerprints," Opt. Express 11, 2549-2554 (2003). 8. T

  18. On the prediction of threshold friction velocity of wind erosion using soil reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Junran; Flagg, Cody; Okin, Gregory S.; Painter, Thomas H.; Dintwe, Kebonye; Belnap, Jayne

    2015-12-01

    Current approaches to estimate threshold friction velocity (TFV) of soil particle movement, including both experimental and empirical methods, suffer from various disadvantages, and they are particularly not effective to estimate TFVs at regional to global scales. Reflectance spectroscopy has been widely used to obtain TFV-related soil properties (e.g., moisture, texture, crust, etc.), however, no studies have attempted to directly relate soil TFV to their spectral reflectance. The objective of this study was to investigate the relationship between soil TFV and soil reflectance in the visible and near infrared (VIS-NIR, 350-2500 nm) spectral region, and to identify the best range of wavelengths or combinations of wavelengths to predict TFV. Threshold friction velocity of 31 soils, along with their reflectance spectra and texture were measured in the Mojave Desert, California and Moab, Utah. A correlation analysis between TFV and soil reflectance identified a number of isolated, narrow spectral domains that largely fell into two spectral regions, the VIS area (400-700 nm) and the short-wavelength infrared (SWIR) area (1100-2500 nm). A partial least squares regression analysis (PLSR) confirmed the significant bands that were identified by correlation analysis. The PLSR further identified the strong relationship between the first-difference transformation and TFV at several narrow regions around 1400, 1900, and 2200 nm. The use of PLSR allowed us to identify a total of 17 key wavelengths in the investigated spectrum range, which may be used as the optimal spectral settings for estimating TFV in the laboratory and field, or mapping of TFV using airborne/satellite sensors.

  19. On the prediction of threshold friction velocity of wind erosion using soil reflectance spectroscopy

    USGS Publications Warehouse

    Li, Junran; Flagg, Cody B.; Okin, Gregory S.; Painter, Thomas H.; Dintwe, Kebonye; Belnap, Jayne

    2015-01-01

    Current approaches to estimate threshold friction velocity (TFV) of soil particle movement, including both experimental and empirical methods, suffer from various disadvantages, and they are particularly not effective to estimate TFVs at regional to global scales. Reflectance spectroscopy has been widely used to obtain TFV-related soil properties (e.g., moisture, texture, crust, etc.), however, no studies have attempted to directly relate soil TFV to their spectral reflectance. The objective of this study was to investigate the relationship between soil TFV and soil reflectance in the visible and near infrared (VIS–NIR, 350–2500 nm) spectral region, and to identify the best range of wavelengths or combinations of wavelengths to predict TFV. Threshold friction velocity of 31 soils, along with their reflectance spectra and texture were measured in the Mojave Desert, California and Moab, Utah. A correlation analysis between TFV and soil reflectance identified a number of isolated, narrow spectral domains that largely fell into two spectral regions, the VIS area (400–700 nm) and the short-wavelength infrared (SWIR) area (1100–2500 nm). A partial least squares regression analysis (PLSR) confirmed the significant bands that were identified by correlation analysis. The PLSR further identified the strong relationship between the first-difference transformation and TFV at several narrow regions around 1400, 1900, and 2200 nm. The use of PLSR allowed us to identify a total of 17 key wavelengths in the investigated spectrum range, which may be used as the optimal spectral settings for estimating TFV in the laboratory and field, or mapping of TFV using airborne/satellite sensors.

  20. Terahertz spectroscopic investigations of leather in terahertz wave range

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2012-03-01

    Pulsed THz time-domain spectroscopy is a coherent technique, in which both the amplitude and the phase of a THz pulse are measured. Recently, material characterization using THz spectroscopy has been applied to biochemicals, pharmaceuticals, polymers and semiconductors and has given us important information. Moreover, THz imaging has progressed and is expected to be applicable for the identification of narcotics and explosives. The most important and characteristic point of THz spectroscopy is said to be its ability to observe intermolecular vibrations in contrast to infrared spectroscopy (IR), which observes intramolecular vibrations. Coherent detection enables direct calculations of both the imaginary and the real parts of the refractive index without using the Kramers-Kronig relations. Terahertz wave spectroscopy has been used to study the properties and absorption spectra characteristic of materials. In this paper, the spectral characteristics of cow skin, pig skin sheep skin, horse skin and deer skin have been measured with terahertz time-domain spectroscopy in the range of 0.1~2.0THz. The results show that THz-TDS technology provides an important tool for quality analysis and detection of leathers.

  1. Terahertz spectroscopic investigations of leather in terahertz wave range

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2011-11-01

    Pulsed THz time-domain spectroscopy is a coherent technique, in which both the amplitude and the phase of a THz pulse are measured. Recently, material characterization using THz spectroscopy has been applied to biochemicals, pharmaceuticals, polymers and semiconductors and has given us important information. Moreover, THz imaging has progressed and is expected to be applicable for the identification of narcotics and explosives. The most important and characteristic point of THz spectroscopy is said to be its ability to observe intermolecular vibrations in contrast to infrared spectroscopy (IR), which observes intramolecular vibrations. Coherent detection enables direct calculations of both the imaginary and the real parts of the refractive index without using the Kramers-Kronig relations. Terahertz wave spectroscopy has been used to study the properties and absorption spectra characteristic of materials. In this paper, the spectral characteristics of cow skin, pig skin sheep skin, horse skin and deer skin have been measured with terahertz time-domain spectroscopy in the range of 0.1~2.0THz. The results show that THz-TDS technology provides an important tool for quality analysis and detection of leathers.

  2. A new, low temperature long-pass cell for mid-infrared to terahertz spectroscopy and synchrotron radiation use

    SciTech Connect

    Kwabia Tchana, Fridolin; Willaert, Fabrice; Landsheere, Xavier; Flaud, Jean-Marie; Lago, Leatitia; Chapuis, Mylène; Herbeaux, Christian; Roy, Pascale; Manceron, Laurent

    2013-09-15

    A new cell has been designed for accurate spectroscopic measurements in the 80–400 K temperature range with variable path lengths from 3 to more than 141 m. The spectral coverage at these temperatures ranges from the visible to less than 10 cm{sup ?1}, thanks to the use of diamond windows. The design of the cryostat and vacuum setups allows vibration-free operation. The equipment provides temperature homogeneity and pressure control to better than 2% over the 100–400 K and the 0.1–1000 mbar ranges. Remote-controlled opto-mechanical systems enable in situ adjustments as well as changes of the optical path length within half an hour, in order to optimize measurement time in an open user facility. It allows then to meet the specific requirements of high resolution measurements on the Far-Infrared AILES beamline at SOLEIL as well at the LISA facility, in Créteil, in the mid-IR. This new instrument opens up the way for many experiments in the field of high-resolution gas-phase IR spectroscopy, in particular, in quantitative spectroscopy for atmospheric applications: measurements of absorption line parameters (absolute intensities, cross sections, and pressure-induced widths) using Fourier transform spectroscopy. The design and performance of the equipment are briefly presented and illustrated on spectroscopic examples.

  3. Feedstock and Web Analysis Using Mid-Infrared Diffuse Reflectance Spectroscopy and Imaging Spectroradiometry

    SciTech Connect

    G.L. Powell; J.E. Parks II

    1997-09-15

    Potential applications of mid-infrared (MIR) spectroscopy in the forest products industry include on-line analysis of feedstock and web materials; these applications differ dramatically in purpose, speed, and overall chemical heterogeneity. Characterization of feedstock will enable sorting of the stock and/or wet chemistry adjustment prior to the web stage of paper production. Sorting will require imaging of the stock as well as classification of the wide variety of chemistry found in recycled stock. At the opposite end of the manufacturing process, on-line analysis of the web will enable adjustment of machine parameters to maximize product quality and minimize waste. Spectroscopic requirements for web analysis include high-speed capability and measurement precision. If successful, both applications could result in a reduction of resource waste, a reduction of plant pollution, and a reduction of energy use while simultaneously improving product quality. Here the progress towards feedstock and web analysis with MIR spectroscopy is presented. To date, work has progressed in three main areas: Diffuse Reflectance mid-Infrared Fourier Transform (DRIFT) spectroscopy of cellulose-based materials, chemometrics analysis, and research of MIR instrumentation for prototype development. The DRIFT spectroscopy data represents a database of the chemistries and spectroscopic signatures of interest to the applications discussed here. Over 50,000 spectra were obtained from cellulose-based materials infised with a wide variety of non-cellulose chemistry. Chemometrics analysis was performed on the DRIFT database to determine the quantitative and qualitative limits of the technique. Emphasis was placed on qualitative evaluation of spectroscopic signatures unique to the particular classes of cellulose-based material; thus, the degree to which classes could be sorted was determined. Finally, investigations of MIR instrumentation suitable for transfer of the technique from the lab-based instrument to a field ready prototype were made.

  4. Technique for examining biological materials using diffuse reflectance spectroscopy and the kubelka-munk function

    DOEpatents

    Alfano, Robert R.; Yang, Yuanlong

    2003-09-02

    Method and apparatus for examining biological materials using diffuse reflectance spectroscopy and the Kubelka-Munk function. In one aspect, the method is used to determine whether a tissue sample is cancerous or not and comprises the steps of (a) measuring the diffuse reflectance from the tissue sample at a first wavelength and at a second wavelength, wherein the first wavelength is a wavelength selected from the group consisting of 255-265 nm and wherein the second wavelength is a wavelength selected from the group consisting of 275-285 nm; (b) using the Kubelka-Munk function to transform the diffuse reflectance measurement obtained at the first and second wavelengths; and (c) comparing a ratio or a difference of the transformed Kubelka-Munk measurements at the first and second wavelengths to appropriate standards determine whether or not the tissue sample is cancerous. One can use the spectral profile of KMF between 250 nm to 300 nm to determine whether or not the tissue sample is cancerous or precancerous. According to the value at the first and second wavelengths determine whether or not the malignant tissue is invasive or mixed invasive and in situ or carcinoma in situ.

  5. Time-Domain TeraHertz Spectroscopy and Observational Probes of Prebiotic Interstellar Gas and Ice Chemistry

    NASA Astrophysics Data System (ADS)

    McGuire, Brett Andrew

    Understanding the origin of life on Earth has long fascinated the minds of the global community, and has been a driving factor in interdisciplinary research for centuries. Beyond the pioneering work of Darwin, perhaps the most widely known study in the last century is that of Miller & Urey, who examined the possibility of the formation of prebiotic chemical precursors on the primordial Earth. More recent studies have shown that amino acids, the chemical building blocks of the biopolymers that comprise life as we know it on Earth, are present in meteoritic samples, and that the molecules extracted from the meteorites display isotopic signatures indicative of an extraterrestrial origin. The most recent major discovery in this area has been the detection of glycine (NH2CH2COOH), the simplest amino acid, in pristine cometary samples returned by the NASA STARDUST mission. Indeed, the open questions left by these discoveries, both in the public and scientific communities, hold such fascination that NASA has designated the understanding of our "Cosmic Origins" as a key mission priority. Despite these exciting discoveries, our understanding of the chemical and physical pathways to the formation of prebiotic molecules is woefully incomplete. This is largely because we do not yet fully understand how the interplay between grain-surface and sub-surface ice reactions and the gasphase affects astrophysical chemical evolution, and our knowledge of chemical inventories in these regions is incomplete. The research presented here aims to directly address both these issues, so that future work to understand the formation of prebiotic molecules has a solid foundation from which to work. From an observational standpoint, a dedicated campaign to identify hydroxylamine (NH2OH), potentially a direct precursor to glycine, in the gas-phase was undertaken. No trace of NH2OH was found. These observations motivated a refinement of the chemical models of glycine formation, and have largely ruled out a gas-phase route to the synthesis of the simplest amino acid in the ISM. A molecular mystery in the case of the carrier of a series of transitions was resolved using observational data toward a large number of sources, confirming the identity of this important carbon-chemistry intermediate B11244 as l-C3H+ and identifying it in at least two new environments. Finally, the doubly-nitrogenated molecule carbodiimide HNCNH was identified in the ISM for the first time through maser emission features in the centimeter-wavelength regime. In the laboratory, a TeraHertz Time-Domain Spectrometer was constructed to obtain the experimental spectra necessary to search for solid-phase species in the ISM in the THz region of the spectrum. These investigations have shown a striking dependence on large-scale, long-range (i.e. lattice) structure of the ices on the spectra they present in the THz. A database of molecular spectra has been started, and both the simplest and most abundant ice species, which have already been identified, as well as a number of more complex species, have been studied. The exquisite sensitivity of the THz spectra to both the structure and thermal history of these ices may lead to better probes of complex chemical and dynamical evolution in interstellar environments.

  6. Spectral interference of terahertz pulses from two laser filaments in air

    NASA Astrophysics Data System (ADS)

    Chen, Yanping; Zhang, Zhelin; Zhang, Zhen; Yuan, Xiaohui; Liu, Feng; Chen, Min; Xu, Jianqiu; Yu, Jin; Sheng, Zhengming; Zhang, Jie

    2015-06-01

    Spectral interference is experimentally demonstrated by two terahertz pulses emitting from filaments induced by two successive femtosecond laser pulses in air. Here, a leading pulse is set to be weaker than a trailing pulse and their temporal separation is larger than the pulse duration of the terahertz pulses. When the leading pulse is stronger than the trailing pulse, the frequency modulation within the whole terahertz envelope is greatly deteriorated due to nonlinear effects applying on the trailing pulse through the plasmas generated by the leading pulses. Such unique terahertz spectrum may find applications in terahertz spectroscopy.

  7. Reflectance spectroscopy of ferric sulfate-bearing montmorillonites as Mars soil analog materials

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Pieters, C. M.; Burns, R. G.; Edwards, J. O.; Mancinelli, R. L.; Froschl, H.

    1995-01-01

    Spectroscopic analyses have shown that smectites enhanced in the laboratory with additional ferric species exhibit important similarities to those of the soils on Mars. Ferrihydrite in these chemically treated smectites has features in the visible to near-infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. New samples have been prepared with sulfate as well, because S was found by Viking to be a major component in the surface material on Mars. A suite of ferrihydrite-bearing and ferric sulfate-bearing montmorillonites, prepared with variable Fe3+ and S concentrations and variable pH conditions, has been analyzed using reflectance spectroscopy in the visible and infrared regions, Mossbauer spectroscopy at room temperature and 4 K, differential thermal analysis, and X-ray diffraction. These analyses support the formation of ferrihydrite of variable crystallinity in the ferrihydrite-bearing montmorillonites and a combination of schwertmannite and ferrihydrite in the ferric sulfate-bearing montmorillonites. Small quantities of poorly crystalline or nanophase forms of other ferric materials may also be present in these samples. The chemical formation conditions of the ferrihydrite-bearing and ferric sulfate-bearing montmorillonites influence the character of the low temperature Mossbauer sextets and the visible reflectance spectra. An absorption minimum is observed at 0.88-0.89 micrometers in spectra of the ferric sulfate-bearing samples, and at 0.89-0.92 micrometers in spectra of the ferrihydrate-bearing montmorillonites. Mossbauer spectra of the ferric sulfate-bearing montmorillonites indicate variable concentrations of ferrihydrite and schwertmannite in the interlaminar spaces and along grain surfaces. Dehydration under reduced atmospheric pressure conditions induces a greater effect on the adsorbed and interlayer water in ferrihydrite-bearing montmorillonite than on the water in ferric sulfate-bearing montmorillonite. Reflectance spectra of ferric sulfate-bearing montmorillonite include a strong 3-micrometers band that is more resistant to dry atmospheric conditions than the 3-micrometers band in spectra of similarly prepared ferrihydrite-bearing montmorillonites.

  8. Quantitative assessment of hydrocarbon contamination in soil using reflectance spectroscopy: a "multipath" approach.

    PubMed

    Schwartz, Guy; Ben-Dor, Eyal; Eshel, Gil

    2013-11-01

    Petroleum hydrocarbons are contaminants of great significance. The commonly used analytic method for assessing total petroleum hydrocarbons (TPH) in soil samples is based on extraction with 1,1,2-Trichlorotrifluoroethane (Freon 113), a substance prohibited to use by the Environmental Protection Agency. During the past 20 years, a new quantitative methodology that uses the reflected radiation of solids has been widely adopted. By using this approach, the reflectance radiation across the visible, near infrared-shortwave infrared region (400-2500 nm) is modeled against constituents determined using traditional analytic chemistry methods and then used to predict unknown samples. This technology is environmentally friendly and permits rapid and cost-effective measurements of large numbers of samples. Thus, this method dramatically reduces chemical analytical costs and secondary pollution, enabling a new dimension of environmental monitoring. In this study we adapted this approach and developed effective steps in which hydrocarbon contamination in soils can be determined rapidly, accurately, and cost effectively solely from reflectance spectroscopy. Artificial contaminated samples were analyzed chemically and spectrally to form a database of five soils contaminated with three types of petroleum hydrocarbons (PHCs), creating 15 datasets of 48 samples each at contamination levels of 50-5000 wt% ppm (parts per million). A brute force preprocessing approach was used by combining eight different preprocessing techniques with all possible datasets, resulting in 120 different mutations for each dataset. The brute force was done based on an innovative computing system developed for this study. A new parameter for evaluating model performance scoring (MPS) is proposed based on a combination of several common statistical parameters. The effect of dividing the data into training validation and test sets on modeling accuracy is also discussed. The results of this study clearly show that predicting TPH levels at low concentrations in selected soils at high precision levels is viable. Dividing a dataset into training, validation, and test groups affects the modeling process, and different preprocessing methods, alone or in combination, need to be selected based on soil type and PHC type. MPS was found to be a better parameter for selecting the best performing model than ratio of prediction to deviation, yielding models with the same performance but less complicated and more stable. The use of the "all possibilities" system proved to be mandatory for efficient optimal modeling of reflectance spectroscopy data. PMID:24160885

  9. Analysis of a seventeenth-century panel painting by reflection terahertz time-domain imaging (THz-TDI): contribution of ultrafast optics to museum collections inspection

    NASA Astrophysics Data System (ADS)

    Koch Dandolo, Corinna L.; Filtenborg, Troels; Skou-Hansen, Jacob; Jepsen, Peter Uhd

    2015-11-01

    Terahertz time-domain imaging (THz -TDI) has been applied for nondestructive visualization of a hidden painting and other subsurface composition layers of a seventeenth-century panel painting belonging to the National Gallery of Denmark. Plan-type and cross-sectional scans realized by THz have been compared with images obtained by X-radiography, thus helping in a deep understanding of the strengths and limitations of this technique for art diagnostic purposes and in defining its rule among the other complementary investigation tools for nondestructive inspection of art pieces.

  10. Fast determination of total ginsenosides content in ginseng powder by near infrared reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Hua-cai; Chen, Xing-dan; Lu, Yong-jun; Cao, Zhi-qiang

    2006-01-01

    Near infrared (NIR) reflectance spectroscopy was used to develop a fast determination method for total ginsenosides in Ginseng (Panax Ginseng) powder. The spectra were analyzed with multiplicative signal correction (MSC) correlation method. The best correlative spectra region with the total ginsenosides content was 1660 nm~1880 nm and 2230nm~2380 nm. The NIR calibration models of ginsenosides were built with multiple linear regression (MLR), principle component regression (PCR) and partial least squares (PLS) regression respectively. The results showed that the calibration model built with PLS combined with MSC and the optimal spectrum region was the best one. The correlation coefficient and the root mean square error of correction validation (RMSEC) of the best calibration model were 0.98 and 0.15% respectively. The optimal spectrum region for calibration was 1204nm~2014nm. The result suggested that using NIR to rapidly determinate the total ginsenosides content in ginseng powder were feasible.

  11. Reflection-Absorption Infrared Spectroscopy of Thin Films Using an External Cavity Quantum Cascade Laser

    SciTech Connect

    Phillips, Mark C.; Craig, Ian M.; Blake, Thomas A.

    2013-02-04

    We present experimental demonstrations using a broadly tunable external cavity quantum cascade laser (ECQCL) to perform Reflection-Absorption InfraRed Spectroscopy (RAIRS) of thin layers and residues on surfaces. The ECQCL compliance voltage was used to measure fluctuations in the ECQCL output power and improve the performance of the RAIRS measurements. Absorption spectra from self-assembled monolayers of a fluorinated alkane thiol and a thiol carboxylic acid were measured and compared with FTIR measurements. RAIRS spectra of the explosive compounds PETN, RDX, and tetryl deposited on gold substrates were also measured. Rapid measurement times and low noise were demonstrated, with < 1E-3 absorbance noise for a 10 second measurement time.

  12. Point-contact Andreev-reflection spectroscopy in anisotropic superconductors: The importance of directionality (Review Article)

    NASA Astrophysics Data System (ADS)

    Daghero, D.; Tortello, M.; Pecchio, P.; Stepanov, V. A.; Gonnelli, R. S.

    2013-03-01

    Point-contact Andreev-reflection spectroscopy (PCARS) has demonstrated to be one of the most effective experimental tools for the investigation of fundamental properties of superconductors such as the superconducting gap and the electron-phonon (or, more generally, electron-boson) coupling. By reviewing relevant examples reported in literature and presenting new results, in this paper we show that when the direction of the interface with respect to the crystallographic axes can be controlled (as in single crystals and epitaxial films) PCARS can provide invaluable information about the anisotropy of the pairing wavefunction or—in the case of multiband superconductors—on the number, amplitude and symmetry of the energy gaps. Moreover, the analysis of PCARS results within a suitable 3D generalization of the BTK model allows obtaining qualitative information about the topology of the Fermi surface.

  13. Andreev Reflection Spectroscopy of Nb-doped Bi2Se3 Topological Insulator

    NASA Astrophysics Data System (ADS)

    Kurter, C.; Finck, A. D. K.; Qiu, Y.; Huemiller, E.; Weis, A.; Atkinson, J.; Medvedeva, J.; Hor, Y. S.; van Harlingen, D. J.

    2015-03-01

    Doped topological insulators are speculated to realize p-wave superconductivity with unusual low energy quasiparticles, such as surface Andreev bound states. We present point contact spectroscopy of thin exfoliated flakes of Nb-doped Bi2Se3 where superconductivity persists up to ~ 1 K, compared to 3.2 K in bulk crystals. The critical magnetic field is strongly anisotropic, consistent with quasi-2D behavior. Andreev reflection measurements of devices with low resistance contacts result in prominent BTK-like behavior with an enhanced conductance plateau at low bias. For high resistance contacts, we observe a split zero bias conductance anomaly and additional features at the superconducting gap. Our results suggest that this material is a promising platform for studying topological superconductivity. We acknowledge support from Microsoft Project Q.

  14. Experimental analysis of bruises in human volunteers using radiometric depth profiling and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Vidovi?, Luka; Milani?, Matija; Majaron, Boris

    2015-07-01

    We combine pulsed photothermal radiometry (PPTR) depth profiling with diffuse reflectance spectroscopy (DRS) measurements for a comprehensive analysis of bruise evolution in vivo. While PPTR enables extraction of detailed depth distribution and concentration profiles of selected absorbers (e.g. melanin, hemoglobin), DRS provides information in a wide range of visible wavelengths and thus offers an additional insight into dynamics of the hemoglobin degradation products. Combining the two approaches enables us to quantitatively characterize bruise evolution dynamics. Our results indicate temporal variations of the bruise evolution parameters in the course of bruise self-healing process. The obtained parameter values and trends represent a basis for a future development of an objective technique for bruise age determination.

  15. Quantitative characterization of traumatic bruises by combined pulsed photothermal radiometry and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Vidovi?, Luka; Milani?, Matija; Randeberg, Lise L.; Majaron, Boris

    2015-02-01

    We apply diffuse reflectance spectroscopy (DRS) and pulsed photothermal radiometry (PPTR) for characterization of the bruise evolution process. While DRS provides information in a wide range of visible wavelengths, the PPTR enables extraction of detailed depth distribution and concentration profiles of selected absorbers (e.g. melanin, hemoglobin). In this study, we simulate experimental DRS spectra and PPTR signals using the Monte Carlo technique and focus on characterization of a suitable fitting approach for their analysis. We find inverse Monte Carlo to be superior to the diffusion approximation approach for the inverse analysis of DRS spectra. The analysis is then augmented with information obtainable by the fitting of the PPTR signal. We show that both techniques can be coupled in a combined fitting approach. The combining of two complementary techniques improves the robustness and accuracy of the inverse analysis, enabling a comprehensive quantitative characterization of the bruise evolution dynamics.

  16. Monitoring laser cleaning of titanium alloys by probe beam reflection and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Whitehead, D. J.; Crouse, P. L.; Schmidt, M. J. J.; Li, L.; Turner, M. W.; Smith, A. J. E.

    2008-10-01

    Studies have shown excimer laser cleaning to be an effective non-chemical alternative method for removing contaminants from surfaces of titanium alloys in preparation for electron beam welding and diffusion bonding, with reference to aerospace applications. Among several important criteria for process acceptability, is the absence of oxide formation. This paper investigates the viability of using a probe beam reflection (PBR) system and laser plume emission spectroscopy (PES) for detection of incipient oxide formation on three typical aerospace titanium alloys, viz. Ti64, Ti6246, and IMI834. These diagnostic techniques have been shown to be capable of sensing different components in the emission plume and yield quantitative results. Results from this work correlate closely with previously reported cleaning mechanisms. The oxidation threshold, as well as the operating window for successful decontamination, is discussed.

  17. Attenuated total reflectance Fourier transform infrared spectroscopy analysis of red seal inks on questioned document.

    PubMed

    Nam, Yun Sik; Park, Jin Sook; Kim, Nak-Kyoon; Lee, Yeonhee; Lee, Kang-Bong

    2014-07-01

    Seals are traditionally used in the Far East Asia to stamp an impression on a document in place of a signature. In this study, an accuser claimed that a personal contract regarding mining development rights acquired by a defendant was devolved to the accuser because the defendant stamped the devolvement contract in the presence of the accuser and a witness. The accuser further stated that the seal ink stamped on the devolvement contract was the same as that stamped on the development rights application document. To verify this, the seals used in two documents were analyzed using micro-attenuated total reflectance Fourier transform infrared spectroscopy and infrared spectra. The findings revealed that the seals originated from different manufacturers. Thus, the accuser's claim on the existence of a devolvement contract was proved to be false. PMID:24844350

  18. [Applications of near infrared reflectance spectroscopy technique to determination of forage mycotoxins].

    PubMed

    Xu, Qing-Fang; Han, Jian-Guo; Yu, Zhu; Yue, Wen-Bin

    2010-05-01

    The near infrared reflectance spectroscopy technique (NIRS) has been explored at many fields such as agriculture, food, chemical, medicine, and so on, due to its rapid, effective, non-destructive, and on-line characteristics. Fungi invasion in forage materials during processing and storage would generate mycotoxins, which were harmful for people and animal through food chains. The determination of mycotoxins included the overelaborated pretreatments such as milling, extracting, chromatography and subsequent process such as enzyme linked immunosorbent assay, high performance liquid chromatography, and thin layer chromatography. The authors hope that high precision and low detection limit spectrum instrument, and software technology and calibration model of mycotoxins determination, will fast measure accurately the quality and quantity of mycotoxins, which will provide basis for reasonable process and utilization of forage and promote the application of NIRS in the safety livestock product. PMID:20672610

  19. Inexpensive diffuse reflectance spectroscopy system for measuring changes in tissue optical properties

    NASA Astrophysics Data System (ADS)

    Glennie, Diana L.; Hayward, Joseph E.; McKee, Daniel E.; Farrell, Thomas J.

    2014-10-01

    The measurement of changes in blood volume in tissue is important for monitoring the effects of a wide range of therapeutic interventions, from radiation therapy to skin-flap transplants. Many systems available for purchase are either expensive or difficult to use, limiting their utility in the clinical setting. A low-cost system, capable of measuring changes in tissue blood volume via diffuse reflectance spectroscopy is presented. The system consists of an integrating sphere coupled via optical fibers to a broadband light source and a spectrometer. Validation data are presented to illustrate the accuracy and reproducibility of the system. The validity and utility of this in vivo system were demonstrated in a skin blanching/reddening experiment using epinephrine and lidocaine, and in a study measuring the severity of radiation-induced erythema during radiation therapy.

  20. Reflection-absorption infrared spectroscopy of thin films using an external cavity quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Phillips, Mark C.; Craig, Ian M.; Blake, Thomas A.

    2013-01-01

    We present experimental demonstrations using a broadly tunable external cavity quantum cascade laser (ECQCL) to perform Reflection-Absorption InfraRed Spectroscopy (RAIRS) of thin layers and residues on surfaces. The ECQCL compliance voltage was used to measure fluctuations in the ECQCL output power and improve the performance of the RAIRS measurements. Absorption spectra from self-assembled monolayers of a fluorinated alkane thiol and a thiol carboxylic acid were measured and compared with FTIR measurements. RAIRS spectra of the explosive compounds PETN, RDX, and tetryl deposited on gold substrates were also measured. Rapid measurement times and low noise were demonstrated, with <1E-3 absorbance noise for a 10 second measurement time.

  1. Comparison of visible and near infrared reflectance spectroscopy on fat to authenticate dietary history of lambs.

    PubMed

    Huang, Y; Andueza, D; de Oliveira, L; Zawadzki, F; Prache, S

    2015-11-01

    Since consumers are showing increased interest in the origin and method of production of their food, it is important to be able to authenticate dietary history of animals by rapid and robust methods used in the ruminant products. Promising breakthroughs have been made in the use of spectroscopic methods on fat to discriminate pasture-fed and concentrate-fed lambs. However, questions remained on their discriminatory ability in more complex feeding conditions, such as concentrate-finishing after pasture-feeding. We compared the ability of visible reflectance spectroscopy (Vis RS, wavelength range: 400 to 700 nm) with that of visible-near-infrared reflectance spectroscopy (Vis-NIR RS, wavelength range: 400 to 2500 nm) to differentiate between carcasses of lambs reared with three feeding regimes, using partial least square discriminant analysis (PLS-DA) as a classification method. The sample set comprised perirenal fat of Romane male lambs fattened at pasture (P, n=69), stall-fattened indoors on commercial concentrate and straw (S, n=55) and finished indoors with concentrate and straw for 28 days after pasture-feeding (PS, n=65). The overall correct classification rate was better for Vis-NIR RS than for Vis RS (99.0% v. 95.1%, P<0.05). Vis-NIR RS allowed a correct classification rate of 98.6%, 100.0% and 98.5% for P, S and PS lambs, respectively, whereas Vis RS allowed a correct classification rate of 98.6%, 94.5% and 92.3% for P, S and PS lambs, respectively. This study suggests the likely implication of molecules absorbing light in the non-visible part of the Vis-NIR spectra (possibly fatty acids), together with carotenoid and haem pigments, in the discrimination of the three feeding regimes. PMID:26165321

  2. In-vivo reflection spectroscopy measurements in pig brain during stereotactic surgery

    NASA Astrophysics Data System (ADS)

    Antonsson, Johan; Eriksson, Ola; Wardell, Karin

    2003-07-01

    Radio frequency (RF) lesioning in the human brain is a common surgical therapy for relieving severe pain as well as for movement disorders such as Parkinsonia. During the procedure a small electrode is introduced by stereotactic means towards a target area localized by CT or MRI. An RF-current is applied through the electrode tip when positioned in the target area. The tissue in the proximity of the tip is heated by the current and finally coagulated. The overall aim of this study was to improve the RF-technique and its ability to estimate lesion size by means of optical methods. Therefore, the optical differences between white and gray matter, as well as lesioned and unlesioned tissue were investigated. Reflection spectroscopy measurements in the range of 450-800 nm were conducted on fully anesthetized pigs during stereotactic RF-lesioning (n=6). Light from a tungsten lamp was guided to the electrode tip through optical fibers, inserted along a 2 mm in diameter monopolar RF-electrode. Measurements were performed in steps of 0-10 mm from the target in each hemisphere towards the entry point of the skull. In the central gray of the porcine brain measurements were performed both before and after the creation of a lesion. A total of 55 spectra were collected during this study. Correlation to tissue type was done using post-operative MR-images. The spectral signature for white and gray matter differs significantly for the entire spectral range of 450-800 nm. Pre- and post-lesioning reflection spectroscopy showed the largest differences below 600 and above 620 nm, which implies that lasers within this wavelength range may be useful for in-vivo measurements of tissue optical changes during RF-lesioning.

  3. Investigating Ultrasonic Diffraction Grating Spectroscopy and Reflection Techniques for Characterizing Slurry Properties

    SciTech Connect

    Burgess, L.W.; Brodsky, A.M.

    2005-12-15

    The U.S. Department of Energy (DOE) has millions of gallons of radioactive liquid and sludge wastes that must be retrieved from underground storage tanks. This waste, in the form of slurries, must be transferred and processed to a final form, such as glass logs. On-line instrumentation to measure the properties of these slurries in real-time during transport is needed in order to prevent plugging and reduce excessive dilution. The results, describes a collaborative effort between Pacific Northwest National Laboratory (PNNL) and the University of Washington to develop a completely new method for using ultrasonics to measure the particle size and viscosity of a slurry. The concepts are based on work in optics on grating-light-reflection spectroscopy (GLRS) at the University of Washington and work on ultrasonic diffraction grating spectroscopy (UDGS) carried out at PNNL. The objective of the research was to extend the GLRS theory for optics to ultrasonics, and to demonstrate its capabilities of UDGS. The proposed ultrasonic method could result in an instrument that would be simple, rugged, and very compact, allowing it to be implemented as part of a pipeline wall at facilities across the DOE complex

  4. Multipitched Diffraction Gratings for Surface Plasmon Resonance-Enhanced Infrared Reflection Absorption Spectroscopy.

    PubMed

    Petefish, Joseph W; Hillier, Andrew C

    2015-11-01

    We demonstrate the application of metal-coated diffraction gratings possessing multiple simultaneous pitch values for surface enhanced infrared absorption (SEIRA) spectroscopy. SEIRA increases the magnitude of vibrational signals in infrared measurements by one of several mechanisms, most frequently involving the enhanced electric field associated with surface plasmon resonance (SPR). While the majority of SEIRA applications to date have employed nanoparticle-based plasmonic systems, recent advances have shown how various metals and structures lead to similar signal enhancement. Recently, diffraction grating couplers have been demonstrated as a highly tunable platform for SEIRA. Indeed, gratings are an experimentally advantageous platform due to the inherently tunable nature of surface plasmon excitation at these surfaces since both the grating pitch and incident angle can be used to modify the spectral location of the plasmon resonance. In this work, we use laser interference lithography (LIL) to fabricate gratings possessing multiple pitch values by subjecting photoresist-coated glass slides to repetitive exposures at varying orientations. After metal coating, these gratings produced multiple, simultaneous plasmon peaks associated with the multipitched surface, as identified by infrared reflectance measurements. These plasmon peaks could then be coupled to vibrational modes in thin films to provide localized enhancement of infrared signals. We demonstrate the flexibility and tunability of this platform for signal enhancement. It is anticipated that, with further refinement, this approach might be used as a general platform for broadband enhancement of infrared spectroscopy. PMID:26458177

  5. Identification of species' blood by attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy.

    PubMed

    Mistek, Ewelina; Lednev, Igor K

    2015-09-01

    Blood is one of the most common and informative forms of biological evidence found at a crime scene. A very crucial step in forensic investigations is identifying a blood stain's origin. The standard methods currently employed for analyzing blood are destructive to the sample and time-consuming. In this study, attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy is used as a confirmatory, nondestructive, and rapid method for distinction between human and animal (nonhuman) blood. Partial least squares-discriminant analysis (PLS-DA) models were built and demonstrated complete separation between human and animal donors, as well as distinction between three separate species: human, cat, and dog. Classification predictions of unknown blood donors were performed by the model, resulting in 100 % accuracy. This study demonstrates ATR FT-IR spectroscopy's great potential for blood stain analysis and species discrimination, both in the lab and at a crime scene since portable ATR FT-IR instrumentation is commercially available. PMID:26195028

  6. Early detection of cell activation events by means of attenuated total reflection Fourier transform infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Titus, Jitto; Filfili, Chadi; Hilliard, Julia K.; Ward, John A.; Unil Perera, A. G.

    2014-06-01

    Activation of Jurkat T-cells in culture following treatment with anti-CD3 (Cluster of Differentiation 3) antibody is detectable by interrogating the treated T-cells using the Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) Spectroscopy technique. Cell activation was detected within 75 min after the cells encountered specific immunoglobulin molecules. Spectral markers noted following ligation of the CD3 receptor with anti CD3 antibody provides proof-of-concept that ATR-FTIR spectroscopy is a sensitive measure of molecular events subsequent to cells interacting with anti-CD3 Immunoglobulin G. The resultant ligation of the CD3 receptor results in the initiation of well defined, specific signaling pathways that parallel the measurable molecular events detected using ATR-FTIR. Paired t-test with post-hoc Bonferroni corrections for multiple comparisons has resulted in the identification of statistically significant spectral markers (p < 0.02) at 1367 and 1358 cm-1. Together, these data demonstrate that early treatment-specific cellular events can be measured by ATR-FTIR and that this technique can be used to identify specific agents via the responses of the cell biosensor at different time points postexposure.

  7. High pressure sample cell for total internal reflection fluorescence spectroscopy at pressures up to 2500 bar.

    PubMed

    Koo, Juny; Czeslik, Claus

    2012-08-01

    Total internal reflection fluorescence (TIRF) spectroscopy is a surface sensitive technique that is widely used to characterize the structure and dynamics of molecules at planar liquid-solid interfaces. In particular, biomolecular systems, such as protein adsorbates and lipid membranes can easily be studied by TIRF spectroscopy. Applying pressure to molecular systems offers access to all kinds of volume changes occurring during assembly of molecules, phase transitions, and chemical reactions. So far, most of these volume changes have been characterized in bulk solution, only. Here, we describe the design and performance of a high pressure sample cell that allows for TIRF spectroscopy under high pressures up to 2500 bar (2.5 × 10(8) Pa), in order to expand the understanding of volume effects from the bulk phase to liquid-solid interfaces. The new sample cell is based on a cylindrical body made of Nimonic 90 alloy and incorporates a pressure transmitting sample cuvette. This cuvette is composed of a fused silica prism and a flexible rubber gasket. It contains the sample solution and ensures a complete separation of the sample from the liquid pressure medium. The sample solution is in contact with the inner wall of the prism forming the interface under study, where fluorescent molecules are immobilized. In this way, the new high pressure TIRF sample cell is very useful for studying any biomolecular layer that can be deposited at a planar water-silica interface. As examples, high pressure TIRF data of adsorbed lysozyme and two phospholipid membranes are presented. PMID:22938334

  8. Tunable terahertz quantum cascade lasers with external gratings

    E-print Network

    Lee, Alan Wei Min

    We demonstrate a frequency tunable external cavity terahertz quantum cascade laser using an abutted antireflection-coated silicon lens to reduce facet reflection and as a beam-forming element, with an external grating ...

  9. Near IR Scanning Angle Total Internal Reflection Raman Spectroscopy at Smooth Gold Films

    SciTech Connect

    McKee, Kristopher; Meyer, Matthew; Smith, Emily

    2012-04-13

    Total internal reflection (TIR) Raman and reflectivity spectra were collected for nonresonant analytes as a function of incident angle at sapphire or sapphire/smooth 50 nm gold interfaces using 785 nm excitation. For both interfaces, the Raman signal as a function of incident angle is well-modeled by the calculated interfacial mean square electric field (MSEF) relative to the incident field times the thickness of the layer being probed in the Raman measurement (D{sub RS}). The Raman scatter was reproducibly enhanced at the interface containing a gold film relative to the sapphire interface by a factor of 4.3–4.6 for aqueous pyridine or 2.2–3.7 for neat nitrobenzene, depending on the analyzed vibrational mode. The mechanism for the increased Raman signal is the enhanced MSEF at incident angles where propagating surface plasmons are excited in the metal film. The background from the TIR prism was reduced by 89–95% with the addition of the gold film, and the percent relative uncertainty in peak area was reduced from 15 to 1.7% for the 1347 cm–1 mode of nitrobenzene. Single monolayers of benzenethiol (S/N = 6.8) and 4-mercaptopyridine (S/N = 16.5) on gold films were measured by TIR Raman spectroscopy with 785 nm excitation (210 mW) without resonant enhancement in 1 min.

  10. Near-infrared reflectance spectroscopy-based methods for phytase registration in feed industry.

    PubMed

    Yang, Haifeng; Lv, Xiaowen; Wang, Jing; Li, Junguo; Li, Hui; Qin, Yuchang

    2007-09-19

    The application of biotechnological products in the feed industry has undergone explosive growth in recent years, and phytase from microorganism accounts for one-third of the entire feed enzyme market. In this study, some differences in the composition of protein and denaturation temperature between two commercial phytases were determined by HPLC and differential scanning calorimetry, which were derived from the same origin of E. coli. At the same time, we found that it was advantageous for near-infrared reflectance spectroscopy (NIRS) to display the protein differences in the commercial phytase, which is most important for ensuring the traceability of biotechnological products in feed and food safety control. Furthermore, NIRS could track the changes in phytase during the spray-drying process and the change of enzyme activity during storage of phytase. Our experiments proved that the information from NIRS could describe well the individual characteristics of the commercial phytase, which indicated that near-infrared reflectance spectra could be exploited to use in the registration system of commercial phytase. PMID:17715890

  11. Impact of one-layer assumption on diffuse reflectance spectroscopy of skin

    NASA Astrophysics Data System (ADS)

    Hennessy, Ricky; Markey, Mia K.; Tunnell, James W.

    2015-02-01

    Diffuse reflectance spectroscopy (DRS) can be used to noninvasively measure skin properties. To extract skin properties from DRS spectra, you need a model that relates the reflectance to the tissue properties. Most models are based on the assumption that skin is homogenous. In reality, skin is composed of multiple layers, and the homogeneity assumption can lead to errors. In this study, we analyze the errors caused by the homogeneity assumption. This is accomplished by creating realistic skin spectra using a computational model, then extracting properties from those spectra using a one-layer model. The extracted parameters are then compared to the parameters used to create the modeled spectra. We used a wavelength range of 400 to 750 nm and a source detector separation of 250 ?m. Our results show that use of a one-layer skin model causes underestimation of hemoglobin concentration [Hb] and melanin concentration [mel]. Additionally, the magnitude of the error is dependent on epidermal thickness. The one-layer assumption also causes [Hb] and [mel] to be correlated. Oxygen saturation is overestimated when it is below 50% and underestimated when it is above 50%. We also found that the vessel radius factor used to account for pigment packaging is correlated with epidermal thickness.

  12. Pink berry grape (Vitis vinifera L.) characterization: Reflectance spectroscopy, HPLC and molecular markers.

    PubMed

    Rustioni, Laura; De Lorenzis, Gabriella; Hâr?a, Monica; Failla, Osvaldo

    2016-01-01

    Color has a fundamental role for the qualitative evaluation and cultivar characterization of fruits. In grape, a normally functional pigment biosynthesis leads to the accumulation of a high quantity of anthocyanins. In this work, 28 Vitis vinifera L. cultivars accumulating low anthocyanins in berries were studied to characterize the biosynthetic dysfunctions in both a phenotypic and genotypic point of view. Reflectance spectroscopy, HPLC profiles and molecular markers related to VvMybA1 and VvMybA2 genes allowed a detailed description of the pigment-related characteristics of these cultivars. Data were consistent concerning the heterozygosity of the non-functional allele in both investigated genes, resulting in a low colored phenotype as described by reflectance. However, the variability in berry colour among our samples was not fully explained by MybA locus, probably due to specific interferences among the biosynthetic pathways, as suggested by the anthocyanin profile variations detected among our samples. The results presented in this work confirmed the importance of the genetic background: grapes accumulating high levels of cyanidin-3-O-glucosides (di-substituted anthocyanin) are generally originated by white cultivar retro-mutations and they seem to preserve the anomalies in the flavonoid hydroxylases enzymes which negatively affect the synthesis of tri-substituted anthocyanins. PMID:26687319

  13. Improved depth resolution in near-infrared diffuse reflectance spectroscopy using obliquely oriented fibers

    NASA Astrophysics Data System (ADS)

    Thilwind, Rachel Estelle; 't Hooft, Gert; Uzunbajakava, Natallia E.

    2009-03-01

    We demonstrate a significant improvement of depth selectivity when using obliquely oriented fibers for near-infrared (NIR) diffuse reflectance spectroscopy. This is confirmed by diffuse reflectance measurements of a two-layer tissue-mimicking phantom across the spectral range from 1000 to 1940 nm. The experimental proof is supported by Monte Carlo simulations. The results reveal up to fourfold reduction in the mean optical penetration depth, twofold reduction in its variation, and a decrease in the number of scattering events when a single fiber is oriented at an angle of 60 deg. The effect of reducing the mean optical penetration depth is enhanced by orienting both fibers inwardly. Using outwardly oriented fibers enables more selective probing of deeper layers, while reducing the contribution from surface layers. We further demonstrate that the effect of an inward oblique arrangement can be approximated to a decrease in fiber-to-fiber separation in the case of a perpendicular fiber arrangement. This approximation is valid in the weak- or absorption-free regime. Our results assert the advantages of using obliquely oriented fibers when attempting to specifically address superficial tissue layers, for example, for skin cancer detection, or in noninvasive glucose monitoring. Such flexibility could be further advantageous in a range of minimally invasive applications, including catheter-based interventions.

  14. Rapid estimation of nutritional elements on citrus leaves by near infrared reflectance spectroscopy

    PubMed Central

    Galvez-Sola, Luis; García-Sánchez, Francisco; Pérez-Pérez, Juan G.; Gimeno, Vicente; Navarro, Josefa M.; Moral, Raul; Martínez-Nicolás, Juan J.; Nieves, Manuel

    2015-01-01

    Sufficient nutrient application is one of the most important factors in producing quality citrus fruits. One of the main guides in planning citrus fertilizer programs is by directly monitoring the plant nutrient content. However, this requires analysis of a large number of leaf samples using expensive and time-consuming chemical techniques. Over the last 5 years, it has been demonstrated that it is possible to quantitatively estimate certain nutritional elements in citrus leaves by using the spectral reflectance values, obtained by using near infrared reflectance spectroscopy (NIRS). This technique is rapid, non-destructive, cost-effective and environmentally friendly. Therefore, the estimation of macro and micronutrients in citrus leaves by this method would be beneficial in identifying the mineral status of the trees. However, to be used effectively NIRS must be evaluated against the standard techniques across different cultivars. In this study, NIRS spectral analysis, and subsequent nutrient estimations for N, K, Ca, Mg, B, Fe, Cu, Mn, and Zn concentration, were performed using 217 leaf samples from different citrus trees species. Partial least square regression and different pre-processing signal treatments were used to generate the best estimation against the current best practice techniques. It was verified a high proficiency in the estimation of N (Rv = 0.99) and Ca (Rv = 0.98) as well as achieving acceptable estimation for K, Mg, Fe, and Zn. However, no successful calibrations were obtained for the estimation of B, Cu, and Mn. PMID:26257767

  15. Flexible waveguide enabled single-channel terahertz endoscopic system

    NASA Astrophysics Data System (ADS)

    Doradla, Pallavi; Alavi, Karim; Joseph, Cecil S.; Giles, Robert H.

    2015-03-01

    Colorectal cancer is the third most commonly diagnosed cancer in the world. The current standard of care for colorectal cancer is the conventional colonoscopy, which relies exclusively on the Physician's experience. Continuous wave terahertz (THz) imaging has the potential to offer a safe, noninvasive medical imaging modality for detecting cancers. The current study demonstrates the design and development of a prototype terahertz endoscopic system based on flexible metal-coated terahertz waveguides. A CO2 pumped Far-Infrared molecular gas laser operating at 584 GHz frequency was used for illuminating the tissue, while the reflected signals were detected using liquid Helium cooled silicon bolometer. The continuous-wave terahertz imaging system utilizes a single waveguide channel to transmit the radiation and collect the back reflected intrinsic terahertz signal from the sample and is capable of operation in both transmission and reflection modalities. The two dimensional reflectance images obtained using a prototype terahertz endoscopic system showed intrinsic contrast between cancerous and normal regions of the colorectal tissue, thereby demonstrating the potential impact of terahertz imaging for in vivo cancer detection.

  16. Nonlinear terahertz superconducting plasmonics

    SciTech Connect

    Wu, Jingbo; Liang, Lanju; Jin, Biaobing E-mail: tonouchi@ile.osaka-u.ac.jp Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng E-mail: tonouchi@ile.osaka-u.ac.jp; Zhang, Caihong; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi E-mail: tonouchi@ile.osaka-u.ac.jp; Wang, Huabing

    2014-10-20

    Nonlinear terahertz (THz) transmission through subwavelength hole array in superconducting niobium nitride (NbN) film is experimentally investigated using intense THz pulses. The good agreement between the measurement and numerical simulations indicates that the field strength dependent transmission mainly arises from the nonlinear properties of the superconducting film. Under weak THz pulses, the transmission peak can be tuned over a frequency range of 145 GHz which is attributed to the high kinetic inductance of 50?nm-thick NbN film. Utilizing the THz pump-THz probe spectroscopy, we study the dynamic process of transmission spectra and demonstrate that the transition time of such superconducting plasmonic device is within 5 ps.

  17. The importance of environmental conditions in reflectance spectroscopy of laboratory analogs for Mars surface materials

    NASA Technical Reports Server (NTRS)

    Bishop, J.; Murchie, S.; Pratt, S.; Mustard, J.; Pieters, C.

    1993-01-01

    Reflectance spectra are presented here for a variety of particulate, ferric-containing analogs to Martian soil (Fe(3+)-doped smectites and palagonites) to facilitate interpretation of remotely acquired spectra. The analog spectra were measured under differing environmental conditions to evaluate the influence of exposure history on water content and absorption features due to H2O in these samples. Each of these materials contains structural OH bonded to metal cations, adsorbed H2O, and bound H2O (either in a glass, structural site, or bound to a cation). Previous experiments involving a variety of Mars analogs have shown that the 3 micron H2O band in spectra of palagonites is more resistant to drying than the 3 micron H2O band in spectra of montmorillonites. Other experiments have shown that spectra of ferrihydrite and montmorillonites doped with ferric sulfate also contain sufficient bound H2O to retain a strong 3 micron band under dry conditions. Once the effects of the environment on bound water in clays, oxides, and salts are better understood, the hydration bands measured via reflectance spectroscopy can be used to gain information about the chemical composition and moisture content of real soil systems. Such information would be especially useful in interpreting observations of Mars where subtle spatial variations in the strengths of metal-OH and H2O absorptions have been observed in telescopic and ISM spectra. We measured bidirectional reflectance spectra of several Mars soil analogs under controlled environmental conditions to assess the effects of moisture content on the metal-OH and H2O absorptions. The samples analyzed include chemically altered montmorillonites, ferrihydrite. and palagonites from Hawaii and Iceland. Procedures for preparation of the cation-exchanged montmorillonites, ferric-salt doped montmorillonites, and ferric oxyhydroxides are described in detail elsewhere.

  18. The importance of environmental conditions in reflectance spectroscopy of laboratory analogs for Mars surface materials

    NASA Astrophysics Data System (ADS)

    Bishop, J.; Murchie, S.; Pratt, S.; Mustard, J.; Pieters, C.

    Reflectance spectra are presented here for a variety of particulate, ferric-containing analogs to Martian soil (Fe(3+)-doped smectites and palagonites) to facilitate interpretation of remotely acquired spectra. The analog spectra were measured under differing environmental conditions to evaluate the influence of exposure history on water content and absorption features due to H2O in these samples. Each of these materials contains structural OH bonded to metal cations, adsorbed H2O, and bound H2O (either in a glass, structural site, or bound to a cation). Previous experiments involving a variety of Mars analogs have shown that the 3 micron H2O band in spectra of palagonites is more resistant to drying than the 3 micron H2O band in spectra of montmorillonites. Other experiments have shown that spectra of ferrihydrite and montmorillonites doped with ferric sulfate also contain sufficient bound H2O to retain a strong 3 micron band under dry conditions. Once the effects of the environment on bound water in clays, oxides, and salts are better understood, the hydration bands measured via reflectance spectroscopy can be used to gain information about the chemical composition and moisture content of real soil systems. Such information would be especially useful in interpreting observations of Mars where subtle spatial variations in the strengths of metal-OH and H2O absorptions have been observed in telescopic and ISM spectra. We measured bidirectional reflectance spectra of several Mars soil analogs under controlled environmental conditions to assess the effects of moisture content on the metal-OH and H2O absorptions. The samples analyzed include chemically altered montmorillonites, ferrihydrite. and palagonites from Hawaii and Iceland. Procedures for preparation of the cation-exchanged montmorillonites, ferric-salt doped montmorillonites, and ferric oxyhydroxides are described in detail elsewhere.

  19. Nondestructive inspection of organic films on sandblasted metals using diffuse reflectance infrared spectroscopy

    SciTech Connect

    Powell, G.L.; Cox, R.L.; Barber, T.E.; Neu, J.T.

    1996-07-08

    Diffuse reflectance infrared spectroscopy is a very useful tool for the determination of surface contamination and characterization of films in manufacturing applications. Spectral data from the surfaces of a host of practical materials may be obtained with sufficient insensitivity to characterize relatively thick films, such as paint, and the potential exists to detect very thin films, such as trace oil contamination on metals. The SOC 400 Surface Inspection Machine/InfraRed (SIMIR) has been developed as a nondestructive inspection tool to exploit this potential in practical situations. This SIMIR is a complete and ruggidized Fourier transform infrared spectrometer with a very efficient and robust barrel ellipse diffuse reflectance optical collection system and operating software system. The SIMIR weighs less than 8 Kg, occupies less than 14 L volume, and may be manipulated into any orientation during operation. The surface to be inspected is placed at the focal point of the SIMIR by manipulating the SIMIR or the surface. The SIMIR may or may not contact the surface being inspected. For flat or convex items, there are no size limits to items being inspected. For concave surfaces, the SIMIR geometry limits the surface to those having a radius of curvature greater than 0.2 m. For highly reflective metal surfaces, the SIMIR has a noise level approaching 1 {times} 10{sup {minus}4} absorbance units, which is sufficient for detecting nanometer thick organic film residues on metals. The use of this nondestructive inspection tool is demonstrated by the spatial mapping of organic stains on sand blasted metals in which organic stains such as silicone oils, mineral oils, and triglycerides are identified both qualitatively and quantitatively over the surface of the metal specimen.

  20. Historical perspective and modern applications of Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR).

    PubMed

    Blum, Marc-Michael; John, Harald

    2012-01-01

    Vibrational spectroscopy has a long history as an important spectroscopic method in chemical and pharmaceutical analysis. Instrumentation for infrared (IR) spectroscopy was revolutionized by the introduction of Fourier Transform Infrared (FTIR) spectrometers. In addition, easier sampling combined with better sample-to-sample reproducibility and user-to-user spectral variation became available with attenuated total reflectance (ATR) probes and their application for in situ IR spectroscopy. These innovations allow many new applications in chemical and pharmaceutical analysis, such as the use of IR spectroscopy in Process Analytical Chemistry (PAC), the quantitation of drugs in complex matrix formulations, the analysis of protein binding and function and in combination with IR microscopy to the emergence of IR imaging technologies. The use of ATR-FTIR instruments in forensics and first response to 'white powder' incidents is also discussed. A short overview is given in this perspective article with the aim to renew and intensify interest in IR spectroscopy. PMID:22113892

  1. Terahertz vibration-rotation-tunneling spectroscopy of the water tetramer-d8: Combined analysis of vibrational bands at 4.1 and 2.0 THz

    E-print Network

    Cohen, Ronald C.

    of vibrational bands at 4.1 and 2.0 THz Wei Lin,a Jia-Xiang Han,b Lynelle K. Takahashi, Heather A. Harker,c Frank their TZ2P diff//DZP diff CCSD po- tential energy surface of the water trimer. Terahertz vibration

  2. Experimental Investigation on Terahertz Spectra of Amphetamine Type Stimulants

    NASA Astrophysics Data System (ADS)

    Sun, Jin-Hai; Shen, Jing-Ling; Liang, Lai-Shun; Xu, Xiao-Yu; Liu, Hai-Bo; Zhang, Cun-Lin

    2005-12-01

    The spectral absorption features of three amphetamine-type stimulants (ATS) belonging to illicit drugs have been studied with terahertz (THz) time-domain spectroscopy (THz-TDS) and the characteristic absorption spectra (fingerprint spectra) are obtained in the range from 0.2 to 2.5 THz. Fingerprint spectra of illicit drugs in terahertz band are bases to detect and to inspect nondestructively illicit drugs with terahertz technique. With fingerprint spectra of illicit drugs and strong penetrability for cloths, paper bags and leathered or plastic luggage terahertz technique would be better than other techniques in illicit drugs detection and inspection. Thus, this work would contribute to the building of corresponding fingerprint spectra database of illicit drugs and provide experimental bases for using of terahertz detection apparatus in drugs nondestructive detection and inspection in the future.

  3. In-situ measurement of epithelial tissue optical properties: Development and implementation of diffuse reflectance spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Wang, Quanzeng

    Cancer is a severe threat to human health. Early detection is considered the best way to increase the chance for survival. While the traditional cancer detection method, biopsy, is invasive, noninvasive optical diagnostic techniques are revolutionizing the way that cancer is diagnosed. Reflectance spectroscopy is one of these optical spectroscopy techniques showing promise as a diagnostic tool for pre-cancer detection. When a neoplasia occurs in tissue, morphologic and biochemical changes happen in the tissue, which in turn results in the change of optical properties and reflectance spectroscopy. Therefore, a pre-cancer can be detected by extracting optical properties from reflectance spectroscopy. This dissertation described the construction of a fiberoptic based reflectance system and the development of a series of modeling studies. This research is aimed at establishing an improved understanding of the optical properties of mucosal tissues by analyzing reflectance signals at different wavelengths. The ultimate goal is to reveal the potential of reflectance-based optical diagnosis of pre-cancer. The research is detailed in Chapter 3 through Chapter 5. Although related with each other, each chapter was designed to become a journal paper ultimately. In Chapter 3, a multi-wavelength, fiberoptic system was constructed, evaluated and implemented to determine internal tissue optical properties at ultraviolet A and visible wavelengths. A condensed Monte Carlo model was deployed to simulate light-tissue interaction and generate spatially distributed reflectance data. These data were used to train an inverse neural network model to extract tissue optical properties from reflectance. Optical properties of porcine mucosal and liver tissues were finally measured. In Chapter 4, the condensed Monte Carlo method was extended so that it can rapidly simulate reflectance from a single illumination-detection fiber thus enabling the calculation of large data sets. The model was implemented to study spectral reflectance changes due to breast cancer. The effect of adding an illumination-detection fiber to a linear array fiber for optical property determination was also evaluated. In Chapter 5, an investigation of extracting the optical properties from two-layer tissues was performed. The relationship between spatially-resolved reflectance distributions and optical properties in two-layer tissue was investigated. Based on all the aforementioned studies, spatially resolved reflectance system coupled with condensed Monte Carlo and neural network models was found to be objective and appear to be sensitive and accurate in quantitatively assessing optical property change of mucosal tissues.

  4. Diffuse-Reflectance Fourier-Transform Mid-Infrared Spectroscopy as a Method of Characterizing Changes in Soil Organic Matter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffuse-Reflectance Fourier-Transform Mid-Infrared Spectroscopy (FTIR) can be used quickly and non destructively to identify and quantify the presence of important organic functional groups in environmental samples. However, soils contain myriad organic and inorganic components that absorb in the M...

  5. Diffuse-reflectance fourier-transform mid-infrared spectroscopy as a method of characterizing changes in soil organic matter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffuse-Reflectance Fourier-Transform Mid-Infrared Spectroscopy (MidIR) can identify the presence of important organic functional groups in soil organic matter (SOM). Soils contain myriad organic and inorganic components that absorb in the MidIR so spectral interpretation needs to be validated in or...

  6. Reflectance-difference spectroscopy of mixed arsenic-rich phases of gallium arsenide ,,001... M. J. Begarney,1

    E-print Network

    Li, Lian

    Reflectance-difference spectroscopy of mixed arsenic-rich phases of gallium arsenide ,,001... M. J. At the same time, gallium atoms are liberated to the surface, disrupting the c(4 4) ordering. At about 1.4 ML on the presence of adsorbates, such as alkyl groups and gallium adatoms. By contrast, the intensity

  7. Determination of In-shell Peanuts Moisture, Oil and Fatty Acids Composition Using Near Infrared Reflectance Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Oil and moisture content of peanuts are important factors in peanut grading. A method that could rapidly and nondestructively measure these parameters for in-shell peanuts would be extremely useful. NIR reflectance spectroscopy was used to analyze the moisture, total oil and fatty acid content of V...

  8. PREDICTION OF COLOR, TENDERNESS, AND SENSORY CHARACTERISTICS OF BEEF STEAKS BY VISIBLE AND NEAR INFRARED REFLECTANCE SPECTROSCOPY. A FEASIBILITY STUDY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Color, texture and sensory attributes of 24 beef carcasses at 2, 4, 8, 14, and 21 days post mortem were predicted by visible/near infrared (visible/NIR) reflectance spectroscopy in 400-1080 nm region. Predicting the Hunter a*, b*, and E* values yielded the coefficient of determination (R**2) in cal...

  9. Application of Near Infrared Reflectance Spectroscopy on Determination of Moisture, Total oil and Protein Contents of In-shell Peanuts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Moisture, total oil and protein content of peanuts are important factors in peanut grading. A method that could rapidly and nondestructively measure these parameters for in-shell peanuts would be extremely useful. NIR reflectance spectroscopy was used to analyze the moisture, total oil and protein ...

  10. SEARCHING FOR THE PARENT BODIES OF METEORITES THROUGH REFLECTANCE SPECTROSCOPY: CURRENT STATE. T. Hiroi, Dept. of Geological

    E-print Network

    Hiroi, Takahiro

    SEARCHING FOR THE PARENT BODIES OF METEORITES THROUGH REFLECTANCE SPECTROSCOPY: CURRENT STATE. T_hiroi@brown.edu) Introduction: Some meteoriticists may falsely assume that the parent bodies of meteorites they are studying do is not important. I understand the difficulty of using two very different methods: Analyzing meteorites

  11. Use of visible-near infrared reflectance spectroscopy to assess soil quality related to long-term tillage effects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Visible-near infrared diffuse reflectance spectroscopy (VNIRDRS) is emerging as an effective method for rapid evaluation of soil properties and may be promising for the simultaneous determination of soil quality indicators. This study employed VNIRDRS to analyze treatment effects associated with lo...

  12. Secondary cell wall development in cotton fibers as examined with attenuated total reflection Fourier transform infrared spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton fibers harvested at 18, 20, 24, 28, 32, 36 and 40 days after flowering were examined using attenuated total reflection Fourier transform-infrared (ATR FT-IR) spectroscopy. The selected harvesting points coincide with secondary cell wall (SCW) development in the fibers. Progressive but moderat...

  13. Reflections.

    ERIC Educational Resources Information Center

    Wilde, Sandra

    1996-01-01

    Reflects on four significant issues discussed in this issue devoted to teaching writers to spell: (1) how much time should be spent on spelling; (2) how kids can be helped to care more about spelling; (3) how stakeholders can be helped to understand the point of what educators are doing with spelling; and (4) where the national climate is heading…

  14. Non-invasive identification of metal-oxalate complexes on polychrome artwork surfaces by reflection mid-infrared spectroscopy.

    PubMed

    Monico, Letizia; Rosi, Francesca; Miliani, Costanza; Daveri, Alessia; Brunetti, Brunetto G

    2013-12-01

    In this work a reflection mid-infrared spectroscopy study of twelve metal-oxalate complexes, of interest in art conservation science as alteration compounds, was performed. Spectra of the reference materials highlighted the presence of derivative-like and/or inverted features for the fundamental vibrational modes as result of the main contribution from the surface component of the reflected light. In order to provide insights in the interpretation of theses spectral distortions, reflection spectra were compared with conventional transmission ones. The Kramers-Kronig (KK) algorithm, employed to correct for the surface reflection distortions, worked properly only for the derivative-like bands. Therefore, to pay attention to the use of this algorithm when interpreting the reflection spectra is recommended. The outcome of this investigation was exploited to discriminate among different oxalates on thirteen polychrome artworks analyzed in situ by reflection mid-infrared spectroscopy. The visualization of the ?s(CO) modes (1400-1200 cm(-1)) and low wavenumber bands (below 900 cm(-1)) in the raw reflection profiles allowed Ca, Cu and Zn oxalates to be identified. Further information about the speciation of different hydration forms of calcium oxalates were obtained by using the KK transform. The work proves reflection mid-infrared spectroscopy to be a reliable and sensitive spectro-analytical method for identifying and mapping different metal-oxalate alteration compounds on the surface of artworks, thus providing conservation scientists with a non-invasive tool to obtain information on the state of conservation and causes of alteration of artworks. PMID:23954542

  15. Widely tunable room temperature semiconductor terahertz source

    SciTech Connect

    Lu, Q. Y.; Slivken, S.; Bandyopadhyay, N.; Bai, Y.; Razeghi, M.

    2014-11-17

    We present a widely tunable, monolithic terahertz source based on intracavity difference frequency generation within a mid-infrared quantum cascade laser at room temperature. A three-section ridge waveguide laser design with two sampled grating sections and a distributed-Bragg section is used to achieve the terahertz (THz) frequency tuning. Room temperature single mode THz emission with a wide tunable frequency range of 2.6–4.2 THz (?47% of the central frequency) and THz power up to 0.1 mW is demonstrated, making such device an ideal candidate for THz spectroscopy and sensing.

  16. Point-contact Andreev-reflection spectroscopy in MgB 2: The role of substitutions

    NASA Astrophysics Data System (ADS)

    Gonnelli, R. S.; Daghero, D.; Ummarino, G. A.; Tortello, M.; Delaude, D.; Stepanov, V. A.; Karpinski, J.

    2007-06-01

    We summarize the results of point-contact Andreev-reflection (PCAR) spectroscopy in MgB 2 doped by chemical substitutions, either magnetic (Mn) or non-magnetic (Al, C), obtained by us and by other groups in the last four years. Despite the variety of samples used (crystals and polycrystals of various origin) and some minor differences in the experimental techniques, these measurements have directly provided a complete and consistent picture of the effects of chemical substitutions on the gaps of MgB 2 shedding light on other relevant parameters (scattering rates, DOSs) affected by doping. In Al-doped crystals and polycrystals, the gap amplitudes ?? and ?? - obtained through a two-band Blonder-Tinkham-Klapwijk (BTK) fit of the Andreev-reflection conductance curves - decrease on increasing the Al content x (i.e. on decreasing the critical temperature of the contacts TcA), but remain clearly distinct with no evidence of gap merging even when TcA is of the order of 10 K. The case of C-substituted MgB 2 is less clear: the merging of the two gaps at x ? 0.13 was observed in single crystals grown at ETH, while the persistence of two gaps up to x = 0.10 - with apparently no tendency to merging at higher x - was found in other crystals and polycrystals. Finally, in Mn-doped single crystals the effects of pair-breaking magnetic scattering strongly suppress the critical temperature and the gaps, which however remain clearly distinct from each other down to Tc ? 10 K. In all cases, the analysis of the ?? and ?? data as a function of TcA (or of the doping content x) within the two-band Eliashberg theory gives interesting information about the effects of substitutions on the different scattering channels (interband and intraband, magnetic or non-magnetic).

  17. Total reflection infrared spectroscopy of water-ice and frozen aqueous NaCl solutions

    SciTech Connect

    Walker, Rachel L.; Searles, Keith; Willard, Jesse A.; Michelsen, Rebecca R. H.

    2013-12-28

    Liquid-like and liquid water at and near the surface of water-ice and frozen aqueous sodium chloride films were observed using attenuated total reflection infrared spectroscopy (ATR-IR). The concentration of NaCl ranged from 0.0001 to 0.01 M and the temperature varied from the melting point of water down to 256 K. The amount of liquid brine at the interface of the frozen films with the germanium ATR crystal increased with salt concentration and temperature. Experimental spectra are compared to reflection spectra calculated for a simplified morphology of a uniform liquid layer between the germanium crystal and the frozen film. This morphology allows for the amount of liquid observed in an experimental spectrum to be converted to the thickness of a homogenous layer with an equivalent amount of liquid. These equivalent thickness ranges from a nanometer for water-ice at 260 K to 170 nm for 0.01 M NaCl close to the melting point. The amounts of brine observed are over an order of magnitude less than the total liquid predicted by equilibrium thermodynamic models, implying that the vast majority of the liquid fraction of frozen solutions may be found in internal inclusions, grain boundaries, and the like. Thus, the amount of liquid and the solutes dissolved in them that are available to react with atmospheric gases on the surfaces of snow and ice are not well described by thermodynamic equilibrium models which assume the liquid phase is located entirely at the surface.

  18. Total reflection infrared spectroscopy of water-ice and frozen aqueous NaCl solutions.

    PubMed

    Walker, Rachel L; Searles, Keith; Willard, Jesse A; Michelsen, Rebecca R H

    2013-12-28

    Liquid-like and liquid water at and near the surface of water-ice and frozen aqueous sodium chloride films were observed using attenuated total reflection infrared spectroscopy (ATR-IR). The concentration of NaCl ranged from 0.0001 to 0.01 M and the temperature varied from the melting point of water down to 256 K. The amount of liquid brine at the interface of the frozen films with the germanium ATR crystal increased with salt concentration and temperature. Experimental spectra are compared to reflection spectra calculated for a simplified morphology of a uniform liquid layer between the germanium crystal and the frozen film. This morphology allows for the amount of liquid observed in an experimental spectrum to be converted to the thickness of a homogenous layer with an equivalent amount of liquid. These equivalent thickness ranges from a nanometer for water-ice at 260 K to 170 nm for 0.01 M NaCl close to the melting point. The amounts of brine observed are over an order of magnitude less than the total liquid predicted by equilibrium thermodynamic models, implying that the vast majority of the liquid fraction of frozen solutions may be found in internal inclusions, grain boundaries, and the like. Thus, the amount of liquid and the solutes dissolved in them that are available to react with atmospheric gases on the surfaces of snow and ice are not well described by thermodynamic equilibrium models which assume the liquid phase is located entirely at the surface. PMID:24387384

  19. Analysis of total oil and fatty acids composition by near infrared reflectance spectroscopy in edible nuts

    NASA Astrophysics Data System (ADS)

    Kandala, Chari V.; Sundaram, Jaya

    2014-10-01

    Near Infrared (NIR) Reflectance spectroscopy has established itself as an important tool in quantifying water and oil present in various food materials. It is rapid and nondestructive, easier to use, and does not require processing the samples with corrosive chemicals that would render them non-edible. Earlier, the samples had to be ground into powder form before making any measurements. With the development of new soft ware packages, NIR techniques could now be used in the analysis of intact grain and nuts. While most of the commercial instruments presently available work well with small grain size materials such as wheat and corn, the method present here is suitable for large kernel size products such as shelled or in-shell peanuts. Absorbance spectra were collected from 400 nm to 2500 nm using a NIR instrument. Average values of total oil contents (TOC) of peanut samples were determined by standard extraction methods, and fatty acids were determined using gas chromatography. Partial least square (PLS) analysis was performed on the calibration set of absorption spectra, and models were developed for prediction of total oil and fatty acids. The best model was selected based on the coefficient of determination (R2), Standard error of prediction (SEP) and residual percent deviation (RPD) values. Peanut samples analyzed showed RPD values greater than 5.0 for both absorbance and reflectance models and thus could be used for quality control and analysis. Ability to rapidly and nondestructively measure the TOC, and analyze the fatty acid composition, will be immensely useful in peanut varietal improvement as well as in the grading process of grain and nuts.

  20. Reflection electron energy-loss spectroscopy and imaging for surface studies in transmission electron microscopes.

    PubMed

    Wang, Z L; Bentley, J

    1992-02-15

    A review is given on the techniques and applications of high-energy reflection electron energy-loss spectroscopy (REELS) and reflection electron microscopy (REM) for surface studies in scanning transmission electron microscopes (STEM) and conventional transmission electron microscopes (TEM). A diffraction method is introduced to identify a surface orientation in the geometry of REM. The surface dielectric response theory is presented and applied for studying alpha-alumina surfaces. Domains of the alpha-alumina (012) surface initially terminated with oxygen can be reduced by an intense electron beam to produce Al metal; the resistance to beam damage of surface domains initially terminated with Al+3 ions is attributed to the screening effect of adsorbed oxygen. Surface energy-loss near-edge structure (ELNES), extended energy-loss fine structure (EXELFS), and microanalysis using REELS are illustrated based on the studies of TiO2 and MgO. Effects of surface resonances (or channeling) on the REELS signal-to-background ratio are described. The REELS detection of a monolayer of oxygen adsorption on diamond (111) surfaces is reported. It is shown that phase contrast REM image content can be significantly increased with the use of a field emission gun (FEG). Phase contrast effects close to the core of a screw dislocation are discussed and the associated Fresnel fringes around a surface step are observed. Finally, an in situ REM experiment is described for studying atomic desorption and diffusion processes on alpha-alumina surfaces at temperatures of 1,300-1,400 degrees C. PMID:1498353

  1. Field spectroscopy sampling strategies for improved measurement of Earth surface reflectance

    NASA Astrophysics Data System (ADS)

    Mac Arthur, A.; Alonso, L.; Malthus, T. J.; Moreno, J. F.

    2013-12-01

    Over the last two decades extensive networks of research sites have been established to measure the flux of carbon compounds and water vapour between the Earth's surface and the atmosphere using eddy covariance (EC) techniques. However, contributing Earth surface components cannot be determined and (as the ';footprints' are spatially constrained) these measurements cannot be extrapolated to regional cover using this technique. At many of these EC sites researchers have been integrating spectral measurements with EC and ancillary data to better understand light use efficiency and carbon dioxide flux. These spectroscopic measurements could also be used to assess contributing components and provide support for imaging spectroscopy, from airborne or satellite platforms, which can provide unconstrained spatial cover. Furthermore, there is an increasing interest in ';smart' database and information retrieval systems such as that proposed by EcoSIS and OPTIMISE to store, analyse, QA and merge spectral and biophysical measurements and provide information to end users. However, as Earth surfaces are spectrally heterogeneous and imaging and field spectrometers sample different spatial extents appropriate field sampling strategies require to be adopted. To sample Earth surfaces spectroscopists adopt either single; random; regular grid; transect; or 'swiping' point sampling strategies, although little comparative work has been carried out to determine the most appropriate approach; the work by Goetz (2012) is a limited exception. Mac Arthur et al (2012) demonstrated that, for two full wavelength (400 nm to 2,500 nm) field spectroradiometers, the measurement area sampled is defined by each spectroradiometer/fore optic system's directional response function (DRF) rather than the field-of-view (FOV) specified by instrument manufacturers. Mac Arthur et al (2012) also demonstrated that each reflecting element within the sampled area was not weighted equally in the integrated measurement recorded. There were non-uniformities of spectral response with the spectral ';weighting' per wavelength interval being positionally dependent and unique to each spectroradiometer/fore optic system investigated. However, Mac Arthur et al (2012) did not provide any advice on how to compensate for these systematic errors or advise on appropriate sampling strategies. The work reported here will provide the first systematic study of the effect of field spectroscopy sampling strategies for a range of different Earth surface types. Synthetic Earth surface hyperspectral data cubes for each surface type were generated and convolved with a range of the spectrometer/fore optic system directional response functions generated by Mac Arthur et al 2013, to simulate spectroscopic measurements of Earth surfaces. This has enabled different field sampling strategies to be directly compared and their suitability for each measurement purpose and surface type to be assessed and robust field spectroscopy sampling strategy recommendations to be made. This will be particularly of interest to the carbon and water vapour flux communities and assist the development of sampling strategies for field spectroscopy from rotary-wing Unmanned Aerial Vehicles, which will aid acquiring measurements in the spatial domain, and generally further the use of field spectroscopy for quantitative Earth observation.

  2. Assessment of biophysical tumor response to PDT in pancreatic cancer using localized reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Isabelle, Martin; Klubben, William; He, Ting; Laughney, Ashley M.; Glaser, Adam; Krishnaswamy, Venkataramanan; Hoopes, P. Jack; Hasan, Tayyaba; Pogue, Brian W.

    2011-02-01

    Biophysical changes such as inflammation and necrosis occur immediately following PDT and may be used to assess the treatment response to PDT treatment in-vivo. This study uses localized reflectance measurements to quantify the scatter changes in tumor tissue occurring in response to verteporfin-based PDT treatment in xenograft pancreas tumors. Nude mice were implanted with subcutaneous AsPC-1 pancreatic tumors cells in matrigel, and allowed to establish solid tumors near 100mm3 volume. The mice were sensitized with 1mg/kg of the active component of verteporfin (benzoporphryin derivative, BPD), one hour before light delivery. The optical irradiation was performed using a 1 cm cylindrical interstitial diffusing tip fiber with 20J of red light (690nm). Tumor tissue was excised progressively and imaged, from 1 day to 4 weeks, after PDT treatment. The tissue sections were stained and analyzed by an expert veterinary pathologist, who provided information on tissue regions of interest. This information was correlated with variations in scattering and absorption parameters elucidated from the spectral images and the degree of necrosis and inflammation involvement was identified. Areas of necrosis and dead cells exhibited the lowest average scatter irradiance signature (3.78 and 4.07 respectively) compared to areas of viable pancreatic tumor cells and areas of inflammation (5.81 and 7.19 respectively). Bilirubin absorbance parameters also showed a lower absorbance value in necrotic tissue and areas of dead cells (0.05 and 0.1 respectively) compared to tissue areas for viable pancreatic tumor cells and areas of inflammation (0.28 and 0.35). These results demonstrate that localized reflectance spectroscopy is an imaging modality that can be used to identify tissue features associated with PDT treatment (e.g. necrosis and inflammation) that can be correlated with histopathologically-reviewed H&E stained slides. Further study of this technique may provide means for automated discrimination of tissue features based on scatter and absorbance maps elucidated from reflectance spectral datasets and provide a valuable tool for treatment response monitoring during PDT and enabling more effective treatment planning. These results are relevant to verteporfin-based PDT trial for treatment pancreatic cancer in non-surgical candidate cases (VERTPAC-1 University College London, PI Pereira), where individualized assessment of damage and response could be beneficial, if this study is proven to be a well-controlled imaging tool.

  3. Diffuse near-infrared reflectance spectroscopy during heatstroke in a mouse model: pilot study

    NASA Astrophysics Data System (ADS)

    Abookasis, David; Zafrir, Elad; Nesher, Elimelech; Pinhasov, Albert; Sternklar, Shmuel; Mathews, Marlon S.

    2012-10-01

    Heatstroke, a form of hyperthermia, is a life-threatening condition characterized by an elevated core body temperature that rises above 40°C (104°F) and central nervous system dysfunction that results in delirium, convulsions, or coma. Without emergency treatment, the victim lapses into a coma and death soon follows. The study presented was conducted with a diffuse reflectance spectroscopy (DRS) setup to assess the effects of brain dysfunction that occurred during heatstroke in mice model (n=6). It was hypothesized that DRS can be utilized in small animal studies to monitor change in internal brain tissue temperature during heatstroke injury since it induces a sequence of pathologic changes that change the tissue composition and structure. Heatstroke was induced by exposure of the mice body under general anesthesia, to a high ambient temperature. A type of DRS in which the brain tissue was illuminated through the intact scalp with a broadband light source and diffuse reflected spectra was employed, taking in the spectral region between 650 and 1000 nm and acquired at an angle of 90 deg at a position on the scalp ˜12 mm from the illumination site. The temperature at the onset of the experiment was ˜34°C (rectal temperature) with increasing intervals of 1°C until mouse death. The increase in temperature caused optical scattering signal changes consistent with a structural alteration of brain tissue, ultimately resulting in death. We have found that the peak absorbance intensity and its second derivative at specific wavelengths correlate well with temperature with an exponential dependence. Based on these findings, in order to estimate the influence of temperature on the internal brain tissue a reflectance-temperature index was established and was seen to correlate as well with measured temperature. Overall, results indicate variations in neural tissue properties during heatstroke and the feasibility to monitor and assess internal temperature variations using DRS. Although several approaches have described the rise in temperature and its impact on tissue, to the best of our knowledge no information is available describing the ability to monitor temperature during heatstroke with DRS. The motivation of this study was to successfully describe this ability.

  4. Diffuse reflectance spectroscopy and optical polarization imaging of in-vivo biological tissue

    NASA Astrophysics Data System (ADS)

    Mora-Núñez, A.; Castillejos, Y.; García-Torales, G.; Martínez-Ponce, G.

    2013-11-01

    A number of optical techniques have been reported in the scientific literature as accomplishable methodologies to diagnose diseases in biological tissue, for instance, diffuse reflectance spectroscopy (DRS) and optical polarization imaging (OPI). The skin is the largest organ in the body and consists of three primary layers, namely, the epidermis (the outermost layer exposed to the world), the dermis, and the hypodermis. The epidermis changes from to site to site, mainly because of difference in hydration. A lower water content increase light scattering and reduce the penetration depth of radiation. In this work, two hairless mice have been selected to evaluate their skin features by using DRS and OPI. Four areas of the specimen body were chosen to realize the comparison: back, abdomen, tail, and head. From DRS, it was possible to distinguish the skin nature because of different blood irrigation at dermis. In the other hand, OPI shows pseudo-depolarizing regions in the measured Mueller images related to a spatially varying propagation of the scattered light. This provides information about the cell size in the irradiated skin.

  5. Quantitative orientation measurements in thin lipid films by attenuated total reflection infrared spectroscopy.

    PubMed Central

    Picard, F; Buffeteau, T; Desbat, B; Auger, M; Pézolet, M

    1999-01-01

    Quantitative orientation measurements by attenuated total reflectance (ATR) infrared spectroscopy require the accurate knowledge of the dichroic ratio and of the mean-square electric fields along the three axes of the ATR crystal. In this paper, polarized ATR spectra of single supported bilayers of the phospholipid dimyristoylphosphatidic acid covered by either air or water have been recorded and the dichroic ratio of the bands due to the methylene stretching vibrations has been calculated. The mean-square electric field amplitudes were calculated using three formalisms, namely the Harrick thin film approximation, the two-phase approximation, and the thickness- and absorption-dependent one. The results show that for dry bilayers, the acyl chain tilt angle varies with the formalism used, while no significant variations are observed for the hydrated bilayers. To test the validity of the different formalisms, s- and p-polarized ATR spectra of a 40-A lipid layer were simulated for different acyl chain tilt angles. The results show that the thickness- and absorption-dependent formalism using the mean values of the electric fields over the film thickness gives the most accurate values of acyl chain tilt angle in dry lipid films. However, for lipid monolayers or bilayers, the tilt angle can be determined with an acceptable accuracy using the Harrick thin film approximation. Finally, this study shows clearly that the uncertainty on the determination of the tilt angle comes mostly from the experimental error on the dichroic ratio and from the knowledge of the refractive index. PMID:9876167

  6. 3D Effect in Determination of Spin Polarization using Andreev Reflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gifford, Jessica; Snider, Charles; Martinez, Jonny; Chen, Tingyong

    2013-03-01

    Andreev Reflection Spectroscopy (ARS) has been utilized to measure spin polarization of magnetic materials, as well as the superconducting gap of superconductors. These values are extracted by a modified Blonder-Tinkham-Klapwijk (BTK) model or the more recent Chen-Tesanovic-Chien (CTC) model. Both consider the F/S interface as one dimensional (1D). However, a tip may have a point angle with three dimensional (3D) effects. We present both theoretical and experimental studies of the 3D effects in the determination of spin polarization. We have found that for an ideal interface without interfacial scattering (Z), the 3D ARS spectra are the same as 1D spectra. But for non-ideal interfaces the 3D effect can drastically change the conductance spectra depending on the point angle of the tip. The 3D spectra can be well described by the 1D model with a different interfacial scattering factor and a slightly different inelastic scattering factor. The spin polarization and superconducting gap is the same as the1D model, demonstrating that 1D ARS model can be utilized to determine spin polarization as long as Z is not of any concern. Finally, we apply the both the 1D and the 3D models to a set of ARS data and show that the extracted spin polarization value is the same for both models.

  7. A Monte Carlo study of reflection electron energy loss spectroscopy spectrum of a carbon contaminated surface

    SciTech Connect

    Da, B.; Li, Z. Y.; Chang, H. C.; Ding, Z. J.; Mao, S. F.

    2014-09-28

    It has been experimentally found that the carbon surface contamination influences strongly the spectrum signals in reflection electron energy loss spectroscopy (REELS) especially at low primary electron energy. However, there is still little theoretical work dealing with the carbon contamination effect in REELS. Such a work is required to predict REELS spectrum for layered structural sample, providing an understanding of the experimental phenomena observed. In this study, we present a numerical calculation result on the spatially varying differential inelastic mean free path for a sample made of a carbon contamination layer of varied thickness on a SrTiO{sub 3} substrate. A Monte Carlo simulation model for electron interaction with a layered structural sample is built by combining this inelastic scattering cross-section with the Mott's cross-section for electron elastic scattering. The simulation results have clearly shown that the contribution of the electron energy loss from carbon surface contamination increases with decreasing primary energy due to increased individual scattering processes along trajectory parts carbon contamination layer. Comparison of the simulated spectra for different thicknesses of the carbon contamination layer and for different primary electron energies with experimental spectra clearly identifies that the carbon contamination in the measured sample was in the form of discontinuous islands other than the uniform film.

  8. Feasibility of quantitative diffuse reflectance spectroscopy for targeted measurement of renal ischemia during laparoscopic partial nephrectomy

    NASA Astrophysics Data System (ADS)

    Goel, Utsav O.; Maddox, Michael M.; Elfer, Katherine N.; Dorsey, Philip J.; Wang, Mei; McCaslin, Ian Ross; Brown, J. Quincy; Lee, Benjamin R.

    2014-10-01

    Reduction of warm ischemia time during partial nephrectomy (PN) is critical to minimizing ischemic damage and improving postoperative kidney function, while maintaining tumor resection efficacy. Recently, methods for localizing the effects of warm ischemia to the region of the tumor via selective clamping of higher-order segmental artery branches have been shown to have superior outcomes compared with clamping the main renal artery. However, artery identification can prolong operative time and increase the blood loss and reduce the positive effects of selective ischemia. Quantitative diffuse reflectance spectroscopy (DRS) can provide a convenient, real-time means to aid in artery identification during laparoscopic PN. The feasibility of quantitative DRS for real-time longitudinal measurement of tissue perfusion and vascular oxygenation in laparoscopic nephrectomy was investigated in vivo in six Yorkshire swine kidneys (n=three animals). DRS allowed for rapid identification of ischemic areas after selective vessel occlusion. In addition, the rates of ischemia induction and recovery were compared for main renal artery versus tertiary segmental artery occlusion, and it was found that the tertiary segmental artery occlusion trends toward faster recovery after ischemia, which suggests a potential benefit of selective ischemia. Quantitative DRS could provide a convenient and fast tool for artery identification and evaluation of the depth, spatial extent, and duration of selective tissue ischemia in laparoscopic PN.

  9. Quantification of Al-goethite from diffuse reflectance spectroscopy and magnetic methods

    NASA Astrophysics Data System (ADS)

    Jiang, Zhaoxia; Liu, Qingsong; Colombo, Claudio; Barrón, Vidal; Torrent, José; Hu, Pengxiang

    2014-01-01

    As one of the most abundant iron oxides in soils, the presence and nature of goethite is controlled by the soil conditions and burial history. The visible diffuse reflectance spectroscopy (DRS) is a useful tool for quantifying goethite. However, aluminium (Al) substitution for goethite is very common in soils and the effects of Al content on the DRS properties of goethite have not been fully resolved. In this study, two series of Al substituted goethites (Al-goethite) and 20 Chinese loess/palaeosol samples were investigated using both DRS and magnetic methods to test the feasibility of quantifying Al-goethite with the DRS method. Results show that the peak positions and amplitudes of the goethite DRS band are significantly influenced by Al substitution. Specifically, the goethite concentration proxy, the amplitude of the DRS band, is relatively stable only when Al substitution ranged between about 4 and 16 mol per cent. Practically, in order to resolve the difficulty in measuring Al content in natural samples, the unblocking temperature (Tb) is proposed as the proxy for Al substitution of goethite. When Tb of Al-goethite was above 250 K, the amplitude of DRS can be used to reliably trace the goethite concentration variation in natural samples. For example, the DRS spectra for the Chinese loess-palaeosol samples support the idea that only haematite is enhanced via pedogenesis. In contrast, the origin of goethite seems to be mostly related to the aeolian inputs.

  10. Measurement of the fractional oxygenation of leghemoglobin in intact detached pea nodules by reflectance spectroscopy

    SciTech Connect

    Monroe, J.D.; Owens, T.G. ); LaRue, T.A. )

    1989-10-01

    A method is presented for the rapid measurement of the spectral properties of detached nodules of pea (Pisum sativum L. cv Sparkle) by diffuse reflectance spectroscopy. After correcting the spectra for surface light scattering, the spectrum of leghemoglobin is obtained. From this, the fractional oxygenation of leghemoglobin and the internal O{sub 2} concentration can be calculated. With this method, we determined internal O{sub 2} while measuring nitrogenase activity (C{sub 2}H{sub 2}) in detached pea nodules over a range of external O{sub 2} concentrations. Nitrogenase activity was maximum when leghemoglobin was 25% oxygenated, corresponding to a calculated free O{sub 2} concentration of 45 nanomolar in infected cells. Advantages of this method over previous methods which employed transmitted light are: (a) many nodules can be assayed simultaneously, (b) nitrogenase activity (C{sub 2}H{sub 2}) can be determined at the same time as spectra are recorded, and (c) spectra can be obtained from nodules submerged in buffer containing metabolic effectors.

  11. Detection of canine skin and subcutaneous tumors by visible and near-infrared diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cugmas, Blaž; Plavec, Tanja; Bregar, Maksimilijan; Nagli?, Peter; Pernuš, Franjo; Likar, Boštjan; Bürmen, Miran

    2015-03-01

    Cancer is the main cause of canine morbidity and mortality. The existing evaluation of tumors requires an experienced veterinarian and usually includes invasive procedures (e.g., fine-needle aspiration) that can be unpleasant for the dog and the owner. We investigate visible and near-infrared diffuse reflectance spectroscopy (DRS) as a noninvasive optical technique for evaluation and detection of canine skin and subcutaneous tumors ex vivo and in vivo. The optical properties of tumors and skin were calculated in a spectrally constrained manner, using a lookup table-based inverse model. The obtained optical properties were analyzed and compared among different tumor groups. The calculated parameters of the absorption and reduced scattering coefficients were subsequently used for detection of malignant skin and subcutaneous tumors. The detection sensitivity and specificity of malignant tumors ex vivo were 90.0% and 73.5%, respectively, while corresponding detection sensitivity and specificity of malignant tumors in vivo were 88.4% and 54.6%, respectively. The obtained results show that the DRS is a promising noninvasive optical technique for detection and classification of malignant and benign canine skin and subcutaneous tumors. The method should be further investigated on tumors with common origin.

  12. Reflectance anisotropy spectroscopy as a tool for mechanical characterization of metallic thin films

    NASA Astrophysics Data System (ADS)

    Wyss, A.; Schamel, M.; Sologubenko, A. S.; Denk, R.; Hohage, M.; Zeppenfeld, P.; Spolenak, R.

    2015-10-01

    In the present work reflectance anisotropy spectroscopy (RAS) is evaluated as a new tool for the mechanical characterization of metallic thin films on viscoelastic substrates. Cu and Cu-Zn thin films of thicknesses in the range from 50 to 1000?nm were sputter-deposited onto a viscoelastic polyimide substrate and subjected to uniaxial tensile loading. The changes in the mechanical, electrical and optical response of the films upon loading were monitored by simultaneous acquisition of total strain, electrical resistance and the RA-signal. The RA-spectrum of pure copper reveals a feature at a photon energy of ~4.0?eV that linearly increases with strain at the beginning of loading (elastic regime) and saturates at later stages (plastic regime). Post-mortem SEM studies of samples loaded to different strain values confirmed that this saturation corresponds to the onset of plastic deformation, defined by the appearance of slip lines. Concurrent measurements of the electrical resistance confirmed the absence of cracking at the onset of the 4.0?eV RA-signal saturation. Therefore we claim that the RAS technique can be employed for yield point determination. Besides the applicability of the RAS technique for pure metals, chemical sensitivity of RAS in terms of peak position was observed in the case of Cu-Zn thin films.

  13. Spectral characteristics of chlorites and Mg-serpentines using high- resolution reflectance spectroscopy

    USGS Publications Warehouse

    King, T.V.V.; Clark, R.N.

    1989-01-01

    The present laboratory study using high-resolution reflectance spectroscopy (0.25-2.7 ??m) focuses on two primary phyllosilicate groups, serpentines and chlorites. The results show that it is possible to spectrally distinguish between isochemical end-members of the Mg-rich serpentine group (chrysotile, antigorite, and lizardite) and to recognize spectral variations in chlorites as a function of Fe/Mg ratio (~8-38 wt% Fe). The position and relative strength of the 1.4-??m absorption feature in the trioctahedral chlorites appear to be correlated to the total iron content and/or the Mg/Si ratio and the loss on ignition values of the sample. Spectral differences in the 2.3-??m wavelength region can be attributed to differences in lattice environments and are characteristic for specific trioctahedral chlorites. The 1.4-??m feature in the isochemical Mg-rich serpentines (total iron content ~1.5-7.0 wt%) show marked spectral differences, apparently due to structural differences. -Authors

  14. [Near-infrared reflectance spectroscopy analytic model established for the IVDMD of Cichorium intybus L].

    PubMed

    Hu, Chao; Bai, Shi-qie; Zhang, Yu; Yan, Jia-jun; You, Ming-hong; Li, Da-xu; Bai, Ling; Zhang Jin

    2014-08-01

    Chicory (Cichorium intybus L.) is a new type of forage grasses of high yield and quality with a great value of popularization and utilization. In vitro dry matter digestibility (IVDMD) is one of the important indicators of the nutritional value of forage evaluation. For the study of establishment of Chicory IVDMD NIRS quantitative analysis model, seventy-two species with different genotypes, different growth stages of 204 chicory samples of aboveground material were collected, and by Fourier transform near-infrared diffuse reflectance spectroscopy, through the use of different regression algorithms, can comparing different spectral ranges and spectral pretreatment methods, eight chicory IVDMD NIRS calibration models were established, and the best calibration model parameters were chosen. Its calibration coefficient of determination (Ri) and external validation coefficient of determination (Rval2) were 0.95317 and 0.90455, calibration standard deviation (RMSEC) and predictive standard deviation (RMSEP) was 1.977 99% and 2.008 82%, and the correlation coefficient (r) between predicted values and chemical values was 0.95108. The results show that using NIRS to determine chicory IVDMD is feasible, and provided a rapid analysis method for the determination IVDMD of chicory. PMID:25508718

  15. [Near-infrared reflectance spectroscopy analytic model established for the IVDMD of Cichorium intybus L].

    PubMed

    Hu, Chao; Bai, Shi-qie; Zhang, Yu; Yan, Jia-jun; You, Ming-hong; Li, Da-xu; Bai, Ling; Zhang Jin

    2014-08-01

    Chicory (Cichorium intybus L.) is a new type of forage grasses of high yield and quality with a great value of popularization and utilization. In vitro dry matter digestibility (IVDMD) is one of the important indicators of the nutritional value of forage evaluation. For the study of establishment of Chicory IVDMD NIRS quantitative analysis model, seventy-two species with different genotypes, different growth stages of 204 chicory samples of aboveground material were collected, and by Fourier transform near-infrared diffuse reflectance spectroscopy, through the use of different regression algorithms, can comparing different spectral ranges and spectral pretreatment methods, eight chicory IVDMD NIRS calibration models were established, and the best calibration model parameters were chosen. Its calibration coefficient of determination (Ri) and external validation coefficient of determination (Rval2) were 0.95317 and 0.90455, calibration standard deviation (RMSEC) and predictive standard deviation (RMSEP) was 1.977 99% and 2.008 82%, and the correlation coefficient (r) between predicted values and chemical values was 0.95108. The results show that using NIRS to determine chicory IVDMD is feasible, and provided a rapid analysis method for the determination IVDMD of chicory. PMID:25474939

  16. Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry

    E-print Network

    Budin?evi?, I; Bissell, M L; Cocolios, T E; de Groote, R P; De Schepper, S; Fedosseev, V N; Flanagan, K T; Franchoo, S; Ruiz, R F Garcia; Heylen, H; Lynch, K M; Marsh, B A; Neyens, G; Procter, T J; Rossel, R E; Rothe, S; Strashnov, I; Stroke, H H; Wendt, K D A

    2014-01-01

    The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich $^{218m,219,229,231}\\text{Fr}$ isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the $7s~^{2}S_{1/2}$ to $8p~^{2}P_{3/2}$ atomic transition. The $\\delta\\langle r^{2}\\rangle^{A,221}$ values for $^{218m,219}\\text{Fr}$ and $^{229,231}\\text{Fr}$ follow the observed increasing slope of the charge radii beyond $N~=~126$. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that $^{220}\\text{Fr}$ has a weakly inverted odd-even staggering while $^{228}\\text{Fr}$ has normal staggering. This suggests that both isotopes reside at the borders of a region of inverted staggering, which has been associated with reflection-asymmetric shapes. The $g(^{219}\\text{Fr}) = +0.69(1)$ value supports a $\\pi 1h_{9/2}$ shell model configuration for the ground state. The $g(^{229,231}\\text{Fr})$ values support the tentative $I^{\\pi}(^...

  17. Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry

    NASA Astrophysics Data System (ADS)

    Budin?evi?, I.; Billowes, J.; Bissell, M. L.; Cocolios, T. E.; de Groote, R. P.; De Schepper, S.; Fedosseev, V. N.; Flanagan, K. T.; Franchoo, S.; Garcia Ruiz, R. F.; Heylen, H.; Lynch, K. M.; Marsh, B. A.; Neyens, G.; Procter, T. J.; Rossel, R. E.; Rothe, S.; Strashnov, I.; Stroke, H. H.; Wendt, K. D. A.

    2014-07-01

    The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich 218m,219,229,231Fr isotopes were measured with the newly installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at the On-Line Isotope Mass Separator (ISOLDE), CERN, probing the 7s2S1/2 to 8p2P3/2 atomic transition. The ?A,221 values for 218m,219Fr and 229,231Fr follow the observed increasing slope of the charge radii beyond N =126. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that 220Fr has a weakly inverted odd-even staggering while 228Fr has normal staggering. This suggests that both isotopes reside at the borders of a region of inverted staggering, which has been associated with reflection-asymmetric shapes. The g(219Fr )=+0.69(1) value supports a ?1h9/2 shell-model configuration for the ground state. The g(229,231Fr ) values support the tentative I?(229,231Fr)=(1/2+) spin and point to a ?s1/2-1 intruder ground-state configuration.

  18. Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry

    E-print Network

    I. Budin?evi?; J. Billowes; M. L. Bissell; T. E. Cocolios; R. P. de Groote; S. De Schepper; V. N. Fedosseev; K. T. Flanagan; S. Franchoo; R. F. Garcia Ruiz; H. Heylen; K. M. Lynch; B. A. Marsh; G. Neyens; T. J. Procter; R. E. Rossel; S. Rothe; I. Strashnov; H. H. Stroke; K. D. A. Wendt

    2014-07-02

    The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich $^{218m,219,229,231}\\text{Fr}$ isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the $7s~^{2}S_{1/2}$ to $8p~^{2}P_{3/2}$ atomic transition. The $\\delta\\langle r^{2}\\rangle^{A,221}$ values for $^{218m,219}\\text{Fr}$ and $^{229,231}\\text{Fr}$ follow the observed increasing slope of the charge radii beyond $N~=~126$. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that $^{220}\\text{Fr}$ has a weakly inverted odd-even staggering while $^{228}\\text{Fr}$ has normal staggering. This suggests that both isotopes reside at the borders of a region of inverted staggering, which has been associated with reflection-asymmetric shapes. The $g(^{219}\\text{Fr}) = +0.69(1)$ value supports a $\\pi 1h_{9/2}$ shell model configuration for the ground state. The $g(^{229,231}\\text{Fr})$ values support the tentative $I^{\\pi}(^{229,231}\\text{Fr}) = (1/2^{+})$ spin, and point to a $\\pi s_{1/2}^{-1}$ intruder ground state configuration.

  19. Attenuated total reflectance-FT-IR spectroscopy for gunshot residue analysis: potential for ammunition determination.

    PubMed

    Bueno, Justin; Sikirzhytski, Vitali; Lednev, Igor K

    2013-08-01

    The ability to link a suspect to a particular shooting incident is a principal task for many forensic investigators. Here, we attempt to achieve this goal by analysis of gunshot residue (GSR) through the use of attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FT-IR) combined with statistical analysis. The firearm discharge process is analogous to a complex chemical process. Therefore, the products of this process (GSR) will vary based upon numerous factors, including the specific combination of the firearm and ammunition which was discharged. Differentiation of FT-IR data, collected from GSR particles originating from three different firearm-ammunition combinations (0.38 in., 0.40 in., and 9 mm calibers), was achieved using projection to latent structures discriminant analysis (PLS-DA). The technique was cross (leave-one-out), both internally and externally, validated. External validation was achieved via assignment (caliber identification) of unknown FT-IR spectra from unknown GSR particles. The results demonstrate great potential for ATR-FT-IR spectroscopic analysis of GSR for forensic purposes. PMID:23745950

  20. Reflectance difference spectroscopy a powerful tool to study adsorption and growth

    NASA Astrophysics Data System (ADS)

    Hohage, M.; Sun, L. D.; Zeppenfeld, P.

    2005-02-01

    Changes in the optical anisotropy of the Cu(110) surface due to adsorption and growth have been studied by reflectance difference spectroscopy (RDS). The optical anisotropy signal at 2.13 eV was found to be extremely sensitive to small quantities of CO, while the signal at 4.3 eV turned out to be particularly sensitive to the transition from a (3×1) to a (2×1) CO superstructure. In the case of the oxygen covered Cu(110), we have successfully monitored and analyzed the transition between two oxygen induced Cu(110) reconstructions: The c(6×2)O and the (2×1)O phases have clearly distinguishable RDS features, and the transition between them leads to a gradual transformation of the related RDS spectra. For the system Co on Cu(110)(2×1)O characteristic features of a CoCuO alloy phase have been identified, which allow to monitor the crucial stages of the Co thin film growth. The alloying and de-alloying are easily recognized with RDS.

  1. Monte Carlo modeling of surface excitation in reflection electron energy loss spectroscopy spectrum for rough surfaces

    NASA Astrophysics Data System (ADS)

    Da, B.; Mao, S. F.; Zhang, G. H.; Wang, X. P.; Ding, Z. J.

    2012-08-01

    It has been experimentally found that the surface roughness influences strongly the surface and bulk plasmon excitation by glancing-angle reflection electron energy loss spectroscopy (REELS). However, there is still little theoretical work dealing with the surface roughness effect in REELS. Such a work is required to predict REELS spectra accurately, providing an understanding of the experimental phenomena observed. In this study, we use a finite element triangle mesh method build in a fully 3D rough surface model based on the surface topography measured by atomic force microscopy. Then REELS spectra for these rough surfaces are theoretically simulated by using Monte Carlo simulation including surface plasmon excitation and bulk plasmon excitation. The simulation results for Al sample with different surface roughnesses agree well with experimental data. Based on the analysis of the maximum depth of backscattered electrons and the depth distribution of surface bulk excitation under different conditions of roughness, the influence of surface roughness to the surface excitation in REELS spectra can be well understood.

  2. Optical characterization of thin nickel films on polymer substrates using reflectance difference spectroscopy

    SciTech Connect

    Rinnerbauer, V.; Schmidegg, K.; Hohage, M.; Sun, L. D.; Flores-Camacho, J. M.; Zeppenfeld, P.

    2009-06-15

    We have used reflectance difference spectroscopy (RDS) and its extension, azimuth-dependent RDS (ADRDS), to study the properties of sputtered and evaporated nickel films on biaxially oriented poly(ethylene terephtalate) (PET) films in a roll to roll web-coating process. From the full set of ADRDS spectra we extract and analyze both the intrinsic RDS spectra and the azimuthal orientation of the effective optical anisotropy of the samples. From the latter, contributions to the RDS spectra arising from the nickel layer and the PET substrate with different orientations of the optical eigenaxes can be inferred. We find an attenuation of the characteristic RDS signal of the PET substrate with increasing nickel film thickness which is in good agreement with the theoretical prediction. For film thicknesses above 20 nm another contribution to the RDS signal attributed to the optical anisotropy of the deposited nickel layers can be observed. Its strength depends on the deposition method, and is considerably larger for evaporated films than for sputtered ones. With increasing nickel film thickness, the azimuthal orientation of the sample anisotropy changes from the initial value of the PET substrate by about 20 deg.toward the machine direction of the foil. We demonstrate that RDS is also a valuable tool for inline monitoring in the roll to roll process, as the attenuation of the RDS signal, under proper consideration of the orientation of the effective anisotropy, is a function of the film thickness and characteristic for the deposited material.

  3. Electronic and optical properties of Fe, Pd, and Ti studied by reflection electron energy loss spectroscopy

    SciTech Connect

    Tahir, Dahlang; Kraaer, Jens; Tougaard, Sven

    2014-06-28

    We have studied the electronic and optical properties of Fe, Pd, and Ti by reflection electron energy-loss spectroscopy (REELS). REELS spectra recorded for primary energies in the range from 300?eV to 10?keV were corrected for multiple inelastically scattered electrons to determine the effective inelastic-scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic-electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(?1/?) by using the QUEELS-?(k,?)-REELS software package. The complex dielectric functions ?(k,?), in the 0–100?eV energy range, for Fe, Pd, and Ti were determined from the derived Im(?1/?) by Kramers-Kronig transformation and then the refractive index n and extinction coefficient k. The validity of the applied model was previously tested and found to give consistent results when applied to REELS spectra at energies between 300 and 1000?eV taken at widely different experimental geometries. In the present paper, we provide, for the first time, a further test on its validity and find that the model also gives consistent results when applied to REELS spectra in the full range of primary electron energies from 300?eV to 10000?eV. This gives confidence in the validity of the applied method.

  4. Fast Pyrolysis of Wood for Biofuels: Spatiotemporally Resolved Diffuse Reflectance In?situ Spectroscopy of Particles.

    PubMed

    Paulsen, Alex D; Hough, Blake R; Williams, C Luke; Teixeira, Andrew R; Schwartz, Daniel T; Pfaendtner, Jim; Dauenhauer, Paul J

    2014-02-20

    Fast pyrolysis of woody biomass is a promising process capable of producing renewable transportation fuels to replace gasoline, diesel, and chemicals currently derived from nonrenewable sources. However, biomass pyrolysis is not yet economically viable and requires significant optimization before it can contribute to the existing oil-based transportation system. One method of optimization uses detailed kinetic models for predicting the products of biomass fast pyrolysis, which serve as the basis for the design of pyrolysis reactors capable of producing the highest value products. The goal of this work is to improve upon current pyrolysis models, usually derived from experiments with low heating rates and temperatures, by developing models that account for both transport and pyrolysis decomposition kinetics at high heating rates and high temperatures (>400?°C). A new experimental technique is proposed herein: spatiotemporally resolved diffuse reflectance in?situ spectroscopy of particles (STR-DRiSP), which is capable of measuring biomass composition during fast pyrolysis with high spatial (10??m) and temporal (1?ms) resolution. Compositional data were compared with a comprehensive 2D single-particle model, which incorporated a multistep, semiglobal reaction mechanism, prescribed particle shrinkage, and thermophysical properties that varied with temperature, composition, and orientation. The STR-DRiSP technique can be used to determine the transport-limited kinetic parameters of biomass decomposition for a wide variety of biomass feedstocks. PMID:24678023

  5. Rapid Assessment of Mineral Concentration in Meadow Grasses by Near Infrared Reflectance Spectroscopy

    PubMed Central

    Ward, Alastair; Nielsen, Anne Lisbeth; Møller, Henrik

    2011-01-01

    A near infrared reflectance spectroscopy (NIRS) method for rapid determination of nitrogen, phosphorous and potassium in diverse meadow grasses was developed with a view towards utilizing this material for biogas production and organic fertilizer. NIRS spectra between 12,000 cm?1 and 4,000 cm?1 were used. When validated on samples from different years to those used for the calibration set, the NIRS prediction of nitrogen was considered moderately useful with R2 = 0.77, ratio of standard error of prediction to reference data range (RER) of 9.32 and ratio of standard error of prediction to standard deviation of reference data (RPD) of 2.33. Prediction of potassium was less accurate, with R2 = 0.77, RER of 6.56 and RPD of 1.45, whilst prediction of phosphorous was not considered accurate enough to be of any practical use. This work is of interest from the point of view of both the removal of excess nutrients from formerly intensively farmed areas and also for assessing the plant biomass suitability for conversion into carbon neutral energy through biogas production. PMID:22163878

  6. [Attenuated Total Reflection Infrared Spectroscopy for Degradation Profile of High Density Polyethylene after Weathering Aging].

    PubMed

    Guo, Jun-jun; Yan, Hua; Bao, He-bin; Wang, Xue-mei; Hu, Zhi-de; Yang, Jian-jian

    2015-06-01

    High density polyethylene (HDPE) was widely used as rotational packaging case in the material reserve field. The chemical changes of HDPE, exposed to particular climatic conditions of tropic marine atmosphere for one year-long in Wanning Hainan, were elucidated by the attenuated total reflection infrared spectroscopy (ATR-FTIR). The structural changes were studied qualitatively, mainly from the polymeric chain breaking, branching and oxidation to distinguish the degradation profile. The variations of crystallinity & carbonyl index were also studied quantitatively according to the characteristic peaks intensity & area ratio. Finally, the relationships between structural changes and mechanical properties were investigated. The results showed that the polymeric chain breaking & branching play a leading role before 3 months in the aging progress. Then oxidation phenomena gradually takes place during 3-6 months. The chain branching & oxidation were predominant factors after 6 months. Nine months later, the oxidation was saturated gradually. Furthermore, the aging process is positively correlated to the temperature and irradiation. After 12 months aging, the carbonyl index increased by 112 times and crystallinity was 10% higher than before. The tensile/bending modulus deceased faster than tensile/bending strength of HDPE. The linear degree of tensile modulus and carbonyl index was 0.97. The degree of linearity of tensile strength and crystallinity calculated by feature bands (720-730 cm(-1)) was 0.96. It showed that the mechanical properties of HDPE can be speculated from the structural changes by ATR-FTIR. PMID:26601359

  7. Non-invasive evaluation of therapeutic response in keloid scar using diffuse reflectance spectroscopy

    PubMed Central

    Hsu, Chao-Kai; Tzeng, Shih-Yu; Yang, Chao-Chun; Lee, Julia Yu-Yun; Huang, Lynn Ling-Huei; Chen, Wan-Rung; Hughes, Michael; Chen, Yu-Wen; Liao, Yu-Kai; Tseng, Sheng-Hao

    2015-01-01

    The pathogenesis and ideal treatment of keloid are still largely unknown, and it is essential to develop an objective assessment of keloid severity to evaluate the therapeutic response. We previously reported that our diffuse reflectance spectroscopy (DRS) system could assist clinicians in understanding the functional and structural condition of keloid scars. The purpose of this study was to understand clinical applicability of our DRS system on evaluating the scar severity and therapeutic response of keloid. We analyzed 228 spectral data from 71 subjects with keloid scars. The scars were classified into mild (0-3), moderate (4-7) and severe (8-11) according to the Vancouver scar scale. We found that as the severity of the scar increased, collagen concentration and water content increased, and the reduced scattering coefficient at 800 nm and oxygen saturation (SaO2) decreased. Using the DRS system, we found that collagen bundles aligned in a specific direction in keloid scars, but not in normal scars. Water content and SaO2 may be utilized as reliable parameters for evaluating the therapeutic response of keloid. In conclusion, the results obtained here suggest that the DRS has potential as an objective technique with which to evaluate keloid scar severity. In addition, it may be useful as a tool with which to track longitudinal response of scars in response to various therapeutic interventions. PMID:25780731

  8. Plasmon-enhanced terahertz photodetection in graphene

    NASA Astrophysics Data System (ADS)

    Cai, Xinghan; Sushkov, Andrei; Jadidi, Mohammad; Myers-Ward, R. L.; Boyd, A. K.; Daniels, K. M.; Gaskill, D. Kurt; Murphy, Thomas; Drew, H. Dennis; Fuhrer, Michael

    2015-03-01

    Graphene is a promising material for high speed room-temperature terahertz photodetection. However, the limited absorption in monolayer graphene remains a key challenge. We present here a large area terahertz detector that utilizes a plasmonic resonance in sub-wavelength graphene micro-ribbons to increase the absorption efficiency, and exploits the hot-electron photothermoelectric effect for detection. Through Fourier transform infrared spectroscopy we show that by tailoring the orientation of the graphene ribbons with respect to an array of sub-wavelength bimetallic electrodes, the plasmonic resonance can be efficiently excited, with a gate-tunable resonance frequency in the terahertz range. Polarization-dependent photoresponse measurements show an enhanced photothermal voltage between the outermost electrodes due to the plasmonically enhanced absorption. This work was sponsored by the US ONR (N000140911064, N000141310712 and N000141310865), the US NSF (ECCS 1309750), IARPA, and the Australian Research Council.

  9. Photocarrier dynamics in undoped and Na-doped Cu2ZnSnS4 single crystals revealed by ultrafast time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Quang Phuong, Le; Okano, Makoto; Yamashita, Genki; Nagai, Masaya; Ashida, Masaaki; Nagaoka, Akira; Yoshino, Kenji; Kanemitsu, Yoshihiko

    2015-06-01

    We investigated the effects of sodium doping on the photocarrier dynamics in Cu2ZnSnS4 (CZTS) single crystals using optical pump-THz probe transient reflectivity (THz-TR) and time-resolved photoluminescence (PL) spectroscopy. The THz-TR and PL decay dynamics are influenced by sodium doping, and their sodium-induced changes are consistent with each other. These time-resolved measurements revealed that the lifetime of photocarriers increases with sodium doping. This result indicates that a part of defects is suppressed by doping sodium into CZTS and implies that sodium doping improves the charge transport properties of CZTS, leading to an improvement in the performance of CZTS-based solar cells.

  10. A polarization-independent broadband terahertz absorber

    SciTech Connect

    Shi, Cheng; Zang, XiaoFei E-mail: ymzhu@usst.edu.cn; Wang, YiQiao; Chen, Lin; Cai, Bin; Zhu, YiMing E-mail: ymzhu@usst.edu.cn

    2014-07-21

    A highly efficient broadband terahertz absorber is designed, fabricated, and experimentally as well as theoretically evaluated. The absorber comprises a heavily doped silicon substrate and a well-designed two-dimensional grating. Due to the destructive interference of waves and diffraction, the absorber can achieve over 95% absorption in a broad frequency range from 1 to 2 THz and for angles of incidence from 0° to 60°. Such a terahertz absorber is also polarization-independent due to its symmetrical structure. This omnidirectional and broadband absorber have potential applications in anti-reflection coatings, imaging systems, and so on.

  11. A New Diffuse Reflecting Material with Applications Including Integrating Cavity Ring-Down Spectroscopy 

    E-print Network

    Cone, Michael Thomas

    2014-04-16

    ever produced. The material is a high-purity fumed silica, or quartz powder. We demonstrate the application of this new material to several areas of integrating cavity enhanced spectroscopy, including absorption, Raman, and fluorescence spectroscopy...

  12. The potential of terahertz imaging for cancer diagnosis: A review of investigations to date

    PubMed Central

    Yu, Calvin; Fan, Shuting; Sun, Yiwen; Pickwell-MacPherson, Emma

    2012-01-01

    The terahertz region lies between the microwave and infrared regions of the electromagnetic spectrum such that it is strongly attenuated by water and very sensitive to water content. Terahertz radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. Because of these characteristic properties, there has been an increasing interest in terahertz imaging and spectroscopy for biological applications within the last few years and more and more terahertz spectra are being reported, including spectroscopic studies of cancer. The presence of cancer often causes increased blood supply to affected tissues and a local increase in tissue water content may be observed: this acts as a natural contrast mechanism for terahertz imaging of cancer. Furthermore the structural changes that occur in affected tissues have also been shown to contribute to terahertz image contrast. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques. In particular investigations relating to the potential of terahertz imaging and spectroscopy for cancer diagnosis will be highlighted. PMID:23256057

  13. Terahertz imaging: applications and perspectives.

    PubMed

    Jansen, Christian; Wietzke, Steffen; Peters, Ole; Scheller, Maik; Vieweg, Nico; Salhi, Mohammed; Krumbholz, Norman; Jördens, Christian; Hochrein, Thomas; Koch, Martin

    2010-07-01

    Terahertz (THz) spectroscopy, and especially THz imaging, holds large potential in the field of nondestructive, contact-free testing. The ongoing advances in the development of THz systems, as well as the appearance of the first related commercial products, indicate that large-scale market introduction of THz systems is rapidly approaching. We review selected industrial applications for THz systems, comprising inline monitoring of compounding processes, plastic weld joint inspection, birefringence analysis of fiber-reinforced components, water distribution monitoring in polymers and plants, as well as quality inspection of food products employing both continuous wave and pulsed THz systems. PMID:20648121

  14. Exploiting Optical Contrasts for Cervical Precancer Diagnosis via Diffuse Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chang, Vivide Tuan-Chyan

    Among women worldwide, cervical cancer is the third most common cancer with an incidence rate of 15.3 per 100,000 and a mortality rate of 7.8 per 100,000 women. This is largely attributed to the lack of infrastructure and resources in the developing countries to support the organized screening and diagnostic programs that are available to women in developed nations. Hence, there is a critical global need for a screening and diagnostic paradigm that is effective in low-resource settings. Various strategies are described to design an optical spectroscopic sensor capable of collecting reliable diffuse reflectance data to extract quantitative optical contrasts for cervical cancer screening and diagnosis. A scalable Monte Carlo based optical toolbox can be used to extract absorption and scattering contrasts from diffuse reflectance acquired in the cervix in vivo. [Total Hb] was shown to increase significantly in high-grade cervical intraepithelial neoplasia (CIN 2+), clinically the most important tissue grade to identify, compared to normal and low-grade intraepithelial neoplasia (CIN 1). Scattering was not significantly decreased in CIN 2+ versus normal and CIN 1, but was significantly decreased in CIN relative to normal cervical tissues. Immunohistochemistry via anti-CD34, which stains the endothelial cells that line blood vessels, was used to validate the observed absorption contrast. The concomitant increase in microvessel density and [total Hb] suggests that both are reactive to angiogenic forces from up-regulated expression of VEGF in CIN 2+. Masson's trichrome stain was used to assess collagen density changes associated with dysplastic transformation of the cervix, hypothesized as the dominant source of decreased scattering observed. Due to mismatch in optical and histological sampling, as well as the small sample size, collagen density and scattering did not change in a similar fashion with tissue grade. Dysplasia may also induce changes in cross-linking of collagen without altering the amount of collagen present. Further work would be required to elucidate the exact sources of scattering contrast observed. Common confounding variables that limit the accuracy and clinical acceptability of optical spectroscopic systems are calibration requirements and variable probe-tissue contact pressures. Our results suggest that using a real-time self-calibration channel, as opposed to conventional post-experiment diffuse reflectance standard calibration measurements, significantly improved data integrity for the extraction of scattering contrast. Extracted [total Hb] and scattering were also significantly associated with applied contact probe pressure in colposcopically normal sites. Hence, future contact probe spectroscopy or imaging systems should incorporate a self-calibration channel and ensure spectral acquisition at a consistent contact pressure to collect reliable data with enhanced absorption and scattering contrasts. Another method to enhance optical contrast is to selectively interrogate different depths in the dysplastic cervix. For instance, scattering has been shown to increase in the epithelium (increase in nuclear-to-cytoplasmic ratio) while decrease in the stroma (re-organization of the extra-cellular matrix and changes in of collagen fiber cross-links). A fiber-optic probe with 45° illumination and collection fibers with a separation distance of 330 ?m was designed and constructed to selectively interrogate the cervical epithelium. Mean extraction errors from liquid phantoms with optical properties mimicking the cervical epithelium for ?a and ?s' were 11.3 % and 12.7 %, respectively. Diffuse reflectance spectra from 9 sites in four loop electrosurgical excision procedure (LEEP) patients were analyzed. Preliminary data demonstrate the utility of the oblique fiber geometry in extracting scattering contrast in the cervical epithelium. Further work is needed to study the systematic error in optical property extraction and to incorporate simultaneous extraction of epithelial and stromal contrasts using both flat an

  15. Terahertz Physics

    NASA Astrophysics Data System (ADS)

    Lewis, R. A.

    2013-01-01

    1. Introduction; Part I. Basics: 2. Oscillations; 3. Combining oscillations; 4. Light; 5. Matter; 6. Interaction of light and matter; Part II. Components: 7. Sources; 8. Optics; 9. Detectors; Part III. Applications: 10. Spectroscopy; 11. Imaging; Glossary; Appendices; Index.

  16. Prediction of phosphorus adsorbed and iron oxides using diffuse reflectance spectroscopy in areas of sugarcane

    NASA Astrophysics Data System (ADS)

    Camargo, Livia; Marques, José, Jr.

    2014-05-01

    Traditional technologies for measuring phosphorus adsorbed (Pads) and other soil attributes of agronomic importance are relatively unfeasible when aims to mapping large areas using the characterization of the spatial variability of soil attributes. These mappings need a large number of samples, which makes it expensive in mappings scale detail. This arouses in scientific society the need to develop methodologies able to assess these attributes within the landscape quickly, nondestructive, and not expensive. The diffuse reflectance spectroscopy (DRS) has been used to aid the characterization of soil attributes view of these requirements. In this sensing, the objective of this study was to evaluate the ability of DRS to estimate the Pads, clay, Fe extracted by dithionite-citrate-bicarbonate (Fedcb), contents of goethite (Gt) and hematite (Hm) and ratio Gt/(Gt + Hm) in Oxisols in The Northeastern State of São Paulo. Soil samples were collected in the transects each 25 m (100 samples). Geomorphic surfaces (GSs) were mapped in detail to support soil mapping. The soil in GS I was a Typic Hapludox, that in GS II a Typic Hapludox and Typic Eutrudox, and that in GS III a Typic Eutrudox. The soil samples were taken to the laboratory for chemical, physical and mineralogical analysis and DRS spectra were obtained over 380-2300 nm. Chemometric calibration and validation (using a one-out crossvalidation procedure) were done on absorbance measurements [Log10 (1/Reflectance)] by Partial least-squares regression (PLSR) analysis. The calibration accuracy was evaluated via the determination coefficient (R2), RMSE and the ratio performance deviation (RPD). The graph of Variable Importance in the Projection (VIP) for the Pad was built. The DRS was effective in predicting the attributes studied whereas the obtained models for the prediction of clay, Fedcb and Gt with greater accuracy (RPD> 1.4) were calibrated in the visible (380-800 nm) and to predict Pads, ratio Gt/(Gt + Hm) and Hm were calibrated in the visible + near infrared (801-2300 nm). The highest peaks of VIP for the Pads have been found in wavelengths: 480-580 nm and 780-980 nm which are assigned to crystalline iron oxides, mainly Gt and Hm. This result demonstrates the influence of these oxides on the P adsorption. In weathered soils, P adsorption is mainly correlated to iron oxides and aluminum clay fraction due phosphate interact with the functional groups of these oxides.

  17. Terahertz spectroscopy of isotopic acrylonitrile

    NASA Astrophysics Data System (ADS)

    Kra?nicki, Adam; Kisiel, Zbigniew; Drouin, Brian J.; Pearson, John C.

    2011-12-01

    Rotational spectra of four isotopically enriched, singly substituted species of acrylonitrile have been studied up to 1.2 THz. Extensive analysis of the spectra recorded for H 213C dbnd CHCN, H 2C dbnd CH 13CN, H 2C dbnd CHC 15N, and H 2C dbnd CDCN, revealed the presence of the same characteristic perturbations between the ground state and the v11 = 1 excited vibrational state, that have recently been identified in the parent molecule. For this reason transitions in v11 = 1 have also been assigned in each of the four isotopic species and a coupled state analysis of g.s. and v11 = 1 was performed on a total of around 3000 lines for each species. The derived precise values of E( v11 = 1) are found to be consistent with estimates from anharmonic force field calculations. In addition, transitions for six new doubly substituted isotopic species of acrylonitrile, H 213C dbnd 13CHCN, H 213C dbnd CH 13CN, H 2C dbnd 13CH 13CN, H 213C dbnd CHC 15N, H 2C dbnd 13CHC 15N, and H 2C dbnd CH 13C 15N, have been assigned, and their ground state spectroscopic constants have been determined. Rotational constants for all known isotopic species of acrylonitrile have been combined with ab initio calculation of vibration-rotation constants in the first evaluation of the reSE geometry of this molecule.

  18. Perfect terahertz absorber using fishnet based metafilm

    SciTech Connect

    Azad, Abul Kalam; Shchegolkov, Dmitry Yu; Chen, Houtong; Taylor, Antoinette; Smirnova, E I; O' Hara, John F

    2009-01-01

    We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials with desired values. Although the initial idea of metamaterials was to obtain a negative index medium, however, the evolution of metamaterials (MMs) offers a variety of practically applicable devices for controlling electromagnetic wave such as tunable filters, modulators, phase shifters, compact antenna, absorbers, etc. Terahertz regime, a crucial domain of the electromagnetic wave, is suffering from the scarcity of the efficient devices and might take the advantage of metamaterials. Here, we demonstrate design, fabrication, and characterization of a terahertz absorber based on a simple fishnet metallic film separated from a ground mirror plane by a dielectric spacer. Such absorbers are in particular important for bolometric terahertz detectors, high sensitivity imaging, and terahertz anechoic chambers. Recently, split-ring-resonators (SRR) have been employed for metamaterial-based absorbers at microwave and THz frequencies. The experimental demonstration reveals that such absorbers have absorptivity close to unity at resonance frequencies. However, the downside of these designs is that they all employ resonators of rather complicated shape with many fine parts and so they are not easy to fabricate and are sensitive to distortions.

  19. Terahertz real-time imaging for nondestructive detection

    NASA Astrophysics Data System (ADS)

    Zhang, LiangLiang; Karpowicz, Nick; Zhang, CunLin; Zhao, YueJin; Zhang, XiCheng

    2008-03-01

    We present a real time imaging measurement in the terahertz (THz) frequency region. The dynamic subtraction technique is used to reduce long-term optical background drift. The reflective images of two targets, a Nikon camera's lens cap and a plastic toy gun, are obtained. For the lens cap, the image data were processed to be false color images. For the toy gun, we show that even under an optically opaque canvas bag, a clear terahertz image is obtained. It is shown that terahertz real time imaging can be used to nondestructively detect concealed objects.

  20. Diffuse reflectance spectroscopy of epithelial tissue with a smart fiber-optic probe

    PubMed Central

    Yu, Bing; Shah, Amy; Nagarajan, Vivek K.; Ferris, Daron G.

    2014-01-01

    Diffuse reflectance spectroscopy (DRS) with a fiber-optic probe can noninvasively quantify the optical properties of epithelial tissues and has shown the potential as a cost-effective, fast and sensitive tool for diagnosis of early precancerous changes in the cervix and oral cavity. However, current DRS systems are susceptible to several sources of systematic and random errors, such as uncontrolled probe-to-tissue pressure and lack of a real-time calibration that can significantly impair the measurement accuracy, reliability and validity of this technology as well as its clinical utility. In addition, such systems use bulky, high power and expensive optical components which impede their widespread use in low- and middle-income countries (LMICs) where epithelial cancer related death is disproportionately high. In this paper we report a portable, easy-to-use and low cost, yet accurate and reliable DRS device that can aid in the screening and diagnosis of oral and cervical cancer. The device uses an innovative smart fiber-optic probe to eliminate operator bias, state-of-the-art photonics components to reduce size and power consumption, and automated software to reduce the need of operator training. The device showed a mean error of 1.4 ± 0.5% and 6.8 ± 1.7% for extraction of phantom absorption and reduced scattering coefficients, respectively. A clinical study on healthy volunteers indicated that a pressure below 1.0 psi is desired for oral mucosal tissues to minimize the probe effects on tissue physiology and morphology. PMID:24688805