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ABSTRACT: Terahertz (THz) region in the vibrational spectra of a certain molecule reveals the intramolecular vibrations between weakly bonded or nonbonded groups. Additional information can be acquired by photoinduced transitions between metastable states of the target agent. Different isomers of stilbene and its derivatives can be utilized in order to obtain the spectral “THz fingerprint” using multistate spectral-sensing technology. Also, stilbene and its derivatives are able to form “capping” with DNA, thus making them a very important covalent linker with DNA terminus to increase the fidelity of DNA duplexes as oligonucleotide hybridization probes. We study photoinduced transitions of stilbene and its derivatives and the change of vibrational spectra as a result of these transitions. All derivatives have vibrational frequencies in the THz region with a large difference in frequencies between two isomers.
IEEE Transactions on Nanotechnology 10/2010; · 2.29 Impact Factor
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ABSTRACT: A fluorescence enhancement in the visible range under UV excitation has been observed in 2-(diphenylacetyl)-1,3-indanedione-l-(p-(dimethylamino)benzaldazine) (DIPAIN) II and its derivatives when associating with trichothecene mycotoxins on the solid support. Chromatographic study has shown that it is the molecular complex formed by weak association between DIPAIN II and 12,13-epoxytrichothec-9-ene-3,4,8,15-tetraol 4,15-diacetate 8-(3-methylbutanoate) (T-2) toxin that is directly related to the enhanced fluorescence activity. Previously, a model was proposed by other group to predict a mechanism of the interaction between the molecules in the complex. In this model, five functional groups and regions of DIPAIN II were identified as possible interaction sites with the toxin compounds. More than one area could interact with the compound at the same time. Inspired by these ideas, three mixture conformations of DIPAIN II and T-2 toxin are generated and studied in this paper. The initial geometric structures of two molecules were constructed according to the published papers, and optimization was performed using the Hartree-Fock and the density functional theories followed by calculations of the excited-state energy. The optimization results indicate that there is no chemical bonding between DIPAIN II and T-2 toxin. Nonbonded interactions between T-2 toxin and DIPAIN II could be responsible for the fluorescence enhancement. This conclusion is in agreement with the prediction of the model. The excitation energies are consistent with the experiment results.
IEEE Sensors Journal 04/2010; · 1.52 Impact Factor
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ABSTRACT: A summary is provided for terahertz attenuation signatures measured in spore-laden samples of Bacillus subtilis in three different forms: 1) concentrated powder; 2) dilute powder; and 3) aerosol. In addition to a surprising spectral narrowness, some signatures also display an increase in peak signature strength (per spore) with dilution of the sample. A model is constructed to explain this phenomenology based on the presence of optical phonons and electromagnetic interaction with the spore wall. Specifically, the spheroidal Bacillus spores admit surface modes that interact with radiation via polaritonic coupling and are underdamped if isolated from each other through a dilution or aerosol levitation. Hence, the results defy longstanding assumptions that the biomolecular-related terahertz vibrations are necessarily overdamped and have immeasurably weak attenuation
IEEE Sensors Journal 11/2006; · 1.52 Impact Factor
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ABSTRACT: Due to recent advances in hyperspectral imaging sensors many subtle unknown signal sources that cannot be resolved by multispectral sensors can be now uncovered for target detection, discrimination, and identification. Because the information about such sources is generally not available, automatic target recognition (ATR) presents a great challenge to hyperspectral image analysts. Many approaches developed for ATR are based on second-order statistics in the past years. This paper investigates ATR techniques using high order statistics. For ATR in hyperspectral imagery, most interesting targets usually occur with low probabilities and small population and they generally cannot be described by second-order statistics. Under such circumstances, using high-order statistics to perform target detection have been shown by experiments in this paper to be more effective than using second order statistics. In order to further address a challenging issue in determining the number of signal sources needed to be detected, a recently developed concept of virtual dimensionality (VD) is used to estimate this number. The experiments demonstrate that using high-order statistics-based techniques in conjunction with the VD to perform ATR are indeed very effective
IEEE Transactions on Aerospace and Electronic Systems 11/2006; · 1.10 Impact Factor
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ABSTRACT: One of the challenges in remote sensing image processing is subpixel detection where the target size is smaller than the ground sampling distance, therefore, embedded in a single pixel. Under such a circumstance, these targets can be only detected spectrally at the subpixel level, not spatially as ordinarily conducted by classical image processing techniques. This paper investigates a more challenging issue than subpixel detection, which is the estimation of target size at the subpixel level. More specifically, when a subpixel target is detected, we would like to know "what is the size of this particular target within the pixel?". The proposed approach is to estimate the abundance fraction of a subpixel target present in a pixel, then find what portion it contributes to the pixel that can be used to determine the size of the subpixel target by multiplying the ground sampling distance. In order to make our idea work, the subpixel target abundance fraction must be accurately estimated to truly reflect the portion of a subpixel target occupied within a pixel. So, a fully constrained linear unmixing method is required to reliably estimate the abundance fractions of a subpixel target for its size estimation. In this paper, a recently developed fully constrained least squares linear unmixing is used for this purpose. Experiments are conducted to demonstrate the utility of the proposed method in comparison with an unconstrained linear unmixing method, unconstrained least squares method, two partially constrained least square linear unmixing methods, sum-to-one constrained least squares, and nonnegativity constrained least squares.
IEEE Transactions on Geoscience and Remote Sensing 07/2004; · 2.89 Impact Factor
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ABSTRACT: Constrained Energy Minimization (CEM) has been widely used for target detection in hyperspectral remote sensing imagery. It detects the desired target signal source using a unity constraint while suppressing noise and unknown signal sources by minimizing the average output power. Base on the design CEM can only detect one target source at a time. In order to simultaneously detect multiple targets in a single image, several approaches are developed, including Multiple-Target CEM (MTCEM), Sum CEM (SCEM) and Winner-Take-All CEM (WTACEM). Interestingly, the sensitivity of noise and interference seems to play a role in the detection performance. Unfortunately, this issue has not been investigated. In this paper, we take up this problem and conduct a quantitative study of the noise and interference suppression abilities of LCMV, SCEM, WTACEM for multiple-target detection.
Advances in Techniques for Analysis of Remotely Sensed Data, 2003 IEEE Workshop on; 11/2003
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ABSTRACT: This paper presents a detailed assessment of terahertz-frequency spectroscopy as a technique for the remote detection of biological warfare agents. Design studies are presented for a differential-absorption-radar (DAR) approach that utilizes the spectral signatures of Bacillus (B.) subtillus spores within the terahertz (THz) regime as the detection mechanism. The signature data used in these studies is taken from laboratory measurements performed on uniform thin films of B. Subtillus spores and the system performance is assessed for both incoherent and coherent detector modalities. These studies consider DAR remote sensing of biological (bin) clouds at significant ranges (i.e., 1 km) and include the effects of realistic atmospheric conditions. A high-level remote-sensor design is used to estimate the probabilities of detection (p<sub>d</sub>) and false-alarm (p<sub>fa</sub>) associated with this general technique. These studies suggest useful remote-detection performance can be achieved (i.e., p<sub>d</sub> > 0.9 & p<sub>ra</sub> 10<sup>-4</sup> for bio-cloud densities <10<sup>3</sup> cm<sup>-3</sup>) at 1 km ranges if the THz signature information remains predictably stable under varying atmospheric conditions (e.g., changes in humidity, spore activity state, etc). Furthermore, a realistic bio-agent airframe attack scenario is utilized to demonstrate standoff detection of bio-clouds with ∼100% confidence while outside the threat-level concentrations. All together, these results demonstrate that standoff detection of bio-agents is feasible for threat-level concentrations in practical battlefield environments at sufficient ranges to provide for early warning.
Microwave Symposium Digest, 2003 IEEE MTT-S International; 07/2003
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D L Woolard,
T R Globus,
B L Gelmont,
M Bykhovskaia,
A C Samuels,
D Cookmeyer,
J L Hesler,
T W Crowe, J O Jensen,
J L Jensen,
W R Loerop
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ABSTRACT: A detailed investigation of phonon modes in DNA macromolecules is presented. This work presents experimental evidence to confirm the presence of multiple dielectric resonances in the submillimeter-wave spectra (i.e., approximately 0.01-10 THz) obtained from DNA samples. These long-wave (i.e., approximately 1-30 cm(-1)) absorption features are shown to be intrinsic properties of the particular DNA sequence under study. Most importantly, a direct comparison of spectra between different DNA samples reveals a large number of modes and a reasonable level of sequence-specific uniqueness. This work establishes the initial foundation for the future use of submillimeter-wave spectroscopy in the identification and characterization of DNA macromolecules.
Physical Review E 06/2002; 65(5 Pt 1):051903. · 2.26 Impact Factor
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D L Woolard,
T Koscica,
D L Rhodes,
H L Cui,
R A Pastore, J O Jensen,
J L Jensen,
W R Loerop,
R H Jacobsen,
D Mittleman,
M C Nuss
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ABSTRACT: Developing methods for alternative testing is increasingly important due to dwindling funding resources and increasing costs associated with animal testing and legislation. We propose to test the feasibility of a new and novel method for detecting DNA mutagenesis using millimeter wave spectroscopy. Although millimeter wave spectroscopy has been known since the 1950s, the cost was prohibitive and studies did not extend to large biological proteins such as DNA. Recent advances have made this technology feasible for developing laboratory and field equipment. We present preliminary findings for lesion-induced vibrational modes in DNA observed from 80 to 1000 gigahertz (GHz). These findings suggest that there are vibrational modes that can be used as identification resonances. These modes are associated with localized defects of the DNA polymers. They are unique for each defect/lesion, and should be easy to detect. We described a field-detecting detector based on the local modes.
Journal of Applied Toxicology 17(4):243-6. · 2.48 Impact Factor
