Simple fiber-optic confocal microscopy with nanoscale depth resolution beyond the diffraction barrier

A novel fiber-optic confocal approach for ultrahigh depth-resolution (相似文献   

In vivo quantitative three-dimensional localization of tumor labeled with exogenous specific fluorescence markers

We introduce a diffused optical detection system based on the administration of a fluorophore-antibody conjugate to diseased tissue. The conjugate interacts with the antigens expressed by the diseased tissue, resulting in fluorescent labeling of the antigen. By combining an optical detection system with a reconstruction algorithm developed on the basis of the random-walk model, we were able to determine the position of the fluorophore (and, thus, of the diseased cells) in the tissue. We present three-dimensional reconstructions of the location of a fluorophore (FITC-fluorescein isothiocyanate) in the tongues of mice. Measurements were performed with the fluorophore embedded at various simulated depths. The simulations were performed with agarose-based gel slabs applied to the tongue as tissuelike phantoms. Reconstructed fluorophore locations agree well with the actual values.     

Interface Modifications of InAs Quantum‐Dots Solids and their Effects on FET Performance

InAs nanocrystals field‐effect transistors with an ON/OFF ratio of 10⁵ are reported. By tailoring the interface regions in the active layer step‐by‐step, the evolution of the ON/OFF ratio can be followed from approximately 5 all the way to around 10⁵. The formation of a semiconducting solid from colloidal nanocrystals is achieved through targeted design of the nanocrystal–nanocrystal interaction. The manipulation characteristics of the nanocrystal interfaces include the matrix surrounding the inorganic core, the interparticle distance, and the order of nanocrystals in the 3D array. Through careful analysis of device characteristics following each treatment, the effect of each on the physical properties of the films are able to be verified. The enhanced performance is related to interparticle spacing, reduction in sub‐gap states, and better electronic order (lower σ parameter). Films with enhanced charge transport qualities retain their quantum‐confined characteristics throughout the procedure, thus making them useful for optoelectronic applications.     

An Alternative Approach to Analyze Fluorescence Lifetime Images as a Base for a Tumor Early Diagnosis System

Fluorescence lifetime imaging is a very promising imaging method for early detection of malignant tumors. It offers many advantages over conventional fluorescence methods, especially because the acquired signal does not rely on the fluorophore concentration in the tissue. As in all imaging method, the goal is to determine the exact location of a malignant tumor. However, since we are dealing with optical imaging, the inverse problem, i.e., extracting the tumor location coordinates is not an easy task to fulfill. In this paper, we describe an alternative method of interpreting the fluorescence lifetime image. The method extracts four features from each decay curve. We show that from these features one can extract the location of the tumor. The theoretical model is compared to the experimental results obtained from tissue-like phantoms.     

Inverse method 3-D reconstruction of localized in vivofluorescence-application to Sjogren syndrome

The development of specific fluorescently labeled cell surface markers have opened the possibility of specific and quantitative noninvasive diagnosis of tissue changes. We are developing a fluorescence scanning imaging system that can perform a “noninvasive optical biopsy” of the Sjogren syndrome (SS) which may replace the currently used histological biopsy. The diagnosis of SS is based on the quantification of the number of topical preadministered fluorescent antibodies which specifically bind to the lymphocytes infiltrating the minor salivary glands. We intend to scan the lower lip, and for each position of the scan, generate a two-dimensional (2-D) image of fluorescence using a charge-coupled device (CCD) camera. We have shown previously that our diffuse fluorescent photon migration theory predicts adequately the positions and strengths of one and two fluorescent targets embedded at different depths in tissue-like phantoms. An inverse reconstruction algorithm based on our theoretical findings has been written in C⁺⁺ and uses 2-D images to predict the strength and location of embedded fluorophores. However, due to large numbers of variables, which include the optical properties of the tissue at the excitation and emission wavelengths, and the positions and strengths of an unknown number of fluorophore targets, the validity of the final result depends on assumptions (such as the number of targets) and the input values for the optical parameters. Our results show that the number of fluorophore targets reconstructed for each scan is limited to two, and at least the scattering coefficient at the excitation wavelength is needed a priori to obtain good results. The latter can be obtained by measurements of spatially resolved diffuse reflectance at the excitation wavelength that provides the product of the absorption and scattering coefficients     

Sensing of Alkylating Agents Using Organic Field‐Effect Transistors

Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields, such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical warfare agents. The detection and identification of alkylating agent is not a trivial issue because of their high reactivity and simple structure. Here, a novel polythiophene derivative that is capable of reacting with alkylating agents is reported, along with its application in direct electrical sensing of alkylators using an organic field‐effect transistor, OFET, device. Upon reacting with alkylators, the OFET containing the new polythiophene analogue as its channel becomes conductive, and the gate effect is lost; this is in marked contrast to the response of the OFET to “innocent” vapors, such as alcohols and acetone. By following the drain–source current under gate bias, one can easily follow the processes of absorption of the analyte to the polythiophene channel and their subsequent reaction.     

Analysis of the power spectral deviation of the general transfer function GSC

In recent work, we considered a microphone array located in a reverberated room, where general transfer functions (TFs) relate the source signal and the microphones, for enhancing a speech signal contaminated by interference. It was shown that it is sufficient to use the ratio between the different TFs rather than the TFs themselves in order to implement the suggested algorithm. An unbiased estimate of the TFs ratios was obtained by exploiting the nonstationarity of the speech signal. In this correspondence, we present an analysis of a distortion indicator, namely power spectral density (PSD) deviation, imposed on the desired signal by our newly suggested transfer function generalized sidelobe canceller (TF-GSC) algorithm. It is well known that for speech signals, PSD deviation between the reconstructed signal and the original one is the main contribution for speech quality degradation. As we are mainly dealing with speech signals, we analyze the PSD deviation rather than the regular waveform distortion. The resulting expression depends on the TFs involved, the noise field, and the quality of estimation of the TF's ratios. For the latter dependency, we provide an approximated analysis of estimation procedure that is based on the signal's nanstationarity and explore its dependency on the actual speech signal and on the signal-to-noise ratio (SNR) level. The theoretical expression is then used to establish empirical evaluation of the PSD deviation for several TFs of interest, various noise fields, and a wide range of SNR levels. It is shown that only a minor amount of PSD deviation is imposed on the beamformer output. The analysis presented in this correspondence is in good agreement with the actual performance presented in the former TF-GSC paper.     

Dual-Source Transfer-Function Generalized Sidelobe Canceller

Full-duplex hands-free man/machine interface often suffers from directional nonstationary interference, such as a competing speaker, as well as stationary interferences which may comprise both directional and nondirectional signals. The transfer-function generalized sidelobe canceller (TF-GSC) exploits the nonstationarity of the speech signal to enhance it when the undesired interfering signals are stationary. Unfortunately, the assumptions leading to the derivation of the TF-GSC are violated when a nonstationary interference is present. In this paper, we propose an adaptive beamformer, based on the TF-GSC, that is suitable for cancelling nonstationary interferences in noisy reverberant environments. We modify two of the TF-GSC components to enable suppression of the nonstationary undesired signal. A modified fixed beamformer (FBF) is designed to block the nonstationary interfering signal while maintaining the desired speech signal. A modified blocking matrix (BM) is designed to block both the desired signal and the nonstationary interference. We introduce a novel method for updating the blocking matrix in double talk scenarios, which exploits the nonstationarity of both the desired and interfering speech signals. Experimental results demonstrate the performance of the proposed algorithm in noisy and reverberant environments and show its superiority over the original TF-GSC.     

Current status of flexible waveguides for IR laser radiationtransmission

Minimal invasive surgery (MIS) is the preferred method for performing medical operations today due to its lower cost, fast healing, and minimal post-operative pain and discomfort to the treated patients. It is rapidly expanding with the development and miniaturization of two-dimensional (2-D) and three-dimensional (3-D) endoscopic imaging systems. Laser surgery has also proved itself to be a preferred tool of operation over standard tools in a lot of the cases. Development of a reliable flexible fiber or waveguide will enable surgeons to bring the laser beam transcendoscopically within body cavities. It will combine the endoscopy technique with the advantageous laser interaction with tissue to create a powerful surgical tool which will be the ultimate choice of operating procedure. A number of research groups have suggested flexible waveguides for the mid-IR region between 2.5 and 11 μm, which contains very important and useful laser wavelengths and is not covered by silica fibers. The chief goals for the development of such delivery devices are summarized. The different solutions suggested are broadly described and thoroughly analyzed for their performance and potential