Realization of morphing logic gates in a repressilator with quorum sensing feedback

We demonstrate how a genetic ring oscillator network with quorum sensing feedback can operate as a robust logic gate. Specifically we show how a range of logic functions, namely AND/NAND, OR/NOR and XOR/XNOR, can be realized by the system, thus yielding a versatile unit that can morph between different logic operations. We further demonstrate the capacity of this system to yield complementary logic operations in parallel. Our results then indicate the computing potential of this biological system, and may lead to bio-inspired computing devices.     

Long-term trend in CHF2Cl (HCFC-22) from high spectral resolution infrared solar absorption measurements and comparison with in situ measurements

The average tropospheric volume mixing ratio of CHF₂Cl (HCFC-22) has been retrieved from a time series of high spectral resolution ground-based infrared solar absorption spectra recorded with the McMath Fourier transform spectrometer located at the U.S. National Solar Observatory facility on Kitt Peak in southern Arizona (31.9°N, 111.6°W, 2.09 km altitude) for the time period October 1987–November 2002. The retrievals are based on fits to the well-isolated, unresolved 2ν₆ Q branch at 829.05 cm⁻¹ and the SFIT2 retrieval algorithm. The measured daily averages show a near linear rise per year in the mean tropospheric volume mixing ratio as a function of time with a best fit yielding an average increase rate of (5.66±0.15) parts per trillion (10⁻¹²) by volume per year, corresponding to (6.47±0.17)%yr⁻¹, 1 sigma, at the beginning of the time series. The tropospheric mixing ratios retrieved from the solar spectra have been compared with monthly average surface flask sampling measurements from the Climate Monitoring and Diagnostic Laboratory (CMDL) station at Niwot Ridge, Colorado (40.0°N, 105.5°W, 3013 m altitude), archived measurement from the same location, and early CMDL northern hemisphere Pacific cruise measurements. The average ratio of the retrieved tropospheric mixing ratio relative to the CMDL surface mixing ratio is 1.053 for the overlapping 1987 to 2002 time period. The retrieved mean tropospheric mixing ratio is consistent with the surface measurements within the errors estimated for the remote sensing observations.     

Comparison of single and multiple scattering approaches for the simulation of limb-emission observations in the mid-IR

The validity of single scattering radiative transfer calculations for simulation of limb-emission measurements of clouds in the mid-infrared spectral region was investigated by comparison with a multiple scattering model. For in limb direction optically thin clouds, like polar stratospheric clouds, errors of the single scattering scheme range below 3%. For optically thick clouds deviations are below 3% in case of low single scattering albedo (ω₀=0.24) increasing up to 10-30% for ω₀=0.84. Clouds which are optically thick in limb, but thin in nadir direction, can cause limb radiances which are by a factor of 1.7 higher than the blackbody radiance at cloud altitude.     

A linearized vector radiative transfer model for atmospheric trace gas retrieval

We present a plane parallel radiative transfer model for polarized light, that provides the intensity vector as well as the derivatives of the four Stokes parameters with respect to atmospheric trace gas profiles. These derivatives are essential for retrieval of height resolved trace gas information from satellite measurements of backscattered sunlight. The model uses the Gauss-Seidel iteration technique for solving the radiative transfer equation. For the first time, the forward-adjoint radiative perturbation theory is applied for the linearization of a radiative transfer model including polarization. The accuracy of the model is better than 0.025% for all four Stokes parameters and better than 0.03% for the derivatives.     

Optical technique for classification, recognition and identification of obscured objects

The capability to classify, recognize and to identify objects from spatially low resolution images has high significance in security related applications especially in a case that recognition of camouflaged object is required.In this paper we present a novel approach in which the scenery containing obscured objects which we wish to classify, recognize or identify is illuminated by spatially coherent beam (e.g. laser) and therefore secondary speckles pattern is reflected from the objects. By special image processing algorithm developed for this research and which is basically based upon temporal tracking of the random speckle pattern one may extract the temporal signature of the object. And right after, to use it for its classification (e.g. its separation from the other objects in the scenery), its recognition and identification even in a case that the imager provides poor spatial resolution that by itself does not allow doing the specified detection related operations.     

Learning-based compressed sensing for infrared image super resolution

This paper presents an infrared image super-resolution method based on compressed sensing (CS). First, the reconstruction model under the CS framework is established and a Toeplitz matrix is selected as the sensing matrix. Compared with traditional learning-based methods, the proposed method uses a set of sub-dictionaries instead of two coupled dictionaries to recover high resolution (HR) images. And Toeplitz sensing matrix allows the proposed method time-efficient. Second, all training samples are divided into several feature spaces by using the proposed adaptive k-means classification method, which is more accurate than the standard k-means method. On the basis of this approach, a complex nonlinear mapping from the HR space to low resolution (LR) space can be converted into several compact linear mappings. Finally, the relationships between HR and LR image patches can be obtained by multi-sub-dictionaries and HR infrared images are reconstructed by the input LR images and multi-sub-dictionaries. The experimental results show that the proposed method is quantitatively and qualitatively more effective than other state-of-the-art methods.     

Toward unified satellite climatology of aerosol properties: Direct comparisons of advanced level 2 aerosol products

The development of a unified satellite climatology of aerosol properties requires accurate quantification and deep understanding of the underlying factors contributing to discrepancies between individual satellite products. In this paper we compare the most recent level 2 results obtained for coincident pixels viewed at essentially the same time by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging Spectroradiometer (MISR) instruments flown on the EOS Terra platform. This strategy eliminates potential sampling effects and provides a virtually direct comparison of spatially and temporally collocated MODIS and MISR retrievals. We show that the MODIS and MISR Ångström exponent datasets reveal essentially no correlation. Although the corresponding aerosol optical thickness (AOT) datasets can agree worse than expected over the oceans, still the agreement is often satisfactory. However, the agreement over the land is often poor or even unacceptable. Of the collocated pixels for which there is a MODIS aerosol retrieval, only ∼40% or fewer pixels have a MISR aerosol retrieval, and vice versa. These findings further illustrate the complexity of the problem of aerosol retrievals from satellite observations and indicate that the creation of a meaningful unified MODIS-MISR aerosol climatology will be a nontrivial task.     

Experimental investigation of the quality of lensless super-resolution ghost imaging via sparsity constraints

Ghost imaging via sparsity constraints (GISC) can nonlocally realize super-resolution imaging. Factors influencing the quality of lensless super-resolution GISC are investigated and the experimental results show that, the quality of GISC is enhanced as the object?s sparse ratio in the representation basis or the spatial transverse coherence lengths on the object plane are decreased. The differences between ghost imaging (GI) and GISC are also discussed.     

Designing of Optical Fiber Sensing Probe

Evanescent wave configuration has been extensively used in the development of fiber-optic sensor for different biomedical applications. In the present investigation we have theoretically proposed the designing of single-mode and multimode optical fiber sensing probes, which can be prepared by removing a few centimeters of cladding near the distal end of the step index optical fiber. In this theoretical study, we found that the removal of cladding causes V-number mismatching and this has led to the loss of signal acquisition from the sensing region. Therefore, to minimize these losses we have proposed to reduce the radius by step etch and tapering technique. It was found that step etching and tapering enhances the strength and penetration depth of the evanescent wave significantly.     

Interfacial p-n heterojunction of polyaniline-nickel ferrite nanocomposite as room temperature liquefied petroleum gas sensor

In this work, we introduce polyaniline–nickel ferrite (PANI-NF) nanostructured composite to detect liquefied petroleum gas (LPG) at room temperature. The composite synthesized by relatively simple method of in-situ chemical polymerization was structurally characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The presence of characteristic absorption bands of both PANI and NF in the FTIR spectrum of the composite with small shifts confirmed interfacial interaction of PANI with NF. The XRD studies also confirmed interfacial interaction between PANI and NF in the composite and its crystalline nature with an average crystallite size of 20 nm. Highly agglomerated granular porous morphology favourable for LPG adsorption was revealed by SEM image of the composite. The TEM image of the composite clearly showed nanosized NF particles embedded in PANI matrix. The LPG sensing performance of the composite at room temperature was tested using a film prepared by depositing the composite on an ordinary glass substrate by cost-effective spin coating technique. The maximum sensing response of the composite was found to be 57% at 700 ppm of LPG, with a response time of 50 s and a recovery time of 200 s. The composite was found to be stable for a period of one month. The sensing mechanism has been discussed on the basis of formation of interfacial p–n heterojunction barrier.