Performance Study of Adaptive Filtering in Bispectrum Signal Reconstruction

The problem of reconstructing a signal waveform when the observed realizations are corrupted by intensive noise and random shifts is considered in this paper. Several ways of performing bispectrum filtering are proposed and investigated. First, it is shown that the signal reconstruction is more efficient if one applies smoothing to the recovered real and imaginary parts of the Fourier spectrum separately instead of filtering the magnitude and phase spectra recovered from a bispectrum estimate. Second, several nonadaptive filters are studied, and it is demonstrated that the proper choice of the filter type and its parameters is critical. Some adaptive filtering techniques based on the Z-parameter and on local polynomial approximation (LPA)-intersection of confidence intervals (ICI) are discussed. The performances of nonadaptive and adaptive filtering techniques in the bispectrum-based signal reconstruction are studied using the mean-squared error as the criterion. It is shown that the use of LPA-ICI and other adaptive filters provides improvement of signal reconstruction in comparison to the conventional bispectrum method and the combined bispectrum filtering methods proposed earlier for nonadaptive filters. The benefits achieved are mainly observed for low (smaller than unity) signal-to-noise ratios.     

Suppression of Proliferation of Human Glioblastoma Cells by Combined Phosphodiesterase and Multidrug Resistance-Associated Protein 1 Inhibition

The paucity of currently available therapies for glioblastoma multiforme requires novel approaches to the treatment of this brain tumour. Disrupting cyclic nucleotide-signalling through phosphodiesterase (PDE) inhibition may be a promising way of suppressing glioblastoma growth. Here, we examined the effects of 28 PDE inhibitors, covering all the major PDE classes, on the proliferation of the human U87MG, A172 and T98G glioblastoma cells. The PDE10A inhibitors PF-2545920, PQ10 and papaverine, the PDE3/4 inhibitor trequinsin and the putative PDE5 inhibitor MY-5445 potently decreased glioblastoma cell proliferation. The synergistic suppression of glioblastoma cell proliferation was achieved by combining PF-2545920 and MY-5445. Furthermore, a co-incubation with drugs that block the activity of the multidrug resistance-associated protein 1 (MRP1) augmented these effects. In particular, a combination comprising the MRP1 inhibitor reversan, PF-2545920 and MY-5445, all at low micromolar concentrations, afforded nearly complete inhibition of glioblastoma cell growth. Thus, the potent suppression of glioblastoma cell viability may be achieved by combining MRP1 inhibitors with PDE inhibitors at a lower toxicity than that of the standard chemotherapeutic agents, thereby providing a new combination therapy for this challenging malignancy.     

Carrier generation-recombination in the Gunn effect

It is conventional to assume that the Gunn Instability develops on a time scale fast compared with the carrier generation-recombination processes. This enables one to account for the motion of Gunn Domains by means of a phenomenological model in which the impurity ionization remains at its thermal equilibrium value. The standard Gunn Effect model has been modified to include the space-time dependent impurity ionization expected if the carrier generation-recombination processes become important.A dispersion relation describing the linear response of the system to small perturbations for the case of field dependent recombination has been derived and used to deduce a simple stability criterion. The time evolution of the electric field when this condition is violated has been studied via a numerical solution of the phenomenological equations. Under appropriate conditions both fast and slow moving instabilities have been found to occur.     

Engineering nanostructured porous SiO2 surfaces for bacteria detection via "direct cell capture"

An optical label-free biosensing platform for bacteria detection ( Escherichia coli K12 as a model system) based on nanostructured oxidized porous silicon (PSiO(2)) is introduced. The biosensor is designed to directly capture the target bacteria cells on its surface with no prior sample processing (such as cell lysis). The optical reflectivity spectrum of the PSiO(2) nanostructure displays Fabry-Pe?rot fringes characteristic of thin-film interference, enabling direct, real-time observation of bacteria attachment within minutes. The PSiO(2) optical nanostructure is synthesized and used as the optical transducer element. The porous surface is conjugated with specific monoclonal antibodies (immunoglobulin G's) to provide the active component of the biosensor. The immobilization of the antibodies onto the biosensor system is confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, fluorescent labeling experiments, and refractive interferometric Fourier transform spectroscopy. We show that the immobilized antibodies maintain their immunoactivity and specificity when attached to the sensor surface. Exposure of these nanostructures to the target bacteria results in "direct cell capture" onto the biosensor surface. These specific binding events induce predictable changes in the thin-film optical interference spectrum of the biosensor. Our preliminary studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations. The current detection limit of E. coli K12 bacteria is 10(4) cells/mL within several minutes.     

Using FlAsH to probe conformational changes in a large HEAT repeat protein

We have investigated the use of FlAsH, a small fluorogenic molecule that binds to tetracysteine motifs, to probe folding of the 15-HEAT repeat protein PR65A. PR65A is one of a special class of modular non-globular proteins known as tandem repeat proteins, which are composed of small structural motifs that stack to form elongated, one-dimensional architectures. We were able to introduce linear and bipartite tetracysteine motifs at several sites along the α-helical HEAT array of PR65A without disrupting the structure or stability. When the linear tetracysteine motif CCPGCC was used, FlAsH fluorescence reported globally on the folding of the protein. When the tetracysteine motif was displayed in bipartite mode through the engineering of pairs of cysteines on adjacent HEAT repeats, FlAsH fluorescence became a reporter of local conformation and of oligomerisation. Thus, by designing FlAsH-binding sites at different locations along the repeat array one can interrogate specific properties of PR65A, paving the way for structure-function analysis of this protein both in vitro and in the cell.     

A portable class of 3‐transistor current references with low‐power sub‐0.5 V operation

This work proposes a new class of current references based on only 3 transistors that allows sub‐0.5 V operation. The circuit consists of a 2‐transistor block that generates a proportional‐to‐absolute‐temperature or a complementary‐to‐absolute‐temperature voltage and a load transistor. The idea of a 3T current reference is validated by circuit simulations for different complementary metal‐oxide‐semiconductor technologies and by experimental measurements on a large set of test chips fabricated with a commercial 0.18 μm complementary metal‐oxide‐semiconductor process. As compared to the state‐of‐art competitors, the 3T current reference exhibits competitive performance in terms of temperature coefficient (578 ppm/°C), line sensitivity (3.9%/V), and power consumption (213 nW) and presents a reduction by a factor of 2 to 3 in terms of minimum operating voltage (0.45 V) and an improvement of 1 to 2 orders of magnitude in terms of area occupation (750 μm²). In spite of the extremely reduced silicon area, the fabricated chips exhibit low‐process sensitivity (2.7%). A digital trimming solution to significantly reduce the process sensitivity is also presented and validated by simulations.     

Highly efficient (infra)red conversion of InGaN light emitting diodes by nanocrystals, enhanced by colour selective mirrors

Colloidal nanocrystal layers deposited onto the enclosure of InGaN light emitting diodes are demonstrated to operate as nano-phosphors for colour conversion with high colour stability. Depending on the choice of the nanocrystal material (either CdSe/ZnS or PbS nanocrystals are applied), the diode emission at 470?nm is converted to red or to infrared light, with similar quantum efficiencies. The colour conversion is further improved by dielectric mirrors with high reflectivity at the emission band of the nanocrystals, resulting in an almost doubling of the nanocrystal light extraction from the devices, which increases the nanocrystal device efficiency up to 19.1%.     

Spin-Flip Raman Scattering on Electrons and Holes in Two-Dimensional (PEA)2PbI4 Perovskites

The class of Ruddlesden–Popper type (PEA)₂PbI₄ perovskites comprises 2D structures whose optical properties are determined by excitons with a large binding energy of about 260 meV. It complements the family of other 2D semiconductor materials by having the band structure typical for lead halide perovskites, that can be considered as inverted compared to conventional III–V and II–VI semiconductors. Accordingly, novel spin phenomena can be expected for them. Spin-flip Raman scattering is used here to measure the Zeeman splitting of electrons and holes in a magnetic field up to 10 T. From the recorded data, the electron and hole Landé factors (g-factors) are evaluated, their signs are determined, and their anisotropies are measured. The electron g-factor value changes from +2.11 out-of-plane to +2.50 in-plane, while the hole g-factor ranges between -0.13 and -0.51. The spin flips of the resident carriers are arranged via their interaction with photogenerated excitons. Also the double spin-flip process, where a resident electron and a resident hole interact with the same exciton, is observed showing a cumulative Raman shift. Dynamic nuclear spin polarization induced by spin-polarized holes is detected in corresponding changes of the hole Zeeman splitting. An Overhauser field of the polarized nuclei acting on the holes as large as 0.6 T can be achieved.