Photonically-enabled RF front-end for wideband flexible down-conversion.

We demonstrate a flexible RF photonics down-converter that enables spectral folding of a 2-18 GHz RF band into a common 2 GHz wide intermediate frequency (IF) band for identification of specific signals of interest. The system can then be reconfigured for selective down-conversion of a given sub-band to a common IF output. We present an analysis of the performance of the down-converter and experimentally demonstrate both the spectral folding and selective modes. A sensitivity of -42 dBm in an IF bandwidth of 2 GHz and a spurious free dynamic range of 103 dB.Hz2/3 is achieved in the spectral folding mode.

Enhancement of out-of-band rejection in optical filters based on phase-sensitive amplification.

We present a novel optical filter based on amplification and deamplification in a phase-sensitive amplifier (PSA), whose out-of-band rejection is enhanced by slightly imbalancing the inputs to the PSA. The out-of-band rejection of the PSA-based filter with balanced input signal and idler powers is given by G2 in the optical domain, where G is the maximum phase-sensitive gain. By unbalancing the input to the PSA, the optical out-of-band rejection is significantly enhanced beyond G2, thus enabling filters with high rejection even with moderate-gain PSAs. We demonstrate a filter with optical and electrical extinctions of 29 dB and 60 dB, respectively, using a moderate PSA gain of only 10 dB. Further, this technique allows for ultrawideband frequency tuning, spanning multiterahertz bandwidths along with filter response reconfigurability. These novel concepts will be invaluable for optical signal processing in high-performance analog and digital systems.

Novel intraocular shielding device for eye plaque brachytherapy using magnetite nanoparticles: A proof-of-concept study using radiochromic film and Monte Carlo simulations.

PURPOSE: Eye plaque brachytherapy is a mainstay treatment for uveal melanomas despite potential toxicities to normal tissues. This work proposes a nanoparticle ferrofluid as a novel intraocular shielding device. With a modified magnetic plaque, the shielding particles are drawn to the tumor surface, attenuating dose beyond the tumor while maintaining prescription dose to the target. METHODS AND MATERIALS: Ferromagnetic nanoparticles suspended in a silicone polymer were synthesized to provide a high-density shielding medium. The ferrofluid's half-value layer (HVL) was quantified for 125I photons using radiochromic film and Monte Carlo methods. A magnetic COMS plaque was created and evaluated in its ability to attract ferrofluid over the tumor. Two ferrofluid shielding mediums were evaluated in their ability to attenuate dose at adjacent structures with in vitro measurements using radiochromic film, in addition to Monte Carlo studies. RESULTS: The shielding medium's HVL measured approximately 1.3 mm for an 125I photon spectrum, using film and Monte Carlo methods. With 0.8 mL of shielding medium added to the vitreous humor, it proved to be effective at reducing dose to normal tissues of the eye. Monte Carlo-calculated dose reductions of 65%, 80%, and 78% at lateral distances 5, 10, and 18 mm from a tumor (5-mm apical height) in a modeled 20-mm COMS plaque. CONCLUSIONS: The magnitude of dose reduction could reduce the likelihood of normal tissue side effects for plaque brachytherapy patients, including patients with normal tissues close to the plaque or tumor. Additional studies, safety considerations, and preclinical work must supplement these findings before use.

Characterization of time-resolved laser differential phase using 3D complementary cumulative distribution functions.

An experimental method for characterizing the time-resolved phase noise of a fast switching tunable laser is discussed. The method experimentally determines a complementary cumulative distribution function of the laser's differential phase as a function of time after a switching event. A time resolved bit error rate of differential quadrature phase shift keying formatted data, calculated using the phase noise measurements, was fitted to an experimental time-resolved bit error rate measurement using a field programmable gate array, finding a good agreement between the time-resolved bit error rates.

High-bandwidth generation of duobinary and alternate-mark-inversion modulation formats using SOA-based signal processing.

We report on the novel all-optical generation of duobinary (DB) and alternate-mark-inversion (AMI) modulation formats at 42.6 Gb/s from an input on-off keyed signal. The modulation converter consists of two semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer gates. A detailed SOA model numerically confirms the operational principles and experimental data shows successful AMI and DB conversion at 42.6 Gb/s. We also predict that the operational bandwidth can be extended beyond 40 Gb/s by utilizing a new pattern-effect suppression scheme, and demonstrate dramatic reductions in patterning up to 160 Gb/s. We show an increasing trade-off between pattern-effect reduction and mean output power with increasing bitrate.

Lost interest for existing compounds: New boosts.

Development of new drugs is typically thought of as a bottom-up endeavor where basic science identifies a target, various strategies are used to generate drugs that stimulate or inhibit the target, the drugs are first tested for safety and efficacy in animals and finally efficacy and safety are evaluated in a well defined clinical development process. However, this is not the only way that new drug products are developed. Many new products come from re-initiating development of discontinued drugs, finding new uses for existing drugs, creating a new product by obtaining marketing approval in expanded territories, obtaining approvals for new formulations or a single isomer of a previously approved racemic drug, converting products from prescription to over-the- counter use or converting folk medicines or vitamins to modern pharmaceuticals. Based on this long and successful history of contributions to modern therapeutics, these alternative sources of new products should not be neglected.

Loss resilience for two-qubit state transmission using distributed phase sensitive amplification.

We transmit phase-encoded non-orthogonal quantum states through a 5-km long fibre-based distributed optical phase-sensitive amplifier (OPSA) using telecom-wavelength photonic qubit pairs. The gain is set to equal the transmission loss to probabilistically preserve input states during transmission. While neither state is optimally aligned to the OPSA, each input state is equally amplified with no measurable degradation in state quality. These results promise a new approach to reduce the effects of loss by encoding quantum information in a two-qubit Hilbert space which is designed to benefit from transmission through an OPSA.

Cell uptake and in vitro toxicity of magnetic nanoparticles suitable for drug delivery.

Magnetic targeting is useful for intravascular or intracavitary drug delivery, including tumor chemotherapy or intraocular antiangiogenic therapy. For all such in vivo applications, the magnetic drug carrier must be biocompatible and nontoxic. In this work, we investigated the toxic properties of magnetic nanoparticles coated with polyethylenoxide (PEO) triblock copolymers. Such coatings prevent the aggregation of magnetic nanoparticles and guarantee consistent magnetic and nonmagnetic flow properties. It was found that the PEO tail block length inversely correlates with toxicity. The nanoparticles with the shortest 0.75 kDa PEO tails were the most toxic, while particles coated with the 15 kDa PEO tail block copolymers were the least toxic. Toxicity responses of the tested prostate cancer cell lines (PC3 and C4-2), human umbilical vein endothelial cells (HUVECs), and human retinal pigment epithelial cells (HRPEs) were similar. Furthermore, all cell types took up the coated magnetic nanoparticles. It is concluded that magnetite nanoparticles coated with triblock copolymers containing PEO tail lengths of above 2 kDa are biocompatible and appropriate for in vivo application.