Generation of reactive oxygen species and oxidative stress in <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by a novel semiconductor catalyst

The objective of this study was to investigate antimicrobial mechanisms of a new catalytic material (charge transfer auto oxidation–reduction type catalyst, CT catalyst) that may have great potential for application in water/wastewater treatment. Generation of reactive oxygen species (ROS) in bacteria-free solution, induction of ROS and oxidative damage in bacteria (including E. coli and S. aureus) were examined for the CT catalyst. The results showed that significantly higher (p < 0.05, via t-test) amount of hydroxyl radicals was generated by the CT catalyst compared with the control, particularly after 6 h of contact time that more than twice of the amount of the control was produced. The generation of ROS in the bacteria was greater under higher pH and temperature levels, which closely related with the oxidative damage in cells. The results indicated that CT catalyst induced oxidative damage in the bacteria might serve as an important mechanism interpreting the anti-microbial function of the CT catalyst.     

Governing nanobiotechnology: lessons from agricultural biotechnology regulation

This article uses lessons from biotechnology to help inform the design of oversight for nanobiotechnology. Those lessons suggest the following: first, oversight needs to be broadly defined, encompassing not just regulatory findings around safety and efficacy, but also public understanding and acceptance of the technology and its products. Second, the intensity of scrutiny and review should reflect not just risks but also perceptions of risk. Finally, a global marketplace argues for uniform standards or commercially practical solutions to differences in standards. One way of designing oversight to achieve these purposes is to think about it in three phases—precaution, prudence, and promotion. Precaution comes early in the technology or product’s development and reflects real and perceived uncertainties. Prudence governs when risks and hazards have been identified, containment approaches established, and benefits broadly defined. Transparency and public participation rise to the fore. The promotional phase moves toward shaping public understanding and acceptance and involves marketing issues rather than safety ones. This flexible, three-phase approach to oversight would have avoided some of the early regulatory problems with agricultural biotechnology. It also would have led to a more risk-adjusted pathway to regulatory approval. Furthermore, it would avoid some of the arbitrary, disruptive marketing issues that have arisen.     

Highly hydrated poly(allylamine)/silica magnetic resin

The creation of multifunctional nanomaterials by combining organic and inorganic components is a growing trend in nanoscience. The unique size-dependent properties of magnetic nanoparticles (MNPs) make them amenable to numerous applications such as carriers of expensive biological catalysts, in magnetically assisted chemical separation of heavy metals and radionuclides from contaminated water sources. The separation of minor actinides from high-level radionuclide waste requires a sorbent stable in acidic pH, with ease of surface functionalization, and a high capacity for binding the molecules of interest. For the described experiments, the MNPs with 50 nm average size were used (size distribution from 20 to 100 nm and an iron content of 80–90 w/w%). The MNPs that have been double coated with an initial silica coating for protection against iron solubilization and oxidation in nitric acid solution (pH 1) and a second silica/polymer composite coating incorporating partially imbedded poly(allylamine) (PA). The final product is magnetic, highly swelling, containing >95% water, with >0.5 mmol amines g^?1 available for functionalization. The amine groups of the magnetic resin were functionalized with the chelating molecules diethylenetriaminepentaacetic acid (DTPA) and N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) for separation of minor actinides from used nuclear fuel.     

An organic programmable diode with pentacene, zinc oxide nanoparticles and polymethylsilsesquioxane

In this paper, we proposed an organic programmable diode as a memory device. This device consists of layers of pentacene and zinc oxide nanoparticles embedded in polymethylsilsesquioxane. The device exhibits a change in current flow of an order up to 10⁵ and is comparable or better to many reported organic diode memory devices. A two-barrier model has been used to explain the memory effect of the organic diode. The device can be written and erased multiple times similar to a flash memory.     

Simple all-microwave entangling gate for fixed-frequency superconducting qubits

We demonstrate an all-microwave two-qubit gate on superconducting qubits which are fixed in frequency at optimal bias points. The gate requires no additional subcircuitry and is tunable via the amplitude of microwave irradiation on one qubit at the transition frequency of the other. We use the gate to generate entangled states with a maximal extracted concurrence of 0.88, and quantum process tomography reveals a gate fidelity of 81%.     

Slow-light-enhanced upconversion for photovoltaic applications in one-dimensional photonic crystals

We present an approach to realizing enhanced upconversion efficiency in erbium (Er)-doped photonic crystals. Slow-light-mode pumping of the first Er excited state transition can result in enhanced emission from higher-energy levels that may lead to finite subbandgap external quantum efficiency in crystalline silicon solar cells. Using a straightforward electromagnetic model, we calculate potential field enhancements of more than 18× within he slow-light mode of a one-dimensional photonic crystal and discuss design trade-offs and considerations for photovoltaics.     

Highly sensitive miniature photonic crystal fiber refractive index sensor based on mode field excitation

A highly sensitive miniature photonic crystal fiber refractive index sensor based on field mode excitation is presented. The sensor is fabricated by melting one end of a photonic crystal fiber into a rounded tip and splicing and collapsing the other end with a single-mode fiber. The rounded tip is able to induce cladding mode excitation, which resulted in an additional phase delay. Linear response of 262.28 nm/refractive index unit in the refractive index range of 1.337 to 1.395 is obtained for the physical length of a 953 μm sensor. The sensor is also shown to be insensitive to environmental temperature.     

Performance of conformal guided mode resonance filters

Guided mode resonance (GMR) filters are highly functional micro-optics capable of narrowband spectral filtering. GMR devices have previously been demonstrated on flat substrates using a wide range of materials and configurations. In this Letter, we apply a soft lithographic technique followed by the deposition of dielectric layers to generate GMR filters on a concave lens surface. Resonances of the resulting conformal GMR filters are experimentally measured and characterized, and the results are compared to the performance of similar GMR filters fabricated on flat surfaces.     

Bidirectional passively mode-locked soliton fiber laser with a four-port circulator

We present an all-fiber bidirectional passively mode-locked soliton laser with what we believe is a novel cavity configuration. Using a four-port circulator, we incorporate two different semiconductor saturable absorber mirrors (SESAMs) into the laser cavity, which enables bidirectional mode locking. The laser allows the generation of two independent countercirculating mode-locked pulse trains, each with an individual fundamental repetition rate that can be adjusted by varying the SESAM pigtail length. Two countercirculating pulse trains with repetition rates of 21.3 and 15.2 MHz are obtained simultaneously. By controlling the intracavity loss imposed on these two pulse trains, either one of the two pulse trains can be switched on or off. The bidirectional operation with other repetition rates is also demonstrated.     

High-power broadband laser source tunable from 3.0 μm to 4.4 μm based on a femtosecond Yb:fiber oscillator

We describe a tunable broadband mid-IR laser source based on difference-frequency mixing of a 100?MHz femtosecond Yb:fiber laser oscillator and a Raman-shifted soliton generated with the same laser. The resulting light is tunable over 3.0?μm to 4.4?μm, with a FWHM bandwidth of 170?nm and maximum average output power up to 125?mW. The noise and coherence properties of this source are also investigated and described.