A classic pump–probe experiment is performed on SF6. Using 30 psec pulses from two independently tunable CO2 lasers, we have studied the intramolecular energy transfer processes occurring in a collisionless environment. Distinct from nanosecond pulse experiments, we find an extremely narrow and deep hole burning feature at the pump wavelength. Experimental results exhibit both discrete state bottlenecking effects and quasicontinuum absorption. New evidence of an extremely rapid collisional relaxation is found, which may be related to rotational hole filling.

This paper describes the geometric structure of a strange attractor observed from the simplest known chaotic electronic circuit which the author conceived and proposed to Professor Matsumoto from Waseda University in 1983. Computer simulation of this circuit by Professor Matsumoto in October 1983 confirmed its rich chaotic dynamics [1]. Subsquent laboratory experiments using an operational amplifier circuit further confirmed the robust nature of the chaotic attractor [2], and its rich bifurcation phenomena [3]. The strange attractor is now widely known as the double scroll [4] because it resembles, from a distance, a pair of Saturn plants attached to the opposite ends of a tube formed by rolling two long strips of paper together into a scroll whose cross section consists of two tightly wound spirals.

The synthesis and utilization of polymeric catalyst 1 bearing proline moieties as active sites is reported. This catalyst aggregate was applied successfully in aldol reactions of aldehydes and ketones in aqueous media. In a self-­aldol process of butanal, mainly reversibly formed β-hydroxyaldehyde 2 was obtained, whereas the formation of aldol condensation product 3 could be suppressed. These results were transferred to more complex dynamic catalytic cross-aldol reactions, giving rise to α,β-unsaturated ketones 4, favored over formation of self-condensation product 5. The likewise expected ketones 6 were not observed.

Nanoscale tip-induced polymerization of a sulfur thin film affords a simple negative tone resist that can be used as mask for substrate etching in fluorinated solutions or as a chemical template for the directed self-assembly of gold nanocrystals. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

We cast the problem of very-low-threshold, daylight-pumped lasers in a general thermodynamic framework. We calculate that the requirements to reach threshold are that the Stokes shift of such a laser be greater than 13.3kT and that the absorption ratio of the pump/emission band and the geometrical aspect ratio both be greater than exp (13.3). We describe some luminescent material systems that might be able to satisfy these rigid requirements.

Abstract A new simple circuit model for the MOS (metal‐oxide‐semiconductor) structure is presented. the model consists of three elements, namely, a linear capacitor, a non‐linear capacitor and a C‐dynamic element. Each component bears a simple relationship to the physical operating mechanism inside the MOS structure. the model can be used for simulating arbitrary MOS structure circuits under all operating conditions. In particular, it is capable of reproducing the structure's frequency‐dependent small‐signal characteristics. the model is also shown to exhibit many important and interesting dynamic behaviours under forward, reverse and sinusoidal operating modes. The model is based mainly upon the device's physical operating principles. But perhaps the most significant implication of this model is that it is the first ever to use a dynamic element to model the MOS structure from a physical approach.

A "generalized brightness theorem" is derived that describes the thermodynamic limitations of the fluorescent planar concentrator. The maximum brightness concentration ratio allowed by thermodynamics is exp (hΔν/kT) where Δν is the Stokes shift in fluorescence.

Abstract The in situ preparation of monolithic capillary columns comprising copolymers of butyl methacrylate with ethylene dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and pentaerythritol tetraacrylate using thermal polymerization within 250 μm ID capillaries and their application for μ‐HPLC separations of proteins has been studied. For all crosslinkers, optimization of the porogenic mixture consisting of 1‐propanol and 1,4‐butanediol yielded monoliths with pore sizes above 1 μm suitable for rapid separations at low back pressure. Very good separations were achieved for a protein mixture consisting of ribonuclease A, cytochrome c, myoglobin, and ovalbumin with all tested columns.

The double scroll attractor has been experimentally observed from an extremely simple circuit using an op amp. The purpose of this brief note is to give an alternate realization of the circuit using only two transistors as the active elements.

We have investigated the transport properties in the direction perpendicular to the substrate of regioregular poly(3-hexyl-thiophene) of different molecular weights (MW) in a diode geometry. In these devices, which exhibit space-charge-limited behavior, we find that the mobility values at room temperature increase from 1.33×10−5cm2∕Vsto3.30×10−4cm2∕Vs as the MW is increased from 2.9to31.1kg∕mol. The mobility is found to be field independent for high MW films, but field dependent for the low MW films. The current–voltage characteristics of the diodes are also studied as a function of temperature from 160Kto300K. The activation energy for carrier transport, extracted from the Arrhenius plot, is found to decrease gradually from 143meVto126meV as the MW is increased.

Abstract Techniques formerly developed in the theory of Poincaré half‐maps are modified and applied to the three‐region piecewise‐linear continuous dynamical system associated with Chua's circuit. Both transfer and return maps, induced by the trajectories inside the intermediate region in state space, are formulated as implicit equations. the boundaries of the domains of these maps are determined explicitly, using the method for calculating the initial points of touching trajectories subject to appropriate switching dynamics. A charting of the canonical parameter space of the dynamics that acts on the intermediate region is indicated. Among other things, this chart reveals the existence of new types of chaotic attractors different from the double scroll and Rössler attractors previously discovered from Chua's circuit.

We have used single-molecule-resolved scanning tunneling microscopy to measure the photomechanical switching rates of azobenzene-derived molecules at a gold surface during exposure to UV and visible light. This enables the direct determination of both the forward and reverse photoswitching cross sections for surface-mounted molecules at different wavelengths. In a dramatic departure from molecular behavior in solution-based environments, visible light does not efficiently reverse the reaction for azobenzene-derived molecules at a gold surface.

The preparation of nanoporous size-selective hypercrosslinked polymer networks containing 37−92% of pores small enough for hydrogen adsorption but too small to allow penetration of nitrogen has been studied. Polyaniline and diaminobenzene were coupled with diiodobenzene and tribromobenzene using Ullman and Buchwald synthetic routes. The resulting porous polymer networks consist of aromatic rings linked through a trivalent nitrogen atom. The Buchwald reaction appears to be more effective than the Ullman synthesis for the production of such materials. The use of solvents with higher Hildebrand solubility coefficients during synthesis affords polymers with higher surface areas. The nanoporous polymers possess unusually high initial enthalpies of adsorption of hydrogen reaching values of up to −18 kJ/mol.

We introduce a passive micromixer with novel architecture using photopatterned porous polymer monoliths (PPM) and demonstrate an improvement in mixing efficiency by monitoring the fluorescence of an on-chip labeling reaction. UV light was used to photopattern a periodic arrangement of PPM structures directly within the channel of a plastic microfluidic chip. By optimizing the composition of the polymerization solution and irradiation time we demonstrate the ability to photopattern PPM in regularly repeating 100 microm segments at the tee-junction of the disposable device. To evaluate the efficiency of this dual functional mixer-reactor fluorescamine and lysine were introduced in separate channels upstream of the tee-junction and the intensity of laser-induced fluorescence resulting from the fluorogenic labeling reaction was monitored. The fluorescence level after the photopatterned periodic monolith configuration was 22% greater than both an equivalent 1 cm continuous segment of PPM and an open channel. Results indicate that this periodic arrangement of PPM, with regularly spaced open areas between 100 microm plugs of PPM, is directly responsible for enhancing the mixing and overall rate of chemical reaction in the system. In addition to facilitating preparation of a dual functional mixer-reactor, the ability to accurately photopattern PPM is an enabling technology for seamlessly integrating multiple monoliths into a single device. This technology will be particularly important to proteomic applications requiring preconcentration, enzymatic digestion and two-dimensional separations.

This paper proves that the recent result in [1] when specialized to transistor circuits is equivalent to the Nielsen-Willson theorem. The proof is graph-theoretic in nature.