Mechanism for self-synchronization of femtosecond pulses in atwo-color Ti:sapphire laser

An experimental and theoretical analysis of the nonlinear coupling mechanism between the two solitary pulses circulating in a two-color femtosecond laser is presented. Two operation regimes; synchronized; and nonsynchronized; and a hysteresis of the transition between the two regimes are clearly observed; while independent modelocking and tunability of the output pulse trains is found in both regimes. Pulses in the range from 15 to 100 fs are synchronized with a timing jitter below 2 fs. The combined effects of cross-phase modulation and negative group velocity dispersion are shown to be responsible for the strong pulse correlation in the synchronized regime. Our experimental observations are in agreement with numerical simulations, thus confirming the theoretical model     

Scale and scope of environmental planning transformations: The Israeli case

This paper explores the scale and scope of transformations in the environmental planning field, and the factors that may advance or impede their widespread adoption. A conceptual model is offered which examines scope (defined as type, breadth and structure of the transformation), and the scale of its impact (categorized as stakeholder, organizational, institutional or societal) and applies it to the analysis of several cases in Israel where environmental transformations, affecting the way in which planning is conducted, have been adopted. Conclusions include identification of conditions for facilitating and advancing transformations, including knowledge of innovative alternatives, initiative, willingness to adopt new practices, and identification of policy windows that emerge during conflict, reform, or crisis. The fostering of relations between environmental non-government organizations and planning systems and leadership roles are also significant in catalyzing environmental transformation.     

QFT application for headphone's active noise cancellation

A quantitative feedback theory design for attenuation of acoustic noise in earphones and headphones is described. Identification including uncertainty is measured for several ears and device location in the ear neighbourhood. Theoretical limitations are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

A brief commentary on the usefulness of studying fears of snakes.

Used therapy analogue studies with Ss who feared snakes or rats to evaluate types of behavior therapy. In a small pilot study Es were able to desensitize 4 Ss to fears of snakes or laboratory rats. However, the 2 control Ss also overcame their fears of snakes. They had been instructed to hold the snake when it was presented to them and to act unafraid. They were also told that they would overcome their fears in this manner. It is suggested that any "technique" that helps a person confront the fear of snakes may "cure" him, that studying the treatment of snake fears may be irrelevant to the understanding of treating clinical neuroses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of localized pontine lesions on auditory brain-stem evoked potentials and binaural processing in humans

Potassium channels are involved in the control of neuronal excitability by fixing the membrane potential, shaping the action potential, and setting firing rates. Recently, attention has been focused on identifying the factors influencing excitability in second-order auditory and vestibular neurons. Located in the brainstem, second-order auditory and vestibular neurons are sites for convergence of inputs from first-order auditory or vestibular ganglionic cells with other sensory systems and also motor areas. Typically, second-order auditory neurons exhibit two distinct firing patterns in response to depolarization: tonic, with a repetitive firing of action potentials, and phasic, characterized by only one or a few action potentials. In contrast, all mature vestibular second-order neurons fire tonically on depolarization. Already, certain fundamental roles have emerged for potassium currents in these neurons. In mature auditory and vestibular neurons, I(K), the delayed rectifier, is required for the fast repolarization of action potentials. In tonically firing auditory neurons, I(A), the transient outward rectifier, defines the discharge pattern. I(DS), a delayed rectifier-like current distinguished by its low threshold of activation, is found in phasically firing auditory and some developing vestibular neurons where it limits firing to one or a few spikes, and also may contribute to forming short-duration excitatory postsynaptic potential (EPSPs). Also, I(DS) sets the threshold for action potential generation rather high, which may prevent spontaneous discharge in phasically firing cells. During development, there is a gradual acquisition and loss of some potassium conductances, suggesting developmental regulation. As there are similarities in membrane properties of second-order auditory and vestibular neurons, investigations on firing pattern and its underlying mechanisms in one system should help to uncover fundamental properties of the other.     

Quantification of the Effectiveness of Various Adhesives in Holding an SMA Actuator Wire During Joule Heating

Shape memory alloy (SMA) actuator wires undergo a large contraction (～4%) and resistance change (～7%) in response to a material phase change induced by heating. However, a major impediment to using SMA wires as embedded actuators or sensors in practical applications is the challenge of attaching the small wires to the surrounding structure without adding significant bulk to the system.

This work systematically determines the bond strength of different adhesives that could be used to attach small (<100-µm diameter) SMA wires to a structure by exposing the adhesive bond to the thermal and mechanical loading expected during typical embedded SMA applications.

Results show that for all adhesives tested, bonding strength is reduced as heating current is increased; however, some two-part epoxies and contact adhesives are still able to maintain 6 MPa of bonding strength to a heated SMA wire. This number can be used to determine how much adhesive is needed to hold different diameter wires for a range of applications.     

Pharmacology and pharmacokinetics of methotrexate in rheumatic disease. Practical issues in treatment and design

Methotrexate (MTX) is among the most effective drugs for treatment of rheumatoid arthritis and has been proven valuable in the treatment of multiple other disorders of immune regulation. MTX has been administered at a wide range of doses and dose intervals, in conjunction with multiple other drugs, and in patients with a broad range of concomitant disorders. To design a safe and effective MTX treatment plan for an individual patient, the provider must have knowledge of the pharmacology and drug interactions of this effective but potentially dangerous medication. The first section of the article reviews MTX structure, pharmacology pharmacokinetics, and mechanisms of action in rheumatic disease. The second section examines factors that can be used to increase MTX efficacy and decrease toxicity.