Real time vibronic coupling dynamics in organic conjugated systems

In this work we show the potentialities of applying impulsive coherent vibrational spectroscopy to conjugated systems relevant for applications. We studied films of sexithiophene, a candidate for large area molecular electronics, poly-phenylene vinylene, a prototype electroluminescent material, and polydiacetylene, very promising for applications in photonic devices. These experiments demonstrate the possibility of studying coherent molecular dynamics in organic systems with extremely high time resolution

Towards fully integrated CMOS RF receivers

The evolution of the mobile telephony is demanding new multi-function terminals (cellular and cordless phones, GPS, pagers) compatible with a variety of standard (GSM, DCS, DECT, CDMA). At the same time the reduction of cost, size and power dissipation is mandatory. All this requires an higher integration level for the RF part, that is presently using a big number of components. This explains the big research effort put in silicon RF circuits particularly in CMOS technology. In this paper the state of the art of CMOS RF circuits is outlined. In particular some results regarding critical building blocks obtained by the STMicroelectronics and Pavia University research team are given. Future evelopments and the progress needed to successfully implement them are also pointed out

Na(+) -K(+) -2Cl(-) cotransporter type 2 trafficking and activity: The role of interacting proteins.

The central role of Na+–K+–2Cl− cotransporter type 2 (NKCC2) in vectorial transepithelial salt reabsorption in thick ascending limb cells from Henle’s loop in the kidney is evidenced by the effects of loop diuretics, the pharmacological inhibitors of NKCC2, that are amongst the most powerful antihypertensive drugs available to date. Moreover, genetic mutations of the NKCC2 encoding gene resulting in impaired apical targeting and function of NKCC2 transporter give rise to a pathological phenotype known as type I Bartter syndrome, characterised by a severe volume depletion, hypokalaemia and metabolic alkalosis with high prenatal mortality. On the contrary, excessive NKCC2 activity has been linkedwith inherited hypertension in humans and in rodent models. Interestingly, in animal models of hypertension, NKCC2 upregulation is achieved by post-translational mechanisms underlining the need to analyse the molecular mechanisms involved in the regulation of NKCC2 trafficking and activity to gain insights in the pathogenesis of hypertension

Electromagnetic Transition in Waveguide with Application to Lasers

The electromagnetic transition of two-level atomic systems in a waveguide is calculated. Compared with the result in free space, the spontaneous emission rate decrease because the phase space is smaller, and meanwhile, some resonance appears in some cases. Moreover, the influence of non-uniform electromagnetic field in a waveguide on absorption and stimulated emission is considered. Applying the results to lasers, a method to enhance the laser power is proposed.Comment: 4 pages, 2 figure

Non-Markovian Decay and Lasing Condition in an Optical Microcavity Coupled to a Structured Reservoir

The decay dynamics of the classical electromagnetic field in a leaky optical resonator supporting a single mode coupled to a structured continuum of modes (reservoir) is theoretically investigated, and the issue of threshold condition for lasing in presence of an inverted medium is comprehensively addressed. Specific analytical results are given for a single-mode microcavity resonantly coupled to a coupled resonator optical waveguide (CROW), which supports a band of continuous modes acting as decay channels. For weak coupling, the usual exponential Weisskopf-Wigner (Markovian) decay of the field in the bare resonator is found, and the threshold for lasing increases linearly with the coupling strength. As the coupling between the microcavity and the structured reservoir increases, the field decay in the passive cavity shows non exponential features, and correspondingly the threshold for lasing ceases to increase, reaching a maximum and then starting to decrease as the coupling strength is further increased. A singular behavior for the "laser phase transition", which is a clear signature of strong non-Markovian dynamics, is found at critical values of the coupling between the microcavity and the reservoir.Comment: to appear in Phys. Rev. A (December 2006 issue

Suspended liquid particle disturbance on laser-induced blast wave and low density distribution

The impurity effect of suspended liquid particles on the laser-induced gas breakdown was experimentally investigated in quiescent gas. The focus of this study is the investigation of the influence of the impurities on the shock wave structure as well as the low density distribution. A 532 nm Nd:YAG laser beam with an 188 mJ/pulse was focused on the chamber filled with suspended liquid particles 0.9 ± 0.63 μm in diameter. Several shock waves are generated by multiple gas breakdowns along the beam path in the breakdown with particles. Four types of shock wave structures can be observed: (1) the dual blast waves with a similar shock radius, (2) the dual blast waves with a large shock radius at the lower breakdown, (3) the dual blast waves with a large shock radius at the upper breakdown, and (4) the triple blast waves. The independent blast waves interact with each other and enhance the shock strength behind the shock front in the lateral direction. The triple blast waves lead to the strongest shock wave in all cases. The shock wave front that propagates toward the opposite laser focal spot impinges on one another, and thereafter a transmitted shock wave (TSW) appears. The TSW interacts with the low density core called a kernel; the kernel then longitudinally expands quickly due to a Richtmyer-Meshkov-like instability. The laser-particle interaction causes an increase in the kernel volume which is approximately five times as large as that in the gas breakdown without particles. In addition, the laser-particle interaction can improve the laser energy efficiency

Performance analysis of an optical distance sensor for roll angle estimation in sport motorcycles

n/

A smart current control of a measurement station for superconducting cable test

Peer Reviewe