Stimulated Raman scattering in a non-eigenmode regime

Stimulated Raman scattering (SRS) in plasma in a non-eigenmode regime is studied theoretically and numerically. Different from normal SRS with the eigen electrostatic mode excited, the non-eigenmode SRS is developed at plasma density 0.25nc when the laser amplitude is larger than a certain threshold. To satisfy the phase-matching conditions of frequency and wavenumber, the excited electrostatic mode has a constant frequency around half of the incident light frequency, which is no longer the eigenmode of electron plasma wave. Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero. Super-hot electrons are produced by the non-eigen electrostatic wave. Our theoretical model is validated by particle-in-cell simulations. The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than

Modeling, Design and Optimization of IC Power Delivery with On-Chip Regulation

As IC technology continues to follow the Moore’s Law, IC designers have been constantly challenged with power delivery issues. While useful power must be reliably delivered to the on-die functional circuits to fulfill the desired functionality and performance, additional power overheads arise due to the loss associated with voltage conversion and parasitic resistance in the metal wires. Hence, one of the key IC power delivery design challenges is to develop voltage conversion/regulation circuits and the corresponding design strategies to provide a guaranteed level of power integrity while achieving high power efficiency and low area overhead. On-chip voltage regulation, a significant ongoing design trend, offers appealing active supply noise suppression close to the loads and is well positioned to address many power delivery challenges. However, to realize the full potential of on-chip voltage regulation requires systemic optimization of and tradeoffs among settling time, steady-state error, power supply noise, power efficiency, stability and area overhead, which are the key focuses of this dissertation. First, we develop new low-dropout voltage regulators (LDOs) that are well optimized for low power applications. To this end, dropout voltage, bias current and speed are important competing design objectives. This dissertation presents new flipped voltage follower (FVF) based topologies of on-chip voltage regulators that handle ultra-fast load transients in nanoseconds while achieving significant improvement on bias current consumption. An active frequency compensation is embedded to achieve high area efficiency by employing a smaller amount of compensation capacitors, the major silicon area contributor. Furthermore, in one of the proposed topologies an auxiliary digital feedback loop is employed in order to lower quiescent power consumption further. Second, coping with supply noise is becoming increasingly more difficult as design complexity grows, which leads to increased spatial and temporal load heterogeneity, and hence larger voltage variations in a given power domain. Addressing this challenge through a distributed methodology wherein multiple voltage regulators are placed across the same voltage domain is particularly promising. This distributive nature allows for even faster suppression of multiple hot spots by the nearby regulators within the power domain and can significantly boost power integrity. Nevertheless, reasoning about the stability of such distributively regulated power networks becomes rather complicated as a result of complex interactions between multiple active regulators and the large passive subnetwork. Coping with this stability challenge requires new theory and stability-ensuring design practice, as targeted by this dissertation. For the first time, we adopt and develop a hybrid stability framework for large power delivery networks with distributed voltage regulation. This framework is local in the sense that both the checking and assurance of network stability can be dealt with on the basis of each individual voltage regulator, leading to feasible design of large power delivery networks that would be computationally impossible otherwise. Accordingly, we propose a new hybrid stability margin concept, examine its tradeoffs with power efficiency, supply noise and silicon area, and demonstrate the resulted key design implications pertaining to new stability-ensuring LDO circuit design techniques and circuit topologies. Finally, we develop an automated hybrid stability design flow that is computationally efficient and provides a practical guarantee of network stability

Extreme case of Faraday effect: magnetic splitting of ultrashort laser pulses in plasmas

The Faraday effect, caused by a magnetic-field-induced change in the optical properties, takes place in a vast variety of systems from a single atomic layer of graphenes to huge galaxies. Currently, it plays a pivot role in many applications such as the manipulation of light and the probing of magnetic fields and material's properties. Basically, this effect causes a polarization rotation of light during its propagation along the magnetic field in a medium. Here, we report an extreme case of the Faraday effect where a linearly polarized ultrashort laser pulse splits in time into two circularly polarized pulses of opposite handedness during its propagation in a highly magnetized plasma. This offers a new degree of freedom for manipulating ultrashort and ultrahigh power laser pulses. Together with technologies of ultra-strong magnetic fields, it may pave the way for novel optical devices, such as magnetized plasma polarizers. In addition, it may offer a powerful means to measure strong magnetic fields in laser-produced plasmas.Comment: 18 pages, 5 figure

Distribution of Heavy Metals in Core Sediments from Baihua Lake

AbstractIn the present research, five core sediments from Baihua Lake, a man-made reservoir located in the karst area on the Yunnan-Guizhou Plateau in China, were analyzed to study the distribution, origin and contamination of three selected heavy metals (Cu, Zn and Mn). The results showed that the concentrations of these heavy metals in sediments varied from different sampling locations and layers. The average concentrations of these heavy metals at the same sampling location followed the order of Mn>Zn>Cu. The mean concentrations of Zn and Mn in the samples at the depth of 0-5cm and the depth of 5-10cm of the core sediments were higher than those in the other layers. All of Cu, Zn and Mn presented similar distribution characteristics at sampling site CFZ, and different distribution characteristics from the other four sampling locations. A statistical analysis indicated that there were some correlations between the concentrations of these three heavy metals and other studied six elements occurring in the core sediment samples. Three components were obtained with principal component analysis (PCA) analysis of heavy metals concentrations in core sediment samples

4,4′-Methyl­enedianilinium bis­(3-carb­oxy-4-hydroxy­benzene­sulfonate) monohydrate

Co-crystallization of 4,4′-methyl­enediphenyl­amine (MDA) and 5-sulfosalicylic acid (5-H2SSA) yields the title salt, C13H16N2 2+·2C7H5O6S−·H2O. The asymmetric unit is comprised of one dication, two anions and one water mol­ecule. In the crystal structure, the components of the salt are linked by a combination of inter­molecular O—H⋯O, N—H⋯O and weak C—H⋯O hydrogen bonds into a three-dimensional framework. In addition, two weak π–π inter­actions [with centroid–centroid distances of 3.8734 (15) and 3.7465 (15) Å] and one C—H⋯π inter­action further stabilize the crystal structure

Plasma modulator for high-power intense lasers

A type of plasma-based optical modulator is proposed for the generation of broadband high-power laser pulses. Compared with normal optical components, plasma-based optical components can sustain much higher laser intensities. Here we illustrate via theory and simulation that a high-power sub-relativistic laser pulse can be self-modulated to a broad bandwidth over 100% after it passes through a tenuous plasma. In this scheme, the self-modulation of the incident picoseconds sub-relativistic pulse is realized via stimulated Raman forward rescattering in the quasi-linear regime, where the stimulated Raman backscattering is heavily dampened. The optimal laser and plasma parameters for this self-modulation have been identified. For a laser with asub-relativistic intensity of I ∼ 1017W/cm2, the time scale for the development of self-modulation is around 103 light periods when stimulated Raman forward scattering has been fully developed. Consequently, the spatial scale required for such a self-modulation is in the order of millimeters. For a tenuous plasma, the energy conversion efficiency of this self-modulation is around 90%. Theoretical predictions are verified by both one-dimensional and two-dimensional particle-in-cell simulations

Clotrimazole inhibits the Ca2+-ATPase (SERCA) by interfering with Ca2+ binding and favoring the E2 conformation.

Clotrimazole (CLT) is an antimycotic imidazole derivative that is known to inhibit cytochrome P-450, ergosterol biosynthesis and proliferation of cells in culture, and to interfere with cellular Ca(2+) homeostasis. We found that CLT inhibits the Ca(2+)-ATPase of rabbit fast-twitch skeletal muscle (SERCA1), and we characterized in detail the effect of CLT on this calcium transport ATPase. We used biochemical methods for characterization of the ATPase and its partial reactions, and we also performed measurements of charge movements following adsorption of sarcoplasmic reticulum vesicles containing the ATPase onto a gold-supported biomimetic membrane. CLT inhibits Ca(2+)-ATPase and Ca(2+) transport with a K(I) of 35 mum. Ca(2+) binding in the absence of ATP and phosphoenzyme formation by the utilization of ATP in the presence of Ca(2+) are also inhibited within the same CLT concentration range. On the other hand, phosphoenzyme formation by utilization of P(i) in the absence of Ca(2+) is only minimally inhibited. It is concluded that CLT inhibits primarily Ca(2+) binding and, consequently, the Ca(2+)-dependent reactions of the SERCA cycle. It is suggested that CLT resides within the membrane-bound region of the transport ATPase, thereby interfering with binding and the conformational effects of the activating cation