Search results for "efficiency"
showing 10 items of 1430 documents
Phase conjugation in BaTiO 3 by use of the indirect photorefractive coupling of orthogonally polarized light waves
1998
A phase-conjugate wave is generated when an ordinary (extraordinary) signal wave is mixed with two counterpropagating extraordinary (ordinary) waves in the plane normal to the BaTiO3 polar axis. The photorefractive grating that couples the ordinary and the extraordinary waves appears if the incident waves induce a noticeable conical parametric scattering; this grating is a difference grating of many noisy scattering gratings recorded by means of the usual diffusion-mediated charge transport. For comparable intensities of signal and pump waves this type of nonlinear wave mixing is much more efficient than that which is due to the circular bulk photovoltaic effect.
The role of nonlinear optical absorption in narrowband difference-frequency terahertz-wave generation
2010
We present a general analysis of the influence of nonlinear optical absorption on terahertz generation via optical difference frequency generation, when reaching for the quantum conversion efficiency limit. By casting the equations governing the process in a suitably normalized form, including either two-photon- or three-photon-absorption terms, we have been able to plot universal charts for phase matched optical-to-terahertz conversion for different values of the nonlinear absorption coefficients. We apply our analysis to some experiments reported to date, in order to understand to what extent multiphoton absorption could have played a role and also to predict the maximum achievable conver…
Energy Recovery of Multiple Charge Sharing Events in Room Temperature Semiconductor Pixel Detectors
2021
Multiple coincidence events from charge-sharing and fluorescent cross-talk are typical drawbacks in room-temperature semiconductor pixel detectors. The mitigation of these distortions in the measured energy spectra, using charge-sharing discrimination (CSD) and charge-sharing addition (CSA) techniques, is always a trade-off between counting efficiency and energy resolution. The energy recovery of multiple coincidence events is still challenging due to the presence of charge losses after CSA. In this work, we will present original techniques able to correct charge losses after CSA even when multiple pixels are involved. Sub-millimeter cadmium–zinc–telluride (CdZnTe or CZT) pixel detectors we…
The impact of grain size on the efficiency of embedded SIMD image processing architectures
2004
Pixel-per-processing element (PPE) ratio-the amount of image data directly mapped to each processing element-has a significant impact on the area and energy efficiency of embedded SIMD architectures for image processing applications. This paper quantitatively evaluates the impact of PPE ratio on system performance and efficiency for focal-plane SIMD image processing architectures by comparing throughput, area efficiency, and energy efficiency for a range of common application kernels using architectural and workload simulation. While the impact of grain size is affected by the mix of executed instructions within an application program, the most efficient PPE ratio often does not occur at PE…
Enantioselective Total Syntheses of (+)-Hippolachnin A, (+)-Gracilioether A, (-)-Gracilioether E, and (-)-Gracilioether F.
2018
The Plakortin polyketides represent a structurally and biologically fascinating class of marine natural products. Herein, we report a unified strategy that enables the divergent syntheses of various Plakortin polyketides with high step-economy and overall efficiency. As proof-of-concept cases, the enantioselective total syntheses of (+)-hippolachnin A, (+)-gracilioether A, (-)-gracilioether E, and (-)-gracilioether F have been accomplished based on a series of bio-inspired, rationally designed, or serendipitously discovered transformations, which include (1) an organocatalytic asymmetric 1,4-conjugate addition to assemble the common chiral γ-butenolide intermediate enroute to all of the afo…
Physiological,anatomical and biomass partitioning responses to ozone in the Mediterranean endemic plant Lamottea dianae
2011
Ozone effects on the perennial forb Lamottea dianae were studied in an open-top chamber experiment. Ozone was found to induce reductions in CO 2 assimilation and water use efficiency in the leaves of this species. These reductions were mainly related to a decline in the in vivo CO 2 fixation capacity of Rubisco (V c,max), rather than to stomatal limitations or photoinhibitory damage (F v:F m). In addition to chloroplast degeneration, other observed effects were callose accumulation, formation of pectinaceous wart-like cell wall exudates and phloem alterations. Moreover, ozone exposure significantly reduced root dry biomass. The possible relevance of these adverse effects for Mediterranean f…
Light trapping by plasmonic nanoparticles
2020
Abstract Metallic nanoparticles sustaining localized surface plasmon resonances are of great interest for enhancing light trapping in thin film photovoltaics. In this chapter, we explore the correlation between the structural and optical properties of self-assembled silver nanostructures fabricated by a solid-state dewetting process on various substrates relevant for silicon photovoltaics and later integrated into plasmonic back reflectors. Our study allows us to optimize the performance of nanostructures by identifying the fabrication conditions in which desirable circular and uniformly spaced nanoparticles are obtained. Second, we introduce a novel optoelectronic spectroscopic method that…
Isolation, culture and plant regeneration from protoplasts of Sideritis angustifolia
1998
Summary Factors promoting high yields of viable protoplasts from leaves of Sideritis angustifolia are reported. Isolated protoplasts divided and gave rise to callus when plated in modified liquid MS medium with growth regulators. Best plating efficiency was obtained when protoplast were cultured in the presence of 6 μM BA and 2 μM NAA. Calli were then transferred onto solidified regeneration media. Adventitious bud differentiation was only observed in calli grown on medium containing 8 μM BA and 2 μM NAA. These buds proliferated quickly when placed on hormone-free medium and subsequendy regenerated new buds and shoots. Once developed shoots were excised, the remaining tissues maintained thi…
Morphogenesis in leaf and single-cell cultures of mature Juniperus oxycedrus
1996
Single cells were mechanically isolated from leaf-derived callus of mature Juniperus oxycedrus L. These cells divided and gave rise to callus when plated on medium containing growth regulators. Best plating efficiency was obtained on a modified Schenk and Hildebrandt medium supplemented with 0.6 micro M 2,4-dichlorophenoxyacetic acid and 100 mg l(-1) casein hydrolyzate. Although single-cell-derived callus showed poor morphogenic potential, both adventitious shoots and embryogenic tissues differentiated from the callus. We also achieved induction of somatic embryogenesis in leaf explants of mature J. oxycedrus trees cultured in the presence of 6.0 or 10.0 micro M 2,4-dichlorophenoxyacetic ac…
Imigrācijas politika un tās efektivitāte Latvijā
2018
Bakalaura darba tēma: „Imigrācijas politika un tās efektivitāte Latvijā”. Pētījuma objekts ir imigrācijas politika, priekšmets – imigrantu integrācija Latvijā. Pētījuma galvenie uzdevumi: 1) integrācijas procesu izvērtēšana saistībā ar Latvijas politiku; 2) integrācijas iespēju analīze; 3) galveno imigrācijas politikas struktūru un integrācijas attīstības izpēte; Pētījuma teorētisko bāzi veido citu autoru darbi par migrācijas jēdzienu, imigrācijas politiku un tendencēm Latvijā. Darba empīriskā daļa balstās uz esošo pētījumu izpēti, statistisko datu apkopošanu, normatīvo aktu un politikas dokumentu analīzi. Darba rezultāti saistīti ar imigrācijas politikas vērtējumu 8 integrācijas jomās: dar…