Chlorophyll (Chl) a fluorescence parameters and rapid light curves of soybean [Glycine max (L.) Merrill] were measured by pulse amplitude modulation fluorometry. Measurements were taken during different stages of soybean growth under field conditions with 20% enhancement in ultraviolet-B (UV-B) radiation. Results showed that supplemental UV-B radiation decreased Chl contents by 5.5% (P=0.048), 8.7% (P=0.046), and 10.5% (P=0.005) in seedling, in branching-flowering, and in pod-setting stages, respectively. In the branching-flowering and pod-setting stages, maximum quantum yield of photosystem (PS) II photochemistry (Fv/Fm) decreased by 6.1% (P=0.001) and 3.0% (P=0.009), respectively. Supplemental UV-B radiation significantly decreased the effective quantum yield (Y). The photosynthetic capacity at light saturation (Pm) also decreased in both the seedling and branching-flowering stages by 28.9% (P=0.007) and 15.5% (P=0.041), respectively. However, Y and Pm showed no significant difference in the trefoil and pod-setting stages with and without the UV treatment. The light saturation parameter (E k) decreased by 21.1% (P=0.000) and 23.2% (P=0.029) in the trefoil and seedling stages, respectively. Moreover, the initial slope (α) decreased by 21.1% (P=0.001) in the branching-flowering stage. Nonphotochemical quenching (NPQ) in the seedling stage and photochemical quenching coefficient (qp) in the
branching-flowering stage decreased significantly under UV-B treatments. The results of the present study suggest that supplemental UV-B radiation adversely affected Chl content and electron transport activity in PSII and consequently decreased the photosynthetic efficiency of soybean plants., Z. Hu ... [et al.]., and Obsahuje bibliografii
Experimentální fyzikové prokázali, že neutrina jsou hmotné částice, ale zatím určili jen hranice jejich hmotnosti. Stručně popisujeme přednosti a nedostatky použitých metod a zmiňujeme se o navrhovaných způsobech určení této fundamentální fyzikální veličiny., Experimental physicists proved that neutrinos are massive particles but until now they have determined only the upper and lower limits of their mass. In this review we describe advantages and drawbacks of the applied methods. There are also some proposals mentioned for the measurement of this fundamental quantity., Otokar Dragoun., and Obsahuje bibliografii
The new observations of planetary rings, including those acquired during the encounters of Voyager with Jupiter, Saturn and Uranus and the discovery of incomplete rings around Neptune, reveal the great importance of resonances in determining the dynamics and the shape of planetary rings. Several types of resonances play a part in planetary rings. Current questions of interest are related to the nonlinear theory of density waves, the confinement of the Uranian rings, and the arcs of rings around Neptune.
The laser-induced breakdown spectroscopy (LIBS) is an atomic emission based method, which is currently becoming more popular. Speed and multi-elemental analysis are some of the main advantages of this method. Higher limits of detection (LOD) in comparison to other atomic analytical methods, such as X-ray fluorescence spectrometry (XRF) and inductively coupled plasma based methods, are some of the limitations of this method. The application of nanoparticles on the surface of studied sample, so called Nanoparticle Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS), is one of the ways to achieve improvement of the limits of detection while preserving the main advantages of the LIBS method. In this paper the improvement of detection limits by application of silver nanoparticles on the surface of studied sample is presented in comparison to the classical LIBS method. At the same time, the effect of two different Nd:YAG laser wavelengths, 532 nm and 1064 nm, on the LOD’s improvement of selected elements of studied samples is investigated for LIBS and NELIBS experiments. In the end of the paper, the parameters of craters (diameter and volume) are investigated for both chosen ablation laser wavelengths. and Spektrometria laserom budenej (mikro)plazmy (LIBS) je metódou atómovej emisnej spektrometrie, ktorá v súčasnosti naberá na popularite. Medzi hlavné výhody tejto metódy patria rýchlosť a viacprvková analýza. K obmedzeniam metódy patria o niečo vyššie limity detekcie (LOD) oproti ostatným prvkovým analytickým metódam, ako sú napr. rentgenová fluorescenčná spektrometria (XRF) a metódy indukčne viazanej plazmy (ICP). Jedným zo spôsobov, ako dosiahnuť zníženie limitov detekcie pri zachovaní hlavných výhod metódy, je aplikácia nanočastíc na povrch študovanej vzorky, tzv. nanočasticami zosilnená spektrometria laserom budenej (mikro)plazmy (NELIBS).V tejto práci je prezentované zlepšenie detekčných limitov pri aplikácii strieborných nanočastíc na povrch študovaných vzoriek v porovnaní s klasickou LIBS metódou. Súčasne je sledovaný aj vplyv dvoch rôznych vlnových dĺžok Nd:YAG lasera, 532 nm a 1064 nm, na zlepšenie LOD vybraných prvkov študovaných vzoriek v LIBS a NELIBS experimente. Nakoniec boli sledované parametre kráterov, priemer a objem, a to v porovnaní LIBS vs. NELIBS pre obe vybrané vlnové dĺžky ablačných laserov.