The coffee plant is native to shaded environments and its seedlings are often produced in shaded nurseries. However, some nursery managers, in an effort to improve the acclimation of seedlings to field conditions after transplantation, produce seedlings in full sun exposure. In this study, the morphological and physiological parameters of arabica coffee (Coffea arabica) seedlings produced in full sun (T1) and in shade (T2) were examined. The biomass accumulation and relative growth rate of T1 and T2 seedlings were similar. The T1 seedlings had less biomass allocation to shoots, a lower leaf mass ratio and a lower leaf area ratio; however, they had a greater net assimilation rate (rate of increase in plant mass per unit leaf area), which was associated with a greater net photosynthetic rate. There were no alterations in the concentrations of total chlorophylls or in the chlorophyll a/b ratio when comparing T1 and T2 seedlings. No indications of photoinhibition or photooxidative damage were observed in the T1 plants, which were shown to have a more robust antioxidant system than the T2 plants. Seedlings transferred from shade to full sun (T3) were not capable of utilising the incident extra light to fix CO2. These seedlings showed a remarkable nocturnal retention of zeaxanthin and a significantly increased deepoxidation state of the xanthophyll cycle, even at predawn, but the activity of antioxidant enzymes was lower than in the T1 and T2 plants. Despite the acclimation capacity of T3 seedlings to the new light environment, they exhibited chronic photoinhibition and considerable photooxidative damage throughout the seven days following the transfer to full sun exposure. We further discuss the practical implications of producing coffee seedlings in full sunlight and under shade. and G. A. B. K. Moraes ... [et al.].
In this paper, a theoretical approach of a wideband preamplifier using a high-end operation amplifier OPA847 will be presented. This device is designed to be used for a low noise, wide band measuring. The level of optimization is based on a noise model for the electrical part of the receiver. During the process of amplifier designing, all the noise components have been investigated separately, using operational amplifiers models. Although this preamplifier was designed to serve for the purposes of flame sensors evaluate, it can be also used to other purposes requiring wide band amplifier with low noise, under only a minimal modification. and V tomto příspěvku bych rád přiblížil teoretický postup návrhu
širokopásmového předzesilovače, využívajícího moderní integrovaný
předzesilovač OPA847, který je určen pro nízkošumová
měření. Stupeň optimalizace je založen na šumovém modelu pro
elektrickou část přijímače. Během návrhu zesilovače byla každá
šumová složka zkoumána zvlášť s využitím modelu operačního
zesilovače. Přestože byl tento předzesilovač navržen pro účely
měření detektorů plamene. Může být s výhodou využit všude jinde,
kde je vyžadován širokopásmový, nízkošumový předzesilovač a to
jen s minimálními úpravami.
Three vernacular texts from late-13th-century Bohemia, in Middle High German and Old Czech, integrate motifs associated with the Holy Land, pilgrimage and the crusades. The romance Wilhalm von Wenden manifests the late Přemyslids’ royal ideology by portraying an independent, pious ruler who derives authority from Jerusalem. The Alexandreis explores the psychology of a military expedition to provide ground for moral reflection and draws on cartography to exploit the symbolism of Jerusalem’s geographic centrality. The crusade-related details in the Legend of Saint James the Less attest to an informed use of intertextual practices.
Portrét kanadského fyzika, který získal v r. 2009 Nobelovu cenu za vynález zobrazovacího polovodičového obvodu - CCD senzoru. and Rubrika: Nobelova cena za fyziku
Seasonal variability of maximum quantum yield of PSII photochemistry (Fv/Fm) was studied in needles of Taxus baccata seedlings acclimated to full light (HL, 100% solar irradiance), medium light (ML, 18% irradiance) or low light (LL, 5% irradiance). In HL plants, Fv/Fm was below 0.8 (i.e. state of photoinhibition) throughout the whole experimental period from November to May, with the greatest decline in January and February (when Fv/Fm value reached 0.37). In ML seedlings, significant declines of Fv/Fm occurred in January (with the lowest level at 0.666), whereas the decline in LL seedlings (down to 0.750) was not significant. Full recovery of Fv/Fm in HL seedlings was delayed until the end of May, in contrast to ML and LL seedlings. Fv/Fm was significantly correlated with daily mean (T mean), maximal (T max) and minimal (T min) temperature and T min was consistently the best predictor of Fv/Fm in HL and ML needles. Temperature averages obtained over 3 or 5 days prior to measurement were better predictors of Fv/Fm than 1- or 30-day averages. Thus our results indicate a strong light-dependent seasonal photoinhibition in needles of T. baccata as well as suggest a coupling of Fv/Fm to cumulative temperature from several preceding days. The dependence of sustained winter photoinhibition on light level to which the plants are acclimated was further demonstrated when plants from the three light environments were exposed to full daylight over single days in December, February and April and Fv/Fm was followed throughout the day to determine residual sensitivity of electron transport to ambient irradiance. In February, the treatment revealed a considerable midday increase in photoinhibition in ML plants, much less in HL (already downregulated) and none in LL plants. This suggested a greater capacity for photosynthetic utilization of electrons in LL plants and a readiness for rapid induction of photoinhibition in ML plants. Further differences between plants acclimated to contrasting light regimes were revealed during springtime de-acclimation, when short term regeneration dynamics of Fv/Fm and the relaxation of nonphotochemical quenching (NPQ) indicated a stronger persistent thermal mechanism for energy dissipation in HL plants. The ability of Taxus baccata to sustain winter photoinhibition from autumn until late spring can be beneficial for protection against an excessive light occurring together with frosts but may also restrict photosynthetic carbon gain by this shade-tolerant species when growing in well illuminated sites. and P. Robakowski, T. Wyka.