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991.
Breaking the 10% Efficiency Barrier in Organic Photovoltaics: Morphology and Device Optimization of Well‐Known PBDTTT Polymers 下载免费PDF全文
With the advances in organic photovoltaics (OPVs), the invention of model polymers with superior properties and wide applicability is of vital importance to both the academic and industrial communities. The recent inspiring advances in OPV research have included the emergence of poly(benzodithiophene‐co‐thieno[3,4‐b]thiophene) (PBDTTT)‐based materials. Through the combined efforts on PBDTTT polymers, over 10% efficiencies have been realized recently in various types of OPV devices. This review attempts to critically summarize the recent advances with respect to five well‐known PBDTTT polymers and their design considerations, basic properties, photovoltaic performance, as well as device application in conventional, inverted, tandem solar cells. These PBDTTT polymers also make great contributions to the rapid advances in the field of emerging ternary blends and fullerene‐free OPVs with top performances. Addtionally, new challenges in developing novel photovoltaic polymers with more superior properties are prospected. More importantly, the research of highly efficient PBDTTT‐based polymers provides useful insights and builds fundamentals for new types of OPV applications with various architectures. 相似文献
992.
Swimming performance of silver eels is severely impaired by the swim-bladder parasite Anguillicola crassus 总被引:1,自引:0,他引:1
A.P. Palstra D.F.M. Heppener C. Székely 《Journal of experimental marine biology and ecology》2007,352(1):244-256
Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activities - related to parasite weight - reduce swimming endurance, while mechanical damage of the swim-bladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (< 0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (< 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds. 相似文献
993.
Quantifying nitrogen (N) fertiliser use efficiency (NFUE) in pastoral systems has important implications for fertiliser management
from both economic and environmental points of view. The potential of a decision tree approach for modelling NFUE in New Zealand
pastures was investigated. The decision tree model suggested that the time of applying N fertiliser was the most important
factor influencing NFUE, with August or September (early spring in New Zealand) being the best time of application. The interaction
of rainfall and temperature, rainfall, phosphorus (P) fertiliser history, soil Olsen P and slope were other important factors
influencing NFUE. The model was validated for 11 of the 16 trials tested with a predictive accuracy of 69%. The mechanisms
by which these factors influenced NFUE and the uncertainty associated with the model prediction were discussed. It was concluded
that this type of modelling approach can be used to predict NFUE and thereby to assist decisions on when and where to apply
N fertiliser in pastures for increasing productivity while reducing the environmental impact. 相似文献
994.
About 20-year-old desert plants of C4 species, Haloxylon ammodendron, growing at the southern edge of the Badain Jaran Desert in China, were selected to study the photosynthetic characteristics
and changes in chlorophyll fluorescence when plants were subject to a normal arid environment (AE), moist atmospheric conditions
during post-rain (PR), and the artificial supplement of soil water (SW). Results showed that under high radiation, in the
AE, the species down-regulated its net assimilation rate (A) and maximum photochemical efficiency of PS II (Fv/Fm), indicating photoinhibition. However, under the PR and SW environments,
A was up-regulated, with a unimodal diurnal course of A and a small diurnal change in Fv/Fm, suggesting no photoinhibition. When the air humidity or SW content was increased, the
light compensation points were reduced; light saturation points were enhanced; while light saturated rate of CO2 assimilation (A
max) and apparent quantum yield of CO2 assimilation (ΦC) increased. ΦC was higher while the A
max was reduced under PR relative to the SW treatment. It was concluded that under high-radiation conditions drought stress causes
photoinhibition of H. ammodendron. Increasing air humidity or soil moisture content can reduce photoinhibition and increase the efficiency of solar energy
use. 相似文献
995.
A controlled growth chamber experiment was conducted to investigate the short-term water use and photosynthetic responses
of 30-d-old carrot seedlings to the combined effects of CO2 concentration (50–1 050 μmol mol−1) and moisture deficits (−5, −30, −55, and −70 kPa). The photosynthetic response data was fitted to a non-rectangular hyperbola
model. The estimated parameters were compared for effects of moisture deficit and elevated CO2 concentration (EC). The carboxylation efficiency (α) increased in response to mild moisture stress (−30 kPa) under EC when
compared to the unstressed control. However, moderate (−55 kPa) and extreme (−70 kPa) moisture deficits reduced α under EC.
Maximum net photosynthetic rate (P
Nmax) did not differ between mild water deficit and unstressed controls under EC. Moderate and extreme moisture deficits reduced
P
Nmax by nearly 85 % compared to controls. Dark respiration rate (R
D) showed no consistent response to moisture deficit. The CO2 compensation concentration (Γ) was 324 μmol mol−1 for −75 kPa and ranged 63–93 μmol mol−1 for other moisture regimes. Interaction between moisture deficit and EC was noticed for P
N, ratio of intercellular and ambient CO2 concentration (C
i/C
a), stomatal conductance (g
s
), and transpiration rate (E). P
N was maximum and C
i/C
a was minimum at −30 kPa moisture deficit and at C
a of 350 μmol mol−1. The g
s and E showed an inverse relationship at all moisture deficit regimes and EC. Water use efficiency (WUE) increased with moisture
deficit up to −55 kPa and declined thereafter. EC showed a positive influence towards sustaining P
N and increasing WUE only under mild moisture stress, and no beneficial effects of EC were noticed at moderate or extreme moisture
deficits. 相似文献
996.
O. Urban A. Ač J. Kalina T. Priwitzer M. Šprtová V. Špunda M. V. Marek 《Photosynthetica》2007,45(3):392-399
Temperature responses of carbon assimilation processes were studied in four dominant species from mountain grassland ecosystem,
i.e. Holcus mollis (L.), Hypericum maculatum (Cr.), Festuca rubra (L.), and Nardus stricta (L.), using the gas exchange technique. Leaf temperature (T
L) of all species was adjusted within the range 13–30 °C using the Peltier thermoelectric cooler. The temperature responses
of metabolic processes were subsequently modelled using the Arrhenius exponential function involving the temperature coefficient
Q
10. The expected increase of global temperature led to a significant increase of dark respiration rate (R
D; Q
10 = 2.0±0.5), maximum carboxylation rate (V
Cmax; Q
10 = 2.2±0.6), and maximum electron transport rate (J
max; Q
10 = 1.6±0.4) in dominant species of mountain grassland ecosystems. Contrariwise, the ratio between J
max and V
Cmax linearly decreased with T
L [y = −0.884 T
L + 5.24; r
2 = 0.78]. Hence temperature did not control the ratio between intercellular and ambient CO2 concentration, apparent quantum efficiency, and photon-saturated CO2 assimilation rate (P
max). P
max primarily correlated with maximum stomatal conductance irrespective of T
L. Water use efficiency tended to decrease with T
L [y = −0.21 T
L + 8.1; r
2 = 0.87]. 相似文献
997.
We determined the interactive effects of irradiance, elevated CO2 concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3
levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m−2 s−1), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO2 concentrations (C
a), AC and EC (350 and 750 μmol mol−1, respectively). Rates of net photosynthesis (P
N) and transpiration (E) and stomatal conductance (g
s
) were measured, along with water use efficiency (WUE) and ratio of internal and external CO2 concentrations (C
i/C
a). P
N revealed an interactive effect between PAR and C
a. As PAR increased so did P
N under both C
a regimes. The g
s
showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters.
Maximum WUE occurred at 15 °C and 1 200 μmol m−2 s− 1 PAR under EC. The C
i
/C
a
was influenced independently by temperature and C
a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO2 concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on
P
N and WUE. 相似文献
998.
We compared delayed fluorescence (DF) excitation spectrometry with radiocarbon (14C) technique using a monoalgal culture of Chlorella vulgaris grown under natural temperature and irradiance. This was done by monitoring the DF, in parallel to quantum efficiency (QE)
and index of radiant energy utilization efficiency (Ψ) as calculated on the basis of carbon uptake measurements by radiocarbon
technique. During the diurnal cycle, temperature, irradiance, and chlorophyll (Chl) contents were monitored in the algal culture
that was kept in an open transparent plastic tank submerged at the surface of Lake Kinneret, Israel. The DF signal correlated
with both the QE (r
2 = 0.869, p<0.01) and Ψ (r
2 = 0.977, p<0.01) during a diurnal cycle. We suggest that, besides the measurement of active Chl and phytoplankton population composition,
the DF signal provides additional information on the QE and Ψ in phytoplankton population. 相似文献
999.
Photochemical efficiency, photosynthetic capacity, osmoprotectants, and relative water content (RWC) were recorded in saplings
of two evergreen plants (Boehmeria rugulosa Wedd. and Olea glandulifera Wall. ex G. Don) grown inside (GL) and outside (OP) a glasshouse during the winter season. The OP plants experienced 2.0–2.5 °C lower
air temperature and dew formation in comparison to GL plants. Diurnal observations indicated no change in RWC in the leaves
of GL and OP plants, while significant reduction in both transpiration and net photosynthetic (P
N) rates was observed in OP plants: the reduction in P
N was much more prominent as was also reflected by poor water use efficiency of these plants. Similarly, OP plants also showed
decrease in the apparent quantum yield and irradiance-saturated CO2 assimilation rate. The decrease in P
N was not associated with decreased stomatal conductance. However, a significant reduction in the ratio of variable to maximum
chlorophyll (Chl) fluorescence (Fv/Fm) and Chl content was recorded in the OP plants which also contained more total soluble saccharides but less proline contents.
The greater enhancement of P
N at 15 °C in comparison to measurements taken at 10 °C in OP plants over GL plants probably indicated an increase in mesophyll
capacity of the OP plants’ growth at increased temperature. Hence the enhanced growth and productivity of plants grown in
sheltered environments could be associated to their higher photosynthetic activity that may have important bearing on their
field establishment and productivity in the long run. The response varied with plant species; reduction in P
N was greater in B. rugulosa than in O. glandulifera. However, the recovery of OP plants in terms of Fv/Fm in the subsequent months revealed that photosynthetic system of these plants is revocable. 相似文献
1000.
以pUC19、pECBAC1、pCLD04541DNA以及3个不同大小的BACDNA为材料,研究了E.coli DH10B菌株在5个不同脉冲电场下的转化效率。研究发现,随着DNA片段大小的增加,最高转化效率和最适场强迅速减小。利用DH10B细胞转化pUC19 DNA的最适场强是21kV/cm,而190kb BAC DNA仅为13kV/cm;在最适场强下,40kb BAC DNA的转化效率约是190kb BAC DNA的50倍。通过大量数据绘制了不同因素影响下转化效率的变化曲线,优化了E.coli DH10B菌株电转化条件,为质粒的重组转化以及大片段基因组文库的构建奠定了基础。 相似文献