Gap Plots Research Articles

The incident photons cut-off energy, the optical linear equations and the electron phonon interactions in ZnO thin films annealed at different temperatures

The using RF-magnetron sputtering, the ZnO thin films were deposited on glass substrates at room temperature. Then using an electrical furnace in the presence of argon gas, they were annealed at different temperatures (400–600 °C). It was found that with taking Nc = 4, Za = 2, Ne = 8 for ZnO films for covalently bonded crystalline and amorphous chalcogenides, the constant β has values of about 0.37 ± 0.04 and for halides and most oxides that have ionic structure the constant β has values of about 0.26 ± 0.04 eV. It can be seen that with increasing annealing temperature absorption edge these films have a shifting behavior towards larger wavelength. Due to shifting behavior of defects distribution of atoms into films, the values of the cut-off energy, E cut-off and the λ cut-off of these films were about 3.48 eV and 355 nm, respectively. The ZnO films annealed at 500 °C specially above 3 eV have maximum value of optical density. The different linears fitting of ln (⍺) for films were obtained as y = Ex + F where 10<E < 12.5 and 14<F < 16. The ZnO films annealed at 600 °C have minimum value of electron phonon interaction (Ee-p) in a bout of 0.858 eV. The optical band gap and disordering energy plots of these films can be fitted by linear relationship EU and Eg = 0.0989–0.148 EU. We found that as deposited ZnO films have minimum value of steepness parameter σ in about of 30.93 × 10 −2eV.

Electrical, morphological, optical and mathematical simulations equations studies in CAZO, CZO, AZO and ZNO films

Purpose In this paper, it can be seen from AFM images of the as-deposited ZnO and CZO films, and the particle size and shape are not clear, while by increasing annealing temperature, they become distinguishable. By increasing temperature to 600°C, ZnO and CZO, CAZO and aluminum-doped zinc oxide (AZO) films particles became almost spherical. Due to high content of Cu in CZO target, and of Al in AZO target which was 5% weight ratio, doping plays a great role in the subject. Therefore, the annealing processing strongly affect the size and the shape of nanoparticles. Design/methodology/approach In this paper, the authors tried to study, in detail, nobel optical characterizations of ZnO films doped by transition metals in different annealing temperature. The authors found that the values of skin depth, optical density, electron–phonon interaction, steepness parameter, band tail width, direct and indirect carriers transitions and the dissipation factor, free carriers density and roughness of films affect the optical properties, especially the optical absorptions of ZnO films doped by transition metals. Also these properties were affected by annealing temperatures. The authors also found that topography characterizations strongly were affected by these parameters. Findings The CZO films have maximum value of coordination number ß, with considering NC = 4, Za = 2, Ne = 8. The CZO films annealed at 500 °C have maximum value of optical density. The as-deposited CAZO films have maximum value of steepness parameters in about of 0.13 eV. The as-deposited AZO films have maximum value of dispersion energy Ed in about of 5.75 eV. Optical gap and disordering energy plots of films can be fitted by linear relationships Eg = 0.49 + 0.2 EU and Eg = 0.52 + 0.5 EU, respectively. Originality/value With considering Nc = 4, Za = 2, Ne = 8 for ZnO films, coordination number ß has maximum value of 0.198. CZO nanocomposites films annealed at 500°C have maximum value of optical density. Different linear fitting of ln (α) for films were obtained as y = Ax + B where 5&lt;A &lt; 17 and 5&lt;B &lt; 12. As-deposited CAZO nanocomposites films have minimum value of electron phonon interaction in about of 4.91 eV. Optical gap and disordering energy plots can be fitted by linear relationships Eg = 0.49 + 0.2 EU and Eg = 0.52 + 0.5 EU for as-deposited films and films annealed at 500°C, respectively. Steepness parameters of as-deposited CAZO nanocomposites films have maximum value of 0.13 eV. Dispersion energy Ed for as-deposited AZO nanocomposites films has maximum value of 5.75 eV.

Bandgap engineering approach for designing CuO/Mn3O4/CeO2 heterojunction as a novel photocatalyst for AOP-assisted degradation of Malachite green dye

A ternary nanohybrid CuO/Mn3O4/CeO2 was developed in the present work using a co-precipitation-assisted hydrothermal method. The designed photocatalyst's structural, morphology, elemental composition, electronic states of elements, and optical properties were studied using corresponding analytical techniques. Results from PXRD, TEM/HRTEM, XPS, EDAX, and PL showed that the desired nanostructure had formed. Using Tauc's energy band gap plot, it was determined that the nanostructures band gap was ~ 2.44 eV, which showed the band margins of the various moieties, CeO2, Mn3O4, and CuO, had modified. Thus, improved redox conditions led to a substantial decrease in the recombination rate of electron–hole pairs, which was further explained by a PL study in that charge separation plays a key role. Under exposure to visible light irradiation for 60 min, it was revealed that the photocatalyst achieved 98.98% of photodegradation efficiency for malachite green (MG) dye. The process of photodegradation proceeded according to a pseudo-first-order reaction kinetic model with an excellent rate of reaction of 0.07295 min−1 with R2 = 0.99144. The impacts of different reaction variables, inorganic salts, and water matrices were investigated. This research seeks to create a ternary nanohybrid photocatalyst with high photostability, visible spectrum activity, and reusability up to four cycles.

Weak effects of birds, bats, and ants on their arthropod prey on pioneering tropical forest gap vegetation.

The relative roles of plants competing for resources versus top-down control of vegetation by herbivores, in turn impacted by predators, during early stages of tropical forest succession remain poorly understood. Here we examine the impact of insectivorous birds, bats, and ants exclusion on arthropods communities on replicated 5 × 5 m of pioneering early successional vegetation plots in lowland tropical forest gaps in Papua New Guinea. In plots from which focal taxa of predators were excluded we observed increased biomass of herbivorous and predatory arthropods, and increased density, and decreased diversity of herbivorous insects. However, changes in the biomass of plants, herbivores, and arthropod predators were positively correlated or uncorrelated between these three trophic levels and also between individual arthropod orders. Arthropod abundance and biomass correlated strongly with the plant biomass irrespective of the arthropods' trophic position, a signal of bottom-up control. Patterns in herbivore specialization confirm lack of a strong top-down control and were largely unaffected by the exclusion of insectivorous birds, bats, and ants. No changes of plant-herbivore interaction networks were detected except for decrease in modularity of the exclosure plots. Our results suggest weak top-down control of herbivores, limited compensation between arthropod and vertebrate predators, and limited intra-guild predation by birds, bats, and ants. Possible explanations are strong bottom-up control, a low activity of the higher order predators, especially birds, possibly also bats, in gaps, and continuous influx of herbivores from surrounding mature forest matrix.

Rodent-mediated plant seed dispersal: What happens to the seeds after entering the gaps with different sizes?

In general, it is accepted that gap formation significantly affects the placement of scatter‐hoarded seeds by small rodents, but the effects of different forest gap sizes on the seed‐eating and scatter‐hoarding behaviors of small rodents remain unclear. Thus, we examined the effects of a closed‐canopy forest, forest edge, and gaps with different sizes on the spatial dispersal of Quercus variabilis acorns and cache placement by small rodents using coded plastic tags in the Taihang Mountains, China. The seeds were removed rapidly, and there were significant differences in the seed‐eating and caching strategies between the stand types. We found that Q. variabilis acorns were usually eaten after being removed from the closed‐canopy forest and forest edges. By contrast, the Q. variabilis acorns in the forest gap stands were more likely to be scatter‐hoarded. The dispersal distances of Q. variabilis acorns were significantly longer in the forest gap plots compared with the closed canopy and forest edge plots. However, the proportion of scatter‐hoarded seeds did not increase significantly as the gap size increased. In small‐scale oak reforestation projects or research, creating small gaps to promote rodent‐mediated seed dispersal may effectively accelerate forest recovery and successional processes.

Calibrating Wiedemann-99 Model Parameters to Trajectory Data of Mixed Vehicular Traffic

We propose a new methodology for calibrating Wiedemann-99 vehicle-following parameters for mixed traffic (different conventional vehicle classes) based on trajectory data. The existing acceleration equations of the Wiedemann model are modified to represent more realistic driving behavior. Exploratory analysis of simulation data revealed that different Wiedemann-99 model parameters could lead to similar macroscopic behavior, highlighting the importance of calibration at the microscopic level. Therefore, the proposed methodology is based on optimizing performance measures at the microscopic level (acceleration, speed, and trajectory profiles) to estimate suitable calibration parameters. Further, the goodness of fit for the observed data is sensitive to the numerical integration method used to compute vehicles’ velocity and position. We found that the calibrated parameters using the proposed methodology perform better than other approaches for calibrating mixed traffic. The results reveal that the calibrated parameter values and, consequently, the thresholds that delineate closing, following, emergency braking, and opening regimes, vary between two-wheelers and cars. The window (in the relative speed versus gap plot) for the unconscious following is larger for cars while the free-flow regime is more extensive for two-wheelers. Moreover, under the same relative speed and gap stimulus, two-wheelers and cars may be in different regimes and display different acceleration responses. Thus, accurate calibration of each vehicle’s parameters is essential for developing micro-simulation models for mixed traffic. The calibration analysis results of strict and overlapping staggered car following signify an impact of staggered car following compared with strict car following which demands separate calibration for strict and staggered following.

Fabrication of Zinc Oxide Nanoparticles by pulsed laser ablation in liquid – PLAL and Study their physical Properties

ZnO NPs are manufactured using pulsed laser ablation in double distilled water (DDW). Nd:Yag laser used as a source of energy for this research by immersing the zinc-target in DDW water. The glass container with laser pulses was rotated to prevent etching effect and getting homogenous distribution particles. By changing the parameters (laser energy and number of pulses), the results were collected and examined using an ultra violet-visible spectrum and electron scanning microscope. The calculations revealed the colloidal spherical shape and the homogeneous structure for the ZnO NPs. The band gap plot display varies in the band gap proportional with particle size, this result agree with effective mass model.

When is a Match Sufficient? A Score-based Balance Metric for the Synthetic Control Method

Abstract In some applications, researchers using the synthetic control method (SCM) to evaluate the effect of a policy may struggle to determine whether they have identified a “good match” between the control group and treated group. In this paper, we demonstrate the utility of the mean and maximum Absolute Standardized Mean Difference (ASMD) as a test of balance between a synthetic control unit and treated unit, and provide guidance on what constitutes a poor fit when using a synthetic control. We explore and compare other potential metrics using a simulation study. We provide an application of our proposed balance metric to the 2013 Los Angeles (LA) Firearm Study [9]. Using Uniform Crime Report data, we apply the SCM to obtain a counterfactual for the LA firearm-related crime rate based on a weighted combination of control units in a donor pool of cities. We use this counterfactual to estimate the effect of the LA Firearm Study intervention and explore the impact of changing the donor pool and pre-intervention duration period on resulting matches and estimated effects. We demonstrate how decision-making about the quality of a synthetic control can be improved by using ASMD. The mean and max ASMD clearly differentiate between poor matches and good matches. Researchers need better guidance on what is a meaningful imbalance between synthetic control and treated groups. In addition to the use of gap plots, the proposed balance metric can provide an objective way of determining fit.

First-principle calculations of structural and optoelectronic properties of cubic CdxZn1−xSySe1−y quaternary alloys with modified Becke–Johnson (mBJ) functional

First-principle calculations in association with modified Becke–Johnson (mBJ-GGA) potentials have been performed on optoelectronic properties of CdxZn1−xSySe1−y quaternary alloys. Each semiconductor specimen within this quaternary system is a direct band gap (Γ–Γ) semiconductor. An increase in anionic (S) concentration y results in nonlinear decrease in lattice constant and increase in bulk modulus and fundamental band gap (Eg) at each cationic (Cd) concentration x. In contrast, reverse trend is observed in cationic concentration (x) dependence of each of these parameters at each anionic concentration (y). Calculated lattice constant and band gap versus concentrations (x, y) contour plots are useful in designing new quaternary alloys with targeted optoelectronic properties. An increase in calculated Eg results in decrease in each of the calculated static dielectric constant $$ \varepsilon_{1} (0) $$ , static refractive index n(0), static reflectivity R(0) and vice versa. On the other hand, an increase in calculated Eg results in the enhancement in calculated critical point energy (Ec) in each of the imaginary dielectric function $$ \varepsilon_{2} (\omega ) $$ , extinction coefficient $$ k(\omega ) $$ , optical conductivity $$ \sigma (\omega ) $$ , absorption $$ \alpha (\omega ) $$ spectra and vice versa. Calculations have also shown that zinc blende GaAs and ZnSe are suitable substrates for the growth of several CdxZn1−xSySe1−y quaternary alloys.

A DFT-D2 study on Mo4-xCox (x = 0–3) cluster-decorated graphene and the adsorption of SO2F2 and SOF2 on Mo4-decorated graphene

The current study reports a detailed investigation of the adsorption behavior of Mo4, Mo3Co, Mo2Co2, and MoCo3 clusters on graphene by studying their binding energy, charge transfer, band gap, electron density difference plots, and density of states (DOS) plots. The magnetic properties of these surfaces have also been reported. Owing to the strong adsorption power of small metal cluster-decorated graphene surfaces, we have further utilized the Mo4-decorated graphene for the adsorption of SO2F2 and SOF2 gases, which are two gases that are released from the decomposition of SF6, a gas used as an insulating medium in gas-insulated switchgear. The use of Mo4-decorated graphene surface resulted in the dissociative adsorption of these gases with high adsorption energy and large charge transfer. In contrast, only physisorption occurred on pristine graphene. Further details of the adsorption were investigated by studying the DOS and partial DOS (PDOS) plots before and after adsorption. The band gap and electron density difference plots have also been reported. Graphical abstract

Soil and Nutrient Cycling Responses in Riparian Forests to the Loss of Ash (Fraxinus spp. L) from Emerald Ash Borer (Agrilus planipennis, Fairmaire)

Emerald ash borer (EAB) is an alien invasive species that is spreading across Canada and the United States killing ash trees. In riparian forests where ash may be abundant; loss of ash can induce significant structural changes; including the creation of canopy gaps; changes in light penetration; expansion of ground vegetation; and alteration of soil nitrogen and carbon cycling. In 2014 and 2015, we examined the effects of EAB-caused gaps in riparian forests on soil nutrient dynamics. Two sites with different infestation timelines, a “new” site (mortality in past 2–3 years) and an “old” site (infested 10 years previous) were selected to determine temporal differences in effects of canopy gaps created by ash loss on litterfall, herbaceous ground vegetation, and soil nutrient cycling. Within both sites, plots with clustered dead ash (canopy gap plots—CG) were paired with nearby plots of full canopy and no ash (canopy closed plots—CC), and differences between paired plots determined. Total litterfall was observed at all sites but was only significant at the new infestation site. Reductions in leaf litter deposition in CG plots resulted in reduced N and C flux to the forest floor but soil C and N concentrations, and nitrogen mineralization rates, were not significantly different between CG and CC plots. Nitrate concentration in soil solution was significantly greater in CG plots compared to CC plots at the new infestation sites but showed the opposite trend at the old infestation sites. Herbaceous ground vegetation biomass was significantly greater (up to 10×) in CG plots than in CC plots. Overall, despite changes to riparian forest canopy structure and litterfall, there was no significant difference in soil nutrient cycling between EAB-induced canopy gaps and closed canopy plots after 10 years, suggesting a high resilience of riparian forest soils to EAB infestation

Molecular Docking of a Bio Material [1-{[(Z)-Cyclopentylidene] Amino}-3-Phenylthiourea] by First Principles Study

Molecular Docking and complete quantum chemical studies of 1-{[(Z)-Cyclopentylidene] amino}-3-phenylthiourea have been done by using DFT/ B3LYP method and 6-311 G (d, p) as the basis set. We have compared optimized geometry of title molecule with experimental data. A detailed interpretation of the vibrational assignments of title molecule is reported. Molecular Electrostatic Potential (MESP) generated by a chemical species is widely used as a tool for exploring its properties and locating potential sites for interaction with other moieties. Nonlinear optics (NLO) is the branch of optics that describes the behavior of materials in nonlinear media. In quantum chemistry, a natural bond orbital or NBO is a calculated bonding orbital with maximum electron density. Time-dependent density functional theory (TDDFT) is a quantum mechanical theory used in physics and chemistry to investigate the properties and dynamics of many-body systems in the presence of time-dependent potentials, such as electric or magnetic fields.The electronic properties of title molecule are discussed with help of molecular FHOMO, FLUMO composition, band gap, and MESP plots. The NLO, NBO, UV spectra of title molecule also calculated with same level of theory. Some biological parameter Log P and Log S are also calculated which suggests that the title molecule have good ability to deliver drugs in various diseases.

How forest gaps shaped plant diversity along an elevational gradient in Wolong National Nature Reserve?

Understanding the underlying ecological processes that control plant diversity within (α-diversity) and among (β-diversity) forest gaps is important for managing natural forest ecosystems, and it is also a prerequisite for identifying the formation and maintenance mechanisms of forest plant communities. In this study, we focused on the interrelationships among habitat type (gap/non-gap plots), gap size, elevation and environmental factors, and we explored their effects on plant diversity (α-diversity and β-diversity). To do this, a total of 21 non-gap (i.e., closed canopy) plots (100 m2) and 63 gap plots, including 21 with large gaps (200–410 m2), 21 with medium gaps (100–200 m2) and 21 with small gaps (38.5–100 m2), were selected along an elevational gradient in a subalpine coniferous forest of southwestern China. Using structural equation models (SEMs), we analyzed how forest gaps affected plant diversity (α-diversity and β-diversity) along an elevational gradient. The results showed that (1) as elevation increased, unimodal patterns of α-diversity were found in different-sized gaps, and β-diversity showed a consistent sinusoidal function pattern in different-sized gaps. The gap size was positively related to α-diversity, but this effect disappeared above 3500 masl. Moreover, the patterns of α-diversity and β-diversity in non-gap plots were irregular along the elevational gradient. (2) SEMs demonstrated that many environmental factors, such as the annual mean air temperature (AMAT), ultraviolet-A radiation (365 nm, UV-A365), ultraviolet-B1 radiation (297 nm, UV-B297), moss thickness (MT), soil carbon/nitrogen ratio (C/N ratio), NH4-N and NO3-N, were significantly affected by elevation, which then affected α-diversity and β-diversity. The photosynthetic photon flux density (PPFD), UV-A365 and UV-B297 were significantly higher in plots with forest gaps than in the non-gap plots. Moreover, the PPFD and UV-A365 were positively and directly affected by gap size. Surprisingly, except for the NH4-N and the C/N ratios, the below-ground environmental factors showed little or no relationships with forest gaps. All of these effects contributed to plant diversity. Overall, the above-ground environmental factors were more sensitive to gap-forming disturbances than the below-ground environmental factors, which affected α-diversity and β-diversity. The predicted pathway in the SEMs of the elevational effects on α-diversity and β-diversity was relatively complicated compared with the effects of forest gaps. These results can provide valuable insights into the underlying mechanisms driving the diversity-habitat relationship in the subalpine coniferous forests of southwestern China.

林窗尺度对侧柏人工林土壤微生物量和功能多样性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 林窗尺度对侧柏人工林土壤微生物量和功能多样性的影响 DOI: 10.5846/stxb201605261016 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"973"重点基础研究发展计划项目（2012CB416904）；国家林业公益性行业科研专项（201104075）；江苏省高校优势学科建设工程项目资助（PAPD） Effects of forest gap size on the biomass and functional diversity of soil microbes in Platycladus orientalis plantations Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:微生物活性是影响土壤碳循环等地下生态系统过程的重要因素。以徐州市侧柏（Platycladus orientalis （L.） Franco）人工林为研究对象，以未受干扰的侧柏林为对照（CK），设置半径分别为4、8、12m的3种尺度近圆形林窗，从林窗边缘（D1）到距林缘4m （D2）及8m处林下（D3）水平梯度上分析土壤微生物量碳（MBC）、氮（MBN）和代谢功能多样性的变化。结果表明：1）与CK相比，林窗样地土壤MBC总体降低，MBN含量显著下降（P<0.05），MBC/MBN显著上升（P<0.05）。在3种尺度林窗中，MBC在大林窗偏小，MBN在小林窗偏小；MBC/MBN总体上随林窗尺度增大而减小。2）与CK相比，大中林窗降低了土壤微生物代谢活性（AWCD），小林窗变化不大。从D1到D3点，小林窗的AWCD先降后升，中林窗呈上升趋势，大林窗则相反。而且林窗降低了土壤微生物对各类碳源的利用，主要利用聚合物类和氨基酸类碳源，中林窗样点对碳水化合物和氨基酸类小分子碳源的利用最低。3）林窗总体提高了土壤微生物功能多样性，其中多样性（H'）、丰富度（S）和均匀度（E）3个指数在各点之间均无显著差异，小林窗和CK的优势度指数（Ds）显著大于（P<0.05）大林窗。侧柏林人工林窗对土壤微生物量和功能多样性的影响有着明显的尺度和位置梯度效应，林窗有望促进侧柏林土壤碳固持和大分子物质降解，提高其应对全球气候变化的能力，综合而言，中尺度林窗对侧柏林生态功能的发挥较为有利。 Abstract:The metabolic activity of microbes profoundly influences underground ecological processes, similar to the soil carbon cycle. However, even though forest gap research has addressed underground processes, studies of microbial functional diversity remain scarce. In the present study, we mainly investigated changes in the microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial functional diversity (AWCD) of the soil along a horizontal gradient of large, medium, and small forest gaps (radii of 4, 8, and 12m, respectively) in a plantation of Platycladus orientalis (L.) Franco in Xuzhou (China) during the summer. The corresponding gap sizes, which were calculated as the ratio of gap radius to the height of trees at the edge of the gap, were 1.5, 1, and 0.5, respectively. Three forest gap gradients, namely, forest gap edge (D1), 4m outside the gap (D2), and 8m outside the gap (D3), were chosen. After forest gap formation, soil MBC decreased on the whole and MBN decreased significantly (P<0.05), where as the MBC/MBN ratio increased significantly (P<0.05). Among the three gap types, the MBC and MBN were lowest in the large and small gaps, respectively, with minimum levels of 2069.42 and 126.21mg/kg. Meanwhile, the MBC/MBN ratio varied from 10.50 to 19.96 and generally decreased with increasing gap size. In addition, forest gaps reduced soil AWCD, and the effect size varied with gap size, with the smallest effects observed in the small gaps. From D1 to D3, the AWCD of the small gaps initially declined and then increased, whereas it continuously increased in the medium gaps and continuously decreased in the large gaps. Furthermore, forest gaps also reduced the carbon consumption of soil microbes, and the use of carbohydrates and amino acids was the lowest in the medium gaps, whereas that of polymers was the highest in the medium and small gaps. In D1, the soil microbes consumed less carbon in the medium gaps than in the small gaps. The present study also revealed that forest gaps improved microbial functional diversity. Although there were no significant differences between the diversity (H'), richness (S), and evenness (E) indices of the three gradients, the dominance index (Ds) values of D3 and D1 were significantly higher in the small gap and control plot and were significantly greater than those of D1 and D2 in the large gap (P<0.05). The effect of forest gap on the diversity indices varied with gap scale and location. The main carbon sources used by the soil microbes were polymers and amino acids. In short, the effect size of forest gap on soil MBC, MBN, and microbial functional diversity in P. orientalis plantations vary remarkably with scale. Therefore, forest gaps can promote soil carbon sequestration and macromolecular substances degradation and improve the ability of forest ecosystems to adapt to global climate change. Furthermore, medium gaps were the most efficient for improving the ecological function of forest plantations. 参考文献 相似文献 引证文献

Density functional theory design D-D-A type small molecule with 1.03 eV narrow band gap: effect of electron donor unit for organic photovoltaic solar cell

ABSTRACTSix new low-band-gap copolymers of donor–donor–acceptor (D-D-A) architecture have been designed using density functional theory and time-dependent density functional theory methods in order to use them in organic photovoltaic cell (OPVC). Phenanthro[3,4-d:9,10-d′]bis([1,2,3]thiadiazole)-10,12-dicarbonitrile moiety has been used as an acceptor for all compounds. We insert benzo[1,2-b:4,5-b′]dithiophene and N,N-diphenylbenzo[1,2-b:4,5-b′]dithiophen-2-amine units as donor to complete designing of copolymers. In order to tuning the optical and electronic properties, we have modified the donor unit by substituted with amine, methoxyamine, N-methylenethiophen-2-amine, methoxy, alkoxy moieties. The band gap (Eg), HOMO and LUMO values and plots, open circuit voltage (VOC) as well as optical properties have been analysed for designed copolymers. The optimised copolymers exhibit low-band-gap lying in the range of 1.03–2.24 eV. DPTD-6 copolymer presents the optimal properties to be used as an active layer due to its low Eg (1.03 eV) and a moderate VOC (0.56 eV). Thus, OPVC based on this copolymer in bulk-heterojunction composites with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an acceptor has been modelled. Eg and VOC values of composite material DPTD-6:PCBM are found as 1.32 and 0.65 eV, respectively. A model band diagram has been established for OPVC, simulating the energy transfer between active layers.

The effect of interspecific variation in photosynthetic plasticity on 4-year growth rate and 8-year survival of understorey tree seedlings in response to gap formations in a cool-temperate deciduous forest.

Gap formation increases the light intensity in the forest understorey. The growth responses of seedlings to the increase in light availability show interspecific variation, which is considered to promote biodiversity in forests. At the leaf level, some species increase their photosynthetic capacity in response to gap formation, whereas others do not. Here we address the question of whether the interspecific difference in the photosynthetic response results in the interspecific variation in the growth response. If so, the interspecific difference in photosynthetic response would also contribute to species coexistence in forests. We also address the further relevant question of why some species do not increase their photosynthetic capacity. We assumed that some cost of photosynthetic plasticity may constrain acquisition of the plasticity in some species, and hypothesized that species with larger photosynthetic plasticity exhibit better growth after gap formation and lower survivorship in the shade understorey of a cool-temperate deciduous forest. We created gaps by felling canopy trees and studied the relationship between the photosynthetic response and the subsequent growth rate of seedlings. Naturally growing seedlings of six deciduous woody species were used and their mortality was examined for 8 years. The light-saturated rate of photosynthesis (Pmax) and the relative growth rate (RGR) of the seedlings of all study species increased at gap plots. The extent of these increases varied among the species. The stimulation of RGR over 4 years after gap formation was strongly correlated with change in photosynthetic capacity of newly expanded leaves. The increase in RGR and Pmax correlated with the 8-year mortality at control plots. These results suggest a trade-off between photosynthetic plasticity and the understorey shade tolerance. Gap-demanding species may acquire photosynthetic plasticity, sacrificing shade tolerances, whereas gap-independent species may acquire shade tolerances, sacrificing photosynthetic plasticity. This strategic difference among species would contribute to species coexistence in cool-temperate deciduous forests.

Surface fuels in recent Phytophthora ramorum created gaps and adjacent intact Quercus agrifolia forests, East Bay Regional Parks, California, USA

Phytophthora ramorum, cause of “sudden oak death” or SOD, has had significant impacts on composition and structure in coastal forests of central and northern coastal California and southwestern Oregon. Despite the proximity of susceptible coast live oak (Quercus agrifolia) forests to densely populated urban areas, the impacts of SOD on their fuels have not been studied. We sampled surface fuels and vegetation structure in 16 plots in both SOD-caused gaps and intact stands (32 plots total) across two parks in the East Bay Regional Park District, east of San Francisco Bay. Plots were selected from a set of randomly placed pre-existing locations used in determining the disease distribution and intensity across the park system. Among the vegetation characteristics examined, only coast live oak basal area and live and dead tree density, canopy cover and maximum forb height differed between SOD created gap plots and adjacent intact forest plots. However, surface fuels such as vegetation cover, litter cover, wood cover, duff depth, fuels height, ladder fuels abundance, 1h, 10h, 100h, and 1000h fuels were greater in gap plots than intact forest plots. Although no fire behavior models were run, surface fuels suggest SOD created gaps may facilitate passive crown fire due to increased ladder and other fuels. This study represents a spatially explicit (gap focused) point-in-time estimate of surface fuels that will continue to change through time as disease progresses through these stands causing vegetation changes as fuels accumulate and decompose.

Optical transmission matrix as a probe of the photonic strength

We demonstrate that optical transmission matrices (TM) of disordered complex media provide a powerful tool to extract the photonic interaction strength, independent of surface effects. We measure TM of strongly scattering GaP nanowires and plot the singular value density of the measured matrices and a random matrix model. By varying the free parameters of the model, the transport mean free path and effective refractive index, we retrieve the photonic interaction strength. From numerical simulations we conclude that TM statistics is hardly sensitive to surface effects, in contrast to enhanced backscattering or total transmission based methods.

Effects of forest gap size on the growth and form quality of Taxus wallichina var. mairei in Cunninghamia lanceolata forests

In order to clarify the effects of forest gap size on the growth and stem form quality of Taxus wallichina var. mairei and effectiveness of the precious timbers cultivation, 25 sample plots in Cunninghamia lanceolata forest gaps were established in Mingxi County, Fujian Province, China to determine the indices of the growth, stem form and branching indices of T. wallichina var. mairei seedlings. The relationships between the gap size and growth, stem form and branching were investigated. The 25 sample plots were located at five microhabitats which were classified based on gap size as follows: Class1, 2, 3, 4 and 5, which had a gap size of 25-50 m2, 50-75 m2, 75-100 m2, 100-125 m2 and 125-150 m2, respectively. The evaluation index system of precious timbers was built by using hierarchical analysis. The 5 classes of forest gaps were evaluated comprehensively by using the multiobjective decision making method. The results showed that gap size significantly affected 11 indices, i.e., height, DBH, crown width, forking rate, stem straightness, stem fullness, taperingness, diameter height ratio, height under living branch, interval between branches, and max-branch base diameter. Class1and 2 both significantly promoted the growth of height, DBH and crown width, and both significantly inhibited forking rate and taperingness, and improved stem straightness. Class2 significantly improved stem fullness and diameter height ratio. Class1and 2 significantly improved height under living branch and reduced max-branch base diameter. Class 1 significantly increased interval between branches. Class1and2 significantly improved the comprehensive evaluation score of precious timbers. This study suggested that controlled cutting intensity could be used to create forest gaps of 25-75 m2, which improved the precious timber cultivating process of T. wallichina var. mairei in C. lanceolata forests.

The effect of treefall gaps on the understorey structure and composition of the tropical dry forest of Nizanda, Oaxaca, Mexico: implications for forest regeneration

Abstract:The role of canopy gaps in tropical dry forest (TDF) dynamics remains unclear. Here, 75 canopy gaps, mostly formed by the fall of Bursera spp. and Pachycereus pecten-aboriginum individuals, are described, and their potential consequences for forest regeneration are analysed in a Mexican TDF. In 50 randomly selected gaps, understorey vegetation was sampled with a paired design (inside and outside gaps) and by distinguishing two plant height categories. In total, 1940 plants were recorded (63% in gaps and 37% in non-gap plots). Community attributes (density, community cover, taxonomic richness and Shannon diversity) were significantly higher for both height categories in gap plots. Conversely, neither an NMDS ordination nor a multinomial classification of 187 species by habitat affinities revealed floristic segregation between gaps and non-gaps; almost all species were classified as habitat generalists, with only a few opportunistic forbs (but no single tree species) being classified as gap specialists. The most important effects of gap formation are significant increases in plant abundance and species richness, but not a different species composition. Against earlier views that gap-phase dynamics is inconsequential for TDF dynamics, these results suggest a more active, albeit modest, role of treefall gaps in TDF, through promoting an abundant establishment.