Scaling relationships between the total number of leaves and the total leaf area per culm of two dwarf bamboo species.

Total leaf area per plant is an important measure of the photosynthetic capacity of an individual plant that together with plant density drives the canopy leaf area index, that is, the total leaf area per unit ground area. Because the total number of leaves per plant (or per shoot) varies among conspecifics and among mixed species communities, this variation can affect the total leaf area per plant and per canopy but has been little studied. Previous studies have shown a strong linear relationship between the total leaf area per plant (or per shoot) (A T) and the total number of leaves per plant (or per shoot) (N T) on a log-log scale for several growth forms. However, little is known whether such a scaling relationship also holds true for bamboos, which are a group of Poaceae plants with great ecological and economic importance in tropical, subtropical, and warm temperate regions. To test whether the scaling relationship holds true in bamboos, two dwarf bamboo species (Shibataea chinensis Nakai and Sasaella kongosanensis 'Aureostriatus') with a limited but large number of leaves per culm were examined. For the two species, the leaves from 480 and 500 culms, respectively, were sampled and A T was calculated by summing the areas of individual leaves per culm. Linear regression and correlation analyses reconfirmed that there was a significant log-log linear relationship between A T and N T for each species. For S. chinensis, the exponent of the A T versus N T scaling relationship was greater than unity, whereas that of S. kongosanensis 'Aureostriatus' was smaller than unity. The coefficient of variation in individual leaf area increased with increasing N T for each species. The data reconfirm that there is a strong positive power-law relationship between A T and N T for each of the two species, which may reflect adaptations of plants in response to intra- and inter-specific competition for light.

Inequality Measure of Leaf Area Distribution for a Drought-Tolerant Landscape Plant.

Measuring the inequality of leaf area distribution per plant (ILAD) can provide a useful tool for quantifying the influences of intra- and interspecific competition, foraging behavior of herbivores, and environmental stress on plants' above-ground architectural structures and survival strategies. Despite its importance, there has been limited research on this issue. This paper aims to fill this gap by comparing four inequality indices to measure ILAD, using indices for quantifying household income that are commonly used in economics, including the Gini index (which is based on the Lorenz curve), the coefficient of variation, the Theil index, and the mean log deviation index. We measured the area of all leaves for 240 individual plants of the species Shibataea chinensis Nakai, a drought-tolerant landscape plant found in southern China. A three-parameter performance equation was fitted to observations of the cumulative proportion of leaf area vs. the cumulative proportion of leaves per plant to calculate the Gini index for each individual specimen of S. chinensis. The performance equation was demonstrated to be valid in describing the rotated and right shifted Lorenz curve, given that >96% of root-mean-square error values were smaller than 0.004 for 240 individual plants. By examining the correlation between any of the six possible pairs of indices among the Gini index, the coefficient of variation, the Theil index, and the mean log deviation index, the data show that these indices are closely related and can be used interchangeably to quantify ILAD.

Impact of government budget on health prepayment levels: evidence from OECD countries.

BACKGROUND: Health prepayment, a key indicator under the Sustainable Development Goals monitoring framework, is strongly associated with household financial protection; however, the impact of government health budget on the level of prepayment has rarely been discussed. AIMS: To address the following research questions. (1) Does a higher government health budget translate into higher prepayment rates in the healthcare financing system? (2) What are the effects of government health budget on public prepayment and private prepaid plans? (3) What are the heterogeneities between groups of countries with different income levels and public health prepayment systems? METHODS: Analysis of panel co-integration, impulse response function, and variance decomposition were conducted in 34 Organisation for Economic Co-operation and Development (OECD) members for the period 1995-2016. RESULTS: Government health budget has a long-running equilibrium relationship with the level of public and total prepayment. However, a stable relationship could not be confirmed with private prepaid plans. Moreover, government health budget played a significant positive role in explaining the fluctuations in the total and public prepayments over a long time, that is, 51 and 37 periods, respectively. Considering differences between groups of countries, the impacts are greater for those with higher income levels and more public-dominated health-financing systems. CONCLUSIONS: Government health budget has a long-time relationship with the levels of both total prepaid expenditure and public prepayment. By contrast, it does not systematically crowd out private prepaid plans.

Theoretical estimation of size effects on the electronic transport in tailored graphene nanoribbons.

Focusing on the potential applications of tailored graphene nanoribbons (t-GNRs), in this work, we systematically study size effects on the electronic transport in t-GNR-based molecular junctions. As a result of the manufacturing error generated during the processing or synthesis of t-GNRs using techniques such as ion beam lithography, the final dimensions of the as-fabricated devices often deviate from the design values, giving rise to a size distribution around the mean value which could considerably affect the device performance. To simulate the effects of the manufacturing error, a series of t-GNR-based junctions with various dimensions have been modelled and systematically investigated using density functional theory (DFT) coupled with the non-equilibrium Green's function (NEGF). For junctions that consist of an acene chain connected with two graphene nanosheets, it is found that the chain length has little influence on the electronic transport and that, on the other hand, the junction conductivity is significantly altered by its width due to the different number and nature of the electron transfer pathways. Furthermore, increasing the width of the junction leads to a clear odd-even variation of decreasing amplitude in its transport behavior. These findings underpin further fundamental and device-based studies of t-GNRs.

Electronic and transport properties of graphene nanoflakes with the protrusion of different widths.

Theoretical investigation on the transport properties of graphene nanoflakes (GNFs) with protrusions has been performed with density-functional calculations by considering the influence of the structural symmetry. It is found that GNFs with different widths of protrusions exhibit distinctly different transport properties, depending on whether they are mirror symmetric with respect to the midplane (σ) between the two edges. For the symmetric models, electrons primarily pass through the edges of the GNFs with a small transmission probability. On the contrary, the electrons prefer to transit along one side of the GNFs with a high probability in the asymmetric models. Therefore, the conductivity of asymmetric models is greater than that of symmetric models.

Intrinsic electronic and transport properties of graphene nanoribbons with different widths.

The intrinsic electronic and transport properties of a series of zigzag graphene nanoribbons (ZGNRs) have been investigated systematically using density functional theory coupled with the non-equilibrium Green's function (NEGF) method. It is found that ZGNRs with various ribbon widths have completely different transport properties under bias, depending on whether the number of zigzag chains is odd or even. ZGNRs with odd number except 1-ZGNR possess small current regardless of the bias applied. In contrast, ZGNRs with even number have much larger current and behave as a resistor having a linear current-voltage relationship. The results also reveal that the narrow ZGNRs, e.g., 1-ZGNR and 2-ZGNR, have different transport behaviors, which are governed by the edge-effect and the unique electronic structure.

Wearable strain sensor based on highly conductive carbon nanotube/polyurethane composite fibers.

Highly conductive and stretchable fibers have recently attracted increasing attention owing to their potential for application in flexible wearable electronics. Carboxylated carbon nanotubes (c-CNTs) are coated onto flexible fibers as a convenient way of fabricating wearable strain sensors. However, the conductivity of a c-CNT is reduced due to the destruction of the graphitized structure of the CNT during carboxylation. It still remains a significant challenge to endow c-CNT composite fibers with high conductivity. In this study, highly conductive fibers were prepared by coating metal ion-linked c-CNTs onto polyurethane (PU) fibers in order to improve the electron transport rate between the c-CNTs. The metal-coordination junctions formed by Fe2+ ions and carboxyl significantly enhanced the conductivity of the PU/CNT@Fe2+ fibers (up to 72 S m-1). The high conductivity is the result of coordination junctions with strong electronic state coupling facilitating electron transport, which was proved by density functional theory calculations. The resulting coordination effect enhanced the interaction between the c-CNTs, which made the conductive network more flexible. The strain sensor based on PU/CNT@Fe2+ fibers exhibited high sensitivity (gauge factor = 36 at 50% strain), a large strain range, inconspicuous drift and durability. The fibrous strain sensor was successfully used to monitor joint movement and facial expression.