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Miscanthus sinensis is a C4 perennial grass species that is widely used as forage, ornamental grass and bioenergy crop due to its broad adaption and great biological traits. Recent studies indicated that M. sinensis could also grow in marginal lands which were contaminated with heavy metals, and exhibited important ecological restoration potential. In this study, transcriptome characterization of candidate genes related to chromium (Cr) uptake, transport and accumulation in M. sinensis were employed to investigate the molecular mechanism of plant tolerance to heavy metal stress. The result showed that following treatment of 200 mg/L of Cr, plant roots could accumulate most Cr and localize mainly in cell walls and soluble fractions, whereas Cr in stems and leaves was primarily in soluble fractions. A total of 83,645 differentially expressed genes (DEGs) were obtained after the treatment. Many genes involved in heavy metal transport, metal ion chelation and photosynthesis were found to be Cr-induced DEGs. Co-expression and weighted correlation network analysis revealed that Glutathion metabolism and ABC transporters pathways play an important role in Cr tolerance of M. sinensis. A hypothesis schematic diagram for the Cr uptake, transport and accumulation of M. sinensis cells were suggested, which could provide a molecular and genetic basis for future candidate genes validation and breeding of such crops.

Chromium (Cr) is a heavy metal in nature, which poses a potential risk to toxicity to both animals and plants when releasing into the environment. However, the regulation of microRNA (miRNA)-mediated response to heavy metal Cr has not been studied in Miscanthus sinensis. In this study, based on high-throughput miRNA sequencing, a total of 104 conserved miRNAs and 158 nonconserved miRNAs were identified. Among them, there were 45 differentially expressed miRNAs in roots and 13 differentially expressed miRNAs in leaves. The hierarchical clustering analysis showed that these miRNAs were preferentially expressed in a certain tissue. There were 833 differentially expressed target genes of 45 miRNAs in roots and 280 differentially expressed target genes of 13 miRNA in leaves. After expression trend analysis, five significantly enriched modules were obtained in roots, and three significantly enriched trend blocks in leaves. Based on the candidate gene annotation and gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) function analysis, miR167a, novel_miR15, and novel_miR22 and their targets were potentially involved in Cr transportation and chelation. Besides, miR156a, miR164, miR396d, and novel_miR155 were identified as participating in the physiological and biochemical metabolisms and the detoxification of Cr of plants. The results demonstrated the critical role of miRNA-mediated responses to Cr treatment in M. sinensis, which involves ion uptake, transport, accumulation, and tolerance characteristics.

NAC is one of the largest family of plant-specific transcription factors, and it plays important roles in plant development and stress responses. The study identified 72 LpNACs genes from the perennial ryegrass genome database. Gene length, MW and pI of NAC family transcription factors varied, but the gene structure and motifs were relatively conserved in bioinformatics analysis. Phylogenetic analyses of perennial ryegrass, rice and Arabidopsis were performed to study the evolutionary and functional relationships in various species. The expression of LpNAC genes that respond to various abiotic stresses including high salinity, ABA, high temperature, polyethylene glycol (PEG) and heavy metal was comprehensively analyzed. The present study provides a basic understanding of the NAC gene family in perennial ryegrass for further abiotic stress studies and improvements in breeding.

Quantitative real-time PCR (qRT-PCR) has been widely used for studying gene expression at the transcript level. Its accuracy usually relies on the reference genes that are utilized for data normalization. Miscanthus sinensis, a perennial C4 grass with high biomass and strong resistance to adversities, is often utilized as a high value energy crop. However, no reliable reference genes have been investigated for normalizing gene expression for this species. In this study, 12 candidate reference genes were selected to identify their stability under five different abiotic stress treatments (drought, salt, cadmium, chromium and arsenic) by using geNorm, NormFinder, BestKeeper and RefFinder softwares. The results showed that 18S rRNA and Unigene33312 were the best reference genes under drought treatments. Unigene33312 and Unigene33024 were found to be the most stably expressed genes under salt stress and Cd stress. Moreover, Unigene33024 and PP2A were the most suitable reference genes under Cr stress and Unigene33024 and Sb09g019750 were deemed more suitable reference genes under As stress. In total, considering all the samples, Unigene33024 and PP2A were the most stable genes while ACTIN and Unigene26576 were the least stable reference genes for internal control. The expression patterns of two target genes (Cu/Zn SOD and CAT) were used to further verify those selected reference genes under different conditions. The results showed that the most and the least stable reference genes had clearly different expression patterns. This work comprehensively estimated the stability of reference genes in M. sinensis which may give insight to the reference genes selection in other tissues as well as other related varieties. These suggested reference genes would assist in further putative gene expression validation in M. sinensis.

We propose an algorithm to remove a parabolic wavefront from a convergent or divergent beam in the Wigner function. Using this approach we numerically collimate the beam. This avoids a dense sampling in phase space to describe a convergent wavefront. Thereby we reduce the required computer memory, but maintain computational accuracy and physical effects. Furthermore, we compare two algorithms, shearing and Radon transform, to propagate the Wigner function in free space. We use the fast Fourier transform to accurately perform shearing. However, zero-padding is necessary to circumvent aliasing. We prove that the Radon transform is a more efficient approach for a long propagated distance.

We propagate partially coherent light through discontinuous surfaces and analyze the optical effects in phase space. The discontinuous surfaces are classified into two types, those with discontinuity in space and those with discontinuity in slope. Results are discussed based on the Wigner function. This approach explains the performance of segmented elements during the transition from the refractive into the diffractive regime. At first the diffraction effects generated by a single discontinuity (e.g. a phase step and a linear axicon) are investigated. Later on we discuss surfaces with periodic discontinuities, e.g. gratings, to study the formation of multiple diffracted orders. A kinoform lens is given as a further example to visualize the change from pure refraction to diffraction. Moreover, we present the beam homogenizing effect in phase space generated by lens arrays.

Here we report on the growth of TiO2 nanotube arrays (TNAs) on Ti foil with laser-drilled microhole arrays (MHAs). The MHAs promoted the adhesion of the TNA film to Ti substrate, which is well suited for flexible dye-sensitized solar cells (DSSCs). The MHA photoanode and TNAs were characterized by SEM, 3D optical profiling, XRD and TEM. For such a flexible MHA photoanode, the TNA-based DSSC was assembled using a platinized conductive glass counter electrode, and a conversion efficiency of 3.45% was achieved under AM 1.5 condition. A flexible TNA-based DSSC was also fabricated using a flexible MHA photoanode combined with a platinized indium tin oxide-polyethylene naphthalate counter electrode, which achieved 2.67% photovoltaic conversion efficiency under simulated AM 1.5 sunlight.

Randomly oriented ZnO microsheets were successfully self-assembled on TiO2 nanoparticle (TN) film to act as the scattering layer via a cathodic electrodeposition process. The light scattering properties of ZnO microsheets were studied by UV-Vis spectrometer in the 400–800 nm wavelength range. It was found that ZnO microsheets exhibited excellent ability to scatter the incident light for ZnO microsheet-TiO2 nanoparticle (ZT) composite films. The results showed that dye-sensitized solar cells (DSSCs) fabricated with ZT composite films showed higher short-circuit density (Jsc) and conversion efficiency than TN-based DSSCs, due to the light scattering properties of ZnO microsheets.

Various TiO2 nanomaterials, such as nanosheets, nanoflowers, and nanowires were directly self assembled on titanium substrate on a large scale under hydrothermal conditions. The morphology of the formed TiO2 nanomaterials could be easily tuned by varying the experimental parameters of temperature, reaction time, and the NaOH concentration. A possible formation mechanism was suggested on the basis of the shape evolution of TiO2 nanostructures by SEM images in combination with XRD patterns of as-grown samples. The optical properties of TiO2 nanosheets, nanoflowers, and nanowires were characterized by reflectance spectroscopy. The studies revealed that the absorption capability of visible light is obviously different for TiO2 with different morphologies. Moreover, TiO2 nanosheets exhibited better light trapping than TiO2 nanoflowers and TiO2 nanowires due to their unique nanostructure.

Large-scale macroporous TiO2 nanowires (MTN) were directly grown on spiral-shaped titanium wires as photoanodes of dye-sensitized solar cells (DSSCs) via a facile hydrothermal reaction without any seeds, templates, and TiO2 powder. The MTN thin film was characterized by SEM, XRD and TEM. The studies revealed that the MTN thin film had better mechanical properties and provided an efficient pathway for the diffusion of liquid electrolyte. The efficiency of 0.86% for the 3D DSSC was obtained with a J sc of 2.30 mA/cm2, V oc of 616 mV, and FF of 0.61. This MNT-based mini 3D DSSC is a promising photovoltaic device for applications in the fields of high-integrated micro-electronic equipment.

Low resistance dye-sensitized solar cells (DSSCs) based on all-titanium substrates were proposed in this paper. To minimize the internal resistance of DSSCs, the titanium wires and titanium sheets were used as the substrates of the photoanode and the counter electrode, respectively. Compared with the FTO substrate, titanium wires could absorb much diffused light by back reflection since the reflectivity in the titanium sheet was highly increased up to 53.12%. Furthermore, the transmittance of the front cover was increased by 13.2% using the super white glass instead of FTO substrate. The thickness of TiO2 thin film coated on titanium wire was optimized to achieve a high cell performance. The efficiency of 5.6% for the cell was obtained with a Jsc of 15.41 mA cm−2, Voc of 0.59 V, and FF of 0.62. The results showed that the titanium-based DSSCs had superiority for producing the large-scale DSSCs without metal grid line.

We consider the problem of distributed coverage control for mobile sensor networks operating in environments cluttered with polygonal obstacles which interfere with both the navigation and sensing by the nodes. A gradient-based motion control scheme is developed to maximize the joint detection probability of random events in such mission spaces, taking into account the discontinuities that are introduced by obstacles in the sensing probability models. The optimization scheme requires only local information at each node. We also propose a modified objective function which allows a more balanced coverage when necessary. An interactive simulation environment has been developed through which we illustrate the adaptive and distributed properties of the coverage algorithm in a variety of mission spaces with obstacles.

The Wigner function is a useful tool to analyze partially coherent light. Particularly the propagation of light in optical systems can be described by the Wigner function, while including effects of coherence and diffraction. Here we concentrate on discontinuous optical surfaces where diffraction effects can be dominant, such as the kinoform lenses, gratings, and lens arrays. To calculate the change of the Wigner function in an optical system, we treat the optical components as thin phase elements. A Wigner function describes signals in space vs. spatial frequency, resembling position vs. angle in geometrical optics. Therefore the ABCD matrix can be used to model the paraxial propagation of partially coherent light. This propagation can be computed efficiently with a shearing transformation. However, the implementation of Wigner functions for a highly convergent or divergent beam requires many sampling points. To overcome this drawback, we apply a method to remove the parabolic wavefront from the beam, transforming it into a quasi-collimated beam without losing physical effects or computational accuracy. We discuss a kinoform lens as a first example with the partially coherent light. The Wigner function vividly visualizes the essential effects such as the focal shift and multiple foci for wavelengths different from the design wavelength. As another example for Wigner functions, we analyze the lens arrays for beam homogenizing. The Wigner functions visualize the beam-shaping contribution of individual lenslets including their diffraction effects. In conclusion, the Wigner function offers a convenient approach to analyze the design of components where diffraction effects are important.

A sensor network consists of a collection of (possibly mobile) sensing devices that can coordinate their actions through wireless communication and aim at performing various tasks (e.g., surveillance, environmental monitoring) over a region sometimes referred to as the “mission space”. The performance of a sensor network is sensitive to the location of its nodes in the mission space. This leads to the basic “coverage control” problem of properly, and possibly optimally, deploying sensors in order to meet the overall system's objectives [1],[2],[3],[4],[5]. Clearly, to achieve such a goal, the nodes must share, at least partially, their state information. However, this may require a large amount of information exchange. Moreover, sensor nodes are frequently small, inexpensive devices with limited resources. Aside from energy required to move (if nodes are mobile), communication is known to be by far the largest consumer of the limited energy of a node [6], compared to other functions such as sensing and computation. Therefore, it is crucial to reduce communication between nodes to the minimum possible. This in turn imposes a constraint on the optimization task performed by each node, since it requires that actions be taken without full knowledge of other nodes' states. Standard synchronization schemes require that nodes periodically exchange state information which is clearly inefficient and, in fact, unnecessary since often the state of a node may not have changed much or may have only changed in a predictable way. This motivates us to seek not only distributed but also asynchronous optimization mechanisms in which a node communicates with others only when it considers it indispensable; in other words, each node tries to minimize the cost of communication by transmitting state information only under certain conditions and only as a last resort. This poses questions such as “what should the conditions be for a node to take such communication actions?” and “under what conditions, if any, can we guarantee that the resulting optimization scheme possesses desirable properties such as convergence to an optimum?”