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Very recently, a stable structure of layered transition metal phosphides MP2 (M = Ni, Pd and Pt) has been discovered. This study reveals that these three materials are semiconductor materials with a direct band gap (0.5–0.85 eV) and also have very high hole and electron mobility. The electron mobility of the PtP2 monolayer is surprisingly as high as 14.4 × 104 cm2 V−1 s−1. Based on their excellent electronic properties, herein we predict the thermoelectric (TE) performance of MP2 monolayers by using first-principles and Boltzmann transport equation. The calculation results show that the single-layer NiP2, PdP2 and PtP2 have low lattice thermal conductivity 7.6 W m−1 K−1, 9.0 W m−1 K−1 and 17.8 W m−1 K−1 at room temperature, respectively, which is mainly caused by the small phonon group velocity, low relaxation time, high Gruneisen parameter and large phonon scattering phase space. Because of the ultra-high carrier mobility and the highly degenerate band structure, MP2 monolayers have large Seebeck coefficient, and the value of PdP2 reaches up to 283 μV K−1 at 300 K. The good phonon and electrical transport properties give the MP2 monolayers a high TE figure of merit (ZT). The maximum ZT of NiP2 and PdP2 monolayers at 500 K is 1.52 (p-type) and 1.95 (n-type), respectively, and the corresponding concentration of maximum ZT MP2 monolayers is around 1011 cm−2. Overall, our work indicates that the MP2 monolayers are the promising candidates in TE applications.

Through first-principles calculations and using the Boltzmann transport equation, we explore the thermoelectric (TE) properties of CaP3 from the three-dimensional (3D) bulk form to a two-dimensional (2D) monolayer. Herein, our results prove that reducing the dimensionality not only can avoid the poor TE performance along certain crystal orientations, but also can effectively reduce the thermal conductivity. More remarkably, the Seebeck coefficients of the monolayer exhibit a dramatic enhancement compared to its bulk form. Some inherent phonon properties, such as the low acoustic phonon group velocity of ∼1.41 km s−1, large Gruneisen parameters of ∼30, and short phonon relaxation time, can greatly hinder its heat transport ability, leading to an ultralow lattice thermal conductivity of ∼0.65 W m−1 K−1 for the monolayer at room temperature. The size effect is much less sensitive due to the short intrinsic phonon mean free path (MFP). The maximum figure of merit (ZT) for n-type doping at 700 K can reach 6.39 in the nanosheet along the a direction, which is enhanced nearly two times compared to its bulk form (2.83), due to the quantum confinement effect. Collectively, this work shows that low-dimensional nanostructure technology can effectively improve the thermoelectric conversion of this class of materials.

Hexagonal M2C3 compound is a new predicted functional material with desirable band gaps, a large optical absorption coefficient, and ultrahigh carrier mobility, implying its potential applications in photoelectricity and thermoelectric (TE) devices. Based on density-functional theory and Boltzmann transport equation, we systematically research the TE properties of M2C3. Results indicate that the Bi2C3 possesses low phonon group velocity (~2.07 km/s), low optical modes (~2.12 THz), large Gr&uuml, neisen parameters (~4.46), and short phonon relaxation time. Based on these intrinsic properties, heat transport ability will be immensely restrained and therefore lead to a low thermal conductivity (~4.31 W/mK) for the Bi2C3 at 300 K. A twofold degeneracy is observed at conduction bands along &Gamma, M direction, which gives a high n-type electrical conductivity. Its low thermal conductivity and high Seebeck coefficient lead to an excellent TE response. The maximum thermoelectric figure of merit (ZT) of n-type can approach 1.41 for Bi2C3. This work shows a perspective for applications of TE and stimulate further experimental synthesis.

GaN epilayer is grown on maskless periodically grooved sapphire by metal organic chemical vapor deposition (MOCVD) in this article. Wing tilt is detected by high resolution X-ray rocking curve. Inhomogeneous deformations between the wing and mesa regions are found by atomic force microscopy (AFM) characterization. The stress distribution is investigated using finite-element simulations. Inhomogeneous stress distribution in the mesa and wing regions is shown, which is also confirmed by micro-Raman spectroscopy. The results show that the wing tilt in GaN layers grown on maskless periodically grooved sapphire mainly originates from the different deformations for mesa and wing region caused by inhomogeneous stress distribution.

Mycoplasma bovis is a major bacterial pathogen causing mastitis in dairy cattle, pneumonia and arthritis, and reduced weight gain in calves and reproductive problems in both dairy cattle and bulls, resulting in significant economic losses. The objective of the present investigation was to examine the M. bovis seroprevalence in dairy cattle in Guangzhou, subtropical Southern China by using an enzyme-linked immunosorbent assay (ELISA). A total of 370 serum samples of dairy cattle were collected between July, 2009 and March, 2010 from 5 different farms and examined for M. bovis antibodies using a commercially available ELISA kit. The overall seroprevalence of M. bovis infection in dairy cattle was 5.95% (22/370). One year-old dairy cattle had the highest seroprevalence (10.5%), followed by dairy cattle of 3 year-old (9.61%). Dairy cattle without pregnancy had the highest seroprevalence (9.26%), followed by dairy cattle with 2 pregnancies (8.62%). However, no statistically significant association was found between M. bovis infection and ages or numbers of pregnancies (P>0.05). These results indicate that M. bovis infection was present in dairy cattle in Guangzhou, subtropical Southern China, and integrated strategies and measures should be executed to control and prevent M. bovis infection and disease outbreak in the study region. Key words: Mycoplasma bovis, seroprevalence, dairy cattle, China, enzyme-linked immunosorbent assay (ELISA).

Endocytosis is a fundamental cellular event in membrane retrieval after exocytosis and in the regulation of receptor-mediated signal transduction. In contrast to the well-studied depolarization-induced membrane recycling, little is known about the kinetics of ligand-induced endocytosis of G-protein-coupled receptors in neurons. Here we investigated the kinetics of ligand-receptor binding-induced endocytosis in rat sensory neurons using a membrane capacitance assay. The time constant of ADP-induced endocytosis of P2Y-receptors was determined as 1.7s. The ADP-induced endocytosis was blocked by antagonists against P2Y, phosphorylation, and clathrin. However, block of dynamin was without effect. The ADP-induced endocytosis was confirmed independently by a single vesicle image technique using a styryl FM2-10. Finally, the receptors were internalized in response to ADP, as determined by GFP-labeled P2Y. We conclude that ligand-receptor binding leads to rapid endocytosis in the cytoplasm of rat dorsal root ganglion neurons.