Over-the-Horizon communications systems for Uavs based on intelligent antennas

Nowadays, the communication links limit the autonomy of Unmanned Aerial Vehicles (UAV). In this paper, a multichannel long-range communication link for UAVs with high quality of service, moderate bandwidth and affordable cost is proposed. This link is deployed by using a second UAV as a communications relay and it provides bidirectional coverage for telemetry and telecommand and a high-capacity downlink for video. Our highly compact system can be installed on mediumsized UAVs for air-air links in order to offer greater flight autonomy. This system is based on an active circular array of linearly polarized circular patch antennas which are selectively activated depending on the desired direction of the beam

A Marine Sulfate-Reducing Bacterium Producing Multiple Antibiotics: Biological and Chemical Investigation

A marine sulfate-reducing bacterium SRB-22 was isolated by means of the agar shake dilution method and identified as Desulfovibrio desulfuricans by morphological, physiological and biochemical characteristics and 16S rDNA analysis. In the bioassay, its extract showed broad-spectrum antimicrobial activity using the paper disc agar diffusion method. This isolate showed a different antimicrobial profile than either ampicillin or nystatin and was found to produce at least eight antimicrobial components by bioautography. Suitable fermentation conditions for production of the active constituents were determined to be 28 day cultivation at 25 °C to 30 °C with a 10% inoculation ratio. Under these conditions, the SRB-22 was fermented, extracted and chemically investigated. So far an antimicrobial compound, mono-n-butyl phthalate, and an inactive compound, thymine, have been isolated and characterized

Preparation and toughening mechanism of Al2O3 composite ceramic toughened by B4C@TiB2 core–shell units

In this paper, the concept of incorporating core–shell structured units as secondary phases to toughen Al2O3 ceramics is proposed. Al2O3 composite ceramics toughened by B4C@TiB2 core–shell units are successfully synthesized using a combination of molten salt methodology and spark plasma sintering. The synthesis of B4C@TiB2 core–shell toughening units stems from the prior production of core–shell structural B4C@TiB2 powders, and this core–shell structure is effectively preserved within the Al2O3 matrix after sintering. The B4C@TiB2 core–shell toughening unit consists of a micron-sized B4C core enclosed by a shell approximately 500 nm in thickness, composed of numerous nanosized TiB2 grains. The regions surrounding these core–shell units exhibit distinct geometric structures and encompass multidimensional variations in phase composition, grain dimensions, and thermal expansion coefficients. Consequently, intricate stress distributions emerge, fostering the propagation of cracks in multiple dimensions. This behavior consumes a considerable amount of crack propagation energy, thereby enhancing the fracture toughness of the Al2O3 matrix. The resulting Al2O3 composite ceramics display relative density of 99.7%±0.2%, Vickers hardness of 21.5±0.8 GPa, and fracture toughness 6.92±0.22 MPa·m1/2

Carbon Monoxide-Assisted Synthesis of Single-Crystalline Pd Tetrapod Nanocrystals through Hydride Formation

通讯作者地址: Zheng, NF (通讯作者),Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Coll Chem & Chem Engn, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Coll Chem & Chem Engn, Xiamen 361005, Peoples R China 2. Xiamen Univ, Dept Chem, Coll Chem & Chem Engn, Xiamen 361005, Peoples R China 3. Xiamen Univ, Dept Phys, Xiamen 361005, Peoples R China 电子邮件地址: [email protected]; [email protected] monoxide can adsorb specifically on Pd(111) to induce the formation of unique Pd nanostructures. In the copresence of CO and H-2 single-crystalline Pd tetrapod nanocrystals have now been successfully prepared. The Pd tetrapods are enclosed by (111) surfaces and are yielded through hydride formation. Density functional theory calculations revealed that the formation of PdHx in the presence of H, reduces the binding energy of CO on Pd and thus helps to decrease the CO coverage during the synthesis, which is essential to the formation of the PdHx tetrapod nanocrystals. In addition to tetrapod nanocrystals, tetrahedral nanocrystals were also produced in the copresence of CO and H-2 when the reaction temperature was ramped to further lower the CO coverage. Upon aging in air, the as-prepared PdHx nanocrystals exhibited a shape-dependent hydrogen releasing behavior. The conversion rate of PdHx tetrapod nanocrystals into metallic Pd was faster than that of tetrahedral nanocrystals.MOST of China 2011CB932403 2009CB930703 NSFC 21131005 21021061 20925103 20973139 21133004 Fok Ying Tung Education Foundation 121011 Fundamental Research Funds for the Central Universitie

Freestanding palladium nanosheets with plasmonic and catalytic properties

通讯作者地址: Huang, XQ (通讯作者), Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 2. Xiamen Univ, Dept Chem, Coll Chem & Chem Engn, Xiamen 361005, Peoples R China 3. Xiamen Univ, Dept Phys, Xiamen 361005, Peoples R China 电子邮件地址: [email protected] metal films can exhibit quantum size and surface effects that give rise to unique physical and chemical properties(1-7). Metal films containing just a few layers of atoms can be fabricated on substrates using deposition techniques(7), but the production of freestanding ultrathin structures remains a significant challenge. Here we report the facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick, using carbon monoxide as a surface confining agent. The as-prepared nanosheets are blue in colour and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region. The combination of photothermal stability and biocompatibility makes palladium nanosheets promising candidates for photothermal therapy. The nanosheets also exhibit electrocatalytic activity for the oxidation of formic acid that is 2.5 times greater than that of commercial palladium black catalyst.NSF of China 20925103 20871100 20721001 20703032 MOST of China 2009CB930703 2011CB932403 Fok Ying Tung Education Foundation 121011 NSF of Fujian 2009J06005 Key Scientific Project of Fujian Province 2009HZ0002-

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead