Characterization of A Novel Avalanche Photodiode for Single Photon Detection in VIS-NIR Range

In this work we investigate operation in the Geiger mode of the new single photon avalanche photo diode (SPAD) SAP500 manufactured by Laser Components. This SPAD is sensitive in the range 400-1000nm and has a conventional reach-through structure which ensures good quantum efficiency at the long end of the spectrum. By use of passive and active quenching schemes we investigate detection efficiency, timing jitter, dark counts, afterpulsing, gain and other important parameters and compare them to the "standard" low noise SPAD C30902SH from Perkin Elmer. We conclude that SAP500 offers better combination of detection efficiency, low noise and timing precision

Surface plasmon-based techniques for the analysis of plasma deposited functional films and surfaces

Herein we demonstrate that two surface plasmon-based techniques (i.e., SPR and OWS) allow for sensitive and real-time monitoring of plasma polymers of different thicknesses ranging from several nanometers to micrometers. Firstly, the fundamentals and the implementation of SPR/OWS are given. Examples about the use of SPR and OWS for the characterization of plasma deposited thin films are then presented, with emphasis on the stability and the swelling of those films in humid atmospheres and in aqueous media. The binding behavior of biological species (e.g., nucleic acid, protein, etc.) onto plasma polymer surfaces as seen by SPR and OWS are also discussed. The results clearly show that surface plasmon optics will play an essential part in the understanding and the future development of plasma deposited polymers

Synergistic Catalytic Effects of Carbon Nanotube and Nano-Sized TiO2 on the Hydrogen Sorption of Magnesium Hydride

Different TiO2 such as anatase, rutile and sintered C/anatase were added to magnesium hydride by high-energy ball milling in order to improve the hydrogenation properties of magnesium hydride. The results showed that sintered C/anatase were easily distributed uniform in the MgH2 matrix and resulted in the good hydrogen sorption of magnesium hydride such as the faster kinetic of hydrogenation and good cycling. Its excellent properties came from the synergistic catalytic effect of TiH formed after de/hydrogenation cycles and nano carbon tubes

Engraved bones from the archaic hominin site of Lingjing,Henan Province

The production of abstract engravings is considered an indicator of modern human cognition and a means for the long-term recording and transmission of information. This article reports the discovery of two engraved bones from the Lingjing site in Henan Province, China, dated to 105–125 kya. The carefully engraved nature of the incisions, made on weathered rib fragments, precludes the possibility of unintentional or utilitarian origins. Residue analysis demonstrates the presence of ochre within the incised lines on one specimen. This research provides the first evidence for the deliberate use of ochred engravings for symbolic purposes by East Asian Late Pleistocene hominins

Investigation method of borehole collapse with the multi-field coupled model during drilling in clayey silt hydrate reservoirs

The global reserves of natural gas hydrates are extremely abundant, which is attracting more and more scientists attention. However, hydrate reservoirs are usually clayey silt hydrate reservoirs with low strength, borehole collapse is a key issue during the drilling operation in these clayey silt hydrate reservoirs in the South China Sea. Therefore, investigation method exploration of borehole collapse simulation for wellbores drilled in hydrate-bearing sediments is of great importance for safely and efficiently developing hydrate in deep water. The finite element model coupled seepage, deformation and heat transfer is developed, and borehole collapse investigation during the overbalanced drilling operation in hydrate-bearing sediment is carried out. The results show that changes in temperature and/or pore pressure do not necessarily lead to the hydrate dissociation. For the investigation case, the temperature front reaches to the position of 35.72 cm from borehole within the near-wellbore area when the drilling operation lasted for 3 hours, but hydrate only dissociates for 17.94cm from the borehole, which is smaller than the temperature disturbance distance. Moreover, the applicability of the investigation method developed herein is verified by comparing the equivalent plastic strains obtained by the coupled model developed in this paper and the simplified model (which neglects the seepage and the heat transfer) respectively. All these results demonstrate that both the investigation method and the finite element model can be used for borehole stability simulation in hydrate-bearing sediment

Flame-retardant coating by alternate assembly of poly(vinylphosphonic acid) and polyethylenimine for ramie fabrics

A novel intumescent flame retardant coating, consisting of poly(vinylphosphonic acid) (PVPA) as the acid source and branched polyethylenimine (BPEI) as the blowing agent, was constructed on the surface of ramie fabrics by alternate assembly to remarkably improve the flame retardancy of ramie. The PVPA/BPEI coating on the surface of individual fibers of ramie fabric pyrolyzes to form protective char layer upon heating/burning and improves the flame retardancy of ramie. Thermogravimetric analysis reveals that the PVPA/BPEI-coated ramie fabrics left as much as 25.8 wt% residue at 600 °C, while the control (uncoated) fabric left less than 1.4 wt% residue. Vertical flame test shows that all PVPA/BPEI-coated fabrics have shorter after-flame time, and the residues well preserved the original weave structure and fiber morphology, whereas, the uncoated fabric left only ashes. Microscale combustion calorimetry shows that the PVPA/BPEI coatings greatly reduce the total heat release by as much as 66% and the heat release capacity by 76%, relative to those of the uncoated fabric. © Chinese Chemical Society