Sub-laser-cycle electron pulses for probing molecular dynamics

Experience shows that the ability to make measurements in any new time regime opens new areas of science. Currently, experimental probes for the attosecond time regime (10(-18) 10(-15) s) are being established. The leading approach is the generation of attosecond optical pulses by ionizing atoms with intense laser pulses. This nonlinear process leads to the production of high harmonics during collisions between electrons and the ionized atoms. The underlying mechanism implies control of energetic electrons with attosecond precision. We propose that the electrons themselves can be exploited for ultrafast measurements. We use a 'molecular clock', based on a vibrational wave packet in H(2)(+) to show that distinct bunches of electrons appear during electron ion collisions with high current densities, and durations of about 1 femtosecond (10(-15) s). Furthermore, we use the molecular clock to study the dynamics of non-sequential double ionization.     

LaConf:A Localized Address Autoconfiguration Scheme for Wireless Ad Hoc Networks

We propose a localized address autoconfiguration (LaConf) scheme for wireless ad hoc networks.Address allocation information is maintained on the network border nodes,called addressing agents (AAs),which are locally identified by a geographic routing protocol GFG (Greedy-FACE-Greedy).When a node joins the network,it acquires an address from a neighboring AA (if any exists) by local communication or from the head AA (a geographic extreme AA) by GFG-based multi-hop communication.A Geographic Hash Table (GHT) ...     

Computer-Aided Detection System on Tangled Roller

Introduction Intheposttreatmentofchoppedfibreproduction,the thirddraftingrollerandtensionheat settingrolleroftenwere tangledbybrokentowforthereasonofhighspeed,hightemperatureofrollersurface,orotheradditionalforeign factors.While,thetworollerswerekeysegmentinthewhole technology.Itwouldleadtooneormoredrumcavedin,and eventobediscardediftheequipmenthadnotbeenstoppedintime.Usually,suchaccidentwouldbringgreatloss,what wouldnotbegotback.Sothetotalsetofequipmentrequiredthatdetectormusthavegoodperfo…     

Mutations in GRIN2A and GRIN2B encoding regulatory subunits of NMDA receptors cause variable neurodevelopmental phenotypes

N-methyl-D-aspartate (NMDA) receptors mediate excitatory neurotransmission in the mammalian brain. Two glycine-binding NR1 subunits and two glutamate-binding NR2 subunits each form highly Ca2(+)-permeable cation channels which are blocked by extracellular Mg2(+) in a voltage-dependent manner. Either GRIN2B or GRIN2A, encoding the NMDA receptor subunits NR2B and NR2A, was found to be disrupted by chromosome translocation breakpoints in individuals with mental retardation and/or epilepsy. Sequencing of GRIN2B in 468 individuals with mental retardation revealed four de novo mutations: a frameshift, a missense and two splice-site mutations. In another cohort of 127 individuals with idiopathic epilepsy and/or mental retardation, we discovered a GRIN2A nonsense mutation in a three-generation family. In a girl with early-onset epileptic encephalopathy, we identified the de novo GRIN2A mutation c.1845C>A predicting the amino acid substitution p.N615K. Analysis of NR1-NR2A(N615K) (NR2A subunit with the p.N615K alteration) receptor currents revealed a loss of the Mg2(+) block and a decrease in Ca2(+) permeability. Our findings suggest that disturbances in the neuronal electrophysiological balance during development result in variable neurological phenotypes depending on which NR2 subunit of NMDA receptors is affected.     

Probing molecular dynamics with attosecond resolution using correlated wave packet pairs

Spectroscopic measurements with increasingly higher time resolution are generally thought to require increasingly shorter laser pulses, as illustrated by the recent monitoring of the decay of core-excited krypton using attosecond photon pulses. However, an alternative approach to probing ultrafast dynamic processes might be provided by entanglement, which has improved the precision of quantum optical measurements. Here we use this approach to observe the motion of a D2+ vibrational wave packet formed during the multiphoton ionization of D2 over several femtoseconds with a precision of about 200 attoseconds and 0.05 ?ngstr?ms, by exploiting the correlation between the electronic and nuclear wave packets formed during the ionization event. An intense infrared laser field drives the electron wave packet, and electron recollision probes the nuclear motion. Our results show that laser pulse duration need not limit the time resolution of a spectroscopic measurement, provided the process studied involves the formation of correlated wave packets, one of which can be controlled; spatial resolution is likewise not limited to the focal spot size or laser wavelength.     

计算机辅助鉴定技术在海洋浮游植物分类鉴定中的应用

本文对计算机辅助鉴定技术在海洋浮游植物分类鉴定中的应用进行了探讨,总结了不同技术的特点,并在总结计算机辅助鉴定技术在海洋浮游植物分类鉴定方面应用现状的基础上,对其发展前景做出了展望。     

Three-dimensional control of light in a two-dimensional photonic crystal slab

Optoelectronic devices are increasingly important in communication and information technology. To achieve the necessary manipulation of light (which carries information in optoelectronic devices), considerable efforts are directed at the development of photonic crystals--periodic dielectric materials that have so-called photonic bandgaps, which prohibit the propagation of photons having energies within the bandgap region. Straightforward application of the bandgap concept is generally thought to require three-dimensional (3D) photonic crystals; their two-dimensional (2D) counterparts confine light in the crystal plane, but not in the perpendicular z direction, which inevitably leads to diffraction losses. Nonetheless, 2D photonic crystals still attract interest because they are potentially more amenable to fabrication by existing techniques and diffraction losses need not seriously impair utility. Here we report the fabrication of a waveguide-coupled photonic crystal slab (essentially a free-standing 2D photonic crystal) with a strong 2D bandgap at wavelengths of about 1.5 microm, yet which is capable of fully controlling light in all three dimensions. These features confirm theoretical calculations on the possibility of achieving 3D light control using 2D bandgaps, with index guiding providing control in the third dimension, and raise the prospect of being able to realize unusual photonic-crystal devices, such as thresholdless lasers.     

Tomographic imaging of molecular orbitals

Single-electron wavefunctions, or orbitals, are the mathematical constructs used to describe the multi-electron wavefunction of molecules. Because the highest-lying orbitals are responsible for chemical properties, they are of particular interest. To observe these orbitals change as bonds are formed and broken is to observe the essence of chemistry. Yet single orbitals are difficult to observe experimentally, and until now, this has been impossible on the timescale of chemical reactions. Here we demonstrate that the full three-dimensional structure of a single orbital can be imaged by a seemingly unlikely technique, using high harmonics generated from intense femtosecond laser pulses focused on aligned molecules. Applying this approach to a series of molecular alignments, we accomplish a tomographic reconstruction of the highest occupied molecular orbital of N2. The method also allows us to follow the attosecond dynamics of an electron wave packet.