L-shell ionization accompanied by one-electron capture in Cq+, Oq+ (q=2,3)-Ne collisions

The L-shell ionization processes of a Ne gas target associated with single-electron capture by bombardment of Cq+ and Oq+ (q=2,3) are investigated using the projectile-recoil-ion coincidence method in the energy range from 80 to 400 keV/u (v(p)=1.8-4 a.u.). The cross-section ratios (R-k1) of k-fold ionization to single capture are compared with the results for He2+-Ne collisions by Dubois [Phys. Rev. A 36, 2585 (1987)]. All the velocity dependences are quite similar. The ratios increase as the projectile energy increases in the lower-energy region, reach the maxima for projectile energies around E-max=160q(1/2) keV/u, and then decrease at higher energies. These results qualitatively agree with our calculations in terms of the Bohr-Lindhard model within the independent-electron approximation.

Angular distribution of characteristic photons after radiative electron capture at strong central fields

We investigate the difference in the angular distribution of Ly-alpha(1) and K alpha(1) photons from hydrogenlike and heliumlike ions of uranium after radiative electron capture to the L shell. The strong anisotropy in the former case is changed to a very small one in the latter case. Our calculations support the observation. The effect takes place even in the limiting case of noninteracting electrons, being caused by the Pauli principle.

Average energy loss measured in single and double electron capture collisions of He2 on Ar at low velocities

Employing the recoil ion momentum spectroscopy we investigate the collision between He2+ and argon atoms. By measuring the recoil longitudinal momentum the energy losses of projectile are deduced for capture reaction channels. It is found that in most cases for single- and double-electron capture, the inner electron in the target atom is removed, the recoil ion is in singly or multiply excited states (hollow ion is formed), which indicates that electron correlation plays an important role in the process. The captured electrons prefer the ground states of the projectile. It is experimentally demonstrated that the average energy losses are directly related to charge transfer and electronic configuration.

State-selective electron capture for keV He2+ ions on helium collisions studied by recoil momentum spectroscopy

State-selective single electron capture cross sections are measured by recoil ion momentum spectroscopy technique for He2+ on He at 30 keV incident energy. The cross sections for capture into ground and excited states are obtained and compared to classical model calculations as well as to the quantum mechanical calculations. The experimental results are in good agreement with quantum mechanical results.

Probabilistic modelling of soil moisture dynamics of irrigated cropland in the North China Plain

A probabilistic soil moisture dynamic model is used to estimate the soil moisture probability distribution and plant water stress of irrigated cropland in the North China Plain. Soil moisture and meteorological data during the period of 1998 to 2003 were obtained from an irrigated cropland ecosystem with winter wheat and maize in the North China Plain to test the probabilistic soil moisture dynamic model. Results showed that the model was able to capture the soil moisture dynamics and estimate long-term water balance reasonably well when little soil water deficit existed. The prediction of mean plant water stress during winter wheat and maize growing season quantified the suitability of the wheat-maize rotation to the soil and climate environmental conditions in North China Plain under the impact of irrigation. Under the impact of precipitation fluctuations, there is no significant bimodality of the average soil moisture probability density function.

A electrochemiluminescence aptasensor for detection of thrombin incorporating the capture aptamer labeled with gold nanoparticles immobilized onto the thio-silanized ITO electrode

A novel electrochemiluminescence (ECL) aptasensor was proposed for sensitive and cost-effective detection of the target thrombin adopted an aptamer-based sandwich format. To detect thrombin, capture aptamers; labeled with gold nanoparticles (AuNPs) were first immobilized onto the thio-silanized ITO electrode surface through strong Au-S bonds. After catching the target thrombin, signal aptamers; tagged with ECL labels were attached to the assembled electrode surface. As a result, an AuNPs-capture-aptamer/thrombin/ECL-tagged signal-aptamer sandwich type was formed.

PLLA-PCys co-electrospun fibers for capture and elution of glutathione S-transferase

The copolymer poly(L-lactic acid)-b-poly(L-cysteine) (PLA-b-PCys) was co-electrospun with PLGA into ultrafine fibers. The reduced glutathione (GSH) was conjugated to the fiber surfaces via disulfide bonds. The glutathione S-transferase (GST) was captured onto the GSH fibers via specific substrate-enzyme interaction between the bound GSH and GST. The captured GST was eluted with free GSH aqueous solution and lyophilized to get pure GST powders. The results show that the GSH moieties on the fiber surface retain the bioactivity of the free GSH and thus they can bind specifically with GST and the GST in solution is captured onto the fiber surface. In addition, the bound GSH is not as active as free GSH so that the captured GST can be eluted off from the fiber by free GSH aqueous solution. Based on this principle, GST itself or its fused proteins can be separated and purified very easily. The preliminary purification efficiency is 6.5 mg center dot(g(PCys))(-1). Further improvements are undertaken.

A study of resonance electron capture ionization on a quadrupole tandem mass spectrometer

Procedures that allow the realization of resonance electron capture (REC) mode on a commercial triple-quadrupole mass spectrometer, after some simple modifications, are described, REC mass spectrometry (MS) and tandem mass spectrometry (MS/MS) experiments were performed and spectra for some compounds were recorded. In particular, the charge-remote fragmentation (CRF) spectra of [M - H](-) ions of docosanoic and docosenoic acids under low-energy collisionally activated dissociation (CAD) conditions were obtained, and showed that there were no significant differences for [M - H](-) ions produced at different resonances (i,e. for [M - H](-) ions with different structures). This observation was explained on the basis of results obtained from deuterium-labeled fatty acids, which showed that different CRF ions (but with the same m/z value in the absence of labels) could be produced by different mechanisms, and all of them were obviously realized under CAD conditions that made spectra practically indistinguishable. The other example, which compared the REC-MS/MS spectrum of [M - H](-) ions and EI-MS/MS spectrum of M+. ions of daidzein, demonstrated the potential of the REC-MS/MS technique for more complex structure elucidation. Copyright (C) 2000 John Wiley & Sons, Ltd.

Review on study of resonance electron capture mass spectrometry

Resonance electron capture mass spectrometry, in which an additional information coordinate, the energy of electron capture, is applied, has a high sensitivity and a high specificity. It is extensively used to study the structure elucidation, the mechanism of ion formation and the detection, identification and quantification of organic substances in mixture.

Probability distribution of the four-phase structure invariants of isomorphously related structure factors and its applications

The probability distribution of the four-phase structure invariants (4PSIs) involving four pairs of structure factors is derived by integrating the direct methods with isomorphous replacement (IR). A simple expression of the reliability parameter for 16 types of invariant is given in the case of a native protein and a heavy-atom derivative. Test calculations on a protein and its heavy-atom derivative using experimental diffraction data show that the reliability for 4PSI estimates is comparable with that for the three-phase structure invariants (3PSIs), and that a large-modulus invariants method can be used to improve the accuracy.

A STUDY OF CHARGE SEPARATION AND ELECTRON-CAPTURE INDUCED DECOMPOSITION SPECTRA OF PHENYLENEDIAMINE ISOMERS

The structures and decomposition reactions of doubly charged phenylenediamines were studied by means of charge separation (CS) and electron capture induced decomposition (ECID) spectra. The deisomerization of the three isomers is prior to the metastable d

Probability distribution of random wave-current forces

Based on the second-order solutions obtained for the three-dimensional weakly nonlinear random waves propagating over a steady uniform current in finite water depth, the joint statistical distribution of the velocity and acceleration of the fluid particle in the current direction is derived using the characteristic function expansion method. From the joint distribution and the Morison equation, the theoretical distributions of drag forces, inertia forces and total random forces caused by waves propagating over a steady uniform current are determined. The distribution of inertia forces is Gaussian as that derived using the linear wave model, whereas the distributions of drag forces and total random forces deviate slightly from those derived utilizing the linear wave model. The distributions presented can be determined by the wave number spectrum of ocean waves, current speed and the second order wave-wave and wave-current interactions. As an illustrative example, for fully developed deep ocean waves, the parameters appeared in the distributions near still water level are calculated for various wind speeds and current speeds by using Donelan-Pierson-Banner spectrum and the effects of the current and the nonlinearity of ocean waves on the distribution are studied. (c) 2006 Elsevier Ltd. All rights reserved.

松辽徐家围子断陷层序地层充填模式及含油气性特征

Based on the principle and method of sequence, the author describes the sequence-filling model of the rifting basin of Xujiaweizi and its gas exploration potential. The object of this paper belongs to the area around Shengping-Wangjiatun anticline. Its srtatigraphy includes Huoshiling Formation (neutral and basic volcanic rocks), Shahezi Formation (coal bedding and mud and some sandstone) and Yingcheng Formation from bottom to top. These stratigraphy units are defined by author as mesosequences respectively. The author emphasizes that the main control factors of sequence change with the types of basin and stage of basin. So the sequence is researched according to the types of basin. This viewpoint is very new, and it is consistent with the principle of sequence. Volcanic action is very frequent and acute, topography difference is obvious. Between the volcanic events, Shahezi Formation is formed, which mainly consists-of sedimentary rocks. Based on the datum from seismic section and drilling core and well-logging, the author analyzes the single unit and unit set and system tract and sedimentary fancies, then, according to the accommodation space change and marking of sequence boundary, Shahezi Formation is divided into two Third-scale sequences. The sedimentary fancies and depth distribution are described. The author also pointed out that the volcanic rocks consume the accommodation space, so volcanic rocks can influence the development of sequence. Based on the concept of accommodation space, the author put volcanic rocks into sequence frame, which normally consists of sedimentary rocks. The topography of volcanic is controlled by lithology of volcanic rocks, the pattern of volcanic eruption and the topography before volcanic eruption. The topography of volcanic can influence sedimentation and the filling pattern of sedimentary rocks. The author describes the composition and lithology fancies and depth distribution of volcanic rocks. The volcanic rocks and Volcanic building, volcanic structure is recognized on seismic section. The author paid a special attention to the relationship between sedimentation and volcanism. Finally, the author analyses the combination of source-reservoir-cover unit in sequence frame. The mudstone of Shahezi Formation has a great depth, the Kerogene in it belongs to type II and III, which tends to produce gas. The Yingcheng Formation lies between Shahezi Formation and Denglouku Formation, belonging to good reservoir. The volcanic rocks of Huoshiling Formation often formed high building, which can capture the gas produced from Shahezi Formation. The stratigraphy of rifting basin of Xujiaweizi has the great potential of gas exploration. This paper claims the following creative points: 1. The author applied the principle and method of sequence to rifting basin, greatly extending its research area and topic issues. 2. The author pointed out that basin of different type and of different stage has a different type of sequence. This is caused by the different main control factors of sequence. 3. Put volcanic rocks into the sequence frame, discussing the probability of regarding the volcanic rocks as the component of sequence, dealing with the relationship between sedimentation and volcanism and its influence to the source-reservoir-cover system. 4. The author pointed out that the filling pattern of rifting basin are determined by the filling pattern of megasequence, whose filling pattern is determined by the filling pattern of system tract and the change of accommodation space.

Finding Edges and Lines in Images

The problem of detecting intensity changes in images is canonical in vision. Edge detection operators are typically designed to optimally estimate first or second derivative over some (usually small) support. Other criteria such as output signal to noise ratio or bandwidth have also been argued for. This thesis is an attempt to formulate a set of edge detection criteria that capture as directly as possible the desirable properties of an edge operator. Variational techniques are used to find a solution over the space of all linear shift invariant operators. The first criterion is that the detector have low probability of error i.e. failing to mark edges or falsely marking non-edges. The second is that the marked points should be as close as possible to the centre of the true edge. The third criterion is that there should be low probability of more than one response to a single edge. The technique is used to find optimal operators for step edges and for extended impulse profiles (ridges or valleys in two dimensions). The extension of the one dimensional operators to two dimentions is then discussed. The result is a set of operators of varying width, length and orientation. The problem of combining these outputs into a single description is discussed, and a set of heuristics for the integration are given.

Handsignals Recognition From Video Using 3D Motion Capture Data

Hand signals are commonly used in applications such as giving instructions to a pilot for airplane take off or direction of a crane operator by a foreman on the ground. A new algorithm for recognizing hand signals from a single camera is proposed. Typically, tracked 2D feature positions of hand signals are matched to 2D training images. In contrast, our approach matches the 2D feature positions to an archive of 3D motion capture sequences. The method avoids explicit reconstruction of the 3D articulated motion from 2D image features. Instead, the matching between the 2D and 3D sequence is done by backprojecting the 3D motion capture data onto 2D. Experiments demonstrate the effectiveness of the approach in an example application: recognizing six classes of basketball referee hand signals in video.