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The parallel track scraping principle of conventional PDC bits largely limits the cutting efficiency and working life in deep formations. Cross-cutting polycrystalline diamond compact (PDC) bit may be an efficient drilling tool that increases the rock-breaking efficiency through both cross-cutting and alternate-cutting modes of the PDC cutter. The motion track equation of the cross-cutting PDC bit was derived by using the compound coordinate system, and the motion track was analyzed. Meanwhile, through the unit experiment and discrete element simulation, the cutting force, volume-specific load, and crack propagation were analyzed under different cutting modes. Through establishing a nonlinear dynamic model of the bit-rock system, the speed-up mechanism of the novel bit was analyzed based on rock damage, rock stress state, and motion characteristic of the bit during the rock-breaking process. Compared with unidirectional cutting, cross-cutting produces less cutting force, more brittle fracture, and a greater decrease of formation strength. The novel PDC bit can put more rock elements into a tensile stress condition than a conventional PDC bit, and the plastic energy dissipation ratio of the cross-cutting PDC bit is lower while the damage energy consumption ratio is higher than they are for conventional bits, which is beneficial to increasing the ratio of fracture failure and improving rock-breaking efficiency. Laboratory drilling tests show that the cross-cutting PDC bit can create mesh-like bottom-hole features. Drilling contrast experiments show that a mesh-like bottom-hole pattern can be obtained by using the cross-cutting PDC bit, of which the ROP is obviously higher than that of the conventional bit when drilling in sandstone or limestone formation. Meanwhile, the influence of deviation angle, weight on bit, and rock properties on cutting efficiency of the cross-cutting PDC bit are studied.

Zhuofu Wu, 1, 2 Sitong Zhang, 1 Xiaojun Wang, 2 Can Cai, 2 Guang Chen, 1 Li Ma 2 1Key Laboratory of Straw Biology and Utilization, The Ministry of Education, College of Life Science, Jilin Agricultural University, Changchun 130118, People’s Republic of China; 2Department of Physics, Georgia Southern University, Statesboro, GA 30460, USACorrespondence: Guang ChenCollege of Life Science, Jilin Agricultural University, No. 2888 Xincheng Avenue, Changchun 130118, People’s Republic of ChinaTel/Fax +86 431 8453 2942Email guangc61@gmail.com Li MaDepartment of Physics, Georgia Southern University, 65 Georgia Avenue, Math/Physics Building Room 1003, Statesboro, GA 30460, USATel +1 912 478 5950Fax +1 912 478 0471Email lma@GeorgiaSouthern.eduPurpose: Combinedsuperoxide dismutase (SOD)/catalase mimetics have attracted much attention because of their efficacy against reactive oxygen species-associated diseases; however, their application is often limited owing to their poor stability and the absence of favorable grafting sites. To address this, we developed a new class of SOD/catalase mimetics based on hybrid nanoflowers, which exhibit superior stability and possess the desired grafting sites for drugs and endogenous molecules.Methods: In this work, for the first time, we used polynitroxylated human serum albumin (PNA) to mediate the formation of hybrid copper-based nanoflowers. H 2O 2 depletion and O 2 evolution assays were first performed to determine the catalase-like activity of the hybrid nanoflowers. Next, the xanthine oxidase/cytochrome c method was used to assay the SOD-like activity of the nanoflowers. Further characteristics of the nanoflowers were evaluated using scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), and Fourier-transform infrared spectroscopy (FTIR). Operational stability was assessed via the reusability assay.Results: The H 2O 2 depletion and O 2 evolution assays indicated that PNA-incorporated nanoflowers have genuine catalase-like activity. Kinetic analysis revealed that the reactions of the incorporated nanoflowers with H 2O 2 not only obey Michaelis–Menton kinetics, but that the nanoflowers also possess a higher affinity for H 2O 2 than that of native catalase. The FTIR spectra corroborated the presence of PNA in the hybrid nanoflowers, while the EPR spectra confirmed the intermolecular interaction of nitroxides bound to the human serum albumin incorporated into the nanoflowers. The remarkable operational reproducibility of the hybrid nanoflowers in catalase-like and SOD-like reactions was verified across successive batches.Conclusion: Herein, a comparison of Michaelis constants showed that the hybrid nanoflower, a catalase mimetics, outperforms the native catalase. Acting as a “better-than-nature” enzyme mimetics, the hybrid nanoflower with superior stability and desired ligand grafting sites will find widespread utilization in the medical sciences.Keywords: catalase, superoxide dismutase, polynitroxylated human serum albumin, reactive oxygen species, copper-based nanoflowers

Author's abstract: In this work, nitroxide 2,2,6,6-tetramethylpiperdine 1-oxyl (Tempo), human serum albumin (HSA), CuSO4 and phosphate buffered saline (PBS) were used to synthesis the hybrid nanoflowers. Scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), and Fourier-transform infrared spectroscopy (FTIR) were used for characterization of the nanoflowers. The SEM spectra illustrated the morphologies of the hybrid nanoflowers. The FTIR spectra corroborated the presence of PNA in the hybrid nanoflowers, while the EPR spectra confirmed the intermolecular interaction of nitroxides bound to the human serum albumin incorporated into the nanoflowers. The catalase mimetic activity and corresponding kinetic parameters of nanoflowers were determined using the H2O2 depletion and O2 evolution assays. The superoxide dismutase mimetic activity of the nanoflowers was determined by the xanthine oxidase/cytochrome c method. And the reusability of the hybrid nanoflowers was assessed via the H2O2 depletion assay and the xanthine oxidase/cytochrome c method. Kinetic analysis revealed that the reactions of the incorporated nanoflowers with H2O2 obey Michaelis-Menton kinetics and the nanoflowers possess a higher affinity for H2O2 than nature catalase. the hybrid nanoflowers with superior stability and desired ligand grafting sites will find widespread utilization in the medical sciences.

The joint peristimulus time histogram (JPSTH) and cross-correlogram provide a visual representation of correlated activity for a pair of neurons, and the way this activity may increase or decrease over time. In a companion paper (Cai et al. 2004a) we showed how a Bootstrap evaluation of the peaks in the smoothed diagonals of the JPSTH may be used to establish the likely validity of apparent time-varying correlation. As noted by Brody (1999a,b) and Ben-Shaul et al. (2001), trial-to-trial variation can confound correlation and synchrony effects. In this paper we elaborate on that observation, and present a method of estimating the time-dependent trial-to-trial variation in spike trains that may exceed the natural variation displayed by Poisson and non-Poisson point processes. The statistical problem is somewhat subtle because relatively few spikes per trial are available for estimating a firing-rate function that fluctuates over time. The method developed here uses principal components of the trial-to-trial variability in firing rate functions to obtain a small number of parameters (typically two or three) that characterize the deviation of each trial's firing rate function from the across-trial average firing rate, represented by the smoothed PSTH. The Bootstrap significance test of Cai et al. (2004a) is then modified to accommodate these general excitability effects. This methodology allows an investigator to assess whether excitability effects are constant or time-varying, and whether they are shared by two neurons. It is shown that trial-to-trial variation can, in the absence of synchrony, lead to an increase in correlation in spike counts between two neurons as the length of the interval over which spike counts are computed is increased. In data from two V1 neurons we find that highly statistically significant evidence of dependence disappears after adjustment for time-varying trial-to-trial variation.

The joint peristimulus time histogram (JPSTH) provides a visual representation of the dynamics of correlated activity for a pair of neurons. There are many ways to adjust the JPSTH for the time-varying firing-rate modulation of each neuron, and then to define a suitable measure of time-varying correlated activity. Our approach is to introduce a statistical model for the time-varying joint spiking activity so that the joint firing rate can be estimated more efficiently. We have applied an adaptive smoothing method, which has been shown to be effective in capturing sudden changes in firing rate, to the ratio of joint firing probability to the probability of firing predicted by independence. A Bootstrap procedure, applicable to both Poisson and non-Poisson data, was used to define a statistical significance test of whether a large ratio could be due to chance alone. A numerical simulation showed that the Bootstrap-based significance test has very nearly the correct rejection probability, and can have markedly better power to detect departures from independence than does an approach based on testing contiguous bins in the JPSTH. In a companion paper (Cai et al. 2004b) we show how this formulation can accommodate latency and time-varying excitability effects, which can confound spike timing effects.

In this paper, a general matrix structure for shortened turbo product codes (TPC) and an improved decoding algorithm based on Chase decoder are presented. In the proposed algorithm, the decoding complexity is decreased by reducing the number of candidate codewords and, an efficient method to estimate the extrinsic information without competing codeword is designed, too. Compared with the conventional algorithm, simulation results show that considerable coding gains can be obtained by the proposed decoding algorithm with decreasing decoding complexity.

A completely different formulation for simulation of the high order Laue zone (HOLZ) diffractions is derived. It refers to the new method, i.e. the Taylor series (TS) method. To check the validity and accuracy of the TS method, we take polyvinglidene fluoride (PVDF) crystal as an example to calculate the exit wavefunction by the conventional multi-slice (CMS) method and the TS method. The calculated results show that the TS method is much more accurate than the CMS method and is independent of the slice thicknesses. Moreover, the pure first order Laue zone wavefunction by the TS method can reflect the major potential distribution of the first reciprocal plane.

A three-dimensional (3D) reconstruction of icosahedral virus is carried out by the icosahedral symmetry-adapted function (ISAF) method in spherical coordinates. In order to reduce the influence of noise, it is better to use the basis functions that have identical symmetry with the object reconstructed. It is verified that the ISAF method has stronger ability to reduce the influence of noise to grain the resolution better than that of the conventional method by the simulation of 3D reconstruction.