Sparse Multicategory Generalized Distance Weighted Discrimination in Ultra-High Dimensions

Distance weighted discrimination (DWD) is an appealing classification method that is capable of overcoming data piling problems in high-dimensional settings. Especially when various sparsity structures are assumed in these settings, variable selection in multicategory classification poses great challenges. In this paper, we propose a multicategory generalized DWD (MgDWD) method that maintains intrinsic variable group structures during selection using a sparse group lasso penalty. Theoretically, we derive minimizer uniqueness for the penalized MgDWD loss function and consistency properties for the proposed classifier. We further develop an efficient algorithm based on the proximal operator to solve the optimization problem. The performance of MgDWD is evaluated using finite sample simulations and miRNA data from an HIV study.     

ULTRASTRUCTURAL STUDIES OF THE LIGHT-INDUCED CHLOROPLAST SHRINKAGE*

Both Class I (intact) and Class II (without the outer plastid membrane) chloroplasts of Spinacea oleracea exhibit a shrinkage of the thylakoid volume under conditions which lead to the well known light-induced light scattering increases. In the present report this shrinkage has been measured on micrographs prepared by the freeze-etch technique. In cloroplasts kept in darkness through the freezing or in those treated with DCMU prior to exposure to red light, the thylakoids are in a slightly swollen condition: in plastids exposed to red light and no inhibitor, the thylakoid membranes are closely appressed, giving the thylakoid a shrunken appearance relative to the control. It is further shown that Class I chloroplasts which are actively fixing CO₂ do not give appreciable light scattering changes, but lowering the pH away from the optimum for ATP formation (and CO₂ fixation) or adding the uncoupler quinacrine restores the light-induced scattering increases.     

Total absorption and the energy dependence of the partial oscillator strengths for “photoionization” of the valence orbitals of H2O using an electron-electron coincidence method

Partial oscillator strengths (β dependent), from threshold to 49 eV, for the ionisation of 1b₁, 2a₁, 1b₂, 1a₁ electrons from the valence shell of water vapour have been determined using fast (3.5 keV) electron impact with coincidence detection of the scattered and ejected electrons. The total oscillator strength (photoabsorption) was determined from the forward scattered electron intensity and placed on an absolute basis by normalisation to a total f value of 8 for the valence shell.     

Voltage-driven DNA translocations through a nanopore

We measure current blockade and time distributions for single-stranded DNA polymers during voltage-driven translocations through a single alpha-hemolysin pore. We use these data to determine the velocity of the polymers in the pore. Our measurements imply that, while polymers longer than the pore are translocated at a constant speed, the velocity of shorter polymers increases with decreasing length. This velocity is nonlinear with the applied field. Based on this data, we estimate the effective diffusion coefficient and the energy penalty for extending a molecule into the pore.     

Fractionation of cadmium in tobacco and cigarette smoke condensate using XANES and sequential leaching with ICP-MS/MS

Analytical and Bioanalytical Chemistry - Fractionation data for cadmium in tobacco products, as obtained by sequential leaching of cadmium species with ICP-MS/MS analysis, and separately by X-ray...     

过渡金属氧化物掺杂对铜锰氧化物催化CO氧化性能的影响

以乙酸铜和乙酸锰为铜锰前驱体,以NH₄HCO₃为沉淀剂,相应金属硝酸盐为掺杂剂,采用共沉淀法制备了不同过渡金属氧化物掺杂的铜锰氧化物催化剂.?采用N₂物理吸附、X射线衍射,氢气-程序升温还原和原位红外漫反射光谱等方法对催化剂进行了表征,考察了系列催化剂上CO反应性能.?结果表明,掺杂过渡金属氧化物可以调变催化剂对CO的吸附能力,进而影响催化剂性能.     

DNA conformation and base number simultaneously determined in a nanopore

When dsDNA polymers containing identical number of base pairs were electrophoresed through a nanopore in a voltage biased silicon nitride membrane, the measured time integral of blocked ionic current (the event-charge-deficit, ecd, Fologea, D., Gershow, M., Ledden, B., McNabb, D. S. et al.., Nano Lett. 2005, 5, 1905-1909) for each translocation event was the same regardless of whether the molecules were in a linear, circular relaxed, or supercoiled form. Conversely, when DNA polymers containing different numbers of base pairs were electrophoresed through a nanopore, the ecd depended strongly on, and predicted the value of, the molecule's number of base pairs. Measurements showed that the magnitude of the current blockages was strongly affected by a molecule's form. The current blockages exhibited characteristic differences that distinguished among single-stranded linear, double-stranded linear, circular relaxed, and supercoiled forms. Because the data that establish ecd are usually determined concomitantly with current blockade measurements, our results show that a single nanopore assay can simultaneously determine both DNA conformation and base number.     

Effects of active carbon pore size distributions on adsorption of toxic organic compounds

The use of active carbons for the removal of toxic organic compounds, for example from air or smoke, is of significant interest. In this paper, the equilibrium and dynamic adsorption characteristics of two active carbons are explored; one microporous coconut based and the other micro-mesoporous derived from a synthetic resin. Benzene, acetaldehyde and acrylonitrile were chosen as the probe toxicant vapours and adsorption was measured at a temperature of 298 K. The nitrogen equilibrium data (at 77 K), analysed using the BET, Dubinin-Radushkevich equations and DFT models, showed a higher overall adsorption capacity, more supermicroporosity and a higher proportion of pores wider than 2 nm for the synthetic resin based material. A micropore distribution biased toward the ultramicropore width-range was observed for the nutshell material. As a consequence, the characteristic adsorption energies in micropores are higher for the nutshell material than the resin based carbon. The effect of these different pore size characteristics on the adsorption kinetics, obtained by fitting the data to the linear driving force (LDF) model, is that the resulting adsorption rate constants are higher across much of the relative pressure range (p/p ^s ) studied for the resin based carbon compared to the nutshell material. Significantly, the wider pores of the resin-based carbon result in higher rates of adsorption in the micropore filling domain. When evaluated under dynamic conditions in cigarette smoke, improved toxicant removal was observed using the resin based carbon.     

Eddies in a bottleneck: an arbitrary Debye length theory for capillary electroosmosis

Using an applied electrical field to drive fluid flows becomes desirable as channels become smaller. Although most discussions of electroosmosis treat the case of thin Debye layers, here electroosmotic flow (EOF) through a constricted cylinder is presented for arbitrary Debye lengths (kappa(-1)) using a long wavelength perturbation of the cylinder radius. The analysis uses the approximation of small potentials. The varying diameter of the cylinder produces radially and axially varying effective electric fields, as well as an induced pressure gradient. We predict the existence of eddies for certain constricted geometries and propose the possibility of electrokinetic trapping in these regions. We also present a leading-order criterion which predicts central eddies in very narrow constrictions at the scale of the Debye length. Eddies can be found both in the center of the channel and along the perimeter, and the presence of the eddies is a consequence of the induced pressure gradient that accompanies electrically driven flow into a narrow constriction.     

Measurement of the energy dependences of the photoelectron angular distribution parameters for Ar 3p and Kr 4p electrons using an electron-electron coincidence experiment

The energy dependence of the photoelectron angular distribution parameter (β) has been measured for Ar 3p and Kr 4p electrons in the energy ranges 4–54 eV and 4–40 eV above threshold respectively, using 3.5 keV electron impact with coincidence detection of the scattered and ejected electrons. This energy range is considerably greater than that covered in previous experiments. The data over the whole energy range are compared with the Hartree-Fock calculations of Kennedy and Manson and with those of Amusia et al., using the random phase approximation with exchange method. For Ar the calculations of Amusia et al., which take into account many-electron correlations, are shown to agree more closely with the present data. The data are also shown to be in very good agreement with earlier experimental data obtained over a more limited energy range using electron synchrotron radiation.