Sensitive detection and separation of fluorescent derivatives using capillary electrophoresis with laser-induced fluorescence detection with 532 nm Nd:YAG laser

Capillary electrophoresis with laser-induced fluorescence detection (CELIF) is a powerful tool for separation and sensitive determination of fluorescent species. Biologically active compounds, such as amino acids, peptides and proteins may exhibit native fluorescence, which is however often low and/or an expensive laser is required for excitation in UV. Therefore, labelling of the analytes with a fluorescent dye is usually necessary.In this work, a home-built CELIF instrument with diode pumped frequency-doubled continuous wave Nd:YAG excitation laser with feedback power regulation (532 0;nm) was constructed. The suitability of this type of laser for LIF detection in a separation method was found excellent. A limit of detection (LOD) (S/N=3) of 2×10⁻¹³ 0;mol/l was achieved with rhodamine B, which is comparable to those obtained using similar instruments with Ar⁺ laser [Y.F. Cheng, N.J. Dovichi, Science 242 (1988) 562, E.S. Yeung et al., J. Chromatogr. 608 (1992) 73]. LOD of a protein derivatized according to modified procedures [M.J. Little et al., Anal. Chim. Acta 339 (1997) 279, A. Chersi et al., Biochim. Biophys. Acta 1336 (1997) 83] was determined. Detection of the derivatives was found to be limited by insufficient reaction recovery at low analyte concentration, chemical noise, separation efficiency and quality of the derivatizing reagent rather than by the detector performance. As a consequence, a huge gap between the detection ability of CELIF instruments and LOD determined in real samples is revealed.     

Weak Barriers in Nonlinear Potential Theory

We characterize regular boundary points for p-harmonic functions using weak barriers. We use this to obtain some consequences on boundary regularity. The results also hold for 013/11118_2007_9064_Article_IEq1.gif" alt="$\mathcal{A}$" align="middle" border="0">-harmonic functions under the usual assumptions on 013/11118_2007_9064_Article_IEq2.gif" alt="$\mathcal{A}$" align="middle" border="0">, and for Cheeger p-harmonic functions in metric spaces.      

On characterization and perturbation of local -semigroups

Let 0" HEIGHT="41" ALIGN="MIDDLE" BORDER="0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img1.gif" ALT="$ S(\cdot)$"> be a 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img2.gif" ALT="$ (C_0)$">-group with generator 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img3.gif" ALT="$ -B$">, and let 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img4.gif" ALT="$ \{T(t);0\le t<\tau\}$"> be a local 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img5.gif" ALT="$ C$">-semigroup commuting with 0" HEIGHT="41" ALIGN="MIDDLE" BORDER="0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img6.gif" ALT="$ S(\cdot)$">. Then the operators 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img7.gif" ALT="$ V(t):=S(-t)T(t)$">, 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img8.gif" ALT="$ 0\le t<\tau$">, form a local 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img9.gif" ALT="$ C$">-semigroup. It is proved that if 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img10.gif" ALT="$ C$"> is injective and 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img11.gif" ALT="$ A$"> is the generator of 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img12.gif" ALT="$ T(\cdot)$">, then 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img13.gif" ALT="$ A+B$"> is closable and 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img14.gif" ALT="$ \overline{A+B}$"> is the generator of 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img15.gif" ALT="$ V(\cdot)$">. Also proved are a characterization theorem for local 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img16.gif" ALT="$ C$">-semigroups with 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img17.gif" ALT="$ C$"> not necessarily injective and a theorem about solvability of the abstract inhomogeneous Cauchy problem: 0" SRC="http://www.ams.org/proc/2007-135-04/S0002-9939-06-08549-2/gif-abstract0/img18.gif" ALT="$ u'(t)=Au(t)+Cf(t), 0<t<\tau; u(0)=Cx.$">

     

Modification of n-Si(1 1 1) wafer with olefin carboxyl acids and olefin sulfite acids and the photovoltaic properties of the electrodes

n-Si(1 0;1 0;1) crystalline electrode was modified by carboxyl acid groups and sulfonic groups. The flat band potential (U_fb), relation between flat band potential and the carbon numbers to the modified samples and relation between photocurrent density and potential of the modified electrodes were studied. ATR-IR spectra and XPS analysis show that the organic compounds were connected to n-Si(1 0;1 0;1) wafer by Si0" alt="single bond" src="http://cdn.els-cdn.com/sd/entities/sbnd" class="glyphImg">C bond. Calculation indicates that the surface modification ratio increased with the carbon number of organic groups decreased. Mott-Schottky plots gives the flat band potential of the samples to shift to negative positions with the carbon number decreased in both of the two different systems and the flat band potential of the sample with the group of 0" alt="single bond" src="http://cdn.els-cdn.com/sd/entities/sbnd" class="glyphImg">(CH₂)₃SO₃H reaches to −0.82 0;V, which is more negative than reported, and the flat band potential of all the samples in this paper are more negative than the sample with methyl group [B. Ashish, N.S. Lewis, J. Phys. Chem. B 102 (1998) 1067; S. Takabayashi, M. Ohashi, K. Mashima, Y. Liu, S. Yamazaki, Y. Nakato, Langmuir 21 (2005) 8832]. The photocurrent and photovoltage of the modifications are stable enough under solar illumination for a long time.     

Chemisorption of 1,1-dichloroethene on the Si(1 1 1)-7 × 7 surface

Chemisorption of 1,1-dichloroethene (Cl₂C0" alt="double bond; length as m-dash" src="http://cdn.els-cdn.com/sd/entities/dbnd" class="glyphImg">CH₂) to a Si(1 0;1 0;1)-7 0;× 0;7 surface was studied by means of X-ray photoelectron spectroscopy using synchrotron radiation, recording chlorine 2p and carbon 1s spectra. For carbon 1s, spectral assignment of the chemisorbed species is based on quantum chemical calculations of chemical shifts in model compounds.The results confirm the identity of covalently bonded 1-chlorovinyl (-CCl0" alt="double bond; length as m-dash" src="http://cdn.els-cdn.com/sd/entities/dbnd" class="glyphImg">CH₂) and vinylidene (0" alt="2 bonds on the lefthand side" src="http://cdn.els-cdn.com/sd/entities/lbond2" class="glyphImg">C0" alt="double bond; length as m-dash" src="http://cdn.els-cdn.com/sd/entities/dbnd" class="glyphImg">CH₂) adspecies. Upon chemisorption at room temperature it was found that about one-third of the molecules break one C-Cl bond while about two-thirds of the adsorbates break two C-Cl bonds. We do not, however, find evidence for isomerization of 0" alt="2 bonds on the lefthand side" src="http://cdn.els-cdn.com/sd/entities/lbond2" class="glyphImg">C0" alt="double bond; length as m-dash" src="http://cdn.els-cdn.com/sd/entities/dbnd" class="glyphImg">CH₂ to di-bonded vinylene (-CH0" alt="double bond; length as m-dash" src="http://cdn.els-cdn.com/sd/entities/dbnd" class="glyphImg">CH-).     

Ordered arrangement of 9-aminoanthracene on Au(1 1 1) surfaces: A scanning tunneling microscopy study

We present a scanning tunneling microscopy (STM) investigation of 9-aminoanthracene (AA) on the reconstructed Au(1 0;1 0;1) surface. The bare Au(1 0;1 0;1) surface shows the herringbone reconstruction which is conserved upon deposition of the organic molecules. Most of the AA molecules are found to decorate the regions of fcc-stacking of the gold surface where a periodic linear arrangement is observed. The orientation of the long molecule axis of individual molecules is along the 0" style="vertical-align:bottom" width="40" alt="View the MathML source" title="View the MathML source" src="http://ars.els-cdn.com/content/image/1-s2.0-S0039602807009363-si1.gif">-directions of the Au substrate. In addition, for individual domains of the surface reconstruction, one of the three possible orientations is preferred. On substrate areas which exhibit a high step density, the steps are completely decorated by AA molecules. A detailed analysis of the STM images reveals that the molecules are located on top terrace levels. The fine structure of individual molecules on the terrace shows a clear dependence on the tunneling voltage and resembles the molecular orbitals of the free AA molecule.     

Beam-helicity asymmetry in photon and pion electroproduction in the Δ(1232)-resonance region at Q2 = 0.35(GeV/c)2

The beam-helicity asymmetry has been measured simultaneously for the reactions 0050_2007_Article_100341_TeX2GIFIEq1.gif" alt="$ \;\stackrel{{\rightarrow}}{{e}}\;$" align="middle" border="0"> p→epγ and 0050_2007_Article_100341_TeX2GIFIEq2.gif" alt="$ \;\stackrel{{\rightarrow}}{{e}}\;$" align="middle" border="0"> p→ep`0; <sup>0</sup> in the Δ(1232)-resonance region at Q <sup>2</sup> = 0.35(GeV/c)<sup>2</sup>. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on dispersion relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some γ <sup>(*)</sup> N→`0;N multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels (γ and `0; ⁰) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization.     

The Experimental Approach to Effective Stress Law of Coal Mass by Effect of Methane

Effective stress law of all kinds of coal samples, including steam coal, fat coal, corking coal, thin coal and anthracite, under pore pressure of gas, is experimentally studied using a newly developed test machine. These samples are taken from Coal Mines in Wuda, Hebi, Yanzhou, Yangquan, Qingshui, and Gujiao in China. The experiment results show that, under pore pressure of gas, the tested coal samples comply with Biot0/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s effective stress law, 0/11242_2004_Article_5123348_TeX2GIFIE1.gif" alt=" $${\sigma '}_{ij} = {\sigma}_{ij} - {\alpha}p{\delta}_{ij}$$ " align="middle" border="0"> where the Biot0/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s coefficient 0/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> is not a constant, and is bilinear function of volumetric stress (0/xxlarge920.gif" alt="THgr" align="BASELINE" BORDER="0">) and pore pressure (p), that is, 0/11242_2004_Article_5123348_TeX2GIFIE2.gif" alt=" $$\alpha = a_1 + a_2 \Theta + a_3 p + a_4 \Theta p$$ " align="middle" border="0"> We define four areas according to the numerical feature of 0/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">, that is, functionless area of pore pressure, normal function area, fracturing function area, and quasi-soil function area. The effective stress law of coal mass introduced by this paper is a constitutive equation in the study of coupled solid and fluid. This has significance in the drainage and outburst of methane in coal seam.     

Some Results on Dynamics of Special Double-Loop ΣΔ-Modulators

The dynamic behaviour of a specific two-dimensional state space model with discontinuity is studied. This model arises from the study of double-loop 05q83w6tg0527/xxlarge931.gif" alt="Sgr" align="BASELINE" BORDER="0">05q83w6tg0527/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">-modulators with constant input. Using mathematical tools we explain certain simulation results, and some properties are derived. Simulations based on time-varying input are also provided.