Measurement of the neutron F2 structure function via spectator tagging with CLAS

We report on the first measurement of the F(2) structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ?100 MeV/c and their angles to ?100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F(2)(n) data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65相似文献   

Vibrational spectra of cyclic C8 in solid argon

Vapors from solid and powdered carbon, emitted from an oven cycled between 2000 and 3000 K, were co-condensed with argon onto a CsI substrate maintained at 10 K. The cycling process produced a multilayered matrix with regions of high carbon density alternating with layers of argon. FTIR measurements including ¹³C isotopic data, supported by ab initio calculations, allow the assignment of a band observed at 1817.8 cm⁻¹ to the ν₁₂(e_u) fundamental of cyclic C₈.     

One-dimensional metal–organic frameworks built by coordinating 2,4,6-tris(4-pyridyl)-1,3,5-triazine linker with copper nodes: CO2 adsorption properties

The reaction between 2,4,6-tris(4-pyridyl)-1,3,5-triazine (4-tpt) and copper(II) hexafluoroacetylacetone (Cu(hfa)₂) yields two different 1D metal–organic frameworks (MOFs), [(Cu(hfa)₂)₂(4-tpt)]_n ( 1 ) and [Cu(hfa)₂(4-tpt)]_n ( 2 ). The Cu:4-tpt ratio in the new MOFs is determined by the reaction medium, particularly, the solvent used. The two compounds have been fully characterized, including crystal structure elucidation. [(Cu(hfa)₂)₂(4-tpt)]_n ( 1 ), with a 2:1 Cu:4-tpt ratio, could be precipitated in either 1,1,2-trichloroethane or supercritical CO₂. In ( 1 ), 4-tpt shows a tritopic coordination mode, but only half of the Cu(hfa)₂ subunits act as a node, thus connecting two 4-tpt and giving a 1D network. The other half of Cu(hfa)₂ subunits are connected only to one pyridine and thus protrude along the chains. The later Cu(hfa)₂ fragments show a labile character and can be dissolved in diethyl ether to give the second MOF [Cu(hfa)₂(4-tpt)]_n ( 2 ), with a 1:1 Cu:4-tpt ratio. The compound ( 2 ) has also a 1D structure, with all the incorporated copper atoms acting as nodes. In this case, the packing of the chains defines accessible channels, which are perpendicular to the chain axis. After activation, N₂ adsorption/desorption measurements at 77 K confirm the microporous character of ( 2 ) with an apparent surface area of 190 m² g⁻¹. Besides, at 273 K this material clearly shows a significant adsorption of CO₂ prompted by noncoordinated nitrogen in the triazine linker.     

Spline quasi-interpolation in the Bernstein basis and its application to digital elevation models

A nonstandard low-cost spline approximation method for approximating bivariate functions is constructed. It is applied for Digital Elevation approximation and then its accuracy in the downscaling process is studied.     

Characterization of therapeutic mAb charge heterogeneity by iCIEF coupled to mass spectrometry (iCIEF–MS)

Imaged capillary isoelectric focusing (iCIEF) has emerged as an important technique for therapeutic monoclonal antibody (mAb) charge heterogeneity analysis in the biopharmaceutical context, providing imaged detection and quantitation by UV without a mobilization step. Besides quantitation, the characterization of separated charge variants ideally directly by online electrospray ionization–mass spectrometry (ESI–MS) is crucial to ensure product quality, safety, and efficacy. Straightforward direct iCIEF–MS coupling combining high separation efficiency and quantitative results of iCIEF with the characterization power of MS enables deep characterization of mAb charge variants. A short technical setup and optimized methodical parameters (30 nl/min mobilization rate, 2%–4% ampholyte concentration, 0.5–2 mg/ml sample concentration) allow successful mAb charge variant peak assignment from iCIEF to MS. Despite a loss of separation resolution during the transfer, separated intact mAb charge variants, including deamidation as well as major and minor glycoforms even from low abundant charge variants, could be characterized by online ESI–MS with high precision. The presented setup provides a large potential for mAb charge heterogeneity characterization in biopharmaceutical applications.