Preparation and evaluation of poly(polyethylene glycol methyl ether acrylate-co-polyethylene glycol diacrylate) monolith for protein analysis

A poly(polyethylene glycol methyl ether acrylate-co-polyethylene glycol diacrylate) monolith was prepared by UV-initiated polymerization. Methanol and ethyl ether were selected as porogens from a variety of organic solvents to achieve the desirable characteristics of the monolith. The preparation of the monolith could be achieved within 10 min. The monolith was macroscopically homogeneous, had low flow resistance, and did not swell or shrink significantly in tetrahydrofuran. Inverse size-exclusion data indicate that the monolith had a total porosity of 75.4% and an internal porosity of 9.1%. The monolith could be used for size-exclusion separation of peptides, although it could not separate proteins with molecular masses between 10 and 100 K due to its unique pore size distribution. It was found to resist adsorption of proteins in capillary liquid chromatography when using 100 mM phosphate buffer (pH 7.0) containing 0.5 M NaCl. Complete recovery of both acidic and basic proteins was achieved. The monolith can be used for applications in which inert materials are required for protein analysis.     

Bounds and exact theories for the transport properties of inhomogeneous media

We investigate the bounds of Milton on the transport coefficient of a two-component composite, in their application to the square and hexagonal arrays of cylinders, and the three cubic lattices of spheres. We show that, in all five cases, as more information is supplied about the geometry of the composite, the bounds converge to the precise point obtained from an exact theory specific to the geometry in question. We illustrate the use of the bounds in determining whether a set of known values of the transport coefficient adequately specifies the general behaviour of that quantity. We determine the values of two structure-dependent parameters for cell materials with spheroidal cells and the value of one parameter for hexagonal and square arrays of cylinders with missing array elements. These parameters determine bounds both on the transport and on the elastic properties of the respective materials.     

Classical scattering of Atoms by a model surface

A classical model of atom/surface scattering is presented in which the gas-surface interaction consists of a corrugated hard wall plus attractive square well. New analytic solutions for the scattering intensity for monoenergetic beams are given for both one- and two-dimensional surfaces. Explicit formulae for trapping probabilities and rainbow angles are obtained. An oven beam velocity distribution is incorporated into the model, and calculated results are presented both for in-plane and out-of-plane scattering. Comparisons are made with the Ne/LiF data of Smith, O'Keefe, and Palmer and with the classical calculations of McClure. Objections to the classical rainbow scattering interpretation are discussed.     

Mitotic and amitotic cell replication in malignant melanoma: the role of subdivisional cell replication

It is widely assumed that significant mitotic activity is typical of malignant melanoma and many believe that significant mitotic activity is essential for this diagnosis. We have studied mitotic activity in 205 malignant melanomas and have found that mitotic activity is often minimal or absent, even in malignant melanomas which have recurred or metastasized. Based on our previous work suggesting that new cells can form from nucleoli via nucleolar stalks, we also studied nucleolar stalks in our cases. These were present in greater numbers than mitoses and help explain the anomaly of infrequent mitoses in a highly malignant neoplasm.     

Spectroscopic and picosedond time-resolved studies of vibrational relaxation in naphthazarine in solid neon

Very extensive vibrationally unrelaxed florescence is observed following dye-laser excitation of single vibronic levels of naphthazarine. The rates and pathways of its vibrational relaxation are examined by means of picosecond emission spectroscopy. Analysis of its vibrational and electronic spectra establishes a C_2v symmetry for free naphthazarine.     

One-pot borylation/amination reactions: syntheses of arylamine boronate esters from halogenated arenes

[reaction: see text] A one-pot protocol for converting 1,3- and 1,4-substituted aryl halides to arylamine boronate esters is described. This is achieved by sequential Ir-catalyzed aromatic borylation at the least hindered C-H bond of the aryl halide and subsequent Pd-catalyzed C-N coupling at the halide position of the crude arylboronic ester.     

Thermodynamic response functions of fluids: a microscopic approach based on NpT Monte Carlo

On the basis of NpT Monte Carlo simulations, a detailed analysis on the microscopic origins of some specific features of thermodynamic response functions of fluids is performed. Specifically, the residual isobaric heat capacity C(p) (res), the isobaric thermal expansivity alpha(p), and the isothermal compressibility kappa(T) for Lennard-Jones methane and optimized potential for liquid simulations (OPLS) methanol have been determined via standard techniques. For the former, data along the liquid, gas, and supercritical regions are presented, while a wide temperature range at a single supercritical pressure is covered for the latter. They have been obtained by computing the various pairwise fluctuations contributing to each property. Attention is mainly focused on isothermal and isobaric maxima found for both C(p) (res) and alpha(p), which have been rationalized at a molecular level using qualitative arguments. It is encountered that maxima emerge as a natural consequence of the destruction of fluid structure as temperature is increased or as pressure is decreased. The results for Lennard-Jones methane reveal the competition of energetic and volumetric effects, while those for OPLS methanol evidence that hydrogen-bonding is dominant as energetic effects are concerned. Further discussion on previous results and alternative approaches using equations of state as well as on closely related topics such as "maxima and critical phenomena" is included.     

Synthesis and characterization of nanostructured iron compounds prepared from the decomposition of iron pentacarbonyl dispersed into carbon materials with varying porosities

This work describes the production and characterization of carbon-iron nanocomposites obtained from the decomposition of iron pentacarbonyl (Fe(CO)₅) mixed with different carbon materials: a high surface area activated carbon (AC), powdered graphite (G), milled graphite (MG), and carbon black (CB). The nanocomposites were prepared either under argon or in ambient atmosphere, with a fixed ratio of Fe(CO)₅ (4.0 mL) to carbon precursor (2.0 g). The images of scanning electron microscopy and the analysis of textural properties indicated the presence of nanostructured Fe compounds homogeneously dispersed into the different classes of pores of the carbon matrices. The elemental Fe content was always larger for samples prepared in ambient atmosphere, reaching values in the range of 20–32 wt%. On the other hand, samples prepared under argon showed reduced Fe content, with values in the range 5–10 wt% for samples prepared from precursors with low surface area (G, MG, and CB) and a much higher value (~19 wt%) for samples prepared from the precursor of high surface area (AC). Mössbauer spectroscopy and X-ray diffractometry showed that the nanoparticles were mostly composed of iron oxides in the case of the samples prepared in oxygen-rich ambient atmosphere and also for the AC-derived nanocomposite prepared under argon, which is consistent with the large oxygen content of this precursor. For the other precursors, with reduced or no oxygen content, metallic iron and iron carbides were found to be the dominant phases in samples prepared under oxygen-free atmosphere. The samples prepared in ambient atmosphere and the AC-derived sample prepared under argon exhibited superparamagnetic behavior at room temperature, as revealed by temperature-dependent magnetization curves and Mössbauer spectroscopy.