Hydrolysis characteristics of tissue fractions resulting from mechanical separation of corn stover

Corn stover has potential as a resource for both fiber and chemical needs if separation strategies can be developed to deal with its heterogeneity. Relative hydrolysis characteristics were assessed for pith (sclerenchyma and parenchyma) and fiber (collenchyma) tissue fractions derived from mechanical separation of corn stover to determine whether classification by tissue type resulted in fractions with different hydrolysis response. The physical characteristics of the tissue fractions were analyzed. The hydrolysis behavior of the fractions was evaluated under both acidic and basic conditions. The results from the hydrolysis experiments are compared with previously reported compositional analysis for the tissue fractions.     

Lasers for plasma diagnostics,time resolved measurement and molecular fluorometry in analytical science

In chemical measurement and characterization, lasers are playing a unique role in improving sensitivity, enhancing spatial and spectral resolution, and enabling time resolution on the fastest time scales that are chemically significant. Furthermore, lasers have permitted entirely new classes of measurements to be undertaken that would not be possible without the high radiant power, directionality, and coherence of a laser beam. In this paper, a number of these capabilities are illustrated with examples from the authors' laboratory. Prominent among these examples is the use of a high-power pulsed laser for producing scattering and fluorescence from species in an inductively coupled plasma (ICP). With the appropriate laser and photometric equipment, such measurements enable the determination of time-resolved and spatially resolved values for electron concentration, electron energy distribution, gas-kinetic temperature, and the concentrations of important sample and intrinsic species that the plasma contains. Another example shows how either a continuous wave (CW) or repetitively pulsed laser can be coupled with relatively simple electronic instrumentation to permit measurements to be obtained on a sub-nanosecond time scale. Interestingly, a recent development might obviate the need for a sophisticated laser in such schemes. Lastly, a relatively simple experimental configuration can be used to determine as few as 10⁶ molecules in a real sample. In this arrangement, a single aliquot of the sample is dispensed in a volume as small as 6 nL. This aliquot, in droplet from, then constitutes the sample cell itself. As the droplet falls through the focused laser beam, its contents can be determined with extraordinarily high sensitivity. Methods to improve even this detection capability will be outlined.     

Determination of the molecular structure of diacetylene from high-resolution FTIR spectroscopy

The high-resolution infrared absorption spectra of eight²H or¹³C substituted isotopomers of diacetylene have been recorded, and the bands corresponding to thev ₄ fundamental andv ₆ combination of the major isotopomer have been analyzed using a Loomis-Wood-type program. Effective ground-state rotational constants have been obtained from ground-state combination differences. A number ofr ₀,r _s,r _m , and (r _m )_corr structures have been calculated from the available data and are compared to those obtained by ab initio methods. The (r _m )_corr structure, which is a reliable near-equilibrium structure of diacetylene, isr _C–H=106.131(13) pm;r _C–C=137.081(16) pm;r _C-C=120.964(14). (r _m )_corr structures of the related molecules cyanogen, cyanoacetylene, and cyanodiacetylene have been calculated, and near-equilibrium structures of triacetylene and dicyanoacetylene have been predicted.     

The dynamics of water-protein interaction studied by ultrafast optical Kerr-effect spectroscopy

Changes in the ultrafast dynamics and terahertz Raman spectrum accompanying a helix-to-coil transition of a homo-polypeptide have been observed for the first time. Formation of the alpha-helix is associated with a shift to lower frequency of a broad Raman band attributable to solvent-peptide intermolecular hydrogen bonding. This band facilitates direct spectroscopic observation of so-called hydration water near a peptide and yields the first quantitative estimate of the time scale of the ultrafast dynamics in the solvation shell, which range from 0.18 to 0.33 ps (185-100 cm(-1)) depending on the secondary structure of the peptide. Such fast motions of solvent molecules have been referred to as the "lubricant of life" and are thought to play key roles in determining structure and activity of proteins.     

Biomolecular profiling of metastatic prostate cancer cells in bone marrow tissue using FTIR microspectroscopy: a pilot study

Prostate cancer (CaP) cells preferentially metastasise to the bone marrow, a microenvironment that plays a substantial role in the sustenance and progression of the CaP tumour. Here we use a combination of FTIR microspectroscopy and histological stains to increase molecular specificity and probe the biochemistry of metastatic CaP cells in bone marrow tissue derived from a limited source of paraffin-embedded biopsies of different patients. This provides distinction between the following dominant metabolic processes driving the proliferation of the metastatic cells in each of these biopsies: glycerophospholipid synthesis from triacylglyceride, available from surrounding adipocytes, in specimen 1, through significantly high (p ≤ 0.05) carbohydrate (8.23 ± 1.44 cm⁻¹), phosphate (6.13 ± 1.5 cm⁻¹) and lipid hydrocarbon (24.14 ± 5.9 cm⁻¹) signals compared with the organ-confined CaP control (OC CaP), together with vacuolation of cell cytoplasm; glycolipid synthesis in specimen 2, through significantly high (p ≤ 0.05) carbohydrate (5.51 ± 0.04 cm⁻¹) and high lipid hydrocarbon (17.91 ± 2.3 cm⁻¹) compared with OC CaP, together with positive diastase-digested periodic acid Schiff staining in the majority of metastatic CaP cells; glycolysis in specimen 3, though significantly high (p ≤ 0.05) carbohydrate (8.86 ± 1.78 cm⁻¹) and significantly lower (p ≤ 0.05) lipid hydrocarbon (11.67 ± 0.4 cm⁻¹) than OC CaP, together with negative diastase-digested periodic acid Schiff staining in the majority of metastatic CaP cells. Detailed understanding of the biochemistry underpinning the proliferation of tumour cells at metastatic sites may help towards refining chemotherapeutic treatment.     

Modeling Biological Systems: The Belousov–Zhabotinsky Reaction

In this essay I examine the ways in which the Belousov–Zhabotinsky (BZ) reaction is being used by biologists to model a variety of biological systems and processes. The BZ reaction is characterized as a functional model of biological phenomena. It is able to play this role because, though based on very different substrates, the model and system modeled are examples of the same type of excitable medium. Lessons are drawn from this case about the relationships between the sciences of chemistry and biology.     

Transparency enhancement in semicrystalline PEEK through variation of polymer morphology

We report a processing window in which transparent semicrystalline poly(ether ether ketone) (PEEK) can be produced. The transparent PEEK film reported is 100 μm in thickness and has light transmittance of 54%; while ordinary semicrystalline PEEK film of the same thickness and degree of crystallinity, but produced outside the processing window, is virtually opaque (with the light transmittance close to 0%). First processing conditions for producing the transparent PEEK film are discussed, and second characterization of the transparent PEEK film is detailed. Results suggest that the main processing condition for developing the transparent PEEK film is forming temperature, defined as the highest temperature that the film is exposed to during thermal treatment. Using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and small-angle x-ray scattering (SAXS), we characterized morphology of the PEEK films. TEM shows that the morphology in the transparent PEEK film has a locally oriented lamellar structure, instead of the commonly observed spherulites or sheaves. DSC results suggest that the new morphology is formed in the melt with a high density of residual crystals that act as nucleating agents during the crystallization process, which is known as a self-seeding effect. SAXS spectra show that specimens with higher forming temperature produce broader diffraction peak at larger Q value that is defined as 4π sin θ/λ. We conclude from the study that the light transmittance enhancement is morphology related, and can be achieved through control of processing conditions. © 1996 John Wiley & Sons, Inc.     

Molecular simulation of thermophysical properties of aromatic polymers containing oxetane ring in the main chain

Molecular simulation techniques have been applied to newly synthesized aromatic polymers, containing oxetane rings in the main chain, to characterize the shape of rod‐like macromolecules. Single chains and periodic unit cells of a series of aromatic polymers with degree of polymerization 15 were used in the simulations, in accordance with the experimentally obtained one. The total potential energy was minimized and then NVE and NPT molecular dynamics simulations were performed for 1,000 ps at 11 temperatures between 10 and 1,000 K. The coefficient of asymmetry was calculated from the computer‐generated structures. The predictive capability of the NPT molecular dynamics simulation and Polymer Properties modules of Cerius² were used to estimate the orientational properties (order parameter), glass transition temperature, cohesive energy, and decomposition temperature of the polymers simulated. In general, there is a good‐to‐excellent agreement between simulated results and available experimental data of the above investigated properties. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2334–2352, 1999     

Experimental Critical-Exponent Values for Fluids

After a review of the history and an assessment of the current status of the subject, we present light-scattering data to determine the critical correlation-function exponents for an aqueous electrolyte solution yielding the experimental values γ=1.238±0.012, ν=0.629±0.003, η=0.032±0.013. We conclude the paper with some comments concerning the temperature dependence of non-asymptotic effective critical-exponent values of fluids.     

TIME-TEMPERATURE-MISCIBILITY AND MORPHOLOGY OF POLYOLEFIN BLENDS

Miscibility and crystallization have been studied for polypropylene-polyethylene and polyethylene-polyethyleneblends. In the case of the polypropylene blends the composition of interest is 20% polypropylene. At this composition thepolypropylene has been found to be soluble in linear low density polyethylene but insoluble in high, low and very lowdensity polyethylenes. The miscibility has been concluded from the crystallization kinetics and polarised optical microscopywith a hot stage. Polyethylene-polyethylene blends have been formed from polymers with similar average branching contentbut where they have different melting temperatures. Important consequences are to introduce long branches into apolyethylene that only has short branches, and to modify the morphology of a polyethylenes so that haze, gloss and strainhardening are improved. Polyethylene blends must be developed after careful consideration of the branch content anddistribution within each of the constituents. It is not sufficient to simply blend polyethylenes, with the desired range ofproperties, without regard to the miscibility of the blend composition.