Mass loss of wood and its components during transmission electron microscopy

The loss of mass of wood and its polymeric constituents in transmission electron microscopy has been determined by measurement of the decrease in the continuum x-ray intensity for various doses of irradiation. It was found that for doses higher than 5 × 10^?8 C/μm², 42% of the original mass of the wood remained on the grid. The corresponding percentages for cellulose, xylan, and lignin were 32, 45, and 70, respectively. The significance of these results in the use of transmission electron microscopy for imaging and for quantitative microbeam analysis is discussed.     

Low-loss ring resonators fabricated from silicon based integrated optics technologies

The fabrication of low-loss ring resonators using silicon based integrated optics technologies is reported. Propagation losses of 0.028+or-0.009 dB/cm have been deduced from finesse measurements.<>     

12-hour pattern of the waking state in the normal infant and in the infant who has survived the 'syndrome of sudden infant death' (author's transl)

The authors report the results of 16 sleep EEGs carried out on 5 infants said to have survived the syndrome of sudden infant death (near-miss group) and 5 controls. The recordings were performed at 1.5 months, 3 months and 4.5 months, times when the risk of sudden death is maximum. The EEG appearance and the organization of sleep patterns have been studied in both groups. The various states of wakefulness, and the modalities of sleep and waking were subjected to statistical analysis with respect to age. The study showed no significant difference between the percentages of different states of wakefulness in the control and 'near-miss' group, but there were more sleep onsets in active sleep (REM) in this group compared with the controls and there were fewer waking periods, although when they occurred these were more prolonged.     

Effect of solvent on the polymorphism of poly(4-methylpentene-1): 1. Solution-grown single crystals

The morphology and structure of poly 4-methylpentene-1 single crystals grown in a variety of solvent systems is studied by electron microscopy, electron and X-ray diffraction. Depending on the solvent, two different crystalline structures are identified. The usual modification I is formed in a xylene-amylacetate mixture. Modification III is grown in decalin and in a xylene-cyclohexane mixture. In a slowly cooled xylene solution, a mixture of single crystals of both structures is obtained. These results confirm earlier work and show that there is a definite dependence of the structure of the solution-grown polymer crystals on the crystallization temperature. Finally, a refined characterization of modification III single crystals is presented.     

Chia (Salvia hispanica L.) oil extraction: Study of processing parameters

The processing parameters related with chia oil extraction employing screw press have not been studied yet. A Box–Behnken experimental design was used to study the optimization process by response surface analysis. The independent variables considered were seed moisture content, restriction die, screw press speed and barrel temperature, while the response variables measured were oil yield, fines content in oil and oil quality (acidity, peroxide index, K₂₃₂, K₂₇₀, values, antioxidant activity and total tocopherol content). Since chemical quality data of chia seeds oil pressed at different conditions was not affected, the response was optimize to maximize oil yield. The results suggested that 0.113 g/g dry solids (0.101 g/g seed), 6 mm restriction die, 20 rpm screw press speed and 30 °C barrel temperature were the best processing combination to maximize oil yield.     

In situ synthesis of ferrites in ionic and neutral cellulose gels

The filaments of a tyrecord rayon were modified by two methods to enhance the degree of swelling of the material: (1) carboxyl and sulfonic acid substituents were introduced into the rayon and (2) the filaments were swollen in sodium hydroxide. The water-swollen filaments were rendered magnetic by in situ synthesis of ferrites and the resulting magnetic filaments were characterized by transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). Two other non-ionic, highly swollen cellulose gels were used as matrices for in situ synthesis of ferrites: a never-dried, wet-spun model cellulose filament and a never-dried bacterial cellulose membrane. TEM micrographs of thin cross-sections of the magnetic gels showed that the nanometre-sized ferrites were uniformly distributed whereas the treated rayon filaments had ferrites predominantly at the filament surface. All the materials were superparamagnetic as determined by VSM. However, a ferrimagnetic component was detected after several reaction cycles for the bacterial cellulose membrane by Mössbauer spectroscopy.     

On the mechanism of the mercerization of cellulose in wood

When spruce wood was treated with 20% aqueous NaOH, only partial conversion of cellulose I to cellulose II took place. In contrast, complete conversion occurred when a low yield kraft pulp from the same wood was mercerized. This difference in behavior is interpreted in terms of restricted swelling of the wood in the mercerizing alkali; this treatment preserves some memory of meridional order. Differences in polarity of the molecules in cellulose I and cellulose II are also considered as a possible reason for the difficulty in mercerizing the cellulose in wood.     

Synthesis and characterization of poly(N-vinyl pyrrolidone-alt-maleic anhydride): Conjugation with bovine serum albumin

Alternate N-vinyl pyrrolidone/maleic anhydride (NVPMA) copolymers were obtained by radical solution polymerization in dioxane with various MA contents in the monomer feed. The conversion of each monomer was monitored by proton nuclear magnetic resonance spectroscopy (¹H NMR), and the kinetics investigation showed that both monomers had identical polymerization rates if both monomers were present in the reaction mixture. The presence of excess NVP in the polymerization medium increased the kinetics of the polymerization and the molar masses of the resulting polymers. This increase was attributed to a cosolvent effect due to NVP, which is a better solvent for the polymer than dioxane. The hydrolysis rate constant of the polymers increased with pH, and NVPMA copolymers were more prone to hydrolysis (by a factor 10) than the methyl vinyl ether ones. Finally, the immobilization of bovin serum albumin (BSA) was investigated. A 25 mM phosphate buffer (pH 5.5) was the best medium to covalently bind 5 BSA molecules onto a 29 kDa NVPMA copolymer and 13 BSA molecules onto a 58 kDa sample, with grafting efficiencies > 90%. Noncovalent interactions with the hydrolyzed form of the polymer and BSA occured at pHs lower than the isoelectric point of BSA, and the resulting complexes were insoluble in water. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3327–3337, 2001     

A novel growth-factor-dependent myeloid cell line derived from mouse bone marrow cells contains progenitors endowed with high proliferative potential

We describe two modified methods for median-to-ulnar motor conduction comparison in the diagnosis of median neuropathy at the wrist: the median-thenar to ulnar-thenar latency difference (TTLD), and the median-thenar to ulnar-hypothenar latency difference (THLD). We also describe an F-wave ulnar-to-median comparative test, the F-wave latency difference (FWLD). The abnormal cutoffs based upon 34 normal controls are: TTLD, 0.8 ms; THLD, 1.2 ms; FWLD, 0.6 ms. In 50 patients (79 hands) with clinically defined carpal tunnel syndrome and electrophysiological evidence of median neuropathy at the wrist (based upon a prolonged median nerve palm-wrist latency), the diagnostic sensitivities were: 95-98%, 85-88%, and 75-78%, respectively. These tests are therefore highly sensitive. They are easily performed and require minimal additional effort to incorporate into commonly used clinical electrodiagnostic routines. They may be advantageous when a concomitant polyneuropathy is present, and they may also help avoid technical pitfalls and aid in identification of anatomic variants.