Oxidation of substrates having labile hydrogens by superoxide in the presence of phosgene dimer

Superoxide (O₂^?) oxidized substrates having labile hydrogens to ketones in the presence of phosgene dimer. Oxidations with similar treatment of alkynes were examined. The reaction mechanism was also discussed.     

Temporal variation of tritium concentration in tree-ring cellulose

Tritium concentration of organically bound hydrogen has been measured during the 1941 to 1987 period using a cellulose fraction extracted from pine tree grown in Tatsunokuchi-machi, Ishikawa Prefecture, Japan. It was concluded that most of the tritium bound in cellulose was supplied from the mixture of underground water in the root zone of the pine tree. Underground water was strongly influenced by the precipitation and waters with different residence times. This revised version was published online in July 2006 with corrections to the Cover Date.     

Temporal variation of tritium concentration in tree-ring cellulose over the past 50 years

Concentration of organically-bound tritium in the tree-ring cellulose of a pine tree grown in Shika-machi, Ishikawa prefecture, Japan (37.1°N, 136.5°E), was measured during the ring-years from 1949 to 1999. The results were compared with those of a pine tree grown in Tatsunokuchi-machi, Ishikawa prefecture, Japan (36.4°N, 136.5° E). The annual variation of tritium in tree rings demonstrated two differences between the Shika-machi tree and the Tatsunokuchi-machi tree. No secondary peak appeared in the period after the maximum peak of 1963 for the Shika-machi tree, while two peaks appeared in 1966 and 1970 for the Tatsunokuchi-machi tree. In addition, the height of the 1963 peak was 30% higher for the Shika-machi tree than for the Tatsunokuchi-machi tree. These differences are considered to be caused by the influence that the underground water in the root zone of the Tatsunokuchi-machi tree was strongly affected by water which was transported to the tree site from mountain regions as compared to the Shika-machi tree.This study was supported in part by a Grant from the Ishikawa Prefectural Institute of Public Health and Environmental Science.     

Temporal variation of tritium concentration in tree-ring cellulose over the past 50 years

Concentration of organically-bound tritium in the tree-ring cellulose of a pine tree grown in Shika-machi, Ishikawa prefecture, Japan (37.1°N, 136.5°E), was measured during the ring-years from 1949 to 1999. The results were compared with those of a pine tree grown in Tatsunokuchi-machi, Ishikawa prefecture, Japan (36.4°N, 136.5° E). The annual variation of tritium in tree rings demonstrated two differences between the Shika-machi tree and the Tatsunokuchi-machi tree. No secondary peak appeared in the period after the maximum peak of 1963 for the Shika-machi tree, while two peaks appeared in 1966 and 1970 for the Tatsunokuchi-machi tree. In addition, the height of the 1963 peak was 30% higher for the Shika-machi tree than for the Tatsunokuchi-machi tree. These differences are considered to be caused by the influence that the underground water in the root zone of the Tatsunokuchi-machi tree was strongly affected by water which was transported to the tree site from mountain regions as compared to the Shika-machi tree.This study was supported in part by a Grant from the Ishikawa Prefectural Institute of Public Health and Environmental Science.     

Effect of cellulose crystallinity on bacterial cellulose assembly

Bacterial cellulose (BC) is a promising biomaterial as well as a model system useful for investigating cellulose biosynthesis. BC produced under static cultivation condition is a hydrous pellicle consisting of an interconnected network of fibrils assembled in numerous dense layers. The mechanisms responsible for this layered BC assembly remain unknown. This study used calcofluor as a fluorescent marker to examine BC layer formation at the air/liquid interface. Layers are found to move downward into the media after formation while new layers continue to form at the air/liquid interface. Calcoflour is also known to reduce the crystallinity of cellulose, changing the mechanical properties of the formed BC microfibrils. Consecutive addition and accumulation of calcofluor in the culture medium is found to disrupt the layered assembly of BC. BC crystalllinity decreased by 22 % in the presence of 12 % calcofluor (v/v) in the medium as compared to BC produced without calcofluor. This result suggests that cellulose crystallinity and the mechanical properties which crystallinity provides to cellulose are major factors influencing the layered BC structure formed during biosynthesis.     

Carbon-14 dating of tree rings for tritium measurement

The carbon-14 concentration in tree-ring cellulose of an 80-year-old pine tree which has been used for tritium measurement was measured during the 1941–1987 period. This was done to determine the formation year of each tree ring in order to study the pathway of tritium uptake into the tree rings. In the 1941 to 1953 period, the Δ¹⁴C value remained slightly lower than 0%., It began to increase from 1954 to a small broad peak of 250% between 1959 and 1961, followed by rapid increase to the highest value of approximately 800% in 1964. Since 1964, it had been diminishing year by year to reach a level of 190% in 1987. The two peak years coincided with those in the known carbon-14 patterns in tree rings. However, there existed a difference in the amplitude of the Δ¹⁴C values during the period of 1963–1967.     

X-ray measurement of cellulose crystallite orientation in cotton fibers

The orientation of crystallites in a bundle of parallel cotton fibers was studied by x-ray diffraction. The intensity distributions of the 101 and 002 diffraction rings showed the distributions of (101) and (002) planes to be identical within the limits of accuracy. Therefore, the crystallites in the cotton fibers very likely had random orientation about their long axes. The orientation distribution of these axes was calculated by using the intensity distribution of the 002 diffraction ring. The cylindrically symmetrical density distribution J(β) thus obtained was multiplied by sin β to obtain the distribution of relative numbers of crystallites at given angles β to the long axis of the fiber. The average 〈β〉 was found to be in agreement with the value of 〈sin²β〉 measured from the 002 diffraction ring. The intensity distributions on the 101 and 002 diffraction rings showed small fluctuations. These fluctuations appeared much stronger in the J(β) and sin β J(β) distributions, indicating clear discontinuities in the pitch angle distribution.     

Effect of tritium on hydrogen isotope exchange reaction in a heterogeneous system

In order to reveal the effect of tritium (³H or T) on hydrogen isotope exchange, the exchange reaction between a certain compound (solid or liquid) and a tritiated one (gas or solid) was observed in gas-solid or liquid-solid systems. The reaction was analyzed using the data obtained and theA-McKay plot method, and it has been quantitatively clarified that the effect of T on the reactivity of a material is changed with (1) the degree of polymerization of the material, (2) the kind of functional groups in the material, and (3) the reaction system.     

Effect of plasma treatment on cellulose fiber

Cotton cellulose fibers were modified in inert plasma. Surface morphology of the modified fibers was studied by SEM and changes in the surface composition by XPS and FTIR. Standard goniometry was used for determination of contact angle as a function of modified fiber aging. Absorptivity of modified fibers was determined by gravimetry and fiber width in physiological solution, simulating body liquids, by confocal microscopy. Antibacterial effect of pristine and plasma treated samples was examined by following growth of Escherichia coli. Plasma treatment led to surface ablation, changes in surface morphology and fiber width. Surface of the plasma modified fibers was oxidized and their water absorptivity was reduced. The plasma modification did not affect E. coli growth substantially.     

Fate of the benzene hydrogens in ergot alkaloids biosynthesis

Feeding experiments with specifically labelled precursors showed that in ergot alkaloids biosynthesis, the isoprenylation of tryptophan occurs without intermediate hydroxylation.     

Effect of microcrystal cellulose and cellulose whisker on biocompatibility of cellulose-based electrospun scaffolds

To investigate the potential application of microcrystal cellulose (MCC) and cellulose whisker (CW) in the electrospun vascular tissue scaffolds, cellulose acetate (CA) and cellulose composite scaffolds containing MCC and CW were electrospun from CA solutions and deacetylation. Structure and morphology of MCC, CW and the fibrous composite scaffolds were investigated using FT-IR, SEM, TEM and AFM. The wettability of the scaffolds was evaluated by water contact angle analysis. The effect of MCC and CW on the biocompatibility of the scaffolds for vascular smooth muscle cells (VSMC) was assayed by MTT test, fluorescent imaging and SEM. The biocomposite scaffolds displayed multi-scaled structure and morphology. The scaffolds containing MCC and CW simultaneously exhibited significantly higher cell viability compared to those with only MCC or CW and no filler. Cell viability and morphology within the scaffolds become better with increasing content of MCC and CW. The composite scaffolds with both micro- and nano-scale organization could mimic the native extracellular matrix more closely, and further produce synergistic enhancement on VSMC viability, adhesion and proliferation. This study provides the potential applications of renewable cellulose-based particulates in biomedical field.     

Development of continuous inflow tritium measurement in water technology using electrolysis and a plastic scintillator

Our goal was to develop a mobile tritium monitor for continuous inflow system for water sample. The system is based on electrolysis and a plastic scintillator detection system. The minimum detectable activity (MDA) of the prototype system is 431 kBq L^?1, while the MDA of a commercially available product is 740 kBq L^?1. We expected to achieve a 5.73-times lower MDA by optimizing detection geometry using a multi-hydrogen-gas-channel. The system can be applied either as a mobile leakage surveying method or as a fixed-type monitor for detecting tritium in drinking water by adapting conventional background reduction technologies.     

Moisture absorption measurement and modelling of a cellulose acetate

Cellulose - With a view toward the application of highly hygroscopic polymers as a humidity responsive self-actuator, the evaluation of the real time moisture concentration in the material becomes...     

Effect of crystallinity on radiation-induced graft copolymerization on cellulose

With vinyl monomers, viz., styrene, butyl methacrylate, dimethylaminoethyl methacrylate, and ethyl acrylate, it was noted that higher per cent grafting was obtained with “recrystallized” cellulose than with “amorphous” cellulose. The possibility of the production of a porous structure in cellulose as a result of γ-irradiation followed by the dissolution of the reactive regions is suggested. DTA and DTG data of irradiated cellulose triacetate (CTA) reveal lowering of the melting point on irradiation, indicating a decrease in crystallinity. Decrease in density of cellulose on irradiation by γ-rays also indicates loosening of the structure of cellulose. It is postulated that grafting occurs in those regions of cellulose which were crystalline before irradiation, as well as in less crystallinie regions.     

Effect of VUV-excimer lamp treatment on cellulose fiber

Vacuum ultra-violet-excimer lamp effect on cellulose fiber was studied to examine the effect on surface chemistry of cellulose. We focused on composition of a superficial layer of cellulose, which was studied by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Along with the surface composition, surface morphology was studied by scanning electron microscopy. The vacuum ultra-violet-excimer exposure in various atmospheres can be advantageously utilized as cellulose pre-treatment with tailored properties. N₂ atmosphere is suitable for cleaning of cellulose surface, NH₃ atmosphere for functionalization with amine and amide groups, and air atmosphere for increase or decrease of wettability, depending on exposure time.     

Effect of temperature on high pressure cellulose compression

The effect of temperature during cellulose compression has been studied using mechanical testing, particle size analysis, density and pressure–volume–temperature (PVT) measurements, crystallinity index, scanning electron microscope photographs and water sorption isotherms. Commercial cellulose powder samples with different crystallinity levels were compacted at high pressure (177 MPa) for 10 min at two different temperatures: 25 and 160 °C. Three point bending test results for compressed samples are discussed. When pressure was applied directly to powders at room temperature, the cellulose sample with the highest level of crystallinity showed an increase in its crystallinity index of about 5 %, while this was about 22 % for the sample with the lowest level. These increases were even higher at 160 °C attaining 8 and 33 % respectively. Using density measurements, a densification phase related to this crystallinization was observed, and the PVT diagrams from different cellulose samples showed that this was associated with high temperatures. Water sorption isotherms were made on cellulose samples before and after compression. They showed a diminution of cellulose sorption capacity after compression at 160 °C, revealing the effect of temperature on high-pressure cellulose compression, reducing specific surface area. Events of this nature suggest a sintering mechanism, when temperature is associated with high pressure during cellulose compression.