Detergency and mechanism of soil removal in detergent-enzyme system

Enzyme effects on detergency were studied at a relatively low temperature (20 C) using naturally solied fabrics (collars on working clothing) and 2 types of artificially soiled cotton cloths, milk-soiled and carbon-milk-soiled. Results of the test showed that protease has a favorable effect on detergency even at 20 C and improves the removal of common soils solid or oily, as well as protein-based soils. The protease also was proved fully effective under mechanical agitation in the presence of detergents. Futhermore, the role of enzyme was discussed based upon gel filtration of the washing bath which treated the milk-soiled cloths. The degradation of protein by protease to a molecular weight of ca. 10,000 to 50,000 was proved to be fairly important for removal of soil protein. It also was found that endo-peptidase action is more effective than exo-peptidase action. Based upon these findings, a problem in activity evaluation method for enzymes as detergent compoments also was presented.     

Inhibitory action of conjugated C18-fatty acids on DNA polymerases and DNA topoisomerases

We reported previously that unsaturated linear-chain FA of the cis-configuration with a C18-hydrocarbon chain such as linoleic acid (18:2delta9c,12c) could potently inhibit the activities of mammalian DNA polymerases and DNA topoisomerases, but their saturated forms could not. There are chemically two classes of unsaturated FA, normal and conjugated, but only the conjugated forms show potent antitumor activity. In this report, we study the inhibitory effects of chemically synthesized conjugated C18-FA on mammalian DNA polymerases and DNA topoisomerases as compared with normal unsaturated FA. The conjugated alpha-eleostearic acid (18:3delta9c,11t, 13t) was the strongest of all the FA tested. For the inhibition, the conjugated form is crucially important. The energy-minimized 3-D structures of the FA were calculated, and both a length of less than 20 A and a width of 8.13-9.24 A in the C18-FA structure were found to be important for enzyme inhibition. The 3-D structure of the active site of both DNA polymerases and topoisomerases must have had a pocket to join alpha-eleostearic acid, and this pocket was 12.03 A long and 9.24 A wide.     

Effect of screw rotation speed on the properties of polystyrene/organoclay nanocomposites prepared by a twin‐screw extruder

We discuss the effect of screw rotation speed on the mechanical and rheological properties and clay dispersion state of polystyrene (PS)/organoclay (clay) nanocomposites prepared by melt compounding with a counterrotating‐type twin‐screw extruder. Poly(styrene‐co‐vinyloxazolin) (OPS) was used as an additional material. The Young's modulus of the PS/OPS/clay nanocomposites showed the maximum value at a screw rotation speed of 70 rpm in this study. This implied the existence of an optimized screw rotation speed for the melt compounding of the polymer/clay nanocomposites. For PS/clay systems without the addition of OPS, the peak intensity from clay increased and the distance between clay platelets in the nanocomposites decreased with the screw rotation speed. On the other hand, inverse results were obtained for PS/OPS/clay systems. According to the transmission electron microscopy photographs, the PS/OPS/clay nanocomposite at 70 and 100 rpm had fully exfoliated clay platelets. The dynamic rheological properties of the PS/clay nanocomposites were almost the same as those of neat PS. On the other hand, the storage and loss moduli of the PS/OPS/clay nanocomposites at the same frequency were larger than those of the PS/clay system. On the whole, the bonding between clay platelets and PS was important for increasing the viscosity and elasticity in the melts of the PS/clay system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1165–1173, 2006     

The notch sensitivity of polymeric materials

Stress–strain tests were made on about five dozen polymeric materials using unnotched and notched specimens containing six different types of notches. Notches decrease the strength, but they decrease the elongation to break even more drastically in general. Notch sensitivity factors are defined for strength and for energy to fracture in such a manner that the greater the notch sensitivity factor, the greater is the effect of a notch relative to the unnotched material. The notch sensitivity factor for breaking (or yield) strength is not the same as the notch sensitivity factor for energy to fracture as measured by the area under the stress–strain curve. Brittle polymers and composites tend to have greater notch sensitivity factors for strength than ductile polymers. For brittle polymers, the notch sensitivity factor for energy to fracture tends to increase with the elongation to break of the unnotched polymer. Notches generally are more detrimental to ductile polymers than to brittle ones as far as the energy to fracture is concerned. For ductile polymers, the shape of the stress–strain curve is important in determining the sensitivity to notches. The ratio of the upper to lower yield strengths should be small for low notch sensitivity. It is desirable to have the breaking strength greater than the yield strength. Glass fibers and filler in ductile matrices increase the notch sensitivity for strength but decrease the sensitivity for energy to fracture relative to the unfilled polymer. Rubber–filled polymers have a reduced notch sensitivity for strength relative to the unfilled polymer, but the notch sensitivity for energy to fracture may be either increased or decreased, depending upon the system. The energy to fracture for notched specimens correlates better with Izod impact strength than does the energy to fracture for unnotched specimens. It is recommended that notched stress–strain specimens be routinely measured along with unnotched specimens.     

A new medical microrobot for minimal invasive surgery

A new medical microrobot to drive endoscopes into endocoeles is presented. The structure of the microrobot is very simple; it consists of a right spirally grooved micromotor, a left spirally grooved cylinder and a flexible coupling. When the micromotor rotates, a hydrodynamic mucus film is formed because highly viscous mucus exists in endocoeles. The mucus film can prevent direct contact between the microrobot and the endocoele, and the injury to organic tissues may be avoided. The locomotion speed and the hydrodynamic mucus film thickness formed when the microrobot drives endoscopes into endocoeles have been calculated according to hydrodynamic lubrication theory. The results indicate that the microrobot can be suspended to drive endoscopes quickly into endocoeles. This has been confirmed by experiments.     

Supported metal model catalyst surfaces examined by scanning tunnelling microscopy

Topographic and/or barrier-height images of ultrafine Pt and Au metal particles supported on a vacuum-deposited carbon film or titanium oxide thin films grown on titanium metal sheets were obtained. The topographic images of colloidal Au particles (5-nm diameter) adsorbed on a titanium oxide thin film showed a structure elongated in the direction normal to the x scan, indicating their weak interaction with the support surface. The topographic images of Pt vacuum-deposited on a carbon film showed c. 4-nm diameter particles, larger than those observed in electron microscopy. The problems inherent to the STM observation of such dispersed metal systems are identified. In the case of Pt particles vacuum-deposited on titanium oxide film, its barrier-height image gave better indication of different phases on the surface than its topographic image. The significance of obtaining barrier-height images along with topographic images for such sample systems is demonstrated.     

Effect of growth conditions on advantages of hup− strain for H2 photoproduction by Rubrivivax gelatinosus

H₂ photoproduction by growing cultures of hup^? mutant and parental strain RL2 of Rubrivivax gelatinosus was compared. We checked the influence of different substrates, presence of air and N₂, culture shaking, inoculum concentrations. At low inoculum concentration, hup^? strain demonstrated significant advantage over the parental strain in microaerobic conditions, while under N₂–Ar atmosphere it was lower and vanished in anaerobic conditions (Ar only). This advantage was evident when using substrates with low degree of reduction (malate and succinate). Culture shaking under microaerobic conditions and in presence of N₂ completely prevented H₂ production by both strains. The high inoculum concentration inhibited H₂ production under microaerobic conditions and in presence of N₂, unlike to anaerobic conditions. With inoculum concentration increase, H₂ production decreased not gradually but stepwise which means some metabolic shift. H₂ production by hup^? strain seems to be more tolerant to air traces than by parental strain.     

Counterexamples to the long-standing conjecture on the complexity of BDD binary operations

In this article, we disprove the long-standing conjecture, proposed by R.E. Bryant in 1986, that his binary decision diagram (BDD) algorithm computes any binary operation on two Boolean functions in linear time in the input–output sizes. We present Boolean functions for which the time required by Bryant?s algorithm is a quadratic of the input–output sizes for all nontrivial binary operations, such as ∧, ∨, and ⊕. For the operations ∧ and ∨, we show an even stronger counterexample where the output BDD size is constant, but the computation time is still a quadratic of the input BDD size. In addition, we present experimental results to support our theoretical observations.     

Study of the conditions of irradiating laser for removal of toner from used paper

Though it is said that the paperless age arrived with the spread of personal computers, the amount of office paper used shows no tendency to decrease. In general, used paper is recovered and recycled in order to preserve the environment. But labor and expense are required for the recovery of used paper and the recycled paper is lower in quality. If we could reuse used paper repeatedly without these disadvantages, for example, by using copying machines that could print again by removing the toner on used paper, it would be very convenient and ecological. We therefore studied the removal of toner from used paper by the laser ablation technique. As an optical source, an SHG‐YAG laser was chosen. The energy density of irradiation with an SHG‐YAG laser for the removal of toner from used paper was examined. At an energy density of approximately 12 mJ/mm², which was the average value, the toner was removed sufficiently to allow reuse of the paper. The conditions of the laser irradiation, specifically the laser scanning speed and the number of irradiations, were studied. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(1): 8–14, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21214