Arrhenius plot for a reaction catalyzed by a single molecule of β-galactosidase

The activity of a single enzyme molecule of Escherichia coli β-galactosidase was measured using a capillary electrophoresis continuous flow assay. As the enzyme molecule traversed the capillary the incubation temperature was increased from 27 to 37 °C, providing a continuous record of the change in rate with temperature. This data was used to develop a single enzyme molecule Arrhenius plot, from which the activation energy of the reaction was determined to be 31 kJ mol(-1).     

Investigation of the interactions between molecules of β-Carotene, Vitamin A and CNTs by MD simulations

Two typical phenomena (wrapping and filling), mainly about the interactions between biological molecules and carbon nanotubes (CNTs), were investigated by performing molecular dynamics (MD) simulations. We calculated the center of mass (COM) distance and the interaction energy between the biological molecules and single-walled nanotubes (SWNTs). The influence of nanotube wall number, chirality, radius and temperature was also investigated by a series of MD simulations. The results indicated that Vitamin A and β-Carotene were two promising biomaterials for decoration of CNTs. The interactions between biological molecules and CNTs could be influenced by those four factors. The general conclusions derived from this study may be of importance in medical and biological areas.     

Low energy laser initiation of single crystals of β-lead azide

Unfocused low energy Q-switched and non-Q-switched ruby laser irradiation of individual single crystals of-lead azide of size 40m×200m×10mm has been studied using high-speed photography. It was found that the initiation of fast reaction occurs at isolated sites which are probably defects and act as absorption centres in the dielectric which is otherwise transparent to the ruby wavelength of 694.3 nm. It has also been shown that it is the power and not the energy of the incident beam that controls the initiation under these low energy irradiation conditions. Finally, the variation of the time delay to initiation with the incident laser energy suggests a thermal mechanism of initiation.     

Measurement and Correlation of Electrical Conductivity of β-Cyclodextrin in Water Solution

The electrical conductivity of 4% β-cyclodextrin in water solution had been measured by electrode method from（323.65~353.65） K at atmospheric pressure. The expe...     

Towards a ‘catalyst activity map’ regarding the nucleation and growth of single walled carbon nanotubes

Quantification using scanning electron microscopy (SEM) of single walled carbon nanotubes (SWNTs) grown per unit area using a Co-Fe (50:50) catalyst system, prepared by the incorporation of the appropriate metal salts into a Spin-On Glass substrate, at 900°C. The effects of substrate, as well as catalyst precursor concentration, were investigated. SWNT growth density is maximised with a catalyst precursor concentration of ≥2.5 mM, associated with the formation of catalyst nanoparticles of a critical size for SWNT nucleation. Samples were subjected to secondary growth, using a range of H₂:CH₄ ratios to determine the optimum precursor composition. It was found that nucleation and growth stages are optimal under different conditions. Optimum conditions for nucleation resulted in >10× increase in SWNT density. Optimisation is dependent on temperature and the partial pressure of reagent gas species.     

Structural and electronic characteristics of Fe-doped β-Ga2O3 single crystals and the annealing effects

Journal of Materials Science - As capture traps, Fe impurities were intentionally incorporated into beta-gallium oxide (β-Ga2O3) crystals to compensate for unintentional n-type conductivity...     

Role of kinetic energy of impinging molecules in the α-sexithiophene growth

We report on the α-sexithiophene sub-monolayer growth with supersonic molecular beam deposition by investigating how the kinetic energy of the impinging molecules influences the growth on substrates with different surface wettabilities and temperatures. The results show that the energy of the impinging molecules affects the morphology of the molecular film increasing the coverage and the island size, and reducing the fractality of the sub-monolayer islands. The possibility of directing growth of more ordered islands could improve the performances of electronic devices, which are greatly affected by the structure of the first monolayers.     

A Brief Introduction of the Monthly Journal of “Measurement Technique”

The first of this journal was published in June,1957 and it has become a nation-wide technical journal in China, Now it is edited by the Information Service of the State Bureau of Metrology. The papers dealed with the following problems will be earried in the journal:     

Measurement of small holes by means of the “magic eye”

Conclusions Estimation of the errors in measuring diameters of small holes by means of a universal microscope and a magic eye has shown that it is the most accurate contact method and can be recommended for measuring holes of the first grade of accuracy.     

Fine tuning of the electronic structure of π-conjugated molecules for molecular electronics

Molecular components with their inherent scalability are expected to be promising supplements for nanoscale electronic devices. Here we report on how to specifically tune the electronic structure of chemisorbed molecules and thus to gain control of molecular transport properties. The electronic structure of our prototype π-conjugated carboxylic acid anchored on the Cu(110) surface is modified systematically by inserting nitrogen atoms in a six-membered aromatic ring, a carboxylic functional group at the aromatic ring or both. Depending on the specific nature of the substituent, the relative position of the occupied or unoccupied electronic states with respect to the Fermi level can be specifically controlled and thus the transport properties of the studied molecular systems are modified intentionally, as proven by our scanning tunneling spectroscopy measurements. On the basis of the insight gained by our systematic experiment and first-principles calculations we are also able to predict the specific molecular character (σ or π) of the orbitals involved in the transport process of a carboxylate-Cu(110) system, depending on the functionalization pattern employed.     

Measurement of the monochromatic emissivity of coatings at 100–400°C

Results of measurement of the normal emissivities of certain coatings by a two-beam method in the 2–25 range are reported.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 27, No. 2, pp. 203–207, August, 1974.     

SEM Measurement of the linear dimensions of relief submicron structures by the method of “invariant” points

The Monte Carlo method is used to simulate video signals from a scanning electron microscope in backscattered electrons from slit-like structures with a rectangular profile and widths of 0.1, 0.5, and 4.0 m.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 22–23, August, 1995.     

Measurement of driver calibration and the impact of feedback on drivers’ estimates of performance

Recent studies focused on driver calibration show that drivers are often miscalibrated, either over confident or under confident, and the magnitude of this miscalibration changes under different conditions. Previous work has demonstrated behavioral and performance benefits of feedback, yet these studies have not explicitly examined the issue of calibration. The objective of this study was to examine driver calibration, i.e., the degree to which drivers are accurately aware of their performance, and determine whether feedback alters driver calibration. Twenty-four drivers completed a series of driving tasks (pace clocks, traffic light, speed maintenance, and traffic cones) on a test track. Drivers drove three different blocks around the test track: (1) baseline block, where no participants received feedback; (2) feedback block, where half of the participants received performance feedback while the other half received no feedback; (3) a no feedback block, where no participants received feedback. Results indicated that across two different calibration measures, drivers were sufficiently calibrated to the pace clocks, traffic light, and traffic cone tasks. Drivers were not accurately aware of their performance regarding speed maintenance, though receiving feedback on this task improved calibration. Proper and accurate measurements of driver calibration are needed before designing performance feedback to improve calibration as these feedback systems may not always yield the intended results.     

Dependence of the Coordinate Measurement Error of Geometric Elements’ Shape Characteristics on the Control Point Number

Measurement Techniques - This article presents issues in estimating the coordinate measurement error of geometric elements’ shape characteristics of products depending on the control point...     

Effect of the Nature of Fluid and Structure of β-Diketone on Supercritical Extraction of Metal β-Diketonate Complexes

Extraction of uranium with trifluoromethyl alkyl diketones differing in the length of the alkyl chain was studied. The size of the alkyl group only slightly affects the extraction. Extraction of complexes formed by uranyl nitrate with -diketones in pentafluoroethane (Freon-125) was studied. The complexes are efficiently extracted with both super- and subcritical Freon-125. In contrast to extraction of these complexes in supercritical CO₂, in extraction with Freon-125 the complexes do not decompose.     

Integrated capillary electrophoresis on flexible silicone microdevices: analysis of DNA restriction fragments and detection of single DNA molecules on microchips

Microchips for integrated capillary electrophoresis systems were produced by molding a poly(dimethylsiloxane) (PDMS) silicone elastomer against a microfabricated master. The good adhesion of the PDMS devices on clean planar surfaces allows for a simple and inexpensive generation of networks of sealed microchannels, thus removing the constraints of elaborate bonding procedures. The performance of the devices is demonstrated with both fast separations of φX-174/HaeIII DNA restriction fragments labeled with the intercalating dye YOYO-1 and fluorescently labeled peptides. Detection limits in the order of a few zeptomoles (10(-)(21) mol) have been achieved for each injected DNA fragment, corresponding to a mass detection limit of ～2 fg for the 603 base pair fragment. Single λ-DNA molecules intercalated with YOYO-1 at a base pair-to-dye ratio of 10:1 could be detected with an uncomplicated laser-induced fluorescence detection setup. High single-molecule detection efficiency (>50%) was achieved under electrophoretically controlled mass transport conditions in PDMS microchannels.