Direct observation of PFPE lubricant molecules by cryogenic AFM under ultra-high vacuum

Surface lubrication is one of the essential technologies in modern magnetic disk systems and improvement of the surface lubrication is very important in the development of next generation systems. In this study, we used AFM for the direct observation of perfluoropolyether (PFPE) lubricant molecules on atomically flat surfaces. We used a cryogenic non-contact AFM to observe the molecules in a frozen state of micro-Brownian motion of PFPE segments, because the glass transition temperature of PFPE is very low. To avoid freezing a trace amount of water vapor on the sample surface at liquid nitrogen temperatures, the AFM observation was performed under ultra-high vacuum. We observed that on a gold surface the size of the molecules increases with repeated AFM scans. This is because the mechanical stimulus causes the fusion of PFPE lubricant molecules to form reversed micelles at the non-polar surface. At a hydrophilic silicon wafer surface, however, we succeeded in observing single lubricant molecules. This is because almost all PFPE lubricant molecules are fixed to the hydrophilic solid surface by polar–polar bond formation and they cannot move around on the surface and thus they cannot fuse to each other. As formation of the reversed micelle structure is a rather general phenomenon in the PFPE lubricant thin layer at non-polar surfaces, we also will discuss briefly the expected molecular structures of PFPE lubricants at the surface of the carbon overcoat of magnetic disks.     

Electron microscopic visualization of collagen aggregates without chemical staining.

Lateral, uni-directional aggregates of collagen, segment-long-spacing crystallites (SLS), were made by dialyzing collagen solutions against acetic acid containing ATP, and were examined by transmission electron microscopes without electron staining. There detected were at least 20 dark (electron dense) cross-striations within SLS. The banding pattern was compared with the biochemical and biophysical properties of the amino acid side chains along the collagen molecule. The banding pattern of unstained SLS was mostly correlated with the intramolecular distribution of basic amino acid residues. Since basic amino acids have relatively large side chains, the distribution of mass (molecular weight of amino acids) along the molecule (local density profile) partially explained the cross-striation. Addition of fractions of molecular weight of ATP to basic residues made the local density profile much better correlate to the banding pattern. We conclude that the electron microscopic banding pattern of unstained SLS was generated by the local amount of material or local density profile along the collagen aggregates, which was enhanced by ATP bound to positively charged basic residues. The concept that the electron density correlates with the amount of material is fundamental in electron microscopy, and it has been proven with biological materials in this paper.     

Development of a colon delivery capsule and the pharmacological activity of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in beagle dogs

A peroral dosage form was examined to deliver recombinant human granulocyte colony-stimulating factor (rhG-CSF) to the colon in beagle dogs. A new gelatin capsule with its inside surface coated with ethylcellulose was prepared for this purpose. RhG-CSF was dissolved with propylene glycol and was filled in the capsule. Several kinds of ethylcellulose-gelatin capsules with an ethylcellulose layer of thickness 46 to 221 mm were used. The capsule was filled with propylene glycol solution containing fluorescein as an absorption marker, castor oil derivative and citric acid. The hardness of the capsule was tested after the gelatin layer was dissolved using a hardness tester and was dependent on the thickness of the ethylcellulose layer of the capsule. The time, Tmax, at which plasma fluorescein level reaches its maximum following oral administration of ethylcellulose capsules was used as a parameter for the in-vivo disintegration time of the ethylcellulose capsule into the colon. Capsules of thickness 84 mm with a Tmax of 4-6 h were filled with rhG-CSF solution containing fluorescein and were administered to dogs. After administration, blood samples were collected for 96 h and the blood total leucocyte (BTL) counts were measured as a pharmacological index of rhG-CSF. The maximum BTL count appeared at 10 h then gradually decreased and returned to its normal level at 48 h. These results suggest the usefulness of ethylcellulose capsules for the delivery of rhG-CSF to the colon and the possibility of a new oral rhG-CSF dosage form has been elucidated.     

Electrochemical DNA methylation detection for enzymatically digested CpG oligonucleotides

We describe the electrochemical detection of DNA methylation through the direct oxidation of both 5-methylcytosine (mC) and cytosine (C) in 5'-CG-3' sequence (CpG) oligonucleotides using a sputtered nanocarbon film electrode after digesting a longer CpG oligonucleotide with endonuclease P1. Direct electrochemistry of the longer CpG oligonucleotides was insufficient for obtaining the oxidation currents of these bases because the CG rich sequence inhibited the direct oxidation of each base in the longer CpG oligonucleotides, owing to the conformational structure and its very low diffusion coefficient. To detect C methylation with better quantitativity and sensitivity in the relatively long CpG oligonucleotides, we successfully used an endonuclease P1 to digest the target CpG oligonucleotide and yield an identical mononucleotide 2'-deoxyribonucleoside 5'-monophosphate (5'-dNMP). Compared with results obtained without P1 treatment, we achieved 4.4 times higher sensitivity and a wider concentration range for mC detection with a resolution capable of detecting a subtle methylated cytosine difference in the CpG oligonucleotides (60mer).     

Synchronous Composite Packet Switching-A Switching Architecture for Broadband ISDN

A new switching architecture for broadband ISDN, "Synchronous Composite Packet Switching (SCPS)," is proposed and evaluated. It efficiently integrates circuit and packet switching functions on a single switching system and accommodates very high speed-up to several tens of Mbit/s-communication services, such as very high speed bursts of data, still picture, and motion video, as well as 64 kbit/s or less voice and data services. The SCPS system comprises plural switch modules and plural Very high speed synchronous loops. In the SCPS system, messages on plural circuit switched channels are assembled into quasi-packets, called "composite packets," and switched synchronously between switch modules, maintaining complete time transparency and short absolute delay time. A system parameter design to obtain high system efficiency and appropriate system modularity is explained, and an example for a very large capacity transit switch of 4 Gbit/s throughput is presented. System implementation problems to realize the SCPS principle, such as efficient implementation of the composite packet assembling and loop transmission functions, are investigated and an experimental system constructed for circuit switching part is presented. The most remarkable characteristic of the SCPS is that it efficiently integrates64 times nkbit/s circuit switching with packet switching. Moreover, the SCPS system retains compatibility with existing networks and the possibiliy of evolution toward a future broadband ISDN. On the basis of the above investigations and experimental system construction, the authors conclude that the SCPS is one of the most practical switching architectures for the coming broadband ISDN era.     

A voltage-source PWM rectifier-inverter with feedforward control of instantaneous power

In general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage-source inverters. Rectifiers of this type, however, cause many problems such as poor power factor and harmonics. Recently, voltage-source PWM rectifier-inverters have been studied to provide the following advantages: (1) harmonic-free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. However, it is difficult for a conventional voltage-source PWM rectifier-inverter to regulate the capacitor voltage on transient states because it has only a voltage feedback loop. This paper describes a voltage-source PWM rectifier-inverter with feedforward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feedforward control of instantaneous power contributes greatly to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed, and some interesting experimental results of a laboratory model are shown.     

Finding the range: Linguistic analysis and its role in computer-assisted literary study

This article describes how linguistic analysis can be used to change the computer from being a generator of data that can be used to develop a critical analysis to being a tool that provides a means to explore the processes and inputs that generate different interpretations of literary works. Using Michael Gregory's Communication Linguistics model to analyze Shakespeare's Sonnet CXXX, we see how the linguistic structure of the poem allows for multiple readings of the text. The article goes on to describe how this kind of analysis can be extended by employing artificial intelligence as a means to explore the interaction between language and meaning.Stephen N. Matsuba is currently completing his doctorate in English at York University, Canada.     

Gastrointestinal bleeding (introduction)

Gastrointestinal (GI) bleeding is a common and important problem for all clinicians. Patients may present with signs of bleeding, such as hematemesis, melena, or hematochezia. The patient must first be hemodynamically stabilized. Initial assessment of patients with GI bleeding includes thorough history taking and physical examination. Patients with acute bleeding or an unstable condition must be resuscitated immediately and the source of bleeding must be localized to the upper or lower GI tract. Panendoscopy is often the initial diagnostic test and is useful to stop GI bleeding, at the same time.     

Integrated computerisation of operating procedures

The computerisation of procedures can address not only the way procedures are presented or displayed, but also how they are generated and maintained. The computerisation of procedure generation will result in an improved basis for procedure display, and also make it possible to maintain the procedures on the level of internal representation rather than on the level of display. This paper describes a project, which focused on developing a system for computerised procedure generation (CPG) based on the principles of cognitive systems engineering. The CPG system was integrated with an already existing system for computerised procedure presentation, and enhanced with a number of other functions to produce a system for integrated computerisation of operating procedures.