Efficiency of repeated batch penicillin fermentation using two fermentors. Computer simulation and optimisation

Repeated batch operation using two fermentors (RBTF) to penicillin fermentation was demonstrated by computer simulation to improve productivity. Three operation modes were compared: chemostat, repeated batch operation using a single fermentor (RBSF) and RBTF; in each case account was made of the lag period before growth. The simulated fermentor performances were assessed on the basis of the penicillin productivity and concentration; the simulation was based on published batch fermentation data. It was shown that RBTF was superior to RBSF and chemostat. The advantage of RBTF increased as the lag period became greater.     

The distribution of soap in the polymerization system for preparation of carboxylated polystyrene latexes

The distribution of soap in the polymerization system for preparation of carboxylated polystyrene latexes has been investigated. The critical micelle concentration (CMC) for sodium dodecyl sulfate (SDS) in the polymerization system was determined by surface tension measurement to be 0.173 mmole/l. The solubility of styrene (St) in the aqueous phase of the polymerization system was determined by NMR measurement to be 4.52 mmole/l. It was confirmed by NMR measurement that at the concentration of SDS higher than the CMC, St is solubilized in the interior of the SDS micelles, and the concentration of solubilized St is almost proportional to the concentration of micellar SDS. From this relationship, the number and radius of SDS micelles containing solubilized St can be determined.     

Reactive compatibilization of PE/PS blends. Effect of copolymer chain length on interfacial adhesion and mechanical behavior

This paper deals with in situ compatibilization of PE/PS blends via Friedel-Crafts reaction, performed at the interphase. Two polyethylenes having different molecular weights, and the same PS, were used along a wide range of catalyst concentration. The influence of the graft copolymer architecture and content on the efficiency of blend compatibilization was studied. The emulsifying effect, morphological aspects and mechanical behavior were also assessed for these blends. The amount of copolymer formed increases with catalyst concentration and the short chain length fraction of the homopolymers. The high molecular weight (MW) copolymers behaved as better compatibilizers as they showed, at the cmc, greater graft copolymer concentration than the low MW ones. A substantial increase in interfacial adhesion and particle size reduction was observed, even at catalyst concentrations as low as 0.3 wt%. In correspondence, mechanical properties, like ductility and yield strength, were enhanced by the effect of this Friedel-Crafts reaction's compatibilization.     

Development of a flexible autonomous robot without sensors or controllers

Recently, various robots with many degrees of freedom, such as rescue robots and domestic robots, have been developed and used in practical applications. It is difficult to control such robots autonomously in real environments, because in order to control the many degrees of freedom, we have to observe many states, calculate huge amounts of information, and operate many actuators. In this study, we consider a flexible robot without sensors or controllers that can determine the inclination of a slope and climb up the slope. In order to demonstrate the effectiveness of the proposed framework, we have developed a prototype robot and conducted experiments. The result indicates that the robot could determine the inclination and climb up a gentle slope autonomously. Thus, we have realized an autonomous robot that has no explicit sensors or controllers.     

Automatic Tuning System for Integrator-Based Continuous-Time Filters

This paper proposes an automatic tuning system to adjust frequency characteristics of integrated continuous-time filters especially at high frequencies. Frequency characteristic deterioration of a filter using integrators with electrically controllable unity-gain frequencies can be easily evaluated and compensated even when they are affected by deviations of element values and parasitic elements. The compensation requires detection of both frequency and excess phase shifts of the integrators. Their two values are electrically detected by two detection systems usually used in the conventional frequency tuning system. The proposed system is stable, simple and easy to be implemented on an integrated circuit. As an example a 4th-order biquad bandpass filter with 10 MHz center frequency, 2 MHz passband width, and 0.5 dB passband ripples is designed using a bipolar process. Simulation results by SPICE show the effectiveness of the proposed system.     

New amphoteric surfactants containing a phosphoric acid group: I. syntheses and physicochemical properties of sodium 2-(n-2-hydroxyalkyl-n-methylamino)ethyl hydrogen phosphate

A series of new amphoteric surfactants having a phosphoric acid group, a tertiary amino group and a 2-hydroxyalkyl group, sodium 2-(N-2-hydroxyalkyl-N-methyl-amino)ethyl hydrogen phosphates (alkyl: n-tetradecyl, n-hexadecyl, n-octadecyl), were prepared by an addition reaction of 1,2-epoxyalkanes to N-methylaminoethanol, followed by the introduction of a phosphoric acid group and neutralization with sodium hydroxide. The structures of these compounds were confirmed by spectroscopy and elemental analysis. The solubility in solvents, Krafft point, surface tension, critical micelle concentration (CMC), occupation area of the molecule at the surface of aqueous solutions and foaming power were measured. It was shown that a 2-hydroxyethyl group in a long alkyl chain seemed to behave as a hydrophobic part.     

Boroxine Nanotubes: Moisture‐Sensitive Morphological Transformation and Guest Release

Boroxines, (R‐BO)₃, which can be easily synthesized via a dehydration reaction of boronic acids, R–B(OH)₂, selectively self‐assemble in toluene into nanofibers, nanorods, nanotapes, and nanotubes, depending on the aromatic substituent (R). Spectroscopic measurements show that the nanotube consists of a J‐aggregate of the boroxine. Humidification converts the morphology from the nanotube to a sheet as a result of the hydrolysis of the boroxine components and subsequent molecular‐packing rearrangement from the J‐aggregate to an H‐aggregate. Such a transformation leads to the compulsive release of guest molecules encapsulated in the hollow cylinder of the nanotube. The hydrolysis and the molecular‐packing rearrangement described above are suppressed by coordination of pyridine to the boron atom, with the resulting moiety acting as a Lewis acid of the boroxine component. The pyridine‐coordinated nanotube is transformed into a helical coil by humidification. Guest release during the nanotube‐to‐helical‐coil transformation is much slower than during the nanotube‐to‐sheet transformation, but faster than from a nanotube that did not undergo morphological transformation. The storage and release of guest molecules from the boroxine nanotubes can be precisely controlled by adjusting the moisture level and the concentration of Lewis bases, such as amines.     

Simple Short-Pulse CO<Subscript>2</Subscript> Laser Excited by Longitudinal Discharge without High-Voltage Switch

We have developed a longitudinally excited CO₂ laser without a high-voltage switch. The laser produces a short laser pulse similar to those from TEA and Q-switched CO₂ lasers. This system, which is the simplest short-pulse CO₂ laser yet constructed, includes a pulsed power supply, a high-speed step-up transformer, a storage capacitor, and a laser tube. At high pressure (4.2 kPa and above), a rapid discharge produces a short laser pulse with a sharp spike pulse. In mixed gas (CO₂: N₂: He = 1: 1: 2) at a pressure of 9.0 kPa, the laser pulse contains a spike pulse of 218 ns and has a pulse tail length of 16.7 μs.     

Photovoltaic display module in a mobile GPS

We have developed a mobile global positioning system (GPS) that operates on just photovoltaic (PV) cells. The system receives wireless signals from satellites and shows one's present location accurately on a map without the need for a battery. A PV display module, which combines a transparent LCD with a-Si PV cells and has a power generation function, is added to ordinary PV cells to increase the total amount of power generated. The PV display module enables 40% more power generation than a system without the module.