Model studies in the lepadin series: synthesis of enantiopure decahydroquinolines by aminocyclization of 2-(3-aminoalkyl)cyclohexenones

Syntheses of enantiopure 3-acetoxy-2-methyldecahydroquinolines are accomplished by coupling cyclohexenyllithium 3 with α-amino epoxides and an aminocyclization of 2-(3-aminoalkyl)cyclohexenones (i.e., 5 and 9) as the key steps. The procedure allows the incorporation of alkyl substituents at C(5) to give enantiopure 2,3,5-trisubstitued decahydroquinolines.     

Continuous particle separation in a microchannel having asymmetrically arranged multiple branches

A new method for continuous size separation and collection of particles in microfabricated devices, asymmetric pinched flow fractionation (AsPFF), has been proposed and demonstrated. This method improves the separation scheme of pinched flow fractionation (PFF), which utilizes a laminar flow profile inside a microchannel. In this study, multiple branch channels with different channel dimensions were arranged at the end of the pinched segment, so that the flow rate distributions to each branch channel were varied, and a large part of the liquid was forced to go through one branch channel (drain channel). In the proposed channel system, the flow profile inside the microchannel was asymmetrically amplified, enabling the separation of one-order smaller particles compared with PFF. After introducing the method, we examined the effect of the asymmetric amplification by controlling the outlet of the drain channel. Also, a mixture of 1.0 approximately 5.0 microm particles was separated, and erythrocytes were successfully separated from blood. The results indicate that the AsPFF method could be applied to the separation of much smaller-size particles, since more precise separation can be achieved simply by changing the geometries of branch channels.     

X-ray photoelectron spectra of Ti4+ in TiO2. Evidence of band structure

Satellite structure has been observed at about 3.1, 5.4, 6.4 and 14.5 eV below the main peaks in the X-ray photoelectron spectra of the Ti and O levels of TiO₂. These satellites arise from transitions, accompanying primary photoemission, between predominantly O_2p states of the ligand and various excited states in the conduction band. The energies found fit the transitions calculated by Daude et al. for an electronic band structure calculated by a combined tight-binding and pseudopotential method.     

Enantioselective formal synthesis of uleine alkaloids from phenylglycinol-derived bicyclic lactams

A two-step route for the enantioselective construction of the tetracyclic ring system of uleine alkaloids, involving the stereoselective conjugate addition of an appropriate indole-containing nucleophile to a chiral bicyclic delta-lactam and the subsequent cyclization on the indole 3-position of the resulting 4,5-disubstituted 2-piperidone, has culminated in the formal total synthesis of several alkaloids of this group.     

Hydrodynamic filtration for on-chip particle concentration and classification utilizing microfluidics

We propose here a new method for continuous concentration and classification of particles in microfluidic devices, named hydrodynamic filtration. When a particle is flowing in a microchannel, the center position of the particle cannot be present in a certain distance from sidewalls, which is equal to the particle radius. The proposed method utilizes this fact, and is performed using a microchannel having multiple side branch channels. By withdrawing a small amount of liquid repeatedly from the main stream through the side channels, particles are concentrated and aligned onto the sidewalls. Then the concentrated and aligned particles can be collected according to size through other side channels (selection channels) in the downstream of the microchannel. Therefore, continuous introduction of a particle suspension into the microchannel enables both particle concentration and classification at the same time. In this method, the flow profile inside a precisely fabricated microchannel determines the size limit of the filtered substances. So the filtration can be performed even when the channel widths are much larger than the particle size, without the problem of channel clogging. In this study, concentrations of polymer microspheres with diameters of 1-3 microm were increased 20-50-fold, and they were collected independently according to size. In addition, selective enrichment of leukocytes from blood was successfully performed.     

Radiative Striations and Surface Roughness of Alkoxide-Derived Spin Coating Films

Spin coating silica films were prepared from acid-catalyzed tetraethoxysilane (TEOS) solutions, and the magnitude of radiative striations formed on the surface of the resulting films was quantitatively evaluated by measuring surface roughness using a contact probe profilometer. Wave-like transverse profiles were obtained on the films prepared. Surface roughness parameters, Ra (arithmetical mean deviation), Rz (ten point height of irregularities) and S (mean spacing of local peaks), were determined. When the gel films were heated at higher temperatures (500°C), the film thickness decreased up to 22%, while none of Ra, Rz or S varied with heat-treatment temperature, indicating that the surface of the films is already densified at room temperature. Higher substrate rotation speeds caused decrease in Ra, Rz and S, revealing that the striations decreased both in amplitude and wavelength. Application of viscous sols aged for longer periods of time resulted in increased amplitude (Rz) of striations without change in wavelength (S).     

The Orienteering Problem with Time Windows

The orienteering problem with time windows, denoted by OPTW, belongs to a class of routeing and scheduling problems that arise in physical distribution. It may be modelled as a problem on a graph. It considers a set of nodes (customers), each with an associated profit and service duration (time window), and a set of arcs, each with an associated travel time. The objective of the problem is to construct an acyclic path beginning at a specified origin and ending at a specified destination that maximizes the total profit while observing time window constraints on all nodes and not exceeding a designated time limit. The problem is classified as NP-hard and, thus, an exact algorithm that executes in reasonable computational time is unlikely to exist. Since the problem is highly-constrained, we were able to develop a heuristic (referred to as the ‘tree’ heuristic) based upon an exhaustive search of the feasible solution space. The tree heuristic systematically generates a list of feasible paths and then selects the most profitable path from the list. In comparison with an insertion heuristic, the tree heuristic was found to produce improved values of total profit for heavily-constrained, modest-sized problems with reasonable computational effort.