Enzymatic Transesterification of 3,7-Dimethyl-4,7- octadien-1-ol Using Lipases

Enzymatic transesterification of (±)-3,7-dimethyl-4,7-octadien-1-ol ( 1 ) using various lipases and vinyl esters resulted in the formation of (S)-(+)-1-acyloxy-3,7-dimethyl-4,7-octadiene ((S)- 2 ) and (R)-(-)-3,7-dimethyl-4,7-octadien-1-ol ((R)- 1 ). Cyclization of (R)- 1 with iodine afforded (4R)-(-)-cis-4-methyl-2-(2-methyl-1-propenyl)tetrahydropyran ((-)-rose oxide). © 1997 SCI.     

Degradation of natural estrogen and identification of the metabolites produced by soil isolates of Rhodococcus sp. and Sphingomonas sp.

Five bacterial strains capable of utilizing 17β-estradiol (E2) and estrone (E1) were isolated from soil samples. Using their morphological and physiological features and 16S rDNA sequences, we classified these isolates into two groups: Group A (Rhodococcus sp. strains ED6, ED7, and ED10) and Group B (Sphingomonas sp. strains ED8 and ED9). All isolates used E2 and E1 as the sole carbon sources and showed high E1 and E2 degradation activities. In all strains, more than 50% of 0.8 mg of E1 or E2 was degraded in 4 mL of inorganic medium over 24 h, and 90% was degraded over 120 h. By incubating the resting ED8 cells with E2 and the meta-cleavage inhibitor 3-chlorocatechol, we identified two metabolites, 4-hydroxyestrone (4-OH-E1) and 4-hydroxyestradiol (4-OH-E2), and confirmed their identity using authentic chemicals. The 4-OH-E1 and 4-OH-E2 compounds were assumed to be intermediate metabolites formed before meta-cleavage, as they were not identified in culture without 3-chlorocatechol. Degradation of E2 by strain ED8 can be initiated by hydroxylation of the C-4 position, followed by meta-cleavage of the benzene ring. When strains ED8 degraded E2, we further identified hydroxy-E2, keto-E1 and -E2, and an additional degradation product via mass spectrometry. The presence of these compounds implied degradation through a second pathway initiated through an attack of the saturated ring.     

First-Principles Study of Semiconducting Clathrate Ba<Subscript>8</Subscript>Al<Subscript>16</Subscript>Ge<Subscript>30</Subscript>

We calculated electronic structures of Ba₈Al₁₆Ge₃₀ in some Al-Ge framework configurations without nearest-neighbor Al-Al bonds by using a first-principles method. The calculated band structures are similar in outline but different in detail. We also calculated thermoelectric properties by using the electronic structures to analyze the experimental results on a sintered Ba₈Al₁₆Ge₃₀ sample. The calculated properties nearly agree with the experimental results; however, the calculated temperature dependences of electrical conductivity are slightly different from one another, because of differences in electronic structure. In this paper, we discuss the temperature dependence from the viewpoints of nonparabolic band effects.     

Spatial Distribution of the Seebeck Coefficient in Zn<Subscript>13</Subscript>Sb<Subscript>10</Subscript> Determined by a Seebeck Microprobe Measurement System

A Seebeck microprobe (SMP) measurement system has been developed and employed to determine the spatial distribution of the Seebeck coefficient of a polycrystalline Zn₁₃Sb₁₀ specimen prepared by a gradient freeze (GF) method. The spatial distribution of the Seebeck coefficient strongly reflects that of the grains observed using an optical polarizing microscope, the magnitude of which ranges from 100 μV/K to 130 μV/K. This fact strongly indicates that the observed spatial distribution of the Seebeck coefficient arises from the anisotropic Seebeck effect of grains with different crystal orientations in the polycrystalline Zn₁₃Sb₁₀.     

A 3.0 V 40 Mb/s hard disk drive read channel IC

This paper presents a high performance low power BiCMOS mixed signal ASIC that integrates all the electronics required by a hard disk drive (HDD) read channel. The IC includes the automatic gain control (AGC) circuit, a programmable continuous-time filter, two pulse qualifiers, the servo demodulator, the time base generator, the data synchronizer, and the encoder/decoder. Constant density recording with data rates between 14 and 40 Mb/s in 1,7 Run Length Limited (RLL) format and embedded 4-burst servo are supported. All the chip's specifications are guaranteed for supply voltages ranging from 3.0-5.5 V. Programming and testing are achieved via a 3-terminal bi-directional serial interface and internal registers. Nominal power dissipation at 3.0 V supply and 40 Mb/s data rate is 360 mW. Pulse pairing and write data jitter, two key performance parameters, each measured less than 300 ps     

A Si bipolar 28-GHz dynamic frequency divider

A dynamic frequency divider applying the regenerative frequency division principle has been developed. A spiral inductor on the silicon substrate used as a load is characterized, and an improved one-port model with the substrate resistance is discussed. A 1/16 frequency divider was implemented with a silicon bipolar technology with a cutoff frequency of 40 GHz. The operation frequency range was 11.8-28.1 GHz, covering the Ka band (18-26.5 GHz). The inductive load has improved the maximum operation frequency by 7%, compared with a conventional circuit. Complemented with a 21-GHz static frequency divider previously reported by the authors, the whole microwave frequency range up to 26.5 GHz has been completely covered with the silicon bipolar technology. The maximum operation frequency of a silicon MMIC has been extended to the millimeter-wave frequency region for the first time     

Nanomanipulation of biological samples using a compact atomic force microscope under scanning electron microscope observation

We introduce a compact nanomanipulator that can be operated inside the sample chamber of a scanning electron microscope (SEM) for biological sample manipulation. The design of the nanomanipulator is based on that of an atomic force microscope (AFM). A self-sensitive cantilever is used to realize the compact body and thus it is possible to put a pair of the standalone AFM units on the sample stage in the SEM chamber. Using this system, we accomplished nanodissection of biological samples as well as AFM imaging under SEM observation. We then fabricated the surface of a rat renal glomerulus by scan-scratching and succeeded in making a small hole on the wall of a blood capillary. As a result, it was possible to observe the internal structure of the capillary, which had been hidden beneath the surface wall. Furthermore, using two AFM units on the sample stage of the SEM, we successfully dissected the lens fiber cells taken from a rat eye in a multi-probe operation using the two cantilevers. This system is expected to become a very useful tool for micro- and nanometer-scale anatomy and engineering applications.     

Analysis of turbine generator steady-state reactances for load conditions

This paper describes variations of turbine generator steady-state reactances for load conditions. When the turbine generator is of small size, magnetic saturation of the stator and rotor core is a problem. Therefore, it is important to understand the variations of the reactances for load conditions. The reactances of a 592-MVA turbine generator are calculated with d- and q-axis equations considering magnetic saturation and two-dimensional numerical magnetic field analysis. The results are as follows. (1) The equivalent synchronous reactances considering cross-magnetizing are smaller than the original synchronous reactances for load conditions. (2) Numerical values of the d- and q-axis mutual reactance and the field and q-axis mutual reactance are at their maximum when the d-axis linkage flux is nearly equal to the q-axis linkage flux under constant voltage. (3) The d-axis synchronous reactance drops with increasing reactive power under constant voltage and active power, but the q-axis synchronous reactance increases. (4) The variation of the equivalent d-axis synchronous reactance with increasing reactive power is similar to that of the d-axis synchronous reactance, but the variation of the equivalent q-axis synchronous reactance is different from that of the q-axis synchronous reactance. © 1998 Scripta Technica. Electr Eng Jpn, 123(3): 73–83, 1998     

The COX-2 Selective Blocker Etodolac Inhibits TNFα-Induced Apoptosis in Isolated Rabbit Articular Chondrocytes

Chondrocyte apoptosis contributes to the disruption of cartilage integrity in osteoarthritis (OA). Recently, we reported that activation of volume-sensitive Cl⁻ current (I_Cl,vol) mediates cell shrinkage, triggering apoptosis in rabbit articular chondrocytes. A cyclooxygenase (COX) blocker is frequently used for the treatment of OA. In the present study, we examined in vitro effects of selective blockers of COX on the TNFα-induced activation of I_Cl,vol in rabbit chondrocytes using the patch-clamp technique. Exposure of isolated chondrocytes to TNFα resulted in an obvious increase in membrane Cl⁻ conductance. The TNFα-evoked Cl⁻ current exhibited electrophysiological and pharmacological properties similar to those of I_Cl,vol. Pretreatment of cells with selective COX-2 blocker etodolac markedly inhibited I_Cl,vol activation by TNFα as well as subsequent apoptotic events such as apoptotic cell volume decrease (AVD) and elevation of caspase-3/7 activity. In contrast, a COX-1 blocker had no effect on the decrease in cell volume or the increase in caspase-3/7 activity induced by TNFα. Thus, the COX-2-selective blocker had an inhibitory effect on TNFα-induced apoptotic events, which suggests that this drug would have efficacy for the treatment of OA.     

Intramolecular acyl migration and enzymatic hydrolysis of 2-O-α-D-glucopyranosyl-6-O-(2-pentylheptanoyl)-L-ascorbic acid

2-O-α-D-Glucopyranosyl-6-O-(2-pentylheptanoyl)-L-ascorbic acid (6-bDode-AA-2G) underwent an intramolecular acyl migration to yield approximately 12% of 2-O-α-D-glucopyranosyl-5-O-(2-pentylheptanoyl)-L-ascorbic acid (5-bDode-AA-2G) in neutral solutions for 3 days. In small intestine homogenate from guinea pigs for 12h, 6-bDode-AA-2G, which hardly underwent acyl migration to give 5-bDode-AA-2G, was predominantly hydrolyzed with α-glucosidase and then with esterase to ascorbic acid.