Neutral shift [five years of continuous operation with adjustable frequency drives]

The combined efforts of the AFD supplier and end-user have resulted in an extremely reliable electrical adjustable speed drive system. Almost three years into the run of the first unit, all parties are confident of the ability to meet the five-year run target that was identified at the outset. The redundancy of the power cells in this particular design, together with the neutral shift control has practically eliminated the power components as a source of operational failure. Future development efforts will include applying redundancy and fault tolerance to the drive control processor to further enhance system reliability.     

Solvent vapor treatment controls surface wettability in PMMA femtosecond-laser-ablated microchannels

A solvent vapor treatment was applied to femtosecond-laser-ablated microchannels in PMMA to selectively restore the original hydrophilic wetting behavior of the pristine surface. The hydrophobic surface of the microchannels from the submicron porosity induced by ablation becomes smoother and more transparent after the treatment. This simple and low-cost method, together with suitable masking, can produce wettability patterns that may be exploited to develop passive microfluidic elements such as valves and mixers.     

The Industrial Base

Abstract

Images and Enterprise is one of the books in the Johns Hopkins Studies in the History of Technology Series and, as such, is a study of the American photographic industry within the overall field of technology. It covers the period 1839-1925, and deals with technical, business and, to a lesser extent, social aspects. These are traced from the industry's disorganized, diffuse beginnings to the point where the market became dominated by a few highly organized, technologically oriented fmus. When the daguerreotype process was introduced in 1839, its practitioners and even their immediate suppliers were compelled to look to a number of sources for the necessary materials: cabinet makers supplied camera boxes, chemical firms the required elements and compounds, miniature-case makers produced containers for the finished pictures, and the brass industry manufactured the silver-coated copper plates. The need for general supply houses was not immediately perceived. Much had to be imported, and European producers played a big role during the early years in providing lenses, fine chemicals and plates for American users.     

A Hotelling style model of spatial competition for a convenience good

Ordinarily people do not make special purpose trips to acquire goods like gasoline or groceries but instead buy them as the need arises in the course of their daily lives. Such goods are commonly called convenience goods. We modify Hotelling??s model of spatial competition so that we can analyze the price equilibrium of duopolists that retail a convenience good. Certain features of the duopolists?? demand functions suggest that price competition is more severe in the convenience goods model than in the Hotelling model. The same features complicate the analysis because they mean that a pure strategy price equilibrium does not exist for many locational configurations. Although we are not able to find the mixed strategy price equilibrium analytically, we do present some numerical results on equilibrium prices that broadly confirm this suggestion. We also provide a more general product differentiation interpretation of the convenience good model.     

Frank Lloyd Wright and the Concrete Slab and Column

This paper traces the development of Frank Lloyd Wright's ideas on the place of the concrete column and slab in architecture. It deals with his first employment of the slab at Unity Temple (Oak Park, 1904) and his use of the form in residential projects during the next few years. It surveys American literature on concrete construction and briefly analyses the contribution of Claude A.P. Turner and the employment of the Turner system in two Chicago buildings that Wright would have known. It discusses his project for the San Francisco Call (1912) and the use of the Barton system in the Richland Center warehouse for A.D. German (1915). It further discusses his first probable knowledge of the more sophisticated concrete slabs of Maillart, published in 1926, and of Maillart's invention of a proto lily-pad capital. This capital is also to be seen in Wright's champagne glass designed for Leerdam (1930) and in his project for the Salem Capitol Journal of 1931. Finally it is argued that the much admired lily-pad columns at the Johnson Wax office building (Racine, 1937-39) are really a series of three-hinged bents rather than shell construction.     

Molecular species of wax esters in jaw fat of atlantic bottlenose dolphin,Tursiops truncatus

The jaw fat of the Atlantic bottlenose dolphin (Tursiops truncatus) contains unusual wax esters which can be separated into short chain (<C₂₄) and long chain (>C₂₄) fractions by thin layer chromatography. The short chain wax esters (28 wt. %) have been characterized as a 72∶24∶4 mixture of isovaleroyl, isobutoryl, and 2-methylbutyrol, esters of C₁₄–C₁₈ n- and iso-alcohols. The intact <C₂₄ esters have been resolved into individual molecular species by gas liquid chromatography on open-tubular polyester columns. The long chain wax esters (12 wt. %) contain C₁₀–C₂₂ n- and iso-acids esterified to the same C₁₄–C₁₈ n- and iso-alcohols. Gas liquid chromatography of the intact, hydrogenated >C₂₄ esters on a short JXR column has characterized them according to carbon number and the number of methyl branches they contain.     

Retention behavior of phenols, anilines, and alkylbenzenes in liquid chromatographic separations using subcritical water as the mobile phase

The unique characteristic of subcritical water is its widely tunable physical properties. For example, the polarity (measured by dielectric constant) of water is significantly decreased by raising water temperature. At temperatures of 200-250 °C (under moderate pressure to keep water in the liquid state), the polarity of pure water is similar to that of pure methanol or acetonitrile at ambient conditions. Therefore, pure subcritical water may be able to serve as the mobile phase for reversed-phase separations. To investigate the retention behavior in subcritical water separation, the retention factors of BTEX (benzene, toluene, ethylbenzene, and m-xylene), phenol, aniline, and their derivatives have been determined using subcritical water, methanol/water, and acetonitrile/water systems. Subcritical water separations were also performed using alumina, silica-bonded C18, and poly(styrene-divinylbenzene) columns to study the influence of the stationary phase on analyte retention under subcritical water conditions.     

N-methyl-D-aspartic acid stimulation of vasopressin release: role in osmotic regulation and modulation by gonadal steroids

Previous experiments demonstrated that excitatory amino acids participate in the osmotic regulation of vasopressin secretion, but the specific involvement of N-methyl-D-aspartic acid (NMDA) receptors was not evaluated. This was demonstrated in the present studies. NMDA stimulated vasopressin release from perifused explants of the hypothalamo-neurohypophyseal system (HNS), and osmotic stimulation of vasopressin release was inhibited by MK-801 (10 microM) and AP5 (100 microM) NMDA receptor antagonists. The effective concentration of NMDA was dependent upon the Mg2+ concentration of the perifusate with stimulation observed at 1 microM NMDA in Mg2+-replete compared with 5 microM in low-Mg2+ medium. Previous experiments also demonstrated that estradiol and dihydrotestosterone (DHT) inhibited osmotically stimulated vasopressin secretion, and a nongenomic mechanism of action was suggested by the ability of steroids conjugated to bovine serum albumin to replicate the effect. Experiments were performed to explore the potential role of NMDA receptors in this mechanism. Estradiol (50 pg/ml) and DHT (3 ng/ml) inhibited NMDA stimulated vasopressin release in perifused HNS explants. These results suggest a role of NMDA receptors in the mediation of vasopressin secretion in osmotically stimulated release. Furthermore, estradiol and DHT may exert their inhibitory effect on osmotically stimulated vasopressin release via the NMDA receptor.     

Experience with reduction mammaplasty following breast conservation surgery and radiation therapy

Little is known about the outcome of breast reduction in the previously radiated breast. With the increased popularity of breast conservation in the management of breast cancer, it is inevitable that more women with breast cancer who have had a breast radiated will be seeking breast reduction. Although it would be expected that reduction of the radiated breast would be more challenging and would yield less-pleasing results, it has been unclear whether reduction in the radiated breast could be safely performed without interfering with mammography and cancer surveillance. Our experience using different techniques in three patients demonstrates that such reductions can be effectively and safely done if certain principles are followed. Pedicles should be designed to be broader and shorter than usual, and breast flaps should be undermined or elevated either minimally or not at all.     

Pharmacokinetics of 2-oxothiazolidine-4-carboxylate, a cysteine prodrug, and cysteine

The pharmacokinetics of both 2-oxothiazolidine-4-carboxylate (OTZ), a prodrug of cysteine, and total blood cysteine (cysteine plus cystine) were investigated in 18 healthy volunteers. OTZ was given either as a single, 2-hour intravenous infusion (56-66 mg/kg) or similarly infused (70-100 mg/kg) every 8 hours for four doses. Blood was assayed for OTZ, total blood cysteine, and glutathione. The pharmacokinetics of OTZ were analyzed alone and simultaneously with total cysteine using the NONMEM software package (University of California at San Francisco. The pharmacokinetics of OTZ were best described by Michaelis-Menten kinetics with parallel first-order elimination. OTZ was efficiently removed from the plasma. The Michaelis-Menten route of elimination was attributed to conversion of OTZ to total cysteine. At plasma OTZ concentrations equal to the Michaelis constant Km, 84% of OTZ was converted to total cysteine. These findings suggest that OTZ administered intravenously is an efficient means of increasing total blood cysteine.