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I briefly describe the Lick Observatory Supernova Search with the 0.76-m Katzman Automatic Imaging Telescope. I then present an overview of optical observations of Type II, IIb, Ib, and Ic supernovae (SNe), all of which are thought to arise from core collapse in massive progenitors that have previously experienced different amounts of mass loss. SNe IIn are distinguished by relatively narrow emission lines with little or no P-Cygni absorption component; they probably have unusually dense circumstellar gas with which the ejecta interact. Some SNe IIn, however, might actually be super-outbursts of luminous variable stars; rarely, they may even be SNe Ia in disguise. Plausible detections of the progenitors of a few SNe II have been made. Spectropolarimetry of core-collapse SNe reveals that asphericity increases toward the core.
Quantitation of photosystem II (PSII) activity in spinach chloroplasts is presented. Rates of PSII electron‐transport were estimated from the concentration of PSII reaction‐centers (Chl/PSII = 380:1 when measured spectrophotometrically in the ultraviolet [ΔA 320 ] and green [ΔA 540–550 ] regions of the spectrum) and from the rate of light utilization by PSII under limiting excitation conditions. Rates of PSII electron‐transport were measured under the same light‐limiting conditions using 2,5‐dimethylbenzoquinone or 2,5‐dichlorobenzoquinone as the PSII artificial electron acceptors. Evaluation is presented on the limitations imposed in the measurement of PSII electron flow to artificial quinones in chloroplasts. Limitations include the static quenching of excitation energy in the pigment bed by added quinones, the fraction of PSII centers (PSII β ) with low affinity to native and added quinones, and the loss of reducing equivalents to molecular oxygen. Such artifacts lowered the yield of steady‐state electron transport in isolated chloroplasts and caused underestimation of PSII electron‐transport capacity. The limitations described could explain the low PSII concentration estimates in higher plant chloroplasts (Chl/PSII = 600 ± 50) resulting from proton flash yield and/or oxygen flash‐yield measurements. It is implied that quantitation of PSII by repetitive flash‐yield methods requires assessment of the slow turnover of electrons by PSII β and, in the presence of added quinones, assessment of the PSII quantum yield.
This paper considers the support of real-time applications in an Integrated Services Packet Network (ISPN). We first review the characteristics of real-time applications. We observe that, contrary to the popular view that real-time applications necessarily require a fixed delay bound, some real-time applications are more flexible and can adapt to current network conditions. We then propose an ISPN architecture that supports two distinct kinds of real-time service: guaranteed service, which is the traditional form of real-time service discussed in most of the literature and involves pre-computed worst-case delay bounds, and predicted service which uses the measure performance of the network in computing delay bounds. We then propose a packet scheduling mechanism that can support both of these real-time services as well as accommodate datagram traffic. We also discuss two other aspects of an overall ISPN architecture: the service interface and the admission control criteria.
There is widespread agreement on the need for architectural change in the Internet, but very few believe that current ISPs will ever effect such changes. In this paper we ask what makes an architecture evolvable, by which we mean capable of gradual change led by the incumbent providers. This involves both technical and economic issues, since ISPs have to be able, and incented, to offer new architectures. Our study suggests that, with very minor modifications, the current Internet architecture could be evolvable.
In order to declare the accurate vitamin A effectiveness of foodstuffs and synthetic vitamin A preparations, the biological activity of the individual isomers has to be known. Total activity is expressed as all-trans vitamin A equivalents which are calculated by multiplication of analytical content of each isomer with the corresponding biopotency factor. The biological activity of four cis and three or four dicis isomers of vitamin A acetate and palmitate was determined by means of rat vaginal smear assays. The purity of the compounds, the content and isomerisation in stock solutions were checked by HPLC methods prior to their dilution and application to the experimental animals. Based on analytical contents the following activities were found for vitamin A acetate isomers: all-trans 1.00, 13-cis 0.76, 11-cis 0.31, 9-cis 0.19, 7-cis 0.18, 9,13-dicis 0.16, 11,13-dicis 0.18, 9,11-dicis approx. 0.03. The corresponding values for vitamin A palmitate were: all-trans 1.00, 13-cis 0.73, 11-cis 0.34, 9-cis 0.19, 7-cis 0.14, 9,13-dicis 0.21, 11,13-dicis 0.20, 9,11-dicis approx. 0.04, 7,11-dicis approx. 0.12. The vitamin A activity of the cis isomers ranged from about 0.75 for 13-cis to about 0.05 for 9,11-dicis. For the cis series, a biopotency relationship depending on the distance between the beta-ionone ring system and the cis configuration could be observed.
Algorithms in computational geometry often use the real-RAM model of computation. In particular, this model assumes that exact real numbers can be stored in and retrieved from memory in constant $O$ (1) time, and that field operations (+, -, *, /) and certain other operations (like square root, sine and cosine) are also "exact," and can be applied in constant time.
Peg-in-hole insertion is not only a longstanding problem in robotics but the most common automated mechanical assembly task. In this paper we present a high precision, self-calibrating peg-in-hole insertion strategy using several very simple, inexpensive, and accurate optical sensors. The self-calibrating feature allows us to achieve successful dead-reckoning insertions with tolerances of 25 microns without any accurate initial position information for the robot, pegs, or holes. The program we implemented works for any cylindrical peg, and the sensing steps do not depend on the peg diameter, which the program does not know. The key to the strategy is the use of a fixed sensor to localize both a mobile sensor and the peg, while the mobile sensor localizes the hole. Our strategy is extremely fast, localizing pegs as they are in route to their insertion location without pausing. The result is that insertion times are dominated by the transport time between pick and place operations.
Disclosed herein is a sequential functionalization methodology for the covalent modification of nanotubes with between one and four repeat units of a polymer. Covalent attachment of oligomer units to the surface of nanotubes results in oligomer units forming an organic sheath around the nanotubes, polymer-functionalized-nanotubes (P-NTs). P-NTs possess chemical functionality identical to that of the functionalizing polymer, and thus provide nanoscale scaffolds which may be readily dispersed within a monomer solution and participate in the polymerization reaction to form a polymer-nanotube/polymer composite. Formation of polymer in the presence of P-NTs leads to a uniform dispersion of nanotubes within the polymer matrix, in contrast to aggregated masses of nanotubes in the case of pristine-NTs. The covalent attachment of oligomeric units to the surface of nanotubes represents the formation of a functional nanoscale building block which can be readily dispersed and integrated within the polymer to form a novel composite material.
