Largest extension of a finite convex geometry

We present a new embedding of a finite join-semidistributive lattice into a finite atomistic join-semidistributive lattice. This embedding turns out to be the largest extension, when applied to a finite convex geometry.In Celebration of the Sixtieth Birthday of Ralph N. McKenzieReceived September 18, 2002; accepted in final form September 29, 2003.     

The Lattice of Completions of an Ordered Set

For any ordered set P, the join dense completions of P form a complete lattice K(P) with least element O(P), the lattice of order ideals of P, and greatest element M(P), the Dedekind–MacNeille completion P. The lattice K(P) is isomorphic to an ideal of the lattice of all closure operators on the lattice O(P). Thus it inherits some local structural properties which hold in the lattice of closure operators on any complete lattice. In particular, if K(P) is finite, then it is an upper semimodular lattice and an upper bounded homomorphic image of a free lattice, and hence meet semidistributive.     

Reflections on lower bounded lattices

Lattices in the variety of lower bounded lattices of rank k are characterized. A sufficient condition for a lattice to be lower bounded is given, and used to produce a new example of a non-finitely-generated lower bounded lattice. Lattices that are subdirect products of finite lower bounded lattices are characterized.In memory of Ivan RivalReceived September 18, 2003; accepted in final form October 5, 2004.This revised version was published online in August 2005 with a corrected cover date.     

High-performance liquid chromatographic method for simple and rapid determination of linezolid in human plasma

A simple high-performance liquid chromatographic (HPLC) method was developed and validated for rapid quantification of linezolid in human plasma. Protein precipitation using a mixture of 5% trichloroacetic acid and methanol (3:1, v/v) provided a straightforward method of sample preparation and the internal standard eperezolid was employed. A concentration range from 0.20 to 40.0 mg/L was utilized to construct calibration curves, and analysis of low- (0.40 mg/L), medium- (7.50 mg/L) and high-quality (25.0 mg/L) control samples revealed excellent reproducibility (相似文献   

Lattices with large minimal extensions

This paper characterizes those finite lattices which are a maximal sublattice of an infinite lattice. There are 145 minimal lattices with this property, and a finite lattice has an infinite minimal extension if and only if it contains one of these 145 as a sublattice. Received October 5, 1998; accepted in final form May 19, 1999.     

High-power microwave generation using a ferroelectric cathodeelectron gun

A two-stage 500 kV 200-A ferroelectric electron gun has been designed, fabricated, tested, and used in a high power microwave amplifier experiment. We report on the operational characteristics of the gun including measurements of the beam dynamics. The optimum conditions for application of the trigger and its timing are also reported. Faraday cup measurement shows that the beam radius is 4.1 mm, in good agreement with simulation. The gun is designed for use in traveling-wave tube amplifiers, and testing of an X-band amplifier driven by the gun is reported. A peak output power of 5.9 MW has been observed from a single stage amplifier driven by a 100 A. 450 kV beam. This corresponds to energy converging efficiency of 13.1% and is the first observation of high power (~MW) microwave generation using the beam generated from a ferroelectric cathode,     

Ferroelectric sources and their application to pulsed power: areview

We present in this review an account of recent research into the use of ferroelectrics as electron beam sources for pulsed power applications. The work is reviewed according to the ferroelectric material used and the switching process employed. Most of the current research uses PLZT or PZT, which can be ferroelectric, antiferroelectric, or paraelectric depending on the stoichiometry. Switching is accomplished by the application of a fast-rising electric field to the ferroelectric material. The most commonly used materials are PLZT 2/95/5 and PLZT 8/65/35 or PZT (with no lanthanum): in the former case, the applied field switches the material from the antiferroelectric state to the ferroelectric state, and in the latter cases, around a hysteresis loop. Results have been reported with ferroelectric cathodes where current densities of up to a few hundred amperes per square centimeter have been achieved, with pulse durations of several microseconds. With shorter duration pulses and PLZT cathodes, repetition rates of up to 2 MHz have been achieved. In this paper, we focus on the results reported in the literature, and include a brief account of the physical interpretation of the data. The possible use of ferroelectric sources for pulsed power applications is indicated     

Dimension may exceed width

A partially ordered set with no infinite antichains may have arbitrarily large dimension.