Optical communications system Patent

Specifications and drawings for semipassive optical communication syste

Electronic motor control system Patent

Electronic circuit system for controlling electric motor spee

Hodge theory and derived categories of cubic fourfolds

Cubic fourfolds behave in many ways like K3 surfaces. Certain cubics - conjecturally, the ones that are rational - have specific K3s associated to them geometrically. Hassett has studied cubics with K3s associated to them at the level of Hodge theory, and Kuznetsov has studied cubics with K3s associated to them at the level of derived categories. These two notions of having an associated K3 should coincide. We prove that they coincide generically: Hassett's cubics form a countable union of irreducible Noether-Lefschetz divisors in moduli space, and we show that Kuznetsov's cubics are a dense subset of these, forming a non-empty, Zariski open subset in each divisor.Comment: 37 pages. Applications to algebraic cycles added, and other improvements following referees' suggestions. This is a slightly expanded version of the paper to appear in Duke Math

How Wide is the Scope of Hold-Up-Based Theories? Contractual Form and Market Thickness in Trucking

How far do the contractual implications of hold-up-based theories (Klein, Crawford, and Alchian (1978), Williamson (1979, 1985)) extend? I investigate this in the context of trucking. Quasi-rents in trucking are generally smaller than in the contexts studied in the previous empirical literature. They vary with hauls' distance and the thickness of local markets. I find that doubling the thickness of the market increases the likelihood that simple spot arrangements govern transactions by about 30% for long hauls. I find weaker evidence of relationships between local market thickness and contractual form for short hauls -- hauls for which quasi-rents are particularly small. Contracts' role as protectors of quasi-rents becomes less important as quasi-rents decrease, but exists over a surprisingly large range.

Inter-Regional Transfer Trade Flows in the English Football League

This paper examines the pattern and extent of inter-regional transfers of professional footballers between clubs in the English football league system over the period 1990-1991 to 1999-2000. Our study emlploys a variant form of an established trade flow model and, in presenting and confirming tbe pattern and extent of inter-regional transfers, it indicates the wider applications of the conventional trade model.

The properties of nerve cell precursors in hydra

Two signals, the head activator and an injury stimulus, control differentiation of nerve cells from uncommitted stem cells in hydra [Th. Holstein, H. C. Schaller, and C. N. David, (1986) Dev. Biol. 115, 9–17]. The time of action of these signals in the precursor cell cycle was determined. Methanol extracts of hydra containing 10−13 M head activator cause nerve cell commitment in S phase of the precursor cell cycle. Committed precursors complete the cell cycle, divide, and arrest in G1. Injury relieves the G1 block and precursors differentiate nerve cells. Under these conditions the time from commitment to nerve differentiation is 12 hr, the time from the end of S phase to nerve differentiation is 9 hr, and the time from the G1 block to nerve differentiation is 4 hr. Committed precursors blocked in G1 are unstable, decaying with a half-life of 12 hr if not stimulated to differentiate by an injury stimulus

Pacific herring, Clupea harengus pallasi, studies in San Francisco Bay, Monterey Bay, and the Gulf of the Farallones, July 1982 to March 1983

Herring stocks were hydroacoustically surveyed and sampled in San Francisco Bay from November 1982 to March 1983. Twelve discrete herring schools were identified, all of which spawned between November 7 and February 23. One additional school was found in the Bay in March but showed no evidence of spawning. Total biomass estimate from hydroacoustic surveys was 67,040 tons. Based on MRR biomass estimates from spawned egg counts, an additional 10,000 tons may have spawned in November and December without being detected hydroacoustically. The largest schools occurred in January and February. Hydroacoustic estimates of biomass for individual schools during the season ranged from 270 to 22,300 tons. Sixty-seven samples, containing a total of 12,232 herring, were collected with variable mesh gill net and midwater trawl or obtained from the commercial roundhaul and gill net fisheries. In general, a trend was observed of decreasing mean size and age as the season progressed. Schools spawning in November and December consisted primarily of 4-, 5-, 6-, and 7-yr-old fish. Schools sampled from January to March were predominantly 2-, 3-, 4-, and 5-yr-old herring. The 1978, 1979, and 1980 yr classes (ages 5, 4, and 3 yr) were strong, comprising up to 90% of the samples. The 1981 yr class (2-yr olds) was relatively weak. Abundant rainfall and resultant low salinity in San Francisco Bay surface waters apparently delayed or prevented herring from spawning in February and March. A relationship may exist between relative abundance of young-of-the-year fish, as noted from midwater trawl samples collected by the Department's Bay-Delta Study, and the resultant year class strength of newly recruited 2-yr-old herring in San Francisco Bay's spawning stocks. (57pp.