Magic-sized cadmium selenide (CdSe) nanocrystals have been pyrolytically synthesized. These ultra-small nanocrystals exhibit broadband emission (420-710 nm) that covers most of the visible spectrum while not suffering from self absorption. This behavior is a direct result of the extremely narrow size distribution and unusually large Stokes shift (40-50 nm). The intrinsic properties of these ultra-small nanocrystals make them an ideal material for applications in solid state lighting and also the perfect platform to study the molecule-to-nanocrystal transition.

Alloy nanocrystals provide an additional degree of freedom in selecting desirable properties for nanoscale engineering because their physical and optical properties depend on both size and composition. We report the pyrolytic synthesis of homogeneously alloyed CdS(x)Se(1-x) nanocrystals in all proportions. The nanocrystals are characterized using UV-visible absorption spectroscopy, transmission electron microscopy, X-ray diffractrometry, and Rutherford backscattering spectrometry to determine precisely structure, size, and composition. The dependence of band gap on nanocrystal size and composition is elucidated, yielding a bowing constant of 0.29, in agreement with bulk values. In addition, the morphology of the resultant nanocrystals can be altered by changing the reaction conditions, generating structures ranging from homogeneous, spherical nanocrystals to one-dimensional gradient nanorods.

White-light emission from ultrasmall CdSe nanocrystals offers an alternative approach to the realization of solid-state lighting as an appealing technology for consumers. Unfortunately, their extremely small size limits the feasibility of traditional methods for nanocrystal characterization. This paper reports the first images of their structure, which were obtained using aberration-corrected atomic number contrast scanning transmission electron microscopy (Z-STEM). With subangstrom resolution, Z-STEM is one of the few available methods that can be used to directly image the nanocrystal's structure. The initial images suggest that they are crystalline and approximately four lattice planes in diameter. In addition to the structure, for the first time, the exciton dynamics were measured at different wavelengths of the white-light spectrum using ultrafast fluorescence upconversion spectroscopy. The data suggest that a myriad of trap states are responsible for the broad-spectrum emission. It is hoped that the information presented here will provide a foundation for the future development and improvement of white-light-emitting nanocrystals.

Fluctuations in year-class size of striped bass (Morone saxatilis) are believed related to early-lifestage mortality. Factors associated with food and feeding of larvae were studied in the laboratory as they relate to mortality, point of no return, development, and energetics. Mortality of feeding larvae was directly related to density of Artemia salina nauplii. Highest mortality coincided with total oil globule absorption. Starved larvae lived an average 31 days after fertilization and did not display a well-defined point of no return. Growth and differentiation directly correlated with food density. Starvation affected the rate of ossification and altered cells and tissues as early as 7 days after hatching. Most of the endogenous energy of newly fertilized eggs is in oil. The rate of oil utilization was inversely related to food density. Daily food rations were estimated after ingestion and digestion rates were determined, and increased with larva size, age, and prey density.Between 1879 and 1882, 432 juvenile striped bass (Morone saxatilis) from the Navesink River, New Jersey, were released into the San Francisco Bay-Delta estuary. The transplant was so successful that, within 10 years, the commercial fishery landed 554 t (Skinner 1962). In less than 100 years, the Pacific range of striped bass has expanded south to 30 km below the United States-Mexico border and north to Barkley Sound, British Columbia (Miller and Lea 1972). Over the intervening years, sport and commercial catch records have indicated considerable fluctuations in the Pacific striped bass population (Smith and Kato 1979), and present estimates place the population at 33 to 40% of its peak 1960 estimate of 3.0 to 4.5 x 10 • fish. Recent field data indicate that mortality during the first 60 days after hatching determines the size of the adult population. Further, abundance of young-of-the-year juveniles is directly related to river outflows and diversion volumes in the Sacramento-San Joaquin River Delta (Chadwick et al. 1977). However, aside from direct export of eggs and larvae out of the estuary via water diversions, the actual causes of mortality remain undetermined. As part of a cooperative research program involving the