We discuss the formation of gold metal colloids in a variety of surfactant/solvent systems. Static and dynamic light scattering, small angle x-ray and neutron scattering, TEM analysis, and UV-visible absorbance are used to characterize the kinetics of formation and final colloid stability. These gold colloids exhibit a dramatic blueshift and broadening of the plasmon resonance with decreasing colloid size. Several types of reduction method are discussed and differences between micelle (water-free) or microemulsions as reaction media are compared. Use of inverse micelles allows smaller clusters to be formed with greater long-term stability.

A temperature-sensitive mutation, parat', in Drosophila melanogaster causes an immediate, but reversible, paralysis of adult flies when they are shifted from 220C to 290C. The mutation is a sex-linked recessive that maps 2.8 units to the left off. Wild-type flies observed for 2-hr periods exhibited normal mobility at all temperatures between 220C and 350C. From 220C to 250C, parat" flies were wild type in walking, climbing, and flying ability.At 1-degree intervals above 250C, parats flies became increasingly debilitated; at 290C, complete paralysis occurred. After flies were maintained for prolonged intervals at 290C, some activity could be recovered at that temperature. Studies of the behavior of mosaics at 290C revealed a requirement of the (+) allele in the head for mobility, and a thoracic component for proper leg movement. Normal electroretinograms were obtained at both 220Cand 30'C. The results suggest a temperature-sensitive defect in the nervous system.The genetic regulation of neural structure and function, and the relationship of such regulation to behavior, are of fundamental biological interest. The ready induction and recovery of mutations affecting behavior in Drosophila, and their genetic manipulation, is now being exploited in several laboratories (1-3). By selecting flies manifesting the phenotype of paralysis, we felt that mutations affecting nerves and/or muscles could be efficiently obtained. However, flies exhibiting such a mutant phenotype would not be expected to be viable; therefore, we searched for mutations that showed conditional paralysis that was temperature dependent (4). This report concerns the discovery and properties of such a mutation, paralytic-temperature-sensitive (para s), in Drosophila melanogaster. METHODS AND MATERIALS ScreeningNewly emerged adult Oregon-R males were fed the mutagen ethyl methanesulfonate dissolved in a 1% sucrose solution (0.025 M) (5). 24 hr later, they were mated at 220C to attached-X-bearing females in 125-ml bottles. Adult progeny were then placed in a heated plexiglass screening apparatus that allowed the ready separation of immobilized flies from those retaining normal movement (6). 1000-8000 adults (at a time) were placed in the box and left for 1/4-2 hr before selection. All motionless flies were then returned to 220C and any that regained mobility were mated (males to XX females, females to Oregon-R males); all offspring of fertile individuals were tested for paralysis at 290C. The specific properties and details of analysis of the temperature-sensitive paralytic mutant are discussed in the next section. RESULTS Table 1 shows the results of the screening. The bulk of the immobilized flies recovered were dead or sterile at 220C. However, out of an estimated 250,000 flies screened, one was detected (by R.W.) that carried a mutation causing a temperature-sensitive paralysis. Genetic properties The temperature-sensitive paralyzed fly was a male; all of its male progeny were paralyzed upon shifting to 290C, whereas the females were not, ther...

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When a soft magnetic particle suspension is subjected to a vertical uniaxial magnetic field the particles polarize, the positive dipolar interactions causing particle chain formation. If instead an audio-frequency rotating magnetic field is applied in a horizontal plane, the particles experience an average interaction that to first order is a negative dipolar interaction, causing particle sheet formation in the biaxial field plane. When a vertical uniaxial field and a horizontal biaxial field are simultaneously applied with the field amplitudes balanced, the positive and negative dipolar interactions cancel to first order, and one might expect no dipolar interactions at all. But in this balanced triaxial field an isotropic second-order dipolar interaction of surprising magnitude remains. This triaxial interaction can be attractive or repulsive, and exhibits strong many-body interactions that lead to a variety of unexpected effects, including stable clusters with molecular geometries, the emergence of a particle foam, and the production of vortices in the fluid. By manipulating the triaxial field, a variety of particle structures can be made that cannot be produced by any other known means.

Shudderer is an X-linked dominant mutation of Drosophila melanogaster. The mutant is characterized by sporadically occurring leg jerks which cause the fly to lurch and shudder. This behavior was suppressed by adding lithium chloride, lithium acetate, or ammonium chloride to the fly's diet. These same salts also restored the fly's reactive climbing abilities toward normal levels.

Total geometry optimizations are reported for Cr(CO),, HMn(CO),, Fe(CO),, (C,H,)CT(CO)~. A variety of basis sets were examined, and, based on the results, a relatively compact and accurate basis set is proposed. The differences between the calculated and experimental metal-carbonyl, metal-benzene, and metal-nitrosyl bond distances average 0.03, 0.08, and 0.07 A, respectively. Calculated metal-cyclopentadienyl bond lengths were found to be an average of 0.15 8, longer than experimental bond lengths. Addition of electron correlation at the perfect pairing GVB level reduced the average difference in the metal-cyclopentadienyl bond length to 0.08 8,.Ni(CO)4, Cr(C6H6)29 Fe(C5H5),, Ni(C4H4)29 Cr(NO),, (CsHs)Mn(CO)3, and

Gold colloidal suspensions are produced from both inverse micelle solutions and microemulsions through both chemical and photolytic reduction of the appropriate salt.A variety of surfactant/solvent combinations yield varying results with respect to metalloid growth kinetics and stability as revealed through dynamic light scattering, smallangle x-ray and neutron scattering, and transmission electron microscopy.

Overview Melting TechnologiesRemelting is performed to facilitate the production of clean, fully dense, homogeneous castings of superalloys and aerospace titanium alloys and is crucial to the defectfree production of these important materials. Modern electroslag remelting and vacuum arc remelting control systems are closedloop, single input-single output systems that oversimplify the physical properties of the processes; the ever-increasing demand for cleaner, more highly engineered, chemically tuned alloys has pushed these control methodologies to their limit. A new generation of these controllers is being developed by the Specialty Metals Process Consortium and Sandia National Laboratories to answer the challenges of remelting control for the next generation of alloys; these control systems will use multiple sensor inputs and apply material-specific system and process models.