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Manganese ferrite clusters (MFCs) are spherical assemblies of tens to hundreds of primary nanocrystals whose magnetic properties are valuable in diverse applications. Here we describe how to form these materials in a hydrothermal process that permits the independent control of product cluster size (from 30 to 120 nm) and manganese content of the resulting material. Parameters such as the total amount of water added to the alcoholic reaction media and the ratio of manganese to iron precursor are important factors in achieving multiple types of MFC nanoscale products. A fast purification method uses magnetic separation to recover the materials making production of grams of magnetic nanomaterials quite efficient. We overcome the challenge of magnetic nanomaterial aggregation by applying highly charged sulfonate polymers to the surface of these nanomaterials yielding colloidally stable MFCs that remain non-aggregating even in highly saline environments. These non-aggregating, uniform, and tunable materials are excellent prospective materials for biomedical and environmental applications.

Precisely timed activation of genetically targeted cells is a powerful tool for studying neural circuits and controlling cell-based therapies. Magnetic control of cell activity or “magnetogenetics” using magnetic nanoparticle heating of temperature-sensitive ion channels enables remote, non-invasive activation of neurons for deep-tissue applications and studies of freely behaving animals. However, the in vivo response time of thermal magnetogenetics is currently tens of seconds, which prevents the precise temporal modulation of neural activity similar to light-based optogenetics. Moreover, magnetogenetics has not provided a means to selectively activate multiple channels to drive behavior. Here we produce sub-second behavioral responses in Drosophila melanogaster by combining magnetic nanoparticles with a rate-sensitive thermoreceptor (TRPA1-A). Furthermore, by tuning the properties of magnetic nanoparticles to respond to different magnetic field strengths and frequencies, we can achieve sub-second, multichannel stimulation, analogous to multi-color optogenetic stimulation. These results bring magnetogenetics closer to the temporal resolution and multiplexed stimulation possible with optogenetics while maintaining the minimal invasiveness and deep-tissue stimulation only possible by magnetic control.

Two experiments examined the performance of preschool children in tasks requiring the generalized matching of faces to faces and names to faces under the control of instructional stimuli (background color) that specified the basis by which faces were to be matched on a given trial. The children first learned to recite all the names, and to select all the faces, in a fixed order (the forward order). They then learned to select the faces in response to their spoken names. When the faces appeared on a white background, subjects selected the face named. On a gray background, they selected the face whose name was next forward. Subsequently, over a series of tests, when subjects were presented with novel, but similar stimuli with the same names, and with completely novel stimuli with novel names, control by the white and gray background colors generalized. In the second experiment, on trials with the gray background, when the face bearing the next-forward relation was not present, the children learned to select an appropriate substitute (two faces forward). This performance also generalized to novel stimuli. Together with earlier findings, these data suggest that widely generalized relational matching performances may arise because the labels for these relations are generically and metaphorically extended tacts.

This study investigated how the absence of a specified stimulus can control behavior. Four children were trained in nonidentity matching, and as a control, four were trained in identity matching. Both performances were produced by training overt mediating responses, so that in identity matching, the selection of a particular comparison was evoked by the repetition of a sample tact to the comparison, and in nonidentity, by the inability to repeat the sample tact to the comparison. Successful generalization of the performances indicated that they were indeed controlled by these general features rather than by stimulus-specific features. Comparison selection thus served as an autoclitic report about other verbal behavior. In particular, generalized nonidentity matching indicated that sensitivity to discrepancies between what a sample specifies, and what is actually presented, can be accounted for behaviorally, without recourse to hypothesized cognitive mediators.

Preface SECTION I. ENVIRONMENTAL APPLICATIONS AND IMPLICATIONS 1. Overview: Environmental Applications and Implications How does nanotechnology relate to the environment? 2. Environmental technologies at the nanoscale 3. Reassessing risk assessment 4. The environmental impact of engineered nanomaterials Section II. Environmental Implications: Toxicology and biological interactions of nano-materials 1. Toxicology and biological interactions of nano-materials: An Overview 2. A role for immunology in nanotechnology. 3. Effects and fate of inhaled ultrafine particles. 4. Toxicity of single-walled carbon nanotubes in the lungs of mice exposed by intratracheal instillation 5. Pulmonary-toxicity-screening studies with single-wall carbon nanotubes. Section III. Environmental Implications: Nanoparticle geochemistry in water and air 1. Nanoparticles and the environment 2. Nano-scale heavy-metal phases on atmospheric and groundwater colloids. 3. Recent insights into the formation and chemical composition of atmospheric nanoparticles from the Aerosol Nucleation and Real-time Characterization Experiment. 4. Outer-sphere coordination of uranyl carbonate by modified cyclodextrins: implications for speciation and remediation Section IV. Environmental Implications: Metrology for nano-sized materials 1. Metrology for nano-sized materials: An Overview. 2. Molecular-dynamics simulation of forces between colloidal nanoparticles. 3. Growth and characterization of single-crystal multilayer nanostructures for fast-ion conduction. 4 esel nanoparticles. Section V. Environmental Applications: Sensors and Sensor systems 1. Sensors and Sensor systems: An Overview 2. Sorptive properties of monolayer-protected gold nanoparticle films for chemical vapor sensors and arrays. 3. Semiconductor nanostructures for detection and degradation of low-level organic contaminants from water. 4. Luminescent Silole Nanoparticules as Chemical Sensors for Carcinogenic Chromium(VI) and Arsenic(V) 5. A Nanocontact Sensor for Heavy Metal Ion Detections 6. Ultrasensitive Pathogen Quantification in Drinking Water Using Highly Piezoelectric Microcantilevers 7. Nanostructured sorbents for solid-phase microextraction and environmental assay. 8. Photosynthetic biosensors for rapid monitoring of primary source drinking water Section VI. Environmental Applications: Treatment/Remediation using Nanotechnology 1. Environmental Applications: Treatment/Remediation using Nanotechnology 2. Activation of gold nanoparticles on titania: A novel DeSOx catalyst. 3. Fabrication of two-dimensional and three-dimensional platinum nanoparticle systems for chemisorption and catalytic-reaction studies. 4. Nano-biotechnology in using enzymes for environmental remediation: Single-enzyme nanoparticles. 5. Charge development on ferritin: An electrokinetic study of a protein containing a ferrihydrite nanoparticle 6. A Bioengineering approach to the production of metal and metal oxide nanoparticles 7. Dendritic nanoscale chelating agents: Synthesis, characterization and environmental applications. 8. Iron nanoparticles for site remediation 9. Membrane-based nanostructured metals for reductive degradation of hazardous organics. 10. Porous membranes containing zero-valent iron nanorods for water treatment. Section VII. Environmental Applications: Nanocatalysts for environmental technology 1. Nanocatalysts for environmental technology 2. Nanocrystalline metal oxides: A new family of mesoporous inorganic materials useful for destructive adsorption of environmental toxins. 3. Development of nanocrystalline zeolite materials as environmental catalysts. 4. A Vibrational spectroscopic study of the CO + NO reaction: From Pd single crystals at ultrahigh vacuum to Pd clusters supported on SiO2 thin films at elevated pressures. 5. Nanostructured catalysts for environmental applications 6. Catalytic oxidations using nanosized octahedral molecular sieves. Section VIII. Environmental Applications: Environmentally benign nano-manufacturing 1. Environmentally benign nano-manufacturing: An Overview 2. Synthesis of surfactant-templated aerogels with tunable nanoporosity. Section IX. Environmental Applications: Nanotech-enabled Green energy and Power Sources 1. Energy and the environment: Perpetual dilemma or nanotechnology-enabled opportunity? 2. Electrochemistry at nanometer length scales 3. Using mesoporous nanoarchitectures to improve battery performance 4. Nanostructured superlattice thin-film thermoelectric devices 5. Membraneless fuel cells: An application of microfluidics 6. Hybrid photoelectrochemical-fuel cell

The valence band maximum of semiconductor clusters shifts with size. We attribute this phenomenon to both quantum confinement and dielectric solvation effects.