Small Finds, Space, and Social Context: Exploring Agency in Historical Archaeology

The George Washington Foundation Department of Archaeology has combined a number of excavation and artifact-recovery techniques with a deliberate approach to artifact research and analysis in the laboratory to enhance interpretations of past behaviors. This article describes the elements of this approach and provides a case study involving the numerous 18th-century wig hair curler fragments found at the boyhood home of George Washington. The historical record together with the material culture assemblage allow us to demonstrate that the Washington family engaged in a home-based system of wig maintenance, allowing the economically struggling Washington boys to don wigs, an essential element of male gentry attire. This approach illustrates that conscientious recovery and analysis of small finds, such as wig curlers, can provide data used to reveal a great deal about the agency and consumer motivations of their owners

Size-dependent complex dielectric function of Ni, Mo, W, Pb, Zn and Na nanoparticles. Application to sizing

This work determines the size dependent metal nanoparticle (NP) dielectric function from a top-down approach using the bulk experimental refractive index as a starting point. Freeelectron damping constant (γfree) and plasma frequency (ωp) parameters in the Drude model are calculated for nickel (Ni), molybdenum (Mo), tungsten (W), lead (Pb), zinc (Zn) and sodium (Na) using a method developed in our group. Determined γfree and ωp parameters allow to develop an expression that improves the precision in reproducing the discrete metal bulk dielectric function in a wide wavelength range (UV-FIR). The bulk dielectric function is modified for describing the nanometric case by adding size corrective terms for free and bound electrons contributions. As an application of this study we characterize Ni spherical NPs synthesized by ultrafast laser ablation of a solid target in water. Using Mie theory together with the size-dependent dielectric function, we theoretically reproduce its experimental extinction spectrum. From this fitting, composition and size distribution of the particles in the colloidal suspension may be derived. Transmission electron microscopy (TEM) results agree with the sizes and structure derived from optical extinction spectroscopy (OES).Fil: Muñetón Arboleda, David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Santillán, Jesica María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de Catamarca; ArgentinaFil: Mendoza Herrera, Luis Joaquin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Muraca, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidade Estadual de Campinas; BrasilFil: Schinca, Daniel Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Scaffardi, Lucia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentin

Highly fluorescent few atoms silver nanoclusters with strong photocatalytic activity synthesized by ultrashort light pulses

While there are conventional chemical synthesis methods to generate metal nanoclusters (NCs), many of them are adversely affected by the unavoidable contamination of the nanoproduct solution, resulting in aggregation, background noise in analytical chemistry, toxicity, and deactivation of the catalyst. In this work, physical method of ultrafast laser ablation as a “green” synthesis approach together with mechanical centrifugation to obtain silver NCs, simplifying widely the chemical synthesis requirements, is proposed. Remarkably, compared with conventional methods for synthesizing Ag NCs, this new approach starts with a colloid that contains nanosized particles as well as smaller species, managing to obtain colloids with few atoms NCs by centrifugation. Those colloids were analyzed by fluorescence spectroscopy observing UV bands corresponding with HOMO-LUMO cluster transitions. Besides, independent HRTEM measurements were made confirming the presence of few atoms Ag NCs, as well as small NPs in different formation stages. Equally important, photocatalytic efficiency of the obtained NCs was studied through degradation of Methylene Blue (MB) when it was mixed with as-prepared or highly centrifuged colloid, showing an enhanced photocatalytic efficiency of 79% as compared to 57% for pure MB after 180 min of illumination. Consequently, this work contributes to establishing a simple approach to synthesize highly fluorescent and photocatalytic NCs.Fil: Santillán, Jesica María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Muñetón Arboleda, David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Muraca, Diego. Universidade Estadual de Campinas; BrasilFil: Schinca, Daniel Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Scaffardi, Lucia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentin

Ligand-free few atoms Ag nanoclusters synthesis and their potential application as photocatalytic agents

We have implemented ultrafast laser ablation synthesis in liquids together with mechanical centrifugation to obtain ligand-free silver nanoclusters (Ag NCs). Given the nature of this technique, the NCs colloids produced are highly pure which avoids additional cleaning protocols. The mechanical centrifugation of the colloids helps to separate the NCs from their larger counterparts (nanoparticles (NPs)), present in the suspension. Synthesized NC colloids are studied by fluorescence spectroscopy observing UV bands corresponding with HOMO-LUMO cluster transitions, and HRTEM measurements where Ag NCs clouds and Ag atomic clusters are observed. Finally, the photocatalytic response of the Ag NCs was studied by the degradation of the standard molecule Methylene Blue (MB) in interaction with white light. It was observed that when MB and Ag NCs are mixed in the solution, degradation of MB is much faster, indicating the strong photocatalytic response of NCs, even at low concentrations.Fil: Santillán, Jesica María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Muñetón Arboleda, David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Muraca, Diego. Universidade Estadual de Campinas; BrasilFil: Schinca, Daniel Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Scaffardi, Lucia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentin

In-situ Electron Microscopy Observation of the Redox Process in Plasmonic Heterogeneous-Photo-Sensitive Nanoparticles

Observation of relevant phenomena related with dynamical redox process in a plasmonic heterogeneous-photocatalyst system composed by silver nanoparticles (NPs) around and in contact with amorphous silver chloride NPs are reported by in-situ transmission electron microscopy. During this process, nanobubbles are initially produced inside the silver chloride NPs, which immediately begin to move within the amorphous phase. Besides, silver atoms inside the silver chloride NPs start to migrate out the occupied volume leaving a space behind, which is filled by crystalline regions of silver chloride located between the pre-existing silver NPs. During the observation time, fast-nucleation, movement, growth, and fast-dissolution of silver NPs take place. Specific space correlation with silver mass loss (or gain) when a new NP is formed (or dissolved), was detected in different regions during the reaction. This mass loss (or gain) takes place on certain places of pre-existing silver NPs. All these phenomena were observed for a configuration comprising at least two silver NPs separated few nanometers apart by a silver chloride NP.Fil: Muraca, Diego. Universidade Estadual de Campinas; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Scaffardi, Lucia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Santillán, Jesica María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Muñetón Arboleda, David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Schinca, Daniel Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Bettini, Jefferson. National Center for Research in Energy and Materials; Brasil. Laboratorio Nacional de Nanotecnología de Brasil; Brasi

Size-dependent complex dielectric function of Ni, Mo, W, Pb, Zn and Na nanoparticles : Application to sizing

This work determines the size dependent metal nanoparticle (NP) dielectric function from a top-down approach using the bulk experimental refractive index as a starting point. Freeelectron damping constant (γfree) and plasma frequency (ωp) parameters in the Drude model are calculated for nickel (Ni), molybdenum (Mo), tungsten (W), lead (Pb), zinc (Zn) and sodium (Na) using a method developed in our group. Determined γfree and ωp parameters allow to develop an expression that improves the precision in reproducing the discrete metal bulk dielectric function in a wide wavelength range (UV-FIR). The bulk dielectric function is modified for describing the nanometric case by adding size corrective terms for free and bound electrons contributions. As an application of this study we characterize Ni spherical NPs synthesized by ultrafast laser ablation of a solid target in water. Using Mie theory together with the size-dependent dielectric function, we theoretically reproduce its experimental extinction spectrum. From this fitting, composition and size distribution of the particles in the colloidal suspension may be derived. Transmission electron microscopy (TEM) results agree with the sizes and structure derived from optical extinction spectroscopy (OES).Facultad de Ciencias ExactasCentro de Investigaciones ÓpticasFacultad de Ingenierí

<i>In situ</i> electron microscopy observation of the redox process in plasmonic heterogeneous-photo-sensitive nanoparticles

Observation of relevant phenomena related with dynamical redox process in a plasmonic heterogeneous-photocatalyst system composed by silver nanoparticles (NPs) around and in contact with amorphous silver chloride NPs are reported by in situ transmission electron microscopy. During this process, nanobubbles are initially produced inside the silver chloride NPs, which immediately begin to move within the amorphous phase. Besides, silver atoms inside the silver chloride NPs start to migrate out the occupied volume leaving a space behind, which is filled by crystalline regions of silver chloride located between the pre-existing silver NPs. During the observation time, fast-nucleation, movement, growth, and fast-dissolution of silver NPs take place. Specific space correlation with silver mass loss (or gain) when a new NP is formed (or dissolved), was detected in different regions during the reaction. This mass loss (or gain) takes place on certain places of pre-existing silver NPs. All these phenomena were observed for a configuration comprising at least two silver NPs separated few nanometers apart by a silver chloride NP.Facultad de IngenieríaCentro de Investigaciones Óptica

First SOLPS‐ITER simulations of ASDEX Upgrade partially detached H‐mode with boron impurity : the missing radiation at the outer strike‐point region

Partially detached H‐modes are the baseline regime for the future ITER operation. The ASDEX Upgrade partially detached H‐mode is modeled using the SOLPS‐ITER code with drifts enabled and compared with experimental data. For the first time, boron (B) impurity is simulated in the Scrape‐off layer (SOL) and divertor. A comparison between divertor diagnostics and discrepancies between Langmuir probe and Divertor Thomson scattering/Stark broadening diagnostic are discussed. In the modeling, experimental target profiles are reproduced if the experimental level of radiation in the SOL and divertor is achieved using nitrogen (N) impurity seeding. Bolometry measurements detect substantial radiation from the partially detached outer strike point. With B radiation, this maximum in bolometry data is reproduced in the modeling, which is not possible with N alone