Ultrathin Boron Growth onto Nanodiamond Surfaces via Electrophilic Boron Precursors.

Diamond as a templating substrate is largely unexplored, and the unique properties of diamond, including its large bandgap, thermal conductance, and lack of cytotoxicity, makes it versatile in emergent technologies in medicine and quantum sensing. Surface termination of an inert diamond substrate and its chemical reactivity are key in generating new bonds for nucleation and growth of an overlayer material. Oxidized high-pressure high temperature (HPHT) nanodiamonds (NDs) are largely terminated by alcohols that act as nucleophiles to initiate covalent bond formation when an electrophilic reactant is available. In this work, we demonstrate a templated synthesis of ultrathin boron on ND surfaces using trigonal boron compounds. Boron trichloride (BCl3), boron tribromide (BBr3), and borane (BH3) were found to react with ND substrates at room temperature in inert conditions. BBr3 and BCl3 were highly reactive with the diamond surface, and sheet-like structures were produced and verified with electron microscopy. Surface-sensitive spectroscopies were used to probe the molecular and atomic structure of the ND constructs' surface, and quantification showed the boron shell was less than 1 nm thick after 1-24 h reactions. Observation of the reaction supports a self-terminating mechanism, similar to atomic layer deposition growth, and is likely due to the quenching of alcohols on the diamond surface. X-ray absorption spectroscopy revealed that boron-termination generated midgap electronic states that were originally predicted by density functional theory (DFT) several years ago. DFT also predicted a negative electron surface, which has yet to be confirmed experimentally here. The boron-diamond nanostructures were found to aggregate in dichloromethane and were dispersed in various solvents and characterized with dynamic light scattering for future cell imaging or cancer therapy applications using boron neutron capture therapy (BNCT). The unique templating mechanism based on nucleophilic alcohols and electrophilic trigonal precursors allows for covalent bond formation and will be of interest to researchers using diamond for quantum sensing, additive manufacturing, BNCT, and potentially as an electron emitter.

Introduction: Race science in the Latin world.

This essay outlines the various analytical frameworks related to the history of race science that contribute to a "Latin" intellectual culture and tradition. In addition to defining Latinity as applied to the history of science, this article examines the troubled relationship between Latin American history and histories of science characterized as global. Similarly, it explores intellectual linkages across the Global South regarding racial mixture and the legacy of colonialism. It concludes by considering how a Latin perspective can illuminate the continued hegemony of ideas and scientific practices originating in North America and northern Europe.

Risky migrations: Race, Latin eugenics, and Cold War development in the International Labor Organization's Puno-Tambopata project in Peru, 1930-60.

Histories of economic development during the Cold War do not typically consider connections to race science and eugenics. By contrast, this article historicizes the debates sparked by the International Labor Organization's Puno-Tambopata project in Peru and demonstrates how Cold War development practice shared common epistemological terrain with racial and eugenic thought from the Andes. The International Labor Organization project's goal of resettling indigenous groups from the Peruvian highlands to lower-lying tropical climates sparked heated debates about the biological specificity of Andean highlanders' physiques and ability to survive in the tropics. Such concerns betrayed the antitypological consensus expressed in the United Nations Educational, Scientific and Cultural Organization (UNESCO) Race Statements and defended by one of the main proponents of the resettlement project, the Swiss-American anthropologist Alfred Métraux. The concern with Andean racial types was central to the research agenda of the acclaimed Peruvian physiologist Carlos Monge, who endorsed modernization projects that did not entail moving highlanders outside of their traditional climate. The debates sparked by the Puno-Tambopata project demonstrate how Cold War development discourse grappled with racial and eugenic thought from Latin America and the Global South and thereby produced projects of indigenous "improvement."

Practical considerations for Ultraviolet-C radiation mediated decontamination of N95 respirator against SARS-CoV-2 virus.

Decontaminating N95 respirators for reuse could mitigate shortages during the COVID-19 pandemic. Although the United States Center for Disease Control has identified Ultraviolet-C irradiation as one of the most promising methods for N95 decontamination, very few studies have evaluated the efficacy of Ultraviolet-C for SARS-CoV-2 inactivation. In addition, most decontamination studies are performed using mask coupons that do not recapitulate the complexity of whole masks. We sought to directly evaluate the efficacy of Ultraviolet-C mediated inactivation of SARS-CoV-2 on N95 respirators. To that end we created a portable UV-C light-emitting diode disinfection chamber and tested decontamination of SARS-CoV-2 at different sites on two models of N95 respirator. We found that decontamination efficacy depends on mask model, material and location of the contamination on the mask. Our results emphasize the need for caution when interpreting efficacy data of UV-C decontamination methods.

Relocating anti-racist science: the 1950 UNESCO Statement on Race and economic development in the global South.

This essay revisits the drafting of the first UNESCO Statement on Race (1950) in order to reorient historical understandings of mid-twentieth-century anti-racism and science. Historians of science have primarily interpreted the UNESCO statements as an oppositional project led by anti-racist scientists from the North Atlantic and concerned with dismantling racial typologies, replacing them with population-based conceptions of human variation. Instead of focusing on what anti-racist scientists opposed, this article highlights the futures they imagined and the applied social-science projects that anti-racist science drew from and facilitated. The scientific experts who participated in drafting the first UNESCO Statement on Race played important roles in late colonial, post-colonial and international projects designed to modernize, assimilate and improve so-called backward communities - typically indigenous or Afro-descendent groups in the global South. Such connections between anti-racist science and the developmental imaginaries of the late colonial period indicate that the transition from fixed racial typologies to sociocultural and psychological conceptualizations of human diversity legitimated the flourishing of modernization discourses in the Cold War era. In this transition to an economic-development paradigm, 'race' did not vanish so much as fragment into a series of finely tuned and ostensibly anti-racist conceptions that offered a moral incentive for scientific elites to intervene in the ways of life of those deemed primitive.