A scheme for generating complex, spatially separated patterns of multiple types of semiconducting and/or metallic nanocrystals is presented. The process is based on lithographic patterning of organic monolayers that contain a photolabile protection group and are covalently bound to SiO2 surfaces. The process results in spatially and chemically distinct interaction sites on a single substrate. Nanocrystal assembly occurs with a high selectivity on just one type of site. We report on the production of binary, tertiary, and quatemary patterns of nanocrystals. We highlight and discuss the differences between nanocrystal/substrate assembly and molecule/substrate assembly. Finally, we investigate the assembled structures using photoluminescence and absorption spectroscopy.

Explanation of how 92 studies provided data regarding 127 analyses. (DOC 36 kb)

Electron microscopy has been instrumental in our understanding of complex biological systems. Although electron microscopy reveals cellular morphology with nanoscale resolution, it does not provide information on the location of different types of proteins. An electron-microscopy-based bioimaging technology capable of localizing individual proteins and resolving protein-protein interactions with respect to cellular ultrastructure would provide important insights into the molecular biology of a cell. Here, we synthesize small lanthanide-doped nanoparticles and measure the absolute photon emission rate of individual nanoparticles resulting from a given electron excitation flux (cathodoluminescence). Our results suggest that the optimization of nanoparticle composition, synthesis protocols and electron imaging conditions can lead to sub-20-nm nanolabels that would enable high signal-to-noise localization of individual biomolecules within a cellular context. In ensemble measurements, these labels exhibit narrow spectra of nine distinct colours, so the imaging of biomolecules in a multicolour electron microscopy modality may be possible.

While existing photovoltaic technologies continue to advance, there are still many exciting opportunities in the area of novel materials. These opportunities arise because there is a substantial need for reducing the costs associated with the preparation and processing of photovoltaics, and because the theoretically possible photovoltaic efficiencies have yet to be achieved in practical devices. Thus it remains reasonable to continue photovoltaic research activity aimed at entirely new approaches to processing and at entirely new materials as the active media. This group identified three areas for further consideration: (a) Nano/molecular composites and hierarchical structures; (b) Organic semiconductors; and (c) Hot carrier devices.

fMRI research is highly prolific but raises multiple concerns. Many competing statistical methods and respective packages are available using different assumptions, none of which applies equally well to all settings. However, the most fundamental concerns are not about the statistical machinery, but about issues of reproducibility, utility, and even construct validity. One can probe how much the field would benefit by statistical refinements, the conduct of larger studies and/or improved reproducibility practices. Alternatively, maybe fMRI research should largely be abandoned with focus shifting toward developing imaging methods with construct validity for granular neuronal activity and higher potential for clinical utility.

H-1 and C-13 nuclear magnetic resonance (NMR) relaxation studies of thiophenol-capped CdS nanocrystals are presented. The transverse and longitudinal relaxation times were investigated as a function of nanocrystal radius, and the transverse relaxation time was also studied as a function of temperature. Both proton and carbon T-2 values were found to increase with nanocrystal radius, contrary to initial expectations. This effect is explained in terms of motion of the thiophenol with respect to the nanocrystalline surface. Theoretical expressions for relaxation due to anisotropic motion are developed based on both bridging and terminal bonding configurations of the thiophenol ligands, and the data are fit to these models. The data are found to be consistent with thiophenol ligands bound in a terminal fashion to a single Cd atom. The temperature dependence of the proton T-2 value is also suprising. T-2 is found to decrease with increasing temperature, and the size of this change scales with the nanocrystal radius. This is explained in terms of an extra component of relaxation due to thermally excited electrons.

BACKGROUND AND PURPOSE: Cancer mortality rates in the Baltic States (Estonia, Latvia, and Lithuania) exceeds the European Union (EU) average, in part due to limited access to radiation therapy (RT). We updated RT capacity and utilization to inform regional planning. Patient/material and methods: We conducted a census of all 11 RT centres (2016-2023) via a standardized questionnaire, cross-validated with national registries and international databases. We compared technology availability, workforce, and utilization with EU countries in relation to the present cancer burden and projections to 2050. This multicentre observational study adhered to STrengthening the Reporting of OBservational Studies in Epidemiology (STROBE) guidelines. RESULTS: Only 35-42% of cancer patients received RT, below the 50% recommendation. Linear accelerator availability ranged from 3.8 to 5.1 per million inhabitants, figures that are almost half those seen in EU countries with higher Gross Domestic Product (GDP) per capita. While the use of intensity modulated RT, volumetric modulated arc therapy and stereotactic RT increased, staffing levels has remained static in recent years. Mortality-to-incidence ratio correlated negatively with GDP (r = -0.7) and RT capacity (r = -0.7). INTERPRETATION: Despite technological progress in the Baltic States, major gaps persist in RT access and workforce levels. Baltic States still underperform compared to EU countries with higher GDP per capita in terms of equipment availability, workforce capacity, and overall cancer outcomes. Future-oriented strategic investments, based on regional collaboration and shared infrastructure are urgently needed, including the development of a regional particle therapy centre, to ensure equitable access to state-of-the art advanced cancer care across the Baltic States.

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Specific, designed, nonperiodic arrangements of gold nanocrystals that are 5 and 10 nm in diameter can be prepared with double-stranded DNA serving as a template (see drawing; A′ and B′ denote oligonucleotide sequences complementary to sequences A and B). The methods described should be applicable to nanocrystals composed of various materials.

Nanotechnology is the creation and utilization of materials, devices, and systems through the control of matter on the nanometer-length scale, that is, at the level of atoms, molecules, and supramolecular structures. The essence of nanotechnology is the ability to work at these levels to generate larger structures with fundamentally new molecular organization. These nanostructures, made with building blocks understood from first principles, are the smallest human-made objects, and they exhibit novel physical, chemical, and biological properties and phenomena. The aim of nanotechnology is to learn to exploit these properties and efficiently manufacture and employ the structures. Control of matter on the nanoscale already plays an important role in scientific disciplines as diverse as physics, chemistry, materials science, biology, medicine, engineering, and computer simulation. For example, it has been shown that carbon nanotubes are ten times as strong as steel with one sixth of the weight, and that nanoparticles can target and kill cancer cells. Nanoscale systems have the potential to make supersonic transport cost- effective and to increase computer efficiency by millions of times. As understanding develops of the way natural and living systems are governed by molecular behavior at nanometer scale, and as this understanding begins to be felt in science and medicine, researchers seek systematic approaches for nanoscale-based manufacturing of human- made products.

The formation of C-N bonds by Pd-catalyzed cross-coupling is one of the most widely practiced reactions in chemical synthesis. Typical reaction conditions involve either a strong base, which limits the scope of substrates, or an insoluble, inorganic base, which complicates running reactions on a large scale. Reaction conditions for C-N couplings with a base that is both mild and soluble are needed. We report the discovery of a combination of a phosphorinane ligand (<b>L147</b>) and a soluble carboxylate base, potassium 2-ethylhexanoate (K-2-EH), which leads to the coupling of a wide range of base-sensitive coupling partners. To explore the enhanced substrate scope of the reaction with this base and catalyst, we evaluated the scope using representative reactants selected from published partners, using chemical descriptors and clustering to ensure their chemical diversity. These results show that the combination of this phosphorinane ligand and K-2-EH can couple primary aliphatic amines, amides, sulfonamides, and heteroaromatic nucleophiles as well as acidic secondary nitrogen nucleophiles, such as arylamines, heteroarylamines, and amides, with a range of electrophiles. A side-by-side comparison to form selected coupling products in the presence of a range of previously reported bases and ligands showed that the products that decomposed under standard reaction conditions were stable with K-2-EH as a base. Finally, models of quantitative structure-reactivity relationships, trained on ligand screening data, were developed to help reveal the structural features that engender reactivity.