Inflammatory exposure drives long-lived impairment of hematopoietic stem cell self-renewal activity and accelerated aging.

Hematopoietic stem cells (HSCs) mediate regeneration of the hematopoietic system following injury, such as following infection or inflammation. These challenges impair HSC function, but whether this functional impairment extends beyond the duration of inflammatory exposure is unknown. Unexpectedly, we observed an irreversible depletion of functional HSCs following challenge with inflammation or bacterial infection, with no evidence of any recovery up to 1 year afterward. HSCs from challenged mice demonstrated multiple cellular and molecular features of accelerated aging and developed clinically relevant blood and bone marrow phenotypes not normally observed in aged laboratory mice but commonly seen in elderly humans. In vivo HSC self-renewal divisions were absent or extremely rare during both challenge and recovery periods. The progressive, irreversible attrition of HSC function demonstrates that temporally discrete inflammatory events elicit a cumulative inhibitory effect on HSCs. This work positions early/mid-life inflammation as a mediator of lifelong defects in tissue maintenance and regeneration.

Constructing Hierarchical Porous Zeolites via Kinetic Regulation.

Zeolites are crystalline inorganic solids with microporous structures, having widespread applications in the fields of catalysis, separation, adsorption, microelectronics, and medical diagnosis. A major drawback of zeolites is the mass transfer limitation due to the small size of the micropores (less than 1 nm). Numerous efforts have been dedicated to integrating mesopores with the microporous zeolite structures by using templating and/or destructive approaches. Here we provide a new strategy for hierarchical pore size zeolite synthesis, without using supramolecular or hard templates. The branching epitaxial growth behavior, as a result of aluminum-zoning, contributes to the formation of the hierarchical porous zeolite structures.

Field-effect modulation of thermoelectric properties in multigated silicon nanowires.

Electric-field-induced charge carriers typically exhibit greater mobility over carriers contributed by chemical dopants and offer a powerful mechanism for thermoelectric power factor enhancement. We fabricate multigated silicon nanowires (Si NWs) and demonstrate significant modulation of electrical conductivity and the Seebeck coefficient with gate bias. Because of the higher mobility of field-effect charge carriers, we demonstrate that power factor for the gated Si NWs is similar to the highest values reported for n-type Si nanostructures despite charge transport only occurring at the NW surface. Field-effect doping is a promising strategy for optimizing power factor and may result in significant power factor enhancement in smaller diameter Si NWs where high average carrier densities can be obtained with induced surface charge.

Remarkable order of a high-performance polymer.

We directly image the rich nanoscale organization of the high performance, n-type polymer poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) using a combination of high-resolution transmission electron microscopy and scanning transmission electron microscopy. We demonstrate that it is possible to spatially resolve "face-on" lamella through the 2.4 nm alkyl stacking distance corresponding to the (100) reflection. The lamella locally transition between ordered and disordered states over a length scale on the order of 10 nm; however, the polymer backbones retain long-range correlations over length-scales approaching a micrometer. Moreover, we frequently observe overlapping structure implying a number of layers may exist throughout the thickness of the film (~20 nm). The results provide a simple picture, a highly ordered lamella nanostructure over nearly the entire film and ordered domains with overlapping layers providing additional interconnectivity, which unifies prior seemingly contradictory conclusions surrounding this remarkable, high-mobility material.

An autonomous photosynthetic device in which all charge carriers derive from surface plasmons.

Solar conversion to electricity or to fuels based on electron-hole pair production in semiconductors is a highly evolved scientific and commercial enterprise. Recently, it has been posited that charge carriers either directly transferred from the plasmonic structure to a neighbouring semiconductor (such as TiO2) or to a photocatalyst, or induced by energy transfer in a neighbouring medium, could augment photoconversion processes, potentially leading to an entire new paradigm in harvesting photons for practical use. The strong dependence of the wavelength at which the local surface plasmon can be excited on the nanostructure makes it possible, in principle, to design plasmonic devices that can harvest photons over the entire solar spectrum and beyond. So far, however, most such systems show rather small photocatalytic activity in the visible as compared with the ultraviolet. Here, we report an efficient, autonomous solar water-splitting device based on a gold nanorod array in which essentially all charge carriers involved in the oxidation and reduction steps arise from the hot electrons resulting from the excitation of surface plasmons in the nanostructured gold. Each nanorod functions without external wiring, producing 5 × 10(13) H2 molecules per cm(2) per s under 1 sun illumination (AM 1.5 and 100 mW cm(-2)), with unprecedented long-term operational stability.

Crystalline polymorphs of [6,6]-phenyl-C61-butyric acid n-butyl ester (PCBNB).

The thermotropic behavior of [6,6]-phenyl-C(61)-butyric acid n-butyl ester (PCBNB) in powder and thin film form was investigated using X-ray diffraction and transmission electron microscopy. Upon heating PCBNB powder above its glass-transition temperature, an amorphous-to-crystalline transition (i.e., cold crystallization) and a subsequent melting of these crystals were observed. A thin film of PCBNB was observed to order on a simple hexagonal lattice (HEX) with the c axis preferentially oriented normal to film at an annealing temperature of 180 °C but became disordered above 200 °C, consistent with the powder results. However, when annealed at 160 °C, the PCBNB thin film ordered on a superlattice of the HEX as indicated both by electron diffraction and high-angle annular dark field scanning TEM (HAADF-STEM) images. The formation of the HEX superlattice polymorph was independent of both solvent and substrate and could be formed both on heating from the amorphous as cast state and by cooling from the HEX structure formed at a higher temperature. HAADF-STEM shows that the superlattice corresponds to a regular deficiency of PCBNB molecules on every fifth (1 1[combining overline] 0 0) plane of the HEX structure.

Plasmonic properties of gold nanoparticles separated from a gold mirror by an ultrathin oxide.

That a nanoparticle (NP) (for example of gold) residing above a gold mirror is almost as effective a surface enhanced Raman scattering (SERS) substrate (when illuminated with light of the correct polarization and wavelength) as two closely coupled gold nanoparticles has been known for some time. The NP-overmirror (NPOM) configuration has the valuable advantage that it is amenable to top-down fabrication. We have fabricated a series of Au-NPOM substrates with varying but thin atomic layer-deposited oxide spacer and measured the SERS enhancement as a function of spacer thickness and angle of incidence (AOI). These were compared with high-quality finite-difference time-domain calculations, which reproduce the observed spacer thickness and AOI dependences faithfully. The SERS intensity is expected to be strongly affected by the AOI on account for the fact that the hot spot formed in the space between the NP and the mirror is most efficiently excited with an electromagnetic field component that is normal to the surface of the mirror. Intriguingly we find that the SERS intensity maximizes at ~60° and show that this is due to the coherent superposition of the incident and the reflected field components. The observed SERS intensity is also shown to be very sensitive to the dielectric constant of the oxide spacer layer with the most intense signals obtained when using a low dielectric constant oxide layer (SiO(2)).

Preparation of protein gradients through the controlled deposition of protein-nanoparticle conjugates onto functionalized surfaces.

This paper describes a simple method for the preparation and characterization of protein density gradients on solid supports. The method employs colloidal metal nanoparticles as protein carriers and optical tags and is capable of forming linear, exponential, 1D, 2D, and multiprotein gradients of varying slope without expensive or sophisticated surface patterning techniques. Surfaces patterned with proteins using the procedures described within are shown to support cell growth and are thus suitable for studies of protein-cell interactions.

Laser-induced temperature jump electrochemistry on gold nanoparticle-coated electrodes.

Laser-induced temperature jumps (LITJs) at gold nanoparticle-coated indium tin oxide (ITO) electrodes in contact with electrolyte solutions have been measured using temperature-sensitive redox probes and an infrared charge-coupled device. Upon irradiation with 532 nm light, interfacial temperature changes of ca. 20 degrees C were recorded for particle coverages of ca. 1 x 1010 cm-2. In the presence of a redox molecule, LITJ yields open-circuit photovoltages and photocurrents that are proportional to the number of particles on the surface. When ssDNA was used to chemisorb nanoparticles to the ITO surface, solution concentrations as low as 100 fM of target ssDNA-modified nanoparticles could be detected at the electrode surface.

Analysis of local strain in aluminum interconnects by convergent beam electron diffraction.

Energy filtered convergent beam electron diffraction was used to investigate localized strain in aluminum interconnects. By analyzing the position of higher order Laue zone lines, it is possible to measure the three-dimensional lattice strain with high accuracy (approximately 10(-4)) and high spatial resolution (10 to 100 nm). In the present article, important details of the strain analysis procedure are outlined. Subsequently, results of measurements of the local variation of thermal strains in narrow, free-standing interconnects are presented. The strain development in single grains during thermal cycling between -170 degrees C and + 100 degrees C was measured in situ and local stress variations along the interconnect were investigated. The interconnects show reversible elastic behavior over the whole temperature range, leading to large stresses at low temperatures. The strain state varies locally within single grains, as well as from grain to grain, by as much as 50% in both types of samples. By comparing the experimental findings with elastic finite element modeling, a detailed understanding of the triaxial strain state could be achieved.

Pattern formation of ion channels with state-dependent charges and diffusion constants in fluid membranes.

A model of mobile, charged ion channels in a fluid membrane is studied. The channels may switch between an open and a closed state according to a simple two-state kinetics with constant rates. The effective electrophoretic charge and the diffusion constant of the channels may be different in the closed and in the open state. The system is modeled by densities of channel species, obeying simple equations of electrodiffusion. The lateral transmembrane voltage profile is determined from a cable-type equation. Bifurcations from the homogeneous, stationary state appear as hard-mode, soft-mode, or hard-mode oscillatory transitions within physiologically reasonable ranges of model parameters. We study the dynamics beyond linear stability analysis and derive nonlinear evolution equations near the transitions to stationary patterns.