Ballistic Phonon Transport in Holey Silicon

When the size of semiconductors is smaller than the phonon mean free path, phonons can carry heat with no internal scattering. Ballistic phonon transport has received attention for both theoretical and practical aspects because Fourier’s law of heat conduction breaks down and the heat dissipation in nanoscale transistors becomes unpredictable in the ballistic regime. While recent experiments demonstrate room-temperature evidence of ballistic phonon transport in various nanomaterials, the thermal conductivity data for silicon in the length scale of 10–100 nm is still not available due to experimental challenges. Here we show ballistic phonon transport prevails in the cross-plane direction of holey silicon from 35 to 200 nm. The thermal conductivity scales linearly with the length (thickness) even though the lateral dimension (neck) is as narrow as 20 nm. We assess the impact of long-wavelength phonons and predict a transition from ballistic to diffusive regime using scaling models. Our results support strong persistence of long-wavelength phonons in nanostructures and are useful for controlling phonon transport for thermoelectrics and potential phononic applications

Additional file 1 of NLRP3 exacerbates EAE severity through ROS-dependent NET formation in the mouse brain

Additional file 1: Supplementary Fig. 1. Gating strategy for Ly6G+CitH3+MPO+ population via flow cytometry analysis. Initially, whole cells were chosen based on a forward scatter area vs. side scatter area dot plot, and singlets were further refined in a forward scatter width vs. forward scatter height dot plot and side scatter width vs. side scatter height dot plot. To distinguish live cells, Zombie Aqua dye, exclusively binding to dead cells, was employed, and the negative cells were gated. Subsequently, neutrophils were identified by gating for Ly6G+ expression in a dot plot. Within the neutrophil gate, the CitH3+ population was selected. Finally, within the CitH3+ population gate, the MPO+ population was selected, representing the co-localized population of Ly6G, CitH3, and MPO

A Rational Design of Highly Controlled Suzuki–Miyaura Catalyst-Transfer Polycondensation for Precision Synthesis of Polythiophenes and Their Block Copolymers: Marriage of Palladacycle Precatalysts with MIDA-Boronates

Herein, we report a highly efficient Suzuki–Miyaura catalyst-transfer polycondensation (SCTP) of 3-alkylthiophenes using bench-stable but highly active Buchwald dialkylbiarylphospine Pd G3 precatalysts and <i>N</i>-methylimidodiacetic (MIDA)-boronate monomers. Initially, the feasibility of the catalyst-transfer process was examined by screening various dialkylbiarylphospine-Pd(0) species. After optimizing a small molecule model reaction, we identified both RuPhos and SPhos Pd G3 precatalysts as excellent catalyst systems for this purpose. On the basis of these model studies, SCTP was tested using either RuPhos or SPhos Pd G3 precatalyst, and 5-bromo-4-<i>n</i>-hexylthien-2-yl-pinacol-boronate. Poly­(3-hexylthiophene) (P3HT) was produced with controlled molecular weight and narrow dispersity for a low degree of polymerization (DP) only, while attempts to synthesize P3HT having a higher DP with good control were unsuccessful. To improve the control, slowly hydrolyzed 5-bromo-4-<i>n</i>-hexylthien-2-yl-MIDA-boronate was introduced as a new monomer. As a result, P3HT and P3EHT (up to 17.6 kg/mol) were prepared with excellent control, narrow dispersity, and excellent yield (>90%). Detailed mechanistic investigation using ³¹P NMR and MALDI-TOF spectroscopy revealed that both fast initiation using Buchwald precatalysts and the suppression of protodeboronation due to the protected MIDA-boronate were crucial to achieve successful living polymerization of P3HT. In addition, a block copolymer of P3HT-<i>b</i>-P3EHT was prepared via SCTP by sequential addition of each MIDA-boronate monomer. Furthermore, the same block copolymer was synthesized by one-shot copolymerization for the first time by using fast propagating pinacol-boronate and slow propagating MIDA-boronate

Direct Formation of Large-Area 2D Nanosheets from Fluorescent Semiconducting Homopolymer with Orthorhombic Crystalline Orientation

Semiconducting polymers have been widely investigated due to their intriguing optoelectronic properties and their high crystallinity that provides a strong driving force for self-assembly. Although there are various reports of successful self-assembly of nanostructures using semiconducting polymers, direct <i>in situ</i> self-assembly of these polymers into two-dimensional (2D) nanostructures has proven difficult, despite their importance for optoelectronics applications. Here, we report the synthesis of a simple conjugated homopolymer by living cyclopolymerization of a 1,6-heptadiyne (having a fluorene moiety) and its efficient <i>in situ</i> formation of large-area 2D fluorescent semiconducting nanostructures. Using high-resolution imaging tools such as atomic force microscopy and transmission electron microscopy, we observed the solvent-dependent self-assembly behaviors of this homopolymer; the identical starting polymer formed 2D nanosheets with different shapes, such as rectangle, raft, and leaf, when dissolved in different solvents. Furthermore, super-resolution optical microscopy enabled the real-time imaging of the fluorescent 2D nanosheets, revealing their stable and uniform shapes, fluorescence, and solution dynamics. Notably, we propose an orthorhombic crystalline packing model to explain the direct formation of 2D nanostructures based on various diffraction patterns, providing important insight for their shape modulation during the self-assembly

Thermal Transport in Silicon Nanowires at High Temperature up to 700 K

Thermal transport in silicon nanowires has captured the attention of scientists for understanding phonon transport at the nanoscale, and the thermoelectric figure-of-merit (ZT) reported in rough nanowires has inspired engineers to develop cost-effective waste heat recovery systems. Thermoelectric generators composed of silicon target high-temperature applications due to improved efficiency beyond 550 K. However, there have been no studies of thermal transport in silicon nanowires beyond room temperature. High-temperature measurements also enable studies of unanswered questions regarding the impact of surface boundaries and varying mode contributions as the highest vibrational modes are activated (Debye temperature of silicon is 645 K). Here, we develop a technique to investigate thermal transport in nanowires up to 700 K. Our thermal conductivity measurements on smooth silicon nanowires show the classical diameter dependence from 40 to 120 nm. In conjunction with Boltzmann transport equation, we also probe an increasing contribution of high-frequency phonons (optical phonons) in smooth silicon nanowires as the diameter decreases and the temperature increases. Thermal conductivity of rough silicon nanowires is significantly reduced throughout the temperature range, demonstrating a potential for efficient thermoelectric generation (e.g., ZT = 1 at 700 K)

<i>Wwox-KO BK5-Cre</i> transgenic mice model gene expression profile study.

<p>(A) Heatmap of the differentially expressed genes between <i>Wwox WT vs. Wwox KO</i> mammary gland epithelial organoid samples (p<0.01; 2 Fold changes). Color scale at bottom of picture is used to represent expression level: low expression is represented by green, and high expression is represented by red. (B) Expression graph of the 913 deregulated probes (136 probes down-modulated and 777 up-modulated) among <i>Wwox WT</i> and <i>Wwox KO</i> mammary epithelial organoid samples. (C) Scatterplot graph showing the representative clusters, after redundancy reduction of the statistical significant GO terms (p<0.025) enriched in the deregulated gene list, in a two dimensional space related to GO terms' semantic similarities. Bubble color indicates the p-value of GO terms (expressed as Log10 p-value) and bubble size indicates the frequency of the GO term in the underlying GOA database (bubbles of more general terms are larger).</p

<i>Wnt5a</i> expression increases in <i>BK5 Wwox KO</i> mammary epithelium.

<p>Semi-quantitative RT-PCR was performed on cDNA synthesized from RNA obtained from mammary epithelial organoids (3 different animals per group) as discussed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036618#s4" target="_blank">Materials and Methods</a>. Lanes from left to right are: (lanes 1–3) 8 week virgin <i>Wwox WT</i>, (lanes 4–6) P18.5 <i>Wwox WT</i>, (lanes 7–9) 8 week virgin <i>Wwox KO</i>, and (lanes 10–12) P18.5 <i>Wwox KO</i>. <i>Wwox</i> expression is shown in the middle panel as further verification of <i>Wwox</i> ablation. <i>Gapdh</i> expression is shown as a normalization control. Each PCR reaction was performed at 24, 26, 28 and 32 cycles to ensure that reaction was in linear range. Results shown at 24 cycles.</p

Graphene and Thin-Film Semiconductor Heterojunction Transistors Integrated on Wafer Scale for Low-Power Electronics

Graphene heterostructures in which graphene is combined with semiconductors or other layered 2D materials are of considerable interest, as a new class of electronic devices has been realized. Here we propose a technology platform based on graphene–thin-film-semiconductor–metal (GSM) junctions, which can be applied to large-scale and power-efficient electronics compatible with a variety of substrates. We demonstrate wafer-scale integration of vertical field-effect transistors (VFETs) based on graphene–In–Ga–Zn–O (IGZO)–metal asymmetric junctions on a transparent 150 × 150 mm² glass. In this system, a triangular energy barrier between the graphene and metal is designed by selecting a metal with a proper work function. We obtain a maximum current on/off ratio (<i>I</i>_on/<i>I</i>_off) up to 10⁶ with an average of 3010 over 2000 devices under ambient conditions. For low-power logic applications, an inverter that combines complementary n-type (IGZO) and p-type (Ge) devices is demonstrated to operate at a bias of only 0.5 V

Biologically Inspired Organic Light-Emitting Diodes

Many animal species employ highly conspicuous traits as courtship signals for successful mating. Fireflies utilize their bioluminescent light as visual courtship signals. In addition to efficient bioluminescent light emission, the structural components of the firefly lantern also contribute to the enhancement of conspicuous optical signaling. Recently, these firefly lantern ultrastructures have attracted much interest and inspired highly efficient light management approaches. Here we report on the unique optical function of the hierarchical ultrastructures found in a firefly (<i>Pyrocoelia rufa</i>) and their biological inspiration of highly efficient organic light-emitting diode (OLED) applications. The hierarchical structures are comprised of longitudinal nanostructures and asymmetric microstructures, which were successfully replicated using geometry-guided resist reflow, replica molding, and polydimethylsiloxane (PDMS) oxidation. The external quantum efficiency (EQE) of the bioinspired OLEDs was enhanced by up to 61%. The bioinspired OLEDs clearly showed side-enhanced super-Lambertian emission with a wide-viewing angle. The highly efficient light extraction and wide-angle illumination suggest how the hierarchical structures likely improve the recognition of firefly optical courtship signals over a wide-angle range. At the same time, the biologically inspired designs provide a new paradigm for designing functional optical surfaces for lighting or display applications

<i>Wwox</i> mRNA expression in <i>BK5-Cre</i> model of Wwox deletion.

<p>qRT-PCR was used to determine the mRNA expression of <i>Wwox</i> in mammary epithelial organoids from <i>BK5 Wwox WT</i> and <i>KO</i> animals. The box plots show dramatically decreased <i>Wwox</i> mRNA levels in epithelium from 8 week virgin (A) and P18.5 days (B) <i>Wwox KO</i> mammary epithelium when compared to their respective <i>WT</i> counterparts. Mammary epithelial organoids were isolated from 3 different <i>WT</i> and 3 different <i>KO</i> mice in each group. Samples from each mouse were run individually in triplicate to assess <i>Wwox</i> expression. Samples were normalized to 18S expression.</p