Measurement of the D*(2010)+ meson width and the D*(2010)+ - D0 mass difference

We measure the mass difference Δm0 between the D*(2010)+ and the D0 and the natural linewidth Γ of the transition D*(2010)+ → D0π+. The data were recorded with the BABAR detector at center-of-mass energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 477  fb(-1). The D0 is reconstructed in the decay modes D0 → K- π+ and D0 → K- π+ π- π+. For the decay mode D0 → K- π+ we obtain Γ = (83.4±1.7±1.5)  keV and Δm0 = (145425.6±0.6±1.7)  keV, [corrected] where the quoted errors are statistical and systematic, respectively. For the D0 → K- π+ π- π+ mode we obtain Γ = (83.2±1.5±2.6)  keV and Δm0 = (145426.6±0.5±1.9)  keV. [corrected] The combined measurements yield Γ = (83.3±1.2±1.4)  keV and Δm0 = (145425.9±0.4±1.7)  keV; the width is a factor of approximately 12 times more precise than the previous value, while the mass difference is a factor of approximately 6 times more precise.

Search for CP violation in B0-B0 mixing using partial reconstruction of B0→D*- Xℓ+ νℓ and a kaon tag

We present results of a search for CP violation in B0- B0 mixing with the BABAR detector. We select a sample of B0→D*- Xℓ+ ν decays with a partial reconstruction method and use kaon tagging to assess the flavor of the other B meson in the event. We determine the CP violating asymmetry ACP≡[N(B0B0)-N(B0B0)]/[N(B0B0)+N(B0B0)]=(0.06±0.17(-0.32)(+0.38))%, corresponding to ΔCP=1-|q/p|=(0.29±0.84(-1.61)(+1.88))×10(-3).

Preparation and characterization of carbon-titania nanocomposite-supported Pd3Co alloy nanoparticles for oxygen reduction

A TiO2-modified carbon (C-TiO2) has been employed as a catalyst support of Pd3Co alloy for electroduction of oxygen. Due to the strong interaction between highly dispersed TiO2 and Pd3Co alloy, the C-TiO2 support was shown to be effective for a fine dispersion of Pd3Co alloys. The degree of sintering of Pd3Co on C-TiO2 could largely decrease during heat-treatment for reduction compared to that on unmodified carbon support (C). In oxygen reduction reaction (ORR), the reduced catalysts (Pd3Co/C-X and Pd3Co/C-TiO2-X; X represents reduction temperature) showed higher catalytic performance than their as-prepared catalysts. The catalytic activities of Pd3Co/C-TiO2-X were largely enhanced compared to those of Pd3Co/C-X. The ORR activity was measured to be the highest on Pd3Co/C-TiO2-300, which was 9 times enhanced activity (at 0.85 V) relative to the best-performed catalyst supported on carbon (Pd3Co/C-400). A positive role of TiO2 for the metal dispersion, the retardation of metal growth during heat-treatment, and the modification of electronic structure of Pd3Co was responsible for the enhanced ORR performance on Pd3Co/C-TiO2-X.

Hofstadter's butterfly and the fractal quantum Hall effect in moiré superlattices

Electrons moving through a spatially periodic lattice potential develop a quantized energy spectrum consisting of discrete Bloch bands. In two dimensions, electrons moving through a magnetic field also develop a quantized energy spectrum, consisting of highly degenerate Landau energy levels. When subject to both a magnetic field and a periodic electrostatic potential, two-dimensional systems of electrons exhibit a self-similar recursive energy spectrum. Known as Hofstadter's butterfly, this complex spectrum results from an interplay between the characteristic lengths associated with the two quantizing fields, and is one of the first quantum fractals discovered in physics. In the decades since its prediction, experimental attempts to study this effect have been limited by difficulties in reconciling the two length scales. Typical atomic lattices (with periodicities of less than one nanometre) require unfeasibly large magnetic fields to reach the commensurability condition, and in artificially engineered structures (with periodicities greater than about 100 nanometres) the corresponding fields are too small to overcome disorder completely. Here we demonstrate that moiré superlattices arising in bilayer graphene coupled to hexagonal boron nitride provide a periodic modulation with ideal length scales of the order of ten nanometres, enabling unprecedented experimental access to the fractal spectrum. We confirm that quantum Hall features associated with the fractal gaps are described by two integer topological quantum numbers, and report evidence of their recursive structure. Observation of a Hofstadter spectrum in bilayer graphene means that it is possible to investigate emergent behaviour within a fractal energy landscape in a system with tunable internal degrees of freedom.

Hierarchical or not? Effect of the length scale and hierarchy of the surface roughness on omniphobicity of lubricant-infused substrates

Lubricant-infused textured solid substrates are gaining remarkable interest as a new class of omni-repellent nonfouling materials and surface coatings. We investigated the effect of the length scale and hierarchy of the surface topography of the underlying substrates on their ability to retain the lubricant under high shear conditions, which is important for maintaining nonwetting properties under application-relevant conditions. By comparing the lubricant loss, contact angle hysteresis, and sliding angles for water and ethanol droplets on flat, microscale, nanoscale, and hierarchically textured surfaces subjected to various spinning rates (from 100 to 10,000 rpm), we show that lubricant-infused textured surfaces with uniform nanofeatures provide the most shear-tolerant liquid-repellent behavior, unlike lotus leaf-inspired superhydrophobic surfaces, which generally favor hierarchical structures for improved pressure stability and low contact angle hysteresis. On the basis of these findings, we present generalized, low-cost, and scalable methods to manufacture uniform or regionally patterned nanotextured coatings on arbitrary materials and complex shapes. After functionalization and lubrication, these coatings show robust, shear-tolerant omniphobic behavior, transparency, and nonfouling properties against highly contaminating media.

Bacterial flagella explore microscale hummocks and hollows to increase adhesion

Biofilms, surface-bound communities of microbes, are economically and medically important due to their pathogenic and obstructive properties. Among the numerous strategies to prevent bacterial adhesion and subsequent biofilm formation, surface topography was recently proposed as a highly nonspecific method that does not rely on small-molecule antibacterial compounds, which promote resistance. Here, we provide a detailed investigation of how the introduction of submicrometer crevices to a surface affects attachment of Escherichia coli. These crevices reduce substrate surface area available to the cell body but increase overall surface area. We have found that, during the first 2 h, adhesion to topographic surfaces is significantly reduced compared with flat controls, but this behavior abruptly reverses to significantly increased adhesion at longer exposures. We show that this reversal coincides with bacterially induced wetting transitions and that flagellar filaments aid in adhesion to these wetted topographic surfaces. We demonstrate that flagella are able to reach into crevices, access additional surface area, and produce a dense, fibrous network. Mutants lacking flagella show comparatively reduced adhesion. By varying substrate crevice sizes, we determine the conditions under which having flagella is most advantageous for adhesion. These findings strongly indicate that, in addition to their role in swimming motility, flagella are involved in attachment and can furthermore act as structural elements, enabling bacteria to overcome unfavorable surface topographies. This work contributes insights for the future design of antifouling surfaces and for improved understanding of bacterial behavior in native, structured environments.

Phase transition in the biconnectivity of scale-free networks

In information-transport and biological systems, sometimes there is more than one pathway between two nodes, so that there is a backup in case one pathway becomes defective. The size of such biconnected nodes can be an important measure of the robustness of a system. The giant biconnected components of diverse real-world networks suggest the importance of scale-free topology in biconnectivity. Thus, here, we consider the critical behavior of the largest biconnected component (BC) as links are added and form a random scale-free network. The critical exponents β((BC)) and β((SC)) associated with the order parameter of the percolation transition of the biconnected component and the single-connected component (SC), respectively, are compared. We obtain a ratio β((BC))/β((SC))=λ-1 for 2<λ<3 and 2 for λ>3, where λ is the exponent of the degree distribution in scale-free networks. We also determine the finite-size scaling behavior of the order parameter analytically and numerically.

Abstract S5-7: Combined Blockade of PI3K/AKT and EGFR/HER3 Enhances Anti-Tumor Activity in Triple Negative Breast Cancer

Background: Up to 60% of triple negative breast cancers (TNBCs) express high levels of EGFR (HER1). Moreover, TNBCs are associated with increased frequency of phosphatase and tension homologue (PTEN) loss of function, leading to hyperactivation of the phosphoinositide 3-kinase (PI3K)/AKT pathway. This provides the rationale for using PI3K/AKT inhibitors in this subset of patients. However, compensatory expression of receptor tyrosine kinases (RTKs) such as HER3 may limit efficacy of PI3K/AKT inhibitors. Therefore, we hypothesize that combined targeting of both HER family receptors and the PI3K/AKT pathway will result in superior antitumor activity compared to single agent blockade in TNBC.

Materials and Methods: TNBC cell lines MDA-MB-231, MDA-MB-468, HCC70, HCC1143 and HCC1937 were treated with MEHD7945A, a dual-action antibody that targets both EGFR and HER3, AKT inhibitor GDC0068, and pan-PI3K inhibitor GDC0941. Cell viability was measured by CellTiter-Glo and Crystal Violet. Both cell line- and patient-derived xenograft models of TNBC were grown subcutaneously in Nu/Nu mice and then treated with MEHD7945A, GDC0068, GDC0941, or the combination of MEHD7945A with either GDC0068 or GDC0941. Tumor size and histology were examined. Circulating tumor cells (CTCs) were isolated from murine peripheral blood by Herring Bone CTC chip. Protein expression was measured by Western blot, Reverse Phase Protein Analysis (RPPA), and immunohistochemistry.

Results: GDC0068 and GDC0941 treatment resulted in variable inhibition of cell viability, with IC50s ranging from 170 nM to &gt;1 µM across all TNBC cell lines. Under full-serum (10% FBS) conditions, MEHD7945A led to a very mild decrease in cell viability in vitro. Combination treatments were modestly more effective than monotherapy in vitro. In vivo, MEHD7945, GDC0941 and GDC0068 showed variable delay in tumor growth whereas combination of MEHD7945A with either GDC0068 or GDC0941 was superior to single agent treatment. While untreated tumors increased over 14 fold in size, tumor growth of MEHD7945, GDC0941 and GDC0068 treated xenografts reached 6, 4 and 2.5 fold increase respectively. However, both combination arms prevented tumor growth, with complete responses achieved in 1/9 mice in each of the combination cohorts. Of note, all the treatments (up to 9 weeks of therapeutic exposure) were well tolerated. Analysis of treated tumors reveals potent inhibition of the PI3K/AKT pathway, with decreased levels phospho-PRAS40, and phospho-S6, as well as decreased expression of total EGFR and HER3. Circulating tumor cells are being used as surrogate markers of pathway inhibition.

Conclusions: Combined therapy with MEHD7945A and either GDC0068 or GDC0941 was superior to monotherapy in preclinical models of TNBC. We observed significantly greater effect with the combination treatment in vivo compared to in vitro. We are currently exploring whether expression/activation of the HER receptors following PI3K/Akt blockade are accentuated in vivo. Additionally, this may be the first mouse model enabling CTC collection from subcutaneous xenografts, allowing for real-time pharmacodynamic investigation. These findings provide the rationale for combined targeting of PI3K/AKT and EGFR/HER3 in triple negative breast cancers.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr S5-7.

Observation of time-reversal violation in the B0 meson system

Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B(0) or B(0)), and J/ψK(L)(0) or ccK(S)(0) final states (referred to as B(+) or B(-)), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B(0) → B(-) and B(-) → B(0), as a function of the time difference between the two B decays. Using 468 × 10(6) BB pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS(T)(+) = -1.37 ± 0.14(stat) ± 0.06(syst) and ΔS(T)(-) = 1.17 ± 0.18(stat) ± 0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.

Screening conditions for rationally engineered electrodeposition of nanostructures (SCREEN): electrodeposition and applications of polypyrrole nanofibers using microfluidic gradients

A rapid screening method for optimizing electrochemical deposition conditions of polypyrrole (PPy) nanostructures is reported. An electrochemical cell is integrated within a low-cost microfluidic system, in which electrochemical deposition is carried out across a linear concentration gradient of a reaction parameter. The protocol, refered to as the screening of conditions for rationally engineered electrodeposition of nanostructures (SCREEN), allows rapid screening of conditions for the production of specific morphologies by characterizing the electrodeposited samples produced within a chemical gradient. To demonstrate the utility of the SCREEN method, applications in tunable optical coatings and superhydrophobic surfaces are presented.

Precision measurement of the B → Xs γ photon energy spectrum, branching fraction, and direct CP asymmetry A(CP)((B → X(s+d)γ)

The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B → X(s)γ plus B → X(d)γ, is studied using a data sample of (382.8 ± 4.2) × 10(6)Υ(4S) → BB decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction B(B → X(s)γ) = (3.21 ± 0.33) × 10(-4) for E(γ) >1.8 GeV and the direct CP asymmetry A(CP) (B → X(s+d)γ) = 0.057 ± 0.063. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame.

Evidence for an excess of B→D*τ(-)ν(τ) decays

Based on the full BABAR data sample, we report improved measurements of the ratios R(D(*))=B(B[over ¯]→D(*)τ(-)ν[over ¯](τ))/B(B[over ¯]→D(*)ℓ(ℓ)(-)ν[over ¯](ℓ)), where ℓ is either e or μ. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D)=0.440±0.058±0.042 and R(D(*))=0.332±0.024±0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, our results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.

Liquid-infused nanostructured surfaces with extreme anti-ice and anti-frost performance

Ice-repellent coatings can have significant impact on global energy savings and improving safety in many infrastructures, transportation, and cooling systems. Recent efforts for developing ice-phobic surfaces have been mostly devoted to utilizing lotus-leaf-inspired superhydrophobic surfaces, yet these surfaces fail in high-humidity conditions due to water condensation and frost formation and even lead to increased ice adhesion due to a large surface area. We report a radically different type of ice-repellent material based on slippery, liquid-infused porous surfaces (SLIPS), where a stable, ultrasmooth, low-hysteresis lubricant overlayer is maintained by infusing a water-immiscible liquid into a nanostructured surface chemically functionalized to have a high affinity to the infiltrated liquid and lock it in place. We develop a direct fabrication method of SLIPS on industrially relevant metals, particularly aluminum, one of the most widely used lightweight structural materials. We demonstrate that SLIPS-coated Al surfaces not only suppress ice/frost accretion by effectively removing condensed moisture but also exhibit at least an order of magnitude lower ice adhesion than state-of-the-art materials. On the basis of a theoretical analysis followed by extensive icing/deicing experiments, we discuss special advantages of SLIPS as ice-repellent surfaces: highly reduced sliding droplet sizes resulting from the extremely low contact angle hysteresis. We show that our surfaces remain essentially frost-free in which any conventional materials accumulate ice. These results indicate that SLIPS is a promising candidate for developing robust anti-icing materials for broad applications, such as refrigeration, aviation, roofs, wires, outdoor signs, railings, and wind turbines.

Truncated p110 ERBB2 induces mammary epithelial cell migration, invasion and orthotopic xenograft formation, and is associated with loss of phosphorylated STAT5

Truncated-ERBB2 isoforms (t-ERBB2s), resulting from receptor proteolysis or alternative translation of the ERBB2 mRNA, exist in a subset of human breast tumors. t-ERBB2s lack the receptor extracellular domain targeted by therapeutic anti-ERBB2 antibodies and antibody–drug conjugates, including trastuzumab, trastuzumab-DM1 and pertuzumab. In clinical studies, expression of t-ERBB2 in breast tumors correlates with metastasis as well as trastuzumab resistance. By using a novel immuno-microarray method, we detect a significant t-ERBB2 fraction in 18 of 31 (58%) of immunohistochemistry (IHC)3+ ERBB2+ human tumor specimens, and further show that t-ERBB2 isoforms are phosphorylated in a subset of IHC3+ samples (10 of 31, 32%). We investigated t-ERBB2 biological activity via engineered expression of full-length and truncated ERBB2 isoforms in human mammary epithelial cells (HMECs), including HMEC and MCF10A cells. Expression of p110 t-ERBB2, but not p95m (m=membrane, also 648CTF) or intracellular ERBB2s, significantly enhanced cell migration and invasion in multiple cell types. In addition, only expression of the p110 isoform led to human breast epithelial cell (HMLE) xenograft formation in vivo. Expression of t-ERBB2s did not result in hyperactivation of the phosphoinositide kinase-3/AKT or mitogen-activated protein kinase signaling pathways in these cells; rather, phosphoproteomic array profiling revealed attenuation of phosphorylated signal transducer and activator of transcription 5 (STAT5) in p110-t-ERBB2-expressing cells compared to controls. Short hairpin-mediated silencing of STAT5 phenocopied p110-t-ERBB2-driven cell migration and invasion, while expression of constitutively active STAT5 reversed these effects. Thus, we provide novel evidence that (1) expression of p110 t-ERBB2 is sufficient for full transformation of HMEC, yielding in vivo xenograft formation, and (2) truncated p110 t-ERBB2 expression is associated with decreased phosphorylation of STAT5.

Search for low-mass dark-sector Higgs bosons

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb(-1) of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the standard model-dark-sector mixing angle and the dark-sector coupling constant.