Myosin VI Lever Arm Rotation: Fixed or Variable?

Two recent articles addressed the power-stroke of myosin VI molecules during stepping. Although both groups measured the angles of fluorescent probes attached on the myosin VI molecule lever arm using polarized fluorescence techniques, they differ about whether the myosin VI lever arm rotation is fixed1 or variable2. Here we discuss the causes of the discrepancy between the two studies and the implications for myosin VI processive motility

MECHANICS OF PARTICLE AND POLYMER ASSEMBLIES

This thesis reports a variety of developments in atomic force microscopy (AFM) methodology and surface preparation techniques. Methodologies of assembling colloidal particles into pre-designed patterns on surfaces were studied. Different interactions, such as electrostatic force, magnetic force, and capillary force of varied topography were used. In the topography-assisted particle assembly, the direct observations of the dynamics revealed that the particles are transported inside or toward the grooves of the pattern in the region where the liquid film is appropriately thin, and the particles¡¯ self-assembly inside the grooves is caused by a lateral capillary force. Scanning probe microscopy was used to examine topography assisted 2D self-assembly of micrometer-size latex particles in wetting films.Based on the adhesive interactions between an AFM tip and sample surfaces, an AFM method for measuring surface elasticity was proposed. The method is particularly useful when there is a large adhesion between the tip and soft samples, when the indentation method would be less accurate. For thin and soft samples, this method has much less interference from the substrate than is found using the indentation method because there is only passive indentation induced by tip-sample adhesion. The model was tested on PDMS polymers with different crosslink density. It was found that soft, less crosslinked PDMS polymers showed obvious viscoelastic behavior when interacting with AFM tips. Systematic studies of the viscoelastic effects found that energy dissipation occurs mainly in the bulk of polymer when an AFM tip indents into a polymer. When the tip is pulled out from the polymer, the energy dissipation occurs both in the bulk and interfaces, which causes a turning point of the adherence force of AFM tip with changes of scan rates. The multiple relaxation rates were characterized and compared with that from other methods.Using AFM imaging and indentation methods, the properties of barnacle adhesive were studied. A multilayered structure of barnacle adhesive plaque was proposed based on layered modulus regions measured by AFM indentation. Analysis shows that there is a strong correlation between the mean Young¡¯s moduli of the outmost softest adhesive layer and the barnacle shear strength, but no correlation for other higher modulus regions. Linear, quadratic, and Griffth¡¯s failure criterion regressions were used in the fit, and showed close correlation

Security of a new two-way continuous-variable quantum key distribution protocol

The original two-way continuous-variable quantum-key-distribution (CV QKD) protocols [S. Pirandola, S. Mancini, S. Lloyd, and S. L. Braunstein, Nature Physics 4, 726 (2008)] give the security against the collective attack on the condition of the tomography of the quantum channels. We propose a family of new two-way CV QKD protocols and prove their security against collective entangling cloner attacks without the tomography of the quantum channels. The simulation result indicates that the new protocols maintain the same advantage as the original two-way protocols whose tolerable excess noise surpasses that of the one-way CV-QKD protocol. We also show that all sub-protocols within the family have higher secret key rate and much longer transmission distance than the one-way CV-QKD protocol for the noisy channel.Comment: 19 pages, 4 figures, accepted for publication in International Journal of Quantum Informatio

Competent Overall Water-Splitting Electrocatalysts derived from ZIF-67 Grown on Carbon Cloth

The design of nonprecious, bifunctional, and highly competent electrocatalysts for both H2 and O2evolution reactions (HER and OER) has attracted increasing interest recently. Herein, we report a cobalt-based electrocatalyst derived from ZIF-67 grown on carbon cloth (Co–P/NC/CC) for overall water splitting electrocatalysis. The as-prepared Co–P/NC/CC catalyst exhibited remarkable catalytic performance in 1 M KOH with Tafel slopes of 52 and 61 mV dec−1 for HER and OER, respectively. When serving as catalysts for both the cathode and anode, our Co–P/NC/CC demonstrated high efficiency and strong robustness. A thorough comparison with other control samples and detailed characterization results revealed that the superior activity and excellent stability of Co–N–C likely originated from the highly porous, self-supported, and binder-free nature of the electrocatalyst, as well as the high conductivity of carbon cloth. Hence, direct decoration of metal organic frameworks on conductive substrates represents an effective approach for the development of electrocatalysts not only promising for water splitting but also for many other applications

Adjusted inference for multiple testing procedure in group sequential designs

Adjustment of statistical significance levels for repeated analysis in group sequential trials has been understood for some time. Similarly, methods for adjustment accounting for testing multiple hypotheses are common. There is limited research on simultaneously adjusting for both multiple hypothesis testing and multiple analyses of one or more hypotheses. We address this gap by proposing adjusted-sequential p-values that reject an elementary hypothesis when its adjusted-sequential p-values are less than or equal to the family-wise Type I error rate (FWER) in a group sequential design. We also propose sequential p-values for intersection hypotheses as a tool to compute adjusted sequential p-values for elementary hypotheses. We demonstrate the application using weighted Bonferroni tests and weighted parametric tests, comparing adjusted sequential p-values to a desired FWER for inference on each elementary hypothesis tested

Experimental evidence of detailed balance in granular systems

The principle of detailed balance (DB) states that every kinetic transition in a system with many micro-states, $\mu$, is balanced, on average, with the opposite transition, $\mu_i\leftrightharpoons\mu_j$. Since its introduction by Boltzmann, this principle has been used by luminaries, such as Einstein, Eddington, Kramers, Pauli, Ehrenfest, Dirac, Onsager, and many others to derive significant results that underpin much of our scientific understanding. The current belief is that DB is satisfied only in equilibrium systems, while non-equilibrium steady states can only be balanced by cycles, such as $A\to B\to C\to A$. We show here experimentally that DB can exist and is commonly and robustly satisfied in a family of quasi-statically cyclically sheared granular systems. We further study the approach to DB as a function of system size and time. Given the significant impact that this principle has had on equilibrium systems, we believe that this discovery paves the way for better models of the dynamics of non-equilibrium systems.Comment: 5 pages, 4 figure