Kinematic chain study of the adjustability of a monolateral external fixator

Abstract

Adjustability of the external fixator reflects two important features–the range of allowable locations of pins and the ease of frame application. In this study, multilink open chain kinematic equations were developed to examine this adjustability of a monolateral external fixator. The entire bone‐fixator system was simulated by a manipulator with four rigid links, two spherical joints, and one prismatic joint. Each of the links and joints was described by a 4×4 homogenous transformational matrix with either X‐Y‐Z or Z‐X‐Z Euler angle representation. The transformation equations were developed by concatenating these transformational matrices. Then the kinematic equations were solved by the least squares optimization method, and the numerical solutions were validated by geometrical solutions and mechanical experiments. The results showed solutions using Z‐X‐Z Euler angle representations were more reliable in predicting the reducibility of the malalignment and could be more conveniently used for direct kinematic study. Increasing the length of the central body, the offset of the telescoping joint, and the rotational range of ball joints and decreasing the pin length increased the adjustability. The adjustability reached its maximum as the initial offset of the telescoping joint reached a critical level. In conclusion, the adjustability of the external fixators was closely related to their designs. This study may assist manufacturers in the design of external fixators and help surgeons better understand the restraints of fixators and hence use such equipment more effectively.     

Hurricane Georges and vegetation change in Puerto Rico using AVHRR satellite data

This study assesses natural disturbances at Puerto Rico resulting from hurricane Georges in September 1998. The study was done using data from the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer (AVHRR) 14 satellite. Specifically, the Luquillo Experimental Forest, the Guanica Dry Forest and five cities were examined using AVHRR data. It was found that although there is probably no significant relationship between Georges and the before/after temperature data, there is a statistically significant relationship between distance to the location affected by the hurricane and the extent of changes in NDVI, a fact that suggests that it is possible to measure hurricane impacts on vegetation by using AVHRR data.     

PBG-excited split-mode resonator bandpass filter

Photonic bandgap structure is used as a design parameter for the fundamental passband in a split-mode microstrip square resonator. A defect in the PBG cells under the resonator, allows coupling between the two degenerate modes. A filter is designed at 2.2 GHz with good agreement between simulated and measured results     

Hexahydropyrrolo[2,3‐b]indoles: A New Class of Structurally Rigid Tricyclic Skeleton for Oxazaborolidine‐Catalyzed Asymmetric Borane Reduction

A new class of structurally rigid tricyclic chiral ligands based on the hexahydropyrrolo[2,3‐b]indole skeleton has been rationally designed and the catalytic abilities in asymmetric catalysis have been shown in the enantioselective borane reduction of prochiral ketones to afford the chiral alcohols in excellent yields and high enantioselectivities (up to 97% ee).     

Excess Phosphine Ligand Plays a Critical Role in the Asymmetric Copper(I) Iodide‐Catalyzed Conjugate Addition of Grignard Reagents to α,β‐Unsaturated Esters

The role of excess ligand in the asymmetric 1,4‐conjugate addition (ACA) of Grignard reagents to α,β‐unsaturated esters compounds catalyzed by copper(I) iodide‐2,2′‐bis(di‐p‐tolylphosphino)‐1,1′‐binaphthyl (CuI‐Tol‐BINAP) is explored herein. In addition, this methodology allows asymmetric induction to be carried out using a non‐chiral phosphine copper complex with excess of a chiral phosphine ligand.     

High-performance graphene-titania platform for detection of phosphopeptides in cancer cells

Phosphopeptides play a crucial role in many biological processes and constitute some of the most powerful biomarkers in disease detection. However they are often present in very low concentration, which makes their detection highly challenging. Here, we demonstrate the use of a solution-dispersible graphene-titania platform for the selective extraction of phosphopeptides from peptide mixtures. This is followed by direct analysis by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS). The efficient charge and energy exchange between graphene and TiO(2) during laser irradiation in SELDI-TOF MS promotes the soft ionization of analytes and affords a detection limit in the attomole range, which is 10(2)-10(5) more sensitive than conventional platforms. The graphene-titania platform can also be used for detecting phosphopeptides in cancer cells (HeLa cells), where it shows high specificity (94%). An expanded library of 967 unique phosphopeptides is detected using significantly reduced loading of extraction matrixes compared to conventional TiO(2) bead-based assays.     

A comprehensive search for stable pt-pd nanoalloy configurations and their use as tunable catalysts

Using density-functional theory, we predict stable alloy configurations (ground states) for a 1 nm Pt-Pd cuboctahedral nanoparticle across the entire composition range and demonstrate their use as tunable alloy catalysts via hydrogen-adsorption studies. Unlike previous works, we use simulated annealing with a cluster expansion Hamiltonian to perform a rapid and comprehensive search that encompasses both high and low-symmetry configurations. The ground states show Pt(core)-Pd(shell) type configurations across all compositions but with specific Pd patterns. For catalysis studies at room temperatures, the ground states are more realistic structural models than the commonly assumed random alloy configurations. Using the ground states, we reveal that the hydrogen adsorption energy increases (decreases) monotonically with at. % Pt for the {111} hollow ({100} bridge) adsorption site. Such trends are useful for designing tunable Pd-Pt nanocatalysts for the hydrogen evolution reaction.     

Highly wrinkled cross-linked graphene oxide membranes for biological and charge-storage applications

Inspired by the amphiphilicity of graphene oxide (GO), the surface of water is used as a template for the assembly of a GO film. Methacrylate-functionalized GO sheets can be cross-linked instantaneously at the water-air interface to form a highly wrinkled membrane spreading over an extended area. The multiple covalent linkages amongst the GO sheets enhances the in-plane stiffness of the film compared to noncovalently bonded GO films. The highly convoluted GO membrane can be used in two applications: the promoting of spontaneous stem-cell differentiation towards bone cell lineage without any chemical inducers, and for supercapacitor electrodes. Due to reduced van der Waals restacking, capacitance values up to 211 F g(-1) can be obtained. The scalable and inexpensive nature of this assembly route enables the engineering of membranes for applications in regenerative medicine and energy-storage devices where secondary structures like nanotopography and porosity are important performance enhancers.     

Development of an anti-influenza drug screening assay targeting nucleoproteins with tryptophan fluorescence quenching

Recent studies have shown that NP (nucleoprotein), which possesses multiple functions in the viral life cycle, is a new potential anti-influenza drug target. NP inhibitors reliably induce conformational changes in NPs, and these changes may confer inhibition of the influenza virus. The six conserved tryptophan residues in NP can be used as an intrinsic probe to monitor the change in fluorescence of the tryptophan residues in the protein upon binding to an NP inhibitor. In the present study, we found that the fluorescence of recombinant NP proteins was quenched following the binding of available NP inhibitors (such as nucleozin) in a concentration- and time-dependent manner, which suggests that the inhibitor induced conformational changes in the NPs. The minimal fluorescence-quenching effect and weak binding constant of nucleozin to the swine-origin influenza virus H1N1pdm09 (SOIV) NP revealed that the SOIV is resistant to nucleozin. We have used the fluorescence-quenching property of tryptophans in NPs that were bound to ligands in a 96-well-plate-based drug screen to assess the ability of promising small molecules to interact with NPs and have identified one new anti-influenza drug, CSV0C001018, with a high SI value. This convenient method for drug screening may facilitate the development of antiviral drugs that target viruses other than the influenza virus, such as HIV and HBV.