In vivo measurements of ion transport in long-living CF mice

The Cftr (Cystic Fibrosis Transmembrane Conductance Regulator) gene codes for an epithelial chloride (C1) channel essential for fluid secretion into the respiratory and gastrointestinal tract and from exocrine glands. Mice lacking CFTR function due to a disruption of Cftr exon 10 or exon 1 (Cftr (m1UNC/m1UNC) or Cftr(m1HSC/m1HFC) mice, respectively) generally suffer from severe gastrointestinal disease resulting in death shortly after birth or at the time of weaning. However, a subgroup of the Cftr(m1HSC/m1HSC) mice have been characterized which exhibit relatively mild intestinal pathology resulting in a noncompromised lifespan compared to the more severely affected Cftr(m1UNC/m1UNC) mice. We compared the ion transport capacity of the intestinal mucosa of the mildly and severely affected CF mice using the in vivo technique of rectal potential difference (PD) measurement and found that the net calcium-activated chloride conductance toward the lumen was much greater in the rectum of mildly affected mice than in the severely affected mice. Hence, the milder phenotype may be related to the expression of a factor which enhances the net calcium-activated chloride conductance into the lumen of the intestinal tract.     

Signal-to-Noise Ratio Evaluations for Nonlinear Amplifiers

This paper presents a solution for the output signal-to-noise ratio of a bandpass nonlinearity which is attractive for numerical evaluations of certain nonlinearities of interest. The solution is obtained by solving a differential equation which results in an expression for thenth order Chebyshev transform of an odd-order nonlinearity in terms of the(n - 1)st-order Chebyshev transform of the derivative of the nonlinearity. The particular cases treated included a linear-logarithmic amplifier, an arctangent limiter, and a piecewise-linear limiter. The approach and results are related to previous efforts.     

Choice of initial conditions in the ML reconstruction of fan-beamtransmission with truncated projection data

The authors investigate the effects of initial conditions in the iterative maximum-likelihood (ML) reconstruction of fan-beam transmission projection data with truncation. In an iterative ML reconstruction, the estimate of the transmission reconstructed image in the previous iteration is multiplied by some factors to obtain the current estimate. Normally, a flat initial condition (FIC) or an image with equal positive pixel values is used as initial condition for an ML reconstruction. Usage of FIC has also been perceived as a way of preventing any bias on the reconstruction which may have come from the initial condition. When projection data have truncation, the authors show that using are FIC in an ML iterative reconstruction can introduce a bias to the reconstruction inside the densely sampled region (DSR), whose projection data have no truncation at any angle. To reduce this bias, the authors propose to use the largest right singular vector (LRSV) of the system matrix as the initial condition, and demonstrate that the bias can be reduced with the LRSV. When data truncation is reduced, the LRSV approaches the FIC. This result does not contradict to the use of FIC when projection data are not truncated. The authors also demonstrate that the reconstructed transmission image using LRSV as initial condition provides a more accurate attenuation coefficient distribution than that using FIC. However, the improvement is mostly in the area outside the DSR     

A new algorithm for the design of multifunctional observers

This paper presents a general algorithm for low-order multifunctional observer design with arbitrary eigenvalues. The feature of this algorithm is that it can generate a functional observer with different orders which are no larger but usually much less thanm(v - 1), wheremis the number of functionals andvis the observability index of(A, C). Since the order needed for the observer varies with the functionals besides other system parameters, this design approach should be practical. The resulting observer system matrix is in its Jordan form. The key step of this algorithm is the generation of the basis for the transformation matrix which relates the system and observer states. The computation of this algorithm is quite reliable. It is based on the block observable lower Hessenberg form of(A, C), and all its initial and major computation involves only the orthogonal operations.     

Molecular Barbed Wire: Threading and Interlocking for the Mechanical Reinforcement of Polymers

The incorporation of pendant iptycene units into polyesters creates a novel polymer‐chain contour resembling “molecular barbed wire.” These types of units contain a unique structural property called the internal molecular‐free volume (IMFV) and have been shown to induce steric interactions between polymer chains through the minimization of the IMFV. This process creates a sterically interconnected polymer‐chain network with high ductility because of two new mechanisms: molecular threading and molecular interlocking. The ability for these mechanisms to enhance the mechanical properties of polyesters is robust across concentration and processing conditions. The size, shape, and concentration of these pendant units affect the mechanical behavior, and results indicate that the larger units do not necessarily produce superior tensile properties. However, the molecular‐barbed‐wire architecture consistently produces enhanced mechanical properties compared to the reference polyester. The particular stress–strain response can be tailored by minute changes to the periphery of the iptycene unit.     

Fabrication and characterization of needle-like nano-HA and HA/MWNT composites

Hydroxyapatite (HA) ceramic has been used in tissue engineering and orthopedics for its good biocompatibility and osteoconductivity. However, its clinical applications are usually limited by the low strength and brittleness. The objective of this research was to develop a new kind of HA composites in which multi-wall carbon nanotubes (MWNTs) were introduced to the HA ceramic matrix to improve the mechanical properties of the resulting composites. A simple chemical wet method was applied to synthesize the HA ceramic particles with the aid of surfactant and ultrasonication technique at normal atmospheric pressure. The morphology and microstructure of the synthesized HA were characterized by XRD and TEM as a function of treatment time. The results showed that the synthesized HA particles are needle-like with a length of 80–160 nm along the (211) direction and an aspect ratio of 5–15. MWNTs were treated with a mixture of nitric acid and sulfuric acid. The HA/MWNT composites were prepared by solution blending. The composites were sintered using a hot-press method. The mechanical properties of the HA/MWNT composites with different volume percentages of MWNTs were examined. The fracture toughness and flexural strength were improved by 50% and 28% separately when the volume percentage of MWNTs reached 7%.