Slip casting of sol–gel-synthesized barium strontium zirconium titanate ceramics

The sol–gel method was used to synthesize two different Ba_0.75Sr_0.25Ti_0.95Zr_0.05O₃ powders: one of high purity and the other of low purity. These two sol–gel-synthesized powders show two distinct particle sizes and surface areas. The slip casting method was applied to these two sol–gel powders followed by a pressureless sintering, which shows large differences in sintered density and grain size for the pressureless sintered disks. Neutron powder diffraction shows a transition to the nonpolar cubic Pm–3m space group at higher temperatures for both materials. Pair distribution function analysis was used to examine the local displacements of the Ti⁴⁺ and Zr⁴⁺ cations. The dielectric constant, loss tangent, and bias were measured on these two materials.     

Betti numbers and minimal free resolutions for multi-state system reliability bounds

Every coherent system has a monomial ideal associated with it and the knowledge of its multigraded Betti numbers provides reliability bounds for the corresponding system, which are the tightest among a certain class of such bounds. Some alternative methods for computing the multigraded Betti numbers are used in this paper and applied in the study of reliability. We obtain special results for well known examples and show that computational commutative algebra techniques can be used beneficially in the reliability analysis of systems of different types.     

Simulations of rebound of an elastic ellipsoid colliding with a plane

Single ellipsoidal particles have been simulated during collision with a semi-infinite plane wall, using a ‘soft-sphere’ technique modified for a non-sphere. These simulations have several complications compared to those for spheres, including greater interaction between normal, tangential and rotational velocities. The normal force is calculated assuming perfectly elastic behaviour; the Hertz formulation specifies the variation of normal stiffness with curvature of the body. It is shown that variations in normal stiffness will cause a torque during rolling. Equations are presented in detail for the calculation of the contact point's location and curvature, and for the time-stepping scheme used in the simulations. It is assumed that motion is in a plane of symmetry of the ellipsoid, with zero initial rotational velocity. The convergence of this scheme is tested, and characteristics of the collision are expressed in terms of dimensionless groups. The resulting rebound behaviour is also quite complicated: multiple collisions are common; the coefficient of restitution varies considerably with initial orientation and can be greater than unity; particles can acquire back-spin or top-spin, and may rebound backwards. Mean values and standard deviations are reported for the rebound velocities from a full sample of initial orientations. The standard deviations are relatively insensitive to aspect ratios in the range 2 to 8. These results may be of use in ‘hard-sphere’ simulations of non-spherical particles colliding with walls.     

Cytokines as determinants of disease and disease interactions

An unusual accidental death due to acute massive occlusion of the right pulmonary arteries by liver tissue is reported. A 17-year-old motorcyclist was run over by a heavy truck, resulting in multiple injuries. Multiple lacerations of the liver and tears in the wall of the inferior vena cava resulted in the complete occlusion of the right pulmonary artery by liver tissue. Although the victim sustained other potentially lethal injuries, the final mechanism of death is attributed to pulmonary embolism.     

Monolithic integration of photodetector with vertical cavity surface emitting laser

For the first time, monolithic integration of a photodetector with a vertical-cavity surface emitting laser (VCSEL) is demonstrated. The authors have designed and fabricated VCSELs with monolithically integrated pin photodetectors which dynamically monitor (and can thus control) the output power of the lasers. The VCSELs lase at room temperature and emit a highly coherent, low-divergence, circular beam directly from the top surface. The integrated photodetector shows a linear response to the laser emission with an effective responsivity of 0.25 A/W.<>     

Current and Future Treatment of Mucopolysaccharidosis (MPS) Type II: Is Brain-Targeted Stem Cell Gene Therapy the Solution for This Devastating Disorder?

Mucopolysaccharidosis type II (Hunter Syndrome) is a rare, x-linked recessive, progressive, multi-system, lysosomal storage disease caused by the deficiency of iduronate-2-sulfatase (IDS), which leads to the pathological storage of glycosaminoglycans in nearly all cell types, tissues and organs. The condition is clinically heterogeneous, and most patients present with a progressive, multi-system disease in their early years. This article outlines the pathology of the disorder and current treatment strategies, including a detailed review of haematopoietic stem cell transplant outcomes for MPSII. We then discuss haematopoietic stem cell gene therapy and how this can be employed for treatment of the disorder. We consider how preclinical innovations, including novel brain-targeted techniques, can be incorporated into stem cell gene therapy approaches to mitigate the neuropathological consequences of the condition.     

Collection-mode near-field imaging with 0.5-THz pulses

High spatial resolution imaging with terahertz pulses is implemented with a novel collection-mode near-field probe. The spatial resolution capabilities of the system are in the range of few micrometers. We demonstrate resolution of 7 μm using 0.5-THz pulses and discuss performance of the collection-mode near-field probes and image properties     

GaAs/AlGaAs multiple quantum well GRIN-SCH vertical cavity surfaceemitting laser diodes

Vertical cavity surface emitting lasers (VCSELs) with GaAs/AlGaAs multiple quantum well (20 wells) graded-index separate-confinement-heterostructure (GRIN-SCH) active regions are discussed. The VCSEL structures, which also contained two Al_xGa_1-xAs/Al_yGa_1-yAs distributed Bragg reflectors, were grown by molecular beam epitaxy and had a threshold current and current density at room temperature pulsed excitation of 16 mA and 14 kA/cm², respectively, near 0.85-μm wavelength. Both single-longitudinal and fundamental transverse mode emission characteristics were observed with a light output greater than 3 mW and a slope efficiency of 0.12 mW/mA     

Long-cavity, multi-electrode DFB lasers for coherent FSK systems

The fabrication and performance characteristics of 1 mm long three-electrode distributed feedback lasers is reported. CW linewidth of 500 kHz has been obtained. The frequency modulation characteristics of these devices exhibit no thermally induced dip and the magnitude of FM is large enough for practical coherent system application.<>