The Alu family of interspersed repeats is comprised of over 500,000 members which may be divided into discrete subfamilies based upon mutations held in common between members. Distinct subfamilies of Alu sequences have amplified within the human genome in recent evolutionary history. Several individual Alu family members have amplified so recently in human evolution that they are variable as to presence and absence at specific loci within different human populations. Here, we report on the distribution of six polymorphic Alu insertions in a survey of 563 individuals from 14 human population groups across several continents. Our results indicate that these polymorphic Alu insertions probably have an African origin and that there is a much smaller amount of genetic variation between European populations than that found between other population groups.

A seismic isolation system for the proposed 'Advanced LIGO' detector upgrade is under development. It consists of a two-stage in-vacuum active isolation platform that is supported by an external hydraulic actuation stage. A fullscale preliminary-design technology demonstrator of the in-vacuum platform has been assembled and is being tested at Stanford's engineering test facility. Unanticipated excess ground motion from local human activity at LIGO Livingston has prompted accelerated development of the external stage for installation and use in the initial Livingston detector. As an interim measure, active external isolation in the laser beam direction is implemented using existing PZT external actuators.

A soft-switching inverter topology (the Class 8) is presented which draws dc source current through a transmission line or a lumped-network approximation of a distributed line. By aligning the inverter switching frequency just below the line's 4-wave resonance, the Class 8 topology enforces odd-and even-harmonic content in its drain voltage and input current, respectively. The symmetrizing action of the transmission-line dynamics results in natural square-wave operation of the switch, reducing the inverter stresses (relative to a Class E) for a given power throughput. The inverter waveforms and normalized power-output capability are analyzed in simple terms, and supported by measurements of an inverter built around a length of distributed line, and an inverter incorporating a lumpedladder network. The latter implementation is constructed with air-core magnetics and inter-layer capacitances that are integrated into the thickness of a printed-circuit board. A comparison with a Class E inverter of similar size and ratings demonstrates the small passive-component values and manufacturing advantages afforded by the Class 8 topology.

Transmission lines and their lumped approximating networks have long been incorporated into radio-frequency power amplifiers to improve efficiency and shape circuit waveforms and are beginning to perform a similar roles in high-frequency switched-mode power electronics. Though lumped line-simulating networks are often preferred to their distributed exemplars for reasons of design flexibility and manufacturability, the impedance peaks and nulls of such lumped networks must be aligned in a precise, harmonic manner to minimize loss and symmetrize converter waveforms. This paper addresses the issue of harmonic frequency alignment in line-simulating networks, presenting new analytic results for predicting the impedance-minimum and impedance-maximum frequencies of networks in a ladder form. Two means of correcting for the observed harmonic misalignment in practical structures will be presented, corroborated by measurements of laminar structures built into the thickness of printed-circuit boards. These structures comprise inductances and capacitances whose dimensions are largely decoupled, such that the simulated line can be accurately analyzed and designed on a lumped basis. The presented techniques will be placed within a power-electronics setting by a representative application incorporating a lumped, line-simulating network.

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