Attitude control system Patent

Development of attitude control system for spacecraft orientatio

How English Became the Global Language, by David Northrup

In this slim volume David Northrup, a retired Boston College professor of history, gives a clear and concise account of the development of English into the twenty-first century’s one truly global language. First he traces how English became the predominant language in the British Isles, overcoming such rivals as Cornish, Welsh, and Gaelic

High power coupled CO2 waveguide laser array

A hollow-bore ridge waveguide technique for phase locking arrays of coupled CO2 rf excited waveguide lasers was demonstrated. Stable phase-locked operation of two- and three-channel arrays has been demonstrated at the 50 W output level. Preliminary experiments with a five-element array generated an output power of 95 W but phase-locked operation was not conclusively demonstrated

Speculations on the postnatural: Restoration, accumulation, and sacrifice at the Salton Sea

Using a regional political ecology lens, this paper explores emerging geographies and politics of a “postnatural” ecomodernist turn in mainstream environmentalism. We examine the unfolding case of ecological restoration and renewable energy development at Southern California’s Salton Sea. Ambitious proposals to restore the massive, increasingly degraded lake (and finance restoration) by reengineering it as a hub for geothermal energy generation and high-tech green industry hinge upon the ambiguity and malleability of restoration in an environment long classified as postnatural. These plans coincide with a broader rush on renewable energy sites in the California desert, and mounting conflicts over water and land with legacy agro-industrial interests. The case illustrates significant problems within postnatural environmentalism. First, it demonstrates how theorizations of the postnatural can intersect with green capitalist projects of re(e)valuation and development, as the Sea’s managers manipulate environmental framings to support accumulation-minded projects, and accumulation imperatives swamp other functionalities of restoration. Meanwhile, despite the flourishing of postnatural discourses, the “pristine” is shown to do continued work as the Sea becomes a sacrifice zone for development deflected from better-protected spaces. This postnatural positioning has rendered the Salton Sea vulnerable to neoliberal austerity and speculation in ways that compromise its future existence

Statistical mechanics of base stacking and pairing in DNA melting

We propose a statistical mechanics model for DNA melting in which base stacking and pairing are explicitly introduced as distinct degrees of freedom. Unlike previous approaches, this model describes thermal denaturation of DNA secondary structure in the whole experimentally accessible temperature range. Base pairing is described through a zipper model, base stacking through an Ising model. We present experimental data on the unstacking transition, obtained exploiting the observation that at moderately low pH this transition is moved down to experimentally accessible temperatures. These measurements confirm that the Ising model approach is indeed a good description of base stacking. On the other hand, comparison with the experiments points to the limitations of the simple zipper model description of base pairing.Comment: 13 pages with figure

The Effects of Stacking on the Configurations and Elasticity of Single Stranded Nucleic Acids

Stacking interactions in single stranded nucleic acids give rise to configurations of an annealed rod-coil multiblock copolymer. Theoretical analysis identifies the resulting signatures for long homopolynucleotides: A non monotonous dependence of size on temperature, corresponding effects on cyclization and a plateau in the extension force law. Explicit numerical results for poly(dA) and poly(rU) are presented.Comment: 4 pages and 2 figures. Accepted in Phys. Rev. E Rapid Com

Objective voice parameters in Colombian school workers with healthy voices

Objectives: To characterize the objective voice parameters among school workers, and to identify associated factors of three object

Evaluation of positive G sub Z tolerance following simulated weightlessness (bedrest)

The magnitude of physiologic changes which are known to occur in human subjects exposed to varying levels of + G sub Z acceleration following bed rest simulation of weightlessness was studied. Bed rest effects were documented by fluid and electrolyte balance studies, maximal exercise capability, 70 deg passive tilt and lower body negative pressure tests and the ability to endure randomly prescribed acceleration profiles of +2G sub Z, +3G sub Z, and +4G sub Z. Six healthy male volunteers were studied during two weeks of bed rest after adequate control observations, followed by two weeks of recovery, followed by a second two-week period of bed rest at which time an Air Force cutaway anti-G suit was used to determine its effectiveness as a countermeasure for observed cardiovascular changes during acceleration. Results showed uniform and significant changes in all measured parameters as a consequence of bed rest including a reduced ability to tolerate +G sub Z acceleration. The use of anti-G suits significantly improved subject tolerance to all G exposures and returned measured parameters such as heart rate and blood pressure towards or to pre-bed-rest (control) values in four of the six cases

A new geometric invariant on initial data for Einstein equations

For a given asymptotically flat initial data set for Einstein equations a new geometric invariant is constructed. This invariant measure the departure of the data set from the stationary regime, it vanishes if and only if the data is stationary. In vacuum, it can be interpreted as a measure of the total amount of radiation contained in the data.Comment: 5 pages. Important corrections regarding the generalization to the non-time symmetric cas