Space physics missions handbook

The purpose of this handbook is to provide background data on current, approved, and planned missions, including a summary of the recommended candidate future missions. Topics include the space physics mission plan, operational spacecraft, and details of such approved missions as the Tethered Satellite System, the Solar and Heliospheric Observatory, and the Atmospheric Laboratory for Applications and Science

Effects of Chemical and Mechanical Weathering Processes on the Degradation of Plastic Debris on Marine Beaches

Plastics are an integral part of everyday life, and the use of plastic products for consumer goods, food packaging, recreational and commercial fishing and medical and sanitary applications continues to increase. The durability, low cost, light weight and hydrophobic nature of plastic make it a desirable material for numerous applications; however, these same characteristics make plastic debris in natural environments a pervasive problem. Increases in plastic use and low economic incentive for recovery, result in accumulation of debris in marine environments. Degradation of plastics through chemical weathering occurs in the open ocean or along shorelines where polymers are exposed to seawater and UVB radiation. Plastic particles were both experimentally degraded, and sampled from beaches on the island of Kauai, Hawaii, U.S.A. and in and near Gros Morne National Park, Newfoundland, Canada. Daily accumulation rates of 484 pieces per day were recorded in Kauai and approximately 6000 plastic particles were collected over a 10 day period. Relationships between composition, surface textures and level of oxidation were studied using FTIR (Fourier Transform Infrared Spectroscopy) and SEM (Scanning Electron Microscopy). Surface textural analysis showed evidence of cracks, fractures, flakes, grooves, pits, adhering particles and vermiculate textures. Increased surface oxidation of different polymer types was determined by measuring increased IR absorbance in the 1710 cm-1 wavenumber region of the IR spectra. Results obtained from both analytical techniques indicate a strong relationship between chemical and mechanical degradation of plastics, suggesting that plastics degrade most efficiently on beaches compared with other natural environments. Vermiculate textures were only present on polyethylene particles sampled from Kauai indicating that biological activity, water salinity or temperature may play key roles in the degradation of plastics in subtropical climates. Analysis of debris collected from Kauaiian beaches indicates that small particles and pellets comprise the largest portion of plastics which is in contrast to Newfoundland beaches which have more intact and nearly intact debris relative to the overall plastic load. Size distribution of plastic debris closely mimicked natural sedimentary grain size distribution in natural environments suggesting that plastics may become a significant component of the sedimentary deposit record

Modeling the Formation of Clouds in Brown Dwarf Atmospheres

Because the opacity of clouds in substellar mass object (SMO) atmospheres depends on the composition and distribution of particle sizes within the cloud, a credible cloud model is essential for accurately modeling SMO spectra and colors. We present a one--dimensional model of cloud particle formation and subsequent growth based on a consideration of basic cloud microphysics. We apply this microphysical cloud model to a set of synthetic brown dwarf atmospheres spanning a broad range of surface gravities and effective temperatures (g_surf = 1.78 * 10^3 -- 3 * 10^5 cm/s^2 and T_eff = 600 -- 1600 K) to obtain plausible particle sizes for several abundant species (Fe, Mg2SiO4, and Ca2Al2SiO7). At the base of the clouds, where the particles are largest, the particle sizes thus computed range from ~5 microns to over 300 microns in radius over the full range of atmospheric conditions considered. We show that average particle sizes decrease significantly with increasing brown dwarf surface gravity. We also find that brown dwarfs with higher effective temperatures have characteristically larger cloud particles than those with lower effective temperatures. We therefore conclude that it is unrealistic when modeling SMO spectra to apply a single particle size distribution to the entire class of objects.Comment: 25 pages; 8 figures. We have added considerable detail describing the physics of the cloud model. We have also added discussions of the issues of rainout and the self-consistent coupling of clouds with brown dwarf atmospheric models. We have updated figures 1, 3, and 4 with new vertical axis labels and new particle sizes for forsterite and gehlenite. Accepted to the Astrophysical Journal, Dec. 2, 200

Perceptually smooth timbral guides by state-space analysis of phase-vocoder parameters

Sculptor is a phase-vocoder-based package of programs that allows users to explore timbral manipulation of sound in real time. It is the product of a research program seeking ultimately to perform gestural capture by analysis of the sound a performer makes using a conventional instrument. Since the phase-vocoder output is of high dimensionality — typically more than 1,000 channels per analysis frame—mapping phase-vocoder output to appropriate input parameters for a synthesizer is only feasible in theory

Twenty-Three Years and Still Waiting for Change: Why It's Time to Give Tipped Minimum Workers the Regular Minimum Wage

Last year marked the 75th anniversary of the Fair Labor Standards Act (FLSA), the legislation that established many of the basic labor protections workers enjoy today, such as a 40-hour workweek, overtime protection, and a national minimum wage. There have been periodic amendments to the FLSA over the years, but the 1966 amendments were especially significant. They extended protections to hotel, restaurant, and other service workers who had previously been excluded from the FLSA, but also introduced a new "subminimum wage" for workers who customarily and regularly receive tips.Unlike temporary subminimum wages (such as those for students, youths, and workers in training), the "tip credit" provision afforded to employers uniquely established a permanent sub-wage for tipped workers, under the assumption that these workers' tips, when added to the sub-wage, would ensure that these workers' hourly earnings were at least equal to the regular minimum wage. The creation of the tip credit -- the difference, paid for by customers' tips, between the regular minimum wage and the sub-wage for tipped workers -- fundamentally changed the practice of tipping. Whereas tips had once been simply a token of gratitude from the served to the server, they became, at least in part, a subsidy from consumers to the employers of tipped workers. In other words, part of the employer wage bill is now paid by customers via their tips.Today this two-tiered wage system continues to exist, yet the subsidy to employers provided by customers in restaurants, salons, casinos, and other businesses that employ tipped workers is larger than it has ever been. At the federal level, it currently stands at $5.12 per hour, as employers are required to pay their tipped staff a "tipped minimum wage" of only$2.13 per hour, and the federal regular minimum wage is currently $7.25. Remarkably, the federal tipped minimum wage has been stuck at$2.13 since 1991 -- a 23-year stretch, over which time inflation has lowered the purchasing power of the federal tipped minimum wage to its lowest point ever.Proposed federal minimum-wage legislation, the Fair Minimum Wage Act of 2014 -- also known as the Harkin -- Miller bill -- would not only increase the federal regular minimum wage to $10.10, but for the first time in decades would also reconnect the subminimum wage for tipped workers back to the regular minimum wage by requiring the former be equal to 70 percent of the latter. This would be a strong step in the right direction; however, we present evidence that tipped workers would be better off still if we simply eliminated the tipped minimum wage, and paid these workers the full regular minimum wage

Proposal for a lunar tunnel-boring machine

A need exists for obtaining a safe and habitable lunar base that is free from the hazards of radiation, temperature gradient, and micrometeorites. A device for excavating lunar material and simultaneously generating living space in the subselenian environment was studied at the conceptual level. Preliminary examinations indicate that a device using a mechanical head to shear its way through the lunar material while creating a rigid ceramic-like lining meets design constraints using existing technology. The Lunar Tunneler is totally automated and guided by a laser communication system. There exists the potential for the excavated lunar material to be used in conjunction with a surface mining process for the purpose of the extraction of oxygen and other elements. Experiments into lunar material excavation and further research into the concept of a mechanical Lunar Tunneler are suggested

The SseC translocon component in Salmonella enterica serovar Typhimurium is chaperoned by SscA

Background: Salmonella enterica is a causative agent of foodborne gastroenteritis and the systemic disease known as typhoid fever. This bacterium uses two type three secretion systems (T3SSs) to translocate protein effectors into host cells to manipulate cellular function. Salmonella pathogenicity island (SPI)-2 encodes a T3SS required for intracellular survival of the pathogen. Genes in SPI-2 include apparatus components, secreted effectors and chaperones that bind to secreted cargo to coordinate their release from the bacterial cell. Although the effector repertoire secreted by the SPI-2 T3SS is large, only three virulence-associated chaperones have been characterized. Results: Here we report that SscA is the chaperone for the SseC translocon component. We show that SscA and SseC interact in bacterial cells and that deletion of sscA results in a loss of SseC secretion, which compromises intracellular replication and leads to a loss of competitive fitness in mice. Conclusions: This work completes the characterization of the chaperone complement within SPI-2 and identifies SscA as the chaperone for the SseC translocon

Amplification free detection of Herpes Simplex Virus DNA

Amplification-free detection of nucleic acids in complex biological samples is an important technology for clinical diagnostics, especially in the case where the detection is quantitative and highly sensitive. Here we present the detection of a synthetic DNA sequence from Herpes Simplex Virus-1 within swine cerebrospinal fluid (CSF), using a sandwich-like, magnetic nanoparticle pull-down assay. Magnetic nanoparticles and fluorescent polystyrene nanoparticles were both modified with DNA probes, able to hybridise either end of the target DNA, forming the sandwich-like complex which can be captured magnetically and detected by fluorescence. The concentration of the target DNA was determined by counting individual and aggregated fluorescent nanoparticles on a planar glass surface within a fluidic chamber. DNA probe coupling for both nanoparticles was optimized. Polystyrene reporter nanoparticles that had been modified with amine terminated DNA probes were also treated with amine terminated polyethylene glycol, in order to reduce non-specific aggregation and target independent adhesion to the magnetic particles. This way, a limit of detection for the target DNA of 0.8 pM and 1 pM could be achieved for hybridisation buffer and CSF respectively, corresponding to 0.072 and 0.090 femtomoles of target DNA, in a volume of 0.090 mL