3-D Laser Shaping of Ceramic and Ceramic Composite Materials

A versatile, automated, laser-based system, capable of producing complex threedimensional shapes of ceramic and ceramic composite materials, through either controlled layer ablation or solid freeform fabrication, is currently under development. The system comprises a 1.2 kW C021aser, positioning system, beam scanner, non-contacting positioning sensor, beam conditioner and CAD/CAM system. This paper reports progress in relating machine parameters (scan rate, feed, beam power and polarization) to process measurables (material removal rate and surface roughness), and demonstrates the potential for rapid prototyping and direct manufacturing of: (a) rotationally symmetric components based on ablative ceramics such as Si3N4 and (b) graphite fuel cell plenumsMechanical Engineerin

Evaluation of Nb-base alloys for the divertor structure in fusion reactors

Argonne National Laboratory is currently positioned to provide access to high-performance regional and national networks. Much of the impetus for this effort is the anticipated needs of the upcoming experimental program at the APS. Some APS Collaborative Access Teams (CATs) are already pressing for network speed improvements and security enhancements. Requirements range from the need for high data rate, secure transmission of experimental data to the desire to establish a ``virtual experimental environment`` at their home institution. In the near future, 155 Megabit/sec (Mb/s) national and regional asynchronous transfer mode (ATM) networks will be operational and available to APS users. Full-video teleconferencing, virtual presence operation of experiments, and high-speed, secure transmission of data are being tested, and in some cases, will be operational. We expect these efforts to enable a substantial improvement in the speed of processing experimental results as well as an increase in convenience to the APS experimentalist

Slit-bearing gastropods in the Jane Longstaff Collection at the Natural History Museum, London from the Visean (Carboniferous) of Dalry, Ayrshire, Scotland

Natural history museums house numerous previously undescribed species and unknown information hidden in their collections. We describe lower Carboniferous slit-bearing gastropods (order Pleurotomariida, subclass Vetigastropoda; and family Goniasmatidae, subclass Caenogastropoda) from previously unreported gastropod collections made by Jane Longstaff (Jane Donald), one of the pioneering paleontologists of Paleozoic gastropods in the late nineteenth and early twentieth centuries. The gastropods were collected from the Lower Limestone Formation (Visean, Brigantian) near Dalry, Ayrshire, Scotland. The collection consists largely of microgastropods, many of which are unusually well-preserved including delicate ornament and protoconchs (larval shells). Three new pleurotomariidan species are described—Biarmeaspira heidelbergerae new species, Neilsonia seussae new species, Tapinotomaria longstaffae new species—in addition to seven species belonging to Borestus Thomas, 1940, Stegocoelia (Stegocoelia) Donald, 1889, Stegocoelia (Hypergonia) Donald, 1892, Donaldospira Batten, 1966, and Platyzona Knight, 1945. The caenogastropod-type protoconch is documented for the first time in Hypergonia, which is therefore placed in Goniasmatidae. The new data confirm that Neilsonia Thomas, 1940 (type genus of Neilsoniinae) belongs to Pleurotomariida and is distinct from the morphologically convergent Peruvispira Chronic, 1949 (Goniasmatidae). The selenizone morphology is identical in Biarmeaspira Mazaev, 2006 and Baylea de Koninck, 1883 during their early ontogeny, and Biarmeaspira develops an angulation on the selenizone (the diagnostic feature) in late ontogeny. This corroborates earlier suggestions that Biarmeaspira evolved from Baylea. Biarmeaspira heidelbergerae n. sp. is the first Carboniferous record of Biarmeaspira, which was previously only known from the Permian. The angulated selenizone evidently evolved several times in Pleurotomariida and the repeated appearance of this character in different groups (e.g., Phymatopleuridae, Eotomariidae, Pleurotomariidae) needs further studies using phylogenetic methods

Mapping submarine glacial landforms using acoustic methods

The mapping of submarine glacial landforms is largely dependent on marine geophysical survey methods capable of imaging the seafloor and sub-bottom through the water column. Full global coverage of seafloor mapping, equivalent to that which exists for the Earth's land surface, has, to date, only been achieved by deriving bathymetry from radar altimeters on satellites such as GeoSat and ERS-1 (Smith & Sandwell 1997). The horizontal resolution is limited by the footprint of the satellite sensors and the need to average out local wave and wind effects, resulting in a cell size of about 15 km (Sandwell et al. 2001). A further problem in high latitudes is that the altimeter data are extensively contaminated by the presence of sea ice, which degrades the derived bathymetry (McAdoo & Laxon 1997). Consequently, the satellite altimeter method alone is not suitable for mapping submarine glacial landforms, given that their morphological characterization usually requires a much finer level of detail. Acoustic mapping methods based on marine echo-sounding principles are currently the most widely used techniques for mapping submarine glacial landforms because they are capable of mapping at a much higher resolution

Impact of chronic consumption of dairy products varying in fatty acid composition on postprandial lipid responses: preliminary insights from the RESET study

Impact of chronic consumption of dairy products varying in fatty acid composition on postprandial lipid responses: preliminary insights from the RESET stud

Realistic simulations of single-spin nondemolition measurement by magnetic resonance force microscopy

A requirement for many quantum computation schemes is the ability to measure single spins. This paper examines one proposed scheme: magnetic resonance force microscopy, including the effects of thermal noise and back-action from monitoring. We derive a simplified equation using the adiabatic approximation, and produce a stochastic pure state unraveling which is useful for numerical simulations.Comment: 33 pages LaTeX, 9 figure files in EPS format. Submitted to Physical Review

Spin-Orbit Effects in the Excitation of Proton and Neutron States in the (p,p') Reaction at 160 MeV, 120 MeV, and 95 MeV

Supported by the National Science Foundation and Indiana Universit

An update on the Hirsch conjecture

The Hirsch conjecture was posed in 1957 in a letter from Warren M. Hirsch to George Dantzig. It states that the graph of a d-dimensional polytope with n facets cannot have diameter greater than n - d. Despite being one of the most fundamental, basic and old problems in polytope theory, what we know is quite scarce. Most notably, no polynomial upper bound is known for the diameters that are conjectured to be linear. In contrast, very few polytopes are known where the bound $n-d$ is attained. This paper collects known results and remarks both on the positive and on the negative side of the conjecture. Some proofs are included, but only those that we hope are accessible to a general mathematical audience without introducing too many technicalities.Comment: 28 pages, 6 figures. Many proofs have been taken out from version 2 and put into the appendix arXiv:0912.423

Infection prevention practices in the Netherlands: results from a National Survey

Objective: To examine the extent to which acute care hospitals in the Netherlands have adopted recommended practices to prevent catheter-associated urinary tract infection (CAUTI), central line-associated bloodstream infection (CLABSI), ventilator-associated pneumonia (VAP), and Clostridioides difficile infection (CDI). Methods: Between 18 July 2017 and 31 October 2017, we surveyed the infection prevention teams of all acute care hospitals in the Netherlands. The survey instrument was based on the 'Translating Healthcare-Associated Infection Prevention Research into Practice' (TRIP) questionnaire and adapted to the Dutch context. Descriptive statistics were used to examine the reported regular use of CAUTI, CLABSI, VAP, and CDI prevention practices as well as the hospital characteristics. Results: Out of 72 eligible hospitals, 47 (65.3%) responded. Surveillance systems for monitoring CAUTI, CLABSI, VAP, and CDI were present in 17.8, 95.4, 26.2, and 77.3% of hospitals, respectively. Antimicrobial stewardship programs have been established in 91.5% of participating hospitals. For CAUTI, the majority of hospitals regularly used aseptic technique during catheter insertion (95%) and portable bladder ultrasound scanners (86.1%). Intermittent catheterization and catheter stop-orders were regularly used by 65.8 and 62.2% of hospitals. For CLABSI, all hospitals regularly used maximum sterile barrier precautions and chlorhexidine gluconate for insertion site antisepsis. Avoidance of the femoral site for central line insertions was regularly used by 65.9% of hospitals. Urinary catheters and central-lines impregnated with antibiotics or antiseptics were rarely used (≤ 5%). Selective decontamination strategies for preventing VAP were used in 84% of hospitals. With the exception of disposable thermometers (31.8%), all prevention practices to prevent CDI were regularly used by more