Restorative Dentistry: Dental composite depth of cure with halogen and blue light emitting diode technology

Objectives To test the hypothesis that a blue light emitting diode (LED) light curing unit (LCU) can produce an equal dental composite depth of cure to a halogen LCU adjusted to give an irradiance of 300 mWcm–2 and to characterise the LCU's light outputs. Materials and methods Depth of cure for three popular composites was determined using a penetrometer. The Student's t test was used to analyse the depth of cure results. A power meter and a spectrometer measured the light output. Results The spectral distribution of the LCUs differed strongly. The irradiance for the LED and halogen LCUs were 290 mWcm–2 and 455 mWcm–2, when calculated from the scientific power meter measurements. The LED LCU cured all three dental composites to a significantly greater (P < 0.05) depth than the halogen LCU. Conclusions An LED LCU with an irradiance 64% of a halogen LCU achieved a significantly greater depth of cure. The LCU's spectral distribution of emitted light should be considered in addition to irradiance as a performance indicator. LED LCUs may have a potential for use in dental practice because their performance does not significantly reduce with time as do conventional halogen LCUs

Spatially and Intertemporally Efficient Waste Management: The Costs of Interstate Flow Control

We examine the intertemporal allocation of the solid waste of cities within the United States to spatially distributed landfills and incinerators, taking into account that capacity at existing and potential landfills is scarce. Amendments have been proposed to restrict waste flows between states by means of quotas and surcharges. We assess the aggregate surplus loss (and its regional distribution) resulting from proposed policies. In addition, we find that limitations on the size of shipments to any one state can have the perverse effect of substantially increasing interstate waste shipments as states export smaller volumes to more destinations.Solid Waste, Efficiency, Hotelling

MegaPipe: the MegaCam image stacking pipeline at the Canadian Astronomical Data Centre

This paper describes the MegaPipe image processing pipeline at the Canadian Astronomical Data Centre. The pipeline combines multiple images from the MegaCam mosaic camera on CFHT and combines them into a single output image. MegaPipe takes as input detrended MegaCam images and does a careful astrometric and photometric calibration on them. The calibrated images are then resampled and combined into image stacks. The astrometric calibration of the output images is accurate to within 0.15 arcseconds relative to external reference frames and 0.04 arcseconds internally. The photometric calibration is good to within 0.03 magnitudes. The stacked images and catalogues derived from these images are available through the CADC website:Comment: Data available at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/megapipe/index.htm

BSE, U.S. Beef Trade and Cattle Feeding Industry

A brief review of the beef and cattle market following the diagnosis of Bovine Spongiform Encephalopathy (BSE) in Canada and U.S. in 2003 is conducted. The focus is on the recent changes in the beef market experienced by major exporting and importing countries with special emphasis on the beef trade and cattle industry in the U.S. A single case of BSE in the U.S. has significantly disrupted global beef trade. Many countries banned beef imports from the U.S. and Canada. Continuation of these bans through 2004, particularly for the U.S., resulted in reduced beef exports. Brazil has become the number one beef exporter with estimated exports of 1.47 million tons in 2004 and is forecast to export 1.62 million tons in 2005. U.S. is the largest beef importer in the world. U.S. beef exports were a record 1.143 million tons in 2003. Beef exports from the U.S. for 2004 have been 0.202 million tons, just 17.7 percent of 2003 exports. The value of beef export losses for 2004 has been estimated as $2.73 billion. U.S. is forecast to export 0.272 million tons in 2005, representing a 35 percent increase over 2004. However, the beef export forecast for 2005 is still far below the pre-BSE levels. On the other hand U.S. beef imports have increased from 1.36 million tons in 2003 to 1.63 million tons in 2004. Imports are expected to reach 1.7 million tons in 2005. The lack of Canadian beef and live cattle imports, in conjunction with already tight U.S. supplies and strong demand, drove both beef and cattle prices up in the latter part of 2003. However, a decline of 29 percent in beef prices was experienced from December 2003 until March 2004 after the diagnosis of BSE in the U.S. BSE has also impacted live cattle trade, especially among the North American Free Trade Agreement (NAFTA) partners.International Relations/Trade,

Do Firms Smooth the Seasonal in Production in a Boom? Theory and Evidence

Using disaggregated production data we show that the size of seasonal cycles changes significantly over the course of the business cycle. In particular, during periods of high economy-wide activity, some industries smooth seasonal fluctuations while others exaggerate them. We interpret this finding using a simple analytical model that describes the conditions under which seasonal and cyclical fluctuations can be separated. Our model implies that seasonal fluctuations can safely be disentangled from cyclical fluctuations only when the marginal cost of production is linear, and the variation in demand and cost satisfy certain (restrictive) conditions. The model also suggests that inventory movements can be used to isolate the role of demand shifts in generating any interaction between seasonal cycles and business cycles. Thus, the empirical analysis involves studying the variation in seasonally unadjusted patterns of production and inventory accumulation over different phases of the business cycle. Our finding that seasonals shrink during booms and that firms carry more inventories into high sales seasons during a boom leads us to conclude that for several industries, marginal cost slopes up at an increasing rate. Conversely, in a couple of industries we find that seasonal swings in production are exaggerated during booms and that inventories are drawn down prior to high sales seasons, suggesting that marginal costs curves flatten as production increases. Overall, we find considerable evidence that there are non-linear interactions between business cycles and seasonal cycles.

(Sp)-1-Diphenylphosphanyl-2-{(S)-[2-(diphenylphosphanyl)phenyl]hydroxymethyl}ferrocene

The absolute configuration of the title compound, [Fe(C5H5)(C36H29OP2)], is Sp at the ferrocene group and S at the asymmetric C atom. Both P atoms have a trigonal-pyramidal conformation. There is a short intramolecular C-H...P contact with an H...P distance of 2.56 Å. The hydroxy group is involved in an intramolecular O-H...[pi]phenyl interaction. The crystal packing shows five very weak intermolecular C-H...[pi] contacts, with H...Cg distances between 3.26 and 3.39 Å (Cg is the centroid of a phenyl or cyclopentadienyl ring). Key indicators: single-crystal X-ray study; T = 162 K; mean &#963;(C–C) = 0.004 Å; R factor = 0.038; wR factor = 0.083; data-to-parameter ratio = 22.3

Commercialization and Human Settlement of the Moon and Cislunar Space A Look Ahead at the Possibilities over the Next 50 Years

Over 50 years have passed since the movie 2001: A Space Odyssey debuted in April 1968. In the film, Dr. Heywood Floyd flies to a large artificial gravity space station orbiting Earth aboard a commercial space plane. He then embarks on a commuter flight to the Moon arriving there 25hours later. Today, on the 50th anniversary of the Apollo 11 lunar landing, the images portrayed in 2001 still remain well beyond our capabilities. This paper examines key technologies and systems (in-situ resource utilization, fission power, advanced chemical and nuclear propulsion),and orbiting infrastructure elements (providing a propellant depot and cargo transfer function),that could be developed by NASA and the private sector in future decades allowing the operational capabilities presented in 2001 to be achieved, albeit on a more spartan scale. Lunar derived propellants (LDPs) will be essential to reducing the launch mass requirements from Earth and developing a reusable lunar transportation system (LTS) that can allow initial outposts to evolve into settlements supporting a variety of commercial activities like in-situ propellant production. Deposits of icy regolith found within permanently shadowed craters at the lunar pole scan supply the feedstock material to produce liquid oxygen (LO2) and hydrogen (LH2) propellan tneeded by surface-based lunar landing vehicles (LLVs) using chemical rocket engines. Along the Moon's nearside equatorial corridor, iron oxide-rich volcanic glass beads from vast pyroclasticdeposits, together with mare regolith, can provide the materials to produce lunar-derived LO2plus other important solar wind implanted (SWI) volatiles, including H2 and helium-3. Mega watt classfission power systems will be essential for providing continuous "24/7" power to LLVs will provide cargo and passenger "orbit-to-surface" access and willalso be used to transport LDP to Space Transportation Nodes (STNs) located in lunar polar(LPO) and equatorial orbits (LLO). Spaced-based, reusable lunar transfer vehicles (LTVs),operating between STNs in low Earth orbit (LEO), LLO, and LPO, and able to refuel with LDPs,can offer unique mission capabilities including short transit time crewed cargo transports. Even acommuter shuttle service similar to that portrayed in 2001 appears possible, allowing 1-way trip times to and from the Moon as short as 24 hours. The performance of LTVs using both RL10B-2chemical rockets, and a variant of the nuclear thermal rocket (NTR), the LO2-Augmented NTR(LANTR), are examined and compared. The bipropellant LANTR engine utilizes its divergent nozzle section as an afterburner into which oxygen is injected and supersonically combusted with reactor-heated hydrogen emerging from the engine's sonic throat. If only 1% of the LDP obtained from icy regolith, volcanic glass, and SWI volatile deposits were available for use in lunar orbit,such a supply could support routine commuter flights to the Moon for many thousands of years!This paper provides a look ahead at what might be possible in the not too distant future,quantifies the operational characteristics of key in-space and surface technologies and systems,and provides conceptual designs for the various architectural elements discussed

An Exonic Splicing Enhancer within a Bidirectional Coding Sequence Regulates Alternative Splicing of an Antisense mRNA

The discovery of increasing numbers of genes with overlapping sequences highlights the problem of expression in the context of constraining regulatory elements from more than one gene. This study identifies regulatory sequences encompassed within two genes that overlap in an antisense orientation at their 3’ ends. The genes encode the α-thyroid hormone receptor gene (TRα or NR1A1) and Rev-erbα (NR1D1). In mammals TRα pre-mRNAs are alternatively spliced to yield mRNAs encoding functionally antagonistic proteins: TRα1, an authentic thyroid hormone receptor; and TRα2, a non-hormone-binding variant that acts as a repressor. TRα2-specific splicing requires two regulatory elements that overlap with Rev-erbα sequences. Functional mapping of these elements reveals minimal splicing enhancer elements that have evolved within the constraints of the overlapping Rev-erbα sequence. These results provide insight into the evolution of regulatory elements within the context of bidirectional coding sequences. They also demonstrate the ability of the genetic code to accommodate multiple layers of information within a given sequence, an important property of the code recently suggested on theoretical grounds

Quantum State Separation, Unambiguous Discrimination and Exact Cloning

Unambiguous discrimination and exact cloning reduce the square-overlap between quantum states, exemplifying the more general type of procedure we term state separation. We obtain the maximum probability with which two equiprobable quantum states can be separated by an arbitrary degree, and find that the established bounds on the success probabilities for discrimination and cloning are special cases of this general bound. The latter also gives the maximum probability of successfully producing N exact copies of a quantum system whose state is chosen secretly from a known pair, given M initial realisations of the state, where N>M. We also discuss the relationship between this bound and that on unambiguous state discrimination.Comment: RevTeX, 5 pages postscrip