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The stability of structural materials in extreme nuclear reactor environments—with high temperature, high radiation and corrosive media—directly affects the lifespan of the reactor. In such extreme environments, an oxide layer on the metal surface acts as a passive layer protecting the metal underneath from corrosion. To predict the irradiation effect on the metal layer in these metal/oxide bilayers, nondestructive depth-resolved positron annihilation lifetime spectroscopy (PALS) and complementary transmission electron microscopy (TEM) were used to investigate small-scale defects created by ion irradiation in an epitaxially grown (100) Fe film capped with a 50 nm Fe2O3 oxide layer. In this study, the evolution of induced vacancies was monitored, from individual vacancy formation at low doses—10^-5 dpa—to larger vacancy cluster formation at increasing doses, showing the sensitivity of positron annihilation spectroscopy techniques. Furthermore, PALS measurements reveal how the presence of a metal-oxide interface modifies the distribution of point defects induced by irradiation. TEM measurements show that irradiation induced dislocations at the interface is the mechanism behind the redistribution of point defects causing their accumulation close to the interface. This work demonstrates that the passive oxide layers formed during corrosion impact the distribution and accumulation of radiation induced defects in the metal underneath, and emphasizes that the synergistic impact of radiation and corrosion will differ from their individual impacts.

The stability of structural materials in extreme nuclear reactor environments—with high temperature, high radiation and corrosive media—directly affects the lifespan of the reactor. In such extreme environments, an oxide layer on the metal surface acts as a passive layer protecting the metal underneath from corrosion. To predict the irradiation effect on the metal layer in these metal/oxide bilayers, nondestructive depth-resolved positron annihilation lifetime spectroscopy (PALS) and complementary transmission electron microscopy (TEM) were used to investigate small-scale defects created by ion irradiation in an epitaxially grown (100) Fe film capped with a 50 nm Fe2O3 oxide layer. In this study, the evolution of induced vacancies was monitored, from individual vacancy formation at low doses—10^-5 dpa—to larger vacancy cluster formation at increasing doses, showing the sensitivity of positron annihilation spectroscopy techniques. Furthermore, PALS measurements reveal how the presence of a metal-oxide interface modifies the distribution of point defects induced by irradiation. TEM measurements show that irradiation induced dislocations at the interface is the mechanism behind the redistribution of point defects causing their accumulation close to the interface. This work demonstrates that the passive oxide layers formed during corrosion impact the distribution and accumulation of radiation induced defects in the metal underneath, and emphasizes that the synergistic impact of radiation and corrosion will differ from their individual impacts.

Molecular emission was imaged with ALMA from numerous components near and within bright H2-emitting knots and absorbing dust globules in the Crab Nebula. These observations provide a critical test of how energetic photons and particles produced in a young supernova remnant interact with gas, cleanly differentiating between competing models. The four fields targeted show contrasting properties but within them, seventeen distinct molecular clouds are identified with CO emission; a few also show emission from HCO+, SiO and/or SO. These observations are compared with Cloudy models of these knots. It has been suggested that the Crab filaments present an exotic environment in which H2 emission comes from a mostly-neutral zone probably heated by cosmic rays produced in the supernova surrounding a cool core of molecular gas. Our model is consistent with the observed CO J=3-2 line strength. These molecular line emitting knots in the Crab present a novel phase of the ISM representative of many important astrophysical environments., Comment: ApJ in press, comments welcome

Molecular emission was imaged with ALMA from numerous components near and within bright H2-emitting knots and absorbing dust globules in the Crab Nebula. These observations provide a critical test of how energetic photons and particles produced in a young supernova remnant interact with gas, cleanly differentiating between competing models. The four fields targeted show contrasting properties but within them, seventeen distinct molecular clouds are identified with CO emission; a few also show emission from HCO+, SiO and/or SO. These observations are compared with Cloudy models of these knots. It has been suggested that the Crab filaments present an exotic environment in which H2 emission comes from a mostly-neutral zone probably heated by cosmic rays produced in the supernova surrounding a cool core of molecular gas. Our model is consistent with the observed CO J=3-2 line strength. These molecular line emitting knots in the Crab present a novel phase of the ISM representative of many important astrophysical environments., Comment: ApJ in press, comments welcome

Language studies in Australian universities have a long and complex history—that differs according to such things as language, institution, national imperative, etc… One essential but often overlooked part of the discipline of languages and cultures in our universities is recording and understanding precisely that history. Recording how and why specific language programs were established, for instance, is important for establishing a permanent record of historical continuity and for understanding the past and the present of language programs in the Australian tertiary sector, as well as their possible interconnections and differences. In this chapter we describe a pilot study exploring the beginnings of Italian language teaching and programs in tertiary institutions in Melbourne—and especially their somewhat inorganic expansion across the city from the late 1950s, into the 1980s and beyond. We are specifically interested in trying to understand how and why Italian language (and Italian Studies more generally) came to be taught in different universities in that city. While we present some of our early findings, including: (a) the effect of institutional type; and (b) the useful assistance of colleagues in other languages, at the same time we also have an interest in mapping out and reflecting on the methodology adopted and the challenges faced. It is hoped that our pilot study might in this way assist and encourage colleagues at other institutions to record the history of language studies in their individual institutions or cities, but who might wonder how to approach the issue in terms of possible data collection and analysis.

Osteoarthritis is highly prevalent, disabling and costly to the person and the community. The burden of this chronic condition is predicted to increase dramatically over the coming decades. Healthcare spending on osteoarthritis is unsustainable and action is needed to improve care delivery. At present, there is an over-emphasis on surgical and pharmacological interventions, despite evidence supporting conservative treatments such as exercise, weight loss and education. While clinical guidelines provide recommendations regarding best practice (ie, what to do), they fail to address how to operationalise these recommendations into clinical practice. Models of care (MoCs) can help bridge the evidence-practice gap by outlining evidence-informed interventions as well as how to implement them within a local system. However, New Zealand has no osteoarthritis MoC. The Mobility Action Programme, funded by the Ministry of Health, is delivering evidence-informed, multi-disciplinary care for osteoarthritis through local initiatives. Although the programme remains under evaluation it presents an opportunity to inform development of a national osteoarthritis MoC for New Zealand. A policy framework, such as a MoC, is needed to scale up successful programs and deliver best practice care nationwide. Ultimately, addressing the burden of osteoarthritis will require system-wide approaches involving public policy responses to target primary prevention.

Helium implantation from transmutation reactions is a major cause of embrittlement and dimensional instability of structural components in nuclear energy systems. Development of novel materials with improved radiation resistance, which is of the utmost importance for progress in nuclear energy, requires guidelines to arrive at favorable parameters more efficiently. Here, we present a methodology that can be used for the design of radiation tolerant materials. We used synchrotron X-ray reflectivity to nondestructively study radiation effects at buried interfaces and measure swelling induced by He implantation in Cu/Nb multilayers. The results, supported by transmission electron microscopy, show a direct correlation between reduced swelling in nanoscale multilayers and increased interface area per unit volume, consistent with helium storage in Cu/Nb interfaces in forms that minimize dimensional changes. In addition, for Cu/Nb layers, a linear relationship is demonstrated between the measured depth-dependent swelling and implanted He density from simulations, making the reflectivity technique a powerful tool for heuristic material design., United States. Dept. of Energy. Office of Basic Energy Sciences (Energy Frontiers Research Center. Award 2008LANL1026), United States. Dept. of Energy (Grant DE-AC02-98CH10886)

The structure of metal/oxide interfaces is important to the radiation resistance of oxide dispersion-strengthened steels. We find evidence of gradual variations in stoichiometry and magnetization across a Fe/Y[subscript 2]O[subscript 3] metal/oxide heterophase interface using neutron and x-ray reflectometry. These findings suggest that the Fe/Y[subscript 2]O[subscript 3] interface is a transitional zone approximately ∼64 Å-thick containing mixtures or compounds of Fe, Y, and O. Our results illustrate the complex chemical and magnetic nature of Fe/oxide interfaces and demonstrate the utility of combined neutron and x-ray techniques as tools for characterizing them., Los Alamos National Laboratory. Laboratory Directed Research and Development Program (Project 20130118DR), United States. Dept. of Energy. Office of Basic Energy Sciences (Los Alamos National Laboratory. Contract DE-AC52-06NA25396)

We use neutron reflectometry to find the critical helium (He) fluence required to form He bubbles at interfaces between fcc and bcc metals. Our findings are in agreement with previous experimental as well as modeling results and provide evidence for the presence of stable He platelets at fcc-bcc interfaces prior to bubble formation. The stable storage of He in interfacial platelets may provide the basis for the design of materials with increased resistance to He-induced degradation., United States. Dept. of Energy. Office of Basic Energy Sciences (Center for Materials in Irradiation and Mechanical Extremes. Award 2008LANL 1026), United States. Dept. of Energy. Office of Basic Energy Sciences (Los Alamos National Laboratory. Contract DE-AC52-06NA25396)

Composite laminates on the nanoscale have shown superior hardness and toughness, but little is known about their high temperature behavior. The mechanical properties (elastic modulus and hardness) were measured as a function of temperature by means of nanoindentation in Al/SiC nanolaminates, a model metal–ceramic nanolaminate fabricated by physical vapor deposition. The influence of the Al and SiC volume fraction and layer thicknesses was determined between room temperature and 150 °C and, the deformation modes were analyzed by transmission electron microscopy, using a focused ion beam to prepare cross-sections through selected indents. It was found that ambient temperature deformation was controlled by the plastic flow of the Al layers, constrained by the SiC, and the elastic bending of the SiC layers. The reduction in hardness with temperature showed evidence of the development of interface-mediated deformation mechanisms, which led to a clear influence of layer thickness on the hardness.

This publication focusses on the status of biomethane (which includes upgraded biogas and bio-SNG)production, grid injection and use in different IEA countries. It also illustrates the options and needs for the development of biomethane supply strategies with the focus on improved trade. Further, an overview of expected future development of the biomethane sector is given.As part of the study, results from a dedicated questionnaire were assessed to get an insight into the opportunities and barriers for biogas and biomethane in the market in a number of countries. This study has been compiled as a joint effort by experts from the Task 37 and 40 of the IEA Bioenergy Implementing Agreement.

Composite laminates on the nanoscale have shown superior hardness and toughness, but little is known about their high temperature behavior. The mechanical properties (elastic modulus and hardness) were measured as a function of temperature by means of nanoindentation in Al/SiC nanolaminates, a model metal–ceramic nanolaminate fabricated by physical vapor deposition. The influence of the Al and SiC volume fraction and layer thicknesses was determined between room temperature and 150 °C and, the deformation modes were analyzed by transmission electron microscopy, using a focused ion beam to prepare cross-sections through selected indents. It was found that ambient temperature deformation was controlled by the plastic flow of the Al layers, constrained by the SiC, and the elastic bending of the SiC layers. The reduction in hardness with temperature showed evidence of the development of interface-mediated deformation mechanisms, which led to a clear influence of layer thickness on the hardness.

This publication focusses on the status of biomethane (which includes upgraded biogas and bio-SNG)production, grid injection and use in different IEA countries. It also illustrates the options and needs for the development of biomethane supply strategies with the focus on improved trade. Further, an overview of expected future development of the biomethane sector is given.As part of the study, results from a dedicated questionnaire were assessed to get an insight into the opportunities and barriers for biogas and biomethane in the market in a number of countries. This study has been compiled as a joint effort by experts from the Task 37 and 40 of the IEA Bioenergy Implementing Agreement.

Biomethane is a promising renewable energy carrier, scoring very well in terms of sustainability, and with great potential in the transformation of the fossil fuel based energy market to a renewable based one. In a joint IEA Bioenergy study a group of scientists examined the state of the art, as well as the development of the biomethane market in selected IEA member countries. Due to its similar properties, biomethane can be used as a substitute for natural gas and benefits from the existing infrastructure and applications. Nevertheless, biomethane is far from market penetration. Within this study a survey was performed with the aim to represent the current market situation of biomethane. A questionnaire was distributed to stakeholders within the participating member countries in the study; around 100 replies were received. A common conclusion is the missing policy framework, acceptance and support which hinder further market development. Further, according to the results of the questionnaire, a reliable and sufficient support for biomethane and the implementation of a biomethane standard would open opportunities and lead to a stable market.

We present a range of steady-state photoionization simulations, corresponding to different assumed shell geometries and compositions, of the unseen postulated rapidly expanding outer shell to the Crab Nebula. The properties of the shell are constrained by the mass that must lie within it, and by limits to the intensities of hydrogen recombination lines. In all cases the photoionization models predict very strong emission from high ionization lines that will not be emitted by the Crab's filaments, alleviating problems with detecting these lines in the presence of light scattered from brighter parts of the Crab. The NIR [Ne VI] $\lambda$7.652 $\mu$m line is a particularly good case; it should be dramatically brighter than the optical lines commonly used in searches. The C IV $\lambda1549\AA$ doublet is predicted to be the strongest absorption line from the shell, which is in agreement with HST observations. We show that the cooling timescale for the outer shell is much longer than the age of the Crab, due to the low density. This means that the temperature of the shell will actually "remember" its initial conditions. However, the recombination time is much shorter than the age of the Crab, so the predicted level of ionization should approximate the real ionization. In any case, it is clear that IR observations present the best opportunity to detect the outer shell and so guide future models that will constrain early events in the original explosion., Comment: Accepted by ApJ

We present a range of steady-state photoionization simulations, corresponding to different assumed shell geometries and compositions, of the unseen postulated rapidly expanding outer shell to the Crab Nebula. The properties of the shell are constrained by the mass that must lie within it, and by limits to the intensities of hydrogen recombination lines. In all cases the photoionization models predict very strong emission from high ionization lines that will not be emitted by the Crab's filaments, alleviating problems with detecting these lines in the presence of light scattered from brighter parts of the Crab. The NIR [Ne VI] $\lambda$7.652 $\mu$m line is a particularly good case; it should be dramatically brighter than the optical lines commonly used in searches. The C IV $\lambda1549\AA$ doublet is predicted to be the strongest absorption line from the shell, which is in agreement with HST observations. We show that the cooling timescale for the outer shell is much longer than the age of the Crab, due to the low density. This means that the temperature of the shell will actually "remember" its initial conditions. However, the recombination time is much shorter than the age of the Crab, so the predicted level of ionization should approximate the real ionization. In any case, it is clear that IR observations present the best opportunity to detect the outer shell and so guide future models that will constrain early events in the original explosion., Comment: Accepted by ApJ

Several parameters indicative of whole muscle aerobic and anaerobic metabolism were compared in heart, diaphragm and two locomotory muscles of sheep (Ovis aries) ranging from 90 days gestation to adult animals. Aerobic metabolism was assessed from myoglobin content, anaerobic metabolism from the pH buffering capacity and the balance between the two from the properties of the lactate dehydrogenase isozymes. We expected the diaphragm and heart, as the two vital pumps of the body, to have substantial aerobic capacity at birth. For the left ventricular myocardium this appears to be true, with the myoglobin level at birth averaging 69% of the adult value. However, the diaphragm had only 15% of the adult myoglobin level, a level similar to that in vastus lateralis and medial gastrocnemius muscles. In the first 18 days postnatally, myoglobin levels in the diaphragm did not change. Anaerobic capacity, as indicated by pH buffering capacity, increased in all four muscles during fetal life, reaching from 69-96% of adult values on day 1 after birth. A rapid increase in pH buffering capacity occurred in all four muscles in the first 6 days postnatally suggesting that anaerobic glycolysis is important to the newborn. We conclude that the work done by the fetal heart leads to the development of a high aerobic capacity by birth, but the activity of the fetal diaphragm does not have this effect.

Understanding how molecules and dust might have formed within a rapidly expanding young supernova remnant is important because of the obvious application to vigorous supernova activity at very high redshift. In previous papers, we found that the H2 emission is often quite strong, correlates with optical low-ionization emission lines, and has a surprisingly high excitation temperature. Here we study Knot 51, a representative, bright example, for which we have available long slit optical and NIR spectra covering emission lines from ionized, neutral, and molecular gas, as well as HST visible and SOAR Telescope NIR narrow-band images. We present a series of CLOUDY simulations to probe the excitation mechanisms, formation processes and dust content in environments that can produce the observed H2 emission. We do not try for an exact match between model and observations given Knot 51's ambiguous geometry. Rather, we aim to explain how the bright H2 emission lines can be formed from within the volume of Knot 51 that also produces the observed optical emission from ionized and neutral gas. Our models that are powered only by the Crab's synchrotron radiation are ruled out because they cannot reproduce the strong, thermal H2 emission. The simulations that come closest to fitting the observations have the core of Knot 51 almost entirely atomic with the H2 emission coming from just a trace molecular component, and in which there is extra heating. In this unusual environment, H2 forms primarily by associative detachment rather than grain catalysis. In this picture, the 55 H2-emitting cores that we have previously catalogued in the Crab have a total mass of about 0.1 M_sun, which is about 5% of the total mass of the system of filaments. We also explore the effect of varying the dust abundance. We discuss possible future observations that could further elucidate the nature of these H2 knots., Comment: 51 pages, 15 figures, accepted for publication in MNRAS, revised Figure 12 results unchanged

(abridged) We study the consequence of star formation (SF) in an self-gravity dominated accretion disk in quasars. The warm skins of the SF disk are governed by the radiation from the inner part of the accretion disk to form Compton atmosphere (CAS). The CAS are undergoing four phases to form broad line regions. Phase I is the duration of pure accumulation supplied by the SF disk. During phase II clouds begin to form due to line cooling and sink to the SF disk. Phase III is a period of preventing clouds from sinking to the SF disk through dynamic interaction between clouds and the CAS. Finally, phase IV is an inevitable collapse of the entire CAS through line cooling. This CAS evolution drives the episodic appearance of BLRs. Geometry and dynamics of BLRs can be self-consistently derived from the thermal instability of the CAS during phases II and III by linear analysis. The metallicity gradient of SF disk gives rise to different properties of clouds from outer to inner part of BLRs. We find that clouds have column density N_H < 10^22cm^{-2} in the metal-rich regions whereas they have N_H > 10^22 cm^{-2} in the metal-poor regions. The metal-rich clouds compose the high ionization line (HIL) regions whereas the metal-poor clouds are in low ionization line (LIL) regions. Metal-rich clouds in HIL regions will be blown away by radiation pressure, forming the observed outflows. The LIL regions are episodic due to the mass cycle of clouds with the CAS in response to continuous injection by the SF disk, giving rise to different types of AGNs. Based on SDSS quasar spectra, we identify a spectral sequence in light of emission line equivalent width from Phase I to IV. A key phase in the episodic appearance of the BLRs is bright type II AGNs with no or only weak BLRs. We discuss observational implications and tests of the theoretical predictions of this model., Comment: 27 pages in emulateapj style, 10 figures, Accepted by ApJ 2012

Several parameters indicative of whole muscle aerobic and anaerobic metabolism were compared in heart, diaphragm and two locomotory muscles of sheep (Ovis aries) ranging from 90 days gestation to adult animals. Aerobic metabolism was assessed from myoglobin content, anaerobic metabolism from the pH buffering capacity and the balance between the two from the properties of the lactate dehydrogenase isozymes. We expected the diaphragm and heart, as the two vital pumps of the body, to have substantial aerobic capacity at birth. For the left ventricular myocardium this appears to be true, with the myoglobin level at birth averaging 69% of the adult value. However, the diaphragm had only 15% of the adult myoglobin level, a level similar to that in vastus lateralis and medial gastrocnemius muscles. In the first 18 days postnatally, myoglobin levels in the diaphragm did not change. Anaerobic capacity, as indicated by pH buffering capacity, increased in all four muscles during fetal life, reaching from 69-96% of adult values on day 1 after birth. A rapid increase in pH buffering capacity occurred in all four muscles in the first 6 days postnatally suggesting that anaerobic glycolysis is important to the newborn. We conclude that the work done by the fetal heart leads to the development of a high aerobic capacity by birth, but the activity of the fetal diaphragm does not have this effect.

Many invasive species have evolved behavioural and morphological characteristics that facilitate their dispersal into new areas, but it is unclear how selection on this level of the phenotype filters through to the underlying physiology. Cane toads have been dispersing westward across northern tropical Australia for more than 70 years. Previous studies of cane toads at the invasive front have identified several behavioural, morphological and locomotory characteristics that have evolved to facilitate dispersal of toads. We assessed a range of physiological characteristics associated with locomotory abilities in toads from the long-established, east coast of Australia, from the invasive front, and from a site in between these locations. We measured time to exhaustion and respiratory gases of toads exercising on a treadmill, time to recovery from exhaustion, blood properties (lactate, haematocrit, haemoglobin, red blood cell count, blood cell volume), and muscle properties associated with locomotion (activities of the enzymes citrate synthase and lactate dehydrogenase, and pH buffering capacity). None of the measured physiological parameters supported the hypothesis that toads from the invasive front possess physiological adaptations that facilitate dispersal compared to toads from areas colonised in the past. The strongest difference among the three groups of toads, time to exhaustion, showed exactly the opposite trend; toads from the long-established populations in the east coast had the longest time to exhaustion. Successful colonisers can employ many characteristics to facilitate their dispersal, so the extent to which behaviour, morphology and physiology co-evolve remains an interesting question. However, in the present case at least, behavioural adaptations do not appear to have altered the organism's underlying physiology.

(abridged) We study the consequence of star formation (SF) in an self-gravity dominated accretion disk in quasars. The warm skins of the SF disk are governed by the radiation from the inner part of the accretion disk to form Compton atmosphere (CAS). The CAS are undergoing four phases to form broad line regions. Phase I is the duration of pure accumulation supplied by the SF disk. During phase II clouds begin to form due to line cooling and sink to the SF disk. Phase III is a period of preventing clouds from sinking to the SF disk through dynamic interaction between clouds and the CAS. Finally, phase IV is an inevitable collapse of the entire CAS through line cooling. This CAS evolution drives the episodic appearance of BLRs. Geometry and dynamics of BLRs can be self-consistently derived from the thermal instability of the CAS during phases II and III by linear analysis. The metallicity gradient of SF disk gives rise to different properties of clouds from outer to inner part of BLRs. We find that clouds have column density N_H < 10^22cm^{-2} in the metal-rich regions whereas they have N_H > 10^22 cm^{-2} in the metal-poor regions. The metal-rich clouds compose the high ionization line (HIL) regions whereas the metal-poor clouds are in low ionization line (LIL) regions. Metal-rich clouds in HIL regions will be blown away by radiation pressure, forming the observed outflows. The LIL regions are episodic due to the mass cycle of clouds with the CAS in response to continuous injection by the SF disk, giving rise to different types of AGNs. Based on SDSS quasar spectra, we identify a spectral sequence in light of emission line equivalent width from Phase I to IV. A key phase in the episodic appearance of the BLRs is bright type II AGNs with no or only weak BLRs. We discuss observational implications and tests of the theoretical predictions of this model., Comment: 27 pages in emulateapj style, 10 figures, Accepted by ApJ 2012

Understanding how molecules and dust might have formed within a rapidly expanding young supernova remnant is important because of the obvious application to vigorous supernova activity at very high redshift. In previous papers, we found that the H2 emission is often quite strong, correlates with optical low-ionization emission lines, and has a surprisingly high excitation temperature. Here we study Knot 51, a representative, bright example, for which we have available long slit optical and NIR spectra covering emission lines from ionized, neutral, and molecular gas, as well as HST visible and SOAR Telescope NIR narrow-band images. We present a series of CLOUDY simulations to probe the excitation mechanisms, formation processes and dust content in environments that can produce the observed H2 emission. We do not try for an exact match between model and observations given Knot 51's ambiguous geometry. Rather, we aim to explain how the bright H2 emission lines can be formed from within the volume of Knot 51 that also produces the observed optical emission from ionized and neutral gas. Our models that are powered only by the Crab's synchrotron radiation are ruled out because they cannot reproduce the strong, thermal H2 emission. The simulations that come closest to fitting the observations have the core of Knot 51 almost entirely atomic with the H2 emission coming from just a trace molecular component, and in which there is extra heating. In this unusual environment, H2 forms primarily by associative detachment rather than grain catalysis. In this picture, the 55 H2-emitting cores that we have previously catalogued in the Crab have a total mass of about 0.1 M_sun, which is about 5% of the total mass of the system of filaments. We also explore the effect of varying the dust abundance. We discuss possible future observations that could further elucidate the nature of these H2 knots., Comment: 51 pages, 15 figures, accepted for publication in MNRAS, revised Figure 12 results unchanged

We used K-band spectra to measure the H2 excitation temperatures in six molecular knots associated with the filaments in the Crab Nebula. The temperatures are quite high - in the range T ~ 2000-3000K, just below the H2 dissociation temperature. This is the temperature range over which the H2 1-0 S(1) line at 2.121\mum has its maximum emissivity per unit mass, so there may be many additional H2 cores with lower temperatures that are too faint to detect. We also measured the electron density in adjacent ionized gas, which on the assumption of gas pressure balance indicates densities in the molecular region n_mol ~ 20,000 H baryons cm-3, although this really is just a lower limit since the H2 gas may be confined by other means. The excited region may be just a thin skin on a much more extensive blob of molecular gas that does not have the correct temperature and density to be as easily detectable. At the opposite extreme, the observed knots could consist of a fine mist of molecular gas in which we are detecting essentially all of the H2. Future CO observations could distinguish between these two cases. The Crab filaments serve as the nearby laboratories for understanding the very much larger filamentary structures that have formed in the intracluster medium of cool-core galaxy clusters., Comment: 16 pages, 5 figures

We have carried out a near-infrared, narrow-band imaging survey of the Crab Nebula, in the H2 2.12 micron and Br-gamma 2.17 micron lines, using the Spartan Infrared camera on the SOAR Telescope. Over a 2.8' x 5.1' area that encompasses about 2/3 of the full visible extent of the Crab, we detect 55 knots that emit strongly in the H2 line. We catalog the observed properties of these knots. We show that they are in or next to the filaments that are seen in optical-passband emission lines. Comparison to HST [S II] and [O III] images shows that the H2 knots are strongly associated with compact regions of low-ionization gas. We also find evidence of many additional, fainter H2 features, both discrete knots and long streamers following gas that emits strongly in [S II]. A pixel-by-pixel analysis shows that about 6 percent of the Crab's projected surface area has significant H2 emission that correlates with [S II] emission. We measured radial velocities of the [S II] lambda6716 emission lines from 47 of the cataloged knots and find that most are on the far (receding) side of the nebula. We also detect Br-gamma emission. It is right at the limit of our survey, and our Br-gamma filter cuts off part of the expected velocity range. But clearly the Br-gamma emission has a quite different morphology than the H2 knots, following the long linear filaments that are seen in H-alpha and in [O III] optical emission lines., Comment: Accepted for publication in the ApJS

We used K-band spectra to measure the H2 excitation temperatures in six molecular knots associated with the filaments in the Crab Nebula. The temperatures are quite high - in the range T ~ 2000-3000K, just below the H2 dissociation temperature. This is the temperature range over which the H2 1-0 S(1) line at 2.121\mum has its maximum emissivity per unit mass, so there may be many additional H2 cores with lower temperatures that are too faint to detect. We also measured the electron density in adjacent ionized gas, which on the assumption of gas pressure balance indicates densities in the molecular region n_mol ~ 20,000 H baryons cm-3, although this really is just a lower limit since the H2 gas may be confined by other means. The excited region may be just a thin skin on a much more extensive blob of molecular gas that does not have the correct temperature and density to be as easily detectable. At the opposite extreme, the observed knots could consist of a fine mist of molecular gas in which we are detecting essentially all of the H2. Future CO observations could distinguish between these two cases. The Crab filaments serve as the nearby laboratories for understanding the very much larger filamentary structures that have formed in the intracluster medium of cool-core galaxy clusters., Comment: 16 pages, 5 figures

It has been suggested that the high metallicity generally observed in active galactic nuclei (AGNs) and quasars originates from ongoing star formation in the self-gravitating part of accretion disks around the supermassive black holes. We designate this region as the star forming (SF) disk, in which metals are produced from supernova explosions (SNexp) while at the same time inflows are driven by SNexp-excited turbulent viscosity to accrete onto the SMBHs. In this paper, an equation of metallicity governed by SNexp and radial advection is established to describe the metal distribution and evolution in the SF disk. We find that the metal abundance is enriched at different rates at different positions in the disk, and that a metallicity gradient is set up that evolves for steady-state AGNs. Metallicity as an integrated physical parameter can be used as a probe of the SF disk age during one episode of SMBH activity. In the SF disk, evaporation of molecular clouds heated by SNexp blast waves unavoidably forms hot gas. This heating is eventually balanced by the cooling of the hot gas, but we show that the hot gas will escape from the SF disk before being cooled, and diffuse into the BLRs forming with a typical rate of $\sim 1\sunmyr$. The diffusion of hot gas from a SF disk depends on ongoing star formation, leading to the metallicity gradients in BLR observed in AGNs. We discuss this and other observable consequences of this scenario., Comment: 11 pages, 5 Figures, ApJ, Vol. 737, in press

We have carried out a near-infrared, narrow-band imaging survey of the Crab Nebula, in the H2 2.12 micron and Br-gamma 2.17 micron lines, using the Spartan Infrared camera on the SOAR Telescope. Over a 2.8' x 5.1' area that encompasses about 2/3 of the full visible extent of the Crab, we detect 55 knots that emit strongly in the H2 line. We catalog the observed properties of these knots. We show that they are in or next to the filaments that are seen in optical-passband emission lines. Comparison to HST [S II] and [O III] images shows that the H2 knots are strongly associated with compact regions of low-ionization gas. We also find evidence of many additional, fainter H2 features, both discrete knots and long streamers following gas that emits strongly in [S II]. A pixel-by-pixel analysis shows that about 6 percent of the Crab's projected surface area has significant H2 emission that correlates with [S II] emission. We measured radial velocities of the [S II] lambda6716 emission lines from 47 of the cataloged knots and find that most are on the far (receding) side of the nebula. We also detect Br-gamma emission. It is right at the limit of our survey, and our Br-gamma filter cuts off part of the expected velocity range. But clearly the Br-gamma emission has a quite different morphology than the H2 knots, following the long linear filaments that are seen in H-alpha and in [O III] optical emission lines., Comment: Accepted for publication in the ApJS

In a sub-arcsec near-infrared survey of the Crab Nebula using the new Spartan Infrared Camera, we have found several knots with high surface brightness in the H_2 2.12 micron line and a very large H_2 2.12 micron to Br-gamma ratio. The brightest of these knots has an intensity ratio I(H_2 2.12 micron)/I(Br-gamma) = 18+/-9, which we show sets a lower limit on the ratio of masses in the molecular and recombination (i.e. ionized) zones M_mol / M_rec >/- 0.9, and a total molecular mass within this single knot M_mol >/- 5E-5 M_sun. We argue that the knot discussed here probably is able to emit so strongly in the 2.12 micron line because its physical conditions are better tuned for such emission than is the case in other filaments. It is unclear whether this knot has an unusually large M_mol / M_rec ratio, or if many other Crab filaments also have similar amounts of molecular gas which is not emitting because the physical conditions are not so well tuned., Comment: Accepted for publication in ApJ Letters

In a sub-arcsec near-infrared survey of the Crab Nebula using the new Spartan Infrared Camera, we have found several knots with high surface brightness in the H_2 2.12 micron line and a very large H_2 2.12 micron to Br-gamma ratio. The brightest of these knots has an intensity ratio I(H_2 2.12 micron)/I(Br-gamma) = 18+/-9, which we show sets a lower limit on the ratio of masses in the molecular and recombination (i.e. ionized) zones M_mol / M_rec >/- 0.9, and a total molecular mass within this single knot M_mol >/- 5E-5 M_sun. We argue that the knot discussed here probably is able to emit so strongly in the 2.12 micron line because its physical conditions are better tuned for such emission than is the case in other filaments. It is unclear whether this knot has an unusually large M_mol / M_rec ratio, or if many other Crab filaments also have similar amounts of molecular gas which is not emitting because the physical conditions are not so well tuned., Comment: Accepted for publication in ApJ Letters

We demonstrate piezoresistive transduction of mechanical motion from out-of-plane flexural micromechanical resonators made from stacked thin films. The resonators are fabricated from two highly doped polycrystalline silicon layers separated by an interlayer dielectric. We examine two interlayer materials: thermal silicon dioxide and stoichiometric silicon nitride. We show that via one-time dielectric breakdown, the film stack functions as a vertical piezoresistor effectively transducing the motion of the resonators. We obtain a gauge factor of 5, which is sufficient to detect the resonator motion. The simple film stack constitutes a vertically oriented piezoresistor that is readily integrated with micro- and nanoscale resonators., Published in Applied Physics Letters, v95 article ID 133113, 1 Oct 2009. Sponsored in part by DARPA. Prepared in collaboration with Global Strategies Group, Crofton, MD, and Cornell University, Ithaca, NY.

Chemically modified graphene (CMG) has emerged as a new material whose many attractive properties complement those of pure graphene. Graphene, a single atomic sheet of carbon bonded in a honeycomb lattice, has remarkable physical properties ranging from near-ballistic electron conduction to extremely high mechanical stiffness (more than five times that of steel). Such extreme properties motivate researchers to investigate these materials for use in applications ranging from high-frequency, low-power electronics, to flexible displays, chemical/biological sensors, and high-frequency electromechanical devices. We have developed a process to form large-area, ultra-thin CMG films that enable us to investigate CMG properties and to explore prototype devices. Using these films we have fabricated state-of-the-art chemical sensors and nanomechanical resonators. For chemical sensors, we have increased the sensitivity and reduced the level of noise by tuning the CMG film chemistry. These optimized sensors are capable of real-time detection of explosives and the three main classes of chemical-warfare agents at parts-per-billion concentrations. For nanomechanics, we have utilized chemical modification to produce suspended films under high tension. These high-stiffness, low-mass resonators display quality factors (up to 4000) and figures of merit well exceeding those of pure graphene resonators and are comparable to diamond thin films. Together, these results demonstrate that CMG is an inexpensive, high-performance material that will find application in a wide range of defense and commercial applications., Featured research. Published in 2009 NRL Review, p88-96. The original document contains color images. All DTIC reproductions will be in black and white.

The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

The Orion Bar is one of the nearest and best-studied photodissociation or photon-dominated regions (PDRs). Observations reveal the presence of H2 lines from vibrationally or rotationally excited upper levels that suggest warm gas temperatures (400 to 700 K). However, standard models of PDRs are unable to reproduce such warm rotational temperatures. In this paper we attempt to explain these observations with new comprehensive models which extend from the H+ region through the Bar and include the magnetic field in the equation of state. We adopt the model parameters from our previous paper which successfully reproduced a wide variety of spectral observations across the Bar. In this model the local cosmic-ray density is enhanced above the galactic background, as is the magnetic field, and which increases the cosmic-ray heating elevating the temperature in the molecular region. The pressure is further enhanced above the gas pressure in the H+ region by the momentum transferred from the absorbed starlight. Here we investigate whether the observed H2 lines can be reproduced with standard assumptions concerning the grain photoelectric emission. We also explore the effects due to the inclusion of recently computed H2 + H2, H2 + H and H2 + He collisional rate coefficients., Comment: Accepted for publication in ApJ (34 pages, including 16 figures)

The Orion Bar is one of the nearest and best-studied photodissociation or photon-dominated regions (PDRs). Observations reveal the presence of H2 lines from vibrationally or rotationally excited upper levels that suggest warm gas temperatures (400 to 700 K). However, standard models of PDRs are unable to reproduce such warm rotational temperatures. In this paper we attempt to explain these observations with new comprehensive models which extend from the H+ region through the Bar and include the magnetic field in the equation of state. We adopt the model parameters from our previous paper which successfully reproduced a wide variety of spectral observations across the Bar. In this model the local cosmic-ray density is enhanced above the galactic background, as is the magnetic field, and which increases the cosmic-ray heating elevating the temperature in the molecular region. The pressure is further enhanced above the gas pressure in the H+ region by the momentum transferred from the absorbed starlight. Here we investigate whether the observed H2 lines can be reproduced with standard assumptions concerning the grain photoelectric emission. We also explore the effects due to the inclusion of recently computed H2 + H2, H2 + H and H2 + He collisional rate coefficients., Comment: Accepted for publication in ApJ (34 pages, including 16 figures)

Superior mechanical and optical properties of single crystal (SC) diamond in combination with a chemically inert and bio-compatible surface enable the design and fabrication of novel nanoscale devices for sensing and signal processing applications. In this letter, we present the first fabrication and operation of high-frequency nanomechanical resonators implemented in 100-nm-thick SC diamond films epitaxially grown on SC synthetic diamond. The method of fabrication is based on introducing a pattern of localized mechanical stress in the epitaxial film and can be potentially extended below 10 nm film thickness. Reduction in film thickness and hence a reduction in the mass of the resonator is motivated by a straightforward gain in performance as a mass sensor. The corresponding increase in resonant frequency greatly facilitates operation in viscous media such as air and water. The exceptional mass sensitivity of nanomechanical resonators, combined with emerging methods of functionalization that provide a diamond surface with the specificity toward analytes of interest, make SC diamond resonators a superb choice for chem/bio sensing applications., Performed in collaboration with Naval Research Lab (NRL) Chemistry Division, Wash., D.C.; SFA, Inc., Largo, MD; and NOVA Research, Inc., Alexandria, VA. Published in NRL Review, p190-191, 2008.

Previous work has shown the Orion Bar to be an interface between ionized and molecular gas, viewed roughly edge on, which is excited by the light from the Trapezium cluster. Much of the emission from any star-forming region will originate from such interfaces, so the Bar serves as a foundation test of any emission model. Here we combine X-ray, optical, IR and radio data sets to derive emission spectra along the transition from H+ to H0 to H2 regions. We then reproduce the spectra of these layers with a simulation that simultaneously accounts for the detailed microphysics of the gas, the grains, and molecules, especially H2 and CO. The magnetic field, observed to be the dominant pressure in another region of the Orion Nebula, is treated as a free parameter, along with the density of cosmic rays. Our model successfully accounts for the optical, IR and radio observations across the Bar by including a significant magnetic pressure and also heating by an excess density of cosmic rays, which we suggest is due to cosmic rays being trapped in the compressed magnetic field. In the Orion Bar, as we had previously found in M17, momentum carried by radiation and winds from the newly formed stars pushes back and compresses the surrounding gas. There is a rough balance between outward momentum in starlight and the total pressure in atomic and molecular gas surrounding the H+ region. If the gas starts out with a weak magnetic field, the starlight from a newly formed cluster will push back the gas and compress the gas, magnetic field, and cosmic rays until magnetic pressure becomes an important factor., Comment: 32 pages, including 10 figures. ApJ (in press). Revised to correct 2 spelling errors

Previous work has shown the Orion Bar to be an interface between ionized and molecular gas, viewed roughly edge on, which is excited by the light from the Trapezium cluster. Much of the emission from any star-forming region will originate from such interfaces, so the Bar serves as a foundation test of any emission model. Here we combine X-ray, optical, IR and radio data sets to derive emission spectra along the transition from H+ to H0 to H2 regions. We then reproduce the spectra of these layers with a simulation that simultaneously accounts for the detailed microphysics of the gas, the grains, and molecules, especially H2 and CO. The magnetic field, observed to be the dominant pressure in another region of the Orion Nebula, is treated as a free parameter, along with the density of cosmic rays. Our model successfully accounts for the optical, IR and radio observations across the Bar by including a significant magnetic pressure and also heating by an excess density of cosmic rays, which we suggest is due to cosmic rays being trapped in the compressed magnetic field. In the Orion Bar, as we had previously found in M17, momentum carried by radiation and winds from the newly formed stars pushes back and compresses the surrounding gas. There is a rough balance between outward momentum in starlight and the total pressure in atomic and molecular gas surrounding the H+ region. If the gas starts out with a weak magnetic field, the starlight from a newly formed cluster will push back the gas and compress the gas, magnetic field, and cosmic rays until magnetic pressure becomes an important factor., Comment: 32 pages, including 10 figures. ApJ (in press). Revised to correct 2 spelling errors

Swimming in a flume at reduced water pO2 resulted in muscle and blood lactate levels in Pacific tarpon Megalops cyprinoides that were significantly higher when fish did not have access to air. Blood glucose and haematological variables were unchanged throughout the regimes of exercise at two swimming speeds and hypoxia. Strenuous exercise with bouts of burst swimming, however, resulted in both high blood lactate and glucose, and perturbed haematological status with elevated haemoglobin and reduced mean cell-haemoglobin concentration. Post-exercise recovery was achieved through aquatic breathing rather than by air breathing. The air-breathing organ in Pacific tarpon therefore prolonged aerobic activity, but gill breathing was used to repay oxygen debt.

The Pacific tarpon is an elopomorph teleost fish with an air-breathing organ (ABO) derived from a physostomous gas bladder. Oxygen partial pressure (PO2) in the ABO was measured on juveniles (238 g) with fiberoptic sensors during exposure to selected aquatic PO2 and swimming speeds. At slow speed (0.65 BL s(-1)), progressive aquatic hypoxia triggered the first breath at a mean PO, of 8.3 kPa. Below this, opercular movements declined sharply and visibly ceased in most fish below 6 kPa. At aquatic PO, of 6.1 kPa and swimming slowly, mean air-breathing frequency was 0.73 min', ABO was PO2 10.9) kPa, breath volume was 23.8 ml kg(-1) rate of oxygen uptake from the ABO was 1. 19 mi kg(-1) min(-1), and oxygen uptake per breath was 2.32 ml kg(-1). At the fastest experimental speed (2.4 BL s(-1)) at 6.1 kPa, ABO oxygen uptake increased to about 1.90 ml kg-1 min(-1), through a variable combination of breathing frequency and oxygen uptake per breath. In normoxic water, tarpon rarely breathed air and apparently closed down ABO perfusion, indicated by a drop in ABO oxygen uptake rate to about 1% of that in hypoxic water. This occurred at a wide range of ABO PO2 (1.7-26.4 kPa), suggesting that oxygen level in the ABO was not regulated by intrinsic receptors.

Pacific tarpon (Megalops cyprinoides) use a modified gas bladder as an air-breathing organ (ABO). We examined changes in cardiac output (V-b) associated with increases in air-breathing that accompany exercise and aquatic hypoxia. Juvenile (0.49 kg) and adult (1.21 kg) tarpon were allowed to recover in a swim flume at 27 'C after being instrumented with a Doppler flow probe around the ventral aorta to monitor band with a fibre-optic o en sensor in the ABO to monitor air-breathing frequency. Under normoxic conditions and in both juveniles and adults, routine air-breathing frequency was 0.03 breaths min(-1) and V-b was about 15 mL min(-1) kg(-1). Normoxic exercise (swimming at about 1.1 body lengths s(-1)) increased air-breathing frequency by 8-fold in both groups (reaching 0.23 breaths min(-1)) and increased Rb by 3-fold for juveniles and 2-fold for adults. Hypoxic exposure (2 kPa O-2) at rest increased air-breathing frequency 19-fold (to around 0.53 breaths min(-1)) in both groups, and while V-b again increased 3-fold in resting juvenile fish, V-b was unchanged in resting adult fish. Exercise in hypoxia increased air-breathing frequency 35-fold (to 0.95 breaths min(-1)) in comparison with resting normoxic fish. While juvenile fish increased V-b nearly 2-fold with exercise in hypoxia, adult fish maintained the same V-b irrespective of exercise state and became agitated in comparison. These results imply that air-breathing during exercise and hypoxia can benefit oxygen delivery, but to differing degrees in juvenile and adult tarpon. We discuss this difference in the context of myocardial oxygen supply.

To assess the effects of unpressurized altitude on visual acuity, refractive error, and corneal stability measures, pre- and post- PRK treatment. Sixteen male and four female subjects volunteered for altitude training and data collection. Two separate unpressurized altitude profiles were undertaken by all subjects; a 12-hour 10,000-ft (10K) and a 20-min 35,000-ft (35K) simulated altitude flights. Baseline "ground level" visual acuity, refractive error, and corneal stability data were collected prior to each profile. These measures were repeated "in-flight" at 3, 7, and 10 hours for the 10K profile and at peak altitude for the 35K profile. The test profiles were re-accomplished approximately 6 months after a subject's PRK treatment date. No significant differences attributed to altitude exposure were found in measurements of pre- or post-PRK visual acuity, refractive error, or corneal stability, under either unpressurized altitude profile. Visual acuity, refractive error, and corneal stability data were not significantly affected by exposure to unpressurized altitude within the design of this study. Comprehensive study data results and analysis are presented., The original document contains color images.

The southwestern (SW) part of the Galactic H II region M17 contains an obscured ionization front that is most easily seen at infrared and radio wavelengths. It is nearly edge-on, thus offering an excellent opportunity to study the way in which the gas changes from fully ionized to molecular as radiation from the ionizing stars penetrates into the gas. M17 is also one of the very few H II regions for which the magnetic field strength can be measured in the photodissociation region ( PDR) that forms the interface between the ionized and molecular gas. Here we model an observed line of sight through the gas cloud, including the H+, H0 (PDR), and molecular layers, in a fully self-consistent single calculation. An interesting aspect of the M17 SW bar is that the PDR is very extended. We show that the strong magnetic field that is observed to be present inevitably leads to a very deep PDR, because the structure of the neutral and molecular gas is dominated by magnetic pressure, rather than by gas pressure, as previously had been supposed.We also show that a wide variety of observed facts can be explained if a hydrostatic geometry prevails, in which the gas pressure from an inner X-ray hot bubble and the outward momentum of the stellar radiation field compress the gas and its associated magnetic field in the PDR, as has already been shown to occur in the Orion Nebula. The magnetic field compression may also amplify the local cosmic-ray density. The pressure in the observed magnetic field balances the outward forces, suggesting that the observed geometry is a natural consequence of the formation of a star cluster within a molecular cloud., Comment: Published as 2007, ApJ,658,1119

We are engaged in a comprehensive program to find reliable elemental abundances in and to probe the physical structure of the Orion Nebula, the brightest and best-resolved H II region. In the course of developing a robust extinction correction covering our optical and ultraviolet FOS and STIS observations, we examined the decrement within various series of He I lines. The decrements of the 2^3S-n^3P, 2^3P-n^3S and 3^3S-n^3P series are not in accord with caseB recombination theory. None of these anomalous He I decrements can be explained by extinction, indicating the presence of additional radiative transfer effects in He I lines ranging from the near-IR to the near-UV. CLOUDY photoionization equilibrium models including radiative transfer are developed to predict the observed He I decrements and the quantitative agreement is quite remarkable. Following from these results, select He I lines are combined with H I and [O II] lines and stellar extinction data to validate a new normalizable analytic expression for the wavelength dependence of the extinction. In so doing, the He+/H+ abundance is also derived., Comment: 42 pages, 10 figures. To be published in ApJ