Krypton and the Fundamental Flaw of the Lennard-Jones Potential.

We have performed a series of neutron scattering experiments on supercritical krypton. Our data and analysis allow us to characterize the Frenkel line crossover in this model monatomic fluid. The data from our measurements was analyzed using Empirical Potential Structure Refinement to determine the short- and medium-range structure of the fluids. We find evidence for several shells of neighbors which form approximately concentric rings of density about each atom. The ratio of second to first shell radius is significantly larger than in any crystal structure. Modeling krypton using a Lennard-Jones potential is shown to give significant errors, notably that the liquid is overstructured. The true potential appears to be longer ranged and with a softer core than the 6-12 powerlaws permit.

Characterization of the high-pressure and high-temperature phase diagram and equation of state of chromium.

The high-pressure and high-temperature phase diagram of chromium has been investigated both experimentally (in situ), using a laser-heated diamond-anvil cell technique coupled with synchrotron powder X-ray diffraction, and theoretically, using ab initio density-functional theory simulations. In the pressure-temperature range covered experimentally (up to 90 GPa and 4500 K, respectively) only the solid body-centred-cubic and liquid phases of chromium have been observed. Experiments and computer calculations give melting curves in agreement with each other that can both be described by the Simon-Glatzel equation [Formula: see text]. In addition, a quasi-hydrostatic equation of state at ambient temperature has been experimentally characterized up to 131 GPa and compared with the present simulations. Both methods give very similar third-order Birch-Murnaghan equations of state with bulk moduli of 182-185 GPa and respective pressure derivatives of 4.74-5.15. According to the present calculations, the obtained melting curve and equation of state are valid up to at least 815 GPa, at which pressure the melting temperature is 9310 K. Finally, from the obtained results, it was possible to determine a thermal equation of state of chromium valid up to 65 GPa and 2100 K.

Structural Markers of the Frenkel Line in the Proximity of Widom Lines.

We have performed a neutron scattering experiment on supercritical fluid nitrogen at 160 K (1.27 TC) over a wide pressure range (7.8 MPa/0.260 g/mL-125 MPa/0.805 g/mL). This has enabled us to study the process by which nitrogen changes from a fluid that exhibits gaslike behavior to one that exhibits rigid liquidlike behavior at a temperature close to, but above, the critical temperature by crossing the Widom lines followed by the Frenkel line on pressure (density) increase. We find that the Frenkel line transition is indicated by a transition to a regime of rigid liquidlike behavior in which the coordination number remains constant within error, in agreement with our previous work at 300 K. The Frenkel line transition takes place at approximately the same density at 160 and 300 K. The data do not conclusively show an additional transition at the location of the known Widom lines. We find that behavior remains gaslike until the Frenkel line is crossed and our data support the hypothesis that Widom line transitions are density increase-driven.

Observation of Liquid-Liquid Phase Transitions in Ethane at 300 K.

We have conducted Raman spectroscopy experiments on liquid ethane (C2H6) at 300 K, obtaining a large amount of data at very high resolution. This has enabled the observation of Raman peaks expected but not previously observed in liquid ethane and a detailed experimental study of the liquid that was not previously possible. We have observed a transition between rigid and nonrigid liquid states in liquid ethane at ca. 250 MPa corresponding to the recently proposed Frenkel line, a dynamic transition between rigid liquid (liquidlike) and nonrigid liquid (gaslike) states beginning in the subcritical region and extending to arbitrarily high pressure and temperature. The observation of this transition in liquid (subcritical) ethane allows a clear differentiation to be made between the Frenkel line (beginning in the subcritical region at higher density than the boiling line) and the Widom lines (emanating from the critical point and not existing in the subcritical region). Furthermore, we observe a narrow transition at ca. 1000 MPa to a second rigid liquid state. We propose that this corresponds to a state in which orientational order must exist to achieve the expected density and can view the transition in analogy to the transition in the solid state away from the orientationally disordered phase I to the orientationally ordered phases II and III.

High Pressure Raman, Optical Absorption, and Resistivity Study of SrCrO4.

We studied the electronic and vibrational properties of monazite-type SrCrO4 under compression. The study extended the pressure range of previous studies from 26 to 58 GPa. The existence of two previously reported phase transitions was confirmed at 9 and 14 GPa, and two new phase transitions were found at 35 and 48 GPa. These transitions involve several changes in the vibrational and transport properties with the new high-pressure phases having a conductivity lower than that of the previously known phases. No evidence of chemical decomposition or metallization of SrCrO4 was detected. A tentative explanation for the reported observations is discussed.

Determining molecular orientation via single molecule SERS in a plasmonic nano-gap.

In this work, plasmonic nano-gaps consisting of a silver nanoparticle coupled to an extended silver film have been fully optimized for single molecule Surface-Enhanced Raman Scattering (SERS) spectroscopy. The SERS signal was found to be strongly dependent on the particle size and the molecule orientation with respect to the field inside the nano-gap. Using Finite Difference Time Domain (FDTD) simulations to complement the experimental measurements, the complex interplay between the excitation enhancement and the emission enhancement of the system as a function of particle size were highlighted. Additionally, in conjunction with Density Functional Theory (DFT), the well-defined field direction in the nano-gap enables to recover the orientation of individual molecules.

Optimal light for greenhouse culture of American ginseng seedlings.

Three greenhouse experiments with American ginseng seedlings growing under light levels from 4.8% to 68% showed a quadratic response for root dry weight, giving an optimal root dry weight of 239 mg (range 160-415 mg) at an optimal light level of 35.6% (range 30.6-43.2%).

Hydrogenation of Graphene by Reaction at High Pressure and High Temperature.

The chemical reaction between hydrogen and purely sp(2)-bonded graphene to form graphene's purely sp(3)-bonded analogue, graphane, potentially allows the synthesis of a much wider variety of novel two-dimensional materials by opening a pathway to the application of conventional chemistry methods in graphene. Graphene is currently hydrogenated by exposure to atomic hydrogen in a vacuum, but these methods have not yielded a complete conversion of graphene to graphane, even with graphene exposed to hydrogen on both sides of the lattice. By heating graphene in molecular hydrogen under compression to modest high pressure in a diamond anvil cell (2.6-5.0 GPa), we are able to react graphene with hydrogen and propose a method whereby fully hydrogenated graphane may be synthesized for the first time.

Theoretical and Experimental Study of the Crystal Structures, Lattice Vibrations, and Band Structures of Monazite-Type PbCrO4, PbSeO4, SrCrO4, and SrSeO4.

The crystal structures, lattice vibrations, and electronic band structures of PbCrO4, PbSeO4, SrCrO4, and SrSeO4 were studied by ab initio calculations, Raman spectroscopy, X-ray diffraction, and optical-absorption measurements. Calculations properly describe the crystal structures of the four compounds, which are isomorphic to the monazite structure and were confirmed by X-ray diffraction. Information is also obtained on the Raman- and IR-active phonons, with all of the vibrational modes assigned. In addition, the band structures and electronic densities of states of the four compounds were determined. All are indirect-gap semiconductors. In particular, chromates are found to have band gaps smaller than 2.5 eV and selenates higher than 4.3 eV. In the chromates (selenates), the upper part of the valence band is dominated by O 2p states and the lower part of the conduction band is composed primarily of electronic states associated with the Cr 3d and O 2p (Se 4s and O 2p) states. Calculations also show that the band gap of PbCrO4 (PbSeO4) is smaller than the band gap of SrCrO4 (SrSeO4). This phenomenon is caused by Pb states, which, to some extent, also contribute to the top of the valence band and the bottom of the conduction band. The agreement between experiments and calculations is quite good; however, the band gaps are underestimated by calculations, with the exception of the bang gap of SrCrO4, for which theory and calculations agree. Calculations also provide predictions of the bulk modulus of the studied compounds.

Using the Peggy Simple Western system for fine needle aspirate analysis.

Simple Western™ assays are capillary-based electrophoretic immunoassays, similar in scope to SDS-PAGE (molecular weight separation, "size") and IEF (isoelectric focusing, "charge") immunoblotting. The enhanced sensitivity and automation of the Simple Western makes it better suited to cancer diagnostics and research than the traditional Western platform. Because of its smaller sample volume requirements, primary cells, such as those obtained from fine needle aspirates (FNAs), and solid tumor slices may be used to generate quantitative comparable data. The Peggy™ instrument is capable of performing either size or charge assays on up to 96 samples in a single unattended run.

Effect of boron nutrition on American ginseng in field and in nutrient cultures.

Field and nutrient cultures of American ginseng (Panax quinquefolius L.) were used to establish foliar symptoms related to boron (B) concentration in leaves and soils, and to evaluate radish as a time-saving model system for B nutrition. Application of excess B, 8 kg/ha versus the recommended 1.5 kg/ha, to field plantings of 2-, 3-, and 4-yr-old American ginseng plants just prior to crop emergence caused, within 4 wk after crop emergence, leaf symptoms of chlorosis followed by necrosis starting at the tips and progressing along the margins. The B concentration in leaves of 2-4-yr-old plants receiving 1.5 kg/ha B was 30 µg/g dry mass compared to 460 µg/g dry mass where 8 kg/ha B was applied. Similarly, B concentration in soils receiving the lower B concentration was 1.8 µg/g dry mass and 2.2-2.8 µg/g dry mass where the higher B concentration was applied. Application of 8 kg/ha B reduced the dry yield of 3rd-yr roots by 20% from 2745 kg/ha to 2196 kg/ha and 4th-yr roots by 26% from 4130 kg/ha to 3071 kg/ha. Ginseng seedlings and radish were grown under greenhouse conditions in nutrient culture with four B concentrations ranging from 0 mg/L to 10 mg/L. At 5 mg/L and 10 mg/L ginseng and radish developed typical leaf B toxicity symptoms similar to those described above for field-grown plants. Increasing B in the nutrient solution from 0.5 mg/L to 10 mg/L decreased, in a linear fashion, the root and leaf dry mass of ginseng, but not radish. Given the many similarities of ginseng and radish to B utilization, radish might be used as a time-saving model system for the study of B, and other micronutrients, in the slow-growing perennial ginseng.

Effect of seeding depth on seedling growth and dry matter partitioning in American ginseng.

Greenhouse and field experiments with American ginseng (Panax quinquefolius L.) stratified seed sown at depths of 10 to 100 mm were carried out to determine effects of seeding depth on seedling emergence, growth and development and to calculate optimum seeding depth. The time to 50% seedling emergence (E50) in the field increased linearly from 17 d at 20 mm seeding depth to 42.5 d at 80 mm. Seedling emergence and root weight (economic yield) at the end of the first year each increased quadratically with the increase of seeding depth. Maximum emergence and root yields were produced at sowing depths of 26.9 and 30.6 mm respectively. In a greenhouse pot experiment, increasing seeding depth from 10 to 100 mm increased partitioning of dry matter to leaves from 23.6% to 26.1%, to stems from 6.9% to 14.2%, and decreased dry matter to roots from 69.5% to 59.7%. Optimum seeding depth was 31.1 mm for a corresponding maximum root weight of 119.9 mg. A predictor equation [X (seeding depth, mm)=Y (seed weight, mg)/9.1+20.96] for seeding depth for ginseng, based on data for ten vegetable crops, their seed weights and suggested seeding depths, predicted a seeding depth of 28.3 mm for ginseng similar to that reported above for most pot and field experiments.

High-pressure synthesis, amorphization, and decomposition of silane.

By compressing elemental silicon and hydrogen in a diamond anvil cell, we have synthesized polymeric silicon tetrahydride (SiH(4)) at 124 GPa and 300 K. In situ synchrotron x-ray diffraction reveals that the compound forms the insulating I4(1)/a structure previously proposed from ab initio calculations for the high-pressure phase of silane. From a series of high-pressure experiments at room and low temperature on silane itself, we find that its tetrahedral molecules break up, while silane undergoes pressure-induced amorphization at pressures above 60 GPa, recrystallizing at 90 GPa into the polymeric crystal structures.

Morphological and Ginsenoside Differences among North American Ginseng Leaves.

Leaf characteristics of mature 2, 3 and 4-year-old North American ginseng (Panax quinquefolius L.) leaves on fruiting and non-fruiting (NF) plants were studied. Leaflets of the 2-year-old plants had the lowest fresh and dry weight, area, volume and internal gas volume. Inflorescence removal in 3-year-old plants did not affect leaf characteristics or ginsenoside concentration but in 4-yearold plants it increased leaf fresh (38.6%) and dry (43.9%) weight, leaf area (29.1%), specific leaf mass (11.4%), leaf volume (43.1%), and leaf thickness (12.1%), and decreased leaf water content (6.2%). Cultivated ginseng, although an understorey plant, had the specific leaf mass, 35.6 g m(-2) (range, 36 to 39 g m(-2)) and a chlorophyll a/b ratio of 2.40 to 2.61, both suggesting the ability to perform like a sunny habitat plant. Also, specific leaf mass of 35.6 g m(-2) is similar to that reported for perennial plants, 36.8 g m(-2), rather than that for annuals, 30.9 g m(-2).

A study of the workforce in emergency medicine: 2007.

INTRODUCTION: This study was undertaken to describe the current status of the emergency medicine workforce in the United States. METHODS: Surveys were distributed in 2008 to 2619 emergency department (ED) medical directors and nurse managers in hospitals in the 2006 American Hospital Association database. RESULTS: Among ED medical directors, 713 responded, for a 27.2% response rate. Currently, 65% of practicing emergency physicians are board certified by the American Board of Emergency Medicine or the American Osteopathic Board of Emergency Medicine. Among those leaving the practice, the most common reasons cited for departure include geographic relocation (46%) and better pay (29%). Approximately 12% of the ED physician workforce is expected to retire in the next 5 years. Among nurse managers, 548 responded, for a 21% response rate. Many nurses (46%) have an associate degree as their highest level of education, 28% have a BSN, and 3% have a graduate degree (MSN or higher). Geographic relocation (44%) is the leading reason for changing employment. Emergency department annual volumes have increased by 49% since 1997, with a mean ED volume of 32 281 in 2007. The average reported ED length of stay is 158 minutes from registration to discharge and 208 minutes from registration to admission. Emergency department spent an average of 49 hours per month in ambulance diversion in 2007. Boarding is common practice, with an average of 318 hours of patient boarding per month. CONCLUSIONS: In the past 10 years, the number of practicing emergency physicians has grown to more than 42 000. The number of board-certified emergency physicians has increased. The number of annual ED visits has risen significantly.

Loss of integrin alpha(v)beta8 on dendritic cells causes autoimmunity and colitis in mice.

The cytokine transforming growth factor-beta (TGF-beta) is an important negative regulator of adaptive immunity. TGF-beta is secreted by cells as an inactive precursor that must be activated to exert biological effects, but the mechanisms that regulate TGF-beta activation and function in the immune system are poorly understood. Here we show that conditional loss of the TGF-beta-activating integrin alpha(v)beta8 on leukocytes causes severe inflammatory bowel disease and age-related autoimmunity in mice. This autoimmune phenotype is largely due to lack of alpha(v)beta8 on dendritic cells, as mice lacking alpha(v)beta8 principally on dendritic cells develop identical immunological abnormalities as mice lacking alpha(v)beta8 on all leukocytes, whereas mice lacking alpha(v)beta8 on T cells alone are phenotypically normal. We further show that dendritic cells lacking alpha(v)beta8 fail to induce regulatory T cells (T(R) cells) in vitro, an effect that depends on TGF-beta activity. Furthermore, mice lacking alpha(v)beta8 on dendritic cells have reduced proportions of T(R) cells in colonic tissue. These results suggest that alpha(v)beta8-mediated TGF-beta activation by dendritic cells is essential for preventing immune dysfunction that results in inflammatory bowel disease and autoimmunity, effects that are due, at least in part, to the ability of alpha(v)beta8 on dendritic cells to induce and/or maintain tissue T(R) cells.

Vascular development of the brain requires beta8 integrin expression in the neuroepithelium.

We showed previously that loss of the integrin beta8 subunit, which forms alphavbeta8 heterodimers, results in abnormal vascular development in the yolk sac, placenta, and brain. Animals lacking the integrin beta8 (itgbeta8) gene die either at midgestation, because of insufficient vascularization of the placenta and yolk sac, or shortly after birth with severe intracerebral hemorrhage. To specifically focus on the role of integrins containing the beta8 subunit in the brain, and to avoid early lethalities, we used a targeted deletion strategy to delete itgbeta8 only from cell types within the brain. Ablating itgbeta8 from vascular endothelial cells or from migrating neurons did not result in cerebral hemorrhage. Targeted deletion of itgbeta8 from the neuroepithelium, however, resulted in bilateral hemorrhage at postnatal day 0, although the phenotype was less severe than in itgbeta8-null animals. Newborn mice lacking itgbeta8 from the neuroepithelium had hemorrhages in the cortex, ganglionic eminence, and thalamus, as well as abnormal vascular morphogenesis, and disorganized glia. Interestingly, adult mice lacking itgbeta8 from cells derived from the neuroepithelium did not show signs of hemorrhage. We propose that defective association between vascular endothelial cells and glia lacking itgbeta8 is responsible for the leaky vasculature seen during development but that an unidentified compensatory mechanism repairs the vasculature after birth.

The ExsA protein of Bacillus cereus is required for assembly of coat and exosporium onto the spore surface.

The outermost layer of spores of the Bacillus cereus family is a loose structure known as the exosporium. Spores of a library of Tn917-LTV1 transposon insertion mutants of B. cereus ATCC 10876 were partitioned into hexadecane; a less hydrophobic mutant that was isolated contained an insertion in the exsA promoter region. ExsA is the equivalent of SafA (YrbA) of Bacillus subtilis, which is also implicated in spore coat assembly; the gene organizations around both are identical, and both proteins contain a very conserved N-terminal cortex-binding domain of ca. 50 residues, although the rest of the sequence is much less conserved. In particular, unlike SafA, the ExsA protein contains multiple tandem oligopeptide repeats and is therefore likely to have an extended structure. The exsA gene is expressed in the mother cell during sporulation. Spores of an exsA mutant are extremely permeable to lysozyme and are blocked in late stages of germination, which require coat-associated functions. Two mutants expressing differently truncated versions of ExsA were constructed, and they showed the same gross defects in the attachment of exosporium and spore coat layers. The protein profile of the residual exosporium harvested from spores of the three mutants--two expressing truncated proteins and the mutant with the original transposon insertion in the promoter region--showed some differences from the wild type and from each other, but the major exosporium glycoproteins were retained. The exsA gene is extremely important for the normal assembly and anchoring of both the spore coat and exosporium layers in spores of B. cereus.

The business of emergency medicine: a model for success.

Today's EPOs and their physicians face an array of daunting challenges. Falling reimbursement, rising malpractice costs. ED and hospital crowding,and demands for improving ED efficiency and patient satisfaction all contribute to the challenging and sometimes threatening environment of EM practice. The EP involved in a busy and often hectic ED shift may feel unduly and unnecessarily distracted when required to continuously acknowledge and address the business aspect of the practice. Nevertheless,regardless of the size and structure, fiscal viability ultimately determines the EPO's ability to continue to offer access to care. This article contends that a comprehensive business strategy drives superior financial performance and supports the organization's mission. The business strategy must identify financial and non-financial determinants of the EPO's success and provide a mechanism for understanding how the organization's resources are converted to value for customers. The section offers a framework for developing this strategy, for identifying possible gaps or deficiencies, and for measuring and monitoring progress in achieving strategic objectives and ultimately, the EPO's mission. The importance of the mission and the dynamic EM environment require that the strategy development process be more than an annual exercise for the leadership of the organization. Though key leaders in any size EPO--set the course for the organization, the entire organization must be aware and understand the strategy before they commit themselves and adopt actions and behaviors that promote it. The model presented here provides a graphic display that lends itself well to consistent communication of a comprehensive strategy in a concise way throughout the organization.Furthermore, the balance of the model, across four perspectives, recognizes the value of balanced organizational objectives and lends itself well to the creation of a measurement system that supports cause and effect relation-ships through leading and lagging indicators. This can prevent the imposition of unproven, arbitrary metrics and expectations.EPOs that expend the time and resources required to develop and implement a comprehensive, well balanced strategy make a long-term investment in their patients and themselves. EPOs that go on to develop credible, efficient measurement systems are not only able to drive more commitment and accountability in the organization, they also have a competitive advantage. They can demonstrate performance history and targeted future performance to differentiate themselves from competitors and to stem efforts to impose unbalanced metrics that do not serve well the hospital, the EPO, and ultimately, patients. The power of such measurement systems, internal and external to the organization, strongly point to the need for consistently defined measures across the industry. Ultimately when faced with changes in the environment,the entire industry will be better equipped to respond in specific ways and to communicate its progress to communities or government authorities.

Population genetic structure of mahogany (Swietenia macrophylla King, Meliaceae) across the Brazilian Amazon, based on variation at microsatellite loci: implications for conservation.

Mahogany (Swietenia macrophylla, Meliaceae) is the most valuable and intensively exploited Neotropical tree. No information is available regarding the genetic structure of mahogany in South America, yet the region harbours most of the unlogged populations of this prized hardwood. Here we report on the genetic diversity within and the differentiation among seven natural populations separated by up to 2100 km along the southern arc of the Brazilian Amazon basin. We analysed the variation at eight microsatellite loci for 194 adult individuals. All loci were highly variable, with the number of alleles per locus ranging from 13 to 27 (mean = 18.4). High levels of genetic diversity were found for all populations at the eight loci (mean HE = 0.781, range 0.754-0.812). We found moderate but statistically significant genetic differentiation among populations considering both estimators of FST and RST, theta = 0.097 and rho = 0.147, respectively. Estimates of theta and rho were significantly greater than zero for all pairwise population comparisons. Pairwise rho-values were positively and significantly correlated with geographical distance under the isolation-by-distance model. Furthermore, four of the populations exhibited a significant inbreeding coefficient. The finding of local differentiation among Amazonian mahogany populations underscores the need for in situ conservation of multiple populations of S. macrophylla across its distribution in the Brazilian Amazon. In addition, the occurrence of microgeographical genetic differentiation at a local scale indicates the importance of maintaining populations in their diverse habitats, especially in areas with mosaics of topography and soil.