299 research outputs found
Far-from-Equilibrium Measurements of Thermodynamic Length
Thermodynamic length is a path function that generalizes the notion of length
to the surface of thermodynamic states. Here, we show how to measure
thermodynamic length in far-from-equilibrium single molecule experiments using
the work fluctuation relations. For these microscopic systems, it proves
necessary to define the thermodynamic length in terms of the Fisher
information. Consequently, the thermodynamic length can be directly related to
the magnitude of fluctuations about equilibrium. The work fluctuation relations
link the work and the free energy change during an external perturbation on a
system. We use this result to determine equilibrium averages at intermediate
points of the protocol in which the system is out-of-equilibrium. This allows
us to extend Bennett's method to determine the potential of mean force, as well
as the thermodynamic length, in single molecule experiments
SELECT Readiness: Assessing the Clinical Learning Environment of a Regional Branch Medical Campus
SELECT Readiness: Lessons Learned in Assessing the Clinical Learning Environment of a Regional Branch Medical Campus
Mapping the Galactic Halo I. The `Spaghetti' Survey
We describe a major survey of the Milky Way halo designed to test for
kinematic substructure caused by destruction of accreted satellites. We use the
Washington photometric system to identify halo stars efficiently for
spectroscopic followup. Tracers include halo giants (detectable out to more
than 100 kpc), blue horizontal branch stars, halo stars near the main sequence
turnoff, and the ``blue metal-poor stars'' of Preston et al (1994). We
demonstrate the success of our survey by showing spectra of stars we have
identified in all these categories, including giants as distant as 75 kpc. We
discuss the problem of identifying the most distant halo giants. In particular,
extremely metal-poor halo K dwarfs are present in approximately equal numbers
to the distant giants for V fainter than 18, and we show that our method will
distinguish reliably between these two groups of metal-poor stars. We plan to
survey 100 square degrees at high galactic latitude, and expect to increase the
numbers of known halo giants, BHB stars and turnoff stars by more than an order
of magnitude. In addition to the strong test that this large sample will
provide for the question `was the Milky Way halo accreted from satellite
galaxies?', we will improve the accuracy of mass measurements of the Milky Way
beyond 50 kpc via the kinematics of the many distant giants and BHB stars we
will find. We show that one of our first datasets constrains the halo density
law over galactocentric radii of 5-20 kpc and z heights of 2-15 kpc. The data
support a flattened power-law halo with b/a of 0.6 and exponent -3.0. More
complex models with a varying axial ratio may be needed with a larger dataset.Comment: 55 pages, 22 figures, to appear in the Astronomical Journa
Structural and spectropotentiometric analysis of Blastochloris viridis heterodimer mutant reaction center
Heterodimer mutant reaction centers (RCs) of Blastochloris viridis were crystallized using microfluidic
technology. In this mutant, a leucine residue replaced the histidine residue which had acted as a fifth ligand
to the bacteriochlorophyll (BChl) of the primary electron donor dimer M site (HisM200). With the loss of the
histidine-coordinated Mg, one bacteriochlorophyll of the special pair was converted into a bacteriopheophytin (BPhe), and the primary donor became a heterodimer supermolecule. The crystals had dimensions
400 × 100 ×100 μm, belonged to space group P43212, and were isomorphous to the ones reported earlier for
the wild type (WT) strain. The structure was solved to a 2.5 Å resolution limit. Electron-density maps
confirmed the replacement of the histidine residue and the absence of Mg. Structural changes in the
heterodimer mutant RC relative to the WT included the absence of the water molecule that is typically
positioned between the M side of the primary donor and the accessory BChl, a slight shift in the position of
amino acids surrounding the site of the mutation, and the rotation of the M194 phenylalanine. The
cytochrome subunit was anchored similarly as in the WT and had no detectable changes in its overall
position. The highly conserved tyrosine L162, located between the primary donor and the highest potential
heme C380, revealed only a minor deviation of its hydroxyl group. Concomitantly to modification of the BChl
molecule, the redox potential of the heterodimer primary donor increased relative to that of the WT
organism (772 mV vs. 517 mV). The availability of this heterodimer mutant and its crystal structure provides
opportunities for investigating changes in light-induced electron transfer that reflect differences in redox
cascades
SELECT Readiness: Results of a Comprehensive Assessment of the Clinical Learning Environment of a Branch Medical Campus
Outcomes of Peginterferon alfa-2a and Ribavirin Combination Therapy in a Resident-Initiated, Multidisciplinary, Hepatitis C Clinic
Rattus management is essential for population persistence in a critically endangered passerine: combining small-scale field experiments and population modelling.
Invasive species are a major threat for island biodiversity, causing species decline and extinction globally. Of all invasive mammals rats are one of the most detrimental and have been the target of numerous control and eradication programmes. In Mauritius rats have contributed to the extinction of 50% of the island's fauna and are thought to be the main threat to the endemic Mauritius olive white-eye (Zosterops chloronothos), a critically endangered passerine. Assessing the impact of rats and suitable control strategies is often problematic in such cases because of the lack of replicate populations for experiments. Here, we illustrate how to overcome this issue by combining a small-scale rat management experiment on olive white-eyes with demographic models that provide estimates of the potential effects of management on vital rates and population growth. We established poison and trapping grids within breeding territories, and show that rat management significantly decreased rat abundance and increased nesting success. An individual-based stochastic simulation model suggested that rat control could produce a 5–6 fold increase in the annual productivity of female olive white-eyes, which in turn would be sufficient to stabilise population growth. In the absence of rat management, our analysis suggests the olive white-eye population will decline by about 14% per annum. By combining low cost field experiments with widely available demographic models we highlight the value of targeted, effective rat management techniques for both short and long-term population management in threatened passerines
Steroid therapy and outcome of parapneumonic pleural effusions (STOPPE): Study protocol for a multicenter, double-blinded, placebo-controlled randomized clinical trial
BACKGROUND: Community-acquired pneumonia (CAP) is a major global disease. Parapneumonic effusions often complicate CAP and range from uninfected (simple) to infected (complicated) parapneumonic effusions and empyema (pus). CAP patients who have a pleural effusion at presentation are more likely to require hospitalization, have a longer length of stay and higher mortality than those without an effusion. Conventional management of pleural infection, with antibiotics and chest tube drainage, fails in about 30% of cases. Several randomized controlled trials (RCT) have evaluated the use of corticosteroids in CAP and demonstrated some potential benefits. Importantly, steroid use in pneumonia has an acceptable safety profile with no adverse impact on mortality. A RCT focused on pediatric patients with pneumonia and a parapneumonic effusion demonstrated shorter time to recovery. The effects of corticosteroid use on clinical outcomes in adults with parapneumonic effusions have not been tested. We hypothesize that parapneumonic effusions develop from an exaggerated pleural inflammatory response. Treatment with systemic steroids may dampen the inflammation and lead to improved clinical outcomes. The steroid therapy and outcome of parapneumonic pleural effusions (STOPPE) trial will assess the efficacy and safety of systemic corticosteroid as an adjunct therapy in adult patients with CAP and pleural effusions.
METHODS: STOPPE is a pilot multicenter, double-blinded, placebo-controlled RCT that will randomize 80 patients with parapneumonic effusions (2:1) to intravenous dexamethasone or placebo, administered twice daily for 48 hours. This exploratory study will capture a wide range of clinically relevant endpoints which have been used in clinical trials of pneumonia and/or pleural infection; including, but not limited to: time to clinical stability, inflammatory markers, quality of life, length of hospital stay, proportion of patients requiring escalation of care (thoracostomy or thoracoscopy), and mortality. Safety will be assessed by monitoring for the incidence of adverse events during the study.
DISCUSSION: STOPPE is the first trial to assess the efficacy and safety profile of systemic corticosteroids in adults with CAP and pleural effusions. This will inform future studies on feasibility and appropriate trial endpoints.
TRIAL REGISTRATION: ACTRN1261800094720
Explorations, Vol. 4, No. 1
Articles include:
Cover: Old Yarmouth Light, 1960, Cape Forchu, Nova Scotia. By and from the collection of Edgar McKay.
The Borderlands Concept: a new look at U.S.-Canada relations, by Victor Konrad and Lauren McKensey
Fundy Tidal Power Project, by Gregory White
Canadian Poet: Ken Norris
Native American Life and Art: a celebration, November, 1986, by Lee-Ann Konrad
The Montreal Canadiens: a cultural institution, by James J. Herlan
U.S. and Canadian Executives: uses of formal and informal plans in top executive decision-making, by Kent Carter
Our Cover Artist: bits and pieces of one man\u27s Nova Scotia, by Edgar McKay The Canadian-American Center and the Canadian Collection of the Fogler Library, by Alice Stewart
Capitalist Development in the New England-Atlantic Provinces Region, by Robert H. Babcock
Atlantic Canadian Members of Parliament as Representatives, by Howard Cody
The Rower and the Pyramid: a tribute to Joe Walsh, by Edward D. Ives
The Canadian-American Center: exercise in excellence, by Rand Erb
Canadian and Maine Potatoes: a bushel of questions, by George K. Griner, Alan S. Kezis, and James D. Leiby
After 20: the Future of the Canadian-American Center, by Victor Konra
- …