Evolution of the Hemifused Intermediate on the Pathway to Membrane Fusion

AbstractThe pathway to membrane fusion in synthetic and biological systems is thought to pass through hemifusion, in which the outer leaflets are fused while the inner leaflets engage in a hemifusion diaphragm (HD). Fusion has been proposed to be completed by lysis of the expanded HD that matures from a localized stalklike initial connection. However, the process that establishes the expanded HD is poorly understood. Here we mathematically modeled hemifusion of synthetic vesicles, where hemifusion and fusion are most commonly driven by calcium and membrane tension. The model shows that evolution of the hemifused state is driven by these agents and resisted by interleaflet frictional and tensile stresses. Predicted HD growth rates depend on tension and salt concentration, and agree quantitatively with experimental measurements. For typical conditions, we predict that HDs expand at ∼30 μm2/s, reaching a final equilibrium area ∼7% of the vesicle area. Key model outputs are the evolving HD tension and area during the growth transient, properties that may determine whether HD lysis occurs. Applying the model to numerous published experimental studies that reported fusion, our results are consistent with a final fusion step in which the HD ruptures due to super-lysis HD membrane tensions

Applying Corn Condensed Distillers Solubles to Hay Windrows Prior to Baling: I. Procedure and Effects on Bale Temperature and Nutrient Composition

Two experiments investigated the effects of applying liquid corn condensed distillers solubles to grass-hay windrows prior to baling on storage, bale temperature, and nutrient composition. Application of the wet material did not impair the ability of hay to expel heat post-baling in either study. Increased CP and decreased NDF for hay treated with corn condensed distillers solubles indicated successful within-bale storage occurred. Results suggest application prior to baling is a feasible strategy for storing liquid co-products while improving forage quality

Room-temperature exciton-polaritons with two-dimensional WS2

Two-dimensional transition metal dichalcogenides exhibit strong optical transitions with significant potential for optoelectronic devices. In particular they are suited for cavity quantum electrodynamics in which strong coupling leads to polariton formation as a root to realisation of inversionless lasing, polariton condensationand superfluidity. Demonstrations of such strongly correlated phenomena to date have often relied on cryogenic temperatures, high excitation densities and were frequently impaired by strong material disorder. At room-temperature, experiments approaching the strong coupling regime with transition metal dichalcogenides have been reported, but well resolved exciton-polaritons have yet to be achieved. Here we report a study of monolayer WS$_2$ coupled to an open Fabry-Perot cavity at room-temperature, in which polariton eigenstates are unambiguously displayed. In-situ tunability of the cavity length results in a maximal Rabi splitting of $\hbar \Omega_{\rm{Rabi}} = 70$ meV, exceeding the exciton linewidth. Our data are well described by a transfer matrix model appropriate for the large linewidth regime. This work provides a platform towards observing strongly correlated polariton phenomena in compact photonic devices for ambient temperature applications.Comment: 12 pages, 6 figure

Volume Fractions of the Kinematic "Near-Critical" Sets of the Quantum Ensemble Control Landscape

An estimate is derived for the volume fraction of a subset $C_{\epsilon}^{P} = \{U : ||grad J(U)|\leq {\epsilon}\}\subset\mathrm{U}(N)$ in the neighborhood of the critical set $C^{P}\simeq\mathrm{U}(\mathbf{n})P\mathrm{U}(\mathbf{m})$ of the kinematic quantum ensemble control landscape J(U) = Tr(U\rho U' O), where $U$ represents the unitary time evolution operator, {\rho} is the initial density matrix of the ensemble, and O is an observable operator. This estimate is based on the Hilbert-Schmidt geometry for the unitary group and a first-order approximation of $||grad J(U)||^2$. An upper bound on these near-critical volumes is conjectured and supported by numerical simulation, leading to an asymptotic analysis as the dimension $N$ of the quantum system rises in which the volume fractions of these "near-critical" sets decrease to zero as $N$ increases. This result helps explain the apparent lack of influence exerted by the many saddles of $J$ over the gradient flow.Comment: 27 pages, 1 figur

Hubble Space Telescope Far Ultraviolet Spectroscopy of the Dwarf Nova VW Hyi in Superoutburst

We obtained three consecutive HST spectroscopic observations of a single superoutburst of the dwarf nova VW Hydri. The spectra cover the beginning, middle, and end of the superoutburst. All of the spectra are dominated by strong absorption lines due to CIII (1175 \AA), Lyman alpha (1216 \AA), NIV (1238 \AA, 1242 \AA), SII (1260-65 \AA), SIII (1300 \AA), CII (1335 \AA), SIV (1394 \AA, 1402 \AA) and CIV (1548 \AA, 1550 \AA). We discuss the evolution of the far UV energy distribution and line structure during the superoutburst. We note the absence of any P Cygni line structure in the STIS spectra. Using state of the art accretion disk models by Wade and Hubeny, we have determined accretion rates for all three spectra, for two white dwarf masses, 0.55 M_{\sun} and 0.8 M-{\sun}. For both white dwarf masses the accretion rate during superoutburst decreased by a factor of two from early to late in the superoutburst. The average accretion rate during superoutburst is $3 - 6 \times 10^{-9}$M_{\sun}/yr depending on the white dwarf mass.Comment: 2007, PASP, in pres

Revealing defect-state photoluminescence in monolayer WS2 by cryogenic laser processing

Understanding the stability of monolayer transition metal dichalcogenides in atmospheric conditions has important consequences for their handling, life-span, and utilization in applications. We show that cryogenic photoluminescence spectroscopy (PL) is a highly sensitive technique to the detection of oxidation induced degradation of monolayer tungsten disulfide (WS2) caused by exposure to ambient conditions. Although long-term exposure to atmospheric conditions causes massive degradation from oxidation that is optically visible, short-term exposure produces no obvious changes to the PL or Raman spectra measured at either room temperature or even cryogenic environment. Laser processing was employed to remove the surface adsorbents, which enables the defect states to be detected via cryogenic PL spectroscopy. Thermal cycling to room temperature and back down to 77 K shows the process is reversible. We also monitor the degradation process of WS2 using this method, which shows that the defect related peak can be observed after one month aging in ambient conditions

Post-Weaning Feed Intake and Performance of Bulls Developed in an Automated Feed Intake Management System

Objective:Our objectives were to compare expected and observed dry matter intake (DMI) and average daily gain (ADG) using modeled nutrient requirement equations, and to evaluate change in DMI over time of beef bull calves fed in an automated feed intake system. Study Description:Feed intake and performance data from purebred Angus, Hereford, and Simmental bull calves across two calf crops [birth years 2021 (n = 40) and 2022 (n = 37)] were utilized for this analysis. Projected DMI and ADG were calculated for each group of bulls by year on an individual basis using the Growing Bull module of the Excel-based Beef Ration and Nutrition Decision Software (BRANDS) formulation program (Iowa State University, Ames, IA). These predicted figures were compared to the Insentec intake data and analyzed via SAS. Results:In 2021–2022, a strong positive correlation (r= 0.78,P\u3c0.01) was observed between actual and predicted DMI. There was a highly correlated (r= 0.84,P\u3c0.01) relationship for the observed and predicted DMI for 2022–2023 as well. Actual ADG for both years was markedly higher than predicted. This result supports that BRANDS more accurately predicts DMI compared to ADG, and that substantial individual intake variation exists. The Bottom Line:DMI increases over time as days of test period increase for growing bulls in an individually fed intake system, and though significant day-to-day variation exists, the BRANDS program appears to more accurately predict DMI than ADG

Sea anemones may thrive in a high CO2 world

Increased seawater pCO 2, and in turn 'ocean acidification' (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef-forming corals (Class: Anthozoa) that appear particularly susceptible to OA via reduced net calcification. However, here we show that OA-like conditions can simultaneously enhance the ecological success of non-calcifying anthozoans, which not only play key ecological and biogeochemical roles in present day benthic ecosystems but also represent a model organism should calcifying anthozoans exist as less calcified (soft-bodied) forms in future oceans. Increased growth (abundance and size) of the sea anemone (Anemonia viridis) population was observed along a natural CO 2 gradient at Vulcano, Italy. Both gross photosynthesis (P G) and respiration (R) increased with pCO 2 indicating that the increased growth was, at least in part, fuelled by bottom up (CO 2 stimulation) of metabolism. The increase of P G outweighed that of R and the genetic identity of the symbiotic microalgae (Symbiodinium spp.) remained unchanged (type A19) suggesting proximity to the vent site relieved CO 2 limitation of the anemones' symbiotic microalgal population. Our observations of enhanced productivity with pCO 2, which are consistent with previous reports for some calcifying corals, convey an increase in fitness that may enable non-calcifying anthozoans to thrive in future environments, i.e. higher seawater pCO 2. Understanding how CO 2-enhanced productivity of non- (and less-) calcifying anthozoans applies more widely to tropical ecosystems is a priority where such organisms can dominate benthic ecosystems, in particular following localized anthropogenic stress. © 2012 Blackwell Publishing Ltd

Effects of Production System on Cow and Calf Performance

Limited traditional forage resources have prompted interest for alternative cow-calf production systems. This study evaluated the effects of two winter cow-calf production systems (cornstalk grazing and dry-lot feeding) on cow-calf performance in a summer-calving, intensively managed cowherd at two locations. Grazing cow-calf pairs on cornstalks resulted in similar or lower ending BW of cows and lower ADG of calves when compared to cow-calf pairs wintered in the dry-lot. A partial budget of incorporating winter cornstalk grazing into an intensive production system suggests that cows wintered on cornstalks may be $137 more profitable compared to cows wintered in the dry-lot

Effects of Production System on Cow and Calf Performance

Limited traditional forage resources have prompted interest for alternative cow-calf production systems. This study evaluated the effects of two winter cow-calf production systems (cornstalk grazing and dry-lot feeding) on cow-calf performance in a summer-calving, intensively managed cowherd at two locations. Grazing cow-calf pairs on cornstalks resulted in similar or lower ending BW of cows and lower ADG of calves when compared to cow-calf pairs wintered in the dry-lot. A partial budget of incorporating winter cornstalk grazing into an intensive production system suggests that cows wintered on cornstalks may be $137 more profitable compared to cows wintered in the dry-lot