Fuel reduction burning reduces wildfire severity during extreme fire events in south-eastern Australia.

Extreme fire events have increased across south-eastern Australia owing to warmer and drier conditions driven by anthropogenic climate change. Fuel reduction burning is widely applied to reduce the occurrence and severity of wildfires; however, targeted assessment of the effectiveness of this practice is limited, especially under extreme climatic conditions. Our study utilises fire severity atlases for fuel reduction burns and wildfires to examine: (i) patterns in the extent of fuel treatment within planned burns (i.e., burn coverage) across different fire management zones, and; (ii) the effect of fuel reduction burning on the severity of wildfires under extreme climatic conditions. We assessed the effect of fuel reduction burning on wildfire severity across temporal and spatial scales (i.e., point and local landscape), while accounting for burn coverage and fire weather. Fuel reduction burn coverage was substantially lower (∼20-30%) than desired targets in fuel management zones focused on asset protection, but within the desired range in zones that focus on ecological objectives. At the point scale, wildfire severity was moderated in treated areas for at least 2-3 years after fuel treatment in shrubland and 3-5 years in forests, relative to areas that did not receive fuel reduction treatments (i.e., unburnt patches). Fuel availability strongly limited fire occurrence and severity within the first 18 months of fuel reduction burning, irrespective of fire weather. Fire weather was the dominant driver of high severity canopy defoliating fire by ∼3-5 years after fuel treatment. At the local landscape scale (i.e., 250 ha), the extent of high canopy scorch decreased marginally as the extent of recently (<5 years) treated fuels increased, though there was a high level of uncertainty around the effect of recent fuel treatment. Our findings demonstrate that during extreme fire events, very recent (i.e., <3 years) fuel reduction burning can aid wildfire suppression locally (i.e., near assets) but will have a highly variable effect on the extent and severity of wildfires at larger scales. The patchy coverage of fuel reduction burns in the wildland-urban interface indicates that considerable residual fuel hazard will often be present within the bounds of fuel reduction burns.

Rate of tree carbon accumulation increases continuously with tree size.

Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

Longitudinal impact of the Women's Health Initiative study on hormone therapy use in Australia.

Purpose: This study aimed to examine the longitudinal impact of evidence changes on menopausal hormone therapy (MHT) use in Australia. Methods: We analyzed two datasets of subsidized and total MHT use (2000-2016) using segmented regression analysis to explore the impact of the Women's Health Initiative (WHI) 2002 and 2007 studies. Analyses were stratified by class, route, and strength. Use was measured in defined daily dose/1000 women/day (DDD/1000/day) or packs/1000 women/month (packs/1000/month). Results: The drop in total MHT use after the WHI 2002 was substantial. The biggest decreases in class, route, and strength were estrogens (28.99 DDD/1000/day, 95% confidence interval [CI] 23.97, 34.01), oral (46.07 DDD/1000/day, 95% CI 41.13, 51.01), and medium strength (34.95 packs/1000/month, 95% CI 30.17, 39.73), respectively. However, vaginal use remained stable (-1.83 DDD/1000/day, 95% CI -3.83, 0.17). Profiles of total and subsidized use were similar over time. Utilization levels were relatively unchanged after 2007. Decreased utilization contributed to product discontinuation, with a lag of up to 4 years. Product discontinuation in 2009 further decreased utilization. Discussion and conclusions: MHT use remained low after 2002 despite evidence favoring its use in women younger than 60 years or within 10 years postmenopause. Continued low use could relate to the WHI 2002 media coverage, therapy objectives, key stakeholder uncertainty, health policies, and medicine availability.

Magnetic and non-magnetic phases of a quantum spin liquid.

A quantum spin-liquid phase is an intriguing possibility for a system of strongly interacting magnetic units in which the usual magnetically ordered ground state is avoided owing to strong quantum fluctuations. It was first predicted theoretically for a triangular-lattice model with antiferromagnetically coupled S = 1/2 spins. Recently, materials have become available showing persuasive experimental evidence for such a state. Although many studies show that the ideal triangular lattice of S = 1/2 Heisenberg spins actually orders magnetically into a three-sublattice, non-collinear 120° arrangement, quantum fluctuations significantly reduce the size of the ordered moment. This residual ordering can be completely suppressed when higher-order ring-exchange magnetic interactions are significant, as found in nearly metallic Mott insulators. The layered molecular system κ-(BEDT-TTF)(2)Cu(2)(CN)(3) is a Mott insulator with an almost isotropic, triangular magnetic lattice of spin-1/2 BEDT-TTF dimers that provides a prime example of a spin liquid formed in this way. Despite a high-temperature exchange coupling, J, of 250 K (ref. 6), no obvious signature of conventional magnetic ordering is seen down to 20 mK (refs 7, 8). Here we show, using muon spin rotation, that applying a small magnetic field to this system produces a quantum phase transition between the spin-liquid phase and an antiferromagnetic phase with a strongly suppressed moment. This can be described as Bose-Einstein condensation of spin excitations with an extremely small spin gap. At higher fields, a second transition is found that suggests a threshold for deconfinement of the spin excitations. Our studies reveal the low-temperature magnetic phase diagram and enable us to measure characteristic critical properties. We compare our results closely with current theoretical models, and this gives some further insight into the nature of the spin-liquid phase.

Exotic magnetism on the quasi-fcc lattices of the d3 double Perovskites La2NaB'O6 (B'=Ru, Os).

We find evidence for long-range and short-range (ζ=70 Å at 4 K) incommensurate magnetic order on the quasi-face-centered-cubic (fcc) lattices of the monoclinic double perovskites La2NaRuO6 and La2NaOsO6, respectively. Incommensurate magnetic order on the fcc lattice has not been predicted by mean field theory, but may arise via a delicate balance of inequivalent nearest neighbor and next nearest neighbor exchange interactions. In the Ru system with long-range order, inelastic neutron scattering also reveals a spin gap Δ âˆ¼ 2.75 meV. Magnetic anisotropy is generally minimized in the more familiar octahedrally coordinated 3d3 systems, so the large gap observed for La2NaRuO6 may result from the significantly enhanced value of spin-orbit coupling in this 4d(3) material.

Spin waves and revised crystal structure of honeycomb iridate Na2IrO3.

We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zigzag magnetic order. The onset of long-range magnetic order below T(N)=15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90° Ir-O-Ir bonds required for dominant Kitaev exchange.

Synthesis of two classes of antibody, gammaM and gammaG or gammaM and gammaA, by identical cells. Amplification of the antibody response to pneumococcal polysaccharide type III.

Class-specific plaque-forming cell (PFC) (gammaM, gamma1, gamma2, and gammaA) responses to type III pneumococcal polysaccharide (SSS-III) were studied in BALB/c x C57BL/6F1 (CBF1) mice with and without induction of an allogeneic effect. Gamma1, gamma2, and gammaA PFC were detected in two ways: (a) With the sequential development of the assay slides, first for direct (gammaM)PFC followed by incubation with class-specific antiimmunoglobulin and complement for the development of additional gamma1, gamma2, and gammaA PFC (gammaM-independent gamma1, gamma2, and gammaA PFC); and (b) by blocking gammaM PFC with goat anti-gammaM and simultaneously developing gamma1, gamma2, and gammaA PFC (total gamma1-, gamma2-, and gammaA-secreting PFC). The results showed that whereas gammaM PFC arose on the 3rd d after immunization, gamma1-, gamma2-, and gammaA-secreting PFC arose on the 4th to 5th d after immunization. They appeared in association with gammaM-secreting PFC because they were detected with the gammaM blocking method but not with the sequential method. By the 7th d most gamma1, gamma2, and gammaA PFC were detected by the sequential method as well, indicating that those antibodies were secreted independently of cells secreting gammaM. When the numbers of double-class-secreting PFC were evaluated on the 5th d, the following results were obtained: 83% of gammaM PFC were secreting either gamma1 (25%), gamma2 (55%), or gammaA (2%). We interpret these data as evidence for an antigen-driven class differentiation from gammaM to gammaA and from gammaM to gammaG in the majority of anti-SSS-III-secreting clones without T-cell help. When an allogeneic effect was provided by inoculation of parental BALB/c spleen cells together with antigen, the numbers of all classes of PFC were increased. Furthermore, the frequency of gammaM-gammaG (108%) or gammaM-gammaA (9%) double-class secretors was increased, and gammaM-independent gammaG and gammaA secretors were detected earlier, indicating an overall maturation-promoting effect. In addition, prolonged appearance of gammaA PFC was dependent on the allogeneic effect.

Neonatal treatment with low doses of anti-idiotypic antibody leads to the expression of a silent clone.

BALB/c mice immunized with bacterial levan (BL) produce an immune response that fails to generate antibody expressing the idiotype (Id) of the beta (2 leads to 6) fructosan-binding myeloma protein ABPC 48 (A48). Pretreatment of newborn BALB/c mice (at 1 d of age) with 0.01-10 microgram of affinity purified BALB/c anti-A48 Id antibody followed by immunization with BL 1-2 mo later produces an anti-BL response that expresses the A48 Id. This shows that A48 Id+ anti-BL clones belong to a normally silent fraction of the anti-BL repertoire. The activation of A48 Id+ anti-BL clones anti-A48 Id antibody is specific because the pretreatment of newborn mice with anti-MOPC 384 Id antibody, followed by immunization with BL, does not lead to its activation. Moreover, pretreatment of mice with anti-A48 Id antibody does not alter the MOPC 460 Id+ component of the anti-TNP response. It is also important to note that the activation of the A48 Id+ clone in pretreated mice requires subsequent immunization with BL.

Generation of anti-type III pneumococcal polysaccharide hybridomas from mice with an X-linked B-lymphocyte defect.

(CBA/N X BALB/c male)F1 mice bear on X-linked defect making them totally unresponsive to T-independent (TI), TI-2 antigens such as type III pneumococcal polysaccharide (SSS-III). We found that somatic cell hybrids between CB nonresponder spleen cells and NS1 plasmacytoma cells secreted antibody specific for SSS-III. The solid-phase binding of such antibody was completely inhibited by the addition of free antigen (SSS-III) and the amount of antibody detected in culture fluids ranged from 10 ng/ml to 10 micrograms/ml. Eight hybridoma clones were identified; all make antibody of the IgM class. These results indicate that the X-linked defect does not result in a deletion of a B-cell subset which responds to TI-2 antigens.

Antibody response of immunodeficient (xid) CBA/N mice to Escherichia coli 0113 lipopolysaccharide, a thymus-independent antigen.

CBA/N mice, which possess an X-linked immunodeficiency (xid), produce a convincing antibody response to lipopolysaccharide derived from Escherichia coli 0113 (LPS 0113), a thymus-independent antigen. The antibody response produced was shown to be specific for the O-polysaccharide moiety of LPS 0113, rather than lipid A or lipid-A-associated protein. The relevance of this finding to the nature of the genetic defect of xid-mice is discussed.

Regulation of the antibody response to type 3 pneumococcal polysaccharide. I. Nature of regulatory cells.

The effect of treatment with antilymphocyte serum (ALS) on the magnitude of the plaque-forming cell (PFC) response to Type III pneumococcal polysaccharide (SSS-III) was assessed in athymic nude mice and thymus-bearing littermate controls. Without ALS treatment, the PFC response was slightly higher in nude than in control mice. Treatment with ALS had no effect on the response of nude mice; however, considerable enhancement was noted in thymus-bearing controls. Such enhancement was ALS dose-dependent and demonstrable under conditions in which there was substantial inactivation of thymic-derived "helper" cells required for an antibody response to erythrocyte antigens. These findings suggest that amplifier and suppressor cells, which have been reported to regulate the magnitude of the antibody response to SSS-III, represent populations of thymic-derived cells (T cells) that are not present in nude mice. The activities of "helper" T cells and regulatory T cells appear to be independent of one another and mediated by separate subpopulations of T cells.

Activation of antigen-specific suppressor T cells by B cells from mice immunized with type III pneumococcal polysaccharide.

The transfer of B lymphocytes from mice immunized with type III pneumococcal polysaccharide (SSS-III) results in antigen-specific suppression of the antibody response of recipients immunized with SSS-III. Such suppression shares many features associated with low-dose paralysis, a phenomenon mediated by suppressor T cells; it reaches maximal levels 3 d after the transfer of viable or irradiated immune B cells and can be eliminated by the depletion of SSS-III-binding cells from spleen cell suspensions before transfer. In a two-step cell transfer experiment, purified T lymphocytes, isolated from recipients previously given immune B cells, caused suppression upon transfer to other mice immunized with SSS-III. Also, B-cell-induced suppression could be abrogated in a competitive manner by the infusion of amplifier T lymphocytes, as was previously demonstrated in the case of low-dose paralysis. These findings suggest that B cell surface components, presumably the idiotypic determinants of cell-associated antibody specific for SSS-III, are instrumental in activating suppressor T cells involved in regulating the magnitude of the antibody response to SSS-III.

Genetic control of the antibody response to type 3 pneumococcal polysaccharide in mice. I. Evidence that an X-linked gene plays a decisive role in determining responsiveness.

The IgM antibody response to Type III pneumococcal polysaccharide (SSS-III) was assessed in F(1), F(2), and backcross progeny derived from high (BALB/cAnN) and extremely low (CBA/HN) responding parental strains of inbred mice. The results of these studies indicated that a major component involved in the antibody response is X-linked, i.e., carried on the X chromosome; this component determines responsiveness to SSS-III in an almost quantal or "all-or-none" manner. Other factors, presumably autosomal genes, regulate the magnitude of the antibody response produced by mice possessing the X-linked gene; these appear to influence independently the number of antibody-producing cells found after immunization and the amount of antibody made by such cells. Strains of inbred mice varied widely in their ability to respond to SSS-III. Responsiveness was not associated with H-2 histocompatibility type. The implications of these findings with respect to the genetic control of the antibody response to SSS-III are discussed.

Genetic control of the antibody response to type 3 pneumococcal polysaccharide in mice. II. Relationship between IgM immunoglobulin levels and the ability to give an IgM antibody response.

Serum IgM immunoglobulin levels and antibody responses to an optimally immunogenic dose of Type III pneumococcal polysaccharide (SSS-III) were assessed for F(1), F(2), and backcross progeny derived from crosses between high responding BALB/cAnN (B) and low responding CBA/HN (C) mice. The results obtained confirmed our original hypothesis, namely, that a major component, present on the X chromosome, governs the ability to respond to SSS-III in a decisive manner. Although all low responding C mice had low IgM levels, both intermediate and high responders had high IgM levels of the same magnitude. Treatment with bacterial lipopolysaccharides (LPS) resulted in a significant increase in the IgM levels of low responding C mice. While the IgM levels attained were similar to those of high responding B mice, not given LPS, no antibody specific for LPS appeared to be produced. These findings suggest that C mice are unable to make an IgM antibody response to SSS-III and other polysaccharide antigens, despite the fact that they possess the capacity to synthesize normal amounts of IgM immunoglobulin.

Coexistence of static magnetism and superconductivity in SmFeAsO(1-x)F(x) as revealed by muon spin rotation.

The recent observation of superconductivity with critical temperatures (Tc) up to 55 K in the pnictide RFeAsO(1-x)F(x), where R is a lanthanide, marks the first discovery of a non-copper-oxide-based layered high-Tc superconductor. It has raised the suspicion that these new materials share a similar pairing mechanism to the cuprate superconductors, as both families exhibit superconductivity following charge doping of a magnetic parent material. In this context, it is important to follow the evolution of the microscopic magnetic properties of the pnictides with doping and hence to determine whether magnetic correlations coexist with superconductivity. Here, we present a muon spin rotation study on SmFeAsO(1-x)F(x), with x=0-0.30 that shows that, as in the cuprates, static magnetism persists well into the superconducting regime. This analogy is quite surprising as the parent compounds of the two families have rather different magnetic ground states: itinerant spin density wave for the pnictides contrasted with the Mott-Hubbard insulator in the cuprates. Our findings therefore suggest that the proximity to magnetic order and associated soft magnetic fluctuations, rather than strong electronic correlations in the vicinity of a Mott-Hubbard transition, may be the key ingredients of high-Tc superconductors.

Crystal structure of DNA recombination protein RuvA and a model for its binding to the Holliday junction.

The Escherichia coli DNA binding protein RuvA acts in concert with the helicase RuvB to drive branch migration of Holliday intermediates during recombination and DNA repair. The atomic structure of RuvA was determined at a resolution of 1.9 angstroms. Four monomers of RuvA are related by fourfold symmetry in a manner reminiscent of a four-petaled flower. The four DNA duplex arms of a Holliday junction can be modeled in a square planar configuration and docked into grooves on the concave surface of the protein around a central pin that may facilitate strand separation during the migration reaction. The model presented reveals how a RuvAB-junction complex may also accommodate the resolvase RuvC.

A mechanism of drug action revealed by structural studies of enoyl reductase.

Enoyl reductase (ENR), an enzyme involved in fatty acid biosynthesis, is the target for antibacterial diazaborines and the front-line antituberculosis drug isoniazid. Analysis of the structures of complexes of Escherichia coli ENR with nicotinamide adenine dinucleotide and either thienodiazaborine or benzodiazaborine revealed the formation of a covalent bond between the 2' hydroxyl of the nicotinamide ribose and a boron atom in the drugs to generate a tight, noncovalently bound bisubstrate analog. This analysis has implications for the structure-based design of inhibitors of ENR, and similarities to other oxidoreductases suggest that mimicking this molecular linkage may have generic applications in other areas of medicinal chemistry.

Crystallization and preliminary X-ray analysis of D-2-hydroxyacid dehydrogenase from Haloferax mediterranei.

D-2-hydroxyacid dehydrogenase (D2-HDH) from Haloferax mediterranei has been overexpressed in Escherichia coli, solubilized in 8 M urea and refolded by rapid dilution. The protein was purified and crystallized by the hanging-drop vapour-diffusion method using ammonium sulfate or PEG 3350 as precipitant. Two crystal forms representing the free enzyme and the nonproductive ternary complex with alpha-ketohexanoic acid and NAD(+) grew under these conditions. Crystals of form I diffracted to beyond 3.0 A resolution and belonged to the monoclinic space group P2(1), with unit-cell parameters a = 66.0, b = 119.6, c = 86.2 A, beta = 96.3 degrees . Crystals of form II diffracted to beyond 2.0 A resolution and belonged to the triclinic space group P1, with unit-cell parameters a = 66.5, b = 75.2, c = 77.6 A, alpha = 109.1, beta = 107.5, gamma = 95.9 degrees. The calculated values for V(M) and analysis of the self-rotation and self-Patterson functions suggest that the asymmetric unit in both crystal forms contains two dimers related by pseudo-translational symmetry.

Probing magnetic order and disorder in the one-dimensional molecular spin chains CuF2(pyz) and [Ln(hfac)3(boaDTDA)] n (Ln = Sm, La) using implanted muons.

We present the results of muon-spin relaxation ([Formula: see text]SR) measurements on antiferromagnetic and ferromagnetic spin chains. In antiferromagnetic CuF2(pyz) we identify a transition to long range magnetic order taking place at [Formula: see text] K, allowing us to estimate a ratio with the intrachain exchange of [Formula: see text] and the ratio of interchain to intrachain exchange coupling as [Formula: see text]. The ferromagnetic chain [Sm(hfac)3(boaDTDA)] n undergoes an ordering transition at [Formula: see text] K, seen via a broad freezing of dynamic fluctuations on the muon (microsecond) timescale and implying [Formula: see text]. The ordered radical moment continues to fluctuate on this timescale down to 0.3 K, while the Sm moments remain disordered. In contrast, the radical spins in [La(hfac)3(boaDTDA)] n remain magnetically disordered down to T = 0.1 K suggesting [Formula: see text].

Differential expression of signal transduction factors in ovarian follicle development: a functional role for betaglycan and FIBP in granulosa cells in cattle.

Ovarian follicles develop in groups yet individual follicles follow different growth trajectories. This growth and development are regulated by endocrine and locally produced growth factors that use a myriad of receptors and signal transduction pathways to exert their effects on theca and granulosa cells. We hypothesize that differential growth may be due to differences in hormonal responsiveness that is partially mediated by differences in expression of genes involved in signal transduction. We used the bovine dominant follicle model, microarrays, quantitative real-time PCR and RNA interference to examine this. We identified 83 genes coding for signal transduction molecules and validated a subset of them associated with different stages of the follicle wave. We suggest important roles for CAM kinase-1 and EphA4 in theca cells and BCAR1 in granulosa cells for the development of dominant follicles and for betaglycan and FIBP in granulosa cells of regressing subordinate follicles. Inhibition of genes for betaglycan and FIBP in granulosa cells in vitro suggests that they inhibit estradiol production in regressing subordinate follicles.