Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt ...occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Niño event. The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events.
has emerged globally as a multidrug-resistant yeast that can spread via nosocomial transmission. An initial phylogenetic study of isolates from Japan, India, Pakistan, South Africa, and Venezuela ...revealed four populations (clades I, II, III, and IV) corresponding to these geographic regions. Since this description,
has been reported in more than 30 additional countries. To trace this global emergence, we compared the genomes of 304
isolates from 19 countries on six continents. We found that four predominant clades persist across wide geographic locations. We observed phylogeographic mixing in most clades; clade IV, with isolates mainly from South America, demonstrated the strongest phylogeographic substructure.
isolates from two clades with opposite mating types were detected contemporaneously in a single health care facility in Kenya. We estimated a Bayesian molecular clock phylogeny and dated the origin of each clade within the last 360 years; outbreak-causing clusters from clades I, III, and IV originated 36 to 38 years ago. We observed high rates of antifungal resistance in clade I, including four isolates resistant to all three major classes of antifungals. Mutations that contribute to resistance varied between the clades, with Y132F in
as the most widespread mutation associated with azole resistance and S639P in
for echinocandin resistance. Copy number variants in
predominantly appeared in clade III and were associated with fluconazole resistance. These results provide a global context for the phylogeography, population structure, and mechanisms associated with antifungal resistance in
In less than a decade,
has emerged in health care settings worldwide; this species is capable of colonizing skin and causing outbreaks of invasive candidiasis. In contrast to other
species,
is unique in its ability to spread via nosocomial transmission and its high rates of drug resistance. As part of the public health response, whole-genome sequencing has played a major role in characterizing transmission dynamics and detecting new
introductions. Through a global collaboration, we assessed genome evolution of isolates of
from 19 countries. Here, we described estimated timing of the expansion of each
clade and of fluconazole resistance, characterized discrete phylogeographic population structure of each clade, and compared genome data to sensitivity measurements to describe how antifungal resistance mechanisms vary across the population. These efforts are critical for a sustained, robust public health response that effectively utilizes molecular epidemiology.
Isothermal reaction kinetics of thiol-epoxy (multifunctional thiol-difunctional epoxy) reactions with and without external catalyst 1,8-diazabicyclo5.4.0undec-7-ene (DBU) were studied using ...differential scanning calorimetry (DSC). Autocatalytic behavior is observed both without DBU and with DBU, which is attributed to autocatalysis effects of hydroxyl products of the reaction. The isothermal curing kinetics are well described by the Kamal autocatalytic model, which is expressed as dα/dt=(k1 + k2αm)(1 − α)n (α: fractional conversion; dα/dt: apparent rate of reaction). Parameters of the reaction, including reaction orders m and n, apparent rate parameters k1 and k2, and activation energies are determined by fitting the experimental data to the Kamal model. For the thiol-epoxy reaction without DBU, the overall reaction order (m + n) is approximately 3 (with m ≈ 2 and n ≈ 1) but decreases to 2 (with m ≈ 1 and n ≈ 1) upon addition of DBU. Based on the most commonly described mechanism for nucleophilic thiol-epoxy reactions in the literature, new reaction schemes are proposed by incorporating the hydroxyl autocatalysis effect as well as the effect of external catalyst DBU on apparent reaction order. The proposed reaction schemes allow for excellent fits to reaction kinetics for thiol-epoxy reactions with and without DBU. In contrast to the strong effect of external DBU catalyst on reaction kinetics, changing the thiol monomer functionality leads to relatively small changes in apparent rate parameters and no change in the order of reaction or reaction mechanism.
Display omitted
•Isothermal kinetics of multifunctional thiol-epoxy reactions are studied by DSC.•Autocatalysis effect due to hydroxyl products is observed both without and with DBU.•DBU exhibits great effects on both rate parameters and apparent reaction orders.•Reaction schemes with hydroxyl autocatalysis and DBU catalysis effects are proposed.•The change in thiol monomer functionality has no effect on reaction mechanism.
In Australia in 2015, Candida auris sternal osteomyelitis was diagnosed in a 65-year-old man with a history of intensive care treatment in Kenya in 2012 and without a history of cardiac surgery. The ...isolate was South Africa clade III. Clinicians should note that C. auris can cause low-grade disease years after colonization.
Apoptosis is essential for normal development and maintenance of homeostasis, and disruption of apoptotic pathways is associated with multiple disease states, including cancer. Although initially ...identified as central regulators of apoptosis at the level of mitochondria, an important role for BCL-2 proteins at the endoplasmic reticulum is now well established. Signaling pathways emanating from the endoplasmic reticulum (ER) are involved in apoptosis initiated by stimuli as diverse as ER stress, oncogene expression, death receptor (DR) ligation and oxidative stress, and the BCL-2 family is almost invariably implicated in the regulation of these pathways. This also includes Ca(2+)-mediated cross talk between ER and mitochondria during apoptosis, which contributes to the mitochondrial dynamics that support the core mitochondrial apoptosis pathway. In addition to the regulation of apoptosis, BCL-2 proteins at the ER also regulate autophagy, a survival pathway that limits metabolic stress, genomic instability and tumorigenesis. In cases where apoptosis is inhibited, however, prolonged autophagy can lead to cell death. This review provides an overview of ER-associated apoptotic and autophagic signaling pathways, with particular emphasis on the BCL-2 family proteins.
The influence of hard-segment structure on the properties of segmented polyhydroxyurethane (PHU) was investigated using three bis-carbonate molecules: divinylbenzene dicyclocarbonate (DVBDCC), ...Bisphenol A dicarbonate (BPADC), and resorcinol bis-carbonate (RBC). These carbonates were formulated with poly(tetramethylene oxide) (PTMO)-based and polybutadiene-co-acrylonitrile (PBN)-based soft segments at 40 wt % hard-segment content, resulting in non-isocyanate polyurethanes (NIPUs). Small-angle X-ray scattering, dynamic mechanical analysis, and tensile testing reveal that hard-segment and soft-segment structures may cooperatively influence segmented PHU properties. With PTMO-based soft segment, BPADC yields phase-mixed PHU because of strong intersegmental hydrogen bonding from the hard-segment hydroxyl groups to the soft segment; in contrast, because of moderate intersegmental hydrogen bonding to the PTMO-based soft segment, DVBDCC and RBC lead to nanophase-separated PHUs with 15–17 nm interdomain spacings with substantial, broad interphase regions and low tensile strengths of ∼0.40 MPa for DVBDCC and ∼0.27 MPa for RBC. By suppressing intersegmental hydrogen bonding via the use of PBN-based soft segment, formulations with all three carbonate molecules lead to nanophase-separated PHUs with interdomain spacings of 11–16 nm, narrow interfaces, and improved tensile strengths ranging from 1.6 to 0.5 MPa in the order DVBDCC > BPADC > RBC. All PBN-based PHUs exhibit reversibility of extension with hysteresis similar to that found in thermoplastic polyurethane elastomers.
Polyhydroxyurethane (PHU) is of major research interest because it is a non-isocyanate polyurethane-like (NIPU) polymer. Here, we demonstrate the ability to tune nanophase separation in linear, ...segmented PHU copolymers via the soft segment. PHUs were synthesized from polytetramethylene oxide (PTMO)- and polybutadiene-co-acrylonitrile (PBN)-based soft segments, with divinyl benzene dicyclocarbonate and Dytek-A as hard segment and chain extender, respectively. These NIPU polymers were characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and tensile testing. SAXS reveals that the NIPUs with 30–40 wt% hard segment are nanophase separated with interdomain spacings of 9–16 nm. DMA reveals that PTMO-based PHUs have broad interphases with a range of local compositions and glass transition temperatures (Tgs), with tan δ ≥ 0.3 over temperature ranges exceeding 70 °C in breadth. In contrast, PBN-based PHUs have sharper interphases, evidenced by narrow tan δ peaks near soft-segment and hard-segment Tgs as well as by DSC and AFM data. FTIR shows that the ratio of hydrogen-bonded carbonyl to free carbonyl is higher in PBN-based PHU than in PTMO-based PHU, consistent with the absence and presence of intersegment hydrogen bonding in PBN-based PHU and PTMO-based PHU, respectively.
Display omitted
•Non-isocyanate, segmented PHUs were made with PTMO and PBN soft segments.•Major tunability in nanophase separation is observed with soft-segment choice.•PTMO soft segment yields nanophase-separated PHU with broad interphases.•PBN soft segment yields nanophase-separated PHU with sharp, narrow interphases.•PTMO-based PHU exhibits broad-T damping character; PBN-based PHU is more like TPU.
Background. Longer-term morbidity and outcomes of Cryptococcus gattii infection are not described. We analyzed clinical, microbiological, and outcome data in Australian patients followed for 12 ...months, to identify prognostic determinants. Methods. Culture-confirmed C. gattii cases from 2000 to 2007 were retrospectively evaluated. Clinical, microbiological, radiological, and outcome data were recorded at diagnosis and at 6 weeks, 6 months, and 12 months. Clinical and laboratory variables associated with mortality and with death and/or neurological sequelae were determined. Results. Annual C. gattii infection incidence was 0.61 per 10 6 population. Sixty-two of 86 (72%) patients had no immunocompromise; 6 of 24 immunocompromised hosts had idiopathic CD4 lymphopenia, and 1 had human immunodeficiency virus/AIDS. Clinical and microbiological characteristics of infection were similar in immunocompromised and healthy hosts. Isolated lung, combined lung and central nervous system (CNS), and CNS only disease was reported in 12%, 51% and 34% of the cases, respectively. Complications in CNS disease included raised intracranial pressure (42%), hydrocephalus (30%), neurological deficits (27%; 6% developed during therapy) and immune reconstitutionlike syndrome (11%). Geometric mean serum cryptococcal antigen (CRAG) titers in CNS disease were 563.9 (vs 149.3 in isolated lung infection). Patient immunocompromise was associated with increased mortality risk. An initial cerebrospinal fluid CRAG titer of ≥256 predicted death and/or neurological sequelae (P = .05). Conclusions. Neurological C. gattii disease predominates in the Australian endemic setting. Lumbar puncture and cerebral imaging, especially if serum CRAG titers are ≥512, are essential. Long-term follow up is required to detect late neurological complications. Immune system evaluation is important because host immunocompromise is associated with reduced survival.
Higher temperatures associated with climate change are anticipated to trigger an earlier start to the growing season, which could increase the terrestrial C sink strength. Greater variability in the ...amount and timing of precipitation is also expected with higher temperatures, bringing increased drought stress to many ecosystems. We experimentally assessed the effects of higher temperature and drought on the foliar phenology and shoot growth of mature trees of two semiarid conifer species. We exposed field‐grown trees to a ~45% reduction in precipitation with a rain‐out structure (‘drought’), a ~4.8 °C temperature increase with open‐top chambers (‘heat’), and a combination of both simultaneously (‘drought + heat’). Over the 2013 growing season, drought, heat, and drought + heat treatments reduced shoot and needle growth in piñon pine (Pinus edulis) by ≥39%, while juniper (Juniperus monosperma) had low growth and little response to these treatments. Needle emergence on primary axis branches of piñon pine was delayed in heat, drought, and drought + heat treatments by 19–57 days, while secondary axis branches were less likely to produce needles in the heat treatment, and produced no needles at all in the drought + heat treatment. Growth of shoots and needles, and the timing of needle emergence correlated inversely with xylem water tension and positively with nonstructural carbohydrate concentrations. Our findings demonstrate the potential for delayed phenological development and reduced growth with higher temperatures and drought in tree species that are vulnerable to drought and reveal potential mechanistic links to physiological stress responses. Climate change projections of an earlier and longer growing season with higher temperatures, and consequent increases in terrestrial C sink strength, may be incorrect for regions where plants will face increased drought stress with climate change.
PDF
