Last glacial maximum radiative forcing from mineral dust aerosols in an Earth System model

The mineral dust cycle in pre-industrial (PI) and last glacial maximum (LGM) simulations with the CMIP5 model HadGEM2-A is evaluated. The modeled global dust cycle is enhanced at the LGM, with larger emissions in the Southern hemisphere, consistent with some previous studies. Two different dust uplift schemes within HadGEM2 both show a similar LGM/PI increase in total emissions (60% and 80%) and global loading (100% and 75%), but there is a factor of three difference in the top of the atmosphere net LGM-PI direct radiative forcing (-1.2Wm−2 and -0.4Wm−2, respectively). This forcing is dominated by the short-wave effects in both schemes. Recent reconstructions of dust deposition fluxes suggest that the LGM increase is overestimated in the Southern Atlantic and underestimated over east Antarctica. The LGM dust deposition reconstructions do not strongly discern between these two dust schemes because deposition is dominated by larger (2-6Îijm diameter) particles for which the two schemes show similar loading in both time periods. The model with larger radiative forcing shows a larger relative emissions increase of smaller particles. This is because of the size-dependent friction velocity emissions threshold and different size distribution of the soil source particles compared with the second scheme. Size-dependence of the threshold velocity is consistent with the theory of saltation, implying that the model with larger radiative forcing is more realistic. However, the large difference in radiative forcing between the two schemes highlights the size distribution at emission as a major uncertainty in predicting the climatic effects of dust cycle changes

An evolved disk surrounding the massive main sequence star MWC 297?

We present the results of the interferometric observations of the circumstellar disk surrounding MWC 297 in the continuum at 230 GHz (1.3 mm) and in the (J=2-1) rotational transitions of $^{12}$CO,$^{13}$CO and C$^{18}$O using the Submillimeter Array. At a distance of 250 pc, MWC 297 is one of the closest, young massive stars (M$_{\star}$ $\sim$10 M$_{\odot}$) to us. Compact continuum emission is detected towards MWC 297 from which we estimate a disk mass (gas+dust) of 0.07 M$_{\odot}$ and a disk radius of $\le$ 80 AU. Our result demonstrates that circumstellar disks can survive around massive stars well into their main sequence phase even after they have become optically visible. Complementing our observations with the data compiled from the literature, we find the submm dust opacity index $\beta$ to be between 0.1 and 0.3. If the emission is optically thin, the low value of $\beta$ indicates the presence of relatively large grains in the disk, possibly because of grain growth. We do not detect any CO emission associated with the continuum source. We argue that the $^{13}$CO emission from the disk is likely optically thin, in which case, we derive an upper limit to the gas mass which implies significant depletion of molecular gas in the disk. The mass of this disk and the evolutionary trends observed are similar to those found for intermediate mass Herbig Ae stars and low mass T Tauri stars.Comment: 4 pages, 3 Figures, accepted for publication in ApJ

Improved climate simulations through a stochastic parameterization of ocean eddies

In climate simulations, the impacts of the sub-grid scales on the resolved scales are conventionally represented using deterministic closure schemes, which assume that the impacts are uniquely determined by the resolved scales. Stochastic parameterization relaxes this assumption, by sampling the sub-grid variability in a computationally inexpensive manner. This study shows that the simulated climatological state of the ocean is improved in many respects by implementing a simple stochastic parameterization of ocean eddies into a coupled atmosphere–ocean general circulation model. Simulations from a high-resolution, eddy-permitting ocean model are used to calculate the eddy statistics needed to inject realistic stochastic noise into a low-resolution, non-eddy-permitting version of the same model. A suite of four stochastic experiments is then run to test the sensitivity of the simulated climate to the noise definition, by varying the noise amplitude and decorrelation time within reasonable limits. The addition of zero-mean noise to the ocean temperature tendency is found to have a non-zero effect on the mean climate. Specifically, in terms of the ocean temperature and salinity fields both at the surface and at depth, the noise reduces many of the biases in the low-resolution model and causes it to more closely resemble the high-resolution model. The variability of the strength of the global ocean thermohaline circulation is also improved. It is concluded that stochastic ocean perturbations can yield reductions in climate model error that are comparable to those obtained by refining the resolution, but without the increased computational cost. Therefore, stochastic parameterizations of ocean eddies have the potential to significantly improve climate simulations

Platelet protective efficacy of 3,4,5 trisubstituted isoxazole analogue by inhibiting ROS-mediated apoptosis and platelet aggregation

Thrombocytopenia is a major hematological concern in oxidative stress-associated pathologies and chronic clinical disorders, where premature platelet destruction severely affects the normal functioning of thrombosis and hemostasis. In addition, frequent exposure of platelets to chemical entities and therapeutic drugs immensely contributes in the development of thrombocytopenia leading to huge platelet loss, which might be fatal sometimes. Till date, there are only few platelet protective molecules known to combat thrombocytopenia. Hence, small molecule therapeutics are extremely in need to relieve the burden on limited treatment strategies of thrombocytopenia. In this study, we have synthesized a series of novel 3,4,5 trisubstituted isoxazole derivatives, among which compound 4a [4-methoxy-N'-(5-methyl-3-phenylisoxazole-4-carbonyl) benzenesulfonohydrazide] was found to significantly ameliorate the oxidative stress-induced platelet apoptosis by restoring various apoptotic markers such as ROS content, cytosolic Ca(2+) levels, eIF2-α phosphorylation, mitochondrial membrane depolarization, cytochrome c release, caspase activation, PS externalization, and cytotoxicity markers. Additionally, compound 4a dose dependently inhibits collagen-induced platelet aggregation. Hence, compound 4a can be considered as a prospective molecule in the treatment regime of platelet activation and apoptosis and other clinical conditions of thrombocytopenia. Further studies might ensure the use of compound 4a as a supplementary therapeutic agent to treat, thrombosis and CVD-associated complications. Over all, the study reveals a platelet protective efficacy of novel isoxazole derivative 4a with a potential to combat oxidative stress-induced platelet apoptosis

Global response of clear-air turbulence to climate change

Clear-air turbulence (CAT) is one of the largest causes of weather-related aviation incidents. Here we use climate model simulations to study the impact that climate change could have on global CAT by the period 2050–2080. We extend previous work by analyzing eight geographic regions, two flight levels, five turbulence strength categories, and four seasons. We find large relative increases in CAT, especially in the midlatitudes in both hemispheres, with some regions experiencing several hundred per cent more turbulence. The busiest international airspace experiences the largest increases, with the volume of severe CAT approximately doubling over North America, the North Pacific, and Europe. Over the North Atlantic, severe CAT in future becomes as common as moderate CAT historically. These results highlight the increasing need to improve operational CAT forecasts and to use them effectively in flight planning, to limit discomfort and injuries among passengers and crew

STAT2 deficiency and susceptibility to viral illness in humans

Severe infectious disease in children may be a manifestation of primary immunodeficiency. These genetic disorders represent important experiments of nature with the capacity to elucidate nonredundant mechanisms of human immunity. We hypothesized that a primary defect of innate antiviral immunity was responsible for unusually severe viral illness in two siblings; the proband developed disseminated vaccine strain measles following routine immunization, whereas an infant brother died after a 2-d febrile illness from an unknown viral infection. Patient fibroblasts were indeed abnormally permissive for viral replication in vitro, associated with profound failure of type I IFN signaling and absence of STAT2 protein. Sequencing of genomic DNA and RNA revealed a homozygous mutation in intron 4 of STAT2 that prevented correct splicing in patient cells. Subsequently, other family members were identified with the same genetic lesion. Despite documented infection by known viral pathogens, some of which have been more severe than normal, surviving STAT2-deficient individuals have remained generally healthy, with no obvious defects in their adaptive immunity or developmental abnormalities. These findings imply that type I IFN signaling [through interferon-stimulated gene factor 3 (ISGF3)] is surprisingly not essential for host defense against the majority of common childhood viral infections