The Mars Pathfinder meteorological station recorded wind, pressure, and temperature fluctuations that have been interpreted as dust devils: warm‐core vortices that form at the bottom of connective ...plumes. We apply a scaling theory Rennó et al., 1998, developed to explain terrestrial dust devil observations, to test the validity of this interpretation and to provide a simple physical interpretation of the general characteristics of Martian dust devils. The theory is based on the thermodynamics of heat engines and predicts the central pressure and the wind speed of the connective vortices. Our findings are as follows: For the best documented candidate event (sol 25), observed wind and pressure fluctuations are consistent with those predicted by the model and hence strengthen the interpretation of this case as a dust devil. A number of other candidates, less well documented, however, also are consistent with passage of a dust devil over or near the lander. Temperature fluctuations observed on other sols permit dust devils an order of magnitude larger than the ones measured by the meteorology package. The strongest dust devils predicted by our theory have a central pressure deficit of about 50 Pa and wind speed of about 60 m s−1. The strongest dust devils are capable of lofting dust and hence support the interpretation of selected Pathfinder images as showing the passage of dust devils within sight of the lander.
Researchers have investigated several therapeutic approaches to treat non-union fractures. Among these, bioactive glasses and glass ceramics have been widely used as grafts. This class of biomaterial ...has the ability to integrate with living bone. Nevertheless, bioglass and bioactive materials have been used mainly as powder and blocks, compromising the filling of irregular bone defects. Considering this matter, our research group has developed a new bioactive glass composition that can originate malleable fibers, which can offer a more suitable material to be used as bone graft substitutes. Thus, the aim of this study was to assess the morphological structure (via scanning electron microscope) of these fibers upon incubation in phosphate buffered saline (PBS) after 1, 7 and 14 days and, also, evaluate the in vivo tissue response to the new biomaterial using implantation in rat tibial defects. The histopathological, immunohistochemistry and biomechanical analyzes after 15, 30 and 60 days of implantation were performed to investigate the effects of the material on bone repair. The PBS incubation indicated that the fibers of the glassy scaffold degraded over time. The histological analysis revealed a progressive degradation of the material with increasing implantation time and also its substitution by granulation tissue and woven bone. Histomorphometry showed a higher amount of newly formed bone area in the control group (CG) compared to the biomaterial group (BG) 15 days post-surgery. After 30 and 60 days, CG and BG showed a similar amount of newly formed bone. The novel biomaterial enhanced the expression of RUNX-2 and RANK-L, and also improved the mechanical properties of the tibial callus at day 15 after surgery. These results indicated a promising use of the new biomaterial for bone engineering. However, further long-term studies should be carried out to provide additional information concerning the material degradation in the later stages and the bone regeneration induced by the fibrous material.
Introduction
Collagen from marine esponges has been used as a promising material for tissue engineering proposals. Similarly, photobiomodulation (PBM) is able of modulating inflammatory processes ...after an injury, accelerating soft and hard tissue healing and stimulating neoangiogenesis. However, the effects of the associated treatments on bone tissue healing have not been studied yet. In this context, the present study aimed to evaluate the biological temporal modifications (using two experimental periods) of marine sponge collagen or sponging (SPG) based scaffold and PBM on newly formed bone using a calvaria bone defect model.
Material and Methods
Wistar rats were distributed into two groups: SPG or SPG/PBM and euthanized into two different experimental periods (15 and 45 days post-surgery). A cranial critical bone defect was used to evaluate the effects of the treatments. Histology, histomorfometry and immunohistological analysis were performed.
Results
Histological findings demonstrated that SPG/PBM-treated animals, 45 days post-surgery, demonstrated a higher amount of connective and newly formed bone tissue at the region of the defect compared to CG. Notwithstanding, no difference among groups were observed in the histomorphometry. Interestingly, for both anti-transforming growth factor-beta (TGF-β) and anti-vascular endothelial growth factor (VEGF) immunostaining, higher values for SPG/PBM, at 45 days post-surgery could be observed.
Conclusion
It can be concluded that the associated treatment can be considered as a promising therapeutical intervention.
ABSTRACT
A one‐dimensional, radiative‐convective model is used to study the equilibria conditions of moist atmospheres. We show that when the hydrologic cycle is included in the model a subcritical ...bifurcation occurs, leading to 2 linearly stable solutions to the radiative‐convective equilibria. In this case, when the net forcing is larger than a critical value, two equilibria are possible. Furthermore, a finite amplitude instability can lead to a runaway greenhouse regime when the solar forcing is larger than a second critical value. In general, previous climate studies with radiative‐convective models did not include a hydrologic cycle. Instead, the atmosphere's water vapor mixing ratio was diagnosed based on the climatological profile of relative humidity. We show that fixing the water vapor relative humidity profile at the climatological value (in the computation of the radiation fluxes only) leads to a unique stable solution to the radiative‐convective equilibria. Thus, the crucial part of the hydrologic cycle which allows multiple solutions is the relaxation of the assumption of a climatological relative humidity profile. Our results do not apply directly to any real planet because of large uncertainties in our calculation due to the absence of clouds and the use of a one‐dimensional model. The 1st equilibrium corresponds to an optically thin atmosphere. In this regime, the system is nearly linear and is in a state of small dissipation. The 2nd equilibrium corresponds to an optically thick atmosphere. In this 2nd regime, the system is highly nonlinear and is in a state of large dissipation.
Toll-like receptor 3 (TLR3) is a pattern-recognition receptor known to initiate an innate immune response when stimulated by double-stranded RNA (dsRNA). Components of TLR3 signaling, including TIR ...domain-containing adapter inducing IFN-α (TRIF), have been demonstrated to contribute to dsRNA-induced cell death through caspase-8 and receptor interacting protein (RIP)1 in various human cancer cells. We provide here a detailed analysis of the caspase-8 activating machinery triggered in response to Poly(I:C) dsRNA. Engagement of TLR3 by dsRNA in both type I and type II lung cancer cells induces the formation of an atypical caspase-8-containing complex that is devoid of classical death receptors of the TNFR superfamily, but instead is physically associated to TLR3. The recruitment of caspase-8 to TLR3 requires RIP1, and is negatively modulated by cellular inhibitor of apoptosis protein (cIAP)2-TNF receptor-associated factor (TRAF)2-TNFR-associated death domain (TRADD) ubiquitin ligase complex, which regulates RIP1 ubiquitination. Intriguingly, unlike Fas- or TRAILR-dependent death signaling, caspase-8 recruitment and activation within the TLR3 death-signaling complex appears not to be stringently dependent on Fas-associated with death domain (FADD). Our findings uncover a novel aspect of the molecular mechanisms involved during apoptosis induced by the innate immune receptor TLR3 in cancer cells.
We compute the dissipation due to the drag of falling raindrops and cloud droplets, and find both to be significant sources of dissipation on Earth and possibly Titan. On other planets, they appear ...to be insignificant. We compare this dissipation with the latent heat transported by the drops and the thermodynamic efficiency with which it can be converted into work. This comparison suggests moist convection on Earth and Titan is similar, but on Jupiter latent heat alone does not provide enough work to lift the condensate against gravity.
Pauluis et al. argue that frictional dissipation of energy around falling hydrometeors is an important entropy source in the tropical atmosphere. Their calculations suggest that the frictional ...dissipation around hydrometeors is about 1/3 of the work available from a reversible convective heat engine. Moreover, based on the residual of the energy budget of a numerical model, not shown in their note, the authors argue that irreversible entropy sources due to diffusion of water vapor and phase changes reduce the mechanical work available from the convective heat engine by about 2/3. Pauluis et al. conclude that only a tiny fraction of the energy potentially available from a convective heat engine is used to perform work. Renno and Ingersoll show that frictional heating can be easily included in the heat engine framework via increases in the thermodynamic efficiency of a reversible heat engine. It is shown that the effect of any other irreversible process is merely to reduce the thermodynamic efficiency of a reversible convective heat engine. Thus, the framework proposed by Renno and Ingersoll is valid even when the heat engine is as irreversible as suggested by Pauluis et al. Since irreversible entropy sources reduce the mechanical work available from the convective heat engine, the study of Pauluis et al. implies that the bulk thermodynamic efficiency of the tropical atmosphere is only a tiny fraction of that predicted by the framework proposed by Renno and Ingersoll. Both theoretical and observational evidence that the calculations performed by Pauluis et al. overestimate the irreversible entropy changes in the real tropical atmosphere is shown. Moreover, evidence that numerical models are highly dissipative when compared with nature is shown. Therefore, the interpretation of Pauluis et al. that the reversible heat engine framework grossly overestimates the rate at which work is performed by tropical convective systems is not agreed with.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Intraseasonal fluctuations associated with the Mexican monsoon system are examined for the semiarid Sonoran Desert region. Daily rain gauge accumulations, radiosonde reports, satellite imagery, and ...global analyses are all analyzed. Composite wet and dry periods during July and August of 1985-92 are compared, and the statistical significance of differences between the composite fields are assessed. Significant differences exist between many of the wet and dry fields over the Sonoran Desert. As the monsoon shifts from dry to wet conditions, the subtropical ridge moves similar to 5 degrees lat northward, and the middle- and upper-tropospheric (700-300 mb) winds back from southwesterly to southeasterly. The midtropospheric transport of water vapor from the southeast strengthens, and the precipitable water values increase by as much as similar to 1.2 cm ( similar to 0.5 in.). Middle-tropospheric air parcels ascend into the region from the southeast, while low-level air parcels continue to stream inland from the Gulf of California and up the slopes of the Sierra Madre Occidental. The surface and midtropospheric air parcels rise at an average rate of similar to 50-75 mb per day and would saturate within 2 days if undiluted. This combination of conditions leads to a more unstable atmosphere and an increase in convective activity. Spectral analysis of precipitation data for southeast Arizona indicates that 75% of the temporal variance is contained in fluctuations longer than 7 days and that a statistically significant peak exists in the 12-18-day band. These results suggest that large-scale, low-frequency dynamics might play an important role in modulating the variability of convective activity over the Sonoran Desert.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
We show that simple thermodynamic models of convective plumes predict the area fraction of convective plumes (i.e., updrafts) in Titan's atmosphere to be ∼12 smaller than on Earth. This result is in ...agreement with predictions by sophisticated dynamical models and with the relative tropospheric cloud cover, which is only ∼1% on Titan. Rainstorms on Titan, being so rare, may be violent.
The combination of different biomaterials can be a promising intervention for the composites manufacture, mainly by adding functional and structural characteristics of each material and guarantee the ...advantages of the use of these composites. In this context, the aim of this study was to develop and evaluated the influence of the incorporation of marine spongin (SPG) into Biosilicate® (BS) in different proportions be used during bone repair. For this purpose, it was to develop and investigate different BS/SPG formulations for physico-chemical and morphological characteristics by pH, loss mass, Fourier transform infrared spectrometer (FTIR) and scanning electron microscope (SEM) analysis. Additionally, the influence of these composites on cell viability, proliferation, and alkaline phosphatase (ALP) activity were investigated. The results revealed that the pH values of all BS groups (with or without SPG) increased over time. A significant mass loss was observed in all composites, mainly with higher SPG percentages. Additionaly, SEM micrographies demonstrated fibers of SPG into BS and material degradation over time. Moreover, FTIR spectral analysis revealed characteristic peaks of PMMA, BS, and SPG in BS/SPG composites. BS/SPG groups demonstrated a positive effect for fibroblast proliferation after 3 and 7 days of culture. Additionally, BS and BS/SPG formulations (at 10% and 20% of SPG) presented similar values of osteoblasts viability and proliferation after 7 days of culture. Furthermore, ALP activity demonstrated no significant difference between BS and BS/SPG scaffolds, at any composition. Based on the present in vitro results, it can be concluded that the incorporation of SPG into BS was possible and produced an improvement in the physical-chemical characteristics and in the biological performance of the graft especially the formulation with 80/20 and 90/10. Future research should focus on in vivo evaluations of this novel composite.
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