Hasil untuk "physics.ao-ph"

J. Rousk, J. Rousk, E. Bååth et al.

C. Lauber, M. Hamady, R. Knight et al.

K. Caldeira, M. Wickett

E. O. Mclean

Gero Miesenböck, D. A. D. Angelis, J. Rothman

Jungmin Lee, R. Durst, R. Wrolstad

Xiaomeng Zhang, Yuxiang Lin, R. Gillies

Boeun Lee, Hyoree Seo, Hae Ri Lee et al.

Chuanxi Wang, zhenzhu xu, Hao Cheng et al.

E. A. Miller, D. Beasley, R. Dunn et al.

The human vaginal microbiome is dominated by bacteria from the genus Lactobacillus, which create an acidic environment thought to protect women against sexually transmitted pathogens and opportunistic infections. Strikingly, lactobacilli dominance appears to be unique to humans; while the relative abundance of lactobacilli in the human vagina is typically >70%, in other mammals lactobacilli rarely comprise more than 1% of vaginal microbiota. Several hypotheses have been proposed to explain humans' unique vaginal microbiota, including humans' distinct reproductive physiology, high risk of STDs, and high risk of microbial complications linked to pregnancy and birth. Here, we test these hypotheses using comparative data on vaginal pH and the relative abundance of lactobacilli in 26 mammalian species and 50 studies (N = 21 mammals for pH and 14 mammals for lactobacilli relative abundance). We found that non-human mammals, like humans, exhibit the lowest vaginal pH during the period of highest estrogen. However, the vaginal pH of non-human mammals is never as low as is typical for humans (median vaginal pH in humans = 4.5; range of pH across all 21 non-human mammals = 5.4–7.8). Contrary to disease and obstetric risk hypotheses, we found no significant relationship between vaginal pH or lactobacilli relative abundance and multiple metrics of STD or birth injury risk (P-values ranged from 0.13 to 0.99). Given the lack of evidence for these hypotheses, we discuss two alternative explanations: the common function hypothesis and a novel hypothesis related to the diet of agricultural humans. Specifically, with regard to diet we propose that high levels of starch in human diets have led to increased levels of glycogen in the vaginal tract, which, in turn, promotes the proliferation of lactobacilli. If true, human diet may have paved the way for a novel, protective microbiome in human vaginal tracts. Overall, our results highlight the need for continuing research on non-human vaginal microbial communities and the importance of investigating both the physiological mechanisms and the broad evolutionary processes underlying human lactobacilli dominance.

Christian Puntini

Using the short-wavelength instability method, we investigate the linear instability of an exact solution describing upward-propagating mountain waves, derived in A. Constantin, \emph{J. Phys. A: Math. Theor.} (2023), under the assumption of a dry adiabatic flow. Within this approach, the stability problem reduces to analysing a system of ordinary differential equations along fluid trajectories. Our results show that the flow becomes unstable when the wave steepness exceeds the critical threshold of $\frac{1}{3}$. Given the representation of the solution in Lagrangian coordinates, the instability analysis will show the existence of an unstable layer of few hundred meters beneath the tropopause where instability may occur, finally leading to a chaotic 3-dimensional fluid motion.

Yirui Cheng, Qingyu Zeng, Qing Han et al.

Exosomes are cup-shaped small (30–150 nm) extracellular vesicles with the structure of lipid bilayer membrane (Tkach and Thery, 2016) containing proteins, mRNAs and microRNAs that mediate intercellular communication (Valadi et al., 2007). Unlike other extracellular vesicles, exosomes are released into the extracellular space when the multivesicular bodies (MVBs) fuse with the plasma membrane (Colombo et al., 2014). Almost all cell types can secret exosomes and exosomes exist in diverse biological fluids, such as blood, urine, saliva, hydrothorax and breast milk (Thery et al., 2006). Up to now, a number of studies have demonstrated the functions of exosomes in disease development and the potential clinical applications in diagnosis and therapy (Shao et al., 2016). To conduct reproducible studies on exosomal content and function, storage conditions need to have minimal impact on exosomes. There have been a few studies providing partial confirmation of the effect of different storage conditions on exosomes currently. Using exosomes from urine (Zhou et al., 2006) and conditioned medium (Lee et al., 2016) respectively to investigate the influence of storage temperature on exosomes as measured by Western blot, both groups have concluded that storage below −70 °C for a long time is the best temperature for the recovery of exosomes. On the other hand, Sokolova et al. (2011) applied nanoparticle tracking analysis (NTA) to measure the size changes of exosomes at different temperatures, revealing that storage at 37 °C led to more reduction in exosome sizes than that at 4 °C. However, in this study no information about changes in the particle concentration was reported. Some other studies revealed the effect of pH, storage temperature and cycles of freezing and thawing only on the yield of exosome isolation, but not on quantity changes during storage (Akers et al., 2016; Ban et al., 2015; Zhao et al., 2017). Therefore, the standard criterion of exosomal preservation condition is still undefined. Herein, we used HEK 293T cells and ExtraPEG method (Rider et al., 2016) to investigate the influence of multiple storage conditions (temperature, cycles of freezing and thawing, pH) on the quantity changes and cellular uptake of exosomes. ExtraPEG is a new polyethylene glycol (PEG) precipitation method for the purification exosomes without affecting their biological activity. Generally, ultracentrifugation (UC) (Mincheva-Nilsson et al., 2016) is most reliable but time-consuming; and precipitation methods such as ExoQuick (patent number: US20130337440 A1) and ExtraPEG can obtain higher yields of exosomes but with impurity of coprecipitated proteins. First, exosomes from the conditioned medium were extracted by ExtraPEG or UC method. After isolation, transmission electron microscope (TEM), NTA and Western blot were performed to analyze exosomes. Exosomes extracted by UC or ExtraPEG were similar in cupshaped structure (Fig. S1A and S1B), size distribution (Fig. S1C and S1D). And as representative exosome biomarkers, ALG-2-interacting protein X (ALIX), heat shock protein 70 (HSP70) and tumor susceptibility gene 101 (TSG101) were detected in exosomal protein while β-tubulin, widely used as an internal reference to analyze intracellular protein levels, was not detected in exosome samples (Fig. S1E and S1F). These data indicated exosomes were successfully isolated by ExtraPEG method and suitable for the following experiments. After isolation, the exosome pellets were divided equally into several portions and each portion was stored at different temperatures (−80 °C, −20 °C, 4 °C, 37 °C and 60 °C), or through 1–5 cycles of freezing to −80 °C and thawing, or at different pH levels (pH 4, pH 7 and pH 10). After 24 h, NTA and Western blot were performed to measure the remaining quantity of exosomes. Regarding temperatures, the exosomes stored at 4 °C had the highest concentration (Fig. 1A). Consistent with the NTA results, the exosomes stored at 4 °C showed higher levels of representative exosome markers ALIX, HSP70 and TSG101 (Fig. 1B). With the increasing cycles of freezing and thawing, the exosomal concentration and protein levels of ALIX, HSP70 and TSG101 all decreased (Fig. 1D and 1E). For different pH levels, the loss of exosomal concentration and three exosome markers ALIX, HSP70 and TSG101 at pH 4 and pH 10 was more than that at pH 7 (Fig. 1E and 1F). Interestingly, exosomes stored at pH 4 decreased more sharply than that at pH 10 (Fig. 1F and 1G), suggesting that acidic

Sandeep J. Sonawane, Rahul S. Kalhapure, T. Govender

Alexander Kochin

The buoyancy force is the cause of ordered vertical movements in the atmosphere, therefore, the analysis of the causes and conditions of its formation is important not only for the formation of convective clouds, but also for understanding all atmospheric transport processes. Due to the absence of rigid boundaries inside the gas, a horizontal pressure gradient in a static state cannot exist in the allocated volume. The pressure inside the allocated volume with a different density is equal to the external pressure and the intra-mass buoyancy force, according to its definition, is formally zero. The observed force of intra-mass buoyancy arises due to the difference in vertical pressure gradients in media with different densities. In this case, the buoyancy force is volumetric, and its value corresponds to generally accepted ratios.

Haibo Li, Di Zhang, Xiaozeng Han et al.

N. Barrow

M. Kosmulski

B. Cerozi, K. Fitzsimmons

A. Škulcová, A. Russ, M. Jablonský et al.

Deep eutectic solvents (DESs) are a unique category of green solvents that have gained attention in biomass processing due to their distinctive properties not offered by traditional solvents. The pH behavior of 17 selected DESs along with their temperature dependence on pH were evaluated in this study. For all investigated DESs, a temperature increase caused a decrease in pH value.

Y. Zou, Zhen Hu, Jian Zhang et al.