摘要 :
Vector beams with the desired polarization structure interacting with matter result in many novel nonlinear optical effects. Herein, we review the tight focusing and weak focusing properties of three types of light beams, namely, ...
展开
Vector beams with the desired polarization structure interacting with matter result in many novel nonlinear optical effects. Herein, we review the tight focusing and weak focusing properties of three types of light beams, namely, linearly polarized beams, cylindrical vector beams, and hybridly polarized beams. In particular, we revisit the second- and third-order nonlinear optical effects in nonlinear optical media under the excitation of several types of vector beams with the desired polarization distribution. The prospects of their applications in nonlinear optical microscopy and materials characterization are also briefly discussed.
收起
摘要 :
This study examined the effects of an upper-level anticyclonic circulation and a lower-level cyclonic circulation on tropical cyclone (TC) genesis. We ran idealized simulations using the Advanced Research Weather Research and Fore...
展开
This study examined the effects of an upper-level anticyclonic circulation and a lower-level cyclonic circulation on tropical cyclone (TC) genesis. We ran idealized simulations using the Advanced Research Weather Research and Forecasting (WRF-ARW) model. The simulation results show that the upper-level anticyclonic circulation makes a negative contribution to TC genesis, while the lower-level cyclonic circulation makes a positive contribution. The upper-level anticyclonic circulation results in slower TC genesis due to a substantial vertical zonal wind shear that shifts the upper-level vortex eastward from its initial position. This shift is unfavorable for the vortex's vertical aligmnent and warm core maintenance. This substantial vertical zonal wind shear is associated with the asymmetric vertical motion and associated diabetic heating, induced by the lower-level beta gyre. The upper-level anticyclonic circulation increases the westerly wind north of the vortex, resulting in a substantial vertical westerly wind shear. Thus, the initial upper-level anticyclonic circulation is unnecessary for TC genesis. The strong upper-level anticyclonic circulation, generally observed with a strong TC, should be considered a result of deep convection. The strong lower-level winds induce large surface heat fluxes and vorticity due to the superposition of the large-scale lower-level cyclonic circulation and vortex. These conditions lead to strengthened convection and diabetic heating and a quick build-up of positive vorticity, resulting in rapid TC genesis.
收起
摘要 :
The effects of intraseasonal oscillation (ISO) of the western North Pacific (WNP) monsoon trough on tropical cyclone (TC) formation were investigated using the Advanced Research Weather Research and Forecasting (ARW) Model. A weak...
展开
The effects of intraseasonal oscillation (ISO) of the western North Pacific (WNP) monsoon trough on tropical cyclone (TC) formation were investigated using the Advanced Research Weather Research and Forecasting (ARW) Model. A weak vortex was specified initially and inserted into the background fields containing climatological-mean anomalies associated with active and inactive phases of monsoon trough ISOs. The diagnosis of simulations showed that monsoon trough ISO can modulate TC development through both dynamic and thermodynamic processes. The dynamic impact is attributed to the lower midtropospheric large-scale vorticity associated with monsoon trough ISO. Interactions between cyclonic vorticity in the lower middle troposphere during the active ISO phase and a vortex lead to the generation of vortex-scale outflow at the midlevel, which promotes the upward penetration of friction-induced ascending motion and thus upward moisture transport. In addition, the low-level convergence associated with active ISO also helps the upward moisture transport. Both processes contribute to stronger diabatic heating and thus promote a positive convection circulation moisture feedback. On the other hand, the large-scale flow associated with inactive ISO suppresses upward motion near the core by inducing the midlevel inflow and the divergence forcing within the boundary layer, both inhibiting TC development. The thermodynamic impact comes from greater background specific humidity associated with active ISO that allows a stronger diabatic heating. Experiments that separated the dynamic and thermodynamic impacts of the ISO showed that the thermodynamic anomaly from active ISO contributes more to TC development, while the dynamic anomalies from inactive ISO can inhibit vortex development completely.
收起
摘要 :
The numerical simulations of tropical cyclone (TC) genesis during the strong and weak monsoon trough (MT) years, in which meteorological fields are composited, are conducted using advanced research weather research and forecasting...
展开
The numerical simulations of tropical cyclone (TC) genesis during the strong and weak monsoon trough (MT) years, in which meteorological fields are composited, are conducted using advanced research weather research and forecasting model. The simulation results show that both tropical disturbances tend to form in the east of the western North Pacific (WNP) near 160A degrees-170A degrees E during the strong and weak MT years. During the strong MT years, there is a faster formation rate of TC. The eastward-extending MT gradually evolves into a closed monsoon gyre over the WNP during the early stage. The following rapid development of TC can be attributed to the enhanced lower-level southwesterly flows induced by the cross-equatorial currents, enhanced easterly winds, and weak vertical wind shear, which provide a favorable environment for TC genesis. The strengthened large-scale circulation spawns abundant convective updrafts resulting in the aggregation of cyclonic vorticity. In contrast, during the weak MT years, the westward-retreated MT gradually evolves into expansive easterly winds over the WNP. Two episodes of convective updrafts are triggered with a longer interval, and thus lead to a slower TC genesis compared with that during the strong MT years.
收起
摘要 :
The present study investigates the relationship of tropical cyclone (TC) genesis between the western North Pacific (WNP) and South China Sea (SCS) from 1979 to 2020. A significantly out-of-phase variation is found between spring [...
展开
The present study investigates the relationship of tropical cyclone (TC) genesis between the western North Pacific (WNP) and South China Sea (SCS) from 1979 to 2020. A significantly out-of-phase variation is found between spring [March-May (MAM)] TC genesis over the WNP and the following summer-fall [June-November (JJASON)] TC genesis over the SCS. More TCs over the WNP in MAM are followed by fewer TCs over the SCS in the succeeding JJASON. Composite analysis and numerical model experiments show that negative sea surface temperature (SST) anomalies during MAM in the tropical central-eastern Pacific (CEP) and southeastern Indian Ocean work together to induce a lower-level cyclonic circulation over the WNP, with the latter more important. The positive specific humidity and ascending motion favor the TC genesis over the WNP in MAM. In the following JJASON, the SST anomalies are reversed in the tropical CEP. The positive precipitation anomalies over the western-central Pacific induced by positive SST anomalies further stimulate an anomalous zonal overturning circulation with anomalous descending motion and boundary layer divergence over the SCS. In addition, the persistent negative SST anomalies around the Maritime Continent (MC) induce an anomalous anticyclone to the west. Both processes lead to negative genesis potential index (GPI) anomalies and thus inhibit the TC genesis over the SCS. This out-of-phase relationship of TC genesis between the WNP and SCS also exists when the El Nino-Southern Oscillation (ENSO) transition years are removed. This find-ing may be helpful to improve the seasonal prediction of the SCS TC activity over the peak TC season.
收起
摘要 :
The renin-angiotensin system (RAS) has currently attracted increasing attention due to its potential function in regulating energy homeostasis, other than the actions on cellular growth, blood pressure, fluid, and electrolyte bala...
展开
The renin-angiotensin system (RAS) has currently attracted increasing attention due to its potential function in regulating energy homeostasis, other than the actions on cellular growth, blood pressure, fluid, and electrolyte balance. The existence of RAS is well established in metabolic organs, including pancreas, liver, skeletal muscle, and adipose tissue, where activation of angiotensin-converting enzyme (ACE) - angiotensin II pathway contributes to the impairment of insulin secretion, glucose transport, fat distribution, and adipokines production. However, the activation of angiotensin-converting enzyme 2 (ACE2) - angiotensin (1-7) pathway, a novel branch of the RAS, plays an opposite role in the ACE pathway, which could reverse these consequences by improving local microcirculation, inflammation, stress state, structure remolding, and insulin signaling pathway. In addition, new studies indicate the protective RAS arm possesses extraordinary ability to enhance brown adipose tissue (BAT) activity and induces browning of white adipose tissue, and consequently, it leads to increased energy expenditure in the form of heat instead of ATP synthesis. Interestingly, ACE2 is the receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is threating public health worldwide. The main complications of SARS-CoV-2 infected death patients include many energy metabolism-related chronic diseases, such as diabetes. The specific mechanism leading to this phenomenon is largely unknown. Here, we summarize the latest pharmacological and genetic tools on regulating ACE/ACE2 balance and highlight the beneficial effects of the ACE2 pathway axis hyperactivity on glycolipid metabolism, as well as the thermogenic modulation.
收起
摘要 :
The present study compares contributions of different environmental factors to the tropical cyclone (TC) genesis over the western North Pacific (WNP) during 2015 and 2016. A local instantaneous view of conditions for the TC genesi...
展开
The present study compares contributions of different environmental factors to the tropical cyclone (TC) genesis over the western North Pacific (WNP) during 2015 and 2016. A local instantaneous view of conditions for the TC genesis is adopted in the present study, which is distinct from the previous view of large-scale temporal averaged conditions. The present study also distinguishes the contributions of three time scale variations (synoptic, intraseasonal, and interannual) of a number of factors. Common to 2015 and 2016, the positive contribution of lower-level vorticity and upward motion to the TC genesis is mainly from the intraseasonal and synoptic components; the contribution of the barotropic energy conversion to the development of synoptic disturbances is larger from climatological mean winds and intraseasonal wind variations than from interannual wind variations; all three time scale variations of mid-level specific humidity contribute positively to the TC genesis; the barotropic energy conversion from climatological mean winds is due to the terms in relation to the meridional shear and zonal convergence of zonal wind. In comparison, the positive contribution of lower-level vorticity and mid-level specific humidity is larger in 2015 than in 2016 on all the three time scales; the contribution of the barotropic energy conversion in relation to the meridional shear of interannual variations of zonal wind and the zonal convergence of intraseasonal variations of zonal wind are larger in 2015 than in 2016; the vertical wind shear on all the three time scales and the sea surface temperature on the interannual time scale have a larger positive contribution to the TC genesis in 2016 than in 2015.
收起
摘要 :
Picea pungens (Engelm.), known for its blue-green needles, has become a likable ornamental species in northeast China since 2000. Nonetheless, a lack of propagation methods that can maintain genetic fidelity and develop seedlings ...
展开
Picea pungens (Engelm.), known for its blue-green needles, has become a likable ornamental species in northeast China since 2000. Nonetheless, a lack of propagation methods that can maintain genetic fidelity and develop seedlings at a large scale prevents the further expansion of the species. Somatic embryogenesis (SE), paired with cryopreservation technologies, may provide a valid alternative. Picea pungens SE is not new, but its practical application has been limited due to low efficiencies in SE initiation and maturation as well as a lack of effective cryopreservation technology. In this study, experiments were carried out to overcome the limitations by modifying culture media. For initiation, the efficiency was enhanced by adjusting concentrations of 2.4-dichlorophenoxy acetic acid (2,4-D), 6-benzyl amino–purine (6-BA) or sucrose supplemented to the induction medium. The concentrations of 4.0 mg/L 2,4-D, 2 mg/L 6-BA, and 5 to 10 g/L sucrose were found optimal in maximizing initiation efficiency. For maturation, the efficiency, expressed as the number of mature somatic embryos per gram of fresh mass cultured (E/gFM), varied greatly with the choices of the basal medium and concentration of abscisic acid (ABA) of the maturation medium. Based on our results, the judicial choices were using the DCR medium as the basal medium and 10 mg/L ABA. The maturation efficiency could also be improved by adjusting the maturation medium’s osmotic pressure by manipulating the concentrations of carbohydrate and Gelrite and culture density. While the maturation medium, using sucrose as carbohydrate source or supplemented with a low (<8 g/L) Gelrite concentration, facilitated maturation, optimal selections were truly genotype-dependent. Our results also suggest that, while the optimal culture density varied with genotype, in general it is needless to culture more than 100 mg embryogenesis tissues per dish (size 10 × 1.5 cm). Based on this study, the optimum pretreatment for embryogenesis tissue cryopreservation was culturing the tissues on the proliferation medium with 0.4 mol/L sorbitol for 24 h, followed by treatment with 5% Dimethyl sulfoxide. This study significantly improved the initiation (achieved a frequency of 0.56) and embryo maturation efficiencies (achieved 1030 E/gFM) and established an effective preculturing protocol for cryopreservation (recovered 1354 E/gFM) for the species. The protocols developed here, paired with the available ones for other SE steps in the literature, form a well-refined SE technology intended for commercial application to Picea pungens.
收起
摘要 :
Our findings establish a role for gut microbes in the progression of estrogen deficiency-induced lipid metabolism disorders and reveal key target bacteria that may have the potential to regulate acylcarnitine synthesis. These find...
展开
Our findings establish a role for gut microbes in the progression of estrogen deficiency-induced lipid metabolism disorders and reveal key target bacteria that may have the potential to regulate acylcarnitine synthesis. These findings suggest a possible route for the use of microbes or acylcarnitine to regulate disorders of lipid metabolism induced by estrogen deficiency. Decreased estrogen level is one of the main causes of lipid metabolism disorders and coronary heart disease in women after menopause. Exogenous estradiol benzoate is effective to some extent in alleviating lipid metabolism disorders caused by estrogen deficiency. However, the role of gut microbes in the regulation process is not yet appreciated. The objective of this study was to investigate the effects of estradiol benzoate supplementation on lipid metabolism, gut microbiota, and metabolites in ovariectomized (OVX) mice and to reveal the importance of gut microbes and metabolites in the regulation of lipid metabolism disorders. This study found that high doses of estradiol benzoate supplementation effectively attenuated fat accumulation in OVX mice. There was a significant increase in the expression of genes enriched in hepatic cholesterol metabolism and a concomitant decrease in the expression of genes enriched in unsaturated fatty acid metabolism pathways. Further screening of the gut for characteristic metabolites associated with improved lipid metabolism revealed that estradiol benzoate supplementation influenced major subsets of acylcarnitine metabolites. Ovariectomy significantly increased the abundance of characteristic microbes that are significantly negatively associated with acylcarnitine synthesis, such as Lactobacillus and Eubacterium ruminantium group bacteria, while estradiol benzoate supplementation significantly increased the abundance of characteristic microbes that are significantly positively associated with acylcarnitine synthesis, such as Ileibacterium and Bifidobacterium spp. The use of pseudosterile mice with gut microbial deficiency greatly facilitated the synthesis of acylcarnitine due to estradiol benzoate supplementation and also alleviated lipid metabolism disorders to a greater extent in OVX mice.IMPORTANCE Our findings establish a role for gut microbes in the progression of estrogen deficiency-induced lipid metabolism disorders and reveal key target bacteria that may have the potential to regulate acylcarnitine synthesis. These findings suggest a possible route for the use of microbes or acylcarnitine to regulate disorders of lipid metabolism induced by estrogen deficiency.
收起
原文获取