Negative feedback loops leading to nitrate homeostasis and oscillatory nitrate assimilation in plants and fungi.

Nitrate is an important nutrient for plants and fungi. For plants it has been shown that cytosolic nitrate levels are under homeostatic control. Here we describe two networks that can obtain robust, i.e. perturbation independent, homeostatic behavior in cytosolic nitrate concentration. One of the networks, a member in the family of outflow controllers, is based on a negative feedback loop containing a nitrate-induced activation of a controller molecule which removes nitrate. In plants this control structure appears to have at least two representations, one where the controller molecule is nitrate reductase removing nitrate for assimilation, while the other controller molecule takes part in the efflux of nitrate out of the cell. The second homeostatic network, a member in the family of inflow controllers, appears to be associated with the uptake of nitrate into the cell, the translocation of cytosolic nitrate into the vacuole for nitrate storage and the transport of nitrate from the vacuole into the cytosol. Interestingly, this control structure automatically adjusts the flux of nitrate uptake into the cytosol by the extent of how much cytosolic nitrate is removed. After the depletion of environmental nitrate, the vacuolar nitrate is sustained by the remobilization of vacuolar nitrate. In lower eukaryotes which lack nitrate storage in the vacuole and a nitrate efflux system, uptake of nitrate by such a controller depends therefore on the nitrate assimilation rate in the cell. Thus, practically no nitrate uptake should occur in lower eukaryotes when nitrate reductase is not functional, a behavior that was previously observed in fungi. Another interesting aspect is that outflow controller can oscillate and generate limit cycle oscillations in the assimilation of nitrate, thus making a link between circadian oscillations in nitrate assimilation and cytosolic nitrate homeostasis

Simultaneous enhance of the thermal shock resistance and slag-penetration resistance for tundish flow-control refractories: The role of microporous magnesia

As the low thermal shock and slag-penetration resistance of the magnesia castables cause the premature failure of tundish flow-control devices leading to the pollution of steel, the microporous magnesia with high closed porosity and intergranular CaZrO3 phase was utilized for simultaneously enhancing the high-temperature performance. The thermomechanical stress and slag corrosion tests indicated that since the micro-closed pores effectively relieved the thermal stress and CaZrO3 absorbed massive crack-propagation energy, the cold modulus of rupture and residual strength ratio respectively reached 14.4 MPa and 73.4% after thermal shock cycles, nearly half higher than that of the fused magnesia based castables. Meanwhile, the synergistic effect of micro-closed pores and intergranular CaZrO3 phase significantly reduced the slag-wettability, improved the interfacial energy and dihedral angle, leading to the decline of slag penetration indice (decreased by ∼34.8%). This study suggests a potential approach to generate new magnesia based castables in tundish for making clean steel

Occupational noise and hypertension in Southern Chinese workers: a large occupational population-based study

Abstract Introduction An increasing number of original studies suggested that occupational noise exposure might be associated with the risk of hypertension, but the results remain inconsistent and inconclusive. In addition, the attributable fraction (AF) of occupational noise exposure has not been well quantified. We aimed to conduct a large-scale occupational population-based study to comprehensively investigate the relationship between occupational noise exposure and blood pressure and different hypertension subtypes and to estimate the AF for hypertension burden attributable to occupational noise exposure. Methods A total of 715,135 workers aged 18–60 years were included in this study based on the Key Occupational Diseases Surveillance Project of Guangdong in 2020. Multiple linear regression was performed to explore the relationships of occupational noise exposure status, the combination of occupational noise exposure and binaural high frequency threshold on average (BHFTA) with systolic and diastolic blood pressure (SBP, DBP). Multivariable logistic regression was used to examine the relationshipassociation between occupational noise exposure status, occupational noise exposure combined with BHFTA and hypertension. Furthermore, the attributable risk (AR) was calculated to estimate the hypertension burden attributed to occupational exposure to noise. Results The prevalence of hypertension among occupational noise-exposed participants was 13·7%. SBP and DBP were both significantly associated with the occupational noise exposure status and classification of occupational noise exposure combined with BHFTA in the crude and adjusted models (all P < 0·0001). Compared with workers without occupational noise exposure, the risk of hypertension was 50% greater among those exposed to occupational noise in the adjusted model (95% CI 1·42–1·58). For participants of occupational noise exposed with BHFTA normal, and occupational noise exposed with BHFTA elevated, the corresponding risks of hypertension were 48% (1·41–1·56) and 56% (1·46–1·63) greater than those of occupational noise non-exposed with BHFTA normal, respectively. A similar association was found in isolated systolic hypertension (ISH) and prehypertension. Subgroup analysis by sex and age showed that the positive associations between occupational noise exposure and hypertension remained statistically significant across all subgroups (all P < 0.001). Significant interactions between occupational noise status, classification of occupational noise exposure combined with BHFTA, and age in relation to hypertension risk were identified (all P for interaction < 0.001). The associations of occupational noise status, classification of occupational noise exposure combined with BHFTA and hypertension were most pronounced in the 18–29 age groups. The AR% of occupational noise exposure for hypertension was 28·05% in the final adjusted model. Conclusions Occupational noise exposure was positively associated with blood pressure levels and the prevalence of hypertension, ISH, and prehypertension in a large occupational population-based study. A significantly increased risk of hypertension was found even in individuals with normal BHFTA exposed to occupational noise, with a further elevated risk observed in those with elevated BHFTA. Our findings provide epidemiological evidence for key groups associated with occupational noise exposure and hypertension, and more than one-fourth of hypertension cases would have been prevented by avoiding occupational noise exposure