Detachment-parallel recharge explains high discharge fluxes at the TAG hydrothermal field

Submarine massive sulfide deposits on slow-spreading ridges are larger and longer-lived than deposits at fast-spreading ridges1,2, likely due to more pronounced tectonic faulting creating stable preferential fluid pathways3,4. The TAG hydrothermal mound at 26°N on the Mid-Atlantic Ridge (MAR) is a typical example located on the hanging wall of a detachment fault5-7. It has formed through distinct phases of high-temperature fluid discharge lasting 10s to 100s of years throughout at least the last 50,000 years8 and is one of the largest sulfide accumulations on the MAR. Yet, the mechanisms that control the episodic behavior, keep the fluid pathways intact, and sustain the observed high heat fluxes of up to 1800 MW9 remain poorly understood. Previous concepts involved long-distance channelized high-temperature fluid upflow along the detachment5,10 but that circulation mode is thermodynamically unfavorable11 and incompatible with TAG's high discharge fluxes. Here, based on the joint interpretation of hydrothermal flow observations and 3-D flow modeling, we show that the TAG system can be explained by episodic magmatic intrusions into the footwall of a highly permeable detachment surface. These intrusions drive episodes of hydrothermal activity with sub-vertical discharge and recharge along the detachment. This revised flow regime reconciles problematic aspects of previously inferred circulation patterns and can be used as guidance to one critical combination of parameters that can generate substantive mineral systems.

Investigation of the Zinc-Copper Catalyst NIAP-06-06 for Steam Conversion of Carbon Monoxide in the Synthesis of Methanol

The possibility to use the zinc-copper catalyst NIAP-06-06 for steam conversion of CO in the synthesis of methanol was explored. The catalyst was characterized by means of TPR H2, XRD and SEM methods and tested in the methanol synthesis in flow and circulation modes at a pressure of 5.0 MPa and gas hourly space velocity of 3000 h–1 over a temperature range of 220–260 °С. The catalyst was shown to be highly active and selective toward the methanol synthesis from a gas with the H2 /СО ratio 3.9, which is obtained by steam conversion of methane. The use of tubular catalytic reactors connected in series in the flow-circulation mode makes it possible to convert more than 70 % of CO and obtain crude methanol with the concentration of 95 %. In the circulation mode, a methanol output of 427.7 kg/(m3 cat·h) was achieved on the catalyst.

A Radionuclide Generator of High-Purity Bi-213 for Instant Labeling

A new two-column 225Ac/213Bi generator was developed specifically for using 225Ac containing an impurity of long lived 227Ac. The parent 225Ac was retained on the first Actinide Resin column, while 213Bi was accumulated on the second column filled with AG MP-50 resin via continuous elution and decay of intermediate 221Fr. The 213Bi accumulation was realized in circulation mode which allowed a compact generator design. It was demonstrated that 213Bi could be quickly and effectively extracted from AG MP-50 in form of complexes with various chelating agents including DTPA and DOTA. The performance of the generator presented and a conventional single-column generator on the base of AG MP-50 was tested and both generators were loaded with 225Ac containing 227Ac impurity. The 213Bi generation efficiencies were comparable and greater than 70%, whereas the developed generator provided a deeper degree of purification of 213Bi from Ac isotopes and decay products of 227Ac.

Research on Indoor Thermal Comfort and Age of Air in Qilou Street Shop under Mechanical Ventilation Scheme: A Case Study of Nanning Traditional Block in Southern China

In hot summers, air conditioning (AC) and mechanical ventilation (such as fans) are used as cooling modes that strongly influence the resultant indoor environment, like thermal comfort and air quality in the shops of a Nanning arcade street (qilou). The air circulation mode in shops greatly affects the indoor thermal environment and level of air freshness. The approaches for effectively improving the indoor thermal comfort and air quality are developed in qilou street shops with air-conditioner in a humid and hot region in southern China. Consequently, the purpose of this study is to assess different ventilation schemes in order to identify the best one. By using two indices, i.e., the predicted mean vote (PMV) and the age of air (AoA), in situ measurement and numerical simulation are conducted to investigate humans’ thermal comfort in extreme summer. Then, the indoor thermal comfort and AoA levels in summer under three different ventilation schemes (upper-inlet–upper-outlet, upper-inlet–bottom-outlet, and side-inlet–side-outlet) are comparatively analyzed through numerical computations of the indoor thermal environment. The results show that the upper-inlet–upper-outlet mode of the AC ventilation scheme led to the creation of a favorable air quality and comfortable thermal environment inside the shop, which will help designers understand the influence of the ventilation scheme on the indoor thermal comfort and health environment.

Performance Evaluation and Sensitivity Analysis of Rural Land Circulation Mode

To evaluate the performance of rural land circulation mode through the analytic network hierarchy process, based on the results of the performance evaluation with analytic network process, we implemented efficiency analysis on five types of rural land circulation mode by two improved efficiency analytic procedures. Finally, we implemented sensitivity analysis for each criterion layer of the evaluation index system with the performance evaluation data, interpreted five types of rural land circulation mode from three perspectives including benefits, costs, and risks with sensitivity analysis results, and drew related conclusions including higher revenue which will lead to smaller difficulty of the rural land circulation. Cost variables were negative variables of the selected rural land circulation mode, and higher risk would lead to the greater difficulty of rural land circulation and related conclusions.

Mechanisms associated with September to November (SON) rainfall over Uganda during the recent decades

This study revisits teleconnections associated with the anomalous events of September to November (SON) rainfall over Uganda during 1981-2019, owing to the recent intensification of extreme events. Empirical Orthogonal Function (EOF), Composite and Correlation analysis are employed to examine the variability of SON rainfall over the study domain and associated circulations anomalies. The first EOF mode (dominant mode) displays a positive monopole pattern and explains 67.2% of the variance. The results revealed that SON rainfall is largely influenced by a Walker circulation mode over the Indian Ocean, whereby, wet events are associated with an ascending limb of the Walker circulation on the western part of the Indian Ocean characterized by convergence at low levels and divergence at upper level. The study showed that SON rainfall is positively (negatively) correlated with Indian Ocean (Atlantic Ocean) sea surface temperatures (SST). Furthermore, Indian Ocean Dipole (IOD) events have impact on SON rainfall with strong positive correlation, whereas Southern Oscillation Index (SOI) revealed negative correlation. The results also reveal that there is a lag in ENSO and IOD episodes during wet/dry events over the region. ENSO and IOD also tend to extend the rainfall season of SON and thus study of extreme events may not be well captured by studies focusing on SON. Future studies might consider the season of October to December or December to February. These phenomena need to be closely monitored and considered when making seasonal forecasts.

A multidecadal-scale tropically-driven global teleconnection over the past millennium and its recent strengthening

In the past 40 years, the global annual mean surface temperature has experienced a non-uniform warming, differing from the spatially uniform warming simulated by the forced responses of large multi-model ensembles to anthropogenic forcing. Rather, it exhibits significant asymmetry between the Arctic and Antarctic, intermittent and spatially varying warming trends along the Northern Hemisphere (NH) mid-latitudes and a slight cooling in the tropical eastern Pacific. In particular, this “wavy” pattern of temperature changes over the NH mid-latitudes features strong cooling over Eurasia in boreal winter. Here, we show that these non-uniform features of surface temperature changes are likely tied together by tropical eastern Pacific sea surface temperatures (SSTs), via a global atmospheric teleconnection. Using six reanalyses, we find that this teleconnection can be consistently obtained as a leading circulation mode in the past century. This tropically-driven teleconnection is associated with a Pacific SST pattern resembling the Interdecadal Pacific Oscillation (IPO), and hereafter referred to as the IPO-related Bipolar Teleconnection (IPO-BT). Further, two paleo-reanalysis reconstruction datasets show that the IPO-BT is a robust recurrent mode over the past 400 and 2000 years. The IPO-BT mode may thus serve as an important internal mode that regulates high-latitude climate variability on multidecadal time scales, favoring a warming (cooling) episode in the Arctic accompanied by cooling (warming) over Eurasia and the Southern Ocean (SO). Thus, the spatial non-uniformity of recent surface temperature trends may be partially explained by the enhanced appearance of the IPO-BT mode by a transition of the IPO toward a cooling phase in the eastern Pacific in the past decades.

The Contribution of Internal Variability to Asian Mid-Latitude Warming

The tropospheric warming in the Northern Hemisphere (NH) mid-latitudes has been an important factor in regulating weather and climate since the 20th century. Apart from anthropogenic forcing leading to the mid-latitude warming, this study investigates the possible contribution of internal variability to Asian mid-latitude warming and its role in East Asian circulation changes in boreal summer, using four reanalysis datasets in the past century and a set of 1800-year preindustrial control simulations of the Community Earth System Model version1 large ensemble (CESM-LE).The surface and tropospheric warming in the Asian mid-latitudes is associated with a strong upper-level geopotential height rise north of the Tibetan Plateau (TP). Linear trends of 200-hPa geopotential height (Z200) confirm a dipole of an anomalous high north of the TP and an anomalous low over the Iranian Plateau in 1958-2017. The leading internal circulation mode bears a striking resemblance to the Z200 trend in the past 60 and 100 years, indicating that the long-term trend may be partially of internal origin. The Asian mid-latitude warming is also found in preindustrial simulations of CESM-LE, further suggesting that internal variability explains at least part of the temperature change in the Asian mid-latitudes, that is in a chain of wave trains along the NH mid-latitudes. The Asian warming decreases meridional gradient of geopotential height, resulting in the weakening of westerly winds over the TP and the TP thermal forcing. Thus, it is essential to consider the role of internal variability in shaping East Asian surface temperature and East Asian summer monsoon changes in the past decades.