Vibration characteristic analysis of the multi-drilling mechanism

For enhancing drilling efficiency and controlling drilling direction, it is necessary to predict and control dynamic behavior of drilling mechanism effectively. In view of the coupling vibration and low drilling efficiency of auger drilling machine, a dynamic coupling model of multi-drilling mechanism was established to analyze the vibration characteristics under different coal hardness, drilling depths and rotating speeds. Simultaneously, the vibration tests of drilling process were conducted on the coal cutting test bed, and the results correspond with the simulation results. The results show that: the vibration displacement magnitude and fluctuation of multi-drilling mechanism increase with the coal hardness, while decrease then increase with the drilling depth, and increase then decrease with the rotating speed. The increases of coal hardness and drilling depth result in difficulty for coal cutting. The cutting torque decreases with rotating speed, while there is little influence on the feeding resistance

Extension of summer (June–August) temperature records for northern Inner Mongolia (1715–2008), China using tree rings

This paper presents a spatially and temporally improved reconstruction of mean summer (June–August) temperature derived from tree-ring width data of Dahurian larch (Larix gmelinii Rupr.) from the northern Great Xing'an Mountains, Northeast China. Three new chronologies were added to the original 2011 reconstruction, and the reconstruction extended back to AD 1715. The reconstruction was generated using a simple linear regression method, verified by independent meteorological data, and accounts for 47.0% of the actual temperature variance during the common period (1957–2008). The reconstruction captures decadal and century-scale regional temperature variability, such as cold decades (1940s, 1930s, 1790s, 1950s and 1850s), warm decades (2000s, 1870s, 1750s, 1980s and 1840s), a cold half-century (ca. 1750–1799), and a warm half-century (ca. 1900–1949). It also reveals slightly higher frequency of cold years (20.4%) than warm years (18.0%), and a recent warming trend. Compared to the original 2011 reconstruction, this reconstruction has lower inter-annual temperature variability, high explained variance and high representativeness of regional climate. The reconstruction also correlates with the East Asian Monsoon and the Pacific Ocean signals, and indicates the feasibility of using tree rings from high latitude Northeast China to reconstruct summer temperature in permafrost forest environments

Vertical Ferroelectricity in Van der Waals Materials: Models and Devices

Ferroelectricity has a wide range of applications in functional electronics and is extremely important for the development of next-generation information storage technology, but it is difficult to achieve due to its special symmetry requirements. In this letter, based on van derWaals stacking, a generic model is proposed for realizing ferroelectric devices, where a freely movable center layer is packaged in two fixed and symmetrically stacked layers. In this model, the ferroelectric phase transition can be realized between the two equivalent and eccentric ground stacking-states with opposite polarizations. By means of first-principles calculations, taking the h-BN/h-BN/h-BN and h-BN/Graphene/h-BN as feasible models, we carefully evaluate the magnitude of ferroelectricity. The corresponding polarizations are estimated as 1.83 and 1.35 pC/m, respectively, which are comparable to the sliding ferroelectricity. Such a new tri-layer model of vertical ferroelectricity can be constructed by arbitrary van derWaals semiconducting materials, and usually holds low switching barrier. Optimized material combinations with remarkable polarization are highly expectable to be discovered from the huge candidate set for future information storage.Comment: 5 pages;4 figure

Clinical efficacy of the combined use of levofloxacin and different courses of isoniazid and rifampicin in the treatment of mild spinal tuberculosis

Purpose: To investigate the clinical effectiveness of the combined use of levofloxacin and different courses of isoniazid and rifampicin in the treatment of mild spinal tuberculosis (TB). Methods: The clinic data of 100 patients with light spinal TB were retrospectively reviewed. A double-blind technique was used to divide the patients into 6-month treatment group (M6 group, n = 32), 12-month treatment group (M12 group, n = 34) and 18-month treatment group (M18 group, n = 34). All patients were given isoniazid and rifampicin, in combination with levofloxacin. The effects of the different treatment courses on mild spinal TB were determined. Results: There were significantly higher post-treatment levels of inflammatory factors in M6 group than in M12 and M18 groups (p < 0.001). Moreover, there were significantly higher Visual Analogue Scale (VAS) score and erythrocyte sedimentation rate (ESR), and larger focus size in M6 group than in M12 and M18 groups (p < 0.05). However, after treatment, M18 group had significantly higher total incidence of adverse reactions than M6 and M12 groups (p < 0.05). Conclusion: Compared with the short-course treatment, long-course treatment with isoniazid and rifampicin in combination with levofloxacin is more effective in reducing the levels of inflammatory factors and decreasing focus size in patients with mild spinal TB. However, patients given the 18-month treatment tend to develop more adverse reactions. Therefore, 12-month treatment with the combined therapy is a better therapeutic option

Cardiac Function Assessment in Fetuses With Ductus Arteriosus Constriction: A Two-Dimensional Echocardiography and FetalHQ Study

BackgroundFetal ductal constriction (DC) is associated with excessive polyphenol-rich food (PRF) consumption during pregnancy. However, the effect of this hemodynamic change on fetal cardiac function still needs to be elucidated. Therefore, this study aimed to evaluate the cardiac function of fetuses with PRF-related DC and to describe serial observations of cardiac function changes.MethodsWe compared the traditional echocardiographic indices, including morphological, hemodynamic, and functional parameters, between study fetuses and controls. For global and segmental deformation analysis of the left and right ventricles, fetalHQ with the speckle-tracking technique was used to calculate sphericity index (SI), global longitudinal strain (GLS), fractional shortening (FS), fractional area change (FAC), etc. In addition, follow-up data were compared with the generalized linear model.ResultsA total of 60 DC fetuses and 60 gestational-matched controls were enrolled in our study, with 20 DC fetuses undertaking a follow-up echocardiogram after 2–3 weeks. Compared with controls, there was a distinct decrease in right ventricular GLS (RVGLS) (−13.39 ± 3.77 vs. −21.59 ± 2.51, p < 0.001), RVFAC (22.20 ± 9.56 vs. 36.01 ± 4.84, p < 0.001), left ventricular GLS (LVGLS) (−19.52 ± 3.24 vs. −23.81 ± 2.01 p < 0.001), and LVFAC (39.64 ± 7.32 vs. 44.89 ± 4.91, p = 0.004). For 24-segment FS analysis, DC fetuses showed lower FS in left ventricular (LV) segments 18–24, with no difference in LV segments 1–17. Right ventricular (RV) FS in segments 4–23 was also reduced in the DC group. The 24-segment SI analysis indicated significantly lower SI in DC than those in controls for LV segments 1–14 and RV segments 19–24. We found that the pulsatility index (PI) of ductus arteriosus (DA) was an independent variable for RVGLS (β = −0.29, p = 0.04). In 20 DC fetuses with follow-up echocardiograms, no obvious difference in myocardial deformation was found between the initial examination and follow-up data.ConclusionLeft and right ventricular performances were both impaired in DC fetuses, along with a series of morphological and hemodynamic changes. Although the state of DA constriction improved on second examinations, cardiac function was not completely restored

Chinese Expert Consensus on Critical Care Ultrasound Applications at COVID-19 Pandemic

The spread of new coronavirus (SARS-Cov-2) follows a different pattern than previous respiratory viruses, posing a serious public health risk worldwide. World Health Organization (WHO) named the disease as COVID-19 and declared it a pandemic. COVID-19 is characterized by highly contagious nature, rapid transmission, swift clinical course, profound worldwide impact, and high mortality among critically ill patients. Chest X-ray, computerized tomography (CT), and ultrasound are commonly used imaging modalities. Among them, ultrasound, due to its portability and non-invasiveness, can be easily moved to the bedside for examination at any time. In addition, with use of 4G or 5G networks, remote ultrasound consultation can also be performed, which allows ultrasound to be used in isolated medial areas. Besides, the contact surface of ultrasound probe with patients is small and easy to be disinfected. Therefore, ultrasound has gotten lots of positive feedbacks from the frontline healthcare workers, and it has played an indispensable role in the course of COVID-19 diagnosis and follow up

Vulnerability of photosynthesis and photosystem I in Jerusalem artichoke (Helianthus tuberosus L.) exposed to waterlogging

Jerusalem artichoke (Helianthus tuberosus L.) is an important energy crop for utilizing coastal marginal land. This study was to investigate waterlogging tolerance of Jerusalem artichoke through photosynthetic diagnose with emphasis on photosystem II (PSII) and photosystem I (PSI) performance. Potted plants were subjected to severe (liquid level 5 cm above vermiculite surface) and moderate (liquid level 5 cm below vermiculite surface) waterlogging for 9 days. Large decreased photosynthetic rate suggested photosynthesis vulnerability upon waterlogging. After 7 days of severe waterlogging, PSII and PSI photoinhibition arose, indicated by significant decrease in the maximal photochemical efficiency of PSII (Fv/Fm) and PSI (Delta MR/MR0), and PSI seemed more vulnerable because of greater decrease in Delta MR/MR0 than Fv/Fm. In line with decreased Delta MR/MR0 and unchanged Fv/Fm after 9 days of moderate waterlogging, the amount of PSI reaction center protein rather than PSII reaction center protein was lowered, confirming greater PSI vulnerability. According to positive correlation between Delta MR/MR0 and efficiency that an electron moves beyond primary quinone and negative correlation between Delta MR/MR0 and PSII excitation pressure, PSI inactivation elevated PSII excitation pressure by depressing electron transport at PSII acceptor side. Thus, PSI vulnerability induced PSII photoinhibition and endangered the stability of whole photosynthetic apparatus under waterlogging. In agreement with photosystems photoinhibition, elevated H2O2 concentration and lipid peroxidation in the leaves corroborated waterlogging induced oxidative stress. In conclusion, Jerusalem artichoke is a waterlogging sensitive species in terms of photosynthesis and PSI vulnerability. Consistently, tuber yield was tremendously reduced by waterlogging, confirming waterlogging sensitivity of Jerusalem artichoke