Positive Exponential Correlation Research Articles

Experimental study and evaluation on the weakening of bursting liability of coal with boreholes

Borehole pressure relief technology is the most commonly used method for stress control in the prevent of coal burst. Because coal burst is a dynamic failure phenomenon of coal driven by energy, compared with stress transfer, the effect of pressure relief should also be evaluated from the perspective of energy storage and dissipation. Uniaxial compressing tests of coal specimens with different boreholes are carried out. With increase of the borehole diameter and number, the peak elastic strain energy, energy release velocity, fragments kinetic energy and ejection velocity of coal all decrease. Compared with intact coal specimen, the kinetic energy of the coal specimen with one 14 mm borehole is droping to 39.91 %, the ejection velocity decreases from 9.74 m·s−1 to 6.07 m·s−1. The uniaxial compressive strength, bursting energy index, and modified bursting energy index of the coal specimen with boreholes show a negative exponential correlation with the diameter and number of boreholes, while the dynamic fracture duration shows a positive exponential correlation. In order to evaluate the effect of borehole pressure relief, energy pre-release index, energy dissipation-increasing index, and bursting liability weakening index are proposed. These three indexes are positively correlated with the diameter and number of boreholes, which can better reflect the effect of pressure in the perspective of energy storage and dissipation.

Quantitative analysis of aortic Na[18F]F uptake in macrocalcifications and microcalcifications in PET/CT scans.

Currently, computed tomography (CT) is used for risk profiling of (asymptomatic) individuals by calculating coronary artery calcium scores. Although this score is a strong predictor of major adverse cardiovascular events, this method has limitations. Sodium [18F]fluoride (Na[18F]F) positron emission tomography (PET) has shown promise as an early marker for atherosclerotic progression. However, evidence on Na[18F]F as a marker for high-risk plaques is limited, particularly on its presentation in clinical PET/CT. Besides, the relationship between microcalcifications visualized by Na[18F]F PET and macrocalcifications detectable on CT is unknown. To establish a match/mismatch score in the aorta between macrocalcified plaque content on CT and microcalcification Na[18F]F PET uptake. Na[18F]F-PET/CT scans acquired in our centre in 2019-2020 were retrospectively collected. The aorta of each low-dose CT was manually segmented. Background measurements were placed in the superior vena cava. The vertebrae were automatically segmented using an open-source convolutional neural network, dilated with 10mm, and subtracted from the aortic mask. Per patient, calcium and Na[18F]F-hotspot masks were retrieved using an in-house developed algorithm. Three match/mismatch analyses were performed: a population analysis, a per slice analysis, and an overlap score. To generate a population image of calcium and Na[18F]F hotspot distribution, all aortic masks were aligned. Then, a heatmap of calcium HU and Na[18F]F-uptake on the surface was obtained by outward projection of HU and uptake values from the centerline. In each slice of the aortic wall of each patient, the calcium mass score and target-to-bloodpool ratios (TBR) were calculated within the calcium masks, in the aortic wall except the calcium masks, and in the aortic wall in slices without calcium. For the overlap score, three volumes were identified in the calcium and Na[18F]F masks: volume of PET (PET+/CT-), volume of CT (PET-/CT+), and overlapping volumes (PET+/CT+). A Spearman's correlation analysis with Bonferroni correction was performed on the population image, assessing the correlation between all HU and Na[18F]F vertex values. In the per slice analysis, a paired Wilcoxon signed-rank test was used to compare TBR values within each slice, while an ANOVA with post-hoc Kruskal-Wallis test was employed to compare TBR values between slices. p-values<0.05 were considered significant. In total, 186 Na[18F]F-PET/CT scans were included. A moderate positive exponential correlation was observed between total aortic calcium mass and total aortic TBR (r=0.68, p<0.001). A strong positive correlation (r=0.77, p<0.0001) was observed between CT values and Na[18F]F values on the population image. Significantly higher TBR values were found outside calcium masks than inside calcium masks (p<0.0001). TBR values in slices where no calcium was present, were significantly lower compared with outside calcium and inside calcium (both p<0.0001). On average, only 3.7% of the mask volumes were overlapping. Na[18F]F-uptake in the aorta behaves similarly to macrocalcification detectable on CT. Na[18F]F-uptake values are also moderately correlated to calcium mass scores (match). Higher uptake values were found just outside macrocalcification masks instead of inside the macrocalcification masks (mismatch). Also, only a small percentage of the Na[18F]F-uptake volumes overlapped with the calcium volumes (mismatch).

Relationship fecundity – morphometrics in the green tiger shrimp, Penaeus semisulcatus De Haan, 1844 (Decapoda, Penaeidae), along the Palk Bay, southern Peninsular India

Abstract The green tiger shrimp, Penaeus semisulcatus, is a commercial species supporting important fishery along the Palk Bay coasts. It is a much sought-after seafood commodity influencing the livelihood of the local fishers. This study aims to investigate the fecundity of the species in relation to its morphometry. Fecundity is an index of reproductive capacity used to calculate a stock’s reproductive potential and the egg’s survival. The absolute fecundity of the shrimp ranged from 26 100 to 750 000 ova alive per female, and the mean absolute fecundity from 59 100 to 583 000 ova alive per female. The relationship between fecundity and the morphometric measurements showed a positive exponential correlation. One-way ANOVA indicated a significant difference in the different size classes’ carapace length, total weight, ovary weight, absolute fecundity, stomach weight, and gastrosomatic index. There was no significant difference between the relative fecundity and the gonadosomatic index. This study provides insight into the reproductive potential of P. semisulcatus for efficient management of the resource in Palk Bay, Tamil Nadu, India.

Characteristics of solid–liquid phase transformation of saturated coral sand subjected to various patterns of cyclic loading

This study conducts a series of undrained cyclic shear tests on saturated coral sand with different initial relative densities ( Dr) subjected to a 90° jump rotation of the principal stress with various initial orientations. Considering liquefiable coral sand as a fluid, an important finding is that the variation in the apparent viscosity with the number of cycles is significantly affected by Dr, the effective mean principal stress ( [Formula: see text] ), cyclic stress ratio, cyclic loading path, and cyclic loading frequency. The average flow coefficient (κ) is introduced to describe the fluidity of saturated coral sand under cyclic loading by considering the variation in the shape of the stress–strain rate curve. A positive exponential correlation is observed between κ and the excess pore water pressure (EPWP) ratio ( ru) under the given cyclic loading modes. Another significant finding is that the solid–liquid phase change time is the turning point of the apparent viscosity and the average flow coefficient gradients with ru. The inversion point’s EPWP ratio is approximately 0.9, defined as the EPWP ratio during the solid–liquid phase transformation ( ruth). The ruth value is not affected by cyclic loading mode, [Formula: see text] , and Dr.

Structural diagenesis and high-quality reservoir prediction of tight sandstones: A case study of the Jurassic Ahe Formation of the Dibei gas reservoir, Kuqa depression, Tarim basin, NW China

• The paleo-tectonic stress was verified to be an important factor for porosity reduction in tight sandstones . • The structural diagenesis of tight sandstone of Ahe Formation was quantitatively characterized. • The favorable reservoir areas were predicted based on structural diagenesis and stress field simulation. Structural diagenesis is an important factor controlling the reservoir characteristics of the Jurassic Ahe Formation (J 1 a) of the Dibei gas reservoir in the northern structural belt of the Kuqa depression, which is mainly manifested as the compaction-attributed porosity reduction by the paleo-tectonic stress and structural fracture formation. Based on the analysis of the reservoir and tectonic stress characteristics, the control effects of the paleo-tectonic stress on porosity reduction and structural fracture characteristics of the Ahe Formation reservoir are quantitatively investigated. With numerical simulation based on the finite element method, the high-quality reservoir area of the Jurassic Ahe Formation of the Dibei gas reservoir is predicted. The results show that paleo-tectonic stress is an important element affecting reservoir physical properties and structural fracture characteristics of the Ahe Formation. The maximum paleo effective compressive stress is negatively linearly correlated with the average reservoir porosity, while it is positively exponentially correlated with the porosity reduction attributed to tectonic compaction. The direction of the maximum paleo effective compressive stress controls the dominant striking direction of structural fractures, and the stress magnitude determines the development degree of structural fractures. A clear positive exponential correlation is found between the maximum paleo effective compressive stress and both the areal density and plane porosity of fractures. The Well DX1-YN2-DB104 district and Well TZ4 district present high gas production, and the circular zone in the central-southern part of the study area has paleo-tectonic stress and reservoir characteristics similar to those of the above two districts. Thus, it is a potential favorable area for high gas production and should be considered a key exploration orientation of the Dibei gas reservoir.

Orthogonal Test Design for the Optimization of Preparation of Steel Slag-Based Carbonated Building Materials with Ultramafic Tailings as Fine Aggregates

The high carbonation potential makes ultramafic tailings ideal aggregates for carbonated building materials. This paper investigates the preparation condition of ultramafic tailings and steel slag through orthogonal experiments. The results show that compressive strength has a positive exponential correlation with the CO2 uptake of the carbonated compacts. The optimized conditions include a slag-tailings ratio of 5:5, a carbonation time of 12 h, a grinding time of 0 min, and a water-solid ratio of 2.5:10, when the compressive strength of the carbonated compacts reaches 29 MPa and the CO2 uptake reaches 66.5 mg CO2/g. The effects on the compressive strength ordered from high to low impact are the slag/tailings ratio, carbonation time, grinding time of steel slag, and water–solid ratio. The effects on the CO2 uptake ordered from high to low impact are the slag–tailings ratio, water–solid ratio, carbonation time, and grinding time of steel slag. A high water–solid ratio hinders the early carbonation reactions, but promotes the long-term carbonation reaction. Steel slag is the main material being carbonated and contributes to the hardening of the compacts through carbonation curing at room temperature. Ultramafic tailings assist steel slag in hardening through minor carbonation and provide fibrous contents. The obtained results lay a solid foundation for the development of tailings-steel slag carbonated materials.

Thermal performance of hydrophobic α-Al2O3 ceramic membrane for solar-thermal membrane coupling water desalination process

A water desalination idea with high-efficiency was presented, which employed a vacuum tube type solar distiller to stuffy-thermal distillation and raw water preheating, and also utilized the hydrophobic α-Al2O3 ceramic membrane distillation (HCMD) modules and preheated raw water to membrane distillation (MD). In order to show the potential of HCMD to improve the photo-thermal conversion efficiency of the vacuum tube type solar distiller, this study explored the thermal performance and water desalination capacity of HCMD module driven by the recovered latent heat of the vacuum tube type solar distiller. The research results indicate that the membrane flux of HCMD had a significant positive exponential correlation with the raw water temperature (Tr). The convective heat transfer coefficient (h) of the hot side surface of hydrophobic α-Al2O3 ceramic membrane (HCM) was positively correlated with Tr and the concentration of raw water (C). The effects of Tr and cooling water temperature (Tc) on the thermal efficiency (η) of HCMD had an interaction. The theoretical maximum of η was close to 67.8%, and the variation range of η corresponding to the temperature range of preheated raw water by the solar distiller was 8.32–42.90%. The rejection rate of the HCM for all measured ions in the raw water was greater than 99.96%. This research was of great theoretical guiding significance for realizing the engineering application of the solar-thermal membrane coupling water desalination system.

Increased Litter Greatly Enhancing Soil Respiration in Betula platyphylla Forests of Permafrost Region, Northeast China

The change of litter input can affect soil respiration (Rs) by influencing the availability of soil organic carbon and nutrients, regulating soil microenvironments, thus resulting in a profound influence on soil carbon cycle of the forest ecosystem. We conducted an aboveground litterfall manipulation experiment in different-aged Betula platyphylla forests (25-, 40- and 61-year-old) of the permafrost region, located in the northeast of China, during May to October in 2018, with each stand treated with doubling litter (litter addition, DL), litter exclusion (no-litter, NL) and control litter (CK). Our results indicated that Rs decreased under NL treatment compared with CK treatment. The effect size lessened with the increase in the stand age; the greatest reduction was found for young Betula platyphylla forest (24.46% for 25-year-old stand) and tended to stabilize with the growth of forest with the reduction of 15.65% and 15.23% for 40-and 61- year-old stands, respectively. Meanwhile, under DL treatment, Rs increased by 27.38%, 23.83% and 23.58% on 25-, 40- and 61-year-old stands, respectively. Our results also showed that the increase caused by DL treatment was larger than the reduction caused by NL treatment, leading to a priming effect, especially on 40- and 61-year-old stands. The change in litter input was the principal factor affecting the change of Rs under litter manipulation. The soil temperature was also a main factor affecting the contribution rate of litter to Rs of different-aged stands, which had a significant positive exponential correlation with Rs. This suggests that there is a significant relationship between litter and Rs, which consequently influences the soil carbon cycle in Betula platyphylla forests of the permafrost region, Northeast China. Our finding indicated the increased litter enhanced the Rs in Betula platyphylla forest, which may consequently increase the carbon emission in a warming climate in the future. It is of great importance for future forest management in the permafrost region, Northeast China.

Spatial variation and structural characteristics of phycobiliproteins from the red algae Furcellaria lumbricalis and Coccotylus truncatus

Phycobiliproteins, red phycoerythrins and blue (allo)phycocyanins, are one of the most highly valued components extracted from cyanobacteria and red algae. In the given study, 95 Furcellaria lumbricalis and 92 Coccotylus truncatus samples were collected from different locations and depths from Kassari Bay, Estonia. Firstly, a strong, positive exponential correlation between the R-phycoerythrin and allophycocyanin concentrations and the collection depth (R>0.75 and R>0.61, respectively) was found. Secondly, a preparative scale purification was performed, and the proteins were further characterised by spectrophotometry, fluorimetry and native mass spectrometry. The obtained purity indices (A566/A280) for the R-phycoerythrins were 1.6 for F. lumbricalis and 2.6 for C. truncatus, thus making them suitable for cosmetics and food industries.Purified R-phycoerythrins from the two algal species had subtle differences in absorption and fluorescence maxima. Based on their slightly different absorption characteristics, R-phycoerythrin from F. lumbricalis would categorise as type III (RIII-PE) and R-phycoerythrin from C. truncatus, alongside with the Sigma 52412 standard, as type II (RII-PE). The native mass spectrometry analysis supported the results by showing different intact complexes with distinct γ-subunits for the R-phycoerythrin types. The R-phycoerythrin hexamers linked to various γ-subunits, which are in turn coupled to different chromophores, could explain the similarities (analytical standard and C. truncatus) and differences (F. lumbricalis) in absorption and fluorescence characteristics among the tested species.

Carbon nanotubes market to garner $5.8 bn, globally, by 2027 at 10.7% CAGR

Phycobiliproteins, red phycoerythrins and blue (allo)phycocyanins, are one of the most highly valued components extracted from cyanobacteria and red algae. In the given study, 95 Furcellaria lumbricalis and 92 Coccotylus truncatus samples were collected from different locations and depths from Kassari Bay, Estonia. Firstly, a strong, positive exponential correlation between the R-phycoerythrin and allophycocyanin concentrations and the collection depth (R > 0.75 and R > 0.61, respectively) was found. Secondly, a preparative scale purification was performed, and the proteins were further characterised by spectrophotometry, fluorimetry and native mass spectrometry. The obtained purity indices (A566/A280) for the R-phycoerythrins were 1.6 for F. lumbricalis and 2.6 for C. truncatus, thus making them suitable for cosmetics and food industries.Purified R-phycoerythrins from the two algal species had subtle differences in absorption and fluorescence maxima. Based on their slightly different absorption characteristics, R-phycoerythrin from F. lumbricalis would categorise as type III (RIII-PE) and R-phycoerythrin from C. truncatus, alongside with the Sigma 52412 standard, as type II (RII-PE). The native mass spectrometry analysis supported the results by showing different intact complexes with distinct γ-subunits for the R-phycoerythrin types. The R-phycoerythrin hexamers linked to various γ-subunits, which are in turn coupled to different chromophores, could explain the similarities (analytical standard and C. truncatus) and differences (F. lumbricalis) in absorption and fluorescence characteristics among the tested species.

ARTHROSCOPIC SHOULDER STABILIZATION IN HIGH SCHOOL FOOTBALL PLAYERS: RECURRENT INSTABILITY WITH RETURN TO CONTACT SPORT

Background:The etiology of recurrent shoulder instability after arthroscopic surgery in the high school American football population remains unknown.Purpose/Hypothesis:To determine the risk of recurrent instability after shoulder arthroscopy upon return to competitive football. The hypothesis was that the rate of recurrence would be greater in high school players with more years of eligibility remaining (YER), suggesting greater likelihood of return to football after surgery.Methods:Consecutive male high school football players with at least one year of eligibility remaining who sustained traumatic in-season shoulder instability episode(s) and underwent arthroscopic labral stabilization by two Orthopaedic Sports surgeons at Rady Children’s Hospital San Diego between 2012 and 2017 were identified. 64 subjects aged 14-17 met inclusion criteria of which 45 were able to be contacted and included in analyses. Average follow up period was 4.06 years. Patients and/or families were contacted by phone to discuss (1) recurrent instability episodes and (2) return to competitive sport and/or recreational athletic activity. Statistics were conducted using chi square analysis to compare recurrence of instability with return to sport.Results:Surgery itself was career ending in 50% of cases due to reported fear of recurrent football-related injury. The hypothesis that career longevity in terms of years of eligibility remaining (YER) affects return to game play in this young active population remains unclear although preliminary results suggest positive exponential correlation. Comparative analysis demonstrates a statistically significant difference between rate of recurrence in high school football players that return to contact sports vs transition to non-contact activity after arthroscopic shoulder stabilization. Interestingly, football players who concurrently played baseball during high school demonstrated decreased risk of postoperative instability episodes.Conclusion:Risk of recurrent instability after shoulder arthroscopy is increased in high school football players who return to competitive contact sports whereas transition to non-contact and/or recreational activity likely confers protective effect. High school football players who play baseball may derive functional benefit from cross training.Figure.Proportion of recurrent shoulder instability after arthroscopic stabilization in high school football players stratified by years of eligibility remaining (YER) demonstrating positive exponential correlation relationship.

Changes in the pore structure of lignite after repeated cycles of liquid nitrogen freezing as determined by nitrogen adsorption and mercury intrusion

As a non-aqueous medium for increasing permeability in coal seams, liquid nitrogen fracturing has been widely studied. The changes of the pores in coal fractured by liquid nitrogen have important effects on coalbed methane (CBM) migration. It is difficult to thoroughly characterize the pore structure in coal using a single method. Therefore, this study carried out a detailed study of the pores in coal samples fractured by liquid nitrogen using both nitrogen adsorption and mercury intrusion. The results show that combining these methods can accurately determine pore sizes and specific surface areas in the samples tested. The maximum liquid nitrogen adsorption capacity and the injected mercury volume in the samples were positively correlated with the freezing times and freeze–thaw cycles. This indicated that the number of pores in the coal gradually increased. Cumulative total pore and seepage pore volumes in the samples showed a positive exponential correlation with freezing time. The volume increases also correlated with the number of freeze–thaw cycles and this increase followed a quadratic function. The cumulative specific surface areas also varied with freezing time but the areas first rose and then fell as the freeze–thaw cycles increased. Liquid nitrogen freezing time significantly affects the micropores and specific surface area. However, freezing time has only a minor effect on the larger seepage pores and the total pore volume. Liquid nitrogen freeze–thaw cycles help the formation of connections between micropores and larger pores and thus promote the development of fracture networks. This provides favorable conditions for CBM production.

模拟增温对羊草生态系统土壤呼吸速率的影响

草地是陆地生态系统的重要组成部分，研究草地系统土壤呼吸速率对全球气候变暖的响应，对预测全球碳循环具有重要作用。采用高度分别为0.5 m（T1）和1.85 m（T2）的开顶式增温箱（OTCs）对羊草生态系统进行模拟增温，仔细观察羊草的生育期，在每个生育期的同一天的晨间t₁时段（9：00-11：00）、午间t₂时段（13：30-15：30）和晚间t₃时段（17：00-19：00）监测土壤呼吸速率。分析不同增温幅度下土壤呼吸速率的变化规律，明确影响土壤碳排放的主要因素，探讨土壤呼吸速率与影响因素间存在的关系。结果显示：1）相对于空白对照C，模拟增温T1和T2导致0-10 cm土壤温度分别显著提高1.18和2.37℃；导致0-10 cm土壤湿度降低2.27%和4.57%；2）在羊草生长阶段，土壤呼吸速率呈现明显的季节性变化特征，同一天的t₁时段、t₂时段和t₃时段土壤呼吸速率峰值分别出现在结实期、抽穗期和开花期。非生长阶段土壤呼吸速率无显著差异；3）不同处理下土壤呼吸速率与近地表气温、0-10 cm土壤温度和地下生物量呈指数正相关关系，与0-10 cm的土壤湿度呈显著二次项负相关关系，与地上生物量表现为二次项正相关关系。研究结果明确了羊草生态系统中土壤碳排放对增温的响应，可为草原生态系统应对气候变化及可持续发展提供理论依据。;Grasslands are one of the major types of terrestrial ecosystems and their soil respiration makes up one of the largest flux of carbon between their ecosystems and the atmosphere. Therefore, revelation of the responses of their soil respiration to global warming can be vital and will shed light on identifying and predicting the global carbon cycle. To simulate climate change, we used two open-top chambers (OTCs) T1 (0.5 m) and T2 (1.85 m) to manipulate warming Leymus chinensis systems and meanwhile observed the growth of Leymus chinensis. The soil respiration of these systems in both OTCs was monitored and the soil respiration rate was measured at the time t₁ (9:00-11:00), t₂ (13:30-15:30), and t₃ (17:00-19:00). The change in the soil respiration of heated Leymus chinensis systems was investigated to identify the main factors contributing to release of soil carbon to atmosphere and put insight into the relationship between the soil respiration and these main factors. The observations showed that T1 and T2 increased annual surface soil temperature by 2.14 and 4.03℃ respectively compared to control, but decreased annual soil moisture by 2.27% and 4.57% in the soil depth range between 0 cm and 10 cm. The results demonstrated that the manipulated heating significantly (p < 0.05) enhanced soil respiration through growth stages and soil respiration patterns changed over seasons. In grain filling, heading, and blossom stage, peak values of soil respiration rate were observed at t₁, t₂ and t₃ in the Leymus chinensis of the same growth day. The soil respiration rate did not change significantly at non-growth stages. The study also found that the soil respiration rate under different treatments had a positive exponential correlation to near-surface air temperature, surface soil temperature, and below-ground biomass. It also had a negative quadratic correlation with surface soil moisture and a positive quadratic correlation with above-ground biomass. This study reveals the change in release of soil carbon from Leymus chinensis systems to atmosphere when they were treated with manipulated warming, which can provide useful information for understanding how grassland ecosystems respond to climate change and sustainable development of animal husbandry.

Physical modeling of inland freshwater lens formation and evolution in drylands

Dryland inland freshwater lenses (IFLs) that have been topographically induced are represented using physically modeled laboratory simulations, to characterize the stages of IFL evolution (i.e. formation, migration, degradation) as a function of recharge rate. Arid regions with shallow brackish to saline groundwater possess IFLs. The position and geometry (i.e. thickness, length) of IFLs over varying temporal and spatial scales is poorly understood due to their transient nature. The physically modeled IFLs in this study formed from an initial recharge pulse, after which IFL geometry was measured over time as it flowed in the direction of simulated groundwater flow. The time required for an IFL to reach the maximum thickness exhibited a negative exponential correlation to recharge rate. At IFL formation, thickness and length were positively correlated, and the ratio of IFL thickness to length exhibited a positive exponential correlation to recharge rate. After IFL formation, the central position of the simulated IFLs migrated laterally in the direction of groundwater flow at a velocity less than the range of applied recharge rates and greater than the groundwater flow velocities. The time required for the IFL to reach a minimum thickness, or IFL degradation, exhibited a positive exponential correlation to recharge rate. The Dupuit-Ghyben-Herzberg solution used to model coastal freshwater lens thickness was tested against the physically modeled IFLs and deemed invalid. A correction factor and modified solution are provided to predict IFL thickness, providing motivation for future analytical and numerical studies on inland variable-density groundwater systems in arid regions globally.

Quantifying the relationship between PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

Abstract. Air quality and visibility are strongly influenced by aerosol loading, which is driven by meteorological conditions. The quantification of their relationships is critical to understanding the physical and chemical processes and forecasting of the polluted events. We investigated and quantified the relationship between PM2.5 (particulate matter with aerodynamic diameter is 2.5 µm and less) mass concentration, visibility and planetary boundary layer (PBL) height in this study based on the data obtained from four long-lasting haze events and seven fog–haze mixed events from January 2014 to March 2015 in Beijing. The statistical results show that there was a negative exponential function between the visibility and the PM2.5 mass concentration for both haze and fog–haze mixed events (with the same R2 of 0.80). However, the fog–haze events caused a more obvious decrease of visibility than that for haze events due to the formation of fog droplets that could induce higher light extinction. The PM2.5 concentration had an inversely linear correlation with PBL height for haze events and a negative exponential correlation for fog–haze mixed events, indicating that the PM2.5 concentration is more sensitive to PBL height in fog–haze mixed events. The visibility had positively linear correlation with the PBL height with an R2 of 0.35 in haze events and positive exponential correlation with an R2 of 0.56 in fog–haze mixed events. We also investigated the physical mechanism responsible for these relationships between visibility, PM2.5 concentration and PBL height through typical haze and fog–haze mixed event and found that a double inversion layer formed in both typical events and played critical roles in maintaining and enhancing the long-lasting polluted events. The variations of the double inversion layers were closely associated with the processes of long-wave radiation cooling in the nighttime and short-wave solar radiation reduction in the daytime. The upper-level stable inversion layer was formed by the persistent warm and humid southwestern airflow, while the low-level inversion layer was initially produced by the surface long-wave radiation cooling in the nighttime and maintained by the reduction of surface solar radiation in the daytime. The obvious descending process of the upper-level inversion layer induced by the radiation process could be responsible for the enhancement of the low-level inversion layer and the lowering PBL height, as well as high aerosol loading for these polluted events. The reduction of surface solar radiation in the daytime could be around 35 % for the haze event and 94 % for the fog–haze mixed event. Therefore, the formation and subsequent descending processes of the upper-level inversion layer should be an important factor in maintaining and strengthening the long-lasting severe polluted events, which has not been revealed in previous publications. The interactions and feedbacks between PM2.5 concentration and PBL height linked by radiation process caused a more significant and long-lasting deterioration of air quality and visibility in fog–haze mixed events. The interactions and feedbacks of all processes were particularly strong when the PM2.5 mass concentration was larger than 150–200 µg m−3.

Concentration dynamics of coarse and fine particulate matter at and around signalised traffic intersections.

The understanding of rapidly evolving concentrations of particulate matter (PMC) at signalised traffic intersections (TIs) is limited, but it is important for accurate exposure assessment. We performed "mobile" and "fixed-site" monitoring of size-resolved PMCs in the 0.25-34 μm range at TIs. On-road mobile measurements were made inside a car under five different ventilation settings on a 6 km long round route, passing through 10 different TIs. Fixed-site measurements were conducted at two types (3- and 4-way) of TIs. The aims were to assess the effects of different ventilation settings on in-vehicle PMCs and their comparison during delay conditions at the TIs with those experienced by pedestrians while crossing these TIs. We also estimated the zone of influence (ZoI) for PM10, PM2.5 and PM1 under different driving conditions and fitted the probability distribution functions to fixed-site data to understand the concentration and exposure dynamics of coarse and fine particles around the studied (3- and 4-way) TIs. The fine particles (PM2.5) showed a strong positive exponential correlation with the air exchange rates under different ventilation settings compared with coarse particles (PM2.5-10) showing an opposite trend. This suggested that the ventilation system of the car was relatively more efficient in removing coarse particles from the incoming outside air. On-road median PM10, PM2.5 and PM1 during delays at the TIs were ∼40%, 16% and 17% higher, respectively, compared with free-flow conditions on the rest of the route. About 7% of the average commuting time spent during delay conditions over all the runs at the TIs corresponded to 10, 7 and 8% of the total respiratory deposition dose (RDD) for PM10, PM2.5 and PM1, respectively. The maximum length of the ZoI for PM2.5 and PM1 was highest at the 4-way TI and the maximum length of the ZoI for PM10 was highest at the 3-way TI. The on-road average RDD rate of PM10 inside the cabin when windows were fully open was up to ∼7-times that for pedestrians at the TIs.

Trends in soil respiration on the eastern slope of the Cofre de Perote Volcano (Mexico): Environmental contributions

A soil respiration dataset was examined to determine the importance of environmental factors relating to seasonal variation in soil surface CO2 flux on the eastern slope of the Cofre de Perote Volcano (Mexico). The results are reported as follows: (1) on the upper section (2500masl), average soil respiration varied from 10.3 to 21.5mgCm−2h−1 in coniferous forest, 14.8 to 30.3mgCm−2h−1 in corn field, and 13.4 to 29.9mgCm−2h−1 in abandoned corn field. Soil respiration decreased in spring, when the soil temperature was higher and soil water was lower, while it increased in summer, with non-limiting conditions of soil water. (2) On the lower section (1650masl), the average soil respiration varied from 22.5 to 89.6mgCm−2h−1 in tropical montane cloud forest, 17.9 to 128.1mgCm−2h−1 in corn–potato–corn rotation, and 63.0 to 203.2mgCm−2h−1 in grassland. Soil respiration began to rise in late spring, corresponding to the transition from the dry to wet season and reaching its highest value in summer. (3) Soil respiration rates showed a positive exponential correlation with soil temperature (R2=0.52; P<0.0001). The model RS=0.031e0.174T+17.21θ−16.32θ2 related soil respiration to soil temperature and soil water, explaining 58% of variation. These results suggest that soil temperature and soil water co-regulate soil respiration. Thus, the dataset suggests that global warming could have a negative effect on soil water availability, resulting in decreasing soil respiration.

Are the pituitary gonadotrophins determinants of complete molar pregnancy? An investigation using the method of least squares

ObjectiveTo look for a relationship between the maternal age-specific incidence of complete molar pregnancy and the age-specific mid-follicular levels of circulating follicle stimulating hormone and luteinizing hormone.DesignCalculation of correlation coefficients between the incidence of complete mole and the circulating levels of follicle stimulating hormone and luteinizing hormone using the method of least squares.SettingEngland and Wales.ParticipantsAll mothers between 23 and 49 years delivering in England and Wales between 2000 and 2009 inclusive and a sample of women between 23 and 49 years from Sheffield (1987).Main outcome measuresThe bivariate correlation coefficients between the incidence of complete mole and the mid-follicular plasma levels of the pituitary gonadotrophins.ResultsExponential correlation between the incidence of complete mole and mid-follicular plasma follicle stimulating hormone, r = 0.965, r 2 = 0.932.Linear correlation between the incidence of complete mole and mid-follicular plasma luteinizing hormone, r = 0.972, r 2 = 0.944.Multivariate exponential regression between the incidence of complete mole and the combination of follicle stimulating and luteinizing hormones. This does not improve the prediction of the incidence of complete mole and it shows that luteinizing hormone is not a significant predictor of the incidence of complete mole in the presence of follicle stimulating hormone.ConclusionsThere is a strong positive exponential correlation between the maternal age-specific incidence of complete mole in England and Wales and the age-related mid-follicular levels of follicle stimulating hormone in a sample of English women.

Genome Analysis of a Transmissible Lineage of Pseudomonas aeruginosa Reveals Pathoadaptive Mutations and Distinct Evolutionary Paths of Hypermutators

Genome sequencing of bacterial pathogens has advanced our understanding of their evolution, epidemiology, and response to antibiotic therapy. However, we still have only a limited knowledge of the molecular changes in in vivo evolving bacterial populations in relation to long-term, chronic infections. For example, it remains unclear what genes are mutated to facilitate the establishment of long-term existence in the human host environment, and in which way acquisition of a hypermutator phenotype with enhanced rates of spontaneous mutations influences the evolutionary trajectory of the pathogen. Here we perform a retrospective study of the DK2 clone type of P. aeruginosa isolated from Danish patients suffering from cystic fibrosis (CF), and analyze the genomes of 55 bacterial isolates collected from 21 infected individuals over 38 years. Our phylogenetic analysis of 8,530 mutations in the DK2 genomes shows that the ancestral DK2 clone type spread among CF patients through several independent transmission events. Subsequent to transmission, sub-lineages evolved independently for years in separate hosts, creating a unique possibility to study parallel evolution and identification of genes targeted by mutations to optimize pathogen fitness (pathoadaptive mutations). These genes were related to antibiotic resistance, the cell envelope, or regulatory functions, and we find that the prevalence of pathoadaptive mutations correlates with evolutionary success of co-evolving sub-lineages.The long-term co-existence of both normal and hypermutator populations enabled comparative investigations of the mutation dynamics in homopolymeric sequences in which hypermutators are particularly prone to mutations. We find a positive exponential correlation between the length of the homopolymer and its likelihood to acquire mutations and identify two homopolymer-containing genes preferentially mutated in hypermutators. This homopolymer facilitated differential mutagenesis provides a novel genome-wide perspective on the different evolutionary trajectories of hypermutators, which may help explain their emergence in CF infections.

Coal strength and Young's modulus related to coal rank, compressional velocity and maceral composition

This paper presents an experimental investigation of coal rank and maceral composition influences on the coal mechanical behaviors. The complete stress–strain behavior, uniaxial compressive strength, Young's modulus, and acoustic compressional velocity were measured and correlated to coal ranks and microstructures. The test results show that coal is an elasto-brittle geo-material and its uniaxial compressive strength and Young's modulus increase as coal rank increases. This occurs because as vitrinite reflectance or coal rank increases, coal has less microporous structure and thus higher uniaxial compressive strength. Therefore, using vitrinite reflectance value instead of vitrinite content is advantageous for correlating coal strength. The experimental results also demonstrate that compressive strength and Young's modulus have positive exponential correlation, even for different types of coal. Therefore, the compressive strength of coal is highly related to its Young's modulus. The uniaxial compressive strength and acoustic compressional velocity of coal are also correlated, but a single correlation does not exist for different coal ranks; instead, different relationships occur for different types of coal.