Ratio Of Total Area Research Articles

Reducing thermal imbalances and flow nonuniformity in solar collectors through the selection of free flow area ratio

The effect of the riser to header diameter ratio and total cross-sectional area ratio on the flow distribution and thermal performance of flat-plate solar collectors is investigated. An analytical model based on the mass and momentum conservation equations is developed to determine the pressure drop and flow distribution in flat plate collectors. A numerical model is also developed to the assess the thermal effects of flow maldistribution. The accuracy of both models is verified against comparison with experimental measurements taken from the open literature. The use of the models is then extended to cover the flow distribution in solar collector networks. It is found that for laminar and turbulent conditions, cross-sectional area ratios and diameter ratios equal or lower than 0.75 and 0.25 respectively, minimize flow nonuniformity and reduce thermal imbalances. The results can be used for design purposes.

Assessing Drivers of Cross-Scale Variability in Peat Smoldering Combustion Vulnerability in Forested Boreal Peatlands

Wildfire represents the largest areal disturbance of forested boreal peatlands and the spatial variability in the severity of these peat fires is both a leading source of uncertainty in boreal wildfire carbon emissions and a major challenge for regional wildfire management. Peat smouldering can emit large quantities of carbon and smoke to the atmosphere, and therefore can contribute to hazardous air quality. The wildland-industry interface and wildland-urban interface are both extensive across the sub-humid boreal plains (BP) ecozone where one-third of the area is covered by peatlands. As such, there is a growing research need to identify drivers of variability in smouldering combustion. This study uses hydrophysical peat properties to assess the drivers of cross-scale variability in peat smouldering combustion vulnerability in forested peatlands across the BP. Using a space-for-time chronosequence across the 120-year fire return interval and three main hydrogeological settings, and by incorporating hummock, hollow and margin locations, cross-scale variability is studied. We find that, based on peat properties such as specific yield (Sy) and gravimetric water content, forested peatland margins represent areas of high peat smouldering vulnerability, and that this is exacerbated with an increasing time-since-fire (stand-age). Although increasing Sy with time-since-fire in peatland middles may buffer water table drawdown, when accounting for increases in canopy fuel load, transpiration, and feather moss dominance forested peatland middles also become more vulnerable to smouldering combustion with time-since-fire. Moreover, the interaction of peatland margins with coarse- and heterogeneous-grained hydrogeological settings leads to lower Sy and higher density margin peat than in fine-grained settings, further increasing smouldering vulnerability. We estimate that forested peatland margins are vulnerable to combustion throughout their entire profile i.e. burn-out, under moderate-high water deficits in the BP. Furthermore, we identify peatland margin: total area ratio as a driver of smouldering vulnerability where small peatlands that are periodically disconnected from regional groundwater systems are the most vulnerable to high total peat carbon loss. We suggest that these drivers of cross-scale variability should be incorporated into peatland and wildfire management strategies, especially in areas near the wildland-industry and wildland-urban interface.

Rock avalanche runout prediction using stochastic analysis of a regional dataset

Rock avalanches involve extremely rapid, flow-like movement of fragmented rock with extreme destructive potential. With increasing development pressures in mountainous regions, there is a need for simple, stochastic estimates of runout distances to aid in hazard assessments and prioritize sites for more detailed investigation. To support the development of an empirical predictive tool, a systematic method was used to describe 49 rock avalanches in the Canadian Cordillera, which had been documented in the literature but not previously compiled into a regional inventory. These cases were described using measured or estimated numerical values for volume, fall height, runout length, total impacted area and the ratio of total impacted area over runout length (referred to as mean path width), and qualitative descriptions of the topographic confinement, substrate material and source geology. Linear regressions were fit to the data, with qualitative attributes treated as indicator variables. A strong relationship was found for runout distance predicted from volume, fall height and lateral confinement. A second relationship was found for mean path width over runout length predicted from volume. These relationships were converted to survival functions to estimate the runout exceedance probability and the mean path width exceedance probability. These survival functions were implemented in a computer tool, called the Probabilistic Runout Estimator—Rock Avalanche (PRE-RA), which can be used to estimate spatial impact probability ranges for rock avalanche runout. An application of this tool was demonstrated using two recent Canadian rock avalanches, which were not used in the dataset to estimate the statistical relationships.

Experimental and Numerical Study of a Methane-Fueled Pre-chamber System in Rapid Compression Machine

ABSTRACT Pre-chamber jet ignition is a promising combustion technology to accelerate burning velocity and improve combustion stability in natural gas engines. In this study, firstly, the ignition characteristics and the dilution limits in passive pre-chamber system with different orifice diameters were experimentally investigated based on a rapid compression machine (RCM). Methane (CH4) was used as the test fuel and CO2/N2 was used as the dilution components to simulate exhaust gas recirculation conditions in engines. Real-time combustion pressures were recorded and combustion images were captured using high-speed photography to visualize the entire jet ignition and combustion process. The experimental results showed that two different ignition behaviors were observed regarding to different orifice diameters. And no capacity of extending CO2/N2 dilution limits in the passive pre-chamber system compared to conventional spark ignition system. Then three-dimensional numerical simulations were conducted based on the experimental results. Simulation results demonstrated two ignition modes, pre-chamber jet flame ignition and pre-chamber jet autoignition, were presented due to the different jet temperatures, concentrations of immediate species, and turbulence intensities. Lastly, based on the numerical model, the effects of pre-chamber structure parameters on the ignition modes and potentials of different dilution state of mixture in pre-chamber for extending dilution limits were numerically studied. It was found that the ratio of total effective cross-sectional area of orifices to pre-chamber volume (At /VPC ) was the key structure parameter of pre-chamber systems to determined different ignition modes. And there was a narrow critical range of At /VPC to achieve pre-chamber jet autoignition (PJAI) mode, beyond which PJFI mode or ignition failure occurred. The actual dilution rate of mixture in the pre-chamber affected the ignition probability and stability in the main chamber. Improving the chemical reactivity of mixture in the pre-chamber was beneficial to effectively extend the dilution limits due to the stronger thermal, chemical, and turbulent effects of pre-chamber jet. Abbreviations: PJI Pre-chamber jet ignition; CSI Conventional spark ignition; NG Natural gas; PM Particulate matter; SI Spark ignition; CI Compression ignition; THC Total hydrocarbon; SCR Selective catalyst reduction; TWC Three-way catalyst; EGR Exhaust gas recirculation; BSFC Brake specific fuel consumption; DI Direct injection; RCM Rapid compression machine; CVB Constant volume bomb; TDC Top dead center; BDC Bottom dead center; CFD Computational fluid dynamics; SOC Start of combustion; PJAI Pre-chamber jet auto-ignition; PJFI Pre-chamber jet flame ignition; TKE Turbulent kinetics energy

Experimental investigation of top burr formation in high-speed micro-milling of Ti6Al4V alloy

Miniaturization with superior quality product of super alloy is the demand of the industry. Ti6Al4V is the demanding super alloy due to its excellent material properties, although this super alloy is known for poor machinability in terms of burr formation, low tool life, and poor surface finish. Therefore, being a popular super alloy, it comes under the difficult-to-cut material. In the current work, burr formation on the machining of Ti6Al4V has been studied. Experimental investigation and characterizations of top burr formation on Ti6Al4V alloy using end milling process were carried out. A scanning electron microscopy identifies the burr formed on the machined surface. A new technique has been introduced to measure the top burr width (i.e. equivalent width) accurately. Equivalent burr width calculated as the ratio of total area of burr generated to the total height. It was observed that equivalent burr width in up milling was increased by 120%, while in down milling, it was decreased by 50% as the speed varies from conventional to high speed. Furthermore, the effects of different cutting parameters and tool parameters on top burr formation have been analyzed to establish correlation among them.

Influence of mixed-use neighborhood developments on the performance of waste-to-energy CHP plant

In this work, the influence of residential and commercial buildings on the performance of waste-to-energy (WtE) combined heat and power (CHP) plant, within a mixed-use neighborhood is quantified. The waste incinerator-based single and double stage CHP plants considered in study are modeled and simulated in Matlab-Simulink. The performance of WtE-CHP plant is evaluated based on hourly electricity and heat generations, heat extraction temperatures, and GHG emissions. The key results indicate that the use of single or double stage CHP plant is decided by various types commercial buildings, commercial land fraction, and commercial land to total area ratio. Considering a commercial land to total land area fraction of 0.25, two stage WtE-CHP plant can be used irrespective to varying proportions of residential buildings types and their unit densities. The heat extraction temperatures of 100–112 °C can be yielded for two stage CHP, whereas, for single stage CHP it lies between 170 and 180 °C. The GHG emissions for WtE-CHP plants decreases with the increase in proportions of offices, single detached houses, and townhouses. However, it increases with the increase fraction of retails and apartments. The energy generation to consumption fraction lies between 17 and 57% for conventional neighborhoods, whereas, for the high-performance neighborhoods it varies between 22 and 65%.

Acute exposure to environmentally relevant concentrations of benzophenone-3 induced genotoxicity in Poecilia reticulata

The organic UV filter benzophenone-3 (BP-3), widely used in the commercial formulations of sunscreens and personal care products, is considered an emerging pollutant and has been associated with several human and environmental health concerns. However, knowledge about their mode of action and ecotoxicity on aquatic biota is scarce. In this scenario, the objective of this work was to evaluate the genotoxic, mutagenic, and erythrotoxicity effects of BP-3 in the guppy Poecilia reticulata after acute exposure. Adult females of P. reticulata were exposed to three non-lethal and environmentally relevant concentrations of BP-3 (10, 100, and 1000 ng L−1) during 96 h of exposure, and the somatic parameter [Fulton condition factor (K)], genotoxicity (comet assay), mutagenicity [micronucleus (MN) and erythrocyte nuclear abnormalities (ENA) tests] and erythrotoxicity parameters (such as total cell area and nucleus-cytoplasmic ratio) were analyzed. Results showed that the general physiological condition (K value) of fish was not affected by acute exposure to BP-3. However, BP-3 induced DNA damage at 100 and 1000 ng L−1 and increased the frequency of total ENA at 1000 ng L−1, specially lobed nucleus, when compared to control group, indicating its genotoxic and mutagenic effects. Furthermore, the BP-3 did not induce significant changes in the total cell area and nucleus-cytoplasmic ratio. In summary, results showed that the BP-3 at environmentally relevant concentration was genotoxic to freshwater fish P. reticulata, confirming its environmental risk.

The Relationship between f Ratio and Seed Yield‐Related Traits in Festulolium

Festulolium is the result of hybridization between Lolium and Festuca species. Amphidiploid festulolium produced by crosses between tetraploid Lolium species (L. multiflorum Lam. and L. perenne L.) and Festuca pratensis (F. pratensis Huds.) exhibits genome balance drift, thereby favoring Lolium over numerous generations. In a previous report, we found no decrease in the f ratio (the ratio of total area of Festuca‐specific genome regions to the total area of all genome regions) in maternally derived progeny over generations, suggesting that seed yield can cause Lolium‐favored genome balance drift. In this study, we investigated seed yield, ripening rate, germination rate, and seed weight in the field for 2 yr in festulolium plants with f ratio over and under 50%. The over 50 f ratio group had significantly lower seed yields, ripening rates, and germination rates than the under 50 f ratio group. Further correlations between seed yield‐related traits and f ratio values revealed that germination rate was negatively correlated with f ratio in the over 50 f ratio group. Simulated next‐generation f ratios were 2% lower than the actual f ratio values of maternal plants. Our study shows that Lolium‐favored genome balance drift can solely be caused by phenotypic differences, regardless of any biases toward Lolium occurring during meiosis.

Multivariate performance optimisation of scaffold boards with selected softwood defects

The uncertainties involved in the prediction of scaffold material performance in the machine grading process have brought forth the necessity to identify the level of influence of wood defects on the scaffold performance required to be optimised for its intended use as a construction material. This paper tackled this important aspect by employing multivariate optimisation and statistical analyses on the previously reported experimental results in the literature on the machine graded scaffold boards from UK Sitka spruce (picea sitchensis) softwoods. Initially, nonlinear multivariate regression analyses were performed for the responses of such variables as failure load, displacement, extreme fibre stress and the critical failure distance to several wood characteristics as contributing factors. The extension of the statistical analysis to the multi-objective optimisation study was accomplished using Response Surface Method (RSM) by considering the mutual interactions between the factors including total and margin knot area ratios, density, rate of growth and slope of grain. This paper represented graphically how the load bearing capacity, the deformation characteristics and the critical failure location points are influenced by the considered factors. The significance of factors and their relative influence on the performance optimisation were finally discussed by providing the essential information on the future use of scaffold board products as construction material.

Spatial assessment of farmland soil pollution and its potential human health risks in China

Soil pollution severely threatens agro-ecosystem stability. It is important to accurately understand the status of farmland pollution in order to protect national food safety and human health. However, information of the combined pollution level of Chinese farmland soil and associated human health risk at the national scale is relatively lacking. In this study, 5597 samples from 1781 farmland soil sites were obtained from 553 reports and combined into pollution databases of heavy metals, organochlorines, and polycyclic aromatic hydrocarbons. Based on the data obtained, this paper demonstrated the current pollution status of farmland soil, and assessed the subsequent human health risk. Results showed that the combined pollution ratio of Chinese farmland soil was 22.10%, with 1.23% of severe pollution level. Moreover, the total non-carcinogenic hazard quotients of farmland soil pollution were within the safety threshold for adults, but there was a slight non-carcinogenic risk for children. For adults, the ratio of total farmland area to total carcinogenic risk quotients above the safety threshold of 1 × 10−5 was only 1.02%, but for children, the ratio was as high as 20.75%. On the other side, food crop and vegetable plantations were the priority control farmland soil compared to other types. Meanwhile, Yunnan, Hunan, Anhui, Henan, and Liaoning were selected as the priority control provinces due to their severe pollutions and high human health risks. This study has provided a comprehensive pollution and health risk assessment. Furthermore, the spatial distribution might provide as the scientific support for accelerating the mapping of soil pollution in China, as well as developing the policy for the contaminated farmland soil management.

Selective extraction of aliphatic amines by functionalized mesoporous silica-coated solid phase microextraction Arrow

Mesoporous silica-coated solid phase microextraction (SPME) Arrow systems were developed for capturing of low-molecular-weight aliphatic amines (LMWAAs) from complicated sample matrices. Specifically, silicas of type MCM-41, SBA-15 and KIT-6 were chosen as substrates to afford size-exclusion selectivity. They possess ordered multidimensional pore-channel structures and mesopore sizes between 3.8 and 8.2 nm. Their surface acidity was enhanced by grafting them with a layer of titanium hydrogenphosphate (-TP). This enhanced the chemical selectivity for basic LMWAAs. The siliceous coatings increased the extraction of ethylamine, diethylamine (DEA) and triethylamine (TEA) by factors of 18.6–102.5, 4.8–10.8 and 2.6–4.0, respectively, when compared to the commercial SPME Arrow with polydimethylsiloxane/divinylbenzene coating. Among them, the MCM-41 and MCM-41-TP coated SPME Arrows demonstrated exceptional selectivity towards LMWAAs that were quantified by gas chromatography-mass spectrometry (GC-MS). The total peak area ratios of LMWAAs/ten competing compounds were 25.4 and 36.3, respectively. The extraction equilibrium was reached within 20–30 min. The MCM-41 and MCM-41-TP derived SPME Arrows gave very similar results (18.4 ± 2.1–376 ± 12 ng g−1 to DEA and TEA) when applied to urban mushroom samples. SPME Arrow with MCM-41 coatings followed by GC-MS was applied also to the analysis of atmospheric air and urine samples resulting in high selectivity due to the size and mesoporous structure of the functionalized silica, and its chemical interactions with the LMWAAs.Graphical abstractScheme of synthesis of the MCM-41 silicas, and the preparation of solid phase microextraction Arrow coatings. They were employed for selective capturing of aliphatic amines from complex sample matrices, followed by gas chromatography-mass spectrometry.

Multi-scale high-throughput phenotyping of apple architectural and functional traits in orchard reveals genotypic variability under contrasted watering regimes

Despite previous reports on the genotypic variation of architectural and functional traits in fruit trees, phenotyping large populations in the field remains challenging. In this study, we used high-throughput phenotyping methods on an apple tree core-collection (1000 individuals) grown under contrasted watering regimes. First, architectural phenotyping was achieved using T-LiDAR scans for estimating convex and alpha hull volumes and the silhouette to total leaf area ratio (STAR). Second, a semi-empirical index (IPL) was computed from chlorophyll fluorescence measurements, as a proxy for leaf photosynthesis. Last, thermal infrared and multispectral airborne imaging was used for computing canopy temperature variations, water deficit, and vegetation indices. All traits estimated by these methods were compared to low-throughput in planta measurements. Vegetation indices and alpha hull volumes were significantly correlated with tree leaf area and trunk cross sectional area, while IPL values showed strong correlations with photosynthesis measurements collected on an independent leaf dataset. By contrast, correlations between stomatal conductance and canopy temperature estimated from airborne images were lower, emphasizing discrepancies across measurement scales. High heritability values were obtained for almost all the traits except leaf photosynthesis, likely due to large intra-tree variation. Genotypic means were used in a clustering procedure that defined six classes of architectural and functional combinations. Differences between groups showed several combinations between architectural and functional traits, suggesting independent genetic controls. This study demonstrates the feasibility and relevance of combining multi-scale high-throughput methods and paves the way to explore the genetic bases of architectural and functional variations in woody crops in field conditions.

Study on maximizing catalytic performance of cobalt(II) 5,10,15,20-tetrakis(4-pyridyl)porphyrin for cyclohexane oxidation

Aiming at the most enhancing the catalytic performance of simple and cheap cobalt(II) 5,10,15,20-tetrakis(4-pyridyl)porphyrin (Co TPyP), guided by the nowadays-advanced various technologies, Co TPyP was anchored onto nanoporous bar with thiol-functionalized silica (npb-SiO2-SH). The resulting npb-SiO2-S-Co TPyP catalyst was characterized using various techniques, determining its structure. The total surface area ratios (TSAR) of the immobilized cobalt porphyrin to the npb-SiO2-SH, and the catalytic cyclohexane oxidation reaction conditions were at the same time optimized via Response Surface Methodology (RSM). Compared with those obtained from traditional optimizing method (TOM), on average, RSM could enhance as high as more than 60% catalyst turnover frequency (TOF) and yields of cyclohexanone and cyclohexanol (KA oil). The anchored 0.05 mg Co TPyP could catalyze the oxidation of 200 mL of cyclohexane, under not using any solvents and additives, offering 2.5 × 106 1/h of TOF, and 19% of yields. The npb-SiO2-S (20%-0.0438)-Co TPyP catalyst showed better reusability, excellent catalytic

Optimal Design of Plant Canopy Based on Light Interception: A Case Study With Loquat.

Canopy architecture determines the light distribution and light interception in the canopy. Reasonable shaping and pruning can optimize tree structure; maximize the utilization of land, space and light energy; and lay the foundation for achieving early fruiting, high yield, health and longevity. Due to the complexity of loquat canopy architecture and the multi-year period of tree growth, the variables needed for experiments in canopy type training are hardly accessible through field measurements. In this paper, we concentrated on exploring the relationship between branching angle and light interception using a three-dimensional (3D) canopy model in loquat (Eriobotrya japonica Lindl). First, detailed 3D models of loquat trees were built by integrating branch and organ models. Second, the morphological models of different loquat trees were constructed by interactive editing. Third, the 3D individual-tree modeling software LSTree integrated with the OpenGL shadow technique, a radiosity model and a modified rectangular hyperbola model was used to calculate the silhouette to total area ratio, the distribution of photosynthetically active radiation within canopies and the net photosynthetic rate, respectively. Finally, the influence of loquat tree organ organization on the light interception of the trees was analyzed with different parameters. If the single branch angle between the level 2 scaffold branch and trunk is approximately 15° and the angles among the level 2 scaffold branches range from 60 to 90°, then a better light distribution can be obtained. The results showed that the branching angle has a significant impact on light interception, which is useful for grower manipulation of trees, e.g., shoot bending (scaffold branch angle). Based on this conclusion, a reasonable tree structure was selected for intercepting light. This quantitative simulation and analytical method provides a new digital and visual method that can aid in the design of tree architecture.

Concentration of FAD as a marker for cervical precancer detection.

.We report the ex vivo results of an in-house fabricated portable device based on polarized fluorescence measurements in the clinical environment. This device measures the polarized fluorescence and elastic scattering spectra with 405-nm laser and white light sources, respectively. The dominating fluorophore with 405-nm excitation is flavin adenine dinucleotide (FAD) with a fluorescence peak around 510 nm. The measured spectra are highly modulated by the interplay of scattering and absorption effects. Due to this, valuable information gets masked. To reduce these effects, intrinsic fluorescence was extracted by normalizing polarized fluorescence spectra with polarized elastic scattering spectra obtained. A number of fluorophores contribute to the fluorescence spectra and need to be decoupled to understand their roles in the progression of cancer. Nelder–Mead method has been utilized to fit the spectral profile with Gaussian to decouple the different bands of contributing fluorophores (FAD and porphyrin). The change in concentration of FAD during disease progression manifests in the change in ratio of total area to FWHM of its Gaussian profile. Receiver operating characteristic (ROC) curve analysis has been used to discriminate different grades of cervical precancer by using the ratio as input parameter. The sensitivity and specificity for discrimination of normal samples from CIN I (cervical intraepithelial neoplasia) are 75% and 54%, respectively. Further, the normal samples can be discriminated from CIN II samples with 100% and 82% sensitivity and specificity, respectively, and the CIN I from CIN II samples can also be discriminated with 100% sensitivity and 90% specificity, respectively. The results show that the change in the concentration of (FAD) can be used as a marker to discriminate the different grades of the cancer and biochemical changes at an early stage of the cancer can also be monitored with this technique.

Stereological examination of effects of ethanol on optic nerve in experimental alcohol model.

The objective of the present study was to perform histological and stereological examination of alcohol-induced changes in the optic nerve, considered an extension of white matter of the brain, in rats. This study included 20 male Wistar albino rats aged 60 days and weighing 190-220 g. The rats were divided into three groups: ethanol ( n = 7), maltodextrin ( n = 7), and control ( n = 6) groups. The ethanol group was administered ethanol at a dose of 6.4% (v/v) instead of water for 18 days; the maltodextrin group received maltodextrin for the same time period, and the control group was the sham group. At the end of the experiment, a 0.5-mm long section of the optic nerve starting from the optic chiasma was dissected and examined with routine microscopic histological examination methods. The modified Cavalieri method was used for stereological measurement. Total tissue area ratios were calculated with a point grid provided by the Shtereom 1.5 software package. The statistical comparison of the groups revealed that the ethanol group had a significant reduction in the number of axons and sheath area of the optic nerve compared to the control and maltodextrin groups ( p < 0.017, p < 0.022, respectively). These results indicate the toxic effects of ethanol on the optic nerve.

Functional traits of acquisitive invasive woody species differ from conservative invasive and native species

One of the most important sources of invasiveness is species’ functional traits and their variability. However there are still few studies on invasive tree species traits conducted along resource gradients that allow for a comparison of acquisitive and conservative strategies. We aimed to assess the differences in trait variation among native alien conservative and alien acquisitive tree species along resource availability gradients (soil fertility and light availability) and to assess the traits variability of the species studied along resources availability gradients. Our study compared invasive tree species in Europe (Prunusserotina Ehrh. Quercusrubra L. and Robiniapseudoacacia L.) with their native competitors (Acerpseudoplatanus L. A.platanoides L. Quercuspetraea (Matt.) Liebl. and Fagussylvatica L.). The study was conducted on 1329 seedlings and saplings collected in a system of 372 study plots in W Poland. For each individual we assessed leaf stem and root mass ratios total biomass leaf area ratio specific leaf area and projected leaf area. Two invasive species (P.serotina and R.pseudoacacia) represented a more acquisitive strategy than native species – along litter pH and light availability gradients these species had higher leaf mass fraction specific leaf area and leaf area ratio. In contrast Q.rubra had the highest total biomass and root mass fraction. Alien species usually had higher coefficients of variation of studied traits. This suggests that relatively high projected leaf area as a way of filling space and outcompeting native species may be reached in two ways – biomass allocation to leaves and control of leaf morphology or by overall growth rate. High variability of invasive species traits also suggests randomness in seedling survival which similarly to the neutral theory of invasion highlights the necessity of including randomness in modelling biological invasions.

Impact of left atrial box surface ratio on the recurrence after ablation for persistent atrial fibrillation.

BackgroundThe posterior wall of the left atrium (LA) is a well‐known substrate for atrial fibrillation (AF) maintenance. Isolation of the posterior wall between the pulmonary veins (box lesion) may improve ablation success. Box lesion surface area size varies depending on the individual anatomy. This retrospective study evaluates the influence of box lesion surface area as a ratio of total LA surface area (box surface ratio) on arrhythmia recurrence.MethodsSeventy consecutive patients with persistent AF (63 ± 11 years, 53 men) undergoing computed tomography (CT) imaging and ablation procedure consisting of a first box lesion were included in this study. Box lesion surface area was measured on electroanatomical maps and total LA surface area was derived from CT. Patients were followed with 24‐h electrocardiography and exercise tests at 3, 6, and 12 months after AF ablation. Arrhythmia recurrence was defined as any AF/atrial tachycardia (AT) beyond 3 months without antiarrhythmic drugs.ResultsDuring a median follow‐up of 13 (interquartile range = 10‐17) months, 42 (60%) patients had AF/AT recurrence. Multivariate Cox proportional regression analysis showed that a larger box surface ratio protected against recurrence (hazard ratio [HR] = 0.81; 95% confidence interval [CI] = 0.690‐0.955; P = 0.012). Left atrial volume index (HR = 1.01 [0.990‐1.024, P = 0.427] and a history of mitral valve surgery (HR = 2.90; 95% CI = 0.970‐8.693; P = 0.057) were not associated with AF recurrence in multivariate analysis.ConclusionA larger box lesion surface area as a ratio of total LA surface area is protective for AF/AT recurrence after ablation for persistent AF.

Rainfall and its possible hysteresis effect on the proportional cover of tropical tidal-wetland mangroves and saltmarsh–saltpans

Mangrove–saltmarsh tidal wetlands are highly dynamic ecosystems, responding and adapting to climate and physical conditions at all spatial and temporal scales. Knowledge of the large-scale ecosystem processes involved and how they might be influenced by climate variables is highly relevant today. For tidal-wetland sites well within the latitudinal range of the mostly tropical mangrove communities, we confirm that average annual rainfall influences vegetative cover, as well as species composition and biomass of tidal wetlands. On the basis of 205 largely unmodified, tropical and subtropical estuaries of northern Australia, a sigmoidal relationship, with a centroid inflection point ~1368mm, was derived between rainfall and the relative amounts of high-biomass mangroves and low-biomass saltmarsh–saltpan vegetation. The presence and probability of observed combinations of these community types were quantified using the wetland cover index, which is the ratio of total mangrove area to that of mangroves plus intertidal saltmarsh and saltpans. Accordingly, periodic changes in rainfall trends are likely manifest as either encroachment or dieback of mangroves along the ecotones separating them from tidal saltmarsh–saltpans. Presented is a new conceptual framework and model that describes how such ecosystem-scale processes take place in tropical and subtropical tidal wetlands.

Use of argyrophilic nucleolar–organizer region-associated protein synthesis in skeletal muscle cells for prediction of chronic carbon monoxide exposure

This study aims to evaluate possible effects of chronic carbon monoxide (CO) exposure on argyrophilic nucleolar–organizer region (AgNOR)-associated protein synthesis in striated muscle cells. Eighteen rats were randomly divided into three groups. Rats in group II and group III were given CO gas (1000 and 3000 ppm, respectively) for 30 min a day for 7 d. Mean AgNOR number per nucleus and ratio of total AgNOR area to nuclear area (TAA/NA) were determined. Both TAA/NA ratio and mean AgNOR number provided information about the existence or absence of exposure. TAA/NA ratio was also an indicator of the level of exposure.