Light Transmission Method Research Articles

Zone of flow: A new finding on the characteristics of airflow within the zone of influence during air sparging in aquifers

Air sparging (AS) is a popular technology for the in-situ remediation of groundwater contaminated by volatile organic compounds. The scope of the zone within which injected air exists, i.e., zone of influence (ZOI) and the airflow characteristics within ZOI are of great interest. However, few studies have shed light on the scope of the zone within which air flows, namely, the zone of flow (ZOF) and its relation with the scope of ZOI. This study focuses on the ZOF characteristics and its relation with ZOI based on quantitative observations of ZOF and ZOI using a quasi-2D transparent flow chamber. The relative transmission intensity obtained by the light transmission method presents a rapid and continuous increasing near the ZOI boundary, providing a criterion for the quantitative determination of ZOI. An integral airflow flux approach is proposed to determine the scope of ZOF based on the airflow flux distributions through aquifers. The ZOF radius decreases with the growth of particle sizes of aquifers; while it increases first and then keeps constant with the increase of sparging pressure. The ZOF radius is around 0.55– 0.82 times of the ZOI radius, which depends on air flow patterns related to particle diameters dp, that is, 0.55– 0.62 for channel flow (dp < 1– 2 mm), while 0.75– 0.82 for bubble flow (dp > 2– 3 mm). The experimental results show that the sparged air is entrapped with little flowing inside ZOI regions that are outside the ZOF, which should be considered carefully in the design of AS.

A new light transmission method to evaluate the through thickness fibre alignment in transparent resin

This work presents a new method to analyse vertical alignment of short fibres inside transparent resin layers using in situ measuring of light transmission through the layer. In this method, a light source is placed on one side of the composite layer and on the opposite side, a phototransistor measures the transmitted light intensity. A feature of the alignment process causes increased light transmission with increased fibre alignment. Using this technique, alignment of short nickel coated carbon fibres inside epoxy resin layers under magnetic field were evaluated and the effect of fibre content, field strength, fibre length and resin thickness on the alignment quality were characterised. An important finding is that the ratio of fibre length and resin thickness showcases a limit to the alignment degree. Finally, an analytical model is introduced which aims to predict average fibre angles based on the sample configuration, showcasing good agreement with experimental results.

Identification of internal cracks in corn seed using convolutional neural networks

The identification of seed quality is very important for which the quality of seed is crucial to the yield and quality of crops. There are two main problems with the acquisition and identification of cracks inside corn seed. One is that most of the methods of near-infrared spectroscopy or X-ray are used to obtain images of cracks inside the seed, the acquisition equipment is expensive and the operation is complicated. The other is the identification of crack images, and the traditional image processing method is usually used which requires professionals to design different model parameters each time, resulting in poor model robustness and low model accuracy. In this study, we originally proposed a simple but effective method to obtain the picture of corn seed internal cracks, which is combined with visible light transmission and ordinary camera acquisition method. We also proposed using the transfer learning methods not only solving the problem of the small scale of our corn seed internal cracks dataset but also avoiding extracting features manually. Our proposed method achieved a promising result, which is able to correctly identify the cracked and intact corn seed 100% in our training stage and testing stage.

High-Resolution Pore-Scale Water Content Measurement in a Translucent Soil Profile from Light Transmission

HighlightsResearch methods are needed to study preferential flow processes at pore scale and high temporal resolution.Novel verification of the light transmission method shows high efficiency to measure rapid transient soil water flow.Recast of a previous physical model allows reliable pore-scale water content quantification in translucent soil profiles.Insights from the light transmission method can inform preferential flow modeling efforts.Abstract. Understanding rapid transient flows in the soil unsaturated zone continues to be a major challenge in hydrology and water quality engineering. For example, surface runoff mitigation by riparian buffers can be limited by rapid transient flows due to the natural propensity of these areas for preferential flow pathways (i.e., caused by roots, wormholes, or wetting/drying cycles). However, current monitoring technologies are limited in their ability to capture rapid soil preferential flows at high spatial and temporal resolutions. Among the state-of-the-art technologies to monitor preferential flow, the light transmission method (LTM) has become a promising tool to quantify pore-scale water contents at a laboratory scale, but its reliability and consistency need further study. The objectives of this study are to recast a previously developed LTM physical model, propose a novel verification method to assess LTM reliability to measure pore-scale water dynamics in laboratory translucent soil profiles, and identify the representative pore radius of translucent soil profiles based on their average number of pores. This study found a high measuring efficiency with LTM for soil moisture and drainage estimations (NSE &amp;gt; 0.98, RMSE &amp;lt; 5.4%), showing its potential for use in laboratory analysis of pore-scale rapid transient water dynamics typically found in preferential flow through the vadose zone. This study also shows that the parameter traditionally associated with the number of pores in a translucent soil profile is a fitting parameter with no direct physical meaning. Keywords: Beer-Lambert law, Fresnel law, Light transmission method, Preferential flow, Riparian buffer, Vadose zone.

Visualization study on aniline-degrading bacteria AN-1 transport in the aquifer with the low-permeability lens

The geological conditions of the contaminated sites will affect the migration of microorganisms in the underground environment. In order to study the effect of low-permeability lens on bacterial transport, green fluorescent protein labeling combined with light transmission method was used to reveal the bacterial transport in the heterogeneous aquifer. The experiment has the advantages of real-time monitoring and no disturbance. The results showed that the bacteria gave priority to bypass the lens to flow away. The lens had a significant effect on hindering the bacterial transport due to adsorption and straining. The larger permeability coefficient ratio between the bulk media and the low-permeability lens was, the more obvious the obstruction was. AN-1 cannot enter the lens until the ratio decreased to the order of 102. With the increase of the flow velocity, the bacterial plume changed a lot. The higher flow velocity reduced the adsorption and retention of AN-1 to the media, resulting in some microorganisms remaining in the pores washed down. When the flow came to 2.0 m·d−1, AN-1 cannot adhere to the media due to the excessive fluid shear stress.

Laboratory investigation of free-phase stray gas migration in shallow aquifers using modified light transmission

Stray gas migration resulting from oil and gas operations can have negative impacts on shallow groundwater resources and the atmosphere. The movement and architecture of free-phase gas can have important implications on the expected effect of stray gas migration. For example, free-phase gas can become trapped in the subsurface and then dissolve, or gas flow can reach the surface. In this study, intermediate-scale laboratory experiments in quasi-two-dimensional flow cells employing a modified light transmission method were used to better understand free-phase gas migration under gravity-destabilized conditions. Quantification of both gas movement and saturation improves our understanding of the expected source architecture of stray gas. The results of this study show that gas flow became discontinuous away from the source and that gas saturations decreased immediately following the stoppage of a leak. The results of this study will lead to enhanced knowledge concerning mass transfer to groundwater both spatially and temporally.

The effect of deformability on the microscale flow behavior of red blood cell suspensions

Red blood cell (RBC) deformability is important for tissue perfusion and a key determinant of blood rheology. Diseases such as diabetes, sickle cell anemia, and malaria, as well as prolonged storage, may affect the mechanical properties of RBCs altering their hemodynamic behavior and leading to microvascular complications. However, the exact role of RBC deformability on microscale blood flow is not fully understood. In the present study, we extend our previous work on healthy RBC flows in bifurcating microchannels [Sherwood et al., “Viscosity and velocity distributions of aggregating and non-aggregating blood in a bifurcating microchannel,” Biomech. Model. Mechanobiol. 13, 259–273 (2014); Sherwood et al., “Spatial distributions of red blood cells significantly alter local hemodynamics,” PLoS One 9, e100473 (2014); and Kaliviotis et al., “Local viscosity distribution in bifurcating microfluidic blood flows,” Phys. Fluids 30, 030706 (2018)] to quantify the effects of impaired RBC deformability on the velocity and hematocrit distributions in microscale blood flows. Suspensions of healthy and glutaraldehyde hardened RBCs perfused through straight microchannels at various hematocrits and flow rates were imaged, and velocity and hematocrit distributions were determined simultaneously using micro-Particle Image Velocimetry and light transmission methods, respectively. At low feed hematocrits, hardened RBCs were more dispersed compared to healthy ones, consistent with decreased migration of stiffer cells. At high hematocrit, the loss of deformability was found to decrease the bluntness of velocity profiles, implying a reduction in shear thinning behavior. The hematocrit bluntness also decreased with hardening of the cells, implying an inversion of the correlation between velocity and hematocrit bluntness with loss of deformability. The study illustrates the complex interplay of various mechanisms affecting confined RBC suspension flows and the impact of both deformability and feed hematocrit on the resulting microstructure.

Quantitative dynamics of reversible platelet aggregation: mathematical modelling and experiments

Although reversible platelet aggregation observed in response to ADP stimulation in the presence of calcium is a well-known phenomenon, its mechanisms are not entirely clear. To study them, we developed a simple kinetic mass-action-law-based mathematical model to use it in combination with experiments. Light transmission platelet aggregometry (LTA) induced by ADP was performed for platelet-rich plasma or washed platelets using both conventional light transmission and aggregate size monitoring method based on optical density fluctuations. Parameter values of the model were determined by means of parameter estimation techniques implemented in COPASI software. The mathematical model was able to describe reversible platelet aggregation LTA curves without assuming changes in platelet aggregation parameters over time, but with the assumption that platelet can enter the aggregate only once. In the model, the mean size of platelet aggregates correlated with the solution transparency. This corresponded with flow cytometry analysis and with optical density fluctuations data on aggregate size. The predicted values of model parameters correlated with ADP concentration used in experiments. These data suggest that, at the start of the aggregation, when platelet integrins switch “on”, large unstable platelet aggregates are rapidly formed, which leads to an increase in light transmission. However, upon fragmentation of these aggregates, the probability of the post-aggregate platelets’ attachment to each other decreases preventing new aggregation and resulting in the reversible aggregation phenomenon.

Automated Machine Vision System for Liquid Particle Inspection of Pharmaceutical Injection

The particle matter inspection for pharmaceutical injection is inevitable in the field of pharmaceutical manufacturing, as it has the direct impact on the quality of the drugs. It is a challenge to inspect the contaminated injection online using an imaging system. This paper introduces a novel and effective inspection machine consisting of three modules, a mechanical system with 120 carousel grips, an image acquisition system with multihigh resolution cameras and a multilight sources station, and a distributed industrial electrical computer control system. Particle visual inspection machine first acquires image sequence using the high-speed image acquisition system. The image capture process at each camera module is alternately synchronized with different LED illumination techniques (light transmission method and light reflection method), enabling independent capture of particle images from the same container. Then, a set of novel algorithms for image registration and fast segmentation are proposed to minimize false rejections even in sensitive conditions, which enable the identification of all the tiny potential defects. Finally, a particle tracking and classification algorithm based on an adaptive local weighted-collaborative sparse model is also presented. The experiments demonstrate that the proposed inspection system can effectively detect the particles in the pharmaceutical infusion solution online, and achieve a performance rate of above 97% average accuracy.

Preferential flow systems amended with biogeochemical components: imaging of a two-dimensional study

Abstract. The vadose zone is a highly interactive heterogeneous system through which water enters the subsurface system by infiltration. This paper details the effects of simulated plant exudate and soil component solutions upon unstable flow patterns in a porous medium (ASTM silica sand; US Silica, Ottawa, IL, USA) through the use of two-dimensional tank light transmission method (LTM). The contact angle (θ) and surface tension (γ) of two simulated plant exudate solutions (i.e., oxalate and citrate) and two soil component solutions (i.e., tannic acid and Suwannee River natural organic matter, SRNOM) were analyzed to determine the liquid–gas and liquid–solid interface characteristics of each. To determine if the unstable flow formations were dependent on the type and concentration of the simulated plant exudates and soil components, the analysis of the effects of the simulated plant exudate and soil component solutions were compared to a control solution (Hoagland nutrient solution with 0.01 M NaCl). Fingering flow patterns, vertical and horizontal water saturation profiles, water saturation at the fingertips, finger dimensions and velocity, and number of fingers were obtained using the light transmission method. Significant differences in the interface properties indicated a decrease between the control and the plant exudate and soil component solutions tested; specifically, the control (θ= 64.5∘ and γ= 75.75 mN m−1) samples exhibited a higher contact angle and surface tension than the low concentration of citrate (θ= 52.6∘ and γ= 70.8 mN m−1). Wetting front instability and fingering flow phenomena were reported in all infiltration experiments. The results showed that the plant exudates and soil components influenced the soil infiltration as differences in finger geometries, velocities, and water saturation profiles were detected when compared to the control. Among the tested solutions and concentrations of soil components, the largest finger width (10.19 cm) was generated by the lowest tannic acid solution concentration (0.1 mg L−1), and the lowest finger width (6.00 cm) was induced by the highest SRNOM concentration (10 mg L−1). Similarly, for the plant exudate solutions, the largest finger width (8.36 cm) was generated by the lowest oxalate solution concentration (0.1 mg L−1), and the lowest finger width (6.63 cm) was induced by the lowest citrate concentration (0.1 mg L−1). The control solution produced fingers with average width of 8.30 cm. Additionally, the wettability of the medium for the citrate, oxalate, and SRNOM solutions increased with an increase in concentration. Our research demonstrates that the plant exudates and soil components which are biochemical compounds produced and released in soil are capable of influencing the process of infiltration in soils. The results of this research also indicate that soil wettability, expressed as (cos θ)1∕2, should be included in the scaling of the finger dimension, i.e., finger width, when using the Miller and Miller (1956) scaling theory for the scaling of flow in porous media.

Experimental study of the moisture distribution on the wetting front during drainage and imbibition in a 2D sand chamber

In the present study, the moisture distribution on the wetting front during drainage and imbibition in a 2D sand chamber is studied thoroughly. Based on the high-resolution data measured by light transmission method, the moisture distribution is observed and then analyzed quantitatively. During drainage and imbibition, different moisture distributions are observed: (a) during drainage, moisture contents fluctuate in a larger range and fingers can be seen on the wetting front; (b) while during imbibition, moisture contents fluctuate in a smaller range and the wetting front is more regular. The Hurst coefficients are successful in capturing different characteristics of the moisture distribution between drainage and imbibition. During imbibition, the Hurst coefficients are around 0.2 on the wetting front; while during drainage, the Hurst coefficients are around 0.5. As the porosity changes from 0.336 to 0.383, the moisture distribution in the sand chamber does not display obvious change. While as the imbibition rate increases from 5 ml/min to 400 ml/min, the moisture distribution on the wetting front becomes more uniform.

Evaluation of recombinant factor VIIa, tranexamic acid and desmopressin to reduce prasugrel-related bleeding: A randomised, placebo-controlled study in a rabbit model.

Prasugrel is a thienopyridine that inhibits platelet aggregation more rapidly and effectively than clopidogrel, with an increased bleeding risk. The current study aimed to evaluate the efficacy of three nonspecific haemostatic drugs - recombinant activated factor VII (rFVIIa), tranexamic acid and desmopressin (DDAVP) - to limit blood loss after administration of prasugrel in a rabbit model of bleeding while also evaluating any prothrombotic effects. Randomised, placebo-controlled study. Faculty of Medicine, University of Geneva, Switzerland, in 2013. Anaesthetised and artificially ventilated rabbits (n=56). Animals were randomly allocated to one of five groups: control (placebo-placebo), prasugrel-placebo, rFVIIa (prasugrel-rFVIIa 150 μg kg), tranexamic acid (prasugrel-tranexamic acid 20 mg kg) or DDAVP (prasugrel-DDAVP 1 μg kg). Two hours after an oral prasugrel loading dose (4 mg kg), a stenosis and an injury were inflicted on the carotid artery to induce cyclic flow reductions (CFRs) due to thrombosis. Haemostatic drugs were administered during the ensuing observation period. Standardised hepatosplenic sections were performed to evaluate the primary endpoint of blood loss, monitored for 15 min. Ear-immersion bleeding time and incidence of CFRs were secondary endpoints. Prasugrel decreased ADP-induced platelet aggregation (light transmission method) from 66 ± 4% (mean ± SD) to 41 ± 7% (P < 0.001) and doubled blood loss: 10.7 g (10.1 to12.7) [median (interquartile range)] vs. 20.0 g (17.0 to 24.4), P = 0.003 in the control and prasugrel-placebo groups, respectively. rFVIIa, tranexamic acid and DDAVP reduced neither hepatosplenic blood loss [19.7 g (14.0 to 27.6), 25.2 g (22.6 to 28.7) and 22.9 g (16.8 to 28.8), respectively] nor bleeding time compared with placebo. Regarding safety, rVIIa induced three or more CFRs in 5/12 rabbits, vs. 0/12 in the prasugrel-placebo group (P = 0.037), whereas tranexamic acid and DDAVP did not increase them. The three studied haemostatic drugs rFVIIa, tranexamic acid and DDAVP failed to reduce prasugrel-related bleeding in this model. rFVIIa-treated rabbits were more prone to arterial thrombotic events. NA.

Light transmission method to explore the migration and distribution of Cr(VI) in a sandy aquifer

The migration and distribution of contaminants in heterogeneous aquifers are mostly investigated through numerical simulations. They are rarely examined through experimental simulations because of sampling difficulties. In this study, we used the light transmission method (LTM) to explore the migration and distribution of hexavalent chromium [Cr(VI)] in homogeneous sandy aquifers with or without a low-permeability bottom and lens (heterogeneous aquifer). Experimental phenomena were observed via images obtained with a high-power light source. The migration distances of pollution plume were also monitored. Under heterogeneous conditions, low-permeability aquifer materials considerably inhibited the migration of Cr(VI) and altered the Cr(VI) migration rate of horizontal and vertical plumes spread to a certain extent. Common horizontal and vertical migration curve equations in all three conditions were also obtained through distance–time curve fitting. The difference between high- and low-concentration zones was accurately revealed, and the experimental phenomenon was further explained. The proposed method could be used for the qualitative investigation and visualization of the migration and distribution of Cr(VI).

LED array light source illuminance distribution and photoelectric detection performance analysis in dust concentration testing system

To improve the reliability of the measurement results of dust concentration and increase the testing range of dust concentration, this paper presents a new light transmission method to measure atmospheric dust concentration. Based on the principles of dust concentration test system, the study focuses on LED array light source illuminance distribution and photoelectric detection performance; analyzes the illumination distribution characteristics and uniformity of the single LED; establishes the illumination distribution calculation model of the array LED uniform light source; deduces a new detection sensitivity and SNR calculation function on dust concentration test system, and research the relationship between dust concentration and sensitivity, SNR and the array LED uniform light source. Through calculation and analysis, the results show that the better the uniformity of the single LED light source, the better the performance of the array LED light source, and the higher the sensitivity of dust concentration test system and the better the test results; By collecting the illuminance of array LED uniform light source in different positions, the illuminance distribution was obtained, the results verifies the established uniform array LED light source model is reasonable and feasible in the dust concentration test system.

Preferential flow in the vadose zone and interface dynamics: Impact of microbial exudates

In the hydrological cycle, the infiltration process is a critical component in the distribution of water into the soil and in the groundwater system. The nonlinear dynamics of the soil infiltration process yield preferential flow which affects the water distribution in soil. Preferential flow is influenced by the interactions between water, soil, plants, and microorganisms. Although the relationship among the plant roots, their rhizodeposits and water transport in soil has been the subject of extensive study, the effect of microbial exudates has been studied in only a few cases. Here the authors investigated the influence of two artificial microbial exudates–catechol and riboflavin–on the infiltration process, particularly unstable fingered flow, one form of preferential flow. Flow experiments investigating the effects of types and concentrations of microbial exudates on unstable fingered flow were conducted in a two-dimensional tank that was filled with ASTM C778 graded silica sand. The light transmission method (LTM) which is based on capturing the light intensity transmitted through a sand-water system and then converting it into degree of water saturation was used to visualize and characterize the flow of water in porous media as well as to image and measure the spatial and temporal distribution of water in porous media. Flow patterns, vertical and horizontal profiles of the degree of water saturation of the fingers, as well as measurements of the fingers dimension (width), number, and velocity were determined using the light transmission method. Interfacial experiments exploring the influence of microbial exudates on the wettability behavior of water were performed by measuring the contact angle and the interfacial tension of the (solid)-gas-microbial exudate solution systems. Unstable wetting front generating fingered flow was observed in all infiltration experiments. The experimental results showed that the microbial exudate addition affected the infiltration process, as the measurements of the degree of saturation profiles and widths of the fingers differed from those of the control NaCl solution. These differences may be due to an improved water holding capacity in the presence of the microbial exudates. The lowest catechol solution concentration (10 μM) produced the largest finger width (9.69 cm) among the tested catechol solution concentrations and all the other solutions including the control solution (7.24 cm). Moreover, the wettability of the medium for the catechol solution increased with an increase in concentration. The highest riboflavin solution concentration (1000 μM) generated the highest finger width (7.75 cm) among the tested riboflavin solution concentrations. However, the wettability of the medium for the riboflavin solution decreased with an increase in concentration. Our study demonstrated that the microbial exudates which are biochemical compounds produced and released by microbes in the environment are capable of influencing the soil infiltration process. The results of this study also demonstrated that the influence of the contact angle expressed as (cosθ)1/2 should be integrated in the scaling of the finger dimension, i.e., finger width, when the Miller and Miller (1956) scaling theory is applied for the hydrodynamic scaling in porous media.

Effects of methanol and formic acid on human platelet aggregation

BackgroundAlthough ethanol is known to inhibit platelet aggregation, the effects of another variant of alcohol, methanol, have not been reported. The purpose of this study was to determine whether methanol and its metabolite, formic acid, affect Ca2+ entry into and subsequent aggregation of platelets in vitro.MethodsCa2+ entry into and aggregation of human platelets were measured by spectrofluorometry using Fura-2/AM as an indicator and the light transmission method, respectively.ResultsThrombin-induced platelet aggregation was significantly augmented by methanol at pharmacological concentrations (0.5–2%) in a concentration-dependent manner. Methanol at 2% significantly attenuated thapsigargin-induced platelet aggregation, which was not significantly affected by lower concentrations (0.5 and 1%) of methanol. Methanol (0.5–2%) did not significantly affect platelet aggregation induced by 1-oleoyl-2-acetyl-sn-glycerol (OAG), or Ca2+ entry into platelets induced by thrombin, thapsigargin, or OAG. Platelet aggregation induced by thrombin, thapsigargin, or OAG was significantly inhibited by formic acid at toxic concentrations (0.01% or higher). Ca2+ entry into platelets induced by thrombin or thapsigargin was also significantly inhibited by formic acid at 0.01% or higher, while that induced by OAG was not affected by formic acid at 0.005 and 0.01% and augmented by that at 0.02%.ConclusionsMethanol at pharmacological doses has diverse effects on platelet aggregation, depending on the aggregation stimuli, without affecting Ca2+ entry into platelets. Formic acid at toxic concentrations has an inhibitory action on platelets aggregation, which was partly explained by the reduction of Ca2+ entry into platelets.

Effect of pressure of the onset of asphaltene precipitation during gas flooding

ABSTRACTIn order to prevent and eliminate the asphaltene precipitation during gas flooding, the rules of the changes of the pressure under different conditions are systematically studied by the laser solid detection system, the light transmission method, and the P–T phase diagram when the asphaltene precipitation occurs. When the pressure is reducing to a certain value, the penetrating light intensity of the crude oil is markedly decreased, which shows that the pressure at this point is the pressure of the onset of asphaltene precipitation (AOPP). The AOPP value decreases with an increase in the temperature. During gas flooding, the AOPP value increases with an increase in the content of gas in the crude oil, and these two nearly do have a linear relationship. According to the P–T phase behaviors of the gas–crude oil system, with an increase in the content of gas in the crude oil, the asphaltene precipitation envelope curve (APE) is gradually moved up, which shows that the possibility of asphaltene precipitation is much higher. During oil production, for the oil reservoirs with rich asphaltene, the production pressure drop should be kept a small value to ensure that the flowing bottom-hole pressure is higher than AOPP and it is necessary to help complement producing energy timely by using water injection, gas injection, etc. Besides, according to the intersection of T–P curve and APE curve in the P–T phase diagram, the location where the asphaltene precipitation occurs in the wellbore can be roughly predicted. The experimental results can provide the theoretical foundation for taking measures to prevent and eliminate the asphaltene precipitation.

Stomatal Closure, Basal Leaf Embolism, and Shedding Protect the Hydraulic Integrity of Grape Stems.

The time scale of stomatal closure and xylem cavitation during plant dehydration, as well as the fate of embolized organs, are under debate, largely due to methodological limitations in the evaluation of embolism. While some argue that complete stomatal closure precedes the occurrence of embolism, others believe that the two are contemporaneous processes that are accompanied by daily xylem refilling. Here, we utilize an optical light transmission method to continuously monitor xylem cavitation in leaves of dehydrating grapevine (Vitis vinifera) in concert with stomatal conductance and stem and petiole hydraulic measurements. Magnetic resonance imaging was used to continuously monitor xylem cavitation and flow rates in the stem of an intact vine during 10 d of dehydration. The results showed that complete stomatal closure preceded the appearance of embolism in the leaves and the stem by several days. Basal leaves were more vulnerable to xylem embolism than apical leaves and, once embolized, were shed, thereby preventing further water loss and protecting the hydraulic integrity of younger leaves and the stem. As a result, embolism in the stem was minimal even when drought led to complete leaf shedding. These findings suggest that grapevine avoids xylem embolism rather than tolerates it.

Experimental investigation on damage evolution in cross-ply laminates subjected to quasi-static and fatigue loading

Abstract In this paper an experimental investigation on damage evolution in cross-ply glass fiber reinforced plastic (GFRP) laminates under quasi-static and fatigue loading is presented. Four configurations of lay-up ([0 2 /90 4 ] s , [0 2 /90 2 ] s , [0/90 4 ] s and [0/90 3 /0/90 3 ] s ) with different thicknesses of cracking plies were selected to study the in-situ behavior in the damage initiation, evolution and saturation. Combined with the imaging features of different damages and the characteristic of damage evolution in the laminates, light transmission method was employed to observe the damage state and to record matrix crack density. In fatigue tests, eight stress levels were chosen for each configuration of laminates, including four lower stress levels below the stress level corresponding to the first transverse crack initiation. A conclusion was drawn from the comparison of the results that the fatigue loading with lower stress level accelerates the process of damage evolution and generates damages more thoroughly at failure.

Visualization method for radiographic films through silver intensity mapping using X‐ray fluorescence

Radiographic films have a large range of applications. In many of these applications, the behavior of characteristic curves is very important for assessing the image quality and radiography setup. Radiographic film digitization and visualization are always performed by light transmission, and the characteristic curve is known as a behavior of optical density as a function of the radiation exposure. Because optical density is a function of metallic silver generated by chemical development in silver halides, when an image is visualized by light transmission, a silver amount map is indirectly seen. However, this measurement is limited by the optical instrument, and a very weak light signal cannot be distinguished from background light or background noise. In this way, highly exposed films can contain areas with different silver concentrations, but this cannot be seen because the optical density measurement is limited. One of the ways through which it is possible to overcome such limitation is to use a different method for ascertaining the quantity of silver remaining on the developed films, and one of the quantitative techniques that suit this purpose is X‐ray fluorescence (XRF). The purpose of this paper is applying μ‐XRF so as to obtain a point‐by‐point silver intensity map to detect objects with low optical contrast on conventional radiographic films. The results of this work have shown a higher linear range in measurement using XRF, and as consequence, small objects and details in low‐contrast or overexposed radiographic images could be visualized by the silver mapping technique, and the same results could not be achieved using light transmission methods. A first approach about spatial resolution and contrast was made showing strong and weak points of this way to scan radiographic films. Copyright © 2017 John Wiley &amp; Sons, Ltd.