High To Low Research Articles

Micro-Scale Numerical Simulation of Fatigue Failure for CFRP Subjected to Multiple-Amplitude Cyclic Loadings Based on Entropy Damage Criterion.

Fatigue failure of carbon fiber-reinforced plastics (CFRPs) under cyclic loadings has attracted the attention of researchers recently. In this study, the entropy-based failure criterion is proposed to investigate the fatigue lifetime of unidirectional CFRPs subjected to multiple-amplitude cyclic loadings. Due to the heterogeneity of CFRPs, a micro-finite element model considering matrix resin and fibers independently is developed, and the entropy-based damage criterion is implemented into a user-subroutine of Abaqus to model the progressive damage of matrix resin. The fatigue lifetime of CFRPs under typical loading sequences consisting of two stages, such as varying from low to high (L-H) or from high to low (H-L) loading sequence, is estimated with the proposed failure criterion. Numerical results show that the initial damage occurs near the area between two fibers, and a transverse crack propagates progressively under the cyclic loading. The difference in predicted lifetime to final failure in L-H and H-L stress levels is 6.3%. Thus, the effect of loading sequence on the fatigue lifetime can be revealed via the proposed entropy-based damage criterion. Comparisons with the conventional linear cumulative damage (LCD) and kinetic crack growth (KCG) theories are also conducted to demonstrate the validity of the proposed method. The entropy-based failure criterion is a promising method to predict the residual strength and fatigue lifetime of CFRP components.

Variable-amplitude fatigue behavior of M30 high-strength bolts in end-plate connection joints

High-strength bolts are widely used in connection joints for steel structures. In this paper, the variable-amplitude fatigue behavior of M30 high-strength bolts in end-plate joints is studied. Variable-amplitude fatigue tests were carried out on 19 M30 high-strength bolts using an Amsler pulse fatigue tester. Four cyclic stress amplitude loading modes, including Low to High (L-H), High to Low (H-L), Low to High to Low (L-H-L), and High to Low to High (H-L-H), were applied to the test specimens. In addition, the variable-amplitude fatigue life of M30 high-strength bolts was studied using two forms of cumulative damage models. The stress - fatigue life (S-N) curve was plotted using the equivalent stress amplitude. The obtained S-N curve was compared with the existing bolt fatigue S-N curve and the current specifications. Finally, fatigue fracture was analyzed from macro and micro perspectives. It was found that for most specimens, fatigue fracture occurs at the first joint thread between the bolt and nut, while for a few bolts, fatigue fracture occurs at the joint between the bolt head and bolt. With a fatigue life of 2 million cycles as the threshold, the fatigue limit is 107.5 MPa, which is 2.67 times higher than that specified by ANSI/AISC 360 – 16. Additionally, the fatigue properties of high-strength bolts in end-plate connections are better than those in bolted sphere joints at higher stress levels. At low stress levels, the contact pressure formed by the extrusion of the end-plate reduces the fatigue life of the bolts. Furthermore, unlike the constant-amplitude fatigue fracture, the variable-amplitude fatigue fracture has an obvious load change boundary line.

The power dependence of the maximum achievable H-mode and (disruptive) L-mode separatrix density in ASDEX Upgrade

In future fusion reactors disruptions must be avoided at all costs. Disruptions due to the density limit (DL) are typically described by the power-independent Greenwald scaling. Recently, a power dependence of the disruptive DL was predicted by several authors (Zanca et al 2019 Nucl. Fusion 59 126011; Giacomin et al 2022 Phys. Rev. Lett. 128 185003; Singh and Diamond 2022 Plasma Phys. Control. Fusion 64 084004; Stroth et al 2022 Nucl. Fusion 62 076008; Brown and Goldston 2021 Nucl. Mater. Energy 27 101002). It is investigated whether this increases the operational range of the tokamak. Increasing the heating power in the L-mode can induce an L-H transition, and therefore a power-dependent DL and the L-H transition cannot be considered independently. The different models are tested on a data base for separatrix parameters at the separatrix of ASDEX Upgrade and compared with the concept (SepOS) presented in Eich and Manz (2021 Nucl. Fusion 61 086017). The disruptive separatrix density scales with the power in good agreement to all models. Also the back transition from high to low (H-L) confinement shows an approximately Greenwald scaling with an additional power dependence according to the SepOS concept. For future devices operating at much higher heating power such a power scaling may allow operation at much higher separatrix densities than are common in H-mode operation. Preconditions to extrapolation for future devices are discussed.

The risk of acute and early HIV (AEH) infection among MSM with different behaviour trajectories: an open cohort study in Tianjin, China, 2011–2019

BackgroundAcute and early HIV (AEH) infection is characterized by a high viral load and infectivity. Approximately 50% of cases of HIV-1 transmission occur during AEH. Understanding sexual behaviour trajectories would be useful for predicting changes in the risk of HIV acquisition. However, few studies have investigated sexual behaviour trajectories and their association with AEH acquisition. This study identified behaviour trajectories among men who have sex with men (MSM), determined the risk of AEH infection, and compared risk factors between different behaviour trajectories.MethodsThe study was based on an ongoing prospective open cohort of voluntary HIV counselling and testing (VHCT) among MSM in Tianjin, China. From 2011 to 2019, 1974 MSM were recruited. Group-based trajectory modelling (GBTM) was used to identify behaviour trajectories by constructing a sexual risk behaviour score. Logistic regression and generalized estimating equation (GEE) were used to compare the risk of AEH infection and risk factors for different behaviour trajectories. All data analyses were performed using SAS 9.4.ResultsThe incidence of AEH infection was 1.76/100 person-years, with 64 AEH infections documented in 3633 person-years of follow-up. Three sexual behaviour trajectories were identified: CL (consistently low risk, 35.46%), CH (consistently high risk, 42.71%) and HTL (high to low risk, 21.83%). MSM in the HTL and CH groups had higher AEH infection rates than MSM in the CL group (6.73%, 3.08% and 1.28%, respectively), with ORs of 5.54 (2.60, 11.82) and 2.44 (1.14, 5.25), respectively. MSM aged 30–50 years old and MSM who underwent HIV testing in the last year were more likely to be in the CH group and HTL group. In addition, the HTL group was characterized by a lower likelihood of local registration and a higher likelihood of working as a MSW.ConclusionMSM in the CH group and the HTL group had a higher risk of AEH infection. In the future, VHCT should be performed more often among younger MSM, and HIV counselling should be given the same priority as HIV testing. In addition, VHCT combined with PrEP may have a better preventive impact on MSM with a high risk of AEH infection.

Abstract TMP105: Time Varying Depression And Incident Stroke In Geographic And Racial Diverse Population

Introduction: Depression is a risk factor for stroke; however, the impact of changes in the level of depressive symptoms on the risk of incident stroke is less well described. Methods: The study included participants from REGARDS, a national longitudinal cohort study of 30,239 Black and White adults aged ≥ 45 years at baseline 2003-2007. Depressive symptoms were assessed longitudinally using the 4-item Center for Epidemiologic Studies Depression Scales (CES-D-4), and scores of 4+ were categorized as “high.” Over up to 18 years of follow-up, for each participant with each serial assessment, we categorized the transition in depression as moving from low to low (LL), low to high (LH), high to low (HL), and high to high (HH), and used Cox regression to assess stroke risk subsequent to the transition, with incremental adjustment for risk factors. Results: Among 20,691 participants, we observed over 80,447 transitions in depressive symptom level and 832 incident strokes. Participants in the HH group had a higher risk for stroke compared to the LL group in both unadjusted {[HR] = 1.46, 95% confidence interval (CI) = 1.08–1.97}, and adjusted models, regardless of adjustment for demographics [HR] = 1.63, (CI = 1.21–2.20), plus SES [HR] = 1.50, (CI = 1.11–2.03), and stroke risk factors [HR] = 1.38, (CI = 1.01–1.90). However, full adjustment attenuated the effect. In both unadjusted and adjusted models, participants in the LH group were at marginally higher risk than LL and those in the HL group had a low risk like that of the LL group (see Table). Conclusion: Transition in levels of depression symptoms directly impacts the risk for stroke. Screening and intervention delivery for depressive symptoms may consider the level of symptoms as a dynamic process.

Persistent eosinophilia and associated organ involvement in Thai patients with systemic sclerosis: Data from the Siriraj scleroderma cohort.

Objectives This study aims to investigate the prevalence of persistent eosinophilia and associated organ complications in Thai patients with systemic sclerosis (SSc).Patients and methods This post-hoc study included 107 adult patients (23 males, 84 females; mean age: 50.4±11.6 years; range, 18 to 79 years) diagnosed with SSc between November 2013 and June 2017. Eosinophilia was defined as an absolute eosinophil count of >500/μL or a percentage count of >7%. Eosinophil levels collected at every visit over one year were categorized as persistently high (PH), persistently low (PL), high-to-low (HL), low-to-high (LH), or variable levels (VL). The study compared variables between PH and non-PH (PL+HL+LH+VL) groups. The patients with baseline eosinophilia were also identified and compared with the non-eosinophilia group.Results The median disease duration was 3.2 years. Of the patients, 79.4% had diffuse cutaneous SSc and 76.7% had anti-Scl-70 positivity. A total of 11.2%, 66.4%, 1.9%, 8.4%, and 12.1% of the patients were categorized into the PH, PL, HL, LH, and VL groups, respectively. Compared to non-PH groups, the PH group had a higher prevalence of anti-centromere antibody (ACA), higher baseline percent predicted total lung capacity, and lower baseline C-reactive protein and creatine phosphokinase (p<0.05 for all). The ACA positivity (odds ratio [OR]: 18.5; 95% confidence interval [CI]: 1.64-208.46) was associated with PH. The patients with baseline eosinophilia (17.8%) had a higher prevalence of non-specific interstitial pneumonia with periodic eosinophilia at the time of diagnosis (100% vs. 6.5%, p<0.0001; OR: 4.667; 95% CI: 1.712-12.724).Conclusion The PH was seldom (11%) in patients with SSc compared to periodic eosinophilia, which was more prevalent (18%). It may be related to ACA positivity and better pulmonary outcomes, whereas periodic eosinophilia may involve interstitial lung disease.

PO-279 Bidirectional Associations Between Physical Activity and Adiposity From Childhood to Early Adulthood

Objective Inverse association between physical activity and adiposity in children and adolescents have been documented in numerous studies. However, few studies have examined the direction of causation between these two variables. We aimed to examine the prospective bidirectional associations between physical activity and adiposity from childhood to early adulthood.&#x0D; Methods A total of 396 girls (mean age, 11.2 years at baseline) participated in a longitudinal study with 1, 2, 4, and 7 year follow-ups. Body height and weight were measured, body composition was assessed by DXA and BMI and fat mass index (FMI) were calculated. Leisure-time physical activity (LTPA) and physical inactivity was obtained from questionnaire and physical activity score and inactivity time was calculated. A bivariate cross-lagged panel model was used to estimate the bidirectional associations between physical activity and measures of adiposity across follow-up waves.&#x0D; We further examined whether persistently high or persistently low physical activity or change of physical activity level from low to high and high to low during pubertal years had differential effects on adiposity. For this, the study participants were first divided into two groups according to the median values of their LTPA scores at baseline and at the 7 year follow-up visit. Then four activity groups were formed: consistently high (CH), consistently low (CL), change from high to low (HL), and change from low to high (LH). Analysis of variance (ANOVA) with least significant difference post hoc test was used to compare differences in adiposity between the LTPA groups.&#x0D; Results BMI at each measurement wave strongly predicted subsequent BMI (standardized path coefficients ranged from 0.87 to 0.95, p &lt; 0.001 for all). Similar pattern was observed for LTPA and physical inactivity, though the path coefficients tended to be notably smaller. This auto-regressive part of the model indicates that the temporal stability of BMI from childhood to early adulthood is higher than the temporal stability of LTPA or physical inactivity over the same time period.&#x0D; The cross-lagged effects indicated that higher BMI at baseline and at 4-year follow-up predicted lower LTPA at 2-year and 7-year follow-ups, respectively (p&lt;0.05 for both), but LTPA did not predict subsequent BMI at any time point. Similarly, higher FMI at baseline and at 2-year follow-up predicted lower LTPA at subsequent follow-up waves (p&lt;0.05 for both). No associations were found between sedentary time and adiposity between any time points.&#x0D; The difference in participation in LTPA between consistently high and consistently low PA groups were on average 4 hours per week (p&lt;0.001); however, no significant difference in FMI was found at baseline, 2-year or 7-year follow-up). Similarly, no significant difference in FMI was found between the groups whose LTPA level changed from high to low or from low to high. &#x0D; Conclusions Our results suggest that reduced physical activity in children and adolescents is the result of increased fatness rather than its cause. Current physical activity recommendations may not be sufficient to combat pediatric obesity.

Perceptual and prefrontal cortex haemodynamic responses to high-intensity interval exercise with decreasing and increasing work-intensity in adolescents.

Affect experienced during high-intensity interval exercise (HIIE) is dependent on work-intensity, but the influence of increasing (low-to-high (L-H)) or decreasing (high-to-low (H-L)) work-intensity during HIIE remains unclear in adolescents. The role of prefrontal cortex haemodynamics in mediating changes in affect during HIIE also remains unexplored in adolescents. We examined affect, enjoyment and cerebral haemodynamic responses to HIIE with increasing or decreasing work intensities in adolescents. Participants (N = 16; 8 boys; age 12.5 ± 0.8 years) performed, on separate days, HIIE cycling consisting of 8 × 1-min work-intervals at 100%-to-70% (HIIEH-L), 70%-to-100% (HIIEL-H) or 85% (HIIECON) peak power separated by 75 s recovery. Affect, enjoyment and cerebral haemodynamics (oxygenation (∆O2Hb), deoxygenation (∆HHb) and tissue oxygenation index (TOI)) were recorded before, during, and after all conditions. Affect and enjoyment were lower during HIIEH-L compared to HIIEL-H and HIIECON at work-intervals 1 to 3 (all P < 0.043, ES > 0.83) but were greater during HIIEH-L than HIIEL-H and HIIECON at work-interval 8 (all P < 0.048, ES > 0.83). ∆O2Hb was similar across conditions (P = 0.87) but TOI and ∆HHb were significantly greater and lower, respectively during HIIEH-L compared to HIIEL-H and HIIECON at work-interval 8 (all P < 0.039, ES > 0.40). Affect was correlated with TOI (all r > 0.92) and ∆HHb (all r > -0.73) across conditions. HIIEH-L offers advancement to the HIIECON and HIIEL-H which bring significant greater affect and enjoyment towards the end HIIE work-interval, implicating the feasibility and adoption of this protocol for health promotion in youth. Also, changes in prefrontal cortex haemodynamics are associated with the affect during HIIE.

Melding a High-Risk Patient for Continuous Flow Left Ventricular Assist Device into a Low-Risk Patient.

The model for end-stage liver disease (MELD) has been used as a predictor of mortality after left ventricular assist device (LVAD) placement. However, improvement or worsening of MELD and how those changes affect outcomes is unknown. We performed a retrospective analysis of 244 patients implanted with a continuous flow (CF) LVAD. Patients were dichotomized at admission into low- or high-risk categories using a cutoff of MELD ≥ 19, and they were reclassified at day of implant forming four groups: Group LL (low to low, remained low risk), LH (low to high, worsened to high risk), HH (high to high, remained high risk), and HL (high to low, improved to low risk). Patients who improved to a low risk (group HL) had the same 1 year survival as those that remained low risk (group LL; 80% vs. 77%; p = 0.6). However, patients who were initially classified as low risk and worsened to a high risk (group LH) had a survival that was worse than those that were consistently high risk (group HH; 55% vs. 10%; p = 0.01). Model for end-stage liver disease reclassification after adjusting for commonly attributed risk factors remained an independent predictor for mortality, including patients classified as Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) 1 and 2. In conclusion, our MELD score reclassification is an independent and powerful predictor of mortality in patients undergoing LVAD implantation.

Effects of Singular-Vector-Type Initial Errors on the Short-Range Prediction of Kuroshio Extension Transition Processes

AbstractThe effects of optimal initial error on the short-range prediction of transition processes between the Kuroshio Extension (KE) bimodalities are analyzed using a reduced-gravity shallow-water model and the singular vector (SV) approach. Emphasis is placed on the spatial structures, growing processes, and effects of the SVs. The results show that the large values of the SVs are mainly located in the first crest region of the KE (around 35°N, 144°E) and in the Kuroshio large meander (KLM) region south of Japan (around 32°N, 139.5°E). The fast growths of the SVs have important impacts on the prediction of transition of the KE bimodality. The initial error with +SV pattern (with positive anomalies in the first crest region of the KE and negative anomalies in the KLM region) tends to strengthen the KE and shift it toward the high-energy state, while the error with −SV pattern is prone to weaken the KE and shift it toward the low-energy state. In addition, the SV-type initial errors grow more quickly in the transition phase of the KE from the high-energy to the low-energy state than in the opposite transition phase. A perturbation energy analysis illustrates that different physical processes are responsible for the error growth in the KE region for different transition phases of the KE; barotropic instability plays a dominant role in the error growth in the low-to-high (LH) energy phase, while the error evolution in the high-to-low (HL) energy phase is mainly caused by advection processes.

Image Pattern Extraction and Compression using Pixel Neighborhood and Weighted PCA Algorithm

Background/ Objective: An image can be compressed by compressing the patterns in itself. The patterns preserve the maximum entropy in an image. If patterns are extracted using the pattern extraction algorithm and compressed using their features, then rest of the image may be compressed to a high degree of decompression. The patterns are therefore principal components of the image and principal component analysis can be applied over that in order to achieve an efficient compression algorithm. The principal component analysis algorithm works fine when compressing the input image and outputs a reasonably good compression ratio. However, the compression ratio becomes dependent upon the number of eigen values/vectors chosen to get compressed image. Method: In the presented work, a selection criterion for selecting the Eigen values/vectors is suggested. The criteria is based on threshold selection that is computed by using different techniques and then taking the arithmetic mean of all thresholds from all techniques. Also, a weighted Eigen values are used for threshold computation and compared with the statistical threshold. The Eigen values/vector less than the threshold are taken into consideration for image compression and a well optimized compression ratio is obtained. Finding: The computation time may be improved by decomposing the input image using haar wavelet transform. The different frequency sub bands consist of low frequency (LL), high to low (HL), low to high (LH) and high (HH) frequency sub bands. As the LL sub band contains maximum information out of the four bands, the principal component algorithm is applied in this band only for compression.

A simple amino acid dose–response method to quantify amino acid requirements of individual meal-fed pigs1

Two experiments were conducted to develop a simplified dose-response technique to estimate the Lys requirement of individual, meal-fed growing pigs. In Exp. 1, we studied adaptation processes that occur during such a dose-response study in meal-fed pigs, and in Exp. 2, we studied the accuracy of this simplified technique to estimate changes in Lys requirement estimates of pigs following changes in energy intake. In Exp. 1, the effect of the Lys supply strategy on the Lys requirement was assessed in 14 barrows fed an increasing [low to high (LH)] or decreasing [high to low (HL)] total Lys supply, with total Lys levels varying from 0.36 to 1.06 g/MJ DE in 7 equidistant steps of 4 d each. Urinary urea and ammonia excretion and whole body N turnover were measured. In Exp. 2, the accuracy of the dose-response technique to determine a shift in Lys requirement was assessed in 20 barrows fed at either 2.2 [low energy (LE)] or 2.7 [high energy (HE)] times the energy requirements for maintenance, with total Lys supply decreasing from 1.10 to 0.37 g Lys/MJ DE in 9 equidistant steps of 3 d each. In Exp. 1, a lower increment in protein synthesis, breakdown, and whole body N turnover with increasing dietary Lys supply was observed in LH pigs than HL pigs (P < 0.01) and the estimated Lys requirement was 0.06 g/MJ DE greater (P = 0.01) in LH pigs than HL pigs. These results indicated that pigs at a decreasing Lys supply strategy require less time for metabolic adaptation to a change in Lys supply than those at an increasing Lys supply. In Exp. 2, the estimated Lys requirement was 2.6 g/d greater (P < 0.001) in HE pigs than LE pigs. The variation in AA requirement estimates between individual pigs was low (4.9% in LH pigs and 3.0% in HL pigs in Exp. 1 and 8.1% in LE pigs and 6.0% in HE pigs in Exp. 2). The present studies indicated that a dose-response technique with a decreasing Lys supply in time and a step length of 3 d with urinary N excretion as response criteria provides a simple, accurate technique to quantitatively estimate a change in AA requirements of individual meal-fed pigs.

A System-Prototype Representing 3D Space via Alternative-Sensing for Visually Impaired Navigation

Offering an alternative mode of interaction with the surrounding 3-D space to the visually impaired for collision free navigation is a goal of great significance that includes several key challenges. In this paper, we study the alternative 3-D space sensation that is interpreted by our computer vision prototype system and transferred to the user via a vibration array. There are two main tasks for conducting such a study. The first task is to detect obstacles in close proximity, and motion patterns in image sequences, both important issues for a safe navigation in a 3-D dynamic space. To achieve this task, the images from the left and right cameras are acquired to produce new stereo images, followed by video stabilization as a preprocessing stage, a nonlinear spatio-temporal diffusion and kernel based density estimation method to assess the motion activity, and finally watershed-based detection of moving regions (or obstacles) of interest. The second task is to efficiently represent the information of the captured static and dynamic visual scenes as 3-D detectable patterns of vibrations applied on the human body to create a 3-D sensation of the space during navigation. To accomplish this task, considering the current limitations imposed by the technology, we create a high-to-low (H-L) image resolution representation scheme to facilitate the mapping onto a low-resolution 2-D array of vibrators. The H-L scheme uses pyramidal modeling to obtain low-resolution images of interest-preserving motion and obstacles-that are mapped onto a vibration array. These patterns are utilized to train and test the performance of the users in free space navigation. Thus, in this paper we study the synergy of these two important schemes to offer an alternative sensation of the 3-D space to the visually impaired via an array of vibrators. Particularly, the motion component is employed as an element for the identification of visual information of interest to be retained during the H-L transformation. The role of the array vibrators is to create a small-scale front representation of the space via various levels of vibrations. Thus, 3-D vibrations applied on the user's body (chest, abdomen) offer a 3-D sensation of the surrounding space and the motion in it. In addition, we present experimental results that indicate the efficiency of this navigation scheme in creating low-resolution 3-D views of the free navigation space and detecting obstacles and moving areas.

Investigation of the cause of the high-to-low mode confinement transition following multifaceted asymmetric radiation from edge formation in DIII-D

The common observation that the onset of a core MARFE (multifaceted asymmetric radiation from edge) is followed immediately by a H-L (high-to-low) confinement mode transition in DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] was investigated by comparing a theoretical prediction of the threshold nonradiative power across the separatrix needed to maintain H mode with an experimental determination of the nonradiative power flowing across the separatrix. It was found that in three shots with continuous gas fueling the increased neutral influx associated with the MARFE formation caused a sharp increase in the predicted threshold nonradiative power crossing the separatrix that was required for the plasma to remain in H mode to a value comparable to the experimental power crossing the separatrix.

Hemispheric specialization of human inferior temporal cortex during coarse-to-fine and fine-to-coarse analysis of natural visual scenes

Recent models of visual recognition have suggested that perceptual analysis may start with a parallel extraction of different spatial frequencies (SF), using a preferential coarse-to-fine (low-to-high SF) sequence of processing. A rapid extraction of low spatial frequency (LSF) information may thus provide an initial and crude parsing of the visual scene, subsequently refined by slow but more detailed high spatial frequency (HSF) information. However, the sequence of SF analysis could be flexible, a high-to-low (HtL) being sometimes preferred to a low-to-high (LtH) SF sequence depending on task demands. Furthermore, it has also been suggested that the right vs. left hemisphere might be differentially specialized in LSF vs. HSF analysis, respectively. By manipulating the temporal succession of LSF and HSF stimuli, the present fMRI study investigated whether such hemispheric specialization may underlie the flexible use of different time-course in SF analysis. Participants performed a matching task between two successive images of natural scenes (LSF or HSF) that were displayed either in an LtH (LSF scene presented first and HSF scene second) or in a reverse HtL sequence. A direct inter-hemispheric comparison of the neural responses evoked by each SF sequence revealed greater activations within the right occipito-temporal cortex for the LtH sequence and within the left occipito-temporal cortex for the HtL sequence. These fMRI results suggest that the hemisphere preferentially engaged during the sequential processing of different SF might be determined by the initial SF-band appearing in this sequence, and that both a coarse-to-fine and fine-to-coarse analysis might independently take place in the two hemispheres.

Thermodynamic optimization and constructal design

This special issue focuses for the first time on a new development in thermodynamic analysisand optimization: the constructal method and the universal process of the generation of energysystem configuration.Why is the generation of configuration important, and why focusing on it is new in science?We all learn that modern thermodynamics grew out of Sadi Carnot’s contemplation of thefunctioning of fire-driven engines. The first law and the second law allow us to analyse andpredict how a given heat engine will perform. This is powerful science; however, the world offlow systems (heat engines, animals, global circulation, etc.) shows that the performance of suchsystems increases in time. The first law and the second law are not enough.Performance increases because one flow configuration morphs into, or is replaced by a newconfiguration that performs better. This parade of better and better drawings is as much a partof physics as the conservation of energy (first law) and the fact that all things flow from high tolow (second law). The principle that accounts for this universal tendency of flow systems in timeis the constructal law, which was stated in 1996: for a finite-size flow system to persist in time (tolive) it must evolve in such a way that it provides easier access to its currents.The generation of flow configuration in accordance with the constructal law is constructaldesign. The thought that the self-organized and self-optimized flow structures of nature (animateand inanimate) can be reasoned based on the constructal law is constructaltheory. The generationof flow configuration belongs in thermodynamics, because starting with the fire-driven engine andending with geophysical flows and living systems, the generation of flow configuration completesthe deterministic edifice that until now rested on only two legs, the first law and the second law.Yildiz Technical University of Istanbul had the vision to organize the first school that taughtthis new, enlarged thermodynamics: The International Summer School of ThermodynamicOptimization and Constructal Design, 19–23 July 2004. Well-known professors were invited tolecture to an international audience of researchers from academia and industry. The lecturerswere Profs. A. Bejan, I. Dincer, Y. Gogus, A. Hepbasli, H. Heperkan, U. Kesgin, S. Lorente,S. Onbasioglu, A. Ozturk and E. Sciubba. This special issue puts on display the mostrepresentative lecture material presented at the summer school. We hope that this historicspecial issue will serve as a guide for future advances in thermodynamics and constructal design.Adrian BejanDuke University, Durham, NC, USAHasan HeperkanYildiz Technical University,Istanbul, TurkeyUgur KesginYildiz Technical University,Istanbul, Turkey

Jumps and bi-stabilities in electron energy distribution in Ar-N2post discharge plasma

The electron energy distribution function (EEDF) in an afterglow ofa pulsed direct current discharge has been measured in an Ar:N2mixture by means of a time-resolved Langmuir probe technique. The vibrationaltemperature, Tv, of N2 molecules has also been experimentallyestimated. The results show that a correlation between an effective electrontemperature, Te, and Tv strongly varies with experimental conditions. Inparticular the conditions exist under which the rapid decrease from high tolow Te values is observed at some moment after the discharge pulse, whilethe vibrational temperature remains almost constant.The theoretical study of the EEDF in Ar:N2 afterglow plasma hasalso been made by the numerical solution of an appropriate Boltzmann equationby taking into account electron-electron collisions as well as superelasticvibrational and superelastic electronic collisions. Calculations show that fora given Tv the value of Te depends on the electron concentration, ne.Moreover, the ranges of ne and Tv exist, where two different solutions ofBoltzmann equations can be obtained.Finally, the comparison of the theoretical and experimental results isperformed and an explanation of the experimentally observed phenomenon is given.

Radar chain study of the May, 1995 storm

We summarize the main features of the ionospheric F region as observed bythe Sondrestrom, Millstone Hill, Arecibo, and Jicamarca incoherent scatter radars during the 1–5May, 1995 CEDAR Storm Study interval. This paper apparently represents the first study of amajor storm interval using the current incoherent scatter radar chain supported by the U.S.National Science Foundation. We focus most attention on 2–3 May, and include additional datafrom IMP-8, the St. Johns magnetometer, SuperDARN, and global total electron content (TEC)maps from GPS. Three intervals of likely penetration of magnetospheric electric field from high tolow latitude are identified on 2 May. A unique feature of this storm are the strong daytimeequatorward wind surges in the neutral meridional wind observed at Millstone Hill. The first ofthese (at 14 UT on 2 May) is apparently due to a travelling atmospheric disturbance launched byintense frictional and Joule heating as observed at Sondrestrom. An evening enhancement in NmF 2 (the dusk effect) is typically seen only on the first day of a geomagneticstorm. However, during this storm a strong dusk effect is seen at Millstone Hill on 2, 3, and 4May, associated with the equatorward wind surges. A penetrating eastward electric field alsocontributed to the dusk effect on 2 May. A large rise in hmF 2 at Arecibo near0000 UT on 3 May is due to the same eastward electric field, which penetrates to the equator,causing a strong upward plasma drift at Jicamarca. This apparently results in a polewardexpansion of the equatorial anomaly zones as seen in GPS total electron content, and an increasein NmF 2 at Arecibo to the largest value seen at midnight in several years.

The Dynamics of Carbon–Nutrient Balance: Effects of Cottonwood Acclimation to Short- and Long-Term Shade on Beetle Feeding Preferences

The carbon–nutrient balance hypothesis (CNBH) predicts that shading should increase leaf palatability to herbivores by decreasing concentrations of carbon (C) -based chemical defenses and increasing nitrogen (N). We measured cottonwood (Populus deltoids) growth, leaf chemistry, and beetle (Plagiodera versicolora) feeding preferences on saplings grown in either continuous high (HH) or low (LL) light, and saplings switched from high to low (HL) or low to high (LH) light for nine days. As expected, based on the CNBH, shading increased total N and decreased total phenol glycoside (C-based secondary metabolites) concentrations in plants from all shade treatments (LL, HL, and LH), relative to HH plants, with plant growth and gross leaf chemistry being affected by initial and final light regime. In contrast, while specific phenol glycoside concentrations were affected by the initial and final light regime, they also showed an initial × final light interaction. Beetles tended to prefer LL to HH plants. Beetles unexpectedly preferred HH to either HL or LH switched plants, most likely because high concentrations of a specific phenol glycoside – salicin – occurred in both switched treatments and inhibited beetle feeding. Plant chemical allocation during light acclimation led to unpredictable changes in specific C-based compounds, even though plant growth and gross chemistry conformed to expectations for shading effects and the CNBH. The response of this herbivore to altered concentrations of a specific compound confounded predictions based on average dynamics of suites of chemicals. Our findings may help explain why relationships between light availability and herbivory in field studies, where light varies on many time scales, can differ from those predicted by the CNBH. Understanding both dynamic plant chemical responses to altered resource availability and controls over allocation to specific compounds would likely enhance future predictability of specific environment-plant-herbivore interactions.

Responses to light changes in tropical deciduous woody seedlings with contrasting growth rates.

We evaluated the responses in growth, biomass allocation, photosynthesis and stomatal conductance, to changes in light in woody seedlings from the tropical deciduous forest in Mexico, which shows a highly seasonal rain pattern. We studied ten species, which differed by 30-fold in relative growth rate (RGR). We analyzed plant growth in two contrasting light levels during 52 days and two transfers: from high to low (HL) and from low to high (LH) light intensity, and the respective controls in high (HH) and low (LL) light for another 52 days. The photosynthetic capacity (A max) and stomatal conductance were measured at the day of the transfer between light conditions and at the end of the experiment. Species with high RGR showed the largest changes in RGR in response to contrasting light conditions (HH/LL ratio), and species with low RGR showed low responses. The fast-growing species were the most plastic, followed by species with intermediate growth rates, with the slow-growing species being the least plastic. Fast-growing species achieved higher maximum photosynthetic capacities (A max) and stomatal conductance and higher response to light than slow-growing species. Species with high RGR showed a low RGR HH/LH ratio, suggesting a large response of L plants when transfered to H. The RGR of the species were associated with species specific leaf area and with the response in the leaf area, net assimilation rate and leaf weight ratio, suggesting the importance of the leaf area produced and the leaf characteristics rather than root:shoot ratio in determining RGR. Considering that seed germination is expected at the beginning of the rainy period, seedlings of most of the species will experience high-light conditions during its early growth. There are large annual variations in the time required for canopy closure (35-75 days). The influence of these variations may have different effect on the species studied. Species with intermediate growth rate and intermediate response to light changes were less affected by light reduction than fast-growing species. The intermediate-RGR species Caesalpiniaeriostachys is the most abundant and widely distributed species, perhaps this could be in part due to its ability to acclimate to both light increases and decreases. The fast-growing species studied here can be found in open sites in the forest and in areas cleared for pasture growth. These fast-growing species eventually reach the canopy, although this may require several canopy openings during their lives, which implies juvenile shade tolerance. In the tropical deciduous forest juvenile pioneer trees also benefit from the temporary high light available caused by the dry period during the rainy season. The slow-growing species Celaenodendronmexicanum forms small patches of monospecific forest; the adult trees are not completely deciduous, and they retain their old leaves for a long time period before shedding. Thus seedlings of this species may receive lower levels of light, in agreement with its shade tolerance and its lower response to light increases.