Dynamic Component Research Articles

Dynamic Component of the Asthenosphere: Lateral Viscosity Variations Due To Dislocation Creep at the Base of Oceanic Plates

AbstractThe asthenosphere is commonly defined as an upper mantle zone with low velocities and high attenuation of seismic waves, and high electrical conductivity. These observations are usually explained by the presence of partial melt, or by a sharp contrast in the water content of the upper mantle. Low viscosity asthenosphere is an essential ingredient of functioning plate tectonics. We argue that a substantial component of asthenospheric weakening is dynamic, caused by dislocation creep at the base of tectonic plates. Numerical simulations of subduction show that dynamic weakening scales with the surface velocity both below the subducting and the overriding plate, and that the viscosity decrease reaches up to two orders of magnitude. The resulting scaling law is employed in an apriori estimate of the lateral viscosity variations (LVV) below Earth's oceans. The obtained LVV help in explaining some of the long‐standing as well as recent problems in mantle viscosity inversions.

Bolt looseness monitoring using dynamic mode decomposition with piezoelectric active sensing

Bolt joints are widely used in multiple industries due to its ease of operation and low-cost. Under the influence of multiple external factors, bolt joint will loosen, which poses risks to structural safety. In this paper, a bolt loosening monitoring approach is proposed based on piezoelectric active sensing and dynamic mode decomposition (DMD). To the best of the author’s knowledge, this research represents the first attempt to detect bolt looseness using DMD method. A high-frequency dynamic response signal of the bolt joint is obtained based on piezoelectric active sensing. DMD is used to decompose the high-frequency dynamic response signal into a series of dynamic mode components. The bolt looseness mainly affects the localized high-frequency and high-order dynamic characteristics of the bolted structure. This paper innovatively proposes that the high frequency component signal constructed by the higher order dynamic component more directly reflect the localized dynamic characteristics of the bolted joint. Then, the signal energy of the constructed high frequency component signal is developed into a health index (HI) to characterize the bolt loosening degree. The experiments were conducted to verify the effectiveness of the proposed method. The experiment results shows that the proposed HI monotonically increases as the tightening of the bolt over the whole range of bolt-preload. Furthermore, the research incorporates different sensor mounting positions and loosening of bolts with various diameters, demonstrating the applicability of the proposed method. The proposed method is significant in detecting loosening of bolt joints, especially in bolt early loosening, and enhances the performance of the piezoelectric active sensing method.

Determination of dynamic component reactions in support bearings of rotor saws for cutting hot rolled (message 2)

For modern rolling production, the issue of strength and reliability of rotary saw designs, which are designed for cutting hot rolled products, is relevant. One of the factors that reduces the reliability of a rotary saw is the insufficient durability of the bearings of the shaft of the high-speed disk, which perceives the cutting forces. Practice shows that the applied methods of calculating the strength of support bearings do not allow taking into account all possible factors that affect the reliability of bearings in the cutting process. First, as it turned out, during operation, the saw blade has a radial beat, possibly due to an error when cutting the teeth of the blade and the eccentric landing of the blade on the seat when replacing it. Also, due to the fact that the process of cutting with a rotary saw is very short-term, the cutting force is considered to be the impact force. The purpose of this work is to determine the durability of the bearings of the disc shaft of a rotary saw, considering such factors as the radial beating of the disc and the shock load during the cutting process. As you know, during long-term operation of the object, the place for landing the cutting disc on the faceplate wears out, sometimes there is an error in the hole when making a new disc. Therefore, there is an eccentricity of the center of gravity of the disc. The presence of this eccentricity is considered in the work when determining the required forces using D'Alembert's principle of conditional balancing of forces. Given that the duration of cutting is a short-term process (lasts 0.105 sec.), when determining the reactions in the supports of the disk shaft that occur under the action of cutting forces, it is possible to consider the cutting process as an impact phenomenon. Due to the fact that the process of cutting with a circular saw is very short-term, the cutting force is considered the impact force. The magnitudes of the reaction forces in the bearings are determined during cutting using the theorems of impact dynamics: the theorem of impulses and the change of kinetic moment. For the possibility of theoretical determination of the effect of disk beating on the reaction in the bearings of the bearing shaft, experimental studies of disk beating and determined cutting forces were carried out

Mechanisms of early and late summer precipitation in Southwest China: dynamic and thermodynamic processes

This study investigates dynamic and thermodynamic components of moisture flux convergence in Southwest China (SW-MFC) and their underlying physical mechanisms during early and late summer. Using precipitation observation and CRA-40 reanalysis datasets from 1979 to 2023, the results show that both dynamic and thermodynamic processes modulate the SW-MFC in early summer (May-June), with dynamics playing a pivotal role. In contrast, the precipitation anomaly in late summer (July-August) is predominantly driven by the dynamic factors. Meanwhile, the large-scale circulation over the northern Indian Peninsula significantly modulates the SW-MFC. In early summer, anomalous convection around the Maritime Continent with the tripole sea surface temperature (SST) mode in the tropical Indo-Pacific can trigger the formation of “double ring” vertical zonal circulation cells. A large-scale westerly anomaly at the lower troposphere over the northern Arabian Sea foster cyclone strengthening over the northern Indian Peninsula, enhancing southerly moisture transport and increasing precipitation over Southwest China. During the late summer, large-scale dipole SST pattern between the subtropical central-eastern Pacific and the Indo-Pacific warm pool generates significant easterly anomalies towards the Maritime Continent. The SST gradient stimulates an extensive anticyclonic shear zone over the western equatorial Pacific, with an intensified low-pressure zone to its north. This atmospheric pattern over Southwest China and Indian Peninsula can form a vertical circulation circle that largely intensifies widespread precipitation. Numerical model experiments can reproduce the mechanisms of tropical Indo-Pacific joint effects on the Southwest precipitation in both early and late summer, providing a theoretical basis for understanding and forecasting summer precipitation over Southwest China.

The Development of New Scoring System to Define the Presence of Instability and the Need of Fusion in Degenerative Lumbar Spinal Stenosis - Jakarta Instability Score.

Systematic review, expert opinion and Delphi technique, and validity and reliability studies. We developed Jakarta Instability Score (JIS) to identify spinal instability and the need of fusion in degenerative lumbar spinal stenosis (LSS). This study consisted of systematic review to find predictors of spinal instability, expert opinion and modified Delphi technique to develop JIS, and validity and reliability studies of the newly developed JIS. A total of 54 studies were included in the systematic reviews to obtain predictors of spinal instability. Through expert opinion and modified Delphi technique, JIS was developed and consisted of the clinical component (back pain), dynamic radiograph component (dynamic translation and angulation), and MRI component (facet joint effusion), each of the component would be scored, and the total scoring would be from 0 to 14. The final scoring would classify patients into three groups: stable group (score of 0 to 4) in which the fusion is not needed, potentially unstable group (score of 5 to 8) in which the decision of fusion is based on surgeon's clinical judgment, and unstable group (score of 9 to 14) in which the fusion is needed. Final step of study concluded that this JIS had a high validity and reliability. The newly developed JIS was a valid and reliable scoring system that could help to identify the presence of instability in LSS and can be used as a guideline to decide whether spinal fusion will be needed.

Strain analysis and non-destructive monitoring of the two-stage hydraulic-driven piston compressor for hydrogen storage

High-pressure gas storage is an important means of hydrogen application in the transportation industry, especially in hydrogen refuelling stations. The hydrogen compressor is the most crucial dynamic component for high-pressure gas storage in hydrogen refuelling stations. An effective control system is required to guarantee the compressor operates safely and efficiently, which is based on the safe and efficient monitoring of the operating condition of the compressor. However, significantly limited literature has been provided for the hydraulic-driven piston compressor. In this paper, a non-destructive testing method for monitoring the dynamic pressure by strain gauge in the hydraulic-driven piston compressor is proposed. The relationship between the strain of the cylinder head and key operating parameters is obtained through finite element analysis, based on which the optimal location for the pressure monitoring is identified. The proposed non-destructive testing method is validated by experiments of a two-stage hydraulic-driven piston compressor. The strain analysis indicates that the circumferential strain in the cylinder head has a good linear relationship with the in-cylinder gas pressure with a value above 99.6 %. The deformation of the four monitoring positions is almost unchanged with a maximum deviation of 0.5 % under different piston positions. A high uniformity of the circumferential strain of the cylinder head is observed from the analysis. Experimental results indicate that the proposed non-destructive monitoring method is effective in obtaining the dynamic pressure in-cylinder during the compressor operation with a maximum deviation of 5.13 % and an average deviation below 2.01 %.

A dynamic generative model can extract interpretable oscillatory components from multichannel neurophysiological recordings.

Modern neurophysiological recordings are performed using multichannel sensor arrays that are able to record activity in an increasingly high number of channels numbering in the 100's to 1000's. Often, underlying lower-dimensional patterns of activity are responsible for the observed dynamics, but these representations are difficult to reliably identify using existing methods that attempt to summarize multivariate relationships in a post-hoc manner from univariate analyses, or using current blind source separation methods. While such methods can reveal appealing patterns of activity, determining the number of components to include, assessing their statistical significance, and interpreting them requires extensive manual intervention and subjective judgement in practice. These difficulties with component selection and interpretation occur in large part because these methods lack a generative model for the underlying spatio-temporal dynamics. Here we describe a novel component analysis method anchored by a generative model where each source is described by a bio-physically inspired state space representation. The parameters governing this representation readily capture the oscillatory temporal dynamics of the components, so we refer to it as Oscillation Component Analysis (OCA). These parameters - the oscillatory properties, the component mixing weights at the sensors, and the number of oscillations - all are inferred in a data-driven fashion within a Bayesian framework employing an instance of the expectation maximization algorithm. We analyze high-dimensional electroencephalography and magnetoencephalography recordings from human studies to illustrate the potential utility of this method for neuroscience data.

Epigenetic underpinnings of the autistic mind: Histone modifications and prefrontal excitation/inhibition imbalance.

Autism spectrum disorder (ASD) is complex neurobehavioral condition influenced by several cellular and molecular mechanisms that are often concerned with synaptogenesis and synaptic activity. Based on the excitation/inhibition (E/I) imbalance theory, ASD could be the result of disruption in excitatory and inhibitory synaptic transmission across the brain. The prefrontal cortex (PFC) is the chief regulator of executive function and can be affected by altered neuronal excitation and inhibition in the course of ASD. The molecular mechanisms involved in E/I imbalance are subject to epigenetic regulation. In ASD, altered enrichment and spreading of histone H3 and H4 modifications such as the activation-linked H3K4me2/3, H3K9ac, and H3K27ac, and repression-linked H3K9me2, H3K27me3, and H4K20me2 in the PFC result in dysregulation of molecules mediating synaptic excitation (ARC, EGR1, mGluR2, mGluR3, GluN2A, and GluN2B) and synaptic inhibition (BSN, EphA7, SLC6A1). Histone modifications are a dynamic component of the epigenetic regulatory elements with a pronounced effect on patterns of gene expression with regards to any biological process. The excitation/inhibition imbalance associated with ASD is based on the excitatory and inhibitory synaptic activity in different regions of the brain, including the PFC, the ultimate outcome of which is highly influenced by transcriptional activity of relevant genes.

PROCESS MONITORING IN HYBRID ELECTRIC VEHICLES BASED ON DYNAMIC NONLINEAR METHOD

Highway third-level faults can significantly deteriorate the reliability and performance of hybrid electric vehicle (HEV) powertrains. This study presents a novel process monitoring method aimed at addressing this issue. We propose a multivariate statistical method based on dynamic nonlinear improvement, namely dynamic neural component analysis (DNCA). This method does not require the establishment of precise analytical models; instead, it only necessitates acquiring data from HEV powertrains. Through numerical simulation and real HEV experiments, we demonstrate the effectiveness of this approach in monitoring highway third-level faults. The testing outcomes demonstrate that DNCA outperforms traditional dynamic methods like dynamic principal component analysis (DPCA), conventional nonlinear methods such as kernel PCA (KPCA) and NCA, as well as traditional dynamic nonlinear methods like DKPCA.

6-Methoxyflavone antagonizes chronic constriction injury and diabetes associated neuropathic nociception expression

Neuropathy is a disturbance of function or a pathological change in nerves causing poor health and quality of life. A proportion of chronic pain patients in the community suffer persistent neuropathic pain symptoms because current drug therapies may be suboptimal so there is a need for new therapeutic modalities. This study investigated the neuroprotective flavonoid, 6-methoxyflavone (6MF), as a potential therapeutic agent and gabapentin as the standard comparator, against neuropathic models. Thus, neuropathic-like states were induced in Sprague-Dawley rats using sciatic nerve chronic constriction injury (CCI) mononeuropathy and systemic administration of streptozotocin (STZ) to induce polyneuropathy. Subsequent behaviors reflecting allodynia, hyperalgesia, and vulvodynia were assessed and any possible motoric side-effects were evaluated including locomotor activity, as well as rotarod discoordination and gait disruption. 6MF (25–75 mg/kg) antagonized neuropathic-like nociceptive behaviors including static- (pressure) and dynamic- (light brushing) hindpaw allodynia plus heat/cold and pressure hyperalgesia in the CCI and STZ models. 6MF also reduced static and dynamic components of vulvodynia in the STZ induced polyneuropathy model. Additionally, 6MF reversed CCI and STZ suppression of locomotor activity and rotarod discoordination, suggesting a beneficial activity on motor side effects, in contrast to gabapentin. Hence, 6MF possesses anti-neuropathic-like activity not only against different nociceptive modalities but also impairment of motoric side effects.

Dynamic radiologic changes in repeated barotraumatic frontal sinusitis: A CARE case report

IntroductionFlight staff are at particular risk of iterative sinus barotrauma. We here report a case of barotraumatic atelectasic frontal sinusitis with dynamic radiologic change in frontal sinus volume. Case reportA 46-year-old air pilot was referred for right frontal pain occurring at each landing. Two sinus CT scans were taken: one after a period of intense flying and the other after a month without flying. In the right frontal sinus, a type-3 Kuhn cell changed in volume from 6×11×12mm to 13×18×19mm. The alteration involved a modification in the medial wall, which was demineralized and changed position within the frontal sinus. Removal during endoscopic frontal sinusotomy allowed complete resolution of pain. DiscussionThis article reports radiologic change in a frontal sinus wall in a setting of repeated barotraumatic frontal sinusitis with a dynamic atelectasic component. In iterative barotrauma, we advocate imaging at different time points. When the ostial obstruction is identified, functional aeration surgery can be applied.

Comprehensive compensation of dynamic hysteresis and creep for piezoelectric actuator

This paper addresses the modeling of dynamic hysteresis and creep in piezoelectric actuators, and employs feedforward open-loop control based on inverse models to compensate for hysteresis and creep phenomena. The comprehensive model consists of quasi-dynamic and dynamic components. The quasi-dynamic model combines the quasi-dynamic Prandtl–Ishlinskii (PI) model with an PI-based linear time-invariant model, while the dynamic part utilizes the auto-regressive exogenous model. The model accurately describes creep and dynamic hysteresis with modeling errors of less than 0.01 μm and 0.14 μm, respectively. The inversion of the comprehensive model has been proven to exhibit unique convergence. Under inverse feedforward control, the improvement in dynamic hysteresis and hysteresis with creep can be achieved at 94% and 83%, respectively. The comprehensive model proposed in this paper accurately describes the dynamic hysteresis and creep phenomena in piezoelectric actuators and realizes open-loop compensation control, achieving precise actuation of piezoelectric actuators.

Empowering software reliability: Leveraging efficient fault detection and removal efficiency

Advancements in science and technology have led to the widespread use of computer systems in various applications, emphasizing the importance of software reliability. Software failures can have severe consequences, making thorough testing crucial. Software reliability growth models (SRGMs) play a significant role in enhancing reliability by predicting improvement over time. This article introduces a comprehensive approach to software reliability that incorporates a dynamic fault detection rate, along with fault removal efficiency. The fault detection rate measures the rate at which faults are identified during testing, reflecting the effectiveness of the testing process. By incorporating this dynamic component, the model provides a more accurate estimation of software reliability and enables adaptive testing strategies and resource allocation. Achieving a high fault detection rate is desirable, but organizations must consider the cost implications and strike a balance between reliability and time-to-market constraints. This article extends the analysis to calculate the optimal release time and optimal warranty period that minimize development costs, subject to the desired reliability. By considering these factors, development teams can make informed decisions regarding the timing of software release and the duration of the warranty period, optimizing both reliability and cost.

YS-SLAM: YOLACT++ based semantic visual SLAM for autonomous adaptation to dynamic environments of mobile robots

Aiming at the problem of poor autonomous adaptability of mobile robots to dynamic environments, this paper propose a YOLACT++ based semantic visual SLAM for autonomous adaptation to dynamic environments of mobile robots. First, a light-weight YOLACT++ is utilized to detect and segment potential dynamic objects, and Mahalanobis distance is combined to remove feature points on active dynamic objects, also, epipolar constraint and clustering are employed to eliminate feature points on passive dynamic objects. Then, in terms of the semantic labels of dynamic and static components, the global semantic map is divided into three parts for construction. The semantic overlap and uniform motion model are chose to track moving objects and the dynamic components are added to the background map. Finally, a 3D semantic octree map is constructed that is consistent with the real environment and updated in real time. A series of simulations and experiments demonstrated the feasibility and effectiveness of the proposed approach.

A Calculation Method for Static Hysteresis Loop and its Applications

Background: Due to experimental equipment limitations, it is usually difficult to measure the quasi-static hysteresis loop at extremely low frequencies, which inevitably introduces errors in the static hysteresis model. Objective: This study aims to propose a method for calculating the static hysteresis loops of grainoriented silicon steel sheets so as to improve the accuracy of the static and dynamic hysteresis model. Methods: The parameters n0 and V0 in the magnetic field strength expression of the excess loss are determined by the measured losses within the range of 0-100Hz. Subsequently, the dynamic components in the quasi-static hysteresis loops are eliminated. Furthermore, a dynamic hysteresis model is established based on the loss and field separation theory, which incorporates the inverse Preisach model. Results: The dynamic hysteresis loops of the grain-oriented silicon steel sheets are measured in the range of 8-250Hz and compared with the results of both the improved model and the original model. Conclusion: Experimental results demonstrate the effectiveness and accuracy of the improved model. The proposed method for calculating static hysteresis loops has universal applicability and is meaningful for accurate simulation and prediction of magnetic properties in soft magnetic materials.

Nature-inspired substituted 3-(imidazol-2-yl) morpholines targeting human topoisomerase IIα: Dynophore-derived discovery

The molecular nanomachine, human DNA topoisomerase IIα, plays a crucial role in replication, transcription, and recombination by catalyzing topological changes in the DNA, rendering it an optimal target for cancer chemotherapy. Current clinical topoisomerase II poisons often cause secondary tumors as side effects due to the accumulation of double-strand breaks in the DNA, spurring the development of catalytic inhibitors. Here, we used a dynamic pharmacophore approach to develop catalytic inhibitors targeting the ATP binding site of human DNA topoisomerase IIα. Our screening of a library of nature-inspired compounds led to the discovery of a class of 3-(imidazol-2-yl) morpholines as potent catalytic inhibitors that bind to the ATPase domain. Further experimental and computational studies identified hit compound 17, which exhibited selectivity against the human DNA topoisomerase IIα versus human protein kinases, cytotoxicity against several human cancer cells, and did not induce DNA double-strand breaks, making it distinct from clinical topoisomerase II poisons. This study integrates an innovative natural product-inspired chemistry and successful implementation of a molecular design strategy that incorporates a dynamic component of ligand-target molecular recognition, with comprehensive experimental characterization leading to hit compounds with potential impact on the development of more efficient chemotherapies.

A VERY COMPLEX CASE OF DORV TYPE FALLOT: A CASE REPORT

Abstract Double outlet right ventricle (DORV) is a rare CHD characterized by ventriculoarterial connection in which both great arteries arise entirely or predominantly from the right ventricle. Its prevalence is 0.9% of all CHDs. Several chromosomal abnormalities have been associated with DORV, including trisomy 13, trisomy 18, and chromosome 22q11 deletion. Hearts with DORV are an extremely heterogeneous group showing various morphological features, connections, and relationships at each level of the cardiac segments and intersegmental junctions. As a consequence, the clinical manifestations and required surgical procedures for patients with DORV are variable. The anatomical spectrum is higly variable: it can be associated with ventricular septal defect, transposition of the great arteries (TGA) and functional single ventricle. We report the case of an infant with prenatal diagnosis of CHD and finding partial duplication of the short arm of the X chromosome. Pregnant woman at 22 weeks comes to the outpatient clinic to perform follow–up ultrasound. At that site finding of CHD which was later confirmed at birth and therefore prostaglandin therapy was started. Echocardiogram showed a wide DIV from malalignment with antero–cephalic deviation of the conal septum with significant aortic destroposition configuring picture of double outlet right ventricle. It also presents a complex right efflux obstruction already at subvalvular pulmonary departure. The pulmonary valve presented dysplastic, with en dome motion, hypoplastic. Pulmonary perfusion appears to be provided predominantly by the Botallo‘s duct originating from the isthmic region of the aorta and leading with a long and tortuous course to the pulmonary confluence near the left pulmnary artery with high velocity flow. The remaining findings are normal. Therefore, in view of the clinical picture, he was subjected to palliative surgery of right systemic–pulmonary shunt between the brachiocephalic trunk and right pulmonary artery (modified Blalock–Taussing surgery) in 3.5mm PTFE and ligation of Botallo‘s duct. At subsequent follow–up, the systemic–pulmonary shunt appeared pervious with regular flow. Wide DIV from anterior malalignment with aorta cavalier to DIV. Severe stenosis at complex pulmonary outflow with max gradient up to 124mmHg with dynamic and valvular component. For the subsequent course of treatment, the patient will be discussed collegially.

Virtual Sensing of Key Variables in the Hydrogen Production Process: A Comparative Study of Data-Driven Models.

Hydrogen is an ideal energy carrier manufactured mainly by the natural gas steam reforming hydrogen production process. The concentrations of CH4, CO, CO2, and H2 in this process are key variables related to product quality, which thus need to be controlled accurately in real-time. However, conventional measurement methods for these concentrations suffer from significant delays or huge acquisition and upkeep costs. Virtual sensors effectively compensate for these shortcomings. Unfortunately, previously developed virtual sensors have not fully considered the complex characteristics of the hydrogen production process. Therefore, a virtual sensor model, called "moving window-based dynamic variational Bayesian principal component analysis (MW-DVBPCA)" is developed for key gas concentration estimation. The MW-DVBPCA considers complicated characteristics of the hydrogen production process, involving dynamics, time variations, and transportation delays. Specifically, the dynamics are modeled by the finite impulse response paradigm, the transportation delays are automatically determined using the differential evolution algorithm, and the time variations are captured by the moving window method. Moreover, a comparative study of data-driven virtual sensors is carried out, which is sporadically discussed in the literature. Meanwhile, the performance of the developed MW-DVBPCA is verified by the real-life natural gas steam reforming hydrogen production process.

Future changes in South Asian summer monsoon circulation under global warming: role of the Tibetan Plateau latent heating

The South Asian summer monsoon (SASM) is a significant monsoon system that exerts a profound impact on climate and human livelihoods. According to 38 models from the Coupled Model Intercomparison Project Phase 6, the SASM circulation is projected to weaken significantly under global warming as seen in the weakened low-level westerly wind over the northern tropical Indian Ocean; however, the associated climate dynamics is still under debate. Here, we identify that the weakened low-level westerly wind is closely related to the enhanced latent heating over the Tibetan Plateau (TP), which corresponds with increased summer precipitation in the future. The intensified TP latent heating triggers an anomalous meridional circulation with ascending motions over the plateau and descending motions to the south, leading to an anomalous low-level anticyclone over the northern tropical Indian Ocean. This anticyclone greatly weakens the prevailing low-level westerlies of the SASM through easterly anomalies at the anticyclone’s southern flank. Moisture budget analysis further reveals that increased atmospheric water vapor, rather than the vertical dynamic component, makes the largest contribution to the increased precipitation over the TP. This result confirms that the enhanced TP latent heating is a driver of atmospheric circulation change and contributes to weakening the SASM circulation.

Population Trend of Colonially Nesting Heron Species in Greece

Heron colonies are dynamic components of wetlands. Therefore, their systematic monitoring is important for the management of both birds and wetlands. During the period 1988–2018, we counted breeding pairs of seven colonial breeding heron species at 65 colonies across 37 wetlands in Greece. We considered as annual variables of a population: (a) years since 1988, (b) Natura 2000 network inclusion, (c) protected area management authority overseeing, (d) wetland type (new or restored), and (e) new colonies (established after 2003). The Cattle Egret Bubulcus ibis and the Squacco Heron Ardeola ralloides had a positive breeding population trend. The Black-crowned Night Heron Nycticorax nycticorax, Little Egret Egretta garzetta, and Grey Heron Ardea cinerea had a negative trend, while the Purple Heron Ardea purpurea population was stable. The Great White Egret Ardea alba bred sporadically at only a few sites which precluded the evaluation of its population trend. The informative population variables differed among species, even of those at the same colony, which suggests trends are also affected by conditions at wintering grounds. The study highlights the need for the systematic monitoring of heron colonies and the protection of foraging/breeding areas in order to reverse the observed negative population trends.