Upstream Branches Research Articles

Effects of different momentum ratios and Reynolds number in a T-junction with an upstream elbow

This study focuses on analysing thermal mixing in T-junctions with varying momentum and Reynolds number ratios, utilizing computational fluid dynamics (CFD) simulations. The T-junction is a critical component of the primary nuclear thermal–hydraulic circuit within a pressurized water-cooled reactor (PWR). The T-junction connects the pressurizer (PRZ) with the steam generator (SG) and the reactor pressure vessel (RPV). Water from the PRZ and the SG are at different temperatures and incomplete thermal mixing occurs when these two fluid streams meet at the T-junction. This incomplete thermal mixing can induce thermal stratification of the water within the T-junction as well as thermal striping phenomena. Thermal striping phenomena can lead to fluctuations of the temperature at the inner pipe wall of the T-junction. Thermal stratification and thermal striping phenomena can induce thermo-mechanical fatigue and eventual pipe failure which can affect the safety of the reactor. Therefore, a high-fidelity, mechanistic understanding of the turbulent thermo-fluid mixing within T-junctions of PWRs might lead to improvements in component reliability and safety within nuclear power plants (NPPs).The primary aim of the research, presented in this paper, is to understand and quantify the effect of variations in the momentum ratio on the turbulent fluid flow within T-junctions. This is achieved by either varying the branch pipe diameter while keeping the inlet velocity constant (part one) or by adjusting the branch pipe inlet velocity while maintaining a constant diameter (part two). Despite the different variations in momentum ratios, the specific momentum ratios under consideration in both parts of the study remain consistent (namely 98 and 66.4). It is also noteworthy that the momentum ratios considered in the paper can be classified as wall-jet and impinging-jet, according to the definition in (Hosseini, Yuki, & Hashizume, 2008). It should be noted that the momentum ratio is manipulated by adjusting the flow parameters, leading to variations in the Reynolds number ratio between the main pipe inlet and the upstream branch pipe at the T-junction. The turbulent flows in the cases that are considered are simulated using the Improved delayed detached eddy simulation (IDDES-SST) model. The numerical results from these simulations indicate, for the considered momentum ratios, that maintaining the same momentum ratio does not produce similar mean flow behaviour and turbulent quantities of interest (QoI). For instance, the size of the flow recirculation zone is more likely linked to the diameter of the branch pipe. Moreover, the turbulent QoI and temperature fluctuations at the determined locations are likely affected by the changed flow recirculation zone as well as the Reynolds number of the branch pipe flow.

Analyzing raw water quality of drinking water of Pelayaran River: Tribute to Brantas River

Raw water quality for drinking water is a strategic issue requiring attention and environmental dynamics. River quality changes are crucial for sustainability and monitoring suitability. Kali Pelayaran, a tributary of the Brantas River, is a key source for drinking water in Sidoarjo Regency. The aim of the research is to analyze the water quality status of the Kali Pelayaran river as a basis for mitigating the sustainability of raw drinking water in Sidoarjo Regency. The length of the segment analyzed starts from the upstream branch of the Brantas River which enters the Pelayaran River to the intake of the Tawangsari WTP, a distance of 21 kilometers. The research method that will be implemented is: analyzing the existing condition of the water quality of the Kali Pelayaran river which is divided into 8 segments by measuring the quality status of the river using the Pollutant Index (IP). Next, use the K-means method to create clustering based on the measured level of quality status. The water and sediment quality parameters analyzed were pH, temperature, DO (Dissolved oxygen), BOD (Biological oxygen demand), COD (Chemical oxygen demand), TDS (Total dissolved solids), and TSS (Total suspended solid). Research conclusions was formulated in an integrated manner regarding the description of current conditions and predictions for the future, presented in the form of tables, graphs, and maps.

Front Profile in Time Backward for the Bistable Reaction-Diffusion Equation on Metric Graphs

In the bistable reaction-diffusion equation on a half-line there exists an entire solution exhibiting the front propagation from the infinity of the line. We glue an arbitrary number of half-lines at a single point (junction) to build a metric graph and examine the front propagation on given half-lines (upstream branches). The aim of the article is to show the existence of an entire solution which converges to the profile of the traveling wave with an arbitrarily assigned phase-shift in each upstream branch as $$t\rightarrow -\infty $$ . The proof is carried out by constructing an appropriate pair of sub-and super-solutions.

Single-microvessel occlusion produces lamina-specific microvascular flow vasodynamics and signs of neurodegenerative change

Recent studies have highlighted the importance of understanding the architecture and function of microvasculature, and dysfunction of these microvessels may underlie neurodegenerative disease. Here, we utilize a high-precision ultrafast laser-induced photothrombosis (PLP) method to occlude single capillaries and then quantitatively study the effects on vasodynamics and surrounding neurons. Analysis of the microvascular architecture and hemodynamics after single-capillary occlusion reveals distinct changes upstream vs. downstream branches, which shows rapid regional flow redistribution and local downstream blood-brain barrier (BBB) leakage. Focal ischemia via capillary occlusions surrounding labeled target neurons induces dramatic and rapid lamina-specific changes in neuronal dendritic architecture. Further, we find that micro-occlusion at two different depths within the same vascular arbor results in distinct effects on flow profiles in layers 2/3 vs layer 4. The current results reveal laminar-scale regulation distinctions in microinfarct response and raise the possibility that relatively greater impacts on microvascular function contribute to cognitive decline in neurodegenerative disease.

Two activating phosphorylation sites of Pbs2 MAP2K in the yeast HOG pathway are differentially dephosphorylated by four PP2C phosphatases Ptc1–Ptc4

To cope with an increased external osmolarity, thebudding yeastSaccharomyces cerevisiaeactivates the Hog1 mitogen-activated protein kinase (MAPK) through the high-osmolarity glycerol (HOG) pathway, which governs adaptive responses to osmostress. In the HOG pathway, two apparently redundant upstream branches, termed SLN1 and SHO1, activate cognate MAP3Ks (MAPKK kinase) Ssk2/22 and Ste11, respectively. These MAP3Ks, when activated, phosphorylate and thus activate the Pbs2 MAP2K (MAPK kinase), which in turn phosphorylates and activates Hog1. Previous studies have shown that protein tyrosine phosphatases and the serine/threonine protein phosphatases type 2C negatively regulate the HOG pathway to prevent its excessive and inappropriate activation, which is detrimental to cell growth. The tyrosine phosphatases Ptp2 and Ptp3 dephosphorylate Hog1 at Tyr-176, whereas the protein phosphatase type 2Cs Ptc1 and Ptc2 dephosphorylate Hog1 at Thr-174. In contrast, the identities of phosphatases that dephosphorylate Pbs2 remained less clear. Here, we examined the phosphorylation status of Pbs2 at the activating phosphorylation sites Ser-514 and Thr-518 (S514 and T518) in various mutants, both in the unstimulated and osmostressed conditions. Thus, we found that Ptc1-Ptc4 collectively regulate Pbs2 negatively, but each Ptc acts differently to the two phosphorylation sites in Pbs2. T518 is predominantly dephosphorylated by Ptc1, while S514 can be dephosphorylated by any of Ptc1-4 to an appreciable extent. We also show that Pbs2 dephosphorylation by Ptc1 requires the adaptor protein Nbp2 that recruits Ptc1 to Pbs2, thus highlighting the complex processes involved in regulating adaptive responses to osmostress.

Sr-Nd isotopic fingerprints of Red River sediments and its implication for provenance discrimination in the South China Sea

The Red River has a sediment discharge of 130 Mt/yr and is one of the most important sources of fluvial materials to the South China Sea (SCS). However, due to the paucity of Sr-Nd isotopic data of the Red River delta sediments, the Sr-Nd isotopic fingerprints of the Red River sediment have not been well defined, which hinders the provenance discrimination of modern sediment in the SCS. This study presents the grain size, element, and Sr-Nd isotope data of Red River delta sediments to examine the controlling factors of sediment Sr-Nd isotopic compositions and better characterize the sediment discharge of the modern Red River to the SCS. Compiled rock Sr-Nd isotopic data in the Red River catchment indicate that catchment bedrock lithology exerts a dominant control on distinct sediment Sr-Nd isotopic features among its main branches, Song Da, Thao River, and Song Lo. The Sr-Nd isotopic compositions of Red River delta sediments are concentrated and between these upstream branches, indicating a result of the mixing process. A Bayesian mixing model shows that the Song Lo, Song Da and Thao River make an approximately equal contribution to the modern Red River delta. However, in delta sediments, the correlation between the 87Sr/86Sr and mean grain size suggests a hydrodynamic sorting effect on sediment 87Sr/86Sr ratios, which should be a concern in the calculation of mixing models. Combining newly measured and published data in the Red River delta, we show that the Sr-Nd isotopic fingerprints of Red River sediment are 0.7304 ± 0.0027 (1σ, n = 32) and − 12.0 ± 0.4 (1σ, n = 32) respectively. Published Sr-Nd isotopic compositions of delta sediments in the Pearl River and Mekong River are also compiled to make a comparison with the Red River. The Mekong River sediment has less radiogenic 87Sr/86Sr of 0.7212 ± 0.0008 (1σ, n = 7) and higher εNd values of −10.1 ± 0.7 (1σ, n = 8), and Pearl River sediment shows higher 87Sr/86Sr ratios of 0.7378 (n = 1) and εNd values of −11.8 ± 0.4 (1σ, n = 6), which is similar to those of Red River sediment. This study provides new insight into the reliable assessment of sediment Sr-Nd isotopic fingerprints for large rivers in SE Asia, which is favorable for the provenance discrimination of modern SCS sediment.

Transformer neural networks for interpretable flood forecasting

Floods are one of the most devastating natural hazards, causing several deaths and conspicuous damages all over the world. In this work, we explore the applicability of the Transformer neural network to the task of flood forecasting. Our goal consists in predicting the water level of a river one day ahead, by using the past water levels of its upstream branches as predictors. The methodology was validated on the severe flood that affected Southeast Europe in May 2014. The results show that the Transformer outperforms recurrent neural networks by more than 4% in terms of the Root Mean Squared Error (RMSE) and 7% in terms of the Mean Absolute Error (MAE). Furthermore, the Transformer requires lower computational costs with respect to recurrent networks. The forecasting errors obtained are considered acceptable according to the domain standards, demonstrating the applicability of the Transformer to the task of flood forecasting.

Embolization of Recurrent Pulmonary Arteriovenous Malformations by Ethylene Vinyl Alcohol Copolymer (Onyx®) in Hereditary Hemorrhagic Telangiectasia: Safety and Efficacy.

Objectives: To evaluate short- and long-term safety and efficacy of embolization with Onyx® for recurrent pulmonary arteriovenous malformations (PAVMs) in hereditary hemorrhagic telangiectasia (HHT). Methods: In total, 45 consecutive patients (51% women, mean (SD) age 53 (18) years) with HHT referred to a reference center for treatment of recurrent PAVM were retrospectively included from April 2014 to July 2021. Inclusion criteria included evidence of PAVM recurrence on CT or angiography, embolization using Onyx® and a minimal 1-year-follow-up CT or angiography. Success was defined based on the standard of reference criteria on unenhanced CT or pulmonary angiography if a recurrence was suspected. PAVMs were analyzed in consensus by two radiologists. The absence of safety distance, as defined by a too-short distance for coil/plug deployment, i.e., between 0.5 and 1 cm, between the proximal extremity of the primary embolic material used and a healthy upstream artery branch, was reported. Results: In total, 70 PAVM were analyzed. Mean (SD) follow-up was 3 (1.3) years. Safety distance criteria were missing in 33 (47%) PAVMs. All procedures were technically successful, with a short-term occlusion rate of 100% using a mean (SD) of 0.6 (0.5) mL of Onyx®. The long-term occlusion rate was 60%. No immediate complication directly related to embolization was reported, nor was any severe long-term complication such as strokes or cerebral abscesses. Conclusions: In HHT, treatment of recurrent PAVM with Onyx® showed satisfactory safety and efficacy, with an immediate occlusion rate of 100% and a long-term rate of 60%.

Two oppositely-charged sf3b1 mutations cause defective development, impaired immune response, and aberrant selection of intronic branch sites in Drosophila.

SF3B1 mutations occur in many cancers, and the highly conserved His662 residue is one of the hotspot mutation sites. To address effects on splicing and development, we constructed strains carrying point mutations at the corresponding residue His698 in Drosophila using the CRISPR-Cas9 technique. Two mutations, H698D and H698R, were selected due to their frequent presence in patients and notable opposite charges. Both the sf3b1-H698D and–H698R mutant flies exhibit developmental defects, including less egg-laying, decreased hatching rates, delayed morphogenesis and shorter lifespans. Interestingly, the H698D mutant has decreased resistance to fungal infection, while the H698R mutant shows impaired climbing ability. Consistent with these phenotypes, further analysis of RNA-seq data finds altered expression of immune response genes and changed alternative splicing of muscle and neural-related genes in the two mutants, respectively. Expression of Mef2-RB, an isoform of Mef2 gene that was downregulated due to splicing changes caused by H698R, partly rescues the climbing defects of the sf3b1-H698R mutant. Lariat sequencing reveals that the two sf3b1-H698 mutations cause aberrant selection of multiple intronic branch sites, with the H698R mutant using far upstream branch sites in the changed alternative splicing events. This study provides in vivo evidence from Drosophila that elucidates how these SF3B1 hotspot mutations alter splicing and their consequences in development and in the immune system.

Evidence for complex dynamics during U2 snRNP selection of the intron branchpoint.

Splicing of pre-mRNA is initiated by binding of U1 to the 5′ splice site and of Msl5-Mud2 heterodimer to the branch site (BS). Subsequent binding of U2 displaces Msl5-Mud2 from the BS to form the prespliceosome, a step governing branchpoint selection and hence 3′ splice site choice, and linking splicing to myelodysplasia and many cancers in human. Two DEAD-box proteins, Prp5 and Sub2, are required for this step, but neither is stably associated with the pre-mRNA during the reaction. Using BS-mutated ACT1 pre-mRNA, we previously identified a splicing intermediate complex, FIC, which contains U2 and Prp5, but cannot bind the tri-snRNP. We show here that Msl5 remains associated with the upstream cryptic branch site (CBS) in the FIC, with U2 binding a few bases downstream of the BS. U2 mutants that restore U2-BS base pairing enable dissociation of Prp5 and allows splicing to proceed. The CBS is required for splicing rescue by compensatory U2 mutants, and for formation of FIC, demonstrating a role for Msl5 in directing U2 to the BS, and of U2-BS base pairing for release of Prp5 and Msl5-Mud2 to form the prespliceosome. Our results provide insights into how the prespliceosome may form in normal splicing reaction.

Vascularized pisiform graft for the treatment of scaphoid nonunion: An anatomical study

Scaphoid fracture can evolve into scaphoid nonunion leading to wrist arthritis. Vascularized bone flaps used to treat scaphoid nonunion are supplied by delicate, small, or short arteries that are not always reliable. The pisiform bone has never been considered as a possible treatment of scaphoid nonunion since the traditionally harvested pedicle is too short. This study aimed to characterize the vascularization of the pisiform with the goal of developing a method of harvesting it with a longer pedicle that can be used as a graft to treat scaphoid nonunion. A cadaver study on 30 upper limbs was done in two parts: firstly, we dissected 20 cadaver specimens and documented the pisiform's vascularization (size, length, and articular surface) as well as anatomical characteristics of the dorsal ulnar artery; secondly, we used 10 cadaver specimens to study an experimental surgical procedure in which a vascularized pisiform graft is used to treat an artificially created nonunion and confirm its feasibility. The pisiform artery originated from the dorsal ulnar artery in all 20 dissections. Its average length of 4.036cm could be increased by 11% by ligating the upstream collateral branches from the dorsal ulnar artery. The pedicled vascularized pisiform flap was grafted to the scaphoid in 10 experimental procedures performed on fresh cadavers. The vascularized pisiform graft consists of a reliable vascular pedicle and well vascularized multi-cortical bone with a cartilaginous surface. However, more studies are needed to confirm the feasibility of this flap as an alternative for treating unstable scaphoid nonunion.

Changing sources and processes sustaining surface CO<sub>2</sub> and CH<sub>4</sub> fluxes along a tropical river to reservoir system

Abstract. Freshwaters are important emitters of carbon dioxide (CO2) and methane (CH4), two potent greenhouse gases (GHGs). While aquatic surface GHG fluxes have been extensively measured, there is much less information about their underlying sources. In lakes and reservoirs, surface GHG can originate from horizontal riverine flow, the hypolimnion, littoral sediments, and water column metabolism. These sources are generally studied separately, leading to a fragmented assessment of their relative role in sustaining CO2 and CH4 surface fluxes. In this study, we quantified sources and sinks of CO2 and CH4 in the epilimnion along a hydrological continuum in a permanently stratified tropical reservoir (Borneo). Results showed that horizontal inputs are an important source of both CO2 and CH4 (>90 % of surface emissions) in the upstream reservoir branches. However, this contribution fades along the hydrological continuum, becoming negligible in the main basin of the reservoir, where CO2 and CH4 are uncoupled and driven by different processes. In the main basin, vertical CO2 inputs and sediment CH4 inputs contributed to on average 60 % and 23 % respectively to the surface fluxes of the corresponding gas. Water column metabolism exhibited wide amplitude and range for both gases, making it a highly variable component, but with a large potential to influence surface GHG budgets in either direction. Overall our results show that sources sustaining surface CO2 and CH4 fluxes vary spatially and between the two gases, with internal metabolism acting as a fluctuating but key modulator. However, this study also highlights challenges and knowledge gaps related to estimating ecosystem-scale CO2 and CH4 metabolism, which hinder aquatic GHG flux predictions.

Large eddy simulation of an inclined jet in crossflow with vortex generators

ABSTRACT Film cooling is one of the essential approaches to cool high-performance turbine blades. Film cooling with delta winglet vortex generator pair (DWVGP) placed upstream of the cooling hole is investigated by large eddy simulation (LES) at the blowing ratio of M=1.0. Film cooling effectiveness and vortical structures are evaluated in the flow field of a jet in crossflow (JICF). Results indicate that film cooling effectiveness increases significantly for the DWVGP case. As a dominant vortex structure, the ubiquitous counter-rotating vortex pair (CRVP) is recognized in the flow field. It has a detrimental effect that lifts the coolant off the cooling surface. The DWVGP evolved anticounter-rotating vortex pair (anti-CRVP) has the opposite sense of rotation to the jet introduced CRVP, which undertakes vorticity decay when developing downstream of the cooling hole. With the downwash effect of anti-CRVP, the reattachment of coolant is earlier, and a wide region of enhanced film cooling effectiveness in the spanwise direction is achieved. The coherent vortex structures including the classical vortices in the flow field and the vortex generator pair introduced vortices are analyzed. The genesis and evolution mechanism of CRVP with and without the vortex generators are discussed. It indicates that three branches of upstream spiral structures from the nozzle tube contribute to the CRVP. The merging of CRVP upstream branches is delayed by the vortex generators evolved anti-CRVP, which postpones the formation of downstream CRVP.

Study of pollution transport through the river confluences by derivation of an analytical model.

Due to the entrance of pollutants in different branches of the river network, it is essential to study contaminant transport at the river confluences. In the present study, it was attempted to investigate the conservative pollution transport at channel confluence by operating a series of experiments in the laboratory flume. In the designed laboratory model, two branches, with different widths of 45, 25 cm, were intersected and a channel confluence was created. Five entrance discharges and three initial contaminant concentrations, introduced using a linear feeder, were chosen as experimental variables. Conservative tracer of sodium chloride solution was used, and the electrical conductivities were measured at eight locations of the main channel and upstream branches with 2 seconds interval. Junction zone was assumed as a control volume, and by applying mass equilibrium to it, a new mathematical model was extracted. It was observed that there is concentration fluctuation in the falling limbs of the experimental breakthrough curves of the junction zone; however, it was diminished by downstream motion. Moreover, the observed pollution graphs had double peak points which changed to a single point with an increase of distance from the confluence position. Operation of the presented model was investigated by variation of its parameters. It was found that the contaminant residence time parameters of the confluence zone have the most significant influence in the simulation of the analytical model. Additionally, it was observed that the values of Gaussian distribution of the upstream branches could displace the position of pulses of resultant breakthrough curves or can overlap them. Moreover, the model performance was examined using statistical goodness of fit parameters like Nash-Sutcliffe, R2, and mean absolute error (MAE). Their values were calculated as 0.88, 0.91, 66.88 (ppm), respectively.

Modeling flow and pressure distributions in multi-branch light-commercial duct systems

This paper describes a numerical model that was developed to predict flow and pressure distribution in three multi-branch air duct systems as a function of upstream static gauge pressure. The duct systems were comprised of a combination of wire-wound flexible ducts and rigid sheet metal ducts. The model used the Darcy equation and the concept of the local loss coefficient, in conjunction with the continuity equation, to perform the calculations. The secant method was utilized to predict the flow rate through the initial upstream branch, and the Newton-Raphson method was employed model the flow through the remaining branches. The model demonstrated that the static gauge pressure rose in the overall flow direction due to the static regain effect, and that flow rate distribution varied in a predictable, characteristic manner in the overall flow direction. The model branch flow predictions were verified experimentally. The model is potentially useful for modeling the performance of variable air volume (VAV) air duct systems that use control strategies that depend on changing the fan speed and/or adjusting damper settings in the branches.

Computational fluid dynamic–discrete element method coupling analysis of particle transport in branched networks

An understanding of the particle transport characteristics in a branched network helps to predict the particle distribution and prevent undesired plugging in various engineering systems. Quantitative analysis of particle flow characteristics is challenging in that experiments are expensive and particle flow is difficult to detect without disturbing the flow. To overcome this difficulty, man-made fractal tree-like branched networks were built, and a coupled computational fluid dynamic and discrete element method model was applied. A series of numerical simulations was carried out to analyze the influence of fractal structure parameters of networks on the particle flow characteristics. The joint influence of inertial, shunt capacity and superposition from upstream branches on particle flow was investigated. The injection position at the inlet determined the particle velocity and its future flow path. The particle density ratio, particle size and bifurcation angle had a greater influence on the shunting of K2 branches than that in the K1 level and Nk22/Nk21 reached a maximum at 60°. Compared with a network with an even number of branches, there was a preferential branch when the branch number was odd. The preferential branch effect or asymmetry degree of the level (K2) branches had a more significant impact on particle shunting than that from the upstream branches (K1).

Cussac cave Gravettian parietal art (Dordogne, France): Updated inventories and new insights into Noaillian rock art

In 2008, the Collective Research Project funded by the French Ministry of Culture undertook the study of the decorated sepulchral cave of Cussac (Dordogne), discovered by Marc Delluc in 2000. In this paper, we present an update of Norbert Aujoulat’s inventory (2001–2005), along with the results of a number of technical, thematic, stylistic and iconographic analyses. This examination confirmed that the rock art assemblage was both homogenous and consistent with the graphic repertoire of the Middle Gravettian (30,500–28,000 calBP), and more precisely the Noaillian facies. Specific thematic and stylistic commonalities with Gargas (French central Pyrenees) and the Basque Country were highlighted.For reasons of conservation and administrative restrictions, the study did not cover the entire cave, but what is referred to as the ‘Downstream Branch’ (the most densely decorated part of the cavity with most of the major panels, such as the Discovery Panel and the Grand Panel) and a long but incomplete portion of the ‘Upstream Branch’. Rich as the site is, this analysis can provide archaeologists with important clues about the meaning of this exceptional site.

A systematic study of blockage in three-dimensional branching networks with an application to model human bronchial tree

A major aim of the present study is to understand and thoroughly document the fluid dynamics in three-dimensional branching networks when an intermediate branch is partially or completely obstructed. Altogether, 26 different three-dimensional networks each comprising six generations of branches (involving 63 straight portions and 31 bifurcation modules) are constructed and appropriately meshed to conduct a systematic study of the effects of varying the locations of a blockage of a given relative extent and varying the extent of a blockage at a fixed location. The side-by-side consideration of two branching configurations (in-plane and $$90^{\circ }$$ out-of-plane) gives a quantitative assessment of the dependence of flow alteration due to blockage on the three-dimensional arrangement of the same individual branches. A blockage in any branch affects the flow in both downstream and upstream branches. The presence of a blockage can make three-dimensional asymmetric alteration to the flow field, even when the blockage itself is geometrically symmetric. The overall mass flow rate entering the network is found to remain nearly unaltered if a blockage is shifted within the same generation but is progressively reduced if the blockage is shifted to upstream generations. A blockage anywhere in the network increases the degree of mass flow asymmetry $$\delta _{\mathrm{G}n} $$ in any generation. The order of magnitude disparity in $$\delta _{\mathrm{G}n} $$ between the in-plane and out-of-plane configurations, characteristic of unobstructed networks, can be significantly reduced in the presence of a single blockage. The present three-dimensional computations show that the effects of blockage on the mass flow distribution in a large network are complex, often non-intuitive and sometimes dramatic, and cannot be captured by any simple one-dimensional model.

Morphological Changes of the Lower Ping and Chao Phraya Rivers, North and Central Thailand: Flood and Coastal Equilibrium Analyses

Abstract The Chao Phraya River flows in the largest river basin of Thailand and represents one of the important agricultural and industrial areas in Southeast Asia. The Ping River is one major upstream branch flowing down slope southwardly, joining the Chao Phraya River in the low-lying central plain and ending its course at the Gulf of Thailand. Surprisingly, the overflow occurs frequently and rapidly at the Lower Ping River where channel slope is high, and in particular area, sand-choked is extensively observed, even in normal rainfall condition. In contrary, at the downstream part, the erosion of river bank and shoreline around the mouth of Chao Phraya River has been spatially increasing in place where there should be a massive sediment supply to form a delta. Here we use Landsat imageries taken in 1987, 1997, 2007 and 2017 to analyze geomorphological changes of rivers. Results show that both rivers have undergone the rapid decreasing of water storage capacity and increasing of sand bar areas in river embayment. The total emerged sand bar area in the Lower Ping River increases from 1987 to 2017 up to 28.8 km2. The excessive trapped bed sediments deposition along the upper reaches is responsible for the shallower of river embankment leading to rapid overflow during flooding. At the Chao Phraya River mouth, a total of 18.8 km2 of the coastal area has been eroded from 1987 to 2017.This is caused by the reducing of sediment supply leading to non-equilibrium in the deltaic zone of the upper Gulf of Thailand. There are several possibility implications from this study involving construction of weir, in-channel sand mining, reservoir sedimentation and coastal erosion management.

Choosing rock art locations: Geological parameters and social behaviours. The example of Cussac Cave (Dordogne, France)

Cussac Cave, discovered in 2000 in the Dordogne department of France, is one of the major decorated and sepulchral sites of the Gravettian period of the Upper Palaeolithic. It contains spectacular engravings, human remains—some of which were deposited in bear hibernation nests—and other well-preserved artefacts and traces of human and animal activity, such as human and cave bear footprints. The exceptional preservation of this cave is due to its recent discovery (followed by an extensive preservation program) and the apparent absence of human frequentation since the Gravettian period. As part of the multidisciplinary research program developed since 2008 (PCR Cussac, dir. J. Jaubert), this study aims to contribute to a better understanding of the factors—natural and/or cultural—that influenced the Gravettian people in their selection and general distribution of rock art panels in the cave. We investigate the nature of the rock support, location, surroundings, accessibility, and visibility of 31 panels. For this purpose, we developed an innovative methodology combining the data recorded in a dedicated database and on topographic documents with data processing using complex statistics (Factor Analysis for Mixed Data - FAMD). Through this work, we identified three groups of panels that reveal three ways of using the cave, two of which appear homogenous. Group 1 is characterized by small panels located in narrow passageways of the Palaeolithic path in the Downstream Branch of the cave. These panels share a strong potential for visual relationships whereas it is impossible for more than four people to see a given panel at the same time. In contrast, Group 3, also mainly located in the Downstream Branch, is composed of large panels with numerous graphic entities. These panels are always located in wide corridors and distant from the natural path, and their field of visibility is thus large enough to accommodate a small group of individuals. They also share visual relationships with other panels. Finally, Group 2 contains fewer intrinsic criteria, though all the panels are situated between the beginning of the Downstream Branch and the Upstream Branch, and they are visually isolated from each other. This study yields evidence of a strong interaction between geological and cultural factors in the selection of the rock art panels in Cussac Cave. The Gravettian people that frequented Cussac Cave linked their cultural goals to what the cave had to offer in terms of geology, geomorphology and available space. They adapted to—and even optimized—both the opportunities and constraints of the cave, thus demonstrating a strong interaction between geological and cultural parameters.