Small Valley Research Articles

ANALYSIS OF THE RESULTS OF AIR QUALITY MONITORING IN THE AREA OF THE CITY OF ZENICA

According to the World Health Organization (WHO), air pollution is the largest single environmental risk to public health. According to the latest estimate of this organization, 9 out of 10 people on the planet breathe polluted air. The development of industry in the relatively small Zenica valley reflected on air quality in the city of Zenica. The problem of high air pollution due to emissions of pollutants from industrial sources, traffic, and individual furnaces, burning of environmentally unsuitable fuels containing high sulfur and ash content has been present in the City of Zenica for a long time. In addition, the low wind speed during the year, which ranges up to 1.5 m/s, with unfavorable temperature inversions, causes the concentrations of pollutants in the air to reach alarmingly high values in a short period. In the wider area of the City of Zenica, air quality has been monitored since 1978 in the network of stationary stations. The paper presents results of air quality monitoring which are analyzed at the Institute Kemal Kapetanovic in Zenica for the sampling period from 01.01.2019. to 31.12.2020. years. Air quality monitoring included sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and particulate matter (PM10) at three locations in the wider area of the city of Zenica. In the wider area of the City of Zenica, air quality has been monitored since 1978 in the network of stationary stations. The paper presents the processed results of air quality monitoring which are analyzed at the Institute Kemal Kapetanovic in Zenica for the sampling period from 01.01.2019 to 31.12.2020. The measured concentrations of pollutants in the ambient air indicate that during the heating season, i.e. the winter months, the air quality in the urban and suburban areas of the city of Zenica is very poor. The data show that the highest hourly concentration of sulfur dioxide was recorded in December at the measuring station AMS Tetovo in the amount of 1100.59 µg/m3, which is located in the settlement next to the metallurgical facilities of the industrial zone Zenica.

Landscape diversity of the forest-steppe in the Tyumen Oblast (Russia)

Forest-steppe landscapes are ecotonic systems that are characterized by a high degree of diversity due to the combination of zonal forest and steppe landscapes, as well as swamps and meadows. The research is based on a comprehensive analysis of literary sources, topographic and thematic maps, satellite images, as well as field expeditions of 1997–2020. In the south-western part of the Tyumen Oblast, 12 types of terrain are differentiated on an area of 30,000 km2, including types of terrain of divides, ridges, flat ridges, flat depressions, hillock depressions, terraces, slopes, lakes and swamps, reed swamps, ravines and girders, floodplains of large rivers, small valleys. The main features of the spatial organization of landscapes in the region and the landscape structure at the level of components are characterized. In the conditions of the region, the main part of landscapes is convenient for economic development and used in various sectors of the economy. Meadow and steppe landscapes, and partly forests are plowed. Pastures and hayfields are widespread on the territory. Such economic activities as sand and peat extraction, wood harvesting, recreational nature use, as well as fishing, hunting, and gathering have been developed. Some landscapes are protected by state as nature reserves.

Spin-Valley Qubit Dynamics in Exchange-Coupled Silicon Quantum Dots

The presence of valley states is a significant obstacle to realizing quantum information technologies in Silicon quantum dots, as leakage into alternate valley states can introduce errors into the computation. We use a perturbative analytical approach to study the dynamics of exchange-coupled quantum dots with valley degrees of freedom. We show that if the valley splitting is large and electrons are not properly initialized to valley eigenstates, then time evolution of the system will lead to spin-valley entanglement. Spin-valley entanglement will also occur if the valley splitting is small and electrons are not initialized to the same valley state. Additionally, we show that for small valley splitting, spin-valley entanglement does not affect measurement probabilities of two-qubit systems; however, systems with more qubits will be affected. This means that two-qubit gate fidelities measured in two-qubit systems may miss the effects of valley degrees of freedom. Our work shows how the existence of valleys may adversely affect multiqubit fidelities even when the system temperature is very low.

La scala concavo-convessa nel Cortile del Belvedere: un ‘Danteum’ bramantesco?

The concave-convex staircase located in the exedra at the end of the Belvedere Court has not had the critical fortune that such an original – and problematic – invention would have deserved. On a formal level, the two flights can be schematically associated to a portion of a valley and a hilly formation made of steps. The stair would, therefore, symbolically indicate the shape of the terrain on which the Belvedere is located: the hill with the villa of Pope Innocent VIII on the one side and a “small valley in the middle” (according to Vasari) on the other. The stair could also contain another level of meaning connected to Bramante’s interest in Dante and to his competence as a cosmographer (Sabba Castiglione). The concave flight can be compared to the reconstruction of Dante’s Inferno, represented as an amphitheatre in Antonio Manetti’s version; while the convex section shows a strong similarity with the mountain of Purgatorio. On a planimetric view, the recomposed figure appears as a set of eight concentric circles that correspond to the eight circles of the Paradiso. The staircase would thus embody the specific features of the place where the Belvedere stands, while also creating a connection with Dante’s map of the otherworld.

Spatiotemporal Spectral-Response Assessment of the Forest Cover of Small Dry Valleys in the Central Russian Forest–Steppe

Spatiotemporal Spectral-Response Assessment of the Forest Cover of Small Dry Valleys in the Central Russian Forest–Steppe

Multi-Dimensional Remote Sensing Analysis Documents Beaver-Induced Permafrost Degradation, Seward Peninsula, Alaska

Beavers have established themselves as a key component of low arctic ecosystems over the past several decades. Beavers are widely recognized as ecosystem engineers, but their effects on permafrost-dominated landscapes in the Arctic remain unclear. In this study, we document the occurrence, reconstruct the timing, and highlight the effects of beaver activity on a small creek valley confined by ice-rich permafrost on the Seward Peninsula, Alaska using multi-dimensional remote sensing analysis of satellite (Landsat-8, Sentinel-2, Planet CubeSat, and DigitalGlobe Inc./MAXAR) and unmanned aircraft systems (UAS) imagery. Beaver activity along the study reach of Swan Lake Creek appeared between 2006 and 2011 with the construction of three dams. Between 2011 and 2017, beaver dam numbers increased, with the peak occurring in 2017 (n = 9). Between 2017 and 2019, the number of dams decreased (n = 6), while the average length of the dams increased from 20 to 33 m. Between 4 and 20 August 2019, following a nine-day period of record rainfall (>125 mm), the well-established dam system failed, triggering the formation of a beaver-induced permafrost degradation feature. During the decade of beaver occupation between 2011 and 2021, the creek valley widened from 33 to 180 m (~450% increase) and the length of the stream channel network increased from ~0.6 km to more than 1.9 km (220% increase) as a result of beaver engineering and beaver-induced permafrost degradation. Comparing vegetation (NDVI) and snow (NDSI) derived indices from Sentinel-2 time-series data acquired between 2017 and 2021 for the beaver-induced permafrost degradation feature and a nearby unaffected control site, showed that peak growing season NDVI was lowered by 23% and that it extended the length of the snow-cover period by 19 days following the permafrost disturbance. Our analysis of multi-dimensional remote sensing data highlights several unique aspects of beaver engineering impacts on ice-rich permafrost landscapes. Our detailed reconstruction of the beaver-induced permafrost degradation event may also prove useful for identifying degradation of ice-rich permafrost in optical time-series datasets across regional scales. Future field- and remote sensing-based observations of this site, and others like it, will provide valuable information for the NSF-funded Arctic Beaver Observation Network (A-BON) and the third phase of the NASA Arctic-Boreal Vulnerability Experiment (ABoVE) Field Campaign.

Determining transition reaches between torrents and downstream rivers using a valley morphology index in a mountainous landscape

AbstractDividing rivers into homogeneous reaches is key for river processes and watershed management. In contrast to downstream fluvially dominated rivers, upstream debris‐flow dominated torrents have steeper channel slopes and smaller valley width/depth ratios. Investigating transition reaches between torrents and fluvially dominated rivers, not only explores the structure of the landscape, but also contributes to hazard management. This study proposed a valley morphology index combining two variables, channel slope and valley width/depth ratio, to determine transition reaches between torrents and rivers. The methodology was applied to 41 mountain streams in Taiwan using a Geographic Information System (GIS)‐based topographic analysis. Plots of valley width/depth ratio versus channel slope were used to determine boundary values of the valley morphology index (Iv) separating torrents from rivers. The plots showed that about 80% of the river basins present “L‐shaped” curves, which indicate sharp decreases in slope for upstream sections and dramatic increases of valley width/depth ratio for downstream sections. Results further demonstrated an average value of Iv 0.0047 across the study sites. Spatial comparison between geographic regions indicated that transition reaches in eastern rivers tend to occur lower in the drainage basin due, in part, to higher terrain. Local factors, such as tributary confluences and landslides promote the transition from torrents to fluvially dominated rivers. Satellite images verified that the approach correctly identified transition reaches, suggesting that it may provide a useful reference for river management.

Los restos faunísticos del sitio arqueológico Tembrao (provincia de Río Negro, Argentina)

En este trabajo se presenta el análisis de los materiales faunísticos del sitio Tembrao, ubicado en un pequeño valle al pie de la meseta de Somuncurá (sur de la provincia de Río Negro). Un fechado realizado sobre restos faunísticos ubica la ocupación del lugar en el Holoceno tardío final. El conjunto está conformado principalmente por restos óseos de mamíferos, entre los que predominan los de artiodáctilos. Se propone que los guanacos habrían sido la presa principal de los cazadores recolectores pre-hispánicos, mientras que los restos de ovejas fueron ingresados por las ocupaciones modernas del paraje Tembrao. Se discute la disponibilidad de recursos faunísticos en cercanías del sitio, especialmente de guanacos sobre la meseta de Somuncurá, y las implicancias de la presencia de elementos foráneos (valvas de almejas fluviales y de moluscos marinos, y probablemente cáscaras de huevos de Rhea americana). En base al análisis se infiere un patrón de subsistencia basado en pocas especies, similar al de otras regiones mesetarias de Norpatagonia y claramente diferenciado de aquel del litoral marino y de los valles fluviales.

Using an Artificial Neural Network to improve operational wind prediction in a small unresolved valley

AbstractThis study improves surface wind predictions in an unresolved valley using an artificial neural network (ANN). Forecasting winds in complex terrain with a mesoscale model is challenging. This study assesses the quality of 3-km wind forecasts by the Weather Research and Forecasting (WRF) model and the potential of post-processing by an ANN within the 1-2 km wide Cadarache Valley in southeast France. Operational wind forecasts for 110m above ground level and the near-surface vertical potential temperature gradient with a lead time of 24-48h were used as ANN input. Observed horizontal wind components at 10m within the valley were used as targets during ANN training. We use the Directional ACCuracy (DACC45, wind direction error ≤ 45°) and mean absolute error to evaluate the WRF direct model output and the ANN results. By post-processing, the score for DACC45 improves from 56% in the WRF direct model output to 79% after applying the ANN. Furthermore, the ANN performed well during the day and night, but poorly during the morning and afternoon transitions. The ANN improves the DACC45 at 10m even for poor WRF forecasts (direction bias ≥ 45°) from 42% to 72%. A shorter lead time and finer grid spacing (1 km) showed negligible impact which suggests that a 3 km grid spacing and a 24-48h lead time is effective and relatively cheap to apply. We find that WRF performs well in near-neutral conditions and poorly in other atmospheric stability conditions. The ANN post-treatment consistently improves the wind forecast for all stability classes to a DACC45 of about 80%. The study demonstrates the ability to improve Cadarache valley wind forecasts using an ANN as post-processing for WRF daily forecasts.

The glacier–rock glacier mountain landsystem: an example from North Iceland

ABSTRACT A valley floor rock glacier in Nautárdalur, eastern Tröllaskagi, northern Iceland, has been investigated since the 1970s. Adjacent valleys are also examined as mountain landsystems. The methodology identifies ‘landform elements’ (features evident on slopes) on transects that can be identified and mapped from Google Earth imagery. Transects can be compared to show similarities and differences between slopes and valleys and can be used to trace debris and ice/snow flow paths within landsystems. The paper confirms that a glacier ice core is present throughout the Nautárdalur rock glacier. Traces of glacier activity can be found in some neighbouring small valleys but where rock glaciers are not present. Previous field observations, when coupled to current Google Earth imagery, indicate glacier ice formation and deformation over the past 200 years. The quantities and timing of weathered debris from headwall cliffs were sufficient to partly cover small glaciers, thus forming rock glaciers in some, but not all, valleys. The landsystem and transect approach thus indicate glacier origins for the rock glaciers identified. No evidence for ‘permafrost creep’ in scree slopes that might produce valley-side rock glaciers has been found.

Influence of ecological and anthropogenic factors on soil transformation in recreational areas of Volgograd (Russia)

In this paper, we studied the soils of recreational areas of Volgograd within three research areas. The survey found that in research area I the soils spatial distribution is mainly represented by the following soil group according to WRB: Urbic Technosols, Urbic Technosols (Mollic) and Gleyic Terric Phaeozem (Mollic, Prototechnic). Buried soils are represented by Gleic Cambisols (Protocalcic). In research area II, among natural soils, the largest areas are occupied by Calcaric Fluvisols (Loamic, Technic, Protovertic), Calcaric Fluvisols (Arenic, Salic), and Gleyic Calcisols (Sodic, Protocalcic, Technic, Salic). The anthropogenic-transformed soils include Urbic Technosols, and Ekranic Technosols are under buildings and road surfaces. In research area III, the natural soils spatial distribution is homogeneous and mainly represented by Gleyic Cambic Calcisols (Protocalcic), Gleyic Cambisols (Protocalcic, Prototechnic), and Calcaric Colluvic Regosols (Arenic, Prototechnic) in the bottoms of small flat-bottom valleys. In irrigation sites occur Urbic Technosols, and on hiking trails – Gleyic Cambisols (Prototechnic). Despite the presence of reclaimed horizons with a high content of phosphorus in the soils (average concentration of 82 mg kg−1), none of the profiles revealed Hortic horizon, but only some of its properties (colour, horizon thickness, zoogenic activity). The thickness of urbic-stratifying layer (Au) varies in a wide range from 10 to 135 cm, and the thickness of reclaimed horizons (A) also varies from 10 to 48 cm. The bulk density in Au horizons is 1.4 g cm−3, in the reclaimed horizons (A) – 1.39 g cm−3. The content of soil carbon in soil surface horizons varies from 0.85% to 4.58% in urbic horizons, and to 1.49% in reclaimed horizons. Chemical analysis of urbic (Au) and reclaimed (A) horizons revealed a low content of easily soluble salts (0.16%) and carbonates (1.5% and 1.7%, respectively).

Natural and Geomorphological Response of the Small Lowland River Valley for Anthropogenic Transformation

The regulation of small rivers and the consequent maintenance works are common in the Central European Lowlands. This article attempts to determine the relationship between the invertebrate fauna (and consequently the biocenosis) of the small lowland river valley and its landforms (morphodynamics) under the conditions of very large and rapid changes caused by river regulation and maintenance. On this basis, an attempt to analyze the response of the ecosystem to rapid transformations associated with engineering works was made. The study covered Kraska, a small river typical for Polish Lowlands, which has been regulated along almost the entire length. The results showed that, in the regulated sections, where the natural forms of the relief were destroyed, there were significantly fewer taxa and significantly smaller numbers of the specimen. Despite the clear negative impact of the regulatory work on the ecosystem, the river in some sections showed the ability to spontaneously restore certain geomorphic features.

Detection of aqueous alteration minerals in Martian open and closed paleolake basins

Candidate closed- and open-basin lakes have been widely observed on the Martian surface. Many of them show the presence of exposed sediments of possible lacustrine origin. Understanding the mineralogy of these structures provide insights on the nature of processes that originated and shaped their interior and on the role of liquid water on Mars. Spectral data obtained from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) have been so far analyzed with particular attention to the possible detection of aqueous alteration minerals. In this work, we mapped 16 closed-basins and 39 open-basins, not present in the past published Martian basins maps. We looked for recent CRISM observations of these and other previously mapped open- and closed-basin lakes. We further confirmed the presence of water alteration minerals in two previously analyzed structures and discovered other deposits of such minerals in two of the newly mapped sites. Light-toned bedrock exposures that show the presence of hydrated minerals (such as Fe/Mg smectites) along with unaltered mafic material (olivine) have been observed. Based on our observations and the comparison with the literature, it can be deduced that the observed deposits are most probably of lacustrine origin. Furthermore, the location of these deposits of altered minerals suggests that, at least in one case (where altered material has been detected on the floor of the outlet valley), the observed minerals have likely been transported within the lacustrine deposits rather than altered in situ. To the best of our knowledge, this is the first time that this occurrence has been observed and it is an indication of presence of such kind of minerals even in small valleys.

Evolution of the Białka valley Pleistocene moraine complex in the High Tatra Mountains

Pleistocene moraine complexes with glacial deposits well beyond the last glacial maximum (LGM) limit are rarely formed and preserved in the face of small valley glaciers due to topographic, tectonic, and glacier-size-specific factors. Here, we show the results of detailed mapping of the Pleistocene terminal moraines in the Białka Valley (High Tatra Mountains, Western Carpathians) formed by a 13 km long valley glacier. To portray post-depositional denudation process in the moraines, we mapped the size distribution of moraine boulders and measured their weathering index using the Schmidt Hammer test. In the moraine complex, three morphological units were distinguished from the younger (inner) to the oldest (outermost): Łysa Polana (ŁP), Rusinowa Polana (RP), and Hurkotne (H). The ŁP unit (LGM) features hummocky moraine relief which does not occur on the two older units. In contrast, surface boulders occur on the ŁP and RP units, but they have been cleared from the oldest H unit due to long-lasting erosion. Consequently, the most weathered boulders occurred in the intermediate age RP moraine (~MIS 6). Our results show that in Central Europe, the persistence of surface granite boulders in the landscape cannot be much longer than that of the penultimate glaciation, which highlights the problem of exposure age dating of old moraines in this area. Both pre-LGM glaciations extended ca. 1 km beyond the LGM moraines, but in the case of the H glaciation, this length reduction (7%) was accompanied by a 220 m valley incision at the glacier front. Therefore, the Białka valley glacier was able to achieve a self-limiting effect even in an area of considerable tectonic uplift. We suggest that vigorous, wet-based glacier erosion occurred in areas with high rates of ice accumulation and mass turnover in the windward NW part of the High Tatras exposed to orographic induced precipitation.

The role of landslides in the evolution of a small mountain river valley (Polish Carpathians)

The role of landslides in the evolution of a small mountain river valley (Polish Carpathians)

Assessing hillslope sediment generation potential by tree throw: a preliminary field study along a small river valley in the Jura Mountains, northwest Switzerland

Abstract. A preliminary field-based investigation was undertaken in a small (< 10 km2) river valley located in the mountainous Jura region of northwest Switzerland. The aims of the work were to assess sediment generation and annual sediment transport rates by tree throw on forested hillslopes and to document surface hydrology characteristics on four fresh tree throw mounds associated with recent tree throws over a 24 d monitoring period. For the tree throw mounds, average sediment recovery ranged from 7.7–28.2 g (dry weight), equivalent to a suspended sediment concentration of 145.2–327.8 g L−1, and runoff coefficients ranged from 1.0 %–4.2 %. Based on a soil bulk density value of 1044 kg m−3, upslope runoff generation areas were denuded by an average of 0.14 mm within the 24 d monitoring period, representing an erosion rate equivalent to 2.1 mm a−1. This means that a ca. 50 cm high tree throw mound could theoretically persist for around 200–250 years. For tree throw work, the dimensions of 215 fallen trees were measured and their locations mapped in 12 separate locations where tree throw was prominent along the river valley, representing a cumulative area equivalent to 5.3 ha (average density equivalent to 43 trees ha−1). The 215 tree throws generated a total of 20.1 m3 of fine sediment (< 2 mm dia.), or the equivalent of 3.8×10-4 m3 m−2. The process of tree throw was originally attributed to two extreme weather events that occurred across west and central Europe in late December 1999. Taking the 18-year period since both storms, this represents an annual sediment transport rate of 2.7×10-5 m3 m−1 a−1. Exploring the relationship with wind on fall direction, however, 65.5 % of mapped tree throws (n= 143) generally fell in a downslope direction irrespective of hillslope aspect on which they were located. Given the similar fall orientation for most trees, this infers that severe storms may not have been responsible for the majority of tree throws, but instead, their upheave might be related to root failure. Given the relative maturity (average age 41 years) of fallen trees in this river valley, our data suggest that once trees attain a certain age, their physiognomy (i.e. height, mass, and centre of gravity) compromises their ability to remain securely anchored. We tentatively attribute this possibility to the presence of bedrock close to the surface, and to the shallow soil profile overlaying the steep rocky slopes. More in-depth studies are required to firstly confirm our findings, and secondly, tree throw studies should be undertaken in other Jura mountain river valleys to assess whether these results are representative.

Quantification of Differential Response of Tumour and Normal Cells to Microbeam Radiation in the Absence of FLASH Effects.

Simple SummaryThis study compares the capabilities of normal and tumour cells to divide after receiving spatially fractionated radiotherapy. For this treatment, a minority of cells (here ∼20%) receive very large, peak doses, whereas the remaining cells are spared and receive only a small valley dose. We show that tumour and normal cells respond differently to this treatment, and that spatially fractionated radiotherapy may have a greater effect on tumour than normal cells. Our work was conducted using laboratory equipment, rather than specialized synchrotron facilities implying that the observed response is present at conventional dose rates and hence purely an effect of the spatial fractionation of the treatment.Microbeam radiotherapy (MRT) is a preclinical method of delivering spatially-fractionated radiotherapy aiming to improve the therapeutic window between normal tissue complication and tumour control. Previously, MRT was limited to ultra-high dose rate synchrotron facilities. The aim of this study was to investigate in vitro effects of MRT on tumour and normal cells at conventional dose rates produced by a bench-top X-ray source. Two normal and two tumour cell lines were exposed to homogeneous broad beam (BB) radiation, MRT, or were separately irradiated with peak or valley doses before being mixed. Clonogenic survival was assessed and compared to BB-estimated surviving fractions calculated by the linear-quadratic (LQ)-model. All cell lines showed similar BB sensitivity. BB LQ-model predictions exceeded the survival of cell lines following MRT or mixed beam irradiation. This effect was stronger in tumour compared to normal cell lines. Dose mixing experiments could reproduce MRT survival. We observed a differential response of tumour and normal cells to spatially fractionated irradiations in vitro, indicating increased tumour cell sensitivity. Importantly, this was observed at dose rates precluding the presence of FLASH effects. The LQ-model did not predict cell survival when the cell population received split irradiation doses, indicating that factors other than local dose influenced survival after irradiation.

GEOLOGIA DE SUPERFÍCIE E ASPECTOS ESTRUTURAIS DA REGIÃO DE RIO TINTO, FAIXA COSTEIRA DA BACIA DA PARAÍBA

Este trabalho apresenta o mapeamento geológico na escala 1:50.000, da região de Rio Tinto, que está localizada na faixa costeira da Bacia da Paraíba, Sub-bacia Miriri. O estudo foi realizado com o apoio de interpretação de imagens de satélite, perfis litológicos de poços, análise de lâminas petrográficas e de padrões geomorfológicos. O embasamento aflora em aproximadamente 10% da área de estudo e é representado por granitóides neoproterozóicos. Cerca de 90% da área é coberta por depósitos Miocênicos-Pleistocênicos e Quaternários das unidades Barreiras, Pós-Barreiras e depósitos litorâneos, de Mangue, terraços Pleistocênicos e sedimentos Elúvio-Coluviais. A análise dos dados cartográficos e de imagens de radar mostrou que a região possui um relevo dominado por tabuleiros e vales formados pela reativação Quaternária do arcabouço estrutural da faixa costeira da bacia. O Rio Mamanguape está inserido na falha homônima com direção ENE-WSW, e a drenagem secundária está encaixada em falhas que possuem direções ENE-WSW, NW-SE e N-S. Os dados dos perfis de poços evidenciaram a ocorrência de grabens e horsts formados pela estruturação tardia da faixa costeira da bacia.

Disastrous Flash Floods Triggered by Moderate to Minor Rainfall Events. Recent Cases in Coastal Benguela (Angola)

The present work focuses on two recent flash floods in coastal Benguela (Angola), both triggered by moderate rainfall but which had disastrous consequences for local populations (namely 71 deaths in 2015 and 17 in 2019). The research involved a regional survey to establish the effects of these floods combined with a geomorphological and socio-economic analysis of the most affected areas to understand the main forcing factors. The two flash floods produced major damage in restricted sectors within very small coastal catchments (<16 km2). The prevalence of fine-grained sedimentary rocks, relatively steep hills, thin soil cover, and vegetation scarcity are natural factors that promote surface runoff. However, socio-economic conditions are most likely the main reasons of flood damage. Namely, rapid population growth with poor planning and making use of low-quality construction materials, the high waste yields that are not properly managed and the absence of flood risk awareness. In the small valleys around the fast-growing cities of coastal Benguela, hazardous flash floods occur recurrently, even after moderate precipitation. Most affected areas are determined by local conditions that compromise drainage at the time of the rainfall event, being very difficult to predict.

Dosing Time Optimization of Enalapril and Propranolol through Inclusion of the Circadian Rhythm in Pharmacokinetic‐Pharmacodynamic Modeling

Arterial hypertension is the modifiable risk factor that most affects mortality in the world. The diagnostic criteria and therapeutic objectives are based on average blood pressure (BP) values. However, BP shows a circadian variation, with an increase during the morning, a small postprandial valley, and a deeper night decrease. Several studies have shown that evening dosing of antihypertensive drugs significantly reduces BP during the night rest and even decreases the cardiovascular risk in the long-term compared to awakening dose. It has been suggested that the variation in the effect of enalapril and propranolol is due to circadian variations in the pharmacokinetics processes and therapeutic target. Pharmacokinetics (PK) - pharmacodynamics (PD) models of antihypertensive drugs have been developed to understand daytime effect changes. However, only the circadian variation in BP has been included and not the relevant pharmacokinetic variations. Furthermore, an algorithm able to find the optimal dosing time for a given starting BP circadian variation profile has not been proposed so far. This work proposes the inclusion of the circadian rhythm in the development of PK-PD models for enalapril and propranolol to evaluate and optimize the chronotherapy of arterial hypertension. To do this, a PK-PD model that includes the circadian rhythm was developed using data from published works. The parameters of the PK-PD models were estimated using a global optimization algorithm and, to assess the relevance of each parameter on the variables, sensitivity and identifiability analyses were performed. Subsequently, an optimization algorithm was created to propose an optimal dosing time. The most sensitive parameters were those related to the circadian rhythm. Optimization of the dosing time by maximizing the effect (total sum of BP reduction over 24 hrs.) indicates that the optimal time of administration is approximately 6:30 am for enalapril (~15% reduction) and 6:00 am for propranolol. However, maximizing the nocturnal fall resulted at 8:00 pm for enalapril (~27% reduction). By comparing the results obtained with the antecedents above, it can be noted that maximizing the effect does not necessarily imply a better therapeutic outcome. Since administration at bedtime has shown to reduce cardiovascular risk, which is consistent with maximizing the dipper percentage in this case. Finally, these analyses were performed using the reported data, which correspond to dipper patterns; however, the optimized times could change depending on the blood pressure profile of each patient.