Delta Valley Research Articles

Some Consequences of the Valley Delta Conjectures

AbstractHaglund et al. (Trans Am Math Soc 370(6):4029–4057, 2018) introduced their Delta conjectures, which give two different combinatorial interpretations of the symmetric function $$\Delta '_{e_{n-k-1}} e_n$$ Δ e n - k - 1 ′ e n in terms of rise-decorated or valley-decorated labelled Dyck paths. While the rise version has been recently proved (D’Adderio and Mellit in Adv Math 402:108342, 2022; Blasiak et al. in A Proof of the Extended Delta Conjecture, arXiv:2102.08815, 2021), not much is known about the valley version. In this work, we prove the Schröder case of the valley Delta conjecture, the Schröder case of its square version (Iraci and Wyngaerd in Ann Combin 25(1):195–227, 2021), and the Catalan case of its extended version (Qiu and Wilson in J Combin Theory Ser A 175:105271, 2020). Furthermore, assuming the symmetry of (a refinement of) the combinatorial side of the extended valley Delta conjecture, we deduce also the Catalan case of its square version (Iraci and Wyngaerd 2021).

Pushing our way from the valley Delta to the generalised valley Delta

In [Haglund, Remmel, Wilson 2018] the authors state two versions of the so called Delta conjecture, the rise version and the valley version. Of the former, they also give a more general statement in which zero labels are also allowed. In [Qiu, Wilson 2020], the corresponding generalisation of the valley version is also formulated. In [D'Adderio, Iraci, Vanden Wyngaerd 2020], the authors use a pushing algorithm to prove the generalised version of the shuffle theorem. An extension of that argument is used in [Iraci, Vanden Wyngaerd 2020] to formulate a valley version of the (generalised) Delta square conjecture, and to suggest a symmetric function identity later stated and proved in [D'Adderio, Romero 2020]. In this paper, we use the pushing algorithm together with the aforementioned symmetric function identity in order to prove that the valley version of the Delta conjecture implies the valley version of the generalised Delta conjecture, which means that they are actually equivalent. Combining this with the results in [Iraci, Vanden Wyngaerd 2020], we prove that the valley version of the Delta conjecture also implies the corresponding generalised Delta square conjecture.

A cross sectional study of the risk factors of hepatitis C infection in North Egypt.

Hepatitis C is a viral infection that has been declared as a global health problem by the World Health Organization. Egypt has the highest prevalence of hepatitis C virus (HCV) which results in a high morbidity and mortality from chronic liver disease, cirrhosis, and even hepatocellular carcinoma. Cities have lower rates of infection than rural areas. Studies about the abnormally high prevalence of HCV in Egypt ascribed that to the governmental campaign to treat Schistosoma. However, these treatment campaigns have stopped more than 35years ago, which means that some other modes of transmission must have been involved. The objective of this work is to study the main reasons of HCV prevalence in the Egyptian Delta valley. A questionnaire-based study was conducted by members of the HCV Fighters project. Responses were collected from 949 volunteers (451 HCV patients and 498 healthy volunteers as control). The data were analyzed using SPSS version 19.0. The two-sample proportion test was used for statistical comparison between groups. The most probable risk factors of HCV transmission in Egypt included regular visits to dental clinics (55.2%), previous surgical operations (54.4%), former blood transfusion (52%), intrafamilial HCV infection (45.9%) and history of bilharzial infection (44.3%). Increasing public awareness about modes of transmission and risk factors of HCV infection is a must, especially within family members of HCV patients. Strict commitment to proper medical care precautions by health care practitioners is required.

Native earthworm population dominance after seven years of tillage, burning, and residue level management in a wheat-soybean, double-crop system

Earthworm density is often reduced in low organic matter soils that are intensively managed for row-crop production, but earthworms can serve as a sensitive bioindicator of response to residue management. This study relates earthworm density and community composition to residue management after seven years of consistent management practices in a wheat (Triticum aestivum L.)-soybean (Glycine max (L.) Merr.), double-crop system in the Lower Mississippi River Valley delta region of eastern Arkansas. Residue management practices included conventional tillage (CT) and no-tillage (NT), N fertilization to produce HIGH and LOW wheat residue levels, and BURN compared to unburned (NO BURN) wheat residue remaining on the soil surface. Total mean earthworm densities ranged from 271 to 508m−2 in the top 20cm across treatments. Both exotic Aporrectodea trapezoides (Dugès) and native Diplocardia sylvicola Gates adult earthworms were present with little difference in diversity among sampled communities; however, more than 65% of adults were D. sylvicola in all treatments. Native, total, or juvenile earthworm densities in different treatment combinations were correlated to different soil properties, including pH, electrical conductivity, and Mehlich-III-K, Ca Mg, S, Cu, and Mn concentrations. Residue level and burning influenced total, juvenile, and native earthworm densities differently in CT and NT. Tillage presumably influenced earthworm density through effects of residue placement at the surface (NT) or within the soil profile (CT). Earthworm densities were greatest in the BURN-HIGH treatment combination under NT, which contrasted with greatest densities in the NO BURN-HIGH which did not differ from the BURN-LOW treatment under CT. Native earthworms predominated with a common exotic species in a wheat-soybean double-crop system in Arkansas where earthworm densities were dependent on the interaction of tillage with burning and fertilization to influence wheat residue amount. Differences in earthworm abundances may serve as a bioindicator of long-term sustainability of common residue management practices in the highly agriculturally productive delta region in the Lower Mississippi River Valley.

Evaluating carbon storage on subalpine lake deltas

AbstractMountainous regions are important contributors to the terrestrial organic carbon (OC) sink that affect global climate through the regulation of carbon‐based greenhouse gases. However, mountain OC dynamics are poorly quantified. We quantified OC storage in subalpine lake deltas in the Washington Central Cascades and Colorado Front Range with the objectives of determining the magnitude of transient carbon storage and understanding the differences in storage between the two ranges. We used field, laboratory, and GIS techniques to determine the magnitude of and controls on the subalpine lake delta OC pool in 26 subalpine lake deltas. Soil moisture, soil texture, mean basin slope, and delta valley confinement are significantly correlated with soil carbon on deltas. Average soil OC concentration on subalpine lake deltas ranges from 3 to 41%, and stocks range from 140 to 1256 Mg C/ha. Surprisingly, the carbon content of subalpine lake deltas is not significantly different between the two regions, despite stark contrasts in their climate, vegetation, and total ecosystem carbon stocks. We present a conceptual model that invokes geomorphic and biogeochemical processes to suggest that carbon is more likely to reach subalpine lake deltas from the upstream basin in the Colorado Front Range compared with the Washington Central Cascades, thus accounting for the similarity in OC storage between the two regions despite differences in total ecosystem carbon stocks and climate. This points to a complex interaction among carbon production, transport, and stability in each region, and supports the idea that geomorphic and biogeochemical processes determine the magnitude of transient OC storage more strongly than primary productivity or climate. Copyright © 2017 John Wiley & Sons, Ltd.

Épidémiologie des bilharzioses humaines en Mauritanie. L’exemple de la rive droite du fleuve Sénégal

A study was performed to determine the transmission and prevalence of human schistosomiasis in the Mauritanian side of the Senegal River basin. Parasitological investigations by Kato-Katz and urine filtration conducted on 1,259 school children indicated a mean prevalence of S. haematobium--29.0%, 25.9% and 34.3%, respectively, in the children of the lower, middle and high valley. Only the school children of the lower delta valley were infected by S. mansoni with a mean prevalence rate of 21.5%. The malacological investigations carried out in the water points of each visited village highlighted the presence of B. pfeifferi, B. senegalensis, B. globosus, B. umbilicatus, B. truncatus and B. forskalii. The last three species are announced for the first time in the Mauritanian side of the Senegal River. The laboratory snail infection experiments indicate that B. senegalensis and B. globosus are the most important intermediate hosts for S. haematobium in the Mauritanian side of the Senegal River basin. However, an incompatibility between the oasis strains of S. haematobium and the snails of the lower valley was noted. In the middle valley and high valley, the infection of the school children takes place during the rainy season, because of the creation of the temporary water points, in the lower valley; the transmission seems to be continuous.

Isotopic Composition and Origin of Indigenous Natural Perchlorate and Co-Occurring Nitrate in the Southwestern United States

Perchlorate (ClO(4)(-)) has been detected widely in groundwater and soils of the southwestern United States. Much of this ClO(4)(-) appears to be natural, and it may have accumulated largely through wet and dry atmospheric deposition. This study evaluates the isotopic composition of natural ClO(4)(-) indigenous to the southwestern U.S. Stable isotope ratios were measured in ClO(4)(-) (delta(18)O, Delta(17)O, delta(37)Cl) and associated NO(3)(-) (delta(18)O, Delta(17)O, delta(15)N) in groundwater from the southern High Plains (SHP) of Texas and New Mexico and the Middle Rio Grande Basin (MRGB) in New Mexico, from unsaturated subsoil in the SHP, and from NO(3)(-)-rich surface caliche deposits near Death Valley, California. The data indicate natural ClO(4)(-) in the southwestern U.S. has a wide range of isotopic compositions that are distinct from those reported previously for natural ClO(4)(-) from the Atacama Desert of Chile as well as all known synthetic ClO(4)(-). ClO(4)(-) in Death Valley caliche has a range of high Delta(17)O values (+8.6 to +18.4 per thousand), overlapping and extending the Atacama range, indicating at least partial atmospheric formation via reaction with ozone (O(3)). However, the Death Valley delta(37)Cl values (-3.1 to -0.8 per thousand) and delta(18)O values (+2.9 to +26.1 per thousand) are higher than those of Atacama ClO(4)(-). In contrast, ClO(4)(-) from western Texas and New Mexico has much lower Delta(17)O (+0.3 to +1.3 per thousand), with relatively high delta(37)Cl (+3.4 to +5.1 per thousand) and delta(18)O (+0.5 to +4.8 per thousand), indicating either that this material was not primarily generated with O(3) as a reactant or that the ClO(4)(-) was affected by postdepositional O isotope exchange. High Delta(17)O values in ClO(4)(-) (Atacama and Death Valley) are associated with high Delta(17)O values in NO(3)(-), indicating that both compounds preserve characteristics of O(3)-related atmospheric production in hyper-arid settings, whereas both compounds have low Delta(17)O values in less arid settings. Although Delta(17)O variations in terrestrial NO(3)(-) can be attributed to mixing of atmospheric (high Delta(17)O) and biogenic (low Delta(17)O) NO(3)(-), variations in Delta(17)O of terrestrial ClO(4)(-) are not readily explained in the same way. This study provides important new constraints for identifying natural sources of ClO(4)(-) in different environments by multicomponent isotopic characteristics, while presenting the possibilities of divergent ClO(4)(-) formation mechanisms and(or) ClO(4)(-) isotopic exchange in biologically active environments.

Contaminated fish consumption in California’s Central Valley Delta

Extensive mercury contamination and angler selection of the most contaminated fish species coincide in California's Central Valley. This has led to a policy conundrum: how to balance the economic and cultural impact of advising subsistence anglers to eat less fish with the economic cost of reducing the mercury concentrations in fish? State agencies with regulatory and other jurisdictional authority lack sufficient data and have no consistent approach to this problem. The present study focused on a critical and contentious region in California's Central Valley (the Sacramento-San Joaquin Rivers Delta) where mercury concentrations in fish and subsistence fishing rates are both high. Anglers and community members were surveyed for their fish preferences, rates of consumption, the ways that they receive health information, and basic demographic information. The rates of fish consumption for certain ethnicities were higher than the rates used by state agencies for planning pollution remediation. A broad range of ethnic groups were involved in catching and eating fish. The majority of anglers reported catching fish in order to feed to their families, including children and women of child-bearing age. There were varied preferences for receiving health information and no correlation between knowledge of fish contamination and rates of consumption. Calculated rates of mercury intake by subsistence anglers were well above the EPA reference dose. The findings here support a comprehensive policy strategy of involvement of the diverse communities in decision-making about education and clean-up and an official recognition of subsistence fishers in the region.

Isostatic response and geomorphological evolution of the Nile valley during the Messinian salinity crisis

Abstract During the Messinian salinity crisis (5.96–5.33 Ma), the Mediterranean Sea was disconnected from the Atlantic Ocean. As a consequence, a dramatic sea-level fall occurred during part of the crisis and deep erosion has been observed on the Mediterranean margins as well as on the continent. Here, we demonstrate that the erosion and the large sea-level fall generated a significant uplift along the Nile River delta valley, due to isostatic rebound. Based on a quantitative analysis, our results suggest that the uplift of the Egyptian margin and of the Nile valley flanks may have triggered an enclosed environment during the Messinian salinity crisis (MSC). We estimated a mean rate of regressive erosion of −2.5 m/y along the River Nile during the MSC and of 1.25 and 0.4 m/y for the smaller rivers. The water discharge of the River Nile necessary to trigger this erosion rate was at least 5 to 25 times superior than the water discharge of the smaller one’s.

Summer mistral at the exit of the Rhône valley

The paper examines the three-dimensional structure and dynamics of the mistral at the Rhône valley exit on 28 June 2001. The mistral refers to a severe wind that develops along the Rhône valley in southern France. This summer mistral event was documented in the framework of the ESCOMPTE field experiment. The dynamical processes driving the circulation of the mistral in the Rhône valley and particularly wake formation and planetary boundary layer (PBL) inhomogeneity at the scale of Rhône valley delta are investigated. Several important data sources are used (airborne Doppler lidar, radiosondes and surface stations) as well as non-hydrostatic mesoscale simulations. This paper analyses experimentally, numerically and theoretically the mechanism of wake formation. It shows that the flow impinging on the Alpine range and the Massif Central becomes supercritical all along the ridge line, including the Rhône valley and continues to accelerate in the lee regions until a hydraulic jump occurs. It leads to the formation of wakes behind and close to the mountain peaks. Compared to the Massif Central wake, the origin of the western Alps wake is rather complicated. In this study, the observations and simulations suggest a combined wall separation/gravity wave breaking mechanism to explain the western Alps wake. Indeed, it is shown that in addition to the flow descending the western Alps slopes and experiencing a strong hydraulic jump, the point where the mistral flow separates from the eastern flank of the Rhône valley located at about 44°N is associated with a ‘flank-shock’ which is an oblique hydraulic jump (i.e. the downstream Froude number is supercritical). Wake formation in the lee of the Alps and the Massif Central causes large inhomogeneity of the PBL with differences between land and sea. In the Massif Central and western Alps wakes, the continental PBL is deeper (1.8 km) than in the mistral flow (1 km), which is consistent with a subcritical regime associated with enhanced turbulent mixing. The supercritical air flow, descending the Massif Central and Alps slopes and transitioning to subcritical flow, increases the near-surface air temperature due to the föhn effect. Over the Mediterranean, the surface heat fluxes are slightly negative (between −50 and 0 W m−2) and the main source of PBL turbulence is mechanical (wind shear). The PBL depth within the mistral flow does not vary over land (1 km), whereas the absence of convection but also of strong winds prevent PBL development over the sea in the wakes of the Massif Central and the Alps (PBL depth of about 0.5 km). Copyright © 2005 Royal Meteorological Society

Hydraulic Modelling of Suspended Sediment Deposition in an Inundated Floodplain of the Nemunas Delta

Floods of meadows in the delta of the river Nemunas contribute to the deposition and retention of sediments and nutrient that would otherwise deposit in the Curonian Lagoon. In grassland area of the Nemunas delta the formation of alluvial soil occurs according to the flood dynamic rules: water discharging into the valley leaves suspended sediments on the soil surface. By mathematical modelling it was established that about 35% of suspended sediments inflow deposited there. Due to sand particles deposited during the study period (1950-1991), the natural river bank levee rose by 0.3 m. Fine clay and silt particles deposited uniformly within the entire model area and formed a 4-6 mm thick layer there. It contained about 50-60 t/ha of silt deposits. The valley soils were naturally fertilized with 250 t of potassium, 950 t of phosphorus, 38,000 t of calcium, and even 147,000 t of organic matter saturated with nitrogen. Certain amount of heavy metals also deposited there. The deposition process has not yet been adequately investigated under the conditions of flow bed covered by grass. It was established that grass cover intensified the sediment deposition in the floodplain. Considering calculation results and measurement data, the process of suspended sediment deposition was analysed and new formulas were derived. It was established that in order to increase sedimentation in the valley, it would be necessary to increase water discharge overflowing from river bed into the delta valley.

Limnologic Analysis of Gusev Crater Paleolake, Mars

The survey of the hydrogeologic system formed by Gusev crater and Ma'adim Vallis (Aeolis subquadrangle of Mars) points out evidence for the existence of an ice-covered lake in Gusev crater. A first lake was formed by the drainage of the aquifer in the region surrounding Gusev before the entry of Ma'adim Vallis in the crater. The existence of a former lake in Gusev is deduced from the morphology of the Ma'adim delta. Its comparison with terrestrial Antarctic analogs argues for the presence of an ice-covered lake in Gusev at the time that the southern part of the crater's rampart was breached by Ma'adim first release, and for a subice–lacustrine construction of the valley's delta. Our survey shows that Ma'adim Vallis may have entered Gusev crater as late as Late Hesperian/Early Amazonian as part of a second lake episode. The relationship between the variation of the Gusev lake water-level, the volume of the lake, and the surface of the lake bed is established by our bathymetric model. The elevation of the former lake is deduced from the elevation of the mesa-like structures in the delta of Ma'adim Vallis. Furthermore, the correlation of the crater frequency of Gusev rampart with Mars' stratigraphic age shows that lakes may have occupied Gusev crater over a period of time covering 2 Gyrs., from the formation of the crater to the last episode of water release from Ma'adim Vallis. Though it is most likely that the lake was episodical, the recurrence of abundant water in Gusev crater makes this site a high priority for missions, either for martian resource exploration, or for the search of life.

Subglacial Preservation of Valley Morphology at Amundsenisen, Western Dronning Maud Land, Antarctica

On the high altitude polar plateau of Amundsenisen, western Dronning Maud Land, East Antarctica, a subglacial valley, with a broad horizontal valley floor interpreted as a sediment floodplain or valley delta, was studied by radio echo sounding. In addition, a small, probably glacial, valley was mapped within the same subglacial massif. Basal ice temperatures were calculated using field data on precipitation, air temperature and ice sheet thickness. Discoveries of old landforms which have been preserved more or less intact beneath the former Fennoscandian and Laurentide ice sheets have received increasing attention during the last decade. The aim of this study is to investigate whether preservation of landforms occurs under the East Antarctic Ice Sheet, and to discuss under that climatological and glaciological circumstances preservation may take place. The results show that the ice sheet covering the investigated localities is frozen to bed, and therefore has an insignificant erosional capability. The observations suggest that a large-scale subglacial sediment deposit and a small valley formed by glacial erosion have survived beneath a cold-based ice sheet marginal zone for a long time period. The process of glacial preservation, recognized for bedrock features and tentatively observed for sediment accumulations, should act on similar large-scale landforms under any cold-based ice sheet, present or past. On the basis of existing studies of the age and stability of the East Antarctic Ice Sheet, a Middle Pliocene age is suggested for the preserved landforms. The presence of the presumed sediment-filled valley further indicates that no prolonged periods of basal melting have occurred at the Amundsenisen study area during the ice sheet history, which includes the Quaternary glaciation periods. Finally, calculations of basal temperature for localities at different altitudes within the same subglacial massif were used to demonstrate local altitudinal control of glacial preservation. © 1997 by John Wiley & Sons, Ltd.

Periodic recurrence of gangrenous dermatitis associated with Clostridium septicum in a broiler chicken operation.

The association of gangrenous dermatitis (GD) of chickens with Clostridium septicum infection was well documented in the United States during the 1960s (Bickford AA: 1971, Proc 20th Western Poult Dis Conf, pp. 6, 7). At about the same time, GD was recognized as a source of considerable economic loss to broiler production operations in the United Kingdom and Australia. 1,3 Subsequently, the potentiating role of immunosuppression induced by infectious bursal disease virus (IBDV) and other viral agents was recognized. Reduction of losses caused by GD requires control procedures for IBDV and other immunosuppressive agents. Recent reports have suggested that there may be an increased incidence of the clostridial diseases of chickens in the United States. Among these diseases, GD associated with C. septicum is a major concern. At the California Veterinary Diagnostic Laboratory System (CVDLS), Turlock Branch, the diagnosis of this disease was once as frequent as 5% of all diagnostic cases (Bristow DL: 1971, Proc 20th Western Poult Dis Conf, p. 11). After producers implemented procedures to limit the effects of IBDV, the diagnosis of GD became a rare event in California. This report documents an unusual annual recurrence of C. septicum-associated GD over 3 consecutive years in a single house of a multiple-house broiler facility. The ranch involved in this report is situated on flat delta valley terrain and consists of 8 broiler houses. The houses are similar in design but differ in size. Three houses are 10,000 sq ft, 3 are 15,000 sq ft, and 2 are 17,500 sq ft. Feed sources, feed delivery systems, ventilation systems, and litter management procedures are uniform on the ranch. A single well serves as the water source for all houses, and hot-water brooding is practiced in all houses. The ranch is operated on a year-round all-in, all-out basis. On February 3, 1993, 7 dead 43-day-old broiler chickens were submitted from house 5 (15,000 sq ft) to CVDLS, Turlock Branch, for necropsy. Mortality in the house had increased suddenly to about 1% per day. Stocking density in all three 15,000-sq-ft buildings had been 19,000 chicks at placement. This density is approximately 8.5% higher than normal for these houses. Climatic conditions were normal for winter with characteristically high humidities and cool temperatures. Litter conditions in the house were described as old and wet. On January 18, 1994, a similar group of 6 dead broiler chickens was submitted from house 5. A sudden increase in mortality had occurred in this house only. The birds were