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Roadside ditches line more than 6.3 million km of roadways in the USA, dissecting the natural topography and altering the flow of runoff from the catchments that drain into them. In agricultural regions, more than 30% of a watershed may directly drain into the roadside ditch system. Quantifying soil erosion and sediment export from agricultural watersheds is a crucial component when considering long-term soil sustainability. Our study evaluated the relation of catchment soil erosion and ditch sedimentation at six representative roadside ditches in Lime Creek watershed (eastern Iowa) and quantified the effectiveness of possible catchment conservation practices to reduce soil erosion and ditch sedimentation. Study results provide clear evidence linking roadside ditches to the agricultural catchments that drain into them. Among the six ditch sites, catchment erosion was found to be inversely related to sediment storage within the ditch due to erosive power of water entering the ditches from their basins. Of four catchment scenarios to reduce soil erosion, no-till with cover and graded terrace did not require land to be taken out of production and provided the most significant reductions in catchment erosion rates. Results indicated that reducing nutrient and sediment loads to ditches by incorporating in-field conservation practices in ditch catchments may be more economical and environmentally sustainable than current management practices for both farmers and roadway managers because they trap detached soil sediments before they enter the ditch.

Evaluating the patterns of NO3-N concentrations at karst springs can be used to infer hydrologic processes and nutrient dynamics in karst aquifers. In this study, NO3-N concentrations observed at two karst springs in northeast Iowa (USA) were evaluated for a 2-year period using high-frequency sensors. Despite similar watershed land use dominated by intense row cropping of corn and soybean production (>70%), NO3-N concentrations and temporal patterns were very different between the two springs. At the Manchester spring, NO3-N stored in overburden materials above the karst-enhanced Silurian-age bedrock provides a continuing source of NO3-N to the spring. Rainfall events mobilize the stored NO3-N and concentrations increase. At Big Spring, the karst system is overlain by a thin layer of sediments and the bedrock is dominated by sinkholes and losing streams. Rainfall events dilute the spring NO3-N concentrations which rapidly decreased during events before rebounding to previous levels. Spectral analyses revealed that concentrations at both springs were a fractal process, with the scaling exponent at Manchester (2.0) considerably larger than that measured at Big Spring (1.4), indicating a higher degree of autocorrelation in NO3-N concentrations at Manchester, consistent with the conceptual model. Overall, results argue for greater use of high-frequency NO3-N monitoring at karst springs to better assess short- and long-term variations in NO3-N concentrations and to unravel karst processes.

Growth and consolidation in the livestock industry in the past 30 years have resulted in more total farm animals being raised on fewer Iowa farms. The effects of this on stream water quality at the landscape scale have largely gone unexplored. The main objective of this work was to quantify the effects on stream nitrate levels of livestock concentration in two western Iowa watersheds relative to seven other nearby watersheds. To achieve this objective, we used data on high-frequency nitrate concentration and stream discharge, commercial nitrogen fertilizer use, and manure-generated nitrogen in each watershed. Our analysis shows much higher stream nitrate in the two watersheds where livestock concentration has been greatest, and little difference in commercial fertilizer inputs with the widespread availability of manure N. Reducing N inputs and better management of manure N, including analysis of crop N availability in soil and manure, can reduce uncertainty regarding fertilization while improving water quality.

Although variations in ecosystem processes associated with rural–urban gradients have focused on heavily populated regions, few studies have been conducted in smaller, urban cluster regions. In this study, we collected soil samples from 45 urban and rural locations near Charles City, Iowa (population ~ 7500) for soil organic carbon (C), nitrogen (N), C/N ratios, and heavy metal analyses and evaluated patterns across land use and landscape conditions. In the urban soils, Pb and As values were higher, whereas mean Zr and Rb concentrations were higher in agricultural soils. C/N ratios were higher in urban clusters compared to agricultural land use. Differences in soil concentrations were more evident when landscape position was considered, with higher concentrations of nutrients and heavy metals measured in floodplains associated with both agricultural and urban cluster areas, respectively. Overall, we conclude that the degree of urbanization and industrial development within the Charles City urban cluster was sufficiently intense to differentiate the urban soils from the surrounding agricultural landscape. Our results extend the analysis of urbanization on soil health beyond typical mega-cities to include measurable impacts around smaller urban clusters which comprise ~ 10% of the U.S. population.

Farmed pothole depressions, common in the Prairie Pothole Region, frequently hold water during wet periods and play an important role in ecosystem dynamics such as flood retention and hosting migratory waterfowl. In this study, we developed a spreadsheet-based daily water budget model of a drained and farmed pothole in Hamilton County, Iowa, to evaluate how site-specific characteristics affect the frequency, depth, and duration of surface ponding. For a 3-year period characterized by a range of precipitation, the model predicted that on an annual basis ponded water would be present in the pothole approximately 14 to 47% of the time. Total ponding days ranged from 51 to 173 days year−1 and maximum ponding depth ranged from 112 to 334 mm. Infiltration rate, catchment-to-pothole ratio, and the presence of a surface intake had the largest impact on ponding depth and duration. Results of this study have implications for management of farmed and drained potholes and we can envision using the PPWB model to test potential strategies for pothole management from both agricultural profitability and ecological perspectives.

The vast majority of prairie-pothole wetlands in a region that extends from northcentral Alberta in Canada to central Iowa in the United States have been drained to facilitate agricultural crop production. However, many of these drained wetlands continue to pond surface water immediately following snowmelt or heavy rains, making them too wet to provide a consistent crop and yet too dry to function as normal wetlands. These systems which we label “drained wetlands” were the subject of a four-year monitoring study (2011–2014) funded by the U.S. EPA that focused on monitoring the wildlife value, hydrology and water quality of drained wetlands of the Des Moines Lobe. Herein we describe highlights from the various monitoring components of the multi-year study and introduce a collection of five papers begins to describe the ecosystem value and complexity of these under-studied wetland systems.

Soil erosion is an ongoing global agricultural crisis. Quantifying and tracking soil erosion and sediment export from agricultural watersheds is a key component for evaluating long-term sustainability. Our study used Revised Universal Soil Loss Equation soil erosion estimates and concentration of total suspended solids in-stream (determined through relationships with in-stream turbidity measurements) to estimate sediment delivery to an Eastern Iowa stream from a 780-ha watershed in 2015. Furthermore, we quantified soil organic carbon (SOC) and nitrogen (N) storage within the plow layer of our study area and used our estimated soil loss values to determine particulate nutrient export to the stream. These values were compared to in-stream nutrient sensor data in order to quantify the proportion of N in-stream coming from soil erosion compared to other sources. Results indicate that soil erosion in 2015 was approximately 7.5 Mg ha−1. Sediment export to the stream was determined to be 279 kg ha−1 and the sediment delivery ratio was estimated to be 3.7%. SOC and N stocks were 40 and 2.5 Mg ha−1, respectively. Approximately 0.01% of total SOC and N were lost from the plow layer in 2015. This study identifies long-term risks to watershed sustainability and water quality associated with soil erosion which directs watershed managers towards Best Management Practices that may more effectively reduce export of soil and nutrients while increasing the sustainability of an essential agricultural industry.

Riparian buffers reduce subsurface nutrient losses to streams but there is a clear need to identify and prioritize locations for riparian buffer placement to optimize buffer performance. Scaling relations can be used to extrapolate hydrologic behavior within river networks and across catchments. We combined field and laboratory measurements of soils and groundwater quality collected at five riparian monitoring sites of different stream-order scales with landscape analysis to accomplish the following objectives: (1) evaluate the degree to which riparian zone patterns and processes are scaled in a pre-Wisconsin glacial landscape; and (2) use the scaling information to identify optimal placement of riparian buffers in the landform region for nutrient reduction benefits. Results indicated that there is proportional scaling of riparian zones within the region in terms of sediment texture, groundwater geochemistry and, to a lesser extent, in groundwater nutrient concentrations. Placement of riparian buffers should be a priority along low order streams (

The prairie pothole region covers 700,000 km2 of North America and once contained millions of pothole wetlands but agricultural drainage was used to convert many these wetlands to agriculture. Termed “drained wetlands” in this study, groundwater hydrology and quality beneath these pothole depressions is poorly understood. In this study we characterized water table levels and nutrient concentrations at eight drained wetland sites in Iowa. During the 2011 to 2014 study period that ranged from drought to above-normal rainfall, water table levels exhibited a clear seasonal pattern, rapidly increasing in the spring with rainfall and decreasing in the late summer due to evapotranspiration (ET) and lateral flow to subsurface drainage tiles. The average water table depth ranged from approximately 90 to 130 cm near the typical tile depth in Iowa (120 cm). Results suggest that ponding observed at the farmed pothole depressions is rarely due to groundwater rise. High concentrations of NO3-N and PO4-P were present in shallow groundwater beneath the drained wetlands, averaging 16.7 and 0.4 mg l−1, respectively. Overall, both groundwater hydrology and quality of drained wetlands appear to be dominated by the agricultural land use.

A fully integrated, physically-based model of a drained and farmed wetland complex in the Prairie Pothole Region of Iowa (termed Ellsworth #2) was developed to investigate hydrologic connectivity of surface and groundwater sources. The model is based on the code HydroGeoSphere, which solves surface and subsurface flow and the interaction between these domains. Physical processes governing the hydrologic response of a wetland, precipitation, plant transpiration, and surface and subsurface evaporation, were included in the model. The model was run for 6 years and predicted water table location was compared against measurements. Results indicated that intermittent ponding was observed in pothole depressions but hydrologic connectivity among three pothole depressions via surface water ponding was rarely established. Extensive subsurface tile drainage system simulated in the model removed a substantial volume of water and reduced the amount and duration of ponding. Groundwater discharge contributed to some degree during nearly all ponding events in the pothole depressions as exfiltration ranged from 1.7 to 23.6 % of annual precipitation. Despite simplifications, the model captures the interactions among hydrologic processes and provides important information for scientists and decision makers to effectively plan for current and future management of these drained and farmed wetland complexes.

Daily nitrate-nitrogen (NO3-N) loads in the Raccoon River, Iowa, were estimated using Ordinary kriging (OK), Cokriging (CK), and a standard rating curve method (LOADEST) based on a dataset of 3451 measurements of NO3-N concentration collected over 19 years. The CK estimation utilizes the temporal correlation of NO3-N load with daily discharge and honors the measured points to improve estimation relative to regression based models. Loads were estimated using the observed concentrations and three subsets of the measured data that correspond to three frequencies (weekly, biweekly, and monthly). Results indicated that daily NO3-N loads were best estimated by CK using measured loads with daily discharge. Daily load estimates produced by OK using weekly data matched well with measured values, but discrepancies emerged when samples were collected less frequently, e.g., biweekly and monthly. For the entire 19-year dataset, compared to measured loads, the estimated total NO3-N load decreased using OK when samples were collected monthly, but increased using CK. Load estimation using the seven-parameter LOADEST model did not perform well for the Raccoon River because the correlation of NO3-N concentration to river discharge was poor. For the site studied, weekly and biweekly sampling may be sufficient to estimate daily NO3-N loads with CK when daily discharge data is available.

Real-time, continuous, in situ water quality sensors were deployed on a fourth-order Iowa (U.S.) stream draining an agricultural watershed to evaluate key in-stream processes affecting concentrations of nitrate during a 24-day late summer (Aug–Sep) period. Overall, nitrate-nitrogen (NO3-N) concentrations declined 0.11 mg L−1 km−1, or about 1.9% km−1 and 35% in total across 18 km. We also calculated stream metabolic rates using in situ dissolved oxygen data and determined stream biotic N demand to be 108–117 mg m−2 day−1. From this, we estimate that 11% of the NO3-N concentration decline measured between two in-situ sensors separated by 2 km was a result of biotic NO3-N demand, while groundwater NO3-N data and estimates of groundwater flow contributions indicate that dilution was responsible for 53%. Because the concentration decline extends linearly across the entire 18 km of stream length, these processes seem consistent throughout the basin downstream of the most upstream sensor site. The nitrate-dissolved oxygen relationship between the two sites separated by 2 km, calculations of biotic NO3-N demand, and diurnal variations in NO3-N concentration all indicate that denitrification by anaerobes is removing less NO3-N than that assimilated by aquatic organisms unable to fix nitrogen for their life processes, and thus the large majority of the NO3-N entering this stream is not retained or removed, but rather transported downstream.

Nitrogen (N) removal within reservoirs can be substantial, but few studies have reported the relative importance of various N-retention pathways. Assessing N-removal processes in reservoirs is important for quantifying the impacts of reservoirs on downstream water quality. In this study, we used a time-series approach to quantify the relative importance of various N-removal processes in the Saylorville Reservoir in Iowa. Dynamic regression modeling of upstream–downstream changes in key water-quality surrogates (pH, hardness, alkalinity, and suspended solids) and their relation to N concentration changes were used to estimate the relative importances of denitrification, N assimilation by algal uptake, and sedimentation of N on N retention in the reservoir. Assuming that decreasing N concentrations in the reservoir are the sum of these three processes, we estimate that denitrification is the dominant N removal process (60.9 %) followed by algal assimilation (37.9 %) and sedimentation (1.2 %). Our approach represents a new method of establishing the relative importance of N-removal processes in reservoirs and quantifying the impacts of reservoirs on downstream water quality.

Florestina is shown to consist of six annual species occurring mostly in arid and semiarid regions of Mexico. Florestina species are morphologically similar and consequently phylogenetic relationships within the genus are poorly understood. We present a phylogenetic study based on morphological characters, DNA sequences of nuclear non-coding spacers (ETS and ITS) and chloroplast non-coding spacers (rpl32-trnL and trnC-petN). The ETS and ITS spacer-based phylogenies allowed several well-supported conclusions: (1) the genus Florestina is monophyletic and Palafoxia is its closest relative; (2) Florestina latifolia and F. platyphylla form a strongly supported clade; (3) four taxa that are morphologically very similar, F. liebmannii, F. pedata, F. simplicifolia, and F. tripteris, are phylogenetically closely related and based on the sequence data we suggest that these should be recognized as only two species, one comprising F. pedata and F. simplicifolia, which shows wide morphological variation throughout its distributional range; and the other comprising F. liebmannii and F. tripteris; (4) F. lobata and F. purpurea are species very distinct from the remainder of the species in Florestina. Our phylogenetic analyses suggest that hybridization and introgression may be involved in the evolutionary history of Florestina.

Spatiotemporal variations of groundwater level due to a white noise recharge time series and a random transmissivity field in a bounded unconfined aquifer was studied. The analytical solutions for the variance and covariance of groundwater level were derived with non-stationary spectral analyses and superposition principle. It was found that the fluctuations of groundwater level are spatially non-stationary due to a fixed head boundary condition and temporal non-stationary at early time but gradually became stationary as time progresses due to effect of the initial condition. The variation in groundwater level is mainly caused by the random source/sink in the case of temporally random recharge and spatially random transmissivity. The effect of heterogeneity is to increase the variation of groundwater level and the maximum effect occurs close to the constant head boundary because of the linear mean hydraulic gradient. The heterogeneity also enhances the correlation of groundwater level, especially at large time intervals and small spatial distances.

The City of Manson, Iowa (USA), lies near the center of the Manson Impact Structure (MIS), a 37-km diameter impact crater that formed about 74 million years ago. The MIS is present at the bedrock surface, but it is completely buried by 20–90 m (70–300 ft) of glacial till and displays no surface expression. Groundwater samples were collected from Manson’s municipal well and nearby domestic wells to assess the sustainability of unusually soft water that typifies the central peak of the Manson Impact Structure. Groundwater quality indices from the various aquifer sources were distinctly different, with groundwater from the central peak of the crater exhibiting low Ca ( 3.7 mg/L; max = 10.0 mg/L) and certain trace elements (e.g. Li, Mo, W). In contrast, groundwater collected from wells in overlying Quaternary aquifers was very hard (high Ca and Mg), with high alkalinity (>261 mg/L as CaCO3), sulfate (58–485 mg/L) and occasionally nitrate-N (up to 6 mg/L). Age-dating techniques using 3H, 14C, and 36Cl suggested water older than 35,000 years to possibly as old as 1,000,000 years within the central peak aquifer, but indicated recent water in overlying aquifers. Pumping of the Manson municipal wells appears to be mining old water of the central peak aquifer and drawing modern water containing elevated hardness and nitrate-N down into the aquifer. The Manson example illustrates a source-water challenge of balancing aquifer quality with sustainability.

Deep confined water from the Cambrian–Ordovician (C–O) aquifer is being increasingly used for ethanol production in Iowa. In this study, we used isotopic age dating to estimate the age of groundwater in the aquifer and assess how groundwater use for all purposes, including ethanol production, may be affecting the long-term sustainability of the aquifer. Eight municipal wells located across the extent of the aquifer in Iowa were sampled for major and minor ions, stable isotopes (δ18O and δD) and the radioactive isotope 36Cl. Multiple lines of evidence from this study suggest that groundwater in the C–O aquifer is older than 10,000 years, with results from 36Cl analyses suggesting groundwater travel times in the aquifer ranging from approximately 70,000 to nearly 180,000 years old from northern to central Iowa. Our study suggests that pumping from the C–O aquifer for all uses, including ethanol production, is extracting old groundwater from the aquifer. To mitigate long-term impacts, we recommend that expansion of new ethanol production should be based on accessibility of sustainable groundwater resources, rather than siting facilities where deep groundwater reserves are needed for production.

Taxonomic changes are made to reflect a reassessment of morphology based on the results of molecular phylogenetic studies. A new genus, Davilanthus, is described to include six species that collectively form the sister group to Simsia, and includes the following species transferred from Viguiera: Davilanthus davilae, Davilanthus hidalgoanus, Davilanthus hypargyreus, Davilanthus huajuapanus, Davilanthus purpusii, and Davilanthus sericeus. Three species formerly placed in Viguiera ser. Grammatoglossae are transferred to Simsia: Simsia benziorum, Simsia ovata, and Simsia rhombifolia.

Comparative analyses were made of agamospermous populations of Eupatorium sessilifolium, which have previously been documented to be polyploid, to determine whether they are alloploid or autoploid in origin and to assess the possibility that they have arisen more than once. There was no variability in ITS sequences among seven agamospermous and eight sexual diploid populations of E. sessilifolium, which is consistent with morphological observations in suggesting that the agamospermous populations were autoploids. The ITS sequence characteristic of E. sessilifolium differs from all other North American species by a minimum of 15 changes, and heterogeneity or polymorphism would be expected if the agamospermous populations were alloploids. Analysis of the chloroplast-based trnC-psbM spacer region showed variability among both sexual diploid and agamospermous populations of E. sessilifolium, which suggested that the agamospermous populations stem from multiple origins. Analysis of ISSR data revealed considerable intraspecific variability within E. sessilifolium, and the distribution of variability, with agamospermous populations showing variability from one another, added further evidence for multiple origins of agamospermous populations. The results in conjunction with distributional evidence that the sexual diploid populations of E. sessilifolium are geographically restricted and uncommon suggest that monitoring of populations might be warranted to evaluate whether measures are needed to enhance their continued survival.

Groundwater recharge is an important component to hydrologic studies but is known to vary considerably across the landscape. The purpose of this study was to examine 4 years of water-level behavior in a transect of four water-table wells installed at Walnut Creek, Iowa, USA to evaluate how groundwater recharge varied along a topographic gradient. The amount of daily water-table rise (WTR) in the wells was summed at monthly and annual scales and estimates of specific yield (Sy) were used to convert the WTR to recharge. At the floodplain site, Sy was estimated from the ratio of WTR to total rainfall and in the uplands was based on the ratio of baseflow to WTR. In the floodplain, where the water table is shallow, recharge occurred throughout the year whenever precipitation occurred. In upland areas where the water table was deeper, WTR occurred in a stepped fashion and varied by season. Results indicated that the greatest amount of water-table rise over the 4-year period was observed in the floodplain (379 mm), followed by the upland (211 mm) and sideslopes (122 mm). Incorporating spatial variability in recharge in a watershed will improve groundwater resource evaluation and flow and transport modeling.

It has been recognized that subsurface lithology plays an important role in controlling nutrient cycling and transport in riparian zones. In Iowa and adjacent states, the majority of alluvium preserved in small and moderate sized valleys consists of Holocene-age organic-rich, and fine-grained loam. In this paper, we describe and evaluate spatial and temporal patterns of lithology and groundwater nutrient concentrations at a riparian well transect across Walnut Creek at the Neal Smith National Wildlife Refuge in Jasper County, Iowa. Land treatment on one side of the stream reduced the grass cover to bare ground and allowed assessment of the effects of land management on nutrient concentrations. Results indicated that groundwater in Holocene alluvium is very nutrient rich with background concentrations of nitrogen, phosphorus and dissolved organic carbon that exceed many environmentally sensitive criteria. Average concentrations of ammonium exceeded 1 mg/l in several wells under grass cover whereas nitrate concentrations exceeded 20 mg/l in wells under bare ground. Phosphate concentrations ranged from 0.1 to 1.3 mg/l and DOC concentrations exceeded 5 mg/l in many wells. Denitrification, channel incision, land management and geologic age of alluvium were found to contribute to variable nutrient loading patterns at the site. Study results indicated that riparian zones of incised streams downcutting through nutrient-rich Holocene alluvium can potentially be a significant source of nutrient loadings to streams.

Excessive nitrate-nitrogen (nitrate) loss from agricultural watersheds is an environmental concern. A common conservation practice to improve stream water quality is to retire vulnerable row croplands to grass. In this paper, a groundwater travel time model based on a geographic information system (GIS) analysis of readily available soil and topographic variables was used to evaluate the time needed to observe stream nitrate concentration reductions from conversion of row crop land to native prairie in Walnut Creek watershed, Iowa. Average linear groundwater velocity in 5-m cells was estimated by overlaying GIS layers of soil permeability, land slope (surrogates for hydraulic conductivity and gradient, respectively) and porosity. Cells were summed backwards from the stream network to watershed divide to develop a travel time distribution map. Results suggested that groundwater from half of the land planted in prairie has reached the stream network during the 10 years of ongoing water quality monitoring. The mean travel time for the watershed was estimated to be 10.1 years, consistent with results from a simple analytical model. The proportion of land in the watershed and subbasins with prairie groundwater reaching the stream (10–22%) was similar to the measured reduction of stream nitrate (11–36%). Results provide encouragement that additional nitrate reductions in Walnut Creek are probable in the future as reduced nitrate groundwater from distal locations discharges to the stream network in the coming years. The high spatial resolution of the model (5-m cells) and its simplicity may make it potentially applicable for land managers interested in communicating lag time issues to the public, particularly related to nitrate concentration reductions over time.

Few hydrology studies have investigated glacial till older than Illinoian time (> 300,000 BP) despite these older tills overlying a large portion of North America. An 8- and 6-well monitoring well nest installed into a 31 m thick pre-Illinoian till sequence near Cedar Rapids, Iowa was characterized using traditional hydrologic methods and chemical tracers. The aquitard system consists of about 9 m of fine-grained oxidized pre-Illinoian till overlying 22 m of unoxidized till and Devonian dolomite bedrock. Hydraulic conductivity ranged from 10−7 m/s in oxidized till and 10−10 m/s in unoxidized till. Hydraulic head relations indicated downward groundwater flow through the till profile with hydraulic gradients steepest near the unoxidized till/bedrock interface. Tritium and nitrate concentrations indicated recent (< 50 years old) recharge to a depth of 9–12 m below land surface. 18O and 2H results ranged between −6.2 to −7.9% and −38.0 to −50.9%, respectively, and plotted near the local Meteoric Water Line. A 1 per mil shift toward less negative 18O values with depth may suggest a climate change signal contained in the till water but more data are needed to verify this trend. Vertical groundwater velocity through the unoxidized till was estimated to range from 0.4 to 5.7 cm/year. The thickness of unoxidized pre-Illinoian till in Linn County was estimated from available records and contoured against vertical travel times to evaluate the effectiveness of pre-Illinoian till in preventing nitrate migration to underlying bedrock aquifers.

Plasmocytic non-Hodgkin's lymphoma is the most common tumor of bone and bone marrow, typically diagnosed by symptoms such as monoclonal paraproteinemia, proteinuria, anemia and hypercalcemia. In its progress, deposits of amyloids in almost all organs can be observed. However, plasmacytomas which are diagnosed by macroglossia of primarily unknown etiology are rare. This case report presents a 61-year-old woman who suffered from a persistent swelling of the tongue with painful ulcerations. A biopsy led to the diagnosis of primary systemic amyloidosis of the light-chain type, which subsequently proved to be a plasmacytoma with lambda light-chains stage II after Durie and Salmon. In the course of the disease the patient developed further deposits of amyloids in the whole gastro-enteric system. Macroglossia as a primary manifestation of plasmacytoma is rarely described in medical literature. However, reports on deposits of amyloid in the tongue in advanced stages of disease are well known.

Chloroplast DNA (cpDNA) restriction site analysis was used to assess relationships among samples of Eupatorieae from eastern North America. A total of 270 cpDNA variants was recorded from 35 species using 13 restriction enzymes. Phylogenetic analysis usingGalinsoga, Flaveria, andHelianthinae as outgroups indicated that samples ofAgeratina, Hofmeisteria, Mikania, andStevia, each of which have relatively high base chromosome numbers, formed an unresolved basal polytomy. The remaining samples examined formed a well-supported clade, within which there was a split betweenBrickellia, which hasx = 9, and a number of genera withx = 10. Within thex = 10 clade, there was an unresolved trichotomy, with one group ofAgeratum, Conoclinium, Fleischmannia, andCritonia, a second ofLiatris andTrilisa, and a third ofEupatorium s.s. Within theEupatorium s.s. clade there were three further clades, withE. sect.Verticillata diverging first, and a subsequent split between species originating from North America and those from Asia. The cpDNA restriction site data provided support for a relatively narrow interpretation ofEupatorium, and indicated that a high chromosome base number is plesiomorphic for Eupatorieae.

Chloroplast DNA (cpDNA) restriction site data were used to analyze phylogenetic relationships within Helianthus. Data from new samples were consistent with previous results and showed the genus to be a well-defined (11 site changes) lineage within subtribe Helianthinae. The affinities of 2 species, Viguiera similis and V. phenax (V. ludens) that have sometimes been included in Helianthus were shown to lie outside the genus. The two species of Phoebanthus, however, formed a phylogenetic ingroup to the perennial Helianthus. Within the genus, cpDNA data indicated that there are four distinct phylogenetic lineages. Two of the lineages each contained a single, annual species (H. agrestis and H. porteri, respectively). The remaining annual species collectively formed a third lineage (sect. Helianthus). The fourth lineage contained all of the perennial species, including those of Phoebanthus. Within the perennial lineage, there was little variation in restriction site characters. The 3 species of series Pumili formed a paraphyletic group at the base of the perennial lineage, and the 3 species of series Ciliares formed a group that was supported by a single restriction site character.

In this paper, we investigate a scheme for approximating a two-person zero-sum game G of incomplete information by means of a natural system Gmn of its finite subgames. The main question is: For large m and n, is an optimal strategy for Gmn necessarily an e-optimal strategy for G?

This paper presents a study of the effects of electron beam (e-beam) exposure on the chemical and physical properties of FLARE™ 1.0X, a non-fluorinated member of the FLARE™ family of poly(arylene ether) dielectric coatings. Spin-coated films of this poly(arylene ether) were cured by large-area e-beam exposure, as well as by conventional thermal processing. Neither swelling nor dissolution was observed for the e-beam cured films after immersion in N-methylpyrrolidone (NMP) at 90 °C for 1 hour. The glass transition temperature (Tg) for films cured with a low e-beam dose is slightly higher than, or nearly the same as, the (Tg) for thermally-cured films (∼ 270 °C). However, the Tg for films cured with a high e-beam dose exceeds 400 °C. Dielectric constants of e-beam cured films and thermally cured films are nearly the same. FTIR spectra of FLARE™ films obtained before and after e-beam exposure suggest that e-beam curing does not induce any significant change in the chemical structure. Increased solvent resistance, higher Tg, and low dielectric constant are properties that make this e-beam cured poly(arylene ether) film an excellent candidate for interlevel dielectric integration processes.

AlthoughViguiera hidalgoana, a new species from Hidalgo, Mexico, bears a superficial resemblance toV. dentata, it is clearly related to certain woody species of seriesGrammatoglossae.

A procedure is presented for obtaining estimates of components of variance for the main effects and interaction in a two-way factorial arrangement of treatments with only partially cross-classified data (sometimes referred to as unbalanced data in a two-way crossed classification model with interaction). The procedure entails the use of two hierarchical analyses of variance in which each main effect is first treated as classes and then as subclasses. The estimation of the variance component for each main effect results from the solution of two simultaneous equations with values used obtained directly from the hierarchical analyses. The interaction component of variance can be obtained from the variance components for main effects. An example is presented for the purpose of illustrating the procedure. Interpretation of the interaction variance component estimated by the method is limited due to the absence of some of the subclasses.

The current North American-Eurasian plate boundary on Iceland's northern insular margin is defined. Overlapping rift zones and en echelon post-glacial volcanic eruptions oblique to the apparent transform direction of the Tjornes Fracture Zone suggest that the fault is in a transient deformational stage.

Die postnatale Ontogenese der Hodenzwischenzellen des Schweins nimmt einen wellenformigen Verlauf und last sich in 4 Phasen unterteilen.

The basic principals of hypothesis testing are reviewed, including the development of the hypothesis, the statistical assumptions made, and the test of the hypothesis. The appropriate experimental design and sampling technique for evaluation of hypotheses posed are discussed. Because the analysis of variance involving the F-test should be used in a wide variety of geological experiments, emphasis is placed on this analysis. Many geological experiments result in the measurement of one or more factors on a continuous scale, whereas others are recorded in a discrete fashion. This necessitates the use of a covariance analysis to evaluate the effect of discrete and continuous factors in the same model. Orthogonal comparisons are discussed as they are used to evaluate specific hypotheses following the general test of hypothesis in the analysis of variance or covariance. All procedures discussed are illustrated using actual palynofloral data.

Die postnatale Ontogenese der Hodenzwischenzellen des Schweines nimmt einen wellenformigen Verlauf und last sich in folgende 4 Phasen unterteilen: Fruhpostnatale Proliferation, prapubertare Hypertrophie, prapubertare Regression und pubertare Proliferation.