Anthropocene streams and base-level controls from historic dams in the unglaciated mid-Atlantic region, USA

Recently, widespread valley-bottom damming for water power was identified as a primary control on valley sedimentation in the mid-Atlantic US during the late seventeenth to early twentieth century. The timing of damming coincided with that of accelerated upland erosion during post-European settlement land-use change. In this paper, we examine the impact of local drops in base level on incision into historic reservoir sediment as thousands of ageing dams breach. Analysis of lidar and field data indicates that historic milldam building led to local base-level rises of 2-5 m (typical milldam height) and reduced valley slopes by half. Subsequent base-level fall with dam breaching led to an approximate doubling in slope, a significant base-level forcing. Case studies in forested, rural as well as agricultural and urban areas demonstrate that a breached dam can lead to stream incision, bank erosion and increased loads of suspended sediment, even with no change in land use. After dam breaching, key predictors of stream bank erosion include number of years since dam breach, proximity to a dam and dam height. One implication of this work is that conceptual models linking channel condition and sediment yield exclusively with modern upland land use are incomplete for valleys impacted by milldams. With no equivalent in the Holocene or late Pleistocene sedimentary record, modern incised stream-channel forms in the mid-Atlantic region represent a transient response to both base-level forcing and major changes in land use beginning centuries ago. Similar channel forms might also exist in other locales where historic milling was prevalent.     

Religiosity, alcohol use attitudes, and alcohol use in a national sample of adolescents.

The purpose of this study was to investigate alcohol use attitudes as a mediator of the relationship between religiosity and the frequency of past month alcohol use in a national sample of adolescents. Data were drawn from 18,314 adolescents who participated in the 2006 and 2007 National Survey on Drug Use and Health. Variables included religiosity, alcohol use attitudes, and past month frequency of alcohol use. Structural equation modeling was used to test alcohol use attitudes as a mediator of the relationship between religiosity and frequency of alcohol use and to test model invariance across 4 racial/ethnic groups. Results suggest that alcohol use attitudes partially mediate the relationship between religiosity and frequency of alcohol use. Furthermore, while the pattern of these relationships is similar across racial/ethnic groups, the magnitude of alcohol use attitudes on frequency of alcohol use differed. Implications for prevention programs include targeting alcohol use attitudes in a variety of settings. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Sorption of Np(V) onto hybrid clay-based materials: Montmorillonite-melanoidin

The sorption of Np(V) onto hybrid clay-based materials (HCMs) prepared from montmorillonite in the Maillard reaction was studied at environmentally relevant concentrations. Above pH 7, the sorption of Np(V) on HCM is weaker than that on the pure montmorillonite, with a reversed trend observed at lower pH values. With increasing pH, increasing amounts of melanoidins are released into the aqueous phase, thus the complexation of Np(V) in the aqueous phase was studied as well. The complexation in the aqueous phase is obviously increasing the mobility of Np(V). The sorption of Np(V) on the HCM is compared to the prediction by the linear additive model.     

Simple d-transposition of the great arteries. Results of early balloon septotomy followed by two-stage surgical correction

The follow-up of 44 patients with simple d-transposition of the great arteries is presented. All had balloon atrial septotomy shortly after birth. If an operation was needed at or before one year of age, atrial septectomy was carried out. Correction was done between the ages of 19 and 64 months. Of the 44 patients, 34 (77 per cent) are living and doing well (27 after the Mustard procedure), 3 (7 per cent) are lost to follow-up, and 7 (16 per cent) are dead. Death was due to technical problems during initial catheterization and balloon septotomy in 2 patients, occurred after septectomy in one (3 per cent), and after the Mustard procedure in one (4 per cent). There was one sudden inexplicable death in a 1 1/2-month-old patient, and 2 patients died with pulmonary vascular obstructive disease. Because of the relatively low over-all mortality and morbidity and the low surgical mortality rate for both palliation and correction, we believe that two-stage surgical correction of transposition of the great arteries is preferable to early one-stage correction in the infant.     

Unsaturated Constitutive Surfaces from Pressuremeter Tests

A methodology to identify the collapse potential of unsaturated soils is proposed in this paper on the basis of pressuremeter test results associated with independent measurements of the in situ matric suction. A solution combining the expansion of a cylindrical cavity to a modified Cam clay critical state model has been introduced and accommodated to the framework of unsaturated soil behavior. This accounts for changes in soil properties induced by suction changes. Interpretation of pressuremeter tests performed under unsaturated and soaked conditions links the amount of collapse to strength and stiffness changes and provides assessment to the constitutive soil parameters that are necessary to define the yield envelopes of the soil. A comprehensive site investigation program comprising field and laboratory tests carried out in two residual soil sites is discussed in order to validate the proposed methodology. Values of shear strength, in situ stress, and yield pressure derived from both field and laboratory data are used as input parameters of a constitutive model adopted for describing the yield envelopes of these unsaturated residual soil sites.     

Knowledge-based approach towards hydrolytic degradation of polymer-based biomaterials

The concept of hydrolytically degradable biomaterials was developed to enable the design of temporary implants that substitute or fulfill a certain function as long as required to support (wound) healing processes or to control the release of drugs. Examples are surgical implants, e.g., sutures, or implantable drug depots for treatment of cancer. In both cases degradability can help to avoid a second surgical procedure for explanation. Although degradable surgical sutures are established in the clinical practice for more than 30 years, still more than 40% of surgical sutures applied in clinics today are nondegradable.1 A major limitation of the established degradable suture materials is the fact that their degradation behavior cannot reliably be predicted by applying existing experimental methodologies. Similar concerns also apply to other degradable implants. Therefore, a knowledge-based approach is clearly needed to overcome the described problems and to enable the tailored design of biodegradable polymer materials. In this Progress Report we describe two methods (as examples for tools for this fundamental approach): molecular modeling combining atomistic bulk interface models with quantum chemical studies and experimental investigations of macromolecule degradation in monolayers on Langmuir-Blodgett (LB) troughs. Finally, an outlook on related future research strategies is provided.     

Occurrence of antibiotics in the aquatic environment

The recent monitoring of drug residues in the aquatic environment has gained much interest as many pharmaceutical compounds can frequently be found in sewage treatment plant (STP) effluents and river water at concentrations up to several microgram/l. This article describes the analysis of various water samples for 18 antibiotic substances, from the classes of macrolid antibiotics, sulfonamides, penicillins and tetracyclines. Samples were preconcentrated via lyophilization and quantified using HPLC-electrospray-tandem-mass spectrometry. The investigated STP effluents and surface water samples showed frequent appearance of an erythromycin degradation product, roxithromycin and sulfamethoxazole with concentrations up to 6 micrograms/l. Neither tetracyclines nor penicillins could be detected at concentration levels above 50 and 20 ng/l, respectively. From the large number of ground water samples that were taken from agricultural areas in Germany, no contamination by antibiotics was detected except for two sites. This indicates that intake from veterinary applications to the aquatic environment is of minor importance.