Water Retention, Bulk Density, Particle Size, and Thermal and Hydraulic Conductivity of Arable Soils in Interior Alaska

The relative proportion of liquid, gas, and solid as constituents of soil depends on factors such as climate, biological activity, and management practices. Therefore, the physical state of soil is a dynamic process, changing with time and position in the profile. Temperature, thermal and hydraulic conductivity, density, and water content are some quantitative properties characterizing the physical state of soil. These properties are important in describing soil processes such as water and heat flow, movement of chemicals, biological activity, and erosion. Water in the soil is subject to a number of forces resulting from the attraction of the soil matrix for water and presence of solutes and gravity. The energy status of water-the sum of these forces-is termed water potential. Processes such as evaporation and plant water uptake are governed by the gradient in water potential in the soil and across the root-soil interface, respectively. The term water potential is more descriptive of the soil water status than water content as movement of water is in response to differences in water potential

Migration of Water During Winter in West Central Minnesota Soils

Soil freezing influences the amount and quality of our water resources, yet, little is known concerning the impacts of soil texture and water content before freezing on water migration in frozen soils. Columns of Hamerly clay loam and Sioux loam at 3 initial water contents were subjected to the vagaries of the field environment at Morris, Minnesota during the winter of 1993-1994 and then sectioned to determine changes in soil water content. Redistribution of water in the frozen soil layer became more apparent with an increase in initial water content. Little movement of water occurred at the lowest initial water content of 0.21 g g-1 (45% pore saturation). Soil water redistribution was more pronounced for the. Sioux loam, but only at the highest initial water content of 0.38 g g-1 (8QO;O pore saturation). Upward water movement appeared greatest when the rate of descent of the freezing front was slowest. Initial water content had a larger effect on water movement in frozen soil profiles than soil texture. Therefore, soil water content at the time of freeze-up in the fall will determine, to a large extent, the rate of water (and consequently solute) movement in soil profiles during winter

Dissipation of Bromide and Metribuzin Affected by Tillage and Crop Residue Management in Subarctic Alaska

Prudent use of agricultural fertilizers and herbicides is paramount for sustaining or improving surface and ground water quality in Subarctic regions, but little information is available that documents the loss of chemicals from agricultural lands in the Subarctic. This study aimed to ascertain more clearly how time of application and land management practices affect the loss of bromide and metribuzin in a Subarctic soil. Potassium bromide (KBr), a surrogate for nitrate, and metribuzin, commonly used to control broadleaf weeds, were applied in the autumn of 1996 and the spring of 1997 to a silt loam that had been subjected to conventional tillage (CT), minimum tillage (disk once [DO]), and no tillage (NT) since 1983. Superimposed on the tillage treatments were the removal or retention of barley (Hordeum vulgare L.) stubble and loose straw. Loss of these chemicals was ascertained by sampling the soil profile at the time of heading of barley, before freeze-up of the soil in autumn, and after spring thaw until September 1998. Tillage and residue treatments did not influence the recovery of autumn-applied or spring-applied Br. However, recovery of Br diminished with time: about 30% of the Br applied in autumn and 45% of that applied in spring remained in the soil profile by September 1998. Tillage, but not residue, treatments influenced the recovery of metribuzin. Recovery of metribuzin at the termination of this study was 6% or more in NT soil and 2% or less in CT and DO soil; greater recovery in NT soil was presumably a result of slower degradation in NT than in CT and DO. This study suggests that bromide (and thus nitrate) and metribuzin are more prone to leaching when applied in autumn and that tillage practices affect retention of metribuzin, but not nitrate, in the soil of Subarctic Alaska.Une utilisation prudente des engrais et des herbicides est cruciale au maintien ou à l’amélioration de la qualité de l’eau de surface et de l’eau souterraine dans les régions subarctiques, mais il existe peu de documentation sur la déperdition des produits chimiques dans le sol des terres agricoles du Subarctique. Cette étude vise à établir avec plus de précision la façon dont le moment de l’application et les pratiques de gestion des terres affectent la déperdition du bromure et de la métribuzine dans un sol subarctique. Le bromure de potassium (KBr), un substitut du nitrate, et la métribuzine, couramment utilisée pour lutter contre les dicotylédones, ont été appliqués en automne 1996 et au printemps 1997 sur un loam limoneux qui avait subi un travail du sol classique (TC), un travail minimum (un seul passage du cultivateur à disque [TM]) et aucun travail (AT) depuis 1983. On a ajouté au travail du sol le déchaumage de l’orge (Hordeum vulgare L.) ou le maintien du chaume et de la paille. On a vérifié la déperdition de ces produits chimiques jusqu’en septembre 1998 en analysant le profil pédologique au moment de l’épiaison de l’orge, avant que le sol gèle à l’automne et après le dégel printanier. Le travail du sol et le traitement des résidus n’ont pas influencé la récupération du Br appliqué en automne ou au printemps. La récupération du Br a cependant diminué avec le temps: en septembre 1998, environ 30 % du Br appliqué à l’automne et 45 % de celui appliqué au printemps persistaient dans le profil pédologique. Le travail du sol, mais pas le traitement des résidus, influençait la récupération de la métribuzine. À la fin de l’étude, la récupération de la métribuzine était de 6 % ou plus dans le sol AT, et de 2 % ou moins dans les sols TC et TM; une récupération plus importante dans le sol AT résultait probablement d’une dégradation plus lente dans le AT que dans le TC et le TM. Cette étude suggère que le bromure (et, par conséquent, le nitrate) et la métribuzine sont plus sujets au lessivage quand ils sont appliqués en automne, et que les pratiques de travail du sol affectent la rétention de la métribuzine, mais pas celle du nitrate, dans le sol de l’Alaska subarctique

Trust as an antecedent to knowledge sharing in virtual communities of practice

2007-2008 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Psychopathy, Gang membership, And moral disengagement among juvenile offenders

Purpose – The purpose of this paper is to investigate the impact of psychopathy factors and gang membership on moral disengagement while controlling for age, ethnicity, having run away from home, family member and/or friend arrests, substance misuse, parental physical fights, violence exposure (victimization and witnessing), and maternal warmth and hostility. Design/methodology/approach – The research is based on data collected from serious juvenile offenders (n=769) as part of the Pathways to Desistance Study. Findings – Six independent variables made a unique statistically significant contribution to the model: gang membership, age, gender, violence exposure, and psychopathy Factors 1 and 2. Psychopathy Factor 1 was the strongest predictor of moral disengagement. Originality/value – Results indicate that youth with heightened psychopathic traits make greater use of strategies to rationalize and justify their harmful behaviour against others. Implications in relation to theory and previous studies are discussed

Spontaneous formation of multilamellar vesicles from aqueous micellar solutions of sodium linear alkylbenzene sulfonate (NaLAS)

We report the spontaneous formation of multilamellar vesicles (MLVs) from low concentration (<30 wt%) aqueous micellar solutions of sodium linear alkylbenezene sulfonate (NaLAS) upon cooling, employing a combination of optical microscopy (OM), Small Angle Neutron Scattering (SANS), and Cryo-TEM. Upon cooling, MLVs grow from, and coexist with, the surfactant micelles, attaining diameters ranging from hundreds of nanometers to a few micrometers depending on the cooling rate, whilst the d-spacing of internal lamellae remains unchanged, at ≃3 nm. While microscale fluid and flow properties of the mixed MLVs and micellar phase depend on rate of cooling, the corresponding nanoscale structure of the surfactant aggregates, resolved by time-resolved SANS, remains unchanged. Our data indicate that the mixed MLV and micellar phases are in thermodynamic equilibrium with a fixed relative volume fraction determined by temperature and total surfactant concentration. Under flow, MLVs aggregate and consequently migrate away from the channel walls, thus reduce the overall hydrodynamic resistance. Our findings demonstrate that the molecular and mesoscopic structure of ubiquitous, low concentration NaLAS solutions, and in turn their flow properties, are dramatically influenced by temperature variation about ambient conditions

Frozen Soils: A Perspective On Past And Future Research For Promoting Sustainable Agricultural Systems

Frozen soils impact many industries which rely· on soil, water, and .air resources in developing and manufacturing products. Most noteworthy is the agricultural industry in the northern United States where soils, which sustain food and fiber production, are subjected to frequent freezing and thawing. Soil freezing and thawing influences soil erodibility, surface and ground water quality, air quality, and biological activity. Many strides toward understanding frozen soil processes and managing lands to minimize the adverse effects of freezing and thawing have been made over the last two decades. Yet, further efforts to identify frozen soil processes which influence wind and water erosion, soil faunal adaptation, soil quality, movement of agricultural chemicals,· and rural and urban water supplies will aid industry and society in meeting future needs for food and water

Thermodynamics of highly interacting blend PCHMA/dPS by TOF-SANS

We investigate the thermodynamics of a highly interacting blend of poly(cyclohexyl methacrylate)/deuterated poly(styrene) (PCHMA/dPS) with small-angle neutron scattering (SANS). This system is experimentally challenging due to the proximity of the blend phase boundary (>200 °C) and degradation temperatures. To achieve the large wavenumber q-range and flux required for kinetic experiments, we employ a SANS diffractometer in time-of-flight (TOF) mode at a reactor source and ancillary microscopy, calorimetry, and thermal gravimetric analysis. Isothermal SANS data are well described by random-phase approximation (RPA), yielding the second derivative of the free energy of mixing (G″), the effective interaction (χ̅) parameter, and extrapolated spinodal temperatures. Instead of the Cahn–Hilliard–Cook (CHC) framework, temperature (T)-jump experiments within the one-phase region are found to be well described by the RPA at all temperatures away from the glass transition temperature, providing effectively near-equilibrium results. We employ CHC theory to estimate the blend mobility and G″(T) conditions where such an approximation holds. TOF-SANS is then used to precisely resolve G″(T) and χ̅(T) during T-jumps in intervals of a few seconds and overall timescales of a few minutes. PCHMA/dPS emerges as a highly interacting partially miscible blend, with a steep dependence of G″(T) [mol/cm3] = −0.00228 + 1.1821/T [K], which we benchmark against previously reported highly interacting lower critical solution temperature (LCST) polymer blends

Factor structure and factorial invariance of the strengths and difficulties questionnaire among children of prisoners and their parents

Parental imprisonment has been linked to a variety of adverse psychological outcomes for children and adolescents. The Strengths and Difficulties Questionnaire (SDQ) has been widely used to assess behavioural and emotional difficulties among 7-17 year olds in the general population and more recently has been utilised among samples of children of prisoners. Previous research has variously tested traditional one-, three- and five- factor solutions to the SDQ, and more recently one bifactor solution has been examined. Based on a sample of children of prisoners (N = 724) and their non-imprisoned parent or caregiver (N = 658), the aim of the present study was to simultaneously compare nine alternative factor structures, including previously tested models and alternative bifactor solutions. Tests of factorial invariance and composite reliability were also performed. The five-factor model was found to provide the best fit for the data. Tests of factorial invariance revealed that the five-factor model provided an equally acceptable, but not identical fit, among boys and girls. Composite reliability scores were low for the Conduct Problems and Peer Problems subscales. The utility of the SDQ in measuring psychological functioning in response to parental imprisonment is discussed

Children of Prisoners: Their Situation and Role in Long-Term Crime Prevention

Studies suggest that maintaining family ties can help reduce the likelihood of reoffending, and that while parental imprisonment can increase a child’s likelihood to offend, positive responses to the situation can aid the children’s well-being, attitude and attainment. Drawing on findings from the recently completed EU-funded COPING Project on the mental health of children of prisoners, this chapter explores the factors that aid a child’s ability to cope with parental imprisonment and the actions that different stakeholders can take to support them. It identifies some of the mental health impacts at different stages of parental imprisonment, the roles played by non-imprisoned parents/carers and by schools, and suggests options for further clarifying the factors that help and hinder children of prisoners in the short and long term