Produktion av träpulver med en ny malningsteknik : analys av specifik energiåtgång och produktens bulkegenskaper

The interest for lignocellulose biomass has grown strongly in the last decades due to its potential to substitute fossil fuels. Pre-processing of biomass is of-ten needed to enable utilization of its full potential. A common pre-processing step is milling where the biomass is fractionated into wood powder usable for e.g. wood powder combustion. There are a number of problematic factors affecting the utilization of wood powder, such as blockings and bridging, as a result of low density and elongated and irregular particle shapes. The aim with this study was to, for a novel milling technology, determine and evaluate the specific energy consumption, wood powder bulk- and flow properties together with a comparison of the results from a hammer mill. This study was carried out by milling of logs and collecting data from wood powder samples. Data from a log mill and a hammer mill’s energy consump-tion, wood powder density and wood powder flowability was collected. The results show that the log mill consumed least energy, when the blade rotation speed was low in combination with high moisture content and high feeding speed. The wood powder’s tapped densities had an interval of 190-320 kg/m3 respectively 150-260 kg/m3 for the loose density. The Hausner ra-tio had an interval of 1.22-1.32, indicating a good to medium-good flowability. The conclusions are that the log mill’s specific energy consumption de-creases with increasing moisture content, increasing moisture content de-creases the tapped- and loose density and that the Hausner ratio is showing promising results.Intresset för lignocellulosarik biomassa har ökat de senaste åren på grund av dess potential att substituera fossila bränslen. Förbehandling av biomassa är ofta en nödvändig åtgärd för att möjliggöra dess fulla potential. Ett vanligt processteg är att mala biomassan till pulverform lämpad för exempelvis pul-verförbränning. Det finns ett antal problematiska faktorer som påverkar an-vändningen av träpulver var av blockeringar och överbyggnad, som ett resul-tat av låg densitet och heterogena partiklar, påverkar flödet vid utnyttjande av träpulver. Syftet med studien var att, för en ny malningsteknik, bestämma och utreda den specifika energiåtgången och träpulvrets bulk- och flödesegenskaper samt att jämföra dessa med resultat från en hammarkvarn. Studien utfördes genom att mala stockar och att samla in data från pro-verna av det producerade träpulvret. Datamaterial från stock- och hammar-kvarnens energiåtgång, träpulvrets densitet samt träpulvrets flödesbarhet samlades in. Resultaten visade att stockkvarnen förbrukade minst energi när klingornas rotationshastighet var låg i kombination med hög matningshastighet och hög fukthalt på råmaterialet. Träpulvrets kompakterade densitet hade intervallet 190-320 kg/m3 respektive 150-260 kg/m3 för den lösa densiteten. Hausner ratio hade ett intervall på 1.22–1.32, vilket indikerar en bra till måttligt bra flödesbarhet. Slutsatserna är att stockkvarnens specifika energiåtgång minskar med ökad fukthalt, ökad fukthalt sänker den kompakterade- och lösa densiteten samt att Hausner ratio uppvisar lovande resultat

Seed production, infestation, and viability in Acacia tortilis (synonym: Vachellia tortilis) and Acacia robusta (synonym: Vachellia robusta) across the Serengeti rainfall gradient

Tree recruitment in savannas proceeds in multiple stages characterized by successive filters occurring at the seed and seedling stages. The “demographic bottleneck” hypothesis suggests that such filters ultimately restrict tree density and prevent trees from dominating grasses in savannas, but many of the demographic transitions underlying this assumption have not been quantified. We investigated how short- (1–2 years) and long-term (40 + years) rainfall patterns influenced seed production, infestation, and viability for two dominant species, Acacia robusta and Acacia tortilis across the Serengeti ecosystem mean annual precipitation gradient over a two-year period. We found that neither production, nor infestation, nor viability was influenced by rainfall. Pod production differed between species and increased with tree height in A. robusta. Mean infestation proportion in 2013 was higher (mean ± SE; 0.28 ± 0.08) in A. tortilis than in A. robusta (0.11 ± 0.05) but the trend reversed in 2014, when A. tortilis (0.33 ± 0.10) had lower infestation than A. robusta (0.61 ± 0.09). Under laboratory conditions, A. tortilis and A. robusta seeds had maximum germination (= viability) proportions of 70 and 20%, respectively. Mean seed viability was more than five-fold higher (0.46 ± 0.19) in A. tortilis than in A. robusta (0.08 ± 0.10). Our study has produced important estimates for seed stage demographic dynamics that can be used for modeling tree dynamics in Serengeti system, and savannas in general

Transpiration dynamics support resource partitioning in African savanna trees and grasses

Citation: Holdo, R. M., & Nippert, J. B. (2015). Transpiration dynamics support resource partitioning in African savanna trees and grasses. Ecology, 96(6), 1466-1472. doi:10.1890/14-1986.1It is still far from clear whether and to what extent trees and grasses partition soil moisture in tropical savannas. A major reason for this is that we don't know how snapshot data on rooting differences translate into ecologically relevant patterns of water use at seasonal scales. We used stable isotopes in soil and stem water to quantify functional rooting profiles in grasses and two tree species in a South African savanna. Concurrently, we measured tree sap-flow velocity, grass canopy temperature (a transpiration correlate), and soil moisture content at multiple depths over the course of a growing season. We used lasso regression to identify the dominant soil moisture layers driving daily variation in tree and grass water-use metrics while controlling for weather variables. We found clear rooting depth differences between grasses (shallow) and trees (deep) from the isotopic data, and these patterns were strongly supported by the water-use data, which showed that grasses and trees predominantly responded to soil moisture availability at 5 and 40 cm depth, respectively. Our results provide a rare example of mechanistic support for the resource partitioning hypothesis in savannas, with important implications for our understanding of tree-grass dynamics under altered precipitation regimes

Disaster Nursing: Looking to the Future in Norway

Health resilience is an integral part of disaster management and lies at the nexus between this and public health considerations. As the largest group of professionals worldwide, nurses face continual challenges in further developing their competences in disaster response and recovery. This paper investigates the trajectory, role and future expectations of the Norwegian nursing profession in health emergency and disaster planning, and offers a future research agenda for those interested in investigating the complex inter-relationship between disaster management and nursing. The paper seeks to respond to observations made in a recent Norwegian report (2013) on behalf of the Norwegian nursing association that highlights the need to investigate nurses’ knowledge in relation to emergency/disaster plans especially in the community health care system. The paper will explore the conceptual nuances between emergencies and disasters and then comments upon supplementary observations of the need for identifying disaster nursing practices and training programs to prepare nurses. By taking this approach, the paper also seeks to provide insights into how future demands of improving nurses´ capacities or implementation as leaders in disaster management – as highlighted by several International studies. In addition, by offering a future research agenda, the intention is that this may contribute to exploration of the role of nursing in handling long-term implications of disaster management

Power and Citizen Deliberation: The Contingent Impacts of Interests, Ideology, and Status Differences

Both advocates and critics of deliberative theory have regarded power relations as problems for public deliberation. Three aspects—interests, ideology and status differences—have been thought to distort deliberative processes. This article discusses a growing body of case studies that indicate that these “problems” may actually, under certain conditions, help facilitate inclusion and equality in deliberation. The crucial task is to specify the mechanisms that explain such unexpected outcomes and the conditions under which they may appear in other cases. This article specifies three such mechanisms that help explain positive outcomes in a number of case studies. The argument for focusing on mechanisms and conditions serves as a correction both to critics who find the theory of deliberation naïve and to advocates who have taken the critique against deliberative theory too lightly

Frostskadors effekt på granens (Picea abies (L.) H. karst) volymutveckling

Kandidatarbetet har behandlat frostskadors effekt på volymutvecklingen hos gran (Picea abies (L.) H. Karst), fram till 20 år efter planteringstillfället. De frostskador som undersöktes var de som drabbade plantorna under de tre första åren efter anläggning. Datamaterialet kom från Hyggesåldersförsöket där över 30 000 plantor ingick, varav en dryg tredjedel följdes upp efter 20 år. Försöket utfördes på två platser, fyra lokaler, i Götaland, två i Asa på Småländska höglandet och två på Tönnersjöheden i Halland. Det statistiska test som utfördes var flervägs- ANOVA i Minitab. Studien visade att frostskador hade en signifikant påverkan på volymutvecklingen i Asa, och för sammanslagningen av alla lokaler. Frostskador på Tönnersjöheden hade däremot inte en statistiskt säkerställd påverkan på volymen. Resultatet visade även att upprepade års frostskador sänkte medelstamsvolymen mer än enstaka års frostskador. När individerna med frostskador jämfördes med de utan, för de fyra lokalerna tillsammans, blev granarnas volym i genomsnitt 6,1 % lägre vid ett års frostskador. Två års skador ledde till 16,2 % volymförlust, och medelvolymen minskade med 26,9 % för plantor som frostskadades under alla tre åren, jämfört med de oskadade. Frostskador kan alltså vara ett betydande problem och skulle kunna förebyggas genom val av proveniens, skärmträd och/eller markberedning. Om det är lönsamt med en anpassad skötsel ur ett ekonomiskt perspektiv för att förebygga frostskador, får senare studier påvisa.This bachelor thesis has examined the effect of frost damage on volume production for Norway spruce (Picea abies (L.) H. Karst). The three first years of frost damage, after the planting was carried out, were studied, the volume was inventoried twenty years later. The datasets derived from Hyggesåldersförsöket, which included more than 30 000 seedlings. Approximately one third were measured after 20 years. The experiment took place at two locations in the southern part of Sweden, Asa an inland site and in Tönnersjöheden a coastal site. The statistical test was carried out using a multiway-ANOVA in Minitab. The study showed that damage caused by frost had a significant effect on the volume production in Asa and for all sites together, but not significantly at Tönnersjöheden. The result showed that the repeated years of frost damage decreased the average stem volume more than a single year. Average volume for trees with frost damage were compared to those without any frost damage for all sites, one year of frost damage had 6,1 % less volume. Two years reduced the average volume with 16,2 %, and the average volume was 26,9 % lower for those seedlings that were injured during all three measured years. Frost damage could be a considerable issue which could be prevented with a different choice of provenances, shelterwood and/or scarification. Whether or not it would be profitable to prevent frost damage with an adapted silviculture, from an economical point of view, additional studies would be required to examine this

Disaster nursing or nursing in disaster: a case study approach to investigate the future requirements of disaster nursing in Norway.

This PhD study has undertaken a critical evaluation of nurses’ role in disasters and mass casualty events with particular reference to remote community settings. Nurses in particular are important in order to reduce the effect of a disaster on the affected population and growing awareness of disaster facilitates and opens up discussion in relation to ‘disaster nursing’. Disaster Nursing (DN) can be briefly defined as providing holistic nursing to affected populations in all phases of a disaster. The main aim has been to critically evaluate the present and future requirements of Disaster Nursing using rural northern Norway as a case study. Rural northern Norway was chosen as a case study because the country as a whole represents an industrially advanced society with comparatively sophisticated health care provision and developed municipal nursing services. A Disaster Nursing (DN) and more generalist Nursing in Disaster (ND) Conceptual Framework (DN-ND) was introduced to understand the routes and processes for developing (more) effective disaster nursing arrangements and education. Interviews of municipal nurses and their leaders working in different districts of rural northern Norway revealed that nurses had little or no influence on or knowledge of local Disaster Management and Health Preparedness plans. The opinions of nurses and leaders also exposed that disaster training and exercises did not involve nurses. However, interviews uncovered the need for improvements in organisation, training and education of nurses to provide health care in disasters. Leaders and nurses express a need for Disaster topics at or in addition to BSc level, and a specialisation at MSc level, thus endorsing the DN-ND conceptual framework although with appropriate local adjustments. Finally, it is demonstrated that only through university academic research in nursing, giving the provision of a permanent comprehensive educational and training strategy can nurses realistically manage to handle health care in relation to disasters for all the differing aspects of, and within the disaster management cycle

Grass competition overwhelms effects of herbivores and precipitation on early tree establishment in Serengeti

1. Savanna ecosystems span a diverse range of climates, edaphic conditions and disturbance regimes, the complexity of which has stimulated long‐standing interest in the mechanisms that maintain tree‐grass coexistence. One hypothesis suggests that tree establishment is strongly limited by one or several demographic bottlenecks at early stages of the tree life cycle. A major impediment to testing this hypothesis is the lack of data on the relative strengths of different bottlenecks across key environmental gradients. 2. To identify demographic bottlenecks that limit early tree establishment (0‐18 months), we conducted a series of transplant experiments with two savanna trees species (Acacia robusta and A. tortilis) across a natural rainfall and soil fertility gradient in the Serengeti ecosystem, Tanzania. We tested the interactive effects of precipitation, herbivory, seed scarification, grass competition, water limitation and tree species identity on two key life stages: germination and early seedling survival (0‐2 months) and juvenile seedling survival (2‐18 months). 3. Germination and early seedling survival increased as a function of rainfall, in the absence of herbivores and when seeds were scarified. Juvenile seedling survival, in contrast, decreased with rainfall but increased in the absence of herbivores. Grass removal had the single strongest (positive) effect on juvenile seedling survival of any treatment. Soil moisture monitoring and grass‐addition treatments revealed that grasses negatively affected seedlings in ways that were not necessarily linked to soil moisture. 4. A demographic model combining all effects across early life stages showed that the strength of grass competition on juvenile seedling survival was the key factor limiting early tree establishment. While rainfall had an unexpected opposing effect on the two life stages, the net effect of mean annual precipitation on early tree establishment was positive. 5. Synthesis: Successful tree establishment in Serengeti is maximized by a seemingly unlikely sequence of events: (1) scarification of seeds by browsers, (2) heavy rainfall to promote germination, (3) intensive grazing (but absence of browsers) and (4) dry conditions during juvenile seedling growth (>2 months) to reduce competition with grasses. By considering a wide suite of conditions and their interactions, our experimental results are relevant to ongoing debates about savanna vegetation dynamics and structural shifts in tree:grass ratios

Predicted Impact of Barriers to Migration on the Serengeti Wildebeest Population

The Serengeti wildebeest migration is a rare and spectacular example of a once-common biological phenomenon. A proposed road project threatens to bisect the Serengeti ecosystem and its integrity. The precautionary principle dictates that we consider the possible consequences of a road completely disrupting the migration. We used an existing spatially-explicit simulation model of wildebeest movement and population dynamics to explore how placing a barrier to migration across the proposed route (thus creating two disjoint but mobile subpopulations) might affect the long-term size of the wildebeest population. Our simulation results suggest that a barrier to migration—even without causing habitat loss—could cause the wildebeest population to decline by about a third. The driver of this decline is the effect of habitat fragmentation (even without habitat loss) on the ability of wildebeest to effectively track temporal shifts in high-quality forage resources across the landscape. Given the important role of the wildebeest migration for a number of key ecological processes, these findings have potentially important ramifications for ecosystem biodiversity, structure, and function in the Serengeti

Controlled Actuation of Self-Propelled Droplets

© 2020, University of Hertfordshire.In this paper we present controlled self-propelled actuation of droplets employing Laplace pressure gradients between two non-parallel superhydrophobic plates. For small angles (cos β ≈ 1) a simplification of available energy-based models can accurately predict the droplets initial acceleration. By adjusting the plates’ spacing and angle (from 0.2° to 1.5°), the value of the droplets initial acceleration can be varied from 0.28 m s^-2 to 3.9 m s^-2 hence showing significant promise for precise controlled actuation. Such an actuation principle could find applications within droplet-based lab-on-a-chip systems where superhydrophobic surfaces could help address the challenges of transporting biomaterial laden droplets.Peer reviewe