Comparative moisture and heat sorption properties of fibre and shiv derived from hemp and flax

Abstract: Unlike many mineral-based insulation materials bio-based lignocellulosic fibre and shiv offer a number of benefits including thermal and hygroscopic properties. The microstructure, porosity and chemical compositions of the plant cell walls play a major role in the moisture exchange process. In this paper, the effects of microstructure, chemical composition, porosity and pore size distribution of both fibre and shiv, from hemp and flax plants, on both moisture and heat sorption were studied for the first time. The physical and chemical characteristics of the fibre and shiv from hemp and flax were studied by using scanning electron microscopy, mercury intrusion porosimetry and Fourier transform infrared spectroscopy. Water moisture sorption and heat of sorption were studied using a dynamic vapour sorption apparatus and a simultaneous thermal analysis system, combined with a humidity generator and using a copper furnace. Results showed that both the fibre and shiv of hemp and flax adsorbed a similar amount of moisture at a given relative humidity, which was dependent on the availability of hydroxyl groups for water in the cell wall. The macroscopic surface area and porosity of the specimen on a large scale had little influence on the availability of hydroxyl groups in the cell wall. The water molecules bound with cell wall molecules through hydrogen bonds over the full range of relative humidities, with a consistent hysteresis difference between the first sorption isotherm and subsequent sequential sorption cycles found in the hemp shiv specimens. For both hemp and flax, the isothermic hysteresis of the shiv was much higher than that of the fibre, which was shown to be dependent on the lignin content. The result of heat sorption indicated that some blocked sorption sites become available to water vapour molecules due to the change in molecular structure of the cell wall during the adsorption process. This study has improved understanding of the hemp and flax sorption behaviour and is important for optimal application of bio-based insulation materials for construction

Priests vs. Nazis in the diocese of Limburg, 1934: the confessional factor

Auf der Grundlage von Angaben aus Handbüchern über den biographischen und beruflichen Werdegang und die ausgeübten Posten wird in dem Beitrag am Beispiel der Diözese Limburg der konfessionelle Faktor in der Auseinandersetzung zwischen Priestern bzw. Pastoren, die das Nazi-Regime kritisiert oder angegriffen haben, und den Nazis untersucht. Zum Vergleich werden nach dem Zufallsprinzip aus den Handbüchern Kontrollgruppen ausgewählt, die den Nazi-Gegnern in der Diözese entsprechen. Die Ergebnisse des Vergleichs der Gegner mit den Mitläufern anhand von veränderlichen Variablen ergaben nur wenige Hinweise auf Abweichungen zwischen den Gruppen, mit Ausnahme des Durchschnittsalters. Am deutlichsten werden Unterschiede bzw. Abweichungen in der Diözese Limburg. Auf der Grundlage der Zahlen der Diözese Limburg wird als weiterer Untersuchungsschritt eine statistische Analyse der meßbaren Charakteristika der Geistlichen der Diözese durchgeführt. (KWübers

The Processes Controlling Primary Succession On An Alaskan Flood Plain

Thesis (Ph.D.) University of Alaska Fairbanks, 1985Life history and competitive processes were more important than facilitative processes in controlling seedling establishment during primary succession on an Alaskan river flood plain. These experimental results contrast with the widely held assumption that facilitation is essential to primary succession. Low soil and plant nitrogen levels in early succession are ameliorated by stands of alder associated with nitrogen-fixing bacteria. Yet seedlings transplanted into each successional stage grew least in alder stands where available nitrogen was highest. Increases in litter depth, root competition, and shade from alder limit most natural seedling establishment to river banks where alder stands have not yet formed but where mineral soil seed beds are available for germination. Colonization of the river banks is also influenced by stochastic factors such as seed production, seed dispersal, and fluctuating river levels. Distinct growth responses of seedlings to successional changes in light, water, and nutrient regimes alter the relative dominance of species in each successional stage. Rapidly growing willow, alder, and poplar seedlings were more tolerant of flooding and silt deposition but less shade-tolerant than the slowly growing spruce. Consequently, only spruce seedlings continued to establish in later stages. Relative longevities are therefore important in explaining the succession: the short-lived willow and alder die first, followed by poplar, and finally the long-lived spruce. Life history (regeneration, growth rate, and longevity), competitive, stochastic, and perhaps facilitative processes were important in the flood plain succession. Understanding plant succession requires examination of the role of each of these processes during establishment, maturation, and senescence phases of the life cycle of each species, rather than differentiation among complex but mutually exclusive successional models

Effect of Coriaria arborea on seed banks during primary succession on Mt Tarawera, New Zealand

An experiment was conducted over two years to investigate the effect of Coriaria arborea, a native nitrogen-fixing shrub, on soil seed banks at sites representing a post-volcanic successional sequence on Mt Tarawera, New Zealand. The sites ranged from bare volcanic ash and lapilli substrate, through low-growing pre-Coriaria vegetation, to dense stands of Coriaria scrub. Soils (to a depth of 50 mm) under recently established Coriaria and older stands had more seedlings (1096 and 1585 seedlings 0.4 m-2, respectively) and species (37 and 45 species 0.4 m-2, respectively) emerge than where there was no Coriaria (243-320 seedlings 0.4 m-2, 14-25 species 0.4 m-2) and were the only soils with Coriaria seedlings. In total, 3488 seedlings representing 63 taxa were recorded. Seeds were still germinating after 24 months but rates declined markedly in the second year. For example, Coriaria reached a germination peak at 8 weeks but continued to germinate sporadically over the 2-year period. Tree species present in young forest within 0.5 km of the sites were absent. Establishment of Coriaria greatly accelerated an underlying trend of gradually increasing abundance and diversity of seeds in the soil with vegetation age. Adventive, wind-dispersed, and annual species were over-represented in the seed banks compared with the regional evergreen forest-dominated flora. These proportions are expected to decline as succession to forest gradually occurs

The use of chronosequences in studies of ecological succession and soil development

1. Chronosequences and associated space-for-time substitutions are an important and often necessary tool for studying temporal dynamics of plant communities and soil development across multiple time-scales. However, they are often used inappropriately, leading to false conclusions about ecological patterns and processes, which has prompted recent strong criticism of the approach. Here, we evaluate when chronosequences may or may not be appropriate for studying community and ecosystem development. 2. Chronosequences are appropriate to study plant succession at decadal to millennial time-scales when there is evidence that sites of different ages are following the same trajectory. They can also be reliably used to study aspects of soil development that occur between temporally linked sites over time-scales of centuries to millennia, sometimes independently of their application to shorter-term plant and soil biological communities. 3. Some characteristics of changing plant and soil biological communities (e.g. species richness, plant cover, vegetation structure, soil organic matter accumulation) are more likely to be related in a predictable and temporally linear manner than are other characteristics (e.g. species composition and abundance) and are therefore more reliably studied using a chronosequence approach. 4. Chronosequences are most appropriate for studying communities that are following convergent successional trajectories and have low biodiversity, rapid species turnover and low frequency and severity of disturbance. Chronosequences are least suitable for studying successional trajectories that are divergent, species-rich, highly disturbed or arrested in time because then there are often major difficulties in determining temporal linkages between stages. 5. Synthesis. We conclude that, when successional trajectories exceed the life span of investigators and the experimental and observational studies that they perform, temporal change can be successfully explored through the judicious use of chronosequences

Segmented waveguides in thin silicon-on-insulator

We have developed new silicon-on-insulator waveguide designs for simultaneously achieving both low-loss optical confinement and electrical contacts, and we present a design methodology based on calculating the Bloch modes of such segmented waveguides. With this formalism, waveguides are designed in a single thin layer of silicon-on-insulator to achieve both optical confinement and minimal insertion loss. Waveguides were also fabricated and tested, and the measured data were found to closely agree with theoretical predictions, demonstrating input insertion loss and propagation loss better than 0.1 dB and -16 dB/cm, respectively

Characterising the anisotropic nature of bio-composites

Buildings contribute substantially to our greenhouse gas emissions and energy demands both in their occupation and construction. Their construction also consumes large volumes of finite resources. Sustainable, low embodied energy, high performance crop based materials therefore offer great potential. Hemp-lime is a bio-composite concrete, mass infill material with a greatly lower embodied energy than equivalent traditional constructions. It also exhibits beneficial hygrothermal properties that can improve both a building’s energy performance and the comfort of its occupants by buffering humidity and temperature. It is however widely considered insufficient structurally, limiting its scope for application. A lack of understanding and acknowledgment that hemp-lime and other similar bio-composites are anisotropic, but instead have a directional internal structure, has hindered the development of stronger and more versatile products. In this work a range of methods based on digital image analysis and computer tomography were trialled with the aim of identifying the nature of hemp-lime’s internal structure and providing a methodology to classify it. The results from both digital imaging and computer tomography scanning indicate that the internal structure of the specimens considered was highly anisotropic; a strong directionality in the hemp particles was found to be induced by the construction process. The novel assessment methods developed to allow the numerical classification the internal structure that may be used in the future to allow the structural optimisation and modelling of bio-composites