Direct measurement of fluorescence lifetime using high speed data acquisition

Time-correlated single photon counting (TCSPC) is commonly used to measure the lifetime of fluorescence from dye molecules. In TCSPC, the sample is excited by a pulsed laser and the arrival time of each of the emitted photons at the detector relative to a trigger is recorded. An important criterion of the technique is that the excitation intensity of the laser has to be low enough such that the detector detects at most one photon per ten laser pulse excitations. As one needs to detect about 10$^4$ to 10$^6$ photons in order to generate a time trace of the fluorescence, the measurement has to be repeated about 10$^7$ times, which makes the technique rather slow. A typical measurement takes about 1s which is very long when the fluorescence lifetimes of most of the dye molecules range from few nanoseconds to microseconds. In this master's thesis, a novel method based on interleaved sampling and waveform averaging to directly measure the fluorescence decay from the dye molecule Rhodamine 6G is presented. A new algorithm using boot-strapped waveform averaging to improve the effective sampling rate as well as the signal to noise ratio of the digitized signal have been implemented and tested. The new algorithm has enabled us to reduce the measurement time to a few tens of a microseconds, which is approximately a million times faster than the TCSPC method.Boot-strapped waveform averaging (BSWA) is a technique that improves the way repetitive signals are processed

Direct Measurement of Fast Transients by Using Boot-strapped Waveform Averaging

An approximation to coherent sampling, also known as boot-strapped waveform averaging, is presented. The method uses digital cavities to determine the condition for coherent sampling. It can be used to increase the effective sampling rate of a repetitive signal and the signal to noise ratio simultaneously. The method is demonstrated by using it to directly measure the fluorescence lifetime from rhodamine 6G by digitizing the signal from a fast avalanche photodiode. The obtained lifetime of 4.4+-0.1 ns is in agreement with the known values

About the consideration of water in the forest landscape and the division of responsibility among the relevant authorities

This report is partly written on behalf of and together with the County Board of Västernorrland and the Swedish Forest Agency of District Västernorrland, who wanted help to clarify two questions. The first question was about whether there have been any changes in how forest owners act when clear cutting riparian forests close to streams. After changes in the Swedish forestry 1994 the riparian zones between the clear cutted area and the stream had increased its width from 1,3 to 6,6 meters and now the authorities wanted updated information about actual status concerning considerations that forestry takes in managing riparian forests. The report also examines the division of responsibility between the Swedish Forest Agency and the Swedish County Boards in the event of damage to watercourses in connection with forestry activities. The Swedish Forest Agency is the licensing authority for forestry and The Swedish County Board is responsible for issues relating to activities in water. The study tried to figure out exactly where the boundary were between them. The conclusion of the measurements of riparian buffer zones is that the forestry companies has become better in considerations to riparian zones close to streams and the average width of buffer zones reaches 12 meters, with a large spread. That is a big step forward but not enough to achieve full ecological function, which requires up to 30 meters wide buffer zones depending on local conditions and distribution in the spatial scale within a catchment. A form has been sent to all Swedish County Boards and local Swedish Forest Agency districts in which they have been asked to answer four questions about their responsibilities regarding forestry close to water. The responses received spread, but overall, a picture is given that it is quite clear how the responsibility is distributed and that it is The Swedish Forest Agency who is the responsible authority in most situations. Both authorities state that issues relating to water in connection with forestry measures are prioritized today, and it is likely that issues will be even greater in the future. Greater opportunities to impose sanctions on those who do wrong and cause damage to water systems are desired from both authorities as it is believed that it would significantly facilitate the work

Are non-wildlife passages effective passages for wildlife?

In order to mitigate barrier effects of highways and exclusion fences on wildlife, many countries have invested in specific wildlife crossing structures placed at selected strategic locations. While such structures may be significant to species conservation or management at local scale, they may not necessarily suffice to maintain landscape connectivity at broad scale. Conventional, non-wildlife road bridges, tunnels and culverts, however, are usually abundant along the major infrastructure corridors and are known to be used by animals at least occasionally. Given the large number and density of such passages, their accumulative effect may well be underestimated. On the other hand, there is uncertainty about how effectiveness of wildlife passages should be judged, because clear objectives and performance targets are undeveloped. We used track inventories to study the relative use of a total of 57 conventional road underpasses in south-central Sweden by common wildlife species such as moose (Alces alces), roe deer (Capreolus capreolus), red fox (Vulpes vulpes), badger (Meles meles) and hares (Lepus spp.). We studied the influence of passage dimensions, design, human disturbance and landscape factors and derived recommendations on limits in size and openness based on selected multiple regressions. Our results support earlier findings in that ungulates are more sensitive to underpass dimensions as medium-sized carnivores and hares. In general, moose and, to some degree also roe deer, used underpasses much less than expected from their occurrence in the surrounding habitat, whereas badgers and foxes, in particular, showed clear preference towards the underpasses. Openness appeared as a strong predictor for the relative use by most species, but also traffic within the underpasses and distance to nearest forest cover were important variables. Landscape attributes, such as habitat composition within 500 m around the passage or the distance to the nearest alternative crossing option, were of less significance to the relative use of underpasses. We estimated that underpasses with a relative openness of 2.3 (and minimum width of 11m), with limited human and vehicular traffic (12 passages per day) and nearby forest cover (distance <15 m) are likely to be used by moose at random, i.e., as much as expected from moose activity on control track beds. Smaller animals, including roe deer, will use such passages more frequently. We propose establishing random passage use (use as expected) as a performance target for non-wildlife crossing structures. Higher targets should be set for adapted wildlife passages. Additional, ecologically scaled performance targets must address the distance between adjacent crossing facilities. We conclude that, at least in Sweden, only a minor proportion of conventional road underpasses built for local access roads provide effective passages to roe deer and smaller species, and only very few to moose. It is worthwhile studying, however, whether other facilities can be created to provide safe passage for wildlife across roads or whether additional protective features can increase the attractiveness of existing structures and thereby provide more costefficient mitigation than the investment in new, adapted wildlife passages

Technology for spring harvesting of hemp for straw fuel

Hemp is an annual energy crop that fits very well in Swedish crop rotations. It is an interesting crop with many benefits, for example its ability to establish a large quantity of biomass in one year. Hemp is easy to grow and out-competes unwanted weeds through its aggressive growth pattern without the need for pesticides. Interest in growing hemp and other energy crops is currently decreasing, apparently because of high grain prices. These high prices give a higher net profit that we believe could partly cover the cost of hemp cultivation, while the hemp in turn would improve the crop rotation and thus repay its debts in the form of increased yields of other crops. The great disadvantage of hemp is the lack of knowledge about spring harvest of the crop. Spring harvest of hemp as straw fuel produces benefits in combustion quality but appears to generate large field losses of biomass that have not yet been accounted for. A satisfactory technique exists for autumn harvest of green hemp for biogas production. In this study we carried out field tests to measure harvesting losses in a hemp field close to Lund, southern Sweden. The hemp was cut using a modified (rapeseed) windrower or a forage harvester with a modified header that lays the material on the ground in a swathe instead of blowing it up into a wagon. The material was later baled using a flex chamber round baler or a big baler. Hemp yield was estimated in the field and averaged 12 tonnes dry matter per hectare. Weighing of bales showed the losses between calculated and measured harvest to be 34%, which is unacceptable in a crop grown specifically for its biomass. Two main sources of biomass losses were crop stubble and material disintegration by machinery use. However after subtracting these losses, losses of 18% were still unexplained. It is practically impossible to prevent losses at spring harvest because plants are very dry and brittle and the material crumbles easily and falls to the ground. Both the machines tested for cutting the hemp worked well, but there was large difference in their capacity. Both the balers tested worked well, with no differences in capacity or field biomass losses.Hampan är en ettårig energigröda som passar väl in i svenska växtföljder. Det är en intressant gröda med många fördelar som t.ex. potentialen att under en växtsäsong bilda en stor mängd biomassa. Hampan är lättodlad och slår ut ogräs med sitt aggressiva växtsätt, utan att kräva någon insats i form av bekämpningsmedel. Det verkar som om intresset för att odla hampa med dagens höga spannmålspriser har sjunkit en aning under våren 2008. Vi anser att spannmålen idag med dess bättre nettovinst kan vara med och bekosta odlingen av hampa. Om hampa införs möjliggörs en bättre växtföljd som på så sätt kan betala tillbaka i ökad skörd i de andra grödorna. Hampans stora nackdel är vårskörd i bal, eftersom man inte har så stor erfarenhet om hur man ska skörda den på bästa sätt. För skörd av grön hampa på hösten till biogasanläggningar finns det teknik som fungerar tillfredställande. En vanlig exakthack med majsbord brukar gå bra. Att skörda hampa torr på våren som stråbränsle är ett mycket intressant alternativ avseende förbränningsegenskaperna. Vårskörd har dock visat sig vara besvärlig och den ger ett stort spill vid strängläggning och pressning i bal. I detta arbete har vi gjort praktiska försök där vi tagit fram en försöksplan på hur man ska mäta spillet vid vårskörd av hampa och sedan genomfört detta hos en odlare utanför Lund. Strängläggningen av hampan gjordes med en modifierad rapshuggare samt en självgående exakthack med en modifierad knivtrumma. Exakthacken placerade materialet på marken i en sträng, istället för att blåsa upp det i en vagn. Det stränglagda materialet pressades sedan med en rundbalspress av flexkammartyp respektive en fyrkantspress. Skörden på fältet mättes med hjälp av skörderutor före strängläggning till i genomsnitt 12 ton torrsubstans per hektar. Den skördade mängden hampa i balar vägdes och visade ett totalt skördespill på ca 34 %, vilket är oacceptabelt för en gröda som är speciellt odlad för att användas som stråbränsle. Spill kan vi härleda till avsatt stubb samt söndersmulning av material som åker igenom maskinerna utan att därefter samlas upp av pressen. Om vi räknar bort spillet i form av stubbhöjd och söndersmulning så har vi fortfarande ett relativt stort spill som uppgår till ca 18 %. Att helt förhindra spill vid vårskörd av hampa är i princip omöjligt då tshalterna är så pass höga att det leder till smulning och förlust av materialet. Vid skördetidpunkten låg grödan bitvis ner, vilket medförde hög stubbhöjd, men annars fungerade båda strängläggningsmaskinerna till belåtenhet och skillnaderna dem emellan ligger främst i kapacitet. Pressningen utfördes med en rundbalspress respektive en fyrkantspress och det uppmättes ingen skillnad i spill mellan dessa pressar

Environmental Assessment of Upgrading Horticultural Side Streams—The Case of Unharvested Broccoli Leaves

: To facilitate transition to a sustainable food system, it is necessary to address food losses. A large proportion of waste occurs during primary production, with large quantities of edible crop parts left in the field at harvest. One such product is broccoli, where normally only around one-third of the edible parts of the plant are harvested in Sweden. Much of the broccoli plant consists of edible leaves and this side stream represents an unused resource with great potential. This study assessed the potential environmental savings that can be achieved by utilising broccoli side streams as a powder in soups and bread. Consequential and attributional life cycle assessments were conducted, based on scenarios relevant for growers in southern Sweden. The results showed that the scenario with the largest saving potential was to process the broccoli side streams into a powder for use in broccoli soup. The main saving was due to substitution of imported broccoli powder, which was assumed to be produced from broccoli florets using a more fossil-based energy mix. The second best scenario was to use the side-stream broccoli powder as a wheat substitute in bread but, since wheat flour is less resource-demanding than imported broccoli powder, the emission savings were lower in this case. However, replacing wheat flour with a vegetable-based product could provide additional health benefits that are important in achieving a healthy, locally available, and environmentally friendly diet suitable for a sustainable food system