Insights into Atmospheric Nucleation

Atmospheric aerosol particles have a strong impact on the global climate. A deep understanding of the physical and chemical processes affecting the atmospheric aerosol climate system is crucial in order to describe those processes properly in global climate models. Besides the climatic effects, aerosol particles can deteriorate e.g. visibility and human health. Nucleation is a fundamental step in atmospheric new particle formation. However, details of the atmospheric nucleation mechanisms have remained unresolved. The main reason for that has been the non-existence of instruments capable of measuring neutral newly formed particles in the size range below 3 nm in diameter. This thesis aims to extend the detectable particle size range towards close-to-molecular sizes (~1nm) of freshly nucleated clusters, and by direct measurement obtain the concentrations of sub-3 nm particles in atmospheric environment and in well defined laboratory conditions. In the work presented in this thesis, new methods and instruments for the sub-3 nm particle detection were developed and tested. The selected approach comprises four different condensation based techniques and one electrical detection scheme. All of them are capable to detect particles with diameters well below 3 nm, some even down to ~1 nm. The developed techniques and instruments were deployed in the field measurements as well as in laboratory nucleation experiments. Ambient air studies showed that in a boreal forest environment a persistent population of 1-2 nm particles or clusters exists. The observation was done using 4 different instruments showing a consistent capability for the direct measurement of the atmospheric nucleation. The results from the laboratory experiments showed that sulphuric acid is a key species in the atmospheric nucleation. The mismatch between the earlier laboratory data and ambient observations on the dependency of nucleation rate on sulphuric acid concentration was explained. The reason was shown to be associated in the inefficient growth of the nucleated clusters and in the insufficient detection efficiency of particle counters used in the previous experiments. Even though the exact molecular steps of nucleation still remain an open question, the instrumental techniques developed in this work as well as their application in laboratory and ambient studies opened a new view into atmospheric nucleation and prepared the way for investigating the nucleation processes with more suitable tools.

Predicting crashes using traffic offences. A meta-analysis that examines potential bias between self-report and archival data

Background Traffic offences have been considered an important predictor of crash involvement, and have often been used as a proxy safety variable for crashes. However the association between crashes and offences has never been meta-analysed and the population effect size never established. Research is yet to determine the extent to which this relationship may be spuriously inflated through systematic measurement error, with obvious implications for researchers endeavouring to accurately identify salient factors predictive of crashes. Methodology and Principal Findings Studies yielding a correlation between crashes and traffic offences were collated and a meta-analysis of 144 effects drawn from 99 road safety studies conducted. Potential impact of factors such as age, time period, crash and offence rates, crash severity and data type, sourced from either self-report surveys or archival records, were considered and discussed. After weighting for sample size, an average correlation of r = .18 was observed over the mean time period of 3.2 years. Evidence emerged suggesting the strength of this correlation is decreasing over time. Stronger correlations between crashes and offences were generally found in studies involving younger drivers. Consistent with common method variance effects, a within country analysis found stronger effect sizes in self-reported data even controlling for crash mean. Significance The effectiveness of traffic offences as a proxy for crashes may be limited. Inclusion of elements such as independently validated crash and offence histories or accurate measures of exposure to the road would facilitate a better understanding of the factors that influence crash involvement.

An agent based adaptive bandwidth allocation scheme for multimedia applications

Bandwidth allocation for multimedia applications in case of network congestion and failure poses technical challenges due to bursty and delay sensitive nature of the applications. The growth of multimedia services on Internet and the development of agent technology have made us to investigate new techniques for resolving the bandwidth issues in multimedia communications. Agent technology is emerging as a flexible promising solution for network resource management and QoS (Quality of Service) control in a distributed environment. In this paper, we propose an adaptive bandwidth allocation scheme for multimedia applications by deploying the static and mobile agents. It is a run-time allocation scheme that functions at the network nodes. This technique adaptively finds an alternate patchup route for every congested/failed link and reallocates the bandwidth for the affected multimedia applications. The designed method has been tested (analytical and simulation)with various network sizes and conditions. The results are presented to assess the performance and effectiveness of the approach. This work also demonstrates some of the benefits of the agent based schemes in providing flexibility, adaptability, software reusability, and maintainability. (C) 2004 Elsevier Inc. All rights reserved.

Viestintää valtuustossa : Valtuutettujen viestintätyyli ja käsitys Helsingin kaupunginvaltuuston kokouksien viestinnästä

The goal of the study was to determine the kind of communication used in the meetings of the City Council. Councillors' addresses were studied by observing their communication styles. A questionnaire was used to study councillors' perception of communication in council meetings as perceived communication climate. A second goal of the study was to develop a method for analysing communication style. The nature of the study was a longitudinal case study. Studies of speech communication at the individual level and those of organisational communication at the community level served as the theoretical frame of reference. Due to the chosen object of study, political research and communication context shaped the frame of reference for the study. Verbal, nonverbal and paraverbal characteristics form the communication style. The perceived communication climate is dynamic in nature and consists of characteristics. The research material was gathered from the meetings of the Helsinki City Council held from 1993 to 1996. The communication style was analysed from meeting addresses (N=1271) given by the permanent members (N=95) of the council. The perceived communication climate was studied using a questionnaire modified from Wiio's OCD2 questionnaire. The questionnaire survey was carried out twice. The first time, 58 questionnaires (68%) were returned and, the second time, 49 questionnaires (58%) were returned. The method of analysis used for communication style was classification and cross tabulation. Based on the subset of material for the first year, five communication style categories were defined Communication style was examined using gender, length of council membership, and political party as subgroups. The results related to the perceived communication climate were analysed as averages and percentages. A comparison of the results from two different measuring times revealed how the perceived communication climate changed during a council term. The finding of the study was that the municipal politicians could be placed in all five communication style categories in each year of their four-year council term. The sizes of the style categories varied only little in the different years. A relatively stable - rather than changing - communication style was more characteristic of individuals during a council term. Gender did not explain an individual's communication style. On the other hand, the length of service in the council and, to some extent, the political party were connected with a certain communication style. Changes in style mainly manifested themselves as variation in communication activity so that activity was highest at the beginning and at the end of the council term. The method of researching communication style developed for this study proved to be functional, though labour-consuming. The perceived communication climate in the Helsinki City Council was good. Women's and men's satisfaction with the communication in the council differed; women's perception became considerably more positive at the end of the council term. Satisfaction with the communication in the council was characteristic of the Coalition Party and the Social Democrat councillors and dissatisfaction was characteristics of the Green councillors. Long council experience increased satisfaction with communication in the council. Only in the case of a few style categories was it possible to show any connection between the communication style and the perceived communication climate. The study confirmed the perception that an individual's communication style in the same communication context was relatively stable in the long term as well.

Investigations of the scaling criteria for a mild combustion burner

In this paper, a new strategy for scaling burners based on "mild combustion" is evolved and adopted to scaling a burner from 3 to a 150 kW burner at a high heat release Late of 5 MW/m(3) Existing scaling methods (constant velocity, constant residence time, and Cole's procedure [Proc. Combust. Inst. 28 (2000) 1297]) are found to be inadequate for mild combustion burners. Constant velocity approach leads to reduced heat release rates at large sizes and constant residence time approach in unacceptable levels of pressure drop across the system. To achieve mild combustion at high heat release rates at all scales, a modified approach with high recirculation is adopted in the present studies. Major geometrical dimensions are scaled as D similar to Q(1/3) with an air injection velocity of similar to 100 m/s (Delta p similar to 600 mm water gauge). Using CFD support, the position of air injection holes is selected to enhance the recirculation rates. The precise role of secondary air is to increase the recirculation rates and burn LIP the residual CO in the downstream. Measurements of temperature and oxidizer concentrations inside 3 kW, 150 kW burner and a jet flame are used to distinguish the combustion process in these burners. The burner can be used for a wide range of fuels from LPG to producer gas as extremes. Up to 8 dB of noise level reduction is observed in comparison to the conventional combustion mode. Exhaust NO emissions below 26 and 3 ppm and temperatures 1710 and 1520 K were measured for LPG and producer gas when the burner is operated at stoichiometry. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Study of gas cavity size hysteresis in a packed bed using DEM

When a high velocity gas jet is introduced into a packed bed a cavity is formed. The size of the cavity shows hysteresis on increasing and decreasing gas flow rates. This hysteresis leads to different cavity sizes at same gas flow rate depending on the bed history. The size of cavity affects the gas flow profiles in the packed bed. In this study the cavity size hysteresis phenomenon has been modeled using discrete element method along with turbulent gas flow. A reasonable agreement has been found between computed and experimental results on cavity size ysteresis. The effect of various parameters, such as nozzle height from the bed bottom and packing height, on the cavity size hysteresis has been studied. It is found that inter-particle interaction forces along with gas drag and bed porosity play an important role in describing the cavity size hysteresis. The injection of gas flow allows the particles to go to an unconstrained state than they were previously in, and their ability to remain in that state, even under decreased gas drag force, leads to the phenomenon of cavity size hysteresis. (c) 2007 Elsevier Ltd. All rights reserved.

Tradeoff between PAPR reduction and decoding complexity in transformed OFDM systems

It is known that in an OFDM system using Hadamard transform or phase alteration before the IDFT operation can reduce the Peak-to-Average Power Ratio (PAPR). Both these techniques can be viewed as constellation precoding for PAPR reduction. In general, using non-diagonal transforms, like Hadamard transform, increases the ML decoding complexity. In this paper we propose the use of block-IDFT matrices and show that appropriate block-IDFT matrices give lower PAPR as well as lower decoding complexity compared to using Hadamard transform. Moreover, we present a detailed study of the tradeoff between PAPR reduction and the ML decoding complexity when using block-IDFT matrices with various sizes of the blocks.

An agent based adaptive bandwidth allocation scheme for multimedia applications

Bandwidth allocation for multimedia applications in case of network congestion and failure poses technical challenges due to bursty and delay sensitive nature of the applications. The growth of multimedia services on Internet and the development of agent technology have made us to investigate new techniques for resolving the bandwidth issues in multimedia communications. Agent technology is emerging as a flexible promising solution for network resource management and QoS (Quality of Service) control in a distributed environment. In this paper, we propose an adaptive bandwidth allocation scheme for multimedia applications by deploying the static and mobile agents. It is a run-time allocation scheme that functions at the network nodes. This technique adaptively finds an alternate patchup route for every congested/failed link and reallocates the bandwidth for the affected multimedia applications. The designed method has been tested (analytical and simulation)with various network sizes and conditions. The results are presented to assess the performance and effectiveness of the approach. This work also demonstrates some of the benefits of the agent based schemes in providing flexibility, adaptability, software reusability, and maintainability. (C) 2004 Elsevier Inc. All rights reserved.

Transposable elements in a marginal plant population

Background
How new forms arise in nature has engaged evolutionary biologists since Darwin's seminal treatise on the origin of species. Transposable elements (TEs) may be among the most important internal sources for intraspecific variability. Thus, we aimed to explore the temporal dynamics of several TEs in individual genotypes from a small, marginal population of Aegilops speltoides. A diploid cross-pollinated grass species, it is a wild relative of the various wheat species known for their large genome sizes contributed by an extraordinary number of TEs, particularly long terminal repeat (LTR) retrotransposons. The population is characterized by high heteromorphy and possesses a wide spectrum of chromosomal abnormalities including supernumerary chromosomes, heterozygosity for translocations, and variability in the chromosomal position or number of 45S and 5S ribosomal DNA (rDNA) sites. We propose that variability on the morphological and chromosomal levels may be linked to variability at the molecular level and particularly in TE proliferation.

Results
Significant temporal fluctuation in the copy number of TEs was detected when processes that take place in small, marginal populations were simulated. It is known that under critical external conditions, outcrossing plants very often transit to self-pollination. Thus, three morphologically different genotypes with chromosomal aberrations were taken from a wild population of Ae. speltoides, and the dynamics of the TE complex traced through three rounds of selfing. It was discovered that: (i) various families of TEs vary tremendously in copy number between individuals from the same population and the selfed progenies; (ii) the fluctuations in copy number are TE-family specific; (iii) there is a great difference in TE copy number expansion or contraction between gametophytes and sporophytes; and (iv) a small percentage of TEs that increase in copy number can actually insert at novel locations and could serve as a bona fide mutagen.

Conclusions
We hypothesize that TE dynamics could promote or intensify morphological and karyotypical changes, some of which may be potentially important for the process of microevolution, and allow species with plastic genomes to survive as new forms or even species in times of rapid climatic change.

Koulun kestävän kehityksen työn merkitys kiinteistön jätehuollossa Case: Helsingin peruskoulujen jätekustannukset ja -määrät

Koulujen kestävän kehityksen työllä tarkoitetaan ekologiseen, taloudelliseen, sosiaaliseen ja kulttuuriseen kestävyyteen pohjautuvaa ympäristökasvatusta. Helsingissä peruskoulujen kestävän kehityksen työvälineet (ympäristökartoitukset ja – ohjelmat) ovat perustuneet koulujen ympäristöasioiden suunnitteluun, opetussuunnitelmien toteutumiseen ja ylläpitotoimintoihin, kuten jätehuoltoon. Opetusvirasto käytti vuosina 2005 ja 2009 ympäristötoiminnan arvioinnissa ympäristötasokuvauksia 1-3, joista arvosana 3 kuvaa ympäristöasioissa edistyneintä koulua. Tutkielman tavoitteena on tutkia ympäristötoiminnan tasojen perusteella ryhmiteltyjen peruskoulujen välisiä eroja jätekustannuksissa ja – määrissä (euroa/henkilö ja kg/henkilö) ja löytää mahdollisesti eroihin vaikuttavia tekijöitä. Tutkielman toimeksiantajana on 4V-Välitä, vaikuta, viihdy, voi hyvin – hanke, jonka yhtenä toiminnan osa-alueena on koulujen kestävän kehityksen työ. Tuloksista tullaan johtamaan tietoa Opetusviraston sekä muiden tahojen, kuten HSY:n ja Palmian ympäristötyöhön sekä Kiinteistöviraston Tilakeskuksen hallinnassa olevien koulukiinteistöjen jätehuollon kehittämiseen. Tutkimusaineistoina käytettiin Helsingin peruskoulujen vuoden 2009 jätekustannuksia ja tutkielman yhteydessä kerätyn jäteseurannan tuloksia vuodelta 2010. Jätekustannus- ja jätemääräaineistot yhdistettiin vuoden 2009 ympäristötoiminnan tasoluokitusten perusteella otokseksi (n=64). Lopullinen jätekustannus- ja jätemääräanalyysi tehtiin 29 koulun otoksella, josta oli rajattu pois kiinteistöt, joilla on koulun toiminnan lisäksi muita käyttötarkoituksia. Analyysiin sisällytettiin myös tarkempi tarkastelu koulujen seka- ja biojätejakeiden kustannuksista ja määristä. Tutkimuksen johtopäätöksenä todettiin, että eri ympäristötasoisten peruskoulujen välillä on huomattavia euro- ja kilomääräisiä eroja henkilöä kohden lasketuissa jätekustannuksissa ja –määrissä. Kokonaisjätemäärässä ei ole tapahtunut merkittävää muutosta tarkasteluvuosien välillä, mutta lajittelu näyttäisi kuitenkin tehostuneen. Tulosten perusteella ympäristöasioissa edistyneiden tason 3 koulujen keskimääräiset sekajätemäärät ja -kustannukset olivat pienimmät tasojen 1 ja 2 kouluihin verrattuna. Biojätemäärät ja –kustannukset olivat suurimmat tason 2 kouluissa. Jätekustannuksiin ja – määriin näyttäisivät vaikuttavan jäteastioiden määrien, kokojen ja tyhjennysrytmien optimointi sekä jäteastioiden täyttöasteet. Peruskoulujen tulisi keskittyä kestävän kehityksen työn avulla jätteiden synnyn ehkäisyyn ja vähentämiseen, jotta jätekustannuksetkin vähentyisivät jätehuollon kehittämistoimenpiteiden seurauksena.

Minimizing total weighted tardiness on a batch-processing machine with non-agreeable release times and due dates

This study considers the scheduling problem observed in the burn-in operation of semiconductor final testing, where jobs are associated with release times, due dates, processing times, sizes, and non-agreeable release times and due dates. The burn-in oven is modeled as a batch-processing machine which can process a batch of several jobs as long as the total sizes of the jobs do not exceed the machine capacity and the processing time of a batch is equal to the longest time among all the jobs in the batch. Due to the importance of on-time delivery in semiconductor manufacturing, the objective measure of this problem is to minimize total weighted tardiness. We have formulated the scheduling problem into an integer linear programming model and empirically show its computational intractability. Due to the computational intractability, we propose a few simple greedy heuristic algorithms and meta-heuristic algorithm, simulated annealing (SA). A series of computational experiments are conducted to evaluate the performance of the proposed heuristic algorithms in comparison with exact solution on various small-size problem instances and in comparison with estimated optimal solution on various real-life large size problem instances. The computational results show that the SA algorithm, with initial solution obtained using our own proposed greedy heuristic algorithm, consistently finds a robust solution in a reasonable amount of computation time.

Room-temperature equal channel angular extrusion of pure magnesium

In this paper, we demonstrate a way to impart severe plastic deformation to magnesium at room temperature to produce ultrafine grain size of similar to 250 nm through equal channel angular extrusion (ECAE). The strategy to deform magnesium at lower temperature or to achieve such grain sizes has been proposed as: (i) to obtain a suitable initial orientation with high Schmid factor for basal slip and low Schmid factor for pyramidal/prismatic slip; (ii) to take advantage of low stacking fault energy of basal and high stacking fault energies of prismatic/pyramidal planes in order to relatively work-harden the basal plane with respect to the pyramidal/prismatic plane; and (iii) to lower the temperature of deformation in steps, leading to continual refinement of grains, resulting in finer grain size. The experimental as well as simulated texture of ECAE-processed samples indicate that the deformation mechanism leading to ultrafine grain size is slip-dominated. The recrystallization mechanism during ECAE has been found to be orientation-dependent. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Studies on pneumatic atomization

A study of atomization has been made with an external mixing-type pneumatic atomizer. The drops were sampled on Vaseline-coated cells using a shutter arrangement and their sizes were measured under a microscope. The effects of liquid viscosity, liquid surface tension, liquid flow rate, air velocity, and nozzle angle on drop size have been studied. A model, which explains adequately the influence of various factors, has been proposed. This model predicts the values of average drop sizes over a wide range of operating conditions. The model also explains the data of other investigators who have used other kinds of pneumatic atomizers.

Monte Carlo simulations of molecular clusters in nucleation

A better understanding of the limiting step in a first order phase transition, the nucleation process, is of major importance to a variety of scientific fields ranging from atmospheric sciences to nanotechnology and even to cosmology. This is due to the fact that in most phase transitions the new phase is separated from the mother phase by a free energy barrier. This barrier is crossed in a process called nucleation. Nowadays it is considered that a significant fraction of all atmospheric particles is produced by vapor-to liquid nucleation. In atmospheric sciences, as well as in other scientific fields, the theoretical treatment of nucleation is mostly based on a theory known as the Classical Nucleation Theory. However, the Classical Nucleation Theory is known to have only a limited success in predicting the rate at which vapor-to-liquid nucleation takes place at given conditions. This thesis studies the unary homogeneous vapor-to-liquid nucleation from a statistical mechanics viewpoint. We apply Monte Carlo simulations of molecular clusters to calculate the free energy barrier separating the vapor and liquid phases and compare our results against the laboratory measurements and Classical Nucleation Theory predictions. According to our results, the work of adding a monomer to a cluster in equilibrium vapour is accurately described by the liquid drop model applied by the Classical Nucleation Theory, once the clusters are larger than some threshold size. The threshold cluster sizes contain only a few or some tens of molecules depending on the interaction potential and temperature. However, the error made in modeling the smallest of clusters as liquid drops results in an erroneous absolute value for the cluster work of formation throughout the size range, as predicted by the McGraw-Laaksonen scaling law. By calculating correction factors to Classical Nucleation Theory predictions for the nucleation barriers of argon and water, we show that the corrected predictions produce nucleation rates that are in good comparison with experiments. For the smallest clusters, the deviation between the simulation results and the liquid drop values are accurately modelled by the low order virial coefficients at modest temperatures and vapour densities, or in other words, in the validity range of the non-interacting cluster theory by Frenkel, Band and Bilj. Our results do not indicate a need for a size dependent replacement free energy correction. The results also indicate that Classical Nucleation Theory predicts the size of the critical cluster correctly. We also presents a new method for the calculation of the equilibrium vapour density, surface tension size dependence and planar surface tension directly from cluster simulations. We also show how the size dependence of the cluster surface tension in equimolar surface is a function of virial coefficients, a result confirmed by our cluster simulations.

Studies on induction of delta-aminolevulinic acid synthetase in mouse liver

Administration of 3,5-diethoxy carbonyl-1,4-dihydrocollidine (DDC) to mice resulted in a striking increase in the level of δ-aminolevulinic acid (ALA) synthetase in liver. Although the enzyme activity was primarily localized in mitochondria and postmicrosomal supernatant fluid, a significant level of activity was also detected in purified nuclei. The time course of induction showed a close parallelism between the bound and free enzyme activities with the former always accounting for a higher percentage of the total activity as compared to the latter. Studies with cycloheximide indicated a half-life of around 3 hr for both the bound and free ALA synthetase. Actinomycin D and hemin prevented enzyme induction when administered along with DDC, but when administered 12 hr after DDC treatment Actinomycin D did not lead to a decay of either the bound or free enzyme activity and hemin inhibited the bound enzyme activity but not the free enzyme level. The molecular sizes of the mitochondrial and cytosolic ALA synthetase(s) were found to be similar on sephadex columns.