Novel surgical and imaging methods of the middle ear and temporal bone

Välikorvaleikkauksiin usein liittyvän välikorvan ja kuuloluuketjun kirurgisen rekonstruktion tavoitteena on luoda olosuhteet, jotka mahdollistavat hyvän kuulon sekä välikorvan säilymisen tulehduksettomana ja ilmapitoisena. Välikorvan rekonstruktiossa on käytetty implanttimateriaaleina perinteisesti potilaan omia kudoksia sekä tarvittaessa erilaisia hajoamattomia biomateriaaleja, mm. titaania ja silikonia. Ongelmana biomateriaalien käytössä voi olla bakteerien adherenssi eli tarttuminen vieraan materiaalin pintaan, mikä saattaa johtaa biofilmin muodostumiseen. Tämä voi aiheuttaa kroonisen, huonosti antibiootteihin reagoivan infektion kudoksessa, mikä usein käytännössä johtaa uusintaleikkaukseen ja implantin poistoon. Maitohappo- ja glykolihappopohjaiset biologisesti hajoavat polymeerit ovat olleet kliinisessä käytössä jo vuosikymmeniä. Niitä on käytetty erityisesti tukimateriaaleina mm. ortopediassa sekä kasvo- ja leukakirurgiassa. Niitä ei ole toistaiseksi käytetty välikorvakirurgiassa. Korvan kuvantamiseen käytetään ensisijaisesti tietokonetomografiaa (TT). TT-tutkimuksen ongelmana on potilaan altistuminen suhteellisen korkealle sädeannokselle, joka kasvaa kumulatiivisesti, jos kuvaus joudutaan toistamaan. Väitöskirjatyö selvittää uuden, aiemmin kliinisessä työssä rutiinisti lähinnä hampaiston ja kasvojen alueen kuvantamiseen käytetyn rajoitetun kartiokeila-TT:n soveltuvuutta korvan alueen kuvantamiseen. Väitöskirjan kahdessa ensimmäisessä osatyössä tutkittiin ja verrattiin kahden kroonisia ja postoperatiivisia korvainfektioita aiheuttavan bakteerin, Staphylococcus aureuksen ja Pseudomonas aeruginosan, in vitro adherenssia titaanin, silikonin ja kahden eri biohajoavan polymeerin (PLGA) pintaan. Lisäksi tutkittiin materiaalien albumiinipinnoituksen vaikutusta adherenssiin. Kolmannessa osatyössä tutkittiin eläinmallissa PLGA:n biokompatibiliteettia eli kudosyhteensopivuutta kokeellisessa välikorvakirurgiassa. Chinchillojen välikorviin istutettiin PLGA-materiaalia, eläimiä seurattiin, ja ne lopetettiin 6 kk:n kuluttua operaatiosta. Biokompatibiliteetin arviointi perustui kliinisiin havaintoihin sekä kudosnäytteisiin. Neljännessä osatyössä tutkittiin kartiokeila-TT:n soveltuvuutta korvan alueen kuvantamiseen vertaamalla sen tarkkuutta perinteisen spiraali-TT:n tarkkuuteen. Molemmilla laitteilla kuvattiin ohimo- eli temporaaliluita korvan alueen kliinisesti ja kirurgisesti tärkeiden rakenteiden kuvantumisen tarkkuuden arvioimiseksi. Viidennessä osatyössä arvioitiin myös operoitujen temporaaliluiden kuvantumista kartiokeila-TT:ssa. Bakteeritutkimuksissa PLGA-materiaalin pintaan tarttui keskimäärin korkeintaan saman verran tai vähemmän bakteereita kuin silikonin tai titaanin. Albumiinipinnoitus vähensi bakteeriadherenssia merkitsevästi kaikilla materiaaleilla. Eläinkokeiden perusteella PLGA todettiin hyvin siedetyksi välikorvassa. Korvakäytävissä tai välikorvissa ei todettu infektioita, tärykalvon perforaatioita tai materiaalin esiin työntymistä. Kudosnäytteissä näkyi lievää tulehdusreaktiota ja fibroosia implantin ympärillä. Temporaaliluutöissä rajoitettu kartiokeila-TT todettiin vähintään yhtä tarkaksi menetelmäksi kuin spiraali-TT välikorvan ja sisäkorvan rakenteiden kuvantamisessa, ja sen aiheuttama kertasäderasitus todettiin spiraali-TT:n vastaavaa huomattavasti vähäisemmäksi. Kartiokeila-TT soveltui hyvin välikorvaimplanttien ja postoperatiivisen korvan kuvantamiseen. Tulokset osoittavat, että PLGA on välikorvakirurgiaan soveltuva, turvallinen ja kudosyhteensopiva biomateriaali. Biomateriaalien pinnoittaminen albumiinilla vähentää merkittävästi bakteeriadherenssia niihin, mikä puoltaa pinnoituksen soveltamista implanttikirurgiassa. Kartiokeila-TT soveltuu korvan alueen kuvantamiseen. Sen tarkkuus kliinisesti tärkeiden rakenteiden osoittamisessa on vähintään yhtä hyvä ja sen potilaalle aiheuttama sädeannos pienempi kuin nykyisen korva-spiraali-TT:n. Tämä tekee menetelmästä spiraali-TT:aa potilasturvallisemman vaihtoehdon erityisesti, jos potilaan tilanne vaatii seurantaa ja useampia kuvauksia, ja jos halutaan kuvata rajoitettuja alueita uni- tai bilateraalisesti.

Predicting the temporal response of seagrass meadows to dredging using Dynamic Bayesian Networks

Predicting temporal responses of ecosystems to disturbances associated with industrial activities is critical for their management and conservation. However, prediction of ecosystem responses is challenging due to the complexity and potential non-linearities stemming from interactions between system components and multiple environmental drivers. Prediction is particularly difficult for marine ecosystems due to their often highly variable and complex natures and large uncertainties surrounding their dynamic responses. Consequently, current management of such systems often rely on expert judgement and/or complex quantitative models that consider only a subset of the relevant ecological processes. Hence there exists an urgent need for the development of whole-of-systems predictive models to support decision and policy makers in managing complex marine systems in the context of industry based disturbances. This paper presents Dynamic Bayesian Networks (DBNs) for predicting the temporal response of a marine ecosystem to anthropogenic disturbances. The DBN provides a visual representation of the problem domain in terms of factors (parts of the ecosystem) and their relationships. These relationships are quantified via Conditional Probability Tables (CPTs), which estimate the variability and uncertainty in the distribution of each factor. The combination of qualitative visual and quantitative elements in a DBN facilitates the integration of a wide array of data, published and expert knowledge and other models. Such multiple sources are often essential as one single source of information is rarely sufficient to cover the diverse range of factors relevant to a management task. Here, a DBN model is developed for tropical, annual Halophila and temperate, persistent Amphibolis seagrass meadows to inform dredging management and help meet environmental guidelines. Specifically, the impacts of capital (e.g. new port development) and maintenance (e.g. maintaining channel depths in established ports) dredging is evaluated with respect to the risk of permanent loss, defined as no recovery within 5 years (Environmental Protection Agency guidelines). The model is developed using expert knowledge, existing literature, statistical models of environmental light, and experimental data. The model is then demonstrated in a case study through the analysis of a variety of dredging, environmental and seagrass ecosystem recovery scenarios. In spatial zones significantly affected by dredging, such as the zone of moderate impact, shoot density has a very high probability of being driven to zero by capital dredging due to the duration of such dredging. Here, fast growing Halophila species can recover, however, the probability of recovery depends on the presence of seed banks. On the other hand, slow growing Amphibolis meadows have a high probability of suffering permanent loss. However, in the maintenance dredging scenario, due to the shorter duration of dredging, Amphibolis is better able to resist the impacts of dredging. For both types of seagrass meadows, the probability of loss was strongly dependent on the biological and ecological status of the meadow, as well as environmental conditions post-dredging. The ability to predict the ecosystem response under cumulative, non-linear interactions across a complex ecosystem highlights the utility of DBNs for decision support and environmental management.

Extending temporal simulations

Direct numerical simulations (DNS) of spatially growing turbulent shear layers may be performed as temporal simulations by solving the governing equations with some additional terms while imposing streamwise periodicity. These terms are functions of the means whose spatial growth is calculated easily and accurately from statistics of the temporal DNS. Equations for such simulations are derived.

A Model of Anomalous Chain Translocation Dynamics

A model of polymer translocation based on the stochastic dynamics of the number of monomers on one side of a pore-containing surface is formulated in terms of a one-dimensional generalized Langevin equation, in which the random force is assumed to be characterized by long-ranged temporal correlations. The model is introduced to rationalize anomalies in measured and simulated values of the average time of passage through the pore, which in general cannot be satisfactorily accounted for by simple Brownian diffusion mechanisms. Calculations are presented of the mean first passage time for barrier crossing and of the mean square displacement of a monomeric segment, in the limits of strong and weak diffusive bias. The calculations produce estimates of the exponents in various scaling relations that are in satisfactory agreement with available data.

Delamination of Surfactant-Intercalated Brucite-Like Hydroxy Salts of Cobalt and Copper and Solvothermal Decomposition of the Resultant Colloidal Dispersions

Surfactant anion intercalated hydroxy salts of copper and cobalt of the formula M(OH)(2-x)(surf)(x)center dot mH(2)O [M = Cu, Co; surf = dodecyl sulfate. dodecyl benzene sulfonate. and x = 0.5 for Cu and 0.67 for Co] delaminate readily in 1-butanol to give translucent colloidal dispersions that are stable for months. The extent of delamination and the colloidal dispersion observed in these solids is higher than what had been observed for layered double hydroxides. The dispersions yield the corresponding nanoparticulate oxides on solvothermal decomposition. While the copper hydroxy salt forms similar to 300 nm dendrimer-like CuO nanostructures comprising nanorods of similar to 10 nm diameter, the cobalt analogue forms similar to 20 nm superparamagnetic particles of Co3O4.

Design of multiunit electronic exchanges through decomposition

In this paper, we exploit the idea of decomposition to match buyers and sellers in an electronic exchange for trading large volumes of homogeneous goods, where the buyers and sellers specify marginal-decreasing piecewise constant price curves to capture volume discounts. Such exchanges are relevant for automated trading in many e-business applications. The problem of determining winners and Vickrey prices in such exchanges is known to have a worst-case complexity equal to that of as many as (1 + m + n) NP-hard problems, where m is the number of buyers and n is the number of sellers. Our method proposes the overall exchange problem to be solved as two separate and simpler problems: 1) forward auction and 2) reverse auction, which turns out to be generalized knapsack problems. In the proposed approach, we first determine the quantity of units to be traded between the sellers and the buyers using fast heuristics developed by us. Next, we solve a forward auction and a reverse auction using fully polynomial time approximation schemes available in the literature. The proposed approach has worst-case polynomial time complexity. and our experimentation shows that the approach produces good quality solutions to the problem. Note to Practitioners- In recent times, electronic marketplaces have provided an efficient way for businesses and consumers to trade goods and services. The use of innovative mechanisms and algorithms has made it possible to improve the efficiency of electronic marketplaces by enabling optimization of revenues for the marketplace and of utilities for the buyers and sellers. In this paper, we look at single-item, multiunit electronic exchanges. These are electronic marketplaces where buyers submit bids and sellers ask for multiple units of a single item. We allow buyers and sellers to specify volume discounts using suitable functions. Such exchanges are relevant for high-volume business-to-business trading of standard products, such as silicon wafers, very large-scale integrated chips, desktops, telecommunications equipment, commoditized goods, etc. The problem of determining winners and prices in such exchanges is known to involve solving many NP-hard problems. Our paper exploits the familiar idea of decomposition, uses certain algorithms from the literature, and develops two fast heuristics to solve the problem in a near optimal way in worst-case polynomial time.

Direct probe of end-segment distribution in tethered polymer chains

End-tethered chains made of an adsorbed diblock copolymer of polystyrene (PS)-polyisoprene (PI) bearing an end-segment including a Ge atom are built by the Langmuir-Schaeffer technique. They are studied both in the dry state and in a good solvent for the PI chain using grazing incidence X-ray standing waves. The analysis of the signal provides a direct measurement of the end-segment distribution which is found to be singular and mostly localized to a plane in the dry case. In the good solvent case, end-segments are found to span the entire assembly and compare very well with results obtained by Kreer et al.

Gaussian mixture model based switched split vector quantization of LSF parameters

We address the issue of rate-distortion (R/D) performance optimality of the recently proposed switched split vector quantization (SSVQ) method. The distribution of the source is modeled using Gaussian mixture density and thus, the non-parametric SSVQ is analyzed in a parametric model based framework for achieving optimum R/D performance. Using high rate quantization theory, we derive the optimum bit allocation formulae for the intra-cluster split vector quantizer (SVQ) and the inter-cluster switching. For the wide-band speech line spectrum frequency (LSF) parameter quantization, it is shown that the Gaussian mixture model (GMM) based parametric SSVQ method provides 1 bit/vector advantage over the non-parametric SSVQ method.

Computationally efficient optimum weighting function for vector quantization of LSF parameters

We propose a new weighting function which is computationally simple and an approximation to the theoretically derived optimum weighting function shown in the literature. The proposed weighting function is perceptually motivated and provides improved vector quantization performance compared to several weighting functions proposed so far, for line spectrum frequency (LSF) parameter quantization of both clean and noisy speech data.

Tuning the beta-turn segment in designed peptide beta-hairpins: Construction of a stable type I ' beta-turn nucleus and hairpin-helix transition promoting segments

Designed octapeptides Boc-Leu-Val-Val-Aib-(D)Xxx-Leu- Val-Val-OMe ((D)Xxx = (D)Ala, 3a; (D)Val, 3c and (D)Pro, 5a) and Boc-Leu-Phe-Val-Aib-DAla-Leu-Phe-Val-OMe (3b) have been investigated to construct models of a stable type I' beta-turn nucleated hairpin and to generate systems for investigating helix-hairpin conformational transitions. Peptide 5a, which contains a central Aib-(D)Pro segment, is shown to adopt a stable type I' beta-turn nucleated hairpin structure, stabilized by four cross-strand hydrogen bonds. The stability of the structure in diverse solvents is established by the observation of all diagnostic NOEs expected in a beta-hairpin conformation. Replacement of (D)Pro5 by (D)Ala/(D)Val (3a-c) results in sequences that form beta-hairpins in hydrogen bonding solvents like CD3OH and DMSO-d(6). However, in CDCl3 evidence for population of helical conformations is obtained. Peptide 6b (Boc-Leu-Phe-Val-Aib-Aib-Leu-Phe-Val-OMe), which contains a centrally positioned Aib-Aib segment, provides a clear example of a system, which exhibits a helical conformation in CDCl3 and a significant population of both helices and hairpins in CD3OH and DMSO-d(6). The coexistence of multiple conformations is established by the simultaneous observation of diagnostic NOEs. Control over stereochemistry of the central beta-turn permits generation of models for robust beta-hairpins and also for the construction of systems that may be used to probe helix-hairpin conformational transitions. (c) 2006 Wiley Periodicals, Inc.

Context-dependency of a complex fruit-frugivore mutualism: temporal variation in crop size and neighborhood effects

The quantity of fruit consumed by dispersers is highly variable among individuals within plant populations. The outcome Of Such selection operated by firugivores has been examined mostly with respect to changing spatial contexts. The influence of varying temporal contexts on frugivore choice, and their possible demographic and evolutionary consequences is poorly understood. We examined if temporal variation in fruit availability across a hierarchy of nested temporal levels (interannual, intraseasonal, 120 h, 24 h) altered frugivore choice for a complex seed dispersal system in dry tropical forests of southern India. The interactions between Phyllanthus emblica and its primary disperser (ruminants) was mediated by another frugivore (a primate),which made large quantities of fruit available on the ground to ruminants. The direction and strength of crop size and neighborhood effects on this interaction varied with changing temporal contexts.Fruit availability was higher in the first of the two study years, and at the start of the season in both years. Fruit persistence on trees,determined by primate foraging, was influenced by crop size andconspecific neighborhood densities only in the high fruit availability year. Fruit removal by ruminants was influenced by crop size in both years and neighborhood densities only in the high availability year. In both years, these effects were stronger at the start of the season.Intraseasonal reduction in fruit availability diminished inequalities in fruit removal by ruminants and the influence of crop size and fruiting neighborhoods. All trees were not equally attractive to frugivores in a P. emblica population at all points of time. Temporal asymmetry in frugivore-mediated selection could reduce potential for co-evolution between firugivores and plants by diluting selective pressures. Inter-dependencies; formed between disparate animal consumers can add additional levels of complexity to plant-frugivore mutualistic networks and have potential reproductive consequences for specific individuals within populations.

Analysis of Energy Quantization Effects on Single-Electron Transistor Circuits

In this paper, the effects of energy quantization on different single-electron transistor (SET) circuits (logic inverter, current-biased circuits, and hybrid MOS-SET circuits) are analyzed through analytical modeling and Monte Carlo simulations. It is shown that energy quantizationmainly increases the Coulomb blockade area and Coulomb blockade oscillation periodicity, and thus, affects the SET circuit performance. A new model for the noise margin of the SET inverter is proposed, which includes the energy quantization effects. Using the noise margin as a metric, the robustness of the SET inverter is studied against the effects of energy quantization. An analytical expression is developed, which explicitly defines the maximum energy quantization (termed as ``quantization threshold'') that an SET inverter can withstand before its noise margin falls below a specified tolerance level. The effects of energy quantization are further studiedfor the current-biased negative differential resistance (NDR) circuitand hybrid SETMOS circuit. A new model for the conductance of NDR characteristics is also formulated that explains the energy quantization effects.

Evaluation and modelling of the spatial and temporal variability of particulate matter in urban areas

This thesis contains three subject areas concerning particulate matter in urban area air quality: 1) Analysis of the measured concentrations of particulate matter mass concentrations in the Helsinki Metropolitan Area (HMA) in different locations in relation to traffic sources, and at different times of year and day. 2) The evolution of traffic exhaust originated particulate matter number concentrations and sizes in local street scale are studied by a combination of a dispersion model and an aerosol process model. 3) Some situations of high particulate matter concentrations are analysed with regard to their meteorological origins, especially temperature inversion situations, in the HMA and three other European cities. The prediction of the occurrence of meteorological conditions conducive to elevated particulate matter concentrations in the studied cities is examined. The performance of current numerical weather forecasting models in the case of air pollution episode situations is considered. The study of the ambient measurements revealed clear diurnal variation of the PM10 concentrations in the HMA measurement sites, irrespective of the year and the season of the year. The diurnal variation of local vehicular traffic flows seemed to have no substantial correlation with the PM2.5 concentrations, indicating that the PM10 concentrations were originated mainly from local vehicular traffic (direct emissions and suspension), while the PM2.5 concentrations were mostly of regionally and long-range transported origin. The modelling study of traffic exhaust dispersion and transformation showed that the number concentrations of particles originating from street traffic exhaust undergo a substantial change during the first tens of seconds after being emitted from the vehicle tailpipe. The dilution process was shown to dominate total number concentrations. Minimal effect of both condensation and coagulation was seen in the Aitken mode number concentrations. The included air pollution episodes were chosen on the basis of occurrence in either winter or spring, and having at least partly local origin. In the HMA, air pollution episodes were shown to be linked to predominantly stable atmospheric conditions with high atmospheric pressure and low wind speeds in conjunction with relatively low ambient temperatures. For the other European cities studied, the best meteorological predictors for the elevated concentrations of PM10 were shown to be temporal (hourly) evolutions of temperature inversions, stable atmospheric stability and in some cases, wind speed. Concerning the weather prediction during particulate matter related air pollution episodes, the use of the studied models were found to overpredict pollutant dispersion, leading to underprediction of pollutant concentration levels.

A dynamical approach to the spatio-temporal features of the Portevin-Le Chatelier effect

We show that the extended Ananthakrishna's model exhibits all the features of the Portevin - Le Chatelier effect including the three types of bands. The model reproduces the recently observed crossover from a low dimensional chaotic state at low and medium strain rates to a high dimensional power law state of stress drops at high strain rates. The dynamics of crossover is elucidated through a study of the Lyapunov spectrum.