The Nobel Prize for Physics 1920 was awarded to C.-E. Guillaume for his discovery of properties of nickel steels. He had previously observed that certain iron-nickel alloys exhibit the Invar effect i.e. an extremely low thermal expansion coefficient over a wide range of temperature. The decades since then have seen the observation of similar phenomena in other iron-based materials such as iron-platinum and iron-palladium. Moreover, there has been a great deal of theoretical work on the mechanism behind the Invar anomaly in the above-mentioned systems. However, despite many years of intensive research, a widely accepted microscopic theory of the effects is still lacking. The present thesis aims at providing an insight into the physical nature of the thermal expansion of ferromagnetic random face-centered cubic iron-nickel, ironplatinum and iron-palladium bulk solids. First, the thermal expansion coefficient is modeled as a function of temperature. The theory relies on the disordered local moment (DLM) formalism. However, contrary to all the previous models, the mapping between equilibrium states and partially disordered local moment (PDLM) states involves the probability that an iron-iron nearest-neighbour pair shows anti-parallel local magnetic moments, and the average lattice constant of the system at a finite temperature is calculated by minimization of an energy. The approach is applied to iron-nickel alloys. The model qualitatively reproduces several experimentally observed properties of disordered fcc iron-nickel solids. This includes Guillaume’s famous plot of the thermal expansion coefficient at room temperature as a function of concentration. Second, for the purpose of studying the origin of the anomalous expansion, the anomalous and normal contributions to the thermal expansion coefficient are defined, then evaluated for iron-nickel alloys. The results support the idea that the peculiar behaviour of the expansivity, , originates solely from the anomalous contribution,αa. Subsequently, the anomalous contribution is modeled for iron-nickel systems. In formulating the model, the following observation is taken into account; the average lattice spacing of an Fe100−xNix alloy at temperature T in a partially disordered local moment state is strongly negatively correlated with the probability that a nearest-neighbour pair has each of its two sites occupied by an iron atom and exhibits anti-ferromagnetically aligned magnetic moments (XFFAP). The quantity αa(x, T ) is estimated for several couples of values of the parameters x and T . Model results are found to agree qualitatively and quantitatively well with data obtained from the definition of αa. Thus, the model can successfully explain the basic process leading to the anomalous thermal expansion. It is consistent with the theory that the coefficient αa is controlled by the temperature derivative of XFFAP. Finally, the anomalous contribution to the thermal expansion coefficient of Fe72Pt28 and Fe66Pd34 solids is modeled as that of Fe65Ni35. A good agreement between the model results and experimental data for the expansivity as a function of temperature is noted. In conclusion, the Invar effects in disordered fcc iron-nickel, iron-platinum and iron-palladium alloys may have a common origin.

One of the most endangered assemblages of species in Europe is saproxylic beetles associated with old trees. To be able to conserve these species there is a need of developing methods to survey the fauna and to evaluate the conservation value of different oak habitats, develop instruments for landscape planning and detailed knowledge of species habitat requirements. The results are based on a data set from window and pit-fall trapping of saproxylic beetles at 94 different sites spread over four regions in southern Sweden. Additionally, 48 wooden boxes with artificial wood mould, consisting mainly of oak saw dust and oak leaves and some varying additional substrates, were studied for three years at three of the sites and their vicinities. A comparison of three methods to assess species richness and composition of the saproxylic beetle fauna in standing hollow oaks showed that all trapping methods were effective in detecting species, but as they partially target different assemblages of species it is profitable to combine the methods. Window traps gave most species but wood mould sampling is the cheapest method to sample the fauna. It was possible to predict the conservation value individual oak patches with sets of indicator species of saproxylic beetles with regard to number of species or presence of conservation priority species. Indicator sets of species effectively caught with pitfall traps gave the overall best predictions. When comparing different treatment of species indata, the explanatory power of predictions was strongest for presence/absence data. Predictions of species number and an index worked well within the same regions but gave varied result for three other regions, which shows that transferability of indicators between regions may be doubtful. Species richness was greatest in stands with large, free-standing trees. Among individual trees, large girth as well as low canopy cover, increased frequency of occurrence for several species. Forest regrowth was found to be detrimental for many beetle species. An evaluation of to what extent artificial habitats, mimicking the conditions in hollow oaks, can be exploited by saproxylic beetles showed that nearly 70% of the species found in hollow oaks was found in artificial wood mould boxes. A dead hen added to the artificial wood mould gave a higher number of beetle specimens. The number of species associated with tree hollows in oak decreased with distance from sites with hollow oaks. An analysis of species assemblages at 38 sites and positions of 33 000 large/hollow oaks showed that different beetle species dependent on a single substrate, hollow oaks, responded to different scales. The total species richness responded to a scale of 859 m and the characteristic scale of response for single species varied between 52 m and 5284 m. Several species were sensitive both to smaller and larger scales. As most sites with endangered beetles living in old oaks are small and isolated, ongoing management directed to keep old oaks free standing and sun exposed and to ensure the recruitment of young oaks, and the restoration of abandoned pasture woodlands should have a high priority in nature conservation. Artificial habitats may in critical areas be created to fill gaps in old oak habitat for parts of the species assemblage. To preserve the saproxylic beetle fauna dependent on old oaks, it is important to retain and create suitable habitats both in local stands and at the landscape level, from single hectares up to hundreds of hectares depending on the species. In some landscape, creations of new oak areas in the fragmented landscape are crucial for long-term survival of sensitive species.

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The (111) surfaces of Si and Ge were studied by scanning tunneling microscopy (STM) and photoelectron spectroscopy (PES) that are complementary techniques used to obtain structural and electronic properties of surfaces. The (111) surfaces have been of great interest because of the complex reconstructions formed by annealing. Adsorption of different types of atoms on these surfaces has been widely explored by many research groups. In this thesis work, both clean and modified Si(111) and Ge(111) surfaces were extensively studied to gain information about their atomic and electronic structures. Hydrogen plays a significant role in surface science, specifically in passivating dangling bonds of semiconductor surfaces. There has been a significant number of studies performed on hydrogen exposure of the Si(111)7x7 surface. However, most studies were done after higher exposures resulting in a 1x1 surface. In this thesis work, low hydrogen exposures were employed such that the 7x7 structure was preserved. STM images revealed that the hydrogen atoms preferentially adsorb on the rest atoms at elevated temperatures. A hydrogen terminated rest atom dangling bond is no longer visible in the STM image and the surrounding adatoms become brighter. This implies that there is a charge transfer back to the adatoms. Three types of Htermination (1H, 2H and 3H) were studied in detail by analysing the line profiles of the apparent heights. There are still unresolved issues regarding the electronic structure of the Ge(111)c(2x8) surface. By combining STM, angle-resolved photoelectron spectroscopy (ARPES), and theoretical calculations, new results about the electronic structure of the clean surface have been obtained in this thesis. A more detailed experimental surface band structure showing seven surface state bands is presented. A split surface state band in the photoemission data matched a split between two types of rest atom bands in the calculated surface band structure. A highly dispersive band close to the Fermi level was identified with states below the adatom and rest atom layers and is therefore not a pure surface state. The bias dependent STM images which support the photoemission results were in agreement with simulated images generated from the calculated electronic structure of the c(2x8) surface. Many studies have been devoted to hydrogen adsorption on Si(111)7x7 but only a few have dealt with Ge(111)c(2x8). In this work, hydrogen adsorption on Ge(111)c(2x8) has been studied using STM and ARPES. The preferred adsorption site is the rest atom. As a consequence of the adsorption on the rest atom there is a reverse charge transfer to the adatoms, which makes them appear brighter in the filled-state STM images. Photoemission results showed that for the H-exposed surface, the surface states associated with the rest-atom dangling bonds decreased in intensity while a new peak appeared in the close vicinity of the Fermi level which is not present in the spectrum of the clean surface. This is a clear evidence of a semiconducting to metallic transition of the Ge(111)c(2x8) surface. A higher H exposure on the Ge(111)c(2x8) surface was also done which resulted in a 1x1 surface. The electronic structure was investigated using ARPES. Two surface states were observed that are related to the Ge-Ge backbonds and the Ge-H bonds. Sn/Ge(111) has attracted a lot of attention from the surface science community because of the interesting phase transition from the RT-(√3x√3) phase to the LT-(3x3) phase. Previously, the Sn/Ge(111)√3x√3 surface was considered to be just a simple α- phase surface on which the Sn atoms sit on the T4 sites. However, a core-level study of the RT-(√3x√3) surface showed two components in the Sn 4d core-level spectra which implies that there are two inequivalent Sn atoms. The transition was later on explained by the dynamical fluctuation model. There have been different models proposed for the Sn/Ge(111)3x3 structure such as the 2U1D, 1U2D and IDA models. In this thesis work, the surface was studied using STM. The optimum √3x√3 surface was determined by performing different sample preparations. The LT STM images of the 3x3 surface were investigated and they showed that there are different types of Sn atoms such as up and down atoms. A histogram of the apparent height distribution revealed two peaks, a sharper peak associated with the up atoms and a broader peak for the down atoms. The height distribution was used to produce simulated Sn 4d core-level spectra and the line shape was compared to that of experimental spectra.

Blood and tissue velocities are measured and analyzed in cardiac, vascular, and other applications of diagnostic ultrasound. Errors in system performance might give invalid measurements. We developed two moving string test targets and a rotating cylinder phantom (Doppler phantoms) to characterize Doppler ultrasound systems. These phantoms were initially used to measure such variables as sample volume dimensions, location of the sample volume, and the performance of the spectral analysis. Later, specific tests were designed and performed to detect errors in signal processing, causing time delays and inaccurate velocity estimation in all Doppler modes. In cardiac motion pattern even time delays as short as 30 ms may have clinical relevance. These delays can be obtained with echocardiography by using flow and tissue Doppler and M-mode techniques together with external signals (e.g., electrocardiography (ECG) and phonocardiography). If one or more of these signals are asynchronous in relation to the other signals, an incorrect definition of cardiac time intervals may occur. To determine if such time delays in signal processing are a serious problem, we tested four commercial ultrasound systems. We used the Doppler string phantom and the rotating cylinder phantom to obtain test signals. We found time delays of up to 90 ms in one system, whereas delays were mostly short in the other systems. Further, the time delays varied relative to system settings. In two-dimensional (2D) Doppler the delays were closely related to frame rate. To determine the accuracy in velocity calibration, we tested the same four ultrasound systems using the Doppler phantoms to obtain test signals for flow (PW) and tissue (T-PW) pulse Doppler and for continuous wave (CW) Doppler. The ultrasound systems were tested with settings and transducers commonly used in cardiac applications. In two systems, the observed errors were mostly close to zero, whereas one system systematically overestimated velocity by an average of 4.6%. The detected errors are mostly negliable in clinical practice but might be significant in certain cases and research applications.

Atherosclerosis is a progressive inflammatory disease that causes lipid accumulation in the arterial wall, leading to the formation of plaques. The clinical manifestations of plaque rupture—stroke and myocardial infarction—are increasing worldwide and pose an enormous economic burden for society. Atherosclerosis development reflects a complex interaction between environmental exposures and genetic predisposition. To understand this complexity, we hypothesized that a top-down approach—one in which all molecular activities that drive atherosclerosis are examined simultaneously—is necessary to highlight those that are clinically relevant. To this end, we performed whole-genome expression profiling in multiple tissues isolated from patients with coronary artery disease (CAD). In the Stockholm Atherosclerosis Gene Expression (STAGE) study, biopsies of five tissues (arterial wall with and without atherosclerotic lesions, liver, skeletal muscle and visceral fat) were isolated from 124 CAD patients undergoing coronary artery bypass grafting surgery (CABG) at the Karolinska University Hospital, Solna and carotid lesions from 39 patients undergoing carotid artery surgery at Stockholm Söder Hospital. Detailed clinical characteristics of these patients were assembled together with a total of 303 global gene expression profiles obtained with the Affymetrix GeneChip platform. In paper 1, a two-way clustering analysis of the data identified 60 tissue clusters of functionally related genes. One cluster, partly present in both visceral fat and atherosclerotic lesions, related to atherosclerosis severity as judged by coronary angiograms. Many of the genes in that cluster were also present in a carotid lesion cluster relating to intima-media thickness (IMT) in the carotid patients. The union of all three clusters relating to extent of atherosclerosis—referred to as the “A-module”—was overrepresented with genes belonging to the transendothelial migration of leukocyte (TEML) pathway. The transcription co-factor, Lim domain binding 2 (LDB2), was identified as putative regulator of the A-module and TEML pathway in validation studies including Ldb2-/- mice. In paper 2, we investigated the increased incidence of postoperative complications in CABG patients with diabetes. Using the STAGE compendium, we identified an anti-inflammatory marker, dual-specificity phosphatase 1 (DUSP1), as a novel preoperative blood marker of risk for a prolonged hospital stay after CABG. In paper 3, plaque age was determined with C14-dating in the carotid patients. Interestingly, the strongest correlation with plaque age was not the age of the patients or IMT. Rather, the strongest correlations were with plasma insulin levels and inflammatory gene expression. Taken together, the findings in this thesis show that a top-down approach using multi-tissue gene expression profiling in CAD and C14-dating of plaques can contribute to a better understanding of the molecular processes underlying atherosclerosis development and to the identification of clinically useful biomarkers.

In this work, a selection of unresolved topics regarding the electronic and atomic structures of Si and Ge surfaces, both clean ones and those modified by metal adsorbates, are addressed. The results presented have been obtained using theoretical calculations and experimental techniques such as photoelectron spectroscopy (PES), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Si(001) surfaces with adsorbed alkali metals can function as prototype systems for studying properties of the technologically important family of metal-semiconductor interfaces. In this work, the effect of up to one monolayer (ML) of Li on the Si(001) surface is studied using a combination of experimental and theoretical techniques. Several models for the surface atomic structures have been suggested for 0.5 and 1 ML of Li in the literature. Through the combination of experiment and theory, critical differences in the surface electronic structures between the different atomic models are identified and used to determine the most likely model for a certain Li coverage. In the literature, there are reports of an electronic structure at elevated temperature, that can be probed using angle resolved PES (ARPES), on the clean Ge(001) and Si(001) surfaces. The structure is quite unusual in the sense that it appears at an energy position above the Fermi level. Using results from a combined variable temperature ARPES and LEED study, the origin of this structure is determined. Various explanations for the structure that are available in the literature are discussed. It is found that all but thermal occupation of an ordinarily empty surface state band are inconsistent with our experimental data. In a combined theoretical and experimental study, the surface core-level shifts on clean Si(001) and Ge(001) in the c(4×2) reconstruction are investigated. In the case of the Ge 3d core-level, no previous theoretical results from the c(4×2) reconstruction are available in the literature. The unique calculated Ge 3d surface core-level shifts facilitate the identification of the atomic origins of the components in the PES data. Positive assignments can be made for seven of the eight inequivalent groups of atoms in the four topmost layers in the Ge case. Furthermore, a similar, detailed, assignment of the atomic origins of the shifts on the Si surface is presented that goes beyond previously published results. At a Sn coverage of slightly more than one ML, a 2√3 × 2√3 reconstruction can be obtained on the Si(111) surface. Two aspects of this surface are explored and presented in this work. First, theoretically derived results obtained from an atomic model in the literature are tested against new ARPES and STM data. It is concluded that the model needs to be revised in order to better explain the experimental observations. The second part is focused on the abrupt and reversible transition to a molten 1×1 phase at a temperature of about 463 K. ARPES and STM results obtained slightly below and slightly above the transition temperature reveal that the surface band structure, as well as the atomic structure, changes drastically at the transition. Six surface states are resolved on the surface at low temperature. Above the transition, the photoemission spectra are, on the other hand, dominated by a single strong surface state band. It shows a dispersion similar to that of a calculated surface band associated with the Sn-Si bond on a 1×1 surface with Sn positioned above the top layer Si atoms. There has been extensive studies of the reconstructions on Si surfaces induced by adsorption of the group III metals Al, Ga and In. Recently, this has been expanded to Tl, i.e., the heaviest element in that group. Tl is different from the other elements in group III since it exhibits a peculiar behavior of the 6s2 electrons called the “inert pair effect”. This could lead to a valence state of either 1+ or 3+. In this work, core-level PES is utilized to find that, at coverages up to one ML, Tl exhibits a 1+ valence state on Si(111), in contrast to the 3+ valence state of the other group III metals. Accordingly, the surface band structure of the 1/3 ML √3 x √3 reconstruction is found to be different in the case of Tl, compared to the other group III metals. The observations of a 1+ valence state are consistent with ARPES results from the Si(001):Tl surface at one ML. There, six surface state bands are seen. Through comparisons with a calculated surface band structure, four of those can be identified. The two remaining bands are very similar to those observed on the clean Si(001) surface.

In the growing field of spintronics, development of semiconducting magnets is a high priority. Organic-based molecular magnets are attractive candidates since their properties can be tailor-made by organic chemistry. Other advantages include low weight and low temperature processing. Vanadium tetracyanoethylene, V(TCNE)x, x~2, is particularly interesting since it is one of very few semiconducting magnets with magnetic ordering above room temperature. The aim of the research presented in this thesis was to prepare and characterize thin film organic-based magnets with focus on V(TCNE)x. Photoelectron and absorption spectroscopy studies were performed leading to a more complete picture of the electronic and chemical structure of the material. Depending on the preparation method of V(TCNE)x, the material contains varying amounts of disorder which among other things makes it very air sensitive. In this thesis, a new preparation method for organic-based magnets based on physical vapor deposition is presented and the first result shows that it generates less air sensitive V(TCNE)x than previous methods reported. A new spin valve design based on V(TCNE)x was proposed where the material delivers both spin-filtering and spin-transporting functionality, making use of its fully spin-polarized transport levels. In such devices, the interface of V(TCNE)x with ferromagnetic metals is of great importance and was hence studied. As vanadium ions always are very reactive towards oxygen, substituting vanadium by a less reactive ion would be desirable from both an interface engineering and device packaging perspective. Very few alternatives exist however that orders magnetically above room temperature. In order to find out what are the key design criteria for preparing thin film semiconducting room temperature magnets, we have begun to study systems which order magnetically much below room temperature and compared them with V(TCNE)x.

QC 20100330

Research in the field of conjugated polymers (CPs) has led to the emergence of a number of interesting research areas and commercial applications, including solar cells, flexible displays, printed electronics, biosensors, e-textiles and more. Some of the advantages of organic electronics materials, as compared to their inorganic counterparts, include high elasticity, and mechanical flexibility, which allows for a natural integration of CPs into fabrics, making them ideal for e-texile. In this thesis, a novel approach for creating transistors is presented, through the construction of electrolyte gated transistors, directly embedded on functional textile fibers. Furthermore theoretical and experimental results of the integration of functional woven devices based on these transistors are shown. The realization of woven digital logic and design schemes for devices that can be placed inside living tissue, for applications such as neural communication, are demonstrated. Reducing feature sizes in organic electronics is necessity just as in conventional microelectronics, where Moore's law has been the most impressive demonstration of this over the past decades. Here the scheme of self-assembly (SA) of biomolecular/CP hybrid nano-structures is used for creating nano electronics. It is demonstrated that proteins in the form of amyloid fibrils can be coated with the highly conducting polythiophene derivative (PEDOT-S) through molecular self-assembly in water, to form conducting nanowire networks and nanodevices at molecular dimensions. In a second SA scheme, large area patterning of connected micro-nano lines and nano transistors from the conducting polymer PEDOT-S is demonstrated through assembly of these from fluids using soft lithography. Thereby the problems of large area nano patterning, and nano registration are solved for organic electronics. The construction of functional nanoscopic materials and components through molecular self-assembly has the potential to deliver totally new concepts, and may eventually allow cheap mass production of complex three dimensional nano electronic materials and devices.