Browsing by Title

Sort by: Order: Results:

Now showing items 193-212 of 888
  • Mether, Lotta (Helsingin yliopisto, 2010)
    Currently, we live in an era characterized by the completion and first runs of the LHC accelerator at CERN, which is hoped to provide the first experimental hints of what lies beyond the Standard Model of particle physics. In addition, the last decade has witnessed a new dawn of cosmology, where it has truly emerged as a precision science. Largely due to the WMAP measurements of the cosmic microwave background, we now believe to have quantitative control of much of the history of our universe. These two experimental windows offer us not only an unprecedented view of the smallest and largest structures of the universe, but also a glimpse at the very first moments in its history. At the same time, they require the theorists to focus on the fundamental challenges awaiting at the boundary of high energy particle physics and cosmology. What were the contents and properties of matter in the early universe? How is one to describe its interactions? What kind of implications do the various models of physics beyond the Standard Model have on the subsequent evolution of the universe? In this thesis, we explore the connection between in particular supersymmetric theories and the evolution of the early universe. First, we provide the reader with a general introduction to modern day particle cosmology from two angles: on one hand by reviewing our current knowledge of the history of the early universe, and on the other hand by introducing the basics of supersymmetry and its derivatives. Subsequently, with the help of the developed tools, we direct the attention to the specific questions addressed in the three original articles that form the main scientific contents of the thesis. Each of these papers concerns a distinct cosmological problem, ranging from the generation of the matter-antimatter asymmetry to inflation, and finally to the origin or very early stage of the universe. They nevertheless share a common factor in their use of the machinery of supersymmetric theories to address open questions in the corresponding cosmological models.
  • Lukk, Margus (Helsingin yliopisto, 2010)
    This thesis studies human gene expression space using high throughput gene expression data from DNA microarrays. In molecular biology, high throughput techniques allow numerical measurements of expression of tens of thousands of genes simultaneously. In a single study, this data is traditionally obtained from a limited number of sample types with a small number of replicates. For organism-wide analysis, this data has been largely unavailable and the global structure of human transcriptome has remained unknown. This thesis introduces a human transcriptome map of different biological entities and analysis of its general structure. The map is constructed from gene expression data from the two largest public microarray data repositories, GEO and ArrayExpress. The creation of this map contributed to the development of ArrayExpress by identifying and retrofitting the previously unusable and missing data and by improving the access to its data. It also contributed to creation of several new tools for microarray data manipulation and establishment of data exchange between GEO and ArrayExpress. The data integration for the global map required creation of a new large ontology of human cell types, disease states, organism parts and cell lines. The ontology was used in a new text mining and decision tree based method for automatic conversion of human readable free text microarray data annotations into categorised format. The data comparability and minimisation of the systematic measurement errors that are characteristic to each lab- oratory in this large cross-laboratories integrated dataset, was ensured by computation of a range of microarray data quality metrics and exclusion of incomparable data. The structure of a global map of human gene expression was then explored by principal component analysis and hierarchical clustering using heuristics and help from another purpose built sample ontology. A preface and motivation to the construction and analysis of a global map of human gene expression is given by analysis of two microarray datasets of human malignant melanoma. The analysis of these sets incorporate indirect comparison of statistical methods for finding differentially expressed genes and point to the need to study gene expression on a global level.
  • Ruokolainen, Juha (Helsingin yliopisto, 2004)
  • Wang, Liang (Helsingin yliopisto, 2015)
    In-network caching aims at improving content delivery and alleviating pressures on network bandwidth by leveraging universally networked caches. This thesis studies the design of cooperative in-network caching strategy from three perspectives: content, topology and cooperation, specifically focuses on the mechanisms of content delivery and cooperation policy and their impacts on the performance of cache networks. The main contributions of this thesis are twofold. From measurement perspective, we show that the conventional metric hit rate is not sufficient in evaluating a caching strategy on non-trivial topologies, therefore we introduce footprint reduction and coupling factor, which contain richer information. We show cooperation policy is the key in balancing various tradeoffs in caching strategy design, and further investigate the performance impact from content per se via different chunking schemes. From design perspective, we first show different caching heuristics and smart routing schemes can significantly improve the caching performance and facilitate content delivery. We then incorporate well-defined fairness metric into design and derive the unique optimal caching solution on the Pareto boundary with bargaining game framework. In addition, our study on the functional relationship between cooperation overhead and neighborhood size indicates collaboration should be constrained in a small neighborhood due to its cost growing exponentially on general network topologies.
  • Ojalammi, Sanna (Helsingin yliopisto, 2006)
    This study Contested Lands: Land disputes in semi-arid parts of northern Tanzania. Case Studies of the Loliondo and Sale Division in the Ngorongoro District concentrates on describing the specific land disputes which took place in the 1990s in the Loliondo and Sale Divisions of the Ngorongoro District in northern Tanzania. The study shows the territorial and historical transformation of territories and property and their relation to the land disputes of the 1990s'. It was assumed that land disputes have been firstly linked to changing spatiality due to the zoning policies of the State territoriality and, secondly, they can be related to the State control of property where the ownership of land property has been redefined through statutory laws. In the analysis of the land disputes issues such as use of territoriality, boundary construction and property claims, in geographical space, are highlighted. Generally, from the 1980s onwards, increases in human population within both Divisions have put pressure on land/resources. This has led to the increased control of land/resource, to the construction of boundaries and finally to formalized land rights on village lands of the Loliondo Division. The land disputes have thus been linked to the use of legal power and to the re-creation of the boundary (informal or formal) either by the Maasai or the Sonjo on the Loliondo and Sale village lands. In Loliondo Division land disputes have been resource-based and related to multiple allocations of land or game resource concessions. Land disputes became clearly political and legal struggles with an ecological reference.Land disputes were stimulated when the common land/resource rights on village lands of the Maasai pastoralists became regulated and insecure. The analysis of past land disputes showed that space-place tensions on village lands can be presented as a platform on which spatial and property issues with complex power relations have been debated. The reduction of future land disputes will succeed only when/if local property rights to land and resources are acknowledged, especially in rural lands of the Tanzanian State.
  • Bhattacharya, Sourav (Helsingin yliopisto, 2014)
    In this thesis we develop novel methods for continuous and sustained context inference on mobile platforms. We address challenges present in real-world deployment of two popular context recognition tasks within ubiquitous computing and mobile sensing, namely localization and activity recognition. In the first part of the thesis, we provide a new localization algorithm for mobile devices using the existing GSM communication infrastructures, and then propose a solution for energy-efficient and robust tracking on mobile devices that are equipped with sensors such as GPS, compass, and accelerometer. In the second part of the thesis we propose a novel sparse-coding-based activity recognition framework that mitigates the time-consuming and costly bootstrapping process of activity recognizers employing supervised learning. The framework uses a vast amount of unlabeled data to automatically learn a sensor data representation through a set of extracted characteristic patterns and generalizes well across activity domains and sensor modalities.
  • Liao, Li (Helsingin yliopisto, 2014)
    Atmospheric aerosol particles influence the Earth's climate system, affect air visibility, and harm human health. Aerosol particles originate from both anthropogenic and biogenic sources, either from direct emissions or secondary particle formation. Secondary particle formation from gas phase precursors constitutes the largest fraction of global aerosol budget, yet large uncertainties remain in its mechanisms. This thesis attempted to study the source, the formation mechanisms, and the sink of secondary particles based on data analysis of field measurements and chamber experiments. In addition, numerical simulations were performed to model the processes of secondary particle formation observed in the chamber experiments. We summarized our findings into five main conclusions: 1) Monoterpenes originated from anthropogenic sources (e.g. forest industry) can significantly elevate the local average concentrations and result in a corresponding increase in local aerosol loading; 2) Monoterpenes from biogenic emissions show direct link to secondary particle production: the secondary aerosol masses correlate well with the accumulated monoterpene emissions; 3) Temperature influences biogenic monoterpene emissions, resulting in an indirect effect on the biogenic secondary particle production and corresponding cloud condensation nuclei (CCN) formation; 4) Both data analysis and numerical simulation suggested that nucleation involving the oxidation products of biogenic volatile organic compounds (VOCs) and H2SO4 better explains the nucleation mechanism, yet the specific VOCs participating in the nucleation process remains uncertain; 5) The numerical simulation showed evidence of vapor wall loss effect on the yield of secondary particles from the chamber experiments; a reversible gas-wall partitioning had to be considered to properly capture the observed temporal evolution of particle number size distribution during the chamber experiments. The results of this thesis contribute to the understanding on the role of monoterpenes to secondary particle formation. This thesis raises caution on the parameterization of the temperature dependence of biogenic secondary particle formation in predicting the aerosol production potential due to rising temperatures in the future. This work also points out a way for improving the comprehensive numerical models to better understand the secondary particle formation processes and related climatic effects.
  • Kuusisto-Hjort, Paula (Helsingin yliopisto, 2009)
    Contamination of urban streams is a rising topic worldwide, but the assessment and investigation of stormwater induced contamination is limited by the high amount of water quality data needed to obtain reliable results. In this study, stream bed sediments were studied to determine their contamination degree and their applicability in monitoring aquatic metal contamination in urban areas. The interpretation of sedimentary metal concentrations is, however, not straightforward, since the concentrations commonly show spatial and temporal variations as a response to natural processes. The variations of and controls on metal concentrations were examined at different scales to increase the understanding of the usefulness of sediment metal concentrations in detecting anthropogenic metal contamination patterns. The acid extractable concentrations of Zn, Cu, Pb and Cd were determined from the surface sediments and water of small streams in the Helsinki Metropolitan region, southern Finland. The data consists of two datasets: sediment samples from 53 sites located in the catchment of the Stream Gräsanoja and sediment and water samples from 67 independent catchments scattered around the metropolitan region. Moreover, the sediment samples were analyzed for their physical and chemical composition (e.g. total organic carbon, clay-%, Al, Li, Fe, Mn) and the speciation of metals (in the dataset of the Stream Gräsanoja). The metal concentrations revealed that the stream sediments were moderately contaminated and caused no immediate threat to the biota. However, at some sites the sediments appeared to be polluted with Cu or Zn. The metal concentrations increased with increasing intensity of urbanization, but site specific factors, such as point sources, were responsible for the occurrence of the highest metal concentrations. The sediment analyses revealed, thus a need for more detailed studies on the processes and factors that cause the hot spot metal concentrations. The sediment composition and metal speciation analyses indicated that organic matter is a very strong indirect control on metal concentrations, and it should be accounted for when studying anthropogenic metal contamination patterns. The fine-scale spatial and temporal variations of metal concentrations were low enough to allow meaningful interpretation of substantial metal concentration differences between sites. Furthermore, the metal concentrations in the stream bed sediments were correlated with the urbanization of the catchment better than the total metal concentrations in the water phase. These results suggest that stream sediments show true potential for wider use in detecting the spatial differences in metal contamination of urban streams. Consequently, using the sediment approach regional estimates of the stormwater related metal contamination could be obtained fairly cost-effectively, and the stability and reliability of results would be higher compared to analyses of single water samples. Nevertheless, water samples are essential in analysing the dissolved concentrations of metals, momentary discharges from point sources in particular.
  • Talponen, Jarno (Helsingin yliopisto, 2008)
    The topic of this dissertation is the geometric and isometric theory of Banach spaces. This work is motivated by the known Banach-Mazur rotation problem, which asks whether each transitive separable Banach space is isometrically a Hilbert space. A Banach space X is said to be transitive if the isometry group of X acts transitively on the unit sphere of X. In fact, some weaker symmetry conditions than transitivity are studied in the dissertation. One such condition is an almost isometric version of transitivity. Another investigated condition is convex-transitivity, which requires that the closed convex hull of the orbit of any point of the unit sphere under the rotation group is the whole unit ball. Following the tradition developed around the rotation problem, some contemporary problems are studied. Namely, we attempt to characterize Hilbert spaces by using convex-transitivity together with the existence of a 1-dimensional bicontractive projection on the space, and some mild geometric assumptions. The convex-transitivity of some vector-valued function spaces is studied as well. The thesis also touches convex-transitivity of Banach lattices and resembling geometric cases.
  • Ahmad, Jahir Uddin (Helsingin yliopisto, 2012)
    The oxidation of alcohols to the corresponding carbonyl compounds is a key reaction in the synthesis of organic chemicals. Consequently, a vast number of diverse methods based on copper that accomplish this functional group transformation are reviewed in this work. A successful development from pressurized oxygen to open air and from organic to environmentally friendly water solvent in oxidation of alcohols to the corresponding carbonyl compounds catalyzed by copper is presented. The first direct organocatalytic oxidation of alcohols to aldehydes with O2 in alkaline water was developed. One of the effects metal ions on the reaction was that the Cu ion is the most beneficial recipient of quantitative oxidation. Thus aerobic oxidation of alcohols to the corresponding carbonyl compounds catalyzed by TEMPO/Cu 2 N arylpyrrolecarbaldimine in alkaline water was discovered. The solid and solution structures of sterically hindered salicylaldimine and cis trans isomers of the corresponding Cu(II) complexes are discussed. High yield synthetic routes for mixed ligand Cu(II) complexes derived from salicylaldehyde and the corresponding salicylaldimine were developed. New crystal structures of the above compounds were determined by X ray crystallography. The catalytic property of homo and heteroligated bis(phenoxidoyimino)Cu(II)complexes toward oxidation reactions were investigated. Accordingly, facile base free aerobic oxidations of alcohols to aldehydes and ketones in toluene using low loading of both TEMPO and catalysts under mild conditions were introduced. In addition to the aerobic catalytic methods, oxidation of alcohols to the corresponding carbonyl compounds with H2O2 as an end oxidant in pure water using simple CuSO4 as a catalyst is presented. The effect of various additives, such as acids or bases, radical scavengers and N containing ligands, on the efficiency/selectivity of the catalyst system was studied as well. Finally, highly efficient open air oxidation of alcohols in water catalyzed by in situ made Cu(II) phenoxyimine complexes without additional auxiliarities such as base or co solvent are described.
  • Elers, Kai-Erik (Helsingin yliopisto, 2008)
    Transfer from aluminum to copper metallization and decreasing feature size of integrated circuit devices generated a need for new diffusion barrier process. Copper metallization comprised entirely new process flow with new materials such as low-k insulators and etch stoppers, which made the diffusion barrier integration demanding. Atomic Layer Deposition technique was seen as one of the most promising techniques to deposit copper diffusion barrier for future devices. Atomic Layer Deposition technique was utilized to deposit titanium nitride, tungsten nitride, and tungsten nitride carbide diffusion barriers. Titanium nitride was deposited with a conventional process, and also with new in situ reduction process where titanium metal was used as a reducing agent. Tungsten nitride was deposited with a well-known process from tungsten hexafluoride and ammonia, but tungsten nitride carbide as a new material required a new process chemistry. In addition to material properties, the process integration for the copper metallization was studied making compatibility experiments on different surface materials. Based on these studies, titanium nitride and tungsten nitride processes were found to be incompatible with copper metal. However, tungsten nitride carbide film was compatible with copper and exhibited the most promising properties to be integrated for the copper metallization scheme. The process scale-up on 300 mm wafer comprised extensive film uniformity studies, which improved understanding of non-uniformity sources of the ALD growth and the process-specific requirements for the ALD reactor design. Based on these studies, it was discovered that the TiN process from titanium tetrachloride and ammonia required the reactor design of perpendicular flow for successful scale-up. The copper metallization scheme also includes process steps of the copper oxide reduction prior to the barrier deposition and the copper seed deposition prior to the copper metal deposition. Easy and simple copper oxide reduction process was developed, where the substrate was exposed gaseous reducing agent under vacuum and at elevated temperature. Because the reduction was observed efficient enough to reduce thick copper oxide film, the process was considered also as an alternative method to make the copper seed film via copper oxide reduction.
  • Harun-or-Rashid, S M (Helsingin yliopisto, 2001)
  • Sloth, Martin Snoager (Helsingin yliopisto, 2003)
  • Tolppanen, Sakari (Helsingin yliopisto, 2015)
    Chemistry plays a key role in dealing with several of the big environmental problems of the future, but yet, chemistry education is often seen as irrelevant by students. Therefore, it is evident that ways to make chemistry education more relevant are called for. Educational experts have argued that sustainable development is a context that would bring relevance to science education, including chemistry education, as it bridges the gap between science and society. However, research on students perspective on the relevance of sustainable development is scarce. This thesis examines sustainable development and its education from the students viewpoint. This is done by seeking to answer the research problem: What do international students find relevant in sustainable development and its education? To answer this research problem, this thesis breaks down the problem into four research questions. The first research question examines what type of questions students ask about sustainable development, particularly in the area climate change. The second research question examines the kind of actions students take to make the world a better place. The third research question examines students expectations when applying to a non-formal educational program focused on sustainable development. The last research question examines how these expectations were met through the non-formal educational program. To address the research problem, the thesis adopted a multi-method approach, consisting of descriptive research, case studies and elements of grounded theory. The data was collected before, during and after an international youth camp, the Millennium Youth Camp held in the summers of 2010-2014. The participants of the study were 16-19 -year old students from around the world who were interested in science. The thesis consists of six interconnected studies. The first study examines the type of questions students ask about sustainable development and the second study examines the type of questions students ask about climate change, specifically. The data for these two studies were collected through an online survey from the students applying to the international youth camp. The data were analyzed using content analysis. The results indicate that students ask a variety of academic, societal and moral questions related to sustainable development. These questions cover many relevant aspects of sustainable development, and climate change specifically, and build a premise for student-centered education. In the third study, students attending the international youth camp were interviewed on the type of actions they take to make the world a better place. The data was analyzed though inductive and deductive content analysis and the results show that student actions can be categorized into three distinct groups, namely, personal responsible actions, participatory actions and future oriented actions. The fourth study used quantitative methods to address what type of expectations students have in education for sustainable development. The data was collected from students applying to the non-formal education program. The results show that in addition to wanting more knowledge on specific scientific phenomena and the nature of science, students expect to learn about societal impacts of environmental issues and discuss related moral issues. Studies four, five and six examine how the aforementioned expectations of the students can be met through non-formal education. These studies examine what type of structures and programs in the camp made the educational experience relevant for the students. The thesis concludes by asserting that students questions, actions and expectations can be used to make education for sustainable development more relevant in a number of ways. The thesis discusses the possibilities of (i) moving towards more student-centered learning, in which students questions and actions are the foundation of education, (ii) increasing relevant social and societal discussion with peers and experts, and (iii) providing students with opportunities to work on projects that address student interest. The thesis takes examples from the non-formal educational program studied and discusses how these same methods could be implemented into other similar programs or formal education.
  • Apiola, Mikko (Helsingin yliopisto, 2013)
    It is known that students' learning approaches, types of motivation, and types of self-regulation are connected with learning outcomes. It is also known, that deep learning approaches, self-regulated learning, and intrinsic types of motivation are connected with creativity. However, in computing pedagogy there is a lack in empirically grounded analyses in integration of the varying educational theories to build learning environments that support creativity. The literature of programming education proposes a variety of theoretical, as well as practical viewpoints in relation to the teaching and learning situation. However, little effort has been put on understanding cultural and contextual differences in pedagogy of programming. Literature shows that education is highly context dependent, and that educational design should account for contextual differences. In programming education, the nature and implications of those differences are hitherto unclear. In this study, the paucity in research about creativity-supporting learning environments in computing education, and about contextual differences in the pedagogy of programming are addressed through two case studies. In the first context (CUH) of this study (Department of Computer Science, University of Helsinki, Finland), a method of learning-by-inventing was designed and integrated into a robotics-based programming class, and its effects on students' learning were investigated through qualitative analysis of 144 interviews. In the second context (CTU) of this study (IT Department, Tumaini University, Iringa University College, Iringa, Tanzania) a number of interventions for supporting intrinsic motivation and deep approaches to learning were designed, and their effects on students' learning were studied through qualitative and quantitative methods, and a controlled research setup. In addition, a mixed methods study about contextual factors, which affect the learning environment design was conducted. In context CUH, the results show that the provided environment supported the learning of creative processes through a number of mechanisms. In general, the provided environment was shown to facilitate changes in students' problem management approaches, and extended students' deep and surface learning approaches to computer science related problem solving and problem management. In context CTU the results reveal that students face many similar challenges than students in other educational contexts, and that the standard learning environment does not offer enough support for gaining the requisite development. Learning is also hindered by many contextually unique factors. Testing a model where students work on their homework under guidance, facilitated by active student-teacher collaboration did not result in significant advantage over the control group. However, the qualitative results about guided environments were exclusively positive. In context CUH, the analysis suggests that learning of creativity may be facilitated by supporting deep learning strategies, intrinsic motivation, and self-regulated learning through utilizing a combination of open learning environment configuration, learning-by-inventing, and robotics as the vehicle for learning. Secondly, the analysis suggests challenges in context CTU to be addressed through increasing the number of practical exercises, by selecting the proper amount of guidance required in the learning environment, and by implementing educational action research as a standard component into the learning and teaching environment.
  • Daniel, Laila (Helsingin yliopisto, 2010)
    The ever expanding growth of the wireless access to the Internet in recent years has led to the proliferation of wireless and mobile devices to connect to the Internet. This has created the possibility of mobile devices equipped with multiple radio interfaces to connect to the Internet using any of several wireless access network technologies such as GPRS, WLAN and WiMAX in order to get the connectivity best suited for the application. These access networks are highly heterogeneous and they vary widely in their characteristics such as bandwidth, propagation delay and geographical coverage. The mechanism by which a mobile device switches between these access networks during an ongoing connection is referred to as vertical handoff and it often results in an abrupt and significant change in the access link characteristics. The most common Internet applications such as Web browsing and e-mail make use of the Transmission Control Protocol (TCP) as their transport protocol and the behaviour of TCP depends on the end-to-end path characteristics such as bandwidth and round-trip time (RTT). As the wireless access link is most likely the bottleneck of a TCP end-to-end path, the abrupt changes in the link characteristics due to a vertical handoff may affect TCP behaviour adversely degrading the performance of the application. The focus of this thesis is to study the effect of a vertical handoff on TCP behaviour and to propose algorithms that improve the handoff behaviour of TCP using cross-layer information about the changes in the access link characteristics. We begin this study by identifying the various problems of TCP due to a vertical handoff based on extensive simulation experiments. We use this study as a basis to develop cross-layer assisted TCP algorithms in handoff scenarios involving GPRS and WLAN access networks. We then extend the scope of the study by developing cross-layer assisted TCP algorithms in a broader context applicable to a wide range of bandwidth and delay changes during a handoff. And finally, the algorithms developed here are shown to be easily extendable to the multiple-TCP flow scenario. We evaluate the proposed algorithms by comparison with standard TCP (TCP SACK) and show that the proposed algorithms are effective in improving TCP behavior in vertical handoff involving a wide range of bandwidth and delay of the access networks. Our algorithms are easy to implement in real systems and they involve modifications to the TCP sender algorithm only. The proposed algorithms are conservative in nature and they do not adversely affect the performance of TCP in the absence of cross-layer information.
  • Veikkolainen, Toni (Helsingin yliopisto, 2014)
    A branch of science concentrated on studying the evolution of the Earth's magnetic field has emerged in the last half century. This is called paleomagnetism, and its applications include calculations of field directions and intensity in the past, plate tectonic reconstructions, variations in the conditions in the Earth s deep interior and the climatic history. With the increasing quantity and quality of observations, it has been even possible to construct models of conterminous continent blocks, or supercontinents, of the Pre-Pangaea time. These are crucial for the understanding of the evolution of our planet from the Archean to today. Paleomagnetists have traditionally heavily relied on the theory that when averaged over a period long enough, the Earth s magnetic field can be approximated as being equivalent to that generated by a magnetic dipole located at the center of the Earth and aligned with the axis of rotation. The credibility of this GAD (Geocentric Axial Dipole) hypothesis is strongest in the geologically most recent eras, such as most of the Phanerozoic and notably in the last 400 million years. Attempts to get an adequate view of the magnetic field in the Earth's earlier history have for a long time been challenged by the reliability limitations of Precambrian paleomagnetic data. With the absence of marine magnetic anomalies, observational data need to be gathered from terrestrial rocks, notably those formed within cratonic nuclei, the oldest and most stable parts of continents. To answer the call for a concise and comprehensive compilation of paleomagnetic data from the early history of the Earth, this dissertation introduces a unique database of over 3300 Precambrian paleomagnetic observations worldwide. The data are freely available at the server of the University of Helsinki ( and can be accessed via an online query form. All database entries have been coded according to their terranes, rock formation names, ages, rock types and paleomagnetic reliabilities. A new modified version of the commonly applied Van der Voo (MV) classification criteria for filtering the paleomagnetic data is also presented, along with a novel method for binning the entries cratonically to revise the previously employed way of applying binning via a simple evenly spaced geographic grid. Besides compiling data, tests of the validity of the GAD hypothesis in the Precambrian have been conducted using inclination frequency analysis and asymmetries of magnetic field reversals. Results from two self-contained tests of the GAD hypothesis suggest that the time-averaged Precambrian geomagnetic field may include the geocentric axial quadrupole and the geocentric axial octupole, but both with strengths less than 10% of the geocentric axial dipole, with the quadrupole perhaps being smaller than the octupole. In no other study a model so close to GAD has been reasonably fitted to the Precambrian paleomagnetic data. The weakness of the non-dipolar coefficients required also implies that no substantial adjustments need to be made to the novel models of Precambrian continental assemblies (supercontinents), such as the Paleo-Mesoproterozoic Columbia (Nuna) or the Neoproterozoic Rodinia. Although the supercontinent science still has plenty of uncertainty, it is more plausibly caused by the geological incoherence of the data and the lack of precise age information rather than by long-lived non-dipolar geomagnetic fields.