Extracts from recent PhD theses

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Below are extract from a selection of recent PhD theses:

April 2017


"Longer, lighter blades"

Photo: Colourbox A key aspect of wind energy research is reducing costs. This can be achieved by reducing the total weight of the rotor blades, while at the same increasing their size and performance. However, this requires finding a way to limit the aerodynamic loads on the blades. One possibility is passive control, where the blade is constructed so that the structure load is relieved when deformed. A wind turbine rotor that can be passively relieved is a cost-effective solution, as it allows a lighter design and longer blades without the need for actuators and other mechanical solutions. Christian Pavese from DTU Wind Energy has discovered a method to exploit the full potential of passive control, and demonstrated how integration of passive control as a design variable can pave the way for wind turbine blades where passive load reduction can result in significantly lower blade weight or enhance wind energy production.

"New tool for planning S-train operation"

Photo: Colourbox With annual operating costs amounting to several hundred million kroner, planning is paramount at DSB (the Danish National Railways). A key planning parameter is ensuring adequate seating for passengers. Another is avoiding empty train compartments. Then, of course, there is the railway’s physical infrastructure, the timetable, rolling stock, maintenance, etc. Planning for all these parameters is a time-consuming and complex process—and the planning process is still predominantly manual. Per Thorlacius from DTU Management Engineering has designed automatic planning models which—in contrast to today—integrate all of DSB’s technical requirements for the S-train network. He has shown that the integrated planning models can be used to automate processes, which are currently manual—and not least, secure DSB substantial economic efficiency improvements in S-train operation.

"RNA-vaccine against widespread PRRS"

Photo: Colourbox One of the biggest problems in global pig production is Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), which reduces the immune defence system, causes pneumonia, and in gestating sows can lead to miscarriages, premature birth, or stillborn piglets. Simon Welner from DTU Vet has developed a new vaccine based on RNA sequences that encode for virus peptides which activate a killer T cell response against PRRSV. The sequences are spliced into a living, weakened RNA virus (RNA vector replicon). In an experimental testing of the new RNA vector replicon vaccine, all the vaccinated pigs developed antibodies against the viral vector, but only a few specific killer T cells against PRRSV—and very weak protection against infection. The conclusion is that the design worked, but that there is still a long way to go before developing a functional vaccine against PRRSV.


Marts 2017


"Molecules from intestinal bacteria protect health"

Photo: Janne Marie LaursenBillions of bacteria and microorganisms in our intestines—our intestinal microbiome—play an important role in relation to human health. Janne Marie Laursen from DTU Bioengineering has investigated how specific molecules produced by intestinal bacteria (endotoxins) affect the immune system in the intestines and help develop resistance to insulin—an important factor in type 2 diabetes.
A newly developed method was used to see which bacteria produce different variants of endotoxin. It showed that contrary to expectations, there are far more bacteria in the intestines producing a non-harmful variant of endotoxin than bacteria producing a harmful variant. The method also showed a correlation between insulin resistance and the quantity of endotoxin-producing bacteria in the intestines. Further analyses showed that a particular fatty acid can shut down production of pro-inflammatory proteins and instead produce other proteins that maintain healthy intestinal tissue.
This knowledge will eventually allow people to be treated by changing the composition of intestinal bacteria that cause lifestyle diseases.

Illustration: Tarmmikrobiom_Credit_Janne Marie Laursen / Omslag-hvid-kun-forside_Credit_Janne Marie Laursen

"Better industrial production of graphene"

Photo: Patrick Rebsdorf WhelanThere are great expectations of graphene—an extremely stable material consisting of a single layer of carbon atoms. It is currently used in a number of products, but applications where it can have a major impact—such as transparent electrodes in solar cells and flat screens—are still some way off. Graphene is currently produced via a chemical process whereby it is deposited onto copper. It is then necessary to move the thin graphene layer to another surface before it can be used. This often leads to defects.
Patrick Rebsdorf Whelan from DTU Nanotech is addressing this challenge and has developed new ways to transfer the graphene. In contrast to the existing method, where the copper substrate is etched away, they leave it intact, so it can be used to grow a new layer of graphene. Using these methods, the electronic properties of graphene are also better transferred than using the standard method.
The thesis also shows that the electronic properties of the transferred graphene can be mapped using a method that can be used in industrial production, thus ensuring that the transferred graphene is free of defects.

Illustration: Grafen_ Credit_Patrick Rebsdorf Whelan / PatricksHand_ Credit_Patrick Rebsdorf Whelan

"Natural process solves widely different challenges"

Photo: Niada BajraktariClean water, clean energy and the transition to a bio-based economy are some of the major challenges facing our society. An advanced new filtering process called biomimetic direct osmosis can help to address them. The process builds on a biological cell’s need to transport water in and out of the cell, without allowing anything else to pass.
Protein channels called aquaporins allow water to pass by means of osmosis, whereby the water attempts to dilute a concentrated solution (typically salt). The process can be mimicked by inserting aquaporin proteins into a synthetic membrane. By placing a saline liquid on one side of the membrane, and the fluid you want to filter (e.g. waste water) on the other side, water will be transported from the wastewater over into the saltwater, leaving the contamination behind.
Niada Bajraktari from DTU Environment has looked at five applications for biomimetic osmosis and found that they offer promising results in relation to treating municipal wastewater, concentrating bio-products, and energy production based on strong saline solutions.

Illustration: FOGEO_Credit_Niada Bajraktari / FOROHybrid_Credit_Niada Bajraktari / Osmosis_Credit_Niada Bajraktari


February 2017


"Chip can detect pneumonia"

Cystic fibrosis. Photo: Colourbox Normally, when people suffering from the lung disease cystic fibrosis are tested for pneumonia, they undergo a coughing test. However, in children under eight years, such testing is not possible, and consequently, Rikke Kragh Lauridsen from DTU Nanotech modified a chip—originally designed to detect explosives in the air—to measure whether the patient’s expiratory gases contains the biomarker for hydrogen cyanide. This biomarker indicates that the bacterium Pseudomonas aeruginosa is present in the patient’s respiratory tract.

Patients with cystic fibrosis often develop pneumonia, as their airways are covered in a thick layer of mucus which stop the cilia from cleaning the respiratory tract. Patients are therefore more susceptible to attack from this bacterium, which is otherwise harmless to healthy people.

"Nanomaterials cannot be risk assessed"

Nano. Photo: Colourbox Nanomaterials are now used in a wide range of products—from suntan lotions to mobile phones—but determining whether nanomaterials constitute a risk to the environment continues to pose a challenge for authorities and researchers.

Rune Hjorth from DTU Environment has therefore analysed the applicability of the risk assessment tools and ecotoxicological tests currently available—and the results are not promising.

"Acetone produced at high temperatures"

Acetone. Photo: Colourbox Thermophilic (heat-loving) bacteria possess several properties that make them interesting as host organisms in biotechnology. Among other things, they exhibit increased reaction rates at higher temperatures and a reduced risk of becoming contaminated with bacteria that thrive at moderate temperatures.

Ivan Pogrebnyakov from DTU Biosustain has described the development of a number of genetic and molecular tools that can be used to genetically engineer the thermophilic bacteria Geobacillus thermoglucosidasius—and in the course of this project—he has succeeded for the first time ever in genetically engineering the bacteria to produce acetone.

This research paves the way to expand and improve the biotechnological processes for the production of acetone and potentially create the basis for industrial applications.


January 2017


"‘Small’ energy sources may lead to savings"

 There is an appreciable political desire to save energy in the construction sector. This demands effective solutions. One option features what are known as Thermically Activated Building Systems (TABS), which heat up in cold conditions and cool down when the temperature rises. TABS make it possible to use ‘small’ energy sources such as surplus heat or earthed heat exchangers, which are insufficient sources of energy in and of themselves.

Benjamin Behrendt from DTU Civil Engineering has developed a simulation tool which can, for example, calculate the risk of overheating and the maximum cooling effect so as to avoid under-cooling. The tool is simpler than existing options, and also features a climate classification scale which makes it possible to predict how TABS should be used in buildings throughout Europe.

This classification is needed to calculate whether heating, cooling or both are required to achieve an acceptable indoor climate. The combination of the two tools makes it possible to prepare holistic assessments of construction projects at an early stage


"Chemistry in the embryonic period affects fertility"

Illustration: Hanna Johansson Women can experience reduced fertility on account of disruptions to the development of the ovaries. It is suspected that this, in turn, may be attributable to exposure to endocrine-disrupting substances during the embryonic period. However, this is difficult to prove conclusively given that the effects do not become apparent until adulthood, and because people are typically exposed to extremely small doses. On the other hand, exposure to a wide range of chemicals takes place over a protracted period, which may lead to combination effects. 

Hanna Katarina Lilith Johansson from DTU Food has identified several stages in the early development which are sensitive to exposure to chemicals. Her findings demonstrate that female rats exposed to endocrine-disrupting substances had fewer eggs in their ovaries before puberty, and that at the age of one year they showed signs of early reproductive ageing.

She has identified three biomarkers for influence on the development of the ovaries. However, more studies are required to determine whether they can be used in young individuals to predict disruptions to reproductive ability later in life, and whether the biomarkers can be used for diagnostic purposes in humans.

Illustration Hanna Katarina Lilith Johansson

"DNA analyses help trace source of cancer cells "

Illustration: Colourbox One key characteristic of cancer cells is that they form a variety of mutations that accumulate over time, imbuing the cell with new properties that allow the cancer to gain a foothold and then spread. However, some of these mutations simultaneously make cancer cells vulnerable to treatment.

Andrea Marion Marquard from DTU Bioinformatics has been working to find new points of attack to treat cancer on the basis of these mutations. For example, she has measured patterns of mutations which may reveal whether a cancer tumour is vulnerable to specific types of chemotherapy—a familiar method for some types of cancer (breast/ovarian). Similar patterns can also be identified in other forms of cancer, which means that other patients stand to benefit from this type of treatment.

Andrea Marion Marquard has also demonstrated that DNA analysis can be used to diagnose cancer in cases where the cancer spreads to other organs, but where clinical tests have proved unable to identify the original source organ. In analyses from thousands of cancer patients, the new analysis method succeeded in identifying the source of the cancer in 85 per cent of cases.

Illustration: Colourbox


December 2016


"Improved 3D-printed components"

3D printer, Photo: Colourbox 3D printers have opened up a host of new production opportunities. Printing with metal in particular is highly interesting from an industrial perspective. When working with lightweight metal components, it is common to design parts of the component with a mesh-like microstructure rather than solid metal. However, this is often done without accurate knowledge of the structural implications.

Anders Clausen from DTU Mechanical Engineering has demonstrated how components of this kind can be designed intelligently on the basis of topology optimization—a method used for lightweight components for the aeronautical/aerospace industry, for example. He and his colleagues have developed a method for designing structures with a solid outer shell on top of a porous inner core. They are generally a little less rigid than completely solid structures and therefore tend to deform more easily.

On the other hand, they feature significantly better properties with regard to handling unforeseen loads and denting. He has also shown how it is possible to use 3D printing to design and make a porous microstructure that retains its properties even when strongly deformed.

Photo: Colourbox

"How engineering companies become truly global"

Earth, Photo: Colourbox Most companies have become more global, which has made it increasingly common to outsource or offshore product development. Engineering companies therefore have to make strategic decisions about how to globalize their product development activities.

Erik Stefan Søndergaard from DTU Management Engineering has examined how decisions about global product development are made in these Danish engineering companies, and what information and methods are necessary to reach these decisions. He carried out his survey in close partnership with the companies themselves, backed by field studies in development departments in Denmark, China and Malaysia.

In his thesis, he suggests a structured process for making decisions about outsourcing and offshoring development assignments, helps deal with the lack of specific decision-making tools, develops decision-making theory in the context of outsourcing and offshoring, and contributes to understanding internationalization processes for product development. His thesis forms part of a research project supported by the Danish Industry Foundation and led by Professor Saeema Ahmed-Kristensen.

Photo: Colourbox

"Need for standard assessments of nanomaterials"

Nanotechnology, Photo: Colourbox More and more products are appearing that contain nanomaterials: everything from foods and personal care products, to electronics and domestic appliances. This is because nanoscale materials (measuring 1–100 nm) possess remarkable physical and chemical properties, and are more reactive than larger-scale versions of the same materials. However, given that nanomaterials can potentially be released, exposing both consumers and the environment to risk, and due to insufficient data and uncertainty about what risks they actually pose, there are concerns about how safe these materials are.

Aiga Mackevica from DTU Environment has examined which nanoproducts are available on the European Market, and which ones have already been examined. In addition, she has experimentally investigated the release of nanomaterials from a range of products (and in most cases, the release was minimal): Finally, she examined a number of risk assessment models.

The findings in her thesis indicate a need for standardized data reporting, harmonized exposure assessment, and risk characterization of nanomaterials.

Photo: Colourbox

November 2016


"Nanomaterials at the workplace"

Photo: Colourbox The production and use of nanomaterials is gaining ground in industry and in everyday products, but knowledge about ways of assessing the maximum amount of nanoparticles people should be exposed to at the workplace is scarce. Biase Liguori from DTU Nanotech has tested which control banding models are best suited to carry out such assessments.

Control banding models are simple decision-support tools for assessing the extent to which people are exposed to workplace risks. The tests concluded that the models used today can contribute to decisions about ways of handling risks associated with nanomaterials, but that only two models allow for establishing actual quantitative targets for the amount of nanomaterials tolerated at the workplace.

Photo: Colourbox

"Improved understanding of eczema"

Photo: Colourbox Atopic dermatitis, also known as eczema, is a very common inflammatory skin disease that affects 20-30 per cent of all children and 3-4 per cent of adults. Many people suffering from eczema experience both personal and sleep-related problems.

Therefore, David Adrian Ewald from DTU Bioengineering has made efforts to define the molecular aspects of the disease in the form of new gene-expression analyses, where he has combined published gene expression data with advanced statistical models. The dissertation has helped clarify the molecular basis for atopic dermatitis and thus improved the general understanding of the disease.

The results are intended to be used as a tool to evaluate new pharmaceuticals and to provide a basis for new studies.

Photo: Colourbox

"Artificial molecules for targeted treatment"

Photo: Colourbox Dendrons are artificially produced molecules consisting of branched, ligneous structures which are nearly identical to biological molecules. They possess a wide range of properties that make them useful in many contexts. They are widespread in connection with new materials and cosmetics, among other things, but also in the field of biomedicine. For example, it is possible to attach a large number of biologically active molecules to them, allowing stronger binding to receptors in the body—and thus increasing their medical effect. Sahar Mirsharghi from DTU Vet has studied methods to produce modified dendrons with various functions, for instance to form micelles, which are small spherical compounds of fatty molecules that are to bind to specific cells in the body’s immune system.

Photo: Colourbox


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