Long-term clinical outcome of antiviral therapy for chronic hepatitis B

Treatment of chronic hepatitis B currently consists of long-term therapy with oral nucleos(t)ide analogues or one year peginterferon injections. Within this thesis, Roeland Zoutendijk explores the long term clinical outcome of the currently most potent nucleos(t)ide analogues entecavir and tenofovir on virological, serological and clinical endpoints within several (inter)national cohort studies. Main findings of this thesis are that adaptation of entecavir therapy does not seem necessary in the majority of patients with a partial virological response at week 48, as prolonged therapy after week 48 leads to undetectable HBV DNA in the majority of patients. In addition, achieving a virological response during entecavir therapy is associated with a lower probability of clinical disease progression (development of HCC, hepatic decompensation and death) in patients with cirrhosis, underlining the importance of achieving this endpoint especially in those with more advanced liver disease

Organised crime threat assessments: a critical review

Since the beginning of the 21st century, several national and international government agencies have initiated organised crime threat assessments. Additionally, a few scholars have published methods to assess the risks and threats of organised crime. These governmental bodies and scholars claim that their reports and methods can demonstrate that certain forms of organised crime are more threatening than others and thus help policy-makers set strategic priorities. In this article I discuss these claims by examining the reliability and validity of the operational definitions of the key concepts used, such as organised crime, threat and risk. This examination reveals that most reports and methods provide insufficient detail—and sometimes even no details at all—to guarantee the reliability and validity of their operational definitions. The search for validity is made particularly difficult by the ambiguity surrounding the concepts of organised crime, threat and risk, while the concept of cost is less problematic. Moreover, establishing what constitutes a threat is at its core a normative decision that cannot be left to intelligence analysts or scientists alone. The challenge ahead lies in acknowledging the normative framework of organised crime threat assessments and within that framework maximising the reliability and validity of the operational definitions of key concepts and related measuring instruments

Lights in a sea of darkness: constraining the nature and properties of dark matter using the stellar kinematics in the centres of ultra-faint dwarf galaxies

Dark matter is one of the biggest mysteries of the Universe. Its properties cannot be explained with the known laws of physics and elementary particles. Yet, it is the most abundant form of matter in the Universe.Several dark-matter theories exist, including cold dark matter (CDM), self-interacting dark matter (SIDM), and fuzzy dark matter (FDM). These theories make different predictions for the density profiles of dark-matter haloes (cuspy or cored), depending on the nature (CDM, SIDM, FDM) and properties (self-interaction strength, FDM particle mass) of dark matter. These profiles can be determined from the stellar kinematics of the galaxies hosted by the haloes. Many massive dwarf galaxies show cored profiles. However, baryonic processes such as star formation may also induce cores.In this thesis, I test CDM, SIDM, and FDM using the faintest and most dark matter–dominated galaxies, ultra-faint dwarf galaxies (UFDs), which offer a new perspective on the cusp–core problem. The stellar kinematics of UFDs should not be significantly affected by baryonic processes. I find that UFDs have no detectable cores, implying that the cores of more massive dwarf galaxies are not caused by dark-matter physics. I can also exclude the previously promising particle masses ~10^-22 eV/c^2 for FDM.Large scale structure and cosmolog

Constraining dark matter with ultra-faint dwarf galaxies

Galaxie

The case for two-dimensional galaxy-galaxy lensing

We revisit the performance and biases of the two-dimensional approach to galaxy-galaxy lensing. This method exploits the information for the actual positions and ellipticities of source galaxies, rather than using only the ensemble properties of statistically equivalent samples. We compare the performance of this method with the traditionally used one-dimensional tangential shear signal on a set of mock data that resemble the current state-of-the-art weak lensing surveys. We find that under idealised circumstances the confidence regions of joint constraints for the amplitude and scale parameters of the NFW model in the two-dimensional analysis can be more than three times tighter than the one-dimensional results. Moreover, this improvement depends on the lens number density and it is larger for higher densities. We compare the method against the results from the hydrodynamical EAGLE simulation in order to test for possible biases that might arise due to lens galaxies being missed, and find that the method is able to return unbiased estimates of halo masses when compared to the true properties of the EAGLE galaxies. Because of its advantage in high galaxy density areas, the method is especially suitable for studying the properties of satellite galaxies in clusters of galaxies.Comment: 9 pages, 7 figures, accepted for publication in A&

Fleet scheduling for electric towing of aircraft under limited airport energy capacity

Taxiing aircraft using electric vehicles is seen as an effective solution to meet aviation targets of climate neutrality. However, making the transition to electric taxiing operations is expected to significantly increase the electricity demand at airports. In this paper we propose a mixed-integer linear program to schedule electric vehicles for aircraft towing and battery charging, while considering a limit for the supply of energy. The objective of the schedule is to maximize emissions savings. For computational tractability, we develop an Adaptive Large Neighbourhood Search which makes use of multiple local search heuristics to identify scheduling solutions. For daily scheduling with a small fleet size, the developed heuristic achieves solutions with an average 4% gap to the best linear programming solution. The results show that charging the vehicles during daytime is essential to maximize saved emissions: removing charging opportunities for a few hours during the day reduces the performance by an average of 6.4%. In addition, it is found that fast charging leads to low vehicle downtime, unless the battery size exceeds 750kWh, when charging rates over 150kW become unnecessary. Overall, our model provides support for infrastructure planning of airports during the transition to aircraft electric taxiing

Combinatorial Characterizations of K-matrices

We present a number of combinatorial characterizations of K-matrices. This extends a theorem of Fiedler and Ptak on linear-algebraic characterizations of K-matrices to the setting of oriented matroids. Our proof is elementary and simplifies the original proof substantially by exploiting the duality of oriented matroids. As an application, we show that a simple principal pivot method applied to the linear complementarity problems with K-matrices converges very quickly, by a purely combinatorial argument.Comment: 17 pages; v2, v3: clarified proof of Thm 5.5, minor correction