Pathlengths of open channels in multiple scattering media

We report optical measurements of the spectral width of open transmission channels in a three-dimensional diffusive medium. The light transmission through a sample is enhanced by efficiently coupling to open transmission channels using repeated digital optical phase conjugation. The spectral properties are investigated by enhancing the transmission, fixing the incident wavefront and scanning the wavelength of the laser. We measure the transmitted field to extract the field correlation function and the enhancement of the total transmission. We find that optimizing the total transmission leads to a significant increase in the frequency width of the field correlation function. Additionally we find that the enhanced transmission persists over an even larger frequency bandwidth. This result shows open channels in the diffusive regime are spectrally much wider than previous measurements in the localized regime suggest

Mapping Political Regime Typologies

W dziedzinie badań poświęconych teorii reżimów występuje znaczne zróżnicowanie podejść oraz typologii stawiających sobie za cel wyjaśnienie dynamicznie zmieniającej się rzeczywistości. Zamierzeniem autora niniejszego artykułu było zaproponowanie własnej typologii obejmującej istniejące już typologie, co z kolei posłużyło do opisania i analizy wartości badawczej tychże typologii oraz powiązanych z nimi baz danych. Pozwoliło to na wskazanie relacji między opisanymi typologiami i określenie ich miejsca we właściwych im polach badawczych. Celem tego działania jest dokonanie refleksji nad stosowalnością poszczególnych typologii, pokazanie ich ograniczeń oraz ułatwienie wyboru między nimi badaczom zajmującym się analizą procesów demokratycznych oraz teorią reżimów politycznych, z zastosowaniem zarówno jakościowych, jak i ilościowych metod badawczych.The research field of regime theory has seen a proliferation of different approaches and typologies to explain the ever-changing reality. This paper has created a typology of these regime typologies and their respective datasets in order to describe and analyze their various merits for research. Finally this paper maps various typologies according to their most common research areas. The aim is to maximize the application potential each of specific typology, highlight their limits and aid scholars in their selection of typologies for qualitative or quantitative research in order to get a better understanding of democratization processes or regime theories

Introducing Regime Cluster Theory: Framing Regional Diffusion Dynamics of Democratization and Autocracy Promotion

Recently the role of ideology and hegemony has received increased attention to explain varying dynamics of diffusion and autocratic cooperation. As a result, patterns of interaction in clusters from regions without hegemony or ideology have been overlooked because their autocracy-toautocracy transitions are no threat to the global status of democracy, even when active regime promotion is very common. This article will apply insights from economic cluster theory to political regimes and introduce a typology to differentiate among clusters. Regime Cluster Theory is the first framework that presents three ideal-types of ideological, hegemonic and biotopical regime clusters. With a new concept of ‘biotopical clusters’ the paper explains the dynamics of clusters in often omitted regions, like in Sub Saharan Africa, Latin America during the Cold War, or Central Asia during the 1990s. RCT offers a dynamic approach to recognize and assess patterns of forcible regime promotion per cluster as well as distinguish between their different diffusion patterns (coercive, voluntary, bounded learning, contagion) in four arenas: institutions, ideas, policy and administrative practices. RCT advances the comparative study of regime promotion and diffusion in various regions of the world and hopes to shed new light on related theories of alliance formation, regional institutionalization, and (conflict) spill-over effects

KONFLIKTY ZBROJNE W AFRYCE: PAŃSTWA KRUCHE I ROSNĄCA NIESTABILNOŚĆ

The first part of this article provides an overview of the development of entrenched armed conflicts in Sub Saharan Africa which continue or have resurfaced in 2016. The author (JVdB) aims to expose the underlying causes and nature of the violent contestation by drawing of the works of C. T. Call in order to break open the black box of ‘failed states’ and analyze their legitimacy, capacity and security gaps separately. In addition the author will provide short scenarios of how these conflicts are likely to evolve in the short and medium-term and which (structural) factors will dominate these trends. The second part of this article (by JR) mainly aims at presenting the basic preconditions for the activities of the major terrorist organizations in Africa. With emphasis on the importance of the north-east and north-west regions of this continent in context of terrorist threats. Hence the initial focus was put on Somalia, which as a permanent fragile state remains under the increased influence of the Jihadist organization Al Shabaab, which is an organization with a high potential for increased capacity in the coming years. Next, was sketched out the situation in Egypt, considering, in essence, the activity of the so-called Islamic State in Sinai Peninsula. In this Analysis it also pointed to the intricate internal situation in modern Libya after so-called Arab Spring and international military intervention, where, despite earlier appearances, the terrorist threat was too much positioned, mostly by comprised to the internal conflict between the different Libyan political parties. Finally, efforts were made to illustrate the current terrorist activity in the Mali area, highlighting the importance of Al Qaeda branch AQIM and the situation in Nigeria where Boko Haram group operates.W pierwszej części artykułu zaprezentowano przegląd wybranych konfliktów zbrojnych w Afryce Subsaharyjskiej, które toczyły się lub wybuchły ponownie w 2016 r. Autor (JVdB) postawił sobie za cel wskazanie przyczyn i charakteru brutalnych sporów, przede wszystkim poprzez odwołanie się do prac C. T. Call`a. Dążąc tym samym do rozpatrzenia dylematów związanych z “państwami upadłymi”, analizy problemu legitymizacji władzy, czy też poprzez określenie głównych możliwości oraz dysfunkcji z zakresu bezpieczeństwa, w szczegółowo rozpatrywanych przypadkach. Ponadto, Autor sformułował także scenariusze, starając się wywnioskować jak omawiane konflikty mogą ewoluować zarówno w perspektywie krótko jak i średnioterminowej. Próbując równocześnie odpowiedzieć na pytanie, które czynniki (strukturalne) zdominują ogólne tendencje zmian w regionie. W drugiej części artykułu (przez JR) postawiono sobie cel jakim jest przedstawienie uwarunkowań w zakresie aktywności najważniejszych organizacji terrorystycznych w Afryce. Ze szczególnym podkreśleniem znaczenia rejonu północno-wschodniego oraz północno-zachodniego tego kontynentu. Stąd wstępne skupienie uwagi na obszarze Somalii, która jako państwo słabe pozostaje pod wzmożonym wpływem tamtejszej dżihadystycznej organizacji Asz Szabaab, co więcej organizacji o dużym potencjale w zakresie wzrostu możliwości działania w kolejnych latach. Następnie dokonane zostało zarysowanie sytuacji w przypadku Egiptu, uwzględniając w głównej mierze aktywność tzw. Państwa Islamskiego na Synaju. Wskazano także na skomplikowaną sytuację wewnętrzną w Libii, gdzie jednak wbrew pozorom zagrożenie terrorystyczne było zbyt mocno pozycjonowane, chociażby względem wewnętrznego konfliktu pomiędzy zróżnicowanymi stronnictwami politycznymi. Finalnie spróbowano dokonać zobrazowania obecnej aktywności terrorystycznej w rejonie Mali, podkreślając znaczenie AQIM oraz w rejonie Nigerii, gdzie funkcjonuje Boko Haram

Resampling the transmission matrix in an aberration-corrected Bessel mode basis

The study of the optical transmission matrix (TM) of a sample reveals important statistics of light transport through it. The accuracy of the statistics depends strongly on the orthogonality and completeness of the basis in which the TM is measured. While conventional experimental methods suffer from sampling effects and optical aberrations, we use a basis of Bessel modes of the first kind to faithfully recover the singular values, eigenvalues and eigenmodes of light propagation through a finite thickness of air

Optical transmission matrix measurement sampled on a dense hexagonal lattice

The optical transmission matrix (TM) characterizes the transmission properties of a sample. We show a novel experimental procedure for measuring the TM of light waves in a slab geometry based on sampling the light field on a hexagonal lattice at the Rayleigh criterion. Our method enables the efficient measurement of a large fraction of the complete TM without oversampling while minimizing sampling crosstalk and the associated distortion of the statistics of the matrix elements. The procedure and analysis described here is demonstrated on a clear sample which serves as an important reference for other systems and geometries such as dense scattering media.Comment: 12 pages, 6 figure

IT and productivity: A firm level analysis. National Bank of Belgium Working Paper No. 346

Using a novel comprehensive data set of IT investment at the firm level, we find that a firm investing an additional euro in IT increases value added by 1 euro and 38 cents on average. This marginal product of IT investment increases with firm size and varies across sectors. IT explains about 10% of productivity dispersion across firms. While we find substantial returns of IT at the firm level, such returns are much lower at the aggregate level. This is due to underinvestment in IT (IT capital deepening is low) and misallocation of IT investments

Troubles in the heart of the EU – Political crisis in Belgium

Troubles in the heart of the EU – Political crisis in BelgiumTroubles in the heart of the EU – Political crisis in Belgiu

Early-life Determinants of Stunted Adolescent Girls and Boys in Matlab, Bangladesh

This paper presents the results of a longitudinal study, conducted in Matlab, Bangladesh, that examined to what extent the level of stunting in adolescence can be predicted by nutritional status in early childhood and maternal height. A linked set of data collected from the same individuals at two moments in time, i.e. early childhood (1988–1989) and adolescence (2001), was analyzed. The study found that the odds of being stunted in adolescence could be explained by the combined effect of being stunted in childhood and having a mother whose height was less than 145 cm. Also, girls were more likely than boys to be stunted in childhood, whereas boys were more likely than girls to be stunted in adolescence. The latter is probably attributable to differences in the pace of maturation. In terms of policy and (reproductive health) programmes, it is important to recall that adolescent girls whose height and weight were subnormal (weight <45 kg and height <145 cm) might run an obstetric risk. Following these cut-off points, 83% and 23% of 16-year-old girls in this study would face obstetric risk, respectively, for weight and height if they marry and become pregnant soon