Market Orchestrators:The Effects of Certification on Platforms and Their Complementors

We study how a multisided platform’s decision to certify a subset of its complementors affects those complementors and ultimately the platform itself. Kiva, a microfinance platform, introduced a social performance badging program in December 2011. The badging program appears to have been beneficial to Kiva—it led to more borrowers, lenders, total funding, and amount of funding per lender. To better understand the mechanisms behind this performance increase, we study how the badging program changed the bundle of products offered by Kiva’s complementors. We find that Kiva’s certification leads badged microfinance institutions to reorient their loan portfolio composition to align with the certification and that the extent of portfolio reorientation varies across microfinance institutions, depending on underlying demand- and supply-side factors. We further show that certified microfinance institutions that do align their loan portfolios enjoy stronger demand-side benefits than do certified microfinance institutions that do not align their loan portfolios. We therefore demonstrate that platforms can influence the product offerings and performance of their complementors—and, subsequently, the performance of the ecosystem overall—through careful enactment of governance strategies, a process we call “market orchestration.

Quantum resistance metrology in graphene

We have performed a metrological characterization of the quantum Hall resistance in a 1 $\mu$m wide graphene Hall-bar. The longitudinal resistivity in the center of the $\nu=\pm 2$ quantum Hall plateaus vanishes within the measurement noise of 20 m$\Omega$ upto 2 $\mu$A. Our results show that the quantization of these plateaus is within the experimental uncertainty (15 ppm for 1.5$\mu$A current) equal to that in conventional semiconductors. The principal limitation of the present experiments are the relatively high contact resistances in the quantum Hall regime, leading to a significantly increased noise across the voltage contacts and a heating of the sample when a high current is applied

Parameterization Models for Traceable Characterization of Planar CPW SOL Calibration Standards

International audienceMethods for traceable characterization and uncertainty evaluation of planar 1-port CPW short-open-load (SOL) devices are developed. The agreement of modelling and verification measurement results greatly supports the application of the proposed parameterization models and used FEM-based EM modelling of CPW structures for traceable characterization of planar CPW-based SOL devices in the frequency range between a few kHz up to 50 GHz

Ionospheric electron number densities from CUTLASS dual-frequency velocity measurements using artificial backscatter over EISCAT

Using quasi-simultaneous line-of-sight velocity measurements at multiple frequencies from the Hankasalmi Cooperative UK Twin Auroral Sounding System (CUTLASS) on the Super Dual Auroral Radar Network (SuperDARN), we calculate electron number densities using a derivation outlined in Gillies et al. (2010, 2012). Backscatter targets were generated using the European Incoherent Scatter (EISCAT) ionospheric modification facility at Tromsø, Norway. We use two methods on two case studies. The first approach is to use the dual-frequency capability on CUTLASS and compare line-of-sight velocities between frequencies with a MHz or greater difference. The other method used the kHz frequency shifts automatically made by the SuperDARN radar during routine operations. Using ray tracing to obtain the approximate altitude of the backscatter, we demonstrate that for both methods, SuperDARN significantly overestimates Ne compared to those obtained from the EISCAT incoherent scatter radar over the same time period. The discrepancy between the Ne measurements of both radars may be largely due to SuperDARN sensitivity to backscatter produced by localized density irregularities which obscure the background levels

High-latitude artificial aurora using the EISCAT high-gain HF facility

The EISCAT high-frequency (HF) transmitter facility at Ramfjord, Norway, has been used to accelerate F-region electrons sufficiently to excite the oxygen atoms and nitrogen molecules, resulting in optical emissions at 630, 557.7 and 427.8 nm. During O-mode transmissions at 5.423 MHz, using 630 MW effective radiated power, in the hours after sunset on 12 November 2001 several new observations were made, including: (1) The first high-latitude observation of an HF induced optical emission at 427.8 nm and (2) Optical rings being formed at HF on followed by their collapse into a central blob. Both discoveries remain unexplained with current theories

Import of cytochrome c into mitochondria

The import of cytochrome c into mitochondria can be resolved into a number of discrete steps. Here we report on the covalent attachment of heme to apocytochrome c by the enzyme cytochrome c heme lyase in mitochondria from Neurospora crassa. A new method was developed to measure directly the linkage of heme to apocytochrome c. This method is independent of conformational changes in the protein accompanying heme attachment. Tryptic peptides of [35S]cysteine-labelled apocytochrome c, and of enzymatically formed holocytochrome c, were resolved by reverse-phase HPLC. The cysteine-containing peptide to which heme was attached eluted later than the corresponding peptide from apocytochrome c and could be quantified by counting 35S radioactivity as a measure of holocytochrome c formation. Using this procedure, the covalent attachment of heme to apocytochrome c, which is dependent on the enzyme cytochrome c heme lyase, could be measured. Activity required heme (as hemin) and could be reversibly inhibited by the analogue deuterohemin. Holocytochrome c formation was stimulated 5–10-fold by NADH > NADPH > glutathione and was independent of a potential across the inner mitochondrial membrane. NADH was not required for the binding of apocytochrome c to mitochondria and was not involved in the reduction of the cysteine thiols prior to heme attachment. Holocytochrome c formation was also dependent on a cytosolic factor that was necessary for the heme attaching step of cytochrome c import. The factor was a heat-stable, protease-insensitive, low-molecular-mass component of unknown function. Cytochrome c heme lyase appeared to be a soluble protein located in the mitochondrial intermembrane space and was distinct from the previously identified apocytochrome c binding protein having a similar location. A model is presented in which the covalent attachment of heme by cytochrome c heme lyase also plays an essential role in the import pathway of cytochrome c

Synthesis and characterization of Na03RhO206H2O - a semiconductor with a weak ferromagnetic component

We have prepared the oxyhydrate Na03RhO206H2O by extracting Na+ cations from NaRhO2 and intercalating water molecules using an aqueous solution of Na2S2O8. Synchrotron X-ray powder diffraction, thermogravimetric analysis (TGA), and energy-dispersive x-ray analysis (EDX) reveal that a non-stoichiometric Na03(H2O)06 network separates layers of edge-sharing RhO6 octahedra containing Rh3+(4d6, S=0) and Rh4+ (4d5, S=1/2). The resistivities of NaRhO2 and Na03RhO206H2O (T < 300) reveal insulating and semi-conducting behavior with activation gaps of 134 meV and 7.8 meV, respectively. Both Na03RhO206H2O and NaRhO2 show paramagnetism at room temperature, however, the sodium-deficient sample exhibits simultaneously a weak but experimentally reproducible ferromagnetic component. Both samples exhibit a temperature-independent Pauli paramagnetism, for NaRhO2 at T > 50 K and for Na03RhO206H2O at T > 25 K. The relative magnitudes of the temperature-independent magnetic susceptibilities, that of the oxide sample being half that of the oxyhydrate, is consistent with a higher density of thermally accessible electron states at the Fermi level in the hydrated sample. At low temperatures the magnetic moments rise sharply, providing evidence of localized and weakl -ordered electronic spins.Comment: 15 fages 5 figures Solid State Communications in prin

Universiteit Leiden Opleiding Informatica

Abstract S.M.A.C.K. is a small and simple operating system developed at LIACS to run on the BeagleBoard. The simple design allows students to learn how operating systems work. To keep it simple only the most essential features of an operating system are implemented. One essential feature that is missing is support for storage devices. The BeagleBoard does have an SD-card slot, but there are no drivers to use it. The only way to boot is using a RAM disk that is loaded by the boot loader. This is not very convenient. It would make S.M.A.C.K. more user friendly if it was possible to access data on SD-card and directly boot from it. This thesis will describe the implementation of an SD-card driver for S.M.A.C.K. to add a support for a permanent storage device and the implementation of two methods to improve performance: DMA and a buffer cache. Several experiments were then performed to test the effectiveness of DMA and the buffer cache on the BeagleBoard. The results show that a buffer cache and DMA transfers can improve the performance in specific situations.

Addressing post-harvest losses during traditional banana fermentation for increased food security in Southwest Uganda

Postharvest losses (PHL) destroy 20-60% of the food production in East Africa, exacerbating already severe regional food insecurity. Fermenting perishable foods such as fruits may reduce PHL while providing nutritional enrichment, improving shelf-life and food quality, and addressing seasonality in food supply. Fermented banana products have been refined and diversified in Uganda over generations to make the greatest use of available food resources, but still parts of the raw material are being lost during processing. This study aimed at exploring existing traditional methods and efficiency of fermentation of Musa (AAA-EAHB) 'Mbidde' in southwestern Uganda. The study gathered information through participatory explorations (working with brewers) on banana juice (lightly fermented beer with <1% alcohol content [n=20 brewers]), tonto (turbid beer with ~4% alcohol [n=20]), and amarwa (smoky spirit with ~ 40% alcohol [n=20]). Brewers mentioned several losses of material during harvest and processing. Harvesting bananas requires felling the plant causing ripe fruit damage, particularly during harvest for processing banana juice (loss from fresh bananas=6.4%±8.8%) or amarwa (loss=9.3%±9.5%). Second, losses occur when brewers squeeze juice from the raw banana pulp using stems of Imperata cylindrica, which is then discarded or fed to animals together with the adherent fruit pulp (losses from raw banana juice=50.6%±0.2%; from tonto 39.2%±21.4% and amarwa 47.6%±12.5%). Other causes of PHL during processing are excessive peeling for tonto processing (loss of banana flesh=18.6%±5.8%) and losses of intermediate products during distillation of amarwa (loss=75.9%±1.3%). Total losses of banana products during processing were rare and caused by sabotage (mostly by children), mistakes in the brewing process (e.g. addition of too much water), using bananas of wrong ripening stage, and equipment failure (e.g., burst or leaking drums in distillation equipment). Other non-PHL challenges include Banana Xanthomonas Wilt (BXW) and bad weather (up to 50% losses in the field). Despite the general efficiency of traditional fermentation practices, significant portions of fruit are still lost. Reduction in PHL can complement, both culturally and nutritionally, the role that fermented banana products play in Ugandan food systems and contribute to regional food security. Collaborative mechanisms for PHL reduction should target the cited sources of PHL