ABSTRACT Evidence for an extraterrestrial flux of high-energy neutrinos has now been found in multiple searches with the IceCube detector. The first solid evidence was provided by a search for ...neutrino events with deposited energies TeV and interaction vertices inside the instrumented volume. Recent analyses suggest that the extraterrestrial flux extends to lower energies and is also visible with throughgoing, -induced tracks from the Northern Hemisphere. Here, we combine the results from six different IceCube searches for astrophysical neutrinos in a maximum-likelihood analysis. The combined event sample features high-statistics samples of shower-like and track-like events. The data are fit in up to three observables: energy, zenith angle, and event topology. Assuming the astrophysical neutrino flux to be isotropic and to consist of equal flavors at Earth, the all-flavor spectrum with neutrino energies between 25 TeV and 2.8 PeV is well described by an unbroken power law with best-fit spectral index −2.50 0.09 and a flux at 100 TeV of . Under the same assumptions, an unbroken power law with index −2 is disfavored with a significance of 3.8 (p = 0.0066%) with respect to the best fit. This significance is reduced to 2.1 (p = 1.7%) if instead we compare the best fit to a spectrum with index −2 that has an exponential cut-off at high energies. Allowing the electron-neutrino flux to deviate from the other two flavors, we find a e fraction of 0.18 0.11 at Earth. The sole production of electron neutrinos, which would be characteristic of neutron-decay-dominated sources, is rejected with a significance of 3.6 (p = 0.014%).
We examine the relationship between firm performance and corporate governance in microfinance institutions (MFI) using a self-constructed global dataset on MFIs collected from third-party rating ...agencies. Using random effects panel data estimations, we study the effects of board and CEO characteristics, firm ownership type, customer-firm relationship, and competition and regulation on an MFI’s financial performance and outreach to poor clients. We find that financial performance improves with local rather than international directors, an internal board auditor, and a female CEO. The number of credit clients increase with CEO/chairman duality. Outreach is lower in the case of lending to individuals than in the case of group lending. We find no difference between non-profit organisations and shareholder firms in financial performance and outreach, and we find that bank regulation has no effect. The results underline the need for an industry specific approach to MFI governance.
This paper describes the response of the IceCube neutrino telescope located at the geographic south pole to outbursts of MeV neutrinos from the core collapse of nearby massive stars. IceCube was ...completed in December 2010 forming a lattice of 5160 photomultiplier tubes that monitor a volume of ~1 km3 in the deep Antarctic ice for particle induced photons. The telescope was designed to detect neutrinos with energies greater than 100 GeV. Owing to subfreezing ice temperatures, the photomultiplier dark noise rates are particularly low. Hence IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photomultiplier rates on top of the dark noise. With 2 ms timing resolution, IceCube can detect subtle features in the temporal development of the supernova neutrino burst. For a supernova at the galactic center, its sensitivity matches that of a background-free megaton-scale supernova search experiment. The sensitivity decreases to 20 standard deviations at the galactic edge (30 kpc) and 6 standard deviations at the Large Magellanic Cloud (50 kpc). IceCube is sending triggers from potential supernovae to the Supernova Early Warning System. The sensitivity to neutrino properties such as the neutrino hierarchy is discussed, as well as the possibility to
We present the results of a search for neutrino point sources using the IceCube data collected between 2008 April and 2011 May with three partially completed configurations of the detector: the 40-, ...59-, and 79-string configurations. The live-time of this data set is 1040 days. An unbinned maximum likelihood ratio test was used to search for an excess of neutrinos above the atmospheric background at any given direction in the sky. By adding two more years of data with improved event selection and reconstruction techniques, the sensitivity was improved by a factor of 3.5 or more with respect to the previously published results obtained with the 40-string configuration of IceCube. We performed an all-sky survey and a dedicated search using a catalog of a priori selected objects observed by other telescopes. In both searches, the data are compatible with the background-only hypothesis. In the absence of evidence for a signal, we set upper limits on the flux of muon neutrinos. For an E super(-2) neutrino spectrum, the observed limits are (0.9-5) x 10 super(-12) TeV super(-1) cm super(-2) s super(-1) for energies between 1 TeV and 1 PeV in the northern sky and (0.9-23.2) x 10 super(-12) TeV super(-1) cm super(-2) s super(-1) for energies between 10 super(2) TeV and 10 super(2) PeV in the southern sky. We also report upper limits for neutrino emission from groups of sources that were selected according to theoretical models or observational parameters and analyzed with a stacking approach. Some of the limits presented already reach the level necessary to quantitatively test current models of neutrino emission.
Microfinance Mission Drift? Mersland, Roy; Strøm, R. Øystein
World development,
2010, 2010-1-00, 20100101, Letnik:
38, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Claims have been made that microfinance institutions (MFIs) experience mission drift as they increasingly cater to customers who are better off than their original customers. We investigate mission ...drift using average loan size as a main proxy and the MFIs lending methodology, main market, and gender bias as further mission drift measures. We employ a large data set of rated, multi-country MFIs spanning 11 years, and perform panel data estimations with instruments. We find that the average loan size has not increased in the industry as a whole, nor is there a tendency toward more individual loans or a higher proportion of lending to urban costumers. Regressions show that an increase in average profit and average cost tends to increase average loan and the other drift measures. More focus should be given to cost efficiency in the MFI.
Microfinance is a global high–growth industry, in which entrepreneurship is prevalent and substantial. Based on the theoretical argument that microfinance entrepreneur–chief executive officers (CEOs) ...are “motivated agents” with a unique ability to hire and socialize mission–oriented staff, we hypothesize that these CEOs produce more sustainable microfinance institutions (MFIs) with better social performance and lower costs. This study utilizes data from 295 MFIs in 73 developing countries, assessed between 1998 and 2010. Our empirical evidence suggests that entrepreneur–managed MFIs feature higher social performance, greater financial sustainability, and lower costs.
: This paper analyzes the economic rationale for board regulation in place and for introducing new regulation in the future. We relate the value of the firm to the use of employee directors, board ...independence, directors with multiple seats, and to gender diversity. Our evidence shows that the firm creates more value for its owners when the board has no employee directors, when its directors have strong links to other boards, and when gender diversity is low. We find no relationship between firm performance and board independence. These characteristics of value‐creating boards support neither popular opinion nor the current politics of corporate governance.
Membraneless organelles or condensates form through liquid-liquid phase separation
, which is thought to underlie gene transcription through condensation of the large-scale nucleolus
or in smaller ...assemblies known as transcriptional condensates
. Transcriptional condensates have been hypothesized to phase separate at particular genomic loci and locally promote the biomolecular interactions underlying gene expression. However, there have been few quantitative biophysical tests of this model in living cells, and phase separation has not yet been directly linked with dynamic transcriptional outputs
. Here, we apply an optogenetic approach to show that FET-family transcriptional regulators exhibit a strong tendency to phase separate within living cells, a process that can drive localized RNA transcription. We find that TAF15 has a unique charge distribution among the FET family members that enhances its interactions with the C-terminal domain of RNA polymerase II. Nascent C-terminal domain clusters at primed genomic loci lower the energetic barrier for nucleation of TAF15 condensates, which in turn further recruit RNA polymerase II to drive transcriptional output. These results suggest that positive feedback between interacting transcriptional components drives localized phase separation to amplify gene expression.
Liquid-liquid phase separation (LLPS) mediates formation of membraneless condensates such as those associated with RNA processing, but the rules that dictate their assembly, substructure, and ...coexistence with other liquid-like compartments remain elusive. Here, we address the biophysical mechanism of this multiphase organization using quantitative reconstitution of cytoplasmic stress granules (SGs) with attached P-bodies in human cells. Protein-interaction networks can be viewed as interconnected complexes (nodes) of RNA-binding domains (RBDs), whose integrated RNA-binding capacity determines whether LLPS occurs upon RNA influx. Surprisingly, both RBD-RNA specificity and disordered segments of key proteins are non-essential, but modulate multiphase condensation. Instead, stoichiometry-dependent competition between protein networks for connecting nodes determines SG and P-body composition and miscibility, while competitive binding of unconnected proteins disengages networks and prevents LLPS. Inspired by patchy colloid theory, we propose a general framework by which competing networks give rise to compositionally specific and tunable condensates, while relative linkage between nodes underlies multiphase organization.
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•Stress granule formation requires RNA-binding nodes with high network connectivity•Capping of nodes by ligands lacking connectivity prevents condensation•Protein disorder and RNA-binding specificity play non-essential, modulatory roles•Competition of RNP networks for connecting nodes controls multiphase organization
With sufficient RNA-binding interfaces, diverse protein complexes can trigger stress-dependent multiphase condensates, whose composition and spatial organization is determined by overlapping interaction networks.
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