CFP and YFP photostabilities are differentially affected by common mounting fluids

The use of spectrally distinct variants of green fluorescent protein (GFP) such as cyan or yellow mutants (CFP and YFP, respectively) is very common in all different fields of life sciences, e.g. for marking and tracing of specific proteins or cells or to determine protein interactions. In the later case, the quantum physical phenomenon of fluorescence resonance energy transfer (FRET) is visualized by specific microscopy techniques. When we applied a commonly used FRET microscopy technique - the increase in CFP-fluorescence after bleaching of YFP, we noticed that it worked well for live cells, but that most of the FRET-signal was lost in fixed cells mounted in commercial microscopy mounting fluids. Subsequently, we could show that CFP bleached much faster in the mounting medium than in live cells, while the opposite effect was observed for YFP. This change in photostability was not caused by the fixation but directly dependent on the mounting fluid. Furthermore we made the interesting observation that the CFP-fluorescence intensity increased in live cells after illumination at the YFP-excitation wavelength – a phenomenon, which might cause a false-positive signal in the FRET-microscopy technique that is based on bleaching of YFP. All together our results show that it is problematic to use commercially available mounting fluids for fluorescent proteins due to their differential effects on the bleaching kinetics and that the FRET microscopy technique based on bleaching of the acceptor is prone to artefacts at least for the CFP/YFP pair

Inverse zero-sum problems II

Let $G$ be an additive finite abelian group. A sequence over $G$ is called a minimal zero-sum sequence if the sum of its terms is zero and no proper subsequence has this property. Davenport's constant of $G$ is the maximum of the lengths of the minimal zero-sum sequences over $G$. Its value is well-known for groups of rank two. We investigate the structure of minimal zero-sum sequences of maximal length for groups of rank two. Assuming a well-supported conjecture on this problem for groups of the form $C_m \oplus C_m$, we determine the structure of these sequences for groups of rank two. Combining our result and partial results on this conjecture, yields unconditional results for certain groups of rank two.Comment: new version contains results related to Davenport's constant only; other results will be described separatel

ECONOMIC ANALYSIS AND EFFICIENCY IN PUBLIC EXPENDITURE

Benefit-Cost Analysis involves several steps: development of a program information structure (product categories), estimating the production function, pricing benefits and costs, adjusting for opportunity costs, choice of investment criteria, and incorporating uncertainty. Each step involves conflicts of interest that can only be resolved by political (collective) choice of property rights assigning opportunities to the various interest groups. The rules of benefit-cost analysis for public expenditure are equivalent of private property rights established by legislative and court decisions for the market economy. The traditional separation of technical analysis and political choice is not longer tenable. Theory and practice point to a more interactive, iterative relationship between analysts and politicians.Public Economics,

Does the TIPS spread overshoot?

Government securities

Equity financing of the entrepreneurial firm

Equity financing of the entrepreneurial firm has achieved a rapid increase over the past> decade. Venture capital funds, which finance privately held start-ups, raised a record $92.3 billion in 2000. This is a 30-fold increase relative to 1990. At Nasdaq, initial public offerings raised an all-time high of$53.6 billion in 2000, which is 24 times as much as in 1990. This article studies venture equity financing and equity financing through initial public offerings against the background of asymmetric information between the entrepreneur and the (outside) investor. The analysis shows that venture capital financing (i) is superior to initial public offerings when the entrepreneur has low initial wealth relative to the size of the project and (ii) is equivalent otherwise. This result highlights the importance of private equity in financing entrepreneurial enterprises. The Gramm-Leach-Bliley Act of 1999 allows banks to expand the scope of their activities in this arena. The act allows financial holding companies to provide equity financing to nonfinancial enterprises for up to ten years. In particular, the act defines a framework in which financial holding companies can sponsor private equity funds that may provide venture capital to entrepreneurial start-ups.Corporations - Finance ; Gramm-Leach-Bliley Act ; Venture capital

Gambler’s fallacy?

Stock market

Is the current account deficit weighing on the dollar?

Balance of payments ; Budget deficits

SOURCES OF SOCIAL CAPITAL

If the capital metaphor is to be taken seriously, social capital must focus on sources and not consequences. Human motive is the equivalent of physical capital goods which can perform transformative functions such as creating utility for one person out of the consumption of another and solving free rider problems. The focus on consequences of social capital cannot distinguish a gift motivated by affinity from a goods transfer motivated by moral obligation or promise of selfish gain. Motive is important if we are to understand investment and depreciation in social capital. The paper develops and tests a survey instrument to measure the predominant motive describing the relationships among people in eight Michigan communities with different socio-economic characteristics. Such a social capital account would allow community stocks to be compared and tracked over time.Institutional and Behavioral Economics,

The future of the euro

Euro