Metafrontier Functions for the Study of Inter-regional Productivity Differences

The paper uses the concept of metafrontier functions to study regional differences in production technologies. The paper has three components. The first deals with the analytical framework necessary for the definition of metafrontier functions. The second component studies the properties of the metafrontier estimated using nonparametric data envelopment analysis (DEA). The third component focuses on the estimation of metafrontiers within the parametric framework of stochastic frontier analysis (SFA). The empirical application of the models uses cross-country agricultural sector data. The DEA and SFA metafrontiers are presented and discussed.

All the Conditions of Effective Foreign Aid

The conclusion that foreign aid will promote economic growth only when allocated towards good policy regimes has been the subject of considerable debate. Aid effectiveness researchers have variously sought to falsify this result or to find other individual conditions of aid effectiveness. However, economic theory suggests that any factor which influences the expected returns to investment may influence the effect of aid on growth even when aid is partly diverted to consumption. To investigate this hypothesis, �all� of the hypothesized conditions of aid effectiveness are individually tested in a cross-country growth specification. From these tests the most significant and robust individual interactions are simultaneously modeled, thereby deriving multiple conditions of aid effectiveness. The paper concludes that aid is more effective in economies experiencing economic shocks or recovering from war, and less effective in countries which are geographically disadvantaged or at war. We also find a previously unidentified condition of aid ineffectiveness: the inflow of foreign direct investment. This finding renews a justified interest in the policy-aid-growth nexus, insofar as domestic policy determines the distribution of aid and FDI flows, which appear to act as substitutes in the growth process.

Bilateral femoral neck fractures in an adult male following minimal trauma after a simple mechanical fall: a case report

BACKGROUND: Despite being rare there are several reports in the medical literature of bilateral femoral neck fractures in adult patients. They have been reported to have occurred following major trauma, or as a result of primary or secondary bone disease. In this case report we describe for the first time in the literature bilateral femoral neck fractures in a patient following minimal trauma after a simple mechanical fall. CASE PRESENTATION: We describe the case of an 84-year-old gentleman who sustained bilateral intracapsular fractures following a simple mechanical fall. Prompt diagnosis and early surgical intervention resulted in a satisfactory outcome. CONCLUSION: This case highlights that in the elderly, even in the absence of primary and secondary bone disease, bilateral neck of femur fractures can occur following relatively minor trauma. Consequently, the orthopaedic surgeon, emergency physician and general practitioner should be aware of this injury, particularly when managing traumatic injuries in confused patients

A Mathematical Model for Neutrophil Gradient Sensing and Polarization

Directed cell migration in response to chemical cues, also known as chemotaxis, is an important physiological process involved in wound healing, foraging, and the immune response. Cell migration requires the simultaneous formation of actin polymers at the leading edge and actomyosin complexes at the sides and back of the cell. An unresolved question in eukaryotic chemotaxis is how the same chemoattractant signal determines both the cell's front and back. Recent experimental studies have begun to reveal the biochemical mechanisms necessary for this polarized cellular response. We propose a mathematical model of neutrophil gradient sensing and polarization based on experimentally characterized biochemical mechanisms. The model demonstrates that the known dynamics for Rho GTPase and phosphatidylinositol-3-kinase (PI3K) activation are sufficient for both gradient sensing and polarization. In particular, the model demonstrates that these mechanisms can correctly localize the “front” and “rear” pathways in response to both uniform concentrations and gradients of chemical attractants, including in actin-inhibited cells. Furthermore, the model predictions are robust to the values of many parameters. A key result of the model is the proposed coincidence circuit involving PI3K and Ras that obviates the need for the “global inhibitors” proposed, though never experimentally verified, in many previous mathematical models of eukaryotic chemotaxis. Finally, experiments are proposed to (in)validate this model and further our understanding of neutrophil chemotaxis

Towards ultrahigh throughput microinjection: MEMS-based massively-parallelized mechanoporation

We describe a massively-parallelized, MEMS-based device concept for passively delivering exogeneous molecules into living cells via mechanical membrane penetration, i.e., mechanoporation. Details regarding device design and fabrication are discussed, as are results from preliminary live cell studies focused on device validation at the proof-of-concept level. These efforts represent key steps towards our long-term goal of developing instrumentation capable of ultrahigh throughput (UHT) cellular manipulation via active microinjection

A novel NGS library preparation method to characterize native termini of fragmented DNA.

Biological and chemical DNA fragmentation generates DNA molecules with a variety of termini, including blunt ends and single-stranded overhangs. We have developed a Next Generation Sequencing (NGS) assay, XACTLY, to interrogate the termini of fragmented DNA, information traditionally lost in standard NGS library preparation methods. Here we describe the XACTLY method, showcase its sensitivity and specificity, and demonstrate its utility in in vitro experiments. The XACTLY assay is able to report relative abundances of all lengths and types (5' and 3') of single-stranded overhangs, if present, on each DNA fragment with an overall accuracy between 80-90%. In addition, XACTLY retains the sequence of each native DNA molecule after fragmentation and can capture the genomic landscape of cleavage events at single nucleotide resolution. The XACTLY assay can be applied as a novel research and discovery tool for fragmentation analyses and in cell-free DNA