Comparison of on-wafer calibrations using the concept of reference impedance

A novel method that allows to compare different calibration techniques has been developed. It is based on determining the reference impedance of a given Network Analyzer calibration from the reflection coefficient measurement of a physical open circuit. The method has been applied to several on-wafer calibrations.Peer ReviewedPostprint (published version

Current perspectives of the signaling pathways directing neural crest induction.

The neural crest is a migratory population of embryonic cells with a tremendous potential to differentiate and contribute to nearly every organ system in the adult body. Over the past two decades, an incredible amount of research has given us a reasonable understanding of how these cells are generated. Neural crest induction involves the combinatorial input of multiple signaling pathways and transcription factors, and is thought to occur in two phases from gastrulation to neurulation. In the first phase, FGF and Wnt signaling induce NC progenitors at the border of the neural plate, activating the expression of members of the Msx, Pax, and Zic families, among others. In the second phase, BMP, Wnt, and Notch signaling maintain these progenitors and bring about the expression of definitive NC markers including Snail2, FoxD3, and Sox9/10. In recent years, additional signaling molecules and modulators of these pathways have been uncovered, creating an increasingly complex regulatory network. In this work, we provide a comprehensive review of the major signaling pathways that participate in neural crest induction, with a focus on recent developments and current perspectives. We provide a simplified model of early neural crest development and stress similarities and differences between four major model organisms: Xenopus, chick, zebrafish, and mouse

Conjugate Hardy's inequalities with decreasing weights

We prove that for a decreasing weight ω on R+, the conjugate Hardy transform is bounded on Lp(ω ) (1 ≤ p < ∞ ) if and only if it is bounded on the cone of all decreasing functions of Lp(ω ). This property does not depend on p

Pax7 lineage contributions to the mammalian neural crest.

BackgroundNeural crest cells are vertebrate-specific multipotent cells that contribute to a variety of tissues including the peripheral nervous system, melanocytes, and craniofacial bones and cartilage. Abnormal development of the neural crest is associated with several human maladies including cleft/lip palate, aggressive cancers such as melanoma and neuroblastoma, and rare syndromes, like Waardenburg syndrome, a complex disorder involving hearing loss and pigment defects. We previously identified the transcription factor Pax7 as an early marker, and required component for neural crest development in chick embryos. In mammals, Pax7 is also thought to play a role in neural crest development, yet the precise contribution of Pax7 progenitors to the neural crest lineage has not been determined.Methodology/principal findingsHere we use Cre/loxP technology in double transgenic mice to fate map the Pax7 lineage in neural crest derivates. We find that Pax7 descendants contribute to multiple tissues including the cranial, cardiac and trunk neural crest, which in the cranial cartilage form a distinct regional pattern. The Pax7 lineage, like the Pax3 lineage, is additionally detected in some non-neural crest tissues, including a subset of the epithelial cells in specific organs.Conclusions/significanceThese results demonstrate a previously unappreciated widespread distribution of Pax7 descendants within and beyond the neural crest. They shed light regarding the regionally distinct phenotypes observed in Pax3 and Pax7 mutants, and provide a unique perspective into the potential roles of Pax7 during disease and development

Non-equilibrium dynamics of Andreev states in the Kondo regime

The transport properties of a quantum dot coupled to superconducting leads are analyzed. It is shown that the quasiparticle current in the Kondo regime is determined by the non-equilibrium dynamics of subgap states (Andreev states) under an applied voltage. The current at low bias is suppressed exponentially for decreasing Kondo temperature in agreement with recent experiments. We also predict novel interference effects due to multiple Landau-Zener transitions between Andreev states.Comment: Revtex4, 4 pages, 4 figure

Economic growth and investment in the Arab world

This paper analyses the economic growth performance in the Arab world over the last forty years. The Arab world has managed to reduce poverty performance despite its relatively disappointing growth performance. We relate this poor performance of both oil and non-oil producers to investment. Contrary to widespread belief, we do not find evidence that low quantity of investment is the main of low growth. The decline in the investment rate followed rather than preceded the reduction in the aggregate growth rate. We conclude that the low quality of investment projects is the key determinant of growth. The excessive reliance on public investment, the low quality of financial institutions, the bad business environment (due to political and social instability and to excessive public intervention and overregulation) and the low quality of human capital are important determinants of systematically unproductive investment decisions and, thus, low economic growth.Economic growth, investment, the Arab World

Social security, retirement, and the single-mindedness of the electorate

We propose a positive theory that is consistent with two important features of social security programs around the world: (1) they redistribute income from young to old and (2) they induce retirement. We construct a voting model that includes a “political campaign” or “debate” prior to the election. The model incorporates “single-mindedness” of the groups that do not work: while the workers divide their political capital between their “age concerns” and “occupational concerns”, the retired concentrate all their political capital to support their age group. In our model, the elderly end up getting transfers from the government (paid by the young) and distortionary labor income taxes induce the retirement of the elderly. In addition, our model predicts that occupational groups that work more will tend to have more political power. The opposite is true for non-occupational groups (such as the elderly). We provide some evidence that supports these additional predictions.Social Security, retirement, retirement incentives, single-mindedness, political theories of Social Security