Practical quantum cryptography for secure free-space communications

Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.Comment: 12 pages, 4 figure

Ernst Freund as Precursor of the Rational Study of Corporate Law

Gindis, David, Ernst Freund as Precursor of the Rational Study of Corporate Law (October 27, 2017). Journal of Institutional Economics, Forthcoming. Available at SSRN: https://ssrn.com/abstract=2905547, doi: https://dx.doi.org/10.2139/ssrn.2905547The rise of large business corporations in the late 19th century compelled many American observers to admit that the nature of the corporation had yet to be understood. Published in this context, Ernst Freund's little-known The Legal Nature of Corporations (1897) was an original attempt to come to terms with a new legal and economic reality. But it can also be described, to paraphrase Oliver Wendell Holmes, as the earliest example of the rational study of corporate law. The paper shows that Freund had the intuitions of an institutional economist, and engaged in what today would be called comparative institutional analysis. Remarkably, his argument that the corporate form secures property against insider defection and against outsiders anticipated recent work on entity shielding and capital lock-in, and can be read as an early contribution to what today would be called the theory of the firm.Peer reviewe

Magnitude and Complexity of Rectal Mucosa HIV-1-Specific CD8+ T-Cell Responses during Chronic Infection Reflect Clinical Status

The intestinal mucosa displays robust virus replication and pronounced CD4+ T-cell loss during acute human immunodeficiency virus type 1 (HIV-1) infection. The ability of HIV-specific CD8+ T-cells to modulate disease course has prompted intensive study, yet the significance of virus-specific CD8+ T-cells in mucosal sites remains unclear.We evaluated five distinct effector functions of HIVgag-specific CD8+ T-cells in rectal mucosa and blood, individually and in combination, in relationship to clinical status and antiretroviral therapy (ART). In subjects not on ART, the percentage of rectal Gag-specific CD8+ T-cells capable of 3, 4 or 5 simultaneous effector functions was significantly related to blood CD4 count and inversely related to plasma viral load (PVL) (p<0.05). Polyfunctional rectal CD8+ T-cells expressed higher levels of MIP-1beta and CD107a on a per cell basis than mono- or bifunctional cells. The production of TNFalpha, IFN-gamma, and CD107a by Gag-specific rectal CD8+ T-cells each correlated inversely (p<0.05) with PVL, and MIP-1beta expression revealed a similar trend. CD107a and IFN-gamma production were positively related to blood CD4 count (p<0.05), with MIP-1beta showing a similar trend. IL-2 production by rectal CD8+ T-cells was highly variable and generally low, and showed no relationship to viral load or blood CD4 count.The polyfunctionality of rectal Gag-specific CD8+ T-cells appears to be related to blood CD4 count and inversely related to PVL. The extent to which these associations reflect causality remains to be determined; nevertheless, our data suggest a potentially important role for mucosal T-cells in limiting virus replication during chronic infection

Hamlet Without the Prince of Denmark: Relationship Banking and Conditionality Lending in the London Market for Foreign Government Debt, 1815-1913

This paper offers a theory of conditionality lending in 19th century international capital markets. We argue that ownership of reputation signals by prestigious banks rendered them able and willing to monitor government borrowing. Monitoring was a source of rent, and it led bankers to support countries facing liquidity crises in a manner similar to modern descriptions of relationship lending to corporate clients by parent banks. Prestigious bankers' ability to implement conditionality loans and monitor countries' financial policies also enabled them to deal with solvency. We find that, compared with prestigious bankers, bondholders' committees had neither the tools nor the prestige required for effectively dealing with defaulters. Hence such committees were far less important than previous research has claimed

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic

Fluid secretion by isolated tick salivary glands dependent on an intact cytoskeleton

Isolated salivary glands from female Dermacentor variabilis (Say) were pre-treated with either cytochalasin D or nocodazol, followed by stimulation with dopamine. Glands pre-treated with 1 μM-cytochalasin D did not secrete fluid; pre-treatment with 1 nM-cytochalasin D did not significantly reduce fluid secretion. Glands pre-treated with 1 μM-nocodazol had a significant reduction in fluid secretion (P = 0.003); 1 nM-nocodazol did not significantly affect fluid secretion. Ligation of the main salivary duct and pre-treatment with 1 μm-cytochalasin D significantly increased gland weight compared to the dopamine stimulated controls (P = 0.0412). Cytochalasin D-treated type III acini had a significantly larger mean diameter compared to the dopamine control (P = 0.0047). Glands treated with 1 mm-verapamil plus 10 μm-dopamine exhibited a significant decrease in fluid secretion (P = 0.017), and when ligated, had a significantly decreased weight compared to the controls (P = 0.0028). © 1994

Hemocytic encapsulation of implants in the tick Dermacentor variabilis

Implants of Epon, inserted in Dermacentor variabilis (Say) through incisions in the cuticle, were encapsulated by hemocytes. We followed this process at intervals of 1, 3, 6, 12 and 24 h, and every 24 h thereafter up to 120 h. Degranulation of Type 1 granulocytes and coagulation of hemolymph were first seen at 1 h after implantation and were the earliest evidence of encapsulation. By 3 h after implantation, the degranulation and disintegration of granulocytes had formed a matrix at the Epon surface. From 6 h until encapsulation was completed, plasmatocytes and granulocytes continued to respond to degranulation and formed multiple cell layers around the Epon implant. The capsule was complete at 72 h after implantation. Completion was marked by decreasing degranulation, migration of hemocytes from the outermost layers of the capsule, and by the appearance of loosely attached hemocytes on the outer surface of the capsule. The most common junctional complex observed was gap junctions. © 1990 Elsevier Science Publishers B.V

Evidence that dilation of isolated salivary ducts from the tick Dermacentor variabilis (Say) is mediated by nitric oxide

We used pharmacological methods to test the hypothesis that female Dermacentor variabilis salivary ducts dilated when dopamine-stimulated and that dilation was nitric oxide-mediated. Stimulation with dopamine resulted in an increased diameter (19.7%) compared to unstimulated ducts (P\u3c0.005). Pretreatment with L-NAME, an inhibitor of nitric oxide synthase, or cytochalasin D abolished the dilation. Addition of L-arginine to L-NAME- treated ducts partially restored the ability to dilate. A cuticular coil composed of a series of concentric rings ran the length of the duct adjacent to the epithelial cell layer. In stimulated ducts, the center-to-center periodicity of these rings increased from 0.59 μm in unfed ducts to 1.0 μm from partially fed ducts (P\u3c0.05). When the ducts from partially fed females were stimulated with dopamine, the periodicity increased further to 1.75 μm (P\u3c0.05), suggesting the coils moved further apart in response to stimulation. Prominent folds lining the lumen of unstimulated ducts were less pronounced in stimulated preparations, suggesting that the cuticle stretches, thereby increasing lumen size. Actin was localized in epithelial cells as a honeycomb pattern that we suggest links the epithelial cells to the rings. Together, these data support the following hypothesis: stimulated ducts dilated during fluid production; dilation involved an actin-based system, and was mediated by nitric oxide. Dilation of the duct may enhance its role as a reservoir for saliva produced by the acini during the period between imbibition and salivation. (C) 2000 Elsevier Science Ltd