How Rare Are Extraterrestrial Civilizations and When Did They Emerge?

It is shown that, contrary to an existing claim, the near equality between the lifetime of the sun and the timescale of biological evolution on earth does not necessarily imply that extraterrestrial civilizations are exceedingly rare. Furthermore, on the basis of simple assumptions it is demonstrated that a near equality between these two timescales may be the most probable relation. A calculation of the cosmic history of carbon production which is based on the recently determined history of the star formation rate suggests that the most likely time for intelligent civilizations to emerge in the universe, was when the universe was already older then about 10 billion years (for an assumed current age of about 13 billion years).Comment: 11 pages (including 2 figures), accepted for publication in Astrophys. Journa

Effective Lagrangian for Quantum Black Holes

We discuss the most general effective Lagrangian obtained from the assumption that the degrees of freedom to be quantized, in a black hole, are on the horizon. The effective Lagrangian depends only on the induced metric and the extrinsic curvature of the (fluctuating) horizon, and the possible operators can be arranged in an expansion in powers of \mpl/M, where \mpl is the Planck mass and $M$ the black hole mass. We perform a semiclassical expansion of the action with a formalism which preserves general covariance explicitly. Quantum fluctuations over the classical solutions are described by a single scalar field living in the 2+1 dimensional world-volume swept by the horizon, with a given coupling to the background geometry. We discuss the resulting field theory and we compute the black hole entropy with our formalism.Comment: 24 pages, Latex, Nucl. Phys. B, to appea

W-OTS(+) up my Sleeve! A Hidden Secure Fallback for Cryptocurrency Wallets

We introduce a new key generation mechanism where users can generate a back up key\u27\u27, securely nested inside the secret key of a signature scheme. Our main motivation is that in case of leakage of the secret key, established techniques based on zero-knowledge proofs of knowledge are void since the key becomes public. On the other hand, the back up key\u27\u27, which is secret, can be used to generate a proof of ownership\u27\u27, i.e., only the real owner of this secret key can generate such a proof. To the best of our knowledge, this extra level of security is novel, and could have already been used in practice, if available, in digital wallets for cryptocurrencies that suffered massive leakage of account private keys. In this work, we formalize the notion of Proof of Ownership\u27\u27 and Fallback\u27\u27 as new properties. Then, we introduce our construction, which is compatible with major designs for wallets based on ECDSA, and adds a W-OTS(+) signing key as a back up key\u27\u27. Thus offering a quantum secure fallback. This design allows the hiding of any quantum secure signature key pair, and is not exclusive to W-OTS(+). Finally, we briefly discuss the construction of multiple generations of proofs of ownership

The Unique History of the Globular Cluster Omega Centauri

Using current observational data and simple dynamical modeling, we demonstrate that Omega Cen is not special among the Galactic globular clusters in its ability to produce and retain the heavy elements dispersed in the AGB phase of stellar evolution. The multiple stellar populations observed in Omega Cen cannot be explained if it had formed as an isolated star cluster. The formation within a progenitor galaxy of the Milky Way is more likely, although the unique properties of Omega Cen still remain a mystery.Comment: published version with minor change

The impact of social protection and poverty elimination on global tuberculosis incidence: a statistical modelling analysis of Sustainable Development Goal 1.

BACKGROUND: The End TB Strategy and the Sustainable Development Goals (SDGs) are intimately linked by their common targets and approaches. SDG 1 aims to end extreme poverty and expand social protection coverage by 2030. Achievement of SDG 1 is likely to affect the tuberculosis epidemic through a range of pathways. We estimate the reduction in global tuberculosis incidence that could be obtained by reaching SDG 1. METHODS: We developed a conceptual framework linking key indicators of SDG 1 progress to tuberculosis incidence via well described risk factor pathways and populated it with data from the SDG data repository and the WHO tuberculosis database for 192 countries. Correlations and mediation analyses informed the strength of the association between the SDG 1 subtargets and tuberculosis incidence, resulting in a simplified framework for modelling. The simplified framework linked key indicators for SDG 1 directly to tuberculosis incidence. We applied an exponential decay model based on linear associations between SDG 1 indicators and tuberculosis incidence to estimate tuberculosis incidence in 2035. FINDINGS: Ending extreme poverty resulted in a reduction in global incidence of tuberculosis of 33·4% (95% credible interval 15·5-44·5) by 2035 and expanding social protection coverage resulted in a reduction in incidence of 76·1% (45·2-89·9) by 2035; both pathways together resulted in a reduction in incidence of 84·3% (54·7-94·9). INTERPRETATION: Full achievement of SDG 1 could have a substantial effect on the global burden of tuberculosis. Cross-sectoral approaches that promote poverty reduction and social protection expansion will be crucial complements to health interventions, accelerating progress towards the End TB targets. FUNDING: World Health Organization

Ion induced solid flow

Amorphous solids can flow over very long periods of time. Solid flow can also be artificially enhanced by creating defects, as by Ion Beam Sputtering (IBS) in which collimated ions with energies in the 0.1 to 10 keV range impact a solid target, eroding its surface and inducing formation of nanometric structures. Recent experiments have challenged knowledge accumulated during the last two decades so that a basic understanding of self-organized nano-pattern formation under IBS is still lacking. We show that considering the irradiated solid to flow like a highly viscous liquids can account for the complex IBS morphological phase diagram, relegating erosion to a subsidiary role and demonstrating a controllable instance of solid flow at the nanoscale. This new perspective can allow for a full harnessing of this bottom-up route to nanostructuring.Comment: 17 pages, 5 figure

Hawking Radiation as Tunneling for Extremal and Rotating Black Holes

The issue concerning semi-classical methods recently developed in deriving the conditions for Hawking radiation as tunneling, is revisited and applied also to rotating black hole solutions as well as to the extremal cases. It is noticed how the tunneling method fixes the temperature of extremal black hole to be zero, unlike the Euclidean regularity method that allows an arbitrary compactification period. A comparison with other approaches is presented.Comment: 17 pages, Latex document, typos corrected, four more references, improved discussion in section

Phoenixx: Linear consensus with random sampling

We present Phoenixx, a round and leader based Byzantine fault tolerant consensus protocol, that operates in the partial synchrony network communications model. Phoenixx combines the three phase approach from HotStuff, with a novel Endorser Sampling, that selects a subset of nodes, called endorsers, to compress\u27\u27 the opinion of the network. Unlike traditional sampling approaches that select a subset of the network to run consensus on behalf of the network and disseminate the outcome, Phoenixx still requires participation of the whole network. The endorsers, however, assume a special role as they confirm that at least $2f+1$ validators are in agreement and issue a compressed certificate, attesting the network reached a decision. Phoenixx achieves linear communication complexity, while maintaining safety, liveness, and optimistic responsiveness, without using threshold signatures

Microbes and Alzheimer\u27s Disease

We are researchers and clinicians working on Alzheimer\u27s disease (AD) or related topics, and we write to express our concern that one particular aspect of the disease has been neglected, even though treatment based on it might slow or arrest AD progression. We refer to the many studies, mainly on humans, implicating specific microbes in the elderly brain, notably herpes simplex virus type 1 (HSV1), Chlamydia pneumoniae, and several types of spirochaete, in the etiology of AD. Fungal infection of AD brain has also been described, as well as abnormal microbiota in AD patient blood. The first observations of HSV1 in AD brain were reported almost three decades ago. The ever-increasing number of these studies (now about 100 on HSV1 alone) warrants re-evaluation of the infection and AD concept

Sexual Functioning Among Endometrial Cancer Patients Treated With Adjuvant High-Dose-Rate Intra-Vaginal Radiation Therapy

Purpose—We used the Female Sexual Function Index (FSFI) to investigate the prevalence of sexual dysfunction (SD) and factors associated with diminished sexual functioning in early stage endometrial cancer (EC) patients treated with simple hysterectomy and adjuvant brachytherapy. Methods and Materials—A cohort of 104 patients followed in a radiation oncology clinic completed questionnaires to quantify current levels of sexual functioning. The time interval between hysterectomy and questionnaire completion ranged from 5 years. Multivariate regression was performed using the FSFI as a continuous variable (score range, 1.2–35.4). SD was defined as an FSFI score of <26, based on the published validation study. Results—SD was reported by 81% of respondents. The mean (±standard deviation) domain scores in order of highest-to-lowest functioning were: satisfaction, 2.9 (±2.0); orgasm, 2.5 (±2.4); desire, 2.4 (±1.3); arousal, 2.2 (±2.0); dryness, 2.1 (±2.1); and pain, 1.9 (±2.3). Compared to the index population in which the FSFI cut-score was validated (healthy women ages 18–74), all scores were low. Compared to published scores of a postmenopausal population, scores were not statistically different. Multivariate analysis isolated factors associated with lower FSFI scores, including having laparotomy as opposed to minimally invasive surgery (effect size, −7.1 points; 95% CI, −11.2 to −3.1; P<.001), lack of vaginal lubricant use (effect size, −4.4 points; 95% CI, −8.7 to −0.2, P = .040), and short time interval (<6 months) from hysterectomy to questionnaire completion (effect size, −4.6 points; 95% CI, −9.3–0.2; P = .059). Conclusions—The rate of SD, as defined by an FSFI score <26, was prevalent. The postmenopausal status of EC patients alone is a known risk factor for SD. Additional factors associated with poor sexual functioning following treatment for EC included receipt of laparotomy and lack of vaginal lubricant use