Quisquis: A new design for anonymous cryptocurrencies

Despite their usage of pseudonyms rather than persistent identifiers, most existing cryptocurrencies do not provide users with any meaningful levels of privacy. This has prompted the creation of privacy-enhanced cryptocurrencies such as Monero and Zcash, which are specifically designed to counteract the tracking analysis possible in currencies like Bitcoin. These cryptocurrencies, however, also suffer from some drawbacks: in both Monero and Zcash, the set of potential unspent coins is always growing, which means users cannot store a concise representation of the blockchain. Additionally, Zcash requires a common reference string and the fact that addresses are reused multiple times in Monero has led to attacks to its anonymity. In this paper we propose a new design for anonymous cryptocurrencies, Quisquis, that achieves provably secure notions of anonymity. Quisquis stores a relatively small amount of data, does not require trusted setup, and in Quisquis each address appears on the blockchain at most twice: once when it is generated as output of a transaction, and once when it is spent as input to a transaction. Our result is achieved by combining a DDH-based tool (that we call updatable keys) with efficient zero-knowledge arguments

Self-amplified photo-induced gap quenching in a correlated electron material.

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. We show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically depends on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe2, our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains-on a microscopic level-the extremely fast response of this material to ultrafast optical excitation

Z-Channel: Scalable and Efficient Scheme in Zerocash

Decentralized ledger-based cryptocurrencies like Bitcoin present a way to construct payment systems without trusted banks. However, the anonymity of Bitcoin is fragile. Many altcoins and protocols are designed to improve Bitcoin on this issue, among which Zerocash is the first full-fledged anonymous ledger-based currency, using zero-knowledge proof, specifically zk-SNARK, to protect privacy. However, Zerocash suffers two problems: poor scalability and low efficiency. In this paper, we address the above issues by constructing a micropayment system in Zerocash called Z-Channel. First, we improve Zerocash to support multisignature and time lock functionalities, and prove that the reconstructed scheme is secure. Then we construct Z-Channel based on the improved Zerocash scheme. Our experiments demonstrate that Z-Channel significantly improves the scalability and reduces the confirmation time for Zerocash payments

Zether: Towards Privacy in a Smart Contract World

Blockchain-based smart contract platforms like Ethereum have become quite popular as a way to remove trust and add transparency to distributed applications. While different types of important applications can be easily built on such platforms, there does not seem to be an easy way to add a meaningful level of privacy to them. In this paper, we propose Zether, a fully-decentralized, confidential payment mechanism that is compatible with Ethereum and other smart contract platforms. We take an account-based approach similar to Ethereum for efficiency and usability. We design a new smart contract that keeps the account balances encrypted and exposes methods to deposit, transfer and withdraw funds to/from accounts through cryptographic proofs. We describe techniques to protect Zether against replay attacks and front-running situations. We also develop a mechanism to enable interoperability with arbitrary smart contracts. This helps to make several popular applications like auctions, payment channels, voting, etc. confidential. As a part of our protocol, we propose $\Sigma$-Bullets, an improvement of the existing zero-knowledge proof system, Bulletproofs. $\Sigma$-Bullets make Bulletproofs more inter-operable with Sigma protocols, which is of general interest. We implement Zether as an Ethereum smart contract and show the practicality of our design by measuring the amount of gas used by the Zether contract. A Zether confidential transaction costs about 0.014 ETH or approximately $1.51 (as of early Feb, 2019). We discuss how small changes to Ethereum, which are already being discussed independently of Zether, would drastically reduce this cost

Personal non-commercial use only

ABSTRACT. Objective. To investigate whether development of systemic lupus erythematosus (SLE), its clinical manifestations, and autoantibody production are associated with polymorphisms of the mannose-binding lectin Conclusion. A significantly increased prevalence of anti-Smith antibody was associated with the heterozygous genotypes A/B and A/C. Although MBL structural gene polymorphism was not a risk factor for SLE development in this study population, homozygosity of MBL variant alleles may be a weak disease-modifying factor, particularly for renal involvement, in North American patients with SLE

Engineering the fatty acid synthesis pathway in Synechococcus elongatus PCC 7942 improves omega-3 fatty acid production

Background: The microbial production of fatty acids has received great attention in the last few years as feedstock for the production of renewable energy. The main advantage of using cyanobacteria over other organisms is their ability to capture energy from sunlight and to transform CO2 into products of interest by photosynthesis, such as fatty acids. Fatty acid synthesis is a ubiquitous and well-characterized pathway in most bacteria. However, the activity of the enzymes involved in this pathway in cyanobacteria remains poorly explored. Results: To characterize the function of some enzymes involved in the saturated fatty acid synthesis in cyanobacteria, we genetically engineered Synechococcus elongatus PCC 7942 by overexpressing or deleting genes encoding enzymes of the fatty acid synthase system and tested the lipid profile of the mutants. These modifications were in turn used to improve alpha-linolenic acid production in this cyanobacterium. The mutant resulting from fabF overexpression and fadD deletion, combined with the overexpression of desA and desB desaturase genes from Synechococcus sp. PCC 7002, produced the highest levels of this omega-3 fatty acid. Conclusions: The fatty acid composition of S. elongatus PCC 7942 can be significantly modified by genetically engineering the expression of genes coding for the enzymes involved in the first reactions of fatty acid synthesis pathway. Variations in fatty acid composition of S. elongatus PCC 7942 mutants did not follow the pattern observed in Escherichia coli derivatives. Some of these modifications can be used to improve omega-3 fatty acid production. This work provides new insights into the saturated fatty acid synthesis pathway and new strategies that might be used to manipulate the fatty acid content of cyanobacteria.Work in the FDLC laboratory was financed by the Spanish Ministry of Economy and Competitivity (MINECO) Grant BFU2014-55534-C2-1-P. MSM. was recipientof a Ph.D. fellowship (BES-2012-057387) from MINECO

First dose behavioral tolerance to phencyclidine on food-rewarded bar pressing behavior in the rat

The behavioral effects of single doses of phencyclidine (PCP) were examined in drug-naive adult male Holtzman rats trained to press a bar on a fixed ratio (4) schedule (FR 4 ), i.e., a reward of sugarsweetened milk was earned on every fourth bar press. Groups of rats (four to eight rats per group) received specific doses of PCP which were held constant for each group throughout the study. Dose-response curves for PCP given in doses of 1.0, 1.8, 2.4, and 3.2 mg/kg IP were first determined and then redetermined at weekly intervals. A drug-free interval of 7–8 days was maintained between injections given weekly over a period of 4 weeks. The final dose of PCP was administered after a 4-week drug-free period. Evidence was obtained for first dose behavioral tolerance as shown by the significantly shortened duration of suppression of bar pressing on subsequent injections. Although subsequent weekly effects of equal doses of PCP showed no significant differences, they all differed significantly from the first injection. The reduced response to PCP was shown to be due to learned behavioral tolerance as demonstrated when PCP (3.2 mg/kg IP) was given to drug-naive animals in their home cages and 1 week later given the second dose in the operant behavioral situation. Under these circumstances, the second dose of PCP showed a similarly protracted depression of FR 4 responding as other animals given the drug for the first time in the operant situation. Subsequent weekly injections in the operant situation produced similar behavioral tolerance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46412/1/213_2004_Article_BF00426513.pd

Effects of selected opioid agonists and antagonists on DMT-and LSD-25-induced disruption of food-rewarded bar pressing behavior in the rat

Several opioid agonists and antagonists interact with N,N-dimethyltryptamine (DMT) and lysergic acid diethylamide-25 (LSD) in adult male Holtzman rats trained on a positive reinforcement, fixed ratio 4 (FR 4 ) behavioral schedule, i.e., a reward of 0.01 ml sugar-sweetened milk was earned on every fourth bar press. DMT (3.2 and 10.0 mg/kg) and LSD (0.1 mg/kg) given IP with 0.9% NaCl pretreatment, disrupted food-rewarded FR4 bar pressing. Animals were pretreated IP (10–15 min) with predetermined, behaviorally noneffective doses of morphine, methadone, naltrexone, and the (+)-and (-)-enantiomers of naloxone prior to receiving DMT or LSD. Dose-dependent effects were shown with opioid agonist pretreatment. Morphine (0.32–1.0 mg/kg) and methadone (0.32 mg/kg) significantly antagonized the bar pressing disruption induced by DMT and LSD. Larger doses of morphine (3.2 mg/kg) and methadone (1.0–3.2 mg/kg) potentiated only LSD-induced effects, with no effect on DMT-treated groups. The opioid antagonists (-)-naloxone and naltrexone potentiated the disruption of bar pressing induced by DMT and LSD. Failure of (+)-naloxone to potentiate the DMT effects was attributed to a stereospecific opioid antagonist effect of (-)-naloxone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46425/1/213_2004_Article_BF00432428.pd