Strain-Release-Driven Homologation of Boronic Esters:Application to the Modular Synthesis of Azetidines

Azetidines are important motifs in medicinal chemistry, but there are a limited number of methods for their synthesis. Herein, we present a new method for their modular construction by exploiting the high ring strain associated with azabicyclo[1.1.0]­butane. Generation of azabicyclo[1.1.0]­butyl lithium followed by its trapping with a boronic ester gives an intermediate boronate complex which, upon N-protonation with acetic acid, undergoes 1,2-migration with cleavage of the central C–N bond to relieve ring strain. The methodology is applicable to primary, secondary, tertiary, aryl, and alkenyl boronic esters and occurs with complete stereospecificity. The homologated azetidinyl boronic esters can be further functionalized through reaction of the N–H azetidine, and through transformation of the boronic ester. The methodology was applied to a short, stereoselective synthesis of the azetidine-containing pharmaceutical, cobimetinib

A Quantum-Proof Non-Malleable Extractor, With Application to Privacy Amplification against Active Quantum Adversaries

In privacy amplification, two mutually trusted parties aim to amplify the secrecy of an initial shared secret $X$ in order to establish a shared private key $K$ by exchanging messages over an insecure communication channel. If the channel is authenticated the task can be solved in a single round of communication using a strong randomness extractor; choosing a quantum-proof extractor allows one to establish security against quantum adversaries. In the case that the channel is not authenticated, Dodis and Wichs (STOC'09) showed that the problem can be solved in two rounds of communication using a non-malleable extractor, a stronger pseudo-random construction than a strong extractor. We give the first construction of a non-malleable extractor that is secure against quantum adversaries. The extractor is based on a construction by Li (FOCS'12), and is able to extract from source of min-entropy rates larger than $1/2$. Combining this construction with a quantum-proof variant of the reduction of Dodis and Wichs, shown by Cohen and Vidick (unpublished), we obtain the first privacy amplification protocol secure against active quantum adversaries

Effect of ozone and antioxidants on wheat and its pathogen — Bipolaris sorokininana

Tropospheric ozone (O3) adversely affects growth and productivity of crops and also influences crop—pathogen interactions. Adverse effects of O3 on crops can be mitigated by antioxidants application. In the present study through lab and field experiments impact of O3 and antioxidants treatment to wheat was assessed on growth of Bipolaris sorokiniana (BS-75 strain) pathogen responsible for Spot blotch disease, pathogenesis related (PR) proteins and chitinase content. Results showed that growth of Bipolaris was significantly higher in elevated ozone (EO3) exposed plants as compared to control plants. Antioxidants — ascorbic acid (AA), tagetes extract (T) and quercetin (Q) application on culture media and wheat plants, respectively, retarded the growth of Bipolaris sorokiniana. Among the three antioxidants minimum growth of Bipolaris was observed in AA-treated plants as compared to control plants. Reduction in chitinase activity and PR proteins content due to EO3 treatment in wheat plants was 18% and 78%, respectively, as compared to control plants. Increase in chitinase activity and PR proteins content due to antioxidants treatment in wheat plants was 45% and 60%, respectively, as compared to control plants

Dissipative structure formation in cold-rolled Fe and Ni during heavy ion irradiation

We report 4-probe resistivity measurements of cold-rolled Ni and Fe during 100 MeV oxygen ion irradiation, at 300K. The resistivity shows increase and saturation, marked by jumps. Employing 200 MeV silver ion irradiation of Fe and Si(100) and topographically identifying strain at an artificial interface in the latter, we assign the resistivity behavior to atomic rearrangements arising from dissipation of incident ion energy at internal interfaces of Ni and Fe, with positive feedback.}Comment: RevTex+ 7 Postscript figures; Fig 2 (topograph) available on demand to [email protected]. To appear in Phys Rev Let

A New Approach to Measuring Distances in Dense Graphs

The problem of computing distances and shortest paths between vertices in graphs is one of the fundamental issues in graph theory. It is of great importance in many different applications, for example, transportation, and social network analysis. However, efficient shortest distance algorithms are still desired in many disciplines. Basically, the majority of dense graphs have ties between the shortest distances. Therefore, we consider a different approach and introduce a new measure to solve all-pairs shortest paths for undirected and unweighted graphs. This measures the shortest distance between any two vertices by considering the length and the number of all possible paths between them. The main aim of this new approach is to break the ties between equal shortest paths SP, which can be obtained by the Breadth-first search algorithm (BFS), and distinguish meaningfully between these equal distances. Moreover, using the new measure in clustering produces higher quality results compared with SP. In our study, we apply two different clustering techniques: hierarchical clustering and K-means clustering, with four different graph models, and for a various number of clusters. We compare the results using a modularity function to check the quality of our clustering results

Centrality dependence of multiplicity, transverse energy, and elliptic flow from hydrodynamics

The centrality dependence of the charged multiplicity, transverse energy, and elliptic flow coefficient is studied in a hydrodynamic model, using a variety of different initializations which model the initial energy or entropy production process as a hard or soft process, respectively. While the charged multiplicity depends strongly on the chosen initialization, the p_t-integrated elliptic flow for charged particles as a function of charged particle multiplicity and the p_t-differential elliptic flow for charged particles in minimum bias events turn out to be almost independent of the initial energy density profile.Comment: 11 pages RevTex, including 10 postscript figures. Slightly modified discussion of Figs. 5 and 6, updated references. This version to appear in Nuclear Physics