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61.
Kaveh Parvanak Borujeni 《合成通讯》2013,43(18):2705-2710
A simple, effective, and highly chemoselective method to form 2‐tetrahydropyranyl ethers of alcohols and phenols in the presence of silica‐gel‐supported aluminium chloride as a heterogeneous Lewis acid catalyst is described. The catalyst can be easily recovered and reused without appreciable change in its efficiency. 相似文献
62.
Kiumars Kaveh Christopher Manon Takuya Murata 《Journal of Pure and Applied Algebra》2021,225(11):106713
We study the generic tropical initial ideals of a positively graded Cohen-Macaulay algebra R over an algebraically closed field k. Building on work of Römer and Schmitz, we give a formula for each initial ideal, and we express the associated quasivaluations in terms of certain I-adic filtrations. As a corollary, we show that in the case that R is a domain, every initial ideal coming from the codimension 1 skeleton of the tropical variety is prime, so “generic presentations of Cohen-Macaulay domains are well-poised in codimension 1.” 相似文献
63.
An efficient multi-step algorithm is presented for embedding a nonplanar graph on the least possible number of planes. In the first step, the graph is drawn on a plane with the smallest possible number of crossings. Then the appropriate crossing edges are selected and moved onto the second plane. This process is repeated introducing subsequent planes until no crossing remains. 相似文献
64.
The temperature dependence of the resistivity of (TMTSF)2PF6 over the temperature range 25–300 K is in excellent agreement with “libron” theory, if a Bloch (1-phonon) contribution corresponding to λ = 0.16 (a value determined from the Peierls transition temperature) is invoked. This contributes about 10% to the resistivity at 300 K, and about 20% at 40 K. 相似文献
65.
5-Chloroorsellinic acid inhibits the formation of penicillic acid by Penicillium cyclopium at sublethal concentrations. 相似文献
66.
Jorabchi K Westphall MS Smith LM 《Journal of the American Society for Mass Spectrometry》2008,19(6):833-840
We propose and evaluate a new mechanism to account for analyte ion signal enhancement in ultraviolet-laser desorption mass spectrometry of droplets in the presence of corona ions. Our new insights are based on timing control of corona ion production, laser desorption, and peptide ion extraction achieved by a novel pulsed corona apparatus. We demonstrate that droplet charging rather than gas-phase ion-neutral reactions is the major contributor to analyte ion generation from an electrically isolated droplet. Implications of the new mechanism, termed charge assisted laser desorption/ionization (CALDI), are discussed and contrasted with those of the laser desorption atmospheric pressure chemical ionization method (LD-APCI). It is also demonstrated that analyte ion generation in CALDI occurs with external electric fields about one order of magnitude lower than those needed for atmospheric pressure matrix assisted laser desorption/ionization or electrospray ionization of droplets. 相似文献
67.
Given an n × m nonnegative matrix A = (a
ij
) and positive integral vectors
and
having a common one-norm h, the (r,c)-scaling problem is to obtain positive diagonal matrices X and Y, if they exist, such that XAY has row and column sums equal to r and c, respectively. The entropy minimization problem corresponding to A is to find an n × m matrix z = (z
ij
) having the same zero pattern as A, the sum of whose entries is a given number h, its row and column sums are within given integral vectors of lower and upper bounds, and such that the entropy function
consisting of the sum of the terms z
ij
ln (z
ij
/a
ij
) is minimized. When the lower and upper bounds coincide, matrix scaling and entropy minimization are closely related. In
this paper we present several complexity bounds for the
-approximate (r,c)-scaling problem, polynomial in n,m,h,
, and ln
, where V and v are the largest and the smallest positive entries of A, respectively. These bounds, although not polynomial in
, not only provide alternative complexities for the polynomial time algorithms, but could result in better overall complexities.
In particular, our theoretical analysis supports the practicality of the well-known RAS algorithm. In our analysis we obtain
bounds on the norm of scaling vectors which will be used in deriving not only some of the above complexities, but also a complexity
for square nonnegative matrices having positive permanent. In particular, our results extend, nontrivially, many bounds for
the doubly stochastic scaling of square nonnegative matrices previously given by Kalantari and Khachiyan to the case of general
(r,c)-scaling. Finally, we study a more general entropy minimization problem where row and column sums are constrained to lie
in prescribed intervals, and the sum of all entries is also prescribed. Balinski and Demange described an RAS type algorithm
for its continuous version, but did not analyze its complexity. We show that this algorithm produces an
-approximate solution within complexity polynomial in n, m, h, and
. 相似文献
68.
Dr. Patricia Korn Arno Classen Dr. Sudarshan Murthy Dr. Riccardo Guareschi Mirko M. Maksimainen Barbara E. Lippok Albert Galera-Prat Sven T. Sowa Catharina Voigt Prof. Dr. Giulia Rossetti Prof. Dr. Lari Lehtiö Prof. Dr. Carsten Bolm Prof. Dr. Bernhard Lüscher 《ChemistryOpen》2021,10(10):939-948
Intracellular ADP-ribosyltransferases catalyze mono- and poly-ADP-ribosylation and affect a broad range of biological processes. The mono-ADP-ribosyltransferase PARP10 is involved in signaling and DNA repair. Previous studies identified OUL35 as a selective, cell permeable inhibitor of PARP10. We have further explored the chemical space of OUL35 by synthesizing and investigating structurally related analogs. Key synthetic steps were metal-catalyzed cross-couplings and functional group modifications. We identified 4-(4-cyanophenoxy)benzamide and 3-(4-carbamoylphenoxy)benzamide as PARP10 inhibitors with distinct selectivities. Both compounds were cell permeable and interfered with PARP10 toxicity. Moreover, both revealed some inhibition of PARP2 but not PARP1, unlike clinically used PARP inhibitors, which typically inhibit both enzymes. Using crystallography and molecular modeling the binding of the compounds to different ADP-ribosyltransferases was explored regarding selectivity. Together, these studies define additional compounds that interfere with PARP10 function and thus expand our repertoire of inhibitors to further optimize selectivity and potency. 相似文献
69.
Mohammad Kaveh Yousef Abbaspour-Gilandeh Ebrahim Taghinezhad Dorota Witrowa-Rajchert Magorzata Nowacka 《Molecules (Basel, Switzerland)》2021,26(7)
Most agricultural products are harvested with a moisture content that is not suitable for storage. Therefore, the products are subjected to a drying process to prevent spoilage. This study evaluates an infrared rotary dryer (IRRD) with three levels of infrared power (250, 500, and 750 W) and three levels of rotation speed (5, 10, and 15 rpm) to dry terebinth. Response surface methodology (RSM) was used to illustrate and optimize the interaction between the independent variables (infrared power and rotation speed) and the response variables (drying time, moisture diffusivity, shrinkage, color change, rehydration rate, total phenolic content, and antioxidant activity). As infrared power and rotation speed increased, drying time, rehydration rate, antioxidant activity, and total phenolic content decreased, while the other parameters were increased. According to the results, the optimum drying conditions of terebinth were determined in the IRRD at an infrared power of 250 W and drum rotation speed of 5 rpm. The optimum values of the response variables were 49.5 min for drying time, 8.27 × 10−9 m2/s for effective moisture diffusivity, 2.26 for lightness, 21.60 for total color changes, 34.75% for shrinkage, 2.4 for rehydration rate, 124.76 mg GAE/g d.m. for total phenolic content and 81% for antioxidant activity. 相似文献
70.
Kaveh Khosravi Shirin Naserifar Boshra Mahmoudi Kobra Khalaji 《Phosphorus, sulfur, and silicon and the related elements》2017,192(3):316-321
A catalyst free and chemoselective oxidation of sulfides to sulfoxides or sulfones was developed using 1,1,2,2-tetrahydroperoxy-1,2-diphenylethane as a new oxidant. This scope has shown the achievement of various sulfoxides and sulfones which were obtained selectively in high yields at room temperature. 相似文献