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41.
Complex adaptive systems have been the subject of much recent attention. It is by now well established that members ("agents") tend to self-segregate into opposing groups characterized by extreme behavior. However, the study of such adaptive systems has mostly been restricted to simple situations in which the prize-to-fine ratio R equals unity. In this Letter we explore the dynamics of evolving populations with various different values of the ratio R, and demonstrate that extreme behavior is in fact not a generic feature of adaptive systems. In particular, we show that "confusion" and "indecisiveness" take over in times of depression, in which case cautious agents perform better than extreme ones. 相似文献
42.
Theoretical studies of charge transport in deoxyribonucleic acid (DNA) and peptide nucleic acid (PNA) indicate that structure and dynamics modulate the charge transfer rates, and that different members of a structural ensemble support different charge transport mechanisms. Here, we review the influences of nucleobase geometry, electronic structure, solvent environment, and thermal conformational fluctuations on the charge transfer mechanism. We describe an emerging framework for understanding the diversity of charge transport mechanisms seen in nucleic acids. 相似文献
43.
Prasanna A. Yakkala Samir R. Panda Syed Shafi V. G. M. Naidu M. Shahar Yar Philemon N. Ubanako Samson A. Adeyemi Pradeep Kumar Yahya E. Choonara Eugene V. Radchenko Vladimir A. Palyulin Ahmed Kamal 《Molecules (Basel, Switzerland)》2022,27(21)
A series of new 1,2,4-triazolo-linked bis-indolyl conjugates (15a–r) were prepared by multistep synthesis and evaluated for their cytotoxic activity against various human cancer cell lines. It was observed that they were more susceptible to colon and breast cancer cells. Conjugates 15o (IC50 = 2.04 μM) and 15r (IC50 = 0.85 μM) illustrated promising cytotoxicity compared to 5-fluorouracil (5-FU, IC50 = 5.31 μM) against the HT-29 cell line. Interestingly, 15o and 15r induced cell cycle arrest at the G0/G1 phase and disrupted the mitochondrial membrane potential. Moreover, these conjugates led to apoptosis in HT-29 at 2 μM and 1 μM, respectively, and also enhanced the total ROS production as well as the mitochondrial-generated ROS. Immunofluorescence and Western blot assays revealed that these conjugates reduced the expression levels of the PI3K-P85, β-catenin, TAB-182, β-actin, AXIN-2, and NF-κB markers that are involved in the β-catenin pathway of colorectal cancer. The results of the in silico docking studies of 15r and 15o further support their dual inhibitory behaviour against PI3K and tankyrase. Interestingly, the conjugates have adequate ADME-toxicity parameters based on the calculated results of the molecular dynamic simulations, as we found that these inhibitors (15r) influenced the conformational flexibility of the 4OA7 and 3L54 proteins. 相似文献
44.
The empirical entropy is a key statistical measure of data frequency vectors, enabling one to estimate how diverse the data are. From the computational point of view, it is important to quickly compute, approximate, or bound the entropy. In a distributed system, the representative (“global”) frequency vector is the average of the “local” frequency vectors, each residing in a distinct node. Typically, the trivial solution of aggregating the local vectors and computing their average incurs a huge communication overhead. Hence, the challenge is to approximate, or bound, the entropy of the global vector, while reducing communication overhead. In this paper, we develop algorithms which achieve this goal. 相似文献
45.
Truncation and acylation were combined to investigate the broad-spectrum bactericidal and hemolytic peptide S4(1-15). Substitution of up to seven residues with dodecanoic acid (C(12)) gradually led to specific antipseudomonal activity: out of 40 bacterial strains tested in vitro, C(12)-S4(8-15) displayed similar minimal inhibitory concentrations (MICs) as S4(1-15) against Pseudomonas aeruginosa sp. (identical MIC(90)) but was practically inactive against most other bacteria or erythrocytes. Surface plasmon resonance and isothermal titration calorimetry experiments revealed the binding properties of S4(1-15) to be consistent with its nonselective activities, while discriminative activities of C(12)-S4(8-15) correlated with high binding affinity to a membrane containing pseudomonal lipopolysaccharides and with lower affinities to membranes containing nonpseudomonal lipopolysaccharides or cholesterol. Various mechanistic studies failed to detect significant differences in secondary structure, bactericidal kinetics, or ability to perturb the cytoplasmic membrane, pointing to a similar mode of action. 相似文献
46.
In this paper we consider four previously known parameters of sign matrices from a complexity-theoretic perspective. The main
technical contributions are tight (or nearly tight) inequalities that we establish among these parameters. Several new open
problems are raised as well.
Supported by the ISF.
Supported by the ARC. 相似文献
47.
We consider computationally-efficient truthful mechanisms that use the VCG payment scheme, and study how well they can approximate
the social welfare in auction settings. We present a novel technique for setting lower bounds on the approximation ratio of
this type of mechanisms. Our technique is based on setting lower bounds on the communication complexity by analyzing combinatorial
properties of the algorithms. Specifically, for combinatorial auctions among submodular (and thus also subadditive) bidders
we prove an $\Omega \left( {m^{\tfrac{1}
{6}} } \right)$\Omega \left( {m^{\tfrac{1}
{6}} } \right) lower bound, which is close to the known upper bound of ${\rm O}\left( {m^{\tfrac{1}
{2}} } \right)${\rm O}\left( {m^{\tfrac{1}
{2}} } \right), and qualitatively higher than the constant factor approximation possible from a purely computational point of view. 相似文献
48.
Wierzbinski E de Leon A Yin X Balaeff A Davis KL Reppireddy S Venkatramani R Keinan S Ly DH Madrid M Beratan DN Achim C Waldeck DH 《Journal of the American Chemical Society》2012,134(22):9335-9342
Charge transfer (CT) properties are compared between peptide nucleic acid structures with an aminoethylglycine backbone (aeg-PNA) and those with a γ-methylated backbone (γ-PNA). The common aeg-PNA is an achiral molecule with a flexible structure, whereas γ-PNA is a chiral molecule with a significantly more rigid structure than aeg-PNA. Electrochemical measurements show that the CT rate constant through an aeg-PNA bridging unit is twice the CT rate constant through a γ-PNA bridging unit. Theoretical calculations of PNA electronic properties, which are based on a molecular dynamics structural ensemble, reveal that the difference in the CT rate constant results from the difference in the extent of backbone fluctuations of aeg- and γ-PNA. In particular, fluctuations of the backbone affect the local electric field that broadens the energy levels of the PNA nucleobases. The greater flexibility of the aeg-PNA gives rise to more broadening, and a more frequent appearance of high-CT rate conformations than in γ-PNA. 相似文献
49.
Hod S 《Physical review letters》2010,105(20):208701
Motivated by novel results in the theory of network synchronization, we analyze the effects of nonzero time delays in stochastic synchronization problems with linear couplings in an arbitrary network. We determine analytically the fundamental limit of synchronization efficiency in a noisy environment with uniform time delays. We show that the optimal efficiency of the network is achieved for λτ = π(3/2)/(2√π + 4) ≈ 0.738, where λ is the coupling strength (relaxation coefficient) and τ is the characteristic time delay in the communication between pairs of nodes. Our analysis reveals the underlying mechanism responsible for the trade-off phenomena observed in recent numerical simulations of network synchronization problems. 相似文献
50.
Ultra-compact objects describe horizonless solutions of the Einstein field equations which, like black-hole spacetimes, possess null circular geodesics (closed light rings). We study analytically the physical properties of spherically symmetric ultra-compact isotropic fluid spheres with a polytropic equation of state. It is shown that these spatially regular horizonless spacetimes are generally characterized by two light rings \(\{r^{\text {inner}}_{\gamma },r^{\text {outer}}_{\gamma }\}\) with the property \(\mathcal{C}(r^{\text {inner}}_{\gamma })\le \mathcal{C}(r^{\text {outer}}_{\gamma })\), where \(\mathcal{C}\equiv m(r)/r\) is the dimensionless compactness parameter of the self-gravitating matter configurations. In particular, we prove that, while black-hole spacetimes are characterized by the lower bound \(\mathcal{C}(r^{\text {inner}}_{\gamma })\ge 1/3\), horizonless ultra-compact objects may be characterized by the opposite dimensionless relation \(\mathcal{C}(r^{\text {inner}}_{\gamma })\le 1/4\). Our results provide a simple analytical explanation for the interesting numerical results that have recently presented by Novotný et al. (Phys Rev D 95:043009, 2017). 相似文献