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关键词： Cycle   Stability   Turán number  

摘要： Starting from the stability theorem of Erdős and Simonovits, there have been interesting studies on stability of graphs forbidding certain substructures in terms of edge numbers, minimum degrees or numbers of cliques. In this paper we obtain strong structural stability of $C_{2k+1}$-free in terms of the number of copies of $C_4$. Let $\mathcal{N}(F,G)$ be the number of copies of F in G. We show that a $C_{2k+1}$-free graph G must be very close to $K_{\lfloor \frac{n}{2}\rfloor ,\lceil \frac{n}{2}\rceil }$ when

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关键词： AMS   36Cl   Nuclear waste   Radiochemistry  

摘要： The detection limit for ³⁶Cl (T_1/2 = 0.301 My) using mass spectrometry techniques is primarily constrained by the system’s ability to discriminate between ³⁶Cl and its stable isobar ³⁶S. Conventional accelerator mass spectrometry (AMS) systems typically operating at terminal voltages of 3 MV and above, achieve background levels for the isotopic ratio of ³⁶Cl/³⁵Cl on the order of 10⁻¹⁵ using techniques based on the stopping power difference. However, compact AMS systems are limited in their ability to discriminate heavy isobars due to their lower operating terminal voltages (i.e., 1 MV and below). Driven by the need to study ³⁶Cl in low- and intermediate-level nuclear waste (LILW), for which ³⁶Cl/³⁵Cl atom ratios on the order of 10⁻⁹ represent the detection limit of radiometric techniques, the performance of the 1 MV AMS system for the analysis of ³⁶Cl at the Centro Nacional de Aceleradores (CNA, Seville, Spain) was investigated in this work. Two strategies were adopted: (i) optimisation of radiochemistry and control of the ³⁶S signal using ³³S as a proxy, and (ii) exploitation of the partial overlap between the ³⁶Cl and ³⁶S signals in a ΔE–Eres gas detector. These approaches yielded background levels of approximately 10⁻⁹ and 10⁻¹⁰, respectively. To enable these experiments, the stripping process of chlorine in helium gas at terminal voltages below 1 MV was investigated. Results from standard samples and blanks are presented in this paper.

关键词： 葡萄籽原花青素   尿毒症   认知功能   细胞外信号调节激酶/核因子E2相关因子2/血红素加氧酶1信号通路  

摘要： 目的探讨葡萄籽原花青素(grape seed proanthocyanidin extract,GSPE)对尿毒症大鼠认知功能的影响及其机制。方法将30只雄性大鼠随机分为正常对照(NC)组、尿毒症模型(UC)组、低剂量GSPE(L-GSPE)组、中剂量GSPE(M-GSPE)组和高剂量GSPE(H-GSPE)组,每组6只。采用5/6肾切除法建立尿毒症大鼠模型。通过Morris水迷宫实验检测大鼠的学习记忆能力,并采用Western blot法测定海马组织中磷酸化细胞外信号调节激酶(phosphorylated extracellular signal-regulated kinase,p-ERK)、核因子E2相关因子2(nuclear factor erythroid 2-related factor 2,Nrf2)和血红素加氧酶1(heme oxygenase-1,HO-1)的蛋白表达水平。结果与UC组相比,M-GSPE组和H-GSPE组大鼠的平均逃避潜伏期显著缩短(P<0.05),穿越平台次数显著增加(P<0.05);海马组织中p-ERK、Nrf2和HO-1蛋白表达水平均显著升高。结论本研究证实GSPE可通过激活细胞外信号调节激酶(extracellular signalregulated kinase,ERK)/Nrf2/HO-1信号通路改善尿毒症大鼠的认知功能障碍。

关键词： Bivariate exponential distribution   Correlated queues   Customer abandonment   Markov modulated fluid flow process  

摘要： This paper analyzes a single-server queueing system that integrates correlated interarrival and service processes with customer abandonment, which is a challenging combination that has remained largely unaddressed in the queueing literature due to the analytical difficulties of modeling these features simultaneously. Such queueing systems have many applications in telecommunications networks, service systems (e.g., call centers), and healthcare (e.g., emergency department), where both correlation and abandonment play critical roles. In the queueing system, interarrival and service times are modeled using a bivariate exponential distribution, which captures any possible dependencies between them. Customers may abandon the system if their sojourn/waiting time exceeds a random patience threshold, which follows a general discrete distribution. We employ a multi-layer Markov-modulated fluid flow (MMFF) process to characterize the evolution of the age of the customer in service. Through this framework, we derive closed-form expressions for key performance metrics, including sojourn time distributions, abandonment probabilities, and the probability distribution of queue length, which goes beyond the mean and variance typically provided by MMFF theory. We develop efficient recursive algorithms for computing these distributions, making the results practically implementable. Furthermore, we analyze the impact of the correlation coefficient on system performance, offering managerial insights into how dependency structures affect operational outcomes. Numerical results indicate that increasing the correlation between interarrival times and service times does not always result in a shorter queue.

关键词： Gag polyprotein   human T-cell leukemia virus type 1   human immunodeficiency virus type 1   matrix protein domain   plasma membrane  

摘要： The matrix (MA) domain of the Gag polyprotein is critical for directing retroviral assembly at the plasma membrane (PM), yet the determinants mediating human T-cell leukemia virus type 1 (HTLV-1) Gag targeting remain incompletely defined. While Gag myristoylation and basic residue-mediated electrostatic interactions are known to be crucial for Gag-PM interactions, recent evidence with HTLV-1 MA has implicated limited dependence on specific lipid headgroup recognition for Gag interaction with the PM. Here, we have analyzed the role of non-basic residues in HTLV-1 MA in membrane interactions and particle assembly. We identified several residues (i.e., L19, D42, S70, and L71) that were essential for Gag targeting to the PM, where mutation of these amino acid residues led to Gag targeting to internal locations that colocalized with late endosomal markers. Mutation of L19 and D42 was found to alter the MA structure. Taken together, these data indicate that mutation of MA non-basic amino acid residues affected particle production and also led to Gag localization to internal membranes that colocalized with late endosomal markers. These observations indicate that non-basic residues play an important role in efficient particle assembly and release of HTLV-1 from cells.

关键词： 1,5-Diamino-2-hydroxypentane   3-Hydroxylysine   l-lysine 3-hydroxylase   l   SpLDC   Pathway enhancement  

摘要： 1,5-Diamino-2-hydroxypentane (2-OH-PDA) is a novel aliphatic β-amino alcohol with potential for a wide range of applications, and its efficient and green synthesis has attracted increasing attention. In this study, we developed a biosynthetic pathway for 2-OH-PDA from glucose. Firstly, the Fe²⁺/α-ketoglutarate (α-KG)-dependent l-Lysine-3-hydroxylase (K3H) was heterologously expressed in E coli NT1003 capable of highly producing l-lysine to construct a biosynthetic pathway strain of 3-hydroxylysine (3-OH-lysine). By intensifying the pathway, introducing a glutamate oxidation system, and optimizing the fermentation conditions, 40.2 g/L 3-OH-lysine were achieved in the fed-batch fermentation. Then, lysine decarboxylase (SpLDC) was used to catalyze the decarboxylation of 3-OH-lysine to 2-OH-PDA, yielding 29.2 g/L with a molar conversion efficiency of 99.7%. This study provides an economical, efficient and green route for the biosynthesis of 2-OH-PDA.

关键词： Aminomethylation   Catalyst-free   Glyoxylic acid monohydrate   pyrazolo[1,5-a]pyrimidines  

摘要： We report the first catalyst-free, C3-selective aminomethylation of 7-aminopyrazolo[1,5-a]pyrimidines using commercially available glyoxylic acid monohydrate as a safe and practical methylene source. This one-pot protocol operates under mild conditions, accommodates a wide range of substituted pyrazolo[1,5-a]pyrimidines and secondary amines, and delivers target products in moderate to excellent yields. Mechanistic studies suggest two plausible stepwise pathways. The method is scalable and allows for further functionalization, underscoring its utility in synthetic and medicinal chemistry.

摘要： The authors regret that Figure 2D in the original manuscript was incorrect. A revised Figure 2 includes the correct Figure 2D. The revised Figure legend is actually the same as the original and is: Fig. 2. Gross morphology of GIT1 WT and KO brain....

关键词： Polyethylene oxide   Ionic liquid   Viscosity   Molar conductivity  

摘要： Viscosity and electrical conductivity of ternary systems (poly(ethylene oxide) + 1-alkyl-4-methyl pyridinium bromide + water) were studied. The results imply that thermodynamic quality of solvent (1-alkyl-4-methyl pyridinium bromide aqueous solutions) is decreased with increasing temperature. The flow activation energy was calculated and correlated in terms of polymer concentration. The sign of initial slope of the activation energy versus polymer concentration at zero concentration indicate that thermodynamic quality of 1-alkyl-4-methyl pyridinium bromide aqueous solutions is decreased by increment temperature. The limiting molar conductivity${\Lambda }^o$and the association constant K_A for the ionic liquids in aqueous solutions of poly (ethylene oxide) were obtained by low concentration chemical model (lcCM) conductivity equation. The interaction between poly (ethylene oxide) and 1-alkyl-4-methyl pyridinium bromide was investigated by UV-Vis method. The hydrogen bonding between the pyridinium cation and the oxygen atom of poly(ethylene oxide) was confirmed using the results of UV-Vis spectroscopy.