A pH-Sensitive Zwitterionic Iron Complex Probe with High Biocompatibility for Tumor-Specific Magnetic Resonance Imaging

Accurate diagnosis of tumor characteristics, including its location and boundary, is of immense value to subsequent therapy. Activatable magnetic resonance imaging (MRI) contrast agents that respond to tumor-specific microenvironments, such as the redox state, pH, and enzyme activity, enable better mapping of tumor tissue. However, the practical application of most reported activatable agents is hampered by problems including potential toxicity, inefficient elimination, and slow activation. In this study, we developed a zwitterionic iron complex (Fe-ZDS) as a positive MRI contrast agent for tumor-specific imaging. Fe-ZDS could dissociate in weakly acidic solution rapidly, accompanied by clear longitudinal relaxivity (r₁) enhancement, which enabled the complex to act as a pH-sensitive contrast agent for tumor-specific MR imaging. In vivo experiments showed that Fe-ZDS rapidly enhanced the tumor-to-normal contrast ratio by >40 %, which assisted in distinguishing the tumor boundary. Furthermore, Fe-ZDS circulated freely in the bloodstream and was excreted relatively safely via kidneys owing to its zwitterionic nature. Therefore, Fe-ZDS is an ideal candidate for a tumor-specific MRI contrast agent and holds considerable potential for clinical translation.     

Compressibility of random walker trajectories on growing networks

We find that the simple coupling of network growth to the position of a random walker on the network generates a traveling wave in the probability distribution of nodes visited by the walker. We argue that the entropy of this probability distribution is bounded as the network size tends to infinity. This means that the growth of a space coupled to a random walker situated in it constrains its dynamics to a set of typical random walker trajectories, and walker trajectories inside the growing space are compressible.     

Exploring the electro‐optical properties of conjugated polymers based on oligo‐selenophene and oligo(3,4‐ethylenedioxyselenophene)

For seeking high‐efficiency narrow‐band‐gap donor materials to enhance short‐circuit current density for organic solar cells, a series of oligo‐selenophene (OS) and oligo(3,4‐ethylenedioxyselenophene) (OEDOS) with various chain lengths were designed and characterized using density functional theory (DFT) and time‐dependent DFT calculations. Based on the results, it can be seen that with increasing chain length of the oligomers in both syn‐ and anti‐adding manners, the bond length alternation is decreased which indicates that the π‐electron delocalization is increased. Also, when the chain length is increased the electronic energy gap and the optical energy gap are decreased. It can be concluded that the syn‐(OS)_n=10,14,15, anti‐(OS)_n=14 and anti‐(OEDOS)_n=7–12 oligomers can act as low‐band‐gap polymers. Therefore they can absorb more sunlight based on maximum wavelength (higher than 620 nm). Furthermore, a red shift in the simulated absorption spectra of (OS)_n and (OEDOS)_n donors is observed. It is found that (OS)_n=14,15 with syn configuration of the extended oligomers is the most suitable donor for the design of high‐performance organic solar cells possessing a narrow electronic band gap, high exciton lifetime and broad and intense absorption spectra that cover the solar spectrum leading to complete light‐harvesting efficiency.     

Buprofezin dissipation and safety assessment in open field cabbage and cauliflower using GC/ITMS employing an analyte protectant

An analytical method for the determination of buprofezin residues in cabbage and cauliflower was developed and validated using gas chromatography with ion trap mass spectrometry. The analyte protectant d ‐sorbitol was used at a concentration level of 0.5 mg mL^?1 in acetonitrile instead of in matrix for constructing the calibration curves of the buprofezin standard. The average recoveries ranged from 91.3 to 96.8%, with an RSD of ≤2.7%. The limits of detection and quantitation of the method in cabbage and cauliflower were 1.3, 1.7 and 4.3, 6.2 μg kg^?1, respectively. The residual levels and dissipation kinetics of buprofezin 25% wettabe powder in cabbage and cauliflower cultivated under open field conditions was investigated at the single (T1) and double (T2) recommended rates of application. Half‐life periods were found to be 1.73 and 2.1 days in cabbage, whereas in cauliflower, these values were 1.85 and 2.36 days at T1 and T2, respectively. Based on the dissipation study, and the maximum residue limit value of 0.05 mg kg^?1, the proposed pre‐harvest interval of buprofezin in cabbage was 3–6 days and that in cauliflower was 4–10 days. The results showed that buprofezin is safe for application at both recommended application rates.     

Mathematical Modeling of Nylon 6/6,6 Copolymerization in Batch Reactor: Investigating Recipes without Water and with Cyclic Dimer

A model is used to simulate batch copolymerization of caprolactam with hexamethylene diamine (HMD) and adipic acid (ADA) to produce nylon 6/6,6. Four different recipes are considered: a recipe containing caprolactam and an aqueous solution of HMD and ADA, a recipe containing caprolactam and dry HMD/ADA salt, and two recipes with a portion of the caprolactam replaced by nylon 6 cyclic dimer (CD). Consuming CD would be advantageous because CD is an undesirable side product from nylon 6 production. Simulation results lead to three important findings: (i) operation using dry salt rather than aqueous salt solution leads to higher degree of polymerization, (ii) substantial quantities of CD can be consumed to produce nylon 6/6,6 copolymer, and (iii) including water in the recipe is beneficial for achieving improved consumption of CD. The results of this study will be helpful in designing experiments aimed at improving industrial nylon 6/6,6 copolymerization processes.     

Salen–Mg-doped NH2–MIL-101(Cr) for effective CO2 adsorption under ambient conditions

A novel metal-doped metal–organic framework (MOF) was developed by incorporating salen–Mg into NH₂–MIL-101(Cr) structure under ambient conditions. The Schiff base complex was successfully prepared by condensing salicylaldehyde with a free amino group and then coordinating metal ions. Such a structure can endow the sample with higher CO₂ adsorption performance. At 0°C and 1 bar, the salen–Mg-modified sample achieves the maximum adsorption capacity of 2.18 mmol g⁻¹ for CO₂, which was 5.8% higher than the pristine salen–MOF under the same conditions. Notably, the Freundlich model indicates that the CO₂ adsorption process of all samples conforms to reversible adsorption. However, the correlation coefficients (R²) of the Mg-doped sample are lower than that of the pristine sample. Besides, the CO₂/N₂ adsorption selectivity and isosteric heat also show a similar trend. These results indicate that the salen–Mg can enhance the interaction between the material and CO₂ molecules.     

Homogenization of Periodically Heterogeneous Thin Beams

Consider an elastic thin three-dimensional body made of a periodic distribution of elastic inclusions. When both the thickness of the beam and the size of the heterogeneities tend simultaneously to zero the authors obtain three different one-dimensional models of beam depending upon the limit of the ratio of these two small parameters.     

Decay rate for viscoelastic wave equation of variable coefficients with delay and dynamic boundary conditions

In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method.     

Lamb波频域逆散射全聚焦成像方法研究

Lamb波因其传播距离远、衰减小常被用于板状结构的无损检测中,在基于Lamb波损伤检测的诸多成像技术中,全聚焦方法(Total Focus Method,TFM)方法因其成像分辨率高、信噪比高而受青睐。然而Lamb波的频散效应导致时域延时量不能被准确计算,进而影响传统TFM方法对损伤定位及成像的精度;此外,既有的TFM方法仅以回波幅值作为成像指标,忽略了Lamb波与损伤的相互作用,故而不能通过损伤表面的物理参数增强成像质量。针对这两个问题,本文首先在时域TFM基础上发展了频域TFM,在计算中纳入频散关系以规避频散的影响;其次以包含明确的损伤特征参数--反射率为成像指标,结合频域TFM方法建立损伤逆散射模型,以实现对损伤的准确成像。仿真和实验结果表明:频域逆散射TFM成像方法能够实现对铝板结构中的损伤检测,在工程实践中具有应用价值。