Node-Aligned Graph-to-Graph: Elevating Template-free Deep Learning Approaches in Single-Step Retrosynthesis.

Single-step retrosynthesis in organic chemistry increasingly benefits from deep learning (DL) techniques in computer-aided synthesis design. While template-free DL models are flexible and promising for retrosynthesis prediction, they often ignore vital 2D molecular information and struggle with atom alignment for node generation, resulting in lower performance compared to the template-based and semi-template-based methods. To address these issues, we introduce node-aligned graph-to-graph (NAG2G), a transformer-based template-free DL model. NAG2G combines 2D molecular graphs and 3D conformations to retain comprehensive molecular details and incorporates product-reactant atom mapping through node alignment, which determines the order of the node-by-node graph outputs process in an autoregressive manner. Through rigorous benchmarking and detailed case studies, we have demonstrated that NAG2G stands out with its remarkable predictive accuracy on the expansive data sets of USPTO-50k and USPTO-FULL. Moreover, the model's practical utility is underscored by its successful prediction of synthesis pathways for multiple drug candidate molecules. This proves not only NAG2G's robustness but also its potential to revolutionize the prediction of complex chemical synthesis processes for future synthetic route design tasks.

Nitrogen Loss and Migration in Rice Fields under Different Water and Fertilizer Modes.

Irrigating aquaculture wastewater in appropriate irrigation and drainage modes in paddy fields could reduce water and fertilizer loss. However, the precise mechanisms involved in the degradation and movement of nitrogen in various water and fertilizer modes are still not fully understood. This study involves conducting a controlled experiment using barrels to examine the effects of various water quality, irrigation and drainage methods, and fertilization levels. The aim is to analyze the patterns of nitrogen degradation, loss, migration, and absorption in surface water, underground drainage, and soil leakage at different depths. The results showed the following: (1) The paddy field has a significant purification effect on aquaculture wastewater after one day of irrigation, reached at 78.55-96.06%. (2) Aquaculture wastewater irrigation increased nitrogen concentration in the plough layer, which helps rice roots absorb nitrogen and boosts plant TN. (3) In special dry years, underground seepage is the predominant method of nitrogen loss, and underground drainage nitrogen concentration peaks 2-6 days after fertilization. (4) Under aquaculture wastewater irrigation, the TN loss load of II decreased by 27.65-42.45% than FSI. Compared with IA-80, the TN degradation rate of IA in surface water increased by 18.51%, TN loss load decreased by 5.48%, TN absorption rate significantly increased by 14.61%, and yield increased by 31.14% significantly. IA is recommended in special dry years, which can improve the TN absorption rate and ensure high yield while significantly reducing the loss load of nitrogen. The findings can provide a basis for the purification of aquaculture wastewater through paddy field ecosystems in response to fertilizer supply levels.

The effect and optimal parameters of repetitive transcranial magnetic stimulation on lower extremity motor function in stroke patient: a systematic review and meta-analysis.

PURPOSE: This study aimed to evaluate the efficacy of repetitive transcranial magnetic stimulation (rTMS) in treating lower limb motor dysfunction after stroke and explore the optimal stimulation parameters. METHODS: PubMed, Embase, Cochrane Library, and other relevant databases were systematically queried for randomised controlled trials (RCTs) investigating the efficacy of rTMS in addressing lower limb motor dysfunction post-stroke. The search encompassed records from inception to July 2022. The assessed outcomes encompassed parameters such as the Fugl-Meyer motor function score for lower limbs, balance function, and Barthel index (BI). Three independent researchers were responsible for research selection, data extraction, and quality assessment. Study screening, data extraction, and bias evaluation were performed independently by two reviewers. Data synthesis was undertaken using Review Manager 5.3, while Stata version 14.0 software was employed for generating the funnel plot. RESULTS: A total of 13 studies and 428 patients were included. The meta-analysis indicated that rTMS had a positive effect on the BI (MD = 5.87, 95% CI [0.99, 10.76], p = 0.02, I2 = 86%, N of studies = 8, N of participants = 248). Subgroup analysis was performed on the stimulation frequency, treatment duration, and different stroke stages (stimulation frequency was low-frequency (LF)-rTMS (MD = 4.45, 95% CI [1.05, 7.85], p = 0.01, I2 = 0%, N of studies = 4, N of participants = 120); treatment time ≤ 15 d: (MD = 4.41, 95% CI [2.63, 6.18], p < 0.00001, I2 = 0%, N of studies = 4, N of participants = 124); post-stroke time ≤6 months: (MD = 4.37, 95% CI [2.42, 6.32], p < 0.0001, I2 = 0%, N of studies = 5, N of participants = 172). CONCLUSION: LF-rTMS had a significant improvement effect on BI score, while high-frequency (HF)-rTMS and iTBS had no significant effect. And stroke time ≤6 months in patients with treatment duration ≤15 d had the best treatment effect.

Stroke Lower limb dysfunction is a common complication after stroke, seriously affecting the daily life of patients.Lower limb motor function improved significantly within 6 months after low frequency treatment.To maximise motor gains in patients with lower limb motor dysfunction following stroke in the shortest possible time, it is recommended to initiate early rehabilitation therapy using low-frequency transcranial magnetic stimulation during the subacute phase of stroke.

The efficacy of exoskeleton robotic training on ambulation recovery in patients with spinal cord injury: A meta-analysis.

OBJECTIVE: To discuss the efficacy of exoskeleton robotic training on ambulation recovery in patients with spinal cord injury (SCI). METHODS: PubMed, Embase, and Cochrane Central Register of Controlled Trials were searched systematically from their inception to April 2022 for studies on exoskeleton robotic training in patients with SCI. The language was restricted to English. The retrieved studies were screened to select eligible clinical trials. Meta-analysis was performed using Review Manager 5.4. RESULTS: Eleven randomized clinical trials (RCTs) involving 456 participants were included in the meta-analysis. The results of the meta-analysis showed that exoskeleton robotic training was more effective in improving FIM [SMD = 0.58, 95%CI = (0.07, 1.10), P = 0.03], LEMS [MD = 4.64, 95%CI = (3.58, 5.70), P<0.05], MAS [MD = 0.76, 95%CI = (0.48, 1.03), P<0.05] and BBS [MD = -3.11, 95%CI = (-12.59, 6.36), P<0.05] in patients with SCI, compared to conventional gait training(CGT). Subgroup analysis showed that the exoskeleton robotic could significantly improve the walking endurance and walking speed of patients with a duration of injury within 6 months. The sensitivity of inverted funnel plot analysis is low, suggesting that the analysis results of this study are relatively stable. CONCLUSION: Exoskeleton robotic training improves ambulation in patients with SCI, especially for patients with a course of injury within six months.

Sulfur stereogenic centers in transition-metal-catalyzed asymmetric C-H functionalization: generation and utilization.

Transition-metal-catalyzed enantioselective C-H functionalization has emerged as a powerful tool for the synthesis of enantioenriched compounds in chemical and pharmaceutical industries. Sulfur-based functionalities are ubiquitous in many of the biologically active compounds, medicinal agents, functional materials, chiral auxiliaries and ligands. This perspective highlights recent advances in sulfur functional group enabled transition-metal-catalyzed enantioselective C-H functionalization for the construction of sulfur stereogenic centers, as well as the utilization of chiral sulfoxides to realize stereoselective C-H functionalization.

Electrochemical Radical Silyl-Oxygenation of Activated Alkenes.

An efficient electrochemical radical silyl-oxygenation of electron-deficient alkenes is demonstrated, which gives access to a variety of new highly functionalized silicon-containing molecules, including ß-silyl-cyanohydrin derivatives in good yields with excellent chemo- and regio-selectivity. This electrochemical radical silylation process conducts under mild conditions without the use of transition metal catalyst or chemical oxidant and exhibits a wide scope of substrate silanes with high functional-group tolerance. The ability to access silyl radicals using electrochemical Si-H activation offers new perspectives for the synthesis of valuable organosilicon compounds in a sustainable and green manner.

Lewis acid-assisted Ir(iii) reductive elimination enables construction of seven-membered-ring sulfoxides.

Iridium has played an important role in the evolution of C-H activation chemistry over the last half century owing to its high reactivity towards stoichiometric C-H bond cleavage; however, the use of Ir(iii) complexes in catalytic C-H functionalization/C-C bond formation appears to have fallen off significantly. The main problem lies in the reductive elimination step, as iridium has a tendency to form stable and catalytically inactive Ir(iii) species. Herein, with a rationally designed Lewis acid assisted oxidatively induced strategy, the sluggish Ir(iii) reductive elimination is successfully facilitated, enabling the facile C-C bond formation. The X-ray crystal structure of a silver salt adduct of iridacycle and DFT calculations demonstrate that the sulfoxide group acts as a key bridge connecting the Ir(iii) metal centre with the silver Lewis acid, which facilitates the reductive elimination of the Ir(iii) metallacycle. Further identification of oxidants was carried out by performing stoichiometric reactions, which enables the development of catalytic construction of various highly functionalized seven-membered-ring sulfoxides, that are of great interest in medicinal chemistry and materials science.

Synthesis of (±)-Merrilactone†A by a Desymmetrization Strategy.

A concise synthesis of (±)-merrilactone A has been accomplished featuring desymmetrization of a Cs -symmetric dilactone, RhI -catalyzed intramolecular hydroacylation of a 4-alkynal, and TiIII -mediated reductive radical cyclization of epoxy-allene.