bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preceding winter Okhotsk Sea ice as a precursor to the following winter extreme precipitation in South China
Authors: Ji Kai , Zhang Zhongshi , Ding Ruiqiang , Li Jianping , Tian Yurun , Gao Yongqi , Zheng Jiayu 
Published: May 2022

AbstractThe winter extreme precipitation over South China (SC) experiences a large year‐to‐year variability, causing uncertainty in its prediction. Here, we find that the boreal winter sea ice concentration (SIC) in the Okhotsk Sea can serve as a precursor to the following winter's extreme precipitation frequency (EPF) over SC, which has important implications for its prediction. Further analysis reveals that the Okhotsk Sea SIC anomalies help to reinforce North Pacific Oscillation‐like atmospheric variability over the North Pacific, which induces the development of El Niño‐Southern Oscillation (ENSO)‐like SST anomalies in the equatorial eastern Pacific. The ENSO may act as a “power amplifier” to boost the impact of the Okhotsk Sea winter SIC anomalies on the following winter EPF over SC via a positive atmosphere–ocean feedback process. Our findings suggest that the Okhotsk Sea SIC may act as a potential precursor for the winter EPF over SC leading by about 1 year, and further improve our understanding of extratropical‐tropical interactions and aid predictability of winter extreme precipitation over SC.
Multi‐information source Bayesian optimization of culture media for cellular agriculture
Authors: Cosenza Zachary , Astudillo Raul , Frazier Peter I. , Baar Keith , Block David E. 
Published: May 2022

AbstractCulture media used in industrial bioprocessing and the emerging field of cellular agriculture is difficult to optimize due to the lack of rigorous mathematical models of cell growth and culture conditions, as well as the complexity of the design space. Rapid growth assays are inaccurate yet convenient, while robust measures of cell number can be time‐consuming to the point of limiting experimentation. In this study, we optimized a cell culture media with 14 components using a multi‐information source Bayesian optimization algorithm that locates optimal media conditions based on an iterative refinement of an uncertainty‐weighted desirability function. As a model system, we utilized murine C2C12 cells, using AlamarBlue, LIVE stain, and trypan blue exclusion cell counting assays to determine cell number. Using this experimental optimization algorithm, we were able to design media with 181% more cells than a common commercial variant with a similar economic cost, while doing so in 38% fewer experiments than an efficient design‐of‐experiments method. The optimal medium generalized well to long‐term growth up to four passages of C2C12 cells, indicating the multi‐information source assay improved measurement robustness relative to rapid growth assays alone.
Recombinant Snail Sialic Acid Aldolase is Promiscuous towards Aliphatic Aldehydes
Authors: Hu Zi‐Xuan , Cheng Cheng , Li Yu‐Qian , Qi Xiao‐Han , Wang Ting , Liu Li , Voglmeir Josef 
Published: May 2022

AbstractAldolases are enzymes that reversibly catalyze the cleavage of carbon‐carbon bonds. Here we describe a recombinant sialic acid aldolase originating from the freshwater snail Biomphalaria glabrata (sNPL), and compare its substrate spectrum with a sialic acid aldolase originating from chicken (chNPL). In contrast to vertebrate animals which can synthesize, degrade, and incorporate sialic acids on glycoconjugate ubiquitously, snails (as all mollusks) cannot synthesize sialic acids endogenously, and therefore the biological function and substrate scope of sNPL ought to differ significantly from vertebrate sialic aldolases such as chNPL. sNPL was active towards a series of sialic acid derivatives but was in contrast to chNPL unable to catalyze the cleavage of N‐acetylneuraminic acid into N‐acetylmannosamine and pyruvate. Interestingly, chNPL and sNPL showed contrasting C4(R)/(S) diastereoselectivity towards the substrates d‐mannose and d‐galactose in the presence of pyruvate. In addition, sNPL was able to synthesize a series of 4‐hydroxy‐2‐oxoates using the corresponding aliphatic aldehyde substrates in the presence of pyruvate, which could be not achieved by chNPL.
Mechanistic Investigations on Hydrogenation, Isomerization and Hydrosilylation Reactions Mediated by a Germyl‐Rhodium System
Authors: Bajo Sonia , Theulier Cyril A. , Campos Jesús 
Published: May 2022

AbstractWe recently disclosed a dehydrogenative double C−H bond activation reaction in the unusual pincer‐type rhodium‐germyl complex [(ArMes)2ClGeRh] (ArMes=C6H3‐2,6‐(C6H2‐2,4,6‐Me3)2). Herein we investigate the catalytic applications of this Rh/Ge system in several transformations, namely trans‐semihydrogenation of internal alkynes, trans‐isomerization of olefins and hydrosilylation of alkynes. We have compared the activity and selectivity of this catalyst against other common rhodium precursors, as well as related sterically hindered rhodium complexes, being the one with the germyl fragment superior in terms of selectivity towards E‐isomers. To increase this selectivity, a tandem catalytic protocol that incorporates the use of a heterogeneous catalyst for the trans‐semihydrogenation of internal alkynes has been devised. Kinetic mechanistic investigations provide important information regarding the individual catalytic cycles that comprise the overall trans‐semihydrogenation of internal alkynes.
Sulfur and Azobenzenes, a Profitable Liaison: Straightforward Synthesis of Photoswitchable Thioglycosides with Tunable Properties
Authors: Berry Jonathan , Lindhorst Thisbe K. , Despras Guillaume 
Published: May 2022

AbstractAzobenzene photoswitches are valuable tools for controlling properties of molecular systems with light. We have been investigating azobenzene glycoconjugates to probe carbohydrate‐protein interactions and to design glycoazobenzene macrocycles with chiroptical and physicochemical properties modulated by light irradiation. To date, direct conjugation of glycosides to azobenzenes was performed by reactions providing target compounds in limited yields. We therefore sought a more effective and reliable coupling method. In this paper, we report on a straightforward thioarylation of azobenzene derivatives with glycosyl thiols as well as other thiols, thereby increasing the scope of azobenzene conjugation. Even challenging unsymmetrical conjugates can be achieved in good yields via sequential or one‐pot procedures. Importantly, red‐shifted azoswitches, which are addressed with visible light, were easily functionalized. Additionally, by oxidation of the sulfide bridge to the respective sulfones, both the photochromic and the thermal relaxation properties of the core azobenzene can be tuned. Utilizing this option, we realized orthogonal three‐state photoswitching in mixtures containing two distinct azobenzene thioglycosides.
Experimental and Theoretical Study of NiII‐ and PdII‐Promoted Double Geminal C(sp3)−H Bond Activation Providing Facile Access to NHC Pincer Complexes: Isolated Intermediates and Mechanism
Authors: He Fengkai , Gourlaouen Christophe , Pang Huan , Braunstein Pierre 
Published: May 2022

AbstractWe report the first examples of metal‐promoted double geminal activation of C(sp3)−H bonds of the N−CH2−N moiety in an imidazole‐type heterocycle, leading to nickel and palladium N‐heterocyclic carbene complexes under mild conditions. Reaction of the new electron‐rich diphosphine 1,3‐bis((di‐tert‐butylphosphaneyl)methyl)‐2,3‐dihydro‐1H‐benzo[d]imidazole (1) with [PdCl2(cod)] occurred in a stepwise fashion, first by single C−H bond activation yielding the alkyl pincer complex [PdCl(PC
HP)] (3) with two trans phosphane donors and a covalent Pd−C
bond. Activation of the C−H bond of the resulting α‐methine C
H−M group occurred subsequently when 3 was treated with HCl to yield the NHC pincer complex [PdCl(PCNHCP)]Cl (2). Treatment of 1 with [NiBr2(dme)] also afforded a NHC pincer complex, [NiBr(PCNHCP)]Br (6), but the reactions leading to the double geminal C−H bond activation of the N−CH2−N group were too fast to allow identification or isolation of an intermediate analogous to 3. The determination of six crystal structures, the isolation of reaction intermediates and DFT calculations provided the basis for suggesting the mechanism of the stepwise transformation of a N−CH2−N moiety in the N−CNHC−N unit of NHC pincer complexes and explain the key differences observed between the Pd and Ni chemistries.
Tuning Deazaflavins Towards Highly Potent Reducing Photocatalysts Guided by Mechanistic Understanding – Enhancement of the Key Step by the Internal Heavy Atom Effect
Authors: Pavlovska Tetiana , Král Lesný David , Svobodová Eva , Hoskovcová Irena , Archipowa Nataliya , Kutta Roger Jan , Cibulka Radek 
Published: May 2022

AbstractDeazaflavins are well suited for reductive chemistry acting via a consecutive photo‐induced electron transfer, in which their triplet state and semiquinone – the latter is formed from the former after electron transfer from a sacrificial electron donor – are key intermediates. Guided by mechanistic investigations aiming to increase intersystem crossing by the internal heavy atom effect and optimising the concentration conditions to avoid unproductive excited singlet reactions, we synthesised 5‐aryldeazaflavins with Br or Cl substituents on different structural positions via a three‐component reaction. Bromination of the deazaisoalloxazine core leads to almost 100 % triplet yield but causes photo‐instability and enhances unproductive side reactions. Bromine on the 5‐phenyl group in ortho position does not affect the photostability, increases the triplet yield, and allows its efficient usage in the photocatalytic dehalogenation of bromo‐ and chloroarenes with electron‐donating methoxy and alkyl groups even under aerobic conditions. Reductive powers comparable to lithium are achieved.
The Aryl Sulfide Synthesis via Sulfide Transfer
Authors: Liang Xinyu , Wen Kaikai , Shi Qinqin , Zhang Bei‐Bei , Pei Shurui , Lin Qijie , Ma Bowei , Wang Song , Zhang Meng , Li Xiang , Wang Zhi‐Xiang , Huang Hui 
Published: May 2022

AbstractAryl sulfides are in great demands in drugs and materials sciences. To avoid using nucleophilic and noxious thiols, many efforts have been focused on exploring novel sulfide resources. Herein, a reductive Pd‐catalyzed, Ni‐mediated method to synthesize aryl sulfides via a sulfide transfer reaction is developed. The utility and scope of this reaction is exemplified by various aryl electrophiles and aryl sulfides. Mechanistic studies reveal two competing catalytic cycles of sulfide transfer and aryl transfer in this reaction, where the former one is favored over the later one because of the large energy barrier difference during the transmetalation. Moreover, two important chemicals are late‐stage functionalized by this method, exhibiting the potential applications in drugs and materials science.
Direct Perfluoroalkylation of C−H Bonds in (Hetero)arenes
Authors: Baguia Hajar , Evano Gwilherm 
Published: May 2022

AbstractPerfluoroalkylated (hetero)arenes represent an extremely important family of molecules commonly utilized in many areas such as medicinal chemistry, agrochemistry and material sciences. Due to their unique properties, they have attracted significant interest from synthetic chemists and various methods have been developed for their synthesis. Among them, the direct perfluoroalkylation of C(sp2)−H bonds in (hetero)arenes is one of the most attractive and straightforward ones, provided that it proceeds with high levels of regioselectivity. In this review article, a comprehensive overview of advances in this field is presented, with a special focus on the reaction mechanisms involved in these transformations and their regioselectivity. All methods available have been classified according to the nature of the perfluoroalkyl chain introduced, trifluoromethylation reactions being overviewed in a separate section, and to the nature of the reagents/catalysts required.
Formal Umpolung Addition of Phosphites to 2‐Azaaryl Ketones under Chiral Brønsted Base Catalysis: Enantioselective Protonation Utilizing [1,2]‐Phospha‐Brook Rearrangement
Authors: Kondoh Azusa , Hirozane Takayuki , Terada Masahiro 
Published: May 2022

AbstractThe formal enantioselective umpolung addition of dialkyl phosphites to 2‐azaaryl ketones was developed under Brønsted base catalysis. The reaction involves the enantioselective protonation of the transient α‐oxygenated (2‐azaaryl)methyl anion generated through the 1,2‐addition of the anion of dialkyl phosphite to the 2‐azaaryl ketone and the subsequent [1,2]‐phospha‐Brook rearrangement. A chiral bis(guanidino)iminophosphorane organosuperbase efficiently catalyzed the reaction to provide enantio‐enriched phosphates in high yields with good to high enantioselectivities. This is a rare example of the catalytic enantioselective protonation of transient carbanions other than enolates, constructing a trisubstituted stereogenic center α to 2‐azaarenes.
Organic and Inorganic Nitrogen forms as Affected by Phosphorus Additions in a Maize–Mustard Cropping System
Authors: Zhang Yang , Zhang Xiaojia , Zhou Chuan , Lei Ping , Sootahar Mahendar Kumar , Ni Jiupai 
Published: May 2022

AbstractPhosphorus (P) availability affects the accumulation and enrichment of soil nitrogen (N) forms. However, the effect of P addition on the distribution and turnover of soil N forms in the mustard–maize rotation system is unclear. A field experiment is conducted to investigate the effect of P addition on the turnover of soil N forms in a mustard–maize rotation system. The results show that after maize harvesting, the levels of ammonium N in soil with P addition are smaller compared to those without P addition. The organic N forms in soil with P addition are greater compared without P addition after mustard harvest. Moreover, the hydrolysable ammonium N and unknown hydrolysable N in soil with P addition are smaller than those without P addition after maize harvest. Structured equation model results show the intensities of hydrolysable amino acid N, hydrolysable amino sugar N, and unknown hydrolysable N transformed into ammonium N in soil with P addition are greater than those without P addition, and the intensities of these organic N forms transformed into nitrate N are weaker. The results indicate that P addition affect the accumulation and enrichment of soil N by altering the turnover of soil N forms.
An ECG denoising method combining variational modal decomposition and wavelet soft threshold
Authors: Hu Xiaoxu , Yu Qingwen , Yu Hongpeng 
Published: May 2022

AbstractCardio‐cerebrovascular disease is one of the malignant diseases with the highest morbidity and mortality in the world. Medical research shows that the factors that induce heart blood cerebrovascular disease are diverse, and electrocardiogram (ECG) has important reference significance for the diagnosis and pathological research of cardiovascular and cerebrovascular diseases. This paper proposes a method of denoising ECG signals by combining variational mode decomposition with wavelet soft‐threshold. First perform variational modal decomposition on the ECG signal to obtain several modal components, and then the decomposed modals components are denoised by wavelet threshold, and finally the signal reconstruction of the denoised modal components is carried out through Matlab simulation experiment analysis. Compared with the soft‐threshold denoising method of ensemble empirical mode decomposition (EEMD), the soft‐threshold denoising method of complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), the variational modal decomposition wavelet threshold denoising algorithm combined with ECG signal denoising has better denoising effect. This method is used to denoise the ECG signal from the MIT‐BIH database of the Massachusetts Institute of Technology. Under the condition of ensuring the smoothness of the ECG signal image, the signal‐to‐noise ratio value is 27.1121 and the mean square error value is 0.0535, which has achieved good results.
Mitochondrial GCN5L1 regulates glutaminase acetylation and hepatocellular carcinoma
Authors: Zhang Taotao , Cui Yunlong , Wu Yanjin , Meng Jiahui , Han Linmeng , Zhang Jiaqi , Zhang Chunyu , Yang Chenxi , Chen Lu , Bai Xue , Zhang Kai , Wu Kaiyuan , Sack Michael N. , Wang Lingdi , Zhu Lu 
Published: May 2022

AbstractBackgroundGlutaminolysis is a critical metabolic process that promotes cancer cell proliferation, including hepatocellular carcinoma (HCC). Delineating the molecular control of glutaminolysis could identify novel targets to ameliorate this oncogenic metabolic pathway. Here, we evaluated the role of general control of amino acid synthesis 5 like 1 (GCN5L1), a regulator of mitochondrial protein acetylation, in modulating the acetylation and activity of glutaminase to regulate HCC development.MethodsCell proliferation was determined by MTT, 2D and soft agar clone formation assays and orthotopic tumour assays in nude mice. GLS1/2 acetylation and activities were measured in cells and tumours to analyse the correlation with GCN5L1 expression and mTORC1 activation.ResultsHepatic GCN5L1 ablation in mice markedly increased diethylnitrosamine (DEN)‐induced HCC, and conversely, the transduction of mitochondrial‐restricted GCN5L1 protected wild‐type mice against HCC progression in response to DEN and carbon tetrachloride (CCl4) exposure. GCN5L1–depleted HepG2 hepatocytes enhanced tumour growth in athymic nude mice. Mechanistically, GCN5L1 depletion promoted cell proliferation through mTORC1 activation. Interestingly, liver–enriched glutaminase 2 (GLS2) appears to play a greater role than ubiquitous and canonical tumour–enriched glutaminase 1 (GLS1) in promoting murine HCC. Concurrently, GCN5L1 promotes acetylation and inactivation of both isoforms and increases enzyme oligomerisation. In human HCC tumours compared to adjacent tissue, there were variable levels of mTORC1 activation, GCN5L1 levels and glutaminase activity. Interestingly, the levels of GCN5L1 inversely correlated with mTORC1 activity and glutaminase activity in these tumours.ConclusionsOur study identified that glutaminase activity, rather than GLS1 or GLS2 expression, is the key factor in HCC development that activates mTORC1 and promotes HCC. In the Kaplan–Meier analysis of liver cancer, we found that HCC patients with high GCN5L1 expression survived longer than those with low GCN5L1 expression. Collectively, GCN5L1 functions as a tumour regulator by modulating glutaminase acetylation and activity in the development of HCC.
Optimizing the stochastic deployment of small base stations in an interleave division multiple access‐based heterogeneous cellular networks
Authors: Noma‐Osaghae Etinosa , Misra Sanjay , Koyuncu Murat 
Published: May 2022

SummaryThe use of small base stations (SBSs) to improve the throughput of cellular networks gave rise to the advent of heterogeneous cellular networks (HCNs). Still, the interleave division multiple access (IDMA) performance in sleep mode active HCNs has not been studied in the existing literature. This research examines the 24‐h throughput, spectral efficiency (SE), and energy efficiency (EE) of an IDMA‐based HCN and compares the result with orthogonal frequency division multiple access (OFDMA). An energy‐spectral‐efficiency (ESE) model of a two‐tier HCN was developed. A weighted sum modified particle swarm optimization (PSO) algorithm simultaneously maximized the SE and EE of the IDMA‐based HCN. The result obtained showed that the IDMA performs at least 68% better than the OFDMA on the throughput metric. The result also showed that the particle swarm optimization algorithm produced the Pareto optimal front at moderate traffic levels for all varied network parameters of SINR threshold, SBS density, and sleep mode technique. The IDMA‐based HCN can improve the throughput, SE, and EE via sleep mode techniques. Still, the combination of network parameters that simultaneously maximize the SE and EE is interference limited. In sleep mode, the performance of the HCN is better if the SBSs can adapt to spatial and temporal variations in network traffic.
Maternal survival costs in an asocial mammal
Authors: Kanaziz Rachel , Huyvaert Kathryn P. , Wells Caitlin P. , Van Vuren Dirk H. , Aubry Lise M. 
Published: May 2022

AbstractMaternal characteristics, social dynamics, and environmental factors can all influence reproduction and survival and shape trade‐offs that might arise between these components of fitness. Short‐lived mammals like the golden‐mantled ground squirrel (GMGS; Callospermophilus lateralis) tend to maximize effort toward current reproduction at the expense of survival but may be complicated by other aspects of the species’ life history and environment. Here, we use 25 years of data (1995–2020) collected from a population of GMGS at the Rocky Mountain Biological Research Laboratory in Gothic, Colorado, to test the effect of several maternal characteristics (e.g., age, experience, and timing of litter emergence), social context (e.g., litter sex ratio and kin density), and environmental context (e.g., date of bare ground and length of vegetative growing season) on survival of reproductive female GMGS using Cox proportional hazard models. Our results indicated that social dynamics (i.e., density) and environmental conditions (i.e., standardized first day of permanent snow cover and length of growing season) explained significant variation in annual maternal survival, while maternal characteristics did not. A higher density of related breeding females and the total number of females (both related and unrelated to the focal mother) were associated with an increase in the mortality hazard. A later standardized date of the first day of permanent snow cover and a shorter growing season both reduced the maternal mortality hazard. Together, our results suggest that factors extrinsic to the squirrels affect maternal survival and thus may also influence local population growth and dynamics in GMGS and other short‐lived, territorial mammal species.