bluuebunny/crossref_metadata_2025_split huggingface dataset:
Weighted validation of heteroscedastic regression models for better selection
Authors: Jung Yoonsuh , Kim Hayoung 
Published: August 2021

AbstractIn this paper, we suggest a method for improving model selection in the presence of heteroscedasticity. For this purpose, we measure the heteroscedasticity in the data using the inter‐quartile range (IQR) of the fitted values under the framework of cross‐validation. To find the IQR, we fit 0.25 and 0.75 generic quantile regression using the training data. The two models then predict the values of the response variable at 0.25 and 0.75 quantiles in the test data, which yields predicted IQR. To reduce the effect of heteroscedastic data in the model selection, we propose to use weighted prediction error. The inverse of the predicted IQR is utilized to estimate the weights. The proposed method reduces the impact of large prediction errors via weighted prediction and leads to better model and parameter selection. The benefits of the proposed method are demonstrated in simulations and with two real data sets.
Correlation Analysis of Target Selectivity and Side Effects of FDA‐Approved Kinase Inhibitors**
Authors: Bayazeid Omer , Rahman Taufiq 
Published: August 2021

AbstractKinase inhibitors (KIs) represent a popular class of therapeutic agents and chemical probes but most of them tend to be polypharmacological. Receptor and non‐receptor Tyrosine KIs can target more than 100 kinases simultaneously compare to other KIs. We here analyze the molecular targets of 41 U.S. Food and Drug Administration (FDA)‐approved KIs. We chose 18 drugs (Tyrosine KIs) and sought out to evaluate their selectivity profile and engagement with a number of targets in vivo at clinically relevant doses. We also wanted to see whether there prevails any correlation between the target engagement profile and the reported side effects for specific KIs chosen as test cases. To explore all clinical targets of the 18 KIs, we considered the free (unbound) maximum serum concentration (Cmax) of each KI and only chose targets for which the cognate affinities lie within the reported free Cmax values, thereby allowing plausible interaction in clinical doses. We retrieved the side effects of those KIs that is reported in the FDA adverse event reporting system. We illustrate how correlation analysis of target‐side effect can give a new insight into the off target of KIs and their effect on increasing the toxicity of KIs. These analyses could aid our understanding of the structural‐activity relationship of KIs.
Preparation and Performance Study of Antibacterial Materials Based on GO−TiO2
Authors: Li Hongxia , Wu Jie , Gao Xiang , Li Tiantian , Zhang Mengmeng , Niu Xiaohui , Zhang Deyi , Wang Yi , Fan Haiyan , Wang Kunjie 
Published: August 2021

AbstractA composite of graphene oxide (GO) and titanium (IV) oxide was prepared through a hydrothermal treatment by mixing TiO2 with GO. The GO was obtained by using an improved Hummers’ method. The composite (TiO2‐GO) only indicated a weak antibacterial effect against Escherichia coli under dark conditions. Upon introduction of silver‐based nanomaterials, two new composites viz. GO−TiO2−Ag and GO−TiO2−Ag2S were prepared also through hydrothermal reaction. While both composites exhibit stronger antibacterial activities against E. coli than TiO2‐GO in dark, GO−TiO2−Ag composite exhibited higher bactericidal rate (92 %) than GO−TiO2−Ag2S (40 %).
Copper Fluoride Doped Polypyrrole for Portable and Enhanced Ammonia Sensing at Room Temperature
Authors: Salimi Mohsen , Rahmani Fereidoon , Hosseini Seyed Mohammad R. M. 
Published: August 2021

AbstractPoint‐of‐care (POC) monitoring of breath ammonia has emerged as a great approach for non‐invasive chronic kidney disease (CKD) diagnosis. Polypyrrole (PPy) is recognized as a suitable polymer material for breath ammonia sensing. Here we describe the copper fluoride (CuF2) doping effect on sensing performance of the ammonia gas sensor based on PPy. At first, PPy was synthesized by chemical oxidative polymerization and characterized by scanning electron microscopy, energy dispersive X‐ray analysis, and Fourier Transform Infrared Spectroscopy techniques. The CuF2was doped to the polymer by an aqueous ion exchange process. A portable sensing system was developed for portable ammonia detection by measuring the resistance variation of the fabricated electrode from synthesized materials. The gas‐sensing results disclose that the CuF2‐PPy based sensor displays the highest response to 2 ppm NH3, which is 3 times higher than that of the pure PPy sensor. The low limit of detection (LOD) value for pure PPy was found to be 0.19 ppm, which has been decreased to 0.02 ppm for CuF2 doped PPy. The CuF2‐PPy resistive sensor exhibits a sustainable, selective, and stable sensing response to ammonia even in the presence of 60 % humidity. Moreover, the fabricated setup is low‐cost, user‐friendly, and suitable enough to be used at the point of care and CKD diagnosis applications.
Boosting Catalytic Efficiency of Metal‐Organic Frameworks with Electron‐Withdrawing Effect for Lewis‐Acid Catalysis
Authors: Li Siyu , Wang Wenyang , Lei Shengbin , Cui Jian‐zhong 
Published: August 2021

AbstractMetal Organic Frameworks (MOFs) have the characterization of high specific surface area, abundant metal active sites and tunable pores, making them become emerging heterogeneous catalysts. Furthermore, the clear structure of MOFs provides an excellent opportunity to explore the internal relationship between catalytic activity and structure. In addition, precise synthesis of controllable catalytic sites from the molecular level can achieve efficient catalytic preparation of high value‐added chemicals. Here, we synthesize a series of MOFs (MIL‐101(Fe)‐X; X=H, NO2, Br, Cl) with different substituents on the terephthalate linker. Then the catalytic activity of MIL‐101(Fe)‐X was evaluated for Knoevenagel reaction with different substrates. The order of reactivity of MIL‐101(Fe)‐X is closely related to the ability of the electron withdrawing effect. The MIL‐101(Fe)‐NO2 showed the best conversion at low temperature (99.9 % at 25 °C). While the activity of pristine MIL‐101 only can reach 80.78 % of under same condition. This work illustrates the versatility of electronic effect on catalytic activity and brings possibility to tune the activity of MOFs through introducing organic ligands with different functional groups.
Improvement of the Catalytic Performances of SBA‐15 in the Formylation of Aniline upon the Introduction of Template‐Free Nano‐Faujasite in Its Synthesis Gel
Authors: Baghdad Karima , Hasnaoui Mohammed Abdelkrim , Launay Franck 
Published: August 2021

AbstractFaujasite nanoparticles with average size of 10–40 nm were obtained without any organic structure directing agents (Green synthesis), then used as precursors for the synthesis of NaY/SBA‐15 composites. Two types of composites were obtained with meso/micro porosity (C1 and C2).The inorganic salt, NH4F, has a crucial effect on their morphologies, therefore, their textural and catalytic properties have been mostly influenced. The resulting materials were characterized by X‐ray Diffraction (XRD), N2 sorption, Scanning Electron Microscopy (SEM) .The both composites have been successfully used as catalysts for the N‐formylation reaction of aniline. As a result, N‐phenylformamide was obtained with up to 90 % yield and 100 % selectivity at 50 °C in 4 h (solvent‐free conditions) .The catalytic tests were monitored by gas chromatography (GC) and the nature of the products was confirmed by NMR.
The Formation of Polyethylene Using α‐Diiminonickel Precatalyst in the Presence of CoCp2 and AgOTf
Authors: Xing Yusheng , Yu Haojie , Wang Li , Wang Nan , Zhu Lei , Liang Ruixue 
Published: August 2021

AbstractThe controllable preparation of polyolefin products has always been the goal pursued by researchers, while the structure of polyolefin will have a greater impact on the performance and application of the material. Here, we used a redox active nickel catalyst to modulate the properties of polyethylene through multiple control of reaction conditions. Reductant CoCp2 and oxidant AgOTf were used to induce the valence change of the nickel species and then affected the ethylene polymerization performance. Chain structure, molecular weight, melting point and other properties of polyethylene were investigated to evaluate the catalytic performance. Besides, the characterization indicated that the addition of reductant into the catalytic system might help to change the state of the nickel active center.
Cross‐linking of γ‐Cyclodextrin Using Non‐toxic Polyethylene Glycol Spacer Units
Authors: Dossi Eleftheria , Bolton Morgan , Kister Guillaume , Afsar Ashfaq 
Published: August 2021

AbstractThe crystalline cyclic oligosaccharide γ‐cyclodextrin (γCD) is a natural, non‐toxic and biodegradable precursor that can be used to prepare innovative polymers. We cross‐linked γCD with variable quantities of non‐toxic polyethylene glycol diglycidyl ether (PEGDGE) in aqueous NaOH to form 3D structures with tunable physicochemical properties. Mixtures with a 5 : 1 PEGDGE:γCD molar ratio produced a cross‐linked material that was soluble in water and organic solvents, underwent glass transition at −23 °C. The properties of this material were further modified by additional curing with PEGDGE or nitration reaction. Curing produced an insoluble polymeric material with excellent swelling abilities (200 % in water) and decreased glass transition temperature to −37 °C. The nitrated cross‐linked γCD was soluble in common organic solvents and underwent glass transition at +19 °C, achieving thermal stability below 190 °C. These novel γCD polymers are promising materials for applications in the pharmaceutical and food industries and environmental remediation.
Optically Active Functionalized Building Blocks for Peptidyl Olefin Peptidomimetics
Authors: Lerman Ekaterina , Levinger Shlomo , Albeck Amnon 
Published: August 2021

AbstractPeptidyl olefins can function as bio‐active peptide isosteres or as intermediates in the synthesis of other peptidomimetics. We previously developed a stereoselective chemo‐enzymatic approach to optically active C‐terminal building blocks for the synthesis of peptidyl olefins. These building units include a sulfone functionality, to enable a Julia‐Kocienski reaction with N‐terminal aldehydes. Here, we extend this synthetic methodology to building blocks that are functionalized at their side chains with oxygen, nitrogen or halogen. The method features key enzymatic hydrolysis of prochiral diesters to the corresponding hydroxy esters, a step that introduces the optical activity. The ordering of the subsequent chemical reactions, either protection‐methanolysis‐functionalization or functionalization‐methanolysis‐protection, determines the absolute stereochemistry of the final building blocks.
Computational Study on Adsorption Characteristics of Phenol and Guaiacol Over Single and Multiple Nitrogen‐Doped Graphene
Authors: Agrawal Kushagra , Kishore Nanda 
Published: August 2021

AbstractThe experimental synthesis of nitrogen‐doped graphene (N‐doped graphene) has opened the door for its application in many catalytically important processes. In this study, the authors report the properties of N‐doped graphene, like the electron density distribution, charge distribution, electrostatic potential, etc. Subsequently, the adsorption characteristics such as the charge transfer, adsorption energy, dipole moment change, etc., are presented for the bio‐oil model compounds (phenol and guaiacol) to realize the potential of N‐doped graphene in bio‐oil deoxygenation. The density functional theory (DFT) method is employed for calculating all the aforementioned properties. It is found that doping with nitrogen significantly alters the electronic properties of graphene favourably. For strong adsorption, either a high charge transfer between the catalyst and the model compound and/or a strong delocalization of the charge on the surface is desired. Both phenol and guaiacol show similar adsorption energy on non‐defective and defective N‐doped graphene; and increasing the doping does not increase the adsorption energy on the surface.
Synthesis and Characterization of Antioxidant Biphenyl Appended 1,2,3‐Triazoles as Potential Chemo‐Sensor for Sn2+ Ions: Excellent Selectivity and Low Detection Limit
Authors: Singh Gurjaspreet , Priyanka  , Sushma  , Pawan  , Mohit  , Satija Pinky , Esteban Maria Angeles , González‐Silvera D. , Espinosa‐Ruíz Cristóbal 
Published: August 2021

AbstractDesigning of chemo‐sensors is a new scope of intrigue among researchers. After inspecting the beneficial and harmful effects of Sn(II) metal ions in living species, 1,2,3‐ Triazole based chemo‐sensor 4 a have been synthesized via click route. In the current article, literarily new 1,2,3‐Triazoles (4 a–4 d) have been synthesized and identified via various spectroscopic means such as NMR(1H & 13C), IR and mass spectrometry. Triazole 4 a was explored for recognition properties via absorption and emission spectroscopy and found specific and selective for Sn(II) metal ions. The recognition of Sn2+ metal ions by probe 4a was not interfered because of other tested metal cations. The probe has very low detection limit of 0.47×10−7 M and 3.8×10−9 M via ultraviolet and fluorescence spectroscopy respectively which is lower than many previously reported sensors. The B−H plot and stern volmer's plot confirmed a high binding affinity between probe 4a and tin (II) metal ion. The association constant (Ka) and stern volmer constant (Ksv) were calculated as 13.36×105 M−1 and 12.6×106 M−1 from B−H plot and stern volmer's plot respectively. The Stoichiometric ratio between chemo‐sensor 4 a and Sn2+ metal ions was confirmed as 1 : 1 by the job's plot. Moreover, in this study, the synthesized compounds 4(a–d) were examined for their antioxidant properties. The total antioxidant activity (TAA) results indicate that the synthesized triazoles 4(a–d) found to be excellent postulant for radical scavenging. TAA values for 4 a, 4 b, 4 c and 4 d are found to be 4.65±0.2, 6.79±0.3, 6.29±0.2, 5.06±0.1 (mM)(eq. ascorbic acid) per 100 mM of particle respectively.
Determination of Angelica archangelica’s Antioxidant Capacity and Mineral Content
Authors: Topal Meryem , Ozturk Sarıkaya S. Beyza , Topal Fevzi 
Published: August 2021

AbstractThe aim of this study was to determine the mineral contents by ICP‐MS and the antioxidant capacity of Angelica archangelica plant, which is not well known in the literature. For this purpose, ethyl alcohol extracts of the branches and leaves of the plant; different bioanalytical methods such as reducing capacity by Fe3+−Fe2+ transformation method, Fe3+‐TPTZ reducing capacity by FRAP method, Cu2+‐Cu+ reducing capacity by CUPRAC method, the ferric ions (Fe2+) chelating activity by using bipyridyl reagent, DPPH (1,1‐diphenyl‐2‐picryl‐hydrazyl) free radical, DMPD (N,N‐dimethyl‐p‐phenylenediamine), ABTS (2,2’‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) radical scavenging activities, total antioxidant activity determination according to thiocyanate method, total phenolic and total flavonoid activity were used. As standard, BHT, BHA, α‐Tocopherol, Trolox were used. A. archangelica branches and leaves demonstrated 88.13 % and 93.90 % inhibition of linoleic acid emulsion peroxidation at 20 mg mL−1 concentration. Also, it was determined that both leaves and branches of A. archangelica plant were dense with P, Mg, Ca and K minerals with ICP‐MS device. It is considered that the results of the manuscript will guide the antioxidant studies, medicine, cosmetics, pharmacology and food sector.
Design, Synthesis and Conformational Studies of Cyclic Tetrapeptides having βγ Fused Turns as HDAC Inhibitors
Authors: Ghosh Uttam , Basu Moumita , Pal Sudip , Meena Sanjeev , Datta Dipak , Ampapathi Ravi Sankar , Kundu Tapas K , Singh Gajendra , Chakraborty Tushar Kanti 
Published: August 2021

AbstractHistone deacetylases (HDACs) belong to a class of major targets for the development of anticancer drugs for which cyclic peptide‐based molecules are attracting wide attention. Here we show the synthesis, conformational and in silico analysis of tetrahydrofuran amino acid (TAA) based 15‐membered cyclic tetrapeptides (CTPs) containing hydroxamic acid side chain as potential HDAC inhibitors. NMR based solution studies in protected and deprotected forms reveal that the macrocycles are stabilized by 10‐membered β‐turn as well as a 7‐membered γ‐turn. This type of fused structures within the same macrocycle is not frequently sighted. Our initial in silico docking results indicated that the hydroxamic acid protected CTPs show promising binding with the class‐1 HDACs. We also noticed that the C‐chain with hydroxamic functional group attached on the ornithine sidechain did not affect the core structure of the peptide ring. Moreover, some of these cyclic tetrapeptides with hydroxamic acid side chain exhibited an induction of acetylation of histones on preliminary cell‐based experiments. Our initial results provide an insight into the development of HDAC inhibitors based on the CTPs with novel βγ fused turns which have not been explored yet.
Zinc‐Catalyzed Depolymerization of the End‐of‐Life Poly(ethylene 2,5‐furandicarboxylate)
Authors: Alberti Christoph , Matthiesen Konstantin , Wehrmeister Moritz , Bycinskij Sergej , Enthaler Stephan 
Published: August 2021

AbstractThe depolymerization of end‐of‐life polymers to valued chemicals (waste‐to‐chemicals) can be a suitable tool for the transformation from a linear to a circular economy. Therefore, the depolymerization of end‐of‐life poly(ethylene 2,5‐furandicarboxylate), discussed as sustainable substitute of poly(ethylene terephthalate), was studied. In more detail, in the presence of catalytic amounts of zinc(II) acetate poly(ethylene 2,5‐furandicarboxylate) was converted by methanolysis to dimethyl 2,5‐furandicarboxylate and ethylene glycol using microwave heating. Turnover frequencies up to 396 h1 were realized. Interestingly, the products dimethyl 2,5‐furandicarboxylate and ethylene glycol can be used as building blocks for the zinc‐catalyzed resynthesis of poly(ethylene 2,5‐furandicarboxylate); therefore a recycling is realizable.
Enantioselective Synthesis of 3‐Acetyl Coumarin Substituted 3‐Hydroxy Oxindoles and Pyranocoumarin Fused Spirooxindoles
Authors: Pratap Reddy Gajulapalli V. , Kumarswamyreddy Nandarapu , Lokesh Kanduru , Kesavan Venkitasamy 
Published: August 2021

AbstractEnantioselective construction of bioinspired coumarin and oxindole hybrid structures always enduring challenges in organic chemistry due to the generation of asymmetric quaternary/spiro center at the C3 position of oxindole. Herein, we demonstrated a facile enantioselective synthesis of highly functionalized 3,3’‐disubstituted oxindole derivatives containing 3‐acetyl coumarins and pyranocoumarin fused spirooxindoles using L‐proline derived bifunctional thiourea organocatalyst through Aldol reaction and Michael addition/cyclization. The L‐proline derived thiourea catalyst well performed with broad substrate scope to produce desired products in very good yields (up to 95 %) and excellent enantioselectivities (up to 99 % ee).
Presence of antibodies to Crimean Congo haemorrhagic fever virus in sheep in Tunisia, North Africa
Authors: Khamassi Khbou Médiha , Romdhane Rihab , Bouaicha Zaafouri Faten , Bouajila Mohsen , Sassi Limam , Appelberg Sofia K. , Schulz Ansgar , Mirazimi Ali , Groschup Martin H. , Rekik Mourad , Benzarti M'hammed , Gharbi Mohamed 
Published: August 2021

AbstractCrimean–Congo haemorrhagic fever (CCHF) is an emerging tick‐borne disease causing severe and fatal haemorrhagic syndrome in humans. Hyalomma spp. ticks are the primary vectors and sheep are important CCHF virus (CCHFV)‐amplifying hosts. In this study, blood samples and ticks collected in October 2019 from 270 sheep from 15 farms across Tunisia constituted the main research material. Moreover, the sera of the same animals taken at different periods between 2018 and 2019 were also used to obtain comparative results. To investigate the presence of anti‐CCHFV antibodies in sheep, all sera were tested using ELISA. Reactive sera were further characterised by a virus neutralisation test (VNT). Overall, one out of the 270 tested sheep was both ELISA‐ and strongly VNT‐positive to CCHFV. Another two sheep were borderline ELISA‐positive but did not exhibit neutralising antibodies. Ninety‐one ticks were collected from all sampled sheep, of which 34 (37.4%) belonged to Hyalomma spp. This is the first report of anti‐CCHFV antibodies in sheep from Tunisia. Both the results of this study and the recent CCHFV detection in ticks collected from camels in southern Tunisia indicate that further studies are needed to determine the competent tick vector in the country and to characterise the epidemiological cycle of CCHFV.
Synergistic effect of talc/calcined kaolin binary fillers on rigid PVC: Improved properties of PVC composites
Authors: Mallem Oum Keltoum , Zouai Foued , Gumus Omer Yunus , Benabid Fatma Zohra , Bedeloglu Ayse Celik , Benachour Djafer 
Published: August 2021

AbstractThis study aims to develop poly(vinyl chloride) (PVC) composites prepared by melt mixing by using a combination of talc and calcined kaolin as filler in order to improve the disadvantages of rigid PVC, which is widely used in industry, such as poor mechanical properties and low thermal stability. In addition, PVC/talc and PVC/calcined kaolin composites were also examined for comparison. The calcined kaolin is modified with urea to increase the surface area (chemical treatment), while the surface of both fillers is coated with stearic acid for good compatibility with PVC (mechanical treatment). Scanning electron microscopy micrographs showed homogeneous distribution of mechanically processed fillers. Attenuated total reflectance–Fourier‐transform infrared spectroscopy analysis revealed successful coating of the fillers with stearic acid. Also, new bands were detected in the spectrum of urea‐treated calcined kaolin, showing an effective chemical treatment. It has been observed that the treatment of fillers improves the mechanical properties of PVC. Thermogravimetric results showed that delaminated calcined kaolin increased the thermal stability of PVC composites. The results of this study proved that binary filler composites combine good properties of both (synergistic effect) and good filler dispersion can be obtained by using stearic acid and urea.
$$ \mathcal{N} $$ = 4 supersymmetric Yang-Mills thermodynamics to order λ2
Authors: Du Qianqian , Strickland Michael , Tantary Ubaid 
Published: August 2021

AbstractWe calculate the resummed perturbative free energy of$$ \mathcal{N} $$N= 4 supersymmetric Yang-Mills in four spacetime dimensions (SYM4,4) through second order in the ’t Hooft couplingλat finite temperature and zero chemical potential. Our final result is ultraviolet finite and all infrared divergences generated at three-loop level are canceled by summing over SYM4,4ring diagrams. Non-analytic terms at$$ \mathcal{O} $$O(λ3/2) and$$ \mathcal{O} $$O(λ2logλ) are generated by dressing theA0and scalar propagators. The gauge-field Debye massmDand the scalar thermal massMDare determined from their corresponding finite-temperature self-energies. Based on this, we obtain the three-loop thermodynamic functions of SYM4,4to$$ \mathcal{O} $$O(λ2). We compare our final result with prior results obtained in the weak- and strong-coupling limits and construct a generalized Padé approximant that interpolates between the weak-coupling result and the large-Ncstrong-coupling result. Our results suggest that the$$ \mathcal{O} $$O(λ2) weak-coupling result for the scaled entropy density is a quantitatively reliable approximation to the scaled entropy density for 0 ≤λ≲ 2.