Non-degenerate valleys in the half-metallic ferromagnet Fe/WS2_2

We present a first principles investigation of the electronic properties of monolayer WS$_2$ coated with an overlayer of Fe. Our ab initio calculations reveal that the system is a half-metallic ferromagnet with a gap of $\sim 1$ eV for the majority spin channel. Furthermore, the combined effect of time-reversal symmetry breaking due to the magnetic Fe overlayer and the large spin-orbit coupling induced by W gives rise to non-degenerate K and K$'$ valleys. This has a tremendous impact on the excited state properties induced by externally applied circularly polarized light. Our analysis demonstrates that the latter induces a singular hot spot structure of the transition probability around the K and K$'$ valleys for right and left circular polarization, respectively. We trace back the emergence of this remarkable effect to the strong momentum dependent spin-noncollinearity of the valence band involved. As a main consequence, a strong valley-selective magnetic circular dichroism is obtained, making this system a prime candidate for spintronics and photonics applications

Synthesis of a staurosporine analogue possessing a 7-azaindole unit instead of an indole moiety

The synthesis of a new staurosporine analogue possessing a 7-azaindole unit instead of an indole moiety is described. This synthesis could be achieved by coupling a sugar moiety previously tosylated in 2′ position to the azaindolocarbazole aglycone. Nucleophilic substitution on the carbon bearing the tosyl group yielded to the key cyclization leading to a compound in which the carbohydrate part is linked to both indole and azaindole nitrogen

Clarification of the Algerian grape juice and their effects on the juice quality

The aim of this study was to find a good clarification method to eliminate the substances in Algerian grape juice and study the effects of the clarification agents on juice quality. The clarified grape juice was subjected to different treatments, namely bentonite, gelatin, combination of gelatin and bentonite, then stored for 4 weeks. The effects of fining treatment by determining the critical micillary concentration of each agent used accelerated stability test on turbidity, tannin contents (ethanol index, condensed tannins, total polyphenol and anthocyanins) and microbiological quality of clarified grape juice were evaluated during storage. Fining treatment and storage had a significant (p < 0.05) effect on turbidity, tannins, total polyphenol, condensed tannins and anthocyanins. However, a better percentage elimination was noted for freshly squeezed grape juice with a combination of gelatin and bentonite corresponding to a turbidity of 6.5 NTU. The clarifiers separately gave lower removal rates than average, up to 83% of tannins present in the freshly squeezed juice has been eliminated using the bentonite. The results obtained are very satisfactory since we were able to obtain a clear juice of good microbial quality while ensuring the preservation of the organoleptic and nutritional qualities during the treatment and the storage of the juice.   Bull. Chem. Soc. Ethiop. 2020, 34(1), 1-11. DOI: https://dx.doi.org/10.4314/bcse.v34i1.

Gamma spectrometry for natural radioactive nuclides in Spa waters in some areas in north Algeria

The work aims to determine the radioactivity levels of Algeria thermal waters which have been used permanently in spas for therapeutic intentions. Eight Spas waters in north Algeria analysis was performed to determine their radioactivity concentration for 226Ra, 232Th, 235U and 40K, using a high-resolution HPGe γ-spectrometry system. Water is imbedded in a Marinelli beakers tightly sealed for 28 days to achieve secular equilibrium between 226Ra and its short-lived daughter products before analyzing by gamma ray spectrometry. The average activity concentrations for spa waters from study areas were 0.045 to 2.077 Bql-1 for 226Ra; 0.17to 3.416 Bql-1 for 232Th; 0.085to 7,235 Bql-1 for 235U and 1.402 to 15.156 Bql-1 for 40K. This study would be useful for used and official authorities for the assessment of radiation exposure risk due to usage of the considered spa waters

Total phenol and flavonoid content, antioxidant and cytotoxicity assessment of Algerian Launaea glomerata (Cass.) Hook.f. extracts

El-Oued province (southeast Algeria), is located in a medicinal plant-rich area; Launaea glomerata (Cass.) Hook. f. is one among them which is a perennial herb spread widely in the arid regions of the Mediterranean Sea. The selection of the studied plant corresponds perfectly to the scientific needs due two reasons, firstly because these samples are used by the Algerian population as herbal remedies for primary health care, secondly, for the lack of published data on it. The aim of this investigation is to provide new data on quantities of phenols, which were estimated at 25.81 mg GAE/g extract and flavonoids (49.13 mg RE/g extract), and the determination of antioxidant activities by three ways (DPPH, CAT, ABTS), the results of IC50 equals to 98.07 mg TE/g extract for DPPH• and 286.5 mg eq. AG/g for ABTS assays, noted that the best inhibition was by the ABTS root. We also conducted a test for the inhibitory ability of extract against cancer cells tested on both human hepatocellular carcinoma (HePG2) and colon cells (HCT116), the results were negative. The data obtained in this work can be useful for the pharmaceutical industry, also used in the Algerian medicinal herbs database.  DOI: http://dx.doi.org/10.5281/zenodo.442970

Palladium-Catalyzed Coupling of 3-Halo-Substituted Coumarins, Chromenes, and Quinolones with Various Nitrogen-Containing Nucleophiles

International audienceAn efficient and general palladium‐catalyzed coupling reaction between 3‐bromocoumarins, 3‐bromoquinolin‐2(1H)‐ones, and 3‐iodo‐2H‐chromenes with a variety of nitrogen‐containing nucleophiles (azole, amide, lactam, sulfonamide, aniline, amine, and urea) is described. The reaction proceeded rapidly and cleanly in dioxane providing the coupling products in good to excellent yields. The chemoselectivity of this reaction was also studied with polyhalocoumarins. Under optimized conditions, these underwent a site‐selective amination at the C‐3–Br bond, regardless of the nature of the nitrogen‐containing nucleophile used

Understanding the phenomena of extraction of essential oils by the microwave accelerated distillation process: case of the Washington Navel variety

In this study, two techniques Hydrodistillation (HD) and Microwave-accelerated distillation (MAD), was used to extract essential oils (EOs), from the peels of citrus fruits Washington Navel (Citrus sinensis L. Osbeck) collected from Tipaza province, north Algeria during April 2018. The extraction yield and time of EOs were (0.28% and 180 min) using HD extraction and (0.27% versus 30 min) using MAD extraction. After using gas chromatography analyses (GC-FID) and (GC-MS), 21 aromatic compounds obtained and identified for both extraction approaches. On the other hand, and in order to better comprehension the extraction phenomena, two models of extraction processes were applied, The first one considers the existence of a single site with a constant speed ruled by the equation of the quasi-stationary state, whereas, the second assumes that there are two distinct sites: The first is part of the fraction easily accessible with a very high desorption rate k1 (fast fraction), the second contains the fraction that is difficult to extract, with a low desorption speed k2 (slow fraction). The results showed that, the application of the two sites model can describe accurately the used extraction methods in this study. The data from HD extraction modeling indicate that this method extraction is fast fraction (f equal 0.79), then MAD method (f equal 0.40). DOI: http://dx.doi.org/10.5281/zenodo.388185

HPLC-DAD analysis, antimicrobial and antioxidant properties of aromatic Herb Melissa officinalis L., aerial parts extracts

Treating specific tissues without affecting other regions is a difficult task. It is desirable to target the particular tissue where the chemical has its biological effect. To study this phenomenon computationally, in this work we numerically study a mathematical model which is written as a nonlinear system composed by three parabolic partial differential equations. The variables involved in the model are the concentration of the chemical, the concentration of the binding protein and the concentration of the chemical bound to the protein. Our aim is to propose a fully discrete approximation of this problem, using the Finite Element Method and a semi-implicit Euler scheme, in order to solve it numerically. This discrete problem is analysed, obtaining a discrete stability property and some a priori error estimates that show the algorithm converges linearly if the continuous solution is regular enough. Also, some representative examples are shown, as well as the numerical verification of the convergence.Universidade de Vig

Synthesis of Isocoumarin via PTSA-Catalyzed Annulation of Diarylalkynes

International audiencep-Toluenesulfonic acid (PTSA) in EtOH was used as a mild acid-catalyst for the annulation of various functionalized diarylalkynes under microwave irradiation. This free-metal process allowed the synthesis of a range of 3-arylsubstituted isocoumarins in good yields

Synthesis and biological evaluation of oxindoles and benzimidazolines derivatives

The synthesis of new oxindoles and benzimidazolinones derivatives bearing a sugar residue on the aromatic nitrogen is described. The presence of the glycoside moiety should enhance the solubility of these heterocyclic compounds and/or improve the interaction with the active site of the biological targets. The inhibitory activities of these new compounds toward five kinases were examined: KDR (VEGFR-2), FGFR-1, PDGFR-β, EGFR and Tie 2. Furthermore, the antibacterial activities of the prepared compounds were tested against two Gram-positive bacteria Bacillus cereus and Streptomyces chartreusis, a Gram-negative bacterium Escherichia coli and a yeast Candida albican