A normative approach to radicalization in social networks

In recent decades, the massification of online social connections has made information globally accessible in a matter of seconds. Unfortunately, this has been accompanied by a dramatic surge in extreme opinions, without a clear solution in sight. Using a model performing probabilistic inference in large-scale loopy graphs through exchange of messages between nodes, we show how circularity in the social graph directly leads to radicalization and the polarization of opinions. We demonstrate that these detrimental effects could be avoided by actively decorrelating the messages in social media feeds. This approach is based on an extension of Belief Propagation (BP) named Circular Belief Propagation (CBP) that can be trained to drastically improve inference within a cyclic graph. CBP was benchmarked using data from Facebook and Twitter. This approach could inspire new methods for preventing the viral spreading and amplification of misinformation online, improving the capacity of social networks to share knowledge globally without resorting to censorship.Comment: 23 pages, 8 figures, 1 supplementary materia

Chemical composition and antimicrobial activity of essential oils of Ocimum basilicum, Ocimum canum and Ocimum gratissimum in function of harvesting time

BACKGROUND: The aim of present the study was to investigate the chemical composition and the antimicrobial activity of essential oils of Ocimum basilicum, Ocimum canum and Ocimum gratissimum from Benin as affected by harvesting time. The chemical composition of hydrodistillated essential oils were analyzed by GC-FID (gas chromatography – flame ionization detector) and GC-MS (gas chromatography-mass spectrometry). Disc diffusion and broth microdilution assays were used to evaluate the antibacterial activity of essential oils against two foodborne pathogens. RESULTS: Based on the composition analysis, major components were as follows: estragol (43.0 -44.7 %) and linalool (24.6 -29.8 %) in O. basilicum oils; carvacrol (12.0 -30.8 %) and p-cymene (19.5 -26.2 %) in O. canum oils; thymol (28.3 -37.7 %) and γ-terpinene (12.5 -19.3 %) in O. gratissimum oils. The tested oils and their components exhibited notable antimicrobial activities against Listeria monocytogenes and Salmonella typhimurium. The O. canum and O. gratissimum oils collected at 7h and 19h showed significant higher activities against L. monocytogenes and S. typhimurium (MICs and MBCs 0.34 – 2.5 µL/mL) (p < 0.05), whereas O. basilicum showed lower activity (MICs and MBCs 2.0 – 8.0 µL/mL) at any daytime of harvest, the weakest being at 19h (MIC and MBC 12.0 – 32.0 µL/mL). CONCLUSION: The daytime of harvest can influence the composition of oils and their activities on bacteria

A normative approach to radicalization in social networks

In recent decades, the massification of online social connections has made information globally accessible in a matter of seconds. Unfortunately, this has been accompanied by a dramatic surge in extreme opinions, without a clear solution in sight. Using a model performing probabilistic inference in large-scale loopy graphs through exchange of messages between nodes, we show how circularity in the social graph directly leads to radicalization and the polarization of opinions. We demonstrate that these detrimental effects could be avoided by actively decorrelating the messages in social media feeds. This approach is based on an extension of Belief Propagation (BP) named Circular Belief Propagation (CBP) that can be trained to drastically improve inference within a cyclic graph. CBP was benchmarked using data from Facebook and Twitter. This approach could inspire new methods for preventing the viral spreading and amplification of misinformation online, improving the capacity of social networks to share knowledge globally without resorting to censorship

Synthesis, characterization and trypanocidal activity of some aromatic thiosemicarbazones and their 1,3,4-thiadiazolines derivatives

The thiosemicarbazones of six aromatic ketones were synthesized as well as their 1,3,4-thiadiazolines derivatives obtained by cyclization under acetylating condition with yields going from 40 to 90%. The products purity was confirmed by mass spectrometry coupled with high-performance liquid chromatography (LC/MS) and there were characterized using spectrometry IR, NMR 1H and 13C (nuclear magnetic resonance). These compounds were then tested in vitro on Trypanosoma brucei brucei according to the “LILIT, Alamar Blue” method for a comparison of their trypanocidal activity. Thus, all thiosemicarbazones appeared much more active than their corresponding 1,3,4-thiadiazolines. Thiosemicarbazone 6a (IC50 = 9.62 µM) was the most active of all thiosemicarbazones tested and it is the same for its thiadiazoline 6b (IC50 = 49.03 µM) among 1,3,4-thiadiazolines

Chemical composition and seasonal variation of essential oil of Sclerocarya birrea (A. Rich.) Hochst subsp birrea leaves from Benin

Essential oils from fresh leaves of Sclerocarya birrea (A. Rich.) Hochst. were extracted by steam distillation. The oil yield from plant collected during the hot season (February) was 0.10±0.02 and 0.24±0.01% from plant collected during the cold season (August). GC/FID and GC/MS analysis allowed us to identify a total of 49 compounds, representing 98% of the hydrodistillate. The oils contained about 96% sesquiterpenes among which 38±0.034% of 7-epi-α-selinene during the hot season and 51.7±0.12% of 7-epi-α- selinene during the cold. The main components of the oil from the hot period were 7-epi-α-selinene (38±0.03%), α-muurolene (25±0.03%), valencene (17±0.06%), β-selinene (4.3±0.01), β-caryophyllene (3.2±0.02) allo-aromadendrene-epoxide (1.5±0.03) and 14-hydrox-α-humulene (1.5±0.03). The essential oil from the cold season was characterized by 7-epi-α-selinene (51.7±0.12%), β-selinene (15.1±0.2%), valencene (12.9±0.05%), α-selinene (8.1±0.03) and β-caryophyllene (1.8±0.02%). This is the first report of these components in the essential oil of Sclerocarya birrea

Synthesis, caracterization, trypanosomal activities on Trypanosoma bruceibrucei and toxicity against Artemiasalina leach of N(4)-aryl semicarbazones and thiosemicarbazones

N(4)-phenyl substituted semicarbazones and thiosemicarbazones (1-4) of propiophenone and 4'- methylacetophenone have been synthesized and characterized by spectrometrical methods analyses (IR, RMN 1H & 13C, SM). All compounds were evaluated for their in vitro trypanosomal activity against the bloodstream form of the strain 427 of Trypanosomabruceibrucei and have been tested on larvaeofbrine shrimp, Artemiasalina LEACH, for their toxic activity. The selectivity index (SI) of each molecule was too designed. In the group, propiophenone 4- phenyl-3-thiosemicarbazone 4 has exhibited greater trypanocidal activity with a half-inhibitory concentration (IC 50) value equal to 7.63 micromolar (μM). 4'-methylacetophenone 4-phenylsemicarbazone 1 showed moderate antitrypanosomal activity (IC 50 = 62.54 μM). Other, 2 and 3, presented little or no activity against the parasite (IC 50> 100 μM). Except propiophenone 4-phenylsemicarbazone 2 which offered a toxic activity on larvae given the halflethal concentration LC 50 = 107.49 μM and SI = 0.518 281 μM and SI > 1, compounds 1, 3 and 4). They turn out quite selective on the parasite. Synthesized compounds could constitute a new class of anti-trypanosomal drug candidates

Allelopathic effects on cowpea ( Vigna unguiculata (L.) Walp) plant and cytotoxic activities of sterols and triterpenes isolated from Justicia anselliana (NEES) T. Anders

Purification of the allelopathic ethanol extract of Justicia anselliana aerial part led to the isolation of three known compounds: two sterols (stigmasterol and β-sitosterol) and one triterpene (lupeol). Their structures were determined by analysis of spectroscopic data and confirmed by GC/MS analysis. All isolated compounds were tested for their allelopathic effects on cowpea (Vigna unguiculata) growth and for their cytotoxic activity on human (HeLa, WI-38 and Mel-43) and mouse (J774) cells. All isolated compounds showed an inhibitory effect on the three parameters measured on cowpea (Vigna unguiculata) germination (rate of germination, shoot length and fresh weight). The highest rate of inhibition of cowpea=s germination was observed with 200 ppm of lupeol (-28.4 % ± 0.7%) whereas all three parameters were inhibited very meaningfully by 200 ppm stigmasterol (-26.6% ± 0.5%; -24.2% ± 0.7% and -21.1% ± 0.7% respectively for germination, shoot length and fresh weight of Vigna unguiculata (L.) Walp). None of the isolated compounds was toxic on J774 (murine macrophages), WI-38 (human lung fibroblasts), human HeLa (human cervix carcinoma cells) and melanoma Mel-43 cell. This is the first report of the allelopathic activities of lupeol, stigmasterol and β-sitosterol on cowpea (Vigna unguiculata)

Conspiracy beliefs and perceptual inference in times of political uncertainty

Socio-political crises with uncertain issues accumulated in recent years, providing fertile ground for the emergence of conspiracy ideations. Computational models constitute valuable tools for understanding the mechanisms at play in the formation and rigidification of these unshakeable beliefs. Here, the Circular Inference model was used to capture associations between changes in perceptual inference, and the dynamics of conspiracy ideations in times of uncertainty. Large populations from three polarized countries performed a bistable perception task and conspiracy beliefs assessments, around major socio-political events. We show that when uncertainty peaks, an overweighting of sensory information is associated with conspiracy ideations. Progressively, this exploration strategy gives way to an exploitation strategy, in which increased adherence to conspiracy theories is associated with the amplification of prior information. Overall, the Circular Inference model sheds new light on the possible mechanisms underlying the progressive rigidification of conspiracy theories when facing highly uncertain situations