What determines IPO underpricing ? Evidence from a frontier market

This paper empirically analyzes the short run performance of Tunisian initial public offerings (IPO). It sheds light on the determinants of IPO’s in a context of a frontier market characterized by high information asymmetry, low information efficiency, thin trading and the presence of “noise” traders. Using a sample of 34 Tunisian IPO’s from the period 1992-2008, we find that the average market adjusted initial return for the first three trading days is about 17.8 percent. The level of underpricing is related to retained capital, underwriter’s price support, oversubscription, listing delay and the offer price. Age of the firm, its size and the size of the offer do not seem to reduce the amount of money left on the table by issuers. It appears also that underpricing is driven by irrational investors (ipoers) seeking for short-run capital gains. These results remain unchanged after controlling for the presence of institutional investors and the existence of liquidity contract.Initial public offerings; Short-run underpricing; Underwriter’s price support.

What determines IPO underpricing ? Evidence from a frontier market

This paper empirically analyzes the short run performance of Tunisian initial public offerings (IPO). It sheds light on the determinants of IPO’s in a context of a frontier market characterized by high information asymmetry, low information efficiency, thin trading and the presence of “noise” traders. Using a sample of 34 Tunisian IPO’s from the period 1992-2008, we find that the average market adjusted initial return for the first three trading days is about 17.8 percent. The level of underpricing is related to retained capital, underwriter’s price support, oversubscription, listing delay and the offer price. Age of the firm, its size and the size of the offer do not seem to reduce the amount of money left on the table by issuers. It appears also that underpricing is driven by irrational investors (ipoers) seeking for short-run capital gains. These results remain unchanged after controlling for the presence of institutional investors and the existence of liquidity contract

Border surveillance monitoring using Quadcopter UAV-Aided Wireless Sensor Networks

In this paper we propose a novel cooperative bordersurveillance solution, composed of a Wireless Sensor Network (WSN) deployed terrestrially to detect and track trespassers, and a set of lightweight unmanned aircraft vehicles (UAVs) in the form of quadcopters that interact with the deployed WSN to improve the border surveillance, the detection and investigation of network failures, the maintenance of the sensor network, the tracking of trespasser, the capture and transmission of realtime video of the intrusion scene, and the response to hostage situations. A heuristic-based scheduling algorithm is described to optimize the tracking mission by increasing the rate of detected trespassers spotted by the quadcopters. Together with the design of the electrical, mechanical and software architecture of the proposed VTail quadcopter, we develop in this paper powerless techniques to accurately localize terrestrial sensors using RFID technology, compute the optimal positions of the new sensors to drop, relay data between isolated islands of nodes, and wake up sensors to track intruders. The developed VTail prototype is tested to provide valid and accurate parameters’ values to the simulation. The latter is conducted to evaluate the performance of the proposed WSN-based surveillance solution

Synthesis of (Z)-3-Allyl-5-(4-nitrobenzylidene)-2-sulfanylidene-1,3-thiazolidin-4-one and Determination of Its Crystal Structure

International audienceTo extend the existing library of arylidenerhodanines which display a potential biological activity, 3-N-allylrhodanine 1 was condensed under Knoevenagel conditions with p-nitrobenzaldehyde in acetic acid to afford the π-conjugated heterocyclic compound 3-allyl-5-(4-nitrobenzylidene)-2-sulfanylidene-1,3-thiazolidin-4-one 2. Compound 2 was characterized by IR and NMR spectroscopy, and its UV-vis spectrum was compared with that of compound 3-allyl-5-(4-methoxybenzylidene)-2-sulfanylidene-1,3-thiazolidin-4-one 3. The molecular structure is ascertained by a single-crystal X-ray diffraction study performed at 100 K

Three-Component Access to Functionalized Spiropyrrolidine Heterocyclic Scaffolds and Their Cholinesterase Inhibitory Activity

International audienceA novel one-pot [3+2]-cycloaddition reaction of (E)-3-arylidene-1-phenyl-succinimides, cyclic 1,2-diketones (isatin, 5-chloro-isatin and acenaphtenequinone), and diverse α-aminoacids such as 2-phenylglycine or sarcosine is reported. The reaction provides succinimide-substituted dispiropyrrolidine derivatives with high regio-and diastereoselectivities under mild reaction conditions. The stereochemistry of these N-heterocycles has been confirmed by four X-ray diffraction studies. Several synthetized compounds show higher inhibition on acetylcholinesterase (AChE) than butyrylcholinesterase (BChE). Of the 17 synthesized compounds tested, five exhibit good AChE inhibition with IC 50 of 11.42 to 22.21 µM. A molecular docking study has also been undertaken for compound 4n possessing the most potent AChE inhibitory activity, disclosing its binding to the peripheral anionic site of AChE enzymes

Highly diastereoselective construction of novel dispiropyrrolo[2,1- a ]isoquinoline derivatives via multicomponent 1,3-dipolar cycloaddition of cyclic diketones-based tetrahydroisoquinolinium N -ylides

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Exploring the probing capacities of MSA capped CdTe semiconductor quantum dots as optical chemsensors via analytical and isotherms modeling for selective Hg2+ detection

Abstract Heavy metal ions bioaccumulation can cause severe damage to environment and human health. Hence, the development of an effective detection assay of trace amounts of these ions is of great importance. Here, CdTe quantum dots (QDs) capped with mercaptosuccinic acid (MSA) ligands have been synthesized in aqueous solution with significant stability and good fluorescence properties. Photophysical characterization was performed using FTIR, XRD, HRTEM and UV–Vis. Absorption, PL and PLRT techniques, seeking their subsequent application as fluorescent probes for metal cations. CdTe-MSA QDs showed selective sensitivity toward Hg2+ ions by monitoring quantitative fluorescence quenching with increasing analyte content. Under optimal conditions, the linear range for the detection was 0.2–6 μM with a detection limit of 0.05 μM. According to the Stern–Volmer model, it can be inferred that a static quenching mechanism via Hg2+ selective binding to MSA carboxylate groups is operating with electron transfer process. Excess of mercuric ions further decreased and red shifted the fluorescence possibly due to competitive cation exchanges. To further explain the corresponding ligation mechanisms, adsorption behavior study was conducted via several isotherms as well as statistical physics models. The pseudo-first-order model can describe the adsorption kinetics of Hg2+ on CdTe-MSA QDs more accurately and the experimental data fitted well the Langmuir isotherm model of monolayer adsorption on homogeneous surface. Furthermore, this spontaneous process conforms to the Hill model as a physisorption with an adsorption energy of 32 kJ.mol−1 associated with the electrostatic interactions and hydrogen bonding. The developed system was assayed in the Hg2+ trace amount detection in real tap water and showed satisfactory accuracy performance meeting analytical requirements. The relevant results demonstrated that CdTe-MSA QDs could be deployed as promising Hg2+ fluorescent chemosensing system with high sensitivity and selectivity over wide linear detection range that have great potential for real water samples analysis

Design of Novel Enantiopure Dispirooxindolopyrrolidine-Piperidones as Promising Candidates toward COVID-19: Asymmetric Synthesis, Crystal Structure and In Silico Studies

International audienceDespite the effectiveness of COVID-19 vaccines, there is still an urgent need for discovering new anti-viral drugs to address the awful spread and transmission of the rapidly modifiable virus. In this study, the ability of a small library of enantiomerically pure spirooxindolopyrrolidine-grafted piperidones to inhibit the main protease of SARS-CoV-2 (Mpro) is evaluated. These spiroheterocycles were synthesized by 1,3-dipolar cycloaddition of various stabilized azomethine ylides with chiral dipolarophiles derived from N-[(S)-(-)-methylbenzyl]-4-piperidone. The absolute configuration of contiguous carbons was confirmed by a single crystal X-ray diffraction analysis. The binding of these compounds to SARS-CoV-2 Mpro was investigated using molecular docking and molecular dynamics simulation. Three compounds 4a, 4b and 4e exhibited stable binding modes interacting with the key subsites of the substrate-binding pocket of SARS-CoV-2 Mpro. The synthesized compounds represent potential leads for the development of novel inhibitors of SARS-CoV-2 main protease protein for COVID-19 treatment

Synthesis, antidiabetic activity and molecular docking study of rhodanine-substitued spirooxindole pyrrolidine derivatives as novel α-amylase inhibitors

International audienceIn a sustained search for novel α-amylase inhibitors for the treatment of type 2 diabetes mellitus (T2DM), we report herein the synthesis of a series of nineteen novel rhodanine-fused spiro[pyrrolidine-2,3’-oxindoles]. They were obtained by one-pot three component [3+2] cycloaddition of stabilized azomethine ylides, generated in situ by condensation of glycine methyl ester and the cyclic ketones 1H-indole-2,3-dione (isatin), with (Z)-5-arylidine-2-thioxothiazolidin-4-ones. The highlight of this protocol is the efficient high-yield construction of structurally diverse rhodanine-fused spiro[pyrrolidine-2,3'-oxindoles] scaffolds, including four contiguous stereocenters, along with excellent regio- and diastereoselectivities. The stereochemistry of all compounds was confirmed by NMR and corroborated by an X-ray diffraction study performed on one derivative. All cycloadducts were evaluated in vitro for their α-amylase inhibitory activity and showed good α-amylase inhibition with IC50 values ranging between 1.49± 0.10 and 3.06± 0.17µM, with respect to the control drug acarbose (IC50= 1.56µM). Structural activity relationships (SARs) were also established for all synthesized compounds and the binding interactions of the most active spiropyrrolidine derivatives were modelled by means of molecular in silico docking studies. The most potent compounds 5g, 5k, 5s and 5l were further screened in vivo for their hypoglycemic activity in alloxan-induced diabetic rats, showing a reduction of the blood glucose level. Therefore, these spiropyrrolidine derivatives may be considered as promising candidates for the development of new classes of antidiabetic drugs