Impact of Metal Ions in Porphyrin‐Based Applied Materials for Visible‐Light Photocatalysis: Key Information from Ultrafast Electronic Spectroscopy

Protoporphyrin IX‐zinc oxide (PP‐ZnO) nanohybrids have been synthesized for applications in photocatalytic devices. High‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), and steady‐state infrared, absorption, and emission spectroscopies have been used to analyze the structural details and optical properties of these nanohybrids. Time‐resolved fluorescence and transient absorption techniques have been applied to study the ultrafast dynamic events that are key to photocatalytic activities. The photocatalytic efficiency under visible‐light irradiation in the presence of naturally abundant iron(III) and copper(II) ions has been found to be significantly retarded in the former case, but enhanced in the latter case. More importantly, femtosecond (fs) transient absorption data have clearly demonstrated that the residence of photoexcited electrons from the sensitizer PP in the centrally located iron moiety hinders ground‐state bleach recovery of the sensitizer, affecting the overall photocatalytic rate of the nanohybrid. The presence of copper(II) ions, on the other hand, offers additional stability against photobleaching and eventually enhances the efficiency of photocatalysis. In addition, we have also explored the role of UV light in the efficiency of photocatalysis and have rationalized our observations from femtosecond‐ to picosecond‐resolved studies.     

Extraction and Characterization of Chitin and Chitosan from Parapenaeus longirostris from Moroccan Local Sources

The contents of the exoskeleton of Parapenaeus longirostris from Moroccan local sources were analyzed and the percentages of inorganic salt, protein, lipid, and chitin were determined. Chitin in the α form was extracted from Parapenaeus longirostris shells by 0.25 M HCl and 1 M NaOH treatment for demineralization and deproteinization, respectively. The obtained chitin was converted into the more useful soluble chitosan. The chemical structure and physico-chemical properties of chitin and chitosan were characterized using Fourier transform-infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, X-ray diffractometry (XRD), and scanning electron microscopy (SEM). The molecular weight (MW) of chitosan was determined by viscometric methods. The degree of acetylation (DA) of chitin and chitosan was determined by the ¹H NMR technique. To the best of our knowledge this is the first report on the extraction and characterization of chitin and chitosan from Parapenaeus longirostris.     

Synthesis of New Heterocycles,Part II: Synthesis of New Benzopyranobenzoxazinone Ring System Involving a Novel Rearrangement

The complex of N,N-diethyl o-nitrophenoxy acetamide and POCl₃ on reaction with substituted salicylaldehyde yielded 3-(o-nitrophenoxy) coumarins. These on reaction with triethylphosphite yielded hitherto unknown benzoypranobenzoxazine ring system through a novel rearrangement.     

Microwave-assisted synthesis,antimicrobial, antiquorum-sensing and cytotoxic activities of a new series of isatin-β-thiocarbohydrazones

Abstract

New isatin-β-thiocarbohydrazone hybrids 4-17 were designed relied on isatin scaffold to generate various analogs with expected antimicrobial activity. The new hybrids were estimated for antibacterial effectiveness over S. aureus, B. cereus and E. coli, and antifungal efficacy over C. albicans and A. fumigatus. Compound 14 evinced the highest efficacy over A. fumigatus and C. albicans. In addition, 5 and 12 showed eminent efficacy toward A. fumigatus, where compounds 4, 7, 9, 11, 13, 15 and 16 exhibited moderate activity over the same fungus. Moreover, 6 and 9 displayed moderate activity over C. albicans. The new compounds were also estimated for antiquorum-sensing effectiveness against C. violacium, where compound 17 showed interesting activity. In vitro cytotoxicity assay of the new analogs was done over Hela and COS-7 cancer cell lines. All analogs have IC₅₀ values >50?μM toward both cell lines.     

Preparation of Nitriles by the Modification of Mitsunobu-Wilk Procedure III Carbon Elongation of Hydroxy Esters

An efficient one-step procedure for the conversion of hydroxy esters into the corresponding nitrile esters using triphenylphosphine (PPh₃)-diethyl azodicarboxylate (DEAD) in the presence of acetone cyanohydrin is described.     

Packet Recycling and Delayed ACK for Improving the Performance of TCP over MANETs

Most of the schemes that were proposed to improve the performance of transmission control protocol (TCP) over mobile ad hoc networks (MANETs) are based on a feedback from the network, which can be expensive (require extra bandwidth) and unreliable. Moreover, most of these schemes consider only one cause of packet loss. They also resume operation based on the same stand-by parameters that might vary in the new route. Therefore, we propose two techniques for improving the performance of TCP over MANETs. The first one, called TCP with packet recycling (TCP-PR), allows the nodes to recycle the packets instead of dropping them after reaching the retransmission limit at the MAC layer. In the second technique, which is called TCP with adaptive delay window (TCP-ADW), the receiver delays sending TCP ACK for a certain time that is dynamically changed according to the congestion window and the trip time of the received packet. TCP-PR and TCP-ADW are simple, easy to implement, do not require network feedback, compatible with the standard TCP, and do not require distinguishing between the causes of packet loss. Our thorough simulations show that the integration of our two techniques improves the performance of TCP over MANETs.     

On the Capacity of Secondary Networks Over Opportunistic Spectrum Access in Rayleigh Fading Channels

In this paper the effect of the opportunistic spectrum access on the spectrum utilization is studied in terms of the secondary network capacity measured at the secondary receiver. A mathematical model is developed to represent the secondary network capacity in Rayleigh fading channel. An exact analytical solution for the capacity is derived for both sensing and accessing fading channels. A numerical evaluation of the channel capacity is presented for different channel sensing and accessing schemes. The effects of detection and accessing channel parameters on the capacity are investigated. The analytical results that are validated by substantial simulations showed how the utilization of the network can be increased significantly by the suggested opportunistic spectrum accessing technique. It was found that when having a good sensing system with a high secondary user signal to noise ratio, accessing the licensed band increases and drives the spectrum utilization to its maximum. In addition, this work shows how the capacity can be positively affected by three factors: the secondary accessing channel, the primary user interference and the desired quality of service (QoS) of primary user. The awareness of a proper sensing scheme can maximize the spectrum utilization without degrading the QoS of primary users.     

A reformulation of the nonsmooth approaches of M. Frémond and J.J. Moreau for rigid body dynamics

This paper deals with the nonsmooth dynamics of a rigid bodies system. The proposed theory is inspired by the formalism of J.J. Moreau and that of M. Frémond and relies on the notion of percussion which is the integral of the contact force during the duration of the collision. Contrary to classical discrete element models, it is here assumed that percussions can be expressed as a function of only the velocity before the impact. This assumption is checked for the usual mechanical constitutive laws for collisions derived from a pseudopotential of dissipation or the Coulomb friction law. Motion equations are then reformulated taking into account simultaneous collisions of solids. A mathematical study of the new model is presented: the existence and uniqueness of the solution are discussed according to the regularity of both the forces (Lebesgue‐density occurring during the regular evolution of the system) and the percussions (Dirac‐density describing the collision). In the light of the principles of thermodynamics, a condition on the internal percussion assuring that the collision is thermodynamically admissible, is established. Finally, an application of this new model to the motion of a system of rigid disks, including simultaneous collisions is presented.     

GRPIA: a new algorithm for computing interpolation polynomials

Numerical Algorithms - Let x0,x1, ? , xn, be a set of n + 1 distinct real numbers (i.e., xm ≠ xj, for m ≠ j) and let ym,k, for m = 0, 1, ? , n, and k = 0, 1, ? , rm,...     

Support vector regression with digital band pass filtering for the quantitative analysis of near‐infrared spectra

This paper proposes a novel calibration technique based on combining support vector regression with a digital band pass (DBP) filter for the quantitative analysis of near‐infrared spectra. The efficacy of the proposed method is investigated and validated in the determination of glucose from near‐infrared spectra of a mixture composed of urea, triacetin and glucose. In this paper, the DBP filtering was implemented as a pre‐processing technique in the frequency domain as a Gaussian band pass filter and in the time domain as a Chebyshev filter. The grid‐search optimization method was used to optimize the filter parameters. The results demonstrate that utilization of the optimized DBP filters as a pre‐processing technique improved the performance of the predictive models. Copyright © 2013 John Wiley & Sons, Ltd.