Analytical applications of calixarenes from 2005 up-to-date

Calixarenes, as nano-baskets, are considered an important group of macrocycles as the third famous host molecules after cyclodextrins and crown ethers have been subject to extensive researches in construction of many extractants, transporters, stationary phases, electrode ionophores and optical and electrochemical sensors over the past four decades. Because of the recent rapid growth in the publications of calixarene applications, this review paper has focused on different analytical applications of calixarenes in the main fields of separation, electroanalysis, spectroscopy and chemometrics. The objectives and the results of about 300 references mainly were published in recent 6 years with emphasis on the analytical applications were reviewed.     

DDoS attack detection in IEEE 802.16 based networks

Achieving high data rate transmission, WiMAX has acquired noticeable attention by communication industry. One of the vulnerabilities of the WiMAX network which leads to DDoS attack is sending a high volume of ranging request messages to base station (BS) in the initial network entry process. In the initial network entry process, BS and subscriber station (SS) exchange management messages. Since some of these messages are not authenticated, malicious SSs can attack the network by exploiting this vulnerability which may increase the traffic load of the BS and prevent it from serving the SSs. So, detecting such attacks is one of the most important issues in such networks. In this research, an artificial neural network (ANN) based approach is proposed in order to detect DDoS attacks in IEEE 802.16 networks. Although lots of studies have been devoted to the detection of DDoS attack, some of them focus just on some statistical features of the traffic and some other focus on packets’ headers. The proposed approach exploits both qualitative and quantitative methods. It detects the attack by feeding some features of the network traffic under attack to an appropriate ANN structure. To evaluate the method, first a typical attacked network is implemented in OPNet simulator, and then by using the proposed system, the efficiency of the method is evaluated. The results show that by choosing suitable time series we can classify 93 % of normal traffic and 91 % of attack traffic.     

RP-HPLC prefractionation and its application in expressional proteomics analysis of an in vitro viral infection model

Prefractionation of complex protein mixtures is an efficient method for increasing the separation power of 2-DE. RP-HPLC has been successfully utilized as a prefractionation method prior to 2-DE. Here we describe the optimization of an efficient RP-HPLC method for prefractionation of baby hamster kidney cell solubilized proteins. A step gradient elution of acetonitrile was optimized and collected fractions were further examined by SDS-PAGE and 2-DE. By utilizing this method an effective increase in separation power of 2-DE is accomplished. Moreover, we describe the application of this method to expressional proteome analysis of a virally infected cell model.     

Experimental and computational investigation of C-N bond activation in ruthenium N-heterocyclic carbene complexes

A combination of experimental studies and density functional theory calculations is used to study C-N bond activation in a series of ruthenium N-alkyl-substituted heterocyclic carbene (NHC) complexes. These show that prior C-H activation of the NHC ligand renders the system susceptible to irreversible C-N activation. In the presence of a source of HCl, C-H activated Ru(I(i)Pr(2)Me(2))'(PPh(3))(2)(CO)H (1, I(i)Pr(2)Me(2) = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) reacts to give Ru(I(i)PrHMe(2))(PPh(3))(2)(CO)HCl (2, I(i)PrHMe(2) = 1-isopropyl-4,5-dimethylimidazol-2-ylidene) and propene. The mechanism involves (i) isomerization to a trans-phosphine isomer, 1c, in which hydride is trans to the metalated alkyl arm, (ii) C-N cleavage to give an intermediate propene complex with a C2-metalated imidazole ligand, and (iii) N-protonation and propene/Cl(-) substitution to give 2. The overall computed activation barrier (ΔE(++)(calcd)) corresponds to the isomerization/C-N cleavage process and has a value of +24.4 kcal/mol. C-N activation in 1c is promoted by the relief of electronic strain arising from the trans disposition of the high-trans-influence hydride and alkyl ligands. Experimental studies on analogues of 1 with different C4/C5 carbene backbone substituents (Ru(I(i)Pr(2)Ph(2))'(PPh(3))(2)(CO)H, Ru(I(i)Pr(2))'(PPh(3))(2)(CO)H) or different N-substituents (Ru(IEt(2)Me(2))'(PPh(3))(2)(CO)H) reveal that Ph substituents promote C-N activation. Calculations confirm that Ru(I(i)Pr(2)Ph(2))'(PPh(3))(2)(CO)H undergoes isomerization/C-N bond cleavage with a low barrier of only +21.4 kcal/mol. Larger N-alkyl groups also facilitate C-N bond activation (Ru(I(t)Bu(2)Me(2))'(PPh(3))(2)(CO)H, ΔE(++)(calcd) = +21.3 kcal/mol), and in this case the reaction is promoted by the formation of the more highly substituted 2-methylpropene.     

A review on lignocellulose/poly (vinyl alcohol) composites: cleaner approaches for greener materials

Cellulose - Lignocellulose (LC) is an abundant resource in nature often neglected, underutilised, and even disposed of with an extra cost. Though extracting cellulose or starch from LC is very...     

A model of the vertical apparent mass and the fore-and-aft cross-axis apparent mass of the human body during vertical whole-body vibration

The apparent mass of the human body reflects gross movements caused by whole-body vibration and can be used to predict the influence of body dynamics on seat transmissibility. With vertical excitation, various models fit the measured vertical apparent mass of the human body, but experiments also show high fore-and-aft forces on the seat (the fore-and-aft cross-axis apparent mass) that have not influenced current models. This paper defines a model that predicts the vertical apparent mass and the fore-and-aft cross-axis apparent mass of the seated human body during vertical excitation. A three degree-of-freedom model with vertical, fore-and-aft and rotational (i.e. pitch) degrees of freedom has been developed with twelve model parameters (representing inertia, stiffness, damping, and geometry) optimised to the measured vertical apparent mass and the measured fore-and-aft cross-axis apparent mass of the body. The model provides close fits to the moduli and phases for both median data and the responses of 12 individual subjects. The optimum model parameters found by fitting to the median apparent mass of 12 subjects were similar to the medians of the same parameters found by fitting to the individual apparent masses of the same 12 subjects. The model suggests the seated human body undergoes fore-and-aft motion on a seat when exposed to vertical excitation, with the primary resonance frequency of the apparent mass arising from vertical motion of the body. According to the model, changes in the vertical, fore-and-aft, or rotational degree of freedom have an effect on the resonance in the fore-and-aft cross-axis apparent mass.     

Preparation and characterization of durable micro/nanocapsules for use in self-healing anticorrosive coatings

In the field of coatings, extensive laboratory research has been conducted in the last decade. In the present work, effectiveness of epoxy resin filled micro/nanocapsules was investigated for future using in healing of cracks generated in coatings. Micro/nanocapsules were prepared by in situ polymerization of urea–formaldehyde resin to form shell over epoxy resin droplets. The optimal process parameters for synthesizing the micro/nanocapsules were selected. The as-synthesized capsules were studied by various characterizations techniques, including scanning electron microscope (SEM), particle size analyzer (PSA), Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that micro/nanocapsules containing epoxy resins can be synthesized successfully. The rough outer surface of microcapsule is composed of agglomerated urea–formaldehyde nanoparticles. They basically exhibit good storage stability at room temperature, and they are chemically stable before the heating temperature is up to approximately 250°C.     

Synthesis of 1,2,4‐triazolo[1,5‐d]‐1,2,4‐triazine‐5‐thiones

In an attempt to discover bicyclic compounds containing the 1,2,4‐triazine moiety, 1,2,4‐triazolo[1,5‐d]‐1,2,4‐triazine‐5‐thiones from one pot reaction of arylnitriles with 4‐amino‐1,2,4‐triazine‐3‐thione‐5‐one in the presence of potassium tert‐butoxide were synthesized.     

Synthesis of Aluminum‐Rich Analcime Using an Ethylene Diamine Derivative as Template

The hydrothermal synthesis of analcime (ANA) with N,N′‐dibenzyl‐N,N,N′,N′‐tetramethylethylenediamine (DBTMED) as template was systematically studied. The various parameters that affect the crystallization of analcime, such as temperature, time, Al source, and Si/Al ratio were investigated. Systematic variations of these parameters revealed that ANA was obtained from the reaction mixture with the optimized ratios of SiO₂/Al₂O₃ = 5–9.5 in presence of DBTMED, whereas template‐free clear solution methods require SiO₂/Al₂O₃ ratio of greater than 25. When experiments were conducted at 130 and 150 °C for 4 days, a mixture of analcime and zeolite P was present in the samples, and a pure analcime sample could be obtained with heating in the temperature range 160–180 °C. When microwave and conventional heating were used, analcime could be obtained after 2 days. The obtained products were characterized by XRD, SEM, and IR spectroscopy.