Self-Assembly Propensity Dictates Lifetimes in Transient Naphthalimide–Dipeptide Nanofibers

Transient self-assembly of dipeptide nanofibers with lifetimes that are predictably variable through dipeptide sequence design are presented. This was achieved using 1,8-naphthalimide ( NI ) amino acid methyl-esters (Phe, Tyr, Leu) that are biocatalytically coupled to amino acid-amides (Phe, Tyr, Leu, Val, Ala, Ser) to form self-assembling NI -dipeptides. However, competing hydrolysis of the dipeptides results in disassembly. It was demonstrated that the kinetic parameters like lifetimes of these nanofibers can be predictably regulated by the thermodynamic parameter, namely the self-assembly propensity of the constituent dipeptide sequence. These lifetimes could vary from minutes, to hours, to permanent gels that do not degrade. Moreover, the in-built NI fluorophore was utilized to image the transient nanostructures in solution with stimulated emission depletion (STED) based super-resolution fluorescence microscopy.     

Some common fixed point theorems for Banach operator pairs with applications in best approximation

The ordered pair (T,I) of two self-maps of a metric space (X,d) is called a Banach operator pair if the set F(I) of fixed points of I is T-invariant i.e. T(F(I))⊆F(I). Some common fixed point theorems for a Banach operator pair and the existence of common fixed points of best approximation are presented in this paper. The results prove, generalize and extend some results of Al-Thagafi [M.A. Al-Thagafi, Common fixed points and best approximation, J. Approx. Theory 85 (1996) 318-323], Carbone [A. Carbone, Applications of fixed point theorems, Jnanabha 19 (1989) 149-155], Chen and Li [J. Chen, Z. Li, Common fixed points for Banach operator pairs in best approximations, J. Math. Anal. Appl. 336 (2007) 1466-1475], Habiniak [L. Habiniak, Fixed point theorems and invariant approximation, J. Approx. Theory 56 (1989) 241-244], Jungck and Sessa [G. Jungck, S. Sessa, Fixed point theorems in best approximation theory, Math. Japon. 42 (1995) 249-252], Sahab, Khan and Sessa [S.A. Sahab, M.S. Khan, S. Sessa, A result in best approximation theory, J. Approx. Theory 55 (1988) 349-351], Shahzad [N. Shahzad, Invariant approximations and R-subweakly commuting maps, J. Math. Anal. Appl. 257 (2001) 39-45] and of few others.     

Fabrication of novel coated pyrolytic graphite electrodes for the selective nano-level monitoring of Cd ions in biological and environmental samples using polymeric membrane of newly synthesized macrocycle

Novel 5-amino-1,3,4-thiadiazole-2-thiol unit based macrocyclic ionophore 5,11,17-trithia-1,3,7,9,13,15,19,20,21-nonaazatetracyclo[14.2.1.1^4,7.1^10,13]henicosa-4(20),10(21),16(19)-triene-6,12,18-trithione (M₁), was synthesized and characterized. Preliminary studies on M₁ have showed that it has more the affinity toward Cd²⁺ ion. Thus, the macrocyclic ionophore (M₁) was used as electroactive material in the fabrication of PVC-membrane electrodes such as polymeric membrane electrode (PME), coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) were prepared and its performance characteristic were compared with. The electroanalytical studies performed on PME, CGE and CPGE revealed that CPGE having membrane composition M₁:PVC:1-CN:NaTPB in the ratio of 7:37:54:2 exhibits the best potentiometric characteristics in terms of detection limit of 7.58 × 10⁻⁹ mol L⁻¹, Nernstian slope of 29.6 mV decade⁻¹ of activity. The sensor was found to be independent of pH in the range 2.5–8.5. The sensor showed a fast response time of 10 s and could be used over a period of 4 months without any significant divergence in its potentiometric characteristics. The sensor has been employed for monitoring of the Cd²⁺ ion in real samples and also used as an indicator electrode in the potentiometric titration of Cd²⁺ ion with EDTA.     

Microwave and electrical properties of Co-Ti substituted M-type Ba hexagonal ferrite

The microwave characteristics of Co²⁺ and Ti⁴⁺ ions substituted, BaCo _x Ti _x Fe_(12?2x)O₁₉ (x = 0.1, 0.3, 0.5, 0.7, 0.9) ferrite have been studied as a function of thickness, frequency and substitution. The results depict reflection loss of ? 31.94 dB at 10.47 GHz in x = 0.9. The highest static electrical current is observed at lower substitution. The model accompanying microwave absorption is used to evaluate microwave absorption characteristics. The electromagnetic and static electrical characteristics are improved with the substitution of Co²⁺ and Ti⁴⁺ ions. The compositions for possible electromagnetic applications are also explored.     

Use of XAD-2 Macroreticular Resin for the Recovery of Aldicarb and its Metabolites in Drinking Water

Abstract

A simplified method for the determination of aldicarb and its oxidation products, aldicarb sulfoxide, and aldicarb sulfone, in water has been developed. Aldicarb and its metabolites are adsorbed on Amberlite XAD-2 polymer resin and then eluted with acetone. The eluate is analyzed for aldicarb and aldicarb sulfoxide by high performance liquid chromatography (HPLC) with UV detection at 254 nm. Total aldicarb residues can be determined by a colorimetric method. Typical detection limits in drinking water are 1 μg/1.     

Common fixed points and invariant approximation of <Emphasis Type="Italic">R</Emphasis>-subweakly commuting maps in convex metric spaces

Sufficient conditions for the existence of a common fixed point of R-subweakly commuting mappings are established within the framework of a convex metric space. As applications, we obtain various results on the best approximation for this class of mappings generalizing the results known from the literature.