Indirect polarographic determination of stability constants

The stability constants of cadmium thiosulphate complexes have been determined in 25% methanol medium. The stability constants of thiosulphate complexes of zinc and lanthanum have been determined by the indirect method using cadmium as the indicator ion.     

Effect of complexing agents on the disproportionation of uranium (V)

The effect of lactate, thiocyanate, sulphate, oxalic acid and fluoride on the disproportionation of uranium (V) formed at the dropping mercury electrode has been studied. The rate constants for the disproportionation reaction are calculated and the results are discussed on the basis of the stability of the complexes.     

Electron impact induced hydrogen migrations in organic molecules: IV—novel hydrogen transfers in alkyl o-methoxybenzoates

Simultaneous hydrogen transfers—one from the methoxy group and the other from the alkyl group—to both the oxygen atoms of the ester function result in the formation of a common ion at m/z 152 in the alkyl o-methoxybenzoates on electron impact. Expulsion of the formyl radical from this ion leads to a fragment resembling the protonated benzoic acid. Another novel feature in these compounds is the loss of H₂O from the [M? R]⁺ ion which arises through an ortho effect during a secondary fragmentation process.     

Spectrum of density fluctuations in a particlefluid system—II. Polydisperse spheres

This paper presents an extension of the analysis shown in Part I to a polydisperse particle-fluid system. The density autocorrelation is shown to be a function of two quantities, a generalized Overlap function for which an analytical expression is derived, and the radial distribution function (RDF). In Fourier transform space, the density spectrum again appears to be a strong function of the mean particle size, and secondarily the mean particle separation distance. One unusual result is previously observed oscillations in the density spectrum of a monodisperse system of particles are severely dampened or even eliminated in the polydisperse case, depending on the width of the particle size distribution. Apparently contributions from different particle correlations interfere with each other, thereby reducing the coherent oscillations seen in the monodisperse particle-fluid system. Furthermore at large wavenumbers, the spectrum decays with a −2 power-law, independent of the shape of the particle size distribution. This behavior can be traced to the Overlap function which controls the behavior of the spectrum beyond the first peak. Remarkably the −2 power-law spectrum is determined by the shape of the particles (i.e. spheres) rather than their spatial distribution (RDF).

The effect of an asymptotically large pressure gradient on the correlation of several important higher-order moments is revisited for the polydisperse system. The relatively simple relationships developed for the monodisperse system are lost in the polydisperse case because particles of different sizes will be influenced differently by an applied pressure gradient. The result is moments that are of different order in velocity can no longer be related to each other (as they were in the monodisperse system), even in this idealized flow. A more comprehensive understanding of this phenomenon can only be achieved through direct numerical simulation or experiment.     

Differential etching of chalcogenides for infrared photonic waveguide structures

Chemical etching rates for two different chalcogenide glass compositions, As₄₀S₆₀ and As₂₄S₃₈Se₃₈, were studied using sodium hydroxide based etchant solutions. Etching was performed using a variation of standard photolithographic masking and wet-etching techniques. Variations in etch rate with NaOH concentration and glass composition were observed. The depth of etch was characterized using an optical profilometer. Etch rate differences as large as three orders of magnitude between these two glasses were observed at low NaOH concentration (0.053 M). We present a single variable etch rate curve of etch depth per time (nm/s) versus NaOH overall solution concentration (in M) for these two different chalcogenide glasses. This technology shows promise for fabricating photonic structures and has potential applications in fabricating novel photonic bandgap structures that will function in the long-wave infrared (LWIR) regime.     

JKR adhesion in cylindrical contacts

Planar JKR adhesive solutions use the half-plane assumption and do not permit calculation of indenter approach or visualization of adhesive force–displacement curves unless the contact is periodic. By considering a conforming cylindrical contact and using an arc crack analogy, we obtain closed-form indenter approach and load–contact size relations for a planar adhesive problem. The contact pressure distribution is also obtained in closed-form. The solutions reduce to known cases in both the adhesion-free and small-contact solution (Barquins, 1988) limits. The cylindrical system shows two distinct regimes of adhesive behavior; in particular, contact sizes exceeding the critical (maximum) size seen in adhesionless contacts are possible. The effects of contact confinement on adhesive behavior are investigated. Some special cases are considered, including contact with an initial neat-fit and the detachment of a rubbery cylinder from a rigid cradle. A comparison of the cylindrical solution with the half-plane adhesive solution is carried out, and it indicates that the latter typically underestimates the adherence force. The cylindrical adhesive system is novel in that it possesses stable contact states that may not be attained even on applying an infinite load in the absence of adhesion.     

New ICT probes: synthesis and photophysical studies of N-phenylaza-15-crown-5 aryl/heteroaryl oxadiazoles under acidic condition and in the presence of selected metal ions

Molecular probes 6 and 7, incorporating N-phenylaza-15-crown-5 and aryl/heteroaryl oxadiazole have been designed to function as the new intramolecular charge transfer (ICT) probes. Photophysical properties have been studied under acidic condition as well as in the presence of selected metal ions, Ca²⁺, Ba²⁺, Mg²⁺, Na⁺, K⁺, and Li⁺. The changes in the ICT character of the probes, following the addition of trifluoroacetic acid, were interpreted in terms of site and degree of protonations. Based on the cation affinity, the ICT bands in both UV-vis and emission spectra experienced varying degrees of blue shifts due to removal of the aza-crown ether nitrogen from conjugation. The cation-induced spectral shifts and the stability constants revealed binding strength in the order Ca²⁺>Ba²⁺?Li⁺>Na⁺>K⁺>Mg²⁺. Competitive experiments performed in a matrix of ions also indicated superior interaction of 6 and 7 with Ca²⁺. The excited state decay profiles remained largely unperturbed in the presence of metal ions. The studied probes displayed positive solvatochromism and the Stokes shifts and excited state lifetimes increased with increasing solvent polarity. These findings can be rationalized by invoking highly polar nature of the emittive states. The chemoionophores 6 and 7 constitute potentially interesting Ca²⁺ sensitive probes due to their relatively high binding interaction for Ca²⁺ (log K_s=3.55-3.10) vis-a-vis that of biologically interfering Mg²⁺ (log K_s=1.67-1.30).     

Review of Building Integrated Photovoltaics System for Electric Vehicle Charging

The transition to sustainable transportation has fueled the need for innovative electric vehicle (EV) charging solutions. Building Integrated Photovoltaics (BIPV) systems have emerged as a promising technology that combines renewable energy generation with the infra-structure of buildings. This paper comprehensively reviews the BIPV system for EV charging, focusing on its technology, application, and performance. The review identifies the gaps in the existing literature, emphasizing the need for a thorough examination of BIPV systems in the context of EV charging. A detailed review of BIPV technology and its application in EV charging is presented, covering aspects such as the generation of solar cell technology, BIPV system installation, design options and influencing factors. Furthermore, the review examines the performance of BIPV systems for EV charging, focusing on energy, economic, and environmental parameters and their comparison with previous studies. Additionally, the paper explores current trends in energy management for BIPV and EV charging, highlighting the need for effective integration and recommending strategies to optimize energy utilization. Combining BIPV with EV charging provides a promising approach to power EV chargers, enhances building energy efficiency, optimizes the building space, reduces energy losses, and decreases grid dependence. Utilizing BIPV-generated electricity for EV charging provides electricity and fuel savings, offers financial incentives, and increases the market value of the building infrastructure. It significantly lowers greenhouse gas emissions associated with grid and vehicle emissions. It creates a closed-loop circular economic system where energy is produced, consumed, and stored within the building. The paper underscores the importance of effective integration between Building Integrated Photovoltaics (BIPV) and Electric Vehicle (EV) charging, emphasizing the necessity of innovative grid technologies, energy storage solutions, and demand-response energy management strategies to overcome diverse challenges. Overall, the study contributes to the knowledge of BIPV systems for EV charging by presenting practical energy management, effectiveness and sustainability implications. It serves as a valuable resource for researchers, practitioners, and policymakers working towards sustainable transportation and energy systems.     

Chiral,sequence-definable foldamer-derived macrocycles

Nature''s oligomeric macromolecules have been a long-standing source of inspiration for chemists producing foldamers. Natural systems are frequently conformationally stabilised by macrocyclisation, yet this approach has been rarely adopted in the field of foldamer chemistry. Here we present a new class of chiral cyclic trimers and tetramers formed by macrocyclisation of open-chain foldamer precursors. Symmetrical products are obtained via a [2 + 2] self-assembly approach, while full sequence control is demonstrated through linear synthesis and cyclisation of an unsymmetrical trimer. Structural characterisation is achieved through a combined X-ray and DFT approach, which indicates the tetramers adopt a near-planar conformation, while the trimers adopt a shallow bowl-like shape. Finally, a proof-of-concept experiment is conducted to demonstrate the macrocycles'' capacity for cation binding.

Dipole-controlled pre-organization enables the cyclization of sequence-defined foldamers into macrocycles. The structure and properties of trimeric and tetrameric macrocycles are explored, and their ability to bind cationic guests is demonstrated.