Controlling the lifetime of cucurbit[8]uril based self-abolishing nanozymes

Nature has evolved a unique mechanism of self-regulatory feedback loops that help in maintaining an internal cellular environment conducive to growth, healing and metabolism. In biology, enzymes display feedback controlled switchable behaviour to upregulate/downregulate the generation of metabolites as per the need of the cells. To mimic the self-inhibitory nature of certain biological enzymes under laboratory settings, herein, we present a cucurbit[8]uril based pH responsive supramolecular peptide amphiphile (SPA) that assembles into hydrolase mimetic vesicular nanozymes upon addition of alkaline TRIS buffer (activator) but disintegrates gradually owing to the catalytic generation of acidic byproducts (deactivator). The lifetime of these nanozymes could be manipulated in multiple ways, either by varying the amount of catalytic groups on the surface of the vesicles, by changing the acid generating substrate, or by changing the ratio between the activator and the substrate. The self-inhibitory nanozymes displayed highly tunable lifetimes ranging from minutes to hours, controlled and in situ generation of deactivating agents and efficient reproducibility across multiple pH cycles.

Self-inhibitory feedback regulated transient assembly of a CB[8] based nanozyme is reported whose lifetime can be manipulated in multiple ways, ranging from minutes to hours.     

Metal‐Free Catalyst for the Chemoselective Methylation of Amines Using Carbon Dioxide as a Carbon Source

N‐methylation of amines is an important step in the synthesis of many pharmaceuticals and has been widely applied in the preparation of other key intermediates and chemicals. Therefore, the development of efficient methylation methods has attracted considerable attention. In this respect, carbon dioxide is an attractive C₁ building block because it is an abundant, renewable, and nontoxic carbon source. Consequently, we developed a highly chemoselective, metal‐free catalytic system that operates under ambient conditions for the N‐methylation of amines.     

Quality Related Safety Evaluation of a South African Traditional Formulation (PHELA®) as Novel Anti-Biofilm Candidate

A South African traditional formulation, PHELA^®, is consumed by the traditional people for severe chest problems with coughing, diarrhea, oral ulcers etc. The present study focused on establishing the anti-infective properties of a safe and standardized poly-herbal formulation through a series of criteria and specifications.     

Loss of collectivity in 79Rb

High-spin states in ⁷⁹Rb were populated in the reaction at E(beam) = 60 MeV. The lifetimes of the excited states of the positive-parity yrast band and of the negative-parity band in ⁷⁹Rb were measured by the Doppler Shift Attenuation Method. The deduced transition quadrupole moments Q_t are found to have a decreasing trend with rotational frequency for both the bands, consistent with those found experimentally in neighbouring nuclei. An erratum to this article is available at .     

Compressive stress in polycrystalline volmer-weber films

The Volmer-Weber mode for growing polycrystalline films, which comprises island, network, and channel stages before the films become continuous, is well known for its complex stress behavior with compressive and tensile stress alternating in the initial three growth stages. Recently, two new mechanisms for the compressive stress have been proposed [Phys. Rev. Lett. 88, 156103 (2002); 89, 126103 (2002)], which account for the reversibility of stress generation and relaxation. We show that the two mechanisms play only minor roles for the development of compressive stress, which is confirmed to be due to capillarity effects in the precoalescence stage.     

Fragment angular momenta in low and medium energy fission of242Pu

Independent isomeric yield ratios of¹²⁸Sb were determined radiochemically in the thermal neutron induced fission of²⁴¹Pu and 34 MeV alpha particle induced fission of²³⁸U, both involving the same compound nucleus (²⁴²Pu). Fragment angular momenta estimated from the measured isomer ratios using the statistical model analysis showed significantly larger fragment angular momenta in the medium energy fissioning system compared to the low energy fissioning system. This has been attributed to the effect of higher excitation energy and angular momentum in the entrance channel leading to increased fragment temperature, moments of inertia and angular velocity. An attempt was made to calculate the fragment angular momentum in the medium energy fission using the Fermi gas model for the fissioning nucleus, taking into account the multichance fission, saddle shapes of the fissioning nuclei and the angular velocity components of the fissioning nuclei both along and orthogonal to the fission axis. The calculated angular momenta agree well with the experimental results.     

Cognition friendly interaction: A concept of partnership in human computer interaction

This paper identifies yet another field of research, the discipline of human computer interaction, where the concept of self-similar fluctuations can play a vital role. A concept of interaction between computation and cognition is developed that is friendly toward the cognitive process. It is argued that friendly interactions must have a memory and be antipersistent. To cast this in a mathematical form, fluctuations in the interactions recorded over a period of time are studied, and it is shown that these fluctuations must necessarily be self-similar with the value of the self-similarity parameter confined to the interval (0, 1/2), for the interaction to be friendly. A statistical measure of complexity, of the interaction process, is also formulated as a function of the self-similarity parameter. Finally the question is raised as how to build a friendly software and a possible evolutionary process through which friendly softwares may emerge is indicated. (c) 2001 American Institute of Physics.     

4f-electric quadrupolar effects on the lattice constants and magnetism of RCu2Ge2 (R=rare-earths)

The temperature dependence of the lattice constants of the alloys, RCu₂Ge₂ (R=Nd, Tb, Dy, Ho and Tm) shows the existence of a lattice strain due to the alignment of the 4f-electric quadrupole at low temperatures. This strain could be related to the deviation of the Néel temperatures (T _N ) from that predicted by de Gennes scaling, thereby indicating the role of the quadrupole on the magnetism. On the other hand, in PrCu₂Ge₂, for which the enhancement ofT _N is the largest in thisR series, the lattice constants interestingly behave as if the 4f-quadrupole moment is almost quenched and the anomalous magnetism in this case is attributed to some degree of 4f-delocalisation.