Understanding the reactivity properties of Au<SUB>n</SUB> (6 &#8804; n &#8804; 13) clusters using density functional theory based reactivity descriptors

Relativistic density functional theory (DFT) based calculations have been performed on gold clusters with six to thirteen atoms (Aun; n = 6-13). The ground state geometries of these clusters as obtained from our calculations are presented and discussed. This work proposes that atoms in a ground state conformation can be classified into distinct types of reactive sites in a given geometry. Based on symmetry, susceptibility of various types of reactive sites in the ground state geometry toward an impending electrophilic and/or a nucleophilic attack has also been studied using DFT based reactivity descriptors. The studies have also been extended to high energy isomers in these cluster sizes. The reactivity of various sites as a function of cluster size and shape was thus analyzed. The study shows that as a general rule the size and shape of the cluster influences the number and position of available sites for an electrophilic and/or nucleophilic attack. This makes the reactivity patterns of these clusters highly complex. The study also highlights as to how for a cluster with seven atoms (Au7) various conformations are likely to coexist indicating that the reactivity patterns of various high energy conformations are also important while dealing with small sized Au clusters

FORMULATION, IN-VITRO RELEASE KINETICS AND STABILITY INTERPRETATION OF SUSTAINED RELEASE TABLETS OF METFORMIN HYDROCHLORIDE

Objective: The objective of the present study was to formulate, study the in-vitro release kinetics and stability of sustained release tablets of metformin hydrochloride.Methods: Sustained release formulations that would maintain the plasma level for 8 – 12 h might be sufficient for daily dosing of metformin. The granules of metformin hydrochloride were prepared by wet granulation method using polymers such as ethyl cellulose (EC) and hydroxyl propyl methyl cellulose E15 (HPMC E15).Results: The granules were evaluated by determining the angle of repose (26.010±0.110 to 31.950±0.100), bulk density, tapped density, Hausner ratio and Carr's index. It shows satisfactory results. The tablets were subjected to measurement of thickness (4.78 ± 0.07 to 5.20±0.13 mm), weight variation (within limit), drug content (98.08±0.20 to 99.22±0.22%), hardness (9.27±0.16 to10.30±0.97 kg/cm2), friability (0.2to 0.3%w/w), and in-vitro release studies.Conclusion: It was found that as the concentration of HPMC increased the drug release rate declined due to formation of viscous layer. The release can be fine tuned by adding a hydrophobic polymer like EC in the hydrophilic matrix of HPMC. The release mechanisms were analyzed and were found that the release data was best fitted with Higuchi equation although there is no significant difference between the correlation coefficients of Zero-order and Higuchi model. The result also shows different parameters of stability studies and compare with initial results of different batches.Â

What is conservation paleobiology? Tracking 20¿years of research and development

Conservation paleobiology has coalesced over the last two decades since its formal coining, united by the goal of applying geohistorical records to inform the conservation, management, and restoration of biodiversity and ecosystem services. Yet, the field is still attempting to form an identity distinct from its academic roots. Here, we ask a deceptively simple question: What is conservation paleobiology? To track its development as a field, we synthesize complementary perspectives from a survey of the scientific community that is familiar with conservation paleobiology and a systematic literature review of publications that use the term. We present an overview of conservation paleobiology’s research scope and compare survey participants’ perceptions of what it is and what it should be as a field. We find that conservation paleobiologists use a variety of geohistorical data in their work, although research is typified by near-time records of marine molluscs and terrestrial mammals collected over local to regional spatial scales. Our results also confirm the field’s broad disciplinary basis: survey participants indicated that conservation paleobiology can incorporate information from a wide range of disciplines spanning conservation biology, ecology, historical ecology, paleontology, and archaeology. Finally, we show that conservation paleobiologists have yet to reach a consensus on how applied the field should be in practice. The survey revealed that many participants thought the field should be more applied but that most do not currently engage with conservation practice. Reflecting on how conservation paleobiology has developed over the last two decades, we discuss opportunities to promote community cohesion, strengthen collaborations within conservation science, and align training priorities with the field’s identity as it continues to crystallize

What is conservation paleobiology? Tracking 20 years of research and development

Conservation paleobiology has coalesced over the last two decades since its formal coining, united by the goal of applying geohistorical records to inform the conservation, management, and restoration of biodiversity and ecosystem services. Yet, the field is still attempting to form an identity distinct from its academic roots. Here, we ask a deceptively simple question: What is conservation paleobiology? To track its development as a field, we synthesize complementary perspectives from a survey of the scientific community that is familiar with conservation paleobiology and a systematic literature review of publications that use the term. We present an overview of conservation paleobiology’s research scope and compare survey participants’ perceptions of what it is and what it should be as a field. We find that conservation paleobiologists use a variety of geohistorical data in their work, although research is typified by near-time records of marine molluscs and terrestrial mammals collected over local to regional spatial scales. Our results also confirm the field’s broad disciplinary basis: survey participants indicated that conservation paleobiology can incorporate information from a wide range of disciplines spanning conservation biology, ecology, historical ecology, paleontology, and archaeology. Finally, we show that conservation paleobiologists have yet to reach a consensus on how applied the field should be in practice. The survey revealed that many participants thought the field should be more applied but that most do not currently engage with conservation practice. Reflecting on how conservation paleobiology has developed over the last two decades, we discuss opportunities to promote community cohesion, strengthen collaborations within conservation science, and align training priorities with the field’s identity as it continues to crystallize