Photocontrolled pesticide delivery systems have broad
prospects
for application in agriculture. Here, a novel photoresponsive herbicide
delivery system was fabricated by functionalizing silica microsphere
surfaces with cinnamamide and encapsulating the silica-cinnamamide
with γ-cyclodextrin (γ-CD) to form a double-layered microsphere
shell loaded with pendimethalin (pendimethalin@silica-cinnamamide/γ-CD).
The microspheres showed remarkable loading capacity for pendimethalin
(approximately 30.25% w/w) and displayed excellent photoresponsiveness
and controlled release. The cumulative drug release rate exceeded
80% over 72 h under UV or sunlight irradiation. The herbicidal activity
of the microspheres against Echinochloa crusgalli (L.) Beauv. was almost the same as that of pendimethalin under UV
or sunlight. A bioactivity survey confirmed that the pendimethalin@silica-cinnamamide/γ-CD
microspheres exhibited longer duration weed control than commercial
pendimethalin. Allium cepa chromosomal
aberration assays demonstrated that the microspheres showed lower
genotoxicity than pendimethalin. These advantages indicate that pendimethalin@silica-cinnamamide/γ-CD
microspheres constitute an environmentally friendly herbicidal formulation.
For any real α ∈ [0, 1], Nikiforov defined the A α -matrix of a graph G as, where A(G) and D(G) are the adjacency matrix and the diagonal matrix of vertex degrees of G, respectively. The largest eigenvalue of A α (G) is called the α-index or the A α -spectral radius of G. A graph is minimally k-connected if it is k-connected and deleting any arbitrary chosen edge always leaves a graph which is not k-connected. In this paper, we characterize the extremal graphs with the maximum α-index for α ∈ [ 1 2 , 1) among all minimally 2-connected graphs with given order or size, respectively.
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