Keggin-type polyaluminum species (ε-Al 13 , δ-Al 13 , Al 26 , Al 30 , Al 32 ) can form upon partial hydrolysis of Al 3+ -bearing solutions and are important species for water purification and contaminant transport. While the structural features for the major Al 3+ polyaluminum species have been delineated, much less is known regarding heteroatom substitution and resultant structures other than the previously identified ε-GaAl 12 7+ and ε-GeAl 12 8+ cations. Single-atom substitution within polyaluminum species can change the surface reactivity within water treatment scenarios; thus, it is important to understand heteroatom incorporation within this system. The present work describes the synthesis and characterization of two novel Ga 3+ -substituted Keggin-type p o l y a l u m i n u m s p e c i e s . N a [ G a O 4 A l 1 2 ( O H ) 2 4 ( H 2 O ) 1 2 ] ( 2 , 6 -N D S ) 4 ( H 2 O ) 2 0 . 5 ( δ -G a A l 1 2 ) and [Ga 2 O 8 Al 28.5 Ga 0.5 (OH) 58 (H 2 O) 27 (SO 4 ) 2 ](SO 4 ) 4 Cl 7 (H 2 O) 8.5 (Ga 2.5 Al 28.5) were crystallized from a thermally aged, partially hydrolyzed Ga 3+ /Al 3+ solution. Structural refinement from single-crystal X-ray diffraction indicated fully occupied Ga 3+ within tetrahedral site(s) of both isolated species. Partial substitution was observed for octahedral sites for the larger Ga 2.5 Al 28.5 cluster. The chemical compositions of both clusters were confirmed by inductively coupled plasma mass spectrometry (ICP-MS). Density functional theory (DFT) calculations corroborated the structural refinement, with the energetics of Ga 3+ substitution suggesting preferential substitution within tetrahedral sites for both species. Additional theoretical work suggests that the rotated trimer in δ-GaAl 12 is highly reactive, which can serve as the driving force in the formation of the Ga 2.5 Al 28.5 cluster.

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Respiratory epithelium in the conducting airways of the human body is one of the primary targets of SARS-CoV-2 infection, however, there is a paucity of studies describing the association between COVID-19 and physical characteristics of the conducting airways. To better understand the pathophysiology of COVID-19 on the size of larger conducting airways, we determined the luminal area of the central airways in patients with a history of COVID-19 compared to a height-matched cohort of controls using a case–control study design. Using three-dimensional reconstruction from low-dose high-resolution computed tomography, we retrospectively assessed airway luminal cross-sectional area in 114 patients with COVID-19 (66 females, 48 males) and 114 healthy, sex- and height-matched controls (66 females, 48 males). People with a history of smoking, cardiopulmonary disease, or a body mass index greater than 40 kg·m−2 were excluded. Luminal areas of seven conducting airways were analyzed, including trachea, left and right main bronchus, intermediate bronchus, left and right upper lobe, and left lower lobe. For the central conducting airways, luminal area was ~ 15% greater patients with COVID-19 compared to matched controls (p < 0.05). Among patients with COVID-19, there were generally no differences in the luminal areas of the conducting airways between hospitalized patients compared to patients who did not require COVID-19-related hospitalization. Our findings suggest that males and females with COVID-19 have pathologically larger conducting airway luminal areas than healthy, sex- and height-matched controls.