Anomalously Efficient Dehydrogenation of NH3 on Ir4 + and Ir5 Hirabayashi, Shinichi; Ichihashi, Masahiko
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
07/2022, Letnik:
126, Številka:
27
Journal Article
Recenzirano
Gas-phase reactions of iridium cluster cations, Ir n + (n = 1–8), with ammonia are studied at near-thermal energies. In single collision reactions, dehydrogenation of NH3 proceeds at n = 1–5, and in ...particular, Ir4 + and Ir5 + are found to be significantly reactive. This size dependence is quite different from those of other platinum group metal cluster cations, where usually only the dimers are able to dehydrogenate NH3. Moreover, the sequentially dehydrogenated products, Ir4,5(NH) m + (m = 2–5), are chiefly observed under multiple collision conditions. This observation suggests that the NH species on Ir4,5 + possibly encourages, or at least does not prohibit, the adsorption of the coming NH3 molecule and the dehydrogenation.
To meet the increasing demand for small-scale NH
3
production, catalysts that work under milder conditions than those of the Haber–Bosch process are essential. In this study, Ru clusters and ...nanoparticles were impregnated on five different CeO
2
supports to prepare Ru/CeO
2
catalysts for NH
3
synthesis at 400 °C and 0.1 MPa. The basicity of the CeO
2
support and Ru particle size significantly influenced the catalytic activity. The catalytic activity increased with decreasing Ru particle size, reaching the maximum of ~ 200 mmol g
Ru
−1
h
−1
at ~ 1 nm, which is ascribed to a high proportion of unique active sites different from the B
5
-type sites. Our findings demonstrate that Ru cluster catalysts are advantageous over Ru nanoparticle catalysts for NH
3
synthesis.
Graphical Abstract
BACKGROUND:Because subcutaneously injected hyaluronic acid filler is absorbed over 6 months to 1 year after the treatment of facial wrinkles, frequent retreatment may be required. However, persistent ...long-term effects are often clinically observed when hyaluronic acid filler is injected as a bolus for facial augmentation. Therefore, the authors investigated, over time, the changes in volume and histologic features of subcutaneous bolus injections of hyaluronic acid.
METHODS:Hyaluronic acid filler was subcutaneously injected as a bolus into the dorsum of 6-week-old rats. At several time points (immediately after injection and 4, 8, 16, 32, and 64 weeks thereafter), magnetic resonance imaging was introduced to observe morphologic changes and to measure volume. Histologic examination of sectioned tissues was also performed.
RESULTS:The average volume increased for up to 4 weeks after injection and then gradually decreased, with 74.8 percent of the injected volume remaining after 64 weeks, with no statistical difference compared to the initial volume. Histologic analysis revealed that lattice structures were created by fibroblasts and collagen fibers, and blood vessels and adipocytes were also generated in the filler.
CONCLUSIONS:Although subcutaneous bolus injections of hyaluronic acid filler exhibited flattening, the total volume was maintained even after 64 weeks. Histologically, hyaluronic acid filler acted as a scaffold for autogenous tissue replacement by means of fibroblast migration and proliferation, collagen induction, and angiogenesis, followed by proliferation of adipocytes. This study demonstrates that the total volume is maintained long-term by replacing part of the injected hyaluronic acid filler with autologous tissues.
Mutations in the inositol 1,4,5-triphosphate receptor type 1 gene (
ITPR1
) have been identified in families with early-onset spinocerebellar ataxia type 29 (SCA29) and late-onset SCA15, but have not ...been found in sporadic infantile-onset cerebellar ataxia. We examined if mutations of
ITPR1
are also involved in sporadic infantile-onset SCA. Sixty patients with childhood-onset cerebellar atrophy of unknown etiology and their families were examined by whole-exome sequencing. We found de novo heterozygous
ITPR1
missense mutations in four unrelated patients with sporadic infantile-onset, nonprogressive cerebellar ataxia. Patients displayed nystagmus, tremor, and hypotonia from very early infancy. Nonprogressive ataxia, motor delay, and mild cognitive deficits were common clinical findings. Brain magnetic resonance imaging revealed slowly progressive cerebellar atrophy.
ITPR1
missense mutations cause infantile-onset cerebellar ataxia.
ITPR1
-related SCA includes sporadic infantile-onset cerebellar ataxia as well as SCA15 and SCA29.
Abstract Two siblings born to non-consanguineous parents showed nystagmus and sudden opistotonic posturing from the early infancy, and subsequent developmental delay and marked choreiform movements ...with hypotonia in the childhood. The brother had a mild postnatal microcephaly. Brain MRI of the sister showed mild delay of myelination, dilated anterior horn and mild cerebellar atrophy. Whole exome sequencing (WES) revealed compound heterozygous mutations in MED17 gene in both siblings: c.1013-5A>G and c.1484T>G mutations transmitted from their father and mother, respectively. The c.1013-5A>G mutation caused insertion of 4 bases of intron 6 in the transcript, resulting in frameshift (p. Ser338Asnfs*15), and mutant transcript underwent nonsense-mediated mRNA decay in lymphoblastoid cells derived from two siblings. The c.1484T>G mutation substituted a leucine residue, which is highly conserved among the vertebrates, and was predicted to be damaging by in silico analysis programs. Both mutations were not registered in dbSNP data and in our 575 control exomes. These results suggest that the siblings’ mutations are likely to be pathogenic. This is the second case report concerning MED17 mutations. Compared with the first reported cases of Caucasian Jewish origin, the clinical symptoms and courses are much milder and slower, respectively, in our cases. Genotype difference (a homozygous mutation versus compound heterozygous mutations) might explain these clinical differences between two cases, though early-onset nystagmus and later choreiform movements were unique in our cases. Clinical spectrum and phenotype–genotype correlations in this rare mutation should be further elucidated.
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► Reactions of composition-selected CenOm+ with O2 have been investigated. ► The Ce(II) clusters dissociate after the oxidation with high efficiency. ► The Ce(III) clusters can weakly ...bind O2 to form the Ce(IV) clusters. ► The Ce(IV) clusters give no detectable reaction products.
Reactions of composition-selected cerium oxide cluster cations, CenOm+ (n=2–6; m⩽2n), with O2 have been studied under single collision conditions. The formation of CenOm+2+ is observed only for CenOm+ with the average oxidation number (AON) of ∼3 for Ce atoms, Ce(III) clusters. In contrast, Ce(II) clusters with AON<3 dominantly give the product ions, CenOm+1+, Cen-1Om+, and Cen-2Om-2+, after the oxidation of the parent clusters. Combined with collision-induced dissociation studies, it is concluded that O2 is bound weakly to the Ce(III) cluster, whereas O2 added to the Ce(II) cluster is incorporated as atoms rapidly and then the cluster decomposes.
Anomalously Efficient Dehydrogenation of NH 3 on Ir 4 + and Ir 5 Hirabayashi, Shinichi; Ichihashi, Masahiko
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
07/2022, Letnik:
126, Številka:
27
Journal Article
Gas-phase reactions of tungsten carbide and nitride cluster cations, W n C m + (n = 1–5, m ≤ 5) and W n N m + (n = 1–6, m ≤ 2), with methane are investigated at near thermal energies. Most of the ...clusters react readily with CH4 to form W n C m+1H2 + or W n N m CH2 + under single collision conditions, in contrast to the almost no reactivity of pure tungsten clusters. This result indicates that the introduction of carbon or nitrogen atoms can enhance the reactivity of tungsten clusters toward the CH4 dehydrogenation. In addition, the formation and the release of an ethylene molecule are strongly suggested in the reaction of WC+ with CH4 as a minor reaction channel. Nearly all the nitride cluster cations, W n N m + (n ≥ 2), exhibit higher reactivity than their corresponding carbides, W n C m +, whereas WN+ is less reactive than WC+. Furthermore, the multiple collision reactions of the highly reactive tungsten nitride species such as WN+ and W4N+ lead to the formation of W n N m C x H2x + (x = 2, 3), which shows that the dehydrogenation of more than one CH4 molecule occurs.
Reactions of copper oxide cluster cations, Cu n O m + (n = 3–7; m ≤ 5), with ammonia, NH3, are studied at near thermal energies using a guided ion beam tandem mass spectrometer. The single-collision ...reactions of specific clusters such as Cu4O2 +, Cu5O3 +, Cu6O3 +, Cu7O3 +, and Cu7O4 + give rise to the release of H2O after NH3 adsorption efficiently and result in the formation of Cu n O m–1NH+. These Cu n O m + clusters commonly have Cu average oxidation numbers of 1.0–1.4. On the other hand, the formation of Cu n O m–1H2 +, i.e., the release of HNO, is dominantly observed for Cu7O5 + with a higher Cu oxidation number. Density functional theory calculations are performed for the reaction Cu5O3 + + NH3 → Cu5O2NH+ + H2O as a typical example of H2O release. The calculations show that this reaction occurs almost thermoneutrally, consistent with the experimental observation. Further, our experimental studies indicate that the multiple-collision reactions of Cu5O3 + and Cu7O4 + with NH3 lead to the production of Cu5 + and Cu7O+, respectively. This suggests that the desirable NH3 oxidation to N2 and H2O proceeds on these clusters.
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