Mobile Kink Solitons in a Van der Waals Charge-Density-Wave Layer

Kinks, point-like geometrical defects along dislocations, domain walls, and DNA, are stable and mobile, as solutions of a sine-Gordon wave equation. While they are widely investigated for crystal deformations and domain wall motions, electronic properties of individual kinks have received little attention. In this work, electronically and topologically distinct kinks are discovered along electronic domain walls in a correlated van der Waals insulator of 1$T$-TaS$_2$. Mobile kinks and antikinks are identified as trapped by pinning defects and imaged in scanning tunneling microscopy. Their atomic structures and in-gap electronic states are unveiled, which are mapped approximately into Su-Schrieffer-Heeger solitons. The twelve-fold degeneracy of the domain walls in the present system guarantees an extraordinarily large number of distinct kinks and antikinks to emerge. Such large degeneracy together with the robust geometrical nature may be useful for handling multilevel information in van der Waals materials architectures.Comment: 12 pages, 4 figure

Discovery of Fluidic LiBH_4 on Scaffold Surfaces and Its Application for Fast Co-confinement of LiBH_4−Ca(BH_4)_2 into Mesopores

Generation of fluidic LiBH_4 molecules, ƒ-LiBH_4, was demonstrated by NMR spectroscopy of LiBH_4 bulk powder mixed with silica scaffold surface materials under minor heat treatment. In the presence of the fumed silica or mesoporous MCM-41 and SBA-15, LiBH_4 shows increased translational mobility at relatively low temperature (ca. 95 °C) and becomes liquid-like by evidence from ^1H–^(11)B J-coupling in ^1H and ^(11)B MAS NMR or substantial line narrowing of ^7Li static NMR. This high diffusional mobility of LiBH_4 at the molecular level has never been seen for bulk LiBH_4, and the property is attributed to the interfacial interaction with the mesoporous scaffold surfaces. While ƒ-LiBH_4 facilitates the confinement of LiBH_4 itself into various scaffold materials, LiBH_4 migrates along the SBA-15 surface to reach other metal borohydride particles, Ca(BH_4)_2 in this case, and promotes the formation of similarly fluidic LiBH_4–Ca(BH_4)_2 composite (LC solid solution) for coconfinement into mesopores. In situ variable temperature (VT) NMR spectroscopy detects the co-infiltration process of eutectic LiBH_4–Ca(BH_4)_2 composite (LC) into mesopores of SBA-15. The infiltration rates measured for LiBH_4 bulk powder or LC composite showed dependence on pore sizes (MCM-41 vs SBA-15) and heat treatment conditions (static vs MAS)

Boron-nitrogen based hydrides and reactive composites for hydrogen storage

Hydrogen forms chemical compounds with most other elements and forms a variety of different chemical bonds. This fascinating chemistry of hydrogen has continuously provided new materials and composites with new prospects for rational design and the tailoring of properties. This review highlights a range of new boron and nitrogen based hydrides and illustrates how hydrogen release and uptake properties can be improved. © 2014 Elsevier Ltd

Central nervous system superficial siderosis related to spinal lesions

Superficial siderosis is a rare disease of the central nervous system, which is characterized by chronic intrathecal hemorrhage leading to hemosiderin deposition on the leptomeninges and subpial layers of the brain and spinal cord. Patients with the syndrome typically present with sensorineural hearing loss, myelopathy, cerebellar ataxia, pyramidal signs, and cognitive impairment. The most common etiologies of the disease include bleeding of unknown cause, ruptured aneurysms, arteriovenous malformation, and traumatic injury of the brain. Here, we describe two patients diagnosed with superficial siderosis caused by spinal lesions, which is an unusual cause of chronic bleeding due to the presence of the disease

In Situ NMR Study on the Interaction between LiBH_4–Ca(BH_4)_2 and Mesoporous Scaffolds

We discuss the use of nuclear magnetic resonance (NMR) spectroscopy to investigate the physical state of the eutectic composition of LiBH_(4)–Ca(BH_4)_2 (LC) infiltrated into mesoporous scaffolds and the interface effect of various scaffolds. Eutectic melting and the melt infiltration of mixed borohydrides were observed through in situ NMR. In situ and ex situ NMR results for LC mixed with mesoporous scaffolds indicate that LiBH_4 and Ca(BH_4)_2 exist as an amorphous mixture inside of the pores after infiltration. Surprisingly, the confinement of the eutectic LC mixture within the mesopores is initiated below the melting temperature, which indicates a certain interaction between the borohydrides and the mesoporous scaffolds. The confined borohydrides remain inside of the pores after cooling. These phenomena were not observed in microporous or nonporous materials, and this observation highlights the importance of the pore structure of the scaffolds. Such surface interactions may be associated with a faster dehydrogenation of the nanoconfined borohydrides