Tracking and readout characteristics of a minute aperture mounted optical head slider flying above a chromium patterned medium

Recent rapid progress in a digital network society necessitates storage devices with higher-density and faster transfer rates. In optical storage, a novel recording principle is eagerly awaited that will drastically improve recording density without being restricted by a wavelength shortening limit or a numerical aperture (NA) limit of the optics utilized. Storage based on the “near-field” principle is thought to be one of the most promising breakthroughs for overcoming various limitations governing traditional optical recording. We have already proposed an integrated optical head slider assembly that relies on the novel near-field principle for its operation; it is mounted on a minute tapered aperture and has a planar focusing lens and a micro silicon mirror. Readout signals corresponding to a 200-nm-long bit have demonstrated a frequency band up to approximately 10 MHz, using a chromium patterned medium. In this study, we have investigated the accuracy of the tracking characteristics of an aperture-mounted head slider by using linearly arranged 1-mm-long line-and-space patterns. Based on the step or inverse step responses that occur when an aperture flies obliquely across the linearly arranged pattern region boundary, we present a simple method of predicting accurate tracking characteristics in detail, and also by using a 350-nm line-and-space pattern signal, we were able to predict both tracking characteristics and tracking sensitivities of arbitrary wide tracks to a track width of 100 nm.     

Solvent Mediated Nanoscale Quasi-Periodic Chirality Reversal in Self-Assembled Molecular Networks Featuring Mirror Twin Boundaries

Grain boundaries in polycrystals have a prominent impact on the properties of a material, therefore stimulating the research on grain boundary engineering. Structure determination of grain boundaries of molecule-based polycrystals with submolecular resolution remains elusive. Reducing the complexity to monolayers has the potential to simplify grain boundary engineering and may offer real-space imaging with submolecular resolution using scanning tunneling microscopy (STM). Herein, the authors report the observation of quasi-periodic nanoscale chirality switching in self-assembled molecular networks, in combination with twinning, as revealed by STM at the liquid/solid interface. The width of the chiral domain structure peaks at 12–19 nm. Adjacent domains having opposite chirality are connected continuously through interdigitated alkoxy chains forming a 1D defect-free domain border, reflecting a mirror twin boundary. Solvent co-adsorption and the inherent conformational adaptability of the alkoxy chains turn out to be crucial factors in shaping grain boundaries. Moreover, the epitaxial interaction with the substrate plays a role in the nanoscale chirality reversal as well.     

Bacterially Secretable Single-Chain Tandem Macrocyclic Peptides for High Affinity and Inhibitory Activity

The inhibition of protein-protein interactions (PPIs) is an effective approach for therapy. Owing to their large binding surface areas to target proteins, macrocyclic peptides are suitable molecules for PPI inhibition. In this study, we developed single-chain tandem macrocyclic peptides (STaMPtides) that inhibits the vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2). They were artificially designed to comprise two different VEGFR2-binding macrocyclic peptides linked in tandem by peptide linkers and secreted by Corynebacterium glutamicum. Most potent VEGFR2-inhibitory STaMPtides with length-optimized linkers exhibited >1000 times stronger inhibitory activity than their parental monomeric peptides, possibly due to the avidity effect of heterodimerization. Our approach of using STaMPtides for PPI inhibition may be used to inhibit other extracellular factors, such as growth factors and cytokines.     

Bifidobacterial GH146 β-l-Arabinofuranosidase (Bll4HypBA1) as the Last Enzyme for the Complete Removal of Oligoarabinofuranosides from Hydroxyproline-Rich Glycoproteins

In plant cell walls, the hydroxyproline-rich glycoproteins (HRGPs) such as extensin contain oligoarabinofuranoside linked to a hydroxyproline (Hyp) residue. The mature arabinooligosaccharide was revealed to be a tetrasaccharide (α-l -Araf-(1→3)-β-l -Araf-(1→2)-β-l -Araf-(1→2)-β-l -Araf, l -Araf₄), whose linkages are targets of the bifidobacterial and Xanthomonas arabinooligosaccharide-degrading enzymes. The l -Araf₄ motif was cleaved by GH43 α-l -arabinofuranosidase (Arafase) and converted to an l -Araf₃-linked structure. The latter is then cleaved by GH121 β-l -arabinobiosidase (HypBA2), producing β-l -Araf-(1→2)-l -Ara (β-l -arabinobiose) and mono-β-l -Araf linked to the HRGP backbone. In bifidobacteria, the β-l -arabinobiose is then hydrolyzed by GH127 β-l -Arafase (Bll1HypBA1), a mechanistically unique cysteine glycosidase. We recently identified the distantly related homologue from Xanthomonas euvesicatoria as GH146 β-l -Arafase along with paralogues from Bifidobacterium longum, one of which, Bll4HypBA1 (BLLJ_0089), can degrade l -Araf₁-Hyp in a similar way to that of GH146. As the chemical synthesis of the extensin hydrophilic motif 1 a , which possesses three distinct linkages that connect four oligoAraf residues [Hyp(l -Araf_n) (n=4, 3, 1)], was achieved previously, we precisely monitored the step-wise enzymatic cleavage of 1 a in addition to that of potato lectin. The results unequivocally revealed that this enzyme specifically degrades the Hyp(l -Araf₁) motif.     

Impact of Narrowing Density of States in Semiconducting Polymers on Performance of Organic Field-Effect Transistors

To improve the performance of organic field-effect transistors (OFETs) employing π-conjugated polymers, a basic understanding of the relationships between the material properties and device characteristics is crucial. Although the density of states (DOS) distribution is one of the essential material properties of semiconducting polymers, insights into how the DOS shape affects the mobility (µ), subthreshold swing (S), and contact resistance (R_C) in OFETs remain lacking. In this study, by combining sensitive DOS measurements and multilayered OFET structures, it is experimentally demonstrated that narrower DOS widths in the polymer channels lead to higher µ, smaller S, and lower R_C. By contrast, variation of the DOS in the bulk layer does not affect the performance. These results demonstrate a direct relationship between the polymer properties and OFET performance and highlight the importance of controlling the DOS width in π-conjugated polymers.     

The effects of engine oil additives on valve train wear

Preventing valve train wear in automotive engines is one of the most important properties of an engine oil. However, the influence of engine oil additives on valve train wear has not been sufficiently clarified. In this investigation, the antiwear performance of additives (such as ashless dispersants, metallic detergents and zinc dithiophosphate - ZDTP) and the influence of the interaction of the additives were evaluated. Secondly, metallic detergents were considered. An overbased calcium sulphonate and an overbased phenate were found to have good anti-scuffing performance when evaluated in engine tests and in Falex wear tests. However, from the results of four-ball tests, these additives did not appear to have many extreme pressure properties. From surface analyses, it was determined that a calcium carbonate film was formed on the sliding surface of the Falex test piece, and this film provided good protection against wear. Finally, the interaction of ZDTP, succinimides and calcium detergents and their influence on valve train wear were studied. The decomosition temperature of ZDTP increased with certain additives. including the succinimide. As a result, scuffing was more prone, at temperatures below those increased temperatures. Also, changes in additive concentration on the sliding surface, due to competitive adsorption, altered the antiwear performance of the oil.