Observation of spider silk by femtosecond pulse laser second harmonic generation microscopy

An asymmetric β-sheet structure of spider silk is said to induce optical second harmonic generation. In this paper, using an in-house nonscanning type femtosecond pulse laser second harmonic generation microscope, we characterized the behavior of the β-sheet of spider silk under an applied external force. The orientation of the β-sheets was more unidirectional when the silk was extended. One of the origins of the high mechanical strength of the dragline is suggested to be the physical arrangement of its β-sheets.     

NiII,PdII Complexes with Pyrene‐based Thiosemicarbazones: Syntheses,Molecular Structures,and Excimeric Emissions

A series of Ni^II and Pd^II complexes with pyrene‐based thiosemicarbazones were conveniently prepared. The crystal structures of Ni(L²)₂ , Pd(L¹)₂ , and Pd(L²) ₂ were determined. X‐ray crystallographic analysis reveals that the complexes are of mononuclear structure with two pyrenyl rings cofacially aligned. The photoluminescence spectra of the complexes exhibit moderate characteristic excimeric emissions arising from intramolecular π–π stacking between pyrenyl rings.     

Iterative Regularization Methods for the Multiple-Sets Split Feasibility Problem in Hilbert Spaces

In this paper, we introduce iterative regularization methods for solving the multiple-sets split feasibility problem, that is to find a point closest to a family of closed convex subsets in one space such that its image under a bounded linear mapping will be closest to another family of closed convex subsets in the image space. We consider the cases, when the families are either finite or infinite. We also give two numerical examples for illustrating our main method.

     

Sum frequency generation study of immobilized 3-aminopropyltriethoxysilane self-assembled layer on Si(111) substrates

Distribution and orientation of 3-aminopropyltriethoxysilane (APTES) on a sensing surface play critical role on biosensor, but have not been fully investigated. In this work, the quality of APTES SAM immobilized on the Si(111) substrate was studied by observing sum frequency generation (SFG) response. The polarization, azimuthal angle, and position-dependent SFG spectra of APTES coverage were obtained. In ppp and psp-SFG spectra, the CH₂ and CH₃ vibrational and NH stretching modes were clearly seen around 3000 cm⁻¹ and around 3300 cm⁻¹ regions, respectively. The spp and ssp-SFG spectra presented too weak signals that the vibrational regions were not clear. The positional and azimuthal angle dependence of the SFG spectra was observed from 0^o to 360^o with the step of 45^o rotation around the surface normal. The 0° is defined as the [ ] direction of Si(111) crystal lying in the incident plane and opposite to the incident k vectors. The appearance of the NH mode was observed to be strongly dependent on the position. The results indicate that the distribution and orientation of APTES molecules were not well ordered on the Si surfaces, suggesting that SFG is an efficient method to check the quality of APTES coverage immobilized on substrates.     

A Quaternary Code Correcting a Burst of at Most Two Deletion or Insertion Errors in DNA Storage

Due to the properties of DNA data storage, the errors that occur in DNA strands make error correction an important and challenging task. In this paper, a new code design of quaternary code suitable for DNA storage is proposed to correct at most two consecutive deletion or insertion errors. The decoding algorithms of the proposed codes are also presented when one and two deletion or insertion errors occur, and it is proved that the proposed code can correct at most two consecutive errors. Moreover, the lower and upper bounds on the cardinality of the proposed quaternary codes are also evaluated, then the redundancy of the proposed code is provided as roughly 2log48n.