Densi-melting effect for ultra-precision laser beam figuring with clustered overlapping technology at full-spatial-frequency.

Laser beam figuring (LBF), as a processing technology for ultra-precision figuring, is expected to be a key technology for further improving optics performance. To the best of our knowledge, we firstly demonstrated CO2 LBF for full-spatial-frequency error convergence at negligible stress. We found that controlling the subsidence and surface smoothing caused by material densification and melt under specific parameters range is an effective way to ensure both form error and roughness. Besides, an innovative "densi-melting" effect is further proposed to reveal the physical mechanism and guide the nano-precision figuring control, and the simulated results at different pulse durations fit well with the experiment results. Plus, to suppress the laser scanning ripples (mid-spatial-frequency (MSF) error) and reduce the control data volume, a clustered overlapping processing technology is proposed, where the laser processing in each sub-region is regarded as tool influence function (TIF). Through the overlapping control of TIF figuring depth, we achieved LBF experiments for the form error root mean square (RMS) reduced from 0.009λ to 0.003λ (λ=632.8 nm) without destroying microscale roughness (0.447 nm to 0.453 nm) and nanoscale roughness (0.290 nm to 0.269 nm). The establishment of the densi-melting effect and the clustered overlapping processing technology prove that LBF provides a new high-precision, low-cost manufacturing method for optics.

Fourier convolution-parallel neural network framework with library matching for multi-tool processing decision-making in optical fabrication.

Intelligent manufacturing of ultra-precision optical surfaces is urgently desired but rather difficult to achieve due to the complex physical interactions involved. The development of data-oriented neural networks provides a new pathway, but existing networks cannot be adapted for optical fabrication with a high number of feature dimensions and a small specific dataset. In this Letter, for the first time to the best of our knowledge, a novel Fourier convolution-parallel neural network (FCPNN) framework with library matching was proposed to realize multi-tool processing decision-making, including basically all combination processing parameters (tool size and material, slurry type and removal rate). The number of feature dimensions required to achieve supervised learning with a hundred-level dataset is reduced by 3-5 orders of magnitude. Under the guidance of the proposed network model, a 260 mm × 260 mm off-axis parabolic (OAP) fused silica mirror successfully achieved error convergence after a multi-process involving grinding, figuring, and smoothing. The peak valley (PV) of the form error for the OAP fused silica mirror decreased from 15.153λ to 0.42λ and the root mean square (RMS) decreased from 2.944λ to 0.064λ in only 25.34 hours. This network framework has the potential to push the intelligence level of optical manufacturing to a new extreme.

Transcription factors in the development of inner ear hair cells.

Inner ear hair cells are the sensory receptors that detect and convert sound vibrations and head movements into neural signals. However, in humans, these cells are unable to regenerate if they are damaged or lost. Over thepast decade,there has been an exponential increase in interest and progress in understanding of the development of the inner ear and of hair cells, aiming to gain insights into hair cell repair or even regeneration. In hair cell development, various transcription factors have been found to be involved in the processes of hair cell proliferation, differentiation and survival. Among these transcription factors, Math1, Gata3, Sox2 and Atoh1 have been highlighted for their crucial role in the fate of hair cells. In this article, we will summarize the current understanding of the role of transcription factors in hair cell development, focusing on the role and possible mechanisms of Math1, Gata3, Sox2 and Atoh1.

Pharyngeal wall floppiness: a novel technique to detect upper airway collapsibility in patients with OSAS.

OBJECTIVE: To measure pharyngeal wall floppiness (PWF) under different pressures, a novel method and technique were introduced in the present study. STUDY DESIGN: A prospective clinical study. SUBJECTS AND METHODS: Forty-seven healthy subjects (32 male; mean age, 37.9 years) and 49 patients with obstructive sleep apnea syndrome (OSAS) (46 male; mean age, 41.45 years) were recruited. The pharyngeal cavity volume was measured by acoustic reflection under positive (10 cm H2O) and negative (-10 cm H2O) pressures. The pharyngeal cavity volume was detected from the segment of 10 to 20 cm from the incisor. Moreover, PWF was calculated from the difference of pharyngeal cavity volumes under positive and negative pressures divided by the sum of the volumes under positive and negative pressures. The measurements were conducted on a group of 7 subjects weekly over 3 consecutive weeks to evaluate test-retest variability. RESULTS: The mean PWF was 0.19 ± 0.11 in healthy subjects and 0.24 ± 0.07 in the OSAS group, with a significant difference (P < .01). There was moderate positive correlation between PWF and age or body mass index in healthy subjects. In the 7 subjects, the mean measured interclass correlation coefficient was 0.9 (P < .05) in 3 consecutive weekly measurements. CONCLUSION: The OSAS population had greater PWF compared to healthy subjects. The age dependency of PWF in healthy subjects implied which might play important roles in the development of OSAS. This noninvasive and reproducible technique might be a useful tool in OSAS clinical applications.

[Hyperfine structure study of binary sodium phosphates by Raman spectroscopy].

Quantum chemistry ab initio calculation was applied to study the hyperfine structure of binary sodium phosphates. A series of phosphate model clusters were designed to simulate the microstructure of phosphates with different components. Closed-shell Hatree-Fock method (RHF) and the basis sets of 6-31G (d, p) were employed to optimize structures and calculate Raman frequencies of these phosphate model clusters. SIT (stress index of tetrahedron), which was well used in the study of silicate microstructures, had been adjusted before it was introduced to describe the microstructure of binary sodium phosphates. It was suggested that SIT of phosphates has good relationship with the Raman shift of the corresponding structures, which means SIT could also be used to study the hyperfine structure of binary sodium phosphates. Raman spectra of both solid and molten Na5P3O10 were determined in the range of room temperature to 1 473 K. A phase transition between 873 and 1 073 K was observed, and the main peaks of Na5P3O10 shifted to a lower frequency with increasing temperature. The microstructure units of Na5P3O10 crystal are the types of Q1(2) and Q2(11) with a ratio of 2 : 1. With the increase in the temperature, various new microstructure units including Q0 , Q1(1), Q1(2), Q2(11), Q2(12) and Q2(22) appeared while Na5 P3 O10 was heated above the melting point, which led to the broadening and asymmetry of Raman spectra of molten Na5P3O10. It came to an understanding that the microstructure units of phosphates may change at different temperature, especially above the melting points. The introduction of SIT and hyperfine structure could help analyze the Raman spectra of phosphates both qualitatively and quantitatively.

[Raman spectroscopic study of binary PbO-TeO2 glasses].

Raman spectra of lead tellurite glasses and their melts were measured. Results show that four coordinate tellurite units convert into three coordinate units with increasing the concentration of PbO, and the number of non-bridging oxygen bonds (NBO) increases accordingly in this system. Three spectral peaks in the high frequency range were assigned to stretching vibration of bridging oxygen in four coordinate tellurite units (Q(b)), stretching vibration of non-bridging oxygen in four coordinate tellurite units (Q(nb)) and in three coordinate tellurite units (T(nb)). The relative density of four coordinate structure units decreases and the three coordinate tellurite units considerably exist in tellurite glasses when the concentration of PbO > 50%. Besides, the Raman frequencies of the three species' peaks become blue-shifted because of the temperature induced crystallization at high temperature, and the peak intensities increase and the peaks sharpen. The peaks merge together and become much broader while the glass is heated above the melting point because of multiple microstructure units coexisting.

[Ab initio calculation of hyperfine structure and Raman spectra of binary alkali metal silicates].

Ab initio calculation method of quantum chemistry was used to optimize several typical binary alkali metals silicates model clusters under restricted Hartree-Fock method with 6-31G(d) basis sets. The symmetric stretching vibrational frequency of non-bridging oxygen in the high frequency range, its Raman optical activity (ROA) and the influence of different cations of those model clusters were also calculated and evaluated with the concept of hyperfine micro-structure. It was shown that the symmetric stretching vibrational frequency of non-bridging oxygen in the high frequency range is related closely to the environmental hyperfine micro-structure, and ROA enhancement of Q3 species occurs as Q4 species is its nearest neighbor. It can be inferred that the Raman scattering properties of silicates might be predominantly determined by hyperfine micro-structure instead of crude SiO4 tetrahedron as primary micro-structure. It was found that large cation can enhance ROA of the symmetric stretching vibration of non-bridging oxygen by charge transfer mechanism, while ROA weakening effect can be expected on small model clusters due to the excessive charge transfer.

[Analysis of different methods for denoising of high temperature Raman spectra].

Combined with time accumulated resolution and space resolution the SU-HTRS(T/S) set has been realized at Shanghai University. It is impossible to avoid noise at high temperature, so different mathematic methods, such as Savitzky-Golay method, FFT and wavelet methods have been adopted for denoising. For various noise levels, the effects of three methods on the peak location, intensity and covering area as well as the smoothing degree of the reduced spectra were analyzed. It can be concluded that Savitzky-Golay method is simple and quick, while wavelet method offers the best results in denoising process.

[Structure and Raman spectra of titanium oxides].

Under the first-principle density functional theory, structures of several titanium oxides (TiO, Ti2O3, Ti3O5, anatase and rutile) were optimized, and the obtained the structure parameter that coincides with the X-ray crystal diffraction result. The optimized structure parameters coincide well with those obtained by X-ray diffraction method. Molecular vibrational modes were also studied and assigned. Double Numeric including D-polarization function basis set was used with local density approximation, and the local exchange-correlation energy was described with Vosko-Wilk-Nusair and spin non-restricted function. The calculated vibrational wavenumbers were used to interpret observed experimental Raman spectra of those titanium oxides. By comparing the Raman spectra of those titanium oxides with the calculated results, the characteristic peaks of various titanium oxides could be assigned. So the types of titanium oxides could be diagnosed and recognized. This will help to investigate the correlation between the structure and property of materials.

[High temperature Raman spectroscopy techniques and its applications].

Based on the frequency and time domain characters of heat radiation, high temperature Raman spectroscopy techniques were aralyzed and summarized. Thereby, two high temperature Raman systems were set up. One is an accumulated time-resolved macro-Raman spectroscopy system, and the other is an accumulated time-resolved and confocal coupled micro-Raman spectroscopy system. Finally, their applications in the study of high temperature processes such as melt structure and phase transformation, crystallization as well as samples with high fluorescence were intrtoduced.

[Raman active vibrations of aluminosilicates].

Raman spectra of aluminosilicate minerals, namely kyanite, andalusite, and sillimanite and K2O-Al2O3-SiO2 glasses were recorded. Four alumino-silicon tetrahedral model clusters were calculated by self-consistent (SCF) molecular orbital ab-ini-tio calculation of the quantum chem (QC) method. The result shows a decrease tendency in Raman frequencies in the 800-1200 cm(-1) frequency region with increase in four-coordinated Al content, which is assigned to the Si--Onb symmetry stretching vibrations. The Raman spectra in the 700-800 cm(-1) frequency region is attributed to Al-Onb symmetry stretching vibrations.

[Raman spectra study of tellurium dioxide (TeO2) crystal].

The room temperature and high temperature Raman spectra of solid/melt growth boundary layers of TeO2 grown from melt were measured by high-temperature laser-micro-Raman spectrum. By analyzing, vibrational modes of the room temperature Raman spectra peaks of TeO2 crystal from band 200-800 cm-1 were confirmed, the expansion and frequency shift of each peak of the high temperature Raman spectra were interpreted and the possible structure group of the melt was proposed. So, certain foundation for studying the growth theory of functional crystal materials was provided.

[Raman spectroscopic study of silicon-oxygen tetrahedrons microstructure in x CaSiO3.LiBO2 solid solutions].

Raman spectra of xCaSiO3.LiBO2 (by weight ratio, x = 0, 0.25, 0.33, 0.50) crystals were measured. The microstructure of different silicon-oxygen tetrahedrons and their abundant variations with silica contents were studied. It shows that all the silicon-oxygen tetrahedrons are isolated by Si-Ob-B bondings or free SiO4(4-). No evidence suggests that there exist considerable Si-Ob-Si bondings. The abundance of Q2, Q4 species increases with the increasing silica content, there exists barely Q3 species even at high silica content. And the sum of integrated Raman peaks for all Qi species are linearly correlated with silica concentration in crystal, which offers the possibility to analysis silica in minerals, slags, glasses and soil samples directly.