Revealing true coupling strengths in two-dimensional spectroscopy with sparsity-based signal recovery

Analysis of complex multidimensional optical spectra by linear prediction

We apply Linear Prediction from Singular Value Decomposition (LPSVD) to two-dimensional complex optical data in the time-domain to generate spectra with advantages over discrete Fourier transformation (DFT). LPSVD is a non-iterative procedure that fits time-domain complex data to the sum of damped sinusoids, or Lorentzian peaks in the spectral domain. Because the fitting is linear, it is not necessary to give initial guess parameters as in nonlinear fits. Although LPSVD is a one-dimensional algorithm, it can be performed column-wise on two-dimensional data. The method has been extensively used in 2D NMR spectroscopy, where spectral peaks are typically nearly ideal Lorentzians, but to our knowledge has not been applied in the analogous optical technique, where peaks can be far from Lorentzian. We apply LPSVD to the analysis of zero, one, and two quantum electronic two-dimensional spectra from a semiconductor microcavity. The spectra consist of non-ideal, often overlapping peaks. We find that LPSVD achieves a very good fit even on non-ideal data. It reduces noise and eliminates discrete distortions inherent in the DFT. We also use it to isolate and analyze weak features of interest.

3D Printing in Cranioplasty for Giant Cranial Deformity with Multi-Dimensional Nuclear Magnetic Simulation

This article is based on 3D printing technology, through multi-dimensional nuclear magnetic stimulation to the in-depth study of the application of plastic surgery in patients with giant cranial deformity cranial reduction, first of all, patients with CT scan of the brain, based on CT data for 3D reconstruction, 3D geometric modeling, using 3D printing Prepare multiple skull 1:1 scale, solid models, perform surgical planning and drills, determine the surgical plan (related parameters such as surgical time, cranial cavity volume, frontal plane ratio, anterior-posterior diameter, left-right diameter, head-to-height ratio, etc.), it can increase the patient’s speed and stride, and complete a variety of material tests. The 3D printing group had lower pain VAS scores at 1 h and 24 h after surgery than the traditional data group. The same data observed from different dimensions may yield different results, but also enable people to understand the nature of things more comprehensively and clearly. It was statistically significant (P < 0.05). The postoperative swelling of the 3D printing group was less than that of the customary group, and the difference was statistically significant (P < 0.05). Through 12 months of follow up observation, the power of 3D printing is higher than that of the habitual group, and the difference is statistically significant (P < 0.05). This technology has an important guiding significance in future related treatment technology.

Full molecular dynamics simulations of molecular liquids for single-beam spectrally controlled two-dimensional Raman spectroscopy

Single-beam spectrally controlled (SBSC) two-dimensional (2D) Raman spectroscopy is a unique 2D vibrational measurement technique utilizing trains of short pulses that are generated from a single broadband pulse by pulse shaping. This approach overcomes the difficulty of 2D Raman spectroscopy in dealing with small-signal extraction and avoids complicated low-order cascading effects, thus providing a new possibility for measuring the intramolecular and intermolecular modes of molecular liquids using fifth-order 2D Raman spectroscopy. Recently, for quantitatively investigating the mode-mode coupling mechanism, Hurwitz et al. [Opt. Express 28, 3803 (2020)] have developed a new pulse design for this measurement to separate the contributions of the fifth- and third-order polarizations, which are often overlapped in the original single-beam measurements. Here, we describe a method for simulating these original measurements and the new 2D Raman measurements on the basis of a second-order response function approach. We carry out full molecular dynamics simulations for carbon tetrachloride and liquid water using an equilibrium-nonequilibrium hybrid algorithm, with the aim of explaining the key features of the SBSC 2D Raman spectroscopic method from a theoretical point of view. The predicted signal profiles and intensities provide valuable information that can be applied to 2D spectroscopy experiments, allowing them to be carried out more efficiently.

Single beam low frequency 2D Raman spectroscopy

Low frequency Raman spectroscopy resolves the slow vibrations resulting from collective motions of molecular structures. This frequency region is extremely challenging to access via other multidimensional methods such as 2D-IR. In this paper, we describe a new scheme which measures 2D Raman spectra in the low frequency regime. We separate the pulse into a spectrally shaped pump and a transform-limited probe, which can be distinguished by their polarization states. Low frequency 2D Raman spectra in liquid tetrabromoethane are presented, revealing coupling dynamics at frequencies as low as 115 cm^-1. The experimental results are supported by numerical simulations which replicate the key features of the measurement. This method opens the door for the deeper exploration of vibrational energy surfaces in complex molecular structures.