Resting CD4؉ T cells are the best-defined reservoir of latent human immunodeficiency virus type 1 (HIV-1) infection, but how the reservoir is formed is unclear. Understanding how the reservoir of latently infected cells forms is critical because it is a major barrier to curing HIV infection.

A newly developed self-modeling curve resolution method, band-target entropy minimization (BTEM), is described. This method starts with the data decomposition of a set of spectroscopic mixture data using singular value decomposition. It is followed by the transformation of the orthonormal basis vectors/loading vectors into individual pure component spectra one at a time. The transformation is based in part on some seminal ideas borrowed from information entropy theory with the desire to maximize the simplicity of the recovered pure component spectrum. Thus, the proper estimate is obtained via minimization of the proposed information entropy function or via minimization of derivative and area of the spectral estimate. Nonnegativity constraints are also imposed on the recovered pure component spectral estimate and its corresponding concentrations. As its name suggests, in this method, one targets a spectral feature readily observed in loading vectors to retain, and then combinations of the loading vectors are searched to achieve the global minimum value of an appropriate objective function. The major advantage of this method is its one spectrum at a time approach and its capability of recovering minor components having low spectroscopic signals. To illustrate the application of BTEM, spectral resolution was performed on FT-IR measurements of very highly overlapping mixture spectra containing six organic species with a two-component background interference (air). BTEM estimates were also compared with the estimates obtained using other self-modeling curve resolution techniques, i.e., SIMPLISMA, IPCA, OPA-ALS, and SIMPLISMA-ALS.

In the preceding paper in this issue, the concept of band-target entropy minimization (BTEM) was introduced, and it was successfully applied to spectral reconstruction from a stoichiometric organometallic reaction system after spectral preconditioning. In this contribution, the BTEM algorithm is reapplied to semi-batch homogeneous catalytic reactions without spectral preconditioning. The homogeneous catalytic hydroformylation of 3,3-dimethylbut-1-ene, starting with Rh4(σ-CO)9(μ-CO)3 as catalyst precursor in n-hexane as solvent, was studied at 298 K and variable total pressure, using high pressure in situ infrared spectroscopy as the analytical tool. The non-preconditioned data were then subjected to BTEM in order to recover the pure component spectra of the species present. The pure component spectra of background moisture and carbon dioxide, hexane, dissolved CO in hexane, and the dissolved species present, namely the organic reactant 3,3-dimethylbut-1-ene, the organic product 4,4-dimethylpentanal, the catalyst precursor Rh4(σ-CO)9(μ-CO)3, the observable organometallic intermediate RCORh(CO)4, and Rh6(CO)16, were all readily recovered. An unexpected finding was a very well resolved spectrum with two terminal CO vibrations centered at 2068 and 2076 cm-1 (almost exactly overlapping with Rh4(σ-CO)9(μ-CO)3, but without bridging carbonyls). With reasonable certainty we are assigning this new spectrum to the previously unknown complex Rh4(σ-CO)12. The results indicate that spectral reconstruction, using no libraries and no a priori information, is indeed possible from semi-batch runs. This finding holds promise for rapid and cost-effective spectroscopic system identification of reactive organometallic and homogeneous catalytic systems.

The chemical nature of the organic cations governs the optoelectronic properties of two-dimensional organic-inorganic perovskites. But its mechanism is not fully understood. Here, we apply femtosecond broadband sum frequency generation vibrational spectroscopy to investigate the molecular conformation of spacer organic cations in two-dimensional organic-inorganic perovskite films and establish a correlation among the conformation of the organic cations, the charge carrier mobility, and broadband emission. Our study indicates that both the mobility and broadband emission show strong dependence on the molecular conformational order of organic cations. The gauche defect and local chain distortion of organic cations are the structural origin of the in-plane mobility reduction and broad emission in two-dimensional organic-inorganic perovskites. Both of the interlayer distance and the conformational order of the organic cations affect the out-of-plane mobility. This work provides molecular-level understanding of the conformation of organic cations in optimizing the optoelectronic properties of two-dimensional organic-inorganic perovskites.

Keywords: Phosphorus / Tautomerism / NMR spectroscopy / IR spectroscopy The tautomeric behaviour of five secondary phosphane oxides (SPOs) with different electronic properties has been investigated by NMR and IR spectroscopy, density functional theory calculations and X-ray structural analysis. Proof is given that only with strong electron-withdrawing groups on the phosphorus atom can the relevant trivalent phosphinous