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Microfluidic technology provides a solution to the challenge of continuous CaCO$_3$ particle synthesis. In this study, we utilized a 3D-printed microfluidic chip to synthesize CaCO$_3$ micro and nanoparticles in vaterite form. Our primary focus was on investigating a continuous one-phase synthesis method tailored for the crystallization of these particles. By employing a combination of confocal and scanning electron microscopy, along with Raman spectroscopy, we were able to thoroughly evaluate the synthesis efficiency. This evaluation included aspects such as particle size distribution, morphology, and polymorph composition. The results unveiled the existence of two distinct synthesis regimes within the 3D-printed microfluidic chips, featuring a channel cross-section of 2 mm$^2$. In the first regime, characterized by turbulence, particles with an average diameter of around 2 $\mu$m were produced, displaying a broad size distribution. Conversely, the second regime, marked by laminar flow, led to the synthesis of submicron particles (approximately 800-900 nm in diameter) and even nanosized particles (70-80 nm). This research significantly contributes valuable insights to both the understanding and optimization of microfluidic synthesis processes, particularly in achieving controlled production of submicron and nanoscale particles., Comment: 12 pages, 7 figures

We describe the properties of a continuous-wave room-temperature quantum cascade laser operating at the long wavelength of 17 $\mu$m. Long wavelength mid-infrared quantum cascade lasers offer new opportunities for chemical detection, vibrational spectroscopy and metrological measurements using molecular species. In particular, probing low energy vibrational transitions would be beneficial to the spectroscopy of large and complex molecules, reducing intramolecular vibrational energy redistribution which acts as a decoherence channel. By performing linear absorption spectroscopy of the v2 fundamental vibrational mode of N2O molecules, we have demonstrated the spectral range and spectroscopic potential of this laser, and characterized its free-running frequency noise properties. Finally, we also discuss the potential application of this specific laser in an experiment to test fundamental physics with ultra-cold molecules.

We present the study of the decay $J/\psi \rightarrow \rho\pi$. The results are based on of 5.2~million $J/\psi$ events collected by the KEDR detector at the VEPP-4M collider. The branching fractions are measured to be $\B(J/\psi \rightarrow \rho\pi) = \big(2.072\pm 0.017 \pm 0.062 \big)\cdot 10^{-2}$ and $\B(J/\psi \rightarrow \pi^+\pi^-\pi^0) = \big(1.878 \pm 0.013 \pm 0.051 \big)\cdot 10^{-2}$, where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.

We present an experimental study of the turn-on delay in pulsed mid-infrared quantum cascade lasers. We report the unexpectedly long delay time depending on the pumping current, which does not agree with conventional theoretical predictions for step-like excitation. Similar behavior has been observed in InP- and InAs-based QCLs emitting near 8${\mu}$m. Numerical simulations performed using a model based on rate equations for excitation by current pulses with non-zero rise time provide fair agreement with our observations.

Low-temperature heat capacities (Cp) of nanostructured rock salt (rs-ZnO) and wurtzite (w-ZnO) polymorphs of zinc oxide were measured in the 2-315 K temperature range. No significant influence of nanostructuring on Cp of w-ZnO has been observed. The measured Cp of rock salt ZnO is lower than that of wurtzite ZnO below 100 K and is higher above this temperature. Using available thermodynamic data, we established that the equilibrium pressure between nanocrystalline w-ZnO and rs-ZnO is close to 4.6 GPa at 300 K (half as much as the onset pressure of direct phase transformation) and slightly changes with temperature up to 1000 K.

The present work continues a series of the KEDR measurements of the $R$ value that started in 2010 at the VEPP-4M $e^+e^-$ collider. By combining new data with our previous results in this energy range we measured the values of $R_{\text{uds}}$ and $R$ at nine center-of-mass energies between 3.08 and 3.72 GeV. The total accuracy is about or better than $2.6\%$ at most of energy points with a systematic uncertainty of about $1.9\%$. Together with the previous precise $R$ measurement at KEDR in the energy range 1.84-3.05 GeV, it constitutes the most detailed high-precision $R$ measurement near the charmonium production threshold., Comment: arXiv admin note: text overlap with arXiv:1610.02827 and substantial text overlap with arXiv:1510.02667

The product of the electronic width of the $\psi(2S)$ meson and the branching fraction of its decay to the muon pair was measured in the $e^{+}e^{-} \to \psi(2S) \to \mu^{+}\mu^{-}$ process using nine data sets corresponding to an integrated luminosity of about 6.5 pb$^{-1}$ collected with the KEDR detector at the VEPP-4M electron-positron collider: \[ \Gamma_{ee}\times\mathcal{B}_{\mu\mu} = 19.3 \pm 0.3 \pm 0.5 ~\text{eV}. \] Adding the previous KEDR results on hadronic and leptonic channels, the values of the $\psi(2S)$ electronic width were obtained under two assumptions: either with the assumption of lepton universality \[ \Gamma_{ee} = 2.279 \pm 0.015 \pm 0.042 ~\text{keV} \] or without it, summing up hadronic and three independent leptonic channels: \[ \Gamma_{ee} = 2.282 \pm 0.015 \pm 0.042 ~\text{keV}. \]

We propose an experiment to search for a new gauge boson A' in $e^+e^-$ annihilation by means of a positron beam incident on a gas hydrogen target internal to the bypass at the VEPP-3 storage ring. The search method is based on a missing mass spectra in the reaction $e^+e^-\rightarrow \gamma$ A'. It allows observation of the A' signal independently of its decay modes and life time. The projected result of this experiment corresponds to an upper limit on the square of the coupling constant $\varepsilon^2=3\cdot 10^{-8}$ with a signal-to-noise ratio of two to one at an A' mass of 5-20 MeV., Comment: 20 pages, 17 figures

The enthalpies of dissolution of metastable rock salt and thermodynamically stable wurtzite polymorphs of zinc oxide in aqueous H2SO4 have been measured in direct calorimetric experiments at 303 K and 0.1 MPa and the obtained results enabled determination of the standard enthalpy of the rock salt-to-wurtzite phase transition in ZnO, {\Delta}trH = -11.7+/-0.3 kJ/mol.

Very recently Leitner et al. [Thermochimica Acta 572 (2013) 1-5] have tried to extract the thermodynamic data of rock-salt ZnO from ab initio and experimental data available in the literature. In this Comment we show that neglecting (i) the strongly pronounced kinetic features of the pressure-induced phase transition in ZnO at room temperature and (ii) results of calorimetric measurements available in the literature [Russ. Chem. Bull. 59 (2010) 325-328] makes the proposed set of thermodynamic functions completely incorrect., Comment: This Comment on the paper published in Thermochimica Acta was deemed unpublishable because "it is out of the scope for Thermochimica Acta" (Editor's decision of 4 November 2013)

Lattice parameter of metastable high-pressure phase of zinc oxide, rock-salt ZnO was measured in the 10-300 K temperature range using synchrotron X-ray powder diffraction. No phase transition was observed down to 10 K. The lattice parameter of rock-salt ZnO was found to increase from 4.266 {\AA} in the 10-80 K range up to 4.2752(3) {\AA} at 298 K, while the volume thermal expansion coefficient increases from slight negative values below 40 K up to 4.77\times10^-5 K^-1 at 298 K., Comment: 4 pages, 3 figures, 1 table

A signature of the scattering between microcavity polaritons and longitudinal optical phonons has been observed in the electroluminescence spectrum of an intersubband device operating in the light-matter strong coupling regime. By electrical pumping we resonantly populate the upper polariton branch at different energies as a function of the applied bias. The electroluminescent signal arising from these states is seconded by a phonon replica from the lower branch.

Luminescence spectra of NiO have been investigated under vacuum ultraviolet (VUV) and soft X-ray (XUV) excitation. Photoluminescence (PL) spectra show broad emission bands centered at about 2.3 and 3.2 eV. The PL excitation (PLE) spectral evolution and lifetime measurements reveal that two mechanisms with short and long decay times, attributed to the d($e_g$)-d($e_g$) and p($\pi$)-d charge transfer (CT) transitions in the range 4-6\,eV, respectively, are responsible for the observed emissions, while the most intensive p($\sigma$)-d CT transition at 7\,eV appears to be a weak if any PL excitation mechanism. The PLE spectra recorded in the 4-7\,eV range agree with the RIXS and reflectance data. Making use of the XUV excitation allows us to avoid the predominant role of the surface effects in luminescence and reveal bulk luminescence with puzzling well isolated doublet of very narrow lines with close energies near 3.3\,eV characteristic for recombination transitions in self-trapped \emph{d}-\emph{d} CT excitons formed by coupled Jahn-Teller Ni$^+$ and Ni$^{3+}$ centers. This conclusion is supported both by a comparative analysis of the luminescence spectra for NiO and solid solutions Ni$_{x}$Zn$_{1-x}$O, and by a comprehensive cluster model assignement of different \emph{p}-\emph{d} and \emph{d}-\emph{d} CT transitions, their relaxation channels. To the best of our knowledge it is the first observation of the self-trapping for \emph{d}-\emph{d} CT excitons. Our paper shows the time resolved luminescence measurements provide an instructive tool for elucidation of the \emph{p}-\emph{d} and \emph{d}-\emph{d} CT excitations and their relaxation in 3d oxides., Comment: 7 pages, 6 figures

X-ray diffraction with synchrotron radiation has been used for the first time to study chemical interaction in the MnO-ZnO system at 4.8 GPa and temperatures up to 1600 K. Above 750 K, the chemical reaction between MnO and ZnO has been observed that resulted in the formation of rock salt (rs) Mn1-xZnxO solid solutions (0.3 \leq x \leq 0.7). The lattice parameters of these solid solutions have been in situ measured at high pressure as a function of temperature, and corresponding thermal expansion coefficients have been calculated., Comment: 9 pages, 2 figures, 2 tables

X-ray diffraction with synchrotron radiation has been used for the first time to study chemical interaction in the FeO-ZnO system at 4.8 GPa and temperatures up to 1300 K. Above 750 K, the chemical reaction between FeO and ZnO has been observed that resulted in the formation of rock salt (rs) Fe1-xZnxO solid solutions (0.3 \leq x \leq 0.85). The lattice parameters of these solid solutions have been in situ measured as a function of temperature under pressure, and corresponding thermal expansion coefficients have been calculated., Comment: 9 pages, 2 figures, 1 table