Point-of-care lung ultrasound in the diagnosis of childhood pneumonia.

Introduction: Lung ultrasound is emerging as a rapid, simple and safe alternative for diagnosing pneumonia since it has a higher sensitivity than X-rays and lower radiation exposure than computerized tomography. This is a prospective observational study done at a tertiary care centre in Chennai to study the diagnostic utility of lung ultrasound in pneumonia.

Methods: Children aged 1 month to 12 years who were admitted to the hospital with complaints of cough, fever and/or breathing difficulty and on examination had tachypnea and/or chest indrawing were included in the study.

Lattice dynamics and vibrational properties of scheelite-type alkali-metal perrhenates.

The present work provides insight into the structural, vibrational, and elastic properties of scheelite-type alkali-metal perrhenates AReO(= Na, K, Rb, and Cs) via first-principles calculations. Sodium, potassium, and rubidium perrhenates are isostructural and crystallize in a tetragonal structure, whereas cesium perrhenate crystallizes in an orthorhombic structure. All the phonon frequencies and their corresponding mode assignments were estimated through the linear response method within density-functional-perturbation theory.

Evidences for local non-centrosymmetricity and strong phonon anomaly in EuCuAs: a Raman spectroscopy and lattice dynamics study.

Phonon modes and their association with the electronic states have been investigated for the metallic EuCuAssystem. In this work, we present the Raman spectra of this pnictide system which clearly shows the presence of seven well defined peaks above 100 cmthat is consistent with the locally non-centrosymmetriccrystal structure, contrary to that what is expected from the accepted symmorphicstructure. Lattice dynamics calculations using thesymmetry attest that there is a commendable agreement between the calculated phonon spectra at the Γ point and the observed Raman mode frequencies, with the most intense peak at∼232 cmbeing ascribed to the A1gmode.

Ferroelectric polymorphic phenomena in the layered antiferromagnet Cu(OH).

Ferroic orders and their associated structural phase transitions are paramount in the understanding of a multitude of unconventional condensed matter phenomena. On this note, our investigation focuses on the polymorphic ferroelectric (FE) phase transitions of Copper(II) hydroxide, Cu(OH), considering an antiferromagnetic ground state. By employing the first-principles studies and group theory analysis, we have provided a systematic theoretical investigation of vibrational properties in the hypotheticalhigh-symmetry phase to unveil the symmetry-allowed ferroic phases.

Deep Earth Chronicles: High-Pressure Investigation of Phenakite Mineral BeSiO.

Beryllium silicate, recognized as the mineral phenakite (BeSiO), is a prevalent constituent in Earth's upper mantle. This study employs density-functional theory (DFT) calculations to explore the structural, mechanical, dynamical, thermodynamic, and electronic characteristics of this compound under both ambient and high-pressure conditions. Under ideal conditions, the DFT calculations align closely with experimental findings, confirming the mechanical and dynamical stability of the crystalline structure.

Understanding the Re-entrant Phase Transition in a Non-magnetic Scheelite.

The stereochemical activity of lone pair electrons plays a central role in determining the structural and electronic properties of both chemically simple materials such as HO, as well as more complex condensed phases such as photocatalysts or thermoelectrics. TlReO is a rare example of a non-magnetic material exhibiting a re-entrant phase transition and emphanitic behavior in the long-range structure. Here, we describe the role of the Tl 6s lone pair electrons in these unusual phase transitions and illustrate its tunability by chemical doping, which has broad implications for functional materials containing lone pair bearing cations.

Lattice dynamics across the ferroelastic phase transition in BaZnTeO: a Raman and first-principles study.

Structural phase transitions drive several unconventional phenomena including some illustrious ferroic attributes which are relevant for technological advancements. On this note, we have investigated the ferroelastic structural transition of perovskite-type trigonal BaZnTeO across ∼ 150 K. With the help of Raman spectroscopy and density-functional theory (DFT)-based calculations, we report new intriguing observations associated with the phase transition in BaZnTeO.

Electronic structure, phonons and optical properties of baryte type scintillators TlXO(XCl, Br).

This article thoroughly addresses the structural, mechanical, vibrational, electronic band structure and the optical properties of the unexplored thallous perchlorate and perbromate fromcalculations. The zone centered vibrational phonon frequencies shows, there is a blue shift in the mid and high frequency range from Cl → Br due to change in mass and force constant with respect to oxygen atom. From the band structure it is clear that the top of the valence band is due to thalliumstates, whereas the bottom of the conduction band is due to halogenand oxygenstates, showing similar magnitude of dispersion and exhibits a charge transfer character.

Anisotropic transport and optical birefringence of triclinic bulk and monolayer NbXY(X = S, Se and Y = Cl, Br, I).

A systematic analysis of the electronic, thermoelectric and optical properties of triclinic van der Waal's solids NbXY(X = S, Se and Y = Cl, Br, I) is carried out within the framework of density functional theory for bulk and monolayer. The investigated compounds are semiconductors in bulk and monolayer, with band gap values ranging from 1.1 to 1.

Time-Domain Terahertz Spectroscopy and Density Functional Theory Studies of Nitro/Nitrogen-Rich Aryl-Tetrazole Derivatives.

The paper reports the time-domain THz spectroscopy studies of noncentrosymmetric energetic nitro/nitrogen-rich aryl-tetrazole high-energy molecules. The fingerprint spectra in the THz domain reveal the role of different functional groups attached to position "1" of the tetrazole moiety, which controls the energetic properties. These responses are deliberated through density functional theory (DFT) calculations.

High-Pressure Studies of Hydrogen-Bonded Energetic Material 3,6-Dihydrazino--tetrazine Using DFT.

Hydrogen bonding is an important noncovalent interaction that plays a key role in most of the CHNO-based energetic materials, which has a great impact on the structural, stability, and vibrational properties. By analyzing the structural changes, IR spectra, and the Hirshfeld surfaces, we investigated the high-pressure behavior of 3,6-dihydrazino--tetrazine (DHT) to provide detailed description of hydrogen bonding interactions using dispersion-corrected density functional theory. The strengthening of hydrogen bonding is observed by the pressure-induced weakening of covalent N-H bonds, which is consistent with the red shift of NH/NH stretching vibrational modes.

Structure-property correlation studies of alkaline-earth metal-azides M(N) (M = Sr, Ba).

Inorganic metal azides M(N) (M  =  Sr, Ba) and metal nitrates M(NO) (M  =  Sr, Ba) are interesting materials due to their wide range of industrial usefulness as gas generators, pyrotechnics, photo graphic materials and explosives. In this work, we explore the mechanical, vibrational (infrared, phonon dispersion), Born effective charge (BEC) and thermodynamic properties of these materials to understand the sensitivity correlation studies using plane wave pseudopotential method. As these materials are layered with crucial non bonding interactions, the generalized gradient approximation with Tkatchenko-Scheffler (for Sr(N)) and Ortmann-Bechstedt-Schmidt (for Ba(N)) dispersion correction methods are adopted to compute accurate ground state properties with norm-conserving pseudopotentials.

Ti-fraction-induced electronic and magnetic transformations in titanium oxide films.

Titanium dioxide has been widely used in modern industrial applications, especially as an effective photocatalyst. Recently, freestanding TiO films with a markedly reduced bandgap of ∼1.8 eV have been synthesized, indicating that the dimension has a considerable influence on the bulk band gap (>∼3 eV) and enhances the adsorption range of visible light.

Structure evolution of chromium-doped boron clusters: toward the formation of endohedral boron cages.

The electron-deficient nature of boron endows isolated boron clusters with a variety of interesting structural and bonding properties that can be further enriched through metal doping. In the current work, we report the structural and electronic properties of a series of chromium-doped boron clusters. The global minimum structures for CrB clusters with an even number of ranging from 8 to 22 are proposed through extensive first-principles swarm-intelligence structure searches.