High frequency atomic tunneling yields ultralow and glass-like thermal conductivity in chalcogenide single crystals

Crystalline solids exhibiting glass-like thermal conductivity have attracted substantial attention both for fundamental interest and applications such as thermoelectrics. In most crystals, the competition of phonon scattering by anharmonic interactions and crystalline imperfections leads to a non-monotonic trend of thermal conductivity with temperature. Defect-free crystals that exhibit the glassy trend of low thermal conductivity with a monotonic increase with temperature are desirable because they are intrinsically thermally insulating while retaining useful properties of perfect crystals. However, this behavior is rare, and its microscopic origin remains unclear. Here, we report the observation of ultralow and glass-like thermal conductivity in a hexagonal perovskite chalcogenide single crystal, BaTiS₃, despite its highly symmetric and simple primitive cell. Elastic and inelastic scattering measurements reveal the quantum mechanical origin of this unusual trend. A two-level atomic tunneling system exists in a shallow double-well potential of the Ti atom and is of sufficiently high frequency to scatter heat-carrying phonons up to room temperature. While atomic tunneling has been invoked to explain the low-temperature thermal conductivity of solids for decades, our study establishes the presence of sub-THz frequency tunneling systems even in high-quality, electrically insulating single crystals, leading to anomalous transport properties well above cryogenic temperatures

An ontology-based nurse call management system (oNCS) with probabilistic priority assessment

<p>Abstract</p> <p>Background</p> <p>The current, place-oriented nurse call systems are very static. A patient can only make calls with a button which is fixed to a wall of a room. Moreover, the system does not take into account various factors specific to a situation. In the future, there will be an evolution to a mobile button for each patient so that they can walk around freely and still make calls. The system would become person-oriented and the available context information should be taken into account to assign the correct nurse to a call.</p> <p>The aim of this research is (1) the design of a software platform that supports the transition to mobile and wireless nurse call buttons in hospitals and residential care and (2) the design of a sophisticated nurse call algorithm. This algorithm dynamically adapts to the situation at hand by taking the profile information of staff members and patients into account. Additionally, the priority of a call probabilistically depends on the risk factors, assigned to a patient.</p> <p>Methods</p> <p>The <it>ontology-based Nurse Call System (oNCS) </it>was developed as an extension of a <it>Context-Aware Service Platform</it>. An ontology is used to manage the profile information. Rules implement the novel nurse call algorithm that takes all this information into account. Probabilistic reasoning algorithms are designed to determine the priority of a call based on the risk factors of the patient.</p> <p>Results</p> <p>The <it>oNCS </it>system is evaluated through a prototype implementation and simulations, based on a detailed dataset obtained from Ghent University Hospital. The arrival times of nurses at the location of a call, the workload distribution of calls amongst nurses and the assignment of priorities to calls are compared for the <it>oNCS </it><it>system </it>and the current, place-oriented nurse call system. Additionally, the performance of the system is discussed.</p> <p>Conclusions</p> <p>The execution time of the nurse call algorithm is on average 50.333 ms. Moreover, the <it>oNCS system </it>significantly improves the assignment of nurses to calls. Calls generally have a nurse present faster and the workload-distribution amongst the nurses improves.</p

Increasing Sensitivity in Determining Chemical Shifts in One Dimensional Lorentzian NMR Spectra

An algorithm is presented for one-dimensional NMR systems that employs nonlinear, non-Fourier methods to convert noisy time-dependent free induction decay (FID) data to a denoised frequency spectrum that gives reliable chemical shifts and coupling constants when the spectrum is Lorentzian. It is formulated in a way that increases frequency sensitivity and resolution and, for nuclei of low natural abundance, potentially avoids enrichment totally or in part. The algorithm should also be of use in analytical chemistry where enrichment is not possible. In effect, the useful limit of detection is significantly lowered. The algorithm uses new “phasing” and “feature stability upon accumulation” methods to reliably separate signal from noise at low signal-to-noise ratios where the Fourier spectrum requires many more transients to be definitive as to what is signal and what is noise. The long-standing problem of “false features” that plagued many prior attempts to employ nonlinear methods is thereby resolved for Lorentzian spectra. Examples are reported, and the limitations of the algorithm are discussed

Structure of Cyclic Nucleoside Phosphonate Ester Prodrugs: An Inquiry

The configuration at phosphorus in cyclic (<i>S</i>)-HPMPC (<b>1</b>, cidofovir) and (<i>S</i>)-HPMPA (<b>2</b>) phenyl ester (<b>5</b> and <b>6</b>, respectively) diastereomers (<b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>5</b>, <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b>, <b>(</b><i><b>S</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b>) was determined by X-ray crystallography and correlated to their ¹H and ³¹P NMR spectra in solution. <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>5</b> and <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b> have chair conformations with the nucleobase substituent equatorial and the P-OPh axial. Perhaps surprisingly, <b>(</b><i><b>S</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b> is (<i>a</i>, <i>a</i>) in the crystal and exists largely as an equilibrium of (<i>a</i>, <i>a</i>)/(<i>e</i>, <i>e</i>) conformers in chloroform or acetonitrile

Structure of Cyclic Nucleoside Phosphonate Ester Prodrugs: An Inquiry

The configuration at phosphorus in cyclic (<i>S</i>)-HPMPC (<b>1</b>, cidofovir) and (<i>S</i>)-HPMPA (<b>2</b>) phenyl ester (<b>5</b> and <b>6</b>, respectively) diastereomers (<b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>5</b>, <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b>, <b>(</b><i><b>S</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b>) was determined by X-ray crystallography and correlated to their ¹H and ³¹P NMR spectra in solution. <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>5</b> and <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b> have chair conformations with the nucleobase substituent equatorial and the P-OPh axial. Perhaps surprisingly, <b>(</b><i><b>S</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b> is (<i>a</i>, <i>a</i>) in the crystal and exists largely as an equilibrium of (<i>a</i>, <i>a</i>)/(<i>e</i>, <i>e</i>) conformers in chloroform or acetonitrile

Structure of Cyclic Nucleoside Phosphonate Ester Prodrugs: An Inquiry

The configuration at phosphorus in cyclic (<i>S</i>)-HPMPC (<b>1</b>, cidofovir) and (<i>S</i>)-HPMPA (<b>2</b>) phenyl ester (<b>5</b> and <b>6</b>, respectively) diastereomers (<b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>5</b>, <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b>, <b>(</b><i><b>S</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b>) was determined by X-ray crystallography and correlated to their ¹H and ³¹P NMR spectra in solution. <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>5</b> and <b>(</b><i><b>R</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b> have chair conformations with the nucleobase substituent equatorial and the P-OPh axial. Perhaps surprisingly, <b>(</b><i><b>S</b></i>_<b>p</b><b>)</b><i><b>-</b></i><b>6</b> is (<i>a</i>, <i>a</i>) in the crystal and exists largely as an equilibrium of (<i>a</i>, <i>a</i>)/(<i>e</i>, <i>e</i>) conformers in chloroform or acetonitrile