Neutron Diffraction Measurements and First Principles Study of Thermal Motion of Atoms in Select M_{n+1}AX_n and Binary MX Transition Metal Carbide Phases

Herein, we compare the thermal vibrations of atoms in select ternary carbides with the formula Mn+1AXn ("MAX phases," M = Ti, Cr; A = Al, Si, Ge; X = C, N) as determined from first principles phonon calculations to those obtained from high-temperature neutron powder diffraction studies. The transition metal carbides TiC, TaC, and WC are also studied to test our methodology on simpler carbides. Good qualitative and quantitative agreement is found between predicted and experimental values for the binary carbides. For all the MAX phases studied - Ti3SiC2, Ti3GeC2, Ti2AlN, Cr2GeC and Ti4AlN3 - density functional theory calculations predict that the A element vibrates with the highest amplitude and does so anisotropically with a higher amplitude within the basal plane, which is in line with earlier results from high-temperature neutron diffraction studies. In some cases, there are quantitative differences in the absolute values between the theoretical and experimental atomic displacement parameters, such as reversal of anisotropy or a systematic offset of temperature-dependent atomic displacement parameters. The mode-dependent Gr\"uneisen parameters are also computed to explore the anharmonicity in the system

Advantages and disadvantages of different nasal CPAP systems in newborns

Objective: To compare three different systems of continuous positive airway pressure (CPAP): the naso-pharyngeal tube and two-prong systems in newborns, focusing on duration of CPAP, side effects and cost. Design: Randomized clinical study. Patients: Between July 2000 and September 2001 newborns were randomized to three different CPAP systems. Forty infants in two weight groups (>2500g and 1250-2500g; 20 patients in each group) were included. Results: In the group >2500g the median duration of CPAP was 1.1days (range 0.25-14.3days). The median time on a naso-pharyngeal CPAP was 1day (range 0.25-14.3days), on Hudson prongs 1.6days (range 0.5-3.3days) and on the Infant Flow system 0.7days (range 0.3-13.6days; p>0.05 for comparison between groups, Fisher's exact test). With naso-pharyngeal CPAP, 2 patients developed moderate nasal injuries. On Hudson, 2 patients developed moderate and three mild nasal injuries. One patient on the Infant Flow showed mild and one moderate nasal injuries. In the weight group 1250-2500g the median duration of CPAP was 1.1days (range 0.1-7.0days). The median time on the naso-pharyngeal tube was 0.9days (range 0.1-7days), on Hudson prongs 1.1days (range 0.7-6.6days) and on the Infant Flow system 1.3days (range 0.25-5.9days; p>0.05 for comparison between groups, Fisher's exact test). With a naso-pharygeal tube, one infant developed mild and one moderate nasal injuries. On Hudson prongs, two had moderate nasal injuries. On Infant Flow, one newborn showed a severe nasal injury and two mild injuries. None of the patients developed a pneumothorax. Conclusion: The naso-pharyngeal tube is an easy, safe and economical CPAP system usable with every common ventilator. For very low birth weight newborns, a prong system may have advantage

Experimental measurement of stress at a four-domain junction in lead zirconate titanate

A junction between two lamellar bands of ferroelectric domains in a lead zirconate titanate (PZT) ceramic is analysed using Kikuchi diffraction patterns in the transmission electron microscope. Indexing of the diffraction patterns allowed the determination of the 3D relative orientation of the 4 different domains at the junction and thus the characterisation of the domain boundaries. The local c/a ratio could also be determined from the misorientations at the domain boundaries. Analysis of the data showed that large stresses were concentrated at the junction, and that this is inevitable at such band junctions. Such stress concentrations could act as nuclei for cracking of the ceramic under additional loading in service, perhaps particularly as a consequence of extended electromechanical cycling. Moreover, the stresses would increase with increasing c/a making the issues all the more serious for Ti-rich compositions having larger c/a ratios

Individualising drug dispensaries in a university hospital

BACKGROUND: In hospitals and other healthcare institutions drugs are routinely stored in designated satellite areas on the wards. Often ad hoc decisions are made by clinicians and nurses regarding drug type and quantity to be stored. As a result the number of different drugs and drug packages in storage tends to increase, which may lead to inefficient drug handling and become a potential risk factor in the medication control process. Based on an extended analysis of drug inventories on three different wards it was hypothesized that a ward-individualised formulary (WIF) can halve the number of different drugs and drug packages in a drug dispensary and hence reduce bound capital, money lost through expired drugs, and facilitate safer drug handling. The interdisciplinary intervention described here took place on three 40-bed wards in a 700-bed university hospital housing patients in general internal medicine, haematology, nephrology and oncology. METHODS: A WIF was defined by including all drugs from the hospital formulary ordered at least three times in the past six months. A pharmacist, a nurse and a clinician reviewed the inclusion list of drugs and clinicians were strongly encouraged to prescribe drugs primarily from the WIF. Drugs excluded from the WIF were removed from the drug dispensaries and the number of included drug packages stored in the remote dispensaries was reduced according to their order history. Drug inventory on the wards was monitored from February 2004 to April 2006. RESULTS: The initial drug dispensary inventories on wards A, B and C consisted of 2031, 1667 and 1536 packages with 943, 897 and 831 different drugs valued at h 83 931, h 44 590 and h 57 285. respectively. After adjusting the drug dispensaries according to the WIF drug dispensary inventories on wards A, B and C consisted of 808 (-60%), 600 (-64%) and 485 (-68%) packages with 415 (-56%), 334 (-63%) and 376 (-55%) different drugs valued euro 28 012 (-67%), euro 10 381 (-77%) an euro 17 898 (-69%). The overall reductions the number of packages, the different drugs and the drug value were comparable (<50%) and remained low during the entire observation time (A: 18 months, B: 13 months, C: 8 months). CONCLUSION: Rearranging dispensaries by individualizing the drug inventory according to the needs of the ward by introducing a WIF is a valuable means to significantly (<50%) reduce [1] the number of drug packages, [2] the number of different drugs stored and [3] the capital bound drugs. The positive effects of the WIF are supported by the interdisciplinary interaction of the different professional groups involved in the medication process. The leaner drug dispensaries offer optimal basic conditions for introducing new IT-based systems to further increase the safety of the medication process

Classical double-layer atoms: artificial molecules

The groundstate configuration and the eigenmodes of two parallel two-dimensional classical atoms are obtained as function of the inter-atomic distance (d). The classical particles are confined by identical harmonic wells and repel each other through a Coulomb potential. As function of d we find several structural transitions which are of first or second order. For first (second) order transitions the first (second) derivative of the energy with respect to d is discontinuous, the radial position of the particles changes discontinuously (continuously) and the frequency of the eigenmodes exhibit a jump (one mode becomes soft, i.e. its frequency becomes zero).Comment: 4 pages, RevTex, 5 ps figures, to appear in Phys.Rev.Let

Local spectroscopy and atomic imaging of tunneling current, forces and dissipation on graphite

Theory predicts that the currents in scanning tunneling microscopy (STM) and the attractive forces measured in atomic force microscopy (AFM) are directly related. Atomic images obtained in an attractive AFM mode should therefore be redundant because they should be \emph{similar} to STM. Here, we show that while the distance dependence of current and force is similar for graphite, constant-height AFM- and STM images differ substantially depending on distance and bias voltage. We perform spectroscopy of the tunneling current, the frequency shift and the damping signal at high-symmetry lattice sites of the graphite (0001) surface. The dissipation signal is about twice as sensitive to distance as the frequency shift, explained by the Prandtl-Tomlinson model of atomic friction.Comment: 4 pages, 4 figures, accepted at Physical Review Letter

Pediatric epstein-barr virus carriers with or without tonsillar enlargement may substantially contribute to spreading of the virus

BACKGROUND: Human-to-human transmission of the persistent infection establishing Epstein-Barr virus (EBV) occurs via saliva. Tonsils act as important portal of entry and exit of EBV. The contagiousness of pediatric EBV carriers and the role played by tonsillar enlargement (TE) are not known. METHODS: We compared EBV shedding in mouthwash samples from pediatric EBV carriers with or without TE to that in mouthwash samples from pediatric patients with infectious mononucleosis (IM), the symptomatic form of primary infection if delayed after the age of 5 years. EBV DNA was quantified by polymerase chain reaction, and contagiousness was assessed using the cord lymphocyte transformation assay. RESULTS: EBV carriers with TE shed EBV DNA at an almost similar frequency (although in lower amounts) as pediatric patients with acute IM but more frequently (P <.001) and in higher amounts (P = .038) than EBV carriers without TE. EBV DNA levels in mouthwash samples from EBV carriers with TE mirrored levels in tonsils and gradually declined after tonsillectomy. Almost half of the mouthwash samples from pediatric EBV carriers contained infectious EBV. CONCLUSIONS: Pediatric EBV carriers--in particular, those with TE-may considerably contribute to the spreading of EBV in industrialized countries

Head-to-head comparison of length of stay, patients' outcome and satisfaction in Switzerland before and after SwissDRG-Implementation in 2012 in 2012: an observational study in two tertiary university centers.

On 1 January 2012 Swiss Diagnosis Related Groups (DRG), a new uniform payment system for in-patients was introduced in Switzerland with the intention to replace a "cost-based" with a "case-based" reimbursement system to increase efficiency. With the introduction of the new payment system we aim to answer questions raised regarding length of stay as well as patients' outcome and satisfaction. This is a prospective, two-centre observational cohort study with data from University Hospital Basel and the Cantonal Hospital Aarau, Switzerland, from January to June 2011 and 2012, respectively. Consecutive in-patients with the main diagnosis of either community-acquired pneumonia, exacerbation of COPD, acute heart failure or hip fracture were included. A questionnaire survey was sent out after discharge investigating changes before and after SwissDRG implementation. Our primary endpoint was LOS. Of 1,983 eligible patients 841 returned the questionnaire and were included into the analysis (429 in 2011, 412 in 2012). The median age was 76.7 years (50.8% male). Patients in the two years were well balanced in regard to main diagnoses and co-morbidities. Mean LOS in the overall patient population was 10.0 days and comparable between the 2011 cohort and the 2012 cohort (9.7 vs 10.3; p = 0.43). Overall satisfaction with care changed only slightly after introduction of SwissDRG and remained high (89.0% vs 87.8%; p = 0.429). Investigating the influence of the implementation of SwissDRG in 2012 regarding LOS patients' outcome and satisfaction, we found no significant changes. However, we observed some noteworthy trends, which should be monitored closely

Local Anisotropy of Fluids using Minkowski Tensors

Statistics of the free volume available to individual particles have previously been studied for simple and complex fluids, granular matter, amorphous solids, and structural glasses. Minkowski tensors provide a set of shape measures that are based on strong mathematical theorems and easily computed for polygonal and polyhedral bodies such as free volume cells (Voronoi cells). They characterize the local structure beyond the two-point correlation function and are suitable to define indices $0\leq \beta_\nu^{a,b}\leq 1$ of local anisotropy. Here, we analyze the statistics of Minkowski tensors for configurations of simple liquid models, including the ideal gas (Poisson point process), the hard disks and hard spheres ensemble, and the Lennard-Jones fluid. We show that Minkowski tensors provide a robust characterization of local anisotropy, which ranges from $\beta_\nu^{a,b}\approx 0.3$ for vapor phases to $\beta_\nu^{a,b}\to 1$ for ordered solids. We find that for fluids, local anisotropy decreases monotonously with increasing free volume and randomness of particle positions. Furthermore, the local anisotropy indices $\beta_\nu^{a,b}$ are sensitive to structural transitions in these simple fluids, as has been previously shown in granular systems for the transition from loose to jammed bead packs

Distance dependence of force and dissipation in non-contact atomic force microscopy on Cu(100) and Al(111)

The dynamic characteristics of a tip oscillating in the nc-AFM mode in close vicinity to a Cu(100)-surface are investigated by means of phase variation experiments in the constant amplitude mode. The change of the quality factor upon approaching the surface deduced from both frequency shift and excitation versus phase curves yield to consistent values. The optimum phase is found to be independent of distance. The dependence of the quality factor on distance is related to 'true' damping, because artefacts related to phase misadjustment can be excluded. The experimental results, as well as on-resonance measurements at different bias voltages on an Al(111) surface, are compared to Joule dissipation and to a model of dissipation in which long-range forces lead to viscoelastic deformations