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

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

Phenyl-triazine oligomers for light-driven hydrogen evolution

The design of stable, yet highly tunable organic photocatalysts which orchestrate multi-step electron transfer reactions is at the heart of the newly emerging field of polymer photocatalysis. Covalent triazine frameworks such as the archetypal CTF-1 have been theorized to constitute a new class of photocatalytically active polymers for light-driven water splitting. Here, we revisit the ionothermal synthesis of CTF-1 by trimerization of 1,4-dicyanobenzene catalyzed by the Lewis acid zinc chloride and demonstrate that the microporous black polymer CTF-1 is essentially inactive for hydrogen evolution. Instead, highly photoactive phenyl-triazine oligomers (PTOs) with higher crystallinity as compared to CTF-1 are obtained by lowering the reaction temperature to 300 °C and prolonging the reaction time to >150 hours. The low reaction temperature of the PTOs largely prevents incipient carbonization and thus results in a carbon-to-nitrogen weight ratio close to the theoretical value of 3.43. The oligomers were characterized by MALDI-TOF and quantitative solid-state NMR spectroscopy, revealing variations in size, connectivity and thus nitrile-to-triazine ratios depending on the initial precursor dilution. The most active PTO samples efficiently and stably reduce water to hydrogen with an average rate of 1076 (±278) μmol h−1 g−1 under simulated sunlight illumination, which is competitive with the best carbon nitride-based and purely organic photocatalysts. The photocatalytic activity of the PTOs is found to sensitively depend on the polymerization degree, thus suggesting a prominent role of the unreacted nitrile moieties in the photocatalytic process. Notably, PTOs even show moderate hydrogen production without the addition of any co-catalyst

Classical Many-particle Clusters in Two Dimensions

We report on a study of a classical, finite system of confined particles in two dimensions with a two-body repulsive interaction. We first develop a simple analytical method to obtain equilibrium configurations and energies for few particles. When the confinement is harmonic, we prove that the first transition from a single shell occurs when the number of particles changes from five to six. The shell structure in the case of an arbitrary number of particles is shown to be independent of the strength of the interaction but dependent only on its functional form. It is also independent of the magnetic field strength when included. We further study the effect of the functional form of the confinement potential on the shell structure. Finally we report some interesting results when a three-body interaction is included, albeit in a particular model.Comment: Minor corrections, a few references added. To appear in J. Phys: Condensed Matte

Searching for Voltage Graph-Based LDPC Tailbiting Codes with Large Girth

The relation between parity-check matrices of quasi-cyclic (QC) low-density parity-check (LDPC) codes and biadjacency matrices of bipartite graphs supports searching for powerful LDPC block codes. Using the principle of tailbiting, compact representations of bipartite graphs based on convolutional codes can be found. Bounds on the girth and the minimum distance of LDPC block codes constructed in such a way are discussed. Algorithms for searching iteratively for LDPC block codes with large girth and for determining their minimum distance are presented. Constructions based on all-ones matrices, Steiner Triple Systems, and QC block codes are introduced. Finally, new QC regular LDPC block codes with girth up to 24 are given.Comment: Submitted to IEEE Transactions on Information Theory in February 201