Chemical Partitioning at Crystalline Defects in PtAu as a Pathway to Stabilize Electrocatalysts

Dissolution of electrocatalysts during long-term and dynamic operation is a challenging problem in energy conversion and storage devices such as fuel cells and electrolyzers. To develop stable electrocatalysts, we adopt the design concept of segregation engineering, which uses solute segregation prone to electrochemical dissolution at internal defects, i.e., grain boundaries and dislocations. We showcase the feasibility of this approach by stabilizing a model Pt catalyst with an addition of more noble Au (approximately 5 atomic percent). We characterized the defects' nanoscale structure and chemistry, and monitored the electrochemical dissolution of Pt and PtAu alloys by online inductively coupled plasma mass spectrometry. Once segregated to defects, Au atoms can stabilize and hence passivate the most vulnerable sites against electrochemical dissolution and improve the stability and longevity of the Pt electrocatalysts by more than an order of magnitude. This opens pathways to use solute segregation to defects for the development of more stable nanoscale electrocatalysts, a concept applicable for a wide range of catalytic systems

Arecibo Pulsar Survey Using ALFA. I. Survey Strategy and First Discoveries

We report results from the initial stage of a long-term pulsar survey of the Galactic plane using the Arecibo L-band Feed Array (ALFA), a seven-beam receiver operating at 1.4 GHz with 0.3 GHz bandwidth. The search targets Galactic latitudes |b| < 5 deg in the longitude ranges 32 deg < l < 77 deg and 168 deg < l < 77 deg. Data discussed here were collected over a 100 MHz passband centered on 1.42 GHz using a spectrometer that recorded 256 channels every 64 microsec. In a preliminary, standard period-DM analysis, we have detected 29 previously known pulsars and discovered 11 new ones. One of these, with a period of 69 ms and a low characteristic age of 82 kyr, is a plausible candidate for association with the unidentified EGRET source 3EG J1928+1733. Another is a non-recycled pulsar in a relativistic binary with orbital period of 3.98 hr. We also search the data for isolated dispersed pulses, a technique that yielded discovery of an extremely sporadic radio emitter with a spin period of 1.2 s. Simulations we have carried out indicate that about 1000 new pulsars will be found in the ALFA survey. In addition to providing a large sample for use in population analyses and for probing the magnetoionic interstellar medium, the survey maximizes the chances of finding rapidly spinning millisecond pulsars and pulsars in compact binary systems. Our search algorithms will exploit the multiple data streams from ALFA to discriminate between radio frequency interference and celestial signals, including pulsars and possibly new classes of transient radio sources.Comment: 10 pp, 9 figures, accepted by the Astrophysical Journa

An Eccentric Binary Millisecond Pulsar in the Galactic Plane

Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 ms in a highly eccentric (e = 0.44) 95-day orbit around a solar mass companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster then ejecting it into the Galactic disk or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74+/-0.04 Msun, an unusually high value.Comment: 28 pages, 4 figures inc Supplementary On-Line Material. Accepted for publication in Science, published on Science Express: 10.1126/science.115758

The fitness of African malaria vectors in the presence and limitation of host behaviour

&lt;p&gt;Background Host responses are important sources of selection upon the host species range of ectoparasites and phytophagous insects. However little is known about the role of host responses in defining the host species range of malaria vectors. This study aimed to estimate the relative importance of host behaviour to the feeding success and fitness of African malaria vectors, and assess its ability to predict their known host species preferences in nature.&lt;/p&gt; &lt;p&gt;Methods Paired evaluations of the feeding success and fitness of African vectors Anopheles arabiensis and Anopheles gambiae s.s in the presence and limitation of host behaviour were conducted in a semi-field system (SFS) at Ifakara Health Institute, Tanzania. In one set of trials, mosquitoes were released within the SFS and allowed to forage overnight on a host that was free to exhibit natural behaviour in response to insect biting. In the other, mosquitoes were allowed to feed directly on from the skin surface of immobile hosts. The feeding success and subsequent fitness of vectors under these conditions were investigated on 6 host types (humans, calves, chickens, cows, dogs and goats) to assess whether physical movements of preferred host species (cattle for An. arabiensis, humans for An. gambiae s.s.) were less effective at preventing mosquito bites than those of common alternatives.&lt;/p&gt; &lt;p&gt;Results Anopheles arabiensis generally had greater feeding success when applied directly to host skin than when foraging on unrestricted hosts (in five of six host species). However, An. gambiae s.s obtained blood meals from free and restrained hosts with similar success from most host types (four out of six). Overall, the blood meal size, oviposition rate, fecundity and post-feeding survival of mosquito vectors were significantly higher after feeding on hosts free to exhibit behaviour, than those who were immobilized during feeding trials.&lt;/p&gt; &lt;p&gt;Conclusions Allowing hosts to move freely during exposure to mosquitoes was associated with moderate reductions in mosquito feeding success, but no detrimental impact to the subsequent fitness of mosquitoes that were able to feed upon them. This suggests that physical defensive behaviours exhibited by common host species including humans do not impose substantial fitness costs on African malaria vectors.&lt;/p&gt

PSR J1856+0245: Arecibo Discovery of a Young, Energetic Pulsar Coincident with the TeV Gamma-ray Source HESS J1857+026

We present the discovery of the Vela-like radio pulsar J1856+0245 in the Arecibo PALFA survey. PSR J1856+0245 has a spin period of 81ms, a characteristic age of 21kyr, and a spin-down luminosity Edot = 4.6 x 10^36 ergs/s. It is positionally coincident with the TeV gamma-ray source HESS J1857+026, which has no other known counterparts. Young, energetic pulsars create wind nebulae, and more than a dozen pulsar wind nebulae have been associated with very-high-energy (100GeV-100TeV) gamma-ray sources discovered with the HESS telescope. The gamma-ray emission seen from HESS J1857+026 is potentially produced by a pulsar wind nebula powered by PSR J1856+0245; faint X-ray emission detected by ASCA at the pulsar's position supports this hypothesis. The inferred gamma-ray efficiency is epsilon_gamma = L_gamma/Edot = 3.1% (1-10TeV, for a distance of 9kpc), comparable to that observed in similar associations.Comment: 13 pages, 1 figure, accepted for publication in The Astrophysical Journal Letter

Study of measured pulsar masses and their possible conclusions

We study the statistics of 61 measured masses of neutron stars (NSs) in binary pulsar systems, including 18 double NS (DNS) systems, 26 radio pulsars (10 in our Galaxy) with white dwarf (WD) companions, 3 NSs with main-sequence companions, 13 NSs in X-ray binaries, and one undetermined system. We derive a mean value of M = 1.46 +/- 0.30 solar masses. When the 46 NSs with measured spin periods are divided into two groups at 20 milliseconds, i.e., the millisecond pulsar (MSP) group and others, we find that their mass averages are, respectively, M=1.57 +/- 0.35 solar masses and M=1.37+/- 0.23 solar masses. In the framework of the pulsar recycling hypothesis, this suggests that an accretion of approximately 0.2 solar mass is sufficient to spin up a neutron star and place it in the millisecond pulsar group. An empirical relation between the accreting mass and MSP spin period is \Delta M=0.43 (solar mass)(P/1 ms)^{-2/3}. UNlike the standard recycling process, if a MSP is formed by the accretion induced collapse (AIC) of a white dwarf with a mass less than Chandrasekha limit, e.g. 1.35 solar mass, then the binary MSPs involved in AICs is not be higher than 20%, which imposes a constraint on the AIC origin of MSPs.Comment: 6 pages, 5 figures, in press, Astronomy and Astrophysics 2011, 527, 8

Intermolecular interactions of decamethoxinum and acetylsalicylic acid in systems of various complexity levels

Intermolecular interactions between decamethoxinum (DEC) and acetylsalicylic acid (ASА) have been studied in the phospholipid-containing systems of escalating complexity levels. The host media for these substances were solvents, L-α-dipalmitoylphosphatidylcholine (DPPC) membranes, and samples of human erythrocytes. Peculiar effects caused by DEC-ASА interaction have been observed in each system using appropriate techniques: (a) DEC-ASА non-covalent complexes formation in DPPC-containing systems were revealed by mass spectrometry with electrospray ionization; (b) joint DEC-ASА action on DPPC model membranes led to increasing of membrane melting temperature Tm, whereas individual drugs caused pronounced Tm decreasing, which was demonstrated by differential scanning calorimetry; (c) deceleration of DEC-induced haemolysis of erythrocytes under joint DEC-ASА application was observed by optical microscopy

Procalcitonin in early prediction of acute severe pancreatitis

The aim of the study was to analyze the prognostic potential of procalcitonin in acute pancreatitis complicated by ascites-peritonitis. Materials and methods: The study analyzed the results of a comprehensive examination and treatment of 18 patients with acute pancreatitis complicated by enzymatic ascites-peritonitis, including 13 patients who were treated in the surgical department of KP “Poltava Regional Clinical Hospital. MV Sklifosovsky POR “, and 5 patients of other emergency hospitals in Poltava, in the period from 2017 to 2019. In addition to standard screening methods, these patients were additionally tested for procalcitonin to predict an adverse course in the early period. Results: To assess the relationship between the presence of elevated procalcitonin levels at the time of hospitalization of 0.5 ng / ml and above and unsatisfactory treatment results, differences were assessed using an accurate Fisher test. When comparing differences in the development of infectious complications in the dynamics of the disease in patients of the study group depending on the presence of elevated concentrations of procalcitonin or its absence at the time of hospitalization, a significant difference was found (p <0.05). Conclusions: In our opinion, the use of procalcitonin as a predictor of infectious complications in the dynamics of the disease will determine the category of patients in whom reducing the risk of flora translocation through the use of early oral antibiotic prophylaxis and parenteral drugs tropic to pancreatic tissue may reduce the incidence of purulent complications. In another category of patients, antibacterial therapy is not advisable due to the low risk of purulent-septic complications

The young, highly relativistic binary pulsar J1906+0746

We report the discovery of PSR J1906+0746, a young 144-ms pulsar in a highly relativistic 3.98-hr orbit with an eccentricity of 0.085 and expected gravitational wave coalescence time of 300 Myr. The new pulsar was found during precursor survey observations with the Arecibo 1.4-GHz feed array system and retrospectively detected in the Parkes Multibeam plane pulsar survey data. From radio follow-up observations with Arecibo, Jodrell Bank, Green Bank, and Parkes, we have measured the spin-down and binary parameters of the pulsar and its basic spectral and polarization properties. We also present evidence for pulse profile evolution, which is likely due to geodetic precession, a relativistic effect caused by the misalignment of the pulsar spin and total angular momentum vectors. Our measurements show that PSR J1906+0746 is a young object with a characteristic age of 112 kyr. From the measured rate of orbital periastron advance 7.57+/-0.03 deg/yr, we infer a total system mass of 2.61+/-0.02 Msun. While these parameters suggest that the PSR J1906+0746 binary system might be a younger version of the double pulsar system, intensive searches for radio pulses from the companion have so far been unsuccessful. It is therefore not known whether the companion is another neutron star or a massive white dwarf. Regardless of the nature of the companion, a simple calculation suggests that the Galactic birth rate of binaries similar to PSR J1906+0746 is 60/Myr. This implies that PSR J1906+0746 will make a significant contribution to the computed cosmic inspiral rate of compact binary systems.Comment: 19 pages, 3 figures, accepted for publication in Ap