Effect of Ligand Modification on the Mechanism of Electrocatalytic Hydrogen Production by Ni(pyridinethiolate)3- Derivatives.

The effects of ligand modification on the catalytic mechanism of hydrogen production by Ni(PyS)3- derivatives, made with electron-withdrawing and -donating substitutions to the pyridinethiolate (PyS)- ligands, are studied experimentally and computationally using density functional theory. Thermodynamic data, spin density maps, and frontier molecular orbital diagrams were generated for reaction intermediates. Comparison of computed values for E0 and p Ka with experimental values supports the proposed mechanisms. The rate of electrochemical hydrogen production is correlated with the effect of ligand modification. Notably, the presence of an electron-donating substituent favors an alternative mechanism for hydrogen production. Computationally it was determined that the electron-donating substituent causes deviation from the original chemical-electrochemical-chemical-electrochemical (CECE) mechanism of Ni(PyS)3- to a CCEE mechanism, while the CECE mechanism is maintained for all catalysts substituted with electron-withdrawing groups.

Photocatalytic water reduction using a polymer coated carbon quantum dot sensitizer and a nickel nanoparticle catalyst.

Hydrogen gas is produced photocatalytically using 470 nm light, PVP-coated carbon quantum dots (CQDs) as the photosensitizer, and nickel nanoparticles (NiNPs) as the catalyst. The effect of the amount of polyvinylpyrrolidone (PVP) on the ability of the CQD/NiNP composites to catalyze proton reduction was studied. A maximum of 330 mmols H2/g CQD is produced using 68 µg ml-1 of CQDs and 6 µg ml-1 of NiNPs, with activity persisting for 4 h when 20 wt%-PVP-coated CQDs were used. The H2 production quantum yield under these conditions is 6%. It was found that composites having higher weight percent PVP had decreased rates of H2 production, but increased duration. Increasing the weight percent of PVP coating also increases the fluorescence quantum yield of CQDs. Fluorescence quenching titrations reveal that H2 production could occur by either a reductive or oxidative quenching mechanism. The nanomaterials, prepared using simple methods, are used as the photosensitizer and catalyst in the proton reduction system that operates using visible light.

Opiate effects on isolation stress in domestic fowl.

In an attempt to examine the role of opioid system functioning in social attachment and isolation stress in young domestic fowl, the effects of morphine (5.0 mg/kg) and naloxone (5.0 mg/kg) were evaluated on distress vocalizations, thermal nociception, thermoregulation, and respiration following 15 min of isolation in 7-day-old White-Leghorn cockerels. Morphine decreased and naloxone increased distress vocalizations in isolated chicks. Isolation produced an increase in jump response latencies (i.e., hypoalgesia) on a standard hot-plate test. In general, morphine decreased and naloxone increased mean jump latencies in both isolated and nonisolated chicks. Isolation produced an increase in core body temperature (i.e., hyperthermia); morphine decreased and naloxone increased core body temperatures independent of the isolation manipulation. Social isolation did not affect respiration. However, morphine depressed respiration in both isolated and nonisolated chicks. These results support the notion that opioid systems modulate social attachment and isolation stress.

Out of controll: one aspect of infertility.

A perceived loss of control over many aspects of life often accompanies the problem of infertility. While most couples feel the effects of this lack of control in their lifestyle, relationship, and reproductive capacities, there are also some benfits inherent in giving up some control of the problem to outside sources. Nursing interventions are discussed which incorporate the concept of control into the plan of care for the infertile couple.

Routine angiographic evaluation of neck and extremity injuries.

Traumatic arterial injuries are becoming more common in civilian practice. In this study arteriography was done in 91 wounds of the neck and extremities regardless of physical findings (excluding exsanguinating or trivial injuries). Physical findings suggestive of the presence or absence of arterial injury were tabulated and compared with arteriographic findings. Physical findings were often found to be unreliable, yielding a false negative result in 20% and a false positive result in 42%. It is concluded that angiography is a safe, reliable method of diagnosis and should be routinely employed in all patients with major penetrating injuries of the neck and extremities as well as in selected patients with blunt injuries.