Optimizing Struvite Production for Phosphate Recovery in WWTP

Struvite, a crystalline structure comprised of ions of magnesium (Mg+2), ammonium (NH4–N), and phosphate (PO4–P), is commonly encountered in wastewater treatment plants (WWTPs) through struvite encrustation. The gradual accumulation of this crystal in pipes and fittings leads to high costs due to downtime and replacement of parts. Technologies that are used to reduce this problem are ideally located in biological nutrient removal plants downstream of anaerobic digesters, as high levels of NH4–N and PO4–P typically characterize anaerobic digester supernatants. In 2003–2004, two technical-scale, struvite recovery studies were conducted on-site at the City of Penticton, B.C., Canada and the City of Richmond, B.C., Canada using a novel technology developed by the environmental engineering group at the University of British Columbia. The results of these studies showed an average reduction of 80% in phosphate and a dense, spherical product, 5–10 times larger than any commercially available struvite to date. Overall, the recovery of struvite has enormous commercial potential, which results in WWTP becoming more sustainable, concurrently reducing problems typically associated with their operation.     

Method for setting the absolute frequency of a tunable, 1.5 μmtwo-section DBR laser

A technique for setting the absolute frequency of a 1.5-μm two-section distributed Bragg reflector (DBR) laser using an Er:YAG optical filter as a frequency discriminator is described. The absolute frequency of the laser was controlled with an accuracy better than 300 MHz over a tuning range of several hundred gigahertz. The frequency drift with laser temperature was -130 MHz/°C, and the tuning rate with current in the active region was 40 MHz/mA     

Simple narrow-linewidth 1.5 ?m InGaAsP DFB external-cavity laser

An external-cavity laser consisting of a 1.5 ?m-wavelength antireflection-coated DFB laser chip, a microscope objective and a mirror provides a stable, single-frequency, narrow-linewidth (?f=40 kHz) output. Because the laser operates in the strong feedback regime, it is immune to external optical perturbations. Single-longitudinal-mode operation is maintained by the DFB grating, and the linewidth is reduced by the extended passive cavity.     

Exercise capacity and mid-term survival in patients with tricuspid atresia and complex congenital cardiac malformations after modified Fontan-operation

A 68-year-old man experienced systemic pruritus since he was 63 years old, and systemic sclerosis and skin pigmentation were observed when he was 64. When he developed dyspnea the same year, he was admitted and SSc was diagnosed on the basis of the clinical and skin biopsy findings, lung fibrosis on X-P and TBLB findings. At 65, his dyspnea reappeared along with elevated blood pressure, acute renal failure and lung congestion, and he was diagnosed as having a scleroderma renal crisis (SRC) from the clinical and renal biopsy findings. Hemodialysis was started because he showed mental disturbance, and this and other acute symptoms were subsequently reduced. As he showed no recovery from his renal failure, the patient has been maintained on hemodialysis for over four years now. In the meantime, his sclerosis has improved and antinuclear antibody almost disappeared. Hemodialysis appears to be the most likely reason for his improvement, although spontaneous remission, D-penicillamine and angiotensin converting enzyme (ACE) inhibitor therapy may also have contributed, considering the short period and the small amount of drugs given until improvement.     

It is time to move from the nursing process to critical thinking

As we reflect on the concept of critical thinking in perioperative nursing practice, we should ask ourselves whether we think critically. If not, we must learn the principles of critical thinking and apply them in our clinical practice settings. Our perioperative nurse managers and directors must demonstrate critical thinking in leading other nurses in the delivery of quality, cost-effective, service-oriented patient care. They also must identify peers who use critical thinking skills to support and sustain them in their quest.     

Influence of oxygen and water related surface defects on the dye sensitized TiO2 solar cell

Oxygen- and water-related surface defects on porous TiO₂ (anatase) can be well controlled by the oxygen and water partial pressures and therefore such defects are of technological relevance for dye sensitized TiO₂ solar cells. We investigated the action of oxygen and water-related surface defects in situ by impedance spectroscopy, photoconductivity, photoluminescence, and optical transmission as well as by characterizing solar cells which were prepared under respective conditions. Oxygen loss from the TiO₂ surface leads to electrical doping by Ti³⁺/oxygen donor states. Such defects create recombination paths for injected electrons back into the electrolyte. Pre-treatment of porous TiO₂ by chemisorption of water increases the open circuit voltage of the solar cells without altering the short circuit current. Water-related surface defects decrease the saturation current of the diode, probably by raising the barrier height at the TiO₂/electrolyte interface.