8,322 research outputs found
Primary Events in Photosynthetic Reaction Centers and Antennas: A Femtosecond Visible - Pump - Mid-Infrared - Probe Study
No full textGrondelle, R. van [Promotor]Jones, M.R. [Copromotor
Sequential injection analysis Ferrozine spectrophotometry versus Luminol chemiluminescence for continuous online monitoring of the concentration and speciation of iron
No full textWe designed two sequential injection analysis systems (Luminol chemiluminescent and Ferrozine spectrophotometric) that are capable of monitoring the concentration of soluble iron(II) and reducible iron(III) in natural waters over extended periods (>120 h). The method based on Luminol chemiluminescence estimated the iron(II) concentration as the difference in signal with or without the addition of the strong iron(II) ligand, Ferrozine (TM) (iron complexing reagent). Iron(II) in the sample without the iron complexing reagent induced a chemiluminescence signal whereas iron(II) in the presence of the iron complexing reagent did not induce a signal. The second method, based on Ferrozine (TM) spectrophotometry, measured iron(II) and reducible iron(III) in a 100 cm path length liquid wave capillary cell. Both methods provided stability for >120 h and yielded similar analytical detection limits equal to ten standard deviations of the blank; 2.2 nM for Luminol chemiluminescence with a calibration concentration range of 0 - 12 nM, and 3.9 nM for Ferrozine (TM) spectrophotometry with a calibration concentration range of 0 - 120 nM. The two chemical techniques do not appear to be directly comparable for practical monitoring purposes, and we suggest that Luminol-chemiluminescence is unable to measure strong ligand complexes of iron(II). Both methods used iron(II) as the analytical standard rather than a reduced iron(III) standard. The analysis based on the iron(II) standard was able to be performed without additional buffers and reducing reagents, which significantly minimized contamination.11Nsciescopu
Determination of environmental H2O2 for extended periods by chemiluminescence with real-time inhibition of iron interferences
No full textSoluble iron hinders the accurate analysis of hydrogen peroxide (H2O2) in environmental systems. We present a chemiluminescence sequential injection (SIA) system capable of the continuous analysis of H2O2 over extended periods (48 h) by the real-time addition of an iron complexing reagent (ICR; masking compounds) which inhibits > 98% of the interference caused by iron species. The measurement error based on repeat analysis of a sample within 10 min was +/- 2.2%, and over 48 h was +/- 6%. The preparation and analysis of standards, the ability for discrete and continuous sampling, and the real-time addition of the ICR to minimize chemical interference were integrated within the SIA system. Evaluation of the analytical probe showed that the optimum concentration and pH of the luminol reagent for the analysis of H2O2 were 100 mu M luminol and pH = 10.7, respectively; this enabled the analysis over a concentration range of 0.25-900 nM H(2)O(2)at a detection limit of 0.14 nM. The proposed SIA system requires only small amounts of reagents (33 mu L luminol and 24 mu L ICR) and sample (240 mu L). We used the system to measure the H2O2 concentration in a coastal seawater sample that was subject to natural photochemical reactions and the direct input of rainwater, both of which introduce soluble iron. Rainwater H2O2 increased the H2O2 concentration in the coastal seawater sample by a factor of up to 40 relative to the amounts produced by natural photochemical reactions. The H2O2 concentration in the coastal seawater sample showed high short-term variability.11Nsciescopu
Widespread morphoea following radiotherapy for carcinoma of the breast
No full textWe report a case of a 60-year-old lady who was treated with radiotherapy for breast cancer of both breasts 8 years apart. Thirteen years after the first dose of radiotherapy she developed localized morphoea in all the irradiated skin of the chest wall and also the gaiter regions of both lower legs. Radiation-induced localized morphoea has been previously reported; however, there is no previous publication of an occurrence at a distant site as in this case. This case demonstrates that morphoea can occur distant to the original breast carcinoma and site of radiotherapy. We postulate that radiotherapy can induce neoantigen formation, which initiates a T cell response and subsequent tissue growth factor alpha release. Tissue growth factor alpha induces fibroblast activation and collagen production may persist due to a positive feedback mechanism within the fibroblast. The reason why the disease did not generalize remains unclear
Ocean acidification from explosive volcanism as a cause for mass mortality of pteropods (abstract of paper presented at: 19th Annual V. M. Goldschmidt Conference, Davos, Switzerland, 21-26 June 2009)
No full text
Primary cutaneous nodular amyloidosis associated with psoriasis
No full textPrimary cutaneous nodular amyloidosis (PCNA) presents as solitary or multiple firm, waxy nodules with a predilection for acral areas. Histologically, PCNA can be identical to myeloma-associated systemic amyloidosis with monoclonal immunoglobulin light chain deposits. We describe a patient in whom PCNA developed in a scar in an area affected by chronic plaque psoriasis. PCNA has previously been associated with other autoimmune diseases, but to our knowledge, this is the first association with psoriasis. Interestingly, T helper (Th)17 cells, which are crucial in psoriasis pathogenesis, have recently been implicated in promotion of myeloma and plasma cell dyscrasias. The association of psoriasis and plasma-cell light chain production in the skin, as in this case, suggests a possible role for Th17 cells in PCNA formation. The dermatopathological literature of this rare but important disease is discussed
The successful use of a novel microwave device in the treatment of a plantar wart
No full textPlantar warts, caused by the human papilloma virus (HPV), are a commonly encountered condition presenting in clinic. In adults, an array of various therapies exists, frequently with modest results particularly with plantar lesions. Microwaves have had limited uses for medical purposes. Recently a new portable microwave device has been approved for the treatment of skin lesions. Prior research has demonstrated immuno-stimulatory effects against HPV infection. We report the application of a novel portable medical microwave unit to treat a long-standing plantar wart which had failed to respond to other treatment modalities
- …
