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- Hansson, Karl-Martin, 1973, et al.
(författare)
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Formation of HNCO, HCN, and NH3 from the pyrolysis of bark and nitrogen-containing model compounds
- 2004
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Ingår i: Combustion and Flame. - 1556-2921 .- 0010-2180. ; 137, s. 265-277
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Tidskriftsartikel (refereegranskat)abstract
- Bark pellets have been pyrolyzed in a fluidized bed reactor at temperatures between 700 and 1000C. Identifiednitrogen-containing species were hydrogen cyanide (HCN), ammonia (NH3), and isocyanic acid (HNCO). Quantification of HCN and to some extent of NH3 was unreliable at 700 and 800C due to low concentrations. HNCO could not be quantified with any accuracy at any temperature for bark, due to the low concentrations found. Since most of the nitrogen in biomass is bound in proteins, various protein-rich model compounds were pyrolyzed with the aim of finding features that are protein-specific, making conclusions regarding the model compounds applica-ble for biomass fuels in general. The model compounds used were a whey protein isolate, soya beans, yellow peas,and shea nut meal. The split between HCN and NH3 depends on the compound and temperature. It was found that the HCN/NH3 ratio is very sensitive to temperature and increases with increasing temperature for all compounds, including bark. Comparing the ratio for the different compounds at a fixed temperature, the ratio was found to decrease with decreasing release of volatile nitrogen. The temperature dependence implies that heating rate andthereby particle size affect the split between HCN and NH3. For whey, soya beans, and yellow peas, HNCO was also quantified. It is suggested that most HCN and HNCO are produced from cracking of cyclic amides formed as primary pyrolysis products. The dependence of the HNCO/HCN ratio on the compound is fairly small, but the temperature dependence of the ratio is substantial, decreasing with increasing temperature. The release of nitrogen-containing species does not seem to be greatly affected by the other constituents of the fuel, and proteins appear to be suitable model compounds for the nitrogen in biomass.
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- Hansson, Karl-Martin, 1973, et al.
(författare)
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The temperature’s influence on the selectivity between HNCO and HCN from pyrolysis of 2,5-diketopiperazine and 2-pyridone
- 2003
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Ingår i: Fuel. - 0016-2361. ; 82, s. 2163-2172
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Tidskriftsartikel (refereegranskat)abstract
- Two cyclic amides, 2-pyridone and 2,5-diketopiperazine (DKP), were pyrolysed at temperatures ranging from 700 to 1100C. Pyridone is the only one of the four main nitrogen functionalities found in coal that is likely to form HNCO under pyrolysis. DKP is a primary pyrolysis product from proteins, which are the main nitrogen source in biomass. The formation of HNCO from biomass has been suggested to originate from DKP and other cyclic amides. The aromatic 2-pyridone was thermally more stable than the non-aromatic DKP. Both amides formed HCN, HNCO and NH3. The NH3 yields, about 3–4% for 2-pyridone and 10% for DKP, were almost independent of temperature. The HCN yield on the other hand showed strong temperature dependence and increased with temperature for both of the cyclic amides. The HNCO yield decreased with increasing temperature for DKP over the whole temperature interval. For 2-pyridone, the pyrolysis was incomplete at the lowest temperature in the investigation. Between 900 and 1100C, the pyrolysis of 2-pyridone was complete and the HNCO yield decreased with increasing temperature. The HNCO/HCN ratio for both of the cyclic amides decreased with increasing temperature over the whole investigated temperature range. The finding in literature that the HNCO formation from cracking of coal tars produced a maximum HNCO yield at an intermediate temperature, is explained by the thermal stability of pyridone at low temperatures and the selectivity towards HCN at high temperatures.
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- Hyllienmark, Lars, et al.
(författare)
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Nerve conduction defects are retarded by tight metabolic control in type I diabetes
- 2001
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Ingår i: Muscle and Nerve. - 0148-639X .- 1097-4598. ; 24:2, s. 240-246
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Tidskriftsartikel (refereegranskat)abstract
- This follow-up study examines whether the development of nerve dysfunction is retarded by tight metabolic control in patients with type I diabetes mellitus. Seventy-one patients and 115 age-matched healthy control subjects underwent studies of nerve conduction in peroneal and sural nerves. The presence of diabetes was associated with a reduction in peroneal motor nerve conduction velocity (MCV) by 5.9 m/s, sural sensory nerve conduction velocity (SCV) by 3.4 m/s, and sural sensory nerve action potential (SNAP) amplitude by 22%. Dysfunction in peroneal MCV, sural SCV, and sural SNAP were related to long-term poor metabolic control. Eleven of 12 patients with HbA1c <6.5% had normal nerve conduction or abnormality in only one nerve as compared to 2 of 15 patients with HbA1c >8.0%. It is concluded that tight long-term metabolic control (HbA1c <6.5%) can retard nerve dysfunction in patients with type I diabetes mellitus and a mean disease duration of 12 years.
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- Johansson, S., et al.
(författare)
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Small, novel proteins from the mistletoe Phoradendron tomentosum exhibit highly selective cytotoxicity to human breast cancer cells
- 2003
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Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 60:1, s. 165-175
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Tidskriftsartikel (refereegranskat)abstract
- Four novel proteins (phoratoxins C-F) have been isolated from the North American mistletoe Phoradendron tomentosum. The amino acid sequences of these phoratoxins were determined unambiguously using a combination of Edman degradation and trypsin enzymatic digestion, and by electrospray ionization tandem mass spectrometry sequencing. Phoratoxins C, E and F consist of 46 amino acid residues; and phoratoxin D of 41. All proteins had six cysteines, similar to the earlier described phoratoxins A and B, which are thionins. The cytotoxicity of each protein was evaluated in a human cell line panel that represented several cytotoxic drug-resistance mechanisms. For the half-maximal inhibitory concentrations (IC50 values) of the different cell lines in the panel, correlation with those of standard drugs was low. The most potent cytotoxic phoratoxin C was further tested on primary cultures of human tumor cells from patients. The solid tumor samples from breast cancer cells were 18 times more sensitive to phoratoxin C than the tested hematological tumor samples.
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