76 research outputs found
Peptide Receptor Radionuclide Therapy with 177Lu-octreotate: clinical aspects
Somatostatin is a neuropeptide with a variety of functions and is produced in several
tissues. The isoform somatostatin-14 (SS-14) is more biologically active than SS-28. Its
main physiological function is to inhibit secretion of hormones such as growth hormone
or thyroid stimulating hormone in the pituitary, insulin or glucagon in the pancreas
and of exocrine gut secretion.
The effects of somatostatin are mediated by binding to the somatostatin receptor (sst),
which are G-protein-coupled receptors. Five sst subtypes have been identified (sst1 - sst5)
which all have different roles. The naturally occurring SS-14 and SS-28 have high affinity
for all these subtypes.
Several tumours (Table 1), amongst others gastroenteropancreatic tumours (GEPNET),
have overexpression of sst on the cell surface. This makes sst a possible target for therapy
with somatostatin analogues to try and inhibit the secretion of bioactive substances by
these tumours and possibly to slow down tumour growth. However, the biological half-life
of SS-14 and SS-28 is short, and this makes it impossible to use them for therapeutic goals.
With the invention of the cyclic octapeptide octreotide, half-life increased significantly
and octreotide then could be used in treatment of patients with sst-positive tumours
Fundamental limits of NO formation in fuel-rich premixed methane-air flames
Increasingly stringent regulations on pollutant emission are the driving force for designers of natural-gas-fired combustion systems to find ways of controlling NOx formation. To achieve significant emissions reduction, more insight is needed into the mechanisms of NO formation. Martijn van Essen’s thesis provides insight into the effects of two NOx control strategies, flue-gas recirculation (FGR) and burner stabilization, on NO formation. Since many combustion systems operate under fuel-rich (oxygen deficient) conditions, the focus of the thesis was on fuel-rich premixed methane-air flames. The experiments were performed at reduced pressures, to facilitate the measurements of the distributions of temperature and concentrations of key species (CH, OH and NO) using the optical technique laser-induced fluorescence (LIF). Towards this end, a low-pressure flame cell was constructed, and protocols for quantifying the LIF measurements were implemented. The experimental results were compared with detailed calculations based on a chemical mechanism widely used in combustion. The experimental results demonstrate that both burner stabilization and FGR are promising techniques for lowering NO emissions in fuel-rich flames. A comparison with detailed calculations allowed tracing the mechanistic origins of the observed reduction in NO formation rate. However, due to the existence of multiple formation mechanisms, more research is needed in order to improve predictive power of the flame models, particularly under very rich conditions. The quantitative results in this thesis are ideally suited for improving these model
The Effect of Humidity on the Knock Behavior in a Medium BMEP Lean-Burn High-Speed Gas Engine
The effects of air humidity on the knock characteristics of fuels are investigated in a lean-burn, high-speed medium BMEP engine fueled with a CH4 + 4.7 mole% C3H8 gas mixture. Experiments are carried out with humidity ratios ranging from 4.3 to 11 g H2O/kg dry air. The measured pressure profiles at non-knocking conditions are compared with calculated pressure profiles using a model that predicts the time-dependent in-cylinder conditions (P, T) in the test engine (“combustion phasing”). This model was extended to include the effects of humidity. The results show that the extended model accurately computes the in-cylinder pressure history when varying the water fraction in air. Increasing the water vapor content in air decreases the peak pressure and temperature significantly, which increases the measured Knock Limited Spark Timing (KLST); at 4.3 g H2O/kg dry air the KLST is 19 °CA BTDC while at 11 g H2O/kg dry air the KLST is 21 °CA BTDC for the same fuel. Excellent agreement is observed between the calculated knock resistance (using the Propane Knock Index, PKI) and the measured knock resistance (KLST) for the range in water content in air studied in this work. Since the effect of water on autoignition delay time is negligible, the observed increase in knock resistance of the fuel-air mixture is due a decrease in pressure and temperature of the end gas with increasing water content in as a result of changes in the mass burning rate, and thermophysical properties of the fuel-air mixture
Hormonal crises following receptor radionuclide therapy with the radiolabeled somatostatin analogue [177Lu-DOTA0,Tyr 3]octreotate
Introduction: Receptor radionuclide therapy is a promising treatment modality for patients with neuroendocrine tumors for whom alternative treatments are limited. The aim of this study was to investigate the incidence of hormonal crises after therapy with the radiolabeled somatostatin analogue [177Lu-DOTA0,Tyr3]octreotate (177Lu-octreotate). Materials and methods: All177Lu- octreotate treatments between January 2000 and January 2007 were investigated. Four hundred seventy-six patients with gastroenteropancreatic neuroendocrine tumors and three patients with metastatic pheochromocytoma were included fo
Experimental and Modeling Investigation of the Effectof H2S Addition to Methane on the Ignition and Oxidation at High Pressures
The
autoignition and oxidation behavior of CH<sub>4</sub>/H<sub>2</sub>S mixtures has been studied experimentally in a rapid compression
machine (RCM) and a high-pressure flow reactor. The RCM measurements
show that the addition of 1% H<sub>2</sub>S to methane reduces the
autoignition delay time by a factor of 2 at pressures ranging from
30 to 80 bar and temperatures from 930 to 1050 K. The flow reactor
experiments performed at 50 bar show that, for stoichiometric conditions,
a large fraction of H<sub>2</sub>S is already consumed at 600 K, while
temperatures above 750 K are needed to oxidize 10% methane. A detailed
chemical kinetic model has been established, describing the oxidation
of CH<sub>4</sub> and H<sub>2</sub>S as well as the formation and
consumption of organosulfuric species. Computations with the model
show good agreement with the ignition measurements, provided that
reactions of H<sub>2</sub>S and SH with peroxides (HO<sub>2</sub> and
CH<sub>3</sub>OO) are constrained. A comparison of the flow reactor
data to modeling predictions shows satisfactory agreement under stoichiometric
conditions, while at very reducing conditions, the model underestimates
the consumption of both H<sub>2</sub>S and CH<sub>4</sub>. Similar
to the RCM experiments, the presence of H<sub>2</sub>S is predicted
to promote oxidation of methane. Analysis of the calculations indicates
a significant interaction between the oxidation chemistry of H<sub>2</sub>S and CH<sub>4</sub>, but this chemistry is not well understood
at present. More work is desirable on the reactions of H<sub>2</sub>S and SH with peroxides (HO<sub>2</sub> and CH<sub>3</sub>OO) and
the formation and consumption of organosulfuric compounds
Detection of H2S, SO2 and NO2 in CO2 at pressures ranging from 1-40 bar by using broadband absorption spectroscopy in the UV/VIS range
This paper presents a methodology to quantitatively measure H2S, SO2 and NO2 fractions in gaseous CO2 by using broadband absorption spectroscopy at 1 and 40 bar. The mole fractions of binary- and 3-component mixtures of H2S, SO2 and NO2 in CO2 with known fractions ranging from 35-250 ppm are successfully derived from the measured absorption spectra. The difference between the fitted and experimental mole fractions is less than 10% for all studied mixtures. The results successfully demonstrate that low fractions of H2S, SO2 and NO2 in gaseous CO2 can be accurately measured at pipeline conditions by using broad band absorption spectroscopy
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