From renting to owning: Life course and housing market circumstances

Moving from a rental dwelling to owner occupation is an important event in the housing career of a household. The literature shows that considerations of housing consumption, related to household circumstances, play a dominant role in the decision to rent or to buy a dwelling. The analysis in this article substantiates again that family status must have reached a certain stability, and prospects of a substantial permanent income must be good, before the move from renting to owning is considered. But general economic circumstances which manifest themselves into changes in housing market conditions, also have measurable influences on the decision for renting or owning. In the Netherlands, the propensity for renters to buy a dwelling were low between 1978 and 1982 when prices of owner occupation were falling, mortgage interest rate was high and income prospects were uncertain. Government policy certainly has an influence on the decision of households to rent or to buy a dwelling. In the long term government promotion of one particular tenure sector over a long period may well stimulate household preference for this sector. And by consistently building large parts of new construction in one tenure, opportunities of moving in or into this sector are increased as this article illustrates for Randstad Holland.     

A 40 keV cyclotron for radioisotope dating

We have built and begun testing a small low energy negative ion cyclotron for direct detection of ¹⁴C. At present, the cyclotron is operated in a high resolution mode at the 31st harmonic, with 1–2 kV on the dees. The high harmonic and a minimum number of turns of approximately 100, should give a fwhm mass resolution of about $\text{1}\text{30000}$ — sufficient to suppress the background from molecular ions such as ¹³CH^?. Background such as scattered ions of ¹²C^? and ¹³C^? should be totally suppressed by the cyclotron acceleration process. (At the 88″ cyclotron at LBL we found that ions only 1% off-resonance are suppressed by more than a factor of 10¹⁷.) A miniature Cs sputter source located at the center of the cyclotron is expected to provide more than 1 μA of negative carbon ions. Negative ions are used in order to eliminate the interference from ¹⁴N. Unlike high energy cyclotrons, focussing is obtained solely from the axial components of the accelerating electric field. The magnetic field is kept flat to within 1 part in 10⁴ in order to maintain exact isochronism throughout the several thousand accelerating rf cycles. The low final energy of 40 keV eliminates any danger from radiation or need for shielding, and the final orbit radius of only 10.5 cm, reduce the size and cost of the machine to that of conventional mass spectrometers.     

Liver parenchymal cells differ from the fat-storing cells in their lipid composition

The neutral lipid and phospholipid compositions of purified sinusoidal (fat-storing, endothelial and Kupffer) cells, parenchymal cells and liver homogenates were determined by thin layer chromatography. In addition, the retinoid content of the same purified cell populations was determined by high performance liquid chromatography. From each cell type, both a lipid droplet fraction and a pellet fraction (containing the majority of the remaining cell organelles) were prepared by differential centrifugation. Electron microscopic analysis showed that lipid droplets isolated from fat-storing cells were larger (up to 8 μm) than those isolated from parenchymal cells (up to 2.5 μm). Moreover, the parenchymal lipid droplets seemed to be surrounded by a membranous structure, while the fat-storing lipid droplets seemed not to be. Both fat-storing and parenchymal cells contained high concentrations of neutral lipids, 57.9 μg and 71.0 μg/10⁶ cells, respectively, while endothelial and Kupffer cells contained only 8.6 μg and 13.8 μg/10⁶ cells of neutral lipids, respectively. Sixty-five percent of fat-storing cell lipid droplet fractions comprised esters of retinol and cholesterol. This combined ester fraction contained mainly retinyl esters. In addition, considerable quantities (20%) of triglycerides were present. Parenchymal cell lipid droplet fractions comprised triglycerides (62%) and cholesteryl esters (up to 30%). The pellet fractions prepared from all four cell types consisted mainly of cholesterol (41–67%) and free fatt acids (20–28%). The phospholipid content was much higher in parenchymal cells than in the sinusoidal liver cell types. The relative proportions of the four major phospholipid classes were comparable in all liver cell types analyzed. It is concluded that parenchymal cell lipid droplets comprised mainly triglycerides and cholesteryl esters, which is in agreement with the function of parenchymal cells in lipid metabolism. Fat-storing cell lipid droplets consisted of retinyl esters and triglycerides, which correlates well with their function in retionid storage and metabolism.     

Identification of temperature-dependent water quality changes during a deep well injection experiment in a pyritic aquifer

Artificial recharge is a technique used increasingly to supplement drinking water supplies. To assess the potential water quality changes that occur during subsurface passage, a comprehensive deep-well injection experiment was carried out for a recharge scheme, where pretreated, aerobic surface water was injected at 300 m depth into an anaerobic aquifer. Water quality parameters were recorded over the 854-days long injection phase. The evolution of the major ion and redox chemistry was analyzed with a three-dimensional reactive multicomponent transport model. It was found that the oxidation of pyrite was the main driverforwater quality changes and that reaction rates depended significantly on the spatially/temporally varying groundwater temperature. With the temperature-dependency of the oxidation reactions incorporated into the model, the simulations give an accurate picture of the temporal and spatial evolution of the hydrochemical changes that occurred during the experiment. To delineate the influence of physical and chemical processes on local concentration changes the results of the reactive transport model simulations were compared with the corresponding results from nonreactive simulations. The study emphasizes the suitability of mechanistic multicomponent reactive transport modeling as an integrative tool for data analysis when physical transport and chemical processes interact.     

The use of hybrid computers for system-parameter estimation

This paper is devoted to the question in what way system-parameter estimation problems can be solved by means of hybrid equipment and what approaches are best suited for such problems.The combination of an analog model of the system under study and the digital computer taking care of the adjustment of that model is still an attractive scheme, in spite of the strong competition due to the rapid development of purely digital techniques.Advantages and problems are pointed out. Some illustrative examples are summarized.     

Quantitative T 2 * assessment of acute and chronic myocardial ischemia/reperfusion injury in mice

Object

Imaging of myocardial infarct composition is essential to assess efficacy of emerging therapeutics. T ₂ ^* mapping has the potential to image myocardial hemorrhage and fibrosis by virtue of its short T ₂ ^* . We aimed to quantify T ₂ ^* in acute and chronic myocardial ischemia/reperfusion (I/R) injury in mice.

Materials and methods

I/R-injury was induced in C57BL/6 mice (n?=?9). Sham-operated mice (n?=?8) served as controls. MRI was performed at baseline, and 1, 7 and 28?days after surgery. MRI at 9.4?T consisted of Cine, T ₂ ^* mapping and late-gadolinium-enhancement (LGE). Mice (n?=?6) were histologically assessed for hemorrhage and collagen in the fibrotic scar.

Results

Baseline T ₂ ^* values were 17.1?±?2.0?ms. At day 1, LGE displayed a homogeneous infarct enhancement. T ₂ ^* in infarct (12.0?±?1.1?ms) and remote myocardium (13.9?±?0.8?ms) was lower than at baseline. On days 7 and 28, LGE was heterogeneous. T ₂ ^* in the infarct decreased to 7.9?±?0.7 and 6.4?±?0.7?ms, whereas T ₂ ^* values in the remote myocardium were 14.2?±?1.1 and 15.6?±?1.0?ms. Histology revealed deposition of iron and collagen in parallel with decreased T ₂ ^* .

Conclusion

T ₂ ^* values are dynamic during infarct development and decrease significantly during scar maturation. In the acute phase, T ₂ ^* values in infarcted myocardium differ significantly from those in the chronic phase. T ₂ ^* mapping was able to confirm the presence of a chronic infarction in cases where LGE was inconclusive. Hence, T ₂ ^* may be used to discriminate between acute and chronic infarctions.     

Schraubpfähle: Herstellung,Tragfähigkeit und numerische Modellierung

Screw piles: construction methods, bearing capacity and numerical modeling. In the last years the technology of screw‐piling has been developed to overcome the shortcomings of the non‐displacement piles (e.g. bored or flight auger piles) that are always accompanied by soil disturbance, which affect negatively the pile bearing capacity. On the contrary, the screw piles can be considered more or less as full displacement piles, which are comparable with the conventional displacement driven piles. Due to vibration free installation and minimal noise disturbance of the environment they can be applied in urban areas, where driven piles are not appropriate. The full displacement screw piles offer meaningful advantages in terms of environmental engineering. This relatively new piling technology is used successfully as an efficient foundation system that fulfils both stability and serviceability requirements. The use of standard compact machines with high productivity simplifies site operations and contributes to economical performance of the system at the same time. A general overview of the pile system ‐installation techniques, process and bearing capacity – will be described and discussed. First numerical analyses, calibrated on pile load tests to check the validity of the numerical model were applied.