Wind tunnel calibration of the ''Arcasonde 1-A'' at simulated altitudes between 35 and 57 km

Subsonic wind tunnel calibration of Arcasonde 1-A atmospheric temperature sensing unit at simulated altitudes between 35 and 56 k

The role of the embryonic microenvironment in hematopoietic cell development

The adult hematopoietic system is comprised of a hierarchy of cells with the hematopoietic stem cell (HSC) at its foundation. HSCs give rise to progenitors that differentiate into mature hematopoietic cells, which perform the physiological functions of the hematopoietic system. The mature hematopoietic cells have a limited life span and need to be continuously replaced during adult life through the differentiation of HSCs. However, the pool of HSCs also has to be kept intact. The decision whether a dividing HSC differentiates towards a mature hematopoietic cell or preserves it self in an undifferentiated state is a tightly regulated process. An important player in this regulation is the so-called microenvironment (cells surrounding the HSCs). The adult hematopoietic system resides mainly within the bone marrow microenvironment. The hematopoietic supportive microenvironment changes during the development of an organism. Within the embryo the first HSCs are generated in close association with the dorsal aorta (major blood vessel). The dorsal aorta is part of a larger structure referred to as the aorta-gonad-mesonephros (AGM) region. During later stages in development, HSCs are found in the yolk sac, placenta and fetal liver. The fetal liver will eventually harbour the HSCs until birth when they colonize the bone marrow. All these hematopoietic tissues are believed to provide a specialized microenvironment for the generation, expansion and/or maintenance of HSCs. Despite the fact that new insights into the interactions of HSCs and the bone marrow microenvironment have been revealed in the last few years, the interplay between the embryonic microenvironment and the HSCs remains under intensive investigation. To bette! r understand how HSCs communicate with the microenvironments we studied the role of growth factors FGFs and IL-1 and the Runx1 transcription factor in the HSC supportive microenvironments provided by embryonic cell lines and embryos. As an interesting family of growth factors, the Fibroblast Growth Factors (FGFs) have previously been implicated to play a role in the communication between the bone marrow microenvironment and HSCs. As described in chapter 2, our studies showed that FGFs not only influence adult hematopoiesis, but are also regulators of embryonic hematopoiesis. More specifically, FGFs influence the supportive capacities of the AGM microenvironment for hematopoietic progenitors. As it is known that inbred mouse strains differ in HSC pool size as well as cycling activity, we compared the effects of FGFs on the bone marrow supportive microenvironment in six mouse strains. We showed that indeed there are strain-specific hematopoieticThe full text of this item cannot yet be made available, due to a publisher's embarg

The Deelen infrasound array for recording sonic booms and events of CTBT interest

The Seismology Division of the Royal Netherlands Meteorological Institute (KNMI) has build up expertise in infrasound measurements by investigating low frequency events in order to distinguish between seismic and sonic events. KNMI operates, amongst others, a sixteen element microbarometer array with an aperture of 1.5 km, the Deelen Infrasound Array (DIA). Sonic booms and events of Comprehensive Test Ban Treaty (CTBT) interest are recorded within the frequency range of 100 seconds and 40 Hertz. Recently, KNMI and Microflown Technologies B.V. started a collaboration concerning infrasound measurements. This paper reports the use of a novel sensor. The so-called Microflown [1] is an acoustic sensor, sensitive for frequencies from 0Hz up to 1kHz. The Microflown is developed at the University of Twente and commercialised by Microflown Technologies B.V [3]

Maximal regularity for non-autonomous evolution equations

We consider the maximal regularity problem for non-autonomous evolution equations of the form $u(t) + A(t) u(t) = f(t)$ with initial data $u(0) = u\_0$ . Each operator $A(t)$ is associated with a sesquilinear form $a(t; *, *)$ on a Hilbert space $H$ . We assume that these forms all have the same domain and satisfy some regularity assumption with respect to t (e.g., piecewise $\alpha$-H{\"o}lder continuous for some \alpha\textgreater{} 1/2). We prove maximal Lp-regularity for all initial values in the real-interpolation space $(H, D(A(0)))\_{1/p,p}$ . The particular case where $p = 2$ improves previously known results and gives a positive answer to a question of J.L. Lions [11] on the set of allowed initial data $u\_0$ .Comment: 19 pages. To appear in Math. An

Will Greenland melting halt the thermohaline circulation ?

Climate projections for the 21st century indicate a gradual decrease of the Atlantic Meridional Overturning Circulation (AMOC). The weakening could be accelerated substantially by meltwater input from the Greenland Ice Sheet (GIS). Here we repeat recent experiments conducted for the Intergovernmental Panel of Climate Change, providing an idealized additional source of freshwater along Greenland’s coast. For conservative and high melting estimates, the AMOC reduction is 35% and 42%, respectively, compared to a weakening of 30% for the original A1B scenario. Even for the high meltwater estimate the AMOC recovers in the 22nd century. The impact of the additional fresh water is limited to further enhancing the static stability in the Irminger and Labrador Seas, whereas the backbone of the overturning is maintained by the overflows across the Greenland-Scotland Ridge. Our results suggest that abrupt climate change initiated by GIS melting is not a realistic scenario for the 21st century

Selectivity and Sustainability of Electroenzymatic Process for Glucose Conversion to Gluconic Acid

Electroenzymatic processes are interesting solutions for the development of new processes based on renewable feedstocks, renewable energies, and green catalysts. High-selectivity and sustainability of these processes are usually assumed. In this contribution, these two aspects were studied in more detail. In a membrane-less electroenzymatic reactor, 97% product selectivity at 80% glucose conversion to gluconic acid was determined. With the help of nuclear magnetic resonance spectroscopy, two main side products were identified. The yields of D-arabinose and formic acid can be controlled by the flow rate and the electroenzymatic reactor mode of operation (fuel cell or ion-pumping). The possible pathways for the side product formation have been discussed. The electroenzymatic cathode was found to be responsible for a decrease in selectivity. The choice of the enzymatic catalyst on the cathode side led to 100% selectivity of gluconic acid at somewhat reduced conversion. Furthermore, sustainability of the electroenzymatic process is estimated based on several sustainability indicators. Although some indicators (like Space Time Yield) are favorable for electroenzymatic process, the E-factor of electroenzymatic process has to improve significantly in order to compete with the fermentation process. This can be achieved by an increase of a cycle time and/or enzyme utilization which is currently low

Hormonal modifications in patients admitted to an internal intensive care unit for acute hypoxaemic respiratory failure

AbstractTo clarify which endocrine modifications can be observed in acute hypoxaemic respiratory failure, 15 severely ill male patients [PAT; median age: 61 (range: 48 years); median height: 173 (range: 12) cm; median mass: 73 (range 31) kg] were investigated immediately upon admission to an intensive care unit (ICU) for this clinical disorder. Before starting treatment, the blood gases were measured and a number of selected hormones with special relevance for an ICU setting were determined. These are known to be modified by acute hypoxaemia in healthy subjects and to possess glucoregulatory properties, or an influence upon cardiocirculation or the vascular volume regulation: insulin, cortisol, adrenaline, noradrenaline, atrial natriuretic peptide, renin, aldosterone, angiotensin converting enzyme, and endothelin-I (ET). To elucidate whether potential endocrine changes resulted from acute hypoxaemia alone, the underlying disease, or unspecific influences connected with the ICU setting, all measurements were compared to those of a completely healthy reference group (REF) with comparable acute experimental hypoxaemia. The latter state was achieved by having the REF breathe a gas mixture with the oxygen content reduced to 14% (H).In the REF, neither the medians nor the distribution of endocrinologic measurements were modified significantly by acute hypoxaemia. In the PAT, the medians were increased considerably, yet with a slight diminution of ET. The distribution of individual values was considerably broader than in the REF with H.In conclusion, considerable increases in the means of the above hormones, with the exception of ET, can be registered in severely ill patients admitted to ICUs with acute hypoxaemic failure. However, such modifications cannot be considered attributable exclusively to acute arterial hypoxaemia. The underlying clinical disorders, such as septicaemia or an unspecific endocrine epiphenomenon, including severe and not only hypoxaemic stress, seem to be predominant