In this paper we study how the scientific production of a representative researcher develops over his/her career. Using Pontryagin’s maximum principle we derive the optimal capital accumulation over ...the life cycle of a scientist. In particular, we are able to identify two regimes of human capital accumulation (say intensive versus normal) and to characterize their optimality depending on the initial human capital level. The paper includes a formal proof of the negative impact of the obscolescence rate as well as the discount rate on human capital production and we show that this reduction is largest at earlier ages.
Abstract
A Schottky barrier radiation detector and pixel imaging sensor fabricated from epitaxially grown SiC semiconductor were analyzed. The detector was based on an 80 μm thick epitaxial SiC ...layer. Capacitance-voltage measurement was performed to study the thickness of the space charge region of the detector as a function of applied bias. The results showed that the detector was completely depleted at a reverse bias higher than 300 V. The impurity concentration profile was also calculated, which indicated a net impurity concentration below 1.5×10
14
cm
-3
. A prototype of a SiC Timpix3 radiation camera was fabricated, and its energy resolution was investigated using the
241
Am radioisotope. The camera exhibited an energy resolution of 4.5 keV for 60 keV gamma photons. X-ray fluorescence photons (from 14 keV to 22 keV) were detected with a resolution below 2.0 keV. The imaging quality of the camera was investigated using a test object. The prototype showed a high-quality image performance with a stable count rate, which was determined from uniform intensity profiles extracted from parts of the test object image. A disadvantage of this prototype is that the radiation hits the detector from the side of the substrate and only then it reaches its active SiC epitaxial layer. This represents a dead layer that reduced the detection efficiency of X-rays below 10 keV.
Abstract
In this work, Schottky detectors based on a high-quality 4H-SiC epitaxial layer with a thickness of 50 µm were prepared. The Schottky contact of Ni/Au metallization with a 3 mm diameter was ...made. Reverse current-voltage characteristics were measured up to a voltage of 300 V with a leakage current of 40 pA at room temperature. Using an α-particle radiation source, the spectrometric characteristics of the 4H-SiC detector were tested. The best energy resolution in the FWHM (Full Width and Half Maximum) about 15 keV for 5.5 MeV α-particles was observed. Furthermore, a 4H-SiC pixel sensor (256 × 256) for the Timepix3 reading chip was prepared. The spectrometric and imaging properties of the new Timepix3 detector based on the 4H-SiC sensor were tested. The results showed high energy resolution and also high-quality X-ray imaging of the biological object.
The impact of sowing dates (early, normal and late) on the crop physiological parameters (leaf area index (LAI), chlorophyll content (SPAD)) and yield of sunflower cultivars (NK Neoma, NK Ferti, ...PR64H42) was observed in 2012, 2013, and 2014 on chernozem soil in Eastern Hungary. The obtained LAImax values were 5.1-5.3 m2/m2 (early sowing date), 4.5-5.2 m2/m2 (normal sowing date) and 4.4-5.2 m2/m2 (late sowing date). Pearson's correlation analysis revealed a close negative correlation between LAImax and sowing date in 2013 and 2014 (r = -0.920**,r = -0.813**) and an average, non-significant correlation between LAImax and sunflower yield (r = 0.575ns, r = 0.509ns). The relative chlorophyll content was not significantly affected by either growing year, sowing date or genotype in the period between May and July (~40). In the case of high infection index (Ii) values (2012), sunflower cultivars had the highest yield in the late sowing date (4.3-5.3 t/ha). However, average Ii values (2013) were associated with the highest yields in normal sowing date (5.1-5.3 t/ha) and moderate Ii values (2014) showed the highest yields in early sowing dates (4.6-5.1 t/ha).
Matra Gravitational and Geophysical Laboratory (MGGL) was established near Gyöngyösoroszi, Hungary in 2015, in the cavern system of an unused ore mine. The laboratory is located 88 m below the ...surface, with the aim of measuring and analysing the advantages of the underground installation's third generation gravitational wave detectors. Specialized instruments have been installed to measure seismic, infrasound and electromagnetic noise, and the variation of the cosmic muon flux. In the preliminary (RUN-0) test period, March-August 2016, data collection was accomplished. In this paper we describe the research potential of the MGGL, list the installed equipment and summarize the experimental results of RUN-0. Here we report on the RUN-0 data, that prepares the systematic and synchronized data collection of the next run period.
In the first part of the paper a brief introduction is given (a) to the magnetotelluric (MT) and magnetovariation (MV) soundings, (b) to electrical resistivity of minerals and rocks, and their ...dependence on temperature and fluid content. The basic geoelectric model in the Pannonian Basin is a (linear) tectonic zone (“dike”) and a series of dikes. In the second part the main crustal and mantle conductivity anomalies observed in the Pannonian Basin (PB) are summarized: (a) deep conductive crustal fractures and their relation to the occurrence of the earthquakes, boundary of the megablock(s) etc., (b) middle crustal conductors as indicators of decrease in stress and seismic activity depending on thermal regime, (c) the conductive asthenosphere and its lateral change in the PB in connection with the heat flow and tectonics. The general relation between the depth of the conductive asthenosphere and the regional heat flow is also presented, (d) MT anisotropy of the resistivity distribution in the PB and its tectonic explanation based on Haas’s tectonic map (
2001
, Fig. 1). All these observations and conclusions are considered as results for further investigations.
We present a new model for the formation of Plio-Pleistocene alkaline basalts in the central part of the Carpathian-Pannonian region (CPR). Based on the structural hydroxyl content of clinopyroxene ...megacrysts, the ‘water’ content of their host basalts is 2.0–2.5 wt.%, typical for island arc basalts. Likewise, the source region of the host basalts is ‘water’ rich (290–660 ppm), akin to the source of ocean island basalts. This high ‘water’ content could be the result of several subduction events from the Mesozoic onwards (e.g. Penninic, Vardar and Magura oceans), which have transported significant amounts of water back to the upper mantle, or hydrous plumes originating from the subduction graveyard beneath the Pannonian Basin.
The asthenosphere with such a relatively high ‘water’ content beneath the CPR may have been above the ‘pargasite dehydration’ (<90 km) or the ‘nominally anhydrous’ (>90 km) solidi. This means that neither decompressional melting nor the presence of voluminous pyroxenite and eclogite lithologies are required to explain partial melting.
While basaltic partial melts have been present in the asthenosphere for a long time, they were not extracted during the syn-rift phase, but were only emplaced at the onset of the subsequent tectonic inversion stage at ~8–5 Ma. We propose that the extraction has been facilitated by evolving vertical foliation in the asthenosphere as a response to the compression between the Adriatic indenter and the stable European platform. The vertical foliation and the prevailing compression effectively squeezed the partial basaltic melts from the asthenosphere. The overlying lithosphere may have been affected by buckling in response to compression, which was probably accompanied by formation of deep faults and deformation zones. These zones formed conduits towards the surface for melts squeezed out of the asthenosphere.
This implies that basaltic partial melts could be present in the asthenosphere in cases where the bulk ‘water’ content is relatively high (>~200 ppm) at temperatures exceeding ~1000–1100 °C. These melts could be extracted even under a compressional tectonic regime, where the combination of vertical foliation in the asthenosphere and deep fractures and deformation zones in the folded lithosphere provides pathways towards the surface. This model is also valid for deep seated transpressional or transtensional fault zones in the lithosphere.
•The asthenosphere at the time of the alkaline basaltic volcanism was wet.•Melt extraction was only initiated in the tectonic inversion stage.•During the inversion the foliation become sub-vertical in the asthenosphere.•Deep fractures in the lithosphere facilitated the melt extraction.•The CPR provides a global template to understand the genesis of alkaline basalts.
Summary of the long term data taking, related to one of the proposed next generation ground-based gravitational detector’s location is presented here. Results of seismic and infrasound noise, ...electromagnetic attenuation and cosmic muon radiation measurements are reported in the underground Matra Gravitational and Geophysical Laboratory near Gyöngyösoroszi, Hungary. The collected seismic data of more than two years is evaluated from the point of view of the Einstein Telescope, a proposed third generation underground gravitational wave observatory. Applying our results for the site selection will significantly improve the signal to noise ratio of the multi-messenger astrophysics era, especially at the low frequency regime.
The acceptability of the combined contraceptive vaginal ring, NuvaRing
®, was assessed during two trials conducted in North America and Europe. Women completed a questionnaire about the ring’s ...clarity of instructions, ease of use, sexual comfort, cycle-related characteristics and satisfaction after 3, 6 and 13 cycles of use. A total of 1950 women (82% of those recruited) completed a questionnaire at cycle 3. At baseline, 66% of participants preferred oral contraceptives, but after three cycles of ring use 81% preferred the ring. On study completion, 97% agreed that the instructions for use were clear; 85% of women and 71% of their partners never/rarely felt the ring during intercourse and 94% of partners never/rarely minded that the woman was using the ring. Overall acceptance was high, 96% were satisfied with the ring and 97% would recommend the ring. Similar responses were seen for women who prematurely discontinued from the studies, except that slightly fewer women were satisfied (60%) and would recommend the ring (75%). Reasons for liking the ring included ‘not having to remember anything’ (45%) and ‘ease of use’ (27%). In conclusion, there is a high level of user and partner acceptability for the contraceptive ring.
Activity of the hypothalamic-pituitary-adrenocortical (HPA) axis is commonly assessed by measuring glucocorticoids such as cortisol (CORT). For many years, CORT was obtained primarily from blood ...plasma or urine, whereas later approaches added saliva and feces for noninvasive monitoring of HPA functioning. Despite the value of all these sample matrices for answering many research questions, they remain limited in the temporal range of assessment. Plasma and saliva are point samples that vary as a function of circadian rhythmicity and are susceptible to confounding by environmental disturbances. Even urine and feces generally assess HPA activity over a period of only 24 h or less. We and others have recently developed and validated methods for measuring the concentration of CORT in the body hair of animals (e.g. rhesus monkeys) and scalp hair of humans. CORT is constantly deposited in the growing hair shaft, as a consequence of which such deposition can serve as a biomarker of integrated HPA activity over weeks and months instead of minutes or hours. Since the advent of this methodological advance, hair CORT has already been used as an index of chronic HPA activity and stress in human clinical and nonclinical populations, in a variety of laboratory-housed and wild-living animal species, and in archival specimens that are many decades or even centuries old. Moreover, because human hair is known to grow at an average rate of about 1 cm/month, several studies suggest that CORT levels in hair segments that differ in proximity to the scalp can, under certain conditions, be used as a retrospective calendar of HPA activity during specific time periods preceding sample collection.
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