Improving the hyperpolarization of (31)p nuclei by synthetic design

Traditional (31)P NMR or MRI measurements suffer from low sensitivity relative to (1)H detection and consequently require longer scan times. We show here that hyperpolarization of (31)P nuclei through reversible interactions with parahydrogen can deliver substantial signal enhancements in a range of regioisomeric phosphonate esters containing a heteroaromatic motif which were synthesized in order to identify the optimum molecular scaffold for polarization transfer. A 3588-fold (31)P signal enhancement (2.34% polarization) was returned for a partially deuterated pyridyl substituted phosphonate ester. This hyperpolarization level is sufficient to allow single scan (31)P MR images of a phantom to be recorded at a 9.4 T observation field in seconds that have signal-to-noise ratios of up to 94.4 when the analyte concentration is 10 mM. In contrast, a 12 h 2048 scan measurement under standard conditions yields a signal-to-noise ratio of just 11.4. (31)P-hyperpolarized images are also reported from a 7 T preclinical scanner

Changes of length of the vegetative period in Poland

It is commonly accepted that the vegetative period is the part of the year during which the mean daily air temperature attains at least 5°C. The report here summarized refers to the study based upon the monthly averages of air temperature from the period 1931-1990, measured at nine weather stations, representing various geographical conditions in Poland. The average dates of the beginning and end of the vegetative period confirm the regularities in the spatial distribution of these characteristics over the area of Poland, which are known from the literature of the subject. The vegetative period starts, generally, at the turn of April, and ends at the turn of November (Tables 1 and 2, Figs. 1 and 2). Length of the vegetative period ranges from 190-200 days in the north-eastern Poland to more than 230 days in the western part of the country. It is the shortest in the mountains, lasting approximately 185 days (Table 3, Figs. 1 and 3). During the 60-year period under study the earliest start of the vegetative period in the lowland part of Poland occurred on January 30th (in 1990), while the latest - on April 25th (1941, 1955). The respective extreme dates for the mountainous areas were March 25th (1934) and May 5th (1980). Thus, within the area of Poland it may happen that vegetation starts to grow already in the last week of January, but it may also start to grow as late as in the first week of May. The dates of the end of the vegetative period for the lowland Poland (Table 2, Figs. 1 and 2) range from October 9th (1946, 1976) to December 3rd ( 1951 ). In mountains the vegetative period ended the earliest on the last day of September ( 1931) and the latest - on November 18th (1963). Thus, the end of the vegetative period may occur in Poland between the last week of September and the first week of December. The length of the vegetative period (Table 3, Figs. 1 and 3) ranges from 170 days (1941) to 291 days - the latter being the absolute maximum of the period under study- in 1990. Hence, the difference between the extreme lengths of the vegetative period amounts to 121 days. In the mountains, though, the shortest vegetative period lasted 159 days (1931), while the longest - 221 days ( 1934). The analysis of the coefficients of correlation (Table 4) of the dates of the beginning and end of the vegetative period with its length showed that the length of this period is more strongly linked with the date of beginning than with the date of end. This is most probably connected with the fact that the starting date of the vegetative period in consecutive years displays greater variability than the ending date. Equations of linear regression (Table 5) indicate that the length of the vegetative period increases at the rate of 1 to 3 days per decade. This is is most probably connected with the acceleration of the start of vegetation by approximately 0.5 to 1.5 days per decade, coupled with the delay of its termination by approximately 0.5 to 1.5 days per decade. The analysis of the periodical changes (Fig. 4) showed that the 7-year cycle of the starting dates of vegetation is worth special attention, along with the 3- and 4-year cycles of the termination dates. The true length of the 7-year cycle for the start of the vegetative period gets bigger as we go from the west (7.6 years) to the east (7.9 years) of the country. The spectra of oscillations of the growing season's end are, on the other hand, characterized by high uniformity over the area of Poland

Impact of relief and land cover on the differences in the local climate of the Pinczow region

In the 1990s, the Chair of Climatology of Warsaw University conducted studies of the local climate in the Nida Basin (vicinity of Pińczów). Compared to the neighbouring areas, the researched area is characterised by specific climatic features. At the same time, this is a region with marked differences in the climatic conditions on the local scale. This results from the diversity of substratum formations, presence of large forest complexes, water bodies and areas transformed by man. The study comprised mapping, which produced a map of topoclimates in the 1 :25000 scale. In addition, meteorological observations were carried out, which allowed to develop a qualitative profile of thermal and humidity conditions in the individual units. The impact of the relief and land cover on the spatial differentiation of climate constituents in various synoptic situations was also defined. The main characteristic feature of the region's relief is the wide Nida Valley. As a concave landform, it is susceptible to the downflow of chilled air from the neighbouring areas, as a result forming pockets of chilled air to the point of reaching an inversion of temperature. At the same time, the wet soils occurring in the valley's bottom are characterised by good thermal conductivity, which can result in delaying the beginning of the occurrence of ground thermal inversion and reducing diurnal amplitude of ground and air temperature. The Pińczów and the Wodzisław hummocks surrounding the valley do not represent so spatially condensed topoclimatic units, which is due to the varied exposure and steepness of slopes, as well as to its surface formations. It is primarily the slopes of the Pińczów Hummock that enjoy favourable thermal conditions. The spacious forest complexes, which occupy large areas on the slopes of both hummocks and smaller ones in the Nida Valley, provide an additional diversity to the topoclimatic conditions

The topo-climatic research at the department of climatology

An important stream of research conducted at the department of Climatology of the University of Warsaw is constituted by the study of climate on a local scale. These studies serve not only the didactic purposes (a significant part of these studies is carried out in the framework of the student exercises), but also bring a rich study materiai, systematically made use of in the research work, of both applied and methodological nature. Until the end of the 1980s the primary areas of interest were Warsaw and its surroundings, and the north-eastern Poland (the region of the Great Masurian Lakes, the Biebrza river swamps, and the Łomża Landscape Park of the river Narew Valley). During the 1990s the topo-climatic research was deployed on a bigger scale, constituting the element of the comprehensive studies associated with protection of nature - elaboration of plans of protection of the National Parks (e.g. the Wigry Lake national Park, or the Stołowe Mountains National Park). In the recent years, in connection with the new formula of the field exercises in the general physical geography, including climatology, the Nida River Basin became another focus of interest. The comprehensive field work: topo-climatic mapping and the meteorological observations conducted in the different regions - landscapes of Poland, allowed for characterisation of the typical conditions in the individual units, and also contributed to the introduction of definite complements into the topo-climatic classification applied, which enhanced the level of precision of the delimitations performed according to it

Th e sources of moisture in the barchans of Western Sahara

The aim of the study was to determine the impact of climatic and meteorological conditions on aeolian sand transport within barchans. The study area was located at Western Sahara, around the towns of Tarfaya and Laâyoune. Particular attention was paid to the factors that increase the moisture content of the surface and subsurface layers of sand dunes. It could be one of the important factors to have an influence on threshold wind velocity. Western Sahara dune fields are situated in the zone of the dominant wind direction from the northern sector, which determines the barchan dunes shape and orientation, as well as the supply of moisture from the Atlantic Ocean. The results of investigations confirm that dunes receive quite a lot of moisture from rainfall and such phenomena as fog as well. Studies have confirmed that the water supply from the fog is comparable to, or even exceeds the amount of water from rainfall in the area. Wetted surface layer reduces the transport of aeolian material, even in case of a wind speed greater than 4-5 ms⁻¹. The presence of fog and dew does not affect the moisture of the deeper sand layers, which occurs after rainfall. Analysis of aeolian sand transport within the barchan dunes in the areas such a Western Sahara, should not be therefore limited to the measurement of wind speed and its direction. It must include the investigations on other meteorological elements, especially air temperature and humidity conditions, responsible for the amount of atmospheric deposits on the dune surface