Effect of ice contamination of liquid-nitrogen drops in film boiling

Previously reported vaporization time data of liquid nitrogen drops in film boiling on a flat plate are about 30 percent shorter than predicted from standard laminar film boiling theory. This theory, however, had been found to successfully correlate the data for conventional fluids such as water, ethanol, benzene, or carbon tetrachloride. Experimental evidence that some of the discrepancy for cryogenic fluids results from ice contamination due to condensation is presented. The data indicate a fairly linear decrease in droplet evaporation time with the diameter of the ice crystal residue. After correcting the raw data for ice contamination along with convection, a comparison of theory with experiment shows good agreement

Film boiling of mercury droplets

Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. Diffusion from the upper surface of the drop appears as a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen

Przyszłość systemu ekologicznego Polski

Areas of the utmost natural and landscape values are subject to different forms of protection. It is generally believed, that the system of protected areas should ensure ecological balance on the regional and national scale. In order for this to happen, the system should be adequately vast, rich and varied, and not subject to degradation. At the end of 2006 the system of protected areas constituted 32,1% of the area of Poland. Despite this fact, the condition of ecological resources of the country is seriously threatened and is diminishing rapidly. Moreover, a lot of protected areas do not efficiently realize the tasks assigned to them. Contrary to a frequently repeated slogan about the improving condition of Poland’s environment, a lot of data proves, that, with the end of the 90s, we entered the stage of environmental loading increase and subsequent degradation of country’s ecological system. The main tendencies observed in the changes in natural environment are: drainage of moist areas, acceleration of surface runoff and a decrease in water abundance of rivers, diminishing of biologically active surface, fragmentation of landscape, thickening of ecological barriers net and spatial isolation of ecosystems, as well as, a decrease in biological and landscape diversity. In the face of such pressure, it is necessary to recognize nature protection and strengthening of the ecological structure of Poland as one of the key elements of new spatial planning policy of the country.Obszary o niemal naturalnym krajobrazie są przedmiotem różnych form ochrony przyrody. Zakłada się, że system obszarów chronionych powinien zapewnić równowagę ekologiczną w skali regionalnej i ogólnokrajowej. Aby tak się stało, system musi być odpowiednio duży, zróżnicowany i nie podlegać degradacji. Z końcem 2006 r. system obszarów chronionych w Polsce obejmował 32,1 % powierzchni kraju. Pomimo tego, stan zasobów ekologicznych jest poważnie zagrożony i gwałtownie się kurczy. Co więcej, wiele obszarów chronionych nie spełnia swej funkcji. W przeciwieństwie do często powtarzanych sloganów o poprawiającym się stanie środowiska w Polsce, wiele danych pokazuje, że wraz końcem lat 90. rozpoczął się okres wzrostu presji na środowisko i degradacji krajowego systemu ekologicznego. Główne obserwowane tendencje to: drenaż obszarów podmokłych, przyspieszenie spływu powierzchniowego, zmniejszenie zasobności wód w rzekach, zmniejszenie powierzchni aktywnej biologicznie, fragmentacja krajobrazu, narastanie barier ekologicznych i przestrzennej izolacji ekosystemów, a także zmniejszenie biologicznej i krajobrazowej różnorodności. Wobec tych zmian, niezbędne jest uznanie ochrony przyrody i systemu ekologicznego Polski za jeden z kluczowych elementów nowej polityki przestrzennej kraju

Optimal Chiller and Thermal Energy Storage Design for Building HVAC Systems

In the context of indoor building temperature regulation, a controller calculates the inputs for the HVAC system that result in appropriate thermal comfort conditions. Additionally, if electricity prices are time dependent, these control actions will also impact economic expenditures. To improve economic performance, Thermal Energy Storage (TES) is typically used in conjunction with HVAC to time-shift chiller cooling loads to times of low energy price. The method of Economic Model Predictive Control (EMPC) has been demonstrated to effectively reduce expenditures. Since TES and chiller sizes have a direct impact on achievable operational savings, an economic analysis considering the investment costs associated with these equipments is necessary. This work presents a novel algorithm intended to optimally select equipment sizes based on Net Present Value analysis and utilizing the recently developed methods of Economic Linear Optimal Control (ELOC) and constrained ELOC. Implementation of the numeric optimization is illustrated with a case study

Private Schooling, Educational Transitions, and Early Labour Market Outcomes: Evidence from Three Anglophone Countries

This article considers the extent to which private-state school differences in post-secondary outcomes can be explained by family background, secondary school achievement, or neither of the above. We find that privately educated children’s more advantaged family backgrounds and higher levels of school achievement are the main reasons why this group is more likely to enter university and work in professional jobs. However, even after accounting for family background and high school achievement, non-trivial private-state school differences in later lifetime outcomes remain. Empirical evidence is presented for three industrialized nations (Australia, England, and the United States), with broadly similar patterns of association observed within each

Expression of aminopeptidase N (APN) on peripheral blood mononuclear cells' surface as a marker of these cells' transendothelial migration properties in the course of multiple sclerosis.

CD13 Ag and CD11a, CD11b, CD18 molecule expression on peripheral blood mononuclear cells (PBMC) were studied as these cells' adherent or transendothelial migration properties in three different multiple sclerosis (MS) patients groups (total 38): with clinically active MS (acute exacerbation of MS and primary chronic progressive MS (CP-MS)) and with MS remission. The control group consisted of patients, suffering from other non-inflammatory neurological diseases (OND). The results of our study suggest that CD11a/CD18 molecules expression on PB lymphocytes, although higher on these cells' surface in the course of MS as compared to OND, does not differentiate clinical forms of MS. CD11a molecule expression on monocytes did not differ significantly in all tested MS patient groups in comparison to OND. Although the expression of CD11b/CD18 molecules on monocytes' surface shows their activation in the course of MS, it does not differentiate them either. However, CD13 Ag of APN expression on PBMC surface may be an immunological marker of MS clinical form. CD13 Ag expression may also be a sensitive marker of these cells' transendothelial migration properties

The immunoregulatory abilities of polymorphonuclear neutrophils in the course of multiple sclerosis.

The polymorphonuclear neutrophils (PMN) possess sufficient potential to affect both immune response and inflammation, however it has not been yet described in the course of multiple sclerosis (MS). We have studied binding of fluorescein isothiocyanate (FITC)- stained TNF-alpha by PMN, the expression of CD11a, CD11b, and CD18 molecules of beta2-integrines and the expression of CD10 (neutral endopeptidase-NEP) and of CD13 (aminopeptidase N; APN) antigens on PMN in three different groups of MS patients. The control group included neurological patients (OND) with noninflammatory diseases. The obtained results have proved that during MS exacerbation and in the course of chronic progressive MS, PMN reveal several forms of preactivation, including significantly higher stained-TNF-alpha binding, higher expression of CD11b and CD18, as well as CD10 and CD13 antigens, in comparison with MS remission or OND. We suggest that the increased expression of these molecules on PMN of MS patients in exacerbation of the disease and to a lower degree in the course of CP-MS is a result of PMN priming, and directly prove the PMN involvement in the disease pathogenesis