On the influence of spike shape at supersonic flow past blunt bodies

Da bi se eliminsala pojava jakog udarnog talasa pri nadzvučnom opstrujavanju projektila, koja zanačajno povećava otpor pri letu krozvazduh, na njegov vrh montira se igla. U radu se daju rezultati eksperimentalnog istraživanja uticaja oblika igle na aerodinamičke koeficijente (uzgona, otpora, momenta propinjanja, kao i položaj centra pritiska) pri nadzvučnom opstrujavanju tela zaobljenog vrha. Eksperiment je izveden u aereotunelu, za jednu vrednost Mahovog i Rejnoldsovog broja, kao i za jednu vrednost napadnog ugla α = 2o. Za telo bez igle, kao i za telo sa četiri različita modela igle merene su aerodinamičke sile i momenti. U radu su predloženi kriterijumi za procenu uticaja igle zasnovani isključivo na rezultataima dobijrenim vizualizacijom strujanja. Igla najboljih karakteristika, od ispitanih konfiguracija, izabrana na osnovu izmerenih aerodinamičkih koeficijenata, uklapa se u ove kvalitativne kriterijume.In order to eliminate the appearance of a strong shock wave at a supersonic flight of a missile, which considerably increases the drag during its flight through the air, a spike is mounted on its nose. Presented paper offers the results of an experimental analysis of the influence of the spike's shape on the aerodynamic coefficients (drag, lift and pitching moment coefficient, as well as the location of the center of pressure) at supersonic flow past blunt-nosed body. The experiment was carried out in a wind tunnel, for one value of Mach and Reynolds numbers, and for one value of the angles of attack, α = 2o. For the body without spike, and with four different spike shapes, the aerodynamic forces and moment were measured. Using only the photos obtained by Schlieren visualization of the flow, the paper proposes a criterion of estimating the aerodynamic effect of the spike shape. The best spike shape from the experimental set of spikes, selected by the measurement of the aerodynamic coefficients, coincided with this qualitative criterion

On the influence of spike shape at supersonic flow past blunt bodies

Da bi se eliminsala pojava jakog udarnog talasa pri nadzvučnom opstrujavanju projektila, koja zanačajno povećava otpor pri letu krozvazduh, na njegov vrh montira se igla. U radu se daju rezultati eksperimentalnog istraživanja uticaja oblika igle na aerodinamičke koeficijente (uzgona, otpora, momenta propinjanja, kao i položaj centra pritiska) pri nadzvučnom opstrujavanju tela zaobljenog vrha. Eksperiment je izveden u aereotunelu, za jednu vrednost Mahovog i Rejnoldsovog broja, kao i za jednu vrednost napadnog ugla α = 2o. Za telo bez igle, kao i za telo sa četiri različita modela igle merene su aerodinamičke sile i momenti. U radu su predloženi kriterijumi za procenu uticaja igle zasnovani isključivo na rezultataima dobijrenim vizualizacijom strujanja. Igla najboljih karakteristika, od ispitanih konfiguracija, izabrana na osnovu izmerenih aerodinamičkih koeficijenata, uklapa se u ove kvalitativne kriterijume.In order to eliminate the appearance of a strong shock wave at a supersonic flight of a missile, which considerably increases the drag during its flight through the air, a spike is mounted on its nose. Presented paper offers the results of an experimental analysis of the influence of the spike's shape on the aerodynamic coefficients (drag, lift and pitching moment coefficient, as well as the location of the center of pressure) at supersonic flow past blunt-nosed body. The experiment was carried out in a wind tunnel, for one value of Mach and Reynolds numbers, and for one value of the angles of attack, α = 2o. For the body without spike, and with four different spike shapes, the aerodynamic forces and moment were measured. Using only the photos obtained by Schlieren visualization of the flow, the paper proposes a criterion of estimating the aerodynamic effect of the spike shape. The best spike shape from the experimental set of spikes, selected by the measurement of the aerodynamic coefficients, coincided with this qualitative criterion

Role of β2 Integrins in the Binding of Thymocytes to Rat Thymic Macrophages

A role of β2 integrins and one of their ligands, ICAM-1, in thymic macrophage (TMF)/thymocyte interactions was studied. TMF were isolated as adherent cells from 4-day old culture of thymic-cell suspensions either from normal or hydrocortisone-treated rats. Adherent cells were 94-98% positive with ED1 (a pan-macrophage marker). The majority of them (75-95%) expressed the CD11b and CD18 molecules, and 60-70% expressed CD54 (ICAM-1). A low proportion of TMF (10-20%) expressed CDlla (LFA-1). The expression of all these antigens was upregulated by IFN-α and TNF-α. The effect of these mAbs on TMF/thymocyte binding was studied using a simple rosette assay by incubating unstimulated or IFN-γ or TNF-α stimulated TMF, grown on microscopic slides with resting or ConA +IL-2 activated thymocytes. It was found that LFA-1/CD18 and ICAM-1 play a significant role in the TMF/thymocyte adhesion. In addition, a LFA-l-dependent/ICAM- 1-independent adhesion pathway was observed, suggesting that LFA-1 might use another ligand. The inhibitory effect of anti-CD18 mAb (WT-3) was higher than the effect of anti-LFA-1 mAb (WT-1) and was a consequence of blocking the CD18 chain both on thymocytes and TMF. No significant difference in the expression and function of adhesion molecules was found between TMF obtained from normal or hydrocortisone-treated rats. The involvement of CD1 1b in these processes was of lesser importance than the role of the CD11a molecule. By using mAbs to different epitopes of the CD11b molecule, such as OX-42 (anti-CD11b/CD11c), ED7, and ED8 (anti-CD11b), it was found that they were either slightly or moderately inhibitory under certain experimental conditions or did not significantly modulate TMF/thymocyte binding. Oχ-42 was slightly stimulatory in some experiments. Cumulatively, these results show that 2 integrins play a significant role in TMF/thymocyte interactions and probably contribute to T-cell development in vivo

Mechanisms Involved in the Binding of Thymocytes to Rat Thymic Dendritic Cells

The effects of monoclonal antibodies (mAbs) to cell-surface molecules, divalent cations, and various cell-signaling and metabolic inhibitors on the binding of thymocytes to rat thymic dendritic cells (TDC) were studied using a rosette assay. It was found that TDC/thymocyte adhesion was stronger and faster at 37°C than at 4°C. Flow cytometric analysis demonstrated that bound thymocytes were predominantly CD4+CD8+ and CD4+CD8-, but in comparison to the phenotype of whole thymocytes, they were enriched in the mature TCRαβhi subset. The binding of thymocytes to TDC at 37°C was almost completely dependent on Ca2+ and Mg2+ and partly on an intact cytoskeleton and calmodulin-dependent protein kinase. The adhesion was independent of new protein synthesis and the activities of protein kinases A and C, tyrosine kinases, as well as phosphotyrosine protein phosphatases. The TDC/thymocyte adhesion at 37°C was partly blocked by anti-LFA-1 (WT.1), anti-CD18 (WT.3), and anti-ICAM-1 (1A29) mAb. MAbs to class II MHC (OX-3 and OX-6), CD4 (W3/25), CD8 (OX-8), and αβTCR (R73) stimulated the adhesion via an LFA-1-dependent pathway, whereas an anti-CD45 mAb (G3C5) stimulated the rosette formation independently of LFA-1. MAbs to CD2 (OX-34), CD11b (ED7), CD11b/c (OX-42), and class I MHC (OX-18) were without significant effects on the adhesion process

REMOTE CONTROL OF THE MECHATRONIC REDESIGNED SLIDER-CRANK MECHANISM IN SERVICE

Slider-crank mechanisms are used in many machines where there is a need to transform rotary motion into translation, and vice versa. Implementation of the control into a mechanical assembly of the slider-crank mechanism offers a wide range of applications of such controlled mechanism in mechatronic systems. This paper shows an example of the remote control of the angular velocity of the crank in a mechatronic redesigned slider-crank mechanism in order to achieve the desired motion of the slider. The remote control is achieved over the Internet connection and the appropriate software which is executed in the user’s internet browser. The aim of this paper is to present the applied control algorithm as well as to explain advantages of the possibility to remotely run a mechatronic redesigned slider-crank mechanism in service. This is done through an example of using a controlled slider-crank mechanism in a remote laboratory experiment

Total Synthesis of ( + )-Swainsonine, (–)- Swainsonine, ( + )-8-epi-Swainsonine and ( + )- Dideoxy-Imino-Lyxitol by an Organocatalyzed Aldolization/Reductive Amination Sequence

A tactical combination of either (S)- or (R)-proline catalyzed aldol reaction followed by intramolecular reductive amination enabled the synthesis of a chiral pyrrolidine derivative with 3 contiguous stereocenters in only 2 synthetic steps, starting from achiral precursors. This product, obtainable in both enantiomeric forms, was further exploited as a common intermediate in total syntheses of the biologically active iminosugars: ( + )-swainsonine, (–)-swainsonine, ( + )-8-epi-swainsonine, and ( + )-dideoxy-imino-lyxitol

The change of phytochemical profile in beet juice and the influence of different storage conditions during one year

Many scientific researches proved the antioxidative impact of beet and its products. The use of vegetable juices is getting more popular in human diet. The way of storage plays an important role in preservation, long life and minimal variability of phytonutrients. The storage of products, usually in inappropriate conditions, leads to additional loss of phytonutrients, which have already been decreased by processing. In this research, we studied the impact of three ways of storage of pasteurised beet juice during one year, on content of some nutrients (total sugars, vitamin C, phenols and total antioxidative capacity). Pasteurised juice was stored in three ways: in light, at room temperature, in dark, at room temperature and in dark, at temperature of 4 °C. The change of content and differences have been followed during one month and confirmed with ANOVA and Tukey's test. The lowest changes of total sugars have been recorded in storage in dark at 4 °C, while in storage in light, the sugar content increased. The losses of vitamin C during one year of storage had linear trend of decrease. Antioxidative capacity of beet juice depends on concentration of phenol compounds and loss of these parameters was similar during period of one year. The best way of storage was dark place at low temperature

Prevalence of Bovine herpesvirus type 4 in aborting dairy cows

Bovine herpesvirus type 4 (BHV-4) is related to many different conditions: infertility, postpartal metritis, vulvovaginitis, mastitis, encephalitis, calf pneumonia, keratoconjunctivitis, cutaneous lesions, digital dermatitis and abortion. In this study a retrospective PCR examination of 100 extracted DNA samples from aborting cows was performed in order to determine: prevalence of BHV-4 in abortive cattle, whether coinfections BHV-4 with other abortifacient pathogens are present in the same sample and to determine the month of gestation when BHV-4 associated abortions were detected. Out of 100 examined samples, the BHV-4 genome was detected in 21 samples (21%). In two samples we detected coinfection of BHV-4 with bovine viral diarrhea virus (BVDV) and in one with Neospora caninum. Most of the BHV-4-associated abortions were detected during the seventh month of gestation. It was concluded that an active BHV-4 infection was present among cows that aborted on the farms examined. The high prevalence of the BHV-4 genome in abortion material suggests that this virus may have cause the abortions. Further studies and examinations are needed to establish causative connection between presence of BHV-4 and abortion

Analytical model of conductive graphite foam based sensors characteristics

Sensors play an important role in the control systems, because they provide the necessary information from surroundings to the controller of an automated systems. Today’s sensors are very sophisticated, with high accuracy, fast acquisition rate and good signal-to-noise ratio. But most of these sensors are too much expensive. Low cost sensor for measuring the force (pressure) or the displacement could be realized by utilizing conductive elastomer that exhibits property of changing the electrical resistance when the elastomer is deformed. This paper introduced a novel conductive graphite foam based sensors. The sensors are formed by inserting two thin copper wires within conductive foam, parallel to each other at the two opposite sides. The main problem of conductive foam based sensors is that the force-electrical resistance characteristic, or the displacement-electrical resistance characteristic, of conductive foam is highly nonlinear. This paper presents the analytical model of the conductive graphite foam sensors for measurement of the displacement. By measuring the changes in the electric resistance between two points of the foam and using the developed analytical model it should be possible to accurately estimate the displacement when the conductive foam is deformed