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  • 1
    Electronic Resource
    Electronic Resource
    Mean flow characteristics of a turbulent plane jet with buoyancy induced curvature (1989)
    Springer
    Experiments in fluids 8 (1989), S. 77-85 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation of heated vertical and inclined plane air jets discharged into quiescent surroundings is described. A unique feature of this data is that Pilot tube measurements were used to define the mean trajectory of the inclined jets so that subsequent hot-wire traverses could be made normal to the curved path. While the mean velocity and temperature profiles are self-similar for the range of exit conditions studied, other aspects of the mean jet development depend on the exit Reynolds and Froude numbers, or the discharge angle. It is noted that variations between this study and other published data suggest further measurements of this flow situation are needed, with particular attention to specific features of the jet apparatus and ambient surroundings, and to the exit Reynolds number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203068
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  • 2
    Electronic Resource
    Electronic Resource
    Turbulence measurements from a plane air jet with buoyancy induced curvature (1994)
    Springer
    Experiments in fluids 16 (1994), S. 336-339 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation of the turbulence structure of a heated plane air jet discharged at various angles into quiescent surroundings is described. Hot-wire anemometry was used to obtain the profiles of mean and turbulent velocities and temperature normal and tangential to the curved path of the flow. Measurements in the buoyancy induced curved region of the jet show the relative influence of the stability induced by both buoyancy and jet curvature on the turbulence structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195433
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  • 3
    Electronic Resource
    Electronic Resource
    Fracture mechanics-based model of abrasive waterjet cutting for brittle materials (1997)
    Springer
    The international journal of advanced manufacturing technology 13 (1997), S. 172-181 
    Details
    ISSN: 1433-3015
    Keywords: Abrasive waterjet ; Cutting of brittle materials ; Waterjet modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Advanced engineering ceramic materials such as silicon carbides and silicon nitride have been used in many engineering applications. The abrasive waterjet is becoming the most recent cutting technique of such materials because of its inherent advantages. In the present study, two elastic-plastic erosion models are adopted to develop an abrasive waterjet model for cutting brittle materials. As a result, two cutting models based on fracture mechanics are derived and introduced. The suggested models predict the maximum depth of cut of the target material as a function of the fracture toughness and hardness as well as the process parameters. It is found that both models predict the same depth of cut within a maximum of ≈ 11%, for the practical range of process parameters used in the present study. The maximum depth of cut predicted by the suggested models are compared with published experimental results for three types of ceramics. The effect of process parameters on the maximum depth of cut for a given ceramic material is also studied and compared with experimental work. The comparison reveals that there is a good agreement between the models' predictions and experimental results, where the difference between the predicted and experimental value of the maximum depth of cut is found to be an average value of 10%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01305869
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  • 4
    Electronic Resource
    Electronic Resource
    On the modelling of abrasive waterjet cutting (1996)
    Springer
    The international journal of advanced manufacturing technology 12 (1996), S. 255-265 
    Details
    ISSN: 1433-3015
    Keywords: Abrasive waterjet technology ; Erosion ; Machining processes ; Material cutting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Abrasive waterjet cutting operates by the impingement of a high-velocity abrasive-laden waterjet against the workpiece. The jet is formed by mixing abrasive particles with high-velocity water in mixing tubes and is forced through a tiny sapphire orifice. The accelerated jet exiting the nozzle travels at more than twice the speed of sound and cuts as it passes through the workpiece. This cutting process is being developed as a net-shape and near-net-shape machining process for cutting many metals and hard-to-machine materials. The narrow kerf produced by the stream results in neither delimitation nor stresses along the cutting path. This new technology offers significant advantages over traditional processes for its ability to cut through most sections of dense or hard materials without the need for secondary machining, to produce contours, and to be integrated into computer-controlled systems. The abrasive waterjet cutting process involves a large number of process and material parameters which are related to the waterjet, the abrasive particles, and workpiece material. Those parameters are expected to effect the material removal rates and the depth of cut. The purpose of the present work is to propose a model which is capable of predicting the maximum depth of cut for different types of materials using different process parameters. A comparison of the results of the proposed model and the models reported in the literature is introduced along with a discussion of the limitations of those models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01239612
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of 3′-deoxy-3′-fluoro and -3′-amino nucleosides from 2-methylthiopyrimidin-4(1H)-ones (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 979-988 
    Details
    ISSN: 1434-4475
    Keywords: Nucleosides, convergent synthesis of ; Nucleosides, 2′,3′-dideoxy-3′-fluoro ; Nucleosides, 2′,3′-dideoxy-3′-amino ; 2-Methylthiopyridin-4(1H)-one nucleosides ; Human immunodeficiency virus ; Herpes simplex virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Methyl-2,3-didesoxy-3-fluoro-5-O-(4-phenylbenzoyl)-β-D-erythro-pentofuranosid (3) und 1,5-di-O-Acetyl-2,3-didesoxy-3-phthalimido-β-D-erythro-pentofuranose (12) wurden in Gegenwart von Trimethylsilyltriflat als Katalysator mit den silylierten 2-Methylthiopyridin-4(1H)-onen2a, b zu den entsprechenden Nucleosiden5–6 und13 kondensiert. Bei diesen Reaktionen tritt als Nebenreaktion eine Öffnung der endocyclischen C-O — Bindung auf, sodaß auch die acyclischen Nucleoside4a, b gebildet werden. Die 3′-Fluoronucleoside wurden mit NH3/MeOH entschützt, die 3′-Phthalimidonucleoside mit Methylamin in Ethanol. Letztere Reaktion resultierte in eine gleichzeitigen Substitution der Pyrimidineinheit unter Austausch der Methylthiogruppe. Das 2-Methylthioanalogon zu 3′-Desoxy-3′-fluorthymidin zeigt mäßige Aktivität gegen HIV-1.
    Notes: Summary Methyl 2,3-dideoxy-3-fluoro-5-O-(4-phenylbenzoyl)-β-D-erythro-pentofuranoside (3) as well as 1,5-di-O-acetyl-2,3-dideoxy-3-phthalimodo-β-D-erythro-pentofuranose (12) were condensed with silylated 2-methylthiopyridin-4(1H)-ones2a, b in the presence of trimethylsilyl triflate as a catalyst to produce the corresponding nucleosides5, 6, 13. In these reactions, an endocyclic cleavage of C-O in3 took place; therefore, acyclic nucleosides4a, b were also formed. All 3′-fluoro nucleosides were deprotected with NH3/MeOH; the 3′-phthalimido nucleosides were deprotected with methylamine in ethanol. The latter method resulted in a concomitant substitution reaction in the pyrimidine moiety with replacement of the methylthio group. The 2-methylthio analogue of 3′-deoxy-3′-fluorothylmidine showed moderate activity against HIV-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807039
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of 5-methylisocytidine derivatives (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 455-459 
    Details
    ISSN: 1434-4475
    Keywords: Herpes simplex virus ; Human immunodeficiency virus ; Isocytidines ; N2-alkyl-5-methyl ; Nucleosides ; convergent synthesis of ; 2-Thiouridine ; 5,S2-dimethyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung N2-substituierte 5-Methylisocytidin-Derivate wurden ausgehend von S2-Methyl-2-thiothymidin entweder durch direkte Substitution der Methylthiogruppe durch eine Aminogruppe und anschließende Kondensation mit 1,2,3,5-tetra-O-Acetyl-β-D-ribofuranose zum acetylierten Nucleosid oder umgekehrt durch Synthese eines acetylierten 5,S2-Dimethyl-2-thiouridins und nachfolgende Behandlung mit dem entsprechenden Amin hergestellt.
    Notes: Summary N2-Substituted 5-methylisocytidine derivatives were synthesized from S2-methyl-2-thiothymine either by direct substitution of the methylthio group by an amino group and subsequent condensation with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose to give the acetylated nucleoside or by the opposite sequence first preparing an acetylated 5,S2-dimethyl-2-thiouridine followed by treatment with the appropriate amine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810888
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of 2-O-ethyl analogues of 3′-azido- and 3′-fluoro-2′,3′-dideoxyuridines and evaluation of their biological activity against HIV (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 811-817 
    Details
    ISSN: 1434-4475
    Keywords: Nucleosides ; convergent synthesis of ; Uridines, 2-O-ethyl ; Uridines, 2′,3′-dideoxy-3′-fluoro ; AZT analogues ; Human immunodeficiency virus ; Herpes simplex virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 2-O-Ethyluracil und 2-O-Ethylthymin wurden mit 1,1,1,3,3,3-Hexamethyldisilazan silyliert und in Gegenwart vonTMS-triflat mit 2,3-Dideoxy-3-fluoro-D-erythro-pentofuranosid, 3-Azido-2,3-dideoxy-D-erythro-pentofuranosid und 2,3-Dideoxy-3-phthalimido-β-D-erythro-pentofuranosederivaten zu den entsprechenden 2-O-Ethyl-Nucleosiden umgesetzt. Entfernung der Schutzgruppe mit gesättigter methanolischer Ammoniaklösung lieferte 2′,3′-Dideoxy-3′-fluor-2-O-ethyluridin; 3′-Azido-2′,3′-dideoxy-3-O-ethyl-uridin wurde durch Entschützung mit Tetrabutylammoniumfluorid in Tetrahydrofuran erhalten. 3′-Amino-2′,3′-dideoxy-3-O-ethyl-uridin konnte nur durch Behandeln des entsprechenden 3′-Azido-Nucleosids mit Triphenylphosphin in Pyridin hergestellt werden. 3′-Deoxy-2-O-ethyl-3′-fluor-thymidin (6b) zeigt geringe Aktivität gegenüber HIV-1.
    Notes: Summary 2-O-Ethyluracil and 2-O-ethylthymine were silylated with 1,1,1,3,3,3-hexamethyldisilazane and condensed in the presence ofTMS triflate with 2,3-dideoxy-3-fluoro-D-erythro-pentofuranoside, 3-azido-2,3-dideoxy-D-erythro-pentofuranoside, and 2,3-dideoxy-3-phthalimido-β-D-erythro-pentofuranose derivatives to give the corresponding 2-O-ethyl nucleosides. Deprotection with saturated methanolic ammonia afforded the 2′,3′-dideoxy-3′-fluoro-2-O-ethyluridines, whereas 3′-azido-2′,3′-dideoxy-3-O-ethyluridine was obtained by deprotection with tetrabutylammonium fluoride in tetrahydrofuran. 3′-Amino-2′,3′-dideoxy-3-O-ethyluridine could be obtained only by treatment of the corresponding 3′-azido nucleoside with triphenylphosphine in pyridine. 3′-Deoxy-2-O-ethyl-3′-fluorothymidine (6b) showed moderate activity against HIV-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807175
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  • 8
    Electronic Resource
    Electronic Resource
    Anion incorporation and its effect on the dielectric constant and growth rate of zirconium oxides (1996)
    Springer
    Journal of applied electrochemistry 26 (1996), S. 1037-1043 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mechanically polished zirconium electrodes were potentiodynamically polarized in phosphate buffer solutions of various pH values and in 0.5 lvl NaOH. The results show that the shape of the I-E curves is independent of the solution pH. At relatively low scan rates, oxygen gas evolution was observed. The oxide film thickness was calculated from the values of the charge consumed in the anodic process assuming 100% current efficiency for oxide formation below oxygen evolution (lower values for the current efficiency are assumed for potentials above oxygen evolution). Capacitance measurements, together with the calculated oxide thickness, were used to estimate values for the dielectric constant of the oxide. Two different values of the dielectric constant were obtained for the oxides formed in the range of potential below and above oxygen evolution. Also, higher dielectric constant values were obtained with increasing solution pH. Anion incorporation was assumed to increase the conductivity of the oxide films and, hence, decrease the dielectric constant. A two-layer structure is proposed for the anodically formed oxide on zirconium in aqueous solutions; an anion-free layer near the metal and an outer layer containing the incorporated anions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242198
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of moisture stress on metabolic products and ions accumulation (1971)
    Springer
    Plant and soil 34 (1971), S. 65-90 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Estimations of the metabolic products and accumulated ions were made at the different stages of development of a number of native and introduced plant species grown under different conditions of moisture stress corresponding to different levels of water supply equivalent to 125, 200, 275 and 350 mm. The increase in moisture stress favours the increase in total available carbohydrates and total nitrogen. With deficiency in soil moisture the majority of accumulated ions (K, Na, Ca, Mg, and Cl) increases and a minority (P and Fe) decreases. The sum of total ions accumulated in the plant tissues increases with decrease in soil moisture and rise in moisture stress. This is accompanied by accumulation of more salts in the cell sap and the consequent rise in osmotic pressure. The nutritive value as determined by total available carbohydrates, total nitrogen, Ca, Mg, and P contents is highly influenced by soil moisture conditions. Plants subjected to higher moisture tension are richer in total nitrogen, total available carbohydrates. calcium, and magnesium, and poorer in phosphorus content. The total nutritive value is not only determined by the percentage of these constituents but also by the dry matter production per plant, the latter is greatly suppressed with deficiency in soil moisture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01372762
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  • 10
    Electronic Resource
    Electronic Resource
    Response of olive and almond orchards to partial irrigation under dry-farming practices in semi-arid regions: (1974)
    Springer
    Plant and soil 41 (1974), S. 13-31 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The response of elements of the water balance of olive plants grown in desert farms to partial irrigation was investigated. Among these are transpiration, leaf relative water content, the number of leaves carried by trees and the osmotic pressure of the leaf sap. The proper time for irrigation and suitable ways of its application were also studied. A method of applying subsurface irrigation, to minimize direct evaporation from the soil, is described. The results show a slight decrease in transpiration rate of irrigated plants compared to the controls. However, an increase in the number of leaves as a result of irrigation was found to result in increased total transpirational water loss. An inverse relation seem to exist between the amount of foliage and its relative water content in periods of no active growth. This relation is reversed during active growth. The osmotic pressure of leaf sap also responded inversely to changes in leaf water content during periods of inactive growth. On time of active growth, relative water content and osmotic pressure rose more or less together. The results indicate that among the methods of irrigation studied, summer subsurface irrigation is more favourable for the water balance of the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017940
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