Thread formation

W. Lee, L.M. Walker, and S.L. Anna, Role of geometry and fluid properties in droplet and thread formation processes in planar flow focusing, Physics of Fluids, 21, (2009). 

For wet spinning there is an additional factor influencing spinnability. The thread formation process is complicated it involves diffusion of solvents out of... 

Negri, M., Ciezki, H. K., Schlechtriem, S. (2013). Spray behavior of non-Newtonian fluids Correlation between rheological measurements and droplets/threads formation. Progress in Propulsion Physics, 4, 211-290. 

This temperature profile is normally used with an open nozzle for prevention of thread formation or drooling. With this profile setting there can be drawbacks as the colder material (which may be hardened) at the nozzle may be injected into the mould to form the produet. 

The preceding description of nodule initiation, development, and nitrogen-ase clearly demonstrates that the host contribution to symbiosis can be grouped into several functions, including recognition, root hair invasion, infection thread formation, nodule differentiation (e.g., meristems, vascular elements, sclerenchyma), carbon assimilation, organic acid production, ammonia assimilation, maintenance of low O2 by Lb, separation of bacteroids and host cytoplasm by the PBM, senescence, and possibly suppression of host defense responses required for nodule compatibility and/or effectiveness. 

The tubular positive plate uses rigid, porous fiber glass tubes covered with a perforated plastic foil as the active material retainer (Fig. 2). Dry lead oxide, PbO, and red lead, Pb O, are typically shaken into the tubes which are threaded over the grid spines. The open end is then sealed by a polyethylene bar. Patents describe a procedure for making a type of tube for the tubular positive plate (90) and a method for filling tubular plates of lead—acid batteries (91). Tubular positive plates are pickled by soaking in a sulfate solution and are then cured. Some proceed directiy to formation and do not requite the curing procedure. 

A sniallcr-diaiiieter pipe, called tubing, is then threaded together and inserted into the casing. If it is expected that oil or gas will flow to the surface via the pressure differential between the well bore and the formation, a wellhead is installed it is equipped with valves to control the flow of oil or gas from the well. The wellhead is known as a Christmas tree. If there is not sufficient pressure differential to cause the oil and the gas to flow naturally, pumping equipment is installed at the lower end of the tubing. 

New boilers, heat exchangers, and other equipment must be provided with a PCC program to remove oil, grease, mill scale, pipe-threading compounds, drawing compounds, and other detritus that otherwise prevent the formation of clean, passivated metal surfaces and encourage... 

More recently, Kim et al. synthesized dendritic [n] pseudorotaxane based on the stable charge-transfer complex formation inside cucurbit[8]uril (CB[8j) (Fig. 17) [59]. Reaction of triply branched molecule 47 containing an electron deficient bipyridinium unit on each branch, and three equiv of CB[8] forms branched [4] pseudorotaxane 48 which has been characterized by NMR and ESI mass spectrometry. Addition of three equivalents of electron-rich dihydrox-ynaphthalene 49 produces branched [4]rotaxane 50, which is stabilized by charge-transfer interactions between the bipyridinium unit and dihydroxy-naphthalene inside CB[8]. No dethreading of CB[8] is observed in solution. Reaction of [4] pseudorotaxane 48 with three equiv of triply branched molecule 51 having an electron donor unit on one arm and CB[6] threaded on a diaminobutane unit on each of two remaining arms produced dendritic [ 10] pseudorotaxane 52 which may be considered to be a second generation dendritic pseudorotaxane. 

To install the screen and riser piping, the drilling equipment extends the borehole to the approximate desired depth of the bottom of the screen. Short sections of screen and/or riser pipe can be assembled above ground. A cap or plug (also with Aush joint threads) is commonly added to the bottom of the lowest section to prevent the enAy of formation materials. Precautions should be taken to keep the sections free of... 

For the case of a thread at rest, the initial growth of a disturbance can be relatively well characterized by linear stability theory. In the initial stages, the deformation of the thread follows the growth of the fastest growing disturbance (Tomotika, 1935). Eventually the interfacial tension driven flow becomes nonlinear, leading to the formation of the smaller satellite drops (Tjahjadi et al., 1992). 

Illustration Satellite formation in capillary breakup. The distribution of drops produced upon disintegration of a thread at rest is a unique function of the viscosity ratio. Tjahjadi et al. (1992) showed through inspection of experiments and numerical simulations that up to 19 satellite drops between the two larger mother drops could be formed. The number of satellite drops decreased as the viscosity ratio was increased. In low-viscosity systems p < 0(0.1)] the breakup mechanism is self-repeating Every pinch-off results in the formation of a rounded surface and a conical one the conical surface then becomes bulbous and a neck forms near the end, which again pinches off and the process repeats (Fig. 21). There is excellent agreement between numerical simulations and the experimental results (Fig. 21). 

The interaction between the dispersed-phase elements at high volume fractions has an impact on breakup and aggregation, which is not well understood. For example, Elemans et al. (1997) found that when closely spaced stationary threads break by the growth of capillary instabilities, the disturbances on adjacent threads are half a wavelength out of phase (Fig. 43), and the rate of growth of the instability is smaller. Such interaction effects may have practical applications, for example, in the formation of monodisperse emulsions (Mason and Bibette, 1996). 

The individual objects that compose the model are screws which simulate the molecules of the helical polymer their individual chirality is responsible for the spontaneous formation of the overall helical structure. In the model, the screws are left-handed and have a rather compact thread, that is, the pitch-to-diameter ratio of the individual screws is small In this case, left-handed screws generate a left-handed overall helical structure. If instead the thread is loose, left-handed screws may generate a right-handed superstructure (see discussion in Section 3). 

Pseudorotaxanes are precursors of both rotaxanes and catenanes they consist of a guest molecule threaded through a macrocyclic host. Stoppering both ends of the threaded molecule gives a rotaxane, cycliza-tion of the thread gives a catenane. Pseudorotaxane formation may occur by spontaneous self-assembly, or may be template-controlled. Anion size can be of paramount importance for such templates - Cl- is effective, Br, I- less good, and PFe ineffective when the recognition motif demands a small template (454). 

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