Typical assemblies

Assemblies. Other units are shown in some of the typical assemblies illustrated in Fig. 23.  [c.44]


Another set of apparatus ( B) adopts the 5 19 joint as standard (apart from 7/12 for thermometers) but connexions to condensers, etc., incorporate internal glass seals. A typical assembly for distillation is depicted in Fig. XII,  [c.1109]

Assemblies. Other units are shown in some of the typical assemblies illustrated in Fig. 23.  [c.44]

As described above, in the air-cooled exchanger a motor and fan assembly forces ambient air over a series of tubes to cool or condense the process fluids carried within. The tubes are typically assembled in a coiled configuration. Air is  [c.19]

Although most units are installed horizontally, inclined, Figure 10-177, and vertical units are also in service. Figures 10-178 and 10-179 show typical assemblies for tube bundles with fabricated or cast end headers and also with flanged cover plates.  [c.253]

Our inspection method is based on an encircling Eddy current coil measuring the structural integrity of the rod, and 8 pancake coils positioned on a typical place over the rods diameter. One inspection block consists of 4 to 6 probe assemblies.  [c.1007]

Proteins are clearly not homopolymers because many energy scales are required to characterize tire polypeptide chain. Besides tire excluded volume interactions and hydrogen bonds tire potential between tire side chain depends on tire nature of tire residues [1]. Therefore, as a caricature of proteins tire heteropolymer model is a better approximation. A convenient limit is tire random heteropolymer for which approximate analytic treatments are possible [11]. In a random heteropolymer tire interactions between tire beads are assumed to be randomly distributed. Some of tire interactions are attractive (which are responsible for conferring globularity to the chain) while otliers are repulsive and tliese residues are better accommodated in an extended confonnation. In proteins water is a good solvent for polar residues while it is a poor solvent for hydrophobic residues. (In a good solvent contacts between tire monomer and solvent are favoured whereas in a poor solvent tire monomers are attracted to each otlier.) Because only 55% of tire residues in proteins are hydrophobic it is clear tliat in a typical protein energetic fmstration plays a role. In addition because of chain connectivity tliere is also topological fmstration. This arises because residues tliat are proximal tend to fonn stmctures on short-lengtli scales. The assembly of such short-lengtli scale stmctures would typically be incompatible witli tire global fold giving rise to topological fmstration. Even if energetic fmstrations are eliminated a polypeptide chain (in fact any biomolecule) is topologically fmstrated [7].  [c.2644]

Finally, FIA is an attractive technique with respect to demands on time, cost, and equipment. When employed for automated analyses, FIA provides for very high sampling rates. Most analyses can be operated with sampling rates of 20-120 samples/h, but rates as high as 1700 samples/h have been realized. Because the volume of the flow injection manifold is small, typically less than 2 mb, consumption of reagents is substantially less than with conventional methods. This can lead to a significant decrease in the cost per analysis. Flow injection analysis requires additional equipment, beyond that used for similar conventional methods of analysis, which adds to the expense of the analysis. On the other hand, flow injection analyzers can be assembled from equipment already available in many laboratories.  [c.658]

Decomposition (fragmentation) of a proportion of the molecular ions (M +) to form fragment ions (A B+, etc.) occurs mostly in the ion source, and the assembly of ions (M +, A+, etc.) is injected into the mass analyzer. For chemical ionization (Cl), the Initial ionization step is the same as in El, but the subsequent steps are different (Figure 1.1). For Cl, the gas pressure in the ion source is typically increased to 10 mbar (and sometimes even up to atmospheric pressure) by injecting a reagent gas (R in Figure 1.1).  [c.1]

A typical filament assembly. Positive ions from the filament are accelerated by a high negative potential of about 1000 V placed on the first collimating plate. The other plates are used for further collimation and centering of the ion beam, which is directed into a suitable mass analyzer. Some positive ions strike the edge of the first collimating slit and produce secondary negative ions and electrons, which would be accelerated back onto the filament without a suppressor grid. This back-bombardment of the filament would lead to the formation of extraneous positive ions. To minimize this process, a suppressor grid (at a potential of about -300 V with respect to the filament) is included to deflect any backscattered ions.  [c.46]

If ions of different m/z values are instantaneously accelerated by an electric field, they attain velocities determined by their m/z values and the accelerating field to which they have been subjected. After flying along an evacuated tube, the ions arrive at a detector in proportion to the velocities they have, the faster ions arriving before slower ones. Because an ion velocity depends upon its m/z value, the ions of smaller m/z value arrive first and those of larger value arrive last. By measuring the flight time of the ions along a TOF tube (analyzer), the m/z values can be deduced, and, therefore, a mass spectrum can be measured. Among the advantages of TOF measurement of mass spectra is the very short time interval needed to measure a full mass spectrum. Typically, a few microseconds is all that is needed to scan from 1 to 2000 mass units. On the human timescale, this speed of scanning appears to be instantaneous. For sake of illustration, a TOF analyzer could be likened to a camera taking snapshots of the m/z values of an assembly (beam) of ions the faster the repetition rate at which the camera shutter is clicked, the greater is the number of mass spectra that can be taken in a very short time. For TOF analyzers, it is not uncommon to measure several thousand mass spectra in one second All such spectra can be added to each other digitally, a process that improves the signal-to-noise ratio in the final accumulated total.  [c.165]

In practice, the frequency (to) is fixed, and typical values are in the range 1-2 MHz. The DC voltage (U) may be 1000 V, and the maximum RF voltage (V) is 6000 V. The pole assemblies range in length from about 50 to 250 mm, depending on application, and pole diameters lie in the range of 6 to 15 mm. Very high mechanical accuracy — to the micron level — in both the rods and their spacing is needed for high performance. For example, with a spacing (r) accurate to 10 r, the maximum resolution would be about 500 (O.Sr/lO" r). Scanning speeds of up to 6000 amu/sec are routine with quadrupoles, and unit mass resolution up to 2000 amu is attainable.  [c.185]

Note that Equation 25.1 shows that the field (F) has no effect along the direction of the central (z) axis of the quadmpole assembly, so, to make ions move in this direction, they must first be accelerated through a small electric potential (typically 5 V) between the ion source and the assembly. Because of the oscillatory nature of the field (F Figure 25.3), an ion trajectory as it moves through the quadmpole assembly is also oscillatory.  [c.187]

A simplified view of an ion tunnel, composed of a series of electrodes. The positive phase (+V cos tot) from an RF generator is laced on alternate rings, and the negative phase (-V cos tot) is placed on the remaining rings. A typical ion tunnel can have 60-80 such rings, and ions are guided along the central axis of the assembly.  [c.382]

Sterilization Considerations. In sterile filtration processes the downstream side of the filter must be sterilized and must remain sterile during the entire process. Presterilized (gamma-irradiated) filters may be available or alternatively, filters may be sterilized by the user. The most common method of sterilization is by steam under pressure. The sterilization process must be vaHdated to ensure that sterile conditions are met for a given system. Methods that involve steam are vaHdated through the use of thermocouples and/or biological indicators to ensure sterilization of the system. The filters may be sterilized in an autoclave. Alternatively, the sterilization may be undertaken in-place, called sterilization in-place (SIP) or in situ sterilization. Most filter manufacturers provide protocols and recommendations for these procedures. SmaH-volume systems tend to be autoclaved larger systems are typically SIP. Minimally, a temperature of 121°C is used for autoclave sterilization more commonly, a sterilization temperature of 125°C is employed. Temperatures in excess of 125°C may affect the plastics used for filter constmction, thereby affecting the physical integrity of the membrane. Standard precautions must be foUowed during autoclaving the system must be purged of air to achieve reHable sterilization, and the filter assembly wrapped using a porous barrier to ensure steam penetration. It is critical that excessive differential pressures are not created during the autoclaving which would result in damage to the membrane. These same considerations are all the more relevant during in situ sterilization. Additionally, in SIP operations the condensate must be drained throughout the steam cycle to prevent accumulation. This is achieved by keeping the drains and steam traps partially open during the steaming cycle. After the steam valve is closed, a noncondensable gas, such as air or nitrogen, is introduced into the housing to prevent formation of a vacuum on the upstream side of the filter. If it is necessary that the system be completely dry prior to use, the air—nitrogen flow can be continued until the system is dry and cool to operating temperature.  [c.141]

Configurations of Virus Filtration Systems. The two principal membrane filtration systems for the removal of viral particles from fluids are single-pass or direct flow filtration and cross- or tangential flow filtration. In the first, the entire volume is filtered through the membrane filter. Typically, the membrane is either a flat sheet cut into disks or a pleated sheet assembled as a cartridge filter. The pore size of these types of membrane filters are generally between 50—100 nm (26). Pleating of the membrane has been used to increase filter surface area and thus increased volume and flow rate of the filtrate. Typically, filters in this format are designed to be used once.  [c.143]

In addition to self-assembly of protein stmctures, in living systems the complex maneuvers needed to achieve properly folded tertiary stmctures are facihtated by the function of a pre-existing protein machinery, of which, the molecular chaperones are an illustrative example (58,59). Chaperones (eg, heatshock protein 70 (Hsp 70) and the chaperonin families of proteins) are proteins that bind to and stabilize an otherwise unstable conformer of another protein, and by controlled binding and release, faciUtate its correct fate in vivo, be it folding to attain proper tertiary stmcture, oligomeric assembly, transport to a particular subceUular compartment, or disposal by degradation. Molecular chaperones do not contain steric information specifying correct folding of a particular protein instead, they prevent incorrect interactions within and between polypeptides in nonnative forms, thus typically enhancing the yield but not the rate of folding reactions (59). Hence, molecular chaperones may be said to be the natural counterparts of assemblers and transporters envisaged as products of nanotechnology (10,12).  [c.200]

Polymers. The individual units in a polymer ate well-defined, but bulk polymer usually lacks the periodic stmcture characteristic of inorganic or small molecule crystalline soHds. The stmcture of semiconducting and conducting polymers is determined by the units of the polymer backbone as well as pendant side-groups (18). Typical conducting polymers are conjugated systems that provide for motion of the electrons through the TT-system, and both linear chain (poly-acetylenes) and aryl chain poly(p-phenylene) polymers are commonly used. As chain length increases during polymer growth, the long-chain polymers become insoluble and precipitate out during synthesis. The chain length in polymeric soHds is thus, influenced by the nature of the solvent and the synthetic process. Although most polymers ate fairly amorphous, chemical substitution has been used to design self-assembled oligomeric films with highly ordered stmctures (19). Film morphology for linear chain polymers can be affected by stretching of the film to orient the chains, resulting in higher crystallinity. The morphology of electrochemically grown conducting polymer thin films has also been shown to be dependent on the nature of the substrate (20).  [c.241]

Resistance Welding. As noted in Table 1, resistance welding comprises several processes the most widely used is resistance spot welding (RSW). The principles of RSW are quite different from those underlying the processes previously described (Fig. 4). The workpieces are firmly clamped between copper electrodes, and an electric current is passed through the assembly. Heat is generated by the electrical resistance of the components, the maximum heat occurring at the interface between the workpieces. A nugget of metal at the interface region is melted, at which time the current is shut off and the clamping force on the electrodes released. The entire sequence typically requires less than a second. Resistance spot welding is widely used in the  [c.343]

Cyanoacrylate adhesives (Super-Glues) are materials which rapidly polymerize at room temperature. The standard monomer for a cyanoacrylate adhesive is ethyl 2-cyanoacrylate [7085-85-0], which readily undergoes anionic polymerization. Very rapid cure of these materials has made them widely used in the electronics industry for speaker magnet mounting, as weU as for wire tacking and other apphcations requiring rapid assembly. Anionic polymerization of a cyanoacrylate adhesive is normally initiated by water. Therefore, atmospheric humidity or the surface moisture content must be at a certain level for polymerization to take place. These adhesives are not cross-linked as are the surface-activated acryhcs. Rather, the cyanoacrylate material is a thermoplastic, and thus, the adhesives typically have poor temperature resistance.  [c.233]

Aerosols are unique. The various components are all part of the product, and in the aerosol industry, the formulating chemist must be familiar with the entire package assembly and each of its components. AH aerosols consist of product concentrate, propeUant, container, and valve (including an actuator and dip tube). There are many variations of these components, and only when each component is properly selected and assembled does a suitable aerosol product result. A typical aerosol system is shown in Figure 1.  [c.344]

Before a metal can begin absorbing hydrogen to form the hydride, it must be heated to 300°C under vacuum to expel all other absorbed gases. Absorption of hydrogen is conducted at 3.4 MPa (34 atm) at room temperature. Formation of hydride causes a volume increase and embrittlement of alloy particles (210—213). An alloy containing Mn, such as 85—90 mol % FeTi and 10—15 mol % Mn, is more easily activated and cycled. Such an alloy releases within the molar range of 1.6—0.1 with a change of hydrogen of 1.5 wt % under a thermal load of 29 kJ/mol (6500 Btu/lb). Hydrogen reservoirs usually consist of an assembly of 16-mm diameter stainless steel tubes containing the hydride. A typical overall weight of a storage tank is about 560 kg, hoi ding 6.35 kg of H2. Hydrogen-release temperatures vary between 30°C and 80°C. Typical H2 equilibrium pressures over an Fe—Ti alloy are shown in Figure 7.  [c.430]

Magnetostrictive gauges typically operate in the following manner. (/) The electronics assembly initiates a short, low current pulse onto a wire that mns through the center of the waveguide material. A timer starts simultaneously. (2) The pulse, along with the magnetic field it generates, travels the length of the gauge. (J) When the pulse reaches the float, the magnetic field from the pulse interacts with the magnetic field generated from the float (Fig. 21) and initiates a torsional twist in the waveguide material. (4) The physical twist creates a sonic wave that travels along the waveguide in both directions and is detected by the strain gauge in the electronics assembly. The timer is stopped as soon as this return signal is detected. The distance from the float (magnet) can be determined accurately based on the time and on the signal transmission properties of the individual waveguide material. (5) If a second float is present on the gauge, a second twist can be detected and recorded as the interface level.  [c.217]

Figure 16a shows a so-called peg wall design, in which thin insulators separate rectangular or square metallic elements, ie, pegs, typically 2—3 cm on a side. The advantage of the design is its superior electrical insulating properties under all operating conditions, and its electrical flexibiUty. The disadvantage is the mechanical complexity arising from the large number of small elements. However, using proper engineering and assembly procedures such walls can be made to operate rehably and have, in fact, been tested at 20 scale for hundreds of hours (103).  [c.430]

For a typical assembly, first part qualification begins with a rigorous dimensional check and painstaking prefit of all details on the bond tool. The assembly details are placed on the tool without adhesive, close contact between bond surfaces is verified and any detail or tool interference is corrected prior to proceeding. This is followed by fabrication of a verification film , or a simulated bond cure cycle of the assembly to allow measurement of the adhesive bondline thickness.  [c.1167]

Tender Assisted Drilling. In some cases oil and gas fields are developed from a number of platforms. Some platforms will accommodate production and processing facilities as well as living quarters. Alternatively these functions may be performed on separate platforms, typically in shallow and calm water. On all offshore structures however, the installation of additional weight or spaoe is costly. Drilling is only carried out during short periods of time if eompared to the overall field life span and it is desirable to have a rig installed only when needed. This is the concept of tender assisted drilling operations. A derrick is assembled from a number of segments transported to the platform by a barge. All the supporting functions such as storage, mud tanks and living quarters are located on the tender, which is a specially built spacious barge anchored alongside. It is thus possible to service a whole field or even several fields using only one or two tender assisted derrick sets. In rough weather, barge type tenders quickly become inoperable  [c.34]

For solids and non-volatile liquids accurate heat capacity measurements are generally made in an adiabatic calorimeter. A typical low temperature aneroid-type adiabatic calorimeter used to make measurements between 4 K and about 300 K is shown in figure B 1.27.1. The primary fimction of the complex assembly is to maintain the calorimeter proper at any desired temperature between 4 K and 300 K. The only energy gain should be from the addition of electrical energy during a measurement. The upper part of the calorimeter contains vessels for holding liquid nitrogen and helium that provide low temperature heat sinks. Construction materials are generally those having high thennal conductivity (e.g. copper) plated with reflectant material (e.g. cliromium) to reduce radiant energy transfer. The calorimeter proper and its surrounding adiabatic shield are suspended by silk lines and can be raised to bring them into good thennal contact with the lower tank, thereby cooling the calorimeter. Wlien the calorimeter proper has reached its desired temperature, thennal contact is broken by lowermg the calorimeter and the adiabatic shield. Adiabatic conditions are maintained by keeping the temperature of the adiabatic shield at the temperature of the calorimeter and heat conduction is  [c.1905]

The architecture of the lipid molecules or the diblock copolymers results in the typical amphiphilic properties, like surface activity and self-assembly. On the most qualitative level, understanding of the self-assembly in lipid systems [3] is provided by a characterization of the molecules as a simple geometrical object ( wedge ) parameterized by its volume, the maximum chain length and the area per head group. The different phases result from simple geometric packing considerations. Suuilar arguments on the balance between chain stretching and interfacial tension yield the qualitative features of the phase diagrams in systems containing diblock copolymers [59].  [c.2376]

Parallelizing this method was not difficult, given that we already had parallel versions of several multipole algorithms to start from. The entire macroscopic assembly, given its precomputed transfer function, is handled by a single processor which has to perform k extra multipole expansions, one for each level of the macroscopic tree. Each processor is already typically performing many hundreds or thousands of such expansions, so the extra work is minimal.  [c.462]

Under normal conditions only combinations of dienes and dienophiles that have FMO s of similar energy can be transformed into a Diels-Alder adduct. When the gap between the FMO s is large, forcing conditions are required, and undesired side reactions and retro Diels-Alder reactions can easily take over. These cases challenge the creativity of the organic chemist and have led to the invention of a number of methods for promoting reluctant Diels-Alder reactions under mild conditions ". One very general approach, performing Diels-Alder reactions under high pressure, makes use of the large negative volume of activation (about -25 to -45 cm per mole) characteristic for this reaction. The rate enhancements are modest, typically in the order of a factor 10 at a pressure of 1500 atm . Selectivities also benefit from an increase in pressure. Another physical method uses ultrasound irradiation. However, the observed accelerations are invariably a result of indirect effects such as the development of low concentrations of catalytically active species and more efficient mixing of the heterogeneous reaction mixtures under ultrasound conditions . Catalysis of Diels-Alder reactions through formation of supramolecrdar assemblies is becoming increasingly popular. Large molecrdes containing a cavity (e.g. cyclodextrins " or related  [c.11]

End views of the quadrupole assembly (a) showing the theoretically desired cross-section and (b) illustrating the practical system. In (b), a positive potential, +(U + Vcoscot), is applied to two opposed rods (A) and a negative potential, -(U + Vcoscot), to the other two (B). The dotted lines indicate planes of zero electric field. The dimension (r) is typically about 5 mm with rod diameters of 12 mm. The x- and y-axes are indicated, with the z-axis being perpendicular to the plane of the paper.  [c.184]

A second class of monolayers based on van der Waal s interactions within the monolayer and chemisorption (in contrast with physisorption in the case of LB films) on a soHd substrate are self-assembled monolayers (SAMs). SAMs are well-ordered layers, one molecule thick, that form spontaneously by the reaction of molecules, typically substituted-alkyl chains, with the surface of soHd materials (193—195). A wide variety of SAM-based supramolecular stmctures have been generated and used as functional components of materials systems in a wide range of technological appHcations ranging from nanoHthography (196,197) to chemical sensing (198—201).  [c.208]

Solar cells and other photovoltaic devices have typically been based on siUcon or other inorganic materials, which can provide high power conversion efficiencies (>25%). However, organic materials can also be used to generate a photovoltage. Photovoltaic effects have been studied in a wide variety of materials including solvent-cast films of BuckrninsterfuUerene (C q) (75) and self-assembled films of alkyl-derivatized metaloporpbyrins (76). Many of these systems produce a photovoltage however, the efficiency is lower than that found in inorganic-based devices.  [c.245]

Low molecular weight complexes that are synthetic analogues of the protein sites have been prepared and extensively investigated in the cases of stmctures (9), (10), and (12). The compounds, which are typically isolated as tetraalkylammonium salts, assemble spontaneously from a reaction system that includes an iron salt (usually FeCl ), thiolate, a source of labile (elemental sulfur or HS ), and a counterion. Individual compounds can be prepared selectively by variation of the ratios of reactants. Both the iron(II) and iron(III) states of the mononuclear cluster are high spin. Strong intramolecular antiferromagnetic coupling occurs in the cluster compounds, which contain bridging sulfides. Several specific oxidation states of the clusters are mixed valence compounds. [Fe2S2(SR)4] has a localized iron(II) and a localized iron(III). In contrast, localized iron(II) andiron(III) sites are not observed for the [4Fe—4S] compounds, all of which have mixed valent oxidation states. The redox activity of these compounds parallels the states but not the potentials observed in the proteins. Substitution reactions of the terminal thiolate Ligands are also noteworthy.  [c.442]

Adhesives and coatings formulations utilize both MDI and TDI along with a variety of polyether and polyester polyols. The largest segment of the business is the one-part or moisture-cured approach, which is heavily reflant on ptepolymets. Optionally, blocked isocyanate technology may be used to provide systems having an extremely long shelf life. Suitable blocking agents include phenols, diethyl malonate [105-53-3] acetone oxime [127-06-0] and S-caprolactam [105-60-2]. Typical appHcafions include flexible film packaging and wood furniture assembly. Two-part reactive adhesives employ a mixture of pure isocyanates and prepolymers and are primarily used for industrial product assembly and commercial constmcfion.  [c.459]

The clean room typically is operated at 18°C and 26% rh, which produces an equiUbtium condition for the desired iatedayer moisture level. The iatedayer is placed oa oae piece of glass, with the gradieat band, if present, carefiiUy positioned above the designated eye position. The adjacent piece is superimposed, excess iatedayer is trimmed, and this "sandwich" is conveyed from the room through a series of heaters and roUs that press the assembly together while expelling air. Temperature is iacreased stepwise to 90°C and pressures of 170—480 kPa (25—70 psi) are appHed. SoHd mbber roUs usually are used with flat laminates, and curved glass requires segmented roUs on a swivel frame (Fig. 4) (7,8). For more complex shapes, peripheral gaskets may be apphed and the assembly may have the air evacuated (9), or the entire assembly may be placed ia a bag aad the air evacuated. The bag may or may aot be removed prior to autoclaviag, but whea usiag an oil autoclave where the oil would damage one of the components, an oil-resistant Teflon or poly(vinyl alcohol) bag can be used (10). The tacked assembly is loaded onto racks for autoclaving, which may be either ia an air or oil vessel capable of pressing the sandwiches at 1.38—1.72 MPa (200—250 psi) and 100—135°C for 30—45 min. Curved laminates and multiple laminates may require longer cycles to allow the polymer material to flow completely.  [c.525]

Wafer Fabrication and Assembly. After epitaxial growth and other processing, the LED wafers are metallized to form ohmic contacts to the device. Typically, alloyed gold—beryllium, AuBe, and gold—zinc, AuZn, are employed as -type contacts whereas gold—germanium, AuGe, is used for n-type contacts. Additional metallization layers consisting of Au or A1 are often employed to facilitate wirebonding to the device. The use of such multilayer metallizations frequendy requires the use of a barrier metallization, usually tungsten, W, or related materials. The alloyed ohmic contacts are patterned ia the transparent light-emitting regions to maximize light extraction because the contact area is generally absorbing as a result of the alloy process.  [c.119]

In plastic box constmction an example of which is shown in Figure 17, the channel is a four-wall assembly. Each wall consists of the individual gas-side surface elements mounted on an electrically insulating board, which is made typically of a fiber glass-reinforced material such as NEMA Grade G-11. The box formed by assembly of the four walls serves as the main stmctural member and the pressure vessel of the channel. Einal gas-side contouring is done by varying the height of the electrodes and insulating wall elements. Gas sealing is done on the edges of the plastic wall, along the corners of the box. The Textron 1A4 channel (Eig. 17) (104) has operated for hundreds of hours. Other channels built in this manner include the Mark VI and Mark VII channels built by Avco (105) and the high performance demonstration experiment (HPDE) channel (106). The most extensive data base has been accumulated for this type of constmction.  [c.431]

See pages that mention the term Typical assemblies : [c.226]    [c.998]    [c.640]    [c.2581]    [c.2585]    [c.2697]    [c.240]    [c.556]    [c.351]    [c.101]   
See chapters in:

Textbook on organic chemistry  -> Typical assemblies