Paper, flat piece

It is called an a-amino acid because the amino group is attached to the a (or number 2) carbon atom. To indicate its three-dimensional structure on a flat piece of paper, the bonds that project out of the plane of the paper and up toward the reader are often drawn as elongated triangles, while bonds that lie behind the plane of the paper are shown as dashed lines. The isomer of alanine having the configuration about the a-carbon atom shown in the following structural formulas is called S-alanine or L-alanine. The isomer which is a mirror image of S-alanine is R-alanine or D-alanine. Pairs of R and S compounds (see Section B for definitions) are known as enantiomorphic forms or enantiomers. 

Today paper is still made in essentially the same way as it has been for decades. Wood chips are treated with solvents to clean and separate wood containing cellulose fiber. This fiber, known as pulp, is spread on a flat surface, where a machine shakes it for even distribution and to interlock individual fibers. This mixture is then rolled and pressed to squeeze out excess water and solvent. A flat piece of wet paper is the result. Finally, the paper is hung to dry. 

With the scissors, cut open the paper lunch sack along the foldable creases on the sides. When finished you will have a flat piece of brown paper. 

Cut out two triangle-shaped pieces from the construction paper for the chick s beak. Fold the flat part of the triangle over one fold. Glue this flat piece to the end of each Styrofoam egg or newspaper ball. Hold in place until it dries. 

The two common methods used to represent a three-dimensional object on a flat piece of paper are orthographic projection and pictorial projection. 

When it is necessary to explore the shapes of molecules beyond what can be shown on a flat piece of paper, chemists resort to physical models or computer-drawn pictures, such as those shown in Figure 2.8. 

Mass spectrometrists have always been concerned with the measurement of the mass and intensity of analyte ions. Investigation/utilization of the shapes of molecules is now possible with ion mobility techniques that utilize differences in the cross sections of ions as they move through a gas. Think in terms of two pieces of paper, one crumpled and the other flat. If dropped at the same time, the crumpled one will hit the floor first because it will encounter less air resistance than the flat piece. A similar situation applies to ions with different shapes as they travel through a gas. Although ion mobility has been examined with home-built instruments for years, only recently has this type of analyzer become available commercially. There are two significantly different types, the high-field asymmetric waveform ion mobility spectrometer (FAIMS) and the ion mobility separator (IMS). The FAIMS separator is placed between the ion source and the analyzer, while the IMS cell is located between the analyzers of an MS/MS instrument. 

Fig. 2.5. Curve relating the mass of screwed up paper balls to their diameter. Note the logarithmic scales. The two straight lines enclosing the experimental results give the slopes that would be obtained for compact balls (the mass varies as the cube of the diameter) or for flat pieces of paper (the mass varies as the square of their linear dimension). The results show that the mass of the balls increases with their diameter to a power close to 2.5...

The coatings in question were obtained by electrochemical deposition in (Li-Na-K)F-K2NbF and (K-Na)Cl-K2NbF7 melts with a soluble anode. Their thicknesses were 5-200 pm. The current cathode density U was varied over the interval 50-1000 A/m2. The deposition was conducted at 970-1070 K onto flat pieces (30x50 mm) and cylinders (0 6x60 mm) of copper and molybdenum substrates, which were separated from the coatings to be studied.The equipment, the reactants and preparation of the latter were basically the same as in earlier papers [5,6]. 

Use of the Hirsch Funnel. The standard filtration system for collecting products purified by recrystallization in the microscale laboratory is vacuum (suction) ffltration with an 11-mm Hirsch funnel. Many reaction products that do not require recrystallization can also be collected directly by vacuum filtration. The Hirsch funnel (Fig.5.23a) is composed of a ceramic cone with a circular flat bed perforated with small holes. The diameter of the bed is covered by a flat piece of filter paper of the same diameter. The funnel is sealed into a filter flask with a Neoprene adapter (Fig. 5.23b). Plastic and glass varieties of this funnel that have a polyethylene or glass frit are now available. It is stfll advisable to use the filter paper disk with these funnels to prevent the frit from clogging or becoming discolored. Regardless of the type of fflter used, always wet the filter paper disk with the solvent being used in the crystallization and then apply the vacuum. This ensures that the filter paper disk is firmly seated on the bed of the filter. 

Place on a flat surface a sheet of emery paper of medium coarseness. It is best glued to a flat piece of wood 2 inches thick, and not less than 8 inches square. Hold the jar firmly and grind with a circular motion. 

A recipe for Antwerp green is given by Fishwick, who was writing in the late eighteenth/early nineteenth centuries For lib of blue vitriol dissolved in [ ] of water, add immediately 11b of purified alkali, 4oz powdered white arsenic, dissolved previously in 1 gallon of boiling water the precipitate, from the mixture of these two solutions is to be well washed, and dry d on white paper spread on flat pieces of chalk [q.v.). This appears to be for the copper arsenite compound commonly known as Scheele s green. 

For the filtration of very small quantities of crystals, the simple apparatus shown in Fig. 46 is often used. It consists of a fine glass rod (sometimes termed a filtration nail ) which is flattened at one end, the flattened surface being preferably roughened. It fits as shown into a small funnel which replaces F (Fig. 45). A circular piece of filter-paper is cut e-g.y with a clean sharp cork-borer) so as to fit completely and snugly over the flat end. After draining, the nail is raised and the filter-paper and crystals are removed with forceps and dried. 

Cover the charge with another piece of paper or cloth, fold over the edges and tape tightly to retain the charge in a flat diamond shape. See Figure 42. 

Get a piece of filter paper large enough to cover all the holes in the bottom plate, yet not curl up the sides of the funnel. It is placed flat on the plate (Fig. 46). 

E. Fisher, 37, 5241 (1943). Incendiary suitable for filling bombs and flares is prepd by mixing thoroughly Mg dust with pulped paper in water and then filtering to produce a uniformly flat sheet or ribbon. After drying, the sheet is cut into pieces... 

You place the globe on an old Oriental carpet covering the hardwood floor of your office. Let s return our attention to hypercubes. Another way to represent a hypercube is to show what it might look like if it was unfolded. You bring out a paper cube that has been taped together and remove some pieces of the tape. By analogy, you can unfold the faces of a paper cube and make it flat (Fig. 4.6). 

Create a collage made of various sizes and types of unpainted paper glued to a collage ground. The pieces of paper should overlap and cover all or most of the ground, and all comers should be secured so that the paper is as flat as possible. Include your handmade paper in the collage. 

Prepare two pieces of flat copper by cleaning them with emery paper. Do not touch the flat surfaces after they are cleaned. 

Use a full 8 X 10 inch sheet of enlarging paper to make your pre-flash test strip or cut a piece into 1 X 10 inch strips. With the paper held flat in an easel, use a black card to cover a 1 inch section of the test strip—this strip will receive no exposure and remain paper-base white. 

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