Common toppings for pizza in the United States include ground beef, mushrooms, onions, pepperoni, pineapple, garlic, chicken, bacon, ham and sausage. Distinct regional types developed in the twentieth century, including California, Chicago, Greek, New Haven, Detroit and New York styles. The first pizzeria in the U.S. was opened in New York's Little Italy in 1905 and since then regions throughout the U.S. offer variations, including deep-dish, stuffed, pockets, turnovers, rolled and pizza-on-a-stick, each with seemingly limitless combinations of sauce and toppings.
Another variation is grilled pizza, created by taking a fairly thin, round (more typically, irregularly shaped) sheet of yeasted pizza dough, placing it directly over the fire of a grill and then turning it over once the bottom has baked and placing a thin layer of toppings on the baked side. Toppings may be sliced thin to ensure that they heat through, and chunkier toppings such as sausage or peppers may be precooked before being placed on the pizza. Garlic, herbs, or other ingredients are sometimes added to the pizza or the crust to maximize the flavor of the dish.
Grilled pizza was offered in the United States at the Al Forno restaurant in Providence, Rhode Island by owners Johanne Killeen and George Germon in 1980. Although it was inspired by a misunderstanding that confused a wood-fired brick oven with a grill, grilled pizza did exist prior to 1980, both in Italy, and in Argentina where it is known as pizza a la parrilla. It has become a popular cookout dish, and there are even some pizza restaurants that specialize in the style. The traditional style of grilled pizza employed at Al Forno restaurant uses a dough coated with olive oil, strained tomato sauce, thin slices of fresh mozzarella, and a garnish made from shaved scallions, and is served uncut. The final product can be likened to flatbread with pizza toppings. Another Providence establishment, Bob & Timmy's Grilled Pizza, was featured in a Providence-themed episode of the Travel Channel's Man v. Food Nation in 2011.
Large slow-speed Diesel engines may require additional support for the side forces on the piston. These engines typically use crosshead pistons. The main piston has a large piston rod extending downwards from the piston to what is effectively a second smaller-diameter piston. The main piston is responsible for gas sealing and carries the piston rings. The smaller piston is purely a mechanical guide. It runs within a small cylinder as a trunk guide and also carries the gudgeon pin.
Lubrication of the crosshead has advantages over the trunk piston as their lubricating oil is not subject to the heat of combustion: the oil is not contaminated by combustion soot particles, it does not break down owing to the heat and a thinner, less viscous oil may be used. The friction of both piston and crosshead may be only half of that for a trunk piston.
Because of the additional weight of these pistons, they are not used for high-speed engines.
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