Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: This article's plot summary may be too long or excessively detailed. Please help improve it by removing unnecessary details and making it more concise. (October 2011) (Learn how and when to remove this template message) Oyuki, a tattooed female assassin the renegade member of a daimyo's personal bodyguard detail is killing every man that is sent up against her. Along with her deadly use of the short blade, she strips to the waist while fighting to reveal elaborate tattoos on her chest and back. On her front is a kintaro grasping her left breast. A portrait of a mountain witch covers her back. She then cuts off her victims' topknots, or chonmage, which brings dishonor to the dead man and his family. Ogami Itto, the disgraced former shogun's executioner, or Kogi Kaishakunin, is hired to kill Oyuki. He tracks down the tattoo artist, who explains that she was a "fine" woman who did not scream as he dug into her flesh with his needles. Meanwhile, Itto's 3-year-old son, Daigoro, has grown restless waiting by the baby cart his father uses to trundle him about in. He goes exploring and finds a pair of performing clowns on the street. When the clowns finish their performance, Daigoro follows them, hoping to see more. But the clowns shoo him away, saying it's time to go home. Now, Daigoro has wandered too far. He is lost, and has become separated from his father. Agents of the Ogamis' mortal enemies, the Yagyu, are never far away. A procession of them, accompanied by the sound of gongs and loud shrieks, sends Daigoro into hiding. Itto must give up his search rather than risk an entanglement with the men, so he travels on alone. Daigoro spends days looking for his father, searching in every temple in the countryside. He enters one temple and sees a figure at the altar praying, but it is not his father. Rather, it is a man whom Daigoro immediately recognizes as someone who is unfriendly. The man follows Daigoro, who wanders into a grass field as it is being lit on fire by farmers. Unwittingly, Daigoro is surrounded by the flames, but he proves his resourcefulness by burying himself and surviving. The man then turns his sword on Daigoro, who raises a stick to defend himself, and in that instant the man realizes who Daigoro is. Just then, Itto comes into the picture, and the two recognize each other. The man, it turns out is Gunbei Yagyu, the outcast son of Retsudo Yagyu. Gunbei and Itto had competed for the post of shogun's executioner, and Gunbei's fierce swordsmanship surely would have won him the post, but in his over zealousness, he ends up pointing his sword at the shogun a taboo movement that costs him the job and makes him an outcast. Itto and Gunbei now have a rematch, but Itto is much improved and is ready for Gunbei. With a swift stroke, he chops off Gunbei's right arm. Gunbei then begs Itto to kill him, but Itto refuses, saying there is nothing to be gained from slaying a man who is already dead. With Gunbei out of the way and father and son reunited, the action then turns on finding the tattooed killer, Oyuki. He first stops at a settlement of street actors that Oyuki was said to be a part of. He talks to the elder and hears more of her story, and it happens that the elder is Oyuki's father, who is opposed to her actions, and cooperates with Itto. Itto finally locates Oyuki at a hot spring and witnesses her in action against more vassals who have come to try to kill her. Then her nemesis, her former instructor who raped her and set her on her bloody vendetta, shows up with his flaming sword and blazing eyes. But she is no longer in his sway, and when he sees her tattoos, he is distracted and killed. Finally, Itto and Oyuki must duel, and he makes quick work of her. She dies a splendid 
 Question: Of what is the portrait that covers her back?
a mountain

Context: Elena Wexler-Kreindler (15 October 1931 -- August 2002) was a Romanian mathematician. 
 Question: The date of birth of Elena Wexler-Kreindler is?
15 october 1931

Context: Warming homes and other buildings is an obvious way that thermal energy can be used. Two common types of home heating systems are hot-water and warm-air heating systems. Both types are described below. You can watch an animation showing how a solar heating system works at this URL: A hot-water heating system uses thermal energy to heat water and then pumps the hot water throughout the building in a system of pipes and radiators. You can see a diagram of this type of heating system in Figure 18.12. Typically, the water is heated in a boiler that burns natural gas or heating oil. There is usually a radiator in each room that gets warm when the hot water flows through it. The radiator transfers thermal energy to the air around it by conduction and radiation. The warm air then circulates throughout the room in convection currents. The hot water cools as it flows through the system and transfers its thermal energy. When it finally returns to the boiler, it is heated again and the cycle repeats. A warm-air heating system uses thermal energy to heat air. It then forces the warm air through a system of ducts. You can see a diagram of this type of heating system in Figure 18.13. Typically, the air is heated in a furnace that burns natural gas or heating oil. When the air is warm, a fan blows it through the ducts and out through vents that are located in each room. Warm air blowing out of a vent moves across the room, pushing cold air out of the way. The cold air enters an intake vent on the opposite side of the room and returns to the furnace with the help of another fan. In the furnace, the cold air is heated, and the cycle repeats. Its easy to see how thermal energy can be used to keep things warm. But did you know that thermal energy can also be used to keep things cool? Cooling systems such as air conditioners and refrigerators transfer thermal energy in order to keep homes and cars cool or to keep food cold. In a refrigerator, for example, thermal energy is transferred from the cool air inside the refrigerator to the warmer air in the kitchen. You read in this chapters "Transfer of Thermal Energy" lesson that thermal energy always moves from a warmer area to a cooler area, so how can it move from the cooler refrigerator to the warmer room? The answer is work. The refrigerator does work to transfer thermal energy in this way. Doing this work takes energy, which is usually provided by electricity. Figure 18.14 explains how a refrigerator does its work. For an animated demonstration of how a refrigerator works, go to this URL: The key to how a refrigerator or other cooling system works is the refrigerant. A refrigerant is a substance, such as FreonTM, that has a low boiling point and changes between liquid and gaseous states as it passes through the cooling system. As a liquid, the refrigerant absorbs thermal energy from the cool air inside the refrigerator and changes to a gas. As a gas, it releases thermal energy to the warm air outside the refrigerator and changes back to a liquid. A combustion engine is a complex machine that burns fuel to produce thermal energy and then uses the energy to do work. Two basic types of combustion engines are external and internal combustion engines. An external combustion engine burns fuel externally, or outside the engine. The burning fuel releases thermal energy that is used to turn water to steam. The pressure of the steam is then used to move a piston back and forth in a cylinder. The kinetic energy of the moving piston can be used to turn a turbine or other device. Figure 18.15 explains in greater detail how this type of engine works. You can see an animated version of an external combustion engine at this URL: [Link] . An internal combustion engine (see Figure 18.16) burns fuel internally, or inside the engine. This type of engine is found in most cars and other motor vehicles. It works in these steps, which keep repeating: 1. A mixture of fuel and air is pulled into a cylinder through a 
 Question: refrigerator or air conditioner

cooling system