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.

[EX Q]: 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?
[EX A]: a mountain

[EX Q]: Context: A machine is any device that makes work easier by changing a force. When you use a machine, you apply force to the machine. This force is called the input force. The machine, in turn, applies force to an object. This force is called the output force. Recall that work equals force multiplied by distance: Work = Force Distance The force you apply to a machine is applied over a given distance, called the input distance. The force applied by the machine to the object is also applied over a distance, called the output distance. The output distance may or may not be the same as the input distance. Machines make work easier by increasing the amount of force that is applied, increasing the distance over which the force is applied, or changing the direction in which the force is applied. Contrary to popular belief, machines do not increase the amount of work that is done. They just change how the work is done. So if a machine increases the force applied, it must apply the force over a shorter distance. Similarly, if a machine increases the distance over which the force is applied, it must apply less force. Examples of machines that increase force are doorknobs and nutcrackers. Figure 16.8 explains how these machines work. In each case, the force applied by the user is less than the force applied by the machine, but the machine applies the force over a shorter distance. Examples of machines that increase the distance over which force is applied are paddles and hammers. Figure 16.9 explains how these machines work. In each case, the machine increases the distance over which the force is applied, but it reduces the strength of the applied force. Some machines change the direction of the force applied by the user. They may or may not also change the strength of the force or the distance over which it is applied. Two examples of machines that work in this way are claw hammers and the rope systems (pulleys) that raise or lower flags on flagpoles. Figure 16.10 explains how these machines work. In each case, the direction of the force applied by the user is reversed by the machine. How does this make it easier to do the job? An exoskeleton suit may seem like science fiction, turning ordinary humans into super heroes. But wearable robots are moving forward into reality. And for paraplegics, the ability to stand and walk that these machines provide is a super power. QUEST meets Austin Whitney and Tamara Mena, two "Exoskeleton Test Pilots" who are now putting this new technology through its paces. For more information on exoskeleton suits, see [Link] MEDIA Click image to the left or use the URL below. URL: You read above that machines do not increase the work done on an object. In other words, you cant get more work out of a machine than you put into it. In fact, machines always do less work on the object than the user does on the machine. Thats because all machines must use some of the work put into them to overcome friction. How much work? It depends on the efficiency of the machine. Efficiency is the percent of input work that becomes output work. It is a measure of how well a machine reduces friction. Consider the ramp in Figure 16.11. Its easier to push the heavy piece of furniture up the ramp to the truck than to lift it straight up off the ground. However, pushing the furniture over the surface of the ramp creates a lot of friction. Some of the force applied to moving the furniture must be used to overcome the friction. It would be more efficient to use a dolly on wheels to roll the furniture up the ramp. Thats because rolling friction is much less than sliding friction. As a result, the efficiency of the ramp would be greater with a dolly. Efficiency can be calculated with the equation: Efficiency = Output work 100% Input work Consider a machine that puts out 6000 joules of work. To produce that much work from the machine requires the user to put in 8000 joules of work. To find the efficiency of the machine, 
 Question: force applied by a machine
[EX A]: output force

[EX Q]: Context: The Na(+)/Ca(2+) exchanger (NCX) plays a role in the regulation of intracellular Ca(2+) levels, and nitric oxide (NO) is involved in many pathological conditions including neurodegenerative disorders. We have previously found that sodium nitroprusside (SNP), an NO donor, causes apoptotic-like cell death in cultured glial cells via NCX-mediated pathways and the mechanism for NO-induced cytotoxicity is cell type-dependent. The present study examined using the specific NCX inhibitor 2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline (SEA0400) whether NCX is involved in NO-induced injury in cultured neuronal cells. The treatment of neuroblastoma SH-SY5Y cells with SNP resulted in apoptosis and the cytotoxicity was blocked by the mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase inhibitor U0126 and the p38 MAP kinase (MAPK) inhibitor SB203580, but not by the c-Jun N-terminal kinase (JNK) inhibitor SP60012. SNP increased Ca(2+) influx and intracellular Ca(2+) levels. In addition, SNP increased ERK and p38 MAPK phosphorylation, and production of reactive oxygen species (ROS) in an extracellular Ca(2+)-dependent manner. These effects of SNP were prevented by SEA0400. SNP-induced cytotoxicity was not affected by inhibitors of the Ca(2+), Na(+) and store-operated/capacitative channels. Moreover, SNP-induced increase in intracellular Ca(2+) levels, ROS production and decrease in cell viability were blocked by a cGMP-dependent protein kinase (PKG) inhibitor. These results suggest that Ca(2+) influx via the reverse of NCX is involved in the cascade of NO-induced neuronal apoptosis and NO activates the NCX through guanylate cyclase/PKG pathway. 
 Question: The small molecule SEA0400 is an inhibitor of which ion antiporter/exchanger?
[EX A]:
na(+)/ca(2+) exchanger