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男，40岁，某蓄电池厂制造工，工龄 20年，主诉阵发性腹部疼痛4小时。患者在发病前常有食欲不振、腹部隐痛、便秘等症状。检查腹软，脐周有压痛，无反跳痛，血象检查白细胞数正常。 为防止其他工人发生类似情况，应采取的根本性预防措施是
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若深度为5的完全二叉树的第5层有3个叶结点，则该二叉树一共有 [3] 个结点。
For three decades we’’ve heard endlessly about the virtues of aerobic (increasing oxygen consumption) exercise. Medical authorities have praised running and jumping as the key to good health, and millions of Americans have taken to the treadmill(踏车) to reap the rewards. But the story is changing. Everyone from the American Heart Association to the surgeon general’’s office has recently embraced strength training as a complement to aerobics. And as weight lifting has gone mainstream, so has the once obscure practice known as "Super Slow" training. Enthusiasts claim that by pumping iron at a snail’’s pace-making each "rep"(repeat) last 14 seconds instead of the usual seven-you can safely place extraordinary demands on your muscles, and call forth an extraordinary response. Slow lifting may not be the only exercise you need, as some advocates believe, but the benefits are often dramatic. Almost anyone can handle this routine. The only requirements are complete focus and a tolerance for deep muscular burn. Fox each exercise-leg press, bench press, shoulder press and so on-you set the machine to provide only moderate resistance. But as you draw out each rep, depriving yourself of impetus, the weight soon feels unbearable. Defying the impulse to stop, you keep going until you can’’t complete a rep. Then you sustain your vain effort for 10 more seconds while the weight sinks gradually toward its cradle. Intense Uncomfortable Totally. But once you embrace muscle failure as the goal of the workout, it can become almost pleasure. The goal is not to burn calories while you’’re exercising but to make your body burn them all the time. Running a few miles many make you sweat, but it expends only 100 calories per mile, and it doesn’’t stimulate much bone or muscle development. Strength training doesn’’t burn many calories, either. But when you push a muscle to failure, you set off a pour of physiological changes. As the muscle recovers over several days, it will thicken-and the new muscle tissue will demand sustenance. By the time you add three pounds of muscle, your body requires an extra 9,000 calories a month just to break even. Hold your diet steady and, very quickly, you are vaporizing body fat. One might have benefited from any strength-training program. But advocates insist the slow technique is safer and more effective than traditional methods. The phrase "to break even" ( Line 7, Par. 3 ) most probably means
感觉胎动明显的时间是
In recent years, railroads have been combining with each other, merging into supersystems, causing heightened concerns about monopoly. As recently as 1995, the top four railroads accounted for under 70 percent of the total ton-miles moved by rails. Next year, after a series of mergers is completed, just four railroads will control well over 90 percent of all the freight moved by major rail carriers. Supporters of the new supersystems argue that these mergers will allow for substantial cost reductions and better coordinated service. Any threat of monopoly, they argue, is removed by fierce competition from trucks. But many shippers complain that for heavy bulk commodities traveling long distances, such as coal, chemicals, and grain, trucking is too costly and the railroads therefore have them by the throat. The vast consolidation within the rail industry means that most shippers are served by only one rail company. Railroads typically charge such" captive" shippers 20 to 30 percent more than they do when another railroad is competing for the business. Shippers who feel they are being overcharged have the right to appeal to the federal government’’ s Surface Transportation Board for rate relief, but the process is expensive, time consuming, and will work only in truly extreme cases. Railroads justify rate discrimination against captive shippers on the grounds that in the long run it reduces everyone’’s cost. If railroads charged all customers the same average rate, they argue, shippers who have the option of switching to trucks or other forms of transportation would do so, leaving remaining customers to shoulder the cost of keeping up the line. It’’ s a theory to which many economists subscribe, but in practice it often leaves railroads in the position of determining which companies will flourish and which will fail. "Do we really want railroads to be the arbiters of who wins and who loses in the marketplace" asks Martin Bercovici, a Washington lawyer who frequently represents shippers. Many captive shippers also worry they will soon be hit with a round of huge rate increases. The railroad industry as a whole, despite its brightening fortunes, still does not earn enough to cover the cost of the capital it must invest to keep up with its surging traffic. Yet railroads continue to borrow billions to acquire one another, with Wall Street cheering them on. Consider the $10.2 billion bid by Norfolk Southern and CSX to acquire Conrail this year. Conrail’’ s net railway operating income in 1996 was just $427 million, less than half of the carrying costs of the transaction. Who’’ s going to pay for the rest of the bill Many captive shippers fear that they will, as Norfolk Southern and CSX increase their grip on the market. What is many captive shippers’’ attitude towards the consolidation in the rail industry
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