division 细分

   Simulated diamonds are a creation of man;they are formed via a technological process. That is why they are also known as “manufactured”, “lab-grown” or “cultured” diamonds. In 1797 it was first discovered that diamonds are comprised of pure carbon. Ever since then, attempts have been made by several people to produce diamonds synthetically. 

   There are two major methods which are used to create simulated diamond crystals. The first and most popular method, which was devised by GE, is known as the High Pressure High Temperature (HPHT)method. There are two different press designs which are used to grow the diamond crystals. The first is the method used by Howard Tracy Hall, which is called the belt press method. In the belt press method, two anvils, one from up and one from down, supply the pressure and heat currents to a cylindrical volume. The second method is known as the cubic press method. In this method, there are six anvils which provide pressure to a cube shaped volume. The second method, devised by the Japanese, is known as Chemical Vapor Deposition (CVD) method. In this method the necessary environment is created for carbon atoms in a gas to settle on a surface for the diamond crystals to grow.

Should Cars Be Allowed into College Campus?

Why are antimicrobials used widely in poultry production?

How was the study conducted with poultry workers and community residents?

What does Ellen K.Silbergeld mean when stating that“One of the major implications of this study is to underscore the importance of the non-hospital environment in the origin of drug resistant infections”?

(B)

   Poultry workers in the United States are 32 times more likely to carry E. coli bacteria resistant to the commonly used antibiotic, gentamicin, than others outside the poultry industry, according to a recent study conducted by researchers at the Johns Hopkins Bloomberg School of Public Health. While drug-resistant bacteria, such as E. coli, are common in the industrial broiler chicken environment, this is the first U.S. research to show exposure occurring at a high level among industrial poultry workers.

   “The use of antimicrobials in industrial food production has been going on for over 50 years in the United States,” said the study’s lead author, Lance B. Price, who serves on the research faculty at the Johns Hopkins School of Medicine, Division of Infectious Disease, and is a scientific advisor to the Johns Hopkins Center for a Livable Future. “Some estimates indicate that well over half of the antimicrobial drugs produced in the United States are used in food animal production. In the U.S. alone, over nine billion food animals are produced annually.”

     The study was conducted with poultry workers and community residents in the eastern shore regions of Maryland and Virginia, and it confirms similar studies in Europe showing that poultry farmers and workers are at risk of exposure to drug resistant E. coli bacteria. The Maryland and Virginia regions on the Delmarva Peninsula are among the top broiler chicken producing regions in the U.S., producing more than 600 million chickens annually.

 In the study, researchers conducted in-depth analyses of 49 study participants, 16 working within the poultry industry and 33 community residents. Stool samples from the participants were tested for resistance to the antimicrobials ampicillin, ciprofloxacin, ceftriazone, gentamicin and tetracycline. Findings showed that poultry workers had 32 times greater odds of being colonized with gentamicin-resistant E. coli than other members of the community.  “One of the major implications of this study is to underscore the importance of the non-hospital environment in the origin of drug resistant infections,” said Ellen K.Silbergeld, PhD, senior author of the study. 

       Price, PhD, and other researchers note that as food animal production shifted from the independent farmer to large-scale, industrialized operations, the use of antimicrobials in feeds intended to stimulate growth has increased. Currently 16 different antimicrobial drugs are approved for use in U.S. poultry production with gentamicin reported to be the most widely used.

What is the passage mainly about?

The expression “broiler chicken” in line 4, para.1, refers to ______. 

Which of the following is NOT true about the new technique of atom laser construction?

What does the author think of the first atom lasers according to the passage?

Why can’t atom waves be seen through a microscope under normal conditions?