Tag: science & technology

In metal cutting, material removal occurs through intense shear deformation along the shear plane. The cutting tool creates high stresses that cause the material to fail in shear, forming chips that curl away. This is a plastic deformation process, not linear translation.

Spherical roller bearings have a self-aligning feature due to their spherical raceway geometry, which accommodates misalignment between shaft and housing. Roller and needle roller bearings don't have this capability.

Kaplan turbine is a propeller-type reaction turbine with adjustable blades, designed for low-head applications. It's an axial flow turbine (water flows parallel to shaft), not mixed or outward flow. The 'low' in option B likely means 'low-head' despite the grammatical issue.

The M-system (mean line system) and E-system (envelope system) are two methods for assessing surface finish in metrology. M-system uses mean line as reference, while E-system uses envelope of surface peaks. They quantify roughness, waviness, and other surface texture parameters.

Bacillus anthracis is the correct causative agent of anthrax, a gram-positive bacterial infection. Junin virus causes Argentine hemorrhagic fever, not anthrax. Yersinia is a different bacterial genus, and Plasmodium causes malaria.

Dengue fever is caused by flaviviruses, specifically Dengue virus (DENV), transmitted by Aedes mosquitoes. Bacillus cereus is a bacterium causing food poisoning. BK virus causes respiratory infections. Machupo virus causes Bolivian hemorrhagic fever.

Clostridium perfringens is a common bacterial cause of food poisoning, typically associated with improperly cooked meats and gravies that have been left at unsafe temperatures. While multiple bacteria can cause food poisoning, C. perfringens is one of the most frequently identified pathogens in foodborne outbreaks.

Trypanosoma brucei is the protozoan parasite that causes African sleeping sickness (African trypanosomiasis), transmitted by tsetse flies. The other options are incorrect: Fonsecaea causes chromoblastomycosis, Clostridium difficile causes antibiotic-associated diarrhea, and Ehrlichia causes ehrlichiosis.

Plasmodium genus (specifically P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi) is the definitive causative agent of malaria, transmitted by Anopheles mosquitoes. The other options are incorrect: Taenia causes tapeworm infection, Clonorchis causes liver fluke infection, and Histoplasma is a fungal pathogen.

Paper was invented in China during the Han Dynasty, traditionally credited to Cai Lun around 105 CE. Although earlier forms existed, Cai Lun standardized the process using mulberry bark, hemp, and rags. China maintained a monopoly on papermaking for centuries before it spread to the Islamic world and then Europe.