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How is immunity reached after a vaccine is given? Include the roles of both T cells and B cells.

The vaccine contains either dead or attenuated pathogens, or they can contain just antigens from the pathogen. When one is injected with a vaccine the white blood cells within the body are able to recognise ...
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Answered by Chizara L. • Biology tutor
3067 Views

Consider the unit hyperbola, whose equation is given by x^2 - y^2 = 1. We denote the origin, (0, 0) by O. Choose any point P on the curve, and label its reflection in the x axis P'. Show that the line OP and the tangent line to P' meet at a right angle.

We differentiate our equation with respect to x to find that 2x - 2y(dy/dx) = 0, and rearrange to find that dy/dx = x/y. We set P = (x, y). The slope of OP is given by y/x, and the slope of the tangent at P'...
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Answered by Dylan C. • Maths tutor
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Show that the volume of the solid formed by the curve y=cos(x/2), as it is rotated 360° around the x-axis between x= π/4 and x=3π/4, is of the form π^2/a. Find the constant a.

After sketching a diagram of the curve and the solid for clarity, we see that we need to use the formula V = π∫ y 2 dx (with upper and lower bounds of 3π/4 and π/4 respectively) to calculate the volume of th...
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Answered by Nicholas C. • Maths tutor
3876 Views

Describe how to perform a flame test to identify an unknown compound.

The equipment needed is a bunsen burner, a wire loop, some HCl, and the compound being tested (usually in powder form). Set up the bunsen burner so that it is on a blue flame. Take the wire loop and dip it i...
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Answered by Martha N. • Chemistry tutor
3865 Views

‘The most important contribution to the creation of a united Italy in 1861 was made by Cavour.’ How far do you agree?

This question is rooted in broader debates about historical causation. Such debates can be identified in most A Level questions and can essentially be boiled down to assessing the most important agents of ch...
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Answered by Jack B. • History tutor
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