Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Development of hard water sensor using Fluorescence Resonance Energy
  Transfer   A method is presented for the sensing of water hardness by determining the
concentration of calcium and magnesium in water, based on Fluorescence
resonance energy transfer (FRET) process. The principle of the proposed sensor
is based on the change of FRET efficiency between two laser dyes Acriflavine
(Acf) and Rhodamine B (RhB) in presence of permanent hard water components
(CaCl2 and MgCl2). Nanodimensional clay platelet laponite was used to enhance
the efficiency of the sensor.

27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin