Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quartz-enhanced photoacoustic spectroscopy as a platform for
  non-invasive trace gas analyser targeting breath analysis   An innovative and novel quartz-enhanced photoacoustic spectroscopy (QEPAS)
sensor for highly sensitive and selective breath gas analysis is introduced.
The QEPAS sensor consists of two acoustically coupled micro-resonators (mR)
with an off-axis 20 kHz quartz tuning fork (QTF). The complete acoustically
coupled mR system is optimized based on finite element simulations and
experimentally verified. Due to the very low fabrication costs the QEPAS sensor
presents a clear breakthrough in the field of photoacoustic spectroscopy by
introducing novel disposable gas chambers in order to avoid cleaning after each
test. The QEPAS sensor is pumped resonantly by a nanosecond pulsed single-mode
mid-infrared optical parametric oscillator (MIR OPO). Spectroscopic
measurements of methane and methanol in the 3.1 $\mu$m to 3.7 $\mu$m wavelength
region is conducted. Demonstrating a resolution bandwidth of 1 cm$^{-1}$. An
Allan deviation analysis shows that the detection limit at optimum integration
time for the QEPAS sensor is 32 ppbv@190s for methane and that the background
noise is solely due to the thermal noise of the QTF. Spectra of both individual
molecules as well as mixtures of molecules were measured and analyzed. The
molecules are representative of exhaled breath gasses that are bio-markers for
medical diagnostics.

31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin