Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical funnel to guide and focus virus particles for X-ray laser
  imaging   The need for precise manipulation of nanoparticles in gaseous or near-vacuum
environments is encountered in many studies that include aerosol morphology,
nanodroplet physics, nanoscale optomechanics, and biomolecular physics.
Photophoretic forces, whereby momentum exchange between a particle and
surrounding gas is induced with optical light, were recently shown to be a
robust means of trapping and manipulating nanoparticles in air. We previously
proposed a photophoretic "optical funnel" concept for the delivery of
bioparticles to the focus of an x-ray free-electron laser (XFEL) beam for
femtosecond x-ray diffractive imaging. Here, we describe the formation of a
high-aspect-ratio optical funnel and provide a first experimental demonstration
of this concept by transversely compressing and concentrating a high-speed beam
of aerosolized viruses by a factor of three in a low-pressure environment.
These results pave the way toward improved sample delivery efficiency for XFEL
imaging experiments as well as other forms of imaging and spectroscopy.

16
The categories of this paper are: stat
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph