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\section{Scientific Justification}  Recent analyses of far-infrared (Herschel) observations indicates a close relationship between filamentary structures and star formation. Numerical simulations plus morphological evidence Herschel in dust (especially recent Herschel)  maps suggest that stars form through gravitational fragmentation in filaments. As explained below, recent analyses of multi-scale, kinematically-resolved, observations of the B5 region in Perseus appear to show that gravitationally bound cores form from fragmenting filments relatively quickly. L1689B is analogous to B5 in that it offers a relatively simple case of a young pre-stellar core sitting on a single filament, with a velocity gradient along the filament at parsec scales. We propose VLA observations of NH_3 (1, 1) and (2, 2) line emission of L1689B in order to trace the kinematics from the filament to the core, and {\bf in order to examine the star forming and fragmentation processes in the filament at an early stage}. \subsection{The case of B5 in the Perseus molecular cloud}  B5 in the Perseus molecular cloud was identified as a young pre-stellar core. Herschel observations shows that B5 sits in a filamentary strcutre, which extends for \~ 2 pc. FCRAO (40-arcsec-resolution) observations of ^{12}CO (1-0) and ^{13}CO (1-0) line emission show that the B5 region has a complicated velocity structure with multiple velocity components along the line of sight. In higher resolution (30-arcsec) GBT observations of NH_3 (1, 1) and (2, 2) hyperfine lines, the B5 NH_3 core embedded in the surrounding CO mess is seen to have a sub-sonic velocity disperson, conforming to the theory of star formation in {\it coherent cores}. By combining the GBT observations with even-higher-resolution VLA NH_3 mapping, we \citep{Pineda_2011} found fragmentation {\it within} the coherent core. Combining an improved version of the VLA NH_3 data cube with additional sub-mm continuum information about the embedded sources shows that the B5 case offers the first direct evidence of star formation through filament fragmentation (Pineda, Goodman et al. to appear in Nature on February 12, 2015, see Figure xx).