421 research outputs found
Coherent, multi-heterodyne spectroscopy using stabilized optical frequency combs
The broadband, coherent nature of narrow-linewidth fiber frequency combs is
exploited to measure the full complex spectrum of a molecular gas through
multi-heterodyne spectroscopy. We measure the absorption and phase shift
experienced by each of 155,000 individual frequency comb lines, spaced by 100
MHz and spanning from 1495 nm to 1620 nm, after passing through a hydrogen
cyanide gas. The measured phase spectrum agrees with Kramers-Kronig
transformation of the absorption spectrum. This technique can provide a full
complex spectrum rapidly, over wide bandwidths, and with hertz-level accuracy.Comment: 4 pages, 3 figure
Interviewing suspects: examining the association between skills, questioning, evidence disclosure, and interview outcomes
The interviewing of suspects is an important element in the investigation of crime. However, studies concerning actual performance of investigators when undertaking such interviews remain sparse. Nevertheless, in England and Wales, since the introduction of a prescribed framework over 20 years ago, field studies have generally shown an improvement in interviewing performance, notwithstanding ongoing concerns largely relating to the more demanding aspects (such as building/maintaining rapport, intermittent summarising and the logical development of topics). Using a sample of 70 real-life interviews, the present study examined questioning and various evidence disclosure strategies (which have also been found demanding), examining their relationships between interview skills and interview outcomes. It was found that when evidence was disclosed gradually (but revealed later), interviews were generally both more skilled and involved the gaining of comprehensive accounts, whereas when evidence was disclosed either early or very late, interviews were found to be both less skilled and less likely to involve this outcome. These findings contribute towards an increased research base for the prescribed framework
Spectroscopy of the Methane {\nu}3 Band with an Accurate Mid-Infrared Coherent Dual- Comb Spectrometer
We demonstrate a high-accuracy dual-comb spectrometer centered at 3.4 \mu m.
The amplitude and phase spectra of the P, Q, and partial R-branch of the
methane {\nu}3 band are measured at 25 MHz to 100 MHz point spacing with ~kHz
resolution and a signal-to-noise ratio of up to 3500. A fit of the absorbance
and phase spectra yield the center frequency of 132 rovibrational lines. The
systematic uncertainty is estimated to be 300 kHz, which is 10-3 of the Doppler
width and a tenfold improvement over Fourier transform spectroscopy. These data
are the first high- accuracy molecular spectra obtained with a direct comb
spectrometer.Comment: journal articl
Observation of Caustics in the Trajectories of Cold Atoms in a Linear Magnetic Potential
We have studied the spatial and temporal dynamics of a cold atom cloud in the
conservative force field of a ferromagnetic guide, after laser cooling has been
switched off suddenly. We observe outgoing 'waves' that correspond to caustics
of individual trajectories of trapped atoms. This provides detailed information
on the magnetic field, the energy distribution and the spin states.Comment: 21 pages, incl. 12 figure
Coherent Dual Comb Spectroscopy at High Signal to Noise
Two frequency combs can be used to measure the full complex response of a
sample in a configuration which can be alternatively viewed as the equivalent
of a dispersive Fourier transform spectrometer, infrared time domain
spectrometer, or a multiheterodyne laser spectrometer. This dual comb
spectrometer retains the frequency accuracy and resolution inherent to the comb
sources. We discuss, in detail, the specific design of our coherent dual-comb
spectrometer and demonstrate the potential of this technique by measuring the
first overtone vibration of hydrogen cyanide, centered at 194 THz (1545 nm). We
measure the fully normalized, complex response of the gas over a 9 THz
bandwidth at 220 MHz frequency resolution yielding 41,000 resolution elements.
The average spectral signal-to-noise ratio (SNR) is 2,500 for both the
fractional absorption and the phase, with a peak SNR of 4,000 corresponding to
a fractional absorption sensitivity of 0.025% and phase sensitivity of 250
microradians. As the spectral coverage of combs expands, this dual-comb
spectroscopy could provide high frequency accuracy and resolution measurements
of a complex sample response across a range of spectral regions.Comment: 18 pages, 8 figures updated references, updated to match publication
versio
Nutritional intakes of highly trained adolescent swimmers before, during, and after a national lockdown in the COVID-19 pandemic
Strict lockdown measures were introduced in response to the COVID-19 pandemic, which caused mass disruption to adolescent swimmersâ daily routines. To measure how lockdown impacted nutritional practices in this cohort, three-day photograph food diaries were analysed at three time points: before (January), during (April), and after (September) the first UK lockdown. Thirteen swimmers (aged 15 ± 1 years) from a high-performance swimming club submitted satisfactory food diaries at all time points. During lockdown, lower amounts of energy (45.3 ± 9.8 vs. 31.1 ± 7.7 kcalâkg BMâday-1, p0.05), despite fewer training hours being completed (15.0 ± 1.4 vs. 19.1 ± 2.2 hâweek-1, p<0.001). These findings highlight the ability of adolescent swimmers to alter their nutrition based on their changing training circumstances when receiving sport nutrition support. However, some individuals displayed signs of suboptimal nutrition during lockdown that were not corrected once training resumed. This warrants future research to develop interactive education workshops that maintain focus and motivation towards optimal nutrition practices in isolated periods away from training
The 3â-5â exoribonuclease Dis3 regulates the expression of specific microRNAs in Drosophila wing imaginal discs
Dis3 is a highly conserved exoribonuclease which degrades RNAs in the 3'-5' direction. Mutations in Dis3 are associated with a number of human cancers including multiple myeloma and acute myeloid leukaemia. In this work, we have assessed the effect of a Dis3 knockdown on Drosophila imaginal disc development and on expression of mature microRNAs. We find that Dis3 knockdown severely disrupts the development of wing imaginal discs in that the flies have a "no wing" phenotype. Use of RNA-seq to quantify the effect of Dis3 knockdown on microRNA expression shows that Dis3 normally regulates a small subset of microRNAs, with only 11 (10.1%) increasing in level > 2-fold and 6 (5.5%) decreasing in level >2-fold. Of these microRNAs, miR-252-5p is increased 2.1-fold in Dis3-depleted cells compared to controls while the level of the miR-252 precursor is unchanged, suggesting that Dis3 can act in the cytoplasm to specifically degrade this mature miRNA. Furthermore, our experiments suggest that Dis3 normally interacts with the exosomal subunit Rrp40 in the cytoplasm to target miR-252-5p for degradation during normal wing development. Another microRNA, miR-982-5p, is expressed at lower levels in Dis3 knockdown cells, while the miR-982 precursor remains unchanged, indicating that Dis3 is involved in its processing. Our study therefore reveals an unexpected specificity for this ribonuclease towards microRNA regulation, which is likely to be conserved in other eukaryotes and may be relevant to understanding its role in human disease
Estimating vehicle carbon dioxide emissions from Boulder, Colorado, using horizontal path-integrated column measurements
We performed 7.5 weeks of path-integrated concentration
measurements of CO2, CH4, H2O, and HDO over the city of Boulder, Colorado. An open-path dual-comb spectrometer simultaneously
measured time-resolved data across a reference path, located near the
mountains to the west of the city, and across an over-city path that
intersected two-thirds of the city, including two major commuter arteries. By
comparing the measured concentrations over the two paths when the wind is
primarily out of the west, we observe daytime CO2 enhancements over
the city. Given the warm weather and the measurement footprint, the dominant
contribution to the CO2 enhancement is from city vehicle traffic. We
use a Gaussian plume model combined with reported city traffic patterns to
estimate city emissions of on-road CO2 as (6.2±2.2)âĂâ105 metric tons (t) CO2 yrâ1
after correcting for non-traffic sources. Within the uncertainty, this value
agrees with the city's bottom-up greenhouse gas inventory for the on-road
vehicle sector of 4.5Ă105 t CO2 yrâ1. Finally, we
discuss experimental modifications that could lead to improved estimates from
our path-integrated measurements.</p
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