2,714 research outputs found
Determination of the Rb ng-series quantum defect by electric-field-induced resonant energy transfer between cold Rydberg atoms
Resonant energy transfer between cold Rydberg atoms was used to determine
Rydberg atom energy levels, at precisions approaching those obtainable in
microwave spectroscopy. Laser cooled Rb atoms from a magneto-optical trap were
optically excited to 32d Rydberg states. The two-atom process 32d(j=5/2) +
32d(j=5/2) -> 34p(j=3/2) + 30g is resonant at an electric field of
approximately 0.3 V/cm. This process is driven by the electric dipole-dipole
interaction, which is allowed due to the partial f character that the g state
acquires in an electric field. The experimentally observed resonant field,
together with the Stark map calculation is used to make a determination of the
Rb ng-series quantum defect: delta_g (n=30) = 0.00405(6)
Reexamining Black-Body Shifts for Hydrogenlike Ions
We investigate black-body induced energy shifts for low-lying levels of
atomic systems, with a special emphasis on transitions used in current and
planned high-precision experiments on atomic hydrogen and ionized helium.
Fine-structure and Lamb-shift induced black-body shifts are found to increase
with the square of the nuclear charge number, whereas black-body shifts due to
virtual transitions decrease with increasing nuclear charge as the fourth power
of the nuclear charge. We also investigate the decay width acquired by the
ground state of atomic hydrogen, due to interaction with black-body photons.
The corresponding width is due to an instability against excitation to higher
excited atomic levels, and due to black-body induced ionization. These effects
limit the lifetime of even the most fundamental, a priori absolutely stable,
"asymptotic" state of atomic theory, namely the ground state of atomic
hydrogen.Comment: 11 pages; LaTe
Constraining Stellar Feedback: Shock-ionized Gas in Nearby Starburst Galaxies
(abridged) We investigate the properties of feedback-driven shocks in 8
nearby starburst galaxies using narrow-band imaging data from the Hubble Space
Telescope (HST). We identify the shock--ionized component via the line
diagnostic diagram \oiii/\hb vs. \sii (or \nii)/\ha, applied to resolved
regions 3--15 pc in size. We divide our sample into three sub-samples:
sub-solar (Holmberg II, NGC 1569, NGC 4214, NGC 4449, and NGC 5253), solar (He
2-10, NGC 3077) and super-solar (NGC 5236) for consistent shock measurements.
For the sub-solar sub-sample, we derive three scaling relations: (1) , (2) , and
(3) , where
is the \ha luminosity from shock--ionized gas, the SFR per
unit half-light area, the total \ha luminosity, and
the absolute H-band luminosity from 2MASS normalized to solar luminosity. The
other two sub--samples do not have enough number statistics, but appear to
follow the first scaling relation. The energy recovered indicates that the
shocks from stellar feedback in our sample galaxies are fully radiative. If the
scaling relations are applicable in general to stellar feedback, our results
are similar to those by Hopkins et al. (2012) for galactic super winds. This
similarity should, however, be taken with caution at this point, as the
underlying physics that enables the transition from radiative shocks to gas
outflows in galaxies is still poorly understood.Comment: 29 pages, 14 figures, accepted for publication in the Ap
Spectroscopic observation of resonant electric dipole-dipole interactions between cold Rydberg atoms
Resonant electric dipole-dipole interactions between cold Rydberg atoms were
observed using microwave spectroscopy. Laser-cooled Rb atoms in a
magneto-optical trap were optically excited to 45d Rydberg states using a
pulsed laser. A microwave pulse transferred a fraction of these Rydberg atoms
to the 46p state. A second microwave pulse then drove atoms in the 45d state to
the 46d state, and was used as a probe of interatomic interactions. The
spectral width of this two-photon probe transition was found to depend on the
presence of the 46p atoms, and is due to the resonant electric dipole-dipole
interaction between 45d and 46p Rydberg atoms.Comment: 5 pages, 3 figures. Accepted for publication in Phys. Rev. Lett.
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Exploring women's sensory experiences of undergoing colposcopy and related procedures: implications for preparatory sensory information provision
INTRODUCTION: Some women experience distress during colposcopy examinations which is partly related to women's fear, or experience, of pain during the procedure. However, little is known about women's sensory experiences of colposcopy (other than pain) or what might impact on these experiences. The aim of this study was to explore women's sensory experiences of colposcopy and related procedures and identify factors which influenced negative sensory experiences. METHODS: In-depth interviews were conducted with 23 women who had undergone, for the first time, a colposcopy (some with related procedures, including punch biopsies and loop excision) as part of follow-up for abnormal cervical cytology. Interviews were analysed thematically using the Framework Approach to organise the data and identify emerging higher-order themes. RESULTS: Women described a range of sensory experiences including pain or discomfort, cramping, stinging and cold sensations (due to the application of acetic acid to the cervix). Four key themes emerged as important aspects of the overall sensory experience: levels of pain, treatment-specific sensations, anaesthetic-specific sensations and solution-specific sensations. Factors that may influence women having a negative sensory experience were sensory expectations of the procedure(s) and lack of preparatory sensory information. DISCUSSION: Our study provides unique in-depth insight into women's sensory experiences of colposcopy and related procedures and suggests women require more preparatory sensory information. The issues identified as contributing to women having a negative sensory experience may help inform the development of pre-colposcopy information which may better prepare women with abnormal cervical cytology for follow-up examinations
Identifying novel hypoxia-associated markers of chemoresistance in ovarian cancer
BACKGROUND
Ovarian cancer is associated with poor long-term survival due to late diagnosis and development of chemoresistance. Tumour hypoxia is associated with many features of tumour aggressiveness including increased cellular proliferation, inhibition of apoptosis, increased invasion and metastasis, and chemoresistance, mostly mediated through hypoxia-inducible factor (HIF)-1α. While HIF-1α has been associated with platinum resistance in a variety of cancers, including ovarian, relatively little is known about the importance of the duration of hypoxia. Similarly, the gene pathways activated in ovarian cancer which cause chemoresistance as a result of hypoxia are poorly understood. This study aimed to firstly investigate the effect of hypoxia duration on resistance to cisplatin in an ovarian cancer chemoresistance cell line model and to identify genes whose expression was associated with hypoxia-induced chemoresistance.
METHODS
Cisplatin-sensitive (A2780) and cisplatin-resistant (A2780cis) ovarian cancer cell lines were exposed to various combinations of hypoxia and/or chemotherapeutic drugs as part of a 'hypoxia matrix' designed to cover clinically relevant scenarios in terms of tumour hypoxia. Response to cisplatin was measured by the MTT assay. RNA was extracted from cells treated as part of the hypoxia matrix and interrogated on Affymetrix Human Gene ST 1.0 arrays. Differential gene expression analysis was performed for cells exposed to hypoxia and/or cisplatin. From this, four potential markers of chemoresistance were selected for evaluation in a cohort of ovarian tumour samples by RT-PCR.
RESULTS
Hypoxia increased resistance to cisplatin in A2780 and A2780cis cells. A plethora of genes were differentially expressed in cells exposed to hypoxia and cisplatin which could be associated with chemoresistance. In ovarian tumour samples, we found trends for upregulation of ANGPTL4 in partial responders and down-regulation in non-responders compared with responders to chemotherapy; down-regulation of HER3 in partial and non-responders compared to responders; and down-regulation of HIF-1α in non-responders compared with responders.
CONCLUSION
This study has further characterized the relationship between hypoxia and chemoresistance in an ovarian cancer model. We have also identified many potential biomarkers of hypoxia and platinum resistance and provided an initial validation of a subset of these markers in ovarian cancer tissues
Studying the galactic outflow in NGC 1569
We present deep WIYN H-alpha imaging of the dwarf irregular starburst galaxy
NGC 1569, together with WIYN SparsePak spatially-resolved optical spectroscopy
of the galactic outflow. This leads on from our previous detailed analyses of
the state of the ISM in the central regions of this galaxy. Our deep imaging
reveals previously undetected ionized filaments in the outer halo. Through
combining these results with our spectroscopy we have been able to re-define
the spatial extent of the previously catalogued superbubbles, and derive
estimates for their expansion velocities, which we find to be in the range
50-100 km/s. The implied dynamical ages of <25 Myr are consistent with the
recent star- and cluster-formation histories of the galaxy. Detailed
decomposition of the multi-component H-alpha line has shown that within a
distinct region ~700x500 pc in size, roughly centred on the bright super star
cluster A, the profile is composed of a bright, narrow (FWHM <= 70 km/s)
feature with an underlying, broad component (FWHM ~ 150 km/s). Applying the
conclusions found in our previous work regarding the mechanism through which
the broad component is produced, we associate the faint, broad emission with
the interaction of the hot, fast-flowing winds from the young star clusters
with cool clumps of ISM material. This interaction generates turbulent mixing
layers on the surface of the clouds and the evaporation and/or ablation of
material into the outflow. Under this interpretation, the extent of the broad
component region may indicate an important transition point in the outflow,
where ordered expansion begins to dominate over turbulent motion. In this
context, we present a multi-wavelength discussion of the evolutionary state of
the outflow.Comment: 17 pages, 12 figures, 2 tables, accepted for publication in MNRA
Absolute frequency measurements of 85Rb nF7/2 Rydberg states using purely optical detection
A three-step laser excitation scheme is used to make absolute frequency
measurements of highly excited nF7/2 Rydberg states in 85Rb for principal
quantum numbers n=33-100. This work demonstrates the first absolute frequency
measurements of rubidium Rydberg levels using a purely optical detection
scheme. The Rydberg states are excited in a heated Rb vapour cell and Doppler
free signals are detected via purely optical means. All of the frequency
measurements are made using a wavemeter which is calibrated against a GPS
disciplined self-referenced optical frequency comb. We find that the measured
levels have a very high frequency stability, and are especially robust to
electric fields. The apparatus has allowed measurements of the states to an
accuracy of 8.0MHz. The new measurements are analysed by extracting the
modified Rydberg-Ritz series parameters.Comment: 12 pages, 5 figures, submitted to New. J. Phy
Socio-economic variations in anticipated adverse reactions to testing HPV positive: Implications for the introduction of primary HPV-based cervical screening
Some cervical cancer screening programmes are replacing cytology with human papillomavirus (HPV) DNA testing as the primary screening test. Concerns have been previously raised around the potential psychosocial impact of testing positive for HPV. We analysed socio-economic variations in anticipated adverse reactions to testing positive for HPV in women of screening age in the general population. A questionnaire was mailed to a random sample of 5553 women aged 20-64 in 2010, selected through primary care in Ireland. This included questions on: socio-economics; HPV knowledge; and women's anticipated adverse psychosocial responses to testing HPV positive (shame, anxiety, stigma and worry). Multivariable linear regression was used to identify socio-economic factors significantly associated with each anticipated adverse reaction. The response rate was 62% (n = 3470). In multivariate analyses, having only attained primary level education were significantly associated with higher mean scores for all four adverse outcomes. Religion was significantly associated with all four adverse outcomes. Age was associated with anxiety and worry; younger women (<30 years) had the highest mean scores. Being married/cohabiting was significantly associated with significantly lower shame and worry scores. Not working was significantly associated with higher mean anxiety and worry scores. Our large population-based survey found significant socio-economic variations in anticipated adverse reactions to testing HPV positive. In order to minimise possible negative impacts on screening uptake and alleviate potential adverse psychological effects of HPV-based screening on women, screening programmes may need to develop specific messages around HPV infection and HPV screening that target certain subgroups of women
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