Quantum dynamics of crystals of molecular nanomagnets inside a resonant cavity

It is shown that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. Strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing evidence of the coherent microwave radiation by the crystals. A similar dependence has been found for a crystal placed between Fabry-Perot superconducting mirrors. These observations open the possibility of building a nanomagnetic microwave laser pumped by the magnetic field

The UK HeartSpare study: randomised evaluation of voluntary deep-inspiratory breath-hold in women undergoing breast radiotherapy

Purpose: to determine whether voluntary deep-inspiratory breath-hold (v_DIBH) and deep-inspiratory breath-hold with the active breathing coordinator™ (ABC_DIBH) in patients undergoing left breast radiotherapy are comparable in terms of normal-tissue sparing, positional reproducibility and feasibility of delivery.Methods: following surgery for early breast cancer, patients underwent planning-CT scans in v_DIBH and ABC_DIBH. Patients were randomised to receive one technique for fractions 1–7 and the second technique for fractions 8–15 (40?Gy/15 fractions total). Daily electronic portal imaging (EPI) was performed and matched to digitally-reconstructed radiographs. Cone-beam CT (CBCT) images were acquired for 6/15 fractions and matched to planning-CT data. Population systematic (?) and random errors (?) were estimated. Heart, left-anterior-descending coronary artery, and lung doses were calculated. Patient comfort, radiographer satisfaction and scanning/treatment times were recorded. Within-patient comparisons between the two techniques used the paired t-test or Wilcoxon signed-rank test.Results: twenty-three patients were recruited. All completed treatment with both techniques. EPI-derived ? were ?1.8?mm (v_DIBH) and ?2.0?mm (ABC_DIBH) and ? ?2.5?mm (v_DIBH) and ?2.2?mm (ABC_DIBH) (all p non-significant). CBCT-derived ? were ?3.9?mm (v_DIBH) and ?4.9?mm (ABC_DIBH) and ? ??4.1?mm (v_DIBH) and ??3.8?mm (ABC_DIBH). There was no significant difference between techniques in terms of normal-tissue doses (all p non-significant). Patients and radiographers preferred v_DIBH (p?=?0.007, p?=?0.03, respectively). Scanning/treatment setup times were shorter for v_DIBH (p?=?0.02, p?=?0.04, respectively).Conclusions: v_DIBH and ABC_DIBH are comparable in terms of positional reproducibility and normal tissue sparing. v_DIBH is preferred by patients and radiographers, takes less time to deliver, and is cheaper than ABC_DIB

PACS : do clinical users benefit from it as a training adjunct?

BACKGROUND: Over the past four years, Steve Biko Academic Hospital has been in the process of implementing and refining the use of a picture archiving and communications system (PACS). As part of a post-implementation refining process, it was necessary to evaluate user-perceptions in order to improve on good system qualities and correct flaws. AIM: The aim of this study was to assess whether medical clinicians perceived PACS as a positive adjunct to training and teaching opportunities – specifically those opportunities related to radiological image viewing and interpretation as part of patient case discussions. METHOD: Standardised questionnaires with ‘free text’ and ‘option selection’ questions were distributed to clinicians who, as part of their training, rotated at Steve Biko Academic Hospital (where a PACS is in place) as well as other teaching hospitals without a PACS. Between February 2009 and May 2009, approximately 400 questionnaires were distributed. As a result of constant academic rotations, leave schedules of medical staff and posts vacated, questionnaires could not be distributed to the entire target population that was estimated to be in the region of 550 medical clinicians (comprising senior medical students, interns, medical officers, registrars and consultants). Of the 400 questionnaires distributed, 189 completed questionnaires were returned. Completion of the questionnaires was voluntary and anonymous. RESULTS AND CONCLUSION: Although a PACS relates specifically to the archiving and retrieval of radiological images and reports, it became clear from the feedback received from medical clinicians (who are ward-based, theatre-based or clinic-based users of a digital system) that many other factors, such as lack of adequate hardware and sub-optimal personal IT proficiency, contributed to some of the negative PACS-related perceptions and ‘lost teaching opportunities’ reported. Negative comments specifically related to PACS as a training adjunct included the frustrations associated with PACS downtime (especially during the period in 2009 when many electrical power cuts were experienced nationwide, resulting in network interruptions) and slow image retrieval during peak work-flow times. The advantages of PACS as a positive training adjunct were highlighted in the areas of multi-site viewing and consultation, the possibility of image manipulation and measurement tools, and better overall image quality. Clinicians felt that their training experience was also enhanced because of better patient follow-up made possible by access to all previous radiological imaging of a particular patient. Of the clinicians who completed the questionnaires, 63.5% felt that the PACS at Steve Biko Academic Hospital contributed positively to their training by creating more overall learning opportunities than other training environments without a PACS.http://www.sajr.org.za/index.php/saj

PACS : do clinical users benefit from it as a training adjunct?

BACKGROUND: Over the past four years, Steve Biko Academic Hospital has been in the process of implementing and refining the use of a picture archiving and communications system (PACS). As part of a post-implementation refining process, it was necessary to evaluate user-perceptions in order to improve on good system qualities and correct flaws. AIM: The aim of this study was to assess whether medical clinicians perceived PACS as a positive adjunct to training and teaching opportunities – specifically those opportunities related to radiological image viewing and interpretation as part of patient case discussions. METHOD: Standardised questionnaires with ‘free text’ and ‘option selection’ questions were distributed to clinicians who, as part of their training, rotated at Steve Biko Academic Hospital (where a PACS is in place) as well as other teaching hospitals without a PACS. Between February 2009 and May 2009, approximately 400 questionnaires were distributed. As a result of constant academic rotations, leave schedules of medical staff and posts vacated, questionnaires could not be distributed to the entire target population that was estimated to be in the region of 550 medical clinicians (comprising senior medical students, interns, medical officers, registrars and consultants). Of the 400 questionnaires distributed, 189 completed questionnaires were returned. Completion of the questionnaires was voluntary and anonymous. RESULTS AND CONCLUSION: Although a PACS relates specifically to the archiving and retrieval of radiological images and reports, it became clear from the feedback received from medical clinicians (who are ward-based, theatre-based or clinic-based users of a digital system) that many other factors, such as lack of adequate hardware and sub-optimal personal IT proficiency, contributed to some of the negative PACS-related perceptions and ‘lost teaching opportunities’ reported. Negative comments specifically related to PACS as a training adjunct included the frustrations associated with PACS downtime (especially during the period in 2009 when many electrical power cuts were experienced nationwide, resulting in network interruptions) and slow image retrieval during peak work-flow times. The advantages of PACS as a positive training adjunct were highlighted in the areas of multi-site viewing and consultation, the possibility of image manipulation and measurement tools, and better overall image quality. Clinicians felt that their training experience was also enhanced because of better patient follow-up made possible by access to all previous radiological imaging of a particular patient. Of the clinicians who completed the questionnaires, 63.5% felt that the PACS at Steve Biko Academic Hospital contributed positively to their training by creating more overall learning opportunities than other training environments without a PACS.http://www.sajr.org.za/index.php/saj

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

Erratum: "A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo" (2021, ApJ, 909, 218)

[no abstract available

Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society