Eclipsing binaries are important benchmark objects to test and calibrate stellar structure and evolution models. This is especially true for binaries with a fully convective M-dwarf component for ...which direct measurements of these stars' masses and radii are difficult using other techniques. Within the potential of M-dwarfs to be exoplanet host stars, the accuracy of theoretical predictions of their radius and effective temperature as a function of their mass is an active topic of discussion. Not only the parameters of transiting exoplanets but also the success of future atmospheric characterisation rely on accurate theoretical predictions. We present the analysis of five eclipsing binaries with low-mass stellar companions out of a sub-sample of 23, for which we obtained ultra high-precision light curves using the CHEOPS satellite. The observation of their primary and secondary eclipses are combined with spectroscopic measurements to precisely model the primary parameters and derive the M-dwarfs mass, radius, surface gravity, and effective temperature estimates using the PYCHEOPS data analysis software. Combining these results to the same set of parameters derived from TESS light curves, we find very good agreement (better than 1\% for radius and better than 0.2% for surface gravity). We also analyse the importance of precise orbits from radial velocity measurements and find them to be crucial to derive M-dwarf radii in a regime below 5% accuracy. These results add five valuable data points to the mass-radius diagram of fully-convective M-dwarfs.
As the link between executives and bedside nurses, nurse managers assume roles that bridge both organizational and professional goals. Nurse retention is one of the many responsibilities that ...characterize the nurse manager's work. To better understand the pivotal role of nurse managers, the authors describe the views of 32 nurse managers regarding their roles and the characteristics they need to promote retention.
The accuracy of theoretical mass, radius and effective temperature values for M-dwarf stars is an active topic of debate. Differences between observed and theoretical values have raised the ...possibility that current theoretical stellar structure and evolution models are inaccurate towards the low-mass end of the main sequence. To explore this issue we use the CHEOPS satellite to obtain high-precision light curves of eclipsing binaries with low mass stellar companions. We use these light curves combined with the spectroscopic orbit for the solar-type companion to measure the mass, radius and effective temperature of the M-dwarf star. Here we present the analysis of three eclipsing binaries. We use the pycheops data analysis software to fit the observed transit and eclipse events of each system. Two of our systems were also observed by the TESS satellite -- we similarly analyse these light curves for comparison. We find consistent results between CHEOPS and TESS, presenting three stellar radii and two stellar effective temperature values of low-mass stellar objects. These initial results from our on-going observing programme with CHEOPS show that we can expect to have ~24 new mass, radius and effective temperature measurements for very low mass stars within the next few years.
The American Stroke Association (ASA) assembled a multidisciplinary group of experts to develop recommendations regarding the potential effectiveness of establishing an identification program for ...stroke centers and systems. "Identification" refers to the full spectrum of models for assessing and recognizing standards of quality care (self-assessment, verification, certification, and accreditation). A primary consideration is whether stroke center identification might improve patient outcomes.
In February 2001, ASA, with the support of the Stroke Council's Executive Committee, decided to embark on an evaluation of the potential impact of stroke center identification. HealthPolicy R&D was selected to prepare a comprehensive report. The investigators reported on models outside the area of stroke, ongoing initiatives within the stroke community (such as Operation Stroke), and state and federal activities designed to improve care for stroke patients. The investigators also conducted interviews with thought leaders in the stroke community, representing a diverse sampling of specialties and affiliations. In October 2001, the Advisory Working Group on Stroke Center Identification developed its consensus recommendations. This group included recognized experts in neurology, emergency medicine, emergency medical services, neurological surgery, neurointensive care, vascular disease, and stroke program planning.
There are a variety of existing identification programs, generally falling within 1 of 4 categories (self-assessment, verification, certification, and accreditation) along a continuum with respect to intensity and scope of review and consumption of resources. Ten programs were evaluated, including Peer Review Organizations, trauma centers, and new efforts by the National Committee on Quality Assurance and the Joint Commission on the Accreditation of Healthcare Organizations to identify providers and disease management programs. The largest body of literature on clinical outcomes associated with identification programs involves trauma centers. Most studies support that trauma centers and systems lead to improved mortality rates and patient outcomes. The Advisory Working Group felt that comparison to the trauma model was most relevant given the need for urgent evaluation and treatment of stroke. The literature in other areas generally supports the positive impact of identification programs, although patient outcomes data have less often been published. In the leadership interviews, participants generally expressed strong support for pursuing some form of voluntary identification program, although concerns were raised that this effort could meet with some resistance.
Identification of stroke centers and stroke systems competencies is in the best interest of stroke patients in the United States, and ASA should support the development and implementation of such processes. The purpose of a stroke center/systems identification program is to increase the capacity for all hospitals to treat stroke patients according to standards of care, recognizing that levels of involvement will vary according to the resources of hospitals and systems.
The structure of the Asn$^{102}$ mutant of trypsin was determined in order to distinguish whether the reduced activity of the mutant at neutral pH results from an altered active site conformation or ...from an inability to stabilize a positive charge on the active site histidine. The active site structure of the Asn$^{102}$ mutant of trypsin is identical to the native enzyme with respect to the specificity pocket, the oxyanion hole, and the orientation of the nucleophilic serine. The observed decrease in rate results from the loss of nucleophilicity of the active site serine. This decreased nucleophilicity may result from stabilization of a His$^{57}$ tautomer that is unable to accept the serine hydroxyl proton.
Laser debonding of ceramic orthodontic brackets Tocchio, R M; Williams, P T; Mayer, F J ...
American journal of orthodontics and dentofacial orthopedics,
02/1993, Letnik:
103, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Laser light energy has been shown in other studies to degrade resins by thermal softening, thermal ablation, or photoablation. If this technology could be successfully applied to bracket debonding, ...fracturing of both bracket and enamel during debonding might be eliminated. Both polycrystalline alumina and single crystal alumina (sapphire) ceramic orthodontic brackets were bonded to the labial surfaces of lower deciduous bovine incisor teeth with the acid-etch technique as currently practiced in dentistry. Under an externally applied stress of either zero or 0.8 MPa, the brackets were debonded by irradiating the labial surfaces of the brackets with laser light at wavelengths of 248 nm, 308 nm, and 1060 nm, and at light power densities of between about 3 and 33 W/cm2. Debonding times were measured, and the surfaces created by debonding were examined with both light and scanning electron microscopy to determine the extent of bracket and enamel damage. The results showed that under the conditions of this study, no enamel or bracket damage was present in any sample. The polycrystalline brackets debonding times were about 3 seconds, 5 seconds, and 24 seconds for 248 nm, 308 nm, and 1060 nm of radiation, respectively. The debonding of polycrystalline brackets is caused by thermal softening of the bonding resin resulting from heating of the bracket. The hot bracket then slides off the tooth. All sapphire brackets debonded in less than 1 second. At sufficiently high power levels, debonding of sapphire brackets is caused by either thermal ablation or photoablation resulting from direct interaction of the light beam with the resin.
CHEOPS is a space telescope specifically designed to monitor transiting exoplanets orbiting bright stars. In September 2023, CHEOPS completed its nominal mission and remains in excellent operational ...conditions. The mission has been extended until the end of 2026. Scientific and instrumental data have been collected throughout in-orbit commissioning and nominal operations, enabling a comprehensive analysis of the mission's performance. In this article, we present the results of this analysis with a twofold goal. First, we aim to inform the scientific community about the present status of the mission and what can be expected as the instrument ages. Secondly, we intend for this publication to serve as a legacy document for future missions, providing insights and lessons learned from the successful operation of CHEOPS. To evaluate the instrument performance in flight, we developed a comprehensive monitoring and characterisation programme. It consists of dedicated observations that allow us to characterise the instrument's response. In addition to the standard collection of nominal science and housekeeping data, these observations provide input for detecting, modelling, and correcting instrument systematics, discovering and addressing anomalies, and comparing the instrument's actual performance with expectations. The precision of the CHEOPS measurements has enabled the mission objectives to be met and exceeded. Careful modelling of the instrumental systematics allows the data quality to be significantly improved during the light curve analysis phase, resulting in more precise scientific measurements. CHEOPS is compliant with the driving scientific requirements of the mission. Although visible, the ageing of the instrument has not affected the mission's performance.
Observations of low-mass stars have frequently shown a disagreement between observed stellar radii and radii predicted by theoretical stellar structure models. This ``radius inflation'' problem could ...have an impact on both stellar and exoplanetary science. We present the final results of our observation programme with the CHEOPS satellite to obtain high-precision light curves of eclipsing binaries with low mass stellar companions (EBLMs). Combined with the spectroscopic orbits of the solar-type companion, we can derive the masses, radii and effective temperatures of 23 M-dwarf stars. We use the PYCHEOPS data analysis software to analyse their primary and secondary occultations. For all but one target, we also perform analyses with TESS light curves for comparison. We have assessed the impact of starspot-induced variation on our derived parameters and account for this in our radius and effective temperature uncertainties using simulated light curves. We observe trends for inflation with both metallicity and orbital separation. We also observe a strong trend in the difference between theoretical and observational effective temperatures with metallicity. There is no such trend with orbital separation. These results are not consistent with the idea that observed inflation in stellar radius combines with lower effective temperature to preserve the luminosity predicted by low-mass stellar models. Our EBLM systems are high-quality and homogeneous measurements that can be used in further studies into radius inflation.
A&A 641, A25 (2020) The Transiting Exoplanet Survey Satellite (TESS) is observing bright known
planet-host stars across almost the entire sky. These stars have been subject
to extensive ground-based ...observations, providing a large number of radial
velocity (RV) measurements. In this work we use the new TESS photometric
observations to characterize the star $\lambda^2$ Fornacis, and following this
to update the parameters of the orbiting planet $\lambda^2$ For b. We measure
the p-mode oscillation frequencies in $\lambda^2$ For, and in combination with
non-seismic parameters estimate the stellar fundamental properties using
stellar models. Using the revised stellar properties and a time series of
archival RV data from the UCLES, HIRES and HARPS instruments spanning almost 20
years, we refit the orbit of $\lambda^2$ For b and search the RV residuals for
remaining variability. We find that $\lambda^2$ For has a mass of
$1.16\pm0.03$M$_\odot$ and a radius of $1.63\pm0.04$R$_\odot$, with an age of
$6.3\pm0.9$Gyr. This and the updated RV measurements suggest a mass of
$\lambda^2$ For b of $16.8^{+1.2}_{-1.3}$M$_\oplus$, which is $\sim5$M$_\oplus$
less than literature estimates. We also detect a periodicity at 33 days in the
RV measurements, which is likely due to the rotation of the host star. While
previous literature estimates of the properties of $\lambda^2$ are ambiguous,
the asteroseismic measurements place the star firmly at the early stage of its
subgiant evolutionary phase. Typically only short time series of photometric
data are available from TESS, but by using asteroseismology it is still
possible to provide tight constraints on the properties of bright stars that
until now have only been observed from the ground. This prompts a reexamination
of archival RV data from the past few decades to update the characteristics of
the planet hosting systems observed by TESS for which asteroseismology is
possible.
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