In shift-symmetric Horndeski theories, a static and spherically symmetric black hole can support linearly time-dependent scalar hair. However, it was shown that such a solution generically suffers from ghost or gradient instability in the vicinity of the horizon. In the present paper, we explore the possibility to avoid the instability, and present a new example of theory and its black hole solution with a linearly time-dependent scalar configuration. We also discuss the stability of solutions with static scalar hair for a special case where nonminimal derivative coupling to the Einstein tensor appears.
Background
We developed an augmented reality (AR)-based portable navigation system in which the surgeon can view the pelvic plane and placement angle of an acetabular cup on the display of a smartphone during THA.
Questions/purposes
(1) Is acetabular component placement more accurate using the AR-based portable navigation system compared with the conventional freehand technique? (2) Is intraoperative measurement of placement angle more accurate when using the AR-based portable navigation system compared with a goniometer?
Methods
Forty-six patients were randomly assigned to undergo acetabular cup placement during THA using the AR-based portable navigation system (AR navigation group) or placement of a mechanical alignment guide (conventional group). All surgeries were performed with the patient in the lateral decubitus position. We compared the absolute value of the difference between the targeted placement angle and postoperative measured placement angle between the groups using two types of imaging (radiography and CT).
Results
In terms of radiographic inclination, the mean differences between the targeted placement angle and postoperative measured angle were smaller in the AR navigation group than in the conventional group for both radiographs and CT images (2.3° ± 1.4° versus 3.9° ± 2.4°, respectively; p = 0.009 and 1.9° ± 1.3° versus 3.4° ± 2.6°, respectively; p = 0.02). There were no differences in radiographic anteversion between the two groups. No complications were associated with the use of the AR-based portable navigation system.
Conclusions
This system yielded no differences in acetabular anteversion accuracy, and no clinically important differences in acetabular inclination. Therefore, at this time we cannot recommend this device as its costs and risks cannot be justified based on the absence of a clinically meaningful difference in cup placement accuracy. Although we detected no complications, this was a small series, and this approach adds both surgical time and pins in the ilium.
Level of Evidence
Level I, therapeutic study.
These studies suggest that knowledge of the initial depth distribution of fallout radionuclides is important for future decontamination work and countermeasures to reduce the transfer of radionuclides to agricultural products. In order to determine how the initial depth distribution of the radioactive substances varies depending on field type, such as wheat fields, rice paddies, orchards, and forestland, we need to take measurements at locations with different land-use patterns but with nearly equal exposure to radioactive fallout. The Fukushima Agricultural Technology Centre has wheat fields, rice paddies, orchards, and forestland all enclosed within a 500 × 500 m test site. At this test site, we sampled and determined the depth profiles of radiocesium and radioiodine for each type of land use. On the basis of these depth profiles, we derived an estimate of the deposition density to clarify the influence that land use has on the distribution pattern of radionuclides in soils. Several other studies have been also conducted in this issue for the distribution of the radionuclides on land and mechanism of retention of radiocesium at soil surface (
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