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Formal Methods in System Design 2017is an approach to enforce safety properties at runtime. A shield monitors the system and corrects any erroneous output values instantaneously. The shield deviates from...
is an approach to enforce safety properties at runtime. A shield monitors the system and corrects any erroneous output values instantaneously. The shield deviates from the given outputs as little as it can and recovers to hand back control to the system as soon as possible. In the first part of this paper, we consider shield synthesis for reactive hardware systems. First, we define a general framework for solving the shield synthesis problem. Second, we discuss two concrete shield synthesis methods that automatically construct shields from a set of properties: (1) shields, which guarantee recovery in a finite time. (2) shields, which attempt to work with the system to recover as soon as possible. Next, we discuss an extension of -stabilizing and admissible shields, where erroneous output values of the reactive system are corrected while liveness properties of the system are preserved. Finally, we give experimental results for both synthesis methods. In the second part of the paper, we consider shielding a human operator instead of shielding a reactive system: the outputs to be corrected are not initiated by a system but by a human operator who works with an autonomous system. The challenge here lies in giving simple and intuitive explanations to the human for any interferences of the shield. We present results involving mission planning for unmanned aerial vehicles.
PubMed: 32009740
DOI: 10.1007/s10703-017-0276-9 -
Current Opinion in HIV and AIDS Sep 2020The surface of the HIV-1 Env glycoprotein, the target of neutralizing antibodies, is extensively covered by N-linked glycans that create a glycan shield. Broadly... (Review)
Review
PURPOSE OF REVIEW
The surface of the HIV-1 Env glycoprotein, the target of neutralizing antibodies, is extensively covered by N-linked glycans that create a glycan shield. Broadly neutralizing antibodies (bNAbs), the primary targets of HIV-1 vaccine design, have to negotiate this glycan shield. Here, we review the barriers and opportunities that the HIV-1 glycan shield presents for vaccine induction of bNAbs.
RECENT FINDINGS
Glycan shields can impact the nature of the antibody response and influence the development of neutralization breadth in HIV-1 infections. The architecture of the glycan shield arising from glycan interactions and dynamics have been modeled, and its fine structure, that is, the site-wise glycan heterogeneity, has been determined for some isolates. Although the extent of glycan shielding is conserved, the precise number, location and processing of glycans, however, is strain-dependent. New insights continue to reveal how such differences can impact bNAb activity and development. Novel approaches have exploited the glycan shield for designing immunogens that bind the germline precursors of bNAbs, a critical roadblock for vaccine-induction of bNAbs.
SUMMARY
The HIV-1 glycan shield can significantly impact the induction and maturation of bNAbs, and a better understanding of how to manipulate it will improve immunogen design.
Topics: Antibodies, Neutralizing; Broadly Neutralizing Antibodies; Epitopes; HIV Antibodies; HIV Infections; HIV-1; Humans; Polysaccharides; env Gene Products, Human Immunodeficiency Virus
PubMed: 32675574
DOI: 10.1097/COH.0000000000000639 -
Materials (Basel, Switzerland) Feb 2022The shielding performance of shielding clothing is typically improved by increasing the shielding material content, but this lowers the tensile strength of the material....
The shielding performance of shielding clothing is typically improved by increasing the shielding material content, but this lowers the tensile strength of the material. The weight and wearability of the shielding suit are also adversely affected. Important considerations when developing shielding fabric are thickness and flexibility to allow the wearer sufficient mobility. Insufficient thickness lowers the shielding performance, whereas excessive thickness decreases the flexibility of the garment. This study aimed to develop a composite shield that reproduces the shielding performance and meets the flexibility of the process technology. The new shield was manufactured by combining two layers: the shielding fabric fabricated from tungsten wire and a shielding sheet produced by mixing a polymer (PDMS) with tungsten powder. These two shields were bonded to develop a double hybrid composite. Compared with the existing shielding sheet (produced from lead equivalent of 0.55 mmPb), the shielding performance of the hybrid composite shield improved by approximately 17% on average and the tensile strength was 53% higher. The hybrid composite shield has a thickness of 1.35 ± 0.02 mm and delivers the same shielding performance as the lead equivalent. The new hybrid composite shield offers higher wearer mobility while shielding against radiation exposure in medical institutions.
PubMed: 35207876
DOI: 10.3390/ma15041338 -
Journal of Clinical Medicine Apr 2023Fetal magnetocardiography (fMCG) has proven to be an important tool for the prenatal monitoring of electrical cardiac activity; however, the high cost of superconducting...
Fetal magnetocardiography (fMCG) has proven to be an important tool for the prenatal monitoring of electrical cardiac activity; however, the high cost of superconducting quantum instrumentation (SQUID) poses a limitation for the dissemination of fMCG as a routine clinical technique. Recently, optically pumped magnetometers (OPMs) operating within person-sized, cylindrical shields have made fMCG more practical, but environmental magnetic interference entering through the shield opening substantially degrades the quality of fMCG signals. The goal of this study was to further attenuate these interferences by placing the OPM array within a small ferrite shield. FMCG recordings were made with and without the ferrite shield in ten subjects inside a person-sized, three-layer mu-metal cylindrical shield. Although the fetal signal was slightly attenuated, the environmental interference was reduced substantially, and maternal interference was also diminished. This increased the signal-to-noise ratio significantly and improved the resolution of the smaller waveform components. The performance improvement was highest in the axial direction and compensated for a major weakness of open-ended, person-sized shields. The ferrite shield is especially beneficial for the deployment of triaxial OPM sensors, which require effective shielding in all directions.
PubMed: 37176519
DOI: 10.3390/jcm12093078 -
Journal of Radiological Protection :... Jul 2023The goal of this study is to investigate the effect of the location and width of a single lead shield on the dose rate of staff and caregivers in a hospital room with an...
The goal of this study is to investigate the effect of the location and width of a single lead shield on the dose rate of staff and caregivers in a hospital room with an I-131 patient. The best orientation of the patient and caregiver relative to the shield was determined based on minimizing staff and caregiver radiation dose rates. Shielded and unshielded dose rates were simulated using a Monte Carlo computer simulation and validated using real-world ionisation chamber measurements. Based on a radiation transport analysis using an adult voxel phantom published by the International Commission on Radiological Protection, placing the shield near the caregiver yielded the lowest dose rates. However, this strategy reduced the dose rate in only a tiny area of the room. Furthermore, positioning the shield near the patient in the caudal direction provided a modest dose rate reduction while shielding a large room area. Finally, increased shield width was associated with decreasing dose rates, but only a four-fold dose-rate reduction was observed for standard width shields. The recommendations of this case study may be considered as potential candidate room configurations where radiation dose rates are minimized, however these findings must be weighed against additional clinical, safety, and comfort considerations.
Topics: Adult; Humans; Radiation Dosage; Radiopharmaceuticals; Caregivers; Iodine Radioisotopes; Computer Simulation; Phantoms, Imaging
PubMed: 37413983
DOI: 10.1088/1361-6498/ace4d4 -
Radiography (London, England : 1995) May 2022Little research has focused on the accuracy of gonad shield placement, especially by students. While studies have investigated the presence of gonad shields they do not...
Gonad shield placement accuracy in pelvic radiographs for male patients: A prospective phantom study and survey of third year undergraduate diagnostic radiography students".
INTRODUCTION
Little research has focused on the accuracy of gonad shield placement, especially by students. While studies have investigated the presence of gonad shields they do not aim to measure accuracy but only look at repeatability. This study aimed to establish students' knowledge of gonad shields and their accuracy in placing it.
METHODS
Following an invitation email and informed consent, students completed a 7-question questionnaire and placed a gonad shield on a Pixi full body adult phantom (male configuration). The phantom was x-rayed and images were assessed for gonad shield positioning in terms of obscuring bony anatomy, correct orientation and distance from a "gold standard" position.
RESULTS
36% of images displayed shields covering bony anatomy while 16% of shields were incorrectly orientated. All shields incorrectly orientated also covered bony anatomy. Statistical significance was seen between incorrect shield orientation and the obscuring of bony anatomy (p = 0.01). Dispersion of positioning error measurements ranged from -6.80 mm (better placed than the "gold standard") to 62.35 mm inferiorly, with an average 28.22 mm inferiorly.
CONCLUSION
The average misplacement of 28.22 mm suggests participants placed the gonad shielding lower than necessary to avoid obscuring bony anatomy. The 36% of misplaced shields, while lower than in previous studies, is still a significant number of radiographs that would require repeats.
IMPLICATIONS FOR PRACTICE
Given the associated difficulties surrounding gonad shields and their placement, this study supports previous research suggesting that the benefit of using gonad shielding is questionable.
Topics: Adult; Gonads; Humans; Male; Prospective Studies; Radiography; Students; Surveys and Questionnaires
PubMed: 35232660
DOI: 10.1016/j.radi.2022.02.001 -
Medical Physics Dec 2020To present a system for the treatment of prostate cancer in a single-fraction regimen using Yb-based rotating shield brachytherapy (RSBT) with a single-catheter robotic...
PURPOSE
To present a system for the treatment of prostate cancer in a single-fraction regimen using Yb-based rotating shield brachytherapy (RSBT) with a single-catheter robotic delivery system. The proposed system is innovative because it can deliver RSBT through multiple implanted needles independently, in serial, using flexible catheters, with no inter-needle shielding effects and without the need to rotate multiple shielded catheters inside the needles simultaneously, resulting in a simple, mechanically robust, delivery approach. RSBT was compared to conventional Ir-based high-dose-rate brachytherapy (HDR-BT) in a treatment planning study with dose escalation and urethral sparing goals, representing single-fraction brachytherapy monotherapy and brachytherapy as a boost to external beam radiotherapy, respectively. A prototype mechanical delivery system was constructed and quantitatively evaluated as a proof of concept.
METHODS
Treatment plans for twenty-six patients with single fraction prescriptions of 20.5 and 15 Gy, were created for dose escalation and urethral sparing, respectively. The RSBT and HDR-BT delivery systems were modeled with one partially shielded 999 GBq (27 Ci) Yb source and one 370 GBq (10 Ci) Ir source, respectively. A prototype angular drive system for helical source delivery was constructed. Mechanical accuracy measurements of source translational position and angular orientation in a simulated treatment delivery setup were obtained using the prototype system.
RESULTS
For dose escalation, with equivalent urethra D , PTV D for RSBT vs HDR-BT increased from 22.6 ± 0.0 Gy (average ± standard deviation) to 29.3 ± 0.9 Gy, or 29.9 % ± 3.0%, with treatment times of 51.4 ± 6.1 min for RSBT and 15.8 ± 2.3 min for 10 Ci Ir-based HDR-BT. For urethra sparing, with equivalent PTV D , urethra D for RSBT vs HDR-BT decreased for RSBT vs HDR-BT from 15.6 ± 0.4 Gy to 12.0 ± 0.4 Gy, or 23.1% ± 3.5%, with treatment times of 30.0 ± 3.7 min for RSBT and 12.3 ± 1.8 min for HDR-BT. Differences between measured vs predicted rotating catheter positions (corresponding to source position) were within 0.18 mm ± 0.12 mm longitudinally and 0.07° ± 0.78°.
CONCLUSION
Yb-based RSBT can increase PTV D or decrease urethral D relative to HDR-BT with treatment times of less than 1 h using a single-source robotic delivery system with treatment delivered in a single fraction. The prototype helical delivery system was able to demonstrate adequate mechanical accuracy.
Topics: Brachytherapy; Humans; Male; Prostatic Neoplasms; Radiation Protection; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted
PubMed: 33051866
DOI: 10.1002/mp.14533 -
The Review of Scientific Instruments Jun 2019The rapid development of the optically pumped magnetometer (OPM) has offered a much more flexible method for magnetoencephalography (MEG). Without using liquid helium...
The rapid development of the optically pumped magnetometer (OPM) has offered a much more flexible method for magnetoencephalography (MEG). Without using liquid helium and its associated dewar device in the OPM detectors, the large and expensive magnetically shielded room (MSR) for traditional MEG systems could be replaced by a compact shield. In the present work, an economic and compact cylindrical shield was designed and built to meet the low-field working requirement of the OPM in detecting human brain neuronal activities. The performance of the compact shield was evaluated and further compared with that of a commercial MSR. Our results showed that the residual magnetic fields and background noise of the compact shield were lower than or comparable to those of the MSR. The remnant field in the shield is found to be 4.2 nT, a factor of 13 000 smaller than the geomagnetic field which is applied to the transverse direction of the shield, and the longitudinal shielding factors measured using a known alternating-current magnetic field are approximately 191, 205, and 3130 at 0.1 Hz, 1 Hz, and 10 Hz, respectively; in addition, the evoked dynamic waveforms in the human auditory cortex that were recorded separately in these two shields demonstrated consistency. Our findings suggested that a compact shield is feasible for OPM-based MEG applications with high performance and low cost.
Topics: Equipment Design; Magnetoencephalography; Magnetometry; Optical Phenomena
PubMed: 31254989
DOI: 10.1063/1.5066250 -
Cell Reports Apr 2023Animal reservoirs of sarbecoviruses represent a significant risk of emergent pandemics, as evidenced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)...
Animal reservoirs of sarbecoviruses represent a significant risk of emergent pandemics, as evidenced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Vaccines remain successful at limiting severe disease and death, but the potential for further coronavirus zoonosis motivates the search for pan-coronavirus vaccines. This necessitates a better understanding of the glycan shields of coronaviruses, which can occlude potential antibody epitopes on spike glycoproteins. Here, we compare the structure of 12 sarbecovirus glycan shields. Of the 22 N-linked glycan attachment sites present on SARS-CoV-2, 15 are shared by all 12 sarbecoviruses. However, there are significant differences in the processing state at glycan sites in the N-terminal domain, such as N165. Conversely, glycosylation sites in the S2 domain are highly conserved and contain a low abundance of oligomannose-type glycans, suggesting a low glycan shield density. The S2 domain may therefore provide a more attractive target for immunogen design efforts aiming to generate a pan-coronavirus antibody response.
Topics: Animals; SARS-CoV-2; COVID-19; Severe acute respiratory syndrome-related coronavirus; Glycosylation; Polysaccharides
PubMed: 36972173
DOI: 10.1016/j.celrep.2023.112307 -
Medicine Jun 2021Radiosensitivity in the breasts increases the risk of carcinogenesis from exposure to the ionizing radiation of computed tomography (CT) administered in the course of... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Radiosensitivity in the breasts increases the risk of carcinogenesis from exposure to the ionizing radiation of computed tomography (CT) administered in the course of medical attention. Bismuth shielding techniques have been used to reduce radiation, but image noise increased, degrading image quality.
PURPOSE
The aim of this study was to investigate how the use of iterative reconstruction (IR) combined with bismuth shielding influences image quality.
MATERIALS AND METHODS
Women aged at least 20 years with body mass indexes <28 were recruited and randomly assigned to 1 of 3 CT scanning protocols without shielding, with a bismuth breast shield before the scout view, or with a bismuth breast shield after the scout view. All obtained images were reconstructed using an IR algorithm. To evaluate radiation dose, 2 Gafchromic films were placed over the clothes, 1 near each nipple.
RESULTS
Average dose reduction was significant (27.99%, P < .05) when bismuth shielding was applied after the scout view. Using the contrast-to-noise ratio, the image quality was found to be superior when the IR algorithm was applied. Using quantitative evaluations by 2 radiologists applying a 4-point Likert scale, significant differences in image quality were not found among the 3 protocols.
CONCLUSION
Bismuth breast shields, particularly when used after acquiring scout images, are effective at reducing radiation dose without undermining the diagnostic value of the images when the IR technique is applied.
Topics: Adult; Artifacts; Bismuth; Breast; Female; Humans; Image Processing, Computer-Assisted; Prospective Studies; Protective Devices; Radiation Dosage; Radiation Protection; Radiation Tolerance; Tomography, X-Ray Computed
PubMed: 34160391
DOI: 10.1097/MD.0000000000026277