scholarly journals Stress and force measurement uncertainties in 3D granular materials

2021 ◽  
Vol 249 ◽  
pp. 02009
Author(s):  
Ryan C. Hurley
Keyword(s):  
Granular Media ◽  
Force Measurement ◽  
Level Energy ◽  
Particle Fracture ◽  
X Ray ◽  
Sources Of Uncertainty ◽  
Strong Force ◽  
The Past ◽  
Wave Phenomena ◽  
Force Network

We have developed and employed a 3D particle stress tensor and contact force inference technique that employs synchrotron X-ray tomography and diffraction with an optimization algorithm. We have used this technique to study stress and force heterogeneity, particle fracture mechanics, contact-level energy dissipation, and the origin of wave phenomena in 3D granular media for the past five years. Here, we review the technique, describe experimental and numerical sources of uncertainty, and use experimental data and discrete element method simulations to study the method’s accuracy. We find that inferred forces in the strong force network of a 3D granular material are accurately determined even in the presence of noisy stress measurements.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

scholarly journals Workload for radiologists during on-call hours: dramatic increase in the past 15 years

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
R. J. M. Bruls ◽  
R. M. Kwee
Keyword(s):  
Western Europe ◽  
Kendall Test ◽  
Kendall’S Tau ◽  
Kendall's Tau ◽  
X Ray ◽  
The Past ◽  
Relative Value ◽  
Burn Out ◽  
Picture Archiving And Communication ◽  
Ct Studies

Abstract Background The objective of this study is to investigate the workload for radiologists during on-call hours and to quantify the 15-year trend in a large general hospital in Western Europe. Methods Data regarding the number of X-ray, ultrasound and computed tomography (CT) studies during on-call hours (weekdays between 6.00 p.m. and 7.00 a.m., weekends, and national holidays) between 2006 and 2020 were extracted from the picture archiving and communication system. All studies were converted into relative value units (RVUs) to estimate the on-call workload. The Mann–Kendall test was performed to assess the temporal trend. Results The total RVUs during on-call hours showed a significant increase between 2006 and 2020 (Kendall's tau-b = 0.657, p = 0.001). The overall workload in terms of RVUs during on-call hours has quadrupled. The number of X-ray studies significantly decreased (Kendall's tau-b = − 0.433, p = 0.026), whereas the number of CT studies significantly increased (Kendall's tau-b = 0.875, p < 0.001) between 2006 and 2020. CT studies which increased by more than 500% between 2006 and 2020 are CT for head trauma, brain CTA, brain CTV, chest CT (for suspected pulmonary embolism), spinal CT, neck CT, pelvic CT, and CT for suspected aortic dissection. The number of ultrasound studies did not change significantly (Kendall's tau-b = 0.202, p = 0.298). Conclusions The workload for radiologists during on-call hours increased dramatically in the past 15 years. The growing amount of CT studies is responsible for this increase. Radiologist and technician workforce should be matched to this ongoing increasing trend to avoid potential burn-out and to maintain quality and safety of radiological care.

scholarly journals A Magnetorheological Fluids-Based Robot-Assisted Catheter/Guidewire Surgery System for Endovascular Catheterization

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 640
Author(s):  
Linshuai Zhang ◽  
Shuoxin Gu ◽  
Shuxiang Guo ◽  
Takashi Tamiya
Keyword(s):  
Collision Detection ◽  
Endovascular Procedures ◽  
Force Feedback ◽  
Force Measurement ◽  
Occupational Hazards ◽  
Robot Assisted ◽  
X Ray ◽  
Surgical Safety ◽  
Surgical Tool ◽  
Haptic Cues

A teleoperated robotic catheter operating system is a solution to avoid occupational hazards caused by repeated exposure radiation of the surgeon to X-ray during the endovascular procedures. However, inadequate force feedback and collision detection while teleoperating surgical tools elevate the risk of endovascular procedures. Moreover, surgeons cannot control the force of the catheter/guidewire within a proper range, and thus the risk of blood vessel damage will increase. In this paper, a magnetorheological fluid (MR)-based robot-assisted catheter/guidewire surgery system has been developed, which uses the surgeon’s natural manipulation skills acquired through experience and uses haptic cues to generate collision detection to ensure surgical safety. We present tests for the performance evaluation regarding the teleoperation, the force measurement, and the collision detection with haptic cues. Results show that the system can track the desired position of the surgical tool and detect the relevant force event at the catheter. In addition, this method can more readily enable surgeons to distinguish whether the proximal force exceeds or meets the safety threshold of blood vessels.

Filtration of micron-sized particles in granular media revealed by x-ray computed tomography

2005 ◽  
Vol 76 (10) ◽  
pp. 103704 ◽  
Author(s):  
F. A. H. Al-Abduwani ◽  
R. Farajzadeh ◽  
W. M. G. T. van den Broek ◽  
P. K. Currie ◽  
P. L. J. Zitha
Keyword(s):  
Computed Tomography ◽  
Granular Media ◽  
X Ray ◽  
X Ray Computed

scholarly journals Turner Syndrome, Uncommonly Diagnosed Cause of Short Stature: Case Report and Review of Literature

2013 ◽  
Vol 33 (1) ◽  
pp. 74-76
Author(s):  
S Basnet ◽  
A Eleena ◽  
AK Sharma
Keyword(s):  
Growth Hormone ◽  
Short Stature ◽  
Turner Syndrome ◽  
Age Estimation ◽  
Bone Age ◽  
Review Of Literature ◽  
X Ray ◽  
Dysmorphic Features ◽  
The Past ◽  
Hormone Analysis

Many children are frequently brought to the paediatric clinic for evaluation of short stature. Evaluation for these children does not go beyond x-ray for bone age estimation and growth hormone analysis. Most of them are considered having constitutional or genetic cause for their short stature. However, shuttle dysmorphic features could be missed in many of them. Hence, many children might be having chromosomal anomaly as an underlying cause. We report a case of 40 months who had been evaluated several times in the past for pneumonia, otitis media and short stature is finally diagnosed to have Turner syndrome. DOI: http://dx.doi.org/10.3126/jnps.v33i1.8174 J Nepal Paediatr Soc. 2013;33(1):74-76

Strain Measurement by X-ray Diffraction Methods

1949 ◽  
Vol 1 (3) ◽  
pp. 211-224
Author(s):  
G. B. Greenough
Keyword(s):  
Strain Measurement ◽  
Plastic Anisotropy ◽  
Stress And Strain ◽  
Routine Method ◽  
X Ray Diffraction ◽  
Strain Measurements ◽  
X Ray ◽  
The Past ◽  
Polycrystalline Metals ◽  
The Individual

SummaryMany papers have been written on the measurement of strain by X-ray diffraction methods and on the interpretation of these strains in terms of stresses. Whereas, during the past few years, the experimental methods of determining the strains have. remained largely unchanged, research has shown that the older techniques for calculating stresses from strains are not always valid.In this paper an attempt is made to describe some of the principles of strain measurement by X-ray diffraction methods to those who are unfamiliar with the methods. The types of stress and strain systems which may exist in polycrystalline metals are then considered, particular attention being paid to the effect of the elastic and plastic anisotropy of the individual crystals. Some indication is given as to how the earlier methods of interpreting X-ray strain measurements should be modified, but no rigid routine method is proposed for use in a general case.

Amiodarone – induced pulmonary nodules mimiking metastatic lung disease – investigation by somatostatin radio peptide scaning

2005 ◽  
Vol 4 (2) ◽  
pp. 63-65
Author(s):  
Veronica Varney ◽  
◽  
Mary Warren ◽  
M Palmer ◽  
◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Pulmonary Nodules ◽  
Alcoholic Cardiomyopathy ◽  
X Ray ◽  
The Past ◽  
Previous Diagnosis ◽  
Metastatic Lung ◽  
Chest X Ray ◽  
200Mg Daily

A 61 year old former paramedic presented to A&E complaining of palpitations. He was found to be in atrial fibrillation, which reverted spontaneously to sinus rhythm. A chest x-ray taken at that time showed multiple pulmonary nodules consistent with metastatic malignancy (Figure 1). In the past he had been treated with amiodarone 200mg daily for 6 years following a previous diagnosis of atrial fibrillation, which had been attributed to alcoholic cardiomyopathy. He had discontinued the drug 8 months earlier, after selfdiagnosing hypotension and bradycardia. A previous chest X-ray, taken before starting amiodarone, was normal.

scholarly journals A Personal History of Using Crystals and Crystallography to Understand Biology and Advanced Drug Discovery

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 676
Author(s):  
Tom L. Blundell
Keyword(s):  
Growth Factors ◽  
Drug Discovery ◽  
Cell Surface ◽  
Small Molecule ◽  
Personal History ◽  
X Ray ◽  
Surface Receptors ◽  
The Past ◽  
Industry Collaboration ◽  
History Of

Over the past 60 years, the use of crystals to define structures of complexes using X-ray analysis has contributed to the discovery of new medicines in a very significant way. This has been in understanding not only small-molecule inhibitors of proteins, such as enzymes, but also protein or peptide hormones or growth factors that bind to cell surface receptors. Experimental structures from crystallography have also been exploited in software to allow prediction of structures of important targets based on knowledge of homologues. Crystals and crystallography continue to contribute to drug design and provide a successful example of academia–industry collaboration.

Sign in / Sign up

Export Citation Format

Share Document