Shock-induced structural instability and dynamic strength of metals

A description is given of the experimental technique devised to apply the method outlined theoretically in part I to the measurement of the dynamic compressive yield strength of various steels, duralumin, copper, lead, iron and silver. A polished piece of armour steel was employed as a target, and cylindrical specimens were fired at it at various measured velocities from Service weapons. The distance between the weapon and target was made short to ensure normal impact, and apparatus was devised for the precise measurement of striking velocity over this short range. The dynamic compressive yield strength was computed from the density of the specimen, the striking velocity, and from measurements of the dimensions of the test piece before and after test. Details are given of the accuracy of the various measurements, and of their effect on the values of yield strength. The method was found to be inaccurate at low and high velocities. For instance, with mild steel, satisfactory results were only obtainable within the range 400 to 2500 ft. /sec. The range of velocities within which satisfactory results could be obtained varied with the quality of the material tested, soft metals giving results within a much lower range than that necessary for harder materials. Because of its failure at low velocities, the method could not be employed to bridge the gap between static and dynamic tests. The rate of strain employed in the dynamic tests could not be measured, but was estimated to be of the order of 10,000 in. /in. /sec. With the materials tested little change of dynamic strength occurred within the range of striking velocities employed, probably because the rate of strain did not vary to any great extent with the striking velocity. Within the range of weapons available, that is, from a 0·303 in. rifle up to a 13 pdr. gun (calibre 3·12 in.), little change of dynamic strength occurred with alteration of the initial dimensions of the specimens, probably because the corresponding change of rate of strain was not large. In general, the dynamic compressive yield strength S was greater than the static strength Y represented by the compressive stress giving 0·2% permanent strain. For steels of various types, regardless of chemical composition and heat treatment, there was a relation between S / Y and the static strength Y , the ratio decreasing from approximately 3 when Y was 20 tons/sq. in. to 1 when Y was 120 tons/sq. in. A similar relation occurred with duralumin, S / Y varying from 2·5 at Y = 8 tons/sq. in. to 1·4 at Y = 25 tons/sq. in. Dynamic compressive yield values were obtained for soft materials such as pure lead, copper and Armco iron, which, under static conditions, gave no definite yield values. A plot of the unstrained length of the specimen X , expressed as X / L (where L = initial overall length), versus the final overall length L 1 , expressed as L 1 / L , was made for the various materials. Any specified value of X / L was associated with greater values of L 1 / L for the more ductile materials, such as copper and lead, than for the brittle materials, such as armour plate and duralumin.

Download Full-text

An epilepsy-causing mutation leads to co-translational misfolding of the Kv7.2 channel

BMC Biology ◽

10.1186/s12915-021-01040-1 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Janire Urrutia ◽

Alejandra Aguado ◽

Carolina Gomis-Perez ◽

Arantza Muguruza-Montero ◽

Oscar R. Ballesteros ◽

...

Keyword(s):

Structural Instability ◽

Binding Assays ◽

Iq Motif ◽

Channel Function ◽

Human Epilepsy ◽

Pathogenic Variants ◽

In Silico Studies ◽

Nascent Chain

Abstract Background The amino acid sequence of proteins generally carries all the necessary information for acquisition of native conformations, but the vectorial nature of translation can additionally determine the folding outcome. Such consideration is particularly relevant in human diseases associated to inherited mutations leading to structural instability, aggregation, and degradation. Mutations in the KCNQ2 gene associated with human epilepsy have been suggested to cause misfolding of the encoded Kv7.2 channel. Although the effect on folding of mutations in some domains has been studied, little is known of the way pathogenic variants located in the calcium responsive domain (CRD) affect folding. Here, we explore how a Kv7.2 mutation (W344R) located in helix A of the CRD and associated with hereditary epilepsy interferes with channel function. Results We report that the epilepsy W344R mutation within the IQ motif of CRD decreases channel function, but contrary to other mutations at this site, it does not impair the interaction with Calmodulin (CaM) in vitro, as monitored by multiple in vitro binding assays. We find negligible impact of the mutation on the structure of the complex by molecular dynamic computations. In silico studies revealed two orientations of the side chain, which are differentially populated by WT and W344R variants. Binding to CaM is impaired when the mutated protein is produced in cellulo but not in vitro, suggesting that this mutation impedes proper folding during translation within the cell by forcing the nascent chain to follow a folding route that leads to a non-native configuration, and thereby generating non-functional ion channels that fail to traffic to proper neuronal compartments. Conclusions Our data suggest that the key pathogenic mechanism of Kv7.2 W344R mutation involves the failure to adopt a configuration that can be recognized by CaM in vivo but not in vitro.

Download Full-text

Free-standing reduced graphene oxide (rGO) membrane for salt-rejecting solar desalination via size effect

Nanophotonics ◽

10.1515/nanoph-2020-0396 ◽

2020 ◽

Vol 9 (15) ◽

pp. 4601-4608 ◽

Cited By ~ 1

Author(s):

Pengyu Zhuang ◽

Hanyu Fu ◽

Ning Xu ◽

Bo Li ◽

Jun Xu ◽

...

Keyword(s):

Graphene Oxide ◽

Reduced Graphene Oxide ◽

Conversion Efficiency ◽

High Salinity ◽

Interlayer Spacing ◽

Structural Instability ◽

Solar Thermal ◽

Free Standing ◽

Solar Desalination ◽

Reduced Graphene

AbstractInterfacial solar vapor generation has revived the solar-thermal-based desalination due to its high conversion efficiency of solar energy. However, most solar evaporators reported so far suffer from severe salt-clogging problems during solar desalination, leading to performance degradation and structural instability. Here, we demonstrate a free-standing salt-rejecting reduced graphene oxide (rGO) membrane serving as an efficient, stable, and antisalt-fouling solar evaporator. The evaporation rate of the membrane reaches up to 1.27 kg m−2 h−1 (solar–thermal conversion efficiency ∼79%) under one sun, out of 3.5 wt% brine. More strikingly, due to the tailored narrow interlayer spacing, the rGO membrane can effectively reject ions, preventing salt accumulation even for high salinity brine (∼8 wt% concentration). With enabled salt-antifouling capability, flexibility, as well as stability, our rGO membrane serves as a promising solar evaporator for high salinity brine treatment.

Download Full-text

An Analysis of Acoustic Cavitation Thresholds of Water Based on the Incubation Time Criterion Approach

Fluids ◽

10.3390/fluids6040134 ◽

2021 ◽

Vol 6 (4) ◽

pp. 134

Author(s):

Ivan Smirnov ◽

Natalia Mikhailova

Keyword(s):

Incubation Time ◽

Dynamic Strength ◽

Acoustic Cavitation ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Accurate Estimation ◽

Ultrasound Frequency ◽

Time Criterion ◽

Good Potential ◽

Cavitation Threshold

Researchers are still working on the development of models that facilitate the accurate estimation of acoustic cavitation threshold. In this paper, we have analyzed the possibility of using the incubation time criterion to calculate the threshold of the onset of acoustic cavitation depending on the ultrasound frequency, hydrostatic pressure, and temperature of a liquid. This criterion has been successfully used by earlier studies to calculate the dynamic strength of solids and has recently been proposed in an adapted version for calculating the cavitation threshold. The analysis is carried out for various experimental data for water presented in the literature. Although the criterion assumes the use of macroparameters of a liquid, we also considered the possibility of taking into account the size of cavitation nuclei and its influence on the calculation result. We compared the results of cavitation threshold calculations done using the incubation time criterion of cavitation and the classical nucleation theory. Our results showed that the incubation time criterion more qualitatively models the results of experiments using only three parameters of the liquid. We then discussed a possible relationship between the parameters of the two approaches. The results of our study showed that the criterion under consideration has a good potential and can be conveniently used for applications where there are special requirements for ultrasound parameters, maximum negative pressure, and liquid temperature.

Download Full-text

Can We Extrapolate SINS Score to Evaluate Instability in Spinal Tuberculosis?

Global Spine Journal ◽

10.1177/21925682211030876 ◽

2021 ◽

pp. 219256822110308

Author(s):

Yogesh Kishorkant Pithwa ◽

Vikrant Sinha Roy

Keyword(s):

Prospective Observational Study ◽

Surgical Intervention ◽

Spinal Tuberculosis ◽

Neurological Status ◽

Structural Instability ◽

Stable Group ◽

Surgical Decision ◽

Helpful Tool ◽

Surgical Decision Making

Study Design: Prospective Observational Study. Objectives: To assess the feasibility of utilizing SINS score, originally suggested for neoplastic conditions, to assess structural instability in spinal tuberculosis. Methods: Patients with an established diagnosis of spinal tuberculosis were included in the study. Based on SINS scoring, patients classified as those with “indeterminate stability” were managed with or without surgery based on other parameters including neurological status, severity of pain, medical comorbidities, etc. Results: Eighty [39 males, 41 females] patients prospectively evaluated with mean age 46.74 ± 17.3 years. Classification done into stable [n = 7], indeterminate [n = 45] and unstable [n = 28] groups based on SINS scoring. All the patients in unstable group were treated with surgical stabilization whereas none in the stable group required surgical stabilization. In the indeterminate group, 26 patients underwent surgical stabilization, while 19 treated non-operatively. Major determinants predisposing to surgical intervention in “indeterminate group” were pain [14 of 26 patients] and neurological status [11 of 26 patients]. Mean follow-up 38.5 ± 22.61 months with minimum follow-up being 24 months. Preoperative VAS score for pain improved from median of 9/10 to 1/10 following surgery [ P < .0001]. In the non-operative group, the improvement was from median score of 6/10 to 1/10 [ P < .0001]. Preoperative ODI improved in non-operative and operative group from median of 42% and 70%, respectively to 10% and 12%, respectively in the postoperative period [ P < .0001 for both groups]. Conclusions: SINS scoring can be a helpful tool in surgical decision-making even in spinal tuberculosis. Further refinement of the score can be done with a larger, multicenter study.

Download Full-text