The role of quasi-plasticity in the extreme contact damage tolerance of the stomatopod dactyl club

The structure of the stomatopod dactyl club--an ultrafast, hammer-like device used by the animal to shatter hard seashells--offers inspiration for impact-tolerant ceramics. Here, we present the micromechanical principles and related micromechanisms of deformation that impart the club with high impact tolerance. By using depth-sensing nanoindentation with spherical and sharp contact tips in combination with post-indentation residual stress mapping by Raman microspectroscopy, we show that the impact surface region of the dactyl club exhibits a quasi-plastic contact response associated with the interfacial sliding and rotation of fluorapatite nanorods, endowing the club with localized yielding. We also show that the subsurface layers exhibit strain hardening by microchannel densification, which provides additional dissipation of impact energy. Our findings suggest that the club's macroscopic size is below the critical size above which Hertzian brittle cracks are nucleated.

Erythromycin stearate, 1.5 g, for the oral prophylaxis of streptococcal bacteraemia in patients undergoing dental extraction: efficacy and tolerance

Erythromycin stearate, 1.5 g, was effective in reducing the prevalence of streptococcal bacteraemia following dental extraction when administered orally under supervision 1 h before extraction. Blood samples were collected from adult patients for culture and erythromycin assay 1 to 2 min after the dental procedure. High dilution techniques involving the use of 1 litre bottles of broth were used to inactivate erythromycin present in blood cultures. Viridans streptococci were isolated from 6 of 40 patients receiving erythromycin (15%) compared with 18 of 42 control patients (43%). The mean serum erythromycin concentration at the time of extraction was 3.7 mg/l for 34 patients receiving erythromycin who had negative blood cultures compared with 1.8 mg/l for the six patients given erythromycin who had viridans streptococci isolated from the blood. Both the 1.5 g erythromycin stearate and placebo oral doses were well tolerated in a double blind comparative study which included 109 adult dental patients.

Biomechanical Design of the Mantis Shrimp Saddle: A Biomineralized Spring Used for Rapid Raptorial Strikes

Stomatopods deliver one of the fastest strikes in the animal kingdom using their powerful “dactyl clubs.” This kinematic performance is enabled by a power amplification device whereby elastic energy is stored in a saddle-shape mineralized bilayer structure. We combined a set of comprehensive micro-mechanical measurements with finite element modeling (FEM) to quantitatively elucidate the saddle biomechanical design. Dynamic nano-scale testing reveals that viscoelastic dissipation is minimized in the highly mineralized layer, whereas micro-bending experiments on miniature cantilevers highlight the critical role of the bilayer arrangement in optimizing storage of elastic energy. FEM shows that the saddle shape prevents stress concentration and the stresses remain well within the elastic range during loading, while the neutral surface coincides with the bilayer interface to prevent interfacial delamination. The study unveils the multi-scale design behind the intriguing ability of the saddle to store a high density of elastic energy using stiff but intrinsically brittle materials.

Video Abstract

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Mantis shrimp delivers one of the most powerful strikes in the animal kingdom

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During a strike, the elastic energy is stored in a saddle-shaped mineralized spring

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The saddle is a bilayer structure with optimized distribution of components

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The biomechanical design of the saddle ensures efficient storage of elastic energy

Comparison of intravenous teicoplanin with intramuscular amoxycillin for the prophylaxis of streptococcal bacteraemia in dental patients

Teicoplanin 400 mg, given as an intravenous bolus dose after induction of general anaesthesia, was highly effective in reducing the prevalence of streptococcal bacteraemia following dental extraction. Pulse rate and blood pressure monitoring did not show any adverse cardiovascular reactions after this dose which was extremely well tolerated. Blood samples were collected from adult patients for culture and antibiotic assay about two minutes after the dental procedure. Viridans streptococci were isolated from one of 40 patients receiving teicoplanin (2.5%) compared with 13 of 40 (32.5%) control patients. Another group of patients investigated received amoxycillin 1.0 g, intramuscularly shortly before anaesthesia, and viridans streptococci were isolated from 10 of 40 (25%) patients in this group. The mean serum teicoplanin and amoxycillin concentrations at the time of extraction were 37 and 10 mg/l respectively. Although amoxycillin was administered with lignocaine patients occasionally complained of pain following intramuscular injection. The results of this study suggest that the 400 mg intravenous bolus dose of teicoplanin is more suitable than 1.0 g intramuscular amoxycillin for the parenteral prophylaxis of streptococcal endocarditis in patients with cardiac lesions who require a dental procedure. Also as the teicoplanin dose is easy to administer and free of cardiovascular reactions or 'red man' syndrome it is probably more suitable than vancomycin for providing prophylaxis in patients allergic to penicillin.

Multi-scale structural design and biomechanics of the pistol shrimp snapper claw

The Arthropoda, the largest phylum of the Animal Kingdom, have successfully evolved to survive various ecological constraints under a wide range of environmental conditions. Central to this survival are the structural designs developed in their exoskeletons and their raptorial appendages for protection and hunting. One such example, the pistol shrimp, is a shallow-water crustacean that is well-known for its aggressive hunting behavior, using its snapper claw to trigger the nucleation of cavitation bubbles that strike targets. In this study, we conducted a multi-scale structural/nanomechanics relationship study of this biotool to analyze its mechanical response to contact stresses. We found that the pistol shrimp snapper claw, which exhibits the capacity to emit a high-velocity water jet during rapid closure actions, is more brittle than other mineralized biotools, exhibiting accelerated wear damage under contact stresses. However, due to an angular offset between the dactylus and pollex of the snapper claw, the appendage never engages in any mechanical contact during the snapping action. This feature is in stark contrast to that reported in other fast raptorial appendages of crustaceans, notably the mantis shrimp dactyl club, which is designed to shatter close range targets in contact mode and exhibits a superior resistance to contact damage and wear. These findings suggest that adaptation of hunting appendages goes beyond their macroscopic morphology, and that multi-scale structural design concomitantly adapted to function, with enhanced structural complexification for tools that are subjected to more intense contact stresses.

STATEMENT OF SIGNIFICANCE

The evolution success of crustaceans is largely due to the diversification of their mineralized exoskeletons and hunting appendages, which exhibit a large palette of morphometric characteristics that have adapted to meet particular functions. We explored the "snapper claw" of the pistol shrimp, which is used to generate cavitation bubbles and strike prey. Our multi-scale structure-property relationship study reveals that the snapper claw is more brittle than other fast raptorial appendages - such as the stomatopod dactyl club - because it is not directly subjected to direct contact forces during action. This study implies that when higher mechanical stresses are needed to meet the function, the internal structure is built of a more complex architecture that allows to mitigate internal structural damage.

The pharmacokinetics and tolerance of oral erythromycin stearate compared with erythromycin ethylsuccinate: implications for preventing endocarditis

Serum concentrations of erythromycin were monitored in 11 healthy adult volunteers following single dose oral administration of erythromycin stearate, 1.5 g, and erythromycin ethylsuccinate 3.0 g. Peak serum concentrations occurred at 30 min to 2 h after the dose, usually at 1 h. Mean serum peak erythromycin concentrations (standard deviation) were 4.8 mg/l (+/- 2.0) following 1.5 g erythromycin stearate and 2.8 mg/l (+/- 1.4) after 3.0 g erythromycin ethylsuccinate. Both types of erythromycin frequently caused mild gastrointestinal side-effects but there were fewer side-effects associated with erythromycin ethylsuccinate. However, because of the increased serum erythromycin concentrations between 1 and 6 h after the dose of the stearate preparation compared to ethylsuccinate we recommend erythromycin stearate, 1.5 g, as the preferred loading dose, given 1 h before the dental procedure, for preventing endocarditis in susceptible patients allergic to penicillin.

Activity of teicoplanin compared with vancomycin alone, and combined with gentamicin, against penicillin tolerant viridans streptococci and enterococci causing endocarditis

Teicoplanin had greater inhibitory activity than vancomycin against most of 22 penicillin tolerant strains of streptococci, but both drugs failed to kill 99.9% of the inoculum when tested alone at concentrations less than 16mg 1(-1). Bactericidal synergy between teicoplanin combined with gentamicin and vancomycin combined with gentamicin was always demonstrated in further tests with 16 penicillin tolerant strains. Teicoplanin had greater bactericidal activity than vancomycin against five of seven strains of viridans streptococci and five of nine strains of enterococci in MBC experiments, where each drug was combined with gentamicin. Killing curve experiments with five penicillin tolerant streptococci showed teicoplanin and vancomycin to have similar bactericidal activity within 24 h when tested at 5 mg 1(-1) with 2 mg 1(-1) gentamicin. However, at 0.5 mg 1(-1) only teicoplanin had a bactericidal synergic effect with gentamicin.

Clinical comparison of anaerobic blood-culture media for detecting bacteraemia due to viridans streptococci and oral anaerobes

Brain heart infusion cysteine broth, with and without Panmede (a papain digest of ox liver) and Fastidious Anaerobe Broth, with and without Liquoid, were compared by inoculating the broths with blood collected from each of 51 patients, 2 min after dental extraction. Bacteraemia caused by viridans streptococci or oral non-sporing anaerobes or both was detected in 39 patients (76%). Detection of bacteraemia caused by viridans streptococci and anaerobes was more rapidly achieved by the addition of Panmede to brain heart infusion broth. Significantly more cases of bacteraemia caused by viridans streptococci were detected by use of the Panmede-containing medium than by use of Fastidious Anaerobe Broth after incubation of the broths for only 1 day. Use of brain heart infusion cysteine broth with and without Panmede, and Fastidious Anaerobe Broth permitted detection of bacteraemia caused by viridans streptococci in 26, 11 and 22 patients respectively during incubation for 2 weeks. Bacteraemia caused by anaerobes was detected by use of these three media in 24, 13 and 23 patients respectively. The addition of Liquoid to Fastidious Anaerobe Broth had no significant effect on the detection of bacteraemia caused by viridans streptococci or anaerobes. The Panmede-containing blood-culture medium should be a useful anaerobic broth in the investigation of patients with suspected endocarditis, because viridans streptococci are also rapidly detected.

In silico study combining QSAR, docking and molecular dynamics simulation on 2,4-disubstituted pyridopyrimidine derivatives

2,4-Disubstituted pyridopyrimidine derivatives were studied against ABCG2 enzyme. The modeling of pyridopyrimidine derivatives were done using two methods of multiple linear regression and support vector regression and four molecular descriptors of BIC4, log p, VRA2, and binding energy were selected for modeling. The statistical results were satisfactory. The interactions of ABCG2 enzyme with pyridopyrimidine derivatives were investigated using molecular docking method. Based on the results, increasing of binding energy and hydrophobicity of the compounds increase their inhibitory activity. Protein stability in complex with pharmaceutical derivatives was discussed using molecular dynamics simulation method.

The biomechanics of the locust ovipositor valves: a unique digging apparatus

The female locust has a unique mechanism for digging in order to deposit its eggs deep in the ground. It uses two pairs of sclerotized valves to displace the granular matter, while extending its abdomen as it propagates underground. This ensures optimal conditions for the eggs to incubate and provides them with protection from predators. Here, the direction-dependent biomechanics of the locust's major, dorsal digging valves are quantified and analysed under forces in the physiological range and beyond, considering the hydration level as well as the females' sexual maturation state. Our findings reveal that the responses of the valves to compression forces in the digging and propagation directions change upon sexual maturation to follow their function and depend on environmental conditions. In addition, mature females, which lay eggs, have stiffer valves, up to approximately 19 times the stiffness of the pre-mature locusts. The valves are stiffer in the major working direction, corresponding to soil shuffling and compression, compared with the direction of propagation. Hydration of the valves reduces their stiffness but increases their resilience against failure. These findings provide mechanical and materials guidelines for the design of novel non-drilling burrowing tools, including three-dimensionally printed anisotropic materials based on composites

Evaluation of sHLA-G levels in serum of patients with prostate cancer identify as a potential of tumor marker

Prostate cancer is the most common cancer type in men and is the second cause of death, due to cancer, in patients over 50, after lung cancer. Prostate specific antigen (PSA) is a widely used tumor marker for prostate cancer. Recently, PSA is discovered in non-prostatic cancer tissues in men and women raising doubts about its specificity for prostatic tissues. PSA exists in low serum level in healthy men and in higher levels in many prostate disorders, including prostatitis and prostate cancer. Thus, a supplementary tumor marker is needed to accurately diagnose the cancer and to observe the patient after treatment. Recently, soluble human leukocyte antigen-G (sHLA-G) has been introduced as a new tumor marker for different cancer types, including colorectal, breast, lung, and ovary. The present descriptive-experimental study was carried out including patients with malignant prostate tumor, patients with benign prostate tumor, and a group of health men as the control group, as judged by an oncologist as well as a pathologist. After sterile blood sampling, sHLA-G was measured by enzyme-linked immunosorbent assay in each group. The data was then analyzed using one-way ANOVA. P≤0.05 was considered as statistically significant. The results showed that the mean of sHLA-G level was high in patients. Also, it was found that there was a significant difference in sHLA serum level between the three groups. The data revealed that sHLA-G can be a novel supplementary tumor marker in addition to PSA to diagnose prostate cancer.

Bactericidal activity of netilmicin compared with gentamicin and streptomycin, alone and in combination with penicillin, against penicillin tolerant viridans streptococci and enterococci

Netilmicin was compared with gentamicin and streptomycin for in-vitro activity against 30 strains of penicillin-tolerant streptococci including 16 strains of enterococci. Both netilmicin and gentamicin tested alone at 4 mg/l caused 99.9% kill of more than half of the 13 strains of viridans streptococci tested, whereas streptomycin, 4 mg/l, had no bactericidal effect against these strains. Netilmicin, gentamicin and streptomycin tested alone at 8.0 mg/l against 10 strains of Streptococcus faecalis resulted in 99.9% kill of six, one and zero strains respectively. Combinations of penicillin with 2 mg/l of either netilmicin or gentamicin resulted in bactericidal synergy against 12 of 13 strains of viridans streptococci and all 10 strains of S. faecalis after 18 to 24 h incubation. Parallel experiments showed that higher concentration of penicillin were required to obtain 99.9% kill of 10 streptococcal strains when 4 mg/l streptomycin was compared with 2 mg/l of the other aminoglycosides. Killing curves showed similar bactericidal synergy for netilmicin-penicillin and gentamicin-penicillin combinations against most streptococci tested after 24 h incubation but there was sometimes a greater bactericidal effect noted with netilmicin after only 6 h incubation of the broth or after 48 h incubation. The results of this in-vitro study suggest that netilmicin is at least as effective as gentamicin as a bactericidal synergic agent with penicillin against penicillin-tolerant viridans streptococci and S. faecalis strains isolated from patients with endocarditis. Neither gentamicin or netilmicin were effective as bactericidal synergic agents with penicillin against 4 of 6 strains of S. faecium tested.

Chemometrics-assisted kinetic-potentiometric methods for simultaneous determination of Fe(II), Al(III), and Zr(IV) using a fluoride ion-selective electrode

Partial least-squares (PLS) and principal component regression (PCR) were used for the simple, accurate, and simultaneous determination of Fe(III), Al(III), and Zr(IV) using the kinetic data from a novel potentiometric method. The complex forming reaction rate of Fe(III), Al(III), and Zr(IV) with fluoride ions was monitored by a fluoride ion-selective electrode. The experimental data showed the good ability of ion-selective electrodes as detectors, not only for the direct determination of fluoride ion, but also for simultaneous kinetic-potentiometric analysis using the PLS and PCR methods. The methods are based on the differences observed in the complexation rate of fluoride ions. Results have demonstrated that the simultaneous determination of Fe(III), Al(III), and Zr(IV) can be performed in concentration ranges of 0.5-18.5, 0.2-14.0, and 0.4-21.0 microg/mL, respectively. After the application of PLS, the total root mean square error of prediction (RMSEP) was found to be 0.121, 0.122, and 0.129 for the 10-sample experiment of Fe(III), Al(III), and Zr(IV), respectively. For PCR, the RMSEP was found to be 0.156, 0.162, and 0.178 for the 10-sample experiment of Fe(III), Al(III), and Zr(IV), respectively. The effects of certain foreign ions upon the reaction rate were determined for assessing the selectivity of the method. The proposed methods (H-point standard addition, PLS, and PCR) were evaluated using a set of synthetic sample mixtures, and applied for the simultaneous determination of Fe(III), Al(III), and Zr(IV) in water samples.