Adhesion between rubber and glass in dry and lubricated condition

We study the adhesion between differently processed glass and filled bromobutyl rubber in dry conditions, in water, and in silicone oil. The boundary line between contact and non-contact in adhesion experiments can be considered as a mode I crack, and we show that viscoelastic energy dissipation, close to the opening (or closing) crack tip and surface roughness, strongly affects the work of adhesion. We observe strong adhesion hysteresis and, in contrast to the Johnson-Kendall-Roberts theory prediction for elastic solids, this results in a pull-off force (and work of adhesion) which depends on the loading force and contact time. In particular, for the system immersed in water and silicone oil, we register very weak adhesive bonding. For glass ball with baked-on silicone oil, the pull-off force is nearly independent of the contact time, but this is not observed for the unprocessed glass surface.

Rubber friction: The contribution from the area of real contact

There are two contributions to the friction force when a rubber block is sliding on a hard and rough substrate surface, namely, a contribution F_ad = τ_f A from the area of real contact A and a viscoelastic contribution F_visc from the pulsating forces exerted by the substrate asperities on the rubber block. Here we present experimental results obtained at different sliding speeds and temperatures, and we show that the temperature dependency of the shear stress τ_f, for temperatures above the rubber glass transition temperature T_g, is weaker than that of the bulk viscoelastic modulus. The physical origin of τ_f for T > T_g is discussed, and we propose that its temperature dependency is determined by the rubber molecule segment mobility at the sliding interface, which is higher than in the bulk because of increased free-volume effect due to the short-wavelength surface roughness. This is consistent with the often observed reduction in the glass transition temperature in nanometer-thick surface layers of glassy polymers. For temperatures T < T_g, the shear stress τ_f is nearly velocity independent and of similar magnitude as observed for glassy polymers such as PMMA or polyethylene. In this case, the rubber undergoes plastic deformations in the asperity contact regions and the contact area is determined by the rubber penetration hardness. For this case, we propose that the frictional shear stress is due to slip at the interface between the rubber and a transfer film adsorbed on the concrete surface.

Rubber contact mechanics: adhesion, friction and leakage of seals

We study the adhesion, friction and leak rate of seals for four different elastomers: Acrylonitrile Butadiene Rubber (NBR), Ethylene Propylene Diene (EPDM), Polyepichlorohydrin (GECO) and Polydimethylsiloxane (PDMS). Adhesion between smooth clean glass balls and all the elastomers is studied both in the dry state and in water. In water, adhesion is observed for the NBR and PDMS elastomers, but not for the EPDM and GECO elastomers, which we attribute to the differences in surface energy and dewetting. The leakage of water is studied with rubber square-ring seals squeezed against sandblasted glass surfaces. Here we observe a strongly non-linear dependence of the leak rate on the water pressure ΔP for the elastomers exhibiting adhesion in water, while the leak rate depends nearly linearly on ΔP for the other elastomers. We attribute the non-linearity to some adhesion-related phenomena, such as dewetting or the (time-dependent) formation of gas bubbles, which blocks fluid flow channels. Finally, rubber friction is studied at low sliding speeds using smooth glass and sandblasted glass as substrates, both in the dry state and in water. The measured friction coefficients are compared to theory, and the origin of the frictional shear stress acting in the area of real contact is discussed. The NBR rubber, which exhibits the strongest adhesion both in the dry state and in water, also shows the highest friction both in the dry state and in water.

Retrospective study of efficacy and safety of neoadjuvant docetaxel, carboplatin, and trastuzumab in HER2-positive locally advanced and oligometastatic breast cancer: An Indian experience

BACKGROUND

The neoadjuvant chemotherapy in HER2-positive breast cancer consists of a chemotherapy backbone and HER2-directed therapy. The increase in cardiotoxicity by the use of trastuzumab with an anthracycline-based regimen has led to the use of nonanthracycline-based alternative regimens. The docetaxel, carboplatin, and trastuzumab (TCH) are one such regimen. The efficacy and toxicity of this regimen have not been widely studied in Indian patients.

AIMS

This retrospective study aims to evaluate the efficacy and toxicity of neoadjuvant TCH regimen in locally advanced and oligometastatic HER2-positive breast cancer in Indian patients.

METHODOLOGY

The hospital records between January 2014 and December 2016 were reviewed to identify patients with locally advanced and oligometastatic HER2-positive breast cancer treated with uniform 3-weekly neoadjuvant chemotherapy protocol-containing docetaxel (75 mg/m2), carboplatin (AUC = 6), and trastuzumab (8 mg/kg loading followed by 6 mg/kg) (TCH). The primary outcome was the pathologic complete response (pCR), which was defined as an absence of invasive and noninvasive cancer in breast or lymphnode.

RESULTS

Thirty-two patients with mean age 46 years met our inclusion criteria, of these 24 patients had locally advanced breast cancer, and eight patients had oligometastatic breast cancer. 13 (40.6%) patients had hormone-positive breast cancer. The objective response rate as assessed clinically was 100%, and pCR rate was 36.3%. The patients with oligometastatic breast cancer also showed a good response to chemotherapy with three patients showing pCR and four patients showing resolution disease at metastatic sites. The patients experienced very few Grade III/IV toxicities, and no patient had clinical congestive heart failure.

CONCLUSION

The TCH protocol is an efficacious neoadjuvant chemotherapy regimen for locally advanced and oligometastatic breast cancer and is safe and well tolerated in this population.

Introducing leprosy post-exposure prophylaxis into the health systems of India, Nepal and Indonesia: a case study

Background

Leprosy has a wide range of clinical and socio-economic consequences. India, Indonesia and Nepal contribute significantly to the global leprosy burden. After integration, the health systems are pivotal in leprosy service delivery. The Leprosy Post Exposure Prophylaxis (LPEP) program is ongoing to investigate the feasibility of providing single dose rifampicin (SDR) as post-exposure prophylaxis (PEP) to the contacts of leprosy cases in various health systems. We aim to compare national leprosy control programs, and adapted LPEP strategies in India, Nepal and Indonesia. The purpose is to establish a baseline of the health system’s situation and document the subsequent adjustment of LPEP, which will provide the context for interpreting the LPEP results in future.

Methods

The study followed the multiple-case study design with single units of analysis. The data collection methods were direct observation, in-depth interviews and desk review. The study was divided into two phases, i.e. review of national leprosy programs and description of the LPEP program. The comparative analysis was performed using the WHO health system frameworks (2007).

Results

In all countries leprosy services including contact tracing is integrated into the health systems. The LPEP program is fully integrated into the established national leprosy programs, with SDR and increased documentation, which need major additions to standard procedures. PEP administration was widely perceived as well manageable, but the additional LPEP data collection was reported to increase workload in the first year.

Conclusions

The findings of our study led to the recommendation that field-based leprosy research programs should keep health systems in focus. The national leprosy programs are diverse in terms of organizational hierarchy, human resource quantity and capacity. We conclude that PEP can be integrated into different health systems without major structural and personal changes, but provisions are necessary for the additional monitoring requirements.

Electronic supplementary material

The online version of this article (10.1186/s12913-017-2611-7) contains supplementary material, which is available to authorized users.

Effect of Microbial inoculation in combating the aluminium toxicity effect on growth of Zea mays

The present study is aimed at improving the aluminium tolerance in maize crop employing the potential of microbial inoculants in conferring resistance to these toxicities via production of certain chelating compounds like siderophores, exopolysachharides and organic acids. Acid soils have now-a-days become one of the key factors for limiting growth of many agriculturally important crops. Aluminium  is one of the major elements present in acid soils and is mainly responsible for toxicity in the soil. This aluminium is rapidly soluble in soil water and hence absorbed by plant roots under conditions where soil pH is below 5. This toxicity leads to severe root growth inhibition, thereby limiting the production of maize crops. It was observed that use of microbial inoculums can be helpful in elimination of these toxic compounds and prevent the inhibition of root growth . It was found that the soils contaminated with aluminium toxicity decreased the root length of maize plant significantly by 65% but Bacillus and Burkholderia inoculation increased this root length significantly by 1.4- folds and 2- folds respectively thereby combating the effect of aluminium toxicity. Aluminium concentration was found maximum in roots of plants which were grown under aluminium stress condition. But this aluminium accumulation decreased ̴ 2-folds when Burkholderia was used as seed inoculants under aluminium stress conditions. Also, at 60mM aluminium accumulation, phosphorus solubilisation in roots was found to be increased upto 30% on Burkholderia inoculation. However, Bacillus inoculation didn't show any significant difference in either of the case. Thus, the inoculation of seeds with Burkholderia isolates could prove to be a boon in sequestering aluminium toxicity in Zea mays.

The effect of surface roughness and viscoelasticity on rubber adhesion

Adhesion between silica glass or acrylic balls and silicone elastomers and various industrial rubbers is investigated. The work of adhesion during pull-off is found to strongly vary depending on the system, which we attribute to the two opposite effects: (1) viscoelastic energy dissipation close to an opening crack tip and (2) surface roughness. Introducing surface roughness on the glass ball is found to increase the work of adhesion for soft elastomers, while for the stiffer elastomers it results in a strong reduction in the work of adhesion. For the soft silicone elastomers a strong increase in the work of adhesion with increasing pull-off velocity is observed, which may result from the non-adiabatic processes associated with molecular chain pull-out. In general, the work of adhesion is decreased after repeated contacts due to the transfer of molecules from the elastomers to the glass ball. Thus, extracting the free chains (oligomers) from the silicone elastomers is shown to make the work of adhesion independent of the number of contacts. The viscoelastic properties (linear and nonlinear) of all of the rubber compounds are measured, and the velocity dependent crack opening propagation energy at the interface is calculated. Silicone elastomers show a good agreement between the measured work of adhesion and the predicted results, but carbon black filled hydrogenated nitrile butadiene rubber compounds reveal that strain softening at the crack tip may play an important role in determining the work of adhesion. Additionally, adhesion measurement under submerged conditions in distilled water and water + soap solutions are also performed: a strong reduction in the work of adhesion is measured for the silicone elastomers submerged in water, and a complete elimination of adhesion is found for the water + soap solution attributed to an osmotic repulsion between the negatively charged surface of the glass and the elastomer.

Thermoelectric and Structural Characterization of Al-Doped ZnO/Y₂O₃ Multilayers

The influence of Y2O3 nanolayers on thermoelectric performance and structure of 2% Al-doped ZnO (AZO) thin films has been studied. Multilayers based on five 50 nm thick AZO layers alternated with few nanometers thick Y2O3 layers were prepared by pulsed laser deposition on Al2O3 single crystals by alternate ablation of AZO target and Y2O3 target. The number of laser shots on Y2O3 target was maintained very low (5, 10 and 15 pulses in three separate experiments. The main phase (AZO) presents polycrystalline orientation and typical columnar growth not affected by the presence of Y2O3 nanolayers. The multilayer with 15 laser shots of Y2O3 showed best thermoelectric performance with electrical conductivity σ 48 S/cm and Seebeck coefficient S = −82 μV/K, which estimate power factor (S2·σ) about 0.03 × 10−3 W m−1 K−2 at 600 K. The value of thermal conductivity (κ) was found 10.03 W m−1 K−1 at 300 K, which is one third of typical value previously reported for bulk AZO. The figure of merit, ZT = S2·σ·T/κ, is calculated 9.6 × 10−4 at 600 K. These results demonstrated the feasibility of nanoengineered defects insertion for the depression of thermal conductivity.

The Global Relationship between Chromatin Physical Topology, Fractal Structure, and Gene Expression

Most of what we know about gene transcription comes from the view of cells as molecular machines: focusing on the role of molecular modifications to the proteins carrying out transcriptional reactions at a loci-by-loci basis. This view ignores a critical reality: biological reactions do not happen in an empty space, but in a highly complex, interrelated, and dense nanoenvironment that profoundly influences chemical interactions. We explored the relationship between the physical nanoenvironment of chromatin and gene transcription in vitro. We analytically show that changes in the fractal dimension, D, of chromatin correspond to simultaneous increases in chromatin accessibility and compaction heterogeneity. Using these predictions, we demonstrate experimentally that nanoscopic changes to chromatin D within thirty minutes correlate with concomitant enhancement and suppression of transcription. Further, we show that the increased heterogeneity of physical structure of chromatin due to increase in fractal dimension correlates with increased heterogeneity of gene networks. These findings indicate that the higher order folding of chromatin topology may act as a molecular-pathway independent code regulating global patterns of gene expression. Since physical organization of chromatin is frequently altered in oncogenesis, this work provides evidence pairing molecular function to physical structure for processes frequently altered during tumorigenesis.

Three-dimensional printing and patient-specific pre-contoured plate: future of acetabulum fracture fixation?

PURPOSE

Due to the complexity of acetabulum, achieving anatomical contouring intra-operatively is difficult for surgeon. A 3D (dimensional) real model can facilitate us both in contouring the plate pre-operatively and in better pre-operative planning. Patient-specific pre-contoured plate in acetabular fracture has been studied by few researchers but randomized case-control study was lacking. Hence, we conducted a case-control study to evaluate the accuracy of patient-specific pre-contoured plate.

MATERIALS AND METHODS

Prospective randomized case control study was conducted. 21 patients were included. 10 patients were distributed in "case" group and remaining 11 in "control" group.

INCLUSION CRITERIA

Displaced acetabulum fractures with displacement of ≥3 mm in adults who reported within 3 weeks of injury. Exclusion criteria were: Open fractures, associated Morel-Lavallée lesion and patients with >3 weeks old fracture. In case group, patient-specific real 3D model of fractured acetabulum was generated using rapid prototyping technology and plates were contoured pre-operatively. Control group was treated using intra-operative contoured plates. Both the groups were compared using parameters: Blood loss, Surgery time, post-operative reduction on X-ray, post-surgical residual displacement and reduction achieved as evaluated by CT scan.

RESULTS

Reduced blood loss (100 ml less in case group) and surgical time (12 min less in case group) and better post-operative reduction were observed in case than control. In control group, 4 patients even had step of 2-3 mm, which was not seen in case group. All the pre-contoured plates fitted well to the pelvis intra-operatively. Reduction achieved as evaluated by CT was more in "case" group with statistically significant outcomes (p < 0.05).

CONCLUSION

Patient-specific pre-contoured plate made using 3D model is a better implant than intra-operatively contoured plate. Real-time 3D pelvis model is an accurate technique for pre-operative planning in acetabular fractures.

Three-dimensional printing and patient-specific pre-contoured plate: future of acetabulum fracture fixation?

PURPOSE

Due to the complexity of acetabulum, achieving anatomical contouring intra-operatively is difficult for surgeon. A 3D (dimensional) real model can facilitate us both in contouring the plate pre-operatively and in better pre-operative planning. Patient-specific pre-contoured plate in acetabular fracture has been studied by few researchers but randomized case-control study was lacking. Hence, we conducted a case-control study to evaluate the accuracy of patient-specific pre-contoured plate.

MATERIALS AND METHODS

Prospective randomized case control study was conducted. 21 patients were included. 10 patients were distributed in "case" group and remaining 11 in "control" group.

INCLUSION CRITERIA

Displaced acetabulum fractures with displacement of ≥3 mm in adults who reported within 3 weeks of injury. Exclusion criteria were: Open fractures, associated Morel-Lavallée lesion and patients with >3 weeks old fracture. In case group, patient-specific real 3D model of fractured acetabulum was generated using rapid prototyping technology and plates were contoured pre-operatively. Control group was treated using intra-operative contoured plates. Both the groups were compared using parameters: Blood loss, Surgery time, post-operative reduction on X-ray, post-surgical residual displacement and reduction achieved as evaluated by CT scan.

RESULTS

Reduced blood loss (100 ml less in case group) and surgical time (12 min less in case group) and better post-operative reduction were observed in case than control. In control group, 4 patients even had step of 2-3 mm, which was not seen in case group. All the pre-contoured plates fitted well to the pelvis intra-operatively. Reduction achieved as evaluated by CT was more in "case" group with statistically significant outcomes (p < 0.05).

CONCLUSION

Patient-specific pre-contoured plate made using 3D model is a better implant than intra-operatively contoured plate. Real-time 3D pelvis model is an accurate technique for pre-operative planning in acetabular fractures.

Assessing the Impact of Tissue Target Concentration Data on Uncertainty in In Vivo Target Coverage Predictions

Understanding pharmacological target coverage is fundamental in drug discovery and development as it helps establish a sequence of research activities, from laboratory objectives to clinical doses. To this end, we evaluated the impact of tissue target concentration data on the level of confidence in tissue coverage predictions using a site of action (SoA) model for antibodies. By fitting the model to increasing amounts of synthetic tissue data and comparing the uncertainty in SoA coverage predictions, we confirmed that, in general, uncertainty decreases with longitudinal tissue data. Furthermore, a global sensitivity analysis showed that coverage is sensitive to experimentally identifiable parameters, such as baseline target concentration in plasma and target turnover half‐life and fixing them reduces uncertainty in coverage predictions. Overall, our computational analysis indicates that measurement of baseline tissue target concentration reduces the uncertainty in coverage predictions and identifies target‐related parameters that greatly impact the confidence in coverage predictions.