En route to controlled catalytic CVD synthesis of densely packed and vertically aligned nitrogen-doped carbon nanotube arrays

The catalytic chemical vapour deposition (c-CVD) technique was applied in the synthesis of vertically aligned arrays of nitrogen-doped carbon nanotubes (N-CNTs). A mixture of toluene (main carbon source), pyrazine (1,4-diazine, nitrogen source) and ferrocene (catalyst precursor) was used as the injection feedstock. To optimize conditions for growing the most dense and aligned N-CNT arrays, we investigated the influence of key parameters, i.e., growth temperature (660, 760 and 860 °C), composition of the feedstock and time of growth, on morphology and properties of N-CNTs. The presence of nitrogen species in the hot zone of the quartz reactor decreased the growth rate of N-CNTs down to about one twentieth compared to the growth rate of multi-wall CNTs (MWCNTs). As revealed by electron microscopy studies (SEM, TEM), the individual N-CNTs (half as thick as MWCNTs) grown under the optimal conditions were characterized by a superior straightness of the outer walls, which translated into a high alignment of dense nanotube arrays, i.e., 5 × 108 nanotubes per mm2 (100 times more than for MWCNTs grown in the absence of nitrogen precursor). In turn, the internal crystallographic order of the N-CNTs was found to be of a ‘bamboo’-like or ‘membrane’-like (multi-compartmental structure) morphology. The nitrogen content in the nanotube products, which ranged from 0.0 to 3.0 wt %, was controlled through the concentration of pyrazine in the feedstock. Moreover, as revealed by Raman/FT-IR spectroscopy, the incorporation of nitrogen atoms into the nanotube walls was found to be proportional to the number of deviations from the sp2-hybridisation of graphene C-atoms. As studied by XRD, the temperature and the [pyrazine]/[ferrocene] ratio in the feedstock affected the composition of the catalyst particles, and hence changed the growth mechanism of individual N-CNTs into a ‘mixed base-and-tip’ (primarily of the base-type) type as compared to the purely ‘base’-type for undoped MWCNTs

Additive Manufacturing of Biomechanically Tailored Meshes for Compliant Wearable and Implantable Devices

Additive manufacturing (AM) of medical devices such as orthopedic implants and hearing aids is highly attractive because of AM’s potential to match the complex form and mechanics of individual human bodies. Externally worn and implantable tissue-support devices, such as ankle or knee braces, and hernia repair mesh, offer a new opportunity for AM to mimic tissue-like mechanics and improve both patient outcomes and comfort. Here, it is demonstrated how explicit programming of the toolpath in an extrusion AM process can enable new, flexible mesh materials having digitally tailored mechanical properties and geometry. Meshes are fabricated by extrusion of thermoplastics, optionally with continuous fiber reinforcement, using a continuous toolpath that tailors the elasticity of unit cells of the mesh via incorporation of slack and modulation of filament-filament bonding. It is shown how the tensile mesh mechanics can be engineered to match the nonlinear response of muscle, incorporate printed mesh into an ankle brace with directionally specific inversion stiffness, and present further concepts for tailoring their 3D geometry for medical applications.Financial support was provided by a National Science Foundation Science, Engineering, and Education for Sustainability postdoctoral fellowship (Award number: 1415129) to S.W.P.; a Samsung Scholarship to J.L; the School of Engineering and Sciences from Tecnologico de Monterrey to R.R.; the Manufacturing Demonstration Facility, Oak Ridge National Laboratory, the Department of Energy, UT-Batelle, Oak Ridge Associated Universities, the DOE’s Advanced Manufacturing Office to G.D.; the German Academic Exchange Service (DAAD) to C.M.; and the Eric P. and Evelyn E. Newman Fund and NSF-CRCNS-1724135 to N.H

Appropriate criteria for identification of near-miss maternal morbidity in tertiary care facilities: A cross sectional study

<p>Abstract</p> <p>Background</p> <p>The study of severe maternal morbidity survivors (near miss) may be an alternative or a complement to the study of maternal death events as a health care indicator. However, there is still controversy regarding the criteria for identification of near-miss maternal morbidity. This study aimed to characterize the near miss maternal morbidity according to different sets of criteria.</p> <p>Methods</p> <p>A descriptive study in a tertiary center including 2,929 women who delivered there between July 2003 and June 2004. Possible cases of near miss were daily screened by checking different sets of criteria proposed elsewhere. The main outcome measures were: rate of near miss and its primary determinant factors, criteria for its identification, total hospital stay, ICU stay, and number and kind of special procedures performed.</p> <p>Results</p> <p>There were two maternal deaths and 124 cases of near miss were identified, with 102 of them admitted to the ICU (80.9%). Among the 126 special procedures performed, the most frequent were central venous access, echocardiography and invasive mechanical ventilation. The mean hospital stay was 10.3 (± 13.24) days. Hospital stay and the number of special procedures performed were significantly higher when the organ dysfunction based criteria were applied.</p> <p>Conclusion</p> <p>The adoption of a two level screening strategy may lead to the development of a consistent severe maternal morbidity surveillance system but further research is needed before worldwide near miss criteria can be assumed.</p

Risk factors for peripartum hysterectomy among women with postpartum haemorrhage: analysis of data from the WOMAN trial.

BACKGROUND: Peripartum hysterectomy can cause significant morbidity and mortality. Most studies of peripartum hysterectomy are from high income countries. This cohort study examined risk factors for peripartum hysterectomy using data from Africa, Asia, Europe and the Americas. METHODS: We used data from the World Maternal Antifibrinolytic (WOMAN) trial carried out in 193 hospitals in 21 countries. Peripartum hysterectomy was defined as hysterectomy within 6 weeks of delivery as a complication of postpartum haemorrhage. Univariable and multivariable random effects logistic regression models were used to analyse risk factors. A hierarchical conceptual framework guided our multivariable analysis. RESULTS: Five percent of women had a hysterectomy (1020/20,017). Haemorrhage from placenta praevia/accreta carried a higher risk of hysterectomy (17%) than surgical trauma/tears (5%) and uterine atony (3%). The adjusted odds ratio (AOR) for hysterectomy in women with placenta praevia/accreta was 3.2 (95% CI: 2.7-3.8), compared to uterine atony. The risk of hysterectomy increased with maternal age. Caesarean section was associated with fourfold higher odds of hysterectomy than vaginal delivery (AOR 4.3, 95% CI: 3.6-5.0). Mothers in Asia had a higher hysterectomy incidence (7%) than mothers in Africa (5%) (AOR: 1.2, 95% CI: 0.9-1.7). CONCLUSIONS: Placenta praevia/accreta is associated with a higher risk of peripartum hysterectomy. Other risk factors for hysterectomy are advanced maternal age, caesarean section and giving birth in Asia

A population-based surveillance study on severe acute maternal morbidity (near-miss) and adverse perinatal outcomes in Campinas, Brazil: The Vigimoma Project

BACKGROUND: Auditing of sentinel health events based on best-practice protocols has been recommended. This study describes a population-based investigation on adverse perinatal events including severe acute maternal morbidity (near-miss), maternal and perinatal mortality, as a health intervention to help improve the surveillance system. METHODS: From October to December 2005, all cases of maternal death (MD), near-miss (NM), fetal deaths (FD), and early neonatal deaths (END), occurring in Campinas, Brazil, were audited by maternal mortality committees. RESULTS: A total of 4,491 liveborn infants (LB) and 159 adverse perinatal events (35.4/1000 LB) were revised, consisting of 4 MD (89/100.000 LB) and 95 NM (21.1/1000 LB), 23.7 NM for each MD. In addition, 32 FD (7.1/1000 LB) and 28 END (6.2/1000 LB) occurred. The maternal death/near miss rate was 23.7:1. Some delay in care was recognized for 34%, and hypertensive complications comprised 57.8% of the NM events, followed by postpartum hemorrhage. CONCLUSION: Auditing near miss cases expanded the understanding of the spectrum from maternal morbidity to mortality and the importance of promoting adhesion to clinical protocols among maternal mortality committee members. Hypertensive disorders and postpartum hemorrhage were identified as priority topics for health providers training, and organization of care

Additive Manufacturing of Cellulosic Materials with Robust Mechanics and Antimicrobial Functionality

Additive manufacturing of pure cellulosic objects is demonstrated via extrusion of cellulose acetate and conversion to cellulose, rendering parts with isotropic strength and high toughness. Ease of functionalization is shown by addition of antimicrobial dye to the printing ink, which kills 95% of bacteria upon exposure to light

Facile processing of zeolite based catalyst support for carbon nanotube synthesis

Before many of the most promising applications of carbon nanotubes can be realized, nanotube characteristics including chirality, length and diameter must be optimised. One of the most important aspects of supported carbon nanotube synthesis is the interaction of the catalyst with the substrate. The highly uniform and dense pore structures of zeolites make them ideally suited for improving carbon nanotube synthesis, but their powder form renders them incompatible with many commonly used and highly developed synthesis techniques. Existing methods for making planar substrates from zeolites are complex and unsuitable for incorporation into carbon nanotube synthesis. We present an investigation into facile methods for forming zeolites into substrates, demonstrating that these are compatible with many different CNT synthesis techniques and even able to support the growth of aligned arrays of CNTs that are hundreds of microns long. These substrates can be easily produced and incorporated into existing CNT synthesis processes and should therefore aid in the use of zeolites in CNT synthesis generally. This method is also compatible with any powder based porous material such as activated alumina or silica gel, allowing the production of substrates with a wide variety of pore size distributions and surface properties. © 2012 Published by Elsevier B.V

Automated recognition and correction of warp deformation in extrusion additive manufacturing

Warp deformation is a common error encountered in additive manufacturing. It is typically caused by residual internal stresses in the manufactured part that arise as material cools. These errors are challenging to prevent or correct as they build over time and thus are only visible long after the actions that caused them. As a result, existing work in extrusion additive man- ufacturing has attempted warp detection but not correction or prevention. We report a hybrid approach combining deep learning, computer vision, and expert heuristics to correct or prevent warp. We train a deep convolutional neural network using diverse labelled images to recognise warp in real-time. We compute five metrics from detection candidates to predict the severity of warp deformation and proportionately update print settings. This enables the first demon- stration of automated warp detection and correction both during printing and for future prints.This work has been funded by the Engineering and Physical Sciences Research Council (EP- SRC) PhD Studentship EP/N509620/1 to Douglas Brion, Royal Society award RGS/R2/192433 to Sebastian Pattinson, Academy of Medical Sciences award SBF005/1014 to Sebastian Pattin- 600 son, Engineering and Physical Sciences Research Council award EP/V062123/1 to Sebastian Pattinson, and An Isaac Newton Trust award to Sebastian Pattinson