In this paper, we describe curved hole drilling via the reflection of a laser beam off the sidewall of the drilled hole. A slightly offset laser beam forms a tilted surface at the bottom of the hole, controlling the angle of curvature. An ultraviolet laser beam operating at a wavelength of 266nm was used. To visualize the hole formation process, borosilicate glass was used as the laser workpiece. This method was able to drill a curved hole with an average angle of ∼3° with curvature beginning at a depth of 400–600μm. A curved hole with a diameter of <50μm was achieved. A branched hole was also demonstrated by using the reflection of the tilted sidewall. The curved hole formation process was recorded with a high speed camera. Once the ablated sidewall reached a certain depth, drilling ceased as the laser energy fell below the ablation threshold. Ultimately, judicious selection of an appropriate laser fluence and sidewall angle allow the formation of curved holes.
Contributors:Sean P. Heffron, Carlos L. Alviar, Christopher Towe, Benjamin P. Geisler, Leon Axel, Aubrey C. Galloway, Adam H. Skolnick
We describe a 21-year-old woman who presented with chest pain and dyspnea on exertion and who was found to have a large pericardial mass. Multimodality imaging was instrumental in narrowing the differential diagnosis and planning surgical treatment, which included coronary artery bypass and right-sided heart reconstruction. The final pathologic diagnosis was lymphohemangioma; to our knowledge, this was the largest cardiac/pericardial vascular tumor ever to be reported in the literature.
Contributors:J. William Schopf, Cléber Pereira Calça, Amanda K. Garcia, Anatoliy B. Kudryavtsev, Paulo A. Souza, Cristina M. Félix, Thomas R. Fairchild
Acid maceration, used to isolate compression-preserved flattened spores and pollen from fine-grained clastic rocks, can yield copious quantities of palynomorphs and high-quality morphological information. Such maceration, however, is generally not applicable to organic-walled microfossils three-dimensionally permineralized in chemically precipitated rocks (e.g., most fossiliferous cherts), its use resulting in disintegration or destruction of the fossils as they are freed from their embedding supporting matrix. In this study of bisaccate pollen grains permineralized in stromatolitic chert of the late Early Permian Assistência Formation (Irati Subgroup) of southeastern Brazil, we compare the morphology of specimens imaged by scanning electron microscopy in acid-resistant residues with that of grains embedded in petrographic thin sections and imaged by transmitted light optical microscopy, confocal laser scanning microscopy, and Raman spectroscopy. The results document numerous benefits of the use of these three techniques for studies of permineralized palynomorphs in situ.
Contributors:Kosmas Ellinas, Katerina Tsougeni, Panagiota S. Petrou, George Boulousis, Dimitris Tsoukleris, Evangelia Pavlatou, Angeliki Tserepi, Sotirios E. Kakabakos, Evangelos Gogolides
Cyclo-olefin polymer (COP) surfaces are micro–nanotextured using O2 plasma chemistry in one-step process. These surfaces subsequently display multiple functionality, (A) they are stable in time (i.e. non ageing), functional, high surface area, substrates suitable for biomolecule binding, after thermal annealing in order to induce accelerated hydrophobic recovery while preserving the chemical functionality created by the plasma. (B) Alternatively, they are robust and environmentally stable superhydrophobic and superoleophobic surfaces, after mechanical stabilization via wetting–drying and gas-phase coating with a perfluoroctyltrichlorosilane monolayer (PFOTS) or plasma deposited Teflon-like polymer layer. The plasma treated, micro–nanotextured surfaces used for biomolecule binding exhibit remarkable retention of the initially immobilized biomolecule compared to untreated COP surfaces (up to 75%), after washing with aggressive washing solutions (sodium dodecyl sulfate), while showing excellent intensity, uniformity and sensitivity. The superoleophobic COP material surfaces exhibit very high static contact angles (SCA >150°) and very low hysteresis (CAH <10°), for a wide range of liquids from water (surface tension: 72.8mN/m) to hexadecane (surface tension: 27mN/m). In addition, these superhydrophobic and superoleophobic surfaces exhibit excellent stability against environmental ageing after 60 continuous cycles of exposure to various harsh environmental conditions (heat, moisture, UV irradiation) in a controlled environment. Finally, the two presented functionalities are combined for the first time on the same COP substrate, creating localized rough hydrophilic and antifouling patterns that exhibit spatially selective biomolecule immobilization inside a microfluidic device.
Contributors:Patrick Plouffe, Dominique M. Roberge, Arturo Macchi
The flow regimes and mass transfer rates in five complex micro-reactors with different mixing mechanisms were investigated using the two-phase alkaline hydrolysis of 4-nitrophenyl acetate. n-Butanol and toluene were used as organic solvents. Using n-butanol in curvature-based micro-mixers, the flow regime evolved from slug to parallel to drop/dispersed flow with increasing flow rates. In obstacle-based micro-mixers, no parallel flow was observed. Using toluene, no parallel flow was observed for all reactors. The conversion of 4-nitrophenyl acetate was found to be strongly dependent on the flow regime. In slug and parallel flow, the conversion generally decreased with an increase in flow rate whereas it typically increased in drop flow and was constant or slightly decreased in dispersed flow. The different micro-mixers were compared using the overall volumetric mass transfer coefficient, Korga, which was primarily a function of the rate of energy dissipation within the dispersed flow regime. The geometry itself impacts the resulting flow regime and rate of energy dissipation at a given flow rate. The micro-reactors were then compared using modified Damköhler’s numbers. Curvature-based reactors were found to be inadequate for liquid–liquid reactions under the studied conditions, as they favor parallel flow patterns and yield relatively low interphase mass transfer rates.
Contributors:Haiqiao Wei, Dongzhi Gao, Lei Zhou, Jiaying Pan, Kang Tao, Zigang Pei
In present study, a new designed constant volume combustion bomb (CVCB) equipped with an orifice plate and visualized by high speed schlieren photography has been employed to study the turbulent flame propagation effected by flame acceleration in the end gas region. The orifice plate is employed to achieve flame acceleration and obtain different turbulent flames at different equivalence ratios. We investigate the flame propagation speed, the formation mechanism of compression front, the influence of flame acceleration on the end-gas as well as the flame structure changes. The results show that the laminar flame can be accelerated and transferred to a wrinkled turbulent flame through the orifice plate significantly and there forms a clear compression front ahead of the turbulent flame. The flame propagation speed without orifice plate shows the trend of initial increase and consequence decrease in the confined space. Moreover, the turbulent flame propagation speed shows the significantly different trend and demonstrates the “M” shape evolution including the self-acceleration, unstable and deceleration process. Finally, the evolution of turbulent flame in the end gas of the confined chamber was described in detail with three stages: compression front formation, flame front distortion and reverse propagation.
Contributors:D. Muraro, A. Larrieu, M. Lucas, J. Chopard, H. Byrne, C. Godin, J. King
The growth of the root of Arabidopsis thaliana is sustained by the meristem, a region of cell proliferation and differentiation which is located in the root apex and generates cells which move shootwards, expanding rapidly to cause root growth. The balance between cell division and differentiation is maintained via a signalling network, primarily coordinated by the hormones auxin, cytokinin and gibberellin. Since these hormones interact at different levels of spatial organisation, we develop a multi-scale computational model which enables us to study the interplay between these signalling networks and cell-cell communication during the specification of the root meristem. We investigate the responses of our model to hormonal perturbations, validating the results of our simulations against experimental data. Our simulations suggest that one or more additional components are needed to explain the observed expression patterns of a regulator of cytokinin signalling, ARR1, in roots not producing gibberellin. By searching for novel network components, we identify two mutant lines that affect significantly both root length and meristem size, one of which also differentially expresses a central component of the interaction network (SHY2). More generally, our study demonstrates how a multi-scale investigation can provide valuable insight into the spatio-temporal dynamics of signalling networks in biological tissues.
Contributors:Tianliang Zhai, Qifeng Zheng, Zhiyong Cai, Hesheng Xia, Shaoqin Gong
Superhydrophobic and crosslinked poly(vinyl alcohol) (PVA)/cellulose nanofibril (CNF) aerogel microspheres were prepared via a combination of the water-in-oil (W/O) emulsification process with the freeze-drying process, followed by thermal chemical vapor deposition of methyltrichlorosilane. The oil phase and the cooling agent were judiciously selected to ensure that the frozen ice microspheres can be easily separated from the emulsion system. The silanized microspheres were highly porous with a bulk density ranging from 4.66 to 16.54mg/cm3. The effects of the solution pH, stirring rate, and emulsifier concentration on the morphology and microstructure of the aerogel microspheres were studied. The highly porous structure of the ultralight aerogel microspheres demonstrated an ultrahigh crude oil absorption capacity (up to 116 times its own weight). This study provides a novel approach for the large-scale preparation of polymeric aerogel microspheres with well-controlled particle sizes that can be used for various applications including oil and chemical spill/leak clean-up.