New Materials and Methods for Hierarchically Structured Tissue Scaffolds

2004 ◽  
Vol 845 ◽  
Author(s):  
Benita M. Comeau ◽  
Yusif Umar ◽  
Kenneth E. Gonsalves ◽  
Clifford L. Henderson
Keyword(s):  
Cell Growth ◽  
Control Cell ◽  
Three Dimensional ◽  
Physical Structure ◽  
Tissue Scaffolds ◽  
Structure Control ◽  
Polymeric Scaffold ◽  
Building Process ◽  
Multi Wavelength ◽  
Physical And Chemical

ABSTRACTThe overall goal of our work is to develop new methods and materials for the fabrication of hierarchically structured, three-dimensional (3D) tissue scaffolds. Conventional scaffolds commonly lack substantial mechanical strength, and there is difficulty in controlling porosity, pore distribution, and pore interconnectivity. Additionally, the chemical nature of these scaffolds is typically homogenous. The ability to chemically modify selected areas on a scaffold is one method to direct cell growth in deliberate patterns; which could aid in the engineering of complex, functioning tissues. The general aim of this work is to address these issues through the application of stereolithography (SL) to the fabrication of hierarchically structured scaffolds.In order to achieve this goal, photopolymerizable materials must be developed that are both compatible with cell growth and with SL processing. SL methods are designed to produce arbitrary control over the physical structure of the part. In addition to physical structure control, control over the local surface chemistry of the scaffold is also desired. This would permit the use of both physical and chemical cues to control cell behavior in a tissue engineering construct. Chemical control could be achieved in SL methods by using photopolymerizable materials that can also be selectively chemically modified during the SL part building process. This paper provides an update on our work directed at using combined photoradical initiated polymerization and photoacid generator based chemical modification of a polymeric scaffold via multi-wavelength SL to produce hierarchically structured scaffolds.

Incorporation of spatial variability in modeling non-point source groundwater nitrate pollution

1996 ◽  
Vol 33 (4-5) ◽  
pp. 233-240 ◽  
Author(s):  
F. S. Goderya ◽  
M. F. Dahab ◽  
W. E. Woldt ◽  
I. Bogardi
Keyword(s):  
Spatial Variability ◽  
Point Source ◽  
Three Dimensional ◽  
Nitrate Contamination ◽  
Geostatistical Simulation ◽  
Chemical Measurements ◽  
Spatially Distributed ◽  
Potential Benefits ◽  
Zone Modeling ◽  
Physical And Chemical

A methodology for incorporation of spatial variability in modeling non-point source groundwater nitrate contamination is presented. The methodology combines geostatistical simulation and unsaturated zone modeling for estimating the amount of nitrate loading to groundwater. Three dimensional soil nitrogen variability and 2-dimensional crop yield variability are used in quantifying potential benefits of spatially distributed nitrogen input. This technique, in combination with physical and chemical measurements, is utilized as a means of illustrating how the spatial statistical properties of nitrate leaching can be obtained for different scenarios of fixed and variable rate nitrogen applications.

Dysregulation of HOX as a Potential Therapeutic Target in Breast Cancer

2020 ◽  
Vol 27 ◽  
Author(s):  
Ji-Yeon Lee ◽  
Myoung Hee Kim
Keyword(s):  
Breast Cancer ◽  
Hox Genes ◽  
Therapeutic Potential ◽  
Expression Patterns ◽  
Genome Structure ◽  
Control Cell ◽  
Three Dimensional ◽  
Cellular Processes ◽  
Hox Protein

: HOX genes belong to the highly conserved homeobox superfamily, responsible for the regulation of various cellular processes that control cell homeostasis, from embryogenesis to carcinogenesis. The abnormal expression of HOX genes is observed in various cancers, including breast cancer; they act as oncogenes or as suppressors of cancer, according to context. In this review, we analyze HOX gene expression patterns in breast cancer and examine their relationship, based on the three-dimensional genome structure of the HOX locus. The presence of non-coding RNAs, embedded within the HOX cluster, and the role of these molecules in breast cancer have been reviewed. We further evaluate the characteristic activity of HOX protein in breast cancer and its therapeutic potential.

scholarly journals Porous scaffolds with the structure of an interpenetrating polymer network made by gelatin methacrylated nanoparticle-stabilized high internal phase emulsion polymerization targeted for tissue engineering

RSC Advances ◽  
2021 ◽  
Vol 11 (37) ◽  
pp. 22544-22555
Author(s):  
Atefeh Safaei-Yaraziz ◽  
Shiva Akbari-Birgani ◽  
Nasser Nikfarjam
Keyword(s):  
Tissue Engineering ◽  
Extracellular Matrix ◽  
Cell Growth ◽  
Polymer Network ◽  
Synthetic Polymers ◽  
Tissue Scaffolds ◽  
Interpenetrating Polymer Network ◽  
Porous Scaffolds ◽  
Promising Strategy ◽  
Internal Phase

The interlacing of biopolymers and synthetic polymers is a promising strategy to fabricate hydrogel-based tissue scaffolds to biomimic a natural extracellular matrix for cell growth.

Three-dimensional wake transition

1996 ◽  
Vol 328 ◽  
pp. 345-407 ◽  
Author(s):  
C. H. K. Williamson
Keyword(s):  
Shear Layer ◽  
Three Dimensional ◽  
Streamwise Vortex ◽  
Physical Structure ◽  
Small Scale ◽  
Half Cycle ◽  
Vortex Loops ◽  
Wake Transition ◽  
Mode A ◽  
Flow States

It is now well-known that the wake transition regime for a circular cylinder involves two modes of small-scale three-dimensional instability (modes A and B), depending on the regime of Reynolds number (Re), although almost no understanding of the physical origins of these instabilities, or indeed their effects on near-wake formation, have hitherto been made clear. We address these questions in this paper. In particular, it is found that the two different modes A and B scale on different physical features of the flow. Mode A has a larger spanwise wavelength of around 3–4 diameters, and scales on the larger physical structure in the flow, namely the primary vortex core. The wavelength for mode A is shown to be the result of an ‘elliptic instability’ in the nearwake vortex cores. The subsequent nonlinear growth of vortex loops is due to a feedback from one vortex to the next, involving spanwise-periodic deformation of core vorticity, which is then subject to streamwise stretching in the braid regios. This mode gives an out-of-phase streamwise vortex pattern.In contrast, mode-B instability has a distinctly smaller wavelength (1 diameter) which scales on the smaller physical structure in the flow, the braid shear layer. It is a manifestation of an instability in a region of hyperbolic flow. It is quite distinct from other shear flows, in that it depends on the reverse flow of the bluff-body wake; the presence of a fully formed streamwise vortex system, brought upstream from a previous half-cycle, in proximity to the newly evolving braid shear layer, leads to an in-phase stream-wise vortex array, in strong analogy with the ‘Mode 1’ of Meiburg & Lasheras (1988) for a forced unseparated wake. In mode B, we also observe amalgamation of streamwise vortices from a previous braid with like-sign vortices in the subsequent braid.It is deduced that the large scatter in previous measurements concerning mode A is due to the presence of vortex dislocations. Dislocations are triggered at the sites of some vortex loops of mode A, and represent a natural breakdown of the periodicity of mode A instability. By minimizing or avoiding the dislocations which occur from end contamination or which occur during wake transition, we find an excellent agreement of both critical Re and spanwise wavelength of mode A with the recent secondary stability analysis of Barkley & Henderson (1996).Wake transition is further characterized by velocity and pressure measurements. It is consistent that, when mode-A instability and large-scale dislocations appear, one finds a reduction of base suction, a reduction of (two-dimensional) Reynolds stress level, a growth in size of the formation region, and a corresponding drop in Strouhal frequency. Finally, the present work leads us to a new clarification of the possible flow states through transition. Right through this regime of Re, there exist two distinct and continuous Strouhal frequency curves: the upper one corresponds with purley small- scale instabilities (e.g. denoted as mode A), while the lower curve corresponds with a combination of small-scale plus dislocation structures (e.g. mode A*). However, some of the flow states are transient or ‘unstable’, and the natural transitioning wake appears to follow the scenario: (2D→A*→B).

scholarly journals Size-controlled human adipose-derived stem cell spheroids hybridized with single-segmented nanofibers and their effect on viability and stem cell differentiation

2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Jinkyu Lee ◽  
Sangmin Lee ◽  
Sung Min Kim ◽  
Heungsoo Shin
Keyword(s):  
Stem Cell ◽  
Cell Function ◽  
Average Length ◽  
Three Dimensional ◽  
Stem Cell Differentiation ◽  
Cell Spheroids ◽  
Significant Difference ◽  
Vitro Analysis ◽  
Physical And Chemical

Abstract Background Fabrication of three-dimensional stem cell spheroids have been studied to improve stem cell function, but the hypoxic core and limited penetration of nutrients and signaling cues to the interior of the spheroid were challenges. The incorporation of polymers such as silica and gelatin in spheroids resulted in relatively relaxed assembly of composite spheroids, and enhancing transport of nutrient and biological gas. However, because of the low surface area between cells and since the polymers were heterogeneously distributed throughout the spheroid, these polymers cannot increase the cell to extracellular matrix interactions needed to support differentiation. Methods We developed the stem cell spheroids that incorporate poly(ι-lactic acid) single-segmented fibers synthesized by electrospinning and physical and chemical fragmentation. The proper mixing ratio was 2000 cells/μg fibers (average length of the fibers was 50 μm - 100 μm). The SFs were coated with polydopamine to increase cell binding affinity and to synthesize various-sized spheroids. The function of spheroids was investigated by in vitro analysis depending on their sizes. For statistical analysis, Graphpad Prism 5 software (San Diego, CA, USA) was used to perform one-way analysis of variance ANOVA with Tukey’s honest significant difference test and a Student’s t-test (for two variables) (P < 0.05). Results Spheroids of different sizes were created by modulating the amount of cells and fibers (0.063 mm2–0.322 mm2). The fibers in the spheroid were homogenously distributed and increased cell viability, while cell-only spheroids showed a loss of DNA contents, internal degradation, and many apoptotic signals. Furthermore, we investigated stemness and various functions of various-sized fiber-incorporated spheroids. In conclusion, the spheroid with the largest size showed the greatest release of angiogenic factors (released VEGF: 0.111 ± 0.004 pg/ng DNA), while the smallest size showed greater effects of osteogenic differentiation (mineralized calcium: 18.099 ± 0.271 ng/ng DNA). Conclusion The spheroids incorporating polydopamine coated single-segmented fibers showed enhanced viability regardless of sizes and increased their functionality by regulating the size of spheroids which may be used for various tissue reconstruction and therapeutic applications.

Investigation of atmospheric hydrogen cyanide: a modelling perspective

2021 ◽  
Author(s):  
Antonio G. Bruno ◽  
Jeremy J. Harrison ◽  
David P. Moore ◽  
Martyn P. Chipperfield ◽  
Richard J. Pope
Keyword(s):  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Hydrogen Cyanide ◽  
Three Dimensional ◽  
Oxidation Reactions ◽  
Loss Mechanism ◽  
Mixing Ratios ◽  
The Individual ◽  
Atmospheric Loss ◽  
Physical And Chemical

&lt;p&gt;Hydrogen cyanide (HCN) is one of the most abundant cyanides present in the global atmosphere, and is a tracer of biomass burning, especially for peatland fires. The HCN lifetime is 2&amp;#8211;5 months in the troposphere but several years in the stratosphere. Understanding the physical and chemical mechanisms of HCN variability is important due to its non-negligible role in the nitrogen cycle. The main source of tropospheric HCN is biomass burning with minor contributions from industry and transport. The main loss mechanism of atmospheric HCN is the reaction with the hydroxyl radical (OH). Ocean uptake is also important, while in the stratosphere oxidation by reaction with O(&lt;sup&gt;1&lt;/sup&gt;D) needs to be considered.&lt;/p&gt;&lt;p&gt;HCN variability can be investigated using chemical model simulations, such as three-dimensional (3-D) chemical transport models (CTMs). Here we use an adapted version of the TOMCAT 3-D CTM at a 1.2&amp;#176;x1.2&amp;#176; spatial resolution from the surface to ~60 km for 12 idealised HCN tracers which quantify the main loss mechanisms of HCN, including ocean uptake, atmospheric oxidation reactions and their combinations. The TOMCAT output of the HCN distribution in the period 2004-2020 has been compared with HCN profiles measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) over an altitude grid from 6 to 42 km. HCN model data have also been compared with ground-based measurements of HCN columns from NDACC FTIR stations and with in-situ volume mixing ratios (VMRs) from NOAA ground-based measurement sites.&lt;/p&gt;&lt;p&gt;The model outputs for the HCN tracer with full treatment of the loss processes generally agree well with ACE-FTS measurements, as long as we use recent laboratory values for the atmospheric loss reactions. Diagnosis of the individual loss terms shows that decay of the HCN profile in the upper stratosphere is due mainly to the O(&lt;sup&gt;1&lt;/sup&gt;D) sink. In order to test the magnitude of the tropospheric OH sink and the magnitude of the ocean sink, we also show the comparisons of the model tracers with surface-based observations. The implications of our results for understanding HCN and its variability are then discussed.&lt;/p&gt;

scholarly journals Tribo-electricity and friction. II.—Glass and solid elements

1928 ◽  
Vol 118 (779) ◽  
pp. 97-108 ◽  
Keyword(s):  
Physical Structure ◽  
Reliable Data ◽  
Chemical Characteristics ◽  
Continuous Line ◽  
Physical And Chemical Characteristics ◽  
Parallel Lines ◽  
Quantitative Results ◽  
Physical And Chemical

1. Experience teaches us that the arrangement of solids in a tribo-electric series is fallacious. We shall show in the next paper that in the case of three solids (A, B, C) A may be positive to B; and B to C; and yet C be positive to A. This may occur when the bodies are of different classes, say, metal, textile, glass, which have different physical and chemical characteristics. In the case of one material, one characteristic predominates; in another, another may be paramount. The true arrangement may prove ultimately to be in branching or parallel lines, rather than in one continuous line or series. The problem is to obtain reliable data of sign and amount of charge when two standard solids are rubbed together. The only hope of progress lies in the use of material of known composition and—even more important—of definite surface cleanliness and physical structure. Further, to obtain quantitative results the rubbing should be performed, not by hand, but in some regulated machine to insure consistency of action.

Interfacial Structure Control and Three-Dimensional X-ray Imaging of an Epoxy Monolith Bonding System with Surface Modification

Langmuir ◽  
2020 ◽  
Vol 36 (37) ◽  
pp. 10923-10932
Author(s):  
Nanako Sakata ◽  
Yoshihiro Takeda ◽  
Masaru Kotera ◽  
Yasuhito Suzuki ◽  
Akikazu Matsumoto
Keyword(s):  
Surface Modification ◽  
Three Dimensional ◽  
Interfacial Structure ◽  
X Ray ◽  
Structure Control ◽  
Bonding System ◽  
X Ray Imaging

scholarly journals Three-Dimensional Nanoscale Mapping of State-of-the-Art Field-Effect Transistors (FinFETs)

2017 ◽  
Vol 23 (5) ◽  
pp. 916-925
Author(s):  
Pritesh Parikh ◽  
Corey Senowitz ◽  
Don Lyons ◽  
Isabelle Martin ◽  
Ty J. Prosa ◽  
...  
Keyword(s):  
Field Effect ◽  
Focused Ion Beam ◽  
Field Effect Transistors ◽  
Ion Beam ◽  
Semiconductor Industry ◽  
Three Dimensional ◽  
Atom Probe ◽  
Physical Structure ◽  
Oxide Semiconductor ◽  
Device Performance

AbstractThe semiconductor industry has seen tremendous progress over the last few decades with continuous reduction in transistor size to improve device performance. Miniaturization of devices has led to changes in the dopants and dielectric layers incorporated. As the gradual shift from two-dimensional metal-oxide semiconductor field-effect transistor to three-dimensional (3D) field-effect transistors (finFETs) occurred, it has become imperative to understand compositional variability with nanoscale spatial resolution. Compositional changes can affect device performance primarily through fluctuations in threshold voltage and channel current density. Traditional techniques such as scanning electron microscope and focused ion beam no longer provide the required resolution to probe the physical structure and chemical composition of individual fins. Hence advanced multimodal characterization approaches are required to better understand electronic devices. Herein, we report the study of 14 nm commercial finFETs using atom probe tomography (APT) and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy (STEM-EDS). Complimentary compositional maps were obtained using both techniques with analysis of the gate dielectrics and silicon fin. APT additionally provided 3D information and allowed analysis of the distribution of low atomic number dopant elements (e.g., boron), which are elusive when using STEM-EDS.

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