Semiconductor Materials for High Frequency Solid State Sources.

DTIC Science & Technology

1985-01-18

saturation on near and submicron-scale device performance. The motivation for this is as follows: Presently, individual semiconductors are accepted or...basis of all FET scaling procedures; and is a major motivating factor for going to submicron structures. This scaling was tested with the 4 following...performance. The motivation for this is as follows: Presently, individual semiconductors are accepted or rejected as candidate device materials based, in

Deploying Liquid Filaments and Suspensions with an Electrohydrodynamic Liquid Bridge

NASA Astrophysics Data System (ADS)

Saville, D. A.

2005-11-01

We show that a dynamic liquid bridge can be formed by deploying the filament issuing from a Taylor Cone onto a surface with the nozzle and surface held at different electric potentials. This configuration differs sharply form the familiar `electrospinning' configuration where the filament whips violently. Nevertheless, although the aspect ratio (length/diameter) exceeds the Plateau limit by more than two orders of magnitude the bridge is stable. Here we report on the stability characteristics and show that such a bridge can be used to `print' sub-micron scale features on a moving surface with both clear fluids and suspensions.

All-electrical detection of spin dynamics in magnetic antidot lattices by the inverse spin Hall effect

DOE PAGES

Jungfleisch, Matthias B.; Zhang, Wei; Ding, Junjia; ...

2016-02-03

The understanding of spin dynamics in laterally confined structures on sub-micron length scales has become a significant aspect of the development of novel magnetic storage technologies. Numerous ferromagnetic resonance measurements, optical characterization by Kerr microscopy and Brillouin light scattering spectroscopy and x-ray studies were carried out to detect the dynamics in patterned magnetic antidot lattices. Here, we investigate Oersted-field driven spin dynamics in rectangular Ni80Fe20/Pt antidot lattices with different lattice parameters by electrical means. When the system is driven to resonance, a dc voltage across the length of the sample is detected that changes its sign upon field reversal, whichmore » is in agreement with a rectification mechanism based on the inverse spin Hall effect. Furthermore, we show that the voltage output scales linearly with the applied microwave drive in the investigated range of powers. Lastly, our findings have direct implications on the development of engineered magnonics applications and devices.« less

Resistive switching characteristics of polymer non-volatile memory devices in a scalable via-hole structure.

PubMed

Kim, Tae-Wook; Choi, Hyejung; Oh, Seung-Hwan; Jo, Minseok; Wang, Gunuk; Cho, Byungjin; Kim, Dong-Yu; Hwang, Hyunsang; Lee, Takhee

2009-01-14

The resistive switching characteristics of polyfluorene-derivative polymer material in a sub-micron scale via-hole device structure were investigated. The scalable via-hole sub-microstructure was fabricated using an e-beam lithographic technique. The polymer non-volatile memory devices varied in size from 40 x 40 microm(2) to 200 x 200 nm(2). From the scaling of junction size, the memory mechanism can be attributed to the space-charge-limited current with filamentary conduction. Sub-micron scale polymer memory devices showed excellent resistive switching behaviours such as a large ON/OFF ratio (I(ON)/I(OFF) approximately 10(4)), excellent device-to-device switching uniformity, good sweep endurance, and good retention times (more than 10,000 s). The successful operation of sub-micron scale memory devices of our polyfluorene-derivative polymer shows promise to fabricate high-density polymer memory devices.

Contact resistance and overlapping capacitance in flexible sub-micron long oxide thin-film transistors for above 100 MHz operation

NASA Astrophysics Data System (ADS)

Münzenrieder, Niko; Salvatore, Giovanni A.; Petti, Luisa; Zysset, Christoph; Büthe, Lars; Vogt, Christian; Cantarella, Giuseppe; Tröster, Gerhard

2014-12-01

In recent years new forms of electronic devices such as electronic papers, flexible displays, epidermal sensors, and smart textiles have become reality. Thin-film transistors (TFTs) are the basic blocks of the circuits used in such devices and need to operate above 100 MHz to efficiently treat signals in RF systems and address pixels in high resolution displays. Beyond the choice of the semiconductor, i.e., silicon, graphene, organics, or amorphous oxides, the junctionless nature of TFTs and its geometry imply some limitations which become evident and important in devices with scaled channel length. Furthermore, the mechanical instability of flexible substrates limits the feature size of flexible TFTs. Contact resistance and overlapping capacitance are two parasitic effects which limit the transit frequency of transistors. They are often considered independent, while a deeper analysis of TFTs geometry imposes to handle them together; in fact, they both depend on the overlapping length (LOV) between source/drain and the gate contacts. Here, we conduct a quantitative analysis based on a large number of flexible ultra-scaled IGZO TFTs. Devices with three different values of overlap length and channel length down to 0.5 μm are fabricated to experimentally investigate the scaling behavior of the transit frequency. Contact resistance and overlapping capacitance depend in opposite ways on LOV. These findings establish routes for the optimization of the dimension of source/drain contact pads and suggest design guidelines to achieve megahertz operation in flexible IGZO TFTs and circuits.

Submicron bidirectional all-optical plasmonic switches

PubMed Central

Chen, Jianjun; Li, Zhi; Zhang, Xiang; Xiao, Jinghua; Gong, Qihuang

2013-01-01

Ultra-small all-optical switches are of importance in highly integrated optical communication and computing networks. However, the weak nonlinear light-matter interactions in natural materials present an enormous challenge to realize efficiently switching for the ultra-short interaction lengths. Here, we experimentally demonstrate a submicron bidirectional all-optical plasmonic switch with an asymmetric T-shape single slit. Sharp asymmetric spectra as well as significant field enhancements (about 18 times that in the conventional slit case) occur in the symmetry-breaking structure. Consequently, both of the surface plasmon polaritons propagating in the opposite directions on the metal surface are all-optically controlled inversely at the same time with the on/off switching ratios of >6 dB for the device lateral dimension of <1 μm. Moreover, in such a submicron structure, the coupling of free-space light and the on-chip bidirectional switching are integrated together. This submicron bidirectional all-optical switch may find important applications in the highly integrated plasmonic circuits. PMID:23486232

Formation of Titania Submicron-Scale Rod Arrays on Titanium Substrate and In Vitro Biocompatibility

DTIC Science & Technology

2005-01-01

vitro bioactivity. INTRODUCTION Commercially available pure titanium (c.p. Ti) and its alloys are widely used for dental and orthopedic implants because...days. DISCUSSION The submicron-scale rod arrays of rutile can be obtained on titanium surfaces after the heat treatment when the alkali- borate glass ...modification of titanium implants have been already developed or proposed to provide them with the ability of direct bonding to bone tissues. Note

Mechanical characterization of Ti-6Al-4V titanium alloy at multiple length scales using spherical indentation stress-strain measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan S.; Kalidindi, Surya R.

Recent advances in spherical indentation stress-strain protocols and analyses have demonstrated the capability for measuring reliably the local mechanical responses in polycrystalline metal samples at different length scales, ranging from sub-micron (regions within individual grains) to several hundreds of microns (regions covering several grains). These recent advances have now made it possible to study systematically the mechanical behavior of a single material system at different length scales, with tremendous potential to obtain new insights into the role of individual phases, interfaces, and other microscale constituents on the macroscale mechanical response of the material. In this paper, we report spherical indentationmore » stress-strain measurements with different indenter sizes (microns to millimeters) on Ti-6Al-4V (Ti-64) which capture the mechanical response of single phase alpha-Ti-64, single colony (alpha-beta), few colonies, and many colonies of Ti-64. The results show that the average mechanical response (indentation modulus and yield strength) from multiple indentations remains relatively unchanged from single phase alpha to many colonies of Ti-64, while the variance in the response decreases with indenter size. In conclusion, the work-hardening response in indentation tests follows a similar behavior up to indentation zones of many colonies, which shows significantly higher work hardening rates.« less

Mechanical characterization of Ti-6Al-4V titanium alloy at multiple length scales using spherical indentation stress-strain measurements

DOE PAGES

Weaver, Jordan S.; Kalidindi, Surya R.

2016-12-01

Recent advances in spherical indentation stress-strain protocols and analyses have demonstrated the capability for measuring reliably the local mechanical responses in polycrystalline metal samples at different length scales, ranging from sub-micron (regions within individual grains) to several hundreds of microns (regions covering several grains). These recent advances have now made it possible to study systematically the mechanical behavior of a single material system at different length scales, with tremendous potential to obtain new insights into the role of individual phases, interfaces, and other microscale constituents on the macroscale mechanical response of the material. In this paper, we report spherical indentationmore » stress-strain measurements with different indenter sizes (microns to millimeters) on Ti-6Al-4V (Ti-64) which capture the mechanical response of single phase alpha-Ti-64, single colony (alpha-beta), few colonies, and many colonies of Ti-64. The results show that the average mechanical response (indentation modulus and yield strength) from multiple indentations remains relatively unchanged from single phase alpha to many colonies of Ti-64, while the variance in the response decreases with indenter size. In conclusion, the work-hardening response in indentation tests follows a similar behavior up to indentation zones of many colonies, which shows significantly higher work hardening rates.« less

Stencil Nano Lithography Based on a Nanoscale Polymer Shadow Mask: Towards Organic Nanoelectronics

PubMed Central

Yun, Hoyeol; Kim, Sangwook; Kim, Hakseong; Lee, Junghyun; McAllister, Kirstie; Kim, Junhyung; Pyo, Sengmoon; Sung Kim, Jun; Campbell, Eleanor E. B.; Hyoung Lee, Wi; Wook Lee, Sang

2015-01-01

A stencil lithography technique has been developed to fabricate organic-material-based electronic devices with sub-micron resolution. Suspended polymethylmethacrylate (PMMA) membranes were used as shadow masks for defining organic channels and top electrodes. Arrays of pentacene field effect transistors (FETs) with various channel lengths from 50 μm down to 500 nm were successfully produced from the same batch using this technique. Electrical transport measurements showed that the electrical contacts of all devices were stable and the normalized contact resistances were much lower than previously studied organic FETs. Scaling effects, originating from the bulk space charge current, were investigated by analyzing the channel-length-dependent mobility and hysteresis behaviors. This novel lithography method provides a reliable means for studying the fundamental transport properties of organic materials at the nanoscale as well as enabling potential applications requiring the fabrication of integrated organic nanoelectronic devices. PMID:25959389

Stencil nano lithography based on a nanoscale polymer shadow mask: towards organic nanoelectronics.

PubMed

Yun, Hoyeol; Kim, Sangwook; Kim, Hakseong; Lee, Junghyun; McAllister, Kirstie; Kim, Junhyung; Pyo, Sengmoon; Sung Kim, Jun; Campbell, Eleanor E B; Hyoung Lee, Wi; Wook Lee, Sang

2015-05-11

A stencil lithography technique has been developed to fabricate organic-material-based electronic devices with sub-micron resolution. Suspended polymethylmethacrylate (PMMA) membranes were used as shadow masks for defining organic channels and top electrodes. Arrays of pentacene field effect transistors (FETs) with various channel lengths from 50 μm down to 500 nm were successfully produced from the same batch using this technique. Electrical transport measurements showed that the electrical contacts of all devices were stable and the normalized contact resistances were much lower than previously studied organic FETs. Scaling effects, originating from the bulk space charge current, were investigated by analyzing the channel-length-dependent mobility and hysteresis behaviors. This novel lithography method provides a reliable means for studying the fundamental transport properties of organic materials at the nanoscale as well as enabling potential applications requiring the fabrication of integrated organic nanoelectronic devices.

A study of microindentation hardness tests by mechanism-based strain gradient plasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Y.; Xue, Z.; Gao, H.

2000-08-01

We recently proposed a theory of mechanism-based strain gradient (MSG) plasticity to account for the size dependence of plastic deformation at micron- and submicron-length scales. The MSG plasticity theory connects micron-scale plasticity to dislocation theories via a multiscale, hierarchical framework linking Taylor's dislocation hardening model to strain gradient plasticity. Here we show that the theory of MSG plasticity, when used to study micro-indentation, indeed reproduces the linear dependence observed in experiments, thus providing an important self-consistent check of the theory. The effects of pileup, sink-in, and the radius of indenter tip have been taken into account in the indentation model.more » In accomplishing this objective, we have generalized the MSG plasticity theory to include the elastic deformation in the hierarchical framework. (c) 2000 Materials Research Society.« less

Acoustic Emission Patterns and the Transition to Ductility in Sub-Micron Scale Laboratory Earthquakes

NASA Astrophysics Data System (ADS)

Ghaffari, H.; Xia, K.; Young, R.

2013-12-01

We report observation of a transition from the brittle to ductile regime in precursor events from different rock materials (Granite, Sandstone, Basalt, and Gypsum) and Polymers (PMMA, PTFE and CR-39). Acoustic emission patterns associated with sub-micron scale laboratory earthquakes are mapped into network parameter spaces (functional damage networks). The sub-classes hold nearly constant timescales, indicating dependency of the sub-phases on the mechanism governing the previous evolutionary phase, i.e., deformation and failure of asperities. Based on our findings, we propose that the signature of the non-linear elastic zone around a crack tip is mapped into the details of the evolutionary phases, supporting the formation of a strongly weak zone in the vicinity of crack tips. Moreover, we recognize sub-micron to micron ruptures with signatures of 'stiffening' in the deformation phase of acoustic-waveforms. We propose that the latter rupture fronts carry critical rupture extensions, including possible dislocations faster than the shear wave speed. Using 'template super-shear waveforms' and their network characteristics, we show that the acoustic emission signals are possible super-shear or intersonic events. Ref. [1] Ghaffari, H. O., and R. P. Young. "Acoustic-Friction Networks and the Evolution of Precursor Rupture Fronts in Laboratory Earthquakes." Nature Scientific reports 3 (2013). [2] Xia, Kaiwen, Ares J. Rosakis, and Hiroo Kanamori. "Laboratory earthquakes: The sub-Rayleigh-to-supershear rupture transition." Science 303.5665 (2004): 1859-1861. [3] Mello, M., et al. "Identifying the unique ground motion signatures of supershear earthquakes: Theory and experiments." Tectonophysics 493.3 (2010): 297-326. [4] Gumbsch, Peter, and Huajian Gao. "Dislocations faster than the speed of sound." Science 283.5404 (1999): 965-968. [5] Livne, Ariel, et al. "The near-tip fields of fast cracks." Science 327.5971 (2010): 1359-1363. [6] Rycroft, Chris H., and Eran Bouchbinder. "Fracture Toughness of Metallic Glasses: Annealing-Induced Embrittlement." Physical review letters 109.19 (2012): 194301. [7] Buehler, Markus J., Farid F. Abraham, and Huajian Gao. "Hyperelasticity governs dynamic fracture at a critical length scale." Nature 426.6963 (2003): 141-146.

High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy

PubMed Central

Hihath, Sahar; Santala, Melissa K.; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

2016-01-01

Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combination of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Our results allow for improved safety during laser ablation in manufacturing and medical applications. PMID:26965073

High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy

DOE PAGES

Hihath, Sahar; Santala, Melissa K.; Cen, Xi; ...

2016-03-11

Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combinationmore » of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Ultimately, our results allow for improved safety during laser ablation in manufacturing and medical applications.« less

High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy

NASA Astrophysics Data System (ADS)

Hihath, Sahar; Santala, Melissa K.; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

2016-03-01

Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combination of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Our results allow for improved safety during laser ablation in manufacturing and medical applications.

High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy.

PubMed

Hihath, Sahar; Santala, Melissa K; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

2016-03-11

Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combination of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Our results allow for improved safety during laser ablation in manufacturing and medical applications.

Carbonized Micro- and Nanostructures: Can Downsizing Really Help?

PubMed Central

Naraghi, Mohammad; Chawla, Sneha

2014-01-01

In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs) with diameters of 5–10 μm to submicron thick carbon nanofibers (CNFs). Our research points to radial inhomogeneity, skin–core structure, as a size-dependent feature of polyacrylonitrile-based CFs. This inhomogeneity is a surface effect, caused by suppressed diffusion of oxygen and stabilization byproducts during stabilization through skin. Hence, reducing the precursor diameters from tens of microns to submicron appears as an effective strategy to develop homogeneous carbonized structures. Our research establishes the significance of this downsizing in developing lightweight structural materials by comparing intrinsic strength of radially inhomogeneous CFs with that of radially homogeneous CNF. While experimental studies on the strength of CNFs have targeted randomly oriented turbostratic domains, via continuum modeling, we have estimated that strength of CNFs can reach 14 GPa, when the basal planes of graphitic domains are parallel to nanofiber axis. The CNFs in our model are treated as composites of amorphous carbon (matrix), reinforced with turbostratic domains, and their strength is predicted using Tsai–Hill criterion. The model was calibrated with existing experimental data. PMID:28788651

Complex, multi-scale small intestinal topography replicated in cellular growth substrates fabricated via chemical vapor deposition of Parylene C.

PubMed

Koppes, Abigail N; Kamath, Megha; Pfluger, Courtney A; Burkey, Daniel D; Dokmeci, Mehmet; Wang, Lin; Carrier, Rebecca L

2016-08-22

Native small intestine possesses distinct multi-scale structures (e.g., crypts, villi) not included in traditional 2D intestinal culture models for drug delivery and regenerative medicine. The known impact of structure on cell function motivates exploration of the influence of intestinal topography on the phenotype of cultured epithelial cells, but the irregular, macro- to submicron-scale features of native intestine are challenging to precisely replicate in cellular growth substrates. Herein, we utilized chemical vapor deposition of Parylene C on decellularized porcine small intestine to create polymeric intestinal replicas containing biomimetic irregular, multi-scale structures. These replicas were used as molds for polydimethylsiloxane (PDMS) growth substrates with macro to submicron intestinal topographical features. Resultant PDMS replicas exhibit multiscale resolution including macro- to micro-scale folds, crypt and villus structures, and submicron-scale features of the underlying basement membrane. After 10 d of human epithelial colorectal cell culture on PDMS substrates, the inclusion of biomimetic topographical features enhanced alkaline phosphatase expression 2.3-fold compared to flat controls, suggesting biomimetic topography is important in induced epithelial differentiation. This work presents a facile, inexpensive method for precisely replicating complex hierarchal features of native tissue, towards a new model for regenerative medicine and drug delivery for intestinal disorders and diseases.

Stress transfer mechanisms at the submicron level for graphene/polymer systems.

PubMed

Anagnostopoulos, George; Androulidakis, Charalampos; Koukaras, Emmanuel N; Tsoukleri, Georgia; Polyzos, Ioannis; Parthenios, John; Papagelis, Konstantinos; Galiotis, Costas

2015-02-25

The stress transfer mechanism from a polymer substrate to a nanoinclusion, such as a graphene flake, is of extreme interest for the production of effective nanocomposites. Previous work conducted mainly at the micron scale has shown that the intrinsic mechanism of stress transfer is shear at the interface. However, since the interfacial shear takes its maximum value at the very edge of the nanoinclusion it is of extreme interest to assess the effect of edge integrity upon axial stress transfer at the submicron scale. Here, we conduct a detailed Raman line mapping near the edges of a monolayer graphene flake that is simply supported onto an epoxy-based photoresist (SU8)/poly(methyl methacrylate) matrix at steps as small as 100 nm. We show for the first time that the distribution of axial strain (stress) along the flake deviates somewhat from the classical shear-lag prediction for a region of ∼ 2 μm from the edge. This behavior is mainly attributed to the presence of residual stresses, unintentional doping, and/or edge effects (deviation from the equilibrium values of bond lengths and angles, as well as different edge chiralities). By considering a simple balance of shear-to-normal stresses at the interface we are able to directly convert the strain (stress) gradient to values of interfacial shear stress for all the applied tensile levels without assuming classical shear-lag behavior. For large flakes a maximum value of interfacial shear stress of 0.4 MPa is obtained prior to flake slipping.

Probing the electrical switching of a memristive optical antenna by STEM EELS

PubMed Central

Schoen, David T.; Holsteen, Aaron L.; Brongersma, Mark L.

2016-01-01

The scaling of active photonic devices to deep-submicron length scales has been hampered by the fundamental diffraction limit and the absence of materials with sufficiently strong electro-optic effects. Plasmonics is providing new opportunities to circumvent this challenge. Here we provide evidence for a solid-state electro-optical switching mechanism that can operate in the visible spectral range with an active volume of less than (5 nm)3 or ∼10−6 λ3, comparable to the size of the smallest electronic components. The switching mechanism relies on electrochemically displacing metal atoms inside the nanometre-scale gap to electrically connect two crossed metallic wires forming a cross-point junction. These junctions afford extreme light concentration and display singular optical behaviour upon formation of a conductive channel. The active tuning of plasmonic antennas attached to such junctions is analysed using a combination of electrical and optical measurements as well as electron energy loss spectroscopy in a scanning transmission electron microscope. PMID:27412052

Sintering mantle mineral aggregates with submicron grains: examples of olivine and clinopyroxene

NASA Astrophysics Data System (ADS)

Tsubokawa, Y.; Ishikawa, M.

2017-12-01

Physical property of the major mantle minerals play an important role in the dynamic behavior of the Earth's mantle. Recently, it has been found that nano- to sub-micron scale frictional processes might control faulting processes and earthquake instability, and ultrafine-grained mineral aggregates thus have attracted the growing interest. Here we investigated a method for preparing polycrystalline clinoyproxene and polycrystalline olivine with grain size of sub-micron scale from natural crystals, two main constituents of the upper mantle. Nano-sized powders of both minerals are sintered under argon flow at temperatures ranging from 1130-1350 °C for 0.5-20 h. After sintering at 1180 °C and 1300 °C, we successfully fabricated polycrystalline clinopyroxene and polycrystalline olivine with grain size of < 500 nm, respectively. Our experiments demonstrate future measurements of ultrafine-grained mineral aggregates on its physical properties of Earth's mantle.

Fabrication and electrical characterization of sub-micron diameter through-silicon via for heterogeneous three-dimensional integrated circuits

NASA Astrophysics Data System (ADS)

Abbaspour, R.; Brown, D. K.; Bakir, M. S.

2017-02-01

This paper presents the fabrication and electrical characterization of high aspect-ratio (AR) sub-micron diameter through silicon vias (TSVs) for densely interconnected three-dimensional (3D) stacked integrated circuits (ICs). The fabricated TSV technology features an AR of 16:1 with 680 nm diameter copper (Cu) core and 920 nm overall diameter. To address the challenges in scaling TSVs, scallop-free low roughness nano-Bosch silicon etching and direct Cu electroplating on a titanium-nitride (TiN) diffusion barrier layer have been developed as key enabling modules. The electrical resistance of the sub-micron TSVs is measured to be on average 1.2 Ω, and the Cu resistivity is extracted to be approximately 2.95 µΩ cm. Furthermore, the maximum achievable current-carrying capacity (CCC) of the scaled TSVs is characterized to be approximately 360 µA for the 680 nm Cu core.

Electron beam fabrication of a microfluidic device for studying submicron-scale bacteria

PubMed Central

2013-01-01

Background Controlled restriction of cellular movement using microfluidics allows one to study individual cells to gain insight into aspects of their physiology and behaviour. For example, the use of micron-sized growth channels that confine individual Escherichia coli has yielded novel insights into cell growth and death. To extend this approach to other species of bacteria, many of whom have dimensions in the sub-micron range, or to a larger range of growth conditions, a readily-fabricated device containing sub-micron features is required. Results Here we detail the fabrication of a versatile device with growth channels whose widths range from 0.3 μm to 0.8 μm. The device is fabricated using electron beam lithography, which provides excellent control over the shape and size of different growth channels and facilitates the rapid-prototyping of new designs. Features are successfully transferred first into silicon, and subsequently into the polydimethylsiloxane that forms the basis of the working microfluidic device. We demonstrate that the growth of sub-micron scale bacteria such as Lactococcus lactis or Escherichia coli cultured in minimal medium can be followed in such a device over several generations. Conclusions We have presented a detailed protocol based on electron beam fabrication together with specific dry etching procedures for the fabrication of a microfluidic device suited to study submicron-sized bacteria. We have demonstrated that both Gram-positive and Gram-negative bacteria can be successfully loaded and imaged over a number of generations in this device. Similar devices could potentially be used to study other submicron-sized organisms under conditions in which the height and shape of the growth channels are crucial to the experimental design. PMID:23575419

Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zimmermann, Elizabeth A.; Schaible, Eric; Bale, Hrishikesh

2011-08-10

The structure of human cortical bone evolves over multiple length-scales from its basic constituents of collagen and hydroxyapatite at the nanoscale to osteonal structures at nearmillimeter dimensions, which all provide the basis for its mechanical properties. To resist fracture, bone’s toughness is derived intrinsically through plasticity (e.g., fibrillar sliding) at structural-scales typically below a micron and extrinsically (i.e., during crack growth) through mechanisms (e.g., crack deflection/bridging) generated at larger structural-scales. Biological factors such as aging lead to a markedly increased fracture risk, which is often associated with an age-related loss in bone mass (bone quantity). However, we find that age-relatedmore » structural changes can significantly degrade the fracture resistance (bone quality) over multiple lengthscales. Using in situ small-/wide-angle x-ray scattering/diffraction to characterize sub-micron structural changes and synchrotron x-ray computed tomography and in situ fracture-toughness measurements in the scanning electron microscope to characterize effects at micron-scales, we show how these age-related structural changes at differing size-scales degrade both the intrinsic and extrinsic toughness of bone. Specifically, we attribute the loss in toughness to increased non-enzymatic collagen cross-linking which suppresses plasticity at nanoscale dimensions and to an increased osteonal density which limits the potency of crack-bridging mechanisms at micron-scales. The link between these processes is that the increased stiffness of the cross-linked collagen requires energy to be absorbed by “plastic” deformation at higher structural levels, which occurs by the process of microcracking.« less

Spatially Resolved Distribution of Fe Species around Microbes at the Submicron Scale in Natural Bacteriogenic Iron Oxides.

PubMed

Suga, Hiroki; Kikuchi, Sakiko; Takeichi, Yasuo; Miyamoto, Chihiro; Miyahara, Masaaki; Mitsunobu, Satoshi; Ohigashi, Takuji; Mase, Kazuhiko; Ono, Kanta; Takahashi, Yoshio

2017-09-27

Natural bacteriogenic iron oxides (BIOS) were investigated using local-analyzable synchrotron-based scanning transmission X-ray microscopy (STXM) with a submicron-scale resolution. Cell, cell sheath interface (EPS), and sheath in the BIOS were clearly depicted using C-, N-, and O- near edge X-ray absorption fine structure (NEXAFS) obtained through STXM measurements. Fe-NEXAFS obtained from different regions of BIOS indicated that the most dominant iron mineral species was ferrihydrite. Fe(II)- and/or Fe(III)-acidic polysaccharides accompanied ferrihydrite near the cell and EPS regions. Our STXM/NEXAFS analysis showed that Fe species change continuously between the cell, EPS, and sheath under several 10-nm scales.

Impact of Device Scaling on Deep Sub-micron Transistor Reliability: A Study of Reliability Trends using SRAM

NASA Technical Reports Server (NTRS)

White, Mark; Huang, Bing; Qin, Jin; Gur, Zvi; Talmor, Michael; Chen, Yuan; Heidecker, Jason; Nguyen, Duc; Bernstein, Joseph

2005-01-01

As microelectronics are scaled in to the deep sub-micron regime, users of advanced technology CMOS, particularly in high-reliability applications, should reassess how scaling effects impact long-term reliability. An experimental based reliability study of industrial grade SRAMs, consisting of three different technology nodes, is proposed to substantiate current acceleration models for temperature and voltage life-stress relationships. This reliability study utilizes step-stress techniques to evaluate memory technologies (0.25mum, 0.15mum, and 0.13mum) embedded in many of today's high-reliability space/aerospace applications. Two acceleration modeling approaches are presented to relate experimental FIT calculations to Mfr's qualification data.

Advances toward submicron resolution optics for x-ray instrumentation and applications

NASA Astrophysics Data System (ADS)

Cordier, Mark; Stripe, Benjamin; Yun, Wenbing; Lau, S. H.; Lyon, Alan; Reynolds, David; Lewis, Sylvia J. Y.; Chen, Sharon; Semenov, Vladimir A.; Spink, Richard I.; Seshadri, Srivatsan

2017-08-01

Sigray's axially symmetric x-ray optics enable advanced microanalytical capabilities for focusing x-rays to microns-scale to submicron spot sizes, which can potentially unlock many avenues for laboratory micro-analysis. The design of these optics allows submicron spot sizes even at low x-ray energies, enabling research into low atomic number elements and allows increased sensitivity of grazing incidence measurements and surface analysis. We will discuss advances made in the fabrication of these double paraboloidal mirror lenses designed for use in laboratory x-ray applications. We will additionally present results from as-built paraboloids, including surface figure error and focal spot size achieved to-date.

Fabrication of submicron structures in nanoparticle/polymer composite by holographic lithography and reactive ion etching

NASA Astrophysics Data System (ADS)

Zhang, A. Ping; He, Sailing; Kim, Kyoung Tae; Yoon, Yong-Kyu; Burzynski, Ryszard; Samoc, Marek; Prasad, Paras N.

2008-11-01

We report on the fabrication of nanoparticle/polymer submicron structures by combining holographic lithography and reactive ion etching. Silica nanoparticles are uniformly dispersed in a (SU8) polymer matrix at a high concentration, and in situ polymerization (cross-linking) is used to form a nanoparticle/polymer composite. Another photosensitive SU8 layer cast upon the nanoparticle/SU8 composite layer is structured through holographic lithography, whose pattern is finally transferred to the nanoparticle/SU8 layer by the reactive ion etching process. Honeycomb structures in a submicron scale are experimentally realized in the nanoparticle/SU8 composite.

A novel low temperature soft reflow process for the fabrication of deep-submicron (<0.35 μm) T-gate pseudomorphic high electron mobility transistor structures

NASA Astrophysics Data System (ADS)

Ian, Ka Wa; Exarchos, Michael; Missous, Mohamed

2013-02-01

We report a new and simple low temperature soft reflow process using solvent vapour. The combination of this soft reflow and conventional i-line lithography enables low cost, highly efficient fabrication at the deep-submicron scale. Compared to the conventional thermal reflow process, the key benefits of the new soft reflow process are its low temperature operation (<50 °C), greater shrinkage of the structure size (up to 75%) and better controllability. Gate openings reflowed from 1 μm to 250 nm have been routinely and reproducibly achieved by utilizing the saturation characteristics of the process. The feasibility of this soft reflow process is demonstrated in the fabrication of a 350 nm T-gate pseudomorphic high electron mobility transistor. By shrinking the gate length by a factor of three (from a 1 μm initial opening), the output current is improved by 60% (500 mA mm-1 from 300 mA mm-1) and fT and fMAX are increased to 70 GHz (from 20 GHz) and 120 GHz (from 40 GHz) respectively. The proposed soft reflow could potentially be applied on other compatible substrates such as polymer based material for organic or thin film devices, potentially leading to many new possible applications.

Stress Transfer Mechanisms at the Submicron Level for Graphene/Polymer Systems

PubMed Central

2015-01-01

The stress transfer mechanism from a polymer substrate to a nanoinclusion, such as a graphene flake, is of extreme interest for the production of effective nanocomposites. Previous work conducted mainly at the micron scale has shown that the intrinsic mechanism of stress transfer is shear at the interface. However, since the interfacial shear takes its maximum value at the very edge of the nanoinclusion it is of extreme interest to assess the effect of edge integrity upon axial stress transfer at the submicron scale. Here, we conduct a detailed Raman line mapping near the edges of a monolayer graphene flake that is simply supported onto an epoxy-based photoresist (SU8)/poly(methyl methacrylate) matrix at steps as small as 100 nm. We show for the first time that the distribution of axial strain (stress) along the flake deviates somewhat from the classical shear-lag prediction for a region of ∼2 μm from the edge. This behavior is mainly attributed to the presence of residual stresses, unintentional doping, and/or edge effects (deviation from the equilibrium values of bond lengths and angles, as well as different edge chiralities). By considering a simple balance of shear-to-normal stresses at the interface we are able to directly convert the strain (stress) gradient to values of interfacial shear stress for all the applied tensile levels without assuming classical shear-lag behavior. For large flakes a maximum value of interfacial shear stress of 0.4 MPa is obtained prior to flake slipping. PMID:25644121

Changes of propagation light in optical fiber submicron wires

NASA Astrophysics Data System (ADS)

Stasiewicz, K. A.; Łukowski, A.; Jaroszewicz, L. R.

2013-05-01

At the moment technology allows to miniaturize measurement system to several micrometers. Application of an optical fiber taper in such system needs to manufacture a new one with diameters below single micrometers which is very difficult and expensive. Another way to obtain this level of diameters is the process of tapering from the existing fibers. In the paper, experimental results of propagation light from a supercontinnum sources of the wavelength generates the wavelength of 350-2000 nm, in different optical fiber submicron wires made from tapers manufactured from single mode fibers are presented. Biconical optical fibers' tapers were manufactured in low pressure gas burner technique. There are presented spectral characteristics of a propagated beam. For the test, there was manufactured an optical fiber submicron wires with a different length of waist region with a diameter near one micrometer. We put to the test a taper made from a standard telecommunication fiber SMF-28 with a cutoff wavelength equal to 1260.

A Facile Method for Separating and Enriching Nano and Submicron Particles from Titanium Dioxide Found in Food and Pharmaceutical Products.

PubMed

Faust, James J; Doudrick, Kyle; Yang, Yu; Capco, David G; Westerhoff, Paul

2016-01-01

Recent studies indicate the presence of nano-scale titanium dioxide (TiO2) as an additive in human foodstuffs, but a practical protocol to isolate and separate nano-fractions from soluble foodstuffs as a source of material remains elusive. As such, we developed a method for separating the nano and submicron fractions found in commercial-grade TiO2 (E171) and E171 extracted from soluble foodstuffs and pharmaceutical products (e.g., chewing gum, pain reliever, and allergy medicine). Primary particle analysis of commercial-grade E171 indicated that 54% of particles were nano-sized (i.e., < 100 nm). Isolation and primary particle analysis of five consumer goods intended to be ingested revealed differences in the percent of nano-sized particles from 32%‒58%. Separation and enrichment of nano- and submicron-sized particles from commercial-grade E171 and E171 isolated from foodstuffs and pharmaceuticals was accomplished using rate-zonal centrifugation. Commercial-grade E171 was separated into nano- and submicron-enriched fractions consisting of a nano:submicron fraction of approximately 0.45:1 and 3.2:1, respectively. E171 extracted from gum had nano:submicron fractions of 1.4:1 and 0.19:1 for nano- and submicron-enriched, respectively. We show a difference in particle adhesion to the cell surface, which was found to be dependent on particle size and epithelial orientation. Finally, we provide evidence that E171 particles are not immediately cytotoxic to the Caco-2 human intestinal epithelium model. These data suggest that this separation method is appropriate for studies interested in isolating the nano-sized particle fraction taken directly from consumer products, in order to study separately the effects of nano and submicron particles.

A Facile Method for Separating and Enriching Nano and Submicron Particles from Titanium Dioxide Found in Food and Pharmaceutical Products

PubMed Central

Yang, Yu; Capco, David G.; Westerhoff, Paul

2016-01-01

Recent studies indicate the presence of nano-scale titanium dioxide (TiO2) as an additive in human foodstuffs, but a practical protocol to isolate and separate nano-fractions from soluble foodstuffs as a source of material remains elusive. As such, we developed a method for separating the nano and submicron fractions found in commercial-grade TiO2 (E171) and E171 extracted from soluble foodstuffs and pharmaceutical products (e.g., chewing gum, pain reliever, and allergy medicine). Primary particle analysis of commercial-grade E171 indicated that 54% of particles were nano-sized (i.e., < 100 nm). Isolation and primary particle analysis of five consumer goods intended to be ingested revealed differences in the percent of nano-sized particles from 32%‒58%. Separation and enrichment of nano- and submicron-sized particles from commercial-grade E171 and E171 isolated from foodstuffs and pharmaceuticals was accomplished using rate-zonal centrifugation. Commercial-grade E171 was separated into nano- and submicron-enriched fractions consisting of a nano:submicron fraction of approximately 0.45:1 and 3.2:1, respectively. E171 extracted from gum had nano:submicron fractions of 1.4:1 and 0.19:1 for nano- and submicron-enriched, respectively. We show a difference in particle adhesion to the cell surface, which was found to be dependent on particle size and epithelial orientation. Finally, we provide evidence that E171 particles are not immediately cytotoxic to the Caco-2 human intestinal epithelium model. These data suggest that this separation method is appropriate for studies interested in isolating the nano-sized particle fraction taken directly from consumer products, in order to study separately the effects of nano and submicron particles. PMID:27798677

Large-scale self-assembly of uniform submicron silver sulfide material driven by precise pressure control

NASA Astrophysics Data System (ADS)

Qi, Juanjuan; Chen, Ke; Zhang, Shuhao; Yang, Yun; Guo, Lin; Yang, Shihe

2017-03-01

The controllable self-assembly of nanosized building blocks into larger specific structures can provide an efficient method of synthesizing novel materials with excellent properties. The self-assembly of nanocrystals by assisted means is becoming an extremely active area of research, because it provides a method of producing large-scale advanced functional materials with potential applications in the areas of energy, electronics, optics, and biologics. In this study, we applied an efficient strategy, namely, the use of ‘pressure control’ to the assembly of silver sulfide (Ag2S) nanospheres with a diameter of approximately 33 nm into large-scale, uniform Ag2S sub-microspheres with a size of about 0.33 μm. More importantly, this strategy realizes the online control of the overall reaction system, including the pressure, reaction time, and temperature, and could also be used to easily fabricate other functional materials on an industrial scale. Moreover, the thermodynamics and kinetics parameters for the thermal decomposition of silver diethyldithiocarbamate (Ag(DDTC)) are also investigated to explore the formation mechanism of the Ag2S nanosized building blocks which can be assembled into uniform sub-micron scale architecture. As a method of producing sub-micron Ag2S particles by means of the pressure-controlled self-assembly of nanoparticles, we foresee this strategy being an efficient and universally applicable option for constructing other new building blocks and assembling novel and large functional micromaterials on an industrial scale.

Mechanical Properties of Organized Microcomposites Fabricated by Interference Lithography

NASA Astrophysics Data System (ADS)

Singamaneni, Srikanth; Chang, Sehoon; Jang, Ji-Hyun; Davis, Whitney; Thomas, Edwin; Tsukruk, Vladimir

2009-03-01

We demonstrate that organized, porous, polymer microstructures with continuous open nanoscale pores and sub-micron spacings obtained via interference lithography can be successfully utilized in a highly non-traditional field of ordered microcomposites. Organized microcomposite structures are fabricated by employing two independent strategies, namely, capillary infiltration and in situ polymerization of the rubbery component into the porous glassy microframes. The mechanical properties and ultimate fracture behavior of the single and bicomponent microframes are investigated at different length scales. The ordered single and bi-component microstructures with high degree of control over the microscopic organization of the polymeric phases result in excellent mechanical properties. Combining hard and soft polymer components provides multifunctional materials and coatings with synergetic properties and is frequently utilized for design of advanced polymeric composites.

Rapid fabrication of micro-nanometric tapered fiber lens and characterization by a novel scanning optical microscope with submicron resolution.

PubMed

Zheng, Shouguo; Zeng, Xinhua; Luo, Wei; Jradi, Safi; Plain, Jérôme; Li, Miao; Renaud-Goud, Philippe; Deturche, Régis; Wang, Zengfu; Kou, Jieting; Bachelot, Renaud; Royer, Pascal

2013-01-14

In numerous applications of optical scanning microscopy, a reference tapered fiber lens with high symmetry at sub-wavelength scale remains a challenge. Here, we demonstrate the ability to manufacture it with a wide range of geometry control, either for the length from several hundred nanometers to several hundred microns, or for the curvature radius from several tens of nanometers to several microns on the endface of a single mode fiber. On this basis, a scanning optical microscope has been developed, which allows for fast characterization of various sub-wavelength tapered fiber lenses. Focal position and depth of microlenses with different geometries have been determined to be ranged from several hundreds of nanometers to several microns. FDTD calculations are consistent with experimental results.

The fabrication of integrated carbon pipes with sub-micron diameters

NASA Astrophysics Data System (ADS)

Kim, B. M.; Murray, T.; Bau, H. H.

2005-08-01

A method for fabricating integrated carbon pipes (nanopipettes) of sub-micron diameters and tens of microns in length is demonstrated. The carbon pipes are formed from a template consisting of the tip of a pulled alumino-silicate glass capillary coated with carbon deposited from a vapour phase. This method renders carbon nanopipettes without the need for ex situ assembly and facilitates parallel production of multiple carbon-pipe devices. An electric-field-driven transfer of ions in a KCl solution through the integrated carbon pipes exhibits nonlinear current-voltage (I-V) curves, markedly different from the Ohmic I-V curves observed in glass pipettes under similar conditions. The filling of the nanopipette with fluorescent suspension is also demonstrated.

New strategies for submicron characterization the carbon binding of reactive minerals in long-term contrasting fertilized soils: implications for soil carbon storage

NASA Astrophysics Data System (ADS)

Xiao, Jian; He, Xinhua; Hao, Jialong; Zhou, Ying; Zheng, Lirong; Ran, Wei; Shen, Qirong; Yu, Guanghui

2016-06-01

Mineral binding is a major mechanism for soil carbon (C) stabilization. However, the submicron information about the in situ mechanisms of different fertilization practices affecting organo-mineral complexes and associated C preservation remains unclear. Here, we applied nano-scale secondary ion mass spectrometry (NanoSIMS), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS) to examine differentiating effects of inorganic versus organic fertilization on interactions between highly reactive minerals and soil C preservation. To examine such interactions, soils and their extracted colloids were collected during a 24-year long-term fertilization period (1990-2014) (no fertilization, control; chemical nitrogen (N), phosphorus (P), and potassium (K) fertilization, NPK; and NPK plus swine manure fertilization, NPKM). The results for different fertilization conditions showed a ranked soil organic matter concentration with NPKM > NPK > control. Meanwhile, oxalate-extracted Al (Alo), Fe (Feo), short-range ordered Al (Alxps), Fe (Fexps), and dissolved organic carbon (DOC) ranked with NPKM > control > NPK, but the ratios of DOC / Alxps and DOC / Fexps ranked with NPKM > NPK > control. Compared with the NPK treatment, the NPKM treatment enhanced the C-binding loadings of Al and Fe minerals in soil colloids at the submicron scale. Furthermore, a greater concentration of highly reactive Al and Fe minerals was presented under NPKM than under NPK. Together, these submicron-scale findings suggest that both the reactive mineral species and their associations with C are differentially affected by 24-year long-term inorganic and organic fertilization.

2D materials in electro-optic modulation: energy efficiency, electrostatics, mode overlap, material transfer and integration

NASA Astrophysics Data System (ADS)

Ma, Zhizhen; Hemnani, Rohit; Bartels, Ludwig; Agarwal, Ritesh; Sorger, Volker J.

2018-02-01

Here we discuss the physics of electro-optic modulators deploying 2D materials. We include a scaling laws analysis and show how energy-efficiency and speed change for three underlying cavity systems as a function of critical device length scaling. A key result is that the energy-per-bit of the modulator is proportional to the volume of the device, thus making the case for submicron-scale modulators possible deploying a plasmonic optical mode. We then show how Graphene's Pauli-blocking modulation mechanism is sensitive to the device operation temperature, whereby a reduction of the temperature enables a 10× reduction in modulator energy efficiency. Furthermore, we show how the high-index tunability of graphene is able to compensate for the small optical overlap factor of 2D-based material modulators, which is unlike classical silicon-based dispersion devices. Lastly, we demonstrate a novel method towards a 2D material printer suitable for cross-contamination free and on-demand printing. The latter paves the way to integrate 2D materials seamlessly into taped-out photonic chips.

Optical manipulation of lipid and polymer nanotubes with optical tweezers

NASA Astrophysics Data System (ADS)

Reiner, Joseph E.; Kishore, Rani; Pfefferkorn, Candace; Wells, Jeffrey; Helmerson, Kristian; Howell, Peter; Vreeland, Wyatt; Forry, Samuel; Locascio, Laurie; Reyes-Hernandez, Darwin; Gaitan, Michael

2004-10-01

Using optical tweezers and microfluidics, we stretch either the lipid or polymer membranes of liposomes or polymersomes, respectively, into long nanotubes. The membranes can be grabbed directly with the optical tweezers to produce sub-micron diameter tubes that are several hundred microns in length. We can stretch tubes up to a centimeter in length, limited only by the travel of our microscope stage. We also demonstrate the cross linking of a pulled polymer nanotube.

Photonic Devices Based on Surface and Composition-Engineered Infrared Colloidal Nanocrystals

DTIC Science & Technology

2012-01-27

NQD/P3HT solar cells , the need for submicron-phase-separated polymer-NQD blends is therefore expressed by the limiting exciton diffusion length ...P3HT:PbSe are very critical in designing the PM-HJ solar cells : The thickness of P3HT should approximate to the thickness of exciton diffuse length in... cells , luminescent solar concentrators, light emitting diodes, lasers, photonic crystals, CdSe, PbSe, Germanium Jian Xu Pennsylvania State University

Synchrotron-based X-ray fluorescence microscopy enables multiscale spatial visualization of ions involved in fungal lignocellulose deconstruction

NASA Astrophysics Data System (ADS)

Kirker, Grant; Zelinka, Sam; Gleber, Sophie-Charlotte; Vine, David; Finney, Lydia; Chen, Si; Hong, Young Pyo; Uyarte, Omar; Vogt, Stefan; Jellison, Jody; Goodell, Barry; Jakes, Joseph E.

2017-01-01

The role of ions in the fungal decay process of lignocellulose biomaterials, and more broadly fungal metabolism, has implications for diverse research disciplines ranging from plant pathology and forest ecology, to carbon sequestration. Despite the importance of ions in fungal decay mechanisms, the spatial distribution and quantification of ions in lignocellulosic cell walls and fungal hyphae during decay is not known. Here we employ synchrotron-based X-ray fluorescence microscopy (XFM) to map and quantify physiologically relevant ions, such as K, Ca, Mn, Fe, and Zn, in wood being decayed by the model brown rot fungus Serpula lacrymans. Two-dimensional XFM maps were obtained to study the ion spatial distributions from mm to submicron length scales in wood, fungal hyphae with the dried extracellular matrix (ECM) from the fungus, and Ca oxalate crystals. Three-dimensional ion volume reconstructions were also acquired of wood cell walls and hyphae with ECM. Results show that the fungus actively transports some ions, such as Fe, into the wood and controls the distribution of ions at both the bulk wood and cell wall length scales. These measurements provide new insights into the movement of ions during decay and illustrate how synchrotron-based XFM is uniquely suited study these ions.

High-order multipole radiation from quantum Hall states in Dirac materials

NASA Astrophysics Data System (ADS)

Gullans, Michael J.; Taylor, Jacob M.; Imamoǧlu, Ataç; Ghaemi, Pouyan; Hafezi, Mohammad

2017-06-01

We investigate the optical response of strongly disordered quantum Hall states in two-dimensional Dirac materials and find qualitatively different effects in the radiation properties of the bulk versus the edge. We show that the far-field radiation from the edge is characterized by large multipole moments (>50 ) due to the efficient transfer of angular momentum from the electrons into the scattered light. The maximum multipole transition moment is a direct measure of the coherence length of the edge states. Accessing these multipole transitions would provide new tools for optical spectroscopy and control of quantum Hall edge states. On the other hand, the far-field radiation from the bulk appears as random dipole emission with spectral properties that vary with the local disorder potential. We determine the conditions under which this bulk radiation can be used to image the disorder landscape. Such optical measurements can probe submicron-length scales over large areas and provide complementary information to scanning probe techniques. Spatially resolving this bulk radiation would serve as a novel probe of the percolation transition near half filling.

Using a micro-molding process to fabricate polymeric wavelength filters

NASA Astrophysics Data System (ADS)

Chuang, Wei-Ching; Lee, An-Chen; Ho, Chi-Ting

2008-08-01

A procedure for fabricating a high aspect ratio periodic structure on a UV polymer at submicron order using holographic interferometry and molding processes is described. First, holographic interferometry using a He-Cd (325 nm) laser was used to create the master of the periodic line structure on an i-line sub-micron positive photoresist film. A 20 nm nickel thin film was then sputtered on the photoresist. The final line pattern on a UV polymer was obtained from casting against the master mold. Finally, a SU8 polymer was spun on the polymer grating to form a planar waveguide or a channel waveguide. The measurement results show that the waveguide length could be reduced for the waveguide having gratings with a high aspect ratio.

CMOS-compatible batch processing of monolayer MoS2 MOSFETs

NASA Astrophysics Data System (ADS)

Xiong, Kuanchen; Kim, Hyun; Marstell, Roderick J.; Göritz, Alexander; Wipf, Christian; Li, Lei; Park, Ji-Hoon; Luo, Xi; Wietstruck, Matthias; Madjar, Asher; Strandwitz, Nicholas C.; Kaynak, Mehmet; Lee, Young Hee; Hwang, James C. M.

2018-04-01

Thousands of high-performance 2D metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on wafer-scale chemical vapor deposited MoS2 with fully-CMOS-compatible processes such as photolithography and aluminum metallurgy. The yield was greater than 50% in terms of effective gate control with less-than-10 V threshold voltage, even for MOSFETs having deep-submicron gate length. The large number of fabricated MOSFETs allowed statistics to be gathered and the main yield limiter to be attributed to the weak adhesion between the transferred MoS2 and the substrate. With cut-off frequencies approaching the gigahertz range, the performances of the MOSFETs were comparable to that of state-of-the-art MoS2 MOSFETs, whether the MoS2 was grown by a thin-film process or exfoliated from a bulk crystal.

Magnetization reversal and confinement effects across the metamagnetic phase transition in mesoscale FeRh structures

NASA Astrophysics Data System (ADS)

Ander Arregi, Jon; Horký, Michal; Fabianová, Kateřina; Tolley, Robert; Fullerton, Eric E.; Uhlíř, Vojtěch

2018-03-01

The effects of mesoscale confinement on the metamagnetic behavior of lithographically patterned FeRh structures are investigated via Kerr microscopy. Combining the temperature- and field-dependent magnetization reversal of individual sub-micron FeRh structures provides specific phase-transition characteristics of single mesoscale objects. Relaxation of the epitaxial strain caused by patterning lowers the metamagnetic phase transition temperature by more than 15 K upon confining FeRh films below 500 nm in one lateral dimension. We also observe that the phase transition becomes highly asymmetric when comparing the cooling and heating cycles for 300 nm-wide FeRh structures. The investigation of FeRh under lateral confinement provides an interesting platform to explore emergent metamagnetic phenomena arising from the interplay of the structural, magnetic and electronic degrees of freedom at the mesoscopic length scale.

Recent advances in the biomimicry of structural colours.

PubMed

Dumanli, Ahu Gümrah; Savin, Thierry

2016-12-21

Nature has mastered the construction of nanostructures with well-defined macroscopic effects and purposes. Structural colouration is a visible consequence of the particular patterning of a reflecting surface with regular structures at submicron length scales. Structural colours usually appear bright, shiny, iridescent or with a metallic look, as a result of physical processes such as diffraction, interference, or scattering with a typically small dissipative loss. These features have recently attracted much research effort in materials science, chemistry, engineering and physics, in order to understand and produce structural colours. In these early stages of photonics, researchers facing an infinite array of possible colour-producing structures are heavily inspired by the elaborate architectures they find in nature. We review here the recent technological strategies employed to artificially mimic the structural colours found in nature, as well as some of their current and potential applications.

The Physics and Operation of Ultra-Submicron Length Semiconductor Devices.

DTIC Science & Technology

1994-05-01

300 mei heterostructure diode at T=3001( with Fenni statistics and flat band conditions In all of the calculations with a heterostructure barrier, once...25 24- 22- 21- 0 50 100 150 200 Obhnce (mre Figure 8. Self-consistent T=300K calculation with Fenni statistics showing the density and donor

Submicron Silicon MOSFET

NASA Technical Reports Server (NTRS)

Daud, T.

1986-01-01

Process for making metal-oxide/semiconductor field-effect transistors (MOSFET's) results in gate-channel lengths of only few hundred angstroms about 100 times as small as state-of-the-art devices. Gates must be shortened to develop faster MOSFET's; proposed fabrication process used to study effects of size reduction in MOS devices and eventually to build practical threedimensional structures.

Sub-microanalysis of solid samples with near-field enhanced atomic emission spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Xiaohua; Liang, Zhisen; Meng, Yifan; Wang, Tongtong; Hang, Wei; Huang, Benli

2018-03-01

A novel approach, which we have chosen to name it as near-field enhanced atomic emission spectroscopy (NFE-AES), was proposed by introducing a scanning tunnelling microscope (STM) system into a laser-induced breakdown spectrometry (LIBS). The near-field enhancement of a laser-illuminated tip was utilized to improve the lateral resolution tremendously. Using the hybrid arrangement, pure metal tablets were analyzed to verify the performance of NFE-AES both in atmosphere and in vacuum. Due to localized surface plasmon resonance (LSPR), the incident electromagnetic field is enhanced and confined at the apex of tip, resulting in sub-micron scale ablation and elemental emission signal. We discovered that the signal-to-noise ratio (SNR) and the spectral resolution obtained in vacuum condition are better than those acquired in atmospheric condition. The quantitative capability of NFE-AES was demonstrated by analyzing Al and Pb in Cu matrix, respectively. Submicron-sized ablation craters were achieved by performing NFE-AES on a Si wafer with an Al film, and the spectroscopic information from a crater of 650 nm diameter was successfully obtained. Due to its advantage of high lateral resolution, NFE-AES imaging of micro-patterned Al lines on an integrated circuit of a SIM card was demonstrated with a sub-micron lateral resolution. These results reveal the potential of the NFE-AES technique in sub-microanalysis of solids, opening an opportunity to map chemical composition at sub-micron scale.

[Corrosion resistant properties of different anodized microtopographies on titanium surfaces].

PubMed

Fangjun, Huo; Li, Xie; Xingye, Tong; Yueting, Wang; Weihua, Guo; Weidong, Tian

2015-12-01

To investigate the corrosion resistant properties of titanium samples prepared by anodic oxidation with different surface morphologies. Pure titanium substrates were treated by anodic oxidation to obtain porous titanium films in micron, submicron, and micron-submicron scales. The surface morphologies, coating cross-sectional morphologies, crystalline structures, and surface roughness of these samples were characterized. Electrochemical technique was used to measure the corrosion potential (Ecorr), current density of corrosion (Icorr), and polarization resistance (Rp) of these samples in a simulated body fluid. Pure titanium could be modified to exhibit different surface morphologies by the anodic oxidation technique. The Tafel curve results showed that the technique can improve the corrosion resistance of pure titanium. Furthermore, the corrosion resistance varied with different surface morphologies. The submicron porous surface sample demonstrated the best corrosion resistance, with maximal Ecorr and Rp and minimal Icorr. Anodic oxidation technology can improve the corrosion resistance of pure titanium in a simulated body fluid. The submicron porous surface sample exhibited the best corrosion resistance because of its small surface area and thick barrier layer.

Energy dissipation in micron- and submicron-thick single crystal diamond mechanical resonators

NASA Astrophysics Data System (ADS)

Liao, Meiyong; Toda, Masaya; Sang, Liwen; Hishita, Shunichi; Tanaka, Shuji; Koide, Yasuo

2014-12-01

The authors report the resonance frequency and the energy dissipation of single crystal diamond cantilevers with different dimensions, which were fabricated by ion implantation assisted technique. The resonance frequency well followed the inverse power law relationship with the length of the cantilevers and exhibited a high reproducibility with varying the dimensions. The energy dissipation decreased with increasing the cantilever length and saturated or reduced at a certain value. For the shorter cantilevers, clamping loss governed the energy dissipation. As the cantilever length increased to a certain value, defects relaxation or surface effect became dominant. The possible origins for these energy dissipations were discussed.

Readout characteristics of a minute aperture-mounted optical head slider flying above a submicron wide metal patterned medium track

NASA Astrophysics Data System (ADS)

Ohkubo, Toshifumi; Hirota, Terunao; Oumi, Manabu; Hirata, Masakazu; Nakajima, Kunio

2004-10-01

Advances in a digital network society require both higher densities and higher transfer rates in all sorts of storage devices. In optical recording, the trend toward higher recording density and larger storage capacity requires novel surface recording technologies that would drastically improve recording density. To satisfy these severe requirements, we have already proposed a compact integrated optical head slider assembly for proximity optical recording based on the "near field principle". Using the optical head slider, we have successfully demonstrated readout signals from 200 to 150-nm-long bit patterns at frequency bands up to approximately 10 MHz. However, from the practical point of view, it is quite necessary to evaluate readout signals from patterns of smaller (sub-micron to sub-sub-micron) track width in order to prove high-density recording potential. In this paper, we have investigated tracking accuracy characteristics utilizing sub-micron sized alternate patterns of 1-mm length formed in a straight line in the circumferential direction of the medium. Arranging precisely the head's relative position to these recorded patterns, we have successfully obtained readout signals just crossing the sub-micron line-and-space pattern's boundaries. Assuming that an aperture runs along an accurate trajectory of the arc of a circle, readout signal amplitude variations when crossing the pattern edge at a right angle have precisely predicted. Also, the influences of track width on maximum readout signal intensity and tracking sensitivity are discussed in detail.

Modelling crystal plasticity by 3D dislocation dynamics and the finite element method: The Discrete-Continuous Model revisited

NASA Astrophysics Data System (ADS)

Vattré, A.; Devincre, B.; Feyel, F.; Gatti, R.; Groh, S.; Jamond, O.; Roos, A.

2014-02-01

A unified model coupling 3D dislocation dynamics (DD) simulations with the finite element (FE) method is revisited. The so-called Discrete-Continuous Model (DCM) aims to predict plastic flow at the (sub-)micron length scale of materials with complex boundary conditions. The evolution of the dislocation microstructure and the short-range dislocation-dislocation interactions are calculated with a DD code. The long-range mechanical fields due to the dislocations are calculated by a FE code, taking into account the boundary conditions. The coupling procedure is based on eigenstrain theory, and the precise manner in which the plastic slip, i.e. the dislocation glide as calculated by the DD code, is transferred to the integration points of the FE mesh is described in full detail. Several test cases are presented, and the DCM is applied to plastic flow in a single-crystal Nickel-based superalloy.

High contrast ion acceleration at intensities exceeding 10{sup 21} Wcm{sup −2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dollar, F.; Zulick, C.; Matsuoka, T.

2013-05-15

Ion acceleration from short pulse laser interactions at intensities of 2×10{sup 21}Wcm{sup −2} was studied experimentally under a wide variety of parameters, including laser contrast, incidence angle, and target thickness. Trends in maximum proton energy were observed, as well as evidence of improvement in the acceleration gradients by using dual plasma mirrors over traditional pulse cleaning techniques. Extremely high efficiency acceleration gradients were produced, accelerating both the contaminant layer and high charge state ions from the bulk of the target. Two dimensional particle-in-cell simulations enabled the study of the influence of scale length on submicron targets, where hydrodynamic expansion affectsmore » the rear surface as well as the front. Experimental evidence of larger electric fields for sharp density plasmas is observed in simulation results as well for such targets, where target ions are accelerated without the need for contaminant removal.« less

Simultaneous sizing and electrophoretic mobility measurement of sub-micron particles using Brownian motion

PubMed Central

Palanisami, Akilan; Miller, John H.

2011-01-01

The size and surface chemistry of micron scale particles are of fundamental importance in studies of biology and air particulate pollution. However, typical electrophoretic measurements of these and other sub-micron scale particles (300 nm – 1 μm) cannot resolve size information within heterogeneous mixtures unambiguously. Using optical microscopy, we monitor electrophoretic motion together with the Brownian velocity fluctuations—using the latter to measure size by either the Green-Kubo relation or by calibration from known size standards. Particle diameters are resolved to ±12% with 95% confidence. Strikingly, the size resolution improves as particle size decreases due to the increased Brownian motion. The sizing ability of the Brownian assessed electrophoresis method described here complements the electrophoretic mobility resolution of traditional capillary electrophoresis. PMID:20882556

Digenetic Changes in Macro- to Nano-Scale Porosity in the St. Peter Sandstone:L An (Ultra) Small Angle Neutron Scattering and Backscattered Electron Imagining Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anovitz, Lawrence; Cole, David; Rother, Gernot

2013-01-01

Small- and Ultra-Small Angle Neutron Scattering (SANS and USANS) provide powerful tools for quantitative analysis of porous rocks, yielding bulk statistical information over a wide range of length scales. This study utilized (U)SANS to characterize shallowly buried quartz arenites from the St. Peter Sandstone. Backscattered electron imaging was also used to extend the data to larger scales. These samples contain significant volumes of large-scale porosity, modified by quartz overgrowths, and neutron scattering results show significant sub-micron porosity. While previous scattering data from sandstones suggest scattering is dominated by surface fractal behavior over many orders of magnitude, careful analysis of ourmore » data shows both fractal and pseudo-fractal behavior. The scattering curves are composed of subtle steps, modeled as polydispersed assemblages of pores with log-normal distributions. However, in some samples an additional surface-fractal overprint is present, while in others there is no such structure, and scattering can be explained by summation of non-fractal structures. Combined with our work on other rock-types, these data suggest that microporosity is more prevalent, and may play a much more important role than previously thought in fluid/rock interactions.« less

Development of an Efficient Meso- scale Multi-phase Flow Solver in Nuclear Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Taehun

2015-10-20

The proposed research aims at formulating a predictive high-order Lattice Boltzmann Equation for multi-phase flows relevant to nuclear energy related application - namely, saturated and sub-cooled boiling in reactors, and liquid- liquid mixing and extraction for fuel cycle separation. An efficient flow solver will be developed based on the Finite Element based Lattice Boltzmann Method (FE- LBM), accounting for phase-change heat transfer and capable of treating multiple phases over length scales from the submicron to the meter. A thermal LBM will be developed in order to handle adjustable Prandtl number, arbitrary specific heat ratio, a wide range of temperature variations,more » better numerical stability during liquid-vapor phase change, and full thermo-hydrodynamic consistency. Two-phase FE-LBM will be extended to liquid–liquid–gas multi-phase flows for application to high-fidelity simulations building up from the meso-scale up to the equipment sub-component scale. While several relevant applications exist, the initial applications for demonstration of the efficient methods to be developed as part of this project include numerical investigations of Critical Heat Flux (CHF) phenomena in nuclear reactor fuel bundles, and liquid-liquid mixing and interfacial area generation for liquid-liquid separations. In addition, targeted experiments will be conducted for validation of this advanced multi-phase model.« less

The fabrication of vertically aligned and periodically distributed carbon nanotube bundles and periodically porous carbon nanotube films through a combination of laser interference ablation and metal-catalyzed chemical vapor deposition.

PubMed

Yuan, Dajun; Lin, Wei; Guo, Rui; Wong, C P; Das, Suman

2012-06-01

Scalable fabrication of carbon nanotube (CNT) bundles is essential to future advances in several applications. Here, we report on the development of a simple, two-step method for fabricating vertically aligned and periodically distributed CNT bundles and periodically porous CNT films at the sub-micron scale. The method involves laser interference ablation (LIA) of an iron film followed by CNT growth via iron-catalyzed chemical vapor deposition. CNT bundles with square widths ranging from 0.5 to 1.5 µm in width, and 50-200 µm in length, are grown atop the patterned catalyst over areas spanning 8 cm(2). The CNT bundles exhibit a high degree of control over square width, orientation, uniformity, and periodicity. This simple scalable method of producing well-placed and oriented CNT bundles demonstrates a high application potential for wafer-scale integration of CNT structures into various device applications, including IC interconnects, field emitters, sensors, batteries, and optoelectronics, etc.

Mesoscale martensitic transformation in single crystals of topological defects

PubMed Central

Martínez-González, José A.; Ramírez-Hernández, Abelardo; Zhou, Ye; Sadati, Monirosadat; Zhang, Rui; Nealey, Paul F.; de Pablo, Juan J.

2017-01-01

Liquid-crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of double-twisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by the existence of grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with precision by relying on chemically nanopatterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of mesocrystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local reorganization of the crystalline array, without diffusion of the double-twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the submicron regime, is found to be martensitic in nature when one considers the collective behavior of the double-twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal nucleation and the controlled growth of soft matter. PMID:28874557

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xiao; Martínez-González, José A.; Hernández-Ortiz, Juan P.

Liquid crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of doubletwisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with considerable precision by relying on chemically nano-patterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of meso-crystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local re-organization of the crystalline array,more » without diffusion of the double twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the sub-micron regime, is found to be martensitic in nature, with the diffusion-less feature associated to the collective behavior of the double twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal-nucleation and the controlled growth of soft matter.« less

Submicron FETs Using Molecular Beam Epitaxy.

DTIC Science & Technology

1981-01-01

2rin w2Cgs Req + 2(rw 2Cg2 Req + rin 2Reqgs Podell 9 has found empirically for one-micron gate length FETs that R =1.25 (10) eq gm Using Eq. (10) in...Transmission, Modulation, and Noise (McGraw- Hill, NY, 1959), p. 223. 9. A. Podell , to be published. 10. P. Wolf, "Microwave Properties of Schottky-Barrier

Modeling of Quantum Transport in Semiconductor Devices (The Physics and Operation of Ultra-Submicron Length Semiconductor Devices).

DTIC Science & Technology

1994-05-01

Open Systems and Contacts ...................... 16 A Ballistic Transport .......................... 17 B Role of the Boundaries and Contacts...15 Other Devices ................................ 90 V Modeling with the Green’s Functions 91 16 Homogeneous, Low-Field Systems .................. 93 A...The Retarded Function ..................... 95 B The "Less-Than" Function ................... 99 17 Homogeneous, High-Field Systems

Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Kuan-Kan; Woon, Wei Yen; Chang, Ruey-Dar

We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

NASA Astrophysics Data System (ADS)

Hu, Kuan-Kan; Chang, Ruey-Dar; Woon, Wei Yen

2015-10-01

We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

Velocity overshoot decay mechanisms in compound semiconductor field-effect transistors with a submicron characteristic length

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jyegal, Jang, E-mail: jjyegal@inu.ac.kr

Velocity overshoot is a critically important nonstationary effect utilized for the enhanced performance of submicron field-effect devices fabricated with high-electron-mobility compound semiconductors. However, the physical mechanisms of velocity overshoot decay dynamics in the devices are not known in detail. Therefore, a numerical analysis is conducted typically for a submicron GaAs metal-semiconductor field-effect transistor in order to elucidate the physical mechanisms. It is found that there exist three different mechanisms, depending on device bias conditions. Specifically, at large drain biases corresponding to the saturation drain current (dc) region, the velocity overshoot suddenly begins to drop very sensitively due to the onsetmore » of a rapid decrease of the momentum relaxation time, not the mobility, arising from the effect of velocity-randomizing intervalley scattering. It then continues to drop rapidly and decays completely by severe mobility reduction due to intervalley scattering. On the other hand, at small drain biases corresponding to the linear dc region, the velocity overshoot suddenly begins to drop very sensitively due to the onset of a rapid increase of thermal energy diffusion by electrons in the channel of the gate. It then continues to drop rapidly for a certain channel distance due to the increasing thermal energy diffusion effect, and later completely decays by a sharply decreasing electric field. Moreover, at drain biases close to a dc saturation voltage, the mechanism is a mixture of the above two bias conditions. It is suggested that a large secondary-valley energy separation is essential to increase the performance of submicron devices.« less

Frequency equation for the submicron CMOS ring oscillator using the first order characterization

NASA Astrophysics Data System (ADS)

Koithyar, Aravinda; Ramesh, T. K.

2018-05-01

By utilizing the first order behavior of the device, an equation for the frequency of operation of the submicron CMOS ring oscillator is presented. A 5-stage ring oscillator is utilized as the initial design, with different Beta ratios, for the computation of the operating frequency. Later on, the circuit simulation is performed from 5-stage till 23-stage, with the range of oscillating frequency being 3.0817 and 0.6705 GHz respectively. It is noted that the output frequency is inversely proportional to the square of the device length, and when the value of Beta ratio is used as 2.3, a difference of 3.64% is observed on an average, in between the computed and the simulated values of frequency. As an outcome, the derived equation can be utilized, with the inclusion of an empirical constant in general, for arriving at the ring oscillator circuit’s output frequency.

Magneto-transport Characterization of Thin Film In-plane and Cross-plane Conductivity

NASA Astrophysics Data System (ADS)

Tang, Yang; Grayson, Matthew

Thin films with highly anisotropic in-plane and cross-plane conductivities are widely used in devices, such as infrared emitters and detectors, and the proper magneto-transport characterization in both directions can reveal information about the doping density, impurities, carrier life times and band structure. This work introduces a novel method for deducing the complete anisotropic electrical conductivity tensor of such an anisotropic resistive layer atop a highly conducting bottom contact, which is a standard part of the device structure. Three strip-line contacts separated by a length scale comparable to the film thickness are applied atop the resistive thin film layer of interest, with the highly conducting back-plane as a back-contact. The potential distribution in the device is modeled, using both scaling and conformal transformation to minimize the calculated volume. As a proof of concept, triple strip-line devices for GaAs and GaAs/AlGaAs superlattice thin films are fabricated. To achieve narrow strip-line contacts with sub-micron scale widths, non-annealed Ni/Au contacts form ohmic contacts to a patterned n+-GaAs cap layer atop the anisotropic thin films. Preliminary experimental data will be presented as a validation of this method. Acknowledgment: Funded by AFOSR FA9550-15-1-0377 and AFOSR FA9550-15-1-0247.

Methodologies in determining mechanical properties of thin films using nanoindentation

NASA Astrophysics Data System (ADS)

Han, Seung Min Jane

Thin films are critical components of microelectronic and MEMS devices, and evaluating their mechanical properties is of current interest. As the dimensions of the devices become smaller and smaller, however, understanding the mechanical properties of materials at sub-micron length scales becomes more challenging. The conventional methods for evaluating strengths of materials in bulk form cannot be applied, and new methodologies are required for accurately evaluating mechanical properties of thin films. In this work, development of methodologies using the nanoindenter was pursued in three parts: (1) creation of a new method for extracting thin film hardness, (2) use of combinatorial methods for determining compositions with desired mechanical properties, and (3) use of microcompression testing of sub-micron sized pillars to understand plasticity in Al-Sc multilayers. The existing nanoindentation hardness model by Oliver & Pharr is unable to accurately determine the hardness of thin films on substrates with an elastic mismatch. Thus, a new method of analysis for extracting thin film hardness from film/substrate systems, that eliminates the effect of elastic mismatch of the underlying substrate, surface roughness, and also pile-up/sink-in, is needed. Such a method was developed in the first part of this study. The feasibility of using the nanoindentation hardness together with combinatorial methods to efficiently scan through mechanical properties of Ti-Al metallic alloys was examined in the second part of this study. The combinatorial approach provides an efficient method that can be used to determine alloy compositions that might merit further exploration and development as bulk materials. Finally, the mechanical properties of Al-Al3Sc multilayers with bilayer periods ranging from 6-100 nm were examined using microcompression. The sub-micron sized pillars were prepared using the focused ion beam (FIB) and compression tested with the flat tip of the nanoindenter. The measured yield strengths show the trend of increasing strength with decreasing bilayer period, and agree with the nanoindentation hardness results using the suitable Tabor correction factor. Strain softening was observed at large strains, and a new model for the true stress and true strain was developed to account for the inhomogeneous deformation geometry.

Submicron cubic boron nitride as hard as diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Guoduan; Kou, Zili, E-mail: kouzili@scu.edu.cn, E-mail: yanxz@hpstar.ac.cn; Lei, Li

Here, we report the sintering of aggregated submicron cubic boron nitride (sm-cBN) at a pressure of 8 GPa. The sintered cBN compacts exhibit hardness values comparable to that of single crystal diamond, fracture toughness about 5-fold that of cBN single crystal, in combination with a high oxidization temperature. Thus, another way has been demonstrated to improve the mechanical properties of cBN besides reducing the grain size to nano scale. In contrast to other ultrahard compacts with similar hardness, the sm-cBN aggregates are better placed for potential industrial application, as their relative low pressure manufacturing perhaps be easier and cheaper.

Demonstration of submicron square-like silicon waveguide using optimized LOCOS process.

PubMed

Desiatov, Boris; Goykhman, Ilya; Levy, Uriel

2010-08-30

We demonstrate the design, fabrication and experimental characterization of a submicron-scale silicon waveguide that is fabricated by local oxidation of silicon. The use of local oxidation process allows defining the waveguide geometry and obtaining smooth sidewalls. The process can be tuned to precisely control the shape and the dimensions of the waveguide. The fabricated waveguides are measured using near field scanning optical microscope at 1550 nm wavelength. These measurements show mode width of 0.4 µm and effective refractive index of 2.54. Finally, we demonstrate the low loss characteristics of our waveguide by imaging the light scattering using an infrared camera.

Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Runguang; Xie, Qingge; Wang, Yan-Dong

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial-temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (μXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem μXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands.more » Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through μXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials.« less

Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

DOE PAGES

Li, Runguang; Xie, Qingge; Wang, Yan-Dong; ...

2017-12-28

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial-temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (μXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem μXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands.more » Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through μXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials.« less

Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

PubMed Central

Li, Runguang; Xie, Qingge; Wang, Yan-Dong; Liu, Wenjun; Wang, Mingguang; Wu, Guilin; Li, Xiaowu; Zhang, Minghe; Lu, Zhaoping; Geng, Chang; Zhu, Ting

2018-01-01

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial−temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (μXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem μXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands. Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through μXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials. PMID:29284751

Ultrarapid Multimode Microwave Synthesis of Nano/Submicron β-SiC

PubMed Central

Johnson, Michael; He, Wenzhi; Li, Guangming; Zhao, Chen; Yu, Luling; Huang, Juwen; Zhu, Haochen

2018-01-01

This paper presents the design, development and realization of a fast and novel process for the synthesis of 3C silicon carbide (β-SiC) nanorods and submicron powder. Using SiO2 (or Si) and activated carbon (AC), this process allows β-SiC to be synthesized with almost 100% purity in timeframes of seconds or minutes using multimode microwave rotary tube reactors under open-air conditions. The synthesis temperature used was 1460 ± 50 °C for Si + AC and 1660 ± 50 °C for SiO2 + AC. The shortest β-SiC synthesis time achieved was about 20 s for Si + AC and 100 s for SiO2 + AC. This novel synthesis method allows for scaled-up flow processes in the rapid industrial-scale production of β-SiC, having advantages of time/energy saving and carbon dioxide emission reduction over comparable modern processes. PMID:29470417

Two stage dual gate MESFET monolithic gain control amplifier for Ka-band

NASA Technical Reports Server (NTRS)

Sokolov, V.; Geddes, J.; Contolatis, A.

1987-01-01

A monolithic two stage gain control amplifier has been developed using submicron gate length dual gate MESFETs fabricated on ion implanted material. The amplifier has a gain of 12 dB at 30 GHz with a gain control range of over 30 dB. This ion implanted monolithic IC is readily integrable with other phased array receiver functions such as low noise amplifiers and phase shifters.

Product Reliability Trends, Derating Considerations and Failure Mechanisms with Scaled CMOS

NASA Technical Reports Server (NTRS)

White, Mark; Vu, Duc; Nguyen, Duc; Ruiz, Ron; Chen, Yuan; Bernstein, Joseph B.

2006-01-01

As microelectronics is scaled into the deep sub-micron regime, space and aerospace users of advanced technology CMOS are reassessing how scaling effects impact long-term product reliability. The effects of electromigration (EM), time-dependent-dielectric-breakdown (TDDB) and hot carrier degradation (HCI and NBTI) wearout mechanisms on scaled technologies and product reliability are investigated, accelerated stress testing across several technology nodes is performed, and FA is conducted to confirm the failure mechanism(s).

Hedberg Research Conference on Fundamental Controls on Flow in Carbonates: Request for Travel Support for Post-Doctoral Fellows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyrak-Nolte, Laura J.

Carbonate reservoirs pose a scientific and engineering challenge to geophysical prediction and monitoring of fluid flow in the subsurface. Difficulties in interpreting hydrological, reservoir and other exploration data arise because carbonates are composed of a hierarchy of geological structures, constituents and processes that span a wide spectrum of length and time scales. What makes this problem particularly challenging is that length scales associated with physical structure and processes are often not discrete, but overlap, preventing the definition of discrete elements at one scale to become the building blocks of the next scale. This is particularly true for carbonates where complicatedmore » depositional environments, subsequent post-deposition diagenesis and geochemical interactions result in pores that vary in scale from submicron to centimeters to fractures, variation in fabric composition with fossils, minerals and cement, as well as variations in structural features (e.g., oriented inter- and intra layered - interlaced bedding and/or discontinuous rock units). In addition, this complexity is altered by natural and anthropogenic processes such as changes in stress, fluid content, reactive fluid flow, etc. Thus an accurate geophysical assessment of the flow behavior of carbonate reservoirs requires a fundamental understanding of the interplay of textural and structural features subjected to physical processes that affect and occur on various length and time scales. To address this complexity related to carbonates, a Hedberg conference on “Fundamental Controls on Flow in Carbonates” was held July 8 to 13, 2012, to bring together industry and academic scientists to stimulate innovative ideas that can accelerate research advances related to flow prediction and recovery in carbonate reservoirs. Participants included scientist and engineers from multiple disciplines (such as hydrology, structural geology, geochemistry, reservoir engineering, geophysics, geomechanics, numerical modeling, physical experiments, sedimentology, well-testing, statistics, mathematics, visualization, etc.) who encompass experience as well as the latest advances in these multi-faceted fields. One of the goals was to include early career scientists and engineers (post-doctoral fellows, assistant professors, etc.). With this grant 10 early career scientists and engineers were supported to attend the conference. This reports contains a brief overview of the conference and the list of support participants supported by this grant. Full details of the outcomes of the conference are given in the publication found in the Attachment section of this report.« less

Imaging at an x-ray absorption edge using free electron laser pulses for interface dynamics in high energy density systems [Resonant phase contrast imaging for interface physics

DOE PAGES

Beckwith, M. A.; Jiang, S.; Schropp, A.; ...

2017-05-01

Tuning the energy of an x-ray probe to an absorption line or edge can provide material-specific measurements that are particularly useful for interfaces. Simulated hard x-ray images above the Fe K-edge are presented to examine ion diffusion across an interface between Fe 2O 3 and SiO 2 aerogel foam materials. The simulations demonstrate the feasibility of such a technique for measurements of density scale lengths near the interface with submicron spatial resolution. A proof-of-principle experiment is designed and performed at the Linac coherent light source facility. Preliminary data show the change of the interface after shock compression and heating withmore » simultaneous fluorescence spectra for temperature determination. Here, the results provide the first demonstration of using x-ray imaging at an absorption edge as a diagnostic to detect ultrafast phenomena for interface physics in high-energy-density systems.« less

Ultrashort broadband polarization beam splitter based on a combined hybrid plasmonic waveguide.

PubMed

Chang, Ken-Wei; Huang, Chia-Chien

2016-01-20

We propose an ultracompact broadband polarization beam splitter (PBS) based on a combined hybrid plasmonic waveguide (HPW). The proposed PBS separates transverse-electric (TE) and transverse-magnetic (TM) modes using a bent lower HPW with vertical nanoscale gaps and a straight upper HPW with a horizontal nanoscale gap, respectively, without relying on an additional coupling region. This design considerably reduces the length of the PBS to the submicron scale (920 nm, the shortest PBS reported to date) while offering polarization extinction ratios (PERs) of ~19 dB (~18 dB) and insertion losses (ILs) of ~0.6 dB (~0.3 dB) for the TE (TM) mode over an extremely broad band of 400 nm (from λ = 1300 nm to 1700 nm, covering entirely second and third telecom windows). The length of the designed PBS can be reduced further to 620 nm while still offering PERs of 15 dB, realizing a densely photonic integrated circuit. Considering the fabrication tolerance, the designed PBS allows for large geometrical deviations of ± 20 nm while restricting PER variations to within 1 dB, except for those in the nanoscale gaps smaller than 10nm. Additionally, we also address the input and ouput coupling efficiencies of the proposed PBS.

Micro electro-mechanical heater

DOEpatents

Oh, Yunje; Asif, Syed Amanulla Syed; Cyrankowski, Edward; Warren, Oden Lee

2016-04-19

A sub-micron scale property testing apparatus including a test subject holder and heating assembly. The assembly includes a holder base configured to couple with a sub-micron mechanical testing instrument and electro-mechanical transducer assembly. The assembly further includes a test subject stage coupled with the holder base. The test subject stage is thermally isolated from the holder base. The test subject stage includes a stage subject surface configured to receive a test subject, and a stage plate bracing the stage subject surface. The stage plate is under the stage subject surface. The test subject stage further includes a heating element adjacent to the stage subject surface, the heating element is configured to generate heat at the stage subject surface.

Micro electro-mechanical heater

DOEpatents

Oh, Yunje; Asif, Syed Amanulla Syed; Cyrankowski, Edward; Warren, Oden Lee

2017-09-12

A sub-micron scale property testing apparatus including a test subject holder and heating assembly. The assembly includes a holder base configured to couple with a sub-micron mechanical testing instrument and electro-mechanical transducer assembly. The assembly further includes a test subject stage coupled with the holder base. The test subject stage is thermally isolated from the holder base. The test subject stage includes a stage subject surface configured to receive a test subject, and a stage plate bracing the stage subject surface. The stage plate is under the stage subject surface. The test subject stage further includes a heating element adjacent to the stage subject surface, the heating element is configured to generate heat at the stage subject surface.

Enhanced sub-micron colloidal particle separation with interdigitated microelectrode arrays using mixed AC/DC dielectrophoretic scheme.

PubMed

Swaminathan, Vikhram V; Shannon, Mark A; Bashir, Rashid

2015-04-01

Dielectrophoretic separation of particles finds a variety of applications in the capture of species such as cells, viruses, proteins, DNA from biological systems, as well as other organic and inorganic contaminants from water. The ability to capture particles is constrained by poor volumetric scaling of separation force with respect to particle diameter, as well as the weak penetration of electric fields in the media. In order to improve the separation of sub-micron colloids, we present a scheme based on multiple interdigitated electrode arrays under mixed AC/DC bias. The use of high frequency longitudinal AC bias breaks the shielding effects through electroosmotic micromixing to enhance electric fields through the electrolyte, while a transverse DC bias between the electrode arrays enables penetration of the separation force to capture particles from the bulk of the microchannel. We determine the favorable biasing conditions for field enhancement with the help of analytical models, and experimentally demonstrate the improved capture from sub-micron colloidal suspensions with the mixed AC/DC electrostatic excitation scheme over conventional AC-DEP methods.

Characterization and evaluation of femtosecond laser-induced sub-micron periodic structures generated on titanium to improve osseointegration of implants

NASA Astrophysics Data System (ADS)

Lee, Bryan E. J.; Exir, Hourieh; Weck, Arnaud; Grandfield, Kathryn

2018-05-01

Reproducible and controllable methods of modifying titanium surfaces for dental and orthopaedic applications are of interest to prevent poor implant outcomes by improving osseointegration. This study made use of a femtosecond laser to generate laser-induced periodic surface structures with periodicities of 300, 620 and 760 nm on titanium substrates. The reproducible rippled patterns showed consistent submicron scale roughness and relatively hydrophobic surfaces as measured by atomic force microscopy and contact angle, respectively. Transmission electron microscopy and Auger electron spectroscopy identified a thicker oxide layer on ablated surfaces compared to controls. In vitro testing was conducted using osteosarcoma Saos-2 cells. Cell metabolism on the laser-ablated surfaces was comparable to controls and alkaline phosphatase activity was notably increased at late time points for the 620 and 760 nm surfaces compared to controls. Cells showed a more elongated shape on laser-ablated surfaces compared to controls and showed perpendicular alignment to the periodic structures. This work has demonstrated the feasibility of generating submicron features on an implant material with the ability to influence cell response and improve implant outcomes.

Controlled motion of domain walls in submicron amorphous wires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ţibu, Mihai; Lostun, Mihaela; Rotărescu, Cristian

Results on the control of the domain wall displacement in cylindrical Fe{sub 77.5}Si{sub 7.5}B{sub 15} amorphous glass-coated submicron wires prepared by rapid quenching from the melt are reported. The control methods have relied on conical notches with various depths, up to a few tens of nm, made in the glass coating and in the metallic nucleus using a focused ion beam (FIB) system, and on the use of small nucleation coils at one of the sample ends in order to apply magnetic field pulses aimed to enhance the nucleation of reverse domains. The notch-based method is used for the firstmore » time in the case of cylindrical ultrathin wires. The results show that the most efficient technique of controlling the domain wall motion in this type of samples is the simultaneous use of notches and nucleation coils. Their effect depends on wire diameter, notch depth, its position on the wire length, and characteristics of the applied pulse.« less

Electrokinetic effects on motion of submicron particles in microchannel

NASA Astrophysics Data System (ADS)

Sato, Yohei; Hishida, Koichi

2006-11-01

Two-fluid mixing utilizing electrokinetically driven flow in a micro-channel is investigated by micron-resolution particle image velocimetry and an image processing technique. Submicron particles are transported and mixed with deionized water by electrophoresis. The particle electrophoretic velocity that is proportional to an applied electric field is measured in a closed cell, which is used to calculate the electroosmotic flow velocity. At a constant electric field, addition of pressure-driven flow to electrokinetically driven flow in a T-shaped micro-channel enhances two-fluid mixing because the momentum flux is increased. On the other hand, on application of an alternative sinusoidal electric field, the velocity difference between pressure-driven and electroosmotic flows has a significant effect on increasing the length of interface formed between two fluids. It is concluded from the present experiments that the transport and mixing process in the micro-channel will be enhanced by accurate flow-rate control of both pressure-driven and electroosmotic flows.

Spatiotemporally Controlled Microchannels of Periodontal Mimic Scaffolds

PubMed Central

Park, C.H.; Kim, K.H.; Rios, H.F.; Lee, Y.M.; Giannobile, W.V.; Seol, Y.J.

2014-01-01

Physiologic bioengineering of the oral, dental, and craniofacial complex requires optimized geometric organizations of fibrous connective tissues. A computer-designed, fiber-guiding scaffold has been developed to promote tooth-supporting periodontal tissue regeneration and functional restoration despite limited printing resolution for the manufacture of submicron-scaled features. Here, we demonstrate the use of directional freeze-casting techniques to control pore directional angulations and create mimicked topographies to alveolar crest, horizontal, oblique, and apical fibers of natural periodontal ligaments. For the differing anatomic positions, the gelatin displayed varying patterns of ice growth, determined via internal pore architectures. Regardless of the freezing coordinates, the longitudinal pore arrangements resulted in submicron-scaled diameters (~50 µm), along with corresponding high biomaterial porosity (~90%). Furthermore, the horizontal + coronal ((x→−y→) freezing orientation facilitated the creation of similar structures to major fibers in the periodontal ligament interface. This periodontal tissue-mimicking microenvironment is a potential tissue platform for the generation of naturally oriented ligamentous tissues consistent with periodontal ligament neogenesis. PMID:25216511

Scattering theory of nonlinear thermoelectricity in quantum coherent conductors.

PubMed

Meair, Jonathan; Jacquod, Philippe

2013-02-27

We construct a scattering theory of weakly nonlinear thermoelectric transport through sub-micron scale conductors. The theory incorporates the leading nonlinear contributions in temperature and voltage biases to the charge and heat currents. Because of the finite capacitances of sub-micron scale conducting circuits, fundamental conservation laws such as gauge invariance and current conservation require special care to be preserved. We do this by extending the approach of Christen and Büttiker (1996 Europhys. Lett. 35 523) to coupled charge and heat transport. In this way we write relations connecting nonlinear transport coefficients in a manner similar to Mott's relation between the linear thermopower and the linear conductance. We derive sum rules that nonlinear transport coefficients must satisfy to preserve gauge invariance and current conservation. We illustrate our theory by calculating the efficiency of heat engines and the coefficient of performance of thermoelectric refrigerators based on quantum point contacts and resonant tunneling barriers. We identify, in particular, rectification effects that increase device performance.

Fractional-topological-charge-induced vortex birth and splitting of light fields on the submicron scale

NASA Astrophysics Data System (ADS)

Fang, Yiqi; Lu, Qinghong; Wang, Xiaolei; Zhang, Wuhong; Chen, Lixiang

2017-02-01

The study of vortex dynamics is of fundamental importance in understanding the structured light's propagation behavior in the realm of singular optics. Here, combining with the large-angle holographic lithography in photoresist, a simple experiment to trace and visualize the vortex birth and splitting of light fields induced by various fractional topological charges is reported. For a topological charge M =1.76 , the recorded microstructures reveal that although it finally leads to the formation of a pair of fork gratings, these two vortices evolve asynchronously. More interestingly, it is observed on the submicron scale that high-order topological charges M =3.48 and 3.52, respectively, give rise to three and four characteristic forks embedded in the samples with one-wavelength resolution of about 450 nm. Numerical simulations based on orbital angular momentum eigenmode decomposition support well the experimental observations. Our method could be applied effectively to study other structured matter waves, such as the electron and neutron beams.

New constraints on deformation processes in serpentinite from sub-micron Raman Spectroscopy and TEM

NASA Astrophysics Data System (ADS)

Smith, S. A. F.; Tarling, M.; Rooney, J. S.; Gordon, K. C.; Viti, C.

2017-12-01

Extensive work has been performed to characterize the mineralogical and mechanical properties of the various serpentine minerals (i.e. antigorite, lizardite, chrysotile, polyhedral and polygonal serpentine). However, correct identification of serpentine minerals is often difficult or impossible using conventional analytical techniques such as optical- and SEM-based microscopy, X-ray diffraction and infrared spectroscopy. Transmission Electron Microscopy (TEM) is the best analytical technique to identify the serpentine minerals, but TEM requires complex sample preparation and typically results in very small analysis areas. Sub-micron confocal Raman spectroscopy mapping of polished thin sections provides a quick and relatively inexpensive way of unambiguously distinguishing the main serpentine minerals within their in-situ microstructural context. The combination of high spatial resolution (with a diffraction-limited system, 366 nm), large-area coverage (up to hundreds of microns in each dimension) and ability to map directly on thin sections allows intricate fault rock textures to be imaged at a sample-scale, which can then form the target of more focused TEM work. The potential of sub-micron Raman Spectroscopy + TEM is illustrated by examining sub-micron-scale mineral intergrowths and deformation textures in scaly serpentinites (e.g. dissolution seams, mineral growth in pressure shadows), serpentinite crack-seal veins and polished fault slip surfaces from a serpentinite-bearing mélange in New Zealand. The microstructural information provided by these techniques has yielded new insights into coseismic dehydration and amorphization processes and the interplay between creep and localised rupture in serpentinite shear zones.

Size-Tuned Plastic Flow Localization in Irradiated Materials at the Submicron Scale

NASA Astrophysics Data System (ADS)

Cui, Yinan; Po, Giacomo; Ghoniem, Nasr

2018-05-01

Three-dimensional discrete dislocation dynamics (3D-DDD) simulations reveal that, with reduction of sample size in the submicron regime, the mechanism of plastic flow localization in irradiated materials transitions from irradiation-controlled to an intrinsic dislocation source controlled. Furthermore, the spatial correlation of plastic deformation decreases due to weaker dislocation interactions and less frequent cross slip as the system size decreases, thus manifesting itself in thinner dislocation channels. A simple model of discrete dislocation source activation coupled with cross slip channel widening is developed to reproduce and physically explain this transition. In order to quantify the phenomenon of plastic flow localization, we introduce a "deformation localization index," with implications to the design of radiation-resistant materials.

Studying the Physics and Operation of Multi-Terminal Near-Micron and Sub-Micron Length, Hot Electron Semiconductor Devices.

DTIC Science & Technology

1988-02-15

Reprint 4 is a broad discussion of the consequences of the intracollisional field effect . In reprint 5, the uniform field momentum and energy balance...been submitted for publication. An extensive discussion of the effects of nonparabolicity on the moment equations is near completion. A study of the... effect . These effects are discussed later. A . Self-Energy Corrections I n the presence of a strong monochromatic source, one, in general, would

Measurement of carbon condensates using small-angle x-ray scattering during detonation of high explosives

NASA Astrophysics Data System (ADS)

Willey, T. M.; Bagge-Hansen, M.; Lauderbach, L.; Hodgin, R.; Hansen, D.; May, C.; van Buuren, T.; Dattelbaum, D. M.; Gustavsen, R. L.; Watkins, E. B.; Firestone, M. A.; Jensen, B. J.; Graber, T.; Bastea, S.; Fried, L.

2017-01-01

The lack of experimental validation for processes occurring at sub-micron length scales on time scales ranging from nanoseconds to microseconds hinders detonation model development. Particularly, quantification of late-time energy release requires measurement of carbon condensation kinetics behind detonation fronts. A new small-angle x-ray scattering (SAXS) endstation has been developed for use at The Dynamic Compression Sector to observe carbon condensation during detonation. The endstation and beamline demonstrate unprecedented fidelity; SAXS profiles can be acquired from single x-ray pulses, which in 24-bunch mode are about 80 ps in duration and arrive every 153.4 ns. This paper presents both the current temporal capabilities of this beamline, and the ability to distinguish different carbon condensate morphologies as they form behind detonation fronts. To demonstrate temporal capabilities, three shots acquired during detonation of hexanitrostilbene (HNS) are interleaved to show the evolution of the SAXS in about 50 ns steps. To show fidelity of the SAXS, the scattering from carbon condensates at several hundred nanoseconds varies with explosive: scattering from HNS is consistent with a complex morphology that we assert is associated with sp2 carbon., while Comp B scattering is consistent with soots containing three-dimensional diamond nanoparticles.

Study of Polymer Crystallization by Physical Vapor Deposition

NASA Astrophysics Data System (ADS)

Jeong, Hyuncheol

When a polymer is confined under the submicron length scale, confinement size and interfaces can significantly impact the crystallization kinetics and resulting morphology. The ability to tune the morphology of confined polymer systems is of critical importance for the development of high-performance polymer microelectronics. The wisdom from the research on confined crystallization suggests that it would be beneficial to have a processing route in which the crystallization of polymers is driven by interface and temperature effects at a nanometer-scale confinement. In practice, for atomic and small-molecular systems, physical vapor deposition (PVD) has been recognized as the most successful processing route for the precise control of the film structure at surface utilizing confinement effects. While standard PVD technologies are not generally applicable to the deposition of the chemically fragile macromolecules, the development of matrix-assisted pulsed laser evaporation (MAPLE) now enables the non-destructive PVD of high-molecular weight polymers. In this thesis work, we investigated the use of MAPLE for the precise control of the crystallization of polymer films at a molecular level. We also sought to decipher the rules governing the crystallization of confined polymers, by using MAPLE as a tool to form confined polymer systems onto substrates with a controlled temperature. We first explored the early stages of film growth and crystallization of poly(ethylene oxide) (PEO) at the substrate surface formed by MAPLE. The unique mechanism of film formation in MAPLE, the deposition of submicron-sized polymer droplets, allowed for the manifestation of confinement and substrate effects in the crystallization of MAPLE-deposited PEO. Furthermore, we also focused on the property of the amorphous PEO film formed by MAPLE, showing the dependence of polymer crystallization kinetics on the thermal history of the amorphous phase. Lastly, we probed how MAPLE processing affected the semi-crystalline structure in MAPLE-deposited polyethylene (PE) films. Depositing PE at various temperatures remarkably allowed for the tunability of the melting temperature and crystallinity of the PE films, thus manipulating the semi-crystalline structure. By comparing the structure of PE formed by different processing routes, i.e., MAPLE and melt-crystallization, we discussed how processing routes affect the development of semi-crystalline phase in polymer films.

Ultrashort broadband polarization beam splitter based on a combined hybrid plasmonic waveguide

PubMed Central

Chang, Ken-Wei; Huang, Chia-Chien

2016-01-01

We propose an ultracompact broadband polarization beam splitter (PBS) based on a combined hybrid plasmonic waveguide (HPW). The proposed PBS separates transverse-electric (TE) and transverse-magnetic (TM) modes using a bent lower HPW with vertical nanoscale gaps and a straight upper HPW with a horizontal nanoscale gap, respectively, without relying on an additional coupling region. This design considerably reduces the length of the PBS to the submicron scale (920 nm, the shortest PBS reported to date) while offering polarization extinction ratios (PERs) of ~19 dB (~18 dB) and insertion losses (ILs) of ~0.6 dB (~0.3 dB) for the TE (TM) mode over an extremely broad band of 400 nm (from λ = 1300 nm to 1700 nm, covering entirely second and third telecom windows). The length of the designed PBS can be reduced further to 620 nm while still offering PERs of 15 dB, realizing a densely photonic integrated circuit. Considering the fabrication tolerance, the designed PBS allows for large geometrical deviations of ±20 nm while restricting PER variations to within 1 dB, except for those in the nanoscale gaps smaller than 10nm. Additionally, we also address the input and ouput coupling efficiencies of the proposed PBS. PMID:26786972

Focused ion beam assisted three-dimensional rock imaging at submicron scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomutsa, Liviu; Radmilovic, Velimir

2003-05-09

Computation of effective flow properties of fluids in porous media based on three dimensional (3D) pore structure information has become more successful in the last few years, due to both improvements in the input data and the network models. Computed X-ray microtomography has been successful in 3D pore imaging at micron scale, which is adequate for many sandstones. For other rocks of economic interest, such as chalk and diatomite, submicron resolution is needed in order to resolve the 3D-pore structure. To achieve submicron resolution, a new method of sample serial sectioning and imaging using Focused Ion Beam (FIB) technology hasmore » been developed and 3D pore images of the pore system for diatomite and chalk have been obtained. FIB was used in the milling of layers as wide as 50 micrometers and as thin as 100 nanometers by sputtering of atoms from the sample surface. The focused ion beam, consisting of gallium ions (Ga+) accelerated by potentials of up to 30 kV and currents up to 20,000 pA, yields very clean, flat surfaces in which the pore-grain boundaries appear in high contrast. No distortion of the pore boundaries due to the ion milling is apparent. After each milling step, as a new surface is exposed, an image of the surface is generated. Using secondary electrons or ions, resolutions as high as 10 nm can be obtained. Afterwards, the series of 2D images can be stacked in the computer and, using appropriate interpolation and surface rendering algorithms, the 3D pore structure is reconstructed.« less

Large magnetic penetration depth and thermal fluctuations in a superconducting Ca10(Pt3As8)[(Fe1 xPtx)2As2]5 (x = 0.097) single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim J.; Nazaretski E.; Ronning, F.

2012-05-18

We have measured the temperature dependence of the absolute value of the magnetic penetration depth {lambda}(T) in a Ca{sub 10}(Pt{sub 3}As{sub 8})[(Fe{sub 1-x}Pt{sub x}){sub 2}As{sub 2}]{sub 5} (x = 0.097) single crystal using a low-temperature magnetic force microscope (MFM). We obtain {lambda}{sub ab}(0) {approx} 1000 nm via extrapolating the data to T = 0. This large {lambda} and pronounced anisotropy in this system are responsible for large thermal fluctuations and the presence of a liquid vortex phase in this low-temperature superconductor with a critical temperature of 11 K, consistent with the interpretation of the electrical transport data. The superconducting parametersmore » obtained from {lambda} and coherence length {zeta} place this compound in the extreme type II regime. Meissner responses (via MFM) at different locations across the sample are similar to each other, indicating good homogeneity of the superconducting state on a submicron scale.« less

In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

DOE PAGES

Liu, Y.; Wang, H.; Zhang, X.

2015-11-30

Though abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. We applied numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction in order to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. We briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. Moreover, in the amorphous CuZrAl, in situ nanoindentationmore » studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.« less

Ultra-broadband unidirectional launching of surface plasmon polaritons by a double-slit structure beyond the diffraction limit.

PubMed

Chen, Jianjun; Sun, Chengwei; Li, Hongyun; Gong, Qihuang

2014-11-21

Surface-plasmon-polariton (SPP) launchers, which can couple the free space light to the SPPs on the metal surface, are among the key elements for the plasmonic devices and nano-photonic systems. Downscaling the SPP launchers below the diffraction limit and directly delivering the SPPs to the desired subwavelength plasmonic waveguides are of importance for high-integration plasmonic circuits. By designing a submicron double-slit structure with different slit widths, an ultra-broadband (>330 nm) unidirectional SPP launcher is realized theoretically and experimentally based on the different phase delays of SPPs propagating along the metal surface and the near-field interfering effect. More importantly, the broadband and unidirectional properties of the SPP launcher are still maintained when the slit length is reduced to a subwavelength scale. This can make the launcher occupy only a very small area of <λ(2)/10 on the metal surface. Such a robust unidirectional SPP launcher beyond the diffraction limit can be directly coupled to a subwavelength plasmonic waveguide efficiently, leading to an ultra-tight SPP source, especially as a subwavelength localized guided SPP source.

Charge ordered ferromagnetic phase in La_0.5Ca_0.5MnO_3

NASA Astrophysics Data System (ADS)

Mathur, Neil

2003-03-01

Charge order and ferromagnetism should be mutually exclusive in the manganites, because ferromagnetism in these materials is normally promoted by delocalised electrons. Surprisingly, a phase that is both strongly charge ordered and fully ferromagnetic is observed [1] at 90 K in La_0.5Ca_0.5MnO_3, using Fresnel imaging, dark-field TEM and electron holography. This new phase coexists with the two low temperature phases that were already known to coexist in La_0.5Ca_0.5MnO_3. (One of these expected phases is ferromagnetic but not charge-ordered, the other is charge-ordered but not ferromagnetic.) Strain fields could be responsible for the novel microscopic texture presented here - perhaps creating conditions in which nearest neighbour hopping is sufficient to promote ferromagnetism. Similarly, strain fields are believed to cause sub-micron phase separation in the manganites. It therefore seems that the manganites can adapt to their environments over a wide range of length scales [2]. [1] http://xxx.lanl.gov/abs/cond-mat/0209436 [2] Neil Mathur and Peter Littlewood, Physics Today, early 2003.

High resolution microdiffraction studies using synchrotron radiation

NASA Astrophysics Data System (ADS)

Spolenak, R.; Tamura, N.; Valek, B. C.; MacDowell, A. A.; Celestre, R. S.; Padmore, H. A.; Brown, W. L.; Marieb, T.; Batterman, B. W.; Patel, J. R.

2002-04-01

The advent of third generation synchrotron light sources in combination with x-ray focusing devices such as Kirkpatrick-Baez mirrors make Laue diffraction on a submicron length scale possible. Analysis of Laue images enables us to determine the deviatoric part of the 3D strain tensor to an accuracy of 2×10-4 in strain with a spatial resolution comparable to the grain size in our thin films. In this paper the application of x-ray microdiffraction to the temperature dependence of the mechanical behavior of a sputtered blanket Cu film and of electroplated damascene Cu lines will be presented. Microdiffraction reveals very large variations in the strain of a film or line from grain to grain. When the strain is averaged over a macroscopic region the results are in good agreement with direct macroscopic stress measurements. However, the strain variations are so large that in some cases in which the average stress is tensile there are some grains actually under compression. The full implications of these observations are still being considered, but it is clear that the mechanical properties of thin film materials are now accessible with new visibility.

Characterisation of inorganic microparticles in pigment cells of human gut associated lymphoid tissue.

PubMed Central

Powell, J J; Ainley, C C; Harvey, R S; Mason, I M; Kendall, M D; Sankey, E A; Dhillon, A P; Thompson, R P

1996-01-01

Macrophages at the base of human gut associated lymphoid tissue (GALT), become loaded early in life with dark granular pigment that is rich in aluminium, silicon, and titanium. The molecular characteristics, intracellular distribution, and source of this pigment is described. Laser scanning and electron microscopy showed that pigmented macrophages were often closely related to collagen fibres and plasma cells in GALT of both small and large intestine and contained numerous phagolysosomes, previously described as granules, that are rich in electron dense submicron sized particles. Morphological assessment, x ray microanalysis, and image electron energy loss spectroscopy showed three distinct types of microparticle: type I - spheres of titanium dioxide, 100-200 nm diameter, characterised as the synthetic food-additive polymorph anatase; type II - aluminosilicates, < 100-400 nm in length, generally of flaky appearance, often with adsorbed surface iron, and mostly characteristic of the natural clay mineral kaolinite; and type III - mixed environmental silicates without aluminium, 100-700 nm in length and of variable morphology. Thus, this cellular pigment that is partly derived from food additives and partly from the environment is composed of inert inorganic microparticles and loaded into phagolysosomes of macrophages within the GALT of all human subjects. These observations suggest that the pathogenicity of this pigment should be further investigated since, in susceptible individuals, the same intracellular distribution of these three types of submicron particle causes chronic latent granulomatous inflammation. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 PMID:8675092

IDENTIFICATION AND RESPONSES TO POTENTIAL EFFECTS OF SCR AND WET SCRUBBERS ON SUBMICRON PARTICULATE EMISSIONS AND PLUME CHARACTERISTICS

EPA Science Inventory

Applications of selective catalytic reduction (SCR) systems and wet flue gas desulfurization (FGD) scrubbers on coal-fired boilers have led to substantial reductions in emissions of nitrogen oxides (NOX) and sulfur dioxide (SO2). However, observations of pilot- and full-scale tes...

Photochemical potential of forest fire smoke

Treesearch

W. Henry Benner; Paul Urone; Charles K. McMahon; Paul Ryan

1977-01-01

A stainless steel laboratory chamber to hold the entire combustion products from a small scale pine needle fire was useful for measuring the photochemical activity of pine needle fire smoke. Particle size distributions indicated that the nucleation of small numbers of submicron particles was sufficient to increase the amount of light a plume would scatter. Artificial...

Aerosol reactor production of uniform submicron powders

NASA Technical Reports Server (NTRS)

Flagan, Richard C. (Inventor); Wu, Jin J. (Inventor)

1991-01-01

A method of producing submicron nonagglomerated particles in a single stage reactor includes introducing a reactant or mixture of reactants at one end while varying the temperature along the reactor to initiate reactions at a low rate. As homogeneously small numbers of seed particles generated in the initial section of the reactor progress through the reactor, the reaction is gradually accelerated through programmed increases in temperature along the length of the reactor to promote particle growth by chemical vapor deposition while minimizing agglomerate formation by maintaining a sufficiently low number concentration of particles in the reactor such that coagulation is inhibited within the residence time of particles in the reactor. The maximum temperature and minimum residence time is defined by a combination of temperature and residence time that is necessary to bring the reaction to completion. In one embodiment, electronic grade silane and high purity nitrogen are introduced into the reactor and temperatures of approximately 770.degree. K. to 1550.degree. K. are employed. In another embodiment silane and ammonia are employed at temperatures from 750.degree. K. to 1800.degree. K.

Aerosol reactor production of uniform submicron powders

DOEpatents

Flagan, Richard C.; Wu, Jin J.

1991-02-19

A method of producing submicron nonagglomerated particles in a single stage reactor includes introducing a reactant or mixture of reactants at one end while varying the temperature along the reactor to initiate reactions at a low rate. As homogeneously small numbers of seed particles generated in the initial section of the reactor progress through the reactor, the reaction is gradually accelerated through programmed increases in temperature along the length of the reactor to promote particle growth by chemical vapor deposition while minimizing agglomerate formation by maintaining a sufficiently low number concentration of particles in the reactor such that coagulation is inhibited within the residence time of particles in the reactor. The maximum temperature and minimum residence time is defined by a combination of temperature and residence time that is necessary to bring the reaction to completion. In one embodiment, electronic grade silane and high purity nitrogen are introduced into the reactor and temperatures of approximately 770.degree. K. to 1550.degree. K. are employed. In another embodiment silane and ammonia are employed at temperatures from 750.degree. K. to 1800.degree. K.

Lungs deposition and pharmacokinetic study of submicron budesonide particles in Wistar rats intended for immediate effect in asthma.

PubMed

Rauf, Abdul; Bhatnagar, Aseem; Sisodia, S S; Khar, Roop K; Ahmad, Farhan J

2017-01-01

The purpose of the present investigation was to study the aerosolization, lungs deposition and pharmacokinetic study of inhalable submicron particles of budesonide in male Wistar rats. Submicron particles were prepared by antisolvent nanoprecipitation method and freeze-dried to obtain free flowing powder. The freeze-drying process yielded dry powder with desirable aerodynamic properties for inhalation therapy. An in-house model inhaler was designed to deliver medicine to lungs, optimized at dose level of 10 mg for 30 sec of fluidization. The in vitro aerosolization study demonstrates that submicron particles dissolve faster with improved aerosolization effect as compared to micronized budesonide. Both submicron and micron particles were compared for in vivo lungs deposition. The results showed that relatively high quantity of submicron particles reaches deep into the lungs as compared to micron particles. Most pronounced effect observed with submicron particles from pharmacokinetic parameters was the enhancement in peak plasma concentration (C max ) by 28.85 %, and increase in area under concentration curve (AUC 0-8h ) by 30.33 % compared to micron sized particles. The results suggested that developed submicronized formulation of budesonide can be used for pulmonary drug delivery for high deposition to deep lungs tissues.

Magnetoresistance and magnetization in submicron ferromagnetic gratings

NASA Astrophysics Data System (ADS)

Shearwood, C.; Blundell, S. J.; Baird, M. J.; Bland, J. A. C.; Gester, M.; Ahmed, H.; Hughes, H. P.

1994-05-01

A technique for engineering micron and submicron scale structures from magnetic films of transition metals has been developed using a combination of electron- and ion-beam lithography enabling high-quality arrays of submicron magnetic Fe wires to be fabricated. This process can be used to fabricate novel devices from a variety of metal combinations which would not be possible by the usual liftoff metallization method. The structure and magnetic properties are reported of an epitaxial 25 nm Fe(001)/GaAs(001) film and the wire gratings which are fabricated from it. The width of the wires in the grating is 0.5 μm for all structures studied, but the separation of each wire is varied in the range 0.5 to 16 μm. An artificially induced shape anisotropy field of around 1 kG, consistent with a magnetostatic calculation, was observed for all separations studied. The field dependence of the magneto-optic Kerr effect and magnetoresistance (MR) data is consistent with a twisted magnetization configuration across the width of the sample beneath saturation for transverse applied fields. In this case, the detailed form of the field dependence of the MR is strikingly modified from that observed in the continuous film and is consistent with coherent rotation of the magnetization.

A SELF-CONSISTENT MODEL OF THE CIRCUMSTELLAR DEBRIS CREATED BY A GIANT HYPERVELOCITY IMPACT IN THE HD 172555 SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, B. C.; Melosh, H. J.; Lisse, C. M.

2012-12-10

Spectral modeling of the large infrared excess in the Spitzer IRS spectra of HD 172555 suggests that there is more than 10{sup 19} kg of submicron dust in the system. Using physical arguments and constraints from observations, we rule out the possibility of the infrared excess being created by a magma ocean planet or a circumplanetary disk or torus. We show that the infrared excess is consistent with a circumstellar debris disk or torus, located at {approx}6 AU, that was created by a planetary scale hypervelocity impact. We find that radiation pressure should remove submicron dust from the debris diskmore » in less than one year. However, the system's mid-infrared photometric flux, dominated by submicron grains, has been stable within 4% over the last 27 years, from the Infrared Astronomical Satellite (1983) to WISE (2010). Our new spectral modeling work and calculations of the radiation pressure on fine dust in HD 172555 provide a self-consistent explanation for this apparent contradiction. We also explore the unconfirmed claim that {approx}10{sup 47} molecules of SiO vapor are needed to explain an emission feature at {approx}8 {mu}m in the Spitzer IRS spectrum of HD 172555. We find that unless there are {approx}10{sup 48} atoms or 0.05 M{sub Circled-Plus} of atomic Si and O vapor in the system, SiO vapor should be destroyed by photo-dissociation in less than 0.2 years. We argue that a second plausible explanation for the {approx}8 {mu}m feature can be emission from solid SiO, which naturally occurs in submicron silicate ''smokes'' created by quickly condensing vaporized silicate.« less

Microscale Investigation of Thermo-Fluid Transport in the Transition FIL, Region of an Evaporating Capillary Meniscus Using a Microgravity Environment

NASA Technical Reports Server (NTRS)

Kihm, K. D.; Allen, J. S.; Hallinan, K. P.; Pratt, D. M.

2004-01-01

In order to enhance the fundamental understanding of thin film evaporation and thereby improve the critical design concept for two-phase heat transfer devices, microscale heat and mass transport is to be investigated for the transition film region using state-of-the-art optical diagnostic techniques. By utilizing a microgravity environment, the length scales of the transition film region can be extended sufficiently, from submicron to micron, to probe and measure the microscale transport fields which are affected by intermolecular forces. Extension of the thin film dimensions under microgravity will be achieved by using a conical evaporator made of a thin silicon substrate under which concentric and individually controlled micro-heaters are vapor-deposited to maintain either a constant surface temperature or a controlled temperature variation. Local heat transfer rates, required to maintain the desired wall temperature boundary condition, will be measured and recorded by the concentric thermoresistance heaters controlled by a Wheatstone bridge circuit, The proposed experiment employs a novel technique to maintain a constant liquid volume and liquid pressure in the capillary region of the evaporating meniscus so as to maintain quasi-stationary conditions during measurements on the transition film region. Alternating use of Fizeau interferometry via white and monochromatic light sources will measure the thin film slope and thickness variation, respectively. Molecular Fluorescence Tracking Velocimetry (MFTV), utilizing caged fluorophores of approximately 10-nm in size as seeding particles, will be used to measure the velocity profiles in the thin film region. An optical sectioning technique using confocal microscopy will allow submicron depthwise resolution for the velocity measurements within the film for thicknesses on the order of a few microns. Digital analysis of the fluorescence image-displacement PDFs, as described in the main proposal, can further enhance the depthwise resolution.

Fabrication and characterization of sub-micron scale hall devices from 2-dimensional electron gas at the heterostrutcure of GaAs/AlGaAs

NASA Astrophysics Data System (ADS)

Keswani, Neeti; Nakajima, Yoshikata; Chauhan, Neha; Kumar, Sakthi; Ohno, H.; Das, Pintu

2018-05-01

In this work, we report the fabrication and transport properties of sub-micron Hall devices to be used for nanomagnetic studies. Hall bars were fabricated using electron-beam lithography followed by wet etching of GaAs/AlGaAs heterostructures containing two-dimensional electron gas (2-DEG). Metallization using multiple metallic layers were used to achieve ohmic contacts with the 2-DEG which is about 240 nm below the surface. Detailed characterization of the metallic layers using X-ray Photoelectron Spectroscopy (XPS) demonstrate the role of alloy formation and diffusion to form ohmic contacts with the 2-DEG. Electronic transport measurements show the metallic character of the 2-DEG. Hall effect and magnetoresistance were measured to estimate the carrier mobility of 4.2×104 cm2/V-s at 5 K in dark.

Electrothermal enrichment of submicron particles in an insulator-based dielectrophoretic microdevice.

PubMed

Kale, Akshay; Song, Le; Lu, Xinyu; Yu, Liandong; Hu, Guoqing; Xuan, Xiangchun

2018-03-01

Insulator-based dielectrophoresis (iDEP) exploits in-channel hurdles and posts etc. to create electric field gradients for various particle manipulations. However, the presence of such insulating structures also amplifies the Joule heating in the fluid around themselves, leading to both temperature gradients and electrothermal flow. These Joule heating effects have been previously demonstrated to weaken the dielectrophoretic focusing and trapping of microscale and nanoscale particles. We find that the electrothermal flow vortices are able to entrain submicron particles for a localized enrichment near the insulating tips of a ratchet microchannel. This increase in particle concentration is reasonably predicted by a full-scale numerical simulation of the mass transport along with the coupled charge, heat and fluid transport. Our model also predicts the electric current and flow pattern in the fluid with a good agreement with the experimental observations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructure and mechanical properties of Al-3Fe alloy processed by equal channel angular extrusion

NASA Astrophysics Data System (ADS)

Fuxiao, Yu; Fang, Liu; Dazhi, Zhao; Toth, Laszlo S.

2014-08-01

Al-Fe alloys are attractive for applications at temperatures beyond those normally associated with the conventional aluminum alloys. Under proper solidification condition, a full eutectic microstructure can be generated in Al-Fe alloys at Fe concentration well in excess of the eutectic composition of 1.8 wt.% Fe. The microstructure in this case is characterized by the metastable regular eutectic Al-Al6Fe fibers of nano-scale in diameter, instead of the equilibrium eutectic Al-Al3Fe phase. In this study, the microstructure and mechanical properties of the Al-3Fe alloy with metastable Al6Fe particles deformed by equal channel angular extrusion were investigated. Severe plastic deformation results in a microstructure consisting of submicron equiaxed Al grains with a uniform distribution of submicron Al6Fe particles on the grain boundaries. The room temperature tensile properties of the alloy with this microstructure will be presented.

Aerosol emissions from prescribed fires in the United States: A synthesis of laboratory and aircraft measurements

Treesearch

A. A. May; G. R. McMeeking; T. Lee; J. W. Taylor; J. S. Craven; I. Burling; A. P. Sullivan; S. Akagi; J. L. Collett; M. Flynn; H. Coe; S. P. Urbanski; J. H. Seinfeld; R. J. Yokelson; S. M. Kreidenweis

2014-01-01

Aerosol emissions from prescribed fires can affect air quality on regional scales. Accurate representation of these emissions in models requires information regarding the amount and composition of the emitted species. We measured a suite of submicron particulate matter species in young plumes emitted from prescribed fires (chaparral and montane ecosystems in California...

Submicron Emulsions and Their Applications in Oral Delivery.

PubMed

Mundada, Veenu; Patel, Mitali; Sawant, Krutika

2016-01-01

A "submicron emulsion" is an isotropic mixture of drug, lipids, and surfactants, usually with hydrophilic cosolvents and with droplet diameters ranging from 10 to 500 nm. Submicron emulsions are of increasing interest in medicine due to their kinetic stability, high solubilizing capacity, and tiny globule size. Because of these properties, they have been applied in various fields, such as personal care, cosmetics, health care, pharmaceuticals, and agrochemicals. Submicron emulsions are by far the most advanced nanoparticulate systems for the systemic delivery of biologically active agents for controlled drug delivery and targeting. They are designed mainly for pharmaceutical formulations suitable for various routes of administration like parenteral, ocular, transdermal, and oral. This review article describes the marked potential of submicron emulsions for oral drug delivery owing to their numerous advantages like reduced first pass metabolism, inhibition of P-glycoprotein efflux system, and enhanced absorption via intestinal lymphatic pathway. To overcome the limitations of liquid dosage forms, submicron emulsions can be formulated into solid dosage forms such as solid self-emulsifying systems. This article covers various types of submicron emulsions like microemulsion, nanoemulsion, and self-emulsifying drug delivery system (SEDDS), and their potential pharmaceutical applications in oral delivery with emphasis on their advantages, limitations, and advancements.

Predictive Mechanical Characterization of Macro-Molecular Material Chemistry Structures of Cement Paste at Nano Scale - Two-phase Macro-Molecular Structures of Calcium Silicate Hydrate, Tri-Calcium Silicate, Di-Calcium Silicate and Calcium Hydroxide

NASA Astrophysics Data System (ADS)

Padilla Espinosa, Ingrid Marcela

Concrete is a hierarchical composite material with a random structure over a wide range of length scales. At submicron length scale the main component of concrete is cement paste, formed by the reaction of Portland cement clinkers and water. Cement paste acts as a binding matrix for the other components and is responsible for the strength of concrete. Cement paste microstructure contains voids, hydrated and unhydrated cement phases. The main crystalline phases of unhydrated cement are tri-calcium silicate (C3S) and di-calcium silicate (C2S), and of hydrated cement are calcium silicate hydrate (CSH) and calcium hydroxide (CH). Although efforts have been made to comprehend the chemical and physical nature of cement paste, studies at molecular level have primarily been focused on individual components. Present research focuses on the development of a method to model, at molecular level, and analysis of the two-phase combination of hydrated and unhydrated phases of cement paste as macromolecular systems. Computational molecular modeling could help in understanding the influence of the phase interactions on the material properties, and mechanical performance of cement paste. Present work also strives to create a framework for molecular level models suitable for potential better comparisons with low length scale experimental methods, in which the sizes of the samples involve the mixture of different hydrated and unhydrated crystalline phases of cement paste. Two approaches based on two-phase cement paste macromolecular structures, one involving admixed molecular phases, and the second involving cluster of two molecular phases are investigated. The mechanical properties of two-phase macromolecular systems of cement paste consisting of key hydrated phase CSH and unhydrated phases C3S or C2S, as well as CSH with the second hydrated phase CH were calculated. It was found that these cement paste two-phase macromolecular systems predicted an isotropic material behavior. Also, these systems exhibited a high bulk modulus, compared to the elastic modulus. These results are an indication and concur with the high compression strength of cement paste seen at engineering length scale. In addition, the bulk modulus of two-phase systems consisting of hydrated CSH and unhydrated C3S or C2S was found to increase with higher levels of unhydrated components. The interaction energies of two-phase cement paste molecular structures studied in the present work were calculated, showing that a higher interaction is attained when the two phases are admixed as small components instead of cluster of phases. Finally, the mechanical behavior under shear deformation was predicted by using a quasi-static deformation method and analyzed for a representative two-phase (CSH and C2S) macromolecular structure of cement paste.

A miracle happening to a laser beam in a soap film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Startsev, Aleksandr V; Stoilov, Yurii Yu

2003-05-31

When a 10 {mu}W - 3 W laser beam (for example, at 632.8 nm) is focused into a usual soap film of thickness between 10 nm and 10 {mu}m from the side or through a defect on the film surface, the self-channeling of the beam propagating in the film is observed. The beam also exhibits self-branching into submicron filaments, the so-called whiskers of length several tens of centimetres. The results of experiments on the dynamics of behaviour of these whiskers in a soap film, their polariton nature, and possible applications are discussed. (letters)

Theoretical study of nanophotonic directional couplers comprising near-field-coupled metal nanoparticles.

PubMed

Holmström, Petter; Yuan, Jun; Qiu, Min; Thylén, Lars; Bratkovsky, Alexander M

2011-04-11

The properties of integrated-photonics directional couplers composed of near-field-coupled arrays of metal nanoparticles are analyzed theoretically. It is found that it is possible to generate very compact, submicron length, high field-confinement and functionality devices with very low switch energies. The analysis is carried out for a hypothetical lossless silver to demonstrate the potential of this type of circuits for applications in telecom and interconnects. Employing losses of real silver, standalone devices with the above properties are still feasible in optimized metal nanoparticle structures. © 2011 Optical Society of America

Evolution of Shock Melt Compositions in Lunar Regoliths

NASA Technical Reports Server (NTRS)

Vance, A. M.; Christoffersen, R.; Keller, L. P.; Berger, E. L.; Noble, S. K.

2016-01-01

Space weathering processes - driven primarily by solar wind ion and micrometeorite bombardment, are constantly changing the surface regoliths of airless bodies, such as the Moon. It is essential to study lunar soils in order to fully under-stand the processes of space weathering, and how they alter the optical reflectance spectral properties of the lunar surface relative to bedrock. Lunar agglutinates are aggregates of regolith grains fused together in a glassy matrix of shock melt produced during micrometeorite impacts into the lunar regolith. The formation of the shock melt component in agglutinates involves reduction of Fe in the target material to generate nm-scale spherules of metallic Fe (nanophase Fe0 or npFe0). The ratio of elemental Fe, in the form of npFe0, to FeO in a given bulk soil indicates its maturity, which increases with length of surface exposure as well as being typically higher in the finer-size fraction of soils. The melting and mixing process in agglutinate formation remain poorly understood. This includes incomplete knowledge regarding how the homogeneity and overall compositional trends of the agglutinate glass portions (agglutinitic glass) evolve with maturity. The aim of this study is to use sub-micrometer scale X-ray compositional mapping and image analysis to quantify the chemical homogeneity of agglutinitic glass, correlate its homogeneity to its parent soil maturity, and identify the principal chemical components contributing to the shock melt composition variations. An additional focus is to see if agglutinitic glass contains anomalously high Fe sub-micron scale compositional domains similar to those recently reported in glassy patina coatings on lunar rocks.

Detection of submicron-sized raft-like domains in membranes by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Pencer, J.; Mills, T.; Anghel, V.; Krueger, S.; Epand, R. M.; Katsaras, J.

2005-12-01

Using coarse grained models of heterogeneous vesicles we demonstrate the potential for small-angle neutron scattering (SANS) to detect and distinguish between two different categories of lateral segregation: 1) unilamellar vesicles (ULV) containing a single domain and 2) the formation of several small domains or “clusters” (~10 nm in radius) on a ULV. Exploiting the unique sensitivity of neutron scattering to differences between hydrogen and deuterium, we show that the liquid ordered (lo) DPPC-rich phase can be selectively labeled using chain deuterated dipalymitoyl phosphatidylcholine (dDPPC), which greatly facilitates the use of SANS to detect membrane domains. SANS experiments are then performed in order to detect and characterize, on nanometer length scales, lateral heterogeneities, or so-called “rafts”, in ~30 nm radius low polydispersity ULV made up of ternary mixtures of phospholipids and cholesterol. For 1:1:1 DOPC:DPPC:cholesterol (DDC) ULV we find evidence for the formation of lateral heterogeneities on cooling below 30 °C. These heterogeneities do not appear when DOPC is replaced by SOPC. Fits to the experimental data using coarse grained models show that, at room temperature, DDC ULV each exhibit approximately 30 domains with average radii of ~10 nm.

Time-resolved optical absorption microspectroscopy of magnetic field sensitive flavin photochemistry

NASA Astrophysics Data System (ADS)

Antill, Lewis M.; Beardmore, Joshua P.; Woodward, Jonathan R.

2018-02-01

The photochemical reactions of blue-light receptor proteins have received much attention due to their very important biological functions. In addition, there is also growing evidence that the one particular class of such proteins, the cryptochromes, may be associated with not only a biological photo-response but also a magneto-response, which may be responsible for the mechanism by which many animals can respond to the weak geomagnetic field. Therefore, there is an important scientific question over whether it is possible to directly observe such photochemical processes, and indeed the effects of weak magnetic fields thereon, taking place both in purified protein samples in vitro and in actual biochemical cells and tissues. For the former samples, the key lies in being able to make sensitive spectroscopic measurements on very small volumes of samples at potentially low protein concentrations, while the latter requires, in addition, spatially resolved measurements on length scales smaller than typical cellular components, i.e., sub-micron resolution. In this work, we discuss a two- and three-color confocal pump-probe microscopic approach to this question which satisfies these requirements and is thus useful for experimental measurements in both cases.

Separating the signal from the noise: Expanding flow cytometry into the sub-micron range.

EPA Science Inventory

Cytometry Part A Special Section: Separating the signal from the noise: Expanding flow cytometry into the sub-micron range. The current Cytometry Part A Special Section presents three studies that utilize cytometers to study sub-micron particles. The three studies involve the 1...

Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

DOEpatents

Li, Ting [Ventura, CA

2011-04-26

The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

Morphology and magnetic properties of CeCo5 submicron flakes prepared by surfactant-assisted high-energy ball milling

NASA Astrophysics Data System (ADS)

Zhang, J. J.; Gao, H. M.; Yan, Y.; Bai, X.; Su, F.; Wang, W. Q.; Du, X. B.

2012-10-01

CeCo5 permanent magnetic alloy has been processed by surfactant assisted high energy ball milling. Heptane and oleic acid were used as the solvent and surfactant, respectively. The amount of surfactant used was 50% by weight of the starting powder. The produced particles were deposited on a piece of copper (4 mm in length and width) under a magnetic field of 27 kOe applied along the copper surface and immobilized by ethyl α-cyanoacrylate. Scanning electron microscope pictures show that the particles are flakes, several μm in length and width and tens of nm in thickness. X-ray diffraction patterns and magnetic measurements prove that the flakes are crystalline with c-axes magnetic anisotropy. The easy magnetization axis is oriented perpendicular to the surface of the flake. A maximum coercivity of 3.3 kOe was obtained for the sample milled for 40 min.

Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ting

The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE processmore » is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.« less

Progress Report for the Joint Services Electronics Program

DTIC Science & Technology

1991-06-30

AIGaAs MODFET layers. Both wet etching and reactive ion etching have been used to fabricate the channels. The CAIBE method will also be investigated in...potential for fabricating nanometer scale device structures through surface modification of various types. Using this JSEP research as a foundation...Kerkhoven, "Calculation of velocity overshoot in submicron devices using an augmented drift-diffusion model," Solid-State Electron. (to appear). (JSEP/NSF

Self-assembly of resins and asphaltenes facilitates asphaltene dissolution by an organic acid.

PubMed

Hashmi, Sara M; Firoozabadi, Abbas

2013-03-15

Asphaltene precipitation occurs in petroleum fluids under certain unfavorable conditions, but can be controlled by tuning composition. Aromatic solvents in large quantities can prevent precipitation entirely and can dissolve already precipitated asphaltenes. Some polymeric surfactants can dissolve asphaltenes when added at much lower concentrations than required by aromatic solvents. Other dispersants can truncate asphaltene precipitation at the sub-micron length scale, creating stable colloidal asphaltene dispersants. One particular asphaltene dispersant, dodecylbenzene sulfonic acid (DBSA), can do both, namely: (1) stabilize asphaltene colloids and (2) dissolve asphaltenes to the molecular scale. Acid-base interactions are responsible for the efficiency of DBSA in dissolving asphaltenes compared to aromatic solvents. However, many details remain to be quantified regarding the action of DBSA on asphaltenes, including the effect of petroleum fluid composition. For instance, resins, naturally amphiphilic components of petroleum fluids, can associate with asphaltenes, but it is unknown whether they cooperate or compete with DBSA. Similarly, the presence of metals is known to hinder asphaltene dissolution by DBSA, but its effect on colloidal asphaltene stabilization has yet to be considered. We introduce the concepts of cooperativity and competition between petroleum fluid components and DBSA in stabilizing and dissolving asphaltenes. Notably, we find that resins cooperatively interact with DBSA in dissolving asphaltenes. We use UV-vis spectroscopy to investigate the interactions responsible for the phase transitions between unstable suspensions, stable suspensions, and molecular solutions of asphaltenes. Copyright © 2012 Elsevier Inc. All rights reserved.

Microfluidics: Science and Engineering at the Edge of the Continuum

NASA Astrophysics Data System (ADS)

Breuer, Kenny

2002-11-01

The widespread growth of microengineering and the development of a new generation of micron- and nanometer scale diagnostic techniques has focussed much recent attention on the mechanics of fluids at the micron and sub-micron scale. Challenges with both scientific and engineering relevance have been raised by this activity, ranging from the prediction of viscous damping and lubrication effects in MEMS to the design of microengines to the understanding of bacterial propulsion. Identifying and addressing these challenges form the basis of this talk. >From a scientific perspective, a question that refuses to die is that of the applicability of the continuum hypothesis, and the possible existence of new physical phenomena only observable in small systems. To be brief, the reports of the demise of the Navier-Stokes equations are greatly exaggerated and to illustrate this we will review the more recent work on near-continuum fluid mechanics in micron and sub-micron scale devices with an emphasis on our own experiments on the breakdown of the continuum description in both gaseous and liquid flows. From an engineering perspective, the tight coupling between fluids, structures and manufacturing result in flows characterized by unfamiliar parameter regimes and unconventional geometries. We will look at several examples of such microfluidic engineering, drawn from MEMS (inertial instruments, microengines) and biology (bacterial propulsion) that illustrate the the unique design challenges that we encounter in microfluidic devices and the solutions (and lack of solutions) to these problems.

Sub-micron Cu/SSZ-13: Synthesis and application as selective catalytic reduction (SCR) catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prodinger, Sebastian; Derewinski, Miroslaw A.; Wang, Yilin

For the first time, sub-micron Cu/SSZ-13, obtained by modifying an existing synthesis procedure, was shown to be an effective and stable catalyst for selective catalytic reduction reactions, such as NO reduction. Characterization of the materials with X-ray diffraction, N2-physisorption and 27Al MAS NMR shows that hydrothermal aging, simulating SCR reaction conditions, is more destructive in respect to dealumination for smaller particles prior to Cu-exchange. However, the catalytic performance and hydrothermal stability for Cu/SSZ-13 is independent of the particle size. In particular, the stability of tetrahedral framework Al is improved in the sub-micron Cu/SSZ-13 catalysts of comparable Cu loading. This indicatesmore » that variations in the Al distribution for different SSZ-13 synthesis procedures have a more critical influence on stabilizing isolated Cu-ions during harsh hydrothermal aging than the particle size. This study is of high interest for applications in vehicular DeNOx technologies where high loadings of active species on wash coats can be achieved by using sub-micron Cu/SSZ-13. The authors would like to thank B. W. Arey and J. J. Ditto for performing electron microscope imaging. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. S. P and M. A. D also acknowledge support by the Materials Synthesis and Simulation Across Scales (MS3 Initiative) conducted under the Laboratory Directed Research & Development Program at PNNL. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.« less

Dynamic high-resolution patterning for biomedical, materials, and semiconductor research

NASA Astrophysics Data System (ADS)

Garner, Harold R.; Joshi, Amruta; Mitnala, Sandhya N.; Huebschman, Michael L.; Shandy, Surya; Wallek, Brandi; Wong, Season

2009-02-01

By combining unique light sources, a Texas Instruments DLP system and a microscope, a submicron dynamic patterning system has been created. This system has a resolution of 0.5 microns, and can illuminate with rapidly changing patterns of visible, UV or pulsed laser light. This system has been used to create digital masks for the production of micron scale electronic test circuits and has been used in biological applications. Specifically we have directed light on a sub-organelle scale to cells to control their morphology and motility with applications to tissue engineering, cell biology, drug discovery and neurology.

Bi-stability resistant to fluctuations

NASA Astrophysics Data System (ADS)

Caruel, M.; Truskinovsky, L.

2017-12-01

We study a simple micro-mechanical device that does not lose its snap-through behavior in an environment dominated by fluctuations. The main idea is to have several degrees of freedom that can cooperatively resist the de-synchronizing effect of random perturbations. As an inspiration we use the power stroke machinery of skeletal muscles, which ensures at sub-micron scales and finite temperatures a swift recovery of an abruptly applied slack. In addition to hypersensitive response at finite temperatures, our prototypical Brownian snap spring also exhibits criticality at special values of parameters which is another potentially interesting property for micro-scale engineering applications.

Engineering design of sub-micron topographies for simultaneously adherent and reflective metal-polymer interfaces

NASA Technical Reports Server (NTRS)

Brown, Christopher A.

1993-01-01

The approach of the project is to base the design of multi-function, reflective topographies on the theory that topographically dependent phenomena react with surfaces and interfaces at certain scales. The first phase of the project emphasizes the development of methods for understanding the sizes of topographic features which influence reflectivity. Subsequent phases, if necessary, will address the scales of interaction for adhesion and manufacturing processes. A simulation of the interaction of electromagnetic radiation, or light, with a reflective surface is performed using specialized software. Reflectivity of the surface as a function of scale is evaluated and the results from the simulation are compared with reflectivity measurements made on multi-function, reflective surfaces.

Geometrical Vortex Lattice Pinning and Melting in YBaCuO Submicron Bridges.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papari, G. P.; Glatz, A.; Carillo, F.

Since the discovery of high-temperature superconductors (HTSs), most efforts of researchers have been focused on the fabrication of superconducting devices capable of immobilizing vortices, hence of operating at enhanced temperatures and magnetic fields. Recent findings that geometric restrictions may induce self-arresting hypervortices recovering the dissipation-free state at high fields and temperatures made superconducting strips a mainstream of superconductivity studies. Here in this paper we report on the geometrical melting of the vortex lattice in a wide YBCO submicron bridge preceded by magnetoresistance (MR) oscillations fingerprinting the underlying regular vortex structure. Combined magnetoresistance measurements and numerical simulations unambiguously relate the resistancemore » oscillations to the penetration of vortex rows with intermediate geometrical pinning and uncover the details of geometrical melting. Our findings offer a reliable and reproducible pathway for controlling vortices in geometrically restricted nanodevices and introduce a novel technique of geometrical spectroscopy, inferring detailed information of the structure of the vortex system through a combined use of MR curves and large-scale simulations.« less

Analysis of submicron-sized niflumic acid crystals prepared by electrospray crystallization.

PubMed

Ambrus, Rita; Radacsi, Norbert; Szunyogh, Tímea; van der Heijden, Antoine E D M; Ter Horst, Joop H; Szabó-Révész, Piroska

2013-03-25

Interest in submicron-sized drug particles has emerged from both laboratory and industrial perspectives in the last decade. Production of crystals in the nano size scale offers a novel way to particles for drug formulation solving formulation problems of drugs with low solubility in class II of the Biopharmaceutical Classification System. In this work niflumic acid nanoparticles with a size range of 200-800nm were produced by the novel crystallization method, electrospray crystallization. Their properties were compared to those from evaporative and anti-solvent crystallizations, using the same organic solvent, acetone. There is a remarkable difference in the product crystal size depending on the applied methods. The size and morphology were analyzed by scanning electron microscopy and laser diffraction. The structure of the samples was investigated using differential scanning calorimetry, Fourier-transformed infrared spectroscopy and X-ray powder diffraction. The particles produced using electrospray crystallization process were probably changing from amorphous to crystalline state after the procedure. Copyright © 2012 Elsevier B.V. All rights reserved.

Geometrical Vortex Lattice Pinning and Melting in YBaCuO Submicron Bridges.

DOE PAGES

Papari, G. P.; Glatz, A.; Carillo, F.; ...

2016-12-23

Since the discovery of high-temperature superconductors (HTSs), most efforts of researchers have been focused on the fabrication of superconducting devices capable of immobilizing vortices, hence of operating at enhanced temperatures and magnetic fields. Recent findings that geometric restrictions may induce self-arresting hypervortices recovering the dissipation-free state at high fields and temperatures made superconducting strips a mainstream of superconductivity studies. Here in this paper we report on the geometrical melting of the vortex lattice in a wide YBCO submicron bridge preceded by magnetoresistance (MR) oscillations fingerprinting the underlying regular vortex structure. Combined magnetoresistance measurements and numerical simulations unambiguously relate the resistancemore » oscillations to the penetration of vortex rows with intermediate geometrical pinning and uncover the details of geometrical melting. Our findings offer a reliable and reproducible pathway for controlling vortices in geometrically restricted nanodevices and introduce a novel technique of geometrical spectroscopy, inferring detailed information of the structure of the vortex system through a combined use of MR curves and large-scale simulations.« less

Novel wafer stepper with violet LED light source

NASA Astrophysics Data System (ADS)

Ting, Yung-Chiang; Shy, Shyi-Long

2014-03-01

Novel wafer stepper by using contact or proximity printing will be developed, using violet LED light source to replace Hg Arc. lamp or laser. Mirror, filter and condenser lens for Hg Arc. Lamp or laser and reduction lens for projection printing can be discarded. Reliability and manufacturing cost of wafer stepper can be improved. Exposure result by using IP3600 resist and wafer stepper with violet LED light source (wave-length 360nm to 410 nm) will be obtained. This novel wafer stepper can be used for 3DIC, MEMS and bio-chip lithography application by using thin and thick resist with sub-micron to 100 micron thickness.

Fabrication process of superconducting integrated circuits with submicron Nb/AlOx/Nb junctions using electron-beam direct writing technique

NASA Astrophysics Data System (ADS)

Aoyagi, Masahiro; Nakagawa, Hiroshi

1997-07-01

For enhancing operating speed of a superconducting integrated circuit (IC), the device size must be reduced into the submicron level. For this purpose, we have introduced electron beam (EB) direct writing technique into the fabrication process of a Nb/AlOx/Nb Josephson IC. A two-layer (PMMA/(alpha) M-CMS) resist method called the portable conformable mask (PCM) method was utilized for having a high aspect ratio. The electron cyclotron resonance (ECR) plasma etching technique was utilized. We have fabricated micron or submicron-size Nb/AlOx/Nb Josephson junctions, where the size of the junction was varied from 2 micrometer to 0.5 micrometer at 0.1 micrometer intervals. These junctions were designed for evaluating the spread of the junction critical current. We achieved minimum-to-maximum Ic spread of plus or minus 13% for 0.81-micrometer-square (plus or minus 16% for 0.67-micrometer-square) 100 junctions spreading in 130- micrometer-square area. The size deviation of 0.05 micrometer was estimated from the spread values. We have successfully demonstrated a small-scale logic IC with 0.9-micrometer-square junctions having a 50 4JL OR-gate chain, where 4JL means four junctions logic family. The circuit was designed for measuring the gate delay. We obtained a preliminary result of the OR- gate logic delay, where the minimum delay was 8.6 ps/gate.

Design and synthesis of heterobimetallic Ru(II)-Ln(III) complexes as chemodosimetric ensembles for the detection of biogenic amine odorants.

PubMed

Chow, Cheuk-Fai; Lam, Michael H W; Wong, Wai-Yeung

2013-09-03

The detection of neutral biogenic amines plays a crucial role in food safety. Three new heterobimetallic Ru(II)-Ln(III) donor-acceptor complexes, KPrRu, KNdRu, and KSmRu, K{[Ru((II))((t)Bubpy)(CN)4]2-Ln((III))(H2O)4} (where (t)Bubpy = 4,4'-di-tert-butyl-2,2'-bipyridine), have been synthesized and characterized. Their photophysical and X-ray crystallographic data were reported in this study. These complexes were found to be selective for biogenic amine vapors, such as histamine, putrescine, and spermidine, with a detection limit down to the ppb level. The sensitivities of these complexes to the amines were recorded as ~log K = 3.6-5.0. Submicron rods of the complexes, with a nanoscale diameter and microscale length, were obtained through a simple precipitation process. Free-standing polymeric films with different degrees of porosity were fabricated by blending the submicron rods with polystyrene polymer. The polymer with the highest level of porosity exhibited the strongest luminescence enhancement after amine exposure. Real time monitoring of gaseous biogenic amines was applied to real fish samples (Atlantic mackerel) by studying the spectrofluorimetric responses of the Ru(II)-Ln(III) blended polymer film.

High-Resolution Phase-Contrast Imaging of Submicron Particles in Unstained Lung Tissue

NASA Astrophysics Data System (ADS)

Schittny, J. C.; Barré, S. F.; Mokso, R.; Haberthür, D.; Semmler-Behnke, M.; Kreyling, W. G.; Tsuda, A.; Stampanoni, M.

2011-09-01

To access the risks and chances of deposition of submicron particles in the gas-exchange area of the lung, a precise three-dimensional (3D)-localization of the sites of deposition is essential—especially because local peaks of deposition are expected in the acinar tree and in individual alveoli. In this study we developed the workflow for such an investigation. We administered 200-nm gold particles to young adult rats by intratracheal instillation. After fixation and paraffin embedding, their lungs were imaged unstained using synchrotron radiation x-ray tomographic microscopy (SRXTM) at the beamline TOMCAT (Swiss Light Source, Villigen, Switzerland) at sample detector distances of 2.5 mm (absorption contrast) and of 52.5 mm (phase contrast). A segmentation based on a global threshold of grey levels was successfully done on absorption-contrast images for the gold and on the phase-contrast images for the tissue. The smallest spots containing gold possessed a size of 1-2 voxels of 370-nm side length. We conclude that a combination of phase and absorption contrast SRXTM imaging is necessary to obtain the correct segmentation of both tissue and gold particles. This method will be used for the 3D localization of deposited particles in the gas-exchange area of the lung.

Separation of submicron bioparticles by dielectrophoresis.

PubMed Central

Morgan, H; Hughes, M P; Green, N G

1999-01-01

Submicron particles such as latex spheres and viruses can be manipulated and characterized using dielectrophoresis. By the use of appropriate microelectrode arrays, particles can be trapped or moved between regions of high or low electric fields. The magnitude and direction of the dielectrophoretic force on the particle depends on its dielectric properties, so that a heterogeneous mixture of particles can be separated to produce a more homogeneous population. In this paper the controlled separation of submicron bioparticles is demonstrated. With electrode arrays fabricated using direct write electron beam lithography, it is shown that different types of submicron latex spheres can be spatially separated. The separation occurs as a result of differences in magnitude and/or direction of the dielectrophoretic force on different populations of particles. These differences arise mainly because the surface properties of submicron particles dominate their dielectrophoretic behavior. It is also demonstrated that tobacco mosaic virus and herpes simplex virus can be manipulated and spatially separated in a microelectrode array. PMID:10388776

Use of metallic glasses for fabrication of structures with submicron dimensions

DOEpatents

Wiley, John D.; Perepezko, John H.

1986-01-01

Patterned structures of submicron dimension formed of supported or unsupported amorphous metals having submicron feature sizes characterized by etching behavior sufficient to allow delineation of sharp edges and smooth flat flanks, resistance to time-dependent dimensional changes caused by creep, flow, in-diffusion of unwanted impurities, out-diffusion of constituent atoms, void formation, grain growth or phase separation and resistance to phase transformations or compound formation.

Sub-micron particle sampler apparatus and method for sampling sub-micron particles

DOEpatents

Gay, D.D.; McMillan, W.G.

1984-04-12

Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however, the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis. 6 figures.

Brownian trail rectified

NASA Astrophysics Data System (ADS)

Hurd, Alan J.; Ho, Pauline

The experiments described here indicate when one of Nature's best fractals -- the Brownian trail -- becomes nonfractal. In most ambient fluids, the trail of a Brownian particle is self-similar over many decades of length. For example, the trail of a submicron particle suspended in an ordinary liquid, recorded at equal time intervals, exhibits apparently discontinuous changes in velocity from macroscopic lengths down to molecular lengths: the trail is a random walk with no velocity memory from one step to the next. In ideal Brownian motion, the kinks in the trail persist to infinitesimal time intervals, i.e., it is a curve without tangents. Even in real Brownian motion in a liquid, the time interval must be shortened to approximately 10(-8) s before the velocity appears continuous. In sufficiently rarefied environments, this time resolution at which a Brownian trail is rectified from a curve without tangents to a smoothly varying trajectory is greatly lengthened, making it possible to study the kinetic regime by dynamic light scattering. Our recent experiments with particles in a plasma have demonstrated this capability. In this regime, the particle velocity persists over a finite step length allowing an analogy to an ideal gas with Maxwell-Boltzmann velocities; the particle mass could be obtained from equipartition. The crossover from ballistic flight to hydrodynamic diffusion was also seen.

Cavity cooling of an optically levitated submicron particle

PubMed Central

Kiesel, Nikolai; Blaser, Florian; Delić, Uroš; Grass, David; Kaltenbaek, Rainer; Aspelmeyer, Markus

2013-01-01

The coupling of a levitated submicron particle and an optical cavity field promises access to a unique parameter regime both for macroscopic quantum experiments and for high-precision force sensing. We report a demonstration of such controlled interactions by cavity cooling the center-of-mass motion of an optically trapped submicron particle. This paves the way for a light–matter interface that can enable room-temperature quantum experiments with mesoscopic mechanical systems. PMID:23940352

Reliability Considerations of ULP Scaled CMOS in Spacecraft Systems

NASA Technical Reports Server (NTRS)

White, Mark; MacNeal, Kristen; Cooper, Mark

2012-01-01

NASA, the aerospace community, and other high reliability (hi-rel) users of advanced microelectronic products face many challenges as technology continues to scale into the deep sub-micron region. Decreasing the feature size of CMOS devices not only allows more components to be placed on a single chip, but it increases performance by allowing faster switching (or clock) speeds with reduced power compared to larger scaled devices. Higher performance, and lower operating and stand-by power characteristics of Ultra-Low Power (ULP) microelectronics are not only desirable, but also necessary to meet low power consumption design goals of critical spacecraft systems. The integration of these components in such systems, however, must be balanced with the overall risk tolerance of the project.

Modular apparatus for electrostatic actuation of common atomic force microscope cantilevers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Christian J., E-mail: christian.long@nist.gov; Maryland Nanocenter, University of Maryland, College Park, Maryland 20742; Cannara, Rachel J.

2015-07-15

Piezoelectric actuation of atomic force microscope (AFM) cantilevers often suffers from spurious mechanical resonances in the loop between the signal driving the cantilever and the actual tip motion. These spurious resonances can reduce the accuracy of AFM measurements and in some cases completely obscure the cantilever response. To address these limitations, we developed a specialized AFM cantilever holder for electrostatic actuation of AFM cantilevers. The holder contains electrical contacts for the AFM cantilever chip, as well as an electrode (or electrodes) that may be precisely positioned with respect to the back of the cantilever. By controlling the voltages on themore » AFM cantilever and the actuation electrode(s), an electrostatic force is applied directly to the cantilever, providing a near-ideal transfer function from drive signal to tip motion. We demonstrate both static and dynamic actuations, achieved through the application of direct current and alternating current voltage schemes, respectively. As an example application, we explore contact resonance atomic force microscopy, which is a technique for measuring the mechanical properties of surfaces on the sub-micron length scale. Using multiple electrodes, we also show that the torsional resonances of the AFM cantilever may be excited electrostatically, opening the door for advanced dynamic lateral force measurements with improved accuracy and precision.« less

In situ visualisation and characterisation of the capacity of highly reactive minerals to preserve soil organic matter (SOM) in colloids at submicron scale.

PubMed

Xiao, Jian; Wen, Yongli; Li, Huan; Hao, Jialong; Shen, Qirong; Ran, Wei; Mei, Xinlan; He, Xinhua; Yu, Guanghui

2015-11-01

Mineral-organo associations (MOAs) are a mixture of identifiable biopolymers associated with highly reactive minerals and microorganisms. However, the in situ characterization and correlation between soil organic matter (SOM) and highly reactive Al and Fe minerals are still unclear for the lack of technologies, particularly in the long-term agricultural soil colloids at submicron scale. We combined several novel techniques, including nano-scale secondary ion mass spectrometry (NanoSIMS), X-ray absorption near edge structure (XANES) and confocal laser scanning microscopy (CLSM) to characterise the capacity of highly reactive Al and Fe minerals to preserve SOM in Ferralic Cambisol in south China. Our results demonstrated that: (1) highly reactive minerals were strongly related to SOM preservation, while SOM had a more significant line correlation with the highly reactive Al minerals than the highly reactive Fe minerals, according to the regions of interest correlation analyses using NanoSIMS; (2) allophane and ferrihydrite were the potential mineral species to determine the SOM preservation capability, which was evaluated by the X-ray photoelectron spectroscopy (XPS) and Fe K-edge XANES spectroscopy techniques; and (3) soil organic biopolymers with dominant compounds, such as proteins, polysaccharides and lipids, were distributed at the rough and clustered surface of MOAs with high chemical and spatial heterogeneity according to the CLSM observation. Our results also promoted the understanding of the roles played by the highly reactive Al and Fe minerals in the spatial distribution of soil organic biopolymers and SOM sequestration. Copyright © 2015 Elsevier Ltd. All rights reserved.

Surface morphological, structural, electrical and optical properties of GaN-based light-emitting diodes using submicron-scaled Ag islands and ITO thin films

NASA Astrophysics Data System (ADS)

Lee, Young-Woong; Reddy, M. Siva Pratap; Kim, Bo-Myung; Park, Chinho

2018-07-01

An ITO-Ag islands complex as a new transparent conducting electrode (TCE) structure (on the 5 nm-thick p-InGaN/90 nm-thick p-GaN) for achieving high-performance and more reliable GaN-based LEDs were fabricated. A normal LED with a conventional ITO TCE was also compared. The surface morphological, structural, electrical and optical properties of fabricated GaN-based light-emitting diodes using a complex electrode of submicron-scaled Ag islands and ITO thin films are explored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), current-voltage (I-V) and output power-current (L-I) techniques. Surface morphology investigations revealed Ag islands formed uniformly on the p-InGaN/p-GaN surface during rapid thermal annealing at 400 °C for 1 min in N2 ambient. The ohmic properties and overall device-performance of the suggested contact and device structures were superior to those in the conventional ITO contact and normal ITO LED structures. Based on the results of XRD and XPS measurements, the formation of the intermetallic gallide phases (AgGa) is responsible for better performance characteristics of the ITO-Ag islands device. The significant improvements are described in terms of the conducting bridge influence, highly effective micro-mirror effect, and wider photon window via the roughened structure.

[Nasal submicron emulsion of Scutellariae Radix extract preparation technology research based on phase transfer of solute technology].

PubMed

Shi, Ya-jun; Shi, Jun-hui; Chen, Shi-bin; Yang, Ming

2015-07-01

Based on the demand of nasal drug delivery high drug loadings, using the unique phase transfer of solute, integrating the phospholipid complex preparation and submicron emulsion molding process of Scutellariae Radix extract, the study obtained the preparation of the high drug loadings submicron emulsion of Scutellariae Radix extract. In the study of drug solution dispersion method, the uniformity of drug dispersed as the evaluation index, the traditional mixing method, grinding, homogenate and solute phase transfer technology were investigated, and the solute phase transfer technology was adopted in the last. With the adoption of new technology, the drug loading capacity reached 1.33% (phospholipid complex was 4%). The drug loading capacity was improved significantly. The transfer of solute method and timing were studied as follows,join the oil phase when the volume of phospholipid complex anhydrous ethanol solution remaining 30%, the solute phase transfer was completed with the continued recycling of anhydrous ethanol. After drug dissolved away to oil phase, the preparation technology of colostrum was determined with the evaluation index of emulsion droplet form. The particle size of submicron emulsion, PDI and stability parameters were used as evaluation index, orthogonal methodology were adopted to optimize the submicron emulsion ingredient and main influential factors of high pressure homogenization technology. The optimized preparation technology of Scutellariae Radix extract nasal submicron emulsion is practical and stable.

Submicron Protein Particle Characterization using Resistive Pulse Sensing and Conventional Light Scattering Based Approaches.

PubMed

Barnett, Gregory V; Perhacs, Julia M; Das, Tapan K; Kar, Sambit R

2018-02-08

Characterizing submicron protein particles (approximately 0.1-1μm) is challenging due to a limited number of suitable instruments capable of monitoring a relatively large continuum of particle size and concentration. In this work, we report for the first time the characterization of submicron protein particles using the high size resolution technique of resistive pulse sensing (RPS). Resistive pulse sensing, dynamic light scattering and size-exclusion chromatography with in-line multi-angle light scattering (SEC-MALS) are performed on protein and placebo formulations, polystyrene size standards, placebo formulations spiked with silicone oil, and protein formulations stressed via freeze-thaw cycling, thermal incubation, and acid treatment. A method is developed for monitoring submicron protein particles using RPS. The suitable particle concentration range for RPS is found to be approximately 4 × 10 7 -1 × 10 11 particles/mL using polystyrene size standards. Particle size distributions by RPS are consistent with hydrodynamic diameter distributions from batch DLS and to radius of gyration profiles from SEC-MALS. RPS particle size distributions provide an estimate of particle counts and better size resolution compared to light scattering. RPS is applicable for characterizing submicron particles in protein formulations with a high degree of size polydispersity. Data on submicron particle distributions provide insights into particles formation under different stresses encountered during biologics drug development.

Penetration of sub-micron particles into dentinal tubules using ultrasonic cavitation.

PubMed

Vyas, N; Sammons, R L; Pikramenou, Z; Palin, W M; Dehghani, H; Walmsley, A D

2017-01-01

Functionalised silica sub-micron particles are being investigated as a method of delivering antimicrobials and remineralisation agents into dentinal tubules. However, their methods of application are not optimised, resulting in shallow penetration and aggregation. The aim of this study is to investigate the impact of cavitation occurring around ultrasonic scalers for enhancing particle penetration into dentinal tubules. Dentine slices were prepared from premolar teeth. Silica sub-micron particles were prepared in water or acetone. Cavitation from an ultrasonic scaler (Satelec P5 Newtron, Acteon, France) was applied to dentine slices immersed inside the sub-micron particle solutions. Samples were imaged with scanning electron microscopy (SEM) to assess tubule occlusion and particle penetration. Qualitative observations of SEM images showed some tubule occlusion. The particles could penetrate inside the tubules up to 60μm when there was no cavitation and up to ∼180μm when there was cavitation. The cavitation bubbles produced from an ultrasonic scaler may be used to deliver sub-micron particles into dentine. This method has the potential to deliver such particles deeper into the dentinal tubules. Cavitation from a clinical ultrasonic scaler may enhance penetration of sub-micron particles into dentinal tubules. This can aid in the development of novel methods for delivering therapeutic clinical materials for hypersensitivity relief and treatment of dentinal caries. Copyright © 2016 Elsevier Ltd. All rights reserved.

Design and characterization of submicron formulation for a poorly soluble drug: the effect of Vitamin E TPGS and other solubilizers on skin permeability enhancement.

PubMed

Ghosh, Indrajit; Michniak-Kohn, Bozena

2012-09-15

In transdermal drug delivery systems (TDDS), it is a challenge to achieve stable and prolonged high permeation rates across the skin since the concentrations of the drug dissolved in the matrix have to be high in order to maintain zero order release kinetics. Several attempts have been reported to improve the permeability of poorly soluble drug compounds using supersaturated systems, however, due to thermodynamic challenges, there was a high tendency for the drug to nucleate immediately after formulating or even during storage. The present study focuses on the efficiency of drug crystals at the submicron/nano range in presence of different solubilizers to improve the permeation rate. Effect of several solubilizers, e.g. Pluronic F-127, Vitamin E TPGS, propylene glycol were studied on the submicron suspension systems of ibuprofen as a model drug. Various stabilizers such as hydroxylpropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP) were examined to evaluate their crystal inhibitory effects on particle growth of the drug compound at submicron range. The overall permeation enhancement process through the skin seems to be influenced by the presence of solubilizers and also the presence of submicron drug crystal. The most promising stable formulation was developed with Vitamin E TPGS+HPMC submicron suspension, which produced higher permeation rate compared to other vehicles. Copyright © 2012 Elsevier B.V. All rights reserved.

Self-associated submicron IgG1 particles for pulmonary delivery: effects of non-ionic surfactants on size, shape, stability, and aerosol performance.

PubMed

Srinivasan, Asha R; Shoyele, Sunday A

2013-03-01

The ability to produce submicron particles of monoclonal antibodies of different sizes and shapes would enhance their application to pulmonary delivery. Although non-ionic surfactants are widely used as stabilizers in protein formulations, we hypothesized that non-ionic surfactants will affect the shape and size of submicron IgG particles manufactured through precipitation. Submicron particles of IgG1 were produced by a precipitation process which explores the fact that proteins have minimum solubility but maximum precipitation at the isoelectric point. Non-ionic surfactants were used for size and shape control, and as stabilizing agents. Aerosol performance of the antibody nanoparticles was assessed using Andersen Cascade Impactor. Spinhaler® and Handihaler® were used as model DPI devices. SEM micrographs revealed that the shape of the submicron particles was altered by varying the type of surfactant added to the precipitating medium. Particle size as measured by dynamic light scattering was also varied based on the type and concentration of the surfactant. The surfactants were able to stabilize the IgG during the precipitation process. Polyhedral, sponge-like, and spherical nanoparticles demonstrated improved aerosolization properties compared to irregularly shaped (>20 μm) unprocessed particles. Stable antibody submicron particles of different shapes and sizes were prepared. Careful control of the shape of such particles is critical to ensuring optimized lung delivery by dry powder inhalation.

Visible/near-infrared spectra of experimentally shocked plagioclase feldspars

USGS Publications Warehouse

Johnson, J. R.; Horz, F.

2003-01-01

High shock pressures cause structural changes in plagioclase feldspars such as mechanical fracturing and disaggregation of the crystal lattice at submicron scales, the formation of diaplectic glass (maskelynite), and genuine melting. Past studies of visible/ near-infrared spectra of shocked feldspars demonstrated few spectral variations with pressure except for a decrease in the depth of the absorption feature near 1250-1300 nm and an overall decrease in reflectance. New visible/near-infrared spectra (400-2500 nm) of experimentally shocked (17-56 GPa) albite- and anorthite-rich rock powders demonstrate similar trends, including the loss of minor hydrated mineral bands near 1410, 1930, 2250, and 2350 nm. However, the most interesting new observations are increases in reflectance at intermediate pressures, followed by subsequent decreases in reflectance at higher pressures. The amount of internal scattering and overall sample reflectance is controlled by the relative proportions of micro-fractures, submicron grains, diaplectic glass, and melts formed during shock metamorphism. We interpret the observed reflectance increases at intermediate pressures to result from progressively larger proportions of submicron feldspar grains and diaplectic glass. The ensuing decreases in reflectance occur after diaplectic glass formation is complete and the proportion of genuine melt inclusions increases. The pressure regimes over which these reflectance variations occur differ between albite and anorthite, consistent with thermal infrared spectra of these samples and previous studies of shocked feldspars. These types of spectral variations associated with different peak shock pressures should be considered during interpretation and modeling of visible/near-infrared remotely sensed spectra of planetary and asteroidal surfaces.

Coupled CaAl-NaSi diffusion in plagioclase feldspar: Experiments and applications to cooling rate speedometry

NASA Astrophysics Data System (ADS)

Grove, Timothy L.; Baker, Michael B.; Kinzler, Rosamond J.

1984-10-01

The rate of CaAl-NaSi interdiffusion in plagioclase feldspar was determined under 1 atm anhydrous conditions over the temperature range 1400° to 1000°C in calcic plagioclase (An 80-81) by homogenizing coherent exsolution lamellae. The dependence of the average interdiffusion coefficient on temperature is given by the expression: D˜ = 10.99 ( cm 2/sec) exp (-123.4( kcal/mol)/RT), (T in °K). This value is for diffusion perpendicular to the (03 1¯) interface of the lamellae. CaAl-NaSi interdiffusion is 4 to 5 orders of magnitude slower than oxygen diffusion in the temperature range 1400° to 1200°C and possibly 10 orders of magnitude slower at subsolidus temperatures. The large differences in diffusion rates explain the apparent contradiction posed by the plagioclases of large layered intrusions ( e.g., the Skaergaard), which retain delicate Ca, Na compositional zoning profiles on the micron scale, but have undergone complete oxygen isotopic exchange with heated meteoric groundwater from the surrounding wall rocks. CaAl-NaSi diffusion is slow, the closure temperature is high (within the solidus-liquidus interval), and Ca-Na zoning is preserved. Oxygen diffusion is faster, the closure temperature is lower (350°-400°C) and the feldspars exchange oxygen with the low-temperature hydrothermal fluids. The complex micron-scale oscillatory zones in plagioclase can also be used as cooling rate speedometers for volcanic and plutonic plagioclase. Cooling histories typical of large mafic intrusions ( e.g. the Stillwater) are slow, begin at high initial temperatures (1200°C) and result in homogenization of oscillatory zones on the scale of 10 microns. The oscillatory zones found in the plagioclase of granodioritic plutons are preserved because cooling is initiated at a lower temperature (1000°C) limiting diffusion to submicron length scales despite the slow cooling rate of the intrusion.

Curation and Analysis of Samples from Comet Wild-2 Returned by NASA's Stardust Mission

NASA Technical Reports Server (NTRS)

Nakamura-Messenger, Keiko; Walker, Robert M.

2015-01-01

The NASA Stardust mission returned the first direct samples of a cometary coma from comet 81P/Wild-2 in 2006. Intact capture of samples encountered at 6 km/s was enabled by the use of aerogel, an ultralow dense silica polymer. Approximately 1000 particles were captured, with micron and submicron materials distributed along mm scale length tracks. This sample collection method and the fine scale of the samples posed new challenges to the curation and cosmochemistry communities. Sample curation involved extensive, detailed photo-documentation and delicate micro-surgery to remove particles without loss from the aerogel tracks. This work had to be performed in highly clean facility to minimize the potential of contamination. JSC Curation provided samples ranging from entire tracks to micrometer-sized particles to external investigators. From the analysis perspective, distinguishing cometary materials from aerogel and identifying the potential alteration from the capture process were essential. Here, transmission electron microscopy (TEM) proved to be the key technique that would make this possible. Based on TEM work by ourselves and others, a variety of surprising findings were reported, such as the observation of high temperature phases resembling those found in meteorites, rarely intact presolar grains and scarce organic grains and submicrometer silicates. An important lesson from this experience is that curation and analysis teams must work closely together to understand the requirements and challenges of each task. The Stardust Mission also has laid important foundation to future sample returns including OSIRIS-REx and Hayabusa II and future cometary nucleus sample return missions.

Interaction between Convection and Heat Transfer in Crystal Growth

NASA Technical Reports Server (NTRS)

1998-01-01

Crystals are integral components in some of our most sophisticated and rapidly developing industries. Single crystals are solids with the most uniform structures that can be obtained on an atomic scale. Because of their structural uniformity, crystals can transmit acoustic and electromagnetic waves and charged particles with essentially no scattering or interferences. This transparency, which can be selectively modified by controlled additions of impurities known as dopants, is the foundation of modern electronic industry. It has brought about widespread application of crystals in transistors, lasers, microwave devices, infrared detectors, magnetic memory devices, and many other magnets and electro-optic components. The performance of a crystal depends strongly on its compositional homogeneity. For instance, in modern microcircuitry, compositional variations of a few percent (down to a submicron length scale) can seriously jeopardize predicted yields. Since crystals are grown by carefully controlled phase transformations, the compositional adjustment in the solid is often made during growth from the nutrient. Hence, a detailed understanding of mass transfer in the nutrient is essential. Moreover, since mass transfer is often the slowest process during growth, it is usually the rate limiting mechanism. Crystal growth processes are usually classified according to the nature of the parent phase. Nevertheless, whether the growth occurs by solidification from a melt (melt growth), nucleation from a solution (solution growth), condensation from a vapor (physical vapor transport) or chemical reaction of gases (chemical vapor deposition), the parent phase is a fluid. As is with most non-equilibrium processes involving fluids, liquid or vapor, fluid motion plays an important role, affecting both the concentration and temperature gradients at the soli-liquid interface.

Magnetic and Optical Properties of Submicron-Size Hollow Spheres

PubMed Central

Ye, Quan-Lin; Yoshikawa, Hirofumi; Awaga, Kunio

2010-01-01

Magnetic hollow spheres with a controlled diameter and shell thickness have emerged as an important class of magnetic nanomaterials. The confined hollow geometry and pronouncedly curved surfaces induce unique physical properties different from those of flat thin films and solid counterparts. In this paper, we focus on recent progress on submicron-size spherical hollow magnets (e.g., cobalt- and iron-based materials), and discuss the effects of the hollow shape and the submicron size on magnetic and optical properties.

Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics.

PubMed

Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Jaung, Jae Yun; Kim, Yong-Hoon; Park, Sung Kyu

2015-09-28

The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics

NASA Astrophysics Data System (ADS)

Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Yun Jaung, Jae; Kim, Yong-Hoon; Kyu Park, Sung

2015-09-01

The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

Study on Buckling of Stiff Thin Films on Soft Substrates as Functional Materials

NASA Astrophysics Data System (ADS)

Ma, Teng

In engineering, buckling is mechanical instability of walls or columns under compression and usually is a problem that engineers try to prevent. In everyday life buckles (wrinkles) on different substrates are ubiquitous -- from human skin to a rotten apple they are a commonly observed phenomenon. It seems that buckles with macroscopic wavelengths are not technologically useful; over the past decade or so, however, thanks to the widespread availability of soft polymers and silicone materials micro-buckles with wavelengths in submicron to micron scale have received increasing attention because it is useful for generating well-ordered periodic microstructures spontaneously without conventional lithographic techniques. This thesis investigates the buckling behavior of thin stiff films on soft polymeric substrates and explores a variety of applications, ranging from optical gratings, optical masks, energy harvest to energy storage. A laser scanning technique is proposed to detect micro-strain induced by thermomechanical loads and a periodic buckling microstructure is employed as a diffraction grating with broad wavelength tunability, which is spontaneously generated from a metallic thin film on polymer substrates. A mechanical strategy is also presented for quantitatively buckling nanoribbons of piezoelectric material on polymer substrates involving the combined use of lithographically patterning surface adhesion sites and transfer printing technique. The precisely engineered buckling configurations provide a route to energy harvesters with extremely high levels of stretchability. This stiff-thin-film/polymer hybrid structure is further employed into electrochemical field to circumvent the electrochemically-driven stress issue in silicon-anode-based lithium ion batteries. It shows that the initial flat silicon-nanoribbon-anode on a polymer substrate tends to buckle to mitigate the lithiation-induced stress so as to avoid the pulverization of silicon anode. Spontaneously generated submicron buckles of film/polymer are also used as an optical mask to produce submicron periodic patterns with large filling ratio in contrast to generating only ˜100 nm edge submicron patterns in conventional near-field soft contact photolithography. This thesis aims to deepen understanding of buckling behavior of thin films on compliant substrates and, in turn, to harness the fundamental properties of such instability for diverse applications.

Characterization of Minerals of Geochronological Interest by EPMA and Atom Probe Tomography

NASA Astrophysics Data System (ADS)

Snoeyenbos, D.; Jercinovic, M. J.; Reinhard, D. A.; Hombourger, C.

2012-12-01

Isotopic and chemical dating techniques for zircon and monazite rely on several assumptions: that initial common Pb is low to nonexistent, that the analyzed domain is chronologically homogeneous, and that any relative migration of radiogenic Pb and its parent isotopes has not exceeded the analyzed domain. Yet, both zircon and monazite commonly contain significant submicron heterogeneities that may challenge these assumptions and can complicate the interpretation of chemical and isotopic data. Compositional mapping and submicron quantitative analysis by EPMA and FE-EPMA have been found to be useful techniques both for the characterization of these heterogeneities, and for quantitative geochronological determinations within the analytical limits of these techniques and the statistics of submicron sampling. Complementary to high-resolution EPMA techniques is Atom Probe Tomography (APT), wherein a specimen with dimensions of a few hundreds of nanometers is field evaporated atom by atom. The original position of each atom is identified, along with its atomic species and isotope. The result is a reconstruction allowing quantitative three-dimensional study of the specimen at the atomic scale, with low detection limits and high mass resolution. With the introduction of laser-induced thermal pulsing to achieve field evaporation, the technique is no longer limited to conductive specimens. There exists the capability to explore the compositional and isotopic structure of insulating materials at sub-nanometer resolution. Minerals of geochronological interest have been studied by an analytical method involving first compositional mapping and submicron quantitative analysis by EPMA and FE-EPMA, and subsequent use of these data to select specific sites for APT specimen extraction by FIB. Examples presented include 1) zircon from the Taconian of New England, USA, containing a fossil resorption front included between an unmodified igneous core, and a subsequent metamorphic overgrowth, with significant redistribution of U, Th, P and Y along microfracture arrays extending into the overgrowth, and 2) Paleoproterozoic monazite in thin bands <1μm wide along cleavage planes within much older (Neoarchean) monazite from the Boothia mainland of the Western Churchill Province, Canada.

The National Submicron Facility.

ERIC Educational Resources Information Center

Wolf, Edward D.

1979-01-01

Describes the activities of the National Submicron Facility which was established at Cornell University in Ithaca, New York to serve as an information resource for the nation's research community in microstructure science and engineering. (HM)

Resistance to protein adsorption and adhesion of fibroblasts on nanocrystalline diamond films: the role of topography and boron doping.

PubMed

Alcaide, María; Papaioannou, Stavros; Taylor, Andrew; Fekete, Ladislav; Gurevich, Leonid; Zachar, Vladimir; Pennisi, Cristian Pablo

2016-05-01

Boron-doped nanocrystalline diamond (BNCD) films exhibit outstanding electrochemical properties that make them very attractive for the fabrication of electrodes for novel neural interfaces and prosthetics. In these devices, the physicochemical properties of the electrode materials are critical to ensure an efficient long-term performance. The aim of this study was to investigate the relative contribution of topography and doping to the biological performance of BNCD films. For this purpose, undoped and boron-doped NCD films were deposited on low roughness (LR) and high roughness (HR) substrates, which were studied in vitro by means of protein adsorption and fibroblast growth assays. Our results show that BNCD films significantly reduce the adsorption of serum proteins, mostly on the LR substrates. As compared to fibroblasts cultured on LR BNCD films, cells grown on the HR BNCD films showed significantly reduced adhesion and lower growth rates. The mean length of fibronectin fibrils deposited by the cells was significantly increased in the BNCD coated substrates, mainly in the LR surfaces. Overall, the largest influence on protein adsorption, cell adhesion, proliferation, and fibronectin deposition was due to the underlying sub-micron topography, with little or no influence of boron doping. In perspective, BNCD films displaying surface roughness in the submicron range may be used as a strategy to reduce the fibroblast growth on the surface of neural electrodes.

Uncovering the Physical Basis Connecting Environment and Tribological Performance of Ultrananocrystalline Diamond

DTIC Science & Technology

2012-10-05

Anisotropic Nanotribological Properties,” Journal of the Mechanical Behavior of Biomedical Materials, Vol. 4, Issue 4, pp. 515-522 (SCI) Kuo -Cheng Chen...Nanodiamond With the Polymer Used as an Additive in Lubricant Oil,” Journal of Materials Chemistry, Vol. 21, pp. 13213-13222 (SCI) Chih- Jung Chen, Ray...Deep Submicron to Nano-Scale,” Journal of Mechanics, Vol. 28, Issue 3, pp. 507-511 (SCI) Yeau-Ren Jeng, Yi-Min Wang, Hua-Chiang Wen, Shih -Ming Huang

Influence of Mechanical Loading on the Integrity and Performance of Energy Harvesting and Storage Materials at the Micron and Submicron Scales

DTIC Science & Technology

2016-04-01

the failure process of photovoltaic ( PV ) amorphous Si thin film solar cells using commercial solar cell modules PT15-300 manufactured by Iowa Thin...this research project and the results and conclusions. This research program focused on the mechanics of materials employed in thin film solar cells...experimental results and references are provided to publications for further details. 1. MECHANICAL DURABILITY OF THIN FILM SI SOLAR CELLS We investigated

Logarithmic singularities and quantum oscillations in magnetically doped topological insulators

NASA Astrophysics Data System (ADS)

Nandi, D.; Sodemann, Inti; Shain, K.; Lee, G. H.; Huang, K.-F.; Chang, Cui-Zu; Ou, Yunbo; Lee, S. P.; Ward, J.; Moodera, J. S.; Kim, P.; Yacoby, A.

2018-02-01

We report magnetotransport measurements on magnetically doped (Bi,Sb ) 2Te3 films grown by molecular beam epitaxy. In Hall bar devices, we observe logarithmic dependence of transport coefficients in temperature and bias voltage which can be understood to arise from electron-electron interaction corrections to the conductivity and self-heating. Submicron scale devices exhibit intriguing quantum oscillations at high magnetic fields with dependence on bias voltage. The observed quantum oscillations can be attributed to bulk and surface transport.

[Geographic variation of seed morphological traits of Picea schrenkiana var. tianschanica in Tianshan Mountains, Xinjiang of Northwest China].

PubMed

Liu, Gui-Feng; Zang, Run-Guo; Liu, Hua; Bai, Zhi-Qiang; Guo, Zhong-Jun; Ding, Yi

2012-06-01

Taking the Picea schrenkiana var. tianschanica forests at three sites with different longitudes (Zhaosu, Tianchi, and Qitai) in Tianshan Mountains as the objects, the cones were collected along an altitudinal gradient to analyze the variation of their seed morphological traits (seed scale length and width, seed scale length/width ratio, seed wing length and width, seed wing length/ width ratio, seed length and width, and seed length/width ratio). All the seed traits except seed width tended to decrease with increasing altitude. The seed traits except seed wing width, seed width, and seed length/width ratio all had significant negative correlations with altitude. Seed scale length and width and seed scale length/width ratio had significant positive correlations with longitude. Seed scale length, seed scale length/width ratio, and seed wing length/width ratio had significant negative correlations with slope degree. No significant correlations were observed between the seed traits except seed wing width and the slope aspect. Altitude was the main factor affecting the seed scale length, seed scale length/width ratio, and seed wing length/width ratio.

Mass-spectrometric identification of primary biological particle markers: indication for low abundance of primary biological material in the pristine submicron aerosol of Amazonia

NASA Astrophysics Data System (ADS)

Schneider, J.; Freutel, F.; Zorn, S. R.; Chen, Q.; Farmer, D. K.; Jimenez, J. L.; Martin, S. T.; Artaxo, P.; Wiedensohler, A.; Borrmann, S.

2011-07-01

The abundance of marker compounds for primary biological particles in submicron aerosol was investigated by means of aerosol mass spectrometry. Mass spectra of amino acids, carbohydrates, small peptides, and proteins, all of which are key building blocks of biological particles, were recorded in laboratory experiments. Several characteristic marker peaks were identified. The identified marker peaks were compared with mass spectra recorded during AMAZE-08, a field campaign conducted in the pristine rainforest of the Central Amazon Basin, Brazil, during the wet season of February and March 2008. The low abundance of identified marker peaks places upper limits of 7.5 % for amino acids and 5.6 % for carbohydrates on the contribution of primary biological aerosol particles (PBAPs) to the submicron organic aerosol mass concentration during this time period. Upper limits for the absolute submicron concentrations for both compound classes range from 0.01 to 0.1 μg m-3. Carbohydrates and protein amino acids make up for about two thirds of the dry mass of a biological cell. Thus, our findings suggest an upper limit for the PBAPs mass fraction of about 20 % to the submicron organic aerosol.

Thermophoretic motion behavior of submicron particles in boundary-layer-separation flow around a droplet.

PubMed

Wang, Ao; Song, Qiang; Ji, Bingqiang; Yao, Qiang

2015-12-01

As a key mechanism of submicron particle capture in wet deposition and wet scrubbing processes, thermophoresis is influenced by the flow and temperature fields. Three-dimensional direct numerical simulations were conducted to quantify the characteristics of the flow and temperature fields around a droplet at three droplet Reynolds numbers (Re) that correspond to three typical boundary-layer-separation flows (steady axisymmetric, steady plane-symmetric, and unsteady plane-symmetric flows). The thermophoretic motion of submicron particles was simulated in these cases. Numerical results show that the motion of submicron particles around the droplet and the deposition distribution exhibit different characteristics under three typical flow forms. The motion patterns of particles are dependent on their initial positions in the upstream and flow forms. The patterns of particle motion and deposition are diversified as Re increases. The particle motion pattern, initial position of captured particles, and capture efficiency change periodically, especially during periodic vortex shedding. The key effects of flow forms on particle motion are the shape and stability of the wake behind the droplet. The drag force of fluid and the thermophoretic force in the wake contribute jointly to the deposition of submicron particles after the boundary-layer separation around a droplet.

Mechanisms of structural colour in the Morpho butterfly: cooperation of regularity and irregularity in an iridescent scale.

PubMed Central

Kinoshita, Shuichi; Yoshioka, Shinya; Kawagoe, Kenji

2002-01-01

Structural colour in the Morpho butterfly originates from submicron structure within a scale and, for over a century, its colour and reflectivity have been explained as interference of light due to the multilayer of cuticle and air. However, this model fails to explain the extraordinarily uniform colour of the wing with respect to the observation direction. We have performed microscopic, optical and theoretical investigations, and have found that the separate lamellar structure with irregular heights is extremely important. Using a simple model, we have shown that the combined action of interference and diffraction is essential for the structural colour of the Morpho butterfly. PMID:12137569

Superlubrication by phonon confinement

NASA Astrophysics Data System (ADS)

Wada, Noriyuki; Ishikawa, Makoto; Shiga, Takuma; Shiomi, Junichiro; Suzuki, Masaru; Miura, Kouji

2018-04-01

The superlubrication described here, involving confined phonons, is easily achievable and very simple because it uses only submicron islands, smaller than the mean free path of the phonons, to confine phonons. We can achieve superlubrication with a friction force of piconewton order at the submicron island. We can call this phononic lubrication or self-lubrication because phonons induced by tip shearing are confined within the submicron islands and decrease the friction during the subsequent sliding. Phonon confinement should make it possible to directly develop applications for lubricants and ultimately to open a novel avenue of tribology.

Time and length scales within a fire and implications for numerical simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

TIESZEN,SHELDON R.

2000-02-02

A partial non-dimensionalization of the Navier-Stokes equations is used to obtain order of magnitude estimates of the rate-controlling transport processes in the reacting portion of a fire plume as a function of length scale. Over continuum length scales, buoyant times scales vary as the square root of the length scale; advection time scales vary as the length scale, and diffusion time scales vary as the square of the length scale. Due to the variation with length scale, each process is dominant over a given range. The relationship of buoyancy and baroclinc vorticity generation is highlighted. For numerical simulation, first principlesmore » solution for fire problems is not possible with foreseeable computational hardware in the near future. Filtered transport equations with subgrid modeling will be required as two to three decades of length scale are captured by solution of discretized conservation equations. By whatever filtering process one employs, one must have humble expectations for the accuracy obtainable by numerical simulation for practical fire problems that contain important multi-physics/multi-length-scale coupling with up to 10 orders of magnitude in length scale.« less

Effect of Proximity of Features on the Damage Threshold During Submicron Additive Manufacturing Via Two-Photon Polymerization

DOE PAGES

Saha, Sourabh K.; Divin, Chuck; Cuadra, Jefferson A.; ...

2017-05-12

Two-photon polymerization (TPP) is a laser writing process that enables fabrication of millimeter scale three-dimensional (3D) structures with submicron features. In TPP, writing is achieved via nonlinear two-photon absorption that occurs at high laser intensities. Thus, it is essential to carefully select the incident power to prevent laser damage during polymerization. Currently, the feasible range of laser power is identified by writing small test patterns at varying power levels. Here in this paper, we demonstrate that the results of these tests cannot be generalized, because the damage threshold power depends on the proximity of features and reduces by as muchmore » as 47% for overlapping features. We have identified that this reduction occurs primarily due to an increase in the single-photon absorptivity of the resin after curing. We have captured the damage from proximity effects via X-ray 3D computed tomography (CT) images of a non-homogenous part that has varying feature density. Part damage manifests as internal spherical voids that arise due to boiling of the resist. We have empirically quantified this proximity effect by identifying the damage threshold power at different writing speeds and feature overlap spacings. In addition, we present a first-order analytical model that captures the scaling of this proximity effect. Based on this model and the experiments, we have identified that the proximity effect is more significant at high writing speeds; therefore, it adversely affects the scalability of manufacturing. The scaling laws and the empirical data generated here can be used to select the appropriate TPP writing parameters.« less

Effect of Proximity of Features on the Damage Threshold During Submicron Additive Manufacturing Via Two-Photon Polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saha, Sourabh K.; Divin, Chuck; Cuadra, Jefferson A.

Two-photon polymerization (TPP) is a laser writing process that enables fabrication of millimeter scale three-dimensional (3D) structures with submicron features. In TPP, writing is achieved via nonlinear two-photon absorption that occurs at high laser intensities. Thus, it is essential to carefully select the incident power to prevent laser damage during polymerization. Currently, the feasible range of laser power is identified by writing small test patterns at varying power levels. Here in this paper, we demonstrate that the results of these tests cannot be generalized, because the damage threshold power depends on the proximity of features and reduces by as muchmore » as 47% for overlapping features. We have identified that this reduction occurs primarily due to an increase in the single-photon absorptivity of the resin after curing. We have captured the damage from proximity effects via X-ray 3D computed tomography (CT) images of a non-homogenous part that has varying feature density. Part damage manifests as internal spherical voids that arise due to boiling of the resist. We have empirically quantified this proximity effect by identifying the damage threshold power at different writing speeds and feature overlap spacings. In addition, we present a first-order analytical model that captures the scaling of this proximity effect. Based on this model and the experiments, we have identified that the proximity effect is more significant at high writing speeds; therefore, it adversely affects the scalability of manufacturing. The scaling laws and the empirical data generated here can be used to select the appropriate TPP writing parameters.« less

Electrosprayed Polyvinylpyrrolidone (PVP) Submicron Particles Loaded by Green Tea Extracts

NASA Astrophysics Data System (ADS)

Kamaruddin; Sriyanti, I.; Edikresnha, D.; Munir, M. M.; Khairurrijal, K.

2018-05-01

Electrospraying technique has been successfully used to synthesize composite submicron particles of polyvinylpyrrolidone (PVP) and green tea extract (GTE). The precursor solutions were PVP in ethanol (15 wt%) and GTE in ethanol (10 wt%), which were then mixed at varying ratio. The mixed solution then underwent electrospraying process at an applied voltage of 15 kV, a distance of collector to the nozzle at 15 cm, and a flow rate of 3 µL/min. The composite submicron particles of PVP-GTE showed smooth and fine spherical morphology without fibers or beaded fibers. To a certain degree, the increase of GTE content in the PVP-GTE mixed solution decreased the average diameter of PVP-GTE composite particles. Moreover, the analysis of the FTIR spectra confirmed the existing molecular interaction between PVP and GTE in the composite submicron particles as shown by the shift of PVP wavenumber towards GTE, which has typically smaller wavenumber.

Enhancement in electrical conductivity of pastes containing submicron Ag-coated Cu filler with palmitic acid surface modification

NASA Astrophysics Data System (ADS)

Choi, Eun Byeol; Lee, Jong-Hyun

2017-09-01

The fabrication and applied use of submicron Ag-coated Cu (Cu@Ag) particles as a filler material for epoxy-based conductive pastes having the advantages of a lower material cost and antioxidation behavior were studied. Submicron Cu@Ag particles were successfully prepared and surface-modified using palmitic acid. Diffuse reflectance infrared Fourier transform spectroscopy and thermogravimetric differential scanning calorimetry results indicated the formation of an organic layer by the chemical interaction between the Cu@Ag surface and palmitic acid and the survival of the organic layer after treatment at 160 °C for 3 h in air. The printed pastes containing both commercial micron Cu@Ag flakes and the fabricated submicron Cu@Ag particles showed a greatly reduced electrical resistivity (4.68 × 10-4 Ω cm) after surface modification compared to an initial value of 1.85 × 10-3 Ω cm when cured.

ORGANIC COMPOUNDS MEASURED IN PM2.5 DURING NEOPS

EPA Science Inventory

Secondary formation of submicron ambient particulate matter occurs when organic and inorganic constituents having sufficiently low volatility condense onto preexisting particles in the atmosphere. The presence of the resulting submicron particles has led to three important env...

Submicron-Scale Heterogeneities in Nickel Sorption of Various Cell-Mineral Aggregates Formed by Fe(II)-Oxidizing Bacteria.

PubMed

Schmid, Gregor; Zeitvogel, Fabian; Hao, Likai; Ingino, Pablo; Adaktylou, Irini; Eickhoff, Merle; Obst, Martin

2016-01-05

Fe(II)-oxidizing bacteria form biogenic cell-mineral aggregates (CMAs) composed of microbial cells, extracellular organic compounds, and ferric iron minerals. CMAs are capable of immobilizing large quantities of heavy metals, such as nickel, via sorption processes. CMAs play an important role for the fate of heavy metals in the environment, particularly in systems characterized by elevated concentrations of dissolved metals, such as mine drainage or contaminated sediments. We applied scanning transmission (soft) X-ray microscopy (STXM) spectrotomography for detailed 3D chemical mapping of nickel sorbed to CMAs on the submicron scale. We analyzed different CMAs produced by phototrophic or nitrate-reducing microbial Fe(II) oxidation and, in addition, a twisted stalk structure obtained from an environmental biofilm. Nickel showed a heterogeneous distribution and was found to be preferentially sorbed to biogenically precipitated iron minerals such as Fe(III)-(oxyhydr)oxides and, to a minor extent, associated with organic compounds. Some distinct nickel accumulations were identified on the surfaces of CMAs. Additional information obtained from scatter plots and angular distance maps, showing variations in the nickel-iron and nickel-organic carbon ratios, also revealed a general correlation between nickel and iron. Although a high correlation between nickel and iron was observed in 2D maps, 3D maps revealed this to be partly due to projection artifacts. In summary, by combining different approaches for data analysis, we unambiguously showed the heterogeneous sorption behavior of nickel to CMAs.

The dynamics of submicron-sized dust particles lost from Phobos

NASA Technical Reports Server (NTRS)

Horanyi, M.; Tatrallyay, M.; Juhasz, A.; Luhmann, J. G.

1991-01-01

The dynamics of submicron-sized dielectric particles lost from the Martian moon Phobos are studied in connection with the possible detection of dust by the Phobos 2 spacecraft. The motion of these small dust grains is influenced not only by gravity but also by solar radiation pressure and electromagnetic forces. The plasma environment of Mars is described by applying a hybrid gasdynamic-cometary model. Some of the submicron-sized grains ejected at speeds on the order of a few tens meters per second can stay in orbit around Mars for several months forming a nonuniform and time-dependent dust halo.

10.3%-efficient submicron-thick Cu(In,Ga)Se2 solar cells with absorber fabricated by sputtering In2Se3, CuGaSe2 and Cu2Se targets

NASA Astrophysics Data System (ADS)

Peng, Xiao; Zhao, Ming; Zhuang, Daming; Sun, Rujun; Zhang, Leng; Wei, Yaowei; Lv, Xunyan; Wu, Yixuan; Ren, Guoan

2018-06-01

We reported a new method to fabricate submicron-thick CIGS with smooth surface by sputtering In2Se3, CuGaSe2 and Cu2Se targets with post-selenization. The influence of gallium content on the properties of CIGS thin film was evaluated by the crystallinity and the cells performance. The most suitable value of Ga content in our submicron-thick CIGS is 0.32 and cells based on it demonstrated the highest efficiency of 10.3%.

Sub-micron particle sampler apparatus

DOEpatents

Gay, Don D.; McMillan, William G.

1987-01-01

Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

Method for sampling sub-micron particles

DOEpatents

Gay, Don D.; McMillan, William G.

1985-01-01

Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

Quantitative assessment of submicron scale anisotropy in tissue multifractality by scattering Mueller matrix in the framework of Born approximation

NASA Astrophysics Data System (ADS)

Das, Nandan Kumar; Dey, Rajib; Chakraborty, Semanti; Panigrahi, Prasanta K.; Meglinski, Igor; Ghosh, Nirmalya

2018-04-01

A number of tissue-like disordered media exhibit local anisotropy of scattering in the scaling behavior. Scaling behavior contains wealth of fractal or multifractal properties. We demonstrate that the spatial dielectric fluctuations in a sample of biological tissue exhibit multifractal anisotropy. Multifractal anisotropy encoded in the wavelength variation of the light scattering Mueller matrix and manifesting as an intriguing spectral diattenuation effect. We developed an inverse method for the quantitative assessment of the multifractal anisotropy. The method is based on the processing of relevant Mueller matrix elements in Fourier domain by using Born approximation, followed by the multifractal analysis. The approach promises for probing subtle micro-structural changes in biological tissues associated with the cancer and precancer, as well as for non-destructive characterization of a wide range of scattering materials.

Study of nanoscale structures in hydrated biomaterials using small-angle neutron scattering

PubMed Central

Luk, Arnold; Murthy, N. Sanjeeva; Wang, Wenjie; Rojas, Ramiro; Kohn, Joachim

2012-01-01

Distribution of water in three classes of biomedically relevant and degradable polymers was investigated using small-angle neutron scattering. In semicrystalline polymers, such as poly(lactic acid) and poly(glycolic acid), water was found to diffuse preferentially into the noncrystalline regions. In amorphous polymers, such as poly(D,L-lactic acid) and poly(lactic-co-glycolic acid), the scattering after 7-days of incubation was attributed to water in microvoids that form following the hydrolytic degradation of the polymer. In amorphous copolymers containing hydrophobic segments (desaminotyrosyl-tyrosine ethyl ester) and hydrophilic blocks (poly(ethylene glycol) PEG), a sequence of distinct regimes of hydration were observed: homogeneous distribution (~ 10 Å length scales) at <13 wt% PEG (~ 1 water per EG), clusters of hydrated domains (~50 Å radius) separated at 24 wt% PEG (1 to 2 water per EG), uniformly distributed hydrated domains at 41 wt% PEG (~ 4 water per EG), and phase inversion at > 50 wt% PEG ( > 6 water per EG ). Increasing PEG content increased the number of these domains with only a small decrease in distance between the domains. These discrete domains appeared to coalesce to form submicron droplets at ~60 °C, above the melting temperature of crystalline PEG. Significance of such observations on the evolution of μm size channels that form during hydrolytic erosion is discussed. PMID:22227373

Size dependence of yield strength simulated by a dislocation-density function dynamics approach

NASA Astrophysics Data System (ADS)

Leung, P. S. S.; Leung, H. S.; Cheng, B.; Ngan, A. H. W.

2015-04-01

The size dependence of the strength of nano- and micron-sized crystals is studied using a new simulation approach in which the dynamics of the density functions of dislocations are modeled. Since any quantity of dislocations can be represented by a density, this approach can handle large systems containing large quantities of dislocations, which may handicap discrete dislocation dynamics schemes due to the excessive computation time involved. For this reason, pillar sizes spanning a large range, from the sub-micron to micron regimes, can be simulated. The simulation results reveal the power-law relationship between strength and specimen size up to a certain size, beyond which the strength varies much more slowly with size. For specimens smaller than ∼4000b, their strength is found to be controlled by the dislocation depletion condition, in which the total dislocation density remains almost constant throughout the loading process. In specimens larger than ∼4000b, the initial dislocation distribution is of critical importance since the presence of dislocation entanglements is found to obstruct deformation in the neighboring regions within a distance of ∼2000b. This length scale suggests that the effects of dense dislocation clusters are greater in intermediate-sized specimens (e.g. 4000b and 8000b) than in larger specimens (e.g. 16 000b), according to the weakest-link concept.

Modifications of Ti-6Al-4V surfaces by direct-write laser machining of linear grooves

NASA Astrophysics Data System (ADS)

Ulerich, Joseph P.; Ionescu, Lara C.; Chen, Jianbo; Soboyejo, Winston O.; Arnold, Craig B.

2007-02-01

As patients who receive orthopedic implants live longer and opt for surgery at a younger age, the need to extend the in vivo lifetimes of these implants has grown. One approach is to pattern implant surfaces with linear grooves, which elicit a cellular response known as contact guidance. Lasers provide a unique method of generating these surface patterns because they are capable of modifying physical and chemical properties over multiple length scales. In this paper we explore the relationship between surface morphology and laser parameters such as fluence, pulse overlap (translation distance), number of passes, and machining environment. We find that using simple procedures involving multiple passes it is possible to manipulate groove properties such as depth, shape, sub-micron roughness, and chemical composition of the Ti-6Al-4V oxide layer. Finally, we demonstrate this procedure by machining several sets of grooves with the same primary groove parameters but varied secondary characteristics. The significance of the secondary groove characteristics is demonstrated by preliminary cell studies indicating that the grooves exhibit basic features of contact guidance and that the cell proliferation in these grooves are significantly altered despite their similar primary characteristics. With further study it will be possible to use specific laser parameters during groove formation to create optimal physical and chemical properties for improved osseointegration.

Smart materials systems through mesoscale patterning

NASA Astrophysics Data System (ADS)

Aksay, Ilhan A.; Groves, John T.; Gruner, Sol M.; Lee, P. C. Y.; Prud'homme, Robert K.; Shih, Wei-Heng; Torquato, Salvatore; Whitesides, George M.

1996-02-01

We report work on the fabrication of smart materials with two unique strategies: (1) self- assembly and (2) laser stereolithography. Both methods are akin to the processes used by biological systems. The first one is ideal for pattern development and the fabrication of miniaturized units in the submicron range and the second one in the 10 micrometer to 1 mm size range. By using these miniaturized units as building blocks, one can also produce smart material systems that can be used at larger length scales such as smart structural components. We have chosen to focus on two novel piezoceramic systems: (1) high-displacement piezoelectric actuators, and (2) piezoceramic hydrophone composites possessing negative Poisson ratio matrices. High-displacement actuators are essential in such applications as linear motors, pumps, switches, loud speakers, variable-focus mirrors, and laser deflectors. Arrays of such units can potentially be used for active vibration control of helicopter rotors as well as the fabrication of adaptive rotors. In the case of piezoceramic hydrophone composites, we utilize matrices having a negative Poisson's ratio in order to produce highly sensitive, miniaturized sensors. We envision such devices having promising new application areas such as the implantation of hydrophones in small blood vessels to monitor blood pressure. Negative Poisson ratio materials have promise as robust shock absorbers, air filters, and fasteners, and hence, can be used in aircraft and land vehicles.

Survival of Submicron Refractory Presolar Grains in Stardust and Stardust Analog Craters

NASA Astrophysics Data System (ADS)

Croat, T. K.; Floss, C.; Kearsley, A. T.; Burchell, M. J.

2013-09-01

FIB-TEM studies of Stardust analog craters demonstrate intact survival of refractory minerals (such as TiC, TiN and SiC). The Al craters resulting from submicron projectiles show physical properties somewhat different from those of larger projectiles.

Dehomogenized Elastic Properties of Heterogeneous Layered Materials in AFM Indentation Experiments.

PubMed

Lee, Jia-Jye; Rao, Satish; Kaushik, Gaurav; Azeloglu, Evren U; Costa, Kevin D

2018-06-05

Atomic force microscopy (AFM) is used to study mechanical properties of biological materials at submicron length scales. However, such samples are often structurally heterogeneous even at the local level, with different regions having distinct mechanical properties. Physical or chemical disruption can isolate individual structural elements but may alter the properties being measured. Therefore, to determine the micromechanical properties of intact heterogeneous multilayered samples indented by AFM, we propose the Hybrid Eshelby Decomposition (HED) analysis, which combines a modified homogenization theory and finite element modeling to extract layer-specific elastic moduli of composite structures from single indentations, utilizing knowledge of the component distribution to achieve solution uniqueness. Using finite element model-simulated indentation of layered samples with micron-scale thickness dimensions, biologically relevant elastic properties for incompressible soft tissues, and layer-specific heterogeneity of an order of magnitude or less, HED analysis recovered the prescribed modulus values typically within 10% error. Experimental validation using bilayer spin-coated polydimethylsiloxane samples also yielded self-consistent layer-specific modulus values whether arranged as stiff layer on soft substrate or soft layer on stiff substrate. We further examined a biophysical application by characterizing layer-specific microelastic properties of full-thickness mouse aortic wall tissue, demonstrating that the HED-extracted modulus of the tunica media was more than fivefold stiffer than the intima and not significantly different from direct indentation of exposed media tissue. Our results show that the elastic properties of surface and subsurface layers of microscale synthetic and biological samples can be simultaneously extracted from the composite material response to AFM indentation. HED analysis offers a robust approach to studying regional micromechanics of heterogeneous multilayered samples without destructively separating individual components before testing. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Viscoelastic properties of cell walls of single living plant cells determined by dynamic nanoindentation

PubMed Central

Hayot, Céline M.; Forouzesh, Elham; Goel, Ashwani; Avramova, Zoya; Turner, Joseph A.

2012-01-01

Plant development results from controlled cell divisions, structural modifications, and reorganizations of the cell wall. Thereby, regulation of cell wall behaviour takes place at multiple length scales involving compositional and architectural aspects in addition to various developmental and/or environmental factors. The physical properties of the primary wall are largely determined by the nature of the complex polymer network, which exhibits time-dependent behaviour representative of viscoelastic materials. Here, a dynamic nanoindentation technique is used to measure the time-dependent response and the viscoelastic behaviour of the cell wall in single living cells at a micron or sub-micron scale. With this approach, significant changes in storage (stiffness) and loss (loss of energy) moduli are captured among the tested cells. The results reveal hitherto unknown differences in the viscoelastic parameters of the walls of same-age similarly positioned cells of the Arabidopsis ecotypes (Col 0 and Ws 2). The technique is also shown to be sensitive enough to detect changes in cell wall properties in cells deficient in the activity of the chromatin modifier ATX1. Extensive computational modelling of the experimental measurements (i.e. modelling the cell as a viscoelastic pressure vessel) is used to analyse the influence of the wall thickness, as well as the turgor pressure, at the positions of our measurements. By combining the nanoDMA technique with finite element simulations quantifiable measurements of the viscoelastic properties of plant cell walls are achieved. Such techniques are expected to find broader applications in quantifying the influence of genetic, biological, and environmental factors on the nanoscale mechanical properties of the cell wall. PMID:22291130

Nanoforging - Innovation in three-dimensional processing and shaping of nanoscaled structures.

PubMed

Landefeld, Andreas; Rösler, Joachim

2014-01-01

This paper describes the shaping of freestanding objects out of metallic structures in the nano- and submicron size. The technique used, called nanoforging, is very similar to the macroscopic forging process. With spring actuated tools produced by focused ion beam milling, controlled forging is demonstrated. With only three steps, a conical bar stock is transformed to a flat- and semicircular bent bar stock. Compared with other forming techniques in the reduced scale, nanoforging represents a beneficial approach in forming freestanding metallic structures, due to its simplicity, and supplements other forming techniques.

Performance and Power Optimization for Cognitive Processor Design Using Deep-Submicron Very Large Scale Integration (VLSI) Technology

DTIC Science & Technology

2010-03-01

DATES COVERED (From - To) October 2008 – October 2009 4 . TITLE AND SUBTITLE PERFORMANCE AND POWER OPTIMIZATION FOR COGNITIVE PROCESSOR DESIGN USING...Computations 2  2.2  Cognitive Models and Algorithms for Intelligent Text Recognition 4   2.2.1 Brain-State-in-a-Box Neural Network Model. 4   2.2.2...The ASIC-style design and synthesis flow for FPU 8  Figure 4 : Screen shots of the final layouts 10  Figure 5: Projected performance and power roadmap

Fabrication of pullulan and pectin submicron fibers by electrospinning

USDA-ARS?s Scientific Manuscript database

Pullulan (PUL), a food grade polysaccharide, was fabricated into fibrous mats from fibers of submicron size by electrospinning. The effects of inorganic salts and polyanions present in the electrospinning solution on the properties of the resultant fibers was investigated. The inclusion of exogenous...

Novel submicronized rebamipide liquid with moderate viscosity: significant effects on oral mucositis in animal models.

PubMed

Nakashima, Takako; Sako, Nobutomo; Matsuda, Takakuni; Uematsu, Naoya; Sakurai, Kazushi; Ishida, Tatsuhiro

2014-01-01

This study aimed at developing a novel rebamipide liquid for an effective treatment of oral mucositis. The healing effects of a variety of liquids comprising submicronized rebamipide crystals were investigated using a rat cauterization-induced oral ulcer model. Whereas 2% rebamipide liquid comprising micro-crystals did not exhibit significant curative effect, 2% rebamipide liquids comprising submicronized crystals with moderate viscosities exhibited healing effects following intra-oral administration. The 2% and 4% optimized rebamipide liquids showed significant healing effects in the rat oral ulcer model (p<0.01). In addition, in the rat radiation-induced glossitis model, whereby the injury was caused to the tongue by exposing only around the rat's snout to a 15 Gy of X-irradiation, the 2% optimized rebamipide liquid significantly reduced the percent area of ulcerated injury (p<0.05). In conclusion, the submicronized rebamipide liquid with moderate viscosity following intra-oral administration showed better both healing effect in the rat oral ulcer model and preventive effect in the rat irradiation-induced glossitis model.

Improvement of dissolution behavior of poorly water soluble drugs by biodegradable polymeric submicron carriers containing sparingly methylated β-cyclodextrin.

PubMed

Singhavi, Dilesh J; Khan, Shagufta; Yeole, Pramod G

2013-04-01

The objective of this study was to develop submicron carriers of two drugs that are practically insoluble in water, i.e. meloxicam and aceclofenac, to improve their dissolution behavior. The phase solubility of the drugs was studied using different concentrations of sparingly methylated β-cyclodextrin, Kleptose(®) Crysmeβ (Crysmeb), in the presence and absence of 0.2 % w/v water-soluble chitosan. Drug-loaded submicron particles (SMPs) were prepared using chitosan chlorhydrate and Crysmeb by the ionotropic gelation method. The SMPs were characterized in terms of powder X-ray diffraction, Fourier transforms infrared spectroscopy, size determination, process yield, drug loading, encapsulation efficiency, surface morphology and in vitro release. The drug loading in the SMPs was enhanced in the presence of Crysmeb. The in vitro drug release was found to be enhanced with SMPs prepared using higher concentrations of Crysmeb. These results indicate that SMPs formed from chitosan chlorhydrate and Crysmeb are promising submicron carriers for enhancing the dissolution of meloxicam and aceclofenac.

The effects of surface-charged submicron polystyrene particles on the structure and performance of PSF forward osmosis membrane

NASA Astrophysics Data System (ADS)

Zuo, Hao-Ran; Fu, Jia-Bei; Cao, Gui-Ping; Hu, Nian; Lu, Hui; Liu, Hui-Qing; Chen, Peng-Peng; Yu, Jie

2018-04-01

Monodisperse surface-charged submicron polystyrene particles were designed, synthesized, and blended into polysulfone (PSF) support layer to prepare forward osmosis (FO) membrane with high performance. The membrane incorporated with particles were characterized with respect to morphology, porosity, and internal osmotic pressure (IOP). Results showed that the polymer particles not only increased the hydrophilicity and porosity of support layer, but also generated considerable IOP, which helped markedly decreasing the structure parameter from 1550 to 670 μm. The measured mass transfer parameters further confirmed the beneficial effects of the surface-charged submicron polymer particles on the performance of FO membrane. For instance, the water permeability coefficient (5.37 L m-2 h-1 bar-1) and water flux (49.7 L m-2 h-1) of the FO membrane incorporated with 5 wt% particles were almost twice as much as that of FO membrane without incorporation. This study suggests that monodisperse surface-charged submicron polymer particles are potential modifiers for improving the performance of FO membranes.

SiO2/ZnO Composite Hollow Sub-Micron Fibers: Fabrication from Facile Single Capillary Electrospinning and Their Photoluminescence Properties.

PubMed

Song, Guanying; Li, Zhenjiang; Li, Kaihua; Zhang, Lina; Meng, Alan

2017-02-24

In this work, SiO2/ZnO composite hollow sub-micron fibers were fabricated by a facile single capillary electrospinning technique followed by calcination, using tetraethyl orthosilicate (TEOS), polyvinylpyrrolidone (PVP) and ZnO nanoparticles as raw materials. The characterization results of the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) spectra indicated that the asprepared composite hollow fibers consisted of amorphous SiO2 and hexagonal wurtzite ZnO. The products revealed uniform tubular structure with outer diameters of 400-500 nm and wall thickness of 50-60 nm. The gases generated and the directional escaped mechanism was proposed to illustrate the formation of SiO2/ZnO composite hollow sub-micron fibers. Furthermore, a broad blue emission band was observed in the photoluminescence (PL) of SiO2/ZnO composite hollow sub-micron fibers, exhibiting great potential applications as blue light-emitting candidate materials.

Degradation of CMOS image sensors in deep-submicron technology due to γ-irradiation

NASA Astrophysics Data System (ADS)

Rao, Padmakumar R.; Wang, Xinyang; Theuwissen, Albert J. P.

2008-09-01

In this work, radiation induced damage mechanisms in deep submicron technology is resolved using finger gated-diodes (FGDs) as a radiation sensitive tool. It is found that these structures are simple yet efficient structures to resolve radiation induced damage in advanced CMOS processes. The degradation of the CMOS image sensors in deep-submicron technology due to γ-ray irradiation is studied by developing a model for the spectral response of the sensor and also by the dark-signal degradation as a function of STI (shallow-trench isolation) parameters. It is found that threshold shifts in the gate-oxide/silicon interface as well as minority carrier life-time variations in the silicon bulk are minimal. The top-layer material properties and the photodiode Si-SiO2 interface quality are degraded due to γ-ray irradiation. Results further suggest that p-well passivated structures are inevitable for radiation-hard designs. It was found that high electrical fields in submicron technologies pose a threat to high quality imaging in harsh environments.

Polarization-dependent imaging contrast in abalone shells

NASA Astrophysics Data System (ADS)

Metzler, Rebecca A.; Zhou, Dong; Abrecht, Mike; Chiou, Jau-Wern; Guo, Jinghua; Ariosa, Daniel; Coppersmith, Susan N.; Gilbert, P. U. P. A.

2008-02-01

Many biominerals contain micro- or nanocrystalline mineral components, organized accurately into architectures that confer the material with improved mechanical performance at the macroscopic scale. We present here an effect which enables us to observe the relative orientation of individual crystals at the submicron scale. We call it polarization-dependent imaging contrast (PIC), as it is an imaging development of the well-known x-ray linear dichroism. Most importantly, PIC is obtained in situ, in biominerals. We present here PIC in the prismatic and nacreous layers of Haliotis rufescens (red abalone), confirm it in geologic calcite and aragonite, and corroborate the experimental data with theoretical simulated spectra. PIC reveals different and unexpected aspects of nacre architecture that have inspired theoretical models for nacre formation.

Development of the fine-particle agglomerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, P.; Balasic, P.

1999-07-01

This paper presents the current status of the commercial development of a new technology to more efficiently control fine particulate emissions. The technology is based on an invention by Environmental Elements Corporation (EEC) which utilizes laminar flow to promote contact of fine submicron particles with larger particles to form agglomerates prior to their removal in a conventional particulate control device, such as an ESP. As agglomerates the particles are easily captured in the control device, whereas a substantial amount would pass through if allowed to remain as fine particles. EEC has developed the laminar-flow agglomerator technology through the laboratory proof-of-conceptmore » stage, which was funded by a DOE SBIR grant, to pilot-scale and full-scale demonstrations.« less

Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics

PubMed Central

Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Yun Jaung, Jae; Kim, Yong-Hoon; Kyu Park, Sung

2015-01-01

The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics. PMID:26411932

Scalable sub-micron patterning of organic materials toward high density soft electronics

DOE PAGES

Kim, Jaekyun; Kim, Myung -Gil; Kim, Jaehyun; ...

2015-09-28

The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. Inmore » this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. As a result, the successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.« less

Fluorescence correlation spectroscopy diffusion laws to probe the submicron cell membrane organization.

PubMed

Wawrezinieck, Laure; Rigneault, Hervé; Marguet, Didier; Lenne, Pierre-François

2005-12-01

To probe the complexity of the cell membrane organization and dynamics, it is important to obtain simple physical observables from experiments on live cells. Here we show that fluorescence correlation spectroscopy (FCS) measurements at different spatial scales enable distinguishing between different submicron confinement models. By plotting the diffusion time versus the transverse area of the confocal volume, we introduce the so-called FCS diffusion law, which is the key concept throughout this article. First, we report experimental FCS diffusion laws for two membrane constituents, which are respectively a putative raft marker and a cytoskeleton-hindered transmembrane protein. We find that these two constituents exhibit very distinct behaviors. To understand these results, we propose different models, which account for the diffusion of molecules either in a membrane comprising isolated microdomains or in a meshwork. By simulating FCS experiments for these two types of organization, we obtain FCS diffusion laws in agreement with our experimental observations. We also demonstrate that simple observables derived from these FCS diffusion laws are strongly related to confinement parameters such as the partition of molecules in microdomains and the average confinement time of molecules in a microdomain or a single mesh of a meshwork.

Mechanisms of Current Transfer in Electrodeposited Layers of Submicron Semiconductor Particles

NASA Astrophysics Data System (ADS)

Zhukov, N. D.; Mosiyash, D. S.; Sinev, I. V.; Khazanov, A. A.; Smirnov, A. V.; Lapshin, I. V.

2017-12-01

Current-voltage ( I- V) characteristics of conductance in multigrain layers of submicron particles of silicon, gallium arsenide, indium arsenide, and indium antimonide have been studied. Nanoparticles of all semiconductors were obtained by processing initial single crystals in a ball mill and applied after sedimentation onto substrates by means of electrodeposition. Detailed analysis of the I- V curves of electrodeposited layers shows that their behavior is determined by the mechanism of intergranular tunneling emission from near-surface electron states of submicron particles. Parameters of this emission process have been determined. The proposed multigrain semiconductor structures can be used in gas sensors, optical detectors, IR imagers, etc.

Topography of calcium phosphate ceramics regulates primary cilia length and TGF receptor recruitment associated with osteogenesis.

PubMed

Zhang, Jingwei; Dalbay, Melis T; Luo, Xiaoman; Vrij, Erik; Barbieri, Davide; Moroni, Lorenzo; de Bruijn, Joost D; van Blitterswijk, Clemens A; Chapple, J Paul; Knight, Martin M; Yuan, Huipin

2017-07-15

The surface topography of synthetic biomaterials is known to play a role in material-driven osteogenesis. Recent studies show that TGFβ signalling also initiates osteogenic differentiation. TGFβ signalling requires the recruitment of TGFβ receptors (TGFβR) to the primary cilia. In this study, we hypothesize that the surface topography of calcium phosphate ceramics regulates stem cell morphology, primary cilia structure and TGFβR recruitment to the cilium associated with osteogenic differentiation. We developed a 2D system using two types of tricalcium phosphate (TCP) ceramic discs with identical chemistry. One sample had a surface topography at micron-scale (TCP-B, with a bigger surface structure dimension) whilst the other had a surface topography at submicron scale (TCP-S, with a smaller surface structure dimension). In the absence of osteogenic differentiation factors, human bone marrow stromal cells (hBMSCs) were more spread on TCP-S than on TCP-B with alterations in actin organization and increased primary cilia prevalence and length. The cilia elongation on TCP-S was similar to that observed on glass in the presence of osteogenic media and was followed by recruitment of transforming growth factor-β RII (p-TGFβ RII) to the cilia axoneme. This was associated with enhanced osteogenic differentiation of hBMSCs on TCP-S, as shown by alkaline phosphatase activity and gene expression for key osteogenic markers in the absence of additional osteogenic growth factors. Similarly, in vivo after a 12-week intramuscular implantation in dogs, TCP-S induced bone formation while TCP-B did not. It is most likely that the surface topography of calcium phosphate ceramics regulates primary cilia length and ciliary recruitment of p-TGFβ RII associated with osteogenesis and bone formation. This bioengineering control of osteogenesis via primary cilia modulation may represent a new type of biomaterial-based ciliotherapy for orthopedic, dental and maxillofacial surgery applications. The surface topography of synthetic biomaterials plays important roles in material-driven osteogenesis. The data presented herein have shown that the surface topography of calcium phosphate ceramics regulates mesenchymal stromal cells (e.g., human bone marrow mesenchymal stromal cells, hBMSCs) with respect to morphology, primary cilia structure and TGFβR recruitment to the cilium associated with osteogenic differentiation in vitro. Together with bone formation in vivo, our results suggested a new type of biomaterial-based ciliotherapy for orthopedic, dental and maxillofacial surgery by the bioengineering control of osteogenesis via primary cilia modulation. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

SCIL nanoimprint solutions: high-volume soft NIL for wafer scale sub-10nm resolution

NASA Astrophysics Data System (ADS)

Voorkamp, R.; Verschuuren, M. A.; van Brakel, R.

2016-10-01

Nano-patterning materials and surfaces can add unique functionalities and properties which cannot be obtained in bulk or micro-structured materials. Examples range from hetro-epitaxy of semiconductor nano-wires to guiding cell expression and growth on medical implants. [1] Due to the cost and throughput requirements conventional nano-patterning techniques such as deep UV lithography (cost and flat substrate demands) and electron-beam lithography (cost, throughput) are not an option. Self-assembly techniques are being considered for IC manufacturing, but require nano-sized guiding patterns, which have to be fabricated in any case.[2] Additionally, the self-assembly process is highly sensitive to the environment and layer thickness, which is difficult to control on non-flat surfaces such as PV silicon wafers or III/V substrates. Laser interference lithography can achieve wafer scale periodic patterns, but is limited by the throughput due to intensity of the laser at the pinhole and only regular patterns are possible where the pattern fill fraction cannot be chosen freely due to the interference condition.[3] Nanoimprint lithography (NIL) is a promising technology for the cost effective fabrication of sub-micron and nano-patterns on large areas. The challenges for NIL are related to the technique being a contact method where a stamp which holds the patterns is required to be brought into intimate contact with the surface of the product. In NIL a strong distinction is made between the type of stamp used, either rigid or soft. Rigid stamps are made from patterned silicon, silica or plastic foils and are capable of sub-10nm resolution and wafer scale patterning. All these materials behave similar at the micro- to nm scale and require high pressures (5 - 50 Bar) to enable conformal contact to be made on wafer scales. Real world conditions such as substrate bow and particle contaminants complicate the use of rigid stamps for wafer scale areas, reducing stamp lifetime and yield. Soft stamps, usually based on silicone rubber, behave fundamentally different compared to rigid stamps on the macro-, micro- and nanometer level. The main limitation of traditional silicones is that they are too soft to support sub-micron features against surface tension based stamp deformation and collapse [4] and handling a soft stamp to achieve accurate feature placement on wafer scales to allow overlay alignment with sub-100nm overlay accuracy.

Multi-Scale Transport Properties of Fine-Grained Rocks: A Case Study of the Kirtland Formation, San Juan Basin, USA

NASA Astrophysics Data System (ADS)

Heath, J. E.; Dewers, T. A.; McPherson, B. J.; Wilson, T. H.; Flach, T.

2009-12-01

Understanding and characterizing transport properties of fine-grained rocks is critical in development of shale gas plays or assessing retention of CO2 at geologic storage sites. Difficulties arise in that both small scale (i.e., ~ nm) properties of the rock matrix and much larger scale fractures, faults, and sedimentological architecture govern migration of multiphase fluids. We present a multi-scale investigation of sealing and transport properties of the Kirtland Formation, which is a regional aquitard and reservoir seal in the San Juan Basin, USA. Sub-micron dual FIB/SEM imaging and reconstruction of 3D pore networks in core samples reveal a variety of pore types, including slit-shaped pores that are co-located with sedimentary structures and variations in mineralogy. Micron-scale chemical analysis and XRD reveal a mixture of mixed-layer smectite/illite, chlorite, quartz, and feldspar with little organic matter. Analysis of sub-micron digital reconstructions, mercury capillary injection pressure, and gas breakthrough measurements indicate a high quality sealing matrix. Natural full and partially mineralized fractures observed in core and in FMI logs include those formed from early soil-forming processes, differential compaction, and tectonic events. The potential impact of both fracture and matrix properties on large-scale transport is investigated through an analysis of natural helium from core samples, 3D seismic data and poro-elastic modeling. While seismic interpretations suggest considerable fracturing of the Kirtland, large continuous fracture zones and faults extending through the seal to the surface cannot be inferred from the data. Observed Kirtland Formation multi-scale transport properties are included as part of a risk assessment methodology for CO2 storage. Acknowledgements: The authors gratefully acknowledge the U.S. Department of Energy’s (DOE) National Energy Technology Laboratory for sponsoring this project. The DOE’s Basic Energy Science Office funded the dual FIB/SEM analysis. The Kirtland Formation overlies the coal seams of the Fruitland into which CO2 has been injected as a Phase II demonstration of the Southwest Regional Partnership on Carbon Sequestration. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy under contract DE-ACOC4-94AL85000.

Mass-spectrometric identification of primary biological particle markers and application to pristine submicron aerosol measurements in Amazonia

NASA Astrophysics Data System (ADS)

Schneider, J.; Freutel, F.; Zorn, S. R.; Chen, Q.; Farmer, D. K.; Jimenez, J. L.; Martin, S. T.; Artaxo, P.; Wiedensohler, A.; Borrmann, S.

2011-11-01

The detection of primary biological material in submicron aerosol by means of thermal desorption/electron impact ionization aerosol mass spectrometry was investigated. Mass spectra of amino acids, carbohydrates, small peptides, and proteins, all of which are key building blocks of biological particles, were recorded in laboratory experiments. Several characteristic marker fragments were identified. The intensity of the marker signals relative to the total organic mass spectrum allows for an estimation of the content of primary biological material in ambient organic aerosol. The developed method was applied to mass spectra recorded during AMAZE-08, a field campaign conducted in the pristine rainforest of the central Amazon Basin, Brazil, during the wet season of February and March 2008. The low abundance of identified marker fragments places upper limits of 7.5% for amino acids and 5.6% for carbohydrates on the contribution of primary biological aerosol particles (PBAP) to the submicron organic aerosol mass concentration during this time period. Upper limits for the absolute submicron concentrations for both compound classes range from 0.01 to 0.1 μg m-3. Carbohydrates and proteins (composed of amino acids) make up for about two thirds of the dry mass of a biological cell. Thus, our findings suggest an upper limit for the PBAP mass fraction of about 20% to the submicron organic aerosol measured in Amazonia during AMAZE-08.

Intrinsic Size Effect in Scaffolded Porous Calcium Silicate Particles and Mechanical Behavior of Their Self-Assembled Ensembles.

PubMed

Hwang, Sung Hoon; Shahsavari, Rouzbeh

2018-01-10

Scaffolded porous submicron particles with well-defined diameter, shape, and pore size have profound impacts on drug delivery, bone-tissue replacement, catalysis, sensors, photonic crystals, and self-healing materials. However, understanding the interplay between pore size, particle size, and mechanical properties of such ultrafine particles, especially at the level of individual particles and their ensemble states, is a challenge. Herein, we focus on porous calcium-silicate submicron particles with various diameters-as a model system-and perform extensive 900+ nanoindentations to completely map out their mechanical properties at three distinct structural forms from individual submicron particles to self-assembled ensembles to pressure-induced assembled arrays. Our results demonstrate a notable "intrinsic size effect" for individual porous submicron particles around ∼200-500 nm, induced by the ratio of particle characteristic diameter to pore characteristic size distribution. Increasing this ratio results in a brittle-to-ductile transition where the toughness of the submicron particles increases by 120%. This size effect becomes negligible as the porous particles form superstructures. Nevertheless, the self-assembled arrays collectively exhibit increasing elastic modulus as a function of applied forces, while pressure-induced compacted arrays exhibit no size effect. This study will impact tuning properties of individual scaffolded porous particles and can have implications on self-assembled superstructures exploiting porosity and particle size to impart new functionalities.

Multi Scale Modeling of Continuous Aramid Fiber Reinforced Polymer Matrix Composites Used in Ballistic Protection Applications

DTIC Science & Technology

2014-11-16

related to identification of the type and the extent of data generated at a finer length scale to the adjacent coarser length scale, as well as seamless ...data generated at a finer length scale to the adjacent coarser length scale, as well as seamless integration of different length scales into a unified...composite laminate consisting of 32 laminae and impacted (at a 0° obliquity angle and an incident velocity of 500 m/s) by a 0.30 caliber steel

Experimental studies of MOS inversion and accumulation layers: Quantum mechanical effects and mobility

NASA Astrophysics Data System (ADS)

Chindalore, Gowrishankar L.

The development of fast, multi-functional, and energy efficient integrated circuits, is made possible by aggressively scaling the gate lengths of the MOS devices into the sub-quarter micron regime. However, with the increasing cost of fabrication, there is a strong need for the development of reliable and accurate device simulation capabilities. The development of the theoretical models for simulators is guided by extensive experimental data, which enable an experimental verification of the models, and lead to a better understanding of the underlying physics. This dissertation presents the methodology and the results for one such experimental effort, where two important physical effects in the inversion layer and the accumulation layer of a MOS device, namely, the quantum mechanical (QM) effects and the carrier mobility are investigated. Accordingly, this dissertation has been divided into two parts, with the first part discussing the increase in the threshold voltage and the accumulation electrical oxide thickness due to QM effects. The second part discusses the methodology and the experimental results for the extraction of the majority carrier mobilities in the accumulation layers of a MOSFET. The continued scaling of the MOS gate length requires decreased gate oxide thickness (tox) and increased channel doping (NB) in order to improve device performance while suppressing the short- channel effects. The combination of the two result in large enough transverse electric fields to cause significant quantization of the carriers in the potential well at the Si/SiO2 interface. Hence, compared to the classical calculations (where the QM effects are ignored), the QM effects are found to lead to an increase in the experimental threshold voltage by approximately 100mV, and an overestimation of the physical oxide thickness by approximately 3-4A, in MOSFET devices with a gate oxide thickness and the doping level anticipated for technologies with sub-quarter micron gate lengths. Thus, the experimental results indicate the need for using accurate QM models for simulating sub-quarter micron devices. Carrier mobility is a fundamental semiconductor device transport parameter that has been extensively characterized for both electrons and holes in the silicon bulk and MOS inversion layers. Accumulation layer mobility (μacc) has become increasingly important as the MOS devices have scaled to deep submicron gate lengths, and much effort has been required to achieve increased drive current. However, very little experimental data has been reported for carrier mobility in the MOS accumulation layers (Sun80, Man89). Hence, in this research work, the accumulation layer mobilities were extracted using buried-channel MOSFETs for both the electrons and holes, and for a wide range of doping levels at temperatures ranging from 25C to 150C. The experimental μacc is found to be greater than the corresponding bulk and the inversion layer mobilities, at low to moderate effective fields. However, at very high effective fields, where phonon and surface roughness scattering are dominant, the mobility behavior is found to be very similar to that of the inversion carriers. The extensive set of experimental data will enable the development of accurate local accumulation mobility models for inclusion in 2-D device simulators.

Advantages and challenges of the spray-drying technology for the production of pure drug particles and drug-loaded polymeric carriers.

PubMed

Sosnik, Alejandro; Seremeta, Katia P

2015-09-01

Spray-drying is a rapid, continuous, cost-effective, reproducible and scalable process for the production of dry powders from a fluid material by atomization through an atomizer into a hot drying gas medium, usually air. Often spray-drying is considered only a dehydration process, though it also can be used for the encapsulation of hydrophilic and hydrophobic active compounds within different carriers without substantial thermal degradation, even of heat-sensitive substances due to fast drying (seconds or milliseconds) and relatively short exposure time to heat. The solid particles obtained present relatively narrow size distribution at the submicron-to-micron scale. Generally, the yield% of spray-drying at laboratory scale with conventional spray-dryers is not optimal (20-70%) due to the loss of product in the walls of the drying chamber and the low capacity of the cyclone to separate fine particles (<2 μm). Aiming to overcome this crucial drawback in early development stages, new devices that enable the production of submicron particles with high yield, even for small sample amounts, have been introduced into the market. This review describes the most outstanding advantages and challenges of the spray-drying method for the production of pure drug particles and drug-loaded polymeric particles and discusses the potential of this technique and the more advanced equipment to pave the way toward reproducible and scalable processes that are critical to the bench-to-bedside translation of innovative pharmaceutical products. Copyright © 2015 Elsevier B.V. All rights reserved.

A multi-topographical-instrument analysis: the breast implant texture measurement

NASA Astrophysics Data System (ADS)

Garabédian, Charles; Delille, Rémi; Deltombe, Raphaël; Anselme, Karine; Atlan, Michael; Bigerelle, Maxence

2017-06-01

Capsular contracture is a major complication after implant-based breast augmentation. To address this tissue reaction, most manufacturers texture the outer breast implant surfaces with calibrated salt grains. However, the analysis of these surfaces on sub-micron scales has been under-studied. This scale range is of interest to understand the future of silicone particles potentially released from the implant surface and the aetiology of newly reported complications, such as Anaplastic Large Cell Lymphoma. The surface measurements were accomplished by tomography and by two optical devices based on interferometry and on focus variation. The robustness of the measurements was investigated from the tissue scale to the cellular scale. The macroscopic pore-based structure of the textured implant surfaces is consistently measured by the three instruments. However, the multi-scale analyses start to be discrepant in a scale range between 50 µm and 500 µm characteristic of a finer secondary roughness regardless of the pore shape. The focus variation and the micro-tomography would fail to capture this roughness regime because of a focus-related optical artefact and of step-shaped artefact respectively.

Finite-size scaling above the upper critical dimension in Ising models with long-range interactions

NASA Astrophysics Data System (ADS)

Flores-Sola, Emilio J.; Berche, Bertrand; Kenna, Ralph; Weigel, Martin

2015-01-01

The correlation length plays a pivotal role in finite-size scaling and hyperscaling at continuous phase transitions. Below the upper critical dimension, where the correlation length is proportional to the system length, both finite-size scaling and hyperscaling take conventional forms. Above the upper critical dimension these forms break down and a new scaling scenario appears. Here we investigate this scaling behaviour by simulating one-dimensional Ising ferromagnets with long-range interactions. We show that the correlation length scales as a non-trivial power of the linear system size and investigate the scaling forms. For interactions of sufficiently long range, the disparity between the correlation length and the system length can be made arbitrarily large, while maintaining the new scaling scenarios. We also investigate the behavior of the correlation function above the upper critical dimension and the modifications imposed by the new scaling scenario onto the associated Fisher relation.

Silicon photonics: Design, fabrication, and characterization of on-chip optical interconnects

NASA Astrophysics Data System (ADS)

Hsieh, I.-Wei

In recent years, the research field of silicon photonics has been developing rapidly from a concept to a demonstrated technology, and has gathered much attention from both academia and industry communities. Its many potential applications in long-haul telecommunication, mid-range data-communication, on-chip optical interconnection networks, and nano-scale sensing as well as its compatibility with electronic integrated circuits have driven much effort in realizing silicon photonics both as a disruptive technology for existing markets and as an enabling technology for new ones. Despite the promising future of silicon photonics, many fundamental issues still remain to be understood---both in the linear- and nonlinear-optical regimes. There are also many engineering challenges to make silicon photonics the gold standard in photonic integrated circuits. In this thesis, we focus on the design, fabrication, and characterization of active and passive silicon-on-insulator (SOI) photonic devices. The SOI material system differs from most conventional optical material platforms because of its high-refractive-index-contrast, which enables engineers to design very compact integrated photonic networks with sub-micron transverse waveguide dimensions and sharp bends. On the other hand, because most analytical formulas for designing waveguide devices are valid only in low-index-contrast cases, SOI photonic devices need to be analyzed numerically for accurate results. The second chapter of this thesis describes some common numerical methods such as Beam Propagation Method (BPM) and Finite Element Method (FEM) for waveguide-design simulations, and presents two design studies based on these methods. The compatibility of silicon photonic integrated circuits with conventional CMOS fabrication technology is another important aspect that distinguishes silicon photonics from others such as III-V materials and lithium niobate. However, the requirements for fabricating silicon photonic devices are quite different from those of electronic devices. Minimizing propagation losses by reducing sidewall roughness to nanometer scale over a device length of several millimeters or even centimeters has prompted researchers in academia and industry to refine the fabrication process. Chapter 3 of this thesis summarizes our efforts in fabricating silicon photonic devices using standard CMOS technology. Chapter 4 describes the characterization of nonlinear effects, including self-phase modulation (SPM), cross-phase modulation (XPM), and supercontinuum generation in silicon-wire waveguides. Silicon-wire waveguides are strip waveguides with submicron transverse dimensions, which allow strong light confinement inside the silicon core. This strong optical confinement, in addition to the large third-order nonlinear optical susceptibility of crystalline silicon, leads to a net nonlinearity which is several orders of magnitude higher than the nonlinearity of silica fiber. Significant nonlinear effects can be observed and characterized over a device length of only several millimeters in silicon wires with very small input power. These effects provide opportunities for engineers to design active silicon photonic devices which are compact and energy-efficient. Chapter 5 presents a realization of an integrated SOI optical isolator, which is a critical yet often overlooked component in photonic integrated circuits. This study shows the feasibility to make a hybrid garnet/SOI active device with very promising results. Finally, Chapter 6 summarizes our demonstration of transmitting terabit-scale data streams in silicon-wire waveguides, which is an important first-step towards enabling intra-chip interconnection networks with ultra-high bandwidths. Although the scope of this thesis is limited to providing only fractional views of the whole silicon photonics area, it provides enough references for interested readers to conduct further literature research in other aspects of silicon photonics. It is the author's hope that the thesis would convey to its readers the significance and potential of this exciting emerging technology.

Effect of Vaporizer Temperature on Ambient Non-Refractory Submicron Aerosol Composition and Mass Spectra Measured by the Aerosol Mass Spectrometer

EPA Science Inventory

Aerodyne Aerosol Mass Spectrometers (AMS) are routinely operated with a constant vaporizer temperature (Tvap) of 600^oC in order to facilitate quantitative detection of non-refractory submicron (NR-PM1) species. By analogy with other thermal desorption instrument...

IMPACT OF AEROSOL LIQUID WATER ON SECONDARY ORGANIC AEROSOL YIELDS OF IRRADIATED TOLUENE/PROPYLENE/NOX/(NH4)2SO4/AIR MIXUTRES

EPA Science Inventory

Laboratory experiments were conducted to assess whether the presence of liquid water on pre-existing submicron ammonium sulfate aerosols affects yields of condensible organic compounds. Toluene/propylene/NOX/air mixtures were irradiated in the presence of submicron ammonium su...

Mountain pine beetle-killed lodgepole pine for the production of submicron lignocellulose fibrils

Treesearch

Ingrid Hoeger; Rolland Gleisner; Jose Negron; Orlando J. Rojas; J. Y. Zhu

2014-01-01

The elevated levels of tree mortality attributed to mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins) in western North American forests create forest management challenges. This investigation introduces the production of submicron or nanometer lignocellulose fibrils for value-added materials from the widely available resource represented by dead pines after...

A new route for the synthesis of submicron-sized LaB{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lihong, Bao; Wurentuya,; Wei, Wei

Submicron crystalline LaB{sub 6} has been successfully synthesized by a solid-state reaction of La{sub 2}O{sub 3} with NaBH{sub 4} at 1200 °C. The effects of reaction temperature on the crystal structure, grain size and morphology were investigated by X-ray diffraction, scanning electron microscope and transmission electron microscope. It is found that when the reaction temperature is in the range of 1000–1100 °C, there are ultrafine nanoparticles and nanocrystals that coexist. When the reaction temperature elevated to 1200 °C, the grain morphology transformed from ultrafine nanoparticle to submicron crystals completely. High resolution transmission electron microscope images fully confirm the formation ofmore » LaB{sub 6} cubic structure. - Highlights: • Single-phased LaB{sub 6} have been synthesized by a solid-state reaction in a continuous evacuating process. • The reaction temperature has a important effect on the phase composition. • The grain size increase from nano-size to submicron with increasing reaction temperature.« less

Investigation of the enhanced spatial density of submicron lunar ejecta between L values 1.2 and 3.0 in the earth's magnetosphere: Theory

NASA Technical Reports Server (NTRS)

Alexander, W. M.; Tanner, W. G.; Goad, H. S.

1987-01-01

Initial results from the measurement conducted by the dust particle experiment on the lunar orbiting satellite Lunar Explorer 35 (LE 35) were reported with the data interpreted as indicating that the moon is a significant source of micrometeroids. Primary sporadic and stream meteoroids impacting the surface of the moon at hypervelocity was proposed as the source of micron and submicron particles that leave the lunar craters with velocities sufficient to escape the moon's gravitational sphere of influence. No enhanced flux of lunar ejecta with masses greater than a nanogram was detected by LE 35 or the Lunar Orbiters. Hypervelocity meteoroid simulation experiments concentrating on ejecta production combined with extensive analyses of the orbital dynamics of micron and submicron lunar ejecta in selenocentric, cislunar, and geocentric space have shown that a pulse of these lunar ejecta, with a time correlation relative to the position of the moon relative to the earth, intercepts the earth's magnetopause surface (EMPs). As shown, a strong reason exists for expecting a significant enhancement of submicron dust particles in the region of the magnetosphere between L values of 1.2 and 3.0. This is the basis for the proposal of a series of experiments to investigate the enhancement or even trapping of submicron lunar ejecta in this region. The subsequent interaction of this mass with the upper-lower atmosphere of the earth and possible geophysical effects can then be studied.

Particle size distribution and composition in a mechanically ventilated school building during air pollution episodes.

PubMed

Parker, J L; Larson, R R; Eskelson, E; Wood, E M; Veranth, J M

2008-10-01

Particle count-based size distribution and PM(2.5) mass were monitored inside and outside an elementary school in Salt Lake City (UT, USA) during the winter atmospheric inversion season. The site is influenced by urban traffic and the airshed is subject to periods of high PM(2.5) concentration that is mainly submicron ammonium and nitrate. The school building has mechanical ventilation with filtration and variable-volume makeup air. Comparison of the indoor and outdoor particle size distribution on the five cleanest and five most polluted school days during the study showed that the ambient submicron particulate matter (PM) penetrated the building, but indoor concentrations were about one-eighth of outdoor levels. The indoor:outdoor PM(2.5) mass ratio averaged 0.12 and particle number ratio for sizes smaller than 1 microm averaged 0.13. The indoor submicron particle count and indoor PM(2.5) mass increased slightly during pollution episodes but remained well below outdoor levels. When the building was occupied the indoor coarse particle count was much higher than ambient levels. These results contribute to understanding the relationship between ambient monitoring station data and the actual human exposure inside institutional buildings. The study confirms that staying inside a mechanically ventilated building reduces exposure to outdoor submicron particles. This study supports the premise that remaining inside buildings during particulate matter (PM) pollution episodes reduces exposure to submicron PM. New data on a mechanically ventilated institutional building supplements similar studies made in residences.

Mineral Precipitation in Fractures: Multiscale Imaging and Geochemical Modeling

NASA Astrophysics Data System (ADS)

Hajirezaie, S.; Peters, C. A.; Swift, A.; Sheets, J. M.; Cole, D. R.; Crandall, D.; Cheshire, M.; Stack, A. G.; Anovitz, L. M.

2017-12-01

For subsurface energy technologies such as geologic carbon sequestration, fractures are potential pathways for fluid migration from target formations. Highly permeable fractures may become sealed by mineral precipitation. In this study, we examined shale specimens with existing cemented fractures as natural analogues, using an array of imaging methods to characterize mineralogy and porosity at several spatial scales. In addition, we used reactive transport modeling to investigate geochemical conditions that can lead to extensive mineral precipitation and to simulate the impacts on fracture hydraulic properties. The naturally-cemented fractured rock specimens were from the Upper Wolfcamp formation in Texas, at 10,000 ft depth. The specimens were scanned using x-ray computed tomography (xCT) at resolution of 13 microns. The xCT images revealed an original fracture aperture of 1.9 mm filled with several distinct mineral phases and vuggy void regions, and the mineral phase volumes and surface areas were quantified and mapped in 3D. Specimens were thin-sectioned and examined at micron- and submicron-scales using petrographic microscopy (PM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and small angle X-ray scattering (SAXS). Collectively these methods revealed crystals of dolomite as large as 900 microns in length overlain with a heterogeneous mixture of carbonate minerals including calcite, dolomite, and Fe-rich dolomite, interspersed at spatial scales as small as 5 microns. In addition, secondary precipitation of SiO2 was found to fill some of the void space. This multiscale imaging was used to inform the reactive transport modeling employed to examine the conditions that can cause the observed mineral precipitation in fractures at a larger scale. Two brines containing solutions that when mixed would lead to precipitation of various carbonate minerals were simulated as injectants into a fracture domain. In particular, the competing effects of transport dynamics and reaction kinetics were investigated in the context of profiles of the precipitated minerals and permeability behavior of the fracture flow path. This study contributes rich knowledge toward mastering the subsurface for energy production and storage and for the management of energy waste streams.

Generation of sub-micron particles and secondary pollutants from building materials by ozone reaction

NASA Astrophysics Data System (ADS)

Aoki, Taisuke; Tanabe, Shin-ichi

This study reports results from two different experiments examining reactions between ozone and common building materials that can lead to the formation of secondary products and particulate-phase materials. Monitored species include sub-micron particles and volatile organic compounds (VOCs). In the first set of experiments, various building materials were placed in a 20 L stainless-steel chamber and exposed to ozone. The materials included expanded polystyrene, a natural rubber adhesive, cedar board, Japanese Cyprus board and silver fir board, as well as d-limonene, which is a known constituent of certain woods and cleaning products. The combination of ozone and either d-limonene, cedar board or cypress board produced sub-micron particles, with most of the increase occurring in the size range of 0.01- 0.5μm diameter. This was not observed for the other materials. In the case of cedar board, the consequence of ozone exposure over an extended time interval was monitored. As the exposure time elapsed, the concentration of sub-micron particles moderately decreased. In the second set of experiments, unwaxed or waxed plastic tiles were placed in the 20 L chamber and exposed to ozone. Sub-micron particles and organic compounds were measured during the course of the experiments. In the case of the waxed tile, the number of 0.01- 1.0μm size particles grew about 50×108particlesm-3; particle growth was significantly less for the un-waxed tile. For both the waxed and un-waxed tiles, the emission rates of heptane, nonane, nonanal, and decanal increased after ozone was added to the supply air. (However, it is not clear if some or all of this production was due to ozone reacting with the sorbent used for sampling or with compounds captured by the sorbent.) This study provides further evidence that ozone-initiated reactions with building materials can be a significant source of both sub-micron particles and secondary organic compounds in indoor environments.

Fabrication of magnetic and fluorescent chitin and dibutyrylchitin sub-micron particles by oil-in-water emulsification.

PubMed

Blanco-Fernandez, Barbara; Chakravarty, Shatadru; Nkansah, Michael K; Shapiro, Erik M

2016-11-01

Chitin is a carbohydrate polymer with unique pharmacological and immunological properties, however, because of its unwieldy chemistry, the synthesis of discreet sized sub-micron particles has not been well reported. This work describes a facile and flexible method to fabricate biocompatible chitin and dibutyrylchitin sub-micron particles. This technique is based on an oil-in-water emulsification/evaporation method and involves the hydrophobization of chitin by the addition of labile butyryl groups onto chitin, disrupting intermolecular hydrogen bonds and enabling solubility in the organic solvent used as the oil phase during fabrication. The subsequent removal of butyryl groups post-fabrication through alkaline saponification regenerates native chitin while keeping particles morphology intact. Examples of encapsulation of hydrophobic dyes and nanocrystals are demonstrated, specifically using iron oxide nanocrystals and coumarin 6. The prepared particles had diameters between 300-400nm for dibutyrylchitin and 500-600nm for chitin and were highly cytocompatible. Moreover, they were able to encapsulate high amounts of iron oxide nanocrystals and were able to label mammalian cells. We describe a technique to prepare sub-micron particles of highly acetylated chitin (>90%) and dibutyrylchitin and demonstrate their utility as carriers for imaging. Chitin is a polysaccharide capable of stimulating the immune system, a property that depends on the acetamide groups, but its insolubility limits its use. No method for sub-micron particle preparation with highly acetylated chitins have been published. The only approach for the preparation of sub-micron particles uses low acetylation chitins. Dibutyrylchitin, a soluble chitin derivative, was used to prepare particles by oil in water emulsification. Butyryl groups were then removed, forming chitin particles. These particles could be suitable for encapsulation of hydrophobic payloads for drug delivery and cell imaging, as well as, adjuvants for vaccines. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

From Tomography to Material Properties of Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Mansour, Nagi N.; Panerai, Francesco; Ferguson, Joseph C.; Borner, Arnaud; Barnhardt, Michael; Wright, Michael

2017-01-01

A NASA Ames Research Center (ARC) effort, under the Entry Systems Modeling (ESM) project, aims at developing micro-tomography (micro-CT) experiments and simulations for studying materials used in hypersonic entry systems. X-ray micro-tomography allows for non-destructive 3D imaging of a materials micro-structure at the sub-micron scale, providing fiber-scale representations of porous thermal protection systems (TPS) materials. The technique has also allowed for In-situ experiments that can resolve response phenomena under realistic environmental conditions such as high temperature, mechanical loads, and oxidizing atmospheres. Simulation tools have been developed at the NASA Ames Research Center to determine material properties and material response from the high-fidelity tomographic representations of the porous materials with the goal of informing macroscopic TPS response models and guiding future TPS design.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Novel Route to Fabrication of Metal-Sandwiched Nanoscale Tapered Structures

NASA Astrophysics Data System (ADS)

Zhang, Yang; Yu, Da-Peng

2009-08-01

Tapered dielectric structures in metal have exhibited extraordinary performance in both surface plasmon polariton (SPP) waveguiding and SPP focusing. This is crucial to plasmonic research and industrial plasmonic device integration. We present a method that facilitates easy fabrication of smooth-surfaced sub-micron tapered structures in large scale simply with electron beam lithography (EBL). When a PMMA layer is spin-coated on previously-EBL-defined PMMA structures, steep edges can be transformed into a declining slope to form tapered PMMA structures, scaled from 10 nm to 1000 nm. Despite the simplicity of our method, patterns with PMMA surface smoothness can be well-positioned and replicated in large numbers, which therefore gives scientists easy access to research on the properties of tapered structures.

Length scale effects and multiscale modeling of thermally induced phase transformation kinetics in NiTi SMA

NASA Astrophysics Data System (ADS)

Frantziskonis, George N.; Gur, Sourav

2017-06-01

Thermally induced phase transformation in NiTi shape memory alloys (SMAs) shows strong size and shape, collectively termed length scale effects, at the nano to micrometer scales, and that has important implications for the design and use of devices and structures at such scales. This paper, based on a recently developed multiscale model that utilizes molecular dynamics (MDs) simulations at small scales and MD-verified phase field (PhF) simulations at larger scales, reports results on specific length scale effects, i.e. length scale effects in martensite phase fraction (MPF) evolution, transformation temperatures (martensite and austenite start and finish) and in the thermally cyclic transformation between austenitic and martensitic phase. The multiscale study identifies saturation points for length scale effects and studies, for the first time, the length scale effect on the kinetics (i.e. developed internal strains) in the B19‧ phase during phase transformation. The major part of the work addresses small scale single crystals in specific orientations. However, the multiscale method is used in a unique and novel way to indirectly study length scale and grain size effects on evolution kinetics in polycrystalline NiTi, and to compare the simulation results to experiments. The interplay of the grain size and the length scale effect on the thermally induced MPF evolution is also shown in this present study. Finally, the multiscale coupling results are employed to improve phenomenological material models for NiTi SMA.

Atomic Force Microscope Mediated Chromatography

NASA Technical Reports Server (NTRS)

Anderson, Mark S.

2013-01-01

The atomic force microscope (AFM) is used to inject a sample, provide shear-driven liquid flow over a functionalized substrate, and detect separated components. This is demonstrated using lipophilic dyes and normal phase chromatography. A significant reduction in both size and separation time scales is achieved with a 25-micron-length column scale, and one-second separation times. The approach has general applications to trace chemical and microfluidic analysis. The AFM is now a common tool for ultra-microscopy and nanotechnology. It has also been demonstrated to provide a number of microfluidic functions necessary for miniaturized chromatography. These include injection of sub-femtoliter samples, fluidic switching, and sheardriven pumping. The AFM probe tip can be used to selectively remove surface layers for subsequent microchemical analysis using infrared and tip-enhanced Raman spectroscopy. With its ability to image individual atoms, the AFM is a remarkably sensitive detector that can be used to detect separated components. These diverse functional components of microfluidic manipulation have been combined in this work to demonstrate AFM mediated chromatography. AFM mediated chromatography uses channel-less, shear-driven pumping. This is demonstrated with a thin, aluminum oxide substrate and a non-polar solvent system to separate a mixture of lipophilic dyes. In conventional chromatographic terms, this is analogous to thin-layer chromatography using normal phase alumina substrate with sheardriven pumping provided by the AFM tip-cantilever mechanism. The AFM detection of separated components is accomplished by exploiting the variation in the localized friction of the separated components. The AFM tip-cantilever provides the mechanism for producing shear-induced flows and rapid pumping. Shear-driven chromatography (SDC) is a relatively new concept that overcomes the speed and miniaturization limitations of conventional liquid chromatography. SDC is based on a sliding plate system, consisting of two flat surfaces, one of which has a recessed channel. A fluid flow is produced by axially sliding one plate past another, where the fluid has mechanical shear forces imposed at each point along the channel length. The shear-induced flow rates are very reproducible, and do not have pressure or voltage gradient limitations. SDC opens up a new range of enhanced separation kinetics by permitting the sample confinement with submicron dimensions. Small, highly confined liquid is advantageous for chromatographic separation because the separation rate is known to scale according to the square of the confined sample diameter. In addition, because shear-driven flows are not limited by fluid velocity, shear-driven liquid chromatography may provide up to 100,000 plate efficiency.

Structure and dynamics of hyaluronic acid semidilute solutions: a dielectric spectroscopy study.

PubMed

Vuletić, T; Dolanski Babić, S; Ivek, T; Grgicin, D; Tomić, S; Podgornik, R

2010-07-01

Dielectric spectroscopy is used to investigate fundamental length scales describing the structure of hyaluronic acid sodium salt (Na-HA) semidilute aqueous solutions. In salt-free regime, the length scale of the relaxation mode detected in MHz range scales with HA concentration as c(HA)(-0.5) and corresponds to the de Gennes-Pfeuty-Dobrynin correlation length of polyelectrolytes in semidilute solution. The same scaling was observed for the case of long, genomic DNA. Conversely, the length scale of the mode detected in kilohertz range also varies with HA concentration as c(HA)(-0.5) which differs from the case of DNA (c(DNA)(-0.25)). The observed behavior suggests that the relaxation in the kilohertz range reveals the de Gennes-Dobrynin renormalized Debye screening length, and not the average size of the chain, as the pertinent length scale. Similarly, with increasing added salt the electrostatic contribution to the HA persistence length is observed to scale as the Debye length, contrary to scaling pertinent to the Odijk-Skolnick-Fixman electrostatic persistence length observed in the case of DNA. We argue that the observed features of the kilohertz range relaxation are due to much weaker electrostatic interactions that lead to the absence of Manning condensation as well as a rather high flexibility of HA as compared to DNA.

Deviation from threshold model in ultrafast laser ablation of graphene at sub-micron scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gil-Villalba, A.; Xie, C.; Salut, R.

We investigate a method to measure ultrafast laser ablation threshold with respect to spot size. We use structured complex beams to generate a pattern of craters in CVD graphene with a single laser pulse. A direct comparison between beam profile and SEM characterization allows us to determine the dependence of ablation probability on spot-size, for crater diameters ranging between 700 nm and 2.5 μm. We report a drastic decrease of ablation probability when the crater diameter is below 1 μm which we interpret in terms of free-carrier diffusion.

Dislocation Multiplication by Single Cross Slip for FCC at Submicron Scales

NASA Astrophysics Data System (ADS)

Cui, Yi-Nan; Liu, Zhan-Li; Zhuang, Zhuo

2013-04-01

The operation mechanism of single cross slip multiplication (SCSM) is investigated by studying the response of one dislocation loop expanding in face-centered-cubic (FCC) single crystal using three-dimensional discrete dislocation dynamic (3D-DDD) simulation. The results show that SCSM can trigger highly correlated dislocation generation in a short time, which may shed some light on understanding the large strain burst observed experimentally. Furthermore, we find that there is a critical stress and material size for the operation of SCSM, which agrees with that required to trigger large strain burst in the compression tests of FCC micropillars.

Nanoforging – Innovation in three-dimensional processing and shaping of nanoscaled structures

PubMed Central

Rösler, Joachim

2014-01-01

Summary Background: This paper describes the shaping of freestanding objects out of metallic structures in the nano- and submicron size. The technique used, called nanoforging, is very similar to the macroscopic forging process. Results: With spring actuated tools produced by focused ion beam milling, controlled forging is demonstrated. With only three steps, a conical bar stock is transformed to a flat- and semicircular bent bar stock. Conclusion: Compared with other forming techniques in the reduced scale, nanoforging represents a beneficial approach in forming freestanding metallic structures, due to its simplicity, and supplements other forming techniques. PMID:25161840

Convergent beam electron-diffraction investigation of lattice mismatch and static disorder in GaAs/GaAs1-xNx intercalated GaAs/GaAs1-xNx:H heterostructures

NASA Astrophysics Data System (ADS)

Frabboni, S.; Grillo, V.; Gazzadi, G. C.; Balboni, R.; Trotta, R.; Polimeni, A.; Capizzi, M.; Martelli, F.; Rubini, S.; Guzzinati, G.; Glas, F.

2012-09-01

Hydrogen incorporation in diluted nitride semiconductors dramatically modifies the electronic and structural properties of the crystal through the creation of nitrogen-hydrogen complexes. We report a convergent beam electron-diffraction characterization of diluted nitride semiconductor-heterostructures patterned at a sub-micron scale and selectively exposed to hydrogen. We present a method to determine separately perpendicular mismatch and static disorder in pristine and hydrogenated heterostructures. The roles of chemical composition and strain on static disorder have been separately assessed.

Physical-mathematical model of condensation process of the sub-micron dust capture in sprayer scrubber

NASA Astrophysics Data System (ADS)

Shilyaev, M. I.; Khromova, E. M.; Grigoriev, A. V.; Tumashova, A. V.

2011-09-01

A physical-mathematical model of the heat and mass exchange process and condensation capture of sub-micron dust particles on the droplets of dispersed liquid in a sprayer scrubber is proposed and analysed. A satisfactory agreement of computed results and experimental data on soot capturing from the cracking gases is obtained.

Method of producing non-agglomerating submicron size particles

DOEpatents

Bourne, Roy S.; Eichman, Clarence C.; Welbon, William W.

1989-01-01

Submicron size particles are produced by using a sputtering process to deposit particles into a liquid. The liquid is processed to recover the particles therefrom, and the particles have sizes in the range of twenty to two hundred Angstroms. Either metallic or non-metallic particles can be produced, and the metallic particles can be used in "metallic inks".

High density submicron magnetoresistive random access memory (invited)

NASA Astrophysics Data System (ADS)

Tehrani, S.; Chen, E.; Durlam, M.; DeHerrera, M.; Slaughter, J. M.; Shi, J.; Kerszykowski, G.

1999-04-01

Various giant magnetoresistance material structures were patterned and studied for their potential as memory elements. The preferred memory element, based on pseudo-spin valve structures, was designed with two magnetic stacks (NiFeCo/CoFe) of different thickness with Cu as an interlayer. The difference in thickness results in dissimilar switching fields due to the shape anisotropy at deep submicron dimensions. It was found that a lower switching current can be achieved when the bits have a word line that wraps around the bit 1.5 times. Submicron memory elements integrated with complementary metal-oxide-semiconductor (CMOS) transistors maintained their characteristics and no degradation to the CMOS devices was observed. Selectivity between memory elements in high-density arrays was demonstrated.

Reactivity of chlorine radical with submicron palmitic acid particles: kinetic measurements and products identification

NASA Astrophysics Data System (ADS)

Mendez, M.; Ciuraru, R.; Gosselin, S.; Batut, S.; Visez, N.; Petitprez, D.

2013-06-01

The heterogeneous reaction of Cl. radicals with sub-micron palmitic acid (PA) particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by homogeneous condensation of PA vapors and introduced in the reactor where chlorine atoms are produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (γ) has been determined from the rate loss of PA measured by GC/MS analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, γ = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analyses have shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although, the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2 which leads to an uptake coefficient γ = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids are identified by GC/MS. Formation of alcohols and monocarboxylic acids are also suspected. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface, but also in bulk by mechanisms which are still unclear. Furthermore the identified reaction products are explained by a chemical mechanism showing the pathway of the formation of more functionalized products. They help to understand the aging of primary tropospheric aerosol containing fatty acids.

Reactivity of chlorine radical with submicron palmitic acid particles: kinetic measurements and product identification

NASA Astrophysics Data System (ADS)

Mendez, M.; Ciuraru, R.; Gosselin, S.; Batut, S.; Visez, N.; Petitprez, D.

2013-12-01

The heterogeneous reaction of Cl• radicals with submicron palmitic acid (PA) particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by homogeneous condensation of PA vapours and introduced into the reactor, where chlorine atoms were produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (γ) has been determined from the rate loss of PA measured by gas chromatography-mass spectrometer (GC/MS) analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, γ = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analysis has shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2, which leads to an uptake coefficient γ = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids were identified by GC/MS. The formation of alcohols and monocarboxylic acids is also suspected. A reaction pathway for the main products and more functionalized species is proposed. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface but also in bulk by mechanisms which are still unclear. They help to understand the aging of primary tropospheric aerosol containing fatty acids.

An examination of the shrinking-core model of sub-micron aluminum combustion

NASA Astrophysics Data System (ADS)

Buckmaster, John; Jackson, Thomas L.

2013-04-01

We revisit the shrinking-core model of sub-micron aluminum combustion with particular attention to the mass flux balance at the reaction front which necessarily leads to a displacement velocity of the alumina shell surrounding the liquid aluminum. For the planar problem this displacement simply leads to an equal displacement of the entire alumina layer, and therefore a straightforward mathematical framework can be constructed. In this way we are able to construct a single curve which defines the burn time for arbitrary values of the diffusion coefficient of O atoms, the reaction rate, the characteristic length of the combustion field, and the O atom mass concentration within the alumina provided that it is much smaller than the aluminum density. This demonstrates a transition between a 'd 2-t' law for fast chemistry and a 'd-t' law for slow chemistry. For the spherical geometry, the one of physical interest, the outward displacement velocity creates not a simple displacement, but a stress field which, when examined within the framework of linear elasticity, strongly suggests the creation of internal cracking. We note that if the molten aluminum is pushed into these cracks by the high internal pressure characteristic of the stress field, its surface, where reaction occurs, could be fractal in nature and affect the fundamental nature of the burning law. Indeed, if this ingredient is added to the planar model, a single curve for the burn time can again be derived, and this describes a transition from a 'd 2-t' law to a 'd ν-t' law, where 0<ν<1.

Rapid localized deactivation of self-assembled monolayers by propagation-controlled laser-induced plasma and its application to self-patterning of electronics and biosensors

NASA Astrophysics Data System (ADS)

Kim, Jongsu; Kwon, Seung-Gab; Back, Seunghyun; Kang, Bongchul

2018-03-01

We present a novel laser-induced surface treatment process to rapidly control the spatial wettabilities of various functional solutions with submicron to micron resolutions. Ultrathin hydrophobic self-assembled monolayers (SAMs) that little absorb typical laser lights due to short penetration depth were selectively deactivated by instantaneous interaction with laser-induced metallic plasmas. The spatial region of the deactivated SAM, which corresponds to process resolution, is adjustable by controlling the spatial propagation of the plasma. This method leads to the parallel formation of hydrophilic functional solutions on glass substrates with a minimum resolution on the submicron scale. To show its feasibility in device engineering fields, this method was applied to the cost-effective fabrication of electronics and biosensors. Rapid self-patterning of electronic and biological functional solutions (silver nanoparticle solution and streptavidin protein solution) was successfully realized by selective deactivation of two different SAMs (tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) for electronics and the hetero-hybrid SAM (octadecyltrichlorosilane (OTS)/2-[methoxy(polyethyleneoxy)propyl] trichlorosilane (PEG)) for biosensors). As a result, this method can be exploited for the rapid and low-cost fabrication of various thin film devices such as electronics, biosensors, energy, displays, and photonics.

A bioactive coating with submicron-sized titania crystallites fabricated by induction heating of titanium after tensile deformations.

PubMed

Li, Ning-Bo; Xu, Wen-Hua; Xiao, Gui-Yong; Zhao, Jun-Han; Lu, Yu-Peng

2017-11-01

Thermal oxidation technology was widely investigated as one of effective surface modification method for improving the bioactivity and biocompatibility of titanium and its alloys. In this work, the induction heat oxidization method, a fast, efficient, economical and environmental protective technology, was applied to prepare the submicron-morphological oxide coating with variable rutile TiO 2 equiaxed crystallites on the surface of pure Ti substrates after cold-drawing with 10-20% deformations. The results showed the plastic-deformed Ti cylinders recrystallized during induction heating treatment (IHT) for 10-20s which resulted in evolution of microstructures as well as slight improvement of microhardness. The surface characteristics of TiO 2 crystallites in oxidation layers were determined by the microstructural evolutions of Ti substrate in terms of the nucleation and growth of TiO 2 crystallites. Specially, the oxidized surface with 50-75nm roughness and more uniform and finer equiaxed oxide grains remarkablely improved the apatite deposition after bioactive evaluation in 1.5 × SBF for 7 days. This work provided a potential method to create controlled bioactive oxide coatings with submicro-/nano-scaled TiO 2 crystallites on titanium substrate in terms of the role of metallographic microstructure in the formation process of titanium oxides. Copyright © 2017 Elsevier Ltd. All rights reserved.

4D nano-tomography of electrochemical energy devices using lab-based X-ray imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heenan, T. M. M.; Finegan, D. P.; Tjaden, B.

Electrochemical energy devices offer a variety of alternate means for low-carbon, multi-scale energy conversion and storage. Reactions in these devices are supported by electrodes with characteristically complex microstructures. To meet the increasing capacity and lifetime demands across a range of applications, it is essential to understand microstructural evolutions at a cell and electrode level which are thought to be critical aspects influencing material and device lifetime and performance. X-ray computed tomography (CT) has become a highly employed method for non-destructive characterisation of such microstructures with high spatial resolution. However, sub-micron resolutions present significant challenges for sample preparation and handling particularlymore » in 4D studies, (three spatial dimensions plus time). Here, microstructural information is collected from the same region of interest within two electrode materials: a solid oxide fuel cell and the positive electrode from a lithium-ion battery. Using a lab-based X-ray instrument, tomograms with sub-micron resolutions were obtained between thermal cycling. The intricate microstructural evolutions captured within these two materials provide model examples of 4D X-ray nano-CT capabilities in tracking challenging degradation mechanisms. This technique is valuable in the advancement of electrochemical research as well as broader applications for materials characterisation.« less

Hyperuniform disordered photonic bandgap materials, from microwave to infrared wavelength regime

NASA Astrophysics Data System (ADS)

Man, Weining

Recently, we have introduced a new class of hyperuniform disordered (HUD) photonic bandgap (PBG) materials enabled by a novel constrained optimization method for engineering the material's Fourier transform to be continuous, isotropic and stealthy. Their structure factor S (k) is equal to zero for small kand exhibits a broad ring of maximum values around a characteristic wave-length range. Experimentally, an isotropic complete PBG (at all angles and for all polarizations) in an alumina-based HUD structure and single-polarized PBGs for plastic-based HUD structure have been demonstrated. Using measured and simulated transmission and phase delay information through these HUD structures, we also unfolded their band structures and reconstructed the effective dispersion relations of propagating electromagnetic modes in them. The intrinsic isotropy in these disordered structures is an inherent advantage associated with the lack of crystalline order, offering unprecedented freedom for functional defect design impossible to achieve in photonic crystals. In the microwave regime, we have shown the creation of freeform waveguides, which can channel photons robustly along arbitrarily curved paths and around sharp bends, and be decorated with defects to produce sharply resonant structures useful for filtering and frequency splitting. Recent simulation and experimental results for waveguides and modulators based on submicron-scale planar hyperuniform disordered PBG structures further highlight their ability to serve as highly compact, flexible and energy-efficient platforms for photonic integrated circuits. NSF DMR-1308084, EPSRC (UK) DTG Grant KD5050, EPSRC (UK) Strategic Equipment Grant EP/M008576/1, NSF SBIR-1345168, NSF MRI-1040444.

Femtosecond few- to single-electron point-projection microscopy for nanoscale dynamic imaging

PubMed Central

Bainbridge, A. R.; Barlow Myers, C. W.; Bryan, W. A.

2016-01-01

Femtosecond electron microscopy produces real-space images of matter in a series of ultrafast snapshots. Pulses of electrons self-disperse under space-charge broadening, so without compression, the ideal operation mode is a single electron per pulse. Here, we demonstrate femtosecond single-electron point projection microscopy (fs-ePPM) in a laser-pump fs-e-probe configuration. The electrons have an energy of only 150 eV and take tens of picoseconds to propagate to the object under study. Nonetheless, we achieve a temporal resolution with a standard deviation of 114 fs (equivalent to a full-width at half-maximum of 269 ± 40 fs) combined with a spatial resolution of 100 nm, applied to a localized region of charge at the apex of a nanoscale metal tip induced by 30 fs 800 nm laser pulses at 50 kHz. These observations demonstrate real-space imaging of reversible processes, such as tracking charge distributions, is feasible whilst maintaining femtosecond resolution. Our findings could find application as a characterization method, which, depending on geometry, could resolve tens of femtoseconds and tens of nanometres. Dynamically imaging electric and magnetic fields and charge distributions on sub-micron length scales opens new avenues of ultrafast dynamics. Furthermore, through the use of active compression, such pulses are an ideal seed for few-femtosecond to attosecond imaging applications which will access sub-optical cycle processes in nanoplasmonics. PMID:27158637

Three-Dimensional Imaging and Numerical Reconstruction of Graphite/Epoxy Composite Microstructure Based on Ultra-High Resolution X-Ray Computed Tomography

NASA Technical Reports Server (NTRS)

Czabaj, M. W.; Riccio, M. L.; Whitacre, W. W.

2014-01-01

A combined experimental and computational study aimed at high-resolution 3D imaging, visualization, and numerical reconstruction of fiber-reinforced polymer microstructures at the fiber length scale is presented. To this end, a sample of graphite/epoxy composite was imaged at sub-micron resolution using a 3D X-ray computed tomography microscope. Next, a novel segmentation algorithm was developed, based on concepts adopted from computer vision and multi-target tracking, to detect and estimate, with high accuracy, the position of individual fibers in a volume of the imaged composite. In the current implementation, the segmentation algorithm was based on Global Nearest Neighbor data-association architecture, a Kalman filter estimator, and several novel algorithms for virtualfiber stitching, smoothing, and overlap removal. The segmentation algorithm was used on a sub-volume of the imaged composite, detecting 508 individual fibers. The segmentation data were qualitatively compared to the tomographic data, demonstrating high accuracy of the numerical reconstruction. Moreover, the data were used to quantify a) the relative distribution of individual-fiber cross sections within the imaged sub-volume, and b) the local fiber misorientation relative to the global fiber axis. Finally, the segmentation data were converted using commercially available finite element (FE) software to generate a detailed FE mesh of the composite volume. The methodology described herein demonstrates the feasibility of realizing an FE-based, virtual-testing framework for graphite/fiber composites at the constituent level.

Comparison of Morphologies of Apollo 17 Dust Particles with Lunar Simulant, JSC-1

NASA Technical Reports Server (NTRS)

Liu, Yang; Taylor, Lawrence A.; Hill, Eddy; Kihm, Kenneth D.; Day, James D. M.

2005-01-01

Lunar dust (< 20 microns) makes up approx.20 wt.% of the lunar soil. Because of the abrasive and adhering nature of lunar soil, a detailed knowledge of the morphology (size, shape and abundance) of lunar dust is important for dust mitigation on the Moon. This represents a critical step towards the establishment of long-term human presence on the Moon (Taylor et al. 2005). Machinery design for in-situ resource utilization (ISRU) on the Moon also requires detailed information on dust morphology and general physical/chemical characteristics. Here, we report a morphological study of Apollo 17 dust sample 70051 and compare it to lunar soil stimulant, JSC-1. W e have obtained SEM images of dust grains from sample 70051 soil (Fig. 1). The dust grains imaged are composed of fragments of minerals, rocks, agglutinates and glass. Most particles consist largely of agglutinitic impact glass with their typical vesicular textures (fine bubbles). All grains show sub-angular to angular shapes, commonly with sharp edges, common for crushed glass fragments. There are mainly four textures: (1) ropey-textured pieces (typical for agglutinates), (2) angular shards, (3) blocky bits, and (4) Swiss-cheese grains. This last type with its high concentration of submicron bubbles, occurs on all scales. Submicron cracks are also present in most grains. Dust-sized grains of lunar soil simulant, JSC-1, were also studied. JSC-1 is a basaltic tuff with relatively high glass content (approx.50%; McKay et al. 1994). It was initially chosen in the early 90s to approximate the geotechnical properties of the average lunar soil (Klosky et al. 1996). JSC-1 dust grains also show angular blocky and shard textures (Fig. 2), similar to those of lunar dust. However, the JSC-1 grains lack the Swiss-cheese textured particles, as well as submicron cracks and bubbles in most grains.

The role of jet and film drops in controlling the mixing state of submicron sea spray aerosol particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaofei; Deane, Grant B.; Moore, Kathryn A.

Covering 71% of the Earth’s surface, oceans represent a significant global source of atmospheric aerosols. The size and composition of sea spray aerosols (SSA) affect their ability to serve as cloud seeds and thus understanding the factors controlling their composition is critical to predicting their impact on clouds and climate. SSA particles have been shown to be an external mixture of particles with different compositions. Film and jet drop production mechanisms ultimately determine the individual particle compositions which are comprised of an array of salt/organic mixtures ranging from pure sea salt to nearly pure organic particles. It is often assumedmore » that the majority of submicron SSA are formed by film drops produced from bursting hydrophobic organic-rich bubble film caps at the sea surface, and in contrast, jet drops are postulated to produce larger supermicron particles from underlying seawater comprised largely of salts and water soluble organic species. However, here we show that jet drops produced by bursting sub-100 m bubbles account for up to 40 % of all submicron particles. They have distinct chemical compositions, organic volume fractions and ice nucleating activities from submicron film drops. Thus a substantial fraction of submicron particles will not necessarily be controlled by the composition of the sea surface microlayer as has been assumed in many studies. This finding has significant ramifications for the size-resolved mixing states of SSA particles which must be taken into consideration when accessing SSA impacts on clouds.« less

The role of jet and film drops in controlling the mixing state of submicron sea spray aerosol particles

DOE PAGES

Wang, Xiaofei; Deane, Grant B.; Moore, Kathryn A.; ...

2017-06-19

Covering 71% of the Earth’s surface, oceans represent a significant global source of atmospheric aerosols. The size and composition of sea spray aerosols (SSA) affect their ability to serve as cloud seeds and thus understanding the factors controlling their composition is critical to predicting their impact on clouds and climate. SSA particles have been shown to be an external mixture of particles with different compositions. Film and jet drop production mechanisms ultimately determine the individual particle compositions which are comprised of an array of salt/organic mixtures ranging from pure sea salt to nearly pure organic particles. It is often assumedmore » that the majority of submicron SSA are formed by film drops produced from bursting hydrophobic organic-rich bubble film caps at the sea surface, and in contrast, jet drops are postulated to produce larger supermicron particles from underlying seawater comprised largely of salts and water soluble organic species. However, here we show that jet drops produced by bursting sub-100 m bubbles account for up to 40 % of all submicron particles. They have distinct chemical compositions, organic volume fractions and ice nucleating activities from submicron film drops. Thus a substantial fraction of submicron particles will not necessarily be controlled by the composition of the sea surface microlayer as has been assumed in many studies. This finding has significant ramifications for the size-resolved mixing states of SSA particles which must be taken into consideration when accessing SSA impacts on clouds.« less

Method of producing submicron size particles and product produced thereby

DOEpatents

Bourne, R.S.; Eichman, C.C.; Welbon, W.W.

1988-05-11

Submicron size particles are produced by using a sputtering process to deposit particles into a liquid. The liquid is processed to recover the particles therefrom, and the particles have sizes in the range of twenty to two hundred Angstroms. Either metallic or non-metallic particles can be produced, and the metallic particles can be used in ''metallic inks.'' 4 figs.

Preparation of 1,3,5-triamo-2,4,6-trinitrobenzene of submicron particle size

DOEpatents

Rigdon, Lester P [Livermore, CA; Moody, Gordon L [Tracy, CA; McGuire, Raymond R [Brentwood, CA

2001-05-01

A method is disclosed for the preparation of very small particle size, relatively pure 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Particles of TATB prepared according to the disclosed method are of submicron size and have a surface area in the range from about 3.8 to 27 square meters per gram.

Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene of submicron particle size

DOEpatents

Rigdon, Lester P.; Moody, Gordon L.; McGuire, Raymond R.

2001-01-01

A method is disclosed for the preparation of very small particle size, relatively pure 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Particles of TATB prepared according to the disclosed method are of submicron size and have a surface area in the range from about 3.8 to 27 square meters per gram.

Preparation, Characterization, and Enhanced Thermal and Mechanical Properties of Epoxy-Titania Composites

PubMed Central

Rubab, Zakya; Siddiqi, Humaira M.; Saeed, Shaukat

2014-01-01

This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl4 as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young's modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress. PMID:24578638

Interference from Proteins and Surfactants on Particle Size Distributions Measured by Nanoparticle Tracking Analysis (NTA).

PubMed

Bai, Kelvin; Barnett, Gregory V; Kar, Sambit R; Das, Tapan K

2017-04-01

Characterization of submicron protein particles continues to be challenging despite active developments in the field. NTA is a submicron particle enumeration technique, which optically tracks the light scattering signal from suspended particles undergoing Brownian motion. The submicron particle size range NTA can monitor in common protein formulations is not well established. We conducted a comprehensive investigation with several protein formulations along with corresponding placebos using NTA to determine submicron particle size distributions and shed light on potential non-particle origin of size distribution in the range of approximately 50-300 nm. NTA and DLS are performed on polystyrene size standards as well as protein and placebo formulations. Protein formulations filtered through a 20 nm filter, with and without polysorbate-80, show NTA particle counts. As such, particle counts above 20 nm are not expected in these solutions. Several other systems including positive and negative controls were studied using NTA and DLS. These apparent particles measured by NTA are not observed in DLS measurements and may not correspond to real particles. The intent of this article is to raise awareness about the need to interpret particle counts and size distribution from NTA with caution.

Aerodynamics and deposition effects of inhaled submicron drug aerosol in airway diseases.

PubMed

Faiyazuddin, Md; Mujahid, Md; Hussain, Talib; Siddiqui, Hefazat H; Bhatnagar, Aseem; Khar, Roop K; Ahmad, Farhan J

2013-01-01

Particle engineering is the prime focus to improve pulmonary drug targeting with the splendor of nanomedicines. In recent years, submicron particles have emerged as prettyful candidate for improved fludisation and deposition. For effective deposition, the particle size must be in the range of 0.5-5 μm. Inhalers design for the purpose of efficient delivery of powders to lungs is again a crucial task for pulmonary scientists. A huge number of DPI devices exist in the market, a significant number are awaiting FDA approval, some are under development and a large number have been patented or applied for patent. Even with superior design, the delivery competence is still deprived, mostly due to fluidisation problems which cause poor aerosol generation and deposition. Because of the cohesive nature and poor flow characteristics, they are difficult to redisperse upon aerosolization with breath. These problems are illustrious in aerosol research, much of which is vastly pertinent to pulmonary therapeutics. A technical review is presented here of advances that have been utilized in production of submicron drug particles, their in vitro/in vivo evaluations, aerosol effects and pulmonary fate of inhaled submicron powders.

Plasma-Assisted Dry Etching of Ferroelectric Capacitor Modules and Application to a 32M Ferroelectric Random Access Memory Devices with Submicron Feature Sizes

NASA Astrophysics Data System (ADS)

Lee, Sang-Woo; Joo, Suk-Ho; Cho, Sung Lae; Son, Yoon-Ho; Lee, Kyu-Mann; Nam, Sang-Don; Park, Kun-Sang; Lee, Yong-Tak; Seo, Jung-Suk; Kim, Young-Dae; An, Hyeong-Geun; Kim, Hyoung-Joon; Jung, Yong-Ju; Heo, Jang-Eun; Lee, Moon-Sook; Park, Soon-Oh; Chung, U-In; Moon, Joo-Tae

2002-11-01

In the manufacturing of a 32M ferroelectric random access memory (FRAM) device on the basis of 0.25 design rule (D/R), one of the most difficult processes is to pattern a submicron capacitor module while retaining good ferroelectric properties. In this paper, we report the ferroelectric property of patterned submicron capacitor modules with a stack height of 380 nm, where the 100 nm-thick Pb(Zr, Ti)O3 (PZT) films were prepared by the sol-gel method. After patterning, overall sidewall slope was approximately 70° and cell-to-cell node separation was made to be 80 nm to prevent possible twin-bit failure in the device. Finally, several heat treatment conditions were investigated to retain the ferroelectric property of the patterned capacitor. It was found that rapid thermal processing (RTP) treatment yields better properties than conventional furnace annealing. This result is directly related to the near-surface chemistry of the PZT films, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The resultant switching polarization value of the submicron capacitor was approximately 30 μC/cm2 measured at 3 V.

Computer aided design of monolithic microwave and millimeter wave integrated circuits and subsystems

NASA Astrophysics Data System (ADS)

Ku, Walter H.

1987-08-01

This interim technical report presents results of research on the computer aided design of monolithic microwave and millimeter wave integrated circuits and subsystems. A specific objective is to extend the state-of-the-art of the Computer Aided Design (CAD) of the monolithic microwave and millimeter wave integrated circuits (MIMIC). In this reporting period, we have derived a new model for the high electron mobility transistor (HEMT) based on a nonlinear charge control formulation which takes into consideration the variation of the 2DEG distance offset from the heterointerface as a function of bias. Pseudomorphic InGaAs/GaAs HEMT devices have been successfully fabricated at UCSD. For a 1 micron gate length, a maximum transconductance of 320 mS/mm was obtained. In cooperation with TRW, devices with 0.15 micron and 0.25 micron gate lengths have been successfully fabricated and tested. New results on the design of ultra-wideband distributed amplifiers using 0.15 micron pseudomorphic InGaAs/GaAs HEMT's have also been obtained. In addition, two-dimensional models of the submicron MESFET's, HEMT's and HBT's are currently being developed for the CRAY X-MP/48 supercomputer. Preliminary results obtained are also presented in this report.

Role of medium heterogeneity and viscosity contrast in miscible flow regimes and mixing zone growth: A computational pore-scale approach

NASA Astrophysics Data System (ADS)

Afshari, Saied; Hejazi, S. Hossein; Kantzas, Apostolos

2018-05-01

Miscible displacement of fluids in porous media is often characterized by the scaling of the mixing zone length with displacement time. Depending on the viscosity contrast of fluids, the scaling law varies between the square root relationship, a sign for dispersive transport regime during stable displacement, and the linear relationship, which represents the viscous fingering regime during an unstable displacement. The presence of heterogeneities in a porous medium significantly affects the scaling behavior of the mixing length as it interacts with the viscosity contrast to control the mixing of fluids in the pore space. In this study, the dynamics of the flow and transport during both unit and adverse viscosity ratio miscible displacements are investigated in heterogeneous packings of circular grains using pore-scale numerical simulations. The pore-scale heterogeneity level is characterized by the variations of the grain diameter and velocity field. The growth of mixing length is employed to identify the nature of the miscible transport regime at different viscosity ratios and heterogeneity levels. It is shown that as the viscosity ratio increases to higher adverse values, the scaling law of mixing length gradually shifts from dispersive to fingering nature up to a certain viscosity ratio and remains almost the same afterwards. In heterogeneous media, the mixing length scaling law is observed to be generally governed by the variations of the velocity field rather than the grain size. Furthermore, the normalization of mixing length temporal plots with respect to the governing parameters of viscosity ratio, heterogeneity, medium length, and medium aspect ratio is performed. The results indicate that mixing length scales exponentially with log-viscosity ratio and grain size standard deviation while the impact of aspect ratio is insignificant. For stable flows, mixing length scales with the square root of medium length, whereas it changes linearly with length during unstable flows. This scaling procedure allows us to describe the temporal variation of mixing length using a generalized curve for various combinations of the flow conditions and porous medium properties.

Submicron-scale mineralogy of lithotypes and the implications for trace element associations: Blue Gem coal, Knox County, Kentucky

DOE PAGES

Hower, James C.; Berti, Debora; Hochella, Michael F.; ...

2018-04-16

Transmission electron microscopy accompanied by energy-dispersive spectroscopy and selected area electron diffraction of density-gradient separates from two lithotypes of the low-ash, low-sulfur Blue Gem coal, eastern Kentucky, revealed an array of previously unrecognized (in this coal, and arguable in most others) sub-micron minerals, some <10 nm in size. The first sample representing the 1.22–1.24 specific gravity fraction of the middle bench contains a mineral identified as a La-, Ce-, Nd-bearing monazite; other minerals with CrFe, CuFeS, FeZn-S, and Pb; and areas, probably comprising agglomerates of several grains, if not several minerals, with concentrations of Mg, Ca, Ti, Fe, Zn, Zr,more » and Mo. The second sample representing the 1.30–1.31 specific gravity fraction of the basal lithotype has aggregates of particles enriched in Mg, Ca, Ti, and Fe. Individual grains not specifically quantified include CrNiMnCuFeS, AgS, and CuS. Detailed investigation of one area (most of the variation within a <4 μm 2 region) demonstrates the presence of greenockite (CdS); minute phases containing NiCoGe and AgCdBi, the latter with a more evident S association than the former; metallic Bi; nisnite (Ni 3Sn); silver cadmium; manganosite (MnO); and siderite. Some minerals, such as the monazite, are most likely of detrital or tuffaceous origin. Many of the other assemblages could be of hydrothermal origin, a hypothesis supported by known regional geochemical and coal rank trends, but not previously demonstrated in mineral assemblages at the 10's of nm scale in this region.« less

Submicron-scale mineralogy of lithotypes and the implications for trace element associations: Blue Gem coal, Knox County, Kentucky

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hower, James C.; Berti, Debora; Hochella, Michael F.

Transmission electron microscopy accompanied by energy-dispersive spectroscopy and selected area electron diffraction of density-gradient separates from two lithotypes of the low-ash, low-sulfur Blue Gem coal, eastern Kentucky, revealed an array of previously unrecognized (in this coal, and arguable in most others) sub-micron minerals, some <10 nm in size. The first sample representing the 1.22–1.24 specific gravity fraction of the middle bench contains a mineral identified as a La-, Ce-, Nd-bearing monazite; other minerals with CrFe, CuFeS, FeZn-S, and Pb; and areas, probably comprising agglomerates of several grains, if not several minerals, with concentrations of Mg, Ca, Ti, Fe, Zn, Zr,more » and Mo. The second sample representing the 1.30–1.31 specific gravity fraction of the basal lithotype has aggregates of particles enriched in Mg, Ca, Ti, and Fe. Individual grains not specifically quantified include CrNiMnCuFeS, AgS, and CuS. Detailed investigation of one area (most of the variation within a <4 μm 2 region) demonstrates the presence of greenockite (CdS); minute phases containing NiCoGe and AgCdBi, the latter with a more evident S association than the former; metallic Bi; nisnite (Ni 3Sn); silver cadmium; manganosite (MnO); and siderite. Some minerals, such as the monazite, are most likely of detrital or tuffaceous origin. Many of the other assemblages could be of hydrothermal origin, a hypothesis supported by known regional geochemical and coal rank trends, but not previously demonstrated in mineral assemblages at the 10's of nm scale in this region.« less

Clinical significance of MUC13 in pancreatic ductal adenocarcinoma.

PubMed

Khan, Sheema; Zafar, Nadeem; Khan, Shabia S; Setua, Saini; Behrman, Stephen W; Stiles, Zachary E; Yallapu, Murali M; Sahay, Peeyush; Ghimire, Hemendra; Ise, Tomoko; Nagata, Satoshi; Wang, Lei; Wan, Jim Y; Pradhan, Prabhakar; Jaggi, Meena; Chauhan, Subhash C

2018-01-15

Poor prognosis of pancreatic cancer (PanCa) is associated with lack of an effective early diagnostic biomarker. This study elucidates significance of MUC13, as a diagnostic/prognostic marker of PanCa. MUC13 was assessed in tissues using our in-house generated anti-MUC13 mouse monoclonal antibody and analyzed for clinical correlation by immunohistochemistry, immunoblotting, RT-PCR, computational and submicron scale mass-density fluctuation analyses, ROC and Kaplan Meir curve analyses. MUC13 expression was detected in 100% pancreatic intraepithelial neoplasia (PanIN) lesions (Mean composite score: MCS = 5.8; AUC >0.8, P < 0.0001), 94.6% of pancreatic ductal adenocarcinoma (PDAC) samples (MCS = 9.7, P < 0.0001) as compared to low expression in tumor adjacent tissues (MCS = 4, P < 0.001) along with faint or no expression in normal pancreatic tissues (MCS = 0.8; AUC >0.8; P < 0.0001). Nuclear MUC13 expression positively correlated with nodal metastasis (P < 0.05), invasion of cancer to peripheral tissues (P < 0.5) and poor patient survival (P < 0.05; prognostic AUC = 0.9). Submicron scale mass density and artificial intelligence based algorithm analyses also elucidated association of MUC13 with greater morphological disorder (P < 0.001) and nuclear MUC13 as strong predictor for cancer aggressiveness and poor patient survival. This study provides significant information regarding MUC13 expression/subcellular localization in PanCa samples and supporting the use anti-MUC13 MAb for the development of PanCa diagnostic/prognostic test. Copyright © 2018 International Hepato-Pancreato-Biliary Association Inc. Published by Elsevier Ltd. All rights reserved.

Analysis of leaf surfaces using scanning ion conductance microscopy.

PubMed

Walker, Shaun C; Allen, Stephanie; Bell, Gordon; Roberts, Clive J

2015-05-01

Leaf surfaces are highly complex functional systems with well defined chemistry and structure dictating the barrier and transport properties of the leaf cuticle. It is a significant imaging challenge to analyse the very thin and often complex wax-like leaf cuticle morphology in their natural state. Scanning electron microscopy (SEM) and to a lesser extent Atomic force microscopy are techniques that have been used to study the leaf surface but their remains information that is difficult to obtain via these approaches. SEM is able to produce highly detailed and high-resolution images needed to study leaf structures at the submicron level. It typically operates in a vacuum or low pressure environment and as a consequence is generally unable to deal with the in situ analysis of dynamic surface events at submicron scales. Atomic force microscopy also possess the high-resolution imaging required and can follow dynamic events in ambient and liquid environments, but can over exaggerate small features and cannot image most leaf surfaces due to their inherent roughness at the micron scale. Scanning ion conductance microscopy (SICM), which operates in a liquid environment, provides a potential complementary analytical approach able to address these issues and which is yet to be explored for studying leaf surfaces. Here we illustrate the potential of SICM on various leaf surfaces and compare the data to SEM and atomic force microscopy images on the same samples. In achieving successful imaging we also show that SICM can be used to study the wetting of hydrophobic surfaces in situ. This has potentially wider implications than the study of leaves alone as surface wetting phenomena are important in a range of fundamental and applied studies. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Length-scale dependent mechanical properties of Al-Cu eutectic alloy: Molecular dynamics based model and its experimental verification

NASA Astrophysics Data System (ADS)

Tiwary, C. S.; Chakraborty, S.; Mahapatra, D. R.; Chattopadhyay, K.

2014-05-01

This paper attempts to gain an understanding of the effect of lamellar length scale on the mechanical properties of two-phase metal-intermetallic eutectic structure. We first develop a molecular dynamics model for the in-situ grown eutectic interface followed by a model of deformation of Al-Al2Cu lamellar eutectic. Leveraging the insights obtained from the simulation on the behaviour of dislocations at different length scales of the eutectic, we present and explain the experimental results on Al-Al2Cu eutectic with various different lamellar spacing. The physics behind the mechanism is further quantified with help of atomic level energy model for different length scale as well as different strain. An atomic level energy partitioning of the lamellae and the interface regions reveals that the energy of the lamellae core are accumulated more due to dislocations irrespective of the length-scale. Whereas the energy of the interface is accumulated more due to dislocations when the length-scale is smaller, but the trend is reversed when the length-scale is large beyond a critical size of about 80 nm.

Sub-micron lines patterning into silica using water developable chitosan bioresist films for eco-friendly positive tone e-beam and UV lithography

NASA Astrophysics Data System (ADS)

Caillau, Mathieu; Chevalier, Céline; Crémillieu, Pierre; Delair, Thierry; Soppera, Olivier; Leuschel, Benjamin; Ray, Cédric; Moulin, Christophe; Jonin, Christian; Benichou, Emmanuel; Brevet, Pierre-François; Yeromonahos, Christelle; Laurenceau, Emmanuelle; Chevolot, Yann; Leclercq, Jean-Louis

2018-03-01

Biopolymers represent natural, renewable and abundant materials. Their use is steadily growing in various areas (food, health, building …) but, in lithography, despite some works, resists, solvents and developers are still oil-based and hazardous chemicals. In this work, we replaced synthetic resist by chitosan, a natural, abundant and hydrophilic polysaccharide. High resolution sub-micron patterns were obtained through chitosan films as water developable, chemically unmodified, positive tone mask resist for an eco-friendly electron beam and deep-UV (193 nm) lithography process. Sub-micron patterns were also successfully obtained using a 248 nm photomasker thanks to the addition of biosourced photoactivator, riboflavin. Patterns were then transferred by plasma etching into silica even for high resolution patterns.

Elastic properties of protein functionalized nanoporous polymer films

DOE PAGES

Charles T. Black; Wang, Haoyu; Akcora, Pinar

2015-12-16

Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Lastly, our results show that proteinmore » functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces.« less

Generation of the Submicron Soft X-Ray Beam Using a Fresnel Zone Plate

NASA Astrophysics Data System (ADS)

Nishikino, M.; Kawazome, H.; Tanaka, M.; Kishimoto, M.; Hasegawa, N.; Ochi, Y.; Kawachi, T.; Sukegawa, K.; Yamatani, H.; Nagashima, K.; Kato, Y.

We have developed a fully coherent x-ray laser at 13.9 nm and the application research has been started. The generation of submicron x-ray beam is important for the application of high intensity x-ray beam, such as the non-linear optics, the material science, and the biology. The submicron x-ray bee am is generated by the soft x-ray laser with using a Fresnel zone plate. The spot diameter is estimated about 680 nm (290 nm at FWHM) by the theoretical calculation. In this experiment, the diameter of the x-ray beam is measured by the knife-edge scan. The diameter and the intensity are estimated 730 nm (310 nm at FWHM) and 3x1011 W/cm2, respectively.

The application of chemical and isotopic tracers to characterize aerosol sources and processing in marine air

NASA Astrophysics Data System (ADS)

Turekian, Vaughan Charles

2000-12-01

Aerosol production, transport, chemical and physical evolution and deposition impact the environment by influencing radiation budgets, altering the composition of the atmosphere, and delivering nutrients to marine and terrestrial ecosystems. The objective of this research was to combine high-resolution chemical measurements with stable isotopic analysis in order to characterize the sources and processing of carbon, nitrogen and sulfur bearing compounds, associated with sized aerosols on Bermuda, during spring. Chemical tracers combined with forward and backward trajectories demonstrated the transport of biomass burning products from North America to Bermuda. The size distributions of NH4+ from 1998 differed from those during spring, 1997, a year without the large-scale burning. These results suggest that transport of biomass burning products altered the pH of the aerosols. Marine and continentally derived carbon was associated with all aerosol size fractions. Supermicron radius sea- salt aerosol was enriched in marine derived carbon by 2 orders of magnitude compared to bulk surface seawater. Enrichments of oxalate relative to methanesulfonic acid (MSA) in supermicron radius aerosol suggested in situ formation of oxalate within the sea-salt solution, or direct injection from the organic rich surface microlayer. Compound specific isotope analysis of oxalic acid, indicated a marine source for all aerosol size fractions, indicating formation from in the gas phase for the submicron radius aerosol. Stable sulfur isotopes indicated that the biogenic non- sea-salt (nss) SO42-/MSA ratio varied with aerosol size indicating that MSA may not be a conservative tracer of biogenic nss SO4 2- in bulk aerosol sampling. The calculated biogenic nss SO 42-/MSA based on stable isotopes and sized aerosol sampling, was 3 times lower than previous estimates for Bermuda. Stable nitrogen isotope values for submicron and supermicron aerosol where significantly different, consistent with their different chemical compositions. Results suggested that HNO3 incorporation into supermicron aerosol was essentially unidirectional whereas submicron aerosol was both a source and a sink for NH3(g). Variable aerosol liquid water content over the relatively longer atmospheric lifetimes of submicron aerosol may lead to multiple NH3 phase changes. This study was the first to combine sized aerosol sampling, high-resolution chemical analysis and multiple stable isotopes to characterize both the sources and the processing of aerosols in marine air. The results of this study, therefore, provide crucial information for source apportionment of environmentally important atmospheric species in continentally impacted, marine air.

Mesoscopic Length Scale Controls the Rheology of Dense Suspensions

NASA Astrophysics Data System (ADS)

Bonnoit, Claire; Lanuza, Jose; Lindner, Anke; Clement, Eric

2010-09-01

From the flow properties of dense granular suspensions on an inclined plane, we identify a mesoscopic length scale strongly increasing with volume fraction. When the flowing layer height is larger than this length scale, a diverging Newtonian viscosity is determined. However, when the flowing layer height drops below this scale, we evidence a nonlocal effective viscosity, decreasing as a power law of the flow height. We establish a scaling relation between this mesoscopic length scale and the suspension viscosity. These results support recent theoretical and numerical results implying collective and clustered granular motion when the jamming point is approached from below.

Mesoscopic length scale controls the rheology of dense suspensions.

PubMed

Bonnoit, Claire; Lanuza, Jose; Lindner, Anke; Clement, Eric

2010-09-03

From the flow properties of dense granular suspensions on an inclined plane, we identify a mesoscopic length scale strongly increasing with volume fraction. When the flowing layer height is larger than this length scale, a diverging Newtonian viscosity is determined. However, when the flowing layer height drops below this scale, we evidence a nonlocal effective viscosity, decreasing as a power law of the flow height. We establish a scaling relation between this mesoscopic length scale and the suspension viscosity. These results support recent theoretical and numerical results implying collective and clustered granular motion when the jamming point is approached from below.

The role of plasma density scale length on the laser pulse propagation and scattering in relativistic regime

NASA Astrophysics Data System (ADS)

Pishdast, Masoud; Ghasemi, Seyed Abolfazl; Yazdanpanah, Jamal Aldin

2017-10-01

The role of plasma density scale length on two short and long laser pulse propagation and scattering in under dense plasma have been investigated in relativistic regime using 1 D PIC simulation. In our simulation, different density scale lengths and also two short and long pulse lengths with temporal pulse duration τL = 60 fs and τL = 300 fs , respectively have been used. It is found that laser pulse length and density scale length have considerable effects on the energetic electron generation. The analysis of total radiation spectrum reveals that, for short laser pulses and with reducing density scale length, more unstable electromagnetic modes grow and strong longitudinal electric field generates which leads to the generation of more energetic plasma particles. Meanwhile, the dominant scattering mechanism is Raman scattering and tends to Thomson scattering for longer laser pulse.

Quasi-Continuum Reduction of Field Theories: A Route to Seamlessly Bridge Quantum and Atomistic Length-Scales with Continuum

DTIC Science & Technology

2016-04-01

AFRL-AFOSR-VA-TR-2016-0145 Quasi-continuum reduction of field theories: A route to seamlessly bridge quantum and atomistic length-scales with...field theories: A route to seamlessly bridge quantum and atomistic length-scales with continuum Principal Investigator: Vikram Gavini Department of...calculations on tens of thousands of atoms, and enable continuing efforts towards a seamless bridging of the quantum and continuum length-scales

Radially polarized tip-enhanced near-field coherent anti-Stokes Raman scattering microscopy for vibrational nano-imaging

NASA Astrophysics Data System (ADS)

Lin, Jian; Zi Jian Er, Kenneth; Zheng, Wei; Huang, Zhiwei

2013-08-01

We report a radially polarized tip-enhanced near-field coherent anti-Stokes Raman scattering (RP-TE-CARS) microscopy technique for high-contrast vibrational imaging of subcellular organelles at nano-scale resolutions. The radially polarized pump and Stokes laser beams are tightly focused onto the sample while a gold-coated metallic probe is placed at the upper surface of the sample to enhance the electric field and CARS signals. The back-scattered CARS signal is measured with the gold-coated nano-tip being stationary at the focal region of laser beams. The RP-TE-CARS signal is ˜6-fold higher than that using linearly polarized laser excitation. We demonstrate the good performance of the RP-TE-CARS technique developed by imaging sub-micron polystyrene beads and mitochondria at nano-scale resolutions.

Gold-carbon composite thin films for electrochemical gas sensor prepared by reactive plasma sputtering

NASA Astrophysics Data System (ADS)

Okamoto, A.; Suzuki, Y.; Yoshitake, M.; Ogawa, S.; Nakano, N.

1997-01-01

We have investigated the properties of gold-carbon composite thin films prepared by a plasma sputtering deposition using argon and methane mixture gas. These composite films have an uneven surface in submicron scale or consist of nano-scale particles of gold polycrystalline. Such morphological properties can be controlled by the sputtering voltage and the partial pressure of methane gas. The working electrode of electrochemical gas sensor has needed a stable gas sensitivity and a good gas selectivity. Our composite film is one of the excellent candidates for a thin film working electrode of electrochemical gas sensor. It is described that the output current of sensor is related to the preparation conditions of the thin films and increase linearly as the concentration of PH 3 gas ranging from 0.1 to 1.0 ppm is increasing.

High speed automated microtomography of nuclear emulsions and recent application

NASA Astrophysics Data System (ADS)

Tioukov, V.; Aleksandrov, A.; Consiglio, L.; De Lellis, G.; Vladymyrov, M.

2015-12-01

The development of high-speed automatic scanning systems was the key-factor for massive and successful emulsions application for big neutrino experiments like OPERA. The emulsion detector simplicity, the unprecedented sub-micron spatial resolution and the unique ability to provide intrinsically 3-dimensional spatial information make it a perfect device for short-living particles study, where the event topology should be precisely reconstructed in a 10-100 um scale vertex region. Recently the exceptional technological progress in image processing and automation together with intensive R&D done by Italian and Japanese microscopy groups permit to increase the scanning speed to unbelievable few years ago m2/day scale and so greatly extend the range of the possible applications for emulsion-based detectors to other fields like: medical imaging, directional dark matter search, nuclear physics, geological and industrial applications.

Chemical composition of submicron and fine particulate matter collected in Krakow, Poland. Consequences for the APARIC project.

PubMed

Samek, Lucyna; Furman, Leszek; Mikrut, Magdalena; Regiel-Futyra, Anna; Macyk, Wojciech; Stochel, Grażyna; van Eldik, Rudi

2017-11-01

Submicron particulate matter containing particles with an aerodynamic diameter ≤1 μm (PM1) are not monitored continuously by Environmental Protection Agencies around the World and are seldom studied. Numerous studies have indicated that people exposed to ultrafine (≤100 nm), submicron and fine particulate matter containing particles with an aerodynamic diameter ≤2.5 μm (PM2.5), can suffer from respiratory track diseases, cardiovascular, immunological or heart diseases and others. Inorganic pollutants containing redox active transition metals and small gaseous molecules, are involved in the generation of reactive oxygen and reactive nitrogen species. Inhalation of this kind of particles can affect immune-toxicity. Environmental pollution may aggravate the course of autoimmune diseases, in particular influence the mechanisms of the autoimmune system. Important factors that influence the toxicity of particulate matter, are particle size distribution, composition and concentration. This report deals with the composition of PM1 and PM2.5 fractions collected in Krakow, Poland. In spring 2015, the mean concentrations of PM1 and PM2.5 were 19 ± 14 and 27 ± 19 μg/m 3 , respectively. The PM2.5 fraction contained approximately 70 ± 17% of submicron particulate matter. In spring 2016, the mean concentrations of PM1 and PM2.5 were 12 ± 5 and 22 ± 12 μg/m 3 , respectively. The PM2.5 fraction contained approximately 60 ± 15% of submicron particulate matter. The concentrations of the elements Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr and Pb in both fractions were determined by X-ray fluorescence spectrometry. Most of the analyzed metals had higher concentrations in the fine fraction than in the submicron one. Concentrations of V and As were below the detection limit in both fractions, whereas concentrations of Mn and Ca were below the detection limits in the PM1 fraction. The results are discussed in terms of the consequences they may have on the APARIC project presently underway in Krakow. Copyright © 2017 Elsevier Ltd. All rights reserved.

CNTs in situ attached to α-Fe2O3 submicron spheres for enhancing lithium storage capacity.

PubMed

Gao, Guo; Zhang, Qiang; Cheng, Xin-Bing; Qiu, Peiyu; Sun, Rongjin; Yin, Ting; Cui, Daxiang

2015-01-14

In this work, we developed a facile hydrothermal method for synthesis of hybrid α-Fe2O3-carbon nanotubes (CNTs) architectures (α-Fe2O3-CNTs-1 and α-Fe2O3-CNTs-2). The CNTs are in situ attached to the α-Fe2O3 submicron spheres and form three-dimensional network robust architectures. The increase in the amount of CNTs in the network α-Fe2O3-CNTs architectures will significantly enhance the cycling and rate performance, as the flexible and robust CNTs could ensure the fast electron transport pathways, enhance the electronic conductivity, and improve the structural stability of the electrode. As for pure α-Fe2O3 submicron spheres, the capacity decreased significantly and retained at 377.4 mAh g(-1) after 11 cycles, and the capacity has a slightly increasing trend at the following cycling. In contrast, the network α-Fe2O3-CNTs-2 electrode shows the most remarkable performance. At the 60th cycle, the capacity of network α-Fe2O3-CNTs-2 (764.5 mAh g(-1)) is 1.78 times than that of α-Fe2O3 submicron spheres (428.3 mAh g(-1)). The long-term cycling performance (1000 cycles) of samples at a high current density of 5 C showed that the capacity of α-Fe2O3 submicron spheres fade to ∼37.3 mAh g(-1) at the 400th cycle and gradually increased to ∼116.7 mAh g(-1) at the 1000th cycle. The capacity of network α-Fe2O3-CNTs-2 maintained at ∼220.2 mAh g(-1) before the 400th cycle, arrived at ∼326.5 mAh g(-1) in the 615th, cycle and retained this value until 1000th cycle. The network α-Fe2O3-CNTs-2 composite could significantly enhance the cycling and rate performance than pure α-Fe2O3 submicron spheres composite.

Organic Functional Group Composition of Submicron Aerosol Particles at Alert, Nunavut, during 2012-2014

NASA Astrophysics Data System (ADS)

Russell, L. M.; Leaitch, W. R.; Liu, J.; Desiree, T. S.; Huang, L.; Sharma, S.; Chivulescu, A.; Veber, D.; Zhang, W.

2016-12-01

Long-term measurements of submicron aerosol particle chemical composition and size distributions are essential for evaluating whether global climate models correctly transport particles from lower latitudes to polar regions, especially in the winter months when satellite retrieval of aerosol properties is limited. In collaboration with ongoing measurements by the Dr. Neil Trivett Global Atmospheric Watch observatory at Alert, Nunavut (82.5°N; elevation 185 m-ASL), we measured the organic functional group composition of submicron aerosol particles sampled from the 10-m inlet from April 2012 to October 2014. The sampling site is approximately 10 km from the Alert station, and vehicle traffic is restricted except when filter sampling is stopped, making the impact of local emissions on submicron particle mass concentrations small. The organic functional group (OFG) composition is measured by Fourier Transform Infrared spectroscopy of samples collected on pre-loaded Teflon filters and stored and shipped frozen to La Jolla, California, for analysis. Samples were collected weekly to complement the twice hourly online measurements of non-refractory organic and inorganic composition by an Aerodyne ACSM. Organic components are shown to contribute a substantial fraction of the measured aerosol submicron mass year round. These measurements illustrate the seasonal contributions to the aerosol size distribution from OFG and illustrate the potential sources of the OFG at this remote site. The three largest OFG sources are transported fossil fuel combustion emissions from lower latitudes, sea spray and other marine particles, and episodic contributions from wildfires, volcanoes, and other high-latitude events. These sources are similar to those identified from earlier OFG measurements at Barrow, Alaska, and during the ICEALOT cruise in the Arctic Ocean.

Prospects for charge sensitive amplifiers in scaled CMOS

NASA Astrophysics Data System (ADS)

O'Connor, Paul; De Geronimo, Gianluigi

2002-03-01

Due to its low cost and flexibility for custom design, monolithic CMOS technology is being increasingly employed in charge preamplifiers across a broad range of applications, including both scientific research and commercial products. The associated detectors have capacitances ranging from a few tens of fF to several hundred pF. Applications call for pulse shaping from tens of ns to tens of μs, and constrain the available power per channel from tens of μW to tens of mW. At the same time a new technology generation, with changed device parameters, appears every 2 years or so. The optimum design of the front-end circuitry is examined taking into account submicron device characteristics, weak inversion operation, the reset system, and power supply scaling. Experimental results from recent prototypes will be presented. We will also discuss the evolution of preamplifier topologies and anticipated performance limits as CMOS technology scales down to the 0.1 μm/1.0 V generation in 2006.

Inherent length-scales of periodic solar wind number density structures

NASA Astrophysics Data System (ADS)

Viall, N. M.; Kepko, L.; Spence, H. E.

2008-07-01

We present an analysis of the radial length-scales of periodic solar wind number density structures. We converted 11 years (1995-2005) of solar wind number density data into radial length series segments and Fourier analyzed them to identify all spectral peaks with radial wavelengths between 72 (116) and 900 (900) Mm for slow (fast) wind intervals. Our window length for the spectral analysis was 9072 Mm, approximately equivalent to 7 (4) h of data for the slow (fast) solar wind. We required that spectral peaks pass both an amplitude test and a harmonic F-test at the 95% confidence level simultaneously. From the occurrence distributions of these spectral peaks for slow and fast wind, we find that periodic number density structures occur more often at certain radial length-scales than at others, and are consistently observed within each speed range over most of the 11-year interval. For the slow wind, those length-scales are L ˜ 73, 120, 136, and 180 Mm. For the fast wind, those length-scales are L ˜ 187, 270 and 400 Mm. The results argue for the existence of inherent radial length-scales in the solar wind number density.

Space environment and lunar surface processes

NASA Technical Reports Server (NTRS)

Comstock, G. M.

1979-01-01

The development of a general rock/soil model capable of simulating in a self consistent manner the mechanical and exposure history of an assemblage of solid and loose material from submicron to planetary size scales, applicable to lunar and other space exposed planetary surfaces is discussed. The model was incorporated into a computer code called MESS.2 (model for the evolution of space exposed surfaces). MESS.2, which represents a considerable increase in sophistication and scope over previous soil and rock surface models, is described. The capabilities of previous models for near surface soil and rock surfaces are compared with the rock/soil model, MESS.2.

Formation and deposition of volcanic sulfate aerosols on Mars

NASA Technical Reports Server (NTRS)

Settle, M.

1979-01-01

The paper considers the formation and deposition of volcanic sulfate aerosols on Mars. The rate limiting step in sulfate aerosol formation on Mars is the gas phase oxidation of SO2 by chemical reactions with O, OH, and HO2; submicron aerosol particles would circuit Mars and then be removed from the atmosphere by gravitational forces, globally dispersed, and deposited over a range of equatorial and mid-latitudes. Volcanic sulfate aerosols on Mars consist of liquid droplets and slurries containing sulfuric acid; aerosol deposition on a global or hemispheric scale could account for the similar concentrations of sulfur within surficial soils at the two Viking lander sites.

A study of 3-dimensionally periodic carbon nanostructures

NASA Astrophysics Data System (ADS)

Yin, Ming; Bleiweiss, Michael; Amirzadeh, Jafar; Datta, Timir; Arammash, Fouzi

2012-02-01

Electronic structures with intricate periodic 3-dimensional arrangements at the submicron scale were investigated. These may be fabricated using artificial porous opal substrates as the templates in which the targeted conducting medium is introduced. In the past these materials were reported to show interesting electronic behaviors. [Michael Bleiweiss, et al ``Localization and Related Phenomena in Multiply Connected Nanostructured,'' BAPS, Z30.011, Nanostructured Materials Session, March 2001, Seattle]. Several materials were studied in particular disordered carbon which has been reported to show quantum transport including fractional hall steps. The results of these measurements, including the observation of localization phenomena, will be discussed. Comparisons will be made with literature data.

Inversion layer on the Ge(001) surface from the four-probe conductance measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wojtaszek, Mateusz; Lis, Jakub, E-mail: j.lis@uj.edu.pl; Zuzak, Rafal

2014-07-28

We report four-probe conductance measurements with sub-micron resolution on atomically clean Ge(001) surfaces. A qualitative difference between n-type and p-type crystals is observed. The scaling behavior of the resistance on n-type samples indicates two-dimensional current flow, while for the p-type crystal a three-dimensional description is appropriate. We interpret this in terms of the formation of an inversion layer at the surface. This result points to the surface states, i.e., dangling bonds, as the driving force behind band bending in germanium. It also explains the intrinsic character of band bending in germanium.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neiman, Aleksei A., E-mail: nasa@ispms.tsc.ru; Lotkov, Aleksandr I.; Gudimova, Ekaterina Y.

The paper reports on a study of regularities of formation gradient nano-, submicron and microstructural conditions in the surface layers of the samples after pulsed electron-beam melting of tantalum coating on the substrate NiTi alloy. Experimentally revealed the presence of submicron columnar structure in the upper layers of the tantalum coating. After irradiation modified NiTi surface takes on a layered structure in which each layer differs in phase composition and structural phase state.

Synthesis of submicron CaZrO{sub 3} in combustion reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaliullin, Sh. M., E-mail: khaliullin@ihim.uran.ru; Zhuravlev, V. D.; Bamburov, V. G.

Submicron CaZrO{sub 3} powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO{sub 3} powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics.

Experimental demonstration of an on-chip polarization splitter in a submicron asymmetric dielectric-coated metal slit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jianjun, E-mail: jjchern@pku.edu.cn; Sun, Chengwei; Gong, Qihuang

A submicron asymmetric dielectric-coated metal slit with a Fabry–Perot (FP) nano-resonator is experimentally fabricated to realize an ultra-small on-chip polarization splitter. In the hybrid plasmonic structure, both of the transverse-electric (TE) and transverse-magnetic (TM) modes can be efficiently generated on the front metal surface. Based on the quite different resonant conditions and the different field confinements of the two orthogonal polarization modes in the FP resonator, the TM and TE modes are generated to propagate in the opposite directions along the metal surface. In this device, there are no coupling waveguide regions, and the excitation and the splitting of themore » TE and TM modes are integrated into the same asymmetric nano-slit. This considerably shrinks the device dimension to only about 850 nm (about one wavelength). In such a submicron asymmetric slit, the measured extinction ratios for the two opposite directions can reach up to (η{sub L}/η{sub R}){sup TM} ≈ 1:14 and (η{sub L}/η{sub R}){sup TE} ≈ 11:1 at λ = 820 nm. This on-chip submicron polarization splitter is of importance in highly integrated photonic circuits.« less

Wet-spinning fabrication of shear-patterned alginate hydrogel microfibers and the guidance of cell alignment

PubMed Central

Yang, You; Sun, Jing; Liu, Xiaolu; Guo, Zhenzhen; He, Yunhu; Wei, Dan; Zhong, Meiling; Guo, Likun; Zhang, Xingdong

2017-01-01

Abstract Native tissue is naturally comprised of highly-ordered cell-matrix assemblies in a multi-hierarchical way, and the nano/submicron alignment of fibrous matrix is found to be significant in supporting cellular functionalization. In this study, a self-designed wet-spinning device appended with a rotary receiving pool was used to continuously produce shear-patterned hydrogel microfibers with aligned submicron topography. The process that the flow-induced shear force reshapes the surface of hydrogel fiber into aligned submicron topography was systematically analysed. Afterwards, the effect of fiber topography on cellular longitudinal spread and elongation was investigated by culturing rat neuron-like PC12 cells and human osteosarcoma MG63 cells with the spun hydrogel microfibers, respectively. The results suggested that the stronger shear flow force would lead to more distinct aligned submicron topography on fiber surface, which could induce cell orientation along with fiber axis and therefore form the cell-matrix dual-alignment. Finally, a multi-hierarchical tissue-like structure constructed by dual-oriented cell-matrix assemblies was fabricated based on this wet-spinning method. This work is believed to be a potentially novel biofabrication scheme for bottom-up constructing of engineered linear tissue, such as nerve bundle, cortical bone, muscle and hepatic cord. PMID:29026644

Detecting Submicron Pattern Defects On Optical Photomasks Using An Enhanced El-3 Electron-Beam Lithography Tool

NASA Astrophysics Data System (ADS)

Simpson, R. A.; Davis, D. E.

1982-09-01

This paper describes techniques to detect submicron pattern defects on optical photomasks with an enhanced direct-write, electron-beam lithographic tool. EL-3 is a third generation, shaped spot, electron-beam lithography tool developed by IBM to fabricate semiconductor devices and masks. This tool is being upgraded to provide 100% inspection of optical photomasks for submicron pattern defects, which are subsequently repaired. Fixed-size overlapped spots are stepped over the mask patterns while a signal derived from the back-scattered electrons is monitored to detect pattern defects. Inspection does not require pattern recognition because the inspection scan patterns are derived from the original design data. The inspection spot is square and larger than the minimum defect to be detected, to improve throughput. A new registration technique provides the beam-to-pattern overlay required to locate submicron defects. The 'guard banding" of inspection shapes prevents mask and system tolerances from producing false alarms that would occur should the spots be mispositioned such that they only partially covered a shape being inspected. A rescanning technique eliminates noise-related false alarms and significantly improves throughput. Data is accumulated during inspection and processed offline, as required for defect repair. EL-3 will detect 0.5 um pattern defects at throughputs compatible with mask manufacturing.

Tailoring sub-micron PLGA particle release profiles via centrifugal fractioning

PubMed Central

Dutta, Dipankar; Salifu, Mariama; Sirianni, Rachael W.; Stabenfeldt, Sarah E.

2016-01-01

Poly(D,L-lactic-co-glycolic) acid (PLGA)-based submicron particles are uniquely posed to overcome limitations of conventional drug delivery systems. However, tailoring cargo/payload release profiles from PLGA micro/nanoparticles typically requires optimization of the multi-parameter formulation, where small changes may cause drastic shifts in the resulting release profiles. In this study, we aimed to establish whether refining the average diameter of submicron particle populations after formulation alters protein release profiles. PLGA particles were first produced via double emulsion-solvent evaporation method to encapsulate bovine serum albumin. Particles were then subjected to centrifugal fractioning protocols varying in both spin time and force to determine encapsulation efficiency and release profile of differently sized populations that originated from a single batch. We found the average particle diameter was related to marked alterations in encapsulation efficiencies (range: 36.4–49.4%), burst release (range: 15.8–49.1%), and time for total cargo release (range: 38–78 days). Our data corroborate previous reports relating PLGA particle size with such release characteristics, however, this is the first study, to our knowledge, to directly compare particle population size while holding all formulation parameters constant. In summary, centrifugal fractioning to selectively control the population distribution of sub-micron PLGA particles represents a feasible tool to tailor release characteristics. PMID:26517011

The study on the entrapment efficiency and in vitro release of puerarin submicron emulsion.

PubMed

Yue, Peng-Fei; Lu, Xiu-Yun; Zhang, Zeng-Zhu; Yuan, Hai-Long; Zhu, Wei-Feng; Zheng, Qin; Yang, Ming

2009-01-01

The entrapment efficiency (EE) and release in vitro are very important physicochemical characteristics of puerarin submicron emulsion (SME). In this paper, the performance of ultrafiltration (UF), ultracentrifugation (UC), and microdialysis (MD) for determining the EE of SME were evaluated, respectively. The release study in vitro of puerarin from SME was studied by using MD and pressure UF technology. The EE of SME was 86.5%, 72.8%, and 55.8% as determined by MD, UF, and UC, respectively. MD was not suitable for EE measurements of puerarin submicron oil droplet, which could only determine the total EE of submicron oil droplet and liposomes micelles, but it could be applied to determine the amount of free drug in SMEs. Although UC was the fastest and simplest to use, its results were the least reliable. UF was still the relatively accurate method for EE determination of puerarin SME. The release of puerarin SME could be evaluated by using MD and pressure UF, but MD seemed to be more suitable for the release study of puerarin emulsion. The drug release from puerarin SME at three drug concentrations was initially rapid, but reached a plateau value within 30 min. Drug release of puerarin from the SME occurred via burst release.

Solute-specific scaling of inorganic nitrogen and phosphorus uptake in streams

NASA Astrophysics Data System (ADS)

Hall, R. O., Jr.; Baker, M. A.; Rosi-Marshall, E. J.; Tank, J. L.; Newbold, J. D.

2013-11-01

Stream ecosystem processes such as nutrient cycling may vary with stream position in the network. Using a scaling approach, we examined the relationship between stream size and nutrient uptake length, which represents the mean distance that a dissolved solute travels prior to removal from the water column. Ammonium (NH4+) uptake length increased proportionally with stream size measured as specific discharge (discharge/stream width) with a scaling exponent = 1.01. In contrast, uptake lengths for nitrate (NO3-) and soluble reactive phosphorus (SRP) increased more rapidly than increases in specific discharge (scaling exponents = 1.19 for NO3- and 1.35 for SRP). Additionally, the ratio of inorganic nitrogen (N) uptake length to SRP uptake length declined with stream size; there was relatively lower demand for SRP compared to N as stream size increased. Finally, we related the scaling of uptake length with specific discharge to that of stream length using Hack's law and downstream hydraulic geometry. Ammonium uptake length increased less than proportionally with distance from the headwaters, suggesting a strong role for larger streams and rivers in regulating nutrient transport.

The Snakelike Chain Character of Unstructured RNA

PubMed Central

Jacobson, David R.; McIntosh, Dustin B.; Saleh, Omar A.

2013-01-01

In the absence of base-pairing and tertiary structure, ribonucleic acid (RNA) assumes a random-walk conformation, modulated by the electrostatic self-repulsion of the charged, flexible backbone. This behavior is often modeled as a Kratky-Porod “wormlike chain” (WLC) with a Barrat-Joanny scale-dependent persistence length. In this study we report measurements of the end-to-end extension of poly(U) RNA under 0.1 to 10 pN applied force and observe two distinct elastic-response regimes: a low-force, power-law regime characteristic of a chain of swollen blobs on long length scales and a high-force, salt-valence-dependent regime consistent with ion-stabilized crumpling on short length scales. This short-scale structure is additionally supported by force- and salt-dependent quantification of the RNA ion atmosphere composition, which shows that ions are liberated under stretching; the number of ions liberated increases with increasing bulk salt concentration. Both this result and the observation of two elastic-response regimes directly contradict the WLC model, which predicts a single elastic regime across all forces and, when accounting for scale-dependent persistence length, the opposite trend in ion release with salt concentration. We conclude that RNA is better described as a “snakelike chain,” characterized by smooth bending on long length scales and ion-stabilized crumpling on short length scales. In monovalent salt, these two regimes are separated by a characteristic length that scales with the Debye screening length, highlighting the determining importance of electrostatics in RNA conformation. PMID:24314087

Ultra-Rapid 2-D and 3-D Laser Microprinting of Proteins

NASA Astrophysics Data System (ADS)

Scott, Mark Andrew

When viewed under the microscope, biological tissues reveal an exquisite microarchitecture. These complex patterns arise during development, as cells interact with a multitude of chemical and mechanical cues in the surrounding extracellular matrix. Tissue engineers have sought for decades to repair or replace damaged tissue, often relying on porous scaffolds as an artificial extracellular matrix to support cell development. However, these grafts are unable to recapitulate the complexity of the in vivo environment, limiting our ability to regenerate functional tissue. Biomedical engineers have developed several methods for printing two- and three-dimensional patterns of proteins for studying and directing cell development. Of these methods, laser microprinting of proteins has shown the most promise for printing sub-cellular resolution gradients of cues, but the photochemistry remains too slow to enable large-scale applications for screening and therapeutics In this work, we demonstrate a novel high-speed photochemistry based on multi-photon photobleaching of fluorescein, and we build the fastest 2-D and 3-D laser microprinter for proteins to date. First, we show that multiphoton photobleaching of a deoxygenated solution of biotin-4-fluorescein onto a PEG monolayer with acrylate end-group can enable print speeds of almost 20 million pixels per second at 600 nanometer resolution. We discovered that the mechanism of fluorescein photobleaching evolves from a 2-photon to 3- and 4-photon regime at higher laser intensities, unlocking faster printing kinetics. Using this 2-D printing system, we develop a novel triangle-ratchet method for directing the polarization of single hippocampal neurons. This ability to determine which neurite becomes an axon, and which neuritis become dendrites is an essential step for developing defined in vitro neural networks. Next, we modify our multiphoton photobleaching system to print in three dimensions. For the first time, we demonstrate 3-D printing of full length proteins in collagen, fibrin and gelatin methacrylate scaffolds, as well as printing in agarose and agarose methacrylate scaffolds. We also present a novel method for 3-D printing collagen scaffolds at unprecedented speeds, up to 14layers per second, generating complex shapes in seconds with sub-micron resolution. Finally, we demonstrate that 3-D printing of scaffold architecture and protein cues inside the scaffold can be combined, for the first time enabling structures with complex sub-micron architectures and chemical cues for directing development. We believe that the ultra-rapid printing technology presented in this thesis will be a key enabler in the development of complex, artificially engineered tissues and organs. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

Experimental evidence for two thermodynamic length scales in neutralized polyacrylate gels

NASA Astrophysics Data System (ADS)

Horkay, Ferenc; Hecht, Anne-Marie; Grillo, Isabelle; Basser, Peter J.; Geissler, Erik

2002-11-01

The small angle neutron scattering (SANS) behavior of fully neutralized sodium polyacrylate gels is investigated in the presence of calcium ions. Analysis of the SANS response reveals the existence of three characteristic length scales, two of which are of thermodynamic origin, while the third length is associated with the frozen-in structural inhomogeneities. This latter contribution exhibits power law behavior with a slope of about -3.6, reflecting the presence of interfaces. The osmotically active component of the scattering signal is defined by two characteristic length scales, a correlation length ξ and a persistence length L.

Physics of sub-micron cosmic dust particles

NASA Technical Reports Server (NTRS)

Roy, N. L.

1974-01-01

Laboratory tests with simulated micrometeoroids to measure the heat transfer coefficient are discussed. Equations for ablation path length for electrically accelerated micrometeoroids entering a gas target are developed which yield guidelines for the laboratory measurement of the heat transfer coefficient. Test results are presented for lanthanum hexaboride (LaB sub 6) microparticles in air, argon, and oxygen targets. The tests indicate the heat transfer coefficient has a value of approximately 0.9 at 30 km/sec, and that it increases to approximately unity at 50 km/sec and above. Test results extend to over 100 km/sec. Results are also given for two types of small particle detectors. A solid state capacitor type detector was tested from 0.61 km/sec to 50 km/sec. An impact ionization type detector was tested from 1.0 to 150 km/sec using LaB sub 6 microparticles.

The Columbia University Sub-micron Charged Particle Beam

PubMed Central

Randers-Pehrson, Gerhard; Johnson, Gary W.; Marino, Stephen A.; Xu, Yanping; Dymnikov, Alexander D.; Brenner, David J.

2009-01-01

A lens system consisting of two electrostatic quadrupole triplets has been designed and constructed at the Radiological Research Accelerator Facility (RARAF) of Columbia University. The lens system has been used to focus 6-MeV 4He ions to a beam spot in air with a diameter of 0.8 µm. The quadrupole electrodes can withstand voltages high enough to focus 4He ions up to 10 MeV and protons up to 5 MeV. The quadrupole triplet design is novel in that alignment is made through precise construction and the relative strengths of the quadrupoles are accomplished by the lengths of the elements, so that the magnitudes of the voltages required for focusing are nearly identical. The insulating sections between electrodes have had ion implantation to improve the voltage stability of the lens. The lens design employs Russian symmetry for the quadrupole elements. PMID:20161365

Fabrication of an Absorber-Coupled MKID Detector and Readout for Sub-Millimeter and Far-Infrared Astronomy

NASA Technical Reports Server (NTRS)

Brown, Ari-David; Hsieh, Wen-Ting; Moseley, S. Harvey; Stevenson, Thomas R.; U-yen, Kongpop; Wollack, Edward J.

2010-01-01

We have fabricated absorber-coupled microwave kinetic inductance detector (MKID) arrays for sub-millimeter and far-infrared astronomy. Each detector array is comprised of lambda/2 stepped impedance resonators, a 1.5 micrometer thick silicon membrane, and 380 micrometer thick silicon walls. The resonators consist of parallel plate aluminum transmission lines coupled to low impedance Nb microstrip traces of variable length, which set the resonant frequency of each resonator. This allows for multiplexed microwave readout and, consequently, good spatial discrimination between pixels in the array. The Al transmission lines simultaneously act to absorb optical power and are designed to have a surface impedance and filling fraction so as to match the impedance of free space. Our novel fabrication techniques demonstrate high fabrication yield of MKID arrays on large single crystal membranes and sub-micron front-to-back alignment of the microstrip circuit.

Fabrication of an Absorber-Coupled MKID Detector and Readout for Sub-Millimeter and Far-Infrared Astronomy

NASA Technical Reports Server (NTRS)

Brown, Ari-David; Hsieh, Wen-Ting; Moseley, S. Harvey; Stevenson, Thomas R.; U-yen, Kongpop; Wollack, Edward J.

2010-01-01

We have fabricated absorber-coupled microwave kinetic inductance detector (MKID) arrays for sub-millimeter and farinfrared astronomy. Each detector array is comprised of lambda/2 stepped impedance resonators, a 1.5µm thick silicon membrane, and 380µm thick silicon walls. The resonators consist of parallel plate aluminum transmission lines coupled to low impedance Nb microstrip traces of variable length, which set the resonant frequency of each resonator. This allows for multiplexed microwave readout and, consequently, good spatial discrimination between pixels in the array. The Al transmission lines simultaneously act to absorb optical power and are designed to have a surface impedance and filling fraction so as to match the impedance of free space. Our novel fabrication techniques demonstrate high fabrication yield of MKID arrays on large single crystal membranes and sub-micron front-to-back alignment of the microstrip circuit.

Heterogeneous microring and Mach-Zehnder modulators based on lithium niobate and chalcogenide glasses on silicon

DOE PAGES

Rao, Ashutosh; Patil, Aniket; Chiles, Jeff; ...

2015-08-20

In this study, thin films of lithium niobate are wafer bonded onto silicon substrates and rib-loaded with a chalcogenide glass, Ge 23Sb 7S 70, to demonstrate strongly confined single-mode submicron waveguides, microring modulators, and Mach-Zehnder modulators in the telecom C band. The 200 μm radii microring modulators present 1.2 dB/cm waveguide propagation loss, 1.2 × 10 5 quality factor, 0.4 GHz/V tuning rate, and 13 dB extinction ratio. The 6 mm long Mach-Zehnder modulators have a half-wave voltage-length product of 3.8 V.cm and an extinction ratio of 15 dB. The demonstrated work is a key step towards enabling wafer scalemore » dense on-chip integration of high performance lithium niobate electro-optical devices on silicon for short reach optical interconnects and higher order advanced modulation schemes.« less

Supramolecular structure of 5-aminosalycilic acid/halloysite composites.

PubMed

Viseras, Maria-Teresa; Aguzzi, Carola; Cerezo, Pilar; Cultrone, Giuseppe; Viseras, Cesar

2009-05-01

This paper assesses the supramolecular structure of nanocomposites prepared by including the anti-inflammatory drug 5-aminosalycilic acid in halloysite nanotubes. Halloysite tubes have sub-micron individual lengths with outer diameters ∼0.1 µm, as observed by FESEM. The mercury intrusion plots showed bimodal profiles with pore dimensions ∼10 and 0.06 µm. X-ray diffraction and thermogravimetric results revealed changes in the hydration form of the clay after the interaction. The groups associated to the interaction were studied by FTIR. The location of the drug in the composites was determined after uranium staining of its amino groups by X-EDS microanalysis coupled with HREM. The drug was located both inside and on the surface of the halloysite nanotubes. These results confirm the occurrence of two concomitant interaction mechanisms: rapid adsorption of 5-ASA at the external halloysite surface followed by slow adsorption of the drug inside the tubes.

Sub-micrometer epsilon-near-zero electroabsorption modulators enabled by high-mobility cadmium oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campione, Salvatore; Wood, Michael; Serkland, Darwin K.

Here, epsilon-near-zero materials provide a new path for tailoring light-matter interactions at the nanoscale. In this paper, we analyze a compact electroabsorption modulator based on epsilon-near-zero confinement in transparent conducting oxide films. The non-resonant modulator operates through field-effect carrier density tuning. We compare the performance of modulators composed of two different conducting oxides, namely indium oxide (In2O3) and cadmium oxide (CdO), and show that better modulation performance is achieved when using high-mobility (i.e. low-loss) epsilon-near-zero materials such as CdO. In particular, we show that non-resonant electroabsorption modulators with sub-micron lengths and greater than 5 dB extinction ratios may be achievedmore » through the proper selection of high-mobility transparent conducting oxides, opening a path for device miniaturization and increased modulation depth.« less

The magnetoresistance of sub-micron Fe wires

NASA Astrophysics Data System (ADS)

Blundell, S. J.; Shearwood, C.; Gester, M.; Baird, M. J.; Bland, J. A. C.; Ahmed, H.

1994-07-01

A novel combination of electron- and ion-beam lithography has been used to prepare Fe gratings with wire widths of 0.5 μm and wire separations in the range 0.5-4 μm from an Fe/GaAs (001) film of thickness 25 nm. With an in-plane magnetic field applied perpendicular to the length of the wires, a harder magnetisation loop is observed using the magneto-optic Kerr effect (MOKE), compared with that observed in the unprocessed film. We observe a strong effect in the magnetoresistance (MR) when the magnetic field is applied transverse to the wires. It is believed that this effect originates from the highly non-uniform demagnetising field in each wire of the grating. These results demonstrate that the combination of MOKE and MR measurements can provide important information about the magnetisation reversal processes in magnetic gratings and can be used to understand the effect of shape anisotropy on magnetic properties.

Heterogeneous microring and Mach-Zehnder modulators based on lithium niobate and chalcogenide glasses on silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Ashutosh; Patil, Aniket; Chiles, Jeff

In this study, thin films of lithium niobate are wafer bonded onto silicon substrates and rib-loaded with a chalcogenide glass, Ge 23Sb 7S 70, to demonstrate strongly confined single-mode submicron waveguides, microring modulators, and Mach-Zehnder modulators in the telecom C band. The 200 μm radii microring modulators present 1.2 dB/cm waveguide propagation loss, 1.2 × 10 5 quality factor, 0.4 GHz/V tuning rate, and 13 dB extinction ratio. The 6 mm long Mach-Zehnder modulators have a half-wave voltage-length product of 3.8 V.cm and an extinction ratio of 15 dB. The demonstrated work is a key step towards enabling wafer scalemore » dense on-chip integration of high performance lithium niobate electro-optical devices on silicon for short reach optical interconnects and higher order advanced modulation schemes.« less

Sub-micrometer epsilon-near-zero electroabsorption modulators enabled by high-mobility cadmium oxide

DOE PAGES

Campione, Salvatore; Wood, Michael; Serkland, Darwin K.; ...

2017-07-06

Here, epsilon-near-zero materials provide a new path for tailoring light-matter interactions at the nanoscale. In this paper, we analyze a compact electroabsorption modulator based on epsilon-near-zero confinement in transparent conducting oxide films. The non-resonant modulator operates through field-effect carrier density tuning. We compare the performance of modulators composed of two different conducting oxides, namely indium oxide (In2O3) and cadmium oxide (CdO), and show that better modulation performance is achieved when using high-mobility (i.e. low-loss) epsilon-near-zero materials such as CdO. In particular, we show that non-resonant electroabsorption modulators with sub-micron lengths and greater than 5 dB extinction ratios may be achievedmore » through the proper selection of high-mobility transparent conducting oxides, opening a path for device miniaturization and increased modulation depth.« less

Transition from two-dimensional photonic crystals to dielectric metasurfaces in the optical diffraction with a fine structure

PubMed Central

Rybin, Mikhail V.; Samusev, Kirill B.; Lukashenko, Stanislav Yu.; Kivshar, Yuri S.; Limonov, Mikhail F.

2016-01-01

We study experimentally a fine structure of the optical Laue diffraction from two-dimensional periodic photonic lattices. The periodic photonic lattices with the C4v square symmetry, orthogonal C2v symmetry, and hexagonal C6v symmetry are composed of submicron dielectric elements fabricated by the direct laser writing technique. We observe surprisingly strong optical diffraction from a finite number of elements that provides an excellent tool to determine not only the symmetry but also exact number of particles in the finite-length structure and the sample shape. Using different samples with orthogonal C2v symmetry and varying the lattice spacing, we observe experimentally a transition between the regime of multi-order diffraction, being typical for photonic crystals to the regime where only the zero-order diffraction can be observed, being is a clear fingerprint of dielectric metasurfaces characterized by effective parameters. PMID:27491952

Scaling Effects on Materials Tribology: From Macro to Micro Scale.

PubMed

Stoyanov, Pantcho; Chromik, Richard R

2017-05-18

The tribological study of materials inherently involves the interaction of surface asperities at the micro to nanoscopic length scales. This is the case for large scale engineering applications with sliding contacts, where the real area of contact is made up of small contacting asperities that make up only a fraction of the apparent area of contact. This is why researchers have sought to create idealized experiments of single asperity contacts in the field of nanotribology. At the same time, small scale engineering structures known as micro- and nano-electromechanical systems (MEMS and NEMS) have been developed, where the apparent area of contact approaches the length scale of the asperities, meaning the real area of contact for these devices may be only a few asperities. This is essentially the field of microtribology, where the contact size and/or forces involved have pushed the nature of the interaction between two surfaces towards the regime where the scale of the interaction approaches that of the natural length scale of the features on the surface. This paper provides a review of microtribology with the purpose to understand how tribological processes are different at the smaller length scales compared to macrotribology. Studies of the interfacial phenomena at the macroscopic length scales (e.g., using in situ tribometry) will be discussed and correlated with new findings and methodologies at the micro-length scale.

Scaling Effects on Materials Tribology: From Macro to Micro Scale

PubMed Central

Stoyanov, Pantcho; Chromik, Richard R.

2017-01-01

The tribological study of materials inherently involves the interaction of surface asperities at the micro to nanoscopic length scales. This is the case for large scale engineering applications with sliding contacts, where the real area of contact is made up of small contacting asperities that make up only a fraction of the apparent area of contact. This is why researchers have sought to create idealized experiments of single asperity contacts in the field of nanotribology. At the same time, small scale engineering structures known as micro- and nano-electromechanical systems (MEMS and NEMS) have been developed, where the apparent area of contact approaches the length scale of the asperities, meaning the real area of contact for these devices may be only a few asperities. This is essentially the field of microtribology, where the contact size and/or forces involved have pushed the nature of the interaction between two surfaces towards the regime where the scale of the interaction approaches that of the natural length scale of the features on the surface. This paper provides a review of microtribology with the purpose to understand how tribological processes are different at the smaller length scales compared to macrotribology. Studies of the interfacial phenomena at the macroscopic length scales (e.g., using in situ tribometry) will be discussed and correlated with new findings and methodologies at the micro-length scale. PMID:28772909

Length scale effects of friction in particle compaction using atomistic simulations and a friction scaling model

NASA Astrophysics Data System (ADS)

Stone, T. W.; Horstemeyer, M. F.

2012-09-01

The objective of this study is to illustrate and quantify the length scale effects related to interparticle friction under compaction. Previous studies have shown as the length scale of a specimen decreases, the strength of a single crystal metal or ceramic increases. The question underlying this research effort continues the thought—If there is a length scale parameter related to the strength of a material, is there a length scale parameter related to friction? To explore the length scale effects of friction, molecular dynamics (MD) simulations using an embedded atom method potential were performed to analyze the compression of two spherical FCC nickel nanoparticles at different contact angles. In the MD model study, we applied a macroscopic plastic contact formulation to determine the normal plastic contact force at the particle interfaces and used the average shear stress from the MD simulations to determine the tangential contact forces. Combining this information with the Coulomb friction law, we quantified the MD interparticle coefficient of friction and showed good agreement with experimental studies and a Discrete Element Method prediction as a function of contact angle. Lastly, we compared our MD simulation friction values to the tribological predictions of Bhushan and Nosonovsky (BN), who developed a friction scaling model based on strain gradient plasticity and dislocation-assisted sliding that included a length scale parameter. The comparison revealed that the BN elastic friction scaling model did a much better job than the BN plastic scaling model of predicting the coefficient of friction values obtained from the MD simulations.

ThermoYield actuators: nano-adjustable set-and-forget optics mounts

NASA Astrophysics Data System (ADS)

DeTienne, Michael D.; Bruccoleri, Alexander R.; Chalifoux, Brandon; Heilmann, Ralf K.; Tedesco, Ross E.; Schattenburg, Mark L.

2017-08-01

The X-ray optics community has been developing technology for high angular resolution, large collecting area X-ray telescopes such as the Lynx X-ray telescope concept. To meet the high collecting area requirements of such telescope concepts, research is being conducted on thin, segmented optics. The mounts that fixture and align segmented optics must be the correct length to sub-micron accuracy to satisfy the angular resolution goals of such a concept. Set-andforget adjustable length optical mounting posts have been developed to meet this need. The actuator consists of a cylinder made of metal. Halfway up the height of the metal cylinder, a reduced diameter cylindrical neck is cut. To change the length of this actuator, an axial compressive or tensile force is applied to the actuator. A high-current electrical pulse is sent through the actuator, and this electrical current resistively heats the neck of the actuator. This heating temporarily reduces the yield strength of the neck, so that the applied force plastically deforms the neck. Once the current stops and the neck cools, the neck will regain yield strength, and the plastic deformation will stop. All of the plastic deformation that occurred during heating is now permanent. Both compression and expansion of these actuators has been demonstrated in steps ranging from 6 nanometers to several microns. This paper will explain the concept of ThermoYield actuation, explore X-ray telescope applications, describe an experimental setup, show and discuss data, and propose future ideas.

How much a galaxy knows about its large-scale environment?: An information theoretic perspective

NASA Astrophysics Data System (ADS)

Pandey, Biswajit; Sarkar, Suman

2017-05-01

The small-scale environment characterized by the local density is known to play a crucial role in deciding the galaxy properties but the role of large-scale environment on galaxy formation and evolution still remain a less clear issue. We propose an information theoretic framework to investigate the influence of large-scale environment on galaxy properties and apply it to the data from the Galaxy Zoo project that provides the visual morphological classifications of ˜1 million galaxies from the Sloan Digital Sky Survey. We find a non-zero mutual information between morphology and environment that decreases with increasing length-scales but persists throughout the entire length-scales probed. We estimate the conditional mutual information and the interaction information between morphology and environment by conditioning the environment on different length-scales and find a synergic interaction between them that operates up to at least a length-scales of ˜30 h-1 Mpc. Our analysis indicates that these interactions largely arise due to the mutual information shared between the environments on different length-scales.

Size-dependent elastic/inelastic behavior of enamel over millimeter and nanometer length scales.

PubMed

Ang, Siang Fung; Bortel, Emely L; Swain, Michael V; Klocke, Arndt; Schneider, Gerold A

2010-03-01

The microstructure of enamel like most biological tissues has a hierarchical structure which determines their mechanical behavior. However, current studies of the mechanical behavior of enamel lack a systematic investigation of these hierarchical length scales. In this study, we performed macroscopic uni-axial compression tests and the spherical indentation with different indenter radii to probe enamel's elastic/inelastic transition over four hierarchical length scales, namely: 'bulk enamel' (mm), 'multiple-rod' (10's microm), 'intra-rod' (100's nm with multiple crystallites) and finally 'single-crystallite' (10's nm with an area of approximately one hydroxyapatite crystallite). The enamel's elastic/inelastic transitions were observed at 0.4-17 GPa depending on the length scale and were compared with the values of synthetic hydroxyapatite crystallites. The elastic limit of a material is important as it provides insights into the deformability of the material before fracture. At the smallest investigated length scale (contact radius approximately 20 nm), elastic limit is followed by plastic deformation. At the largest investigated length scale (contact size approximately 2 mm), only elastic then micro-crack induced response was observed. A map of elastic/inelastic regions of enamel from millimeter to nanometer length scale is presented. Possible underlying mechanisms are also discussed. (c) 2009 Elsevier Ltd. All rights reserved.

Implementation of a flow-dependent background error correlation length scale formulation in the NEMOVAR OSTIA system

NASA Astrophysics Data System (ADS)

Fiedler, Emma; Mao, Chongyuan; Good, Simon; Waters, Jennifer; Martin, Matthew

2017-04-01

OSTIA is the Met Office's Operational Sea Surface Temperature (SST) and Ice Analysis system, which produces L4 (globally complete, gridded) analyses on a daily basis. Work is currently being undertaken to replace the original OI (Optimal Interpolation) data assimilation scheme with NEMOVAR, a 3D-Var data assimilation method developed for use with the NEMO ocean model. A dual background error correlation length scale formulation is used for SST in OSTIA, as implemented in NEMOVAR. Short and long length scales are combined according to the ratio of the decomposition of the background error variances into short and long spatial correlations. The pre-defined background error variances vary spatially and seasonally, but not on shorter time-scales. If the derived length scales applied to the daily analysis are too long, SST features may be smoothed out. Therefore a flow-dependent component to determining the effective length scale has also been developed. The total horizontal gradient of the background SST field is used to identify regions where the length scale should be shortened. These methods together have led to an improvement in the resolution of SST features compared to the previous OI analysis system, without the introduction of spurious noise. This presentation will show validation results for feature resolution in OSTIA using the OI scheme, the dual length scale NEMOVAR scheme, and the flow-dependent implementation.

Optical coherence tomography as an accurate inspection and quality evaluation technique in paper industry

NASA Astrophysics Data System (ADS)

Prykäri, Tuukka; Czajkowski, Jakub; Alarousu, Erkki; Myllylä, Risto

2010-05-01

Optical coherence tomography (OCT), a technique for the noninvasive imaging of turbid media, based on low-coherence interferometry, was originally developed for the imaging of biological tissues. Since the development of the technique, most of its applications have been related to the area of biomedicine. However, from early stages, the vertical resolution of the technique has already been improved to a submicron scale. This enables new possibilities and applications. This article presents the possible applications of OCT in paper industry, where submicron or at least a resolution close to one micron is required. This requirement comes from the layered structure of paper products, where layer thickness may vary from single microns to tens of micrometers. This is especially similar to the case with high-quality paper products, where several different coating layers are used to obtain a smooth surface structure and a high gloss. In this study, we demonstrate that optical coherence tomography can be used to measure and evaluate the quality of the coating layer of a premium glossy photopaper. In addition, we show that for some paper products, it is possible to measure across the entire thickness range of a paper sheet. Furthermore, we suggest that in addition to topography and tomography images of objects, it is possible to obtain information similar to gloss by tracking the magnitude of individual interference signals in optical coherence tomography.

Submicron Aerosol Characterization of Water by a Differential Mobility Particle Sizer.

DTIC Science & Technology

1987-02-01

7 :-711 no0 StIHICRON AEROSOL CHARACTERIZATION OF WATER DY A vi1 DIFFERENTIAL NOBILITY PA.. (U) DEFENCE RESEARCH ESTABLISHMENT SUFFIELD RALSTON... WATER BY A DIFFERENTIAL MOBILITY PARTICLE SIZER (U) by B. Kournikakis, A. Gunning, J. Fildes and J. Ho Project No. 251SD EL .TE APR 099?07uD February...RESEARCH ESTABLISHMENT SUFFIELD RALSTON ALBERTA SUFFIELD MEMORANDUM NO. 1193 SUBMICRON AEROSOL CHARACTERIZATION OF WATER BY Accession For A DIFFERENTIAL

Artificial submicron or nanometer speckle fabricating technique and electron microscope speckle photography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Zhanwei; Xie Huimin; Fang Daining

2007-03-15

In this article, a novel artificial submicro- or nanometer speckle fabricating technique is proposed by taking advantage of submicro or nanometer particles. In the technique, submicron or nanometer particles were adhered to an object surface by using ultrasonic dispersing technique. The particles on the object surface can be regarded as submicro or nanometer speckle by using a scanning electronic microscope at a special magnification. In addition, an electron microscope speckle photography (EMSP) method is developed to measure in-plane submicron or nanometer deformation of the object coated with the artificial submicro or nanometer speckles. The principle of artificial submicro or nanometermore » speckle fabricating technique and the EMSP method are discussed in detail in this article. Some typical applications of this method are offered. The experimental results verified that the artificial submicro or nanometer speckle fabricating technique and EMSP method is feasible.« less

Vortex states in a submicron Bi2212 crystal probed by intrinsic Josephson junctions

NASA Astrophysics Data System (ADS)

Ooi, S.; Tachiki, M.; Mochiku, T.; Wang, H. B.; Komori, K.; Hirata, K.; Arisawa, S.

2018-03-01

To study the pancake-vortex states confined in a submicron Bi2Sr2CaCu2O8+y (Bi2212) crystal, we have measured the c-axis resistance and I-V characteristics of a stack of intrinsic Josephson junctions with a lateral dimension less than 1 µm. Although the stack was accidentally shunted by a parallel resistance of 7.5 kΩ, the I-V characteristics show homogeneous multiple branches after the subtraction of the component. The penetrations of single vortices into the submicron stack were clearly observed in the resistance measurements. A vortex phase diagram was constructed by mapping the c-axis resistance on an H-T plane. Temperature dependence of the first-vortex penetration field is consistent with the theoretical estimation on the formation of a pancake-vortex stack in the center of a superconducting strip.

Contact ice nucleation by submicron atmospheric aerosols

NASA Technical Reports Server (NTRS)

Deshler, T.

1982-01-01

An apparatus designed to measure the concentrations of submicron contact ice nuclei is described. Here, natural forces transfer nuclei to supercooled sample drops suspended in an aerosol stream. Experimental measurements of the scavenging rate of the sample drops for several humidities and aerosol sizes are found to be in agreement with theory to within a factor of two. This fact, together with the statistical tests showing a difference between the data and control samples, is seen as indicating that a reliable measurement of the concentrations of submicron contact ice nuclei has been effected. A figure is included showing the ice nucleus concentrations as a function of temperature and assumed aerosol radius. For a 0.01 micron radius, the average is 1/liter at -15 C and 3/liter at -18 C. It is noted that the measurements are in fair agreement with ice crystal concentrations in stable winter clouds measured over Elk Mountain, WY (Vali et al., 1982).

Submicron x-ray diffraction and its applications to problems in materials and environmental science

NASA Astrophysics Data System (ADS)

Tamura, N.; Celestre, R. S.; MacDowell, A. A.; Padmore, H. A.; Spolenak, R.; Valek, B. C.; Meier Chang, N.; Manceau, A.; Patel, J. R.

2002-03-01

The availability of high brilliance third generation synchrotron sources together with progress in achromatic focusing optics allows us to add submicron spatial resolution to the conventional century-old x-ray diffraction technique. The new capabilities include the possibility to map in situ, grain orientations, crystalline phase distribution, and full strain/stress tensors at a very local level, by combining white and monochromatic x-ray microbeam diffraction. This is particularly relevant for high technology industry where the understanding of material properties at a microstructural level becomes increasingly important. After describing the latest advances in the submicron x-ray diffraction techniques at the Advanced Light Source, we will give some examples of its application in material science for the measurement of strain/stress in metallic thin films and interconnects. Its use in the field of environmental science will also be discussed.

Fabrication and characterization of high current-density, submicron, NbN/MgO/NbN tunnel junctions

NASA Technical Reports Server (NTRS)

Stern, J. A.; Leduc, Henry G.; Judas, A. J.

1992-01-01

At near-millimeter wavelengths, heterodyne receivers based on SIS tunnel junctions are the most sensitive available. However, in order to scale these results to submillimeter wavelengths, certain device properties should be scaled. The tunnel-junction's current density should be increased to reduce the RC product. The device's area should be reduced to efficiently couple power from the antenna to the mixer. Finally, the superconductor used should have a large energy gap to minimize RF losses. Most SIS mixers use Nb or Pb-alloy tunnel junctions; the gap frequency for these materials is approximately 725 GHz. Above the gap frequency, these materials exhibit losses similar to those in a normal metal. The gap frequency in NbN films is as-large-as 1440 GHz. Therefore, we have developed a process to fabricate small area (down to 0.13 sq microns), high current density, NbN/MgO/NbN tunnel junctions.

Electron backscatter diffraction as a domain analysis technique in BiFeO(3)-PbTiO(3) single crystals.

PubMed

Burnett, T L; Comyn, T P; Merson, E; Bell, A J; Mingard, K; Hegarty, T; Cain, M

2008-05-01

xBiFeO(3)-(1-x)PbTiO(3) single crystals were grown via a flux method for a range of compositions. Presented here is a study of the domain configuration in the 0.5BiFeO(3)-0.5PbTiO(3) composition using electron backscatter diffraction to demonstrate the ability of the technique to map ferroelastic domain structures at the micron and submicron scale. The micron-scale domains exhibit an angle of approximately 85 degrees between each variant, indicative of a ferroelastic domain wall in a tetragonal system with a spontaneous strain, c/a - 1 of 0.10, in excellent agreement with the lattice parameters derived from x-ray diffraction. Contrast seen in forescatter images is attributed to variations in the direction of the electrical polarization vector, providing images of ferroelectric domain patterns.

TID Simulation of Advanced CMOS Devices for Space Applications

NASA Astrophysics Data System (ADS)

Sajid, Muhammad

2016-07-01

This paper focuses on Total Ionizing Dose (TID) effects caused by accumulation of charges at silicon dioxide, substrate/silicon dioxide interface, Shallow Trench Isolation (STI) for scaled CMOS bulk devices as well as at Buried Oxide (BOX) layer in devices based on Silicon-On-Insulator (SOI) technology to be operated in space radiation environment. The radiation induced leakage current and corresponding density/concentration electrons in leakage current path was presented/depicted for 180nm, 130nm and 65nm NMOS, PMOS transistors based on CMOS bulk as well as SOI process technologies on-board LEO and GEO satellites. On the basis of simulation results, the TID robustness analysis for advanced deep sub-micron technologies was accomplished up to 500 Krad. The correlation between the impact of technology scaling and magnitude of leakage current with corresponding total dose was established utilizing Visual TCAD Genius program.

Rapid Antibiotic Susceptibility Testing of Uropathogenic E. coli by Tracking Submicron Scale Motion of Single Bacterial Cells.

PubMed

Syal, Karan; Shen, Simon; Yang, Yunze; Wang, Shaopeng; Haydel, Shelley E; Tao, Nongjian

2017-08-25

To combat antibiotic resistance, a rapid antibiotic susceptibility testing (AST) technology that can identify resistant infections at disease onset is required. Current clinical AST technologies take 1-3 days, which is often too slow for accurate treatment. Here we demonstrate a rapid AST method by tracking sub-μm scale bacterial motion with an optical imaging and tracking technique. We apply the method to clinically relevant bacterial pathogens, Escherichia coli O157: H7 and uropathogenic E. coli (UPEC) loosely tethered to a glass surface. By analyzing dose-dependent sub-μm motion changes in a population of bacterial cells, we obtain the minimum bactericidal concentration within 2 h using human urine samples spiked with UPEC. We validate the AST method using the standard culture-based AST methods. In addition to population studies, the method allows single cell analysis, which can identify subpopulations of resistance strains within a sample.

Coarsening of stripe patterns: variations with quench depth and scaling.

PubMed

Tripathi, Ashwani K; Kumar, Deepak

2015-02-01

The coarsening of stripe patterns when the system is evolved from random initial states is studied by varying the quench depth ε, which is a measure of distance from the transition point of the stripe phase. The dynamics of the growth of stripe order, which is characterized by two length scales, depends on the quench depth. The growth exponents of the two length scales vary continuously with ε. The decay exponents for free energy, stripe curvature, and densities of defects like grain boundaries and dislocations also show similar variation. This implies a breakdown of the standard picture of nonequilibrium dynamical scaling. In order to understand the variations with ε we propose an additional scaling with a length scale dependent on ε. The main contribution to this length scale comes from the "pinning potential," which is unique to systems where the order parameter is spatially periodic. The periodic order parameter gives rise to an ε-dependent potential, which can pin defects like grain boundaries, dislocations, etc. This additional scaling provides a compact description of variations of growth exponents with quench depth in terms of just one exponent for each of the length scales. The relaxation of free energy, stripe curvature, and the defect densities have also been related to these length scales. The study is done at zero temperature using Swift-Hohenberg equation in two dimensions.

Interactions between a fractal tree-like object and hydrodynamic turbulence: flow structure and characteristic mixing length

NASA Astrophysics Data System (ADS)

Meneveau, C. V.; Bai, K.; Katz, J.

2011-12-01

The vegetation canopy has a significant impact on various physical and biological processes such as forest microclimate, rainfall evaporation distribution and climate change. Most scaled laboratory experimental studies have used canopy element models that consist of rigid vertical strips or cylindrical rods that can be typically represented through only one or a few characteristic length scales, for example the diameter and height for cylindrical rods. However, most natural canopies and vegetation are highly multi-scale with branches and sub-branches, covering a wide range of length scales. Fractals provide a convenient idealization of multi-scale objects, since their multi-scale properties can be described in simple ways (Mandelbrot 1982). While fractal aspects of turbulence have been studied in several works in the past decades, research on turbulence generated by fractal objects started more recently. We present an experimental study of boundary layer flow over fractal tree-like objects. Detailed Particle-Image-Velocimetry (PIV) measurements are carried out in the near-wake of a fractal-like tree. The tree is a pre-fractal with five generations, with three branches and a scale reduction factor 1/2 at each generation. Its similarity fractal dimension (Mandelbrot 1982) is D ~ 1.58. Detailed mean velocity and turbulence stress profiles are documented, as well as their downstream development. We then turn attention to the turbulence mixing properties of the flow, specifically to the question whether a mixing length-scale can be identified in this flow, and if so, how it relates to the geometric length-scales in the pre-fractal object. Scatter plots of mean velocity gradient (shear) and Reynolds shear stress exhibit good linear relation at all locations in the flow. Therefore, in the transverse direction of the wake evolution, the Boussinesq eddy viscosity concept is appropriate to describe the mixing. We find that the measured mixing length increases with increasing streamwise locations. Conversely, the measured eddy viscosity and mixing length decrease with increasing elevation, which differs from eddy viscosity and mixing length behaviors of traditional boundary layers or canopies studied before. In order to find an appropriate length for the flow, several models based on the notion of superposition of scales are proposed and examined. One approach is based on spectral distributions. Another more practical approach is based on length-scale distributions evaluated using fractal geometry tools. These proposed models agree well with the measured mixing length. The results indicate that information about multi-scale clustering of branches as it occurs in fractals has to be incorporated into models of the mixing length for flows through canopies with multiple scales. The research is supported by National Science Foundation grant ATM-0621396 and AGS-1047550.

The snakelike chain character of unstructured RNA.

PubMed

Jacobson, David R; McIntosh, Dustin B; Saleh, Omar A

2013-12-03

In the absence of base-pairing and tertiary structure, ribonucleic acid (RNA) assumes a random-walk conformation, modulated by the electrostatic self-repulsion of the charged, flexible backbone. This behavior is often modeled as a Kratky-Porod "wormlike chain" (WLC) with a Barrat-Joanny scale-dependent persistence length. In this study we report measurements of the end-to-end extension of poly(U) RNA under 0.1 to 10 pN applied force and observe two distinct elastic-response regimes: a low-force, power-law regime characteristic of a chain of swollen blobs on long length scales and a high-force, salt-valence-dependent regime consistent with ion-stabilized crumpling on short length scales. This short-scale structure is additionally supported by force- and salt-dependent quantification of the RNA ion atmosphere composition, which shows that ions are liberated under stretching; the number of ions liberated increases with increasing bulk salt concentration. Both this result and the observation of two elastic-response regimes directly contradict the WLC model, which predicts a single elastic regime across all forces and, when accounting for scale-dependent persistence length, the opposite trend in ion release with salt concentration. We conclude that RNA is better described as a "snakelike chain," characterized by smooth bending on long length scales and ion-stabilized crumpling on short length scales. In monovalent salt, these two regimes are separated by a characteristic length that scales with the Debye screening length, highlighting the determining importance of electrostatics in RNA conformation. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Length-scale dependent mechanical properties of Al-Cu eutectic alloy: Molecular dynamics based model and its experimental verification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiwary, C. S., E-mail: cst.iisc@gmail.com; Chattopadhyay, K.; Chakraborty, S.

2014-05-28

This paper attempts to gain an understanding of the effect of lamellar length scale on the mechanical properties of two-phase metal-intermetallic eutectic structure. We first develop a molecular dynamics model for the in-situ grown eutectic interface followed by a model of deformation of Al-Al{sub 2}Cu lamellar eutectic. Leveraging the insights obtained from the simulation on the behaviour of dislocations at different length scales of the eutectic, we present and explain the experimental results on Al-Al{sub 2}Cu eutectic with various different lamellar spacing. The physics behind the mechanism is further quantified with help of atomic level energy model for different lengthmore » scale as well as different strain. An atomic level energy partitioning of the lamellae and the interface regions reveals that the energy of the lamellae core are accumulated more due to dislocations irrespective of the length-scale. Whereas the energy of the interface is accumulated more due to dislocations when the length-scale is smaller, but the trend is reversed when the length-scale is large beyond a critical size of about 80 nm.« less

Taming active turbulence with patterned soft interfaces.

PubMed

Guillamat, P; Ignés-Mullol, J; Sagués, F

2017-09-15

Active matter embraces systems that self-organize at different length and time scales, often exhibiting turbulent flows apparently deprived of spatiotemporal coherence. Here, we use a layer of a tubulin-based active gel to demonstrate that the geometry of active flows is determined by a single length scale, which we reveal in the exponential distribution of vortex sizes of active turbulence. Our experiments demonstrate that the same length scale reemerges as a cutoff for a scale-free power law distribution of swirling laminar flows when the material evolves in contact with a lattice of circular domains. The observed prevalence of this active length scale can be understood by considering the role of the topological defects that form during the spontaneous folding of microtubule bundles. These results demonstrate an unexpected strategy for active systems to adapt to external stimuli, and provide with a handle to probe the existence of intrinsic length and time scales.Active nematics consist of self-driven components that develop orientational order and turbulent flow. Here Guillamat et al. investigate an active nematic constrained in a quasi-2D geometrical setup and show that there exists an intrinsic length scale that determines the geometry in all forcing regimes.

Investigating the annual behaviour of submicron secondary inorganic and organic aerosols in London

NASA Astrophysics Data System (ADS)

Young, D. E.; Allan, J. D.; Williams, P. I.; Green, D. C.; Flynn, M. J.; Harrison, R. M.; Yin, J.; Gallagher, M. W.; Coe, H.

2014-07-01

For the first time, the behaviour of non-refractory inorganic and organic submicron particulate through an entire annual cycle is investigated using measurements from an Aerodyne compact time-of-flight aerosol mass spectrometer (cToF-AMS) located at a UK urban background site in North Kensington, London. We show secondary aerosols account for a significant fraction of the submicron aerosol burden and that high concentration events are governed by different factors depending on season. Furthermore, we demonstrate that on an annual basis there is no variability in the extent of secondary organic aerosol (SOA) oxidation, as defined by the oxygen content, irrespective of amount. This result is surprising given the changes in precursor emissions and contributions as well as photochemical activity throughout the year; however it may make the characterisation of SOA in urban environments more straightforward than previously supposed. Organic species, nitrate, sulphate, ammonium, and chloride were measured during 2012 with average concentrations (±one standard deviation) of 4.32 (±4.42), 2.74 (±5.00), 1.39 (±1.34), 1.30 (±1.52) and 0.15 (±0.24) μg m-3, contributing 43, 28, 14, 13 and 2% to the total submicron mass, respectively. Components of the organic aerosol fraction are determined using positive matrix factorisation (PMF) where five factors are identified and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2). OOA1 and OOA2 represent more and less oxygenated OA with average concentrations of 1.27 (±1.49) and 0.14 (±0.29) μg m-3, respectively, where OOA1 dominates the SOA fraction (90%). Diurnal, monthly, and seasonal trends are observed in all organic and inorganic species, due to meteorological conditions, specific nature of the aerosols, and availability of precursors. Regional and transboundary pollution as well as other individual pollution events influence London's total submicron aerosol burden. High concentrations of non-refractory submicron aerosols in London are governed by particulate emissions in winter, especially nitrate and SFOA, whereas SOA formation drives the high concentrations during the summer. The findings from this work could have significant implications for modelling of urban air pollution as well as for the effects of atmospheric aerosols on health and climate.

Evaluating Model Parameterizations of Submicron Aerosol Scattering and Absorption with in situ Data from ARCTAS 2008

NASA Technical Reports Server (NTRS)

Alvarado, Matthew J.; Lonsdale, Chantelle R.; Macintyre, Helen L.; Bian, Huisheng; Chin, Mian; Ridley, David A.; Heald, Colette L.; Thornhill, Kenneth L.; Anderson, Bruce E.; Cubison, Michael J.;

Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

NASA Astrophysics Data System (ADS)

Alvarado, Matthew J.; Lonsdale, Chantelle R.; Macintyre, Helen L.; Bian, Huisheng; Chin, Mian; Ridley, David A.; Heald, Colette L.; Thornhill, Kenneth L.; Anderson, Bruce E.; Cubison, Michael J.; Jimenez, Jose L.; Kondo, Yutaka; Sahu, Lokesh K.; Dibb, Jack E.; Wang, Chien

2016-07-01

Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10-23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

Experimental opto-mechanics with levitated nanoparticles: towards quantum control and thermodynamic cycles (Presentation Recording)

NASA Astrophysics Data System (ADS)

Kiesel, Nikolai; Blaser, Florian; Delic, Uros; Grass, David; Dechant, Andreas; Lutz, Eric; Bathaee, Marzieh; Aspelmeyer, Markus

2015-08-01

Combining optical levitation and cavity optomechanics constitutes a promising approach to prepare and control the motional quantum state of massive objects (>10^9 amu). This, in turn, would represent a completely new type of light-matter interface and has, for example, been predicted to enable experimental tests of macrorealistic models or of non-Newtonian gravity at small length scales. Such ideas have triggered significant experimental efforts to realizing such novel systems. To this end, we have recently successfully demonstrated cavity-cooling of a levitated sub-micron silica particle in a classical regime at a pressure of approximately 1mbar. Access to higher vacuum of approx. 10^-6 mbar has been demonstrated using 3D-feedback cooling in optical tweezers without cavity-coupling. Here we will illustrate our strategy towards trapping, 3D-cooling and quantum control of nanoparticles in ultra-high vacuum using cavity-based feedback cooling methods and clean particle loading with hollow-core photonic crystal fibers. We will also discuss the current experimental progress both in 3D-cavity cooling and HCPCF-based transport of nanoparticles. As yet another application of cavity-controlled levitated nanoparticles we will show how to implement a thermodynamic Sterling cycle operating in the underdamped regime. We present optimized protocols with respect to efficiency at maximum power in this little explored regime. We also show that the excellent level of control in our system will allow reproducing all relevant features of such optimized protocols. In a next step, this will enable studies of thermodynamics cycles in a regime where the quantization of the mechanical motion becomes relevant.

Mode structure of planar optical antennas on dielectric substrates

DOE PAGES

Word, Robert C.; Konenkamp, Rolf

2016-08-08

Here, we report a numerical study, supported by photoemission electron microscopy (PEEM), of sub-micron planar optical antennas on transparent substrate. We find these antennas generate intricate near-field spatial field distributions with odd and even numbers of nodes. We show that the field distributions are primarily superpositions of planar surface plasmon polariton modes confined to the metal/substrate interface. The mode structure provides opportunities for coherent switching and optical control in sub-micron volumes.

Study of Submicron Particle Size Distributions by Laser Doppler Measurement of Brownian Motion.

DTIC Science & Technology

1984-10-29

o ..... . 5-1 A.S *6NEW DISCOVERIES OR INVENTIONS .. o......... ......... 6-1 APPENDIX: COMPUTER SIMULATION OF THE BROWNIAN MOTION SENSOR SIGNALS...scattering regime by analysis of the scattered light intensity and particle mass (size) obtained using the Brownian motion sensor . 9 Task V - By application...of the Brownian motion sensor in a flat-flame burner, the contractor shall assess the application of this technique for In-situ sizing of submicron

Hierarchical Microspheres Constructed from Chitin Nanofibers Penetrated Hydroxyapatite Crystals for Bone Regeneration.

PubMed

Duan, Bo; Shou, Kangquan; Su, Xiaojuan; Niu, Yahui; Zheng, Guan; Huang, Yao; Yu, Aixi; Zhang, Yu; Xia, Hong; Zhang, Lina

2017-07-10

Chitin exists abundantly in crab and shrimp shells as the template of the minerals, which inspired us to mineralize it for fabricating bone grafting materials. In the present work, chitin nanofibrous microspheres were used as the matrix for in situ synthesis of hydroxyapatite (HA) crystals including microflakes, submicron-needles, and submicron-spheres, which were penetrated by long chitin nanofibers, leading to the hierarchical structure. The shape and size of the HA crystals could be controlled by changing the HA synthesis process. The tight interface adhesion between chitin and HA through the noncovanlent bonds occurred in the composite microspheres, and HAs were homogeneously dispersed and bounded to the chitin nanofibers. In our findings, the inherent biocompatibilities of the both chitin and HA contributed the bone cell adhesion and osteoconduction. Moreover, the chitin microsphere with submicron-needle and submicron-sphere HA crystals remarkably promoted in vitro cell adhesion and in vivo bone healing. It was demonstrated that rabbits with 1.5 cm radius defect were almost cured completely within three months in a growth factor- and cell-free state, as a result of the unique surface microstructure and biocompatibilities of the composite microspheres. The microsphere scaffold displayed excellent biofunctions and an appropriate biodegradability. This work opened up a new avenue to construct natural polymer-based organic-inorganic hybrid microspheres for bone regeneration.

Performance of Renormalization Group Algebraic Turbulence Model on Boundary Layer Transition Simulation

NASA Technical Reports Server (NTRS)

Ahn, Kyung H.

1994-01-01

The RNG-based algebraic turbulence model, with a new method of solving the cubic equation and applying new length scales, is introduced. An analysis is made of the RNG length scale which was previously reported and the resulting eddy viscosity is compared with those from other algebraic turbulence models. Subsequently, a new length scale is introduced which actually uses the two previous RNG length scales in a systematic way to improve the model performance. The performance of the present RNG model is demonstrated by simulating the boundary layer flow over a flat plate and the flow over an airfoil.

Empirical scaling of the length of the longest increasing subsequences of random walks

NASA Astrophysics Data System (ADS)

Mendonça, J. Ricardo G.

2017-02-01

We provide Monte Carlo estimates of the scaling of the length L n of the longest increasing subsequences of n-step random walks for several different distributions of step lengths, short and heavy-tailed. Our simulations indicate that, barring possible logarithmic corrections, {{L}n}∼ {{n}θ} with the leading scaling exponent 0.60≲ θ ≲ 0.69 for the heavy-tailed distributions of step lengths examined, with values increasing as the distribution becomes more heavy-tailed, and θ ≃ 0.57 for distributions of finite variance, irrespective of the particular distribution. The results are consistent with existing rigorous bounds for θ, although in a somewhat surprising manner. For random walks with step lengths of finite variance, we conjecture that the correct asymptotic behavior of L n is given by \\sqrt{n}\\ln n , and also propose the form for the subleading asymptotics. The distribution of L n was found to follow a simple scaling form with scaling functions that vary with θ. Accordingly, when the step lengths are of finite variance they seem to be universal. The nature of this scaling remains unclear, since we lack a working model, microscopic or hydrodynamic, for the behavior of the length of the longest increasing subsequences of random walks.

Two years of near real-time observations of the chemical composition of submicron aerosols in Cape Corsica obtained by Q-ACSM

NASA Astrophysics Data System (ADS)

Sciare, Jean; Dulac, François; Crenn, Vincent; Hamonou, Eric; Baisnée, Dominique; Nicolas, José B.; Pont, Véronique; Lambert, Dominique; Gheusi, François; Mallet, Marc; Tison, Emmanuel; Sauvage, Stéphane; Bourrianne, Thierry; Roberts, Gregory; Colomb, Aurélie; Pichon, Jean-Marc; Sellegri, Karine; Savelli, Jean-Luc

2015-04-01

As part of the MISTRALS/ChArMEx (Mediterranean Integrated Studies aT Regional And Local Scales/the Chemistry-Aerosol Mediterranean Experiment; http://www.mistrals-home.org; http://charmex.lsce.ipsl.fr) and the CORSiCA (http://www.obs-mip.fr/corsica) programs, 2-year continuous observations of near real-time chemical composition of submicron aerosols were performed between June 2012 & July 2014 at the Cape Corsica atmospheric supersite (http://gaw.empa.ch/gawsis/reports.asp?StationID=2076203042), a remote marine site in the Western Mediterranean. Submicron organic aerosols (OA) and the major inorganic salts (sulfate, ammonium, nitrate) were monitored every 30 min using a Quadripole Aerosol Chemical Speciation Monitor (Q-ACSM; Aerodyne Res. Inc. MA, USA). Quality control of this large dataset (24-month continuous observations) was performed through closure studies (using co-located SMPS and TEOM-FDMS measurements), direct comparisons with other on-line / off-line instruments running in parallel (filter sampling, OPC, nephelometer …), and large intercomparison of 13 Q-ACSM performed within the EU-FP7 ACTRIS program (http://www.actris.net/). Source apportionment of OA was then performed on a monthly basis using the SourceFinder software (SoFi, http://www.psi.ch/acsm-stations/me-2) allowing the distinction between hydrogen- and oxygen-like organic aerosols (HOA and OOA, respectively). This monthly resolved source apportionment was first compared with co-located real-time tracer measurements (NOx, BC, CO, VOC …) available at the Cape Corsica station. Seasonal patterns of the various properties of (secondary) OOA (OSc, O/C ratio …) were then investigated from monthly resolved source apportionment results (monthly OOA mass spectra) obtained over the period June 2012 - July 2014. Acknowledgements: Atmospheric measurements performed at Cape Corsica Station were funded by CNRS-INSU, ADEME, CEA, and METEO-FRANCE. This work was carried out in the framework of the CORSiCA project funded by the Collectivité Territoriale de Corse through the Fonds Européen de Développement Régional of the European Operational Program 2007-2013 and the Contrat de Plan Etat Région.

Novel Translucent and Strong Submicron Alumina Ceramics for Dental Restorations.

PubMed

Zhao, M; Sun, Y; Zhang, J; Zhang, Y

2018-03-01

An ideal ceramic restorative material should possess excellent aesthetic and mechanical properties. We hypothesize that the high translucency and strength of polycrystalline ceramics can be achieved through microstructural tailoring. The aim of this study is to demonstrate the superior optical and mechanical properties of a new class of submicron grain-sized alumina ceramics relative to the current state-of-the-art dental ceramic materials. The translucency, the in-line transmission ( T IT ) in particular, of these submicron alumina ceramics has been examined with the Rayleigh-Gans-Debye light-scattering model. The theoretical predictions related very well with the measured T IT values. The translucency parameter ( TP) and contrast ratio ( CR) of the newly developed aluminas were measured with a reflectance spectrophotometer on a black-and-white background. For comparison, the T IT , TP, and CR values for a variety of dental ceramics, mostly measured in-house but also cited from the literature, were included. The flexural strength of the aluminas was determined with the 4-point bending test. Our findings have shown that for polycrystalline alumina ceramics, an average grain size <1 µm coupled with a porosity level <0.7% could yield translucency values ( T IT , TP, CR) similar to those of the commercial high-translucency porcelains. These values are far superior to the high-translucency lithium disilicate glass-ceramic and zirconias, including the most translucent cubic-containing zirconias. The strength of these submicron grain-sized aluminas was significantly higher than that of the cubic-containing zirconia (e.g., Zpex Smile) and lithia-based glass-ceramics (e.g., IPS e.max CAD HT). A coarse-grained alumina could also reach a translucency level comparable to that of dental porcelain. However, the relatively low strength of this material has limited its clinical indications to structurally less demanding applications, such as orthodontic brackets. With a combined high strength and translucency, the newly developed submicron grain-sized alumina may be considered a suitable material for dental restorations.

Submicron particle monitoring of paving and related road construction operations.

PubMed

Freund, Alice; Zuckerman, Norman; Baum, Lisa; Milek, Debra

2012-01-01

This study identified activities and sources that contribute to ultrafine and other submicron particle exposure that could trigger respiratory symptoms in highway repair workers. Submicron particle monitoring was conducted for paving, milling, and pothole repair operations in a major metropolitan area where several highway repair workers were identified as symptomatic for respiratory illness following exposures at the 2001 World Trade Center disaster site. Exposure assessments were conducted for eight trades involved in road construction using a TSI P-Trak portable condensation particle counter. Direct readings near the workers' breathing zones and observations of activities and potential sources were logged on 7 days on 27 workers using four different models of pavers and two types of millers. Average worker exposure levels ranged from 2 to 3 times background during paving and from 1 to 4 times background during milling. During asphalt paving, average personal exposures to submicron particulates were 25,000-60,000, 28,000-70,000, and 23,000-37,000 particles/ cm(3) for paver operators, screed operators, and rakers, respectively. Average personal exposures during milling were 19,000-111,000, 28,000-81,000, and 19,000 particles/cm(3) for the large miller operators, miller screed operators, and raker, respectively. Personal peak exposures were measured up to 467,000 and 455,000 particles/cm(3) in paving and milling, respectively. Several sources of submicron particles were identified. These included the diesel and electric fired screed heaters; engine exhaust from diesel powered construction vehicles passing by or idling; raking, dumping, and paving of asphalt; exhaust from the hotbox heater; pavement dust or fumes from milling operations, especially when the large miller started and stopped; and secondhand cigarette smoke. To reduce the potential for health effects in workers, over 40 recommendations were made to control exposures, including improved maintenance of paver ventilation systems; diesel fume engineering controls; reduced idling; provision of cabs for the operators; and improved dust suppression systems on the milling machine.

Co-existence of a few and sub micron inhomogeneities in Al-rich AlGaN/AlN quantum wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iwata, Yoshiya; Oto, Takao; Banal, Ryan G.

2015-03-21

Inhomogeneity in Al-rich AlGaN/AlN quantum wells is directly observed using our custom-built confocal microscopy photoluminescence (μ-PL) apparatus with a reflective system. The μ-PL system can reach the AlN bandgap in the deep ultra-violet spectral range with a spatial resolution of 1.8 μm. In addition, cathodoluminescence (CL) measurements with a higher spatial resolution of about 100 nm are performed. A comparison of the μ-PL and CL measurements reveals that inhomogeneities, which have different spatial distributions of a few- and sub-micron scales that are superimposed, play key roles in determining the optical properties.

Spectroscopic ellipsometry and polarimetry for materials and systems analysis at the nanometer scale: state-of-the-art, potential, and perspectives

PubMed Central

Bergmair, Michael; Bruno, Giovanni; Cattelan, Denis; Cobet, Christoph; de Martino, Antonello; Fleischer, Karsten; Dohcevic-Mitrovic, Zorana; Esser, Norbert; Galliet, Melanie; Gajic, Rados; Hemzal, Dušan; Hingerl, Kurt; Humlicek, Josef; Ossikovski, Razvigor; Popovic, Zoran V.; Saxl, Ottilia

2009-01-01

This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems and devices at the nanoscale. These techniques include spectroscopic ellipsometry, polarimetry, and reflectance anisotropy. We give an overview of the various ellipsometry strategies for the measurement and analysis of nanometric films, metal nanoparticles and nanowires, semiconductor nanocrystals, and submicron periodic structures. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about process control, geometry factors, anisotropy, defects, and quantum confinement effects of nanostructures. PMID:21170135

RGB generation by four-wave mixing in small-core holey fibers

NASA Astrophysics Data System (ADS)

Horak, Peter; Dupriez, Pascal; Poletti, Francesco; Petrovich, Marco N.; Jeong, Yoonchan; Nilsson, Johan; Richardson, David J.; Payne, David N.

2007-09-01

We report the generation of white light comprising red, green, and blue spectral bands from a frequency-doubled fiber laser in submicron-sized cores of microstructured holey fibers. Picosecond pulses of green light are launched into a single suspended core of a silica holey fiber where energy is transferred by an efficient four-wave mixing process into a red and blue sideband whose wavelengths are fixed by birefringent phase matching due to a slight asymmetry of the structure arising during the fiber fabrication. Numerical models of the fiber structure and of the nonlinear processes confirm our interpretation. Finally, we discuss power scaling and limitations of this white light source.

Improving hydro-formability of stainless steel tubes by tube channel pressing

NASA Astrophysics Data System (ADS)

Kitano, Y.; Yuasa, M.; Miyamoto, H.; Farshidi, M. H.; Bagherpour, E.

2017-05-01

Tube channel pressing (TCP), which is one of the severe plastic deformation (SPD) technologies to refine grain size into submicron size for tubular materials, have been applied to ferritic stainless steel tubes for one pass, in order to alleviate ridging and enhance the hydro-formability. It was found that grain-scale shear bands were introduced by one-pass TCP, and texture and microstructure was successfully modified by promoting recrystallization of deformation microstructure, which is otherwise hard-to-recrystallize, in the post-TCP annealing. Elongation to failure, strain-hardening exponent (n-value) and Lankford values of both longitudinal and circumferential directions increased in comparison to with the tube fabricated by conventional process.

X-ray free-electron laser studies of dense plasmas

NASA Astrophysics Data System (ADS)

Vinko, Sam M.

2015-10-01

> The high peak brightness of X-ray free-electron lasers (FELs), coupled with X-ray optics enabling the focusing of pulses down to sub-micron spot sizes, provides an attractive route to generating high energy-density systems on femtosecond time scales, via the isochoric heating of solid samples. Once created, the fundamental properties of these plasmas can be studied with unprecedented accuracy and control, providing essential experimental data needed to test and benchmark commonly used theoretical models and assumptions in the study of matter in extreme conditions, as well as to develop new predictive capabilities. Current advances in isochoric heating and spectroscopic plasma studies on X-ray FELs are reviewed and future research directions and opportunities discussed.

Tip vortices in the actuator line model

NASA Astrophysics Data System (ADS)

Martinez, Luis; Meneveau, Charles

2017-11-01

The actuator line model (ALM) is a widely used tool to represent the wind turbine blades in computational fluid dynamics without the need to resolve the full geometry of the blades. The ALM can be optimized to represent the `correct' aerodynamics of the blades by choosing an appropriate smearing length scale ɛ. This appropriate length scale creates a tip vortex which induces a downwash near the tip of the blade. A theoretical frame-work is used to establish a solution to the induced velocity created by a tip vortex as a function of the smearing length scale ɛ. A correction is presented which allows the use of a non-optimal smearing length scale but still provides the downwash which would be induced using the optimal length scale. Thanks to the National Science Foundation (NSF) who provided financial support for this research via Grants IGERT 0801471, IIA-1243482 (the WINDINSPIRE project) and ECCS-1230788.

High Proportions of Sub-micron Particulate Matter in Icelandic Dust Storms in 2015

NASA Astrophysics Data System (ADS)

Dagsson Waldhauserova, Pavla; Arnalds, Olafur; Olafsson, Haraldur; Magnusdottir, Agnes

2017-04-01

Iceland is extremely active dust region and desert areas of over 44,000 km2 acknowledge Iceland as the largest Arctic and European desert. Frequent dust events, up to 135 dust days annually, transport dust particles far distances towards the Arctic and Europe. Satellite MODIS pictures have revealed dust plumes exceeding 1,000 km. The annual dust deposition was calculated as 40.1 million tons yr-1. Two dust storms were measured in transverse horizontal profile about 90 km far from different dust sources in southwestern Iceland in the summer of 2015. Aerosol monitor DustTrak DRX 8533EP was used to measure PM mass concentrations corresponding to PM1, PM2.5, PM4, PM10 and the total PM15 at several places within the dust plume. Images from camera network operated by the Icelandic Road and Coastal Administration were used to estimate the visibility and spatial extent of measured dust events. A numerical simulation of surface winds was carried out with the numerical model HIRLAM with horizontal resolution of 5 km and used to calculate the total dust flux from the sources. The in situ measurements inside the dust plumes showed that aeolian dust can be very fine. The study highlights that suspended volcanic dust in Iceland causes air pollution with extremely high PM1 concentrations comparable to the polluted urban stations in Europe or Asia rather than reported dust event observations from around the world. The PM1/PM2.5 ratios are generally low during dust storms outside of Iceland, much lower than > 0.9 and PM1/PM10 ratios of 0.34-0.63 found in our study. It shows that Icelandic volcanic dust consists of higher proportion of submicron particles compared to crustal dust. The submicron particles are predicted to travel long distances. Moreover, such submicron particles pose considerable health risk because of high potential for entering the lungs. Icelandic volcanic glass has often fine pipe-vesicular structures known from asbestos and high content of heavy metals. Previous in situ measurements at the dust source in 2013 revealed extremely high number concentrations of submicron particles, specifically in the size range 0.3-0.337 μm. The PM2.5/PM10 ratios of mass concentrations seem to be lower at the dust sources that in some distance from the sources as measured in 2015. Common dust storms in Iceland are of several hundred thousand tons of magnitude from relatively well defined main dust sources. Numerical simulations were used calculate the total dust flux from the sources as 180,000 - 280,000 tons in this study. The mean PM1 (PM10) concentrations inside of the dust plumes varied from 97 to 241 µg m-3 (PM10 = 158 to 583 µg m-3). The extent of moderate dust events was calculated as 2.450 km2 to 4.220 km2 of the land area suggesting the regional scale of the events. Dust plumes reported here passed the most densely inhabited areas of Iceland, health risk warnings for the general public were, however, not issued. The data provided stresses the need for such warning system and is an important step towards its development.

Modeling of Ceiling Fire Spread and Thermal Radiation.

DTIC Science & Technology

1981-10-01

under a PMMA ceiling and flame lengths under an inert ceiling are found to be in reasonable agreement with full-scale behavior. Although fire spread...5 3 Flame Lengths under Full-Scale Ceilings 12 4 Correlation of Flame Length under Inert Ceilings 16 5 Correlation of Flame Length under No 234 Model...Ceilings 17 6 Correlation of Flame Length under No B8811 Model Ceilings 18 7 Correlation of Flame Length under No. 223 Model Ceilings 19 8

Natural Length Scales Shape Liquid Phase Continuity in Unsaturated Flows

NASA Astrophysics Data System (ADS)

Assouline, S.; Lehmann, P. G.; Or, D.

2015-12-01

Unsaturated flows supporting soil evaporation and internal drainage play an important role in various hydrologic and climatic processes manifested at a wide range of scales. We study inherent natural length scales that govern these flow processes and constrain the spatial range of their representation by continuum models. These inherent length scales reflect interactions between intrinsic porous medium properties that affect liquid phase continuity, and the interplay among forces that drive and resist unsaturated flow. We have defined an intrinsic length scale for hydraulic continuity based on pore size distribution that controls soil evaporation dynamics (i.e., stage 1 to stage 2 transition). This simple metric may be used to delineate upper bounds for regional evaporative losses or the depth of soil-atmosphere interactions (in the absence of plants). A similar length scale governs the dynamics of internal redistribution towards attainment of field capacity, again through its effect on hydraulic continuity in the draining porous medium. The study provides a framework for guiding numerical and mathematical models for capillary flows across different scales considering the necessary conditions for coexistence of stationarity (REV), hydraulic continuity and intrinsic capillary gradients.

The effects of nutrient solution sterilization on the growth and yield of hydroponically grown lettuce

NASA Technical Reports Server (NTRS)

Schwartzkopf, S. H.; Dudzinski, D.; Minners, R. S.

1987-01-01

Two methods of removing bacteria from hydroponic nutrient solution [ultraviolet (UV) radiation and submicronic filter] were evaluated for efficiency and for their effects on lettuce (Lactuca sativa L.) production. Both methods were effective in removing bacteria; but, at high intensity, the ultraviolet sterilizer significantly inhibited the production of plants grown in the treated solution. Bacterial removal by lower intensity UV or a submicronic filter seemed to promote plant growth slightly, but showed no consistent, statistically significant effect.

Fabrication of submicron proteinaceous structures by direct laser writing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serien, Daniela; Takeuchi, Shoji, E-mail: takeuchi@iis.u-tokyo.ac.jp; ERATO Takeuchi Biohybrid Innovation Project, Japan Science and Technology Agency, 4-6-1 Komaba, Meguro-ku, 153-8505 Tokyo

In this paper, we provide a characterization of truly free-standing proteinaceous structures with submicron feature sizes depending on the fabrication conditions by model-based analysis. Protein cross-linking of bovine serum albumin is performed by direct laser writing and two-photon excitation of flavin adenine dinucleotide. We analyze the obtainable fabrication resolution and required threshold energy for polymerization. The applied polymerization model allows prediction of fabrication conditions and resulting fabrication size, alleviating the application of proteinaceous structure fabrication.

Oxygen-Barrier Coating for Titanium

NASA Technical Reports Server (NTRS)

Clark, Ronald K.; Unnam, Jalaiah

1987-01-01

Oxygen-barrier coating for titanium developed to provide effective and low-cost means for protecting titanium alloys from oxygen in environment when alloys used in high-temperature mechanical or structural applications. Provides protective surface layer, which reduces extent of surface oxidation of alloy and forms barrier to diffusion of oxygen, limiting contamination of substrate alloy by oxygen. Consists of submicron layer of aluminum deposited on surface of titanium by electron-beam evaporation, with submicron layer of dioxide sputtered onto aluminum to form coat.

Study of 1/f Noise in Solids.

DTIC Science & Technology

1983-01-01

Nyquist 1928, Callen and Greene 1952) or from a quantum statistical mechanical approach ( Kubo 1957). The other five properties are somewhat more subtle...then a continued decrease. LAJ The noise In GaAs n+n-n * mesas of submicron dimensions is very lc,.. 1he we * * Hooge parameter is of the order of W7...processes. + - + The noise in GaAs n n n mesas of submicron dimensions is very low. The Hooge parameter is of order 10- 7 , indicating that collisions are

Sub-micron particles in northwest Atlantic shelf water

NASA Astrophysics Data System (ADS)

Longhurst, A. R.; Koike, I.; Li, W. K. W.; Rodriguez, J.; Dickie, P.; Kepay, P.; Partensky, F.; Bautista, B.; Ruiz, J.; Wells, M.; Bird, D. F.

1992-01-01

The existence of numerous (1.0 × 10 7 ml -1) sub-micron particles has been confirmed in northwest Atlantic shelf water. These particles were counted independently by two different resistive-pulse instruments, and their existence confirmed by our ability to reduce their numbers by ultracentrifugation, serial dilution and surface coagulation in a bubbling column. There are important implications for the dynamics of DOM in seawater if, as seems probable, these particles represent a fraction of "dissolved" organic material in seawater.

Failure analysis of fuel cell electrodes using three-dimensional multi-length scale X-ray computed tomography

NASA Astrophysics Data System (ADS)

Pokhrel, A.; El Hannach, M.; Orfino, F. P.; Dutta, M.; Kjeang, E.

2016-10-01

X-ray computed tomography (XCT), a non-destructive technique, is proposed for three-dimensional, multi-length scale characterization of complex failure modes in fuel cell electrodes. Comparative tomography data sets are acquired for a conditioned beginning of life (BOL) and a degraded end of life (EOL) membrane electrode assembly subjected to cathode degradation by voltage cycling. Micro length scale analysis shows a five-fold increase in crack size and 57% thickness reduction in the EOL cathode catalyst layer, indicating widespread action of carbon corrosion. Complementary nano length scale analysis shows a significant reduction in porosity, increased pore size, and dramatically reduced effective diffusivity within the remaining porous structure of the catalyst layer at EOL. Collapsing of the structure is evident from the combination of thinning and reduced porosity, as uniquely determined by the multi-length scale approach. Additionally, a novel image processing based technique developed for nano scale segregation of pore, ionomer, and Pt/C dominated voxels shows an increase in ionomer volume fraction, Pt/C agglomerates, and severe carbon corrosion at the catalyst layer/membrane interface at EOL. In summary, XCT based multi-length scale analysis enables detailed information needed for comprehensive understanding of the complex failure modes observed in fuel cell electrodes.

Design and optimization of surface profilometer based on coplanar guide rail

NASA Astrophysics Data System (ADS)

Chen, Shuai; Dai, Yifan; Hu, Hao; Tie, Guipeng

2017-10-01

In order to implement the sub-micron precision measurement, a surface profilometer which based on the coplanar guide rail is designed. This profilometer adopts the open type air floating load and is driven by the magnetic force. As to achieve sub-micron accuracy, the flatness of granite guide working face and aerodynamic block are both processed to the micron level based on the homogenization of air flotation film theory. Permanent magnet which could reduce the influence of the driving disturbance to the measurement accuracy is used as the driving part. In this paper, the bearing capacity and the air floating stiffness of air floating block are both simulated and analyzed as to optimize the design parameters firstly. The layout and magnetic force of the magnet are also simulated. According to the simulation results, type selection and the position arrangement of the magnets are then confirmed. The test results on the experimental platform show that the surface profilometer based on coplanar guide rail possess the basis for realizing the submicron precision measurement.

Investigation of optimal route to fabricate submicron-sized Sm{sub 2}Fe{sub 17} particles with reduction-diffusion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okada, Shusuke, E-mail: shusuke-okada@aist.go.jp; Takagi, Kenta; Ozaki, Kimihiro

Submicron-sized Sm{sub 2}Fe{sub 17} powder samples were fabricated by a non-pulverizing process through reduction-diffusion of precursors prepared by a wet-chemical technique. Three precursors having different morphologies, which were micron-sized porous Sm-Fe oxide-impregnated iron nitrate, acicular goethite impregnated-samarium nitrate, and a conventional Sm-Fe coprecipitate, were prepared and subjected to hydrogen reduction and reduction-diffusion treatment to clarify whether these precursors could be convert to Sm{sub 2}Fe{sub 17} without impurity phases and which precursor is the most attractive for producing submicron-sized Sm{sub 2}Fe{sub 17} powder. As a result, all three precursors were successfully converted to Sm{sub 2}Fe{sub 17} powders without impurity phases, andmore » the synthesis route using iron-oxide particle-impregnated samarium oxide was revealed to have the greatest potential among the three routes.« less

Single Mode ZnO Whispering-Gallery Submicron Cavity and Graphene Improved Lasing Performance.

PubMed

Li, Jitao; Lin, Yi; Lu, Junfeng; Xu, Chunxiang; Wang, Yueyue; Shi, Zengliang; Dai, Jun

2015-07-28

Single-mode ultraviolet (UV) laser of ZnO is still in challenge so far, although it has been paid great attention along the past decades. In this work, single-mode lasing resonance was realized in a submicron-sized ZnO rod based on serially varying the dimension of the whispering-gallery mode (WGM) cavities. The lasing performance, such as the lasing quality factor (Q) and the lasing intensity, was remarkably improved by facilely covering monolayer graphene on the ZnO submicron-rod. The mode structure evolution from multimodes to single-mode was investigated systematically based on the total internal-wall reflection of the ZnO microcavities. Graphene-induced optical field confinement and lasing emission enhancement were revealed, indicating an energy coupling between graphene SP and ZnO exciton emission. This result demonstrated the response of graphene in the UV wavelength region and extended its potential applications besides many previous reports on the multifunctional graphene/semiconductor hybrid materials and devices in advanced electronics and optoelectronics areas.

Hierarchical TiO{sub 2} submicron-sized spheres for enhanced power conversion efficiency in dye-sensitized solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hao; State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000; Guo, Zhiguang, E-mail: zguo@licp.cas.cn

Hierarchical TiO{sub 2} submicron-sized sphere scattering layer, with relatively large surface area and effective light scattering, shows enhanced power conversion efficiency in dye-sensitized solar cells. - Highlights: • Hierarchical TiO{sub 2} submicron-sized spheres (TiO{sub 2} HSSs) with diameters of 400–600 nm were synthesized. • The HSSs composed of nanoparticles of ∼14 nm have a relatively large surface area of ∼35 m{sup 2}/g. • DSC exhibited the highest cell efficiency (6.23%) compared with ones with pure P25 (5.50%) or HSS (2.00%) photoanodes. - Abstract: Hierarchical TiO{sub 2} submicron-sized spheres (TiO{sub 2} HSSs) with diameters of 400–600 nm were synthesized by amore » facile one-step solvothermal method in ethanol solvent. The HSSs composed of nanoparticles of ∼14 nm have a relatively large surface area of ∼35 m{sup 2}/g. When applied as the scattering overlayer in dye-sensitized solar cells (DSCs), such TiO{sub 2} HSSs effectively improved light harvesting and led to the increase of photocurrent in DSCs. Furthermore, bilayer-structured photoanode also provided fast electron transportation and long electron lifetime as confirmed by electrochemical impedance spectra. As a result, DSC based on P25 nanoparticle underlayer and HSS-2 overlayer exhibited the highest cell efficiency (6.23%) compared with ones with pure P25 (5.50%) or HSS-2 (2.00%) photoanodes.« less

Ballistic thermophoresis of adsorbates on free-standing graphene.

PubMed

Panizon, Emanuele; Guerra, Roberto; Tosatti, Erio

2017-08-22

The textbook thermophoretic force which acts on a body in a fluid is proportional to the local temperature gradient. The same is expected to hold for the macroscopic drift behavior of a diffusive cluster or molecule physisorbed on a solid surface. The question we explore here is whether that is still valid on a 2D membrane such as graphene at short sheet length. By means of a nonequilibrium molecular dynamics study of a test system-a gold nanocluster adsorbed on free-standing graphene clamped between two temperatures [Formula: see text] apart-we find a phoretic force which for submicron sheet lengths is parallel to, but basically independent of, the local gradient magnitude. This identifies a thermophoretic regime that is ballistic rather than diffusive, persisting up to and beyond a 100-nanometer sheet length. Analysis shows that the phoretic force is due to the flexural phonons, whose flow is known to be ballistic and distance-independent up to relatively long mean-free paths. However, ordinary harmonic phonons should only carry crystal momentum and, while impinging on the cluster, should not be able to impress real momentum. We show that graphene and other membrane-like monolayers support a specific anharmonic connection between the flexural corrugation and longitudinal phonons whose fast escape leaves behind a 2D-projected mass density increase endowing the flexural phonons, as they move with their group velocity, with real momentum, part of which is transmitted to the adsorbate through scattering. The resulting distance-independent ballistic thermophoretic force is not unlikely to possess practical applications.

Ballistic thermophoresis of adsorbates on free-standing graphene

PubMed Central

Panizon, Emanuele; Guerra, Roberto; Tosatti, Erio

2017-01-01

The textbook thermophoretic force which acts on a body in a fluid is proportional to the local temperature gradient. The same is expected to hold for the macroscopic drift behavior of a diffusive cluster or molecule physisorbed on a solid surface. The question we explore here is whether that is still valid on a 2D membrane such as graphene at short sheet length. By means of a nonequilibrium molecular dynamics study of a test system—a gold nanocluster adsorbed on free-standing graphene clamped between two temperatures ΔT apart—we find a phoretic force which for submicron sheet lengths is parallel to, but basically independent of, the local gradient magnitude. This identifies a thermophoretic regime that is ballistic rather than diffusive, persisting up to and beyond a 100-nanometer sheet length. Analysis shows that the phoretic force is due to the flexural phonons, whose flow is known to be ballistic and distance-independent up to relatively long mean-free paths. However, ordinary harmonic phonons should only carry crystal momentum and, while impinging on the cluster, should not be able to impress real momentum. We show that graphene and other membrane-like monolayers support a specific anharmonic connection between the flexural corrugation and longitudinal phonons whose fast escape leaves behind a 2D-projected mass density increase endowing the flexural phonons, as they move with their group velocity, with real momentum, part of which is transmitted to the adsorbate through scattering. The resulting distance-independent ballistic thermophoretic force is not unlikely to possess practical applications. PMID:28774954

Λ(t)CDM model as a unified origin of holographic and agegraphic dark energy models

NASA Astrophysics Data System (ADS)

Chen, Yun; Zhu, Zong-Hong; Xu, Lixin; Alcaniz, J. S.

2011-04-01

Motivated by the fact that any nonzero Λ can introduce a length scale or a time scale into Einstein's theory, r=ct=3/|Λ|. Conversely, any cosmological length scale or time scale can introduce a Λ(t), Λ(t)=3/rΛ2(t)=3/(c2tΛ2(t)). In this Letter, we investigate the time varying Λ(t) corresponding to the length scales, including the Hubble horizon, the particle horizon and the future event horizon, and the time scales, including the age of the universe and the conformal time. It is found out that, in this scenario, the Λ(t)CDM model can be taken as the unified origin of the holographic and agegraphic dark energy models with interaction between the matter and the dark energy, where the interacting term is determined by Q=-ρ. We place observational constraints on the Λ(t)CDM models originating from different cosmological length scales and time scales with the recently compiled “Union2 compilation” which consists of 557 Type Ia supernovae (SNIa) covering a redshift range 0.015⩽z⩽1.4. In conclusion, an accelerating expansion universe can be derived in the cases taking the Hubble horizon, the future event horizon, the age of the universe and the conformal time as the length scale or the time scale.

Similarity and Scale Invariance of Velocity and Temperature Structure Functions within and above Dense Canopies

NASA Astrophysics Data System (ADS)

Ghannam, K.; Katul, G. G.; Chamecki, M.

2016-12-01

The scale-wise properties of turbulent flow statistics are conventionally quantified using the structure function D_ss (r)= <〖(Δs)〗^2 > describing velocity (s=u) or scalar (s=c) concentration increments Δs=s(x+r)-s(x) at various scales or separation distances r, where <.> is Reynolds averaging over coordinates of statistical homogeneity. For locally homogeneous and isotropic turbulence, the structure function can unfold statistical invariance of the form D_ss (βr)=β^p D_ss (r) as has been demonstrated by Kolmogorov's theory for the inertial subrange in the absence of intermittency corrections. For scales larger than inertial, scale invariance need not hold though universal scaling properties can still emerge provided an appropriate length and velocity scales are identified. One recent study on the structure function of the streamwise velocity (s=u) in smooth and rough wall-bounded flows argued that a logarithmic scaling of the form D_ss/(u_*^2 )=A+B ln(r/l_ɛ ) exists at any height z above the wall (or roughness elements), with,l_ɛ,〖 u〗_*, A and B being a dissipation length scale, the friction velocity, and two similarity constants to be determined. Whether this scaling is valid across all atmospheric stability regimes in the roughness sublayer (RSL) and the possible co-existence of length scales other than l_ɛ that collapse D_ss (r) for velocity and temperature frames the scope of this work. Using year-round field measurements within and above an Amazonian canopy, the work here explores the aforementioned scaling for the streamwise (s=u) and vertical velocity (s=w) components, along with its extension to active scalars (s=T, the air temperature) inside canopies and in the RSL above canopies. While the premise is that a length scale such as l_ɛ may serve as a master closure length scale for turbulent momentum and heat flux budgets, the role of the vorticity thickness, the Obukhov length, the adjustment length scale, and height z are also explored for various scale (or r) regimes. Because the RSL blends D_ss (r) from its form inside the canopy to its form in the well-studied atmospheric surface layer, the scaling laws derived here offer a new perspective on the thickness of the RSL for momentum and scalars and its variations with atmospheric stability.

Constant Stress Drop Fits Earthquake Surface Slip-Length Data

NASA Astrophysics Data System (ADS)

Shaw, B. E.

2011-12-01

Slip at the surface of the Earth provides a direct window into the earthquake source. A longstanding controversy surrounds the scaling of average surface slip with rupture length, which shows the puzzling feature of continuing to increase with rupture length for lengths many times the seismogenic width. Here we show that a more careful treatment of how ruptures transition from small circular ruptures to large rectangular ruptures combined with an assumption of constant stress drop provides a new scaling law for slip versus length which (1) does an excellent job fitting the data, (2) gives an explanation for the large crossover lengthscale at which slip begins to saturate, and (3) supports constant stress drop scaling which matches that seen for small earthquakes. We additionally discuss how the new scaling can be usefully applied to seismic hazard estimates.

Investigating the annual behaviour of submicron secondary inorganic and organic aerosols in London

NASA Astrophysics Data System (ADS)

Young, D. E.; Allan, J. D.; Williams, P. I.; Green, D. C.; Flynn, M. J.; Harrison, R. M.; Yin, J.; Gallagher, M. W.; Coe, H.

2015-06-01

For the first time, the behaviour of non-refractory inorganic and organic submicron particulate through an entire annual cycle is investigated using measurements from an Aerodyne compact time-of-flight aerosol mass spectrometer (cToF-AMS) located at a UK urban background site in North Kensington, London. We show that secondary aerosols account for a significant fraction of the submicron aerosol burden and that high concentration events are governed by different factors depending on season. Furthermore, we demonstrate that on an annual basis there is no variability in the extent of secondary organic aerosol (SOA) oxidation, as defined by the oxygen content, irrespective of amount. This result is surprising given the changes in precursor emissions and contributions as well as photochemical activity throughout the year; however it may make the characterisation of SOA in urban environments more straightforward than previously supposed. Organic species, nitrate, sulphate, ammonium, and chloride were measured during 2012 with average concentrations (±1 standard deviation) of 4.32 (±4.42), 2.74 (±5.00), 1.39 (±1.34), 1.30 (±1.52), and 0.15 (±0.24) μg m-3, contributing 44, 28, 14, 13, and 2 % to the total non-refractory submicron mass (NR-PM1) respectively. Components of the organic aerosol fraction are determined using positive matrix factorisation (PMF), in which five factors are identified and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2). OOA1 and OOA2 represent more and less oxygenated OA with average concentrations of 1.27 (±1.49) and 0.14 (±0.29) μg m-3 respectively, where OOA1 dominates the SOA fraction (90%). Diurnal, monthly, and seasonal trends are observed in all organic and inorganic species due to meteorological conditions, specific nature of the aerosols, and availability of precursors. Regional and transboundary pollution as well as other individual pollution events influence London's total submicron aerosol burden. High concentrations of non-refractory submicron aerosols in London are governed by particulate emissions in winter, especially nitrate and SFOA, whereas SOA formation drives the high concentrations during the summer. The findings from this work could have significant implications for modelling of urban air pollution as well as for the effects of atmospheric aerosols on health and climate.

Three-dimensional culture and interaction of cancer cells and dendritic cells in an electrospun nano-submicron hybrid fibrous scaffold

PubMed Central

Kim, Tae-Eon; Kim, Chang Gun; Kim, Jin Soo; Jin, Songwan; Yoon, Sik; Bae, Hae-Rahn; Kim, Jeong-Hwa; Jeong, Young Hun; Kwak, Jong-Young

2016-01-01

An artificial three-dimensional (3D) culture system that mimics the tumor microenvironment in vitro is an essential tool for investigating the cross-talk between immune and cancer cells in tumors. In this study, we developed a 3D culture system using an electrospun poly(ε-caprolactone) (PCL) nanofibrous scaffold (NFS). A hybrid NFS containing an uninterrupted network of nano- and submicron-scale fibers (400 nm to 2 µm) was generated by deposition onto a stainless steel mesh instead of an aluminum plate. The hybrid NFS contained multiplanar pores in a 3D structure. Surface-seeded mouse CT26 colon cancer cells and bone marrow-derived dendritic cells (BM-DCs) were able to infiltrate the hybrid NFS within several hours. BM-DCs cultured on PCL nanofibers showed a baseline inactive form, and lipopolysaccharide (LPS)-activated BM-DCs showed increased expression of CD86 and major histocompatibility complex Class II. Actin and phosphorylated FAK were enriched where unstimulated and LPS-stimulated BM-DCs contacted the fibers in the 3D hybrid NFS. When BM-DCs were cocultured with mitoxantrone-treated CT26 cells in a 3D hybrid NFS, BM-DCs sprouted cytoplasm to, migrated to, synapsed with, and engulfed mitoxantrone-treated CT26 cancer cells, which were similar to the naturally occurring cross-talk between these two types of cells. The 3D hybrid NFS developed here provides a 3D structure for coculture of cancer and immune cells. PMID:27042051

Three-dimensional culture and interaction of cancer cells and dendritic cells in an electrospun nano-submicron hybrid fibrous scaffold.

PubMed

Kim, Tae-Eon; Kim, Chang Gun; Kim, Jin Soo; Jin, Songwan; Yoon, Sik; Bae, Hae-Rahn; Kim, Jeong-Hwa; Jeong, Young Hun; Kwak, Jong-Young

2016-01-01

An artificial three-dimensional (3D) culture system that mimics the tumor microenvironment in vitro is an essential tool for investigating the cross-talk between immune and cancer cells in tumors. In this study, we developed a 3D culture system using an electrospun poly(ε-caprolactone) (PCL) nanofibrous scaffold (NFS). A hybrid NFS containing an uninterrupted network of nano- and submicron-scale fibers (400 nm to 2 µm) was generated by deposition onto a stainless steel mesh instead of an aluminum plate. The hybrid NFS contained multiplanar pores in a 3D structure. Surface-seeded mouse CT26 colon cancer cells and bone marrow-derived dendritic cells (BM-DCs) were able to infiltrate the hybrid NFS within several hours. BM-DCs cultured on PCL nanofibers showed a baseline inactive form, and lipopolysaccharide (LPS)-activated BM-DCs showed increased expression of CD86 and major histocompatibility complex Class II. Actin and phosphorylated FAK were enriched where unstimulated and LPS-stimulated BM-DCs contacted the fibers in the 3D hybrid NFS. When BM-DCs were cocultured with mitoxantrone-treated CT26 cells in a 3D hybrid NFS, BM-DCs sprouted cytoplasm to, migrated to, synapsed with, and engulfed mitoxantrone-treated CT26 cancer cells, which were similar to the naturally occurring cross-talk between these two types of cells. The 3D hybrid NFS developed here provides a 3D structure for coculture of cancer and immune cells.

Driven, underdamped Frenkel-Kontorova model on a quasiperiodic substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanossi, A.; Ro''der, J.; Bishop, A. R.

2001-01-01

We consider the underdamped dynamics of a chain of atoms subject to a dc driving force and a quasiperiodic substrate potential. The system has three inherent length scales which we take to be mutually incommensurate. We find that when the length scales are related by the spiral mean (a cubic irrational) there exists a value of the interparticle interaction strength above which the static friction is zero. When the length scales are related by the golden mean (a quadratic irrational) the static friction is always nonzero. >From considerations based on the connection of this problem to standard map theory, wemore » postulate that zero static friction is generally possible for incommensurate ratios of the length scales involved. However, when the length scales are quadratic irrationals, or have some commensurability with each other, the static friction will be nonzero for all choices of interaction parameters. We also comment on the nature of the depinning mechanisms and the steady states achieved by the moving chain.« less

Brillouin Scattering of Picosecond Laser Pulses in Preformed, Short-Scale-Length Plasmas

NASA Astrophysics Data System (ADS)

Gaeris, A. C.; Fisher, Y.; Delettrez, J. A.; Meyerhofer, D. D.

1996-11-01

Brillouin scattering (BS) has been studied in short-scale-length, preformed plasmas. The backscattered and specularly reflected light resulting from the interaction of high-power picosecond pulses with preformed silicon plasmas has been measured. A first laser pulse forms a short-scale-length plasma -- without significant BS -- while a second delayed pulse interacts with an expanded, drifting underdense region of the plasma with density scale length (0 <= Ln <= 600 λ _L). The pulses are generated at λ L = 1054 nm, with intensities up to 10^16 W/cm^2. The backscattered light spectra, threshold intensities, and enhanced reflectivities have been determined for different plasma-density scale lengths and are compared to Liu, Rosenbluth, and White's(C. S. Liu, M. N. Rosenbluth, and R. B. White, Phys. Fluids 17, 1211 (1974).) WKB treatment of stimulated Brillouin scattering in inhomogeneous drifting plasmas. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

Experiments on integral length scale control in atmospheric boundary layer wind tunnel

NASA Astrophysics Data System (ADS)

Varshney, Kapil; Poddar, Kamal

2011-11-01

Accurate predictions of turbulent characteristics in the atmospheric boundary layer (ABL) depends on understanding the effects of surface roughness on the spatial distribution of velocity, turbulence intensity, and turbulence length scales. Simulation of the ABL characteristics have been performed in a short test section length wind tunnel to determine the appropriate length scale factor for modeling, which ensures correct aeroelastic behavior of structural models for non-aerodynamic applications. The ABL characteristics have been simulated by using various configurations of passive devices such as vortex generators, air barriers, and slot in the test section floor which was extended into the contraction cone. Mean velocity and velocity fluctuations have been measured using a hot-wire anemometry system. Mean velocity, turbulence intensity, turbulence scale, and power spectral density of velocity fluctuations have been obtained from the experiments for various configuration of the passive devices. It is shown that the integral length scale factor can be controlled using various combinations of the passive devices.

Reynolds number scaling of straining motions in turbulence

NASA Astrophysics Data System (ADS)

Elsinga, Gerrit; Ishihara, T.; Goudar, M. V.; da Silva, C. B.; Hunt, J. C. R.

2017-11-01

Strain is an important fluid motion in turbulence as it is associated with the kinetic energy dissipation rate, vorticity stretching, and the dispersion of passive scalars. The present study investigates the scaling of the turbulent straining motions by evaluating the flow in the eigenframe of the local strain-rate tensor. The analysis is based on DNS of homogeneous isotropic turbulence covering a Reynolds number range Reλ = 34.6 - 1131. The resulting flow pattern reveals a shear layer containing tube-like vortices and a dissipation sheet, which both scale on the Kolmogorov length scale, η. The vorticity stretching motions scale on the Taylor length scale, while the flow outside the shear layer scales on the integral length scale. These scaling results are consistent with those in wall-bounded flow, which suggests a quantitative universality between the different flows. The overall coherence length of the vorticity is 120 η in all directions, which is considerably larger than the typical size of individual vortices, and reflects the importance of spatial organization at the small scales. Transitions in flow structure are identified at Reλ 45 and 250. Below these respective Reynolds numbers, the small-scale motions and the vorticity stretching motions appear underdeveloped.

Influence of Turbulent Flow and Fractal Scaling on Effective Permeability of Fracture Network

NASA Astrophysics Data System (ADS)

Zhu, J.

2017-12-01

A new approach is developed to calculate hydraulic gradient dependent effective permeability of a fractal fracture network where both laminar and turbulent flows may occur in individual fractures. A critical fracture length is used to distinguish flow characteristics in individual fractures. The developed new solutions can be used for the case of a general scaling relationship, an extension to the linear scaling. We examine the impact on the effective permeability of the network of fractal fracture network characteristics, which include the fractal scaling coefficient and exponent, fractal dimension, ratio of minimum over maximum fracture lengths. Results demonstrate that the developed solution can explain more variations of the effective permeability in relation to the fractal dimensions estimated from the field observations. At high hydraulic gradient the effective permeability decreases with the fractal scaling exponent, but increases with the fractal scaling exponent at low gradient. The effective permeability increases with the scaling coefficient, fractal dimension, fracture length ratio and maximum fracture length.

End-monomer Dynamics in Semiflexible Polymers

PubMed Central

Hinczewski, Michael; Schlagberger, Xaver; Rubinstein, Michael; Krichevsky, Oleg; Netz, Roland R.

2009-01-01

Spurred by an experimental controversy in the literature, we investigate the end-monomer dynamics of semiflexible polymers through Brownian hydrodynamic simulations and dynamic mean-field theory. Precise experimental observations over the last few years of end-monomer dynamics in the diffusion of double-stranded DNA have given conflicting results: one study indicated an unexpected Rouse-like scaling of the mean squared displacement (MSD) 〈r2(t)〉 ~ t1/2 at intermediate times, corresponding to fluctuations at length scales larger than the persistence length but smaller than the coil size; another study claimed the more conventional Zimm scaling 〈r2(t)〉 ~ t2/3 in the same time range. Using hydrodynamic simulations, analytical and scaling theories, we find a novel intermediate dynamical regime where the effective local exponent of the end-monomer MSD, α(t) = d log〈r2(t)〉/d log t, drops below the Zimm value of 2/3 for sufficiently long chains. The deviation from the Zimm prediction increases with chain length, though it does not reach the Rouse limit of 1/2. The qualitative features of this intermediate regime, found in simulations and in an improved mean-field theory for semiflexible polymers, in particular the variation of α(t) with chain and persistence lengths, can be reproduced through a heuristic scaling argument. Anomalously low values of the effective exponent α are explained by hydrodynamic effects related to the slow crossover from dynamics on length scales smaller than the persistence length to dynamics on larger length scales. PMID:21359118

Size reduction of submicron magnesium particles prepared by pulsed wire discharge

NASA Astrophysics Data System (ADS)

Duy Hieu, Nguyen; Tokoi, Yoshinori; Tanaka, Kenta; Sasaki, Toru; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi

2018-02-01

In this study, the submicron magnesium particle size was reduced by adjusting ambient gas pressure and input energy. The mean diameter of the prepared particles was determined from transmission electron microscopy images. The geometric mean particle diameter decreased with increasing relative energy, which was defined as the charging energy divided by the evaporation energy of a wire. By this method, Mg particles with a geometric mean diameter of 41.9 nm were prepared. To our knowledge, they are the smallest passivated Mg particles prepared by any method.

Enhanced performance of a structured cyclo olefin copolymer-based amorphous silicon solar cell

NASA Astrophysics Data System (ADS)

Zhan, Xinghua; Chen, Fei; Gao, Mengyu; Tie, Shengnian; Gao, Wei

2017-07-01

The submicron array was fabricated onto a cyclo olefin copolymer (COC) film by a hot embossing method. An amorphous silicon p-i-n junction and transparent conductive layers were then deposited onto it through a plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering. The efficiency of the fabricated COC-based solar cell was measured and the result demonstrated 18.6% increase of the solar cell efficiency when compared to the sample without array structure. The imprinted polymer solar cells with submicron array indeed increase their efficiency.

Fabrication of submicron metallic grids with interference and phase-mask holography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Joong-Mok; Kim, Tae-Geun; Constant, Kristen

2011-01-25

Complex, submicron Cu metallic mesh nanostructures are made by electrochemical deposition using polymer templates made from photoresist. The polymer templates are fabricated with photoresist using two-beam interference holography and phase mask holography with three diffracted beams. Freestanding metallic mesh structures are made in two separate electrodepositions with perpendicular photoresist grating templates. Cu mesh square nanostructures having large (52.6%) open areas are also made by single electrodeposition with a photoresist template made with a phase mask. These structures have potential as electrodes in photonic devices.

Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

DOEpatents

Mazur, Eric [Concord, MA; Shen, Mengyan [Arlington, MA

2008-10-28

The present invention generally provides semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

DOEpatents

Mazur, Eric , Shen; Mengyan, [Belmont, MA

2011-02-08

The present invention generally provides semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

Rayleigh instability at small length scales.

PubMed

Gopan, Nandu; Sathian, Sarith P

2014-09-01

The Rayleigh instability (also called the Plateau-Rayleigh instability) of a nanosized liquid propane thread is investigated using molecular dynamics (MD). The validity of classical predictions at small length scales is verified by comparing the temporal evolution of liquid thread simulated by MD against classical predictions. Previous works have shown that thermal fluctuations become dominant at small length scales. The role and influence of the stochastic nature of thermal fluctuations in determining the instability at small length scale is also investigated. Thermal fluctuations are seen to dominate and accelerate the breakup process only during the last stages of breakup. The simulations also reveal that the breakup profile of nanoscale threads undergo modification due to reorganization of molecules by the evaporation-condensation process.

Principles of gas phase processing of ceramics during combustion

NASA Technical Reports Server (NTRS)

Zachariah, Michael R.

1993-01-01

In recent years, ceramic materials have found applications in an increasingly wider range of industrial processes, where their unique mechanical, electrical and optical properties are exploited. Ceramics are especially useful for applications in high temperature, corrosive environments, which impose particularly stringent requirements on mechanical reliability. One approach to provide such materials is the manufacture of submicron (and more recently nanometer scale) particles, which may subsequently be sintered to produce a material with extremely high mechanical integrity. However, high quality ceramic materials can only be obtained if particles of known size, polydispersity, shape and chemical purity can be produced consistently, under well controlled conditions. These requirements are the fundamental driving force for the renewed interest in studying particle formation and growth of such materials.

Tin in a chondritic interplanetary dust particle

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1989-01-01

Submicron platey Sn-rich grains are present in chondritic porous interplanetary dust particle (IDP) W7029 A and it is the second occurrence of a tin mineral in a stratospheric micrometeorite. Selected Area Electron Diffraction data for the Sn-rich grains match with Sn2O3 and Sn3O4. The oxide(s) may have formed in the solar nebula when tin metal catalytically supported reduction of CO or during flash heating on atmospheric entry of the IDP. The presence of tin is consistent with enrichments for other volatile trace elements in chondritic IDPs and may signal an emerging trend toward nonchondritic volatile element abundances in chondritic IDPs. The observation confirms small-scale mineralogical heterogeneity in fine-grained chondritic porous interplanetary dust.

VLSI technology for smaller, cheaper, faster return link systems

NASA Technical Reports Server (NTRS)

Nanzetta, Kathy; Ghuman, Parminder; Bennett, Toby; Solomon, Jeff; Dowling, Jason; Welling, John

1994-01-01

Very Large Scale Integration (VLSI) Application-specific Integrated Circuit (ASIC) technology has enabled substantially smaller, cheaper, and more capable telemetry data systems. However, the rapid growth in available ASIC fabrication densities has far outpaced the application of this technology to telemetry systems. Available densities have grown by well over an order magnitude since NASA's Goddard Space Flight Center (GSFC) first began developing ASIC's for ground telemetry systems in 1985. To take advantage of these higher integration levels, a new generation of ASIC's for return link telemetry processing is under development. These new submicron devices are designed to further reduce the cost and size of NASA return link processing systems while improving performance. This paper describes these highly integrated processing components.

Local Measurement of the Penetration Depth in the Pnictide Superconductor Ba(Fe_0.95 Co_0.05)_2 As_2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsushita, Y.

2010-01-11

We use magnetic force microscopy (MFM) to measure the local penetration depth {lambda} in Ba(Fe{sub 0.95}Co{sub 0.05}){sub 2}As{sub 2} single crystals and use scanning SQUID susceptometry to measure its temperature variation down to 0.4 K. We observe that superfluid density {rho}{sub s} over the full temperature range is well described by a clean two-band fully gapped model. We demonstrate that MFM can measure the important and hard-to-determine absolute value of {lambda}, as well as obtain its temperature dependence and spatial homogeneity. We find {rho}{sub s} to be uniform on the submicron scale despite the highly disordered vortex pinning.

Molecular sorting by electrical steering of microtubules in kinesin-coated channels.

PubMed

van den Heuvel, Martin G L; de Graaff, Martijn P; Dekker, Cees

2006-05-12

Integration of biomolecular motors in nanoengineered structures raises the intriguing possibility of manipulating materials on nanometer scales. We have managed to integrate kinesin motor proteins in closed submicron channels and to realize active electrical control of the direction of individual kinesin-propelled microtubule filaments at Y junctions. Using this technique, we demonstrate molecular sorting of differently labeled microtubules. We attribute the steering of microtubules to electric field-induced bending of the leading tip. From measurements of the orientation-dependent electrophoretic motion of individual, freely suspended microtubules, we estimate the net applied force on the tip to be in the picoNewton range and we infer an effective charge of 12 e- per tubulin dimer under physiological conditions.

Biologically Inspired Synthesis Route to Three-Dimensionally Structured Inorganic Thin Films

DOE PAGES

Schwenzer, Birgit; Morse, Daniel E.

2008-01-01

Inorganic thin films (hydroxide, oxide, and phosphate materials) that are textured on a submicron scale have been prepared from aqueous metal salt solutions at room temperature using vapor-diffusion catalysis. This generic synthesis approach mimics the essential advantages of the catalytic and structure-directing mechanisms observed for the formation of silica skeletons of marine sponges. Chemical composition, crystallinity, and the three-dimensional morphology of films prepared by this method are extremely sensitive to changes in the synthesis conditions, such as concentrations, reaction times, and the presence and nature of substrate materials. Focusing on different materials systems, the reaction mechanism for the formation ofmore » these thin films and the influence of different reaction parameters on the product are explained.« less

Phononic band gap and mechanical anisotropy in spider silk

NASA Astrophysics Data System (ADS)

Papadopoulos, Periklis; Gomopoulos, Nikos; Kremer, Friedrich; Fytas, George

2010-03-01

Spider dragline silk is a semi-crystalline biopolymer exhibiting superior properties compared to synthetic polymers with similar chemical structure, such as polyamides. This is ascribed to the hierarchical nanostructure that is created in the spinning duct. During this process the aqueous solution of the two protein constituents of dragline silk is crystallized, while the macromolecules maintain their high orientation, leading to a high value of the Young's modulus (in the order of 10 GPa) along the fiber. We employed spontaneous Brillouin light scattering to measure the longitudinal modulus (M//,,M) along the two symmetry directions of the native fiber with increased (decreased) pre-strain created by stretching (supercontracting after hydration). A strong mechanical anisotropy is found; at about 18% strain M///M˜5. Most important, an unexpected finding is the first observation of a unidirectional hypersonic phononic band gap in biological structures. This relates to the existence of a strain-dependent correlation length of the mechanical modulus in the submicron range along the fiber axis.

Microstructural Characterization of Alloy 617 Crept into the Tertiary Regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lillo, Thomas Martin; Wright, Richard Neil

2015-07-01

The microstructure of Alloy 617 was characterized following creep tests interrupted at total creep strains ranging from 2-20%. A range of creep temperatures (750-1000oC) and initial creep stresses (10-145 MPa) produced creep test durations ranging from 1 to 5800 hours. Image analysis of optical photomicrographs on longitudinal sections of the gage length was used to document the fraction of creep porosity as a function of creep parameters. Creep porosity was negligible below tertiary creep strains of 10% and increased with tertiary creep strain, thereafter. For a given temperature and total creep strain, creep porosity increased with decreasing creep stress. Creepmore » porosity increased linearly with duration of the creep experiment. TEM performed on the gage sections did not reveal significant creep cavity formation on grain boundaries at the sub-micron level. It was concluded that the onset of tertiary creep did not result from creep cavitation and more likely arose due to the formation of low energy dislocation substructures with increasing tertiary strain.« less

Modelling of the hole-initiated impact ionization current in the framework of hydrodynamic equations

NASA Astrophysics Data System (ADS)

Lorenzini, Martino; Van Houdt, Jan

2002-02-01

Several research papers have shown the feasibility of the hydrodynamic transport model to investigate impact ionization in semiconductor devices by means of mean-energy-dependent generation rates. However, the analysis has been usually carried out for the case of the electron-initiated impact ionization process and less attention has been paid to the modelling of the generation rate due to impact ionization events initiated by holes. This paper therefore presents an original model for the hole-initiated impact ionization in silicon and validates it by comparing simulation results with substrate currents taken from p-channel transistors manufactured in a 0.35 μm CMOS technology having three different channel lengths. The experimental data are successfully reproduced over a wide range of applied voltages using only one fitting parameter. Since the impact ionization of holes triggers the mechanism responsible for the back-bias enhanced gate current in deep submicron nMOS devices, the model can be exploited in the development of non-volatile memories programmed by secondary electron injection.

White light generation using photonic crystal fiber with sub-micron circular lattice

NASA Astrophysics Data System (ADS)

Saghaei, Hamed; Ghanbari, Ashkan

2017-08-01

In this paper, we study a photonic crystal fiber (PCF) with circular lattice and engineer linear and nonlinear parameters by varying the diameter of air-holes. It helps us obtain low and high zero dispersion wavelengths in the visible and nearinfrared regions. We numerically demonstrate that by launching 100 fs input pulses of 1, 2, and 5 kW peak powers with center wavelength of 532 nm from an unamplified Ti:sapphire laser into a 100 mm length of the engineered PCF, supercontinua as wide as 290, 440 and 830 nm can be obtained, respectively. The spectral broadening is due to the combined action of self-phase modulation, stimulated Raman scattering and parametric four-wave-mixing generation of the pump pulses. The third and the widest spectrum covers the entire visible range and a part of near infrared region making it a suitable source for both white light applications and optical coherence tomography to measure retinal oxygen metabolic response to systemic oxygenation.

First PIC simulations modeling the interaction of ultra-intense lasers with sub-micron, liquid crystal targets

NASA Astrophysics Data System (ADS)

McMahon, Matthew; Poole, Patrick; Willis, Christopher; Andereck, David; Schumacher, Douglass

2014-10-01

We recently introduced liquid crystal films as on-demand, variable thickness (50-5000 nanometers), low cost targets for intense laser experiments. Here we present the first particle-in-cell (PIC) simulations of short pulse laser excitation of liquid crystal targets treating Scarlet (OSU) class lasers using the PIC code LSP. In order to accurately model the target evolution, a low starting temperature and field ionization model are employed. This is essential as large starting temperatures, often used to achieve large Debye lengths, lead to expansion of the target causing significant reduction of the target density before the laser pulse can interact. We also present an investigation of the modification of laser pulses by very thin targets. This work was supported by the DARPA PULSE program through a grant from ARMDEC, by the US Department of Energy under Contract No. DE-NA0001976, and allocations of computing time from the Ohio Supercomputing Center.

Saw-tooth refractive x-ray optics with sub-micron resolution

NASA Astrophysics Data System (ADS)

Cederstrom, Bjorn; Ribbing, Carolina; Lundqvist, Mats

2002-11-01

Saw-tooth refractive x-ray lenses have been used to focus a synchrotron beam to sub-μm line width. These lenses are free from spherical aberration and work in analogy with 1-D focusing parabolic compound refractive lenses. However, the focal length can be varied by a simple mechanical procedure. Silicon lenses were fabricated by wet anisotropic etching, and epoxy replicas were molded from the silicon masters. Theses lenses provided 1-D intensity gains up to a factor of 40 and the smallest focal line width was 0.74 μm, very close to the theoretical expectation. Two crossed lenses were put in series to obtain 2-D focusing and the 80 μm by 275 μm source was imaged to 1.0 μm by 5.4 μm. Beryllium lenses were fabricated using conventional computer-controlled milling. The focal line width was 1.7 μm, nearly 3 times larger than predicted by theory. This can be attributed to large surface roughness and a bent lens shape.

Fiber optic interferometry for industrial process monitoring and control applications

NASA Astrophysics Data System (ADS)

Marcus, Michael A.

2002-02-01

Over the past few years we have been developing applications for a high-resolution (sub-micron accuracy) fiber optic coupled dual Michelson interferometer-based instrument. It is being utilized in a variety of applications including monitoring liquid layer thickness uniformity on coating hoppers, film base thickness uniformity measurement, digital camera focus assessment, optical cell path length assessment and imager and wafer surface profile mapping. The instrument includes both coherent and non-coherent light sources, custom application dependent optical probes and sample interfaces, a Michelson interferometer, custom electronics, a Pentium-based PC with data acquisition cards and LabWindows CVI or LabView based application specific software. This paper describes the development evolution of this instrument platform and applications highlighting robust instrument design, hardware, software, and user interfaces development. The talk concludes with a discussion of a new high-speed instrument configuration, which can be utilized for high speed surface profiling and as an on-line web thickness gauge.

Direct determination of the local Hamaker constant of inorganic surfaces based on scanning force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krajina, Brad A.; Kocherlakota, Lakshmi S.; Overney, René M., E-mail: roverney@u.washington.edu

The energetics involved in the bonding fluctuations between nanometer-sized silicon dioxide (SiO{sub 2}) probes and highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS{sub 2}) could be quantified directly and locally on the submicron scale via a time-temperature superposition analysis of the lateral forces between scanning force microscopy silicon dioxide probes and inorganic sample surfaces. The so-called “intrinsic friction analysis” (IFA) provided direct access to the Hamaker constants for HOPG and MoS{sub 2}, as well as the control sample, calcium fluoride (CaF{sub 2}). The use of scanning probe enables nanoscopic analysis of bonding fluctuations, thereby overcoming challenges associated with largermore » scale inhomogeneity and surface roughness common to conventional techniques used to determine surface free energies and dielectric properties. A complementary numerical analysis based on optical and electron energy loss spectroscopy and the Lifshitz quantum electrodynamic theory of van der Waals interactions is provided and confirms quantitatively the IFA results.« less

Direct determination of the local Hamaker constant of inorganic surfaces based on scanning force microscopy

NASA Astrophysics Data System (ADS)

Krajina, Brad A.; Kocherlakota, Lakshmi S.; Overney, René M.

2014-10-01

The energetics involved in the bonding fluctuations between nanometer-sized silicon dioxide (SiO2) probes and highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS2) could be quantified directly and locally on the submicron scale via a time-temperature superposition analysis of the lateral forces between scanning force microscopy silicon dioxide probes and inorganic sample surfaces. The so-called "intrinsic friction analysis" (IFA) provided direct access to the Hamaker constants for HOPG and MoS2, as well as the control sample, calcium fluoride (CaF2). The use of scanning probe enables nanoscopic analysis of bonding fluctuations, thereby overcoming challenges associated with larger scale inhomogeneity and surface roughness common to conventional techniques used to determine surface free energies and dielectric properties. A complementary numerical analysis based on optical and electron energy loss spectroscopy and the Lifshitz quantum electrodynamic theory of van der Waals interactions is provided and confirms quantitatively the IFA results.

Direct determination of the local Hamaker constant of inorganic surfaces based on scanning force microscopy.

PubMed

Krajina, Brad A; Kocherlakota, Lakshmi S; Overney, René M

2014-10-28

The energetics involved in the bonding fluctuations between nanometer-sized silicon dioxide (SiO2) probes and highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS2) could be quantified directly and locally on the submicron scale via a time-temperature superposition analysis of the lateral forces between scanning force microscopy silicon dioxide probes and inorganic sample surfaces. The so-called "intrinsic friction analysis" (IFA) provided direct access to the Hamaker constants for HOPG and MoS2, as well as the control sample, calcium fluoride (CaF2). The use of scanning probe enables nanoscopic analysis of bonding fluctuations, thereby overcoming challenges associated with larger scale inhomogeneity and surface roughness common to conventional techniques used to determine surface free energies and dielectric properties. A complementary numerical analysis based on optical and electron energy loss spectroscopy and the Lifshitz quantum electrodynamic theory of van der Waals interactions is provided and confirms quantitatively the IFA results.

Nanoscale infrared spectroscopy as a non-destructive probe of extraterrestrial samples.

PubMed

Dominguez, Gerardo; Mcleod, A S; Gainsforth, Zack; Kelly, P; Bechtel, Hans A; Keilmann, Fritz; Westphal, Andrew; Thiemens, Mark; Basov, D N

2014-12-09

Advances in the spatial resolution of modern analytical techniques have tremendously augmented the scientific insight gained from the analysis of natural samples. Yet, while techniques for the elemental and structural characterization of samples have achieved sub-nanometre spatial resolution, infrared spectral mapping of geochemical samples at vibrational 'fingerprint' wavelengths has remained restricted to spatial scales >10 μm. Nevertheless, infrared spectroscopy remains an invaluable contactless probe of chemical structure, details of which offer clues to the formation history of minerals. Here we report on the successful implementation of infrared near-field imaging, spectroscopy and analysis techniques capable of sub-micron scale mineral identification within natural samples, including a chondrule from the Murchison meteorite and a cometary dust grain (Iris) from NASA's Stardust mission. Complementary to scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy probes, this work evidences a similarity between chondritic and cometary materials, and inaugurates a new era of infrared nano-spectroscopy applied to small and invaluable extraterrestrial samples.

Excess entropy scaling for the segmental and global dynamics of polyethylene melts.

PubMed

Voyiatzis, Evangelos; Müller-Plathe, Florian; Böhm, Michael C

2014-11-28

The range of validity of the Rosenfeld and Dzugutov excess entropy scaling laws is analyzed for unentangled linear polyethylene chains. We consider two segmental dynamical quantities, i.e. the bond and the torsional relaxation times, and two global ones, i.e. the chain diffusion coefficient and the viscosity. The excess entropy is approximated by either a series expansion of the entropy in terms of the pair correlation function or by an equation of state for polymers developed in the context of the self associating fluid theory. For the whole range of temperatures and chain lengths considered, the two estimates of the excess entropy are linearly correlated. The scaled bond and torsional relaxation times fall into a master curve irrespective of the chain length and the employed scaling scheme. Both quantities depend non-linearly on the excess entropy. For a fixed chain length, the reduced diffusion coefficient and viscosity scale linearly with the excess entropy. An empirical reduction to a chain length-independent master curve is accessible for both dynamic quantities. The Dzugutov scheme predicts an increased value of the scaled diffusion coefficient with increasing chain length which contrasts physical expectations. The origin of this trend can be traced back to the density dependence of the scaling factors. This finding has not been observed previously for Lennard-Jones chain systems (Macromolecules, 2013, 46, 8710-8723). Thus, it limits the applicability of the Dzugutov approach to polymers. In connection with diffusion coefficients and viscosities, the Rosenfeld scaling law appears to be of higher quality than the Dzugutov approach. An empirical excess entropy scaling is also proposed which leads to a chain length-independent correlation. It is expected to be valid for polymers in the Rouse regime.

Scaling in Free-Swimming Fish and Implications for Measuring Size-at-Time in the Wild

PubMed Central

Broell, Franziska; Taggart, Christopher T.

2015-01-01

This study was motivated by the need to measure size-at-age, and thus growth rate, in fish in the wild. We postulated that this could be achieved using accelerometer tags based first on early isometric scaling models that hypothesize that similar animals should move at the same speed with a stroke frequency that scales with length-1, and second on observations that the speed of primarily air-breathing free-swimming animals, presumably swimming ‘efficiently’, is independent of size, confirming that stroke frequency scales as length-1. However, such scaling relations between size and swimming parameters for fish remain mostly theoretical. Based on free-swimming saithe and sturgeon tagged with accelerometers, we introduce a species-specific scaling relationship between dominant tail beat frequency (TBF) and fork length. Dominant TBF was proportional to length-1 (r2 = 0.73, n = 40), and estimated swimming speed within species was independent of length. Similar scaling relations accrued in relation to body mass-0.29. We demonstrate that the dominant TBF can be used to estimate size-at-time and that accelerometer tags with onboard processing may be able to provide size-at-time estimates among free-swimming fish and thus the estimation of growth rate (change in size-at-time) in the wild. PMID:26673777

BMP delivery complements the guiding effect of scaffold architecture without altering bone microstructure in critical-sized long bone defects: A multiscale analysis.

PubMed

Cipitria, A; Wagermaier, W; Zaslansky, P; Schell, H; Reichert, J C; Fratzl, P; Hutmacher, D W; Duda, G N

2015-09-01

Scaffold architecture guides bone formation. However, in critical-sized long bone defects additional BMP-mediated osteogenic stimulation is needed to form clinically relevant volumes of new bone. The hierarchical structure of bone determines its mechanical properties. Yet, the micro- and nanostructure of BMP-mediated fast-forming bone has not been compared with slower regenerating bone without BMP. We investigated the combined effects of scaffold architecture (physical cue) and BMP stimulation (biological cue) on bone regeneration. It was hypothesized that a structured scaffold directs tissue organization through structural guidance and load transfer, while BMP stimulation accelerates bone formation without altering the microstructure at different length scales. BMP-loaded medical grade polycaprolactone-tricalcium phosphate scaffolds were implanted in 30mm tibial defects in sheep. BMP-mediated bone formation after 3 and 12 months was compared with slower bone formation with a scaffold alone after 12 months. A multiscale analysis based on microcomputed tomography, histology, polarized light microscopy, backscattered electron microscopy, small angle X-ray scattering and nanoindentation was used to characterize bone volume, collagen fiber orientation, mineral particle thickness and orientation, and local mechanical properties. Despite different observed kinetics in bone formation, similar structural properties on a microscopic and sub-micron level seem to emerge in both BMP-treated and scaffold only groups. The guiding effect of the scaffold architecture is illustrated through structural differences in bone across different regions. In the vicinity of the scaffold increased tissue organization is observed at 3 months. Loading along the long bone axis transferred through the scaffold defines bone micro- and nanostructure after 12 months. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Age-related Changes in the Fracture Resistance of Male Fischer F344 Rat Bone

PubMed Central

Uppuganti, Sasidhar; Granke, Mathilde; Makowski, Alexander J.; Does, Mark D.; Nyman, Jeffry S.

2015-01-01

In addition to the loss in bone volume that occurs with age, there is a decline in material properties. To test new therapies or diagnostic tools that target such properties as material strength and toughness, a pre-clinical model of aging would be useful in which changes in bone are similar to those that occur with aging in humans. Toward that end, we hypothesized that similar to human bone, the estimated toughness and material strength of cortical bone at the apparent-level decreases with age in the male Fischer F344 rat. In addition, we tested whether the known decline in trabecular architecture in rats translated to an age-related decrease in vertebra (VB) strength and whether non-X-ray techniques could quantify tissue changes at micron and sub-micron length scales. Bones were harvested from 6-, 12-, and 24-month (mo.) old rats (n=12 per age). Despite a loss in trabecular bone with age, VB compressive strength was similar among the age groups. Similarly, whole-bone strength (peak force) in bending was maintained (femur) or increased (radius) with aging. There was though an age-related decrease in post-yield toughness (radius) and bending strength (femur). The ability to resist crack initiation was actually higher for the 12-mo. and 24-mo. than for 6-mo. rats (notch femur), but the estimated work to propagate the crack was less for the aged bone. For the femur diaphysis region, porosity increased while bound water decreased with age. For the radius diaphysis, there was an age-related increase in non-enzymatic and mature enzymatic collagen crosslinks. Both Raman spectroscopy and reference point indentation detected differences in tissue properties with age, though the trends did not necessarily match observations from human tissue. PMID:26610688

Age-related changes in the fracture resistance of male Fischer F344 rat bone.

PubMed

Uppuganti, Sasidhar; Granke, Mathilde; Makowski, Alexander J; Does, Mark D; Nyman, Jeffry S

2016-02-01

In addition to the loss in bone volume that occurs with age, there is a decline in material properties. To test new therapies or diagnostic tools that target such properties as material strength and toughness, a pre-clinical model of aging would be useful in which changes in bone are similar to those that occur with aging in humans. Toward that end, we hypothesized that similar to human bone, the estimated toughness and material strength of cortical bone at the apparent-level decreases with age in the male Fischer F344 rat. In addition, we tested whether the known decline in trabecular architecture in rats translated to an age-related decrease in vertebra (VB) strength and whether non-X-ray techniques could quantify tissue changes at micron and sub-micron length scales. Bones were harvested from 6-, 12-, and 24-month (mo.) old rats (n=12 per age). Despite a loss in trabecular bone with age, VB compressive strength was similar among the age groups. Similarly, whole-bone strength (peak force) in bending was maintained (femur) or increased (radius) with aging. There was though an age-related decrease in post-yield toughness (radius) and bending strength (femur). The ability to resist crack initiation was actually higher for the 12-mo. and 24-mo. than for 6-mo. rats (notch femur), but the estimated work to propagate the crack was less for the aged bone. For the femur diaphysis region, porosity increased while bound water decreased with age. For the radius diaphysis, there was an age-related increase in non-enzymatic and mature enzymatic collagen crosslinks. Raman spectroscopy analysis of embedded cross-sections of the tibia mid-shaft detected an increase in carbonate subsitution with advanced aging for both inner and outer tissue. Published by Elsevier Inc.

Nanoparticles in liquid crystals, and liquid crystals in nanoparticles

NASA Astrophysics Data System (ADS)

de Pablo, Juan

2015-03-01

Liquid crystals are remarkably sensitive to interfacial interactions. Small perturbations at a liquid crystal interface, for example, can be propagated over relatively long length scales, thereby providing the basis for a wide range of applications that rely on amplification of molecular events into macroscopic observables. Our recent research efforts have focused on the reverse phenomenon; that is, we have sought to manipulate the interfacial assembly of nanoparticles or the organization of surface active molecules by controlling the structure of a liquid crystal. This presentation will consist of a review of the basic principles that are responsible for liquid crystal-mediated interactions, followed by demonstrations of those principles in the context of two types of systems. In the first, a liquid crystal is used to direct the assembly of nanoparticles; through a combination of molecular and continuum models, it is found that minute changes in interfacial energy and particle size lead to liquid-crystal induced attractions that can span multiple orders of magnitude. Theoretical predictions are confirmed by experimental observations, which also suggest that LC-mediated assembly provides an effective means for fabrication of plasmonic devices. In the second type of system, the structure of a liquid crystal is controlled by confinement in submicron droplets. The morphology of the liquid crystal in a drop depends on a delicate balance between bulk and interfacial contributions to the free energy; that balance can be easily perturbed by adsorption of analytes or nanoparticles at the interface, thereby providing the basis for development of hierarchical assembly of responsive, anisotropic materials. Theoretical predictions also indicate that the three-dimensional order of a liquid crystal can be projected onto a two-dimensional interface, and give rise to novel nanostructures that are not found in simple isotropic fluids.

Applications of the discrete Enskog-Boltzmann approach

NASA Astrophysics Data System (ADS)

Chu, Kwang-Hua Rainer

1998-08-01

The continuous progress of micromachining technology has led to a growing interest in MicroElectroMechanical System (MEMS) for applications ranging from simple microsensors and microactuators to sophisticated microsystems. The characteristic length scale of these microdevices will be of the order of sub-microns so that the gas flow in this environment is within the rarified gas (RG) regime. In this PhD work, the mass/momentum/energy transport of the monatomic gases along the microchannel and the dispersion/attenuation of 1-D ultrasound propagation (plane wave) of RG are investigated by using the Discrete Enskog-Boltzmann approaches. We applied the 4-velocity coplanar model to plane Poiseuille flow of RG in microchannels. Firstly we reported a steady-state solution for this flow with a final-stage uniform density distribution. Then, we modified the model by introducing a density ratio to accomodate the density variations along the microchannel and to include the grazing-collision effects. We also borrowed thee idea from the Extended Irreversible/Reversible Thermodynamics to derive the pressure-gradient for the dimensional velocity field. Our results show the Knudsen minimum of the non- dimensional volume flow rate for Knudsen number (Kn) around 1.5. Using the macroscopic velocity fields, with Cercignani's comments for the 'Kinetic Temperature', we can calculate the related temperature distribution across the microchannel. We also checked the thermodynamic or equilibrium properties of 4-, 6-, and 8-velocity models, by calculating the dispersion relation of 1-D plane ultrasound wave propagation in the RG regime which has large Kn of O(1). The results (after comparison with the measurements) confirmed that the 4-velocity model is the most suitable model for our applications.

A novel inlet system for online chemical analysis of semi-volatile submicron particulate matter

NASA Astrophysics Data System (ADS)

Eichler, P.; Müller, M.; D'Anna, B.; Wisthaler, A.

2015-03-01

We herein present a novel modular inlet system designed to be coupled to low-pressure gas analyzers for online chemical characterization of semi-volatile submicron particles. The "chemical analysis of aerosol online" (CHARON) inlet consists of a gas-phase denuder for stripping off gas-phase analytes, an aerodynamic lens for particle collimation combined with an inertial sampler for the particle-enriched flow and a thermodesorption unit for particle volatilization prior to chemical analysis. The denuder was measured to remove gas-phase organics with an efficiency > 99.999% and to transmit particles in the 100-750 nm size range with a 75-90% efficiency. The measured average particle enrichment factor in the subsampling flow from the aerodynamic lens was 25.6, which is a factor of 3 lower than the calculated theoretical optimum. We coupled the CHARON inlet to a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) which quantitatively detects most organic analytes and ammonia. The combined CHARON-PTR-ToF-MS setup is thus capable of measuring both the organic and the ammonium fraction in submicron particles in real time. Individual organic compounds can be detected down to levels of 10-20 ng m-3. Two proof-of-principle studies were carried out for demonstrating the analytical power of this new instrumental setup: (i) oxygenated organics and their partitioning between the gas and the particulate phase were observed from the reaction of limonene with ozone and (ii) nicotine was measured in cigarette smoke particles demonstrating that selected organic target compounds can be detected in submicron particles in real time.

In situ 3-D mapping of pore structures and hollow grains of interplanetary dust particles with phase contrast X-ray nanotomography

NASA Astrophysics Data System (ADS)

Hu, Z. W.; Winarski, R. P.

2016-09-01

Unlocking the 3-D structure and properties of intact chondritic porous interplanetary dust particles (IDPs) in nanoscale detail is challenging, which is also complicated by atmospheric entry heating, but is important for advancing our understanding of the formation and origins of IDPs and planetary bodies as well as dust and ice agglomeration in the outer protoplanetary disk. Here, we show that indigenous pores, pristine grains, and thermal alteration products throughout intact particles can be noninvasively visualized and distinguished morphologically and microstructurally in 3-D detail down to ~10 nm by exploiting phase contrast X-ray nanotomography. We have uncovered the surprisingly intricate, submicron, and nanoscale pore structures of a ~10-μm-long porous IDP, consisting of two types of voids that are interconnected in 3-D space. One is morphologically primitive and mostly submicron-sized intergranular voids that are ubiquitous; the other is morphologically advanced and well-defined intragranular nanoholes that run through the approximate centers of ~0.3 μm or lower submicron hollow grains. The distinct hollow grains exhibit complex 3-D morphologies but in 2-D projections resemble typical organic hollow globules observed by transmission electron microscopy. The particle, with its outer region characterized by rough vesicular structures due to thermal alteration, has turned out to be an inherently fragile and intricately submicron- and nanoporous aggregate of the sub-μm grains or grain clumps that are delicately bound together frequently with little grain-to-grain contact in 3-D space.

Geant4-DNA track-structure simulations for gold nanoparticles: The importance of electron discrete models in nanometer volumes.

PubMed

Sakata, Dousatsu; Kyriakou, Ioanna; Okada, Shogo; Tran, Hoang N; Lampe, Nathanael; Guatelli, Susanna; Bordage, Marie-Claude; Ivanchenko, Vladimir; Murakami, Koichi; Sasaki, Takashi; Emfietzoglou, Dimitris; Incerti, Sebastien

2018-05-01

Gold nanoparticles (GNPs) are known to enhance the absorbed dose in their vicinity following photon-based irradiation. To investigate the therapeutic effectiveness of GNPs, previous Monte Carlo simulation studies have explored GNP dose enhancement using mostly condensed-history models. However, in general, such models are suitable for macroscopic volumes and for electron energies above a few hundred electron volts. We have recently developed, for the Geant4-DNA extension of the Geant4 Monte Carlo simulation toolkit, discrete physics models for electron transport in gold which include the description of the full atomic de-excitation cascade. These models allow event-by-event simulation of electron tracks in gold down to 10 eV. The present work describes how such specialized physics models impact simulation-based studies on GNP-radioenhancement in a context of x-ray radiotherapy. The new discrete physics models are compared to the Geant4 Penelope and Livermore condensed-history models, which are being widely used for simulation-based NP radioenhancement studies. An ad hoc Geant4 simulation application has been developed to calculate the absorbed dose in liquid water around a GNP and its radioenhancement, caused by secondary particles emitted from the GNP itself, when irradiated with a monoenergetic electron beam. The effect of the new physics models is also quantified in the calculation of secondary particle spectra, when originating in the GNP and when exiting from it. The new physics models show similar backscattering coefficients with the existing Geant4 Livermore and Penelope models in large volumes for 100 keV incident electrons. However, in submicron sized volumes, only the discrete models describe the high backscattering that should still be present around GNPs at these length scales. Sizeable differences (mostly above a factor of 2) are also found in the radial distribution of absorbed dose and secondary particles between the new and the existing Geant4 models. The degree to which these differences are due to intrinsic limitations of the condensed-history models or to differences in the underling scattering cross sections requires further investigation. Improved physics models for gold are necessary to better model the impact of GNPs in radiotherapy via Monte Carlo simulations. We implemented discrete electron transport models for gold in Geant4 that is applicable down to 10 eV including the modeling of the full de-excitation cascade. It is demonstrated that the new model has a significant positive impact on particle transport simulations in gold volumes with submicron dimensions compared to the existing Livermore and Penelope condensed-history models of Geant4. © 2018 American Association of Physicists in Medicine.

Genetic parameters for different growth scales in GIFT strain of Nile tilapia (Oreochromis niloticus).

PubMed

He, J; Gao, H; Xu, P; Yang, R

2015-12-01

Body weight, length, width and depth at two growth stages were observed for a total of 5015 individuals of GIFT strain, along with a pedigree including 5588 individuals from 104 sires and 162 dams was collected. Multivariate animal models and a random regression model were used to genetically analyse absolute and relative growth scales of these growth traits. In absolute growth scale, the observed growth traits had moderate heritabilities ranging from 0.321 to 0.576, while pairwise ratios between body length, width and depth were lowly inherited and maximum heritability was only 0.146 for length/depth. All genetic correlations were above 0.5 between pairwise growth traits and genetic correlation between length/width and length/depth varied between both growth stages. Based on those estimates, selection index of multiple traits of interest can be formulated in future breeding program to improve genetically body weight and morphology of the GIFT strain. In relative growth scale, heritabilities in relative growths of body length, width and depth to body weight were 0.257, 0.412 and 0.066, respectively, while genetic correlations among these allometry scalings were above 0.8. Genetic analysis for joint allometries of body weight to body length, width and depth will contribute to genetically regulate the growth rate between body shape and body weight. © 2015 Blackwell Verlag GmbH.

Desert bird associations with broad-scale boundary length: Applications in avian conservation

USGS Publications Warehouse

Gutzwiller, K.J.; Barrow, W.C.

2008-01-01

1. Current understanding regarding the effects of boundaries on bird communities has originated largely from studies of forest-non-forest boundaries in mesic systems. To assess whether broad-scale boundary length can affect bird community structure in deserts, and to identify patterns and predictors of species' associations useful in avian conservation, we studied relations between birds and boundary-length variables in Chihuahuan Desert landscapes. Operationally, a boundary was the border between two adjoining land covers, and broad-scale boundary length was the total length of such borders in a large area. 2. Within 2-km radius areas, we measured six boundary-length variables. We analysed bird-boundary relations for 26 species, tested for assemblage-level patterns in species' associations with boundary-length variables, and assessed whether body size, dispersal ability and cowbird-host status were correlates of these associations. 3. The abundances or occurrences of a significant majority of species were associated with boundary-length variables, and similar numbers of species were related positively and negatively to boundary-length variables. 4. Disproportionately small numbers of species were correlated with total boundary length, land-cover boundary length and shrubland-grassland boundary length (variables responsible for large proportions of boundary length). Disproportionately large numbers of species were correlated with roadside boundary length and riparian vegetation-grassland boundary length (variables responsible for small proportions of boundary length). Roadside boundary length was associated (positively and negatively) with the most species. 5. Species' associations with boundary-length variables were not correlated with body size, dispersal ability or cowbird-host status. 6. Synthesis and applications. For the species we studied, conservationists can use the regressions we report as working models to anticipate influences of boundary-length changes on bird abundance and occurrence, and to assess avifaunal composition for areas under consideration for protection. Boundary-length variables associated with a disproportionate or large number of species can be used as foci for landscape management. Assessing the underlying causes of bird-boundary relations may improve the prediction accuracy of associated models. We therefore advocate local- and broad-scale manipulative experiments involving the boundary types with which species were correlated, as indicated by the regressions. ?? 2008 The Authors.

Resolving Properties of Polymers and Nanoparticle Assembly through Coarse-Grained Computational Studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grest, Gary S.

2017-09-01

Coupled length and time scales determine the dynamic behavior of polymers and polymer nanocomposites and underlie their unique properties. To resolve the properties over large time and length scales it is imperative to develop coarse grained models which retain the atomistic specificity. Here we probe the degree of coarse graining required to simultaneously retain significant atomistic details a nd access large length and time scales. The degree of coarse graining in turn sets the minimum length scale instrumental in defining polymer properties and dynamics. Using polyethylene as a model system, we probe how the coarse - graining scale affects themore » measured dynamics with different number methylene group s per coarse - grained beads. Using these models we simulate polyethylene melts for times over 500 ms to study the viscoelastic properties of well - entangled polymer melts and large nanoparticle assembly as the nanoparticles are driven close enough to form nanostructures.« less

Effect of length scale on mechanical properties of Al-Cu eutectic alloy

NASA Astrophysics Data System (ADS)

Tiwary, C. S.; Roy Mahapatra, D.; Chattopadhyay, K.

2012-10-01

This paper attempts a quantitative understanding of the effect of length scale on two phase eutectic structure. We first develop a model that considers both the elastic and plastic properties of the interface. Using Al-Al2Cu lamellar eutectic as model system, the parameters of the model were experimentally determined using indentation technique. The model is further validated using the results of bulk compression testing of the eutectics having different length scales.

Energy Spectra of Higher Reynolds Number Turbulence by the DNS with up to 122883 Grid Points

NASA Astrophysics Data System (ADS)

Ishihara, Takashi; Kaneda, Yukio; Morishita, Koji; Yokokawa, Mitsuo; Uno, Atsuya

2014-11-01

Large-scale direct numerical simulations (DNS) of forced incompressible turbulence in a periodic box with up to 122883 grid points have been performed using K computer. The maximum Taylor-microscale Reynolds number Rλ, and the maximum Reynolds number Re based on the integral length scale are over 2000 and 105, respectively. Our previous DNS with Rλ up to 1100 showed that the energy spectrum has a slope steeper than - 5 / 3 (the Kolmogorov scaling law) by factor 0 . 1 at the wavenumber range (kη < 0 . 03). Here η is the Kolmogorov length scale. Our present DNS at higher resolutions show that the energy spectra with different Reynolds numbers (Rλ > 1000) are well normalized not by the integral length-scale but by the Kolmogorov length scale, at the wavenumber range of the steeper slope. This result indicates that the steeper slope is not inherent character in the inertial subrange, and is affected by viscosity.

Resolving Dynamic Properties of Polymers through Coarse-Grained Computational Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salerno, K. Michael; Agrawal, Anupriya; Perahia, Dvora

2016-02-05

Coupled length and time scales determine the dynamic behavior of polymers and underlie their unique viscoelastic properties. To resolve the long-time dynamics it is imperative to determine which time and length scales must be correctly modeled. In this paper, we probe the degree of coarse graining required to simultaneously retain significant atomistic details and access large length and time scales. The degree of coarse graining in turn sets the minimum length scale instrumental in defining polymer properties and dynamics. Using linear polyethylene as a model system, we probe how the coarse-graining scale affects the measured dynamics. Iterative Boltzmann inversion ismore » used to derive coarse-grained potentials with 2–6 methylene groups per coarse-grained bead from a fully atomistic melt simulation. We show that atomistic detail is critical to capturing large-scale dynamics. Finally, using these models we simulate polyethylene melts for times over 500 μs to study the viscoelastic properties of well-entangled polymer melts.« less

Electropolishing effect on roughness metrics of ground stainless steel: a length scale study

NASA Astrophysics Data System (ADS)

Nakar, Doron; Harel, David; Hirsch, Baruch

2018-03-01

Electropolishing is a widely-used electrochemical surface finishing process for metals. The electropolishing of stainless steel has vast commercial application, such as improving corrosion resistance, improving cleanness, and brightening. The surface topography characterization is performed using several techniques with different lateral resolutions and length scales, from atomic force microscopy in the nano-scale (<0.1 µm) to stylus and optical profilometry in the micro- and mesoscales (0.1 µm-1 mm). This paper presents an experimental length scale study of the surface texture of ground stainless steel followed by an electropolishing process in the micro and meso lateral scales. Both stylus and optical profilometers are used, and multiple cut-off lengths of the standard Gaussian filter are adopted. While the commonly used roughness amplitude parameters (Ra, Rq and Rz) fail to characterize electropolished textures, the root mean square slope (RΔq) is found to better describe the electropolished surfaces and to be insensitive to scale.

Length scales and pinning of interfaces

PubMed Central

Tan, Likun

2016-01-01

The pinning of interfaces and free discontinuities by defects and heterogeneities plays an important role in a variety of phenomena, including grain growth, martensitic phase transitions, ferroelectricity, dislocations and fracture. We explore the role of length scale on the pinning of interfaces and show that the width of the interface relative to the length scale of the heterogeneity can have a profound effect on the pinning behaviour, and ultimately on hysteresis. When the heterogeneity is large, the pinning is strong and can lead to stick–slip behaviour as predicted by various models in the literature. However, when the heterogeneity is small, we find that the interface may not be pinned in a significant manner. This shows that a potential route to making materials with low hysteresis is to introduce heterogeneities at a length scale that is small compared with the width of the phase boundary. Finally, the intermediate setting where the length scale of the heterogeneity is comparable to that of the interface width is characterized by complex interactions, thereby giving rise to a non-monotone relationship between the relative heterogeneity size and the critical depinning stress. PMID:27002068

Current sheet extension and reconnection scaling in collisionless, hyperresistive, Hall MHD

NASA Astrophysics Data System (ADS)

Sullivan, B. P.; Bhattacharjee, A.; Huang, Y. M.

2009-11-01

We present Sweet-Parker type scaling arguments in the context of collisionless, hyper-resistive, Hall magnetohyrdodynamics (MHD). The predicted steady state scalings are consistent with those found by Chac'on et al. [PRL 99, 235001 (2007)], and Uzdensky, [PoP 16, 040702 (2009)], though our methods differ slightly. As with those studies, no prediction of electron dissipation region length is made. Numerical experiments confirm that both cusp like & extended geometries are realizable. Importantly, the length of the electron dissipation region (taken as a parameter by several recent studies) is found to depend on the level of hyper-resistivity. Although hyper-resistivity can produce modestly extended dissipation regions, the dissipation regions observed here are much shorter than those seen in many kinetic studies. The thickness of the dissipation region scales in a similar way as the length,so that the reconnection rate is not strongly sensitive to the level of hyperresistivity. The length of the electron dissipation region depends on electron inertia as well.The limitations of scaling theories that do not predict the length of the electron dissipation region are emphasized.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirtley, John R., E-mail: jkirtley@stanford.edu; Rosenberg, Aaron J.; Palmstrom, Johanna C.

Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ{sub 0}/Hz{sup 1/2}. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes themore » spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.« less

Kinetics of Sub-Micron Grain Size Refinement in 9310 Steel

NASA Astrophysics Data System (ADS)

Kozmel, Thomas; Chen, Edward Y.; Chen, Charlie C.; Tin, Sammy

2014-05-01

Recent efforts have focused on the development of novel manufacturing processes capable of producing microstructures dominated by sub-micron grains. For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermo-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel. Starting with initial bainitic grain sizes of 40 to 50 μm, various levels of grain refinement were observed following hot deformation of 9310 steel samples at temperatures and strain rates ranging from 755 K to 922 K (482 °C and 649 °C) and 1 to 0.001/s, respectively. The resulting deformation microstructures were characterized using scanning electron microscopy and electron backscatter diffraction techniques to quantify the extent of carbide coarsening and grain refinement occurring during deformation. Microstructural models based on the Zener-Holloman parameter were developed and modified to include the effect of the ferrite/carbide interactions within the system. These models were shown to effectively correlate microstructural attributes to the thermal mechanical processing parameters.

Scanning digital lithography providing high speed large area patterning with diffraction limited sub-micron resolution

NASA Astrophysics Data System (ADS)

Wen, Sy-Bor; Bhaskar, Arun; Zhang, Hongjie

2018-07-01

A scanning digital lithography system using computer controlled digital spatial light modulator, spatial filter, infinity correct optical microscope and high precision translation stage is proposed and examined. Through utilizing the spatial filter to limit orders of diffraction modes for light delivered from the spatial light modulator, we are able to achieve diffraction limited deep submicron spatial resolution with the scanning digital lithography system by using standard one inch level optical components with reasonable prices. Raster scanning of this scanning digital lithography system using a high speed high precision x-y translation stage and piezo mount to real time adjust the focal position of objective lens allows us to achieve large area sub-micron resolved patterning with high speed (compared with e-beam lithography). It is determined in this study that to achieve high quality stitching of lithography patterns with raster scanning, a high-resolution rotation stage will be required to ensure the x and y directions of the projected pattern are in the same x and y translation directions of the nanometer precision x-y translation stage.

Submicron particulate organic matter in the urban atmosphere: a new method for real-time measurement, molecular-level characterization and source apportionment

NASA Astrophysics Data System (ADS)

Müller, Markus; Eichler, Philipp; D'Anna, Barbara; Tan, Wen; Wisthaler, Armin

2017-04-01

We used a novel chemical analytical method for measuring submicron particulate organic matter in the atmosphere of three European cities (Innsbruck, Lyon, Valencia). Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) was used in combination with the "chemical analysis of aerosol online" (CHARON) inlet for detecting particulate organic compounds on-line (i.e. without filter pre-collection), in real-time (1-min time resolution), at ng m-3 concentrations, with molecular-level resolution (i.e. obtaining molecular weight and elemental composition information). The CHARON-PTR-ToF-MS system monitored molecular tracers associated with different particle sources including levoglucosan from biomass combustion, PAHs from vehicular traffic, nicotine from cigarette smoking, and monoterpene oxidation products secondarily formed from biogenic emissions. The tracer information was used for interpreting positive matrix factorization (PMF) data which allowed us to apportion the sources of submicron particulate organic matter in the different urban environments. This work was funded through the PIMMS ITN, which was supported by the European Commission's 7th Framework Programme under grant agreement number 287382.

Online submicron particle sizing by dynamic light scattering using autodilution

NASA Technical Reports Server (NTRS)

Nicoli, David F.; Elings, V. B.

1989-01-01

Efficient production of a wide range of commercial products based on submicron colloidal dispersions would benefit from instrumentation for online particle sizing, permitting real time monitoring and control of the particle size distribution. Recent advances in the technology of dynamic light scattering (DLS), especially improvements in algorithms for inversion of the intensity autocorrelation function, have made it ideally suited to the measurement of simple particle size distributions in the difficult submicron region. Crucial to the success of an online DSL based instrument is a simple mechanism for automatically sampling and diluting the starting concentrated sample suspension, yielding a final concentration which is optimal for the light scattering measurement. A proprietary method and apparatus was developed for performing this function, designed to be used with a DLS based particle sizing instrument. A PC/AT computer is used as a smart controller for the valves in the sampler diluter, as well as an input-output communicator, video display and data storage device. Quantitative results are presented for a latex suspension and an oil-in-water emulsion.

Preparation and characterization of SiO2-coated submicron-sized L10 Fe-Pt particles

NASA Astrophysics Data System (ADS)

Hayashi, Yoshiaki; Ogawa, Tomoyuki; Ishiyama, Kazushi

2018-05-01

The development of magnets with higher performance is attracting increasing interest. The optimization of their microstructure is essential to enhance their properties, and a microstructure comprising magnetically isolated hard magnetic grains of a single-domain size has been proposed as an ideal structure for enhancing the coercivity of magnets. To obtain magnets with an ideal structure, we consider the fabrication of magnets by an approach based on core/shell nanoparticles with a hard magnetic core and a non-magnetic shell. In this study, to obtain particles for our proposed approach, we attempted to fabricate L10 Fe-Pt/SiO2-core/shell particles with submicron-sized cores less than the critical single-domain size. The fabrication of such core/shell particles was confirmed from morphology observations and XRD analysis of the particles. Although the formation of more desirable core/shell particles with submicron-sized single-crystal cores in the single-domain size range was not achieved, the fabricated core/shell particles showed a high coercivity of 25 kOe.

An analytical model with flexible accuracy for deep submicron DCVSL cells

NASA Astrophysics Data System (ADS)

Valiollahi, Sepideh; Ardeshir, Gholamreza

2018-07-01

Differential cascoded voltage switch logic (DCVSL) cells are among the best candidates of circuit designers for a wide range of applications due to advantages such as low input capacitance, high switching speed, small area and noise-immunity; nevertheless, a proper model has not yet been developed to analyse them. This paper analyses deep submicron DCVSL cells based on a flexible accuracy-simplicity trade-off including the following key features: (1) the model is capable of producing closed-form expressions with an acceptable accuracy; (2) model equations can be solved numerically to offer higher accuracy; (3) the short-circuit currents occurring in high-low/low-high transitions are accounted in analysis and (4) the changes in the operating modes of transistors during transitions together with an efficient submicron I-V model, which incorporates the most important non-ideal short-channel effects, are considered. The accuracy of the proposed model is validated in IBM 0.13 µm CMOS technology through comparisons with the accurate physically based BSIM3 model. The maximum error caused by analytical solutions is below 10%, while this amount is below 7% for numerical solutions.

Submicron polycaprolactone particles as a carrier for imaging contrast agent for in vitro applications.

PubMed

Iqbal, Muhammad; Robin, Sophie; Humbert, Philippe; Viennet, Céline; Agusti, Geraldine; Fessi, Hatem; Elaissari, Abdelhamid

2015-12-01

Fluorescent materials have recently attracted considerable attention due to their unique properties and high performance as imaging agent in biomedical fields. Different imaging agents have been encapsulated in order to restrict its delivery to a specific area. In this study, a fluorescent contrast agent was encapsulated for in vitro application by polycaprolactone (PCL) polymer. The encapsulation was performed using modified double emulsion solvent evaporation technique with sonication. Fluorescent nanoparticles (20 nm) were incorporated in the inner aqueous phase of double emulsion. A number of samples were fabricated using different concentrations of fluorescent contrast agent. The contrast agent-containing submicron particle was characterized by a zetasizer for average particle size, SEM and TEM for morphology observations and fluorescence spectrophotometer for encapsulation efficiency. Moreover, contrast agent distribution in the PCL matrix was determined by confocal microscopy. The incorporation of contrast agent in different concentrations did not affect the physicochemical properties of PCL particles and the average size of encapsulated particles was found to be in the submicron range. Copyright © 2015 Elsevier B.V. All rights reserved.

Full-dispersion Monte Carlo simulation of phonon transport in micron-sized graphene nanoribbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, S., E-mail: smei4@wisc.edu; Knezevic, I., E-mail: knezevic@engr.wisc.edu; Maurer, L. N.

2014-10-28

We simulate phonon transport in suspended graphene nanoribbons (GNRs) with real-space edges and experimentally relevant widths and lengths (from submicron to hundreds of microns). The full-dispersion phonon Monte Carlo simulation technique, which we describe in detail, involves a stochastic solution to the phonon Boltzmann transport equation with the relevant scattering mechanisms (edge, three-phonon, isotope, and grain boundary scattering) while accounting for the dispersion of all three acoustic phonon branches, calculated from the fourth-nearest-neighbor dynamical matrix. We accurately reproduce the results of several experimental measurements on pure and isotopically modified samples [S. Chen et al., ACS Nano 5, 321 (2011);S. Chenmore » et al., Nature Mater. 11, 203 (2012); X. Xu et al., Nat. Commun. 5, 3689 (2014)]. We capture the ballistic-to-diffusive crossover in wide GNRs: room-temperature thermal conductivity increases with increasing length up to roughly 100 μm, where it saturates at a value of 5800 W/m K. This finding indicates that most experiments are carried out in the quasiballistic rather than the diffusive regime, and we calculate the diffusive upper-limit thermal conductivities up to 600 K. Furthermore, we demonstrate that calculations with isotropic dispersions overestimate the GNR thermal conductivity. Zigzag GNRs have higher thermal conductivity than same-size armchair GNRs, in agreement with atomistic calculations.« less

Minimal Length Scale Scenarios for Quantum Gravity.

PubMed

Hossenfelder, Sabine

2013-01-01

We review the question of whether the fundamental laws of nature limit our ability to probe arbitrarily short distances. First, we examine what insights can be gained from thought experiments for probes of shortest distances, and summarize what can be learned from different approaches to a theory of quantum gravity. Then we discuss some models that have been developed to implement a minimal length scale in quantum mechanics and quantum field theory. These models have entered the literature as the generalized uncertainty principle or the modified dispersion relation, and have allowed the study of the effects of a minimal length scale in quantum mechanics, quantum electrodynamics, thermodynamics, black-hole physics and cosmology. Finally, we touch upon the question of ways to circumvent the manifestation of a minimal length scale in short-distance physics.

A new length scale for quantum gravity: A resolution of the black hole information loss paradox

NASA Astrophysics Data System (ADS)

Singh, Tejinder P.

We show why and how Compton wavelength and Schwarzschild radius should be combined into one single new length scale, which we call the Compton-Schwarzschild length. Doing so offers a resolution of the black hole information loss paradox, and suggests Planck mass remnant black holes as candidates for dark matter. It also compels us to introduce torsion, and identify the Dirac field with a complex torsion field. Dirac equation and Einstein equations, are shown to be mutually dual limiting cases of an underlying gravitation theory which involves the Compton-Schwarzschild length scale, and includes a complex torsion field.

The electrostatic persistence length of polymers beyond the OSF limit.

PubMed

Everaers, R; Milchev, A; Yamakov, V

2002-05-01

We use large-scale Monte Carlo simulations to test scaling theories for the electrostatic persistence length l(e) of isolated, uniformly charged polymers with Debye-Hückel intrachain interactions in the limit where the screening length kappa(-1) exceeds the intrinsic persistence length of the chains. Our simulations cover a significantly larger part of the parameter space than previous studies. We observe no significant deviations from the prediction l(e) proportional to kappa(-2) by Khokhlov and Khachaturian which is based on applying the Odijk-Skolnick-Fixman theories of electrostatic bending rigidity and electrostatically excluded volume to the stretched de Gennes-Pincus-Velasco-Brochard polyelectrolyte blob chain. A linear or sublinear dependence of the persistence length on the screening length can be ruled out. We show that previous results pointing into this direction are due to a combination of excluded-volume and finite chain length effects. The paper emphasizes the role of scaling arguments in the development of useful representations for experimental and simulation data.

Micro-scale and meso-scale architectural cues cooperate and compete to direct aligned tissue formation

PubMed Central

Gilchrist, Christopher L.; Ruch, David S.; Little, Dianne; Guilak, Farshid

2014-01-01

Tissue and biomaterial microenvironments provide architectural cues that direct important cell behaviors including cell shape, alignment, migration, and resulting tissue formation. These architectural features may be presented to cells across multiple length scales, from nanometers to millimeters in size. In this study, we examined how architectural cues at two distinctly different length scales, “micro-scale” cues on the order of ~1–2 μm, and “meso-scale” cues several orders of magnitude larger (>100 μm), interact to direct aligned neo-tissue formation. Utilizing a micro-photopatterning (μPP) model system to precisely arrange cell-adhesive patterns, we examined the effects of substrate architecture at these length scales on human mesenchymal stem cell (hMSC) organization, gene expression, and fibrillar collagen deposition. Both micro- and meso-scale architectures directed cell alignment and resulting tissue organization, and when combined, meso cues could enhance or compete against micro-scale cues. As meso boundary aspect ratios were increased, meso-scale cues overrode micro-scale cues and controlled tissue alignment, with a characteristic critical width (~500 μm) similar to boundary dimensions that exist in vivo in highly aligned tissues. Meso-scale cues acted via both lateral confinement (in a cell-density-dependent manner) and by permitting end-to-end cell arrangements that yielded greater fibrillar collagen deposition. Despite large differences in fibrillar collagen content and organization between μPP architectural conditions, these changes did not correspond with changes in gene expression of key matrix or tendon-related genes. These findings highlight the complex interplay between geometric cues at multiple length scales and may have implications for tissue engineering strategies, where scaffold designs that incorporate cues at multiple length scales could improve neo-tissue organization and resulting functional outcomes. PMID:25263687

On the saturation of the refractive index structure function. II - Influence of the correlation length on astronomical 'seeing'

NASA Technical Reports Server (NTRS)

Venkatakrishnan, P.

1987-01-01

A physical length scale in the wavefront corresponding to the parameter (r sub 0) characterizing the loss in detail in a long exposure image is identified, and the influence of the correlation scale of turbulence as r sub 0 approaches this scale is shown. Allowing for the effect of 2-point correlations in the fluctuations of the refractive index, Venkatakrishnan and Chatterjee (1987) proposed a modified law for the phase structure function. It is suggested that the departure of the phase structure function from the 5/3 power law for length scales in the wavefront approaching the correlation scale of turbulence may lead to better 'seeing' at longer wavelengths.

Solar potential scaling and the urban road network topology

NASA Astrophysics Data System (ADS)

Najem, Sara

2017-01-01

We explore the scaling of cities' solar potentials with their number of buildings and reveal a latent dependence between the solar potential and the length of the corresponding city's road network. This scaling is shown to be valid at the grid and block levels and is attributed to a common street length distribution. Additionally, we compute the buildings' solar potential correlation function and length in order to determine the set of critical exponents typifying the urban solar potential universality class.

Scale effects between body size and limb design in quadrupedal mammals.

PubMed

Kilbourne, Brandon M; Hoffman, Louwrens C

2013-01-01

Recently the metabolic cost of swinging the limbs has been found to be much greater than previously thought, raising the possibility that limb rotational inertia influences the energetics of locomotion. Larger mammals have a lower mass-specific cost of transport than smaller mammals. The scaling of the mass-specific cost of transport is partly explained by decreasing stride frequency with increasing body size; however, it is unknown if limb rotational inertia also influences the mass-specific cost of transport. Limb length and inertial properties--limb mass, center of mass (COM) position, moment of inertia, radius of gyration, and natural frequency--were measured in 44 species of terrestrial mammals, spanning eight taxonomic orders. Limb length increases disproportionately with body mass via positive allometry (length ∝ body mass(0.40)); the positive allometry of limb length may help explain the scaling of the metabolic cost of transport. When scaled against body mass, forelimb inertial properties, apart from mass, scale with positive allometry. Fore- and hindlimb mass scale according to geometric similarity (limb mass ∝ body mass(1.0)), as do the remaining hindlimb inertial properties. The positive allometry of limb length is largely the result of absolute differences in limb inertial properties between mammalian subgroups. Though likely detrimental to locomotor costs in large mammals, scale effects in limb inertial properties appear to be concomitant with scale effects in sensorimotor control and locomotor ability in terrestrial mammals. Across mammals, the forelimb's potential for angular acceleration scales according to geometric similarity, whereas the hindlimb's potential for angular acceleration scales with positive allometry.

Scale Effects between Body Size and Limb Design in Quadrupedal Mammals

PubMed Central

Kilbourne, Brandon M.; Hoffman, Louwrens C.

2013-01-01

Recently the metabolic cost of swinging the limbs has been found to be much greater than previously thought, raising the possibility that limb rotational inertia influences the energetics of locomotion. Larger mammals have a lower mass-specific cost of transport than smaller mammals. The scaling of the mass-specific cost of transport is partly explained by decreasing stride frequency with increasing body size; however, it is unknown if limb rotational inertia also influences the mass-specific cost of transport. Limb length and inertial properties – limb mass, center of mass (COM) position, moment of inertia, radius of gyration, and natural frequency – were measured in 44 species of terrestrial mammals, spanning eight taxonomic orders. Limb length increases disproportionately with body mass via positive allometry (length ∝ body mass0.40); the positive allometry of limb length may help explain the scaling of the metabolic cost of transport. When scaled against body mass, forelimb inertial properties, apart from mass, scale with positive allometry. Fore- and hindlimb mass scale according to geometric similarity (limb mass ∝ body mass1.0), as do the remaining hindlimb inertial properties. The positive allometry of limb length is largely the result of absolute differences in limb inertial properties between mammalian subgroups. Though likely detrimental to locomotor costs in large mammals, scale effects in limb inertial properties appear to be concomitant with scale effects in sensorimotor control and locomotor ability in terrestrial mammals. Across mammals, the forelimb's potential for angular acceleration scales according to geometric similarity, whereas the hindlimb's potential for angular acceleration scales with positive allometry. PMID:24260117

The prospects of transition metal dichalcogenides for ultimately scaled CMOS

NASA Astrophysics Data System (ADS)

Thiele, S.; Kinberger, W.; Granzner, R.; Fiori, G.; Schwierz, F.

2018-05-01

MOSFET gate length scaling has been a main source of progress in digital electronics for decades. Today, researchers still spend considerable efforts on reducing the gate length and on developing ultimately scaled MOSFETs, thereby exploring both new device architectures and alternative channel materials beyond Silicon such as two-dimensional TMDs (transition metal dichalcogenide). On the other hand, the envisaged scaling scenario for the next 15 years has undergone a significant change recently. While the 2013 ITRS edition required a continuation of aggressive gate length scaling for at least another 15 years, the 2015 edition of the ITRS suggests a deceleration and eventually a levelling off of gate length scaling and puts more emphasis on alternative options such as pitch scaling to keep Moore's Law alive. In the present paper, future CMOS scaling is discussed in the light of emerging two-dimensional MOSFET channel, in particular two-dimensional TMDs. To this end, the scaling scenarios of the 2013 and 2015 ITRS editions are considered and the scaling potential of TMD MOSFETs is investigated by means of quantum-mechanical device simulations. It is shown that for ultimately scaled MOSFETs as required in the 2013 ITRS, the heavy carrier effective masses of the Mo- and W-based TMDs are beneficial for the suppression of direct source-drain tunneling, while to meet the significantly relaxed scaling targets of the 2016 ITRS heavy-effective-mass channels are not needed.

Silica-protected micron and sub-micron capsules and particles for self-healing at the microscale.

PubMed

Jackson, Aaron C; Bartelt, Jonathan A; Marczewski, Kamil; Sottos, Nancy R; Braun, Paul V

2011-01-03

A generalized silica coating scheme is used to functionalize and protect sub-micron and micron size dicyclopentadiene monomer-filled capsules and polymer-protected Grubbs' catalyst particles. These capsules and particles are used for self-healing of microscale damage in an epoxy-based polymer. The silica layer both protects the capsules and particles, and limits their aggregation when added to an epoxy matrix, enabling the capsules and particles to be dispersed at high concentrations with little loss of reactivity. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

DOEpatents

Mazur, Eric; Shen, Mengyan

2013-12-03

The present invention generally provides a semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

Resolving the multipolar scattering modes of a submicron particle using parametric indirect microscopic imaging

NASA Astrophysics Data System (ADS)

Ullah, Kaleem; Liu, Xuefeng; Krasnok, Alex; Habib, Muhammad; Song, Li; Garcia-Camara, Braulio

2018-07-01

In this work, we show the spatial distribution of the scattered electromagnetic field of dielectric particles by using a new super-resolution method based on polarization modulation. Applying this technique, we were able to resolve the multipolar distribution of a Cu2O particle with a radius of 450 nm. In addition, FDTD and Mie simulations have been carried out to validate and confirm the experimental results. The results are helpful to understand the resonant modes of dielectric submicron particles which have a broad range of potential applications, such as all-optical devices or nanoantennas.

Sub-micron resolution of localized ion beam induced charge reduction in silicon detectors damaged by heavy ions

DOE PAGES

Auden, Elizabeth C.; Pacheco, Jose L.; Bielejec, Edward; ...

2015-12-01

In this study, displacement damage reduces ion beam induced charge (IBIC) through Shockley-Read-Hall recombination. Closely spaced pulses of 200 keV Si ++ ions focused in a 40 nm beam spot are used to create damage cascades within 0.25 μm 2 areas. Damaged areas are detected through contrast in IBIC signals generated with focused ion beams of 200 keV Si ++ ions and 60 keV Li + ions. IBIC signal reduction can be resolved over sub-micron regions of a silicon detector damaged by as few as 1000 heavy ions.

Sub-micron resolution of localized ion beam induced charge reduction in silicon detectors damaged by heavy ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Auden, Elizabeth C.; Pacheco, Jose L.; Bielejec, Edward

In this study, displacement damage reduces ion beam induced charge (IBIC) through Shockley-Read-Hall recombination. Closely spaced pulses of 200 keV Si ++ ions focused in a 40 nm beam spot are used to create damage cascades within 0.25 μm 2 areas. Damaged areas are detected through contrast in IBIC signals generated with focused ion beams of 200 keV Si ++ ions and 60 keV Li + ions. IBIC signal reduction can be resolved over sub-micron regions of a silicon detector damaged by as few as 1000 heavy ions.

Characteristics of the Dust-Plasma Interaction Near Enceladus' South Pole

NASA Technical Reports Server (NTRS)

Shafiq, Muhammad; Wahlund, J.-E.; Morooka, M. W; Kurth, W. S.; Farrell, W. M.

2010-01-01

We present RPWS Langmuir probe data from the third Enceladus flyby (E3) showing (he presence of dusty plasma near Enceladus' South Pole. There is a sharp rise in both the electron and ion number densities when the spacecraft traverses through Enceladus plume. The ion density near Enceladus is found to increase abruptly from about 10(exp 2) cm (exp -3) before the closest approach to 10(exp 5) cm (exp -3) just 30 s after the closest approach, an amount two orders of magnitude higher than the electron density. Assuming that the inconsistency between the electron and ion number densities is due to the presence of dust particles that are collecting the missing electron charges, we present dusty plasma characteristics down to sub-micron particle sizes. By assuming a differential dust number density for a range in dust sizes and by making use of Langmuir probe data, the dust densities for certain lower limits in dust size distribution were estimated. In order to achieve the dust densities of micrometer and larger sized grains comparable to the ones reported in the literature. we show that the power law size distribution must hold down to at least 0.03 micron such that the total differential number density is dominated by the smallest sub-micron sized grains. The total dust number density in Enceladus' plume is of the order of l0(exp 2) cm(exp -3) reducing to 1 cm(exp -3) in the E- ring. The dust density for micrometer and larger sized grains is estimated to be about 10(exp -4) cm(exp -3) in the plume while it is about 10(exp -6) - 10(exp -7) cm(exp -3) in the E-ring. Dust charge for micron sized grains is estimated to be about eight thousand electron charges reducing to below one hundred electron charges for 0.03 micron sized grains. The effective dusty plasma Debye length is estimated and compared with intergrain distance as well as the electron Debye length. The maximum dust charging time of 1.4 h is found for 0.03 11mmicron sized grains just 1 min before the closest approach. The charging time decreases substantially in the plume where it is only a fraction of a second for 1 micron sized grains, 1 s for 0.l micron sized grains and about 10 s for 0.03 micron sized grains.

A variable mixing-length ratio for convection theory

NASA Technical Reports Server (NTRS)

Chan, K. L.; Wolff, C. L.; Sofia, S.

1981-01-01

It is argued that a natural choice for the local mixing length in the mixing-length theory of convection has a value proportional to the local density scale height of the convective bubbles. The resultant variable mixing-length ratio (the ratio between the mixing length and the pressure scale height) of this theory is enhanced in the superadiabatic region and approaches a constant in deeper layers. Numerical tests comparing the new mixing length successfully eliminate most of the density inversion that typically plagues conventional results. The new approach also seems to indicate the existence of granular motion at the top of the convection zone.

Assessing self-care and social function using a computer adaptive testing version of the pediatric evaluation of disability inventory.

PubMed

Coster, Wendy J; Haley, Stephen M; Ni, Pengsheng; Dumas, Helene M; Fragala-Pinkham, Maria A

2008-04-01

To examine score agreement, validity, precision, and response burden of a prototype computer adaptive testing (CAT) version of the self-care and social function scales of the Pediatric Evaluation of Disability Inventory compared with the full-length version of these scales. Computer simulation analysis of cross-sectional and longitudinal retrospective data; cross-sectional prospective study. Pediatric rehabilitation hospital, including inpatient acute rehabilitation, day school program, outpatient clinics; community-based day care, preschool, and children's homes. Children with disabilities (n=469) and 412 children with no disabilities (analytic sample); 38 children with disabilities and 35 children without disabilities (cross-validation sample). Not applicable. Summary scores from prototype CAT applications of each scale using 15-, 10-, and 5-item stopping rules; scores from the full-length self-care and social function scales; time (in seconds) to complete assessments and respondent ratings of burden. Scores from both computer simulations and field administration of the prototype CATs were highly consistent with scores from full-length administration (r range, .94-.99). Using computer simulation of retrospective data, discriminant validity, and sensitivity to change of the CATs closely approximated that of the full-length scales, especially when the 15- and 10-item stopping rules were applied. In the cross-validation study the time to administer both CATs was 4 minutes, compared with over 16 minutes to complete the full-length scales. Self-care and social function score estimates from CAT administration are highly comparable with those obtained from full-length scale administration, with small losses in validity and precision and substantial decreases in administration time.

The dynamics of oceanic fronts. Part 1: The Gulf Stream

NASA Technical Reports Server (NTRS)

Kao, T. W.

1970-01-01

The establishment and maintenance of the mean hydrographic properties of large scale density fronts in the upper ocean is considered. The dynamics is studied by posing an initial value problem starting with a near surface discharge of buoyant water with a prescribed density deficit into an ambient stationary fluid of uniform density. The full time dependent diffusion and Navier-Stokes equations for a constant Coriolis parameter are used in this study. Scaling analysis reveals three independent length scales of the problem, namely a radius of deformation or inertial length scale, Lo, a buoyance length scale, ho, and a diffusive length scale, hv. Two basic dimensionless parameters are then formed from these length scales, the thermal (or more precisely, the densimetric) Rossby number, Ro = Lo/ho and the Ekman number, E = hv/ho. The governing equations are then suitably scaled and the resulting normalized equations are shown to depend on E alone for problems of oceanic interest. Under this scaling, the solutions are similar for all Ro. It is also shown that 1/Ro is a measure of the frontal slope. The governing equations are solved numerically and the scaling analysis is confirmed. The solution indicates that an equilibrium state is established. The front can then be rendered stationary by a barotropic current from a larger scale along-front pressure gradient. In that quasisteady state, and for small values of E, the main thermocline and the inclined isopycnics forming the front have evolved, together with the along-front jet. Conservation of potential vorticity is also obtained in the light water pool. The surface jet exhibits anticyclonic shear in the light water pool and cyclonic shear across the front.

Rating disease progression of Friedreich’s ataxia by the International Cooperative Ataxia Rating Scale: analysis of a 603-patient database

PubMed Central

Coppard, Nicholas; Cooper, Jonathon M.; Delatycki, Martin B.; Dürr, Alexandra; Di Prospero, Nicholas A.; Giunti, Paola; Lynch, David R.; Schulz, J. B.; Rummey, Christian; Meier, Thomas

2013-01-01

The aim of this cross-sectional study was to analyse disease progression in Friedreich’s ataxia as measured by the International Cooperative Ataxia Rating Scale. Single ratings from 603 patients with Friedreich’s ataxia were analysed as a function of disease duration, age of onset and GAA repeat lengths. The relative contribution of items and subscales to the total score was studied as a function of disease progression. In addition, the scaling properties were assessed using standard statistical measures. Average total scale progression per year depends on the age of disease onset, the time since diagnosis and the GAA repeat length. The age of onset inversely correlates with increased GAA repeat length. For patients with an age of onset ≤14 years associated with a longer repeat length, the average yearly rate of decline was 2.5 ± 0.18 points in the total International Cooperative Ataxia Rating Scale for the first 20 years of disease duration, whereas patients with a later onset progress more slowly (1.8 ± 0.27 points/year). Ceiling effects in posture, gait and lower limb scale items lead to a reduced sensitivity of the scale in the severely affected population with a total score of >60 points. Psychometric scaling analysis shows generally favourable properties for the total scale, but the subscale grouping could be improved. This cross-sectional study provides a detailed characterization of the International Cooperative Ataxia Rating Scale. The analysis further provides rates of change separated for patients with early and late disease onset, which is driven by the GAA repeat length. Differences in the subscale dynamics merit consideration in the design of future clinical trials applying this scale as a neurological assessment instrument in Friedreich’s ataxia. PMID:23365101

A MEMS Infrared Thermopile Fabricated from Silicon-On-Insulator with Phononic Crystal Structures and Carbon Nanotube Absorption Layer

NASA Astrophysics Data System (ADS)

Gray, Kory Forrest

The goal of this project was to examine the possibility of creating a novel thermal infrared detector based on silicon CMOS technology that has been enhanced by the latest nano-engineering discoveries. Silicon typically is not thought as an efficient thermoelectric material. However recent advancements in nanotechnology have improved the potential for a highly sensitive infrared detector based on nano-structured silicon. The thermal conductivity of silicon has been shown to be reduced from 150 W/mK down to 60 W/mK just by decreasing the scale of the silicon from bulk down to the sub-micron scale. Further reduction of the thermal conductivity has been shown by patterning silicon with a phonon crystal structure which has been reported to have thermal conductivities down to 10 W/mK. The phonon crystal structure consists of a 2D array of holes that are etched into the silicon. The size and pitch of the holes are on the order of the mean free path of the phonons in silicon which is approximately 200-500nm. This particular device had 200nm holes on a 400nm pitch. The Seebeck coefficient of silicon can also be enhanced by the reduction of the material from the bulk to sub-micron scale and with degenerate level doping. The combination of decreased thermal conductivity and increased Seebeck coefficient allow silicon to be a promising material for thermoelectric infrared detectors. The highly doped silicon is desired to reduce the electrical resistance of the device. The low electrical resistance is required to reduce the Johnson noise of the device which is the dominant noise source for most thermal detectors. This project designed a MEMS thermopile using a silicon-on-insulator substrate, and a CMOS compatible process. The basic thermopile consists of a silicon dioxide membrane with phononic crystal patterned silicon thermocouples around the edges of the membrane. Vertical aligned, multi-walled, carbon nanotubes were used as the infrared absorption layer. A MEMS thermoelectric detector with a D* of 3 * 107 cm Hz 0.5/W was demonstrated with a time response of 3-10 milliseconds. With this initial research, it is possible to improve the D* to the high 108 cm Hz 0.5/W range by slightly changing the design of the thermopile and patterning the absorption layer.

Sub-micron elastic property characterization of materials using a near-field scanning optical microscope

NASA Astrophysics Data System (ADS)

Blodgett, David W.; Spicer, James B.

2001-12-01

The ability to characterize the sub-surface mechanical properties of a bulk or thin film material at the sub-micron level has applications in the microelectronics and thin film industries. In the microelectronics industry, with the decrease of line widths and the increase of component densities, sub-surface voids have become increasingly detrimental. Any voids along an integrated circuit (IC) line can lead to improper electrical connections between components and can cause failure of the device. In the thin film industry, the detection of impurities is also important. Any impurities can detract from the film's desired optical, electrical, or mechanical properties. Just as important as the detection of voids and impurities, is the measurement of the elastic properties of a material on the nanometer scale. These elastic measurements provide insight into the microstructural properties of the material. We have been investigating a technique that couples the high-resolution surface imaging capabilities of the apertureless near-field scanning optical microscope (ANSOM) with the sub-surface characterization strengths of high-frequency ultrasound. As an ultrasonic wave propagates, the amplitude decreases due to geometrical spreading, attenuation from absorption, and scattering from discontinuities. Measurement of wave speeds and attenuation provides the information needed to quantify the bulk or surface properties of a material. The arrival of an ultrasonic wave at or along the surface of a material is accompanied with a small surface displacement. Conventional methods for the ultrasound detection rely on either a contact transducer or optical technique (interferometric, beam deflection, etc.). However, each of these methods is limited by the spatial resolution dictated by the detection footprint. As the footprint size increases, variations across the ultrasonic wavefront are effectively averaged, masking the presence of any nanometer-scale sub-surface or surface mechanical property variations. The use of an ANSOM for sensing ultrasonic wave arrivals reduces the detection footprint allowing any nanometer scale variations in the microstructure of a material to be detected. In an ANSOM, the ultrasonic displacement is manifested as perturbations on the near-field signal due to the small variations in the tip-sample caused by the wave arrival. Due to the linear dependence of the near-field signal on tip-sample separation, these perturbations can be interpreted using methods identical to those for conventional ultrasonic techniques. In this paper, we report results using both contact transducer (5 MHz) and laser-generated ultrasound.

Chiral spiral waveguides based on MMI crossings: theory and experiments

NASA Astrophysics Data System (ADS)

Cherchi, Matteo; Ylinen, Sami; Harjanne, Mikko; Kapulainen, Markku; Vehmas, Tapani; Aalto, Timo

2016-03-01

We introduce a novel type of chiral spiral waveguide where the usual waveguide crossings are replaced by 100:0 Multimode Interferometers (MMIs), i.e. 2x2 splitters that couple all the input light in the cross output port. Despite the topological equivalence with the standard configuration, we show how resorting to long MMIs has non-trivial advantages in terms of footprint and propagation length. An accurate analytic model is also introduced to show the impact of nonidealities on the spiral performances, including propagation loss and cross-talk. We have designed and fabricated three chiral spirals on our platform, based on 3 μm thick silicon strip waveguides with 0.13 dB/cm propagation loss, and 1.58 mm long MMIs. The fabricated spirals have 7, 13 and 49 loops respectively, corresponding to the effective lengths 6.6 cm, 12.5 cm and 47.9 cm. The proposed model is successfully applied to the experimental results, highlighting MMI extinction ratio of about 16.5 dB and MMI loss of about 0.08 dB, that are much worse compared to the simulated 50 dB extinction and 0.01 dB loss. This imposes an upper limit to the number of rounds, because light takes shortcuts through the bar MMI ports. Nevertheless, the novel chiral spiral waveguides outperform what is achievable in mainstream silicon photonics platforms based on submicron waveguides in terms of length and propagation losses, and they are promising candidates for the realization of integrated gyroscopes. They can be significantly further improved by replacing the MMIs with adiabatic 100:0 splitters, ensuring lower cross-talk and broader bandwidth.

A Two-length Scale Turbulence Model for Single-phase Multi-fluid Mixing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwarzkopf, J. D.; Livescu, D.; Baltzer, J. R.

2015-09-08

A two-length scale, second moment turbulence model (Reynolds averaged Navier-Stokes, RANS) is proposed to capture a wide variety of single-phase flows, spanning from incompressible flows with single fluids and mixtures of different density fluids (variable density flows) to flows over shock waves. The two-length scale model was developed to address an inconsistency present in the single-length scale models, e.g. the inability to match both variable density homogeneous Rayleigh-Taylor turbulence and Rayleigh-Taylor induced turbulence, as well as the inability to match both homogeneous shear and free shear flows. The two-length scale model focuses on separating the decay and transport length scales,more » as the two physical processes are generally different in inhomogeneous turbulence. This allows reasonable comparisons with statistics and spreading rates over such a wide range of turbulent flows using a common set of model coefficients. The specific canonical flows considered for calibrating the model include homogeneous shear, single-phase incompressible shear driven turbulence, variable density homogeneous Rayleigh-Taylor turbulence, Rayleigh-Taylor induced turbulence, and shocked isotropic turbulence. The second moment model shows to compare reasonably well with direct numerical simulations (DNS), experiments, and theory in most cases. The model was then applied to variable density shear layer and shock tube data and shows to be in reasonable agreement with DNS and experiments. Additionally, the importance of using DNS to calibrate and assess RANS type turbulence models is highlighted.« less

A New Method of Absorption-Phase Nanotomography for 3D Observation of Mineral-Organic-Water Textiles and its Application to Pristine Carbonaceous Chondrites

NASA Technical Reports Server (NTRS)

Tsuchiyama, A.; Nakato, A.; Matsuno, J.; Sugimoto, M.; Uesugi, K.; Takeuchi, A.; Nakano, T.; Vaccaro, E.; Russel, S.; Nakamura-Messenger, K.;

Aerosol emissions from prescribed fires in the United States: A synthesis of laboratory and aircraft measurements

NASA Astrophysics Data System (ADS)

May, A. A.; McMeeking, G. R.; Lee, T.; Taylor, J. W.; Craven, J. S.; Burling, I.; Sullivan, A. P.; Akagi, S.; Collett, J. L.; Flynn, M.; Coe, H.; Urbanski, S. P.; Seinfeld, J. H.; Yokelson, R. J.; Kreidenweis, S. M.

2014-10-01

Aerosol emissions from prescribed fires can affect air quality on regional scales. Accurate representation of these emissions in models requires information regarding the amount and composition of the emitted species. We measured a suite of submicron particulate matter species in young plumes emitted from prescribed fires (chaparral and montane ecosystems in California; coastal plain ecosystem in South Carolina) and from open burning of over 15 individual plant species in the laboratory. We report emission ratios and emission factors for refractory black carbon (rBC) and submicron nonrefractory aerosol and compare field and laboratory measurements to assess the representativeness of our laboratory-measured emissions. Laboratory measurements of organic aerosol (OA) emission factors for some fires were an order of magnitude higher than those derived from any of our aircraft observations; these are likely due to higher-fuel moisture contents, lower modified combustion efficiencies, and less dilution compared to field studies. Nonrefractory inorganic aerosol emissions depended more strongly on fuel type and fuel composition than on combustion conditions. Laboratory and field measurements for rBC were in good agreement when differences in modified combustion efficiency were considered; however, rBC emission factors measured both from aircraft and in the laboratory during the present study using the Single Particle Soot Photometer were generally higher than values previously reported in the literature, which have been based largely on filter measurements. Although natural variability may account for some of these differences, an increase in the BC emission factors incorporated within emission inventories may be required, pending additional field measurements for a wider variety of fires.

Investigation of the influence of humidity on the ultrasonic agglomeration of submicron particles in diesel exhausts.

PubMed

Riera-Franco de Sarabia, E; Elvira-Segura, L; González-Gómez, I; Rodríguez-Maroto, J J; Muñoz-Bueno, R; Dorronsoro-Areal, J L

2003-06-01

Removing very fine particles in the 0.01-1 micro m range generated in diesel combustion is important for air pollution abatement because of the impact such particles have on the environment. By forming larger particles, acoustic agglomeration of submicron particles is presented as a promising process for enhancing the efficiency of the current filtration systems for particle removal. Nevertheless, some authors have pointed out that acoustic agglomeration is much more efficient for larger particles than for smaller particles. This paper studies the effect of humidity on the acoustic agglomeration of diesel exhausts particles in the nanometer size range at 21 kHz. For the agglomeration tests, the experimental facility basically consists of a pilot scale plant with a diesel engine, an ultrasonic agglomeration chamber a dilution system, a nozzle atomizer, and an aerosol sampling and measuring station. The effect of the ultrasonic treatment, generated by a linear array of four high-power stepped-plate transducers on fumes at flow rates of 900 Nm(3)/h, was a small reduction in the number concentration of particles at the outlet of the chamber. However, the presence of humidity raised the agglomeration rate by decreasing the number particle concentration by up to 56%. A numerical study of the agglomeration process as a linear combination of the orthokinetic and hydrodynamic agglomeration coefficients resulting from mutual radiation pressure also found that acoustic agglomeration was enhanced by humidity. Both results confirm the benefit of using high-power ultrasound together with humidity to enhance the agglomeration of particles much smaller than 1 micro m.

A smartphone-based chip-scale microscope using ambient illumination.

PubMed

Lee, Seung Ah; Yang, Changhuei

2014-08-21

Portable chip-scale microscopy devices can potentially address various imaging needs in mobile healthcare and environmental monitoring. Here, we demonstrate the adaptation of a smartphone's camera to function as a compact lensless microscope. Unlike other chip-scale microscopy schemes, this method uses ambient illumination as its light source and does not require the incorporation of a dedicated light source. The method is based on the shadow imaging technique where the sample is placed on the surface of the image sensor, which captures direct shadow images under illumination. To improve the image resolution beyond the pixel size, we perform pixel super-resolution reconstruction with multiple images at different angles of illumination, which are captured while the user is manually tilting the device around any ambient light source, such as the sun or a lamp. The lensless imaging scheme allows for sub-micron resolution imaging over an ultra-wide field-of-view (FOV). Image acquisition and reconstruction are performed on the device using a custom-built Android application, constructing a stand-alone imaging device for field applications. We discuss the construction of the device using a commercial smartphone and demonstrate the imaging capabilities of our system.

A smartphone-based chip-scale microscope using ambient illumination

PubMed Central

Lee, Seung Ah; Yang, Changhuei

2014-01-01

Portable chip-scale microscopy devices can potentially address various imaging needs in mobile healthcare and environmental monitoring. Here, we demonstrate the adaptation of a smartphone’s camera to function as a compact lensless microscope. Unlike other chip-scale microscopy schemes, this method uses ambient illumination as its light source and does not require the incorporation of a dedicated light source. The method is based on the shadow imaging technique where the sample is placed on the surface of the image sensor, which captures direct shadow images under illumination. To improve the imaging resolution beyond the pixel size, we perform pixel super-resolution reconstruction with multiple images at different angles of illumination, which are captured while the user is manually tilting the device around any ambient light source, such as the sun or a lamp. The lensless imaging scheme allows for sub-micron resolution imaging over an ultra-wide field-of-view (FOV). Image acquisition and reconstruction is performed on the device using a custom-built android application, constructing a stand-alone imaging device for field applications. We discuss the construction of the device using a commercial smartphone and demonstrate the imaging capabilities of our system. PMID:24964209

Microphase separation of comb copolymers with two different lengths of side chains

NASA Astrophysics Data System (ADS)

Aliev, M. A.; Kuzminyh, N. Yu.

2009-10-01

The phase behavior of the monodisperse AB comb copolymer melt contained the macromolecules of special architecture is discussed. Each macromolecule is assumed to be composed of two comb blocks which differ in numbers of side chains and numbers of monomer units in these chains. It is shown (by analysis of the structure factor of the melt) that microphase separation at two different length scales in the melt is possible. The large and small length scales correspond to separation between comb blocks and separation between monomer units in repeating fragments of blocks, respectively. The classification diagrams indicated which length scale is favored for a given parameters of chemical structure of macromolecules are constructed.

Radial distribution of dust, stars, gas, and star-formation rate in DustPedia⋆ face-on galaxies

NASA Astrophysics Data System (ADS)

Casasola, V.; Cassarà, L. P.; Bianchi, S.; Verstocken, S.; Xilouris, E.; Magrini, L.; Smith, M. W. L.; De Looze, I.; Galametz, M.; Madden, S. C.; Baes, M.; Clark, C.; Davies, J.; De Vis, P.; Evans, R.; Fritz, J.; Galliano, F.; Jones, A. P.; Mosenkov, A. V.; Viaene, S.; Ysard, N.

2017-09-01

Aims: The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the DustPedia sample. Methods: This study is performed by exploiting the multi-wavelength DustPedia database, from ultraviolet (UV) to sub-millimeter bands, in addition to molecular (12CO) and atomic (Hi) gas maps and metallicity abundance information available in the literature. We fitted the surface-brightness profiles of the tracers of dust and stars, the mass surface-density profiles of dust, stars, molecular gas, and total gas, and the SFR surface-density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H2 conversion factor (αCO) per galaxy by using dust- and gas-mass profiles. Results: Although each galaxy has its own peculiar behavior, we identified a common trend of the exponential scale-lengths versus wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec2 radius decrease from UV to 70 μm, from 0.4 to 0.2, and then increase back up to 0.3 at 500 microns. The main result is that, on average, the dust-mass surface-density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 μm surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 μm scale-length tend to increase from earlier to later types, the scale-length at 70 μm tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 μm that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types. Our αCO determinations are in the range (0.3-9) M⊙ pc-2 (K km s-1)-1, almost invariant by using a fixed dust-to-gas ratio mass (DGR) or a DGR depending on metallicity gradient. DustPedia is a project funded by the EU under the heading "Exploitation of space science and exploration data". It has the primary goal of exploiting existing data in the Herschel Space Observatory and Planck Telescope databases.

Creation of current filaments in the solar corona

NASA Technical Reports Server (NTRS)

Mikic, Z.; Schnack, D. D.; Van Hoven, G.

1989-01-01

It has been suggested that the solar corona is heated by the dissipation of electric currents. The low value of the resistivity requires the magnetic field to have structure at very small length scales if this mechanism is to work. In this paper it is demonstrated that the coronal magnetic field acquires small-scale structure through the braiding produced by smooth, randomly phased, photospheric flows. The current density develops a filamentary structure and grows exponentially in time. Nonlinear processes in the ideal magnetohydrodynamic equations produce a cascade effect, in which the structure introduced by the flow at large length scales is transferred to smaller scales. If this process continues down to the resistive dissipation length scale, it would provide an effective mechanism for coronal heating.

Enhanced endothelial cell density on NiTi surfaces with sub-micron to nanometer roughness

PubMed Central

Samaroo, Harry D; Lu, Jing; Webster, Thomas J

2008-01-01

The shape memory effect and superelastic properties of NiTi (or Nitinol, a nickel-titanium alloy) have already attracted much attention for various biomedical applications (such as vascular stents, orthodontic wires, orthopedic implants, etc). However, for vascular stents, conventional approaches have required coating NiTi with anti-thrombogenic or anti-inflammatory drug-eluting polymers which as of late have proven problematic for healing atherosclerotic blood vessels. Instead of focusing on the use of drug-eluting anti-thrombogenic or anti-inflammatory proteins, this study focused on promoting the formation of a natural anti-thrombogenic and anti-inflammatory surface on metallic stents: the endothelium. In this study, we synthesized various NiTi substrates with different micron to nanometer surface roughness by using dissimilar dimensions of constituent NiTi powder. Endothelial cell adhesion on these compacts was compared with conventional commercially pure (cp) titanium (Ti) samples. The results after 5 hrs showed that endothelial cells adhered much better on fine grain (<60 μm) compared with coarse grain NiTi compacts (<100 μm). Coarse grain NiTi compacts and conventional Ti promoted similar levels of endothelial cell adhesion. In addition, cells proliferated more after 5 days on NiTi with greater sub-micron and nanoscale surface roughness compared with coarse grain NiTi. In this manner, this study emphasized the positive pole that NiTi with sub-micron to nanometer surface features can play in promoting a natural anti-thrombogenic and anti-inflammatory surface (the endothelium) on a vascular stent and, thus, suggests that more studies should be conducted on NiTi with sub-micron to nanometer surface features. PMID:18488418

Influence of glass particle size of resin cements on bonding to glass ceramic: SEM and bond strength evaluation.

PubMed

Valentini, Fernanda; Moraes, Rafael R; Pereira-Cenci, Tatiana; Boscato, Noéli

2014-05-01

This study investigated the effect of the filler particle size (micron or submicron) of experimental resin cements on the microtensile bond strength to a glass-ceramic pretreated with hydrofluoric acid (HFA) etching or alumina airborne-particle abrasion (AA). Cements were obtained from a Bis-GMA/TEGDMA mixture filled with 60 mass% micron-sized (1 ± 0.2 µm) or submicron-sized (180 ± 30 µm) Ba-Si-Al glass particles. Ceramic blocks (PM9; VITA) were treated with 10% HFA for 60 s or AA for 15 s. Silane and adhesive were applied. Ceramic blocks were bonded to resin composite blocks (Z250; 3M ESPE) using one of the cements. Bonded specimens were sectioned into beams (n = 20/group) and subjected to microtensile bond strength tests. Data were analyzed using ANOVA and Student-Newman-Keuls' tests (5%). Failure modes were classified under magnification. Morphologies of the treated ceramic surfaces and bonded interfaces were evaluated by scanning electron microscopy. The HFA-submicron group had lower bond strengths than the other groups. All AA-submicron specimens debonded prematurely. Mixed failures were predominant for HFA groups, whereas interfacial failures predominated for AA groups. SEM revealed a honeycomb-like aspect in the HFA-treated ceramic, whereas the AA-treated groups showed an irregular retentive pattern. Continuity of cement infiltration along the bonded interface was more uniform for HFA-treated compared to AA-treated specimens. Cracks toward the bulk of the ceramic were observed in AA-treated specimens. Particle size significantly influenced the ceramic bond strength, whereas surface treatment had a minor effect. Copyright © 2014 Wiley Periodicals, Inc.

Single-crystal and textured polycrystalline Nd2Fe14B flakes with a submicron or nanosize thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, BZ; Zheng, LY; Li, WF

2012-02-01

This paper reports on the fabrication, structure and magnetic property optimization of Nd2Fe14B single-crystal and [0 0 1] textured poly-nanocrystalline flakes prepared by surfactant-assisted high-energy ball milling (HEBM). Single-crystal Nd2Fe14B flakes first with micron and then with submicron thicknesses were formed via continuous basal cleavage along the (1 1 0) planes of the irregularly shaped single-crystal microparticles during the early stage of HEBM. With further milling, [0 0 1] textured polycrystalline submicron Nd2Fe14B flakes were formed. Finally, crystallographically anisotropic polycrystalline Nd2Fe14B nanoflakes were formed after milling for 5-6 h. Anisotropic magnetic behavior was found in all of the flake samples.more » Nd2Fe14B flakes prepared with either oleic acid (OA) or oleylamine (OY) as the surfactant exhibited similar morphology, structure and magnetic properties. Both the addition of some low-melting-point eutectic Nd70Cu30 alloy and an appropriate post-annealing can increase the coercivity of the Nd2Fe14B flakes. The coercivity of Nd2Fe14B nanoflakes with an addition of 16.7 wt.% Nd70Cu30 by milling for 5 h in heptane with 20 wt.% OY increased from 3.7 to 6.8 kOe after annealing at 450 degrees C for 0.5 h. The mechanism for formation and coercivity enhancement of Nd2Fe14B single-crystal and textured poly-nanocrystalline flakes with a submicron or nanosize thickness was discussed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

A novel submicron emulsion system loaded with vincristine–oleic acid ion-pair complex with improved anticancer effect: in vitro and in vivo studies

PubMed Central

Zhang, Ting; Zheng, Yong; Peng, Qiang; Cao, Xi; Gong, Tao; Zhang, Zhirong

2013-01-01

Background Vincristine (VCR), which is a widely used antineoplastic drug, was integrated with a submicron-emulsion drug-delivery system to enhance the anticancer effect. Methods After the formation of a VCR-oleic acid ion-pair complex (VCR-OA), the VCR-OA-loaded submicron emulsion (VCR-OA-SME), prepared by classical high-pressure homogenization, was characterized and its in vitro anticancer effects were evaluated. Results The submicron-emulsion formulation exhibited a homogeneous round shape. The mean particle size, zeta potential, and encapsulation efficiency were 157.6 ± 12.6 nm, −26.5 ± 5.0 mV and 78.64% ± 3.44%, respectively. An in vitro release study of the VCR-OA-SME revealed that 12.4% of the VCR was released within the first 2 hours (initial burst-release phase) and the rest of the drug was detected in the subsequent sustained-release phase. Compared with VCR solution, the pharmacokinetic study of VCR-OA-SME showed relatively longer mean residence time (mean residence time [0–∞] increased from 187.19 to 227.56 minutes), higher maximum concentration (from 252.13 ng/mL to 533.34 ng/mL), and greater area under the curve (area under the curve [0–∞] from 11,417.77 μg/L/minute to 17,164.34 μg/L/minute. Moreover, the VCR-OA-SME exhibited higher cytotoxicity (P < 0.05) on tumor cells by inducing cell arrest in the G2/M phase or even apoptosis (P < 0.05). Conclusion The VCR-OA-SME formulation in our study displayed great potential for an anticancer effect for VCR. PMID:23658485

High flexibility of DNA on short length scales probed by atomic force microscopy.

PubMed

Wiggins, Paul A; van der Heijden, Thijn; Moreno-Herrero, Fernando; Spakowitz, Andrew; Phillips, Rob; Widom, Jonathan; Dekker, Cees; Nelson, Philip C

2006-11-01

The mechanics of DNA bending on intermediate length scales (5-100 nm) plays a key role in many cellular processes, and is also important in the fabrication of artificial DNA structures, but previous experimental studies of DNA mechanics have focused on longer length scales than these. We use high-resolution atomic force microscopy on individual DNA molecules to obtain a direct measurement of the bending energy function appropriate for scales down to 5 nm. Our measurements imply that the elastic energy of highly bent DNA conformations is lower than predicted by classical elasticity models such as the worm-like chain (WLC) model. For example, we found that on short length scales, spontaneous large-angle bends are many times more prevalent than predicted by the WLC model. We test our data and model with an interlocking set of consistency checks. Our analysis also shows how our model is compatible with previous experiments, which have sometimes been viewed as confirming the WLC.

Scale effects in crystal plasticity

NASA Astrophysics Data System (ADS)

Padubidri Janardhanachar, Guruprasad

The goal of this research work is to further the understanding of crystal plasticity, particularly at reduced structural and material length scales. Fundamental understanding of plasticity is central to various challenges facing design and manufacturing of materials for structural and electronic device applications. The development of microstructurally tailored advanced metallic materials with enhanced mechanical properties that can withstand extremes in stress, strain, and temperature, will aid in increasing the efficiency of power generating systems by allowing them to work at higher temperatures and pressures. High specific strength materials can lead to low fuel consumption in transport vehicles. Experiments have shown that enhanced mechanical properties can be obtained in materials by constraining their size, microstructure (e.g. grain size), or both for various applications. For the successful design of these materials, it is necessary to have a thorough understanding of the influence of different length scales and evolving microstructure on the overall behavior. In this study, distinction is made between the effect of structural and material length scale on the mechanical behavior of materials. A length scale associated with an underlying physical mechanism influencing the mechanical behavior can overlap with either structural length scales or material length scales. If it overlaps with structural length scales, then the material is said to be dimensionally constrained. On the other hand, if it overlaps with material length scales, for example grain size, then the material is said to be microstructurally constrained. The objectives of this research work are: (1) to investigate scale and size effects due to dimensional constraints; (2) to investigate size effects due to microstructural constraints; and (3) to develop a size dependent hardening model through coarse graining of dislocation dynamics. A discrete dislocation dynamics (DDD) framework where the scale of analysis is intermediate between a fully discretized (e.g. atomistic) and fully continuum is used for this study. This mesoscale tool allows to address all the stated objectives of this study within a single framework. Within this framework, the effect of structural and the material length scales are naturally accounted for in the simulations and need not be specified in an ad hoc manner, as in some continuum models. It holds the promise of connecting the evolution of the defect microstructure to the effective response of the crystal. Further, it provides useful information to develop physically motivated continuum models to model size effects in materials. The contributions of this study are: (a) provides a new interpretation of mechanical size effect due to only dimensional constraint using DDD; (b) a development of an experimentally validated DDD simulation methodology to model Cu micropillars; (c) a coarse graining technique using DDD to develop a phenomenological model to capture size effect on strain hardening; and (d) a development of a DDD framework for polycrystals to investigate grain size effect on yield strength and strain hardening.

Post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon lithography [A post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oakdale, James S.; Ye, Jianchao; Smith, William L.

Here, two photon polymerization (TPP) is a precise, reliable, and increasingly popular technique for rapid prototyping of micro-scale parts with sub-micron resolution. The materials of choice underlying this process are predominately acrylic resins cross-linked via free-radical polymerization. Due to the nature of the printing process, the derived parts are only partially cured and the corresponding mechanical properties, i.e. modulus and ultimate strength, are lower than if the material were cross-linked to the maximum extent. Herein, post-print curing via UV-driven radical generation, is demonstrated to increase the overall degree of cross-linking of low density, TPP-derived structures.

Post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon lithography [A post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon polymerization

DOE PAGES

Oakdale, James S.; Ye, Jianchao; Smith, William L.; ...

2016-11-28

Here, two photon polymerization (TPP) is a precise, reliable, and increasingly popular technique for rapid prototyping of micro-scale parts with sub-micron resolution. The materials of choice underlying this process are predominately acrylic resins cross-linked via free-radical polymerization. Due to the nature of the printing process, the derived parts are only partially cured and the corresponding mechanical properties, i.e. modulus and ultimate strength, are lower than if the material were cross-linked to the maximum extent. Herein, post-print curing via UV-driven radical generation, is demonstrated to increase the overall degree of cross-linking of low density, TPP-derived structures.

Downscaling of conventional laser cladding technique to microengineering

NASA Astrophysics Data System (ADS)

del Val, J.; Comesaña, R.; Lusquiños, F.; Riveiro, A.; Quintero, F.; Pou, J.

To get an adequate response to the high increase of micro-products demand, new techniques have been developed by different types of industries in the last years. One approach is to adapt the laser surface cladding technique to the scale of microengineering. A new experimental configuration has been developed based on a highly stable high power laser with a high beam quality and a micro-feeder adequate to supply submicron particles. This work collects our efforts to extend the operation range of the laser cladding to the laser micro-cladding in order to produce micro-coatings. The viability of this new technique has been demonstrated by depositing coatings with geometrical characteristics in the micrometer range (minimum values obtained: 32 μm of width and 12 μm of height).

Phase-shift, stimuli-responsive drug carriers for targeted delivery

PubMed Central

O’Neill, Brian E; Rapoport, Natalya

2011-01-01

The intersection of particles and directed energy is a rich source of novel and useful technology that is only recently being realized for medicine. One of the most promising applications is directed drug delivery. This review focuses on phase-shift nanoparticles (that is, particles of submicron size) as well as micron-scale particles whose action depends on an external-energy triggered, first-order phase shift from a liquid to gas state of either the particle itself or of the surrounding medium. These particles have tremendous potential for actively disrupting their environment for altering transport properties and unloading drugs. This review covers in detail ultrasound and laser-activated phase-shift nano- and micro-particles and their use in drug delivery. Phase-shift based drug-delivery mechanisms and competing technologies are discussed. PMID:22059114

Exploring Hominin and Non-hominin Primate Dental Fossil Remains with Neutron Microtomography

NASA Astrophysics Data System (ADS)

Zanolli, Clément; Schillinger, Burkhard; Beaudet, Amélie; Kullmer, Ottmar; Macchiarelli, Roberto; Mancini, Lucia; Schrenk, Friedemann; Tuniz, Claudio; Vodopivec, Vladimira

Fossil dental remains are an archive of unique information for paleobiological studies. Computed microtomography based on X-ray microfocus sources (X-μCT) and Synchrotron Radiation (SR-μCT) allow subtle quantification at the micron and sub-micron scale of the meso- and microstructural signature imprinted in the mineralized tissues, such as enamel and dentine, through high-resolution ;virtual histology;. Nonetheless, depending on the degree of alterations undergone during fossilization, X-ray analyses of tooth tissues do not always provide distinct imaging contrasts, thus preventing the extraction of essential morphological and anatomical details. We illustrate here by three examples the successful application of neutron microtomography (n-μCT) in cases where X-rays have previously failed to deliver contrasts between dental tissues of fossilized specimen.

An instrument for in situ coherent x-ray studies of metal-organic vapor phase epitaxy of III-nitrides.

PubMed

Ju, Guangxu; Highland, Matthew J; Yanguas-Gil, Angel; Thompson, Carol; Eastman, Jeffrey A; Zhou, Hua; Brennan, Sean M; Stephenson, G Brian; Fuoss, Paul H

2017-03-01

We describe an instrument that exploits the ongoing revolution in synchrotron sources, optics, and detectors to enable in situ studies of metal-organic vapor phase epitaxy (MOVPE) growth of III-nitride materials using coherent x-ray methods. The system includes high-resolution positioning of the sample and detector including full rotations, an x-ray transparent chamber wall for incident and diffracted beam access over a wide angular range, and minimal thermal sample motion, giving the sub-micron positional stability and reproducibility needed for coherent x-ray studies. The instrument enables surface x-ray photon correlation spectroscopy, microbeam diffraction, and coherent diffraction imaging of atomic-scale surface and film structure and dynamics during growth, to provide fundamental understanding of MOVPE processes.

An instrument for in situ coherent x-ray studies of metal-organic vapor phase epitaxy of III-nitrides

NASA Astrophysics Data System (ADS)

Ju, Guangxu; Highland, Matthew J.; Yanguas-Gil, Angel; Thompson, Carol; Eastman, Jeffrey A.; Zhou, Hua; Brennan, Sean M.; Stephenson, G. Brian; Fuoss, Paul H.

2017-03-01

We describe an instrument that exploits the ongoing revolution in synchrotron sources, optics, and detectors to enable in situ studies of metal-organic vapor phase epitaxy (MOVPE) growth of III-nitride materials using coherent x-ray methods. The system includes high-resolution positioning of the sample and detector including full rotations, an x-ray transparent chamber wall for incident and diffracted beam access over a wide angular range, and minimal thermal sample motion, giving the sub-micron positional stability and reproducibility needed for coherent x-ray studies. The instrument enables surface x-ray photon correlation spectroscopy, microbeam diffraction, and coherent diffraction imaging of atomic-scale surface and film structure and dynamics during growth, to provide fundamental understanding of MOVPE processes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weigel, Peter O.; Savanier, Marc; DeRose, Christopher T.

Here, we demonstrate a photonic waveguide technology based on a two-material core, in which light is controllably and repeatedly transferred back and forth between sub-micron thickness crystalline layers of Si and LN bonded to one another, where the former is patterned and the latter is not. In this way, the foundry-based wafer-scale fabrication technology for silicon photonics can be leveraged to form lithium-niobate based integrated optical devices. Using two different guided modes and an adiabatic mode transition between them, we demonstrate a set of building blocks such as waveguides, bends, and couplers which can be used to route light underneathmore » an unpatterned slab of LN, as well as outside the LN-bonded region, thus enabling complex and compact lightwave circuits in LN alongside Si photonics with fabrication ease and low cost.« less

Aerosol based direct-write micro-additive fabrication method for sub-mm 3D metal-dielectric structures

NASA Astrophysics Data System (ADS)

Rahman, Taibur; Renaud, Luke; Heo, Deuk; Renn, Michael; Panat, Rahul

2015-10-01

The fabrication of 3D metal-dielectric structures at sub-mm length scale is highly important in order to realize low-loss passives and GHz wavelength antennas with applications in wearable and Internet-of-Things (IoT) devices. The inherent 2D nature of lithographic processes severely limits the available manufacturing routes to fabricate 3D structures. Further, the lithographic processes are subtractive and require the use of environmentally harmful chemicals. In this letter, we demonstrate an additive manufacturing method to fabricate 3D metal-dielectric structures at sub-mm length scale. A UV curable dielectric is dispensed from an Aerosol Jet system at 10-100 µm length scale and instantaneously cured to build complex 3D shapes at a length scale  <1 mm. A metal nanoparticle ink is then dispensed over the 3D dielectric using a combination of jetting action and tilted dispense head, also using the Aerosol Jet technique and at a length scale 10-100 µm, followed by the nanoparticle sintering. Simulation studies are carried out to demonstrate the feasibility of using such structures as mm-wave antennas. The manufacturing method described in this letter opens up the possibility of fabricating an entirely new class of custom-shaped 3D structures at a sub-mm length scale with potential applications in 3D antennas and passives.

Multi Length Scale Imaging of Flocculated Estuarine Sediments; Insights into their Complex 3D Structure

NASA Astrophysics Data System (ADS)

Wheatland, Jonathan; Bushby, Andy; Droppo, Ian; Carr, Simon; Spencer, Kate

2015-04-01

Suspended estuarine sediments form flocs that are compositionally complex, fragile and irregularly shaped. The fate and transport of suspended particulate matter (SPM) is determined by the size, shape, density, porosity and stability of these flocs and prediction of SPM transport requires accurate measurements of these three-dimensional (3D) physical properties. However, the multi-scaled nature of flocs in addition to their fragility makes their characterisation in 3D problematic. Correlative microscopy is a strategy involving the spatial registration of information collected at different scales using several imaging modalities. Previously, conventional optical microscopy (COM) and transmission electron microscopy (TEM) have enabled 2-dimensional (2D) floc characterisation at the gross (> 1 µm) and sub-micron scales respectively. Whilst this has proven insightful there remains a critical spatial and dimensional gap preventing the accurate measurement of geometric properties and an understanding of how structures at different scales are related. Within life sciences volumetric imaging techniques such as 3D micro-computed tomography (3D µCT) and focused ion beam scanning electron microscopy [FIB-SEM (or FIB-tomography)] have been combined to characterise materials at the centimetre to micron scale. Combining these techniques with TEM enables an advanced correlative study, allowing material properties across multiple spatial and dimensional scales to be visualised. The aims of this study are; 1) to formulate an advanced correlative imaging strategy combining 3D µCT, FIB-tomography and TEM; 2) to acquire 3D datasets; 3) to produce a model allowing their co-visualisation; 4) to interpret 3D floc structure. To reduce the chance of structural alterations during analysis samples were first 'fixed' in 2.5% glutaraldehyde/2% formaldehyde before being embedding in Durcupan resin. Intermediate steps were implemented to improve contrast and remove pore water, achieved by the addition of heavy metal stains and washing samples in a series of ethanol solutions and acetone. Gross-scale characterisation involved scanning samples using a Nikon Metrology HM X 225 µCT. For micro-scale analysis a working surface was revealed by microtoming the sample. Ultrathin sections were then collected and analysed using a JEOL 1200 Ex II TEM, and FIB-tomography datasets obtained using an FEI Quanta 3D FIB-SEM. Finally, to locate the surface and relate TEM and FIB-tomography datasets to the original floc, samples were rescanned using the µCT. Image processing was initially conducted in ImageJ. Following this datasets were imported into Amira 5.5 where pixel intensity thresholding allowed particle-matrix boundaries to be defined. Using 'landmarks' datasets were then registered to enable their co-visualisation in 3D models. Analysis of registered datasets reveals the complex non-fractal nature of flocs, whose properties span several of orders of magnitude. Primary particles are organised into discrete 'bundles', the arrangement of which directly influences their gross morphology. This strategy, which allows the co-visualisation of spatially registered multi-scale 3D datasets, provides unique insights into the true nature floc which would other have been impossible.

Accurate aging of juvenile salmonids using fork lengths

USGS Publications Warehouse

Sethi, Suresh; Gerken, Jonathon; Ashline, Joshua

2017-01-01

Juvenile salmon life history strategies, survival, and habitat interactions may vary by age cohort. However, aging individual juvenile fish using scale reading is time consuming and can be error prone. Fork length data are routinely measured while sampling juvenile salmonids. We explore the performance of aging juvenile fish based solely on fork length data, using finite Gaussian mixture models to describe multimodal size distributions and estimate optimal age-discriminating length thresholds. Fork length-based ages are compared against a validation set of juvenile coho salmon, Oncorynchus kisutch, aged by scales. Results for juvenile coho salmon indicate greater than 95% accuracy can be achieved by aging fish using length thresholds estimated from mixture models. Highest accuracy is achieved when aged fish are compared to length thresholds generated from samples from the same drainage, time of year, and habitat type (lentic versus lotic), although relatively high aging accuracy can still be achieved when thresholds are extrapolated to fish from populations in different years or drainages. Fork length-based aging thresholds are applicable for taxa for which multiple age cohorts coexist sympatrically. Where applicable, the method of aging individual fish is relatively quick to implement and can avoid ager interpretation bias common in scale-based aging.

Porotic paradox: distribution of cortical bone pore sizes at nano- and micro-levels in healthy vs. fragile human bone.

PubMed

Milovanovic, Petar; Vukovic, Zorica; Antonijevic, Djordje; Djonic, Danijela; Zivkovic, Vladimir; Nikolic, Slobodan; Djuric, Marija

2017-05-01

Bone is a remarkable biological nanocomposite material showing peculiar hierarchical organization from smaller (nano, micro) to larger (macro) length scales. Increased material porosity is considered as the main feature of fragile bone at larger length-scales. However, there is a shortage of quantitative information on bone porosity at smaller length-scales, as well as on the distribution of pore sizes in healthy vs. fragile bone. Therefore, here we investigated how healthy and fragile bones differ in pore volume and pore size distribution patterns, considering a wide range of mostly neglected pore sizes from nano to micron-length scales (7.5 to 15000 nm). Cortical bone specimens from four young healthy women (age: 35 ± 6 years) and five women with bone fracture (age: 82 ± 5 years) were analyzed by mercury porosimetry. Our findings showed that, surprisingly, fragile bone demonstrated lower pore volume at the measured scales. Furtnermore, pore size distribution showed differential patterns between healthy and fragile bones, where healthy bone showed especially high proportion of pores between 200 and 15000 nm. Therefore, although fragile bones are known for increased porosity at macroscopic level and level of tens or hundreds of microns as firmly established in the literature, our study with a unique assessment range of nano-to micron-sized pores reveal that osteoporosis does not imply increased porosity at all length scales. Our thorough assessment of bone porosity reveals a specific distribution of porosities at smaller length-scales and contributes to proper understanding of bone structure which is important for designing new biomimetic bone substitute materials.

Assessing self-care and social function using a computer adaptive testing version of the Pediatric Evaluation of Disability Inventory Accepted for Publication, Archives of Physical Medicine and Rehabilitation

PubMed Central

Coster, Wendy J.; Haley, Stephen M.; Ni, Pengsheng; Dumas, Helene M.; Fragala-Pinkham, Maria A.

2009-01-01

Objective To examine score agreement, validity, precision, and response burden of a prototype computer adaptive testing (CAT) version of the Self-Care and Social Function scales of the Pediatric Evaluation of Disability Inventory (PEDI) compared to the full-length version of these scales. Design Computer simulation analysis of cross-sectional and longitudinal retrospective data; cross-sectional prospective study. Settings Pediatric rehabilitation hospital, including inpatient acute rehabilitation, day school program, outpatient clinics; community-based day care, preschool, and children’s homes. Participants Four hundred sixty-nine children with disabilities and 412 children with no disabilities (analytic sample); 38 children with disabilities and 35 children without disabilities (cross-validation sample). Interventions Not applicable. Main Outcome Measures Summary scores from prototype CAT applications of each scale using 15-, 10-, and 5-item stopping rules; scores from the full-length Self-Care and Social Function scales; time (in seconds) to complete assessments and respondent ratings of burden. Results Scores from both computer simulations and field administration of the prototype CATs were highly consistent with scores from full-length administration (all r’s between .94 and .99). Using computer simulation of retrospective data, discriminant validity and sensitivity to change of the CATs closely approximated that of the full-length scales, especially when the 15- and 10-item stopping rules were applied. In the cross-validation study the time to administer both CATs was 4 minutes, compared to over 16 minutes to complete the full-length scales. Conclusions Self-care and Social Function score estimates from CAT administration are highly comparable to those obtained from full-length scale administration, with small losses in validity and precision and substantial decreases in administration time. PMID:18373991

Hierarchical roughness of sticky and non-sticky superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Raza, Muhammad; Kooij, Stefan; van Silfhout, Arend; Zandvliet, Harold; Poelsema, Bene

2011-11-01

The importance of superhydrophobic substrates (contact angle >150° with sliding angle <10°) in modern technology is undeniable. We present a simple colloidal route to manufacture superstructured arrays with single- and multi-length-scaled roughness to obtain sticky and non-sticky superhydrophobic surfaces. The largest length scale is provided by (multi-)layers of silica spheres (1 μm, 500nm and 150nm diameter). Decoration with gold nanoparticles (14nm, 26nm and 47nm) gives rise to a second length scale. To lower the surface energy, gold nanoparticles are functionalized with dodecanethiol and the silica spheres by perfluorooctyltriethoxysilane. The morphology was examined by helium ion microscopy (HIM), while wettability measurements were performed by using the sessile drop method. We conclude that wettability can be controlled by changing the surface chemistry and/or length scales of the structures. To achieve truly non-sticky superhydrophobic surfaces, hierarchical roughness plays a vital role.

On the physics of electron ejection from laser-irradiated overdense plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thévenet, M.; Vincenti, H.; Faure, J.

2016-06-15

Using 1D and 2D PIC simulations, we describe and model the backward ejection of electron bunches when a laser pulse reflects off an overdense plasma with a short density gradient on its front side. The dependence on the laser intensity and gradient scale length is studied. It is found that during each laser period, the incident laser pulse generates a large charge-separation field, or plasma capacitor, which accelerates an attosecond bunch of electrons toward vacuum. This process is maximized for short gradient scale lengths and collapses when the gradient scale length is comparable to the laser wavelength. We develop amore » model that reproduces the electron dynamics and the dependence on laser intensity and gradient scale length. This process is shown to be strongly linked with high harmonic generation via the Relativistic Oscillating Mirror mechanism.« less

Scale effects and morphological diversification in hindlimb segment mass proportions in neognath birds.

PubMed

Kilbourne, Brandon M

2014-01-01

In spite of considerable work on the linear proportions of limbs in amniotes, it remains unknown whether differences in scale effects between proximal and distal limb segments has the potential to influence locomotor costs in amniote lineages and how changes in the mass proportions of limbs have factored into amniote diversification. To broaden our understanding of how the mass proportions of limbs vary within amniote lineages, I collected data on hindlimb segment masses - thigh, shank, pes, tarsometatarsal segment, and digits - from 38 species of neognath birds, one of the most speciose amniote clades. I scaled each of these traits against measures of body size (body mass) and hindlimb size (hindlimb length) to test for departures from isometry. Additionally, I applied two parameters of trait evolution (Pagel's λ and δ) to understand patterns of diversification in hindlimb segment mass in neognaths. All segment masses are positively allometric with body mass. Segment masses are isometric with hindlimb length. When examining scale effects in the neognath subclade Land Birds, segment masses were again positively allometric with body mass; however, shank, pedal, and tarsometatarsal segment masses were also positively allometric with hindlimb length. Methods of branch length scaling to detect phylogenetic signal (i.e., Pagel's λ) and increasing or decreasing rates of trait change over time (i.e., Pagel's δ) suffer from wide confidence intervals, likely due to small sample size and deep divergence times. The scaling of segment masses appears to be more strongly related to the scaling of limb bone mass as opposed to length, and the scaling of hindlimb mass distribution is more a function of scale effects in limb posture than proximo-distal differences in the scaling of limb segment mass. Though negative allometry of segment masses appears to be precluded by the need for mechanically sound limbs, the positive allometry of segment masses relative to body mass may underlie scale effects in stride frequency and length between smaller and larger neognaths. While variation in linear proportions of limbs appear to be governed by developmental mechanisms, variation in mass proportions does not appear to be constrained so.

Scale effects and morphological diversification in hindlimb segment mass proportions in neognath birds

PubMed Central

2014-01-01

Introduction In spite of considerable work on the linear proportions of limbs in amniotes, it remains unknown whether differences in scale effects between proximal and distal limb segments has the potential to influence locomotor costs in amniote lineages and how changes in the mass proportions of limbs have factored into amniote diversification. To broaden our understanding of how the mass proportions of limbs vary within amniote lineages, I collected data on hindlimb segment masses – thigh, shank, pes, tarsometatarsal segment, and digits – from 38 species of neognath birds, one of the most speciose amniote clades. I scaled each of these traits against measures of body size (body mass) and hindlimb size (hindlimb length) to test for departures from isometry. Additionally, I applied two parameters of trait evolution (Pagel’s λ and δ) to understand patterns of diversification in hindlimb segment mass in neognaths. Results All segment masses are positively allometric with body mass. Segment masses are isometric with hindlimb length. When examining scale effects in the neognath subclade Land Birds, segment masses were again positively allometric with body mass; however, shank, pedal, and tarsometatarsal segment masses were also positively allometric with hindlimb length. Methods of branch length scaling to detect phylogenetic signal (i.e., Pagel’s λ) and increasing or decreasing rates of trait change over time (i.e., Pagel’s δ) suffer from wide confidence intervals, likely due to small sample size and deep divergence times. Conclusions The scaling of segment masses appears to be more strongly related to the scaling of limb bone mass as opposed to length, and the scaling of hindlimb mass distribution is more a function of scale effects in limb posture than proximo-distal differences in the scaling of limb segment mass. Though negative allometry of segment masses appears to be precluded by the need for mechanically sound limbs, the positive allometry of segment masses relative to body mass may underlie scale effects in stride frequency and length between smaller and larger neognaths. While variation in linear proportions of limbs appear to be governed by developmental mechanisms, variation in mass proportions does not appear to be constrained so. PMID:24876886

Neandertal clavicle length

PubMed Central

Trinkaus, Erik; Holliday, Trenton W.; Auerbach, Benjamin M.

2014-01-01

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Sub-micron accurate track navigation method ``Navi'' for the analysis of Nuclear Emulsion

NASA Astrophysics Data System (ADS)

Yoshioka, T.; Yoshida, J.; Kodama, K.

2011-03-01

Sub-micron accurate track navigation in Nuclear Emulsion is realized by using low energy signals detected by automated Nuclear Emulsion read-out systems. Using those much dense ``noise'', about 104 times larger than the real tracks, the accuracy of the track position navigation reaches to be sub micron only by using the information of a microscope field of view, 200 micron times 200 micron. This method is applied to OPERA analysis in Japan, i.e. support of human eye checks of the candidate tracks, confirmation of neutrino interaction vertexes and to embed missing track segments to the track data read-out by automated systems.