The Physics of Ultracold Sr2 Molecules: Optical Production and Precision Measurement

NASA Astrophysics Data System (ADS)

Osborn, Christopher Butler

Colloidal quantum dots have desirable optical properties which can be exploited to realize a variety of photonic devices and functionalities. However, colloidal dots have not had a pervasive utility in photonic devices because of the absence of patterning methods. The electronic chip industry is highly successful due to the well-established lithographic procedures. In this thesis we borrow ideas from the semiconductor industry to develop lithographic techniques that can be used to pattern colloidal quantum dots while ensuring that the optical properties of the quantum dots are not affected by the process. In this thesis we have developed colloidal quantum dot based waveguide structures for amplification and switching applications for all-optical signal processing. We have also developed colloidal quantum dot based light emitting diodes. We successfully introduced CdSe/ZnS quantum dots into a UV curable photo-resist, which was then patterned to realize active devices. In addition, "passive" devices (devices without quantum dots) were integrated to "active" devices via waveguide couplers. Use of photo-resist devices offers two distinct advantages. First, they have low scattering loss and secondly, they allow good fiber to waveguide coupling efficiency due to the low refractive index which allows for large waveguide cross-sections while supporting single mode operation. Practical planar photonic devices and circuits incorporating both active and passive structures can now be realized, now that we have patterning capabilities of quantum dots while maintaining the original optical attributes of the system. In addition to the photo-resist host, we also explored the incorporation of colloidal quantum dots into a dielectric silicon dioxide and silicon nitride one-dimensional microcavity structures using low temperature plasma enhanced chemical vapor deposition. This material system can be used to realize microcavity light emitting diodes that can be realized on any substrate. As a proof of concept demonstration we show a 1550 nm emitting all-dielectric vertical cavity structure embedded with PbS quantum dots. Enhancement in spontaneous emission from the dots embedded in the microcavity is also demonstrated.

Patterned mist deposition of tri-colour CdSe/ZnS quantum dot films toward RGB LED devices

NASA Astrophysics Data System (ADS)

Pickering, S.; Kshirsagar, A.; Ruzyllo, J.; Xu, J.

2012-06-01

In this experiment a technique of mist deposition was explored as a way to form patterned ultra-thin-films of CdSe/ZnS core/shell nanocrystalline quantum dots using colloidal solutions. The objective of this study was to investigate the feasibility of mist deposition as a patterning method for creating multicolour quantum dot light emitting diodes. Mist deposition was used to create three rows of quantum dot light emitting diodes on a single device with each row having a separate colour. The colours chosen were red, green and yellow with corresponding peak wavelengths of 620 nm, 558 nm, and 587 nm. The results obtained from this experiment show that it is possible to create multicolour devices on a single substrate. The peak brightnesses obtained in this experiment for the red, green, and yellow were 508 cd/m, 507 cd/m, and 665 cd/m, respectively. The similar LED brightness is important in display technologies using colloidal quantum dots in a precursor solution to ensure one colour does not dominate the emitted spectrum. Results obtained in-terms of brightness were superior to those achieved with inkjet deposition. This study has shown that mist deposition is a viable method for patterned deposition applied to quantum dot light emitting diode display technologies.

The 2055 freight transportation system and the impact of near term rail movements on TxDOT planning : project summary.

DOT National Transportation Integrated Search

2017-01-01

Based on the research and input from the private sector, four themes emerged that frame the role of TxDOT in preparing for an efficient, reliable, and safe freight transportation system in 2055: : TxDOT is expected to be a facilitator/manager of ...

Brain networks involved in tactile speed classification of moving dot patterns: the effects of speed and dot periodicity

PubMed Central

Yang, Jiajia; Kitada, Ryo; Kochiyama, Takanori; Yu, Yinghua; Makita, Kai; Araki, Yuta; Wu, Jinglong; Sadato, Norihiro

2017-01-01

Humans are able to judge the speed of an object’s motion by touch. Research has suggested that tactile judgment of speed is influenced by physical properties of the moving object, though the neural mechanisms underlying this process remain poorly understood. In the present study, functional magnetic resonance imaging was used to investigate brain networks that may be involved in tactile speed classification and how such networks may be affected by an object’s texture. Participants were asked to classify the speed of 2-D raised dot patterns passing under their right middle finger. Activity in the parietal operculum, insula, and inferior and superior frontal gyri was positively related to the motion speed of dot patterns. Activity in the postcentral gyrus and superior parietal lobule was sensitive to dot periodicity. Psycho-physiological interaction (PPI) analysis revealed that dot periodicity modulated functional connectivity between the parietal operculum (related to speed) and postcentral gyrus (related to dot periodicity). These results suggest that texture-sensitive activity in the primary somatosensory cortex and superior parietal lobule influences brain networks associated with tactually-extracted motion speed. Such effects may be related to the influence of surface texture on tactile speed judgment. PMID:28145505

Temporal stability of visual search-driven biometrics

NASA Astrophysics Data System (ADS)

Yoon, Hong-Jun; Carmichael, Tandy R.; Tourassi, Georgia

2015-03-01

Previously, we have shown the potential of using an individual's visual search pattern as a possible biometric. That study focused on viewing images displaying dot-patterns with different spatial relationships to determine which pattern can be more effective in establishing the identity of an individual. In this follow-up study we investigated the temporal stability of this biometric. We performed an experiment with 16 individuals asked to search for a predetermined feature of a random-dot pattern as we tracked their eye movements. Each participant completed four testing sessions consisting of two dot patterns repeated twice. One dot pattern displayed concentric circles shifted to the left or right side of the screen overlaid with visual noise, and participants were asked which side the circles were centered on. The second dot-pattern displayed a number of circles (between 0 and 4) scattered on the screen overlaid with visual noise, and participants were asked how many circles they could identify. Each session contained 5 untracked tutorial questions and 50 tracked test questions (200 total tracked questions per participant). To create each participant's "fingerprint", we constructed a Hidden Markov Model (HMM) from the gaze data representing the underlying visual search and cognitive process. The accuracy of the derived HMM models was evaluated using cross-validation for various time-dependent train-test conditions. Subject identification accuracy ranged from 17.6% to 41.8% for all conditions, which is significantly higher than random guessing (1/16 = 6.25%). The results suggest that visual search pattern is a promising, temporally stable personalized fingerprint of perceptual organization.

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

Yoon, Hong-Jun; Carmichael, Tandy; Tourassi, Georgia

Previously, we have shown the potential of using an individual s visual search pattern as a possible biometric. That study focused on viewing images displaying dot-patterns with different spatial relationships to determine which pattern can be more effective in establishing the identity of an individual. In this follow-up study we investigated the temporal stability of this biometric. We performed an experiment with 16 individuals asked to search for a predetermined feature of a random-dot pattern as we tracked their eye movements. Each participant completed four testing sessions consisting of two dot patterns repeated twice. One dot pattern displayed concentric circlesmore » shifted to the left or right side of the screen overlaid with visual noise, and participants were asked which side the circles were centered on. The second dot-pattern displayed a number of circles (between 0 and 4) scattered on the screen overlaid with visual noise, and participants were asked how many circles they could identify. Each session contained 5 untracked tutorial questions and 50 tracked test questions (200 total tracked questions per participant). To create each participant s "fingerprint", we constructed a Hidden Markov Model (HMM) from the gaze data representing the underlying visual search and cognitive process. The accuracy of the derived HMM models was evaluated using cross-validation for various time-dependent train-test conditions. Subject identification accuracy ranged from 17.6% to 41.8% for all conditions, which is significantly higher than random guessing (1/16 = 6.25%). The results suggest that visual search pattern is a promising, fairly stable personalized fingerprint of perceptual organization.« less

Large-area ordered Ge-Si compound quantum dot molecules on dot-patterned Si (001) substrates

NASA Astrophysics Data System (ADS)

Lei, Hui; Zhou, Tong; Wang, Shuguang; Fan, Yongliang; Zhong, Zhenyang

2014-08-01

We report on the formation of large-area ordered Ge-Si compound quantum dot molecules (CQDMs) in a combination of nanosphere lithography and self-assembly. Truncated-pyramid-like Si dots with {11n} facets are readily formed, which are spatially ordered in a large area with controlled period and size. Each Si dot induces four self-assembled Ge-rich dots at its base edges that can be fourfold symmetric along <110> directions. A model based on surface chemical potential accounts well for these phenomena. Our results disclose the critical effect of surface curvature on the diffusion and the aggregation of Ge adatoms and shed new light on the unique features and the inherent mechanism of self-assembled QDs on patterned substrates. Such a configuration of one Si QD surrounded by fourfold symmetric Ge-rich QDs can be seen as a CQDM with unique features, which will have potential applications in novel devices.

Anticipatory smooth eye movements with random-dot kinematograms

PubMed Central

Santos, Elio M.; Gnang, Edinah K.; Kowler, Eileen

2012-01-01

Anticipatory smooth eye movements were studied in response to expectations of motion of random-dot kinematograms (RDKs). Dot lifetime was limited (52–208 ms) to prevent selection and tracking of the motion of local elements and to disrupt the perception of an object moving across space. Anticipatory smooth eye movements were found in response to cues signaling the future direction of global RDK motion, either prior to the onset of the RDK or prior to a change in its direction of motion. Cues signaling the lifetime of the dots were not effective. These results show that anticipatory smooth eye movements can be produced by expectations of global motion and do not require a sustained representation of an object or set of objects moving across space. At the same time, certain properties of global motion (direction) were more sensitive to cues than others (dot lifetime), suggesting that the rules by which prediction operates to influence pursuit may go beyond simple associations between cues and the upcoming motion of targets. PMID:23027686

Site-Control of InAs/GaAs Quantum Dots with Indium-Assisted Deoxidation

PubMed Central

Hussain, Sajid; Pozzato, Alessandro; Tormen, Massimo; Zannier, Valentina; Biasiol, Giorgio

2016-01-01

Site-controlled epitaxial growth of InAs quantum dots on GaAs substrates patterned with periodic nanohole arrays relies on the deterministic nucleation of dots into the holes. In the ideal situation, each hole should be occupied exactly by one single dot, with no nucleation onto planar areas. However, the single-dot occupancy per hole is often made difficult by the fact that lithographically-defined holes are generally much larger than the dots, thus providing several nucleation sites per hole. In addition, deposition of a thin GaAs buffer before the dots tends to further widen the holes in the [110] direction. We have explored a method of native surface oxide removal by using indium beams, which effectively prevents hole elongation along [110] and greatly helps single-dot occupancy per hole. Furthermore, as compared to Ga-assisted deoxidation, In-assisted deoxidation is efficient in completely removing surface contaminants, and any excess In can be easily re-desorbed thermally, thus leaving a clean, smooth GaAs surface. Low temperature photoluminescence showed that inhomogeneous broadening is substantially reduced for QDs grown on In-deoxidized patterns, with respect to planar self-assembled dots. PMID:28773333

Nanosilicon dot arrays with a bit pitch and a track pitch of 25 nm formed by electron-beam drawing and reactive ion etching for 1 Tbit/in.{sup 2} storage

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

Hosaka, Sumio; Sano, Hirotaka; Shirai, Masumi

2006-11-27

The formation of very fine Si dots with a bit pitch and a track pitch of less than 25 nm using electron-beam (EB) lithography on ZEP520 and calixarene EB resists and CF{sub 4} reactive ion etching has been demonstrated. The experimental results indicate that the calixarene resist is very suitable for forming an ultrahigh-packed bit array pattern of Si dots. This result promises to open the way toward 1 Tbit/in.{sup 2} storage using patterned media with a dot size of <15 nm.

Self-organised silicide nanodot patterning by medium-energy ion beam sputtering of Si(100): local correlation between the morphology and metal content.

PubMed

Redondo-Cubero, A; Galiana, B; Lorenz, K; Palomares, F J; Bahena, D; Ballesteros, C; Hernandez-Calderón, I; Vázquez, L

2016-11-04

We have produced self-organised silicide nanodot patterns by medium-energy ion beam sputtering (IBS) of silicon targets with a simultaneous and isotropic molybdenum supply. Atomic force microscopy (AFM) studies show that these patterns are qualitatively similar to those produced thus far at low ion energies. We have determined the relevance of the ion species on the pattern ordering and properties. For the higher ordered patterns produced by Xe(+) ions, the pattern wavelength depends linearly on the ion energy. The dot nanostructures are silicide-rich as assessed by x-ray photoelectron spectroscopy (XPS) and emerge in height due to their lower sputtering yield, as observed by electron microscopy. Remarkably, a long wavelength corrugation is observed on the surface which is correlated with both the Mo content and the dot pattern properties. Thus, as assessed by electron microscopy, the protrusions are Mo-rich with higher and more spaced dots on their surface whereas the valleys are Mo-poor with smaller dots that are closer to each other. These findings indicate that there is a correlation between the local metal content of the surface and the nanodot pattern properties both at the nanodot and the large corrugation scales. These results contribute to advancing the understanding of this interesting nanofabrication method and aid in developing a comprehensive theory of nanodot pattern formation and evolution.

Fabrication and single-electron-transfer operation of a triple-dot single-electron transistor

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

Jo, Mingyu, E-mail: mingyujo@eis.hokudai.ac.jp; Uchida, Takafumi; Tsurumaki-Fukuchi, Atsushi

2015-12-07

A triple-dot single-electron transistor was fabricated on silicon-on-insulator wafer using pattern-dependent oxidation. A specially designed one-dimensional silicon wire having small constrictions at both ends was converted to a triple-dot single-electron transistor by means of pattern-dependent oxidation. The fabrication of the center dot involved quantum size effects and stress-induced band gap reduction, whereas that of the two side dots involved thickness modulation because of the complex edge structure of two-dimensional silicon. Single-electron turnstile operation was confirmed at 8 K when a 100-mV, 1-MHz square wave was applied. Monte Carlo simulations indicated that such a device with inhomogeneous tunnel and gate capacitances canmore » exhibit single-electron transfer.« less

Spectrum of dermoscopic patterns in lichen planus: a case series from China.

PubMed

Tan, Cheng; Min, Zhong-Sheng; Xue, Yanning; Zhu, Wen-Yuan

2014-01-01

Dermoscopy has been shown to be a promising method to facilitate the diagnosis of lichen planus (LP) outside of China. To investigate the spectrum of dermoscopic patterns in Chinese LP patients. The clinical data and dermoscopic patterns of nine LP cases with a total of 43 lesions were evaluated. To the naked eye, 20.97% of the lesions exhibited graying Wickham striae (WS); however, 37.5% presented with white streaks of annular, reticular, or leaf venation patterns under dermoscopy. Blue-white veils were occasionally observed in the center. Pigment patterns varied from dots, globules, and peppered pigment to pigmented lines, which were unrelated to the pigment network of the skin. At the periphery of the WS, red fine lines ran parallel to the delicate white streaming lines. WS exhibits five morphological patterns (leaf venation, reticular, white dots, circular and radial streaming) and three color patterns (homogeneous crystalline white, blue-white veil and yellowish-white). The pigment patterns consisted of dots/globules, peppered pigments and pigment. streaming lines.

Consequences of elastic anisotropy in patterned substrate heteroepitaxy.

PubMed

Dixit, Gopal Krishna; Ranganathan, Madhav

2018-06-13

The role of elastic anisotropy on quantum dot formation and evolution on a pre-patterned substrate is evaluated within the framework of a continuum model. We first extend the formulation for surface evolution to take elastic anisotropy into account. Using a small slope approximation, we derive the evolution equation and show how it can be numerically implemented up to linear and second order for stripe and egg-carton patterned substrates using an accurate and efficient procedure. The semi--infinite nature of the substrate is used to solve the elasticity problem subject to other boundary conditions at the free surface and at the film--substrate interface. The positioning of the quantum dots with respect to the peaks and valleys of the pattern is explained by a competition between the length scale of the pattern and the wavelength of the Asaro--Tiller--Grinfeld instability, which is also affected by the elastic anisotropy. The alignment of dots is affected by a competition between the elastic anisotropy of the film and the pattern orientation. A domain of pattern inversion, wherein the quantum dots form exclusively in the valleys of the patterns is identified as a function of the average film thickness and the elastic anisotropy, and the time--scale for this inversion as function of height is analyzed. © 2018 IOP Publishing Ltd.

Calibration and Use of B Dot Probes for Electromagnetic Measuring

DTIC Science & Technology

1977-08-09

response. E. Time Domain Reflectometry Measurements Pulse impedance measurements for the 1.75-in. diameter double-gap probe design were first performed...Far Field (Radiation) Patterns of a B Dot Probe 1. Anechoic Chamber The facility utilized for the probe patterns was the NASA 120-ft chamber at

Patterned growth of individual and multiple vertically aligned carbon nanofibers

NASA Astrophysics Data System (ADS)

Merkulov, V. I.; Lowndes, D. H.; Wei, Y. Y.; Eres, G.; Voelkl, E.

2000-06-01

The results of studies of patterned growth of vertically aligned carbon nanofibers (VACNFs) prepared by plasma-enhanced chemical vapor deposition are reported. Nickel (Ni) dots of various diameters and Ni lines with variable widths and shapes were fabricated using electron beam lithography and evaporation, and served for catalytic growth of VACNFs whose structure was determined by high resolution transmission electron microscopy. It is found that upon plasma pre-etching and heating up to 600-700 °C, thin films of Ni break into droplets which initiate the growth of VACNFs. Above a critical dot size multiple droplets are formed, and consequently multiple VACNFs grow from a single evaporated dot. For dot sizes smaller than the critical size only one droplet is formed, resulting in a single VACNF. In the case of a patterned line, the growth mechanism is similar to that from a dot. VACNFs grow along the line, and above a critical linewidth multiple VACNFs are produced across the line. The mechanism of the formation of single and multiple catalyst droplets and subsequently of VACNFs is discussed.

A non-genetic approach to labelling acute myeloid leukemia and bone marrow cells with quantum dots.

PubMed

Zheng, Yanwen; Tan, Dongming; Chen, Zheng; Hu, Chenxi; Mao, Zhengwei J; Singleton, Timothy P; Zeng, Yan; Shao, Xuejun; Yin, Bin

2014-06-01

The difficulty in manipulation of leukemia cells has long hindered the dissection of leukemia pathogenesis. We have introduced a non-genetic approach of marking blood cells, using quantum dots. We compared quantum dots complexed with different vehicles, including a peptide Tat, cationic polymer Turbofect and liposome. Quantum dots-Tat showed the highest efficiency of marking hematopoietic cells among the three vehicles. Quantum dots-Tat could also label a panel of leukemia cell lines at varied efficiencies. More uniform intracellular distributions of quantum dots in mouse bone marrow and leukemia cells were obtained with quantum dots-Tat, compared with the granule-like formation obtained with quantum dots-liposome. Our results suggest that quantum dots have provided a photostable and non-genetic approach that labels normal and malignant hematopoietic cells, in a cell type-, vehicle-, and quantum dot concentration-dependent manner. We expect for potential applications of quantum dots as an easy and fast marking tool assisting investigations of various types of blood cells in the future.

Patterning of inflorescences and flowers by the F-Box protein DOUBLE TOP and the LEAFY homolog ABERRANT LEAF AND FLOWER of petunia.

PubMed

Souer, Erik; Rebocho, Alexandra B; Bliek, Mattijs; Kusters, Elske; de Bruin, Robert A M; Koes, Ronald

2008-08-01

Angiosperms display a wide variety of inflorescence architectures differing in the positions where flowers or branches arise. The expression of floral meristem identity (FMI) genes determines when and where flowers are formed. In Arabidopsis thaliana, this is regulated via transcription of LEAFY (LFY), which encodes a transcription factor that promotes FMI. We found that this is regulated in petunia (Petunia hybrida) via transcription of a distinct gene, DOUBLE TOP (DOT), a homolog of UNUSUAL FLORAL ORGANS (UFO) from Arabidopsis. Mutation of DOT or its tomato (Solanum lycopersicum) homolog ANANTHA abolishes FMI. Ubiquitous expression of DOT or UFO in petunia causes very early flowering and transforms the inflorescence into a solitary flower and leaves into petals. Ectopic expression of DOT or UFO together with LFY or its homolog ABERRANT LEAF AND FLOWER (ALF) in petunia seedlings activates genes required for identity or outgrowth of organ primordia. DOT interacts physically with ALF, suggesting that it activates ALF by a posttranslational mechanism. Our findings suggest a wider role than previously thought for DOT and UFO in the patterning of flowers and indicate that the different roles of LFY and UFO homologs in the spatiotemporal control of floral identity in distinct species result from their divergent expression patterns.

Pattern transfer with stabilized nanoparticle etch masks

NASA Astrophysics Data System (ADS)

Hogg, Charles R.; Picard, Yoosuf N.; Narasimhan, Amrit; Bain, James A.; Majetich, Sara A.

2013-03-01

Self-assembled nanoparticle monolayer arrays are used as an etch mask for pattern transfer into Si and SiOx substrates. Crack formation within the array is prevented by electron beam curing to fix the nanoparticles to the substrate, followed by a brief oxygen plasma to remove excess carbon. This leaves a dot array of nanoparticle cores with a minimum gap of 2 nm. Deposition and liftoff can transform the dot array mask into an antidot mask, where the gap is determined by the nanoparticle core diameter. Reactive ion etching is used to transfer the dot and antidot patterns into the substrate. The effect of the gap size on the etching rate is modeled and compared with the experimental results.

Flight Attendant Fatigue Recommendation 2: Flight Attendant Work/Rest Patterns, Alertness, and Performance Assessment

DTIC Science & Technology

2010-12-01

Recommendation II: Flight Attendant Work/Rest Patterns, Alertness, and Performance Assessment DOT/FAA/AM-10/22 Office of Aerospace Medicine Washington, DC...Recipient’s Catalog No. DOT/FAA/AM-10/22 4. Title and Subtitle 5. Report Date December 2010 6. Performing Organization Code Flight...Attendant Fatigue Recommendation II: Flight Attendant Work/Rest Patterns, Alertness, and Performance Assessment 7. Author(s) 8. Performing

The JWST/NIRCam Coronagraph: Mask Design and Fabrication

NASA Technical Reports Server (NTRS)

Krista, John E.; Balasubramanian, Kunjithapatha; Beichman, Charles A.; Echternach, Pierre M.; Green, Joseph J.; Liewer, Kurt M.; Muller, Richard E.; Serabyn, Eugene; Shaklan, Stuart B.; Trauger, John T.;

Sign Life-Cycle Policies and Practices : Transportation Research Synthesis

DOT National Transportation Integrated Search

2017-10-01

MnDOT Metro District Traffic Engineering is interested in the practices that other state departments of transportation (DOTs) use to determine traffic sign life expectancy and replacement. Of particular interest is the state of the practice regarding...

A Functional Measurement Study on Averaging Numerosity

ERIC Educational Resources Information Center

Tira, Michael D.; Tagliabue, Mariaelena; Vidotto, Giulio

2014-01-01

In two experiments, participants judged the average numerosity between two sequentially presented dot patterns to perform an approximate arithmetic task. In Experiment 1, the response was given on a 0-20 numerical scale (categorical scaling), and in Experiment 2, the response was given by the production of a dot pattern of the desired numerosity…

Studies of mist deposition for the formation of quantum dot CdSe films

NASA Astrophysics Data System (ADS)

Price, S. C.; Shanmugasundaram, K.; Ramani, S.; Zhu, T.; Zhang, F.; Xu, J.; Mohney, S. E.; Zhang, Q.; Kshirsagar, A.; Ruzyllo, J.

2009-10-01

Films of CdSe(ZnS) colloidal nanocrystalline quantum dots (NQDs) were deposited on bare silicon, glass and polymer coated silicon using mist deposition. This effort is a part of an exploratory investigation in which this deposition technique is studied for the first time as a method to form semiconductor NQD films. The process parameters, including deposition time, solution concentration and electric field, were varied to change the thickness of the deposited film. Blanket films and films deposited through a shadow mask were created to investigate the method's ability to pattern films during the deposition process. The differences between these deposition modes in terms of film morphology were observed. Overall, the results show that mist deposition of quantum dots is a viable method for creating thin, patterned quantum dot films using colloidal solution as the precursor. It is concluded that this technique shows very good promise for quantum dot (light emitting diode, LED) fabrication.

Using online surveys and Facebook ads to solicit customer feedback : research summary.

DOT National Transportation Integrated Search

2017-03-01

The Missouri Department of Transportation : (MoDOT) developed the Tracker system to : assess agency performance in pursuit of its : mission to provide a world-class transportation : system that delights our customers. MoDOT : customers expect t...

High Frequency Magnetic Field Direction Finding Using MGL-S9A B-dot Sensors

DTIC Science & Technology

2013-03-21

relationship for incident plane wave on a linear array . . . . . . . . . . . 26 3.1 B-dot sensor design in CST Microwave Studio...CST Microwave Studio with an infinite PEC ground plane. . . . . . . . . . . . . . . 50 4.2 Radiation pattern of a single B-dot sensor at 32 MHz...simulated in CST Microwave Studio with an infinite PEC ground plane. . . . . . . . . . . . . . . 50 4.3 Radiation efficiency of single loop versus B-dot

Category Formation in Autism: Can Individuals with Autism Form Categories and Prototypes of Dot Patterns?

ERIC Educational Resources Information Center

Gastgeb, Holly Zajac; Dundas, Eva M.; Minshew, Nancy J.; Strauss, Mark S.

2012-01-01

There is a growing amount of evidence suggesting that individuals with autism have difficulty with categorization. One basic cognitive ability that may underlie this difficulty is the ability to abstract a prototype. The current study examined prototype and category formation with dot patterns in high-functioning adults with autism and matched…

Spatially Controlled Fabrication of Brightly Fluorescent Nanodiamond-Array with Enhanced Far-Red Si-V Luminescence

PubMed Central

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia

2014-01-01

We demonstrate a novel approach to precise pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by scanning probe “Dip-Pen” nanolithography technique using electrostatically-driven transfer of nanodiamonds from “inked” cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond-dots in the far-red is achieved by incorporating Si-V defect centers in subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink, mechanism of ink transport, and effect of humidity, dwell time on nanodiamond patterning are investigated. The precision-patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm, 61 nm ± 3 nm, respectively and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm, 245 nm ± 23 nm, respectively using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of the next generation fluorescent based devices and applications. PMID:24394286

Electrically pumped continuous wave quantum dot lasers epitaxially grown on patterned, on-axis (001) Si

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

Norman, Justin; Kennedy, M. J.; Selvidge, Jennifer

High performance III-V lasers at datacom and telecom wavelengths on on-axis (001) Si are needed for scalable datacenter interconnect technologies. We demonstrate electrically injected quantum dot lasers grown on on-axis (001) Si patterned with {111} v-grooves lying in the [110] direction. No additional Ge buffers or substrate miscut was used. The active region consists of five InAs/InGaAs dot-in-a-well layers. Here, we achieve continuous wave lasing with thresholds as low as 36 mA and operation up to 80°C.

Electrically pumped continuous wave quantum dot lasers epitaxially grown on patterned, on-axis (001) Si

DOE PAGES

Norman, Justin; Kennedy, M. J.; Selvidge, Jennifer; ...

2017-02-14

High performance III-V lasers at datacom and telecom wavelengths on on-axis (001) Si are needed for scalable datacenter interconnect technologies. We demonstrate electrically injected quantum dot lasers grown on on-axis (001) Si patterned with {111} v-grooves lying in the [110] direction. No additional Ge buffers or substrate miscut was used. The active region consists of five InAs/InGaAs dot-in-a-well layers. Here, we achieve continuous wave lasing with thresholds as low as 36 mA and operation up to 80°C.

Effect of organic materials used in the synthesis on the emission from CdSe quantum dots

NASA Astrophysics Data System (ADS)

Lee, Jae-Won; Yang, Ho-Soon; Hong, K. S.; Kim, S. M.

2013-12-01

Quantum-dot nanocrystals have particular optical properties due to the quantum confinement effect and the surface effect. This study focuses on the effect of surface conditions on the emission from quantum dots. The quantum dots prepared with 1-hexadecylamine (HDA) in the synthesis show strong emission while the quantum dots prepared without HDA show weak emission, as well as emission from surface energy traps. The comparison of the X-ray patterns of these two sets of quantum dots reveals that HDA forms a layer on the surface of quantum dot during the synthesis. This surface passivation with a layer of HDA reduces surface energy traps, therefore the emission from surface trap levels is suppressed in the quantum dots synthesized with HDA.

Non-conscious processing of motion coherence can boost conscious access.

PubMed

Kaunitz, Lisandro; Fracasso, Alessio; Lingnau, Angelika; Melcher, David

2013-01-01

Research on the scope and limits of non-conscious vision can advance our understanding of the functional and neural underpinnings of visual awareness. Here we investigated whether distributed local features can be bound, outside of awareness, into coherent patterns. We used continuous flash suppression (CFS) to create interocular suppression, and thus lack of awareness, for a moving dot stimulus that varied in terms of coherence with an overall pattern (radial flow). Our results demonstrate that for radial motion, coherence favors the detection of patterns of moving dots even under interocular suppression. Coherence caused dots to break through the masks more often: this indicates that the visual system was able to integrate low-level motion signals into a coherent pattern outside of visual awareness. In contrast, in an experiment using meaningful or scrambled biological motion we did not observe any increase in the sensitivity of detection for meaningful patterns. Overall, our results are in agreement with previous studies on face processing and with the hypothesis that certain features are spatiotemporally bound into coherent patterns even outside of attention or awareness.

Perceived spatial displacement of motion-defined contours in peripheral vision.

PubMed

Fan, Zhao; Harris, John

2008-12-01

The perceived displacement of motion-defined contours in peripheral vision was examined in four experiments. In Experiment 1, in line with Ramachandran and Anstis' finding [Ramachandran, V. S., & Anstis, S. M. (1990). Illusory displacement of equiluminous kinetic edges. Perception, 19, 611-616], the border between a field of drifting dots and a static dot pattern was apparently displaced in the same direction as the movement of the dots. When a uniform dark area was substituted for the static dots, a similar displacement was found, but this was smaller and statistically insignificant. In Experiment 2, the border between two fields of dots moving in opposite directions was displaced in the direction of motion of the dots in the more eccentric field, so that the location of a boundary defined by a diverging pattern is perceived as more eccentric, and that defined by a converging as less eccentric. Two explanations for this effect (that the displacement reflects a greater weight given to the more eccentric motion, or that the region containing stronger centripetal motion components expands perceptually into that containing centrifugal motion) were tested in Experiment 3, by varying the velocity of the more eccentric region. The results favoured the explanation based on the expansion of an area in centripetal motion. Experiment 4 showed that the difference in perceived location was unlikely to be due to differences in the discriminability of contours in diverging and converging patterns, and confirmed that this effect is due to a difference between centripetal and centrifugal motion rather than motion components in other directions. Our result provides new evidence for a bias towards centripetal motion in human vision, and suggests that the direction of motion-induced displacement of edges is not always in the direction of an adjacent moving pattern.

Avalanches and diffusion in bubble rafts

NASA Astrophysics Data System (ADS)

Maloney, C. E.

2015-07-01

Energy dissipation distributions and particle displacement statistics are studied in the mean-field version of Durian's bubble model. A two-dimensional (2D) bi-disperse mixture is simulated at various strain rates, \\dotγ , and packing ratios, ϕ, above the rigidity onset at φ=φc . Well above φc , and at sufficiently low \\dotγ , the system responds in a highly bursty way, reminiscent of other dynamically critical systems with a power-law distribution of energy dissipation. As one increases \\dotγ at fixed ϕ or tunes φ→ φc at fixed \\dotγ , the bursty behavior vanishes. Displacement distributions are non-Fickian at short times but cross to a Fickian regime at a universal strain, Δγ* , independent of \\dotγ and ϕ. Despite the profound differences in short-time dynamics, at intermediate Δγ the systems exhibit qualitatively similar spatial patterns of deformation with lines of slip extending across large fractions of the simulation cell. These deformation patterns explain the observed diffusion constants and the universal crossover time to Fickian behavior.

Threshold matrix for digital halftoning by genetic algorithm optimization

NASA Astrophysics Data System (ADS)

Alander, Jarmo T.; Mantere, Timo J.; Pyylampi, Tero

1998-10-01

Digital halftoning is used both in low and high resolution high quality printing technologies. Our method is designed to be mainly used for low resolution ink jet marking machines to produce both gray tone and color images. The main problem with digital halftoning is pink noise caused by the human eye's visual transfer function. To compensate for this the random dot patterns used are optimized to contain more blue than pink noise. Several such dot pattern generator threshold matrices have been created automatically by using genetic algorithm optimization, a non-deterministic global optimization method imitating natural evolution and genetics. A hybrid of genetic algorithm with a search method based on local backtracking was developed together with several fitness functions evaluating dot patterns for rectangular grids. By modifying the fitness function, a family of dot generators results, each with its particular statistical features. Several versions of genetic algorithms, backtracking and fitness functions were tested to find a reasonable combination. The generated threshold matrices have been tested by simulating a set of test images using the Khoros image processing system. Even though the work was focused on developing low resolution marking technology, the resulting family of dot generators can be applied also in other halftoning application areas including high resolution printing technology.

Toward the in vivo study of captopril-conjugated quantum dots

NASA Astrophysics Data System (ADS)

Manabe, Noriyoshi; Hoshino, Akiyoshi; Liang, Yi-qiang; Goto, Tomomasa; Kato, Norihiro; Yamamoto, Kenji

2005-04-01

Photo-luminescent semiconductor quantum dots are nanometer-size probes that have the potential to be applied to the fields of the bio-imaging and the study of the cell mobility inside the body. At the same time, on the other hand, quantum dots are expected to carry some kind of molecules to the local organ inside of the animal body, which leads to the expectation that they can be used as a medicine-carrier. For this purpose, we conjugate (2S)-1-[(2s)-2-Methyl-3-sulfanylpropionyl]pyrrolidine-2-carboxylic acid (cap) with the quantum dot. Cap has the effect as an anti-hypertension drug, which inhibits angiotensin 1 converting enzyme. We conjugated the quantum dot with cap by the exchange reaction avoiding the regions which holds medicinal effect. Quantum dot conjugated with cap (QD-cap) were 3-times brighter than thioglycerol-coated quantum dots (QD-OH). The particle size of cap was 1.1nm and that of QD-cap was 12nm. QD-cap was permeated into the HeLa cells, while QD-MUA were taken into the HeLa cells by endocytosis. In addition, no apoptosis was detected against the cells that permeated QD-cap, because there was no damage to DNA. These results indicated that QD-conjugated medicines (QD-medicine) could be safe in the experiment on the level of the cell. More over, when QD-cap was intravenously injected into Stroke-prone Spontaneously Hypertensive Rats (SHRSP), they reduced blood pressure at systole. Therefore, the anti-hypertension effect of cap remained after conjugated with the quantum dot. These results suggested that QD-medicine were effective on the animal level.

Optical signatures of coupled quantum dots.

PubMed

Stinaff, E A; Scheibner, M; Bracker, A S; Ponomarev, I V; Korenev, V L; Ware, M E; Doty, M F; Reinecke, T L; Gammon, D

2006-02-03

An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.

Optical Signatures of Coupled Quantum Dots

NASA Astrophysics Data System (ADS)

Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Korenev, V. L.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.

2006-02-01

An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.

Spatially controlled fabrication of a bright fluorescent nanodiamond-array with enhanced far-red Si-V luminescence.

PubMed

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia; Catledge, Shane A

2014-01-31

We demonstrate a novel approach to precisely pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by a scanning probe 'dip-pen' nanolithography technique using electrostatically driven transfer of nanodiamonds from 'inked' cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond dots in the far-red is achieved by incorporating Si-V defect centers in a subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink and mechanism of ink transport, and the effect of humidity and dwell time on nanodiamond patterning are investigated. The precision patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm and 61 nm ± 3 nm, respectively, and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm and, 245 nm ± 23 nm, respectively, using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of next generation fluorescence-based devices and applications.

Study on Dynamic Development of Three-dimensional Weld Pool Surface in Stationary GTAW

NASA Astrophysics Data System (ADS)

Huang, Jiankang; He, Jing; He, Xiaoying; Shi, Yu; Fan, Ding

2018-04-01

The weld pool contains abundant information about the welding process. In particular, the type of the weld pool surface shape, i. e., convex or concave, is determined by the weld penetration. To detect it, an innovative laser-vision-based sensing method is employed to observe the weld pool surface of the gas tungsten arc welding (GTAW). A low-power laser dots pattern is projected onto the entire weld pool surface. Its reflection is intercepted by a screen and captured by a camera. Then the dynamic development process of the weld pool surface can be detected. By observing and analyzing, the change of the reflected laser dots reflection pattern, for shape of the weld pool surface shape, was found to closely correlate to the penetration of weld pool in the welding process. A mathematical model was proposed to correlate the incident ray, reflected ray, screen and surface of weld pool based on structured laser specular reflection. The dynamic variation of the weld pool surface and its corresponding dots laser pattern were simulated and analyzed. By combining the experimental data and the mathematical analysis, the results show that the pattern of the reflected laser dots pattern is closely correlated to the development of weld pool, such as the weld penetration. The concavity of the pool surface was found to increase rapidly after the surface shape was changed from convex to concave during the stationary GTAW process.

Spin fine structure of optically excited quantum dot molecules

NASA Astrophysics Data System (ADS)

Scheibner, M.; Doty, M. F.; Ponomarev, I. V.; Bracker, A. S.; Stinaff, E. A.; Korenev, V. L.; Reinecke, T. L.; Gammon, D.

2007-06-01

The interaction between spins in coupled quantum dots is revealed in distinct fine structure patterns in the measured optical spectra of InAs/GaAs double quantum dot molecules containing zero, one, or two excess holes. The fine structure is explained well in terms of a uniquely molecular interplay of spin-exchange interactions, Pauli exclusion, and orbital tunneling. This knowledge is critical for converting quantum dot molecule tunneling into a means of optically coupling not just orbitals but also spins.

Imaging Dot Patterns for Measuring Gossamer Space Structures

NASA Technical Reports Server (NTRS)

Dorrington, A. A.; Danehy, P. M.; Jones, T. W.; Pappa, R. S.; Connell, J. W.

2005-01-01

A paper describes a photogrammetric method for measuring the changing shape of a gossamer (membrane) structure deployed in outer space. Such a structure is typified by a solar sail comprising a transparent polymeric membrane aluminized on its Sun-facing side and coated black on the opposite side. Unlike some prior photogrammetric methods, this method does not require an artificial light source or the attachment of retroreflectors to the gossamer structure. In a basic version of the method, the membrane contains a fluorescent dye, and the front and back coats are removed in matching patterns of dots. The dye in the dots absorbs some sunlight and fluoresces at a longer wavelength in all directions, thereby enabling acquisition of high-contrast images from almost any viewing angle. The fluorescent dots are observed by one or more electronic camera(s) on the Sun side, the shade side, or both sides. Filters that pass the fluorescent light and suppress most of the solar spectrum are placed in front of the camera(s) to increase the contrast of the dots against the background. The dot image(s) in the camera(s) are digitized, then processed by use of commercially available photogrammetric software.

Modeling photovoltaic performance in periodic patterned colloidal quantum dot solar cells.

PubMed

Fu, Yulan; Dinku, Abay G; Hara, Yukihiro; Miller, Christopher W; Vrouwenvelder, Kristina T; Lopez, Rene

2015-07-27

Colloidal quantum dot (CQD) solar cells have attracted tremendous attention mostly due to their wide absorption spectrum window and potentially low processability cost. The ultimate efficiency of CQD solar cells is highly limited by their high trap state density. Here we show that the overall device power conversion efficiency could be improved by employing photonic structures that enhance both charge generation and collection efficiencies. By employing a two-dimensional numerical model, we have calculated the characteristics of patterned CQD solar cells based of a simple grating structure. Our calculation predicts a power conversion efficiency as high as 11.2%, with a short circuit current density of 35.2 mA/cm2, a value nearly 1.5 times larger than the conventional flat design, showing the great potential value of patterned quantum dot solar cells.

Quality DOTS management and empowering tuberculosis patients.

PubMed

Chugh, Satish

2009-03-01

Central Tuberculosis Division (CTD) has covered whole of India under DOTS. IMA is a proud partner of RNTCP which is managed by CTD. International Standards for Tuberculosis Care is expected from all healthcare providers. The basic principles of care is same worldwide. IMA GFATM RNTCP PPM is completing 2 years of its inception. Sensitisation programme and district training programmes has yielded DOTS/DMC centres in the target states. IMA is having 100% commitment for containing tuberculosis in India. There are International Standards for quality management in tuberculosis control, some of the Standards are elaborated in this write-up. In the Indian context, DOTS needs some innovations that is discussed in this article.

Scalable quantum computer architecture with coupled donor-quantum dot qubits

DOEpatents

Schenkel, Thomas; Lo, Cheuk Chi; Weis, Christoph; Lyon, Stephen; Tyryshkin, Alexei; Bokor, Jeffrey

2014-08-26

A quantum bit computing architecture includes a plurality of single spin memory donor atoms embedded in a semiconductor layer, a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, wherein a first voltage applied across at least one pair of the aligned quantum dot and donor atom controls a donor-quantum dot coupling. A method of performing quantum computing in a scalable architecture quantum computing apparatus includes arranging a pattern of single spin memory donor atoms in a semiconductor layer, forming a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, applying a first voltage across at least one aligned pair of a quantum dot and donor atom to control a donor-quantum dot coupling, and applying a second voltage between one or more quantum dots to control a Heisenberg exchange J coupling between quantum dots and to cause transport of a single spin polarized electron between quantum dots.

Fan fault diagnosis based on symmetrized dot pattern analysis and image matching

NASA Astrophysics Data System (ADS)

Xu, Xiaogang; Liu, Haixiao; Zhu, Hao; Wang, Songling

2016-07-01

To detect the mechanical failure of fans, a new diagnostic method based on the symmetrized dot pattern (SDP) analysis and image matching is proposed. Vibration signals of 13 kinds of running states are acquired on a centrifugal fan test bed and reconstructed by the SDP technique. The SDP pattern templates of each running state are established. An image matching method is performed to diagnose the fault. In order to improve the diagnostic accuracy, the single template, multiple templates and clustering fault templates are used to perform the image matching.

Hemispheric specialization in quantification processes.

PubMed

Pasini, M; Tessari, A

2001-01-01

Three experiments were carried out to study hemispheric specialization for subitizing (the rapid enumeration of small patterns) and counting (the serial quantification process based on some formal principles). The experiments consist of numerosity identification of dot patterns presented in one visual field, with a tachistoscopic technique, or eye movements monitored through glasses, and comparison between centrally presented dot patterns and lateralized tachistoscopically presented digits. Our experiments show left visual field advantage in the identification and comparison tasks in the subitizing range, whereas right visual field advantage has been found in the comparison task for the counting range.

Black Hole Disk Accretion in Supernovae

NASA Astrophysics Data System (ADS)

Nomura, H.; Mineshige, S.; Hirose, M.; Nomoto, K.; Suzuki, T.

Hydrodynamical disk accretion flow onto a new-born black hole in a supernova is studied using the SPH (Smoothed Particle Hydrodynamics) method. It has been suggested that a mass of ~0.1Modot falls back to a black hole by a reverse shock. If the progenitor was rotating before the explosion, the accreting material should have a certain amount of angular momentum, thus forming an accretion disk. Disk material will eventually accrete towards the central object via viscosity with a supercritical accretion rate, dotM / dotMc > 106, for first several tens of days. (Here, dotMc is the Eddington luminosity divided by c2.) We then expect that such an accretion disk is optically thick and advection-dominated; that is, the disk is so hot that produced energy and photons are advected inward rather than being radiated away. Thus, the disk luminosity is much less than the Eddington luminosity (~1038erg s-1). The disk becomes hot and dense; for dotM / dotMc ~106 and the viscosity parameter alphavis ~0.01, for example, T ~109K and rho ~103gcm-3 in the vicinity of the central object. Efficient nucleosynthesis is hence expected even for reasonable viscosity magnitudes, although produced elements may be swallowed by the black hole.

Diagnostic delay amongst tuberculosis patients in Jogjakarta Province, Indonesia is related to the quality of services in DOTS facilities.

PubMed

Ahmad, Riris Andono; Mahendradhata, Yodi; Utarini, Adi; de Vlas, Sake J

2011-04-01

To understand determinants of care-seeking patterns and diagnostic delay amongst tuberculosis (TB) patients diagnosed at direct observed treatment short course (DOTS) facilities in Jogjakarta, Indonesia. Cross-sectional survey amongst newly diagnosed TB patients in 89 DOTS facilities whose history of care-seeking was reconstructed through retrospective interviews gathering data on socio-demographic determinants, onset of TB symptoms, type of health facilities visited, duration of each care-seeking action were recorded. Two hundred and fifty-three TB patients were included in the study whose median duration of patients' delay was 1 week and whose total duration of diagnostic delay was 5.4 weeks. The median number of visits was 4. Many of the patients' socio-demographic determinants were not associated with the care-seeking patterns, and no socio-demographic determinants were associated with the duration of diagnostic delay. More than 60% of TB patients started their care-seeking processes outside DOTS facilities, but the number of visits in DOTS facilities was greater during the overall care-seeking process. Surprisingly, patient's immediate visits to a DOTS facility did not correspond to shorter diagnostic delay. Diagnostic delay in Jogjakarta province was not associated with patients' socio demographic factors, but rather with the health system providing DOTS services. This suggests that strengthening the health system and improving diagnostic quality within DOTS services is now a more rational strategy than expanding the TB programme to engage more providers. © 2010 Blackwell Publishing Ltd.

Grating-dot two-dimensional barcode patterns with extra binary data for encoding secret information

NASA Astrophysics Data System (ADS)

Lih Yeh, Sheng; Lin, Shyh Tsong

2013-02-01

The usual two-dimensional (2D) barcode patterns do not encrypt secret information. However, secret information is sometimes needed to increase the security features of barcode patterns. Therefore, this paper proposes 2D barcode patterns created by two-beam writers to encrypt extra binary data for encoding secret information. The proposed 2D barcode patterns are composed of many grating dots and the fringes of the grating dots are classified into four types. The first type of fringe possesses a pitch of 1.1 μm and an orientation of -45°, the second type of fringe possesses a pitch of 1.2 μm and an orientation of -45°, the third type of fringe possesses a pitch of 1.1 μm and an orientation of 45°and the fourth type of fringe possesses a pitch of 1.2 μm and an orientation of 45°. All the fringes with a 1.1 μm pitch can show a color and all the fringes with a 1.2 μm pitch can show another color when a microscope is used to inspect them. Therefore, extra binary data for encoding secret information can be formed with the two pitches. On the other hand, all the fringes with a -45° orientation can become bright for a viewing direction and all the fringes with a 45° orientation can become bright for another viewing direction when one looks at them. Therefore, the grating dots with the -45° fringe orientation and the grating dots with the 45° fringe orientation can be used to show a positive barcode image and a negative barcode image, respectively. Both the positive and negative barcode images can be used to derive the barcode data. The experiment shows that the proposed barcode patterns can be used conveniently and correctly.

Luminescent Quantum Dots as Ultrasensitive Biological Labels

NASA Astrophysics Data System (ADS)

Nie, Shuming

2000-03-01

Highly luminescent semiconductor quantum dots have been covalently coupled to biological molecules for use in ultrasensitive biological detection. This new class of luminescent labels is considerably brighter and more resistant againt photobleaching in comparison with organic dyes. Quantum dots labeled with the protein transferrin undergo receptor-mediated endocytosis (RME) in cultured HeLa cells, and those dots that were conjugated to immunomolecules recognize specific antibodies or antigens. In addition, we show that DNA functionalized quantum dots can be used to target specific genes by hybridization. We expect that quantum dot bioconjugates will have a broad range of biological applications, such as ligand-receptor interactions, real-time monitoring of molecular trafficking inside living cells, multicolor fluorescence in-situ hybridization (FISH), high-sensitivity detection in miniaturized devices (e.g., DNA chips), and fluorescent tagging of combinatorial chemical libraries. A potential clinical application is the use of quantum dots for ultrasensitive viral RNA detection, in which as low as 100 copies of hepatitis C and HIV viruses per ml blood should be detected.

Holographic assembly of semiconductor CdSe quantum dots in polymer for volume Bragg grating structures with diffraction efficiency near 100%

NASA Astrophysics Data System (ADS)

Liu, Xiangming; Tomita, Yasuo; Oshima, Juro; Chikama, Katsumi; Matsubara, Koutatsu; Nakashima, Takuya; Kawai, Tsuyoshi

2009-12-01

We report on the fabrication of centimeter-size transmission Bragg gratings in semiconductor CdSe quantum dots dispersed 50 μm thick photopolymer films. This was done by holographic assembly of CdSe quantum dots in a photopolymerizable monomer blend. Periodic patterning of CdSe quantum dots in polymer was confirmed by a fluorescence microscope and confocal Raman imaging. The diffraction efficiency from the grating of 1 μm spacing was near 100% in the green with 0.34 vol % CdSe quantum dots, giving the refractive index modulation as large as 5.1×10-3.

Transport properties of a quantum dot and a quantum ring in series

NASA Astrophysics Data System (ADS)

Seo, Minky; Chung, Yunchul

2018-01-01

The decoherence mechanism of an electron interferometer is studied by using a serial quantum dot and ring device. By coupling a quantum dot to a quantum ring (closed-loop electron interferometer), we were able to observe both Coulomb oscillations and Aharonov-Bohm interference simultaneously. The coupled device behaves like an ordinary double quantum dot at zero magnetic field while the conductance of the Coulomb blockade peak is modulated by the electron interference at finite magnetic fields. By injecting one electron at a time (by exploiting the sequential tunneling of a quantum dot) into the interferometer, we were able to study the visibility of the electron interference at non-zero bias voltage. The visibility was found to decay rapidly as the electron energy was increased, which was consistent with the recently reported result for an electron interferometer. However, the lobe pattern and the sudden phase jump became less prominent. These results imply that the lobe pattern and the phase jump in an electron interferometer may be due to electron interactions inside the interferometer, as is predicted by the theory.

Manipulating fluids: Advances in micro-fluidics, opto-fluidics and fluidic self assembly

NASA Astrophysics Data System (ADS)

Vyawahare, Saurabh

This dissertation describes work in three inter-related areas---micro-fluidics, opto-fluidics and fluidic self-assembly. Micro-fluidics has gotten a boost in recent years with the development of multilayered elastomeric devices made of poly (dimethylsiloxane) (PDMS), allowing active elements like valves and pumps. However, while PDMS has many advantages, it is not resistant to organic solvents. New materials and/or new designs are needed for solvent resistance. I describe how novel fluorinated elastomers can replace PDMS when combined with the three dimensional (3-D) solid printing. I also show how another 3-D fabrication method, multilayer photo-lithography, allows for fabrication of devices integrating filters. In general, 3-D fabrications allow new kinds of micro-fluidic devices to be made that would be impossible to emulate with two dimensional chips. In opto-fluidics, I describe a number of experiments with quantum dots both inside and outside chips. Inside chips, I manipulate quantum dots using hydrodynamic focusing to pattern fine lines, like a barcode. Outside chips, I describe our attempts to create quantum dot composites with micro-spheres. I also show how evaporated gold films and chemical passivation can then be used to enhance the emission of quantum dots. Finally, within fluids, self assembly is an attractive way to manipulate materials, and I provide two examples: first, a DNA-based energy transfer molecule that relies on quantum mechanics and self-assembles inside fluids. This kind of molecular photonics mimics parts of the photosynthetic apparatus of plants and bacteria. The second example of self-assembly in fluids describes a new phenomena---the surface tension mediated self assembly of particles like quantum dots and micro-spheres into fine lines. This self assembly by capillary flows can be combined with photo-lithography, and is expected to find use in future nano- and micro-fabrication schemes. In conclusion, advances in fludics, integrating materials like quantum dots and solvent resistant elastomers along with 3-D fabrication and methods of self assembly, provide a new set of tools that significantly expand our control over fluids.

The geographic epidemiology of Mycobacterium tuberculosis disease in Baltimore, 1971-1995

NASA Astrophysics Data System (ADS)

Obasanjo, Olugbenga Olufemi

Given the reemergence of Tuberculosis (TB) in the United States (U.S.) in the 1980s and 1990s, several strategies have emerged to combat the disease. A successful tool has been Directly Observed Therapy (DOT). Chaulk, et al. showed that DOT was responsible for the maintaining the decline in TB rates in Baltimore through the corresponding period of an upswing in rates nationally. In this study, we measure the impact of DOT on the geographic pattern of TB in Baltimore. We used Geographical Information System (GIS) methods to compare the geographic patterns of TB in Baltimore before and after the introduction of DOT in the city. We identified both predictors of TB, and differences in geographic units in Baltimore over time. We measured the impact of the introduction of DOT and Rifampin on various treatment outcomes for TB at about the same time. Despite the drop in numbers of TB cases, the spatial distribution of cases generally remained unchanged until 1995. This was confirmed by the fact that similar predictors were identified in all of the years that were analyzed. However, higher proportions of TB cases were found among blacks and females in more recent years. Death rates have increased significantly while corresponding relapse rates and the mean length of therapy have declined significantly. Rifampin was associated with a longer length of therapy before DOT, but with a shorter duration of therapy following the introduction of DOT. In all of the years analyzed, losses to follow-up (LTFU) do not differ from those completing therapy and are not spatially clustered relative to those completing therapy. DOT has been effective in reducing the numbers of TB cases in Baltimore city-wide without an emphasis on so-called "high-risk" patients for LTFU. Thus, any declines in TB case rates are not due to a decline in a particular group or geographic sector of the city. Universal DOT is effective and does not cause a geographic clustering of difficult-to-reach patients. This study effectively quantifies the effect of DOT in ensuring treatment completion for TB. This study also identifies changing patterns of TB disease in the city. These changing patterns, along with a leveling-off in the reduction of the annual incidence of TB in Baltimore, imply that newer approaches to controlling TB in the city need to be developed. Improving case findings through contact tracing and the use of Deoxyribonucleic Acid (DNA) fingerprinting are two strategies that have been added to strengthen and improve the TB control program. This study will provide a mechanism by which to measure the success of these new programs.

STEM and our future transportation leaders.

DOT National Transportation Integrated Search

2016-02-10

Between 2012 to 2022, 40 to 50 percent of the transportation workforce is expected to : retire taking valuable knowledge with them. State Departments of Transportation (DOT) : are expected to play a significant role in replenishing the workforce pipe...

Fabrication of nanoscale heterostructures comprised of graphene-encapsulated gold nanoparticles and semiconducting quantum dots for photocatalysis.

PubMed

Li, Yuan; Chopra, Nitin

2015-05-21

Patterned growth of multilayer graphene shell encapsulated gold nanoparticles (GNPs) and their covalent linking with inorganic quantum dots are demonstrated. GNPs were grown using a xylene chemical vapor deposition process, where the surface oxidized gold nanoparticles catalyze the multilayer graphene shell growth in a single step process. The graphene shell encapsulating gold nanoparticles could be further functionalized with carboxylic groups, which were covalently linked to amine-terminated quantum dots resulting in GNP-quantum dot heterostructures. The compositions, morphologies, crystallinity, and surface functionalization of GNPs and their heterostructures with quantum dots were evaluated using microscopic, spectroscopic, and analytical methods. Furthermore, optical properties of the derived architectures were studied using both experimental methods and simulations. Finally, GNP-quantum dot heterostructures were studied for photocatalytic degradation of phenol.

Size quantization patterns in self-assembled InAs/GaAs quantum dots

NASA Astrophysics Data System (ADS)

Colocci, M.; Bogani, F.; Carraresi, L.; Mattolini, R.; Bosacchi, A.; Franchi, S.; Frigeri, P.; Taddei, S.; Rosa-Clot, M.

1997-07-01

Molecular beam epitaxy has been used for growing self-assembled InAs quantum dots. A continuous variation of the InAs average coverage across the sample has been obtained by properly aligning the (001) GaAs substrate with respect to the molecular beam. Excitation of a large number of dots (laser spot diameter ≈ 100 μm) results in structured photoluminescence spectra; a clear quantization of the dot sizes is deduced from the distinct luminescence bands separated in energy by an average spacing of 20-30 meV. We ascribe the individual bands of the photoluminescence spectrum after low excitation to families of dots with roughly the same diameter and heights differing by one monolayer.

Structural properties of templated Ge quantum dot arrays: impact of growth and pre-pattern parameters

NASA Astrophysics Data System (ADS)

Tempeler, J.; Danylyuk, S.; Brose, S.; Loosen, P.; Juschkin, L.

2018-07-01

In this study we analyze the impact of process and growth parameters on the structural properties of germanium (Ge) quantum dot (QD) arrays. The arrays were deposited by molecular-beam epitaxy on pre-patterned silicon (Si) substrates. Periodic arrays of pits with diameters between 120 and 20 nm and pitches ranging from 200 nm down to 40 nm were etched into the substrate prior to growth. The structural perfection of the two-dimensional QD arrays was evaluated based on SEM images. The impact of two processing steps on the directed self-assembly of Ge QD arrays is investigated. First, a thin Si buffer layer grown on a pre-patterned substrate reshapes the pre-pattern pits and determines the nucleation and initial shape of the QDs. Subsequently, the deposition parameters of the Ge define the overall shape and uniformity of the QDs. In particular, the growth temperature and the deposition rate are relevant and need to be optimized according to the design of the pre-pattern. Applying this knowledge, we are able to fabricate regular arrays of pyramid shaped QDs with dot densities up to 7.2 × 1010 cm‑2.

Structural properties of templated Ge quantum dot arrays: impact of growth and pre-pattern parameters.

PubMed

Tempeler, J; Danylyuk, S; Brose, S; Loosen, P; Juschkin, L

2018-07-06

In this study we analyze the impact of process and growth parameters on the structural properties of germanium (Ge) quantum dot (QD) arrays. The arrays were deposited by molecular-beam epitaxy on pre-patterned silicon (Si) substrates. Periodic arrays of pits with diameters between 120 and 20 nm and pitches ranging from 200 nm down to 40 nm were etched into the substrate prior to growth. The structural perfection of the two-dimensional QD arrays was evaluated based on SEM images. The impact of two processing steps on the directed self-assembly of Ge QD arrays is investigated. First, a thin Si buffer layer grown on a pre-patterned substrate reshapes the pre-pattern pits and determines the nucleation and initial shape of the QDs. Subsequently, the deposition parameters of the Ge define the overall shape and uniformity of the QDs. In particular, the growth temperature and the deposition rate are relevant and need to be optimized according to the design of the pre-pattern. Applying this knowledge, we are able to fabricate regular arrays of pyramid shaped QDs with dot densities up to 7.2 × 10 10 cm -2 .

Formation mechanism of dot-line square superlattice pattern in dielectric barrier discharge

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

Liu, Weibo; Dong, Lifang, E-mail: donglfhbu@163.com, E-mail: pyy1616@163.com; Wang, Yongjie

We investigate the formation mechanism of the dot-line square superlattice pattern (DLSSP) in dielectric barrier discharge. The spatio-temporal structure studied by using the intensified-charge coupled device camera shows that the DLSSP is an interleaving of three different subpatterns in one half voltage cycle. The dot square lattice discharges first and, then, the two kinds of line square lattices, which form square grid structures discharge twice. When the gas pressure is varied, DLSSP can transform from square superlattice pattern (SSP). The spectral line profile method is used to compare the electron densities, which represent the amounts of surface charges qualitatively. Itmore » is found that the amount of surface charges accumulated by the first discharge of DLSSP is less than that of SSP, leading to a bigger discharge area of the following discharge (lines of DLSSP instead of halos of SSP). The spatial distribution of the electric field of the surface charges is simulated to explain the formation of DLSSP. This paper may provide a deeper understanding for the formation mechanism of complex superlattice patterns in DBD.« less

Theory of Spin States of Quantum Dot Molecules

NASA Astrophysics Data System (ADS)

Ponomarev, I. V.; Reinecke, T. L.; Scheibner, M.; Stinaff, E. A.; Bracker, A. S.; Doty, M. F.; Gammon, D.; Korenev, V. L.

2007-04-01

The photoluminescence spectrum of an asymmetric pair of coupled InAs quantum dots in an applied electric field shows a rich pattern of level anticrossings, crossings and fine structure that can be understood as a superposition of charge and spin configurations. We present a theoretical model that provides a description of the energy positions and intensities of the optical transitions in exciton, biexciton and charged exciton states of coupled quantum dots molecules.

Time-dependent wave packet simulations of transport through Aharanov-Bohm rings with an embedded quantum dot.

PubMed

Kreisbeck, C; Kramer, T; Molina, R A

2017-04-20

We have performed time-dependent wave packet simulations of realistic Aharonov-Bohm (AB) devices with a quantum dot embedded in one of the arms of the interferometer. The AB ring can function as a measurement device for the intrinsic transmission phase through the quantum dot, however, care has to be taken in analyzing the influence of scattering processes in the junctions of the interferometer arms. We consider a harmonic quantum dot and show how the Darwin-Fock spectrum emerges as a unique pattern in the interference fringes of the AB oscillations.

How supernovae launch galactic winds?

NASA Astrophysics Data System (ADS)

Fielding, Drummond; Quataert, Eliot; Martizzi, Davide; Faucher-Giguère, Claude-André

2017-09-01

We use idealized three-dimensional hydrodynamic simulations of global galactic discs to study the launching of galactic winds by supernovae (SNe). The simulations resolve the cooling radii of the majority of supernova remnants (SNRs) and thus self-consistently capture how SNe drive galactic winds. We find that SNe launch highly supersonic winds with properties that agree reasonably well with expectations from analytic models. The energy loading (η _E= \\dot{E}_wind/ \\dot{E}_SN) of the winds in our simulations are well converged with spatial resolution while the wind mass loading (η _M= \\dot{M}_wind/\\dot{M}_\\star) decreases with resolution at the resolutions we achieve. We present a simple analytic model based on the concept that SNRs with cooling radii greater than the local scaleheight break out of the disc and power the wind. This model successfully explains the dependence (or lack thereof) of ηE (and by extension ηM) on the gas surface density, star formation efficiency, disc radius and the clustering of SNe. The winds our simulations are weaker than expected in reality, likely due to the fact that we seed SNe preferentially at density peaks. Clustering SNe in time and space substantially increases the wind power.

Path perception during rotation: influence of instructions, depth range, and dot density

NASA Technical Reports Server (NTRS)

Li, Li; Warren, William H Jr

2004-01-01

How do observers perceive their direction of self-motion when traveling on a straight path while their eyes are rotating? Our previous findings suggest that information from retinal flow and extra-retinal information about eye movements are each sufficient to solve this problem for both perception and active control of self-motion [Vision Res. 40 (2000) 3873; Psych. Sci. 13 (2002) 485]. In this paper, using displays depicting translation with simulated eye rotation, we investigated how task variables such as instructions, depth range, and dot density influenced the visual system's reliance on retinal vs. extra-retinal information for path perception during rotation. We found that path errors were small when observers expected to travel on a straight path or with neutral instructions, but errors increased markedly when observers expected to travel on a curved path. Increasing depth range or dot density did not improve path judgments. We conclude that the expectation of the shape of an upcoming path can influence the interpretation of the ambiguous retinal flow. A large depth range and dense motion parallax are not essential for accurate path perception during rotation, but reference objects and a large field of view appear to improve path judgments.

Experimental observation of Fano effect in Ag nanoparticle-CdTe quantum dot hybrid system

NASA Astrophysics Data System (ADS)

Gurung, Sabina; Jayabalan, J.; Singh, Asha; Khan, Salahuddin; Chari, Rama

2018-04-01

We have experimentally measured the optical properties of Ag nanoparticle-CdTe quantum dot hybrid system and compared it with that of bare CdTe quantum dot colloid. It has been shown that the photoluminescence line shape of CdTe quantum dots becomes asymmetric in presence of Ag nanoparticles. The observed changes in the PL spectrum closely match the expected changes in the line shape due to Fano interaction between discrete level and continuum levels. Our experiment shows that a very small fraction of metal nanoparticles in the metal-semiconductor hybrid is sufficient to induce such changes in line shape which is in contrary to the earlier reported theoretical prediction on metal-semiconductor hybrid.

Growth patterns of self-assembled InAs quantum dots near the two-dimensional to three-dimensional transition

NASA Astrophysics Data System (ADS)

Colocci, M.; Bogani, F.; Carraresi, L.; Mattolini, R.; Bosacchi, A.; Franchi, S.; Frigeri, P.; Rosa-Clot, M.; Taddei, S.

1997-06-01

Self-assembled InAs quantum dots have been grown by molecular beam epitaxy in such a way as to obtain a continuous variation of InAs coverages across the wafer. Structured photoluminescence spectra are observed after excitation of a large number of dots; deconvolution into Gaussian components yields narrow emission bands (full width at half-maximum 20-30 meV) separated in energy by an average spacing of 30-40 meV. We ascribe the individual bands of the photoluminescence spectra after low excitation to families of dots with similar shapes and with heights differing by one monolayer, as strongly supported by numerical calculations of the fundamental electronic transitions in quantum dot structures.

Direct laser interference patterning of magnetic thin films

NASA Astrophysics Data System (ADS)

Aktag, Aliekber

Recently, patterned magnetic thin films have attracted much attention for a variety of applications such as high density magnetic recording, magnetoresistive sensing, and magnetic random access memories. In the case of magnetic recording, one scheme calls for the films to be patterned into single domain "dots", where every dot represents a thermally stable bit. In this thesis, we extended a technique called direct laser interference patterning (DLIP), originally developed by Polushkin and co-workers, to pattern and locally modify the materials properties of magnetic thin films. In this technique, a high-intensity Nd:YAG pulse laser beam was split into two, three, or four beams, which are then recombined to interfere on a sample surface. The interference intensity maxima can modify the local materials properties of the film through local "annealing" or, more drastically, by ablation. We carried out some preliminary investigations of the DLIP process in several films including co-sputtered Co-C, amorphous Dy/Co:SiO2 multilayers, and Co/SiO2 multilayers in order to refine our techniques. We successfully produced regular arrays of lines, dots, or antidots formed by ablation of the thin film. The preliminary studies also showed that, in the regime of more modest pulse energies, it is possible to modify the magnetic properties of the films without noticeably changing the film topography. We then prepared perpendicular magnetic anisotropy Co/Pt multilayers with a SiO x passivation layer and applied DLIP at fairly modest intensities to pattern the film. We then studied the structural and magnetic changes that occurred in some detail. X-ray diffraction scans showed the Co/Pt:SiO x multilayer films to be nanocrystalline before and after patterning. Atomic force microscopy images showed no evidence for topographic changes of the Co/Pt:SiOx during patterning. In contrast, magnetic force microscopy showed regular periodic dot arrays, indicating that the local magnetic properties were significantly affected by the patterning process. Alternating-gradient-force magnetometry and magneto-optic measurements also showed that the magnetic properties were markedly changed by the DLIP process. Our results offer strong evidence that local heating causes the moments to change from perpendicular to in-plane, with the consequent formation of an "anisotropy lattice": dots of in-plane magnetization within a matrix of perpendicular magnetization. We also carried out some optical interference calculations to predict the light intensity distributions for two, three, and four interfering beams of light. We found that the patterns could be controlled by varying the angles of incidence, the polarizations of the beams, and the wavelength and intensity of the beams, and that a wide variety of patterns are possible. The predicted patterns were in quite good agreement with those observed experimentally.

Comparison of low frequency charge noise in identically patterned Si/SiO{sub 2} and Si/SiGe quantum dots

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

Freeman, Blake M.; Schoenfield, Joshua S.; Jiang, HongWen

We investigate and compare the charge noise in Si/SiO{sub 2} and Si/SiGe gate defined quantum dots with identically patterned gates by measuring the low frequency 1/f current noise through the biased quantum dots in the coulomb blockade regime. The current noise is normalized and used to extract a measurement of the potential energy noise in the system. Additionally, the temperature dependence of this noise is investigated. The measured charge noise in Si/SiO{sub 2} compares favorably with that of the SiGe device as well as previous measurements made on other substrates suggesting Si/SiO{sub 2} is a potential candidate for spin basedmore » quantum computing.« less

49 CFR 40.389 - What factors may the Director consider?

Code of Federal Regulations, 2013 CFR

2013-10-01

... WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Public Interest Exclusions § 40.389 What factors may the... duration of the noncompliance; (c) Whether there is a pattern or prior history of noncompliance; (d... DOT agency regulation, the degree to which the noncompliance affects matters common to the DOT drug...

Motion fading is driven by perceived, not actual angular velocity.

PubMed

Kohler, P J; Caplovitz, G P; Hsieh, P-J; Sun, J; Tse, P U

2010-06-01

After prolonged viewing of a slowly drifting or rotating pattern under strict fixation, the pattern appears to slow down and then momentarily stop. Here we examine the relationship between such 'motion fading' and perceived angular velocity. Using several different dot patterns that generate emergent virtual contours, we demonstrate that whenever there is a difference in the perceived angular velocity of two patterns of dots that are in fact rotating at the same angular velocity, there is also a difference in the time to undergo motion fading for those two patterns. Conversely, whenever two patterns show no difference in perceived angular velocity, even if in fact rotating at different angular velocities, we find no difference in the time to undergo motion fading. Thus, motion fading is driven by the perceived rather than actual angular velocity of a rotating stimulus. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Nanowire–quantum-dot lasers on flexible membranes

NASA Astrophysics Data System (ADS)

Tatebayashi, Jun; Ota, Yasutomo; Ishida, Satomi; Nishioka, Masao; Iwamoto, Satoshi; Arakawa, Yasuhiko

2018-06-01

We demonstrate lasing in a single nanowire with quantum dots as an active medium embedded on poly(dimethylsiloxane) membranes towards application in nanowire-based flexible nanophotonic devices. Nanowire laser structures with 50 quantum dots are grown on patterned GaAs(111)B substrates and then transferred from the as-grown substrates on poly(dimethylsiloxane) transparent flexible organosilicon membranes, by means of spin-casting and curing processes. We observe lasing oscillation in the transferred single nanowire cavity with quantum dots at 1.425 eV with a threshold pump pulse fluence of ∼876 µJ/cm2, which enables the realization of high-performance multifunctional NW-based flexible photonic devices.

Creation of Frustrated Systems by d-dot Array

NASA Astrophysics Data System (ADS)

Masahiko, Machida

2004-03-01

When a square shape dot of High-Tc superconductor is embedded in s-wave superconducting matrix, half quantized vortices are spontaneously generated at the corners of the dot. This feature gives the magnetic interactions between neighboring dots in array systems composed of sevaral dots of High-Tc superconductor and allows us to make magnetic interaction systems. We propose that we can create interesting frustrated systems like the spin-ice by setting the dots in various manners. In order to demonstrate which types of frustrated systems are possible, we perform numerical simulations for the time-dependent Ginzburg-Landau equation describing dynamics of the superconducting order parameters with d-wave and s-wave symmetries. The simulations reveal that the proposed system has two parameters originated from the magnetic interaction between emerged half vortices. We tune the parameters and show various patterns of half vortices from the Ising to the ice model.

RKKY interaction in a chirally coupled double quantum dot system

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

Heine, A. W.; Tutuc, D.; Haug, R. J.

2013-12-04

The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the so-called Kondo chessboard pattern in the transport through the quantum dots. The two quantum dots become therefore chirally coupled via the edge channels formed in the open conducting area. In regions where both quantum dots exhibit Kondo transport the presence of the RKKY exchange interaction is probed by an analysis of the temperature dependence. The thus obtainedmore » Kondo temperature of one dot shows an abrupt increase at the onset of Kondo transport in the other, independent of the magnetic field polarity, i.e. edge state chirality in the central region.« less

Thresholded-Rewards Decision Problems: Acting Effectively in Timed Domains

DTIC Science & Technology

2009-04-02

intermediate reward (score difference). 89 5.8 Regions covered by each role in each play. (a) RoboCup play. The defender’s region is colored with dark dots; the...colored with dark dots; the middle defender’s region is colored with a light checkerboard pattern, and the front defender’s region is colored with...defender’s region is colored with dark dots; the supporter’s region is colored with diagonal lines. The attacker’s region is the entire field. (b

Pure visual imagery as a potential approach to achieve three classes of control for implementation of BCI in non-motor disorders

NASA Astrophysics Data System (ADS)

Sousa, Teresa; Amaral, Carlos; Andrade, João; Pires, Gabriel; Nunes, Urbano J.; Castelo-Branco, Miguel

2017-08-01

Objective. The achievement of multiple instances of control with the same type of mental strategy represents a way to improve flexibility of brain-computer interface (BCI) systems. Here we test the hypothesis that pure visual motion imagery of an external actuator can be used as a tool to achieve three classes of electroencephalographic (EEG) based control, which might be useful in attention disorders. Approach. We hypothesize that different numbers of imagined motion alternations lead to distinctive signals, as predicted by distinct motion patterns. Accordingly, a distinct number of alternating sensory/perceptual signals would lead to distinct neural responses as previously demonstrated using functional magnetic resonance imaging (fMRI). We anticipate that differential modulations should also be observed in the EEG domain. EEG recordings were obtained from twelve participants using three imagery tasks: imagery of a static dot, imagery of a dot with two opposing motions in the vertical axis (two motion directions) and imagery of a dot with four opposing motions in vertical or horizontal axes (four directions). The data were analysed offline. Main results. An increase of alpha-band power was found in frontal and central channels as a result of visual motion imagery tasks when compared with static dot imagery, in contrast with the expected posterior alpha decreases found during simple visual stimulation. The successful classification and discrimination between the three imagery tasks confirmed that three different classes of control based on visual motion imagery can be achieved. The classification approach was based on a support vector machine (SVM) and on the alpha-band relative spectral power of a small group of six frontal and central channels. Patterns of alpha activity, as captured by single-trial SVM closely reflected imagery properties, in particular the number of imagined motion alternations. Significance. We found a new mental task based on visual motion imagery with potential for the implementation of multiclass (3) BCIs. Our results are consistent with the notion that frontal alpha synchronization is related with high internal processing demands, changing with the number of alternation levels during imagery. Together, these findings suggest the feasibility of pure visual motion imagery tasks as a strategy to achieve multiclass control systems with potential for BCI and in particular, neurofeedback applications in non-motor (attentional) disorders.

Measurement of a heavy-hole hyperfine interaction in InGaAs quantum dots using resonance fluorescence.

PubMed

Fallahi, P; Yilmaz, S T; Imamoğlu, A

2010-12-17

We measure the strength and the sign of hyperfine interaction of a heavy hole with nuclear spins in single self-assembled quantum dots. Our experiments utilize the locking of a quantum dot resonance to an incident laser frequency to generate nuclear spin polarization. By monitoring the resulting Overhauser shift of optical transitions that are split either by electron or exciton Zeeman energy with respect to the locked transition using resonance fluorescence, we find that the ratio of the heavy-hole and electron hyperfine interactions is -0.09 ± 0.02 in three quantum dots. Since hyperfine interactions constitute the principal decoherence source for spin qubits, we expect our results to be important for efforts aimed at using heavy-hole spins in quantum information processing.

Visual motion integration by neurons in the middle temporal area of a New World monkey, the marmoset

PubMed Central

Solomon, Selina S; Tailby, Chris; Gharaei, Saba; Camp, Aaron J; Bourne, James A; Solomon, Samuel G

2011-01-01

Abstract The middle temporal area (MT/V5) is an anatomically distinct region of primate visual cortex that is specialized for the processing of image motion. It is generally thought that some neurons in area MT are capable of signalling the motion of complex patterns, but this has only been established in the macaque monkey. We made extracellular recordings from single units in area MT of anaesthetized marmosets, a New World monkey. We show through quantitative analyses that some neurons (35 of 185; 19%) are capable of signalling pattern motion (‘pattern cells’). Across several dimensions, the visual response of pattern cells in marmosets is indistinguishable from that of pattern cells in macaques. Other neurons respond to the motion of oriented contours in a pattern (‘component cells’) or show intermediate properties. In addition, we encountered a subset of neurons (22 of 185; 12%) insensitive to sinusoidal gratings but very responsive to plaids and other two-dimensional patterns and otherwise indistinguishable from pattern cells. We compared the response of each cell class to drifting gratings and dot fields. In pattern cells, directional selectivity was similar for gratings and dot fields; in component cells, directional selectivity was weaker for dot fields than gratings. Pattern cells were more likely to have stronger suppressive surrounds, prefer lower spatial frequencies and prefer higher speeds than component cells. We conclude that pattern motion sensitivity is a feature of some neurons in area MT of both New and Old World monkeys, suggesting that this functional property is an important stage in motion analysis and is likely to be conserved in humans. PMID:21946851

Working towards TB elimination the WHO Regional Strategic Plan (2006-2015).

PubMed

Nair, Nani; Cooreman, Erwin

2006-03-01

DOTS has expanded rapidly in the South-East Asia Region over the period of the Partnership's first Global Plan (2001-2005), with almost 100% geographical coverage achieved in 2005. All countries have made impressive progress in improving coverage and quality. This progress has been made possible through strong political commitment and large investments in TB control for improved infrastructure, reliable drug supply, increased staffing, improved laboratory services, and intensified training and supervision. Accomplishing the objectives outlined in this document will require sustaining the progress in all countries and particularly in the five high burden countries for achieving major regional and global impact. National TB programmes will need to be supported to maintain or surpass the 70% case detection and 85% treatment success rates. The achievement of the TB-related targets linked to the MDGs will also depend on how effectively initiatives such as DOTS-Plus, PPM DOTS and interventions for TB/ HIV among others, are implemented. National governments and development partners must fulfill their commitments to mobilizing and sustaining adequate resources to support the full range of activities envisaged. The benefits of full and effective implementation of all the planned interventions would be substantial. These will result in 20 to 25 million TB cases being treated in DOTS program mes and more than 150 000 drug-resistant cases receiving treatment through DOTS-Plus during the period 2006-2015. In addition, at least 250 000 HIV-infected TB patients may also receive anti-retroviral therapy. As a consequence, the prevalence of TB is expected to fall below 175/100 000 and the number of TB deaths is expected to fall to between 100 000 and 150 000 per year. There would also be substantial economic benefits given that TB disproportionately affects adults in their most productive years. Considering these aspects, it is expected that the TB incidence will decline significantly during this period so that the Millennium Development Goals would be met by or ahead of 2015.

Selective LPCVD growth of graphene on patterned copper and its growth mechanism

NASA Astrophysics Data System (ADS)

Zhang, M.; Huang, B.-C.; Wang, Y.; Woo, J. C. S.

2016-12-01

Copper-catalyzed graphene low-pressure chemical-vapor deposition (LPCVD) growth has been regarded as a viable solution towards its integration to CMOS technology, and the wafer-bonding method provides a reliable alternative for transferring the selective graphene grown on a patterned metal film for IC manufacturing. In this paper, selective LPCVD graphene growth using patterned copper dots has been studied. The Raman spectra of grown films have demonstrated large dependence on the growth conditions. To explain the results, the growth mechanisms based on surface adsorption and copper-vapor-assisted growth are investigated by the comparison between the blanket copper films with/without the additional copper source. The copper vapor density is found to be critical for high-quality graphene growth. In addition, the copper-vapor-assisted growth is also evidenced by the carbon deposition on the SiO2 substrate of the patterned-copper-dot sample and chamber wall during graphene growth. This growth mechanism explains the correlation between the growth condition and Raman spectrum for films on copper dots. The study on the copper-catalyzed selective graphene growth on the hard substrate paves the way for the synthesis and integration of the 2D material in VLSI.

Four-Dimensional Screening Anti-Counterfeiting Pattern by Inkjet Printed Photonic Crystals.

PubMed

Hou, Jue; Zhang, Huacheng; Su, Bin; Li, Mingzhu; Yang, Qiang; Jiang, Lei; Song, Yanlin

2016-10-06

A four-dimensional screening anti-counterfeiting QR code composed of differently shaped photonic crystal (PC) dots has been fabricated that could display four images depending on different lighting conditions. By controlling the rheology of poly(dimethylsiloxane) (PDMS), three kinds of PC dots could be sequentially integrated into one pattern using the layer-by-layer printing strategy. The information can be encoded and stored in shapes and read out by the difference in optical properties. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

L10 FePtCu bit patterned media

NASA Astrophysics Data System (ADS)

Brombacher, C.; Grobis, M.; Lee, J.; Fidler, J.; Eriksson, T.; Werner, T.; Hellwig, O.; Albrecht, M.

2012-01-01

Chemically ordered 5 nm-thick L10 FePtCu films with strong perpendicular magnetic anisotropy were post-patterned by nanoimprint lithography into a dot array over a 3 mm-wide circumferential band on a 3 inch Si wafer. The dots with a diameter of 30 nm and a center-to-center pitch of 60 nm appear as single domain and reveal an enhanced switching field as compared to the continuous film. We demonstrate successful recording on a single track using shingled writing with a conventional hard disk drive write/read head.

Impact of DOTS expansion on tuberculosis related outcomes and costs in Haiti.

PubMed

Jacquet, Vary; Morose, Willy; Schwartzman, Kevin; Oxlade, Olivia; Barr, Graham; Grimard, Franque; Menzies, Dick

2006-08-15

Implementation of the World Health Organization's DOTS strategy (Directly Observed Treatment Short-course therapy) can result in significant reduction in tuberculosis incidence. We estimated potential costs and benefits of DOTS expansion in Haiti from the government, and societal perspectives. Using decision analysis incorporating multiple Markov processes (Markov modelling), we compared expected tuberculosis morbidity, mortality and costs in Haiti with DOTS expansion to reach all of the country, and achieve WHO benchmarks, or if the current situation did not change. Probabilities of tuberculosis related outcomes were derived from the published literature. Government health expenditures, patient and family costs were measured in direct surveys in Haiti and expressed in 2003 US$. Starting in 2003, DOTS expansion in Haiti is anticipated to cost $4.2 million and result in 63,080 fewer tuberculosis cases, 53,120 fewer tuberculosis deaths, and net societal savings of $131 million, over 20 years. Current government spending for tuberculosis is high, relative to the per capita income, and would be only slightly lower with DOTS. Societal savings would begin within 4 years, and would be substantial in all scenarios considered, including higher HIV seroprevalence or drug resistance, unchanged incidence following DOTS expansion, or doubling of initial and ongoing costs for DOTS expansion. A modest investment for DOTS expansion in Haiti would provide considerable humanitarian benefit by reducing tuberculosis-related morbidity, mortality and costs for patients and their families. These benefits, together with projected minimal Haitian government savings, argue strongly for donor support for DOTS expansion.

Iris structure and minor physical anomalies in schizophrenia.

PubMed

Trixler, Dániel; Tényi, Tamás

2017-10-01

This study compared five human iris characteristics and minor physical anomalies (MPAs) between patients with schizophrenia (n = 32) and controls (n = 31). Correlations between iris characteristics and MPAs were expected, due to their same ectodermic origin. Iris macro photos were taken and quantified in five categories mentioned before. MPAs were also examined in both groups. Our results show significant differences in the frequency of pigment dots of the iris and total number of MPAs between groups. Other significant differences were found in the extension of concentric furrows, as they were more common in healthy subjects, while Wolfflin nodules occurred significantly more often in patients with schizophrenia. Expected difference in Fuch's crypts could not be observed between groups. Light eye color was positively correlated to pigment dots and Wolfflin nodules, and negatively correlated with concentric furrows. Dark eye color showed positive correlation with concentric furrows, and negative correlation with pigment dots and concentric furrows. A gender effect could also been observed: male individuals showed moderate positive correlations between pigment dots and total MPAs frequency, while this couldn't be observed in the female group. Our findings suggest possible connections between iris characteristics and MPAs, where males are more prone to deviations. Copyright © 2017 Elsevier B.V. All rights reserved.

Coherent manipulation of a Si/SiGe-based singlet-triplet qubit

NASA Astrophysics Data System (ADS)

Gyure, Mark

2012-02-01

Electrically defined silicon-based qubits are expected to show improved quantum memory characteristics in comparison to GaAs-based devices due to reduced hyperfine interactions with nuclear spins. Silicon-based qubit devices have proved more challenging to build than their GaAs-based counterparts, but recently several groups have reported substantial progress in single-qubit initialization, measurement, and coherent operation. We report [1] coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure, forming two levels of a singlet-triplet qubit. We measure a nuclei-induced T2^* of 360 ns, an increase over similar measurements in GaAs-based quantum dots by nearly two orders of magnitude. We also describe the results from detailed modeling of our materials and devices that show this value for T2^* is consistent with theoretical expectations for our estimated dot sizes and a natural abundance of ^29Si. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the United States Department of Defense or the U.S. Government. Approved for public release, distribution unlimited.[4pt] [1] B. M. Maune et al., ``Coherent Singlet-Triplet Oscillations in a Silicon-based Double Quantum Dot,'' accepted by Nature.

The fabrication of highly ordered block copolymer micellar arrays: control of the separation distances of silicon oxide dots

NASA Astrophysics Data System (ADS)

Yoo, Hana; Park, Soojin

2010-06-01

We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-b-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm × 5 cm.

The fabrication of highly ordered block copolymer micellar arrays: control of the separation distances of silicon oxide dots.

PubMed

Yoo, Hana; Park, Soojin

2010-06-18

We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-b-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm x 5 cm.

Improvement in crystal quality and optical properties of n-type GaN employing nano-scale SiO2 patterned n-type GaN substrate.

PubMed

Jo, Min Sung; Sadasivam, Karthikeyan Giri; Tawfik, Wael Z; Yang, Seung Bea; Lee, Jung Ju; Ha, Jun Seok; Moon, Young Boo; Ryu, Sang Wan; Lee, June Key

2013-01-01

n-type GaN epitaxial layers were regrown on the patterned n-type GaN substrate (PNS) with different size of silicon dioxide (SiO2) nano dots to improve the crystal quality and optical properties. PNS with SiO2 nano dots promotes epitaxial lateral overgrowth (ELOG) for defect reduction and also acts as a light scattering point. Transmission electron microscopy (TEM) analysis suggested that PNS with SiO2 nano dots have superior crystalline properties. Hall measurements indicated that incrementing values in electron mobility were clear indication of reduction in threading dislocation and it was confirmed by TEM analysis. Photoluminescence (PL) intensity was enhanced by 2.0 times and 3.1 times for 1-step and 2-step PNS, respectively.

DNA nanosensor based on biocompatible graphene quantum dots and carbon nanotubes.

PubMed

Qian, Zhao Sheng; Shan, Xiao Yue; Chai, Lu Jing; Ma, Juan Juan; Chen, Jian Rong; Feng, Hui

2014-10-15

An ultrasensitive nanosensor based on fluorescence resonance energy transfer (FRET) between biocompatible graphene quantum dots and carbon nanotubes for DNA detection was reported. We take advantage of good biocompatibility and strong fluorescence of graphene quantum dots, base pairing specificity of DNA and unique fluorescence resonance energy transfer between graphene quantum dots and carbon nanotubes to achieve the analysis of low concentrations of DNA. Graphene quantum dots with high quantum yield up to 0.20 were prepared and served as the fluorophore of DNA probe. FRET process between graphene quantum dots-labeled probe and oxidized carbon nanotubes is easily achieved due to their efficient self-assembly through specific π-π interaction. This nanosensor can distinguish complementary and mismatched nucleic acid sequences with high sensitivity and good reproducibility. The detection method based on this nanosensor possesses a broad linear span of up to 133.0 nM and ultralow detection limit of 0.4 nM. The constructed nanosensor is expected to be highly biocompatible because of all its components with excellent biocompatibility. Copyright © 2014 Elsevier B.V. All rights reserved.

The impact of disorder on charge transport in three dimensional quantum dot resonant tunneling structures

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

Puthen-Veettil, B., E-mail: b.puthen-veettil@unsw.edu.au; Patterson, R.; König, D.

Efficient iso-entropic energy filtering of electronic waves can be realized through nanostructures with three dimensional confinement, such as quantum dot resonant tunneling structures. Large-area deployment of such structures is useful for energy selective contacts but such configuration is susceptible to structural disorders. In this work, the transport properties of quantum-dot-based wide-area resonant tunneling structures, subject to realistic disorder mechanisms, are studied. Positional variations of the quantum dots are shown to reduce the resonant transmission peaks while size variations in the device are shown to reduce as well as broaden the peaks. Increased quantum dot size distribution also results in amore » peak shift to lower energy which is attributed to large dots dominating transmission. A decrease in barrier thickness reduces the relative peak height while the overall transmission increases dramatically due to lower “series resistance.” While any shift away from ideality can be intuitively expected to reduce the resonance peak, quantification allows better understanding of the tolerances required for fabricating structures based on resonant tunneling phenomena/.« less

Thermal effect of Zn quantum dots grown on Si(111): competition between relaxation and reconstraint

NASA Astrophysics Data System (ADS)

Kao, Li-Chi; Huang, Bo-Jia; Zheng, Yu-En; Tu, Kai-Teng; Chiu, Shang-Jui; Ku, Ching-Shun; Lo, Kuang Yao

2018-01-01

Zn dots are potential solutions for metal contacts in future nanodevices. The metastable states that exist at the interface between Zn quantum dots and oxide-free Si(111) surfaces can suppress the development of the complete relaxation and increase the size of Zn dots. In this work, the actual heat consumption of the structural evolution of Zn dots resulting from extrinsic thermal effect was analyzed. Zn dots were coherently grown on oxide-free Si(111) through magnetron RF sputtering. A compensative optical method combined with reflective second harmonic generation and synchrotron x-ray diffraction (XRD) was developed to statistically analyze the thermal effect on the Zn dot system. Pattern matching (3 m) between the Zn and oxide-free Si(111) surface enabled Si(111) to constrain Zn dots from a liquid to solid phase. Annealing under vacuum induced smaller, loose Zn dots to be reconstrained by Si(111). When the size of the Zn dots was in the margin of complete relaxation, the Zn dot was partially constrained by potential barriers (metastable states) between Zn(111) and one of the six in-planes of Si〈110〉. The thermal disturbance exerted by annealing would enable partially constrained ZnO/Zn dots to overcome the potential barrier and be completely relaxed, which is obvious on the transition between Zn(111) and Zn(002) peak in synchrotron XRD. Considering the actual irradiated surface area of dots array in a wide-size distribution, the competition between reconstrained and relaxed Zn dots on Si(111) during annealing was statistically analyzed.

Investigations into the formation of nanocrystalline quantum dot thin films by mist deposition process

NASA Astrophysics Data System (ADS)

Kshirsagar, Aditya

Semiconductor nanocrystalline quantum dots (NQDs) have material properties remarkably different compared to bulk semiconductors with the same material composition. These NQDs have various novel applications in the electronic and photonic industry, such as light emitting diodes (LEDs) and flat-panel displays. In these applications, ultra-thin films of NQDs in the monolayer regime are needed to ensure optimal current transport properties and device efficiency. There is ongoing search to find a suitable method to deposit and pattern such ultra-thin films of quantum dots with few monolayer thicknesses. Several competing approaches are available, each with its pros and cons. This study explores mist deposition as the technique to fill this void. In this study, ultra-thin films of quantum dots are deposited on diverse substrates and are characterized to understand the mechanics of mist deposition. Various applications of blanket deposited and patterned quantum dot films are studied. The results discussed here include atomic force microscopy analysis of the films to study surface morphology, fluorescence microscopy to study light emission and optical microscope images to study patterning techniques. These results demonstrate the ability of mist deposition to form 1-4 monolayers thick, uniform, defect-free patterned films with root mean square (RMS) surface roughness less than 2 nm. LEDs fabricated using mist deposition show a peak luminescence greater than 500 cd/m2 for matched red, yellow and green devices using Alq3 as the electron transport layer, and over 9000 cd/m2 for red devices using ZnO as the electron transport layer, respectively. In addition to the experimental approach to study the process and explore potential applications, simulation and modeling are carried out to understand the various aspects of mist deposition. A mathematical model is presented which discusses the atomization process of the precursor solution, the physics involved during the deposition process, and the mechanics of film formation. Results of film morphology simulation using Monte Carlo techniques and process simulation using multi-physics approach are discussed. Problems in pattern transfer due to electrostatic effects when using shadow masks are presented in a separate chapter.

Taking a(c)count of eye movements: Multiple mechanisms underlie fixations during enumeration.

PubMed

Paul, Jacob M; Reeve, Robert A; Forte, Jason D

2017-03-01

We habitually move our eyes when we enumerate sets of objects. It remains unclear whether saccades are directed for numerosity processing as distinct from object-oriented visual processing (e.g., object saliency, scanning heuristics). Here we investigated the extent to which enumeration eye movements are contingent upon the location of objects in an array, and whether fixation patterns vary with enumeration demands. Twenty adults enumerated random dot arrays twice: first to report the set cardinality and second to judge the perceived number of subsets. We manipulated the spatial location of dots by presenting arrays at 0°, 90°, 180°, and 270° orientations. Participants required a similar time to enumerate the set or the perceived number of subsets in the same array. Fixation patterns were systematically shifted in the direction of array rotation, and distributed across similar locations when the same array was shown on multiple occasions. We modeled fixation patterns and dot saliency using a simple filtering model and show participants judged groups of dots in close proximity (2°-2.5° visual angle) as distinct subsets. Modeling results are consistent with the suggestion that enumeration involves visual grouping mechanisms based on object saliency, and specific enumeration demands affect spatial distribution of fixations. Our findings highlight the importance of set computation, rather than object processing per se, for models of numerosity processing.

Perceptual Strategies of Pigeons to Detect a Rotational Centre—A Hint for Star Compass Learning?

PubMed Central

Helduser, Sascha; Mouritsen, Henrik; Güntürkün, Onur

2015-01-01

Birds can rely on a variety of cues for orientation during migration and homing. Celestial rotation provides the key information for the development of a functioning star and/or sun compass. This celestial compass seems to be the primary reference for calibrating the other orientation systems including the magnetic compass. Thus, detection of the celestial rotational axis is crucial for bird orientation. Here, we use operant conditioning to demonstrate that homing pigeons can principally learn to detect a rotational centre in a rotating dot pattern and we examine their behavioural response strategies in a series of experiments. Initially, most pigeons applied a strategy based on local stimulus information such as movement characteristics of single dots. One pigeon seemed to immediately ignore eccentric stationary dots. After special training, all pigeons could shift their attention to more global cues, which implies that pigeons can learn the concept of a rotational axis. In our experiments, the ability to precisely locate the rotational centre was strongly dependent on the rotational velocity of the dot pattern and it crashed at velocities that were still much faster than natural celestial rotation. We therefore suggest that the axis of the very slow, natural, celestial rotation could be perceived by birds through the movement itself, but that a time-delayed pattern comparison should also be considered as a very likely alternative strategy. PMID:25807499

Design strategy for terahertz quantum dot cascade lasers.

PubMed

Burnett, Benjamin A; Williams, Benjamin S

2016-10-31

The development of quantum dot cascade lasers has been proposed as a path to obtain terahertz semiconductor lasers that operate at room temperature. The expected benefit is due to the suppression of nonradiative electron-phonon scattering and reduced dephasing that accompanies discretization of the electronic energy spectrum. We present numerical modeling which predicts that simple scaling of conventional quantum well based designs to the quantum dot regime will likely fail due to electrical instability associated with high-field domain formation. A design strategy adapted for terahertz quantum dot cascade lasers is presented which avoids these problems. Counterintuitively, this involves the resonant depopulation of the laser's upper state with the LO-phonon energy. The strategy is tested theoretically using a density matrix model of transport and gain, which predicts sufficient gain for lasing at stable operating points. Finally, the effect of quantum dot size inhomogeneity on the optical lineshape is explored, suggesting that the design concept is robust to a moderate amount of statistical variation.

Biosynthesis of luminescent CdS quantum dots using plant hairy root culture

NASA Astrophysics Data System (ADS)

Borovaya, Mariya N.; Naumenko, Antonina P.; Matvieieva, Nadia A.; Blume, Yaroslav B.; Yemets, Alla I.

2014-12-01

CdS nanoparticles have a great potential for application in chemical research, bioscience and medicine. The aim of this study was to develop an efficient and environmentally-friendly method of plant-based biosynthesis of CdS quantum dots using hairy root culture of Linaria maroccana L. By incubating Linaria root extract with inorganic cadmium sulfate and sodium sulfide we synthesized stable luminescent CdS nanocrystals with absorption peaks for UV-visible spectrometry at 362 nm, 398 nm and 464 nm, and luminescent peaks at 425, 462, 500 nm. Transmission electron microscopy of produced quantum dots revealed their spherical shape with a size predominantly from 5 to 7 nm. Electron diffraction pattern confirmed the wurtzite crystalline structure of synthesized cadmium sulfide quantum dots. These results describe the first successful attempt of quantum dots synthesis using plant extract.

Negative-tone imaging with EUV exposure toward 13nm hp

NASA Astrophysics Data System (ADS)

Tsubaki, Hideaki; Nihashi, Wataru; Tsuchihashi, Toru; Yamamoto, Kei; Goto, Takahiro

2016-03-01

Negative-tone imaging (NTI) with EUV exposure has major advantages with respect to line-width roughness (LWR) and resolution due in part to polymer swelling and favorable dissolution mechanics. In NTI process, both resist and organic solvents play important roles in determining lithography performances. The present study describes novel chemically amplified resist materials based on NTI technology with EUV using a specific organic solvents. Lithographic performances of NTI process were described in this paper under exposures using ASML NXE:3300 EUV scanner at imec. It is emphasized that 14 nm hp was nicely resolved under exposure dose of 37 mJ/cm2 without any bridge and collapse, which are attributed to the low swelling character of NTI process. Although 13 nm hp resolution was potentially obtained, a pattern collapse still restricts its resolution in case coating resist film thickness is 40 nm. Dark mask limitation due mainly to mask defectivity issue makes NTI with EUV favorable approach for printing block mask to produce logic circuit. A good resolution of CD-X 21 nm/CD-Y 32 nm was obtained for block mask pattern using NTI with usable process window and dose of 49 mJ/cm2. Minimum resolution now reaches CD-X 17 nm / CD-Y 23 nm for the block. A 21 nm block mask resolution was not affected by exposure dose and explored toward low dose down to 18 mJ/cm2 by reducing quencher loading. In addition, there was a negligible amount of increase in LCDU for isolated dot pattern when decreasing exposure dose from 66 mJ/cm2 to 24 mJ/cm2. On the other hand, there appeared tradeoff relationship between LCDU and dose for dense dot pattern, indicating photon-shot noise restriction, but strong dependency on patterning features. Design to improve acid generation efficiency was described based on acid generation mechanism in traditional chemically amplified materials which contains photo-acid generator (PAG) and polymer. Conventional EUV absorber comprises of organic compounds is expected to have 1.6 times higher EUV absorption than polyhydroxystyrene based on calculation. However, observed value of acid amount was comparable or significantly worse than polyhydroxystyrene.

Interleukin-13 conjugated quantum dots for identification of glioma initiating cells and their extracellular vesicles.

PubMed

Madhankumar, A B; Mrowczynski, Oliver D; Patel, Suhag R; Weston, Cody L; Zacharia, Brad E; Glantz, Michael J; Siedlecki, Christopher A; Xu, Li-Chong; Connor, James R

2017-08-01

Cadmium selenide (CdSe) based quantum dots modified with polyethylene glycol and chemically linked to interleukin-13 (IL13) were prepared with the aim of identifying the high affinity receptor (IL13Rα2) which is expressed in glioma stem cells and exosomes secreted by these cancer stem cells. IL13 conjugated quantum dots (IL13QD) were thoroughly characterized for their physicochemical properties including particle size and surface morphology. Furthermore, the specific binding of the IL13QD to glioma cells and to glioma stem cells (GSC) was verified using a competitive binding study. The exosomes were isolated from the GSC conditioned medium and the expression of IL13Rα2 in the GSC and exosomes was verified. The binding property of IL13QD to the tumor associated exosomes was initially confirmed by transmission electron microscopy. The force of attraction between the quantum dots and U251 glioma cells and the exosomes was investigated by atomic force microscopy, which indicated a higher force of binding interaction between the IL13QD and IL13Rα2 expressing glioma cells and exosomes secreted by glioma stem cells. Flow cytometry of the IL13QD and exosomes from the culture media and cerebrospinal fluid (CSF) of patients with glioma tumors indicated a distinctly populated complex pattern different from that of non-targeted quantum dots and bovine serum albumin (BSA) conjugated quantum dots confirming specific binding potential of the IL13QD to the tumor associated exosomes. The results of this study demonstrate that IL13QD can serve as an ex vivo marker for glioma stem cells and exosomes that can inform diagnosis and prognosis of patients harboring malignant disease. Functionalized quantum dots are flexible semiconductor nanomaterials which have an immense application in biomedical research. In particular, when they are functionalized with biomolecules like proteins or antibodies, they have the specialized ability to detect the expression of receptors and antigens in cells and tissues. In this study we designed a cytokine (interleukin-13) functionalized quantum dot to detect a cancer associated receptor expressed in cancer stem cells and the extracellular vesicles (exosomes) secreted by the cancer cells themselves. The binding pattern of these cytokine modified quantum dots to the cancer stem cells and exosomes alters the physical properties of the complex in the fixed and suspended form. This altered binding pattern can be monitored by a variety of techniques, including transmission electron microscopy, atomic force microscopy and flow cytometry, and subsequent characterization of this quantum dot binding profile provides useful data that can be utilized as a fingerprint to detect cancer disease progression. This type of functionalized quantum dot fingerprint is especially useful for invasive cancers including brain and other metastatic cancers and may allow for earlier detection of disease progression or recurrence, thus saving the lives of patients suffering from this devastating disease. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Scanning gate imaging of two coupled quantum dots in single-walled carbon nanotubes.

PubMed

Zhou, Xin; Hedberg, James; Miyahara, Yoichi; Grutter, Peter; Ishibashi, Koji

2014-12-12

Two coupled single wall carbon nanotube quantum dots in a multiple quantum dot system were characterized by using a low temperature scanning gate microscopy (SGM) technique, at a temperature of 170 mK. The locations of single wall carbon nanotube quantum dots were identified by taking the conductance images of a single wall carbon nanotube contacted by two metallic electrodes. The single electron transport through single wall carbon nanotube multiple quantum dots has been observed by varying either the position or voltage bias of a conductive atomic force microscopy tip. Clear hexagonal patterns were observed in the region of the conductance images where only two sets of overlapping conductance rings are visible. The values of coupling capacitance over the total capacitance of the two dots, C(m)/C(1(2)) have been extracted to be 0.21 ∼ 0.27 and 0.23 ∼ 0.28, respectively. In addition, the interdot coupling (conductance peak splitting) has also been confirmed in both conductance image measurement and current-voltage curves. The results show that a SGM technique enables spectroscopic investigation of coupled quantum dots even in the presence of unexpected multiple quantum dots.

Capture of visual direction in dynamic vergence is reduced with flashed monocular lines.

PubMed

Jaschinski, Wolfgang; Jainta, Stephanie; Schürer, Michael

2006-08-01

The visual direction of a continuously presented monocular object is captured by the visual direction of a closely adjacent binocular object, which questions the reliability of nonius lines for measuring vergence. This was shown by Erkelens, C. J., and van Ee, R. (1997a,b) [Capture of the visual direction: An unexpected phenomenon in binocular vision. Vision Research, 37, 1193-1196; Capture of the visual direction of monocular objects by adjacent binocular objects. Vision Research, 37, 1735-1745] stimulating dynamic vergence by a counter phase oscillation of two square random-dot patterns (one to each eye) that contained a smaller central dot-free gap (of variable width) with a vertical monocular line oscillating in phase with the random-dot pattern of the respective eye; subjects adjusted the motion-amplitude of the line until it was perceived as (nearly) stationary. With a continuously presented monocular line, we replicated capture of visual direction provided the dot-free gap was narrow: the adjusted motion-amplitude of the line was similar as the motion-amplitude of the random-dot pattern, although large vergence errors occurred. However, when we flashed the line for 67 ms at the moments of maximal and minimal disparity of the vergence stimulus, we found that the adjusted motion-amplitude of the line was smaller; thus, the capture effect appeared to be reduced with flashed nonius lines. Accordingly, we found that the objectively measured vergence gain was significantly correlated (r=0.8) with the motion-amplitude of the flashed monocular line when the separation between the line and the fusion contour was at least 32 min arc. In conclusion, if one wishes to estimate the dynamic vergence response with psychophysical methods, effects of capture of visual direction can be reduced by using flashed nonius lines.

Expression analysis of LC3B and p62 indicates intact activated autophagy is associated with an unfavorable prognosis in colon cancer.

PubMed

Niklaus, Monique; Adams, Olivia; Berezowska, Sabina; Zlobec, Inti; Graber, Franziska; Slotta-Huspenina, Julia; Nitsche, Ulrich; Rosenberg, Robert; Tschan, Mario P; Langer, Rupert

2017-08-15

Autophagy is a lysosomal degradation and recycling process implicated in cancer progression and therapy resistance. We assessed the impact of basal autophagy in colon cancer (CC) in vitro and ex vivo . Functional autophagy was demonstrated in CC cell lines (LoVo; HT-29) showing a dose-dependent increase of the autophagy markers LC3B, p62 and autophagic vesciles upon increasing concentrations of the autophagy inhibitor chloroquine, which was demonstrated by immunoblotting, immunofluorescence and electron microscopy. Next, tissue microarrays with 292 primary resected CC, with cores from different tumor regions, and normal mucosa were analyzed by immunohistochemistry for LC3B and p62. CC tissue showed LC3B dot-like, p62 dot-like, cytoplasmic and nuclear staining in various levels without significant intratumoral heterogeneity. Tumoral LC3B and p62 expression was significantly higher than in normal tissue (p<0.001). No associations between staining patterns and pathological features (e.g. TNM categories; grading) were observed. Both low LC3B dot-like and low p62 dot-like-cytoplasmic staining were associated with worse overall survival (p=0.005 and p=0.002). The best prognostic discrimination, however, was seen for a combination of LC3B dot-like/p62 dot-like-cytoplasmic staining: high expression of both markers, indicative of impaired activated autophagy, was associated with the best overall survival. In contrast, high LC3B dot-like/low p62 dot-like-cytoplasmic expression, indicative of intact activated autophagy, was associated with the worst outcome (p<0.001 in univariate and HR=0.751; CI=0.607-0.928; p=0.008 in multivariate analysis). These specific expression patterns of LC3B and p62 pointing to different states of autophagy associated with diverging clinical outcomes highlighte the potential significance of basal autophagy in CC biology.

Real-time quantitative Schlieren imaging by fast Fourier demodulation of a checkered backdrop

NASA Astrophysics Data System (ADS)

Wildeman, Sander

2018-06-01

A quantitative synthetic Schlieren imaging (SSI) method based on fast Fourier demodulation is presented. Instead of a random dot pattern (as usually employed in SSI), a 2D periodic pattern (such as a checkerboard) is used as a backdrop to the refractive object of interest. The range of validity and accuracy of this "Fast Checkerboard Demodulation" (FCD) method are assessed using both synthetic data and experimental recordings of patterns optically distorted by small waves on a water surface. It is found that the FCD method is at least as accurate as sophisticated, multi-stage, digital image correlation (DIC) or optical flow (OF) techniques used with random dot patterns, and it is significantly faster. Efficient, fully vectorized, implementations of both the FCD and DIC/OF schemes developed for this study are made available as open source Matlab scripts.

Low-density, radiatively inefficient rotating-accretion flow on to a black hole

NASA Astrophysics Data System (ADS)

Inayoshi, Kohei; Ostriker, Jeremiah P.; Haiman, Zoltán; Kuiper, Rolf

2018-05-01

We study low-density axisymmetric accretion flows on to black holes (BHs) with two-dimensional hydrodynamical simulations, adopting the α-viscosity prescription. When the gas angular momentum is low enough to form a rotationally supported disc within the Bondi radius (RB), we find a global steady accretion solution. The solution consists of a rotational equilibrium distribution around r ˜ RB, where the density follows ρ ∝ (1 + RB/r)3/2, surrounding a geometrically thick and optically thin accretion disc at the centrifugal radius RC(

Green biosynthesis of biocompatible CdSe quantum dots in living Escherichia coli cells

NASA Astrophysics Data System (ADS)

Yan, Zhengyu; Qian, Jing; Gu, Yueqing; Su, Yilong; Ai, Xiaoxia; Wu, Shengmei

2014-03-01

A green and efficient biosynthesis method to prepare fluorescence-tunable biocompatible cadmium selenide quantum dots using Escherichia coli cells as biological matrix was proposed. Decisive factors in biosynthesis of cadmium selenide quantum dots in a designed route in Escherichia coli cells were elaborately investigated, including the influence of the biological matrix growth stage, the working concentration of inorganic reactants, and the co-incubation duration of inorganic metals to biomatrix. Ultraviolet-visible, photoluminescence, and inverted fluorescence microscope analysis confirmed the unique optical properties of the biosynthesized cadmium selenide quantum dots. The size distribution of the nanocrystals extracted from cells and the location of nanocrystals foci in vivo were also detected seriously by transmission electron microscopy. A surface protein capping layer outside the nanocrystals was confirmed by Fourier transform infrared spectroscopy measurements, which were supposed to contribute to reducing cytotoxicity and maintain a high viability of cells when incubating with quantum dots at concentrations as high as 2 μM. Cell morphology observation indicated an effective labeling of living cells by the biosynthesized quantum dots after a 48 h co-incubation. The present work demonstrated an economical and environmentally friendly approach to fabricating highly fluorescent quantum dots which were expected to be an excellent fluorescent dye for broad bio-imaging and labeling.

Refractory Materials for Flame Deflector Protection System Corrosion Control: Refractory Ceramics Literature Survey

NASA Technical Reports Server (NTRS)

Calle, Luz Marina; Hintze, Paul E.; Parlier, Christopher R.; Curran, Jerome P.; Kolody, Mark; Perusich, Stephen; Whitten, Mary C.; Trejo, David; Zidek, Jason; Sampson, Jeffrey W.;

Studies of silicon quantum dots prepared at different substrate temperatures

NASA Astrophysics Data System (ADS)

Al-Agel, Faisal A.; Suleiman, Jamal; Khan, Shamshad A.

2017-03-01

In this research work, we have synthesized silicon quantum dots at different substrate temperatures 193, 153 and 123 K at a fixed working pressure 5 Torr. of Argon gas. The structural studies of these silicon quantum dots have been undertaken using X-ray diffraction, Field Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM). The optical and electrical properties have been studied using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Fluorescence spectroscopy and I-V measurement system. X-ray diffraction pattern of Si quantum dots prepared at different temperatures show the amorphous nature except for the quantum dots synthesized at 193 K which shows polycrystalline nature. FESEM images of samples suggest that the size of quantum dots varies from 2 to 8 nm. On the basis of UV-visible spectroscopy measurements, a direct band gap has been observed for Si quantum dots. FTIR spectra suggest that as-grown Si quantum dots are partially oxidized which is due exposure of as-prepared samples to air after taking out from the chamber. PL spectra of the synthesized silicon quantum dots show an intense peak at 444 nm, which may be attributed to the formation of Si quantum dots. Temperature dependence of dc conductivity suggests that the dc conductivity enhances exponentially by raising the temperature. On the basis above properties i.e. direct band gap, high absorption coefficient and high conductivity, these silicon quantum dots will be useful for the fabrication of solar cells.

Temperature characteristics of epitaxially grown InAs quantum dot micro-disk lasers on silicon for on-chip light sources

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

Wan, Yating; Li, Qiang; Lau, Kei May, E-mail: eekmlau@ust.hk

2016-07-04

Temperature characteristics of optically pumped micro-disk lasers (MDLs) incorporating InAs quantum dot active regions are investigated for on-chip light sources. The InAs quantum dot MDLs were grown on V-groove patterned (001) silicon, fully compatible with the prevailing complementary metal oxide-semiconductor technology. By combining the high-quality whispering gallery modes and 3D confinement of injected carriers in quantum dot micro-disk structures, we achieved lasing operation from 10 K up to room temperature under continuous optical pumping. Temperature dependences of the threshold, lasing wavelength, slope efficiency, and mode linewidth are examined. An excellent characteristic temperature T{sub o} of 105 K has been extracted.

Green-noise halftoning with dot diffusion

NASA Astrophysics Data System (ADS)

Lippens, Stefaan; Philips, Wilfried

2007-02-01

Dot diffusion is a halftoning technique that is based on the traditional error diffusion concept, but offers a high degree of parallel processing by its block based approach. Traditional dot diffusion however suffers from periodicity artifacts. To limit the visibility of these artifacts, we propose grid diffusion, which applies different class matrices for different blocks. Furthermore, in this paper we will discuss two approaches in the dot diffusion framework to generate green-noise halftone patterns. The first approach is based on output dependent feedback (hysteresis), analogous to the standard green-noise error diffusion techniques. We observe that the resulting halftones are rather coarse and highly dependent on the used dot diffusion class matrices. In the second approach we don't limit the diffusion to the nearest neighbors. This leads to less coarse halftones, compared to the first approach. The drawback is that it can only cope with rather limited cluster sizes. We can reduce these drawbacks by combining the two approaches.

Blindness to a simultaneous change of all elements in a scene, unless there is a change in summary statistics.

PubMed

Saiki, Jun; Holcombe, Alex O

2012-03-06

Sudden change of every object in a display is typically conspicuous. We find however that in the presence of a secondary task, with a display of moving dots, it can be difficult to detect a sudden change in color of all the dots. A field of 200 dots, half red and half green, half moving rightward and half moving leftward, gave the appearance of two surfaces. When all 200 dots simultaneously switched color between red and green, performance in detecting the switch was very poor. A key display characteristic was that the color proportions on each surface (summary statistics) were not affected by the color switch. When the color switch is accompanied by a change in these summary statistics, people perform well in detecting the switch, suggesting that the secondary task does not disrupt the availability of this statistical information. These findings suggest that when the change is missed, the old and new colors were represented, but the color-location pattern (binding of colors to locations) was not represented or not compared. Even after extended viewing, changes to the individual color-location pattern are not available, suggesting that the feeling of seeing these details is misleading.

Diffusion orientation transform revisited.

PubMed

Canales-Rodríguez, Erick Jorge; Lin, Ching-Po; Iturria-Medina, Yasser; Yeh, Chun-Hung; Cho, Kuan-Hung; Melie-García, Lester

2010-01-15

Diffusion orientation transform (DOT) is a powerful imaging technique that allows the reconstruction of the microgeometry of fibrous tissues based on diffusion MRI data. The three main error sources involving this methodology are the finite sampling of the q-space, the practical truncation of the series of spherical harmonics and the use of a mono-exponential model for the attenuation of the measured signal. In this work, a detailed mathematical description that provides an extension to the DOT methodology is presented. In particular, the limitations implied by the use of measurements with a finite support in q-space are investigated and clarified as well as the impact of the harmonic series truncation. Near- and far-field analytical patterns for the diffusion propagator are examined. The near-field pattern makes available the direct computation of the probability of return to the origin. The far-field pattern allows probing the limitations of the mono-exponential model, which suggests the existence of a limit of validity for DOT. In the regimen from moderate to large displacement lengths the isosurfaces of the diffusion propagator reveal aberrations in form of artifactual peaks. Finally, the major contribution of this work is the derivation of analytical equations that facilitate the accurate reconstruction of some orientational distribution functions (ODFs) and skewness ODFs that are relatively immune to these artifacts. The new formalism was tested using synthetic and real data from a phantom of intersecting capillaries. The results support the hypothesis that the revisited DOT methodology could enhance the estimation of the microgeometry of fiber tissues.

Coping with tuberculosis and directly observed treatment: a qualitative study among patients from South India.

PubMed

Yellappa, Vijayashree; Lefèvre, Pierre; Battaglioli, Tullia; Narayanan, Devadasan; Van der Stuyft, Patrick

2016-07-19

In India, the Revised National TB control programme (RNTCP) offers free diagnosis and treatment for tuberculosis (TB), based on the Directly Observed Treatment Short course (DOTS) strategy. We conducted a qualitative study to explore the experience and consequences of having TB on patients enrolled in DOTS and their caretakers in Tumkur district, located in a southern state of India, Karnataka. We conducted 33 in-depth interviews on a purposive sample of TB patients from three groups: (1) patients who reached RNTCP directly on their own and took DOTS at RNTCP; (2) patients who were referred by private practitioners (PPs) to RNTCP and took DOTS at RNTCP; and (3) patients diagnosed by RNTCP and took DOTS from PPs. Data was analyzed using a thematic approach with the support of NVivo9. The study revealed that TB and DOTS have a large impact on patient's lives, which is often extended to the family and caretakers. The most vulnerable patients faced the most difficulty in accessing and completing DOTS. The family was the main source of support during patient's recovery. Patients residing in rural areas and, taking DOTS from the government facilities had to overcome many barriers to adhere to the DOTS therapy, such as long travelling distance to DOTS centers, inconvenient timings and unfavorable attitude of the RNTCP staff, when compared to patients who took DOTS from PPs. Advantages of taking DOTS from PPs cited by the patients were privacy, flexibility in timings, proximity and more immediate access to care. Patients and their family had to cope with stigmatization and fear and financial hardships that surfaced from TB and DOTS. Young patients living in urban areas were more worried about stigmatisation, than elderly patients living in rural areas. Patients who were referred by PPs experienced more financial problems compared to those who reached RNTCP services directly. Our study provided useful information about patient's needs and expectations while taking DOTS. The development of mechanisms within RNTCP towards patient centered care is needed to enable patients and caretakers cope with disease condition and adhere to DOTS.

Peptide-coated semiconductor quantum dots and their applications in biological imaging of single molecules in live cells and organisms

NASA Astrophysics Data System (ADS)

Pinaud, Fabien Florent

2007-12-01

A new surface chemistry has been developed for the solubilization and biofunctionalization of inorganic semiconductor nanocrystals fluorescent probes, also known as quantum dots. This chemistry is based on the surface coating of quantum dots with custom-designed polycysteine peptides and yields water-soluble, small, monodispersed and colloidally stable probes that remain bright and photostable in complex biological milieus. This peptide coating strategy was successfully tested on several types of core and core-shell quantum dots emitting from the visible (e.g. CdSe/ZnS) to the NIR spectrum range (e.g. CdTe/CdSe/ZnS). By taking advantage of the versatile physico-chemical properties of peptides, a peptide "toolkit" was designed and employed to impart several biological functions to individual quantum dots and control their biochemical activity at the nanometer scale. These biofunctionalized peptide-coated quantum dots were exploited in very diverse biological applications. Near-infrared emitting quantum dot probes were engineered with optimized blood circulation and biodistribution properties for in vivo animal imaging. Visible emitting quantum dots were used for single molecule tracking of raft-associated GPI-anchored proteins in live cells. This last application revealed the presence of discrete and non-caveolar lipid microdomains capable of impeding free lateral diffusions in the plasma membrane of Hela cells. Imaging and tracking of peptide-coated quantum dots provided the first direct evidence that microdomains having the composition and behavior expected for lipid rafts can induce molecular compartmentalization in the membrane of living cells.

Concentric superlattice pattern in dielectric barrier discharge

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

Feng, Jianyu; Dong, Lifang, E-mail: donglfhbu@163.com; Wei, Lingyan

2016-09-15

The concentric superlattice pattern with three sub-lattices is observed in the dielectric barrier discharge in air/argon for the first time. Its spatiotemporal structure investigated by an intensified charge-coupled device shows that it is an interleaving of three different sub-lattices, which are concentric-ring, concentric-framework, and concentric-dot, respectively. The images of single-frame indicate that the concentric-ring and concentric-framework are composed of individual filaments. By using the optical emission spectrum method, it is found that plasma parameters of the concentric-dot are different from those of the concentric-ring and concentric-framework. The spatiotemporal dynamics of the concentric superlattice pattern is dependent upon the effective fieldmore » of the distribution of the wall charges field and the applied field.« less

Specific detection of the cleavage activity of mycobacterial enzymes using a quantum dot based DNA nanosensor

NASA Astrophysics Data System (ADS)

Jepsen, Morten Leth; Harmsen, Charlotte; Godbole, Adwait Anand; Nagaraja, Valakunja; Knudsen, Birgitta R.; Ho, Yi-Ping

2015-12-01

We present a quantum dot based DNA nanosensor specifically targeting the cleavage step in the reaction cycle of the essential DNA-modifying enzyme, mycobacterial topoisomerase I. The design takes advantages of the unique photophysical properties of quantum dots to generate visible fluorescence recovery upon specific cleavage by mycobacterial topoisomerase I. This report, for the first time, demonstrates the possibility to quantify the cleavage activity of the mycobacterial enzyme without the pre-processing sample purification or post-processing signal amplification. The cleavage induced signal response has also proven reliable in biological matrices, such as whole cell extracts prepared from Escherichia coli and human Caco-2 cells. It is expected that the assay may contribute to the clinical diagnostics of bacterial diseases, as well as the evaluation of treatment outcomes.We present a quantum dot based DNA nanosensor specifically targeting the cleavage step in the reaction cycle of the essential DNA-modifying enzyme, mycobacterial topoisomerase I. The design takes advantages of the unique photophysical properties of quantum dots to generate visible fluorescence recovery upon specific cleavage by mycobacterial topoisomerase I. This report, for the first time, demonstrates the possibility to quantify the cleavage activity of the mycobacterial enzyme without the pre-processing sample purification or post-processing signal amplification. The cleavage induced signal response has also proven reliable in biological matrices, such as whole cell extracts prepared from Escherichia coli and human Caco-2 cells. It is expected that the assay may contribute to the clinical diagnostics of bacterial diseases, as well as the evaluation of treatment outcomes. Electronic supplementary information (ESI) available: Characterization of the QD-based DNA Nanosensor. See DOI: 10.1039/c5nr06326d

The cost-effectiveness of directly observed highly-active antiretroviral therapy in the third trimester in HIV-infected pregnant women.

PubMed

McCabe, Caitlin J; Goldie, Sue J; Fisman, David N

2010-04-13

In HIV-infected pregnant women, viral suppression prevents mother-to-child HIV transmission. Directly observed highly-active antiretroviral therapy (HAART) enhances virological suppression, and could prevent transmission. Our objective was to project the effectiveness and cost-effectiveness of directly observed administration of antiretroviral drugs in pregnancy. A mathematical model was created to simulate cohorts of one million asymptomatic HIV-infected pregnant women on HAART, with women randomly assigned self-administered or directly observed antiretroviral therapy (DOT), or no HAART, in a series of Monte Carlo simulations. Our primary outcome was the quality-adjusted life expectancy in years (QALY) of infants born to HIV-infected women, with the rates of Caesarean section and HIV-transmission after DOT use as intermediate outcomes. Both self-administered HAART and DOT were associated with decreased costs and increased life-expectancy relative to no HAART. The use of DOT was associated with a relative risk of HIV transmission of 0.39 relative to conventional HAART; was highly cost-effective in the cohort as a whole (cost-utility ratio $14,233 per QALY); and was cost-saving in women whose viral loads on self-administered HAART would have exceeded 1000 copies/ml. Results were stable in wide-ranging sensitivity analyses, with directly observed therapy cost-saving or highly cost-effective in almost all cases. Based on the best available data, programs that optimize adherence to HAART through direct observation in pregnancy have the potential to diminish mother-to-child HIV transmission in a highly cost-effective manner. Targeted use of DOT in pregnant women with high viral loads, who could otherwise receive self-administered HAART would be a cost-saving intervention. These projections should be tested with randomized clinical trials.

Atmospheric Pressure During Landing

NASA Technical Reports Server (NTRS)

1997-01-01

This figure shows the variation with time of pressure (dots) measured by the Pathfinder MET instrument during the landing period shown in image PIA00797. The two diamonds indicate the times of bridal cutting and 1st impact. The overall trend in the data is of pressure increasing with time. This is almost certainly due to the lander rolling downhill by roughly 10 m. The spacing of the horizontal dotted lines indicates the pressure change expected from 10 m changes in altitude. Bounces may also be visible in the data.

The Attentional White Bear Phenomenon: The Mandatory Allocation of Attention to Expected Distractor Locations

ERIC Educational Resources Information Center

Tsal, Yehoshua; Makovski, Tal

2006-01-01

The authors devised a prestimulus-probe method to assess the allocation of attention as a function of participants' top-down expectancies concerning distractor and target locations. Participants performed the flanker task, and distractor locations remained fixed. On some trials, instead of the flanker display, either 2 simultaneous dots or a…

DNA-Mediated Patterning of Single Quantum Dot Nanoarrays: A Reusable Platform for Single-Molecule Control

NASA Astrophysics Data System (ADS)

Huang, Da; Freeley, Mark; Palma, Matteo

2017-03-01

We present a facile strategy of general applicability for the assembly of individual nanoscale moieties in array configurations with single-molecule control. Combining the programming ability of DNA as a scaffolding material with a one-step lithographic process, we demonstrate the patterning of single quantum dots (QDs) at predefined locations on silicon and transparent glass surfaces: as proof of concept, clusters of either one, two, or three QDs were assembled in highly uniform arrays with a 60 nm interdot spacing within each cluster. Notably, the platform developed is reusable after a simple cleaning process and can be designed to exhibit different geometrical arrangements.

Characterization of CuCl quantum dots grown in NaCl single crystals via optical measurements, X-ray diffraction, and transmission electron microscopy

NASA Astrophysics Data System (ADS)

Miyajima, Kensuke; Akatsu, Tatsuro; Itoh, Ken

2018-05-01

We evaluated the crystal size, shape, and alignment of the lattice planes of CuCl quantum dots (QDs) embedded in NaCl single crystals by optical measurements, X-ray diffraction (XRD) patterns, and transmission electron microscopy (TEM). We obtained, for the first time, an XRD pattern and TEM images for CuCl QDs in NaCl crystals. The XRD pattern showed that the lattice planes of the CuCl QDs were parallel to those of the NaCl crystals. In addition, the size of the QDs was estimated from the diffraction width. It was apparent from the TEM images that almost all CuCl QDs were polygonal, although some cubic QDs were present. The mean size and size distribution of the QDs were also obtained. The dot size obtained from optical measurements, XRD, and TEM image were almost consistent. Our new findings can help to reveal the growth mechanism of semiconductor QDs embedded in a crystallite matrix. In addition, this work will play an important role in progressing the study of optical phenomena originating from assembled semiconductor QDs.

Illusory displacement of equiluminous kinetic edges.

PubMed

Ramachandran, V S; Anstis, S M

1990-01-01

A stationary window was cut out of a stationary random-dot pattern. When a field of dots was moved continuously behind the window (a) the window appeared to move in the same direction even though it was stationary, (b) the position of the 'kinetic edges' defining the window was also displaced along the direction of dot motion, and (c) the edges of the window tended to fade on steady fixation even though the dots were still clearly visible. The illusory displacement was enhanced considerably if the kinetic edge was equiluminous and if the 'window' region was seen as 'figure' rather than 'ground'. Since the extraction of kinetic edges probably involves the use of direction-selective cells, the illusion may provide insights into how the visual system uses the output of these cells to localize the kinetic edges.

Image Halftoning Using Optimized Dot Diffusion

DTIC Science & Technology

1998-01-01

ppvnath@sys.caltech.edu ABSTRACT The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error diffusion ...digital halftoning : ordered dither [1], error diffusion [2], neural-net based methods [8], and more recently direct binary search (DBS) [7]. Ordered...from periodic patterns. On the other hand error diffused halftones do not suffer from periodicity and offer blue noise characteristic [3] which is

Antibacterial activity of microstructured sacrificial anode thin films by combination of silver with platinum group elements (platinum, palladium, iridium).

PubMed

Köller, Manfred; Bellova, Petri; Javid, Siyamak Memar; Motemani, Yahya; Khare, Chinmay; Sengstock, Christina; Tschulik, Kristina; Schildhauer, Thomas A; Ludwig, Alfred

2017-05-01

Five different Ag dots arrays (16 to 400dots/mm 2 ) were fabricated on a continuous platinum, palladium, or iridium thin film and for comparison also on titanium film by sputter deposition and photolithographic patterning. To analyze the antibacterial activity of these microstructured films Staphylococcus aureus (S. aureus) were placed onto the array surfaces and cultivated overnight. To analyze the viability of planktonic as well as surface adherent bacteria, the applied bacterial fluid was subsequently aspirated, plated on blood agar plates and adherent bacteria were detected by fluorescence microscopy. A particular antibacterial effect towards S. aureus was induced by Ag dot arrays on each of the platinum group thin film (sacrificial anode system for Ag) in contrast to Ag dot arrays fabricated on the Ti thin films (non-sacrificial anode system for Ag). Among platinum group elements the Ir-Ag system exerted the highest antibacterial activity which was accompanied by most advanced dissolution of the Ag dots and Ag ion release compared to Ag dots on Pt or Pd. Copyright © 2016 Elsevier B.V. All rights reserved.

Video over IP design guidebook.

DOT National Transportation Integrated Search

2009-12-01

Texas Department of Transportation (TxDOT) engineers are responsible for the design, evaluation, and : implementation of video solutions across the entire state. These installations occur with vast differences in : requirements, expectations, and con...

A second and more promising round of E-health enterprises.

PubMed

Fifer, Sheila K; Thomas, Norrie

2002-11-01

After several years of false starts and failed enterprises, E-medicine is starting to generate practical applications in health care. The new generation of E-businesses is benefiting from the dot-com bust, which has driven away expectations of high financial returns from enterprises based on overblown, ill-fitting models taken from non-health care industries. The more successful new models are adapted to hospital operations and practice patterns, and are backed by money and management indigenous to medicine. However, they are also fragmented, in thus far unconnected pieces of E-network services for discrete clinical activities, such as scripting, lab-testing, patient monitoring, and condition-specific diagnostics and treatment. The new question about E-medicine practice may be not "When will it happen?" but "when will the fragmented E-health systems be connected?"

Creation of wettability contrast patterns on metallic surfaces via pen drawn masks

NASA Astrophysics Data System (ADS)

Choi, Won Tae; Yang, Xiaolong; Breedveld, Victor; Hess, Dennis W.

2017-12-01

Micropatterned surfaces with wettability contrast have attracted considerable attention due to potential applications in 2D microfluidics, bioassays, and water harvesting. A simple method to develop wettability contrast patterns on metallic surfaces by using a commercial marker is described. A marker-drawn ink pattern on a copper surface displays chemical resistance to an aqueous solution of sodium bicarbonate and ammonium persulfate, thereby enabling selective nanowire growth in areas where ink is absent. Subsequent ink removal by an organic solvent followed by fluorocarbon film deposition yields a stable hydrophobic/super-hydrophobic patterned copper surface. Using this approach, hydrophobic dot and line patterns were constructed. The adhesion force of water droplets to the dots was controlled by adjusting pattern size, thus enabling controlled droplet transfer between two surfaces. Anisotropy of water droplet adhesion to line patterns can serve as a basis for directional control of water droplet motion. This general approach has also been employed to generate wettability contrast on aluminum surfaces, thereby demonstrating versatility. Due to its simplicity, low cost, and virtual independence of solid surface material, ink marker pens can be employed to create wettability patterns for a variety of applications, in fields as diverse as biomedicine and energy.

Masked priming for the comparative evaluation of camouflage conspicuity.

PubMed

Brunyé, Tad T; Eddy, Marianna D; Cain, Matthew S; Hepfinger, Lisa B; Rock, Kathryn

2017-07-01

Human observer test and evaluation of camouflage patterns is critical for understanding relative pattern conspicuity against a range of background scenes. However, very few validated methodologies exist for this purpose, and those that do carry several limitations. Five experiments examined whether masked priming with a dot probe could be used to reliably differentiate camouflage patterns. In each experiment, participants were primed with a camouflaged target appearing on the left or right of the screen, and then made a speeded response to a dot probe appearing on the same (congruent) or different (incongruent) side. Across experiments we parametrically varied prime duration between 35, 42, 49, 56, and 63 ms. Results demonstrated that as prime duration increased, a response time disadvantage for incongruent trials emerged with certain camouflage patterns. Interestingly, the most conspicuous patterns showed behavioral differences at a relatively brief (49 ms) prime duration, whereas behavioral differences were only found at longer prime durations for less conspicuous patterns; this overall results pattern matched that predicted by a visual salience model. Together, we demonstrate the viability of masked priming for the test and evaluation of camouflage patterns, and correlated outcomes for saliency models and primed object processing. Published by Elsevier Ltd.

Sleep and wake phase of heart beat dynamics by artificial insymmetrised patterns

NASA Astrophysics Data System (ADS)

Dudkowska, A.; Makowiec, D.

2004-05-01

In order to determine differences between healthy patients and patients with congestive heart failure we apply the artificial insymmetrised pattern (AIP) method. The AIP method by exploring a human eye ability to extract regularities and read symmetries in a dot pattern, serves a tool for qualitative discrimination of heart rate states.

Laser-Induced-Fluorescence Photogrammetry and Videogrammetry

NASA Technical Reports Server (NTRS)

Danehy, Paul; Jones, Tom; Connell, John; Belvin, Keith; Watson, Kent

2004-01-01

An improved method of dot-projection photogrammetry and an extension of the method to encompass dot-projection videogrammetry overcome some deficiencies of dot-projection photogrammetry as previously practiced. The improved method makes it possible to perform dot-projection photogrammetry or videogrammetry on targets that have previously not been amenable to dot-projection photogrammetry because they do not scatter enough light. Such targets include ones that are transparent, specularly reflective, or dark. In standard dot-projection photogrammetry, multiple beams of white light are projected onto the surface of an object of interest (denoted the target) to form a known pattern of bright dots. The illuminated surface is imaged in one or more cameras oriented at a nonzero angle or angles with respect to a central axis of the illuminating beams. The locations of the dots in the image(s) contain stereoscopic information on the locations of the dots, and, hence, on the location, shape, and orientation of the illuminated surface of the target. The images are digitized and processed to extract this information. Hardware and software to implement standard dot-projection photogrammetry are commercially available. Success in dot-projection photogrammetry depends on achieving sufficient signal-to-noise ratios: that is, it depends on scattering of enough light by the target so that the dots as imaged in the camera(s) stand out clearly against the ambient-illumination component of the image of the target. In one technique used previously to increase the signal-to-noise ratio, the target is illuminated by intense, pulsed laser light and the light entering the camera(s) is band-pass filtered at the laser wavelength. Unfortunately, speckle caused by the coherence of the laser light engenders apparent movement in the projected dots, thereby giving rise to errors in the measurement of the centroids of the dots and corresponding errors in the computed shape and location of the surface of the target. The improved method is denoted laser-induced-fluorescence photogrammetry.

Ultrafast atomic-scale visualization of acoustic phonons generated by optically excited quantum dots

PubMed Central

Vanacore, Giovanni M.; Hu, Jianbo; Liang, Wenxi; Bietti, Sergio; Sanguinetti, Stefano; Carbone, Fabrizio; Zewail, Ahmed H.

2017-01-01

Understanding the dynamics of atomic vibrations confined in quasi-zero dimensional systems is crucial from both a fundamental point-of-view and a technological perspective. Using ultrafast electron diffraction, we monitored the lattice dynamics of GaAs quantum dots—grown by Droplet Epitaxy on AlGaAs—with sub-picosecond and sub-picometer resolutions. An ultrafast laser pulse nearly resonantly excites a confined exciton, which efficiently couples to high-energy acoustic phonons through the deformation potential mechanism. The transient behavior of the measured diffraction pattern reveals the nonequilibrium phonon dynamics both within the dots and in the region surrounding them. The experimental results are interpreted within the theoretical framework of a non-Markovian decoherence, according to which the optical excitation creates a localized polaron within the dot and a travelling phonon wavepacket that leaves the dot at the speed of sound. These findings indicate that integration of a phononic emitter in opto-electronic devices based on quantum dots for controlled communication processes can be fundamentally feasible. PMID:28852685

Evaporation-Induced Assembly of Quantum Dots into Nanorings

PubMed Central

Chen, Jixin; Liao, Wei-Ssu; Chen, Xin; Yang, Tinglu; Wark, Stacey E.; Son, Dong Hee; Batteas, James D.; Cremer, Paul S.

2011-01-01

Herein, we demonstrate the controlled formation of two-dimensional periodic arrays of ring-shaped nanostructures assembled from CdSe semiconductor quantum dots (QDs). The patterns were fabricated by using an evaporative templating method. This involves the introduction of an aqueous solution containing both quantum dots and polystyrene microspheres onto the surface of a planar hydrophilic glass substrate. The quantum dots became confined to the meniscus of the microspheres during evaporation, which drove ring assembly via capillary forces at the polystyrene sphere/glass substrate interface. The geometric parameters for nanoring formation could be controlled by tuning the size of the microspheres and the concentration of the QDs employed. This allowed hexagonal arrays of nanorings to be formed with thicknesses ranging from single dot necklaces to thick multilayer structures over surface areas of many square millimeters. Moreover, the diameter of the ring structures could be simultaneously controlled. A simple model was employed to explain the forces involved in the formation of nanoparticle nanorings. PMID:19206264

Block QCA Fault-Tolerant Logic Gates

NASA Technical Reports Server (NTRS)

Firjany, Amir; Toomarian, Nikzad; Modarres, Katayoon

2003-01-01

Suitably patterned arrays (blocks) of quantum-dot cellular automata (QCA) have been proposed as fault-tolerant universal logic gates. These block QCA gates could be used to realize the potential of QCA for further miniaturization, reduction of power consumption, increase in switching speed, and increased degree of integration of very-large-scale integrated (VLSI) electronic circuits. The limitations of conventional VLSI circuitry, the basic principle of operation of QCA, and the potential advantages of QCA-based VLSI circuitry were described in several NASA Tech Briefs articles, namely Implementing Permutation Matrices by Use of Quantum Dots (NPO-20801), Vol. 25, No. 10 (October 2001), page 42; Compact Interconnection Networks Based on Quantum Dots (NPO-20855) Vol. 27, No. 1 (January 2003), page 32; Bit-Serial Adder Based on Quantum Dots (NPO-20869), Vol. 27, No. 1 (January 2003), page 35; and Hybrid VLSI/QCA Architecture for Computing FFTs (NPO-20923), which follows this article. To recapitulate the principle of operation (greatly oversimplified because of the limitation on space available for this article): A quantum-dot cellular automata contains four quantum dots positioned at or between the corners of a square cell. The cell contains two extra mobile electrons that can tunnel (in the quantummechanical sense) between neighboring dots within the cell. The Coulomb repulsion between the two electrons tends to make them occupy antipodal dots in the cell. For an isolated cell, there are two energetically equivalent arrangements (denoted polarization states) of the extra electrons. The cell polarization is used to encode binary information. Because the polarization of a nonisolated cell depends on Coulomb-repulsion interactions with neighboring cells, universal logic gates and binary wires could be constructed, in principle, by arraying QCA of suitable design in suitable patterns. Heretofore, researchers have recognized two major obstacles to realization of QCA-based logic gates: One is the need for (and the difficulty of attaining) operation of QCA circuitry at room temperature or, for that matter, at any temperature above a few Kelvins. It has been theorized that room-temperature operation could be made possible by constructing QCA as molecular-scale devices. However, in approaching the lower limit of miniaturization at the molecular level, it becomes increasingly imperative to overcome the second major obstacle, which is the need for (and the difficulty of attaining) high precision in the alignments of adjacent QCA in order to ensure the correct interactions among the quantum dots.

Development of a video over IP guidebook.

DOT National Transportation Integrated Search

2009-09-01

Texas Department of Transportation (TxDOT) engineers are responsible for the design, evaluation, and implementation of video solutions across the entire state. These installations occur with vast differences in requirements, expectations, and constra...

The upper spatial limit for perception of displacement is affected by preceding motion.

PubMed

Stefanova, Miroslava; Mateeff, Stefan; Hohnsbein, Joachim

2009-03-01

The upper spatial limit D(max) for perception of apparent motion of a random dot pattern may be strongly affected by another, collinear, motion that precedes it [Mateeff, S., Stefanova, M., &. Hohnsbein, J. (2007). Perceived global direction of a compound of real and apparent motion. Vision Research, 47, 1455-1463]. In the present study this phenomenon was studied with two-dimensional motion stimuli. A random dot pattern moved alternately in the vertical and oblique direction (zig-zag motion). The vertical motion was of 1.04 degrees length; it was produced by three discrete spatial steps of the dots. Thereafter the dots were displaced by a single spatial step in oblique direction. Each motion lasted for 57ms. The upper spatial limit for perception of the oblique motion was measured under two conditions: the vertical component of the oblique motion and the vertical motion were either in the same or in opposite directions. It was found that the perception of the oblique motion was strongly influenced by the relative direction of the vertical motion that preceded it; in the "same" condition the upper spatial limit was much shorter than in the "opposite" condition. Decreasing the speed of the vertical motion reversed this effect. Interpretations based on networks of motion detectors and on Gestalt theory are discussed.

Factors influencing epitaxial growth of three-dimensional Ge quantum dot crystals on pit-patterned Si substrate.

PubMed

Ma, Y J; Zhong, Z; Yang, X J; Fan, Y L; Jiang, Z M

2013-01-11

We investigated the molecular beam epitaxy growth of three-dimensional (3D) Ge quantum dot crystals (QDCs) on periodically pit-patterned Si substrates. A series of factors influencing the growth of QDCs were investigated in detail and the optimized growth conditions were found. The growth of the Si buffer layer and the first quantum dot (QD) layer play a key role in the growth of QDCs. The pit facet inclination angle decreased with increasing buffer layer thickness, and its optimized value was found to be around 21°, ensuring that all the QDs in the first layer nucleate within the pits. A large Ge deposition amount in the first QD layer favors strain build-up by QDs, size uniformity of QDs and hence periodicity of the strain distribution; a thin Si spacer layer favors strain correlation along the growth direction; both effects contribute to the vertical ordering of the QDCs. Results obtained by atomic force microscopy and cross-sectional transmission electron microscopy showed that 3D ordering was achieved in the Ge QDCs with the highest ever areal dot density of 1.2 × 10(10) cm(-2), and that the lateral and the vertical interdot spacing were ~10 and ~2.5 nm, respectively.

Novel Phenotypic and Genotypic Findings in X-Linked Retinoschisis

PubMed Central

Tsang, Stephen H.; Vaclavik, Veronika; Bird, Alan C.; Robson, Anthony G.; Holder, Graham E.

2009-01-01

Objective To describe atypical phenotypes associated with the retinoschisis (X-linked, juvenile) 1 mutation (RS1). Methods Seven patients with multiple fine white dots at the macula and reduced visual acuity were evaluated. Six patients underwent pattern and full-field electroretinography (ERG). On-off ERG, optical coherence tomography, and fundus autofluorescence imaging were performed in some patients. Mutational screening of RS1 was prompted by the ERG findings. Results Fine white dots resembling drusenlike deposits and sometimes associated with retinal pigment epithelial abnormalities were present in the maculae. An electronegative bright-flash ERG configuration was present in all patients tested, and abnormal pattern ERG findings confirmed macular dysfunction. A parafoveal ring of high-density autofluorescence was present in 3 eyes; 1 patient showed high-density foci concordant with the white dots. Optical coherence tomography did not show foveal schisis in 3 of 4 eyes. All patients carried mutations in RS1, including 1 with a novel 206T→C mutation in exon 4. Conclusions Multiple fine white dots at the macula may be the initial fundus feature in RS1 mutation. Electrophysiologic findings suggest dysfunction after phototransduction and enable focused mutational screening. Autofluorescence imaging results suggest early retinal pigment epithelium involvement; a parafoveal ring of high-density autofluorescence has not previously been described in this disorder. PMID:17296904

Priming Infants to Use Pattern Information in an Object Individuation Task: The Role of Comparison

ERIC Educational Resources Information Center

Wilcox, Teresa; Smith, Tracy; Woods, Rebecca

2011-01-01

There is evidence that 4.5-month-olds do not always use surface pattern to individuate objects but that they can be primed to attend to pattern differences through select experiences. For example, if infants are first shown events in which the pattern of an object predicts its function (dotted containers pound and striped containers pour), they…

Nucleosynthesis inside Supernova-Driven Supercritical Accretion Disks

NASA Astrophysics Data System (ADS)

Fujimoto, Shin-Ichirou; Arai, Kenzo; Matsuba, Ryuichi; Hashimoto, Masa-Aki; Koike, Osamu; Mineshige, Shin

2001-06-01

We have investigated nucleosynthesis in a supercritical accretion disk around a compact object of 1.4Msolar, using the self-similar solution of an optically thick advection dominated flow. Supercritical accretion is expected to occur in a supernova with fallback material accreting onto a new-born compact object. It has been found that appreciable nuclear reactions take place even for a reasonable value of the viscosity parameter, αvissimeq 0.01, when the accretion rate dot{m}=dot{M}c2/(16LEdd) > 105, where LEdd is the Eddington luminosity. If dot{m} ge 4 × 106, all heavy elements are destroyed to 4He through photodisintegrations at the inner part of the disk. Even 4He is also disintegrated to protons and neutrons near the inner edge when dot{m} ge 2 × 107. If the fallback matter of the supernova explosion has the composition of a helium-rich layer of the progenitor, a considerable amount of 44Ti could be ejected via a jet from the disk.

The spatial distribution of umbral dots and granules

NASA Astrophysics Data System (ADS)

Lawrence, J. K.

1983-08-01

It is pointed out that the study of point patterns in two dimensions is of extremely broad interest in both the natural and social sciences. The subjects to which this study has been applied include tree distributions in forests, bird nesting patterns, the growth of towns, crystal formation in rocks, and the distribution of galaxies on the sky. The present investigation is concerned with the particular example of the distribution of umbral dots and their similarity, or dissimilarity, to photospheric granules. Attention is given to a collection of N points in an area A, statistical comparisons of distributions, and studies conducted by Bumba and Suda (1980) and Adjabshirzadeh and Koutchmy (1980, 1982).

Enhanced asymmetric magnetization reversal in nanoscale Co/CoO arrays: competition between exchange bias and magnetostatic coupling.

PubMed

Girgis, E; Portugal, R D; Loosvelt, H; Van Bael, M J; Gordon, I; Malfait, M; Temst, K; Van Haesendonck, C; Leunissen, L H A; Jonckheere, R

2003-10-31

Magnetization reversal was studied in square arrays of square Co/CoO dots with lateral size varying between 200 and 900 nm. While reference nonpatterned Co/CoO films show the typical shift and increased width of the hysteresis loop due to exchange bias, the patterned samples reveal a pronounced size dependence. In particular, an anomaly appears in the upper branch of the magnetization cycle and becomes stronger as the dot size decreases. This anomaly, which is absent at room temperature in the patterned samples, can be understood in terms of a competition between magnetostatic interdot interaction and exchange anisotropy during the magnetic switching process.

Deciphering RNA-Recognition Patterns of Intrinsically Disordered Proteins.

PubMed

Srivastava, Ambuj; Ahmad, Shandar; Gromiha, M Michael

2018-05-29

Intrinsically disordered regions (IDRs) and protein (IDPs) are highly flexible owing to their lack of well-defined structures. A subset of such proteins interacts with various substrates; including RNA; frequently adopting regular structures in the final complex. In this work; we have analysed a dataset of protein⁻RNA complexes undergoing disorder-to-order transition (DOT) upon binding. We found that DOT regions are generally small in size (less than 3 residues) for RNA binding proteins. Like structured proteins; positively charged residues are found to interact with RNA molecules; indicating the dominance of electrostatic and cation-π interactions. However, a comparison of binding frequency shows that interface hydrophobic and aromatic residues have more interactions in only DOT regions than in a protein. Further; DOT regions have significantly higher exposure to water than their structured counterparts. Interactions of DOT regions with RNA increase the sheet formation with minor changes in helix forming residues. We have computed the interaction energy for amino acids⁻nucleotide pairs; which showed the preference of His⁻G; Asn⁻U and Ser⁻U at for the interface of DOT regions. This study provides insights to understand protein⁻RNA interactions and the results could also be used for developing a tool for identifying DOT regions in RNA binding proteins.

High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling

PubMed Central

Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

2017-01-01

An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs. PMID:28211516

High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling

NASA Astrophysics Data System (ADS)

Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

2017-02-01

An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs.

High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling.

PubMed

Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

2017-02-17

An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs.

Correlative Light- and Electron Microscopy Using Quantum Dot Nanoparticles.

PubMed

Killingsworth, Murray C; Bobryshev, Yuri V

2016-08-07

A method is described whereby quantum dot (QD) nanoparticles can be used for correlative immunocytochemical studies of human pathology tissue using widefield fluorescence light microscopy and transmission electron microscopy (TEM). To demonstrate the protocol we have immunolabeled ultrathin epoxy sections of human somatostatinoma tumor using a primary antibody to somatostatin, followed by a biotinylated secondary antibody and visualization with streptavidin conjugated 585 nm cadmium-selenium (CdSe) quantum dots (QDs). The sections are mounted on a TEM specimen grid then placed on a glass slide for observation by widefield fluorescence light microscopy. Light microscopy reveals 585 nm QD labeling as bright orange fluorescence forming a granular pattern within the tumor cell cytoplasm. At low to mid-range magnification by light microscopy the labeling pattern can be easily recognized and the level of non-specific or background labeling assessed. This is a critical step for subsequent interpretation of the immunolabeling pattern by TEM and evaluation of the morphological context. The same section is then blotted dry and viewed by TEM. QD probes are seen to be attached to amorphous material contained in individual secretory granules. Images are acquired from the same region of interest (ROI) seen by light microscopy for correlative analysis. Corresponding images from each modality may then be blended to overlay fluorescence data on TEM ultrastructure of the corresponding region.

Effect of injection routes on the biodistribution, clearance, and tumor uptake of carbon dots.

PubMed

Huang, Xinglu; Zhang, Fan; Zhu, Lei; Choi, Ki Young; Guo, Ning; Guo, Jinxia; Tackett, Kenneth; Anilkumar, Parambath; Liu, Gang; Quan, Qimeng; Choi, Hak Soo; Niu, Gang; Sun, Ya-Ping; Lee, Seulki; Chen, Xiaoyuan

2013-07-23

The emergence of photoluminescent carbon-based nanomaterials has shown exciting potential in the development of benign nanoprobes. However, the in vivo kinetic behaviors of these particles that are necessary for clinical translation are poorly understood to date. In this study, fluorescent carbon dots (C-dots) were synthesized and the effect of three injection routes on their fate in vivo was explored by using both near-infrared fluorescence and positron emission tomography imaging techniques. We found that C-dots are efficiently and rapidly excreted from the body after all three injection routes. The clearance rate of C-dots is ranked as intravenous > intramuscular > subcutaneous. The particles had relatively low retention in the reticuloendothelial system and showed high tumor-to-background contrast. Furthermore, different injection routes also resulted in different blood clearance patterns and tumor uptakes of C-dots. These results satisfy the need for clinical translation and should promote efforts to further investigate the possibility of using carbon-based nanoprobes in a clinical setting. More broadly, we provide a testing blueprint for in vivo behavior of nanoplatforms under various injection routes, an important step forward toward safety and efficacy analysis of nanoparticles.

Laser direct-write and crystallization of FeSi II micro-dot array for NIR light-emitting device application

NASA Astrophysics Data System (ADS)

Narazaki, Aiko; Kurosaki, Ryozo; Sato, Tadatake; Kawaguchi, Yoshizo; Niino, Hiroyuki

2007-02-01

We printed FeSi II micro-dot array on various kinds of substrates utilizing laser-induced forward transfer (LIFT). An amorphous FeSi II was deposited by sputtering on a transparent plate as a source film. A single KrF excimer laser pulse through a mask-projection system was imaged with a small micrometer-sized grid pattern onto a film/plate interface, resulting in the deposition of FeSi II micro-dot array on a facing substrate with a high number density of 10 4 mm -2. FeSi II in the β crystalline phase is a promising eco-friendly semiconductor because of NIR electroluminescence used for optical networking as well as abundant components reserve on the earth and non-toxicity. However, the β-FeSi II film fabrication generally required high-temperature multi-processes which hamper its integration and performance reproducibility. Using the LIFT of micro-dot array, we succeeded in room-temperature preparation of β-FeSi II. Micro-Raman spectroscopy confirmed the β crystalline phase in the micro-dots deposited on an unheated silica glass substrate. Thus, the LIFT is useful for integrating functional micro-dot array accompanied by the crystallization at lower temperatures.

Carbon dot-Au(i)Ag(0) assembly for the construction of an artificial light harvesting system.

PubMed

Jana, Jayasmita; Aditya, Teresa; Pal, Tarasankar

2018-03-06

Artificial light harvesting systems (LHS) with inorganic counterparts are considered to be robust as well as mechanistically simple, where the system follows the donor-acceptor principle with an unchanged structural pattern. Plasmonic gold or silver nanoparticles are mostly chosen as inorganic counterparts to design artificial LHS. To capitalize on its electron accepting capability, Au(i) has been considered in this work for the synergistic stabilization of a system with intriguingly fluorescing silver(0) clusters produced in situ. Thus a stable fluorescent Au(i)Ag(0) assembly is generated with electron accepting capabilities. On the other hand, carbon dots have evolved as new fluorescent probes due to their unique physicochemical properties. Utilizing the simple electronic behavior of carbon dots, an electronic interaction between the fluorescent Au(i)Ag(0) and a carbon dot has been investigated for the construction of a new artificial light harvesting system. This coinage metal assembly allows surface energy transfer where it acts as an acceptor, while the carbon dot behaves as a good donor. The energy transfer efficiency has been calculated experimentally to be significant (81.3%) and the Au(i)Ag(0)-carbon dot assembly paves the way for efficient artificial LHS.

Realization of 95% of the Rec. 2020 color gamut in a highly efficient LCD using a patterned quantum dot film.

PubMed

Kim, Hyo-Jun; Shin, Min-Ho; Lee, Jae-Yong; Kim, Ji-Hoon; Kim, Young-Joo

2017-05-15

An optically efficient liquid-crystal display (LCD) structure using a patterned quantum dot (QD) film and a short-pass filter (SPF) was proposed and fabricated. The patterned QD film contributed to the generation of 95% in the area ratio (or 90% in the coverage ratio) of the Rec. 2020 color gamut. This was achieved by avoiding the problem of interaction between white backlight and broad transmittance spectra of color filters (CFs) as seen in a conventional LCD with a mixed QD film as a reference. The patterned QD film can maintain the narrow bandwidth of the green and the red QD colors before passing through the CFs. Additionally, the optical intensities of the red, green, and blue spectra were enhanced to 1.63, 1.72, and 2.16 times the reference LCD values, respectively. This was a result of separated emission of the red and green patterned QD film and reflection of the red and green light to the forward direction by the SPF.

SMS reminders to improve the tuberculosis cure rate in developing countries (TB-SMS Cameroon): a protocol of a randomised control study

PubMed Central

2014-01-01

Background Tuberculosis is a public health problem in Cameroon, just like in many other countries in the world. The National Tuberculosis Control Programme (PNLT) put in place by the state, aims to fight tuberculosis through the implementation of international directives (Directly Observed Treatment Short, DOTS). Despite the deployment of this strategy across the world, its implementation is difficult in the context of low-resource countries. Some expected results are not achieved. In Cameroon, the cure rate for patients with sputum positive pulmonary tuberculosis (TPM+) after 6 months is only about 65%, 20% below the target. This is mainly due to poor patient adherence to treatment. By relying on the potential of mobile Health, the objective of this study is to evaluate the effect of SMS reminders on the cure rate of TPM + patients, measured using 6-month bacilloscopy. Methods/design This is a blinded, randomised controlled multicentre study carried out in Cameroon. The research hypothesis is that sending daily SMS messages to remind patients to take their prescribed tuberculosis medication, together with the standard DOTS strategy, will increase the cure rate from 65% (control group: DOTS, no SMS intervention) to 85% (intervention group: DOTS, with SMS intervention) in a group of new TPM + patients. In accordance with each treatment centre, the participants will be randomly allocated into the two groups using a computer program: the intervention group and the control group. A member of the research team will send daily SMS messages. Study data will be collected by health professionals involved in the care of patients. Data analysis will be done by the intention-to-treat method. Discussion The achieving of expected outcomes by the PNLT through implementation of DOTS requires several challenges. Although it has been demonstrated that the DOTS strategy is effective in the fight against tuberculosis, its application remains difficult in developing countries. This study explores the potential of mHealth to support DOTS strategy. It will gather new evidence on the effectiveness of mHealth-based interventions and SMS reminders in the improvement of treatment adherence and the cure rate of tuberculosis patients, especially in a low-resource country such as Cameroon. Trial registration The trial is registered on the Pan-African Clinical Trials Registry (http://www.pactr.org) under unique identification number: PACTR201307000583416. PMID:24460827

Image Halftoning and Inverse Halftoning for Optimized Dot Diffusion

DTIC Science & Technology

1998-01-01

systems.caltech.edu, ppvnath@sys.caltech.edu ABSTRACT The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error ... halftoning : ordered dither [3], error diffusion [4], neural-net based methods [2], and more recently direct binary search (DBS) [10]. Ordered dithering is a...patterns. On the other hand error diffused halftones do not suffer from periodicity and offer blue noise characteristic [11] which is found to be

Long-wavelength infrared (LWIR) quantum-dot infrared photodetector (QDIP) focal plane array

NASA Astrophysics Data System (ADS)

Gunapala, S. D.; Bandara, S. V.; Hill, C. J.; Ting, D. Z.; Liu, J. K.; Rafol, S. B.; Blazejewski, E. R.; Mumolo, J. M.; Keo, S. A.; Krishna, S.; Chang, Y. C.; Shott, C. A.

2006-05-01

We have exploited the artificial atomlike properties of epitaxially self-assembled quantum dots for the development of high operating temperature long wavelength infrared (LWIR) focal plane arrays. Quantum dots are nanometer-scale islands that form spontaneously on a semiconductor substrate due to lattice mismatch. QDIPs are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages over II-VI material based focal plane arrays. QDIPs are fabricated using robust wide bandgap III-V materials which are well suited to the production of highly uniform LWIR arrays. We have used molecular beam epitaxy (MBE) technology to grow multi-layer LWIR quantum dot structures based on the InAs/InGaAs/GaAs material system. JPL is building on its significant QWIP experience and is basically building a Dot-in-the-Well (DWELL) device design by embedding InAs quantum dots in a QWIP structure. This hybrid quantum dot/quantum well device offers additional control in wavelength tuning via control of dot-size and/or quantum well sizes. In addition the quantum wells can trap electrons and aide in ground state refilling. Recent measurements have shown a 10 times higher photoconductive gain than the typical QWIP device, which indirectly confirms the lower relaxation rate of excited electrons (photon bottleneck) in QDIPs. Subsequent material and device improvements have demonstrated an absorption quantum efficiency (QE) of ~ 3%. Dot-in-the-well (DWELL) QDIPs were also experimentally shown to absorb both 45o and normally incident light. Thus we have employed a reflection grating structure to further enhance the quantum efficiency. JPL has demonstrated wavelength control by progressively growing material and fabricating devices structures that have continuously increased in LWIR response. The most recent devices exhibit peak responsivity out to 8.1 microns. Peak detectivity of the 8.1μm devices has reached ~ 1 x 1010 Jones at 77 K. Furthermore, we have fabricated the first long-wavelength 640x512 pixels QDIP focal plane array. This QDIP focal plane array has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60K operating temperature. In addition, we have managed to increase the quantum efficiency of these devices from 0.1% (according to the data published in literature) to 20% in discrete devices. This is a factor of 200 increase in quantum efficiency. With these excellent results, for the first time QDIP performance has surpassed the QWIP performance. Our goal is to operate these long-wavelength detectors at much higher operating temperature than 77K, which can be passively achieved in space. This will be a huge leap in high performance infrared detectors specifically applicable to space science instruments.

Long-Wavelength Infrared (LWIR) Quantum Dot Infrared Photodetector (QDIP) Focal Plane Array

NASA Technical Reports Server (NTRS)

Gunapala, Sarath D.; Bandara, S. V.; Liu, J. K.; Hill, C. J.; Rafol, S. B.; Mumolo, J. M.; Shott, C. A.

2006-01-01

We have exploited the artificial atomlike properties of epitaxially self-assembled quantum dots for the development of high operating temperature long wavelength infrared (LWIR) focal plane arrays. Quantum dots are nanometer-scale islands that form spontaneously on a semiconductor substrate due to lattice mismatch. QDIPs are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages over II-VI material based focal plane arrays. QDIPs are fabricated using robust wide bandgap III-V materials which are well suited to the production of highly uniform LWIR arrays. We have used molecular beam epitaxy (MBE) technology to grow multi-layer LWIR quantum dot structures based on the InAs/InGaAs/GaAs material system. JPL is building on its significant QWIP experience and is basically building a Dot-in-the-Well (DWELL) device design by embedding InAs quantum dots in a QWIP structure. This hybrid quantum dot/quantum well device offers additional control in wavelength tuning via control of dot-size and/or quantum well sizes. In addition the quantum wells can trap electrons and aide in ground state refilling. Recent measurements have shown a 10 times higher photoconductive gain than the typical QWIP device, which indirectly confirms the lower relaxation rate of excited electrons (photon bottleneck) in QDPs. Subsequent material and device improvements have demonstrated an absorption quantum efficiency (QE) of approx. 3%. Dot-in-the-well (DWELL) QDIPs were also experimentally shown to absorb both 45 deg. and normally incident light. Thus we have employed a reflection grating structure to further enhance the quantum efficiency. JPL has demonstrated wavelength control by progressively growing material and fabricating devices structures that have continuously increased in LWIR response. The most recent devices exhibit peak responsivity out to 8.1 microns. Peak detectivity of the 8.1 micrometer devices has reached approx. 1 x 10(exp 10) Jones at 77 K. Furthermore, we have fabricated the first long-wavelength 640x512 pixels QDP focal plane array. This QDIP focal plane may has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60K operating temperature. In addition, we have managed to increase the quantum efficiency of these devices from 0.1% (according to the data published in literature) to 20% in discrete devices. This is a factor of 200 increase in quantum efficiency. With these excellent results, for the first time QDIP performance has surpassed the QWIP performance. Our goal is to operate these long-wavelength detectors at much higher operating temperature than 77K which can be passively achieved in space. This will be a huge leap in high performance infrared detectors specifically applicable to space science instruments.

Nanoimprint-Transfer-Patterned Solids Enhance Light Absorption in Colloidal Quantum Dot Solar Cells.

PubMed

Kim, Younghoon; Bicanic, Kristopher; Tan, Hairen; Ouellette, Olivier; Sutherland, Brandon R; García de Arquer, F Pelayo; Jo, Jea Woong; Liu, Mengxia; Sun, Bin; Liu, Min; Hoogland, Sjoerd; Sargent, Edward H

2017-04-12

Colloidal quantum dot (CQD) materials are of interest in thin-film solar cells due to their size-tunable bandgap and low-cost solution-processing. However, CQD solar cells suffer from inefficient charge extraction over the film thicknesses required for complete absorption of solar light. Here we show a new strategy to enhance light absorption in CQD solar cells by nanostructuring the CQD film itself at the back interface. We use two-dimensional finite-difference time-domain (FDTD) simulations to study quantitatively the light absorption enhancement in nanostructured back interfaces in CQD solar cells. We implement this experimentally by demonstrating a nanoimprint-transfer-patterning (NTP) process for the fabrication of nanostructured CQD solids with highly ordered patterns. We show that this approach enables a boost in the power conversion efficiency in CQD solar cells primarily due to an increase in short-circuit current density as a result of enhanced absorption through light-trapping.

Selective directed self-assembly of coexisting morphologies using block copolymer blends

NASA Astrophysics Data System (ADS)

Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

2016-08-01

Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. Here we expand on traditional DSA chemical patterning. A blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This is in contrast to the typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.

Focal-Plane Arrays of Quantum-Dot Infrared Photodetectors

NASA Technical Reports Server (NTRS)

Gunapala, Sarath; Wilson, Daniel; Hill, Cory; Liu, John; Bandara, Sumith; Ting, David

2007-01-01

Focal-plane arrays of semiconductor quantum-dot infrared photodetectors (QDIPs) are being developed as superior alternatives to prior infrared imagers, including imagers based on HgCdTe devices and, especially, those based on quantum-well infrared photodetectors (QWIPs). HgCdTe devices and arrays thereof are difficult to fabricate and operate, and they exhibit large nonunformities and high 1/f (where f signifies frequency) noise. QWIPs are easier to fabricate and operate, can be made nearly uniform, and exhibit lower 1/f noise, but they exhibit larger dark currents, and their quantization only along the growth direction prevents them from absorbing photons at normal incidence, thereby limiting their quantum efficiencies. Like QWIPs, QDIPs offer the advantages of greater ease of operation, greater uniformity, and lower 1/f noise, but without the disadvantages: QDIPs exhibit lower dark currents, and quantum efficiencies of QDIPs are greater because the three-dimensional quantization of QDIPs is favorable to the absorption of photons at normal or oblique incidence. Moreover, QDIPs can be operated at higher temperatures (around 200 K) than are required for operation of QWIPs. The main problem in the development of QDIP imagers is to fabricate quantum dots with the requisite uniformity of size and spacing. A promising approach to be tested soon involves the use of electron-beam lithography to define the locations and sizes of quantum dots. A photoresist-covered GaAs substrate would be exposed to the beam generated by an advanced, high-precision electron beam apparatus. The exposure pattern would consist of spots typically having a diameter of 4 nm and typically spaced 20 nm apart. The exposed photoresist would be developed by either a high-contrast or a low-contrast method. In the high-contrast method, the spots would be etched in such a way as to form steep-wall holes all the way down to the substrate. The holes would be wider than the electron beam spots perhaps as wide as 15 to 20 nm, but may be sufficient to control the growth of the quantum dots. In the low-contrast method, the resist would be etched in such a way as to form dimples, the shapes of which would mimic the electron-beam density profile. Then by use of a transfer etching process that etches the substrate faster than it etches the resist, either the pattern of holes or a pattern comprising the narrow, lowest portions of the dimples would be imparted to the substrate. Having been thus patterned, the substrate would be cleaned. The resulting holes or dimples in the substrate would serve as nucleation sites for the growth of quantum dots of controlled size in the following steps. The substrate would be cleaned, then placed in a molecular-beam-epitaxy (MBE) chamber, where native oxide would be thermally desorbed and the quantum dots would be grown.

Application of a Dot Blot Hybridization Platform to Assess Streptococcus uberis Population Structure in Dairy Herds

PubMed Central

Albuquerque, Pedro; Ribeiro, Niza; Almeida, Alexandre; Panschin, Irena; Porfirio, Afonso; Vales, Marta; Diniz, Francisca; Madeira, Helena; Tavares, Fernando

2017-01-01

Streptococcus uberis is considered one of the most important pathogens associated with bovine mastitis. While traditionally acknowledged as an environmental pathogen, S. uberis has been shown to adopt a contagious epidemiological pattern in several dairy herds. Since different control strategies are employed depending on the mode of transmission, in-depth studies of S. uberis populations are essential to determine the best practices to control this pathogen. In this work, we optimized and validated a dot blot platform, combined with automatic image analysis, to rapidly assess the population structure of infective S. uberis, and evaluated its efficiency when compared to multilocus sequence analysis (MLSA) genotyping. Two dairy herds with prevalent S. uberis infections were followed in a 6 month period, in order to collect and characterize isolates from cows with persistent infections. These herds, located in Portugal (Barcelos and Maia regions), had similar management practices, with the herd from Barcelos being smaller and having a better milking parlor management, since infected cow segregation was immediate. A total of 54 S. uberis isolates were obtained from 24 different cows from the two herds. To overcome operator-dependent analysis of the dot blots and increase the technique's consistency and reliability, the hybridization signals were converted into probability values, with average probabilities higher than 0.5 being considered positive results. These data allowed to confirm the isolates' identity as S. uberis using taxa-specific markers and to determine the presence of virulence- and antibiotic resistance-related genes. In addition, MLSA allowed to disclose the most prevalent S. uberis clonal lineages in both herds. Seven different clusters were identified, with Barcelos showing a high clonal diversity and Maia a dominant lineage infecting most cows, suggesting distinct epidemiological patterns, with S. uberis displaying an environmental or contagious transmission pattern depending on the herd. Overall, this work showed the utility of dot blot and MLSA to characterize population structure and epidemiological patterns of mastitis-causing S. uberis. This approach allowed to disclose prevalent virulence patterns and clonal lineages of S. uberis in two distinct herds, and gain insights on the impact of herd management practices on pathogen population structure. PMID:28174566

The response of neurons in areas V1 and MT of the alert rhesus monkey to moving random dot patterns.

PubMed

Snowden, R J; Treue, S; Andersen, R A

1992-01-01

We studied the response of single units to moving random dot patterns in areas V1 and MT of the alert macaque monkey. Most cells could be driven by such patterns; however, many cells in V1 did not give a consistent response but fired at a particular point during stimulus presentation. Thus different dot patterns can produce a markedly different response at any particular time, though the time averaged response is similar. A comparison of the directionality of cells in both V1 and MT using random dot patterns shows the cells of MT to be far more directional. In addition our estimates of the percentage of directional cells in both areas are consistent with previous reports using other stimuli. However, we failed to find a bimodality of directionality in V1 which has been reported in some other studies. The variance associated with response was determined for individual cells. In both areas the variance was found to be approximately equal to the mean response, indicating little difference between extrastriate and striate cortex. These estimates are in broad agreement (though the variance appears a little lower) with those of V1 cells of the anesthetized cat. The response of MT cells was simulated on a computer from the estimates derived from the single unit recordings. While the direction tuning of MT cells is quite wide (mean half-width at half-height approximately 50 degrees) it is shown that the cells can reliably discriminate much smaller changes in direction, and the performance of the cells with the smallest discriminanda were comparable to thresholds measured with human subjects using the same stimuli (approximately 1.1 degrees). Minimum discriminanda for individual cells occurred not at the preferred direction, that is, the peak of their tuning curves, but rather on the steep flanks of their tuning curves. This result suggests that the cells which may mediate the discrimination of motion direction may not be the cells most sensitive to that direction.

Temperature dependent photoluminescence and micromapping of multiple stacks InAs quantum dots

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

Xu, Ming, E-mail: ming.xu@lgep.supelec.fr; Jaffré, Alexandre, E-mail: ming.xu@lgep.supelec.fr; Alvarez, José, E-mail: ming.xu@lgep.supelec.fr

2015-02-27

We utilized temperature dependent photoluminescence (PL) techniques to investigate 1, 3 and 5 stack InGaAs quantum dots (QDs) grown on cross-hatch patterns. PL mapping can well reproduce the QDs distribution as AFM and position dependency of QD growth. It is possible to observe crystallographic dependent PL. The temperature dependent spectra exhibit the QDs energy distribution which reflects the size and shape. The inter-dot carrier coupling effect is observed and translated as a red shift of 120mV on the [1–10] direction peak is observed at 30K on 1 stack with regards to 3 stacks samples, which is assigned to lateral coupling.

Surface ordering of (In,Ga)As quantum dots controlled by GaAs substrate indexes

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

Wang, Zh.M.; Seydmohamadi, Sh.; Lee, J.H.

Self-organized surface ordering of (In,Ga)As quantum dots in a GaAs matrix was investigated using stacked multiple quantum dot layers prepared by molecular-beam epitaxy. While one-dimensional chain-like ordering is formed on singular and slightly misorientated GaAs(100) surfaces, we report on two-dimensional square-like ordering that appears on GaAs(n11)B, where n is 7, 5, 4, and 3. Using a technique to control surface diffusion, the different ordering patterns are found to result from the competition between anisotropic surface diffusion and anisotropic elastic matrix, a similar mechanism suggested before by Solomon [Appl. Phys. Lett. 84, 2073 (2004)].

Spin properties of charged Mn-doped quantum dota)

NASA Astrophysics Data System (ADS)

Besombes, L.; Léger, Y.; Maingault, L.; Mariette, H.

2007-04-01

The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier are analyzed. The emission of the neutral, negatively and positively charged excitons coupled with a single magnetic atom (Mn) are observed in the same individual quantum dot. The spectrum of the charged excitons in interaction with the Mn atom shows a rich pattern attributed to a strong anisotropy of the hole-Mn exchange interaction slightly perturbed by a small valence-band mixing. The anisotropy in the exchange interaction between a single magnetic atom and a single hole is revealed by comparing the emission of a charged Mn-doped quantum dot in longitudinal and transverse magnetic field.

Spin measurement in an undoped Si/SiGe double quantum dot incorporating a micromagnet

NASA Astrophysics Data System (ADS)

Wu, Xian; Ward, Daniel; Prance, Jonathan; Kim, Dohun; Shi, Zhan; Mohr, Robert; Gamble, John; Savage, Donald; Lagally, Max; Friesen, Mark; Coppersmith, Susan; Eriksson, Mark

2014-03-01

We present measurements on a double dot formed in an accumulation-mode undoped Si/SiGe heterostructure. The double dot incorporates a proximal micromagnet to generate a stable magnetic field difference between the quantum dots. The gate design incorporates two layers of gates, and the upper layer of gates is split into five different sections to decrease crosstalk between different gates. A novel pattern of the lower layer gates enhances the tunability of tunnel rates. We will describe our attempts to create a singlet-triplet qubit in this device. This work was supported in part by ARO(W911NF-12-0607), NSF(DMR-1206915), and the United States Department of Defense. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the US Government. Now works at Lancaster University, UK.

Spectroscopy of Charged Quantum Dot Molecules

NASA Astrophysics Data System (ADS)

Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.; Korenev, V. L.

2006-03-01

Spins of single charges in quantum dots are attractive for many quantum information and spintronic proposals. Scalable quantum information applications require the ability to entangle and operate on multiple spins in coupled quantum dots (CQDs). To further the understanding of these systems, we present detailed spectroscopic studies of InAs CQDs with control of the discrete electron or hole charging of the system. The optical spectrum reveals a pattern of energy anticrossings and crossings in the photoluminescence as a function of applied electric field. These features can be understood as a superposition of charge and spin configurations of the two dots and represent clear signatures of quantum mechanical coupling. The molecular resonance leading to these anticrossings is achieved at different electric fields for the optically excited (trion) states and the ground (hole) states allowing for the possibility of using the excited states for optically induced coupling of the qubits.

Outsourcing of KyTC project delivery functions.

DOT National Transportation Integrated Search

2005-06-01

The rise in daily travelers on highways due to population growth, and higher quality and service expectations of the public, are putting increased demands on DOTs today. These demands, combined with decreasing staff sizes and changing resources, are ...

Improvement of Charge Transportation in Si Quantum Dot-Sensitized Solar Cells Using Vanadium Doped TiO2.

PubMed

Seo, Hyunwoong; Ichida, Daiki; Hashimoto, Shinji; Itagaki, Naho; Koga, Kazunori; Shiratani, Masaharu; Nam, Sang-Hun; Boo, Jin-Hyo

2016-05-01

The multiple exciton generation characteristics of quantum dots have been expected to enhance the performance of photochemical solar cells. In previous work, we first introduced Si quantum dot for sensitized solar cells. The Si quantum dots were fabricated by multi-hollow discharge plasma chemical vapor deposition, and were characterized optically and morphologically. The Si quantum dot-sensitized solar cells had poor performance due to significant electron loss by charge recombination. Although the large Si particle size resulted in the exposure of a large TiO2 surface area, there was a limit to ho much the particle size could be decreased due to the reduced absorbance of small particles. Therefore, this work focused on decreasing the internal impedance to improve charge transfer. TiO2 was electronically modified by doping with vanadium, which can improve electron transfer in the TiO2 network, and which is stable in the redox electrolyte. Photogenerated electrons can more easily arrive at the conductive electrode due to the decreased internal impedance. The dark photovoltaic properties confirmed the reduction of charge recombination, and the photon-to-current conversion efficiency reflected the improved electron transfer. Impedance analysis confirmed a decrease in internal impedance and an increased electron lifetime. Consequently, these improvements by vanadium doping enhanced the overall performance of Si quantum dot-sensitized solar cells.

Quantum dot lasers: From promise to high-performance devices

NASA Astrophysics Data System (ADS)

Bhattacharya, P.; Mi, Z.; Yang, J.; Basu, D.; Saha, D.

2009-03-01

Ever since self-organized In(Ga)As/Ga(AI)As quantum dots were realized by molecular beam epitaxy, it became evident that these coherently strained nanostructures could be used as the active media in devices. While the expected advantages stemming from three-dimensional quantum confinement were clearly outlined, these were not borne out by the early experiments. It took a very detailed understanding of the unique carrier dynamics in the quantum dots to exploit their full potential. As a result, we now have lasers with emission wavelengths ranging from 0.7 to 1.54 μm, on GaAs, which demonstrate ultra-low threshold currents, near-zero chip and α-factor and large modulation bandwidth. State-of-the-art performance characteristics of these lasers are briefly reviewed. The growth, fabrication and characteristics of quantum dot lasers on silicon substrates are also described. With the incorporation of multiple quantum dot layers as a dislocation filter, we demonstrate lasers with Jth=900 A/cm 2. The monolithic integration of the lasers with guided wave modulators on silicon is also described. Finally, the properties of spin-polarized lasers with quantum dot active regions are described. Spin injection of electrons is done with a MnAs/GaAs tunnel barrier. Laser operation at 200 K is demonstrated, with the possibility of room temperature operation in the near future.

Fabrication of three dimensional patterns of wide dimensional range using microbes and their applications

NASA Astrophysics Data System (ADS)

Mehta, Sunita; Murugeson, Saravanan; Prakash, Balaji; Deepak

2015-10-01

Inspired by the wound healing property of certain trees, we report a novel microbes based additive process for producing three dimensional patterns, which has a potential of engineering applications in a variety of fields. Imposing a two dimensional pattern of microbes on a gel media and allowing them to grow in the third dimension is known from its use in biological studies. Instead, we have introduced an intermediate porous substrate between the gel media and the microbial growth, which enables three dimensional patterns in specific forms that can be lifted off and used in engineering applications. In order to demonstrate the applicability of this idea in a diverse set of areas, two applications are selected. In one, using this method of microbial growth, we have fabricated microlenses for enhanced light extraction in organic light emitting diodes, where densely packed microlenses of the diameters of hundreds of microns lead to luminance increase by a factor of 1.24X. In another entirely different type of application, braille text patterns are prepared on a normal office paper where the grown microbial colonies serve as braille tactile dots. Braille dot patterns thus prepared meet the standard specifications (size and spacing) for braille books.

Navigation Performance of Global Navigation Satellite Systems in the Space Service Volume

NASA Technical Reports Server (NTRS)

Force, Dale A.

2013-01-01

GPS has been used for spacecraft navigation for many years center dot In support of this, the US has committed that future GPS satellites will continue to provide signals in the Space Service Volume center dot NASA is working with international agencies to obtain similar commitments from other providers center dot In support of this effort, I simulated multi-constellation navigation in the Space Service Volume In this presentation, I extend the work to examine the navigational benefits and drawbacks of the new constellations center dot A major benefit is the reduced geometric dilution of precision (GDOP). I show that there is a substantial reduction in GDOP by using all of the GNSS constellations center dot The increased number of GNSS satellites broadcasting does produce mutual interference, raising the noise floor. A near/far signal problem can also occur where a nearby satellite drowns out satellites that are far away. - In these simulations, no major effect was observed Typically, the use of multi-constellation GNSS navigation improves GDOP by a factor of two or more over GPS alone center dot In addition, at the higher altitudes, four satellite solutions can be obtained much more often center dot This show the value of having commitments to provide signals in the Space Service Volume Besides a commitment to provide a minimum signal in the Space Service Volume, detailed signal gain information is useful for mission planning center dot Knowledge of group and phase delay over the pattern would also reduce the navigational uncertainty

Filling schemes of silver dots inkjet-printed on pixelated nanostructured surfaces

NASA Astrophysics Data System (ADS)

Alan, Sheida; Jiang, Hao; Shahbazbegian, Haleh; Patel, Jasbir N.; Kaminska, Bozena

2017-03-01

Recently, our group demonstrated an inkjet-based technique to enable high-throughput, versatile and full-colour printing of structural colours on generic pixelated nanostructures, termed as molded ink on nanostructured surfaces. The printed colours are controlled by the area of printed silver on the pixelated red, green and blue polymer nanostructure arrays. This paper investigates the behaviour of jetted silver ink droplets on nanostructured surfaces and the microscale dot patterns implemented during printing process, for achieving accurate and consistent colours in the printed images. The surface wettability and the schemes of filling silver dots inside the subpixels are crucial to the quality of printed images. Several related concepts and definitions are introduced, such as filling ratio, full dots per subpixel (DPSP), number of printable colours, colour leaking and dot merging. In our experiments, we first chemically modified the surface to control the wettability and dot size. From each type of modified surface, various filling schemes were experimented and the printed results were evaluated with comprehensive considerations on the number of printable colours and the negative effects of colour leaking and dot merging. Rational selection of the best filling scheme resulted in a 2-line filling scheme using 20 μm dot spacing and line spacing capable of printing 9261 different colours with 121 pixel per inch display resolution, on low-wettability surface. This study is of vital importance for scaling up the printing technique in industrial applications and provides meaningful insights for inkjet-printing on nanostructures.

Immunohistochemical assessment of NY-ESO-1 expression in esophageal adenocarcinoma resection specimens.

PubMed

Hayes, Stephen J; Hng, Keng Ngee; Clark, Peter; Thistlethwaite, Fiona; Hawkins, Robert E; Ang, Yeng

2014-04-14

To assess NY-ESO-1 expression in a cohort of esophageal adenocarcinomas. A retrospective search of our tissue archive for esophageal resection specimens containing esophageal adenocarcinoma was performed, for cases which had previously been reported for diagnostic purposes, using the systematised nomenclature of human and veterinary medicine coding system. Original haematoxylin and eosin stained sections were reviewed, using light microscopy, to confirm classification and tumour differentiation. A total of 27 adenocarcinoma resection specimens were then assessed using immunohistochemistry for NY-ESO-1 expression: 4 well differentiated, 14 moderately differentiated, 4 moderate-poorly differentiated, and 5 poorly differentiated. Four out of a total of 27 cases of esophageal adenocarcinoma examined (15%) displayed diffuse cytoplasmic and nuclear expression for NY-ESO-1. They displayed a heterogeneous and mosaic-type pattern of diffuse staining. Diffuse cytoplasmic staining was not identified in any of these structures: stroma, normal squamous epithelium, normal submucosal gland and duct, Barrett's esophagus (goblet cell), Barrett's esophagus (non-goblet cell) and high grade glandular dysplasia. All adenocarcinomas showed an unexpected dot-type pattern of staining at nuclear, paranuclear and cytoplasmic locations. Similar dot-type staining, with varying frequency and size of dots, was observed on examination of Barrett's metaplasia, esophageal submucosal gland acini and the large bowel negative control, predominantly at the crypt base. Furthermore, a prominent pattern of apical (luminal) cytoplasmic dot-type staining was observed in some cases of Barrett's metaplasia and also adenocarcinoma. A further morphological finding of interest was noted on examination of haematoxylin and eosin stained sections, as aggregates of lymphocytes were consistently noted to surround submucosal glands. We have demonstrated for the first time NY-ESO-1 expression by esophageal adenocarcinomas, Barrett's metaplasia and normal tissues other than germ cells.

Immunohistochemical assessment of NY-ESO-1 expression in esophageal adenocarcinoma resection specimens

PubMed Central

Hayes, Stephen J; Hng, Keng Ngee; Clark, Peter; Thistlethwaite, Fiona; Hawkins, Robert E; Ang, Yeng

2014-01-01

AIM: To assess NY-ESO-1 expression in a cohort of esophageal adenocarcinomas. METHODS: A retrospective search of our tissue archive for esophageal resection specimens containing esophageal adenocarcinoma was performed, for cases which had previously been reported for diagnostic purposes, using the systematised nomenclature of human and veterinary medicine coding system. Original haematoxylin and eosin stained sections were reviewed, using light microscopy, to confirm classification and tumour differentiation. A total of 27 adenocarcinoma resection specimens were then assessed using immunohistochemistry for NY-ESO-1 expression: 4 well differentiated, 14 moderately differentiated, 4 moderate-poorly differentiated, and 5 poorly differentiated. RESULTS: Four out of a total of 27 cases of esophageal adenocarcinoma examined (15%) displayed diffuse cytoplasmic and nuclear expression for NY-ESO-1. They displayed a heterogeneous and mosaic-type pattern of diffuse staining. Diffuse cytoplasmic staining was not identified in any of these structures: stroma, normal squamous epithelium, normal submucosal gland and duct, Barrett’s esophagus (goblet cell), Barrett’s esophagus (non-goblet cell) and high grade glandular dysplasia. All adenocarcinomas showed an unexpected dot-type pattern of staining at nuclear, paranuclear and cytoplasmic locations. Similar dot-type staining, with varying frequency and size of dots, was observed on examination of Barrett’s metaplasia, esophageal submucosal gland acini and the large bowel negative control, predominantly at the crypt base. Furthermore, a prominent pattern of apical (luminal) cytoplasmic dot-type staining was observed in some cases of Barrett’s metaplasia and also adenocarcinoma. A further morphological finding of interest was noted on examination of haematoxylin and eosin stained sections, as aggregates of lymphocytes were consistently noted to surround submucosal glands. CONCLUSION: We have demonstrated for the first time NY-ESO-1 expression by esophageal adenocarcinomas, Barrett’s metaplasia and normal tissues other than germ cells. PMID:24744590

Triggerfish uses chromaticity and lightness for object segregation

PubMed Central

2017-01-01

Humans group components of visual patterns according to their colour, and perceive colours separately from shape. This property of human visual perception is the basis behind the Ishihara test for colour deficiency, where an observer is asked to detect a pattern made up of dots of similar colour with variable lightness against a background of dots made from different colour(s) and lightness. To find out if fish use colour for object segregation in a similar manner to humans, we used stimuli inspired by the Ishihara test. Triggerfish (Rhinecanthus aculeatus) were trained to detect a cross constructed from similarly coloured dots against various backgrounds. Fish detected this cross even when it was camouflaged using either achromatic or chromatic noise, but fish relied more on chromatic cues for shape segregation. It remains unknown whether fish may switch to rely primarily on achromatic cues in scenarios where target objects have higher achromatic contrast and lower chromatic contrast. Fish were also able to generalize between stimuli of different colours, suggesting that colour and shape are processed by fish independently. PMID:29308267

High performance organic distributed Bragg reflector lasers fabricated by dot matrix holography.

PubMed

Wan, Wenqiang; Huang, Wenbin; Pu, Donglin; Qiao, Wen; Ye, Yan; Wei, Guojun; Fang, Zongbao; Zhou, Xiaohong; Chen, Linsen

2015-12-14

We report distributed Bragg reflector (DBR) polymer lasers fabricated using dot matrix holography. Pairs of distributed Bragg reflector mirrors with variable mirror separations are fabricated and a novel energy transfer blend consisting of a blue-emitting conjugated polymer and a red-emitting one is spin-coated onto the patterned substrate to complete the device. Under optical pumping, the device emits sing-mode lasing around 622 nm with a bandwidth of 0.41 nm. The working threshold is as low as 13.5 μJ/cm² (~1.68 kW/cm²) and the measured slope efficiency reaches 5.2%. The distributed feedback (DFB) cavity and the DBR cavity resonate at the same lasing wavelength while the DFB laser shows a much higher threshold. We further show that flexible DBR lasers can be conveniently fabricated through the UV-imprinting technique by using the patterned silica substrate as the mold. Dot matrix holography represents a versatile approach to control the number, the size, the location and the orientation of DBR mirrors, thus providing great flexibility in designing DBR lasers.

Directed self-assembly of nanogold using a chemically modified nanopatterned surface

NASA Astrophysics Data System (ADS)

Nidetz, Robert; Kim, Jinsang

2012-02-01

Electron-beam lithography (EBL) was used to define an aminosilane nanopatterned surface in order to electrostatically self-assemble gold nanoparticles (Au NPs). The chemically modified nanopatterned surfaces were immersed into a Au NP solution to allow the Au NPs to self-assemble. Equilibrium self-assembly was achieved in only 20 min. The number of Au NPs that self-assembled on an aminosilane dot was controlled by manipulating the diameters of both the Au NPs and the dots. Adding salt to the Au NP solution enabled the Au NPs to self-assemble in greater numbers on the same sized dot. However, the preparation of the Au NP solution containing salt was sensitive to spikes in the salt concentration. These spikes led to aggregation of the Au NPs and non-specific deposition of Au NPs on the substrate. The Au NP patterned surfaces were immersed in a sodium hydroxide solution in order to lift-off the patterned Au NPs, but no lift-off was observed without adequate physical agitation. The van der Waals forces are too strong to allow for lift-off despite the absence of electrostatic forces.

Leveraging Crystal Anisotropy for Deterministic Growth of InAs Quantum Dots with Narrow Optical Linewidths

DTIC Science & Technology

2013-08-29

similar layer thicknesses. This offset indicates that the electric field profile of our Schottky diode is different than for unpatterned samples, implying...sacrificing uniformity by further optimizing the substrate Figure 3. (a) Schematic of the Schottky diode heterostructure, indicating the patterned substrate...and negative (X−) trions are indicated . (c) Distribution of linewidths for 80 PL lines from dots grown in high density arrays such as those in Figure 2b

Quantum-dot-tagged microbeads for multiplexed optical coding of biomolecules.

PubMed

Han, M; Gao, X; Su, J Z; Nie, S

2001-07-01

Multicolor optical coding for biological assays has been achieved by embedding different-sized quantum dots (zinc sulfide-capped cadmium selenide nanocrystals) into polymeric microbeads at precisely controlled ratios. Their novel optical properties (e.g., size-tunable emission and simultaneous excitation) render these highly luminescent quantum dots (QDs) ideal fluorophores for wavelength-and-intensity multiplexing. The use of 10 intensity levels and 6 colors could theoretically code one million nucleic acid or protein sequences. Imaging and spectroscopic measurements indicate that the QD-tagged beads are highly uniform and reproducible, yielding bead identification accuracies as high as 99.99% under favorable conditions. DNA hybridization studies demonstrate that the coding and target signals can be simultaneously read at the single-bead level. This spectral coding technology is expected to open new opportunities in gene expression studies, high-throughput screening, and medical diagnostics.

Identification of prefrontal cortex (BA10) activation while performing Stroop test using diffuse optical tomography

NASA Astrophysics Data System (ADS)

Khadka, Sabin; Chityala, Srujan R.; Tian, Fenghua; Liu, Hanli

2011-03-01

Stroop test is commonly used as a behavior-testing tool for psychological examinations that are related to attention and cognitive control of the human brain. Studies have shown activations in Broadmann area 10 (BA10) of prefrontal cortex (PFC) during attention and cognitive process. The use of diffuse optical tomography (DOT) for human brain mapping is becoming more prevalent. In this study we expect to find neural correlates between the performed cognitive tasks and hemodynamic signals detected by a DOT system. Our initial observation showed activation of oxy-hemoglobin concentration in BA 10, which is consistent with some results seen by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Our study demonstrates the possibility of combining DOT with Stroop test to quantitatively investigate cognitive functions of the human brain at the prefrontal cortex.

Cavity-photon contribution to the effective interaction of electrons in parallel quantum dots

NASA Astrophysics Data System (ADS)

Gudmundsson, Vidar; Sitek, Anna; Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei

2016-05-01

A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron-electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field.

Create your own stimulus: Manipulating movements according to social categories

PubMed Central

Koppensteiner, Markus; Primes, Georg; Stephan, Pia

2017-01-01

People ascribe purposeful behaviour to the movements of artificial objects and social qualities to human body motion. We investigated how people associate simple motion cues with social categories. For a first rating-experiment we converted the body movements of speakers into stick-figure animations; for a second rating-experiment we used animations of one single dot. Rating-experiments were “reversed” because we asked participants to alter the movements (i.e., vertical amplitude, horizontal amplitude, and velocity) of the stimuli according to different instructions (e.g., create a stimulus of high dominance). Participants equipped stick figures and dot animations with expansive movements to represent high dominance. Expansive and fast movements (i.e., high velocity) were mainly associated with high aggressiveness. Fast movements were also associated with low friendliness, low trustworthiness, and low competence. Overall, patterns found for stick figure and dot animations were similar indicating that certain motion cues convey social information even when only a dot and no body form is visible. The “reverse approach” we propose here makes the impact of different components directly observable. The data generated by this method offers better insights into the interplay of these components and the ways in which they form meaningful patterns. The proposed method can be extended to other types of nonverbal cues and a variety of social categories. PMID:28339490

First search for atmospheric and extraterrestrial neutrino-induced cascades with the IceCube detector

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

Abbasi, R.; Aguilar, J. A.; Andeen, K.

2011-10-01

We report on the first search for atmospheric and for diffuse astrophysical neutrino-induced showers (cascades) in the IceCube detector using 257 days of data collected in the year 2007-2008 with 22 strings active. A total of 14 events with energies above 16 TeV remained after event selections in the diffuse analysis, with an expected total background contribution of 8.3{+-}3.6. At 90% confidence we set an upper limit of E{sup 2}{Phi}{sub 90%CL}<3.6x10{sup -7} GeV{center_dot}cm{sup -2}{center_dot}s{sup -1}{center_dot}sr{sup -1} on the diffuse flux of neutrinos of all flavors in the energy range between 24 TeV and 6.6 PeV assuming that {Phi}{proportional_to}E{sup -2} andmore » the flavor composition of the {nu}{sub e} ratio {nu}{sub {mu}} ratio {nu}{sub {tau}} flux is 1 ratio 1 ratio 1 at the Earth. The atmospheric neutrino analysis was optimized for lower energies. A total of 12 events were observed with energies above 5 TeV. The observed number of events is consistent with the expected background, within the uncertainties.« less

Periodic vortex pinning by regular structures in Nb thin films: magnetic vs. structural effects

NASA Astrophysics Data System (ADS)

Montero, Maria Isabel; Jonsson-Akerman, B. Johan; Schuller, Ivan K.

2001-03-01

The defects present in a superconducting material can lead to a great variety of static and dynamic vortex phases. In particular, the interaction of the vortex lattice with regular arrays of pinning centers such as holes or magnetic dots gives rise to commensurability effects. These commensurability effects can be observed in the magnetoresistance and in the critical current dependence with the applied field. In recent years, experimental results have shown that there is a dependence of the periodic pinning effect on the properties of the vortex lattice (i.e. vortex-vortex interactions, elastic energy and vortex velocity) and also on the dots characteristics (i.e. dot size, distance between dots, magnetic character of the dot material, etc). However, there is not still a good understanding of the nature of the main pinning mechanisms by the magnetic dots. To clarify this important issue, we have studied and compared the periodic pinning effects in Nb films with rectangular arrays of Ni, Co and Fe dots, as well as the pinning effects in a Nb film deposited on a hole patterned substrate without any magnetic material. We will discuss the differences on pinning energies arising from magnetic effects as compared to structural effects of the superconducting film. This work was supported by NSF and DOE. M.I. Montero acknowledges postdoctoral fellowship by the Secretaria de Estado de Educacion y Universidades (Spain).

Spin wave eigenmodes in single and coupled sub-150 nm rectangular permalloy dots

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

Carlotti, G., E-mail: giovanni.carlotti@fisica.unipg.it; Madami, M.; Tacchi, S.

2015-05-07

We present the results of a Brillouin light scattering investigation of thermally excited spin wave eigenmodes in square arrays of either isolated rectangular dots of permalloy or twins of dipolarly coupled elements, placed side-by-side or head-to-tail. The nanodots, fabricated by e-beam lithography and lift-off, are 20 nm thick and have the major size D in the range between 90 nm and 150 nm. The experimental spectra show the presence of two main peaks, corresponding to modes localized either at the edges or in the center of the dots. Their frequency dependence on the dot size and on the interaction with adjacent elements hasmore » been measured and successfully interpreted on the basis of dynamical micromagnetic simulations. The latter enabled us also to describe the spatial profile of the eigenmodes, putting in evidence the effects induced by the dipolar interaction between coupled dots. In particular, in twinned dots the demagnetizing field is appreciably modified in proximity of the “internal edges” if compared to the “external” ones, leading to a splitting of the edge mode. These results can be relevant for the exploitation of sub-150 nm magnetic dots in new applications, such as magnonic metamaterials, bit-patterned storage media, and nano-magnetic logic devices.« less

The Problem with Precision: Managing Expectations for Air Power

DTIC Science & Technology

2013-03-01

contributed to inflated expectations about discrimination in warfare. The World War II strategic bombing campaign was portrayed in film footage of...skies dotted with bombers, escorts, free-falling bombs from open bomb bay doors, and impressive explosions on the ground below; what the films did not...Committee on Public Information in order to influence America’s public opinion on the World War.88 The organization used films , newspapers, radio

The One-Pot Directed Assembly of Cylinder-Forming Block Copolymer on Adjacent Chemical Patterns for Bimodal Patterning.

PubMed

Chang, Tzu-Hsuan; Xiong, Shisheng; Liu, Chi-Chun; Liu, Dong; Nealey, Paul F; Ma, Zhenqiang

2017-09-01

The direct self-assembly of cylinder-forming poly(styrene-block-methyl-methacrylate) (PS-b-PMMA) block copolymer is successfully assembled into two orientations, according to the underlying guiding pattern in different areas. Lying-down and perpendicular cylinders are formed, respectively, depending on the design of chemical pattern: sparse line/space pattern or hexagonal dot array. The first chemical pattern composed of prepatterned cross-linked polystyrene (XPS) line/space structure has a period (L S ) equal to twice the intercylinder period of the block copolymer (L 0 ). The PS-b-PMMA thin film on the prepared chemical template after thermal annealing forms a lying-down cylinder morphology when the width of the PS strips is less than the width of PS block in the PS-b-PMMA block copolymer. The morphology is only applicable at the discrete thickness of the PS-b-PMMA film. In addition to forming the lying-down cylinders directly on the XPS guiding pattern, the cylinder-forming block copolymer can also be assembled in a perpendicular way on the second guiding pattern (the hexagonal dot array). The block copolymer films are registered into two orientations in a single directed self-assembly process. The features of the assembled patterns are successfully transferred down to the silicon oxide substrate. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dermoscopy of pigmented lesions on mucocutaneous junction and mucous membrane.

PubMed

Lin, J; Koga, H; Takata, M; Saida, T

2009-12-01

The dermoscopic features of pigmented lesions on the mucocutaneous junction and mucous membrane are different from those on hairy skin. Differentiation between benign lesions and malignant melanomas of these sites is often difficult. To define the dermoscopic patterns of lesions on the mucocutaneous junction and mucous membrane, and assess the applicability of standard dermoscopic algorithms to these lesions. An unselected consecutive series of 40 lesions on the mucocutaneous junction and mucous membrane was studied. All the lesions were imaged using dermoscopy devices, analysed for dermoscopic patterns and scored with algorithms including the ABCD rule, Menzies method, 7-point checklist, 3-point checklist and the CASH algorithm. Benign pigmented lesions of the mucocutaneous junction and mucous membrane frequently presented a dotted-globular pattern (25%), a homogeneous pattern (25%), a fish scale-like pattern (18.8%) and a hyphal pattern (18.8%), while melanomas of these sites showed a multicomponent pattern (75%) and a homogeneous pattern (25%). The fish scale-like pattern and hyphal pattern were considered to be variants of the ring-like pattern. The sensitivities of the ABCD rule, Menzies method, 7-point checklist, 3-point checklist and CASH algorithm in diagnosing mucosal melanomas were 100%, 100%, 63%, 88% and 100%; and the specificities were 100%, 94%, 100%, 94% and 100%, respectively. The ring-like pattern and its variants (fish scale-like pattern and hyphal pattern) are frequently observed as well as the dotted-globular pattern and homogeneous pattern in mucosal melanotic macules. The algorithms for pigmented lesions on hairy skin also apply to those on the mucocutaneous junction and mucous membrane with high sensitivity and specificity.

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

Wang, L. W.; Franceschetti, A.; Zunger, A.

We have developed a "linear combination of bulk bands" method that permits atomistic, pseudopotential electronic structure calculations for .apprx.10(sup6) atom nanostructures. Application to (GaAs)n/A1As)n (001) superlattices (SL's) reveals even-odd oscillations in the ..Gamma..-X coupling magnitude Vrx(n), which vanishes for n = odd, even for abrupt and segregated SL's, respectively. Surprisingly, in contrast with recent expectations, OD quantum dots are found here to have a smaller ..Gamma..-X coupling than equivalent 2D SL's. Our analysis shows that for large quantum dots this is largely due to the existence of level repulsion from many X states.

Visual Prediction Error Spreads Across Object Features in Human Visual Cortex

PubMed Central

Summerfield, Christopher; Egner, Tobias

2016-01-01

Visual cognition is thought to rely heavily on contextual expectations. Accordingly, previous studies have revealed distinct neural signatures for expected versus unexpected stimuli in visual cortex. However, it is presently unknown how the brain combines multiple concurrent stimulus expectations such as those we have for different features of a familiar object. To understand how an unexpected object feature affects the simultaneous processing of other expected feature(s), we combined human fMRI with a task that independently manipulated expectations for color and motion features of moving-dot stimuli. Behavioral data and neural signals from visual cortex were then interrogated to adjudicate between three possible ways in which prediction error (surprise) in the processing of one feature might affect the concurrent processing of another, expected feature: (1) feature processing may be independent; (2) surprise might “spread” from the unexpected to the expected feature, rendering the entire object unexpected; or (3) pairing a surprising feature with an expected feature might promote the inference that the two features are not in fact part of the same object. To formalize these rival hypotheses, we implemented them in a simple computational model of multifeature expectations. Across a range of analyses, behavior and visual neural signals consistently supported a model that assumes a mixing of prediction error signals across features: surprise in one object feature spreads to its other feature(s), thus rendering the entire object unexpected. These results reveal neurocomputational principles of multifeature expectations and indicate that objects are the unit of selection for predictive vision. SIGNIFICANCE STATEMENT We address a key question in predictive visual cognition: how does the brain combine multiple concurrent expectations for different features of a single object such as its color and motion trajectory? By combining a behavioral protocol that independently varies expectation of (and attention to) multiple object features with computational modeling and fMRI, we demonstrate that behavior and fMRI activity patterns in visual cortex are best accounted for by a model in which prediction error in one object feature spreads to other object features. These results demonstrate how predictive vision forms object-level expectations out of multiple independent features. PMID:27810936

Entanglement loss in molecular quantum-dot qubits due to interaction with the environment.

PubMed

Blair, Enrique P; Tóth, Géza; Lent, Craig S

2018-05-16

We study quantum entanglement loss due to environmental interaction in a condensed matter system with a complex geometry relevant to recent proposals for computing with single electrons at the nanoscale. We consider a system consisting of two qubits, each realized by an electron in a double quantum dot, which are initially in an entangled Bell state. The qubits are widely separated and each interacts with its own environment. The environment for each is modeled by surrounding double quantum dots placed at random positions with random orientations. We calculate the unitary evolution of the joint system and environment. The global state remains pure throughout. We examine the time dependence of the expectation value of the bipartite Clauser-Horne-Shimony-Holt (CHSH) and Brukner-Paunković-Rudolph-Vedral (BPRV) Bell operators and explore the emergence of correlations consistent with local realism. Though the details of this transition depend on the specific environmental geometry, we show how the results can be mapped on to a universal behavior with appropriate scaling. We determine the relevant disentanglement times based on realistic physical parameters for molecular double-dots.

Entanglement loss in molecular quantum-dot qubits due to interaction with the environment

NASA Astrophysics Data System (ADS)

Blair, Enrique P.; Tóth, Géza; Lent, Craig S.

2018-05-01

We study quantum entanglement loss due to environmental interaction in a condensed matter system with a complex geometry relevant to recent proposals for computing with single electrons at the nanoscale. We consider a system consisting of two qubits, each realized by an electron in a double quantum dot, which are initially in an entangled Bell state. The qubits are widely separated and each interacts with its own environment. The environment for each is modeled by surrounding double quantum dots placed at random positions with random orientations. We calculate the unitary evolution of the joint system and environment. The global state remains pure throughout. We examine the time dependence of the expectation value of the bipartite Clauser–Horne–Shimony–Holt (CHSH) and Brukner–Paunković–Rudolph–Vedral (BPRV) Bell operators and explore the emergence of correlations consistent with local realism. Though the details of this transition depend on the specific environmental geometry, we show how the results can be mapped on to a universal behavior with appropriate scaling. We determine the relevant disentanglement times based on realistic physical parameters for molecular double-dots.

Non-equilibrium transport in the quantum dot: quench dynamics and non-equilibrium steady state

NASA Astrophysics Data System (ADS)

Culver, Adrian; Andrei, Natan

We present an exact method of calculating the non-equilibrium current driven by a voltage drop across a quantum dot. The system is described by the two lead Anderson model at zero temperature with on-site Coulomb repulsion and non-interacting, linearized leads. We prepare the system in an initial state consisting of a free Fermi sea in each lead with the voltage drop given as the difference between the two Fermi levels. We quench the system by coupling the dot to the leads at t = 0 and following the time evolution of the wavefunction. In the long time limit a new type of Bethe Ansatz wavefunction emerges, which satisfies the Lippmann-Schwinger equation with the two Fermi seas serving as the boundary conditions. This exact, non-perturbative solution describes the non-equilibrium steady state of the system. We describe how to use this solution to compute the infinite time limit of the expectation value of the current operator at a given voltage, which would yield the I-V characteristic of the dot. Research supported by NSF Grant DMR 1410583.

Fingerprints of transverse and longitudinal coupling between induced open quantum dots in the longitudinal magnetoconductance through antidot lattices

NASA Astrophysics Data System (ADS)

Ujevic, Sebastian; Mendoza, Michel

2010-07-01

We propose numerical simulations of longitudinal magnetoconductance through a finite antidot lattice located inside an open quantum dot with a magnetic field applied perpendicular to the plane. The system is connected to reservoirs using quantum point contacts. We discuss the relationship between the longitudinal magnetoconductance and the generation of transversal couplings between the induced open quantum dots in the system. The system presents longitudinal magnetoconductance maps with crossovers (between transversal bands) and closings (longitudinal decoupling) of fundamental quantum states related to the open quantum dots induced by the antidot lattice. A relationship is observed between the distribution of antidots and the formed conductance bands, allowing a systematic follow up of the bands as a function of the applied magnetic field and quantum point-contact width. We observed a high conductance intensity [between n and (n+1) quantum of conductance, n=1,2,… ] in the regions of crossover and closing of states. This suggests transversal couplings between the induced open quantum dots of the system that can be modulated by varying both the antidots potential and the quantum point-contact width. A new continuous channel (not expected) is induced by the variation in the contact width and generate Fano resonances in the conductance. These resonances can be manipulated by the applied magnetic field.

Ferromagnetic resonance response of electron-beam patterned arrays of ferromagnetic nanoparticles

NASA Astrophysics Data System (ADS)

Jung, Sukkoo; Watkins, Byron; Feller, Jeffrey; Ketterson, John; Chandrasekhar, Venkat

2001-03-01

We report on the fabrication and the dynamic magnetic properties of periodic permalloy dot arrays. Electron-beam lithography and e-gun evaporation have been used to make the arrays with the aspect ratio of 2 (dot diameter : 40 nm, height : 80 nm) and periods of 100 - 200 nm. The magnetic properties of the arrays and their interactions have been investigated by ferromagnetic resonance (FMR), magnetic force microscopy (MFM), and SQUID magnetometry. The measured FMR data show that the position and magnitude of resonant absorption peaks strongly depend on the angle between magnetic field and the lattice structure. The results of dot arrays with various kinds of structural parameters will be presented. Supported by Army Research Office, DAAD19-99-1-0334/P001

Spontaneous generation of frequency combs in QD lasers

NASA Astrophysics Data System (ADS)

Columbo, Lorenzo Luigi; Bardella, Paolo; Gioannini, Mariangela

2018-02-01

We report a systematic analysis of the phenomenon of self-generation of optical frequency combs in single section Fabry-Perot Quantum Dot lasers using a Time Domain Travelling Wave model. We show that the carriers grating due to the standing wave pattern (spatial hole burning) peculiar of Quantum Dots laser and the Four Wave Mixing are the key ingredients to explain spontaneous Optical Frequency Combs in these devices. Our results well agree with recent experimental evidences reported in semiconductor lasers based on Quantum Dots and Quantum Dashes active material and pave the way to the development of a simulation tool for the design of these comb laser sources for innovative applications in the field of high-data rate optical communications.

Local modifications of magnetism and structure in FePt (001) epitaxial thin films by focused ion beam: Two-dimensional perpendicular patterns

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

Albertini, F.; Nasi, L.; Casoli, F.

Focused ion beam was utilized to locally modify magnetism and structure of L1{sub 0} FePt perpendicular thin films. As a first step, we have performed a magnetic, morphological, and structural study of completely irradiated FePt films with different Ga{sup +} doses (1x10{sup 13} -4x10{sup 16} ions/cm{sup 2}) and ion beam energy of 30 keV. For doses of 1x10{sup 14} ions/cm{sup 2} and above a complete transition from the ordered L1{sub 0} to the disordered A1 phase was found to occur, resulting in a drop of magnetic anisotropy and in the consequent moment reorientation from out-of-plane to in-plane. The lowest effectivemore » dose in disordering the structure (1x10{sup 14} ions/cm{sup 2}) was found not to affect the film morphology. Taking advantage of these results, continuous two-dimensional (2D) patterns of perpendicular magnetic structures (250 nm dots, 1 {mu}m dots, 1 {mu}m-large stripes) were produced by focused ion beam without affecting the morphology. The 2D patterns were revealed by means of magnetic force microscopy, that evidenced peculiar domain structures in the case of 1 {mu}m dots.« less

Texas perpetual pavements : new design guidelines.

DOT National Transportation Integrated Search

2010-06-01

Since 2001, the State of Texas has been designing and constructing perpetual pavements : on some of its heavily trafficked highways where the expected 20-year truck-traffic estimate of : 18 kip ESALs is in excess of 30 million (TxDOT, 2001). To date,...

Snow and ice control at extreme temperatures.

DOT National Transportation Integrated Search

2011-04-25

As expected, most state and provincial DOTs that we spoke with are using traditional methods to prevent and : remove snow and ice at very low temperatures. In addition to a review of current research, we spoke with six winter : maintenance profession...

A Single Mechanism Can Account for Human Perception of Depth in Mixed Correlation Random Dot Stereograms

PubMed Central

Cumming, Bruce G.

2016-01-01

In order to extract retinal disparity from a visual scene, the brain must match corresponding points in the left and right retinae. This computationally demanding task is known as the stereo correspondence problem. The initial stage of the solution to the correspondence problem is generally thought to consist of a correlation-based computation. However, recent work by Doi et al suggests that human observers can see depth in a class of stimuli where the mean binocular correlation is 0 (half-matched random dot stereograms). Half-matched random dot stereograms are made up of an equal number of correlated and anticorrelated dots, and the binocular energy model—a well-known model of V1 binocular complex cells—fails to signal disparity here. This has led to the proposition that a second, match-based computation must be extracting disparity in these stimuli. Here we show that a straightforward modification to the binocular energy model—adding a point output nonlinearity—is by itself sufficient to produce cells that are disparity-tuned to half-matched random dot stereograms. We then show that a simple decision model using this single mechanism can reproduce psychometric functions generated by human observers, including reduced performance to large disparities and rapidly updating dot patterns. The model makes predictions about how performance should change with dot size in half-matched stereograms and temporal alternation in correlation, which we test in human observers. We conclude that a single correlation-based computation, based directly on already-known properties of V1 neurons, can account for the literature on mixed correlation random dot stereograms. PMID:27196696

Self-organized microstructures induced by MeV ion beam on silicon surface

NASA Astrophysics Data System (ADS)

Ahmad, Muthanna

2017-02-01

Micro patterning of self organized structure on silicon surface is induced by ion implantation of energetic (MeV) copper ions. This work reports for the first time the ability of using energetic ions for producing highly ordered ripples and dots of micro sizes. The experiments are realized at the Tandem ion beam accelerator (3 MV) at the IBA laboratory of the Atomic Energy Commission of Syria. Similarly to nano patterning formed by slow ions, the formation of micro patterned structures dots and ripples is observed to be depending on the angle of ion beam incidence, energy and ion fluence. The observation of such microstructures formation is limited to a range of ion energies (few MeV) at fluence higher than 1.75 × 1017 ion cm-2. The patterned surface layer is completely amorphousized by the ion implantation. Shadowing effect is observed in the formation of microripples and superstructures in the top of ripples. The superstructure develops new morphology that is not observed before. This morphology has butterfly shape with symmetry in its structure.

Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology.

PubMed

Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping

2015-04-28

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.

Implementing the global plan to stop TB, 2011-2015--optimizing allocations and the Global Fund's contribution: a scenario projections study.

PubMed

Korenromp, Eline L; Glaziou, Philippe; Fitzpatrick, Christopher; Floyd, Katherine; Hosseini, Mehran; Raviglione, Mario; Atun, Rifat; Williams, Brian

2012-01-01

The Global Plan to Stop TB estimates funding required in low- and middle-income countries to achieve TB control targets set by the Stop TB Partnership within the context of the Millennium Development Goals. We estimate the contribution and impact of Global Fund investments under various scenarios of allocations across interventions and regions. Using Global Plan assumptions on expected cases and mortality, we estimate treatment costs and mortality impact for diagnosis and treatment for drug-sensitive and multidrug-resistant TB (MDR-TB), including antiretroviral treatment (ART) during DOTS for HIV-co-infected patients, for four country groups, overall and for the Global Fund investments. In 2015, China and India account for 24% of funding need, Eastern Europe and Central Asia (EECA) for 33%, sub-Saharan Africa (SSA) for 20%, and other low- and middle-income countries for 24%. Scale-up of MDR-TB treatment, especially in EECA, drives an increasing global TB funding need--an essential investment to contain the mortality burden associated with MDR-TB and future disease costs. Funding needs rise fastest in SSA, reflecting increasing coverage need of improved TB/HIV management, which saves most lives per dollar spent in the short term. The Global Fund is expected to finance 8-12% of Global Plan implementation costs annually. Lives saved through Global Fund TB support within the available funding envelope could increase 37% if allocations shifted from current regional demand patterns to a prioritized scale-up of improved TB/HIV treatment and secondly DOTS, both mainly in Africa--with EECA region, which has disproportionately high per-patient costs, funded from alternative resources. These findings, alongside country funding gaps, domestic funding and implementation capacity and equity considerations, should inform strategies and policies for international donors, national governments and disease control programs to implement a more optimal investment approach focusing on highest-impact populations and interventions.

Implementing the Global Plan to Stop TB, 2011–2015 – Optimizing Allocations and the Global Fund’s Contribution: A Scenario Projections Study

PubMed Central

Korenromp, Eline L.; Glaziou, Philippe; Fitzpatrick, Christopher; Floyd, Katherine; Hosseini, Mehran; Raviglione, Mario; Atun, Rifat; Williams, Brian

2012-01-01

Background The Global Plan to Stop TB estimates funding required in low- and middle-income countries to achieve TB control targets set by the Stop TB Partnership within the context of the Millennium Development Goals. We estimate the contribution and impact of Global Fund investments under various scenarios of allocations across interventions and regions. Methodology/Principal Findings Using Global Plan assumptions on expected cases and mortality, we estimate treatment costs and mortality impact for diagnosis and treatment for drug-sensitive and multidrug-resistant TB (MDR-TB), including antiretroviral treatment (ART) during DOTS for HIV-co-infected patients, for four country groups, overall and for the Global Fund investments. In 2015, China and India account for 24% of funding need, Eastern Europe and Central Asia (EECA) for 33%, sub-Saharan Africa (SSA) for 20%, and other low- and middle-income countries for 24%. Scale-up of MDR-TB treatment, especially in EECA, drives an increasing global TB funding need – an essential investment to contain the mortality burden associated with MDR-TB and future disease costs. Funding needs rise fastest in SSA, reflecting increasing coverage need of improved TB/HIV management, which saves most lives per dollar spent in the short term. The Global Fund is expected to finance 8–12% of Global Plan implementation costs annually. Lives saved through Global Fund TB support within the available funding envelope could increase 37% if allocations shifted from current regional demand patterns to a prioritized scale-up of improved TB/HIV treatment and secondly DOTS, both mainly in Africa − with EECA region, which has disproportionately high per-patient costs, funded from alternative resources. Conclusions/Significance These findings, alongside country funding gaps, domestic funding and implementation capacity and equity considerations, should inform strategies and policies for international donors, national governments and disease control programs to implement a more optimal investment approach focusing on highest-impact populations and interventions. PMID:22719954

Development and Application of Explicitly Correlated Wave Function Based Methods for the Investigation of Optical Properties of Semiconductor Nanomaterials

NASA Astrophysics Data System (ADS)

Elward, Jennifer Mary

Semiconductor nanoparticles, or quantum dots (QDs), are well known to have very unique optical and electronic properties. These properties can be controlled and tailored as a function of several influential factors, including but not limited to the particle size and shape, effect of composition and heterojunction as well as the effect of ligand on the particle surface. This customizable nature leads to extensive experimental and theoretical research on the capabilities of these quantum dots for many application purposes. However, in order to be able to understand and thus further the development of these materials, one must first understand the fundamental interaction within these nanoparticles. In this thesis, I have developed a theoretical method which is called electron-hole explicitly correlated Hartee-Fock (eh-XCHF). It is a variational method for solving the electron-hole Schrodinger equation and has been used in this work to study electron-hole interaction in semiconductor quantum dots. The method was benchmarked with respect to a parabolic quantum dot system, and ground state energy and electron-hole recombination probability were computed. Both of these properties were found to be in good agreement with expected results. Upon successful benchmarking, I have applied the eh-XCHF method to study optical properties of several quantum dot systems including the effect of dot size on exciton binding energy and recombination probability in a CdSe quantum dot, the effect of shape on a CdSe quantum dot, the effect of heterojunction on a CdSe/ZnS quantum dot and the effect of quantum dot-biomolecule interaction within a CdSe-firefly Luciferase protein conjugate system. As metrics for assessing the effect of these influencers on the electron-hole interaction, the exciton binding energy, electron-hole recombination probability and the average electron-hole separation distance have been computed. These excitonic properties have been found to be strongly infuenced by the changing composition of the particle. It has also been found through this work that the explicitly correlated method performs very well when computing these properties as it provides a feasible computational route to compare to both experimental and other theoretical results.

Fabrication of three dimensional patterns of wide dimensional range using microbes and their applications

PubMed Central

Mehta, Sunita; Murugeson, Saravanan; Prakash, Balaji; Deepak

2015-01-01

Inspired by the wound healing property of certain trees, we report a novel microbes based additive process for producing three dimensional patterns, which has a potential of engineering applications in a variety of fields. Imposing a two dimensional pattern of microbes on a gel media and allowing them to grow in the third dimension is known from its use in biological studies. Instead, we have introduced an intermediate porous substrate between the gel media and the microbial growth, which enables three dimensional patterns in specific forms that can be lifted off and used in engineering applications. In order to demonstrate the applicability of this idea in a diverse set of areas, two applications are selected. In one, using this method of microbial growth, we have fabricated microlenses for enhanced light extraction in organic light emitting diodes, where densely packed microlenses of the diameters of hundreds of microns lead to luminance increase by a factor of 1.24X. In another entirely different type of application, braille text patterns are prepared on a normal office paper where the grown microbial colonies serve as braille tactile dots. Braille dot patterns thus prepared meet the standard specifications (size and spacing) for braille books. PMID:26486847

Linearly polarized emission from an embedded quantum dot using nanowire morphology control.

PubMed

Foster, Andrew P; Bradley, John P; Gardner, Kirsty; Krysa, Andrey B; Royall, Ben; Skolnick, Maurice S; Wilson, Luke R

2015-03-11

GaAs nanowires with elongated cross sections are formed using a catalyst-free growth technique. This is achieved by patterning elongated nanoscale openings within a silicon dioxide growth mask on a (111)B GaAs substrate. It is observed that MOVPE-grown vertical nanowires with cross section elongated in the [21̅1̅] and [1̅12] directions remain faithful to the geometry of the openings. An InGaAs quantum dot with weak radial confinement is realized within each nanowire by briefly introducing indium into the reactor during nanowire growth. Photoluminescence emission from an embedded nanowire quantum dot is strongly linearly polarized (typically >90%) with the polarization direction coincident with the axis of elongation. Linearly polarized PL emission is a result of embedding the quantum dot in an anisotropic nanowire structure that supports a single strongly confined, linearly polarized optical mode. This research provides a route to the bottom-up growth of linearly polarized single photon sources of interest for quantum information applications.

Large dynamic range digital nanodot gradients of biomolecules made by low-cost nanocontact printing for cell haptotaxis.

PubMed

Ricoult, Sébastien G; Pla-Roca, Mateu; Safavieh, Roozbeh; Lopez-Ayon, G Monserratt; Grütter, Peter; Kennedy, Timothy E; Juncker, David

2013-10-11

A novel method is introduced for ultrahigh throughput and ultralow cost patterning of biomolecules with nanometer resolution and novel 2D digital nanodot gradients (DNGs) with mathematically defined slopes are created. The technique is based on lift-off nanocontact printing while using high-resolution photopolymer stamps that are rapidly produced at a low cost through double replication from Si originals. Printed patterns with 100 nm features are shown. DNGs with varying spacing between the dots and a record dynamic range of 4400 are produced; 64 unique DNGs, each with hundreds of thousands of dots, are inked and printed in 5.5 min. The adhesive response and haptotaxis of C2C12 myoblast cells on DNGs demonstrated their biofunctionality. The great flexibility in pattern design, the massive parallel ability, the ultra low cost, and the extreme ease of polymer lift-off nanocontact printing will facilitate its use for various biological and medical applications. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pattern-projected schlieren imaging method using a diffractive optics element

NASA Astrophysics Data System (ADS)

Min, Gihyeon; Lee, Byung-Tak; Kim, Nac Woo; Lee, Munseob

2018-04-01

We propose a novel schlieren imaging method by projecting a random dot pattern, which is generated in a light source module that includes a diffractive optical element. All apparatuses are located in the source side, which leads to one-body sensor applications. This pattern is distorted by the deflections of schlieren objects such that the displacement vectors of random dots in the pixels can be obtained using the particle image velocity algorithm. The air turbulences induced by a burning candle, boiling pot, heater, and gas torch were successfully imaged, and it was shown that imaging up to a size of 0.7 m  ×  0.57 m is possible. An algorithm to correct the non-uniform sensitivity according to the position of a schlieren object was analytically derived. This algorithm was applied to schlieren images of lenses. Comparing the corrected versions to the original schlieren images, we showed a corrected uniform sensitivity of 14.15 times on average.

Fabrication of carbon quantum dots with nano-defined position and pattern in one step via sugar-electron-beam writing.

PubMed

Weng, Yuyan; Li, Zhiyun; Peng, Lun; Zhang, Weidong; Chen, Gaojian

2017-12-14

Quantum dots (QDs) are promising materials in nanophotonics, biological imaging, and even quantum computing. Precise positioning and patterning of QDs is a prerequisite for realizing their actual applications. Contrary to the traditional two discrete steps of fabricating and positioning QDs, herein, a novel sugar-electron-beam writing (SEW) method is reported for producing QDs via electron-beam lithography (EBL) that uses a carefully chosen synthetic resist, poly(2-(methacrylamido)glucopyranose) (PMAG). Carbon QDs (CQDs) could be fabricated in situ through electron beam exposure, and the nanoscale position and luminescence intensity of the produced CQDs could be precisely controlled without the assistance of any other fluorescent matter. We have demonstrated that upon combining an electron beam with a glycopolymer, in situ production of CQDs occurs at the electron beam spot center with nanoscale precision at any place and with any patterns, an advancement that we believe will stimulate innovations in future applications.

Selective directed self-assembly of coexisting morphologies using block copolymer blends

PubMed Central

Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

2016-01-01

Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. Here we expand on traditional DSA chemical patterning. A blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This is in contrast to the typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist. PMID:27480327

Surface structuring in polypropylene using Ar+ beam sputtering: Pattern transition from ripples to dot nanostructures

NASA Astrophysics Data System (ADS)

Goyal, Meetika; Aggarwal, Sanjeev; Sharma, Annu; Ojha, Sunil

2018-05-01

Temporal variations in nano-scale surface morphology generated on Polypropylene (PP) substrates utilizing 40 keV oblique argon ion beam have been presented. Due to controlled variation of crucial beam parameters i.e. ion incidence angle and erosion time, formation of ripple patterns and further its transition into dot nanostructures have been realized. Experimental investigations have been supported by evaluation of Bradley and Harper (B-H) coefficients estimated using SRIM (The Stopping and Range of Ions in Matter) simulations. Roughness of pristine target surfaces has been accredited to be a crucial factor behind the early time evolution of nano-scale patterns over the polymeric surface. Study of Power spectral density (PSD) spectra reveals that smoothing mechanism switch from ballistic drift to ion enhanced surface diffusion (ESD) which can be the most probable cause for such morphological transition under given experimental conditions. Compositional analysis and depth profiling of argon ion irradiated specimens using Rutherford Backscattering Spectroscopy (RBS) has also been correlated with the AFM findings.

Selective directed self-assembly of coexisting morphologies using block copolymer blends

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

Stein, A.; Wright, G.; Yager, K. G.

Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. We expand on traditional DSA chemical patterning. Moreover, a blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This contrastsmore » with typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.« less

Selective directed self-assembly of coexisting morphologies using block copolymer blends

DOE PAGES

Stein, A.; Wright, G.; Yager, K. G.; ...

2016-08-02

Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. We expand on traditional DSA chemical patterning. Moreover, a blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This contrastsmore » with typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.« less

Intravitreal silicon-based quantum dots as neuroprotective factors in a model of retinal photoreceptor degeneration.

PubMed

Olson, Jeffrey L; Velez-Montoya, Raul; Mandava, Naresh; Stoldt, Conrad R

2012-08-17

To study the intravitreal application of silicon quantum dots (QDs) and their capabilities to deliver electrical stimulation to the retinal cells and to assess the potential effect on retinal electrophysiology and anatomy. A Royal College of Surgeon rat model of retinal degeneration was used in this study. A total of 32 eyes were used, divided in four groups of 8 eyes each; the first group received the silicon-based QD, the second group received an inactive gold-based QD, the third group received a sham injection, and the fourth group was used as a control. An electroretinogram (ERG) was done at baseline and thereafter every week for 9 weeks. At the end of the follow-up, eyes were collected for further pathologic analysis and nuclei cell counts. Eyes within the silicon-based QD group showed a definite but transient increase in the waves of the ERG, especially in the rod response compared with the sham and control groups (P < 0.05). The pathologic examination demonstrated a higher nuclei count in the QD group, consistent with a higher cell survival rate than that in the sham and control groups in which cells degenerated as expected. Intravitreal injection of silicon-based QD seems to be safe and well tolerated, with no evident toxic reaction and demonstrates a beneficial effect by prolonging cell survival rate and improving ERG patterns in a well-established model of retinal degeneration. (ClinicalTrials.gov numbers NCT00407602, NCT01490827.).

Design, experiments and simulation of voltage transformers on the basis of a differential input D-dot sensor.

PubMed

Wang, Jingang; Gao, Can; Yang, Jie

2014-07-17

Currently available traditional electromagnetic voltage sensors fail to meet the measurement requirements of the smart grid, because of low accuracy in the static and dynamic ranges and the occurrence of ferromagnetic resonance attributed to overvoltage and output short circuit. This work develops a new non-contact high-bandwidth voltage measurement system for power equipment. This system aims at the miniaturization and non-contact measurement of the smart grid. After traditional D-dot voltage probe analysis, an improved method is proposed. For the sensor to work in a self-integrating pattern, the differential input pattern is adopted for circuit design, and grounding is removed. To prove the structure design, circuit component parameters, and insulation characteristics, Ansoft Maxwell software is used for the simulation. Moreover, the new probe was tested on a 10 kV high-voltage test platform for steady-state error and transient behavior. Experimental results ascertain that the root mean square values of measured voltage are precise and that the phase error is small. The D-dot voltage sensor not only meets the requirement of high accuracy but also exhibits satisfactory transient response. This sensor can meet the intelligence, miniaturization, and convenience requirements of the smart grid.

Controllable growth of GeSi nanostructures by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Ma, Yingjie; Zhou, Tong; Zhong, Zhenyang; Jiang, Zuimin

2018-06-01

We present an overview on the recent progress achieved on the controllable growth of diverse GeSi alloy nanostructures by molecular beam epitaxy. Prevailing theories for controlled growth of Ge nanostructures on patterned as well as inclined Si surfaces are outlined firstly, followed by reviews on the preferential growth of Ge nanoislands on patterned Si substrates, Ge nanowires and high density nanoislands grown on inclined Si surfaces, and the readily tunable Ge nanostructures on Si nanopillars. Ge nanostructures with controlled geometries, spatial distributions and densities, including two-dimensional ordered nanoislands, three-dimensional ordered quantum dot crystals, ordered nanorings, coupled quantum dot molecules, ordered nanowires and nanopillar alloys, are discussed in detail. A single Ge quantum dot-photonic crystal microcavity coupled optical emission device demonstration fabricated by using the preferentially grown Ge nanoisland technique is also introduced. Finally, we summarize the current technology status with a look at the future development trends and application challenges for controllable growth of Ge nanostructures. Project supports by the Natural Science Foundation of China (Nos. 61605232, 61674039) and the Open Research Project of State Key Laboratory of Surface Physics from Fudan University (Nos. KF2016_15s, KF2017_05).

Dense periodical patterns in photonic devices: Technology for fabrication and device performance

NASA Astrophysics Data System (ADS)

Chandramohan, Sabarish

For the fabrication, focused ion beam parameters are investigated to successfully fabricate dense periodical patterns, such as gratings, on hard transition metal nitride such as zirconium nitride. Transition metal nitrides such as titanium nitride and zirconium nitride have recently been studied as alternative materials for plasmonic devices because of its plasmonic resonance in the visible and near-infrared ranges, material strength, CMOS compatibility and optical properties resembling gold. Coupling of light on the surface of these materials using sub-micrometer gratings gives additional capabilities for wider applications. Here we report the fabrication of gratings on the surface of zirconium nitride using gallium ion 30keV dual beam focused ion beam. Scanning electron microscope imaging and atomic force microscope profiling is used to characterize the fabricated gratings. Appropriate values for FIB parameters such as ion beam current, magnification, dwell time and milling rate are found for successful milling of dense patterns on zirconium nitride. For the device performance, a real-time image-processing algorithm is developed to enhance the sensitivity of an optical miniature spectrometer. The novel approach in this design is the use of real-time image-processing algorithm to average the image intensity along the arc shaped images registered by the monochromatic inputs on the CMOS image sensor. This approach helps to collect light from the entire arc and thus enhances the sensitivity of the device. The algorithm is developed using SiTiO2 planar waveguide. The accuracy of the mapping from x-pixel number scale of the CMOS image sensor to the wavelength spectra of the miniature spectrometer is demonstrated by measuring the spectrum of a known LED source using a conventional desktop spectrometer and comparing it with the spectrum measured by the miniature spectrometer. The sensitivity of miniature spectrometer is demonstrated using two methods. In the first method, the input laser power is attenuated to 0.1 nW and the spectra is measured using the miniature spectrometer. Even at low input power of 0.1nW, the spectrum of monochromatic inputs is observed well above the noise level. Second method is by quantitative analysis, which measures the absorption of CdSeS/ZnS quantum dots drop casted between the gratings of Ta2O5 planar single-mode waveguide. The expected guided mode attenuation introduced by monolayer of quantum dots is found to be approximately 11 times above the highest noise level from the absorption measurements. Thus, the miniature spectrometer is capable of detecting the signal from the noise level even with the absorption introduced by monolayer of quantum dots.

Directed Block Copolymer Assembly versus Electron Beam Lithography for Bit-Patterned Media with Areal Density of 1 Terabit/inch(2) and Beyond.

PubMed

Yang, Xiaomin; Wan, Lei; Xiao, Shuaigang; Xu, Yuan; Weller, Dieter K

2009-07-28

The directed self-assembly of block copolymer (BCP) offers a new route to perfect nanolithographic patterning at sub-50 nm length scale with molecular scale precision. We have explored the feasibility of using the BCP approach versus the conventional electron beam (e-beam) lithography to create highly dense dot patterns for bit-patterned media (BPM) applications. Cylinder-forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA) directly self-assembled on a chemically prepatterned substrate. The nearly perfect hexagonal arrays of perpendicularly oriented cylindrical pores at a density of approximately 1 Terabit per square inch (Tb/in.(2)) are achieved over an arbitrarily large area. Considerable gains in the BCP process are observed relative to the conventional e-beam lithography in terms of the dot size variation, the placement accuracy, the pattern uniformity, and the exposure latitude. The maximum dimensional latitude in the cylinder-forming BCP patterns and the maximum skew angle that the BCP can tolerate have been investigated for the first time. The dimensional latitude restricts the formation of more than one lattice configuration in certain ranges. More defects in BCP patterns are observed when using low molecular weight BCP materials or on non-hexagonal prepatterns due to the dimensional latitude restriction. Finally, the limitations and challenges in the BCP approach that are associated with BPM applications will be briefly discussed.

Silver electrodeposition on nanostructured gold: from nanodots to nanoripples.

PubMed

Dos Santos Claro, P C; Fonticelli, M; Benítez, G; Azzaroni, O; Schilardi, P L; Luque, N B; Leiva, E; Salvarezza, R C

2006-07-28

Silver nanodots and nanoripples have been grown on nanocavity-patterned polycrystalline Au templates by controlled electrodeposition. The initial step is the growth of a first continuous Ag monolayer followed by preferential deposition at nanocavities. The Ag-coated nanocavities act as preferred sites for instantaneous nucleation and growth of the three-dimensional metallic centres. By controlling the amount of deposited Ag, dots of approximately 50 nm average size and approximately 4 nm average height can be grown with spatial and size distributions dictated by the template. The dots are in a metastable state. Further Ag deposition drives the dot surface structure to nanoripple formation. Results show that electrodeposition on nanopatterned electrodes can be used to prepare a high density of nanostructures with a narrow size distribution and spatial order.

Spin-sensitive interference due to Majorana state on the interface between normal and superconducting leads

NASA Astrophysics Data System (ADS)

Barański, J.; Kobiałka, A.; Domański, T.

2017-02-01

We investigate the subgap spectrum and transport properties of the quantum dot on the interface between the metallic and superconducting leads and additionally side-coupled to the edge of the topological superconducting (TS) chain, hosting the Majorana quasiparticle. Due to the chiral nature of the Majorana states only one spin component of the quantum dot electrons (say \\uparrow ) is directly affected, however the proximity induced on-dot pairing transmits its influence on the opposite spin as well. We investigate the unique interferometric patterns driven by the Majorana quasiparticle that are different for each spin component. We also address the spin-sensitive interplay with the Kondo effect manifested at the same zero-energy and we come to the conclusion that quantum interferometry can unambiguously identify the Majorana quasiparticle.

Effects of two-photon absorption on all optical logic operation based on quantum-dot semiconductor optical amplifiers

NASA Astrophysics Data System (ADS)

Zhang, Xiang; Dutta, Niloy K.

2018-01-01

We investigate all-optical logic operation in quantum-dot semiconductor optical amplifier (QD-SOA) based Mach-Zehnder interferometer considering the effects of two-photon absorption (TPA). TPA occurs during the propagation of sub-picosecond pulses in QD-SOA, which leads to a change in carrier recovery dynamics in quantum-dots. We utilize a rate equation model to take into account carrier refill through TPA and nonlinear dynamics including carrier heating and spectral hole burning in the QD-SOA. The simulation results show the TPA-induced pumping in the QD-SOA can reduce the pattern effect and increase the output quality of the all-optical logic operation. With TPA, this scheme is suitable for high-speed Boolean logic operation at 320 Gb/s.

78 FR 59422 - Delayed Applications

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-26

... Applications AGENCY: Office of Hazardous Materials Safety, Pipeline and Hazardous Materials Safety Administration (PHMSA), DOT. ACTION: List of applications delayed more than 180 days. SUMMARY: In accordance with... applications that have been in process for 180 days or more. The reason(s) for delay and the expected...

Epitaxial Zn quantum dots coherently grown on Si(1 1 1): growth mechanism, nonlinear optical and chemical states analyses

NASA Astrophysics Data System (ADS)

Huang, Bo-Jia; Kao, Li-Chi; Brahma, Sanjaya; Jeng, Yu-En; Chiu, Shang-Jui; Ku, Ching-Shun; Lo, Kuang-Yao

2017-05-01

Oxide- and defect-free metal/semiconductor interface is important to improve Ohmic contact for the suppression of electron scattering and the avoidance of an extrinsic surface state in estimating the barrier of the Schottky contact at the nanodevice interface. This study reports the growth mechanism of Zn quantum dots coherently grown on Si(1 1 1) and the physical phenomena of the crystalline, nonlinear optics, and the chemical states of Zn quantum dots. Epitaxial Zn quantum dots were coherently formed on a non-oxide Si(1 1 1) surface through the liquid- to solid-phase transformation as a result of pattern matching between the Zn(0 0 2) and Si(1 1 1) surfaces. The growth mechanism of constrained Zn quantum dots grown through strategic magnetron radio frequency sputtering is complex. Some factors, such as substrate temperature, hydrogen gas flow, and negative DC bias, influence the configuration of epitaxial Zn quantum dots. In particular, hydrogen gas plays an important role in reducing the ZnO+ and native oxide that is bombarded by accelerated ions, thereby enhancing the Zn ion surface diffusion. The reduction reaction can be inspected by distinguishing the chemical states of ZnO/Zn quantum dots from natural oxidation or the states of Zn 3d through the analysis of x-ray absorption near the edge structure spectrum. The complex growth mechanism can be systematically understood by analyzing a noncancelled anisotropic 3 m dipole from reflective second harmonic generation and inspecting the evolution between the Zn(0 0 2) and Zn(1 1 1) peaks of the collective ZnO/Zn quantum dots in synchrotron XRD.

Investigation of Change in the Computational Technique of the Sun’s Physical Ephemeris in The Astronomical Almanac

DTIC Science & Technology

2007-03-22

the new method. Initially, Fig. 1 might look a little odd since one might expect P to show a signature of the obliquity , that is, a 23.5◦ oscillation... ecliptic . To clarify the changes and to ensure that the program is working as expected, it is useful to set the Sun’s pole orthogonal to the ecliptic ...Figure 2 shows the same data as Fig. 1, but with this change. The dot-dash line in Fig. 2 shows the effect of obliquity , exactly as expected. The

Ge/Si(001) heterostructures with dense arrays of Ge quantum dots: morphology, defects, photo-emf spectra and terahertz conductivity

PubMed Central

2012-01-01

Issues of Ge hut cluster array formation and growth at low temperatures on the Ge/Si(001) wetting layer are discussed on the basis of explorations performed by high resolution STM and in-situ RHEED. Dynamics of the RHEED patterns in the process of Ge hut array formation is investigated at low and high temperatures of Ge deposition. Different dynamics of RHEED patterns during the deposition of Ge atoms in different growth modes is observed, which reflects the difference in adatom mobility and their ‘condensation’ fluxes from Ge 2D gas on the surface for different modes, which in turn control the nucleation rates and densities of Ge clusters. Data of HRTEM studies of multilayer Ge/Si heterostructures are presented with the focus on low-temperature formation of perfect films. Heteroepitaxial Si p–i–n-diodes with multilayer stacks of Ge/Si(001) quantum dot dense arrays built in intrinsic domains have been investigated and found to exhibit the photo-emf in a wide spectral range from 0.8 to 5 μm. An effect of wide-band irradiation by infrared light on the photo-emf spectra has been observed. Photo-emf in different spectral ranges has been found to be differently affected by the wide-band irradiation. A significant increase in photo-emf is observed in the fundamental absorption range under the wide-band irradiation. The observed phenomena are explained in terms of positive and neutral charge states of the quantum dot layers and the Coulomb potential of the quantum dot ensemble. A new design of quantum dot infrared photodetectors is proposed. By using a coherent source spectrometer, first measurements of terahertz dynamical conductivity (absorptivity) spectra of Ge/Si(001) heterostructures were performed at frequencies ranged from 0.3 to 1.2 THz in the temperature interval from 300 to 5 K. The effective dynamical conductivity of the heterostructures with Ge quantum dots has been discovered to be significantly higher than that of the structure with the same amount of bulk germanium (not organized in an array of quantum dots). The excess conductivity is not observed in the structures with the Ge coverage less than 8 Å. When a Ge/Si(001) sample is cooled down the conductivity of the heterostructure decreases. PMID:22824144

Ge/Si(001) heterostructures with dense arrays of Ge quantum dots: morphology, defects, photo-emf spectra and terahertz conductivity.

PubMed

Yuryev, Vladimir A; Arapkina, Larisa V; Storozhevykh, Mikhail S; Chapnin, Valery A; Chizh, Kirill V; Uvarov, Oleg V; Kalinushkin, Victor P; Zhukova, Elena S; Prokhorov, Anatoly S; Spektor, Igor E; Gorshunov, Boris P

2012-07-23

: Issues of Ge hut cluster array formation and growth at low temperatures on the Ge/Si(001) wetting layer are discussed on the basis of explorations performed by high resolution STM and in-situ RHEED. Dynamics of the RHEED patterns in the process of Ge hut array formation is investigated at low and high temperatures of Ge deposition. Different dynamics of RHEED patterns during the deposition of Ge atoms in different growth modes is observed, which reflects the difference in adatom mobility and their 'condensation' fluxes from Ge 2D gas on the surface for different modes, which in turn control the nucleation rates and densities of Ge clusters. Data of HRTEM studies of multilayer Ge/Si heterostructures are presented with the focus on low-temperature formation of perfect films.Heteroepitaxial Si p-i-n-diodes with multilayer stacks of Ge/Si(001) quantum dot dense arrays built in intrinsic domains have been investigated and found to exhibit the photo-emf in a wide spectral range from 0.8 to 5 μm. An effect of wide-band irradiation by infrared light on the photo-emf spectra has been observed. Photo-emf in different spectral ranges has been found to be differently affected by the wide-band irradiation. A significant increase in photo-emf is observed in the fundamental absorption range under the wide-band irradiation. The observed phenomena are explained in terms of positive and neutral charge states of the quantum dot layers and the Coulomb potential of the quantum dot ensemble. A new design of quantum dot infrared photodetectors is proposed.By using a coherent source spectrometer, first measurements of terahertz dynamical conductivity (absorptivity) spectra of Ge/Si(001) heterostructures were performed at frequencies ranged from 0.3 to 1.2 THz in the temperature interval from 300 to 5 K. The effective dynamical conductivity of the heterostructures with Ge quantum dots has been discovered to be significantly higher than that of the structure with the same amount of bulk germanium (not organized in an array of quantum dots). The excess conductivity is not observed in the structures with the Ge coverage less than 8 Å. When a Ge/Si(001) sample is cooled down the conductivity of the heterostructure decreases.

Gamma-Ray Pulsar Candidates for GLAST

NASA Technical Reports Server (NTRS)

Thompson, D. J.

2008-01-01

The Gamma-ray Large Area Space Telescope (GLAST) will be launched this year, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit greater than 100 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d2, where E-dot is the energy loss due to rotational spin-down, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d2) times efficiency, assumed proportional to l/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will rely on radio and X-ray timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

Gamma-Ray Pulsar Candidates for GLAST

NASA Technical Reports Server (NTRS)

Thompson, David J.; Smith, D. A.; Dumora, D.; Guillemot, L.; Parent, D.; Reposeur, T.; Grove, E.; Romani, R. W.; Thorsett, S. E.

2007-01-01

The Gamma-ray Large Area Space Telescope (GLAST) will be launched less than a year from now, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio Erequencies, are likely to emit greater than l00 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d^2, where E-dot is the energy loss due to rotational spindown, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d^2) times efficiency, assumed proportional to 1/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will need timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

Geometrical behavior of hydrogen bonding patterns in the alpha-dodecyl-omega-hydroxy-tris(oxyethylene)-water system monitored by near infrared spectroscopy.

PubMed

Ohno, Keiichi; Takao, Hiroshi; Katsumoto, Yukiteru

2006-03-01

Changes in the geometry of hydrogen bonding patterns in the alpha-dodecyl-omega-hydroxy-tris(oxyethylene) (C(12)E(3))-water system have been investigated by near infrared (NIR) spectroscopy. In the 5,300-4,600 cm(-1) region, the characteristic bands for C(12)E(3) and water can be separately investigated, since the combination bands of the OH stretching and its COH bending of alcohols are observed at 5,000-4,650 cm(-1), whereas the combination bands of the OH stretching and its HOH bending of water, at 5,300-5,000 cm(-1). The NIR result has revealed that the addition of water to C(12)E(3) promotes the formation of the OHcdots, three dots, centeredOHcdots, three dots, centeredO hydrogen bonds.

A new pattern associative memory model for image recognition based on Hebb rules and dot product

NASA Astrophysics Data System (ADS)

Gao, Mingyue; Deng, Limiao; Wang, Yanjiang

2018-04-01

A great number of associative memory models have been proposed to realize information storage and retrieval inspired by human brain in the last few years. However, there is still much room for improvement for those models. In this paper, we extend a binary pattern associative memory model to accomplish real-world image recognition. The learning process is based on the fundamental Hebb rules and the retrieval is implemented by a normalized dot product operation. Our proposed model can not only fulfill rapid memory storage and retrieval for visual information but also have the ability on incremental learning without destroying the previous learned information. Experimental results demonstrate that our model outperforms the existing Self-Organizing Incremental Neural Network (SOINN) and Back Propagation Neuron Network (BPNN) on recognition accuracy and time efficiency.

Tactile perception in blind Braille readers: a psychophysical study of acuity and hyperacuity using gratings and dot patterns.

PubMed

Grant, A C; Thiagarajah, M C; Sathian, K

2000-02-01

It is not clear whether the blind are generally superior to the sighted on measures of tactile sensitivity or whether they excel only on certain tests owing to the specifics of their tactile experience. We compared the discrimination performance of blind Braille readers and age-matched sighted subjects on three tactile tasks using precisely specified stimuli. Initially, the blind significantly outperformed the sighted at a hyperacuity task using Braille-like dot patterns, although, with practice, both groups performed equally well. On two other tasks, hyperacute discrimination of gratings that differed in ridge width and spatial-acuity-dependent discrimination of grating orientation, the performance of the blind did not differ significantly from that of sighted subjects. These results probably reflect the specificity of perceptual learning due to Braille-reading experience.

Conflicting accountabilities: Doctor's dilemma in TB control in rural India.

PubMed

Fochsen, Grethe; Deshpande, Kirti; Ringsberg, Karin C; Thorson, Anna

2009-02-01

The aim of this study was to analyse how the implementation strategy of direct observed treatment short course (DOTS) has shaped and influenced patient-provider encounters in a district tuberculosis centre (DTC) in a rural district of India. Qualitative methods, combining observations and interviews, were carried out in a DTC focusing on the medical encounters between a TB doctor and his patients. The findings showed that the TB doctor seemed to be working with a dilemma, defined as conflicting accountabilities, in the medical encounters. In an organization perceived as inefficient and resource-constrained, the doctor struggled to find a balance between meeting the obligations of the DOTS programme and meeting the needs and expectations of the patients. Strategies to deal with these conflicting accountabilities were identified as limiting patients' involvement, struggling to maintain authority, and transferring responsibility. Professional involvement and patient participation were seen as part of a linked process in this study, and the importance of empowering doctors and health care workers who are implementing DOTS is emphasized. The development of DOTS guidelines needs to be based on the actual process of health care delivery, and staff empowering efforts should also include strengthening of public health care infrastructure.

78 FR 28276 - Operating Limitations at John F. Kennedy International Airport

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-14

... Limitations at John F. Kennedy International Airport AGENCY: Federal Aviation Administration (FAA), DOT... duration of the Order. The reasons for issuing the Order have not changed appreciably since it was implemented. Without the operational limitations imposed by this Order, the FAA expects severe congestion...

78 FR 28280 - Operating Limitations at Newark Liberty International Airport

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-14

... Limitations at Newark Liberty International Airport AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... duration of the Order. The reasons for issuing the Order have not changed appreciably since it was implemented. Without the operational limitations imposed by this Order, the FAA expects severe congestion...

Development of a Quantum Dot, 0.6 eV InGaAs Thermophotovoltaic (TPV) Converter

NASA Technical Reports Server (NTRS)

Forbes, David; Sinharoy, Samar; Raffalle, Ryne; Weizer, Victor; Homann, Natalie; Valko, Thomas; Bartos,Nichole; Scheiman, David; Bailey, Sheila

2007-01-01

Thermophotovoltaic (TPV) power conversion has to date demonstrated conversion efficiencies exceeding 20% when coupled to a heat source. Current III-V semiconductor TPV technology makes use of planar devices with bandgaps tailored to the heat source. The efficiency can be improved further by increasing the collection efficiency through the incorporation of InAs quantum dots. The use of these dots can provide sub-gap absorption and thus improve the cell short circuit current without the normal increase in dark current associated with lowering the bandgap. We have developed self-assembled InAs quantum dots using the Stranski-Krastanov growth mode on 0.74 eV In0.53GaAs lattice-matched to InP and also on lattice-mismatched 0.6 eV In0.69GaAs grown on InP through the use of a compositionally graded InPAsx buffer structure, by metalorganic vapor phase epitaxy (MOVPE). Atomic force microscopy (AFM) measurements showed that the most reproducible dot pattern was obtained with 5 monolayers of InAs grown at 450 C. The lattice mismatch between InAs and In0.69GaAs is only 2.1%, compared to 3.2% between InAs and In0.53GaAs. The smaller mismatch results in lower strain, making dot formation somewhat more complicated, resulting in quantum dashes, rather than well defined quantum dots in the lattice-mismatched case. We have fabricated 0.6 eV InGaAs planer TPV cells with and without the quantum dashes

Measuring tides and binary parameters from gravitational wave data and eclipsing timings of detached white dwarf binaries

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

Shah, Sweta; Nelemans, Gijs, E-mail: s.shah@astro.ru.nl

The discovery of the most compact detached white dwarf (WD) binary SDSS J065133.33+284423.3 has been discussed in terms of probing the tidal effects in WDs. This system is also a verification source for the space-based gravitational wave (GW) detector, eLISA, or the evolved Laser Interferometer Space Antenna, which will observe short-period compact Galactic binaries with P {sub orb} ≲ 5 hr. We address the prospects of performing tidal studies using eLISA binaries by showing the fractional uncertainties in the orbital decay rate, f-dot , and the rate of that decay, f{sup ¨} expected from both the GW and electromagnetic (EM)more » data for some of the high-f binaries. We find that f-dot and f{sup ¨} can be measured using GW data only for the most massive WD binaries observed at high frequencies. From timing the eclipses for ∼10 yr, we find that f-dot can be known to ∼0.1% for J0651. We find that from GW data alone, measuring the effects of tides in binaries is (almost) impossible. We also investigate the improvement in the knowledge of the binary parameters by combining the GW amplitude and inclination with EM data with and without f-dot . In our previous work, we found that EM data on distance constrained the 2σ uncertainty in chirp mass to 15%-25% whereas adding f-dot reduces it to 0.11%. EM data on f-dot also constrain the 2σ uncertainty in distance to 35%-19%. EM data on primary mass constrain the secondary mass m {sub 2} to factors of two to ∼40% whereas adding f-dot reduces this to 25%. Finally, using single-line spectroscopic data constrains 2σ uncertainties in both the m {sub 2}, d to factors of two to ∼40%. Adding EM data on f-dot reduces these 2σ uncertainties to ≤25% and 6%-19%, respectively. Thus we find that EM measurements of f-dot and radial velocity are valuable in constraining eLISA binary parameters.« less

Coffee Shops, Classrooms and Conversations: public engagement and outreach in a large interdisciplinary research Hub

NASA Astrophysics Data System (ADS)

Holden, Jennifer A.

2014-05-01

Public engagement and outreach activities are increasingly using specialist staff for co-ordination, training and support for researchers, they are also becoming expected for large investments. Here, the experience of public engagement and outreach a large, interdisciplinary Research Hub is described. dot.rural, based at the University of Aberdeen UK, is a £11.8 million Research Councils UK Rural Digital Economy Hub, funded as part of the RCUK Digital Economy Theme (2009-2015). Digital Economy research aims to realise the transformational impact of digital technologies on aspects of the environment, community life, cultural experiences, future society, and the economy. The dot.rural Hub involves 92 researchers from 12 different disciplines, including Geography, Hydrology and Ecology. Public Engagement and Outreach is embedded in the dot.rural Digital Economy Hub via an Outreach Officer. Alongside this position, public engagement and outreach activities are compulsory part of PhD student contracts. Public Engagement and Outreach activities at the dot.rural Hub involve individuals and groups in both formal and informal settings organised by dot.rural and other organisations. Activities in the realms of Education, Public Engagement, Traditional and Social Media are determined by a set of Underlying Principles designed for the Hub by the Outreach Officer. The underlying Engagement and Outreach principles match funding agency requirements and expectations alongside researcher demands and the user-led nature of Digital Economy Research. All activities include researchers alongside the Outreach Officer are research informed and embedded into specific projects that form the Hub. Successful public engagement activities have included participation in Café Scientifique series, workshops in primary and secondary schools, and online activities such as I'm a Scientist Get Me Out of Here. From how to engage 8 year olds with making hydrographs more understandable to members of the public to blogging birds and engaging with remote, rural communities to Spiegeltents. This presentation will share successful public engagement and outreach events alongside some less successful experiences and lessons learnt along the way.

Direct-writing lithography using laser diode beam focused with single elliptical microlens

NASA Astrophysics Data System (ADS)

Hasan, Md. Nazmul; Haque, Muttahid-Ull; Trisno, Jonathan; Lee, Yung-Chun

2015-10-01

A lithography method is proposed for arbitrary patterning using an elliptically diverging laser diode beam focused with a single planoconvex elliptical microlens. Simulations are performed to model the propagation properties of the laser beam and to design the elliptical microlens, which has two different profiles in the x- and y-axis directions. The microlens is fabricated using an excimer laser dragging method and is then attached to the laser diode using double-sided optically cleared adhesive (OCA) tape. Notably, the use of OCA tape removes the need for a complicated alignment procedure and thus significantly reduces the assembly cost. The minimum focused spot of the laser diode beam is investigated by performing single-shot exposure tests on a photoresist (PR) layer. Finally, the practical feasibility of this lithography technique to generate an arbitrary pattern is demonstrated by dotted and continuous features through thin chromium layer deposition on PR and a metal lift-off process. The results show that the minimum feature size for the dotted patterns is around 6.23 μm, while the minimum linewidths for continuous patterns is 6.44 μm. In other words, the proposed focusing technique has significant potential for writing any arbitrary high-resolution pattern for applications like printed circuit board fabrication.

Probability, not linear summation, mediates the detection of concentric orientation-defined textures.

PubMed

Schmidtmann, Gunnar; Jennings, Ben J; Bell, Jason; Kingdom, Frederick A A

2015-01-01

Previous studies investigating signal integration in circular Glass patterns have concluded that the information in these patterns is linearly summed across the entire display for detection. Here we test whether an alternative form of summation, probability summation (PS), modeled under the assumptions of Signal Detection Theory (SDT), can be rejected as a model of Glass pattern detection. PS under SDT alone predicts that the exponent β of the Quick- (or Weibull-) fitted psychometric function should decrease with increasing signal area. We measured spatial integration in circular, radial, spiral, and parallel Glass patterns, as well as comparable patterns composed of Gabors instead of dot pairs. We measured the signal-to-noise ratio required for detection as a function of the size of the area containing signal, with the remaining area containing dot-pair or Gabor-orientation noise. Contrary to some previous studies, we found that the strength of summation never reached values close to linear summation for any stimuli. More importantly, the exponent β systematically decreased with signal area, as predicted by PS under SDT. We applied a model for PS under SDT and found that it gave a good account of the data. We conclude that probability summation is the most likely basis for the detection of circular, radial, spiral, and parallel orientation-defined textures.

Pattern transfer from nanoparticle arrays

NASA Astrophysics Data System (ADS)

Hogg, Charles R., III

This project contributes to the long-term extensibility of bit-patterned media (BPM), by removing obstacles to using a new and smaller class of self-assembling materials: surfactant-coated nanoparticles. Self-assembly rapidly produces regular patterns of small features over large areas. If these patterns can be used as templates for magnetic bits, the resulting media would have both high capacity and high bit density. The data storage industry has identified block copolymers (BCP) as the self-assembling technology for the first generation of BPM. Arrays of surfactant-coated nanoparticles have long shown higher feature densities than BCP, but their patterns could not previously be transferred into underlying substrates. I identify one key obstacle that has prevented this pattern transfer: the particles undergo a disordering transition during etching which I have called "cracking". I compare several approaches to measuring the degree of cracking, and I develop two novel techniques for preventing it and allowing pattern transfer. I demonstrate two different kinds of pattern transfer: positive (dots) and negative (antidots). To make dots, I etch the substrate between the particles with a directional CF4-based reactive ion etch (RIE). I find the ultrasmall gaps (just 2 nm) cause a tremendous slowdown in the etch rate, by a factor of 10 or more---an observation of fundamental significance for any pattern transfer at ultrahigh bit densities. Antidots are made by depositing material in the interstices, then removing the particles to leave behind a contiguous inorganic lattice. This lattice can itself be used as an etch mask for CF4-based RIE, in order to increase the height contrast. The antidot process promises great generality in choice of materials, both for the antidot lattice and the particles themselves; here, I present lattices of Al and Cr, ternplated from arrays of 13.7 nm-diameter Fe3O4 or 30 nm-diameter MnO nanoparticles. The fidelity of transfer is also noticeably better for antidots than for dots, making antidots the more promising technique for industrial applications. The smallest period for which I have shown pattern transfer (15.7 nm) is comparable to (but slightly smaller than) the smallest period currently shown for pattern transfer from block copolymers (17 nm); hence, my results compare favorably with the state of the art. Ultimately, by demonstrating that surfactant-coated nanoparticles can be used as pattern masks, this work increases their viability as an option to continue the exponential growth of bit density in magnetic storage media.

Cydonia Craters

NASA Image and Video Library

2003-03-22

In this image from NASA Mars Odyssey, eroded mesas and secondary craters dot the landscape in an area of Cydonia Mensae. The single oval-shaped crater displays a butterfly ejecta pattern, indicating that the crater formed from a low-angle impact.

Study of interfaces in an Axisymmetric Supersonic Jet using Background Oriented Schlieren (BOS)

NASA Astrophysics Data System (ADS)

Echeverría, Carlos; Porta, David; Aguayo, Alejandro; Cardoso, Hiroki; Stern, Catalina

2014-11-01

We have used several techniques to study a small axisymmetric supersonic jet: Rayleigh scattering, Schlieren Toepler and PIV. Each technique gives different kind of information. In this paper, a BOS set-up is used to study the structure of the shock pattern. A shadowgraph of a dot matrix is obtained with and without a flow. The displacement field of the dots is related to changes in the index of refraction, which can be related, through the Gladstone-Dale equation, to changes in density. Previous results with this technique were not conclusive because of the relative size of the dots compared to the diameter of the nozzle. Measurements have been taken for three different exit speeds. We acknowledge support from UNAM through DGAPA PAPIIT IN117712 and the Graduate Program in Mechanical Engineering.

The Effects of Anchor Groups on (1) TiO2-Catalyzed Photooxidation and (2) Linker-Assisted Assembly on TiO2

NASA Astrophysics Data System (ADS)

Anderson, Ian Mark

Quantum dot-sensitized solar cells (QDSSCs) are a popular target for research due to their potential for highly efficient, easily tuned absorption. Typically, light is absorbed by quantum dots attached to a semiconductor substrate, such as TiO2, via bifunctional linker molecules. This research aims to create a patterned monolayer of linker molecules on a TiO2 film, which would in turn allow the attachment of a patterned layer of quantum dots. One method for the creation of a patterned monolayer is the functionalization of a TiO2 film with a linker molecule, followed by illumination with a laser at 355 nm. This initiates a TiO 2-catalyzed oxidation reaction, causing loss of surface coverage. A second linker molecule can then be adsorbed onto the TiO2 surface in the illuminated area. Towards that end, the behaviors of carboxylic and phosphonic acids adsorbed on TiO2 have been studied. TiO2 films were functionalized by immersion in solutions a single adsorbate and surface coverage was determined by IR spectroscopy. It is shown that phosphonic acids attain higher surface coverage than carboxylic acids, and will displace them from TiO2 when in a polar solvent. Alkyl chain lengths, which can influence stabilities of monolayers, are shown not to have an effect on this relationship. Equilibrium binding data for the adsorption of n-hexadecanoic acid to TiO2 from a THF solution are presented. It is shown that solvent polarity can affect monolayer stability; carboxylates and phosphonates undergo more desorption into polar solvents than nonpolar. Through illumination, it was possible to remove nearly all adsorbed linkers from TiO2. However, the illuminated areas were found not to be receptive to attachment by a second adsorbate. A possible reason for this behavior is presented. I also report on the synthesis and characterization of a straight-chain, thiol-terminated phosphonic acid. Initial experiments involving monolayer formation and quantum dot attachment are presented. Finally, it was found that quantum dots attach in high amounts to linker-functionalized TiO2 when suspended in pyridine. This increased surface attachment was present even when the linker molecule used lacked a functional group which would bind to the CdSe surface.

Dermoscopic Findings of Jellyfish Stings Caused by Pelagia noctiluca.

PubMed

Del Pozo, L J; Knöpfel, N; Martín-Santiago, A; Escudero-Góngora, M M; Saus, C; Izquierdo-Herce, N; Bauzà-Alonso, A

2016-01-01

Jellyfish are free-living members of the phylum Cnidaria who share a specialized stinging cell, the cnidocyte. Pelagia noctiluca is the most frequent and toxic jellyfish species found in the Balearic beaches and cnidocytes are arranged in pigmented clusters called "warts". Dermoscopy continues to expand its use much beyond the pigmentary lesions and to date, there is no data regarding dermoscopic findings in jellyfish stings. The aim of the present work was to study the dermoscopic findings of jellyfish stings in the island of Mallorca. We retrospectively reviewed the clinical and dermoscopic images of 25 episodes of jellyfish stings caused by P. noctiluca that occurred between 2009 and 2015. Overall, the following dermoscopic features were found: brown dots (84%), pinkish hue (56%), pinpoint brown crusts (44%), scale-crust (40%), brown "Chinese characters pattern" (32%), "serpentine" ulceration (28%), linear purpura (20%), and whitish-yellow crusts (15%). Vessels were mainly dotted (36%) or reticular (16%). Scale-crust, serpentine ulceration and pinkish hue were significantly more frequent in lesions older than 2 days. Our study identifies 4 dermoscopic features that may represent the contact with P. noctiluca cnidocytes: brown dots, brown "Chinese characters pattern", pinpoint brown crusts and whitish-yellow crusts. A peculiar finding of "serpentine ulceration" with brown dots would be very suggestive of P. noctiluca sting. We believe dermoscopy is a valuable tool in the diagnosis of jellyfish stings when a clear history of contact is lacking. Further studies are needed to validate our findings in other jellyfish species. Copyright © 2016 AEDV. Published by Elsevier España, S.L.U. All rights reserved.

Revised text for TxDOT manual procedures for establishing speed zones, chapter 5, section 2.

DOT National Transportation Integrated Search

2010-02-01

Warning signs are intended to improve curve safety by alerting the driver to a change in : geometry that may not be apparent or expected. These signs notify drivers of the change : through the use of one or more of the curve warning signs identified ...

Ordering and bandgap reduction in InAs{sub 1{minus}x}Sb{sub x} alloys

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

Follstaedt, D.M.; Biefeld, R.M.; Kurtz, S.R.

1995-02-01

InAs{sub 1{minus}x}Sb{sub x} alloys grown by MBE and MOCVD are found to have reduced emission energies due to CuPt-type order, even for Sb concentrations as low as x = 0.07 ({Delta}E = 25--65 meV). Cross-section TEM examination of such alloys shows the two {l_brace}111{r_brace}{sub B} variants are separated into regions 1--2 {mu}m across with platelet domains 10--40 nm thick on habit planes tilted {approximately}30{center_dot} from the (001) growth surface. Nomarski optical images show a cross-hatched surface pattern expected for lattice-mismatched layers. The local tilt of the surface correlates with the dominant variant in each region. InAs{sub 1{minus}x}Sb{sub x}/In{sub 1{minus}y}Ga{sub y}Asmore » strained-layer superlattices with low Sb content and flat surfaces also show CuPt ordering.« less

“String of pearls pattern”: report of three cases of non clear-cell acanthoma*

PubMed Central

Espinosa, Ana Elena Domínguez; Akay, Bengu Nisa; González-Ramírez, Roger Adrian

2017-01-01

The coiled and dotted vessels in a serpiginous arrangement or “string of pearls” is considered a classical vascular pattern associated with clear cell acanthoma. We present three cases of epidermal tumors different from clear cell acanthoma that have the same “string of pearls” vascular pattern. Even though most authors keep considering the “string of pearls” vascular pattern an almost pathognomonic sign of clear-cell acanthoma, the cases presented here suggest that some other epidermal tumors can also show this pattern. PMID:29267474

Magnetization reversal in magnetic dot arrays: Nearest-neighbor interactions and global configurational anisotropy

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

Van de Wiele, Ben; Fin, Samuele; Pancaldi, Matteo

2016-05-28

Various proposals for future magnetic memories, data processing devices, and sensors rely on a precise control of the magnetization ground state and magnetization reversal process in periodically patterned media. In finite dot arrays, such control is hampered by the magnetostatic interactions between the nanomagnets, leading to the non-uniform magnetization state distributions throughout the sample while reversing. In this paper, we evidence how during reversal typical geometric arrangements of dots in an identical magnetization state appear that originate in the dominance of either Global Configurational Anisotropy or Nearest-Neighbor Magnetostatic interactions, which depends on the fields at which the magnetization reversal setsmore » in. Based on our findings, we propose design rules to obtain the uniform magnetization state distributions throughout the array, and also suggest future research directions to achieve non-uniform state distributions of interest, e.g., when aiming at guiding spin wave edge-modes through dot arrays. Our insights are based on the Magneto-Optical Kerr Effect and Magnetic Force Microscopy measurements as well as the extensive micromagnetic simulations.« less

Auditory Discrimination of Lexical Stress Patterns in Hearing-Impaired Infants with Cochlear Implants Compared with Normal Hearing: Influence of Acoustic Cues and Listening Experience to the Ambient Language.

PubMed

Segal, Osnat; Houston, Derek; Kishon-Rabin, Liat

2016-01-01

To assess discrimination of lexical stress pattern in infants with cochlear implant (CI) compared with infants with normal hearing (NH). While criteria for cochlear implantation have expanded to infants as young as 6 months, little is known regarding infants' processing of suprasegmental-prosodic cues which are known to be important for the first stages of language acquisition. Lexical stress is an example of such a cue, which, in hearing infants, has been shown to assist in segmenting words from fluent speech and in distinguishing between words that differ only the stress pattern. To date, however, there are no data on the ability of infants with CIs to perceive lexical stress. Such information will provide insight to the speech characteristics that are available to these infants in their first steps of language acquisition. This is of particular interest given the known limitations that the CI device has in transmitting speech information that is mediated by changes in fundamental frequency. Two groups of infants participated in this study. The first group included 20 profoundly hearing-impaired infants with CI, 12 to 33 months old, implanted under the age of 2.5 years (median age of implantation = 14.5 months), with 1 to 6 months of CI use (mean = 2.7 months) and no known additional problems. The second group of infants included 48 NH infants, 11 to 14 months old with normal development and no known risk factors for developmental delays. Infants were tested on their ability to discriminate between nonsense words that differed on their stress pattern only (/dóti/ versus /dotí/ and /dotí/ versus /dóti/) using the visual habituation procedure. The measure for discrimination was the change in looking time between the last habituation trial (e.g., /dóti/) and the novel trial (e.g., /dotí/). (1) Infants with CI showed discrimination between lexical stress pattern with only limited auditory experience with their implant device, (2) discrimination of stress patterns in infants with CI was reduced compared with that of infants with NH, (3) both groups showed directional asymmetry in discrimination, that is, increased discrimination from the uncommon to the common stress pattern in Hebrew (/dóti/ versus /dotí/) compared with the reversed condition. The CI device transmitted sufficient acoustic information (amplitude, duration, and fundamental frequency) to allow discrimination between stress patterns in young hearing-impaired infants with CI. The present pattern of results is in support of a discrimination model in which both auditory capabilities and "top-down" interactions are involved. That is, the CI infants detected changes between stressed and unstressed syllables after which they developed a bias for the more common weak-strong stress pattern in Hebrew. The latter suggests that infants with CI were able to extract the statistical distribution of stress patterns by listening to the ambient language even after limited auditory experience with the CI device. To conclude, in relation to processing of lexical stress patterns, infants with CI followed similar developmental milestones as hearing infants thus establishing important prerequisites for early language acquisition.

Understanding chemically processed solar cells based on quantum dots

NASA Astrophysics Data System (ADS)

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-12-01

Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum.

STS-52 CANEX-2 Canadian Target Assembly (CTA) held by RMS over OV-102's PLB

NASA Image and Video Library

1992-11-01

STS052-71-057 (22 Oct-1 Nov 1992) --- This 70mm frame, photographed with a handheld Hasselblad camera aimed through Columbia's aft flight deck windows, captures the operation of the Space Vision System (SVS) experiment above the cargo bay. Target dots have been placed on the Canadian Target Assembly (CTA), a small satellite, in the grasp of the Canadian-built remote manipulator system (RMS) arm. SVS utilized a Shuttle TV camera to monitor the dots strategically arranged on the satellite, to be tracked. As the satellite moved via the arm, the SVS computer measured the changing position of the dots and provided real-time television display of the location and orientation of the CTA. This type of displayed information is expected to help an operator guide the RMS or the Mobile Servicing System (MSS) of the future when berthing or deploying satellites. Also visible in the frame is the U.S. Microgravity Payload (USMP-01).

Understanding chemically processed solar cells based on quantum dots.

PubMed

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-01-01

Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO 2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum.

A combined reconstruction-classification method for diffuse optical tomography.

PubMed

Hiltunen, P; Prince, S J D; Arridge, S

2009-11-07

We present a combined classification and reconstruction algorithm for diffuse optical tomography (DOT). DOT is a nonlinear ill-posed inverse problem. Therefore, some regularization is needed. We present a mixture of Gaussians prior, which regularizes the DOT reconstruction step. During each iteration, the parameters of a mixture model are estimated. These associate each reconstructed pixel with one of several classes based on the current estimate of the optical parameters. This classification is exploited to form a new prior distribution to regularize the reconstruction step and update the optical parameters. The algorithm can be described as an iteration between an optimization scheme with zeroth-order variable mean and variance Tikhonov regularization and an expectation-maximization scheme for estimation of the model parameters. We describe the algorithm in a general Bayesian framework. Results from simulated test cases and phantom measurements show that the algorithm enhances the contrast of the reconstructed images with good spatial accuracy. The probabilistic classifications of each image contain only a few misclassified pixels.

Summary of the GIS Implementation Plan for the TxDOT PMIS

DOT National Transportation Integrated Search

2001-08-01

Successful GIS implementation involves not only the information technologies themselves, but also the personnel and skills needed. The organization and institutional arrangements that govern the patterns of management and information flow are also cr...

Landau-Zener-Stückelberg-Majorana Interferometry of a Single Hole

NASA Astrophysics Data System (ADS)

Bogan, Alex; Studenikin, Sergei; Korkusinski, Marek; Gaudreau, Louis; Zawadzki, Piotr; Sachrajda, Andy S.; Tracy, Lisa; Reno, John; Hargett, Terry

2018-05-01

We perform Landau-Zener-Stückelberg-Majorana (LZSM) spectroscopy on a system with strong spin-orbit interaction (SOI), realized as a single hole confined in a gated double quantum dot. Analogous to electron systems, at a magnetic field B =0 and high modulation frequencies, we observe photon-assisted tunneling between dots, which smoothly evolves into the typical LZSM funnel-shaped interference pattern as the frequency is decreased. In contrast to electrons, the SOI enables an additional, efficient spin-flip interdot tunneling channel, introducing a distinct interference pattern at finite B . Magnetotransport spectra at low-frequency LZSM driving show the two channels to be equally coherent. High-frequency LZSM driving reveals complex photon-assisted tunneling pathways, both spin conserving and spin flip, which form closed loops at critical magnetic fields. In one such loop, an arbitrary hole spin state is inverted, opening the way toward its all-electrical manipulation.

Food-related attentional bias. Word versus pictorial stimuli and the importance of stimuli calorific value in the dot probe task.

PubMed

Freijy, Tanya; Mullan, Barbara; Sharpe, Louise

2014-12-01

The primary aim of this study was to extend previous research on food-related attentional biases by examining biases towards pictorial versus word stimuli, and foods of high versus low calorific value. It was expected that participants would demonstrate greater biases to pictures over words, and to high-calorie over low-calorie foods. A secondary aim was to examine associations between BMI, dietary restraint, external eating and attentional biases. It was expected that high scores on these individual difference variables would be associated with a bias towards high-calorie stimuli. Undergraduates (N = 99) completed a dot probe task including matched word and pictorial food stimuli in a controlled setting. Questionnaires assessing eating behaviour were administered, and height and weight were measured. Contrary to predictions, there were no main effects for stimuli type (pictures vs words) or calorific value (high vs low). There was, however, a significant interaction effect suggesting a bias towards high-calorie pictures, but away from high-calorie words; and a bias towards low-calorie words, but away from low-calorie pictures. No associations between attentional bias and any of the individual difference variables were found. The presence of a stimulus type by calorific value interaction demonstrates the importance of stimuli type in the dot probe task, and may help to explain inconsistencies in prior research. Further research is needed to clarify associations between attentional bias and BMI, restraint, and external eating. Copyright © 2014 Elsevier Ltd. All rights reserved.

Design, Experiments and Simulation of Voltage Transformers on the Basis of a Differential Input D-dot Sensor

PubMed Central

Wang, Jingang; Gao, Can; Yang, Jie

2014-01-01

Currently available traditional electromagnetic voltage sensors fail to meet the measurement requirements of the smart grid, because of low accuracy in the static and dynamic ranges and the occurrence of ferromagnetic resonance attributed to overvoltage and output short circuit. This work develops a new non-contact high-bandwidth voltage measurement system for power equipment. This system aims at the miniaturization and non-contact measurement of the smart grid. After traditional D-dot voltage probe analysis, an improved method is proposed. For the sensor to work in a self-integrating pattern, the differential input pattern is adopted for circuit design, and grounding is removed. To prove the structure design, circuit component parameters, and insulation characteristics, Ansoft Maxwell software is used for the simulation. Moreover, the new probe was tested on a 10 kV high-voltage test platform for steady-state error and transient behavior. Experimental results ascertain that the root mean square values of measured voltage are precise and that the phase error is small. The D-dot voltage sensor not only meets the requirement of high accuracy but also exhibits satisfactory transient response. This sensor can meet the intelligence, miniaturization, and convenience requirements of the smart grid. PMID:25036333

Structured illumination diffuse optical tomography for noninvasive functional neuroimaging in mice.

PubMed

Reisman, Matthew D; Markow, Zachary E; Bauer, Adam Q; Culver, Joseph P

2017-04-01

Optical intrinsic signal (OIS) imaging has been a powerful tool for capturing functional brain hemodynamics in rodents. Recent wide field-of-view implementations of OIS have provided efficient maps of functional connectivity from spontaneous brain activity in mice. However, OIS requires scalp retraction and is limited to superficial cortical tissues. Diffuse optical tomography (DOT) techniques provide noninvasive imaging, but previous DOT systems for rodent neuroimaging have been limited either by sparse spatial sampling or by slow speed. Here, we develop a DOT system with asymmetric source-detector sampling that combines the high-density spatial sampling (0.4 mm) detection of a scientific complementary metal-oxide-semiconductor camera with the rapid (2 Hz) imaging of a few ([Formula: see text]) structured illumination (SI) patterns. Analysis techniques are developed to take advantage of the system's flexibility and optimize trade-offs among spatial sampling, imaging speed, and signal-to-noise ratio. An effective source-detector separation for the SI patterns was developed and compared with light intensity for a quantitative assessment of data quality. The light fall-off versus effective distance was also used for in situ empirical optimization of our light model. We demonstrated the feasibility of this technique by noninvasively mapping the functional response in the somatosensory cortex of the mouse following electrical stimulation of the forepaw.

Sharpening of carbon nanocone tips during plasma-enhanced chemical vapor growth

NASA Astrophysics Data System (ADS)

Merkulov, Vladimir I.; Melechko, Anatoli V.; Guillorn, Michael A.; Lowndes, Douglas H.; Simpson, Michael L.

2001-12-01

In situ tip sharpening of vertically aligned carbon nanocones (VACNCs) was demonstrated. VACNCs were synthesized on patterned catalyst dots of 100 nm in diameter using dc plasma-enhanced chemical vapor deposition. The VACNC tip diameter was found to decrease with growth time. This enables synthesis of ultra-sharp VACNCs even for relatively large catalyst dot sizes, which is quite important for practical applications. We also find that for a given set of growth parameters the diameter of the initially formed catalyst nanoparticle determines the maximum length of the growing VACNC. The mechanism of VACNC growth and sharpening is discussed.

A 5-mC Dot Blot Assay Quantifying the DNA Methylation Level of Chondrocyte Dedifferentiation In Vitro.

PubMed

Jia, Zhaofeng; Liang, Yujie; Ma, Bin; Xu, Xiao; Xiong, Jianyi; Duan, Li; Wang, Daping

2017-05-17

The dedifferentiation of hyaline chondrocytes into fibroblastic chondrocytes often accompanies monolayer expansion of chondrocytes in vitro. The global DNA methylation level of chondrocytes is considered to be a suitable biomarker for the loss of the chondrocyte phenotype. However, results based on different experimental methods can be inconsistent. Therefore, it is important to establish a precise, simple, and rapid method to quantify global DNA methylation levels during chondrocyte dedifferentiation. Current genome-wide methylation analysis techniques largely rely on bisulfite genomic sequencing. Due to DNA degradation during bisulfite conversion, these methods typically require a large sample volume. Other methods used to quantify global DNA methylation levels include high-performance liquid chromatography (HPLC). However, HPLC requires complete digestion of genomic DNA. Additionally, the prohibitively high cost of HPLC instruments limits HPLC's wider application. In this study, genomic DNA (gDNA) was extracted from human chondrocytes cultured with varying number of passages. The gDNA methylation level was detected using a methylation-specific dot blot assay. In this dot blot approach, a gDNA mixture containing the methylated DNA to be detected was spotted directly onto an N + membrane as a dot inside a previously drawn circular template pattern. Compared with other gel electrophoresis-based blotting approaches and other complex blotting procedures, the dot blot method saves significant time. In addition, dot blots can detect overall DNA methylation level using a commercially available 5-mC antibody. We found that the DNA methylation level differed between the monolayer subcultures, and therefore could play a key role in chondrocyte dedifferentiation. The 5-mC dot blot is a reliable, simple, and rapid method to detect the general DNA methylation level to evaluate chondrocyte phenotype.

Theory of Charged Quantum Dot Molecules

NASA Astrophysics Data System (ADS)

Ponomarev, I. V.; Scheibner, M.; Stinaff, E. A.; Bracker, A. S.; Doty, M. F.; Ware, M. E.; Gammon, D.; Reinecke, T. L.; Korenev, V. L.

2006-03-01

Recent optical spectroscopy of excitonic molecules in coupled quantum dots (CQDs) tuned by electric field reveal a richer diversity in spectral line patterns than in their single quantum dot counterparts. We developed a theoretical model that allows us to classify energies and intensities of various PL transitions. In this approach the electric field induced resonance tunneling of the electron and hole states occurs at different biases due to the inherent asymmetry of CQDs. The truncated many-body basis configurations for each molecule are constructed from antisymmetrized products of single-particle states, where the electron occupies only one ground state level in single QD and the hole can occupy two lowest levels of CQD system. The Coulomb interaction between particles is treated with perturbation theory. As a result the observed PL spectral lines can be described with a small number of parameters. The theoretical predictions account well for recent experiments.

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

Wang, K; Zhang, B; Eslami, S

Purpose: We present a newly developed on-board optical tomography system for SARRP. Innovative features include the compact design and fast acquisition optical method to perform 3D soft tissue radiation guidance. Because of the on-board feature and the combination of the CBCT, diffusive optical tomography (DOT), bioluminescence and fluorescence tomography (BLT and FT), this integrated system is expected to provide more accurate soft tissue guidance than an off-line system as well as highly sensitive functional imaging in preclinical research. Methods: Images are acquired in the order of CBCT, DOT and then BLT/FT, where the SARRP CBCT and DOT are used tomore » provide the anatomical and optical properties information to enhance the subsequent BLT/FT optical reconstruction. The SARRP stage is redesigned to include 9 imbedded optical fibers in contact with the animal's skin. These fibers, connected to a white light lamp or laser, serve as the light sources for the DOT or FT, respectively. A CCD camera with f/1.4 lens and multi-spectral filter set is used as the optical detector and is mounted on a portable cart ready to dock into the SARRP. No radiation is delivered during optical image acquisition. A 3-way mirror system capable of 180 degree rotation around the animal reflects the optical signal to the camera at multiple projection angles. A special black-painted dome covers the stage and provides the light shielding. Results: Spontaneous metastatic bioluminescent liver and lung tumor models will be used to validate the 3D BLT reconstruction. To demonstrate the capability of our FT system, GastroSense750 fluorescence agent will be used to imaging the mouse stomach and intestinal region in 3D. Conclusion: We expect that this integrated CBCT and optical tomography on-board a SARRP will present new research opportunities for pre-clinical radiation research. Supported by NCI RO1-CA 158100.« less

Highway research : DOT's actions to implement best practices for setting research agendas and evaluating outcomes : statement of Katherine Siggerud, Acting Director, Physical Infrastructure Team

DOT National Transportation Integrated Search

2003-04-10

The Federal Highway Administration (FHWA) is the primary federal agency involved in highway research. Given the expectations of highway research and the level of resources dedicated to it, it is important to know that FHWA is conducting high quality ...

Why do adults with dyslexia have poor global motion sensitivity?

PubMed

Conlon, Elizabeth G; Lilleskaret, Gry; Wright, Craig M; Stuksrud, Anne

2013-01-01

Two experiments aimed to determine why adults with dyslexia have higher global motion thresholds than typically reading controls. In Experiment 1, the dot density and number of animation frames presented in the dot stimulus were manipulated because of findings that use of a high dot density can normalize coherence thresholds in individuals with dyslexia. Dot densities were 14.15 and 3.54 dots/deg(2). These were presented for five (84 ms) or eight (134 ms) frames. The dyslexia group had higher coherence thresholds in all conditions than controls. However, in the high dot density, long duration condition, both reader groups had the lowest thresholds indicating normal temporal recruitment. These results indicated that the dyslexia group could sample the additional signals dots over space and then integrate these with the same efficiency as controls. In Experiment 2, we determined whether briefly presenting a fully coherent prime moving in either the same or opposite direction of motion to a partially coherent test stimulus would systematically increase and decrease global motion thresholds in the reader groups. When the direction of motion in the prime and test was the same, global motion thresholds increased for both reader groups. The increase in coherence thresholds was significantly greater for the dyslexia group. When the motion of the prime and test were presented in opposite directions, coherence thresholds were reduced in both groups. No group threshold differences were found. We concluded that the global motion processing deficit found in adults with dyslexia can be explained by undersampling of the target motion signals. This might occur because of difficulties directing attention to the relevant motion signals in the random dot pattern, and not a specific difficulty integrating global motion signals. These effects are most likely to occur in the group with dyslexia when more complex computational processes are required to process global motion.

Why do adults with dyslexia have poor global motion sensitivity?

PubMed Central

Conlon, Elizabeth G.; Lilleskaret, Gry; Wright, Craig M.; Stuksrud, Anne

2013-01-01

Two experiments aimed to determine why adults with dyslexia have higher global motion thresholds than typically reading controls. In Experiment 1, the dot density and number of animation frames presented in the dot stimulus were manipulated because of findings that use of a high dot density can normalize coherence thresholds in individuals with dyslexia. Dot densities were 14.15 and 3.54 dots/deg2. These were presented for five (84 ms) or eight (134 ms) frames. The dyslexia group had higher coherence thresholds in all conditions than controls. However, in the high dot density, long duration condition, both reader groups had the lowest thresholds indicating normal temporal recruitment. These results indicated that the dyslexia group could sample the additional signals dots over space and then integrate these with the same efficiency as controls. In Experiment 2, we determined whether briefly presenting a fully coherent prime moving in either the same or opposite direction of motion to a partially coherent test stimulus would systematically increase and decrease global motion thresholds in the reader groups. When the direction of motion in the prime and test was the same, global motion thresholds increased for both reader groups. The increase in coherence thresholds was significantly greater for the dyslexia group. When the motion of the prime and test were presented in opposite directions, coherence thresholds were reduced in both groups. No group threshold differences were found. We concluded that the global motion processing deficit found in adults with dyslexia can be explained by undersampling of the target motion signals. This might occur because of difficulties directing attention to the relevant motion signals in the random dot pattern, and not a specific difficulty integrating global motion signals. These effects are most likely to occur in the group with dyslexia when more complex computational processes are required to process global motion. PMID:24376414

Feasibility of tuberculosis treatment monitoring by video directly observed therapy: a binational pilot study.

PubMed

Garfein, R S; Collins, K; Muñoz, F; Moser, K; Cerecer-Callu, P; Raab, F; Rios, P; Flick, A; Zúñiga, M L; Cuevas-Mota, J; Liang, K; Rangel, G; Burgos, J L; Rodwell, T C; Patrick, K

2015-09-01

Although directly observed therapy (DOT) is recommended worldwide for monitoring anti-tuberculosis treatment, transportation and personnel requirements limit its use. To evaluate the feasibility and acceptability of 'video DOT' (VDOT), which allows patients to record and transmit medication ingestion via videos watched remotely by health care providers to document adherence. We conducted a single-arm trial among tuberculosis (TB) patients in San Diego, California, USA, (n = 43) and Tijuana, Mexico (n = 9) to represent high- and low-resource settings. Pre-/post-treatment interviews assessed participant characteristics and experiences. Adherence was defined as the proportion of observed doses to expected doses. The mean age was 37 years (range 18-86), 50% were male, and 88% were non-Caucasian. The mean duration of VDOT use was 5.5 months (range 1-11). Adherence was similar in San Diego (93%) and Tijuana (96%). Compared to time on in-person DOT, 92% preferred VDOT, 81% thought VDOT was more confidential, 89% never/rarely had problems recording videos, and 100% would recommend VDOT to others. Seven (13%) participants were returned to in-person DOT and six (12%) additional participants had their phones lost, broken or stolen. VDOT was feasible and acceptable, with high adherence in both high- and low-resource settings. Efficacy and cost-effectiveness studies are needed.

Electron-Electron and Electron-Phonon interactions effects on the tunnel electronic spectrum of PbS quantum dots

NASA Astrophysics Data System (ADS)

Wang, Hongyue; Lhuillier, Emmanuel; Yu, Qian; Mottaghizadeh, Alireza; Ulysse, Christian; Zimmers, Alexandre; Dubertret, Benoit; Aubin, Herve

2015-03-01

We present a tunnel spectroscopy study of the electronic spectrum of single PbS Quantum Dots (QDs) trapped between nanometer-spaced electrodes, measured at low temperature T=5 K. The carrier filling of the QD can be controlled either by the drain voltage in the shell filling regime or by a gate voltage. In the empty QD, the tunnel spectrum presents the expected signature of the 8x degenerated excited levels. In the drain controlled shell filling regime, the levels degeneracies are lifted by the global electrostatic Coulomb energy of the QD; in the gate controlled shell filling regime, the levels degeneracies are lifted by the intra-Coulomb interactions. In the charged quantum dot, electron-phonons interactions lead to the apparition of Franck-Condon side bands on the single excited levels and possibly Franck Condon blockade at low energy. The sharpening of excited levels at higher gate voltage suggests that the magnitude of electron-phonon interactions is decreased upon increasing the electron filling in the quantum dot. This work was supported by the French ANR Grants 10-BLAN-0409-01, 09-BLAN-0388-01, by the Region Ile-de-France in the framework of DIM Nano-K and by China Scholarship Council.

Environmental Barrier Coatings Having a YSZ Top Coat

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Gray, Hugh (Technical Monitor)

2002-01-01

Environmental barrier coatings (EBCs) with a Si bond coat, a yttria-stabilized zirconia (YSZ) top coat, and various intermediate coats were investigated. EBCs were processed by atmospheric pressure plasma spraying. The EBC durability was determined by thermal cycling tests in water vapor at 1300 C and 1400 C, and in air at 1400 C and 1500 C. EBCs with a mullite (3Al2O3 (dot) 2SiO2) + BSAS (1 - xBaO (dot) xSrO (dot) Al2O3 (dot) 2SiO2) intermediate coat were more durable than EBCs with a mullite intermediate coat, while EBCs with a mullite/BSAS duplex intermediate coat resulted in inferior durability. The improvement with a mullite + BSAS intermediate coat was attributed to enhanced compliance of the intermediate coat due to the addition of a low modulus BSAS second phase. Mullite + BSAS/YSZ and BSAS/YSZ interfaces produced a low melting (less than 1400 C) reaction product, which is expected to degrade the EBC performance by increasing the thermal conductivity. EBCs with a mullite + BSAS / graded mullite + YSZ intermediate coat showed the best durability among the EBCs investigated in this study. This improvement was attributed to diffused CTE (Coefficient of Thermal Expansion) mismatch stress and improved chemical stability due to the compositionally graded mullite+YSZ layer.

Videodermoscopy does not enhance diagnosis of scalp contact dermatitis due to topical minoxidil.

PubMed

Tosti, Antonella; Donati, Aline; Vincenzi, Colombina; Fabbrocini, Gabriella

2009-07-01

Videodermoscopy (VD) is a noninvasive diagnostic tool that provides useful information for the differential diagnosis of scalp disorders. The aim of this study was to investigate if dermoscopy may help the clinician in the diagnosis of contact dermatitis of the scalp. We analyzed the dermoscopic images taken from 7 patients with contact dermatitis due to topical minoxidil, 6 patients complaining of intense scalp itching during treatment with topical minoxidil but with negative patch tests and 19 controls. The following dermoscopic patterns described for scalp diseases were evaluated: Vascular patterns (simple loops, twisted loops and arborizing lines), follicular/perifollicular patterns (yellow dots, empty ostia, white dots, peripilar signs), white scales, yellow scales, follicular plugging, hair diameter diversity, honeycomb pattern and short regrowing hairs. Findings were graded from 0-4, according to severity in 20-fold magnifications. Statistical analysis included univariate analysis and Chi-square test by SPSS version 12. There were no statistical differences in the analysis of the vascular patterns and scales between the 3 groups. We were not able to detect dermoscopic features that can help the clinician in distinguishing scalp contact dermatitis due to topical minoxidil from other conditions that cause severe scalp itching. In particular, minoxidil contact dermatitis does not produce increase or alterations in the morphology of the scalp vessels or significant scalp scaling when evaluated with dermoscopy.

Ferritin-Templated Quantum-Dots for Quantum Logic Gates

NASA Technical Reports Server (NTRS)

Choi, Sang H.; Kim, Jae-Woo; Chu, Sang-Hyon; Park, Yeonjoon; King, Glen C.; Lillehei, Peter T.; Kim, Seon-Jeong; Elliott, James R.

2005-01-01

Quantum logic gates (QLGs) or other logic systems are based on quantum-dots (QD) with a stringent requirement of size uniformity. The QD are widely known building units for QLGs. The size control of QD is a critical issue in quantum-dot fabrication. The work presented here offers a new method to develop quantum-dots using a bio-template, called ferritin, that ensures QD production in uniform size of nano-scale proportion. The bio-template for uniform yield of QD is based on a ferritin protein that allows reconstitution of core material through the reduction and chelation processes. One of the biggest challenges for developing QLG is the requirement of ordered and uniform size of QD for arrays on a substrate with nanometer precision. The QD development by bio-template includes the electrochemical/chemical reconsitution of ferritins with different core materials, such as iron, cobalt, manganese, platinum, and nickel. The other bio-template method used in our laboratory is dendrimers, precisely defined chemical structures. With ferritin-templated QD, we fabricated the heptagonshaped patterned array via direct nano manipulation of the ferritin molecules with a tip of atomic force microscope (AFM). We also designed various nanofabrication methods of QD arrays using a wide range manipulation techniques. The precise control of the ferritin-templated QD for a patterned arrangement are offered by various methods, such as a site-specific immobilization of thiolated ferritins through local oxidation using the AFM tip, ferritin arrays induced by gold nanoparticle manipulation, thiolated ferritin positioning by shaving method, etc. In the signal measurements, the current-voltage curve is obtained by measuring the current through the ferritin, between the tip and the substrate for potential sweeping or at constant potential. The measured resistance near zero bias was 1.8 teraohm for single holoferritin and 5.7 teraohm for single apoferritin, respectively.

A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Ochoukov, R.; Bobkov, V.; Faugel, H.; Fünfgelder, H.; Noterdaeme, J.-M.

2015-11-01

A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k//) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (ktor). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k// as strap phasing is moved away from the dipole configuration. This result is the opposite of the ktor trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k//, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.

A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade.

PubMed

Ochoukov, R; Bobkov, V; Faugel, H; Fünfgelder, H; Noterdaeme, J-M

2015-11-01

A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k(//)) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k(tor)). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k(//) as strap phasing is moved away from the dipole configuration. This result is the opposite of the k(tor) trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k(//), as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.

Numerosity but not texture-density discrimination correlates with math ability in children.

PubMed

Anobile, Giovanni; Castaldi, Elisa; Turi, Marco; Tinelli, Francesca; Burr, David C

2016-08-01

Considerable recent work suggests that mathematical abilities in children correlate with the ability to estimate numerosity. Does math correlate only with numerosity estimation, or also with other similar tasks? We measured discrimination thresholds of school-age (6- to 12.5-years-old) children in 3 tasks: numerosity of patterns of relatively sparse, segregatable items (24 dots); numerosity of very dense textured patterns (250 dots); and discrimination of direction of motion. Thresholds in all tasks improved with age, but at different rates, implying the action of different mechanisms: In particular, in young children, thresholds were lower for sparse than textured patterns (the opposite of adults), suggesting earlier maturation of numerosity mechanisms. Importantly, numerosity thresholds for sparse stimuli correlated strongly with math skills, even after controlling for the influence of age, gender and nonverbal IQ. However, neither motion-direction discrimination nor numerosity discrimination of texture patterns showed a significant correlation with math abilities. These results provide further evidence that numerosity and texture-density are perceived by independent neural mechanisms, which develop at different rates; and importantly, only numerosity mechanisms are related to math. As developmental dyscalculia is characterized by a profound deficit in discriminating numerosity, it is fundamental to understand the mechanism behind the discrimination. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Classroom Proven Motivational Mathematics Games, Monograph No. 1.

ERIC Educational Resources Information Center

Michigan Council of Teachers of Mathematics.

This collection includes 50 mathematical games and puzzles for classroom use at all grade levels. Also included is a wide variety of activities with cubes, flash cards, graphs, dots, number patterns, geometric shapes, cross-number puzzles, and magic squares. (MM)

Detection Techniques for Biomolecules using Semi-Conductor Nanocrystals and Magnetic Beads as Labels

NASA Astrophysics Data System (ADS)

Chatterjee, Esha

Continued interest in the development of miniaturized and portable analytical platforms necessitates the exploration of sensitive methods for the detection of trace analytes. Nanomaterials, on account of their unique physical and chemical properties, are not only able to overcome many limitations of traditional detection reagents but also enable the exploration of many new signal transduction technologies. This dissertation presents a series of investigations of alternative detection techniques for biomolecules, involving the use of semi-conductor nanocrystals and magnetic beads as labels. Initial research focused on the development of quantum dot-encapsulating liposomes as a novel fluorescent label for immunoassays. This hybrid nanomaterial was anticipated to overcome the drawbacks presented by traditional fluorophores as well as provide significant signal amplification. Quantum dot-encapsulating liposomes were synthesized by the method of thin film hydration and characterized. The utility of these composite nanostructures for bioanalysis was demonstrated. However, the longterm instability of the liposomes hampered quantitative development. A second approach for assay development exploited the ability of gold nanoparticles to quench the optical signals obtained from quantum dots. The goal of this study was to demonstrate the feasibility of using aptamer-linked nanostructures in FRET-based quenching for the detection of proteins. Thrombin was used as the model analyte in this study. Experimental parameters for the assay were optimized. The assay simply required the mixing of the sample with the reagents and could be completed in less than an hour. The limit of detection for thrombin by this method was 5 nM. This homogeneous assay can be easily adapted for the detection of a wide variety of biochemicals. The novel technique of ferromagnetic resonance generated in magnetic bead labels was explored for signal transduction. This inductive detection technique lends itself to miniaturization, is capable of mass production and is inexpensive to fabricate. The device consisted of a microwave circuit in which a slotline and a coplanar waveguide were integrated with a biochemically activated sensor area. The magnetic beads were immobilized at the sensor area by bio-specific reactions. Experiments conducted on this prototype show promising results for using ferromagnetic resonance -based detection of magnetic labels for fabrication of portable and inexpensive sensor devices. The next stage of work addresses the issue of patterning of sensing surfaces with biomolecules. The ability to selectively immobilize biomolecules on surfaces has far-reaching applications, including sensor development. A simple and widely applicable method for the photopatterning of chitosan films with biotin was presented. Chitosan is a biocompatible and biodegradable polymer. The proposed method was capable of forming spatially defined biotin features on the order of tens of microns, together with a significant reduction of non-specific protein binding and increase in hydrophilicity of the sensor surface. The entire patterning process, inclusive of the blocking step, could be completed in under an hour. This straightforward method for the selective patterning of the biocompatible polymer chitosan is expected to be widely useful in the field of bioanalysis.

The Self-Assembly of Nanogold for Optical Metamaterials

NASA Astrophysics Data System (ADS)

Nidetz, Robert A.

2011-12-01

Optical metamaterials are an emerging field that enables manipulation of light like never before. Producing optical metamaterials requires sub-wavelength building blocks. The focus here was to develop methods to produce building blocks for metamaterials from nanogold. Electron-beam lithography was used to define an aminosilane patterned chemical template in order to electrostatically self-assemble citrate-capped gold nanoparticles. Equilibrium self-assembly was achieved in 20 minutes by immersing chemical templates into gold nanoparticle solutions. The number of nanoparticles that self-assembled on an aminosilane dot was controlled by manipulating the diameters of the dots and nanoparticles. Adding salt to the nanoparticle solution enabled the nanoparticles to self-assemble in greater numbers on the same sized dot. However, the preparation of the nanoparticle solution containing salt was sensitive to spikes in the salt concentration which led to aggregation of the nanoparticles and non-specific deposition. Gold nanorods were also electrostatically self-assembled. Polyelectrolyte-coated gold nanorods were patterned with limited success. A polyelectrolyte chemical template also patterned gold nanorods, but the gold nanorods preferred to pattern on the edges of the pattern. Ligand-exchanged gold nanorods displayed the best self-assembly, but suffered from slow kinetics. Self-assembled gold nanoparticles were cross-linked with poly(diallyldimethylammonium chloride). The poly(diallyldimethylammonium chloride) allowed additional nanoparticles to pattern on top of the already patterned nanoparticles. Cross-linked nanoparticles were lifted-off of the substrate by sonication in a sodium hydroxide solution. The presence of van der Waals forces and/or amine bonding prevent the nanogold from lifting-off without sonication. A good-solvent evaporation process was used to self-assemble poly(styrene) coated gold nanoparticles into spherical microbead assemblies. The use of larger nanoparticles and larger poly(styrene) ligands resulted in larger and smaller assemblies, respectively. Stirring the solution resulted in a wider size distribution of microbead assemblies due to the stirring's shear forces. Two undeveloped methods to self-assemble nanogold were investigated. One method used block-copolymer thin films as chemical templates to direct the electrostatic self-assembly of nanogold. Another method used gold nanorods that are passivated with different ligands on different faces. The stability of an alkanethiol ligand in different acids and bases was investigated to determine which materials could be used to produce Janus nanorods.

Feasibility and Cost-Effectiveness of Treating Multidrug-Resistant Tuberculosis: A Cohort Study in the Philippines

PubMed Central

Tupasi, Thelma E; Gupta, Rajesh; Quelapio, Ma Imelda D; Orillaza, Ruth B; Mira, Nona Rachel; Mangubat, Nellie V; Belen, Virgil; Arnisto, Nida; Macalintal, Lualhati; Arabit, Michael; Lagahid, Jaime Y; Espinal, Marcos; Floyd, Katherine

2006-01-01

Background Multidrug-resistant tuberculosis (MDR-TB) is an important global health problem, and a control strategy known as DOTS-Plus has existed since 1999. However, evidence regarding the feasibility, effectiveness, cost, and cost-effectiveness of DOTS-Plus is still limited. Methodology/Principal Findings We evaluated the feasibility, effectiveness, cost, and cost-effectiveness of a DOTS-Plus pilot project established at Makati Medical Center in Manila, the Philippines, in 1999. Patients with MDR-TB are treated with regimens, including first- and second-line drugs, tailored to their drug susceptibility pattern (i.e., individualised treatment). We considered the cohort enrolled between April 1999 and March 2002. During this three-year period, 118 patients were enrolled in the project; 117 were considered in the analysis. Seventy-one patients (61%) were cured, 12 (10%) failed treatment, 18 (15%) died, and 16 (14%) defaulted. The average cost per patient treated was US$3,355 from the perspective of the health system, of which US$1,557 was for drugs, and US$837 from the perspective of patients. The mean cost per disability-adjusted life year (DALY) gained by the DOTS-Plus project was US$242 (range US$85 to US$426). Conclusions Treatment of patients with MDR-TB using the DOTS-Plus strategy and individualised drug regimens can be feasible, comparatively effective, and cost-effective in low- and middle-income countries. PMID:16968123

Feasibility and cost-effectiveness of treating multidrug-resistant tuberculosis: a cohort study in the Philippines.

PubMed

Tupasi, Thelma E; Gupta, Rajesh; Quelapio, Ma Imelda D; Orillaza, Ruth B; Mira, Nona Rachel; Mangubat, Nellie V; Belen, Virgil; Arnisto, Nida; Macalintal, Lualhati; Arabit, Michael; Lagahid, Jaime Y; Espinal, Marcos; Floyd, Katherine

2006-09-01

Multidrug-resistant tuberculosis (MDR-TB) is an important global health problem, and a control strategy known as DOTS-Plus has existed since 1999. However, evidence regarding the feasibility, effectiveness, cost, and cost-effectiveness of DOTS-Plus is still limited. We evaluated the feasibility, effectiveness, cost, and cost-effectiveness of a DOTS-Plus pilot project established at Makati Medical Center in Manila, the Philippines, in 1999. Patients with MDR-TB are treated with regimens, including first- and second-line drugs, tailored to their drug susceptibility pattern (i.e., individualised treatment). We considered the cohort enrolled between April 1999 and March 2002. During this three-year period, 118 patients were enrolled in the project; 117 were considered in the analysis. Seventy-one patients (61%) were cured, 12 (10%) failed treatment, 18 (15%) died, and 16 (14%) defaulted. The average cost per patient treated was US3,355 dollars from the perspective of the health system, of which US1,557 dollars was for drugs, and US837 dollars from the perspective of patients. The mean cost per disability-adjusted life year (DALY) gained by the DOTS-Plus project was US242 dollars (range US85 dollars to US426 dollars). Treatment of patients with MDR-TB using the DOTS-Plus strategy and individualised drug regimens can be feasible, comparatively effective, and cost-effective in low- and middle-income countries.

Photoelectron transport tuning of self-assembled subbands

NASA Astrophysics Data System (ADS)

Xiong, Zhengwei; Wang, Xinmin; Wu, Weidong; Wang, Xuemin; Peng, Liping; Zhao, Yan; Yan, Dawei; Jiang, Tao; Shen, Changle; Zhan, Zhiqiang; Cao, Linhong; Li, Weihua

2016-02-01

Conventionally, electrical transport of quantum subbands occurs at very high electric fields, indicating that the medium is easy to break down. In the experiments and practical applications, the extreme condition is difficult to satisfy. For quantum information transmission, low power consumption and convenient implementation are what we expect. In this paper, we engineered a special quantum dot array (QDA) embedded in a single crystal matrix. By external optical field excitation, we found a series of subbands made of the self-assembled QDA discretely located in the matrix. Changing the spacing between the quantum dots leads to the variation of subband spacing. Artificially manipulating the microcosmic QDA system can bring interesting macroscopic effects, such as an enhanced absorption intensity in the ultraviolet range, a blue-shift of the surface plasmon resonance peak and nonlinear absorption changed from two-photon absorption to saturated absorption. The intrinsic mechanism of the subband optical response was revealed due to the strong quantum confinement effect and dominant intraband transitions. The weak surface plasmon resonance absorption of Ni QDA gave an excellent figure of merit of the order of 10-10. The composite films are expectation enough to become a prime candidate for nonlinear applications near 532 nm. Therefore with interplay of the weak optical field and subbands, we achieved a tunable photoelectron transport process.Conventionally, electrical transport of quantum subbands occurs at very high electric fields, indicating that the medium is easy to break down. In the experiments and practical applications, the extreme condition is difficult to satisfy. For quantum information transmission, low power consumption and convenient implementation are what we expect. In this paper, we engineered a special quantum dot array (QDA) embedded in a single crystal matrix. By external optical field excitation, we found a series of subbands made of the self-assembled QDA discretely located in the matrix. Changing the spacing between the quantum dots leads to the variation of subband spacing. Artificially manipulating the microcosmic QDA system can bring interesting macroscopic effects, such as an enhanced absorption intensity in the ultraviolet range, a blue-shift of the surface plasmon resonance peak and nonlinear absorption changed from two-photon absorption to saturated absorption. The intrinsic mechanism of the subband optical response was revealed due to the strong quantum confinement effect and dominant intraband transitions. The weak surface plasmon resonance absorption of Ni QDA gave an excellent figure of merit of the order of 10-10. The composite films are expectation enough to become a prime candidate for nonlinear applications near 532 nm. Therefore with interplay of the weak optical field and subbands, we achieved a tunable photoelectron transport process. Electronic supplementary information (ESI) available: Tables 1 and 2. See DOI: 10.1039/c5nr07861j

An improved P300 pattern in BCI to catch user’s attention

NASA Astrophysics Data System (ADS)

Jin, Jing; Zhang, Hanhan; Daly, Ian; Wang, Xingyu; Cichocki, Andrzej

2017-06-01

Objective. Brain-computer interfaces (BCIs) can help patients who have lost control over most muscles but are still conscious and able to communicate or interact with the environment. One of the most popular types of BCI is the P300-based BCI. With this BCI, users are asked to count the number of appearances of target stimuli in an experiment. To date, the majority of visual P300-based BCI systems developed have used the same character or picture as the target for every stimulus presentation, which can bore users. Consequently, users attention may decrease or be negatively affected by adjacent stimuli. Approach. In this study, a new stimulus is presented to increase user concentration. Honeycomb-shaped figures with 1-3 red dots were used as stimuli. The number and the positions of the red dots in the honeycomb-shaped figure were randomly changed during BCI control. The user was asked to count the number of the dots presented in each flash instead of the number of times they flashed. To assess the performance of this new stimulus, another honeycomb-shaped stimulus, without red dots, was used as a control condition. Main results. The results showed that the honeycomb-shaped stimuli with red dots obtained significantly higher classification accuracies and information transfer rates (p  <  0.05) compared to the honeycomb-shaped stimulus without red dots. Significance. The results indicate that this proposed method can be a promising approach to improve the performance of the BCI system and can be an efficient method in daily application.

An improved P300 pattern in BCI to catch user's attention.

PubMed

Jin, Jing; Zhang, Hanhan; Daly, Ian; Wang, Xingyu; Cichocki, Andrzej

2017-06-01

Brain-computer interfaces (BCIs) can help patients who have lost control over most muscles but are still conscious and able to communicate or interact with the environment. One of the most popular types of BCI is the P300-based BCI. With this BCI, users are asked to count the number of appearances of target stimuli in an experiment. To date, the majority of visual P300-based BCI systems developed have used the same character or picture as the target for every stimulus presentation, which can bore users. Consequently, users attention may decrease or be negatively affected by adjacent stimuli. In this study, a new stimulus is presented to increase user concentration. Honeycomb-shaped figures with 1-3 red dots were used as stimuli. The number and the positions of the red dots in the honeycomb-shaped figure were randomly changed during BCI control. The user was asked to count the number of the dots presented in each flash instead of the number of times they flashed. To assess the performance of this new stimulus, another honeycomb-shaped stimulus, without red dots, was used as a control condition. The results showed that the honeycomb-shaped stimuli with red dots obtained significantly higher classification accuracies and information transfer rates (p  <  0.05) compared to the honeycomb-shaped stimulus without red dots. The results indicate that this proposed method can be a promising approach to improve the performance of the BCI system and can be an efficient method in daily application.

Far from the equilibrium crystallization of oxide quantum dots in dried inorganic gels

NASA Astrophysics Data System (ADS)

Costille, B.; Dumoulin, M.; Ntsame Abagha, A. M.; Thune, E.; Guinebretière, R.

2018-06-01

We synthesized, through the sol-gel process, far from the equilibrium amorphous materials in which heterogeneous crystallization allowed the formation of oxide quantum dots. The isothermal evolutions of the mean size of the nanocrystals and the crystallinity of the materials were determined through x-ray diffraction experiments. The heterogeneous crystallization is characterized by a kinetic behavior that is far from that expected, according to the classical nucleation theory. We demonstrate that the evolution of the crystallinity is characterized by an Avrami exponent largely smaller than 1. Finally, nanocrystals exhibiting a size significantly below their Bohr radius are obtained and the number of these nanocrystals increases during isothermal treatment, whereas their mean size remains quasi-constant.

Photogrammetry and Videogrammetry Methods Development for Solar Sail Structures. Masters Thesis awarded by George Washington Univ.

NASA Technical Reports Server (NTRS)

Pappa, Richard S. (Technical Monitor); Black, Jonathan T.

2003-01-01

This report discusses the development and application of metrology methods called photogrammetry and videogrammetry that make accurate measurements from photographs. These methods have been adapted for the static and dynamic characterization of gossamer structures, as four specific solar sail applications demonstrate. The applications prove that high-resolution, full-field, non-contact static measurements of solar sails using dot projection photogrammetry are possible as well as full-field, non-contact, dynamic characterization using dot projection videogrammetry. The accuracy of the measurement of the resonant frequencies and operating deflection shapes that were extracted surpassed expectations. While other non-contact measurement methods exist, they are not full-field and require significantly more time to take data.

Mesoscopic Elastic Distortions in GaAs Quantum Dot Heterostructures.

PubMed

Pateras, Anastasios; Park, Joonkyu; Ahn, Youngjun; Tilka, Jack A; Holt, Martin V; Reichl, Christian; Wegscheider, Werner; Baart, Timothy A; Dehollain, Juan Pablo; Mukhopadhyay, Uditendu; Vandersypen, Lieven M K; Evans, Paul G

2018-05-09

Quantum devices formed in high-electron-mobility semiconductor heterostructures provide a route through which quantum mechanical effects can be exploited on length scales accessible to lithography and integrated electronics. The electrostatic definition of quantum dots in semiconductor heterostructure devices intrinsically involves the lithographic fabrication of intricate patterns of metallic electrodes. The formation of metal/semiconductor interfaces, growth processes associated with polycrystalline metallic layers, and differential thermal expansion produce elastic distortion in the active areas of quantum devices. Understanding and controlling these distortions present a significant challenge in quantum device development. We report synchrotron X-ray nanodiffraction measurements combined with dynamical X-ray diffraction modeling that reveal lattice tilts with a depth-averaged value up to 0.04° and strain on the order of 10 -4 in the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. Elastic distortions in GaAs/AlGaAs heterostructures modify the potential energy landscape in the 2DEG due to the generation of a deformation potential and an electric field through the piezoelectric effect. The stress induced by metal electrodes directly impacts the ability to control the positions of the potential minima where quantum dots form and the coupling between neighboring quantum dots.

Shape-specific perceptual learning in a figure-ground segregation task.

PubMed

Yi, Do-Joon; Olson, Ingrid R; Chun, Marvin M

2006-03-01

What does perceptual experience contribute to figure-ground segregation? To study this question, we trained observers to search for symmetric dot patterns embedded in random dot backgrounds. Training improved shape segmentation, but learning did not completely transfer either to untrained locations or to untrained shapes. Such partial specificity persisted for a month after training. Interestingly, training on shapes in empty backgrounds did not help segmentation of the trained shapes in noisy backgrounds. Our results suggest that perceptual training increases the involvement of early sensory neurons in the segmentation of trained shapes, and that successful segmentation requires perceptual skills beyond shape recognition alone.

All MBE grown InAs/GaAs quantum dot lasers on on-axis Si (001).

PubMed

Kwoen, Jinkwan; Jang, Bongyong; Lee, Joohang; Kageyama, Takeo; Watanabe, Katsuyuki; Arakawa, Yasuhiko

2018-04-30

Directly grown III-V quantum dot (QD) laser on on-axis Si (001) is a good candidate for achieving monolithically integrated Si photonics light source. Nowadays, laser structures containing high quality InAs / GaAs QD are generally grown by molecular beam epitaxy (MBE). However, the buffer layer between the on-axis Si (001) substrate and the laser structure are usually grown by metal-organic chemical vapor deposition (MOCVD). In this paper, we demonstrate all MBE grown high-quality InAs/GaAs QD lasers on on-axis Si (001) substrates without using patterning and intermediate layers of foreign material.

Quantum Monte Carlo Studies of Interaction-Induced Localization in Quantum Dots and Wires

NASA Astrophysics Data System (ADS)

Devrim Güçlü, A.

2009-03-01

We investigate interaction-induced localization of electrons in both quantum dots and inhomogeneous quantum wires using variational and diffusion quantum Monte Carlo methods. Quantum dots and wires are highly tunable systems that enable the study of the physics of strongly correlated electrons. With decreasing electronic density, interactions become stronger and electrons are expected to localize at their classical positions, as in Wigner crystallization in an infinite 2D system. (1) Dots: We show that the addition energy shows a clear progression from features associated with shell structure to those caused by commensurability of a Wigner crystal. This cross-over is, then, a signature of localization; it occurs near rs˜20. For higher values of rs, the configuration symmetry of the quantum dot becomes fully consistent with the classical ground state. (2) Wires: We study an inhomogeneous quasi-one-dimensional system -- a wire with two regions, one at low density and the other high. We find that strong localization occurs in the low density quantum point contact region as the gate potential is increased. The nature of the transition from high to low density depends on the density gradient -- if it is steep, a barrier develops between the two regions, causing Coulomb blockade effects. We find no evidence for ferromagnetic spin polarization for the range of parameters studied. The picture emerging here is in good agreement with the experimental measurements of tunneling between two wires. Collaborators: C. J. Umrigar (Cornell), Hong Jiang (Fritz Haber Institut), Amit Ghosal (IISER Calcutta), and H. U. Baranger (Duke).

A novel electrochemiluminescent biosensor based on resonance energy transfer between poly(9,9-di-n-octylfluorenyl-2,7-diyl) and 3,4,9,10-perylenetetracar-boxylic acid for insulin detection.

PubMed

Zhang, Han; Zuo, Fumei; Tan, Xingrong; Xu, Shenghao; Yuan, Ruo; Chen, Shihong

2018-05-01

An electrochemiluminescencent (ECL) biosensor was designed for the determination of insulin using a novel ECL resonance energy transfer (ECL-RET) strategy. In this strategy, carboxyl poly(9,9-dioctyfluorenyl-2,7-diyl) dots (PFO dots) were worked as ECL donor and 3,4,9,10-perylenetetracar-boxylic acid (PTCA) exploited as ECL acceptor, and hydrogen peroxide (H 2 O 2 ) employed as the coreactant. The ECL donor and ECL acceptor were separately labeled with primary antibody (Ab 1 ) and secondary antibody (Ab 2 ), forming a sensing interface to the analyte target, insulin. In this expected sandwich-type ECL biosensor, PFO dots acted as sensing platform and PTCA employed as labels to quench the ECL emission of PFO dots. During the determination process, ECL signal of PFO dots was decreased in a gradual way by the increase of insulin concentration, and the quenching mechanism was also investigated. Under the optimal experimental conditions, the constructed biosensor exhibited an excellent performance, including a wide linear range from 1.0 × 10 -5 ng/mL to 1.0 × 10 2 ng/mL, low detection limit of 3.0 × 10 -6 ng/mL, good stability and selectivity for the detection of insulin. This pair of PFO-PTCA, as a new donor-acceptor pair in ECL-RET system, would provide a promising platform for bioanalysis in ECL field. Copyright © 2017 Elsevier B.V. All rights reserved.

Connecting the Dots: Postsecondary's Role in Preparing K-12 Students

ERIC Educational Resources Information Center

Partnership for Assessment of Readiness for College and Careers, 2012

2012-01-01

For the first time in the nation's history 46 States and the District of Columbia have agreed that all K-12 students will be educated along a common continuum of high academic expectations known as the Common Core State Standards (CCSS). Having clear, consistent standards in English language arts/literacy and mathematics will help ensure that all…

2D and 3D surface photopatterning via laser-promoted homopolymerization of a perfluorophenyl azide-substituted BODIPY.

PubMed

Raffy, Guillaume; Bofinger, Robin; Tron, Arnaud; Guerzo, André Del; McClenaghan, Nathan D; Vincent, Jean-Marc

2017-11-09

An innovative photopatterning process is described that allows, in a single laser-promoted operation, the covalent attachment of a molecule on a surface (2D patterning - xy dimensions) and its photopolymerization to grow micro-/nanostructures with spatial control in a third z-dimension. The surface patterning process, based on nitrene reactivity, was harnessed using the highly fluorescent azide-substituted boron difluoride dipyrromethene (BODIPY) 1 that was prepared in a single synthetic step from the parent pentafluorophenyl BODIPY on reacting with NaN 3 . Using the laser of a fluorescence microscope (375 nm or 532 nm) 1 could be grafted on adapted surfaces and then homopolymerised. In this study we show that using glass coverslips coated with PEG/high density alkyne groups (density of ∼1 × 10 14 per cm 2 ), the patterning process was much more spatially confined than when using PEG only coating. Varying the irradiation time (1 to 15 s) or laser power (0.14-3.53 μW) allowed variation of the amount of deposited BODIPY to afford, in the extreme case, pillars of a height up to 800 nm. AFM and MS studies revealed that the nano/microstructures were formed of particles of photopolymerized 1 having a mean diameter of ca. 30 nm. The emission spectra and fluorescence lifetimes for the patterned structures were measured, revealing a red-shift (from ∼560 nm up to 620 nm) of the maximum emission and a shortening (from ∼6 ns to 0.8 ns) of the fluorescence lifetimes in areas where the density of BODIPY is high. As an application of the patterning process, a figure formed of 136 dots/pillars was prepared. The confocal hyperspectral fluorescence image revealed that the figure is clearly resolved and constituted by highly photoluminescent red dots whose fluorescence intensities and emission color proved to be highly reproducible. SEM and AFM studies showed that the luminescent dots were pillars with a conical shape, an average height of 710 ± 28 nm and a FWHM of 400 ± 20 nm.

Print quality analysis for ink-saving algorithms

NASA Astrophysics Data System (ADS)

Ortiz Segovia, Maria V.; Bonnier, Nicolas; Allebach, Jan P.

2012-01-01

Ink-saving strategies for CMYK printers have evolved from their earlier stages where the 'draft' print mode was the main option available to control ink usage. The savings were achieved by printing alternate dots in an image at the expense of reducing print quality considerably. Nowadays, customers are not only unwilling to compromise quality but have higher expectations regarding both visual print quality and ink reduction solutions. Therefore, the need for more intricate ink-saving solutions with lower impact on print quality is evident. Printing-related factors such as the way the printer places the dots on the paper and the ink-substrate interaction play important and complex roles in the characterization and modeling of the printing process that make the ink reduction topic a challenging problem. In our study, we are interested in benchmarking ink-saving algorithms to find the connections between different ink reduction levels of a given ink-saving method and a set of print quality attributes. This study is mostly related to CMYK printers that use dispersed dot halftoning algorithms. The results of our efforts to develop such an evaluation scheme are presented in this paper.

Understanding chemically processed solar cells based on quantum dots

PubMed Central

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-01-01

Abstract Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum. PMID:28567179

Non-equilibrium transport in the quantum dot: quench dynamics and non-equilibrium steady state

NASA Astrophysics Data System (ADS)

Culver, Adrian; Andrei, Natan

We calculate the non-equilibrium current driven by a voltage drop across a quantum dot. The system is described by the two lead Anderson model at zero temperature with on-site Coulomb repulsion and non-interacting, linearized leads. We prepare the system in an initial state consisting of a free Fermi sea in each lead with the voltage drop given as the difference between the two Fermi levels. We quench the system by coupling the dot to the leads at t =0 and following the time evolution of the wavefunction. In the long time limit a new type of Bethe Ansatz wavefunction emerges, which satisfies the Lippmann-Schwinger equation with the two Fermi seas serving as the boundary conditions. The solution describes the non-equilibrium steady state of the system. We use this solution to compute the infinite time limit of the expectation value of the current operator at a given voltage, yielding the I-V characteristic. The calculation is non-perturbative and exact. Research supported by NSF Grant DMR 1410583.

Convergent evolution: floral guides, stingless bee nest entrances, and insectivorous pitchers

NASA Astrophysics Data System (ADS)

Biesmeijer, Jacobus C.; Giurfa, Martin; Koedam, Dirk; Potts, Simon G.; Joel, Daniel M.; Dafni, Amots

2005-09-01

Several recent hypotheses, including sensory drive and sensory exploitation, suggest that receiver biases may drive selection of biological signals in the context of sexual selection. Here we suggest that a similar mechanism may have led to convergence of patterns in flowers, stingless bee nest entrances, and pitchers of insectivorous plants. A survey of these non-related visual stimuli shows that they share features such as stripes, dark centre, and peripheral dots. Next, we experimentally show that in stingless bees the close-up approach to a flower is guided by dark centre preference. Moreover, in the approach towards their nest entrance, they have a spontaneous preference for entrance patterns containing a dark centre and disrupted ornamentation. Together with existing empirical evidence on the honeybee's and other insects’ orientation to flowers, this suggests that the signal receivers of the natural patterns we examined, mainly Hymenoptera, have spontaneous preferences for radiating stripes, dark centres, and peripheral dots. These receiver biases may have evolved in other behavioural contexts in the ancestors of Hymenoptera, but our findings suggest that they have triggered the convergent evolution of visual stimuli in floral guides, stingless bee nest entrances, and insectivorous pitchers.

Convergent evolution: floral guides, stingless bee nest entrances, and insectivorous pitchers.

PubMed

Biesmeijer, Jacobus C; Giurfa, Martin; Koedam, Dirk; Potts, Simon G; Joel, Daniel M; Dafni, Amots

2005-09-01

Several recent hypotheses, including sensory drive and sensory exploitation, suggest that receiver biases may drive selection of biological signals in the context of sexual selection. Here we suggest that a similar mechanism may have led to convergence of patterns in flowers, stingless bee nest entrances, and pitchers of insectivorous plants. A survey of these non-related visual stimuli shows that they share features such as stripes, dark centre, and peripheral dots. Next, we experimentally show that in stingless bees the close-up approach to a flower is guided by dark centre preference. Moreover, in the approach towards their nest entrance, they have a spontaneous preference for entrance patterns containing a dark centre and disrupted ornamentation. Together with existing empirical evidence on the honeybee's and other insects' orientation to flowers, this suggests that the signal receivers of the natural patterns we examined, mainly Hymenoptera, have spontaneous preferences for radiating stripes, dark centres, and peripheral dots. These receiver biases may have evolved in other behavioural contexts in the ancestors of Hymenoptera, but our findings suggest that they have triggered the convergent evolution of visual stimuli in floral guides, stingless bee nest entrances, and insectivorous pitchers.

Inkjet printed fluorescent nanorod layers exhibit superior optical performance over quantum dots

NASA Astrophysics Data System (ADS)

Halivni, Shira; Shemesh, Shay; Waiskopf, Nir; Vinetsky, Yelena; Magdassi, Shlomo; Banin, Uri

2015-11-01

Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the reduced absorption/emission overlap, accompanied by low energy transfer efficiencies between the nanorods as supported by steady state and time resolved fluorescence measurements. The new seeded nanorod inks enable patterning of thin fluorescent layers, for demanding light emission applications such as signage and displays.Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the reduced absorption/emission overlap, accompanied by low energy transfer efficiencies between the nanorods as supported by steady state and time resolved fluorescence measurements. The new seeded nanorod inks enable patterning of thin fluorescent layers, for demanding light emission applications such as signage and displays. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06248a

Effects of perceived school well-being and negative emotionality on students' attentional bias for academic stressors.

PubMed

Scrimin, Sara; Moscardino, Ughetta; Altoè, Gianmarco; Mason, Lucia

2016-06-01

Previous research indicates that children can display different attention allocation patterns in response to threat. However, data are lacking on the possible existence of an attentional bias in response to academic stressors, and whether variables related to school well-being (SWB) and students' individual characteristics may influence such attentional patterns. We aimed to investigate whether students show an attentional bias for school-related stressors. We sought to identify groups of students who differ in their perceived SWB, and to test whether they display different attention allocation patterns. We also examined whether negative emotionality moderates the expected association between students' SWB and attentional bias. Eighth-grade students completed a dot-probe detection task to register attentional patterns towards or away from an academic threatening word. SWB in terms of school anxiety, school-based stress, and perceived class climate was also assessed via self-reports. In addition, participants reported on their negative emotionality. The results indicated that students showed an attentional bias towards words describing academic stressors. Cluster analyses allowed the identification of two groups of students with high versus low SWB. Regression analysis indicated that those with low SWB were more likely to show a greater bias and that negative emotionality moderated this relationship. Specifically, within the context of low SWB, students with high negative emotionality were more prone to biased attention towards school-related stressors compared with students with low negative emotionality. The present data indicate a perceptual bias for the detection of academic threats. Within the school practice, teachers should promote SWB and devote specific attention to students with high negative emotionality to reduce a biased allocation of attention in response to school-related stressors. © 2016 The British Psychological Society.

Perceptual grouping across eccentricity.

PubMed

Tannazzo, Teresa; Kurylo, Daniel D; Bukhari, Farhan

2014-10-01

Across the visual field, progressive differences exist in neural processing as well as perceptual abilities. Expansion of stimulus scale across eccentricity compensates for some basic visual capacities, but not for high-order functions. It was hypothesized that as with many higher-order functions, perceptual grouping ability should decline across eccentricity. To test this prediction, psychophysical measurements of grouping were made across eccentricity. Participants indicated the dominant grouping of dot grids in which grouping was based upon luminance, motion, orientation, or proximity. Across trials, the organization of stimuli was systematically decreased until perceived grouping became ambiguous. For all stimulus features, grouping ability remained relatively stable until 40°, beyond which thresholds significantly elevated. The pattern of change across eccentricity varied across stimulus feature, in which stimulus scale, dot size, or stimulus size interacted with eccentricity effects. These results demonstrate that perceptual grouping of such stimuli is not reliant upon foveal viewing, and suggest that selection of dominant grouping patterns from ambiguous displays operates similarly across much of the visual field. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quantum dot-based microfluidic biosensor for cancer detection

NASA Astrophysics Data System (ADS)

Ghrera, Aditya Sharma; Pandey, Chandra Mouli; Ali, Md. Azahar; Malhotra, Bansi Dhar

2015-05-01

We report results of the studies relating to fabrication of an impedimetric microfluidic-based nucleic acid sensor for quantification of DNA sequences specific to chronic myelogenous leukemia (CML). The sensor chip is prepared by patterning an indium-tin-oxide (ITO) coated glass substrate via wet chemical etching method followed by sealing with polydimethylsiloxane (PDMS) microchannel for fluid control. The fabricated microfluidic chip comprising of a patterned ITO substrate is modified by depositing cadmium selenide quantum dots (QCdSe) via Langmuir-Blodgett technique. Further, the QCdSe surface has been functionalized with specific DNA probe for CML detection. The probe DNA functionalized QCdSe integrated miniaturized system has been used to monitor target complementary DNA concentration by measuring the interfacial charge transfer resistance via hybridization. The presence of complementary DNA in buffer solution significantly results in decreased electro-conductivity of the interface due to presence of a charge barrier for transport of the redox probe ions. The microfluidic DNA biosensor exhibits improved linearity in the concentration range of 10-15 M to 10-11 M.

Nanoscale probing of image-dipole interactions in a metallic nanostructure

PubMed Central

Ropp, Chad; Cummins, Zachary; Nah, Sanghee; Fourkas, John T.; Shapiro, Benjamin; Waks, Edo

2015-01-01

An emitter near a surface induces an image dipole that can modify the observed emission intensity and radiation pattern. These image-dipole effects are generally not taken into account in single-emitter tracking and super-resolved imaging applications. Here we show that the interference between an emitter and its image dipole induces a strong polarization anisotropy and a large spatial displacement of the observed emission pattern. We demonstrate these effects by tracking the emission of a single quantum dot along two orthogonal polarizations as it is deterministically positioned near a silver nanowire. The two orthogonally polarized diffraction spots can be displaced by up to 50 nm, which arises from a Young’s interference effect between the quantum dot and its induced image dipole. We show that the observed spatially varying interference fringe provides a useful measure for correcting image-dipole-induced distortions. These results provide a pathway towards probing and correcting image-dipole effects in near-field imaging applications. PMID:25790228

Near-infrared light-mediated photodynamic/photothermal therapy nanoplatform by the assembly of Fe3O4 carbon dots with graphitic black phosphorus quantum dots

PubMed Central

Zhang, Ming; Wang, Wentao; Cui, Yingjun; Zhou, Ninglin; Shen, Jian

2018-01-01

Background Recently, combined photodynamic therapy (PDT) and photothermal therapy (PTT) has become a desired treatment for cancer. However, the development of economic, high-efficiency, and safe photosensitizers/photothermal agents remains a significant challenge. Methods A novel nanocomposite has been developed via the assembly of iron oxide carbon dot (Fe3O4-CDs) nanoparticles and black phosphorus quantum dots (genipin [GP]-polyglutamic acid [PGA]-Fe3O4-CDs@BPQDs), and this nanocomposite shows a broad light-absorption band and a photodegradable character. Results In vitro and in vivo assays indicated that GP-PGA-Fe3O4-CDs@BPQDs were highly biocompatible and exhibited excellent tumor-inhibition efficacy, due to the synergistic PTT and PDT via a near-infrared laser. Importantly, in vivo tumor magnetic resonance imaging (MRI) results illustrated that GP-PGA-Fe3O4-CDs@BPQDs can be specifically applied for enhanced T2 MRI of tumors. This work presents the first combined application of a PDT and PTT effect deriving from BPQDs and MRI from Fe3O4-CDs, which may promote utilization of black BPQDs in biomedicine. Conclusion As expected, GP-PGA-Fe3O4-CDs@BPQDs displayed a dramatically enhanced ability to destroy tumor cells, due to the synergistic combination of PTT and PDT. PMID:29785107

Fast radio bursts as giant pulses from young rapidly rotating pulsars

NASA Astrophysics Data System (ADS)

Lyutikov, Maxim; Burzawa, Lukasz; Popov, Sergei B.

2016-10-01

We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages ˜ tens to hundreds of years) born with regular magnetic field but very short - few milliseconds - spin periods. We assume that FRBs are extra-Galactic events coming from distances d ≲ 100 Mpc and that most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell. We then predict that for a given burst the DM should decrease with time and that FRBs are not expected to be seen below ˜300 MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star-forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers dot{E} in young energetic pulsars is consistent with equal birth rate per decade of dot{E}. Accepting this injection distribution and scaling the intrinsic brightness of FRBs with dot{E}, we predict the following properties of a large sample of FRBs: (I) the brightest observed events come from a broad distribution in distances; (II) for repeating bursts brightness either remains nearly constant (if the spin-down time is longer than the age of the pulsar) or decreases with time otherwise; in the latter case DM ∝ dot{E}.

A novel monodisperse SiO2@C-dot for the rapid and facile identification of latent fingermarks using self-quenching resistant solid-state fluorescence.

PubMed

Peng, Di; Liu, Xiang; Huang, Mengjun; Wang, Dan; Liu, Renlong

2018-04-24

Solid powder fluorescence shows great potential for application in medicine, biology, and engineering, especially in the identification of latent fingermarks in forensic science. However, conventional developing methods suffer from some drawbacks, such as low contrast, low sensitivity, low selectivity, and high toxicity. To conquer these challenges, novel SiO2@C-dot microspheres were prepared via a facile one-pot hydrothermal method by using citric acid as a carbon source and aminosilane as a nitrogen source. Interestingly, the results showed that the resultant powders possess good monodispersity, high fluorescence emission, and resistance to self-quenching. Additionally, the mechanism for the solid-state fluorescence of SiO2@C-dot compounds was also investigated. More importantly, the fingermarks on various surfaces, including transparent glasses, ceramic tiles, transparent plastics, aluminum alloys, plastic cards, painted woods, artificial leathers, and Chinese paper money, developed by the powders have indicated well-defined papillary ridges under a 365 nm UV lamp. The novel strategy of using monodisperse SiO2@C-dot microspheres as a fluorescent label for developing latent fingermarks showed greater advantages compared to conventional methods, which was also demonstrated using the automatic fingerprint identification system. It is simple, rapid, low-cost, nontoxic, and effective, and is expected to be a promising alternative for the development of latent fingerprints in forensic science.

The marginal band system in nymphalid butterfly wings.

PubMed

Taira, Wataru; Kinjo, Seira; Otaki, Joji M

2015-01-01

Butterfly wing color patterns are highly complex and diverse, but they are believed to be derived from the nymphalid groundplan, which is composed of several color pattern systems. Among these pattern systems, the marginal band system, including marginal and submarginal bands, has rarely been studied. Here, we examined the color pattern diversity of the marginal band system among nymphalid butterflies. Marginal and submarginal bands are usually expressed as a pair of linear bands aligned with the wing margin. However, a submarginal band can be expressed as a broken band, an elongated oval, or a single dot. The marginal focus, usually a white dot at the middle of a wing compartment along the wing edge, corresponds to the pupal edge spot, one of the pupal cuticle spots that signify the locations of color pattern organizing centers. A marginal band can be expressed as a semicircle, an elongated oval, or a pair of eyespot-like structures, which suggest the organizing activity of the marginal focus. Physical damage at the pupal edge spot leads to distal dislocation of the submarginal band in Junonia almana and in Vanessa indica, suggesting that the marginal focus functions as an organizing center for the marginal band system. Taken together, we conclude that the marginal band system is developmentally equivalent to other symmetry systems. Additionally, the marginal band is likely a core element and the submarginal band a paracore element of the marginal band system, and both bands are primarily specified by the marginal focus organizing center.

Selenium quantum dots: Preparation, structure, and properties

NASA Astrophysics Data System (ADS)

Qian, Fuli; Li, Xueming; Tang, Libin; Lai, Sin Ki; Lu, Chaoyu; Lau, Shu Ping

2017-01-01

An interesting class of low-dimensional nanomaterials, namely, selenium quantum dots (SeQDs), which are composed of nano-sized selenium particles, is reported in this study. The SeQDs possess a hexagonal crystal structure. They can be synthesized in large quantity by ultrasound liquid-phase exfoliation using NbSe2 powders as the source material and N-Methyl-2-pyrrolidone (NMP) as the dispersant. During sonication, the Nb-Se bonds dissociate; the SeQDs are formed, while niobium is separated by centrifugation. The SeQDs have a narrow diameter distribution from 1.9 to 4.6 nm and can be dispersed with high stability in NMP without the need for passivating agents. They exhibit photoluminescence properties that are expected to find useful applications in bioimaging, optoelectronics, as well as nanocomposites.

Distribution of different surface modified carbon dots in pumpkin seedlings.

PubMed

Qian, Kun; Guo, Huiyuan; Chen, Guangcai; Ma, Chuanxin; Xing, Baoshan

2018-05-22

The distribution of surface modified carbon dots (CDs) in the pumpkin seedlings was studied by visualization techniques and their potential phytotoxicity was investigated at both the physiological and biochemical levels. The average size of carbon dots was approximately 4 nm. The fluorescent peaks of bared CDs, CD-PEI and CD-PAA were between 420 nm and 500 nm, indicating CDs could emit blue and green fluorescence. Fluorescent images showed that all three types of CDs could accumulate in the pumpkin roots and translocate to the shoots, although the distribution pattern of each CDs was obviously different. At the biochemical level, the elevated antioxidant enzymes in pumpkin roots suggest that all the CDs could potentially trigger the antioxidant defense systems in pumpkin seedlings. Additionally, such alteration was greater in the roots than in the shoots. Our study represents a new perspective on CD visualization in plant tissues and provide useful information for the potential toxicity of different types of CDs to terrestrial plants, which is of importance to agricultural application.

Development of a tactile display with 5 mm resolution using an array of magnetorheological fluid

NASA Astrophysics Data System (ADS)

Ishizuka, Hiroki; Miki, Norihisa

2017-06-01

In this study, we demonstrate the design and evaluation of a stiffness tactile display using a magnetorheological (MR) fluid. The tactile display is based on the change in mechanical properties under an external magnetic field. In the tactile display, the MR fluid is encapsulated in chambers of 3 mm diameter and arranged at intervals of 2 mm. Magnetic fields were spatially applied to the tactile display using neodymium magnets of 3.5 mm diameter. The design and spatial magnetic field application enable the tactile display to present stiff dots of 5 mm resolution. We confirmed that the tactile display can present a spatial stiff dot and its pattern on the surface by compression experiments. Sensory evaluation revealed that the users were able to perceive the approximate position of the stiff dots. From the experiments, the tactile display has potential as a palpation tactile display and requires improvement to present various types of tissues.

The spectrum of dermatoscopic patterns in blue nevi.

PubMed

Di Cesare, Antonella; Sera, Francesco; Gulia, Andrea; Coletti, Gino; Micantonio, Tamara; Fargnoli, Maria Concetta; Peris, Ketty

2012-08-01

Blue nevi are congenital or acquired, dermal dendritic melanocytic proliferations that can simulate melanocytic and nonmelanocytic lesions including melanoma, cutaneous metastasis of melanoma, Spitz/Reed nevi, and basal cell carcinoma. We sought to investigate global and local dermatoscopic patterns of blue nevi compared with melanomas and basal cell carcinomas. We retrospectively analyzed global and local features in 95 dermatoscopic images of blue nevi and in 190 melanomas and basal cell carcinomas that were selected as control lesions on the basis of similar pigmentation. Lesion pigmentation was classified as monochromatic, dichromatic, or multichromatic. A global pattern characterized by homogeneous pigmentation was observed in all of 95 (100%) blue nevi. Eighty of 95 (84.2%) blue nevi presented a homogeneous pattern consisting of one color (blue, black, or brown) or two colors (blue-brown, blue-gray, or blue-black). Fifteen of 95 (15.8%) blue nevi had a multichromatic (blue, gray, black, brown, and/or red) pigmentation. In all, 47 of 95 (49.5%) blue nevi were characterized by pigmentation in the absence of pigment network or any other local dermatoscopic features. And 48 of 95 (50.5%) blue nevi showed local dermatoscopic patterns including whitish scarlike depigmentation, dots/globules, vascular pattern, streaks, and networklike pattern. The study was retrospective and involved only Caucasian people of Italian origin. The characteristic feature of blue nevi is a homogeneous pigmentation that is blue, blue-gray, blue-brown, or blue-black. We showed that a wide spectrum of local dermatoscopic features (whitish scarlike depigmentation, dots/globules, peripheral streaks or vessels) may also be present. In such cases, clinical and dermatoscopic distinction from melanoma or nonmelanocytic lesions may be difficult or impossible, and surgical excision is necessary. Copyright © 2011 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

Connect the Dots and Pinhole Constellations.

ERIC Educational Resources Information Center

Kominski, John

1991-01-01

Identifies a variety of methods to introduce constellations and asterisms to students in the classroom and planetarium prior to their study of the night sky. Materials used include transparencies, oatmeal boxes, photographic slides, and tracing paper. Exercises incorporate storytelling and prediction of location, movement, and seasonal patterns of…

Associating LIPS and SWOLLEN: delayed attentional disengagement following words in sex contexts.

PubMed

Oosterwijk, Suzanne; van der Leij, Andries R; Rotteveel, Mark

2017-09-01

With a series of three studies, using an adapted dot-probe paradigm, we investigated the elicitation of spontaneous affective meaning. Although it is well established that humans show delays in disengaging their attention from conventional affective stimuli, it is unknown whether contextually acquired affective meaning similarly impacts attention. We examined attentional disengagement following pairs of neutral or slightly ambiguous words that in combination could evoke sex, violence or neutral associations. Study 1 demonstrated slower disengagement following words that conveyed sex or violence associations compared to words that conveyed neutral associations. This pattern was only present for participants who were aware of sex or violence associations. Study 2 replicated these results in a large sample, but only for sex associations. Study 3 replicated the effect while instructing participants explicitly to expect sex and violence associations. Finally, two control studies countered reasonable alternative explanations for our findings. Together, these studies show that contextually driven affective associations can arise quickly with the potential to influence attentional processes. These findings are consistent with theoretical models of emotion and language that highlight the importance of context in the generation of affective meaning.

On the nature of biomaterials.

PubMed

Williams, David F

2009-10-01

The situations in which biomaterials are currently used are vastly different to those of just a decade ago. Although implantable medical devices are still immensely important, medical technologies now encompass a range of drug and gene delivery systems, tissue engineering and cell therapies, organ printing and cell patterning, nanotechnology based imaging and diagnostic systems and microelectronic devices. These technologies still encompass metals, ceramics and synthetic polymers, but also biopolymers, self assembled systems, nanoparticles, carbon nanotubes and quantum dots. These changes imply that our original concepts of biomaterials and our expectations of their performance also have to change. This Leading Opinion Paper addresses these issues. It concludes that many substances which hitherto we may not have thought of as biomaterials should now be considered as such so that, alongside the traditional structural biomaterials, we have substances that have been engineered to perform functions within health care where their performance is directly controlled by interactions with tissues and tissue components. These include engineered tissues, cells, organs and even viruses. This essay develops the arguments for a radically different definition of a biomaterial.

Design optimization of a smooth headlamp reflector to SAE/DOT beam-shape requirements

NASA Astrophysics Data System (ADS)

Shatz, Narkis E.; Bortz, John C.; Dassanayake, Mahendra S.

1999-10-01

The optical design of Ford Motor Company's 1992 Mercury Grand Marquis headlamp utilized a Sylvania 9007 filament source, a paraboloidal reflector and an array of cylindrical lenses (flutes). It has been of interest to Ford to determine the practicality of closely reproducing the on- road beam pattern performance of this headlamp, with an alternate optical arrangement whereby the control of the beam would be achieved solely by means of the geometry of the surface of the reflector, subject to a requirement of smooth-surface continuity; replacing the outer lens with a clear plastic cover having no beam-forming function. To this end the far-field intensity distribution produced by the 9007 bulb was measured at the low-beam setting. These measurements were then used to develop a light-source model for use in ray tracing simulations of candidate reflector geometries. An objective function was developed to compare candidate beam patterns with the desired beam pattern. Functional forms for the 3D reflector geometry were developed with free parameters to be subsequently optimized. A solution was sought meeting the detailed US SAE/DOT constraints for minimum and maximum permissible levels of illumination in the different portions of the beam pattern. Simulated road scenes were generated by Ford Motor Company to compare the illumination properties of the new design with those of the original Grand Marquis headlamp.

Psychophysical estimation of 3D virtual depth of united, synthesized and mixed type stereograms by means of simultaneous observation

NASA Astrophysics Data System (ADS)

Iizuka, Masayuki; Ookuma, Yoshio; Nakashima, Yoshio; Takamatsu, Mamoru

2007-02-01

Recently, many types of computer-generated stereograms (CGSs), i.e. various works of art produced by using computer are published for hobby and entertainment. It is said that activation of brain, improvement of visual eye sight, decrease of mental stress, effect of healing, etc. are expected when properly appreciating a kind of CGS as the stereoscopic view. There is a lot of information on the internet web site concerning all aspects of stereogram history, science, social organization, various types of stereograms, and free software for generating CGS. Generally, the CGS is classified into nine types: (1) stereo pair type, (2) anaglyph type, (3) repeated pattern type, (4) embedded type, (5) random dot stereogram (RDS), (6) single image stereogram (SIS), (7) united stereogram, (8) synthesized stereogram, and (9) mixed or multiple type stereogram. Each stereogram has advantages and disadvantages when viewing directly the stereogram with two eyes by training with a little patience. In this study, the characteristics of united, synthesized and mixed type stereograms, the role and composition of depth map image (DMI) called hidden image or picture, and the effect of irregular shift of texture pattern image called wall paper are discussed from the viewpoint of psychophysical estimation of 3D virtual depth and visual quality of virtual image by means of simultaneous observation in the case of the parallel viewing method.

Oxygen uptake and local Po2 profiles in submerged larvae of phaeoxantha klugii (Coleoptera: Cicindelidae), as well as their metabolic rate in air.

PubMed

Zerm, M; Zinkler, D; Adis, J

2004-01-01

We studied whether oxygen uptake from the surrounding water might enhance survival in submerged third instar larvae of Phaeoxantha klugii, a tiger beetle from the central Amazonian floodplains. Local oxygen partial pressures (Po(2)) were measured with microcoaxial needle electrodes close to larvae submerged in initially air-saturated still water. The Po(2) profiles showed that the larvae exploit oxygen from the aquatic medium. Metabolism in the air of more or less resting larvae was determined by measuring the rate of CO(2) production (sV dot co2) with an infrared gas analyzer at 29 degrees C. The sV dot co2 was around 1.8 mu L g(-1) min(-1), equivalent to an oxygen consumption rate (sV dot o2) of 1.8-2.6 mu L g(-1) min(-1). Oxygen consumption (V dot o2) of individually submerged larvae measured in closed respiration chambers at 19-10.3 kPa Po(2) (initially air saturated, 29 degrees C) ranged between 0.05 and 0.2 mu L min(-1) and was not correlated with body mass. The sV dot o2 ranged between 0.1 and 0.4 mu L min(-1), that is, 4%-22% of the metabolic rate measured in air. Mean V dot o2 decreased with declining Po(2); however, some individuals showed contrary patterns. V dot o2 was additionally measured in dormant larvae, in larvae submerged for 1-2 d in open water or for 30-49 d within sediment, as well as in larvae exposed to anoxia before the measurements. The range of V dot o2 was similar in all groups, indicating that the larvae exploit oxygen from the water whenever available. Similar V dot o2 across the whole range of body mass investigated (0.31-0.76 g) suggests that oxygen uptake occurs by spiracular uptake. Assuming that larvae survive for some time at rates comparable to depressed metabolic rates reported for other insect species, it can be concluded that oxygen uptake from water can sustain aerobic metabolism even under quite severe hypoxia. It might therefore play an important role for survival during inundation periods.

Effects of Ketamine on Context-Processing Performance in Monkeys: A New Animal Model of Cognitive Deficits in Schizophrenia

PubMed Central

Blackman, Rachael K; MacDonald, Angus W; Chafee, Matthew V

2013-01-01

Cognitive deficits are at the crux of why many schizophrenia patients have poor functional outcomes. One of the cognitive symptoms experienced by schizophrenia patients is a deficit in context processing, the ability to use contextual information stored in working memory to adaptively respond to subsequent stimuli. As such, context processing can be thought of as the intersection between working memory and executive control. Although deficits in context processing have been extensively characterized by neuropsychological testing in schizophrenia patients, they have never been effectively translated to an animal model of the disease. To bridge that gap, we trained monkeys to perform the same dot pattern expectancy (DPX) task, which has been used to measure context-processing deficits in human patients with schizophrenia. In the DPX task, the first stimulus in each trial provides the contextual information that subjects must remember in order to appropriately respond to the second stimulus in the trial. We found that administration of ketamine, an N-methyl-D-aspartate receptor antagonist, in monkeys caused a dose-dependent failure in context processing, replicating in monkeys the same specific pattern of errors committed by patients with schizophrenia when performing the same task. Therefore, our results provide the first evidence that context-processing dysfunction can be modeled in animals. Replicating a schizophrenia-like behavioral performance pattern in monkeys performing the same task used in humans provides a strong bridge to better understand the biological basis for this psychiatric disease and its cognitive manifestations using animal models. PMID:23660706

Magnetic vortex chirality determination via local hysteresis loops measurements with magnetic force microscopy

PubMed Central

Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Manzin, Alessandra; Vinai, Franco; Tiberto, Paola

2016-01-01

Magnetic vortex chirality in patterned square dots has been investigated by means of a field-dependent magnetic force microscopy technique that allows to measure local hysteresis loops. The chirality affects the two loop branches independently, giving rise to curves that have different shapes and symmetries as a function of the details of the magnetisation reversal process in the square dot, that is studied both experimentally and through micromagnetic simulations. The tip-sample interaction is taken into account numerically, and exploited experimentally, to influence the side of the square where nucleation of the vortex preferably occurs, therefore providing a way to both measure and drive chirality with the present technique. PMID:27426442

Magnetic vortex chirality determination via local hysteresis loops measurements with magnetic force microscopy.

PubMed

Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Manzin, Alessandra; Vinai, Franco; Tiberto, Paola

2016-07-18

Magnetic vortex chirality in patterned square dots has been investigated by means of a field-dependent magnetic force microscopy technique that allows to measure local hysteresis loops. The chirality affects the two loop branches independently, giving rise to curves that have different shapes and symmetries as a function of the details of the magnetisation reversal process in the square dot, that is studied both experimentally and through micromagnetic simulations. The tip-sample interaction is taken into account numerically, and exploited experimentally, to influence the side of the square where nucleation of the vortex preferably occurs, therefore providing a way to both measure and drive chirality with the present technique.

Magnetic vortex chirality determination via local hysteresis loops measurements with magnetic force microscopy

NASA Astrophysics Data System (ADS)

Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Manzin, Alessandra; Vinai, Franco; Tiberto, Paola

2016-07-01

Magnetic vortex chirality in patterned square dots has been investigated by means of a field-dependent magnetic force microscopy technique that allows to measure local hysteresis loops. The chirality affects the two loop branches independently, giving rise to curves that have different shapes and symmetries as a function of the details of the magnetisation reversal process in the square dot, that is studied both experimentally and through micromagnetic simulations. The tip-sample interaction is taken into account numerically, and exploited experimentally, to influence the side of the square where nucleation of the vortex preferably occurs, therefore providing a way to both measure and drive chirality with the present technique.

Global Fund-supported programmes contribution to international targets and the Millennium Development Goals: an initial analysis.

PubMed

Komatsu, Ryuichi; Low-Beer, Daniel; Schwartländer, Bernhard

2007-10-01

The Global Fund to Fight AIDS, Tuberculosis and Malaria is one of the largest funders to fight these diseases. This paper discusses the programmatic contribution of Global Fund-supported programmes towards achieving international targets and Millennium Development Goals, using data from Global Fund grants. Results until June 2006 of 333 grants supported by the Global Fund in 127 countries were aggregated and compared against international targets for HIV/AIDS, tuberculosis and malaria. Progress reports to the Global Fund secretariat were used as a basis to calculate results. Service delivery indicators for antiretrovirals (ARV) for HIV/AIDS, case detection under the DOTS strategy for tuberculosis (DOTS) and insecticide-treated nets (ITNs) for malaria prevention were selected to estimate programmatic contributions to international targets for the three diseases. Targets of Global Fund-supported programmes were projected based on proposals for Rounds 1 to 4 and compared to international targets for 2009. Results for Global Fund-supported programmes total 544,000 people on ARV, 1.4 million on DOTS and 11.3 million for ITNs by June 2006. Global Fund-supported programmes contributed 18% of international ARV targets, 29% of DOTS targets and 9% of ITNs in sub-Saharan Africa by mid-2006. Existing Global Fund-supported programmes have agreed targets that are projected to account for 19% of the international target for ARV delivery expected for 2009, 28% of the international target for DOTS and 84% of ITN targets in sub-Saharan Africa. Global Fund-supported programmes have already contributed substantially to international targets by mid-2006, but there is a still significant gap. Considerably greater financial support is needed, particularly for HIV, in order to achieve international targets for 2009.

An international marine-atmospheric {sup 222}Rn measurement intercomparison in Bermuda. Part 2: Results for the participating laboratories

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

Colle, R.; Unterweger, M.P.; Hutchinson, J.M.R.

1996-01-01

As part of an international measurement intercomparison of instruments used to measure atmospheric {sup 222}Rn, four participating laboratories made nearly simultaneous measurements of {sup 222}Rn activity concentration in commonly sampled, ambient air over approximately a 2 week period, and three of these four laboratories participated in the measurement comparison of 14 introduced samples with known, but undisclosed (blind) {sup 222}Rn activity concentration. The exercise was conducted in Bermuda in October 1991. The {sup 222}Rn activity concentrations in ambient Bermudian air over the course of the intercomparison ranged from a few hundredths of a Bq {center_dot} m{sup {minus}3} to about 2more » Bq {center_dot} m{sup {minus}3}, while the standardized sample additions covered a range from approximately 2.5 Bq {center_dot} m{sup {minus}3} to 35 Bq {center_dot} m{sup {minus}3}. The overall uncertainty in the latter concentrations was in the general range of 10%, approximating a 3 standard deviation uncertainty interval. The results of the intercomparison indicated that two of the laboratories were within very good agreement with the standard additions, and almost within expected statistical variations. These same two laboratories, however, at lower ambient concentrations, exhibited a systematic difference with an averaged offset of roughly 0.3 Bq {center_dot} m{sup {minus}3}. The third laboratory participating in the measurement of standardized sample additions was systematically low by about 65% to 70%, with respect to the standard addition which was also confirmed in their ambient air concentration measurements. The fourth laboratory, participating in only the ambient measurement part of the intercomparison, was also systematically low by at least 40% with respect to the first two laboratories.« less

Visible diffraction from quasi-crystalline arrays of carbon nanotubes

NASA Astrophysics Data System (ADS)

Butler, Timothy P.; Butt, Haider; Wilkinson, Timothy D.; Amaratunga, Gehan A. J.

2015-08-01

Large area arrays of vertically-aligned carbon nanotubes (VACNTs) are patterned in a quasi-crystalline Penrose tile arrangement through electron beam lithography definition of Ni catalyst dots and subsequent nanotube growth by plasma-enhanced chemical vapour deposition. When illuminated with a 532 nm laser beam high-quality and remarkable diffraction patterns are seen. The diffraction is well matched to theoretical calculations which assume apertures to be present at the location of the VACNTs for transmitted light. The results show that VACNTs act as diffractive elements in reflection and can be used as spatially phased arrays for producing tailored diffraction patterns.

Enhanced Sensitivity of a Surface Acoustic Wave Gyroscope

NASA Astrophysics Data System (ADS)

Zhang, Yanhua; Wang, Wen

2009-10-01

In this paper, we present an optimal design and performance evaluation of a surface acoustic wave (SAW) gyroscope. It consists of a two-port SAW resonator (SAWR) and a SAW sensor (SAWS) structured using a delay line pattern. The SAW resonator provides a stable reference vibration and creates a standing wave, and the vibrating metallic dot array at antinodes of the standing wave induces the second SAW in the normal direction by the Coriolis force, and the SAW sensor is used to detect the secondary SAW. By using the coupling of modes (COM), the SAW resonator was simulated, and the effects of the design parameters on the frequency response of the device were investigated. Also, a theoretical analysis was performed to investigate the effect of metallic dots on the frequency response of the SAW device. The measured frequency response S21 of the fabricated 80 MHz two-port SAW resonator agrees well with the simulated result, that is, a low insertion loss (˜5 dB) and a single steep resonance peak were observed. In the gyroscopic experiments using a rate table, optimal metallic dot thickness was determined, and the sensitivity of the fabricated SAW gyroscope with an optimal metallic dot thickness of ˜350 nm was determined to be 3.2 µV deg-1 s-1.

Validation of a novel attentional bias modification task: the future may be in the cards.

PubMed

Notebaert, Lies; Clarke, Patrick J F; Grafton, Ben; MacLeod, Colin

2015-02-01

Attentional bias modification (ABM) is a promising therapeutic tool aimed at changing patterns of attentional selectivity associated with heightened anxiety. A number of studies have successfully implemented ABM using the modified dot-probe task. However others have not achieved the attentional change required to achieve emotional benefits, highlighting the need for new ABM methods. The current study compared the effectiveness of a newly developed ABM task against the traditional dot-probe ABM task. The new person-identity-matching (PIM) task presented participants with virtual cards, each depicting a happy and angry person. The task encourages selective attention toward or away from threat by requiring participants to make matching judgements between two cards, based either on the identities of the happy faces, or of the angry faces. Change in attentional bias achieved by both ABM tasks was measured by a dot-probe assessment task. Their impact on emotional vulnerability was assessed by measuring negative emotional reactions to a video stressor. The PIM task succeeded in modifying attentional bias, and exerting an impact on emotional reactivity, whereas this was not the case for the dot-probe task. These results are considered in relation to the potential clinical utility of the current task in comparison to traditional ABM methodologies. Copyright © 2014 Elsevier Ltd. All rights reserved.

The excited spin-triplet state of a charged exciton in quantum dots.

PubMed

Molas, M R; Nicolet, A A L; Piętka, B; Babiński, A; Potemski, M

2016-09-14

We report on spectroscopic studies of resonances related to ladder of states of a charged exciton in single GaAlAs/AlAs quantum dot structures. Polarization-resolved photoluminescence, photoluminescence excitation and photon-correlation measurements were performed at low (T  =  4.2 K) temperature also in magnetic field applied in Faraday configuration. The investigated resonances are assigned to three different configurations of a positively charged exciton. Together with a singlet ground state and a conventional triplet state (involving an electron from the ground state electronic s-shell), an excited triplet state, which involved an electron from the excited electronic p-shell was identified in single dots. The appearance of an emission line related to the latter complex is due to a partially suppressed electron relaxation in the investigated dots. An analysis of this emission line allows us to scrupulously determine properties of the excited triplet state and compare them with those of the conventional triplet state. Both triplets exhibit similar patterns of anisotropic fine structure and Zeeman splitting, however their amplitudes significantly differ for those two states. Presented results emphasize the role of the symmetry of the electronic state on the properties of the triplet states of two holes  +  electron excitonic complex.

Attentional Patterns Involved in Coping Strategies in a Sport Context

ERIC Educational Resources Information Center

Bardel, Marie-Heloise; Woodman, Tim; Colombel, Fabienne; Le Scanff, Christine

2012-01-01

We investigated the relationship between coping strategies and attentional bias after a sport competition. We administered the Ways of Coping Checklist (Paulhan, Nuissier, Quintard, Cousson, & Bourgeois, 1994) to 145 athletes immediately after they had participated in a sport competition. We also assessed attentional bias using a dot probe…

Marijuana and driver behaviors : historic and social observations among fatal accident operators and a control sample

DOT National Transportation Integrated Search

1976-05-01

The final report, Part III for DOT HS-310-3-595 is an analysis and evaluation of the data from 1068 motor vehicle operators in the greater Boston area with a focal interest in marijuana use patterns and corresponding demographic, psychosocial, alcoho...

Tidal Love numbers of neutron and self-bound quark stars

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

Postnikov, Sergey; Prakash, Madappa; Lattimer, James M.

Gravitational waves from the final stages of inspiraling binary neutron stars are expected to be one of the most important sources for ground-based gravitational wave detectors. The masses of the components are determinable from the orbital and chirp frequencies during the early part of the evolution, and large finite-size (tidal) effects are measurable toward the end of inspiral, but the gravitational wave signal is expected to be very complex at this time. Tidal effects during the early part of the evolution will form a very small correction, but during this phase the signal is relatively clean. The accumulated phase shiftmore » due to tidal corrections is characterized by a single quantity related to a star's tidal Love number. The Love number is sensitive, in particular, to the compactness parameter M/R and the star's internal structure, and its determination could provide an important constraint to the neutron star radius. We show that Love numbers of self-bound strange quark matter stars are qualitatively different from those of normal neutron stars. Observations of the tidal signature from coalescing compact binaries could therefore provide an important, and possibly unique, way to distinguish self-bound strange quark stars from normal neutron stars. Tidal signatures from self-bound strange quark stars with masses smaller than 1M{sub {center_dot}}are substantially smaller than those of normal stars owing to their smaller radii. Thus tidal signatures of stars less massive than 1M{sub {center_dot}}are probably not detectable with Advanced LIGO. For stars with masses in the range 1-2M{sub {center_dot},} the anticipated efficiency of the proposed Einstein telescope would be required for the detection of tidal signatures.« less

Patterning and templating for nanoelectronics.

PubMed

Galatsis, Kosmas; Wang, Kang L; Ozkan, Mihri; Ozkan, Cengiz S; Huang, Yu; Chang, Jane P; Monbouquette, Harold G; Chen, Yong; Nealey, Paul; Botros, Youssry

2010-02-09

The semiconductor industry will soon be launching 32 nm complementary metal oxide semiconductor (CMOS) technology node using 193 nm lithography patterning technology to fabricate microprocessors with more than 2 billion transistors. To ensure the survival of Moore's law, alternative patterning techniques that offer advantages beyond conventional top-down patterning are aggressively being explored. It is evident that most alternative patterning techniques may not offer compelling advantages to succeed conventional top-down lithography for silicon integrated circuits, but alternative approaches may well indeed offer functional advantages in realising next-generation information processing nanoarchitectures such as those based on cellular, bioinsipired, magnetic dot logic, and crossbar schemes. This paper highlights and evaluates some patterning methods from the Center on Functional Engineered Nano Architectonics in Los Angeles and discusses key benchmarking criteria with respect to CMOS scaling.

Connecting the dots: Illusory pattern perception predicts belief in conspiracies and the supernatural

PubMed Central

Douglas, Karen M.; De Inocencio, Clara

2017-01-01

Abstract A common assumption is that belief in conspiracy theories and supernatural phenomena are grounded in illusory pattern perception. In the present research we systematically tested this assumption. Study 1 revealed that such irrational beliefs are related to perceiving patterns in randomly generated coin toss outcomes. In Study 2, pattern search instructions exerted an indirect effect on irrational beliefs through pattern perception. Study 3 revealed that perceiving patterns in chaotic but not in structured paintings predicted irrational beliefs. In Study 4, we found that agreement with texts supporting paranormal phenomena or conspiracy theories predicted pattern perception. In Study 5, we manipulated belief in a specific conspiracy theory. This manipulation influenced the extent to which people perceive patterns in world events, which in turn predicted unrelated irrational beliefs. We conclude that illusory pattern perception is a central cognitive mechanism accounting for conspiracy theories and supernatural beliefs. PMID:29695889

Connecting the dots: Illusory pattern perception predicts belief in conspiracies and the supernatural.

PubMed

van Prooijen, Jan-Willem; Douglas, Karen M; De Inocencio, Clara

2018-04-01

A common assumption is that belief in conspiracy theories and supernatural phenomena are grounded in illusory pattern perception. In the present research we systematically tested this assumption. Study 1 revealed that such irrational beliefs are related to perceiving patterns in randomly generated coin toss outcomes. In Study 2, pattern search instructions exerted an indirect effect on irrational beliefs through pattern perception. Study 3 revealed that perceiving patterns in chaotic but not in structured paintings predicted irrational beliefs. In Study 4, we found that agreement with texts supporting paranormal phenomena or conspiracy theories predicted pattern perception. In Study 5, we manipulated belief in a specific conspiracy theory. This manipulation influenced the extent to which people perceive patterns in world events, which in turn predicted unrelated irrational beliefs. We conclude that illusory pattern perception is a central cognitive mechanism accounting for conspiracy theories and supernatural beliefs.

All Ultra-High Vacuum In-Situ Growth & Processing Approaches to Realization of Semiconductor Nanostructure Arrays

DTIC Science & Technology

1997-05-15

Quantum Box/Dot, Strained Epitaxy , 3D islands, Patterned Substrates, Molecular Beam Epitaxy Focused Ion Beam , In-Situ Processing, Quantum Box Lasers...Grown on Planar and Patterned GaAs(100) Substrates by Molecular Beam Epitaxy ", J. Vac. Sei. Technol. B13, 642(1995) 5. A. Madhukar, P. Chen, Q. Xie...Formation and Vertical Self-Organization on GaAs(lOO) via Molecular Beam Epitaxy ", Paper presented at MRS Spring 󈨣 Meeting (Apr. 17-21, 1995, San

Growth of high-aspect ratio horizontally-aligned ZnO nanowire arrays.

PubMed

Soman, Pranav; Darnell, Max; Feldman, Marc D; Chen, Shaochen

2011-08-01

A method of fabricating horizontally-aligned zinc-oxide (ZnO) nanowire (NW) arrays with full control over the width and length is demonstrated. SEM images reveal the hexagonal structure typical of zinc oxide NWs. Arrays of high-aspect ratio horizontal ZnO NWs are fabricated by making use of the lateral overgrowth from dot patterns created by electron beam lithography (EBL). An array of patterned wires are lifted off and transferred to a flexible PDMS substrate with possible applications in several key nanotechnology areas.

Electric field controlled spin interference in a system with Rashba spin-orbit coupling

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

Ciftja, Orion, E-mail: ogciftja@pvamu.edu

There have been intense research efforts over the last years focused on understanding the Rashba spin-orbit coupling effect from the perspective of possible spintronics applications. An important component of this line of research is aimed at control and manipulation of electron’s spin degrees of freedom in semiconductor quantum dot devices. A promising way to achieve this goal is to make use of the tunable Rashba effect that relies on the spin-orbit interaction in a two-dimensional electron system embedded in a host semiconducting material that lacks inversion-symmetry. This way, the Rashba spin-orbit coupling effect may potentially lead to fabrication of amore » new generation of spintronic devices where control of spin, thus magnetic properties, is achieved via an electric field and not a magnetic field. In this work we investigate theoretically the electron’s spin interference and accumulation process in a Rashba spin-orbit coupled system consisting of a pair of two-dimensional semiconductor quantum dots connected to each other via two conducting semi-circular channels. The strength of the confinement energy on the quantum dots is tuned by gate potentials that allow “leakage” of electrons from one dot to another. While going through the conducting channels, the electrons are spin-orbit coupled to a microscopically generated electric field applied perpendicular to the two-dimensional system. We show that interference of spin wave functions of electrons travelling through the two channels gives rise to interference/conductance patterns that lead to the observation of the geometric Berry’s phase. Achieving a predictable and measurable observation of Berry’s phase allows one to control the spin dynamics of the electrons. It is demonstrated that this system allows use of a microscopically generated electric field to control Berry’s phase, thus, enables one to tune the spin-dependent interference pattern and spintronic properties with no need for injection of spin-polarized electrons.« less

Mutations in Genes Involved in the Flagellar Export Apparatus of the Solvent-Tolerant Pseudomonas putida DOT-T1E Strain Impair Motility and Lead to Hypersensitivity to Toluene Shocks

PubMed Central

Segura, Ana; Duque, Estrella; Hurtado, Ana; Ramos, Juan L.

2001-01-01

Pseudomonas putida DOT-T1E is a solvent-tolerant strain able to grow in the presence of 1% (vol/vol) toluene in the culture medium. Random mutagenesis with mini-Tn5-′phoA-Km allowed us to isolate a mutant strain (DOT-T1E-42) that formed blue colonies on Luria-Bertani medium supplemented with 5-bromo-4-chloro-3-indolylphosphate and that, in contrast to the wild-type strain, was unable to tolerate toluene shocks (0.3%, vol/vol). The mutant strain exhibited patterns of tolerance or sensitivity to a number of antibiotics, detergents, and chelating agents similar to those of the wild-type strain. The mutation in this strain therefore seemed to specifically affect toluene tolerance. Cloning and sequencing of the mutation revealed that the mini-Tn5-′phoA-Km was inserted within the fliP gene, which is part of the fliLMNOPQRflhBA cluster, a set of genes that encode flagellar structure components. FliP is involved in the export of flagellar proteins, and in fact, the P. putida fliP mutant was nonmotile. The finding that, after replacing the mutant allele with the wild-type one, the strain recovered the wild-type pattern of toluene tolerance and motility unequivocally assigned FliP a function in solvent resistance. An flhB knockout mutant, another gene component of the flagellar export apparatus, was also nonmotile and hypersensitive to toluene. In contrast, a nonpolar mutation at the fliL gene, which encodes a cytoplasmic membrane protein associated with the flagellar basal body, yielded a nonmotile yet toluene-resistant strain. The results are discussed regarding a possible role of the flagellar export apparatus in the transport of one or more proteins necessary for toluene tolerance in P. putida DOT-T1E to the periplasm. PMID:11418551

Nanoscale patterning of Si surface using SPM scratching

NASA Astrophysics Data System (ADS)

Ogino, T.; Nishimura, S.; Shirakashi, J.

2008-03-01

Nanolithography of Si surface using scanning probe microscopy (SPM) scratching with a diamond-coated tip was systematically investigated at a low force regime below 9 μN. The groove patterns with controlled width and depth could be achieved by adjusting the applied force, scan direction and the number of scan cycles. There was no effect of scan speed on the groove size. The minimum groove width of 10 nm was obtained on Si surfaces. Furthermore, more complex nanostructures such as line and space patterns of 30 nm pith and dot arrays of 2.6×1010 cm-2 density were realized. SPM scratching with a diamond-coated tip allows nanoscale patterning of Si surfaces to be performed simply.

A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

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

Ochoukov, R.; Bobkov, V.; Faugel, H.

2015-11-15

A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k{sub //}) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performedmore » on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k{sub tor}). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k{sub //} as strap phasing is moved away from the dipole configuration. This result is the opposite of the k{sub tor} trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k{sub //}, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas’ operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.« less

Adaptive wettability-enhanced surfaces ordered on molded etched substrates using shrink film

NASA Astrophysics Data System (ADS)

Jayadev, Shreshta; Pegan, Jonathan; Dyer, David; McLane, Jolie; Lim, Jessica; Khine, Michelle

2013-01-01

Superhydrophobic surfaces in nature exhibit desirable properties including self-cleaning, bacterial resistance, and flight efficiency. However, creating such intricate multi-scale features with conventional fabrication approaches is difficult, expensive, and not scalable. By patterning photoresist on pre-stressed shrink-wrap film, which contracts by 95% in surface area when heated, such features over large areas can be obtained easily. Photoresist serves as a dry etch mask to create complex and high-aspect ratio microstructures in the film. Using a double-shrink process, we introduce adaptive wettability-enhanced surfaces ordered on molded etched (AWESOME) substrates. We first create a mask out of the children’s toy ‘Shrinky-Dinks’ by printing dots using a laserjet printer. Heating this thermoplastic sheet causes the printed dots to shrink to a fraction of their original size. We then lithographically transfer the inverse pattern onto photoresist-coated shrink-wrap polyolefin film. The film is then plasma etched. After shrinking, the film serves as a high-aspect ratio mold for polydimethylsiloxane, creating a superhydrophobic surface with water contact angles >150° and sliding angles <10°. We pattern a microarray of ‘sticky’ spots with a dramatically different sliding angle compared to that of the superhydrophobic region, enabling microtiter-plate type assays without the need for a well plate.

Search for Proton Decay via p{yields}e{sup +}{pi}{sup 0} and p{yields}{mu}{sup +}{pi}{sup 0} in a Large Water Cherenkov Detector

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

Nishino, H.; Hazama, S.; Higuchi, I.

2009-04-10

We have searched for proton decays via p{yields}e{sup +}{pi}{sup 0} and p{yields}{mu}{sup +}{pi}{sup 0} using data from a 91.7 kt{center_dot}yr exposure of Super-Kamiokande-I and a 49.2 kt{center_dot}yr exposure of Super-Kamiokande-II. No candidate events were observed with expected backgrounds induced by atmospheric neutrinos of 0.3 events for each decay mode. From these results, we set lower limits on the partial lifetime of 8.2x10{sup 33} and 6.6x10{sup 33} years at 90% confidence level for p{yields}e{sup +}{pi}{sup 0} and p{yields}{mu}{sup +}{pi}{sup 0} modes, respectively.

Quantifying Human Response: Linking metrological and psychometric characterisations of Man as a Measurement Instrument

NASA Astrophysics Data System (ADS)

Pendrill, L. R.; Fisher, William P., Jr.

2013-09-01

A better understanding of how to characterise human response is essential to improved person-centred care and other situations where human factors are crucial. Challenges to introducing classical metrological concepts such as measurement uncertainty and traceability when characterising Man as a Measurement Instrument include the failure of many statistical tools when applied to ordinal measurement scales and a lack of metrological references in, for instance, healthcare. The present work attempts to link metrological and psychometric (Rasch) characterisation of Man as a Measurement Instrument in a study of elementary tasks, such as counting dots, where one knows independently the expected value because the measurement object (collection of dots) is prepared in advance. The analysis is compared and contrasted with recent approaches to this problem by others, for instance using signal error fidelity.

Transparent sunlight conversion film based on carboxymethyl cellulose and carbon dots.

PubMed

You, Yaqin; Zhang, Haoran; Liu, Yingliang; Lei, Bingfu

2016-10-20

Transparent sunlight conversion film based on carboxymethyl cellulose (CMC) and carbon dots (CDs) has been developed for the first time through dispersion of CDs in CMC aqueous solution. Due to the hydrogen bonds interaction, CMC can effectively absorb the CDs, whose surfaces are functionalized by lots of polar groups. The results from atomic force microscopy (AFM), scanning electron microscopy (SEM) confirm that the composite film possesses a homogeneous and compact structure. Besides, the CMC matrix neither competes for absorbing excitation light nor absorbs the emissions of CDs, which reserves the inherent optical properties of the individual CDs. The composite films can efficiently convert ultraviolet light to blue light. What's more, the film is transparent and possesses excellent mechanical properties, expected to apply in the field of agricultural planting for sunlight conversion. Copyright © 2016 Elsevier Ltd. All rights reserved.

CdTe/CdS-MPA quantum dots as fluorescent probes to label yeast cells: synthesis, characterization and conjugation with Concanavalin A

NASA Astrophysics Data System (ADS)

Kato, Ilka T.; Santos, Camila C.; Benetti, Endi; Tenório, Denise P. L. A.; Cabral Filho, Paulo E.; Sabino, Caetano P.; Fontes, Adriana; Santos, Beate S.; Prates, Renato A.; Ribeiro, Martha S.

2012-03-01

Candida albicans is the most frequent human opportunistic pathogenic fungus and one of the most important causes of nosocomial infections. In fact, diagnosis of invasive candidiasis presents unique problems. The aim of this work was to evaluate, by fluorescence image analysis, cellular labeling of C. albicans with CdTe/CdS quantum dots conjugated or not to concanavalin A (ConA). Yeast cells were incubated with CdTe/CdS quantum dots (QD) stabilized with mercaptopropionic acid (MPA) (emission peak at 530 nm) for 1 hour. In the overall study we observed no morphological alterations. The fluorescence microscopic analysis of the yeast cells showed that the non-functionalized QDs do not label C. albicans cells, while for the QD conjugated to ConA the cells showed a fluorescence profile indicating that the membrane was preferentially marked. This profile was expected since Concanavalin A is a protein that binds specifically to terminal carbohydrate residues at the membrane cell surface. The results suggest that the QD-labeled Candida cells represent a promising tool to open new possibilities for a precise evaluation of fungal infections in pathological conditions.

Prospects for star formation studies with infrared instruments (TIRCAM2 and TANSPEC) on the 3.6-m Devasthal Optical Telescope

NASA Astrophysics Data System (ADS)

Ojha, Devendra; Ghosh, Swarna Kanti; Sharma, Saurabh; Pandey, Anil Kumar; Baug, Tapas; Ninan, Joe Philip; Kumar, Brijesh; Puravankara, Manoj; D'Costa, Savio; Naik, Milind; Poojari, Satheesha; Bhagat, Shailesh; Jadhav, Rajesh; Meshram, Ganesh; Sandimani, Pradeep; Gharat, Sanjay; Bakalkar, Chandrakant

2018-04-01

We present a brief description of the activities of the infrared astronomy group of Tata Institute of Fundamental Research with special emphasis on the ground-based near infrared instrumentation for star formation studies. We describe the unique capability of TIRCAM2 for observations in the polycyclic aromatic hydrocarbon (λcen˜3.3 μm) and narrow-band L (λcen˜3.59 μm) bands, currently being used by the astronomy community, and of the upcoming TANSPEC, which is being built for India's largest telescope, i.e. the 3.6-m Devasthal Optical Telescope (DOT). The TIRCAM2 on the 3.6-m DOT was successfully commissioned in June 2016, and the subsequent characterization and astronomical observations are presented here. Based on the successful engineering runs on the 3.6-m DOT, TIRCAM2 has been made available to the Indian and Belgian astronomical community for science observations since Early Science Cycle 2017A (May 2017) onwards. The fabrication of TANSPEC is in an advanced stage and the spectrometer is expected to be commissioned by the end of January 2018.

Chiral quantum dot based materials

NASA Astrophysics Data System (ADS)

Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii

2014-05-01

Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.

Electron-Phonon Coupling and Resonant Relaxation from 1D and 1P States in PbS Quantum Dots.

PubMed

Kennehan, Eric R; Doucette, Grayson S; Marshall, Ashley R; Grieco, Christopher; Munson, Kyle T; Beard, Matthew C; Asbury, John B

2018-05-31

Observations of the hot-phonon bottleneck, which is predicted to slow the rate of hot carrier cooling in quantum confined nanocrystals, have been limited to date for reasons that are not fully understood. We used time-resolved infrared spectroscopy to directly measure higher energy intraband transitions in PbS colloidal quantum dots. Direct measurements of these intraband transitions permitted detailed analysis of the electronic overlap of the quantum confined states that may influence their relaxation processes. In smaller PbS nanocrystals, where the hot-phonon bottleneck is expected to be most pronounced, we found that relaxation of parity selection rules combined with stronger electron-phonon coupling led to greater spectral overlap of transitions among the quantum confined states. This created pathways for fast energy transfer and relaxation that may bypass the predicted hot-phonon bottleneck. In contrast, larger, but still quantum confined nanocrystals did not exhibit such relaxation of the parity selection rules and possessed narrower intraband states. These observations were consistent with slower relaxation dynamics that have been measured in larger quantum confined systems. These findings indicated that, at small radii, electron-phonon interactions overcome the advantageous increase in energetic separation of the electronic states for PbS quantum dots. Selection of appropriately sized quantum dots, which minimize spectral broadening due to electron-phonon interactions while maximizing electronic state separation, is necessary to observe the hot-phonon bottleneck. Such optimization may provide a framework for achieving efficient hot carrier collection and multiple exciton generation.

Synthesis and Characterization of Chalcopyrite (CuInS2 and CuhInSe2) Colloidal Nanoparticles for Optoelectronic Applications via Low-Temperature Pyrolysis of Single-Source Precursors

NASA Technical Reports Server (NTRS)

Castro, S. L.; Bailey, S. G.; Raffaelle, R. P.; Banger, K. K.; Fahey, Stephen; Hepp, A. F.

2003-01-01

Nanocrystalline (or quantum dot) materials hold potential as components of next-generation photovoltaic (PV) devices. The inclusion of quantum dots in PV devices has been proposed as a means to improve the efficiency of photon conversion (quantum dot solar cell), enable low-cost deposition of thin-films, provide sites for exciton dissociation, and pathways for electron transport. Quantum dots are also expected to be more resistant to degradation from electron, proton, and alpha particle radiation than the corresponding bulk material, a requirement for use in space solar sells. Chalcopyrite nanocrystals can be produced by low-temperature thermal decomposition of single-source precursors such as (PR3)2CuIn(ER')4 (R = Ph, R' = Et, E = S; R = R' = Ph, E = Se). Single-source precursors are molecules which contain all the necessary elements for synthesis of a desired material. Thermal decomposition of the precursor results in the formation of material with the correct stoichiometry as a nanocrystalline powder or a thin film, often at significantly lower temperatures than those typically employed for thin-film deposition by multi-source evaporation techniques, typically less than 500 C. We show that CuInSz and CuInSe2 nanocrystals can be synthesized from the precursors at temperatures as low as 250 C. The nanocrystals are characterized by optical spectroscopy, X-ray diffraction, and electron microscopy.

Marijuana and Cocaine Effect Expectancies and Drug Use Patterns.

ERIC Educational Resources Information Center

Schafer, John; Brown, Sandra A.

1991-01-01

Content analyzed self-reports from 704 college students and used results to develop Marijuana Effect Expectancy Questionnaire and Cocaine Effect Expectancy Questionnaire. Identified six marijuana expectancies and five cocaine expectancies. Drug effect expectancies distinguished between patterns of nonuse and varying degrees of use of these two…

Quality issues in blue noise halftoning

NASA Astrophysics Data System (ADS)

Yu, Qing; Parker, Kevin J.

1998-01-01

The blue noise mask (BNM) is a halftone screen that produces unstructured visually pleasing dot patterns. The BNM combines the blue-noise characteristics of error diffusion and the simplicity of ordered dither. A BNM is constructed by designing a set of interdependent binary patterns for individual gray levels. In this paper, we investigate the quality issues in blue-noise binary pattern design and mask generation as well as in application to color reproduction. Using a global filtering technique and a local 'force' process for rearranging black and white pixels, we are able to generate a series of binary patterns, all representing a certain gray level, ranging from white-noise pattern to highly structured pattern. The quality of these individual patterns are studied in terms of low-frequency structure and graininess. Typically, the low-frequency structure (LF) is identified with a measurement of the energy around dc in the spatial frequency domain, while the graininess is quantified by a measurement of the average minimum distance (AMD) between minority dots as well as the kurtosis of the local kurtosis distribution (KLK) for minority pixels of the binary pattern. A set of partial BNMs are generated by using the different patterns as unique starting 'seeds.' In this way, we are able to study the quality of binary patterns over a range of gray levels. We observe that the optimality of a binary pattern for mask generation is related to its own quality mertirc values as well as the transition smoothness of those quality metric values over neighboring levels. Several schemes have been developed to apply blue-noise halftoning to color reproduction. Different schemes generate halftone patterns with different textures. In a previous paper, a human visual system (HVS) model was used to study the color halftone quality in terms of luminance and chrominance error in CIELAB color space. In this paper, a new series of psycho-visual experiments address the 'preferred' color rendering among four different blue noise halftoning schemes. The experimental results will be interpreted with respect to the proposed halftone quality metrics.

Asymmetrical Cortical Processing of Radial Expansioncontraction in Infants and Adults

ERIC Educational Resources Information Center

Shirai, Nobu; Birtles, Deirdre; Wattam-Bell, John; Yamaguchi, Masami K.; Kanazawa, So; Atkinson, Janette; Braddick, Oliver

2009-01-01

We report asymmetrical cortical responses (steady-state visual evoked potentials) to radial expansion and contraction in human infants and adults. Forty-four infants (22 3-month-olds and 22 4-month-olds) and nine adults viewed dynamic dot patterns which cyclically (2.1 Hz) alternate between radial expansion (or contraction) and random directional…

Event-Related fMRI of Category Learning: Differences in Classification and Feedback Networks

ERIC Educational Resources Information Center

Little, Deborah M.; Shin, Silvia S.; Sisco, Shannon M.; Thulborn, Keith R.

2006-01-01

Eighteen healthy young adults underwent event-related (ER) functional magnetic resonance imaging (fMRI) of the brain while performing a visual category learning task. The specific category learning task required subjects to extract the rules that guide classification of quasi-random patterns of dots into categories. Following each classification…

Green route for synthesis of multifunctional fluorescent carbon dots from Tulsi leaves and its application as Cr(VI) sensors, bio-imaging and patterning agents.

PubMed

Bhatt, Shreya; Bhatt, Madhuri; Kumar, Anshu; Vyas, Gaurav; Gajaria, Tejal; Paul, Parimal

2018-07-01

We report a one pot green strategy for the synthesis of carbon dots using tulsi leaves and their potential application in sensing of Cr(VI) selectively. The detection mechanism is based on the phenomenon called inner filter effect (IFE) and a good linear static quenching was observed in the range of 1.6 μM to 50 μM with a detection limit of 4.5 ppb. The reversible switching in fluorescence has been tested and a good recovery in fluorescence was observed up to three consecutive cycles upon addition of ascorbic acid as reducing agent. Also the low toxicity, high fluorescence and photostabilty of the CDs make them excellent imaging and patterning agent. The acid and alkali resistant property of these CDs makes it suitable for real sample analysis. The fluorescent CDs were applied for successful detection of Cr(VI) in water with spike-recoveries ranging from 93 to 99%. Copyright © 2018 Elsevier B.V. All rights reserved.

Large-scale Generation of Patterned Bubble Arrays on Printed Bi-functional Boiling Surfaces

NASA Astrophysics Data System (ADS)

Choi, Chang-Ho; David, Michele; Gao, Zhongwei; Chang, Alvin; Allen, Marshall; Wang, Hailei; Chang, Chih-Hung

2016-04-01

Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface.

CoPt/TiN films nanopatterned by RF plasma etching towards dot-patterned magnetic media

NASA Astrophysics Data System (ADS)

Szívós, János; Pothorszky, Szilárd; Soltys, Jan; Serényi, Miklós; An, Hongyu; Gao, Tenghua; Deák, András; Shi, Ji; Sáfrán, György

2018-03-01

CoPt thin films as possible candidates for Bit Patterned magnetic Media (BPM) were prepared and investigated by electron microscopy techniques and magnetic measurements. The structure and morphology of the Direct Current (DC) sputtered films with N incorporation were revealed in both as-prepared and annealed state. Nanopatterning of the samples was carried out by means of Radio Frequency (RF) plasma etching through a Langmuir-Blodgett film of silica nanospheres that is a fast and high throughput technique. As a result, the samples with hexagonally arranged 100 nm size separated dots of fct-phase CoPt were obtained. The influence of the order of nanopatterning and anneling on the nanostructure formation was revealed. The magnetic properties of the nanopatterned fct CoPt films were investigated by Vibrating Sample Magnetometer (VSM) and Magnetic Force Microscopy (MFM). The results show that CoPt thin film nanopatterned by means of the RF plasma etching technique is promising candidate to a possible realization of BPM. Furthermore, this technique is versatile and suitable for scaling up to technological and industrial applications.

Quantum dot-based microfluidic biosensor for cancer detection

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

Ghrera, Aditya Sharma; School of Engineering and Technology, ITM University, Gurgaon-122017; Pandey, Chandra Mouli

2015-05-11

We report results of the studies relating to fabrication of an impedimetric microfluidic–based nucleic acid sensor for quantification of DNA sequences specific to chronic myelogenous leukemia (CML). The sensor chip is prepared by patterning an indium–tin–oxide (ITO) coated glass substrate via wet chemical etching method followed by sealing with polydimethylsiloxane (PDMS) microchannel for fluid control. The fabricated microfluidic chip comprising of a patterned ITO substrate is modified by depositing cadmium selenide quantum dots (QCdSe) via Langmuir–Blodgett technique. Further, the QCdSe surface has been functionalized with specific DNA probe for CML detection. The probe DNA functionalized QCdSe integrated miniaturized system hasmore » been used to monitor target complementary DNA concentration by measuring the interfacial charge transfer resistance via hybridization. The presence of complementary DNA in buffer solution significantly results in decreased electro-conductivity of the interface due to presence of a charge barrier for transport of the redox probe ions. The microfluidic DNA biosensor exhibits improved linearity in the concentration range of 10{sup −15} M to 10{sup −11} M.« less

Quantum dot nanoprobe-based quantitative analysis for prostate cancer (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kang, Benedict J.; Jang, Gun Hyuk; Park, Sungwook; Lee, Kwan Hyi

2016-09-01

Prostate cancer causes one of the leading cancer-related deaths among the Caucasian adult males in Europe and the United State of America. However, it has a high recovery rate indicating when a proper treatment is delivered to a patient. There are cases of over- or under-treatments which exacerbate the disease states indicating the importance of proper therapeutic approach depending on stage of the disease. Recognition of the unmet needs has raised a need for stratification of the disease. There have been attempts to stratify based on biomarker expression patterns in the course of disease progression. To closely observe the biomarker expression patterns, we propose the use of quantitative imaging method by using fabricated quantum dot-based nanoprobe to quantify biomarker expression on the surface of prostate cancer cells. To characterize the cell line and analyze the biomarker levels, cluster of differentiation 44 (CD 44), prostate specific membrane antigen (PSMA), and epithelial cell adhesion molecule (EpCAM) are used. Each selected biomarker per cell line has been quantified from which we established a signature of biomarkers of a prostate cancer cell line.

Number-specific and general cognitive markers of preschoolers' math ability profiles.

PubMed

Gray, Sarah A; Reeve, Robert A

2016-07-01

Different number-specific and general cognitive markers have been claimed to underlie preschoolers' math ability. It is unclear, however, whether similar/different cognitive markers, or combinations of them, are associated with different patterns of emerging math abilities (i.e., different patterns of strength and weakness). To examine this question, 103 preschoolers (40-60 months of age) completed six math tasks (count sequence, object counting, give a number, naming numbers, ordinal relations, and arithmetic), three number-specific markers of math ability (dot enumeration, magnitude comparison, and spontaneous focusing on numerosity), and four general markers (working memory, response inhibition, attention, and vocabulary). A three-step latent profile modeling procedure identified five math ability profiles that differed in their patterns of math strengths and weaknesses; specifically, the profiles were characterized by (a) excellent math ability on all math tasks, (b) good arithmetic ability, (c) good math ability but relatively poor count sequence recitation ability, (d) average ability on all math tasks, and (e) poor ability on all math tasks. After controlling for age, only dot enumeration and spontaneous focusing on numerosity were associated with the math ability profiles, whereas vocabulary was also marginally significant, and these markers were differentially associated with different profiles; that is, different cognitive markers were associated with different patterns of strengths and weaknesses in math abilities. Findings are discussed in terms of their implications for the development of math cognition. Copyright © 2016 Elsevier Inc. All rights reserved.

Upconversion fluorescence tyrosine doped LaF3:Dy quantum dots useful in biolabeling and biotagging

NASA Astrophysics Data System (ADS)

Singh, Amit T.; Khandpekar, M. M.

2018-04-01

Water soluble hexahedral colloidal quantum dots (QDOTs) of Tyrosine doped LaF3:Dy have been synthesized by wet chemical route. The nanoparticles have been irradiated by microwave during synthesis for drying and also to reduce agglomeration. The coating of the LaF3:Dy nanoparticles by the amino acid tyrosine results in colloidal quantum dots. XRD studies indicates hexagonal lattice and confirms JCPDS data. The average particle size obtained by XRD and SEM are 22.89nm and 25.5nm respectively. The average sizes of nanorods obtained from TEM are 55 nm. The presence of elements has been verified with EDAX and ICP-AES technique. The SAED pattern of the samples shows sharp concentric rings indicating the crystalline nature of the synthesized nanoparticles. The FTIR spectra have been used to study the surface modification of the nanoparticles. The optical studies have been done using UV-visible and PL spectra. The PL spectra showed upconversion nature of the synthesized nanoparticles with sharp emission at 618 nm. The nanoparticles synthesized have potential application as biomaterials in bio imaging and biotagging.

Colloidal quantum dot solar cells exploiting hierarchical structuring.

PubMed

Labelle, André J; Thon, Susanna M; Masala, Silvia; Adachi, Michael M; Dong, Haopeng; Farahani, Maryam; Ip, Alexander H; Fratalocchi, Andrea; Sargent, Edward H

2015-02-11

Extremely thin-absorber solar cells offer low materials utilization and simplified manufacture but require improved means to enhance photon absorption in the active layer. Here, we report enhanced-absorption colloidal quantum dot (CQD) solar cells that feature transfer-stamped solution-processed pyramid-shaped electrodes employed in a hierarchically structured device. The pyramids increase, by up to a factor of 2, the external quantum efficiency of the device at absorption-limited wavelengths near the absorber band edge. We show that absorption enhancement can be optimized with increased pyramid angle with an appreciable net improvement in power conversion efficiency, that is, with the gain in current associated with improved absorption and extraction overcoming the smaller fractional decrease in open-circuit voltage associated with increased junction area. We show that the hierarchical combination of micron-scale structured electrodes with nanoscale films provides for an optimized enhancement at absorption-limited wavelengths. We fabricate 54.7° pyramid-patterned electrodes, conformally apply the quantum dot films, and report pyramid CQD solar cells that exhibit a 24% improvement in overall short-circuit current density with champion devices providing a power conversion efficiency of 9.2%.

Differential computation method used to calibrate the angle-centroid relationship in coaxial reverse Hartmann test

NASA Astrophysics Data System (ADS)

Li, Xinji; Hui, Mei; Zhao, Zhu; Liu, Ming; Dong, Liquan; Kong, Lingqin; Zhao, Yuejin

2018-05-01

A differential computation method is presented to improve the precision of calibration for coaxial reverse Hartmann test (RHT). In the calibration, the accuracy of the distance measurement greatly influences the surface shape test, as demonstrated in the mathematical analyses. However, high-precision absolute distance measurement is difficult in the calibration. Thus, a differential computation method that only requires the relative distance was developed. In the proposed method, a liquid crystal display screen successively displayed two regular dot matrix patterns with different dot spacing. In a special case, images on the detector exhibited similar centroid distributions during the reflector translation. Thus, the critical value of the relative displacement distance and the centroid distributions of the dots on the detector were utilized to establish the relationship between the rays at certain angles and the detector coordinates. Experiments revealed the approximately linear behavior of the centroid variation with the relative displacement distance. With the differential computation method, we increased the precision of traditional calibration 10-5 rad root mean square. The precision of the RHT was increased by approximately 100 nm.

Expression of adhesion molecules and cytokeratin 20 in merkel cell carcinomas.

PubMed

Tanaka, Yasushi; Sano, Toshiaki; Qian, Zhi Rong; Hirokawa, Mitsuyoshi

2004-01-01

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin. MCCs often show characteristic paranuclear dot-like immunopositivity for cytokeratin 20 (CK20), a globular aggregation of CK20 intermediate filaments. These aggregates typically form rhabdoid features and fibrous bodies and may be associated with a down-regulation in adhesion molecules (AMs). To date, the relationship between the expression of AMs and CK20 and clinicopathological findings in MCC has not been well examined. In this immunohistochemical study, we assessed the expression of AMs, CK20, and chromogranin A (CgA) on MCCs in 8 men and 23 women with this disease, and also characterized their clinicopathological features. This study is the largest of its kind that has been undertaken to date in Japanese patients. Compared to normal tissue, E-cadherin and alpha- and beta-catenins showed reduced membranous expression in 95.7%, 46.7%, and 45.2% of MCCs, respectively. Nuclear E-cadherin localization was seen in four tumors, all of which predominantly showed a CK20 dot pattern. However, there was no significant relationship between the membranous expression of AMs and a CK20 dot pattern. E-cadherin expression was significantly lower in tumors of > or =2 cm, and tumors negative for E-cadherin more frequently developed outside of the head and neck than within those regions. CgA was more intensely expressed in tumors with uniform nuclei and a dense lymphocytic infiltrate than in those that showed pleomorphisms and that had few, if any, infiltrating lymphocytes. These findings suggest that MCCs have a reduced expression of AMs and that down-regulation of E-cadherin expression may correlate with increased tumor aggressiveness. The fact that no significant relationship was demonstrable between the membranous expression of AMs and the CK20 expression pattern suggests that the mechanism of aggregation of intermediate filaments may be different in different types of tumors.

Photoluminescence enhancement of silicon quantum dot monolayer by plasmonic substrate fabricated by nano-imprint lithography

NASA Astrophysics Data System (ADS)

Yanagawa, Hiroto; Inoue, Asuka; Sugimoto, Hiroshi; Shioi, Masahiko; Fujii, Minoru

2017-12-01

Near-field coupling between a silicon quantum dot (Si-QD) monolayer and a plasmonic substrate fabricated by nano-imprint lithography and having broad multiple resonances in the near-infrared (NIR) window of biological substances was studied by precisely controlling the QDs-substrate distance. A strong enhancement of the NIR photoluminescence (PL) of Si-QDs was observed. Detailed analyses of the PL and PL excitation spectra, the PL decay dynamics, and the reflectance spectra revealed that both the excitation cross-sections and the emission rates are enhanced by the surface plasmon resonances, thanks to the broad multiple resonances of the plasmonic substrate, and that the relative contribution of the two enhancement processes depends strongly on the excitation wavelength. Under excitation by short wavelength photons (405 nm), where enhancement of the excitation cross-section is not expected, the maximum enhancement was obtained when the QDs-substrate distance was around 30 nm. On the other hand, under long wavelength excitation (641 nm), where strong excitation cross-section enhancement is expected, the largest enhancement was obtained when the distance was minimum (around 1 nm). The achievement of efficient excitation of NIR luminescence of Si-QDs by long wavelength photons paves the way for the development of Si-QD-based fluorescence bio-sensing devices with a high bound-to-free ratio.

Enhanced photovoltaic performance of quantum dot-sensitized solar cells with a progressive reduction of recombination using Cu-doped CdS quantum dots

NASA Astrophysics Data System (ADS)

Muthalif, Mohammed Panthakkal Abdul; Lee, Young-Seok; Sunesh, Chozhidakath Damodharan; Kim, Hee-Je; Choe, Youngson

2017-02-01

In this article, we have systematically probed the effect of Cu-doping in CdS quantum dots (QDs) to enhance the photovoltaic performance of the quantum dot-sensitized solar cells (QDSSCs). The Cu-doped CdS photoanodes were prepared by successive ionic layer adsorption and reaction (SILAR) method and the corresponding cell devices were fabricated using CuS counter electrodes with a polysulfide electrolyte. The photovoltaic performance results demonstrate that 3 mM Cu-doped CdS QDs based QDSSCs exhibit the efficiency (η) of 3% including JSC = 9.40 mA cm-2, VOC = 0.637 V, FF = 0.501, which are higher than those with bare CdS (η = 2.05%, JSC = 7.12 mA cm-2, VOC = 0.588 V, FF = 0.489). The structural, topographical and optical properties of the thin films have been studied with the help of X-ray diffraction pattern (XRD), atomic force microscopy (AFM) and UV-vis spectrophotometer. Electrochemical impedance spectroscopy (EIS) and open circuit voltage decay (OCVD) measurements indicate that Cu-dopant can inhibit the charge recombination at the photoanode/electrolyte interface and extend the lifetime of electrons. These results reveal that incorporation of copper metal in CdS QDs is a simple and effective method to improve the photovoltaic properties of QDSSCs.

A tunable digital ishihara plate for pre-school aged children.

PubMed

Gambino, Orazio; Minafo, Ester; Pirrone, Roberto; Ardizzone, Edoardo

2016-08-01

Colors play a fundamental role for children, both in the everyday life and in education. They recognize the surrounding world, and play games making a large use of colors. They learn letters and numbers by means of colors. As a consequence, early diagnosis of color blindness is an crucial to support an individual affected by this visual perception alteration at the initial phase of his/her life. The diagnosis of red-green color deficiencies (protanopia or deuteranopia) is commonly accomplished by means of the Ishihara test, which consists of plates showing dots with different sizes where some of them compose numbers within a gamut of colors while the ones composing the background have different colors. In this paper, a web application written in javascript is presented, that implements a digital Ishihara-like test for pre-school aged children. Instead numbers or letters, It can transform any binary image representing animal shapes, or any other child-friendly shape, into an Ishihara-like image. This digital plate is not static. The operator can increment the dot density to improve the quality of the shape contour and the entire plate can be redrawn with different dot sizes/colors chosen randomly according to the color pattern of the test. Separate controls for brightness and saturation are implemented to calibrate the chromatic aspect of the background and foreground dots.

Reversal of an ancient sex chromosome to an autosome in Drosophila.

PubMed

Vicoso, Beatriz; Bachtrog, Doris

2013-07-18

Although transitions of sex-determination mechanisms are frequent in species with homomorphic sex chromosomes, heteromorphic sex chromosomes are thought to represent a terminal evolutionary stage owing to chromosome-specific adaptations such as dosage compensation or an accumulation of sex-specific mutations. Here we show that an autosome of Drosophila, the dot chromosome, was ancestrally a differentiated X chromosome. We analyse the whole genome of true fruitflies (Tephritidae), flesh flies (Sarcophagidae) and soldier flies (Stratiomyidae) to show that genes located on the dot chromosome of Drosophila are X-linked in outgroup species, whereas Drosophila X-linked genes are autosomal. We date this chromosomal transition to early drosophilid evolution by sequencing the genome of other Drosophilidae. Our results reveal several puzzling aspects of Drosophila dot chromosome biology to be possible remnants of its former life as a sex chromosome, such as its minor feminizing role in sex determination or its targeting by a chromosome-specific regulatory mechanism. We also show that patterns of biased gene expression of the dot chromosome during early embryogenesis, oogenesis and spermatogenesis resemble that of the current X chromosome. Thus, although sex chromosomes are not necessarily evolutionary end points and can revert back to an autosomal inheritance, the highly specialized genome architecture of this former X chromosome suggests that severe fitness costs must be overcome for such a turnover to occur.

Facile synthesis of CsPbBr3/PbSe composite clusters

PubMed Central

Nguyen, Thang Phan; Ozturk, Abdullah; Park, Jongee; Sohn, Woonbae; Lee, Tae Hyung; Jang, Ho Won; Kim, Soo Young

2018-01-01

Abstract In this work, CsPbBr3 and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr3 quantum dots modified the electronic structure of CsPbBr3, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr3 perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr3 quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr3/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr3/PbSe sample with a 1:1 Cs:Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr3 reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr3 quantum dots. PMID:29296127

Pattern formation based on complex coupling mechanism in dielectric barrier discharge

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

Liu, Weibo; College of Aeronautical Engineering, Binzhou University, Binzhou 256603; Dong, Lifang, E-mail: donglfhbu@163.com, E-mail: pyy1616@163.com

2016-08-15

The pattern formation of cinque-dice square superlattice pattern (CDSSP) is investigated based on the complex coupling mechanism in a dielectric barrier discharge (DBD) system. The spatio-temporal structure of CDSSP obtained by using an intensified-charge coupled device indicates that CDSSP is an interleaving of two kinds of subpatterns (mixture of rectangle and square, and dot-line square) which discharge twice in one half voltage, respectively. Selected by the complex coupling of two subpatterns, the CDSSP can be formed and shows good stability. This investigation based on gas discharge theory together with nonlinear theory may provide a deeper understanding for the nonlinear characteristicsmore » and even the formation mechanism of patterns in DBD.« less

Gold-catalyzed oxide nanopatterns for the directed assembly of Ge island arrays on Si.

PubMed

Robinson, Jeremy T; Ratto, Fulvio; Moutanabbir, Oussama; Heun, Stefan; Locatelli, Andrea; Mentes, T Onur; Aballe, Lucia; Dubon, Oscar D

2007-09-01

The heteroepitaxial growth of Ge on Au-patterned Si(001) is investigated using in situ spectromicroscopy. Patterning of a hydrogen-terminated Si surface with a square array of Au dots followed by brief exposure to air leads to the spontaneous, local oxidation of Si. The resulting oxide nanopattern limits the surface migration of Au during annealing up to 600 degrees C, resulting in complete preservation of the Au pattern. Subsequent deposition of Ge induces a redistribution of Au across the surface even as the oxide nanopattern persists. As a result, the oxide pattern drives the growth of Ge islands into an ordered assembly, while Au decorates the surfaces of the Ge islands and modifies their shape.

Structural Color Patterns by Electrohydrodynamic Jet Printed Photonic Crystals.

PubMed

Ding, Haibo; Zhu, Cun; Tian, Lei; Liu, Cihui; Fu, Guangbin; Shang, Luoran; Gu, Zhongze

2017-04-05

In this work, we demonstrate the fabrication of photonic crystal patterns with controllable morphologies and structural colors utilizing electrohydrodynamic jet (E-jet) printing with colloidal crystal inks. The final shape of photonic crystal units is controlled by the applied voltage signal and wettability of the substrate. Optical properties of the structural color patterns are tuned by the self-assembly of the silica nanoparticle building blocks. Using this direct printing technique, it is feasible to print customized functional patterns composed of photonic crystal dots or photonic crystal lines according to relevant printing mode and predesigned tracks. This is the first report for E-jet printing with colloidal crystal inks. Our results exhibit promising applications in displays, biosensors, and other functional devices.

Ultra-large scale AFM of lipid droplet arrays: investigating the ink transfer volume in dip pen nanolithography.

PubMed

Förste, Alexander; Pfirrmann, Marco; Sachs, Johannes; Gröger, Roland; Walheim, Stefan; Brinkmann, Falko; Hirtz, Michael; Fuchs, Harald; Schimmel, Thomas

2015-05-01

There are only few quantitative studies commenting on the writing process in dip-pen nanolithography with lipids. Lipids are important carrier ink molecules for the delivery of bio-functional patters in bio-nanotechnology. In order to better understand and control the writing process, more information on the transfer of lipid material from the tip to the substrate is needed. The dependence of the transferred ink volume on the dwell time of the tip on the substrate was investigated by topography measurements with an atomic force microscope (AFM) that is characterized by an ultra-large scan range of 800 × 800 μm(2). For this purpose arrays of dots of the phospholipid1,2-dioleoyl-sn-glycero-3-phosphocholine were written onto planar glass substrates and the resulting pattern was imaged by large scan area AFM. Two writing regimes were identified, characterized of either a steady decline or a constant ink volume transfer per dot feature. For the steady state ink transfer, a linear relationship between the dwell time and the dot volume was determined, which is characterized by a flow rate of about 16 femtoliters per second. A dependence of the ink transport from the length of pauses before and in between writing the structures was observed and should be taken into account during pattern design when aiming at best writing homogeneity. The ultra-large scan range of the utilized AFM allowed for a simultaneous study of the entire preparation area of almost 1 mm(2), yielding good statistic results.

Ultra-large scale AFM of lipid droplet arrays: investigating the ink transfer volume in dip pen nanolithography

NASA Astrophysics Data System (ADS)

Förste, Alexander; Pfirrmann, Marco; Sachs, Johannes; Gröger, Roland; Walheim, Stefan; Brinkmann, Falko; Hirtz, Michael; Fuchs, Harald; Schimmel, Thomas

2015-05-01

There are only few quantitative studies commenting on the writing process in dip-pen nanolithography with lipids. Lipids are important carrier ink molecules for the delivery of bio-functional patters in bio-nanotechnology. In order to better understand and control the writing process, more information on the transfer of lipid material from the tip to the substrate is needed. The dependence of the transferred ink volume on the dwell time of the tip on the substrate was investigated by topography measurements with an atomic force microscope (AFM) that is characterized by an ultra-large scan range of 800 × 800 μm2. For this purpose arrays of dots of the phospholipid1,2-dioleoyl-sn-glycero-3-phosphocholine were written onto planar glass substrates and the resulting pattern was imaged by large scan area AFM. Two writing regimes were identified, characterized of either a steady decline or a constant ink volume transfer per dot feature. For the steady state ink transfer, a linear relationship between the dwell time and the dot volume was determined, which is characterized by a flow rate of about 16 femtoliters per second. A dependence of the ink transport from the length of pauses before and in between writing the structures was observed and should be taken into account during pattern design when aiming at best writing homogeneity. The ultra-large scan range of the utilized AFM allowed for a simultaneous study of the entire preparation area of almost 1 mm2, yielding good statistic results.

Preliminary constraints on the location of the recently hypothesized new planet of the Solar System from planetary orbital dynamics

NASA Astrophysics Data System (ADS)

Iorio, Lorenzo

2017-01-01

It has been recently proposed that the observed grouping of either the perihelia and the orbital planes of some observed distant Kuiper Belt Objects (KBOs) can be explained by the shepherding influence of a remote (150 au≲ qX≲350 au), still unseen massive object PX having planetary size (5 m_{oplus} ≲ mX≲20 m_{oplus}) and moving along an ecliptically inclined (22 deg≲ IX≲ 40 deg), eccentric (380 au≲ aX ≲980 au) Heliocentric bound orbit located in space at 80 deg≲ΩX≲120 deg and which is anti-aligned (120 deg≲ω_{ X}≲160 deg) with those of the considered KBOs. The trajectory of Saturn is nowadays known at essentially the same accuracy level of the inner planets due to the telemetry of the Cassini spacecraft. Thus, the expected perturbations dot{π}, dot{Ω} due to PX on the Kronian apsidal and draconitic orbital motions are theoretically investigated to tentatively constrain the configuration space of PX itself. To this aim, we compare our predictions dot{π}_{theo}, dot{Ω}_{theo} to the currently available experimental intervals of values Δdot{Ω}_{obs}, Δdot{π}_{ obs} determined by astronomers in the recent past without explicitly modeling and solving for PX itself. As such, our results, despite being plausible and in agreement to a large extent with other constraints released in the literature, should be regarded as proof-of-principle investigations aimed to encourage more accurate analyses in future. It turns out that the admissible region in its configuration space is moderately narrow as far as its position along its orbit, reckoned by the true anomaly fX, is concerned, being concentrated around approximately 130 deg≲ f X≲240 deg. PX is certainly far from its perihelion (fX=0 deg), in agreement with other recent studies. The future analysis of the data from the ongoing New Horizons mission might be helpful in further constraining the scenario considered here for PX. Its impact on the spacecraft's range over a multi-year span is investigated with a preliminary sensitivity analysis.

Development of Representative Rainfall Periods for Green Infrastructure Design: Connecting the Dots Between Climate, Urban Hydrology and Resilience

NASA Astrophysics Data System (ADS)

Albright, C. M.; Traver, R.; Wadzuk, B.

2017-12-01

Analysis of local-to-regional climate data is critical in understanding how changing patterns in rainfall and other atmospheric conditions can affect urban hydrology. Urbanization has caused hydrologic and ecologic modifications to our land surfaces, and altered the dynamics of urban water cycle in complex ways. Green infrastructure (GI) systems, in their simplest form, reduce runoff and flooding, prevent combined sewer overflows and improve quality of receiving waters. However, when viewed through a more holistic lens, GI systems sit at the nexus of hydrology, climate and energy, yet are rarely designed to account for the impacts of these intersections. We must assess urban hydrologic systems beyond their response to a single event or design storm, incorporating multiple temporal scales and all hydrologic processes. This is of utmost importance to design and characterization of urban GI systems because the resilience of these systems will be dictated by their ability to adapt to future behavior of extreme weather patterns and climate. In this study, we characterize long-term hydrologic conditions in Philadelphia to identify periods of record that are most representative of regional climate characteristics, including a representative rainfall year and longer representative periods. Utility of these datasets will be demonstrated by showing that GI systems are able to sustain effective performance for most expected annual precipitation events. Connections between atmospheric (precipitation and temperature) patterns, GI systems and potential removal mechanisms in the urban hydrologic cycle will be presented for Philadelphia and cities with similar climate characteristics. Establishing such connections is critically needed to not only validate what is already known about urban GI, but more importantly, to advance theory and practice by linking the hydrologic benefits of urban GI to broader concepts such as risk, mitigation of extreme events and sustainable communities.

Detecting trap states in planar PbS colloidal quantum dot solar cells

PubMed Central

Jin, Zhiwen; Wang, Aiji; Zhou, Qing; Wang, Yinshu; Wang, Jizheng

2016-01-01

The recently developed planar architecture (ITO/ZnO/PbS-TBAI/PbS-EDT/Au) has greatly improved the power conversion efficiency of colloidal quantum dot photovoltaics (QDPVs). However, the performance is still far below the theoretical expectations and trap states in the PbS-TBAI film are believed to be the major origin, characterization and understanding of the traps are highly demanded to develop strategies for continued performance improvement. Here employing impedance spectroscopy we detect trap states in the planar PbS QDPVs. We determined a trap state of about 0.34 eV below the conduction band with a density of around 3.2 × 1016 cm−3 eV−1. Temperature dependent open-circuit voltage analysis, temperature dependent diode property analysis and temperature dependent build-in potential analysis consistently denotes an below-bandgap activation energy of about 1.17–1.20 eV. PMID:27845392

Potassium doping: Tuning the optical properties of graphene quantum dots

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

Qian, Fuli; Li, Xueming, E-mail: lxmscience@163.com; Lu, Chaoyu

2016-07-15

Doping with hetero-atoms is an effective way to tune the properties of graphene quantum dots (GQDs). Here, potassium-doped GQDs (K-GQDs) are synthesized by a one-pot hydrothermal treatment of sucrose and potassium hydroxide solution. Optical properties of the GQDs are altered as a result of K-doping. The absorption peaks exhibit a blue shift. Multiple photoluminescence (PL) peaks are observed as the excitation wavelength is varied from 380 nm to 620 nm. New energy levels are introduced into the K-GQDs and provide alternative electron transition pathways. The maximum PL intensity of the K-GQDs is obtained at an excitation wavelength of 480 nmmore » which is distinct from the undoped GQDs (375 nm). The strong PL of the K-GQDs at the longer emission wavelengths is expected to make K-GQDs more suitable for bioimaging and optoelectronic applications.« less

Biexciton Auger Recombination Differs in Hybrid and Inorganic Halide Perovskite Quantum Dots.

PubMed

Eperon, Giles E; Jedlicka, Erin; Ginger, David S

2018-01-04

We use time-resolved photoluminescence measurements to determine the biexciton Auger recombination rate in both hybrid organic-inorganic and fully inorganic halide perovskite nanocrystals as a function of nanocrystal volume. We find that the volume scaling of the biexciton Auger rate in the hybrid perovskites, containing a polar organic A-site cation, is significantly shallower than in the fully inorganic Cs-based nanocrystals. As the nanocrystals become smaller, the Auger rate in the hybrid nanocrystals increases even less than expected, compared to the fully inorganic nanocrystals, which already show a shallower volume dependence than other material systems such as chalcogenide quantum dots. This finding suggests there may be differences in the strength of Coulombic interactions between the fully inorganic and hybrid perovskites, which may prove to be crucial in selecting materials to obtain the highest performing devices in the future, and hints that there could be something "special" about the hybrid materials.

Zn(II)-Coordinated Quantum Dot-FRET Nanosensors for the Detection of Protein Kinase Activity

PubMed Central

Lim, Butaek; Park, Ji-In; Lee, Kyung Jin; Lee, Jin-Won; Kim, Tae-Wuk; Kim, Young-Pil

2015-01-01

We report a simple detection of protein kinase activity using Zn(II)-mediated fluorescent resonance energy transfer (FRET) between quantum dots (QDs) and dye-tethered peptides. With neither complex chemical ligands nor surface modification of QDs, Zn(II) was the only metal ion that enabled the phosphorylated peptides to be strongly attached on the carboxyl groups of the QD surface via metal coordination, thus leading to a significant FRET efficiency. As a result, protein kinase activity in intermixed solution was efficiently detected by QD-FRET via Zn(II) coordination, especially when the peptide substrate was combined with affinity-based purification. We also found that mono- and di-phosphorylation in the peptide substrate could be discriminated by the Zn(II)-mediated QD-FRET. Our approach is expected to find applications for studying physiological function and signal transduction with respect to protein kinase activity. PMID:26213934

Zn(II)-Coordinated Quantum Dot-FRET Nanosensors for the Detection of Protein Kinase Activity.

PubMed

Lim, Butaek; Park, Ji-In; Lee, Kyung Jin; Lee, Jin-Won; Kim, Tae-Wuk; Kim, Young-Pil

2015-07-23

We report a simple detection of protein kinase activity using Zn(II)-mediated fluorescent resonance energy transfer (FRET) between quantum dots (QDs) and dye-tethered peptides. With neither complex chemical ligands nor surface modification of QDs, Zn(II) was the only metal ion that enabled the phosphorylated peptides to be strongly attached on the carboxyl groups of the QD surface via metal coordination, thus leading to a significant FRET efficiency. As a result, protein kinase activity in intermixed solution was efficiently detected by QD-FRET via Zn(II) coordination, especially when the peptide substrate was combined with affinity-based purification. We also found that mono- and di-phosphorylation in the peptide substrate could be discriminated by the Zn(II)-mediated QD-FRET. Our approach is expected to find applications for studying physiological function and signal transduction with respect to protein kinase activity.

Proposal on Calculation of Ventilation Threshold Using Non-contact Respiration Measurement with Pattern Light Projection

NASA Astrophysics Data System (ADS)

Aoki, Hirooki; Ichimura, Shiro; Fujiwara, Toyoki; Kiyooka, Satoru; Koshiji, Kohji; Tsuzuki, Keishi; Nakamura, Hidetoshi; Fujimoto, Hideo

We proposed a calculation method of the ventilation threshold using the non-contact respiration measurement with dot-matrix pattern light projection under pedaling exercise. The validity and effectiveness of our proposed method is examined by simultaneous measurement with the expiration gas analyzer. The experimental result showed that the correlation existed between the quasi ventilation thresholds calculated by our proposed method and the ventilation thresholds calculated by the expiration gas analyzer. This result indicates the possibility of the non-contact measurement of the ventilation threshold by the proposed method.

Atlas-guided volumetric diffuse optical tomography enhanced by generalized linear model analysis to image risk decision-making responses in young adults.

PubMed

Lin, Zi-Jing; Li, Lin; Cazzell, Mary; Liu, Hanli

2014-08-01

Diffuse optical tomography (DOT) is a variant of functional near infrared spectroscopy and has the capability of mapping or reconstructing three dimensional (3D) hemodynamic changes due to brain activity. Common methods used in DOT image analysis to define brain activation have limitations because the selection of activation period is relatively subjective. General linear model (GLM)-based analysis can overcome this limitation. In this study, we combine the atlas-guided 3D DOT image reconstruction with GLM-based analysis (i.e., voxel-wise GLM analysis) to investigate the brain activity that is associated with risk decision-making processes. Risk decision-making is an important cognitive process and thus is an essential topic in the field of neuroscience. The Balloon Analog Risk Task (BART) is a valid experimental model and has been commonly used to assess human risk-taking actions and tendencies while facing risks. We have used the BART paradigm with a blocked design to investigate brain activations in the prefrontal and frontal cortical areas during decision-making from 37 human participants (22 males and 15 females). Voxel-wise GLM analysis was performed after a human brain atlas template and a depth compensation algorithm were combined to form atlas-guided DOT images. In this work, we wish to demonstrate the excellence of using voxel-wise GLM analysis with DOT to image and study cognitive functions in response to risk decision-making. Results have shown significant hemodynamic changes in the dorsal lateral prefrontal cortex (DLPFC) during the active-choice mode and a different activation pattern between genders; these findings correlate well with published literature in functional magnetic resonance imaging (fMRI) and fNIRS studies. Copyright © 2014 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.

PREFACE: Semiconductor Nanostructures towards Electronic and Optoelectronic Device Applications II (Symposium K, E-MRS 2009 Spring Meeting)

NASA Astrophysics Data System (ADS)

Nötzel, Richard

2009-07-01

This volume of IOP Conference Series: Materials Science and Engineering contains papers that were presented at the special symposium K at the EMRS 2009 Spring Meeting held 8-12 June in Strasbourg, France, which was entitled 'Semiconductor Nanostructures towards Electronic and Optoelectronic Device Applications II'. Thanks to the broad interest a large variety of quantum dots and quantum wires and related nanostructures and their application in devices could be covered. There was significant progress in the epitaxial growth of semiconductor quantum dots seen in the operation of high-power, as well as mode locked laser diodes and the lateral positioning of quantum dots on patterned substrates or by selective area growth for future single quantum dot based optoelectronic and electronic devices. In the field of semiconductor nanowires high quality, almost twin free structures are now available together with a new degree of freedom for band structure engineering based on alternation of the crystal structure. In the search for Si based light emitting structures, nanocrystals and miniband-related near infrared luminescence of Si/Ge quantum dot superlattices with high quantum efficiency were reported. These highlights, among others, and the engaged discussions of the scientists, engineers and students brought together at the symposium emphasize how active the field of semiconductor nanostructures and their applications in devices is, so that we can look forward to the progress to come. Guest Editor Richard Nötzel COBRA Research Institute Department of Applied Physics Eindhoven University of Technology 5600 MB Eindhoven The Netherlands Tel.: +31 40 247 2047; fax: +31 40 246 1339 E-mail address: r.noetzel@tue.nl

Gamma Radiation Dose Rate in Air due to Terrestrial Radionuclides in Southern Brazil: Synthesis by Geological Units and Lithotypes Covered by the Serra do Mar Sul Aero-Geophysical Project

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

Bastos, Rodrigo O.; Appoloni, Carlos R.; Pinese, Jose P. P.

2008-08-07

The absorbed dose rates in air due to terrestrial radionuclides were estimated from aerial gamma spectrometric data for an area of 48,600 km{sup 2} in Southern Brazil. The source data was the Serra do Mar Sul Aero-Geophysical Project back-calibrated in a cooperative work among the Geological Survey of Brazil, the Geological Survey of Canada, and Paterson, Grant and Watson Ltd. The concentrations of eU (ppm), eTh (ppm) and K (%) were converted to dose rates in air (nGy{center_dot}h{sup -1}) by accounting for the contribution of each element's concentration. Regional variation was interpreted according to lithotypes and a synthesis was performedmore » according to the basic geological units present in the area. Higher values of total dose were estimated for felsic igneous and metamorphic rocks, with average values varying up to 119{+-}24 nGy{center_dot}h{sup -1}, obtained by Anitapolis syenite body. Sedimentary, metasedimentary and metamafic rocks presented the lower dose levels, and some beach deposits reached the lowest average total dose, 18.5{+-}8.2 nGy{center_dot}h{sup -1}. Thorium gives the main average contribution in all geological units, the highest value being reached by the nebulitic gneisses of Atuba Complex, 71{+-}23 nGy{center_dot}h{sup -1}. Potassium presents the lowest average contribution to dose rate in 53 of the 72 units analyzed, the highest contribution being obtained by intrusive alkaline bodies (28{+-}12 nGy{center_dot}h{sup -1}). The general pattern of geographic dose distribution respects well the hypotheses on geo-physicochemical behavior of radioactive elements.« less

Antibiotic Use in Small Community Hospitals.

PubMed

Stenehjem, Edward; Hersh, Adam L; Sheng, Xiaoming; Jones, Peter; Buckel, Whitney R; Lloyd, James F; Howe, Stephen; Evans, R Scott; Greene, Tom; Pavia, Andrew T

2016-11-15

 Antibiotic use and misuse is driving drug resistance. Much of US healthcare takes place in small community hospitals (SCHs); 70% of all US hospitals have <200 beds. Antibiotic use in SCHs is poorly described. We evaluated antibiotic use using data from the National Healthcare and Safety Network antimicrobial use option from the Centers for Disease Control and Prevention.  We used Intermountain Healthcare's monthly antibiotic use reports for 19 hospitals from 2011 to 2013. Hospital care units were categorized as intensive care, medical/surgical, pediatric, or miscellaneous. Antibiotics were categorized based on spectrum of coverage. Antibiotic use rates, expressed as days of therapy per 1000 patient-days (DOT/1000PD), were calculated for each SCH and compared with rates in large community hospitals (LCHs). Negative-binomial regression was used to relate antibiotic use to predictor variables.  Total antibiotic use rates varied widely across the 15 SCHs (median, 436 DOT/1000PD; range, 134-671 DOT/1000PD) and were similar to rates in 4 LCHs (509 DOT/1000PD; 406-597 DOT/1000PD). The proportion of patient-days spent in the respective unit types varied substantially within SCHs and had a large impact on facility-level rates. Broad-spectrum antibiotics accounted for 26% of use in SCHs (range, 8%-36%), similar to the proportion in LCHs (32%; range, 26%-37%). Case mix index, proportion of patient-days in specific unit types, and season were significant predictors of antibiotic use.  There is substantial variation in patterns of antibiotic use among SCHs. Overall usage in SCHs is similar to usage in LCHs. Small hospitals need to become a focus of stewardship efforts. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

Color Charts, Esthetics, and Subjective Randomness

ERIC Educational Resources Information Center

Sanderson, Yasmine B.

2012-01-01

Color charts, or grids of evenly spaced multicolored dots or squares, appear in the work of modern artists and designers. Often the artist/designer distributes the many colors in a way that could be described as "random," that is, without an obvious pattern. We conduct a statistical analysis of 125 "random-looking" art and design color charts and…

Vitronectin (Vn) glycosylation patterned by lectin affinity assays-A potent glycoproteomic tool to discriminate plasma Vn from cancer ascites Vn.

PubMed

Benachour, H; Leroy-Dudal, J; Agniel, R; Wilson, J; Briand, M; Carreiras, F; Gallet, O

2018-05-01

Changes in glycosylation have been associated with human cancer, but their complexity poses an analytical challenge. Ovarian cancer is a major cause of death in women because of an often late diagnosis. At least one-third of patients presents ascites fluid at diagnosis, and almost all have ascites at recurrence. Vitronectin (Vn) is a multifunctional glycoprotein that is suggested to be implicated in ovarian cancer metastasis and is found within ascites. The present study evaluated the potential of using lectin affinity for characterizing the glycosylation pattern of Vn. Human Vn was purified from 1 sample of ovarian cancer ascites or a pool of plasma samples. Consistent findings were observed with both dot blot and lectin array assays. Based on a panel of 40 lectins, the lectin array revealed discriminant patterns of lectin binding to Vn glycans. Interestingly, almost all the highlighted interactions were found to be higher with Vn from ascites relative to the plasma counterpart. Also, the lectin array was able to discriminate profiles of lectin interactions (ConA, SNA-I, PHA-E, PHA-L) between Vn samples that were not evident using dot blot, indicating its high sensitivity. The model of ConA binding during thermal unfolding of Vn confirmed the higher accessibility of mannosylated glycans in Vn from ascites as monitored by turbidimetry. Thus, this study demonstrated the usefulness of lectins and the lectin array as a glycoproteomic tool for high throughput and sensitive analysis of glycosylation patterns. Our data provide novel insights concerning Vn glycosylation patterns in clinical specimens, paving the way for further investigations regarding their functional impact and clinical interest. Copyright © 2017 John Wiley & Sons, Ltd.

The largest glitch observed in the Crab pulsar

NASA Astrophysics Data System (ADS)

Shaw, B.; Lyne, A. G.; Stappers, B. W.; Weltevrede, P.; Bassa, C. G.; Lien, A. Y.; Mickaliger, M. B.; Breton, R. P.; Jordan, C. A.; Keith, M. J.; Krimm, H. A.

2018-05-01

We have observed a large glitch in the Crab pulsar (PSR B0531+21). The glitch occurred around MJD 58064 (2017 November 8) when the pulsar underwent an increase in the rotation rate of Δν = 1.530 × 10-5 Hz, corresponding to a fractional increase of Δν/ν = 0.516 × 10-6 making this event the largest glitch ever observed in this source. Due to our high-cadence and long-dwell time observations of the Crab pulsar we are able to partially resolve a fraction of the total spin-up of the star. This delayed spin-up occurred over a timescale of ˜1.7 days and is similar to the behaviour seen in the 1989 and 1996 large Crab pulsar glitches. The spin-down rate also increased at the glitch epoch by Δ \\dot{ν } / \\dot{ν } = 7 × 10^{-3}. In addition to being the largest such event observed in the Crab, the glitch occurred after the longest period of glitch inactivity since at least 1984 and we discuss a possible relationship between glitch size and waiting time. No changes to the shape of the pulse profile were observed near the glitch epoch at 610 MHz or 1520 MHz, nor did we identify any changes in the X-ray flux from the pulsar. The long-term recovery from the glitch continues to progress as \\dot{ν } slowly rises towards pre-glitch values. In line with other large Crab glitches, we expect there to be a persistent change to \\dot{ν }. We continue to monitor the long-term recovery with frequent, high quality observations.

Optically controlled locking of the nuclear field via coherent dark-state spectroscopy.

PubMed

Xu, Xiaodong; Yao, Wang; Sun, Bo; Steel, Duncan G; Bracker, Allan S; Gammon, Daniel; Sham, L J

2009-06-25

A single electron or hole spin trapped inside a semiconductor quantum dot forms the foundation for many proposed quantum logic devices. In group III-V materials, the resonance and coherence between two ground states of the single spin are inevitably affected by the lattice nuclear spins through the hyperfine interaction, while the dynamics of the single spin also influence the nuclear environment. Recent efforts have been made to protect the coherence of spins in quantum dots by suppressing the nuclear spin fluctuations. However, coherent control of a single spin in a single dot with simultaneous suppression of the nuclear fluctuations has yet to be achieved. Here we report the suppression of nuclear field fluctuations in a singly charged quantum dot to well below the thermal value, as shown by an enhancement of the single electron spin dephasing time T(2)*, which we measure using coherent dark-state spectroscopy. The suppression of nuclear fluctuations is found to result from a hole-spin assisted dynamic nuclear spin polarization feedback process, where the stable value of the nuclear field is determined only by the laser frequencies at fixed laser powers. This nuclear field locking is further demonstrated in a three-laser measurement, indicating a possible enhancement of the electron spin T(2)* by a factor of several hundred. This is a simple and powerful method of enhancing the electron spin coherence time without use of 'spin echo'-type techniques. We expect that our results will enable the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.

Characterization of c-Ki-ras and N-ras oncogenes in aflatoxin B sub 1 -induced rat liver tumors

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

McMahon, G.; Davis, E.F.; Huber, L.J.

c-Ki-ras and N-ras oncogenes have been characterized in aflatoxin B{sub 1}-induced hepatocellular carcinomas. Detection of different protooncogene and oncogene sequences and estimation of their frequency distribution were accomplished by polymerase chain reaction, cloning, and plaque screening methods. Two c-Ki-ras oncogene sequences were identified in DNA from liver tumors that contained nucleotide changes absent in DNA from livers of untreated control rats. Sequence changes involving G{center dot}C to T{center dot}A or G{center dot}C to A{center dot}T nucleotide substitutions in codon 12 were scored in three of eight tumor-bearing animals. Distributions of c-Ki-ras sequences in tumors and normal liver DNA indicated thatmore » the observed nucleotide changes were consistent with those expected to result from direct mutagenesis of the germ-line protooncogene by aflatoxin B{sub 1}. N-ras oncogene sequences were identified in DNA from two of eight tumors. Three N-ras gene regions were identified, one of which was shown to be associated with an oncogene containing a putative activating amino acid residing at codon 13. All three N-ras sequences, including the region detected in N-ras oncogenes, were present at similar frequencies in DNA samples from control livers as well as liver tumors. The presence of a potential germ-line oncogene may be related to the sensitivity of the Fischer rat strain to liver carcinogenesis by aflatoxin B{sub 1} and other chemical carcinogens.« less

Experimental triple-slit interference in a strongly driven V-type artificial atom

NASA Astrophysics Data System (ADS)

Dada, Adetunmise C.; Santana, Ted S.; Koutroumanis, Antonios; Ma, Yong; Park, Suk-In; Song, Jindong; Gerardot, Brian D.

2017-08-01

Rabi oscillations of a two-level atom appear as a quantum interference effect between the amplitudes associated with atomic superpositions, in analogy with the classic double-slit experiment which manifests a sinusoidal interference pattern. By extension, through direct detection of time-resolved resonance fluorescence from a quantum-dot neutral exciton driven in the Rabi regime, we experimentally demonstrate triple-slit-type quantum interference via quantum erasure in a V-type three-level artificial atom. This result is of fundamental interest in the experimental studies of the properties of V-type three-level systems and may pave the way for further insight into their coherence properties as well as applications for quantum information schemes. It also suggests quantum dots as candidates for multipath-interference experiments for probing foundational concepts in quantum physics.

Trichoscopic Findings of Hair Loss in Koreans

PubMed Central

Park, Jin; Kim, Joo-Ik; Kim, Han-Uk; Yun, Seok-Kweon

2015-01-01

Background Trichoscopic findings of hair loss have been well described for the differential diagnosis of alopecia; however, critical findings were not thoroughly investigated or compared among all ethnic groups, including Asians. Objective We aimed to find any characteristic trichoscopic findings in Korean alopecia patients and to verify whether those findings are closely related to previously reported observations. Methods Three hundred and twenty-seven patients with hair loss of various causes and 160 normal scalps were analyzed. Trichoscopic examination was performed with a polarized-light handheld dermoscope. Results A total of 35 patterns of trichoscopic features were represented, and certain features were significantly common or observed exclusively in a particular type of alopecia as follows: yellow dots, exclamation mark hairs, and proximal tapering hairs (alopecia areata), trichoptilosis and pointed hairs (trichotillomania), corkscrew hairs, septate hyphae hairs, and comma hairs (tinea capitis), diffuse white area, fibrotic white dots, and tufting hairs (primary cicatricial alopecia), hair diameter diversity and peripilar sign (androgenetic alopecia), and short nonvellus hairs (telogen effluvium). Conclusion The characteristic trichoscopic features for the differential diagnosis of alopecia in Koreans, shown as follicular, perifollicular, and hair shaft patterns, are similar to those of Caucasians; however, the frequencies of the pigment patterns are different between Koreans and Caucasians because of the contrast effect of the skin and hair color. Therefore, racial difference should be considered in the trichoscopic evaluation for differential diagnosis. PMID:26512168

Secure steganographic communication algorithm based on self-organizing patterns.

PubMed

Saunoriene, Loreta; Ragulskis, Minvydas

2011-11-01

A secure steganographic communication algorithm based on patterns evolving in a Beddington-de Angelis-type predator-prey model with self- and cross-diffusion is proposed in this paper. Small perturbations of initial states of the system around the state of equilibrium result in the evolution of self-organizing patterns. Small differences between initial perturbations result in slight differences also in the evolving patterns. It is shown that the generation of interpretable target patterns cannot be considered as a secure mean of communication because contours of the secret image can be retrieved from the cover image using statistical techniques if only it represents small perturbations of the initial states of the system. An alternative approach when the cover image represents the self-organizing pattern that has evolved from initial states perturbed using the dot-skeleton representation of the secret image can be considered as a safe visual communication technique protecting both the secret image and communicating parties.

Modeling the non-recycled Fermi Gamma-ray pulsar population

DOE PAGES

Perera, B. B. P.; McLaughlin, M. A.; Cordes, J. M.; ...

2013-09-25

Here, we use Fermi Gamma-ray Space Telescope detections and upper limits on non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain how the gamma-ray luminosity L γ depends on the period P and the period derivativemore » $$\\dot{P}$$. We use a Bayesian analysis to calculate a best-fit luminosity law, or dependence of L γ on P and $$\\dot{P}$$, including different methods for modeling the beaming factor. An outer gap (OG) magnetosphere geometry provides the best-fit model, which is $$L_\\gamma \\propto P^{-a} \\dot{P}^{b}$$ where a = 1.36 ± 0.03 and b = 0.44 ± 0.02, similar to but not identical to the commonly assumed $$L_\\gamma \\propto \\sqrt{\\dot{E}} \\propto P^{-1.5} \\dot{P}^{0.5}$$. Given upper limits on gamma-ray fluxes of currently known radio pulsars and using the OG model, we find that about 92% of the radio-detected pulsars have gamma-ray beams that intersect our line of sight. By modeling the misalignment of radio and gamma-ray beams of these pulsars, we find an average gamma-ray beaming solid angle of about 3.7π for the OG model, assuming a uniform beam. Using LAT-measured diffuse fluxes, we place a 2σ upper limit on the average braking index and a 2σ lower limit on the average surface magnetic field strength of the pulsar population of 3.8 and 3.2 × 1010 G, respectively. We then predict the number of non-recycled pulsars detectable by the LAT based on our population model. Using the 2 yr sensitivity, we find that the LAT is capable of detecting emission from about 380 non-recycled pulsars, including 150 currently identified radio pulsars. Using the expected 5 yr sensitivity, about 620 non-recycled pulsars are detectable, including about 220 currently identified radio pulsars. As a result, we note that these predictions significantly depend on our model assumptions.« less

Wind turbine rotor blade monitoring using digital image correlation: a comparison to aeroelastic simulations of a multi-megawatt wind turbine

NASA Astrophysics Data System (ADS)

Winstroth, J.; Schoen, L.; Ernst, B.; Seume, J. R.

2014-06-01

Optical full-field measurement methods such as Digital Image Correlation (DIC) provide a new opportunity for measuring deformations and vibrations with high spatial and temporal resolution. However, application to full-scale wind turbines is not trivial. Elaborate preparation of the experiment is vital and sophisticated post processing of the DIC results essential. In the present study, a rotor blade of a 3.2 MW wind turbine is equipped with a random black-and-white dot pattern at four different radial positions. Two cameras are located in front of the wind turbine and the response of the rotor blade is monitored using DIC for different turbine operations. In addition, a Light Detection and Ranging (LiDAR) system is used in order to measure the wind conditions. Wind fields are created based on the LiDAR measurements and used to perform aeroelastic simulations of the wind turbine by means of advanced multibody codes. The results from the optical DIC system appear plausible when checked against common and expected results. In addition, the comparison of relative out-ofplane blade deflections shows good agreement between DIC results and aeroelastic simulations.

The dynamic-stimulus advantage of visual symmetry perception.

PubMed

Niimi, Ryosuke; Watanabe, Katsumi; Yokosawa, Kazuhiko

2008-09-01

It has been speculated that visual symmetry perception from dynamic stimuli involves mechanisms different from those for static stimuli. However, previous studies found no evidence that dynamic stimuli lead to active temporal processing and improve symmetry detection. In this study, four psychophysical experiments investigated temporal processing in symmetry perception using both dynamic and static stimulus presentations of dot patterns. In Experiment 1, rapid successive presentations of symmetric patterns (e.g., 16 patterns per 853 ms) produced more accurate discrimination of orientations of symmetry axes than static stimuli (single pattern presented through 853 ms). In Experiments 2-4, we confirmed that the dynamic-stimulus advantage depended upon presentation of a large number of unique patterns within a brief period (853 ms) in the dynamic conditions. Evidently, human vision takes advantage of temporal processing for symmetry perception from dynamic stimuli.

Magneto-transport studies of a few hole GaAs double quantum dot in tilted magnetic fields

NASA Astrophysics Data System (ADS)

Studenikin, Sergei; Bogan, Alex; Tracy, Lisa; Gaudreau, Louis; Sachrajda, Andy; Korkusinski, Marek; Reno, John; Hargett, Terry

Compared to equivalent electron devices, single-hole spins interact weakly with lattice nuclear spins leading to extended quantum coherence times. This makes p-type Quantum Dots (QD) particularly attractive for practical quantum devices such as qubit circuits, quantum repeaters, quantum sensors etc. where long coherence time is required. Another property of holes is the possibility to tune their g-factor as a result of the strong anisotropy of the valance band. Hole g-factors can be conveniently tuned in situ from a large value to almost zero by tilting the magnetic field relative to the 2D hole gas surface normal. In this work we explore high-bias magneto-transport properties of a p-type double quantum dot (DQD) device fabricated from a GaAs/AlGaAs heterostructures using lateral split-gate technology. A charge detection technique is used to monitor number of holes and tune the p-DQD in a single hole regime around (1,1) and (2,0) occupation states where Pauli spin-blockaded transport is expected. Four states are identified in quantizing magnetic fields within the high-bias current stripe - three-fold triplet and a singlet which allows determining effective heavy hole g-factor as a function of the tilt angle from 90 to 0 degrees.

Full spectral optical modeling of quantum-dot-converted elements for light-emitting diodes considering reabsorption and reemission effect.

PubMed

Li, Jia-Sheng; Tang, Yong; Li, Zong-Tao; Cao, Kai; Yan, Cai-Man; Ding, Xin-Rui

2018-07-20

Quantum dots (QDs) have attracted significant attention in light-emitting diode (LED) illumination and display applications, owing to their high quantum yield and unique spectral properties. However, an effective optical model of quantum-dot-converted elements (QDCEs) for (LEDs) that entirely considers the reabsorption and reemission effect is lacking. This suppresses the design of QDCE structures and further investigation of light-extraction/conversion mechanisms in QDCEs. In this paper, we proposed a full spectral optical modeling method for QDCEs packaged in LEDs, entirely considering the reabsorption and reemission effect, and its results are compared with traditional models without reabsorption or reemission. The comparisons indicate that the QDCE absorption loss of QD emission light is a major factor decreasing the radiant efficacy of LEDs, which should be considered when designing QDCE structures. According to the measurements of fabricated LEDs, only calculation results that entirely consider reabsorption and reemission show good agreement with experimental radiant efficacy, spectra, and peak wavelength at the same down-conversion efficiency. Consequently, it is highly expected that QDCE will be modeled considering the reabsorption and reemission events. This study provides a simple and effective modeling method for QDCEs, which shows great potential for their structure designs and fundamental investigations.

The role of fear of movement and injury in selective attentional processing in patients with chronic low back pain: a dot-probe evaluation.

PubMed

Roelofs, Jeffrey; Peters, Madelon L; Fassaert, Thijs; Vlaeyen, Johan W S

2005-05-01

The present study sought to investigate to what extent patients with chronic low back pain and pain-free control subjects selectively attend to pain-related stimuli as measured with 2 dot-probe tasks with word stimuli and pictorial stimuli. Selective attentional processing was measured by means of 3 indices: the bias index, a congruency effect, and an incongruency effect. Pain-related fear as a trait measure (Tampa Scale for Kinesiophobia [TSK]) was expected to be positively associated with all indices of selective attentional processing of pain stimuli. Results were analyzed with repeated-measures analysis of variance. An incongruency effect was found for patients and to a significantly less degree for pain-free control subjects on the dot-probe task with pictorial stimuli, indicating that pain patients have difficulty disengaging from threat pictures. Pain-related fear as a trait measure (TSK) was not associated with selective attentional processing of word and pictorial stimuli in either pain patients or control subjects. Results from the present study are discussed, and directions for future research are provided. Demonstrating difficulty to disengage from threat might be clinically relevant because patients might pay less attention to fear-disconfirming information and remain engaged in avoidance, which might eventually lead to prolonged anxiety states.

Full spectral optical modeling of quantum-dot-converted elements for light-emitting diodes considering reabsorption and reemission effect

NASA Astrophysics Data System (ADS)

Li, Jia-Sheng; Tang, Yong; Li, Zong-Tao; Cao, Kai; Yan, Cai-Man; Ding, Xin-Rui

2018-07-01

Quantum dots (QDs) have attracted significant attention in light-emitting diode (LED) illumination and display applications, owing to their high quantum yield and unique spectral properties. However, an effective optical model of quantum-dot-converted elements (QDCEs) for (LEDs) that entirely considers the reabsorption and reemission effect is lacking. This suppresses the design of QDCE structures and further investigation of light-extraction/conversion mechanisms in QDCEs. In this paper, we proposed a full spectral optical modeling method for QDCEs packaged in LEDs, entirely considering the reabsorption and reemission effect, and its results are compared with traditional models without reabsorption or reemission. The comparisons indicate that the QDCE absorption loss of QD emission light is a major factor decreasing the radiant efficacy of LEDs, which should be considered when designing QDCE structures. According to the measurements of fabricated LEDs, only calculation results that entirely consider reabsorption and reemission show good agreement with experimental radiant efficacy, spectra, and peak wavelength at the same down-conversion efficiency. Consequently, it is highly expected that QDCE will be modeled considering the reabsorption and reemission events. This study provides a simple and effective modeling method for QDCEs, which shows great potential for their structure designs and fundamental investigations.

Ecological validity of virtual reality daily living activities screening for early dementia: longitudinal study.

PubMed

Tarnanas, Ioannis; Schlee, Winfried; Tsolaki, Magda; Müri, René; Mosimann, Urs; Nef, Tobias

2013-08-06

Dementia is a multifaceted disorder that impairs cognitive functions, such as memory, language, and executive functions necessary to plan, organize, and prioritize tasks required for goal-directed behaviors. In most cases, individuals with dementia experience difficulties interacting with physical and social environments. The purpose of this study was to establish ecological validity and initial construct validity of a fire evacuation Virtual Reality Day-Out Task (VR-DOT) environment based on performance profiles as a screening tool for early dementia. The objectives were (1) to examine the relationships among the performances of 3 groups of participants in the VR-DOT and traditional neuropsychological tests employed to assess executive functions, and (2) to compare the performance of participants with mild Alzheimer's-type dementia (AD) to those with amnestic single-domain mild cognitive impairment (MCI) and healthy controls in the VR-DOT and traditional neuropsychological tests used to assess executive functions. We hypothesized that the 2 cognitively impaired groups would have distinct performance profiles and show significantly impaired independent functioning in ADL compared to the healthy controls. The study population included 3 groups: 72 healthy control elderly participants, 65 amnestic MCI participants, and 68 mild AD participants. A natural user interface framework based on a fire evacuation VR-DOT environment was used for assessing physical and cognitive abilities of seniors over 3 years. VR-DOT focuses on the subtle errors and patterns in performing everyday activities and has the advantage of not depending on a subjective rating of an individual person. We further assessed functional capacity by both neuropsychological tests (including measures of attention, memory, working memory, executive functions, language, and depression). We also evaluated performance in finger tapping, grip strength, stride length, gait speed, and chair stands separately and while performing VR-DOTs in order to correlate performance in these measures with VR-DOTs because performance while navigating a virtual environment is a valid and reliable indicator of cognitive decline in elderly persons. The mild AD group was more impaired than the amnestic MCI group, and both were more impaired than healthy controls. The novel VR-DOT functional index correlated strongly with standard cognitive and functional measurements, such as mini-mental state examination (MMSE; rho=0.26, P=.01) and Bristol Activities of Daily Living (ADL) scale scores (rho=0.32, P=.001). Functional impairment is a defining characteristic of predementia and is partly dependent on the degree of cognitive impairment. The novel virtual reality measures of functional ability seem more sensitive to functional impairment than qualitative measures in predementia, thus accurately differentiating from healthy controls. We conclude that VR-DOT is an effective tool for discriminating predementia and mild AD from controls by detecting differences in terms of errors, omissions, and perseverations while measuring ADL functional ability.

Bit-Serial Adder Based on Quantum Dots

NASA Technical Reports Server (NTRS)

Fijany, Amir; Toomarian, Nikzad; Modarress, Katayoon; Spotnitz, Mathew

2003-01-01

A proposed integrated circuit based on quantum-dot cellular automata (QCA) would function as a bit-serial adder. This circuit would serve as a prototype building block for demonstrating the feasibility of quantum-dots computing and for the further development of increasingly complex and increasingly capable quantum-dots computing circuits. QCA-based bit-serial adders would be especially useful in that they would enable the development of highly parallel and systolic processors for implementing fast Fourier, cosine, Hartley, and wavelet transforms. The proposed circuit would complement the QCA-based circuits described in "Implementing Permutation Matrices by Use of Quantum Dots" (NPO-20801), NASA Tech Briefs, Vol. 25, No. 10 (October 2001), page 42 and "Compact Interconnection Networks Based on Quantum Dots" (NPO-20855), which appears elsewhere in this issue. Those articles described the limitations of very-large-scale-integrated (VLSI) circuitry and the major potential advantage afforded by QCA. To recapitulate: In a VLSI circuit, signal paths that are required not to interact with each other must not cross in the same plane. In contrast, for reasons too complex to describe in the limited space available for this article, suitably designed and operated QCA-based signal paths that are required not to interact with each other can nevertheless be allowed to cross each other in the same plane without adverse effect. In principle, this characteristic could be exploited to design compact, coplanar, simple (relative to VLSI) QCA-based networks to implement complex, advanced interconnection schemes. To enable a meaningful description of the proposed bit-serial adder, it is necessary to further recapitulate the description of a quantum-dot cellular automation from the first-mentioned prior article: A quantum-dot cellular automaton contains four quantum dots positioned at the corners of a square cell. The cell contains two extra mobile electrons that can tunnel (in the quantum-mechanical sense) between neighboring dots within the cell. The Coulomb repulsion between the two electrons tends to make them occupy antipodal dots in the cell. For an isolated cell, there are two energetically equivalent arrangements (denoted polarization states) of the extra electrons. The cell polarization is used to encode binary information. Because the polarization of a nonisolated cell depends on Coulomb-repulsion interactions with neighboring cells, universal logic gates and binary wires could be constructed, in principle, by arraying QCA of suitable design in suitable patterns. Again, for reasons too complex to describe here, in order to ensure accuracy and timeliness of the output of a QCA array, it is necessary to resort to an adiabatic switching scheme in which the QCA array is divided into subarrays, each controlled by a different phase of a multiphase clock signal. In this scheme, each subarray is given time to perform its computation, then its state is frozen by raising its inter-dot potential barriers and its output is fed as the input to the successor subarray. The successor subarray is kept in an unpolarized state so it does not influence the calculation of preceding subarray. Such a clocking scheme is consistent with pipeline computation in the sense that each different subarray can perform a different part of an overall computation. In other words, QCA arrays are inherently suitable for pipeline and, moreover, systolic computations. This sequential or pipeline aspect of QCA would be utilized in the proposed bit-serial adders.

Non-scarring patchy alopecia in patients with systemic lupus erythematosus differs from that of alopecia areata.

PubMed

Ye, Y; Zhao, Y; Gong, Y; Zhang, X; Caulloo, S; Zhang, B; Cai, Z; Yang, J; McElwee, K J; Zhang, X

2013-12-01

Non-scaring patchy alopecia associated with systematic lupus erythematosus (SLE) is sometimes mis-diagnosed as alopecia areata (AA). Our aim was to differentiate non-scarring patchy SLE alopecia features from patchy AA. Clinical, dermatoscopic and histopathological data from 21 SLE patients with patchy alopecia were compared with data from 21 patients with patchy AA. Incomplete alopecia was common in SLE alopecia patches, while AA patches exhibited complete alopecia. Exclamation-mark hairs, black dots, broken hair and yellow dots were common to AA, while hair shaft thinning and hypopigmentation, angiotelectasis, peripilar sign, perifollicular red dots, white dots and honeycomb pigment patterns were more common in SLE. Interfollicular polymorphous vessels were the most common angiotelectasis presentation in the SLE alopecia patches, but interfollicular arborizing vessels were significantly more common in non-hair-loss-affected SLE regions and in AA hair-loss regions. During follow-up, increased vellus hair was the earliest feature that emerged after treatment both in SLE and AA, while the earliest feature that disappeared was hair shaft hypopigmentation in SLE and broken hair in AA. After treatment, no SLE patients had relapse of alopecia, while 41.7% of AA patients did. Distinct clinical, dermatoscopic and histopathological features were found in SLE-associated alopecia regions, which were different from those of AA. Serological autoantibody tests are of value to confirm the differential diagnosis. Local angiotelectasis and vasculitis close to hair follicles may be involved in the pathogenesis of alopecia in SLE.

DotMapper: an open source tool for creating interactive disease point maps.

PubMed

Smith, Catherine M; Hayward, Andrew C

2016-04-12

Molecular strain typing of tuberculosis isolates has led to increased understanding of the epidemiological characteristics of the disease and improvements in its control, diagnosis and treatment. However, molecular cluster investigations, which aim to detect previously unidentified cases, remain challenging. Interactive dot mapping is a simple approach which could aid investigations by highlighting cases likely to share epidemiological links. Current tools generally require technical expertise or lack interactivity. We designed a flexible application for producing disease dot maps using Shiny, a web application framework for the statistical software, R. The application displays locations of cases on an interactive map colour coded according to levels of categorical variables such as demographics and risk factors. Cases can be filtered by selecting combinations of these characteristics and by notification date. It can be used to rapidly identify geographic patterns amongst cases in molecular clusters of tuberculosis in space and time; generate hypotheses about disease transmission; identify outliers, and guide targeted control measures. DotMapper is a user-friendly application which enables rapid production of maps displaying locations of cases and their epidemiological characteristics without the need for specialist training in geographic information systems. Enhanced understanding of tuberculosis transmission using this application could facilitate improved detection of cases with epidemiological links and therefore lessen the public health impacts of the disease. It is a flexible system and also has broad international potential application to other investigations using geo-coded health information.

Prognostic value of the autophagy markers LC3 and p62/SQSTM1 in early-stage non-small cell lung cancer.

PubMed

Schläfli, Anna M; Adams, Olivia; Galván, José A; Gugger, Mathias; Savic, Spasenija; Bubendorf, Lukas; Schmid, Ralph A; Becker, Karl-Friedrich; Tschan, Mario P; Langer, Rupert; Berezowska, Sabina

2016-06-28

Autophagy is a cellular degrading process that promotes tumor cell survival or cell death in cancer, depending on the progress of oncogenesis. Protein light chain 3 (LC3) and p62/SQSTM1 (p62) are associated with autophagosomal membranes that engulf cytoplasmic content for subsequent degradation. We studied LC3 and p62 expression using immunohistochemistry in a large cohort of 466 stage I/II non-small cell lung cancer (NSCLC) using a tissue microarray. We evaluated dot-like cytoplasmic expression of LC3 and dot-like, cytoplasmic and nuclear staining for p62 in relation to clinico-pathological parameters.LC3 expression correlated with all p62 patterns, as those correlated among each other (p < 0.001 each). There was no correlation with stage, age or gender. A combination of high LC3/high p62 dot-like staining (suggesting impaired autophagy) showed a trend for better outcome (p = 0.11). Interestingly, a combined low cytoplasmic/low nuclear p62 expression regardless of dot-like staining was an independent prognostic factor for longer survival (p = 0.006; HR=1.96), in addition to tumor stage (p = 0.004; HR=1.4).The autophagy markers LC3 and p62 are differentially expressed in NSCLC, pointing towards a biologically significant role. High LC3 levels seem to be linked to lower tumor aggressiveness, while high general p62 expression was significantly associated with aggressive tumor behavior.

Prognostic value of the autophagy markers LC3 and p62/SQSTM1 in early-stage non-small cell lung cancer

PubMed Central

Schläfli, Anna M.; Adams, Olivia; Galván, José A.; Gugger, Mathias; Savic, Spasenija; Bubendorf, Lukas; Schmid, Ralph A.; Becker, Karl-Friedrich; Tschan, Mario P.; Langer, Rupert; Berezowska, Sabina

2016-01-01

Autophagy is a cellular degrading process that promotes tumor cell survival or cell death in cancer, depending on the progress of oncogenesis. Protein light chain 3 (LC3) and p62/SQSTM1 (p62) are associated with autophagosomal membranes that engulf cytoplasmic content for subsequent degradation. We studied LC3 and p62 expression using immunohistochemistry in a large cohort of 466 stage I/II non-small cell lung cancer (NSCLC) using a tissue microarray. We evaluated dot-like cytoplasmic expression of LC3 and dot-like, cytoplasmic and nuclear staining for p62 in relation to clinico-pathological parameters. LC3 expression correlated with all p62 patterns, as those correlated among each other (p < 0.001 each). There was no correlation with stage, age or gender. A combination of high LC3/high p62 dot-like staining (suggesting impaired autophagy) showed a trend for better outcome (p = 0.11). Interestingly, a combined low cytoplasmic/low nuclear p62 expression regardless of dot-like staining was an independent prognostic factor for longer survival (p = 0.006; HR=1.96), in addition to tumor stage (p = 0.004; HR=1.4). The autophagy markers LC3 and p62 are differentially expressed in NSCLC, pointing towards a biologically significant role. High LC3 levels seem to be linked to lower tumor aggressiveness, while high general p62 expression was significantly associated with aggressive tumor behavior. PMID:27250032

SU-F-T-517: Determining the Tissue Equivalence of a Brass Mesh Bolus in a Reconstructed Chest Wall Irradiation

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

Shekel, E; Epstein, D; Levin, D

2016-06-15

Purpose: To determine the tissue equivalence of a brass mesh bolus (RPD) in the setting of a reconstructed chest wall irradiation Methods: We measured breast skin dose delivered by a tangential field plan on an anthropomorphic phantom using Mosfet and nanoDot (Landauer) dosimeters in five different locations on the breast. We also measured skin dose using no bolus, 5mm and 10 mm superflab bolus. In the Eclipse treatment planning system (Varian, Palo Alto, CA) we calculated skin dose for different bolus thicknesses, ranging from 0 to 10 mm, in order to evaluate which calculation best matches the brass mesh measurements,more » as the brass mesh cannot be simulated due to artefacts.Finally, we measured depth dose behavior with the brass mesh bolus to verify that the bolus does not affect the dose to the breast itself beyond the build-up region. Results: Mosfet and nanoDot measurements were consistent with each other.As expected, skin dose measurements with no bolus had the least agreement with Eclipse calculation, while measurements for 5 and 10 mm agreed well with the calculation despite the difficulty in conforming superflab bolus to the breast contour. For the brass mesh the best agreement was for 3 mm bolus Eclipse calculation. For Mosfets, the average measurement was 90.8% of the expected dose, and for nanoDots 88.33% compared to 83.34%, 88.64% and 93.94% (2,3 and 5 mm bolus calculation respectively).The brass mesh bolus increased skin dose by approximately 25% but there was no dose increase beyond the build-up region. Conclusion: Brass mesh bolus is most equivalent to a 3 mm bolus, and does not affect the dose beyond the build-up region. The brass mesh cannot be directly calculated in Eclipse, hence a 3mm bolus calculation is a good reflection of the dose response to the brass mesh bolus.« less

Evidence for Orbital Decay of RX J1914.4+2456: Gravitational Radiation and the Nature of the X-Ray Emission

NASA Technical Reports Server (NTRS)

Strohmayer, Tod E.; White, Nicholas E. (Technical Monitor)

2002-01-01

RX J1914.4+2456 is a candidate double-degenerate binary (AM CVn) with a putative 569 s orbital period. If this identification is correct, then it has one of the shortest binary orbital periods known, and gravitational radiation should drive the orbital evolution and mass transfer if the binary is semi-detached. Here we report the results of a coherent timing study of the archival ROSAT data for RX J1914.4+2456. We performed a phase coherent timing analysis using all five ROSAT observations spanning a four-year period. We demonstrate that all the data can be phase connected, and we show that the 1.756 mHz orbital frequency is increasing at a rate of 1.5 +/- 0.4 x 10(exp -17) Hz/s consistent with the expected loss of angular momentum from the binary system via gravitational radiation. In addition to providing evidence for the emission of gravitational waves, our measurement of the orbital v(dot) constrains models for the X-ray emission and the nature of the secondary. If stable mass accretion drives the X-ray flux, then a positive v(dot) is inconsistent with a degenerate donor. A helium burning dwarf is compatible if indeed such systems can have periods as short as that of RX J1914.4+2456, an open theoretical question. Our measurement of a positive v(dot) is consistent with the unipolar induction model of Wu et al. which does not require accretion to drive the X-ray flux. We discuss how future timing measurements of RX J1914.4+2456 (and systems like it) with for example, Chandra and XMM-Newton, can provide a unique probe of the interaction between mass loss and gravitational radiation. We also discuss the importance of such measurements in the context of gravitational wave detection from space, such as is expected in the future with the LISA mission.

Individual Differences in Nonverbal Number Discrimination Correlate with Event-Related Potentials and Measures of Probabilistic Reasoning

ERIC Educational Resources Information Center

Paulsen, David J.; Woldorff, Marty G.; Brannon, Elizabeth M.

2010-01-01

The current study investigated the neural activity patterns associated with numerical sensitivity in adults. Event-related potentials (ERPs) were recorded while adults observed sequentially presented display arrays (S1 and S2) of non-symbolic numerical stimuli (dots) and made same/different judgments of these stimuli by pressing a button only when…

Controlled formation of GeSi nanostructures on pillar-patterned Si substrate

NASA Astrophysics Data System (ADS)

Zhou, Tong; Zeng, Ceng; Fan, Yongliang; Jiang, Zuimin; Xia, Jinsong; Zhong, Zhenyang; Fudan University Team; Huazhong University of Science; Technology Collaboration

2015-03-01

GeSi quantum nanostructures (QNs) have potential applications in optoelectronic devices due to their unique properties and compatibility with the sophisticated Si technology. However, the disadvantages of poor quantum efficiency of the GeSi QNs on flat Si (001) substrates hinder their optoelectronic applications. Today, numerous growth strategies have been proposed to control the formation of GeSi QNs in hope of improving the optoelectronic performances. One of the ways is to fabricate GeSi QNs on patterned substrates, where the GeSi QNs can be greatly manipulated in aspects of size, shape, composition, orientation and arrangement. Here, self-assembled GeSi QNs on periodic Si (001) sub-micro pillars (SPMs) are systematically studied. By controlling the growth conditions and the diameters of the SPMs, different GeSi QNs, including circularly arranged quantum dots (QDs), quantum rings (QRs), and quantum dot molecules (QDMs), are realized at the top edge of SMPs. Meanwhile, fourfold symmetric GeSi QDMs can be also obtained at the base edges of the SPMs. The promising features of self-assembled GeSi QNs are explained in terms of the surface chemical potential, which disclose the critical effect of surface morphology on the diffusion and the aggregation of Ge adatoms.

Large-scale Generation of Patterned Bubble Arrays on Printed Bi-functional Boiling Surfaces

PubMed Central

Choi, Chang-Ho; David, Michele; Gao, Zhongwei; Chang, Alvin; Allen, Marshall; Wang, Hailei; Chang, Chih-hung

2016-01-01

Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface. PMID:27034255

Optical efficiency enhancement in white organic light-emitting diode display with high color gamut using patterned quantum dot film and long pass filter

NASA Astrophysics Data System (ADS)

Kim, Hyo-Jun; Shin, Min-Ho; Kim, Young-Joo

2016-08-01

A new structure for white organic light-emitting diode (OLED) displays with a patterned quantum dot (QD) film and a long pass filter (LPF) was proposed and evaluated to realize both a high color gamut and high optical efficiency. Since optical efficiency is a critical parameter in white OLED displays with a high color gamut, a red or green QD film as a color-converting component and an LPF as a light-recycling component are introduced to be adjusted via the characteristics of a color filter (CF). Compared with a conventional white OLED without both a QD film and the LPF, it was confirmed experimentally that the optical powers of red and green light in a new white OLED display were increased by 54.1 and 24.7% using a 30 wt % red QD film and a 20 wt % green QD film with the LPF, respectively. In addition, the white OLED with both a QD film and the LPF resulted in an increase in the color gamut from 98 to 107% (NTSC x,y ratio) due to the narrow emission linewidth of the QDs.

Facile synthesis of S, N co-doped carbon dots and investigation of their photoluminescence properties.

PubMed

Zhang, Yue; He, Junhui

2015-08-21

A facile one-pot approach to prepare photoluminescent carbon dots (CDs) was developed through hydrothermal treatment of cysteine and citric acid. The obtained CDs show stable and bright blue emission with a quantum yield of 54% and an average lifetime of 11.61 ns. Moreover, the two-photon induced upconversion fluorescence of the CDs was observed and demonstrated. Interestingly, both down and up conversion fluorescence of the CDs show excitation-independent emission, which is quite different from most of the previously reported CDs. Ultrafast spectroscopy was also employed here to study the photoluminescence (PL) properties of the CDs. After characterization using various spectroscopic techniques, a unique PL mechanism for the as-prepared CDs' fluorescence was proposed accordingly. In addition, the influence of various metal ions on the CD fluorescence was examined and no quenching phenomena were observed. Meanwhile, gold nanoparticles (Au NPs) were found to be good quenchers of CD fluorescence and their quenching behavior was fitted to the Stern-Volmer equation. This provides new opportunities for fluorescence sensor designs and light energy conversion applications. Finally, the as-prepared CDs were inkjet-printed to form a desirable pattern, which is useful for fluorescent patterns, and anti-counterfeiting labeling.

Plasmon-Assisted Selective and Super-Resolving Excitation of Individual Quantum Emitters on a Metal Nanowire.

PubMed

Li, Qiang; Pan, Deng; Wei, Hong; Xu, Hongxing

2018-03-14

Hybrid systems composed of multiple quantum emitters coupled with plasmonic waveguides are promising building blocks for future integrated quantum nanophotonic circuits. The techniques that can super-resolve and selectively excite contiguous quantum emitters in a diffraction-limited area are of great importance for studying the plasmon-mediated interaction between quantum emitters and manipulating the single plasmon generation and propagation in plasmonic circuits. Here we show that multiple quantum dots coupled with a silver nanowire can be controllably excited by tuning the interference field of surface plasmons on the nanowire. Because of the period of the interference pattern is much smaller than the diffraction limit, we demonstrate the selective excitation of two quantum dots separated by a distance as short as 100 nm. We also numerically demonstrate a new kind of super-resolution imaging method that combines the tunable surface plasmon interference pattern on the NW with the structured illumination microscopy technique. Our work provides a novel high-resolution optical excitation and imaging method for the coupled systems of multiple quantum emitters and plasmonic waveguides, which adds a new tool for studying and manipulating single quantum emitters and single plasmons for quantum plasmonic circuitry applications.

A quantum-dot-based fluoroassay for detection of food-borne pathogens.

PubMed

Mohamadi, Elaheh; Moghaddasi, Mohammadali; Farahbakhsh, Afshin; Kazemi, Abbass

2017-09-01

Evaluation of the distribution capability of food-borne pathogens existing in food products by taking the advantage of quantum dots (QDs) for their photoluminescence properties was carried out. Bacteria namely Escherichia coli (E. coli) labelled with CdSe-QDs were examined both on an Agar nutrient and ground fish substrates in order to observe their growth rate in different environments in the Lab. A sample with an appropriate concentration ratio 10 7 CFU/mL of bacteria/CdSe-QDs was empirically selected from the samples which were grown on the Agar containing plates. The selected sample was also tested on a ground fish substrate as a real food sample. The bacterial growth was observed under the irradiation of UV light and the growth patterns were investigated for 3 successive days. The growth patterns indicated that E. coli can stay alive and can be distributed on food products so that the growth can be easily monitored. This approach makes bacterial growth on food products detectable so that it can be used as a bacteria-QD assay for an easy detection of food borne pathogens grown on a food sample. Copyright © 2017 Elsevier B.V. All rights reserved.

A Microfluidic System with Surface Patterning for Investigating Cavitation Bubble(s)-Cell Interaction and the Resultant Bioeffects at the Single-cell Level.

PubMed

Li, Fenfang; Yuan, Fang; Sankin, Georgy; Yang, Chen; Zhong, Pei

2017-01-10

In this manuscript, we first describe the fabrication protocol of a microfluidic chip, with gold dots and fibronectin-coated regions on the same glass substrate, that precisely controls the generation of tandem bubbles and individual cells patterned nearby with well-defined locations and shapes. We then demonstrate the generation of tandem bubbles by using two pulsed lasers illuminating a pair of gold dots with a few-microsecond time delay. We visualize the bubble-bubble interaction and jet formation by high-speed imaging and characterize the resultant flow field using particle image velocimetry (PIV). Finally, we present some applications of this technique for single cell analysis, including cell membrane poration with macromolecule uptake, localized membrane deformation determined by the displacements of attached integrin-binding beads, and intracellular calcium response from ratiometric imaging. Our results show that a fast and directional jetting flow is produced by the tandem bubble interaction, which can impose a highly localized shear stress on the surface of a cell grown in close proximity. Furthermore, different bioeffects can be induced by altering the strength of the jetting flow by adjusting the standoff distance from the cell to the tandem bubbles.

Rotary motion impairs attention to color change in 4-month-old infants.

PubMed

Kavšek, Michael

2013-06-01

Continuous color changes of an array of elements appear to stop changing if the array undergoes a coherent motion. This silencing illusion was demonstrated for adults by Suchow and Alvarez (Current Biology, 2011, vol. 21, pp. 140-143). The current forced-choice preferential looking study examined 4-month-old infants' sensitivity to the silencing illusion. Two experimental conditions were conducted. In the dynamic condition, infants were tested with two rotating rings of circular different-colored dots. In one of these rings the dots continuously changed color, whereas in the other ring the dots did not change color. In the static condition, the global rotary motion was eliminated from the targets. Infants preferred looking at the color-changing target in the static condition but not in the dynamic condition; they attended to the color changes in the static condition but failed to detect them in the dynamic condition. This differential looking pattern is consistent with the hypothesis that the silencing illusion can be established during early infancy. A control group of adults also responded to the silencing phenomenon. This substantiates that the stimuli generate a robust illusory effect. Copyright © 2013 Elsevier Inc. All rights reserved.

Dividing attention between two transparent motion surfaces results in a failure of selective attention

PubMed Central

Ernst, Zachary Raymond; Palmer, John; Boynton, Geoffrey M.

2012-01-01

In object-based attention, it is easier to divide attention between features within a single object than between features across objects. In this study we test the prediction of several capacity models in order to best characterize the cost to dividing attention between objects. Here we studied behavioral performance on a divided attention task in which subjects attended to the motion and luminance of overlapping random dot kinemategrams, specifically red upward moving dots superimposed with green downward moving dots. Subjects were required to detect brief changes (transients) in the motion or luminance within the same surface or across different surfaces. There were two primary results. First, the dual-task deficit was large when attention was divided across two surfaces and near zero when attention was divided within a surface. This is consistent with limited-capacity processing across surfaces and unlimited-capacity processing within a surface—a pattern predicted by established theories of object-based attention. Second and unexpectedly, there was evidence of crosstalk between features: when cued to monitor transients on one surface, response rates were inflated by the presence of a transient on the other surface. Such crosstalk is a failure of selective attention between surfaces. PMID:23149301

Matching and correlation computations in stereoscopic depth perception.

PubMed

Doi, Takahiro; Tanabe, Seiji; Fujita, Ichiro

2011-03-02

A fundamental task of the visual system is to infer depth by using binocular disparity. To encode binocular disparity, the visual cortex performs two distinct computations: one detects matched patterns in paired images (matching computation); the other constructs the cross-correlation between the images (correlation computation). How the two computations are used in stereoscopic perception is unclear. We dissociated their contributions in near/far discrimination by varying the magnitude of the disparity across separate sessions. For small disparity (0.03°), subjects performed at chance level to a binocularly opposite-contrast (anti-correlated) random-dot stereogram (RDS) but improved their performance with the proportion of contrast-matched (correlated) dots. For large disparity (0.48°), the direction of perceived depth reversed with an anti-correlated RDS relative to that for a correlated one. Neither reversed nor normal depth was perceived when anti-correlation was applied to half of the dots. We explain the decision process as a weighted average of the two computations, with the relative weight of the correlation computation increasing with the disparity magnitude. We conclude that matching computation dominates fine depth perception, while both computations contribute to coarser depth perception. Thus, stereoscopic depth perception recruits different computations depending on the disparity magnitude.

Methods for Presenting Braille Characters on a Mobile Device with a Touchscreen and Tactile Feedback.

PubMed

Rantala, J; Raisamo, R; Lylykangas, J; Surakka, V; Raisamo, J; Salminen, K; Pakkanen, T; Hippula, A

2009-01-01

Three novel interaction methods were designed for reading six-dot Braille characters from the touchscreen of a mobile device. A prototype device with a piezoelectric actuator embedded under the touchscreen was used to create tactile feedback. The three interaction methods, scan, sweep, and rhythm, enabled users to read Braille characters one at a time either by exploring the characters dot by dot or by sensing a rhythmic pattern presented on the screen. The methods were tested with five blind Braille readers as a proof of concept. The results of the first experiment showed that all three methods can be used to convey information as the participants could accurately (91-97 percent) recognize individual characters. In the second experiment the presentation rate of the most efficient and preferred method, the rhythm, was varied. A mean recognition accuracy of 70 percent was found when the speed of presenting a single character was nearly doubled from the first experiment. The results showed that temporal tactile feedback and Braille coding can be used to transmit single-character information while further studies are still needed to evaluate the presentation of serial information, i.e., multiple Braille characters.

Children with autism can track others' beliefs in a competitive game.

PubMed

Peterson, Candida C; Slaughter, Virginia; Peterson, James; Premack, David

2013-05-01

Theory of mind (ToM) development, assessed via 'litmus' false belief tests, is severely delayed in autism, but the standard testing procedure may underestimate these children's genuine understanding. To explore this, we developed a novel test involving competition to win a reward as the motive for tracking other players' beliefs (the 'Dot-Midge task'). Ninety-six children, including 23 with autism (mean age: 10.36 years), 50 typically developing 4-year-olds (mean age: 4.40) and 23 typically developing 3-year-olds (mean age: 3.59) took a standard 'Sally-Ann' false belief test, the Dot-Midge task (which was closely matched to the Sally-Ann task procedure) and a norm-referenced verbal ability test. Results revealed that, of the children with autism, 74% passed the Dot-Midge task, yet only 13% passed the standard Sally-Ann procedure. A similar pattern of performance was observed in the older, but not the younger, typically developing control groups. This finding demonstrates that many children with autism who fail motivationally barren standard false belief tests can spontaneously use ToM to track their social partners' beliefs in the context of a competitive game. © 2013 Blackwell Publishing Ltd.

Attention during active visual tasks: counting, pointing, or simply looking

PubMed Central

Wilder, John D.; Schnitzer, Brian S.; Gersch, Timothy M.; Dosher, Barbara A.

2009-01-01

Visual attention and saccades are typically studied in artificial situations, with stimuli presented to the steadily fixating eye, or saccades made along specified paths. By contrast, in the real world saccadic patterns are constrained only by the demands of the motivating task. We studied attention during pauses between saccades made to perform 3 free-viewing tasks: counting dots, pointing to the same dots with a visible cursor, or simply looking at the dots using a freely-chosen path. Attention was assessed by the ability to identify the orientation of a briefly-presented Gabor probe. All primary tasks produced losses in identification performance, with counting producing the largest losses, followed by pointing and then looking-only. Looking-only resulted in a 37% increase in contrast thresholds in the orientation task. Counting produced more severe losses that were not overcome by increasing Gabor contrast. Detection or localization of the Gabor, unlike identification, were largely unaffected by any of the primary tasks. Taken together, these results show that attention is required to control saccades, even with freely-chosen paths, but the attentional demands of saccades are less than those attached to tasks such as counting, which have a significant cognitive load. Counting proved to be a highly demanding task that either exhausted momentary processing capacity (e.g., working memory or executive functions), or, alternatively, encouraged a strategy of filtering out all signals irrelevant to counting itself. The fact that the attentional demands of saccades (as well as those of detection/localization) are relatively modest makes it possible to continually adjust both the spatial and temporal pattern of saccades so as to re-allocate attentional resources as needed to handle the complex and multifaceted demands of real-world environments. PMID:18649913

Dot-in-Well Quantum-Dot Infrared Photodetectors

NASA Technical Reports Server (NTRS)

Gunapala, Sarath; Bandara, Sumith; Ting, David; Hill, cory; Liu, John; Mumolo, Jason; Chang, Yia Chung

2008-01-01

Dot-in-well (DWELL) quantum-dot infrared photodetectors (QDIPs) [DWELL-QDIPs] are subjects of research as potentially superior alternatives to prior QDIPs. Heretofore, there has not existed a reliable method for fabricating quantum dots (QDs) having precise, repeatable dimensions. This lack has constituted an obstacle to the development of uniform, high-performance, wavelength-tailorable QDIPs and of focal-plane arrays (FPAs) of such QDIPs. However, techniques for fabricating quantum-well infrared photodetectors (QWIPs) having multiple-quantum- well (MQW) structures are now well established. In the present research on DWELL-QDIPs, the arts of fabrication of QDs and QWIPs are combined with a view toward overcoming the deficiencies of prior QDIPs. The longer-term goal is to develop focal-plane arrays of radiationhard, highly uniform arrays of QDIPs that would exhibit high performance at wavelengths from 8 to 15 m when operated at temperatures between 150 and 200 K. Increasing quantum efficiency is the key to the development of competitive QDIP-based FPAs. Quantum efficiency can be increased by increasing the density of QDs and by enhancing infrared absorption in QD-containing material. QDIPs demonstrated thus far have consisted, variously, of InAs islands on GaAs or InAs islands in InGaAs/GaAs wells. These QDIPs have exhibited low quantum efficiencies because the numbers of QD layers (and, hence, the areal densities of QDs) have been small typically five layers in each QDIP. The number of QD layers in such a device must be thus limited to prevent the aggregation of strain in the InAs/InGaAs/GaAs non-lattice- matched material system. The approach being followed in the DWELL-QDIP research is to embed In- GaAs QDs in GaAs/AlGaAs multi-quantum- well (MQW) structures (see figure). This material system can accommodate a large number of QD layers without excessive lattice-mismatch strain and the associated degradation of photodetection properties. Hence, this material system is expected to enable achievement of greater densities of QDs and correspondingly greater quantum efficiencies. The host GaAs/AlGaAs MQW structures are highly compatible with mature fabrication processes that are now used routinely in making QWIP FPAs. The hybrid InGaAs-dot/GaAs/AlGaAs-well system also offers design advantages in that the effects of variability of dot size can be partly compensated by engineering quantum-well sizes, which can be controlled precisely.

Galaxies in x-ray selected clusters and groups in Dark Energy Survey Data I: Stellar mass growth of bright central galaxies since Z similar to 1.2

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

Zhang, Y.; Miller, C.; McKay, T.

2016-01-10

Using the science verification data of the Dark Energy Survey for a new sample of 106 X-ray selected clusters and groups, we study the stellar mass growth of bright central galaxies (BCGs) since redshift z similar to 1.2. Compared with the expectation in a semi-analytical model applied to the Millennium Simulation, the observed BCGs become under-massive/under-luminous with decreasing redshift. We incorporate the uncertainties associated with cluster mass, redshift, and BCG stellar mass measurements into an analysis of a redshift-dependent BCG-cluster mass relation, m(*) proportional to (M-200/1.5 x 10(14)M(circle dot))(0.24 +/- 0.08)(1+z)(-0.19 +/- 0.34), and compare the observed relation to themore » model prediction. We estimate the average growth rate since z = 1.0 for BCGs hosted by clusters of M-200,M-z = 10(13.8)M(circle dot); at z = 1.0: m(*, BCG) appears to have grown by 0.13 +/- 0.11 dex, in tension at the similar to 2.5 sigma significance level with the 0.40 dex growth rate expected from the semi-analytic model. We show that the build-up of extended intracluster light after z = 1.0 may alleviate this tension in BCG growth rates.« less

49 CFR 173.304a - Additional requirements for shipment of liquefied compressed gases in specification cylinders.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., carbon bisulfide (disulfide), ethyl chloride, ethylene oxide, nickel carbonyl, spirits of nitroglycerin...; DOT-3B400; DOT-4AA480; DOT-4B400; DOT-4BA400; DOT-4BW400; DOT-3E1800; DOT-39; DOT-3AL400. Carbon...; DOT-3T1800; DOT-3HT2000; DOT-39; DOT-3AL1800. Carbon dioxide, refrigerated liquid (see paragraph (e...

49 CFR 173.304a - Additional requirements for shipment of liquefied compressed gases in specification cylinders.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., carbon bisulfide (disulfide), ethyl chloride, ethylene oxide, nickel carbonyl, spirits of nitroglycerin...; DOT-3B400; DOT-4AA480; DOT-4B400; DOT-4BA400; DOT-4BW400; DOT-3E1800; DOT-39; DOT-3AL400. Carbon...; DOT-3T1800; DOT-3HT2000; DOT-39; DOT-3AL1800. Carbon dioxide, refrigerated liquid (see paragraph (e...

Hexagonally ordered nanodots: Result of substrate rotation during oblique incidence low energy IBS

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

Chowdhury, Debasree, E-mail: debasree.chowdhury@saha.ac.in; Ghose, Debabrata, E-mail: debasree.chowdhury@saha.ac.in

The anisotropic regular patterns are often results during oblique incidence ion beam sputtering (IBS). Simultaneous substrate rotation (SR) during IBS can suppress surface roughening and removes anisotropic nature of surface pattern. Here, the evolution of Si surface morphology as result of with and without SR is studied during oblique incidence low energy Ar{sup +} sputtering. Resultant topography shows smooth surface to hexagonally ordered nanodots at different rotating conditions. Interestingly, surface roughness exhibits non-monotonic dependence on rotation frequency. The underlying mechanism for dot formation can be described within the framework of isotropic DKS equation.

Investigation of writing error in staggered heated-dot magnetic recording systems

NASA Astrophysics Data System (ADS)

Tipcharoen, W.; Warisarn, C.; Tongsomporn, D.; Karns, D.; Kovintavewat, P.

2017-05-01

To achieve an ultra-high storage capacity, heated-dot magnetic recording (HDMR) has been proposed, which heats a bit-patterned medium before recording data. Generally, an error during the HDMR writing process comes from several sources; however, we only investigate the effects of staggered island arrangement, island size fluctuation caused by imperfect fabrication, and main pole position fluctuation. Simulation results demonstrate that a writing error can be minimized by using a staggered array (hexagonal lattice) instead of a square array. Under the effect of main pole position fluctuation, the writing error is higher than the system without main pole position fluctuation. Finally, we found that the error percentage can drop below 10% when the island size is 8.5 nm and the standard deviation of the island size is 1 nm in the absence of main pole jitter.

A study of nitrogen incorporation in pyramidal site-controlled quantum dots

PubMed Central

2011-01-01

We present the results of a study of nitrogen incorporation in metalorganic-vapour-phase epitaxy-grown site-controlled quantum dots (QDs). We report for the first time on a significant incorporation (approximately 0.3%), producing a noteworthy red shift (at least 50 meV) in some of our samples. Depending on the level of nitrogen incorporation/exposure, strong modifications of the optical features are found (variable distribution of the emission homogeneity, fine-structure splitting, few-particle effects). We discuss our results, especially in relation to a specific reproducible sample which has noticeable features: the usual pattern of the excitonic transitions is altered and the fine-structure splitting is suppressed to vanishing values. Distinctively, nitrogen incorporation can be achieved without detriment to the optical quality, as confirmed by narrow linewidths and photon correlation spectroscopy. PMID:22029752

Contact tracing of tuberculosis: a systematic review of transmission modelling studies.

PubMed

Begun, Matt; Newall, Anthony T; Marks, Guy B; Wood, James G

2013-01-01

The WHO recommended intervention of Directly Observed Treatment, Short-course (DOTS) appears to have been less successful than expected in reducing the burden of TB in some high prevalence settings. One strategy for enhancing DOTS is incorporating active case-finding through screening contacts of TB patients as widely used in low-prevalence settings. Predictive models that incorporate population-level effects on transmission provide one means of predicting impacts of such interventions. We aim to identify all TB transmission modelling studies addressing contact tracing and to describe and critically assess their modelling assumptions, parameter choices and relevance to policy. We searched MEDLINE, SCOPUS, COMPENDEX, Google Scholar and Web of Science databases for relevant English language publications up to February 2012. Of the 1285 studies identified, only 5 studies met our inclusion criteria of models of TB transmission dynamics in human populations designed to incorporate contact tracing as an intervention. Detailed implementation of contact processes was only present in two studies, while only one study presented a model for a high prevalence, developing world setting. Some use of relevant data for parameter estimation was made in each study however validation of the predicted impact of interventions was not attempted in any of the studies. Despite a large body of literature on TB transmission modelling, few published studies incorporate contact tracing. There is considerable scope for future analyses to make better use of data and to apply individual based models to facilitate more realistic patterns of infectious contact. Combined with a focus on high burden settings this would greatly increase the potential for models to inform the use of contract tracing as a TB control policy. Our findings highlight the potential for collaborative work between clinicians, epidemiologists and modellers to gather data required to enhance model development and validation and hence better inform future public health policy.

Contact Tracing of Tuberculosis: A Systematic Review of Transmission Modelling Studies

PubMed Central

Begun, Matt; Newall, Anthony T.; Marks, Guy B.; Wood, James G.

2013-01-01

The WHO recommended intervention of Directly Observed Treatment, Short-course (DOTS) appears to have been less successful than expected in reducing the burden of TB in some high prevalence settings. One strategy for enhancing DOTS is incorporating active case-finding through screening contacts of TB patients as widely used in low-prevalence settings. Predictive models that incorporate population-level effects on transmission provide one means of predicting impacts of such interventions. We aim to identify all TB transmission modelling studies addressing contact tracing and to describe and critically assess their modelling assumptions, parameter choices and relevance to policy. We searched MEDLINE, SCOPUS, COMPENDEX, Google Scholar and Web of Science databases for relevant English language publications up to February 2012. Of the 1285 studies identified, only 5 studies met our inclusion criteria of models of TB transmission dynamics in human populations designed to incorporate contact tracing as an intervention. Detailed implementation of contact processes was only present in two studies, while only one study presented a model for a high prevalence, developing world setting. Some use of relevant data for parameter estimation was made in each study however validation of the predicted impact of interventions was not attempted in any of the studies. Despite a large body of literature on TB transmission modelling, few published studies incorporate contact tracing. There is considerable scope for future analyses to make better use of data and to apply individual based models to facilitate more realistic patterns of infectious contact. Combined with a focus on high burden settings this would greatly increase the potential for models to inform the use of contract tracing as a TB control policy. Our findings highlight the potential for collaborative work between clinicians, epidemiologists and modellers to gather data required to enhance model development and validation and hence better inform future public health policy. PMID:24023742

Self-assembled indium arsenide quantum dots: Structure, formation dynamics, optical properties

NASA Astrophysics Data System (ADS)

Lee, Hao

1998-12-01

In this dissertation, we investigate the properties of InAs/GaAs quantum dots grown by molecular beam epitaxy. The structure and formation dynamics of InAs quantum dots are studied by a variety of structural characterization techniques. Correlations among the growth conditions, the structural characteristics, and the observed optical properties are explored. The most fundamental structural characteristic of the InAs quantum dots is their shape. Through detailed study of the reflection high energy electron diffraction patterns, we determined that self-assembled InAs islands possess a pyramidal shape with 136 bounding facets. Cross-sectional transmission electron microscopy images and atomic force microscopy images strongly support this model. The 136 model we proposed is the first model that is consistent with all reported shape features determined using different methods. The dynamics of coherent island formation is also studied with the goal of establishing the factors most important in determining the size, density, and the shape of self- organized InAs quantum dots. Our studies clearly demonstrate the roles that indium diffusion and desorption play in InAs island formation. An unexpected finding (from atomic force microscopy images) was that the island size distribution bifurcated during post- growth annealing. Photoluminescence spectra of the samples subjected to in-situ annealing prior to the growth of a capping layer show a distinctive double-peak feature. The power-dependence and temperature-dependence of the photoluminescence spectra reveals that the double- peak emission is associated with the ground-state transition of islands in two different size branches. These results confirm the island size bifurcation observed from atomic force microscopy images. The island size bifurcation provides a new approach to the control and manipulation of the island size distribution. Unexpected dependence of the photoluminescence line-shape on sample temperature and pump intensity was observed for samples grown at relatively high substrate temperatures. The behavior is modeled and explained in terms of competition between two overlapping transitions. The study underscores that the growth conditions can have a dramatic impact on the optical properties of the quantum dots. This dissertation includes both my previously published and unpublished authored materials.

Characteristics and Travel Patterns of New York Residents: Subpopulations of Persons with a Disability in 2009

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

Hwang, Ho-Ling; Reuscher, Tim; Wilson, Daniel W.

In this study, Oak Ridge National Laboratory (ORNL) was tasked by the NYS Department of Transportation (DOT) to conduct a detailed examination of travel behaviors, and identify patterns and trends, on several NYS subpopulations, including disabled persons. Unlike other studies that concentrated on national level statistics, this research is focused on examining issues associated with travelers among NYS residents only. For each special subpopulation group, ORNL will identify differences, if any, in travel patterns that are attributable to demographic characteristics, household characteristics, modal characteristics, geographic location, and other concepts. Focus will be given to trip frequency, trip chaining, as wellmore » as travel by time of day, trip purpose, and mode choice.« less

Low-Loss Optical Metamaterials Based on Mie Resonances in Semiconductor Nanoparticle Composites

DTIC Science & Technology

2012-12-13

Brillouin zone where two transverse bands with linear dispersion intersect a flat longitudinal band, resulting in triple degeneracy. The fields in the...transmission pattern through Fourier plane imaging. This was accomplished by focusing a laser beam within the structure using a high numerical...conditions, a high frequency magnetic response could be created in metamaterials formed from composites of quantum dots utilizing excitonic resonances

Remote Tactile Displays for Future Soldiers

DTIC Science & Technology

2007-05-01

envisioned as an alternate means of communication for those who are visually 4 or hearing impaired. Oddly, the success of Braille “reading...designers. For example, simply embossing the alphabet in paper to read by touch succumbed to Braille because subtle spatial patterns easily apparent to...fashioned after the six- dot Braille system. Although an alphanumeric code was mastered with surprising rapidity, one striking difficulty emerged

Patterning and Characterization of Carbon Nanotubes Grown in a Microwave Plasma Enhanced Chemical Vapor Deposition Chamber

DTIC Science & Technology

2009-03-01

display [6] of walls can go from two (D- MWCNTs ) to no limit. The distance between the tubes is approximately 0.34 nm closely matching the graphene sheet... MWCNT . . . . . . . . . . . . . . . . . . 9 2.5. Chiral Vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6. Arc Discharge Reactor...17 2.15. MWCNTs from 260 nm Ni Dots . . . . . . . . . . . . . . . . . 19 2.16. Process Flow for Eom Technique

HPV E6/E7 RNA in situ hybridization signal patterns as biomarkers of three-tier cervical intraepithelial neoplasia grade.

PubMed

Evans, Mark F; Peng, Zhihua; Clark, Kelli M; Adamson, Christine S-C; Ma, Xiao-Jun; Wu, Xingyong; Wang, Hongwei; Luo, Yuling; Cooper, Kumarasen

2014-01-01

Cervical lesion grading is critical for effective patient management. A three-tier classification (cervical intraepithelial neoplasia [CIN] grade 1, 2 or 3) based on H&E slide review is widely used. However, for reasons of considerable inter-observer variation in CIN grade assignment and for want of a biomarker validating a three-fold stratification, CAP-ASCCP LAST consensus guidelines recommend a two-tier system: low- or high-grade squamous intraepithelial lesions (LSIL or HSIL). In this study, high-risk HPV E6/E7 and p16 mRNA expression patterns in eighty-six CIN lesions were investigated by RNAscope chromogenic in situ hybridization (CISH). Specimens were also screened by immunohistochemistry for p16INK4a (clone E6H4), and by tyramide-based CISH for HPV DNA. HPV genotyping was performed by GP5+/6+ PCR combined with cycle-sequencing. Abundant high-risk HPV RNA CISH signals were detected in 26/32 (81.3%) CIN 1, 22/22 (100%) CIN 2 and in 32/32 (100%) CIN 3 lesions. CIN 1 staining patterns were typified (67.7% specimens) by abundant diffusely staining nuclei in the upper epithelial layers; CIN 2 lesions mostly (66.7%) showed a combination of superficial diffuse-stained nuclei and multiple dot-like nuclear and cytoplasmic signals throughout the epithelium; CIN 3 lesions were characterized (87.5%) by multiple dot-like nuclear and cytoplasmic signals throughout the epithelial thickness and absence/scarcity of diffusely staining nuclei (trend across CIN grades: P<0.0001). These data are consistent with productive phase HPV infections exemplifying CIN 1, transformative phase infections CIN 3, whereas CIN 2 shows both productive and transformative phase elements. Three-tier data correlation was not found for the other assays examined. The dual discernment of diffuse and/or dot-like signals together with the assay's high sensitivity for HPV support the use of HPV E6/E7 RNA CISH as an adjunct test for deciding lesion grade when CIN 2 grading may be beneficial (e.g. among young women) or when 'LSIL vs. HSIL' assignment is equivocal.

HPV E6/E7 RNA In Situ Hybridization Signal Patterns as Biomarkers of Three-Tier Cervical Intraepithelial Neoplasia Grade

PubMed Central

Evans, Mark F.; Peng, Zhihua; Clark, Kelli M.; Adamson, Christine S.-C.; Ma, Xiao-Jun; Wu, Xingyong; Wang, Hongwei; Luo, Yuling; Cooper, Kumarasen

2014-01-01

Cervical lesion grading is critical for effective patient management. A three-tier classification (cervical intraepithelial neoplasia [CIN] grade 1, 2 or 3) based on H&E slide review is widely used. However, for reasons of considerable inter-observer variation in CIN grade assignment and for want of a biomarker validating a three-fold stratification, CAP-ASCCP LAST consensus guidelines recommend a two-tier system: low- or high-grade squamous intraepithelial lesions (LSIL or HSIL). In this study, high-risk HPV E6/E7 and p16 mRNA expression patterns in eighty-six CIN lesions were investigated by RNAscope chromogenic in situ hybridization (CISH). Specimens were also screened by immunohistochemistry for p16INK4a (clone E6H4), and by tyramide-based CISH for HPV DNA. HPV genotyping was performed by GP5+/6+ PCR combined with cycle-sequencing. Abundant high-risk HPV RNA CISH signals were detected in 26/32 (81.3%) CIN 1, 22/22 (100%) CIN 2 and in 32/32 (100%) CIN 3 lesions. CIN 1 staining patterns were typified (67.7% specimens) by abundant diffusely staining nuclei in the upper epithelial layers; CIN 2 lesions mostly (66.7%) showed a combination of superficial diffuse-stained nuclei and multiple dot-like nuclear and cytoplasmic signals throughout the epithelium; CIN 3 lesions were characterized (87.5%) by multiple dot-like nuclear and cytoplasmic signals throughout the epithelial thickness and absence/scarcity of diffusely staining nuclei (trend across CIN grades: P<0.0001). These data are consistent with productive phase HPV infections exemplifying CIN 1, transformative phase infections CIN 3, whereas CIN 2 shows both productive and transformative phase elements. Three-tier data correlation was not found for the other assays examined. The dual discernment of diffuse and/or dot-like signals together with the assay’s high sensitivity for HPV support the use of HPV E6/E7 RNA CISH as an adjunct test for deciding lesion grade when CIN 2 grading may be beneficial (e.g. among young women) or when ‘LSIL vs. HSIL’ assignment is equivocal. PMID:24625757

Imaging and Manipulating Energy Transfer Among Quantum Dots at Individual Dot Resolution.

PubMed

Nguyen, Duc; Nguyen, Huy A; Lyding, Joseph W; Gruebele, Martin

2017-06-27

Many processes of interest in quantum dots involve charge or energy transfer from one dot to another. Energy transfer in films of quantum dots as well as between linked quantum dots has been demonstrated by luminescence shift, and the ultrafast time-dependence of energy transfer processes has been resolved. Bandgap variation among dots (energy disorder) and dot separation are known to play an important role in how energy diffuses. Thus, it would be very useful if energy transfer could be visualized directly on a dot-by-dot basis among small clusters or within films of quantum dots. To that effect, we report single molecule optical absorption detected by scanning tunneling microscopy (SMA-STM) to image energy pooling from donor into acceptor dots on a dot-by-dot basis. We show that we can manipulate groups of quantum dots by pruning away the dominant acceptor dot, and switching the energy transfer path to a different acceptor dot. Our experimental data agrees well with a simple Monte Carlo lattice model of energy transfer, similar to models in the literature, in which excitation energy is transferred preferentially from dots with a larger bandgap to dots with a smaller bandgap.

Field-effect enhanced triboelectric colloidal quantum dot flexible sensor

NASA Astrophysics Data System (ADS)

Meng, Lingju; Xu, Qiwei; Fan, Shicheng; Dick, Carson R.; Wang, Xihua

2017-10-01

Flexible electronics, which is of great importance as fundamental sensor and communication technologies for many internet-of-things applications, has established a huge market encroaching into the trillion-dollar market of solid state electronics. For the capability of being processed by printing or spraying, colloidal quantum dots (CQDs) play an increasingly important role in flexible electronics. Although the electrical properties of CQD thin-films are expected to be stable on flexible substrates, their electrical performance could be tuned for applications in flexible touch sensors. Here, we report CQD touch sensors employing polydimethylsiloxane (PDMS) triboelectric films. The electrical response of touching activity is enhanced by incorporating CQD field-effect transistors into the device architecture. Thanks to the use of the CQD thin film as a current amplifier, the field-effect CQD touch sensor shows a fast response to various touching materials, even being bent to a large curvature. It also shows a much higher output current density compared to a PDMS triboelectric touch sensor.

Modeling Magnetic Properties in EZTB

NASA Technical Reports Server (NTRS)

Lee, Seungwon; vonAllmen, Paul

2007-01-01

A software module that calculates magnetic properties of a semiconducting material has been written for incorporation into, and execution within, the Easy (Modular) Tight-Binding (EZTB) software infrastructure. [EZTB is designed to model the electronic structures of semiconductor devices ranging from bulk semiconductors, to quantum wells, quantum wires, and quantum dots. EZTB implements an empirical tight-binding mathematical model of the underlying physics.] This module can model the effect of a magnetic field applied along any direction and does not require any adjustment of model parameters. The module has thus far been applied to study the performances of silicon-based quantum computers in the presence of magnetic fields and of miscut angles in quantum wells. The module is expected to assist experimentalists in fabricating a spin qubit in a Si/SiGe quantum dot. This software can be executed in almost any Unix operating system, utilizes parallel computing, can be run as a Web-portal application program. The module has been validated by comparison of its predictions with experimental data available in the literature.

Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

DOE PAGES

Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; ...

2017-05-16

Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the bandmore » edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. As a result, we expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.« less

Optical and magnetic properties of zinc oxide quantum dots doped with cobalt and lanthanum.

PubMed

Yu, Shiyong; Zhao, Jing; Su, Hai-Quan

2013-06-01

Cobalt and Lanthanum-doped ZnO QDs are synthesized by a modified sol-gel method under atmospheric conditions. The as-prepared quantum dots are characterized by X-ray powder diffraction (XRD), energy dispersive X-ray (EDX) analysis and high resolution transmission electron microscopy (HRTEM). The optical properties of the products are studied by fluorescent spectroscopy. With a proper Co and La doping, these nanoparticles possess exceptionally small size and enhanced fluorescence. Hysteresis loops of un-doped ZnO QDs and Co and La-doped ZnO QDs indicate that both the samples show ferromagnetic behavior at room temperature. Finally, these nanoparticles can label the BGC 803 cells successfully in short time and present no evidence of toxicity or adverse affect on cell growth even at the concentration up to 1 mM. We expect that the as-prepared Co and La-doped ZnO QDs can provide a better reliability of the collected data and find promising applications in biological, medical and other fields.

Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

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

Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.

Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the bandmore » edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. As a result, we expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.« less

Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

PubMed Central

Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; McNichols, Brett W.; Miller, Elisa M.; Gu, Jing; Nozik, Arthur J.; Sellinger, Alan; Galli, Giulia; Beard, Matthew C.

2017-01-01

Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the band edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. We expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications. PMID:28508866

Luminescent magnetic quantum dots for in vitro/in vivo imaging and applications in therapeutics.

PubMed

Acharya, Amitabha

2013-06-01

The quest for design of newer/advanced methods for medical diagnosis and targeted therapeutics are of utmost interest and challenging too, because of its importance in clinical diagnosis. Currently available diagnosis methodologies have their own disadvantages. These shortcomings can be overcome by using multimodal imaging systems where two or more imaging modalities may be coupled. Nanoparticles being widely studied for targeted drug delivery and as biological contrasting agents, might play a decisive role in such findings. This review is focused towards the ongoing research in the area of hybrid nanocomposites which can be used for both as MRI contrasting agent (magnetic nanoparticles) and molecular imaging studies (using fluorescent quantum dots) at in vitro and in vivo level. Though several reports are available in literature for such bimodal imaging systems, their clinical trials are very restricted, possibly because of the lack of communication between the in vitro and in vivo studies. This review is expected to bridge the gap between such studies.

Synthesis and characterisation of multifunctional alginate microspheres via the in situ formation of ZnO quantum dots and the graft of 4-(1-pyrenyl) butyric acid to sodium alginate.

PubMed

Luo, Guilin; Wang, Jianxin; Wang, Yingying; Feng, Bo; Weng, Jie

2015-01-01

Growth factor-loaded fluorescent alginate microspheres, which can realise sustained growth factor release and fluorescence imaging, were synthesised by in situ formation of ZnO quantum dots (QDs) and covalent graft of 4-(1-pyrenyl) butyric acid (PBA). BSA was chosen as a growth factor model protein to study the release kinetic of growth factors from alginate microspheres. The microsphere size and fluorescent properties were also investigated. Investigations of cell culture were used for evaluating biocompatibility of BSA-loaded fluorescent microspheres and fluorescence imaging property of ZnO QDs and PBA-grafted sodium alginate from the microspheres. The results show that they have good fluorescent property either to microspheres or to cells and fluorescent microspheres have good biocompatibility and property in sustained release of growth factors. The obtained microspheres will be expected to realise the imaging of cells and materials and also the release of growth factor in tissue engineering or in cell culture.

Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

NASA Astrophysics Data System (ADS)

Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; McNichols, Brett W.; Miller, Elisa M.; Gu, Jing; Nozik, Arthur J.; Sellinger, Alan; Galli, Giulia; Beard, Matthew C.

2017-05-01

Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the band edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. We expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.

Photoinduced Single- and Multiple-Electron Dynamics Processes Enhanced by Quantum Confinement in Lead Halide Perovskite Quantum Dots

DOE PAGES

Vogel, Dayton J.; Kryjevski, Andrei; Inerbaev, Talgat; ...

2017-03-21

Methylammonium lead iodide perovskite (MAPbI 3) is a promising material for photovoltaic devices. A modification of MAPbI 3 into confined nanostructures is expected to further increase efficiency of solar energy conversion. Photoexcited dynamic processes in a MAPbI3 quantum dot (QD) have been modeled by many-body perturbation theory and nonadiabatic dynamics. A photoexcitation is followed by either exciton cooling (EC), its radiative (RR) or nonradiative recombination (NRR), or multiexciton generation (MEG) processes. Computed times of these processes fall in the order of MEG < EC < RR < NRR, where MEG is on the order of a few femtoseconds, EC ismore » in the picosecond range, while RR and NRR are on the order of nanoseconds. Computed time scales indicate which electronic transition pathways can contribute to increase in charge collection efficiency. Simulated mechanisms of relaxation and their rates show that quantum confinement promotes MEG in MAPbI 3 QDs.« less

Single and Multiple Scattered Solar Radiation

DTIC Science & Technology

1982-08-30

so that factor can be expected to vary considerably from one scattering point to the next. The monochromatic intensity at the observer due to all of...the single scattering sources within the line-of-sight is obtained by summing over the optical path the product of the source function and the...the observer. Using a dot product 1)etwecen position_ vectors on the unit sphere, it can be Chown that cosA cost coss cost) cos4o + 0 S 0 0 "+ cost

The influence of the accelerated ageing on the black screen element of the Electroink prints

NASA Astrophysics Data System (ADS)

Majnaric, I.; Bolanca, Z.; Bolanca Mirkovic, I.

2010-06-01

Printing material and prints undergo changes during ageing which can be recognized in deterioration in the physical, chemical and optical properties. The aim of this work is to determine the optical changes of the prints caused by ageing of the printing material and of the prints obtained by the application of the indirect electrophotography. The change of the screen elements in lighter halftone areas, which was obtained by the usage of the microscopic image analysis, has been discussed in the article. For the preparation of samples the following papers were used: fine art paper, recycled paper and offset paper as well as black Electroink. Three sample series were observed: prints on nonaged paper and ElectroInk, prints on aged paper and ElectroInk and prints on aged paper and nonaged ElectroInk. The investigation results show that by ageing of the uncoated printing substrates the decrease of the dots on prints can be expected, while the printing on the aged paper results in the increased reproduction of the halftone dots. The obtained results are the contribution to the explanation of the influence of the accelerated ageing process of papers which are used for printing and the aged prints on the halftone dot changes. Except the mentioned determined scientific contribution the results are applicable in the area of the printing product quality as well as in the forensic science.

Novel method of extracting motion from natural movies.

PubMed

Suzuki, Wataru; Ichinohe, Noritaka; Tani, Toshiki; Hayami, Taku; Miyakawa, Naohisa; Watanabe, Satoshi; Takeichi, Hiroshige

2017-11-01

The visual system in primates can be segregated into motion and shape pathways. Interaction occurs at multiple stages along these pathways. Processing of shape-from-motion and biological motion is considered to be a higher-order integration process involving motion and shape information. However, relatively limited types of stimuli have been used in previous studies on these integration processes. We propose a new algorithm to extract object motion information from natural movies and to move random dots in accordance with the information. The object motion information is extracted by estimating the dynamics of local normal vectors of the image intensity projected onto the x-y plane of the movie. An electrophysiological experiment on two adult common marmoset monkeys (Callithrix jacchus) showed that the natural and random dot movies generated with this new algorithm yielded comparable neural responses in the middle temporal visual area. In principle, this algorithm provided random dot motion stimuli containing shape information for arbitrary natural movies. This new method is expected to expand the neurophysiological and psychophysical experimental protocols to elucidate the integration processing of motion and shape information in biological systems. The novel algorithm proposed here was effective in extracting object motion information from natural movies and provided new motion stimuli to investigate higher-order motion information processing. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

Women's Retirement Expectations: How Stable Are They?

PubMed Central

Hardy, Melissa A.

2009-01-01

Objective Using the National Longitudinal Survey of Mature Women, we examine between- and within-person differences in expected retirement age as a key element of the retirement planning process. The expectation typologies of 1,626 women born between 1923 and 1937 were classified jointly on the basis of specificity and consistency. Methods Latent class analysis was used to determine retirement expectation patterns over a 7-year span. Multinomial logistic regression analyses were employed to estimate the effects of demographic and status characteristics on the likelihood of reporting 4 distinct longitudinal patterns of retirement expectations. Results Substantial heterogeneity in reports of expected retirement age between and within individuals over the 7-year span was found. Demographic and status characteristics, specifically age, race, marital status, job tenure, and recent job change, sorted respondents into different retirement expectation patterns. Conclusions The frequent within-person fluctuations and substantial between-person heterogeneity in retirement expectations indicate uncertainty and variability in both expectations and process of expectation formation. Variability in respondents' reports suggests that studying retirement expectations at multiple time points better captures the dynamics of preretirement planning. PMID:19176483

49 CFR 173.304a - Additional requirements for shipment of liquefied compressed gases in specification cylinders.

Code of Federal Regulations, 2013 CFR

2013-10-01

...-3E1800. Chlorodifluroethane or 1-Chloro-1, 1-difluoroethane (R-142b) 100 DOT-3A150; DOT-3AA150; DOT-3B150...; DOT-3AL225. Dichlorodifluoromethane and difluoroethane mixture (constant boiling mixture) (R-500) (see...; DOT-4BW240; DOT-4E240; DOT-39. 1,1-Difluoroethane (R-152a) (see note 8) 79 DOT-3A150; DOT-3AA150; DOT...

49 CFR 173.304a - Additional requirements for shipment of liquefied compressed gases in specification cylinders.

Code of Federal Regulations, 2012 CFR

2012-10-01

...-3E1800. Chlorodifluroethane or 1-Chloro-1, 1-difluoroethane (R-142b) 100 DOT-3A150; DOT-3AA150; DOT-3B150...; DOT-3AL225. Dichlorodifluoromethane and difluoroethane mixture (constant boiling mixture) (R-500) (see...; DOT-4BW240; DOT-4E240; DOT-39. 1,1-Difluoroethane (R-152a) (see note 8) 79 DOT-3A150; DOT-3AA150; DOT...

Self-consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves. 2. Wave Induced Ring Current Precipitation and Thermal Electron Heating

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.; Liemohn, M. W.

2007-01-01

This paper continues presentation and discussion of the results from our new global self-consistent theoretical model of interacting ring current ions and propagating electromagnetic ion cyclotron waves [Khazanov et al., 2006]. To study the effects of electromagnetic ion cyclotron wave propagation and refraction on the wave induced ring current precipitation and heating of the thermal plasmaspheric electrons, we simulate the May 1998 storm. The main findings after a simulation can be summarized as follows. Firstly, the wave induced ring current precipitation exhibits quite a lot of fine structure, and is highly organized by location of the plasmapause gradient. The strongest fluxes of about 4 x 10(exp 6) (cm(raised dot) s(raised dot) sr(raised dot) (sup -1)) are observed during the maill and early recovery phases of the storm. The very interesting and probably more important finding is that in a number of cases the most intense precipitating fluxes are not connected to the most intense waves in simple manner. The characteristics of the wave power spectral density distribution over the wave normal angle are extremely crucial for the effectiveness of the ring current ion scattering. Secondly, comparison of the global proton precipitating patterns with the results from RAM [Kozyra et al., 1997a] reveals that although we observe a qualitative agreement between the localizations of the wave induced precipitations in the models, there is no quantitative agreement between the magnitudes of the fluxes. The quantitative differences are mainly due to a qualitative difference between the characteristics of the wave power spectral density distributions over the wave normal angle in RAM and in our model. Thirdly, the heat fluxes to plasmaspheric electrons caused by Landau resonate energy absorption from electromagnetic ion cyclotron waves are observed in the postnoon-premidnight MLT sector, and can reach the magnitude of 10(exp 11) eV/(cm(sup 2)(raised dot)s). The Coulomb energy degradation of the RC H(+) and O(+) ions maximizes at about 10(exp 11) (eV/(cm(sup 2) (raised dot) s), and typically leads to electron energy deposition rates of about 2(raised dot) 10(exp 10) (eV/(cm(sup 2)(raised dot)s) which are observed during two periods; 32-48 hours, and 76-86 hours after 1 May, 0000 UT. The theoretically derived spatial structure of the thermal electron heating caused by interaction of the ring current with the plasmasphere is strongly supported by concurrent and conjugate plasma measurements from the plasmasphere, ring current, and topside ionosphere [Gurgiolo et al., 2005]. Finally, the wave induced intense electron heating has a structure of the spot-like patches along the most enhanced density gradients in the plasmasphere boundary layer and can be a possible driver to the observed but still not explained small-scale structures of enhanced emissions in the stable auroral red arcs.

Delayed treatment of tuberculosis patients in rural areas of Yogyakarta province, Indonesia

PubMed Central

Mahendradhata, Yodi; Syahrizal, Bobby M; Utarini, Adi

2008-01-01

Background In year 2000, the entire population in Indonesia was 201 million and 57.6 percent of that was living in rural areas. This paper reports analyses that address to what extent the rural structure influence the way TB patients seek care prior to diagnosis by a DOTS facility. Methods We documented healthcare utilization pattern of smear positive TB patients prior to diagnosis and treatment by DOTS services (health centre, chest clinic, public and private hospital) in Yogyakarta province. We calculated the delay in treatment as the number of weeks between the onset of symptoms and the start of DOTS treatment. Statistical analysis was carried out with Epi Info version 3.3 (October 5, 2004). Results The only factor which was significantly associated with total delay was urban-rural setting (p = < 0.0001). The median total delay for TB patients in urban districts was 8 (1st Quartile = 4; 3rd Quartile = 12) weeks compared to 12 (1st Quartile = 7; 3rd Quartile = 23) weeks for patients in rural districts. Multivariate analysis suggested no confounding between individual factors and urban-rural setting remained as the main factor for total delay (p = < 0.0001). Primary health centre was the first choice provider for most (38.7%) of these TB patients. Urban-rural setting was also the only factor which was significantly associated with choice of first provider (p = 0.03). Conclusion Improving access to DOTS services in rural areas is an area of vital importance in aiming to make progress toward achieving TB control targets in Indonesia. PMID:19036164

High sensitive virus and bacteria detection using plasma-surface-functionalized and antibody-integrated carbon nanomaterials

NASA Astrophysics Data System (ADS)

Nagatsu, Masaaki

2015-09-01

In this study we will present our recent results on the virus and bacteria detection system using the surface-functionalized carbon-encapsulated magnetic nanoparticles (NPs) fabricated by dc arc discharge, and carbon nanotube(CNT) dot-array prepared with a combined thermal and plasma CVD system. Surface functionalization of their surfaces has been carried out by plasma chemical modification using a low-pressure RF plasma for carbon-encapsulated magnetic NPs, and an ultrafine atmospheric pressure plasma jet(APPJ) for CNT dot-array substrate. After immobilization of the relevant biomolecules onto the surface of nano-structured materials, we have carried out the experiments on virus or bacteria detection using these surface-functionalized nano-structured materials. From the preliminary experiments with carbon-encapsulated magnetic NPs, we confirmed that influenza A (H1N1) virus concentration of 17.3-fold was achieved by using anti-influenza A virus hemagglutinin (HA) antibody. We have also confirmed a rapid and sensitive detection of Salmonella using the proposed method. The feasibility of CNT dot-array as a microarray biosensor has been studied by maskless functionalization of amino (-NH2) and carboxyl (-COOH) groups onto CNTs by using a ultrafine APPJ with a micro-capillary. The experimental results of chemical derivatization with the fluorescent dye showed that the CNT dot-array was not only functionalized with amino group and carboxyl group, but was also functionalized without any interference between functional groups. The success of maskless functionalization in the line pattern provides a feasibility of a multi-functionalization CNT dot-array device for future application of a microarray biosensor. This work has been supported in part by Grant-in-Aid for Scientific Research (Nos. 21110010 and 25246029) from the JSPS and the International Research Collaboration and Scientific Publication Grant (DIPA-23.04.1.673453/2015) from DGHE Indonesia.

Imprint lithography template technology for bit patterned media (BPM)

NASA Astrophysics Data System (ADS)

Lille, J.; Patel, K.; Ruiz, R.; Wu, T.-W.; Gao, H.; Wan, Lei; Zeltzer, G.; Dobisz, E.; Albrecht, T. R.

2011-11-01

Bit patterned media (BPM) for magnetic recording has emerged as a promising technology to deliver thermally stable magnetic storage at densities beyond 1Tb/in2. Insertion of BPM into hard disk drives will require the introduction of nanoimprint lithography and other nanofabrication processes for the first time. In this work, we focus on nanoimprint and nanofabrication challenges that are being overcome in order to produce patterned media. Patterned media has created the need for new tools and processes, such as an advanced rotary e-beam lithography tool and block copolymer integration. The integration of block copolymer is through the use of a chemical contrast pattern on the substrate which guides the alignment of di-block copolymers. Most of the work on directed self assembly for patterned media applications has, until recently, concentrated on the formation of circular dot patterns in a hexagonal close packed lattice. However, interactions between the read head and media favor a bit aspect ratio (BAR) greater than one. This design constraint has motivated new approaches for using self-assembly to create suitable high-BAR master patterns and has implications for template fabrication.

OxfordGrid: a web interface for pairwise comparative map views.

PubMed

Yang, Hongyu; Gingle, Alan R

2005-12-01

OxfordGrid is a web application and database schema for storing and interactively displaying genetic map data in a comparative, dot-plot, fashion. Its display is composed of a matrix of cells, each representing a pairwise comparison of mapped probe data for two linkage groups or chromosomes. These are arranged along the axes with one forming grid columns and the other grid rows with the degree and pattern of synteny/colinearity between the two linkage groups manifested in the cell's dot density and structure. A mouse click over the selected grid cell launches an image map-based display for the selected cell. Both individual and linear groups of mapped probes can be selected and displayed. Also, configurable links can be used to access other web resources for mapped probe information. OxfordGrid is implemented in C#/ASP.NET and the package, including MySQL schema creation scripts, is available at ftp://cggc.agtec.uga.edu/OxfordGrid/.

Sequential shrink photolithography for plastic microlens arrays

NASA Astrophysics Data System (ADS)

Dyer, David; Shreim, Samir; Jayadev, Shreshta; Lew, Valerie; Botvinick, Elliot; Khine, Michelle

2011-07-01

Endeavoring to push the boundaries of microfabrication with shrinkable polymers, we have developed a sequential shrink photolithography process. We demonstrate the utility of this approach by rapidly fabricating plastic microlens arrays. First, we create a mask out of the children's toy Shrinky Dinks by simply printing dots using a standard desktop printer. Upon retraction of this pre-stressed thermoplastic sheet, the dots shrink to a fraction of their original size, which we then lithographically transfer onto photoresist-coated commodity shrink wrap film. This shrink film reduces in area by 95% when briefly heated, creating smooth convex photoresist bumps down to 30 µm. Taken together, this sequential shrink process provides a complete process to create microlenses, with an almost 99% reduction in area from the original pattern size. Finally, with a lithography molding step, we emboss these bumps into optical grade plastics such as cyclic olefin copolymer for functional microlens arrays.

Dewetting-Induced Photoluminescent Enhancement of Poly(lauryl methacrylate)/Quantum Dot Thin Films.

PubMed

Geldmeier, Jeffrey; Rile, Lexy; Yoon, Young Jun; Jung, Jaehan; Lin, Zhiqun; Tsukruk, Vladimir V

2017-12-19

A new method for enhancing photoluminescence from quantum dot (QD)/polymer nanocomposite films is proposed. Poly(lauryl methacrylate) (PLMA) thin films containing embedded QDs are intentionally allowed to undergo dewetting on substrates by exposure to a nonsolvent vapor. After controlled dewetting, films exhibited typical dewetting morphologies with increased amounts of scattering that served to outcouple photoluminescence from the film and reduce internal light propagation within the film. Up to a 5-fold enhancement of the film emission was achieved depending on material factors such as the initial film thickness and QD concentration within the film. An increase in initial film thickness was shown to increase the dewetted maximum feature size and its characteristic length until a critical thickness was reached where dewetting became inhibited. A unique light exposure-based photopatterning method is also presented for the creation of high contrast emissive patterns as guided by spatially controlled dewetting.

Action Video Games Improve Direction Discrimination of Parafoveal Translational Global Motion but Not Reaction Times.

PubMed

Pavan, Andrea; Boyce, Matthew; Ghin, Filippo

2016-10-01

Playing action video games enhances visual motion perception. However, there is psychophysical evidence that action video games do not improve motion sensitivity for translational global moving patterns presented in fovea. This study investigates global motion perception in action video game players and compares their performance to that of non-action video game players and non-video game players. Stimuli were random dot kinematograms presented in the parafovea. Observers discriminated the motion direction of a target random dot kinematogram presented in one of the four visual quadrants. Action video game players showed lower motion coherence thresholds than the other groups. However, when the task was performed at threshold, we did not find differences between groups in terms of distributions of reaction times. These results suggest that action video games improve visual motion sensitivity in the near periphery of the visual field, rather than speed response. © The Author(s) 2016.

Reflection high energy electron diffraction observation of surface mass transport at the two- to three-dimensional growth transition of InAs on GaAs(001)

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

Patella, F.; Arciprete, F.; Fanfoni, M.

2005-12-19

We have followed by reflection high-energy electron diffraction the nucleation of InAs quantum dots on GaAs(001), grown by molecular-beam epitaxy with growth interruptions. Surface mass transport gives rise, at the critical InAs thickness, to a huge nucleation of three-dimensional islands within 0.2 monolayers (ML). Such surface mass diffusion has been evidenced by observing the transition of the reflection high-energy electron diffraction pattern from two- to three-dimensional during the growth interruption after the deposition of 1.59 ML of InAs. It is suggested that the process is driven by the As{sub 2} adsorption-desorption process and by the lowering of the In bindingmore » energy due to compressive strain. The last condition is met first in the region surrounding dots at step edges where nucleation predominantly occurs.« less

Adults' Arithmetic Builds on Fast and Automatic Processing of Arabic Digits: Evidence from an Audiovisual Matching Paradigm

PubMed Central

Sasanguie, Delphine; Reynvoet, Bert

2014-01-01

Several studies have shown that performance on symbolic number tasks is related to individual differences in arithmetic. However, it is not clear which process is responsible for this association, i.e. fast, automatic processing of symbols per se or access to the underlying non-symbolic representation of the symbols. To dissociate between both options, adult participants performed an audiovisual matching paradigm. Auditory presented number words needed to be matched with either Arabic digits or dot patterns. The results revealed that a distance effect was present in the dots-number word matching task and absent in the digit-number word matching task. Crucially, only performance in the digit task contributed to the variance in arithmetical abilities. This led us to conclude that adults' arithmetic builds on the ability to quickly and automatically process Arabic digits, without the underlying non-symbolic magnitude representation being activated. PMID:24505308

Sequential shrink photolithography for plastic microlens arrays.

PubMed

Dyer, David; Shreim, Samir; Jayadev, Shreshta; Lew, Valerie; Botvinick, Elliot; Khine, Michelle

2011-07-18

Endeavoring to push the boundaries of microfabrication with shrinkable polymers, we have developed a sequential shrink photolithography process. We demonstrate the utility of this approach by rapidly fabricating plastic microlens arrays. First, we create a mask out of the children's toy Shrinky Dinks by simply printing dots using a standard desktop printer. Upon retraction of this pre-stressed thermoplastic sheet, the dots shrink to a fraction of their original size, which we then lithographically transfer onto photoresist-coated commodity shrink wrap film. This shrink film reduces in area by 95% when briefly heated, creating smooth convex photoresist bumps down to 30 µm. Taken together, this sequential shrink process provides a complete process to create microlenses, with an almost 99% reduction in area from the original pattern size. Finally, with a lithography molding step, we emboss these bumps into optical grade plastics such as cyclic olefin copolymer for functional microlens arrays.

Sequential shrink photolithography for plastic microlens arrays

PubMed Central

Dyer, David; Shreim, Samir; Jayadev, Shreshta; Lew, Valerie; Botvinick, Elliot; Khine, Michelle

2011-01-01

Endeavoring to push the boundaries of microfabrication with shrinkable polymers, we have developed a sequential shrink photolithography process. We demonstrate the utility of this approach by rapidly fabricating plastic microlens arrays. First, we create a mask out of the children’s toy Shrinky Dinks by simply printing dots using a standard desktop printer. Upon retraction of this pre-stressed thermoplastic sheet, the dots shrink to a fraction of their original size, which we then lithographically transfer onto photoresist-coated commodity shrink wrap film. This shrink film reduces in area by 95% when briefly heated, creating smooth convex photoresist bumps down to 30 µm. Taken together, this sequential shrink process provides a complete process to create microlenses, with an almost 99% reduction in area from the original pattern size. Finally, with a lithography molding step, we emboss these bumps into optical grade plastics such as cyclic olefin copolymer for functional microlens arrays. PMID:21863126

Blocking-state influence on shot noise and conductance in quantum dots

NASA Astrophysics Data System (ADS)

Harabula, M.-C.; Ranjan, V.; Haller, R.; Fülöp, G.; Schönenberger, C.

2018-03-01

Quantum dots (QDs) investigated through electron transport measurements often exhibit varying, state-dependent tunnel couplings to the leads. Under specific conditions, weakly coupled states can result in a strong suppression of the electrical current, and they are correspondingly called blocking states. Using the combination of conductance and shot noise measurements, we investigate blocking states in carbon nanotube (CNT) QDs. We report negative differential conductance and super-Poissonian noise. The enhanced noise is the signature of electron bunching, which originates from random switches between the strongly and weakly conducting states of the QD. Negative differential conductance appears here when the blocking state is an excited state. In this case, at the threshold voltage where the blocking state becomes populated, the current is reduced. Using a master equation approach, we provide numerical simulations reproducing both the conductance and the shot noise pattern observed in our measurements.

Design, Implementation and Characterization of a Quantum-Dot-Based Volumetric Display

NASA Astrophysics Data System (ADS)

Hirayama, Ryuji; Naruse, Makoto; Nakayama, Hirotaka; Tate, Naoya; Shiraki, Atsushi; Kakue, Takashi; Shimobaba, Tomoyoshi; Ohtsu, Motoichi; Ito, Tomoyoshi

2015-02-01

In this study, we propose and experimentally demonstrate a volumetric display system based on quantum dots (QDs) embedded in a polymer substrate. Unlike conventional volumetric displays, our system does not require electrical wiring; thus, the heretofore unavoidable issue of occlusion is resolved because irradiation by external light supplies the energy to the light-emitting voxels formed by the QDs. By exploiting the intrinsic attributes of the QDs, the system offers ultrahigh definition and a wide range of colours for volumetric displays. In this paper, we discuss the design, implementation and characterization of the proposed volumetric display's first prototype. We developed an 8 × 8 × 8 display comprising two types of QDs. This display provides multicolour three-type two-dimensional patterns when viewed from different angles. The QD-based volumetric display provides a new way to represent images and could be applied in leisure and advertising industries, among others.

Design, implementation and characterization of a quantum-dot-based volumetric display.

PubMed

Hirayama, Ryuji; Naruse, Makoto; Nakayama, Hirotaka; Tate, Naoya; Shiraki, Atsushi; Kakue, Takashi; Shimobaba, Tomoyoshi; Ohtsu, Motoichi; Ito, Tomoyoshi

2015-02-16

In this study, we propose and experimentally demonstrate a volumetric display system based on quantum dots (QDs) embedded in a polymer substrate. Unlike conventional volumetric displays, our system does not require electrical wiring; thus, the heretofore unavoidable issue of occlusion is resolved because irradiation by external light supplies the energy to the light-emitting voxels formed by the QDs. By exploiting the intrinsic attributes of the QDs, the system offers ultrahigh definition and a wide range of colours for volumetric displays. In this paper, we discuss the design, implementation and characterization of the proposed volumetric display's first prototype. We developed an 8 × 8 × 8 display comprising two types of QDs. This display provides multicolour three-type two-dimensional patterns when viewed from different angles. The QD-based volumetric display provides a new way to represent images and could be applied in leisure and advertising industries, among others.

Pre-seizure state identified by diffuse optical tomography

PubMed Central

Zhang, Tao; Zhou, Junli; Jiang, Ruixin; Yang, Hao; Carney, Paul R.; Jiang, Huabei

2014-01-01

In epilepsy it has been challenging to detect early changes in brain activity that occurs prior to seizure onset and to map their origin and evolution for possible intervention. Here we demonstrate using a rat model of generalized epilepsy that diffuse optical tomography (DOT) provides a unique functional neuroimaging modality for noninvasively and continuously tracking such brain activities with high spatiotemporal resolution. We detected early hemodynamic responses with heterogeneous patterns, along with intracranial electroencephalogram gamma power changes, several minutes preceding the electroencephalographic seizure onset, supporting the presence of a “pre-seizure” state. We also observed the decoupling between local hemodynamic and neural activities. We found widespread hemodynamic changes evolving from local regions of the bilateral cortex and thalamus to the entire brain, indicating that the onset of generalized seizures may originate locally rather than diffusely. Together, these findings suggest DOT represents a powerful tool for mapping early seizure onset and propagation pathways. PMID:24445927

MODELING THE NON-RECYCLED FERMI GAMMA-RAY PULSAR POPULATION

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

Perera, B. B. P.; McLaughlin, M. A.; Cordes, J. M.

2013-10-10

We use Fermi Gamma-ray Space Telescope detections and upper limits on non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain how the gamma-ray luminosity L{sub γ} depends on the period P and the period derivative P-dot . We use a Bayesian analysis to calculate a best-fit luminosity law, or dependence of L{sub γ} on P and P-dot , including different methods for modeling the beaming factor. An outer gap (OG) magnetosphere geometry provides the best-fit model, which is L{sub γ}∝P{sup -a} P-dot {sup b} where a = 1.36 ± 0.03 and b = 0.44 ± 0.02, similar tomore » but not identical to the commonly assumed L{sub γ}∝√( E-dot )∝P{sup -1.5} P-dot {sup 0.5}. Given upper limits on gamma-ray fluxes of currently known radio pulsars and using the OG model, we find that about 92% of the radio-detected pulsars have gamma-ray beams that intersect our line of sight. By modeling the misalignment of radio and gamma-ray beams of these pulsars, we find an average gamma-ray beaming solid angle of about 3.7π for the OG model, assuming a uniform beam. Using LAT-measured diffuse fluxes, we place a 2σ upper limit on the average braking index and a 2σ lower limit on the average surface magnetic field strength of the pulsar population of 3.8 and 3.2 × 10{sup 10} G, respectively. We then predict the number of non-recycled pulsars detectable by the LAT based on our population model. Using the 2 yr sensitivity, we find that the LAT is capable of detecting emission from about 380 non-recycled pulsars, including 150 currently identified radio pulsars. Using the expected 5 yr sensitivity, about 620 non-recycled pulsars are detectable, including about 220 currently identified radio pulsars. We note that these predictions significantly depend on our model assumptions.« less

Highly Parallel Computing Architectures by using Arrays of Quantum-dot Cellular Automata (QCA): Opportunities, Challenges, and Recent Results

NASA Technical Reports Server (NTRS)

Fijany, Amir; Toomarian, Benny N.

2000-01-01

There has been significant improvement in the performance of VLSI devices, in terms of size, power consumption, and speed, in recent years and this trend may also continue for some near future. However, it is a well known fact that there are major obstacles, i.e., physical limitation of feature size reduction and ever increasing cost of foundry, that would prevent the long term continuation of this trend. This has motivated the exploration of some fundamentally new technologies that are not dependent on the conventional feature size approach. Such technologies are expected to enable scaling to continue to the ultimate level, i.e., molecular and atomistic size. Quantum computing, quantum dot-based computing, DNA based computing, biologically inspired computing, etc., are examples of such new technologies. In particular, quantum-dots based computing by using Quantum-dot Cellular Automata (QCA) has recently been intensely investigated as a promising new technology capable of offering significant improvement over conventional VLSI in terms of reduction of feature size (and hence increase in integration level), reduction of power consumption, and increase of switching speed. Quantum dot-based computing and memory in general and QCA specifically, are intriguing to NASA due to their high packing density (10(exp 11) - 10(exp 12) per square cm ) and low power consumption (no transfer of current) and potentially higher radiation tolerant. Under Revolutionary Computing Technology (RTC) Program at the NASA/JPL Center for Integrated Space Microelectronics (CISM), we have been investigating the potential applications of QCA for the space program. To this end, exploiting the intrinsic features of QCA, we have designed novel QCA-based circuits for co-planner (i.e., single layer) and compact implementation of a class of data permutation matrices, a class of interconnection networks, and a bit-serial processor. Building upon these circuits, we have developed novel algorithms and QCA-based architectures for highly parallel and systolic computation of signal/image processing applications, such as FFT and Wavelet and Wlash-Hadamard Transforms.

Microgravity

NASA Image and Video Library

1995-10-20

This drawing depicts one set of flow patterns simulated in the Geophysical Fluid Flow Cell (GFFC) that flew on two Spacelab missions. Silicone oil served as the atmosphere around a rotating steel hemisphere (dotted circle) and an electrostatic field pulled the oil inward to mimic gravity's effects during the experiments. The GFFC thus produced flow patterns that simulated conditions inside the atmospheres of Jupiter and the Sun and other stars. The principal investigator was John Hart of the University of Colorado at Boulder. It was managed by NASA's Marshall Space Flight Center (MSFC). An Acrobat PDF copy of this drawing is available at http://microgravity.nasa.gov/gallery. (Credit: NASA/Marshall Space Flight Center)

Microgravity

NASA Image and Video Library

1995-10-10

This composite image depicts one set of flow patterns simulated in the Geophysical Fluid Flow Cell (GFFC) that flew on two Spacelab missions. Silicone oil served as the atmosphere around a rotating steel hemisphere (dotted circle) and an electrostatic field pulled the oil inward to mimic gravity's effects during the experiments. The GFFC thus produced flow patterns that simulated conditions inside the atmospheres of Jupiter and the Sun and other stars. GFFC flew on Spacelab-3 in 1985 and U.S. Microgravity Laboratory-2 in 1995. The principal investigator was John Hart of the University of Colorado at Boulder. It was managed by NASA's Marshall Space Flight Center. (Credit: NASA/Marshall Space Flight Center)

Fuzzy recurrence plots

NASA Astrophysics Data System (ADS)

Pham, T. D.

2016-12-01

Recurrence plots display binary texture of time series from dynamical systems with single dots and line structures. Using fuzzy recurrence plots, recurrences of the phase-space states can be visualized as grayscale texture, which is more informative for pattern analysis. The proposed method replaces the crucial similarity threshold required by symmetrical recurrence plots with the number of cluster centers, where the estimate of the latter parameter is less critical than the estimate of the former.

Hybrid nanostructures of well-organized arrays of colloidal quantum dots and a self-assembled monolayer of gold nanoparticles for enhanced fluorescence

NASA Astrophysics Data System (ADS)

Liu, Xiaoying; McBride, Sean P.; Jaeger, Heinrich M.; Nealey, Paul F.

2016-07-01

Hybrid nanomaterials comprised of well-organized arrays of colloidal semiconductor quantum dots (QDs) in close proximity to metal nanoparticles (NPs) represent an appealing system for high-performance, spectrum-tunable photon sources with controlled photoluminescence. Experimental realization of such materials requires well-defined QD arrays and precisely controlled QD-metal interspacing. This long-standing challenge is tackled through a strategy that synergistically combines lateral confinement and vertical stacking. Lithographically generated nanoscale patterns with tailored surface chemistry confine the QDs into well-organized arrays with high selectivity through chemical pattern directed assembly, while subsequent coating with a monolayer of close-packed Au NPs introduces the plasmonic component for fluorescence enhancement. The results show uniform fluorescence emission in large-area ordered arrays for the fabricated QD structures and demonstrate five-fold fluorescence amplification for red, yellow, and green QDs in the presence of the Au NP monolayer. Encapsulation of QDs with a silica shell is shown to extend the design space for reliable QD/metal coupling with stronger enhancement of 11 times through the tuning of QD-metal spatial separation. This approach provides new opportunities for designing hybrid nanomaterials with tailored array structures and multiple functionalities for applications such as multiplexed optical coding, color display, and quantum transduction.

Misfit-guided self-organization of anticorrelated Ge quantum dot arrays on Si nanowires.

PubMed

Kwon, Soonshin; Chen, Zack C Y; Kim, Ji-Hun; Xiang, Jie

2012-09-12

Misfit-strain guided growth of periodic quantum dot (QD) arrays in planar thin film epitaxy has been a popular nanostructure fabrication method. Engineering misfit-guided QD growth on a nanoscale substrate such as the small curvature surface of a nanowire represents a new approach to self-organized nanostructure preparation. Perhaps more profoundly, the periodic stress underlying each QD and the resulting modulation of electro-optical properties inside the nanowire backbone promise to provide a new platform for novel mechano-electronic, thermoelectronic, and optoelectronic devices. Herein, we report a first experimental demonstration of self-organized and self-limited growth of coherent, periodic Ge QDs on a one-dimensional Si nanowire substrate. Systematic characterizations reveal several distinctively different modes of Ge QD ordering on the Si nanowire substrate depending on the core diameter. In particular, Ge QD arrays on Si nanowires of around 20 nm diameter predominantly exhibit an anticorrelated pattern whose wavelength agrees with theoretical predictions. The correlated pattern can be attributed to propagation and correlation of misfit strain across the diameter of the thin nanowire substrate. The QD array growth is self-limited as the wavelength of the QDs remains unchanged even after prolonged Ge deposition. Furthermore, we demonstrate a direct kinetic transformation from a uniform Ge shell layer to discrete QD arrays by a postgrowth annealing process.

A Microfluidic System with Surface Patterning for Investigating Cavitation Bubble(s)-Cell Interaction and the Resultant Bioeffects at the Single-Cell Level

PubMed Central

Li, Fenfang; Yuan, Fang; Sankin, Georgy; Yang, Chen; Zhong, Pei

2017-01-01

In this manuscript, we first describe the fabrication protocol of a microfluidic chip, with gold dots and fibronectin-coated regions on the same glass substrate that precisely controls the generation of tandem bubbles and individual cells patterned nearby with well-defined locations and shapes. We then demonstrate the generation of tandem bubbles by using two pulsed lasers illuminating a pair of gold dots with a few-microsecond time delay. We visualize the bubble-bubble interaction and jet formation by high-speed imaging and characterize the resultant flow field using particle image velocimetry (PIV). Finally, we present some applications of this technique for single cell analysis, including cell membrane poration with macromolecule uptake, localized membrane deformation determined by the displacements of attached integrin-binding beads, and intracellular calcium response from ratiometric imaging. Our results show that a fast and directional jetting flow is produced by the tandem bubble interaction, which can impose a highly-localized shear stress on the surface of a cell grown in close proximity. Furthermore, different bioeffects can be induced by altering the strength of the jetting flow by adjusting the standoff distance from the cell to the tandem bubbles. PMID:28117807

Extremely Vivid, Highly Transparent, and Ultrathin Quantum Dot Light-Emitting Diodes.

PubMed

Choi, Moon Kee; Yang, Jiwoong; Kim, Dong Chan; Dai, Zhaohe; Kim, Junhee; Seung, Hyojin; Kale, Vinayak S; Sung, Sae Jin; Park, Chong Rae; Lu, Nanshu; Hyeon, Taeghwan; Kim, Dae-Hyeong

2018-01-01

Displaying information on transparent screens offers new opportunities in next-generation electronics, such as augmented reality devices, smart surgical glasses, and smart windows. Outstanding luminance and transparency are essential for such "see-through" displays to show vivid images over clear background view. Here transparent quantum dot light-emitting diodes (Tr-QLEDs) are reported with high brightness (bottom: ≈43 000 cd m -2 , top: ≈30 000 cd m -2 , total: ≈73 000 cd m -2 at 9 V), excellent transmittance (90% at 550 nm, 84% over visible range), and an ultrathin form factor (≈2.7 µm thickness). These superb characteristics are accomplished by novel electron transport layers (ETLs) and engineered quantum dots (QDs). The ETLs, ZnO nanoparticle assemblies with ultrathin alumina overlayers, dramatically enhance durability of active layers, and balance electron/hole injection into QDs, which prevents nonradiative recombination processes. In addition, the QD structure is further optimized to fully exploit the device architecture. The ultrathin nature of Tr-QLEDs allows their conformal integration on various shaped objects. Finally, the high resolution patterning of red, green, and blue Tr-QLEDs (513 pixels in. -1 ) shows the potential of the full-color transparent display. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced sensitivity of surface acoustic wave-based rate sensors incorporating metallic dot arrays.

PubMed

Wang, Wen; Shao, Xiuting; Liu, Xinlu; Liu, Jiuling; He, Shitang

2014-02-26

A new surface acoustic wave (SAW)-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu) dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs) and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours) frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz∙deg∙s(-1)) and good linearity were observed.

Enhanced Sensitivity of Surface Acoustic Wave-Based Rate Sensors Incorporating Metallic Dot Arrays

PubMed Central

Wang, Wen; Shao, Xiuting; Liu, Xinlu; Liu, Jiuling; He, Shitang

2014-01-01

A new surface acoustic wave (SAW)-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu) dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs) and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours) frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz·deg·s−1) and good linearity were observed. PMID:24577520

Making The Invisible Visible

NASA Technical Reports Server (NTRS)

1978-01-01

In public and private archives throughout the world there are many historically important documents that have become illegible with the passage of time. They have faded, been erased, acquired mold, water and dirt stain, suffered blotting or lost readability in other ways. While ultraviolet and infrared photography are widely used to enhance deteriorated legibility, these methods are more limited in their effectiveness than the space-derived image enhancement technique. The aim of the JPL effort with Caltech and others is to better define the requirements for a system to restore illegible information for study at a low page-cost with simple operating procedures. The investigators' principle tools are a vidicon camera and an image processing computer program, the same equipment used to produce sharp space pictures. The camera is the same type as those on NASA's Mariner spacecraft which returned to Earth thousands of images of Mars, Venus and Mercury. Space imagery works something like television. The vidicon camera does not take a photograph in the ordinary sense; rather it "scans" a scene, recording different light and shade values which are reproduced as a pattern of dots, hundreds of dots to a line, hundreds of lines in the total picture. The dots are transmitted to an Earth receiver, where they are assembled line by line to form a picture like that on the home TV screen.

Computation of the influence of scanning probe microscope (SPM) on quantum dot eigenstates and 2DEG potential

NASA Astrophysics Data System (ADS)

Stopa, Michael

2005-03-01

We calculate the electronic structure of GaAs-AlGaAs two-dimensional electron gas (2DEG) devices, such as quantum dots and quantum point contacts (QPCs) in the presence of a tip of a scanning probe microscope at some distance above the surface. The calculation employs standard density functional theory with exchange and correlation treated in the local density approximation. The position and voltage on the tip are varied and the conditions for depletion of the 2DEG are shown to compare favorably to experiment [1]. We show that the size of the depletion region created (by a negative tip voltage) is unexpectedly small due to focusing of the potential lines by the higher dielectric. We study the interaction of the tip with an isolated quantum dot that contains one or two electrons. The raster pattern of the difference between single particle energies reveals that the tip distorts the shape of the confining potential and suggests that excited state properties, if they can be measured experimentally, can contribute to the resolution of spatial information. [1] M.A. Topinka, R.M. Westervelt, E.J. Heller, ``http://meso.deas.harvard.edu/papers/Topinka, PT 56 12 (2003)'' (Imaging Electron Flow), Physics Today 56, 12 (2003).

Patterned carbon nanotubes fabricated by the combination of microcontact printing and diblock copolymer micelles.

PubMed

Xu, Peng; Ji, Xin; Qi, Junlei; Yang, Hongmin; Zheng, Weitao; Abetz, Volker; Jiang, Shimei; Shen, Jiacong

2010-01-01

A convenient approach to synthesize patterned carbon nanotubes (CNTs) of three morphologies on printed substrates by combination of microcontact printing (microCP) and a plasma-enhanced chemical vapor deposition (PECVD) process is presented. Micelles of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) in toluene were used as nanoreactors to fabricate FeCl3 in the core domains, and the complex solution was used as an ink to print films with polydimethylsiloxane (PDMS) stamps, different morphologies (porous, dots and stripes patterns) of the FeCl3-loaded micellar films were left onto silicon substrates after printed. After removing the polymer by thermal decomposition, the left iron oxide cluster arrays on the substrate were used as catalysts for the growth of CNTs by the process of PECVD, where the CNTs uniformly distributed on the substrates according to the morphologies of patterned catalysts arrays.

Effects of friction reduction of micro-patterned array of rough slider bearing

NASA Astrophysics Data System (ADS)

Kim, M.; Lee, D. W.; Jeong, J. H.; Chung, W. S.; Park, J. K.

2017-08-01

Complex micro-scale patterns have attracted interest because of the functionality that can be created using this type of patterning. This study evaluates the frictional reduction effects of various micro patterns on a slider bearing surface which is operating under mixed lubrication. Due to the rapid growth of contact area under mixed lubrication, it has become important to study the phenomenon of asperity contact in bearings with a heavy load. New analysis using the modified Reynolds equation with both the average flow model and the contact model of asperities is conducted for the rough slider bearing. A numerical analysis is performed to determine the effects of surface roughness on a lubricated bearing. Several dented patterns such as, dot pattern, dashed line patterns are used to evaluate frictional reduction effects. To verify the analytical results, friction test for the micro-patterned samples are performed. From comparing the frictional reduction effects of patterned arrays, the design of them can control the frictional loss of bearings. Our results showed that the design of pattern array on the bearing surface was important to the friction reduction of bearings. To reduce frictional loss, the longitudinal direction of them was better than the transverse direction.

Basic numerical processing, calculation, and working memory in children with dyscalculia and/or ADHD symptoms.

PubMed

Kuhn, Jörg-Tobias; Ise, Elena; Raddatz, Julia; Schwenk, Christin; Dobel, Christian

2016-09-01

Deficits in basic numerical skills, calculation, and working memory have been found in children with developmental dyscalculia (DD) as well as children with attention-deficit/hyperactivity disorder (ADHD). This paper investigates cognitive profiles of children with DD and/or ADHD symptoms (AS) in a double dissociation design to obtain a better understanding of the comorbidity of DD and ADHD. Children with DD-only (N = 33), AS-only (N = 16), comorbid DD+AS (N = 20), and typically developing controls (TD, N = 40) were assessed on measures of basic numerical processing, calculation, working memory, processing speed, and neurocognitive measures of attention. Children with DD (DD, DD+AS) showed deficits in all basic numerical skills, calculation, working memory, and sustained attention. Children with AS (AS, DD+AS) displayed more selective difficulties in dot enumeration, subtraction, verbal working memory, and processing speed. Also, they generally performed more poorly in neurocognitive measures of attention, especially alertness. Children with DD+AS mostly showed an additive combination of the deficits associated with DD-only and A_Sonly, except for subtraction tasks, in which they were less impaired than expected. DD and AS appear to be related to largely distinct patterns of cognitive deficits, which are present in combination in children with DD+AS.