SAM Photovoltaic Model Technical Reference 2016 Update

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

Gilman, Paul; DiOrio, Nicholas A; Freeman, Janine M

This manual describes the photovoltaic performance model in the System Advisor Model (SAM) software, Version 2016.3.14 Revision 4 (SSC Version 160). It is an update to the 2015 edition of the manual, which describes the photovoltaic model in SAM 2015.1.30 (SSC 41). This new edition includes corrections of errors in the 2015 edition and descriptions of new features introduced in SAM 2016.3.14, including: 3D shade calculator Battery storage model DC power optimizer loss inputs Snow loss model Plane-of-array irradiance input from weather file option Support for sub-hourly simulations Self-shading works with all four subarrays, and uses same algorithm for fixedmore » arrays and one-axis tracking Linear self-shading algorithm for thin-film modules Loss percentages replace derate factors. The photovoltaic performance model is one of the modules in the SAM Simulation Core (SSC), which is part of both SAM and the SAM SDK. SAM is a user-friedly desktop application for analysis of renewable energy projects. The SAM SDK (Software Development Kit) is for developers writing their own renewable energy analysis software based on SSC. This manual is written for users of both SAM and the SAM SDK wanting to learn more about the details of SAM's photovoltaic model.« less

Solar cycle modulation of Southern Annular Mode -Energy-momentum analysis-

NASA Astrophysics Data System (ADS)

Kuroda, Y.

2016-12-01

Climate is affected by various factors, including oceanic changes and volcanic eruptions. 11-year solar cycle change is one of such important factors. Observational analysis shows that the Southern Annular Mode (SAM) in late-winter/spring show structural modulation associated with 11-year solar cycle. In fact, SAM-related signal tends to extend from surface to upper stratosphere and persistent longer period in the High Solar (HS) years, whereas it is restricted in the troposphere and not persist in the Low Solar (LS) years. In the present study, we used 35-year record of ERA-Interim reanalysis data and performed wave-energy and momentum analysis on the solar-cycle modulation of the SAM to examine key factors to create such solar-SAM relationship. It is found that enhanced wave-mean flow interaction tends to take place in the middle stratosphere in association with enhanced energy input from diabatic heating on September only in HS years. The result suggests atmospheric and solar conditions on September are keys to create solar-SAM relationship.

Sound Rhythms Are Encoded by Postinhibitory Rebound Spiking in the Superior Paraolivary Nucleus

PubMed Central

Felix, Richard A.; Fridberger, Anders; Leijon, Sara; Berrebi, Albert S.; Magnusson, Anna K.

2013-01-01

The superior paraolivary nucleus (SPON) is a prominent structure in the auditory brainstem. In contrast to the principal superior olivary nuclei with identified roles in processing binaural sound localization cues, the role of the SPON in hearing is not well understood. A combined in vitro and in vivo approach was used to investigate the cellular properties of SPON neurons in the mouse. Patch-clamp recordings in brain slices revealed that brief and well timed postinhibitory rebound spiking, generated by the interaction of two subthreshold-activated ion currents, is a hallmark of SPON neurons. The Ih current determines the timing of the rebound, whereas the T-type Ca2+ current boosts the rebound to spike threshold. This precisely timed rebound spiking provides a physiological explanation for the sensitivity of SPON neurons to sinusoidally amplitude-modulated (SAM) tones in vivo, where peaks in the sound envelope drive inhibitory inputs and SPON neurons fire action potentials during the waveform troughs. Consistent with this notion, SPON neurons display intrinsic tuning to frequency-modulated sinusoidal currents (1–15Hz) in vitro and discharge with strong synchrony to SAMs with modulation frequencies between 1 and 20 Hz in vivo. The results of this study suggest that the SPON is particularly well suited to encode rhythmic sound patterns. Such temporal periodicity information is likely important for detection of communication cues, such as the acoustic envelopes of animal vocalizations and speech signals. PMID:21880918

Sound rhythms are encoded by postinhibitory rebound spiking in the superior paraolivary nucleus.

PubMed

Felix, Richard A; Fridberger, Anders; Leijon, Sara; Berrebi, Albert S; Magnusson, Anna K

2011-08-31

The superior paraolivary nucleus (SPON) is a prominent structure in the auditory brainstem. In contrast to the principal superior olivary nuclei with identified roles in processing binaural sound localization cues, the role of the SPON in hearing is not well understood. A combined in vitro and in vivo approach was used to investigate the cellular properties of SPON neurons in the mouse. Patch-clamp recordings in brain slices revealed that brief and well timed postinhibitory rebound spiking, generated by the interaction of two subthreshold-activated ion currents, is a hallmark of SPON neurons. The I(h) current determines the timing of the rebound, whereas the T-type Ca(2+) current boosts the rebound to spike threshold. This precisely timed rebound spiking provides a physiological explanation for the sensitivity of SPON neurons to sinusoidally amplitude-modulated (SAM) tones in vivo, where peaks in the sound envelope drive inhibitory inputs and SPON neurons fire action potentials during the waveform troughs. Consistent with this notion, SPON neurons display intrinsic tuning to frequency-modulated sinusoidal currents (1-15Hz) in vitro and discharge with strong synchrony to SAMs with modulation frequencies between 1 and 20 Hz in vivo. The results of this study suggest that the SPON is particularly well suited to encode rhythmic sound patterns. Such temporal periodicity information is likely important for detection of communication cues, such as the acoustic envelopes of animal vocalizations and speech signals.

SAMS Acceleration Measurement on Mir From March to September 1996

NASA Technical Reports Server (NTRS)

Moskowitz, Milton E.; Hrovat, Ken; Truong, Duc; Reckart, Timothy

1997-01-01

During NASA Increment 2 (March to September 1996), over 15 gigabytes of acceleration data were collected by the Space Acceleration Measurement System (SAMS) onboard the Russian Space Station, Mir. The data were recorded on 55 optical disks and were returned to Earth on STS-79. During this time, SAMS data were collected in the Kristall and Kvant modules, and in the Priroda module to support the following experiments: the Queen's University Experiments in Liquid Diffusion (QUELD), the Technological Evaluation of the MIM (TEM), the Forced Flow Flame Spreading Test (FFFT), and Candle Flames in Microgravity (CFM). This report points out some of the salient features of the microgravity environment to which these experiments were exposed. Also documented are mission events of interest such as the docked phase of STS-76 operations, an extravehicular activity (EVA) to install and deploy solar panels on the Kvant module, a Progress engine burn to raise Mir's altitude, and an on-orbit SAMS calibration procedure. Also included are a description of the Mir module orientations, and the panel notations within the modules. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. Variations in the acceleration environment caused by unique activities such as crew exercise and life-support fans are presented. The analyses included herein complement those presented in previous mission summary reports published by the Principal Investigator Microgravity Services (PIMS) group.

Nanotribological Properties of Positively and Negatively charged nanodiamonds as additives to solutions

NASA Astrophysics Data System (ADS)

Liu, Zijian; Corley, Steven; Shenderova, Olga; Brenner, Donald; Krim, Jacqueline

2013-03-01

Nano-diamond (ND) particles are known to be beneficial for wear and friction reduction when used as additives in liquids, but the fundamental origins of the improvement in tribological properties has not been established. In order to explore this issue, we have investigated the nanotribological properties of ND coated with self-assembled monolayers (SAM) as additives to solutions, employing gold/chrome coated quartz crystal microbalances (QCM). Measurements were performed with the QCM initially immersed in deionized water. ND particles with positively and negatively charged SAM end groups were then added to the water, while the frequency and amplitude of the QCM were monitored. Negative shifts in both the QCM frequency and amplitude were observed when ND with positively charged SAM end groups were added, while positive shifts in both the QCM frequency and amplitude were observed when ND with negatively charged ND end groups were added. The results are consistent with a lubricating effect for the negatively charged ND, but were only observed for sufficiently small negative ND particle size. Experiments on QCM surfaces with differing textures and roughness are in progress, to determine the separate contributing effects of surface roughness charge-water interactions. Funding provided by NSF DMR.

Feasibility and validity of the structured attention module among economically disadvantaged preschool-age children.

PubMed

Bush, Hillary H; Eisenhower, Abbey; Briggs-Gowan, Margaret; Carter, Alice S

2015-01-01

Rooted in the theory of attention put forth by Mirsky, Anthony, Duncan, Ahearn, and Kellam (1991), the Structured Attention Module (SAM) is a developmentally sensitive, computer-based performance task designed specifically to assess sustained selective attention among 3- to 6-year-old children. The current study addressed the feasibility and validity of the SAM among 64 economically disadvantaged preschool-age children (mean age = 58 months; 55% female); a population known to be at risk for attention problems and adverse math performance outcomes. Feasibility was demonstrated by high completion rates and strong associations between SAM performance and age. Principal Factor Analysis with rotation produced robust support for a three-factor model (Accuracy, Speed, and Endurance) of SAM performance, which largely corresponded with existing theorized models of selective and sustained attention. Construct validity was evidenced by positive correlations between SAM Composite scores and all three SAM factors and IQ, and between SAM Accuracy and sequential memory. Value-added predictive validity was not confirmed through main effects of SAM on math performance above and beyond age and IQ; however, significant interactions by child sex were observed: Accuracy and Endurance both interacted with child sex to predict math performance. In both cases, the SAM factors predicted math performance more strongly for girls than for boys. There were no overall sex differences in SAM performance. In sum, the current findings suggest that interindividual variation in sustained selective attention, and potentially other aspects of attention and executive function, among young, high-risk children can be captured validly with developmentally sensitive measures.

Injection-modulated polarity conversion by charge carrier density control via a self-assembled monolayer for all-solution-processed organic field-effect transistors

NASA Astrophysics Data System (ADS)

Roh, Jeongkyun; Lee, Taesoo; Kang, Chan-Mo; Kwak, Jeonghun; Lang, Philippe; Horowitz, Gilles; Kim, Hyeok; Lee, Changhee

2017-04-01

We demonstrated modulation of charge carrier densities in all-solution-processed organic field-effect transistors (OFETs) by modifying the injection properties with self-assembled monolayers (SAMs). The all-solution-processed OFETs based on an n-type polymer with inkjet-printed Ag electrodes were fabricated as a test platform, and the injection properties were modified by the SAMs. Two types of SAMs with different dipole direction, thiophenol (TP) and pentafluorobenzene thiol (PFBT) were employed, modifying the work function of the inkjet-printed Ag (4.9 eV) to 4.66 eV and 5.24 eV with TP and PFBT treatments, respectively. The charge carrier densities were controlled by the SAM treatment in both dominant and non-dominant carrier-channel regimes. This work demonstrates that control of the charge carrier densities can be efficiently achieved by modifying the injection property with SAM treatment; thus, this approach can achieve polarity conversion of the OFETs.

Status Report on NEAMS System Analysis Module Development

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

Hu, R.; Fanning, T. H.; Sumner, T.

2015-12-01

Under the Reactor Product Line (RPL) of DOE-NE’s Nuclear Energy Advanced Modeling and Simulation (NEAMS) program, an advanced SFR System Analysis Module (SAM) is being developed at Argonne National Laboratory. The goal of the SAM development is to provide fast-running, improved-fidelity, whole-plant transient analyses capabilities. SAM utilizes an object-oriented application framework MOOSE), and its underlying meshing and finite-element library libMesh, as well as linear and non-linear solvers PETSc, to leverage modern advanced software environments and numerical methods. It also incorporates advances in physical and empirical models and seeks closure models based on information from high-fidelity simulations and experiments. This reportmore » provides an update on the SAM development, and summarizes the activities performed in FY15 and the first quarter of FY16. The tasks include: (1) implement the support of 2nd-order finite elements in SAM components for improved accuracy and computational efficiency; (2) improve the conjugate heat transfer modeling and develop pseudo 3-D full-core reactor heat transfer capabilities; (3) perform verification and validation tests as well as demonstration simulations; (4) develop the coupling requirements for SAS4A/SASSYS-1 and SAM integration.« less

Expanding the Chemistry of the Class C Radical SAM Methyltransferase NosN by Using an Allyl Analogue of SAM.

PubMed

Ji, Xinjian; Mandalapu, Dhanaraju; Cheng, Jinduo; Ding, Wei; Zhang, Qi

2018-03-30

The radical S-adenosylmethionine (SAM) superfamily enzymes cleave SAM reductively to generate a highly reactive 5'-deoxyadenosyl (dAdo) radical, which initiates remarkably diverse reactions. Unlike most radical SAM enzymes, the class C radical SAM methyltransferase NosN binds two SAMs in the active site, using one SAM to produce a dAdo radical and the second as a methyl donor. Here, we report a mechanistic investigation of NosN in which an allyl analogue of SAM (allyl-SAM) was used. We show that NosN cleaves allyl-SAM efficiently and the resulting dAdo radical can be captured by the olefin moieties of allyl-SAM or 5'-allylthioadenosine (ATA), the latter being a derivative of allyl-SAM. Remarkably, we found that NosN produced two distinct sets of products in the presence and absence of the methyl acceptor substrate, thus suggesting substrate-triggered production of ATA from allyl-SAM. We also show that NosN produces S-adenosylhomocysteine from 5'-thioadenosine and homoserine lactone. These results support the idea that 5'-methylthioadenosine is the direct methyl donor in NosN reactions, and demonstrate great potential to modulate radical SAM enzymes for novel catalytic activities. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Benchmark Simulation of Natural Circulation Cooling System with Salt Working Fluid Using SAM

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

Ahmed, K. K.; Scarlat, R. O.; Hu, R.

Liquid salt-cooled reactors, such as the Fluoride Salt-Cooled High-Temperature Reactor (FHR), offer passive decay heat removal through natural circulation using Direct Reactor Auxiliary Cooling System (DRACS) loops. The behavior of such systems should be well-understood through performance analysis. The advanced system thermal-hydraulics tool System Analysis Module (SAM) from Argonne National Laboratory has been selected for this purpose. The work presented here is part of a larger study in which SAM modeling capabilities are being enhanced for the system analyses of FHR or Molten Salt Reactors (MSR). Liquid salt thermophysical properties have been implemented in SAM, as well as properties ofmore » Dowtherm A, which is used as a simulant fluid for scaled experiments, for future code validation studies. Additional physics modules to represent phenomena specific to salt-cooled reactors, such as freezing of coolant, are being implemented in SAM. This study presents a useful first benchmark for the applicability of SAM to liquid salt-cooled reactors: it provides steady-state and transient comparisons for a salt reactor system. A RELAP5-3D model of the Mark-1 Pebble-Bed FHR (Mk1 PB-FHR), and in particular its DRACS loop for emergency heat removal, provides steady state and transient results for flow rates and temperatures in the system that are used here for code-to-code comparison with SAM. The transient studied is a loss of forced circulation with SCRAM event. To the knowledge of the authors, this is the first application of SAM to FHR or any other molten salt reactors. While building these models in SAM, any gaps in the code’s capability to simulate such systems are identified and addressed immediately, or listed as future improvements to the code.« less

Human polyhomeotic homolog 3 (PHC3) sterile alpha motif (SAM) linker allows open-ended polymerization of PHC3 SAM.

PubMed

Robinson, Angela K; Leal, Belinda Z; Nanyes, David R; Kaur, Yogeet; Ilangovan, Udayar; Schirf, Virgil; Hinck, Andrew P; Demeler, Borries; Kim, Chongwoo A

2012-07-10

Sterile alpha motifs (SAMs) are frequently found in eukaryotic genomes. An intriguing property of many SAMs is their ability to self-associate, forming an open-ended polymer structure whose formation has been shown to be essential for the function of the protein. What remains largely unresolved is how polymerization is controlled. Previously, we had determined that the stretch of unstructured residues N-terminal to the SAM of a Drosophila protein called polyhomeotic (Ph), a member of the polycomb group (PcG) of gene silencers, plays a key role in controlling Ph SAM polymerization. Ph SAM with its native linker created shorter polymers compared to Ph SAM attached to either a random linker or no linker. Here, we show that the SAM linker for the human Ph ortholog, polyhomeotic homolog 3 (PHC3), also controls PHC3 SAM polymerization but does so in the opposite fashion. PHC3 SAM with its native linker allows longer polymers to form compared to when attached to a random linker. Attaching the PHC3 SAM linker to Ph SAM also resulted in extending Ph SAM polymerization. Moreover, in the context of full-length Ph protein, replacing the SAM linker with PHC3 SAM linker, intended to create longer polymers, resulted in greater repressive ability for the chimera compared to wild-type Ph. These findings show that polymeric SAM linkers evolved to modulate a wide dynamic range of SAM polymerization abilities and suggest that rationally manipulating the function of SAM containing proteins through controlling their SAM polymerization may be possible.

The SAM-responsive SMK box is a reversible riboswitch

PubMed Central

Smith, Angela M.; Fuchs, Ryan T.; Grundy, Frank J.; Henkin, Tina M.

2010-01-01

The SMK (SAM-III) box is an S-adenosylmethionine (SAM)-responsive riboswitch found in the 5′ untranslated region of metK genes, encoding SAM synthetase, in many members of the Lactobacillales. SAM binding causes a structural rearrangement in the RNA that sequesters the Shine-Dalgarno (SD) sequence by pairing with a complementary anti-SD (ASD) sequence; sequestration of the SD sequence inhibits binding of the 30S ribosomal subunit and prevents translation initiation. We observed a slight increase in the half-life of the metK transcript in vivo when Enterococcus faecalis cells were depleted for SAM, but no significant change in overall transcript abundance, consistent with the model that this riboswitch regulates at the level of translation initiation. The half-life of the SAM-SMK box RNA complex in vitro is shorter than that of the metK transcript in vivo, raising the possibility of reversible binding of SAM. We used a fluorescence assay to directly visualize reversible switching between the SAM-free and SAM-bound conformations. We propose that the SMK box riboswitch can make multiple SAM-dependent regulatory decisions during the lifetime of the transcript in vivo, acting as a reversible switch that allows the cell to respond rapidly to fluctuations in SAM pools by modulating expression of the SAM synthetase gene. PMID:21143313

SAMS Acceleration Measurements on MIR

NASA Technical Reports Server (NTRS)

Moskowitz, Milton E.; Hrovat, Kenneth; Finkelstein, Robert; Reckart, Timothy

1997-01-01

During NASA Increment 3 (September 1996 to January 1997), about 5 gigabytes of acceleration data were collected by the Space Acceleration Measurement System (SAMS) onboard the Russian Space Station, Mir. The data were recorded on 11 optical disks and were returned to Earth on STS-81. During this time, SAMS data were collected in the Priroda module to support the following experiments: the Mir Structural Dynamics Experiment (MiSDE) and Binary Colloidal Alloy Tests (BCAT). This report points out some of the salient features of the microgravity environment to which these experiments were exposed. Also documented are mission events of interest such as the docked phase of STS-81 operations, a Progress engine burn, attitude control thruster operation, and crew exercise. Also included are a description of the Mir module orientations, and the panel notations within the modules. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. Variations in the acceleration environment caused by unique activities such as crew exercise and life-support fans are presented. The analyses included herein complement those presented in previous mission summary reports published by the Principal Investigator Microgravity Services (PIMS) group.

Increasing faculty participation in resident education and providing cost-effective self-assessment module credit to faculty through resident-generated didactics.

PubMed

Kim, Hyun; Malatesta, Theresa M; Anné, Pramila R; McAna, John; Bar-Ad, Voichita; Dicker, Adam P; Den, Robert B

Board certified radiation oncologists and medical physicists are required to earn self-assessment module (SAM) continuing medical education (CME) credit, which may require travel costs or usage fees. Data indicate that faculty participation in resident teaching activities is beneficial to resident education. Our hypothesis was that providing the opportunity to earn SAM credit in resident didactics would increase faculty participation in and improve resident education. SAM applications, comprising CME certified category 1 resident didactic lectures and faculty-generated questions with respective answers, rationales, and references, were submitted to the American Board of Radiology for formal review. Surveys were distributed to assess main academic campus physician, affiliate campus physician, physicist, and radiation oncology resident impressions regarding the quality of the lectures. Survey responses were designed in Likert-scale format. Sign-test was performed with P < .05 considered statistically different from neutral. First submission SAM approval was obtained for 9 of 9 lectures to date. A total of 52 SAM credits have been awarded to 4 physicists and 7 attending physicians. Main academic campus physician and affiliate campus physician attendance increased from 20% and 0%, respectively, over the 12 months preceding CME/SAM lectures, to 55.6% and 20%, respectively. Survey results indicated that the change to SAM lectures increased the quality of resident lectures (P = .001), attending physician participation in resident education (P < .0001), physicist involvement in medical resident education (P = .0006), and faculty motivation to attend resident didactics (P = .004). Residents reported an increased amount of time required to prepare lectures (P = .008). We are the first department, to our knowledge, to offer SAM credit to clinical faculty for participation in resident-generated didactics. Offering SAM credit at resident lectures is a cost-effective alternative to purchasing SAM resources, increases faculty attendance, and may improve the quality of radiation oncology resident education. Copyright © 2016 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

S-adenosylmethionine regulates thiopurine methyltransferase activity and decreases 6-mercaptopurine cytotoxicity in MOLT lymphoblasts.

PubMed

Milek, Miha; Karas Kuzelicki, Natasa; Smid, Alenka; Mlinaric-Rascan, Irena

2009-06-15

Six-mercaptopurine (6-MP) is a pro-drug widely used in treatment of various diseases, including acute lymphoblastic leukaemia (ALL). Side-effects of thiopurine therapy have been correlated with thiopurine methyltransferase (TPMT) activity. We propose a novel TPMT-mediated mechanism of S-adenosylmethionine (SAM)-specific effects on 6-mercaptopurine (6-MP) induced cytotoxicity in a model cell line for acute lymphoblastic leukemia (MOLT). Our results show that exogenous SAM (10-50microM) rescues cells from the toxic effects of 6-MP (5microM) by delaying the onset of apoptosis. We prove that the extent of methylthioinosine monophosphate (MeTIMP) induced inhibition of de novo purine synthesis (DNPS) determines the concentrations of intracellular ATP, and consequently SAM, which acts as a positive modulator of TPMT activity. This leads to a greater conversion of 6-MP to inactive 6-methylmercaptopurine, and thus lower availability of thioinosine monophosphate for the biotransformation to cytotoxic thioguanine nucleotides (TGNs) and MeTIMP. We further show that the addition of exogenous SAM to 6-MP treated cells maintains intracellular SAM levels, TPMT activity and protein levels, all of which are diminished in cells incubated with 6-MP. Since TPMT mRNA levels remained unaltered, the effect of SAM appears to be restricted to protein stabilisation rather than an increase of TPMT expression. We thus propose that SAM reverses the extent of 6-MP cytotoxicity, by acting as a TPMT-stabilizing factor. This study provides new insights into the pharmacogenetics of thiopurine drugs. Identification of SAM as critical modulator of TPMT activity and consequently thiopurine toxicity may set novel grounds for the rationalization of thiopurine therapy.

Colibactin assembly line enzymes use S-adenosylmethionine to build a cyclopropane ring

PubMed Central

Zha, Li; Jiang, Yindi; Henke, Matthew T.; Wilson, Matthew R.; Wang, Jennifer X.; Kelleher, Neil L.; Balskus, Emily P.

2017-01-01

Despite containing an α-amino acid, the versatile cofactor S-adenosylmethionine (SAM) is not a known building block for non-ribosomal peptide synthetase (NRPS) assembly lines. Here we report an unusual NRPS module from colibactin biosynthesis that uses SAM for amide bond formation and subsequent cyclopropanation. Our findings showcase a new use for SAM and reveal a novel biosynthetic route to a functional group that likely mediates colibactin’s genotoxicity. PMID:28805802

Synthesis, characterization, and relative stabilities of self-assembled monolayers on gold generated from bidentate n-alkyl xanthic acids.

PubMed

Moore, H Justin; Colorado, Ramon; Lee, Han Ju; Jamison, Andrew C; Lee, T Randall

2013-08-27

A series of self-assembled monolayers (SAMs) on gold were generated by the adsorption of n-alkyl xanthic acids (NAXAs) having the general formula CH3(CH2)nOCS2H (n = 12-15). The structural features of these SAMs were characterized by optical ellipsometry, contact angle goniometry, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). This series of xanthate SAMs were compared to SAMs generated from the corresponding n-alkanethiols and aliphatic dithiocarboxylic acids (ADTCAs). The collected data indicate that the NAXAs generate densely packed and well-ordered monolayers. The contact angles of hexadecane on the xanthate monolayers exhibited a large "odd-even" effect similar to that produced by the ADTCA SAMs. The relative stability of these bidentate xanthate SAMs was evaluated by monitoring the changes in ellipsometric thicknesses and wettability as a function of time under various conditions. The results demonstrate that SAMs formed from NAXAs are much less stable than analogous n-alkanethiolate and ADTCA SAMs.

Targeting EphA2-Sam and Its Interactome: Design and Evaluation of Helical Peptides Enriched in Charged Residues.

PubMed

Mercurio, Flavia A; Marasco, Daniela; Di Natale, Concetta; Pirone, Luciano; Costantini, Susan; Pedone, Emilia M; Leone, Marilisa

2016-11-17

The EphA2 receptor controls diverse physiological and pathological conditions and its levels are often upregulated in cancer. Targeting receptor overexpression, through modulation of endocytosis and consequent degradation, appears to be an appealing strategy for attacking tumor malignancy. In this scenario, the Sam domain of EphA2 plays a pivotal role because it is the site where protein regulators of endocytosis and stability are recruited by means of heterotypic Sam-Sam interactions. Because EphA2-Sam heterotypic complexes are largely based on electrostatic contacts, we have investigated the possibility of attacking these interactions with helical peptides enriched in charged residues. Several peptide sequences with high predicted helical propensities were designed, and detailed conformational analyses were conducted by diverse techniques including NMR, CD, and molecular dynamics (MD) simulations. Interaction studies were also performed by NMR, surface plasmon resonance (SPR), and microscale thermophoresis (MST) and led to the identification of two peptides capable of binding to the first Sam domain of Odin. These molecules represent early candidates for the generation of efficient Sam domain binders and antagonists of Sam-Sam interactions involving EphA2. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The nuclear protein Sam68 is cleaved by the FMDV 3C protease redistributing Sam68 to the cytoplasm during FMDV infection of host cells

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

Lawrence, Paul; Schafer, Elizabeth A.; Rieder, Elizabeth, E-mail: elizabeth.rieder@ars.usda.gov

2012-03-30

Picornavirus infection can lead to disruption of nuclear pore traffic, shut-off of cell translation machinery, and cleavage of proteins involved in cellular signal transduction and the innate response to infection. Here, we demonstrated that the FMDV 3C{sup pro} induced the cleavage of nuclear RNA-binding protein Sam68 C-terminus containing the nuclear localization sequence (NLS). Consequently, it stimulated the redistribution of Sam68 to the cytoplasm. The siRNA knockdown of Sam68 resulted in a 1000-fold reduction in viral titers, which prompted us to study the effect of Sam68 on FMDV post-entry events. Interestingly, Sam68 interacts with the internal ribosomal entry site within themore » 5 Prime non-translated region of the FMDV genome, and Sam68 knockdown decreased FMDV IRES-driven activity in vitro suggesting that it could modulate translation of the viral genome. The results uncover a novel role for Sam68 in the context of picornaviruses and the proteolysis of a new cellular target of the FMDV 3C{sup pro}.« less

Spin polarisation of tt¯γγ production at NLO+PS with GoSam interfaced to MadGraph5_aMC@NLO

DOE PAGES

van Deurzen, Hans; Frederix, Rikkert; Hirschi, Valentin; ...

2016-04-22

Here, we present an interface between the multipurpose Monte Carlo tool MadGraph5_aMC@NLO and the automated amplitude generator GoSam. As a first application of this novel framework, we compute the NLO corrections to pp→ tt¯H and pp→ tt¯γγ matched to a parton shower. In the phenomenological analyses of these processes, we focus our attention on observables which are sensitive to the polarisation of the top quarks.

Spin polarisation of tt¯γγ production at NLO+PS with GoSam interfaced to MadGraph5_aMC@NLO

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

van Deurzen, Hans; Frederix, Rikkert; Hirschi, Valentin

Here, we present an interface between the multipurpose Monte Carlo tool MadGraph5_aMC@NLO and the automated amplitude generator GoSam. As a first application of this novel framework, we compute the NLO corrections to pp→ tt¯H and pp→ tt¯γγ matched to a parton shower. In the phenomenological analyses of these processes, we focus our attention on observables which are sensitive to the polarisation of the top quarks.

System Advisor Model, SAM 2014.1.14: General Description

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

Blair, Nate; Dobos, Aron P.; Freeman, Janine

2014-02-01

This document describes the capabilities of the U.S. Department of Energy and National Renewable Energy Laboratory's System Advisor Model (SAM), Version 2013.9.20, released on September 9, 2013. SAM is a computer model that calculates performance and financial metrics of renewable energy systems. Project developers, policy makers, equipment manufacturers, and researchers use graphs and tables of SAM results in the process of evaluating financial, technology, and incentive options for renewable energy projects. SAM simulates the performance of photovoltaic, concentrating solar power, solar water heating, wind, geothermal, biomass, and conventional power systems. The financial model can represent financial structures for projects thatmore » either buy and sell electricity at retail rates (residential and commercial) or sell electricity at a price determined in a power purchase agreement (utility). SAM's advanced simulation options facilitate parametric and sensitivity analyses, and statistical analysis capabilities are available for Monte Carlo simulation and weather variability (P50/P90) studies. SAM can also read input variables from Microsoft Excel worksheets. For software developers, the SAM software development kit (SDK) makes it possible to use SAM simulation modules in their applications written in C/C++, C#, Java, Python, and MATLAB. NREL provides both SAM and the SDK as free downloads at http://sam.nrel.gov. Technical support and more information about the software are available on the website.« less

The SAM domains of Anks family proteins are critically involved in modulating the degradation of EphA receptors.

PubMed

Kim, Jieun; Lee, Haeryung; Kim, Yujin; Yoo, Sooyeon; Park, Eunjeong; Park, Soochul

2010-04-01

We recently reported that the phosphotyrosine-binding (PTB) domain of Anks family proteins binds to EphA8, thereby positively regulating EphA8-mediated signaling pathways. In the current study, we identified a potential role for the SAM domains of Anks family proteins in EphA signaling. We found that SAM domains of Anks family proteins directly bind to ubiquitin, suggesting that Anks proteins regulate the degradation of ubiquitinated EphA receptors. Consistent with the role of Cbl ubiquitin ligases in the degradation of Eph receptors, our results revealed that the ubiquitin ligase c-Cbl induced the ubiquitination and degradation of EphA8 upon ligand binding. Ubiquitinated EphA8 also bound to the SAM domains of Odin, a member of the Anks family proteins. More importantly, the overexpression of wild-type Odin protected EphA8 and EphA2 from undergoing degradation following ligand stimulation and promoted EphA-mediated inhibition of cell migration. In contrast, a SAM domain deletion mutant of Odin strongly impaired the function of endogenous Odin, suggesting that the mutant functions in a dominant-negative manner. An analysis of Odin-deficient primary embryonic fibroblasts indicated that Odin levels play a critical role in regulating the stability of EphA2 in response to ligand stimulation. Taken together, our studies suggest that the SAM domains of Anks family proteins play a pivotal role in enhancing the stability of EphA receptors by modulating the ubiquitination process.

CD and NMR conformational studies of a peptide encompassing the Mid Loop interface of Ship2-Sam.

PubMed

Mercurio, Flavia A; Scognamiglio, Pasqualina L; Di Natale, Concetta; Marasco, Daniela; Pellecchia, Maurizio; Leone, Marilisa

2014-11-01

The lipid phosphatase Ship2 is a protein that intervenes in several diseases such as diabetes, cancer, neurodegeneration, and atherosclerosis. It is made up of a catalytic domain and several protein docking modules such as a C-terminal Sam (Sterile alpha motif) domain. The Sam domain of Ship2 (Ship2-Sam) binds to the Sam domains of the EphA2 receptor (EphA2-Sam) and the PI3K effector protein Arap3 (Arap3-Sam). These heterotypic Sam-Sam interactions occur through formation of dimers presenting the canonical "Mid Loop/End Helix" binding mode. The central region of Ship2-Sam, spanning the C-terminal end of α2, the α3 and α4 helices together with the α2α3 and α3α4 interhelical loops, forms the Mid Loop surface that is needed to bind partners Sam domains. A peptide encompassing most of the Ship2-Sam Mid Loop interface (Shiptide) capable of binding to both EphA2-Sam and Arap3-Sam, was previously identified. Here we investigated the conformational features of this peptide, through solution CD and NMR studies in different conditions. These studies reveal that the peptide is highly flexible in aqueous buffer, while it adopts a helical conformation in presence of 2,2,2-trifluoroethanol. The discovered structural insights and in particular the identification of a helical motif, may lead to the design of more constrained and possibly cell permeable Shiptide analogs that could work as efficient antagonists of Ship2-Sam heterotypic interactions and embrace therapeutic applications. © 2014 Wiley Periodicals, Inc.

Conformational heterogeneity of the SAM-I riboswitch transcriptional ON state: a chaperone-like role for S-adenosyl methionine.

PubMed

Huang, Wei; Kim, Joohyun; Jha, Shantenu; Aboul-Ela, Fareed

2012-05-18

Riboswitches are promising targets for the design of novel antibiotics and engineering of portable genetic regulatory elements. There is evidence that variability in riboswitch properties allows tuning of expression for genes involved in different stages of biosynthetic pathways by mechanisms that are not currently understood. Here, we explore the mechanism for tuning of S-adenosyl methionine (SAM)-I riboswitch folding. Most SAM-I riboswitches function at the transcriptional level by sensing the cognate ligand SAM. SAM-I riboswitches orchestrate the biosynthetic pathways of cysteine, methionine, SAM, and so forth. We use base-pair probability predictions to examine the secondary-structure folding landscape of several SAM-I riboswitch sequences. We predict different folding behaviors for different SAM-I riboswitch sequences. We identify several "decoy" base-pairing interactions involving 5' riboswitch residues that can compete with the formation of a P1 helix, a component of the ligand-bound "transcription OFF" state, in the absence of SAM. We hypothesize that blockage of these interactions through SAM contacts contributes to stabilization of the OFF state in the presence of ligand. We also probe folding patterns for a SAM-I riboswitch RNA using constructs with different 3' truncation points experimentally. Folding was monitored through fluorescence, susceptibility to base-catalyzed cleavage, nuclear magnetic resonance, and indirectly through SAM binding. We identify key decision windows at which SAM can affect the folding pathway towards the OFF state. The presence of decoy conformations and differential sensitivities to SAM at different transcript lengths is crucial for SAM-I riboswitches to modulate gene expression in the context of global cellular metabolism. Copyright © 2012 Elsevier Ltd. All rights reserved.

S-Adenosylmethionine Attenuates Oxidative Stress and Neuroinflammation Induced by Amyloid-β Through Modulation of Glutathione Metabolism.

PubMed

Li, Qian; Cui, Jing; Fang, Chen; Liu, Min; Min, Guowen; Li, Liang

2017-01-01

Oxidative stress and neuroinflammation are mainly involved in the pathogenic mechanisms of Alzheimer's disease (AD). Amyloid-β (Aβ), the main component of senile plaques, is a kind of strong inducer of oxidative stress. Glutathione is an endogenous antioxidant protecting cells from oxidative injury. S-adenosylmethionine (SAM) produced in the methionine cycle is the primary methyl donor and the precursor of glutathione. In this study, the Aβ intrahippocampal injection rat model and cultured SH-SY5Y cells were used to explore the neuroprotective effect of SAM. We found that SAM could protect cells against Aβ-induced cellular injury by inhibition of oxidative stress and neuroinflammation. SAM administration could increase the endogenous antioxidant glutathione and potentiate the antioxidant enzymes activities. SAM might act as an antioxidant and be a potential candidate therapy for AD patients.

The Growth-Suppressive Function of the Polycomb Group Protein Polyhomeotic Is Mediated by Polymerization of Its Sterile Alpha Motif (SAM) Domain*

PubMed Central

Robinson, Angela K.; Leal, Belinda Z.; Chadwell, Linda V.; Wang, Renjing; Ilangovan, Udayar; Kaur, Yogeet; Junco, Sarah E.; Schirf, Virgil; Osmulski, Pawel A.; Gaczynska, Maria; Hinck, Andrew P.; Demeler, Borries; McEwen, Donald G.; Kim, Chongwoo A.

2012-01-01

Polyhomeotic (Ph), a member of the Polycomb Group (PcG), is a gene silencer critical for proper development. We present a previously unrecognized way of controlling Ph function through modulation of its sterile alpha motif (SAM) polymerization leading to the identification of a novel target for tuning the activities of proteins. SAM domain containing proteins have been shown to require SAM polymerization for proper function. However, the role of the Ph SAM polymer in PcG-mediated gene silencing was uncertain. Here, we first show that Ph SAM polymerization is indeed required for its gene silencing function. Interestingly, the unstructured linker sequence N-terminal to Ph SAM can shorten the length of polymers compared with when Ph SAM is individually isolated. Substituting the native linker with a random, unstructured sequence (RLink) can still limit polymerization, but not as well as the native linker. Consequently, the increased polymeric Ph RLink exhibits better gene silencing ability. In the Drosophila wing disc, Ph RLink expression suppresses growth compared with no effect for wild-type Ph, and opposite to the overgrowth phenotype observed for polymer-deficient Ph mutants. These data provide the first demonstration that the inherent activity of a protein containing a polymeric SAM can be enhanced by increasing SAM polymerization. Because the SAM linker had not been previously considered important for the function of SAM-containing proteins, our finding opens numerous opportunities to manipulate linker sequences of hundreds of polymeric SAM proteins to regulate a diverse array of intracellular functions. PMID:22275371

Ablation of the Sam68 RNA Binding Protein Protects Mice from Age-Related Bone Loss

PubMed Central

Richard, Stéphane; Torabi, Nazi; Franco, Gladys Valverde; Tremblay, Guy A; Chen, Taiping; Vogel, Gillian; Morel, Mélanie; Cléroux, Patrick; Forget-Richard, Alexandre; Komarova, Svetlana; Tremblay, Michel L; Li, Wei; Li, Ailian; Gao, Yun Jing; Henderson, Janet E

2005-01-01

The Src substrate associated in mitosis of 68 kDa (Sam68) is a KH-type RNA binding protein that has been shown to regulate several aspects of RNA metabolism; however, its physiologic role has remained elusive. Herein we report the generation of Sam68-null mice by homologous recombination. Aged Sam68−/− mice preserved their bone mass, in sharp contrast with 12-month-old wild-type littermates in which bone mass was decreased up to approximately 75%. In fact, the bone volume of the 12-month-old Sam68−/− mice was virtually indistinguishable from that of 4-month-old wild-type or Sam68−/− mice. Sam68−/− bone marrow stromal cells had a differentiation advantage for the osteogenic pathway. Moreover, the knockdown of Sam68 using short hairpin RNA in the embryonic mesenchymal multipotential progenitor C3H10T1/2 cells resulted in more pronounced expression of the mature osteoblast marker osteocalcin when differentiation was induced with bone morphogenetic protein-2. Cultures of mouse embryo fibroblasts generated from Sam68+/+ and Sam68−/− littermates were induced to differentiate into adipocytes with culture medium containing pioglitazone and the Sam68−/− mouse embryo fibroblasts shown to have impaired adipocyte differentiation. Furthermore, in vivo it was shown that sections of bone from 12-month-old Sam68−/− mice had few marrow adipocytes compared with their age-matched wild-type littermate controls, which exhibited fatty bone marrow. Our findings identify endogenous Sam68 as a positive regulator of adipocyte differentiation and a negative regulator of osteoblast differentiation, which is consistent with Sam68 being a modulator of bone marrow mesenchymal cell differentiation, and hence bone metabolism, in aged mice. PMID:16362077

Modulation of the Seasonal Cycle of Antarctic Sea Ice Extent Related to the Southern Annular Mode

NASA Astrophysics Data System (ADS)

Doddridge, Edward W.; Marshall, John

2017-10-01

Through analysis of remotely sensed sea surface temperature (SST) and sea ice concentration data, we investigate the impact of winds related to the Southern Annular Mode (SAM) on sea ice extent around Antarctica. We show that positive SAM anomalies in the austral summer are associated with anomalously cold SSTs that persist and lead to anomalous ice growth in the following autumn, while negative SAM anomalies precede warm SSTs and a reduction in sea ice extent during autumn. The largest effect occurs in April, when a unit change in the detrended summertime SAM is followed by a 1.8±0.6 ×105 km2 change in detrended sea ice extent. We find no evidence that sea ice extent anomalies related to the summertime SAM affect the wintertime sea ice extent maximum. Our analysis shows that the wind anomalies related to the negative SAM during the 2016/2017 austral summer contributed to the record minimum Antarctic sea ice extent observed in March 2017.

Structure-guided discovery of the metabolite carboxy-SAM that modulates tRNA function.

PubMed

Kim, Jungwook; Xiao, Hui; Bonanno, Jeffrey B; Kalyanaraman, Chakrapani; Brown, Shoshana; Tang, Xiangying; Al-Obaidi, Nawar F; Patskovsky, Yury; Babbitt, Patricia C; Jacobson, Matthew P; Lee, Young-Sam; Almo, Steven C

2013-06-06

The identification of novel metabolites and the characterization of their biological functions are major challenges in biology. X-ray crystallography can reveal unanticipated ligands that persist through purification and crystallization. These adventitious protein-ligand complexes provide insights into new activities, pathways and regulatory mechanisms. We describe a new metabolite, carboxy-S-adenosyl-l-methionine (Cx-SAM), its biosynthetic pathway and its role in transfer RNA modification. The structure of CmoA, a member of the SAM-dependent methyltransferase superfamily, revealed a ligand consistent with Cx-SAM in the catalytic site. Mechanistic analyses showed an unprecedented role for prephenate as the carboxyl donor and the involvement of a unique ylide intermediate as the carboxyl acceptor in the CmoA-mediated conversion of SAM to Cx-SAM. A second member of the SAM-dependent methyltransferase superfamily, CmoB, recognizes Cx-SAM and acts as a carboxymethyltransferase to convert 5-hydroxyuridine into 5-oxyacetyl uridine at the wobble position of multiple tRNAs in Gram-negative bacteria, resulting in expanded codon-recognition properties. CmoA and CmoB represent the first documented synthase and transferase for Cx-SAM. These findings reveal new functional diversity in the SAM-dependent methyltransferase superfamily and expand the metabolic and biological contributions of SAM-based biochemistry. These discoveries highlight the value of structural genomics approaches in identifying ligands within the context of their physiologically relevant macromolecular binding partners, and in revealing their functions.

Differential phase acoustic microscope for micro-NDE

NASA Technical Reports Server (NTRS)

Waters, David D.; Pusateri, T. L.; Huang, S. R.

1992-01-01

A differential phase scanning acoustic microscope (DP-SAM) was developed, fabricated, and tested in this project. This includes the acoustic lens and transducers, driving and receiving electronics, scanning stage, scanning software, and display software. This DP-SAM can produce mechanically raster-scanned acoustic microscopic images of differential phase, differential amplitude, or amplitude of the time gated returned echoes of the samples. The differential phase and differential amplitude images provide better image contrast over the conventional amplitude images. A specially designed miniature dual beam lens was used to form two foci to obtain the differential phase and amplitude information of the echoes. High image resolution (1 micron) was achieved by applying high frequency (around 1 GHz) acoustic signals to the samples and placing two foci close to each other (1 micron). Tone burst was used in this system to obtain a good estimation of the phase differences between echoes from the two adjacent foci. The system can also be used to extract the V(z) acoustic signature. Since two acoustic beams and four receiving modes are available, there are 12 possible combinations to produce an image or a V(z) scan. This provides a unique feature of this system that none of the existing acoustic microscopic systems can provide for the micro-nondestructive evaluation applications. The entire system, including the lens, electronics, and scanning control software, has made a competitive industrial product for nondestructive material inspection and evaluation and has attracted interest from existing acoustic microscope manufacturers.

Summary report of mission acceleration measurements for Spacehab-01, STS-57 launched 21 June 1993

NASA Technical Reports Server (NTRS)

Finley, Brian; Grodsinsky, Carlos; Delombard, Richard

1994-01-01

The maiden voyage of the commercial Spacehab laboratory module onboard the STS-57 mission was integrated with several accelerometer packages, one of which was the Space Acceleration Measurement System (SAMS). The June 21st 1993, launch was the seventh successful mission for the Office of Life and Microgravity Sciences and Application's (OLMSA) SAMS unit. This flight was also complemented by a second accelerometer system. The Three Dimensional Microgravity Accelerometer (3-DMA), a Code C funded acceleration measurement system, offering an on-orbit residual calibration as a reference for the unit's four triaxial accelerometers. The SAMS accelerometer unit utilized three remote triaxial sensor heads mounted on the forward Spacehab module bulkhead and on one centrally located experiment locker door. These triaxial heads had filter cut-offs set to 5, 50, and 1000 Hz. The mission also included other experiment specific accelerometer packages in various locations.

Optimization of pentacene double floating gate memories based on charge injection regulated by SAM functionalization

NASA Astrophysics Data System (ADS)

Li, S.; Guérin, D.; Lenfant, S.; Lmimouni, K.

2018-02-01

Pentacene based double nano-floating gate memories (NFGM) by using gold nanoparticles (Au NPs) and reduced graphene oxide (rGO) sheets as charge trapping layers are prepared and demonstrated. Particularly, the NFGM chemically treated by 2,3,4,5,6-pentafluorobenzenethiol (PFBT) self-assembled monolayers (SAM) exhibits excellent memory performances, including high mobility of 0.23 cm2V-1s-1, the large memory window of 51 V, and the stable retention property more than 108 s. Comparing the performances of NFGM without treating with PFBT SAM, the improving performances of the memory devices by SAM modification are explained by the increase of charge injection, which could be further investigated by XPS and UPS. In particular, the results highlight the utility of SAM modulations and controlling of charge transport in the development of organic transistor memories.

Sam68 Allows Selective Targeting of Human Cancer Stem Cells.

PubMed

Benoit, Yannick D; Mitchell, Ryan R; Risueño, Ruth M; Orlando, Luca; Tanasijevic, Borko; Boyd, Allison L; Aslostovar, Lili; Salci, Kyle R; Shapovalova, Zoya; Russell, Jennifer; Eguchi, Masakatsu; Golubeva, Diana; Graham, Monica; Xenocostas, Anargyros; Trus, Michael R; Foley, Ronan; Leber, Brian; Collins, Tony J; Bhatia, Mickie

2017-07-20

Targeting of human cancer stem cells (CSCs) requires the identification of vulnerabilities unique to CSCs versus healthy resident stem cells (SCs). Unfortunately, dysregulated pathways that support transformed CSCs, such as Wnt/β-catenin signaling, are also critical regulators of healthy SCs. Using the ICG-001 and CWP family of small molecules, we reveal Sam68 as a previously unappreciated modulator of Wnt/β-catenin signaling within CSCs. Disruption of CBP-β-catenin interaction via ICG-001/CWP induces the formation of a Sam68-CBP complex in CSCs that alters Wnt signaling toward apoptosis and differentiation induction. Our study identifies Sam68 as a regulator of human CSC vulnerability. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

SAMS Acceleration Measurements on Mir (NASA Increment 4)

NASA Technical Reports Server (NTRS)

DeLombard, Richard

1998-01-01

During NASA Increment 4 (January to May 1997), about 5 gigabytes of acceleration data were collected by the Space Acceleration Measurements System (SAMS) onboard the Russian Space Station, Mir. The data were recorded on 28 optical disks which were returned to Earth on STS-84. During this increment, SAMS data were collected in the Priroda module to support the Mir Structural Dynamics Experiment (MiSDE), the Binary Colloidal Alloy Tests (BCAT), Angular Liquid Bridge (ALB), Candle Flames in Microgravity (CFM), Diffusion Controlled Apparatus Module (DCAM), Enhanced Dynamic Load Sensors (EDLS), Forced Flow Flame Spreading Test (FFFr), Liquid Metal Diffusion (LMD), Protein Crystal Growth in Dewar (PCG/Dewar), Queen's University Experiments in Liquid Diffusion (QUELD), and Technical Evaluation of MIM (TEM). This report points out some of the salient features of the microgravity environment to which these experiments were exposed. Also documented are mission events of interest such as the docked phase of STS-84 operations, a Progress engine bum, Soyuz vehicle docking and undocking, and Progress vehicle docking. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. The analyses included herein complement those presented in previous summary reports prepared by the Principal Investigator Microgravity Services (PIMS) group.

Sam68 promotes Schwann cell proliferation by enhancing the PI3K/Akt pathway and acts on regeneration after sciatic nerve crush

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

Wu, Weijie, E-mail: 459586768@qq.com; Liu, Yuxi, E-mail: 924013616@qq.com; Wang, Youhua, E-mail: wyouhua1516@163.com

Sam68 (Src-associated in mitosis of 68 kD), a KH domain RNA-binding protein, is not only important in signaling transduction cascades, but crucial in a variety of cellular processes. Sam68 is reported to be involved in the phospoinositide3-kinase (PI3K) and nuclear factor-kappa B (NF-κB) signaling pathways, and it is closely associated with cell proliferation, RNA metabolism, and tumor progression. However, we know little about the role of Sam68 during peripheral nervous system injury and regeneration. In this study, we investigated the expression of Sam68 and its biological significances in sciatic nerve crush. Interestingly, we found Sam68 had a co-localization with S100 (Schwannmore » cell marker). Moreover, after crush, Sam68 had a spatiotemporal protein expression, which was in parallel with proliferation cell nuclear antigen (PCNA). In vitro, we also observed increased expression of Sam68 during the process of TNF-α-induced Schwann cell proliferation model. Besides, flow cytometry analyses, CCK-8, and EDU were all performed with the purpose of investigating the role of Sam68 in the regulation of Schwann cell proliferation. Even more importantly, we discovered that Sam68 could enhance the phosphorylation of Akt while LY294002 (a PI3K inhibitor) obviously reversed Sam68-induced cell proliferation. Finally, we detected the variance during regeneration progress through the rat walk footprint test. In summary, all these evidences demonstrated that Sam68 might participate in Schwann cell proliferation partially via PI3K/Akt pathway and also regulate regeneration after sciatic nerve crush. -- Highlights: •The dynamic changes and location of Sam68 after sciatic nerve crush. •Sam68 promoted Schwann cell proliferation via PI3K/Akt pathway. •Sam68 modulated functional recovery after sciatic nerve crush.« less

Ultra-thin optical vortex phase plate based on the metasurface and the angular momentum transformation

NASA Astrophysics Data System (ADS)

Wang, Wei; Li, Yan; Guo, Zhongyi; Li, Rongzhen; Zhang, Jingran; Zhang, Anjun; Qu, Shiliang

2015-04-01

The ultra-thin optical vortex phase plate (VPP) has been designed and investigated based on the metasurface of the metal rectangular split-ring resonators (MRSRRs) array. The circularly polarized incident light can convert into corresponding cross-polarization transmission light, and the phase and the amplitude of cross-polarization transmission light can be simultaneously governed by modulating two arms of the MRSRR. The MRSRR has been arranged in a special order for forming an ultra-thin optical VPP that can covert a plane wave into a vortex beam with a variety of the topological charges, and the transformation between spin angular momentum (SAM) and orbital angular momentum (OAM) has been discussed in detail. The multi-spectral characteristics of the VPP have also been investigated, and the operating bandwidth of the designed VPP is 190 nm (in the range of 710-900 nm), which enable a potential implication for integrated optics and vortex optics.

System Advisor Model (SAM) General Description (Version 2017.9.5)

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

Freeman, Janine M; DiOrio, Nicholas A; Blair, Nathan J

This document describes the capabilities of the System Advisor Model (SAM) developed and distributed by the U.S. Department of Energy's National Renewable Energy Laboratory. The document is for potential users and others wanting to learn about the model's capabilities. SAM is a techno-economic computer model that calculates performance and financial metrics of renewable energy projects. Project developers, policy makers, equipment manufacturers, and researchers use graphs and tables of SAM results in the process of evaluating financial, technology, and incentive options for renewable energy projects. SAM simulates the performance of photovoltaic, concentrating solar power, solar water heating, wind, geothermal, biomass, andmore » conventional power systems. The financial models are for projects that either buy and sell electricity at retail rates (residential and commercial) or sell electricity at a price determined in a power purchase agreement (PPA). SAM's simulation tools facilitate parametric and sensitivity analyses, Monte Carlo simulation and weather variability (P50/P90) studies. SAM can also read input variables from Microsoft Excel worksheets. For software developers, the SAM software development kit (SDK) makes it possible to use SAM simulation modules in their applications written in C/C plus plus, C sharp, Java, Python, MATLAB, and other languages. NREL provides both SAM and the SDK as free downloads at https://sam.nrel.gov. SAM is an open source project, so its source code is available to the public. Researchers can study the code to understand the model algorithms, and software programmers can contribute their own models and enhancements to the project. Technical support and more information about the software are available on the website.« less

Simulation of different types of ENSO impacts on South Asian Monsoon in CCSM4

NASA Astrophysics Data System (ADS)

Islam, Siraj ul; Tang, Youmin

2017-02-01

It has been found in observation that there are different types of influences of El Nino Southern Oscillation (ENSO) on the South Asian Monsoon (SAM). A correct description and representation of these teleconnections is critical for climate models to simulate and predict SAM. In this study, we examine these teleconnections in NCAR CAM4 and CCSM4 models, including the strength and weakness of these models in preserving different types of ENSO-SAM relationships. By using observational and simulation dataset, the composite analysis, based on specific selection criteria, is performed for both SAM rainfall and the eastern equatorial Pacific sea surface temperature (SST) anomalies. Anomalous SAM rainfall is characterized in three different types i.e. the indirect influence of the SST anomalies of preceding winter (DJF-only), direct influence of the SST anomalies of concurrent summer (JJAS-only) and the combined influence of both preceding winter and concurrent summer (DJF&JJAS). The analysis reveals that CAM4 uncoupled simulation can reasonably well reproduce the anomalous SAM rainfall in DJF-only and DJF&JJAS types whereas the model fails to simulate the anomalous rainfall in the JJAS-only type. The better performance of CAM4, particularly in DJF&JJAS type, comes from its realistic simulation of moisture content and thermal contrast. Its failure to preserve the ENSO-SAM relationship of JJAS-only type is due to the absence of ENSO induced warming in Northern Indian Ocean via atmospheric circulation which is indirectly linked to the lack of air-sea coupling. The role of Indian Ocean in controlling the ENSO-SAM teleconnections of the DJF&JJAS type is further investigated using CAM4 sensitivity experiments. It is found that in absence of Indian Ocean SST, the anomalous SAM summer rainfall suppresses in the DJF&JJAS type, suggesting the important modulation by Indian Ocean SST probably through the preceding winter equatorial Pacific SST forcing and the atmospheric circulations. On the other hand, CCSM4 shows large systematical errors in DJF-only and DJF&JJAS types and reproduce weak anomalous SAM rainfall. The failure of CCSM4 in simulating DJF-only and DJF&JJAS types is found mainly due to the errors in its SST simulation. The JJAS-only type is better reproduced in the CCSM4 simulation as compared to CAM4 and observation composites. Strong convergence over the SAM region which intensifies the anomalous SAM is seen to be responsible for its better simulation in this type. It is found that the atmospheric circulations in CCSM4 contribute more than the thermal contrast in modulating the intensity of anomalous rainfall in JJAS-only type. This study suggests that, although air-sea coupling is important for better SAM simulation and its relationship with ENSO, the SST bias in coupled model can significantly degrade ENSO-SAM relationship.

Characterization of the near native conformational states of the SAM domain of Ste11 protein by NMR spectroscopy.

PubMed

Gupta, Sebanti; Bhattacharjya, Surajit

2014-11-01

The sterile alpha motif or SAM domain is one of the most frequently present protein interaction modules with diverse functional attributions. SAM domain of the Ste11 protein of budding yeast plays important roles in mitogen-activated protein kinase cascades. In the current study, urea-induced, at subdenaturing concentrations, structural, and dynamical changes in the Ste11 SAM domain have been investigated by nuclear magnetic resonance spectroscopy. Our study revealed that a number of residues from Helix 1 and Helix 5 of the Ste11 SAM domain display plausible alternate conformational states and largest chemical shift perturbations at low urea concentrations. Amide proton (H/D) exchange experiments indicated that Helix 1, loop, and Helix 5 become more susceptible to solvent exchange with increased concentrations of urea. Notably, Helix 1 and Helix 5 are directly involved in binding interactions of the Ste11 SAM domain. Our data further demonstrate that the existence of alternate conformational states around the regions involved in dimeric interactions in native or near native conditions. © 2014 Wiley Periodicals, Inc.

Centennial-scale solar forcing of the South American Monsoon System recorded in stalagmites.

PubMed

Novello, Valdir F; Vuille, Mathias; Cruz, Francisco W; Stríkis, Nicolás M; de Paula, Marcos Saito; Edwards, R Lawrence; Cheng, Hai; Karmann, Ivo; Jaqueto, Plínio F; Trindade, Ricardo I F; Hartmann, Gelvam A; Moquet, Jean S

2016-04-21

The South American Monsoon System (SAMS) is generally considered to be highly sensitive to Northern Hemisphere (NH) temperature variations on multi-centennial timescales. The direct influence of solar forcing on moisture convergence in global monsoon systems on the other hand, while well explored in modeling studies, has hitherto not been documented in proxy data from the SAMS region. Hence little is known about the sensitivity of the SAMS to solar forcing over the past millennium and how it might compete or constructively interfere with NH temperature variations that occurred primarily in response to volcanic forcing. Here we present a new annually-resolved oxygen isotope record from a 1500-year long stalagmite recording past changes in precipitation in the hitherto unsampled core region of the SAMS. This record details how solar variability consistently modulated the strength of the SAMS on centennial time scales during the past 1500 years. Solar forcing, besides the previously recognized influence from NH temperature changes and associated Intertropical Convergence Zone (ITCZ) shifts, appears as a major driver affecting SAMS intensity at centennial time scales.

Sample Analysis at Mars Instrument Simulator

NASA Technical Reports Server (NTRS)

Benna, Mehdi; Nolan, Tom

2013-01-01

The Sample Analysis at Mars Instrument Simulator (SAMSIM) is a numerical model dedicated to plan and validate operations of the Sample Analysis at Mars (SAM) instrument on the surface of Mars. The SAM instrument suite, currently operating on the Mars Science Laboratory (MSL), is an analytical laboratory designed to investigate the chemical and isotopic composition of the atmosphere and volatiles extracted from solid samples. SAMSIM was developed using Matlab and Simulink libraries of MathWorks Inc. to provide MSL mission planners with accurate predictions of the instrument electrical, thermal, mechanical, and fluid responses to scripted commands. This tool is a first example of a multi-purpose, full-scale numerical modeling of a flight instrument with the purpose of supplementing or even eliminating entirely the need for a hardware engineer model during instrument development and operation. SAMSIM simulates the complex interactions that occur between the instrument Command and Data Handling unit (C&DH) and all subsystems during the execution of experiment sequences. A typical SAM experiment takes many hours to complete and involves hundreds of components. During the simulation, the electrical, mechanical, thermal, and gas dynamics states of each hardware component are accurately modeled and propagated within the simulation environment at faster than real time. This allows the simulation, in just a few minutes, of experiment sequences that takes many hours to execute on the real instrument. The SAMSIM model is divided into five distinct but interacting modules: software, mechanical, thermal, gas flow, and electrical modules. The software module simulates the instrument C&DH by executing a customized version of the instrument flight software in a Matlab environment. The inputs and outputs to this synthetic C&DH are mapped to virtual sensors and command lines that mimic in their structure and connectivity the layout of the instrument harnesses. This module executes, and thus validates, complex command scripts prior to their up-linking to the SAM instrument. As an output, this module generates synthetic data and message logs at a rate that is similar to the actual instrument.

Teleconnection stationarity, variability and trends of the Southern Annular Mode (SAM) during the last millennium

NASA Astrophysics Data System (ADS)

Dätwyler, Christoph; Neukom, Raphael; Abram, Nerilie J.; Gallant, Ailie J. E.; Grosjean, Martin; Jacques-Coper, Martín; Karoly, David J.; Villalba, Ricardo

2017-11-01

The Southern Annular Mode (SAM) is the leading mode of atmospheric interannual variability in the Southern Hemisphere (SH) extra-tropics. Here, we assess the stationarity of SAM spatial correlations with instrumental and paleoclimate proxy data for the past millennium. The instrumental period shows that temporal non-stationarities in SAM teleconnections are not consistent across the SH land areas. This suggests that the influence of the SAM index is modulated by regional effects. However, within key-regions with good proxy data coverage (South America, Tasmania, New Zealand), teleconnections are mostly stationary over the instrumental period. Using different stationarity criteria for proxy record selection, we provide new austral summer and annual mean SAM index reconstructions over the last millennium. Our summer SAM reconstructions are very robust to changes in proxy record selection and the selection of the calibration period, particularly on the multi-decadal timescale. In contrast, the weaker performance and lower agreement in the annual mean SAM reconstructions point towards changing teleconnection patterns that may be particularly important outside the summer months. Our results clearly portend that the temporal stationarity of the proxy-climate relationships should be taken into account in the design of comprehensive regional and hemispherical climate reconstructions. The summer SAM reconstructions show no significant relationship to solar, greenhouse gas and volcanic forcing, with the exception of an extremely strong negative anomaly following the AD 1257 Samalas eruption. Furthermore, reconstructed pre-industrial summer SAM trends are very similar to trends obtained by model control simulations. We find that recent trends in the summer SAM lie outside the 5-95% range of pre-industrial natural variability.

Structural investigation of a C-terminal EphA2 receptor mutant: Does mutation affect the structure and interaction properties of the Sam domain?

PubMed

Mercurio, Flavia A; Costantini, Susan; Di Natale, Concetta; Pirone, Luciano; Guariniello, Stefano; Scognamiglio, Pasqualina L; Marasco, Daniela; Pedone, Emilia M; Leone, Marilisa

2017-09-01

Ephrin A2 receptor (EphA2) plays a key role in cancer, it is up-regulated in several types of tumors and the process of ligand-induced receptor endocytosis, followed by degradation, is considered as a potential path to diminish tumor malignancy. Protein modulators of this mechanism are recruited at the cytosolic Sterile alpha motif (Sam) domain of EphA2 (EphA2-Sam) through heterotypic Sam-Sam associations. These interactions engage the C-terminal helix of EphA2 and close loop regions (the so called End Helix side). In addition, several studies report on destabilizing mutations in EphA2 related to cataract formation and located in/or close to the Sam domain. Herein, we analyzed from a structural point of view, one of these mutants characterized by the insertion of a novel 39 residue long polypeptide at the C-terminus of EphA2-Sam. A 3D structural model was built by computational methods and revealed partial disorder in the acquired C-terminal tail and a few residues participating in an α-helix and two short β-strands. We investigated by CD and NMR studies the conformational properties in solution of two peptides encompassing the whole C-terminal tail and its predicted helical region, respectively. NMR binding experiments demonstrated that these peptides do not interact relevantly with either EphA2-Sam or its interactor Ship2-Sam. Molecular dynamics (MD) simulations further indicated that the EphA2 mutant could be represented only through a conformational ensemble and that the C-terminal tail should not largely wrap the EphA2-Sam End-Helix interface and affect binding to other Sam domains. Copyright © 2017 Elsevier B.V. All rights reserved.

S-Adenosylmethionine attenuates bile duct early warm ischemia reperfusion injury after rat liver transplantation.

PubMed

Tang, Yong; Chu, Hongpeng; Cao, Guojun; Du, Xiaolong; Min, Xiaobo; Wan, Chidan

2018-03-01

Warm ischemia reperfusion injury (IRI) plays a key role in biliary complication, which is a substantial vulnerability of liver transplantation. The early pathophysiological changes of IRI are characterized by an excessive inflammatory response. S-Adenosylmethionine (SAM) is an important metabolic intermediate that modulates inflammatory reactions; however, its role in bile duct warm IRI is not known. In this study, male rats were treated with or without SAM (170 μmol/kg body weight) after orthotopic autologous liver transplantation. The histopathological observations showed that bile duct injury in the IRI group was more serious than in the SAM group. The alanine aminotransferase (ALT), alkaline phosphatase (ALP) and direct bilirubin (DBIL) levels in the serum of the IRI group were significantly increased compared to the SAM group (P < .05). Simultaneously, SAM effectively improved the survival of the transplant recipients. Furthermore, the H 2 O 2 and malondialdehyde (MDA) of the IRI group were much higher compared to the SAM group (P < .05). The GSH/GSSG ratio in the SAM group was significantly increased by SAM treatment compared to the IRI group (P < .05). SAM administration significantly inhibited macrophage infiltration in liver and bile duct tissues, down-regulated TNF-α levels and up-regulated IL-10 expression in bile duct tissues compared to the IRI group (P < .05). The number of apoptotic biliary epithelial cells and caspase-3-positive cells in IRI rat livers were much higher compared to those in SAM-treated rats at 24 h after liver transplantation (P < .05). These data suggested that SAM protected bile ducts against warm IRI by suppressing oxidative stress, inflammatory reactions and apoptosis of biliary epithelial cells after liver transplantation.α. Copyright © 2018 Elsevier Ltd. All rights reserved.

Progress & Frontiers in PV Performance

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

Deline, Chris; DiOrio, Nick; Jordan, Dirk

2016-09-12

PowerPoint slides for a presentation given at Solar Power International 2016. Presentation includes System Advisor Model (SAM) introduction and battery modeling, bifacial PV modules and modeling, shade modeling and module level power electronics (MLPE), degradation rates, and PVWatts updates and validation.

Synthesis and characterization of self-assembled monolayers on gold generated from partially fluorinated alkanethiols and aliphatic dithiocarboxylic acids

NASA Astrophysics Data System (ADS)

Colorado, Ramon, Jr.

The formation of novel self-assembled monolayers (SAMs) on gold from the adsorption of four distinct series of partially fluorinated alkanethiols (PFAs) and one series of chelating aliphatic dithiocarboxylic acids (ADTCAs) is reported. The SAMs were characterized by optical ellipsometry, contact angle goniometry, polarization modulation infrared absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). The results for the PFA SAMs provided evidence for both the importance of oriented surface dipoles in influencing interfacial wettabilities and the significance of the degree of fluorination of the PFAs in determining the dispersive interfacial energies of the films. In addition, a series of PFA SAMs was used to demonstrate that the attenuation lengths of photoelectrons in fluorocarbon films are indistinguishable from those in hydrocarbon films. The results for the ADTCA SAMs demonstrated that the use of a chelating headgroup induces structural changes within the monolayers that influence the interfacial properties of the films.

The transcription factor FBI-1 inhibits SAM68-mediated BCL-X alternative splicing and apoptosis.

PubMed

Bielli, Pamela; Busà, Roberta; Di Stasi, Savino M; Munoz, Manuel J; Botti, Flavia; Kornblihtt, Alberto R; Sette, Claudio

2014-04-01

Alternative splicing (AS) is tightly coupled to transcription for the majority of human genes. However, how these two processes are linked is not well understood. Here, we unveil a direct role for the transcription factor FBI-1 in the regulation of AS. FBI-1 interacts with the splicing factor SAM68 and reduces its binding to BCL-X mRNA. This, in turn, results in the selection of the proximal 5' splice site in BCL-X exon 2, thereby favoring the anti-apoptotic BCL-XL variant and counteracting SAM68-mediated apoptosis. Conversely, depletion of FBI-1, or expression of a SAM68 mutant lacking the FBI-1 binding region, restores the ability of SAM68 to induce BCL-XS splicing and apoptosis. FBI-1's role in splicing requires the activity of histone deacetylases, whose pharmacological inhibition recapitulates the effects of FBI-1 knockdown. Our study reveals an unexpected function for FBI-1 in splicing modulation with a direct impact on cell survival.

The transcription factor FBI-1 inhibits SAM68-mediated BCL-X alternative splicing and apoptosis

PubMed Central

Bielli, Pamela; Busà, Roberta; Di Stasi, Savino M; Munoz, Manuel J; Botti, Flavia; Kornblihtt, Alberto R; Sette, Claudio

2014-01-01

Alternative splicing (AS) is tightly coupled to transcription for the majority of human genes. However, how these two processes are linked is not well understood. Here, we unveil a direct role for the transcription factor FBI-1 in the regulation of AS. FBI-1 interacts with the splicing factor SAM68 and reduces its binding to BCL-X mRNA. This, in turn, results in the selection of the proximal 5′ splice site in BCL-X exon 2, thereby favoring the anti-apoptotic BCL-XL variant and counteracting SAM68-mediated apoptosis. Conversely, depletion of FBI-1, or expression of a SAM68 mutant lacking the FBI-1 binding region, restores the ability of SAM68 to induce BCL-XS splicing and apoptosis. FBI-1's role in splicing requires the activity of histone deacetylases, whose pharmacological inhibition recapitulates the effects of FBI-1 knockdown. Our study reveals an unexpected function for FBI-1 in splicing modulation with a direct impact on cell survival. PMID:24514149

Supra-physiological folic acid concentrations induce aberrant DNA methylation in normal human cells in vitro.

PubMed

Charles, Michelle A; Johnson, Ian T; Belshaw, Nigel J

2012-07-01

The micronutrients folate and selenium may modulate DNA methylation patterns by affecting intracellular levels of the methyl donor S-adenosylmethionine (SAM) and/or the product of methylation reactions S-adenosylhomocysteine (SAH). WI-38 fibroblasts and FHC colon epithelial cells were cultured in the presence of two forms of folate or four forms of selenium at physiologically-relevant doses, and their effects on LINE-1 methylation, gene-specific CpG island (CGI) methylation and intracellular SAM:SAH were determined. At physiologically-relevant doses the forms of folate or selenium had no effect on LINE-1 or CGI methylation, nor on intracellular SAM:SAH. However the commercial cell culture media used for the selenium studies, containing supra-physiological concentrations of folic acid, induced LINE-1 hypomethylation, CGI hypermethylation and decreased intracellular SAM:SAH in both cell lines. We conclude that the exposure of normal human cells to supra-physiological folic acid concentrations present in commercial cell culture media perturbs the intracellular SAM:SAH ratio and induces aberrant DNA methylation.

Microgravity acceleration measurement and environment characterization science (17-IML-1)

NASA Technical Reports Server (NTRS)

1992-01-01

The Space Acceleration Measurement System (SAMS) is a general purpose instrumentation system designed to measure the accelerations onboard the Shuttle Orbiter and Shuttle/Spacelab vehicles. These measurements are used to support microgravity experiments and investigation into the microgravity environment of the vehicle. Acceleration measurements can be made at locations remote from the SAMS main instrumentation unit by the use of up to three remote triaxial sensor heads. The prime objective for SAMS on the International Microgravity Lab (IML-1) mission will be to measure the accelerations experienced by the Fluid Experiment System (FES). The SAMS acceleration measurements for FES will be complemented by low level, low frequency acceleration measurements made by the Orbital Acceleration Research Experiment (OARE) installed on the shuttle. Secondary objectives for SAMS will be to measure accelerations at several specific locations to enable the acceleration transfer function of the Spacelab module to be analyzed. This analysis effort will be in conjunction with similar measurements analyses on other Spacelab missions.

Photoinduced work function changes by isomerization of a densely packed azobenzene-based SAM on Au: a joint experimental and theoretical study.

PubMed

Crivillers, N; Liscio, A; Di Stasio, F; Van Dyck, C; Osella, S; Cornil, D; Mian, S; Lazzerini, G M; Fenwick, O; Orgiu, E; Reinders, F; Braun, S; Fahlman, M; Mayor, M; Cornil, J; Palermo, V; Cacialli, F; Samorì, P

2011-08-28

Responsive monolayers are key building blocks for future applications in organic and molecular electronics in particular because they hold potential for tuning the physico-chemical properties of interfaces, including their energetics. Here we study a photochromic SAM based on a conjugated azobenzene derivative and its influence on the gold work function (Φ(Au)) when chemisorbed on its surface. In particular we show that the Φ(Au) can be modulated with external stimuli by controlling the azobenzene trans/cis isomerization process. This phenomenon is characterized experimentally by four different techniques, kelvin probe, kelvin probe force microscopy, electroabsorption spectroscopy and ultraviolet photoelectron spectroscopy. The use of different techniques implies exposing the SAM to different measurement conditions and different preparation methods, which, remarkably, do not alter the observed work function change (Φ(trans)-Φ(cis)). Theoretical calculations provided a complementary insight crucial to attain a deeper knowledge on the origin of the work function photo-modulation.

SAMS Acceleration Measurements on Mir from May 1997 to June 1998 (NASA Increments 5, 6, and 7)

NASA Technical Reports Server (NTRS)

DeLombard, Richard

1999-01-01

During NASA Increments 5, 6, and 7 (May 1997 to June 1998), about eight gigabytes of acceleration data were collected by the Space Acceleration Measurement System (SAMS) onboard the Russian Space Station Mir. The data were recorded on twenty-seven optical disks which were returned to Earth on Orbiter missions STS-86, STS-89, and STS-91. During these increments, SAMS data were collected in the Priroda module to support various microgravity experiments. This report points out some of the salient features of the microgravity acceleration environment to which the experiments were exposed. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. The analyses included herein complement those presented in previous Mir increment summary reports prepared by the Principal Investigator Microgravity Services project.

SAMS Acceleration Measurements on Mir From January to May 1997 (NASA Increment 4)

NASA Technical Reports Server (NTRS)

DeLombard, Richard

1998-01-01

During NASA Increment 4 (January to May 1997), about 5 gigabytes of acceleration data were collected by the Space Acceleration Measurements System (SAMS) onboard the Russian Space Station, Mir. The data were recorded on 28 optical disks which were returned to Earth on STS-84. During this increment, SAMS data were collected in the Priroda module to support the Mir Structural Dynamics Experiment (MiSDE), the Binary Colloidal Alloy Tests (BCAT), Angular Liquid Bridge (ALB), Candle Flames in Microgravity (CFM), Diffusion Controlled Apparatus Module (DCAM), Enhanced Dynamic Load Sensors (EDLS), Forced Flow Flame Spreading Test (FFFT), Liquid Metal Diffusion (LMD), Protein Crystal Growth in Dewar (PCG/Dewar), Queen's University Experiments in Liquid Diffusion (QUELD), and Technical Evaluation of MIM (TEM). This report points out some of the salient features of the microgravity environment to which these experiments were exposed. Also documented are mission events of interest such as the docked phase of STS-84 operations, a Progress engine burn, Soyuz vehicle docking and undocking, and Progress vehicle docking. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. The analyses included herein complement those presented in previous summary reports prepared by the Principal Investigator Microgravity Services (PIMS) group.

Modulating protein behaviors on responsive surface by external electric fields: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Xie, Yun; Pan, Yufang; Zhang, Rong; Liang, Ying; Li, Zhanchao

2015-01-01

Molecular dynamics simulations were employed to investigate the modulation of protein behaviors on the electrically responsive zwitterionic phosphorylcholine self-assembled monolayers (PC-SAMs). Results show that PC-SAMs could sensitively respond to the applied electric fields and exhibit three states with different charge distributions, namely both the negatively charged phosphate groups and the positively charged choline groups are exposed to the solution in the absence of electric fields (state 1), phosphate groups exposed in the presence of positive electric fields (state 2), and choline groups exposed in the presence of negative electric fields (state 3). Under state 1, the adsorption of Cyt c on the PC-SAM is reversible and the orientations of Cyt c are randomly distributed. Under state 2, the adsorption of Cyt c is enhanced due to the electrostatic attractions between the exposed phosphate groups and the positively charged protein; when adsorbed on the PC-SAMs, Cyt c tends to adopt the orientation with the heme plane perpendicular to the surface plane, and the percentage of this orientation increases as the field strength rises up. Under state 3, the adsorption of Cyt c is retarded because of the electrostatic repulsions between the exposed choline groups and the protein; however, if the gaps between PC chains are large enough, Cyt c could insert into the PC-SAM and access the phosphate groups after overcoming a slight energy barrier. Under three states, the basic backbone structures of Cyt c are well kept within the simulation time since the conformation of Cyt c is mainly affected by the surface-generated electric fields, whose strengths are modulated by the external electric fields and are not strong enough to deform protein. The results indicate the possibility of regulating protein behaviors, including promoting or retarding protein adsorption and regulating protein orientations, on responsive surfaces by applying electric fields on the surfaces without worrying protein deformation, which may be helpful in the applications of protein separation and controlled drug delivery.

Female Drosophila melanogaster respond to song-amplitude modulations.

PubMed

Brüggemeier, Birgit; Porter, Mason A; Vigoreaux, Jim O; Goodwin, Stephen F

2018-06-11

Males in numerous animal species use mating songs to attract females and intimidate competitors. We demonstrate that modulations in song amplitude are behaviourally relevant in the fruit fly Drosophila We show that D rosophila melanogaster females prefer amplitude modulations that are typical of melanogaster song over other modulations, which suggests that amplitude modulations are processed auditorily by D. melanogaster Our work demonstrates that receivers can decode messages in amplitude modulations, complementing the recent finding that male flies actively control song amplitude. To describe amplitude modulations, we propose the concept of song amplitude structure (SAS) and discuss similarities and differences to amplitude modulation with distance (AMD).This article has an associated First Person interview with the first author of the paper. © 2018. Published by The Company of Biologists Ltd.

47 CFR 73.14 - AM broadcast definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... in which the carrier wave is modulated in accordance with the system of amplitude modulation and the characteristics of the modulating wave. Amplitude modulator stage. The last amplifier stage of the modulating wave... amplitude of the carrier wave in an amplitude-modulated transmitter when modulation is applied under...

47 CFR 73.14 - AM broadcast definitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... in which the carrier wave is modulated in accordance with the system of amplitude modulation and the characteristics of the modulating wave. Amplitude modulator stage. The last amplifier stage of the modulating wave... amplitude of the carrier wave in an amplitude-modulated transmitter when modulation is applied under...

47 CFR 73.14 - AM broadcast definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... in which the carrier wave is modulated in accordance with the system of amplitude modulation and the characteristics of the modulating wave. Amplitude modulator stage. The last amplifier stage of the modulating wave... amplitude of the carrier wave in an amplitude-modulated transmitter when modulation is applied under...

4-Mercaptophenylboronic acid SAMs on gold: comparison with SAMs derived from thiophenol, 4-mercaptophenol, and 4-mercaptobenzoic acid.

PubMed

Barriet, David; Yam, Chi Ming; Shmakova, Olga E; Jamison, Andrew C; Lee, T Randall

2007-08-14

We report the formation and characterization of self-assembled monolayers (SAMs) derived from the adsorption of 4-mercaptophenylboronic acid (MPBA) on gold. For comparison, SAMs derived from the adsorption of thiophenol (TP), 4-mercaptophenol (MP), and 4-mercaptobenzoic acid (MBA) were also examined. The structure and properties of the SAMs were evaluated by ellipsometry, contact-angle goniometry, polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). Specifically, ellipsometry was used to assess the formation of monolayer films, and contact angle measurements were used to determine the surface hydrophilicity and homogeneity. Separately, PM-IRRAS was used to evaluate the molecular composition and orientation as well as the intermolecular hydrogen bonding within the SAMs. Finally, XPS was used to evaluate the film composition and surface coverage (i.e., packing density), which was observed to increase in the following order: TP < MP < MPBA < MBA. A rationalization for the observed packing differences is presented. The XPS data indicate further that ultrahigh vacuum conditions induce the partial dehydration of MPBA SAMs with the concomitant formation of surface boronic anhydride species. Overall, the analytical data collectively show that the MPBA moieties in the SAMs exist in the acid form rather than the anhydride form under ambient laboratory conditions. Furthermore, stability studies find that MPBA SAMs are surprisingly labile in basic solution, where the terminal B-C bonds are cleaved by the attack of hydroxide ion and strongly basic amine nucleophiles. The unanticipated lability observed here should be considered by those wishing to use MPBA moieties in carbohydrate-sensing applications.

Influence of Threonine Metabolism on S-adenosyl-methionine and Histone Methylation

PubMed Central

Shyh-Chang, Ng; Locasale, Jason W.; Lyssiotis, Costas A.; Zheng, Yuxiang; Teo, Ren Yi; Ratanasirintrawoot, Sutheera; Zhang, Jin; Onder, Tamer; Unternaehrer, Juli J.; Zhu, Hao; Asara, John M.; Daley, George Q.; Cantley, Lewis C.

2013-01-01

Threonine is the only amino acid critically required for the pluripotency of mouse embryonic stem cells (mESCs) but the detailed mechanism remains unclear. We found that threonine (Thr) and S-adenosyl-methionine (SAM) metabolism are coupled in pluripotent stem cells, resulting in regulation of histone methylation. Isotope labeling of mESCs revealed that Thr provides a substantial fraction of both the cellular glycine (Gly) and the acetyl-coenzyme A (CoA) needed for SAM synthesis. Depletion of Thr from the culture medium or threonine dehydrogenase (Tdh) from mESCs decreased accumulation of SAM and decreased tri-methylation of histone H3 lysine-4 (H3K4me3), leading to slowed growth, and increased differentiation. Thus abundance of SAM appears to influence H3K4me3, providing a possible mechanism by which modulation of a metabolic pathway might influence stem cell fate. PMID:23118012

SAM68 is a physiological regulator of SMN2 splicing in spinal muscular atrophy

PubMed Central

Pagliarini, Vittoria; Pelosi, Laura; Bustamante, Maria Blaire; Nobili, Annalisa; Berardinelli, Maria Grazia; D’Amelio, Marcello; Musarò, Antonio

2015-01-01

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by loss of motor neurons in patients with null mutations in the SMN1 gene. The almost identical SMN2 gene is unable to compensate for this deficiency because of the skipping of exon 7 during pre–messenger RNA (mRNA) processing. Although several splicing factors can modulate SMN2 splicing in vitro, the physiological regulators of this disease-causing event are unknown. We found that knockout of the splicing factor SAM68 partially rescued body weight and viability of SMAΔ7 mice. Ablation of SAM68 function promoted SMN2 splicing and expression in SMAΔ7 mice, correlating with amelioration of SMA-related defects in motor neurons and skeletal muscles. Mechanistically, SAM68 binds to SMN2 pre-mRNA, favoring recruitment of the splicing repressor hnRNP A1 and interfering with that of U2AF65 at the 3′ splice site of exon 7. These findings identify SAM68 as the first physiological regulator of SMN2 splicing in an SMA mouse model. PMID:26438828

Information System through ANIS at CeSAM

NASA Astrophysics Data System (ADS)

Moreau, C.; Agneray, F.; Gimenez, S.

2015-09-01

ANIS (AstroNomical Information System) is a web generic tool developed at CeSAM to facilitate and standardize the implementation of astronomical data of various kinds through private and/or public dedicated Information Systems. The architecture of ANIS is composed of a database server which contains the project data, a web user interface template which provides high level services (search, extract and display imaging and spectroscopic data using a combination of criteria, an object list, a sql query module or a cone search interfaces), a framework composed of several packages, and a metadata database managed by a web administration entity. The process to implement a new ANIS instance at CeSAM is easy and fast : the scientific project has to submit data or a data secure access, the CeSAM team installs the new instance (web interface template and the metadata database), and the project administrator can configure the instance with the web ANIS-administration entity. Currently, the CeSAM offers through ANIS a web access to VO compliant Information Systems for different projects (HeDaM, HST-COSMOS, CFHTLS-ZPhots, ExoDAT,...).

Titanium-silicon oxide film structures for polarization-modulated infrared reflection absorption spectroscopy

PubMed Central

Dunlop, Iain E.; Zorn, Stefan; Richter, Gunther; Srot, Vesna; Kelsch, Marion; van Aken, Peter A.; Skoda, Maximilian; Gerlach, Alexander; Spatz, Joachim P.; Schreiber, Frank

2010-01-01

We present a titanium-silicon oxide film structure that permits polarization modulated infrared reflection absorption spectroscopy on silicon oxide surfaces. The structure consists of a ~6 nm sputtered silicon oxide film on a ~200 nm sputtered titanium film. Characterization using conventional and scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy and X-ray reflectometry is presented. We demonstrate the use of this structure to investigate a selectively protein-resistant self-assembled monolayer (SAM) consisting of silane-anchored, biotin-terminated poly(ethylene glycol) (PEG). PEG-associated IR bands were observed. Measurements of protein-characteristic band intensities showed that this SAM adsorbed streptavidin whereas it repelled bovine serum albumin, as had been expected from its structure. PMID:20418963

Simulations For Investigating the Contrast Mechanism of Biological Cells with High Frequency Scanning Acoustic Microscopy

NASA Astrophysics Data System (ADS)

Juntarapaso, Yada

Scanning Acoustic Microscopy (SAM) is one of the most powerful techniques for nondestructive evaluation and it is a promising tool for characterizing the elastic properties of biological tissues/cells. Exploring a single cell is important since there is a connection between single cell biomechanics and human cancer. Scanning acoustic microscopy (SAM) has been accepted and extensively utilized for acoustical cellular and tissue imaging including measurements of the mechanical and elastic properties of biological specimens. SAM provides superb advantages in that it is non-invasive, can measure mechanical properties of biological cells or tissues, and fixation/chemical staining is not necessary. The first objective of this research is to develop a program for simulating the images and contrast mechanism obtained by high-frequency SAM. Computer simulation algorithms based on MatlabRTM were built for simulating the images and contrast mechanisms. The mechanical properties of HeLa and MCF-7 cells were computed from the measurement data of the output signal amplitude as a function of distance from the focal planes of the acoustics lens which is known as V(z) . Algorithms for simulating V(z) responses involved the calculation of the reflectance function and were created based on ray theory and wave theory. The second objective is to design transducer arrays for SAM. Theoretical simulations based on Field II(c) programs of the high frequency ultrasound array designs were performed to enhance image resolution and volumetric imaging capabilities. Phased array beam forming and dynamic apodization and focusing were employed in the simulations. The new transducer array design will be state-of-the-art in improving the performance of SAM by electronic scanning and potentially providing a 4-D image of the specimen.

Coupling the System Analysis Module with SAS4A/SASSYS-1

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

Fanning, T. H.; Hu, R.

2016-09-30

SAS4A/SASSYS-1 is a simulation tool used to perform deterministic analysis of anticipated events as well as design basis and beyond design basis accidents for advanced reactors, with an emphasis on sodium fast reactors. SAS4A/SASSYS-1 has been under development and in active use for nearly forty-five years, and is currently maintained by the U.S. Department of Energy under the Office of Advanced Reactor Technology. Although SAS4A/SASSYS-1 contains a very capable primary and intermediate system modeling component, PRIMAR-4, it also has some shortcomings: outdated data management and code structure makes extension of the PRIMAR-4 module somewhat difficult. The user input format formore » PRIMAR-4 also limits the number of volumes and segments that can be used to describe a given system. The System Analysis Module (SAM) is a fairly new code development effort being carried out under the U.S. DOE Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. SAM is being developed with advanced physical models, numerical methods, and software engineering practices; however, it is currently somewhat limited in the system components and phenomena that can be represented. For example, component models for electromagnetic pumps and multi-layer stratified volumes have not yet been developed. Nor is there support for a balance of plant model. Similarly, system-level phenomena such as control-rod driveline expansion and vessel elongation are not represented. This report documents fiscal year 2016 work that was carried out to couple the transient safety analysis capabilities of SAS4A/SASSYS-1 with the system modeling capabilities of SAM under the joint support of the ART and NEAMS programs. The coupling effort was successful and is demonstrated by evaluating an unprotected loss of flow transient for the Advanced Burner Test Reactor (ABTR) design. There are differences between the stand-alone SAS4A/SASSYS-1 simulations and the coupled SAS/SAM simulations, but these are mainly attributed to the limited maturity of the SAM development effort. The severe accident modeling capabilities in SAS4A/SASSYS-1 (sodium boiling, fuel melting and relocation) will continue to play a vital role for a long time. Therefore, the SAS4A/SASSYS-1 modernization effort should remain a high priority task under the ART program to ensure continued participation in domestic and international SFR safety collaborations and design optimizations. On the other hand, SAM provides an advanced system analysis tool, with improved numerical solution schemes, data management, code flexibility, and accuracy. SAM is still in early stages of development and will require continued support from NEAMS to fulfill its potential and to mature into a production tool for advanced reactor safety analysis. The effort to couple SAS4A/SASSYS-1 and SAM is the first step on the integration of these modeling capabilities.« less

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

Llave, Ezequiel de la; Herrera, Santiago E.; Adam, Catherine

The molecular and electronic structure of Os(II) complexes covalently bonded to self-assembled monolayers (SAMs) on Au(111) surfaces was studied by means of polarization modulation infrared reflection absorption spectroscopy, photoelectron spectroscopies, scanning tunneling microscopy, scanning tunneling spectroscopy, and density functional theory calculations. Attachment of the Os complex to the SAM proceeds via an amide covalent bond with the SAM alkyl chain 40° tilted with respect to the surface normal and a total thickness of 26 Å. The highest occupied molecular orbital of the Os complex is mainly based on the Os(II) center located 2.2 eV below the Fermi edge and themore » LUMO molecular orbital is mainly based on the bipyridine ligands located 1.5 eV above the Fermi edge.« less

Mesospheric effects of solar ultraviolet variations - Further analysis of SME IR ozone and Nimbus 7 SAMS temperature data

NASA Astrophysics Data System (ADS)

Hood, L. L.; Huang, Z.; Bougher, S. W.

1991-07-01

In order to improve the constraints on models of the mesospheric response to solar UV variations, an analysis is conducted of the Solar Mesosphere Explorer (SME) IR ozone data and Nimbus 7 stratosphere and mesosphere sounder (SAMS) temperature data. Maximum low-altitude ozone and temperature-response amplitudes occur at about the same altitude, where a strong coupling between photochemical and thermal components of the mesospheric response is suggested by the simultaneous positive temperature and negative ozone response maxima. Increased Lyman-alpha dissociation of water vapor and temperature feedback are theorized to account for the negative ozone response. HO(x) chemical heating can increase as ozone destruction increases, and can therefore account for the positive temperature response.

Mesospheric effects of solar ultraviolet variations - Further analysis of SME IR ozone and Nimbus 7 SAMS temperature data

NASA Technical Reports Server (NTRS)

Hood, L. L.; Huang, Z.; Bougher, S. W.

1991-01-01

In order to improve the constraints on models of the mesospheric response to solar UV variations, an analysis is conducted of the Solar Mesosphere Explorer (SME) IR ozone data and Nimbus 7 stratosphere and mesosphere sounder (SAMS) temperature data. Maximum low-altitude ozone and temperature-response amplitudes occur at about the same altitude, where a strong coupling between photochemical and thermal components of the mesospheric response is suggested by the simultaneous positive temperature and negative ozone response maxima. Increased Lyman-alpha dissociation of water vapor and temperature feedback are theorized to account for the negative ozone response. HO(x) chemical heating can increase as ozone destruction increases, and can therefore account for the positive temperature response.

Modulation of Conformational Equilibria in the S-Adenosylmethionine (SAM) II Riboswitch by SAM, Mg(2+), and Trimethylamine N-Oxide.

PubMed

McPhie, Peter; Brown, Patrick; Chen, Bin; Dayie, Theodore K; Minton, Allen P

2016-09-13

The dependence of the conformation of the S-adenosylmethionine (SAM) II riboswitch on the concentration of added Mg(2+) ions and SAM, individually and in mixtures, was monitored by circular dichroism (CD) spectroscopy and by measurement of the diffusion coefficient. The results are analyzed in the context of two complementary quantitative models, both of which are consistent with a single underlying physical model. Magnesium binding sites in the open state have an affinity on average higher than the affinity of those in the compact state, but formation of the compact state is accompanied by an increase in the number of binding sites. Consequently, at low Mg(2+) concentrations, Mg(2+) binds preferentially to the open state, favoring its formation, but at high concentrations, Mg(2+) binds preferentially to the compact state. The affinity of the riboswitch for SAM increases drastically with an increased level of binding of Mg(2+) to the compact pseudoknot conformation. The effect of increasing concentrations of trimethylamine N-oxide (TMAO), a well-studied molecular crowding agent, on the conformation of the riboswitch and its affinity for SAM were also monitored by CD spectroscopy and measurement of diffusion. In the absence of added Mg(2+), high concentrations of TMAO were found to induce a conformational change compatible with the formation of the pseudoknot form but have only a small effect on the affinity of the RNA for SAM.

A diverse and intricate signalling network regulates stem cell fate in the shoot apical meristem.

PubMed

Dodsworth, Steven

2009-12-01

At the shoot apex of plants is a small region known as the shoot apical meristem (SAM) that maintains a population of undifferentiated (stem) cells whilst providing cells for developing lateral organs and the stem. All aerial structures of the plant develop from the SAM post-embryogenesis, enabling plants to grow in a characteristic modular fashion with great phenotypic and developmental plasticity throughout their lifetime. The maintenance of the stem cell population is intimately balanced with cell recruitment into differentiating tissues through intercellular communication involving a complex signalling network. Recent studies have shown that diverse regulators function in SAM maintenance, many of which converge on the WUSCHEL (WUS) gene. In this review the diverse regulatory modules that function in SAM maintenance are discussed: transcriptional and epigenetic control, hormonal regulation, and the balance with organogenesis. The central role of WUS as an integrator of multiple signals is highlighted; in addition, accessory feedback loops emerge as a feature enabling dynamic regulation of the stem cell niche.

Identification of cyst nematode B-type CLE peptides and modulation of the vascular stem cell pathway for feeding cell formation

USDA-ARS?s Scientific Manuscript database

Stem cells are important in the continuous formation of various tissues during postembryonic organogenesis. Stem cell pools in the SAM (shoot apical meristem), RAM (root apical meristem) and vascular procambium/cambium are regulated by CLE-receptor kinase-WOX signaling modules. Previous data showed ...

Variable Bandwidth Filtering for Improved Sensitivity of Cross-Frequency Coupling Metrics

PubMed Central

McDaniel, Jonathan; Liu, Song; Cornew, Lauren; Gaetz, William; Roberts, Timothy P.L.; Edgar, J. Christopher

2012-01-01

Abstract There is an increasing interest in examining cross-frequency coupling (CFC) between groups of oscillating neurons. Most CFC studies examine how the phase of lower-frequency brain activity modulates the amplitude of higher-frequency brain activity. This study focuses on the signal filtering that is required to isolate the higher-frequency neuronal activity which is hypothesized to be amplitude modulated. In particular, previous publications have used a filter bandwidth fixed to a constant for all assessed modulation frequencies. The present article demonstrates that fixed bandwidth filtering can destroy amplitude modulation and create false-negative CFC measures. To overcome this limitation, this study presents a variable bandwidth filter that ensures preservation of the amplitude modulation. Simulated time series data were created with theta-gamma, alpha-gamma, and beta-gamma phase-amplitude coupling. Comparisons between filtering methods indicate that the variable bandwidth approach presented in this article is preferred when examining amplitude modulations above the theta band. The variable bandwidth method of filtering an amplitude modulated signal is proposed to preserve amplitude modulation and enable accurate CFC measurements. PMID:22577870

Amplitude Modulations of Acoustic Communication Signals

NASA Astrophysics Data System (ADS)

Turesson, Hjalmar K.

2011-12-01

In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a coupling between 3 -- 8 Hz oscillations and gamma band amplitude. In a behavioral experiment, we found that 3 -- 8 amplitude modulations improved auditory detection in noise. In conclusion, our results suggest that, as in human speech, 3 -- 8 Hz amplitude modulations have a behaviorally important effect, and that this effect probably is mediated by synaptic dynamics.

Ultrafast dynamics of self-assembled monolayers under shock compression: effects of molecular and substrate structure.

PubMed

Lagutchev, Alexei S; Patterson, James E; Huang, Wentao; Dlott, Dana D

2005-03-24

Laser-driven approximately 1 GPa shock waves are used to dynamically compress self-assembled monolayers (SAMs) consisting of octadecanethiol (ODT) on Au and Ag, and pentanedecanethiol (PDT) and benzyl mercaptan (BMT) on Au. The SAM response to <4 ps shock loading and approximately 25 ps shock unloading is monitored by vibrational sum-frequency generation spectroscopy (SFG), which is sensitive to the instantaneous tilt angle of the SAM terminal group relative to the surface normal. Arrival of the shock front causes SFG signal loss in all SAMs with a material time constant <3.5 ps. Thermal desorption and shock recovery experiments show that SAMs remain adsorbed on the substrate, so signal loss is attributed to shock tilting of the methyl or phenyl groups to angles near 90 degrees. When the shock unloads, PDT/Au returns elastically to its native structure whereas ODT/Au does not. ODT evidences a complicated viscoelastic response that arises from at least two conformers, one that remains kinetically trapped in a large-tilt-angle conformation for times >250 ps and one that relaxes in approximately 30 ps to a nearly upright conformation. Although the shock responses of PDT/Au, ODT/Ag, and BMT/Au are primarily elastic, a small portion of the molecules, 10-20%, evidence viscoelastic response, either becoming kinetically trapped in large-tilt states or by relaxing in approximately 30 ps back to the native structure. The implications of the observed large-amplitude monolayer dynamics for lubrication under extreme conditions of high strain rates are discussed briefly.

The mechanisms of the SAMS experiment flown on Nimbus 7 with particular reference to the 2 axis scanning mirror. [infrared radiometer for stratospheric and mesospheric investigations

NASA Technical Reports Server (NTRS)

Hadley, H.

1980-01-01

The stratospheric and mesospheric sounder (SAMS) experiment on Nimbus 7 includes a 2 axis scanning mirror and 7 pressure modulator cells. The SAMS experiment is a limb sounding instrument to measure the temperature profile and minor constituents of the atmosphere. The limb scan requires small mirror steps over a 3 deg range, while the scan in azimuth is in larger steps over a 15 deg range. The mirror is plane, 20 cm in diameter, and of zero expansion glass-ceramic. It is supported on two tilt tables, fitted one on the other, with the axes at right angles. The angle of tilt is adjusted by means of recirculating ball screws which are ion plated with lead for lubrication and driven by stepper motors. The seven gas filled cells are each pressure modulated by a 3 cm diameter, 0.3 cm stroke piston which is supported by diaphragm springs and driven electromagnetically at the system's mechanical resonant frequency. The mean pressure of the filling gas, which is the atmospheric constituent being measured, is changed by varying the temperature of a suitable molecular sieve.

47 CFR 2.201 - Emission, modulation, and transmission characteristics.

Code of Federal Regulations, 2014 CFR

2014-10-01

... carrier is amplitude-modulated (including cases where sub-carriers are angle-modulated): —Double-sideband... is amplitude and angle-modulated either simultaneously or in a pre-established sequence D (5) Emission of pulses: 1 —Sequence of unmodulated pulses P —A sequence of pulses: —Modulated in amplitude K...

47 CFR 2.201 - Emission, modulation, and transmission characteristics.

Code of Federal Regulations, 2013 CFR

2013-10-01

... carrier is amplitude-modulated (including cases where sub-carriers are angle-modulated): —Double-sideband... is amplitude and angle-modulated either simultaneously or in a pre-established sequence D (5) Emission of pulses: 1 —Sequence of unmodulated pulses P —A sequence of pulses: —Modulated in amplitude K...

47 CFR 2.201 - Emission, modulation, and transmission characteristics.

Code of Federal Regulations, 2012 CFR

2012-10-01

... carrier is amplitude-modulated (including cases where sub-carriers are angle-modulated): —Double-sideband... is amplitude and angle-modulated either simultaneously or in a pre-established sequence D (5) Emission of pulses: 1 —Sequence of unmodulated pulses P —A sequence of pulses: —Modulated in amplitude K...

Investigation of focusing and correcting aberrations with binary amplitude and polarization modulation

DOE PAGES

Fiala, Peter; Li, Yunqi; Dorrer, Christophe

2018-01-29

Here, we investigate the focusing and correcting wavefront aberration of an optical wave using binary amplitude and polarization modulation. Focusing is performed by selectively modulating the field in different zones of the pupil to obtain on-axis constructive interference at a given distance. The conventional Soret zone plate (binary amplitude profile) is expanded to a polarization Soret zone plate with twice the focusing efficiency. Binary pixelated devices that approximate the sinusoidal transmission profile of a Gabor zone plate by spatial dithering are also investigated with amplitude and polarization modulation. Wavefront aberrations are corrected by modulation of the field in the pupilmore » plane to prevent destructive interference in the focal plane of an ideal focusing element. Polarization modulation improves the efficiency obtained by amplitude-only modulation, with a gain that depends on the aberration. Experimental results obtained with Cr-on-glass devices for amplitude modulation and liquid crystal devices operating in the Mauguin condition for polarization modulation are in very good agreement with simulations.« less

Investigation of focusing and correcting aberrations with binary amplitude and polarization modulation

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

Fiala, Peter; Li, Yunqi; Dorrer, Christophe

Here, we investigate the focusing and correcting wavefront aberration of an optical wave using binary amplitude and polarization modulation. Focusing is performed by selectively modulating the field in different zones of the pupil to obtain on-axis constructive interference at a given distance. The conventional Soret zone plate (binary amplitude profile) is expanded to a polarization Soret zone plate with twice the focusing efficiency. Binary pixelated devices that approximate the sinusoidal transmission profile of a Gabor zone plate by spatial dithering are also investigated with amplitude and polarization modulation. Wavefront aberrations are corrected by modulation of the field in the pupilmore » plane to prevent destructive interference in the focal plane of an ideal focusing element. Polarization modulation improves the efficiency obtained by amplitude-only modulation, with a gain that depends on the aberration. Experimental results obtained with Cr-on-glass devices for amplitude modulation and liquid crystal devices operating in the Mauguin condition for polarization modulation are in very good agreement with simulations.« less

Relative sideband amplitudes versus modulation index for common functions using frequency and phase modulation. [for design and testing of communication system

NASA Technical Reports Server (NTRS)

Stocklin, F.

1973-01-01

The equations defining the amplitude of sidebands resulting from either frequency modulation or phase modulation by either square wave, sine wave, sawtooth or triangular modulating functions are presented. Spectral photographs and computer generated tables of modulation index vs. relative sideband amplitudes are also included.

The PRIDE (Partnership to Improve Diabetes Education) Toolkit: Development and Evaluation of Novel Literacy and Culturally Sensitive Diabetes Education Materials.

PubMed

Wolff, Kathleen; Chambers, Laura; Bumol, Stefan; White, Richard O; Gregory, Becky Pratt; Davis, Dianne; Rothman, Russell L

2016-02-01

Patients with low literacy, low numeracy, and/or linguistic needs can experience challenges understanding diabetes information and applying concepts to their self-management. The authors designed a toolkit of education materials that are sensitive to patients' literacy and numeracy levels, language preferences, and cultural norms and that encourage shared goal setting to improve diabetes self-management and health outcomes. The Partnership to Improve Diabetes Education (PRIDE) toolkit was developed to facilitate diabetes self-management education and support. The PRIDE toolkit includes a comprehensive set of 30 interactive education modules in English and Spanish to support diabetes self-management activities. The toolkit builds upon the authors' previously validated Diabetes Literacy and Numeracy Education Toolkit (DLNET) by adding a focus on shared goal setting, addressing the needs of Spanish-speaking patients, and including a broader range of diabetes management topics. Each PRIDE module was evaluated using the Suitability Assessment of Materials (SAM) instrument to determine the material's cultural appropriateness and its sensitivity to the needs of patients with low literacy and low numeracy. Reading grade level was also assessed using the Automated Readability Index (ARI), Coleman-Liau, Flesch-Kincaid, Fry, and SMOG formulas. The average reading grade level of the materials was 5.3 (SD 1.0), with a mean SAM of 91.2 (SD 5.4). All of the 30 modules received a "superior" score (SAM >70%) when evaluated by 2 independent raters. The PRIDE toolkit modules can be used by all members of a multidisciplinary team to assist patients with low literacy and low numeracy in managing their diabetes. © 2015 The Author(s).

A unifying view of the broad-spectrum antiviral activity of RSAD2 (viperin) based on its radical-SAM chemistry.

PubMed

Honarmand Ebrahimi, Kourosh

2018-04-25

RSAD2 (cig-5), also known as viperin (virus inhibitory protein, endoplasmic reticulum associated, interferon inducible), is a member of the radical S-adenosylmethionine (SAM) superfamily of enzymes. Since the discovery of this enzyme more than a decade ago, numerous studies have shown that it exhibits antiviral activity against a wide range of viruses. However, there is no clear picture demonstrating the mechanism by which RSAD2 restricts the replication process of different viruses, largely because there is no direct evidence describing its in vivo enzymatic activity. As a result, a multifunctionality model has emerged. According to this model the mechanism by which RSAD2 restricts replication of different viruses varies and in many cases is not dependent on the radical-SAM chemistry of RSAD2. If the radical-SAM activity of RSAD2 is not required for its antiviral function, the question worth asking is: why does the cellular defence mechanism induce the expression of the radical-SAM enzyme RSAD2, which is metabolically expensive due to the requirement for a [4Fe-4S] cluster and usage of SAM? Here, in contrast to the multifunctionality view, I put forward a unifying model. I postulate that the radical-SAM activity of RSAD2 modulates cellular metabolic pathways essential for viral replication and/or cell proliferation and survival. As a result, its catalytic activity restricts the replication of a wide range of viruses via a common cellular function. This view is based on recent discoveries hinting towards possible substrates of RSAD2, re-evaluation of previous studies regarding the antiviral activity of RSAD2, and accumulating evidence suggesting a role of human RSAD2 in the metabolic reprogramming of cells.

Activated Cdc42-associated kinase 1 (ACK1) binds the sterile α motif (SAM) domain of the adaptor SLP-76 and phosphorylates proximal tyrosines.

PubMed

Thaker, Youg R; Recino, Asha; Raab, Monika; Jabeen, Asma; Wallberg, Maja; Fernandez, Nelson; Rudd, Christopher E

2017-04-14

The adaptor protein Src homology 2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) plays a crucial role in T cell activation by linking antigen receptor (T cell receptor, TCR) signals to downstream pathways. At its N terminus, SLP-76 has three key tyrosines (Tyr-113, Tyr-128, and Tyr-145, "3Y") as well as a sterile α motif (SAM) domain whose function is unclear. We showed previously that the SAM domain has two binding regions that mediate dimer and oligomer formation. In this study, we have identified SAM domain-carrying non-receptor tyrosine kinase, activated Cdc42-associated tyrosine kinase 1 (ACK1; also known as Tnk2, tyrosine kinase non-receptor 2) as a novel binding partner of SLP-76. Co-precipitation, laser-scanning confocal microscopy, and in situ proximity analysis confirmed the binding of ACK1 to SLP-76. Further, the interaction was induced in response to the anti-TCR ligation and abrogated by the deletion of SLP-76 SAM domain (ΔSAM) or mutation of Tyr-113, Tyr-128, and Tyr-145 to phenylalanine (3Y3F). ACK1 induced phosphorylation of the SLP-76 N-terminal tyrosines (3Y) dependent on the SAM domain. Further, ACK1 promoted calcium flux and NFAT-AP1 promoter activity and decreased the motility of murine CD4 + primary T cells on ICAM-1-coated plates, an event reversed by a small molecule inhibitor of ACK1 (AIM-100). These findings identify ACK1 as a novel SLP-76-associated protein-tyrosine kinase that modulates early activation events in T cells. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Activated Cdc42-associated kinase 1 (ACK1) binds the sterile α motif (SAM) domain of the adaptor SLP-76 and phosphorylates proximal tyrosines

PubMed Central

Thaker, Youg R.; Recino, Asha; Raab, Monika; Jabeen, Asma; Wallberg, Maja; Fernandez, Nelson; Rudd, Christopher E.

2017-01-01

The adaptor protein Src homology 2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) plays a crucial role in T cell activation by linking antigen receptor (T cell receptor, TCR) signals to downstream pathways. At its N terminus, SLP-76 has three key tyrosines (Tyr-113, Tyr-128, and Tyr-145, “3Y”) as well as a sterile α motif (SAM) domain whose function is unclear. We showed previously that the SAM domain has two binding regions that mediate dimer and oligomer formation. In this study, we have identified SAM domain-carrying non-receptor tyrosine kinase, activated Cdc42-associated tyrosine kinase 1 (ACK1; also known as Tnk2, tyrosine kinase non-receptor 2) as a novel binding partner of SLP-76. Co-precipitation, laser-scanning confocal microscopy, and in situ proximity analysis confirmed the binding of ACK1 to SLP-76. Further, the interaction was induced in response to the anti-TCR ligation and abrogated by the deletion of SLP-76 SAM domain (ΔSAM) or mutation of Tyr-113, Tyr-128, and Tyr-145 to phenylalanine (3Y3F). ACK1 induced phosphorylation of the SLP-76 N-terminal tyrosines (3Y) dependent on the SAM domain. Further, ACK1 promoted calcium flux and NFAT-AP1 promoter activity and decreased the motility of murine CD4+ primary T cells on ICAM-1-coated plates, an event reversed by a small molecule inhibitor of ACK1 (AIM-100). These findings identify ACK1 as a novel SLP-76-associated protein-tyrosine kinase that modulates early activation events in T cells. PMID:28188290

Data handling with SAM and art at the NO vA experiment

DOE PAGES

Aurisano, A.; Backhouse, C.; Davies, G. S.; ...

2015-12-23

During operations, NOvA produces between 5,000 and 7,000 raw files per day with peaks in excess of 12,000. These files must be processed in several stages to produce fully calibrated and reconstructed analysis files. In addition, many simulated neutrino interactions must be produced and processed through the same stages as data. To accommodate the large volume of data and Monte Carlo, production must be possible both on the Fermilab grid and on off-site farms, such as the ones accessible through the Open Science Grid. To handle the challenge of cataloging these files and to facilitate their off-line processing, we havemore » adopted the SAM system developed at Fermilab. SAM indexes files according to metadata, keeps track of each file's physical locations, provides dataset management facilities, and facilitates data transfer to off-site grids. To integrate SAM with Fermilab's art software framework and the NOvA production workflow, we have developed methods to embed metadata into our configuration files, art files, and standalone ROOT files. A module in the art framework propagates the embedded information from configuration files into art files, and from input art files to output art files, allowing us to maintain a complete processing history within our files. Embedding metadata in configuration files also allows configuration files indexed in SAM to be used as inputs to Monte Carlo production jobs. Further, SAM keeps track of the input files used to create each output file. Parentage information enables the construction of self-draining datasets which have become the primary production paradigm used at NOvA. In this study we will present an overview of SAM at NOvA and how it has transformed the file production framework used by the experiment.« less

SAM Theory Manual

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

Hu, Rui

The System Analysis Module (SAM) is an advanced and modern system analysis tool being developed at Argonne National Laboratory under the U.S. DOE Office of Nuclear Energy’s Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. SAM development aims for advances in physical modeling, numerical methods, and software engineering to enhance its user experience and usability for reactor transient analyses. To facilitate the code development, SAM utilizes an object-oriented application framework (MOOSE), and its underlying meshing and finite-element library (libMesh) and linear and non-linear solvers (PETSc), to leverage modern advanced software environments and numerical methods. SAM focuses on modeling advanced reactormore » concepts such as SFRs (sodium fast reactors), LFRs (lead-cooled fast reactors), and FHRs (fluoride-salt-cooled high temperature reactors) or MSRs (molten salt reactors). These advanced concepts are distinguished from light-water reactors in their use of single-phase, low-pressure, high-temperature, and low Prandtl number (sodium and lead) coolants. As a new code development, the initial effort has been focused on modeling and simulation capabilities of heat transfer and single-phase fluid dynamics responses in Sodium-cooled Fast Reactor (SFR) systems. The system-level simulation capabilities of fluid flow and heat transfer in general engineering systems and typical SFRs have been verified and validated. This document provides the theoretical and technical basis of the code to help users understand the underlying physical models (such as governing equations, closure models, and component models), system modeling approaches, numerical discretization and solution methods, and the overall capabilities in SAM. As the code is still under ongoing development, this SAM Theory Manual will be updated periodically to keep it consistent with the state of the development.« less

Hydroclimate variability and regional atmospheric circulation over the past 1,350 years reconstructed from Lake Ohau, New Zealand

NASA Astrophysics Data System (ADS)

Roop, H. A.; Levy, R. H.; Vandergoes, M.; Dunbar, G. B.; Howarth, J. D.; Lorrey, A.; Phipps, S. J.

2016-12-01

Comprehensive understanding of natural climate-system dynamics requires high-resolution paleoclimate records extending beyond the instrumental period. This is particularly the case for the sparsely-instrumented Southern Hemisphere mid-latitudes, where the timing and amplitude of regional and hemispheric-scale climatic events are poorly constrained. Here we present a 1,350-year record of hydroclimatic variability and regional circulation derived from an annually laminated sediment record from Lake Ohau, South Island, New Zealand (44.23°S, 169.85°E). The climate of New Zealand is influenced by climatological patterns originating in both the tropics (e.g. El-Niño-Southern Oscillation, Interdecadal Pacific Oscillation) and the Antarctic (Southern Annular Mode, SAM). Utilizing the annually resolved Lake Ohau hydroclimate record in combination with a tree-ring record of summer temperature from Oroko Swamp, New Zealand (Cook et al., 2002), we generate a circulation index for the Western South Island of New Zealand. This index utilizes the temperature and precipitation anomalies defined by the Regional Climate Regime Classification scheme for New Zealand to assign synoptic scale circulation patterns to 25-year intervals from 900-2000 AD. This circulation index shows significant periods of change, most notably 835 - 985 AD when northerly airflow dominated and from 1385 - 1710 AD when strong southerly airflow persisted. Comparisons with regional SAM and ENSO reconstructions show that dry, warm conditions at Lake Ohau are consistently associated with strengthened tropical teleconnections to New Zealand and a positive SAM, while cold and wet conditions are driven by increased southerly airflow and negative phase SAM. A persistent negative SAM dominates the Little Ice Age (LIA; 1385-1710 AD) interval in the Western South Island. This same period coincides with the Northern Hemisphere LIA.

Technical Note: A fast online adaptive replanning method for VMAT using flattening filter free beams

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

Ates, Ozgur; Ahunbay, Ergun E.; Li, X. Allen, E-mail: ali@mcw.edu

Purpose: To develop a fast replanning algorithm based on segment aperture morphing (SAM) for online replanning of volumetric modulated arc therapy (VMAT) with flattening filter free (FFF) beams. Methods: A software tool was developed to interface with a VMAT research planning system, which enables the input and output of beam and machine parameters of VMAT plans. The SAM algorithm was used to modify multileaf collimator positions for each segment aperture based on the changes of the target from the planning (CT/MR) to daily image [CT/CBCT/magnetic resonance imaging (MRI)]. The leaf travel distance was controlled for large shifts to prevent themore » increase of VMAT delivery time. The SAM algorithm was tested for 11 patient cases including prostate, pancreatic, and lung cancers. For each daily image set, three types of VMAT plans, image-guided radiation therapy (IGRT) repositioning, SAM adaptive, and full-scope reoptimization plans, were generated and compared. Results: The SAM adaptive plans were found to have improved the plan quality in target and/or critical organs when compared to the IGRT repositioning plans and were comparable to the reoptimization plans based on the data of planning target volume (PTV)-V100 (volume covered by 100% of prescription dose). For the cases studied, the average PTV-V100 was 98.85% ± 1.13%, 97.61% ± 1.45%, and 92.84% ± 1.61% with FFF beams for the reoptimization, SAM adaptive, and repositioning plans, respectively. The execution of the SAM algorithm takes less than 10 s using 16-CPU (2.6 GHz dual core) hardware. Conclusions: The SAM algorithm can generate adaptive VMAT plans using FFF beams with comparable plan qualities as those from the full-scope reoptimization plans based on daily CT/CBCT/MRI and can be used for online replanning to address interfractional variations.« less

Improved electro-transformation of highly DNA-restrictive corynebacteria with DNA extracted from starved Escherichia coli.

PubMed

Ankri, S; Reyes, O; Leblon, G

1996-07-01

Differences of up to 33 000-fold in electro-transformability of highly DNA restrictive corynebacteria are observed in the DNA of a shuttle plasmid extracted from Escherichia coli hosts propagated in different nutritional conditions. Growth of the host in minimal medium increases plasmid transformability, whereas growth on rich media decreases it. In the E. coli DH5 alpha host, the starvation-dependent increase DNA transformability is reverted by supplementing with methionine, an obligate 5-adenosyl-methionine (SAM) precursor. This suggests that an E. coli nutritionally modulated SAM-dependent DNA-methyltransferase may be involved in this phenomenon.

Amplitude-dependent relationship between the Southern Annular Mode and the El Niño Southern Oscillation in austral summer

NASA Astrophysics Data System (ADS)

Kim, Baek-Min; Choi, Hyesun; Kim, Seong-Joong; Choi, Wookap

2017-02-01

Co-variability between the Southern Annular Mode (SAM) and the El Niño Southern Oscillation (ENSO) during the austral summer is examined, and it is found that there exists an apparent co-variability of a negative (positive) SAM during the mature period of El Niño (La Niña). However, this co-variability is largely controlled by the small number of strong ENSO cases. When strong ENSO cases are excluded, the correlation becomes non-significant. This behavior in the relationship between SAM and ENSO is supported by a series of general circulation model experiments with prescribed sea surface temperature boundary conditions that represent the incremental strengthening of El Niño (La Niña) conditions. The modeled Antarctic sub-polar jet exhibits similar behavior to that identified through observational analysis. Marked changes in both the magnitude and position of the sub-polar jet are largely controlled by particularly strong transient eddy forcing. Planetary wave forcing plays only a minor role in the co-variability, but it can explain in part the asymmetric response of the sub-polar jet between El Niño and La Niña.

MEG evidence that the central auditory system simultaneously encodes multiple temporal cues.

PubMed

Simpson, Michael I G; Barnes, Gareth R; Johnson, Sam R; Hillebrand, Arjan; Singh, Krish D; Green, Gary G R

2009-09-01

Speech contains complex amplitude modulations that have envelopes with multiple temporal cues. The processing of these complex envelopes is not well explained by the classical models of amplitude modulation processing. This may be because the evidence for the models typically comes from the use of simple sinusoidal amplitude modulations. In this study we used magnetoencephalography (MEG) to generate source space current estimates of the steady-state responses to simple one-component amplitude modulations and to a two-component amplitude modulation. A two-component modulation introduces the simplest form of modulation complexity into the waveform; the summation of the two-modulation rates introduces a beat-like modulation at the difference frequency between the two modulation rates. We compared the cortical representations of responses to the one-component and two-component modulations. In particular, we show that the temporal complexity in the two-component amplitude modulation stimuli was preserved at the cortical level. The method of stimulus normalization that we used also allows us to interpret these results as evidence that the important feature in sound modulations is the relative depth of one modulation rate with respect to another, rather than the absolute carrier-to-sideband modulation depth. More generally, this may be interpreted as evidence that modulation detection accurately preserves a representation of the modulation envelope. This is an important observation with respect to models of modulation processing, as it suggests that models may need a dynamic processing step to effectively model non-stationary stimuli. We suggest that the classic modulation filterbank model needs to be modified to take these findings into account.

Human Cataract Mutations in EPHA2 SAM Domain Alter Receptor Stability and Function

PubMed Central

Park, Jeong Eun; Son, Alexander I.; Hua, Rui; Wang, Lianqing; Zhang, Xue; Zhou, Renping

2012-01-01

The cellular and molecular mechanisms underlying the pathogenesis of cataracts leading to visual impairment remain poorly understood. In recent studies, several mutations in the cytoplasmic sterile-α-motif (SAM) domain of human EPHA2 on chromosome 1p36 have been associated with hereditary cataracts in several families. Here, we have investigated how these SAM domain mutations affect EPHA2 activity. We showed that the SAM domain mutations dramatically destabilized the EPHA2 protein in a proteasome-dependent pathway, as evidenced by the increase of EPHA2 receptor levels in the presence of the proteasome inhibitor MG132. In addition, the expression of wild-type EPHA2 promoted the migration of the mouse lens epithelial αTN4-1 cells in the absence of ligand stimulation, whereas the mutants exhibited significantly reduced activity. In contrast, stimulation of EPHA2 with its ligand ephrin-A5 eradicates the enhancement of cell migration accompanied by Akt activation. Taken together, our studies suggest that the SAM domain of the EPHA2 protein plays critical roles in enhancing the stability of EPHA2 by modulating the proteasome-dependent process. Furthermore, activation of Akt switches EPHA2 from promoting to inhibiting cell migration upon ephrin-A5 binding. Our results provide the first report of multiple EPHA2 cataract mutations contributing to the destabilization of the receptor and causing the loss of cell migration activity. PMID:22570727

Defining efficient enzyme-cofactor pairs for bioorthogonal profiling of protein methylation

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

Islam, Kabirul; Chen, Yuling; Wu, Hong

2013-11-18

Protein methyltransferase (PMT)-mediated posttranslational modification of histone and nonhistone substrates modulates stability, localization, and interacting partners of target proteins in diverse cellular contexts. These events play critical roles in normal biological processes and are frequently deregulated in human diseases. In the course of identifying substrates of individual PMTs, bioorthogonal profiling of protein methylation (BPPM) has demonstrated its merits. In this approach, specific PMTs are engineered to process S-adenosyl-L-methionine (SAM) analogs as cofactor surrogates and label their substrates with distinct chemical modifications for target elucidation. Despite the proof-of-concept advancement of BPPM, few efforts have been made to explore its generality. Withmore » two cancer-relevant PMTs, EuHMT1 (GLP1/KMT1D) and EuHMT2 (G9a/KMT1C), as models, we defined the key structural features of engineered PMTs and matched SAM analogs that can render the orthogonal enzyme–cofactor pairs for efficient catalysis. Here we have demonstrated that the presence of sulfonium-β-sp 2 carbon and flexible, medium-sized sulfonium-δ-substituents are crucial for SAM analogs as BPPM reagents. The bulky cofactors can be accommodated by tailoring the conserved Y1211/Y1154 residues and nearby hydrophobic cavities of EuHMT1/2. Profiling proteome-wide substrates with BPPM allowed identification of >500 targets of EuHMT1/2 with representative targets validated using native EuHMT1/2 and SAM. This finding indicates that EuHMT1/2 may regulate many cellular events previously unrecognized to be modulated by methylation. The present work, therefore, paves the way to a broader application of the BPPM technology to profile methylomes of diverse PMTs and elucidate their downstream functions.« less

Systems, Methods and Apparatus for Position Sensor Digital Conditioning Electronics

NASA Technical Reports Server (NTRS)

Howard, David E. (Inventor); Alhorn, Dean C. (Inventor); Smith, Dennis A. (Inventor); Dutton, Kenneth R. (Inventor)

2012-01-01

Systems, methods and apparatus are provided through which in some implementations determine the amplitude of an amplitude modulated signal, modulated by the position of an object being sensed. In some aspects, the apparatus accepts an excitation signal and the amplitude modulated signal and divides the amplitude modulated by the excitation signal to produce an output signal that is proportional to the position of the object being sensed. In other aspects, the division is performed only when the excitation signal is non-zero, such as close to the peaks in the excitation signal. In other aspects, the excitation signal and amplitude modulated signal are degraded due to an air gap and the degraded signals are used to correct for amplitude fluctuations due to the air gap, and produce an output signal, tolerant of the air gaps, that is proportional to the position of the object being sensed.

Targeting S-adenosylmethionine biosynthesis with a novel allosteric inhibitor of Mat2A

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

Quinlan, Casey L.; Kaiser, Stephen E.; Bolaños, Ben

S-Adenosyl-L-methionine (SAM) is an enzyme cofactor used in methyl transfer reactions and polyamine biosynthesis. The biosynthesis of SAM from ATP and L-methionine is performed by the methionine adenosyltransferase enzyme family (Mat; EC 2.5.1.6). Human methionine adenosyltransferase 2A (Mat2A), the extrahepatic isoform, is often deregulated in cancer. We identified a Mat2A inhibitor, PF-9366, that binds an allosteric site on Mat2A that overlaps with the binding site for the Mat2A regulator, Mat2B. Studies exploiting PF-9366 suggested a general mode of Mat2A allosteric regulation. Allosteric binding of PF-9366 or Mat2B altered the Mat2A active site, resulting in increased substrate affinity and decreased enzymemore » turnover. These data support a model whereby Mat2B functions as an inhibitor of Mat2A activity when methionine or SAM levels are high, yet functions as an activator of Mat2A when methionine or SAM levels are low. The ramification of Mat2A activity modulation in cancer cells is also described.« less

Vibrotactile sensory substitution for object manipulation: amplitude versus pulse train frequency modulation.

PubMed

Stepp, Cara E; Matsuoka, Yoky

2012-01-01

Incorporating sensory feedback with prosthetic devices is now possible, but the optimal methods of providing such feedback are still unknown. The relative utility of amplitude and pulse train frequency modulated stimulation paradigms for providing vibrotactile feedback for object manipulation was assessed in 10 participants. The two approaches were studied during virtual object manipulation using a robotic interface as a function of presentation order and a simultaneous cognitive load. Despite the potential pragmatic benefits associated with pulse train frequency modulated vibrotactile stimulation, comparison of the approach with amplitude modulation indicates that amplitude modulation vibrotactile stimulation provides superior feedback for object manipulation.

Amplitude-modulation detection by gerbils in reverberant sound fields.

PubMed

Lingner, Andrea; Kugler, Kathrin; Grothe, Benedikt; Wiegrebe, Lutz

2013-08-01

Reverberation can dramatically reduce the depth of amplitude modulations which are critical for speech intelligibility. Psychophysical experiments indicate that humans' sensitivity to amplitude modulation in reverberation is better than predicted from the acoustic modulation depth at the receiver position. Electrophysiological studies on reverberation in rabbits highlight the contribution of neurons sensitive to interaural correlation. Here, we use a prepulse-inhibition paradigm to quantify the gerbils' amplitude modulation threshold in both anechoic and reverberant virtual environments. Data show that prepulse inhibition provides a reliable method for determining the gerbils' AM sensitivity. However, we find no evidence for perceptual restoration of amplitude modulation in reverberation. Instead, the deterioration of AM sensitivity in reverberant conditions can be quantitatively explained by the reduced modulation depth at the receiver position. We suggest that the lack of perceptual restoration is related to physical properties of the gerbil's ear input signals and inner-ear processing as opposed to shortcomings of their binaural neural processing. Copyright © 2013 Elsevier B.V. All rights reserved.

Near wall effects on flexible splitter plate behind a cylinder

NASA Astrophysics Data System (ADS)

Venkat Narayanan, K.; Vengadesan, S.; Murali, K.

2017-11-01

Vortex induced vibrations(VIV) of a rigid circular cylinder with a flexible plate attached to its rear end, close to the plane wall is numerically studied for Re = 200. Amplitude modulations were observed in the response of the flexible plate at the ground distance of G/D=0.5. Numerical simulations were conducted for a range of reduced velocities Ur(3,4,5 and 6), which appropriately captures the synchronization range of VIV of the structure. At Ur=3 there is no significant amplitude modulation. As Ur is increased further, the modulation appears. The modulation appears symmetric about the peak amplitude for successive cycles at Ur=4. The phase plots of lift coefficient CL and plate tip displacement revealed the change in sign of energy transfer between the plate and the wake. Amplitude modulation is reflected in the interaction of shed vortices and the plane wall. Shed vortices are convected parallel to the wall when the amplitude of the plate rises to its local maximum during modulation. During the growth and damping phase of the amplitudes in each modulation cycle, the vortex shedding is observed to be oblique towards the wall.

Multidimensional signal modulation and/or demodulation for data communications

DOEpatents

Smith, Stephen F [London, TN; Dress, William B [Camas, WA

2008-03-04

Systems and methods are described for multidimensional signal modulation and/or demodulation for data communications. A method includes modulating a carrier signal in a first domain selected from the group consisting of phase, frequency, amplitude, polarization and spread; modulating the carrier signal in a second domain selected from the group consisting of phase, frequency, amplitude, polarization and spread; and modulating the carrier signal in a third domain selected from the group consisting of phase, frequency, amplitude, polarization and spread.

Generation of an axially super-resolved quasi-spherical focal spot using an amplitude-modulated radially polarized beam.

PubMed

Lin, Han; Jia, Baohua; Gu, Min

2011-07-01

An axially super-resolved quasi-spherical focal spot can be generated by focusing an amplitude-modulated radially polarized beam through a high numerical aperture objective. A method based on the unique depolarization properties of a circular focus is proposed to design the amplitude modulation. The generated focal spot shows a ratio of x:y:z=1:1:1.48 for the normalized FWHM in three dimensions, compared to that of x:y:z=1:0.74:1.72 under linear polarization (in the x direction) illumination. Moreover, the focusable light efficiency of the designed amplitude-modulated beam is 65%, which is more than 3 times higher than the optimized case under linear polarization and thus make the amplitude-modulated radial polarization beam more suitable for a wide range of applications.

Four-dimensional dose distributions of step-and-shoot IMRT delivered with real-time tumor tracking for patients with irregular breathing: Constant dose rate vs dose rate regulation

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

Yang Xiaocheng; Han-Oh, Sarah; Gui Minzhi

2012-09-15

Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase weremore » extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or slower than the planning day. In contrast, DRRT method showed less than 1% reduction in target dose and no noticeable change in OAR dose under the same breathing period irregularities. When {+-}20% variation of target motion amplitude was present as breathing irregularity, the two delivery methods show compatible plan quality if the dose distribution of CDRT delivery is renormalized. Conclusions: Delivery of 4D-IMRT treatment plans, stemmed from 3D step-and-shoot IMRT and preprogrammed using SAM algorithm, is simulated for two dynamic MLC-based real-time tumor tracking strategies: with and without dose-rate regulation. Comparison of cumulative dose distribution indicates that the preprogrammed 4D plan is more accurately and efficiently conformed using the DRRT strategy, as it compensates the interplay between patient breathing irregularity and tracking delivery without compromising the segment-weight modulation.« less

Effect of Time and Deposition Method on Quality of Phosphonic Acid Modifier Self-Assembled Monolayers on Indium Zinc Oxide

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

Sang, Lingzi; Knesting, Kristina M.; Bulusu, Anuradha

Phosphonic acid (PA) self-assembled monolayers (SAMs) are utilized at critical interfaces between transparent conductive oxides (TCO) and organic active layers in organic photovoltaic devices (OPVs). The effects of PA deposition method and time on the formation of close-packed, high-quality monolayers is investigated here for SAMs fabricated by solution deposition, micro-contact printing, and spray coating. The solution deposition isotherm for pentafluorinated benzylphosphonic acid (F5BnPA) on indium-doped zinc oxide (IZO) is studied using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) at room temperature as a model PA/IZO system. Fast surface adsorption occurs within the first min; however, well-oriented high-quality SAMs are reached only aftermore » -48 h, presumably through a continual process of molecular adsorption/desorption and monolayer filling accompanied by molecular reorientation. Two other rapid, soak-free deposition techniques, micro-contact printing and spray coating, are also explored. SAM quality is compared for deposition of phenyl phosphonic acid (PPA), F13-octylphosphonic acid (F13OPA), and pentafluorinated benzyl phosphonic acid (F5BnPA) by solution deposition, micro-contact printing and spray coating using PM-IRRAS. In contrast to micro-contact printing and spray coating techniques, 48-168 h solution deposition at both room temperature and 70 degrees C result in contamination- and surface etch-free close-packed monolayers with good reproducibility. SAMs fabricated by micro-contact printing and spray coating are much less well ordered.« less

[Change in short-term memory in pupils of 5-7th classes in the process of class work].

PubMed

Rybakov, V P; Orlova, N I

2014-01-01

The subject of this study was the investigation of the short-term memory (STM) of visual (SVM) and auditory (SAM) modality in boys and girls of the middle school age, as in the daytime, and during the course of the school week. The obtained data show that in pupils from the 5th to the 7th class SVM and SAM playback volume in children of both genders is significantly increased, while SVM productivity in boys from 6 - 7th classes is higher than in girls of the same age. The amplitude of day changes in SVM and SAM was found to decrease significantly with the age. In all age groups the range of daily fluctuations in short-term memory of both modalities in boys appears to be higher than in girls. In all age groups a significant part of schoolchildren was revealed to possess optimal forms of temporal organization of short-term memory: morning, day and morning-day types, in that while during the school week in pupils of 5th to 7th classes of both genders the number of optimal waveforms of curves of daily dynamics of short-term memory increases, which contributes to the optimization of their mental performance.

Ultrafast Microscopy of Spin-Momentum-Locked Surface Plasmon Polaritons.

PubMed

Dai, Yanan; Dąbrowski, Maciej; Apkarian, Vartkess A; Petek, Hrvoje

2018-06-26

Using two-photon photoemission electron microscopy (2P-PEEM) we image the polarization dependence of coupling and propagation of surface plasmon polaritons (SPPs) launched from edges of a triangular, micrometer size, single-crystalline Ag crystal by linearly or circularly polarized light. 2P-PEEM records interferences between the optical excitation field and SPPs it creates with nanofemto space-time resolution. Both the linearly and circularly polarized femtosecond light pulses excite spatially asymmetric 2PP yield distributions, which are imaged. We attribute the asymmetry for linearly polarized light to the relative alignments of the laser polarization and triangle edges, which affect the efficiency of excitation of the longitudinal component of the SPP field. For circular polarization, the asymmetry is caused by matching of the spin angular momenta (SAM) of light and the transverse SAM of SPPs. Moreover, we show that the interference patterns recorded in the 2P-PEEM images are cast by phase shifts and amplitudes for coupling of light into the longitudinal and transverse components of SPP fields. While the interference patterns depend on the excitation polarization, nanofemto movies show that the phase and group velocities of SPPs are independent of SAM of light in time-reversal invariant media. Simulations of the wave interference reproduce the polarization and spin-dependent coupling of optical pulses into SPPs.

Summary Report of Mission Acceleration Measurements for STS-65, Launched 8 July 1994

NASA Technical Reports Server (NTRS)

Rogers, Melissa J. B.; Delombard, Richard

1995-01-01

The second flight of the International Microgravity Laboratory (IML-2) payload on board the STS-65 mission was supported by three accelerometer instruments: The Orbital Acceleration Research Experiment (OARE) located close to the orbiter center of mass; the Quasi-Steady Acceleration Measurement experiment, and the Space Acceleration Measurement System (SAMS), both in the Spacelab module. A fourth accelerometer, the Microgravity Measuring Device recorded data in the middeck in support of exercise isolation tests.Data collected by OARE and SAMS during IML-2 are displayed in this report. The OARE data represent the microgravity environment below 1 Hz. The SAMS data represent the environment in the 0.01 Hz to 100 Hz range. Variations in the environment caused by unique activities are presented. Specific events addressed are: crew activity, crew exercise, experiment component mixing activities, experiment centrifuge operations, refrigerator/freezer operations and circulation pump operations. The analyses included in this report complement analyses presented in other mission summary reports.

Responses to amplitude modulated infrared stimuli in the guinea pig inferior colliculus

NASA Astrophysics Data System (ADS)

Richter, Claus-Peter; Young, Hunter

2013-03-01

Responses of units in the central nucleus of the inferior colliculus of the guinea pig were recorded with tungsten electrodes. The set of data presented here is limited to high stimulus levels. The effect of changing the modulation frequency and the modulation depth was explored for acoustic and laser stimuli. The selected units responded to sinusoidal amplitude modulated (AM) tones, AM trains of clicks, and AM trains of laser pulses with a modulation of their spike discharge. At modulation frequencies of 20 Hz, some units tended to respond with 40 Hz to the acoustic stimuli, but only at 20 Hz for the trains of laser pulses. For all modes of stimulation the responses revealed a dominant response to the first cycle of the modulation, with decreasing number of action potential during successive cycles. While amplitude modulated tone bursts and amplitude modulated trains of acoustic clicks showed similar patterns, the response to trains of laser pulses was different.

Purely wavelength- and amplitude-modulated quartz-enhanced photoacoustic spectroscopy.

PubMed

Patimisco, Pietro; Sampaolo, Angelo; Bidaux, Yves; Bismuto, Alfredo; Scott, Marshall; Jiang, James; Muller, Antoine; Faist, Jerome; Tittel, Frank K; Spagnolo, Vincenzo

2016-11-14

We report here on a quartz-enhanced photoacoustic (QEPAS) sensor employing a quantum cascade laser (QCL) structure capable of operating in a pure amplitude or wavelength modulation configuration. The QCL structure is composed of three electrically independent sections: Gain, Phase (PS) and Master Oscillator (MO). Selective current pumping of these three sections allows obtaining laser wavelength tuning without changes in the optical power, and power modulation without emission wavelength shifts. A pure QEPAS amplitude modulation condition is obtained by modulating the PS current, while pure wavelength modulation is achieved by modulating simultaneously the MO and PS QCL sections and slowly scanning the DC current level injected in the PS section.

Self-demodulation of amplitude-modulated signal components in amplitude-modulated bone-conducted ultrasonic hearing

NASA Astrophysics Data System (ADS)

Ito, Kazuhito; Nakagawa, Seiji

2015-07-01

A novel hearing aid system utilizing amplitude-modulated bone-conducted ultrasound (AM-BCU) is being developed for use by profoundly deaf people. However, there is a lack of research on the acoustic aspects of AM-BCU hearing. In this study, acoustic fields in the ear canal under AM-BCU stimulation were examined with respect to the self-demodulation effect of amplitude-modulated signal components generated in the ear canal. We found self-demodulated signals with an audible sound pressure level related to the amplitude-modulated signal components of bone-conducted ultrasonic stimulation. In addition, the increases in the self-demodulated signal levels at low frequencies in the ear canal after occluding the ear canal opening, i.e., the positive occlusion effect, indicate the existence of a pathway by which the self-demodulated signals pass through the aural cartilage and soft tissue, and radiate into the ear canal.

Switching circuit to improve the frequency modulation difference-intensity THz quantum cascade laser imaging

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

Saat, N. K.; Dean, P.; Khanna, S. P.

2015-04-24

We demonstrate new switching circuit for difference-intensity THz quantum cascade laser (QCL) imaging by amplitude modulation and lock in detection. The switching circuit is designed to improve the frequency modulation so that it can stably lock the amplitude modulation of the QCL and the detector output. The combination of a voltage divider and a buffer in switching circuit to quickly switch the amplitude of the QCL biases of 15.8 V and 17.2 V is successfully to increase the frequency modulation up to ∼100 Hz.

Broadband metasurface holograms: toward complete phase and amplitude engineering

PubMed Central

Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

2016-01-01

As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography. PMID:27615519

Broadband metasurface holograms: toward complete phase and amplitude engineering.

PubMed

Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

2016-09-12

As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography.

Plasma based optical guiding of an amplitude-modulated electromagnetic beam

NASA Astrophysics Data System (ADS)

Singh, Mamta; Gupta, D. N.

2015-06-01

We propose the stronger optical guiding of an electromagnetic beam in a plasma by considering the amplitude modulation of the fundamental beam. With the advent of high power source of electromagnetic radiation, the electron velocity in a plasma may become quite large (comparable to the light velocity in free space). Thus, the effect of relativistic mass variation must be taken into account. The relativistic effect of the laser propagation in a plasma leads to self-focusing because of the dielectric constant of a plasma being an increasing function of the intensity. The ponderomotive force of the laser beam pushes the electrons out of the region of high intensity, which reduces the local electron density and increases the plasma dielectric function further, leading to even more selffocusing of the laser. In this work, we consider a short pulse laser of finite spot size as an amplitude modulation in time. Our findings show an efficient optical guiding mechanism based on amplitude modulation signal propagation in plasmas. Medium nonlinearity becomes stronger if an amplitude modulated beam is introduced, which contributes significantly in laser guiding in plasmas. Furthermore, the rate of laser self-focusing is increased with modulation index due the fact of stronger Kerr effect. The study related to amplitude modulated optical signal may be useful for communication technology.

[Signal analysis and spectrum distortion correction for tunable diode laser absorption spectroscopy system].

PubMed

Bao, Wei-Yi; Zhu, Yong; Chen, Jun; Chen, Jun-Qing; Liang, Bo

2011-04-01

In the present paper, the signal of a tunable diode laser absorption spectroscopy (TDLAS) trace gas sensing system, which has a wavelength modulation with a wide range of modulation amplitudes, is studied based on Fourier analysis method. Theory explanation of spectrum distortion induced by laser intensity amplitude modulation is given. In order to rectify the spectrum distortion, a method of synchronous amplitude modulation suppression by a variable optical attenuator is proposed. To validate the method, an experimental setup is designed. Absorption spectrum measurement experiments on CO2 gas were carried out. The results show that the residual laser intensity modulation amplitude of the experimental system is reduced to -0.1% of its original value and the spectrum distortion improvement is 92% with the synchronous amplitude modulation suppression. The modulation amplitude of laser intensity can be effectively reduced and the spectrum distortion can be well corrected by using the given correction method and system. By using a variable optical attenuator in the TDLAS (tunable diode laser absorption spectroscopy) system, the dynamic range requirements of photoelectric detector, digital to analog converter, filters and other aspects of the TDLAS system are reduced. This spectrum distortion correction method can be used for online trace gas analyzing in process industry.

Dissociable neural response signatures for slow amplitude and frequency modulation in human auditory cortex.

PubMed

Henry, Molly J; Obleser, Jonas

2013-01-01

Natural auditory stimuli are characterized by slow fluctuations in amplitude and frequency. However, the degree to which the neural responses to slow amplitude modulation (AM) and frequency modulation (FM) are capable of conveying independent time-varying information, particularly with respect to speech communication, is unclear. In the current electroencephalography (EEG) study, participants listened to amplitude- and frequency-modulated narrow-band noises with a 3-Hz modulation rate, and the resulting neural responses were compared. Spectral analyses revealed similar spectral amplitude peaks for AM and FM at the stimulation frequency (3 Hz), but amplitude at the second harmonic frequency (6 Hz) was much higher for FM than for AM. Moreover, the phase delay of neural responses with respect to the full-band stimulus envelope was shorter for FM than for AM. Finally, the critical analysis involved classification of single trials as being in response to either AM or FM based on either phase or amplitude information. Time-varying phase, but not amplitude, was sufficient to accurately classify AM and FM stimuli based on single-trial neural responses. Taken together, the current results support the dissociable nature of cortical signatures of slow AM and FM. These cortical signatures potentially provide an efficient means to dissect simultaneously communicated slow temporal and spectral information in acoustic communication signals.

Dissociable Neural Response Signatures for Slow Amplitude and Frequency Modulation in Human Auditory Cortex

PubMed Central

Henry, Molly J.; Obleser, Jonas

2013-01-01

Natural auditory stimuli are characterized by slow fluctuations in amplitude and frequency. However, the degree to which the neural responses to slow amplitude modulation (AM) and frequency modulation (FM) are capable of conveying independent time-varying information, particularly with respect to speech communication, is unclear. In the current electroencephalography (EEG) study, participants listened to amplitude- and frequency-modulated narrow-band noises with a 3-Hz modulation rate, and the resulting neural responses were compared. Spectral analyses revealed similar spectral amplitude peaks for AM and FM at the stimulation frequency (3 Hz), but amplitude at the second harmonic frequency (6 Hz) was much higher for FM than for AM. Moreover, the phase delay of neural responses with respect to the full-band stimulus envelope was shorter for FM than for AM. Finally, the critical analysis involved classification of single trials as being in response to either AM or FM based on either phase or amplitude information. Time-varying phase, but not amplitude, was sufficient to accurately classify AM and FM stimuli based on single-trial neural responses. Taken together, the current results support the dissociable nature of cortical signatures of slow AM and FM. These cortical signatures potentially provide an efficient means to dissect simultaneously communicated slow temporal and spectral information in acoustic communication signals. PMID:24205309

Methylenetetrahydrofolate Reductase Modulates Methyl Metabolism and Lignin Monomer Methylation in Maize.

PubMed

Wu, Zhenying; Ren, Hao; Xiong, Wangdan; Roje, Sanja; Liu, Yuchen; Su, Kunlong; Fu, Chunxiang

2018-05-30

The brown midrib2 (bm2) mutant of maize, with a modified lignin composition, contains a mutation in the methylenetetrahydrofolate reductase (MTHFR) gene. We here show that a MITE transposon insertion caused downregulation of MTHFR with accompanying decrease in 5-methyl-THF and increase in 5, 10-methylene-THF and THF in the bm2 mutant. Furthermore, MTHFR mutation did not change the content of SAM, the methyl group donor involved in the biosynthesis of guaiacyl (G) and syringyl (S) lignins, but increased the level of S-adenosyl homocysteine (SAH), the de-methylation product of SAM. Moreover, competitive inhibition of the maize caffeoyl CoA O-methyltransferase (CCoAOMT) and caffeic acid O-methyltransferase (COMT) enzyme activities by SAH was found, suggesting that SAH/SAM ratio rather than SAM concentration regulates the transmethylation reactions of lignin intermediates. Phenolic profiling revealed that caffeoyl alcohol glucose derivatives accumulated in the mutant, indicating impaired 3-O-methylation of monolignols. A remarkable increase in the unusual catechyl (C) lignin determined in the mutant demonstrates that MTHFR downregulation mainly affects G lignin biosynthesis, consistent with the observation that CCoAOMT is more sensitive to SAH inhibition than COMT. This study which uncovered a novel regulatory mechanism in lignin biosynthesis and may offer an effective approach to utilize lignocellulosic feedstocks in future.

Generating Data Flow Programs from Nonprocedural Specifications.

DTIC Science & Technology

1983-03-01

With the I-structures, Gajski points out, it is difficult to know ahead of time the optimal memory allocation scheme to pertition large arrays. amory...contention problems may occur for frequently accessed elements stored in the sam memory module. Gajski observes that these are the same problem which

Amplitude Control of Solid-State Modulators for Precision Fast Kicker Applications

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

Watson, J A; Anaya, R M; Caporaso, G C

2002-11-15

A solid-state modulator with very fast rise and fall times, pulse width agility, and multi-pulse burst and intra-pulse amplitude adjustment capability for use with high speed electron beam kickers has been designed and tested at LLNL. The modulator uses multiple solid-state modules stacked in an inductive-adder configuration. Amplitude adjustment is provided by controlling individual modules in the adder, and is used to compensate for transverse e-beam motion as well as the dynamic response and beam-induced steering effects associated with the kicker structure. A control algorithm calculates a voltage based on measured e-beam displacement and adjusts the modulator to regulate beammore » centroid position. This paper presents design details of amplitude control along with measured performance data from kicker operation on the ETA-II accelerator at LLNL.« less

Power-Stepped HF Cross Modulation Experiments at HAARP

NASA Astrophysics Data System (ADS)

Greene, S.; Moore, R. C.; Langston, J. S.

2013-12-01

High frequency (HF) cross modulation experiments are a well established means for probing the HF-modified characteristics of the D-region ionosphere. In this paper, we apply experimental observations of HF cross-modulation to the related problem of ELF/VLF wave generation. HF cross-modulation measurements are used to evaluate the efficiency of ionospheric conductivity modulation during power-stepped modulated HF heating experiments. The results are compared to previously published dependencies of ELF/VLF wave amplitude on HF peak power. The experiments were performed during the March 2013 campaign at the High Frequency Active Auroral Research Program (HAARP) Observatory. HAARP was operated in a dual-beam transmission format: the first beam heated the ionosphere using sinusoidal amplitude modulation while the second beam broadcast a series of low-power probe pulses. The peak power of the modulating beam was incremented in 1-dB steps. We compare the minimum and maximum cross-modulation effect and the amplitude of the resulting cross-modulation waveform to the expected power-law dependence of ELF/VLF wave amplitude on HF power.

Generation and transmission of multilevel quadrature amplitude modulation formats using only one optical modulator: MATLAB Simulink simulation models

NASA Astrophysics Data System (ADS)

Binh, Le Nguyen

2009-04-01

A geometrical and phasor representation technique is presented to illustrate the modulation of the lightwave carrier to generate quadrature amplitude modulated (QAM) signals. The modulation of the amplitude and phase of the lightwave carrier is implemented using only one dual-drive Mach-Zehnder interferometric modulator (MZIM) with the assistance of phasor techniques. Any multilevel modulation scheme can be generated, but we illustrate specifically, the multilevel amplitude and differential phase shift keying (MADPSK) signals. The driving voltage levels are estimated for driving the traveling wave electrodes of the modulator. Phasor diagrams are extensively used to demonstrate the effectiveness of modulation schemes. MATLAB Simulink models are formed to generate the multilevel modulation formats, transmission, and detection in optically amplified fiber communication systems. Transmission performance is obtained for the multilevel optical signals and proven to be equivalent or better than those of binary level with equivalent bit rate. Further, the resilience to nonlinear effects is much higher for MADPSK of 50% and 33% pulse width as compared to non-return-to-zero (NRZ) pulse shaping.

Amplitude modulation reduces loudness adaptation to high-frequency tones.

PubMed

Wynne, Dwight P; George, Sahara E; Zeng, Fan-Gang

2015-07-01

Long-term loudness perception of a sound has been presumed to depend on the spatial distribution of activated auditory nerve fibers as well as their temporal firing pattern. The relative contributions of those two factors were investigated by measuring loudness adaptation to sinusoidally amplitude-modulated 12-kHz tones. The tones had a total duration of 180 s and were either unmodulated or 100%-modulated at one of three frequencies (4, 20, or 100 Hz), and additionally varied in modulation depth from 0% to 100% at the 4-Hz frequency only. Every 30 s, normal-hearing subjects estimated the loudness of one of the stimuli played at 15 dB above threshold in random order. Without any amplitude modulation, the loudness of the unmodulated tone after 180 s was only 20% of the loudness at the onset of the stimulus. Amplitude modulation systematically reduced the amount of loudness adaptation, with the 100%-modulated stimuli, regardless of modulation frequency, maintaining on average 55%-80% of the loudness at onset after 180 s. Because the present low-frequency amplitude modulation produced minimal changes in long-term spectral cues affecting the spatial distribution of excitation produced by a 12-kHz pure tone, the present result indicates that neural synchronization is critical to maintaining loudness perception over time.

Investigating light curve modulation via kernel smoothing. I. Application to 53 fundamental mode and first-overtone Cepheids in the LMC

NASA Astrophysics Data System (ADS)

Süveges, Maria; Anderson, Richard I.

2018-03-01

Context. Recent studies have revealed a hitherto unknown complexity of Cepheid pulsations by discovering irregular modulated variability using photometry, radial velocities, and interferometry. Aim. We aim to perform a statistically rigorous search and characterization of such phenomena in continuous time, applying it to 53 classical Cepheids from the OGLE-III catalog. Methods: We have used local kernel regression to search for both period and amplitude modulations simultaneously in continuous time and to investigate their detectability. We determined confidence intervals using parametric and non-parametric bootstrap sampling to estimate significance, and investigated multi-periodicity using a modified pre-whitening approach that relies on time-dependent light curve parameters. Results: We find a wide variety of period and amplitude modulations and confirm that first overtone pulsators are less stable than fundamental mode Cepheids. Significant temporal variations in period are more frequently detected than those in amplitude. We find a range of modulation intensities, suggesting that both amplitude and period modulations are ubiquitous among Cepheids. Over the 12-year baseline offered by OGLE-III, we find that period changes are often nonlinear, sometimes cyclic, suggesting physical origins beyond secular evolution. Our method detects modulations (period and amplitude) more efficiently than conventional methods that are reliant on certain features in the Fourier spectrum, and pre-whitens time series more accurately than using constant light curve parameters, removing spurious secondary peaks effectively. Conclusions: Period and amplitude modulations appear to be ubiquitous among Cepheids. Current detectability is limited by observational cadence and photometric precision: detection of amplitude modulation below 3 mmag requires space-based facilities. Recent and ongoing space missions (K2, BRITE, MOST, CoRoT) as well as upcoming ones (TESS, PLATO) will significantly improve detectability of fast modulations, such as cycle-to-cycle variations, by providing high-cadence high-precision photometry. High-quality long-term ground-based photometric time series will remain crucial to study longer-term modulations and to disentangle random fluctuations from secular evolution.

High speed cross-amplitude modulation in concatenated SOA-EAM-SOA.

PubMed

Cleary, Ciaran S; Manning, Robert J

2012-06-18

We observe a near-ideal high speed amplitude impulse response in an SOA-EAM-SOA configuration under optimum conditions. Full amplitude recovery times as low as 10 ps with modulation depths of 70% were observed in pump-probe measurements. System behavior could be controlled by the choice of signal wavelength, SOA current biases and EAM reverse bias voltages. Experimental data and impulse response modelling indicated that the slow tail in the gain response of first SOA was negated by a combination of cross-absorption modulation between pump and modulated CW probe, and self-gain modulation of the modulated CW probe in both the EAM and second SOA.

Enhanced resistance to soybean cyst nematode Heterodera glycines in transgenic soybean by silencing putative CLE receptors

USDA-ARS?s Scientific Manuscript database

CLE peptides are small extracellular proteins important in regulating plant meristematic activity through the CLE-receptor kinase-WOX signaling module. Stem cell pools in the SAM (shoot apical meristem), RAM (root apical meristem), and vascular cambium are tightly controlled by CLE signaling pathway...

Maintenance of certification: current attitudes of members of the American Society of Neuroradiology.

PubMed

Yousem, D M

2008-02-01

The maintenance of certification (MOC) process has begun in radiology, and many physicians will be affected by it. We sought to assess the compliance with and knowledge of the MOC steps by American Society of Neuroradiology (ASNR) members. An on-line survey was distributed via e-mail to the members of the ASNR for whom e-mail addresses were available. The survey addressed 3 components of the MOC currently implemented: 1) MOC cognitive examinations, 2) self-assessment modules (SAMs), and 3) continuing medical education (CME) credits. The response rate was 1020/2662 (38.3%). Of those responding, 11% stated that they either do not support the MOC examination (8%) or were unaware of it (3%), 21.4% of respondents have completed an SAM module, but >30% were unaware that they had to complete SAMs or did not know where they were offered. Many members will receive most of their 25 required CME hours for 2007 from sources besides the ASNR annual meeting. Of the small proportion of respondents who made comments (247/1020, 24.2%), those about the MOC process were favorable in 6.1% (15/247), unfavorable in 46.6% (115/247), and neutral in 47.4% (117/247). The MOC process remains poorly understood, with limited compliance. The radiology societies should spend additional effort publicizing the requirements and offering support and products aimed at allowing their members to achieve compliance in a reasonable cost-effective fashion.

Amplitude modulation detection with concurrent frequency modulation.

PubMed

Nagaraj, Naveen K

2016-09-01

Human speech consists of concomitant temporal modulations in amplitude and frequency that are crucial for speech perception. In this study, amplitude modulation (AM) detection thresholds were measured for 550 and 5000 Hz carriers with and without concurrent frequency modulation (FM), at AM rates crucial for speech perception. Results indicate that adding 40 Hz FM interferes with AM detection, more so for 5000 Hz carrier and for frequency deviations exceeding the critical bandwidth of the carrier frequency. These findings suggest that future cochlear implant processors, encoding speech fine-structures may consider limiting the FM to narrow bandwidth and to low frequencies.

Survey view of EXPRESS Rack 4 in the JPM during Expedition 22

NASA Image and Video Library

2009-12-30

iss022e015852 (12/30/2009) --- The image shows a front view of EXpedite the PRocessing of Experiments to Space Station EXPRESS Rack 4 (Rack 4,JPM/1F5) in the Japanese Experiment Module (JEM) Japanese Pressurized Module (JPM). Equipment visible in the EXPRESS Rack includes the Biotechnology Specimen Temperature Controller (BSTC) and the Gas Supply Module (GSM) support hardware for the CBOSS (Cellular Biotechnology Operations Support Systems) investigations, and the Device for the Study of Critical Liquids and Crystallization (DECLIC). Also visible is the Space Acceleration Measurement System (SAMS) II.

Computational Re-design of Synthetic Genetic Oscillators for Independent Amplitude and Frequency Modulation.

PubMed

Tomazou, Marios; Barahona, Mauricio; Polizzi, Karen M; Stan, Guy-Bart

2018-04-25

To perform well in biotechnology applications, synthetic genetic oscillators must be engineered to allow independent modulation of amplitude and period. This need is currently unmet. Here, we demonstrate computationally how two classic genetic oscillators, the dual-feedback oscillator and the repressilator, can be re-designed to provide independent control of amplitude and period and improve tunability-that is, a broad dynamic range of periods and amplitudes accessible through the input "dials." Our approach decouples frequency and amplitude modulation by incorporating an orthogonal "sink module" where the key molecular species are channeled for enzymatic degradation. This sink module maintains fast oscillation cycles while alleviating the translational coupling between the oscillator's transcription factors and output. We characterize the behavior of our re-designed oscillators over a broad range of physiologically reasonable parameters, explain why this facilitates broader function and control, and provide general design principles for building synthetic genetic oscillators that are more precisely controllable. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Framing topographic Rossby waves in the Southern Adriatic Sea

NASA Astrophysics Data System (ADS)

Bonaldo, Davide; Orlic, Mirko; Bergamasco, Andrea; Benetazzo, Alvise; Carniel, Sandro

2017-04-01

Topographic Rossby Waves (TRWs) are oscillatory phenomena associated with modulations induced by seabed morphology in the potential vorticity field. These features could be confined to a single layer or could involve the whole water column, and they are controlled by a combination of the bathymetric gradient and the uniform rotation in the same way as planetary Rossby waves are controlled by the meridional modulation of the Coriolis parameter. In terms of deep-sea circulation, TRWs provide a fundamental contribution by radiating large amounts of energy along and off a continental shelf. Under favorable conditions TRWs can be triggered by a number of factors, such as intense vorticity injections from the wind or the bathymetric perturbations - e.g., a promontory or a canyon crossing the path of a current. In this work we combine observational data and numerical model fields for detecting the presence of TRWs along the Southern Adriatic Margin (SAM, Eastern Mediterranean Sea) and investigating their dynamics during an episode of dense water downflow in spring 2012. Starting from the observation of high-intensity velocity pulses with a period of approximately 2 days, we carry out a sequence of operations on the results of a high-resolution, ocean currents-waves coupled numerical modelling experiment aiming to reproduce dense water formation and migration in the Adriatic Sea in winter-spring 2012. First, we apply a wavelet analysis to modelled velocity time series at several locations off the Italian coast and along the SAM in order to identify the spatial and temporal extent of the pulsing episodes. Then, the properties of the oscillations are assessed via rotary analysis; the propagation of the band-filtered signal along the continental margin is characterized by extracting wave length and propagation velocity, therefore allowing the comparison against theoretical dispersion relations associated with the bathymetry of the SAM. Our results show that the observed modulation was indeed related to a perturbation system propagating south-eastward along the Italian coast and amplified as a train of TRWs along the shelf break and on the continental slope, thus providing, to the best of our knowledge, the first evidence of the existence of such waves on the SAM. This work paves the way to further investigations of these waves and their implications on dense water dynamics and related impacts on the benthic environments.

Phase and Pupil Amplitude Recovery for JWST Space-Optics Control

NASA Technical Reports Server (NTRS)

Dean, B. H.; Zielinski, T. P.; Smith, J. S.; Bolcar, M. R.; Aronstein, D. L.; Fienup, J. R.

2010-01-01

This slide presentation reviews the phase and pupil amplitude recovery for the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam). It includes views of the Integrated Science Instrument Module (ISIM), the NIRCam, examples of Phase Retrieval Data, Ghost Irradiance, Pupil Amplitude Estimation, Amplitude Retrieval, Initial Plate Scale Estimation using the Modulation Transfer Function (MTF), Pupil Amplitude Estimation vs lambda, Pupil Amplitude Estimation vs. number of Images, Pupil Amplitude Estimation vs Rotation (clocking), and Typical Phase Retrieval Results Also included is information about the phase retrieval approach, Non-Linear Optimization (NLO) Optimized Diversity Functions, and Least Square Error vs. Starting Pupil Amplitude.

Timbral Sharpness and Modulations in Frequency and Amplitude: Implications for the Fusion of Musical Sounds.

NASA Astrophysics Data System (ADS)

Goad, Pamela Joy

The fusion of musical voices is an important aspect of musical blend, or the mixing of individual sounds. Yet, little research has been done to explicitly determine the factors involved in fusion. In this study, the similarity of timbre and modulation were examined for their contribution to the fusion of sounds. It is hypothesized that similar timbres will fuse better than dissimilar timbres, and, voices with the same kind of modulation will fuse better than voices of different modulations. A perceptually-based measure, known as sharpness was investigated as a measure of timbre. The advantages of using sharpness are that it is based on hearing sensitivities and masking phenomena of inner ear processing. Five musical instrument families were digitally recorded in performances across a typical playing range at two extreme dynamic levels. Analyses reveal that sharpness is capable of uncovering subtle changes in timbre including those found in musical dynamics, instrument design, and performer-specific variations. While these analyses alone are insufficient to address fusion, preliminary calculations of timbral combinations indicate that sharpness has the potential to predict the fusion of sounds used in musical composition. Three experiments investigated the effects of modulation on the fusion of a harmonic major sixth interval. In the first experiment using frequency modulation, stimuli varied in deviation about a mean fundamental frequency and relative modulation phase between the two tones. Results showed smaller frequency deviations promoted fusion and relative phase differences had a minimal effect. In a second experiment using amplitude modulation, stimuli varied in deviation about a mean amplitude level and relative phase of modulation. Results showed smaller amplitude deviations promoted better fusion, but unlike frequency modulation, relative phase differences were also important. In a third experiment, frequency modulation, amplitude modulation and mixed modulation were arranged in all possible voicings. Results showed frequency modulation in the lower voice and less variance in amplitude envelopes contributed to an increase in fusion. The theory that similar modulations would promote better fusion was only marginally supported. For these experiments, results revealed differences depending on modulation type and that a lesser amount of modulation fosters greater fusion.

Method for the substantial reduction of quenching effects in luminescence spectrometry

DOEpatents

Demas, James N.; Jones, Wesley M.; Keller, Richard A.

1989-01-01

Method for reducing quenching effects in analytical luminescence measurements. Two embodiments of the present invention are described which relate to a form of time resolution based on the amplitudes and phase shifts of modulated emission signals. In the first embodiment, the measured modulated emission signal is substantially independent of sample quenching at sufficiently high frequenices. In the second embodiment, the modulated amplitude and the phase shift between the emission signal and the excitation source are simultaneously measured. Using either method, the observed modulated amplitude may reduced to tis unquenched value.

What do Westerly Wind Reconstructions from Fiordland, New Zealand, say about Southern Hemisphere Paleoclimatic Mechanisms?

NASA Astrophysics Data System (ADS)

Knudson, K. P.; Hendy, I. L.; Neil, H.

2010-12-01

The Southern Hemisphere westerly winds (SWW) have a major influence over deep ocean ventilation around Antarctica and are modulated by inter-annual and decadal climate variability, such as El Niño-Southern Oscillation (ENSO), Inter-decadal Pacific Oscillation (IPO), and Southern Annular Mode (SAM). Fiordland, New Zealand (44.5-46.5°S), is optimally located for reconstructing the SWW, since the fjord sediments record changes in precipitation dependent on the strength and position of the SWW. Here we present a multi-proxy precipitation reconstruction from three New Zealand fjords, demonstrating SWW variability during the late-Holocene, and compare our results to other climate records from New Zealand, Patagonia, and Antarctica. Our fjord sediment analysis uses bulk sediment δ13C and organic C/N ratios to determine the relative contributions of terrestrial organic matter (TOM) versus marine suspended organic matter (SPOM), indicative of terrestrial runoff due to precipitation. Our data indicate dry conditions in Fiordland at 1500-1100 and 750-150 yr B.P., with a reversal at 400 years B.P., and wet conditions at 2300-1600 and 1100-750 yr B.P., with short reversals around 1900 and 900 yr B.P. Our precipitation reconstruction linked to SWW variability provides significant implications for interpreting other Southern Hemisphere climate records and better understanding Pacific basin-wide SWW behavior. Locally, wet periods are likely associated with intervals of increased westerly flow over Fiordland, such as -SAM, El Niño, and/or +IPO, while dry periods may be associated with +SAM, La Niña, and/or -IPO. Comparison of our New Zealand record with Patagonian precipitation records shows differences, which may be attributed to regional variations of the expression of SAM, ENSO, and IPO. In contrast, Fiordland precipitation records appear to correlate to West Antarctic ice cores suggesting a linkage via SAM. Finally, Fiordland precipitation may be modulated by the position of the Subtropical Convergence Zone (STCZ) in the Tasman Sea, which has control over the moisture sources within the SWW path. Therefore, wet periods in Fiordland may be amplified by a southern position of the STCZ that caused the SWW to encounter a warm moisture source before reaching Fiordland.

Modulated Source Interferometry with Combined Amplitude and Frequency Modulation

NASA Technical Reports Server (NTRS)

Gutierrez, Roman C. (Inventor)

1998-01-01

An improved interferometer is produced by modifying a conventional interferometer to include amplitude and/or frequency modulation of a coherent light source at radio or higher frequencies. The phase of the modulation signal can be detected in an interfering beam from an interferometer and can be used to determine the actual optical phase of the beam. As such, this improvement can be adapted to virtually any two-beam interferometer, including: Michelson, Mach-Zehnder, and Sagnac interferometers. The use of an amplitude modulated coherent tight source results in an interferometer that combines the wide range advantages of coherent interferometry with the precise distance measurement advantages of white light interferometry.

TH-E-BRE-04: An Online Replanning Algorithm for VMAT

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

Ahunbay, E; Li, X; Moreau, M

2014-06-15

Purpose: To develop a fast replanning algorithm based on segment aperture morphing (SAM) for online replanning of volumetric modulated arc therapy (VMAT) with flattening filtered (FF) and flattening filter free (FFF) beams. Methods: A software tool was developed to interface with a VMAT planning system ((Monaco, Elekta), enabling the output of detailed beam/machine parameters of original VMAT plans generated based on planning CTs for FF or FFF beams. A SAM algorithm, previously developed for fixed-beam IMRT, was modified to allow the algorithm to correct for interfractional variations (e.g., setup error, organ motion and deformation) by morphing apertures based on themore » geometric relationship between the beam's eye view of the anatomy from the planning CT and that from the daily CT for each control point. The algorithm was tested using daily CTs acquired using an in-room CT during daily IGRT for representative prostate cancer cases along with their planning CTs. The algorithm allows for restricted MLC leaf travel distance between control points of the VMAT delivery to prevent SAM from increasing leaf travel, and therefore treatment delivery time. Results: The VMAT plans adapted to the daily CT by SAM were found to improve the dosimetry relative to the IGRT repositioning plans for both FF and FFF beams. For the adaptive plans, the changes in leaf travel distance between control points were < 1cm for 80% of the control points with no restriction. When restricted to the original plans' maximum travel distance, the dosimetric effect was minimal. The adaptive plans were delivered successfully with similar delivery times as the original plans. The execution of the SAM algorithm was < 10 seconds. Conclusion: The SAM algorithm can quickly generate deliverable online-adaptive VMAT plans based on the anatomy of the day for both FF and FFF beams.« less

Potential impact of the May Southern Hemisphere annular mode on the Indian summer monsoon rainfall

NASA Astrophysics Data System (ADS)

Dou, Juan; Wu, Zhiwei; Zhou, Yefan

2017-04-01

El Niño-Southern Oscillation (ENSO) is probably a most important external forcing to Indian summer monsoon (ISM) rainfall (ISMR), yet the observed ENSO-ISMR relationship has become weak in recent years. It's essential to explore other predominant modes of variability which can contribute to the ISMR. As the leading mode of the variability in Southern Hemisphere (SH) extratropical atmospheric circulation, the SH annular mode (SAM) has potential influence both on the northern and southern hemispheric climate. The present study investigates the relationship between the SAM and ISMR. It is found that the May SAM exhibits a significant positive correlation with the monsoon precipitation over the Indian sub-continent and the adjacent areas in JunetJuly (JJ). Observational and numerical evidences indicate that the May SAM anomaly can trigger a South Indian Ocean dipole (SIOD) sea surface temperature anomaly (SSTA) through air-sea interactions. The SIOD SSTA persisting into the following months of JJ excites abnormal meridional circulation and modulates the low-level cross-equatorial flow. Accordingly, the ascending (or descending) motion and water vapor transportation are enhanced (or suppressed), which favors more (or less) precipitation over the Indian sub-continent and the adjacent areas. In fact, the SIOD SSTA plays an "ocean bridge" role to "prolong" the influence of the May SAM to the subsequent season and in turn impacts on the ISMR. Moreover, an empirical model is established to forecast the JJ ISMR strength based on the ENSO, Indian Ocean Dipole (IOD) and May SAM. The hindcast is carried out for the period 1979-2014, and performs better than the multimodel ensemble mean (MME) obtained from the Development of a European MME system for seasonal to interannual prediction (DEMETER) project. Since all these predictors can be monitored in real time before the early boreal summer, the empirical model might provide a practical real-time forecast tool for predicting ISMR variations.

Potential impact of the May Southern Hemisphere annular mode on the Indian summer monsoon rainfall

NASA Astrophysics Data System (ADS)

Dou, Juan; Wu, Zhiwei; Zhou, Yefan

2017-08-01

El Niño-Southern Oscillation (ENSO) is probably a most important external forcing to Indian summer monsoon (ISM) rainfall (ISMR), yet the observed ENSO-ISMR relationship has become weak in recent years. It's essential to explore other predominant modes of variability which can contribute to the ISMR. As the leading mode of the variability in Southern Hemisphere (SH) extratropical atmospheric circulation, the SH annular mode (SAM) has potential influence both on the northern and southern hemispheric climate. The present study investigates the relationship between the SAM and ISMR. It is found that the May SAM exhibits a significant positive correlation with the monsoon precipitation over the Indian sub-continent and the adjacent areas in June-July (JJ). Observational and numerical evidences indicate that the May SAM anomaly can trigger a South Indian Ocean dipole (SIOD) sea surface temperature anomaly (SSTA) through air-sea interactions. The SIOD SSTA persisting into the following months of JJ excites abnormal meridional circulation and modulates the low-level cross-equatorial flow. Accordingly, the ascending (or descending) motion and water vapor transportation are enhanced (or suppressed), which favors more (or less) precipitation over the Indian sub-continent and the adjacent areas. In fact, the SIOD SSTA plays an "ocean bridge" role to "prolong" the influence of the May SAM to the subsequent season and in turn impacts on the ISMR. Moreover, an empirical model is established to forecast the JJ ISMR strength based on the ENSO, Indian Ocean Dipole and May SAM. The hindcast is carried out for the period 1979-2014, and performs better than the multimodel ensemble mean (MME) obtained from the Development of a European MME system for seasonal to interannual prediction (DEMETER) project. Since all these predictors can be monitored in real time before the early boreal summer, the empirical model might provide a practical real-time forecast tool for predicting ISMR variations.

Task-induced frequency modulation features for brain-computer interfacing.

PubMed

Jayaram, Vinay; Hohmann, Matthias; Just, Jennifer; Schölkopf, Bernhard; Grosse-Wentrup, Moritz

2017-10-01

Task-induced amplitude modulation of neural oscillations is routinely used in brain-computer interfaces (BCIs) for decoding subjects' intents, and underlies some of the most robust and common methods in the field, such as common spatial patterns and Riemannian geometry. While there has been some interest in phase-related features for classification, both techniques usually presuppose that the frequencies of neural oscillations remain stable across various tasks. We investigate here whether features based on task-induced modulation of the frequency of neural oscillations enable decoding of subjects' intents with an accuracy comparable to task-induced amplitude modulation. We compare cross-validated classification accuracies using the amplitude and frequency modulated features, as well as a joint feature space, across subjects in various paradigms and pre-processing conditions. We show results with a motor imagery task, a cognitive task, and also preliminary results in patients with amyotrophic lateral sclerosis (ALS), as well as using common spatial patterns and Laplacian filtering. The frequency features alone do not significantly out-perform traditional amplitude modulation features, and in some cases perform significantly worse. However, across both tasks and pre-processing in healthy subjects the joint space significantly out-performs either the frequency or amplitude features alone. This result only does not hold for ALS patients, for whom the dataset is of insufficient size to draw any statistically significant conclusions. Task-induced frequency modulation is robust and straight forward to compute, and increases performance when added to standard amplitude modulation features across paradigms. This allows more information to be extracted from the EEG signal cheaply and can be used throughout the field of BCIs.

Poly(L-lysine) Interfaces via Dual Click Reactions on Surface-Bound Custom-Designed Dithiol Adsorbates.

PubMed

Shakiba, Amin; Jamison, Andrew C; Lee, T Randall

2015-06-09

Surfaces modified with poly(L-lysine) can be used to immobilize selected biomolecules electrostatically. This report describes the preparation of a set of self-assembled monolayers (SAMs) from three different azide-terminated adsorbates as platforms for performing controlled surface attachments and as a means of determining the parameters that afford stable poly(L-lysine)-modified SAM surfaces having controlled packing densities. A maleimide-terminated alkyne linker was "clicked" to the azide-terminated surfaces via a copper-catalyzed cycloaddition reaction to produce the attachment sites for the polypeptides. A thiol-Michael addition was then used to immobilize cysteine-terminated poly(L-lysine) moieties on the gold surface, avoiding adsorbate self-reactions with this two-step procedure. Each step in this process was analyzed by ellipsometry, X-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy, and contact angle goniometry to determine which adsorbate structure most effectively produced the targeted polypeptide interface. Additionally, a series of mixed SAMs using an azidoalkanethiol in combination with a normal alkanethiol having an equivalent alkyl chain were prepared to provide data to determine how dilution of the azide reactive site on the SAM surface influences the initial click reaction. Overall, the collected data demonstrate the advantages of an appropriately designed bidentate absorbate and its potential to form effective platforms for biomolecule surface attachment via click reactions.

The Achievement Gap between White and Non-White Students

ERIC Educational Resources Information Center

Rojas-LeBouef, Ana; Slate, John R.

2012-01-01

This Collection contains three seminal modules by Authors Ana Rojas-LeBouef and John R. Slate, professors and researchers from Sam Houston State University in Texas. They are nationally recognized scholars in the area of the academic inequity between White and Non-White students. This paper is divided into three chapters. Chapter 1--The…

Masking release for words in amplitude-modulated noise as a function of modulation rate and task

PubMed Central

Buss, Emily; Whittle, Lisa N.; Grose, John H.; Hall, Joseph W.

2009-01-01

For normal-hearing listeners, masked speech recognition can improve with the introduction of masker amplitude modulation. The present experiments tested the hypothesis that this masking release is due in part to an interaction between the temporal distribution of cues necessary to perform the task and the probability of those cues temporally coinciding with masker modulation minima. Stimuli were monosyllabic words masked by speech-shaped noise, and masker modulation was introduced via multiplication with a raised sinusoid of 2.5–40 Hz. Tasks included detection, three-alternative forced-choice identification, and open-set identification. Overall, there was more masking release associated with the closed than the open-set tasks. The best rate of modulation also differed as a function of task; whereas low modulation rates were associated with best performance for the detection and three-alternative identification tasks, performance improved with modulation rate in the open-set task. This task-by-rate interaction was also observed when amplitude-modulated speech was presented in a steady masker, and for low- and high-pass filtered speech presented in modulated noise. These results were interpreted as showing that the optimal rate of amplitude modulation depends on the temporal distribution of speech cues and the information required to perform a particular task. PMID:19603883

Note: Demodulation of spectral signal modulated by optical chopper with unstable modulation frequency.

PubMed

Zhang, Shengzhao; Li, Gang; Wang, Jiexi; Wang, Donggen; Han, Ying; Cao, Hui; Lin, Ling; Diao, Chunhong

2017-10-01

When an optical chopper is used to modulate the light source, the rotating speed of the wheel may vary with time and subsequently cause jitter of the modulation frequency. The amplitude calculated from the modulated signal would be distorted when the frequency fluctuations occur. To precisely calculate the amplitude of the modulated light flux, we proposed a method to estimate the range of the frequency fluctuation in the measurement of the spectrum and then extract the amplitude based on the sum of power of the signal in the selected frequency range. Experiments were designed to test the feasibility of the proposed method and the results showed lower root means square error than the conventional way.

Modulation bandwidth of spin torque oscillators under current modulation

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

Quinsat, M.; CEA, INAC-SPINTEC, F-38054 Grenoble; CNRS, SPINTEC, F-38054 Grenoble

2014-10-13

For practical applications of spin torque nano-oscillators (STNO), one of the most critical characteristics is the speed at which an STNO responds to variations of external control parameters, such as current or/and field. Theory predicts that this speed is limited by the amplitude relaxation rate Γ{sub p} that determines the timescale over which the amplitude fluctuations are damped out. In this study, this limit is verified experimentally by analyzing the amplitude and frequency noise spectra of the output voltage signal when modulating an STNO by a microwave current. In particular, it is shown that due to the non-isochronous nature ofmore » the STNO the amplitude relaxation rate Γ{sub p} determines not only the bandwidth of an amplitude modulation, but also the bandwidth of a frequency modulation. The presented experimental technique will be important for the optimisation of the STNO characteristics for applications in telecommunications or/and data storage and is applicable even in the case when the STNO output signal is only several times higher than noise.« less

Method for the substantial reduction of quenching effects in luminescence spectrometry

DOEpatents

Demas, J.N.; Jones, W.M.; Keller, R.A.

1987-06-26

Method for reducing quenching effects in analytical luminescence measurements. Two embodiments of the present invention are described which relate to a form of time resolution based on the amplitudes and phase shifts of modulated emission signals. In the first embodiment, the measured modulated emission signal is substantially independent of sample quenching at sufficiently high frequencies. In the second embodiment, the modulated amplitude and the phase shift between the emission signal and the excitation source are simultaneously measured. Using either method, the observed modulated amplitude may be reduced to its unquenched value. 3 figs.

Parabolic Trough Collector Cost Update for the System Advisor Model (SAM)

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

Kurup, Parthiv; Turchi, Craig S.

2015-11-01

This report updates the baseline cost for parabolic trough solar fields in the United States within NREL's System Advisor Model (SAM). SAM, available at no cost at https://sam.nrel.gov/, is a performance and financial model designed to facilitate decision making for people involved in the renewable energy industry. SAM is the primary tool used by NREL and the U.S. Department of Energy (DOE) for estimating the performance and cost of concentrating solar power (CSP) technologies and projects. The study performed a bottom-up build and cost estimate for two state-of-the-art parabolic trough designs -- the SkyTrough and the Ultimate Trough. The SkyTroughmore » analysis estimated the potential installed cost for a solar field of 1500 SCAs as $170/m 2 +/- $6/m 2. The investigation found that SkyTrough installed costs were sensitive to factors such as raw aluminum alloy cost and production volume. For example, in the case of the SkyTrough, the installed cost would rise to nearly $210/m 2 if the aluminum alloy cost was $1.70/lb instead of $1.03/lb. Accordingly, one must be aware of fluctuations in the relevant commodities markets to track system cost over time. The estimated installed cost for the Ultimate Trough was only slightly higher at $178/m 2, which includes an assembly facility of $11.6 million amortized over the required production volume. Considering the size and overall cost of a 700 SCA Ultimate Trough solar field, two parallel production lines in a fully covered assembly facility, each with the specific torque box, module and mirror jigs, would be justified for a full CSP plant.« less

Relationship Between Peripheral and Psychophysical Measures of Amplitude Modulation Detection in Cochlear Implant Users.

PubMed

Tejani, Viral D; Abbas, Paul J; Brown, Carolyn J

This study investigates the relationship between electrophysiological and psychophysical measures of amplitude modulation (AM) detection. Prior studies have reported both measures of AM detection recorded separately from cochlear implant (CI) users and acutely deafened animals, but no study has made both measures in the same CI users. Animal studies suggest a progressive loss of high-frequency encoding as one ascends the auditory pathway from the auditory nerve to the cortex. Because the CI speech processor uses the envelope of an ongoing acoustic signal to modulate pulse trains that are subsequently delivered to the intracochlear electrodes, it is of interest to explore auditory nerve responses to modulated stimuli. In addition, psychophysical AM detection abilities have been correlated with speech perception outcomes. Thus, the goal was to explore how the auditory nerve responds to AM stimuli and to relate those physiologic measures to perception. Eight patients using Cochlear Ltd. Implants participated in this study. Electrically evoked compound action potentials (ECAPs) were recorded using a 4000 pps pulse train that was sinusoidally amplitude modulated at 125, 250, 500, and 1000 Hz rates. Responses were measured for each pulse over at least one modulation cycle for an apical, medial, and basal electrode. Psychophysical modulation detection thresholds (MDTs) were also measured via a three-alternative forced choice, two-down, one-up adaptive procedure using the same modulation frequencies and electrodes. ECAPs were recorded from individual pulses in the AM pulse train. ECAP amplitudes varied sinusoidally, reflecting the sinusoidal variation in the stimulus. A modulated response amplitude (MRA) metric was calculated as the difference in the maximal and minimum ECAP amplitudes over the modulation cycles. MRA increased as modulation frequency increased, with no apparent cutoff (up to 1000 Hz). In contrast, MDTs increased as the modulation frequency increased. This trend is inconsistent with the physiologic measures. For a fixed modulation frequency, correlations were observed between MDTs and MRAs; this trend was evident at all frequencies except 1000 Hz (although only statistically significant for 250 and 500 Hz AM rates), possibly an indication of central limitations in processing of high modulation frequencies. Finally, peripheral responses were larger and psychophysical thresholds were lower in the apical electrodes relative to basal and medial electrodes, which may reflect better cochlear health and neural survival evidenced by lower preoperative low-frequency audiometric thresholds and steeper growth of neural responses in ECAP amplitude growth functions for apical electrodes. Robust ECAPs were recorded for all modulation frequencies tested. ECAP amplitudes varied sinusoidally, reflecting the periodicity of the modulated stimuli. MRAs increased as the modulation frequency increased, a trend we attribute to neural adaptation. For low modulation frequencies, there are multiple current steps between the peak and valley of the modulation cycle, which means successive stimuli are more similar to one another and neural responses are more likely to adapt. Higher MRAs were correlated with lower psychophysical thresholds at low modulation frequencies but not at 1000 Hz, implying a central limitation to processing of modulated stimuli.

EFFECTS OF CONTINUOUS-WAVE, PULSED, AND SINUSOIDAL-AMPLITUDE-MODULATED MICROWAVES ON BRAIN ENERGY METABOLISM

EPA Science Inventory

A comparison of the effects of continuous wave, sinusoidal-amplitude modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague Dawley rats (175-225g). Brain NADH fluorescence, adensine triphosphate (ATP) concentrat...

Shading of a computer-generated hologram by zone plate modulation.

PubMed

Kurihara, Takayuki; Takaki, Yasuhiro

2012-02-13

We propose a hologram calculation technique that enables reconstructing a shaded three-dimensional (3D) image. The amplitude distributions of zone plates, which generate the object points that constitute a 3D object, were two-dimensionally modulated. Two-dimensional (2D) amplitude modulation was determined on the basis of the Phong reflection model developed for computer graphics, which considers the specular, diffuse, and ambient reflection light components. The 2D amplitude modulation added variable and constant modulations: the former controlled the specular light component and the latter controlled the diffuse and ambient components. The proposed calculation technique was experimentally verified. The reconstructed image showed specular reflection that varied depending on the viewing position.

System and method of modulating electrical signals using photoconductive wide bandgap semiconductors as variable resistors

DOEpatents

Harris, John Richardson; Caporaso, George J; Sampayan, Stephen E

2013-10-22

A system and method for producing modulated electrical signals. The system uses a variable resistor having a photoconductive wide bandgap semiconductor material construction whose conduction response to changes in amplitude of incident radiation is substantially linear throughout a non-saturation region to enable operation in non-avalanche mode. The system also includes a modulated radiation source, such as a modulated laser, for producing amplitude-modulated radiation with which to direct upon the variable resistor and modulate its conduction response. A voltage source and an output port, are both operably connected to the variable resistor so that an electrical signal may be produced at the output port by way of the variable resistor, either generated by activation of the variable resistor or propagating through the variable resistor. In this manner, the electrical signal is modulated by the variable resistor so as to have a waveform substantially similar to the amplitude-modulated radiation.

Miniature Surface Plasmon Polariton Amplitude Modulator by Beat Frequency and Polarization Control

PubMed Central

Chang, Cheng-Wei; Lin, Chu-En; Yu, Chih-Jen; Yeh, Ting-Tso; Yen, Ta-Jen

2016-01-01

The miniaturization of modulators keeps pace for the compact devices in optical applications. Here, we present a miniature surface plasmon polariton amplitude modulator (SPPAM) by directing and interfering surface plasmon polaritons on a nanofabricated chip. Our results show that this SPPAM enables two kinds of modulations. The first kind of modulation is controlled by encoding angular-frequency difference from a Zeeman laser, with a beat frequency of 1.66 MHz; the second of modulation is validated by periodically varying the polarization states from a polarization generator, with rotation frequencies of 0.5–10 k Hz. In addition, the normalized extinction ratio of our plasmonic structure reaches 100. Such miniaturized beat-frequency and polarization-controlled amplitude modulators open an avenue for the exploration of ultrasensitive nanosensors, nanocircuits, and other integrated nanophotonic devices. PMID:27558516

Temporal-spatial characteristics of phase-amplitude coupling in electrocorticogram for human temporal lobe epilepsy.

PubMed

Zhang, Ruihua; Ren, Ye; Liu, Chunyan; Xu, Na; Li, Xiaoli; Cong, Fengyu; Ristaniemi, Tapani; Wang, YuPing

2017-09-01

Neural activity of the epileptic human brain contains low- and high-frequency oscillations in different frequency bands, some of which have been used as reliable biomarkers of the epileptogenic brain areas. However, the relationship between the low- and high-frequency oscillations in different cortical areas during the period from pre-seizure to post-seizure has not been completely clarified. We recorded electrocorticogram data from the temporal lobe and hippocampus of seven patients with temporal lobe epilepsy. The modulation index based on the Kullback-Leibler distance and the phase-amplitude coupling co-modulogram were adopted to quantify the coupling strength between the phase of low-frequency oscillations (0.2-10Hz) and the amplitude of high-frequency oscillations (11-400Hz) in different seizure epochs. The time-varying phase-amplitude modulogram was used to analyze the phase-amplitude coupling pattern during the entire period from pre-seizure to post-seizure in both the left and right temporal lobe and hippocampus. Channels with strong modulation index were compared with the seizure onset channels identified by the neurosurgeons and the resection channels in the clinical surgery. The phase-amplitude coupling strength (modulation index) increased significantly in the mid-seizure epoch and decrease significantly in seizure termination and post-seizure epochs (p<0.001). The strong phase-amplitude-modulating low- and high-frequency oscillations in the mid-seizure epoch were mainly δ, θ, and α oscillations and γ and ripple oscillations, respectively. The phase-amplitude modulation and strength varied among channels and was asymmetrical in the left and right temporal cortex and hippocampus. The "fall-max" phase-amplitude modulation pattern, i.e., high-frequency amplitudes were largest in the low-frequency phase range [-π, 0], which corresponded to the falling edges of low-frequency oscillations, appeared in the middle period of the seizures at epileptic focus channels. Channels with strong modulation index appeared on the corresponding left or right temporal cortex of surgical resection and overlapped with the clinical resection zones in all patients. The "fall-max" pattern between the phase of low-frequency oscillation and amplitude of high-frequency oscillation that appeared in the middle period of the seizures is a reliable biomarker in epileptogenic cortical areas. The modulation index can be used as a good tool for lateralization and localization for the epileptic focus in patients with epilepsy. Phase-amplitude coupling can provide meaningful reference for accurate resection of epileptogenic focus and provide insight into the underlying neural dynamics of the epileptic seizure in patients with temporal lobe epilepsy. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Task-induced frequency modulation features for brain-computer interfacing

NASA Astrophysics Data System (ADS)

Jayaram, Vinay; Hohmann, Matthias; Just, Jennifer; Schölkopf, Bernhard; Grosse-Wentrup, Moritz

2017-10-01

Objective. Task-induced amplitude modulation of neural oscillations is routinely used in brain-computer interfaces (BCIs) for decoding subjects’ intents, and underlies some of the most robust and common methods in the field, such as common spatial patterns and Riemannian geometry. While there has been some interest in phase-related features for classification, both techniques usually presuppose that the frequencies of neural oscillations remain stable across various tasks. We investigate here whether features based on task-induced modulation of the frequency of neural oscillations enable decoding of subjects’ intents with an accuracy comparable to task-induced amplitude modulation. Approach. We compare cross-validated classification accuracies using the amplitude and frequency modulated features, as well as a joint feature space, across subjects in various paradigms and pre-processing conditions. We show results with a motor imagery task, a cognitive task, and also preliminary results in patients with amyotrophic lateral sclerosis (ALS), as well as using common spatial patterns and Laplacian filtering. Main results. The frequency features alone do not significantly out-perform traditional amplitude modulation features, and in some cases perform significantly worse. However, across both tasks and pre-processing in healthy subjects the joint space significantly out-performs either the frequency or amplitude features alone. This result only does not hold for ALS patients, for whom the dataset is of insufficient size to draw any statistically significant conclusions. Significance. Task-induced frequency modulation is robust and straight forward to compute, and increases performance when added to standard amplitude modulation features across paradigms. This allows more information to be extracted from the EEG signal cheaply and can be used throughout the field of BCIs.

Polarization-sensitive optical coherence tomography using continuous polarization modulation with arbitrary phase modulation amplitude

NASA Astrophysics Data System (ADS)

Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

2012-03-01

We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated on measurements of a three-quarter waveplate and an equine tendon sample by a fiber-based swept-source CPM-PS-OCT system.

Frequency modulation spectroscopy with a THz quantum-cascade laser.

PubMed

Eichholz, R; Richter, H; Wienold, M; Schrottke, L; Hey, R; Grahn, H T; Hübers, H-W

2013-12-30

We report on a terahertz spectrometer for high-resolution molecular spectroscopy based on a quantum-cascade laser. High-frequency modulation (up to 50 MHz) of the laser driving current produces a simultaneous modulation of the frequency and amplitude of the laser output. The modulation generates sidebands, which are symmetrically positioned with respect to the laser carrier frequency. The molecular transition is probed by scanning the sidebands across it. In this way, the absorption and the dispersion caused by the molecular transition are measured. The signals are modeled by taking into account the simultaneous modulation of the frequency and amplitude of the laser emission. This allows for the determination of the strength of the frequency as well as amplitude modulation of the laser and of molecular parameters such as pressure broadening.

Encoding and decoding amplitude-modulated cochlear implant stimuli—a point process analysis

PubMed Central

Shea-Brown, Eric; Rubinstein, Jay T.

2010-01-01

Cochlear implant speech processors stimulate the auditory nerve by delivering amplitude-modulated electrical pulse trains to intracochlear electrodes. Studying how auditory nerve cells encode modulation information is of fundamental importance, therefore, to understanding cochlear implant function and improving speech perception in cochlear implant users. In this paper, we analyze simulated responses of the auditory nerve to amplitude-modulated cochlear implant stimuli using a point process model. First, we quantify the information encoded in the spike trains by testing an ideal observer’s ability to detect amplitude modulation in a two-alternative forced-choice task. We vary the amount of information available to the observer to probe how spike timing and averaged firing rate encode modulation. Second, we construct a neural decoding method that predicts several qualitative trends observed in psychophysical tests of amplitude modulation detection in cochlear implant listeners. We find that modulation information is primarily available in the sequence of spike times. The performance of an ideal observer, however, is inconsistent with observed trends in psychophysical data. Using a neural decoding method that jitters spike times to degrade its temporal resolution and then computes a common measure of phase locking from spike trains of a heterogeneous population of model nerve cells, we predict the correct qualitative dependence of modulation detection thresholds on modulation frequency and stimulus level. The decoder does not predict the observed loss of modulation sensitivity at high carrier pulse rates, but this framework can be applied to future models that better represent auditory nerve responses to high carrier pulse rate stimuli. The supplemental material of this article contains the article’s data in an active, re-usable format. PMID:20177761

Cognitive reappraisal of snake and spider pictures: An event-related potentials study.

PubMed

Langeslag, Sandra J E; van Strien, Jan W

2018-05-30

Fear of snakes and spiders are common animal phobias. Emotion regulation can change the response to emotional stimuli, including snakes and spiders. It is well known that emotion regulation modulates the late positive potential (LPP), which reflects sustained motivated attention. However, research concerning the effect of emotion regulation on the early posterior negativity (EPN), which reflects early selective attention, is scarce. The present research question was whether the EPN and LPP amplitudes are modulated by regulation of emotional responses to snake and spider stimuli. Emotion up- and down-regulation were expected to enhance and reduce the LPP amplitude, respectively, but emotion regulation was not expected to modulate the EPN amplitude. Female participants passively viewed snake, spider, and bird pictures, and up- and down-regulated their emotional responses to the snake and spider pictures using self-focused reappraisal, while their electroencephalogram was recorded. There were EPNs for snakes and spiders vs. birds, as well as for snakes vs. spiders. The LPP amplitude tended to be enhanced for snakes and spiders compared to birds. Most importantly, the LPP amplitude was larger in the up-regulate than in the down-regulate condition for both snakes and spiders, but there was no evidence that the EPN amplitude was modulated by emotion regulation. This suggests that emotion regulation modulated sustained motivated attention, but not early selective attention, to snakes and spiders. The findings are in line with the notion that the emotional modulation of the EPN is more automatic than the emotional modulation of the LPP. Copyright © 2018 Elsevier B.V. All rights reserved.

Importance of envelope modulations during consonants and vowels in segmentally interrupted sentencesa)

PubMed Central

Fogerty, Daniel

2014-01-01

The present study investigated the importance of overall segment amplitude and intrinsic segment amplitude modulation of consonants and vowels to sentence intelligibility. Sentences were processed according to three conditions that replaced consonant or vowel segments with noise matched to the long-term average speech spectrum. Segments were replaced with (1) low-level noise that distorted the overall sentence envelope, (2) segment-level noise that restored the overall syllabic amplitude modulation of the sentence, and (3) segment-modulated noise that further restored faster temporal envelope modulations during the vowel. Results from the first experiment demonstrated an incremental benefit with increasing resolution of the vowel temporal envelope. However, amplitude modulations of replaced consonant segments had a comparatively minimal effect on overall sentence intelligibility scores. A second experiment selectively noise-masked preserved vowel segments in order to equate overall performance of consonant-replaced sentences to that of the vowel-replaced sentences. Results demonstrated no significant effect of restoring consonant modulations during the interrupting noise when existing vowel cues were degraded. A third experiment demonstrated greater perceived sentence continuity with the preservation or addition of vowel envelope modulations. Overall, results support previous investigations demonstrating the importance of vowel envelope modulations to the intelligibility of interrupted sentences. PMID:24606291

Shaping non-diffracting beams with a digital micromirror device

NASA Astrophysics Data System (ADS)

Ren, Yu-Xuan; Fang, Zhao-Xiang; Lu, Rong-De

2016-02-01

The micromechanical digital micromirror device (DMD) performs as a spatial light modulator to shape the light wavefront. Different from the liquid crystal devices, which use the birefringence to modulate the light wave, the DMD regulates the wavefront through an amplitude modulation with the digitally controlled mirrors switched on and off. The advantages of such device are the fast speed, polarization insensitivity, and the broadband modulation ability. The fast switching ability for the DMD not only enables the shaping of static light mode, but also could dynamically compensate for the wavefront distortion due to scattering medium. We have employed such device to create the higher order modes, including the Laguerre-Gaussian, Hermite-Gaussian, as well as Mathieu modes. There exists another kind of beam with shape-preservation against propagation, and self-healing against obstacles. Representative modes are the Bessel modes, Airy modes, and the Pearcey modes. Since the DMD modulates the light intensity, a series of algorithms are developed to calculate proper amplitude hologram for shaping the light. The quasi-continuous gray scale images could imitate the continuous amplitude hologram, while the binary amplitude modulation is another means to create the modulation pattern for a steady light field. We demonstrate the generation of the non-diffracting beams with the binary amplitude modulation via the DMD, and successfully created the non-diffracting Bessel beam, Airy beam, and the Pearcey beam. We have characterized the non-diffracting modes through propagation measurements as well as the self-healing measurements.

Amplitude modulation of quantum-ion-acoustic wavepackets in electron-positron-ion plasmas: Modulational instability, envelope modes, extreme wavesa)

NASA Astrophysics Data System (ADS)

Rahman, Ata-ur-; Kerr, Michael Mc; El-Taibany, Wael F.; Kourakis, Ioannis; Qamar, A.

2015-02-01

A semirelativistic fluid model is employed to describe the nonlinear amplitude modulation of low-frequency (ionic scale) electrostatic waves in an unmagnetized electron-positron-ion plasma. Electrons and positrons are assumed to be degenerated and inertialess, whereas ions are warm and classical. A multiscale perturbation method is used to derive a nonlinear Schrödinger equation for the envelope amplitude, based on which the occurrence of modulational instability is investigated in detail. Various types of localized ion acoustic excitations are shown to exist, in the form of either bright type envelope solitons (envelope pulses) or dark-type envelope solitons (voids, holes). The plasma configurational parameters (namely, the relativistic degeneracy parameter, the positron concentration, and the ionic temperature) are shown to affect the conditions for modulational instability significantly, in fact modifying the associated threshold as well as the instability growth rate. In particular, the relativistic degeneracy parameter leads to an enhancement of the modulational instability mechanism. Furthermore, the effect of different relevant plasma parameters on the characteristics (amplitude, width) of these envelope solitary structures is also presented in detail. Finally, the occurrence of extreme amplitude excitation (rogue waves) is also discussed briefly. Our results aim at elucidating the formation and dynamics of nonlinear electrostatic excitations in superdense astrophysical regimes.

Quantum model for electro-optical amplitude modulation.

PubMed

Capmany, José; Fernández-Pousa, Carlos R

2010-11-22

We present a quantum model for electro-optic amplitude modulation, which is built upon quantum models of the main photonic components that constitute the modulator, that is, the guided-wave beamsplitter and the electro-optic phase modulator and accounts for all the different available modulator structures. General models are developed both for single and dual drive configurations and specific results are obtained for the most common configurations currently employed. Finally, the operation with two-photon input for the control of phase-modulated photons and the important topic of multicarrier modulation are also addressed.

Spectro-temporal modulation masking patterns reveal frequency selectivity.

PubMed

Oetjen, Arne; Verhey, Jesko L

2015-02-01

The present study investigated the possibility that the human auditory system demonstrates frequency selectivity to spectro-temporal amplitude modulations. Threshold modulation depth for detecting sinusoidal spectro-temporal modulations was measured using a generalized masked threshold pattern paradigm with narrowband masker modulations. Four target spectro-temporal modulations were examined, differing in their temporal and spectral modulation frequencies: a temporal modulation of -8, 8, or 16 Hz combined with a spectral modulation of 1 cycle/octave and a temporal modulation of 4 Hz combined with a spectral modulation of 0.5 cycles/octave. The temporal center frequencies of the masker modulation ranged from 0.25 to 4 times the target temporal modulation. The spectral masker-modulation center-frequencies were 0, 0.5, 1, 1.5, and 2 times the target spectral modulation. For all target modulations, the pattern of average thresholds for the eight normal-hearing listeners was consistent with the hypothesis of a spectro-temporal modulation filter. Such a pattern of modulation-frequency sensitivity was predicted on the basis of psychoacoustical data for purely temporal amplitude modulations and purely spectral amplitude modulations. An analysis of separability indicates that, for the present data set, selectivity in the spectro-temporal modulation domain can be described by a combination of a purely spectral and a purely temporal modulation filter function.

Amplitude modulation of sound from wind turbines under various meteorological conditions.

PubMed

Larsson, Conny; Öhlund, Olof

2014-01-01

Wind turbine (WT) sound annoys some people even though the sound levels are relatively low. This could be because of the amplitude modulated "swishing" characteristic of the turbine sound, which is not taken into account by standard procedures for measuring average sound levels. Studies of sound immission from WTs were conducted continually between 19 August 2011 and 19 August 2012 at two sites in Sweden. A method for quantifying the degree and strength of amplitude modulation (AM) is introduced here. The method reveals that AM at the immission points occur under specific meteorological conditions. For WT sound immission, the wind direction and sound speed gradient are crucial for the occurrence of AM. Interference between two or more WTs could probably enhance AM. The mechanisms by which WT sound is amplitude modulated are not fully understood.

Inspection system calibration methods

DOEpatents

Deason, Vance A.; Telschow, Kenneth L.

2004-12-28

An inspection system calibration method includes producing two sideband signals of a first wavefront; interfering the two sideband signals in a photorefractive material, producing an output signal therefrom having a frequency and a magnitude; and producing a phase modulated operational signal having a frequency different from the output signal frequency, a magnitude, and a phase modulation amplitude. The method includes determining a ratio of the operational signal magnitude to the output signal magnitude, determining a ratio of a 1st order Bessel function of the operational signal phase modulation amplitude to a 0th order Bessel function of the operational signal phase modulation amplitude, and comparing the magnitude ratio to the Bessel function ratio.

Planetary period modulations of Saturn's magnetotail current sheet during northern spring: Observations and modeling

NASA Astrophysics Data System (ADS)

Cowley, S. W. H.; Provan, G.

2017-06-01

We study Cassini magnetic field observations at Saturn on a sequence of passes through the near-equatorial magnetotail during 2015, focusing on dual modulation of the plasma/current sheet associated with northern and southern planetary period oscillations (PPOs). Previous study of inner magnetosphere PPOs during this northern spring interval showed that the southern system amplitude was generally half that of the northern during the first part of the year to late August, after which the southern amplitude weakened to less than one-fifth that of the northern. We examine four sequential tail passes in the earlier interval, during which prominent PPO-related tail field modulations were observed, with relative (beat) phases of the two PPO systems being near in phase, antiphase, and two opposite near-quadrature conditions. We find that the radial field displayed opposite "sawtooth" asymmetry modulations under opposite near-quadrature conditions, related to previous findings under equinoctial conditions with near-equal northern and southern PPO amplitudes, while modulations were near symmetric for in-phase and antiphase conditions, but with larger radial field modulations for in-phase and larger colatitudinal field modulations for antiphase. A simple physical mathematical model of dual modulation is developed, which provides reasonable correspondence with these data using one set of current sheet parameters while varying only the relative PPO phases, thus demonstrating that dual modulation can be discerned and modeled even when the northern and southern amplitudes differ by a factor of 2. No such effects were consistently discerned during the later interval when the amplitude ratio was >5.

Heterotypic Sam-Sam association between Odin-Sam1 and Arap3-Sam: binding affinity and structural insights.

PubMed

Mercurio, Flavia A; Marasco, Daniela; Pirone, Luciano; Scognamiglio, Pasqualina L; Pedone, Emilia M; Pellecchia, Maurizio; Leone, Marilisa

2013-01-02

Arap3 is a phosphatidylinositol 3 kinase effector protein that plays a role as GTPase activator (GAP) for Arf6 and RhoA. Arap3 contains a sterile alpha motif (Sam) domain that has high sequence homology with the Sam domain of the EphA2-receptor (EphA2-Sam). Both Arap3-Sam and EphA2-Sam are able to associate with the Sam domain of the lipid phosphatase Ship2 (Ship2-Sam). Recently, we reported a novel interaction between the first Sam domain of Odin (Odin-Sam1), a protein belonging to the ANKS (ANKyrin repeat and Sam domain containing) family, and EphA2-Sam. In our latest work, we applied NMR spectroscopy, surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) to characterize the association between Arap3-Sam and Odin-Sam1. We show that these two Sam domains interact with low micromolar affinity. Moreover, by means of molecular docking techniques, supported by NMR data, we demonstrate that Odin-Sam1 and Arap3-Sam might bind with a topology that is common to several Sam-Sam complexes. The revealed structural details form the basis for the design of potential peptide antagonists that could be used as chemical tools to investigate functional aspects related to heterotypic Arap3-Sam associations. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical Quantification of Harmonic Acoustic Radiation Force Excitation in a Tissue-Mimicking Phantom.

PubMed

Suomi, Visa; Edwards, David; Cleveland, Robin

2015-12-01

Optical tracking was used to characterize acoustic radiation force-induced displacements in a tissue-mimicking phantom. Amplitude-modulated 3.3-MHz ultrasound was used to induce acoustic radiation force in the phantom, which was embedded with 10-μm microspheres that were tracked using a microscope objective and high-speed camera. For sine and square amplitude modulation, the harmonic components of the fundamental and second and third harmonic frequencies were measured. The displacement amplitudes were found to increase linearly with acoustic radiation force up to 10 μm, with sine modulation having 19.5% lower peak-to-peak amplitude values than square modulation. Square modulation produced almost no second harmonic, but energy was present in the third harmonic. For the sine modulation, energy was present in the second harmonic and low energy in the third harmonic. A finite-element model was used to simulate the deformation and was both qualitatively and quantitatively in agreement with the measurements. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Spatial Light Modulators and Applications. 1988 Technical Digest Series, Volume 8

DTIC Science & Technology

1988-06-01

presence of an applied field but without run- ning gratings; then the fringes are allowed to move, with a velocity that optimizes self- in which F0...Laboratories. The optimization of an MQW modulator for both phase and amplitude modulation is reported, along with preliminary structural N.J design for a...Canyon Road Malibu, California 90265 ABSTRACT The optimization of an MOW modulator for both phase and amplitude modulation is reported,along with

Cascaded Amplitude Modulations in Sound Texture Perception

PubMed Central

McWalter, Richard; Dau, Torsten

2017-01-01

Sound textures, such as crackling fire or chirping crickets, represent a broad class of sounds defined by their homogeneous temporal structure. It has been suggested that the perception of texture is mediated by time-averaged summary statistics measured from early auditory representations. In this study, we investigated the perception of sound textures that contain rhythmic structure, specifically second-order amplitude modulations that arise from the interaction of different modulation rates, previously described as “beating” in the envelope-frequency domain. We developed an auditory texture model that utilizes a cascade of modulation filterbanks that capture the structure of simple rhythmic patterns. The model was examined in a series of psychophysical listening experiments using synthetic sound textures—stimuli generated using time-averaged statistics measured from real-world textures. In a texture identification task, our results indicated that second-order amplitude modulation sensitivity enhanced recognition. Next, we examined the contribution of the second-order modulation analysis in a preference task, where the proposed auditory texture model was preferred over a range of model deviants that lacked second-order modulation rate sensitivity. Lastly, the discriminability of textures that included second-order amplitude modulations appeared to be perceived using a time-averaging process. Overall, our results demonstrate that the inclusion of second-order modulation analysis generates improvements in the perceived quality of synthetic textures compared to the first-order modulation analysis considered in previous approaches. PMID:28955191

Cascaded Amplitude Modulations in Sound Texture Perception.

PubMed

McWalter, Richard; Dau, Torsten

2017-01-01

Sound textures, such as crackling fire or chirping crickets, represent a broad class of sounds defined by their homogeneous temporal structure. It has been suggested that the perception of texture is mediated by time-averaged summary statistics measured from early auditory representations. In this study, we investigated the perception of sound textures that contain rhythmic structure, specifically second-order amplitude modulations that arise from the interaction of different modulation rates, previously described as "beating" in the envelope-frequency domain. We developed an auditory texture model that utilizes a cascade of modulation filterbanks that capture the structure of simple rhythmic patterns. The model was examined in a series of psychophysical listening experiments using synthetic sound textures-stimuli generated using time-averaged statistics measured from real-world textures. In a texture identification task, our results indicated that second-order amplitude modulation sensitivity enhanced recognition. Next, we examined the contribution of the second-order modulation analysis in a preference task, where the proposed auditory texture model was preferred over a range of model deviants that lacked second-order modulation rate sensitivity. Lastly, the discriminability of textures that included second-order amplitude modulations appeared to be perceived using a time-averaging process. Overall, our results demonstrate that the inclusion of second-order modulation analysis generates improvements in the perceived quality of synthetic textures compared to the first-order modulation analysis considered in previous approaches.

Obliquity Modulation of the Incoming Solar Radiation

NASA Technical Reports Server (NTRS)

Liu, Han-Shou; Smith, David E. (Technical Monitor)

2001-01-01

Based on a basic principle of orbital resonance, we have identified a huge deficit of solar radiation induced by the combined amplitude and frequency modulation of the Earth's obliquity as possibly the causal mechanism for ice age glaciation. Including this modulation effect on solar radiation, we have performed model simulations of climate change for the past 2 million years. Simulation results show that: (1) For the past 1 million years, temperature fluctuation cycles were dominated by a 100-Kyr period due to amplitude-frequency resonance effect of the obliquity; (2) From 2 to 1 million years ago, the amplitude-frequency interactions. of the obliquity were so weak that they were not able to stimulate a resonance effect on solar radiation; (3) Amplitude and frequency modulation analysis on solar radiation provides a series of resonance in the incoming solar radiation which may shift the glaciation cycles from 41-Kyr to 100-Kyr about 0.9 million years ago. These results are in good agreement with the marine and continental paleoclimate records. Thus, the proposed climate response to the combined amplitude and frequency modulation of the Earth's obliquity may be the key to understanding the glaciation puzzles in paleoclimatology.

Polarization-sensitive optical coherence tomography measurements with different phase modulation amplitude when using continuous polarization modulation

NASA Astrophysics Data System (ADS)

Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

2012-01-01

We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated on measurements of a three-quarter waveplate and an equine tendon sample by a fiber-based swept-source CPM-PS-OCT system.

Thouless dephasing and amplitude modulation of Aharonov-Bohm oscillations in mesoscopic InGaAs/InAlAs interferometers

NASA Astrophysics Data System (ADS)

Heremans, J. J.; Ren, S. L.; Zhang, Yao; Gaspe, C. K.; Vijeyaragunathan, S.; Mishima, T. D.; Santos, M. B.

2014-03-01

Aharonov-Bohm oscillations in the low-temperature magnetoresistance of mesoscopic interferometric rings are investigated for their dependence on bias current and temperature, and to explore origins of the observed amplitude modulation in magnetic field. Single-ring interferometers of radius 650 nm and lithographic arm width 300 nm were fabricated on a high-mobility high-density InGaAs/InAlAs heterostructure. The rings show interference oscillations over a wide range of magnetic fields, with amplitudes subject to modulation with applied magnetic field. The quantum phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by comparative study of the amplitude. The variation of the amplitude with bias current and temperature shows the existence of a critical excitation energy consistent with the Thouless energy for quantum phase smearing. Autocorrelation and Fourier analysis are used to determine the quasi-period of the amplitude modulation, which is found to be consistent with an origin in the magnetic flux threading the finite width of the interferometer arms, changing the mesoscopic realization of the system. Supported by DOE DE-FG02-08ER46532 (VT) and NSF DMR-0520550 (UoO).

Influence of the May Southern annular mode on the South China Sea summer monsoon

NASA Astrophysics Data System (ADS)

Liu, Ting; Li, Jianping; Li, YanJie; Zhao, Sen; Zheng, Fei; Zheng, Jiayu; Yao, Zhixiong

2017-07-01

The possible impact of the May Southern Hemisphere (SH) annular mode (SAM) on the following South China Sea (SCS) summer monsoon (SCSSM) is examined. A close inverse relationship between the two is revealed in the observations. The simultaneous South Pacific dipole (SPD), a dipole-like sea surface temperature anomaly pattern in the South Pacific, acts as the "oceanic bridge" to preserve the May SAM signal and prolong it into June-September. Observational evidence and numerical simulations both demonstrate that the SPD communicates its large thermal inertia signal to the atmosphere, regulating the Southern Pacific Subtropical Jet (SPSJ) variability over eastern Australia. Corresponding to the adjustment of circulation associated with the SPSJ is a prominent tripolar cross-Pacific teleconnection pattern stretching from the SH middle-high latitudes into the NH East Asia coastal region, referred to as the South-North Pacific (SNP) teleconnection pattern. Wave ray tracing analysis manifests that the SNP acts as the "atmospheric bridge" to propagate the related wave energy across the equator and into the Maritime Continent and SCS monsoon region, modulating the vertical motion and middle-lower tropospheric flows, and favoring the out-of-phase variation of the SCSSM. Therefore, the "coupled oceanic-atmospheric bridge" process and the related Rossby wave energy transmission are possible mechanisms for the significant influence of the May SAM on the variability of the following SCSSM. Therefore, the May SAM provides a fresh insight into the prediction of the SCSSM from the perspective of the SH high latitudes.

Tribological properties of self-assembled monolayers of catecholic imidazolium and the spin-coated films of ionic liquids.

PubMed

Liu, Jianxi; Li, Jinlong; Yu, Bo; Ma, Baodong; Zhu, Yangwen; Song, Xinwang; Cao, Xulong; Yang, Wu; Zhou, Feng

2011-09-20

A novel compound of an imidazolium type of ionic liquid (IL) containing a biomimetic catecholic functional group normally seen in mussel adhesive proteins was synthesized. The IL can be immobilized on a silicon surface and a variety of other engineering material surfaces via the catecholic anchor, allowing the tribological protection of these substrates for engineering applications. The surface wetting and adhesive properties and the tribological property of the synthesized self-assembled monolayers (SAMs) are successfully modulated by altering the counteranions. The chemical composition and wettability of the IL SAMs were characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurements. The adhesive and friction forces were measured with an atomic force microscope (AFM) on the nanometer scale. IL composite films were prepared by spin coating thin IL films on top of the SAMs. The macrotribological properties of these IL composite films were investigated with a pin-on-disk tribometer. The results indicate that the presence of IL SAMs on a surface can improve the wettability of spin-coated ionic liquids and thus the film quality and the tribological properties. These films registered a reduced friction coefficient and a significantly enhanced durability and load-carrying capacity. The tribological properties of the composite films are better than those of pure IL films because the presence of the monolayers improves the adhesion and compatibility of spin-coated IL films with substrates. © 2011 American Chemical Society

Sam37 is crucial for formation of the mitochondrial TOM-SAM supercomplex, thereby promoting β-barrel biogenesis.

PubMed

Wenz, Lena-Sophie; Ellenrieder, Lars; Qiu, Jian; Bohnert, Maria; Zufall, Nicole; van der Laan, Martin; Pfanner, Nikolaus; Wiedemann, Nils; Becker, Thomas

2015-09-28

Biogenesis of mitochondrial β-barrel proteins requires two preprotein translocases, the general translocase of the outer membrane (TOM) and the sorting and assembly machinery (SAM). TOM and SAM form a supercomplex that promotes transfer of β-barrel precursors. The SAM core complex contains the channel protein Sam50, which cooperates with Sam35 in precursor recognition, and the peripheral membrane protein Sam37. The molecular function of Sam37 has been unknown. We report that Sam37 is crucial for formation of the TOM-SAM supercomplex. Sam37 interacts with the receptor domain of Tom22 on the cytosolic side of the mitochondrial outer membrane and links TOM and SAM complexes. Sam37 thus promotes efficient transfer of β-barrel precursors to the SAM complex. We conclude that Sam37 functions as a coupling factor of the translocase supercomplex of the mitochondrial outer membrane. © 2015 Wenz et al.

A New Look at the Blazhko Effect in RR Lyrae Stars with High-Quality Data from the MACHO Project

NASA Astrophysics Data System (ADS)

Kurtz, D. W.; Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Griest, K.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Stubbs, C. W.; Sutherland, W.; Tomaney, A.; Welch, D. L.; MACHO Collaboration

We present the first results of the analysis of 22 Blazhko stars. We find: 1) Blazhko RRab stars that are nearly pure amplitude modulators; 2) Blazhko RRab stars that have both amplitude and phase modulation; 3) A Blazhko RRab star that has an abrupt period change; 4) Proof of the Blazhko effect in RRc stars. Our data show the character of the amplitude and phase modulations of the light curves over the Blazhko cycles far better than has been previously possible.

The influence of pitch and loudness changes on the acoustics of vocal tremor.

PubMed

Dromey, Christopher; Warrick, Paul; Irish, Jonathan

2002-10-01

The effect of tremor on phonation is to modulate an otherwise steady sound source in its amplitude, fundamental frequency, or both. The severity of untreated vocal tremor has been reported to change under certain conditions that may be related to muscle tension. In order to better understand the phenomenon of vocal tremor, its acoustic properties were examined as individuals volitionally altered their pitch and loudness. These voice conditions were anticipated to alter the tension of the intrinsic laryngeal muscles. The voices of 10 individuals with a diagnosis of vocal tremor were recorded before participating in a longitudinal treatment study. They produced vowels at low and high pitch and loudness levels as well as in a comfortable voice condition. Acoustic analyses quantified the amplitude and frequency modulations of the speakers' voices across the various conditions. Individual speakers varied in the way the pitch and loudness changes affected their tremor, but the following statistically significant effects for the speakers as a group were observed: Higher pitch phonation was associated with a more rapid rate for both amplitude and frequency modulations. Amplitude modulation become faster for louder phonation. Low-pitched phonotion led to decreases in the extent of amplitude tremor. Varying pitch led to dramatic changes in the phase relationship between amplitude and frequency modulation in some of the speakers, whereas this effect was not apparent in other speakers.

Error compensation of IQ modulator using two-dimensional DFT

NASA Astrophysics Data System (ADS)

Ohshima, Takashi; Maesaka, Hirokazu; Matsubara, Shinichi; Otake, Yuji

2016-06-01

It is important to precisely set and keep the phase and amplitude of an rf signal in the accelerating cavity of modern accelerators, such as an X-ray Free Electron Laser (XFEL) linac. In these accelerators an acceleration rf signal is generated or detected by an In-phase and Quadrature (IQ) modulator, or a demodulator. If there are any deviations of the phase and the amplitude from the ideal values, crosstalk between the phase and the amplitude of the output signal of the IQ modulator or the demodulator arises. This causes instability of the feedback controls that simultaneously stabilize both the rf phase and the amplitude. To compensate for such deviations, we developed a novel compensation method using a two-dimensional Discrete Fourier Transform (DFT). Because the observed deviations of the phase and amplitude of an IQ modulator involve sinusoidal and polynomial behaviors on the phase angle and the amplitude of the rf vector, respectively, the DFT calculation with these basis functions makes a good approximation with a small number of compensation coefficients. Also, we can suppress high-frequency noise components arising when we measure the deviation data. These characteristics have advantages compared to a Look Up Table (LUT) compensation method. The LUT method usually demands many compensation elements, such as about 300, that are not easy to treat. We applied the DFT compensation method to the output rf signal of a C-band IQ modulator at SACLA, which is an XFEL facility in Japan. The amplitude deviation of the IQ modulator after the DFT compensation was reduced from 15.0% at the peak to less than 0.2% at the peak for an amplitude control range of from 0.1 V to 0.9 V (1.0 V full scale) and for a phase control range from 0 degree to 360 degrees. The number of compensation coefficients is 60, which is smaller than that of the LUT method, and is easy to treat and maintain.

First results from SAM-FP: Fabry-Perot observations with ground-layer adaptive optics - the structure and kinematics of the core of 30 Doradus

NASA Astrophysics Data System (ADS)

Mendes de Oliveira, C.; Amram, P.; Quint, Bruno C.; Torres-Flores, S.; Barbá, R.; Andrade, D.

2017-08-01

The aim of this paper is to present the first data set obtained with SOAR Adaptive Module-Fabry-Parot (SAM-FP), a Fabry-Perot instrument mounted inside the SOAR telescope Adaptive-Optics Module. This is the only existing imaging Fabry-Perot interferometer using laser-assisted ground-layer adaptive optics. SAM-FP was used to observe the ionized gas, traced by Hα, in the centre of the 30 Doradus starburst (the Tarantula Nebula) in the Large Magellanic Cloud, with high spatial (˜0.6 arcsec, or 0.15 pc) and spectral (R ≃ 11 200) resolution. Radial velocity, velocity dispersion and monochromatic maps were derived. The region displays a mix of narrow, σ ˜ 20 km s-1 profiles and multiple broader profiles with σ ˜ 70-80 km s-1, indicating the complex nature of the nebula kinematics. A comparison with previously obtained VLT/FLAMES spectroscopy demonstrates that the data agree well in the regions of overlap, but the Fabry-Perot data are superior in spatial coverage. A preliminary analysis of the observations finds a new expanding bubble south of R136, with a projected radius of r = 5.6 pc and an expansion velocity of 29 ± 4 km s-1. In addition, the first-time detailed kinematic maps derived here for several complexes and filaments of 30 Doradus allow identification of kinematically independent structures. These data exemplify the power of the combination of a high-order Fabry-Perot with a wide-field imager (3 × 3 arcmin2 GLAO-corrected field of view) for high-resolution spatial and spectral studies. In particular, SAM-FP data cubes are highly advantageous over multifibre or long-slit data sets for nebula structure studies and to search for small-scale bubbles, given their greatly improved spatial coverage. For reference, this paper also presents two appendices with detailed descriptions of the usage of Fabry-Perot devices, including formulae and explanations for understanding Fabry-Perot observations.

Effect of noise on modulation amplitude and phase in frequency-domain diffusive imaging

PubMed Central

Kupinski, Matthew A.

2012-01-01

Abstract. We theoretically investigate the effect of noise on frequency-domain heterodyne and/or homodyne measurements of intensity-modulated beams propagating through diffusive media, such as a photon density wave. We assumed that the attenuated amplitude and delayed phase are estimated by taking the Fourier transform of the noisy, modulated output data. We show that the estimated amplitude and phase are biased when the number of output photons is small. We also show that the use of image intensifiers for photon amplification in heterodyne or homodyne measurements increases the amount of biases. Especially, it turns out that the biased estimation is independent of AC-dependent noise in sinusoidal heterodyne or homodyne outputs. Finally, the developed theory indicates that the previously known variance model of modulation amplitude and phase is not valid in low light situations. Monte-Carlo simulations with varied numbers of input photons verify our theoretical trends of the bias. PMID:22352660

Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case.

PubMed

Ebeling, Daniel; Solares, Santiago D

2013-01-01

We present an overview of the bimodal amplitude-frequency-modulation (AM-FM) imaging mode of atomic force microscopy (AFM), whereby the fundamental eigenmode is driven by using the amplitude-modulation technique (AM-AFM) while a higher eigenmode is driven by using either the constant-excitation or the constant-amplitude variant of the frequency-modulation (FM-AFM) technique. We also offer a comparison to the original bimodal AFM method, in which the higher eigenmode is driven with constant frequency and constant excitation amplitude. General as well as particular characteristics of the different driving schemes are highlighted from theoretical and experimental points of view, revealing the advantages and disadvantages of each. This study provides information and guidelines that can be useful in selecting the most appropriate operation mode to characterize different samples in the most efficient and reliable way.

Enhanced modulation rates via field modulation in spin torque nano-oscillators

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

Purbawati, A.; Garcia-Sanchez, F.; Buda-Prejbeanu, L. D.

Spin Transfer Nano-Oscillators (STNOs) are promising candidates for telecommunications applications due to their frequency tuning capabilities via either a dc current or an applied field. This frequency tuning is of interest for Frequency Shift Keying concepts to be used in wireless communication schemes or in read head applications. For these technological applications, one important parameter is the characterization of the maximum achievable rate at which an STNO can respond to a modulating signal, such as current or field. Previous studies of in-plane magnetized STNOs on frequency modulation via an rf current revealed that the maximum achievable rate is limited bymore » the amplitude relaxation rate Γ{sub p}, which gives the time scale over which amplitude fluctuations are damped out. This might be a limitation for applications. Here, we demonstrate via numerical simulation that application of an additional rf field is an alternative way for modulation of the in-plane magnetized STNO configuration, which has the advantage that frequency modulation is not limited by the amplitude relaxation rate, so that higher modulation rates above GHz are achievable. This occurs when the modulating rf field is oriented along the easy axis (longitudinal rf field). Tilting the direction of the modulating rf field in-plane and perpendicularly with respect to the easy axis (transverse rf field), the modulation is again limited by the amplitude relaxation rate similar to the response observed in current modulation.« less

How are interannual modes of variability IOD, ENSO, SAM, AMO excited by natural and anthropogenic forcing?

NASA Astrophysics Data System (ADS)

Maher, Nicola; Marotzke, Jochem

2017-04-01

Natural climate variability is found in observations, paleo-proxies, and climate models. Such climate variability can be intrinsic internal variability or externally forced, for example by changes in greenhouse gases or large volcanic eruptions. There are still questions concerning how external forcing, both natural (e.g., volcanic eruptions and solar variability) and anthropogenic (e.g., greenhouse gases and ozone) may excite both interannual modes of variability in the climate system. This project aims to address some of these problems, utilising the large ensemble of the MPI-ESM-LR climate model. In this study we investigate the statistics of four modes of interannual variability, namely the North Atlantic Oscillation (NAO), the Indian Ocean Dipole (IOD), the Southern Annular Mode (SAM) and the El Niño Southern Oscillation (ENSO). Using the 100-member ensemble of MPI-ESM-LR the statistical properties of these modes (amplitude and standard deviation) can be assessed over time. Here we compare the properties in the pre-industrial control run, historical run and future scenarios (RCP4.5, RCP2.6) and present preliminary results.

A Solid-State Modulator for High Speed Kickers

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

Watson, J A; Cook, E G; Chen, Y J

2001-06-11

An all solid-state modulator with multi-pulse burst capability, very fast rise and fall times, pulse width agility, and amplitude modulation capability for use with high-speed beam kickers has been designed and tested at LLNL. The modulator uses multiple solid-state modules stacked in an inductive-adder configuration. It provides a nominal 18kV pulse with {+-} 10% amplitude modulation on the order of several MHz, rise times on the order of 10nS, and can be configured for either positive or negative polarity. The presentation will include measured performance data.

Electrically-driven pure amplitude and frequency modulation in a quantum cascade laser.

PubMed

Shehzad, Atif; Brochard, Pierre; Matthey, Renaud; Blaser, Stéphane; Gresch, Tobias; Maulini, Richard; Muller, Antoine; Südmeyer, Thomas; Schilt, Stéphane

2018-04-30

We present pure amplitude modulation (AM) and frequency modulation (FM) achieved electrically in a quantum cascade laser (QCL) equipped with an integrated resistive heater (IH). The QCL output power scales linearly with the current applied to the active region (AR), but decreases with the IH current, while the emission frequency decreases with both currents. Hence, a simultaneous modulation applied to the current of the AR and IH sections with a proper relative amplitude and phase can suppress the AM, resulting in a pure FM, or vice-versa. The adequate modulation parameters depend on the applied modulation frequency. Therefore, they were first determined from the individual measurements of the AM and FM transfer functions obtained for a modulation applied to the current of the AR or IH section, respectively. By optimizing the parameters of the two modulations, we demonstrate a reduction of the spurious AM or FM by almost two orders of magnitude at characteristic frequencies of 1 and 10 kHz compared to the use of the AR current only.

Conformational order of n-dodecanethiol and n-dodecaneselenol monolayers on polycrystalline copper investigated by PM-IRRAS and SFG spectroscopy

NASA Astrophysics Data System (ADS)

Fonder, G.; Cecchet, F.; Peremans, A.; Thiry, P. A.; Delhalle, J.; Mekhalif, Z.

2009-08-01

Self-assembled monolayers (SAMs) of n-dodecanethiol (C 12H 25SH) and n-dodecaneselenol (C 12H 25SeH) on polycrystalline copper have been elaborated with the purpose of achieving densely packed and crystalline-like assemblies. By combining the surface sensitivity of polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation spectroscopy (SFG), the effect of the self-assembly time (15 min, 30 min, 1 h, 2 h and 24 h) on the formation of n-dodecanethiol and n-dodecaneselenol monolayers on untreated and electrochemically reduced polycrystalline copper has been investigated. On electrochemically reduced copper, PM-IRRAS spectroscopy shows that both molecules are able to form well organized layers. SFG spectroscopy indicates that the C 12H 25SeH SAMs are slightly better ordered than those achieved with C 12H 25SH. On untreated copper, the two molecules lead to different film organizations. Both PM-IRRAS and SFG indicate that C 12H 25SH SAMs are of the same film quality as those obtained on electrochemically reduced copper. On the contrary, C 12H 25SeH monolayers are invariably poorly organized at the molecular level.

Immobilization of Protein A on SAMs for the elaboration of immunosensors.

PubMed

Briand, Elisabeth; Salmain, Michèle; Compère, Chantal; Pradier, Claire-Marie

2006-12-01

Binary mixtures of 11-mercaptoundecanoic acid (MUA) and other thiols of various lengths and terminal functions were chemisorbed on gold-coated surfaces via S-Au bonds to form mixed self-assembled monolayers (SAMs). Several values of the mole fraction of MUA in the thiol mixtures were tested and the structure and composition of the resulted thin films were characterized by X-ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). The results made it clear that co-adsorption of MUA with thiols of similar chain length led to well-ordered monolayers whereas the co-adsorption of MUA with shorter thiols yielded less crystalline-like thin films, but with more reactive carboxylic acid terminal groups. This criterion appeared decisive for efficient covalent binding of Staphylococcus aureus Protein A (PrA), a protein that displays high affinity for the constant fragment (Fc) of antibodies of the IgG type from various mammal species. The ability of immobilized Protein A to recognize and bind a model IgG appeared to be optimal for the mixed SAM of MUA and the short-chain, omega-hydroxythiol 6-mercaptohexanol in the proportion 1-3.

Linkages between the South and East Asian summer monsoons: a review and revisit

NASA Astrophysics Data System (ADS)

Ha, Kyung-Ja; Seo, Ye-Won; Lee, June-Yi; Kripalani, R. H.; Yun, Kyung-Sook

2017-07-01

The relationship between the South Asia monsoon (SAM) and the East Asia monsoon (EAM) possibly modulated by both external forcings and internal dynamics has been a long-standing and controversial issue in climate sciences. This study reviews their linkages as revealed in modern records and model simulations during the past, present and future, and provides a comprehensive explanation of the key mechanisms controlling the diversity of the SAM-EAM relationship. Particular attention is paid to several external forcings that modulate the relationship, including El Niño and Southern Oscillation, Indian Ocean Dipole mode (IODM), boreal summer teleconnections, and Eurasian snow extent on intraseasonal to interdecadal timescales. The major focus is placed on two integral views of the inter-connection between the two monsoon systems: one is the positive inter-correlation, which is associated with decaying El Niño and developing Indian Ocean sea surface temperature (SST) warming anomalies; the other is the negative inter-correlation, resulting from developing El Niño and western Pacific SST cooling. The IODM mode also has a delayed impact on the negative connection by modulating Eurasian snow cover. The observed evidence reveals that the recent intensification of the negative relationship is attributable to the strengthening of the zonal SST gradient along the Indian Ocean, western Pacific, and eastern Pacific. Analysis of experiments in the fifth phase of the Coupled Model Intercomparison Project further indicates a possibility for the negative linkage to be further enhanced under anthropogenic global warming with considerable interdecadal modulation in mid and late twenty-first century.

Auditory fear conditioning modifies steady-state evoked potentials in the rat inferior colliculus.

PubMed

Lockmann, André Luiz Vieira; Mourão, Flávio Afonso Gonçalves; Moraes, Marcio Flávio Dutra

2017-08-01

The rat inferior colliculus (IC) is a major midbrain relay for ascending inputs from the auditory brain stem and has been suggested to play a key role in the processing of aversive sounds. Previous studies have demonstrated that auditory fear conditioning (AFC) potentiates transient responses to brief tones in the IC, but it remains unexplored whether AFC modifies responses to sustained periodic acoustic stimulation-a type of response called the steady-state evoked potential (SSEP). Here we used an amplitude-modulated tone-a 10-kHz tone with a sinusoidal amplitude modulation of 53.7 Hz-as the conditioning stimulus (CS) in an AFC protocol (5 CSs per day in 3 consecutive days) while recording local field potentials (LFPs) from the IC. In the preconditioning session ( day 1 ), the CS elicited prominent 53.7-Hz SSEPs. In the training session ( day 2 ), foot shocks occurred at the end of each CS (paired group) or randomized in the inter-CS interval (unpaired group). In the test session ( day 3 ), SSEPs markedly differed from preconditioning in the paired group: in the first two trials the phase to which the SSEP coupled to the CS amplitude envelope shifted ~90°; in the last two trials the SSEP power and the coherence of SSEP with the CS amplitude envelope increased. LFP power decreased in frequency bands other than 53.7 Hz. In the unpaired group, SSEPs did not change in the test compared with preconditioning. Our results show that AFC causes dissociated changes in the phase and power of SSEP in the IC. NEW & NOTEWORTHY Local field potential oscillations in the inferior colliculus follow the amplitude envelope of an amplitude-modulated tone, originating a neural response called the steady-state evoked potential. We show that auditory fear conditioning of an amplitude-modulated tone modifies two parameters of the steady-state evoked potentials in the inferior colliculus: first the phase to which the evoked oscillation couples to the amplitude-modulated tone shifts; subsequently, the evoked oscillation power increases along with its coherence with the amplitude-modulated tone. Copyright © 2017 the American Physiological Society.

Module 1: Text Versions | State, Local, and Tribal Governments | NREL

Science.gov Websites

local government solar project portal. The link is there on the right, and you can see a screen shot , when we talk about SAM, we're really talking about combining two different things together - one is a power, biomass, combustion power, and solar water heating - so, that's one that comes along with these

Educational Software for Interactive Training of Students on the Theme "Mutual Intersecting of Pyramids and Prisms in Axonometry"

ERIC Educational Resources Information Center

Karaibryamov, Samet; Tsareva, Bistra; Zlatanov, Boyan

2012-01-01

This work acquaints with the program Sam for interactive computer training of students on the theme "Mutual intersecting of pyramids and prisms in axonometry". The program containing three modules--teacher, student and autopilot--allows for briefest time to teach and study the whole variety of the tasks on this theme. A classification of…

Striding Towards Better Physical Therapy

NASA Technical Reports Server (NTRS)

2003-01-01

This paper presents a discussion on a new rehabilitative device that promises to improve physical therapy for patients working to regain the ability to walk after facing traumatic injuries or a degenerative illness. Produced by Enduro Medical Technology, of East Hartford, Connecticut, the Secure Ambulation Module (S.A.M.) creates a stable and secure environment for patients as they stand during ambulation therapy.

Multiple polymer architectures of human Polyhomeotic homolog 3 (PHC3) SAM

PubMed Central

Nanyes, David R.; Junco, Sarah E.; Taylor, Alexander B.; Robinson, Angela K.; Patterson, Nicolle L.; Shivarajpur, Ambika; Halloran, Jonathan; Hale, Seth M.; Kaur, Yogeet; Hart, P. John; Kim, Chongwoo A.

2014-01-01

The self-association of sterile alpha motifs (SAMs) into a helical polymer architecture is a critical functional component of many different and diverse array of proteins. For the Drosophila Polycomb group (PcG) protein Polyhomeotic (Ph), its SAM polymerization serves as the structural foundation to cluster multiple PcG complexes, helping to maintain a silenced chromatin state. Ph SAM shares 64% sequence identity with its human ortholog, PHC3 SAM, and both SAMs polymerize. However, in the context of their larger protein regions, PHC3 SAM forms longer polymers compared to Ph SAM. Motivated to establish the precise structural basis for the differences, if any, between Ph and PHC3 SAM, we determined the crystal structure of the PHC3 SAM polymer. PHC3 SAM utilizes the same SAM-SAM interaction as the Ph SAM six-fold repeat polymer. Yet, PHC3 SAM polymerizes utilizing just five SAMs per turn of the helical polymer rather than the typical six per turn observed for all SAM polymers reported to date. Structural analysis suggested that malleability of the PHC3 SAM would allow formation of not just the five-fold repeat structure but possibly others. Indeed, a second PHC3 SAM polymer in a different crystal form forms a six-fold repeat polymer. These results suggest that the polymers formed by PHC3 SAM, and likely others, are quite dynamic. The functional consequence of the variable PHC3 SAM polymers may be to create different chromatin architectures. PMID:25044168

Antisocial behaviour and psychopathy: Uncovering the externalizing link in the P3 modulation.

PubMed

Pasion, Rita; Fernandes, Carina; Pereira, Mariana R; Barbosa, Fernando

2017-03-22

In 2009, Gao and Raine's meta-analysis analysed P3 modulation over the antisocial spectrum. However, some questions remained open regarding the P3 modulation patterns across impulsive and violent manifestations of antisocial behaviour, phenotypic components of psychopathy, and P3 components. A systematic review of 36 studies was conducted (N=3514) to extend previous results and to address these unresolved questions. A clear link between decreased P3 amplitude and antisocial behaviour was found. In psychopathy, dimensional approaches become more informative than taxonomic models. Distinct etiological pathways of psychopathy were evidenced in cognitive tasks: impulsive-antisocial psychopathic traits mainly predicted blunted P3 amplitude, while interpersonal-affective psychopathic traits explained enhanced P3 amplitude. Supporting the low fear hypothesis, the interpersonal-affective traits were associated with reduced P3 amplitude in emotional-affective learning tasks. From the accumulated knowledge we propose a framework of P3 amplitude modulation that uncovers the externalizing link between psychopathy and antisocial behaviour. However, the main hypotheses are exploratory and call for more data before stablishing robust conclusions. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Sam Domain of EphA2 Receptor and its Relevance to Cancer: A Novel Challenge for Drug Discovery?

PubMed

Mercurio, Flavia A; Leone, Marilisa

2016-01-01

Eph receptors play important functions in developmental processes and diseases and among them EphA2 is well known for its controversial role in cancer. Drug discovery strategies are mainly centered on EphA2 extracellular ligand-binding domain however, the receptor also contains a largely unexplored cytosolic Sam (Sterile alpha motif) domain at the C-terminus. EphA2-Sam binds the Sam domain from the lipid phosphatase Ship2 and the first Sam domain of Odin. Sam-Sam interactions may be important to regulate ligand-induced receptor endocytosis and degradation i.e., processes that could be engaged against tumor malignancy. We critically analyzed literature related to a) Eph receptors with particular emphasis on EphA2 and its role in cancer, b) Sam domains, c) heterotypic Sam-Sam interactions involving EphA2-Sam. While literature data indicate that binding of EphA2-Sam to Ship2-Sam should largely generate pro-oncogenic effects in cancer cells, the correlation between EphA2- Sam/Odin-Sam1 complex and the disease is unclear. Recently a few linear peptides encompassing binding interfaces from either Ship2-Sam and Odin-Sam1 have been characterized but failed to efficiently block heterotypic Sam-Sam interactions involving EphA2-Sam due to the lack of a native like fold. Molecule antagonists of heterotypic EphA2-Sam associations could work as potential anticancer agents or be implemented as tools to further clarify receptor functions and eventually validate its role as a novel target in the field of anti-cancer drug discovery. Due to the failure of linear peptides there is a crucial need for novel approaches, based on cyclic or helical molecules, to target Sam-Sam interfaces.

Extending single molecule fluorescence observation time by amplitude-modulated excitation

PubMed Central

Kisley, Lydia; Chang, Wei-Shun; Cooper, David; Mansur, Andrea P; Landes, Christy F

2014-01-01

We present a hardware-based method that can improve single molecule fluorophore observation time by up to 1500% and super-localization by 47% for the experimental conditions used. The excitation was modulated using an acousto-optic modulator (AOM) synchronized to the data acquisition and inherent data conversion time of the detector. The observation time and precision in super-localization of four commonly used fluorophores were compared under modulated and traditional continuous excitation, including direct total internal reflectance excitation of Alexa 555 and Cy3, non-radiative Förster resonance energy transfer (FRET) excited Cy5, and direct epi-fluorescence wide field excitation of Rhodamine 6G. The proposed amplitude-modulated excitation does not perturb the chemical makeup of the system or sacrifice signal and is compatible with multiple types of fluorophores. Amplitude-modulated excitation has practical applications for any fluorescent study utilizing an instrumental setup with time-delayed detectors. PMID:24587894

Interpretation of frequency modulation atomic force microscopy in terms of fractional calculus

NASA Astrophysics Data System (ADS)

Sader, John E.; Jarvis, Suzanne P.

2004-07-01

It is widely recognized that small amplitude frequency modulation atomic force microscopy probes the derivative of the interaction force between tip and sample. For large amplitudes, however, such a physical connection is currently lacking, although it has been observed that the frequency shift presents a quantity intermediate to the interaction force and energy for certain force laws. Here we prove that these observations are a universal property of large amplitude frequency modulation atomic force microscopy, by establishing that the frequency shift is proportional to the half-fractional integral of the force, regardless of the force law. This finding indicates that frequency modulation atomic force microscopy can be interpreted as a fractional differential operator, where the order of the derivative/integral is dictated by the oscillation amplitude. We also establish that the measured frequency shift varies systematically from a probe of the force gradient for small oscillation amplitudes, through to the measurement of a quantity intermediate to the force and energy (the half-fractional integral of the force) for large oscillation amplitudes. This has significant implications to measurement sensitivity, since integrating the force will smooth its behavior, while differentiating it will enhance variations. This highlights the importance in choice of oscillation amplitude when wishing to optimize the sensitivity of force spectroscopy measurements to short-range interactions and consequently imaging with the highest possible resolution.

Shock compression and flash-heating of molecular adsorbates on the picosecond time scale

NASA Astrophysics Data System (ADS)

Berg, Christopher Michael

An ultrafast nonlinear coherent laser spectroscopy termed broadband multiplex vibrational sum-frequency generation (SFG) with nonresonant suppression was employed to monitor vibrational transitions of molecular adsorbates on metallic substrates during laser-driven shock compression and flash-heating. Adsorbates were in the form of well-ordered self-assembled monolayers (SAMs) and included molecular explosive simulants, such as nitroaromatics, and long chain-length alkanethiols. Based on reflectance measurements of the metallic substrates, femtosecond flash-heating pulses were capable of producing large-amplitude temperature jumps with DeltaT = 500 K. Laser-driven shock compression of SAMs produced pressures up to 2 GPa, where 1 GPa ≈ 1 x 104 atm. Shock pressures were estimated via comparison with frequency shifts observed in the monolayer vibrational transitions during hydrostatic pressure measurements in a SiC anvil cell. Molecular dynamics during flash-heating and shock loading were probed with vibrational SFG spectroscopy with picosecond temporal resolution and sub-nanometer spatial resolution. Flash-heating studies of 4-nitrobenzenethiolate (NBT) on Au provided insight into effects from hot-electron excitation of the molecular adsorbates at early pump-probe delay times. At longer delay times, effects from the excitation of SAM lattice modes and lower-energy NBT vibrations were shown. In addition, flash-heating studies of alkanethiolates demonstrated chain disordering behaviors as well as interface thermal conductances across the Au-SAM junction, which was of specific interest within the context of molecular electronics. Shock compression studies of molecular explosive simulants, such as 4-nitrobenzoate (NBA), demonstrated the proficiency of this technique to observe shock-induced molecular dynamics, in this case orientational dynamics, on the picosecond time scale. Results validated the utilization of these refined shock loading techniques to probe the shock initiation or first bond-breaking reactions in molecular explosives such as delta-HMX: a necessary study for the development of safer and more effective energetic materials.

Multilevel recording of complex amplitude data pages in a holographic data storage system using digital holography.

PubMed

Nobukawa, Teruyoshi; Nomura, Takanori

2016-09-05

A holographic data storage system using digital holography is proposed to record and retrieve multilevel complex amplitude data pages. Digital holographic techniques are capable of modulating and detecting complex amplitude distribution using current electronic devices. These techniques allow the development of a simple, compact, and stable holographic storage system that mainly consists of a single phase-only spatial light modulator and an image sensor. As a proof-of-principle experiment, complex amplitude data pages with binary amplitude and four-level phase are recorded and retrieved. Experimental results show the feasibility of the proposed holographic data storage system.

Glimpsing Speech in the Presence of Nonsimultaneous Amplitude Modulations from a Competing Talker: Effect of Modulation Rate, Age, and Hearing Loss

ERIC Educational Resources Information Center

Fogerty, Daniel; Ahlstrom, Jayne B.; Bologna, William J.; Dubno, Judy R.

2016-01-01

Purpose: This study investigated how listeners process acoustic cues preserved during sentences interrupted by nonsimultaneous noise that was amplitude modulated by a competing talker. Method: Younger adults with normal hearing and older adults with normal or impaired hearing listened to sentences with consonants or vowels replaced with noise…

A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements

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

Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland

2016-07-15

Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signalsmore » with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.« less

Functional significance of the emotion-related late positive potential

PubMed Central

Brown, Stephen B. R. E.; van Steenbergen, Henk; Band, Guido P. H.; de Rover, Mischa; Nieuwenhuis, Sander

2012-01-01

The late positive potential (LPP) is an event-related potential (ERP) component over visual cortical areas that is modulated by the emotional intensity of a stimulus. However, the functional significance of this neural modulation remains elusive. We conducted two experiments in which we studied the relation between LPP amplitude, subsequent perceptual sensitivity to a non-emotional stimulus (Experiment 1) and visual cortical excitability, as reflected by P1/N1 components evoked by this stimulus (Experiment 2). During the LPP modulation elicited by unpleasant stimuli, perceptual sensitivity was not affected. In contrast, we found some evidence for a decreased N1 amplitude during the LPP modulation, a decreased P1 amplitude on trials with a relatively large LPP, and consistent negative (but non-significant) across-subject correlations between the magnitudes of the LPP modulation and corresponding changes in d-prime or P1/N1 amplitude. The results provide preliminary evidence that the LPP reflects a global inhibition of activity in visual cortex, resulting in the selective survival of activity associated with the processing of the emotional stimulus. PMID:22375117

FIBER OPTICS. ACOUSTOOPTICS: Amplitude and phase nonreciprocities of acoustooptic modulators for counterpropagating light waves under the Bragg diffraction conditions

NASA Astrophysics Data System (ADS)

Veselovskaya, T. V.; Klochan, E. L.; Lariontsev, E. G.; Parfenov, S. V.; Shelaev, A. N.

1990-07-01

Theoretical and experimental investigations demonstrated that in real acoustooptic modulators the diffraction of light by a standing ultrasonic wave may give rise to both phase and amplitude nonreciprocities of counterpropagating light waves. Analytic expressions are derived for the dependences of these nonreciprocities on the parameters of the traveling component of an ultrasonic wave in a modulator. It is shown that when the angle of incidence of light on a modulator deviates from the Bragg angle, the phase nonreciprocity may be suppressed, but the amplitude nonreciprocity becomes maximal and its sign is governed by the law of deviation of the angle of incidence from the Bragg angle. A diffraction acoustooptic feedback makes it possible not only to achieve mode locking with an acoustooptic modulator utilizing a traveling ultrasonic wave, but also to control the magnitude and sign of amplitude-frequency nonreciprocities. It is reported that an acoustooptic feedback can be used to generate self-pumping waves in a solid-state mode-locked ring laser and thus stabilize bidirectional lasing in a wide range of the frequency offset between the counterpropagating waves.

Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids

PubMed Central

Jaafar, Miriam; Cuenca, Mariano; Melcher, John; Raman, Arvind

2012-01-01

Summary We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode. PMID:22563531

Integrated optic vector-matrix multiplier

DOEpatents

Watts, Michael R [Albuquerque, NM

2011-09-27

A vector-matrix multiplier is disclosed which uses N different wavelengths of light that are modulated with amplitudes representing elements of an N.times.1 vector and combined to form an input wavelength-division multiplexed (WDM) light stream. The input WDM light stream is split into N streamlets from which each wavelength of the light is individually coupled out and modulated for a second time using an input signal representing elements of an M.times.N matrix, and is then coupled into an output waveguide for each streamlet to form an output WDM light stream which is detected to generate a product of the vector and matrix. The vector-matrix multiplier can be formed as an integrated optical circuit using either waveguide amplitude modulators or ring resonator amplitude modulators.

Human neuromagnetic steady-state responses to amplitude-modulated tones, speech, and music.

PubMed

Lamminmäki, Satu; Parkkonen, Lauri; Hari, Riitta

2014-01-01

Auditory steady-state responses that can be elicited by various periodic sounds inform about subcortical and early cortical auditory processing. Steady-state responses to amplitude-modulated pure tones have been used to scrutinize binaural interaction by frequency-tagging the two ears' inputs at different frequencies. Unlike pure tones, speech and music are physically very complex, as they include many frequency components, pauses, and large temporal variations. To examine the utility of magnetoencephalographic (MEG) steady-state fields (SSFs) in the study of early cortical processing of complex natural sounds, the authors tested the extent to which amplitude-modulated speech and music can elicit reliable SSFs. MEG responses were recorded to 90-s-long binaural tones, speech, and music, amplitude-modulated at 41.1 Hz at four different depths (25, 50, 75, and 100%). The subjects were 11 healthy, normal-hearing adults. MEG signals were averaged in phase with the modulation frequency, and the sources of the resulting SSFs were modeled by current dipoles. After the MEG recording, intelligibility of the speech, musical quality of the music stimuli, naturalness of music and speech stimuli, and the perceived deterioration caused by the modulation were evaluated on visual analog scales. The perceived quality of the stimuli decreased as a function of increasing modulation depth, more strongly for music than speech; yet, all subjects considered the speech intelligible even at the 100% modulation. SSFs were the strongest to tones and the weakest to speech stimuli; the amplitudes increased with increasing modulation depth for all stimuli. SSFs to tones were reliably detectable at all modulation depths (in all subjects in the right hemisphere, in 9 subjects in the left hemisphere) and to music stimuli at 50 to 100% depths, whereas speech usually elicited clear SSFs only at 100% depth.The hemispheric balance of SSFs was toward the right hemisphere for tones and speech, whereas SSFs to music showed no lateralization. In addition, the right lateralization of SSFs to the speech stimuli decreased with decreasing modulation depth. The results showed that SSFs can be reliably measured to amplitude-modulated natural sounds, with slightly different hemispheric lateralization for different carrier sounds. With speech stimuli, modulation at 100% depth is required, whereas for music the 75% or even 50% modulation depths provide a reasonable compromise between the signal-to-noise ratio of SSFs and sound quality or perceptual requirements. SSF recordings thus seem feasible for assessing the early cortical processing of natural sounds.

Phasic action of the tensor muscle modulates the calling song in cicadas

PubMed

Fonseca; Hennig

1996-01-01

The effect of tensor muscle contraction on sound production by the tymbal was investigated in three species of cicadas (Tettigetta josei, Tettigetta argentata and Tympanistalna gastrica). All species showed a strict time correlation between the activity of the tymbal motoneurone and the discharge of motor units in the tensor nerve during the calling song. Lesion of the tensor nerve abolished the amplitude modulation of the calling song, but this modulation was restored by electrical stimulation of the tensor nerve or by mechanically pushing the tensor sclerite. Electrical stimulation of the tensor nerve at frequencies higher than 30­40 Hz changed the sound amplitude. In Tett. josei and Tett. argentata there was a gradual increase in sound amplitude with increasing frequency of tensor nerve stimulation, while in Tymp. gastrica there was a sudden reduction in sound amplitude at stimulation frequencies higher than 30 Hz. This contrasting effect in Tymp. gastrica was due to a bistable tymbal frame. Changes in sound pulse amplitude were positively correlated with changes in the time lag measured from tymbal motoneurone stimulation to the sound pulse. The tensor muscle acted phasically because electrical stimulation of the tensor nerve during a time window (0­10 ms) before electrical stimulation of the tymbal motoneurone was most effective in eliciting amplitude modulations. In all species, the tensor muscle action visibly changed the shape of the tymbal. Despite the opposite effects of the tensor muscle on sound pulse amplitude observed between Tettigetta and Tympanistalna species, the tensor muscle of both acts by modulating the shape of the tymbal, which changes the force required for the tymbal muscle to buckle the tymbal.

Amplitude Modulator Chassis

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

Erbert, G

2009-09-01

The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 psmore » apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.« less

Discriminating Simulated Vocal Tremor Source Using Amplitude Modulation Spectra

PubMed Central

Carbonell, Kathy M.; Lester, Rosemary A.; Story, Brad H.; Lotto, Andrew J.

2014-01-01

Objectives/Hypothesis Sources of vocal tremor are difficult to categorize perceptually and acoustically. This paper describes a preliminary attempt to discriminate vocal tremor sources through the use of spectral measures of the amplitude envelope. The hypothesis is that different vocal tremor sources are associated with distinct patterns of acoustic amplitude modulations. Study Design Statistical categorization methods (discriminant function analysis) were used to discriminate signals from simulated vocal tremor with different sources using only acoustic measures derived from the amplitude envelopes. Methods Simulations of vocal tremor were created by modulating parameters of a vocal fold model corresponding to oscillations of respiratory driving pressure (respiratory tremor), degree of vocal fold adduction (adductory tremor) and fundamental frequency of vocal fold vibration (F0 tremor). The acoustic measures were based on spectral analyses of the amplitude envelope computed across the entire signal and within select frequency bands. Results The signals could be categorized (with accuracy well above chance) in terms of the simulated tremor source using only measures of the amplitude envelope spectrum even when multiple sources of tremor were included. Conclusions These results supply initial support for an amplitude-envelope based approach to identify the source of vocal tremor and provide further evidence for the rich information about talker characteristics present in the temporal structure of the amplitude envelope. PMID:25532813

Numerical study of turbulent channel flow perturbed by spanwise topographic heterogeneity: Amplitude and frequency modulation within low- and high-momentum pathways

NASA Astrophysics Data System (ADS)

Awasthi, Ankit; Anderson, William

2018-04-01

We have studied the effects of topographically driven secondary flows on inner-outer interaction in turbulent channel flow. Recent studies have revealed that large-scale motions in the logarithmic region impose an amplitude and frequency modulation on the dynamics of small-scale structures near the wall. This led to development of a predictive model for near-wall dynamics, which has practical relevance for large-eddy simulations. Existing work on amplitude modulation has focused on smooth-wall flows; however, Anderson [J. Fluid Mech. 789, 567 (2016), 10.1017/jfm.2015.744] addressed the problem of rough-wall turbulent channel flow in which the correlation profiles for amplitude modulation showed trends similar to those reported by Mathis et al. [Phys. Fluids 21, 111703 (2009), 10.1063/1.3267726]. For the present study, we considered flow over surfaces with a prominent spanwise heterogeneity, such that domain-scale turbulent secondary flows in the form of counter-rotating vortices are sustained within the flow. (We also show results for flow over a homogeneous roughness, which serves as a benchmark against the spanwise-perturbed cases.) The vortices are anchored to the topography such that prominent upwelling and downwelling occur above the low and high roughness, respectively. We have quantified the extent to which such secondary flows disrupt the distribution of spectral density across constituent wavelengths throughout the depth of the flow, which has direct implications for the existence of amplitude and frequency modulation. We find that the distinct outer peak associated with large-scale motions—the "modulators"—is preserved within the upwelling zone but vanishes in the downwelling zone. Within the downwelling zones, structures are steeper and shorter. Single- and two-point correlations for inner-outer amplitude and frequency modulation demonstrate insensitivity to resolution across cases. We also show a pronounced crossover between the single- and two-point correlations, a product of modulation quantification based upon Parseval's theorem (i.e., spectral density, but not the wavelength at which energy resides, defines the strength of modulation).

MO-F-16A-03: AAPM Online Learning Support of New ABR MOC Requirements

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

Bloch, C; Ogburn, J; Woodward, M

2014-06-15

In 2002 the American Board of Radiology (ABR) discontinued issuing lifetime board certification. After that time diplomates received a timelimited certificate and must participate in the Maintenance of Certification (MOC) program in order to maintain their certification. Initially certificates were issued with a 10 year expiration period and the MOC had requirements to be met over that 10 year period. The goal was to demonstrate continuous maintenance of clinical competency, however some diplomates were attempting to fulfill most or all of the requirements near the end of the 10 year period. This failed to meet the continuous aspect of themore » goal and so the ABR changed to a sliding 3-year window. This was done to recognize that not every year would be the same, but that diplomates should be able to maintain a reasonable average over any 3 year period.A second significant change occurred in 2013. The initial requirements included 20 selfassessment modules (SAMs) over the original 10 year term. SAMs are a special type of continuing education (CE) credit that were an addition to the 250 standard CE credits required over the 10 year period. In 2013, however, the new requirement is 75 CE credits over the previous 3 years, of which 25 must include self-assessment. Effectively this raised the self-assessment requirement from 20 in 10 years to 25 in 3 years. Previously SAMs were an interactive presentation available in limited quantities at live meetings. However, the new requirement is not for SAMs but CE-SA which includes SAMs, but also includes the online quizzes provided at the AAPM online learning center. All credits earned at the AAPM online learning center fulfill the ABR SA requirement.This talk will be an interactive demonstration of the AAPM online learning center along with a discussion of the MOC requirements.« less

Improving the resolution in proton-detected through-space heteronuclear multiple quantum correlation NMR spectroscopy.

PubMed

Shen, Ming; Trébosc, J; Lafon, O; Pourpoint, F; Hu, Bingwen; Chen, Qun; Amoureux, J-P

2014-08-01

Connectivities and proximities between protons and low-gamma nuclei can be probed in solid-state NMR spectroscopy using two-dimensional (2D) proton-detected heteronuclear correlation, through Heteronuclear Multiple Quantum Correlation (HMQC) pulse sequence. The indirect detection via protons dramatically enhances the sensitivity. However, the spectra are often broadened along the indirect F1 dimension by the decay of heteronuclear multiple-quantum coherences under the strong (1)H-(1)H dipolar couplings. This work presents a systematic comparison of the performances of various decoupling schemes during the indirect t1 evolution period of dipolar-mediated HMQC (D-HMQC) experiment. We demonstrate that (1)H-(1)H dipolar decoupling sequences during t1, such as symmetry-based schemes, phase-modulated Lee-Goldburg (PMLG) and Decoupling Using Mind-Boggling Optimization (DUMBO), provide better resolution than continuous wave (1)H irradiation. We also report that high resolution requires the preservation of (1)H isotropic chemical shifts during the decoupling sequences. When observing indirectly broad spectra presenting numerous spinning sidebands, the D-HMQC sequence must be fully rotor-synchronized owing to the rotor-synchronized indirect sampling and dipolar recoupling sequence employed. In this case, we propose a solution to reduce artefact sidebands caused by the modulation of window delays before and after the decoupling application during the t1 period. Moreover, we show that (1)H-(1)H dipolar decoupling sequence using Smooth Amplitude Modulation (SAM) minimizes the t1-noise. The performances of the various decoupling schemes are assessed via numerical simulations and compared to 2D (1)H-{(13)C} D-HMQC experiments on [U-(13)C]-L-histidine⋅HCl⋅H2O at various magnetic fields and Magic Angle spinning (MAS) frequencies. Great resolution and sensitivity enhancements resulting from decoupling during t1 period enable the detection of heteronuclear correlation between aliphatic protons and ammonium (14)N sites in L-histidine⋅HCl⋅H2O. Copyright © 2014 Elsevier Inc. All rights reserved.

Modeling of Pulses Having Arbitrary Amplitude and Frequency Modulation.

DTIC Science & Technology

1980-03-01

function, fi(t), has been discussed in great detail in Section II. The linearized amplitude modulation, 1(t), is given by: (IV-6) vo A +h( -) TO’ # where "A...10. LCDR Francis Martin Lunney, USN 6143 Gatsby Green Columbia, Maryland 21045 149

Effects of auditory selective attention on chirp evoked auditory steady state responses.

PubMed

Bohr, Andreas; Bernarding, Corinna; Strauss, Daniel J; Corona-Strauss, Farah I

2011-01-01

Auditory steady state responses (ASSRs) are frequently used to assess auditory function. Recently, the interest in effects of attention on ASSRs has increased. In this paper, we investigated for the first time possible effects of attention on AS-SRs evoked by amplitude modulated and frequency modulated chirps paradigms. Different paradigms were designed using chirps with low and high frequency content, and the stimulation was presented in a monaural and dichotic modality. A total of 10 young subjects participated in the study, they were instructed to ignore the stimuli and after a second repetition they had to detect a deviant stimulus. In the time domain analysis, we found enhanced amplitudes for the attended conditions. Furthermore, we noticed higher amplitudes values for the condition using frequency modulated low frequency chirps evoked by a monaural stimulation. The most difference between attended and unattended modality was exhibited at the dichotic case of the amplitude modulated condition using chirps with low frequency content.

Four-amplitude shift keying-single sideband millimeter-wave signal generation with frequency sextupling based on optical phase modulation

NASA Astrophysics Data System (ADS)

Wu, Peng; Ma, Jianxin

2017-03-01

We have proposed and demonstrated a scheme to generate a frequency-sextupling amplitude shift keying (ASK)-single sideband optical millimeter (mm)-wave signal with high dispersion tolerance based on an optical phase modulator (PM) by ably using the-4th-order and +2nd-order sidebands of the optical modulation. The ASK radio frequency signal, superposed by a local oscillator with the same frequency, modulates the lightwave via an optical PM with proper voltage amplitudes, the +2nd-order sideband carries the ASK signal with a constant slope while the -4th-order sideband maintains constant amplitude. These two sidebands can be abstracted by a wavelength selective switch to form a dual-tone optical mm-wave with only one tone carrying the ASK signal. As only one tone bears the ASK signal while the other tone is unmodulated, the generated dual-tone optical mm-wave signal has high dispersion tolerance.

Stability, resolution, and ultra-low wear amplitude modulation atomic force microscopy of DNA: Small amplitude small set-point imaging

NASA Astrophysics Data System (ADS)

Santos, Sergio; Barcons, Victor; Christenson, Hugo K.; Billingsley, Daniel J.; Bonass, William A.; Font, Josep; Thomson, Neil H.

2013-08-01

A way to operate fundamental mode amplitude modulation atomic force microscopy is introduced which optimizes stability and resolution for a given tip size and shows negligible tip wear over extended time periods (˜24 h). In small amplitude small set-point (SASS) imaging, the cantilever oscillates with sub-nanometer amplitudes in the proximity of the sample, without the requirement of using large drive forces, as the dynamics smoothly lead the tip to the surface through the water layer. SASS is demonstrated on single molecules of double-stranded DNA in ambient conditions where sharp silicon tips (R ˜ 2-5 nm) can resolve the right-handed double helix.

DNA adenine methylation of sams1 gene in symbiont-bearing Amoeba proteus.

PubMed

Jeon, Taeck J

2008-10-01

The expression of amoeba sams genes is switched from sams1 to sams2 when amoebae are infected with Legionella jeonii. To elucidate the mechanism for the inactivation of host sams1 gene by endosymbiotic bacteria, methylation states of the sams1 gene of D and xD amoebae was compared in this study. The sams1 gene of amoebae was methylated at an internal adenine residue of GATC site in symbiont-bearing xD amoebae but not in symbiont-free D amoebae, suggesting that the modification might have caused the inactivation of sams1 in xD amoebae. The sams1 gene of xD amoebae was inactivated at the transcriptional level. Analysis of DNA showed that adenine residues in L. jeonii sams were also methylated, implying that L. jeonii bacteria belong to a Dam methylase-positive strain. In addition, both SAM and Met appeared to act as negative regulators for the expression of sams1 whereas the expression of sams2 was not affected in amoebae.

Atomic-level insights into metabolite recognition and specificity of the SAM-II riboswitch.

PubMed

Doshi, Urmi; Kelley, Jennifer M; Hamelberg, Donald

2012-02-01

Although S-adenosylhomocysteine (SAH), a metabolic by-product of S-adenosylmethionine (SAM), differs from SAM only by a single methyl group and an overall positive charge, SAH binds the SAM-II riboswitch with more than 1000-fold less affinity than SAM. Using atomistic molecular dynamics simulations, we investigated the molecular basis of such high selectivity in ligand recognition by SAM-II riboswitch. The biosynthesis of SAM exclusively generates the (S,S) stereoisomer, and (S,S)-SAM can spontaneously convert to the (R,S) form. We, therefore, also examined the effects of (R,S)-SAM binding to SAM-II and its potential biological function. We find that the unfavorable loss in entropy in SAM-II binding is greater for (S,S)- and (R,S)-SAM than SAH, which is compensated by stabilizing electrostatic interactions with the riboswitch. The positively charged sulfonium moiety on SAM acts as the crucial anchor point responsible for the formation of key ionic interactions as it fits favorably in the negatively charged binding pocket. In contrast, SAH, with its lone pair of electrons on the sulfur, experiences repulsion in the binding pocket of SAM-II and is enthalpically destabilized. In the presence of SAH, similar to the unbound riboswitch, the pseudoknot structure of SAM-II is not completely formed, thus exposing the Shine-Dalgarno sequence. Unlike SAM, this may further facilitate ribosomal assembly and translation initiation. Our analysis of the conformational ensemble sampled by SAM-II in the absence of ligands and when bound to SAM or SAH reveals that ligand binding follows a combination of conformational selection and induced-fit mechanisms.

Calcium-dependent control of temporal processing in an auditory interneuron: a computational analysis

PubMed Central

Ponnath, Abhilash

2010-01-01

Sensitivity to acoustic amplitude modulation in crickets differs between species and depends on carrier frequency (e.g., calling song vs. bat-ultrasound bands). Using computational tools, we explore how Ca2+-dependent mechanisms underlying selective attention can contribute to such differences in amplitude modulation sensitivity. For omega neuron 1 (ON1), selective attention is mediated by Ca2+-dependent feedback: [Ca2+]internal increases with excitation, activating a Ca2+-dependent after-hyperpolarizing current. We propose that Ca2+ removal rate and the size of the after-hyperpolarizing current can determine ON1’s temporal modulation transfer function (TMTF). This is tested using a conductance-based simulation calibrated to responses in vivo. The model shows that parameter values that simulate responses to single pulses are sufficient in simulating responses to modulated stimuli: no special modulation-sensitive mechanisms are necessary, as high and low-pass portions of the TMTF are due to Ca2+-dependent spike frequency adaptation and post-synaptic potential depression, respectively. Furthermore, variance in the two biophysical parameters is sufficient to produce TMTFs of varying bandwidth, shifting amplitude modulation sensitivity like that in different species and in response to different carrier frequencies. Thus, the hypothesis that the size of after-hyperpolarizing current and the rate of Ca2+ removal can affect amplitude modulation sensitivity is computationally validated. PMID:20559640

Instrument Reflections and Scene Amplitude Modulation in a Polychromatic Microwave Quadrature Interferometer

NASA Technical Reports Server (NTRS)

Dobson, Chris C.; Jones, Jonathan E.; Chavers, Greg

2003-01-01

A polychromatic microwave quadrature interferometer has been characterized using several laboratory plasmas. Reflections between the transmitter and the receiver have been observed, and the effects of including reflection terms in the data reduction equation have been examined. An error analysis which includes the reflections, modulation of the scene beam amplitude by the plasma, and simultaneous measurements at two frequencies has been applied to the empirical database, and the results are summarized. For reflection amplitudes around 1096, the reflection terms were found to reduce the calculated error bars for electron density measurements by about a factor of 2. The impact of amplitude modulation is also quantified. In the complete analysis, the mean error bar for high- density measurements is 7.596, and the mean phase shift error for low-density measurements is 1.2". .

Interface engineering of semiconductor/dielectric heterojunctions toward functional organic thin-film transistors.

PubMed

Zhang, Hongtao; Guo, Xuefeng; Hui, Jingshu; Hu, Shuxin; Xu, Wei; Zhu, Daoben

2011-11-09

Interface modification is an effective and promising route for developing functional organic field-effect transistors (OFETs). In this context, however, researchers have not created a reliable method of functionalizing the interfaces existing in OFETs, although this has been crucial for the technological development of high-performance CMOS circuits. Here, we demonstrate a novel approach that enables us to reversibly photocontrol the carrier density at the interface by using photochromic spiropyran (SP) self-assembled monolayers (SAMs) sandwiched between active semiconductors and gate insulators. Reversible changes in dipole moment of SPs in SAMs triggered by lights with different wavelengths produce two distinct built-in electric fields on the OFET that can modulate the channel conductance and consequently threshold voltage values, thus leading to a low-cost noninvasive memory device. This concept of interface functionalization offers attractive new prospects for the development of organic electronic devices with tailored electronic and other properties.

75 FR 56147 - Notice of Permits Issued Under the Antarctic Conservation Act of 1978

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-15

... received. Permits were issued on September 9, 2010 to: Sam Feola Permit No. 2011-009. Sam Feola Permit No. 2011-010. Sam Feola Permit No. 2011-011. Sam Feola Permit No. 2011-012. Sam Feola Permit No. 2011-013. Sam Feola Permit No. 2011-014. Sam Feola Permit No. 2011-015. Nadene G. Kennedy, Permit Officer. [FR...

Neural coding of sound envelope in reverberant environments.

PubMed

Slama, Michaël C C; Delgutte, Bertrand

2015-03-11

Speech reception depends critically on temporal modulations in the amplitude envelope of the speech signal. Reverberation encountered in everyday environments can substantially attenuate these modulations. To assess the effect of reverberation on the neural coding of amplitude envelope, we recorded from single units in the inferior colliculus (IC) of unanesthetized rabbit using sinusoidally amplitude modulated (AM) broadband noise stimuli presented in simulated anechoic and reverberant environments. Although reverberation degraded both rate and temporal coding of AM in IC neurons, in most neurons, the degradation in temporal coding was smaller than the AM attenuation in the stimulus. This compensation could largely be accounted for by the compressive shape of the modulation input-output function (MIOF), which describes the nonlinear transformation of modulation depth from acoustic stimuli into neural responses. Additionally, in a subset of neurons, the temporal coding of AM was better for reverberant stimuli than for anechoic stimuli having the same modulation depth at the ear. Using hybrid anechoic stimuli that selectively possess certain properties of reverberant sounds, we show that this reverberant advantage is not caused by envelope distortion, static interaural decorrelation, or spectral coloration. Overall, our results suggest that the auditory system may possess dual mechanisms that make the coding of amplitude envelope relatively robust in reverberation: one general mechanism operating for all stimuli with small modulation depths, and another mechanism dependent on very specific properties of reverberant stimuli, possibly the periodic fluctuations in interaural correlation at the modulation frequency. Copyright © 2015 the authors 0270-6474/15/354452-17$15.00/0.

Atomic-level insights into metabolite recognition and specificity of the SAM-II riboswitch

PubMed Central

Doshi, Urmi; Kelley, Jennifer M.; Hamelberg, Donald

2012-01-01

Although S-adenosylhomocysteine (SAH), a metabolic by-product of S-adenosylmethionine (SAM), differs from SAM only by a single methyl group and an overall positive charge, SAH binds the SAM-II riboswitch with more than 1000-fold less affinity than SAM. Using atomistic molecular dynamics simulations, we investigated the molecular basis of such high selectivity in ligand recognition by SAM-II riboswitch. The biosynthesis of SAM exclusively generates the (S,S) stereoisomer, and (S,S)-SAM can spontaneously convert to the (R,S) form. We, therefore, also examined the effects of (R,S)-SAM binding to SAM-II and its potential biological function. We find that the unfavorable loss in entropy in SAM-II binding is greater for (S,S)- and (R,S)-SAM than SAH, which is compensated by stabilizing electrostatic interactions with the riboswitch. The positively charged sulfonium moiety on SAM acts as the crucial anchor point responsible for the formation of key ionic interactions as it fits favorably in the negatively charged binding pocket. In contrast, SAH, with its lone pair of electrons on the sulfur, experiences repulsion in the binding pocket of SAM-II and is enthalpically destabilized. In the presence of SAH, similar to the unbound riboswitch, the pseudoknot structure of SAM-II is not completely formed, thus exposing the Shine-Dalgarno sequence. Unlike SAM, this may further facilitate ribosomal assembly and translation initiation. Our analysis of the conformational ensemble sampled by SAM-II in the absence of ligands and when bound to SAM or SAH reveals that ligand binding follows a combination of conformational selection and induced-fit mechanisms. PMID:22194311

Some considerations on the vibrational environment of the DSC-DCMIX1 experiment onboard ISS

NASA Astrophysics Data System (ADS)

Jurado, R.; Gavaldà, Jna.; Simón, M. J.; Pallarés, J.; Laverón-Simavilla, A.; Ruiz, X.; Shevtsova, V.

2016-12-01

The present work attempts to characterize the accelerometric environment of the DSC-DCMIX1 thermodiffusion experiment carried out in the International Space Station, from November 7th 2011 until January 16th 2012. Quasi-steady and vibrational/transient data coming from MAMS and SAMS2 sensors have been downloaded from the database of the PIMS NASA website. To be as exhaustive as possible, simultaneous digital signals coming from different SAMS2 sensors located in the Destiny and Columbus modules have also been considered. In order to detect orbital adjustments, dockings, undockings, as well as, quiescent periods, when the experiment runs were active, we have used the quasi-steady eight hours averaged (XA, YA and ZA) acceleration functions as well as the eight hours RMS ones. To determine the spectral contents of the different signals the Thomson multitaper and Welch methods have been used. On the other hand, to suppress the high levels of noise always existing in the raw SAMS2 signals, denoising techniques have been preferred for comparative reboostings considerations. Finally, the RMS values for specific 1/3 octave frequency bands showed that the International Space Station vibratory limit requirements have not been totally accomplished during both quiescent periods and strong disturbances, specially in the low frequency range.

VERY LOW FREQUENCY 16 HZ AMPLITUDE MODULATED ELECTROMAGNETIC RADIATION INCREASES CALCIUM EFFLUX FROM THE FROG HEART

EPA Science Inventory

The effects of continuous and amplitude-modulated radiofrequency electromagnetic waves on calcium efflux from 45Ca preloaded frog hearts were examined. rog hearts, electrically stimulated at their natural beating frequency, were exposed for 30 min to 240 MHz radiowaves in a Crawf...

47 CFR 2.1049 - Measurements required: Occupied bandwidth.

Code of Federal Regulations, 2012 CFR

2012-10-01

... monaural operation—when amplitude modulated 85% by a 7,500 Hz input signal. (2) AM broadcast stereophonic... broadcast stereophonic sound transmitters—when the transmitter is modulated with a 15 kHz input signal to... input signal such that its amplitude and symbol rate represent the maximum rated conditions under which...

47 CFR 2.1049 - Measurements required: Occupied bandwidth.

Code of Federal Regulations, 2011 CFR

2011-10-01

... monaural operation—when amplitude modulated 85% by a 7,500 Hz input signal. (2) AM broadcast stereophonic... broadcast stereophonic sound transmitters—when the transmitter is modulated with a 15 kHz input signal to... input signal such that its amplitude and symbol rate represent the maximum rated conditions under which...

47 CFR 2.1049 - Measurements required: Occupied bandwidth.

Code of Federal Regulations, 2013 CFR

2013-10-01

... monaural operation—when amplitude modulated 85% by a 7,500 Hz input signal. (2) AM broadcast stereophonic... broadcast stereophonic sound transmitters—when the transmitter is modulated with a 15 kHz input signal to... input signal such that its amplitude and symbol rate represent the maximum rated conditions under which...

47 CFR 2.1049 - Measurements required: Occupied bandwidth.

Code of Federal Regulations, 2014 CFR

2014-10-01

... monaural operation—when amplitude modulated 85% by a 7,500 Hz input signal. (2) AM broadcast stereophonic... broadcast stereophonic sound transmitters—when the transmitter is modulated with a 15 kHz input signal to... input signal such that its amplitude and symbol rate represent the maximum rated conditions under which...

Liquid jet response to internal modulated ultrasonic radiation pressure and stimulated drop production.

PubMed

Lonzaga, Joel B; Osterhoudt, Curtis F; Thiessen, David B; Marston, Philip L

2007-06-01

Experimental evidence shows that a liquid jet in air is an acoustic waveguide having a cutoff frequency inversely proportional to the jet diameter. Ultrasound applied to the jet supply liquid can propagate within the jet when the acoustic frequency is near to or above the cutoff frequency. Modulated radiation pressure is used to stimulate large amplitude deformations and the breakup of the jet into drops. The jet response to the modulated internal ultrasonic radiation pressure was monitored along the jet using (a) an optical extinction method and (b) images captured by a video camera. The jet profile oscillates at the frequency of the radiation pressure modulation and where the response is small, the amplitude was found to increase in proportion to the square of the acoustic pressure amplitude as previously demonstrated for oscillating drops [P.L. Marston and R.E. Apfel, J. Acoust. Soc. Am. 67, 27-37 (1980)]. Small amplitude deformations initially grow approximately exponentially with axial distance along the jet. Though aspects of the perturbation growth can be approximated from Rayleigh's analysis of the capillary instability, some detailed features of the observed jet response to modulated ultrasound are unexplained neglecting the effects of gravity.

Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds

PubMed Central

Dietz, Mathias; Marquardt, Torsten; Salminen, Nelli H.; McAlpine, David

2013-01-01

The ability to locate the direction of a target sound in a background of competing sources is critical to the survival of many species and important for human communication. Nevertheless, brain mechanisms that provide for such accurate localization abilities remain poorly understood. In particular, it remains unclear how the auditory brain is able to extract reliable spatial information directly from the source when competing sounds and reflections dominate all but the earliest moments of the sound wave reaching each ear. We developed a stimulus mimicking the mutual relationship of sound amplitude and binaural cues, characteristic to reverberant speech. This stimulus, named amplitude modulated binaural beat, allows for a parametric and isolated change of modulation frequency and phase relations. Employing magnetoencephalography and psychoacoustics it is demonstrated that the auditory brain uses binaural information in the stimulus fine structure only during the rising portion of each modulation cycle, rendering spatial information recoverable in an otherwise unlocalizable sound. The data suggest that amplitude modulation provides a means of “glimpsing” low-frequency spatial cues in a manner that benefits listening in noisy or reverberant environments. PMID:23980161

Characterization of sams genes of Amoeba proteus and the endosymbiotic X-bacteria.

PubMed

Jeon, Taeck J; Jeon, Kwang W

2003-01-01

As a result of harboring obligatory bacterial endosymbionts, the xD strain of Amoeba proteus no longer produces its own S-adenosylmethionine synthetase (SAMS). When symbiont-free D amoebae are infected with symbionts (X-bacteria), the amount of amoeba SAMS decreases to a negligible level within four weeks, but about 47% of the SAMS activity, which apparently comes from another source, is still detected. Complete nucleotide sequences of sams genes of D and xD amoebae are presented and show that there are no differences between the two. Long-established xD amoebae contain an intact sams gene and thus the loss of xD amoeba's SAMS is not due to the loss of the gene itself. The open reading frame of the amoeba's sams gene has 1,281 nucleotides, encoding SAMS of 426 amino acids with a mass of 48 kDa and pI of 6.5. The amino acid sequence of amoeba SAMS is longer than the SAMS of other organisms by having an extra internal stretch of 28 amino acids. The 5'-flanking region of amoeba sams contains consensus-binding sites for several transcription factors that are related to the regulation of sams genes in E. coli and yeast. The complete nucleotide sequence of the symbiont's sams gene is also presented. The open reading frame of X-bacteria sams is 1,146 nucleotides long, encoding SAMS of 381 amino acids with a mass of 41 kDa and pI of 6.0. The X-bacteria SAMS has 45% sequence identity with that of A. proteus.

Molecular tailoring of interfaces for thin film on substrate systems

NASA Astrophysics Data System (ADS)

Grady, Martha Elizabeth

Thin film on substrate systems appear most prevalently within the microelectronics industry, which demands that devices operate in smaller and smaller packages with greater reliability. The reliability of these multilayer film systems is strongly influenced by the adhesion of each of the bimaterial interfaces. During use, microelectronic components undergo thermo-mechanical cycling, which induces interfacial delaminations leading to failure of the overall device. The ability to tailor interfacial properties at the molecular level provides a mechanism to improve thin film adhesion, reliability and performance. This dissertation presents the investigation of molecular level control of interface properties in three thin film-substrate systems: photodefinable polyimide films on passivated silicon substrates, self-assembled monolayers at the interface of Au films and dielectric substrates, and mechanochemically active materials on rigid substrates. For all three materials systems, the effect of interfacial modifications on adhesion is assessed using a laser-spallation technique. Laser-induced stress waves are chosen because they dynamically load the thin film interface in a precise, noncontacting manner at high strain rates and are suitable for both weak and strong interfaces. Photodefinable polyimide films are used as dielectrics in flip chip integrated circuit packages to reduce the stress between silicon passivation layers and mold compound. The influence of processing parameters on adhesion is examined for photodefinable polyimide films on silicon (Si) substrates with three different passivation layers: silicon nitride (SiNx), silicon oxynitride (SiOxNy), and the native silicon oxide (SiO2). Interfacial strength increases when films are processed with an exposure step as well as a longer cure cycle. Additionally, the interfacial fracture energy is assessed using a dynamic delamination protocol. The high toughness of this interface (ca. 100 J/m2) makes it difficult to use more conventional interfacial fracture testing techniques. Self-assembled monolayers (SAMs) provide an enabling platform for molecular tailoring of the chemical and physical properties of an interface in an on-demand fashion. The SAM end-group functionality is systematically varied and the corresponding effect on interfacial adhesion between a transfer printed gold (Au) film and a fused silica substrate is measured. SAMs with four different end groups are investigated: methyl, amine, bromine and thiol. In addition to these four end groups, mixed monolayers of increasing molar ratio of thiol to methyl SAMs in solution are investigated. There is a strong dependence of interfacial chemistry on the adhesion strength of Au films. In addition to the chemical functionality of the SAM, surface roughness of the underlying substrate also has a significant impact on the interfacial strength. Thin films of mechanochemically active polymer are subjected to laser-generated, high amplitude acoustic pulses. Stress wave propagation through the film produces large amplitude stresses (>100 MPa) in short time frames (10-20 ns), leading to very high strain-rates (ca. 107-108 s -1). The polymer system, spiropyran (SP)- linked polystyrene (PS), undergoes a force-induced chemical reaction causing fluorescence and color change. Activation of SP is evident via a fluorescence signal in thin films subject to high strain-rates. In contrast, quasi-static loading of bulk SP-linked PS samples failed to result in SP activation. Mechanoresponsive coatings have potential to indicate deformation under shockwave loading conditions. In addition to SP-linked polymer films, the activation of spiropyran interfacial molecules with different side groups is characterized as they adsorb onto a SAM platform with preferential amine terminating chemistry. The reactivity of SP monolayers due to UV irradiation is evaluated by water contact angle goniometry and fluorescence spectroscopy. Side groups on the interfacial spiropyran molecule affect the reactivity and the proximity of neighboring spiropyrans can prevent efficient mobility.

The Sam-Sam interaction between Ship2 and the EphA2 receptor: design and analysis of peptide inhibitors.

PubMed

Mercurio, Flavia Anna; Di Natale, Concetta; Pirone, Luciano; Iannitti, Roberta; Marasco, Daniela; Pedone, Emilia Maria; Palumbo, Rosanna; Leone, Marilisa

2017-12-12

The lipid phosphatase Ship2 represents a drug discovery target for the treatment of different diseases, including cancer. Its C-terminal sterile alpha motif domain (Ship2-Sam) associates with the Sam domain from the EphA2 receptor (EphA2-Sam). This interaction is expected to mainly induce pro-oncogenic effects in cells therefore, inhibition of the Ship2-Sam/EphA2-Sam complex may represent an innovative route to discover anti-cancer therapeutics. In the present work, we designed and analyzed several peptide sequences encompassing the interaction interface of EphA2-Sam for Ship2-Sam. Peptide conformational analyses and interaction assays with Ship2-Sam conducted through diverse techniques (CD, NMR, SPR and MST), identified a positively charged penta-amino acid native motif in EphA2-Sam, that once repeated three times in tandem, binds Ship2-Sam. NMR experiments show that the peptide targets the negatively charged binding site of Ship2-Sam for EphA2-Sam. Preliminary in vitro cell-based assays indicate that -at 50 µM concentration- it induces necrosis of PC-3 prostate cancer cells with more cytotoxic effect on cancer cells than on normal dermal fibroblasts. This work represents a pioneering study that opens further opportunities for the development of inhibitors of the Ship2-Sam/EphA2-Sam complex for therapeutic applications.

Wireless multi-level terahertz amplitude modulator using active metamaterial-based spatial light modulation.

PubMed

Rout, Saroj; Sonkusale, Sameer

2016-06-27

The ever increasing demand for bandwidth in wireless communication systems will inevitably lead to the extension of operating frequencies toward the terahertz (THz) band known as the 'THz gap'. Towards closing this gap, we present a multi-level amplitude shift keying (ASK) terahertz wireless communication system using terahertz spatial light modulators (SLM) instead of traditional voltage mode modulation, achieving higher spectral efficiency for high speed communication. The fundamental principle behind this higher efficiency is the conversion of a noisy voltage domain signal to a noise-free binary spatial pattern for effective amplitude modulation of a free-space THz carrier wave. Spatial modulation is achieved using an an active metamaterial array embedded with pseudomorphic high-electron mobility (pHEMT) designed in a consumer-grade galium-arsenide (GaAs) integrated circuit process which enables electronic control of its THz transmissivity. Each array is assembled as individually controllable tiles for transmissive terahertz spatial modulation. Using the experimental data from our metamaterial based modulator, we show that a four-level ASK digital communication system has two orders of magnitude improvement in symbol error rate (SER) for a degradation of 20 dB in transmit signal-to-noise ratio (SNR) using spatial light modulation compared to voltage controlled modulation.

Neurometric amplitude-modulation detection threshold in the guinea-pig ventral cochlear nucleus

PubMed Central

Sayles, Mark; Füllgrabe, Christian; Winter, Ian M

2013-01-01

Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (∼5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation frequency are (95% CI) 11.6% (10.0–13.1) for PL units, 9.8% (8.2–11.5) for CT units, and 10.8% (8.4–13.2) for CS units. The most sensitive guinea-pig VCN single unit AM detection thresholds are similar to human psychophysical performance (∼3% AM), while the mean neurometric thresholds approach whole animal behavioural performance (∼10% AM). PMID:23629508

Multipixel frequency-domain imaging of spontaneous canine breast disease using fluorescent contrast agents

NASA Astrophysics Data System (ADS)

Reynolds, Jeffery S.; Thompson, Alan B.; Troy, Tamara L.; Mayer, Ralf H.; Waters, David J.; Sevick-Muraca, Eva M.

1999-07-01

In this paper we demonstrate the ability to detect the frequency-domain fluorescent signal from the contrast agent indocyanine green within the mammary chain of dogs with spontaneous mammary tumors. We use a gain-modulated image intensifier to rapidly capture multi-pixel images of the fluorescent modulation amplitude, modulation phase, and average intensity signals. Excitation is provided by a 100 MHz amplitude-modulated, 780 nm laser diode. Time series images of the uptake and clearance of the contrast agent in the diseased tissue are also presented.

Demodulation techniques for the amplitude modulated laser imager

NASA Astrophysics Data System (ADS)

Mullen, Linda; Laux, Alan; Cochenour, Brandon; Zege, Eleonora P.; Katsev, Iosif L.; Prikhach, Alexander S.

2007-10-01

A new technique has been found that uses in-phase and quadrature phase (I/Q) demodulation to optimize the images produced with an amplitude-modulated laser imaging system. An I/Q demodulator was used to collect the I/Q components of the received modulation envelope. It was discovered that by adjusting the local oscillator phase and the modulation frequency, the backscatter and target signals can be analyzed separately via the I/Q components. This new approach enhances image contrast beyond what was achieved with a previous design that processed only the composite magnitude information.

A health literate approach to the prevention of childhood overweight and obesity

PubMed Central

White, Richard O.; Thompson, Jessica R.; Rothman, Russell L.; Scott, Amanda M. McDougald; Heerman, William J.; Sommer, Evan C.; Barkin, Shari L.

2013-01-01

Objective To describe a systematic assessment of patient educational materials for the Growing Right Onto Wellness (GROW) trial, a childhood obesity prevention study targeting a low health literate population. Methods Process included: (1) expert review of educational content, (2) assessment of the quality of materials including use of the Suitability Assessment of Materials (SAM) tool, and (3) material review and revision with target population. Results 12 core modules were developed and assessed in an iterative process. Average readability was at the 6th grade reading level (SMOG Index 5.63 ± 0.76, and Fry graph 6.0 ± 0.85). SAM evaluation resulted in adjustments to literacy demand, layout & typography, and learning stimulation & motivation. Cognitive interviews with target population revealed additional changes incorporated to enhance participant's perception of acceptability and feasibility for behavior change. Conclusion The GROW modules are a collection of evidence-based materials appropriate for parents with low health literacy and their preschool aged children, that target the prevention of childhood overweight/obesity. Practice implications Most trials addressing the treatment or prevention of childhood obesity use written materials. Due to the ubiquitous prevalence of limited health literacy, our described methods may assist researchers in ensuring their content is both understood and actionable. PMID:24001660

A health literate approach to the prevention of childhood overweight and obesity.

PubMed

White, Richard O; Thompson, Jessica R; Rothman, Russell L; McDougald Scott, Amanda M; Heerman, William J; Sommer, Evan C; Barkin, Shari L

2013-12-01

To describe a systematic assessment of patient educational materials for the Growing Right Onto Wellness (GROW) trial, a childhood obesity prevention study targeting a low health literate population. Process included: (1) expert review of educational content, (2) assessment of the quality of materials including use of the Suitability Assessment of Materials (SAM) tool, and (3) material review and revision with target population. 12 core modules were developed and assessed in an iterative process. Average readability was at the 6th grade reading level (SMOG Index 5.63 ± 0.76, and Fry graph 6.0 ± 0.85). SAM evaluation resulted in adjustments to literacy demand, layout & typography, and learning stimulation & motivation. Cognitive interviews with target population revealed additional changes incorporated to enhance participant's perception of acceptability and feasibility for behavior change. The GROW modules are a collection of evidence-based materials appropriate for parents with low health literacy and their preschool aged children, that target the prevention of childhood overweight/obesity. Most trials addressing the treatment or prevention of childhood obesity use written materials. Due to the ubiquitous prevalence of limited health literacy, our described methods may assist researchers in ensuring their content is both understood and actionable. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Analysis of dynamic system response to product random processes

NASA Technical Reports Server (NTRS)

Sidwell, K.

1978-01-01

The response of dynamic systems to the product of two independent Gaussian random processes is developed by use of the Fokker-Planck and associated moment equations. The development is applied to the amplitude modulated process which is used to model atmospheric turbulence in aeronautical applications. The exact solution for the system response is compared with the solution obtained by the quasi-steady approximation which omits the dynamic properties of the random amplitude modulation. The quasi-steady approximation is valid as a limiting case of the exact solution for the dynamic response of linear systems to amplitude modulated processes. In the nonlimiting case the quasi-steady approximation can be invalid for dynamic systems with low damping.

Improved measurement linearity and precision for AMCW time-of-flight range imaging cameras.

PubMed

Payne, Andrew D; Dorrington, Adrian A; Cree, Michael J; Carnegie, Dale A

2010-08-10

Time-of-flight range imaging systems utilizing the amplitude modulated continuous wave (AMCW) technique often suffer from measurement nonlinearity due to the presence of aliased harmonics within the amplitude modulation signals. Typically a calibration is performed to correct these errors. We demonstrate an alternative phase encoding approach that attenuates the harmonics during the sampling process, thereby improving measurement linearity in the raw measurements. This mitigates the need to measure the system's response or calibrate for environmental changes. In conjunction with improved linearity, we demonstrate that measurement precision can also be increased by reducing the duty cycle of the amplitude modulated illumination source (while maintaining overall illumination power).

Effect of synthetic jet modulation schemes on the reduction of a laminar separation bubble

NASA Astrophysics Data System (ADS)

Seo, J. H.; Cadieux, F.; Mittal, R.; Deem, E.; Cattafesta, L.

2018-03-01

The response of a laminar separation bubble to synthetic jet forcing with various modulation schemes is investigated via direct numerical simulations. A simple sinusoidal waveform is considered as a reference case, and various amplitude modulation schemes, including the square-wave "burst" modulation, are employed in the simulations. The results indicate that burst modulation is less effective at reducing the length of the flow separation than the sinusoidal forcing primarily because burst modulation is associated with a broad spectrum of input frequencies that are higher than the target frequency for the flow control. It is found that such high-frequency forcing delays vortex roll-up and promotes vortex pairing and merging, which have an adverse effect on reducing the separation bubble length. A commonly used amplitude modulation scheme is also found to have reduced effectiveness due to its spectral content. A new amplitude modulation scheme which is tailored to impart more energy at the target frequency is proposed and shown to be more effective than the other modulation schemes. Experimental measurements confirm that modulation schemes can be preserved through the actuator and used to enhance the energy content at the target modulation frequency. The present study therefore suggests that the effectiveness of synthetic jet-based flow control could be improved by carefully designing the spectral content of the modulation scheme.

Aharonov-Bohm oscillations, quantum decoherence and amplitude modulation in mesoscopic InGaAs/InAlAs rings.

PubMed

Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B

2013-10-30

Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms.

FIBER AND INTEGRATED OPTICS, LASER APPLICATIONS, AND OTHER PROBLEMS IN QUANTUM ELECTRONICS: Optical components for the analysis and formation of the transverse mode composition

NASA Astrophysics Data System (ADS)

Golub, M. A.; Sisakyan, I. N.; Soĭfer, V. A.; Uvarov, G. V.

1989-04-01

Theoretical and experimental investigations are reported of new mode optical components (elements) which are analogs of sinusoidal phase diffraction gratings with a variable modulation depth. Expressions are derived for nonlinear predistortion and depth of modulation, which are essential for effective operation of amplitude and phase mode optical components in devices used for analysis and formation of the transverse mode composition of coherent radiation. An estimate is obtained of the energy efficiency of phase and amplitude mode optical components, and a comparison is made with the results of an experimental investigation of a set of phase optical components matched to Gauss-Laguerre modes. It is shown that the improvement in the energy efficiency of phase mode components, compared with amplitude components, is the same as the improvement achieved using a phase diifraction grating, compared with amplitude grating with the same depth of modulation.

Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line.

PubMed

Chakraborty, Arup Lal; Ruxton, Keith; Johnstone, Walter; Lengden, Michael; Duffin, Kevin

2009-06-08

A new fiber-optic technique to eliminate residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy is presented. The modulated laser output is split to pass in parallel through the gas measurement cell and an optical fiber delay line, with the modulation frequency / delay chosen to introduce a relative phase shift of pi between them. The two signals are balanced using a variable attenuator and recombined through a fiber coupler. In the absence of gas, the direct laser intensity modulation cancels, thereby eliminating the high background. The presence of gas induces a concentration-dependent imbalance at the coupler's output from which the absolute absorption profile is directly recovered with high accuracy using 1f detection.

NOTE ON TRAVEL TIME SHIFTS DUE TO AMPLITUDE MODULATION IN TIME-DISTANCE HELIOSEISMOLOGY MEASUREMENTS

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

Nigam, R.; Kosovichev, A. G., E-mail: rakesh@quake.stanford.ed, E-mail: sasha@quake.stanford.ed

Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times have not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is artificially suppressed by a spatial function, and using numerical simulations that the amplitude modulations in combination with the phase-speed filtering may cause systematic shifts ofmore » acoustic travel times. To understand the properties of this procedure, we derive an analytical expression for the cross-covariance of a signal that has been modulated locally by a spatial function that has azimuthal symmetry and then filtered by a phase-speed filter typically used in time-distance helioseismology. Comparing this expression to the Gabor wavelet fitting formula without this effect, we find that there is a shift in the travel times that is introduced by the amplitude modulation. The analytical model presented in this paper can be useful also for interpretation of travel time measurements for the non-uniform distribution of oscillation amplitude due to observational effects.« less

Intelligent Data Transfer for Multiple Sensor Networks over a Broad Temperature Range

NASA Technical Reports Server (NTRS)

Krasowski, Michael (Inventor)

2018-01-01

A sensor network may be configured to operate in extreme temperature environments. A sensor may be configured to generate a frequency carrier, and transmit the frequency carrier to a node. The node may be configured to amplitude modulate the frequency carrier, and transmit the amplitude modulated frequency carrier to a receiver.

Acoustic Measurement Of Periodic Motion Of Levitated Object

NASA Technical Reports Server (NTRS)

Watkins, John L.; Barmatz, Martin B.

1992-01-01

Some internal vibrations, oscillations in position, and rotations of acoustically levitated object measured by use of microphone already installed in typical levitation chamber for tuning chamber to resonance and monitoring operation. Levitating acoustic signal modulated by object motion of lower frequency. Amplitude modulation detected and analyzed spectrally to determine amplitudes and frequencies of motions.

Detection of Sound Rise Time by Adults with Dyslexia

ERIC Educational Resources Information Center

Hamalainen, J.; Leppanen, P.H.T.; Torppa, M.; Muller, K.; Lyytinen, H.

2005-01-01

Low sensitivity to amplitude modulated (AM) sounds is reported to be associated with dyslexia. An important aspect of amplitude modulation cycles are the rise and fall times within the sound. In this study, simplified stimuli equivalent to just one cycle were used and sensitivity to varying rise times was explored. Adult participants with dyslexia…

Radar transponder operation with compensation for distortion due to amplitude modulation

DOEpatents

Ormesher, Richard C [Albuquerque, NM; Tise, Bertice L [Albuquerque, NM; Axline, Jr., Robert M.

2011-01-04

In radar transponder operation, a variably delayed gating signal is used to gate a received radar pulse and thereby produce a corresponding gated radar pulse for transmission back to the source of the received radar pulse. This compensates for signal distortion due to amplitude modulation on the retransmitted pulse.

Contextual Modulation of N400 Amplitude to Lexically Ambiguous Words

ERIC Educational Resources Information Center

Titone, Debra A.; Salisbury, Dean F.

2004-01-01

Through much is known about the N400 component, an event-related EEG potential that is sensitive to semantic manipulations, it is unclear whether modulations of N400 amplitude reflect automatic processing, controlled processing, or both. We examined this issue using a semantic judgment task that manipulated local and global contextual cues. Word…

Probing the nature and resistance of the molecule-electrode contact in SAM-based junctions.

PubMed

Sangeeth, C S Suchand; Wan, Albert; Nijhuis, Christian A

2015-07-28

It is challenging to quantify the contact resistance and to determine the nature of the molecule-electrode contacts in molecular two-terminal junctions. Here we show that potentiodynamic and temperature dependent impedance measurements give insights into the nature of the SAM-electrode interface and other bottlenecks of charge transport (the capacitance of the SAM (C(SAM)) and the resistance of the SAM (R(SAM))), unlike DC methods, independently of each other. We found that the resistance of the top-electrode-SAM contact for junctions with the form of Ag(TS)-SC(n)//GaO(x)/EGaIn with n = 10, 12, 14, 16 or 18 is bias and temperature independent and hence Ohmic (non-rectifying) in nature, and is orders of magnitude smaller than R(SAM). The C(SAM) and R(SAM) are independent of the temperature, indicating that the mechanism of charge transport in these SAM-based junctions is coherent tunneling and the charge carrier trapping at the interfaces is negligible.

Structural basis for diversity in the SAM clan of riboswitches.

PubMed

Trausch, Jeremiah J; Xu, Zhenjiang; Edwards, Andrea L; Reyes, Francis E; Ross, Phillip E; Knight, Rob; Batey, Robert T

2014-05-06

In bacteria, sulfur metabolism is regulated in part by seven known families of riboswitches that bind S-adenosyl-l-methionine (SAM). Direct binding of SAM to these mRNA regulatory elements governs a downstream secondary structural switch that communicates with the transcriptional and/or translational expression machinery. The most widely distributed SAM-binding riboswitches belong to the SAM clan, comprising three families that share a common SAM-binding core but differ radically in their peripheral architecture. Although the structure of the SAM-I member of this clan has been extensively studied, how the alternative peripheral architecture of the other families supports the common SAM-binding core remains unknown. We have therefore solved the X-ray structure of a member of the SAM-I/IV family containing the alternative "PK-2" subdomain shared with the SAM-IV family. This structure reveals that this subdomain forms extensive interactions with the helix housing the SAM-binding pocket, including a highly unusual mode of helix packing in which two helices pack in a perpendicular fashion. Biochemical and genetic analysis of this RNA reveals that SAM binding induces many of these interactions, including stabilization of a pseudoknot that is part of the regulatory switch. Despite strong structural similarity between the cores of SAM-I and SAM-I/IV members, a phylogenetic analysis of sequences does not indicate that they derive from a common ancestor.

Development of frequency modulation reflectometer for KSTAR tokamak: Data analysis based on Gaussian derivative waveleta)

NASA Astrophysics Data System (ADS)

Seo, Seong-Heon; Lee, K. D.

2012-10-01

A frequency modulation reflectometer has been developed to measure the density profile of the KSTAR tokamak. It has two channels operating in X-mode in the frequency range of Q band (33-50 GHz) and V band (50-75 GHz). The full band is swept in 20 μs. The mixer output is directly digitized at the sampling rate of 100 MSamples/s. A new phase detection algorithm is developed to analyze both amplitude and frequency modulated signal. The algorithm is benchmarked for a synthesized amplitude modulation-frequency modulation signal. This new algorithm is applied to the data analysis of KSTAR reflectometer.

Scale interaction and arrangement in a turbulent boundary layer perturbed by a wall-mounted cylindrical element

NASA Astrophysics Data System (ADS)

Tang, Zhanqi; Jiang, Nan

2018-05-01

This study reports the modifications of scale interaction and arrangement in a turbulent boundary layer perturbed by a wall-mounted circular cylinder. Hot-wire measurements were executed at multiple streamwise and wall-normal wise locations downstream of the cylindrical element. The streamwise fluctuating signals were decomposed into large-, small-, and dissipative-scale signatures by corresponding cutoff filters. The scale interaction under the cylindrical perturbation was elaborated by comparing the small- and dissipative-scale amplitude/frequency modulation effects downstream of the cylinder element with the results observed in the unperturbed case. It was obtained that the large-scale fluctuations perform a stronger amplitude modulation on both the small and dissipative scales in the near-wall region. At the wall-normal positions of the cylinder height, the small-scale amplitude modulation coefficients are redistributed by the cylinder wake. The similar observation was noted in small-scale frequency modulation; however, the dissipative-scale frequency modulation seems to be independent of the cylindrical perturbation. The phase-relationship observation indicated that the cylindrical perturbation shortens the time shifts between both the small- and dissipative-scale variations (amplitude and frequency) and large-scale fluctuations. Then, the integral time scale dependence of the phase-relationship between the small/dissipative scales and large scales was also discussed. Furthermore, the discrepancy of small- and dissipative-scale time shifts relative to the large-scale motions was examined, which indicates that the small-scale amplitude/frequency leads the dissipative scales.

Summary Report of Mission Acceleration Measurements for STS-79. Launched 16 Sep. 1996

NASA Technical Reports Server (NTRS)

Rogers, Melissa J. B.; Moskowitz, Milton E.; Hrovat, Kenneth; Reckart, Timothy A.

1997-01-01

The Space Acceleration Measurement System (SAMS) collected acceleration data in support of the Mechanics of Granular Materials experiment during the STS-79 Mir docking mission, September 1996. STS-79 was the first opportunity to record SAMS data on an Orbiter while it was docked to Mir. Crew exercise activities in the Atlantis middeck and the Mir base module are apparent in the data. The acceleration signals related to the Enhanced Orbiter Refrigerator Freezer had different characteristics when comparing the data recorded on Atlantis on STS-79 with the data recorded on Mir during STS-74. This is probably due, at least in part, to different transmission paths and SAMS sensor head mounting mechanisms. Data collected on Atlantis during the STS-79 docking indicate that accelerations due to vehicle and solar array structural modes from Mir transfer to Atlantis and that the structural modes of the Atlantis-Mir complex are different from those of either vehicle independently. A 0.18 Hz component of the SAMS data, present while the two vehicles were docked, was probably caused by the Mir solar arrays. Compared to Atlantis structural modes of about 3.9 and 4.9 Hz, the Atlantis-Mir complex has structural components of about 4.5 and 5.1 Hz. After docking, apparent structural modes appeared in the data at about 0.8 and 1.8 Hz. The appearance, disappearance, and change in the structural modes during the docking and undocking phases of the joint Atlantis-Mir operations indicates that the structural modes of the two spacecraft have an effect on the microgravity environment of each other. The transfer of structural and equipment related accelerations between vehicles is something that should be considered in the International Space Station era.

Creatine supplementation prevents fatty liver in rats fed choline-deficient diet: a burden of one-carbon and fatty acid metabolism.

PubMed

Deminice, Rafael; de Castro, Gabriela Salim Ferreira; Francisco, Lucas Vieira; da Silva, Lilian Eslaine Costa Mendes; Cardoso, João Felipe Rito; Frajacomo, Fernando Tadeu Trevisan; Teodoro, Bruno Gonzaga; Dos Reis Silveira, Leonardo; Jordao, Alceu Afonso

2015-04-01

To examine the effects of creatine (Cr) supplementation on liver fat accumulation in rats fed a choline-deficient diet. Twenty-four rats were divided into 3 groups of 8 based on 4 weeks of feeding an AIN-93 control diet (C), a choline-deficient diet (CDD) or a CDD supplemented with 2% Cr. The CDD diet was AIN-93 without choline. The CDD significantly increased plasma homocysteine and TNFα concentration, as well as ALT activity. In liver, the CDD enhanced concentrations of total fat (55%), cholesterol (25%), triglycerides (87%), MDA (30%), TNFα (241%) and decreased SAM concentrations (25%) and the SAM/SAH ratio (33%). Cr supplementation prevented all these metabolic changes, except for hepatic SAM and the SAM/SAH ratio. However, no changes in PEMT gene expression or liver phosphatidylcholine levels were observed among the three experimental groups, and there were no changes in hepatic triglyceride transfer protein (MTP) mRNA level. On the contrary, Cr supplementation normalized expression of the transcription factors PPARα and PPARγ that were altered by the CDD. Further, the downstream targets and fatty acids metabolism genes, UCP2, LCAD and CPT1a, were also normalized in the Cr group as compared to CDD-fed rats. Cr supplementation prevented fat liver accumulation and hepatic injures in rats fed with a CDD for 4 weeks. Our results demonstrated that one-carbon metabolism may have a small role in mitigating hepatic fat accumulation by Cr supplementation. The modulation of key genes related to fatty acid oxidation pathway suggests a new mechanism by which Cr prevents liver fat accumulation. Copyright © 2015 Elsevier Inc. All rights reserved.

High flow rate nozzle system with production of uniform size droplets

DOEpatents

Stockel, I.H.

1990-10-16

Method steps for production of substantially uniform size droplets from a flow of liquid include forming the flow of liquid, periodically modulating the momentum of the flow of liquid in the flow direction at controlled frequency, generating a cross flow direction component of momentum and modulation of the cross flow momentum of liquid at substantially the same frequency and phase as the modulation of flow direction momentum, and spraying the so formed modulated flow through a first nozzle outlet to form a desired spray configuration. A second modulated flow through a second nozzle outlet is formed according to the same steps, and the first and second modulated flows impinge upon each other generating a liquid sheet. Nozzle apparatus for modulating each flow includes rotating valving plates interposed in the annular flow of liquid. The plates are formed with radial slots. Rotation of the rotating plates is separably controlled at differential angular velocities for a selected modulating frequency to achieve the target droplet size and production rate for a given flow. The counter rotating plates are spaced to achieve a desired amplitude of modulation in the flow direction, and the angular velocity of the downstream rotating plate is controlled to achieve the desired amplitude of modulation of momentum in the cross flow direction. Amplitude of modulation is set according to liquid viscosity. 5 figs.

High flow rate nozzle system with production of uniform size droplets

DOEpatents

Stockel, Ivar H.

1990-01-01

Method steps for production of substantially uniform size droplets from a flow of liquid include forming the flow of liquid, periodically modulating the momentum of the flow of liquid in the flow direction at controlled frequency, generating a cross flow direction component of momentum and modulation of the cross flow momentum of liquid at substantially the same frequency and phase as the modulation of flow direction momentum, and spraying the so formed modulated flow through a first nozzle outlet to form a desired spray configuration. A second modulated flow through a second nozzle outlet is formed according to the same steps, and the first and second modulated flows impinge upon each other generating a liquid sheet. Nozzle apparatus for modulating each flow includes rotating valving plates interposed in the annular flow of liquid. The plates are formed with radial slots. Rotation of the rotating plates is separably controlled at differential angular velocities for a selected modulating frequency to achieve the target droplet size and production rate for a given flow. The counter rotating plates are spaced to achieve a desired amplitude of modulation in the flow direction, and the angular velocity of the downstream rotating plate is controlled to achieve the desired amplitude of modulation of momentum in the cross flow direction. Amplitude of modulation is set according to liquid viscosity.

Analysis of the liver mitochondrial proteome in response to ethanol and S-adenosylmethionine treatments: novel molecular targets of disease and hepatoprotection.

PubMed

Andringa, Kelly K; King, Adrienne L; Eccleston, Heather B; Mantena, Sudheer K; Landar, Aimee; Jhala, Nirag C; Dickinson, Dale A; Squadrito, Giuseppe L; Bailey, Shannon M

2010-05-01

S-adenosylmethionine (SAM) minimizes alcohol hepatotoxicity; however, the molecular mechanisms responsible for SAM hepatoprotection remain unknown. Herein, we use proteomics to determine whether the hepatoprotective action of SAM against early-stage alcoholic liver disease is linked to alterations in the mitochondrial proteome. For this, male rats were fed control or ethanol-containing liquid diets +/- SAM and liver mitochondria were prepared for proteomic analysis. Two-dimensional isoelectric focusing (2D IEF/SDS-PAGE) and blue native gel electrophoresis (BN-PAGE) were used to determine changes in matrix and oxidative phosphorylation (OxPhos) proteins, respectively. SAM coadministration minimized alcohol-dependent inflammation and preserved mitochondrial respiration. SAM supplementation preserved liver SAM levels in ethanol-fed rats; however, mitochondrial SAM levels were increased by ethanol and SAM treatments. With use of 2D IEF/SDS-PAGE, 30 proteins showed significant changes in abundance in response to ethanol, SAM, or both. Classes of proteins affected by ethanol and SAM treatments were chaperones, beta oxidation proteins, sulfur metabolism proteins, and dehydrogenase enzymes involved in methionine, glycine, and choline metabolism. BN-PAGE revealed novel changes in the levels of 19 OxPhos proteins in response to ethanol, SAM, or both. Ethanol- and SAM-dependent alterations in the proteome were not linked to corresponding changes in gene expression. In conclusion, ethanol and SAM treatment led to multiple changes in the liver mitochondrial proteome. The protective effects of SAM against alcohol toxicity are mediated, in part, through maintenance of proteins involved in key mitochondrial energy conserving and biosynthetic pathways. This study demonstrates that SAM may be a promising candidate for treatment of alcoholic liver disease.

Computational evaluation of amplitude modulation for enhanced magnetic nanoparticle hyperthermia.

PubMed

Soetaert, Frederik; Dupré, Luc; Ivkov, Robert; Crevecoeur, Guillaume

2015-10-01

Magnetic nanoparticles (MNPs) can interact with alternating magnetic fields (AMFs) to deposit localized energy for hyperthermia treatment of cancer. Hyperthermia is useful in the context of multimodality treatments with radiation or chemotherapy to enhance disease control without increased toxicity. The unique attributes of heat deposition and transfer with MNPs have generated considerable attention and have been the focus of extensive investigations to elucidate mechanisms and optimize performance. Three-dimensional (3D) simulations are often conducted with the finite element method (FEM) using the Pennes' bioheat equation. In the current study, the Pennes' equation was modified to include a thermal damage-dependent perfusion profile to improve model predictions with respect to known physiological responses to tissue heating. A normal distribution of MNPs in a model liver tumor was combined with empirical nanoparticle heating data to calculate tumor temperature distributions and resulting survival fraction of cancer cells. In addition, calculated spatiotemporal temperature changes were compared among magnetic field amplitude modulations of a base 150-kHz sinusoidal waveform, specifically, no modulation, sinusoidal, rectangular, and triangular modulation. Complex relationships were observed between nanoparticle heating and cancer tissue damage when amplitude modulation and damage-related perfusion profiles were varied. These results are tantalizing and motivate further exploration of amplitude modulation as a means to enhance efficiency of and overcome technical challenges associated with magnetic nanoparticle hyperthermia (MNH).

Amplitude Modulation of Pulsation Modes in Delta Scuti Stars

NASA Astrophysics Data System (ADS)

Bowman, Dominic M.

2017-10-01

The pulsations in δ Sct stars are excited by a heat engine driving mechanism caused by increased opacity in their surface layers, and have pulsation periods of order a few hours. Space based observations in the last decade have revealed a diverse range of pulsational behaviour in these stars, which is investigated using an ensemble of 983 δ Sct stars observed continuously for 4 yr by the Kepler Space Telescope. A statistical search for amplitude modulation of pulsation modes is carried out and it is shown that 61.3 per cent of the 983 δ Sct stars exhibit significant amplitude modulation in at least a single pulsation mode, and that this is uncorrelated with effective temperature and surface gravity. Hence, the majority of δ Sct stars exhibit amplitude modulation, with time-scales of years and longer demonstrated to be significant in these stars both observationally and theoretically. An archetypal example of amplitude modulation in a δ Sct star is KIC 7106205, which contains only a single pulsation mode that varies significantly in amplitude whilst all other pulsation modes stay constant in amplitude and phase throughout the 4-yr Kepler data set. Therefore, the visible pulsational energy budget in this star, and many others, is not conserved over 4 yr. Models of beating of close-frequency pulsation modes are used to identify δ Sct stars with frequencies that lie closer than 0.001 d^{-1}, which are barely resolved using 4 yr of Kepler observations, and maintain their independent identities over 4 yr. Mode coupling models are used to quantify the strength of coupling and distinguish between non-linearity in the form of combination frequencies and non-linearity in the form of resonant mode coupling for families of pulsation modes in several stars. The changes in stellar structure caused by stellar evolution are investigated for two high amplitude δ Sct (HADS) stars in the Kepler data set, revealing a positive quadratic change in phase for the fundamental and first overtone radial modes in KIC 5950759. The observed phase modulation of the radial modes in this star is two orders of magnitude larger than predicted by stellar evolutionary models, yet is consistent with the prediction of increasing periods of radial modes for stars on the main sequence. The statistical analysis of 983 δ Sct stars, including the results from the search for amplitude modulation, is a valuable resource for ongoing and future space missions such as K2, TESS and PLATO, because the high quality 4-yr Kepler data set will not be surpassed for some time. The observational studies of individual stars in this thesis provide strong evidence that non-linear processes are clearly at work in the majority of δ Sct stars, and provide valuable constraints for future asteroseismic modelling.

Improving methionine and ATP availability by MET6 and SAM2 co-expression combined with sodium citrate feeding enhanced SAM accumulation in Saccharomyces cerevisiae.

PubMed

Chen, Hailong; Wang, Zhou; Wang, Zhilai; Dou, Jie; Zhou, Changlin

2016-04-01

S-adenosyl-L-methionine (SAM), biosynthesized from methionine and ATP, exhibited diverse pharmaceutical applications. To enhance SAM accumulation in S. cerevisiae CGMCC 2842 (wild type), improvement of methionine and ATP availability through MET6 and SAM2 co-expression combined with sodium citrate feeding was investigated here. Feeding 6 g/L methionine at 12 h into medium was found to increase SAM accumulation by 38 % in wild type strain. Based on this result, MET6, encoding methionine synthase, was overexpressed, which caused a 59 % increase of SAM. To redirect intracellular methionine into SAM, MET6 and SAM2 (encoding methionine adenosyltransferase) were co-expressed to obtain the recombinant strain YGSPM in which the SAM accumulation was 2.34-fold of wild type strain. The data obtained showed that co-expression of MET6 and SAM2 improved intracellular methionine availability and redirected the methionine to SAM biosynthesis. To elevate intracellular ATP levels, 6 g/L sodium citrate, used as an auxiliary energy substrate, was fed into the batch fermentation medium, and an additional 19 % increase of SAM was observed after sodium citrate addition. Meanwhile, it was found that addition of sodium citrate improved the isocitrate dehydrogenase activity which was associated with the intracellular ATP levels. The results demonstrated that addition of sodium citrate improved intracellular ATP levels which promoted conversion of methionine into SAM. This study presented a feasible approach with considerable potential for developing highly SAM-productive strains based on improving methionine and ATP availability.

Molecular Level Understanding of Interfaces and Excited State Electronic Structure in Organic Solar Cells Using Soft X-ray Techniques

NASA Astrophysics Data System (ADS)

Gliboff, Matthew

Transparent conductive oxides like indium tin oxide (ITO) are common substrates for optoelectronic devices, including organic light emitting diodes and organic solar cells. Tailoring the interface between the oxide and the active layer by adjusting the work function or wettability of the oxide can improve the performance of these devices in both emissive and photovoltaic applications. Molecular design of self-assembled monolayers (SAMs) allows for a range of surface properties using the same oxide material. The molecular ordering and conformation adopted by the SAMs determine properties such as work function and wettability at these critical interfaces. I use angle-dependent near edge x-ray absorption fine structure (NEXAFS) spectroscopy, to determine the molecular orientations of a variety of dipolar phosphonic acid surface modifiers. For a model system, phenylphosphonic acid on indium zinc oxide, the SAMs prove to be surprisingly well-oriented, with the phenyl ring adopting a well-defined tilt angle of 12-16° from the surface normal. The NEXAFS results agree with polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) results and orientations calculated from density functional theory (DFT). These results not only provide a detailed picture of the molecular structure of a technologically important class of SAMs, but they also resolve a long-standing ambiguity regarding the vibrational-mode assignments for phosphonic acids on oxide surfaces, thus improving the utility of PM-IRRAS for future studies. The effect of fluorination on the orientation of these phosponic-acid SAMs is non-trivial, due to the combined effects of the fluorination on binding mode and steric packing. The latter effects are found to be more dominant in aliphatic SAMs, leading to a more upright orientation in the fluorinated SAM. In the aromatic case, the fluorinated SAM adopted a less upright orientation which I attribute to changes in binding mode. The relationship between structure and performance in active layer polymers for organic electronics is not yet well understood. To gain insight into the effect of the excited state electronic structure on device performance, we examine two similar donor-acceptor polymers: PCPDTBT and PCDTBT, which produce devices with internal quantum efficiency (IQE) of 70% and 100% respectively. We use time-dependent density functional theory (TD-DFT) in combination with near edge x-ray absorption fine structure (NEXAFS) and resonant Auger spectroscopy to predict the electronic structure of the lowest unoccupied molecular orbital (LUMO). The resonant Auger results are found to be independent of film morphology and likely dominated by monomer structure. We show that the degree of LUMO localization onto the benzothiadiazole acceptor group in each polymer is similar, indicating that that the differences in IQE between these two polymers are driven by larger-scale morphology and not explained by the electronic structure of the excited state.

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

None

Module-level power electronics, such as DC power optimizers, microinverters, and those found in AC modules, are increasing in popularity in smaller-scale photovoltaic (PV) systems as their prices continue to decline. Therefore, it is important to provide PV modelers with guidelines about how to model these distributed power electronics appropriately in PV modeling software. This paper extends the work completed at NREL that provided recommendations to model the performance of distributed power electronics in NREL’s popular PVWatts calculator [1], to provide similar guidelines for modeling these technologies in NREL's more complex System Advisor Model (SAM). Module-level power electronics - such asmore » DC power optimizers, microinverters, and those found in AC modules-- are increasing in popularity in smaller-scale photovoltaic (PV) systems as their prices continue to decline. Therefore, it is important to provide PV modelers with guidelines about how to model these distributed power electronics appropriately in PV modeling software.« less

Peptide Fragments of Odin-Sam1: Conformational Analysis and Interaction Studies with EphA2-Sam.

PubMed

Mercurio, Flavia A; Di Natale, Concetta; Pirone, Luciano; Scognamiglio, Pasqualina L; Marasco, Daniela; Pedone, Emilia M; Saviano, Michele; Leone, Marilisa

2015-07-27

Odin is a protein belonging to the ANKS family, and has two tandem Sam domains. The first, Odin-Sam1, binds to the Sam domain of the EphA2 receptor (EphA2-Sam); this interaction could be crucial for the regulation of receptor endocytosis and might have an impact on cancer. Odin-Sam1 associates with EphA2-Sam by adopting a "mid-loop/end-helix" model. In this study three peptide sequences, encompassing the mid-loop interacting portion of Odin-Sam1 and its C-terminal α5 helix, were designed. Their conformational properties were analyzed by CD and NMR. In addition, their abilities to interact with EphA2-Sam were investigated by SPR studies. The peptides adopt a predominantly disordered state in aqueous buffer, but a higher helical content is evident in the presence of the cosolvent trifluoroethanol. Dissociation constants towards EphA2-Sam were in the high micromolar range. The structural findings suggest further routes for the design of potential anti-cancer therapeutics as inhibitors of EphA2-Sam heterotypic interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Redox Behavior of the S-Adenosylmethionine (SAM)-Binding Fe-S Cluster in Methylthiotransferase RimO, toward Understanding Dual SAM Activity.

PubMed

Molle, Thibaut; Moreau, Yohann; Clemancey, Martin; Forouhar, Farhad; Ravanat, Jean-Luc; Duraffourg, Nicolas; Fourmond, Vincent; Latour, Jean-Marc; Gambarelli, Serge; Mulliez, Etienne; Atta, Mohamed

2016-10-18

RimO, a radical-S-adenosylmethionine (SAM) enzyme, catalyzes the specific C 3 methylthiolation of the D89 residue in the ribosomal S 12 protein. Two intact iron-sulfur clusters and two SAM cofactors both are required for catalysis. By using electron paramagnetic resonance, Mössbauer spectroscopies, and site-directed mutagenesis, we show how two SAM molecules sequentially bind to the unique iron site of the radical-SAM cluster for two distinct chemical reactions in RimO. Our data establish that the two SAM molecules bind the radical-SAM cluster to the unique iron site, and spectroscopic evidence obtained under strongly reducing conditions supports a mechanism in which the first molecule of SAM causes the reoxidation of the reduced radical-SAM cluster, impeding reductive cleavage of SAM to occur and allowing SAM to methylate a HS - ligand bound to the additional cluster. Furthermore, by using density functional theory-based methods, we provide a description of the reaction mechanism that predicts the attack of the carbon radical substrate on the methylthio group attached to the additional [4Fe-4S] cluster.

Audio-visual speech perception: a developmental ERP investigation

PubMed Central

Knowland, Victoria CP; Mercure, Evelyne; Karmiloff-Smith, Annette; Dick, Fred; Thomas, Michael SC

2014-01-01

Being able to see a talking face confers a considerable advantage for speech perception in adulthood. However, behavioural data currently suggest that children fail to make full use of these available visual speech cues until age 8 or 9. This is particularly surprising given the potential utility of multiple informational cues during language learning. We therefore explored this at the neural level. The event-related potential (ERP) technique has been used to assess the mechanisms of audio-visual speech perception in adults, with visual cues reliably modulating auditory ERP responses to speech. Previous work has shown congruence-dependent shortening of auditory N1/P2 latency and congruence-independent attenuation of amplitude in the presence of auditory and visual speech signals, compared to auditory alone. The aim of this study was to chart the development of these well-established modulatory effects over mid-to-late childhood. Experiment 1 employed an adult sample to validate a child-friendly stimulus set and paradigm by replicating previously observed effects of N1/P2 amplitude and latency modulation by visual speech cues; it also revealed greater attenuation of component amplitude given incongruent audio-visual stimuli, pointing to a new interpretation of the amplitude modulation effect. Experiment 2 used the same paradigm to map cross-sectional developmental change in these ERP responses between 6 and 11 years of age. The effect of amplitude modulation by visual cues emerged over development, while the effect of latency modulation was stable over the child sample. These data suggest that auditory ERP modulation by visual speech represents separable underlying cognitive processes, some of which show earlier maturation than others over the course of development. PMID:24176002

Bilateral Functional Connectivity of the Basal Ganglia in Patients with Parkinson’s Disease and Its Modulation by Dopaminergic Treatment

PubMed Central

Little, Simon; Tan, Huiling; Anzak, Anam; Pogosyan, Alek; Kühn, Andrea; Brown, Peter

2013-01-01

Parkinson’s disease is characterised by excessive subcortical beta oscillations. However, little is known about the functional connectivity of the two basal ganglia across hemispheres and specifically the role beta plays in this. We recorded local field potentials from the subthalamic nucleus bilaterally in 23 subjects with Parkinson’s disease at rest, on and off medication. We found suppression of low beta power in response to levodopa (t22 = −4.4, p<0.001). There was significant coherence between the two sides in the beta range in 19 of the subjects. Coherence was selectively attenuated in the low beta range following levodopa (t22 = −2.7; p = 0.01). We also separately analysed amplitude co-modulation and phase synchronisation in the beta band and found significant amplitude co-modulation and phase locking values in 17 and 16 subjects respectively, off medication. There was a dissociable effect of levodopa on these measures, with a significant suppression only in low beta phase locking value (t22 = −2.8, p = 0.01) and not amplitude co-modulation. The absolute mean values of amplitude co-modulation (0.40±0.03) and phase synchronisation (0.29±0.02) off medication were, however, relatively low, suggesting that the two basal ganglia networks may have to be approached separately with independent sensing and stimulation during adaptive deep brain stimulation. In addition, our findings highlight the functional distinction between the lower and upper beta frequency ranges and between amplitude co-modulation and phase synchronization across subthalamic nuclei. PMID:24376574

Stability Analysis and Internal Heating Effect on Oscillatory Convection in a Viscoelastic Fluid Saturated Porous Medium Under Gravity Modulation

NASA Astrophysics Data System (ADS)

Bhadauria, B. S.; Singh, M. K.; Singh, A.; Singh, B. K.; Kiran, P.

2016-12-01

In this paper, we investigate the combined effect of internal heating and time periodic gravity modulation in a viscoelastic fluid saturated porous medium by reducing the problem into a complex non-autonomous Ginzgburg-Landau equation. Weak nonlinear stability analysis has been performed by using power series expansion in terms of the amplitude of gravity modulation, which is assumed to be small. The Nusselt number is obtained in terms of the amplitude for oscillatory mode of convection. The influence of viscoelastic parameters on heat transfer has been discussed. Gravity modulation is found to have a destabilizing effect at low frequencies and a stabilizing effect at high frequencies. Finally, it is found that overstability advances the onset of convection, more with internal heating. The conditions for which the complex Ginzgburg-Landau equation undergoes Hopf bifurcation and the amplitude equation undergoes supercritical pitchfork bifurcation are studied.

Full complex spatial filtering with a phase mostly DMD. [Deformable Mirror Device

NASA Technical Reports Server (NTRS)

Florence, James M.; Juday, Richard D.

1991-01-01

A new technique for implementing fully complex spatial filters with a phase mostly deformable mirror device (DMD) light modulator is described. The technique combines two or more phase-modulating flexure-beam mirror elements into a single macro-pixel. By manipulating the relative phases of the individual sub-pixels within the macro-pixel, the amplitude and the phase can be independently set for this filtering element. The combination of DMD sub-pixels into a macro-pixel is accomplished by adjusting the optical system resolution, thereby trading off system space bandwidth product for increased filtering flexibility. Volume in the larger dimensioned space, space bandwidth-complex axes count, is conserved. Experimental results are presented mapping out the coupled amplitude and phase characteristics of the individual flexure-beam DMD elements and demonstrating the independent control of amplitude and phase in a combined macro-pixel. This technique is generally applicable for implementation with any type of phase modulating light modulator.

Generation of high-order Bessel vortex beam carrying orbital angular momentum using multilayer amplitude-phase-modulated surfaces in radiofrequency domain

NASA Astrophysics Data System (ADS)

Kou, Na; Yu, Shixing; Li, Long

2017-01-01

A high-order Bessel vortex beam carrying orbital angular momentum (OAM) is generated by using multilayer amplitude-phase-modulated surfaces (APMSs) at 10 GHz. The APMS transmitarray is composed of four-layer conformal square-loop (FCSL) surfaces with both amplitude and phase modulation. The APMS can transform a quasi-spherical wave emitted from the feeding source into a pseudo non-diffractive high-order Bessel vortex beam with OAM. The APMS for a second-order Bessel beam carrying OAM in the n = 2 mode is designed, fabricated, and measured. Full-wave simulation and measurement results confirm that Bessel vortex beams with OAM can be effectively generated using the proposed APMS transmitarray.

Amplitude and phase modulation in microwave ring resonators by doped CVD graphene.

PubMed

Grande, M; Bianco, G V; Capezzuto, P; Petruzzelli, V; Prudenzano, F; Scalora, M; Bruno, G; D'Orazio, A

2018-08-10

In this paper, we numerically and experimentally demonstrate how to modulate the amplitude and phase of a microwave ring resonator by means of few-layers chemical vapour deposition graphene. In particular, both numerical and experimental results show a modulation of about 10 dB and a 90 degrees-shift (quadrature phase shift) when the graphene sheet-resistance is varied. These findings prove once again that graphene could be efficiently exploited for the dynamically tuning and modulation of microwave devices fostering the realization of (i) innovative beam-steering and beam-forming systems and (ii) graphene-based sensors.

Space-Time Variations in Tidal Stress and Cascadia Tremor Amplitude

NASA Astrophysics Data System (ADS)

Klaus, A. J.; Creager, K. C.; Sweet, J.; Wech, A.

2011-12-01

We present a new analysis of the influence of tidal stresses on the amplitude of non-volcanic tremor in Washington State. Tremor counts (Thomas et al., 2009), tremor amplitude (Rubinstein et al., 2008), and strain (Hawthorne and Rubin, 2010) are modulated by tidal stresses in Cascadia as well as in California. However, tremor amplitudes have not yet been extensively studied in Cascadia. Furthermore, Hawthorne and Rubin's Cascadia-wide tidal stress model (2010) allows us to look at the tremor-tide relationship in more detail than ever before. The ability to look at the tidal modulation of tremor amplitude in space as well as time will increase our understanding of this phenomenon and may provide information about the frictional properties of the plate interface. We focus on the August 2010 episodic tremor and slip (ETS) event recorded by the Array of Arrays, a seismic experiment on the Olympic Peninsula. The instrument response is deconvolved, seismograms band-pass filtered at 1.5-5.5 Hz and envelopes are made in 5-minute windows. An inverse problem compensates for site corrections and source-receiver distances to produce, for any given time, a single amplitude measurement at the source. Source locations are determined using an envelope waveform cross-correlation method. Then, we compare the amplitudes, catalog of tremor locations, and the tidal stress at the desired location and time. Amplitudes during the August 2010 ETS event are clearly modulated by tidal stresses. Viewed in the frequency domain, there are clear peaks in the tremor amplitude spectrum at several tidal periods, most prominently the 12.4 and 24 hour periods. Comparison with Hawthorne and Rubin's tidal stress model shows that higher amplitudes are associated with positive shear stress in the downdip direction and, less strongly, with more compressional normal stress.

Improving the productivity of S-adenosyl-l-methionine by metabolic engineering in an industrial Saccharomyces cerevisiae strain.

PubMed

Zhao, Weijun; Hang, Baojian; Zhu, Xiangcheng; Wang, Ri; Shen, Minjie; Huang, Lei; Xu, Zhinan

2016-10-20

S-Adenosyl-l-methionine (SAM) is an important metabolite having prominent roles in treating various diseases. In order to improve the production of SAM, the regulation of three metabolic pathways involved in SAM biosynthesis were investigated in an industrial yeast strain ZJU001. GLC3 encoded glycogen-branching enzyme (GBE), SPE2 encoded SAM decarboxylase, as well as ERG4 and ERG6 encoded key enzymes in ergosterol biosynthesis, were knocked out in ZJU001 accordingly. The results indicated that blocking of either glycogen pathway or SAM decarboxylation pathway could improve the SAM accumulation significantly in ZJU001, while single disruption of either ERG4 or ERG6 gene had no obvious effect on SAM production. Moreover, the double mutant ZJU001-GS with deletion of both GLC3 and SPE2 genes was also constructed, which showed further improvement of SAM accumulation. Finally, SAM2 was overexpressed in ZJU001-GS to give the best SAM-producing recombinant strain ZJU001-GS-SAM2, in which 12.47g/L SAM was produced by following our developed pseudo-exponential fed-batch cultivation strategy, about 81.0% increase comparing to its parent strain ZJU001. The present work laid a solid base for large-scale SAM production with the industrial Saccharomyces cerevisiae strain. Copyright © 2016 Elsevier B.V. All rights reserved.

Active mode locking of lasers by piezoelectrically induced diffraction modulation

NASA Astrophysics Data System (ADS)

Krausz, F.; Turi, L.; Kuti, Cs.; Schmidt, A. J.

1990-04-01

A new amplitude-modulation mode-locking technique is presented. Acoustic waves are generated directly on the faces of a resonant photoelastic medium. The created standing waves cause a highly efficient diffraction modulation of light. The modulation depth of standing-wave mode lockers is related to material and drive parameters and a figure of merit is introduced. With a lithium niobate crystal modulation depths over 10 are achieved at 1.054 μm and 1 W of radio frequency power. Using this device for the active mode locking of a continuous-wave Nd:glass laser pulses as short as 3.8 ps are produced at a repetition rate of 66 MHz. Limitations of amplitude-modulation mode locking by standing acoustic waves are discussed.

Cross-quadrature modulation with the Raman-induced Kerr effect

NASA Astrophysics Data System (ADS)

Levenson, M. D.; Holland, M. J.; Walls, D. F.; Manson, P. J.; Fisk, P. T. H.; Bachor, H. A.

1991-08-01

The Raman-enhanced third-order optical nonlinearity of calcite potentially can support resonant back-action-evading measurement of the optical-field amplitude. In a preliminary experiment, we have observed cross-quadrature modulation transfer between an amplitude-modulated pump beam and an unmodulated probe beam tuned near the Stokes frequency. The theory of Holland et al. [Phys. Rev. A 42, 2995 (1990)] is extended to the case for which intracavity losses are significant in an attempt to account for the observations.

Dynamic single sideband modulation for realizing parametric loudspeaker

NASA Astrophysics Data System (ADS)

Sakai, Shinichi; Kamakura, Tomoo

2008-06-01

A parametric loudspeaker, that presents remarkably narrow directivity compared with a conventional loudspeaker, is newly produced and examined. To work the loudspeaker optimally, we prototyped digitally a single sideband modulator based on the Weaver method and appropriate signal processing. The processing techniques are to change the carrier amplitude dynamically depending on the envelope of audio signals, and then to operate the square root or fourth root to the carrier amplitude for improving input-output acoustic linearity. The usefulness of the present modulation scheme has been verified experimentally.

Adsorption of hydrophobin on different self-assembled monolayers: the role of the hydrophobic dipole and the electric dipole.

PubMed

Peng, Chunwang; Liu, Jie; Zhao, Daohui; Zhou, Jian

2014-09-30

In this work, the adsorptions of hydrophobin (HFBI) on four different self-assembled monolayers (SAMs) (i.e., CH3-SAM, OH-SAM, COOH-SAM, and NH2-SAM) were investigated by parallel tempering Monte Carlo and molecular dynamics simulations. Simulation results indicate that the orientation of HFBI adsorbed on neutral surfaces is dominated by a hydrophobic dipole. HFBI adsorbs on the hydrophobic CH3-SAM through its hydrophobic patch and adopts a nearly vertical hydrophobic dipole relative to the surface, while it is nearly horizontal when adsorbed on the hydrophilic OH-SAM. For charged SAM surfaces, HFBI adopts a nearly vertical electric dipole relative to the surface. HFBI has the narrowest orientation distribution on the CH3-SAM, and thus can form an ordered monolayer and reverse the wettability of the surface. For HFBI adsorption on charged SAMs, the adsorption strength weakens as the surface charge density increases. Compared with those on other SAMs, a larger area of the hydrophobic patch is exposed to the solution when HFBI adsorbs on the NH2-SAM. This leads to an increase of the hydrophobicity of the surface, which is consistent with the experimental results. The binding of HFBI to the CH3-SAM is mainly through hydrophobic interactions, while it is mediated through a hydration water layer near the surface for the OH-SAM. For the charged SAM surfaces, the adsorption is mainly induced by electrostatic interactions between the charged surfaces and the oppositely charged residues. The effect of a hydrophobic dipole on protein adsorption onto hydrophobic surfaces is similar to that of an electric dipole for charged surfaces. Therefore, the hydrophobic dipole may be applied to predict the probable orientations of protein adsorbed on hydrophobic surfaces.

Space acceleration measurement system description and operations on the First Spacelab Life Sciences Mission

NASA Technical Reports Server (NTRS)

Delombard, Richard; Finley, Brian D.

1991-01-01

The Space Acceleration Measurement System (SAMS) project and flight units are briefly described. The SAMS operations during the STS-40 mission are summarized, and a preliminary look at some of the acceleration data from that mission are provided. The background and rationale for the SAMS project is described to better illustrate its goals. The functions and capabilities of each SAMS flight unit are first explained, then the STS-40 mission, the SAMS's function for that mission, and the preparation of the SAMS are described. Observations about the SAMS operations during the first SAMS mission are then discussed. Some sample data are presented illustrating several aspects of the mission's microgravity environment.

Specific Eph receptor-cytoplasmic effector signaling mediated by SAM-SAM domain interactions.

PubMed

Wang, Yue; Shang, Yuan; Li, Jianchao; Chen, Weidi; Li, Gang; Wan, Jun; Liu, Wei; Zhang, Mingjie

2018-05-11

The Eph receptor tyrosine kinase (RTK) family is the largest subfamily of RTKs playing critical roles in many developmental processes such as tissue patterning, neurogenesis and neuronal circuit formation, angiogenesis, etc. How the 14 Eph proteins, via their highly similar cytoplasmic domains, can transmit diverse and sometimes opposite cellular signals upon engaging ephrins is a major unresolved question. Here we systematically investigated the bindings of each SAM domain of Eph receptors to the SAM domains from SHIP2 and Odin, and uncover a highly specific SAM-SAM interaction-mediated cytoplasmic Eph-effector binding pattern. Comparative X-ray crystallographic studies of several SAM-SAM heterodimer complexes, together with biochemical and cell biology experiments, not only revealed the exquisite specificity code governing Eph/effector interactions but also allowed us to identify SAMD5 as a new Eph binding partner. Finally, these Eph/effector SAM heterodimer structures can explain many Eph SAM mutations identified in patients suffering from cancers and other diseases. © 2018, Wang et al.

SAM-VI RNAs selectively bind S-adenosylmethionine and exhibit similarities to SAM-III riboswitches.

PubMed

Mirihana Arachchilage, Gayan; Sherlock, Madeline E; Weinberg, Zasha; Breaker, Ronald R

2018-03-04

Five distinct riboswitch classes that regulate gene expression in response to the cofactor S-adenosylmethionine (SAM) or its metabolic breakdown product S-adenosylhomocysteine (SAH) have been reported previously. Collectively, these SAM- or SAH-sensing RNAs constitute the most abundant collection of riboswitches, and are found in nearly every major bacterial lineage. Here, we report a potential sixth member of this pervasive riboswitch family, called SAM-VI, which is predominantly found in Bifidobacterium species. SAM-VI aptamers selectively bind the cofactor SAM and strongly discriminate against SAH. The consensus sequence and structural model for SAM-VI share some features with the consensus model for the SAM-III riboswitch class, whose members are mainly found in lactic acid bacteria. However, there are sufficient differences between the two classes such that current bioinformatics methods separately cluster representatives of the two motifs. These findings highlight the abundance of RNA structures that can form to selectively recognize SAM, and showcase the ability of RNA to utilize diverse strategies to perform similar biological functions.

Detection and rate discrimination of amplitude modulation in electrical hearing.

PubMed

Chatterjee, Monita; Oberzut, Cherish

2011-09-01

Three experiments were designed to examine temporal envelope processing by cochlear implant (CI) listeners. In experiment 1, the hypothesis that listeners' modulation sensitivity would in part determine their ability to discriminate between temporal modulation rates was examined. Temporal modulation transfer functions (TMTFs) obtained in an amplitude modulation detection (AMD) task were compared to threshold functions obtained in an amplitude modulation rate discrimination (AMRD) task. Statistically significant nonlinear correlations were observed between the two measures. In experiment 2, results of loudness-balancing showed small increases in the loudness of modulated over unmodulated stimuli beyond a modulation depth of 16%. Results of experiment 3 indicated small but statistically significant effects of level-roving on the overall gain of the TMTF, but no impact of level-roving on the average shape of the TMTF across subjects. This suggested that level-roving simply increased the task difficulty for most listeners, but did not indicate increased use of intensity cues under more challenging conditions. Data obtained with one subject, however, suggested that the most sensitive listeners may derive some benefit from intensity cues in these tasks. Overall, results indicated that intensity cues did not play an important role in temporal envelope processing by the average CI listener. © 2011 Acoustical Society of America

Interactions between amplitude modulation and frequency modulation processing: Effects of age and hearing loss.

PubMed

Paraouty, Nihaad; Ewert, Stephan D; Wallaert, Nicolas; Lorenzi, Christian

2016-07-01

Frequency modulation (FM) and amplitude modulation (AM) detection thresholds were measured for a 500-Hz carrier frequency and a 5-Hz modulation rate. For AM detection, FM at the same rate as the AM was superimposed with varying FM depth. For FM detection, AM at the same rate was superimposed with varying AM depth. The target stimuli always contained both amplitude and frequency modulations, while the standard stimuli only contained the interfering modulation. Young and older normal-hearing listeners, as well as older listeners with mild-to-moderate sensorineural hearing loss were tested. For all groups, AM and FM detection thresholds were degraded in the presence of the interfering modulation. AM detection with and without interfering FM was hardly affected by either age or hearing loss. While aging had an overall detrimental effect on FM detection with and without interfering AM, there was a trend that hearing loss further impaired FM detection in the presence of AM. Several models using optimal combination of temporal-envelope cues at the outputs of off-frequency filters were tested. The interfering effects could only be predicted for hearing-impaired listeners. This indirectly supports the idea that, in addition to envelope cues resulting from FM-to-AM conversion, normal-hearing listeners use temporal fine-structure cues for FM detection.

Alzheimer Abeta(1-42) monomer adsorbed on the self-assembled monolayers.

PubMed

Wang, Qiuming; Zhao, Jun; Yu, Xiang; Zhao, Chao; Li, Lingyan; Zheng, Jie

2010-08-03

Amyloid-beta (Abeta) peptide aggregation on the cell membranes is a key pathological event responsible for neuron cell death in Alzheimer's disease (AD). We present a collection of molecular docking and molecular dynamics simulations to study the conformational dynamics and adsorption behavior of Abeta monomer on the self-assembled monolayer (SAM), in comparison to Abeta structure in bulk solution. Two distinct Abeta conformations (i.e., alpha-helix and beta-hairpin) are selected as initial structures to mimic different adsorption states, whereas four SAM surfaces with different end groups in hydrophobicity and charge distribution are used to examine the effect of surface chemistry on Abeta structure and adsorption. Simulation results show that alpha-helical monomer displays higher structural stability than beta-hairpin monomer on all SAMs, suggesting that the preferential conformation of Abeta monomer could be alpha-helical or random structure when bound to surfaces. Structural stability and adsorption behavior of Abeta monomer on the SAMs originates from competitive interactions between Abeta and SAM and between SAM and interfacial water, which involve the conformation of Abeta, the surface chemistry of SAM, and the structure and dynamics of interfacial waters. The relative net binding affinity of Abeta with the SAMs is in the favorable order of COOH-SAM > NH(2)-SAM > CH(3)-SAM > OH-SAM, highlighting the importance of electrostatic and hydrophobic interactions for driving Abeta adsorption at the SAMs, but both interactions contribute differently to each Abeta-SAM complex. This work provides parallel insights into the understanding of Abeta structure and aggregation on cell membrane.

7 CFR 1739.10 - Eligible applicant.

Code of Federal Regulations, 2014 CFR

2014-01-01

...'s number. (d) Register in the System for Award Management (SAM) (formerly Central Contractor... paper, must be registered in the SAM prior to submitting an application. Applicants may register for the SAM at https://www.sam.gov/. (2) The SAM registration must remain active, with current information, at...

Self-tuning bistable parametric feedback oscillator: Near-optimal amplitude maximization without model information

NASA Astrophysics Data System (ADS)

Braun, David J.; Sutas, Andrius; Vijayakumar, Sethu

2017-01-01

Theory predicts that parametrically excited oscillators, tuned to operate under resonant condition, are capable of large-amplitude oscillation useful in diverse applications, such as signal amplification, communication, and analog computation. However, due to amplitude saturation caused by nonlinearity, lack of robustness to model uncertainty, and limited sensitivity to parameter modulation, these oscillators require fine-tuning and strong modulation to generate robust large-amplitude oscillation. Here we present a principle of self-tuning parametric feedback excitation that alleviates the above-mentioned limitations. This is achieved using a minimalistic control implementation that performs (i) self-tuning (slow parameter adaptation) and (ii) feedback pumping (fast parameter modulation), without sophisticated signal processing past observations. The proposed approach provides near-optimal amplitude maximization without requiring model-based control computation, previously perceived inevitable to implement optimal control principles in practical application. Experimental implementation of the theory shows that the oscillator self-tunes itself near to the onset of dynamic bifurcation to achieve extreme sensitivity to small resonant parametric perturbations. As a result, it achieves large-amplitude oscillations by capitalizing on the effect of nonlinearity, despite substantial model uncertainties and strong unforeseen external perturbations. We envision the present finding to provide an effective and robust approach to parametric excitation when it comes to real-world application.

Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds II: single-neuron recordings

PubMed Central

Marquardt, Torsten; Stange, Annette; Pecka, Michael; Grothe, Benedikt; McAlpine, David

2014-01-01

Recently, with the use of an amplitude-modulated binaural beat (AMBB), in which sound amplitude and interaural-phase difference (IPD) were modulated with a fixed mutual relationship (Dietz et al. 2013b), we demonstrated that the human auditory system uses interaural timing differences in the temporal fine structure of modulated sounds only during the rising portion of each modulation cycle. However, the degree to which peripheral or central mechanisms contribute to the observed strong dominance of the rising slope remains to be determined. Here, by recording responses of single neurons in the medial superior olive (MSO) of anesthetized gerbils and in the inferior colliculus (IC) of anesthetized guinea pigs to AMBBs, we report a correlation between the position within the amplitude-modulation (AM) cycle generating the maximum response rate and the position at which the instantaneous IPD dominates the total neural response. The IPD during the rising segment dominates the total response in 78% of MSO neurons and 69% of IC neurons, with responses of the remaining neurons predominantly coding the IPD around the modulation maximum. The observed diversity of dominance regions within the AM cycle, especially in the IC, and its comparison with the human behavioral data suggest that only the subpopulation of neurons with rising slope dominance codes the sound-source location in complex listening conditions. A comparison of two models to account for the data suggests that emphasis on IPDs during the rising slope of the AM cycle depends on adaptation processes occurring before binaural interaction. PMID:24554782

Dynamical and statistical phenomena of circulation and heat transfer in periodically forced rotating turbulent Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Sterl, Sebastian; Li, Hui-Min; Zhong, Jin-Qiang

2016-12-01

In this paper, we present results from an experimental study into turbulent Rayleigh-Bénard convection forced externally by periodically modulated unidirectional rotation rates. We find that the azimuthal rotation velocity θ ˙(t ) and thermal amplitude δ (t ) of the large-scale circulation (LSC) are modulated by the forcing, exhibiting a variety of dynamics including increasing phase delays and a resonant peak in the amplitude of θ ˙(t ) . We also focus on the influence of modulated rotation rates on the frequency of occurrence η of stochastic cessation or reorientation events, and on the interplay between such events and the periodically modulated response of θ ˙(t ) . Here we identify a mechanism by which η can be amplified by the modulated response, and these normally stochastic events can occur with high regularity. We provide a modeling framework that explains the observed amplitude and phase responses, and we extend this approach to make predictions for the occurrence of cessation events and the probability distributions of θ ˙(t ) and δ (t ) during different phases of a modulation cycle, based on an adiabatic approach that treats each phase separately. Last, we show that such periodic forcing has consequences beyond influencing LSC dynamics, by investigating how it can modify the heat transport even under conditions where the Ekman pumping effect is predominant and strong enhancement of heat transport occurs. We identify phase and amplitude responses of the heat transport, and we show how increased modulations influence the average Nusselt number.

SAM Photovoltaic Model Technical Reference

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

Gilman, P.

2015-05-27

This manual describes the photovoltaic performance model in the System Advisor Model (SAM). The U.S. Department of Energy’s National Renewable Energy Laboratory maintains and distributes SAM, which is available as a free download from https://sam.nrel.gov. These descriptions are based on SAM 2015.1.30 (SSC 41).

SAM International Case Studies: DPV Analysis in Mexico

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

McCall, James D

Presentation demonstrates the use of the System Advisor Model (SAM) in international analyses, specifically Mexico. Two analyses are discussed with relation to SAM modelling efforts: 1) Customer impacts from changes to net metering and billing agreements and 2) Potential benefits of PV for Mexican solar customers, the Mexican Treasury, and the environment. Along with the SAM analyses, integration of the International Utility Rate Database (I-URDB) with SAM and future international SAM work are discussed. Presentation was created for the International Solar Energy Society's (ISES) webinar titled 'International use of the NREL System Advisor Model (SAM) with case studies'.

Structural Basis for Methyl Transfer by a Radical SAM Enzyme

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

Boal, Amie K.; Grove, Tyler L.; McLaughlin, Monica I.

2014-10-02

The radical S-adenosyl-l-methionine (SAM) enzymes RlmN and Cfr methylate 23S ribosomal RNA, modifying the C2 or C8 position of adenosine 2503. The methyl groups are installed by a two-step sequence involving initial methylation of a conserved Cys residue (RlmN Cys{sup 355}) by SAM. Methyl transfer to the substrate requires reductive cleavage of a second equivalent of SAM. Crystal structures of RlmN and RlmN with SAM show that a single molecule of SAM coordinates the [4Fe-4S] cluster. Residue Cys{sup 355} is S-methylated and located proximal to the SAM methyl group, suggesting the SAM that is involved in the initial methyl transfermore » binds at the same site. Thus, RlmN accomplishes its complex reaction with structural economy, harnessing the two most important reactivities of SAM within a single site.« less

Mice heterozygous for the Mdr2 gene demonstrate decreased PEMT activity and diminished steatohepatitis on the MCD diet.

PubMed

Igolnikov, Alexander C; Green, Richard M

2006-03-01

The administration of a methionine and choline deficient (MCD) diet to mice serves as an animal model of NASH. The multidrug resistant 2 (Mdr2) P-glycoprotein encodes for the canalicular phospholipid transporter, and Mdr2 (+/-) mice secrete 40% less phosphatidylcholine than wild-type mice. We have hypothesized that phosphatidylethanolamine-N-methyl transferase (PEMT) up-regulation is a consequence of MCD diet administration, and is important for the pathogenesis of steatohepatitis in this model. However, the effect of decreased phosphatidylcholine secretion and modulation of PEMT on the development of diet-induced steatohepatitis in Mdr2 (+/-) mice has not been explored. Thus, the purpose of the study is to examine the effects of the MCD diet on Mdr2 (+/-) mice. Mdr2 (+/-) and Mdr2 (+/+) mice were treated with an MCD or control diet for up to 30 days, and the severity of steatohepatitis, PEMT activity and hepatic S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH) levels were measured. Serum ALT levels, hepatic inflammation, and PEMT activity were significantly lower, and hepatic SAM:SAH ratios were significantly higher in Mdr2 (+/-) mice at 7 and 30 days on the MCD diet. Mdr2 (+/-) mice have diminished susceptibility to MCD diet-induced NASH, which is associated with a relative decrease in PEMT activity and increased SAM:SAH ratios.

The role of surface electrostatics on the stability, function and regulation of human cystathionine β-synthase, a complex multidomain and oligomeric protein.

PubMed

Pey, Angel L; Majtan, Tomas; Kraus, Jan P

2014-09-01

Human cystathionine β-synthase (hCBS) is a key enzyme of sulfur amino acid metabolism, controlling the commitment of homocysteine to the transsulfuration pathway and antioxidant defense. Mutations in hCBS cause inherited homocystinuria (HCU), a rare inborn error of metabolism characterized by accumulation of toxic homocysteine in blood and urine. hCBS is a complex multidomain and oligomeric protein whose activity and stability are independently regulated by the binding of S-adenosyl-methionine (SAM) to two different types of sites at its C-terminal regulatory domain. Here we study the role of surface electrostatics on the complex regulation and stability of hCBS using biophysical and biochemical procedures. We show that the kinetic stability of the catalytic and regulatory domains is significantly affected by the modulation of surface electrostatics through noticeable structural and energetic changes along their denaturation pathways. We also show that surface electrostatics strongly affect SAM binding properties to those sites responsible for either enzyme activation or kinetic stabilization. Our results provide new insight into the regulation of hCBS activity and stability in vivo with implications for understanding HCU as a conformational disease. We also lend experimental support to the role of electrostatic interactions in the recently proposed binding modes of SAM leading to hCBS activation and kinetic stabilization. Copyright © 2014 Elsevier B.V. All rights reserved.

Investigation of gas surface interactions at self-assembled silicon surfaces acting as gas sensors

NASA Astrophysics Data System (ADS)

Narducci, Dario; Bernardinello, Patrizia; Oldani, Matteo

2003-05-01

This paper reports the results of an investigation aimed at using self-assembled monolayers to modify the supramolecular interactions between Si surfaces and gaseous molecules. The specific goal is that of employing molecularly imprinted silicon surfaces to develop a new class of chemical sensors capable to detect species with enhanced selectivity. Single-crystal p-type (0 0 1) silicon has been modified by grafting organic molecules onto its surface by using wet chemistry synthetic methods. Silicon has been activated toward nucleophilic attack by brominating its surface using a modified version of the purple etch, and aromatic fragments have been bonded through the formation of direct Si-C bonds onto it using Grignard reagents or lithium aryl species. Formation of self-assembled monolayers (SAMs) was verified by using vibrational spectroscopy. Porous metal-SAM-Si diodes have been successfully tested as resistive chemical sensors toward NO x, SO x, CO, NH 3 and methane. Current-voltage characteristics measured at different gas compositions showed that the mechanism of surface electron density modulation involves a modification of the junction barrier height upon gas adsorption. Quantum-mechanical simulations of the interaction mechanism were carried out using different computational methods to support such an interaction mechanism. The results obtained appear to open up new relevant applications of the SAM techniques in the area of gas sensing.

Characterization of the SAM domain of the PKD-related protein ANKS6 and its interaction with ANKS3.

PubMed

Leettola, Catherine N; Knight, Mary Jane; Cascio, Duilio; Hoffman, Sigrid; Bowie, James U

2014-07-07

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disorder leading to end-stage renal failure in humans. In the PKD/Mhm(cy/+) rat model of ADPKD, the point mutation R823W in the sterile alpha motif (SAM) domain of the protein ANKS6 is responsible for disease. SAM domains are known protein-protein interaction domains, capable of binding each other to form polymers and heterodimers. Despite its physiological importance, little is known about the function of ANKS6 and how the R823W point mutation leads to PKD. Recent work has revealed that ANKS6 interacts with a related protein called ANKS3. Both ANKS6 and ANKS3 have a similar domain structure, with ankyrin repeats at the N-terminus and a SAM domain at the C-terminus. The SAM domain of ANKS3 is identified as a direct binding partner of the ANKS6 SAM domain. We find that ANKS3-SAM polymerizes and ANKS6-SAM can bind to one end of the polymer. We present crystal structures of both the ANKS3-SAM polymer and the ANKS3-SAM/ANKS6-SAM complex, revealing the molecular details of their association. We also learn how the R823W mutation disrupts ANKS6 function by dramatically destabilizing the SAM domain such that the interaction with ANKS3-SAM is lost. ANKS3 is a direct interacting partner of ANKS6. By structurally and biochemically characterizing the interaction between the ANKS3 and ANKS6 SAM domains, our work provides a basis for future investigation of how the interaction between these proteins mediates kidney function.

Characterization of the SAM domain of the PKD-related protein ANKS6 and its interaction with ANKS3

PubMed Central

2014-01-01

Background Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disorder leading to end-stage renal failure in humans. In the PKD/Mhm(cy/+) rat model of ADPKD, the point mutation R823W in the sterile alpha motif (SAM) domain of the protein ANKS6 is responsible for disease. SAM domains are known protein-protein interaction domains, capable of binding each other to form polymers and heterodimers. Despite its physiological importance, little is known about the function of ANKS6 and how the R823W point mutation leads to PKD. Recent work has revealed that ANKS6 interacts with a related protein called ANKS3. Both ANKS6 and ANKS3 have a similar domain structure, with ankyrin repeats at the N-terminus and a SAM domain at the C-terminus. Results The SAM domain of ANKS3 is identified as a direct binding partner of the ANKS6 SAM domain. We find that ANKS3-SAM polymerizes and ANKS6-SAM can bind to one end of the polymer. We present crystal structures of both the ANKS3-SAM polymer and the ANKS3-SAM/ANKS6-SAM complex, revealing the molecular details of their association. We also learn how the R823W mutation disrupts ANKS6 function by dramatically destabilizing the SAM domain such that the interaction with ANKS3-SAM is lost. Conclusions ANKS3 is a direct interacting partner of ANKS6. By structurally and biochemically characterizing the interaction between the ANKS3 and ANKS6 SAM domains, our work provides a basis for future investigation of how the interaction between these proteins mediates kidney function. PMID:24998259

Molecular dynamics simulations of low-ordered alzheimer β-amyloid oligomers from dimer to hexamer on self-assembled monolayers.

PubMed

Zhao, Jun; Wang, Qiuming; Liang, Guizhao; Zheng, Jie

2011-12-20

Accumulation of small soluble oligomers of amyloid-β (Aβ) in the human brain is thought to play an important pathological role in Alzheimer's disease. The interaction of these Aβ oligomers with cell membrane and other artificial surfaces is important for the understanding of Aβ aggregation and toxicity mechanisms. Here, we present a series of exploratory molecular dynamics (MD) simulations to study the early adsorption and conformational change of Aβ oligomers from dimer to hexamer on three different self-assembled monolayers (SAMs) terminated with CH(3), OH, and COOH groups. Within the time scale of MD simulations, the conformation, orientation, and adsorption of Aβ oligomers on the SAMs is determined by complex interplay among the size of Aβ oligomers, the surface chemistry of the SAMs, and the structure and dynamics of interfacial waters. Energetic analysis of Aβ adsorption on the SAMs reveals that Aβ adsorption on the SAMs is a net outcome of different competitions between dominant hydrophobic Aβ-CH(3)-SAM interactions and weak CH(3)-SAM-water interactions, between dominant electrostatic Aβ-COOH-SAM interactions and strong COOH-SAM-water interactions, and between comparable hydrophobic and electrostatic Aβ-OH-SAM interactions and strong OH-SAM-water interactions. Atomic force microscopy images also confirm that all of three SAMs can induce the adsorption and polymerization of Aβ oligomers. Structural analysis of Aβ oligomers on the SAMs shows a dramatic increase in structural stability and β-sheet content from dimer to trimer, suggesting that Aβ trimer could act as seeds for Aβ polymerization on the SAMs. This work provides atomic-level understanding of Aβ peptides at interface. © 2011 American Chemical Society

Edge-to-edge repair for prevention and treatment of mitral valve systolic anterior motion.

PubMed

Myers, Patrick O; Khalpey, Zain; Maloney, Ann M; Brinster, Derek R; D'Ambra, Michael N; Cohn, Lawrence H

2013-10-01

The edge-to-edge technique has been proposed to prevent systolic anterior motion (SAM) of the mitral valve. There is limited clinical data available on outcomes of this technique for this indication. We reviewed the midterm results of this technique for SAM prevention and treatment. A total of 2226 patients had mitral valve repair between 2000 and 2011, 1148 of which were for myxomatous mitral regurgitation. Beginning in 2000, predictability of postrepair SAM based on the prebypass, intraoperative transesophageal echocardiogram arose in our program. The edge-to-edge technique was used in 65 patients (5.7%) for SAM management, in 53 patients preemptively for transesophageal echocardiogram-based SAM prediction, and in 12 patients for postrepair SAM treatment. There was no operative mortality. Postoperative mitral regurgitation was significantly improved in all patients compared with the preoperative grade (P < .001). SAM was completely eliminated, the mean mitral regurgitation grade in the postoperative period was 0.7 ± 0.9, and the mean transmitral gradient was 1.3 ± 2.2 mm Hg. During a mean follow-up of 26 months, 1 patient in the SAM treatment group presented late recurrence of SAM and no patients developed mitral stenosis (mean transmitral gradient, 2.0 ± 2.6 mm Hg; P = .12). Without SAM prediction and preemptive edge-to-edge technique, the expected rate of SAM would have been 5.7%; however, the observed rate was 1% (12 of 1148 patients). Initiating an expectation for prebypass SAM prediction, combined with a surgical SAM prevention strategy, resulted in a reduced prevalence of SAM compared with our model of observed to-expected-ratios and to published norms. Copyright © 2013 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

47 CFR 78.115 - Modulation limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Modulation limits. 78.115 Section 78.115... SERVICE Technical Regulations § 78.115 Modulation limits. (a) If amplitude modulation is employed, negative modulation peaks shall not exceed 100 percent modulation. [37 FR 3292, Feb. 12, 1972, as amended...

Information theory analysis of patterns of modulation in the advertisement call of the male bullfrog, Rana catesbeianaa)

PubMed Central

Suggs, Dianne N.; Simmons, Andrea Megela

2005-01-01

Male bullfrogs often amplitude modulate the envelopes of the individual notes (croaks) in their multinote advertisement calls. These amplitude modulations change the envelope of the note from smooth and unmodulated to one with varying numbers of modulations. A Markov analysis shows the pattern of change in the envelope to be highly ordered, but not completely so (semi-Markovian). Three simple rules govern the presence or absence of modulations in individual notes. These rules are (1) all calls begin with an unmodulated note; (2) the first note to be modulated will contain only one modulation; and (3) when a change in modulation occurs from one note to the next, it does so with an increase or a decrease of one modulation only. The addition of modulations is correlated with an increase in note duration. Physiologically, the presence of modulations might increase the precision of temporal coding of note periodicities in the central auditory system. PMID:15898673

S-adenosyl-methionine (SAM) alters the transcriptome and methylome and specifically blocks growth and invasiveness of liver cancer cells

PubMed Central

Wang, Yan; Sun, ZhongSheng; Szyf, Moshe

2017-01-01

S-adenosyl methionine (SAM) is a ubiquitous methyl donor that was reported to have chemo- protective activity against liver cancer, however the molecular footprint of SAM is unknown. We show here that SAM selectively inhibits growth, transformation and invasiveness of hepatocellular carcinoma cell lines but not normal primary liver cells. Analysis of the transcriptome of SAM treated and untreated liver cancer cell lines HepG2 and SKhep1 and primary liver cells reveals pathways involved in cancer and metastasis that are upregulated in cancer cells and are downregulated by SAM. Analysis of the methylome using bisulfite mapping of captured promoters and enhancers reveals that SAM hyper-methylates and downregulates genes in pathways of growth and metastasis that are upregulated in liver cancer cells. Depletion of two SAM downregulated genes STMN1 and TAF15 reduces cellular transformation and invasiveness, providing evidence that SAM targets are genes important for cancer growth and invasiveness. Taken together these data provide a molecular rationale for SAM as an anticancer agent. PMID:29340097

S-adenosyl-methionine (SAM) alters the transcriptome and methylome and specifically blocks growth and invasiveness of liver cancer cells.

PubMed

Wang, Yan; Sun, ZhongSheng; Szyf, Moshe

2017-12-19

S-adenosyl methionine (SAM) is a ubiquitous methyl donor that was reported to have chemo- protective activity against liver cancer, however the molecular footprint of SAM is unknown. We show here that SAM selectively inhibits growth, transformation and invasiveness of hepatocellular carcinoma cell lines but not normal primary liver cells. Analysis of the transcriptome of SAM treated and untreated liver cancer cell lines HepG2 and SKhep1 and primary liver cells reveals pathways involved in cancer and metastasis that are upregulated in cancer cells and are downregulated by SAM. Analysis of the methylome using bisulfite mapping of captured promoters and enhancers reveals that SAM hyper-methylates and downregulates genes in pathways of growth and metastasis that are upregulated in liver cancer cells. Depletion of two SAM downregulated genes STMN1 and TAF15 reduces cellular transformation and invasiveness, providing evidence that SAM targets are genes important for cancer growth and invasiveness. Taken together these data provide a molecular rationale for SAM as an anticancer agent.

Electro-optic modulator with ultra-low residual amplitude modulation for frequency modulation and laser stabilization.

PubMed

Tai, Zhaoyang; Yan, Lulu; Zhang, Yanyan; Zhang, Xiaofei; Guo, Wenge; Zhang, Shougang; Jiang, Haifeng

2016-12-01

The reduction of the residual amplitude modulation (RAM) induced by electro-optic modulation is essential for many applications of frequency modulation spectroscopy requiring a lower system noise floor. Here, we demonstrate a simple passive approach employing an electro-optic modulator (EOM) cut at Brewster's angle. The proposed EOM exhibits a RAM of a few parts per million, which is comparable with that achieved by a common EOM under critical active temperature and bias voltage controls. The frequency instability of a 10 cm cavity-stabilized laser induced by the RAM effect of the proposed EOM is below 3×10^-17 for integration times from 1 to 1000 s, and below 4×10^-16 for comprehensive noise contributions for integration times from 1 to 100 s.

Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation

NASA Astrophysics Data System (ADS)

Sosnovtseva, O. V.; Pavlov, A. N.; Mosekilde, E.; Holstein-Rathlou, N.-H.; Marsh, D. J.

2004-09-01

Biological time series often display complex oscillations with several interacting rhythmic components. Renal autoregulation, for instance, involves at least two separate mechanisms both of which can produce oscillatory variations in the pressures and flows of the individual nephrons. Using double-wavelet analysis we propose a method to examine how the instantaneous frequency and amplitude of a fast mode is modulated by the presence of a slower mode. Our method is applied both to experimental data from normotensive and hypertensive rats showing different oscillatory patterns and to simulation results obtained from a physiologically based model of the nephron pressure and flow control. We reveal a nonlinear interaction between the two mechanisms that regulate the renal blood flow in the form of frequency and amplitude modulation of the myogenic oscillations.

Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon

NASA Astrophysics Data System (ADS)

Kiss, L. L.; Bódi, A.

2017-12-01

Context. RV Tauri-type variables are pulsating post-asymptotic giant branch (AGB) stars that evolve rapidly through the instability strip after leaving the AGB. Their light variability is dominated by radial pulsations. Members of the RVb subclass show an additional variability in the form of a long-term modulation of the mean brightness, for which the most popular theories all assume binarity and some kind of circumstellar dust. Here we assess whether or not the amplitude modulations are consistent with the dust obscuration model. Aims: We measure and interpret the overall changes of the mean amplitude of the pulsations along the RVb variability. Methods: We compiled long-term photometric data for RVb-type stars, including visual observations of the American Association of Variable Star Observers, ground-based CCD photometry from the OGLE and ASAS projects, and ultra-precise space photometry of one star, DF Cygni, from theKepler space telescope. After converting all the observations to flux units, we measure the cycle-to-cycle variations of the pulsation amplitude and correlate them to the actual mean fluxes. Results: We find a surprisingly uniform correlation between the pulsation amplitude and the mean flux; they scale linearly with each other for a wide range of fluxes and amplitudes. This means that the pulsation amplitude actually remains constant when measured relative to the system flux level. The apparent amplitude decrease in the faint states has long been noted in the literature but it was always claimed to be difficult to explain with the actual models of the RVb phenomenon. Here we show that when fluxes are used instead of magnitudes, the amplitude attenuation is naturally explained by periodic obscuration from a large opaque screen, one most likely corresponding to a circumbinary dusty disk that surrounds the whole system.

The use of alkanethiol self-assembled monolayers on 316L stainless steel for coronary artery stent nanomedicine applications: an oxidative and in vitro stability study.

PubMed

Mahapatro, Anil; Johnson, Dave M; Patel, Devang N; Feldman, Marc D; Ayon, Arturo A; Agrawal, C Mauli

2006-09-01

The use of self-assembled monolayers (SAMs) on medical devices offers a methodology for the incorporation of nanotechnology into medicine. SAMs are highly ordered nanosized molecular coatings, adding 1 to 10 nm thickness to a surface. This work is part of an overall goal to deliver therapeutic drugs from the surface of metal coronary stents using SAMs. In this study the oxidative and in vitro stability of functional alkylthiol SAMs on 316L stainless steel (SS) has been demonstrated. SAMs of 11-mercaptoundecanoic acid (-COOH SAM) and 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle (CA) measurements collectively confirmed the formation of functional alkylthiol SAMs on 316L SS. Well-formed SAMs (CA: 82 deg +/- 9 deg) were achieved within 48 hours of immersion in ethanolic solutions, after which no significant improvement in CA was observed. The ratio of the thiolate peak (163.5 eV) to the oxidized sulfur (sulfonates) peak (166.5 eV) gives us an indication of the percentage SAMs that would bind to the metal and serve as a drug reservoir in vivo; which in turn represents the stability and viability of these SAMs, keeping in mind the cardiovascular application under consideration. Oxidative and in vitro stability studies showed that alkanethiol SAMs oxidized completely within 14 days. The SAMs tend to desorb and leave the metal surface after longer time periods (21 days) in phosphate-buffered saline (PBS) immersion, whereas for oxidative exposure the SAMs continue to remain on the metal surface in the form of sulfonates. Although the chemistry of bonding of alkylthiol with the 316L SS is not well understood, the nanosized alkylthiol SAMs demonstrate sufficient stability to justify further study on these systems for potential in vivo drug delivery in the chosen coronary artery stent applications.

Active mode locking of lasers by piezoelectrically induced diffraction modulation

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

Krausz, F.; Turi, L.; Kuti, C.

A new amplitude-modulation mode-locking technique is presented. Acoustic waves are generated directly on the faces of a resonant photoelastic medium. The created standing waves cause a highly efficient diffraction modulation of light. The modulation depth of standing-wave mode lockers is related to material and drive parameters and a figure of merit is introduced. With a lithium niobate crystal modulation depths over 10 are achieved at 1.054 {mu}m and 1 W of radio frequency power. Using this device for the active mode locking of a continuous-wave Nd:glass laser pulses as short as 3.8 ps are produced at a repetition rate ofmore » 66 MHz. Limitations of amplitude-modulation mode locking by standing acoustic waves are discussed.« less

Standardized added metabolic activity (SAM): a partial volume independent marker of total lesion glycolysis in liver metastases.

PubMed

Mertens, Jeroen; Dobbeleir, André; Ham, Hamphrey; D'Asseler, Yves; Goethals, Ingeborg; Van de Wiele, Christophe

2012-09-01

The standardized added metabolic activity (SAM) is a new marker of total lesion glycolysis that avoids partial volume effect (PVE) and thresholding. SAM is calculated by drawing a volume of interest (VOI(1)) around the tumour and a larger VOI (VOI(2)) around VOI(1). Subtracting the background activity in VOI(2)-VOI(1) from VOI(1) yields SAM. If VOI(1) is set at a reasonable distance from the tumour, PVE are avoided. Phantom and initial clinical validation data are presented. Spheres of a Jaszczak phantom were filled with a 5.4, 3.64 and 2.0 times higher concentration relative to background activity and positron emission tomography (PET) data were acquired during 10 min. SAM of all spheres was expressed as a percentage of the expected value (the actual activity ratio minus 1). In 15 patients a 10-min list-mode acquisition PET study centred on their primary squamous cell carcinoma (PSCC) was performed and images of 1-10 min reconstructed. SAM1-9min values of PSCC were expressed as a percentage of SAM10min. Nineteen patients suffering from liver metastases treated with chemotherapy underwent PET/CT prior to (scan 1) and after 3-6 cycles of chemotherapy (scan 2). SAM and maximum standardized uptake values (SUV(max)) of the liver lesions on scan 1 (SAM1 and SUV(max)1) and the percentage reduction between both ΔSAM and ΔSUV(max) were related to Response Evaluation Criteria in Solid Tumors (RECIST) response. For the phantom acquisitions, the mean normalized SAM/sphere volume calculated was 94.9 % (SD 5.9 %) of the expected value. In the PSCC patients, the mean difference between SAM1min and SAM10min was only 4 % (SD 5 %). SUV(max)1min and SUV(max)10min proved to be not significantly different, but the variability was slightly larger than that of SAM (SD 6.4 %). SAM1 and ΔSAM values for responders versus non-responders were, respectively, 57 (SD 119) versus 297 (SD 625) for SAM1 (p = 0.2) and 99 % (SD 3 %) versus 32 % (SD 44 %) for ΔSAM (p = 0.001). SUV(max)1 and ΔSUV(max) values in responders versus non-responders were, respectively, 3.9 (SD 2.4) versus 6.3 (SD 3.1) for SUV(max)1 (p = 0.08) and 94 % (SD 17) versus 7 % (SD 40 %) for ΔSUV(max) (p = 0.0001). The AUC of ΔSAM and ΔSUV(max) were not significantly different on receiver-operating characteristic (ROC) analysis (AUC 1.0 and 0.99, respectively, p = 0.6). SAM is a promising parameter for tumour response assessment of liver metastases by means of (18)F-fluorodeoxyglucose PET.

Cross-Modulated Amplitudes and Frequencies Characterize Interacting Components in Complex Systems

NASA Astrophysics Data System (ADS)

Gans, Fabian; Schumann, Aicko Y.; Kantelhardt, Jan W.; Penzel, Thomas; Fietze, Ingo

2009-03-01

The dynamics of complex systems is characterized by oscillatory components on many time scales. To study the interactions between these components we analyze the cross modulation of their instantaneous amplitudes and frequencies, separating synchronous and antisynchronous modulation. We apply our novel technique to brain-wave oscillations in the human electroencephalogram and show that interactions between the α wave and the δ or β wave oscillators as well as spatial interactions can be quantified and related with physiological conditions (e.g., sleep stages). Our approach overcomes the limitation to oscillations with similar frequencies and enables us to quantify directly nonlinear effects such as positive or negative frequency modulation.

Modulating complex beams in amplitude and phase using fast tilt-micromirror arrays and phase masks.

PubMed

Roth, Matthias; Heber, Jörg; Janschek, Klaus

2018-06-15

The Letter proposes a system for the spatial modulation of light in amplitude and phase at kilohertz frame rates and high spatial resolution. The focus is fast spatial light modulators (SLMs) consisting of continuously tiltable micromirrors. We investigate the utilization of such SLMs in combination with a static phase mask in a 4f setup. The phase mask enables the complex beam modulation in a linear optical arrangement. Furthermore, adding so-called phase steps to the phase mask increases both the number of image pixels at constant SLM resolution and the optical efficiency. We illustrate our concept based on numerical simulations.

Research on the trace detection of carbon dioxide gas and modulation parameter optimization based on the TDLAS technology

NASA Astrophysics Data System (ADS)

Zhao, Peng; Tao, Jun; Yu, Chang-rui; Li, Ye

2014-02-01

Based on the technology of tunable diode laser absorption spectroscopy, modulation of the center wavelength of 2004 nm distributed feedback laser diode at a room-temperature, the second harmonic amplitude of CO2 at 2004nm can be obtained. The CO2 concentration can be calculated via the Beer-Lambert law. Sinusoidal modulation parameter is an important factor that affects the sensitivity and accuracy of the system, through the research on the relationship between sinusoidal modulation signal frequency, amplitude and Second harmonic linetype, we finally achieve the detection limit of 10ppm under 12 m optical path.

Transverse Mode Dynamics of VCSELs Undergoing Current Modulation

NASA Technical Reports Server (NTRS)

Goorjian, Peter M.; Ning, C. Z.; Agrawal, Govind

2000-01-01

Transverse mode dynamics of a 20-micron-diameter vertical-cavity surface-emitting laser (VCSEL) undergoing gain switching by deep current modulation is studied numerically. The direct current (dc) level is set slightly below threshold and is modulated by a large alternating current (ac). The resulting optical pulse train and transverse-mode patterns are obtained numerically. The ac frequency is varied from 2.5 GHz to 10 GHz, and the ac amplitude is varied from one-half to four times that of the dc level. At high modulation frequencies, a regular pulse train is not generated unless the ac amplitude is large enough. At all modulation frequencies, the transverse spatial profile switches from single-mode to multiple-mode pattern as the ac pumping level is increased. Optical pulse widths vary in the range 5-30 ps. with the pulse width decreasing when either the frequency is increased or the ac amplitude is decreased. The numerical modeling uses an approximation form of the semiconductor Maxwell-Bloch equations. Temporal evolution of the spatial profiles of the laser (and of carrier density) is determined without any assumptions about the type or number of modes. Keywords: VCSELs, current modulation, gain switching, transverse mode dynamics, computational modeling

Nonlinear Right-Hand Polarized Wave in Plasma in the Electron Cyclotron Resonance Region

NASA Astrophysics Data System (ADS)

Krasovitskiy, V. B.; Turikov, V. A.

2018-05-01

The propagation of a nonlinear right-hand polarized wave along an external magnetic field in subcritical plasma in the electron cyclotron resonance region is studied using numerical simulations. It is shown that a small-amplitude plasma wave excited in low-density plasma is unstable against modulation instability with a modulation period equal to the wavelength of the excited wave. The modulation amplitude in this case increases with decreasing detuning from the resonance frequency. The simulations have shown that, for large-amplitude waves of the laser frequency range propagating in plasma in a superstrong magnetic field, the maximum amplitude of the excited longitudinal electric field increases with the increasing external magnetic field and can reach 30% of the initial amplitude of the electric field in the laser wave. In this case, the energy of plasma electrons begins to substantially increase already at magnetic fields significantly lower than the resonance value. The laser energy transferred to plasma electrons in a strong external magnetic field is found to increase severalfold compared to that in isotropic plasma. It is shown that this mechanism of laser radiation absorption depends only slightly on the electron temperature.

Gene switching in Amoeba proteus caused by endosymbiotic bacteria.

PubMed

Jeon, Taeck J; Jeon, Kwang W

2004-02-01

The expression of genes for S-adenosylmethionine synthetase (SAMS), which catalyzes the synthesis of S-adenosylmethionine (AdoMet), a major methyl donor in cells, was studied in symbiont-free (D) and symbiont-bearing (xD) amoeba strains to determine the effect of bacterial endosymbionts. The symbionts suppressed the expression of the gene in host xD amoebae, but amoebae still exhibited about half the enzyme activity found in symbiont-free D amoebae. The study was aimed at elucidating mechanisms of the suppression of the amoeba's gene and determining the alternative source for the gene product. Unexpectedly, we found a second sams (sams2) gene in amoebae, which encoded 390 amino acids. Results of experiments measuring SAMS activities and amounts of AdoMet in D and xD amoebae showed that the half SAMS activity found in xD amoebae came from the amoeba's SAMS2 and not from their endosymbionts. The expression of amoeba sams genes was switched from sams1 to sams2 as a result of infection with X-bacteria, raising the possibility that the switch in the expression of sams genes by bacteria plays a role in the development of symbiosis and the host-pathogen interactions. This is the first report showing such a switch in the expression of host sams genes by infecting bacteria.

Implication of Taylor's hypothesis on amplitude modulation

NASA Astrophysics Data System (ADS)

Howland, Michael; Yang, Xiang

2017-11-01

Amplitude modulation is a physical phenomenon which describes the non-linear inter-scale interaction between large and small scales in a turbulent wall-bounded flow. The amplitude of the small scale fluctuations are modulated by the large scale flow structures. Due to the increase of amplitude modulation as a function of Reynolds number (Reτ = δuτ / ν), this phenomenon is frequently studied using experimental temporal 1D signals, taken using hot-wire anemometry. Typically, Taylor's frozen turbulence hypothesis has been invoked where the convection by velocity fluctuations is neglected and the mean velocity is used as the convective velocity. At high Reynolds numbers, turbulent fluctuations are comparable to the mean velocity in the near wall region (y+ O(10)), and as a result, using a constant global convective velocity systematically locally compresses or stretches a velocity signal when converting from temporal to spatial domain given a positive or negative fluctuation respectively. Despite this, temporal hot-wire data from wind tunnel or field experiments of high Reynolds number boundary layer flows can still be used for measuring modulation provided that the local fluid velocity is used as the local convective velocity. MH is funded through the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1656518 and the Stanford Graduate Fellowship. XY is funded by the US AFOSR, Grant No. 1194592-1-TAAHO monitored by Dr. Ivett Leyva.

[Amplitude modulation in sound signals by mammals].

PubMed

Nikol'skiĭ, A A

2012-01-01

Periodic variations in amplitude of a signal, or amplitude modulation (AM), affect the structure of communicative messages spectrum. Within the spectrum of AM-signals, side frequencies are formed both above and below the carrier frequency that is subjected to modulation. In case of harmonic signal structure they are presented near fundamental frequency as well as near harmonics. Thus, AM may by viewed as a relatively simple mechanism for controlling the spectrum of messages transmitted by mammals. Examples of AM affecting the spectrum structure of functionally different sound signals are discussed as applied to representatives of four orders of mammals: rodents (Reodentia), duplicidentates (Lagomorpha), pinnipeds (Pinnipedia), and paridigitates (Artiodactia). For the first time, the classification of AM in animals' sound signals is given. Five forms of AM are picked out in sound signals by mammals: absence of AM, continuous AM, fragmented, heterogeneous, and multilevel one. AM presence/absence is related neither with belonging to any specific order nor with some particular function of a signal. Similar forms of AM can occur in different orders of mammals in parallel. On the contrary, different forms of AM can be detected in signals meant for similar functions. The assumption is made about AM-signals facilitating information encoding and jamprotection of messages transmitted by mammals. Preliminry analysis indicates that hard-driving amplitude modulation is incompatible with hard-driving frequency modulation.

Cross-Modulation Interference with Lateralization of Mixed-Modulated Waveforms

ERIC Educational Resources Information Center

Hsieh, I-Hui; Petrosyan, Agavni; Goncalves, Oscar F.; Hickok, Gregory; Saberi, Kourosh

2010-01-01

Purpose: This study investigated the ability to use spatial information in mixed-modulated (MM) sounds containing concurrent frequency-modulated (FM) and amplitude-modulated (AM) sounds by exploring patterns of interference when different modulation types originated from different loci as may occur in a multisource acoustic field. Method:…

78 FR 80369 - Federal Acquisition Regulation; Service Contracts Reporting Requirements

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-31

...-and- materials, and labor-hour contracts and orders above the simplified acquisition threshold (SAT... thresholds established in FAR 4.1703 (e.g., above the SAT for cost-reimbursement, time-and-materials, and... reporting will be made at www.sam.gov (See section 3.10 of the SAM User Guide at https://www.sam.gov/sam/SAM...

Low-voltage differentially-signaled modulators.

PubMed

Zortman, William A; Lentine, Anthony L; Trotter, Douglas C; Watts, Michael R

2011-12-19

For exascale computing applications, viable optical solutions will need to operate using low voltage signaling and with low power consumption. In this work, the first differentially signaled silicon resonator is demonstrated which can provide a 5dB extinction ratio using 3fJ/bit and 500mV signal amplitude at 10Gbps. Modulation with asymmetric voltage amplitudes as low as 150mV with 3dB extinction are demonstrated at 10Gbps as well. Differentially signaled resonators simplify and expand the design space for modulator implementation and require no special drivers.

[The parallelisms in of sound signal of domestic sheep and Northern fur seals].

PubMed

Nikol'skiĭ, A A; Lisitsina, T Iu

2011-01-01

The parallelisms in communicative behavior of domestic sheep and Northern fur seals within a herd are accompanied by parallelisms in parameters of sound signal, the calling scream. This signal ensures ties between babies and their mothers at a long distance. The basis of parallelisms is formed by amplitude modulation at two levels: the one being a direct amplitude modulation of the carrier frequency and the other--modulation of the carrier frequency oscillation. Parallelisms in the signal oscillatory process result in corresponding parallelisms in the structure of its frequency spectrum.

Unanticipated coordination of tris buffer to the Radical SAM cluster of the RimO methylthiotransferase.

PubMed

Molle, Thibaut; Clémancey, Martin; Latour, Jean-Marc; Kathirvelu, Velavan; Sicoli, Giuseppe; Forouhar, Farhad; Mulliez, Etienne; Gambarelli, Serge; Atta, Mohamed

2016-07-01

Radical SAM enzymes generally contain a [4Fe-4S](2+/1+) (RS cluster) cluster bound to the protein via the three cysteines of a canonical motif CxxxCxxC. The non-cysteinyl iron is used to coordinate SAM via its amino-carboxylate moiety. The coordination-induced proximity between the cluster acting as an electron donor and the adenosyl-sulfonium bond of SAM allows for the homolytic cleavage of the latter leading to the formation of the reactive 5'-deoxyadenosyl radical used for substrate activation. Most of the structures of Radical SAM enzymes have been obtained in the presence of SAM, and therefore, little is known about the situation when SAM is not present. In this report, we show that RimO, a methylthiotransferase belonging to the radical SAM superfamily, binds a Tris molecule in the absence of SAM leading to specific spectroscopic signatures both in Mössbauer and pulsed EPR spectroscopies. These data provide a cautionary note for researchers who work with coordinative unsaturated iron sulfur clusters.

47 CFR 95.637 - Modulation standards.

Code of Federal Regulations, 2010 CFR

2010-10-01

... amplitude modulation and frequency or phase modulation of a transmitter are not permitted. (d) When emission... 47 Telecommunication 5 2010-10-01 2010-10-01 false Modulation standards. 95.637 Section 95.637... SERVICES Technical Regulations Technical Standards § 95.637 Modulation standards. (a) A GMRS transmitter...

Self-Assembled Monolayers of Dithiophosphinic Acids on Gold

NASA Astrophysics Data System (ADS)

San Juan, Ronan Roca

This dissertation reports the synthesis of derivatives of dithiophosphinic acids (R1R2DTPAs), and the formation and characterization of DTPA SAMs on gold to build a knowledge base on their nature of binding, organization of the alkyl chains and electrochemical barrier properties. The binding of DTPA molecules on gold depends on the morphology of the gold film: They bind in a mixed monodentate and bidentate modes on standard as-deposited (As-Dep) gold, while they fully chelate on smoother template-stripped (TS) gold. Chapter 2 focuses on van der Waals interactions of various alkyl chain lengths of symmetrical R2DTPA SAMs, which increase with increasing chain lengths similar to those of the analogous n-alkanethiol SAMs, but with alkyl chains that are generally less dense than those of n-alkanethiol SAMs. Chapter 3 addresses why the DTPA compounds do not chelate on the standard As-Dep gold by comparing (C16)2DTPA SAM to (C16 )2DDP SAM. Here, side chain crystallinity stabilizes DTPA SAM structure at the expense of chelation of the DTPA molecules, which leads to a mixture of bidentate and monodentate DTPA molecules, whereas the increased flexibility of the chains in DDP due to the oxygen atoms retains chelation of the DDP molecules. Chapter 4 focuses on the SAMs formed from RlongRshort DTPAs, which shows that the length of the short chain spacer affects SAM packing density and thickness. The SAMs of these molecules also show homogeneous mixing of Rlong and Rshort chains. Chapter 5 investigates PhRDTPA SAMs in preparation for molecular junction studies. The chelation of PhRDTPA molecules on TS gold allows the PhRDTPAs to act as molecular alligator clips. The length of the alkyl chains controls the density of the phenyl group and they fill in the voids between adsorbates to prevent electrical shorting. Finally, Chapter 6 incorporates OH tail group(s) to control the wettability of DTPA SAMs. The presence of OH groups in DTPAs forms hydrophilic SAMs. The symmetrical OH-terminated DTPA forms a SAM with similar packing density to that of an analogous CH3-terminated DTPA SAM, while the OH/CH 3-terminated DTPA forms a thin SAM with low molecular packing, however, the chains of this SAM are homogeneously mixed.

Graphene based terahertz phase modulators

NASA Astrophysics Data System (ADS)

Kakenov, N.; Ergoktas, M. S.; Balci, O.; Kocabas, C.

2018-07-01

Electrical control of amplitude and phase of terahertz radiation (THz) is the key technological challenge for high resolution and noninvasive THz imaging. The lack of active materials and devices hinders the realization of these imaging systems. Here, we demonstrate an efficient terahertz phase and amplitude modulation using electrically tunable graphene devices. Our device structure consists of electrolyte-gated graphene placed at quarter wavelength distance from a reflecting metallic surface. In this geometry, graphene operates as a tunable impedance surface which yields electrically controlled reflection phase. Terahertz time domain reflection spectroscopy reveals the voltage controlled phase modulation of π and the reflection modulation of 50 dB. To show the promises of our approach, we demonstrate a multipixel phase modulator array which operates as a gradient impedance surface.

A hybrid voice/data modulation for the VHF aeronautical channels

NASA Technical Reports Server (NTRS)

Akos, Dennis M.

1993-01-01

A method of improving the spectral efficiency of the existing Very High Frequency (VHF) Amplitude Modulation (AM) voice communication channels is proposed. The technique is to phase modulate the existing voice amplitude modulated carrier with digital data. This allows the transmission of digital information over an existing AM voice channel with no change to the existing AM signal format. There is no modification to the existing AM receiver to demodulate the voice signal and an additional receiver module can be added for processing of the digital data. The existing VHF AM transmitter requires only a slight modification for the addition of the digital data signal. The past work in the area is summarized and presented together with an improved system design and the proposed implementation.

Serum S-adenosylmethionine, but not methionine, increases in response to overfeeding in humans.

PubMed

Elshorbagy, A K; Jernerén, F; Samocha-Bonet, D; Refsum, H; Heilbronn, L K

2016-01-25

Plasma concentration of the methyl donor S-adenosylmethionine (SAM) is linearly associated with body mass index (BMI) and fat mass. As SAM is a high-energy compound and a sensor of cellular nutrient status, we hypothesized that SAM would increase with overfeeding. Forty normal to overweight men and women were overfed by 1250 kcal per day for 28 days. Serum SAM increased from 106 to 130 nmol/l (P=0.006). In stratified analysis, only those with weight gain above the median (high-weight gainers; average weight gain 3.9±0.3 kg) had increased SAM (+42%, P=0.001), whereas low-weight gainers (weight gain 1.5±0.2 kg) did not (Pinteraction=0.018). Overfeeding did not alter serum concentrations of the SAM precursor, methionine or the products, S-adenosyl-homocysteine and homocysteine. The SAM/SAH (S-adenosylhomocysteine) ratio was unchanged in the total population, but increased in high-weight gainers (+52%, P=0.006, Pinteraction =0.005). Change in SAM correlated positively with change in weight (r=0.33, P=0.041) and fat mass (r=0.44, P=0.009), but not with change in protein intake or plasma methionine, glucose, insulin or low-density lipoprotein (LDL)-cholesterol. Overfeeding raised serum SAM in proportion to the fat mass gained. The increase in SAM may help stabilize methionine levels, and denotes a responsiveness of SAM to nutrient state in humans. The role of SAM in human energy metabolism deserves further attention.

Pulse amplitude modulated chlorophyll fluorometer

DOEpatents

Greenbaum, Elias; Wu, Jie

2015-12-29

Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

Interrogation, and detection system

DOEpatents

Baldwin, Howard A.; Depp, Steven W.; Koelle, Alfred R.; Freyman, Robert W.

1978-02-21

The specification relates to a telemetering apparatus comprising a generator which generates at least a single frequency rf signal, a transponder for receiving that signal and for amplitude modulating it in accordance with information selected for transmission, an antenna on the transponder for reflecting the amplitude modulated signal, and a receiver which is preferably located at the generator. The receiver processes the signal to determine the information carried thereby.

Magnified Neural Envelope Coding Predicts Deficits in Speech Perception in Noise.

PubMed

Millman, Rebecca E; Mattys, Sven L; Gouws, André D; Prendergast, Garreth

2017-08-09

Verbal communication in noisy backgrounds is challenging. Understanding speech in background noise that fluctuates in intensity over time is particularly difficult for hearing-impaired listeners with a sensorineural hearing loss (SNHL). The reduction in fast-acting cochlear compression associated with SNHL exaggerates the perceived fluctuations in intensity in amplitude-modulated sounds. SNHL-induced changes in the coding of amplitude-modulated sounds may have a detrimental effect on the ability of SNHL listeners to understand speech in the presence of modulated background noise. To date, direct evidence for a link between magnified envelope coding and deficits in speech identification in modulated noise has been absent. Here, magnetoencephalography was used to quantify the effects of SNHL on phase locking to the temporal envelope of modulated noise (envelope coding) in human auditory cortex. Our results show that SNHL enhances the amplitude of envelope coding in posteromedial auditory cortex, whereas it enhances the fidelity of envelope coding in posteromedial and posterolateral auditory cortex. This dissociation was more evident in the right hemisphere, demonstrating functional lateralization in enhanced envelope coding in SNHL listeners. However, enhanced envelope coding was not perceptually beneficial. Our results also show that both hearing thresholds and, to a lesser extent, magnified cortical envelope coding in left posteromedial auditory cortex predict speech identification in modulated background noise. We propose a framework in which magnified envelope coding in posteromedial auditory cortex disrupts the segregation of speech from background noise, leading to deficits in speech perception in modulated background noise. SIGNIFICANCE STATEMENT People with hearing loss struggle to follow conversations in noisy environments. Background noise that fluctuates in intensity over time poses a particular challenge. Using magnetoencephalography, we demonstrate anatomically distinct cortical representations of modulated noise in normal-hearing and hearing-impaired listeners. This work provides the first link among hearing thresholds, the amplitude of cortical representations of modulated sounds, and the ability to understand speech in modulated background noise. In light of previous work, we propose that magnified cortical representations of modulated sounds disrupt the separation of speech from modulated background noise in auditory cortex. Copyright © 2017 Millman et al.

Inhibition of angiogenesis by S-adenosylmethionine

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

Sahin, Mehmet, E-mail: msahin@akdeniz.edu.tr; Sahin, Emel; Guemueslue, Saadet

2011-04-29

Highlights: {yields} Effects of S-adenosylmethionine (SAM) were investigated in endothelial cells. {yields} Our results showed that SAM decreased proliferation of endothelial cells. {yields} SAM influentially inhibited the percentage of cell migration. {yields} SAM probably stopped migration as independent from its effects on proliferation. {yields} SAM was shown to suppress in vitro angiogenesis. -- Abstract: Metastasis is a leading cause of mortality and morbidity in cancer. One of the steps in metastasis process is the formation of new blood vessels. Aberrant DNA methylation patterns are common in cancer cells. In recent studies, S-adenosylmethionine (SAM), which is a DNA methylating agent, hasmore » been found to have inhibitory effects on some carcinoma cells in vivo and in vitro. In the present study, we have used SAM to investigate whether it is effective against angiogenesis in vitro. Our results have shown that SAM can reduce the formation and organization of capillary-like structures of endothelial cells in tumoral environment. Besides, we have found SAM can block endothelial cell proliferation and the migration of cells towards growth factors-rich media. In conclusion, our study suggests that SAM may be used against angiogenesis as a natural bio-product.« less

Selection and Characteristics of Fermented Salted Seafood (jeotgal)-Originated Strains with Excellent S-adenosyl-L-methionine (SAM) Production and Probiotics Efficacy.

PubMed

Kim, Min-Jeong; Park, Sunhyun; Lee, Ran-Sook; Lim, Sang-Dong; Kim, Hyo Jin; Lee, Myung-Ki

2014-01-01

This study is executed to develop probiotics which produce S-adenosyl-L-methionine (SAM), a methyl group donor of the 5-methyltetrahydrofolate methylation reaction within the animal cell. SAM is an essential substance for the synthesis, activation, and metabolism of hormones, neurotransmitters, nucleic acids, phospholipids, and cell membranes of animals. The SAM is also known as a nutritional supplement to improve brain functions of the human. In this study, the SAM-producing strains are identified in 18 types of salted fish, and then, the strains with excellent SAM productions are being identified, with 1 strain in the Enterococcus genus and 9 strains in the Bacillus genus. Strains with a large amount of SAM production include the lactic acid bacteria such as En. faecium and En. durans, En. sanguinicola, as well as various strains in the Bacil-lus genus. The SAM-overproducing strains show antibacterial activities with certain harmful microbes in addition to the weak acid resistances and strong bile resistances, indicating characteristics of probiotics. It is possible that the jeotgal-originated beneficial strains with overproducing SAM can be commercially utilized in order to manufacture SAM enriched foods.

The Improvement of SAM Accumulation by Integrating the Endogenous Methionine Adenosyltransferase Gene SAM2 in Genome of the Industrial Saccharomyces cerevisiae Strain.

PubMed

Zhao, Weijun; Shi, Feng; Hang, Baojian; Huang, Lei; Cai, Jin; Xu, Zhinan

2016-03-01

S-Adenosyl-L-methionine (SAM) plays important roles in trans-methylation, trans-sulfuration, and polyamine synthesis in all living cells, and it is also an effective cure for liver disease, depressive syndromes, and osteoarthritis. The increased demands of SAM in pharmaceuticals industry have aroused lots of attempts to improve its production. In this study, a multiple-copy integrative plasmid pYMIKP-SAM2 was introduced into the chromosome of wild-type Saccharomyces cerevisiae strain ZJU001 to construct the recombined strain R1-ZJU001. Further studies showed that the recombinant yeast exhibited higher enzymatic activity of methionine adenosyltransferase and improved its SAM biosynthesis. With a three-phase fed-batch strategy in 15-liter bench-top fermentor, 8.81 g/L SAM was achieved after 52 h cultivation of R1-ZJU001, about 27.1 % increase over its parent strain ZJU001, whereas the SAM content was also improved from 64.6 mg/g DCW to 91.0 mg/g DCW. Our results shall provide insights into the metabolic engineering of SAM pathway in yeast for improved productivity of SAM and subsequent industrial applications.

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

Shi, Zhiwei; Walker, Amy V., E-mail: amy.walker@utdallas.edu

The room temperature atomic layerlike deposition (ALLD) of ZnS on functionalized self-assembled monolayers (SAMs) was investigated, using diethyl zinc (DEZ) and in situ generated H{sub 2}S as reactants. Depositions on SAMs with three different terminal groups, –CH{sub 3,} –OH, and –COOH, were studied. It was found that the reaction of DEZ with the SAM terminal group is critical in determining the film growth rate. Little or no deposition is observed on –CH{sub 3} terminated SAMs because DEZ does not react with the methyl terminal group. ZnS does deposit on both –OH and –COOH terminated SAMs, but the grow rate onmore » –COOH terminated SAMs is ∼10% lower per cycle than on –OH terminated SAMs. DEZ reacts with the hydroxyl group on –OH terminated SAMs, while on –COOH terminated SAMs it reacts with both the hydroxyl and carbonyl bonds of the terminal groups. The carbonyl reaction is found to lead to the formation of ketones rather than deposition of ZnS, lowering the growth rate on –COOH terminated SAMs. SIMS spectra show that both –OH and –COOH terminated SAMs are covered by the deposited ZnS layer after five ALLD cycles. In contrast to ZnO ALLD where the composition of the film differs for the first few layers on –COOH and –OH terminated SAMs, the deposited film composition is the same for both –COOH and –OH terminated SAMs. The deposited film is found to be Zn-rich, suggesting that the reaction of H{sub 2}S with the Zn-surface adduct may be incomplete.« less

Calculating rhythmicity of infant breathing using wavelets

NASA Astrophysics Data System (ADS)

Macey, Katherine E.; Page, Wyatt H.; Harper, Ronald M.; Macey, Paul M.; Ford, Rodney P. K.

2000-12-01

Breathing signals are one set of physiological data that may provide information regarding the mechanisms that cause SIDS. Isolated breathing pauses have been implicated in fatal events. Other features of interest include slow amplitude modulation of the breathing signal, a phenomenon whose origin is unclear, and periodic breathing. The latter describes a repetitive series of apnea, and may be considered an extreme manifestation of amplitude modulation with successive cessations of breathing. Rhythmicity is defined to assess the impact of amplitude modulation on breathing signals and describes the extent to which frequency components remain constant for the duration of the signal. The wavelet transform was used to identify sections of constant frequency components within signals. Rhythmicity can be evaluated for all the frequency components in a signal, for individual frequencies. The rhythmicity of eight breathing epochs from sleeping infants at high and low risk for SIDS was calculated. Initial results show breathing from infants at high risk for SIDS exhibits greater rhythmicity of modulating frequencies than breathing from low risk infants.

Contrast gain control in first- and second-order motion perception.

PubMed

Lu, Z L; Sperling, G

1996-12-01

A novel pedestal-plus-test paradigm is used to determine the nonlinear gain-control properties of the first-order (luminance) and the second-order (texture-contrast) motion systems, that is, how these systems' responses to motion stimuli are reduced by pedestals and other masking stimuli. Motion-direction thresholds were measured for test stimuli consisting of drifting luminance and texture-contrast-modulation stimuli superimposed on pedestals of various amplitudes. (A pedestal is a static sine-wave grating of the same type and same spatial frequency as the moving test grating.) It was found that first-order motion-direction thresholds are unaffected by small pedestals, but at pedestal contrasts above 1-2% (5-10 x pedestal threshold), motion thresholds increase proportionally to pedestal amplitude (a Weber law). For first-order stimuli, pedestal masking is specific to the spatial frequency of the test. On the other hand, motion-direction thresholds for texture-contrast stimuli are independent of pedestal amplitude (no gain control whatever) throughout the accessible pedestal amplitude range (from 0 to 40%). However, when baseline carrier contrast increases (with constant pedestal modulation amplitude), motion thresholds increase, showing that gain control in second-order motion is determined not by the modulator (as in first-order motion) but by the carrier. Note that baseline contrast of the carrier is inherently independent of spatial frequency of the modulator. The drastically different gain-control properties of the two motion systems and prior observations of motion masking and motion saturation are all encompassed in a functional theory. The stimulus inputs to both first- and second-order motion process are normalized by feedforward, shunting gain control. The different properties arise because the modulator is used to control the first-order gain and the carrier is used to control the second-order gain.

Volcano Observations Using an Unmanned Autonomous Helicopter : seismic and GPS observations near the active summit area of Sakurajima and Kirishima volcano, Japan

NASA Astrophysics Data System (ADS)

Ohminato, T.; Kaneko, T.; Koyama, T.; Watanabe, A.; Takeo, M.; Iguchi, M.; Honda, Y.

2012-04-01

Observations in the vicinity of summit area of active volcanoes are very important from various viewpoints such as understanding physical processes in the volcanic conduit. It is, however, highly difficult to install observation sensors near active vents because of the risk of sudden eruptions. We have been developing a safe volcano observation system based on an unmanned aerial vehicle (UAV). As an UAV, we adopted an unmanned autonomous helicopter manufactured by Yamaha-Motor Co., Ltd. We have also developed earthquake observation modules and GPS receiver modules that are exclusively designed for UAV installation at summit areas of active volcanoes. These modules are light weight, compact size, and solar powered. For data transmission, a commercial cellular-phone network is used. Our first application of the sensor installation by the UAV is Sakurajima, one of the most active volcanos in Japan. In November 2009, 2010, and 2011, we installed up to four seismic sensors within 2km from the active summit crater. In the 2010 and 2011 operations, we succeeded in pulling up and collecting the sensor modules by using the UAV. In the 2011 experiment, we installed two GPS receivers near the summit area of Sakurajima volcano. We also applied the UAV installation to another active volcano, Shinmoedake in Kirishima volcano group. Since the sub-plinian eruption in February 2011, entering the area 3km from the summit of Shinmoe-dake has been prohibited. In May and November 2011, we installed seismic sensors and GPS receivers in the off-limit zone. Although the ground coupling of the seismic modules is not perfect due to the way they are installed, the signal-to-noise ratio of the seismic signals recorded by these modules is fairly good. Despite the low antenna height of 50 cm from the ground surface, the location errors in horizontal and vertical GPS components are 1cm and 3cm, respectively. For seismic signals associated with eruptions at Sakurajima from November 2010 to November 2011, we measure temporal variation of the amplitude ratio among the summit stations. In order to correct the amplitude variation due to the source amplitude variation, the amplitude of the recorded signals are normalized by using the amplitude of a permanent station, located on the western flank of Sakurajima 5km from the summit. The daily average of the normalized amplitude ratios among the summit stations shows clear temporal variation. The amplitude ratio variation can be classified to three stages. In the first stage, the amplitude ratios among the summit stations are nearly constant. The 2nd stage is characterized by a gradual increase in the amplitude ratio. The third stage is slightly difficult to define but we can say that the amplitude ratios are almost constant with fluctuations larger than that in the first stage. These changes strongly suggest a change in the source depth, probably migration of the source to the shallower portion in the volcanic conduit. Small change in the source position would have been observed as a big change in the observed amplitude ratio due to the closeness of the sensors to the source.

Ectopic shoot meristem generation in monocotyledonous rpk1 mutants is linked to SAM loss and altered seedling morphology.

PubMed

Fiesselmann, Birgit S; Luichtl, Miriam; Yang, Xiaomeng; Matthes, Michaela; Peis, Ottilie; Torres-Ruiz, Ramon A

2015-07-07

In dicot Arabidopsis thaliana embryos two cotyledons develop largely autonomously from the shoot apical meristem (SAM). Recessive mutations in the Arabidopsis receptor-like kinase RPK1 lead to monocotyledonous seedlings, with low (10 %) penetrance due to complex functional redundancy. In strong rpk1 alleles, about 10 % of these (i. e. 1 % of all homozygotes) did not develop a SAM. We wondered whether RPK1 might also control SAM gene expression and SAM generation in addition to its known stochastic impact on cell division and PINFORMED1 (PIN1) polarity in the epidermis. SAM-less seedlings developed a simple morphology with a straight and continuous hypocotyl-cotyledon structure lacking a recognizable epicotyl. According to rpk1's auxin-related PIN1 defect, the seedlings displayed defects in the vascular tissue. Surprisingly, SAM-less seedlings variably expressed essential SAM specific genes along the hypocotyl-cotyledon structure up into the cotyledon lamina. Few were even capable of developing an ectopic shoot meristem (eSM) on top of the cotyledon. The results highlight the developmental autonomy of the SAM vs. cotyledons and suggest that the primary rpk1 defect does not lie in the seedling's ability to express SAM genes or to develop a shoot meristem. Rather, rpk1's known defects in cell division and auxin homeostasis, by disturbed PIN1 polarity, impact on SAM and organ generation. In early embryo stages this failure generates a simplified monocotyledonous morphology. Once generated, this likely entails a loss of positional information that in turn affects the spatiotemporal development of the SAM. SAM-bearing and SAM-less monocotyledonous phenotypes show morphological similarities either to real monocots or to dicot species, which only develop one cotyledon. The specific cotyledon defect in rpk1 mutants thus sheds light upon the developmental implications of the transition from two cotyledons to one.

Variable sequences outside the SAM-binding core critically influence the conformational dynamics of the SAM-III/SMK box riboswitch

PubMed Central

Lu, Changrui; Smith, Angela M; Ding, Fang; Chowdhury, Anirban; Henkin, Tina M; Ke, Ailong

2012-01-01

The SMK box (SAM-III) translational riboswitches were identified in S-adenosyl-L-methionine (SAM) synthetase metK genes in members of the Lactobacillales. This riboswitch switches between two alternative conformations in response to the intracellular SAM concentration and controls metK expression at the level of translation initiation. We previously reported the crystal structure of the SAM-bound SMK box riboswitch. In this study we combined SHAPE chemical probing with mutagenesis to probe the ligand-induced conformational switching mechanism. We revealed that while the majority of the apo SMK box RNA molecules exist in an alternatively base paired (ON) conformation, a subset of them pre-organize into a SAM-bound-like (READY) conformation, which upon SAM exposure is selectively stabilized into the SAM-bound (OFF) conformation through an induced-fit mechanism. Mutagenesis showed that the ON state is only slightly more stable than the READY state, as several single-nucleotide substitutions in a hypervariable region outside the SAM-binding core can alter the folding landscape to favor the READY state. Such SMK variants display a “constitutively-OFF” behavior both in vitro and in vivo. Time-resolved and temperature-dependent SHAPE analyses revealed adaptation of the SMK box RNA to its mesothermal working environment. The latter analysis revealed that the SAM-bound SMK box RNA follows a two-step folding/unfolding process. PMID:21549712

Infrared spectroscopy of large scale single layer graphene on self assembled organic monolayer

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

Woo Kim, Nak; Youn Kim, Joo; Lee, Chul

2014-01-27

We study the effect of self-assembled monolayer (SAM) organic molecule substrate on large scale single layer graphene using infrared transmission measurement on Graphene/SAM/SiO{sub 2}/Si composite samples. From the Drude weight of the chemically inert CH{sub 3}-SAM, the electron-donating NH{sub 2}-SAM, and the SAM-less graphene, we determine the carrier density doped into graphene by the three sources—the SiO{sub 2} substrate, the gas-adsorption, and the functional group of the SAM's—separately. The SAM-treatment leads to the low carrier density N ∼ 4 × 10{sup 11} cm{sup −2} by blocking the dominant SiO{sub 2}- driven doping. The carrier scattering increases by the SAM-treatment rather than decreases. However, the transportmore » mobility is nevertheless improved due to the reduced carrier doping.« less

Segment Alignment Maintenance System for the Hobby-Eberly Telescope

NASA Technical Reports Server (NTRS)

Rakoczy, John; Burdine, Robert (Technical Monitor)

2001-01-01

NASA's Marshall Space Flight Center, in collaboration with Blue Line Engineering of Colorado Springs, Colorado, is developing a Segment Alignment Maintenance System (SAMS) for McDonald Observatory's Hobby-Eberly Telescope (HET). The SAMS shall sense motions of the 91 primary mirror segments and send corrections to HET's primary mirror controller as the mirror segments misalign due to thermo -elastic deformations of the mirror support structure. The SAMS consists of inductive edge sensors. All measurements are sent to the SAMS computer where mirror motion corrections are calculated. In October 2000, a prototype SAMS was installed on a seven-segment cluster of the HET. Subsequent testing has shown that the SAMS concept and architecture are a viable practical approach to maintaining HET's primary mirror figure, or the figure of any large segmented telescope. This paper gives a functional description of the SAMS sub-array components and presents test data to characterize the performance of the subarray SAMS.

Comprehensive time average digital holographic vibrometry

NASA Astrophysics Data System (ADS)

Psota, Pavel; Lédl, Vít; Doleček, Roman; Mokrý, Pavel; Vojtíšek, Petr; Václavík, Jan

2016-12-01

This paper presents a method that simultaneously deals with drawbacks of time-average digital holography: limited measurement range, limited spatial resolution, and quantitative analysis of the measured Bessel fringe patterns. When the frequency of the reference wave is shifted by an integer multiple of frequency at which the object oscillates, the measurement range of the method can be shifted either to smaller or to larger vibration amplitudes. In addition, phase modulation of the reference wave is used to obtain a sequence of phase-modulated fringe patterns. Such fringe patterns can be combined by means of phase-shifting algorithms, and amplitudes of vibrations can be straightforwardly computed. This approach independently calculates the amplitude values in every single pixel. The frequency shift and phase modulation are realized by proper control of Bragg cells and therefore no additional hardware is required.

Immunoassay of S-adenosylmethionine and S-adenosylhomocysteine: the methylation index as a biomarker for disease and health status.

PubMed

Hao, Xiujuan; Huang, Yan; Qiu, Ming; Yin, Chunlin; Ren, Huiming; Gan, Hongjie; Li, Huijun; Zhou, Yaxia; Xia, Jiazhi; Li, Wenting; Guo, Lijuan; Angres, Isaac A

2016-11-28

S-Adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are relevant to a variety of diseases. Previous reports that quantified SAM and SAH were based on HPLC or LC-MS/MS. No antibody against SAM has been generated, and the antibody against SAH cannot be used with blood samples. Immunoassays have not been used to measure SAM and SAH. In this study, ELISA was used to measure blood SAM and SAH levels. Specific antibodies against SAM were produced for the first time using a stable analog as the antigen. The monoclonal antibodies against SAM and SAH were characterized. No cross-reactivity was detected for the analyzed analogs. For the anti-SAM antibodies, the ELISA sensitivity was ~2 nM, and the affinity was 7.29 × 10 10 L/mol. For the anti-SAH antibodies, the sensitivity was ~15 nM, and the affinity was 2.79 × 10 8 L/mol. Using high-quality antibodies against SAM and SAH, immunoassays for the detection of SAM and SAH levels in blood and tissue samples were developed. Clinical investigations using immunoassays to measure SAM, SAH and the methylation index (MI) in normal and diseased samples indicated that (1) the SAM level is age and gender dependent; (2) the SAM level is associated with the severity of liver diseases, inflammatory reactions and other diseases; and (3) the methylation index (MI) is significantly reduced in many diseases and may serve as a screening biomarker to identify potentially unfavorable health conditions. It is possible to generate antibodies against active small biomolecules with weak immunogenicity, such as SAM and SAH, using traditional hybridoma technology. The antigens and antibodies described here will contribute to the development of immunoassays to measure SAM, SAH and related molecules. These assays enable the MI to be measured specifically, accurately, easily and quickly without costly equipment. This preliminary study indicates that the MI could be an effective indicator of general health, except under conditions that may alter the value of the MI, such as special diets and medications.

Jeffries Matusita-Spectral Angle Mapper (JM-SAM) spectral matching for species level mapping at Bhitarkanika, Muthupet and Pichavaram mangroves

NASA Astrophysics Data System (ADS)

Padma, S.; Sanjeevi, S.

2014-12-01

This paper proposes a novel hyperspectral matching algorithm by integrating the stochastic Jeffries-Matusita measure (JM) and the deterministic Spectral Angle Mapper (SAM), to accurately map the species and the associated landcover types of the mangroves of east coast of India using hyperspectral satellite images. The JM-SAM algorithm signifies the combination of a qualitative distance measure (JM) and a quantitative angle measure (SAM). The spectral capabilities of both the measures are orthogonally projected using the tangent and sine functions to result in the combined algorithm. The developed JM-SAM algorithm is implemented to discriminate the mangrove species and the landcover classes of Pichavaram (Tamil Nadu), Muthupet (Tamil Nadu) and Bhitarkanika (Odisha) mangrove forests along the Eastern Indian coast using the Hyperion image dat asets that contain 242 bands. The developed algorithm is extended in a supervised framework for accurate classification of the Hyperion image. The pixel-level matching performance of the developed algorithm is assessed by the Relative Spectral Discriminatory Probability (RSDPB) and Relative Spectral Discriminatory Entropy (RSDE) measures. From the values of RSDPB and RSDE, it is inferred that hybrid JM-SAM matching measure results in improved discriminability of the mangrove species and the associated landcover types than the individual SAM and JM algorithms. This performance is reflected in the classification accuracies of species and landcover map of Pichavaram mangrove ecosystem. Thus, the JM-SAM (TAN) matching algorithm yielded an accuracy better than SAM and JM measures at an average difference of 13.49 %, 7.21 % respectively, followed by JM-SAM (SIN) at 12.06%, 5.78% respectively. Similarly, in the case of Muthupet, JM-SAM (TAN) yielded an increased accuracy than SAM and JM measures at an average difference of 12.5 %, 9.72 % respectively, followed by JM-SAM (SIN) at 8.34 %, 5.55% respectively. For Bhitarkanika, the combined JM-SAM (TAN) and (SIN) measures improved the performance of individual SAM by (16.1 %, 15%) and of JM by (10.3%, 9.2%) respectively.

Spatiotemporal reconstruction of auditory steady-state responses to acoustic amplitude modulations: Potential sources beyond the auditory pathway.

PubMed

Farahani, Ehsan Darestani; Goossens, Tine; Wouters, Jan; van Wieringen, Astrid

2017-03-01

Investigating the neural generators of auditory steady-state responses (ASSRs), i.e., auditory evoked brain responses, with a wide range of screening and diagnostic applications, has been the focus of various studies for many years. Most of these studies employed a priori assumptions regarding the number and location of neural generators. The aim of this study is to reconstruct ASSR sources with minimal assumptions in order to gain in-depth insight into the number and location of brain regions that are activated in response to low- as well as high-frequency acoustically amplitude modulated signals. In order to reconstruct ASSR sources, we applied independent component analysis with subsequent equivalent dipole modeling to single-subject EEG data (young adults, 20-30 years of age). These data were based on white noise stimuli, amplitude modulated at 4, 20, 40, or 80Hz. The independent components that exhibited a significant ASSR were clustered among all participants by means of a probabilistic clustering method based on a Gaussian mixture model. Results suggest that a widely distributed network of sources, located in cortical as well as subcortical regions, is active in response to 4, 20, 40, and 80Hz amplitude modulated noises. Some of these sources are located beyond the central auditory pathway. Comparison of brain sources in response to different modulation frequencies suggested that the identified brain sources in the brainstem, the left and the right auditory cortex show a higher responsiveness to 40Hz than to the other modulation frequencies. Copyright © 2017 Elsevier Inc. All rights reserved.

Novel Active Combustion Control Valve

NASA Technical Reports Server (NTRS)

Caspermeyer, Matt

2014-01-01

This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

Giant Shoot Apical Meristems in Cacti Have Ordinary Leaf Primordia but Altered Phyllotaxy and Shoot Diameter

PubMed Central

MAUSETH, JAMES D.

2004-01-01

• Background and Aims Shoot apical meristems (SAMs) in most seed plants are quite uniform in size and zonation, and molecular genetic studies of Arabidopsis and other model plants are revealing details of SAM morphogenesis. Some cacti have SAMs much larger than those of A. thaliana and other seed plants. This study examined how SAM size affects leaf primordium (LP) size, phyllotaxy and shoot diameter. • Methods. Apices from 183 species of cacti were fixed, microtomed and studied by light microscopy. • Key Results Cactus SAM diameter varies from 93 to 2565 µm, the latter being 36 times wider than SAMs of A. thaliana and having a volume 45 thousand times larger. Phyllotaxy ranges from distichous to having 56 rows of leaves and is not restricted to Fibonacci numbers. Leaf primordium diameter ranges from 44 to 402 µm, each encompassing many more cells than do LP of other plants. Species with high phyllotaxy have smaller LP, although the correlation is weak. There is almost no correlation between SAM diameter and LP size, but SAM diameter is strongly correlated with shoot diameter, with shoots being about 189·5 times wider than SAMs. • Conclusions Presumably, genes such as SHOOT‐MERISTEMLESS, WUSCHEL and CLAVATA must control much larger volumes of SAM tissue in cacti than they do in A. thaliana, and genes such as PERIANTHIA might establish much more extensive fields of inhibition around LP. These giant SAMs should make it possible to more accurately map gene expression patterns relative to SAM zonation and LP sites. PMID:15145794

Differences in reporting of perceived acute effects of alcohol use, marijuana use, and simultaneous alcohol and marijuana use.

PubMed

Lee, Christine M; Cadigan, Jennifer M; Patrick, Megan E

2017-11-01

Although there are serious negative harms associated with simultaneous alcohol and marijuana (SAM) use, little is known about the self-reported acute effects of SAM use and how they may be similar to or different than effects experienced when using alcohol or marijuana only. The current study examines the perceived acute effects of SAM use, compared to using alcohol or marijuana only, as well as demographic and substance use predictors of overall SAM effects. Participants were a community sample of young adults ages 18-23 participating in a longitudinal study on social role transitions and substance use during young adulthood. Young adults who reported SAM use at least once in their lifetime were selected for the present analyses (N=315; mean age=21.42; 58% female) and reported the effects they experienced from typical alcohol use, marijuana use, and SAM use. There were significant differences in the extent to which young adults perceived the effects depending on the substances used. Most effects (i.e., clumsy, confused, dizzy, difficulty concentrating) were rated strongest when engaging in SAM use, compared to typical alcohol or marijuana use alone. Feeling high and feeling marijuana effects were rated strongest when engaging in marijuana use alone compared to SAM use, but feeling drunk was greater during SAM use compared to alcohol use alone. Greater alcohol use and increased time spent high during typical SAM use were associated with greater overall SAM effects. When young adults engage in SAM use they report experiencing greater negative physiological and cognitive effects. Copyright © 2017 Elsevier B.V. All rights reserved.

SAM/SAH Analogs as Versatile Tools for SAM-Dependent Methyltransferases.

PubMed

Zhang, Jing; Zheng, Yujun George

2016-03-18

S-Adenosyl-L-methionine (SAM) is a sulfonium molecule with a structural hybrid of methionine and adenosine. As the second largest cofactor in the human body, its major function is to serve as methyl donor for SAM-dependent methyltransferases (MTases). The resultant transmethylation of biomolecules constitutes a significant biochemical mechanism in epigenetic regulation, cellular signaling, and metabolite degradation. Recently, numerous SAM analogs have been developed as synthetic cofactors to transfer the activated groups on MTase substrates for downstream ligation and identification. Meanwhile, new compounds built upon or derived from the SAM scaffold have been designed and tested as selective inhibitors for important MTase targets. Here, we summarized the recent development and application of SAM analogs as chemical biology tools for MTases.

Modulation of amplitude and latency of motor evoked potential by direction of transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Sato, Aya; Torii, Tetsuya; Iwahashi, Masakuni; Itoh, Yuji; Iramina, Keiji

2014-05-01

The present study analyzed the effects of monophasic magnetic stimulation to the motor cortex. The effects of magnetic stimulation were evaluated by analyzing the motor evoked potentials (MEPs). The amplitude and latency of MEPs on the abductor pollicis brevis muscle were used to evaluate the effects of repetitive magnetic stimulation. A figure eight-shaped flat coil was used to stimulate the region over the primary motor cortex. The intensity of magnetic stimulation was 120% of the resting motor threshold, and the frequency of magnetic stimulation was 0.1 Hz. In addition, the direction of the current in the brain was posterior-anterior (PA) or anterior-posterior (AP). The latency of MEP was compared with PA and AP on initial magnetic stimulation. The results demonstrated that a stimulus in the AP direction increased the latency of the MEP by approximately 2.5 ms. MEP amplitude was also compared with PA and AP during 60 magnetic stimulations. The results showed that a stimulus in the PA direction gradually increased the amplitude of the MEP. However, a stimulus in the AP direction did not modulate the MEP amplitude. The average MEP amplitude induced from every 10 magnetic pulses was normalized by the average amplitude of the first 10 stimuli. These results demonstrated that the normalized MEP amplitude increased up to approximately 150%. In terms of pyramidal neuron indirect waves (I waves), magnetic stimulation inducing current flowing backward to the anterior preferentially elicited an I1 wave, and current flowing forward to the posterior elicited an I3 wave. It has been reported that the latency of the I3 wave is approximately 2.5 ms longer than the I1 wave elicitation, so the resulting difference in latency may be caused by this phenomenon. It has also been reported that there is no alteration of MEP amplitude at a frequency of 0.1 Hz. However, this study suggested that the modulation of MEP amplitude depends on stimulation strength and stimulation direction.

Noncanonical Radical SAM Enzyme Chemistry Learned from Diphthamide Biosynthesis.

PubMed

Dong, Min; Zhang, Yugang; Lin, Hening

2018-05-10

Radical S-adenosylmethionine (SAM) enzymes are a superfamily of enzymes that use SAM and reduced [4Fe-4S] cluster to generate a 5'-deoxyadenosyl radical to catalyze numerous challenging reactions. We have reported a type of noncanonical radical SAM enzymes in the diphthamide biosynthesis pathway. These enzymes also use SAM and reduced [4Fe-4S] clusters, but generate a 3-amino-3-carboxypropyl (ACP) radical to modify the substrate protein, translation elongation factor 2. The regioselective cleavage of a different C-S bond of the sulfonium center of SAM in these enzymes comparing to canonical radical SAM enzymes is intriguing. Here, we highlight some recent findings in the mechanism of these types of enzymes, showing that the diphthamide biosynthetic radial SAM enzymes bound SAM with a distinct geometry. In this way, the unique iron of the [4Fe-4S] cluster in the enzyme can only attack the carbon on the ACP group to form an organometallic intermediate. The homolysis of the organometallic intermediate releases the ACP radical and generates the EF2 radial.

Crystal structures of the SAM-III/SMK riboswitch reveal the SAM-dependent translation inhibition mechanism

PubMed Central

Lu, Changrui; Smith, Angela M; Fuchs, Ryan T; Ding, Fang; Rajashankar, Kanagalaghatta; Henkin, Tina M; Ke, Ailong

2011-01-01

Three distinct classes of S-adenosyl-l-methionine (SAM)-responsive riboswitches have been identified that regulate bacterial gene expression at the levels of transcription attenuation or translation inhibition. The SMK box (SAM-III) translational riboswitch has been identified in the SAM synthetase gene in members of the Lactobacillales. Here we report the 2.2-Å crystal structure of the Enterococcus faecalis SMK box riboswitch. The Y-shaped riboswitch organizes its conserved nucleotides around a three-way junction for SAM recognition. The Shine-Dalgarno sequence, which is sequestered by base-pairing with the anti–Shine-Dalgarno sequence in response to SAM binding, also directly participates in SAM recognition. The riboswitch makes extensive interactions with the adenosine and sulfonium moieties of SAM but does not appear to recognize the tail of the methionine moiety. We captured a structural snapshot of the SMK box riboswitch sampling the near-cognate ligand S-adenosyl-l-homocysteine (SAH) in which SAH was found to adopt an alternative conformation and fails to make several key interactions. PMID:18806797

Crystal structures of the SAM-III/S[subscript MK] riboswitch reveal the SAM-dependent translation inhibition mechanism

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

Lu, C.; Smith, A.M.; Fuchs, R.T.

2010-01-07

Three distinct classes of S-adenosyl-L-methionine (SAM)-responsive riboswitches have been identified that regulate bacterial gene expression at the levels of transcription attenuation or translation inhibition. The SMK box (SAM-III) translational riboswitch has been identified in the SAM synthetase gene in members of the Lactobacillales. Here we report the 2.2-{angstrom} crystal structure of the Enterococcus faecalis SMK box riboswitch. The Y-shaped riboswitch organizes its conserved nucleotides around a three-way junction for SAM recognition. The Shine-Dalgarno sequence, which is sequestered by base-pairing with the anti-Shine-Dalgarno sequence in response to SAM binding, also directly participates in SAM recognition. The riboswitch makes extensive interactions withmore » the adenosine and sulfonium moieties of SAM but does not appear to recognize the tail of the methionine moiety. We captured a structural snapshot of the SMK box riboswitch sampling the near-cognate ligand S-adenosyl-L-homocysteine (SAH) in which SAH was found to adopt an alternative conformation and fails to make several key interactions.« less

SPECIAL ISSUE ON OPTICAL PROCESSING OF INFORMATION: Characteristics of surface-plasmon liquid-crystal light modulators operating under phase modulation conditions

NASA Astrophysics Data System (ADS)

Nazvanov, V. F.; Afonin, O. A.; Grebennikov, A. I.

1995-10-01

Electrically and optically controlled liquid-crystal light modulators based on surface plasmons were developed and investigated in an ellipsometric optical system. The characteristics of these modulators were determined and compared under phase and amplitude modulation conditions.

Visualization of frequency-modulated electric field based on photonic frequency tracking in asynchronous electro-optic measurement system

NASA Astrophysics Data System (ADS)

Hisatake, Shintaro; Yamaguchi, Koki; Uchida, Hirohisa; Tojyo, Makoto; Oikawa, Yoichi; Miyaji, Kunio; Nagatsuma, Tadao

2018-04-01

We propose a new asynchronous measurement system to visualize the amplitude and phase distribution of a frequency-modulated electromagnetic wave. The system consists of three parts: a nonpolarimetric electro-optic frequency down-conversion part, a phase-noise-canceling part, and a frequency-tracking part. The photonic local oscillator signal generated by electro-optic phase modulation is controlled to track the frequency of the radio frequency (RF) signal to significantly enhance the measurable RF bandwidth. We demonstrate amplitude and phase measurement of a quasi-millimeter-wave frequency-modulated continuous-wave signal (24 GHz ± 80 MHz with a 2.5 ms period) as a proof-of-concept experiment.

Convective stability in the Rayleigh-Benard and directional solidification problems - High-frequency gravity modulation

NASA Technical Reports Server (NTRS)

Wheeler, A. A.; Mcfadden, G. B.; Murray, B. T.; Coriell, S. R.

1991-01-01

The effect of vertical, sinusoidal, time-dependent gravitational acceleration on the onset of solutal convection during directional solidification is analyzed in the limit of large modulation frequency. When the unmodulated state is unstable, the modulation amplitude required to stabilize the system is determined by the method of averaging. When the unmodulated state is stable, resonant modes of instability occur at large modulation amplitude. These are analyzed using matched asymptotic expansions to elucidate the boundary-layer structure for both the Rayleigh-Benard and directional solidification configurations. Based on these analyses, a thorough examination of the dependence of the stability criteria on the unmodulated Rayleigh number, Schmidt number, and distribution coefficient, is carried out.

Successful microscopic renal autotransplantation for left renal aneurysm associated with segmental arterial mediolysis.

PubMed

Yoshioka, Takashi; Araki, Motoo; Ariyoshi, Yuichi; Wada, Koichiro; Tanaka, Noriyuki; Nasu, Yasutomo

2017-07-01

Segmental arterial mediolysis (SAM) is an uncommon, nonarteriosclerotic vascular disease. SAM is characterized by lysis of arterial media and can lead to aneurysm formation. The renal arteries are the third most common arteries associated with SAM. We report the case of a 32-year-old man with left renal artery aneurysm associated with SAM. We successfully performed left renal autotransplantation using microscopic vascular reconstruction. SAM is characterized by vascular fragility; therefore, microscopic surgery is favorable for treating aneurysms associated with SAM. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

ER residency of the ceramide phosphoethanolamine synthase SMSr relies on homotypic oligomerization mediated by its SAM domain.

PubMed

Cabukusta, Birol; Kol, Matthijs; Kneller, Laura; Hilderink, Angelika; Bickert, Andreas; Mina, John G M; Korneev, Sergei; Holthuis, Joost C M

2017-01-25

SMSr/SAMD8 is an ER-resident ceramide phosphoethanolamine synthase with a critical role in controlling ER ceramides and suppressing ceramide-induced apoptosis in cultured cells. SMSr-mediated ceramide homeostasis relies on the enzyme's catalytic activity as well as on its N-terminal sterile α-motif or SAM domain. Here we report that SMSr-SAM is structurally and functionally related to the SAM domain of diacylglycerol kinase DGKδ, a central regulator of lipid signaling at the plasma membrane. Native gel electrophoresis indicates that both SAM domains form homotypic oligomers. Chemical crosslinking studies show that SMSr self-associates into ER-resident trimers and hexamers that resemble the helical oligomers formed by DGKδ-SAM. Residues critical for DGKδ-SAM oligomerization are conserved in SMSr-SAM and their substitution causes a dissociation of SMSr oligomers as well as a partial redistribution of the enzyme to the Golgi. Conversely, treatment of cells with curcumin, a drug disrupting ceramide and Ca 2+ homeostasis in the ER, stabilizes SMSr oligomers and promotes retention of the enzyme in the ER. Our data provide first demonstration of a multi-pass membrane protein that undergoes homotypic oligomerization via its SAM domain and indicate that SAM-mediated self-assembly of SMSr is required for efficient retention of the enzyme in the ER.

S-adenosylmethionine directly inhibits binding of 30S ribosomal subunits to the SMK box translational riboswitch RNA

PubMed Central

Fuchs, Ryan T.; Grundy, Frank J.; Henkin, Tina M.

2007-01-01

The SMK box is a conserved riboswitch motif found in the 5′ untranslated region of metK genes [encoding S-adenosylmethionine (SAM) synthetase] in lactic acid bacteria, including Enterococcus, Streptococcus, and Lactococcus sp. Previous studies showed that this RNA element binds SAM in vitro, and SAM binding causes a structural rearrangement that sequesters the Shine–Dalgarno (SD) sequence by pairing with an anti-SD (ASD) element. A model was proposed in which SAM binding inhibits metK translation by preventing binding of the ribosome to the SD region of the mRNA. In the current work, the addition of SAM was shown to inhibit binding of 30S ribosomal subunits to SMK box RNA; in contrast, the addition of S-adenosylhomocysteine (SAH) had no effect. A mutant RNA, which has a disrupted SD-ASD pairing, was defective in SAM binding and showed no reduction of ribosome binding in the presence of SAM, whereas a compensatory mutation that restored SD-ASD pairing restored the response to SAM. Primer extension inhibition assays provided further evidence for SD-ASD pairing in the presence of SAM. These results strongly support the model that SMK box translational repression operates through occlusion of the ribosome binding site and that SAM binding requires the SD-ASD pairing. PMID:17360376

Theoretical analysis of a method for extracting the phase of a phase-amplitude modulated signal generated by a direct-modulated optical injection-locked semiconductor laser

NASA Astrophysics Data System (ADS)

Lee, Hwan; Cho, Jun-Hyung; Sung, Hyuk-Kee

2017-05-01

The phase modulation (PM) and amplitude modulation (AM) of optical signals can be achieved using a direct-modulated (DM) optical injection-locked (OIL) semiconductor laser. We propose and theoretically analyze a simple method to extract the phase component of a PM signal produced by a DM-OIL semiconductor laser. The pure AM component of the combined PM-AM signal can be isolated by square-law detection in a photodetector and can then be used to compensate for the PM-AM signal based on an optical homodyne method. Using the AM compensation technique, we successfully developed a simple and cost-effective phase extraction method applicable to the PM-AM optical signal of a DM-OIL semiconductor laser.

Modulated amplitude waves in collisionally inhomogeneous Bose Einstein condensates

NASA Astrophysics Data System (ADS)

Porter, Mason A.; Kevrekidis, P. G.; Malomed, Boris A.; Frantzeskakis, D. J.

2007-05-01

We investigate the dynamics of an effectively one-dimensional Bose-Einstein condensate (BEC) with scattering length a subjected to a spatially periodic modulation, a=a(x)=a(x+L). This “collisionally inhomogeneous” BEC is described by a Gross-Pitaevskii (GP) equation whose nonlinearity coefficient is a periodic function of x. We transform this equation into a GP equation with a constant coefficient and an additional effective potential and study a class of extended wave solutions of the transformed equation. For weak underlying inhomogeneity, the effective potential takes a form resembling a superlattice, and the amplitude dynamics of the solutions of the constant-coefficient GP equation obey a nonlinear generalization of the Ince equation. In the small-amplitude limit, we use averaging to construct analytical solutions for modulated amplitude waves (MAWs), whose stability we subsequently examine using both numerical simulations of the original GP equation and fixed-point computations with the MAWs as numerically exact solutions. We show that “on-site” solutions, whose maxima correspond to maxima of a(x), are more robust and likely to be observed than their “off-site” counterparts.

High speed ultra-broadband amplitude modulators with ultrahigh extinction >65 dB.

PubMed

Liu, S; Cai, H; DeRose, C T; Davids, P; Pomerene, A; Starbuck, A L; Trotter, D C; Camacho, R; Urayama, J; Lentine, A

2017-05-15

We experimentally demonstrate ultrahigh extinction ratio (>65 dB) amplitude modulators (AMs) that can be electrically tuned to operate across a broad spectral range of 160 nm from 1480 - 1640 nm and 95 nm from 1280 - 1375 nm. Our on-chip AMs employ one extra coupler compared with conventional Mach-Zehnder interferometers (MZI), thus form a cascaded MZI (CMZI) structure. Either directional or adiabatic couplers are used to compose the CMZI AMs and experimental comparisons are made between these two different structures. We investigate the performance of CMZI AMs under extreme conditions such as using 95:5 split ratio couplers and unbalanced waveguide losses. Electro-optic phase shifters are also integrated in the CMZI AMs for high-speed operation. Finally, we investigate the output optical phase when the amplitude is modulated, which provides us valuable information when both amplitude and phase are to be controlled. Our demonstration not only paves the road to applications such as quantum information processing that requires high extinction ratio AMs but also significantly alleviates the tight fabrication tolerance needed for large-scale integrated photonics.

Systematic biochemical characterization of the SAM domains in Eph receptor family from Mus Musculus.

PubMed

Wang, Yue; Li, Qingxia; Zheng, Yunhua; Li, Gang; Liu, Wei

2016-05-13

The Eph receptor family is the largest subfamily of receptor tyrosine kinases and well-known for their pivotal roles in axon guidance, synaptogenesis, artery/venous differentiation and tumorigenesis, etc. Activation of the Eph receptor needs multimerization of the receptors. The intracellular C-terminal SAM domain of Eph receptor was reported to mediate self-association of Eph receptors via the homo SAM-SAM interaction. In this study, we systematically expressed and purified the SAM domain proteins of all fourteen Eph receptors of Mus musculus in Escherichia coli. The FPLC (fast protein liquid chromatography) results showed the recombinant SAM domains were highly homogeneous. Using CD (circular dichroism) spectrometry, we found that the secondary structure of all the SAM domains was typically alpha helical folded and remarkably similar. The thermo-stability tests showed that they were quite stable in solution. SEC-MALS (size exclusion chromatography coupled with multiple angle light scattering) results illustrated 200 μM Eph SAM domains behaved as good monomers in the size-exclusion chromatography. More importantly, DLS (dynamic light scattering) results revealed the overwhelming majority of SAM domains was not multimerized in solution either at 200 μM or 2000 μM protein concentration, which indicating the SAM domain alone was not sufficient to mediate the polymerization of Eph receptor. In summary, our studies provided the systematic biochemical characterizations of the Eph receptor SAM domains and implied their roles in Eph receptor mediated signaling pathways. Copyright © 2016 Elsevier Inc. All rights reserved.

Interferometric millimeter wave and THz wave doppler radar

DOEpatents

Liao, Shaolin; Gopalsami, Nachappa; Bakhtiari, Sasan; Raptis, Apostolos C.; Elmer, Thomas

2015-08-11

A mixerless high frequency interferometric Doppler radar system and methods has been invented, numerically validated and experimentally tested. A continuous wave source, phase modulator (e.g., a continuously oscillating reference mirror) and intensity detector are utilized. The intensity detector measures the intensity of the combined reflected Doppler signal and the modulated reference beam. Rigorous mathematics formulas have been developed to extract bot amplitude and phase from the measured intensity signal. Software in Matlab has been developed and used to extract such amplitude and phase information from the experimental data. Both amplitude and phase are calculated and the Doppler frequency signature of the object is determined.

Microdissection of Shoot Meristem Functional Domains

USDA-ARS?s Scientific Manuscript database

The shoot apical meristem (SAM) maintains a pool of indeterminate cells within the SAM proper, while lateral organs are initiated from the SAM periphery. Laser microdissection–microarray technology was used to compare transcriptional profiles within these SAM domains to identify novel maize genes th...

Amplitude-phase cross talk as a deterioration factor of signal-to-noise ratio in phase-detection noise-cancellation technique for spectral pump/probe measurements and compensation of the amplitude-phase cross talk

NASA Astrophysics Data System (ADS)

Seto, Keisuke; Tarumi, Takashi; Tokunaga, Eiji

2018-06-01

Noise cancellation of the light source is an important method to enhance the signal-to-noise ratio (SNR) and facilitate high-speed detection in pump/probe measurements. We developed a method to eliminate the noise for the multichannel spectral pump/probe measurements with a spectral dispersion of a white probe pulse light. In this method, the sample-induced intensity modulation is converted to the phase modulation of the pulse repetition irrespective of the intensity noise of the light source. The SNR is enhanced through the phase detection of the observed signal with the signal synchronized to the pulse repetition serving as the phase reference (synchronized signal). However, the shot-noise limited performance is not achieved with an intense probe light. In this work, we demonstrate that the performance limitation below the shot noise limit is caused by the amplitude-phase cross talk. It converts the amplitude noise into the phase noise and is caused by the space-charge effect in the photodetector, the reverse bias voltage drop across the load impedance, and the phase detection circuit. The phase delay occurs with an intense light at a PIN photodiode, whereas the phase is advanced in an avalanche photodiode. Although the amplitude distortion characteristics also reduce the performance, the distortion effect is equivalent to the amplitude-phase cross talk. We also propose possible ways to compensate the cross talk effect by using the phase modulation of the synchronized signal for the phase detection based on the instantaneous amplitude.

Basis for ligand discrimination between ON and OFF state riboswitch conformations: The case of the SAM-I riboswitch

PubMed Central

Boyapati, Vamsi Krishna; Huang, Wei; Spedale, Jessica; Aboul-ela, Fareed

2012-01-01

Riboswitches are RNA elements that bind to effector ligands and control gene expression. Most consist of two domains. S-Adenosyl Methionine (SAM) binds the aptamer domain of the SAM-I riboswitch and induces conformational changes in the expression domain to form an intrinsic terminator (transcription OFF state). Without SAM the riboswitch forms the transcription ON state, allowing read-through transcription. The mechanistic link between the SAM/aptamer recognition event and subsequent secondary structure rearrangement by the riboswitch is unclear. We probed for those structural features of the Bacillus subtilis yitJ SAM-I riboswitch responsible for discrimination between the ON and OFF states by SAM. We designed SAM-I riboswitch RNA segments forming “hybrid” structures of the ON and OFF states. The choice of segment constrains the formation of a partial P1 helix, characteristic of the OFF state, together with a partial antiterminator (AT) helix, characteristic of the ON state. For most choices of P1 vs. AT helix lengths, SAM binds with micromolar affinity according to equilibrium dialysis. Mutational analysis and in-line probing confirm that the mode of SAM binding by hybrid structures is similar to that of the aptamer. Altogether, binding measurements and in-line probing are consistent with the hypothesis that when SAM is present, stacking interactions with the AT helix stabilize a partially formed P1 helix in the hybrids. Molecular modeling indicates that continuous stacking between the P1 and the AT helices is plausible with SAM bound. Our findings raise the possibility that conformational intermediates may play a role in ligand-induced aptamer folding. PMID:22543867

Defects in subventricular zone pigmented epithelium-derived factor niche signaling in the senescence-accelerated mouse prone-8.

PubMed

Castro-Garcia, Paola; Díaz-Moreno, María; Gil-Gas, Carmen; Fernández-Gómez, Francisco J; Honrubia-Gómez, Paloma; Álvarez-Simón, Carmen Belén; Sánchez-Sánchez, Francisco; Cano, Juan Carlos Castillo; Almeida, Francisco; Blanco, Vicente; Jordán, Joaquín; Mira, Helena; Ramírez-Castillejo, Carmen

2015-04-01

We studied potential changes in the subventricular zone (SVZ) stem cell niche of the senescence-accelerated mouse prone-8 (SAM-P8) aging model. Bromodeoxyuridine (BrdU) assays with longtime survival revealed a lower number of label-retaining stem cells in the SAM-P8 SVZ compared with the SAM-Resistant 1 (SAM-R1) control strain. We also found that in SAM-P8 niche signaling is attenuated and the stem cell pool is less responsive to the self-renewal niche factor pigmented epithelium-derived factor (PEDF). Protein analysis demonstrated stable amounts of the PEDF ligand in the SAM-P8 SVZ niche; however, SAM-P8 stem cells present a significant expression decrease of patatin-like phospholipase domain containing 2, a receptor for PEDF (PNPLA2-PEDF) receptor, but not of laminin receptor (LR), a receptor for PEDF (LR-PEDF) receptor. We observed changes in self-renewal related genes (hairy and enhancer of split 1 (Hes1), hairy and enhancer of split 1 (Hes5), Sox2] and report that although these genes are down-regulated in SAM-P8, differentiation genes (Pax6) are up-regulated and neurogenesis is increased. Finally, sheltering mammalian telomere complexes might be also involved given a down-regulation of telomeric repeat binding factor 1 (Terf1) expression was observed in SAM-P8 at young age periods. Differences between these 2 models, SAM-P8 and SAM-R1 controls, have been previously detected at more advanced ages. We now describe alterations in the PEDF signaling pathway and stem cell self-renewal at a very young age, which could be involved in the premature senescence observed in the SAM-P8 model. © FASEB.

Basis for ligand discrimination between ON and OFF state riboswitch conformations: the case of the SAM-I riboswitch.

PubMed

Boyapati, Vamsi Krishna; Huang, Wei; Spedale, Jessica; Aboul-Ela, Fareed

2012-06-01

Riboswitches are RNA elements that bind to effector ligands and control gene expression. Most consist of two domains. S-Adenosyl Methionine (SAM) binds the aptamer domain of the SAM-I riboswitch and induces conformational changes in the expression domain to form an intrinsic terminator (transcription OFF state). Without SAM the riboswitch forms the transcription ON state, allowing read-through transcription. The mechanistic link between the SAM/aptamer recognition event and subsequent secondary structure rearrangement by the riboswitch is unclear. We probed for those structural features of the Bacillus subtilis yitJ SAM-I riboswitch responsible for discrimination between the ON and OFF states by SAM. We designed SAM-I riboswitch RNA segments forming "hybrid" structures of the ON and OFF states. The choice of segment constrains the formation of a partial P1 helix, characteristic of the OFF state, together with a partial antiterminator (AT) helix, characteristic of the ON state. For most choices of P1 vs. AT helix lengths, SAM binds with micromolar affinity according to equilibrium dialysis. Mutational analysis and in-line probing confirm that the mode of SAM binding by hybrid structures is similar to that of the aptamer. Altogether, binding measurements and in-line probing are consistent with the hypothesis that when SAM is present, stacking interactions with the AT helix stabilize a partially formed P1 helix in the hybrids. Molecular modeling indicates that continuous stacking between the P1 and the AT helices is plausible with SAM bound. Our findings raise the possibility that conformational intermediates may play a role in ligand-induced aptamer folding.

Optimization of VLf/ELF Wave Generation using Beam Painting

NASA Astrophysics Data System (ADS)

Robinson, A.; Moore, R. C.

2017-12-01

A novel optimized beam painting algorithm (OBP) is used to generate high amplitude very low frequency (VLF) and extremely low frequency (ELF) waves in the D-region of the ionosphere above the High-frequency Active Auroral Research Program (HAARP) observatory. The OBP method creates a phased array of sources in the ionosphere by varying the azimuth and zenith angles of the high frequency (HF) transmitter to capitalize on the constructive interference of propagating VLF/ELF waves. OBP generates higher amplitude VLF/ELF signals than any other previously proposed method. From April through June during 2014, OBP was performed at HAARP over 1200 times. We compare the BP generated signals against vertical amplitude modulated transmissions at 50 % duty cycle (V), oblique amplitude modulated transmissions at 15 degrees zenith and 81 degrees azimuth at 50 % duty cycle (O), and geometric (circle-sweep) modulation at 15 degrees off-zenith angle at 1562.5 Hz, 3125 Hz, and 5000 Hz. We present an analysis of the directional dependence of each signal, its polarization, and its dependence on the properties of the different source region elements. We find that BP increases the received signal amplitudes of VLF and ELF waves when compared to V, O, and GM methods over a statistically significant number of trials.

Cloud Atlas: Discovery of Rotational Spectral Modulations in a Low-mass, L-type Brown Dwarf Companion to a Star

NASA Astrophysics Data System (ADS)

Manjavacas, Elena; Apai, Dániel; Zhou, Yifan; Karalidi, Theodora; Lew, Ben W. P.; Schneider, Glenn; Cowan, Nicolas; Metchev, Stan; Miles-Páez, Paulo A.; Burgasser, Adam J.; Radigan, Jacqueline; Bedin, Luigi R.; Lowrance, Patrick J.; Marley, Mark S.

2018-01-01

Observations of rotational modulations of brown dwarfs and giant exoplanets allow the characterization of condensate cloud properties. As of now, rotational spectral modulations have only been seen in three L-type brown dwarfs. We report here the discovery of rotational spectral modulations in LP261-75B, an L6-type intermediate surface gravity companion to an M4.5 star. As a part of the Cloud Atlas Treasury program, we acquired time-resolved Wide Field Camera 3 grism spectroscopy (1.1–1.69 μm) of LP261-75B. We find gray spectral variations with the relative amplitude displaying only a weak wavelength dependence and no evidence for lower-amplitude modulations in the 1.4 μm water band than in the adjacent continuum. The likely rotational modulation period is 4.78 ± 0.95 hr, although the rotational phase is not well sampled. The minimum relative amplitude in the white light curve measured over the whole wavelength range is 2.41% ± 0.14%. We report an unusual light curve, which seems to have three peaks approximately evenly distributed in rotational phase. The spectral modulations suggests that the upper atmosphere cloud properties in LP261-75B are similar to two other mid-L dwarfs of typical infrared colors, but differ from that of the extremely red L-dwarf WISE0047.

47 CFR 101.811 - Modulation requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... signaling on frequencies below 500 MHz is not authorized. (b) When amplitude modulation is used, the... frequency modulation is used for single channel radiotelephony on frequencies below 500 MHz, the deviation... 47 Telecommunication 5 2010-10-01 2010-10-01 false Modulation requirements. 101.811 Section 101...

Functionalization and Characterization of Gold Nanoparticles

NASA Astrophysics Data System (ADS)

Techane, Sirnegeda D.

2011-12-01

Surface characterization of gold nanoparticles (AuNPs) is necessary to obtain a thorough understanding of the AuNP properties and ultimately realize their full potential in applications. The work described in this dissertation strives to the structure and composition of AuNPs using highly surface sensitive techniques such as X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) in addition to the more widely used characterization techniques such as transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and UV-VIS spectroscopy. Self-assembled monolayers (SAMs) of alkanethiols were used to modify AuNPs surfaces to create positively and negatively charged surfaces. Functionalization with carboxylic acid terminated alkanethiol SAMs (COON-SAMs) was first optimized to produce clean and stable negatively charged AuNPs. Using 14nm and 40nm diameter AuNPs in combination with C11 and C16 chain length COOH-SAMs, it was found that addition of NH4OH during functionalization coupled with dialysis purification produced AuNPs that did not aggregate and did not have unbound thiols. Effects of AuNP size and COOH-SAM chain lengths were studied using 14, 25 and 40nm average diameter AuNPs functionalized with C6, C8, C11 and C16 COOH-SAMs. Flat Au surfaces were also functionalized with the COOH-SAMs for comparison. It was shown that the 14nm AuNPs with C16 COOH-SAMs were the most stable and had crystalline-like, well-ordered SAM structures. The SAMs on the 40nm AuNPs had similar surface chemistry as the SAMs on the flat Au surfaces. The effective photoelectron take-off angle of the C16 COOH-SAM decreased when the size of the AuNP increased. It was also shown that when using Kratos AxisUltra DLD XPS instrument in the hybrid mode, it was important to consider effects of both the hybrid mode and the AuNPs curvature when calculating overlayer thickness of the SAMs on AuNPs. Using the Kratos in the electrostatic mode, the overlayer thickness of C16 COON-SAM was 21A on a flat Au surface, which was comparable with previously reported values. However, the apparent thickness of the same SAM on the 14nm AuNPs was 31A, indicating the curvature of the AuNPs had an effect on the XPS measurements. To produce the positively charged AuNP surfaces, amine terminated alkanethiols (NH2 -thiols) with a C2 chain length were used in one-step AuNP synthesis and functionalization process followed by a ligand-exchange reaction with C11 chain length NH2-thiols. It was found that 14 days were needed for the ligand-exchange to be complete. After the ligand-exchange, it was found that the AuNPs with C11 NH2-SAMs were stable and could be purified, unlike AuNPs with C2 NH2-SAMs which aggregated upon purification. The C11 NH2-SAMs had both unbound and oxidized sulfur, which could be removed/converted after hydrochloric acid treatment. SESSA (simulation of electron spectra for surface analysis) allowed better interpretation of the XPS data of SAMs on AuNPs and flat Au. Comparing SESSA and experimental XPS data, it was found that C16 COON-SAM on a flat Au surface was 20A thick with a 1.5A hydrocarbon contamination overlayer and 1.05 relative surface roughness. After geometric weighing of angle-resolved XPS and SESSA data, it was found that C16 COOH-SAMs on 14nm AuNPs were 17A thick with a 1.5A hydrocarbon contamination. The decreased SAM thickness on the AuNPs is likely due to an increased tilt angle of the alkane chains or increased disorder in the SAM.

Characteristics of spectro-temporal modulation frequency selectivity in humans.

PubMed

Oetjen, Arne; Verhey, Jesko L

2017-03-01

There is increasing evidence that the auditory system shows frequency selectivity for spectro-temporal modulations. A recent study of the authors has shown spectro-temporal modulation masking patterns that were in agreement with the hypothesis of spectro-temporal modulation filters in the human auditory system [Oetjen and Verhey (2015). J. Acoust. Soc. Am. 137(2), 714-723]. In the present study, that experimental data and additional data were used to model this spectro-temporal frequency selectivity. The additional data were collected to investigate to what extent the spectro-temporal modulation-frequency selectivity results from a combination of a purely temporal amplitude-modulation filter and a purely spectral amplitude-modulation filter. In contrast to the previous study, thresholds were measured for masker and target modulations with opposite directions, i.e., an upward pointing target modulation and a downward pointing masker modulation. The comparison of this data set with previous corresponding data with the same direction from target and masker modulations indicate that a specific spectro-temporal modulation filter is required to simulate all aspects of spectro-temporal modulation frequency selectivity. A model using a modified Gabor filter with a purely temporal and a purely spectral filter predicts the spectro-temporal modulation masking data.

Development of a Reduced-Order Three-Dimensional Flow Model for Thermal Mixing and Stratification Simulation during Reactor Transients

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

Hu, Rui

2017-09-03

Mixing, thermal-stratification, and mass transport phenomena in large pools or enclosures play major roles for the safety of reactor systems. Depending on the fidelity requirement and computational resources, various modeling methods, from the 0-D perfect mixing model to 3-D Computational Fluid Dynamics (CFD) models, are available. Each is associated with its own advantages and shortcomings. It is very desirable to develop an advanced and efficient thermal mixing and stratification modeling capability embedded in a modern system analysis code to improve the accuracy of reactor safety analyses and to reduce modeling uncertainties. An advanced system analysis tool, SAM, is being developedmore » at Argonne National Laboratory for advanced non-LWR reactor safety analysis. While SAM is being developed as a system-level modeling and simulation tool, a reduced-order three-dimensional module is under development to model the multi-dimensional flow and thermal mixing and stratification in large enclosures of reactor systems. This paper provides an overview of the three-dimensional finite element flow model in SAM, including the governing equations, stabilization scheme, and solution methods. Additionally, several verification and validation tests are presented, including lid-driven cavity flow, natural convection inside a cavity, laminar flow in a channel of parallel plates. Based on the comparisons with the analytical solutions and experimental results, it is demonstrated that the developed 3-D fluid model can perform very well for a wide range of flow problems.« less

Structure-guided design of fluorescent S-adenosylmethionine analogs for a high-throughput screen to target SAM-I riboswitch RNAs.

PubMed

Hickey, Scott F; Hammond, Ming C

2014-03-20

Many classes of S-adenosylmethionine (SAM)-binding RNAs and proteins are of interest as potential drug targets in diverse therapeutic areas, from infectious diseases to cancer. In the former case, the SAM-I riboswitch is an attractive target because this structured RNA element is found only in bacterial mRNAs and regulates multiple genes in several human pathogens. Here, we describe the synthesis of stable and fluorescent analogs of SAM in which the fluorophore is introduced through a functionalizable linker to the ribose. A Cy5-labeled SAM analog was shown to bind several SAM-I riboswitches via in-line probing and fluorescence polarization assays, including one from Staphylococcus aureus that controls the expression of SAM synthetase in this organism. A fluorescent ligand displacement assay was developed and validated for high-throughput screening of compounds to target the SAM-I riboswitch class. Copyright © 2014 Elsevier Ltd. All rights reserved.

Single-molecule FRET reveals the energy landscape of the full-length SAM-I riboswitch.

PubMed

Manz, Christoph; Kobitski, Andrei Yu; Samanta, Ayan; Keller, Bettina G; Jäschke, Andres; Nienhaus, G Ulrich

2017-11-01

S-adenosyl-L-methionine (SAM) ligand binding induces major structural changes in SAM-I riboswitches, through which gene expression is regulated via transcription termination. Little is known about the conformations and motions governing the function of the full-length Bacillus subtilis yitJ SAM-I riboswitch. Therefore, we have explored its conformational energy landscape as a function of Mg 2+ and SAM ligand concentrations using single-molecule Förster resonance energy transfer (smFRET) microscopy and hidden Markov modeling analysis. We resolved four conformational states both in the presence and the absence of SAM and determined their Mg 2+ -dependent fractional populations and conformational dynamics, including state lifetimes, interconversion rate coefficients and equilibration timescales. Riboswitches with terminator and antiterminator folds coexist, and SAM binding only gradually shifts the populations toward terminator states. We observed a pronounced acceleration of conformational transitions upon SAM binding, which may be crucial for off-switching during the brief decision window before expression of the downstream gene.

System Advisor Model, SAM 2011.12.2: General Description

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

Gilman, P.; Dobos, A.

2012-02-01

This document describes the capabilities of the U.S. Department of Energy and National Renewable Energy Laboratory's System Advisor Model (SAM), Version 2011.12.2, released on December 2, 2011. SAM is software that models the cost and performance of renewable energy systems. Project developers, policy makers, equipment manufacturers, and researchers use graphs and tables of SAM results in the process of evaluating financial, technology, and incentive options for renewable energy projects. SAM simulates the performance of solar, wind, geothermal, biomass, and conventional power systems. The financial model can represent financing structures for projects that either buy and sell electricity at retail ratesmore » (residential and commercial) or sell electricity at a price determined in a power purchase agreement (utility). Advanced analysis options facilitate parametric, sensitivity, and statistical analyses, and allow for interfacing SAM with Microsoft Excel or with other computer programs. SAM is available as a free download at http://sam.nrel.gov. Technical support and more information about the software are available on the website.« less

Structural analysis of a putative SAM-dependent methyltransferase, YtqB, from Bacillus subtilis.

PubMed

Park, Sun Cheol; Song, Wan Seok; Yoon, Sung-il

2014-04-18

S-adenosyl-L-methionine (SAM)-dependent methyltransferases (MTases) methylate diverse biological molecules using a SAM cofactor. The ytqB gene of Bacillus subtilis encodes a putative MTase and its biological function has never been characterized. To reveal the structural features and the cofactor binding mode of YtqB, we have determined the crystal structures of YtqB alone and in complex with its cofactor, SAM, at 1.9 Å and 2.2 Å resolutions, respectively. YtqB folds into a β-sheet sandwiched by two α-helical layers, and assembles into a dimeric form. Each YtqB monomer contains one SAM binding site, which shapes SAM into a slightly curved conformation and exposes the reactive methyl group of SAM potentially to a substrate. Our comparative structural analysis of YtqB and its homologues indicates that YtqB is a SAM-dependent class I MTase, and provides insights into the substrate binding site of YtqB. Copyright © 2014 Elsevier Inc. All rights reserved.

Demonstration of a Segment Alignment Maintenance System on a Seven-Segment Sub-Array of the Hobby-Eberly Telescope

NASA Technical Reports Server (NTRS)

Rakoczy, John; Whitaker, Ann F. (Technical Monitor)

2001-01-01

NASA's Marshall Space Flight Center, in collaboration with Blue Line Engineering of Colorado Springs, Colorado, is developing a Segment Alignment Maintenance System (SAMS) for McDonald Observatory's Hobby-Eberly Telescope (HET). The SAMS shall sense motions of the 91 primary mirror segments and send corrections to HET's primary mirror controller as the mirror segments misalign due to thermo-elastic deformations of the mirror support structure. The SAMS consists of inductive edge sensors supplemented by inclinometers for global radius of curvature sensing. All measurements are sent to the SAMS computer where mirror motion corrections are calculated. In October 2000, a prototype SAMS was installed on a seven-segment cluster of the HET. Subsequent testing has shown that the SAMS concept and architecture are a viable practical approach to maintaining HET's primary mirror figure, or the figure of any large segmented telescope. This paper gives a functional description of the SAMS sub-array components and presents test data to characterize the performance of the sub-array SAMS.

External amplitude and frequency modulation of a terahertz quantum cascade laser using metamaterial/graphene devices.

PubMed

Kindness, S J; Jessop, D S; Wei, B; Wallis, R; Kamboj, V S; Xiao, L; Ren, Y; Braeuninger-Weimer, P; Aria, A I; Hofmann, S; Beere, H E; Ritchie, D A; Degl'Innocenti, R

2017-08-09

Active control of the amplitude and frequency of terahertz sources is an essential prerequisite for exploiting a myriad of terahertz applications in imaging, spectroscopy, and communications. Here we present a optoelectronic, external modulation technique applied to a terahertz quantum cascade laser which holds the promise of addressing a number of important challenges in this research area. A hybrid metamaterial/graphene device is implemented into an external cavity set-up allowing for optoelectronic tuning of feedback into a quantum cascade laser. We demonstrate powerful, all-electronic, control over the amplitude and frequency of the laser output. Full laser switching is performed by electrostatic gating of the metamaterial/graphene device, demonstrating a modulation depth of 100%. External control of the emission spectrum is also achieved, highlighting the flexibility of this feedback method. By taking advantage of the frequency dispersive reflectivity of the metamaterial array, different modes of the QCL output are selectively suppressed using lithographic tuning and single mode operation of the multi-mode laser is enforced. Side mode suppression is electrically modulated from ~6 dB to ~21 dB, demonstrating active, optoelectronic modulation of the laser frequency content between multi-mode and single mode operation.

Using Flanagan's phase vocoder to improve cochlear implant performance

NASA Astrophysics Data System (ADS)

Zeng, Fan-Gang

2004-10-01

The cochlear implant has restored partial hearing to more than 100000 deaf people worldwide, allowing the average user to talk on the telephone in quiet environment. However, significant difficulty still remains for speech recognition in noise, music perception, and tonal language understanding. This difficulty may be related to speech processing strategies in current cochlear implants that emphasized the extraction and encoding of the temporal envelope while ignoring the temporal fine structure in speech sounds. A novel strategy was developed based on Flanagan's phase vocoder [Flanagan and Golden, Bell Syst. Tech. 45, 1493-1509 (1966)], in which frequency modulation was extracted from the temporal fine structure and then added to amplitude modulation in the current cochlear implants. Acoustic simulation results showed that amplitude and frequency modulation contributed complementarily to speech perception with amplitude modulation contributing mainly to intelligibility whereas frequency modulation contributed to speaker identification and auditory grouping. The results also showed that the novel strategy significantly improved cochlear implant performance under realistic listening situations. Overall, the present result demonstrated that Flanagan's classic work on phase vocoder still shed insight on current problems of both theoretical and practical importance. [Work supported by NIH.

Common themes and differences in SAM recognition among SAM riboswitches

PubMed Central

Price, Ian R.; Grigg, Jason C.; Ke, Ailong

2014-01-01

The recent discovery of short cis-acting RNA elements termed riboswitches has caused a paradigm shift in our understanding of genetic regulatory mechanisms. The three distinct superfamilies of S-adenosyl-L-methionine (SAM) riboswitches are the most commonly found riboswitch classes in nature. These RNAs represent three independent evolutionary solutions to achieve specific SAM recognition. This review summarizes research on 1) modes of gene regulatory mechanisms, 2) common themes and differences in ligand recognition, and 3) ligand-induced conformational dynamics among SAM riboswitch families. The body of work on the SAM riboswitch families constitutes a useful primer to the topic of gene regulatory RNAs as a whole. PMID:24863160

Modulator for tone and binary signals. [phase of modulation of tone and binary signals on carrier waves in communication systems

NASA Technical Reports Server (NTRS)

Mcchesney, J. R.; Lerner, T.; Fitch, E. J. (Inventor)

1975-01-01

Tones and binary information are transmitted as phase variations on a carrier wave of constant amplitude and frequency. The carrier and tones are applied to a balanced modulator for deriving an output signal including a pair of sidebands relative to the carrier. The carrier is phase modulated by a digital signal so that it is + or - 90 deg out of phase with the predetermined phase of the carrier. The carrier is combined in an algebraic summing device with the phase modulated signal and the balanced modulator output signal. The output of the algebraic summing device is hard limited to derive a constant amplitude and frequency signal having very narrow bandwidth requirements. At a receiver, the tones and binary data are detected with a phase locked loop having a voltage controlled oscillator driving a pair of orthogonal detection channels.

Modulating the Neutron Flux from a Mirror Neutron Source

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

Ryutov, D D

2011-09-01

A 14-MeV neutron source based on a Gas-Dynamic Trap will provide a high flux of 14 MeV neutrons for fusion materials and sub-component testing. In addition to its main goal, the source has potential applications in condensed matter physics and biophysics. In this report, the author considers adding one more capability to the GDT-based neutron source, the modulation of the neutron flux with a desired frequency. The modulation may be an enabling tool for the assessment of the role of non-steady-state effects in fusion devices as well as for high-precision, low-signal basic science experiments favoring the use of the synchronousmore » detection technique. A conclusion is drawn that modulation frequency of up to 1 kHz and modulation amplitude of a few percent is achievable. Limitations on the amplitude of modulations at higher frequencies are discussed.« less

Exact states in waveguides with periodically modulated nonlinearity

NASA Astrophysics Data System (ADS)

Ding, E.; Chan, H. N.; Chow, K. W.; Nakkeeran, K.; Malomed, B. A.

2017-09-01

We introduce a one-dimensional model based on the nonlinear Schrödinger/Gross-Pitaevskii equation where the local nonlinearity is subject to spatially periodic modulation in terms of the Jacobi {dn} function, with three free parameters including the period, amplitude, and internal form-factor. An exact periodic solution is found for each set of parameters and, which is more important for physical realizations, we solve the inverse problem and predict the period and amplitude of the modulation that yields a particular exact spatially periodic state. A numerical stability analysis demonstrates that the periodic states become modulationally unstable for large periods, and regain stability in the limit of an infinite period, which corresponds to a bright soliton pinned to a localized nonlinearity-modulation pattern. The exact dark-bright soliton complex in a coupled system with a localized modulation structure is also briefly considered. The system can be realized in planar optical waveguides and cigar-shaped atomic Bose-Einstein condensates.

Performance improvement by orthogonal pulse amplitude modulation and discrete multitone modulation signals in hybrid fiber-visible laser light communication system

NASA Astrophysics Data System (ADS)

Zhang, Fangliu; He, Jing; Deng, Rui; Chen, Qinghui; Chen, Lin

2016-10-01

A modulation format, orthogonal pulse amplitude modulation and discrete multitone modulation (O-PAM-DMT), is experimentally demonstrated in a hybrid fiber-visible laser light communication (fiber-VLLC) system using a cost-effective directly modulated laser and blue laser diode. In addition, low overhead is achieved by utilizing only one training sequence to implement synchronization and channel estimation. Through adjusting the ratio of PAM and DMT signal, three types of O-PAM-DMT signals are investigated. After transmission over a 20-km standard single-mode fiber and 5-m free-space VLLC, the receiver sensitivity for 4.36-Gbit/s O-PAM-DMT signals can be improved by 0.4, 1.4, and 2.7 dB, respectively, at a bit error rate of 1×10-3, compared with a conventional DMT signal.

Graphene patterns supported terahertz tunable plasmon induced transparency.

PubMed

He, Xiaoyong; Liu, Feng; Lin, Fangting; Shi, Wangzhou

2018-04-16

The tunable plasmonic induced transparency has been theoretically investigated based on graphene patterns/SiO 2 /Si/polymer multilayer structure in the terahertz regime, including the effects of graphene Fermi level, structural parameters and operation frequency. The results manifest that obvious Fano peak can be observed and efficiently modulated because of the strong coupling between incident light and graphene pattern structures. As Fermi level increases, the peak amplitude of Fano resonance increases, and the resonant peak position shifts to high frequency. The amplitude modulation depth of Fano curves is about 40% on condition that the Fermi level changes in the scope of 0.2-1.0 eV. With the distance between cut wire and double semi-circular patterns increases, the peak amplitude and figure of merit increases. The results are very helpful to develop novel graphene plasmonic devices (e.g. sensors, modulators, and antenna) and find potential applications in the fields of biomedical sensing and wireless communications.

Velocity-Field Measurements of an Axisymmetric Separated Flow Subjected to Amplitude-Modulated Excitation

NASA Technical Reports Server (NTRS)

Trosin, Barry James

2007-01-01

Active flow control was applied at the point of separation of an axisymmetric, backward-facing-step flow. The control was implemented by employing a Helmholtz resonator that was externally driven by an amplitude-modulated, acoustic disturbance from a speaker located upstream of the wind tunnel. The velocity field of the separating/reattaching flow region downstream of the step was characterized using hotwire velocity measurements with and without flow control. Conventional statistics of the data reveal that the separating/reattaching flow is affected by the imposed forcing. Triple decomposition along with conditional averaging was used to distinguish periodic disturbances from random turbulence in the fluctuating velocity component. A significant outcome of the present study is that it demonstrates that amplitude-modulated forcing of the separated flow alters the flow in the same manner as the more conventional method of periodic excitation.

On the benefit of DMT modulation in nonlinear VLC systems.

PubMed

Qian, Hua; Cai, Sunzeng; Yao, Saijie; Zhou, Ting; Yang, Yang; Wang, Xudong

2015-02-09

In a visible light communication (VLC) system, the nonlinear characteristic of the light emitting diode (LED) in transmitter is a limiting factor of system performance. Modern modulation signals with large peak-to-power-ratio (PAPR) suffers uneven distortion. The nonlinear response directly impacts the intensity modulation and direct detection VLC system with pulse-amplitude modulation (PAM). The amplitude of the PAM signal is distorted unevenly and large signal is vulnerable to noise. Orthogonal linear transformations, such as discrete multi-tone (DMT) modulation, can spread the nonlinear effects evenly to each data symbol, thus perform better than PAM signals. In this paper, we provide theoretical analysis on the benefit of DMT modulation in nonlinear VLC system. We show that the DMT modulation is a better choice than the PAM modulation for the VLC system as the DMT modulation is more robust against nonlinearity. We also show that the post-distortion nonlinear elimination method, which is applied at the receiver, can be a reliable solution to the nonlinear VLC system. Simulation results show that the post-distortion greatly improves the system performance for the DMT modulation.

Evaluating SAMS in Hong Kong Schools.

ERIC Educational Resources Information Center

Kwok, Lam-for; Lau, Chi-kuen; Fung, Sun-wai

1999-01-01

Describes the School Administration and Management Systems (SAMS) that was developed to support elementary and secondary schools in Hong Kong in administrative and managerial tasks. Reports results of a survey that investigated the impact of SAMS, evaluated its effectiveness, and identified possible areas of improvement to SAMS operation.…

Local measurement of error field using naturally rotating tearing mode dynamics in EXTRAP T2R

NASA Astrophysics Data System (ADS)

Sweeney, R. M.; Frassinetti, L.; Brunsell, P.; Fridström, R.; Volpe, F. A.

2016-12-01

An error field (EF) detection technique using the amplitude modulation of a naturally rotating tearing mode (TM) is developed and validated in the EXTRAP T2R reversed field pinch. The technique was used to identify intrinsic EFs of m/n  =  1/-12, where m and n are the poloidal and toroidal mode numbers. The effect of the EF and of a resonant magnetic perturbation (RMP) on the TM, in particular on amplitude modulation, is modeled with a first-order solution of the modified Rutherford equation. In the experiment, the TM amplitude is measured as a function of the toroidal angle as the TM rotates rapidly in the presence of an unknown EF and a known, deliberately applied RMP. The RMP amplitude is fixed while the toroidal phase is varied from one discharge to the other, completing a full toroidal scan. Using three such scans with different RMP amplitudes, the EF amplitude and phase are inferred from the phases at which the TM amplitude maximizes. The estimated EF amplitude is consistent with other estimates (e.g. based on the best EF-cancelling RMP, resulting in the fastest TM rotation). A passive variant of this technique is also presented, where no RMPs are applied, and the EF phase is deduced.

ER residency of the ceramide phosphoethanolamine synthase SMSr relies on homotypic oligomerization mediated by its SAM domain

PubMed Central

Cabukusta, Birol; Kol, Matthijs; Kneller, Laura; Hilderink, Angelika; Bickert, Andreas; Mina, John G. M.; Korneev, Sergei; Holthuis, Joost C. M.

2017-01-01

SMSr/SAMD8 is an ER-resident ceramide phosphoethanolamine synthase with a critical role in controlling ER ceramides and suppressing ceramide-induced apoptosis in cultured cells. SMSr-mediated ceramide homeostasis relies on the enzyme’s catalytic activity as well as on its N-terminal sterile α-motif or SAM domain. Here we report that SMSr-SAM is structurally and functionally related to the SAM domain of diacylglycerol kinase DGKδ, a central regulator of lipid signaling at the plasma membrane. Native gel electrophoresis indicates that both SAM domains form homotypic oligomers. Chemical crosslinking studies show that SMSr self-associates into ER-resident trimers and hexamers that resemble the helical oligomers formed by DGKδ-SAM. Residues critical for DGKδ-SAM oligomerization are conserved in SMSr-SAM and their substitution causes a dissociation of SMSr oligomers as well as a partial redistribution of the enzyme to the Golgi. Conversely, treatment of cells with curcumin, a drug disrupting ceramide and Ca2+ homeostasis in the ER, stabilizes SMSr oligomers and promotes retention of the enzyme in the ER. Our data provide first demonstration of a multi-pass membrane protein that undergoes homotypic oligomerization via its SAM domain and indicate that SAM-mediated self-assembly of SMSr is required for efficient retention of the enzyme in the ER. PMID:28120887

47 CFR 90.207 - Types of emissions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... under this part, see § 2.201 of this chapter. (1) The first symbol indicates the type of modulation on the transmitter carrier. A—Amplitude modulation, double sideband with identical information on each sideband. F—Frequency modulation. G—Phase modulation. J—Single sideband with suppressed carrier. P...

QBO/solar modulation of the boreal winter Madden-Julian oscillation: A prediction for the coming solar minimum

NASA Astrophysics Data System (ADS)

Hood, Lon L.

2017-04-01

The Madden-Julian oscillation (MJO), also known as the 30-60 day oscillation, is the strongest of the intraseasonal climate oscillations in the tropics and has significant derivative effects on extratropical circulation and intraseasonal climate. It has recently been shown that the stratospheric quasi-biennial oscillation (QBO) modulates the amplitude of the boreal winter MJO such that MJO amplitudes are larger on average during the easterly phase (QBOE) than during the westerly phase (QBOW). A major possible mechanism is the decrease in static stability in the lowermost stratosphere under QBOE conditions resulting from relative upwelling associated with the QBO-induced meridional circulation. Here evidence is presented that tropical upwelling changes related to the 11 year solar cycle also modulate the boreal winter MJO. Based on 37.3 years of MJO amplitude data, the largest amplitudes and occurrence rates, and the weakest static stabilities in the tropical lower stratosphere, occur during the QBOE phase under solar minimum (SMIN) conditions while the smallest amplitudes and strongest static stabilities occur during the QBOW phase under solar maximum (SMAX) conditions. Conversely, when the QBO and solar forcings are opposed (QBOW/SMIN and QBOE/SMAX), the difference in occurrence rates becomes statistically insignificant. During the coming solar minimum, at least one additional winter in the QBOE/SMIN category should occur (possibly as early as 2017/2018) during which especially large MJO amplitudes are expected and an initial test of these results will be possible.

Amplitude and phase controlled adaptive optics system

NASA Astrophysics Data System (ADS)

Pham, Ich; Ma, Sam

2006-06-01

An adaptive optics (AO) system is used to control the deformable mirror (DM) actuators for compensating the optical effects introduced by the turbulence in the Earth's atmosphere and distortions produced by the optical elements between the distant object and its local sensor. The typical AO system commands the DM actuators while minimizing the measured wave front (WF) phase error. This is known as the phase conjugator system, which does not work well in the strong scintillation condition because both amplitude and phase are corrupted along the propagation path. In order to compensate for the wave front amplitude, a dual DM field conjugator system may be used. The first and second DM compensate for the amplitude and the phase respectively. The amplitude controller requires the mapping from DM1 actuator command to DM2 intensity. This can be obtained from either a calibration routine or an intensity transport equation, which relates the phase to the intensity. Instead of a dual-DM, a single Spatial Light Modulator (SLM) may control the amplitude and phase independently. The technique uses the spatial carrier frequency and the resulting intensity is related to the carrier modulation, while the phase is the average carrier phase. The dynamical AO performance using the carrier modulation is limited by the actuator frequency response and not by the computational load of the controller algorithm. Simulation of the proposed field conjugator systems show significant improvement for the on-axis performance compared to the phase conjugator system.

Effect of S-adenosyl-L-methionine (SAM), an allosteric activator of cystathionine-β-synthase (CBS) on colorectal cancer cell proliferation and bioenergetics in vitro.

PubMed

Módis, Katalin; Coletta, Ciro; Asimakopoulou, Antonia; Szczesny, Bartosz; Chao, Celia; Papapetropoulos, Andreas; Hellmich, Mark R; Szabo, Csaba

2014-09-15

Recent data show that colon cancer cells selectively overexpress cystathionine-β-synthase (CBS), which produces hydrogen sulfide (H2S), to maintain cellular bioenergetics, support tumor growth and stimulate angiogenesis and vasorelaxation in the tumor microenvironment. The purpose of the current study was to investigate the effect of the allosteric CBS activator S-adenosyl-L-methionine (SAM) on the proliferation and bioenergetics of the CBS-expressing colon cancer cell line HCT116. The non-transformed, non-tumorigenic colon epithelial cell line NCM356 was used as control. For assessment of cell proliferation, the xCELLigence system was used. Bioenergetic function was measured by Extracellular Flux Analysis. Experiments using human recombinant CBS or HCT116 homogenates complemented the cell-based studies. SAM markedly enhanced CBS-mediated H2S production in vitro, especially when a combination of cysteine and homocysteine was used as substrates. Addition of SAM (0.1-3 mM) to HCT116 cells induced a concentration-dependent increase H2S production. SAM exerted time- and concentration-dependent modulatory effects on cell proliferation. At 0.1-1 mM SAM increased HCT116 proliferation between 0 and 12 h, while the highest SAM concentration (3 mM) inhibited proliferation. Over a longer time period (12-24 h), only the lowest concentration of SAM used (0.1 mM) stimulated cell proliferation; higher SAM concentrations produced a concentration-dependent inhibition. The short-term stimulatory effects of SAM were attenuated by the CBS inhibitor aminooxyacetic acid (AOAA) or by stable silencing of CBS. In contrast, the inhibitory effects of SAM on cell proliferation was unaffected by CBS inhibition or CBS silencing. In contrast to HCT116 cells, the lower rate of proliferation of the low-CBS expressor NCM356 cells was unaffected by SAM. Short-term (1 h) exposure of HCT116 cells to SAM induced a concentration-dependent increase in oxygen consumption and bioenergetic function at 0.1-1 mM, while 3 mM was inhibitory. Longer-term (72 h) exposure of HCT116 cells to all concentrations of SAM tested suppressed mitochondrial oxygen consumption rate, cellular ATP content and cell viability. The stimulatory effect of SAM on bioenergetics was attenuated in cells with stable CBS silencing, while the inhibitory effects were unaffected. In NCM356 cells SAM exerted smaller effects on cellular bioenergetics than in HCT116 cells. We have also observed a downregulation of CBS in response to prolonged exposure of SAM both in HCT116 and NCM356 cells. Taken together, the results demonstrate that H2S production in HCT116 cells is stimulated by the allosteric CBS activator, SAM. At low-to intermediate levels and early time periods the resulting H2S serves as an endogenous cancer cell growth and bioenergetic factor. In contrast, the inhibition of cell proliferation and bioenergetic function by SAM does not appear to relate to adverse autocrine effects of H2S resulting from CBS over-stimulation but, rather to CBS-independent pharmacological effects. Copyright © 2014 Elsevier Inc. All rights reserved.

Cognitive regulation of saccadic velocity by reward prospect.

PubMed

Chen, Lewis L; Hung, Leroy Y; Quinet, Julie; Kosek, Kevin

2013-08-01

It is known that expectation of reward speeds up saccades. Past studies have also shown the presence of a saccadic velocity bias in the orbit, resulting from a biomechanical regulation over varying eccentricities. Nevertheless, whether and how reward expectation interacts with the biomechanical regulation of saccadic velocities over varying eccentricities remains unknown. We addressed this question by conducting a visually guided double-step saccade task. The role of reward expectation was tested in monkeys performing two consecutive horizontal saccades, one associated with reward prospect and the other not. To adequately assess saccadic velocity and avoid adaptation, we systematically varied initial eye positions, saccadic directions and amplitudes. Our results confirmed the existence of a velocity bias in the orbit, i.e., saccadic peak velocity decreased linearly as the initial eye position deviated in the direction of the saccade. The slope of this bias increased as saccadic amplitudes increased. Nevertheless, reward prospect facilitated velocity to a greater extent for saccades away from than for saccades toward the orbital centre, rendering an overall reduction in the velocity bias. The rate (slope) and magnitude (intercept) of reward modulation over this velocity bias were linearly correlated with amplitudes, similar to the amplitude-modulated velocity bias without reward prospect, which presumably resulted from a biomechanical regulation. Small-amplitude (≤ 5°) saccades received little modulation. These findings together suggest that reward expectation modulated saccadic velocity not as an additive signal but as a facilitating mechanism that interacted with the biomechanical regulation. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

48 CFR 4.1102 - Policy.

Code of Federal Regulations, 2014 CFR

2014-10-01

... SAM database prior to award of a contract or agreement, except for— (1) Purchases under the micro... registration in the SAM database, or use of SAM data, could compromise the safeguarding of classified... (a)(3) of this section to require SAM registration. (c)(1)(i) If a contractor has legally changed its...

78 FR 62627 - Sam Rayburn Dam Rate

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-22

..., Wholesale Rates for Hydro Power and Energy Sold to Sam Rayburn Dam Electric Cooperative, Inc. (Contract No... Schedule SRD-08, Wholesale Rates for Hydro Power and Energy Sold to Sam Rayburn Dam Electric Cooperative... ADMINISTRATION RATE SCHEDULE SRD-13 \\1\\ WHOLESALE RATES FOR HYDRO POWER AND ENERGY SOLD TO SAM RAYBURN DAM...

Shifts in Gamma Phase–Amplitude Coupling Frequency from Theta to Alpha Over Posterior Cortex During Visual Tasks

PubMed Central

Voytek, Bradley; Canolty, Ryan T.; Shestyuk, Avgusta; Crone, Nathan E.; Parvizi, Josef; Knight, Robert T.

2010-01-01

The phase of ongoing theta (4–8 Hz) and alpha (8–12 Hz) electrophysiological oscillations is coupled to high gamma (80–150 Hz) amplitude, which suggests that low-frequency oscillations modulate local cortical activity. While this phase–amplitude coupling (PAC) has been demonstrated in a variety of tasks and cortical regions, it has not been shown whether task demands differentially affect the regional distribution of the preferred low-frequency coupling to high gamma. To address this issue we investigated multiple-rhythm theta/alpha to high gamma PAC in two subjects with implanted subdural electrocorticographic grids. We show that high gamma amplitude couples to the theta and alpha troughs and demonstrate that, during visual tasks, alpha/high gamma coupling preferentially increases in visual cortical regions. These results suggest that low-frequency phase to high-frequency amplitude coupling is modulated by behavioral task and may reflect a mechanism for selection between communicating neuronal networks. PMID:21060716

The physical basis for absorption of light. [effects on wave functions of gas molecules and atoms

NASA Technical Reports Server (NTRS)

Pickett, H. M.

1979-01-01

The effects of light absorption on the wave functions of gas-phase molecules and atoms are investigated by high resolution spectral measurements of radiation emerging from a sample. A Stark-modulated sample of methyl fluoride was irradiated at the 102 GHz rotational transition and the emergent radiation was resolved by means of a spectrum analyzer. For signal oscillator frequencies below or above the molecular resonance by one modulation frequency, the amplitudes of the upper and lower modulation sidebands are found to be of nonuniform intensity, which is inconsistent with amplitude modulation. Emission due to polarization is, however, calculated to be consistent with the results observed, indicating that light absorption should be considered as a subtractive stimulated emission.

Dynamic optical arbitrary waveform shaping based on cascaded optical modulators of single FBG.

PubMed

Chen, Jingyuan; Li, Peili

2015-08-10

A dynamic optical arbitrary waveform generation (O-AWG) with amplitude and phase independently controlled in optical modulators of single fiber Bragg Grating (FBG) has been proposed. This novel scheme consists of several optical modulators. In the optical modulator (O-MOD), a uniform FBG is used to filter spectral component of the input signal. The amplitude is controlled by fiber stretcher (FS) in Mach-Zehnder interference (MZI) structure through interference of two MZI arms. The phase is manipulated via the second FS in the optical modulator. This scheme is investigated by simulation. Consequently, optical pulse trains with different waveforms as well as pulse trains with nonuniform pulse intensity, pulse spacing and pulse width within each period are obtained through FSs adjustment to alter the phase shifts of signal in each O-MOD.

Interaural time sensitivity of high-frequency neurons in the inferior colliculus.

PubMed

Yin, T C; Kuwada, S; Sujaku, Y

1984-11-01

Recent psychoacoustic experiments have shown that interaural time differences provide adequate cues for lateralizing high-frequency sounds, provided the stimuli are complex and not pure tones. We present here physiological evidence in support of these findings. Neurons of high best frequency in the cat inferior colliculus respond to interaural phase differences of amplitude modulated waveforms, and this response depends upon preservation of phase information of the modulating signal. Interaural phase differences were introduced in two ways: by interaural delays of the entire waveform and by binaural beats in which there was an interaural frequency difference in the modulating waveform. Results obtained with these two methods are similar. Our results show that high-frequency cells can respond to interaural time differences of amplitude modulated signals and that they do so by a sensitivity to interaural phase differences of the modulating waveform.

EEG Oscillations Are Modulated in Different Behavior-Related Networks during Rhythmic Finger Movements.

PubMed

Seeber, Martin; Scherer, Reinhold; Müller-Putz, Gernot R

2016-11-16

Sequencing and timing of body movements are essential to perform motoric tasks. In this study, we investigate the temporal relation between cortical oscillations and human motor behavior (i.e., rhythmic finger movements). High-density EEG recordings were used for source imaging based on individual anatomy. We separated sustained and movement phase-related EEG source amplitudes based on the actual finger movements recorded by a data glove. Sustained amplitude modulations in the contralateral hand area show decrease for α (10-12 Hz) and β (18-24 Hz), but increase for high γ (60-80 Hz) frequencies during the entire movement period. Additionally, we found movement phase-related amplitudes, which resembled the flexion and extension sequence of the fingers. Especially for faster movement cadences, movement phase-related amplitudes included high β (24-30 Hz) frequencies in prefrontal areas. Interestingly, the spectral profiles and source patterns of movement phase-related amplitudes differed from sustained activities, suggesting that they represent different frequency-specific large-scale networks. First, networks were signified by the sustained element, which statically modulate their synchrony levels during continuous movements. These networks may upregulate neuronal excitability in brain regions specific to the limb, in this study the right hand area. Second, movement phase-related networks, which modulate their synchrony in relation to the movement sequence. We suggest that these frequency-specific networks are associated with distinct functions, including top-down control, sensorimotor prediction, and integration. The separation of different large-scale networks, we applied in this work, improves the interpretation of EEG sources in relation to human motor behavior. EEG recordings provide high temporal resolution suitable to relate cortical oscillations to actual movements. Investigating EEG sources during rhythmic finger movements, we distinguish sustained from movement phase-related amplitude modulations. We separate these two EEG source elements motivated by our previous findings in gait. Here, we found two types of large-scale networks, representing the right fingers in distinction from the time sequence of the movements. These findings suggest that EEG source amplitudes reconstructed in a cortical patch are the superposition of these simultaneously present network activities. Separating these frequency-specific networks is relevant for studying function and possible dysfunction of the cortical sensorimotor system in humans as well as to provide more advanced features for brain-computer interfaces. Copyright © 2016 the authors 0270-6474/16/3611671-11$15.00/0.

Crystal structure of SAM-dependent methyltransferase from Pyrococcus horikoshii.

PubMed

Pampa, K J; Madan Kumar, S; Hema, M K; Kumara, Karthik; Naveen, S; Kunishima, Naoki; Lokanath, N K

2017-12-01

Methyltransferases (MTs) are enzymes involved in methylation that are needed to perform cellular processes such as biosynthesis, metabolism, gene expression, protein trafficking and signal transduction. The cofactor S-adenosyl-L-methionine (SAM) is used for catalysis by SAM-dependent methyltransferases (SAM-MTs). The crystal structure of Pyrococcus horikoshii SAM-MT was determined to a resolution of 2.1 Å using X-ray diffraction. The monomeric structure consists of a Rossmann-like fold (domain I) and a substrate-binding domain (domain II). The cofactor (SAM) molecule binds at the interface between adjacent subunits, presumably near to the active site(s) of the enzyme. The observed dimeric state might be important for the catalytic function of the enzyme.

SAMS-II Requirements and Operations

NASA Technical Reports Server (NTRS)

Wald, Lawrence W.

1998-01-01

The Space Acceleration Measurements System (SAMS) II is the primary instrument for the measurement, storage, and communication of the microgravity environment aboard the International Space Station (ISS). SAMS-II is being developed by the NASA Lewis Research Center Microgravity Science Division to primarily support the Office of Life and Microgravity Science and Applications (OLMSA) Microgravity Science and Applications Division (MSAD) payloads aboard the ISS. The SAMS-II is currently in the test and verification phase at NASA LeRC, prior to its first hardware delivery scheduled for July 1998. This paper will provide an overview of the SAMS-II instrument, including the system requirements and topology, physical and electrical characteristics, and the Concept of Operations for SAMS-II aboard the ISS.

Non-canonical active site architecture of the radical SAM thiamin pyrimidine synthase.

PubMed

Fenwick, Michael K; Mehta, Angad P; Zhang, Yang; Abdelwahed, Sameh H; Begley, Tadhg P; Ealick, Steven E

2015-03-27

Radical S-adenosylmethionine (SAM) enzymes use a [4Fe-4S] cluster to generate a 5'-deoxyadenosyl radical. Canonical radical SAM enzymes are characterized by a β-barrel-like fold and SAM anchors to the differentiated iron of the cluster, which is located near the amino terminus and within the β-barrel, through its amino and carboxylate groups. Here we show that ThiC, the thiamin pyrimidine synthase in plants and bacteria, contains a tethered cluster-binding domain at its carboxy terminus that moves in and out of the active site during catalysis. In contrast to canonical radical SAM enzymes, we predict that SAM anchors to an additional active site metal through its amino and carboxylate groups. Superimposition of the catalytic domains of ThiC and glutamate mutase shows that these two enzymes share similar active site architectures, thus providing strong evidence for an evolutionary link between the radical SAM and adenosylcobalamin-dependent enzyme superfamilies.

Selective spatial attention modulates bottom-up informational masking of speech

PubMed Central

Carlile, Simon; Corkhill, Caitlin

2015-01-01

To hear out a conversation against other talkers listeners overcome energetic and informational masking. Largely attributed to top-down processes, information masking has also been demonstrated using unintelligible speech and amplitude-modulated maskers suggesting bottom-up processes. We examined the role of speech-like amplitude modulations in information masking using a spatial masking release paradigm. Separating a target talker from two masker talkers produced a 20 dB improvement in speech reception threshold; 40% of which was attributed to a release from informational masking. When across frequency temporal modulations in the masker talkers are decorrelated the speech is unintelligible, although the within frequency modulation characteristics remains identical. Used as a masker as above, the information masking accounted for 37% of the spatial unmasking seen with this masker. This unintelligible and highly differentiable masker is unlikely to involve top-down processes. These data provides strong evidence of bottom-up masking involving speech-like, within-frequency modulations and that this, presumably low level process, can be modulated by selective spatial attention. PMID:25727100

Selective spatial attention modulates bottom-up informational masking of speech.

PubMed

Carlile, Simon; Corkhill, Caitlin

2015-03-02

To hear out a conversation against other talkers listeners overcome energetic and informational masking. Largely attributed to top-down processes, information masking has also been demonstrated using unintelligible speech and amplitude-modulated maskers suggesting bottom-up processes. We examined the role of speech-like amplitude modulations in information masking using a spatial masking release paradigm. Separating a target talker from two masker talkers produced a 20 dB improvement in speech reception threshold; 40% of which was attributed to a release from informational masking. When across frequency temporal modulations in the masker talkers are decorrelated the speech is unintelligible, although the within frequency modulation characteristics remains identical. Used as a masker as above, the information masking accounted for 37% of the spatial unmasking seen with this masker. This unintelligible and highly differentiable masker is unlikely to involve top-down processes. These data provides strong evidence of bottom-up masking involving speech-like, within-frequency modulations and that this, presumably low level process, can be modulated by selective spatial attention.

SAM Companion Documents

EPA Pesticide Factsheets

SAM Companion Documents and Sample Collection Procedures provide information intended to complement the analytical methods listed in Selected Analytical Methods for Environmental Remediation and Recovery (SAM).

S-adenosyl methionine (SAM) attenuates the development of tolerance to analgesic activity of morphine in rats.

PubMed

Katyal, Jatinder; Kumar, Hemant; Joshi, Dinesh; Gupta, Yogendra Kumar

2017-04-03

Development of tolerance to analgesic effect, on chronic administration of morphine, limits its clinical usefulness in pain management. S-adenosyl methionine (SAM) used for arthritis and approved as a supplement in many countries including United States was evaluated for reducing morphine tolerance. Male 'Wistar' rats were used. The analgesic activity was determined using tail flick analgesiometer (Columbus Instruments, USA). Rats given morphine (7mg/kg), intraperitoneally (i.p.), once daily for 5days developed tolerance to analgesic effect. To evaluate the effect of SAM on morphine tolerance, SAM 800mg/kg was administered orally (p.o.), 45min prior to each dose of morphine. The analgesic activity of SAM and opioidergic component in its activity was also evaluated. Co-administration of morphine and SAM reversed morphine tolerance. SAM exhibited analgesic effect after repeated administration which was reversed by naloxone administration. Since safety of SAM on chronic use is documented it can be a good option in morphine tolerance. Role in drug addiction and withdrawal should also be evaluated. Copyright © 2017 Elsevier B.V. All rights reserved.

Expanding Radical SAM Chemistry by Using Radical Addition Reactions and SAM Analogues.

PubMed

Ji, Xinjian; Li, Yongzhen; Xie, Liqi; Lu, Haojie; Ding, Wei; Zhang, Qi

2016-09-19

Radical S-adenosyl-l-methionine (SAM) enzymes utilize a [4Fe-4S] cluster to bind SAM and reductively cleave its carbon-sulfur bond to produce a highly reactive 5'-deoxyadenosyl (dAdo) radical. In almost all cases, the dAdo radical abstracts a hydrogen atom from the substrates or from enzymes, thereby initiating a highly diverse array of reactions. Herein, we report a change of the dAdo radical-based chemistry from hydrogen abstraction to radical addition in the reaction of the radical SAM enzyme NosL. This change was achieved by using a substrate analogue containing an olefin moiety. We also showed that two SAM analogues containing different nucleoside functionalities initiate the radical-based reactions with high efficiencies. The radical adduct with the olefin produced in the reaction was found to undergo two divergent reactions, and the mechanistic insights into this process were investigated in detail. Our study demonstrates a promising strategy in expanding radical SAM chemistry, providing an effective way to access nucleoside-containing compounds by using radical SAM-dependent reactions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal Structure of Bicc1 SAM Polymer and Mapping of Interactions between the Ciliopathy-Associated Proteins Bicc1, ANKS3, and ANKS6.

PubMed

Rothé, Benjamin; Leettola, Catherine N; Leal-Esteban, Lucia; Cascio, Duilio; Fortier, Simon; Isenschmid, Manuela; Bowie, James U; Constam, Daniel B

2018-02-06

Head-to-tail polymers of sterile alpha motifs (SAM) can scaffold large macromolecular complexes. Several SAM-domain proteins that bind each other are mutated in patients with cystic kidneys or laterality defects, including the Ankyrin (ANK) and SAM domain-containing proteins ANKS6 and ANKS3, and the RNA-binding protein Bicc1. To address how their interactions are regulated, we first determined a high-resolution crystal structure of a Bicc1-SAM polymer, revealing a canonical SAM polymer with a high degree of flexibility in the subunit interface orientations. We further mapped interactions between full-length and distinct domains of Bicc1, ANKS3, and ANKS6. Neither ANKS3 nor ANKS6 alone formed macroscopic homopolymers in vivo. However, ANKS3 recruited ANKS6 to Bicc1, and the three proteins together cooperatively generated giant macromolecular complexes. Thus, the giant assemblies are shaped by SAM domains, their flanking sequences, and SAM-independent protein-protein and protein-mRNA interactions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Square Wave Voltammetry of TNT at Gold Electrodes Modified with Self-Assembled Monolayers Containing Aromatic Structures

PubMed Central

Trammell, Scott A.; Zabetakis, Dan; Moore, Martin; Verbarg, Jasenka; Stenger, David A.

2014-01-01

Square wave voltammetry for the reduction of 2,4,6-trinitrotoluene (TNT) was measured in 100 mM potassium phosphate buffer (pH 8) at gold electrodes modified with self-assembled monolayers (SAMs) containing either an alkane thiol or aromatic ring thiol structures. At 15 Hz, the electrochemical sensitivity (µA/ppm) was similar for all SAMs tested. However, at 60 Hz, the SAMs containing aromatic structures had a greater sensitivity than the alkane thiol SAM. In fact, the alkane thiol SAM had a decrease in sensitivity at the higher frequency. When comparing the electrochemical response between simulations and experimental data, a general trend was observed in which most of the SAMs had similar heterogeneous rate constants within experimental error for the reduction of TNT. This most likely describes a rate limiting step for the reduction of TNT. However, in the case of the alkane SAM at higher frequency, the decrease in sensitivity suggests that the rate limiting step in this case may be electron tunneling through the SAM. Our results show that SAMs containing aromatic rings increased the sensitivity for the reduction of TNT when higher frequencies were employed and at the same time suppressed the electrochemical reduction of dissolved oxygen. PMID:25549081

Motor coordination defects in mice deficient for the Sam68 RNA-binding protein.

PubMed

Lukong, Kiven E; Richard, Stéphane

2008-06-03

The role of RNA-binding proteins in the central nervous system and more specifically their role in motor coordination and learning are poorly understood. We previously reported that ablation of RNA-binding protein Sam68 in mice results in male sterility and delayed mammary gland development and protection against osteoporosis in females. Sam68 however is highly expressed in most regions of the brain especially the cerebellum and thus we investigated the cerebellar-related manifestations in Sam68-null mice. We analyzed the mice for motor function, sensory function, and learning and memory abilities. Herein, we report that Sam68-null mice have motor coordination defects as assessed by beam walking and rotorod performance. Forty-week-old Sam68-null mice (n=12) were compared to their wild-type littermates (n=12). The Sam68-null mice exhibited more hindpaw faults in beam walking tests and fell from the rotating drum at lower speeds and prematurely compared to the wild-type controls. The Sam68-null mice were, however, normal for forelimb strength, tail-hang reflex, balance test, grid walking, the Morris water task, recognition memory, visual discrimination, auditory stimulation and conditional taste aversion. Our findings support a role for Sam68 in the central nervous system in the regulation of motor coordination.

Assessment of frequency specific auditory steady-state response using amplitude modulation with 2-order exponential envelope.

PubMed

Cevallos-Larrea, Pablo; Pereira, Thobias; Santos, Wagner; Frota, Silvana M; Infantosi, Antonio F; Ichinose, Roberto M; Tierra-Criollo, Carlos

2016-08-01

This study investigated the performance of Frequency Specific Auditory Steady-State Response (FS-ASSR) detection elicited by the amplitude modulated tone with 2-order exponential envelope (AM2), using objective response detection (ORD) techniques of Spectral F-Test (SFT) and Magnitude Squared Coherence (MSC). ASSRs from 24 normal hearing adults were obtained during binaural multi-tone stimulation of amplitude-modulation (AM) and AM2 at intensities of 60, 45 and 30 dBSPL. The carrier frequencies were 500, 1000, 2000, and 4000 Hz, modulated between 77 and 105 Hz. AM2 achieve FS-ASSR amplitudes higher than AM by 16%, 18% and 12% at 60, 45 and 30 dBSPL, respectively, with a major increase at 500 Hz (22.5%). AMS2PL increased the Detection Rate (DR) up to 8.3% at 500 Hz for 30 dBSPL, which is particularly beneficial for FS-ASSR detection near the hearing threshold. In addition, responses in 1000 and 4000 Hz were consistently increased. The MSC and SFT presented no differences in Detection Rate (DR). False Detection Rate (FDR) was close to 5% for both techniques and tones. Detection times to reach DR over 90% were 3.5 and 4.9 min at 60 and 45 dBSPL, respectively. Further investigation concerning efficient multiple FS-ASSR is still necessary, such as testing subjects with hearing loss.

Cooperation between Magnesium and Metabolite Controls Collapse of the SAM-I Riboswitch.

PubMed

Roy, Susmita; Onuchic, José N; Sanbonmatsu, Karissa Y

2017-07-25

The S-adenosylmethionine (SAM)-I riboswitch is a noncoding RNA that regulates the transcription termination process in response to metabolite (SAM) binding. The aptamer portion of the riboswitch may adopt an open or closed state depending on the presence of metabolite. Although the transition between the open and closed states is critical for the switching process, its atomistic details are not well understood. Using atomistic simulations, we calculate the effect of SAM and magnesium ions on the folding free energy landscape of the SAM-I riboswitch. These molecular simulation results are consistent with our previous wetlab experiments and aid in interpreting the SHAPE probing measurements. Here, molecular dynamics simulations explicitly identify target RNA motifs sensitive to magnesium ions and SAM. In the simulations, we observe that, whereas the metabolite mostly stabilizes the P1 and P3 helices, magnesium serves an important role in stabilizing a pseudoknot interaction between the P2 and P4 helices, even at high metabolite concentrations. The pseudoknot stabilization by magnesium, in combination with P1 stabilization by SAM, explains the requirement of both SAM and magnesium to form the fully collapsed metabolite-bound closed state of the SAM-I riboswitch. In the absence of SAM, frequent open-to-closed conformational transitions of the pseudoknot occur, akin to breathing. These pseudoknot fluctuations disrupt the binding site by facilitating fluctuations in the 5'-end of helix P1. Magnesium biases the landscape toward a collapsed state (preorganization) by coordinating pseudoknot and 5'-P1 fluctuations. The cooperation between SAM and magnesium in stabilizing important tertiary interactions elucidates their functional significance in transcription regulation. Published by Elsevier Inc.

Allosteric monofunctional aspartate kinases from Arabidopsis.

PubMed

Curien, Gilles; Laurencin, Mathieu; Robert-Genthon, Mylène; Dumas, Renaud

2007-01-01

Plant monofunctional aspartate kinase is unique among all aspartate kinases, showing synergistic inhibition by lysine and S-adenosyl-l-methionine (SAM). The Arabidopsis genome contains three genes for monofunctional aspartate kinases. We show that aspartate kinase 2 and aspartate kinase 3 are inhibited only by lysine, and that aspartate kinase 1 is inhibited in a synergistic manner by lysine and SAM. In the absence of SAM, aspartate kinase 1 displayed low apparent affinity for lysine compared to aspartate kinase 2 and aspartate kinase 3. In the presence of SAM, the apparent affinity of aspartate kinase 1 for lysine increased considerably, with K(0.5) values for lysine inhibition similar to those of aspartate kinase 2 and aspartate kinase 3. For all three enzymes, the inhibition resulted from an increase in the apparent K(m) values for the substrates ATP and aspartate. The mechanism of aspartate kinase 1 synergistic inhibition was characterized. Inhibition by lysine alone was fast, whereas synergistic inhibition by lysine plus SAM was very slow. SAM by itself had no effect on the enzyme activity, in accordance with equilibrium binding analyses indicating that SAM binding to aspartate kinase 1 requires prior binding of lysine. The three-dimensional structure of the aspartate kinase 1-Lys-SAM complex has been solved [Mas-Droux C, Curien G, Robert-Genthon M, Laurencin M, Ferrer JL & Dumas R (2006) Plant Cell18, 1681-1692]. Taken together, the data suggest that, upon binding to the inactive aspartate kinase 1-Lys complex, SAM promotes a slow conformational transition leading to formation of a stable aspartate kinase 1-Lys-SAM complex. The increase in aspartate kinase 1 apparent affinity for lysine in the presence of SAM thus results from the displacement of the unfavorable equilibrium between aspartate kinase 1 and aspartate kinase 1-Lys towards the inactive form.

Electroactive Self-Assembled Monolayers Detect Micelle Formation.

PubMed

Dionne, Eric R; Badia, Antonella

2017-02-15

The interfacial electrochemistry of self-assembled monolayers (SAMs) of ferrocenyldodecanethiolate on gold (FcC 12 SAu) electrodes is applied to detect the micellization of some common anionic surfactants, sodium n-alkyl sulfates, sodium n-alkyl sulfonates, sodium diamyl sulfosuccinate, and sodium dodecanoate, in aqueous solution by cyclic voltammetry. The apparent formal redox potential (E°' SAM ) of the FcC 12 SAu SAM is used to track changes in the concentration of the unaggregated surfactant anions and determine the critical micelle concentration (cmc). The effect of added salt (NaF) on the sodium alkyl sulfate concentration dependence of E°' SAM is also investigated. Weakly hydrated anions, such as ClO 4 - , pair with the electrogenerated SAM-bound ferroceniums to neutralize the excess positive charge created at the SAM/electrolyte solution interface and stabilize the oxidized cations. E°' SAM exhibits a Nernstian-type dependence on the anion activity in solution. Aggregation of the surfactant anions into micelles above the cmc causes the free surfactant anion activity to deviate from the molar concentration of added surfactant, resulting in a break in the plot of E°' SAM versus the logarithm of the concentration of anionic surfactant. The concentration at which this deviation occurs is in good agreement with literature or experimentally determined values of the cmc. The effects of Ohmic potential drop, liquid junction potential, and surfactant adsorption behavior on E°' SAM are addressed. Ultimately, the E°' SAM response as a function of the anionic surfactant concentration exhibits the same features reported using potentiometry and surfactant ion-selective electrodes, which provide a direct measure of the free surfactant anion activity, thus making FcC 12 SAu SAM electrodes useful for the detection of surfactant aggregation and micelle formation.

Fragmentation and reactivity in collisions of protonated diglycine with chemically modified perfluorinated alkylthiolate-self-assembled monolayer surfaces

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

Barnes, George L.; Yang Li; Hase, William L.

2011-03-07

Direct dynamics simulations are reported for quantum mechanical (QM)/molecular mechanical (MM) trajectories of N-protonated diglycine (gly{sub 2}-H{sup +}) colliding with chemically modified perfluorinated octanethiolate self-assembled monolayer (SAM) surfaces. The RM1 semiempirical theory is used for the QM component of the trajectories. RM1 activation and reaction energies were compared with those determined from higher-level ab initio theories. Two chemical modifications are considered in which a head group (-COCl or -CHO) is substituted on the terminal carbon of a single chain of the SAM. These surfaces are designated as the COCl-SAM and CHO-SAM, respectively. Fragmentation, peptide reaction with the SAM, and covalentmore » linkage of the peptide or its fragments with the SAM surface are observed. Peptide fragmentation via concerted CH{sub 2}-CO bond breakage is the dominant pathway for both surfaces. HCl formation is the dominant species produced by reaction with the COCl-SAM, while for the CHO-SAM a concerted H-atom transfer from the CHO-SAM to the peptide combined with either a H-atom or radical transfer from the peptide to the surface to form singlet reaction products is the dominant pathway. A strong collision energy dependence is found for the probability of peptide fragmentation, its reactivity, and linkage with the SAM. Surface deposition, i.e., covalent linkage between the surface and the peptide, is compared to recent experimental observations of such bonding by Laskin and co-workers [Phys. Chem. Chem. Phys. 10, 1512 (2008)]. Qualitative differences in reactivity are seen between the COCl-SAM and CHO-SAM showing that chemical identity is important for surface reactivity. The probability of reactive surface deposition, which is most closely analogous to experimental observables, peaks at a value of around 20% for a collision energy of 50 eV.« less

Testing the validity, reliability and utility of the Self-Administration of Medication (SAM) tool in patients undergoing rehabilitation.

PubMed

Anderson, Jessica; Manias, Elizabeth; Kusljic, Snezana; Finch, Sue

2014-01-01

Determination of patients' ability to self-administer medications in the hospital has largely been determined using the subjective judgment of health professionals. To examine the validity, reliability and utility of the Self-Administration of Medication (SAM) tool as an objective means to determine patients' ability to self-administer in a rehabilitation unit of a public teaching hospital in Melbourne, Australia. To assess validity of the SAM tool, associations were examined between the total SAM tool score and of the patients' competence to self-administer from the perceptions of the tool administrator, patients and nurses. Validity also was determined from a principal component analysis. Pearson correlations were calculated for how SAM scores related to scores obtained from the Functional Independence Measure (FIM) and Barthel Score Index (BSI). To assess the SAM tool's reliability, a Cronbach's alpha coefficient was calculated. Utility of the SAM tool was evidenced by documenting its administration time. One hundred patients participated in this study. The SAM tool had a Cronbach's alpha coefficient of 0.75 and took a mean time of 5.36 min to complete. The capability to self-medicate section of the SAM tool had strong correlations with the FIM (r = 0.485) and BSI (r = 0.472) data, respectively, and the total SAM tool had moderate and strong correlations with the nurses' (r = 0.315) and tool administrator's (r = 0.632) perceptions of patients' ability to self-administer, respectively. Bland-Altman and ROC curve analyses showed poor agreement between the total SAM tool score and the nurses' perceptions. The SAM tool demonstrated acceptable overall internal consistency. It only requires a short time to be completed and is more objective than seeking out health professionals' perceptions. Additional research is needed to further validate this approach to determining patients' ability to self-medicate. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

Efficacy of artemether-lumefantrine in relation to drug exposure in children with and without severe acute malnutrition: an open comparative intervention study in Mali and Niger.

PubMed

Denoeud-Ndam, Lise; Dicko, Alassane; Baudin, Elisabeth; Guindo, Ousmane; Grandesso, Francesco; Diawara, Halimatou; Sissoko, Sibiri; Sanogo, Koualy; Traoré, Seydou; Keita, Sekouba; Barry, Amadou; de Smet, Martin; Lasry, Estrella; Smit, Michiel; Wiesner, Lubbe; Barnes, Karen I; Djimde, Abdoulaye A; Guerin, Philippe J; Grais, Rebecca F; Doumbo, Ogobara K; Etard, Jean-François

2016-10-24

Severe acute malnutrition (SAM) affects almost all organs and has been associated with reduced intestinal absorption of medicines. However, very limited information is available on the pharmacokinetic properties of antimalarial drugs in this vulnerable population. We assessed artemether-lumefantrine (AL) clinical efficacy in children with SAM compared to those without. Children under 5 years of age with uncomplicated P. falciparum malaria were enrolled between November 2013 and January 2015 in Mali and Niger, one third with uncomplicated SAM and two thirds without. AL was administered under direct observation with a fat intake consisting of ready-to-use therapeutic food (RUTF - Plumpy'Nut®) in SAM children, twice daily during 3 days. Children were followed for 42 days, with PCR-corrected adequate clinical and parasitological response (ACPR) at day 28 as the primary outcome. Lumefantrine concentrations were assessed in a subset of participants at different time points, including systematic measurements on day 7. A total of 399 children (360 in Mali and 39 in Niger) were enrolled. Children with SAM were younger than their non-SAM counterparts (mean 17 vs. 28 months, P < 0.0001). PCR-corrected ACPR was 100 % (95 % CI, 96.8-100 %) in SAM at both day 28 and 42, versus 98.8 % (96.4-99.7 %) at day 28 and 98.3 % (95.6-99.4 %) at day 42 in non-SAM (P = 0.236 and 0.168, respectively). Compared to younger children, children older than 21 months experienced more reinfections and SAM was associated with a greater risk of reinfection until day 28 (adjusted hazard ratio = 2.10 (1.04-4.22), P = 0.038). Day 7 lumefantrine concentrations were significantly lower in SAM than non-SAM (median 251 vs. 365 ng/mL, P = 0.049). This study shows comparable therapeutic efficacy of AL in children without SAM and in those with SAM when given in combination with RUTF, but a higher risk of reinfection in older children suffering from SAM. This could be associated with poorer exposure to the antimalarials as documented by a lower lumefantrine concentration on day 7. ClinicalTrials.gov: NCT01958905 , registration date: October 7, 2013.

Calibration and Sequence Development Status for the Sample Analysis at Mars Investigation on the Mars Science Laboratory

NASA Technical Reports Server (NTRS)

Mahaffy, Paul R.

2012-01-01

The measurement goals of the Sample Analysis at Mars (SAM) instrument suite on the "Curiosity" Rover of the Mars Science Laboratory (MSL) include chemical and isotopic analysis of organic and inorganic volatiles for both atmospheric and solid samples [1,2]. SAM directly supports the ambitious goals of the MSL mission to provide a quantitative assessment of habitability and preservation in Gale crater by means of a range of chemical and geological measurements [3]. The SAM FM combined calibration and environmental testing took place primarily in 2010 with a limited set of tests implemented after integration into the rover in January 2011. The scope of SAM FM testing was limited both to preserve SAM consumables such as life time of its electromechanical elements and to minimize the level of terrestrial contamination in the SAM instrument. A more comprehensive calibration of a SAM-like suite of instruments will be implemented in 2012 with calibration runs planned for the SAM testbed. The SAM Testbed is nearly identical to the SAM FM and operates in a ambient pressure chamber. The SAM Instrument Suite: SAM's instruments are a Quadrupole Mass Spectrometer (QMS), a 6-column Gas Chromatograph (GC), and a 2-channel Tunable Laser Spectrometer (TLS). Gas Chromatography Mass Spectrometry is designed for identification of even trace organic compounds. The TLS [5] secures the C, H, and O isotopic composition in carbon dioxide, water, and methane. Sieved materials are delivered from the MSL sample acquisition and processing system to one of68 cups of the Sample Manipulation System (SMS). 59 of these cups are fabricated from inert quartz. After sample delivery, a cup is inserted into one of 2 ovens for evolved gas analysis (EGA ambient to >9500C) by the QMS and TLS. A portion of the gas released can be trapped and subsequently analyzed by GCMS. Nine sealed cups contain liquid solvents and chemical derivatization or thermochemolysis agents to extract and transform polar molecules such as amino acids, nucleobases, and carboxylic acids into compounds that are sufficiently volatile to transmit through the GC columns. The remaining 6 cups contain calibrants. SAM FM Calibration Overview: The SAM FM calibration in the Mars chamber employed a variety of pure gases, gas mixtures, and solid materials. Isotope calibration runs for the TLS utilized 13C enriched C02 standards and 0 enriched CH4. A variety of fluorocarbon compounds that spanned the entire mass range of the QMS as well as C3-C6 hydrocarbons were utilized for calibration of the GCMS. Solid samples consisting of a mixture of calcite, melanterite, and inert silica glass either doped or not with fluorocarbons were introduced into the SAM FM cups through the SAM inlet funnel/tube system.

Identification of new ligands for the methionine biosynthesis transcriptional regulator (MetJ) by FAC-MS.

PubMed

Martí-Arbona, Ricardo; Teshima, Munehiro; Anderson, Penelope S; Nowak-Lovato, Kristy L; Hong-Geller, Elizabeth; Unkefer, Clifford J; Unkefer, Pat J

2012-01-01

We have developed a high-throughput approach using frontal affinity chromatography coupled to mass spectrometry (FAC-MS) for the identification and characterization of the small molecules that modulate transcriptional regulator (TR) binding to TR targets. We tested this approach using the methionine biosynthesis regulator (MetJ). We used effector mixtures containing S-adenosyl-L-methionine (SAM) and S-adenosyl derivatives as potential ligands for MetJ binding. The differences in the elution time of different compounds allowed us to rank the binding affinity of each compound. Consistent with previous results, FAC-MS showed that SAM binds to MetJ with the highest affinity. In addition, adenine and 5'-deoxy-5'-(methylthio)adenosine bind to the effector binding site on MetJ. Our experiments with MetJ demonstrate that FAC-MS is capable of screening complex mixtures of molecules and identifying high-affinity binders to TRs. In addition, FAC-MS experiments can be used to discriminate between specific and nonspecific binding of the effectors as well as to estimate the dissociation constant (K(d)) for effector-TR binding. Copyright © 2012 S. Karger AG, Basel.

75 FR 4579 - Certificate of Alternative Compliance for the Tugboat MR SAM

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-28

... Compliance for the Tugboat MR SAM AGENCY: Coast Guard, DHS. ACTION: Notice. SUMMARY: The Coast Guard announces that a Certificate of Alternative Compliance was issued for the tugboat MR SAM as required by 33 U... Title 33, Code of Federal Regulations, Parts 81 and 89, has been issued for the tugboat MR SAM, O.N...

Serotonergic and peptidergic modulation of the buccal mass protractor muscle (I2) in aplysia.

PubMed

Hurwitz, I; Cropper, E C; Vilim, F S; Alexeeva, V; Susswein, A J; Kupfermann, I; Weiss, K R

2000-12-01

Plasticity of Aplysia feeding has largely been measured by noting changes in radula protraction. On the basis of previous work, it has been suggested that peripheral modulation may contribute to behavioral plasticity. However, peripheral plasticity has not been demonstrated in the neuromuscular systems that participate in radula protraction. Therefore in this study we investigated whether contractions of a major radula protraction muscle (I2) are subject to modulation. We demonstrate, first, that an increase in the firing frequency of the cholinergic I2 motoneurons will increase the amplitude of the resulting muscle contraction but will not modulate its relaxation rate. We show, second, that neuronal processes on the I2 muscle are immunoreactive to myomodulin (MM), RFamide, and serotonin (5-HT), but not to small cardioactive peptide (SCP) or buccalin. The I2 motoneurons B31, B32, B61, and B62 are not immunoreactive to RFamide, 5-HT, SCP, or buccalin. However, all four cells are MM immunoreactive and are capable of synthesizing MMa. Third, we show that the bioactivity of the different modulators is somewhat different; while the MMs (i.e., MMa and MMb) and 5-HT increase I2 muscle relaxation rate, and potentiate muscle contraction amplitude, MMa, at high concentrations, depresses muscle contractions. Fourth, our data suggest that cAMP at least partially mediates effects of modulators on contraction amplitude and relaxation rate.

Ultrafast two-photon absorption generated free-carrier modulation in a silicon nanoplasmonic resonator

NASA Astrophysics Data System (ADS)

Nielsen, M. P.; Elezzabi, A. Y.

2014-03-01

Ultrafast all-optical modulation in Ag/HfO2/Si/HfO2/Ag metal-insulator-semiconductor-insulator-metal (MISIM) nanoring resonators through two-photon absorption photogenerated free-carriers is studied using self-consistent 3-D finite difference time domain (FDTD) simulations. The self-consistent FDTD simulations incorporate the two-photon absorption, free carrier absorption, and plasma dispersion effects in silicon. The nanorings are aperture coupled to Ag/HfO2/Si(100nm)/HfO2/Ag MISIM waveguides by 300nm wide and 50nm deep apertures. The effects of pump pulse energy, HfO2 spacer thickness, and device footprint on the modulation characteristics are studied. Nanoring radius is varied between 540nm and 1μm, the HfO2 spacer thickness is varied between 10nm and 20nm, and the pump pulse energy is explored up to 60pJ. Modulation amplitude, switching time, average generated carrier density, and wavelength resonant shift is studied for each of the device configurations. In a compact device footprint of only 1.4μm2, a 13.1dB modulation amplitude was obtained with a switching time of only 2ps using a modest pump pulse energy of 16.0pJ. The larger bandwidth associated with more compact nanorings and thinner spacer layers is shown to result in increased modulation amplitude.

Preparation for Analytical Measurements on Mars

NASA Image and Video Library

2015-03-31

A Sample Analysis at Mars (SAM) team member at NASA's Goddard Space Flight Center, Greenbelt, Maryland, prepares the SAM testbed for an experiment. This test copy of the SAM suite of instruments is inside a chamber that, when closed, can model the pressure and temperature environment that SAM sees inside NASA's Curiosity rover on Mars. Many weeks of testing are often needed to develop and refine sequences of operations that SAM uses for making specific measurements on Mars. This was the case with preparation to pull a volume of gas from the atmosphere and extract the heavy noble gas xenon. SAM's measurements of different types of xenon in the Martian atmosphere provide clues about the planet's history. http://photojournal.jpl.nasa.gov/catalog/PIA19149

Modulation Index Adjustment for Recovery of Pure Wavelength Modulation Spectroscopy Second Harmonic Signal Waveforms.

PubMed

Wei, Wei; Chang, Jun; Wang, Qiang; Qin, Zengguang

2017-01-15

A new technique of modulation index adjustment for pure wavelength modulation spectroscopy second harmonic signal waveforms recovery is presented. As the modulation index is a key parameter in determining the exact form of the signals generated by the technique of wavelength modulation spectroscopy, the method of modulation index adjustment is applied to recover the second harmonic signal with wavelength modulation spectroscopy. By comparing the measured profile with the theoretical profile by calculation, the relationship between the modulation index and average quantities of the scanning wavelength can be obtained. Furthermore, when the relationship is applied in the experimental setup by point-by-point modulation index modification for gas detection, the results show good agreement with the theoretical profile and signal waveform distortion (such as the amplitude modulation effect caused by diode laser) can be suppressed. Besides, the method of modulation index adjustment can be used in many other aspects which involve profile improvement. In practical applications, when the amplitude modulation effect can be neglected and the stability of the detection system is limited by the sampling rate of analog-to-digital, modulation index adjustment can be used to improve detection into softer inflection points and solve the insufficient sampling problem. As a result, measurement stability is improved by 40%.

Modulation Index Adjustment for Recovery of Pure Wavelength Modulation Spectroscopy Second Harmonic Signal Waveforms

PubMed Central

Wei, Wei; Chang, Jun; Wang, Qiang; Qin, Zengguang

2017-01-01

A new technique of modulation index adjustment for pure wavelength modulation spectroscopy second harmonic signal waveforms recovery is presented. As the modulation index is a key parameter in determining the exact form of the signals generated by the technique of wavelength modulation spectroscopy, the method of modulation index adjustment is applied to recover the second harmonic signal with wavelength modulation spectroscopy. By comparing the measured profile with the theoretical profile by calculation, the relationship between the modulation index and average quantities of the scanning wavelength can be obtained. Furthermore, when the relationship is applied in the experimental setup by point-by-point modulation index modification for gas detection, the results show good agreement with the theoretical profile and signal waveform distortion (such as the amplitude modulation effect caused by diode laser) can be suppressed. Besides, the method of modulation index adjustment can be used in many other aspects which involve profile improvement. In practical applications, when the amplitude modulation effect can be neglected and the stability of the detection system is limited by the sampling rate of analog-to-digital, modulation index adjustment can be used to improve detection into softer inflection points and solve the insufficient sampling problem. As a result, measurement stability is improved by 40%. PMID:28098842

Temporal processing and adaptation in the songbird auditory forebrain.

PubMed

Nagel, Katherine I; Doupe, Allison J

2006-09-21

Songbird auditory neurons must encode the dynamics of natural sounds at many volumes. We investigated how neural coding depends on the distribution of stimulus intensities. Using reverse-correlation, we modeled responses to amplitude-modulated sounds as the output of a linear filter and a nonlinear gain function, then asked how filters and nonlinearities depend on the stimulus mean and variance. Filter shape depended strongly on mean amplitude (volume): at low mean, most neurons integrated sound over many milliseconds, while at high mean, neurons responded more to local changes in amplitude. Increasing the variance (contrast) of amplitude modulations had less effect on filter shape but decreased the gain of firing in most cells. Both filter and gain changes occurred rapidly after a change in statistics, suggesting that they represent nonlinearities in processing. These changes may permit neurons to signal effectively over a wider dynamic range and are reminiscent of findings in other sensory systems.

Single SOA based simultaneous amplitude regeneration for WDM-PDM RZ-PSK signals.

PubMed

Wu, Wenhan; Yu, Yu; Zou, Bingrong; Yang, Weili; Zhang, Xinliang

2013-03-25

We propose and demonstrate all-optical amplitude regeneration for the wavelength division multiplexing and polarization division multiplexing (WDM-PDM) return-to-zero phase shift keying (RZ-PSK) signals using a single semiconductor optical amplifier (SOA) and subsequent filtering. The regeneration is based on the cross phase modulation (XPM) effect in the saturated SOA and the subsequent narrow filtering. The spectrum of the distorted signal can be broadened due to the phase modulation induced by the synchronous optical clock signal. A narrow band pass filter is utilized to extract part of the broadened spectrum and remove the amplitude noise, while preserving the phase information. The working principle for multi-channel and polarization orthogonality preserving is analyzed. 4-channel dual polarization signals can be simultaneously amplitude regenerated without introducing wavelength and polarization demultiplexing. An average power penalty improvement of 1.75dB can be achieved for the WDM-PDM signals.

Digital chaos-masked optical encryption scheme enhanced by two-dimensional key space

NASA Astrophysics Data System (ADS)

Liu, Ling; Xiao, Shilin; Zhang, Lu; Bi, Meihua; Zhang, Yunhao; Fang, Jiafei; Hu, Weisheng

2017-09-01

A digital chaos-masked optical encryption scheme is proposed and demonstrated. The transmitted signal is completely masked by interference chaotic noise in both bandwidth and amplitude with analog method via dual-drive Mach-Zehnder modulator (DDMZM), making the encrypted signal analog, noise-like and unrecoverable by post-processing techniques. The decryption process requires precise matches of both the amplitude and phase between the cancellation and interference chaotic noises, which provide a large two-dimensional key space with the help of optical interference cancellation technology. For 10-Gb/s 16-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal over the maximum transmission distance of 80 km without dispersion compensation or inline amplifier, the tolerable mismatch ranges of amplitude and phase/delay at the forward error correction (FEC) threshold of 3.8×10-3 are 0.44 dB and 0.08 ns respectively.

Fluorescence-based classification of Caribbean coral reef organisms and substrates

USGS Publications Warehouse

Zawada, David G.; Mazel, Charles H.

2014-01-01

A diverse group of coral reef organisms, representing several phyla, possess fluorescent pigments. We investigated the potential of using the characteristic fluorescence emission spectra of these pigments to enable unsupervised, optical classification of coral reef habitats. We compiled a library of characteristic fluorescence spectra through in situ and laboratory measurements from a variety of specimens throughout the Caribbean. Because fluorescent pigments are not species-specific, the spectral library is organized in terms of 15 functional groups. We investigated the spectral separability of the functional groups in terms of the number of wavebands required to distinguish between them, using the similarity measures Spectral Angle Mapper (SAM), Spectral Information Divergence (SID), SID-SAM mixed measure, and Mahalanobis distance. This set of measures represents geometric, stochastic, joint geometric-stochastic, and statistical approaches to classifying spectra. Our hyperspectral fluorescence data were used to generate sets of 4-, 6-, and 8-waveband spectra, including random variations in relative signal amplitude, spectral peak shifts, and water-column attenuation. Each set consisted of 2 different band definitions: ‘optimally-picked’ and ‘evenly-spaced.’ The optimally-picked wavebands were chosen to coincide with as many peaks as possible in the functional group spectra. Reference libraries were formed from half of the spectra in each set and used for training purposes. Average classification accuracies ranged from 76.3% for SAM with 4 evenly-spaced wavebands to 93.8% for Mahalanobis distance with 8 evenly-spaced wavebands. The Mahalanobis distance consistently outperformed the other measures. In a second test, empirically-measured spectra were classified using the same reference libraries and the Mahalanobis distance for just the 8 evenly-spaced waveband case. Average classification accuracies were 84% and 87%, corresponding to the extremes in modeled water-column attenuation. The classification results from both tests indicate that a high degree of separability among the 15 fluorescent-spectra functional groups is possible using only a modest number of spectral bands.

Mars Methane at Gale Crater Shows Strong Seasonal Cycle: Updated Results from TLS-SAM on Curiosity

NASA Astrophysics Data System (ADS)

Webster, C. R.; Mahaffy, P. R.; Atreya, S. K.; Flesch, G.; Malespin, C.; McKay, C.; Martinez, G.; Moores, J.; Smith, C. L.; Martin-Torres, F. J.; Gomez-Elvira, J.; Zorzano, M. P.; Wong, M. H.; Trainer, M. G.; Eigenbrode, J. L.; Glavin, D. P.; Steele, A.; Archer, D., Jr.; Sutter, B.; Coll, P. J.; Freissinet, C.; Meslin, P. Y.; Pavlov, A.; Keymeulen, D.; Christensen, L. E.; Gough, R. V.; Schwenzer, S. P.; Navarro-Gonzalez, R.; Pla-García, J.; Rafkin, S. C.; Vicente-Retortillo, Á.; Kahanpää, H.; Viudez-Moreiras, D.; Smith, M. D.; Harri, A. M.; Genzer, M.; Hassler, D.; Lemmon, M. T.; Crisp, J. A.; Zurek, R. W.; Vasavada, A. R.

2017-12-01

In situ measurements of atmospheric methane have been made over a 5-year period at Gale Crater on Mars using the Tunable Laser Spectrometer (TLS) instrument in the Sample Analysis at Mars (SAM) suite on the Curiosity rover. We report two important observations: (i) a background level of mean value of 0.41 ±0.11 (2sem) that is about 5 times lower than some model predictions based on generation from UV degradation of micro-meteorites or interplanetary dust delivered to the martian surface; (ii) "spikes" of elevated levels of 7 ppbv attributed to episodic releases from small local sources, probably to the north of Gale crater1. Reports of plumes, patches or episodic releases of methane in the Martian atmosphere have to date eluded explanation in part because of their lack of repeatability in time or location. Our in situ measurements of the background methane levels exhibit a strong, repeatable seasonal variability. The amplitude of the observed seasonal cycle is 3 times greater than both that expected from the annual sublimation and freezing of polar carbon dioxide and that expected from methane production from ultraviolet (UV) degradation of exogenously-delivered surface material. The observed large seasonal variation in the background, and sporadic observations of higher pulses of 7 ppbv appear consistent with localized small sources of methane release from Martian surface reservoirs that may be occurring throughout the planet. We will present our updated data set, correlations of Mars methane with various other measurements from SAM, REMS, RAD and ChemCam instruments on Curiosity, as well as empirical models of UV surface insolation, and provide preliminary interpretation of results. 1 "Mars Methane Detection and Variability at Gale Crater", C. R. Webster et al., Science, 347, 415-417 (2015) and references therein. The research described here was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).

High speed ultra-broadband amplitude modulators with ultrahigh extinction >65 dB

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

Liu, S.; Cai, H.; DeRose, C. T.

Here, we experimentally demonstrate ultrahigh extinction ratio (>65 dB) amplitude modulators (AMs) that can be electrically tuned to operate across a broad spectral range of 160 nm from 1480 – 1640 nm and 95 nm from 1280 – 1375 nm. Our on-chip AMs employ one extra coupler compared with conventional Mach-Zehnder interferometers (MZI), thus form a cascaded MZI (CMZI) structure. Either directional or adiabatic couplers are used to compose the CMZI AMs and experimental comparisons are made between these two different structures. Furthermore, we investigate the performance of CMZI AMs under extreme conditions such as using 95:5 split ratio couplersmore » and unbalanced waveguide losses. Electro-optic phase shifters are also integrated in the CMZI AMs for high-speed operation. Finally, we investigate the output optical phase when the amplitude is modulated, which provides us valuable information when both amplitude and phase are to be controlled. This demonstration not only paves the road to applications such as quantum information processing that requires high extinction ratio AMs but also significantly alleviates the tight fabrication tolerance needed for large-scale integrated photonics.« less

High speed ultra-broadband amplitude modulators with ultrahigh extinction >65 dB

DOE PAGES

Liu, S.; Cai, H.; DeRose, C. T.; ...

2017-05-04

Here, we experimentally demonstrate ultrahigh extinction ratio (>65 dB) amplitude modulators (AMs) that can be electrically tuned to operate across a broad spectral range of 160 nm from 1480 – 1640 nm and 95 nm from 1280 – 1375 nm. Our on-chip AMs employ one extra coupler compared with conventional Mach-Zehnder interferometers (MZI), thus form a cascaded MZI (CMZI) structure. Either directional or adiabatic couplers are used to compose the CMZI AMs and experimental comparisons are made between these two different structures. Furthermore, we investigate the performance of CMZI AMs under extreme conditions such as using 95:5 split ratio couplersmore » and unbalanced waveguide losses. Electro-optic phase shifters are also integrated in the CMZI AMs for high-speed operation. Finally, we investigate the output optical phase when the amplitude is modulated, which provides us valuable information when both amplitude and phase are to be controlled. This demonstration not only paves the road to applications such as quantum information processing that requires high extinction ratio AMs but also significantly alleviates the tight fabrication tolerance needed for large-scale integrated photonics.« less

Current-induced modulation of backward spin-waves in metallic microstructures

NASA Astrophysics Data System (ADS)

Sato, Nana; Lee, Seo-Won; Lee, Kyung-Jin; Sekiguchi, Koji

2017-03-01

We performed a propagating spin-wave spectroscopy for backward spin-waves in ferromagnetic metallic microstructures in the presence of electric-current. Even with the smaller current injection of 5× {{10}10} A m-2 into ferromagnetic microwires, the backward spin-waves exhibit a gigantic 200 MHz frequency shift and a 15% amplitude change, showing 60 times larger modulation compared to previous reports. Systematic experiments by measuring dependences on a film thickness of mirowire, on the wave-vector of spin-wave, and on the magnitude of bias field, we revealed that for the backward spin-waves a distribution of internal magnetic field generated by electric-current efficiently modulates the frequency and amplitude of spin-waves. The gigantic frequency and amplitude changes were reproduced by a micromagnetics simulation, predicting that the current-injection of 5× {{10}11} A m-2 allows 3 GHz frequency shift. The effective coupling between electric-current and backward spin-waves has a potential to build up a logic control method which encodes signals into the phase and amplitude of spin-waves. The metallic magnonics cooperating with electronics could suggest highly integrated magnonic circuits both in Boolean and non-Boolean principles.

Method of differential-phase/absolute-amplitude QAM

DOEpatents

Dimsdle, Jeffrey William [Overland Park, KS

2007-07-03

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Method of differential-phase/absolute-amplitude QAM

DOEpatents

Dimsdle, Jeffrey William [Overland Park, KS

2008-10-21

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Method of differential-phase/absolute-amplitude QAM

DOEpatents

Dimsdle, Jeffrey William [Overland Park, KS

2009-09-01

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Method of differential-phase/absolute-amplitude QAM

DOEpatents

Dimsdle, Jeffrey William [Overland Park, KS

2007-07-17

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Method of differential-phase/absolute-amplitude QAM

DOEpatents

Dimsdle, Jeffrey William

2007-10-02

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Differential pulse amplitude modulation for multiple-input single-output OWVLC

NASA Astrophysics Data System (ADS)

Yang, S. H.; Kwon, D. H.; Kim, S. J.; Son, Y. H.; Han, S. K.

2015-01-01

White light-emitting diodes (LEDs) are widely used for lighting due to their energy efficiency, eco-friendly, and small size than previously light sources such as incandescent, fluorescent bulbs and so on. Optical wireless visible light communication (OWVLC) based on LED merges lighting and communications in applications such as indoor lighting, traffic signals, vehicles, and underwater communications because LED can be easily modulated. However, physical bandwidth of LED is limited about several MHz by slow time constant of the phosphor and characteristics of device. Therefore, using the simplest modulation format which is non-return-zero on-off-keying (NRZ-OOK), the data rate reaches only to dozens Mbit/s. Thus, to improve the transmission capacity, optical filtering and pre-, post-equalizer are adapted. Also, high-speed wireless connectivity is implemented using spectrally efficient modulation methods: orthogonal frequency division multiplexing (OFDM) or discrete multi-tone (DMT). However, these modulation methods need additional digital signal processing such as FFT and IFFT, thus complexity of transmitter and receiver is increasing. To reduce the complexity of transmitter and receiver, we proposed a novel modulation scheme which is named differential pulse amplitude modulation. The proposed modulation scheme transmits different NRZ-OOK signals with same amplitude and unit time delay using each LED chip, respectively. The `N' parallel signals from LEDs are overlapped and directly detected at optical receiver. Received signal is demodulated by power difference between unit time slots. The proposed scheme can overcome the bandwidth limitation of LEDs and data rate can be improved according to number of LEDs without complex digital signal processing.

Cloud Atlas: Rotational Modulations in the L/T Transition Brown Dwarf Companion HN Peg B

NASA Technical Reports Server (NTRS)

Zhou, Yifan; Apai, Daniel; Metchev, Stanimir; Lew, Ben W. P.; Schneider, Glenn; Marley, Mark S.; Karalidi, Theodora; Manjavacas, Elena; Bedin, Luigi R.; Cowan, Nicolas B.;

Cloud Atlas: Rotational Modulations in the L/T Transition Brown Dwarf Companion HN Peg B

NASA Astrophysics Data System (ADS)

Zhou, Yifan; Apai, Dániel; Metchev, Stanimir; Lew, Ben W. P.; Schneider, Glenn; Marley, Mark S.; Karalidi, Theodora; Manjavacas, Elena; Bedin, Luigi R.; Cowan, Nicolas B.; Miles-Páez, Paulo A.; Lowrance, Patrick J.; Radigan, Jacqueline; Burgasser, Adam J.

2018-03-01

Time-resolved observations of brown dwarfs’ rotational modulations provide powerful insights into the properties of condensate clouds in ultra-cool atmospheres. Multi-wavelength light curves reveal cloud vertical structures, condensate particle sizes, and cloud morphology, which directly constrain condensate cloud and atmospheric circulation models. We report results from Hubble Space Telescope/Wide Field Camera 3 near-infrared G141 taken in six consecutive orbits observations of HN Peg B, an L/T transition brown dwarf companion to a G0V type star. The best-fit sine wave to the 1.1–1.7 μm broadband light curve has an amplitude of 1.206% ± 0.025% and period of 15.4 ± 0.5 hr. The modulation amplitude has no detectable wavelength dependence except in the 1.4 μm water absorption band, indicating that the characteristic condensate particle sizes are large (>1 μm). We detect significantly (4.4σ) lower modulation amplitude in the 1.4 μm water absorption band and find that HN Peg B’s spectral modulation resembles those of early T type brown dwarfs. We also describe a new empirical interpolation method to remove spectral contamination from the bright host star. This method may be applied in other high-contrast time-resolved observations with WFC3.

BPSK optical mm-wave signal generation by septupling frequency via a single optical phase modulator

NASA Astrophysics Data System (ADS)

Wu, Peng; Ma, Jianxin

2016-09-01

In this paper, we have proposed a novel and simple scheme to generate the BPSK optical millimeter wave (MMW) signal with frequency septupling by using an optical phase modulator (PM) and a wavelength selective switch (WSS). In this scheme, the PM is driven by a radio frequency (RF) BPSK signal at the optimized modulation index of 4.89 to assure the 4th and 3rd-order sidebands have equal amplitudes. An wavelength selective switch (WSS) is used to abstract the -4th and +3rd-order sidebands from the spectrum generated by RF BPSK signal modulating the lightwave to form the BPSK optical MMW signal with frequency septupling the driving RF signal. In these two tones, only the +3rd-order sideband bears the BPSK signal while the -4th-order sideband is unmodulated since the phase information is canceled by the even times multiplication of the phase of BPSK signal. The MMW signal can avoid the pulse walk-off effect and the amplitude fading effect caused by the fiber chromatic dispersion. By adjusting the modulation index to assure the two tones have equal amplitude, the generated optical MMW signal has the maximal opto-electrical conversion efficiency and good transmission performance.

Modulation for terrestrial broadcasting of digital HDTV

NASA Technical Reports Server (NTRS)

Kohn, Elliott S.

1991-01-01

The digital modulation methods used by the DigiCipher, DSC-HDTV, ADTV, and ATVA-P digital high-definition television (HDTV) systems are discussed. Three of the systems use a quadrature amplitude modulation method, and the fourth uses a vestigial sideband modulation method. The channel equalization and spectrum sharing of the digital HDTV systems is discussed.

Evaluation of the biomechanics of atherosclerosis by acoustic microscopy

NASA Astrophysics Data System (ADS)

Saijo, Yoshifumi; Nitta, Shin-ichi; Schiott Jorgensen, Claus; Falk, Erling

2001-07-01

Acoustic microscopy provides not only the morphology, but also the biomechanical properties of the biological soft tissues. The biomechanics of atherosclerosis is important because the pathophysiology of atherosclerosis is closely related with mechanical properties and mechanical stress. Rupture of the fibrous cap of atheromatous plaque is the initial event in acute coronary syndrome such as acute myocardial infarction or unstable angina. In addition to extrinsic physical stresses to the plaque, the intrinsic biomechanical property of the plaque is important for assessing the mechanism of the rupture. Two sets of SAMs operating in 100 to 200 MHz and in 800 MHz to 1.3 GHz were equipped to measure the acoustic properties of atherosclerosis of human or mouse arteries. The values of attenuation and sound speed in the tissue components of atherosclerosis were measured by analyzing the frequency dependent characteristics of the amplitude and phase signals. Both values were highest in calcification and lowest in lipid pool. Although attenuation and sound speed were relatively high in intimal fibrosis, the inhomogeneity of acoustic parameters was found within the fibrous cap. Polarized microscopy for the collagen stained with Picrosirius red showed that the attenuation of ultrasound was significantly higher in type I collagen with orange polarized color compared to type III collagen with green color. SAM has shown the possibility to detect the plaque vulnerability and it might improve our understanding of the sudden rupture from micro-mechanical point of view.

Demonstration of micro-projection enabled short-range communication system for 5G.

PubMed

Chou, Hsi-Hsir; Tsai, Cheng-Yu

2016-06-13

A liquid crystal on silicon (LCoS) based polarization modulated image (PMI) system architecture using red-, green- and blue-based light-emitting diodes (LEDs), which offers simultaneous micro-projection and high-speed data transmission at nearly a gigabit, serving as an alternative short-range communication (SRC) approach for personal communication device (PCD) application in 5G, is proposed and experimentally demonstrated. In order to make the proposed system architecture transparent to the future possible wireless data modulation format, baseband modulation schemes such as multilevel pulse amplitude modulation (M-PAM), M-ary phase shift keying modulation (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) which can be further employed by more advanced multicarrier modulation schemes (such as DMT, OFDM and CAP) were used to investigate the highest possible data transmission rate of the proposed system architecture. The results demonstrated that an aggregative data transmission rate of 892 Mb/s and 900 Mb/s at a BER of 10^(-3) can be achieved by using 16-QAM baseband modulation scheme when data transmission were performed with and without micro-projection simultaneously.

Application of ultrasound-tagged photons for measurement of amplitude of vibration of tissue caused by ultrasound: theory, simulation, and experiments.

PubMed

Devi, C Usha; Vasu, R M; Sood, A K

2006-01-01

We investigate the modulation of an optical field caused by its interaction with an ultrasound beam in a tissue mimicking phantom. This modulation appears as a modulation in the intensity autocorrelation, which is measured by a photon counting correlator. The factors contributing to the modulation are: 1. amplitude of vibration of the particles of the tissue, 2. refractive index modulation, and 3. absorption coefficient in the region of the tissue intercepted by the ultrasound beam and light. We show in this work that a significant part of the contribution to this modulation comes from displacement of the tissue particles, which in turn is governed by the elastic properties of the tissue. We establish, both through simulations and experiments using an optical elastography phantom, the effects of the elasticity and absorption coefficient variations on the modulation of intensity autocorrelation. In the case where there is no absorption coefficient variation, we suggest that the depth of modulation can be calibrated to measure the displacement of tissue particles that, in turn, can be used to measure the tissue elasticity.

Isolating spectral cues in amplitude and quasi-frequency modulation discrimination by reducing stimulus duration.

PubMed

Borucki, Ewa; Berg, Bruce G

2017-05-01

This study investigated the psychophysical effects of distortion products in a listening task traditionally used to estimate the bandwidth of phase sensitivity. For a 2000 Hz carrier, estimates of modulation depth necessary to discriminate amplitude modulated (AM) tones and quasi-frequency modulated (QFM) were measured in a two interval forced choice task as a function modulation frequency. Temporal modulation transfer functions were often non-monotonic at modulation frequencies above 300 Hz. This was likely to be due to a spectral cue arising from the interaction of auditory distortion products and the lower sideband of the stimulus complex. When the stimulus duration was decreased from 200 ms to 20 ms, thresholds for low-frequency modulators rose to near-chance levels, whereas thresholds in the region of non-monotonicities were less affected. The decrease in stimulus duration appears to hinder the listener's ability to use temporal cues in order to discriminate between AM and QFM, whereas spectral information derived from distortion product cues appears more resilient. Copyright © 2017. Published by Elsevier B.V.

A pilot study investigating the feasibility of symptom assessment manager (SAM), a Web-based real-time tool for monitoring challenging behaviors.

PubMed

Loi, Samantha M; Wanasinghage, Sangeeth; Goh, Anita; Lautenschlager, Nicola T; Darby, David G; Velakoulis, Dennis

2018-04-01

Improving and minimizing challenging behaviors seen in psychiatric conditions, including behavioral and psychological symptoms of dementia are important in the care of people with these conditions. Yet there is a lack of systematic evaluation of these as a part of routine clinical care. The Neuropsychiatric Inventory is a validated and reliable tool for rating the severity and disruptiveness of challenging behaviors. We report on the evaluation of a Web-based symptom assessment manager (SAM), designed to address the limitation of previous tools using some of the Neuropsychiatric Inventory functions, to monitor behaviors by staff caring for people with dementia and other psychiatric conditions in inpatient and residential care settings. The SAM was piloted in an 8-bed inpatient neuropsychiatry unit over 5 months. Eleven nurses and 4 clinicians were trained in usage of SAM. Primary outcomes were usage of SAM and perceived usability, utility, and acceptance of SAM. Secondary outcomes were the frequencies of documented behavior. Usage data were analyzed using chi-square and logistic regression analyses. The SAM was used for all admitted patients regardless of diagnosis, with a usage rate of 64% for nurses regularly employed in the unit. Staff provided positive feedback regarding the utility of SAM. The SAM appeared to offer individualized behavior assessment by providing a quick, structured, and standardized platform for assessing behavior in a real-world setting. Further research would involve trialing SAM with more staff in alternative settings such as in home or residential care settings. Copyright © 2017 John Wiley & Sons, Ltd.

Purified frequency modulation of a quantum cascade laser with an all-optical approach.

PubMed

Peng, Chen; Zhou, Haijun; Zhu, Liguo; Chen, Tao; Liu, Qiao; Wang, Detian; Li, Jiang; Peng, Qixian; Chen, Gang; Li, Zeren

2017-11-01

Purified frequency modulation (FM) is demonstrated in a standard middle-infrared quantum cascade laser by illuminating its front facet with two near-infrared (NIR) lasers. A 2 mW laser at 1550 nm is utilized to modulate the amplitude and frequency of a quantum cascade laser, and the associated amplitude modulation (AM) is suppressed by a 1.85 mW laser at 850 nm. Due to the hot carrier effect and the increment of electron temperature, the AM has been decreased. In addition, the free carrier concentration increases in the active region due to the two NIR illuminations, which enhance the FM. Purified FM is beneficial in improving the signal fidelity for free-space optical communication and high-speed FM spectroscopy.

Photonic-assisted microwave signal multiplication and modulation using a silicon Mach–Zehnder modulator

PubMed Central

Long, Yun; Zhou, Linjie; Wang, Jian

2016-01-01

Photonic generation of microwave signal is obviously attractive for many prominent advantages, such as large bandwidth, low loss, and immunity to electromagnetic interference. Based on a single integrated silicon Mach–Zehnder modulator (MZM), we propose and experimentally demonstrate a simple and compact photonic scheme to enable frequency-multiplicated microwave signal. Using the fabricated integrated MZM, we also demonstrate the feasibility of microwave amplitude-shift keying (ASK) modulation based on integrated photonic approach. In proof-of-concept experiments, 2-GHz frequency-doubled microwave signal is generated using a 1-GHz driving signal. 750-MHz/1-GHz frequency-tripled/quadrupled microwave signals are obtained with a driving signal of 250 MHz. In addition, a 50-Mb/s binary amplitude coded 1-GHz microwave signal is also successfully generated. PMID:26832305

Synchronization enhancement of indirectly coupled oscillators via periodic modulation in an optomechanical system.

PubMed

Du, Lei; Fan, Chu-Hui; Zhang, Han-Xiao; Wu, Jin-Hui

2017-11-20

We study the synchronization behaviors of two indirectly coupled mechanical oscillators of different frequencies in a doublecavity optomechanical system. It is found that quantum synchronization is roughly vanishing though classical synchronization seems rather good when each cavity mode is driven by an external field in the absence of temporal modulations. By periodically modulating cavity detunings or driving amplitudes, however, it is possible to observe greatly enhanced quantum synchronization accompanied with nearly perfect classical synchronization. The level of quantum synchronization observed here is, in particular, much higher than that for two directly coupled mechanical oscillators. Note also that the modulation on cavity detunings is more appealing than that on driving amplitudes when the robustness of quantum synchronization is examined against the bath's mean temperature or the oscillators' frequency difference.

Magnetoelastoelectric coupling in core-shell nanoparticles enabling directional and mode-selective magnetic control of THz beam propagation

DOE PAGES

Dutta, Moumita; Prasankumar, Rohit Prativadi; Natarajan, Kamaraju; ...

2017-08-07

Magnetoelastoelectric coupling in an engineered biphasic multiferroic nanocomposite enables a novel magnetic field direction-defined propagation control of terahertz (THz) waves. These core–shell nanoparticles are comprised of a ferromagnetic cobalt ferrite core and a ferroelectric barium titanate shell. Furthermore, an assembly of these nanoparticles, when operated in external magnetic fields, exhibits a controllable amplitude modulation when the magnetic field is applied antiparallel to the THz wave propagation direction; yet the same assembly displays an additional phase modulation when the magnetic field is applied along the propagation direction. And while field-induced magnetostriction of the core leads to amplitude modulation, phase modulation ismore » a result of stress-mediated piezoelectricity of the outer ferroelectric shell.« less

High current nonlinear transmission line based electron beam driver

NASA Astrophysics Data System (ADS)

Hoff, B. W.; French, D. M.; Simon, D. S.; Lepell, P. D.; Montoya, T.; Heidger, S. L.

2017-10-01

A gigawatt-class nonlinear transmission line based electron beam driver is experimentally demonstrated. Four experimental series, each with a different Marx bank charge voltage (15, 20, 25, and 30 kV), were completed. Within each experimental series, shots at peak frequencies ranging from 950 MHz to 1.45 GHz were performed. Peak amplitude modulations of the NLTL output voltage signal were found to range between 18% and 35% for the lowest frequency shots and between 5% and 20% for the highest frequency shots (higher modulation at higher Marx charge voltage). Peak amplitude modulations of the electron beam current were found to range between 10% and 20% for the lowest frequency shots and between 2% and 7% for the highest frequency shots (higher modulation at higher Marx charge voltage).

Separation Control Using ZNMF Devices: Flow Physics and Scaling Laws

DTIC Science & Technology

2007-12-31

Unclassified Unclassified (703) Standard Form 298 (Rev 8-98) Prescribed by ANSI-Std Z39-18 N o e c a urom .................cl.........................re...overcome this problem. The piezoelectric actuator is resonantly driven with a carrier waveform, e (t), which is amplitude modulated with a time-harmonic wave...train: e (t)=[1+sin((omt+pm)]Arsin(coct) (3) where A, is the amplitude of the carrier signal, E is the degree of modulation (0 C 1 ), w0 is the

Evolution of Spin and Superorbital Modulation in 4U 0114+650

NASA Astrophysics Data System (ADS)

Hu, Chin-Ping; Ng, Chi-Yung; Chou, Yi

2016-09-01

We report on a systematic analysis of the spin and superorbital modulations of the high-mass X-ray binary 4U 0114+650, which consists of the slowest spinning neutron star known. Utilizing dynamic power spectra, we found that the spin period varied dramatically during the RXTE ASM and Swift BAT observations. This variation consists of a long-term spin-up trend, and two ~1,000 day and one ~600 day random walk epochs previously, MJD 51,000, ~MJD 51,400-52,000, and ~MJD 55,100-56,100. We further found that the events appear together with depressions of superorbital modulation amplitude. This provides evidence of the existence of an accretion disk, although the physical mechanism of superorbital modulation remains unclear. Furthermore, the decrease of the superorbital modulation amplitude may be associated with the decrease of mass accretion rate from the disk, and may distribute the accretion torque of the neutron star randomly in time.

Optical modulation of quantum cascade laser with optimized excitation wavelength.

PubMed

Yang, Tao; Chen, Gang; Tian, Chao; Martini, Rainer

2013-04-15

The excitation wavelength for all-optical modulation of a 10.6 μm mid-infrared (MIR) quantum cascade laser (QCL) was varied in order to obtain maximum modulation depth. Both amplitude and wavelength modulation experiments were conducted at 820 nm and 1550 nm excitation respectively, whereby the latter matches the interband transition in the QCL active region. Experimental results show that for continuous-wave mode-operated QCL, the efficiency of free carrier generation is doubled under 1550 nm excitation compared with 820 nm excitation, resulting in an increase of the amplitude modulation index from 19% to 36%. At the same time, the maximum wavelength shift is more than doubled from 1.05 nm to 2.80 nm. Furthermore, for the first time to our knowledge, we demonstrated the optical switching of a QCL operated in pulse mode by simple variation of the excitation wavelength.

Dual-tone optical vector millimeter wave signal generated by frequency-nonupling the radio frequency 16-star quadrature-amplitude-modulation signal

NASA Astrophysics Data System (ADS)

Wu, Tonggen; Ma, Jianxin

2017-12-01

This paper proposes an original scheme to generate the photonic dual-tone optical millimeter wave (MMW) carrying the 16-star quadrature-amplitude-modulation (QAM) signal via an optical phase modulator (PM) and an interleaver with adaptive photonic frequency-nonupling without phase precoding. To enable the generated optical vector MMW signal to resist the power fading effect caused by the fiber chromatic dispersion, the modulated -5th- and +4th-order sidebands are selected from the output of the PM, which is driven by the precoding 16-star QAM signal. The modulation index of the PM is optimized to gain the maximum opto-electrical conversion efficiency. A radio over fiber link is built by simulation, and the simulated constellations and the bit error rate graph demonstrate that the frequency-nonupling 16-star QAM MMW signal has good transmission performance. The simulation results agree well with our theoretical results.

Real-time measurements of spontaneous breathers and rogue wave events in optical fibre modulation instability

PubMed Central

Närhi, Mikko; Wetzel, Benjamin; Billet, Cyril; Toenger, Shanti; Sylvestre, Thibaut; Merolla, Jean-Marc; Morandotti, Roberto; Dias, Frederic; Genty, Goëry; Dudley, John M.

2016-01-01

Modulation instability is a fundamental process of nonlinear science, leading to the unstable breakup of a constant amplitude solution of a physical system. There has been particular interest in studying modulation instability in the cubic nonlinear Schrödinger equation, a generic model for a host of nonlinear systems including superfluids, fibre optics, plasmas and Bose–Einstein condensates. Modulation instability is also a significant area of study in the context of understanding the emergence of high amplitude events that satisfy rogue wave statistical criteria. Here, exploiting advances in ultrafast optical metrology, we perform real-time measurements in an optical fibre system of the unstable breakup of a continuous wave field, simultaneously characterizing emergent modulation instability breather pulses and their associated statistics. Our results allow quantitative comparison between experiment, modelling and theory, and are expected to open new perspectives on studies of instability dynamics in physics. PMID:27991513

Electrically and spatially controllable PDLC phase gratings for diffraction and modulation of laser beams

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

Hadjichristov, Georgi B., E-mail: georgibh@issp.bas.bg; Marinov, Yordan G.; Petrov, Alexander G.

2016-03-25

We present a study on electrically- and spatially-controllable laser beam diffraction, electrooptic (EO) phase modulation, as well as amplitude-frequency EO modulation by single-layer microscale polymer-dispersed liquid crystal (PDLC) phase gratings (PDLC SLPGs) of interest for device applications. PDLC SLPGs were produced from nematic liquid crystal (LC) E7 in photo-curable NOA65 polymer. The wedge-formed PDLC SLPGs have a continuously variable thickness (2–25 µm). They contain LC droplets of diameters twice as the layer thickness, with a linear-gradient size distribution along the wedge. By applying alternating-current (AC) electric field, the PDLC SLPGs produce efficient: (i) diffraction splitting of transmitted laser beams; (ii)more » spatial redistribution of diffracted light intensity; (iii) optical phase modulation; (iv) amplitude-frequency modulation, all controllable by the driven AC field and the droplet size gradient.« less

Neuroendocrine abnormalities in hypothalamic amenorrhea: spectrum, stability, and response to neurotransmitter modulation.

PubMed

Perkins, R B; Hall, J E; Martin, K A

1999-06-01

To characterize the neuroendocrine patterns of abnormal GnRH secretion in hypothalamic amenorrhea (HA), 49 women with primary and secondary HA underwent frequent sampling of LH in a total of 72 baseline studies over 12-24 h. A subset of women participated in more than one study to address 1) the variability of LH pulse patterns over time; and 2) the impact of modulating opioid, dopaminergic, and adrenergic tone on LH secretory patterns. The frequency and amplitude of LH secretion was compared with that seen in the early follicular phase (EFP) of normally cycling women. The spectrum of abnormalities of LH pulses was 8% apulsatile, 27% low frequency/low amplitude, 8% low amplitude/normal frequency, 43% low frequency/normal amplitude, 14% normal frequency/normal amplitude. Of patients studied overnight, 45% demonstrated a pubertal pattern of augmented LH secretion during sleep. Of patients studied repeatedly, 75% demonstrated at least 2 different patterns of LH secretion, and 33% reverted at least once to a normal pattern of secretion. An increase in LH pulse frequency was seen in 12 of 15 subjects in response to naloxone (opioid receptor antagonist). Clonidine (alpha-2 adrenergic agonist) was associated with a decrease in mean LH in 3 of 3 subjects. An increase in LH pulse frequency was seen in 4 of 8 subjects in response to metoclopramide (dopamine receptor antagonist), but the response was not statistically significant. Baseline abnormalities in LH secretion did not appear to influence response to neurotransmitter modulation. 1) HA represents a spectrum of disordered GnRH secretion that can vary over time; 2) LH pulse patterns at baseline do not appear to influence the ability to respond to neurotransmitter modulation; 3) Opioid and adrenergic tone appear to influence the hypothalamic GnRH pulse generator in some individuals with HA.

Experiencing Earth's inaudible symphony

NASA Astrophysics Data System (ADS)

Marlton, Graeme; Charlton-Perez, Andrew; Harrison, Giles; Robson, Juliet

2017-04-01

Everyday the human body is exposed to thousands of different sounds; smartphones, music, cars and overhead aircraft to name a few. There are some sounds however which we cannot hear as they are below our range of hearing, sound at this level is known as infrasound and is of very low frequency. Such examples of infrasound are the sounds made by glaciers and volcanos, distant mining activities and the sound of the ocean. These sounds are emitted by these sources constantly all over the world and are recorded at infrasound stations, thus providing a recording of Earth's inaudible symphony. The aim of this collaboration between artists and scientists is to create a proof of concept immersive experience in which members of the public are invited to experience and understand infrasound. Participants will sit in an installation and be shown images of natural infrasound sources whilst their seat is vibrated at with an amplitude modulated version of the original infrasound wave. To further enhance the experience, subwoofers will play the same amplitude modulated soundwave to place the feeling of the infrasound wave passing through the installation. Amplitude modulation is performed so that a vibration is played at a frequency that can be felt by the human body but its amplitude varies at the frequency of the infrasound wave. The aim of the project is to see how humans perceive sounds that can't be heard and many did not know were there. The second part of the project is educational in which that this installation can be used to educate the general public about infrasound and its scientific uses. A simple demonstration for this session could be the playing of amplitude modulated infrasound wave that can be heard as opposed to felt as the transport of an installation at this is not possible and the associated imagery.

Somatosensory spatial attention modulates amplitudes, latencies, and latency jitter of laser-evoked brain potentials.

PubMed

Franz, Marcel; Nickel, Moritz M; Ritter, Alexander; Miltner, Wolfgang H R; Weiss, Thomas

2015-04-01

Several studies provided evidence that the amplitudes of laser-evoked potentials (LEPs) are modulated by attention. However, previous reports were based on across-trial averaging of LEP responses at the expense of losing information about intertrial variability related to attentional modulation. The aim of this study was to investigate the effects of somatosensory spatial attention on single-trial parameters (i.e., amplitudes, latencies, and latency jitter) of LEP components (N2 and P2). Twelve subjects participated in a sustained spatial attention paradigm while noxious laser stimuli (left hand) and noxious electrical stimuli (right hand) were sequentially delivered to the dorsum of the respective hand with nonnoxious air puffs randomly interspersed within the sequence of noxious stimuli. Participants were instructed to mentally count all stimuli (i.e., noxious and nonnoxious) applied to the attended location. Laser stimuli, presented to the attended hand (ALS), elicited larger single-trial amplitudes of the N2 component compared with unattended laser stimuli (ULS). In contrast, single-trial amplitudes of the P2 component were not significantly affected by spatial attention. Single-trial latencies of the N2 and P2 were significantly smaller for ALS vs. ULS. Additionally, the across-trial latency jitter of the N2 component was reduced for ALS. Conversely, the latency jitter of the P2 component was smaller for ULS compared with ALS. With the use of single-trial analysis, the study provided new insights into brain dynamics of LEPs related to spatial attention. Our results indicate that single-trial parameters of LEP components are differentially modulated by spatial attention. Copyright © 2015 the American Physiological Society.

Cavity Self-Stabilization and Enhancement of Laser Gyroscopes by (Coupled) Optical Resonators

NASA Technical Reports Server (NTRS)

Smith, David D.

2006-01-01

We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the modulation to determine the conditions for cavity self-stabilization and enhanced gyroscopic sensitivity. Hence, we model cavity rotation or instability by an arbitrary AM/FM modulation, and the dispersive element as a phase and amplitude filter. We find that anomalous dispersion may be used to self-stabilize a laser cavity, provided the magnitude of the group index of refraction is smaller than the phase index of refraction in the cavity. The optimal stabilization is found to occur when the group index is zero. Group indices with magnitudes larger than the phase index (both normal and anomalous dispersion) are found to enhance the sensitivity of a laser gyroscope to rotation. Furthermore, our results indicate that atomic media, even coherent superpositions in multilevel atoms, are not useful for these applications, because the amplitude and phase filters work against one another, i.e., decreasing the modulation frequency increases its amplitude and vice versa, with one exception: negative group indices whose magnitudes are larger than the phase index result in negative, but enhanced, beat frequencies. On the other hand, for optical resonators the dispersion reversal associated with critical coupling enables the amplitude and phase filters to work together under a greater variety of circumstances than for atomic media. We find that for single over-coupled resonators, or in the case of under-coupled coupled-resonator-induced absorption, the absorption and normal dispersion on-resonance increase the contrast and frequency of the beat-note, respectively, resulting in a substantial enhancement of the gyroscopic response. Moreover, for cavity self-stabilization, we propose the use of a variety of coupled-resonator induced transparency that is accompanied by anomalous dispersion.

A Response to Sam McKegney's "Strategies for Ethical Engagement: An Open Letter Concerning Non-Native Scholars of Native Literatures"

ERIC Educational Resources Information Center

Appleford, Rob

2009-01-01

This article presents the author's response to Sam McKegney's "Strategies for Ethical Engagement: An Open Letter Concerning Non-Native Scholars of Native Literatures." In his response to Sam's diagnosis of the malaise currently afflicting non-Aboriginal critics of this literature, the author attempts to consider the "cure" Sam offers (albeit…

Walking with a Slower Friend

ERIC Educational Resources Information Center

Bailey, Herb; Kalman, Dan

2011-01-01

Fay and Sam go for a walk. Sam walks along the left side of the street while Fay, who walks faster, starts with Sam but walks to a point on the right side of the street and then returns to meet Sam to complete one segment of their journey. We determine Fay's optimal path minimizing segment length, and thus maximizing the number of times they meet…

Severe acute malnutrition.

PubMed

Nel, E D

2016-05-01

The mortality and morbidity associated with severe acute malnutrition (SAM) remain high. A summary of recent studies that are of interest to clinicians treating children with SAM is provided. Three important themes emerged in 2015: the use of anthropometry in the diagnosis of SAM and its correlation with body composition; the composition of ready-to-use therapeutic feeds (RUTF); and an improved understanding of the pathophysiology of SAM. Standard anthropometry does not accurately predict body composition and mid-upper arm circumference more accurately reflects fat mass in children. As single measure, mid-upper arm circumference identifies those children who are most likely to die from SAM and is not influenced by dehydration. However, a significant proportion of SAM children requiring treatment will not be detected. Present RUTF formulations are deficient in long chain polyunsaturated fatty acids. Current evidence suggests that preformed docosahexaenoic acid should be added and/or the content of linoleic acid reduced in RUTF. In contrast to an animal model, stabile children with SAM have the same cardiac index as children without SAM. The situation in haemodynamically unstable children is unknown, continued conservative use of intravenous fluids seems advisable. A reduction in variability of the faecal DNA virome may account for increased susceptibility to malnutrition in vulnerable children.

Ontogeny of the Maize Shoot Apical Meristem[W][OA

PubMed Central

Takacs, Elizabeth M.; Li, Jie; Du, Chuanlong; Ponnala, Lalit; Janick-Buckner, Diane; Yu, Jianming; Muehlbauer, Gary J.; Schnable, Patrick S.; Timmermans, Marja C.P.; Sun, Qi; Nettleton, Dan; Scanlon, Michael J.

2012-01-01

The maize (Zea mays) shoot apical meristem (SAM) arises early in embryogenesis and functions during stem cell maintenance and organogenesis to generate all the aboveground organs of the plant. Despite its integral role in maize shoot development, little is known about the molecular mechanisms of SAM initiation. Laser microdissection of apical domains from developing maize embryos and seedlings was combined with RNA sequencing for transcriptomic analyses of SAM ontogeny. Molecular markers of key events during maize embryogenesis are described, and comprehensive transcriptional data from six stages in maize shoot development are generated. Transcriptomic profiling before and after SAM initiation indicates that organogenesis precedes stem cell maintenance in maize; analyses of the first three lateral organs elaborated from maize embryos provides insight into their homology and to the identity of the single maize cotyledon. Compared with the newly initiated SAM, the mature SAM is enriched for transcripts that function in transcriptional regulation, hormonal signaling, and transport. Comparisons of shoot meristems initiating juvenile leaves, adult leaves, and husk leaves illustrate differences in phase-specific (juvenile versus adult) and meristem-specific (SAM versus lateral meristem) transcript accumulation during maize shoot development. This study provides insight into the molecular genetics of SAM initiation and function in maize. PMID:22911570

Threshold-Voltage Shifts in Organic Transistors Due to Self-Assembled Monolayers at the Dielectric: Evidence for Electronic Coupling and Dipolar Effects.

PubMed

Aghamohammadi, Mahdieh; Rödel, Reinhold; Zschieschang, Ute; Ocal, Carmen; Boschker, Hans; Weitz, R Thomas; Barrena, Esther; Klauk, Hagen

2015-10-21

The mechanisms behind the threshold-voltage shift in organic transistors due to functionalizing of the gate dielectric with self-assembled monolayers (SAMs) are still under debate. We address the mechanisms by which SAMs determine the threshold voltage, by analyzing whether the threshold voltage depends on the gate-dielectric capacitance. We have investigated transistors based on five oxide thicknesses and two SAMs with rather diverse chemical properties, using the benchmark organic semiconductor dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene. Unlike several previous studies, we have found that the dependence of the threshold voltage on the gate-dielectric capacitance is completely different for the two SAMs. In transistors with an alkyl SAM, the threshold voltage does not depend on the gate-dielectric capacitance and is determined mainly by the dipolar character of the SAM, whereas in transistors with a fluoroalkyl SAM the threshold voltages exhibit a linear dependence on the inverse of the gate-dielectric capacitance. Kelvin probe force microscopy measurements indicate this behavior is attributed to an electronic coupling between the fluoroalkyl SAM and the organic semiconductor.

(13)C-metabolic flux analysis in S-adenosyl-L-methionine production by Saccharomyces cerevisiae.

PubMed

Hayakawa, Kenshi; Kajihata, Shuichi; Matsuda, Fumio; Shimizu, Hiroshi

2015-11-01

S-Adenosyl-L-methionine (SAM) is a major biological methyl group donor, and is used as a nutritional supplement and prescription drug. Yeast is used for the industrial production of SAM owing to its high intracellular SAM concentrations. To determine the regulation mechanisms responsible for such high SAM production, (13)C-metabolic flux analysis ((13)C-MFA) was conducted to compare the flux distributions in the central metabolism between Kyokai no. 6 (high SAM-producing) and S288C (control) strains. (13)C-MFA showed that the levels of tricarboxylic acid (TCA) cycle flux in SAM-overproducing strain were considerably increased compared to those in the S228C strain. Analysis of ATP balance also showed that a larger amount of excess ATP was produced in the Kyokai 6 strain because of increased oxidative phosphorylation. These results suggest that high SAM production in Kyokai 6 strains could be attributed to enhanced ATP regeneration with high TCA cycle fluxes and respiration activity. Thus, maintaining high respiration efficiency during cultivation is important for improving SAM production. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.