Search results for: J.F. Ryan

Items from 1 to 20 out of 37 results

article

Flexible Circuits and Architectures for Ultralow Power

B.H. Calhoun, J.F. Ryan, S. Khanna, M. Putic, more

Proceedings of the IEEE > 2010 > 98 > 2 > 267 - 282

Subthreshold digital circuits minimize energy per operation and are thus ideal for ultralow-power (ULP) applications with low performance requirements. However, a large range of ULP applications continue to face performance constraints at certain times that exceed the capabilities of subthreshold operation. In this paper, we give two different examples to show that designing flexibility into ULP systems...

article

High Resolution AFM of KcsA Structure and Clustering in a Lipid Bilayer

Joanna A. Sobek, Sonia Antoranz Contera, Sonia Trigueros, Constantina Fotinou, more

Biophysical Journal > 2009 > 96 > 3 Supplement 1 > 370a

article

Nanotubes As Drug Delivery Systems For Prokaryotic And Eukaryotic Cells

Sonia Antoranz Contera, Sonia Trigueros, J.F. Ryan

Biophysical Journal > 2009 > 96 > 3 Supplement 1 > 51a

chapter

Minimizing Offset for Latching Voltage-Mode Sense Amplifiers for Sub-Threshold Operation

J.F. Ryan, B.H. Calhoun

9th International Symposium on Quality Electronic Design (isqed 2008) > 127 - 132

2008 9th International Symposium on Quality Electronic Design (ISQED '08)

This paper examines latch style voltage mode sense amplifiers for operation in the sub-threshold region, where V_DD<V_T. We show that the offset gets worse relative to strong inversion as technology scales. Furthermore, increasing the sizes of devices in the sense amplifier does not yield the reduction of input referred offset according to 1/(WL)^0.5 that is achieved for strong inversion operation...

article

Effect of Acid Treatment on the Structure and Electrical Properties of Nitrogen-Doped Multiwalled Carbon Nanotubes

H.J. Burch, E. Brown, S.A. Contera, N.C. Toledo, more

The Journal of Physical Chemistry C > 2008 > 112 > 6 > 1908 - 1912

article

Electrostatic and Steric Interactions Determine Bacteriorhodopsin Single-Molecule Biomechanics

Kislon Voïtchovsky, Sonia Antoranz Contera, J.F. Ryan

Biophysical Journal > 2007 > 93 > 6 > 2024-2037

Bacteriorhodopsin (bR) is a haloarchaeal membrane protein that converts the energy of single photons into large structural changes to directionally pump protons across purple membrane. This is achieved by a complex combination of local dynamic interactions controlling bR biomechanics at the submolecular level, producing efficient amplification of the retinal photoisomerization. Using single molecule...

article

Time-resolved spectroscopy of non-thermal carrier dynamics in GaN

K. Kyhm, R. Lota, R.A. Taylor, J.F. Ryan, more

Current Applied Physics > 2006 > 6 > 5 > 909-912

The dynamics of carriers in GaN epilayers is investigated using femtosecond pump-probe spectroscopy. After the residual chirp on the continuum probe is removed, the normalized difference spectra (NDS) for different probe energies are synchronized, recovering the full time resolution of our laser pulse. Our Monte-Carlo simulation agrees well with the unchirped NDS spectrum, which shows the development...

article

Differential Stiffness and Lipid Mobility in the Leaflets of Purple Membranes

Kislon Voïtchovsky, Sonia Antoranz Contera, Miya Kamihira, Anthony Watts, more

Biophysical Journal > 2006 > 90 > 6 > 2075-2085

Purple membranes (PM) are two-dimensional crystals formed by bacteriorhodopsin and a variety of lipids. The lipid composition and density in the cytoplasmic (CP) leaflet differ from those of the extracellular (EC) leaflet. A new way of differentiating the two sides of such asymmetric membranes using the phase signal in alternate contact atomic force microscopy is presented. This method does not require...

chapter

Usable Encryption Enabled by AJAX

J.F. Ryan, B.L. Reid

International conference on Networking and Services (ICNS'6) > 116

2006 International Conference on Networking and Services

Open source encryption technologies have been widely available for over 15 years, yet even today the vast majority of email is transmitted over the Internet in plaintext. While studies indicate that most novice users of the Internet are aware of viruses, spy ware and online fraud such as phishing, very few know what encryption is, or how to use it to protect their email communications during transit...

article

Time-resolved gain dynamics in InGaN MQWs using a Kerr gate

R.A. Taylor, J.D. Smith, J.H. Rice, J.F. Ryan, more

Physica E: Low-dimensional Systems and Nanostructures > 2003 > 17 > Complete > 255-257

The Kerr gate technique is used to time-resolve the gain in an In ₀ _. ₀ ₂ Ga ₀ _. ₉ ₈ N/In ₀ _. ₁ ₆ Ga ₀ _. ₈ ₄ N multiple quantum well sample. A new way of analyzing the data in such a variable stripe length method gain experiment is used to analyze the time-resolved spectra. The dynamics of the emission and gain are discussed...

article

Dynamics and gain in highly-excited InGaN MQWs

R.A. Taylor, K. Kyhm, J.D. Smith, J.H. Rice, more

Current Applied Physics > 2002 > 2 > 4 > 321-326

The Kerr gate technique is used to time-resolve the gain in an In ₀ _. ₀ ₂ Ga ₀ _. ₉ ₈ N/In ₀ _. ₁ ₆ Ga ₀ _. ₈ ₄ N multiple quantum well sample. A new way of analyzing the data in such a variable stripe length method gain experiment is used to analyze both the time-integrated and time-resolved spectra. We confirm that the...

article

Growth mechanism and additive effect of high-T _c superconducting crystals

C. Chen, F. Wondre, J.F. Ryan, A.V. Narlikar, more

Journal of Crystal Growth > 2002 > 237-239 > Part 1 > 772-777

Two spiral growth patterns in different scales are observed on the base plane of high-T _c crystals. The nanometer spiral exhibits the top-most atomic layer with weak bonding along c-axis and the step height of one or half-C cell parameter. A cluster model is proposed to understand the growth mechanism and to conduct the additive application. A special additive has been found to improve not...

article

2D-1D crossover from quantum well to quantum wire behaviour in GaAs v-groove structures

R. Roshan, N.I. Cade, A.C. Maciel, J.F. Ryan, more

Physica E: Low-dimensional Systems and Nanostructures > 2002 > 13 > 2-4 > 174-177

The distribution of electron current in GaAs/AlGaAs v-groove quantum wire structures with groove widths varying from 1 to 25μm has been studied using far- and near-field spectroscopy techniques. We find clear evidence of the formation of 'corner' quantum wires in wide grooves which coalesce to form single wires in grooves with widths narrower than ~5μm. Spatially resolved photoluminescence measurements...

article

Optical measurements of carrier relaxation and transport in single GaAs v-groove quantum wire structures

N.I. Cade, R. Roshan, J.F. Ryan, A.C. Maciel, more

Physica B: Physics of Condensed Matter > 2002 > 314 > 1-4 > 413-416

Single GaAs v-groove quantum wire structures, of varying width, have been studied using near-field and far-field photoluminescence (PL) and photoluminescence excitation (PLE) techniques. Strong non-thermal behaviour has been observed in complex quasi-1D/2D systems at temperatures below 40K. Spatially resolved PL measurements in the presence of an applied voltage provide information about the distribution...

article

Saturation of gain in In ₀ _. ₀ ₂ Ga ₀ _. ₉ ₈ N/In ₀ _. ₁ ₆ Ga ₀ _. ₈ ₄ N MQW plasmas

K. Kyhm, R.A. Taylor, J.F. Ryan, T. Someya, more

Physica B: Physics of Condensed Matter > 2002 > 314 > 1-4 > 47-51

A new way of analysing the data in a variable stripe length method gain experiment is presented. The stripe length dependence of the gain is measured in In ₀ _. ₀ ₂ Ga ₀ _. ₉ ₈ N/In ₀ _. ₁ ₆ Ga ₀ _. ₈ ₄ N multiple quantum wells (MQWs). We confirm that this arises from the change of the chemical potential along the excited...

article

Hot phonons and non-thermal carrier states in GaN

K. Kyhm, R.A. Taylor, E.D. O'Sullivan, J.F. Ryan, more

Physica B: Physics of Condensed Matter > 2002 > 314 > 1-4 > 30-34

Non-thermal carrier states at early times are studied using femtosecond pump-probe spectroscopy in GaN. After the residual chirp on the continuum probe is removed, the normalized difference spectra (NDS) for different probe energies are synchronized, recovering the full time resolution of our laser pulse (120fs). Our Monte-Carlo simulation agree well with the unchirped NDS spectrum, which shows the...

article

Ultrafast quasiparticle dynamics in Tl ₂ Ba ₂ CuO ₆ ₊ _δ

D.C. Smith, P. Gay, D.Z. Wang, J.H. Wang, more

Physica C: Superconductivity and its applications > 2000 > 341-348 > Part 4 > 2219-2220

We present measurements of the ultrafast time-resolved reflectance of optimally doped Tl ₂ Ba ₂ CuO ₆ ₊ _δ . The superconducting state response is interpreted in terms of pair formation from non-equilibrium quasiparticles in the nodes of a d-wave superconducting gap. For T T _c the response shows evidence for dynamic superconducting fluctuations.

article

Femtosecond dynamics of BSCCO-2212 in the weak and strong excitation limits

D.C. Smith, P. Gay, C.J. Stevens, C. Chen, more

Physica C: Superconductivity and its applications > 2000 > 341-348 > Part 4 > 2221-2222

We present measurements of the ultrafast optical response of BSCCO-2212 in the weak perturbation limit (photoexcitation density =< 10μJcm ^- ² ), where we focus attention on the dynamics of electronic correlations associated with the pseudogap, and also in the strong perturbation limit (>= 1JJcm ^- ² ), where the superconducting condensate is destroyed.

article

Femtosecond mid-infrared study of YBa ₂ Cu ₃ O ₇ _- _δ

R.A. Kaindl, M. Woerner, T. Elsaesser, D.C. Smith, more

Physica C: Superconductivity and its applications > 2000 > 341-348 > Part 4 > 2213-2216

Femtosecond near-infrared excitation of optimally-doped and underloped YBa ₂ Cu ₃ O ₇ _- _δ leads to an ultrafast fill-in of the much-discussed (ab)-plane mid-infrared conductivity gap. Transients taken from the underdoped material reveal two gap constituents with distinctly different recovery dynamics and saturation behaviour.

article

Anisotropy of non-equilibrium quasi-particle dynamics in single-crystal YBa ₂ Cu ₃ O ₇ _- _δ

P. Gay, C.J. Stevens, D.C. Smith, C. Chen, more

Physica C: Superconductivity and its applications > 2000 > 341-348 > Part 4 > 2269-2270

We report measurements of non-equilibrium quasi-particle dynamics in detwinned single-crystals of YBCO using femtosecond time-resolved reflectance. Distinct contributions arising from the a- and b-axis response are separately identified for the first time using polarised light. The a-axis component is sensitive to carrier correlation in the superconducting state, and appears to be a common feature...

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Search results for: J.F. Ryan

Flexible Circuits and Architectures for Ultralow Power

High Resolution AFM of KcsA Structure and Clustering in a Lipid Bilayer

Nanotubes As Drug Delivery Systems For Prokaryotic And Eukaryotic Cells

Minimizing Offset for Latching Voltage-Mode Sense Amplifiers for Sub-Threshold Operation

Effect of Acid Treatment on the Structure and Electrical Properties of Nitrogen-Doped Multiwalled Carbon Nanotubes

Electrostatic and Steric Interactions Determine Bacteriorhodopsin Single-Molecule Biomechanics

Time-resolved spectroscopy of non-thermal carrier dynamics in GaN

Differential Stiffness and Lipid Mobility in the Leaflets of Purple Membranes

Usable Encryption Enabled by AJAX

Time-resolved gain dynamics in InGaN MQWs using a Kerr gate

Dynamics and gain in highly-excited InGaN MQWs

Growth mechanism and additive effect of high-T _c superconducting crystals

2D-1D crossover from quantum well to quantum wire behaviour in GaAs v-groove structures

Optical measurements of carrier relaxation and transport in single GaAs v-groove quantum wire structures

Saturation of gain in In ₀ _. ₀ ₂ Ga ₀ _. ₉ ₈ N/In ₀ _. ₁ ₆ Ga ₀ _. ₈ ₄ N MQW plasmas

Hot phonons and non-thermal carrier states in GaN

Ultrafast quasiparticle dynamics in Tl ₂ Ba ₂ CuO ₆ ₊ _δ

Femtosecond dynamics of BSCCO-2212 in the weak and strong excitation limits

Femtosecond mid-infrared study of YBa ₂ Cu ₃ O ₇ _- _δ

Anisotropy of non-equilibrium quasi-particle dynamics in single-crystal YBa ₂ Cu ₃ O ₇ _- _δ

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