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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Permeation of halide anions through phospholipid bilayers occurs by the solubility-diffusion mechanism

Two alternative mechanisms are frequently used to describe ionic permeation of lipid bilayers. In the first, ions partition into the hydrophobic phase and then diffuse across (the solubility-diffusion mechanism). The second mechanism assumes that ions traverse the bilayer through transient hydrophilic defects caused by thermal fluctuations (the pore mechanism). The theoretical predictions made by both models were tested for halide anions by measuring the permeability coefficients for chloride, bromide, and iodide as a function of bilayer thickness, ionic radius, and sign of charge. To vary the bilayer thickness systematically, liposomes were prepared from monounsaturated phosphatidylcholines (PC) with chain lengths between 16 and 24 carbon atoms. The fluorescent dye MQAE (N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide) served as an indicator for halide concentration inside the liposomes and was used to follow the kinetics of halide flux across the bilayer membranes. The observed permeability coefficients ranged from 10(-9) to 10(-7) cm/s and increased as the bilayer thickness was reduced. Bromide was found to permeate approximately six times faster than chloride through bilayers of identical thickness, and iodide permeated three to four times faster than bromide. The dependence of the halide permeability coefficients on bilayer thickness and on ionic size were consistent with permeation of hydrated ions by a solubility-diffusion mechanism rather than through transient pores. Halide permeation therefore differs from that of a monovalent cation such as potassium, which has been accounted for by a combination of the two mechanisms depending on bilayer thickness.

NASA Discipline Exobiology↗
NASA NTRS1994

Molecular Dynamics of a Water-Lipid Bilayer Interface

We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

Wilson, Michael A.↗
NASA NTRS1996

Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness

Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths.

NASA Program Exobiology↗
NASA NTRS1996

Mechanism of unassisted ion transport across membrane bilayers

To establish how charged species move from water to the nonpolar membrane interior and to determine the energetic and structural effects accompanying this process, we performed molecular dynamics simulations of the transport of Na+ and Cl- across a lipid bilayer located between two water lamellae. The total length of molecular dynamics trajectories generated for each ion was 10 ns. Our simulations demonstrate that permeation of ions into the membrane is accompanied by the formation of deep, asymmetric thinning defects in the bilayer, whereby polar lipid head groups and water penetrate the nonpolar membrane interior. Once the ion crosses the midplane of the bilayer the deformation "switches sides"; the initial defect slowly relaxes, and a defect forms in the outgoing side of the bilayer. As a result, the ion remains well solvated during the process; the total number of oxygen atoms from water and lipid head groups in the first solvation shell remains constant. A similar membrane deformation is formed when the ion is instantaneously inserted into the interior of the bilayer. The formation of defects considerably lowers the free energy barrier to transfer of the ion across the bilayer and, consequently, increases the permeabilities of the membrane to ions, compared to the rigid, planar structure, by approximately 14 orders of magnitude. Our results have implications for drug delivery using liposomes and peptide insertion into membranes.

NASA Discipline Exobiology↗
NASA NTRS2012

Method of fabricating lipid bilayer membranes on solid supports

The present invention provides a method of producing a planar lipid bilayer on a solid support. With this method, a solution of lipid vesicles is first deposited on the solid support. Next, the lipid vesicles are destabilized by adding an amphipathic peptide solution to the lipid vesicle solution. This destabilization leads to production of a planar lipid bilayer on the solid support. The present invention also provides a supported planar lipid bilayer, where the planar lipid bilayer is made of naturally occurring lipids and the solid support is made of unmodified gold or titanium oxide. Preferably, the supported planar lipid bilayer is continuous. The planar lipid bilayer may be made of any naturally occurring lipid or mixture of lipids, including, but not limited to phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinsitol, cardiolipin, cholesterol, and sphingomyelin.

Cho, Nam-Joon↗
NASA NTRS1992

One GHz leaky SAW velocity of metal layers and bilayers evaporated onto fused quartz

An acoustic microscope operating at 1 GHz was used to determine the surface acoustic wave velocities v of thin film metal layers and metal bilayers deposited onto fused quartz. V(0)'s influence was reduced by gating. This produced a calibrated accuracy of 3 percent. A program was constructed from the explicitly solved 6 x 6 theoretical determinant. Single film thicknesses were decided upon by using this theory to produce a v equal to a standard. Since the single film v's were linear with respect to their thickness, half the single film thicknesses were used for the bilayered films. The velocities for these bilayered films agreed with theory. This experimentally confirms the theoretical technique used here to examine bilayered systems, or a prototype composite interphase. No discrepancy was seen for gold films as others have reported. V(z) seemed insensitive to the formation of intermetallics or CuO. Some annealed and unannealed platinum films did not change the v from that of fused quartz. Two platinum films whose v's were in agreement with theory peeled off with the tape test.

Walikainen, Dale↗
NASA NTRS1994

Interaction of a Model Peptide with a Water--Bilayer System

We discuss a molecular dynamics study of the alanine dipeptide at the interface between water and a glycerol-1-monooleate (GMO) bilayer. The dipeptide is interfacially active and incorporates into the bilayer without disrupting its structure. The interfacial region that is readily penetrated by the dipeptide spans the entire head group portion of the bilayer. The polar groups of the alanine dipeptide mostly remain well solvated by water and the oxygen atoms of GMO, and conformations of the dipeptide are characterized by (phi, psi) angles typical of alpha-helix and beta-sheet structures. When the molecule is deeper in the bilayer, the C(sub 7eq) state also becomes stable. The barrier to the isomerization reaction at the interface is lower than in bulk phases. After 7 ns of trajectories, the system is not fully equilibrated, due to slow collective motions involving GMO head groups. These result in decreased mobility and lower rates of isomerization of the dipeptide at the interface.

Pohorille, A.↗
NASA NTRS2013

Bilayer Protograph Codes for Half-Duplex Relay Channels

Direct to Earth return links are limited by the size and power of lander devices. A standard alternative is provided by a two-hops return link: a proximity link (from lander to orbiter relay) and a deep-space link (from orbiter relay to Earth). Although direct to Earth return links are limited by the size and power of lander devices, using an additional link and a proposed coding for relay channels, one can obtain a more reliable signal. Although significant progress has been made in the relay coding problem, existing codes must be painstakingly optimized to match to a single set of channel conditions, many of them do not offer easy encoding, and most of them do not have structured design. A high-performing LDPC (low-density parity-check) code for the relay channel addresses simultaneously two important issues: a code structure that allows low encoding complexity, and a flexible rate-compatible code that allows matching to various channel conditions. Most of the previous high-performance LDPC codes for the relay channel are tightly optimized for a given channel quality, and are not easily adapted without extensive re-optimization for various channel conditions. This code for the relay channel combines structured design and easy encoding with rate compatibility to allow adaptation to the three links involved in the relay channel, and furthermore offers very good performance. The proposed code is constructed by synthesizing a bilayer structure with a pro to graph. In addition to the contribution to relay encoding, an improved family of protograph codes was produced for the point-to-point AWGN (additive white Gaussian noise) channel whose high-rate members enjoy thresholds that are within 0.07 dB of capacity. These LDPC relay codes address three important issues in an integrative manner: low encoding complexity, modular structure allowing for easy design, and rate compatibility so that the code can be easily matched to a variety of channel conditions without extensive re-optimization. The main problem of half-duplex relay coding can be reduced to the simultaneous design of two codes at two rates and two SNRs (signal-to-noise ratios), such that one is a subset of the other. This problem can be addressed by forceful optimization, but a clever method of addressing this problem is via the bilayer lengthened (BL) LDPC structure. This method uses a bilayer Tanner graph to make the two codes while using a concept of "parity forwarding" with subsequent successive decoding that removes the need to directly address the issue of uneven SNRs among the symbols of a given codeword. This method is attractive in that it addresses some of the main issues in the design of relay codes, but it does not by itself give rise to highly structured codes with simple encoding, nor does it give rate-compatible codes. The main contribution of this work is to construct a class of codes that simultaneously possess a bilayer parity- forwarding mechanism, while also benefiting from the properties of protograph codes having an easy encoding, a modular design, and being a rate-compatible code.

Divsalar, Dariush↗
NASA NTRS2007

Characterizing the Superconducting-to-Normal Transition in Mo/Au Transition-Edge Sensor Bilayers

We are developing arrays of Mo/Au bilayer transition-edge sensors (TES's) for applications in future X-ray astronomy missions such as NASA's Constellation-X. The physical properties of the superconducting-to-normal transition in our TES bilayers, while often reproducible and characterized, are not well understood. The addition of normal metal features on top of the bilayer are found to change the shape and temperature of the transition, and they typically reduce the unexplained 'excess' noise. In order to understand and potentially optimize the properties of the transition, we have been studying the temperature, widths and current dependence of these transitions. We report on the characterization of devices both deposited on silicon substrates and suspended on thin silicon nitride membranes. This includes key device parameters such as the logarithmic resistance sensitivity with temperature alpha, and the logarithmic resistance sensitivity with current beta, of the phase-transition. We investigate alpha and beta as a function of current, both at fixed and varying bias points in the transition. Using Ginzburg-Landau theory for the current dependence of the superconducting transition temperature, we investigate the relationship between alpha and beta and compare our measured and theoretical estimates.

Smith, Stephen J.↗
NASA NTRS2017

Performance of an X-Ray Microcalorimeter with a 240 Micron Absorber and a 50 Micron TES Bilayer

We have been developing superconducting transition-edge sensor (TES) microcalorimeters for a variety of potential astrophysics missions, including Athena. The X-ray Integral Field Unit (X-IFU) instrument on this mission requires close-packed pixels on a 0.25 mm pitch, and high quantum efficiency between 0.2 and 12 keV. The traditional approach within our group has been to use square TES bilayers on molybdenum and gold that are between 100 and 140 microns in size, deposited on silicon nitride membranes to provide a weak thermal conductance to a 50 mK heat bath temperature. It has been shown that normal metal stripes on top of the bilayer are needed to keep the unexplained noise at a level consistent with the expected based upon estimates for the non-equilibrium non-linear Johnson noise.In this work we describe a new approach in which we use a square TES bilayer that is 50 microns in size. While the weak link effect is much stronger in this size of TES, we have found that excellent spectral performance can be achieved without the need for any normal metal strips on top of the TES. A spectral performance of 1.58 eV at 6 KeV has been achieved, the best resolution seen in any of our devices with this pixel size. The absence of normal metal stripes has led to more uniform transition shapes, and more reliable excellent spectral performance. The smaller TES size has meant that that the thermal conductance to the heat bath, determined by the perimeter length of the TES and the membrane thickness, is lower than on previous devices, and thus has a lower count rate capability. This is an advantage for low count-rate applications where the slower speed enables easier multiplexing in the read-out, thus potential higher multiplexing factors. In order to recover the higher count rate capabilities, a potential path exits using thicker silicon nitride membranes to increase the thermal conductance to the heat bath.

Miniussi, Antoine R.↗
NASA NTRS1999

Computer Simulation Studies of Ion Channel Gating: Characteristics of the M2 Channel of Influenza-A Virus in a Phospholipid Bilayer

The 25 amino acids long, transmembrane fragment of the Influenza virus M2 protein forms a homotetrameric channel that transports protons across lipid bilayers. It has been postulated that high efficiency and selectivity of this process is due to gating by four histidine residues that occlude the channel lumen in the closed state. Two mechanisms of gating have been postulated. In one mechanism, the proton is "shuttled" through the gate by attaching to the delta nitrogen atom on the extracellular side of the imidazole ring, followed by the release of the proton attached to the epsilon nitrogen atom on the opposite side. In the second mechanism, the four histidines move away from each other due to electrostatic repulsion upon protonation, thus opening the gate sufficiently that a wire of water molecules can penetrate the gate. Then, protons are transported by "hopping" along the wire. In this paper, both mechanisms are evaluated in a series of molecular dynamics simulations by investigating stability of different protonation states of the channel that are involved in these mechanisms. For the shuttle mechanism, these are states with all epsilon protonated histidines, one biprotonated residue or one histidine protonated in the delta position. For the gate opening mechanism, this is the state in which all four histidines are biprotonated. In addition, a state with two biprotonated histidines is considered. For each system, composed of the protein channel embedded in phospholipid bilayer located between two water lamellae, a molecular dynamics trajectory of approximately 1.3 ns (after equilibration) was obtained. It is found that the states involved in the shuttle mechanism are stable during the simulations. Furthermore, the orientations and dynamics of water molecules near the gate are conducive to proton transfers involved in the shuttle. In contract, the fully biprotonated state, implicated in the gate opening mechanism, is not stable and the channel looses its structural integrity. If only two histidines are biprotonated the channel deforms but remains intact with the gate mostly closed. In summary, the results of this study lend support to the shuttle mechanism but not to the gate opening mechanism of proton gating in M2.

Schweighofer, Karl J.↗
NASA NTRS2000

Computer Simulations of Small Molecules in Membranes: Insights from Computer Simulations into the Interactions of Small Molecules with Lipid Bilayers

Two of Ernest Overton's lasting contributions to biology are the Meyer-Overton relationship between the potency of an anesthetic and its solubility in oil, and the Overton rule which relates the permeability of a membrane to the oil-water partition coefficient of the permeating molecule. A growing body of experimental evidence, however, cannot be reconciled with these theories. In particular, the molecular nature of membranes, unknown to Overton, needs to be included in any description of these phenomena. Computer simulations are ideally suited for providing atomic-level information about the behavior of small molecules in membranes. The authors discuss simulation studies relevant to Overton's ideas. Through simulations it was found that anesthetics tend to concentrate at interfaces and their anesthetic potency correlates better with solubility at the water-membrane interface than with solubility in oil. Simulation studies of membrane permeation revealed the anisotropic nature of the membranes, as evidenced, for example, by the highly nonuniform distribution of free volume in the bilayer. This, in turn, influences the diffusion rates of solutes, which increase with the depth in the membrane. Small solutes tend to move by hopping between voids in the bilayer, and this hopping motion may be responsible for the deviation from the Overton rule of the permeation rates of these molecules.

Pohorille, Andrew↗
NASA NTRS1994

Alpha-helical hydrophobic polypeptides form proton-selective channels in lipid bilayers

Proton translocation is important in membrane-mediated processes such as ATP-dependent proton pumps, ATP synthesis, bacteriorhodopsin, and cytochrome oxidase function. The fundamental mechanism, however, is poorly understood. To test the theoretical possibility that bundles of hydrophobic alpha-helices could provide a low energy pathway for ion translocation through the lipid bilayer, polyamino acids were incorporated into extruded liposomes and planar lipid membranes, and proton translocation was measured. Liposomes with incorporated long-chain poly-L-alanine or poly-L-leucine were found to have proton permeability coefficients 5 to 7 times greater than control liposomes, whereas short-chain polyamino acids had relatively little effect. Potassium permeability was not increased markedly by any of the polyamino acids tested. Analytical thin layer chromatography measurements of lipid content and a fluorescamine assay for amino acids showed that there were approximately 135 polyleucine or 65 polyalanine molecules associated with each liposome. Fourier transform infrared spectroscopy indicated that a major fraction of the long-chain hydrophobic peptides existed in an alpha-helical conformation. Single-channel recording in both 0.1 N HCl and 0.1 M KCl was also used to determine whether proton-conducting channels formed in planar lipid membranes (phosphatidylcholine/phosphatidylethanolamine, 1:1). Poly-L-leucine and poly-L-alanine in HCl caused a 10- to 30-fold increase in frequency of conductive events compared to that seen in KCl or by the other polyamino acids in either solution. This finding correlates well with the liposome observations in which these two polyamino acids caused the largest increase in membrane proton permeability but had little effect on potassium permeability. Poly-L-leucine was considerably more conductive than poly-L-alanine due primarily to larger event amplitudes and, to a lesser extent, a higher event frequency. Poly-L-leucine caused two populations of conductive events, one in the 0.1-0.5 pA range, and one in the 1.0-5.0 pA range, whereas nearly all events caused by poly-L-alanine were in the 0.1-0.5 pA range at an applied voltage of +60 mV. The channel-like activity appeared to switch between conductive and nonconductive states, with most open-times in the range of 50-200 ms. We conclude that hydrophobic polyamino acids produce proton-conducting defects in lipid bilayers that may be used to model functional proton channels in biological membranes.

NASA Discipline Exobiology↗
NASA NTRS1992

Permeability of lipid bilayers to amino acids and phosphate

Permeability coefficients for amino acid classes, including neutral, polar, hydrophobic, and charged species, were measured and compared with values for other ionic solutes such as phosphate. The rates of efflux of glycine, lysine, phenylalanine, serine and tryptophan were determined after they were passively entrapped in large unilamellar vesicles (LUVs) composed of egg phosphatidylcholine (EPC) or dimyristoylphosphatidylcholine (DMPC). The following permeability coefficients were obtained for: glycine, 5.7 x 10(-12) cm s-1 (EPC), 2.0 x 10(-11) cm s-1 (DMPC); serine, 5.5 x 10(-12) cm s-1 (EPC), 1.6 x 10(-11) cm s-1 (DMPC); lysine, 5.1 x 10(-12) cm s-1 (EPC), 1.9 x 10(-11) cm s-1 (DMPC); tryptophan, 4.1 x 10(-10) cm s-1 (EPC); and phenylalanine, 2.5 x 10(-10) cm s-1 (EPC). Decreasing lipid chain length increased permeability slightly, while variations in pH had only minor effects on the permeability coefficients of the amino acids tested. Phosphate permeability was in the range of 10(-12)-10(-13) cm s-1 depending on the pH of the medium. The values for the polar and charged amino acids were surprisingly similar to those previously measured for monovalent cations such as sodium and potassium, which are in the range of 10(-12)-10(-13) cm s-1, depending on conditions and the lipid species used. This observation suggests that the permeation rates for the neutral, polar and charged amino acids are controlled by bilayer fluctuations and transient defects, rather than partition coefficients and Born energy barriers. The results are relevant to the permeation of certain peptides into lipid bilayers during protein translocation and membrane biogenesis.

NASA Discipline Exobiology↗
NASA NTRS2018

Performance of an X-ray Microcalorimeter with a 240 μm Absorber and a 50 μm TES Bilayer

Superconducting transition-edge sensor (TES) microcalorimeters are being developed for a variety of potential astrophysics missions, including Athena. The X-ray integral field unit instrument on this mission requires close-packed pixels on a 0.25 mm pitch, and high quantum efficiency between 0.2 and 12 keV. In this work, we describe a new approach with 50 μm square TESs consisting of a Mo/Au bilayer, deposited on silicon nitride membranes to provide a weak thermal conductance to a ~50 mK heat bath. Larger TESs usually have additional normal metal stripes on top of the bilayer to reduce the noise. However, we have found that excellent spectral performance can be achieved without the need for any normal metal stripes on top of the TES. A spectral performance of 1.58+/-0.12 eV at 5.9 keV has been achieved, the best resolution seen in any of our devices with this pixel size.

Miniussi, Antoine R.↗
NASA NTRS1974

Irregular bilayer structure in vesicles prepared from Halobacterium cutirubrum lipids

Fluorescent probes were used to study the structure of the cell envelope of Halobacterium cutirubrum, and, in particular, to explore the effect of the heterogeneity of the lipids in this organism on the structure of the bilayers. The fluorescence polarization of perylene was followed in vesicles of unfractionated lipids and polar lipids as a function of temperature in 3.4 M solutions of NaCl, NaNO3, and KSCN, and it was found that vesicles of unfractionated lipids were more perturbed by chaotropic agents than polar lipids. The dependence of the relaxation times of perylene on temperature was studied in cell envelopes and in vesicles prepared from polar lipids, unfractionated lipids, and mixtures of polar and neutral lipids.

Lanyi, J. K.↗
NASA NTRS2000

Computer simulation of ion channel gating: the M(2) channel of influenza A virus in a lipid bilayer

The transmembrane fragment of the influenza virus M(2) protein forms a homotetrameric channel that transports protons. In this paper, we use molecular dynamics simulations to help elucidate the mechanism of channel gating by four histidines that occlude the channel lumen in the closed state. We test two competing hypotheses. In the "shuttle" mechanism, the delta nitrogen atom on the extracellular side of one histidine is protonated by the incoming proton, and, subsequently, the proton on the epsilon nitrogen atom is released on the opposite side. In the "water-wire" mechanism, the gate opens because of electrostatic repulsion between four simultaneously biprotonated histidines. This allows for proton transport along the water wire that penetrates the gate. For each system, composed of the channel embedded in a hydrated phospholipid bilayer, a 1.3-ns trajectory was obtained. It is found that the states involved in the shuttle mechanism, which contain either single-protonated histidines or a mixture of single-protonated histidines plus one biprotonated residue, are stable during the simulations. Furthermore, the orientations and dynamics of water molecules near the gate are conducive to proton transfer. In contrast, the fully biprotonated state is not stable. Additional simulations show that if only two histidines are biprotonated, the channel deforms but the gate remains closed. These results support the shuttle mechanism but not the gate-opening mechanism of proton gating in M(2).

NASA Center ARC↗
NASA NTRS2011

Implications of Weak-Link Behavior on the Performance of Mo/Au Bilayer Transition-Edge Sensors

Understanding the physical properties of the superconducting-to-normal transition is fundamental for optimizing the design and performance of transition-edge sensors (TESs). Recent critical current measurements of Mol Au bilayer test structures show that they act as weak superconducting links, exhibiting oscillatory, Fraunhofer-like behavior with applied magnetic field. In this paper we investigate the implications of this behavior for TES X-ray detectors, under operational bias conditions. These devices include normal metal features used for absorber attachment and unexplained noise suppression, which result in modifications to the previously reported critical current behavior. We present measurements of the logarithmic resistance sensitivity with temperature, a, and current, b, as a function of applied magnetic field and bias point within the resistive transition. Results show that these important device parameters exhibit similar oscillatory behavior with applied magnetic field, which in turn affects the signal responsivity and noise, and hence the energy resolution. These results show the significance of the critical current in determining the performance of TESs and hold promise to improve future.

Smith, Stephen J.↗