Saturation Length Research Articles

Analgesic effects of skin-to-skin contact and breastfeeding in procedural pain in healthy term neonates

The effectiveness of skin-to-skin contact to decrease pain from heel-lancing in healthy term neonates and whether breastfeeding in addition to skin-to-skin contact provided a more effective analgesia than skin-to-skin contact alone were investigated. A randomised, controlled trial was conducted in 107 neonates undergoing heel-lance. Infants were randomly assigned to three groups: (i) being breastfed with skin-to-skin contact (group 1, n=35), (ii) being held in their mother's arms with skin-to-skin contact but no breastfeeding (group 2, n=36), or (iii) lying on the table before, during and after painful stimulus (group 3, n=36). Physiological responses to pain were measured by heart rate and oxygen saturation changes and behavioural responses were measured by duration of crying and grimacing. Infants had a mean (SD) birthweight of 3355 (270) g and gestational age of 39.5 (0.6) weeks; at the time of the procedure, mean (SD) postnatal age was 33.1 (5) hours. There was no significant difference between the groups in clinical characteristics and time spent squeezing the heel. Heart rate, oxygen saturation changes and length of crying were significantly reduced in groups 1 and 2 compared with group 3 (p<0.001). No difference was found between group 1 and group 2. Grimacing was less in group 2 than in group 3 (p<0.001). In healthy term neonates, skin-to-skin contact with the mother and breastfeeding with skin-to-skin contact reduce both physiological and behavioural pain response. Breastfeeding in the 1st 2 postnatal days with skin-to-skin contact did not increase the analgesic effect of skin-to-skin contact alone.

Bedforms in a turbulent stream: formation of ripples by primary linear instability and of dunes by nonlinear pattern coarsening

It is widely accepted that both ripples and dunes form in rivers by primary linear instability; the wavelength of the former scaling on the grain size and that of the latter being controlled by the water depth. We revisit here this problem in a theoretical framework that allows to give a clear picture of the instability in terms of dynamical mechanisms. A multi-scale description of the problem is proposed, in which the details of the different mechanisms controlling sediment transport are encoded into three quantities: the saturated flux, the saturation length and the threshold shear stress. Hydrodynamics is linearized with respect to the bedform aspect ratio. We show that the phase shift of the basal shear stress with respect to the topography, responsible for the formation of bedforms, appears in an inner boundary layer where shear stress and pressure gradients balance. This phase shift is sensitive to the presence of the free surface, and the related effects can be interpreted in terms of standing gravity waves excited by topography. The basal shear stress is dominated by this finite depth effect in two ranges of wavelength: when the wavelength is large compared to the flow depth, so that the inner layer extends throughout the flow, and in the resonant conditions, when the downstream material velocity balances the upstream wave propagation. Performing the linear stability analysis of a flat sand bed, the relation between the wavelength at which ripples form and the flux saturation length is quantitatively derived. It explains the discrepancy between measured initial wavelengths and predictions that do not take this lag between flow velocity and sediment transport into account. Experimental data are used to determine the saturation length as a function of grain size and shear velocity. Taking the free surface into account, we show that the excitation of standing waves has a stabilizing effect, independent of the details of the flow and sediment transport models. Consequently, the shape of the dispersion relation obtained from the linear stability analysis of a flat sand bed is such that dunes cannot result from a primary linear instability. We present the results of field experiments performed in the natural sandy Leyre river, which show the formation of ripples by a linear instability and the formation of dunes by a nonlinear pattern coarsening limited by the free surface. Finally, we show that mega-dunes form when the sand bed presents heterogeneities such as a wide distribution of grain sizes.

Simulation of a prebunched free-electron laser with planar wiggler and ion channel guiding

A one-dimensional and nonlinear simulation of a free-electron laser with a prebunched electron beam, a planar wiggler, and ion-channel guiding is presented. Using Maxwell’s equations and full Lorentz force equation of motion for the electron beam, a set of coupled nonlinear differential equations is derived in slowly varying amplitude and wave number approximation and is solved numerically. This set of equations describes self-consistently the longitudinal dependence of radiation amplitude, growth rates, space-charge amplitude, and wave numbers together with the evolution of the electron beam. Because of using full Lorentz force equation of motion, it is possible to treat the injection of the beam into the wiggler. The electron beam is assumed cold, propagates with a relativistic velocity, ions are assumed immobile, and slippage is ignored. The effect of prebunched electron beam on saturation is studied. Ion-channel density is varied and the results for groups I and II orbits are compared with the case when the ion channel is absent. It is found that by using an ion channel/a prebunched electron beam growth rate can be increased, saturation length can be decreased, and the saturated amplitude of the radiation can be increased.

Optimal Charge of a Photocathode Gun for a Compact X-ray Free-Electron Laser

For a photocathode gun, the optimal charge per gun pulse is derived to give the theoretically allowed smallest saturation length of the X-ray free-electron laser based on the self amplified spontaneous emission scheme. The derivation is approximate, but the result is practically independent of specific machine design. The objective is to contribute to the study of a compact X-ray free-electron laser.

Laser assisted emittance exchange: Downsizing the x-ray free electron laser

A technique is proposed to generate electron beam with ultralow transverse emittance through laser assisted transverse-to-longitudinal emittance exchange. In the scheme a laser operating in the TEM10 mode is used to interact with the electron beam in a dispersive region and to initiate the emittance exchange. It is shown that with the proposed technique one can significantly downsize an x-ray free electron laser (FEL), which may greatly extend the availability of these light sources. A hard x-ray FEL operating at 1.5 {angstrom} with a saturation length within 30 meters using a 3.8 GeV electron beam is shown to be practically feasible.

Insuffisance pancréatique exocrine de l’enfant : diagnostic positif et étiologique

Lipid digestion is critical for infant development, and yet, the interconnection between lipid digestion and the microbiota is largely understudied. This review focuses on digestion of the human milk fat globule and summarizes the current understanding of the mechanisms underlying this process in infants. We first discuss the partial hydrolysis of milk fat in the stomach, which leads to rearrangement of lipid droplets, creating a lipid-water interface necessary for duodenal lipolysis. In the first few months of life, secretion of pancreatic triglyceride lipase, phospholipase A2, and bile salts is immature. The dominant lipases aiding fat digestion in the newborn small intestine are therefore pancreatic lipase-related protein 2 and bile salt–stimulated lipase from both the exocrine pancreas and milk. We summarize the interaction between ionic fatty acids and cations to form insoluble fatty acid soaps and how it is influenced by various factors, including cation availability, pH, and bile salt concentration, as well as saturation and chain length of fatty acids. We further argue that the formation of the soap complex does not contribute to lipid bioavailability. Next, the possible roles that the gut microbiota plays in lipid digestion and absorption are discussed. Finally, we provide a perspective on how the manufacturing process of infant formula and dairy products may alter the physical properties and structure of lipid droplets, thereby altering the rate of lipolysis.

Skeletal muscle lipotoxicity in insulin resistance and type 2 diabetes

Patients with insulin resistance and type 2 diabetes (T2DM) commonly exhibit elevated plasma free fat acid (FFA) and muscle fat (triglyceride) levels, which may either represent inborn errors of regulation of lipid metabolism, obesity, insulin resistance of adipose tissue or defective insulin secretion with an elevated rate of lipolysis. Alternatively, accumulation of different fat species in the circulation and tissues in T2DM may occur due to an impairment of oxidation of FFAs by the mitochondria (Petersen et al. 2005). Since the ground-breaking studies by Sir Philip Randle documenting the substrate competition between oxidation of fat and glucose, with phosphofructokinase and pyruvate dehydrogenase enzyme activities playing a key role (Randle et al. 1963), the ‘glucose fatty acid cycle’ and elevated FFA levels have been thought to play an important role in insulin resistance. Indeed, inhibition of lipolysis and FFA levels using a nicotinic acid derivative markedly improved in vivo peripheral insulin action including both oxidative and non-oxidative glucose metabolism in T2DM (Vaag et al. 1991). The extent to which increased availability of plasma FFA levels in itself impairs proximal insulin signalling transduction in healthy subjects is controversial (Storgaard et al. 2004). To this end, studies have suggested various additional, parallel or complementary mechanisms by which fatty acids adversely affect muscle insulin action and glucose uptake including degree of saturation and chain length of fatty acids as well as the conversion of fatty acids to the potentially deleterious lipid species ceramide and diaglycerol. Recent data have emerged that mitochondrial overload and limited capacity of the enzyme carnitine palmitoyl-transferase-1 (CPT-1) to transport cytosolic long-chain acyl CoA into the mitochondria may be involved in the development of fat-induced insulin resistance due to the accumulation of incompletely oxidized lipid intermediates (Koves et al. 2008).

Is There a Fatty Acid Taste?

Taste is a chemical sense that aids in the detection of nutrients and guides food choice. A limited number of primary qualities comprise taste. Accumulating evidence has raised a question about whether fat should be among them. Most evidence indicates triacylglycerol is not an effective taste stimulus, though it clearly contributes sensory properties to foods by carrying flavor compounds and altering texture. However, there is increasing anatomical, electrophysiological, animal behavior, imaging, metabolic, and psychophysical evidence that free fatty acids are detectable when non-taste cues are minimized. Free fatty acids varying in saturation and chain length are detectable, suggesting the presence of multiple transduction mechanisms and/or a nonspecific mechanism in the oral cavity. However, confirmation of "fatty" as a taste primary will require additional studies that verify these observations are taste specific. Oral exposure to free fatty acids likely serves as a warning signal to discourage intake and influences lipid metabolism.

Drain current model for nanoscale double-gate MOSFETs

A closed form inversion charge-based drain current model for a short channel symmetrically driven, lightly doped symmetric double-gate MOSFET (SDGFET) is presented. The model has physical origins, but has some fitting parameters included in order to yield a better match with TCAD device simulations. Velocity saturation and channel length modulation effects are self-consistently included in the model. The incorporation of DIBL effects in the model is based on a solution of the two-dimensional Laplace equation that had been reported earlier and that is believed to be especially suited when the physical gate-oxide thickness is not negligible compared to the silicon body thickness. Addition of support for body doping and low-field mobility degradation is also presented. A very good match is shown in I d–V g , I d–V d and g DS–V d curves and a reasonable match is shown in g m–V g curves, when compared with 2D device simulations. The match in various characteristics is shown for devices as short as 20 nm.

Laser-pumped coherent x-ray free-electron laser

In a laser-pumped x-ray free-electron laser (FEL) an intense laser field replaces the magnetic wiggler field of a conventional FEL. Depending on the intensity and quality of both the electron beam and pump laser, the Thomson backscattered radiation can be coherently amplified. In a conventional FEL the generation of x rays requires electron beam energies in the multi-GeV range. In a laser-pumped x-ray FEL, electron beam energies in the multi-MeV range would be sufficient. To generate coherent x rays with this mechanism a number of physics and technology issues must be addressed. Foremost among these are the stringent requirements placed on the electron beam quality and brightness as well as on the pump laser. The seed radiation for the laser-pumped FEL is the laser-induced spontaneous radiation. The evolution of incoherent radiation into coherent radiation as well as the power gain lengths associated with the coherent x rays are analyzed and discussed. There is excellent agreement between our analytical results and GENESIS simulations for the radiated power, gain length, conversion efficiency, linewidth, and saturation length. These issues, as well as others, necessary to achieve coherent amplified x rays in a laser-pumped FEL are discussed. While a coherent x-ray source would have a number of attractive features, the requirements placed on both the electron beam and pump laser are extremely challenging.

Giant aeolian dune size determined by the average depth of the atmospheric boundary layer

Depending on the wind regime, sand dunes exhibit linear, crescent-shaped or star-like forms resulting from the interaction between dune morphology and sand transport. Small-scale dunes form by destabilization of the sand bed with a wavelength (a few tens of metres) determined by the sand transport saturation length. The mechanisms controlling the formation of giant dunes, and in particular accounting for their typical time and length scales, have remained unknown. Using a combination of field measurements and aerodynamic calculations, we show here that the growth of aeolian giant dunes, ascribed to the nonlinear interaction between small-scale superimposed dunes, is limited by the confinement of the flow within the atmospheric boundary layer. Aeolian giant dunes and river dunes form by similar processes, with the thermal inversion layer that caps the convective boundary layer in the atmosphere acting analogously to the water surface in rivers. In both cases, the bed topography excites surface waves on the interface that in turn modify the near-bed flow velocity. This mechanism is a stabilizing process that prevents the scale of the pattern from coarsening beyond the resonant condition. Our results can explain the mean spacing of aeolian giant dunes ranging from 300 m in coastal terrestrial deserts to 3.5 km. We propose that our findings could serve as a starting point for the modelling of long-term evolution of desert landscapes under specific wind regimes.

Decoherence of Bell states by local interactions with a dynamic spin environment

We study the evolution of a system of two qubits, each of which interacts locally with a spin chain with nontrivial internal Hamiltonian. We present an exact solution to this problem and analyze the dependence of decoherence on the distance between the interaction sites. In the strong coupling regime we find that decoherence increases with increasing distance. In the weak coupling regime the dependence of decoherence with distance is not generic (i.e., it varies according to the initial state). Decoherence becomes independent of distance when the latter is over a saturation length $l$. Numerical results for the Ising chain suggest that the saturation scale is related to the correlation length $\ensuremath{\xi}$. For strong coupling we display evidence of the existence of non-Markovian effects (such as environment-induced interactions between the qubits). As a consequence the system can undergo a quasiperiodic sequence of ``sudden deaths and revivals'' of entanglement, with a time scale related to the distance between qubits.

Synthesis and physical properties of mono-estolides with varying chain lengths

Saturated mono-estolide methyl esters and enriched saturated mono-estolide 2-EH esters were synthesized from oleic and different saturated fatty acids under three different synthetic routes. Estolide numbers (EN), the average number of fatty acid units added to a base fatty acid, varied with synthetic conditions. The attempts at obtaining saturated mono-estolide 2-EH esters, EN = 1, via distillation proved to be challenging, which lead to estolide samples with EN > 1 and the pour point values followed the same trend as the high EN estolides. The other synthetic routes provided saturated mono-estolide methyl esters with EN = 1. The resulting pour point values showed a linear relationship between the saturated capping chain length and pour point. As the saturated capping chain length increased the pour points also increased (higher temperatures): C-2 capped −30 °C, C-10 capped −12 °C, and C-18 capped 3 °C. The saturated mono-estolide methyl ester viscosities also showed an increase in viscosity at 40 and 100 °C as the saturated chain lengths increased. The viscosities for the C-4 saturated mono-estolide methyl ester was 9.5 cSt at 40 °C and 2.6 cSt at 100 °C, while medium chain length derivations (C-10 saturated mono-estolide methyl ester) were 19.7 cSt at 40 °C and 4.2 cSt at 100 °C, and at the longer chain length derivations (C-18 mono-estolide methyl esters) were 27.6 cSt at 40 °C and 10.7 cSt at 100 °C. In general, a new series of saturated oleic mono-estolide methyl esters were synthesized and physical properties were collected. The physical property data indicated that both chain length and EN affect low temperature properties.

Dependence of second-harmonic generation in ferroelectric liquid crystals with a defect on the optical gap

Second-harmonic generation (SHG) in ferroelectric liquid crystal with a twist defect is studied by de Vries' solution. It is shown that the width of the photonic band gap for the SH wave is an important factor to determine the saturation length. SHG is effectively enhanced by using narrow photonic band gaps.

Advanced studies at the VISA FEL in the SASE and seeded modes

The VISA (Visible to Infrared SASE Amplifier) program has been in operation at the BNL ATF since the year 2000. The program has produced numerous results including, demonstrated saturation at 840 nm with a gain length of 18 cm, chirped beam amplification with the observation of anomalously large bandwidth of the emitted radiation, and successful benchmarking of a start-to-end simulation suite to measured results. This paper will review the prior results of the VISA program and discuss planned novel measurements, including detuning studies of a 1 μ m seeded amplifier, and measurements of the orbital angular momentum of the emitted radiation. The installation of a dedicated chicane bunch compressor followed by an x-band linac to mitigate energy spread will allow for high-current operations (reduced saturation length, and deep-saturation studies). Other measurements, such as coherent transition undulator radiation, are also proposed.

Modeling Particulates Effects on the Cathode Current Capacity in Crevice Corrosion

The presence of particulates within thin electrolyte films covering the cathode in corroding systems affects the cathodic current distribution and the total current capacity. These effects are due to increased solution resistance (“volume effect”) and decreased available electrode area (“surface effect”) associated with the presence of the particulates. This work simulates and characterizes the effect of uniform particulate layers embedded within thin electrolyte films on the cathodic current capacity under steady-state conditions. Particulate configurations consisting of varying particle sizes, shapes, arrangements, volume fraction, and electrode coverage were numerically modeled. It is concluded that the effects associated with the particles can be fully accounted for in terms of two corrections: the decrease in the electrolyte conductivity due to volume blockage by the particles is correlated using Bruggeman’s equation, while the electrode surface coverage by the particles is modeled in terms of an area correction to the electrode kinetics. For the range of parameters analyzed, applying these two corrections enables the modeling of particle-containing thin electrolyte films covering the cathode in terms of equivalent homogenous electrolytes with modified properties. The latter can then be analyzed using simpler approaches. Particulate effects on cathode capacity at saturation and saturation length are also quantified.

Effects of ion-channel guiding on the saturation mechanism of a single-pass free-electron laser

In this paper we study the nonlinear dynamics of a single-pass free-electron laser in the presence of an ion-channel guide. A set of coupled nonlinear differential equations in 1D approximation is employed, which governs the self-consistent evolution of an electromagnetic wave in the presence of a cold, cylindrically symmetric electron beam. The electron beam propagates at a relativistic velocity through the combination of a wiggler field and of a channel of immobile ions. The effects of the ion channel on the saturation of an amplifier free-electron laser are illustrated. Numerical simulations are performed using the parameters of the Fermi@Elettra single-pass free-electron laser as a reference. The effect of the ion channel is shown to have an impact on both the saturation length and the output power.

Injection of harmonics generated in gas in a free-electron laser providing intense and coherent extreme-ultraviolet light

Conventional synchrotron radiation sources enable the structure of matter to be studied at near-atomic spatial resolution and picosecond temporal resolution. Free-electron lasers promise to extend this down to femtosecond timescales. The process by which free-electron lasers amplify synchrotron light—known as self-amplified spontaneous emission1,2,3—is only partially temporally coherent, but this can be improved by seeding it with an external laser4,5. Here we explore the use of seed light produced by high-order harmonic generation in a gas6,7,8,9, covering wavelengths from the ultraviolet to soft X-rays. Using the SPring-8 Compact SASE Source test accelerator10,11,12, we demonstrate an increase of three orders of magnitude in the intensity of the fundamental radiation at 160 nm, halving of the free-electron laser saturation length, and the generation of nonlinear harmonics13 at 54 nm and 32 nm. The low seed level used in this demonstration suggests that nonlinear harmonic schemes should enable the generation of fully coherent soft X-rays at wavelengths down to the so-called ‘water window’, vital for the study of biological samples.

Dissipation of Quantum Turbulence in the Zero Temperature Limit

Turbulence, produced by an impulsive spin down from angular velocity Omega to rest of a cube-shaped container, is investigated in superfluid 4He at temperatures 0.08 K-1.6 K. The density of quantized vortex lines L is measured by scattering negative ions. Homogeneous turbulence develops after time t approximately 20/Omega and decays as L proportional, t-3/2. The corresponding energy flux =nu'(kappaL)2 proportional, t-3 is characteristic of quasiclassical turbulence at high Re with a saturated energy-containing length. The effective kinematic viscosity in T=0 limit is nu'=0.003kappa, where kappa=10(-3) cm2 s(-1) is the circulation quantum.

Reply to “Comment on ‘Minimal size of a barchan dune’ ”

We reply to the preceding comment by Andreotti and Claudin [Phys. Rev. E 76, 063301 (2007)] on our paper [Phys. Rev. E 75, 011301 (2007)]. We show that the equations of the dune model used in our calculations are self-consistent and effectively lead to a dependence of the minimal dune size on the wind speed through the saturation length. Furthermore, we show that Meridiani Planum ripples are probably not a good reference to estimate the grain size of Martian dune sands: the soil in the ripple troughs at the landing site is covered with nonerodible elements (``blueberries''), which increase the minimal threshold for saltation by a factor of 2.0. We conclude that, in the absence of large fragments as the ones found at the landing site, basaltic grains of diameter $d=500\ifmmode\pm\else\textpm\fi{}100\text{ }\ensuremath{\mu}\text{m}$ that compose the large, typical dark Martian dunes [K. S. Edgett and P. R. Christensen, J. Geophys. Res. 96, 22765 (1991)] probably saltate during the strongest storms on Mars. We also show that the wind friction speed ${u}_{\ensuremath{\ast}}\ensuremath{\approx}3.0\text{ }\text{m}/\text{s}$ that we found from the calculations of Martian dunes is within the values of maximum wind speeds that occur during Martian storms a few times a decade [R. E. Arvidson et al., Science 222, 463 (1983); H. J. Moore, J. Geophys. Res. 90, 163 (1985); R. Sullivan et al., Nature (London) 436, 58 (2005); D. J. Jerolmack et al., J. Geophys. Res. 111, E12S02 (2006)]. In this manner, the dune model predicts that Martian dunes can be formed under present Martian conditions, with no need to assume other conditions of wind and atmosphere that could have prevailed in the past.