Half-maximum Points Research Articles

Analysis of Tapered Fibre Optic Surface Plasmon Resonance Bio-Sensor Chip With Highly Perturbed Taper Profiles.

A numerical model based on the Transfer matrix method (TMM) is proposed for the first time to study the gold coated tapered fibre optic surface plasmon resonance (SPR) with eight different types of taper profiles namely linear, exponential-linear, Gaussian, quadratic, sinusoidal, error function type and highly perturbed taper profile so-called chirp type of profile. The performance in terms of sensitivity, full width at half maximum (FWHM), detection accuracy (D.A.), amplitude dip, and half power points are estimated with respect to tapering ratio and choices of taper profile. It is found that sensitivity increased almost linearly with the taper ratio of each taper choice for the account of the reduction of detection accuracy. It has been found that sensitivity is highest for the case of chirp taper profile and lowest for the case of quadratic taper profile at low taper ratio. In this study, the aqueous solution is considered for sensor development which is adulterated by biomolecules species like DNA, blood samples, etc.

The estimation of coronary artery calcium thickness by computed tomography angiography based on optical coherence tomography measurements.

Optical coherence tomography (OCT) is recommended to be the most appropriate modality in assessing calcium thickness, however, it has limitations associated with infrared attenuation. Although coronary computed tomography angiography (CCTA) detects calcification, it has low resolution and hence not recommended to measure the calcium size. The aim of this study was to devise a simple algorithm to estimate calcium thickness based on the CCTA image. A total of 68 patients who had CCTA for suspected coronary artery disease and subsequently went on to have OCT were included in the study. 238 lesions of them divided into derivation and validation dataset at 2:1 ratio (47 patients with 159 lesions and 21 with 79, respectively) were analyzed. A new method was developed to estimate calcium thickness from the maximum CT density within the calcification and compared with calcium thickness measured by OCT. Maximum Calcium density and measured calcium-border CT density had a good correlation with a linear equation of y = 0.58x + 201 (r = 0.892, 95% CI 0.855-0.919, p < 0.001). The estimated calcium thickness derived from this equation showed strong agreement with measured calcium thickness in validation and derivation dataset (r2 = 0.481 and 0.527, 95% CI 0.609-0.842 and 0.497-0.782, p < 0.001 in both, respectively), more accurate than the estimation by full width at half maximum and inflection point method. In conclusion, this novel method provided the estimation of calcium thickness more accurately than conventional methods.

Size estimation of coating disbonds using the first derivative images in pulsed thermography

It has been a challenging task to estimate the size of thermal barrier coating disbonds by pulsed thermography, because thermal images are naturally blurred by lateral heat diffusion around the edge of defect. In the present work the first derivative images were employed to weaken the effect of lateral thermal diffusion, in a similar way as for Full Width at Half Maximum (FWHM) based on thermal images. Theoretical analysis introduced the correspondence of thermal profile and the first derivative profile along diameter of an in-plane defect, it’s found that half maximum points of two side dips in the first derivative profile is much closer to the real defect edge than the half maximum points of positive peak in temperature profile. Experimental results suggested that FWHM-1st based on the first derivative images generated more precise estimated values of coating disbonds than FWHM did. In addition, Evolution of FWHM and FWHM-1st in cooling process also revealed that it’s the early images in regular regime of transient heat conduction give more precise estimation of disbonding size instead of traditionally considered early images just at the final instant of optical pulse.

Low threshold L-band mode-locked ultrafast fiber laser assisted by microfiber-based carbon nanotube saturable absorber

We demonstrate a passively mode-locked erbium-doped fiber laser in L-band wavelength region with low mode-locking threshold employing a 1425 nm pump wavelength. The mode-locking regime is generated by microfiber-based saturable absorber using carbon nanotube-polymer composite in a ring cavity. This carbon nanotube saturable absorber shows saturation intensity of 9 MW/cm2. In this work, mode-locking laser threshold is observed at 36.4 mW pump power. At the maximum pump power of 107.6 mW, we obtain pulse duration at full-width half-maximum point of 490 fs and time bandwidth product of 0.33, which corresponds to 3-dB spectral bandwidth of 5.8 nm. The pulse repetition rate remains constant throughout the experiment at 5.8 MHz due to fixed cavity length of 35.5 m. Average output power and pulse energy of 10.8 mW and 1.92 nJ are attained respectively through a 30% laser output extracted from the mode-locked cavity. This work highlights the feasibility of attaining a low threshold mode-locked laser source to be employed as seed laser in L-band wavelength region.

Raman spectroscopy of Lithium modified Sodium Niobate at elevated temperature

ABSTRACTWe have carried out high temperature Raman spectroscopy studies on a technologically important material Li0.12Na0.88NbO3 (LNN12) in a wide temperature range from 298 K to 1073 K. The variations of Raman mode frequencies and full width at half maximum point towards various structural transitions in this temperature range. A new mode which appears around 650 cm−1 at 473 K has been found to have anomalous temperature dependence. Furthermore, the symmetric stretching and the asymmetric stretching modes have opposite temperature dependence in some temperature ranges. At the highest temperature 1073 K (in cubic phase), there are two broad bands centered around 200 cm−1 and 600 cm−1. The transition temperatures obtained by Raman scattering study are found to be consistent with those obtained by powder diffraction techniques. Softening of stretching modes across transitions is correlated with the symmetrization of NbO6 octahedra in the compound.

A NEARLY NAKED SUPERMASSIVE BLACK HOLE

ABSTRACT During a systematic search for supermassive black holes (SMBHs) not in galactic nuclei, we identified the compact, symmetric radio source B3 1715+425 with an emission-line galaxy offset ≈ 8.5 kpc from the nucleus of the brightest cluster galaxy (BCG) in the redshift z = 0.1754 cluster ZwCl 8193. B3 1715+425 is too bright (brightness temperature T b ∼ 3 × 10 10 K at observing frequency ν = 7.6 GHz ) and too luminous (1.4 GHz luminosity L 1.4 GHz ∼ 10 25 W Hz − 1 ) to be powered by anything but an SMBH, but its host galaxy is much smaller ( ∼ 0.9 kpc × 0.6 kpc full width between half-maximum points) and optically fainter (R-band absolute magnitude M r ≈ − 18.2 ) than any other radio galaxy. Its high radial velocity v r ≈ 1860 km s − 1 relative to the BCG, continuous ionized wake extending back to the BCG nucleus, and surrounding debris indicate that the radio galaxy was tidally shredded passing through the BCG core, leaving a nearly naked SMBH fleeing from the BCG with space velocity v ≳ 2000 km s − 1 . The radio galaxy has mass M ≲ 6 × 10 9 M ⊙ and infrared luminosity L IR ∼ 3 × 10 11 L ⊙ close to its dust Eddington limit, so it is vulnerable to further mass loss from radiative feedback.

Direct determination of threshold condition in DG-MOSFETs from the gm/ID curve

In this work we apply the current-based threshold voltage definition (equality between the drift and diffusion components of drain current) to intrinsic symmetric double-gate MOSFETs. We show that the half maximum point of the gm/ID (transconductance-to-current ratio) curve in the linear region corresponds exactly to the condition IDdrift=IDdiff when mobility variation is neglected. Numerical simulations show that the threshold voltages determined from the gm/ID curve and from the IDdrift=IDdiff condition differ by about ϕt/2 (one half of the thermal voltage) when considering realistic mobility variations. Simulation results show that the threshold voltages determined with the gm/ID procedure are close to those obtained with the Y (=ID/gm) function method for a considerable range of silicon film thicknesses, channel lengths, and temperature values. The current-based procedure has also been successfully applied experimentally to a FinFET over a wide temperature range.

The effects of cascade length, kinetics and feedback loops on biological signal transduction dynamics in a simplified cascade model

How intracellular signals are propagated with appropriate strength, duration and fidelity over time is poorly understood. To address these issues, intracellular signal transduction was studied both analytically and numerically using a simplified cascade model. The main observations can be summarized as follows: when the response kinetics is of the Michaelis–Menten type, the signal strength will always reach the same magnitude as the cascade length increases, regardless of the type of stimulus applied (i.e. either continuous or unitary pulse). However, when the response kinetics is of the Hill type (Hill coefficient >1), there exists a stimulation threshold. If the stimulus is below the threshold, the signal decays toward zero; in contrast, if the stimulus is above the threshold, the signal amplitude reaches a nonzero steady state. The time taken for the signal to proceed through the cascade increases as the half-maximum point, or Hill coefficient, increases, whereas the duration of the output signal at the end of the cascade decreases as the half-maximum point increases. In the presence of positive feedback, the stimulation threshold increases; under these conditions, the feedback strength necessary for bistability changes (with power-law characteristics) inversely related to the length of the cascade. In the presence of negative feedback, oscillations are induced when the Hill coefficient is greater than 1 and the cascade has more than two steps. Likewise, the feedback strength required to generate oscillations changes (again with power-law characteristics) inversely with the length of the cascade.

Analysis of the development of a nanosecond pulsed corona on a two-wire transmission line using the method of q-v curves

An indoor two-wire transmission line (TL) was used to investigate the development of corona discharge during the propagation of a short HV pulse, for both polarities. The pulse voltage peak ranged from 40 to 100 kV with a pulse width of 5 ns at the full-width half-maximum points. The charge per unit length q was derived from the measurement of the voltage and current at the beginning of the TL. The q-v hysteresis curves were used to analyze the properties of the corona developed along the TL. It was found that at peak voltages much higher than the corona onset voltage, the q-v curves’ characteristics were similar to those found for μs surge pulses at overhead transmission lines. For peak voltages close to the corona onset, the corona exhibited charge neutralization oscillations and the charge buildup delay time vanished. It was also found that the positive corona is up to about six times more dissipative than the negative one, even though the negative corona onset voltage was somewhat lower than the positive, and q at the peak voltage is similar for both polarities.

Orientation dependence in molecular dynamics simulations of shocked single crystals

The entry distribution in angular momentum and excitation energy for the formation of ${}^{254}\mathrm{No}$ has been measured after the ${}^{208}\mathrm{Pb}{(}^{48}\mathrm{Ca},2n)$ reaction at 215 and 219 MeV. This nucleus is populated up to spin $22\ensuremath{\Elzxh}$ and excitation energy $\ensuremath{\gtrsim}6\mathrm{MeV}$ above the yrast line, with the half-maximum points of the energy distributions at $\ensuremath{\sim}5\mathrm{MeV}$ for spins between $12\ensuremath{\Elzxh}$ and $22\ensuremath{\Elzxh}$. This suggests that the fission barrier is $\ensuremath{\gtrsim}5\mathrm{MeV}$ and that the shell-correction energy persists to high spin.

Entry distribution, fission barrier, and formation mechanism of 254102No

The entry distribution in angular momentum and excitation energy for the formation of 254No has been measured after the 208Pb(48Ca,2n) reaction at 215 and 219 MeV. This nucleus is populated up to spin 22Planck's over 2pi and excitation energy greater, similar6 MeV above the yrast line, with the half-maximum points of the energy distributions at approximately 5 MeV for spins between 12Planck's over 2pi and 22Planck's over 2pi. This suggests that the fission barrier is greater, similar5 MeV and that the shell-correction energy persists to high spin.

The Emission‐Line Properties of Low‐Redshift Quasi‐stellar Objects. II. The Relation to Radio Type

We present optical spectrophotometry of 45 quasars in the redshift range 0.045-0.592. These data are combined with the sample of 87 low-redshift quasar and QSO spectra obtained by Boroson & Green for a more extensive investigation of the relation of the properties of the broad Hβ, [O III] λ5007, and optical Fe II emission lines to the objects' radio, optical, and X-ray continuum parameters. We derive a complete correlation matrix for the quasars and perform two-sample tests on the subsamples of flat radio spectrum (FRS) quasars, steep radio spectrum (SRS) quasars, and radio-quiet objects (QSOs). Our principal findings are as follows: 1. We confirm that the width of the Hβ profile at quarter-maximum and half-maximum points is inversely correlated with the ratio of the 6 cm radio core flux to that measured from the optical continuum at 5500 A, which has been argued to be an indicator of the orientation of the objects' radio axis under beaming models. The Hβ profile widths do not correlate strongly with any line or continuum parameter likely to be an indicator of the intrinsic power of the central engine, including the extended radio luminosity. A principal components analysis of the correlation matrix does not reveal any clear trends separate from the dependence of Hβ profile width on the orientation indicator, and we find no evidence of a decrease in the strength of the profile base component in FRS quasars relative to SRS quasars from a simple line deblending procedure. 2. The two-sample tests reveal several strong differences between the quasar and QSO subsamples, including differences between samples closely matched in optical luminosity. While QSOs are statistically closer to FRS quasars than SRS quasars in their emission-line properties, the FRS quasars still have significantly wider and more redward asymmetric Hβ profiles, stronger [O III] λ5007 emission, and weaker optical Fe II emission. The variance of the Hβ profile width and asymmetry parameters is also significantly larger among the combined sample of FRS and SRS quasars than among the QSOs. From the combined quasar and QSO sample, we confirm that there is an inverse correlation between soft X-ray luminosity and the equivalent width of the optical Fe II emission complex in the range ~λλ4434-4684. 3. The Balmer line profiles of several of the quasars show a division into two components, a core of intermediate (~103 km s-1) velocity width, and a very broad (~104 km s-1) base that is typically redshifted with respect to systemic velocity. This supports evidence that the broad-line region is divided into an inner Very Broad Line Region and an outer Intermediate Line Region. A few objects also display unusually strong emission in He II λ4686 and/or He I λ5876, while in other objects these lines are weak or absent. It is presently unclear whether these differences are intrinsic to the objects or else represent transient events caused by the dynamical evolution of the broad-line gas. The results for the quasar sample are consistent with unified models of FRS and SRS quasars and the interpretation that the change in profile widths arises from differing views of a flattened broad-line region with a strong component of planar motion. Under a unified model we estimate the ratio of planar to random BLR motions to be ~7:1. Assuming that the profile width and asymmetry parameters trace the mass of the central black hole, the distributions of these parameters indicate a larger average hole mass and a larger range of hole masses among the quasars than the QSOs, consistent with the model in which quasar black holes are the rapidly spinning product of the coalescence of two or more black holes at the centers of merged galaxies.

Laser induced fluorescence diagnostic for measuring small magnetic fields

A novel, spatially and temporally resolved diagnostic is being developed to measure small B fields by detecting Zeeman shifts much smaller than the transition linewidth. This diagnostic technique will be used to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as envisioned for particle beam fusion. High sensitivity is achieved by a variation on the Babcock technique using laser-induced fluorescence (LIF) spectroscopy. The LIF from a J=1→0 transition in a probe species is viewed parallel to B. In this direction, ΔM=0 fluorescence is not observed, while ΔM=±1 fluorescence is right- and left-circularly polarized and can be measured separately using polarization filters. If a narrow-band pump laser is tuned to a half-maximum point of the unsplit transition line, the presence of the magnetic field shifts one of the ΔM=±1 absorption transitions into resonance with the laser and shifts the other transition further out of resonance. For small field strengths, the difference in the fluorescence signals is proportional to the Zeeman split.

Beryllium foil transition-radiation source for x-ray lithography

We have measured the total soft-x-ray power from a transition radiator composed of a stack of 25 beryllium foils each 1.0 μm thick which were penetrated by a relativistic electron beam whose maximum power was approximately 7 kW. The maximum total soft-x-ray power was measured to be 15.2 mW for a 245 MeV, 37 μA electron beam. The bandwith of the radiation at the full width half maximum points was calculated to be between 0.6 and 1.6 keV. In addition, we have exposed photoresist-coated silicon wafers at a distance of 3 m from the radiator. Exposure times of the bare resist were as short as 120 s for 5 cm2 of wafer are (resist sensitivity is 55.6 mJ/cm2). The shortest time for mask/wafer exposure was 180 s for 5 cm2.

Sensitivity transformation for vertebrate vision

The visual response to a flash given in the dark is known to saturate according to the Michaelis-Menten relationship. Nevertheless, the incremental response from increasing levels of mean luminance tends to follow a Weber-Fechner relationship well into the saturation range determined from the Michaelis-Menten results. This sensitivity transformation from Michaelis-Menten to Weber-Fechner is an important characteristic of light adaptation in the vertebrate retina. Recent studies concerning the role of calcium in photoreceptor adaptation have shown that the relaxation from peak to plateau in the response of isolated photoreceptors was absent under conditions in which adaptation was blocked. Comparing the pronounced relaxation from peak to plateau in turtle horizontal cells with the absence of such relaxation in the catfish response, we noted also that turtle incremental sensitivity shows a Weber-Fechner relationship while catfish incremental sensitivity more closely follows the local slope of the Michaelis-Menten relation. Based on these observations, we have obtained an expression to relate the relaxation from peak to plateau with the sensitivity transformation. We assume that adaptation shifts the half-maximum point of the Michaelis-Menten curve so that the light response relaxes to a plateau value equal to a specified fraction phi of the peak response. We show that this manipulation alone results in a transformation from Michaelis-Menten kinetics to Weber-Fechner sensitivity.

Developing a More Focal Magnetic Stimulator. Part I

Some general properties of currents induced by magnetic stimulators in volume conductors of any shape are first reviewed. Then, the property of focality (concentration at some internal point) of the current induced in a spherical model of the head is discussed, due to coils of various orientations and configurations. It is shown that one important property for focality is the complete absence of the radial component of current, regardless of the coil used. The theoretically computed current distributions in the sphere produced by three different coils are illustrated. These are (1) a circular coil parallel to the head (very nonfocal). (2) a circular coil erect on the head (more focal), and (3) a figure-eight coil parallel to the head (most focal). A computational search for yet more focal coil configurations shows that the figure-eight focality can only be altered somewhat, but basically not improved. A plot of focality of the figure-eight coil versus the diameter of its coils shows an improvement in focality with decreasing diameter down to one cm. At this diameter, the induced current at a level 2 cm below the coil is concentrated in a band 1.5 cm wide (half-maximum points). Finally, it is noted that as the diameter of the figure-eight coil is decreased, the current in the coil necessary for stimulation increases rapidly, with increasing engineering problems.

Rapid automatic compensation for charging effects during the SIMS depth profiling of semiconductors

Quadrupole mass spectrometer SIMS instruments have an energy bandwith of approximately 10 eV, sufficient to sample the richest portion of the secondary ion emission, provided that the instrumental energy window is correctly placed. Changes > 1 V in the potential of the starting surface can change the instrumental sensitivity due to a shift and shape change in the energy spectrum of emitted ions. We show that non-uniform surface potential changes occur during the depth profiling of semiconductors, which can exceed 10 V even in a simple implant. Serious errors occur in the profiles obtained, which are not necessarily apparent unless specific tests are made whilst profiling. We describe a method for unambiguously identifying the occurrence of surface charging, sensing its magnitude, and applying a compensation potential to the sample under computer control. The method is based on (i) the inclusion in the profile of two channels tuned to the same molecular ion (e.g. Si 2O + in silicon) but set up close to the high and low energy half-maximum points in the energy spectrum and (ii) the experimental observation that the change in instrumental transmission with sample potential in the vicinity of these points is approximately linear. By the application of a simple model for the energy spectrum shape the surface potential can be computed in real time and voltage feedback applied to compensate for any changes.

Measurement of low-energy electrons in the day airglow and day side auroral zone from Atmosphere Explorer C

The photoelectron spectrometer experiment on Atmosphere Explorer C has obtained high-resolution spectra of the energy distribution of 2- to 500-eV electrons in the thermosphere at altitudes above 155 km. The photoelectron spectrum in the day airglow has been measured in detail over a wide range of altitude, latitude, and local time. Structure observed near 27 eV is assigned to photoelectrons ejected from atomic oxygen by the intense solar He II (304 A) radiation. The photoelectron energy distribution is shown to have a sharp cutoff near 60 eV. In addition to the day airglow data, spectra are also presented showing low-energy (100--500 eV) electron precipitation near the polar boundary of the auroral oval at magnetic local times near 0830. The precipitation is a low-energy inverted ''V'' type event occurring over an extremely narrow range of invariant latitude ($delta$$lambda$ approximately 0.3$sup 0$). The electron stream is about 50 eV wide at the half-maximum intensity points and changes in energy from 100 to 500 eV. Instrument calibration in the laboratory, performance of the experiment in orbit, and plans for further analysis of the large body of data which now exists are discussed in detail. (auth)

Artificial injection of electrons into the geomagnetic field by teak and orange, low-altitude bursts of 1958

Recent analysis of Explorer 4 data establishes that a shell of trapped electrons at L = 1.2 approximately 115 km wide at the half-maximum intensity points resulted from the Teak burst 77 km above Johnston Island, August 1, 1958. Maximum unidirectional flux (Ee>0.58 Mev) above background was 1.4 × 105 electrons cm−2 ster−1 sec−1. The shell was observed for about three days from the Johannesburg, Lima, Singapore, and Johnston Island tracking stations. Buildup at the L = 1.2 shell was not immediate, reaching a maximum about 24 hours after the event. Initial observations (Singapore 18 min and Johnston Island 7 hours after the burst) showed maximum trapping at L =. 1.14. It is estimated that between 1019 and 1020 electrons were trapped one hour after the burst. Artificial injection from Orange (43 km) was found to be located principally above Johnston Island and was of short term (less than 1 day) and small magnitude.

Intrinsic coercive force of rare earth iron garnets near the compensation temperature

The intrinsic coercive force of single crystals of those rare earth iron garnets having magnetization compensation temperatures greater than 77°K has been measured as a function of temperature and orientation with particular emphasis given to the temperature range near the magnetization compensation temperature. A single peak in the intrinsic coercive force was observed at the magnetization compensation temperature for almost all of the samples and for all principal orientations. Typically, the peak value of the coercive force was 50 Oe independent of material and orientation with a temperature difference between half-maximum points of less than 3°K. A single-domain model is proposed which concludes that the iron sublattice is primarily responsible for the coercive force near the magnetization compensation temperature and that complete magnetization compensation cannot occur due to the susceptibility of the rare earth sublattice. This leads to a finite coercive force at the magnetization compensation temperature.