Large Interference Effects Research Articles

Influence of the deposition conditions of SnO2 thin films by reactive sputtering on the sensitivity to urban pollutants

Abstract Thin films of SnO 2 were deposited by r.f. magnetron sputtering from a SnO 2 target varying the oxygen concentration from 0 to 20% within the sputtering plasma. The samples were characterized by electrical conductivity measurements for different pollutant gas mixtures. The electrical measurements were performed in a temperature range between 100 and 350°C with NO 2 concentrations varying from 50 to 800 ppb and also with interference gases such as CO (10 ppm) and H 2 O (∼1–80%). The aim of the work was to determine the optimum concentration of oxygen introduced in the sputtering plasma to obtain the best response to these gases on using tin oxide as gas sensor. Techniques such as XPS and GAXRD were used to study the influence of the deposition parameters on the stoichiometry and morphology of the SnO 2 thin films. It was observed that thin films deposited at room temperature and with the sputtering plasma containing 8% of O 2 showed the best sensitivity values, and therefore, the optimum number of adsorption sites needed for a good gas adsorption. These sensors had a SnO 2 grain size of ∼5 nm, all of them were substoichiometric before the thermal treatment and the film growth was columnar. A selective response to NO 2 and CO/air mixtures can be achieved by suitable choice of the sensor operating temperature. The results obtained with a relative humidity (∼1–80%) on the sensitivity to low NO 2 concentrations need further investigation due to the large interference effect of water vapor shown at all operating temperatures.

Minimising mutual coupling in thick substrate microstripantenna arrays

A new method based on the reaction concept, is used to assess the mutual coupling experienced by two adjacent circular microstrip antennas on a thick substrate. The coupling owing to surface waves is separated out from that due to the direct radiation and the large interference effects exhibited by the former create deep nulls in the overall mutual coupling characteristic: the nulls being dependent on the given choice of substrate geometry and element separation distance. Finally, the application of this coupling minimisation technique to practical arrays having many elements is briefly commented on.

Chromium speciation by a surfactant-coated alumina microcolumn using electrothermal atomic absorption spectrometry

A simple and convenient method has been developed for the speciation of chromium(III) and chromium(VI) in aqueous solutions using a sodium dodecyl sulphate coated alumina micro-column (1.5 cm × 5 mm i.d.) and graphite furnace-atomic absorption spectrometry (GF-AAS). Under the optimized conditions (pH 0.6, adjusted with hydrochloric acid; flow rate, 1 ml min −1) chromium(VI) is retained on the column and chromium(III) is collected and determined by GF-AAS. Total chromium is directly determined by GF-AAS and chromium(VI) is calculated by difference. The relative standard deviations (10 replicate analyses) at the 20 μg l −1 level for chromium(III) and chromium(VI) and at the 40 μg l −1 level for total chromium were 1.4%, 3.6% and 1.8%, and the corresponding limits of detection (based on 3σ) were 0.57 μg ml −1, 0.61 μg ml −1 and 0.35 μg l −1 respectively. No large interference effects have been observed from other investigated species and the method has been successfully applied to a range of water samples.

Study of the 3 ππ+- → 0ν τ decay in Aleph

Using Aleph data until 1993, the branching fraction of the τ into three charged π s and one π 0 has been measured to be: B ( τ ± → 3 ππ 0 ) = (4.21 ± ±.14)%. The resonant structure of this channel has also been investigated. We find a clear signal for the ω meson corresponding to a branching ratio of: B ( τ ± → ωπ ) = (1.82 ±.16)%. In this sub-channel, we bound the contribution from any 2 nd -class current to less than 13% at a 95% confidence level. The non- ω part is found to be consistent with single production i.e. ρππ . An estimate of the relative rates of the various charges of the ρ is also performed but remains inaccurate because of large interference effects.

Increased priming interference at a long SOA with brief masked targets.

Abstract This experiment tests a prediction of a model of priming proposed by McLeod and Walley (1989) in which interference is caused by inhibitory processes between nodes in semantic memory. This model predicts that interference normally found in a high cue validity condition at long SOAS will be considerably increased when a brief target is masked. This prediction was confirmed.In a priming task it has typically been found that interference associated with a semantically unrelated prime occurs only when the target follows the prime at a long stimulus onset asynchrony (SOA) and subjects pay attention to the prime, using it as a cue to the target (e.g., Neely, 1977). This pattern of priming interference is well accounted for by Posner and Snyder's (1975) two process model of attention.It has sometimes been found, however, that priming interference occurs with short SOA's: McLeod and Walley (1989), for example, found large interference effects with a short SOA in both a high and a low cue validity condition when brief targets were immediately masked, effects not easily explained by the two process model. To explain these effects, we have proposed a model of priming in which nodes corresponding to concepts in semantic memory may be connected by both excitatory and inhibitory links. Inhibitory links may be an essential mechanism of selective attention, filtering out irrelevant activation (Walley & Weiden, 1973), and may also account for priming and other interference effects.When a node in memory is activated, activation tends to spread to semantically related nodes through excitatory links. At the same time, activation of other nodes is inhibited due to inhibitory links. The more strongly a node is activated, the more strongly it will tend to inhibit other nodes. If more than one node is activated, therefore, the more strongly activated node will win out in the competition for response mechanisms because it will inhibit other nodes more strongly than it is itself being inhibited.In a priming task with a short SOA, nodes corresponding to both the prime and the target are activated and compete with each other through these inhibitory processes. Normally, activation of an unrelated prime node does not present serious competition to the target node because, by the time the target is presented, activation of the prime node has already begun to decay. However, when a very brief target is immediately masked, erasing or overwriting the visual image, processing is interrupted before the target node is fully activated, making it susceptible to inhibition generated by the prime node.With a long SOA in a high cue validity condition, if subjects are using the prime as a cue to develop an expectation regarding the target, then the node in memory corresponding to the expected target would be activated. If the target is unrelated, and therefore unexpected, there will be activation of two competing nodes: the node corresponding to the expected target and the node corresponding to the target actually presented. Because these nodes are both strongly activated at the same time, inhibition generated by the expected target node results in the interference effects typically found.We predicted that interference would be considerably increased in this condition if, as in our earlier studies, targets were brief and immediately masked. In this case, our model suggests that activation of the target node would be considerably reduced and it would therefore be affected even more strongly by inhibition generated by the node corresponding to the expected target.In the following experiment, this prediction was tested. The task was a primed lexical decision with an SOA of 800 ms. Cue validity was either high (75% of prime target pairs related), or low (25% of prime target pairs related). Targets were brief, and masked in either block 1 or block 2 of trials. Masking was blocked because in a previous experiment we had found that subjects had extreme difficulty recognizing brief masked targets mixed with brief unmasked targets. …

Lifetimes of heavy baryons revisited

The presently available experimental information on charmed-baryon lifetimes indicates that the nonrelativistic quark model (NQM) gives a more reliable estimate on various nonspectator effects than the relativistic model. The sizeable lifetime differences among charmed baryons are accounted for by large W-exchange and constructive interference effects. Quantitative features of the total decay widths of bottom baryons are elaborated in NQM. We find that the emerged lifetime pattern is τ(Ξ − b)⋍ τ(Ω − b)≳τ(Λ 0 b)≳τ(Ξ 0 b) with much smaller lifetime differences among them. An estimate of the Λ b lifetime based on the recent observation of the exclusive decay modes Λ b → J/ ψΛ and Λ b→Λ + cl − v ̄ is made.

Large interference effects of small chirp observed in two-photon absorption

It is shown that the populations of excited levels after a multi-photon excitation process are strongly influenced by the exact phase relations between the different frequency components within the excitation pulse (the ‘chirp’ of the pulse). This general effect, which can already show up dramatically if chirp has lengthened the pulse by only 10%, is experimentally demonstrated two systems: two-photon absorption in an atom and frequency-doubling in a nonlinear crystal.

Asymmetric intraspecific competition among larvae of the damselfly Ischnura elegans (Zygoptera: Coenagrionidae)

Abstract. 1. A laboratory competition experiment is described in which the growth and development rates of larvae of the damselfly Ischnura elegans (Lind.) were measured over an entire instar.2. Two larval instars which commonly occur together in the field were used in the experiment; they were maintained with a superabundance of prey and either larvae from the same or the larger/smaller instar.3. Small larvae suffered increased development times and decreased size increases at the moult in the presence of large larvae but similar interference effects were not evident when these smaller larvae were in the presence of other small larvae.4. Development time and size increases of large larvae were not significantly affected by the presence of small larvae.5. Irrespective of the instar combinations investigated, interference effects were reduced when there were more perches available, although in only a few cases was this reduction significant.6. The consequences of the asymmetric competition reported in the experiment for the study of lifetime reproductive success in damselflies are discussed. Late emerging adults may incur reduced reproductive success.

Proposed structure for large quantum interference effects

In this letter we propose and analyze a new semiconductor structure that can be fabricated by present day technology and can lead to large quantum interference effects with potential device applications.

Toponium-Z-mixing

We investigate the phenomenological consequence of mixing between toponium states and the Z boson at e +e − colliders. We find large interference effects in the fermion-antifermion final state, which greatly reduce the observability of toponium states with masses within ≈2.5 GeV of the Z mass. Weak decays of the toponium states, which yield a clear isolated lepton signature, are little affected by the mixing with the Z, and should be observable. We point out that toponium-Z mixing will greatly increase the yield of Higgs photon events, perhaps to an observable level.

Kinematically complete measurement of cross sections and vector and tensor analyzing powers of 4He( [formula omitted], pα)n at [formula omitted

Differential cross sections and vector and tensor analyzing powers have been measured in the breakup reaction 4He( d , pα)n at E d = 10 MeV , for θ α = 46°, θ p = 46° complete coincidence experiment. The kinematics allow for np final-state interaction (FSI) ( E np = 0). A comparison with theoretical predictions based on Faddeev equations is presented. Phenomenologically it appears that there are large interference effects between the different FSI and the importance of Coulomb interaction emerges clearly.

MaximalCPviolation in the six-quark model

Consideration is given to some experimental tests of the Kobayashi-Maskawa model of weak interactions for the case in which the $\mathrm{CP}$-violating effects could be expected to be maximal, that is, $\ensuremath{\delta}=\frac{\ensuremath{\pi}}{2}$. A reanalysis of the model is carried out to verify that $\ensuremath{\delta}=\frac{\ensuremath{\pi}}{2}$ is consistent with existing data. In addition to the usual contributions of the high-energy quark box diagram, this analysis takes into account low-energy dispersive terms, which depend on the energy boundary $\ensuremath{\mu}$. Double penguin diagrams are also shown to give a significant contribution to $\ensuremath{\Delta}m$, depending on $\ensuremath{\mu}$. Fitting of the result for $\ensuremath{\Delta}m(\ensuremath{\mu})$ to the measured mass difference leads to $\ensuremath{\mu}\ensuremath{\approx}1$ GeV, if the top-quark mass ${m}_{t}\ensuremath{\lesssim}45$ GeV. This places an upper limit on ${m}_{t}$ since, for larger ${m}_{t}$, the calculated $\ensuremath{\Delta}m$ is too high for all $\ensuremath{\mu}$. The results of the analysis are applied to the dilepton asymmetry in ${B}^{0}$, ${\overline{B}}^{0}$ production by ${e}^{+}{e}^{\ensuremath{-}}$ collisions and similar effects that can be obtained by comparing antineutrino with neutrino production of dileptons. When large asymmetries are found to occur, the rate is found to be hopelessly small because interference effects are suppressed. Large interference effects can occur if the parameters are chosen appropriately, but then the asymmetry is only 1 or 2%. It is also found that interference effects between ${T}^{0}$ and ${\overline{T}}^{0}$ are enormously suppressed for any choice of the parameters.

Parametrized S matrix models of elastic scattering in chemically reactive systems

The theory of large angle elastic scattering in chemically reactive systems using parametrized S matrix models is investigated Calculations of the large angle scattering are carried out for three new parametrizations, in addition to one that has been used previously. All parametrizations are of the smooth step function type, although their analytic structure in the complex angular momentum plane is completely different. Both meromorphic and non-meromorphic parametrizations are employed. Large angle interference effects are found for all parametrizations provided the opacity function is sufficiently black and the transition from absorbency to transparency is sufficiently rapid.

Three-Body Calculation ofπdElastic Scattering at 142 MeV

We calculate the pion-deuteron elastic scattering at ${E}_{\ensuremath{\pi}}=142$ MeV using nonrelativistic three-body equations in which relativistic kinematics are retained only for the pion. The $\mathrm{NN}$ tensor force is taken into account, and, for the first time, all $S$ and $P$ $\ensuremath{\pi}N$ partial waves are included in an exact way. The coupling between $l=J\ifmmode\pm\else\textpm\fi{}1$ $\ensuremath{\pi}d$ channels is found to be not negligible, and we establish the large interference effects of all other than ${P}_{33}$ $\ensuremath{\pi}N$ channels leading to a rather good description of the experimental data at ${E}_{\ensuremath{\pi}}=142$ MeV.

Acoustic and semantic interference effects in words and pictures

Interference effects for pictures and words were investigated using a probe-recall task. Word stimuli showed acoustic interference effects for items at the end of the list and semantic interference effects for items at the beginning of the list, similar to results of Kintsch and Buschke (1969). Picture stimuli showed large semantic interference effects at all list positions with smaller acoustic interference effects. The results were related to latency data on picture-word processing and interpreted in terms of the differential order, probability, and/or speed of access to acoustic and semantic levels of processing. A levels of processing explanation of picture-word retention differences was related to dual coding theory. Both theoretical positions converge on an explanation of picture-word retention differences as a function of the relative capacity for semantic or associative processing.

Optical and electrical characteristics of MgO.Al 2O 3 spinel and silicon-on-spinel

Conductivity and Hall effect as a function of temperature between 76 and 350K, and photoconductivity as a function of wavelength at 80 and 300K have been measured for a 2− μm thick epitaxial n-Si layer on MgO.Al 2O 3 spinel. In addition, the wavelength dependence of optical transmission (0.2−300 μm) and reflection (0.3−50 μm) have been measured for both Si/spinel and for a similar spinel substrate. Interference fringes in transmission and reflection were used to accurately determine the Si epilayer thickness. The temperature dependence of the carrier concentration in the epilayer is typical of compensated phosphorus-doped Si, but that for the Hall mobility suggests potential-barrier-limited carrier transport. The spinel substrate shows an 80–90 per cent transmitting window between 0.27 and 5.75 μm, and a reflectivity consistent with a refractive index of 1.7. Between 8 and 50 μm spinel is strongly absorbing with peaks in reflectivity at 545 and 745 cm −1 which are attributed to oxygen bonded to Al. Transmission is again observed for spinel beyond 50 μm. The percent transmission and interference fringe spacing near 300 μm indicate a refractive index of ∼ 3, in reasonable accord with the dielectric constant of 8.4 at 1 kHz reported previously. Differences in reflectivity between nonepitaxied spinel and the Si-spinel interface suggest that epitaxy affects the composition near the interface. In addition, unusually large interference effects observed in photoconductivity are ascribed to a photosensitive layer near the Si-spinel interface.

A new method for the evaluation of slotted wind tunnel interference parameters applicable to subsonic oscillatory tests

Until a few years ago it was the practice to neglect lift interference on oscillatory model tests in high-speed subsonic wind tunnels, whatever the working section configuration. However, in 1960 Bratt and Wight discovered a large interference effect on the pitch damping derivative of an M-wing measured in the slotted working section of the 25 in x 20 in tunnel at the National Physical Laboratory. In 1964 Wight reviewed a number of oscillatory tests and showed that in many cases there were significant interference effects on both stiffness and damping derivatives when measured in slotted working sections.

Reduction of wave drag by antisymmetric arrangement of wings and bodies.

The wave interference effects for bodies or wings in a mirror-symmetric arrangement, and in an antisymmetric arrangement are discussed. It is shown that while in the case of a mirror-symmetric arrangement large adverse interference effects can be observed, antisymmetric arrangements provide comparatively much smaller wave drags. The single continuous wing panels also adapt themselves more readily to varying angles of obliquity, and hence, to varying flight speeds. A detailed review is presented of the previous work on the aerodynamic properties and flight stability of oblique elliptic wing combinations. A possible mode of application of these combinations to transport aircraft operating at moderate supersonic speeds is suggested.

Tones and numbers: specificity of interference in immediate memory.

Recognition of the pitch of a tone was severely disrupted by the incorporation of six other tones during a 5-second retention interval, even though the intervening tones could be ignored. However, the requirement to recall six numbers spoken at equal loudness during the identical retention interval produced only a minimum decrement in the same pitch-recognition task. Further, the requirement to remember the tone produced no decrement in recall of the numbers. It is concluded that immediate memory for pitch is subject to a large interference effect which is highly specific in nature and which is not due to some limitation in general short-term memory capacity or to a distraction of attention.

Decay analysis of the low-mass K ππ enhancement into K 890∗ and π− π systems

The low-mass K ππ enhancement is studied in K +p→K + π + π −p and K +p→ →K 0 π + π 0p interactions at 9 GeV/ c. This enhancement consists of two peaks of mass and width M=1260±10 MeV, Γ=40±10 MeV and M=1380±20 MeV, Γ= 120±20 MeV. The main decay modes are K 890 ∗π and ϱK, which interfere strongly. A consistent description of the data requires either an additional decay mode into K + plus an I=0 s-wave π− π system 〈 ϵ 720 0〉 or a large interference effect between two components of the Q, or both.