On neutrino and antineutrino scattering by electrons,and by partons

Assuming a non-derivative point interaction, and Born approximation, there are some simple relations between neutrino and antineutrino scattering on electrons or partons. They have been observed already, for some special cases, in the results of explicit calculations. Here they are obtained from simple general considerations.     

Small-scale anisotropy induced by spectral forcing and by rotation in non-helical and helical turbulence

We study the effect of large-scale spectral forcing on the scale-dependent anisotropy of the velocity field in direct numerical simulations of homogeneous turbulence. ABC-type forcing and helical or non-helical Euler-type forcing are considered. We propose a scale-dependent characterisation of anisotropy based on a modal decomposition of the two-point velocity tensor spectrum. This produces direction-dependent spectra of energy, helicity and polarisation. We examine the conditions that allow anisotropy to develop in the small scales due to forcing and we show that the theoretically expected isotropy is not exactly obtained, even in the smallest scales, for ABC and helical Euler forcings. When adding rotation, the anisotropy level in ABC-forced simulations is similar to that of lower Rossby number Euler-forced runs. Moreover, even at low rotation rate, the natural anisotropy induced by the Coriolis force is visible at all scales, and two distinct wavenumber ranges appear from our fine-grained characterisation, not separated by the Zeman scale but by a scale where rotation and dissipation are balanced.     

Diffraction by extremely small holes in thin absorbing and transparent screens and by disks

The generalization of Bethe-Bouwkamp diffraction theory for the case of diffraction by the hole in absorbing and transparent thin screens and by the disks is proposed. Duality transformation of Bethe-Bouwkamp solution is implemented. The approximate analytical expressions are found for the near electromagnetic diffraction field for extremely small hole or disk.     

Polymerization and depolymerization by ultrasound

Ultrasound has been reported to cause both initiation of polymerization and depolymerization. The effects of the rate of flow of argon gas through styrene during exposure to ultrasound on the polymerization rate and the molecular weight distribution of the polymer formed were investigated. The results indicate that initiation of polymerization occurs primarily only when there is sufficient gas present to form a field of bubbles undergoing stable cavitation. With no gas present, transient cavitation occurs, resulting in depolymerization and the formation of coloured compounds similar to pyrolysis reaction products. These observations explain discrepancies in the sonochemistry literature.     

Thermometry by micro and nanodevices

In this paper we briefly discuss the current provisional temperature scale of 2000 (PLTS-2000) for low temperatures. Electronic thermometry is presented and discussed, focusing on its potential in verifying and realizing a future temperature scale. The discussion covers secondary thermometers such as NIS and SIS thermometers and noise, shot noise and Coulomb blockade primary thermometers. The last one is discussed in more detail.     

Pattern Selection: Determined by Symmetry and Modifiable by Distant Effects

We consider Saffman–Taylor channel flow without surface tension on a high-pressure driven interface, but modify the usual infinite-fluid in infinite-channel configuration. Here we include the treatment of efflux by considering a finite connected body of fluid in an arbitrarily long channel, with its second free interface the efflux of this configuration. We show that there is a uniquely determined translating solution for the driven interface, which is exactly the 1/2 width S–T solution, following from correct symmetry for a finite channel flow. We establish that there exist no perturbations about this solution corresponding to a finger propagating with any other width: Selection is locally unique and isolated. The stability of this solution is anomalous, in that all freely impressible perturbations are stabilities, while unstable modes request power proportional to their strength from the external agencies that drive the flow, and so, in principle, are experimentally controllable. This is very different from the behavior of the usual infinite fluid. We conjecture that surface tension on the efflux interface modifies channel-width according to 1–2=/v (i.e., (2)² B of the literature) with v the velocity of the high-pressure tip, but the surface tension of the efflux. That is, is decreased below 1/2 by the effect of smoothing the distant efflux. The perturbation theory created here to deal with transport between two free boundaries is novel and dependent upon a symmetry implied by the equations of motion.     

谱色散平滑与透镜列阵联用实现均匀照明

为满足激光惯性约束聚变中靶面激光辐照不均匀性低于5%的要求,在目前使用透镜列阵基础上,提出了谱色散平滑与透镜列阵联用方案,对其进行数值计算并分析其平滑效果和应用可行性。结果表明:焦斑的不均匀性从单独使用透镜列阵时的14%降低到与谱色散平滑结合后的3%;对焦斑点功率谱的分析表明谱色散平滑通过抑制焦斑中高频的频谱强度达到平滑效果。该方案可以进一步提高焦斑平滑效果,计算结果对实际应用有着重要的参考意义。     

Change of the photon statistics by one-photon absorption and by simultaneous one-photon and two-photon absorption

With the help of the generating function we investigate the change of photon statistics due to one-photon absorption. Photon distributions with antibunching approach by this process the Poisson distribution. In a second part we consider the simultaneous action of one-photon and two-photon absorption. We present the exact solution and the asymptotic state in the limit of great initial photon numbers.     

炸药爆轰合成纳米金刚石的拉曼光谱和红外光谱研究

用负氧平衡炸药爆轰法合成纳米金刚石,并用粉末X射线衍射(XRD)仪、激光Raman光谱仪和红外光谱仪等分析仪器对其结构进行表征。XRD结果表明,纳米金刚石为立方结构,由于其内部结构的高密度缺陷、杂质原子的夹杂使谱线偏离,晶格常数比静压合成的大颗粒金刚石大0.72%。由于金刚石晶粒细小,Raman光谱特征峰产生宽化,并且向小波数方向偏移了3 cm-1,此外在纳米金刚石中还含有极少量的石墨。红外光谱测试结果中,3 422 cm-1吸收峰为O—H伸缩振动峰;在1 634 cm-1出现了H₂O的弯曲振动峰,表明在纳米金刚石样品粉末中含有水分;2 930和2 857 cm-1是CH₂的反对称和对称伸缩振动吸收峰;2 971 cm-1是CH₃的反对称伸缩振动吸收峰,说明样品中存在极少量的碳氢化合物;1 788 cm-1吸收峰为CO伸缩振动吸收峰。文章从纳米金刚石的生成机理上分析了产生这些峰位的原因,结果表明纳米金刚石属于Ⅰ型金刚石,在它之中含有ⅠaA型和Ⅰb型金刚石,ⅠaA型金刚石的含量比Ⅰb型金刚石多。     

Estimating speech spectra for copy synthesis by linear prediction and by hand

Linear prediction is a widely available technique for analyzing acoustic properties of speech, although this method is known to be error-prone. New tests assessed the adequacy of linear prediction estimates by using this method to derive synthesis parameters and testing the intelligibility of the synthetic speech that results. Matched sets of sine-wave sentences were created, one set using uncorrected linear prediction estimates of natural sentences, the other using estimates made by hand. Phoneme restrictions imposed on linguistic properties allowed comparisons between continuous and intermittent voicing, oral or nasal and fricative manner, and unrestricted phonemic variation. Intelligibility tests revealed uniformly good performance with sentences created by hand-estimation and a minimal decrease in intelligibility with estimation by linear prediction due to manner variation with continuous voicing. Poorer performance was observed when linear prediction estimates were used to produce synthetic versions of phonemically unrestricted sentences, but no similar decline was observed with synthetic sentences produced by hand estimation. The results show a substantial intelligibility cost of reliance on uncorrected linear prediction estimates when phonemic variation approaches natural incidence.     

A New 3D Digitizer by Cutting and Scanning Layer by layer

１ＩｎｔｒｏｄｕｃｔｉｏｎＷｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｔｈｅｒａｐｉｄｐｒｏｔｏｔｙｐｉｎｇ,ｉｔｓｔｗｉｎｎｉｎｇｔｅｃｈｎｉｑｕｅ———ｔｈｅｒｅｖｅｒｓｅｅｎｇｉｎｅｅｒｉｎｇ［１］ｉｓｕｎｄｅｒｇｏｉｎｇａｒａｐｉｄｄｅｖｅｌｏｐ...     

Recognition of nonsense syllables by hearing-impaired listeners and by noise-masked normal hearers

In the present study, speech-recognition performance was measured in four hearing-impaired subjects and twelve normal hearers. The normal hearers were divided into four groups of three subjects each. Speech-recognition testing for the normal hearers was accomplished in a background of spectrally shaped noise in which the noise was shaped to produce masked thresholds identical to the quiet thresholds of one of the hearing-impaired subjects. The question addressed in this study is whether normal hearers with a hearing loss simulated through a shaped masking noise demonstrate speech-recognition difficulties similar to those of listeners with actual hearing impairment. Regarding overall percent-correct scores, the results indicated that two of the four hearing-impaired subjects performed better than their corresponding subgroup of noise-masked normal hearers, whereas the other two impaired listeners performed like the noise-masked normal listeners. A gross analysis of the types of errors made suggested that subjects with actual and simulated losses frequently made different types of errors.     

Isocoumarines: Structural Study by NMR and by AM1 Semi-Empirical Method

Study of a serie of isocoumarins by ¹³C and ¹⁷O NMR spectrometry and AM1 method is reported. These methods gave valuable informations on electronic effect and the structure of isocoumarins.     

Plasma radiation emitted by dense mixtures of rare gases excited by an electron beam and by a discharge

An experimental investigation was made of the radiation emitted from a plasma formed by rare gases (He, Ne, Ar, Kr, Xe) excited by a beam of electrons with different parameters and by discharge pulses (P= 0.1–0.5 atm, I=1 kA, U=10–15 kV, C=0.25 F). An investigation was made of the spectral composition and time characteristics of the radiation, and of their dependences on the excitation conditions. New molecular bands were observed in the near-ultraviolet and visible ranges. The uniquely large widths of these bands could be of interest in the amplification of light in a wide spectral range.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 56–73, January, 1992.     

Characterisation of PMMA microfluidic channels and devices fabricated by hot embossing and sealed by direct bonding

In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp micro-structure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU-8) stamp includes microchannel arrays of approximately 30 μm in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 μm wide and 6 μm in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 °C embossing temperature were optimum for transferring the micro-structure to the PMMA substrate.     

Scarring by homoclinic and heteroclinic orbits

In addition to the well-known scarring effect of periodic orbits, we show here that homoclinic and heteroclinic orbits, which are cornerstones in the theory of classical chaos, also scar eigenfunctions of classically chaotic systems when associated closed circuits in phase space are properly quantized, thus introducing strong quantum correlations. The corresponding quantization rules are also established. This opens the door for developing computationally tractable methods to calculate eigenstates of chaotic systems.