Frequency-comb-referenced molecular spectroscopy in the mid-infrared region

A simple method for absolute-frequency measurements of molecular transitions in the mid-IR region is reported. The method is based on a cw singly resonant optical parametric oscillator (SRO), which is tunable from 3.2 to 3.45?μm. The mid-IR frequency of the SRO is referenced to an optical frequency comb through its pump and signal beams. Sub-Doppler spectroscopy and absolute-frequency measurement of the P(7) transition of the ν3 band of CH4 are demonstrated.     

Engaging concert hall acoustics is made up of temporal envelope preserving reflections

Strong, exciting, and engaging sound is perceived in the best concert halls. Here, it is shown that wideband early reflections that preserve the temporal envelope of sound contribute to the clear and open acoustics with strong bass. Such reflections are fused with the direct sound due to the precedence effect. In contrast, reflections that distort the temporal envelope render the sound weak and muddy because they partially break down the precedence. The presented findings are based on the earlier psychoacoustics research, and confirmed by a perceptual evaluation with six simulated concert halls that have same monaural room acoustical parameter values according to ISO3382-1.     

Parabolic Muckenhoupt weights in the Euclidean space

We introduce a parabolic analogue of Muckenhoupt?s Ap class. We show that these weights satisfy a reverse Hölder type inequality and also prove a John-Nirenberg inequality for a related BMO type class. Both results are multidimensional generalizations of known one-dimensional results. As an application of our methods, we extend a two-dimensional weighted norm inequality of A. Lerner and S. Ombrosi to dimensions n?3.     

Simulation of quantum wells with ‘spikes’ and ‘dips’

The use of thin high-bandgap ‘spikes’ or thin low-bandgap ‘dips’ inside conventional rectangular quantum wells (QWs) gives supplementary flexibility in engineering intra- and inter-band energy level separation. The paper presents simulation and experimental studies on the effects of ‘spikes’ and ‘dips’ on the fundamental quantum well properties.     

From Precursors to Thin Films - Thermoanalytical Techniques in the Thin Film Technology

Processing thin films for advanced applications, for instance in electronics and optoelectronics, involves several steps starting from precursor synthesis and ending up with the devices. Especially when optimizing the first steps of this chain of processes, thermoanalytical techniques play an important role. The review will focus on the main chemical deposition methods (CVD, ALE, spray pyrolysis, sol-gel) giving selected examples of problem-solving by thermal analysis. The techniques discussed are TG, DTA/DSC, EGA and their combinations. High-temperature X-ray diffraction (HTXRD) is also a powerful tool for in situ studies of thin films. The examples are taken from solar cell, superconductor and flat panel electroluminescent display technologies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Oriented crosslinked polyethylene pipes by a novel extrusion method

Crosslinking and stretching (2.5 times along the circumferential direction) of the molten polymer during extrusion produced pipes with dominantly circumferential orientation and a lower degree of axial chain orientation. Differential scanning calorimetry (crystallinity and crystal thickness), density measurements (crystallinity), X-ray diffraction (c-axis orientation), infrared dichroism measurements (crystalline and amorphous chain orientation) and contraction measurements (molecular draw ratio) assessed the microstructure of the pipe material. The mechanical properties of the oriented material were assessed by uniaxial tensile tests. The orientation was biaxial with the main orientation in the circumferential direction and a lesser orientation in the axial direction. The maximum degree of circumferential orientation was obtained at the inner wall of the pipe. The lower degree of crosslinking of the core material allowed slippage of chains during the stretching of the molten polymer and it is suggested that this is the cause of the lower degree of orientation of the core material. The oriented pipe material exhibited a 5-10% higher degree of crystallinity and higher crystal thickness than conventionally crosslinked material. The tensile modulus and the tensile strength of the oriented, cross-linked material was greater along the axial direction than along the circumferential direction. The circumferential and axial moduli for the oriented, crosslinked pipe were greater than the corresponding moduli of the non-oriented cross-linked pipe material. Another pipe based on crosslinked PE that were first circumferentially stretched 2.5 times and later axially stretched 10 times (in the molten state) showed, despite the fact that it exhibited pronounced axial orientation almost a balanced tensile modulus (4.3±0.2 GPa) in the axial-circumferential plane. Atomistic modelling showed that the orientational dependence of the density of the amorphous phase is small.     

Tris(benzophenoneimino)phosphane and Related Compounds

A new group of bases with benzophenoneiminyl (bpi) moiety has been synthesized and characterized in this work. The title compound tris(benzophenoneimino)phosphane (P(bpi)₃) 1 was prepared with a convenient one-pot approach: benzophenone imine was deprotonated using MeMgCl and reacted with PBr₃ in diglyme. The method could be considered as a method of choice for preparing other (amino)phosphanes in case lithio-intermediates and/or protonated phosphane is out of consideration. Phosphane 1 is further used to prepare a range of related phosphonium cations and phosphazenes. Phosphonium cations were deprotonated to assess the stability of the resulting phosphonium ylides. In some cases, the bulky substances were capable of forming P−N heterocycles. Experimental (MeCN) and computational (MeCN, THF, gas-phase) basicities of benzophenone imine, phosphane 1 , phosphonium ylides, and phosphazenes, as well as some representative XRD structures, are presented and discussed.