Internal carotid artery narrowing in children with retropharyngeal lymphadenitis and abscess

BACKGROUND AND PURPOSE: Our purpose was to describe the association between narrowing of the internal carotid artery (ICA) and retropharyngeal abscess in children. METHODS: Neck CT scans from 13 consecutive children with suppurative retropharyngeal lymphadenitis and abscess were evaluated retrospectively for asymmetric ICA diameters at the level of the abscess. Clinical status at the time of illness was established via a chart review. Twenty control CT scans obtained from pediatric patients with normal imaging findings were evaluated prospectively to determine symmetry and size of the ICA. RESULTS: Mean diameter of the normal ICA, contralateral to the retropharyngeal abscess, was 5 mm (range, 3-8 mm), while mean diameter ipsilateral to the abscess was 3 mm (range, 1-5 mm). The diameters of the normal and abnormal ICAs were statistically significantly different. All children were neurologically normal. The right and left ICAs in children with normal CT findings in the neck were symmetrical in diameter. CONCLUSION: Despite dramatic narrowing of the ICA ipsilateral to retropharyngeal lymphadenitis and abscess, no children in this series had neurologic deficits, suggesting that such narrowing is a common, benign, and, most likely, incidental imaging finding.     

基于PLC的碱回收蒸发工段控制系统的设计

根据某造纸厂碱回收蒸发工段的工艺流程和控制要求,从系统硬件组态和软件设计两方面探讨了Simatic S7-300在碱回收蒸发过程中的应用;针对蒸发工段的出效浓黑液浓度难以控制的特点,提出了黑液浓度基于串级控制策略;利用WinCC组态软件实现上位机监控,模拟现场画面,显示所需监控的现场设备.经过运行表明,该系统调节准确,稳定了黑液浓度,降低了能耗,同时节约了设备投资.     

Heterostructures of Single-Wavelength and Dual-Wavelength Quantum-Cascade Lasers

The results of development of the basic structure and technological conditions of growing heterostructures for single- and dual-frequency quantum-cascade lasers are reported. The heterostructure for a dual-frequency quantum-cascade laser includes cascades emitting at wavelengths of 9.6 and 7.6 μm. On the basis of the suggested heterostructure, it is possible to develop a quantum-cascade laser operating at a difference frequency of 8 THz. The heterostructures for the quantum-cascade laser are grown using molecularbeam epitaxy. The methods of X-ray diffraction and emission electron microscopy are used to study the structural properties of the fabricated heterostructures. Good agreement between the specified and realized thicknesses of the epitaxial layers and a high uniformity of the chemical composition and thicknesses of the epitaxial layers over the area of the heterostructure is demonstrated. A stripe-structured quantum-cascade laser is fabricated; its generation at a wavelength of 9.6 μm is demonstrated.     

基于矩量法的螺旋天线设计

螺旋天线具有宽波束、圆极化等特性。以往的轴向螺旋天线多为端射式,辐射方向单一。为弥补这一不足,提出了一种新型的中馈轴向螺旋天线。基于RWG(Rao-Wihon-Glisson)边元的矩量法,采用MATLAB仿真计算出中馈螺旋天线的方向图、反射系数、增益等重要参数。又利用高频结构仿真软件(HFSS)对所设计的中馈螺旋天线进行了仿真。通过两种方法仿真得到的结果吻合较好,仿真结果的正确性得到了验证。实验结果表明:中馈轴向螺旋天线不仅具有以往轴向螺旋天线所具备的定向性好和高增益等优点,还具有两个反向且强度相同的辐射方向,同时天线增益可以达到8dB以上,半功率波束宽度可达33°。这种天线可以应用到多边通信及中继通信等领域。     

基于田口法的潜油电机槽型优化研究

潜油电机作为潜油电泵机组的重要组成部分,其性能指标尤为重要。由于潜油电机细长的结构特征,导致在槽型设计方面不同于普通的异步电动机。 基于田口法,在保证潜油电机定转子外形尺寸、温升条件、机械强度不变的情况下,通过确定6个槽型优化因子(定子斜肩角、定子槽高、定子槽宽、转子斜肩角、转子槽高和转子槽宽)与4个优化目标(电机效率、功率因数、最大转矩倍数及启动转矩倍数),建立潜油电机槽型优化目标正交矩阵,降低了仿真次数。借助于有限元法与电磁设计相结合的场路分析方法,得出不同设计方案的性能指标。通过统计学方法确定各优化因子对优化目标的影响关系和影响程度,确定最终优化方案。最后,以143系列210 kW的潜油电机为例,对其槽型进行优化设计,验证该方法的可行性。     

Technology of the fabrication and launching the production of large-size cemented carbide products for the metallurgy industry of Ukraine

Scientific research, on the basis of which a technology of manufacture large-size cemented carbide products has been developed, and special features of the fabrication of cemented carbide rolls to be used in the metallurgy industry have been considered.     

Translation eukaryotic initiation factor 4G recognizes a specific structural element within the internal ribosome entry site of encephalomyocarditis virus RNA

A complex of eukaryotic initiation factors (eIFs) 4A, 4E, and 4G (collectively termed eIF4F) plays a key role in recruiting mRNAs to ribosomes during translation initiation. The site of ribosomal entry onto most mRNAs is determined by interaction of the 5'-terminal cap with eIF4E; eIFs 4A and 4G may facilitate ribosomal entry by modifying mRNA structure near the cap and by interacting with ribosome-associated factors. eIF4G recruits uncapped encephalomyocarditis virus (EMCV) mRNA to ribosomes without the involvement of eIF4E by binding directly to the approximately 450-nucleotide long EMCV internal ribosome entry site (IRES). We have used chemical and enzymatic probing to map the eIF4G binding site to a structural element within the J-K domain of the EMCV IRES that consists of an oligo(A) loop at the junction of three helices. The oligo(A) loop itself is not sufficient to form stable complexes with eIF4G since alteration of its structural context abolished its interaction with eIF4G. Addition of wild type or trans-dominant mutant forms of eIF4A to binary IRES.eIF4G complexes did not further alter the pattern of chemical/enzymatic modification of the IRES.     

Glass Formation and Luminescence of Glasses in the Ga2S3–GeS2–Nd2S3System

The results of spectral measurements and the differential thermal analysis (DTA) data for glasses in the Ga₂S₃–GeS₂–Nd₂S₃system are presented. The boundaries of the glass formation region in the Ga₂S₃–GeS₂–Nd₂S₃system are determined. It is shown that the luminescence efficiency increases with an increase in the gallium sulfide content due to the displacement of the concentration quenching boundary of Nd³⁺luminescence with a change in the glass matrix composition.