Modeling of distributed parasitics in power FETs

A distributed circuit analysis of power FETs accounting for the lateral source parasitic impedance in addition to the lateral drain and gate parasitic impedances is presented. Both a numerical solution and an exact analytic solution are derived. Using the exact analytic solution, approximate equivalent circuits are derived for FETs of short gate width for two common types of boundary conditions. When the gate and drain terminals are located on opposite sides of the distributed FET, the lateral source parasitic impedance can be represented for short gate width FETs by an equivalent circuit with a negative series impedance in series with the source terminal. The practical consequences on parameter extraction for device modeling are discussed. The availability of an exact analytic solution for the distributed FET should also assist with the synthesis of traveling wave FETs.     

Pharyngocutaneous fistula following total laryngectomy and post-operative vomiting

The significance of post-operative vomiting as a risk factor in the development of a pharyngocutaneous fistula was examined. The case records of 50 consecutive patients undergoing laryngectomies (39 men, 11 women, average age 64 years) were examined, 17 also underwent a simultaneous radical neck dissection. A fistula developed in eight patients (16%) and the median time to its diagnosis was 11 days (range 3-15 days). Several potential risk factors were examined including age, gender, previous radiotherapy, TNM stage, differentiation of tumour, simultaneous radical neck dissection and also the occurrence of vomiting post-operatively. In this series of patients only vomiting in the early post-operative period appeared to be related to the development of a fistula (regression summary: R2 = 0.6, t-value 5.6, P < 0.0001). An episode of vomiting was recorded in eight patients and of these six (75%) subsequently developed a fistula. The median time of post-operative vomiting was 7.5 days (range 1-10 days) and the diagnosis of a fistula occurred at a mean of 1.2 +/- 0.4 days after the episode of vomiting. In a study of this nature it is not possible to conclude that a causal relationship exists between vomiting and fistula development. However, if this is the case a potential means of decreasing the incidence of fistulae following laryngectomy may be available.     

Bioactive albumin functionalized polylactic acid membranes for improved biocompatibility

Biocompatibility is a major challenge for successful application of many biomaterials. In this study the ability to coat chemically and enzymatically activated poly(L-lactic acid) (PLA) membranes with heat denatured human serum albumin to improve biocompatibility was investigated. PLA membranes hydrolyzed with NaOH or cutinase and then treated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, hydrochloride (EDAC) as a heterobifunctional cross-linker promoted the coupling COOH groups on PLA membranes and NH₂ groups of heat denatured human serum albumin. This resulted in increased hydrophilicity (lowest water contact angles of 43° and 35°) and highest antioxidant activity (quenching of 79 μM and 115 μM tetramethylazobisquinone (TMAMQ) for NaOH and cutinase pretreated membranes, respectively). FTIR analysis of modified PLA membranes showed new peaks attributed to human serum albumin (amide bond, NH₂ and side chain stretching) appearing within 3600–3000 cm^?1 and 1700–1500 cm^?1 (Fig. 3). MTT studies also showed that osteoblasts-like and MC-3T3-E1 cells viability increased 2.4 times as compared to untreated PLA membranes. The study therefore shows that this strategy of modifying the surfaces of PLA polymers could significantly improve biocompatibility.     

High Efficiency RF Power Amplifier Designed With Harmonic Real-Time Active Load-Pull

In this work, a high efficiency p-HEMT radio frequency power amplifier (PA) is designed using a new multiharmonic real-time active load-pull using the large signal network analyzer. This technique synthesizes a large set of instantaneous load mismatches to quickly find the optimal harmonic impedances, so as to achieve high PA efficiency in a shortened design cycle. At 2 GHz a demo power amplifier implemented with a p-HEMT demonstrated a power added efficiency (PAE) of 68.5% for 18.0 dBm output power, while achieving a maximum PAE of 75% below the 1 dB compression point for 18.6 dBm output power.     

New Trends and Technological Challenges in the Industrial Production and Purification of Fructo-oligosaccharides

An increased commercial interest in fructo-oligosaccharides (FOS) has emerged in the last decade due to their prebiotic activity. At large scale, the FOS are produced by microbial enzymes from sucrose. A mixture of FOS and other saccharides is obtained in this process. The presence of such saccharides reduces the prebiotic, caloric, and cariogenic value of the final product. Therefore, many efforts have been conducted to obtain a product with increased FOS purity. This review comprises the most important technological and physicochemical aspects including FOS production and recovery processes; safety, dose and health claims concerning its intake; and commercially available FOS.     

Antibody response to Chlamydia pneumoniae infection in children with respiratory illness

Serologic diagnosis of Chlamydia pneumoniae infection has been based on the microimmunofluorescence test (MIF). However, recent prospective studies in children have found that >50% infected with C. pneumoniae failed to develop any antibodies detectable by MIF. In this study, single sera from 46 culture-positive and 42 culture-negative children with respiratory infection and known MIF status were examined by immunoblotting. Forty-one (89.1%) of the single sera from culture-positive and 27 (64.3%) from culture-negative children reacted to C. pneumoniae antigens in immunoblot. C. pneumoniae proteins most frequently recognized by sera from culture-positive patients were at 101-102, 72-76, 50-52, 48-49, 43-44, 41-42, and 30-31 kDa. However, there did not appear to be a correlation of specific band patterns and culture status.     

Isothermal DC and microwave characterizations of power RF siliconLDMOSFETs

Presented in this paper are two new approaches for the acquisition of both isothermal DC current-voltage (I-V) characteristics and microwave S-parameters of power RF LDMOSFETs. In the first approach, a 3D tensor product B-spline representation is used to extract isothermal DC I-V characteristics from DC I-V characteristics measured at various substrate temperatures. The average device surface temperature is measured using an infrared sensor. A single effective thermal resistance is found to map the entire electrothermal profile of the device, justifying the isothermal DC I-V definition used. In the second approach, isothermal I-V and microwave data are directly measured with an efficient procedure that keeps the average device surface temperature constant. Excellent agreement is obtained between the numerical extraction and the direct measurement approach. Finally, the comparison of the transconductance extracted from the isothermal DC I-V and microwave data confirms the presence of a small low-frequency dispersion in LDMOSFETs not due to self-heating