MMIC Amplifier Produces Gain of 10 dB at 235 GHz

The first solid-state amplifier capable of producing gain at a frequency >215 GHz has been demonstrated. This amplifier was fabricated as a monolithic microwave integrated-circuit (MMIC) chip containing InP high-electron-mobility transistors (HEMTs) of 0.07 micron gate length on a 50- m-thick InP substrate

The development of TH2 responses from infancy to 4 years of age and atopic sensitization in areas endemic for helminth infections

BACKGROUND: Helminth infections and allergies are associated with TH(2) responses. Whereas the development of TH(2) responses and allergic disorders in pediatric populations has been examined in affluent countries, no or little data exist from low income regions of the world. The aim of this study is to examine factors influencing the development of TH(2) responses of children born in areas endemic for helminth infections and to relate these factors to atopic sensitization at 4 years of age. METHODS: Data were collected from pregnant mothers on helminth infections, education and socioeconomic status (SES). Total IgE, IL-5 in response to mitogen, and helminth antigens were measured in children at 2, 5, 12, 24 and 48 months of age. Skin prick testing (SPT) and allergen-specific IgE were determined at 4 years of age. RESULTS: Strong TH(2) responses were seen at 5 months of age and increased with time. Although maternal filarial infection was associated with helminth-antigen specific TH(2) responses, it was low maternal education or SES but not helminth infection, which was associated with the development of high total IgE and PHA-induced IL-5. At 4 years of age when allergen reactivity was assessed by SPT, the high general TH(2) responses did not translate into higher prevalence of SPT. The risk factor for SPT reactivity was low maternal education which decreased the risk of SPT positivity to allergens (adjusted OR, 0.32; 95% CI, 0.12 – 0.87) independently of maternal filarial infection which tended to reduce the child’s risk for being SPT positive (adjusted OR, 0.35; 95% CI, 0.07 – 1.70). CONCLUSIONS: In areas endemic for helminths, potent TH(2) responses were seen early in life, but did not translate into a higher SPT reactivity to allergens. Therefore, in many parts of the world TH(2) responses in general and IgE in particular cannot be used for diagnosis of allergic diseases

Modulation-Doped Field-Effect Transistors for High-Power Microwave Applications

118 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997.The effect of drain-sides cap recess distance on InGaAs/GaAs PHEMT device performance at both dc and rf frequencies is investigated. This investigation is achieved though the development of a four-layer electron beam resist technique and sequential wet and dry selective etching. A high linearity of device characteristics is important to minimize intermodulation of high frequency signals under high-power operation. The linearity of device performance is investigated through the comparison of InGaAs/GaAs PHEMTs and doped channel FETs at dc and rf operation. InP is investigated as a channel material for use in high-power FETs due to the intrinsic properties including high breakdown voltage, high electron saturation velocity, high electron velocity at high electric field, and high thermal conductivity. Forming low-resistance ohmic contacts to modulation-doped InP channel heterostructures is a challenging issue and is investigated through the study of ion-implanted alloyed contacts and through cap layer design for nonalloyed contacts.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD