A multifinger microtriode with carbon nanotubes field emission cathode operating at GHz frequency.

Vacuum microelectronic devices play an important role in the field of micro- and nano-electronics and they have been strongly developed in recent decades. Vacuum microelectronics are mainly based on the field emission effect and the employment of electrons in vacuum in a device with dimensions from tenths to hundredths of a micrometer. In this work, we present the development of a carbon-nanotube-based multifinger microtriode operating from 0.5 to 2 GHz. In this frequency range, a minimum RF signal gain of 5 dB is achieved. Such a device represents an optimized alternative to the standard Spindt-type microtriode. The advantage of such multifinger architecture consists in the possibility to reduce the cathode-grid capacitance by reducing the overlap between the two electrodes using a parallel patterning. This approach allows increasing the cut-off frequency of the devices with respect to the Spindt-type triode. We realized a prototype of the multifinger triode and the field emission properties have been characterized. The frequency behavior has been measured, demonstrating the possibility to amplify RF signal.

Isotretinoin increases skin-surface levels of neutrophil gelatinase-associated lipocalin in patients treated for severe acne.

BACKGROUND: A clear-cut need exists for safe and effective alternatives to the use of isotretinoin in severe acne. Lack of data regarding the specifics of isotretinoin's mechanism of action has hampered progress in this area. Recently, the protein neutrophil gelatinase-associated lipocalin (NGAL) has been identified as a mediator of the apoptotic effect of isotretinoin on sebocytes. OBJECTIVES: To establish further the clinical relevance of NGAL and to elucidate the factors that induce NGAL expression in sebocytes. METHODS: Methods were developed to isolate and quantify skin-surface levels of NGAL from normal subjects and patients with acne undergoing treatment with isotretinoin. RESULTS: Patients with acne were found to have higher skin levels of NGAL compared with normal subjects. Studies in SEB-1 sebocytes indicate that NGAL expression is increased in response to Propionibacterium acnes and interleukin (IL)-1ß. In patients, isotretinoin increases NGAL levels by 2·4-fold on the skin surface and this increase precedes decreases in sebum and P. acnes counts. CONCLUSIONS: These data support the hypothesis that NGAL is an important mediator of the early effects of isotretinoin on the sebaceous glands and provide insights into the mechanisms that regulate NGAL expression in the skin.

Planar coupling to high-Q lithium niobate disk resonators.

We demonstrate optical coupling to high-Q lithium niobate disks from an integrated lithium niobate waveguide. The waveguides are made by proton exchange in X-cut lithium niobate substrate. The disks with diameter of 4.7 mm and thickness of 1 mm are made from commercial Z-cut lithium niobate wafers by polishing the edges into a spheroidal profile. Both resonance linewidth and cavity ringdown measurements were performed to calculate the Q factor of the resonator, which is in excess of 10(8). Planar coupling represents the most promising technique for practical applications of whispering gallery mode resonators.