A 200 GHz Monolithic Integrated Power Amplifier in Metamorphic HEMT Technology

A millimeter-wave monolithic integrated circuit power amplifier operating in the frequency range between 186 and 212 GHz is presented. The amplifier, dedicated to high-resolution imaging radar and communication systems, is realized in a 100 nm gate length metamorphic high electron mobility transistor technology. The three-stage design with four parallel transistors in the output stage achieves a linear gain of more than 12 dB and provides a saturated output power of more than 9 dBm and 7 dBm at 192 and 200 GHz, respectively

Instabilitäten von Infiltrationsfronten verursacht durch langzeitige Bewässerung mit behandelten Abwässern

Die Bewässerung von Agrarflächen mit behandelten Abwässern (TWW) ist eine weitverbreitete Praxis in ariden und semi-ariden Gebieten. In Israel liegt auf dieser Wasserressource ein besonderer Fokus, da Abwässer ganzjährig verfügbar sind, Frischwasserressourcen schonen und einen wichtigen Beitrag zur Wiederverwendung von Nährstoffen leisten. Vorangegangene Studien haben gezeigt, dass organische Stoffe die Benetzbarkeit von Mineraloberflächen beeinträchtigen und die Bodenstruktur verändern können. Auf Grund der erhöhten Restmenge an organischen Bestandteilen im TWW kann eine langzeitige Bewässerung im Boden zu Veränderungen der Struktur, Hydrophobizität, präferentiellen Fließwegen und dem Auswaschen von Pflanzenschutzmitteln und Nährstoffen führen. In dieser Studie wurden (i) eine neue Methode zur Quantifizierung von Wassergehaltsänderungen in ungestörten Bodenproben via Radiographie entwickelt und (ii) Instabilitäten von Infiltrationsfronten in Böden, die seit über zwanzig Jahren mit TWW bewässert wurden, detektiert. Wir untersuchten ungestörte Bodenproben von zwei Obstplantagen in Israel mit langzeitiger TWW-Bewässerung, wobei an einem Standort zusätzlich ein Teil mit Frischwasser bewässert wird. Die Proben umfassen zwei unterschiedliche Bodentexturen und zwei unterschiedliche Bewässerungsverfahren: Frischwasser und TWW. Des Weiteren wurden saisonale Abhängigkeiten (Trocken-/ Regenzeit) mit in die Studie eingeschlossen um die Persistenz der Effekte zu erfassen. Ungestörte, zylindrische Bodenproben wurden aus dem Oberboden (0-20 cm) genommen und Bewässerungsversuche innerhalb eines Röntgensystems durchgeführt. Durch Bildanalyse konnten die Ausbreitung der Infiltrationsfronten und räumliche Wassergehaltsänderungen als Funktion der Zeit erfasst werden. Die Versuche wurden mit unterschiedlichen Anfangswassergehalten wiederholt. In dieser Studie konnte gezeigt werden, dass die Stabilität der Infiltrationsfronten in diesen Böden von der Wasserqualität und dem initialen Wassergehalt abgängig sind. Darüber hinaus konnte dargelegt werden, dass langzeitige TWW-Bewässerung zu einer persistenten Veränderung der Benetzbarkeit führen kann, unabhängig von der Saison. Diese Studie liefert einen experimentellen Nachweis über die Notwendigkeit von optimiertem Bewässerungsmanagement um präferentielles Wasserfließen zu vermeiden

Evidence for a remodelling of DNA-PK upon autophosphorylation from electron microscopy studies

The multi-subunit DNA-dependent protein kinase (DNA-PK), a crucial player in DNA repair by non-homologous end-joining in higher eukaryotes, consists of a catalytic subunit (DNA-PKcs) and the Ku heterodimer. Ku recruits DNA-PKcs to double-strand breaks, where DNA-PK assembles prior to DNA repair. The interaction of DNA-PK with DNA is regulated via autophosphorylation. Recent SAXS data addressed the conformational changes occurring in the purified catalytic subunit upon autophosphorylation. Here, we present the first structural analysis of the effects of autophosphorylation on the trimeric DNA-PK enzyme, performed by electron microscopy and single particle analysis. We observe a considerable degree of heterogeneity in the autophosphorylated material, which we resolved into subpopulations of intact complex, and separate DNA-PKcs and Ku, by using multivariate statistical analysis and multi-reference alignment on a partitioned particle image data set. The proportion of dimeric oligomers was reduced compared to non-phosphorylated complex, and those dimers remaining showed a substantial variation in mutual monomer orientation. Together, our data indicate a substantial remodelling of DNA-PK holo-enzyme upon autophosphorylation, which is crucial to the release of protein factors from a repaired DNA double-strand break

Phosphorothioate oligonucleotides, suramin and heparin inhibit DNA-dependent protein kinase activity

Phosphorothioate oligonucleotides and suramin bind to heparin binding proteins including DNA polymerases, and inhibit their functions. In the present study, we report inhibition of DNA-dependent protein kinase activity by phosphorothioate oligonucleotides, suramin and heparin. Inhibitory effect of phosphorothioate oligonucleotides on DNA-dependent protein kinase activity was increased with length and reached a plateau at 36-mer. The base composition of phosphorothioate oligonucleotides did not affect the inhibitory effect. The inhibitory effect by phosphorothioate oligodeoxycytidine 36-mer can be about 200-fold greater than that by the phosphodiester oligodeoxycytidine 36-mer. The inhibitory effect was also observed with purified DNA-dependent protein kinase, which suggests direct interaction between DNA-dependent protein kinase and phosphorothioate oligonucleotides. DNA-dependent protein kinase will have different binding positions for double-stranded DNA and phosphorothioate oligodeoxycytidine 36-mer because they were not competitive in DNA-dependent protein kinase activation. Suramin and heparin inhibited DNA-dependent protein kinase activity with IC50 of 1.7 μM and 0.27 μg ml−1 respectively. DNA-dependent protein kinase activities and DNA double-stranded breaks repair in cultured cells were significantly suppressed by the treatment with suramin in vivo. Our present observations suggest that suramin may possibly result in sensitisation of cells to ionising radiation by inactivation of DNA-dependent protein kinase and the impairment of double-stranded breaks repair

Characterization of an Nmr Homolog That Modulates GATA Factor-Mediated Nitrogen Metabolite Repression in Cryptococcus neoformans

Nitrogen source utilization plays a critical role in fungal development, secondary metabolite production and pathogenesis. In both the Ascomycota and Basidiomycota, GATA transcription factors globally activate the expression of catabolic enzyme-encoding genes required to degrade complex nitrogenous compounds. However, in the presence of preferred nitrogen sources such as ammonium, GATA factor activity is inhibited in some species through interaction with co-repressor Nmr proteins. This regulatory phenomenon, nitrogen metabolite repression, enables preferential utilization of readily assimilated nitrogen sources. In the basidiomycete pathogen Cryptococcus neoformans, the GATA factor Gat1/Are1 has been co-opted into regulating multiple key virulence traits in addition to nitrogen catabolism. Here, we further characterize Gat1/Are1 function and investigate the regulatory role of the predicted Nmr homolog Tar1. While GAT1/ARE1 expression is induced during nitrogen limitation, TAR1 transcription is unaffected by nitrogen availability. Deletion of TAR1 leads to inappropriate derepression of non-preferred nitrogen catabolic pathways in the simultaneous presence of favoured sources. In addition to exhibiting its evolutionary conserved role of inhibiting GATA factor activity under repressing conditions, Tar1 also positively regulates GAT1/ARE1 transcription under non-repressing conditions. The molecular mechanism by which Tar1 modulates nitrogen metabolite repression, however, remains open to speculation. Interaction between Tar1 and Gat1/Are1 was undetectable in a yeast two-hybrid assay, consistent with Tar1 and Gat1/Are1 each lacking the conserved C-terminus regions present in ascomycete Nmr proteins and GATA factors that are known to interact with each other. Importantly, both Tar1 and Gat1/Are1 are suppressors of C. neoformans virulence, reiterating and highlighting the paradigm of nitrogen regulation of pathogenesis

Low-Noise W-Band Amplifiers for Radiometer Applications Using a 70 nm Metamorphic HEMT Technology

W-band low-noise amplifier (LNA)MMICs have been developed using a 70 nm metamorphic HEMT (MHEMT)technology.The short gate length in combination with the high indium content of 80%in the channel lead to a maximum transconductance of 1500 ms/mm for a 2x30 µm device.This results in a transit frequency ft of 290 GHz.Two-and three-stage amplifiers were realized in coplanar waveguide technology (CPW)and achieved a small signal gain of 13 dB and 19 dB,respectively.The noise figure at room temperature of both LNAs was below 3 dB. The on-wafer measured output power at the P-1 dB compression point was 5 dBm.A modification of the three stage LNA showed a noise figure of 2.5 dB,with a small signal gain of 15 dB at 94 GHz

Metamorphic 94 GHz power amplifier MMICs

In this paper, we present the development of two 94 GHz power amplifier MMICs for use in high-resolution synthetic aperture radar (SAR) systems. The amplifier circuits have been realized using a 0.1 mu m InAlAs/InGaAs based depletion type metamorphic high electron mobility transistor (MHEMT) technology in combination with coplanar circuit topology and dual-gate transistors, thus leading to an excellent power and gain performance at millimeter-wave frequencies. The realized two-stage driver amplifier (MPA) MMIC exhibited a small-signal gain of 16 dB and a saturated output power of 20.5 dBm at 94 GHz with a total gate width of 0.72 mm in the output stage. The two-stage high power amplifier (HPA) circuit achieved a linear gain of 10 dB and a saturated output power of 23.3 dBm with a total output periphery of 1.44 mm

Scalable HEMT small-signal model extraction based on a hybrid multibias approach

A multibias approach for HEMT small-signal model extraction is proposed. The method is based on scaling rules and uses a hybrid direct extraction/particle swarm optimization approach. By the use of a reduced number of S-parameter measurements in the optimization procedure, the computational effort is kept low. The extraction procedure is verified with measurements on metamorphic HEMTs, leading to accurate and scalable models in the millimeter-wave range. Furthermore, the robustness of the proposed method against measurement uncertainties is verified by using PHEMT synthetic data, intentionally affected by errors

A versatile and cryogenic mHEMT-model including noise

A versatile scalable small signal model for high electron mobility transistors (HEMTs) of gate length 50 nm and 100 nm has been developed. The model covers a large bias range and includes the temperature dependence from 300 K to 15 K. Especially, it is capable to predict the noise behaviour of the transistor in dependence of ambient temperature and frequency