Interaction of climate change with effects of conspecific and heterospecific density on reproduction

We studied the relationship between temperature and the coexistence of great titParus majorand blue titCyanistes caeruleus, breeding in 75 study plots across Europe and North Africa. We expected an advance in laying date and a reduction in clutch size during warmer springs as a general response to climate warming and a delay in laying date and a reduction in clutch size during warmer winters due to density-dependent effects. As expected, as spring temperature increases laying date advances and as winter temperature increases clutch size is reduced in both species. Density of great tit affected the relationship between winter temperature and laying date in great and blue tit. Specifically, as density of great tit increased and temperature in winter increased both species started to reproduce later. Density of blue tit affected the relationship between spring temperature and blue and great tit laying date. Thus, both species start to reproduce earlier with increasing spring temperature as density of blue tit increases, which was not an expected outcome, since we expected that increasing spring temperature should advance laying date, while increasing density should delay it cancelling each other out. Climate warming and its interaction with density affects clutch size of great tits but not of blue tits. As predicted, great tit clutch size is reduced more with density of blue tits as temperature in winter increases. The relationship between spring temperature and density on clutch size of great tits depends on whether the increase is in density of great tit or blue tit. Therefore, an increase in temperature negatively affected the coexistence of blue and great tits differently in both species. Thus, blue tit clutch size was unaffected by the interaction effect of density with temperature, while great tit clutch size was affected in multiple ways by these interactions terms.Peer reviewe

10 K Room Temperature LNA for SKA Band 1

A room temperature LNA suitable for Square Kilometer Array band 1 (0.35–1.05 GHz) has been designed, fabricated and tested. The design is based on InP HEMTs, and focused on minimizing losses in the input matching network. Noise measurement methods in two different labs were used to confirm the 10 K noise temperature of the LNA. The gain wasflat at 50 dB and the input and output return loss better than 10 dB in most of the band

Cryogenic Kink Effect in InP pHEMTs: A Pulsed Measurements Study

We present a study based on pulsed measurement results of the kink effect observed on the I-V output characteristics in InGaAs/InAlAs/InP pseudomorphic high-electron mobility transistors (InP pHEMTs) at cryogenic temperatures. Pulsed measurements were performed at 300 and $10$ K. Gate and drain lags were observed at both temperatures with a strong increase upon cooling for the drain lag. To study the influence of surface traps in the kink, pulsed measurements of devices passivated by either atomic layer deposited Al\ub2O\ub3 or plasma enhanced chemical vapor deposited Si\ub3N⁴ were compared with no significant differences at 10 K. The influence on the kink effect from the buffer was studied by comparing pulsed measurement data from an InP pHEMT with measurements on a GaAs metamorphic HEMT (GaAs mHEMT). For the GaAs mHEMT, an increase of the drain lag at 10 K was observed when compared with the InP pHEMT. Contrary to the InP HEMT, for the GaAs mHEMT the 0.1 μs pulses were short enough to eliminate the kink when using a quiescent point with VDS = 0. The quality of the pinchoff was sensitive to pulse length and quiescent point for the InP pHEMT but not for the GaAs mHEMT

Cryogenic Broadband Ultra-Low-Noise MMIC LNAs for Radio Astronomy Applications

0.5–13 and 24–40 GHz broadband cryogenic monolithic-microwave integrated-circuit low-noise amplifiers (LNAs)have been designed and fabricated using a 130-nm InP HEMTprocess. Packaged LNAs have been measured at both 300 and15 K. At 300 K, the measured minimum noise temperature ofthe 0.5–13-GHz LNA was 48 K at 7 GHz with a gain between34–40 dB. At 15 K, the measured minimum noise temperature was 3 K at 7 GHz and below 7 K within the entire 0.5–13-GHz band with a gain between 38–44 dB. The 24–40-GHz LNA exhibited a lowest noise temperature of 110 K and an average of 125 K with again of more than 27.5 dB at 300 K. When cooled down to 15 K,the noise temperature dropped to a minimum of 10 K and average of 13.2 K with a gain of 28 dB. The results are of large interest for radio astronomy applications where large bandwidth and low noise figure in the receivers are key figures in the system design

Cryogenic Performance of Low-Noise InP HEMTs: a Monte Carlo Study

In this paper, we present a study of the cryogenic performance of InP high electron mobility transistors (HEMTs) in the low-noise region by means of Monte Carlo simulations. A decrease of the contact resistances and an increase in the electron velocity in the channel together with enhanced channel electron confinement upon cooling of the device are observed, and considered to be the reason for the excellent low-noise behavior of cryogenic InP HEMTs. These findings are supported by a good agreement between simulated and experimental DC, RF, and noise figure data of a 130-nm gate length InP HEMT at 300 and 77 K. An increase of the transconductance g(m) and gate-to-source capacitance C-gs is observed when cooling from 300 to 77 K as a consequence of electron velocity increase and improved channel confinement

Source-drain scaling of ion-implanted InAs/AlSb HEMTs

We report on the lateral scaling of true planar InAs/AlSb high electron mobility transistors (HEMTs) based on ion implantation for device isolation. When reducing the source drain distance, dsd, from 2.5 μm to 1 μm, the HEMTs showed up to 56% higher maximum drain current, 23% higher peak transconductance and T of 185 GHz (+32%). A trade-off in the lateral scaling is needed due to increased gate leakage current and pinch-off degradation for dsd below 1.5 μm. The ability to withstand oxidation of the InAs/AlSb heterostructure makes the planar technology based on ion implantation extremely promising for MMIC integration of InAs/AlSb HEMTs

Planar InAs/AlSb HEMTs With Ion-Implanted Isolation

The fabrication and performance of planar InAs/AlSb high-electron-mobility transistors (HEMTs) based on ion-implantation isolation technology are reported. Ar atoms have been implanted at an energy of 100 keV and with a dose of 2 x 10(15) cm(-2) in order to induce device isolation. The InAs/AlSb HEMT exhibited a maximum drain current of 900 mA/mm, a peak transconductance of 1180 mS/mm, and an f(T)/f(max) ratio of 210 GHz/180 GHz at a low drain bias of 0.3 V. The combination of excellent stability against oxidation with the high device isolation demonstrated by the implantation technique can dramatically improve the suitability of InAs/AlSb HEMTs for high-frequency and ultralow-power MMIC applications

Planar InAs/AlSb HEMTs With Ion-Implanted Isolation

The fabrication and performance of planar InAs/AlSb high-electron-mobility transistors (HEMTs) based on ion-implantation isolation technology are reported. Ar atoms have been implanted at an energy of 100 keV and with a dose of 2 x 10(15) cm(-2) in order to induce device isolation. The InAs/AlSb HEMT exhibited a maximum drain current of 900 mA/mm, a peak transconductance of 1180 mS/mm, and an f(T)/f(max) ratio of 210 GHz/180 GHz at a low drain bias of 0.3 V. The combination of excellent stability against oxidation with the high device isolation demonstrated by the implantation technique can dramatically improve the suitability of InAs/AlSb HEMTs for high-frequency and ultralow-power MMIC applications