Modulated scattering technique in the terahertz domain enabled by current actuated vanadium dioxide switches.

The modulated scattering technique is based on the use of reconfigurable electromagnetic scatterers, structures able to scatter and modulate an impinging electromagnetic field in function of a control signal. The modulated scattering technique is used in a wide range of frequencies up to millimeter waves for various applications, such as field mapping of circuits or antennas, radio-frequency identification devices and imaging applications. However, its implementation in the terahertz domain remains challenging. Here, we describe the design and experimental demonstration of the modulated scattering technique at terahertz frequencies. We characterize a modulated scatterer consisting in a bowtie antenna loaded with a vanadium dioxide switch, actuated using a continuous current. The modulated scatterer behavior is demonstrated using a time domain terahertz spectroscopy setup and shows significant signal strength well above 0.5 THz, which makes this device a promising candidate for the development of fast and energy-efficient THz communication devices and imaging systems. Moreover, our experiments allowed us to verify the operation of a single micro-meter sized VO2 switch at terahertz frequencies, thanks to the coupling provided by the antenna.

Analysis of four scoring systems and monocentric experience to optimize criteria for marginal kidney transplantation.

There is a strong need among the transplantation community to identify common criteria to utilize the pool of expanded criteria donors (ECD), considering the disparity between organ demand and supply as well as the benefits of transplantation on long-term mortality compared with survival on dialysis, also in patients transplanted with these organs. The purpose of this article was to analyze scoring systems proposed in literature by Nyberg, Anglicheau, Rao (Kidney Donor Risk Index), and Schold, seeking to verify whether our clinical and histological allocation strategy matched the Nyberg score. Herein we have reported the results of a preliminary retrospective study on the 5-year outcomes of organs from 60 marginal donors, who were older than 50 years and histologically evaluated before implantation. The donors matched Nyberg class C and D, that is, marginal donors. We noted a tendency toward an association between global and vascular scores with class D (odds ratio 2.2 and 4.3, respectively). Kaplan-Meier graft survival curves were similar to Nyberg data: 83% for class C versus 73% for class D at 5 years. Without any comparison to the Nyberg score, the only feature that was predictive of renal function at 5 years in our population was hypertension in the donor. Further studies are required to identify which of the scoring systems--clinical and/or histological--is more suitable to allocate ECD kidneys and to predict recipient outcomes.

Assessment of cardiovascular risk in waiting-listed renal transplant patients: a single center experience in 558 cases.

Cardiac screening is recommended to prevent cardiovascular death after renal transplantation. This retrospective observational study illustrates the results of application of a cardiac assessment algorithm in a series of 558 renal transplant candidates at a single center in Turin, Italy. A dipyridamole-stress sestamibi myocardial scintiscan (DMS) performed in 302/558 (54.1%) cases was positive in 52 (17.2%), negative in 200 (66.2%), borderline in 16 (5.3%), and with signs of previous necrosis in 34 (11.4%). Coronary lesions detected by angiography in 48.1% of the 52 positives were treated medically (13.5%) or by percutaneous/surgical procedure (34.6%). Coronary lesions were detected in 14.1% of asymptomatic population subgroup. The minor and major cardiovascular event rates and the cardiovascular death rate were 1.9%, 0%, and 0%, respectively, in positive DMS group (high-cardiological risk) vs. 10%, 4.5%, and 3.5% in the negatives (p > 0.5; n.s.). It is suggested that not increased cardiovascular event or deaths rates in the high-risk group reflect early coronary lesion detection and correction. Since 55.9% of cardiovascular events or deaths occurred in the negative group more than 24 months after the DMS, its mandatory repetition every two yr after a negative finding is recommended.