Photocurrent-based detection of Terahertz radiation in graphene

Graphene is a promising candidate for the development of detectors of Terahertz (THz) radiation. A well-known detection scheme due to Dyakonov and Shur exploits the confinement of plasma waves in a field-effect transistor (FET), whereby a dc photovoltage is generated in response to a THz field. This scheme has already been experimentally studied in a graphene FET [L. Vicarelli et al., Nature Mat. 11, 865 (2012)]. In the quest for devices with a better signal-to-noise ratio, we theoretically investigate a plasma-wave photodetector in which a dc photocurrent is generated in a graphene FET. The rectified current features a peculiar change of sign when the frequency of the incoming radiation matches an even multiple of the fundamental frequency of plasma waves in the FET channel. The noise equivalent power per unit bandwidth of our device is shown to be much smaller than that of a Dyakonov-Shur detector in a wide spectral range.Comment: 5 pages, 4 figure

Thermal modeling of terahertz quantum-cascade lasers: comparison of optical waveguides

We compare a set of experimental lattice temperature profiles measured in a surface-emitting terahertz (THz) quantum-cascade laser (QCL) with the results of a 2-D anisotropic heat diffusion model. We evaluate the temperature dependence of the cross-plane thermal conductivity (kappaperp) of the active region which is known to be strongly anisotropic due to its superlattice-like nature. Knowledge of kappaperp and its temperature dependence is crucial in order to improve the temperature performance of THz QCLs and this has been used to investigate the longitudinal lattice temperature distribution of the active region and to compare the thermal properties of metal-metal and semi-insulating surface-plasmon THz optical waveguides using a 3-D anisotropic heat diffusion model

Privileged burial in the Pava Pieve (Siena, 8th century AD)

During the 6th archaeological excavation campaign performed at the «Pieve di Pava» (San Giovanni d’Asso, Siena, Italy) in the summer of 2009, a stone-lined burial of a high-status single individual (US 2378) was discovered, covered by a monolithic slab and placed in front of the altar. The tomb is about 160 cm long, 40 cm wide and over 70 cm deep. The skeletal remains of a young male (18-20 years), not in anatomical connection, were found on the floor of the tomb. 14C dating revealed a period between 650 and 688 AD. Stable isotope analysis (18O, 13C, 15N) attested that he was a member of the local community, with a diet quite rich in animal proteins. We are in presence of the secondary burial of an eminent personage, perhaps a saint, likely to have been transported to the church in a sack of perishable material, possibly textile, which caused their alignment along a curved line, as clearly demonstrated by the circular delimitation of the bones. The body was probably used for the re-consecration of the church, following the restoration works of the 8th century. The paleopathological study diagnosed a case of acromesomelic dysplasia, a congenital anomaly with disproportionate limbs: short, enlarged distal segments (radius-ulna and tibia), almost normal proximal segments (humerus and femur), short stature of about 150 cm, and bilateral fibular agenesis. Tibiae malformation and fibulae agenesis led to bilateral talipes valgus, with major walking problems. Extensive enthesopathies in the upper limbs indicate the use of crutches

The Medici children: (Florence, XVI-XVII centuries): anthropological study and proposal of identification

Exploration of the Medici chapels in San Lorenzo in Florence revealed the burials of nine infantile members of the Medici family. Eight children were found in the intact tomb of the last Grand Duke Giangastone (1671-1737). The crypt contained several small coffins collapsed to the floor or randomly spread over a raised plank, as a result of the disastrous flood of the Arno river in 1966, which partly upset the tomb and left a layer of dry mould. The children’s remains, mostly skeletonised, were found inside the coffins or scattered on the floor or on the plank, probably transported by the water. Another child was exhumed from the chapel of Grand Duke Ferdinand I (1549-1609) and Cristina from Lorena (1565-1636). The infantile remains were submitted to anthropological study, which allowed to establish the number of individuals buried in the crypt, and to estimate the age at death. The anthropological results were compared with information provided by archival documents, related to members of the family who died in infantile age. An identification of the children is proposed

Learning curve and global benchmark values of laparoscopic sleeve gastrectomy: results of first 100 cases of a newly trained surgeon in an Italian center of excellence

To evaluate whether the learning curve for sleeve gastrectomy could be completed after 50 cases. First 100 patients undergoing LSG under a newly trained laparoscopic surgeon were included in this study and divided into two groups of 50 consecutive patients each. Perioperative outcomes were compared to recently introduced global benchmarks. Short-term weight loss was calculated as Total Weight Loss Percent (%TWL) and complications were classified in accordance with the Clavien–Dindo classification. CUSUM analysis was performed for operative time and hospital stay. Mean preoperative age and BMI were 41.8 ± 10.3 years and 42.9 ± 5.4 kg/m2, respectively. Demographics and rate of patients with previous surgery were comparable preoperatively in the two groups. Mean operative time was 92.1 ± 19.3 min and hospital stay was 3.4 ± 0.6 days as per our standard protocol of discharge. Uneventful postoperative course was recorded in 93% of patients and only one case of staple line leak was registered in the first 50 cases (group 1). No statistical difference in BMI and %TWL was found between the two groups at any time of follow-up. Comparison between two groups showed a significant reduction in hospital stay and operative time after the first 50 LSGs (p < 0.05). LSG can be performed by newly trained surgeons proctored by senior tutors. At least 50 cases are needed to meet global benchmark cut-offs and few more cases may be required to reach the plateau of the learning curve

Ten-Year Results of Laparoscopic Sleeve Gastrectomy: Retrospective Matched Comparison with Laparoscopic Adjustable Gastric Banding—Is There a Significant Difference in Long Term?

Background: The laparoscopic sleeve gastrectomy (LSG) is the most common bariatric procedure performed worldwide while the laparoscopic adjustable gastric banding (LAGB) has been almost abandoned. Aim of this study was to retrospectively assess 10-year outcomes of LSG through a matched comparison with LAGB. Materials and Methods: Retrospective search of prospectively maintained database of our university was carried out to find all patients that underwent LSG before December 2010. Each subject with LSG was matched one-to-one with a patient that had undergone LAGB in the same period with correspondent preoperative age, BMI, and sex. Results: A total of 76 patients underwent LSG before 2010 and were all included in this study; a matched group of 76 out of 178 LAGB patients with 10-year follow-up was retrieved from our database. Comparison between the two groups showed better outcomes after LSG at 1 and 5 years but weight loss was comparable with the LAGB group at 10 years (%TWL 22.2 ± 13 vs 21.2 ± 16.1; p = 0.89). No significant difference was found in conversion/removal rate (15.8% vs 18.4%; p = 0.67). Conclusion: LSG is an effective stand-alone bariatric procedure with better outcomes than LAGB in medium term, but results are comparable at 10 years. Subjects undergoing LSG should be informed that conversion to RYGB or OAGB may be necessary to achieve further weight loss or to treat reflux. Graphical abstract: [Figure not available: see fulltext.

Impact of COVID-19 Lockdown on Short-term Weight Loss in a Single Italian Institution

Italy was the first European country to have a major outbreak of COVID-19. Bariatric procedures were stopped and telemedicine had to be implemented. A large percentage of patients struggled to follow postoperative diet and to start physical activity due to social restrictions. We have compared short-term outcomes of patients who had bariatric procedures prior to lockdown with subjects that had undergone obesity surgery in the same period of the previous year at our institution. A total number of 63 patients were included in this study. Weight loss at 1, 3 and 6 postoperative months in the 2019 group was significantly higher at any point of follow-up when compared to 2020. Social limitations and nonattendance of clinical appointments may have compromised early results. Graphical Abstract: [Figure not available: see fulltext.]

Identical Particles and Permutation Group

Second quantization is revisited and creation and annihilation operators areshown to be related, on the same footing both to the algebra h(1), and to the superalgebra osp(1|2) that are shown to be both compatible with Bose and Fermi statistics. The two algebras are completely equivalent in the one-mode sector but, because of grading of osp(1|2), differ in the many-particle case. The same scheme is straightforwardly extended to the quantum case h_q(1) and osp_q(1|2).Comment: 8 pages, standard TEX, DFF 205/5/94 Firenz