True amplification of spin waves in magnonic nano-waveguides.

Magnonic nano-devices exploit magnons - quanta of spin waves - to transmit and process information within a single integrated platform that has the potential to outperform traditional semiconductor-based electronics. The main missing cornerstone of this information nanotechnology is an efficient scheme for the amplification of propagating spin waves. The recent discovery of spin-orbit torque provided an elegant mechanism for propagation losses compensation. While partial compensation of the spin-wave losses has been achieved, true amplification - the exponential increase in the spin-wave intensity during propagation - has so far remained elusive. Here we evidence the operating conditions to achieve unambiguous amplification using clocked nanoseconds-long spin-orbit torque pulses in magnonic nano-waveguides, where the effective magnetization has been engineered to be close to zero to suppress the detrimental magnon scattering. We achieve an exponential increase in the intensity of propagating spin waves up to 500% at a propagation distance of several micrometers.

Giant nonlinear self-phase modulation of large-amplitude spin waves in microscopic YIG waveguides.

Nonlinear self-phase modulation is a universal phenomenon responsible, for example, for the formation of propagating dynamic solitons. It has been reported for waves of different physical nature. However its direct experimental observation for spin waves has been challenging. Here we show that exceptionally strong phase modulation can be achieved for spin waves in microscopic waveguides fabricated from nanometer-thick films of magnetic insulator, which support propagation of spin waves with large amplitudes corresponding to angles of magnetization precession exceeding 10°. At these amplitudes, the nonstationary nonlinear dynamic response of the spin system causes an extreme broadening of the spectrum of spin-wave pulses resulting in a strong spatial variation of the spin-wave wavelength and a temporal variation of the spin-wave phase across the pulse. Our findings demonstrate great complexity of nonlinear wave processes in microscopic magnetic structures and importance of their understanding for technical applications of spin waves in integrated devices.

Evidence for spin current driven Bose-Einstein condensation of magnons.

The quanta of magnetic excitations - magnons - are known for their unique ability to undergo Bose-Einstein condensation at room temperature. This fascinating phenomenon reveals itself as a spontaneous formation of a coherent state under the influence of incoherent stimuli. Spin currents have been predicted to offer electronic control of Bose-Einstein condensates, but this phenomenon has not been experimentally evidenced up to now. Here we show that current-driven Bose-Einstein condensation can be achieved in nanometer-thick films of magnetic insulators with tailored nonlinearities and minimized magnon interactions. We demonstrate that, above a certain threshold, magnons injected by the spin current overpopulate the lowest-energy level forming a highly coherent spatially extended state. We quantify the chemical potential of the driven magnon gas and show that, at the critical current, it reaches the energy of the lowest magnon level. Our results pave the way for implementation of integrated microscopic quantum magnonic and spintronic devices.

High incidence of postoperative infections after pancreaticoduodenectomy: A need for perioperative anti-infectious strategies.

OBJECTIVES: Postoperative infections occur frequently after pancreaticoduodenectomy, especially in patients with bile colonization. Recommendations for perioperative anti-infectious treatment are lacking, and clinical practice is heterogenous. We have analyzed the effects of bile colonization and antibiotic prophylaxis on postoperative infection rates, types and therapeutic consequences. METHODS: Retrospective observational study in patients undergoing pancreaticoduodenectomy with intraoperative bile culture. Data on postoperative infections and non-infectious complications, bile cultures and antibiotic prophylaxis adequacy to biliary bacteria were collected. RESULTS: Among 129 patients, 53% had a positive bile culture and 23% had received appropriate antibiotic prophylaxis. Postoperative documented infection rate was over 40% in patients with or without bile colonization, but antibiotic therapy was more frequent in positive bile culture patients (77% vs. 57%, P=0,008). The median duration of antibiotic therapy was 11 days and included a broad-spectrum molecule in 42% of cases. Two-thirds of documented postoperative infections involved one or more bacteria isolated in bile cultures, which was associated with a higher complication rate. While bile culture yielded Gram-negative bacilli (57%) and Gram-positive cocci (43%), fungal microorganisms were scarce. Adequate preoperative antibiotic prophylaxis according to bile culture was not associated with reduced infectious or non-infectious complication rates. CONCLUSION: Patients undergoing pancreaticoduodenectomy experience a high rate of postoperative infections, often involving bacteria from perioperative bile culture when positive, with no preventive effect of an adequate preoperative antibiotic prophylaxis. Increased postoperative complications in patients with bile colonization may render necessary a perioperative antibiotic treatment targeting bile microorganisms. Further prospective studies are needed to improve the anti-infectious strategy in these patients.

Antibiotics and chronic kidney disease: Dose adjustment update for infectious disease clinical practice.

Antibiotic prescription in chronic kidney disease patients poses a twofold problem. The appropriate use of antibacterial agents is essential to ensure efficacy and to prevent the emergence of resistance, and dosages should be adapted to the renal function to prevent adverse effects. SiteGPR is a French website for health professionals to help with prescriptions to chronic kidney disease patients. A working group of infectious disease specialists and nephrology pharmacists reviewed the indications, dosing regimens, administration modalities, and dose adjustments of antibiotics marketed in France for patients with renal failure. Data available on the SiteGPR website and detailed in the present article aims to provide an evidence-based update of infectious disease recommendations to health professionals managing patients with chronic kidney disease.

Temporal pattern recognition with delayed feedback spin-torque nano-oscillators.

The recent demonstration of neuromorphic computing with spin-torque nano-oscillators has opened a path to energy efficient data processing. The success of this demonstration hinged on the intrinsic short-term memory of the oscillators. In this study, we extend the memory of the spin-torque nano-oscillators through time-delayed feedback. We leverage this extrinsic memory to increase the efficiency of solving pattern recognition tasks that require memory to discriminate different inputs. The large tunability of these non-linear oscillators allows us to control and optimize the delayed feedback memory using different operating conditions of applied current and magnetic field.

Mutual synchronization of spin torque nano-oscillators through a long-range and tunable electrical coupling scheme.

The concept of spin-torque-driven high-frequency magnetization dynamics, allows the potential construction of complex networks of non-linear dynamical nanoscale systems, combining the field of spintronics and the study of non-linear systems. In the few previous demonstrations of synchronization of several spin-torque oscillators, the short-range nature of the magnetic coupling that was used has largely hampered a complete control of the synchronization process. Here we demonstrate the successful mutual synchronization of two spin-torque oscillators with a large separation distance through their long range self-emitted microwave currents. This leads to a strong improvement of both the emitted power and the linewidth. The full control of the synchronized state is achieved at the nanoscale through two active spin transfer torques, but also externally through an electrical delay line. These additional levels of control of the synchronization capability provide a new approach to develop spin-torque oscillator-based nanoscale microwave-devices going from microwave-sources to bio-inspired networks.

Neuromorphic Computing through Time-Multiplexing with a Spin-Torque Nano-Oscillator.

Fabricating powerful neuromorphic chips the size of a thumb requires miniaturizing their basic units: synapses and neurons. The challenge for neurons is to scale them down to submicrometer diameters while maintaining the properties that allow for reliable information processing: high signal to noise ratio, endurance, stability, reproducibility. In this work, we show that compact spin-torque nano-oscillators can naturally implement such neurons, and quantify their ability to realize an actual cognitive task. In particular, we show that they can naturally implement reservoir computing with high performance and detail the recipes for this capability.

Direct observation of dynamic modes excited in a magnetic insulator by pure spin current.

Excitation of magnetization dynamics by pure spin currents has been recently recognized as an enabling mechanism for spintronics and magnonics, which allows implementation of spin-torque devices based on low-damping insulating magnetic materials. Here we report the first spatially-resolved study of the dynamic modes excited by pure spin current in nanometer-thick microscopic insulating Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear self-broadening preventing the formation of the self-localized magnetic bullet, which plays a crucial role in the stabilization of the single-mode magnetization oscillations in all-metallic systems. This peculiarity associated with the efficient nonlinear mode coupling in low-damping materials can be among the main factors governing the interaction of pure spin currents with the dynamic magnetization in high-quality magnetic insulators.

Approaching soft X-ray wavelengths in nanomagnet-based microwave technology.

Seven decades after the discovery of collective spin excitations in microwave-irradiated ferromagnets, there has been a rebirth of magnonics. However, magnetic nanodevices will enable smart GHz-to-THz devices at low power consumption only, if such spin waves (magnons) are generated and manipulated on the sub-100 nm scale. Here we show how magnons with a wavelength of a few 10 nm are exploited by combining the functionality of insulating yttrium iron garnet and nanodisks from different ferromagnets. We demonstrate magnonic devices at wavelengths of 88 nm written/read by conventional coplanar waveguides. Our microwave-to-magnon transducers are reconfigurable and thereby provide additional functionalities. The results pave the way for a multi-functional GHz technology with unprecedented miniaturization exploiting nanoscale wavelengths that are otherwise relevant for soft X-rays. Nanomagnonics integrated with broadband microwave circuitry offer applications that are wide ranging, from nanoscale microwave components to nonlinear data processing, image reconstruction and wave-based logic.

Spin-torque resonant expulsion of the vortex core for an efficient radiofrequency detection scheme.

It has been proposed that high-frequency detectors based on the so-called spin-torque diode effect in spin transfer oscillators could eventually replace conventional Schottky diodes due to their nanoscale size, frequency tunability and large output sensitivity. Although a promising candidate for information and communications technology applications, the output voltage generated from this effect has still to be improved and, more pertinently, reduces drastically with decreasing radiofrequency (RF) current. Here we present a scheme for a new type of spintronics-based high-frequency detector based on the expulsion of the vortex core in a magnetic tunnel junction (MTJ). The resonant expulsion of the core leads to a large and sharp change in resistance associated with the difference in magnetoresistance between the vortex ground state and the final C-state configuration. Interestingly, this reversible effect is independent of the incoming RF current amplitude, offering a fast real-time RF threshold detector.

Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin-orbit torque.

In recent years, spin-orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin-orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin-orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current.

Understanding of Phase Noise Squeezing Under Fractional Synchronization of a Nonlinear Spin Transfer Vortex Oscillator.

We investigate experimentally the synchronization of vortex based spin transfer nano-oscillators to an external rf current whose frequency is at multiple integers, as well as at an integer fraction, of the oscillator frequency. Through a theoretical study of the locking mechanism, we highlight the crucial role of both the symmetries of the spin torques and the nonlinear properties of the oscillator in understanding the phase locking mechanism. In the locking regime, we report a phase noise reduction down to -90 dBc/Hz at 1 kHz offset frequency. Our demonstration that the phase noise of these nanoscale nonlinear oscillators can be tuned and eventually lessened, represents a key achievement for targeted radio frequency applications using spin torque devices.

Magnetic thin-film insulator with ultra-low spin wave damping for coherent nanomagnonics.

Wave control in the solid state has opened new avenues in modern information technology. Surface-acoustic-wave-based devices are found as mass market products in 100 millions of cellular phones. Spin waves (magnons) would offer a boost in today's data handling and security implementations, i.e., image processing and speech recognition. However, nanomagnonic devices realized so far suffer from the relatively short damping length in the metallic ferromagnets amounting to a few 10 micrometers typically. Here we demonstrate that nm-thick YIG films overcome the damping chasm. Using a conventional coplanar waveguide we excite a large series of short-wavelength spin waves (SWs). From the data we estimate a macroscopic of damping length of about 600 micrometers. The intrinsic damping parameter suggests even a record value about 1 mm allowing for magnonics-based nanotechnology with ultra-low damping. In addition, SWs at large wave vector are found to exhibit the non-reciprocal properties relevant for new concepts in nanoscale SW-based logics. We expect our results to provide the basis for coherent data processing with SWs at GHz rates and in large arrays of cellular magnetic arrays, thereby boosting the envisioned image processing and speech recognition.

[Arterio-venous popliteal fistula: a rare late complication of a civilian trauma. A clinical case and review of the literature]. / Fistola artero-venosa poplitea: rara complicanza tardiva di un trauma civile. Caso clinico e revisione della letteratura.

In spite of the relatively high frequency of popliteal injuries following war and civilian traumas, a late development of an arteriovenous fistula can be considered an uncommon complication. We report a case of a chronic arterio-venous popliteal fistula in a young boy, caused five years previously by a blunt trauma, while playing. The tardive onset of symptomatology and the conspicuous enlargement of the vein underline the unusuality of the case. A review of the literature and the technique for fistula repair, using adsorbable suture, are examined.

[Use of defibrotide in the treatment of acute superficial thrombophlebitis of the legs]. / Impiego del defibrotide nel trattamento delle tromboflebiti acute superficiali degli arti.

The efficacy of defibrotide in the treatment of acute thrombophlebitis of the legs has been investigated in 140 patients, randomized into two groups. All patients received defibrotide either alone or as an addition to conventional therapies. Two different schemes of administration were selected and carried out in each group, according to the time of onset of thrombophlebitis. Defibrotide demonstrated a good clinical efficacy in both groups, with a highly significant reduction in those patients receiving defibrotide and conventional therapies. The clinical result were outstanding in two subgroups: extensive thrombophlebitis and brachioaxillary phlebitis.

Longitudinal study of auditory brain-stem response in patients with minor head injuries.

In a longitudinal study of 119 patients with minor head injuries, 13 had abnormal auditory brain-stem responses (ABRs) within 48 hours after trauma. At follow-up examination one month later, ten patients had abnormal ABRs. The ABRs remained stable in most patients; in nine patients they normalized. However, in six patients initially normal ABRs became abnormal. This instability limits the medicolegal application of ABR testing after minor head injury.

Construction of a continent perineal colostomy by using electrostimulated gracilis muscles after abdominoperineal resection: personal technique and experience with 32 cases.

A series of 32 patients operated on for rectal carcinoma is reported. A new technique by using the gracilis muscles to reconstruct a functional anal sphincter after abdominoperineal resection was performed. No operative mortality was recorded. Functionality of the new sphincter was guaranteed by electromyostimulation. Electrostimulation has been useful in both increasing the muscular trophic level and in improving the postoperative bio-feedback. Perineal infection was recorded in 9 patients being the most common complication although it did not compromise the functionality of the new sphincter. In one case acute colonic ischaemia was treated by resection and definitive left colostomy. 17 out of the 27 patients in which a functional follow-up was obtained, scored a "very good" continence to stool and flatus while in 6 patients occasional episodes of incontinence to liquid stool are referred. Local or distant metastases presented in 6 patients. The obtained results encourage in continuing the research with this technique in the attempt to reduce the number of patients that must pay the high price of a definitive abdominal colostomy for cure.