Robotic Sugarbaker parastomal hernia repair: technique and outcomes

PURPOSE

To present a novel technique for the repair of parastomal hernias.

METHODS

A total of 15 patients underwent parastomal hernia repair. A robotic Sugarbaker technique was utilized for repair. The fascial defect was closed prior to robotic intraperitoneal placement of the mesh. Baseline demographics of the patients were obtained, and intra-operative and post-operative outcomes were tracked.

RESULTS

The etiology of the ostomies was oncologic in all but three patients. Five of the stomas were urostomies (33.3%). Patient characteristics were as follows: age 64.9.1 ± 9.3 years, BMI 30.1 ± 4.7 kg/m², smoking history 60.0%, and diabetes 6.7%. The mean size of the hernia defect was 46.0 ± 40.1 cm² with a mesh size of 372.0 ± 101.2 cm². The mean operative time was 182.0 ± 51.9 min. In seven patients, an inferolateral preperitoneal flap was created for mesh placement. Intraoperatively, only one enterotomy was made during dissection, which was repaired without complication. The mean length of stay was 4.2 ± 1.9 days. There was only one hernia recurrence (6.7%). There were no wound complications, surgical site infections, or mesh infections. A mean follow-up time of 14.2 ± 9.4 months was achieved.

CONCLUSIONS

Robotic Sugarbaker parastomal hernia repair is a safe and effective technique. The results demonstrate the feasibility of fascial closure with this technique and a low recurrence rate. The authors propose this technique should be widely considered for parastomal hernia repair.

A systematic review of CT chest in COVID-19 diagnosis and its potential application in a surgical setting

AIM

The aim of this work was to investigate the sensitivity and utility of CT of the chest in diagnosing active SARS-Cov-2 (COVID-19) infection, and its potential application to the surgical setting.

METHOD

A literature review was conducted using Google Scholar® and MEDLINE®/PubMed® to identify current available evidence regarding the sensitivity of CT chest compared with RT-PCR for the diagnosis of COVID-19-positive patients. GRADE criteria and the QUADAS 2 tool were used to assess the level of evidence.

RESULTS

A total of 20 articles were identified that addressed the question of sensitivity of CT for diagnosis of symptomatic and asymptomatic COVID-19-positive patients. Overall sensitivity of CT scan ranged from 57%-100% for symptomatic and 46%-100% for asymptomatic COVID-19 patients, while that of RT-PCR ranged from 39%-89%. CT chest was a better diagnostic modality and capable of detecting active infection earlier in the time course of infection than RT-PCR in symptomatic patients. In asymptomatic patients, disease prevalence seems to play a role in the positive predictive value. Minimal evidence exists regarding the sensitivity of CT in patients who are asymptomatic.

CONCLUSIONS

In surgical patients, CT chest should be considered as an important adjunct for detection of COVID-19 infection in patients who are symptomatic with negative RT-PCR prior to any operation. For surgical patients who are asymptomatic, there is insufficient evidence to recommend routine preoperative CT chest for COVID-19 screening.

[Teicoplanin-induced hypersensitivity syndrome in a diabetic foot patient with malignant ulcer]

A 58-year-old male patient with diabetic foot ulcer was admitted to the Second Affiliated Hospital of Zhejiang University School of Medicine on December 11, 2018. The patient was treated with local debridement, vacuum sealing drainage treatment, and dressing change and discharged after basic wound healing. On January 15, 2019, the patient was hospitalized again due to local infection and rupture of wound surface. He underwent a surgical debridement on the third day after second admission and was given intravenous infusion of 0.4 g teicoplanin twice daily. Histopathological examination after surgery showed keratinizing squamous-cell carcinoma. An extended squamous-cell carcinoma resection plus autologous split-thickness skin grafting and vacuum sealing drainage treatment was carried out on the 10th day after second admission. The patient's whole body turned red after surgery with rash, recurrent fever over 39 ℃, leucopenia, and thrombocytopenia. A multi-disciplinary consultation of physicians attributed these symptoms to teicoplanin-induced hypersensitivity syndrome. After withdrawal of teicoplanin and administration of hormone, the patient's temperature returned to normal, and the leucocyte count and platelet count recovered gradually. The patient was cured and discharged on the 49th day after second admission. The case presented reminds us of need to strictly follow the indications of teicoplanin prior to medication, be resolute to the administration and withdrawal, and be alert to adverse drug reactions when above-mentioned abnormalities occur, meanwhile, infection and rheumatic diseases are excluded.

Stable, highly-responsive and broadband photodetection based on large-area multilayered WS2 films grown by pulsed-laser deposition

The progress in the field of graphene has aroused a renaissance of keen research interest in layered transition metal dichalcogenides (TMDs). Tungsten disulfide (WS2), a typical TMD with favorable semiconducting band gap and strong light-matter interaction, exhibits great potential for highly-responsive photodetection. However, WS2-based photodetection is currently unsatisfactory due to the low optical absorption (2%-10%) and poor carrier mobility (0.01-0.91 cm(2) V(-1) s(-1)) of the thin WS2 layers grown by chemical vapor deposition (CVD). Here, we introduce pulsed-laser deposition (PLD) to prepare multilayered WS2 films. Large-area WS2 films of the magnitude of cm(2) are achieved. Comparative measurements of a WS2-based photoresistor demonstrate its stable broadband photoresponse from 370 to 1064 nm, the broadest range demonstrated in WS2 photodetectors. Benefiting from the large optical absorbance (40%-85%) and high carrier mobility (31 cm(2) V(-1) s(-1)), the responsivity of the device approaches a high value of 0.51 A W(-1) in an ambient environment. Such a performance far surpasses the CVD-grown WS2-based photodetectors (μA W(-1)). In a vacuum environment, the responsivity is further enhanced to 0.70 A W(-1) along with an external quantum efficiency of 137% and a photodetectivity of 2.7 × 10(9) cm Hz(1/2) W(-1). These findings stress that the PLD-grown WS2 film may constitute a new paradigm for the next-generation stable, broadband and highly-responsive photodetectors.

Polarization dependent photocurrent in the Bi2Te3 topological insulator film for multifunctional photodetection

Three dimensional Z₂ Topological insulator (TI) is an unconventional phase of quantum matter possessing insulating bulk state as well as time-reversal symmetry-protected Dirac-like surface state, which is demonstrated by extensive experiments based on surface sensitive detection techniques. This intriguing gapless surface state is theoretically predicted to exhibit many exotic phenomena when interacting with light, and some of them have been observed. Herein, we report the first experimental observation of novel polarization dependent photocurrent of photodetectors based on the TI Bi₂Te₃ film under irradiation of linearly polarized light. This photocurrent is linearly dependent on both the light intensity and the applied bias voltage. To pursue the physical origin of the polarization dependent photocurrent, we establish the basic TI surface state model to treat the light irradiation as a perturbation, and we adopt the Boltzmann equation to calculate the photocurrent. It turns out that the theoretical results are in nice qualitative agreement with the experiment. These findings show that the polycrystalline TI Bi₂Te₃ film working as a multifunctional photodetector can not only detect the light intensity, but also measure the polarization state of the incident light, which is remarkably different from conventional photodetectors that usually only detect the light intensity.

Ultra-broadband and high-responsive photodetectors based on bismuth film at room temperature

Bismuth (Bi) has undergone researches for dozens of years on account of its abundant physics including the remarkably high mobility, exceptional large positive magnetoresistance and the coexistence of an insulating interior as well as metallic surfaces. Very recently, two-dimensional topologically-protected surface states immune to nonmagnetic perturbation such as surface oxidation and impurity scattering were experimentally demonstrated through systematic magnetotransport measurements, e.g. weak antilocalization effect and angular dependent Shubnikov-de Haas oscillations. Such robust metallic surface states, which are efficient in carrier transportation, along with its small bulk gap (14 meV) make Bi favored for high-responsive broadband photodetection. Here, we for the first time demonstrate the stable ultra-broadband photoresponse from 370 nm to 1550 nm with good reproducibility at room temperature based on a Bi photodetector. The fabricated device’s responsivity approaches 250 mA/W, accompanied with a rise time of 0.9 s and a decay time of 1.9 s. The photocurrent is linear dependent on the voltage and incident power, offering good tunability for multi-purpose applications. Thickness-dependent conductance and photocurrent reveal that the bulk is the optically active layer while the surface channel is responsible for carrier transportation. These findings pave an avenue to develop ultra-broadband Bi photodetectors for the next-generation multifunctional optoelectronic devices.

Warping effect-induced optical absorbance increment of topological insulator films for THz photodetectors with high signal-to-noise ratio

Strong optical absorbance makes topological insulator (TI) surfaces a promising high-performance photodetector in the terahertz (THz) to infrared frequency range. Here, we study the optical absorbance of more realistic TI films with hexagonal warping effect using the Fermi's golden rules. It was found that when the warping term is λ ≠ 0, the absorbance is no longer a universal value as that of graphene or ideal Dirac cone, but increases monotonously with the photon energy. The increment is positively correlated with the parameter λ/vF(3) where vF is the Fermi velocity. The relative signal-to-noise ratio (SNR) of the TI film working as a photoresistor-type photodetector is significantly enhanced by the warping effect-induced absorbance increment. These investigations provide useful information for developing TI-based photodetectors with high SNR in the range of THz to infrared frequency.

Electrical tuning of transport properties of topological insulator ultrathin films

Considering that topological insulator (TI) ultrathin films (UTFs) provide an ideal platform for the transport measurement of topologically protected surface states, we have investigated the transport properties of the three-dimensional (3D) TI UTFs through an array of potential barriers. The 3D TI UTF was considered to be thin enough (5 nm) that the top and bottom surface states of the UTF can hybridize to create an energy gap at the Dirac point, which results in a hyperbola-like energy dispersion. It was found that the Klein tunneling effect disappears due to the interaction between the top and bottom surface states. By tuning the barrier strength or the incident energy, three kinds of transport processes can be realized, and the conditions of the transport processes were determined. The oscillatory characters of the transmission (conductance) spectra without a decaying envelope are due to the novel surface states of TIs, which are quite different from that observed for a conventional two-dimensional electron gas. For the structure consisting of two anti-parallel potential barriers, the conductance spectra exhibit a perfect on/off switching effect by tuning the barrier strength, which is favorable for electrically controllable device applications. In the case of a superlattice (SL) structure, due to the mini-gaps induced by the SL geometry, some additional resonant peaks and valleys can be observed in the transmission spectra, and similar characters are also reflected in the conductance spectra. Owing to the Dirac characters of the charge carriers therein, the transmission (conductance) spectra never decay with increasing barrier strength, which is distinguished from that observed for semiconductor SLs. These findings were not only meaningful for understanding the basic physical processes in the transport of TIs, but also useful for developing nanoscaled TI-based devices.

High-performance Bi(2)Te(3)-based topological insulator film magnetic field detector

Topological insulators with the nanoscaled metallic surface state (3-5 nm) are actually of typical functional nanostructures. Significant efforts have been devoted to study new families of topological insulators and identifications of topological surface state, as well as fundamental physics issues relating to spin-polarized surface electronic states in the past few years. However, transport investigations that can provide direct experimental evidence for potentially practical applications of topological insulators are limited, and realization of functional devices based on topological insulators is still under exploration. Here, using the Sn-doping Bi2Te3 polycrystalline topological insulator films, we fabricated high-performance current-controlled magnetic field detectors. When a parallel magnetic field is applied, the as-fabricated device exhibits a stable and reproducible magneto-resistance (MR) switching behavior, and the corresponding MR ratio can be modulated by the applied current. Even under such a low magnetic field (0.5 kG), the device still shows a distinguishable MR switching performance, suggesting that topological insulator devices are very sensitive to external stimulation and potentially applicable to weak magnetic field detection.

Conductivity oscillation of surface state of three-dimensional topological insulators induced by a linearly polarized terahertz field

We have theoretically studied the longitudinal dc conductivity of the surface state of three-dimensional (3D) topological insulators (TIs) under a linearly polarized (LP) terahertz (THz) field irradiation via the Floquet theory and Green's function technique. It was found that, due to the anisotropic quasienergy spectrum under the LP light, the longitudinal conductivities parallel and perpendicular to the polarized direction of the LP light are not the same. When the 3D TI's chemical potential is zero, both of the conductivities undergo an oscillation against the electron-field interaction parameter because of the contribution of the photon modulated side-band transport at different position. The oscillation is dramatically suppressed when the chemical potential is higher or lower than zero. There is a pronounced dip in the dc conductivity at a specific field frequency twice the chemical potential, which can be seen as a gap-induced metal-to-insulator transition of the surface state of 3D TIs. As the dc conductivity of the surface state of 3D TIs has such a pronounced response to the LP THz field, our investigations involving the interaction between TIs and LP THz field actually provided the possibility of TI application in THz devices.