Optical modulator based on a silicon-ITO grating embedded rib structure with a tunable group delay.

An optical modulator based on an engineered silicon-indium tin oxide (Si-ITO) structure is proposed with a tunable group delay. A large group delay is reported by slowing down the light in a Si-ITO grating embedded rib structure. Optical modulation and a tunable group delay are realized by utilizing the electrically tunable permittivity of ITO in the engineered waveguide. The extinction ratio over 8 dB for a 10 µm long device and the modulation efficiency around 12 V-µm are reported for a wide wavelength from 1530 to 1570 nm. The resulting modulation efficiency and the extinction ratio show a significant improvement as compared to conventional modulators based on rib waveguides. We also report around 82 psec electrical tuning in the group delay for a wide wavelength range. This concept is promising in view of realizing tunable delay lines, along with slow light modulators with a reduced device footprint and low energy dissipation.

Optical switch with ultra high extinction ratio using electrically controlled metal diffusion.

An optical switch with ultra high extinction ratio is proposed. Optical switching is realized using the resistive switching effect through the lateral coupling between the input nanophotonic waveguide and output waveguide at a wavelength of 1550 nm. The coupled waveguide system is engineered to increase the number of mode beats in a unit length of the device. An increase in the number of mode beats and controlled diffusion of metal ions through a thin dielectric layer with an applied electric field is responsible for a high optical extinction ratio of 27 dB for a 20 µm long device. Compared to electrical control by plasma dispersion in silicon, the resistive switching effect enables a reduction in the coupling length and an increase in the waveguide absorption, leading to an almost 100 times higher extinction ratio. The proposed compact on-chip silicon-based nanophotonic resistive device is a potential candidate for a large-scale integrated photonic circuit for applications in optical switching, modulation, memory, and computation.

Engineered nanophotonic waveguide with ultra-low dispersion.

A silicon-based engineered hybrid plasmonic waveguide with ultra-low dispersion is proposed. The ridge-shaped structure of the nanophotonic waveguide enables nano-scale confinement with electrically tunable characteristics using the plasma dispersion effect in silicon. The waveguide exhibits ultra-low dispersion of $1.28\;{{\rm ps}^2}/{\rm m}$ at telecommunication wavelength (1550 nm) in C band together with dual flatband dispersion over a wavelength range of 370 nm. The hybrid plasmonic mode is made to be confined in 15 nm thick ${{\rm SiO}_2}$ with a propagation loss of 15.3 dB/mm utilizing the engineered ridge structure comprising Si, ${{\rm SiO}_2}$, and gold. In addition, the proposed waveguide shows six zero-dispersion wavelengths. The imaginary and real parts of the effective refractive index of the guided hybrid plasmonic mode are reported to be tunable with the applied voltage. The reported numerical results can pave the way for achieving intensity modulators and other electrically tunable devices at telecommunication wavelengths. The ultra-low dispersion and electrical tuning make this nanophotonic waveguide an absolute contender for applications including efficient nonlinear signal processing such as wide wavelength conversion based on four-wave mixing, supercontinuum generation, and other nanoscale integrated photonic devices.

Nutrition-related predictors of complications and length of hospital stay following total pelvic exenteration surgery.

BACKGROUND & AIMS: Pelvic exenteration (PE) surgery is now a widely accepted procedure that is increasingly being performed worldwide but has significant morbidity. Although nutrition status, body mass index (BMI) and postoperative nutrition support practices are modifiable risk factors, few studies have examined the relationship of these with clinical outcomes following PE. The aim of this study was therefore to investigate the impact of these factors on postoperative complications and length of hospital stay (LOHS) following PE. METHODS: This was a retrospective cohort study of all patients having total PE surgery at a tertiary teaching hospital from 2012 to 2021 (n = 69). Multivariable analyses were undertaken to confirm univariate associations and adjust for confounding variables. Binary logistic regression was undertaken to explore predictors of infectious and Grade III or above Clavien-Dindo complications, and negative binomial regression to identify predictors of LOHS. RESULTS: Patients who were malnourished according to the Subjective Global Assessment were 5.66 (OR 5.66, 95% CI 1.07-29.74, p = 0.041) times more likely to develop an infectious complication. Increasing BMI was independently associated with development of Grade III or above Clavien-Dindo complications (p = 0.040). For each additional day until full diet commencement, there was a 19% (OR: 1.19, 95% CI 1.05-1.34, p = 0.005) increased incidence of significant complications and a 5.6% (IRR: 1.056, 95% CI: 1.02-1.09, p = 0.002) longer LOHS on multivariable analysis. There was a high rate of prolonged postoperative ileus (78%). The implementation of a nutrition support pathway with routine postoperative parenteral nutrition (PN) resulted in patients achieving adequate nutrition 7 days faster (p < 0.001) with minimal line-related complications (1.4% line-related thrombus). Routine PN did not impact ileus rates (p = 0.33) or time to diet commencement (p = 0.6). CONCLUSIONS: Preoperative malnutrition and higher BMI were associated with complications following PE. Delay to full diet commencement was associated with increased complications and longer LOHS. Routine postoperative PN appears safe and resulted in patients achieving adequate nutrition faster.

All optical modulation in vertically coupled indium tin oxide ring resonator employing epsilon near zero state.

We present an innovative approach to achieve all-optical modulation within an ITO-based vertically coupled ring resonator. This method leverages the material's enhanced nonlinear response in the near-infrared wavelengths, particularly within the epsilon-near-zero (ENZ) state. To enhance the interaction between light and the material while minimizing scattering losses, our approach employs an ITO-based vertically connected ring resonator. The vertical arrangement eliminates the need for etching fine gaps to separate the ring and bus waveguide. The novel waveguide design addresses the necessity of high sensitivity, non-linear effects and compact size opening the possibilities for all-optical signal processing. This unique resonator structure effectively facilitates the coupling of a high-intensity pump wavelength into the ITO-based micro-ring resonator. Consequently, this optical pumping induces electron heating within the ITO material, leading to a significant increase in its nonlinear optical properties. This, in turn, results in a noteworthy alteration of ITO's refractive index, specifically in the unity order, thereby modifying the complex effective index of the optical beam propagating at 1550 nm. Our experimental findings demonstrate an impressive extinction ratio of 18 dB for a 30 µm long device, which highlights the efficiency of our approach in achieving all-optical modulation through the optical pumping of an ITO-based vertically coupled ring resonator. The proposed all-optical modulator has outperformed as compared to conventional waveguide-based modulators in terms of extinction ratio and footprint. This novel technique holds immense potential for advancing high-speed data communication systems in the future. As the demand for advanced processing capabilities, such as artificial intelligence, continues to grow, all-optical modulation emerges as a groundbreaking technology poised to revolutionize the next generation of computing and communication systems.

Are we underusing peripheral parenteral nutrition? A 5-year retrospective review of inpatient parenteral nutrition practices.

BACKGROUND: Peripheral parenteral nutrition (PPN) represents an alternative option to central parenteral nutrition (CPN) for patients requiring short-term parenteral nutrition (PN). We hypothesized that the use of PPN could be increased in certain patient cohorts referred for PN in our facility. METHODS: A retrospective observational study investigating the clinical characteristics of patients receiving PN under the nutrition support team over a 5-year period was undertaken. Patients who received PPN were reviewed descriptively. Of the patients who received CPN, representative samples were grouped into those who received PN for ≤7 or >7-28 days (n = 100 each, randomly assigned). Clinical characteristics considered included indication, duration and referring team for PN, and nutrition status. Descriptive statistics and binary logistic regression model for predictors of PN duration of ≤7 or >7-28 days were derived. RESULTS: Only four patients received PPN for a median of 4 days, most of whom required this route because of loss of central venous access for CPN. A high proportion of patients with no enteral access received CPN for ≤7 days, whereas the majority of patients with malabsorption required >7-28 days of CPN. Being referred for PN following upper gastrointestinal surgery increased the likelihood of CPN use for >7 days (relative risk, 5.7; 95% CI, 1.7-18.9; P = 0.004). CONCLUSION: Within our service, PN referrals for no enteral access may represent a group in whom PPN could be used in the first instance; those referred with an indication of malabsorption or following upper gastrointestinal surgery may benefit from early commencement of CPN.

A candidal oesophageal stricture responsive to fluconazole therapy.

We report a case of candidal oesophageal stricture in an 81 year-old man with a 2 year history of gradual onset dysphagia and odynophagia to solids. Although rare, most cases have reported treatment success with oesophageal balloon dilation. We report the first case of candidal oesophageal stricture resolution with a prolonged course of anti-fungal therapy.