Machine Learning and Causal Approaches to Predict Readmissions and Its Economic Consequences Among Canadian Patients With Heart Disease: Retrospective Study

BACKGROUND

Unplanned patient readmissions within 30 days of discharge pose a substantial challenge in Canadian health care economics. To address this issue, risk stratification, machine learning, and linear regression paradigms have been proposed as potential predictive solutions. Ensemble machine learning methods, such as stacked ensemble models with boosted tree algorithms, have shown promise for early risk identification in specific patient groups.

OBJECTIVE

This study aims to implement an ensemble model with submodels for structured data, compare metrics, evaluate the impact of optimized data manipulation with principal component analysis on shorter readmissions, and quantitatively verify the causal relationship between expected length of stay (ELOS) and resource intensity weight (RIW) value for a comprehensive economic perspective.

METHODS

This retrospective study used Python 3.9 and streamlined libraries to analyze data obtained from the Discharge Abstract Database covering 2016 to 2021. The study used 2 sub-data sets, clinical and geographical data sets, to predict patient readmission and analyze its economic implications, respectively. A stacking classifier ensemble model was used after principal component analysis to predict patient readmission. Linear regression was performed to determine the relationship between RIW and ELOS.

RESULTS

The ensemble model achieved precision and slightly higher recall (0.49 and 0.68), indicating a higher instance of false positives. The model was able to predict cases better than other models in the literature. Per the ensemble model, readmitted women and men aged 40 to 44 and 35 to 39 years, respectively, were more likely to use resources. The regression tables verified the causality of the model and confirmed the trend that patient readmission is much more costly than continued hospital stay without discharge for both the patient and health care system.

CONCLUSIONS

This study validates the use of hybrid ensemble models for predicting economic cost models in health care with the goal of reducing the bureaucratic and utility costs associated with hospital readmissions. The availability of robust and efficient predictive models, as demonstrated in this study, can help hospitals focus more on patient care while maintaining low economic costs. This study predicts the relationship between ELOS and RIW, which can indirectly impact patient outcomes by reducing administrative tasks and physicians' burden, thereby reducing the cost burdens placed on patients. It is recommended that changes to the general ensemble model and linear regressions be made to analyze new numerical data for predicting hospital costs. Ultimately, the proposed work hopes to emphasize the advantages of implementing hybrid ensemble models in forecasting health care economic cost models, empowering hospitals to prioritize patient care while simultaneously decreasing administrative and bureaucratic expenses.

Subnoise detection of a fast random event

Observation of random, nonrepetitive phenomena is of critical importance in astronomy, spectroscopy, biology, and remote sensing. Heralded by weak signals, hidden in noise, they pose basic detection challenges. In contrast to repetitive waveforms, a single-instance signal cannot be separated from noise through averaging. Here, we show that a fast, randomly occurring event can be detected and extracted from a noisy background without conventional averaging. An isolated 80-picosecond pulse was received with confidence level exceeding 99%, even when accompanied by noise. Our detector relies on instantaneous spectral cloning and a single-step, coherent field processor. The ability to extract fast, subnoise events is expected to increase detection sensitivity in multiple disciplines. Additionally, the new spectral-cloning receiver can potentially intercept communication signals that are presently considered secure.

Two-fold transmission reach enhancement enabled by transmitter-side digital backpropagation and optical frequency comb-derived information carriers

We demonstrate a two-fold reach extension of 16 GBaud 16-Quadrature Amplitude Modulation (QAM) wavelength division multiplexed (WDM) system based on erbium doped fiber amplifier (EDFA)-only amplified standard and single mode fiber -based link. The result is enabled by transmitter-side digital backpropagation and frequency referenced carriers drawn from a parametric comb.

High-speed, rate-scalable photonic-assisted digitizer equalization by frequency comb referencing

A scalable analog-to-digital converter based on polychromatic sampling and optical-domain frequency referencing is described. The new architecture relies on low-distortion replication of an optical signal to spectrally distinct copies and subsequent polychromatic parametric sampling. Frequency comb referencing of parametric replication and sampling was used to convert processor distortions into quasi-stationary impairments and enable a practical equalization implementation. The operation of the new digitizer was demonstrated at 30 GS/s, achieving 6.5 effective number of bits in the first Nyquist zone. In contrast to conventional analog-to-digital converters, the new preprocessor sampling bandwidth is not restricted to the first Nyquist zone, and can operate in the second and third Nyquist zones beyond 40 GHz.

Quantum frequency translation of single-photon states in a photonic crystal fiber

We experimentally demonstrate frequency translation of a nonclassical optical field via four-wave mixing (Bragg-scattering process) in a photonic crystal fiber (PCF). The high nonlinearity and the ability to control dispersion in PCF enable efficient translation between nearby photon channels within the visible to-near-infrared spectral range, useful in quantum networks. Heralded single photons at 683 nm were translated to 659 nm with an efficiency of 28.6±2.2 percent. Second-order correlation measurements on the 683- and 659-nm fields yielded g(683)(2) (0)=0.21±0.02 and g(659)(2) (0)=0.19±0.05, respectively, showing the nonclassical nature of both fields.

Bandwidth-efficient phase modulation techniques for stimulated Brillouin scattering suppression in fiber optic parametric amplifiers

Two novel bandwidth efficient pump-dithering Stimulated Brillouin Scattering (SBS) suppression techniques are introduced. The techniques employ a frequency-hopped chirp and an RF noise source to impart phase modulation on the pumps of a two pump Fiber Optical Parametric Amplifier (FOPA). The effectiveness of the introduced techniques is confirmed by measurements of the SBS threshold increase and the associated improvements relative to the current state of the art. Additionally, the effect on the idler signal integrity is presented as measured following amplification from a two pump FOPA employing both techniques. The measured 0.8 dB penalty with pumps dithered by an RF noise source, after accruing 160 ps/nm of dispersion with 38 dB conversion gain in a two-pump FOPA is the lowest reported to date.

Monitoring levels of nephrotoxicity of different aminoglycosides during febrile neutropenia caused by nephrotoxic chemotherapy: a single centre study

PURPOSE

To investigate the possible existence of increased nephrotoxicity caused by once-daily aminoglycosides in febrile neutropenic patients who were previously treated with cisplatin-based nephrotoxic chemotherapy.

METHODS

Thirty-one patients with metastatic tumors received chemotherapy and, as a result, developed febrile neutropenia. Patients were stratified with regard to chemotherapy with cisplatin (n=15) or without cisplatin (n=16). Both groups received i.v. empiric antibiotic treatment which included combinations of once-daily aminoglycosides (amikacin vs. gentamicin) with beta-lactams.

RESULTS

Increased nephrotoxicity due to administered aminoglycosides appeared significantly more frequently (p<0.05) in patients who received cisplatin-based chemotherapy. Increased nephrotoxicity differed significantly between various aminoglycosides regimens (p<0.05), being greater in the gentamicin group.

CONCLUSION

These results showed that cisplatin-based chemotherapy followed by a once-daily aminoglycosides regimen caused increased renal toxicity, which was more pronounced in patients treated with gentamicin vs. those treated with amikacin.

Short wavelength infrared frequency conversion in ultra-compact fiber device

Linear and nonlinear characteristics of devices using millimeter-scale spools of highly nonlinear fiber are experimentally investigated within 2000-2400nm spectral range. Coils with radius larger than 3.5 mm indicate that macro-bending induced radiation loss is negligible up to 2400nm. Devices with smaller diameter coiling resulted in macro-bending losses that dominate over micro-bending losses beyond 2200nm. A tunable short-wave infrared source was constructed using a coin-sized fiber module to demonstrate an efficient nonlinear conversion from 1.26 to 2.2 microm.

1 micros tunable delay using para-metric mixing and optical phase conjugation in Si waveguides: comment

A recent report of 1 micros all-optical delay using silicon convertor elements in the 1550-nm band is analyzed.

730-nm optical parametric conversion from near- to short-wave infrared band

A record 730 nm parametric conversion in silica fiber from the near-infrared to the short-wave infrared band is reported and analyzed. A parametric gain in excess of 30 dB was measured for a signal at 1300 nm (with corresponding idler at 2030 nm). This conversion was performed in a travelling single-pass one-pump parametric architecture and high efficiency is achieved by a combination of high peak power and a nonlinear fiber with a reduced fourth-order dispersion coefficient.

Multicolor multipartite entanglement produced by vector four-wave mixing in a fiber

Multipartite entanglement is a resource for quantum communication and computation. Vector four-wave mixing (FWM) in a fiber, driven by two strong optical pumps, couples the evolution of four weak optical sidebands (modes). Depending on the fiber dispersion and pump frequencies, the mode frequencies can be similar (separated by less than 1 THz) or dissimilar (separated by more than 10 THz). In this report, the discrete- and continuous-variable entanglement produced by vector FWM is studied in detail. Formulas are derived for the variances of, and correlations between, the mode quadratures and photon numbers. These formulas and related results show that the modes are four-partite entangled.

Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber

We study theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in photonic crystal optical fiber. We show that it is possible to engineer two-photon states with specific spectral correlation ("entanglement") properties suitable for quantum information processing applications. We focus on the case exhibiting no spectral correlations in the two-photon component of the state, which we call factorability, and which allows heralding of single-photon pure-state wave packets without the need for spectral post filtering. We show that spontaneous four wave mixing exhibits a remarkable flexibility, permitting a wider class of two-photon states, including ultra-broadband, highly-anticorrelated states.

Impairments in deeply-saturated optical parametric amplifiers for amplitude- and phase-modulated signals

We measure impairment of on-off-keyed and differential-phase-shift-keyed signals imposed by gain saturation in a fiber parametric amplifier. Phase modulation is observed to be more robust, particularly for deep (15 dB) saturation.

Phase-sensitive amplification of chirped optical pulses in fibers

In this paper a detailed analysis is made of the phase-sensitive amplification (PSA) of optical pulses by degenerate four-wave mixing (phase-conjugation) in fibers. Formulas are derived, which show that the amplification level and phase sensitivity depend strongly on the phase of the signal pulse, but weakly on its chirp, and the difference between its carrier frequency and the average pump frequency. Solitons, which are unchirped, and dispersion-managed solitons, which are weakly chirped, are suitable for in-line and post-transmission PSA. Pseudo-linear pulses, which are strongly chirped, are unsuitable for in-line PSA, but post-transmission dispersion compensation makes them suitable for PSA prior to detection.

Unimpaired phase-sensitive amplification by vector four-wave mixing near the zero-dispersion frequency

Phase-sensitive amplification (PSA), which is produced by degenerate four-wave mixing (FWM) in a randomly-birefringent fiber, has the potential to improve the performance of optical communication systems. Scalar FWM, which is driven by parallel pumps, is impaired by the generation of pump-pump and pump-signal harmonics, which limit the level, and modify the phase sensitivity, of the signal gain. In contrast, vector FWM, which is driven by perpendicular pumps, is not impaired by the generation of harmonics. Vector FWM produces PSA with the classical properties of a one-mode squeezing transformation.

Demonstration of low-noise frequency conversion by bragg scattering in a fiber

We experimentally examine the noise properties of a two-pump optical parametric amplifier when converting frequencies using the Bragg-scattering (BS) and phase-conjugation (PC) processes. Using co-polarized pumps and signal, we show that the noise performance is limited by spontaneous Raman scattering. The noise performance of BS is superior to that of PC, and should improve with larger frequency excursions.

Translation of quantum states by four-wave mixing in fibers

Optical frequency conversion by four-wave mixing (Bragg scattering) in a fiber is considered. If the frequencies and polarizations of the waves are chosen judiciously, Bragg scattering enables the translation of individual and entangled states, without the noise pollution associated with parametric amplification (modulation instability or phase conjugation), and with reduced noise pollution associated with stimulated Raman scattering.

Quantum noise properties of parametric processes

In this paper the quantum noise properties of phase-insensitive and phase-sensitive parametric processes are studied. Formulas for the field-quadrature and photon-number means and variances are derived, for processes that involve arbitrary numbers of modes. These quantities determine the signal-to-noise ratios associated with the direct and homo-dyne detection of optical signals. The consequences of the aforementioned formulas are described for frequency conversion, amplification, monitoring, and transmission through sequences of attenuators and amplifiers.

Pump-noise transfer in dual-pump fiber-optic parametric amplifiers: walk-off effects

Transfer of intensity noise from pumps to signal in dual-pump fiber-optic parametric amplifiers is simulated numerically for a realistic configuration in which both pumps are amplified and filtered before they enter the fiber. The walk-off effects induced by different group velocities of pumps, signal, and idler are fully taken into account. It is found that the optical signal-to-noise ratio can be as low as 15 dB when the amplifier length is close to 0.5 km, but it can be improved by 3 dB or so by use of longer fibers.

Quantum noise properties of parametric amplifiers driven by two pump waves

In a parametric amplifier (PA) driven by two pump waves the signal sideband is coupled to three idler sidebands, all of which are frequency-converted (FC) images of the signal, and two of which are phaseconjugated (PC) images of the signal. If such a device is to be useful, the signal must be amplified, and the PC and FC idlers must be produced, with minimal noise. In this paper the quantum noise properties of two-sideband (TS) parametric devices are reviewed and the properties of many-sideband devices are determined. These results are applied to the study of two-pump PAs, which are based on the aforementioned four-sideband (FS) interaction. As a general guideline, the more sidebands that interact, the higher are the noise levels. However, if the pump frequencies are tuned to maximize the frequency bandwidth of the FS interaction, the signal and idler noise-figures are only slightly higher than the noise figures associated with the limiting TS interactions.

Phase-sensitive amplification in a fiber

Phase-sensitive amplification (PSA) has the potential to improve significantly the performance of optical communication systems. PSA is known to occur in chi(2) devices, and in a fiber interferometer, which is an example of a chi(3) device. In this report some four-wave mixing processes are described, which produce PSA directly in fibers.

Four-wave mixing in fibers with random birefringence

Parametric amplification is made possible by four-wave mixing. In low-birefringence fibers the birefringence axes and strength vary randomly with distance. Light-wave propagation in such fibers is governed by the Manakov equation. In this paper the Manakov equation is used to study degenerate and nondegenerate four-wave mixing. The effects of linear and nonlinear wavenumber mismatches, and nonlinear polarization rotation, are included in the analysis. Formulas are derived for the initial quadratic growth of the idler power, and the subsequent exponential growth of the signal and idler powers (which continues until pump depletion occurs). These formulas are valid for arbitrary pump and signal polarizations.

Parametric instabilities driven by orthogonal pump waves in birefringent fibers

The four-sideband model of parametric instabilities driven by orthogonal pump waves in birefringent fibers is developed and validated by numerical simulations. A polynomial eigenvalue equation is derived and used to determine how the spatial growth rates and frequency bandwidths of various instabilities depend on the system parameters. The maximal growth rate is associated with a group-speed matched four-sideband process (coupled modulation instability), whereas broad-bandwidth gain is associated primarily with a two-sideband process (phase conjugation). This four-sideband model facilitates the design of parametric amplifiers driven by two pump waves with different frequencies and polarizations.

Reduction of soliton phase jitter by in-line phase conjugation

The main impairment of differential-phase-shift-keyed communication systems is phase jitter. Noise-induced phase jitter, which is mediated by self-phase modulation, can be reduced significantly by a small number of in-line phase conjugators.

Parametric amplifiers driven by two pump waves with dissimilar frequencies

Parametric amplifiers driven by two pump waves are studied numerically. For typical parameters, one can design an amplifier that produces uniform gain over a range of wavelengths that extends at least 33 nm on either side of the average pump wavelength.

Photorefraction in lead tin-fluorophosphate glasses

Permanent grating patterns have been written directly in lead-tin-fluorophosphate glasses by use of UV radiation. The effect of photorefraction is studied in different tin-fluorophosphate compositions. Recorded gratings are found to be volume rather than surface elements. The induced index changes are comparable with those seen in GeO(2)- SiO(2) glasses.

Spatiotemporal shaping of terahertz pulses

We report temporal shaping of few-cycle terahertz pulses, using a slit in a conductive screen as a high-pass filter. The filter's cutoff frequency was tuned by changing the width of the slit; the slope of the cutoff transition was altered by changing the thickness of the screen. We measured the transmission function of the filters, using large-aperture photoconducting antennas to create and detect the incident and transmitted electric field. Our experimental results were in excellent agreement with the performed finite-difference time-domain simulations of the propagation of the pulse through the slit. When the screen thickness was greater than the slit width, the filter was well modeled by a short, planar waveguide. Using a simple transfer function, we accurately describe the sharp cutoff and dispersion of such a filter.

Nucleolar volume in breast carcinomas

The prognostic value of histopathological typing of breast carcinomas is relatively good. The determination of cell size has been a common and useful parameter in the diagnosis of various malignancies. With modern stereologic methods it is possible to obtain unbiased estimates of nucleolar volume. The aim of this study was to present our data regarding the nucleolar size in breast carcinoma. Patients treated for breast carcinoma (n = 39) were retrieved and randomly selected from the files of the University Institute of Pathology, Nis. Histological sections (4 microns) were cut from each of the routinely processed, paraffin-embedded tissue blocks and stained with hematoxylin and eosin. A Carl Zeiss NU-1 microscope equipped with a x 100 oil-immersion lens (N.A. = 1.25) and eyepiece graticule was used for stereological measurements. A total magnification of x 1600 was used. A simple grid was used for point sampling of nucleolar intercepts, which were measured in one arbitrary direction. By multiplying the averaged, cubed intercept length by pi/3, an unbiased estimate of volume-weighted nucleolar volume was obtained. The nucleolar volume was significantly larger in invasive ductal carcinoma (12.34 +/- 3.48 microns3) than invasive lobular carcinoma (5.6 +/- 2.73 microns 3) and mucinous (colloid) adenocarcinoma (0.88 +/- 0.42 micron 3). Various histological types of breast cancer exhibit differences with regard to nucleolar volume.

Optical switching in lambda/4-shifted nonlinear periodic structures

We show that lambda/4-shifted distributed-feedback nonlinear devices can be used as an all-optical switch at relatively low input intensities. The lambda/4 shift opens a narrow transmission window whose peak position within the stop band depends on the input intensity, a feature that can be used for low-power optical switching. The nonlinear coupled-mode approach is used to analyze the stationary operating regime of such a device and determine the transmittivity as a function of the input intensity. A closed-form solution, rather than a numerical one, is found for what we believe is the first time.

Ultrafast pulse propagation in periodic optical media: a generalized finite-difference time-domain approach

A generalized finite-difference time-domain method is used to model the propagation of ultrafast optical pulses through periodic structures with a frequency-dependent material response. Excellent agreement with a thin multilayer decomposition is found for the cases of dispersive and nondispersive optical media.