Does the degree of polarization of vector beams remain unchanged on atmospheric propagation?

All roads lead to Rome. In this article we propose a novel theoretical framework to demonstrate vector beams whose degree of polarization does not change on atmospheric propagation. Inspired by the Fresnel equations, we derive the reflected and refracted field of vector beams propagating through a phase screen by employing the continuity of electromagnetic field. We generalize the conventional split-step beam propagation method by considering the vectorial properties in the vacuum diffraction and the refractive properties of a single phase screen. Based on this vectorial propagation model, we extensively calculate the change of degree of polarization (DOP) of vector beams under different beam parameters and turbulence parameters both in free-space and satellite-mediated links. Our result is that whatever in the free-space or satellite-mediated regime, the change of DOP mainly fluctuates around the order of 10-13 to 10-6, which is almost negligible.

Analysis and mitigation of the carrier phase delay effect of the digital phase generated carrier algorithm.

We present an improved digital phase generated carrier algorithm based on the synchronous carrier restoration (SCR) method to mitigate the carrier phase delay effect. The most distinguishing feature of this method is that it directly picks up the carrier signal information (frequency and phase) from the interference signal and synchronically accomplishes the processing of carrier signal restoration. In comparison to the traditional method, which adopts the initial carrier signal, total-harmonic-distortion with SCR is only 0.091%, lower than the traditional SCR of 18.38%, and the signal-to-noise ratio increases by 29 dB. Further, we derived the analytic expression of the distortion component and verified it by experiments. This technique may be potentially applied to a long-distance large-scale distributed fiber-optic interferometric sensor array.

Risk factors for readmission of patients with amputation to acute care from inpatient rehabilitation: A retrospective cohort study.

INTRODUCTION: Amputation is a major condition that requires inpatient rehabilitation. Some research has been conducted to explore the risk factors for readmission of patients from inpatient rehabilitation facilities to acute care hospitals. However, few studies have included patients with amputation in the study population. OBJECTIVE: To identify the risk factors for readmission of patients with amputation to acute care hospitals from an inpatient rehabilitation facility. DESIGN: Retrospective cohort study. SETTING: An acute rehabilitation hospital associated with a community-based tertiary medical center. PATIENTS: A retrospective review of 156 independent admissions of 145 patients from June 2019 to July 2022. MAIN OUTCOME MEASURE: The study outcome measure was readmission to acute care from an acute rehabilitation unit. RESULTS: Of the 156 independent admissions, the readmission rate was 19% (29/156). The most common cause of transfer was incision-site complications (9/29, 31%), including wound infection and wound dehiscence. Patients with amputation readmitted to acute care are more likely to be receiving dialysis (p < .001), have a longer length of stay in acute care before admission to the rehabilitation facility (p = .039), and have a lower Section GG score on admission (p < .001). Age, sex, ethnicity, amputation level, and history of diabetes mellitus were not associated with acute care hospital readmission. The logistic regression model revealed that patients being on dialysis was the only significant risk factor predictive of readmission to acute care (odds ratio [OR] 4.82, p = .006). CONCLUSIONS: This study showed that incision-site complications were the most common cause of disruption in inpatient rehabilitation via acute hospital readmission in patients with amputation. Being on dialysis was associated with a higher risk of readmission to acute care hospitals. Based on the results of this study, specific rehabilitation plans might be required for patients with amputation who carry certain risk factors to reduce rehospitalization to the acute care unit.

Piezoelectric optical fiber stretcher for application in an atmospheric optical turbulence sensor.

A piezoelectric optical fiber stretcher has been introduced for working point controlling and low-frequency noise suppression of a fiber-optic atmospheric turbulence sensor. It is actuated by a piezoelectric ceramic stack. The rational structure allows the fiber to extend only along the axial direction, which minimizes the nonlinear birefringence effects for the optical phase shift. What is believed to be a novel method has been proposed to measure its phase-shift coefficient. With the use of this device, the fiber-optic atmospheric turbulence sensor has been tested for the air refractive index measurement.