Dust charge distribution in the interstellar medium

We investigate the equilibrium charge distribution of dust grains in the interstellar medium (ISM). Our treatment accounts for collisional charging by electrons and ions, photoelectric charging due to a background interstellar radiation field, the collection of suprathermal cosmic ray electrons and photoelectric emission due to a cosmic ray induced ultraviolet radiation field within dense molecular clouds. We find that the charge equilibrium assumption is valid throughout the multi-phase ISM conditions investigated here, and should remain valid for simulations with resolutions down to AU scales. The charge distribution of dust grains is size, composition, and ISM environment dependent: local radiation field strength, $G$, temperature, $T$, and electron number density, $n_{\mathrm{e}}$. The charge distribution is tightly correlated with the `charging parameter', $G\sqrt{T}/n_{\mathrm{e}}$. In the molecular medium, both carbonaceous and silicate grains have predominantly negative or neutral charges with narrow distributions. In the cold neutral medium, carbonaceous and silicate grains vary from negative and narrow distributions, to predominantly positive and wide distributions depending on the magnitude of the charging parameter. In the warm neutral medium, grains of all sizes are positively charged with wide distributions. We derive revised parametric expressions that can be used to recover the charge distribution function of carbonaceous and silicate grains from 3.5 {\AA} to 0.25 $\mu$m as a function of the size, composition and ambient ISM parameters. Finally, we find that the parametric equations can be used in environments other than Solar neighborhood conditions, recovering the charge distribution function of dust grains in photon dominated regions.Comment: 13 pages and 9 figures. Accepted for publication in MNRAS. Code developed in this paper can be found: https://github.com/jcibanezm/DustCharg

Dust charge distribution in the interstellar medium

We investigate the equilibrium charge distribution of dust grains in the interstellar medium (ISM). Our treatment accounts for collisional charging by electrons and ions, photoelectric charging due to a background interstellar radiation field, the collection of suprathermal cosmic ray electrons and photoelectric emission due to a cosmic ray induced ultraviolet radiation field within dense molecular clouds. We find that the charge equilibrium assumption is valid throughout the multi-phase ISM conditions investigated here, and should remain valid for simulations with resolutions down to AU scales. The charge distribution of dust grains is size, composition, and ISM environment dependent: local radiation field strength, $G$, temperature, $T$, and electron number density, $n_{\mathrm{e}}$. The charge distribution is tightly correlated with the `charging parameter', $G\sqrt{T}/n_{\mathrm{e}}$. In the molecular medium, both carbonaceous and silicate grains have predominantly negative or neutral charges with narrow distributions. In the cold neutral medium, carbonaceous and silicate grains vary from negative and narrow distributions, to predominantly positive and wide distributions depending on the magnitude of the charging parameter. In the warm neutral medium, grains of all sizes are positively charged with wide distributions. We derive revised parametric expressions that can be used to recover the charge distribution function of carbonaceous and silicate grains from 3.5 {\AA} to 0.25 $\mu$m as a function of the size, composition and ambient ISM parameters. Finally, we find that the parametric equations can be used in environments other than Solar neighborhood conditions, recovering the charge distribution function of dust grains in photon dominated regions.Comment: 13 pages and 9 figures. Accepted for publication in MNRAS. Code developed in this paper can be found: https://github.com/jcibanezm/DustCharg

Global Incidence and Risk Factors Associated With Postoperative Urinary Retention Following Elective Inguinal Hernia Repair

Importance Postoperative urinary retention (POUR) is a well-recognized complication of inguinal hernia repair (IHR). A variable incidence of POUR has previously been reported in this context, and contradictory evidence surrounds potential risk factors.Objective To ascertain the incidence of, explore risk factors for, and determine the health service outcomes of POUR following elective IHR.Design, Setting, and Participants The Retention of Urine After Inguinal Hernia Elective Repair (RETAINER I) study, an international, prospective cohort study, recruited participants between March 1 and October 31, 2021. This study was conducted across 209 centers in 32 countries in a consecutive sample of adult patients undergoing elective IHR.Exposure Open or minimally invasive IHR by any surgical technique, under local, neuraxial regional, or general anesthesia.Main Outcomes and Measures The primary outcome was the incidence of POUR following elective IHR. Secondary outcomes were perioperative risk factors, management, clinical consequences, and health service outcomes of POUR. A preoperative International Prostate Symptom Score was measured in male patients.Results In total, 4151 patients (3882 male and 269 female; median [IQR] age, 56 [43-68] years) were studied. Inguinal hernia repair was commenced via an open surgical approach in 82.2% of patients (n = 3414) and minimally invasive surgery in 17.8% (n = 737). The primary form of anesthesia was general in 40.9% of patients (n = 1696), neuraxial regional in 45.8% (n = 1902), and local in 10.7% (n = 446). Postoperative urinary retention occurred in 5.8% of male patients (n = 224), 2.97% of female patients (n = 8), and 9.5% (119 of 1252) of male patients aged 65 years or older. Risk factors for POUR after adjusted analyses included increasing age, anticholinergic medication, history of urinary retention, constipation, out-of-hours surgery, involvement of urinary bladder within the hernia, temporary intraoperative urethral catheterization, and increasing operative duration. Postoperative urinary retention was the primary reason for 27.8% of unplanned day-case surgery admissions (n = 74) and 51.8% of 30-day readmissions (n = 72).Conclusions The findings of this cohort study suggest that 1 in 17 male patients, 1 in 11 male patients aged 65 years or older, and 1 in 34 female patients may develop POUR following IHR. These findings could inform preoperative patient counseling. In addition, awareness of modifiable risk factors may help to identify patients at increased risk of POUR who may benefit from perioperative risk mitigation strategies