The theory of bremsstrahlung e → eγ by extremely high energy electrons passing through ordinary matter has been qualitatively incomplete. We revisit the suppression of bremsstrahlung by the Landau-Pomeranchuk-Migdal (LPM) effect, here accounting for quantum disruption of that effect from pair production. Our analysis covers the full range of ultra-relativistic electron and photon energies (subject to a few simplifying approximations).

Abstract Very high energy electrons initiate electromagnetic showers in ordinary matter that branch and multiply through bremsstrahlung and pair production. At extremely high energies, the quantum mechanical duration of these processes becomes longer than the mean free time to elastically scatter from the medium, which leads to a very significant suppression of bremsstrahlung (and pair production) known as the Landau-Pomeranchuk-Migdal (LPM) effect. We revisit the LPM effect for bremsstrahlung of energy k γ from an electron of energy E. We find that there are very large corrections to the LPM bremsstrahlung rate for certain regions of (k γ , E) due to quantum overlap of bremsstrahlung and subsequent pair production. This possibility was first raised in the 1960s, when it was argued qualitatively that pair production would significantly decrease the bremsstrahlung rate in those regions of (k γ , E) compared to the already-suppressed LPM bremsstrahlung rate. We find the opposite — quantum overlap of bremsstrahlung with pair production significantly increases the bremsstrahlung rate compared to the LPM calculation — and we verify our qualitative arguments with an analytic calculation of the effect.

Ultra-relativistic electrons initiate electromagnetic showers in ordinary matter that evolve through bremsstrahlung and pair production. At very high energy, the quantum mechanical duration of bremsstrahlung becomes longer than the mean free time to elastically scatter from the medium, leading to a significant suppression known at the Landau-Pomeranchuk-Migdal (LPM) effect. For some ranges of bremsstrahlung photon and initial electron energies (k_γ,E), the duration becomes so long that it will also overlap with subsequent pair production by the bremsstrahlung photon, disrupting LPM suppression and drastically changing LPM predictions. We have previously calculated this change for extremely high energies (k_γ≫ 2 TeV or more, depending on the medium), for which the electron mass and medium-induced photon mass could be ignored. In this paper, we extend that analysis to lower (but still ultra-relativistic) energy by accounting for those masses, leading to a rich map of behavior in different regions of (k_γ,E).

Inside a medium, showers originating from a very high energy particle develop via medium-induced splitting processes such as bremsstrahlung and pair production. During shower development, two consecutive splittings sometimes overlap quantum mechanically, so that they cannot be treated independently. Some of these effects can be absorbed into an effective value of a medium parameter known as q̂ . Previous calculations (with certain simplifying assumptions) have found that, after adjusting the value of q̂ , the leftover effect of overlapping splittings is quite small for purely gluonic large-Nc showers but is very much larger for large-Nf QED showers, at comparable values of Nα. Here, by investigating the same problem for QCD with quarks in the large-Nf limit of many quark flavors, we make a first study of whether the small effect in purely gluonic showers (i) was merely an accident or (ii) is more broadly characteristic of such overlap effects in QCD. We also offer a qualitative explanation for the large size of the effect in QED vs. QCD.

Inside a medium, showers originating from a very high-energy particle may develop via medium-induced splitting processes such as hard bremsstrahlung or pair production. During shower development, two consecutive splittings sometimes overlap quantum mechanically, so that they cannot be treated independently. Some of these effects can be absorbed into an effective value of a medium parameter known as q̂ . Previous calculations (with certain simplifying assumptions) have found that, after adjusting the value of q̂ , the leftover effect of overlapping splittings is quite small for purely gluonic large-Nc showers but is very much larger for large-Nf QED showers, at comparable values of Nα. Those works did not quite make for apples-to-apples comparisons: the gluon shower work investigated energy deposition from a gluon-initiated shower, whereas the QED work investigated charge-deposition from an electron-initiated shower. As a first step to tighten up the comparison, this paper investigates energy deposition in the QED case. Along the way, we develop a framework that should be useful in the future to explore whether the very small effect of overlapping splitting in purely gluonic showers is an artifact of having ignored quarks.

Abstract Mounting evidence supports the use of telehealth to improve burn care access and efficiency. However, barriers to telehealth use remain throughout the United States and may disproportionately affect specific populations, such as rural and non-English-speaking patients. This study analyzes the association between physical proximity to burn care and determinants of telehealth access. The relationship between telehealth-associated measures and proximity to burn care was analyzed with linear regression analysis. County-level data was sourced from the Agency for Healthcare Research and Quality's Social Determinants of Health Database (2020) and the American Community Survey (2021). County-level distances to the nearest American Burn Association (ABA)-verified burn center were calculated based on verified centers listed in the ABA burn center directory (n = 59). A subsequent analysis was performed on income-stratified datasets available for subset counties. Distance was negatively correlated with access to a smartphone (P < 0.0001), broadband internet (P < 0.0001), and cellular data plan (P < 0.0001) and positively correlated with the percent of households with no computing device (P < 0.0001) and no internet access (P < 0.0001). Analysis of income-stratified data revealed similar results. The percent population not speaking English well (P < 0.0001) at all (P = 0.0009) and the proportion of limited English-speaking households (P = 0.0001) decreased as a function of distance. People living furthest from an ABA-verified burn center in the United States are less likely to have adequate access to critical telehealth infrastructure compared to their counterparts living closer to a burn center. However, income impacts overall access and the degree to which access changes with proximity. Conversely, language-associated barriers decrease as distance increases.

ABSTRACT:Mounting evidence supports the use of telehealth to improve burn care access and efficiency. However, barriers to telehealth use remain throughout the United States and may disproportionately affect specific populations, such as rural and non-English-speaking patients. This study analyzes the association between physical proximity to burn care and determinants of telehealth access.The relationship between telehealth-associated measures and proximity to burn care was analyzed with linear regression analysis. County-level data was sourced from the Agency for Healthcare Research and Quality's Social Determinants of Health Database (2020) and the American Community Survey (2021). County-level distances to the nearest American Burn Association (ABA)-verified burn center were calculated based on verified centers listed in the ABA burn center directory (n = 59). A subsequent analysis was performed on income-stratified datasets available for subset counties.Distance was negatively correlated with access to a smartphone (P < 0.0001), broadband internet (P < 0.0001), and cellular data plan (P < 0.0001) and positively correlated with the percent of households with no computing device (P < 0.0001) and no internet access (P < 0.0001). Analysis of income-stratified data revealed similar results. The percent population not speaking English well (P < 0.0001) at all (P = 0.0009) and the proportion of limited English-speaking households (P = 0.0001) decreased as a function of distance.People living furthest from an ABA-verified burn center in the United States are less likely to have adequate access to critical telehealth infrastructure compared to their counterparts living closer to a burn center. However, income impacts overall access and the degree to which access changes with proximity. Conversely, language-associated barriers decrease as distance increases.

Background:Reduction mammaplasty is one of the most common reconstructive procedures performed in plastic surgery. Multiple comorbidities play a role in postoperative wound healing complications; however, there are insufficient data on the subdermal plexus (SDP) as it relates to these comorbidities. The purpose of this study is to evaluate the relationship between body mass index (BMI) and SDP of the superficial breast tissues and examine the association between SDP and postoperative complications.Methods:After Institutional Review Board approval, screening, and informed consent, patients undergoing reduction mammaplasty were selected. Tissue to be discarded was sent to pathology for analysis of immunohistochemistry directed against endothelial cells to determine the density of the SDP. Patients with BMI <35 and ≥35 kg/m2 were compared. Statistical analysis, including 2-tailed t test and Pearson correlation, was conducted.Results:A significant difference in SDP density (standard deviation) was identified between patients with a BMI ≥35 versus <35 kg/m2 (2.65 capillaries/mm2 ± 1.8 vs 1.56 capillaries/mm2 ± 1.2; P = .033). Patients with no historical use of tobacco versus those who used tobacco showed a significantly increased SDP (2.11 capillaries/mm2 ± 1.6 vs 1.20 capillaries/mm2 ± 0.5; P = .009). A significant relationship between postoperative infection (1.00 capillaries/mm2 ± 1.1; P = .041) and hematoma/seroma (0.788 capillaries/mm2 ± 0.1; P = .003) was identified. No significant relationship was found between SDP and delayed wound healing, nipple-areolar complex complications, fat/flap necrosis, or symptomatic scar occurrence.Conclusions:There is a statistically significant increase in SDP seen with increasing BMI, which does not explain the higher rate of wound healing complications after reduction mammaplasty typically seen in the higher BMI patient population. The association between BMI and complications after reduction mammaplasty remains unclear.

Specialized burn centers are critical to minimizing burn-associated morbidity and mortality. However, American Burn Association-verified burn centers are unequally distributed across the United States, and fewer centers are available for pediatric patients relative to adults. The economic burden of transporting patients to these centers contributes significantly to the high cost of burn care. This study quantifies inequitable burn care access in the contiguous United States due to age group and location as a function of physical proximity to a verified burn center and transportation cost. County-level distances to the nearest verified adult or pediatric burn center were determined and mapped. Distance calculations for each population were combined with transport cost data (2022 CMS Ambulance Fee Schedules) to estimate transportation costs for each population (adult vs pediatric, urban vs rural). Pediatric patients reside 30.5 miles further than adults from the nearest center, significantly increasing transportation costs. Ground and air transport costs also increased for rural versus urban patients. Notably, rural patients face almost double the cost of air transport. While physical proximity to burn care appears to differ only modestly across age and region, this marginal increase in distance is associated with significant economic impact. This study highlights physical and economic barriers to burn care access faced by rural and pediatric patients and underscores the critical need to improve equity in burn care access. Future studies should expand on this report's findings to more fully characterize the additional costs associated with inequitable burn care access.

Acquired buried penis is a condition that can have detrimental physical and psychological consequences for patients. Factors such as elevated BMI, chronic scrotal lymphedema, hidradenitis suppurativa, and chronic inflammation can lead to the condition. Surgical intervention is the treatment of choice for advanced disease. Following IRB approval, a retrospective chart review was performed for patients with a diagnosis of acquired buried penis who required surgical intervention. Details of patient history, surgical management including intraoperative and post-operative photography, and complications were reviewed. Seven patient cases were reviewed. The average age at time of surgery was 44 with a mean weight of 344 pounds and an average BMI of 48. Severe scrotal lymphedema and hidradenitis were common concurrent comorbidities. Concurrent scrotoplasty and infraumbilical panniculectomy were standard parts of the operations. Native glans skin was salvageable in all but one case. Penile shaft skin was reconstructed with skin grafts or adjacent tissue transfer. 88% of the cases had some element of wound dehiscence post-operatively. Surgical management of an acquired buried penis can be challenging. The patient demographic with the disease is frequently complicated by morbid obesity, concurrent lymphedema, or hidradenitis. Post-operative complications are expected. The surgical techniques presented can aid in simplifying the management of this challenging surgical population.

Each year, 27.5% of the 150 000 people in the United States who require lower extremity amputation experience significant postoperative complications, including pain, infection, and need for reoperation. Postamputation pain, including RLP and PLP, is debilitating. While the causes of such pain remain unknown, neuroma formation following sensory nerve transection is believed to be a major contributor. Various techniques exist for management of a symptomatic neuroma, but few data exist on which technique is superior. Furthermore, there are few data on primary prevention of neuroma formation following injury or intentional transection. The TMR technique shows promise for both management of PLP and RLP and prevention of neuroma formation. Following amputation, transected sensory nerves are coapted to nearby motor nerve supplying remaining extremity musculature. Not only does this procedure generate increased myoelectric signals for improved prosthesis control, TMR appears to neurophysiologically alter sensory nerves, preventing formation of painful sensory neuromas. The sole RCT to date evaluating the efficacy of TMR showed statistically significant reduction in PLP. TMR is not limited to use in the setting of major limb amputation. It has also been used in the setting of post-mastectomy pain, abdominal wall neuromas, digital amputations, and headache surgeries. This article reviews the origin of TMR and provides a brief description of histologic changes following the procedure, as well as current data regarding the efficacy of TMR with regard to postoperative pain relief. It also seeks to provide a concise, comprehensive resource for providers to facilitate better discussions with patients about treatment options.

Background Achieving a healed perineal wound following chemoradiotherapy and abdominoperineal resection (APR) is challenging for surgeons and patients. Prior studies have shown trunk-based flaps, including vertical rectus abdominis myocutaneous (VRAM) flaps, are superior to both primary closure and thigh-based flaps; however, there has been no direct comparison with gluteal fasciocutaneous flaps. This study evaluates postoperative complications after various methods of perineal flap closure of APR and pelvic exenteration defects. Methods Retrospective review of patients who underwent APR or pelvic exenteration from April 2008 through September 2020 was analyzed for postoperative complications. Flap closure techniques, including VRAM, unilateral (IGAP), and bilateral (BIGAP) inferior gluteal artery perforator fasciocutaneous flaps, were compared. Results Of 116 patients included, the majority underwent fasciocutaneous (BIGAP/IGAP) flap reconstruction (n = 69, 59.6%), followed by VRAM (n = 47, 40.5%). There were no significant differences between group patient demographics, comorbidities, body mass index, or cancer stage. There were no significant differences between BIGAP/IGAP and VRAM groups in minor complications (57% versus 49%, p = 0.426) or major complications (45% versus 36%, p = 0.351), including major/minor perineal wounds. Conclusions Prior studies have shown flap closure is preferable to primary closure after APR and neoadjuvant radiation but lack consensus on which flap offers superior postoperative morbidity. This study comparing outcomes of perineal flap closure showed no significant difference in postoperative complications. Fasciocutaneous flaps are a viable choice for the reconstruction of these challenging defects.

We study whether in-medium showers of high-energy gluons can be treated as a sequence of individual splitting processes g→gg, or whether there is significant quantum overlap between where one splitting ends and the next begins. Accounting for the Landau-Pomeranchuk-Migdal (LPM) effect, we calculate such overlap effects to leading order in high-energy α_{s}(μ) for the simplest theoretical situation. We investigate a measure of overlap effects that is independent of physics that can be absorbed into an effective value q[over ^]_{eff} of the jet-quenching parameter q[over ^].

We give details of our study of whether high-energy gluon showers inside a QCD medium can be treated as a sequence of individual splitting processes $g \to gg$, or whether there is significant quantum overlap between where one splitting ends and the next begins (neglecting effects that can be absorbed into an effective value of the jet quenching parameter $\hat q$ that characterizes the medium). The study is carried out by imagining in-medium gluon shower development in the simplest theoretical situation, which includes imagining a very large, static, homogeneous medium and taking the large $N_{\rm c}$ limit. Along the way, we also show how in-medium shower evolution can be written in terms of a "net" splitting rate $[d\Gamma/dx]_{\rm net}$, and we provide a moderately simple analytic fit to our numerical results for the overlap effects included in that rate, which we hope may be of use to others wishing to study possible consequences of overlapping splittings.

The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. We continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-emission approximations. In this particular paper, we show (i) how the "instantaneous" interactions of Light-Cone Perturbation Theory must be included in the calculation to account for effects of longitudinally-polarized gauge bosons in intermediate states, and (ii) how to compute virtual corrections to LPM emission rates, which will be necessary in order to make infrared-safe calculations of the characteristics of in-medium QCD showering of high-energy partons. In order to develop these topics in as simple a context as possible, we will focus in the current paper not on QCD but on large-N_f QED, where N_f is the number of electron flavors.

for surgeons and trunk-based vertical rectus abdominis myocutaneous flaps (VRAM), are superior to both primary closure and thigh-based flaps, however there has been no direct comparison to gluteal fasciocutaneous flaps. This evalu-ates postoperative complications after various methods of perineal flap closure of APR and pelvic exenteration

A bstract Consider the in-medium splitting g → gg of a very high-energy gluon traversing a QCD medium, accounting for the Landau-Pomeranchuk-Migdal (LPM) effect. It has been known for some time that soft radiative corrections to that splitting generate a double-log correction to the splitting rate, whose effects can be absorbed into running of the medium parameter $$ \hat{q} $$ q ̂ describing the rate of transverse momentum kicks to high-energy particles due to small-angle scattering from the medium. Less has been known about sub-leading, single logarithms in this context. In this paper, we find analytic formulas for those single logs (with various caveats and clarifications).

An important question concerning in-medium high-energy parton showers in a quark-gluon plasma or other QCD medium is whether consecutive splittings of the partons in a given shower can be treated as quantum mechanically independent, or whether the formation times for two consecutive splittings instead have significant overlap. Various previous calculations of the effect of overlapping formation times have either (i) restricted attention to a soft bremsstrahlung limit, or else (ii) used the large- N c limit (where N c = 3 is the number of quark colors). In this paper, we make a first study of the accuracy of the large- N c limit used by those calculations of overlap effects that avoid a soft bremsstrahlung approximation. Specifically, we calculate the 1 / N_c^2 correction to previous N c = ∞ results for overlap g → gg → ggg of two consecutive gluon splittings g → gg . At order 1 / N_c^2 , there is interesting and non-trivial color dynamics that must be accounted for during the overlap of the formation times.

It has been known for many years that soft radiation can give potentially large double-logarithm corrections to p ⊥ broadening of a high-energy particle traveling through QCD matter, but that this soft radiation correction can be absorbed into an effective value q̂ eff for the medium p ⊥ -broadening parameter q̂ . Here “soft” means high energy compared to medium scales but soft compared to the original high-energy particle traveling through the medium. A similar situation arises in the case of soft corrections to hard splitting of a high-energy particle, such as hard g → gg , where double logarithms can also be absorbed using the same effective q̂ eff . In this paper, I study whether the same holds true for potentially large, subleading, single -logarthim corrections. The correspondence is more indirect for single logarithms, but I show (in the large- N c limit) that single logarithms from soft radiation in the case of p ⊥ broadening also determine the single logarithms from soft radiative corrections to hard g → gg splitting. Along the way, there is an interesting variation of the original BDMPS-Z calculation of splitting rates in the q̂ approximation. I also discuss how, for soft-radiative corrections to hard splitting processes, there are two different types of “ q̂ eff ” that come into play, which differ by “ iπ ” terms that multiply single logarithms.