Impact dynamics of granular debris flows based on a small-scale physical model

The peak pressure of a granular debris flow at low Froude conditions can be calculated with knowledge of the stress anisotropy and the bulk density as well as the run-up height at impact. Based on a small-scale physical model, measurements of stress anisotropy and flow density values at impact are presented and applied to existing run-up prediction models, and further compared with back-calculated run-up coefficients from measured maximum impact pressures. For this purpose, we conducted 17 experiments with impact measurements and six experiments without impact measurements at Froude numbers, ranging from 0.84 to 2.41. Our results indicate that run-up heights are best reproduced by predictive models, either based on energy or mass and moment conservation, when anisotropic stress conditions, found in this study to range from 1.2 to 5.0, and bulk density variations due to impact, ranging in this study from 0.8 to 2.3, are considered. The influence of stress anisotropy and density variation on the run-up prediction differs, depending on the modelling approach. For the calculation of run-up heights based on the energy conservation concept, the influence of stress anisotropy becomes more significant with increasing Froude number, whereas for models based on mass and momentum conservation, bulk density variations have a greater influence on the estimation of the potential run-up

Testing the Reliability of Optical Coherence Tomography to Measure Epidermal Thickness and Distinguish Volar and Nonvolar Skin

In persons with limb loss, prosthetic devices cause skin breakdown, largely because residual limb skin (nonvolar) is not intended to bear weight such as palmoplantar (volar) skin. Before evaluation of treatment efficacy to improve skin resiliency, efforts are needed to establish normative data and assess outcome metric reliability. The purpose of this study was to use optical coherence tomography to (i) characterize volar and nonvolar skin epidermal thickness and (ii) examine the reliability of optical coherence tomography. Four orientations of optical coherence tomography images were collected on 33 volunteers (6 with limb loss) at 2 time points, and the epidermis was traced to quantify thickness by 3 evaluators. Epidermal thickness was greater (P \u3c .01) for volar skin (palm) (265.1 ± 50.9 μm, n = 33) than for both nonvolar locations: posterior thigh (89.8 ± 18.1 μm, n = 27) or residual limb (93.4 ± 27.4 μm, n = 6). The inter-rater intraclass correlation coefficient was high for volar skin (0.887–0.956) but low for nonvolar skin (thigh: 0.292–0.391, residual limb: 0.211–0.580). Correlation improved when comparing only 2 evaluators who used the same display technique (palm: 0.827–0.940, thigh: 0.633–0.877, residual limb: 0.213–0.952). Despite poor inter-rater agreement for nonvolar skin, perhaps due to challenges in identifying the dermal–epidermal junction, this study helps to support the utility of optical coherence tomography to distinguish volar from nonvolar skin

Beyond Hip Fracture: Orthopaedic Trauma in an Aging America

Abstract Trauma related death and disability is common among working-age Americans, however the impact on older adults is consequential and increasing. Fractures are the most common traumatic injury diagnosis among Medicare beneficiaries, and though fragility fractures continue to be an important health problem, recent data indicate an increase in high-energy fractures. The purpose of this study was to produce national incidence estimates among US men and women ≥ 65 years using data from the 2003-2014 National Inpatient Sample (NIS). The study cohort included hospitalizations involving upper and/or lower extremity fractures which were further classified by mechanism as high or low energy using external cause of injury codes. Incidence was computed using survey weights provided by NIS, and population estimates from the Census Bureau. The incidence of high-energy fractures increased from 744.1/100,000 persons (95%CI: 681.1–807.1) in 2003 to 821.4/100,000 (95%CI: 795.0 – 874.8) in 2014 in women, and from 359.1/100,000 (95%CI: 331.4–386.8) to 408.2/100,000 (95%CI: 394.–809.2) in men. Over 80% were motor vehicle related. The greatest increase was among those ≥ 85 (1,856.4/100,000 to 2,126.3/100,000 in women; 1,069.1/100,000 to 1,215.1/100,000 in men). Simultaneously, the incidence of low-energy fractures declined: 748.4/100,000 (95%CI: 687.5–809.2) to 443.8/100,000 (95%CI: 423.5 -464.1) in women, and 310.6/100,000 (95%CI: 285 – 336.2) to 206.3/100,000 (95%CI: 196.5 - 216) in men. Results suggest that fractures commonly seen in younger adults will be seen more frequently in older age. It is therefore essential to establish treatment pathways to optimize outcomes for the growing number of injured older adults.</jats:p

A combined model approach for debris-flow impact forces

&amp;lt;p&amp;gt;For the design of mitigation measures knowledge of debris-flow impact forces, usually estimated based on hydrostatic, hydrodynamic, or combined approaches, is essential. As these approaches are based on Newtonian fluids, they must be adjusted by empirical correction factors to account for the solid-fluid nature of debris flows. The values for the correction factors shown in the literature vary over a wide range and several studies showed a clear dependence with the Froude regime of debris flows.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;To better understand the correction factors and to be able to calculate them using parameters that describe the flow behaviour a total of 32 experiments were conducted in the course of the project &amp;amp;#8220;Debris flow impact forces on bridge super structures (DEFSUP)&amp;amp;#8221;, funded by the Austrian Science Fund (FWF). Two different material compositions, different water contents as well as a total impact and a bypassing of the measuring block were tested.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The experimental setup designed within the project consists of a 4 m long semi-circular channel with a diameter of 300 mm and an inclination of 20&amp;amp;#176;. The material is released from a rectangular reservoir in a dam-break scenario and accelerated with zero roughness on a length of 1.2 m and transferred to the semi-circle profile. The subsequently introduced roughness with a grain diameter of 1-2 mm generates a stationary phenomenological debris flow until it hits the measuring setup. With a starting volume of 50 kg, flow heights between 8 and 12 cm and velocities from 0.8 to 2.2 m/s were achieved according to the material composition and different water content. With these different mixtures a Froude-range from 0.6 to 3.6 was covered. In addition, normal stresses and pore water pressures were measured at the exact same point.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;A detailed analysis of the measured impact forces together with the above mentioned measured parameters showed that the hydrodynamic correction factor is a constant mainly corresponding to the liquification ratio of the debris-flow mixture. Hence, the hydrodynamic correction factor can be regarded as a drag coefficient and seems to depend mainly on the internal friction of the flowing medium. At low Froude numbers measured impact forces exceed even a full momentum transfer if the mean bulk density is used for the calculation. This indicates that the impact forces can no longer be described by the hydrodynamic approach alone. For this reason, an additional pressure term based on a hydrostatic approach is considered in the combined concept. This additional pressure term depends on the dynamics of flow (Froude number) and can be modelled via a dynamic earth pressure coefficient.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The findings from these experiments contribute to a better prediction of debris-flows impact forces in terms of their material composition and flow behaviour.&amp;lt;/p&amp;gt;</jats:p

The vaginal microbiome of transgender men receiving gender-affirming hormonal therapy in comparison to that of cisgender women

Abstract The vaginal microbiome of trans men and menopausal women is suspected to be similar due to a lack of estrogen leading to the absence of lactobacilli. However, data are scarce. We performed an analysis of the vaginal microbiome of trans men (n = 25) in comparison to that of menopausal (n = 25) and premenopausal women (n = 25). The vaginal microbiome of trans men and menopausal women showed a higher alpha diversity than that of premenopausal women. Various beta diversity indices (e.g., Bray‒Curtis (Un-)Weigthed Unifrac), showed significant differences in community composition between trans men and premenopausal (p < 0.001) and menopausal women (p < 0.001). The vaginal microbiome of trans men is characterized by a loss of Lactobacillus and an increase in bacteria associated with the intestinal flora (e.g., Campylobacter, Anaerococcus, Dialister, Prevotella). The abundance of Dialister and Prevotella decreased with the length of hormonal therapy in trans men. The Nugent score, Pap smear and HPV status did not differ between the study groups. The vaginal microbiome of trans men differs from that of premenopausal women but shows similarities to that of menopausal women. The duration of hormonal therapy in trans men may have important impacts on the vaginal microbiome and thus possibly on the risk for STIs