Cross-sectional Area Function Research Articles

Limitation of cerebral blood flow by increased venous outflow resistance in elevated ICP.

Extensive investigation and modeling efforts have been dedicated to cerebral pressure autoregulation, which is primarily regulated by the ability of the cerebral arterioles to change their resistance and modulate cerebral blood flow (CBF). However, the mechanisms by which elevated intracranial pressure (ICP) leads to increased resistance to venous outflow have received less attention. We modified our previously described model of intracranial fluid interactions with a newly developed model of a partially collapsed blood vessel, which we termed the "flow control zone" (FCZ). We sought to determine the degree to which ICP elevation causing venous compression at the FCZ becomes the main parameter limiting CBF. The FCZ component was designed using nonlinear functions representing resistance as a function of cross-sectional area and the pressure-volume relations of the vessel wall. We used our previously described swine model of cerebral edema with graduated elevation of ICP to calculate venous outflow resistance and a newly defined parameter, the cerebral resistance index (CRI), which is the ratio between venous outflow resistance and cerebrovascular resistance. Model simulations of cerebral edema and increased ICP led to increased venous outflow resistance. There was a close similarity between model predictions of venous outflow resistance and experimental results in the swine model (cross-correlation coefficient of 0.97, a mean squared error of 0.087, and a mean absolute error of 0.15). CRI was strongly correlated to ICP in the swine model (r2 = 0.77, P = 0.00012, 95% confidence interval [0.15, 0.45]). A CRI value of 0.5 was associated with ICP values above clinically significant thresholds (24 mmHg) in the swine model and a diminished capacity of changes in arteriolar resistance to influence flow in the mathematical model. Our results demonstrate the importance of venous compression at the FCZ in determining CBF when ICP is elevated. The cerebral resistance index may provide an indication of when compression of venous outflow becomes the dominant factor in limiting CBF following brain injury.NEW & NOTEWORTHY The goal of this study was to investigate the effects of venous compression caused by elevated intracranial pressure (ICP) due to cerebral edema, validated through animal experiments. The flow control zone model highlights the impact of cerebral venous compression on cerebral blood flow (CBF) during elevated ICP. The cerebral venous outflow resistance-to-cerebrovascular resistance ratio may indicate when venous outflow compression becomes the dominant factor limiting CBF. CBF regulation descriptions should consider how arterial or venous factors may predominantly influence flow in different clinical scenarios.

Nicotinamide Phosphoribosyltransferase-elevated NAD+ biosynthesis prevents muscle disuse atrophy by reversing mitochondrial dysfunction.

It is well known that muscle disuse atrophy is associated with mitochondrial dysfunction, which is implicated in reduced nicotinamide adenine dinucleotide (NAD+ ) levels. Nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in NAD+ biosynthesis, may serve as a novel strategy to treat muscle disuse atrophy by reversing mitochondrial dysfunction. To investigate the effects of NAMPT on the prevention of disuse atrophy of skeletal muscles predominantly composed of slow-twitch (type I) or fast-twitch (type II) fibres, rabbit models of rotator cuff tear-induced supraspinatus muscle atrophy and anterior cruciate ligament (ACL) transection-induced extensor digitorum longus (EDL) atrophy were established and then administered NAMPT therapy. Muscle mass, fibre cross-sectional area (CSA), fibre type, fatty infiltration, western blot, and mitochondrial function were assayed to analyse the effects and molecular mechanisms of NAMPT in preventing muscle disuse atrophy. Acute disuse of the supraspinatus muscle exhibited significant loss of mass (8.86±0.25 to 5.10±0.79g; P<0.001) and decreased fibre CSA (3939.6±136.1 to 2773.4±217.6μm2 , P<0.001), which were reversed by NAMPT (muscle mass 6.17±0.54g, P=0.0033; fibre CSA, 3219.8±289.4μm2 , P=0.0018). Disuse-induced impairment of mitochondrial function were significantly improved by NAMPT, including citrate synthase activity (40.8±6.3 to 50.5±5.6nmol/min/mg, P=0.0043), and NAD+ biosynthesis (279.9±48.7 to 392.2±43.2pmol/mg, P=0.0023). Western blot revealed that NAMPT increases NAD+ levels by activating NAMPT-dependent NAD+ salvage synthesis pathway. In supraspinatus muscle atrophy due to chronic disuse, a combination of NAMPT injection and repair surgery was more effective than repair in reversing muscle atrophy. Although the predominant composition of EDL muscle is fast-twitch (type II) fibre type that differ from supraspinatus muscle, its mitochondrial function and NAD+ levels are also susceptible to disuse. Similar to the supraspinatus muscle, NAMPT-elevated NAD+ biosynthesis was also efficient in preventing EDL disuse atrophy by reversing mitochondrial dysfunction. NAMPT-elevated NAD+ biosynthesis can prevent disuse atrophy of skeletal muscles that predominantly composed with either slow-twitch (type I) or fast-twitch (type II) fibres by reversing mitochondrial dysfunction.

Daily Dietary Supplementation with Steamed Soybean Improves Muscle Volume and Strength in Healthy People Lacking Exercise.

Various dietary protein supplements are used by the elderly and bedridden to maintain their skeletal muscle mass and functions. High-quality proteins act as an anabolic driver and help to improve muscle strength and performance. Previously, we reported that soy protein significantly attenuates denervation-induced loss of muscle mass and myofiber cross sectional area in mice with inhibition of ubiquitination and degradation of IRS-1 in tibialis anterior muscle. It also increased muscle volume and strength in bedridden patients. In the present study, we investigated the effects of dietary soybean supplementation on muscle functions in taxi drivers lacking vigorous physical exercise. We conducted a case-control study on 25 healthy, male taxi drivers between the ages of 36 and 71 y performing minimal physical exercise. They were divided into two dietary groups: the soybean diet group (n=13) who ate daily meals (dinner) supplemented with 50 g of steamed soybean for 30 d and the control diet group (n=12) who received no soybean supplement. Next, we measured the muscle cross-sectional area (CSA) and muscle strength and function in both the groups before and after 30 d of soybean intake. The body weights of both diet groups did not differ significantly over time. However, after 30 d of soybean supplementation, the soybean-fed group developed significantly higher muscle CSA and grip strength compared to the control groups. In conclusion, dietary soybean supplementation improved muscle function in taxi drivers who lacked exercise.

Essential amino acid enriched meal replacement improves body composition and physical function in obese older adults: A randomized controlled trial.

Older adults are threatened by the risk of muscle atrophy and excess accumulation of adipose tissue. The objective of this study was to determine whether an essential amino acid enriched meal replacement would reduce excess fat and foster skeletal muscle retention, potentially improving physical function in this cohort. Using a double blind, randomized controlled trial, we compared the influence of an experimental meal replacement enriched with essential amino acids (EMR) to a commercially available, widely used meal replacement (Optifast®) provided once/day (q.d.) for four weeks on body composition, skeletal muscle and physical function in obese older participants. Twenty-eight individuals completed either EMR (n=13) or Optifast® (n=15) supplementation protocols. Measurements of body composition, thigh skeletal muscle cross-sectional area (CSA), blood panels, intrahepatic lipid, and physical function were completed pre- and post-supplementation. Body fat mass, visceral fat mass and volume, and intrahepatic lipid were reduced with EMR but not with Optifast®. Thigh muscle CSA increased (Δ 2.4±3.0cm2) with EMR but not Optifast® (Δ-1.8±6.0cm2). There was a significant increase in the distance covered during the 6-min walk test with EMR (Δ 23±27m) but no change in Optifast® (Δ 11±37m). Beneficial alterations in fat and muscle support the use of EMR-based meal replacements in obese older adults. ISRCTN registry under Reference Number ISRCTN15814848.

Application of electrical rock typing for quantification of pore network geometry and cementation factor assessment

Rock typing with its various applications reduces the required time and cost for petrophysical analysis by categorizing similar rocks into distinct groups. Rock typing is divided into different categories, one of which, is electrical rock typing. An application of static electrical rock typing is cementation factor prediction which significantly affects fluid saturation estimation. Many factors, such as pore geometry, affect cementation factor in various means. Hence, achieving an explicit correlation to compute it as a function of these affecting factors is difficult. However, examining petrophysical properties which influence cementation factor is feasible. In this study, two definitions of formation resistivity factor are merged to achieve the cementation factor correlation as a function of effective cross-sectional area, porosity, and electrical tortuosity. To determine effective cross-sectional area and electrical tortuosity in wellbore through a time-efficient and inexpensive method, electrical rock typing is used. The results of this study reveal that Kozeny's factor is perfectly correlated with effective cross-sectional area and electrical tortuosity. Therefore, effective cross-sectional area and electrical tortuosity are computed throughout the wellbore. Moreover, investigating the relation between flowing porosity and rock capacity for transmitting electricity shows that they are directly related. Cementation factor and stagnant porosity also have a direct relationship. The findings of this study aid the assessment of porous media for attaining a clear understanding of petrophysical properties relationships, and their impact on porous media capability for storing and transferring fluid and transmitting electricity. Determining petrophysical properties continuously in wellbore leads to a better comparison between different segments of the reservoir. Regarding the fact that all presented methods are mainly based on log responses, they are easy to apply. However, the availability of enough samples is essential to initiate the analysis. • Obtaining effective cross-sectional area continuously through wellbore. • Developing a method to determine electrical tortuosity through wellbore. • High EQI Samples have a higher flowing porosity, and a lower cementation factor. • As electrical tortuosity increases, m rises due to reduction in flowing porosity.

16-week Combined Exercise Training Improves Muscle Quality In Breast Cancer Survivors

Cancer treatment is associated with skeletal muscle loss, leading to reductions in muscular strength and functional capacity. Exercise training can improve muscular strength in breast cancer survivors (BCS), even without skeletal muscle hypertrophy. Factors such as improved muscle quality (MQ) may contribute to improved function but limited data are available in BCS. PURPOSE: To investigate the effects of exercise training in BCS and healthy controls (HC) on MQ, cross-sectional area (CSA), muscular strength, and physical function and to examine associations between these measures. METHODS: BCS (n = 31, 54 [11] y, 27.5 [5.0] kg/m2) and HC (n = 15, 54 [8] y, 29.3 [4.9] kg/m2) underwent a 16-week combined aerobic and strength training intervention 3x/week for one-hour at a community-based exercise program for BCS. Isokinetic peak torque and maximal voluntary isometric contraction (MVIC) were assessed in the knee extensor muscles. Ultrasound was used to determine muscle CSA and echo intensity of the vastus lateralis. Functional parameters included 6-minute walk (6MWT) and timed up and go (TUG). All measures were taken pre- and post-intervention and were analyzed using a 2x2 repeated measures ANOVA and Pearson’s correlations. Data are mean change [SD]. RESULTS: Echo intensity decreased with training overall (-5.4 [24.6], p = .046), indicating higher MQ, with no change in CSA. A time x group interaction for MVIC showed increased strength after training in BCS (+11.0 [17.2] N·m, p = .001) but not HC (-2.6 [23.7] N·m, p = .673). Physical function improved in both groups (TUG -0.5 [0.9] sec, p < .000; 6 MWT 35.5 [45.0] m, p < .001). At baseline, echo intensity was inversely correlated with MVIC, TUG and 6 MWT in HC only (r = -0.451-0.490, all p < 0.05). No associations in the changes of these variables were observed with training. CONCLUSION: A 16-week exercise intervention improved MQ and functional measures in both BCS and HC, while MVIC increased only in BCS. MQ was moderately correlated with functional and strength measures at baseline in HC but not in BCS. The lack of correlations in BCS suggest that other factors, possibly neural adaptations, may be responsible for the improvements in muscular strength and functional measures seen after an exercise intervention rather than improvements in MQ and CSA.

Planar magnetron discharge with confinement of injected electrons

We have explored the operation and characteristics of a planar magnetron discharge system with central on-axis electron injection and a reflector electrode. The diameter of the magnetron copper target was 125 mm; the operating gas was argon and the pressure range 2 × 10−4 – 2 × 10−3 Torr. To increase the efficiency of electron injection, a negatively-biased reflecting electrode was located on the system axis. We have investigated the effect of the reflector electrode on the characteristics of the magnetron discharge, as a function of reflector shape, cross-sectional area, electrical bias, and distance from the target. It is shown that the simultaneous use of central injection of electrons with their acceleration across the cathode layer of the magnetron discharge, and a cone-shaped reflector electrode allows the current to be increased and the operating pressure to be decreased by a factor of several for a fixed magnetron discharge voltage.

Acute effects of graduated and progressive compression stockings on leg vein cross-sectional area and viscoelasticity in patients with chronic venous disease

ObjectiveTo determine the effects of graduated and progressive elastic compression stockings (ECS) on postural diameter changes and viscoelasticity of leg veins in healthy controls and in limbs with chronic venous disease (CVD). MethodsIn 57 patients whose legs presented with C1s, C3, or C5 CEAP classes of chronic venous disease and were treated primarily with compression, and 54 healthy controls matched for age and body mass index, we recorded interface pressures (IFP) at 9 reference leg levels. Cross-sectional areas of the small saphenous vein (SSV) and a deep calf vein (DCV) were measured with B-mode ultrasound with patients supine and standing, recording the force (PF) applied on the ultrasound probe to collapse each vein with progressive ECS, and with and without graduated 15 to 20 mm Hg and 20 to 36 mm Hg elastic stockings. We chose these veins because they were free of detectable lesion and could be investigated at the same level (mid-height of the calf), and their compression by the ultrasound probe was not hampered by bone structures. ResultsIFP decreased from ankle to knee with graduated 15 to 20 and 20 to 36 mm Hg, but increased with progressive ECS, and were 8.4 to 13.8 mm Hg lower for C1s than for control or C3 and C5 limbs. Without ECS, the SSV median [lower-upper quartile] cross-sectional area was 4.9 mm2 [3.6-7.1 mm2] and 7.1 mm2 [3.0-9.9 mm2] in C3 and C5 limbs versus 2.9 mm2 [1.8-5.2 mm2] and 3.8 mm2 [2.1-5.4 mm2] in controls (P < .01), respectively, while supine and standing. It remained greater in C3 and C5 than in C1s and control limbs wearing any ESC. Wearing compression, especially with progressive ECS, decreased the SSV and DCV cross-sectional area only with patients supine, thus decreasing postural changes, which remained highly diverse between individuals. The SSV cross-sectional area versus PF function traced a hysteresis loop of which the area, related to viscosity, was greater in C3 and C5 limbs than controls, even with graduated 15 to 20 or 20 to 36 mm Hg ECS. Progressive ECS decreased vein viscosity in the supine position, whereas 20 to 36 mm Hg and progressive ECS increased distensibility in the standing position. ConclusionsECS decrease the cross-sectional area of SSV and DCV with patients supine, but not upright. C1s limbs show distinctive features, especially regarding IFP. Graduated 20 to 36 mm Hg and progressive stockings lower viscosity and increase distensibility of the SSV.

Numerical simulation on the header-orifice structure-based liquid-vapor separator used in liquid-separation condenser

Liquid-vapor separation process is a widely used process in many industrial and domestic applications. Liquid-separation condenser using header-orifice as liquid-vapor separator has been widely studied, confirming its superiority of higher heat transfer coefficient and lower pressure drop simultaneously over the conventional condenser. However, research on flow and separation mechanism of the header-orifice liquid-vapor separator is rarely found in existing literatures. Herein, we propose a numerical simulation model based on Volume of Fluid for the header-orifice liquid-vapor separator. The model is verified and applied to study the liquid-vapor separation mechanism of the header-orifice. The major parameters that influence the liquid-separation efficiency are analyzed, including the diameter of a liquid-separation hole, header height and inlet mass flow rate. Multi-factor analysis is also performed to investigate the synergetic effects of the parameters on the liquid-separation efficiency. A correlation of liquid-separation efficiency as a function of cross-section area, two-phase Reynolds number, and modified Weber number is obtained based on the orthogonal experimental method.

Nonintrusive estimation of subsurface geometrical attributes of the melt pool through the sensing of surface oscillations in laser powder bed fusion

Molten pool geometry, whose surface parameters may be extrapolated through direct process observations, has been identified as a fundamental indicator of stability in laser powder bed fusion (LPBF). However, a parameter that cannot be directly measured on industrial systems by means of conventional sensing equipment is the molten pool depth. Indeed, methods based on x-ray imaging demonstrated in the literature have helped to better understand the process. However, retrofitting such solutions to industrial systems does not appear as a viable route currently. Within the present investigation, a nonintrusive sensing method for the indirect measurement of subsurface molten pool geometry based on the detection of surface oscillations is presented. The analysis of frames acquired using a high-speed camera and a secondary illumination light allows the identification of the crests of capillary waves through bright reflections on the surface of the molten pool. The characteristic oscillation frequency of the surface ripples may be correlated with the penetration depth or to other subsurface geometrical parameters. Proof of concept testing of the sensing principle was conducted on two different materials, namely, AISI316L and IN718, by means of single track LPBF depositions. Experiments were conducted at different levels of laser emission power to induce variations in molten pool characteristics. The process was observed by employing an off-axis illumination light and a high-speed camera, which allowed acquisitions with high spatial and temporal resolution. The acquired frames were postprocessed to extract the oscillation indicator, and analysis of the power spectral density of the signal allowed for the identification of the oscillation frequency. Results show that oscillation frequencies range from 3 to 5.5 kHz. Molten pool penetration depth and cross-sectional area could be correlated with the oscillation frequencies for the inline detection of these parameters during LPBF depositions. For both materials, higher oscillation frequencies corresponded to a shallower molten pool and a smaller mass of molten material. Moreover, different characteristic curves of oscillation frequency variations as a function of the melt pool cross-sectional area were determined for IN718 and AISI316L.

Musicians Have Thicker Median Nerve Cross Sectional Area and More Symptoms of Carpal Tunnel Than Non-Musicians.

Musicians spend numerous hours perfecting their skills and art, often leading to overuse injuries of the hand; of specific concern to musicians is carpal tunnel syndrome (CTS). This study evaluated the median nerve cross-sectional area and hand function of musicians and made comparisons to non-musicians. Seventy-six participants took part in the study, 38 music students and professors in the musician group and 38 participants in the control group. Participants completed patient-reported questionnaires to assess the level of pain and hand function. Ultrasound images were collected at the carpal tunnel inlet and outlet. The median nerve cross-sectional area and the depth of the carpal tunnel were measured on ultrasound images using software imbedded in the ultrasound unit. Musicians showed higher levels of hand dysfunction and CTS symptoms than the non-musicians. The median nerve cross-sectional area was greater in musicians than in the non-musician group on both the right (mean difference 1.5 mm2, p=0.002) and left sides (mean difference 0.9 mm2, p=0.036). The depth of the carpal tunnel at the carpal tunnel inlet and outlet did not differ between the groups (p>0.05). The current research identified between-group differences in median nerve cross-sectional area and the level of hand dysfunction. Understanding the interaction between the anatomy of the wrist and wrist and hand dysfunction will benefit clinicians when evaluating and treating musicians.

Acute Effects of Intraocular Pressure-Induced Changes in Schlemm's Canal Morphology on Outflow Facility in Healthy Human Eyes.

PurposeTo estimate the outflow facility coefficient (C) as a function of Schlemm's canal cross-sectional area (SCAR) in healthy subjects using noninvasive oculopression tonometry (OPT).MethodsIn 25 healthy volunteers, intraocular pressure (IOP) decay values were recorded by a ophthalmodynamometer, with a fixed external force (0.15 N) on the inferior-temporal eyelid, every 10 seconds, for four minutes, and again after a 30-minute rest. Schlemm's canal profile images and IOP were obtained pre-procedurally (baseline), immediately (T0), and at 1-minute intervals post-procedurally (T1, T2, T3, and T4). C was calculated for different IOPs. The SCAR, coronal, and the meridional diameter of Schlemm's canal were calculated.ResultsMean C0 for the maximum IOP was 0.020 ± 0.017 µL/min/mm Hg; mean C was 0.018 ± 0.0071 and 0.058 ± 0.0146 µL/min/mm Hg at 40 and 20 mm Hg, respectively. C was nonlinearly dependent on the IOP (R2 = 0.945). The SCAR was 5440 ± 3140.82, 3947.6 ± 2246.8, and 5375.7 ± 2662.7 µm2 at baseline, T0, and T4, respectively. The coronal diameter of SC decreased significantly from the baseline (33.02 ± 11.3 µm) to T0 (26.6 ± 9.37 µm) and recovered at T4 (32.3 ± 9.53 µm). The SCAR and IOP correlated significantly throughout (R2 = 0.9944; P < 0.001). C0 significantly correlated with the SCAR at baseline and with changes in the SCAR and IOP from T0 to T4.ConclusionsSchlemm's canal dimensions are responsible for the IOP-dependent mechanical forces, and these changes appear to directly affect outflow facility.

Association between hip muscle cross-sectional area and hip pain and function in individuals with mild-to-moderate hip osteoarthritis: a cross-sectional study

BackgroundTo examine the associations between hip muscle cross-sectional area and hip pain and function in community-based individuals with mild-to-moderate hip osteoarthritis.MethodsThis study included 27 participants with mild-to-moderate hip osteoarthritis. Cross-sectional area of hip muscles, including psoas major, rectus femoris, gluteus maximus, gluteus medius and minimus, adductor longus and magnus, obturator internus, and obturator externus, were measured from magnetic resonance images. Hip pain and function were evaluated using the Hip Disability and Osteoarthritis Outcome Score (HOOS) categorised into 5 subscales: pain, symptoms, activity of daily living, sport and recreation function, and hip-related quality of life (for each subscale 0 representing extreme problems and 100 representing no problems).ResultsMean age of the 27 participants was 63.2 (SD 7.6) years and 66.7% (n = 18) were female. After adjusting for age and gender, greater cross-sectional area of adductor longus and magnus was associated with a higher HOOS score in quality of life (regression coefficient 1.4, 95% confidence interval (CI) 0.2–2.7, p = 0.02), activity of daily living (regression coefficient 1.3, 95% CI 0.1–2.6, p = 0.04) and sport and recreation function (regression coefficient 1.6, 95% CI 0.1–3.0, p = 0.04). There was a trend towards an association between greater cross-sectional area of psoas major and a higher quality of life score (regression coefficient 3.6, 95% CI − 0.5 to 7.7, p = 0.08). The cross-sectional area of hip muscles was not significantly associated with HOOS pain or symptom score.ConclusionGreater cross-sectional area of hip adductors was associated with better function and quality of life in individuals with mild-to-moderate hip osteoarthritis. Greater cross-sectional area of hip flexors might be associated with better quality of life. These findings, while need to be confirmed in longitudinal studies, suggest that targeting the hip adductor and flexor muscles may improve function and quality of life in those with mild-to-moderate hip osteoarthritis.

The acute effects of cigarette smoke exposure on muscle fiber type dynamics in rats.

Reduced exercise capacity is common in people with chronic obstructive pulmonary diseases (COPD) and chronic smokers and is suggested to be related to skeletal muscle dysfunction. Previous studies using human muscle biopsies have shown fiber-type shifting in chronic smokers particularly those with COPD. These results, however, are confounded with aging effects because people with COPD tend to be older. In the present study, we implemented an acute 7-day cigarette smoke-exposed model using Sprague-Dawley rats to evaluate early effects of cigarette smoking on soleus muscles. Rats (n = 5 per group) were randomly assigned to either a sham air (SA) or cigarette smoking (CS) groups of three different concentrations of total particulate matters (TPM) (CSTPM2.5, CSTPM5, CSTPM10). Significantly lower percentages of type I and higher type IIa fiber were detected in the soleus muscle in CS groups when compared with SA group. Of these, only CSTMP10 group exhibited significantly lower citrate synthase activity and higher muscle tumor necrosis factor-α level than that of SA group. Tumor necrosis factor-α level was correlated with the percentage of type I and IIa fibers. However, no significant between-group differences were found in fiber cross-sectional area, physical activities, or lung function assessments. In conclusion, acute smoking may directly trigger the onset of glycolytic fiber type shift in skeletal muscle independent of aging.

Geomorphology and Species Interactions Control Facilitation Cascades in a Salt Marsh Ecosystem.

Facilitation cascades are chains of positive interactions that occur as frequently as trophic cascades and are equally important drivers of ecosystem function, where they involve the overlap of primary and secondary, or dependent, habitat-forming foundation species [1]. Although it is well recognized that the size and configuration of secondary foundation species' patches are critical features modulating the ecological effects of facilitation cascades [2], the mechanisms governing their spatial distribution are often challenging to discern given that they operate across multiple spatial and temporal scales [1, 3]. We therefore combined regional surveys of southeastern US salt marsh geomorphology and invertebrate communities with a predator exclusion experiment to elucidate the drivers, both geomorphic and biotic, controlling the establishment, persistence, and ecosystem functioning impacts of a regionally abundant facilitation cascade involving habitat-forming marsh cordgrass and aggregations of ribbed mussels. We discovered a hierarchy of physical and biological factors predictably controlling the strength and self-organization of this facilitation cascade across creekshed, landscape, and patch scales. These results significantly enhance our capacity to spatially predict coastal ecosystem function across scales based on easily identifiable metrics of geomorphology that are mechanistically linked to ecological processes. Replication of this approach across vegetated coastal ecosystems has the potential to support management efforts by elucidating the multi-scale linkages between geomorphology and ecology that, in turn, define spatially explicit patterns in community assembly and ecosystem functioning.

A prospective field study of U.S. Army trainees to identify the physiological bases and key factors influencing musculoskeletal injuries: a study protocol

BackgroundMusculoskeletal injuries (MSKIs) are common in military trainees and present a considerable threat to occupational fitness, deployability, and overall military readiness. Despite the negative effects of MSKIs on military readiness, comprehensive evaluations of the key known and possible risk factors for MSKIs are lacking. The U.S. Army Research Institute of Environmental Medicine (ARIEM) is initiating a large-scale research effort, the ARIEM Reduction in Musculoskeletal Injury (ARMI) Study, to better understand the interrelationships among a wide range of potential MSKI risk factors in U.S. Army trainees in order to identify those risk factors that most contribute to MSKI and may be best targeted for effective mitigation strategies.MethodsThis prospective study aims to enroll approximately 4000 (2000 male and 2000 female) U.S. Army trainees undergoing Basic Combat Training (BCT). Comprehensive in-person assessments will be completed at both the beginning and end of BCT. Participants will be asked to complete surveys of personal background information, medical history, physical activity, sleep behaviors, and personality traits. Physical measurements will be performed to assess anthropometrics, tibial microarchitecture and whole body bone mineral density, muscle cross-sectional area, body composition, and muscle function. Blood sampling will be also be conducted to assess musculoskeletal, genetic, and nutritional biomarkers of risk. In addition, participants will complete weekly surveys during BCT that examine MSKI events, lost training time, and discrete risk factors for injury. Participants’ medical records will be tracked for the 2 years following graduation from training to identify MSKI events and related information. Research hypotheses focus on the development of a multivariate prediction model for MSKI.DiscussionResults from this study are expected to inform current understanding of known and potential risk factors for MSKIs that can be incorporated into solutions that optimize Soldier health and enhance military readiness.

A Meta-Analysis of Intracortical Device Stiffness and Its Correlation with Histological Outcomes.

Neural implants offer solutions for a variety of clinical issues. While commercially available devices can record neural signals for short time periods, they fail to do so chronically, partially due to the sustained tissue response around the device. Our objective was to assess the correlation between device stiffness, a function of both material modulus and cross-sectional area, and the severity of immune response. Meta-analysis data were derived from nine previously published studies which reported device material and geometric properties, as well as histological outcomes. Device bending stiffness was calculated by treating the device shank as a cantilevered beam. Immune response was quantified through analysis of immunohistological images from each study, specifically looking at fluorescent markers for neuronal nuclei and astrocytes, to assess neuronal dieback and gliosis. Results demonstrate that the severity of the immune response, within the first 50 µm of the device, is highly correlated with device stiffness, as opposed to device modulus or cross-sectional area independently. In general, commercially available devices are around two to three orders of magnitude higher in stiffness than devices which induced a minimal tissue response. These results have implications for future device designs aiming to decrease chronic tissue response and achieve increased long-term functionality.

The Coefficient of Broad-Crested Weir in Natural Channels

Weirs have been designed and used extensively in hydraulic structures to control the flow depth and discharge. To estimate the discharge over the weir, a weir coefficient is required. The discharge coefficient can be obtained experimentally as a function of the dimensionless total head of the approaching flow or as a function of various parameters. However, a universally acceptable discharge coefficient does not exist. Beside the man-made weirs that have been constructed by hydraulic engineers, some natural channel characteristics and slopes can be simulated as broad-crested weirs that are clearly noticeable in examining water surface profiles. The study area is Centralia watershed in Central Florida, which contains several cascades of step like waterfalls that can be selected for transecting. Cross-section data from 5 transects and detailed hydraulic data was obtained using the Digital terrain model (DTM) and the Triangular Irregular Network (TIN). The Hydrologic Engineering Center-River Analysis System (HEC-RAS) stepbackwater technique was used to calculate water surface profiles for natural channels that are likely used for storm water drainage. The results show that these channels have chains of steps that dissipate the momentum of falling water in steep areas and maintain a steady rate of flow. The weir coefficients were determined by comparing the steady state discharges to the equivalent weir discharges. The results indicate that the weir coefficient can be expressed as a function of weir height and channel cross-section area. The relationship between this function and the weir coefficient showed a high correlation with R2 = 0.991. The results of this study can be used to estimate the discharge in similar reaches in any water surface profile.

Vanishing Viscosity Approach to the Compressible Euler Equations for Transonic Nozzle and Spherically Symmetric Flows

We are concerned with globally defined entropy solutions to the Euler equations for compressible fluid flows in transonic nozzles with general cross-sectional areas. Such nozzles include the de Laval nozzles and other more general nozzles whose cross-sectional area functions are allowed at the nozzle ends to be either zero (closed ends) or infinity (unbounded ends). To achieve this, in this paper, we develop a vanishing viscosity method to construct globally defined approximate solutions and then establish essential uniform estimates in weighted L p norms for the whole range of physical adiabatic exponents $${\gamma\in (1, \infty)}$$ , so that the viscosity approximate solutions satisfy the general L p compensated compactness framework. The viscosity method is designed to incorporate artificial viscosity terms with the natural Dirichlet boundary conditions to ensure the uniform estimates. Then such estimates lead to both the convergence of the approximate solutions and the existence theory of globally defined finite-energy entropy solutions to the Euler equations for transonic flows that may have different end-states in the class of nozzles with general cross-sectional areas for all $${\gamma\in (1, \infty)}$$ . The approach and techniques developed here apply to other problems with similar difficulties. In particular, we successfully apply them to construct globally defined spherically symmetric entropy solutions to the Euler equations for all $${\gamma\in (1, \infty)}$$ .

Scaling up the interplay of fingering and channeling for unstable water/polymer floods in viscous-oil reservoirs

Unstable displacement and the resulting viscous fingers remain a challenge for reservoir simulation as practical gridblock sizes are usually much larger than the viscous finger wavelength. Traditional reservoir simulators do not consider sub-grid viscous fingering effects and tend to overestimate the oil recovery at the field scale. Several previous studies suggested that fingering can be ignored at the field scale because channeling (caused by heterogeneity) is dominant, but they missed the existence of viscous fingering at the small scale, which affects the displacement efficiency. In our work, we consider that fingering and channeling coexist in the field across different scales, based on the fact that the heterogeneity increases with the scale. At the small-scale (e.g., lab-scale) where heterogeneity is small, fingering is dominant and causes oil bypassing. An effective-fingering model was developed to scale up fingering effects. The model divides each gridblock into three dynamic regions: two-phase flow, oil single-phase flow, and bypassed-oil regions. Model parameters represent the maximum fraction of viscous fingering and the growth factors of different regions, and they are used to modify flow functions. Model parameters from history-matches of a set of laboratory experiments show clear power-law correlations with a dimensionless viscous finger number, a function of viscosity ratio, fluid velocity, permeability, interfacial tension, and core cross-sectional area. The correlation was achieved at the lab-scale by considering relatively homogeneous cores. We extended it further to the field scale by performing high-order spatially accurate numerical simulations at the intermediate scale using gridblock sizes that are roughly the same as that of the core. Geostatistical realizations of the permeability field were generated with various variances and correlation lengths. In a statistical way, we were able to quantify the viscous finger number for a gridblock at the field-scale affected by various heterogeneities. It is also observed that channelized permeability distributions increase the viscous finger number drastically, showing the important role of channeling in such cases. This new model was applied to a synthetic field case with high heterogeneity undergoing water/polymer floods. It is observed that the oil recovery was improved by the polymer slug because of the enhancement in both local displacement efficiency and sweep efficiency.