Evolution and irreversibility: Two distinct phenomena and their distinct laws of nature.

To clarify the place of time direction of change in nature (time arrow), the present article shows why Evolution and Irreversibility are two distinct phenomena. Their distinct laws of nature are the Constructal Law and the Second Law, respectively. The demonstration is based on the simplest setting imaginable: a solid body moving in a pool of water. The view is holistic: the system selected for analysis is the body and the pool, not the body alone, and the phenomenon is the evolution of the image (configuration) of the whole. New is also the answer to the question of what flows in this evolving flow configuration. Along the way, important terms are defined: phenomenon, law, irreversibility, nature, design, freedom, theory versus empiricism, information, knowledge, selection, purpose, engine, refrigeration, and wheel. More complex natural settings for the demonstration are in the second part of the article: engines, refrigeration, heating and cooling, the wheel, and a pushed boat sliding on water.

Locomotion rhythm makes power and speed.

This article addresses two questions, why certain animals (frogs, breaststroke swimmers, hovering fliers, jellyfish) push rapidly against the surrounding fluid and then reach forward slowly, and whether this rhythm of propulsion is a manifestation of the universal phenomenon of design evolution in nature. Emphasis is on the distribution of time periods of locomotion in which, during the driving phase of cyclic movement (the motive stroke, phases 1 and 2, in alternating sequence with the dissipative stroke, phase 3), the work is generated (phase 1) and dissipated (phase 2). The relative lengths of the characteristic times t1 and t2 of the phases 1 and 2, are predicted. The relative duration of the proposed three phases of a cycle is the 'rhythm'. The analysis is based on a model of how the effective cross-sections of the stroking body parts impact the surrounding medium, water, or air, and the total power required to account for the kinetic energy losses during phases 2 and 3, which are due to drag forces posed by the surrounding medium. The body configuration (limbs' cross-sections) determines the limbs' velocities that maximize mean power, and the times t1 and t2 within the motive stroke. Emphasis is placed on the freedom to change the evolving design. Freedom is represented in two ways: the number of degrees of freedom in changing the dimensions of the model and its deformation in time, and the effect that evolutionary changes have on the access that the body has to its available space. Freedom to change the locomotion design leads to greater power and speed.

Impact of Social Determinants of Health in Spine Surgery.

PURPOSE OF REVIEW: Social determinants of health (SDH) are factors that affect patient health outcomes outside the hospital. SDH are "conditions in the environments where people are born, live, learn, work, play, worship, and age that affect a wide range of health, functioning, and quality-of-life outcomes and risks." Current literature has shown SDH affecting patient reported outcomes in various specialties; however, there is a dearth in research relating spine surgery with SDH. The aim of this review article is to identify connections between SDH and post-operative outcomes in spine surgery. These are important, yet understudied predictors that can impact health outcomes and affect health equity. RECENT FINDINGS: Few studies have shown associations between SDH pillars (environment, race, healthcare, economic, and education) and spine surgery outcomes. The most notable relationships demonstrate increased disability, return to work time, and pain with lower income, education, environmental locations, healthcare status and/or provider. Despite these findings, there remains a significant lack of understanding between SDH and spine surgery. Our manuscript reviews the available literature comparing SDH with various spine conditions and surgeries. We organized our findings into the following narrative themes: 1) education, 2) geography, 3) race, 4) healthcare access, and 5) economics.

Outcomes in Pediatric Hip FAI Surgery: a Scoping Review.

PURPOSE OF REVIEW: Femoracetabular impingement (FAI) is a common source of hip pain in children and adolescents. While nonoperative therapies and open surgical procedures can be effective, hip arthroscopy is a minimally invasive treatment option with substantial benefit. The purpose of this paper is to evaluate the current role of hip arthroscopy in treating FAI within the pediatric population. This article examines its efficacy through a review of hip arthroscopy outcomes in the contemporary orthopaedic literature. RECENT FINDINGS: Morphologic changes in the acetabulum and proximal femur seen in FAI can be attributed to a multitude of etiologies-including idiopathic FAI, Legg-Calve-Perthes, and slipped capital femoral epiphysis. In general, arthroscopic treatment of FAI secondary to these conditions leads to statistically significant improvements in pain and patient-reported outcomes in the short and long term. In the pediatric athlete, repetitive stress on the hip perpetuates FAI and can drastically hinder performance. Hip arthroscopy allows for a high rate of return to sport with minimal morbidity in this population. Overall, pediatric hip arthroscopy is effective in treating FAI secondary to a wide variety of conditions. Despite its clinical benefits, patients and their families should be counseled regarding alternative treatments, potential complications, and return to play.

Reduced Opioid Prescription After Anterior Cruciate Ligament Reconstruction Does Not Affect Postoperative Pain or Prescription Refills: A Prospective, Surgeon-Blinded, Randomized, Controlled Trial.

PURPOSE: To investigate opioid utilization after anterior cruciate ligament (ACL) reconstruction in the setting of a multimodal pain regimen and assess the feasibility of prescribing fewer opioids to achieve adequate postoperative pain control. METHODS: Patients undergoing ACL reconstruction in conjunction with a multimodal approach to pain control were randomized to receive either 30 or 60 tablets of hydrocodone (10 mg)-acetaminophen (325 mg). Patients were contacted at multiple time points up to 21 days after surgery to assess opioid utilization and medication side effects. We compared the mean number of tablets used between groups as the primary outcome. Preoperative variables associated with an increased risk of higher opioid pain medication requirements were also assessed. RESULTS: The final analysis included 43 patients in the 30-tablet group and 42 in the 60-tablet group. There was no significant difference between groups in the number of tablets consumed (9.5 vs 12.2, P = .22), number of days opioids were required (4.5 vs 6.2, P = .14), 3-month opioid refill rates (12% vs 7%, P = .48), or postoperative pain control at any point up to 21 days after surgery. The 30-tablet group had a significantly smaller proportion of unused tablets compared with the 60-tablet group (69% of prescribed tablets [910 tablets] vs 80% of prescribed tablets [2,027 tablets], P < .001). Opioids were required after surgery by 91% of patients (n = 77), and 81% could have had their pain medication requirements met with a prescription for 15 tablets. Risk factors for increased postoperative opioid use included a family history of substance abuse (ß = 14.1; 95% confidence interval, 5.7-22.4; P = .0014) and increased pain score at 2 hours after surgery (ß = 1.07; 95% confidence interval, 0.064-2.07; P = .037). CONCLUSIONS: Orthopaedic surgeons may significantly reduce the number opioid tablets prescribed after ACL reconstruction without affecting postoperative pain control or refill rates. LEVEL OF EVIDENCE: Level I, randomized controlled trial.

Evaluating the Early Impact of the COVID-19 Pandemic on Sports Surgery Fellowship Education.

Purpose The COVID-19 pandemic forced many hospitals to cancel elective surgeries to minimize the risk of viral transmission and ensure the availability of vital health resources. The unintended consequences of this action on the education and training of orthopaedic sports surgeons are unknown. The purpose of this study is to measure the impact of COVID-19 on orthopaedic sports surgery fellows, their education and training, and their readiness for practice. Methods A comprehensive survey was created and distributed to all U.S. fellows and fellowship directors registered with the American Orthopaedic Society for Sports Medicine. Responses were collected between April 22, 2020, and May 5, 2020. Results Fifty-one sports fellows and twenty-nine sports fellowship directors completed the survey. Over 80.4% of fellows reported a greater than 50% decrease in the case volume since the cessation of elective cases. Average hours worked per week decreased by 58.2% during the pandemic. Fellows reported completing an average of 324.6 ± 97.4 cases prior to the COVID-19 crisis and 86.0% expected to complete at least 11% to 25% fewer cases by graduation compared to previous fellows. 87.5% of fellows were not concerned about their ability to complete their fellowship training but more than one-third of fellows voiced concerns to their fellowship directors regarding their readiness for independent practice. Fellowship directors were generally not concerned that COVID-19 would prevent their fellows from completing the fellowship. At least 54.2% are somewhat concerned about the impact of COVID-19 on their future job opportunities. Conclusions The COVID-19 pandemic has universally affected work hours and case volume of sports fellows. Nevertheless, most sports fellows feel prepared to enter practice and are generally supported by the confidence of their fellowship directors. The results of this survey emphasize the importance of the fellowship year in sports training and highlight the future of online education and simulation as useful adjuncts.

Cell and extracellular matrix growth theory and its implications for tumorigenesis.

Cells associated with an abnormal (cancerous) growth exchange flows, morph freely and grow hand-in-glove with their immediate environment, the extracellular matrix (ECM). The cell structure experiences two mass flows in counterflow. Flowing into the structure are nutrients and flowing out is refuse from the metabolically active biomass within. The physical effect of the evolution of the cell and extracellular structure is more flow and mixing in that space, that is, more mixing than in the absence of a biological growth in that space. The objective of the present theory is to predict the increase in the size of the cell cluster as a function of its structure, and also to predict the critical cluster sizes that mark the transitions from one distinct cluster configuration to the next. This amounts to predicting the timing and the main features of the transitions from single cell to clusters with two, four, eight and more cells, including larger clusters with cells organized on its outer surface. The predicted evolution of the size and configuration of the cell cluster is validated successfully by comparison with measurements from several independent studies of cancerous and non-cancerous growth patterns.

Risk Factors for Increased Consumption of Narcotics After Hip Arthroscopy: A Prospective, Randomized Control Trial.

INTRODUCTION: No accepted standard exists regarding the number of opioids to prescribe after many surgical procedures, and previous literature has indicated that the number of opioids prescribed influences the total number of pills consumed. The goal of this study was to investigate whether prescribing less opioids after hip arthroscopy results in less total postoperative utilization without compromising analgesia and identify risk factors for increased use. METHODS: This study randomized 111 patients to receive either 30 or 60 tablets of hydrocodone/acetaminophen 10 to 325 mg after hip arthroscopy. Demographic information, pain instruments, and scores including International Hip Outcome Tool (iHOT-12) were collected preoperatively. Postoperatively, patients were contacted over the course of 3 weeks to determine their Numeric Pain Rating Scale scores, total number of tablets taken/leftover, and the last day that they required narcotic pain medications, which were calculated and compared for each group. Preoperative variables that increased the risk of higher narcotic pain medication requirements were assessed. RESULTS: Patients in the 60-tablet group had significantly more tablets leftover than the 30-tablet group (49.5 versus 22.0, P < 0.001) and had no significant difference in Numeric Pain Rating Scale scores at 24 hours, 48 hours, or final follow-up. The 30- and 60-tablet groups demonstrated no significant difference in average tablets consumed (9.2 and 10.5, P = 0.60), respectively. Risk factors for increased postoperative opioid use included preoperative opioid use (B = 12.62, 95% confidence interval [CI], 6.28-18.96, P < 0.001) or muscle relaxant use (B = 22.45, 95% CI, 7.59-37.31, P < 0.0036) within 1 year preoperatively. Preoperative iHOT-12 scoring also significantly predicted postoperative opioid consumption in this cohort (B = -0.25, 95% CI, -0.45 to -0.036, P < 0.022). CONCLUSION: The number of leftover tablets after hip arthroscopy can be significantly reduced by prescribing 30 tablets compared with 60 tablets without affecting postoperative pain control. Total tablets prescribed in this cohort did not affect total opioid utilization. Preoperative factors including opioid or muscle relaxant use and iHOT-12 scores can be used to predict postoperative opioid requirements.

Convergent Evolution of Boats with Sails.

This article unveils the geometric characteristics of boats with sails of many sizes, covering the range 102-105 kg. Data from one hundred boat models are collected and tabulated. The data show distinct trends of convergent evolution across the entire range of sizes, namely: (i) the proportionality between beam and draft, (ii) the proportionality between overall boat length and beam, and (iii) the proportionality between mast height and overall boat length. The review shows that the geometric aspect ratios (i)-(iii) are predictable from the physics of evolution toward architectures that offer greater flow access through the medium.

The fastest animals and vehicles are neither the biggest nor the fastest over lifetime.

Here we show how the size of a body affects its maximum average speed of movement through its environment. The theoretical challenge was to predict that 'outliers' must exist, such as the cheetah for terrestrial animals and the jet fighter for airplanes. We show that during a travel that starts from rest and continues at cruising speed, the body size for minimum travel time, or maximum average speed, is not the biggest. The results are compared with extensive data for military aircraft for chase, attack and reconnaissance, in addition to data for commercial aircraft. The paper also explains why in earlier studies of flying (animals, airplanes) the airplane data deviated upward (toward greater speeds) relative to the theoretical trend followed by flying animals, and why the fastest animal flyers are one thousand times smaller than the fastest swimmers. Unlike the biggest animals and airplanes (elephant, whale, commercial jet), which move constantly, the fastest animals and airplanes spend most of their lives at rest. When judged for speed averaged over lifetime, the fastest 'sprinters' are in fact the slowest movers (as in Aesop's fable 'The Tortoise and the Hare').

Whole genome DNA methylation sequencing of the chicken retina, cornea and brain.

Whole genome bisulfite sequencing (WGBS) analysis of DNA methylation uses massively parallel next generation sequencing technology to characterize global epigenetic patterns and fluctuations throughout a range of tissue samples. Development of the vertebrate retina is thought to involve extensive epigenetic reprogramming during embryogenesis. The chicken embryo (Gallus gallus) is a classic model system for studying developmental biology and retinogenesis, however, there are currently no publicly available data sets describing the developing chicken retinal methylome. Here we used Illumina WGBS analysis to characterize genome-wide patterns of DNA methylation in the developing chicken retina as well as cornea and brain in an effort to further our understanding of retina-specific epigenetic regulation. These data will be valuable to the vision research community for correlating global changes in DNA methylation to differential gene expression between ocular and neural tissues during critical developmental time points of retinogenesis in the chicken retina.

Evolution: why all plumes and jets evolve to round cross sections.

Turbulent curtains of smoke rise initially as flat plumes and, above a certain height, they become round plumes. The same evolution of cross-sectional shape is exhibited by jets issuing from flat nozzles. Here we predict based on principle that all such flows should evolve their cross-sectional shapes from flat to round (and not the other way) at a critical distance downstream, which is predictable. The principle is that the prevailing flow architecture provides greater access to the flow of momentum from the moving core (plume, jet) to the still surroundings. For turbulent plumes and jets, the transition distance scales with the long dimensions (L) of the two-dimensional (flat) heat sources and nozzles that drive them. For laminar jets, the transition distance scales with L Re, where Re is the Reynolds number based on nozzle velocity and the smaller dimension of the nozzle cross section. These predictions are confirmed by full numerical experiments of the three-dimensional flow fields of turbulent and laminar jets covering the Re range 10-10(4).

Workplace safety and health programs, practices, and conditions in auto collision repair businesses.

This article describes the results of a pre-intervention safety assessment conducted in 49 auto collision repair businesses and owners' commitments to specific improvements. A 92-item standardized audit tool employed interviews, record reviews, and observations to assess safety and health programs, training, and workplace conditions. Owners were asked to improve at least one-third of incorrect, deficient, or missing (not in compliance with regulations or not meeting best practice) items, of which a majority were critical or highly important for ensuring workplace safety. Two-thirds of all items were present, with the highest fraction related to electrical safety, machine safety, and lockout/tagout. One-half of shops did not have written safety programs and had not conducted recent training. Many had deficiencies in respiratory protection programs and practices. Thirteen businesses with a current or past relationship with a safety consultant had a significantly higher fraction of correct items, in particular related to safety programs, up-to-date training, paint booth and mixing room conditions, electrical safety, and respiratory protection. Owners selected an average of 58% of recommended improvements; they were most likely to select items related to employee Right-to-Know training, emergency exits, fire extinguishers, and respiratory protection. They were least likely to say they would improve written safety programs, stop routine spraying outside the booth, or provide adequate fire protection for spray areas outside the booth. These baseline results suggest that it may be possible to bring about workplace improvements using targeted assistance from occupational health and safety professionals.

The constructal-law physics of why swimmers must spread their fingers and toes.

Here we show theoretically that swimming animals and athletes gain an advantage in force and speed by spreading their fingers and toes optimally. The larger force means larger body mass lifted and greater speed, in accord with the constructal theory of all animal locomotion. The spacing between fingers must be twice the thickness of the boundary layer around one finger. This theoretical prediction is confirmed by computational fluid dynamics simulations of flow across two and four cylinders of diameter D. The optimal spacing is in the range 0.2D-0.4D, and decreases slightly as the Reynolds number (Re) increases from 20 to 100. For example, the total force exerted by two optimally spaced cylinders exceeds by 53% the total force of two cylinders with no spacing when Re=20. These design features hold for both time-dependent and steady-state flows.

Unifying constructal theory of tree roots, canopies and forests.

Here, we show that the most basic features of tree and forest architecture can be put on a unifying theoretical basis, which is provided by the constructal law. Key is the integrative approach to understanding the emergence of "designedness" in nature. Trees and forests are viewed as integral components (along with dendritic river basins, aerodynamic raindrops, and atmospheric and oceanic circulation) of the much greater global architecture that facilitates the cyclical flow of water in nature (Fig. 1) and the flow of stresses between wind and ground. Theoretical features derived in this paper are: the tapered shape of the root and longitudinally uniform diameter and density of internal flow tubes, the near-conical shape of tree trunks and branches, the proportionality between tree length and wood mass raised to 1/3, the proportionality between total water mass flow rate and tree length, the proportionality between the tree flow conductance and the tree length scale raised to a power between 1 and 2, the existence of forest floor plans that maximize ground-air flow access, the proportionality between the length scale of the tree and its rank raised to a power between -1 and -1/2, and the inverse proportionality between the tree size and number of trees of the same size. This paper further shows that there exists an optimal ratio of leaf volume divided by total tree volume, trees of the same size must have a larger wood volume fraction in windy climates, and larger trees must pack more wood per unit of tree volume than smaller trees. Comparisons with empirical correlations and formulas based on ad hoc models are provided. This theory predicts classical notions such as Leonardo's rule, Huber's rule, Zipf's distribution, and the Fibonacci sequence. The difference between modeling (description) and theory (prediction) is brought into evidence.

Functional alpha6-containing nicotinic receptors are present in chick retina.

Despite the fact that the neuronal chick alpha6 subunit was first cloned several years ago and recently has been shown to form acetylcholine (ACh)-activated channels in heterologous systems, no information is yet available concerning the structure and function of the alpha6-containing nicotinic receptors in neuronal tissues. Using subunit-specific antibodies directed against two different epitopes of the chick alpha6 subunit, we performed immunoprecipitation experiments on immunopurified alpha6-containing receptors radiolabeled with the nicotinic agonist [3H]epibatidine (Epi): almost all of the alpha6 receptors contained the beta4 subunit, 51% the beta3 subunit, 42% the alpha3 subunit, and 7.5% the beta2 subunit. Western blot analyses of the purified receptors confirmed the presence of the alpha3, beta3, beta2, and beta4 subunits, and the absence of the alpha4, alpha5, and alpha7 subunits. The alpha6-containing receptors bind [3H]Epi (Kd = 35 pM) and a number of other nicotinic agonists with very high affinity, the rank order being Epi >> cytisine > nicotine > 1, 1-dimethyl-4-phenylpiperazinium > acetylcholine > carbamylcholine. The alpha6 receptors also have a distinct antagonist pharmacological profile with a rank order of potency of alpha-conotoxin MII > methyllycaconitine > dihydro-beta-erythroydine > MG624 > d-tubocurarine > decamethonium > hexamethonium. When reconstituted in lipid bilayers, the alpha6-containing receptors form functional cationic channels with a main conductance state of 48 pS. These channels are activated by nicotinic agonists in a dose-dependent manner, and blocked by the nicotinic antagonist d-tubocurarine.

Liposomes: presentation and actual applicative trends in medicine.

In this paper the main aspects of characterization, handling and applications of liposomes are presented. In the last 25 years much attention has been focused to liposomal systems for optimization of the drug targeting. Several pathways to optimize the drug action of liposomes in various situations as cancer, microbial therapy, vaccines, oral therapy and diagnosis were tested. Certain applications of liposomes especially those implying the phagocytic cells sustain a real interest for industrial applications.