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This article argues that between the 1890s and the 1920s, Cocopa Indians successfully parried the threats of expanding settler nation-states and modern capitalism by adapting ancestral mobility patterns to modern constraints of the U.S.-Mexico border. By moving with the changing flow of the Colorado River and, later, providing a cheap and indispensable migratory labor supply for both U.S. and Mexican farmers and ranchers, Cocopas were surprisingly successful at retaining autonomy within their ancestral homeland, even as both governments sought to enforce the international border and to colonize Cocopa lands. But a series of impediments eventually placed new and lasting limits on Cocopas’ abilities to move freely through their homeland of the Colorado River delta. A detailed account of how and why Cocopas moved, how and why state agents tried to limit their movements, and how and why both of these factors changed over time helps us understand why some Native peoples retained vestiges of autonomy within their ancestral homelands during an era commonly associated with genocide, displacement, or assimilation on both sides of the U.S.-Mexico border. This story shows us that Native movement was not only a geopolitical act but depended upon the specific landscapes in which it occurred. Long after the ink had dried on the map, this portion of the U.S.-Mexico border was rendered unstable by a river that knew no bounds and a people who knew how to move with it.

The crystal structure of Th(BH4)4 is described. Two of the four BH4- ions are terminal and tridentate (κ3), whereas the other two bridge between neighboring ThIV centers in a κ2,κ2 (i.e., bis-bidentate) fashion. Thus, each thorium center is bound to six BH4- groups by 14 Th-H bonds. The six boron atoms describe a distorted octahedron in which the κ3-BH4- ions are mutually cis; the 14 ligating hydrogen atoms define a highly distorted bicapped hexagonal antiprism. The thorium centers are linked into a polymer consisting of interconnected helical chains wound about 4-fold screw axes. The structures of An(BH4)4 (An = Th, U) were also investigated by DFT. The geometries of [An(BH4)6]2-, [An3(BH4)16]4-, and [An5(BH4)26]6- fragments of the polymeric structures were optimized at the B3LYP and/or PBE levels. Most calculated geometries are 14-coordinate and agree with the experimental structures, but isolated [Th(BH4)6]2- units are predicted to feature 16-coordinate ThIV centers.

If plasma polymer thin films are to be synthesised from sustainable and natural precursors of chemically heterogeneous composition, it is important to understand the extent to which this composition influences the mechanism of polymerisation. To this end, a well-studied monoterpene alcohol, terpinen-4-ol, has been targeted for a comparative study with the naturally occurring mix of terpenes (viz. Melaleuca alternifolia oil) from which it is commonly distilled. Positive ion mode mass spectra of both terpinen-4-ol and M. alternifolia oil showed a decrease in disparities between the type and abundance of cationic species formed in their respective plasma environments as applied plasma power was increased. Supplementary biological assay revealed the antibacterial action of both terpinen-4-ol and M. alternifolia derived coatings with respect to S. aureus bacteria, whilst cytocompatibility was demonstrated by comparable eukaryotic cell adhesion to both coatings. Elucidating the processes occurring within the reactive plasmas can enhance the economics of plasma polymer deposition by permitting use of the minimum power, time and precursor pre-processing required to control the extent of monomer fragmentation and fabricate a film of the desired thickness and functionality.

Reclaimed Asphalt Pavement (RAP) is an important component of most Hot Mix Asphalts (HMA). The extent of blending between RAP and virgin binders influences durability and performance of the HMA. Th...

OBJECTIVES: To investigate prescription opiate usage, disposal rates, and methods of disposal after pediatric surgery. METHODS: This was a retrospective chart review of patients RESULTS: A total of 290 patients with a mean age of 9.0 ± 4.7 years (62.8% male) met inclusion criteria. Sixty patients (20.7%) reported using all of their prescription opiate medication, whereas 230 patients (79.3%) did not use all of their pain medication. Of these 230 patients, 141 (61.3%) disposed of their leftover prescription opiates via flushing (56.4%), trash (28.6%), or take-back center (15.0%). At the time of phone survey between 60 and 90 days postoperatively, 88 patients (38.3%) still had leftover pain medication. By 7 days postoperatively, 234 of 290 patients (80.7%) had taken their last prescription opioid. CONCLUSIONS: In our study, 79.3% of patients were overprescribed opiate pain medication after pediatric surgery. Disposal rates at 60 to 90 days for leftover pain medication after pediatric surgery was just >60%. Pediatric patients are often overprescribed prescription opiates after surgery and typically only require a one-week supply of pain medication.

OBJECTIVE: As abuse of prescription narcotics continues to create a growing healthcare crisis throughout the United States, states have passed legislation designed to alter narcotic prescribing habits. West Virginia State Bill 273 limited the quantity of narcotics practitioners were able to prescribe. Our objective was to determine the effect of this bill on narcotic prescribing practices for pediatric surgical patients. METHODS: A hospital-wide database at a pediatric trauma center was queried to identify all pediatric patients undergoing surgery between 1/1/17 and 9/12/19 and all medications prescribed to this cohort. Narcotic prescriptions written for these patients in the two months following surgery were isolated. The percent of patients receiving a post-operative narcotic prescription and the morphine milligram equivalents (MME) per prescription were compared before and after the law’s implementation. RESULTS: The number of pediatric patients identified as having surgery in the study period was 10,176; 6069 were before the law passed and 4107 were after. The percentage of patients receiving a narcotic prescription was 46.0% before the law was passed, decreasing to 36.8% after the law (p

Plasma polymers such as polyterpenol have been investigated for use as biofunctional coatings, insulating/dielectric layers in electronics, and adhesion promoting interlayers in organic electronics. The commercialisation of plasma polymers in these and other biomaterial-related applications is contingent upon their ability to resist degradation in response to sterilising and potentially damaging ionising radiation, such as gamma rays. Hence, this study focusses on the stability of plasma polymerised polyterpenol thin films following exposure to gamma radiation doses ranging from 0 to 100 kGy. Irradiated films were subjected to ellipsometry, current–voltage, dielectric, Fourier transform infrared, and atomic force microscopy characterisation. Stability of polyterpenol was evidenced by the observed lack of radiation-induced variation in its complex refractive index, optical band gap, relative permittivity, dc conductivity, surface chemical functionalities, and surface morphology.

Multiple global change drivers are increasing the present and future novelty of environments and ecological communities. However, most assessments of environmental novelty have focused only on future climate and were conducted at scales too broad to be useful for land management or conservation. Here, using historical county-level data sets of agricultural land use, forest composition, and climate, we conduct a regional-scale assessment of environmental novelty for Wisconsin landscapes from ca. 1890 to 2012. Agricultural land-use data include six cropland types, livestock densities for four livestock species, and human populations. Forestry data comprise biomass-weighted relative abundances for 15 tree genera. Climate data comprise seasonal means for temperature and precipitation. We found that forestry and land use are the strongest cause of environmental novelty (NoveltyForest = 3.66, NoveltyAg = 2.83, NoveltyClimate = 1.60, with Wisconsin's forests transformed by early 20th-century logging and its legacies and multiple waves of agricultural innovation and obsolescence. Climate change is the smallest contributor to contemporary novelty, with precipitation signals stronger than temperature. Magnitudes and causes of environmental novelty are strongly spatially patterned, with novelty in southern Wisconsin roughly twice that in northern Wisconsin. Forestry is the most important cause of novelty in the north, land use and climate change are jointly important in the southwestern Wisconsin, and land use and forest composition are most important in central and eastern Wisconsin. Areas of high regional novelty tend also to be areas of high local change, but local change has not pushed all counties beyond regional baselines. Seven counties serve as the best historical analogues for over one-half of contemporary Wisconsin counties (40/72), and so can offer useful historical counterparts for contemporary systems and help managers coordinate to tackle similar environmental challenges. Multi-dimensional environmental novelty analyses, like those presented here, can help identify the best historical analogues for contemporary ecosystems, places where new management rules and practices may be needed because novelty is already high, and the main causes of novelty. Separating regional novelty clearly from local change and measuring both across many dimensions and at multiple scales thus helps advance ecology and sustainability science alike.

A unique porcine extracellular matrix (ECM) derived injectable tissue construct with 100 nm or 20 nm gold nanoparticles (AuNP) was developed for musculoskeletal tissue engineering applications. ECM has been shown to encourage cellularity and tissue remodeling due to its release of growth factors while AuNP have been shown to reduce reactive oxygen species (ROS) levels. Injectable tissue constructs were created by homogenizing decellularized porcine diaphragm tendon conjugated with 100 nm or 20 nm AuNP at 1x, 4x, and 8x concentrations. Extrusion force testing demonstrated that homogenized tissue constructs were injectable at an appropriate cannula size and force. L-929 murine fibroblasts were used to measure cell viability, cell proliferation, intracellular ROS levels, and cell migration in response to constructs. Enhanced cell viability and proliferation are observed on 1 × 20 nm AuNP constructs. ROS assays demonstrate reduced cellular ROS concentrations from all 20 nm AuNP constructs and from 8 × 100 nm AuNP constructs compared with constructs without nanoparticles. Cellular migration is higher towards 4 × 20 nm AuNP constructs compared with constructs without nanoparticles. Results support the potential use of a porcine ECM derived injectable tissue construct with AuNP as an injectable tissue construct to reduce inflammation and to promote tissue remodeling in musculoskeletal tissue engineering applications.

In the past several decades, processes that rely on the use of polymeric membranes have received considerable attention for the important role they play in biological and industrial fields. Surface properties are critical to membrane applications, yet a number of polymers that are both suitable for membrane manufacturing and possess necessary surface properties is often limited. Thus, modification of membrane surfaces is often used to fulfil diverse requirements. Nonequilibrium plasma treatment is an efficient method to tailor/adapt surface morphology and chemical structure of polymers without changing the bulk properties of the treated material. Plasma conditions play a significant role in controlling physico-chemical properties, and can be used to selectively modify surface energy, roughness, and biocompatibility of the polymer, as well as introduce new surface functional groups, e.g. carboxyl, hydroxyl, or amino functionalities, onto the surface of the membrane. This chapter will review the use of nonequilibrium plasma surface treatment for modification of polymeric membranes. First, the key interactions between physical and chemical effects of cold plasma and material surfaces will be briefly introduced. Then, specific examples for the usage of plasma to improve biological activities and mitigate biofouling properties of membranes will be discussed. Finally, plasma-induced grafting on membranes and plasma modification using several of the most common nonpolymerizable gases will be reviewed.

Radio frequency (R.F.) glow discharge polyterpenol thin films were prepared on silicon wafers and irradiated with I10+ ions to fluences of 1 × 1010 and 1 × 1012 ions/cm2. Post-irradiation characterisation of these films indicated the development of well-defined nano-scale ion entry tracks, highlighting prospective applications for ion irradiated polyterpenol thin films in a variety of membrane and nanotube-fabrication functions. Optical characterisation showed the films to be optically transparent within the visible spectrum and revealed an ability to selectively control the thin film refractive index as a function of fluence. This indicates that ion irradiation processing may be employed to produce plasma-polymer waveguides to accommodate a variety of wavelengths. XRR probing of the substrate-thin film interface revealed interfacial roughness values comparable to those obtained for the uncoated substrate's surface (i.e., both on the order of 5 A), indicating minimal substrate etching during the plasma deposition process.

Extremely low frequency electromagnetic fields (ELF-EMFs) can induce beneficial effects including enhanced protein synthesis and cell proliferation on healing bone and skin wounds. This study investigated the effects of ELF-EMFs on acellular tissue constructs with and without gold nanoparticles (AuNPs) to determine if cell proliferation could be increase and thus provide an enhanced mechanism for in vitro cell seeding on tissue engineered constructs. Different sized AuNPs, 20 and 100 nm, were conjugated to acellular porcine tissue, seeded with L929 murine fibroblasts and exposed to a continuous 12 gauss, 60 Hz electromagnetic field for 2 hours each day up to 10 days. Scanning electron microscopy and cell culture assays were performed to ascertain cell proliferation and viability before and after exposure. Results indicate the ELF-EMF stimulation significantly increased cell proliferation. The presence of AuNPs did not boost the stimulatory effects, but they did demonstrated higher rates of proliferation from day 3 to day 10. In addition, unstimulated 100 nm AuNPs constructs resulted in significant increases in proliferation as compared to unstimulated crosslinked constructs. In conclusion, ELF-EMF stimulation enhanced cellular proliferation and while the presence of AuNPs did not significantly enhance this effect, AuNPs resulted in increased proliferation rates from day 3 to day 10. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1532–1540, 2015.

Tibiotalar dislocations without associated fractures are very uncommon in adults, and only a few studies have been published regarding this injury. More than 50% of these dislocations will be posteromedial, with a high incidence of open injuries, and 25% are pure posterior dislocations. In the present report, we discuss our experience and management of a medial tibiotalar dislocation with no associated fracture. In the present case, the patient was brought to the operating room on presentation to our facility and underwent irrigation and debridement with primary closure of his wound. He was immobilized postoperatively. The patient tolerated the operation well and did not sustain any postoperative complications. He was able to regain function of the injured extremity until he was lost to follow-up. Regarding treatment, the surgery should be speedy, gentle to the soft tissue, and with as little implanted material as possible. Although we do not advocate that our management and treatment of this injury become the standard, the present case provides a good example of some of the challenges often encountered when treating these injuries.

An experimental study to understand the properties of reclaimed asphalt pavement (RAP), virgin binder and their respective blends was conducted. It was found that the current AASHTO (American Association of State Highway and Transportation Officials) M 323 specification recommendation to use one-grade softer performance graded asphalt at>15% RAP addition may not be justified. It is demonstrated that a binder grade change is not necessary up to 25% RAP in most blends. The ability of RAP and virgin binders to blend by diffusion at typical asphalt-mix production and placement temperatures and times was measured by a dynamic shear rheometer. A simulation showed that a complete binder blending in both hot-mix asphalt and warm-mix asphalt applications is reached within minutes after mixing. Nevertheless, binder layer thickness in the mix has a significant impact in these simulations and further understanding of binder film thickness in asphalt mix is necessary to accurately estimate degree of blending. Real mix...

Hydrogenolysis of the dimethyl actinide metal- locenes (C5Me4SiMe3)2UMe2 and (C5Me4H)2AnMe2 (An = Th, U) was examined for comparison with the hydrogenolysis of (C5Me5)2AnMe2 that forms the hydrides ((C5Me5)2ThH2)2, ((C5Me5)2UH2)2, and ((C5Me5)2UH)2. Parallel reactivity is not found with the (C5Me4SiMe3) � and (C5Me4H) �

Collagen has been utilized as a scaffold for tissue engineering applications due to its many advantageous properties. However, collagen in its purified state is mechanically weak and prone to rapid degradation. To mitigate these effects, collagen can be crosslinked. Although enhanced mechanical properties and stability can be achieved by crosslinking, collagen can be rendered less biocompatible either due to changes in the overall microstructure or due to the cytotoxicity of the crosslinkers. We have investigated crosslinking collagen using gold nanoparticles (AuNPs) to enhance mechanical properties and resistance to degradation while also maintaining its natural microstructure and biocompatibility. Rat tail type I collagen was crosslinked with AuNPs using a zero-length crosslinker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Several characterization studies were performed including electron microscopy, collagenase assays, ROS assays, and biocompatibility assays. The results demonstrated that AuNP-collagen scaffolds had increased resistance to degradation as compared to non-AuNP-collagen while still maintaining an open microstructure. Although the biocompatibility assays showed that the collagen and AuNP-collagen scaffolds are biocompatible, the AuNP-collagen demonstrated enhanced cellularity and glycoaminoglycans (GAG) production over the collagen scaffolds. Additionally, the Reactive Oxygen Species (ROS) assays indicated the ability of the AuNP-collagen to reduce oxidation. Overall, the AuNP-collagen scaffolds demonstrated enhanced biocompatibility and stability over non-AuNP scaffolds.

Plasma polymerization (glow discharge or the cold plasma) is used for material surface processing as well as for fabrication of thin films and nanoclusters. The plasma polymerization is a simple, one-step, solvent-free technique used to fabricate materials with a broad spectrum of properties suitable for use in electronics, biomedical, and mechanical fields. The first section of this chapter briefly reviews the mechanisms of plasma polymerization, identifying key parameters that control this process. This is followed by an in-depth discussion of material characteristics, i.e., optical, electrical, chemical and structural properties, typical of plasma polymers, with select examples that focus on the use of plasma polymers as functional materials for advanced and emerging electronics and biomedical applications.

Background: Physicians play a role in the current prescription drug-abuse epidemic. Surgeons often prescribe more postoperative narcotic pain medication than patients routinely need. Although narcotics are effective for severe, acute, postoperative pain, few evidence-based guidelines exist regarding the routinely required amount and duration of use post-hospital discharge. Methods: Patients in a prospective cohort undergoing posterior spinal fusion for idiopathic scoliosis were asked preoperatively to rate their pain level, the level of pain expected each week postoperatively, and their pain tolerance. Post-discharge pain scores and narcotic use were reported at weekly intervals for 4 weeks postoperatively. Demographic data, preoperative Scoliosis Research Society (SRS)-22 scores, operative details, perioperative data, and self-reported pain levels were analyzed with respect to their association with total medication use and refills received. Disposal plans were also assessed. Results: Seventy-two patients were enrolled, and 85% completed the surveys. The mean patient age was 14.9 years; 69% of the patients were female. The cohort was divided into 3 groups on the basis of total medication usage. The mean number of pills used in the middle (average-use) group was 49 pills. In postoperative week 4, narcotic usage was minimal (a mean of 2.9 pills by the highest-use group). Also by this time point, pain scores had, on average, returned to preoperative levels. Older age, male sex, a higher body mass index, and a higher preoperative pain score were associated with increased narcotic use. Sixty-seven percent of the patients planned to dispose of their unused medication, although only 59% of those patients planned on doing so in a manner recommended by the U.S. Food and Drug Administration. Conclusions: Postoperative narcotic dosing may be improved by considering patient age, weight, sex, and preoperative pain score. The precise estimation of individual narcotic needs is complex. Patient and family education on the importance and proper method of narcotic disposal is an essential component of minimizing the availability of unused postoperative medication. Level of Evidence: Prognostic Level I. See Instructions for Authors for a complete description of levels of evidence.

The reactions of LnCl(3) with molten boric acid result in the formation of Ln[B(4)O(6)(OH)(2)Cl] (Ln = La-Nd), Ln(4)[B(18)O(25)(OH)(13)Cl(3)] (Ln = Sm, Eu), or Ln[B(6)O(9)(OH)(3)] (Ln = Y, Eu-Lu). The reactions of AnCl(3) (An = Pu, Am, Cm) with molten boric acid under the same conditions yield Pu[B(4)O(6)(OH)(2)Cl] and Pu(2)[B(13)O(19)(OH)(5)Cl(2)(H(2)O)(3)], Am[B(9)O(13)(OH)(4)]·H(2)O, or Cm(2)[B(14)O(20)(OH)(7)(H(2)O)(2)Cl]. These compounds possess three-dimensional network structures where rare earth borate layers are joined together by BO(3) and/or BO(4) groups. There is a shift from 10-coordinate Ln(3+) and An(3+) cations with capped triangular cupola geometries for the early members of both series to 9-coordinate hula-hoop geometries for the later elements. Cm(3+) is anomalous in that it contains both 9- and 10-coordinate metal ions. Despite these materials being synthesized under identical conditions, the two series do not parallel one another. Electronic structure calculations with multireference, CASSCF, and density functional theory (DFT) methods reveal the An 5f orbitals to be localized and predominately uninvolved in bonding. For the Pu(III) borates, a Pu 6p orbital is observed with delocalized electron density on basal oxygen atoms contrasting the Am(III) and Cm(III) borates, where a basal O 2p orbital delocalizes to the An 6d orbital. The electronic structure of the Ce(III) borate is similar to the Pu(III) complexes in that the Ce 4f orbital is localized and noninteracting, but the Ce 5p orbital shows no interaction with the coordinating ligands. Natural bond orbital and natural population analyses at the DFT level illustrate distinctive larger Pu 5f atomic occupancy relative to Am and Cm 5f, as well as unique involvement and occupancy of the An 6d orbitals.

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the MH(x)Cl(y) compounds (M = Si, P, As, and Sb) and for a number of trivalent, tetravalent, and pentavalent fluorides (SbF(3), BiF(3), GeF(4), SnF(4), PbF(4), AsF(5), SbF(5)) from coupled cluster theory (CCSD(T)) calculations using correlation consistent basis sets and extrapolation to the complete basis set limit. Small-core, relativistic effective core potentials were used for the heavier elements (Ge, As, Sn, Sb, Pb, and Bi), including correlation of the outer core electrons. Additional scalar relativistic (for the lighter elements) and atomic spin-orbit corrections are included in order to achieve near chemical accuracy of ±1.5 kcal/mol. Vibrational zero point energies were computed from scaled harmonic frequencies at the second order Møller-Plesset perturbation theory (MP2) level where possible. Agreement between theory and the available experimental data is excellent. We present a revised heat of formation of the antimony atom in the gas phase. The calculated values will be of use in predicting the behavior of chemical vapor deposition systems.

The unusual uranium reaction system in which uranium(4+) and uranium(3+) hydrides interconvert by formal bimetallic reductive elimination and oxidative addition reactions, [(C(5)Me(5))(2)UH(2)](2) (1) ⇌ [(C(5)Me(5))(2)UH](2) (2) + H(2), was studied by employing multiconfigurational quantum chemical and density functional theory methods. 1 can act as a formal four-electron reductant, releasing H(2) gas as the byproduct of four H(2)/H(-) redox couples. The calculated structures for both reactants and products are in good agreement with the X-ray diffraction data on 2 and 1 and the neutron diffraction data on 1 obtained under H(2) pressure as part of this study. The interconversion of the uranium(4+) and uranium(3+) hydride species was calculated to be near thermoneutral (~-2 kcal/mol). Comparison with the unknown thorium analogue, [(C(5)Me(5))(2)ThH](2), shows that the thorium(4+) to thorium(3+) hydride interconversion reaction is endothermic by 26 kcal/mol.

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the neutral and ionic N(x)F(y) and O(x)F(y) systems using coupled cluster theory with single and double excitations and including a perturbative triples correction (CCSD(T)) method with correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. To achieve near chemical accuracy (±1 kcal/mol), three corrections to the electronic energy were added to the frozen core CCSD(T)/CBS binding energies: corrections for core-valence, scalar relativistic, and first order atomic spin-orbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory where possible. The calculated heats of formation are in good agreement with the available experimental values, except for FOOF because of the neglect of higher order correlation corrections. The F(+) affinity in the N(x)F(y) series increases from N(2) to N(2)F(4) by 63 kcal/mol, while that in the O(2)F(y) series decreases by 18 kcal/mol from O(2) to O(2)F(2). Neither N(2) nor N(2)F(4) is predicted to bind F(-), and N(2)F(2) is a very weak Lewis acid with an F(-) affinity of about 10 kcal/mol for either the cis or trans isomer. The low F(-) affinities of the nitrogen fluorides explain why, in spite of the fact that many stable nitrogen fluoride cations are known, no nitrogen fluoride anions have been isolated so far. For example, the F(-) affinity of NF is predicted to be only 12.5 kcal/mol which explains the numerous experimental failures to prepare NF(2)(-) salts from the well-known strong acid HNF(2). The F(-) affinity of O(2) is predicted to have a small positive value and increases for O(2)F(2) by 23 kcal/mol, indicating that the O(2)F(3)(-) anion might be marginally stable at subambient temperatures. The calculated adiabatic ionization potentials and electron affinities are in good agreement with experiment considering that many of the experimental values are for vertical processes.

This study utilized spectral and thermal analysis of explanted hernia mesh materials to determine material inertness and elucidate reasons for hernia mesh explantation. Composite mesh materials, comprised of polypropylene (PP) and expanded polytetrafluoroethylene (ePTFE) mesh surrounded by a polyethylene terephthalate (PET) ring, were explanted from humans. Scanning electron microscopy (SEM) was conducted to visually observe material defects while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to find chemical signs of surface degradation. Modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA) gave thermal stability profiles that showed changes in heat of fusion and rate of percent weight loss, respectively. ATR-FTIR scans showed higher carbonyl peak areas as compared to pristine for 91% and 55% of ePTFE and PP explants, respectively. Ninety-one percent of ePTFE explants also exhibited higher C--H stretch peak areas. Seventy-three percent of ePTFE explants had higher heats of fusion while 64% of PP explants had lower heats of fusion with respect to their corresponding pristines. Only 9% of PET explants exhibited a lower heat of fusion than pristine. Seventy-three percent of ePTFE explants, 73% of PP explants, and only 18% of PET explants showed a decreased rate of percent weight loss as compared to pristine. The majority of the PP and ePTFE mesh explants demonstrated oxidation and crosslinking, respectively, while the PET ring exhibited breakdown at the sites of high stress. The results showed that all three materials exhibited varied degrees of chemical degradation suggesting that a lack of inertness in vivo contributes to hernia mesh failure.

N(2)F(+) salts are important precursors in the synthesis of N(5)(+) compounds, and better methods are reported for their larger scale production. A new, marginally stable N(2)F(+) salt, N(2)F(+)Sn(2)F(9)(-), was prepared and characterized. An ordered crystal structure was obtained for N(2)F(+)Sb(2)F(11)(-), resulting in the first observation of individual N[triple bond]N and N-F bond distances for N(2)F(+) in the solid phase. The observed N[triple bond]N and N-F bond distances of 1.089(9) and 1.257(8) A, respectively, are among the shortest experimentally observed N-N and N-F bonds. High-level electronic structure calculations at the CCSD(T) level with correlation-consistent basis sets extrapolated to the complete basis limit show that cis-N(2)F(2) is more stable than trans-N(2)F(2) by 1.4 kcal/mol at 298 K. The calculations also demonstrate that the lowest uncatalyzed pathway for the trans-cis isomerization of N(2)F(2) has a barrier of 60 kcal/mol and involves rotation about the N=N double bond. This barrier is substantially higher than the energy required for the dissociation of N(2)F(2) to N(2) and 2 F. Therefore, some of the N(2)F(2) dissociates before undergoing an uncatalyzed isomerization, with some of the dissociation products probably catalyzing the isomerization. Furthermore, it is shown that the trans-cis isomerization of N(2)F(2) is catalyzed by strong Lewis acids, involves a planar transition state of symmetry C(s), and yields a 9:1 equilibrium mixture of cis-N(2)F(2) and trans-N(2)F(2). Explanations are given for the increased reactivity of cis-N(2)F(2) with Lewis acids and the exclusive formation of cis-N(2)F(2) in the reaction of N(2)F(+) with F(-). The geometry and vibrational frequencies of the F(2)N=N isomer have also been calculated and imply strong contributions from ionic N(2)F(+) F(-) resonance structures, similar to those in F(3)NO and FNO.

This study aimed to produce graphitic-polymer nanocomposite thin films via the swift heavy ion irradiation of polyterpenol thin films synthesized from an environmentally sustainable precursor by radio-frequency plasma enhanced chemical vapor deposition. Atomic force microscopy and scanning electron microscopy revealed fluence-dependent surface restructuring of the thin films leading to the formation of interconnected island structures, with no discernible delamination from the underlying aluminum substrate. Raman spectroscopy confirmed the development of D and G peaks associated with graphitic materials, whilst Fourier transform infrared spectroscopy indicated retention of the plasma polymer's chemical functionalities (including hydroxyl groups) within the material after irradiation. Graphitic-polymer nanocomposite films prepared by this dry and solvent-free process have numerous potential applications in biological assay, organic electronics, and membrane technology. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46498.

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for XeF(3)(+), XeF(3)(-), XeF(5)(+), XeF(7)(+), XeF(7)(-), and XeF(8) from coupled cluster theory (CCSD(T)) calculations with effective core potential correlation-consistent basis sets for Xe and including correlation of the nearest core electrons. Additional corrections are included to achieve near chemical accuracy of +/-1 kcal/mol. Vibrational zero point energies were computed at the MP2 level of theory. Unlike the other neutral xenon fluorides, XeF(8) is predicted to be thermodynamically unstable with respect to loss of F(2) with the reaction calculated to be exothermic by 22.3 kcal/mol at 0 K. XeF(7)(+) is also predicted to be thermodynamically unstable with respect to the loss of F(2) by 24.1 kcal/mol at 0 K. For XeF(3)(+), XeF(5)(+), XeF(3)(-), XeF(5)(-), and XeF(7)(-), the reactions for loss of F(2) are endothermic by 14.8, 37.8, 38.2, 59.6, and 31.9 kcal/mol at 0 K, respectively. The F(+) affinities of Xe, XeF(2), XeF(4), and XeF(6) are predicted to be 165.1, 155.3, 172.7, and 132.5 kcal/mol, and the corresponding F(-) affinities are 6.3, 19.9, 59.1, and 75.0 kcal/mol at 0 K, respectively.

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted from high level ab initio electronic structure calculations using the coupled cluster CCSD(T) method with augmented correlation-consistent basis sets extrapolated to the complete basis set (CBS) limit for the H(1,2)O(m)S(n) (m, n = 0-3) compounds, as well as various radicals involved in different bond breaking processes. To achieve near chemical accuracy (+/-1.0 kcal/mol), additional corrections were added to the CBS binding energies based on the frozen core CCSD(T) energies including corrections for core-valence, scalar relativistic, and first-order atomic spin-orbit effects. Geometries were optimized up through the CCSD(T)/aV(T+d)Z level. Vibrational zero point energies were computed at the MP2/aV(T+d)Z level. The calculated heats of formation are in excellent agreement with the available experimental data and allow the prediction of adiabatic bond dissociation energies (BDEs) to within +/-1.0 kcal/mol. The decomposition mechanisms were largely determined by a preference to maintain a strong S=O bond in the dissociated products as opposed to O=O and S=S bonds, exactly matching the ordering of the BDEs in the diatomics. For the H(2)X(2) and H(2)X(3) systems, as well as the HX(3) radicals, the energetically favorable decomposition pathway leads to the formation of XH radicals and breaking the X-X bond as opposed to breaking the X-H bond. For the HX(2) radicals, however, the more thermodynamically favorable pathway leads to a breaking of the H-X bond and forming X(2) molecules.

The heats of formation for BN, HBNH, H2BNH2, and H3BNH3 and their radicals, anions, cations, and protonated species were predicted using the CCSD(T) method with correlation consistent basis sets extrapolated to the complete basis set and core−valence, scalar relativistic, spin−orbit, and zero-point energy corrections. Chemical accuracy (±1 kcal/mol) is obtained for these heats of formation, allowing reliable results for electron and hydride affinities, ionization energies, basicities (neutral proton affinities), acidities (anion proton affinities), and bond dissociation energies of the BNHn (n = 0−6) molecules. The closed shell BNHn molecules, except for H3BNH3 (double diffuse functions on B and N required), do not bind an electron and behave as nitrogen acids and bases. Protonation of H3BNH3 leads to nearly spontaneous H2 release. The closed shell BNHn species exhibit ionization energies similar or smaller than those of hydrocarbons, and for the H2BNH radical, its ionization energy (∼5.9 eV) is close to ...

Atomization energies at 0 K and enthalpies of formation at 0 and 298 K are predicted for the BH(4-n)X(n)(-) and the BH(3-n)X(n)F(-) compounds for (X = F, Cl, Br, I, NH(2), OH, and SH) from coupled cluster theory (CCSD(T)) calculations with correlation-consistent basis sets and with an effective core potential on I. To achieve near chemical accuracy (+/-1.0 kcal/mol), additional corrections were added to the complete basis set binding energies. The hydride, fluoride, and X(-) affinities of the BH(3-n)X(n) compounds were predicted. Although the hydride and fluoride affinities differ somewhat in their magnitudes, they show very similar trends and are both suitable for judging the Lewis acidities of compounds. The only significant differences in their acidity strength orders are found for the boranes substituted with the strongly electron withdrawing and back-donating fluorine and hydroxyl ligands. The highest H(-) and F(-) affinities are found for BI(3) and the lowest ones for B(NH(2))(3). Within the boron trihalide series, the Lewis acidity increases monotonically with increasing atomic weight of the halogen, that is, BI(3) is a considerably stronger Lewis acid than BF(3). For the X(-) affinities in the BX(3), HBX(2), and H(2)BX series, the fluorides show the highest values, whereas the amino and mercapto compounds show the lowest ones. Hydride and fluoride affinities of the BH(3-n)X(n) compounds exhibit linear correlations with the proton affinity of X(-) for most X ligands. Reasons for the correlation are discussed. A detailed analysis of the individual contributions to the Lewis acidities of these substituted boranes shows that the dominant effect in the magnitude of the acidity is the strength of the BX(3)(-)-F bond. The main contributor to the relative differences in the Lewis acidities of BX(3) for X, a halogen, is the electron affinity of BX(3) with a secondary contribution from the distortion energy from planar to pyramidal BX(3). The B-F bond dissociation energy of X(3)B-F(-) and the distortion energy from pyramidal to tetrahedral BX(3)(-) are of less importance in determining the relative acidities. Because the electron affinity of BX(3) is strongly influenced by the charge density in the empty p(z) lowest unoccupied molecular orbital of boron, the amount of pi-back-donation from the halogen to boron is crucial and explains why the Lewis acidity of BF(3) is significantly lower than those of BX(3) with X = Cl, Br, and I.

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for (CH3)H2N-BH3, (CH3)HN=BH2, (BH3)HN=CH2, (CH3)H2B-NH3, (CH3)HB=NH2, and (NH3)HB=CH2, as well as various molecules involved in the different bond-breaking processes, from coupled cluster theory (CCSD(T)) calculations. In order to achieve near-chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core CCSD(T) energies, corrections for core-valence, scalar relativistic, and first-order atomic spin-orbit effects. Scaled vibrational zero-point energies were computed with the MP2 method. The heats of formation were predicted for the respective dimethyl- and trimethyl-substituted ammonia boranes, their dehydrogenated derivatives, and the various molecules involved in the different bond breaking processes, based on isodesmic reaction schemes calculated at the G3(MP2) level. Thermodynamics for dehydrogenation pathways in the monomethyl-substituted molecules were predicted. Dehydrogenation across the B-N bond is more favorable as opposed to dehydrogenation across the B-C and N-C bonds. Methylation at N reduces the exothermocity of the dehydrogenation reaction and makes the reaction more thermoneutral, while methylation at B moves it away from thermoneutral. Various mixtures of CH3NH2BH3 and NH3BH3 were made, and their melting points were measured. The lowest melting mixture contained approximately 35% NH3BH3 by weight and melted at 35-37 degrees C.

Thermochemical properties of a set of small boron (B(n)) and boron oxide (B(n)O(m)) clusters, with n = 1-4 and m = 0-3, their anions, and the B(4)(2-) dianion, were calculated by using coupled-cluster theory CCSD(T) calculations with the aug-cc-pVnZ (n = D, T, Q, 5) basis sets extrapolated to the complete basis set limit with additional corrections. Enthalpies of formation, bond dissociation energies, singlet-triplet or doublet-quartet separation gaps, adiabatic electron affinities (EA), and both vertical electron attachment and detachment energies were evaluated. The predicted heats of formation show agreement close to the error bars of the literature results for boron oxides with the largest error for OBO. Our calculated adiabatic EAs are in good agreement with recent experiments: B (calc, 0.26 eV; exptl, 0.28 eV), B(2) (1.95, 1.80), B(3) (2.88, 2.820 +/- 0.020), B(4) (1.68, 1.60 +/- 0.10), BO (2.50, 2.51), BO(2) (4.48, 4.51), BOB (0.07), B(2)O(2) (0.37), B(3)O (2.05), B(3)O(2) (2.94, 2.94), B(4)O (2.58), and B(4)O(2) (3.14, 3.160 +/- 0.015). The BO bond is strong, so this moiety is maintained in most of the clusters. Thermochemical parameters of clusters are not linearly additive with respect to the number of B atoms. The EA tends to be larger in the dioxides. The growth mechanism of small boron oxides should be determined by a number of factors: (i) formation of BO bonds, (ii) when possible, formation of a cyclic B(3) or B(4), and (iii) combination of a boron cycle and a BO bond. When these factors compete, the strength of the BO bonds tends to compensate the destabilization arising from a loss of binding in the cyclic boron clusters, in such a way that a linear boron oxide prevails. When the B(2) moiety is present in these linear clusters, the oxide derivatives prefer a high spin state.

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for IF, IF2−, IF2+, IF3, IF4−, IF4+, IF5, IF6−, IF6+, IF7, IF8−, BrF6−, and ClF6− from coupled cluster theory [CCSD(T)] calculations with effective-core potential correlation-consistent basis sets for I. In order to achieve near chemical accuracy (±1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen-core coupled-cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first-order atomic spin−orbit effects. Vibrational zero-point energies were computed at the coupled-cluster level of theory except for IF6−, IF7, and IF8−. The calculated heats of formation for the neutral and ionic IFn fluorides were used to predict fluoride affinities. It is shown that high-level calculations are required to predict correctly the steric activity of the free-valence electron pair on the central atoms in IF6− (C3v), BrF6− (Oh...

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for KrF+, KrF-, KrF2, KrF3+, KrF4, KrF5+, and KrF6 from coupled-cluster theory (CCSD(T)) calculations with effective core potential correlation-consistent basis sets for krypton. To achieve near chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core coupled-cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first-order atomic spin-orbit effects. Vibrational zero point energies were computed at the coupled-cluster level of theory. The calculated value for the heat of formation of KrF2 is in excellent agreement with the experimental value. Contrary to the analogous xenon fluorides, KrF2, KrF4, and KrF6 are predicted to be thermodynamically unstable with respect to loss of F2. An analysis of the energetics of KrF4 and KrF6 with respect to fluorine atom loss together with calculations of the transition states for the intramolecular loss of F2 show that fluorine atom loss is the limiting factor determining the kinetic stabilities of these molecules. Whereas KrF4 possesses a marginal energy barrier of 10 kcal/mol toward fluorine atom loss and might be stable at moderately low temperatures, the corresponding barrier in KrF6 is only 0.9 kcal/mol, suggesting that it could exist only at very low temperatures. Although the simultaneous reactions of either two or four fluorine atoms with KrF2 to give KrF4 or KrF6, respectively, are exothermic, they do not represent feasible synthetic approaches because the attack of the fluorine ligands of KrF2 by the fluorine atoms, resulting in F2 abstraction, is thermodynamically favored over oxidative fluorination of the krypton central atom. Therefore, KrF6 could exist only at very low temperatures, and even the preparation of KrF4 will be extremely difficult.

Arousal and cardio-respiratory responses to respiratory stimuli during sleep are important protective mechanisms that rapidly become depressed in the active sleep state when episodes of hypoxia or asphyxia are repeated: whether responses to repeated hypercapnia are similarly depressed is not known. This study aimed to determine if arousal and cardio-respiratory responses also become depressed with repeated episodes of hypercapnia during sleep and whether responses differ in active sleep and quiet sleep. Eight newborn lambs were instrumented to record sleep state and cardio-respiratory variables. Lambs were subjected to two successive 12 h sleep recordings, assigned as either sequential control and test days, or test and control days performed between 12.00 and 00.00 h. The control day was a baseline study in which the lambs breathed air to determine spontaneous arousal probability. During the test day, lambs were exposed to a 60 s episode of normoxic hypercapnia (Fractional inspired CO2 (F(ICO2)) = 0.08 and Fractional inspired O2(F(IO2)) = 0.21 in N2) during every quiet sleep and active sleep epoch. The probability of lambs arousing during the hypercapnic exposure exceeded the probability of spontaneous arousal during quiet sleep (58% versus 21%, chi2 = 54.0, P < 0.001) and active sleep (39% versus 20%, chi2 = 10.0, P < 0.01), though the response was less in active sleep. Exposure to hypercapnia also resulted in a significant increase in ventilation in quiet sleep (150 +/- 22%) and active sleep (97 +/- 23%, P < 0.05), though the increase was smaller in active sleep (P < 0.05). Small (< 5%) blood pressure increases and heart rate decreases were evident during hypercapnia in quiet sleep, but not in active sleep. Arousal and cardio-respiratory responses persisted with repetition of the hypercapnic exposure. In summary, although arousal and cardio-respiratory responses to hypercapnia are less in active sleep compared with quiet sleep, these protective responses are not diminished with repeated exposure to hypercapnia.

The cation−π interaction is proposed as an important mechanism for the adsorption of aromatic hydrocarbons having non-zero quadrupole moments by mineral surfaces. Direct evidence supporting such a mechanism is, however, limited. Using the model mineral calcite, we probe the cation−π interaction with adsorbed benzene, toluene, and ethylbenzene (BTE) molecules using attenuated total reflectance Fourier transform infrared spectroscopy. We show that the presence of calcite increases the energy required to excite the synchronized bending of aromatic C–H bonds of BTE molecules. The unique conformation of this vibrational mode indicates that the planar aromatic rings of BTE molecules are constrained in a tilted face-down position by the cation−π interaction, as further confirmed by density functional theory calculations. Our results suggest that the shift of the excitation energy of the aromatic C–H bending may be used as an infrared signature for the cation−π interaction occurring on mineral surfaces.

During rapid-eye-movement (REM) sleep in adult subjects, the cerebral metabolic rate of oxygen consumption (CMRO(2)) is as high as that during wakefulness. We investigated whether CMRO(2) during active sleep is already at the waking level in newborn life, to support the role of active sleep as a state of endogenous brain activation during early postnatal development. Newborn lambs, 2-5 days old (n = 6), were instrumented with electrodes for sleep-state scoring, catheters for blood sample withdrawal and pressure monitoring, and a transit-time ultrasonic blood-flow probe around the superior sagittal sinus. At the age of 19 +/- 3 days, blood samples were obtained simultaneously from the carotid artery and the superior sagittal sinus during uninterrupted epochs of wakefulness, quiet sleep, and active sleep. The arteriovenous difference in blood oxygen concentration was multiplied by cerebral blood flow to determine CMRO(2). CMRO(2) during active sleep (47 +/- 5 micromol min(-1)) was similar to the value in wakefulness (44 +/- 6 micromol min(-1)) and significantly higher than in quiet sleep (39 +/- 5 micromol min(-1), P < 0.05). These data show that active sleep provides newborn lambs with brain activity at a level similar to that in wakefulness in terms of cerebral oxygen metabolism. The high CMRO(2) during active sleep supports its functional role during early postnatal development, when time spent in active sleep is at a lifetime maximum, albeit constituting a metabolic challenge for newborns, because of the impairment of systemic and cerebral vascular regulation in this sleep state.

The heats of formation for the molecules BH3PH3, BH2PH2, HBPH, AlH3NH3, AlH2NH2, HAlNH, AlH3PH3, AlH2PH2, HAlPH, AlH4-, PH3, PH4, and PH4+, as well as the diatomics BP, AlN, and AlP, have been calculated by using ab initio molecular orbital theory. The coupled cluster with single and double excitations and perturbative triples method (CCSD(T)) was employed for the total valence electronic energies. Correlation consistent basis sets were used, up through the augmented quadruple-ζ, to extrapolate to the complete basis set limit. Additional d core functions were used for Al and P. Core/valence, scalar relativistic, and spin−orbit corrections were included in an additive fashion to predict the atomization energies. Geometries were calculated at the CCSD(T) level up through at least aug-cc-pVTZ and frequencies were calculated at the CCSD(T)/aug-cc-pVDZ level. The heats of formation of the salts [BH4-][PH4+](s), [AlH4-][NH4+](s), and [AlH4-][PH4+](s) have been estimated by using an empirical expression for the ...

Cerebral vessels are extensively innervated by sympathetic nerves arising from superior cervical ganglia, and these nerves might play a protective role during the large arterial pressure surges of active sleep (AS). We studied lambs (n=10) undergoing spontaneous sleep-wake cycles before and after bilateral removal of the superior cervical ganglia (SCGx, n=5) or sham ganglionectomy (n=5). Lambs were instrumented to record cerebral blood flow (CBF, flow probe on the superior sagittal sinus), carotid arterial pressure (P(ca)), intra-cranial pressure (P(ic)), cerebral perfusion pressure (Pcp=Pca-Pic) and cerebral vascular resistance (CVR). Prior to SCGx, CBF (mL min-1) was significantly higher in AS than in Quiet Sleep (QS) and Quiet Wakefulness (QW) (17+/-2, 13+/-3, and 14+/-3 respectively, mean+/-SD, P

Autoregulation is a vital protective mechanism that maintains stable cerebral blood flow as cerebral perfusion pressure changes. We contrasted cerebral autoregulation across sleep-wake states, as little is known about its effectiveness during sleep. Newborn lambs (n= 9) were instrumented to measure cerebral blood flow (flow probe on the superior sagittal sinus) and cerebral perfusion pressure, then studied during active sleep (AS), quiet sleep (QS) and quiet wakefulness (QW). We generated cerebral autoregulation curves by inflating an occluder cuff around the brachiocephalic artery thereby lowering cerebral perfusion pressure. Baseline cerebral blood flow was higher (P < 0.05) and cerebral vascular resistance lower (P < 0.05) in AS than in QW (76 +/- 8% and 133 +/- 15%, respectively, of the AS value, mean +/-s.d.) and in QS (66 +/- 11% and 158 +/- 30%). The autoregulation curve in AS differed from that in QS and QW in three key respects: firstly, the plateau was elevated relative to QS and QW (P < 0.05); secondly, the lower limit of the curve (breakpoint) was higher (P < 0.05) in AS (50 mmHg) than QS (45 mmHg); and thirdly, the slope of the descending limb below the breakpoint was greater (P < 0.05) in AS than QS (56% of AS) or QW (56% of AS). Although autoregulation functions in AS, the higher breakpoint and greater slope of the descending limb may place the brain at risk for vascular compromise should hypotension occur.

The compound Na{[Tc6Br12]2Br} has been obtained from the decomposition of TcBr4 under vacuum in a Pyrex ampule at 450 °C. The stoichiometry of the compound has been confirmed by energy-dispersive X-ray spectroscopy and its structure determined by single-crystal X-ray diffraction. The compound contains a trigonal-prismatic hexanuclear [Tc6Br12] cluster. The cluster is composed of two triangular Tc3Br6 units linked by multiple Tc-Tc bonds. In the Tc3Br6 unit, the average Tc-Tc distance [2.6845(5) Å] is characteristic of Tc-Tc single bonds, while the average Tc-Tc distance between the two triangular units [2.1735(5) Å] is characteristic of Tc≡Tc triple bonds. The electronic structure of the [Tc6Br12] cluster was studied by first-principles calculations, which confirm the presence of single and triple Tc-Tc bonds in the cluster.

Objective By constraining the heart, the chest wall, lungs, and pericardium limit diastolic filling and thus have a major role in determining cardiac output. Although intermittent positive pressure ventilation and the application of positive end-expiratory pressure amplifies this constraint, no clinical method exists to assess the impact that positive end-expiratory pressure has on ventricular constraint in the newborn. In this study, we tested the hypothesis that a change in right atrial pressure (Pra) reflects the change in ventricular constraint associated with a change in airway pressure. Design Experimental, comparative animal study. Setting Ritchie Centre for Baby Health Research cardiovascular laboratory. SUBJECTS Neonatal (4-wk-old, n = 6) and newborn (3-day-old, n = 6) Merino/Border-Leicester cross lambs. Interventions Lambs were anesthetized (alpha-chloralose and ketamine), ventilated, and instrumented to record Pra, thoracic inferior vena caval pressure (Pivc, saline-filled catheters), and pericardial pressure (Pper, liquid-containing balloon). Measurements and main results Changes (Delta) in Pra, Pivc, and Pper were assessed while airway pressure was rapidly reduced from four set levels of continuous positive airway pressure (2.5, 5, 7.5, and 15 cm H2O) to atmospheric pressure. A strong linear relationship was observed between DeltaPra and DeltaPper (DeltaPra = 0.90 DeltaPper - 0.02, r =.98), and between DeltaPivc and DeltaPper (DeltaPivc = 0.86 DeltaPper - 0.02, r =.98) in both the 4-wk-old lambs and the 3-day-old lambs. Conclusions Our experiments demonstrate that, in the newborn and neonatal lamb, DeltaPra provides an accurate measure of the change in ventricular constraint that accompanies a change in airway pressure, and thus may provide a means of quantifying the magnitude of ventricular constraint imposed by positive end-expiratory pressure and mechanical ventilation during neonatal intensive care.