Solid phase crystallization under continuous heating: kinetic and microstructure scaling laws

The kinetics and microstructure of solid-phase crystallization under continuous heating conditions and random distribution of nuclei are analyzed. An Arrhenius temperature dependence is assumed for both nucleation and growth rates. Under these circumstances, the system has a scaling law such that the behavior of the scaled system is independent of the heating rate. Hence, the kinetics and microstructure obtained at different heating rates differ only in time and length scaling factors. Concerning the kinetics, it is shown that the extended volume evolves with time according to αex = [exp(κCt′)]m+1, where t′ is the dimensionless time. This scaled solution not only represents a significant simplification of the system description, it also provides new tools for its analysis. For instance, it has been possible to find an analytical dependence of the final average grain size on kinetic parameters. Concerning the microstructure, the existence of a length scaling factor has allowed the grain-size distribution to be numerically calculated as a function of the kinetic parameters

Development of Asphalt Dynamic Modulus Master Curve Using Falling Weight Deflectometer Measurements, TR-659

The asphalt concrete (AC) dynamic modulus (|E*|) is a key design parameter in mechanistic-based pavement design methodologies such as the American Association of State Highway and Transportation Officials (AASHTO) MEPDG/Pavement-ME Design. The objective of this feasibility study was to develop frameworks for predicting the AC |E*| master curve from falling weight deflectometer (FWD) deflection-time history data collected by the Iowa Department of Transportation (Iowa DOT). A neural networks (NN) methodology was developed based on a synthetically generated viscoelastic forward solutions database to predict AC relaxation modulus (E(t)) master curve coefficients from FWD deflection-time history data. According to the theory of viscoelasticity, if AC relaxation modulus, E(t), is known, |E*| can be calculated (and vice versa) through numerical inter-conversion procedures. Several case studies focusing on full-depth AC pavements were conducted to isolate potential backcalculation issues that are only related to the modulus master curve of the AC layer. For the proof-of-concept demonstration, a comprehensive full-depth AC analysis was carried out through 10,000 batch simulations using a viscoelastic forward analysis program. Anomalies were detected in the comprehensive raw synthetic database and were eliminated through imposition of certain constraints involving the sigmoid master curve coefficients. The surrogate forward modeling results showed that NNs are able to predict deflection-time histories from E(t) master curve coefficients and other layer properties very well. The NN inverse modeling results demonstrated the potential of NNs to backcalculate the E(t) master curve coefficients from single-drop FWD deflection-time history data, although the current prediction accuracies are not sufficient to recommend these models for practical implementation. Considering the complex nature of the problem investigated with many uncertainties involved, including the possible presence of dynamics during FWD testing (related to the presence and depth of stiff layer, inertial and wave propagation effects, etc.), the limitations of current FWD technology (integration errors, truncation issues, etc.), and the need for a rapid and simplified approach for routine implementation, future research recommendations have been provided making a strong case for an expanded research study.

Comparative assessement of intimal hyperplasia development after 14 days in two different experimental settings : tissue culture versus ex vivo continuous perfusion of human saphenous vein

Résumé de l'article : L'hyperplasie intimale est un processus de remodelage vasculaire ubiquitaire après une lésion, pouvant menacer la perméabilité de tout type de reconstruction vasculaire. Les mécanismes physiopathologiques impliqués dans le développement de l'hyperplasie intimale ne sont que partiellement élucidés. Il est par conséquent nécessaire d'effectuer des recherches complémentaires afin d'en améliorer la compréhension et ainsi permettre l'élaboration de nouvelles stratégies thérapeutiques médicamenteuses. La culture de veines en milieu statique permet le développement de l'hyperplasie intimale. Ce modèle maintient la viabilité tissulaire, comme décrit précédemment dans d'autres études, mais empêche l'analyse des paramètres hémodynamiques. La mise au point d'un modèle de perfusion in vitro permettant la perfusion de segments vasculaires représente une approche expérimentale intégrant les différents facteurs hémodynamiques. Le système de perfusion (Ex Vivo Vein Support System) que nous avons élaboré conserve l'intégrité pariétale ainsi que les propriétés vasomotrices des veines pour une durée de 14 jours. Cette étude démontre que les deux modèles permettent le développement de l'hyperplasie intimale. Toutefois, les propriétés vasomotrices ainsi que l'influence des paramètres hémodynamiques ne peuvent être analysées que par l'utilisation du système de perfusion. Ce dernier a permis de perfuser des vaisseaux humains sans contamination bactérienne tout en maintenant l'intégrité cellulaire. Ce modèle de perfusion se rapproche plus des conditions hémodynamiques rencontrées in vivo que le modèle statique. Abstract : Background. Intimal hyperplasia (IH) is a vascular remodeling process which often leads to failure of arterial bypass or hemodialysis access. Experimental and clinical work have provided insight in IH development; however, further studies under precise con-trolled conditions are required to improve therapeutic strategies to inhibit IH development. Ex vivo perfusion of human vessel segments under standardized hemodynamic conditions may provide an adequate experimental approach for this purpose. Therefore, chronically perfused venous segments were studied and compared to traditional static culture procedures with regard to functional and histomorphologic characteristics as well as gene expression. Materials and methods. Static vein culture allowing high tissue viability was performed as previously described. Ex vivo vein support system (EVVSS) was performed using a vein support system consisting of an incubator with a perfusion chamber and a pump. EVVSS allows vessel perfusion under continuous flow while maintaining controlled hemodynamic conditions. Each human saphenous vein was divided in two parts, one cultured in a Pyrex dish and the other part perfused in EVVSS for 14 days. Testing of vasomotion, histomorphometry, expression of CD 31, Factor VIII, MIB 1, α-actin, and PAI-1 were determined before and after 14 days of either experimental conditions. Results, Human venous segments cultured under traditional or perfused conditions exhibited similar IH after 14 days as shown by histomorphometry. Smooth-muscle cell ( SMC) was preserved after chronic perfusion. Although integrity of both endothelial and smooth-muscle cells appears to be maintained in both culture conditions as confirmed by CD31, factor VIII and α-actin expression, a few smooth-muscle cells in the media stained positive for factor VIII. Cell-proliferation marker MIB-1 was also detected in the two settings and PAI-1 mRNA expression and activity increased significantly after 14 days of culture and perfusion. Conclusion. This study demonstrates the feasibility to chronically perfuse human vessels under sterile conditions with preservation of cellular integrity and vascular contractility. To gain insights into the mechanisms leading to IH, it will now be possible to study vascular remodeling not only under static conditions but also in hemodynamic environment mimicking as closely as possible the flow conditions encountered in reconstructive vascular surgery.

A dynamic model of keratinocyte stem cell renewal and differentiation: role of the p21WAF1/Cip1 and Notch1 signaling pathways.

We present here a dynamic model of functional equilibrium between keratinocyte stem cells, transit amplifying populations and cells that are reversibly versus irreversibly committed to differentiation. According to this model, the size of keratinocyte stem cell populations can be controlled at multiple levels, including relative late steps in the sequence of events leading to terminal differentiation and by the influences of a heterogeneous extra-cellular environment. We discuss how work in our laboratory, on the interconnection between the cyclin/CDK inhibitor p21WAF1/Cip1 and the Notch1 signaling pathways, provides strong support to this dynamic model of stem cell versus committed and/or differentiated keratinocyte populations.

Polychlorinated trityl radicals for dynamic nuclear polarization: the role of chlorine nuclei

Polychlorinated trityl radicals bearing carboxylate substituents are water soluble persistent radicals that can be used for dynamic nuclear polarization. In contrast to other trityl radicals, the polarization mechanism differs from the classical solid effect. DFT calculations performed to rationalize this behaviour support the hypothesis that polarization is transferred from the unpaired electron to chlorine nuclei and from these to carbon by spin diffusion. The marked differences observed between neutral and anionic forms of the radical will be discussed.

Continuous electroencephalographic monitoring in critically ill patients with central nervous system infections.

OBJECTIVES: To determine the prevalence, predictors, and clinical significance of electrographic seizures (ESz) and other continuous electroencephalographic monitoring findings in critically ill patients with central nervous system infections. DESIGN: Retrospective cohort study. SETTING: Eighteen-bed neurocritical care unit. PATIENTS: We identified 42 consecutive patients with primary central nervous system infection (viral, 27 patients [64%]; bacterial, 8 patients [18%]; and fungal or parasitic, 7 patients [17%]) who underwent continuous electroencephalographic monitoring between January 1, 1996, and February 28, 2007. MAIN OUTCOME MEASURES: Presence of ESz or periodic epileptiform discharges (PEDs). RESULTS: Electrographic seizures were recorded in 14 patients (33%), and PEDs were recorded in 17 patients (40%). Twenty patients (48%) had either PEDs or ESz. Of the 14 patients with ESz, only 5 (36%) had a clinical correlate. Periodic epileptiform discharges (odds ratio=13.4; P=.001) and viral cause (odds ratio=13.0; P=.02) were independently associated with ESz. Both ESz (odds ratio=5.9; P=.02) and PEDs (odds ratio=6.1; P=.01) were independently associated with poor outcome at discharge (severe disability, vegetative state, or death). CONCLUSIONS: In patients with central nervous system infections undergoing continuous electroencephalographic monitoring, ESz and/or PEDs were frequent, occurring in 48% of our cohort. More than half of the ESz had no clinical correlate. Both ESz and PEDs were independently associated with poor outcome. Additional studies are needed to determine whether prevention or treatment of these electrographic findings improves outcome.

Coping with continuous human disturbance in the wild: insights from penguin heart rate response to various stressors.

ABSTRACT: BACKGROUND: A central question for ecologists is the extent to which anthropogenic disturbances (e.g. tourism) might impact wildlife and affect the systems under study. From a research perspective, identifying the effects of human disturbance caused by research-related activities is crucial in order to understand and account for potential biases and derive appropriate conclusions from the data. RESULTS: Here, we document a case of biological adjustment to chronic human disturbance in a colonial seabird, the king penguin (Aptenodytes patagonicus), breeding on remote and protected islands of the Southern ocean. Using heart rate (HR) as a measure of the stress response, we show that, in a colony with areas exposed to the continuous presence of humans (including scientists) for over 50 years, penguins have adjusted to human disturbance and habituated to certain, but not all, types of stressors. When compared to birds breeding in relatively undisturbed areas, birds in areas of high chronic human disturbance were found to exhibit attenuated HR responses to acute anthropogenic stressors of low-intensity (i.e. sounds or human approaches) to which they had been subjected intensely over the years. However, such attenuation was not apparent for high-intensity stressors (i.e. captures for scientific research) which only a few individuals experience each year. CONCLUSIONS: Habituation to anthropogenic sounds/approaches could be an adaptation to deal with chronic innocuous stressors, and beneficial from a research perspective. Alternately, whether penguins have actually habituated to anthropogenic disturbances over time or whether human presence has driven the directional selection of human-tolerant phenotypes, remains an open question with profound ecological and conservation implications, and emphasizes the need for more knowledge on the effects of human disturbance on long-term studied populations.

Proton NMR of (15)N-choline metabolites enhanced by dynamic nuclear polarization.

Chemical shifts of protons can report on metabolic transformations such as the conversion of choline to phosphocholine. To follow such processes in vivo, magnetization can be enhanced by dynamic nuclear polarization (DNP). We have hyperpolarized in this manner nitrogen-15 spins in (15)N-labeled choline up to 3.3% by irradiating the 94 GHz electron spin resonance of admixed TEMPO nitroxide radicals in a magnetic field of 3.35 T during ca. 3 h at 1.2 K. The sample was subsequently transferred to a high-resolution magnet, and the enhanced polarization was converted from (15)N to methyl- and methylene protons, using the small (2,3)J((1)H,(15)N) couplings in choline. The room-temperature lifetime of nitrogen polarization in choline, T(1)((15)N) approximately 200 s, could be considerably increased by partial deuteration of the molecule. This procedure enables studies of choline metabolites in vitro and in vivo using DNP-enhanced proton NMR.

Mitomycin C with continuous fluorouracil or with cisplatin in combination with radiotherapy for locally advanced anal cancer (European Organisation for Research and Treatment of Cancer phase II study 22011-40014).

PURPOSE: To assess the feasibility and activity of radio-chemotherapy with mitomycin C (MMC) and cisplatin (CDDP) in locally advanced squamous cell anal carcinoma with reference to radiotherapy (RT) combined with MMC and fluorouracil (5-FU). PATIENTS AND METHODS: Patients with measurable disease >4 cmN0 or N+ received RT (36Gy+2 week gap+23.4Gy) with either MMC/CDDP or MMC/5-FU (MMC 10mg/m(2) d1 of each sequence; 5-FU 200mg/m(2)/day c.i.v. daily; CDDP 25mg/m(2) weekly). Forty patients/arm were needed to exclude a RECIST objective response rate (ORR), 8 weeks after treatment, of <75% (Fleming 1, alpha=10%, beta=10%). RESULTS: The ORR was 79.5% (31/39) (lower bound confidence interval [CI]: 68.8%) with MMC/5-FU versus 91.9% (34/ 37) (lower bound CI: 82.8%) with MMC/CDDP. In the MMC/5-FU group, two patients (5.1%) discontinued treatment due to toxicity versus 11 (29.7%) in the MMC/CDDP group. Nine grade 3 haematological events occurred with MMC/CDDP versus none with 5-FU/MMC. The rate of other toxicities did not differ. There was no toxic death. Thirty-one patients in the MMC/5-FU arm (79.5%) and 18 in the MMC/CDDP arm (48.6%) were fully compliant with the protocol treatment (p=0.005). CONCLUSIONS: Radio-chemotherapy with MMC/CDDP seems promising as only MMC/CDDP demonstrated enough activity (RECIST ORR >75%) to be tested further in phase III trials; MMC/5-FU did not. MMC/CDDP also had an overall acceptable toxicity profile.

Dynamic Speed Feedback Signs, 2014

Dynamic speed feedback sign (DSFS) systems are traffic control devices that are programmed to provide a message to drivers exceeding a certain speed thresh¬old. A DSFS system typically consists of a speed-measuring device, which may be loop detectors or radar, and a message sign that displays feedback to drivers who exceed a predetermined speed threshold. The feedback may be the driver’s actual speed, a message like “SLOW DOWN,” or activation of a warning device such as beacons or a curve warning sign. For more on this topic by these authors, see also "Evaluation of Dynamic Speed Feedback Signs on Curves: A National Demonstration Project": http://www.trb.org/main/blurbs/172092.aspx

A new conservative-dynamic treatment for the acute ruptured Achilles tendon.

INTRODUCTION: There is a trend towards surgical treatment of acute ruptured Achilles tendon. While classical open surgical procedures have been shown to restore good functional capacity, they are potentially associated with significant complications like wound infection and paresthesia. Modern mini-invasive surgical techniques significantly reduce these complications and are also associated with good functional results so that they can be considered as the surgical treatment of choice. Nevertheless, there is still a need for conservative alternative and recent studies report good results with conservative treatment in rigid casts or braces. PATIENTS/METHOD: We report the use of a dynamic ankle brace in the conservative treatment of Achilles tendon rupture in a prospective non-randomised study of 57 consecutive patients. Patients were evaluated at an average follow-up time of 5 years using the modified Leppilahti Ankle Score, and the first 30 patients additionally underwent a clinical examination and muscular testing with a Cybex isokinetic dynamometer at 6 and 12 months. RESULTS: We found good and excellent results in most cases. We observed five complete re-ruptures, almost exclusively in case of poor patient's compliance, two partial re-ruptures and one deep venous thrombosis complicated by pulmonary embolism. CONCLUSION: Although prospective comparison with other modern treatment options is still required, the functional outcome after early ankle mobilisation in a dynamic cast is good enough to ethically propose this method as an alternative to surgical treatment.

Live Load Deflections in a Prestressed Steel Beam Bridge, HR-74, 1963

This report describes the measurement of dynamic (live load) deflections in a 240' x 30' three span continuous prestressed steel bridge, skewed 30 degrees. The design assumptions and prestressing procedure are described briefly, and the instrumentation and loading are discussed. The actual deflections are presented in tabular form, and the deflections due to the design live load are calculated. The maximum deflections are presented as a ratio of the span length, and the further use of prestressed steel beams is recommended.

Dynamic models of energy allocation and investment

In dynamic models of energy allocation, assimilated energy is allocated to reproduction, somatic growth, maintenance or storage, and the allocation pattern can change with age. The expected evolutionary outcome is an optimal allocation pattern, but this depends on the environment experienced during the evolutionary process and on the fitness costs and benefits incurred by allocating resources in different ways. Here we review existing treatments which encompass some of the possibilities as regards constant or variable environments and their predictability or unpredictability, and the ways in which production rates and mortality rates depend on body size and composition and age and on the pattern of energy allocation. The optimal policy is to allocate resources where selection pressures are highest, and simultaneous allocation to several body subsystems and reproduction can be optimal if these pressures are equal. This may explain balanced growth commonly observed during ontogeny. Growth ceases at maturity in many models; factors favouring growth after maturity include non-linear trade-offs, variable season length, and production and mortality rates both increasing (or decreasing) functions of body size. We cannot yet say whether these are sufficient to account for the many known cases of growth after maturity and not all reasonable models have yet been explored. Factors favouring storage are also reviewed.

quantiNemo: an individual-based program to simulate quantitative traits with explicit genetic architecture in a dynamic metapopulation.

quantiNemo is an individual-based, genetically explicit stochastic simulation program. It was developed to investigate the effects of selection, mutation, recombination and drift on quantitative traits with varying architectures in structured populations connected by migration and located in a heterogeneous habitat. quantiNemo is highly flexible at various levels: population, selection, trait(s) architecture, genetic map for QTL and/or markers, environment, demography, mating system, etc. quantiNemo is coded in C++ using an object-oriented approach and runs on any computer platform. Availability: Executables for several platforms, user's manual, and source code are freely available under the GNU General Public License at http://www2.unil.ch/popgen/softwares/quantinemo.

Cathodic Protection for a Continuous Box Girder Bridge Deck, HR-553, 1993

Bridge deck deterioration due to corrosive effect of deicers on reinforcing steel is a major problem facing many agencies. Cathodic protection is one method used to prevent reinforcing steel corrosion. The application of a direct current to the embedded reinforcing steel and a sacrificial anode protects the steel from corrosion. This 1992 project involved placing an Elgard Titanium Anode Mesh Cathodic Protection System on a bridge deck. The anode was fastened to the deck after the Class A repair-work and the overlay was placed using the Iowa Low Slump Dense Concrete System. The system was set up initially at 1 mA/sq ft.