Small Bridge Research Articles

Advances in Experimental and Clinical Studies of Chemotaxis

The theory of chemotaxis has been widely accepted, but its mechanisms are disputed. Chemotactic growth of peripheral nerves may be tissue, topographic and end-organ specific. Recent studies indicated that peripheral nerve regeneration lacks topographic specificity, but whether it has end-organ specificity is disputed. Chemotaxis in nerve regeneration is affected by the distance between stumps, volume, and neurotrophic support, as well as the structure of distal nerve stumps. It can be applied to achieve precise repair of nerves and complete recovery of end organ function. Small gap sleeve bridging technique, which is based on this theory shows promising effects but it is still challenging to find the perfect combination of nerve conduits, cells and neurotrophic factors to put it intoits best use. In this paper, we made a comprehensive review of mechanisms, effect factors and applications of chemotaxis.

Irregular excitation patterns in reaction-diffusion systems due to perturbation by secondary pacemakers

Spatiotemporal excitation patterns in the FitzHugh-Nagumo model are studied, which result from the disturbance of a primary pacemaker by a secondary pacemaker. The primary and secondary pacemakers generate regular waves with frequencies f(pace) and f(pert), respectively. The pacemakers are spatially separated, but waves emanating from them encounter each other via a small bridge. This leads to three different types I-III of irregular excitation patterns in disjunct domains of the f(pace)-f(pert) plane. Types I and II are caused by detachments of waves coming from the two pacemakers at corners of the bridge. Type III irregularities are confined to a boundary region of the system and originate from a partial penetration of the primary waves into a space, where circular wave fronts from the secondary pacemaker prevail. For this type, local frequencies can significantly exceed f(pace) and f(pert). The degree of irregularity found for the three different types is quantified by the entropy of the local frequency distribution and an order parameter for phase coherence.

Investigating the influence of minor hydraulic structures on modeling flood events in lowland areas

AbstractFlood inundation models have been recognized to be a valuable tool to reproduce flow dynamics in a given area and support decision‐making processes on flood management measures. In many cases, in the simulation of flood events, only the main river channel and the associated structures are represented within the model. However, during flood events involving lowland areas, the minor drainage network – and the associated hydraulic structures – may have an important role in conveying flow and determining which areas will be flooded. The objective of this study is to investigate whether – and to what extent – small hydraulic structures in drainage networks have an influence in flooding on lowland areas.The case study for this research is the 1990 flood event which occurred in the lowland plain of the Reno River, in Northern Italy. The study area is mainly used for agricultural purposes and has a drainage system with several small bridges and culverts.The influence of the minor hydraulic structures on flood dynamics was analyzed through a combined use of one‐dimensional (1D) and two‐dimensional (2D) hydraulic models. First, a number of detailed and simplified approaches to represent hydraulic structures in the computational grids were analyzed by means of the HECRAS 1D model. Second, these approaches were implemented and tested in several 2D simulations of the flood event. The simulated inundation extents and flood levels were then compared with the observed data and with each other. The analysis of results showed that simplified schematizations were sufficient to obtain good model predictions of peak inundation extent and flood levels, at least for the present case study. Moreover, the influence of the structures on the peak flood inundation extent and flood levels was found to be limited, whereas it showed to be more significant during the drainage phase of the flood. Copyright © 2013 John Wiley & Sons, Ltd.

Small gap sleeve bridging can improve the accuracy of peripheral nerve selective regeneration

The pure motor peripheral nerves animal model, obtained by ablating the dorsal root ganglions (DRGs), was used to investigate the accuracy of peripheral nerve selective regeneration using small gap sleeve bridging compared to epineurium neurorrhaphy. The results showed that the number of improperly regenerated motor axons in the distal stump and the misrouting ratio were significantly lower when the nerve transection was treated by small gap sleeve bridging. This suggests that more accurate reinnervation may be achieved by small gap sleeve bridging than by traditional epineurium neurorrhaphy.

Research on Strengthening Existing Bridges by Widening

This paper aims to put forward a new method of strengthening the existing bridges with narrow decks and low bearing capacity to overcome the high cost and pollution problems in dismantling them. The method, strengthening bridges by built stringers and cross beams, is by widening some parts of a bridge. Based on the basic theory of finite element, we have set up an analysis model of strengthening the bridges by widening, which helps to demonstrate the rationality of this method. Meaningful conclusions have been drawn from the parameter analysis of the rigidity of the new widening stringers, the rigidity of the new cross beams and the relative settlement of the new and the old foundations. This method can be referenced by the reinforcement and maintenance of medium and small bridges.

Design of conductive crown ether based columnar liquid crystals: impact of molecular flexibility and geometry

The influence of the molecular shape on the charge transport in the columnar mesophases of bi-centred crown ether based mesogens is studied. Even though a bent shaped bridging of two aromatic cores promotes the stability and the width of the columnar liquid crystal phase, the quality of the intra-columnar packing and thus the charge carrier mobility are reduced. Keeping instead a linear arrangement of the cores and increasing the molecular flexibility by enlarging the crown is detrimental to the liquid crystal phase stability while the charge carrier mobility is only slightly affected. This leads to the conclusion that the optimal molecular geometry for crown ether based mesogens providing a stable mesophase with good charge transport properties is achieved by using small crown ether bridges connecting two π-systems as linear as possible. We used discotic mesogens based on 12-crown-4, 15-crown-5, 18-crown-6 and 21-crown-7 moieties linking two triphenylene cores. The inter- and intra-columnar structure is studied by detailed small- and wide-angle X-ray scattering experiments, respectively. To study the electronic properties temperature dependent photoconductivity and mobility measurements in the organic field effect transistor setup are carried out.

Fatigue Designed CL-cutting Shape: A new Economic Steel-concrete Connection System and some Applications for Bridges

Continuous shear connection, using a cut steel strip, is an upcoming solution for composite beams. With the activation of friction on the sides of the steel strip this method has already been used to design and build large durable bridges during the sixties. However direct shear transmission into the steel strip though teeth of the cut is also possible and has been scrutinized with the support of the European Research Fund for Coal and Steel. It is characterized by a high initial stiffness, bearing capacity and ductility. It allows new and economic construction methods, as the PreCoBeams (Prefabricated Composite Beam used as formwork).PreCoBeams are for instance composite beams associating steel T-sections acting as tension member with a concrete top chord acting as compression member. Steel parts are generally obtained from rolled steel profiles that are longitudinally cut in two identical T-sections. The cut is performed with a special shape to allow the shear longitudinal transmission between steel and reinforced concrete. In general, prefabricated, composite, longitudinal PreCoBeam bridge elements are produced in factory. They consist of at least one steel T-section associated to a precast first phase concrete flange. Second phase concrete layer is then completed in-situ after erection of the bridge elements on abutments. These PreCoBeam bridges are very economic in design and construction, though the main market drawback for PreCoBeams is the missing design rules for the shear connection.This paper introduces the static and fatigue design of continuous steel plate shear connections used for PreCoBeams derived from the recent research activities. The CL shape of the cutting has been tested in fatigue, ultimate and service limit states and validated in the scope of a bridge application. This concept aims at developing a competitive solution for small span bridges. The various solutions realized in the last years in many European countries, some of them presented in the paper, show clearly its interest.

Landscape Ecology and Rural Roads: Traffic Calming for improving both landscape and wildlife?

AbstractJaarsma C.F., van Langevelde F., Beunen R.: Landscape ecology and rural roads: Traffic calming for improving both landscape and wildlife? Ekologia (Bratislava), Vol. 32, No. 4, p. 352-360, 2013.The concept of traffic calming has successfully improved road safety. This concept applied in rural areas has provided new insights in the mitigation of negative effects of roads and traffic. Earlier studies have shown that the concept, distinguishing between local access roads and rural arterial highways, can also improve landscape connectivity for wildlife. Physical speed-reducing devices are frequently used in the context of traffic calming, but applying these devices may negatively impact the coherence and identity of the landscape. Therefore an alternative approach for speed reduction has been proposed, namely applying local landscape elements (such as hedgerows), plantings and objects of cultural heritage (such as railings of small bridges over local water courses) as speed-reducing devices. We explain this ‘green approach’ with examples from Dutch practice. We conclude that a combination of disciplines is needed to realize this new approach, which may be more cost-effective than the traditional approach and additionally improve the landscape quality. The new insights are at least equally effective from a landscape ecological viewpoint.

Physico-chemical studies of water quality in Banganga (Small River) of Shri Mata Vaishno Devi, Katra, J & K

Banganga is the first major station for a yatries when they undertake their on-foot journey from Katra to Bhawan (Shri Mata Vaishno Devi). The pilgrims reach a small bridge under which flows Banganga, the legendary river associated with the miracles and legends of Mata Vaishno Devi. There is water in the river all through the year. Various physico-chemical and biological parameters were taken into consideration during the course of study, these includes colour, temperature, DO, BOD, COD, pH, total hardness, total suspended solids and Total dissolved solids. Based on the results of this study it has concluded that slight increase of pollutants in downstream of the river was observed in comparison to the upstream, hence it is an alarming position of increasing pollution load in the river.

소규모 교량 자산관리를 위한 계측 테스트베드 구축

While Category 1 and Category 2 bridges are intensively inspected and carefully managed, many small bridges that are not in the Category 1 and 2 are often forgotten until they decay in serious condition. Since many of these small bridges located in the populated city, failure of them would cause huge negative impact on the community. This paper focuses on the small size concrete bridges for timely repair and rehabilitation work for the effective operation and management. Test bed is developed to define the key parameters to forecast the long term performance of the bridges, mostly concrete box bridges. Key parameters suggested in this paper are cumulative fatigue due to repetitive heavy traffic loads and the acid attacks for concrete material deterioration. The cumulative fatigue is measured by the use of the mileage concept. For the long term data collection and inspection, stable and easy to use data collection system is installed as a test bed. The contribution of this research work is on the development of the test bed to define the key parameters of bridge deterioration.

Analysis and Load-carrying Capacity Estimation of Existing Railway Filler-beam Deck Bridges

Abstract In the paper, the actual condition of several existing concrete railway bridges with encased steel beams is discussed. This structural type represents relatively often solution for small span railway bridges in Slovakia. The main conclusions from inspections and in-situ diagnostics are published together with the results of the loadcarrying capacity calculation on the basis of new European codes. Despite of well-known disadvantages, the bridges with filler-beam decks are still demanded by railway authorities because of their big stiffness and small construction depth.

Thermal Characterization of an LTCC Module for Miniature Atomic Clock Packaging

This paper presents the design and thermal characterization of a 15 × 22 mm2 LTCC module dedicated to the packaging of the elements of a miniature atomic clock. This module acts as a carrier for the components of the clock as well as temperature controller; this is particularly attractive since each component of the atomic clock requires precise and well defined working temperatures. For the thermal characterization of the designed module, various thermal simulations have been performed, by finite-element modelling using the software ANSYS; in each simulation a different experimental heating configuration was hypothesized, in order to determine the power required for achieving the desired temperature in the ideal case (module in perfect vacuum with no losses rather than conduction towards the external “cold” zone, through two small bridges) , and also for estimating the thermal losses that convection introduces into the system. The simulations were then experimentally validated by realizing and characterizing the different configurations, yielding results that were consistent with the simulations. The best experimental configuration was found, in which the heating performance was fairly close to the ideal one. The results show that LTCC is a very attractive technology for atomic clock packaging also in terms of dissipated power, provided the system is efficiently insulated.

Stiffness and damage in masonry bridges

Load-related damage to masonry bridges is relatively uncommon. The author is aware of only a small number of cases and nearly all of them are in structures carrying high railway loads. Current assessment tools do not deliver any indication of the failure mechanisms that actually occur. Those mechanisms are characterised by the progressive development of cracks in various positions. Recent observations have made it clear that: bridges with internal spandrel walls create complex stiffness issues; so-called spandrel cracks and apparent ring separation are different manifestations of the same issue; the construction of some small bridges is not as assumed but often includes internal spandrel walls. This paper describes the damage observed, the construction to which it is related and the mechanisms creating damage. No calculations of any form are offered. This paper merely provides a first step in identifying the cause of a problem and a potential approach to analysis. The discussion begins with stone masonry viaducts, progresses to brick viaducts and concludes with problems in small span bridges.

Chronic subdural hematoma associated with the middle fossa arachnoid cyst: pathogenesis and review of its management

The pathogenesis of chronic subdural hematoma (CSDH) associated with an arachnoid cyst (AC) is still not clear. We propose an origin of initial bleeding of CSDH in patients with AC based on our experience and discuss the management of this disease. The total number of operations included in this study was 23. Eleven cases were indicated because of associated CSDH (group 1), and the other cases were due to different reasons (group 2). The relationship of the AC and dura was evaluated in patients who did not have CSDH (group 2) because patients with CSDH would have had structural changes of AC due to hematoma. In group 1, the age distribution was from 8 to 61years (mean 23.0). The development of CSDH was not related with Galassi types. The hematomas were located outside of the outer cyst membrane in six patients and both inside and outside in three patients. In two patients, the location could not be reviewed. After suspicion of the outer cyst membrane as the origin of the bleeding site, we found small bridging vessels between the dura and outer cyst membrane in three of five consecutive patients in group 2. Based on our surgical experience of AC cyst, we found small bridging vessels between the dura and outer membrane of the AC. We suggested that these small vessels are the source of initial bleeding leading to CSDH in AC.

Beetle-inspired adhesion by capillary-bridge arrays: pull-off detachment

Adhesion by capillarity (‘wet’ adhesion) depends on the surface tension of an array of many small liquid bridges acting simultaneously against a substrate. A particular leaf beetle has been previously shown to defend itself using wet adhesion, and a man-made device, inspired by this beetle, has been previously demonstrated to exhibit electronically controlled switchable wet adhesion. In both cases, measurements of detachment under load have been reported as pull-off strengths. In this paper, we pose models for pull-off failure of adhesion and discuss the predictions of these models in relationship to available observations. The focus is on the role of array geometry and how net adhesive failure relates to the instability of a single liquid bridge.

Staged Separation of Craniopagus Conjoined Twins: A Multidisciplinary Approach

During 2003 and 2004, a multidisciplinary team at the Children's Hospital at Montefiore, Bronx, New York, successfully separated twin infants who presented with a total craniopagus vertical O'Connell type 1 conjoining. The twins underwent a series of four staged separation procedures over 10 months. The first three stages involved performing gradual circumferential craniotomies, dividing the dura, ligating large and small bridging veins, separating abutting brains, and inserting skin expanders. The fourth stage involved dividing the remaining dura and veins, transecting shared brain tissue not detected in preoperative imaging, replacing dura in twin B, and replacing skin over native dura in twin A. Planning and carrying out separation of the conjoined twins required organization and cooperation of all the disciplines involved to prepare the children preoperatively, care for them perioperatively and postoperatively, and support the mother during the process.

New beam-to-beam joint with concrete embedding for composite bridges: Experimental study and finite element modelling

This paper deals with a new type of beam-to-beam joint used to connect continuously composite beams in small and medium span bridges. This new joint is realized by encasing totally the two composite beam ends into a massive composite reinforced concrete block. A direct contact between the ends of the bottom flanges of the steel girders over the support ensures the transfer of the compression forces. A half-scale joint specimen has been designed and fabricated. The specimen was first tested at the Structural Laboratory of INSA-Rennes under fatigue loading. Next, the load was monotonically increased up to the specimen failure. The main results of this experimental study are firstly presented. To allow an accurate interpretation of the test results and get a better insight into the joint behaviour, a numerical F.E. model has been developed. The numerical results are presented and compared against experimental ones. Besides, a parametric study has been carried out in order to investigate the influence of key parameters governing the joint behaviour. The influence of the behaviour of this type of joint on the global analysis of a continuous composite beam has then been studied. Finally, a worked example of a two-span continuous railway bridge is presented and effects of intermediate beam-to-beam joint characteristics on the bridge behaviour are discussed.

Railway bridge using small post-tensioned concrete box girder

A girder depth is the critical parameter for rapid construction of bridge and clearance limitation in urban area such as high-density residential district. A standard post-tensioned I-shaped concrete girder usually demands relatively higher girder depth in order to retain sufficient moment arm between compressive and tensile fiber. To elaborate this issue, a small rectangular hollowed section can be used as a replacement of I-shaped standard girder. This small post-tensioned concrete box girder allows more flexible girder depth adjustment rather than standard I-shaped posttensioned girder plus additional torsion resistance benefits of closed section. A 30 m long, 1.7 m high and 3.63 m wide actual small post-tensioned concrete box girder is designed. A laboratory test was performed for its static behaviors by applying 6400 kN amount of load in the form of 4-point bending test. The load-deflection curve and crack patterns at different loading stage are recorded. In addition, to extract the dynamic characteristics, natural frequency and damping ratio of this girder, several forced vibration tests using oscillator are carried out with varying operational frequency. Nonlinear finite element analysis of this 4-point bending test under monotonic static load is discussed with the aid of concrete damaged plasticity using ABAQUS program. Finally, a series of modal dynamic analyses of different span length and girder depth of small post-tensioned girder bridge is performed in order to validate the applicability to railway bridges and compared to the UIC design criteria in the form of time dependent dynamic responses such as deflection, acceleration and end rotation.

Rapid P2Y 12 Inhibition

Acute coronary syndrome (ACS) is still a serious condition associated with decreased quality of life, increased healthcare expenditures, and premature death. The prevalence of ACS is expected to increase with aging of the population and with the epidemics of obesity and diabetes. The short- and long-term mortality after an ACS has been dramatically reduced by the development of revascularization techniques and new antithrombotic agents. The past decade has seen many trials evaluating new oral and parenteral antiplatelet agents with greater potency than aspirin and clopidogrel. Several antiplatelet agents have been developed, with the ultimate goal to obtain optimal antiplatelet therapy for both the acute and the chronic phases of disease. Articles see p 336, 347 Ideally, efficiency requires several pharmacodynamic proprieties, such as a fast onset of action (immediate onset for emergency situations), a strong degree of platelet inhibition (at least stronger than the standard of care [aspirin and clopidogrel]), a narrow interindividual variability with no impact of genetic variants and no drug-to-drug interaction, and an easy administration (an oral drug for maintenance therapy and an intravenous formulation for rapid loading). Of course, this drug should also lead to a convincing reduction of recurrent ischemic events in an adequately powered phase 3 trial. With regard to safety, the illusion of having the same dose of a single antiplatelet drug to treat all clinical situations has passed. The degree of platelet activation and aggregation is different across clinical situations (eg, acute ST-segment–elevation myocardial infarction [STEMI] versus secondary prevention) and varies over time in the same patient. Recent large phase 3 trials have confirmed the importance of dosing and the target population treated with the new agents.1–4 From a safety standpoint, an ideal antiplatelet agent would also have an intravenous and oral formulation, with different doses tested in …

Strengthening Bridges with Prestressed CFRP Strips

Abstract Limitation of bridge’s carrying bearing capacity due to aging and deterioration is a common problem faced by road administration and drivers. Rehabilitation of bridges including strengthening may be applied in order to maintain or upgrade existing bridge parameters. The case studies of strengthening of two small bridges with high modulus prestressed CFRP strips have been presented in the paper. The first one - reinforced concrete slab bridge - and the other - composite steel-concrete girder bridge - have been successfully upgraded with quite new technology. In both cases the additional CFRP reinforcement let increasing of bridge carrying capacity from 15 till 40 metric tons. The CFRP strip prestressing system named Neoxe Prestressing System (NPS), developed by multi-disciplinary team and tested at full scale in Rzeszow University of Technology, has been also described in the paper.