Rate Of Change In Length Research Articles

EP02.38: The rate of change in cervical length between mid‐trimester and symptom onset is associated with intra‐amniotic and systemic inflammation

EP02.38: The rate of change in cervical length between mid‐trimester and symptom onset is associated with intra‐amniotic and systemic inflammation

Change in cervical length and spontaneous preterm birth in nulliparous women with a history of loop electrosurgical excision procedure

Background Prior studies have shown an association between history of loop electrode procedures (LEEP) and spontaneous preterm delivery (SPTD) independent of mid-trimester cervical length. These studies suggest that there may be other factors beyond an individual cervical length, which contribute to identifying at-risk pregnancies. Objective The objective of this study is to determine the association between change in cervical length and SPTD in women with a history of LEEP. Study design This is a retrospective cohort study of singleton nulliparous women with a history of LEEP who received serial cervical length measurements at a single institution between 2012 and 2016. Women with serial cervical lengths and available outcome data were included. The cervical length at different gestational ages and the rate of change in length were compared with the risk for SPTD <37 weeks using Student’s t-test. Results One-hundred-thirty subjects met the inclusion criteria for the study. The mean cervical length (35.3 versus 39.8 mm, p = .042 at 16 weeks; 32.2 versus 37.8 mm, p < .01 at 20 weeks; 29.9 versus 35.6 mm, p = .027 at 24 weeks; 21.6 versus 33.4 mm, p < .01 at 28 weeks) was significantly different between women who had an SPTD <37 weeks compared to women who did not. The average rate of change in transvaginal cervical length between 16 to 28 weeks was significantly different between women who had an SPTD <37 weeks compared to women who did not (−1.4 versus 0.4 mm/week, p < .01). Conclusion Women with a history of LEEP who had an SPTD <37 weeks had a shorter cervical length at 16, 20, 24, and 28 weeks’ gestation and a higher rate of change in cervical length between 16 and 28 weeks than women without a history of SPTD. Our findings support the concept of the preterm birth syndrome as an evolving biophysical process rather than a distinct event, suggesting improved prediction in the setting of prior history of a LEEP with serial imaging.

Model-Free Method for Damage Localization of Grid Structure

A model-free damage identification method for grid structures based on displacement difference is proposed. The inherent relationship between the displacement difference and the position of structural damage was deduced in detail by the Sherman–Morrison–Woodbury formula, and the basic principle of damage localization of the grid structure was obtained. That is, except for the tensile and compressive deformations of the damaged elements, the deformations of other elements were small, and only rigid body displacements occurred before and after the structural damage. According to this rule, a method for identifying the position of the damage was proposed for the space grid structure by using the rate of change of length for each element. Taking a space grid structure with a large number of elements as an example, the elastic modulus reduction method was used to simulate the damage to the elements, and the static and dynamic test parameters were simulated respectively to obtain the difference in displacement before and after the structural damage. The rate of change of length of each element was calculated based on the obtained displacement difference, and data noise was added to the simulation. The results indicated that the element with the larger length change rate in the structure was the most likely to be damaged, and the damaged element can be accurately evaluated even in the presence of noise in data.

A validated combined musculotendon path and muscle-joint kinematics model for the human hand

Neuromusculoskeletal models provide a mathematical tool for understanding and simulating human motor control and neuromechanics. In this work, we propose a combined computational model for the musculotendon paths and muscle-joint kinematics for the human hand, including all extrinsic and intrinsic muscles. This model is implemented based on the anatomical descriptions and a human hand dissection study. The model takes joint angles as input and estimates the musculotendon lengths, length change rates, and excursion moment arms. The proposed model is simulated to generate according moment arms, which are compared with cadaver measurements available from literature in terms of similarity coefficient s. For most muscles compared, high similarity with for 92% of cases is achieved between the modeled and the measured moment arms. These results suggest the correctness of modeled moment arms and imply the feasibility of modeled musculotendon paths, lengths, and length change rates.

Quantitative evaluation method for clarifying ankle plantar flexion angles using anterior drawer and inversion stress tests: a cross-sectional study

BackgroundChronic ankle instability (CAI) may result from repeated, frequent ankle sprains during sports activities. Manual examination for CAI is conducted; however, quantitative methods for the evaluation of CAI have not been established, and the reproducibility of the amount of stress is low. This cross-sectional study aimed to use a stress device and ultrasound for the quantitative evaluation of the change in the length of the anterior talofibular ligament (ATFL) during simulated anterior drawer and ankle inversion stress tests.MethodsQuestionnaires were provided to 160 healthy college students (86 men, 74 women; 320 ankles). We extracted two groups from them: control subjects without a history of ankle injury (n = 64 ankles) and subjects with CAI (n = 54 ankles). We calculated the change in the length of the ATFL with anterior drawer and inversion stress tests at ankle joint plantar flexions of 0°, 20°, and 45° using ultrasound images.ResultsThe anterior length change rates were significantly higher in the CAI group than in the control group at ankle joint plantar flexions of 20° and 45° in men (P < 0.05). The inversion length change rates were significantly higher in the CAI group at ankle joint plantar flexion of 20° in men (P < 0.05). No significant between-group difference in the anterior and inversion length change rates was observed in women.ConclusionsStress ultrasound revealed greater length changes in the ATFL in the CAI group than in the control group. The stress test may be useful at ankle joint plantar flexion of 20° for men.

Optimization based muscle wrapping in biomechanical multibody simulations

AbstractIn musculoskeletal simulations muscle lengths and muscle force directions imply the characteristics of muscles acting around joints. Typically, the anatomical structure of the human body forces muscles to wrap around bones and neighboring tissue, thus most muscle paths cannot be represented adequately as straight lines. Therefore, biomechanical simulations require methods to compute musculotendon paths, their lengths, and their rates of length change to determine the muscle forces. This work focuses on a mechanical analogue to find the shortest path on general smooth surfaces, using a discrete variational principle. In this context, the geodesic path is reinterpreted as the constrained, force‐free motion of a particle in n dimensions. The muscle path is then a G1‐continuous combination of geodesics on adjacent obstacle surfaces [1,3,4].

The effect of muscle length on transcranial magnetic stimulation-induced relaxation rate in the plantar flexors.

Transcranial magnetic stimulation (TMS) of the motor cortex during a maximal voluntary contraction (MVC) permits functionally relevant measurements of muscle group relaxation rate (i.e., when muscles are actively contracting under voluntary control). This study's purpose was twofold: (1) to explore the impact of muscle length on TMS‐induced plantar flexor relaxation rate; and (2) to incorporate ultrasonography to measure relaxation‐induced lengthening of medial gastrocnemius (MG) fascicles and displacement of the muscle–tendon junction (MTJ). Eleven males (24.8 ± 7.0 years) performed 21 brief isometric plantar flexor MVCs. Trials were block‐randomized every three MVCs among 20° dorsiflexion (DF), a neutral ankle position, and 30° plantar flexion (PF). During each MVC, TMS was delivered and ultrasound video recordings captured MG fascicles or MTJ length changes. Peak relaxation rate was calculated as the steepest slope of the TMS‐induced drop in plantar flexor torque or the rate of length change for MG fascicles and MTJ. Torque relaxation rate was slower for PF (−804 ± 162 Nm·s−1) than neutral and DF (−1896 ± 298 and −2008 ± 692 Nm·s−1, respectively). Similarly, MG fascicle relaxation rate was slower for PF (−2.80 ± 1.10 cm·s−1) than neutral and DF (−5.35 ± 1.10 and −4.81 ± 1.87 cm·s−1, respectively). MTJ displacement rate showed a similar trend (P = 0.06), with 3.89 ± 1.93 cm·s−1 for PF compared to rates of 6.87 ± 1.55 and 6.36 ± 2.97 cm·s−1 for neutral and DF, respectively. These findings indicate muscle length affects the torque relaxation rate recorded after TMS during an MVC. Comparable results were obtained from muscle fascicles, indicating ultrasound imaging is suitable for measuring evoked contractile properties during voluntary contraction.

Telomere Shortening, Inflammatory Cytokines, and Anti-Cytomegalovirus Antibody Follow Distinct Age-Associated Trajectories in Humans.

A number of biological parameters have been cited as hallmarks of immune aging. However, it is not clear whether these multiple biological changes are the result of common underlying aging processes and follow correlated trajectories, or whether the patterns of change for multiple parameters vary across individuals and reflect heterogeneity in the aging process. Here, we have studied parameters of immune system aging through longitudinal analysis of telomere length, inflammatory cytokines, and antibody titer to cytomegalovirus (CMV) in 465 subjects ranging in age from 21 to 88 years at the first visit, with an average of 13 years (7–19 years) follow-up. We observed a highly variable rate of change in telomere length of PBMCs with a relatively slow average rate of telomere shortening (−16 bp/year). Similarly, there were significant increases with age in vivo in three inflammation-related cytokines (interferon gamma, IL-6, and IL-10) and in anti-CMV IgG titer, which varied widely across individuals as well. We further observed positive correlative changes among different inflammatory cytokines. However, we did not find significant correlations among the rate of changes in telomere length, inflammatory cytokines, and anti-CMV IgG titers. Our findings thus reveal that age-related trajectories of telomere attrition, elevated circulating inflammatory cytokines, and anti-CMV IgG are independent and that aging individuals do not show a uniform pattern of change in these variables. Immune aging processes are complex and vary across individuals, and the use of multiple biomarkers is essential to evaluation of biological aging of the immune system.

Evaluation of Toluene Adsorption Performance of Mortar Adhesives Using Porous Carbon Material as Adsorbent.

Porous carbon materials are advantageous in adsorbing pollutants due to their wide range of specific surface areas, pore diameter, and pore volume. Among the porous carbon materials in the current study, expanded graphite, xGnP, xGnP C-300, xGnP C-500, and xGnP C-750 were prepared as adsorbent materials. Brunauer–Emmett–Teller (BET) analysis was conducted to select the adsorbent material through the analysis of the specific surface area, pore size, and pore volume of the prepared porous carbon materials. Morphological analysis using SEM was also performed. The xGnP C-500 as adsorbent material was applied to a mortar adhesive that is widely used in the installation of interior building materials. The toluene adsorption performances of the specimens were evaluated using 20 L small chamber. Furthermore, the performance of the mortar adhesive, as indicated by the shear bond strength, length change rate, and water retention rate, was analyzed according to the required test method specified in the Korean standards. It was confirmed that for the mortar adhesives prepared using the xGnP C-500 as adsorbent material, the toluene adsorption performance was excellent and satisfied the required physical properties.

Information Geometry of Non-Equilibrium Processes in a Bistable System with a Cubic Damping

A probabilistic description is essential for understanding the dynamics of stochastic systems far from equilibrium, given uncertainty inherent in the systems. To compare different Probability Density Functions (PDFs), it is extremely useful to quantify the difference among different PDFs by assigning an appropriate metric to probability such that the distance increases with the difference between the two PDFs. This metric structure then provides a key link between stochastic systems and information geometry. For a non-equilibrium process, we define an infinitesimal distance at any time by comparing two PDFs at times infinitesimally apart and sum these distances in time. The total distance along the trajectory of the system quantifies the total number of different states that the system undergoes in time and is called the information length. By using this concept, we investigate the information geometry of non-equilibrium processes involved in disorder-order transitions between the critical and subcritical states in a bistable system. Specifically, we compute time-dependent PDFs, information length, the rate of change in information length, entropy change and Fisher information in disorder-to-order and order-to-disorder transitions and discuss similarities and disparities between the two transitions. In particular, we show that the total information length in order-to-disorder transition is much larger than that in disorder-to-order transition and elucidate the link to the drastically different evolution of entropy in both transitions. We also provide the comparison of the results with those in the case of the transition between the subcritical and supercritical states and discuss implications for fitness.

Telomere shortening and accelerated aging in COPD: findings from the BODE cohort

BackgroundChronic Obstructive Pulmonary Disease (COPD) may be associated with accelerated aging. Telomere shortening is a biomarker of aging. Cross-sectional studies describe shorter telomeres in COPD compared with matched controls. No studies have described telomere length trajectory and its relationship with COPD progression. We investigated telomere shortening over time and its relationship to clinical and lung function parameters in a COPD cohort and smoker controls without COPD.MethodsAt baseline leukocyte telomere length was measured by qPCR in 121 smokers with COPD and 121 without COPD matched by age (T/S0). The measurements were repeated in 70 of those patients with COPD and 73 non-COPD smokers after 3 years of follow up (T/S3).ResultsAt initial measurement, telomeres were shorter in COPD patients when compared to smoker controls (T/S = 0.68 ± 0.25 vs. 0.88 ± 0.52, p = 0.003) independent from age and sex. During the follow-up period, we observed an accelerated telomere shortening in individuals with COPD in contrast to smoker controls (T/S0 = 0.66 ± 0.21 vs. T/S3 = 0.46 ± 0.16, p < 0.001, for the patients with COPD and T/S0 = 0.83 ± 0.56 vs. T/S3 = 0.74 ± 0.52, p = 0.023 for controls; GLIM, p = 0.001). This shortening was inversely related to the baseline telomere length (r = −0.49, p < 0.001). No significant relationship was found between the rate of change in telomere length and change in lung function in the patients with COPD (p > 0.05).ConclusionsCompared with smokers, patients with COPD have accelerated telomere shortening and this rate of attrition depends on baseline telomere length. Furthermore, the telomere length and its rate of shortening did not relate to clinical and lung function parameters changes over 3 years of follow-up.

Developmental mechanisms of macroevolutionary change in the tetrapod axis: A case study of Sauropterygia.

Understanding how developmental processes change on macroevolutionary timescales to generate body plan disparity is fundamental to the study of vertebrate evolution. Adult morphology of the vertebral column directly reflects the mechanisms that generate vertebral counts (somitogenesis) and their regionalisation (homeotic effects) during embryonic development. Sauropterygians were a group of Mesozoic marine reptiles that exhibited an extremely high disparity of presacral vertebral/somite counts. Using phylogenetic comparative methods, we demonstrate that somitogenesis and homeotic effects evolved in a co‐ordinated way among sauropterygians, contrasting with the wider pattern in tetrapods, in which somitogenetic and homeotic shifts are uncorrelated. Changes in sauropterygian body proportions were primarily enabled by homeotic shifts, with a lesser, but important, contribution from differences in postpatterning growth among somites. High body plan plasticity was present in Triassic sauropterygians and was maintained among their Jurassic and Cretaceous descendants. The extreme disparity in the body plan of plesiosaurian sauropterygians did not result from accelerated rates of evolutionary change in neck length, but instead reflect this ancestral versatility of sauropterygian axial development. Our results highlight variation in modes of axial development among tetrapods, and show that heterogeneous statistical models can uncover novel macroevolutionary patterns for animal body plans and the developmental mechanisms that control them.

Seasonality and breeding success of captive and wild Tasmanian devils (Sarcophilus harrisii)

The synchrony and timing of reproductive events are crucially important factors to maximize individual and offspring survival, especially in seasonal environments. To increase our understanding of the physiological basis of seasonality and the influence of associated environmental factors (maximum temperature, day length and rate of day length change associated with different latitudes) on reproduction in Tasmanian devils, we reviewed records and research data from captive facilities throughout Australia in comparison to those from a wild population study (1974–1987). Overall, breeding activity began 2 weeks earlier in the captive than the wild population (week 5.7 ± 0.6 versus week 7.7 ± 0.5 for devils entering into estrus during the first two week phase; n = 24 and n = 23 respectively). If the timing of reproductive activity is considered against absolute day length rather than date, both the captive and wild populations displayed similar distributions (12.9 ± 0.7 h versus 13.0 ± 0.7 h respectively; P < 0.01) confirming day length as a proximal cue involved in eliciting a physiological response to trigger seasonal reproductive activity regardless of location. Wild devils had a higher breeding success (75%; n = 169 versus 43%; n = 115) and larger litter size (3.4 ± 0.9 versus 2.8 ± 1.1 joeys per litter) than captive devils (P < 0.05). Mean maximum temperature at the onset of reproductive activity (P < 0.05) was higher for the captive than the wild population (28.1 ± 4.0 °C versus 22.3 ± 2.7 °C respectively). The drivers for reproductive success in captive Tasmanian devils are likely multifactorial, but our results suggest that elevated temperatures associated with shifts in breeding activity and geographical location should be examined further.

Association between change in cervical length and spontaneous preterm birth in twin pregnancies

There is a lack of consensus on the optimal transvaginal cervical length for determining risk for spontaneous preterm birth in twin pregnancies. Change in transvaginal cervical length over time may reflect early activation of the parturition process, as has been demonstrated in singleton pregnancies. The association between change in transvaginal cervical length and the risk for spontaneous preterm birth has not yet been described in the population of women with diamniotic twin pregnancies. Our primary objective is to determine whether rate of change in transvaginal cervical length in the midtrimester is associated with spontaneous preterm birth in twin gestations. Our secondary objective is to describe parameters for identifying patients at increased risk for spontaneous preterm birth based on change in transvaginal cervical length over time. This is a retrospective cohort of serial transvaginal cervical length performed for twin pregnancies at a single institution from 2008 through 2015. Women with diamniotic twin pregnancies who had transvaginal cervical length measurements at 18 and 22 weeks' gestation and outcome data available were included. Logistic regression was used to determine the relationship between the rate of change in transvaginal cervical length and the risk for the primary outcome of spontaneous preterm birth <35 weeks as well as spontaneous preterm birth <32 weeks. In all, 527 subjects met inclusion criteria for this study. The average rate of change in transvaginal cervical length for patients with spontaneous preterm birth <35 weeks was -0.21 cm/wk (SD 0.27) vs -0.10 cm/wk (SD 0.24) for patients who delivered ≥35 weeks (P < .01). The rate of change in transvaginal cervical length was associated with spontaneous preterm birth <35 weeks when controlling for initial transvaginal cervical length and other important risk factors for spontaneous preterm birth. Results for spontaneous preterm birth <32 weeks were similar. This association remained significant when the rate of weekly change was treated as a dichotomous variable based on an apparent inflection point in the risk for spontaneous preterm birth: women with rapid change in transvaginal cervical length, ≥-0.2 cm/wk, had 3.45 times the odds of spontaneous preterm birth as those with less rapid change (95% confidence interval, 2.15-5.52) when controlling for initial transvaginal cervical length. Change in transvaginal cervical length in the midtrimester is associated with spontaneous preterm birth, and therefore protocols for serial transvaginal cervical length measurement can provide the clinician with information to identify at-risk patients. A decrease of ≥0.2 cm/wk of transvaginal cervical length identifies patients at increased risk for spontaneous preterm birth <35 weeks.

Fermentation of African indigenous leafy vegetables to lower post-harvest losses, maintain quality and increase product safety

To investigate effects of salinity stress on growth, nutrient status, chlorophyll and water consumption, four different saline irrigation waters (S0= 0.3 dS/m-1 control, S1=1.5 dS/m-1, S2=3 dS/m-1, S3=5 dS/m-1) were applied to two-year Chandler saplings which were grafted on Juglans nigra L. (JN), Paradox (PR) and Juglans sieoboldiana L. (JS) walnut rootstocks. Three different salts including NaCl, MgSO4, and CaCl2 were used to prepare saline irrigations. Shoot length change rate (%) was varied between 77.57 (JN) to 81.83 (PR) for S0 salinity treatments and between 55.60 (JS) to 56.84 (PR) for S3 treatments. The plant diameter change rate (%) varied between 75.10 (JN) to 99.22 (PR) for S0 treatments and 60.63 (JN) to 80.97 (PR) for S3 treatments. Average of root length (cm) was between 30.75 cm (JN) to 37.50 cm (PR) for S0 treatments, and 8.91 cm (JN) to 21.50 cm (PR) for S3. Number of roots changed between 19.00 (JS) to 22.16 (PR) for S0 treatments and between 6.41 (JN) and 8.08 (PR) for S3 treatments. Sodium (Na) content (%) in S3 was 1.41, 1.97 and 3.41 in JN, PR, and JS, respectively. Chloride (Cl-) content (ppm) for S3 was 0.88, 0.99 and 0.91 in JN, PR, and JS, respectively. Ca/Na ratios of 0.43, 0.27 and 0.14 and K/Na ratios of 0.24, 0.12 and 0.10 were detected in JN, PR, and JS, respectively. Depending on leaf Na+, Cl- and K contents, K/Na and Ca/Na ratios, the ranking of salinity tolerance of rootstocks were determined as JN˃ PR ˃ JS.

Theoretical investigation of tuning the photonic jet through varying the salt concentration in propagating medium using FDTD method

In this present study the behavior of photonic jet produced from an axicon immersed in aqueous solution of NaCl was investigated, where the aqueous solution NaCl act as a propagating medium. From simulation study it was found that the behavior of photonic jet varies with the different concentration of aqueous solution. In this study the rate of change in the propagation length of photonic jet was found to be 0.0903μm per gm/lit up to a concentration level of 100 gm/lit. However from FDTD analysis minimal variation in intensity level and FWHM of photonic jet were revealed.

무릎넙다리통증증후군 환자에서 무릎관절 각도별 스쿼트 융합운동이 넙다리네갈래근의 근력에 미치는 효과

본 연구의 목적은 넙다리네갈래근 중 안쪽빗넓은근과 가쪽넓은근의 강화를 위해 효과적인 스쿼트 운동자세를 제시하는 데 있다. 연구대상자는 무릎넙다리통증증후군이 있는 20명의 환자로 본 연구에 자발적으로 참여하였다. 대상자들은 무릎관절 굽힘 각도 <TEX>$45^{\circ}$</TEX>, <TEX>$60^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX> 자세에서 정적인 스쿼트 융합운동을 30초 동안 총 5회 실시하였다. 측정변수는 넙다리네갈래근의 최대 수의적 등척성 수축력(MVIC), 넙다리네갈래근 각(Q 각)과 넙다리 둘레이며, 무릎관절 자세에 따라 스쿼트 운동 전후로 측정되었으며 그 변화률을 통계분석에 사용하였다. 연구결과 넙다리네갈래근의 무릎관절 각도별 MVIC 변화율은 <TEX>$90^{\circ}$</TEX> 무릎관절 굽힘에서 유의하게 증가하였으나(p<.05), Q 각과 넙다리 둘레의 변화율엔 유의한 차이가 없었다(p>.05). 따라서 무릎통증증후군 환자의 넙다리네갈래근의 강화를 위해서 무릎관절 <TEX>$90^{\circ}$</TEX> 굽힘된 스쿼트 자세가 효과적임을 제시한다. The purpose of this study was to suggest the effective squat exercise position to strengthening vastus medialis oblique, and vastus lateralis in quadriceps. Subjects were twenty patients with patellofemoral pain syndrome (PFPS) volunteered to participate in this study. All subjects were applied to static squat convergence exercise with knee flexed <TEX>$45^{\circ}$</TEX>, <TEX>$60^{\circ}$</TEX>, and <TEX>$90^{\circ}$</TEX> for 30 seconds total 5 times. Measurement variables were maximal voluntary isometric contraction (MVIC) of the quadriceps, Q angle and length of thigh. Those were measured before and after the squat exercise on knee joint angle, change rate of which were used for statistical analysis. As a result, squat exercise with knee flexed <TEX>$90^{\circ}$</TEX> increase significantly among knee joint angle in the MVIC change rates of quadriceps (p<.05), however the rates of Q-angle and length change of thigh showed no significant difference. Therefore, this findings suggest that squat exercise with knee flexed <TEX>$90^{\circ}$</TEX> strengthen quadriceps effectively in patients with PFPS.

Telomere length change plateaus at 4years of age in Latino children: associations with baseline length and maternal change.

Telomeres are the protective complexes at the end of chromosomes, required for genomic stability. Little is known about predictors of attrition in young children or the relationship between parental and child patterns of telomere change. Telomere length was assessed twice over one year, at 4 and at 5years of age, in Latino preschool children (n=77) and their mothers (n=70) in whole blood leukocytes. Maternal and child rates of attrition during the same time period were compared in 70 mother-child pairs. More children showed lengthened telomeres over one year compared to their mothers and very few children showed attrition (2.6%). Approximately 31% of children and 16% of mothers displayed lengthening over one year while 66% of children showed maintenance in contrast with 74% of mothers. The strongest predictor for child telomere length change was child's baseline telomere length (r=-0.61, p<0.01). Maternal rate of change was associated with child rate of change (r=0.33, p<0.01). After controlling for child baseline telomere length, the relationship between child and maternal rate of change trended towards significance (Coeff=0.20, 95% CI -0.03 to 0.43; p=0.08). We found primarily maintenance and lengthening from 4 to 5years of age in children, with minimal telomere attrition, indicating that most of the telomere loss happens in the first 4years, plateauing by age 4. Lastly, we found close to 10% of the variance in rate of change in children shared by mothers. While some of this shared variance is genetic, there are likely environmental factors that need to be further identified that impact rate of telomere length change.

Developing Updatable Crash Prediction Model for Network Screening: Case Study of Czech Two-Lane Rural Road Segments

This paper focuses on application of crash prediction models in network screening. The two main questions were ( a) What variables should be involved in the model? and ( b) What length should the modeled period be? Answers to these questions should provide guidelines for developing an updatable crash prediction model (i.e., a model that is both reliable and simple so that its updating for periodical network screening is not highly demanding). Data on approximately 1,000 km (600 mi) of a two-lane rural-road network from South Moravia, Czech Republic, were used. On the basis of 8 years of annual crash frequencies, together with exposure and geometrical variables, several variants of prediction models were developed. To study the quality of the models, a series of consistency tests was applied relative to comparison of the models themselves as well as to their diagnostic performance. As a result, simple crash prediction models (that included traffic volume, segment length, and curvature change rate) were found sufficient for network screening. If one supposes that length and curvature are unlikely to change often, only traffic volume data need to be periodically updated. Consistency analyses indicate that this period should be 4 years. Under these conditions, models are being applied in the studied region. Further planned activities include extensions to intersections and also to other Czech regions.

온도응력과 건조수축을 고려한 요소혼입 콘크리트의 품질특성에 관한 연구

Due to a big difference of temperatures between the inside and outside and a high level of hydration heat on the core, some thermal stress is generated in mass Concrete. In turn, it causes the expansion of the concrete members and some cracks of the concrete joints that become the factors threatening the soundness of a concrete structure. Due to the reason, various kinds of low-heat concrete are being developed in domestic and foreign countries. In this study, some urea for industrial use which is used in microorganism cultivation agents, etc., is applied as a concrete mixing material in order to suppress the hydration heat of mass concrete. This is intended to lower down some levels of hydration heat and drying shrinkage of mass concrete. 21 kinds of concrete mixtures in total were designed at 3 kinds of W/B ratios, that is, 45, 50 and 55%. Thus, the dynamic characteristics, durability and hydration heat properties of urea-mixed concrete were verified through some experiments and the optimum mixing design was suggested. As the results of this study, the compressive strength of urea-mixed concrete at the age of 3 days decreased by 40% compared to that of plain concrete, but it showed the tendency recovering up to 95% at maximum at the age of 56days. On the other hand, the maximum temperature of urea-mixed concrete decreased down to <TEX>$7.9^{\circ}C$</TEX> at maximum thanks to the hydration heat compared with that of plain concrete and the point of time reaching the highest temperature of the urea-mixed concrete was delayed by 33.9 hours at maximum compared with that of plain concrete. In addition, it resulted that the length change rate of urea-mixed concrete decreased down to 56% at maximum thanks to the expansion characteristics of <TEX>$CaCO_3$</TEX>.