961 research outputs found
Cellular buckling in stiffened plates
An analytical model based on variational principles for a thin-walled
stiffened plate subjected to axial compression is presented. A system of
nonlinear differential and integral equations is derived and solved using
numerical continuation. The results show that the system is susceptible to
highly unstable local--global mode interaction after an initial instability is
triggered. Moreover, snap-backs in the response showing sequential
destabilization and restabilization, known as cellular buckling or snaking,
arise. The analytical model is compared to static finite element models for
joint conditions between the stiffener and the main plate that have significant
rotational restraint. However, it is known from previous studies that the
behaviour, where the same joint is insignificantly restrained rotationally, is
captured better by an analytical approach than by standard finite element
methods; the latter being unable to capture cellular buckling behaviour even
though the phenomenon is clearly observed in laboratory experiments.Comment: 22 pages, 9 figures, 1 table, accepted for publication. Proceedings
of the Royal Society A, 201
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A modular hybrid simulation framework for complex manufacturing system design
For complex manufacturing systems, the current hybrid Agent-Based Modelling and Discrete Event Simulation (ABM–DES) frameworks are limited to component and system levels of representation and present a degree of static complexity to study optimal resource planning. To address these limitations, a modular hybrid simulation framework for complex manufacturing system design is presented. A manufacturing system with highly regulated and manual handling processes, composed of multiple repeating modules, is considered. In this framework, the concept of modular hybrid ABM–DES technique is introduced to demonstrate a novel simulation method using a dynamic system of parallel multi-agent discrete events. In this context, to create a modular model, the stochastic finite dynamical system is extended to allow the description of discrete event states inside the agent for manufacturing repeating modules (meso level). Moreover, dynamic complexity regarding uncertain processing time and resources is considered. This framework guides the user step-by-step through the system design and modular hybrid model. A real case study in the cell and gene therapy industry is conducted to test the validity of the framework. The simulation results are compared against the data from the studied case; excellent agreement with 1.038% error margin is found in terms of the company performance. The optimal resource planning and the uncertainty of the processing time for manufacturing phases (exo level), in the presence of dynamic complexity is calculated
Study of embryotoxicity of mentha piperita l. during organogenesis in balb/c mice
Mentha piperita (Labiatae), commonly known as peppermint is a native Iranian herb which is used in folk medicine for various purposes. This study was carried out to reveal the teratogenic effect of Mentha piperita on mice fetuses. In this experimental study, pregnant Balb/c mice divided to four groups. Case group received 600 (treatment I) and 1200 (treatment II) mg/kg/day the hydroalcoholic extract of Mentha piperita during 6-15 of gestational days and one control group received normal saline during GD6-GD15 by gavages and other control group did not receive any matter during 6-15 of gestational days. Mice sacrificed at GD18 and embryos were collected. Macroscopic observation was done by stereomicroscope. 20 fetuses of each group were stained by Alizarin red-S and Alcian blue staining method. The Mean weight of fetuses decreased in treatment groups rather than control (P<0.05) but CRL there was no significant difference between treatments and controls groups. In the treatment I (600 mg/kg/day) and treatment II (1200 mg/kg/day), normal saline and control group, no gross congenital malformations were observed in fetuses. Treated fetuses also had no delayed bone ossification as determined by Alizarin red-S and Alcian blue staining method. This study showed that the hydroalcoholic extract of Mentha piperita (600 and 1200 mg/ kg/day) has no teratogenic effect in mice fetuses if used continuously during embryonic period
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Conceptualising the impact of information asymmetry on through-life cost: case study of machine tools sector
Information asymmetry (IA) in terms of contextual variety and importance is one of the most challenging aspects of through-life costing in product-service systems (PSS). IA is an imbalance in the information, data and knowledge shared among the parties involved in a contractual agreement. In manufacturing systems under PSS, interaction and effective communication among several parties who are involved in a contractual agreement, rely on the continuity and accuracy of information and context. In such systems, contextual variety exhibits complexity and uncertainty in through-life costing and subsequently in PSS cost assessment. Although the economic aspect of PSS has been studied previously, the impact of IA on through-life cost and for different PSS solutions has not been detailed. Considering manufacturing value chains, this paper introduces a new concept of PSS-hierarchy to perform through-life costing in the presence of IA for various PSS solutions. Moreover, this paper proposes a generic life-cycle model for different PSS solutions to assess the total cost of ownership (TCO). The proposed model has been developed to support decisions on contract design in manufacturing systems. This study considers the manufacturer, service provider and customer perspectives to develop the TCO model using a machine tool manufacturing case study
Multidrug-resistant enterobacterales in Oman : molecular epidemiology and therapeutic insights
The spread of antibiotic resistance is a concerning issue causing limited treatment options for
bacterial infections, particularly with Gram-negative bacteria. Surveillance and
epidemiological studies help to determine the magnitude of the problem as well as to
establish early measures to slow down the spread of resistance and consequently increase
antibiotic lifespan. Currently, there is a visible paucity of published data about resistance
from the Arabian Peninsula. In this thesis, we studied a collection of carbapenem nonsusceptible
E. coli (n=35) and K. pneumoniae (n=237) isolated in 2015 from various hospitals
in Oman. We aimed at identifying resistance mechanisms, mapping the bacterial population
structure, investigating bacterial fitness, and studying potential treatment options available to
tackle infections caused by such multidrug-resistant strains. These aims were addressed in
five papers as discussed below.
NDM and OXA-48 were the only carbapenemases we found in this collection, both among
E. coli (Paper I) and K. pneumoniae (Paper II). The pattern of resistance among the isolates
from Arabian Peninsula mimics the pattern reported from the Indian subcontinent, most
likely due to the close socioeconomic interactions between them. Both regions lack KPC
enzymes, which are commonly seen in China and the US from strains belong to ST11 and
ST258, respectively. Despite ST11 being predominant in this collection, we did not detect
KPC. Yet, we detected a high-risk clone of E. coli, ST131-H30Rx-CTX-M-15. Additionally,
we identified newly emerging clones of K. pneumoniae and E. coli such as ST231 and
ST1193-H64RxC, respectively.
Nearly 10% of the K. pneumoniae isolates in our collection were colistin resistant which
prompted us to study the mechanisms of colistin resistance (Paper III). MgrB-inactivation
by insertion elements was seen in 8 isolates while other mutations were seen in other
chromosomal genes known to be involved in colistin resistance e.g. pmrB, phoPQ and crrB.
However, we did not detect mcr genes. Collectively, the genetic alterations are thought to
reduce the net negative charge in bacterial cell wall, hence lowering the binding affinity of
colistin. Our data underscores that there is no reduction in the surface charge in colistinresistant
K. pneumoniae, due to the MgrB-insertion (Paper IV). The genetic alteration might
lead to other structural changes in the cell wall such as altering hydrophobicity, which
required further investigation. Also, our data shows no difference in the survival rates of
colistin resistant and susceptible strains in blood, serum and zebrafish model. Thus, gaining
resistance against colistin does not infer a fitness cost in K. pneumoniae with MgrB-insertion
(Paper IV). Additionally, colistin and LL-37 share similar binding mechanism which suggest
there might be a cross-resistance between them. Our data supported this hypothesis, but only
at high concentrations of LL-37 ( ≥ 50 mg/L) (Paper IV).
Finally, we studied available options to treat infections caused by multidrug-resistant strains.
Combining colistin and rifampicin showed good in vitro activity against multidrug-resistant
strains of E. coli (Paper V) and K. pneumoniae (Paper III). To summarise, we conducted
comprehensive genomic analysis of E. coli and K. pneumoniae isolates from Oman to reveal
the resistance mechanism, their impact on bacterial cell structural and if there is a fitness cost
inferred by the resistance mechanisms. Finally, we studied combination therapy as an
available option at hand for tackling infections caused by multidrug-resistant strains
Genetic manipulation of fungal strains for the improvement of heterologous genes expression (a mini-review)
Fungi are eukaryotic microorganisms that influence our everyday lives in areas as diverse as agriculture, medicine and basic science. With the advent of molecular biology, it has been attempted to improve the expression level of heterologous genes, which encode favorable traits in fungal strains. The expression of heterologous genes can be limited in transcription, post-transcription, translation and post-translation levels. Several genetic strategies have been developed to reduce the expression constrains and to enhance genes functionality. Among these strategies can be pointed to the introduction of multicopies of the desired gene, change of AT-rich sequences, gene fusion with a wellexpressed gene, the use of strong promoters and signal sequences, optimization of codon usage, the construction and use of protease-deficient and chaperones/foldases-overproduced strains and the use of native or artificial intron-containing genes. These strategies have often resulted in the expected increase in the expression of heterologus genes. With the isolation of a large number of genes encoding desired traits and the availability of a large collection of wild isolates, the improvement of strains with a better functional performance would be possible.Key words: Strain improvement, gene, heterologous, intron, promoter, codon
The backward crosstalk effect or response grouping in the psychological refractory period paradigm
Background: In the psychological refractory period paradigm, the second response time is increased as the interval between the first and second stimulus is decreased. The response delay for the second stimulus is called the psychological refractory period. In contrast with these findings, some evidence of the backward crosstalk effect has shown that the first reaction time is affected by the second stimulus. The capacity sharing models, in which multiple stimuli can be processed simultaneously, unlike central bottleneck models, are able to provide some explanations for the changes in the reaction time to the first stimulus. However, sometimes these changes could be arisen from response grouping; the first response remains on the processing buffer until the response to the second stimulus is prepared, then both stimuli are responded simultaneously. The questions of this study were whether the second task difficulty and time interval manipulation would affect the first task response or not and in what extend changes are because of response grouping? Materials and Methods: Detection, discrimination and choice tasks were used as the second task in the psychological refractory period paradigm and the time interval between stimuli was 50, 100, 200, 400, or 1000 ms. Results: The type of the second stimulus and time interval between stimuli had an effect on the second-task and first-task reaction times. Conclusion: In the detection group, the first task response time changes were consistent with grouping between the two responses, but in the discrimination group the changes would arise from capacity limitation and were consistent with the backward crosstalk effect
The Effect of Educating Health Promotion Strategies on Self-Care Self-Efficacy in Patients Undergoing Kidney Transplantation: A Double Blind Randomized Trial
Background: Self-care self-efficacy in patients with end stage renal disease, waiting for kidney transplantation, probably decreases due to facing new conditions and side effects of treatment.
Objectives: The current study was conducted to investigate the effect of educating health promotion strategies on self-care self-efficacy in patients undergoing kidney transplantation.
Patients and Methods: A double blind randomized clinical trial was conducted on 52 patients undergoing kidney transplantation in Baqiyatallah Hospital in 2012. Patients were randomly assigned into intervention and control groups. The questionnaire of Strategies Used by People to Promote Health (SUPPH) was employed to measure self-care self-efficacy. At first, the two groups filled the questionnaire. Then, the intervention group was trained regarding health promotion strategies within 4 sessions before the transplantation. The control group was trained according to routine protocol of the transplantation unit. Then, the two groups were followed up for two months, and reassessed at the end of the first and second months after the transplantation. The data were analyzed by descriptive and analytic statistics including independent samples T test, Chi square and repeated measures ANOVA.
Results: In the intervention group, the mean of total self-care self-efficacy was 106.96 ± 25.1 at first, and changed to 135.81 ± 9.65 and 111.19 ± 12.45 after the first and second post-test respectively (P = 0.001). In the control group, the mean of total self-care self-efficacy was 112.73 ± 14.33 at first, and changed to 118.58 ± 17.59 and 108.73 ± 15.93 after the first and second post-test respectively (P = 0.001). Significant differences were observed between the two groups in the first post-test regarding total score of self-care self-efficacy (P = 0.001) and dimensions of reduction of stress (P = 0.001), enjoying life (P = 0.01), and coping (P = 0.001). The mean scores of the intervention group were higher than those of the controls in all domains of self-care self-efficacy in the second post-test. However, the difference was only significant in decision-making dimension (P = 0.04).
Conclusions: Educating health promotion strategies was effective in improving self-care self-efficacy in patients undergoing kidney transplantation. Establishment of a holistic caring program is suggested to integrate the pre-transplantation educations with a continual post discharge follow-up
Effectiveness of Phonological Awareness Skills Training in Improving Decoding Skills of Children with Reading Disabilities
The study aimed to investigate the effectiveness of a phonological awareness skills training program in improving decoding skills of third grade students with reading disabilities. The initial sample included 40 students enrolled in the learning disabilities program in elementary schools in Oman. They were assessed for diagnosing those who have reading disabilities through adopting the procedures of the IQ-achievement discrepancy model. The Raven’s Matrices and a reading achievement test were administered to students. Then, 14 students among those diagnosed with reading disabilities were randomly distributed to an experimental and a control group. Participants in the experimental group received training in phonological awareness for 10 weeks whereas the control group participants did not. The participants of both groups were administered two tests in phonological awareness (PA) and decoding skills (DS) pre and post the training. Results of the study indicated that there were statistically significant differences between the experimental and control groups on the sub-tests of the PA and DS tests except for fluency in reading passages. However, a comparison of the pre and post scores of the experimental groups showed that they obtained significant gains in all sub scores following the training
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