Evaluation of ultrasound technology to break seed dormancy of common lambsquarters (Chenopodium album)

Although seed dormancy is advantageous for annual plants in the wild, unsynchronized germination in the laboratory leads to increased error in measurements. Therefore techniques to promote and synchronize germination are routinely used. Ultrasound is one of the newest methods for breaking dormancy in weed seeds. We have investigated whether ultrasonic waves can be used to break seed dormancy of common lambsquarters (Chenopodium album), a highly competitive annual weed that leads to significant reduction of yields of corn, soybeans, and sugar beets. Ultrasonic waves with frequency of 35kH were applied for 0 (control), 5, 10, 15 and 30 minutes using a completely randomized design. The results showed that the use of ultrasound waves generally enhanced the traits under investigation in the treated samples compared to the control sample. The maximum enhancement of germination percentage (180%), seedling dry weight (78%), and seedling vigor index I (271%) and II (392%) was seen in the common lambsquarters samples treated with ultrasound for 15 minutes and seedling length (40%) at 30 minutes compared to the control samples. Radical lengths were not statistically different from controls under any treatment and plumule length only increased marginally. These changes are reflected in seedling vigor index I and II measurements. For some of these traits, increasing the length of ultrasound treatment to 30 minutes had negative effects. These results demonstrate that ultrasound technology can be used as a quick, and efficient non-destructive method to break seed dormancy in common lambsquarters

Redroot pigweed (Amaranthus retroflexus L.) and lamb's quarters ‎‎(Chenopodium album L.) populations exhibit a high degree of ‎morphological and biochemical diversity

Amaranthus retroflexus L. and Chenopodium album L. are noxious weeds that have a cosmopolitan distribution. These species successfully invade and are adapted to a wide variety of diverse climates. In this paper we evaluated the morphology and biochemistry of 16 populations of A. retroflexus L. and 17 populations of C. album L.. Seeds from populations collected from Spain, France and Iran were grown together at the experimental field of the agriculture research of University of Mohaghegh Ardabili and a suite of morphological traits and biochemical traits were assessed. Among the populations of A. retroflexus L. and of C. album L. were observed significant differences for all the measured traits. The number of branches for A. retroflexus L. (12.22) and inflorescence length (14.34) for C. album L. were the two characteristics that exhibited the maximum coefficient of variation. Principal component analysis of these data identified four principal components for each species that explained 83.54 (A. retroflexus L.) and 88.98 (C. album L.) of the total variation. A dendrogram based on unweighted neighbor-joining method clustered all the A. retroflexus L. and C. album L. into two main clusters and four sub-clusters. Canonical correlation analysis was used to evaluate relationships between climate classification of origin and traits. Similarly, the measured characteristics did not group along Köppen climate classification. Both analyses support the conclusion that A. retroflexus L. and C. album L. exhibit high levels of diversity despite similar environmental histories. Both species also exhibit a high diversity of the measured biochemical compounds indicating they exhibit different metabolic profiles even when grown concurrently and sympatrically. Several of the biochemical constituents identified in our study could serve as effective indices for indirect selection of stresses resistance/tolerance of A. retroflexus L. and C. album L. The diversity of the morphological and biochemical traits observed among these populations illustrates how the unique selection pressures faced by each population can alter the biology of these plants. This understanding provides new insights to how these invasive plant species successfully colonize diverse ecosystems and suggests methods for their management under novel and changing environmental conditions

Composite patch reinforcement of a cracked simply-supported beam traversed by moving mass

In this study dynamic analysis of a metallic beam under travelling mass was investigated. A beam with an edge crack was considered to be reinforced using composite patch. Euler-Bernoulli beam theory was applied to simulate the time-history behavior of the beam under dynamic loading. Crack in the beam was modeled using a rotational spring. Dimension of the composite patch, crack length, stress intensity factor at crack tip and beam deflection are some parameters which were studied in details. Results were validated against those which were found through Finite Element Method

The usefulness of optics-based courses for optometry and vision science alumni: a cross-sectional online survey

Objectives A well-balanced curriculum is critical for ensuring that students graduate with the necessary skills. There is growing interest in evaluating the functional value of non-clinical courses compared to clinical courses. The purpose of this study was to evaluate the views of optometry and vision science professionals on the utility and relevance of optics-based courses.Methods A web-based survey was designed to assess the perceived significance of the optics-based courses. All respondents were alumni of two universities in Jordan that offer an undergraduate degree in optometry. The survey included questions about the professional relevance of optics courses. Respondents were asked to rate several statements related to the relevance and importance of optics courses in current optometry practice on a 5-point Likert scale.Results In total, 205 respondents completed the online survey. There were 161 (78.5%) women and 44 (21.5%) men, with an average age of 28.76 (± 4.86) years. Overall, respondents rated the perceived usefulness of optics courses for their careers with a mean collective value of 20.78 out of a possible 30 points. Female alumni perceived the courses as significantly more useful in their workplace than male alumni did (p = .020). Optometrists in different age groups perceived usefulness differently (p = .001). Alumni who preferred to learn these courses on-site and by hybrid methods perceived optics courses as significantly more useful than those who preferred to learn online (p = .006 and p < .001, respectively).Conclusions The perceived importance of optics-based courses varied according to several factors. However, in general, these courses were deemed helpful in terms of curricular content and practical relevance to practice, regardless of specialisation or the workplace.Key messagesIn terms of the value offered to the professional competencies that an optometrist needs, the practical utility of optics courses in optometry curriculums is contested.Optometrists' perceptions of optics courses were examined using a cross-sectional survey.Respondents rated the perceived usefulness of optics courses for their career, with a mean collective value of 20.78 out 30 points.The highest percentage of respondents in this study expressed their preference for the face-to-face learning method rather than the hybrid method.Male optometrists perceived learning optics courses as significantly less helpful than female optometrists