Cyclic Instability Behaviour of Sand-Silt Mixture Under Partial Cyclic Reversal Loading

Flow liquefaction is one of the most catastrophic failure phenomena in geotechnical engineering. It is a form of instability and can be observed during monotonic loading or cyclic loading. It is referred to as static instability/liquefaction for monotonic loading and cyclic instability for cyclic loading. To investigate the link between these behaviours, a number of stress controlled cyclic triaxial tests were carried out on loose sand-silt mixture under cyclic ‘reversal’ and ‘non-reversal’ loading condition. Cyclic reversal loading was partial reversal. Its peak-trough magnitudes were chosen in such a way that cyclic instability was triggered in compression side of the stress space. Thus it gives an opportunity to compare cyclic instability (both for partial ‘reversal’ and ‘non-reversal’) with static instability observed in monotonic loading condition. The test condition covers a range of initial mean effective confining stresses and void ratio. The equivalent granular state parameter was used to synthesize the test results irrespective of fines contents. Test results showed that cyclic instability was governed by the stress ratio at static instability for the same equivalent granular state parameter irrespective of fines contents. Thus, equivalent granular state parameter can be used as a predictor of cyclic instability for cyclic ‘reversal’ and ‘non-reversal’ loading if cyclic instability is triggered in compression side of the stress space

Present Status of Ganges River Dolphins Platanista gangetica gangetica

Freshwater ecosystem degradation in the Turag River basin is increasing due to rising human settlement, reduced water flow during the dry season, new large land development projects, and toxic emissions caused by brick kilns. The population of river dolphins was estimated through surveys carried out from December 2012 to November 2013. Surveys were conducted on a fortnightly basis. The dolphins were counted within an 18.4 km stretch (known to be the most polluted stretch) of the 75 km long river. A total of 62 dolphin sightings were recorded, both as individual sightings and as groups. The highest monthly count was in August. The best-high-low estimates of 9-11-7 individuals were recorded in August 2013 in river ecology. Seasonal changes in spatial distribution were observed. The survey revealed that rising floodwater stimulated an increase in the dolphin population in the study area from July to October. The maximum encounter rate was also 0.49 sightings km−1 for the month of August. The sightings and encounter rates of dolphins were lower from December to July (dry and premonsoon period) likely due to reduced water flow and adverse water quality of this river

Analysis of Genetic Diversity in Some Rice Varieties and Their Performance in Bangladesh

This study was conducted to evaluate the genetic diversity for several rice features and their association with yields, as well as to identify genotypes of short-duration rice. The experiment was conducted in the field in a natural environment, and data were collected on several plant parameters for each genotype at various phases of plant development. Twenty genotypes of rice were examined based on their morphological and physiological characteristics. From July through December of 2020, the experiment was conducted at the Bangladesh Rice Research Institute's regional station in Shyampur, Rajshahi. There was significant diversity among the twenty rice genotypes for all characteristics tested. The genotype BRRI dhan57 displayed the shortest days to flowering. In terms of days to maturity, the genotype BRRI dhan57 was the earliest, with a maturity time of 107.33 days, followed by BRRI dhan56 and BRRI dhan39. The days to blooming had the highest heritability (99.75%), followed by the days to maturity (99.58%), grain yield (85.30%), thousand grain weight (85.22%), grains per panicle (84.91%), plant height (82.21%), and tillers per hill (21.61%). High heritability scores indicated that the researched qualities were less influenced by the surrounding environment. As a percentage of the mean, the genetic gain was greatest for grain yield (36.33%) and lowest for tillers per hill (6.60%) among the yield-contributing factors. In days to flowering, days to maturity, grains per panicle, and plant height, high heritability and genetic progress were seen. According to the principal component analysis (PCA), the Eigen values of the first four components of the total variance accounted for 89.46% of the total variance, indicating that these components were mostly responsible for the genetic diversity of the current materials. It was the largest cluster, containing seven rice genotypes. Clusters II and V contained five and four genotypes of rice, respectively. Clusters III and IV were the smallest, with only two genotypes apiece. The pattern of distribution of genotypes among various clusters demonstrated the significant genetic variety present in the genotypes, which may be the result of adaptation of these genotypes to certain environmental conditions. The largest value of intercluster distance indicated that cluster III genotypes were extremely distinct from cluster IV genotypes. Negative values in both vectors for tillers per hill suggested that this feature contributed the least to the total diversity. The number of panicles per hill, panicle length, weight per thousand grains, and grain yield were all positive in both directions. According to these statistics, these four characteristics contributed the most to the variety. View Article DOI: 10.47856/ijaast.2022.v09i12.00

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods This study comprised an analysis of GlobalSurg-1 and -2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle- and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 per cent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P < 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P < 0·001) in low- compared with middle- and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P < 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P < 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P < 0·001). Conclusion Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone

Cyclic undrained behaviour of silty sand under partial cyclic reversal

Cyclic undrained behaviour of sand with different fines content was investigated through stress-controlled cyclic triaxial tests with partial stress reversal. The test results were analysed based on the concept of equivalent granular state parameter, Ψ*. Three different Cyclic undrained behaviour of sand with different fines content was investigated through stress-controlled cyclic triaxial tests with partial stress reversal. The test results were analysed based on the concept of equivalent granular state parameter, Ψ*. Three different types of behaviour were observed: namely cyclic instability, cyclic mobility and an in-between transition behaviour. Cyclic instability was observed for loose sand-fines mixtures with a positive Ψ*, and can be related to the instability stress ratio of monotonic test with same equivalent granular void ratio, e* as long as instability was controlled by the compression side of the stress space. On the other hand, cyclic mobility was observed for samples had negative Ψ*. However, transition behaviour was observed for samples with Ψ* values close to zero. observed for loose sand-fines mixtures with a positive *, and can be related to the instability stress ratio of monotonic test with same equivalent granular void ratio, e* as long as instability was controlled by the compression side of the stress space. On the other hand, cyclic mobility was observed for samples had negative *. However, transition behaviour was observed for samples with * values close to zero.

Cyclic instability behaviour of sand silt mixture under partial cyclic reversal loading

Flow liquefaction is one of the most catastrophic failure phenomena in geotechnical engineering. It is a form of instability and can be observed during monotonic loading or cyclic loading. It is referred to as static instability/liquefaction for monotonic loading and cyclic instability for cyclic loading. To investigate the link between these behaviours, a number of stress controlled cyclic triaxial tests were carried out on loose sand-silt mixture under cyclic ‘reversal’ and ‘non-reversal’ loading condition. Cyclic reversal loading was partial reversal. Its peak-trough magnitudes were chosen in such a way that cyclic instability was triggered in compression side of the stress space. Thus it gives an opportunity to compare cyclic instability (both for partial ‘reversal’ and ‘non-reversal’) with static instability observed in monotonic loading condition. The test condition covers a range of initial mean effective confining stresses and void ratio. The equivalent granular state parameter was used to synthesize the test results irrespective of fines contents.

Milk composition at different stages of lactation in first-calving cows of Military Farm at Savar, Bangladesh

Objectives: The present research work was taken up to examine the changing pattern of colos¬trum to normal milk and also to monitor the effect of phages of lactations on compositional changes of milk produced by Holstein-Friesian Crossbred cows of Military Farm Savar. Materials and Methods: A total of 05 milking cows from the first calving were selected. Colostrum samples were gathered on calving and the 5th day after calving. The concentration of major ingre¬dients [fat, protein, lactose, total solids (TS), solid-not-fat (SNF), and ash] changed significantly after birth, the day on 5, similar to normal milk. The average values of specific gravity, fat, protein, lactose, TS, SNF, and ash content of colostrum were observed on day 1 and day 5. Results: The specific gravity was 1.045 and 1.031, respectively. The fat, protein, and lactose con¬tents of colostrum on day 01 and day 05 after calving showed a significant difference. The compo¬sition of whole milk showed that the specific gravity was 1.029. According to the different stages of lactation, it was found that the protein, lactose, fat, TS, SNF, and ash content were lower in the first 2 months of lactation. After 3 months of lactation, it started to increase, and there was a significant change at the end of the sampling period. Conclusion: The composition of colostrum and milk of Holstein-Friesian crossbred cows was within the normal range, and the changing pattern was similar to the other dairy breeds. [Vet. Res. Notes 2023; 3(3.000): 16-21

Cyclic liquefaction behaviour of granular materials with fines.

Liquefaction, a catastrophic failure phenomenon of saturated or nearly saturated granular materials, can be divided into either static or cyclic liquefaction depending on whether the loading condition is monotonic or cyclic. Static liquefaction, also referred to as static instability, is in fact undrained deviatoric strain softening behaviour where instability in the context of continuum mechanics, i.e.d&#963;ijd&#949;<0, is manifested (where &#963;ij and &#949;ij are stress and strain tensors respectively and d represent infinitesimal increments). On the other hand, cyclic liquefaction can occur in the form of either cyclic instability or cyclic mobility. Cyclic instability is a deviatoric strain softening behaviour triggered by a series of cyclic stress pulses and followed the same line of argument as for static instability. Cyclic mobility can be categorised as a state of occurrence of 5% double amplitude (DA) axial strain and the effective stress path travel transiently to near zero in a load cycle, but the imposed peak (and trough) deviator stress can still be developed even a few loading cycles after the occurrence of cyclic mobility. Experimental results on Sydney sand with fines (particles passing 0.075 mm sieve) and coal ash, and different published databases for sands with fines as well as clean sands were used to investigate different aspects of above-mentioned forms of liquefaction giving particular emphasis on cyclic liquefaction.Prior research investigations in linking static and cyclic instability mostly concentrated on clean sand and very limited studies in this regard could be found for sand with fines. In all of those investigations, the linkage between static and cyclic instability was examined by forming replicate test-pairs where a test-pair formed between undrained monotonic and cyclic loading test of one-way or two-way. Also, different characteristics lines have been proposed to define the triggering of cyclic instability. This thesis examines the linkage of static and cyclic instability by forming equivalent as well as replicate test-pairs. The concept of equivalent granular state parameter was proposed to capture the influence of fines content, &#8747;c. An equivalent test-pair was formed by different combinations of fines contents, &#8747;c (less than threshold fines contents, &#8747;thre), initial effective confining stress, p'0 and void ratio, e0, but having same equivalent granular state parameter, &#968;&#8727;(0) where the symbol 0 next to parameters is used to indicate prior to shearing. Experimental results showed that, cyclic instability, under one-way and two-way cyclic loading, triggered shortly after the cyclic ESP crossed the &#951;IS-zone as determined from a corresponding monotonic loading test, where, &#951;IS is the effective stress ratio (q/p&#1523;) at peak of undrained monotonic ESP. Further, this finding is equally applicable for both equivalent and replicate test-pairs. The next step is to predict the triggering of cyclic instability without having a corresponding (equivalent or replicate) monotonic test. This was achieved via the concept of instability curve which is a single relationship between &#951;IS and &#968;*(0) for a range of fines content less than the threshold value. Two instability curves (IC), namely ICcom and ICext as obtained in &#951;IS-&#968;&#8727;(0) space for Sydeny sand with fines were used for predicting cyclic instability of same soil, where subscript com and ext indicate the ICs obtained from data points of undrained monotonic compression and extension tests respectively. Test results showed that ICcom and ICext could be successfully used to predict triggering of cyclic instability in the corresponding stress space capturing the influence of &#8747;c (<&#8747;thre), p'0 and initial static shear stress, q0. The lack of a unified framework in predicting different forms of cyclic liquefaction have been revealed in literature. Thus, published databases for three clean sands and four sands with fines were systematically analysed in context of critical state soil mechanics, CSSM to examine whether it is giving an indicative response. Analysed databases suggested that the occurred form of cyclic liquefaction (cyclic instability and cyclic mobility) could be predicted depending on the corresponding value of the state parameter, &#968;(0), for clean sand; or &#968;&#8727;(0) for sand with fines. In the later case, the influence of &#8747;c (<&#8747;thre) does not have to be separately accounted for as its already captured in the definition of &#968;*(0). Then, these findings were further verified by conducting experimental investigation for Sydney sand with fines. During the experimental investigation, a new form of cyclic liquefaction was identified along with two others as mentioned above. This newly identified form of cyclic liquefaction was referred to as transition behaviour which manifested some (but not all) of the features of both cyclic instability and cyclic mobility. This study demonstrates that all forms of cyclic liquefaction can be predicted through&#968;&#8727;(0) capturing the effect of &#8747;c (<&#8747;thre), p'0 and imposed q0. Therefore, a unified framework for predicting different mode of cyclic liquefaction under CSSM has been achieved.In this thesis, cyclic liquefaction behaviour was also investigated for a coal ash which is predominantly fines. Preliminary experimental results on coal ash also showed three forms of cyclic liquefaction as observed for Sydney sand with fines