bluuebunny/crossref_metadata_2025 huggingface dataset:
Target Templates in Low Target-Distractor Discriminability Visual Search Have Higher Resolution, but the Advantage They Provide is Short-lived
Authors: Lau Jonas Sin-Heng , Pashler Harold , Brady Timothy F.
Published: May 2019

When you search repeatedly for a set of items among very similar distractors, does that make you more efficient in locating the targets? To address this, we had observers search for two categories of targets among the same set of distractors across trials. After a few blocks of trials, the distractor set was replaced. In two experiments, we manipulated the level of discriminability between the targets and distractors before and after the distractors were replaced. Our results suggest that in the presence of repeated distractors, observers generally become more efficient. However, the difficulty of the search task does impact how efficient people are when the distractor set is replaced. Specifically, when the training is easy, people are more impaired in a difficult transfer test. We attribute this effect to the precision of the target template generated during training. In particular, a coarse target template is created when the target and distractors are easy to discriminate. These coarse target templates do not transfer well in a context with new distractors. This suggests that learning with more distinct targets and distractors can result in lower performance when context changes, but observers recover from this effect quickly (within a block of search trials).
Estonian case inflection made simple. A case study in Word and Paradigm morphology with Linear Discriminative Learning.
Authors: Chuang Yu-Ying , Lõo Kaidi , Blevins James P. , Baayen R. H.
Published: May 2019

According to Word and Paradigm Morphology (Matthews, 1974; Blevins, 2016), the word is the basic cognitive unit over which paradigmatic analogy operates to predict form and meaning of novel forms. Baayen et al. (2019b, 2018) introduced a computational formalization of word and paradigm morphology which makes it possible to model the production and comprehension of complex words without requiring exponents, morphemes, inflectional classes, and separate treatment of regular and irregular morphology. This computational model, Linear Discriminative Learning (LDL), makes use of simple matrix algebra to move from words’ forms to meanings (comprehension) and from words’ meanings to their forms (production). In Baayen et al. (2018), we showed that LDL makes accurate predictions for Latin verb conjugations. The present study reports results for noun declension in Estonian. Consistent with previous findings, the model’s predictions for comprehension and production are highly accurate. Importantly, the model achieves this high accuracy without being informed about stems, exponents, and inflectional classes. The speech errors produced by the model look like errors that native speakers might make. When the model is trained on incomplete paradigms, comprehension accuracy for unseen forms is hardly affected, but production accuracy decreases, reflecting the well-known asymmetry between comprehension and production. Unseen principal parts (i.e., nominative, genitive, and partitive singulars) are particularly difficult to produce, possibly due to their more distinctive forms. Removing principal parts from training, however, does not affect accuracy for other case forms. Model performance does not degrade either when the training data includes the alternative forms that are ubiquitous in Estonian. These results are consistent with the claim of Blevins (2008) that Estonian number and case inflection is organized in a way that facilitates the deduction of full paradigms from only a small number of forms.
Effect Size Interpretation, Sample Size Calculation, and Statistical Power in Gerontology
Authors: Brydges Christopher
Published: May 2019

Background and Objectives: Researchers typically use Cohen’s guidelines of Pearson’s r = .10, .30, and .50, and Cohen’s d = 0.20, 0.50, and 0.80 to interpret observed effect sizes as small, medium, or large, respectively. However, these guidelines were not based on quantitative estimates, and are only recommended if field-specific estimates are unknown. The current study investigated the distribution of effect sizes in both individual differences research and group differences research in gerontology to provide estimates of effect sizes in the field.Research Design and Methods: Effect sizes (Pearson’s r, Cohen’s d, and Hedges’ g) were extracted from meta-analyses published in ten top-ranked gerontology journals. The 25th, 50th, and 75th percentile ranks were calculated for Pearson’s r (individual differences) and Cohen’s d or Hedges’ g (group differences) values as indicators of small, medium, and large effects. A priori power analyses were conducted for sample size calculations given the observed effect size estimates.Results: Effect sizes of Pearson’s r = .12, .20, and .32 for individual differences research and Hedges’ g = 0.16, 0.38, and 0.76 for group differences research were interpreted as small, medium, and large effects in gerontology. Discussion and Implications: Cohen’s guidelines appear to overestimate effect sizes in gerontology. Researchers are encouraged to use Pearson’s r = .10, .20, and .30, and Cohen’s d or Hedges’ g = 0.15, 0.40, and 0.75 to interpret small, medium, and large effects in gerontology, and recruit larger samples.
Oxygen Saturation as a Predictor of Adverse Maternal Outcomes in Women with Preeclampsia
Authors: Rani Sweta , Mistri Pallab Kumar
Published: May 2019

Introduction: In preeclampsia, hypoxemia may result from a number of mechanisms. Preeclampsia remains a complex and poorly understood disease. Currently, there are no reliable predictors of preeclampsia for early diagnosis to avoid adverse maternal or perinatal outcomes.

Objective: The objective was to evaluate the efficacy of oxygen saturation (SpO2) as a predictor of adverse maternal outcome in women with preeclampsia.

Methodology: We conducted the cross-sectional study on 182 preeclamptic women selected by random sampling technique. They were divided into two groups on the basis of oxygen saturation: 29 preeclamptic women (Group L) having oxygen saturation 95% or below and 153 women (Group H) having oxygen saturation 96% or above. The groups were statistically compared with respect to age, gestational age, proteinuria, severity of hypertension and developing different adverse effect of preeclampsia. Women with any medical disorders were excluded.

Results: After statistical analysis, it was seen that the women having Spo2 ≤ 95% (L-Group) had experienced more adverse 2 outcomes. They were more hypertensive and more proteinuric, had higher liver enzyme levels, lower platelet counts, and were more likely to have experienced cardio-respiratory symptoms. Women with adverse outcomes were also more likely to have had therapeutic interventions, including corticosteroids, antihypertensives, and magnesium sulphate.

Conclusion: Women having SpO2 ≤ 95% (L-Group) had more adverse 2 outcomes in comparison to SpO2 ≥96%(H-Group).
To Compare the Functional Outcome of Intra Articular Distal end of Radius Fracture Treated by Conventional pop cast and External Fixatator Fixatation
Authors: Gupta Pradeep Kumar , Yadav Ajay Kumar
Published: May 2019

Introduction: Distal end of radius fractures frequently have a high degree of comminution, instability, and associated with soft tissue injuries. Treatment of this distal radius fracture is controversial and there is no single definitive treatment method that is considered the standard of care.

Objective: 1. To compare the functional results of the conventional POP cast and external fixator fixation of intra articular distal end of radius fracture. 2. To compare the radiological changes with that of functional outcome.

Methodology: It was a prospective study comparing the functional outcome of distal intra-articular radius fracture when managed by conventional POP cast and external fixatator fixation. The final outcome was decided on the basis of modified Gartland and Werley scoring system. Total 50 patients (19 – 54 years) were recruited. 30 were treated by closed reduction and POP cast and 20 by external fixation. Radiological parameters were graded according to Schecks criteria and fracture comminution was classified according to Frykman's classification.

Results: The functional outcome of the treatment was a subjective evaluation in which 80% of the patients had pain in external fixation as compared to 63% in closed reduction POP cast group. The restriction of activities was in 10% of the patient in external fixation group as compared with 33% in closed reduction POP cast group. The final scoring system as modification of Gartland and Werley point system had 5 ± 3 conventional pop cast group and 4 ± 4 in external fixation group. (p = 0.3764). On radiological evaluation, there was no significant difference in radial length, radial angle and volar tilt in two groups.

Conclsion: The results show no statistically significant difference between the two modes of interventions. External fixation provides easy mobilization of fingers and reduces edema and stiffness of joints. The active ranges of movements at the wrist joints were significantly better in external fixation group.
Perceived Benefits, Knowledge about Cancer and Attitude towards Promotion of Gutkha Amongst Gutkha users from Nepal
Authors: Basnet Bishal Babu , Sharma Khem Raj
Published: May 2019

Introduction: Gutkha, a mixture of areca nut pieces, tobacco and slaked lime, is a potential carcinogen. It causes oral submucous fibrosis. Many people do not possess this knowledge and thus consume gutkha daily. The consumption is highly prevalent in Nepal because of easy availability of this material. Although ban of advertisement is implemented in Nepal in electronic media, the impact has not been significant.

Objective: To find the prevalence of different beneficial effects cited, to determine awareness about cancer and attitude towards ban of advertisement, production and sale in current gutkha users from rural Terai dwellers of Nepal.

Methodology: We interviewed 1217 households in a community survey in which 151 were current gutkha consumers, their responses about perceived benefits, cancer knowledge and views on ban of its sale and promotion was analyzed. The relationship with demographic variables were tested with Chi-square test with level of significance set at 0.05.

Results: Among the current users, the reason of consuming gutkha was mostly 'feeling of well-being' (38.4%), about 40% thought it can cause cancer. The knowledge was not associated with gender, age group and literacy but statistically related with marital status (p<0.05). Majority were in favor of ban on advertisement (74.2%) and on production, sale and consumption (70.2%).

Conclusion: The level of knowledge of cancer causation is very low and education level had not been significantly associated to knowledge. More gutkha users were in favor of its ban which is a positive finding.
Efficacy of Short Course Antibiotic Prophylaxis in Surgical Treatment of Closed Fracture
Authors: Jha Subash Chandra , Baral Pramod , Shakya Prakash
Published: May 2019

Introduction: Unnecessary and rampant use of antibiotic for perioperative prophylaxis are not only increasing cost of treatment but also are hazardous in terms of increasing antibiotic resistance, super infection with resistant pathogens and antibiotic toxicity.

Objective: Our primary objective is to assess the efficacy of short course antibiotic prophylaxis in preventing surgical site infection (SSI) in surgery of closed orthopedic fracture.

Methodology: Patients fulfilling all the inclusion criteria and willing and able to give informed consent were included in the study. All participants were treated by standard surgical technique following standard surgical protocol. Short course antibiotic prophylaxis was administered in peri-operative period to all patients in given format: Three divided dose of intravenous 1.5 gram cefuroxime during peri-operative period followed by no intravenous or oral antibiotics; 1st dose half an hour before incision; 2nd and 3rd dose repeated at 12 hours interval.

Results: Of total 100 patient included, three developed surgical site infection till one year follow-up. All three patients with surgical site infection were treated successfully with intravenous antibiotic based on the culture sensitivity report. The average cost of antibiotic for short course antibiotic prophylaxis was 1500 NPR for each patient.

Conclusions: There was no significant increase in rate of surgical site infection with short course antibiotic prophylaxis, rather it was less expensive and may have less adverse effect, in terms of antibiotic resistance and antibiotic side effects on long run.
Efficacy of 10% Ichthammol Glycerine Pack and Steroid-antibiotic Pack for Relieving Pain in Acute Otitis Externa. A Comparative Study.
Authors: Shrestha Karuna , Shah Rajeev , Sapkota Srijana
Published: May 2019

Introduction: Otitis externa is a common painful condition presents with generalized infection of external auditory canal, typically reveals erythema and edema of the skin. Aural packing plays an important role in relieving the pain and edema. For packing, either we impregnated with 10% Ichthammol glycerine or steroid-antibiotic ointment.

Objective: To compare the efficacy of 10% Ichthammol Glycerine pack with steroid-antibiotic ointment pack for relieving the pain in acute otitis externa.

Methodology: A prospective, non-randomized clinical trial was carried out in 94 patients at Birat Medical College and Teaching Hospital, Biratnagar, Nepal from February 2018 to July 2018. Patients diagnosed with acute otitis externa were included in this study, where 47 patients were treated with 10% IG pack and remaining 47 patients treated with a combination steroid antibiotic ointment pack. Before aural packing was carried out, pain was assessed using visual analogue scale (VAS). Both groups of patients were evaluated after 48 hours for assessment of pain.

Results: The total number of patients included in this study was 94. Among them 41 (43.6%) were male and 53(56.4%) were female where male and female ratio was 1:1.29. Majority of the patients were below 40 years (83%). Treatment with steroid-antibiotic ointment pack had significant reduction in pain after 48 hours post treatment, none of them had severe pain, 4(8.5%) had moderate pain remaining and 43(91.4%) had only mild pain. Whereas in patients treated with 10% IG pack 1(2.1%) had severe pain, 14(29.7%) had moderate pain and 32(68%) had mild pain. There was statistically significant decrease in pain with steroid-antibiotic pack.

Conclusions: Both treatment modalities are effective but this study showed steroid-antibiotic ointment pack, the combined therapy is more effective than 10% IG pack for relieving the pain in acute otitis externa.
Correlative Analysis Between Serum Anti-mullerian Hormone Concentration and LH:FSH Ratio as Women's Age Advances: A Hospital-based Study
Authors: Mallick Ram Lala , Kafle Santosh Upadhyay , Dahal Prerana , Karna Tapeshwar Lal , Thakur Asmitanand
Published: May 2019

Introduction: A term 'ovarian reserve' is described as quantity of ovarian follicular cohort and quality of oocytes. The assessment of an individual's ovarian reserve comprises evaluation of certain variables like age, follicle stimulating hormone, leutinizing hormone, LH:FSH ratio and prolactin as main task. Recently, scientists have reported anti-mullerian hormone as potential test for ovarian reserve. Recently, it is observed that higher levels of AMH correlate positively with greater number of oocytes with then the improved embryo morphology in in vitro fertilization (IVF) cycles. However, controversy still exists between correlation of AMH and other hormonal tests.

Objectives: To investigate correlation of AMH, FSH, LH, LH:FSH ratio and PRL in women who attended the local hospital.

Methodology: Venipuncture was performed to collect venous blood samples (n=110) under informed written consents. Following separation of sera, circulating levels of AMH was carried out by ELISA and assessment of FSH, LH and PRL were done using Dry chemistry immunoassay analyzer. Data were analyzed using SPSS software version 16.

Results: Our data demonstrated for existence of significant negative correlation between serum LH:FSH ratio and age. Here, the pattern of changes was in accordance to that of serum AMH concentration. So when we compared serum AMH concentrations with values of LH:FSH ratio in relation to age, the existence of a significant correlation was observed. Further, our findings demonstrate a degree of variations among other variables (such as LH, FSH and Prolactin) and are imperative in analytical point of view.

Conclusion: Our findings behind significant correlation between serum LH:FSH ratio and AMH level suggest that LH:FSH ratio can be a marker for ovarian reserve and applied to clinical evaluation with AMH for diagnostic purpose.
Knowledge and Awareness of Basic Life Support among Medical Staffs of Birat Medical College and Teaching Hospital
Authors: Arjyal Batsalya , Rajbanshi Lalit Kumar , Khanal Kanak , Bajracharya Akriti
Published: May 2019

Introduction: It is essential that all the medical professionals should have adequate skill for basic life support (BLS) for better outcome of cardiac arrest patients. The objective of the study is to assess the knowledge and awareness of BLS among the medical doctors, nursing staffs and health care paramedics working in Birat Medical College and Teaching Hospital, Biratnagar.

Methodology: A three-month duration observational questionnaire-based survey was conducted at Birat Medical College and Teaching Hospital, Biratnagar to assess the knowledge, awareness of basic life support among the medical doctors, nursing staffs and health care paramedics. A total of ten questions were designed to assess the knowledge and awareness regarding BLS skill. Three questions were designed to assess the previous experiences on cardiac arrest situation and BLS training. Similarly, two additional questions were added to assess the self-grading of BLS knowledge which included poor, below average, good and excellent.

Result:  It was observed that only 14% participants had previous BLS training. Surprisingly, 76% of the participants had encountered cardiac arrest situation in their clinical practice but they were managing those cases with limited knowledge on BLS. The correct answer to the self-structured questionnaire were ticked by less than 50% of participants and majority of the participants came below average on self-grading of the knowledge and awareness suggesting the need of easy accessibility of BLS training centers in the eastern part of Nepal.

Conclusion: This study revealed that the knowledge and awareness of basic life support skills among the various staffs was mostly below average to poor. Significant amount of cost effective BLS trainings must be conducted so as to develop competent staffs by various training centers
Chicken Pox Associated Bilateral Retinal Vasculitis in an Immunocompetent Young Male; an Unusual Case Report
Authors: Gurung Rajya Laxmi
Published: May 2019

Chicken pox is considered as benign infectious disease with variable ocular manifestations. We report a case of bilateral retinal vasculitis following chicken pox in a healthy 17-year-old male. The retinal manifestation is stabilized by treatment with oral acyclovir in combination with systemic steroids.
Prevalence and associated risk factor of hypertension among individuals of age 18-59 years in South-eastern Nepal: A cross-sectional study
Authors: Pyakurel Prajjwal , Yadav Deepak Kumar , Thapa Jeevan , Thakur Nishant , Sharma Pramita , Koirala Niraj , Yadav Suraj Kumar , Chaurasia Akanksha , Sharma Sumit , Thapa June , Thapa Santosh , Shah Amit , Panta Pratigya , Shrestha Rajina , Dangi Arpana , Acharya Bijay , Pyakurel Ujjwal , Jha Nilambar
Published: May 2019

Background: Hypertension is one of the major risk factors for the rising burden of cardiovascular diseases (CVDs) in developing region. It has also been recognized as one of the major public health problems in the developing countries since the early seventies and the rate is increasing not only in urban areas but in rural areas with low socio-economic condition. 

Methods: A cross sectional study was conducted in Jogidaha Village Development Comittee(VDC) and Triyuga Municipality of Udaypur district of South-Eastern Nepal. A total of 430 participants of age 18-59 years were selected. Semi-structured questionnaire (WHO NCD STEPS instrument) was used to collect information on demographic variables and associated risk factors with use of show cards. Clinical and anthropometric measurement were done. Primary outcome was prevalence of hypertension. Bivariate and multivariate analysis were performed to show strength of association among various risk factors with hypertension. 

Results: The prevalence of hypertension was found to be 25.1%. Prevalence of overweight and obesity was found to be 49.8%. Hypertension was significantly associated with age (AOR=1.09, CI=1.05-1.10) and gender (male >female; AOR= 2.12,CI =1.22-3.68). Similarly, increased waist-hip ratio(7.12; CI 2.87-17.67),alcohol consumption(OR=2.82,CI=1.77-4.52), and use of tobacco products (OR =1.8,CI=1.02-3.20) showed significant association with hypertension.

Conclusion: There is high prevalence of hypertension in rural districts of South-Eastern Nepal. A community-based preventive approach with early detection and treatment and life-style modification is needed to reduce the burden of disease and make sustainable changes.
Non alcoholic fatty liver disease is a predictor of subclinical Carotid Atherosclerosis in the presence of Metabolic Syndrome
Authors: Kemaloglu Cemal , Kemaloglu Melek Didem
Published: May 2019

Objective: The aim of this study is to identify the relationship between carotid intima-media thickness (c-imt) and non-alcoholic fatty liver disease (NAFLD), and to determine whether NAFLD is an independent predictor for the progression of atherosclerosis. 

Method: This is a prospective randomized controlled study. 103 NAFLD patients who have hepatosteatosis with grade II and above were enrolled in this study. Patients were divided into NAFLD with metabolic syndrome (MS) and NAFLD without MS groups and compared with 50 healthy people. Basal demographic characteristics and C-imt of all patients and control group were measured. 

Results: C-imt and carotid cross sectional area rates in the NAFLD groups were significantly higher than those in the control group. The mean and max. c-imt levels were significantly higher in the NAFLD group with metabolic syndrome (p<0,001). Homeostatic Model of Assessment-Insulin Resistance (HOMA-IR) levels were increased in the group with metabolic syndrome than those in the group without metabolic syndrome, with statistical significance (p<0.001). There was no difference in c-imt levels between HOMA-IR positive and negative groups (p=0.254) in patients with NAFLD and without metabolic syndrome. There was only a mild positive corelation between c-imt levels and high sensitive C-Reactive protein (hs-CRP) levels in metabolic syndrome positive group (p=0.026 r=0.30). 

Conclusion: NAFLD was a significant predictor to determine the increased risk of carotid atherosclerosis.
Awareness regarding cardiac rehabilitation among patients with coronary heart disease attending a cardiac care centre, Kathmandu valley
Authors: Shrestha Rosy , Shrestha Sajeeb
Published: May 2019

Introduction: Coronary heart disease (CHD) is gradually emerging as a leading cause of morbidity and mortality of many low middle income countries like Nepal. Cardiac rehabilitation awareness program has been proved to be effective for reducing the mortality as well as improving the quality of life among CHD patients. The aim of this study was to explore the awareness on cardiac rehabilitation (CR) in patients with CHD attending a cardiac care centre, Nepal.

Method: A descriptive cross sectional study design was used to examine 100 CHD patients attending out-patient departments of Shahid Gangalal National Heart Centre (SGNHC), Kathmandu, Nepal. Purposive sampling technique was used for data collection by face to face interview technique with self developed tool. Data was analyzed with descriptive and inferential statistics.

Results: Of all 100 respondents, 55.0% were male and the mean age was 53.23±14.22 years. The median score of awareness was 17 with interquartile range (IQR) 14.0-19.75 and majority (57.0%) of respondents were unaware about CR. The awareness regarding CR was found highest in awareness regarding CHD (75.0%) whereas lowest score was found in time and duration needed for exercise per week (14.0%). The significant influencing variables were age, education status, duration of treatment and participation in CR program for CHD patients.

Conclusion: The awareness on CR program in CHD patients in Nepal is not optimal, especially among 54 and above age group, illiterate people, those receiving treatment equal & more than 1 year duration and the CHD patients who didn’t get chance to participate on awareness programs. Hence, it is strongly recommended that health professionals including nurses should organize and promote CR programs including counseling session to improve the awareness level and ultimately enhance quality of life of CHD patients.
String percolation in AA and p+p collisions
Authors: Bautista I. , Pajares C. , Ramírez And J.E.
Published: May 2019

A brief review of the string percolation model and its results are presented together with the comparison to experimental data. First, it is done an introduction to the quark-gluon phase diagram and the lattice results concerning the connement and the percolation of center domains. It is studied the interaction of the strings produced in nucleus-nucleus and proton-proton collisions showing how the string percolation arises. The main consequences of the string percolation, concerning the dependence on the energy and centrality, on the multiplicities and the mean transverse momentum are obtained comparing with experimental data. It is emphasized the non-abelian character of the color eld of the strings forming the cluster to reproduce the rise of the transverse momentum with multiplicity and the relative suppression of multiplicities. It is also studied dierent observables like multiplicity and transverse momentum distributions, dependence with multiplicity and transverse momentum correlations, forward-backward correlations, the strength of the Bose-Einstein correlations, dependence on the multiplicity of J/ψ  production and its possible suppression in pp collisions at high multiplicity, strangeness enhancement, elliptic ow, and ridge structure. The comparison with the data shows an overall agreement. The thermodynamical properties of the extended cluster formed in the collision are discussed computingits energy and entropy density, shear viscosity over entropy density ratio, bulk viscosity, sound speed and trace anomaly as a function of temperature, showing a remarkable agreement with lattice QCD evaluations. The string percolation can be regarded as the initial frame able to describe the collective behavior produced in AA and pp collisions.
Congruence kinematics in conformal gravity
Authors: Fathi Mohsen
Published: May 2019

In this paper we calculate the kinematical quantities possessed by Raychaudhuri equations, tocharacterize a congruence of time-like integral curves, according to the vacuum radial solution of Weyl theory of gravity. Also the corresponding flows are plotted for denfinite values of constants.
Analytical solution of the bioheat equation for thermal response induced by any electrode array in anisotropic tissues with arbitrary shapes containing multiple-tumor nodules
Authors: Roca Oria E. J. , Bergues Cabrales L. E. , Bory Reyes And J.
Published: May 2019

The Pennes bioheat transfer equation is the most used model to calculate the temperature induced in a tumor when physical therapies like electrochemical treatment, electrochemotherapy and/or radiofrequency are applied. In this work, a modification of the Pennes bioheat equation to study the temperature distribution induced by any electrode array in an anisotropic tissue containing several nodules (primary or metastatic) with arbitrary shape is proposed. For this, the Green functions approach is generalized to include boundaries among two or more media. The analytical solution we obtain in a very compact way, under quite general suppositions, allows calculating the temperature distributions in the tumor volumes and their surfaces, in terms of heat sources, initial temperature and calorific sources at the boundary of tumors.
Dehydroabietyl Glycidyl Ether Grafted Hydroxyethyl Chitosan: Synthesis, Characterization and Physicochemical Properties
Authors: Wang Ting , Cai Zhao-sheng , Zhang Ting-ting , Li Man , Fang Gui-gan , Zhu Xue-mei
Published: May 2019

A series of novel polymeric nonionic surfactants based on water-soluble N,O-hydroxyethyl chitosan (N,O-HECTS) and dehydroabietyl glycidyl ether (DAGE), DAGE-g-N,O-HECTSs, were synthesized by an additive reaction between N,O-HECTS and DAGE. The structures of DAGE-g-N,O-HECTSs were characterized by FT-IR and 1H NMR. The substitution degree of hydroxyethylation (DSHE) of N,O-HECTS and the grafting degree (DG) of DAGE onto N,O-HECTS for DAGE-g-N,O-HECTSs were determined by elemental analysis. The surface activities of DAGE-g-N,O-HECTSs in aqueous solution were investigated by measuring the surface tension. The experimental results showed that the degree of grafting (DG) of DAGE-gN,O-HECTSs could have a significant impact on their critical micelle concentrations (CMCs) and surface tensions at the CMC (γCMC), but the DG of DAGE-g-N,O-HECTSs had almost no effect on the minimum of surface tensions (γmin). When using the DAGE-g-N,O-HECTSs as emulsifier, the increase in DG had a favorable influence on the stability of an emulsion of water and benzene. At a DG greater than 40.45%, the emulsifying power of DAGE-g-N,O-HECTS exceeded that of Tween-60.
Aircraft Landing Gear Fracture
Authors: Witherell Charles E.
Published: May 2019

The right landing gear on a twin-turboprop transport aircraft collapsed during landing. Preliminary examination indicated that the failure occurred at a steel-to-aluminum (7014) pinned drag-strut connection due to fracture of the lower set of drag-strut attachment lugs at the lower end of the oleo cylinder housing. Two lug fractures that were determined to be the primary fractures were analyzed. Results of various examinations indicated that stress-corrosion cracking associated with the origins of the principal fractures in the connection was the cause of failure. It was recommended that the design be modified to avoid dissimilar metal combinations of high corrosion potential.
Analysis of Wing Main Spar Cracking
Authors: Goldsmith N.T. , Clark G.
Published: May 2019

Following the crash of a Mirage III-0 aircraft (apparently caused by engine failure), a small crack was detected in a bolt hole in the wing main spar (AU4SG aluminum alloy). Because this area was considered to be critical to aircraft safety and similar cracking was found in other spars in service, the Royal Australian Air Force requested that the crack growth rate during service be determined. The loading history of the aircraft was made available in the form of flight by-flight records of the counts from the vertical accelerometer sensors fitted to the airframe and a series of “overstress” events recorded during the life of the aircraft. The bolt hole was examined by eddy current testing, visual examination, high-powered light microscope, and scanning electron microscope. Simulation tests were also conducted. The use of simulation specimens permitted actual crack growth rate data to be determined for the configuration of interest.
Failure of a Helicopter Main Rotor Blade
Authors: Kashar Lawrence
Published: May 2019

A Marine Corps helicopter crash was investigated. Efforts were directed to the failure of one of the main rotor blades that had apparently separated in the air. The apparent failure of a blade integrity monitor (BIM) system was also considered. The rotor blade comprised a long, hollow 6061-T651 aluminum alloy extrusion and 26 fiberglass “pockets” that provided the trailing-edge airfoil shape. Visual examination of the fracture surface of the aluminum extrusion indicated fatigue crack growth followed by ductile overload separation. Examination of the fatigue fracture region revealed several pits that appeared to have acted as fracture origin sites. Time to failure was determined using fracture mechanics. It was concluded that failure was caused by a fatigue crack that grew to critical length without detection. The crack originated at pits that resulted from the use of an improperly designed heating element used to cure fiberglass repairs.
Fatigue Failure of Regenerator Screens in a High-Frequency Stirling Engine
Authors: Moore Thomas J. , Hull David R. , Alger Donald L.
Published: May 2019

An investigation of a Stirling engine after an aborted test run revealed that the regenerator screens had suffered substantial damage. During the run, the individual screens oscillated as the helium working fluid was shuttled through the regenerator. In localized areas, the 41 mu m (1600 mu in.) diam type 304 stainless steel wire screening had been torn and pieces were missing. Scanning electron microscope revealed that the fracture had occurred at wire crossover locations by a fatigue mechanism. The problem was solved by sintering the individual screens into a single unit.
Effect of Strain Rate on the Failure Mode of a Rear Axle
Authors: Kashar Lawrence
Published: May 2019

Following an accident in which a light pickup truck left the road and overturned, one of the rear axles, made of approximately 0.30C steel, was found to be fractured adjacent to the bearing lock nut. A keyway was present in the failed area, as were threads for the lock nut. Fracture surfaces of the failed axle and exemplar fractures obtained from simulation tests were studied using scanning electron microscope. The examination showed that the outer perimeter fracture in the axle was very flat and composed of cleavage and that the interior portion was composed of both cleavage and dimples. No evidence of prior cracking was found. The exemplar specimens from the simulation impact testing failed in a manner consistent with that observed in the axle. The examination confirmed that the failure was a one-time impact overload fracture and not the result of any prior crack in the material, indicating that the axle failure did not initiate the accident.
Fatigue Failure of Welded Truck Cross Members
Authors: Proft Thomas L.
Published: May 2019

Four truck cross members intended for use in heavy-duty transport trucks were investigated. Two of the members had cracked on a prototype vehicle and two had been fatigue tested in the laboratory. The cross members were fabricated from SAE 950X plate and consisted of a formed channel section and an internal fillet-welded diaphragm. Sections from each of the cross members were subjected to a complete analysis, including chemical analysis, magnetic particle testing, mechanical testing, scanning electron microscope/fractography, and metallography. The primary mode of failure was found to be fatigue cracking that initiated at the toes of the fillet welds. Secondary fatigue cracking occurred at the torque rod mounting holes. Failure was attributed to cyclic stresses at the weld toes that exceeded the lowered fatigue strength at this location. A design change that eliminated the fillet welds alleviated the problem.
Failure Analysis of Admiralty Brass Condenser Tubes
Authors: Marden Keneth M. , Lewis Keith R.
Published: May 2019

Inhibited admiralty brass (UNS C44300) condenser tubes used in a natural-gas-fired cogeneration plant failed during testing. Two samples, one from a leaking tube and the other from an on leaking tube, were examined. Chemical analyses were conducted on the tubes and corrosion deposits. Stress-corrosion cracking was shown to have caused the failure. The most probable corrosive was ammonia or an ammonium compound in the presence of oxygen and water. All of the tubes were replaced.
Stress-Corrosion Cracking of Stainless Steel Heat Exchanger Tubes in a Fertilizer Plant
Authors: Perumal K.E.
Published: May 2019

Several type 304L (UNS S30400) stainless steel seamless tubes in a high-pressure synthesis gas cooler condensing ammonia in a fertilizer plant leaked in an unexpectedly short time. Representative samples of the tubes were subjected to chemical analysis, hardness tests, and optical microscopy examination. The tests revealed that the tubes conformed to specification. Crack morphology indicated stress-corrosion cracking by chlorides present in the cooling water. Use of a duplex stainless steel (for example, UNS S32304 S31803) as a tube material was recommended.
Corrosion and Cracking of the Internal Surfaces of a Black Liquor Digester
Authors: Port Robert D.
Published: May 2019

Routine inspections of a carbon steel wood pulp digester revealed a sharply increasing number of cracks in the overlay metal on the internal surface of the digester after 1 and 2 years of service. The weld overlay was composed of type 309 stainless steel on the top fourth of the digester and of a proprietary high-nickel material on the bottom three-fourths. Examination revealed three distinct modes of deterioration. General corrosion was linked to the use of unspecified overlay metal. Cracking resulted during installation from the use of a material susceptible to hot cracking. Deep corrosion fissures then developed at hot crack sites as a result of crevice corrosion. Use of the appropriate overlay material was recommended.
Stress-corrosion Fracture in Silver Solid-State Bonds of Uranium
Authors: Beitscher Stanley , Johns W.L.
Published: May 2019

Silver solid-state bonded components containing uranium failed under zero or low applied load several years after manufacture. The final operation in their manufacture was a proof loading that applied a sustained tensile stress to the bond, which all components passed. The components comprised circular cylinders fabricated by plating a thin layer of silver on each of the contact surfaces (uranium and stainless steel) and pressing the parts together at elevated temperature to solid-state bond the two silver surfaces. The manufacturing process produced a high level of residual stress at the bond. The failures appeared to be predominantly located between the silver layer and the uranium substrate. Normal fracture location of specimens taken from similar components was at the silver/silver bond interface. Laboratory testing revealed that the uranium/silver joint was susceptible to premature failure by stress-corrosion cracking under sustained loading if the atmosphere was saturated with water vapor.
Failure Analysis of the Moderator Branch Pipe of a Pressurized Hot Water Reactor
Authors: Florio Antonio , Crespi Juan C.
Published: May 2019

Type 347 stainless steel moderator circuit branch piping in a pressurized hot water reactor was experiencing frequent leakage. Investigation of the problem involved failure analysis of leaking pipe specimens, analytical stress analysis, and determination of “leak-before-break” conditions using fracture mechanics and thermal fatigue simulation tests. Failure analysis indicated that cracking had been initiated by thermal fatigue. Data from the analysis were used in making the leak-before-break predictions. It was determined that the cracks could grow to two-thirds of the circumferential length of the pipe without catastrophic failure. A thin stainless steel sleeve was inserted in the branch pipe to resolve the problem.
Rapid Pitting Failure of Type 304 Stainless Steel Pipework
Authors: Stott Jim
Published: May 2019

Several hundred leaks were reported in the type 304 stainless steel pipelines, vessels, and tanks of a chemical plant at a tropical location within a few weeks after startup. Investigation of the failure involved a site visit, metallographic examination and analysis of the material, analysis of hydrotest waters, and microbiological examination of slime that had formed in certain pipework sections. It was determined that the failure resulted from microbially induced corrosion promoted by the use of poor-quality hydrotest water and uncontrolled hydrotesting practice. Use of appropriate hydrotesting procedures was recommended to prevent similar failures.
Single-Phase Erosion Corrosion of a 460 mm (18 in.) Diam Feedwater Line Break
Authors: Czajkowski Carl J.
Published: May 2019

A 460 mm (18 in.) diam suction line to the main feed water pump for a nuclear power plant failed in a violent, catastrophic manner. Samples of pipe, elbow, and weld materials (ASTM A106 grade B carbon steel, ASTM A234 grade WPB carbon steel, and E7018 carbon steel electrode, respectively) from the suction line were analyzed. Evidence of overall thinning of the elbow and pipe material and ductile tearing of fractures indicated that the feed water pipe failed as a result of an erosion corrosion mechanism, which thinned the wall sufficiently to cause rapid, ductile tearing of the material after its design stress had been exceeded. It was recommended that steel with a higher chromium content be used to mitigate the erosion corrosion potential in the lines and that more rigorous nondestructive (ultrasonic) examinations be performed.
Fatigue Failure of a Carburized Steel Gear From a Helicopter Transmission
Authors: Roth Martin , Sander Karen
Published: May 2019

The failure of a spiral bevel gear from the transmission of a helicopter was discovered when the transmission was removed after an in-flight incident. Two adjacent teeth from the carburized AISI 9310 steel gear were found to have undergone fatigue failure. Internal initiation occurred in a region depleted of chromium and nickel. This condition coincides with a microstructural inhomogeneity consisting of large, soft ferrite grains. Its origin was probably contamination of the solidifying ingot during the consumable vacuum arc remelting operation.
Flow-Induced Vibration Fatigue of Stainless Steel Impeller Blades in a Circulating Water Pump
Authors: Brown Samuel J. , Bravenec Edward V.
Published: May 2019

Several large-diameter type 304L stainless steel impeller/propeller blades in a circulating water pump failed after approximately 8 months of operation. The impeller was a single casting that had been modified with a fillet weld buildup at the blade root. Visual examination indicated that the fracture originated near the blade-to-hub attachment in the area of the weld buildup. Specimens from four failed castings and from an impeller that had developed cracks prior to design modification were subjected to a complete analysis. A number of finite-element-method computer models were also constructed. It was determined that the blades failed by fatigue that had been accelerated by stress-corrosion cracking. The mechanism of failure was flow-induced vibration, in which the vortex-shedding frequencies of the blades were attuned to the natural frequency of the blade/hub configuration. A number of solutions involving material selection and impeller redesign were recommended.
Fracture of a Turbine Impeller Shaft
Authors: D'Antonio Carmine
Published: May 2019

An ASTM A193-83a grade B7 (AISI 4140) steel turbine impeller shaft fractured after 2 months of service. Failure had initiated at three separate points around the periphery of the shaft, each associated with one of three keyways. SEM fractography, metallography, and chemical analysis indicated that the mechanism of fracture initiation was torsional fatigue. Intermittent deceleration and acceleration resulting from power surges during operation of the turbine caused torsional vibration and was considered the most probable source of the required cyclic stress. Final failure took place by torsional shear.
Fractures of Hot Dip Galvanized Steel Anchor Bolts in Chemical Plant Construction Project
Authors: Kerns George E. , Mighton Charles E.
Published: May 2019

Galvanized A36 steel unsleeved shear-type anchor bolts failed during installation. The galvanized steel bolts were approximately 18 mm (0.7 in.) in diameter with a 90 deg bend between the long and short legs. As-fractured, sawcut, and unfractured specimens were examined. Failure analysis revealed dark thumbnail regions at the fracture origins and a very narrow and uniform shear lip. The thumbnail region exhibited zinc deposits with no apparent fracture detail, indicating preexisting cracks that had occurred before galvanizing. The balance of the fracture exhibited a transgranular mode with cleavage and ductile, dimpled shear. Hardness values as high as 35 HRC were measured in the bend area. The as-galvanized bolts fractured in a brittle manner. Failure was attributed to improper bending of the bolts, which provided a severely cold-worked bend area susceptible to strain-age embrittlement.
Failure of a Tied Universal Expansion Joint
Authors: Bowman Ralph D.
Published: May 2019

A tie rod, nut, and bellows from a failed 610 mm (24 in.) diam tied universal expansion joint that carried tail gases consisting of N2 + O2 with slight traces of nitrogen oxides and water were examined. The materials were SA 193-B7 (AISI 4140), SA 194–214, and Incoloy 800H, respectively. Visual examination of the bellows revealed cracks in heavily cold-worked areas (both inside and outside) and considerable corrosion. SEM analysis showed a classical intergranular failure pattern with microcracking. The threaded tie rod microstructure contained spheroidized carbide that was more pronounced at the tie rod end of the failure. Energy-dispersive X-ray analysis of fracture surfaces from the bellows showed the presence of chlorine and sulfur. Failure of the bellows was attributed to stress-corrosion cracking, with chlorine and sulfur being the corroding agents. The rod damage was the result of failure of the bellows, which allowed escaping hot gases to impinge on the tie rods and heat them to approximately 595 deg C (1100 deg F). It was recommended that the insulation be analyzed to determine the origin of the chlorine and sulfur and that it be replaced if necessary.
Brittle Fracture of the Tension Flange of a Steel Box-Girder Bridge
Authors: Hartbower Carl E.
Published: May 2019

A catastrophic brittle fracture occurred in a welded steel (ASTM A517 grade H) trapezoidal cross-section box girder while the concrete deck of a large bridge was being poured. The failure occurred across the full width of a 57 mm (214 in.) thick, 760 mm (30 in.) wide flange and arrested 100 mm (4 in.) down the slant web. Failure analysis revealed a major deficiency in fracture toughness. The failure occurred as a brittle fracture after the formation of a welding hot crack and approximately 40 mm (112 in.) of slow crack growth. It was recommended that bridges fabricated from this grade of steel undergo frequent inspection and that stringent test requirements be imposed as a condition of use in non-redundant main load-carrying components.
Failure of an I-Beam
Authors: Dayal R.K. , Gnanamoorthy J.B. , Rodriguez P.
Published: May 2019

An I-beam of IS-226 specification—I-section dimensions of 450 x l50 x 10 mm (17.7 x 5.9 x 0.4 in.) and a length of 12.41 m (40.7ft)—was flame cut into two section in an open yard near these a coast under normal weather conditions. After approximately 112h, the shorter section of he I-beam split catastrophically along the entire length through the web. Detailed investigation revealed segregation of high levels of carbon, sulfur and phosphorus in the middle of the web and high residual stresses attributed to rolling during fabrication. Flame cutting caused a change in the distribution of the residual stresses, which, aided by low fracture toughness due to the poor quality of the beam, resulted in failure. It was recommended that segregation be avoided in cast ingots used for I-beam manufacture by implementing a better quality-control procedure.