Classical angular momentum of light: A paradox and its resolution

Angular momentum carried by a classical circularly polarized electromagnetic plane wave (light) appears to be identically zero inasmuch as its linear field-momentum density is directed along wave propagation, and, therefore, the angular momentum, being the integrated moment of the linear momentum density about an axis parallel to the direction of propagation, necessarily vanishes — in detail. This, however, contradicts the established fact that circularly polarized light does carry angular momentum that remains classically non-zero. The paradox is resolved in a physically transparent manner by treating this problem as that of a transversely bounded, and hence necessarily non-trans verse, electromagnetic wave propagating along a circular waveguide, in the limit as its radius tends to infinity. We get a non-zero angular momentum that bears the correct ratio to wave energy. This angular momentum derives essentially and exactly from the boundary conditions for the geometry considered. This is an interesting example of surface terms giving a volume (bulk) contribution, much as in the entirely different context of orbital diamagnetism, which was regarded as a surprise of theoretical physics by Rudolf Peierls.[1]     

A novel framework for identifying the interactions between biophysical and social components of an agricultural system: a guide for improving wheat production in Haryana,NW India

Purpose: The purpose of this study is to develop a conceptual framework with related analysis methodologies that identifies the influence of social environment on an established cropping system.

Design/methodology/approach: A stratified survey including 103 villages and 823 farmers was conducted in all districts of Haryana (India). Firstly, technical efficiency (TE) was modeled using biophysical data including grain yield, seeding rate, wheat varieties, tillage, sowing date, seed source, harvesting method and the application of fertilizer, herbicide and irrigation. The relationship between TE and social community factors such as farm size, farmer age, level of education and agricultural support programs was analyzed by regression tree.

Findings: TE was lower with the farmers who only have education to a primary standard. Farmers with high TE scores were mostly between 35 and 40 years of age, and a higher TE association was common for farmers who use technical publications. Social individual factors such as farmers’ views on the future of farming were also analyzed across different TE levels.

Practical implications: Farmers with lower TE are an obvious target for production improvement, particularly given the understanding that the overall production yield gap is small in Haryana.

Theoretical implications: Our conceptual framework shows a quantitative way to establish the socio-ecological linkage, and to identify the opportunities for changes in management with extension services leading to productivity improvement.

Originality/value: This paper provides a novel framework with detailed methodology to effectively identify the socio-economic factors that limit the biophysical production in an agricultural system.     

Postgraduate conception of research methodology: implications for learning and teaching

This qualitative inquiry investigates postgraduate students’ conceptions of research methodology and how it contributes to their learning. It explores factors likely to motivate student choice of research methodology and challenges in understanding research methods. The research was carried out at research-intensive universities in New Zealand and in Malaysia with similar postgraduate programmes. Participants were enrolled in Masters and Ph.D. programmes. Findings revealed that participants share a recognition that research methodology is a significant body of knowledge in postgraduate education. However, there were noticeable differences in perspectives regarding what constitutes research methodology and whether or not it should be conceived as a discipline. To some participants, learning research methodology is less of a discipline but rather an acquisition of a set of isolated facts and skills without necessarily acquiring a deeper understanding of research. Furthermore, postgraduate students choose research methodology based on a number of factors such as familiarity with a method, methodological orientation of the primary supervisor, the domain of study, and the nature of research problems pursued. Participants reported that the key challenges they face in understanding research methodology include framing research questions, understanding the theory or literature and its role in shaping research outcomes, and difficulties in performing data analysis.     

Effects of the COVID-19 pandemic on caregiver mental health and the child caregiving environment in a low-resource,rural context

Early child development has been influenced directly and indirectly by the COVID-19 pandemic, and these effects are exacerbated in contexts of poverty. This study estimates effects of the pandemic and subsequent population lockdowns on mental health, caregiving practices, and freedom of movement among female caregivers of children 6–27 months (50% female), in rural Bangladesh. A cohort (N = 517) was assessed before and during the pandemic (May–June, 2019 and July–September, 2020). Caregivers who experienced more food insecurity and financial loss during the pandemic reported larger increases in depressive symptoms (0.26 SD, 95% CI 0.08–0.44; 0.21 SD, 0.04–0.40) compared to less affected caregivers. Stimulating caregiving and freedom of movement results were inconsistent. Increases in depressive symptoms during the pandemic may have consequences for child development.     

Effect of integrating IoT courses at the freshman level on learning attitude and behaviour in the classroom

Education and Information Technologies - As a technology the effect of the Internet of Things (IoT) is so strong that it has changed the way of living. The transition is also apparent in the field...     

From conventional governance to e-democracy: Tracing the evolution of e-governance research trends using network analysis tools

The adoption of e-governing practices has revolutionised the administrative machinery of governments worldwide by improving efficiency, transparency, and accountability. Researchers and administrators often aim to identify emerging research fronts and the timeline of the evolution to forecast and implement technology. In this work, we systematically investigate the trajectory of the global evolution and emerging research fronts as well as the prospects for e-governance using citation network analysis. The growth curve fitted to the number of articles published per year shows that the research activities are still in the ascendant phase. We visualise the global main path of the citation network and investigate the patterns to trace the knowledge diffusion path, major milestones, and emerging research fronts. The cluster analysis identifies the major topics of research as administration and information system management, e-governance framework design, efficiency or quality evaluation, and the application of social networks and open data leading to e-democracy. The adoption of open data and social networking for user interactions with government that leads to participatory governance are the emerging research trends. We also identify research that can have a future impact based on network parameters. The results contribute to the literature by setting the focus of future research, and assisting administrators in selecting suitable models and methodologies, and manufacturers with the development of required technical devices suitable for the upcoming phase of symbiosis.     

Evaluation of serum adenosine deaminase and 5′-nucleotidase activities as probable markers in ovarian cancer

Adenosine deaminase (ADA) and 5′-nucleotidase (5′-NT) activities were measured in sera of patients with ovarian cancer and patients with benign ovarian tumour. The results were compared with that of a control group consisting of healthy women. ADA levels were significantly increased (P<0.001) in the ovarian cancer group (n=50) but not in the benign group (n=28) when compared to the controls (n=20). The results indicate that ADA and 5′-NT levels may help to differentiate malignant conditions from benign tumours of the ovary in addition to the existing tests such as serum CA-125 levels and histopathological study.     

Effect of feeding Carica papaya (Papita) fruits on blood lipid profile of albino rabbits

Effect of feeding ripe and unripe papaya fruit pulps were investigated on blood lipid profile of normal male adult albino rabbits by giving them pulps separately at the dose of 15 and 30g per day along with standard diet over a period of six weeks. As compared to controls both fruit pulps resulted in highly significant (p<0.001) and consistent lowering of serum cholesterol, low density lipoprotein cholesterol and triglycerides and elevation in phospholipids and high density lipoprotein cholesterol levels at 1,3 and 6 weeks of fruit pulp feeding indicating a dose dependent effect. Observations clearly support medicinal value ofC. Papaya in the management of atherosclerosis, fatty liver, ischaemic changes and consequential myocardial infarction.     

External quality assessment of RIA for thyroid related hormones

An external quality assessment was conducted for RIA of thyroid related hormones. Thirtyfive laboratories (35 for T₄, 34 for T₃ and 23 for TSH) from different parts of country participated in the programme. Twentyfour samples (16 pools: 5 simple and 11 manipulated pools) in 8 batches, 3 per batch per month were sent for analysis of T₄, T₃ and TSH. Some of the samples were repeated 3 times at different occasions to assess the imprecision of the laboratory. The overall mean percent CV obtained for T₄, T₃ and TSH were 22.7, 36.32 and 52.38 respectively. The recovery for added T₄ was 86.73% while that for T₃ was 117.4%. A large variation was obtained for recovery of TSH. For T₄ estimations, 13 laboratories had a desirable performance i. e. bias less than ±10.0% and variability of bias (VB) and imprecision (IP) less than 15.0%. None of the laboratories had a desirable performance for T₃ or TSH. The number of laboratories with acceptable performance i. e. bias between ±10.0–15.0%, VB and IP between 20.0–25.0% for T₄, T₃ and TSH were 4, 3 and 0 respectively. The number of laboratories which required attention (bias between ±15.0–20.0%; VB and IP between 20.0–25.0%) were 5,7 and 1 respectively. The unacceptable results with larger bias, VB and IP for T₄, T₃ and TSH were 6, 18 and 17 respectively. Our results are in general agreement that the performance of T₄ assay is better than T₃ and both in turn are much better than TSH. Quantitation of circulating thyroid hormones (TH) viz. tri-iodothyronine (T₃), thyroxine (T₄) and thyroid stimulating hormone (TSH), which form the largest percentage of hormones estimated in a clinical laboratory is mainly done by radio-immunoassay (RIA) procedures. The reliability and reproducibility of these assays are generally monitored by using internal quality control (IQC) samples in every assay batch. Thus, the IQC provides information whether the assay results are satisfactory and can be released. However, external quality assessment (EQA) is a procedure whereby an external agency undertakes evaluation of the quality of an analytical service by providing samples for analysis to individual laboratories performing the assay. The data gathered is analysed collectively. EQA therefore provides a means by which performance of a laboratory is assessed in relation to other laboratories and matching the assay unbiased by removing systematic error, if present. This is important since RIA procedure involves several steps (collection and storage of samples, quality of the reagents, procedure followed for performance of an assay, counting equipment used and the mode of the data analysis) and therefore prone to systematic errors. We therefore undertook the EQA programme for assessment of thyroid related hormones as a joint collaborative project of Bhabha Atomic Research Centre, India and International Atomic Energy Agency.     

Blood glutathione peroxidase and selenium in abortion

This study was carried out to estimate the levels of glutathione peroxidase and selenium in blood of abortion cases. Glutathione peroxidase and selenium were determined in 52 abortion cases (22 in 1^st trimester, 30 in second trimester), 45 normal pregnant cases and 25 nonpregnant control cases. The selenium concentration in whole blood and plasma in abortion cases was almost the same as in normal pregnant women but significantly low when compared with the control non-pregnant group. The glutathione levels was higher in abortion cases when compared with normal pregnant and non-pregnant control groups. Red cell and plasma glutathione peroxidase activities of women who had abortion were significantly lower compared with both non-pregnant control group and normal pregnancies.