The observation of possible reconnection events in the boundary changes of solar coronal holes

Coronal holes are large scale regions of magnetically open fields which are easily observed in solar soft X-ray images. The boundaries of coronal holes are separatrices between large scale regions of open and closed magnetic fields where one might expect to observe evidence of solar magnetic reconnection. Previous studies by Nolte and colleagues using Skylab X-ray images established that large scale (greater than or equal to 9 x 10(4) km) changes in coronal hole boundaries were due to coronal processes, i.e., magnetic reconnection, rather than to photospheric motions. Those studies were limited to time scales of about one day, and no conclusion could be drawn about the size and time scales of the reconnection process at hole boundaries. Sequences of appropriate Skylab X-ray images were used with a time resolution of about 90 min during times of the central meridian passages of the coronal hole labelled Coronal Hole 1 to search for hole boundary changes which can yield the spatial and temporal scales of coronal magnetic reconnection. It was found that 29 of 32 observed boundary changes could be associated with bright points. The appearance of the bright point may be the signature of reconnection between small scale and large scale magnetic fields. The observed boundary changes contributed to the quasi-rigid rotation of Coronal Hole 1

Multireference Alignment using Semidefinite Programming

The multireference alignment problem consists of estimating a signal from multiple noisy shifted observations. Inspired by existing Unique-Games approximation algorithms, we provide a semidefinite program (SDP) based relaxation which approximates the maximum likelihood estimator (MLE) for the multireference alignment problem. Although we show that the MLE problem is Unique-Games hard to approximate within any constant, we observe that our poly-time approximation algorithm for the MLE appears to perform quite well in typical instances, outperforming existing methods. In an attempt to explain this behavior we provide stability guarantees for our SDP under a random noise model on the observations. This case is more challenging to analyze than traditional semi-random instances of Unique-Games: the noise model is on vertices of a graph and translates into dependent noise on the edges. Interestingly, we show that if certain positivity constraints in the SDP are dropped, its solution becomes equivalent to performing phase correlation, a popular method used for pairwise alignment in imaging applications. Finally, we show how symmetry reduction techniques from matrix representation theory can simplify the analysis and computation of the SDP, greatly decreasing its computational cost

Inter-filament Attractions Narrow the Length Distribution of Actin Filaments

We show that the exponential length distribution that is typical of actin filaments under physiological conditions dramatically narrows in the presence of (i) crosslinker proteins (ii) polyvalent counterions or (iii) depletion mediated attractions. A simple theoretical model shows that in equilibrium, short-range attractions enhance the tendency of filaments to align parallel to each other, eventually leading to an increase in the average filament length and a decrease in the relative width of the distribution of filament lengths.Comment: 5 pages, 4 figure

Motivation to become an entrepreneur: a study of Nigerian women's decisions

Purpose – The paper aims to draw on rational choice theory (RCT) to explore factors underpinning the decision by female entrepreneurs in Nigeria to enter self-employment. Design/methodology/approach – A survey research design involving the use of questionnaire and structured interviews to obtain primary data was adopted. Primary data pertain to 300 female entrepreneurs currently engaged in their businesses in three states within the south-west of the country. A model developed from reviewed literature and multivariate logistic regression analysis was used to analyse data. Findings – Findings suggest the significance of “educational” and “family” capital, an “internal” orientation to social recognition as well as an “external” environment characterised by deregulation of the economy. Results broadly conform to RCT theory postulates of rational behaviour. Research limitations/implications – Inter-regional variances could not be addressed since the data are analysed in aggregate. Analysis of disaggregate data are required to study these differences and also those at the inter-sector (manufacturing/services, etc.) levels. Practical implications – Results from the study indicate that the government measures such as de-regulation which may as yet be in small measures have started to work and that these should be continued. The government can go a step further and identify entrepreneurs with characteristics described in this paper and provide them with the requisite help to get them started on the entrepreneurship route. Originality/value – The study makes a theoretical contribution by applying the lens of rational choice to this specific context. It also makes an original empirical contribution by focussing on an under-researched group by examining the influence of personal, social, market and environmental factors on the probability of females becoming entrepreneur

The female-centric portrait in advertisement: the study focused on television advertising in Sri Lanka

This research focuses on how women are portrayed in the various advertisements that are telecasted on different channels in Sri Lanka and the impact it makes on different people in the society, especially the problems that women face and the consequences they encounter as a result of it. It was in 1979 January that an idea was conceived to commence a television channel in Sri Lanka. In time to come many television channels came into being. At present there are more than 23 television channels operating in Sri Lanka. In Sri Lanka by fixing modern antennas and through internet viewers are able to view various global television channels. Television not only in Sri Lanka but also globally is expanding and globally is recognized as a media that reaches beyond barriers. There has been no systematic research done on the effects of advertisement on female. Therefore I have decided to consider this issue as my research topic. Thus my research objective is to study the birth, growth of advertisement in Sri Lanka and the effects of television advertisement telecasted on female and propose solutions for social development. As primary research methods interviews, questioners, discussions and field work research will be considered. As secondary research methods books, magazines, statistics and television advertisement will be utilized. A sample of viewers will be selected and they will be subjected to research to assess the effect of television advertisement on them with the objective of social development research. Viewers selected as a sample from the research area will be given a standardized questioner and their independent answers will be solicited and subjected to research. After research limits are established, a field work research will be conducted on the television channels that operate in the research area, their wave length and the viewers in the research area plus on the advertisement telecasted in the research area. A variety of books and magazines on television advertisement, society and social ethics will be read and how their subject content is related to the research will be considered. Various data related to television advertisements and its impact on the females will be gathered and subjected to research. In these circumstances people should understand Advertisement as a medium. They should be clearly aware of the various effects of advertisement on society. Media persons working on advertisement should posses’ social ethics. This gives way to social research in the field of Mass Media