Balian-Low Theorems in Several Variables

Recently, Nitzan and Olsen showed that Balian-Low theorems (BLTs) hold for discrete Gabor systems defined on $\mathbb{Z}_d$. Here we extend these results to a multivariable setting. Additionally, we show a variety of applications of the Quantitative BLT, proving in particular nonsymmetric BLTs in both the discrete and continuous setting for functions with more than one argument. Finally, in direct analogy of the continuous setting, we show the Quantitative Finite BLT implies the Finite BLT.Comment: To appear in Approximation Theory 16 conference proceedings volum

Consumer perceptions and demand for biofortified sweet potato-based biscuit: The case of Akarabo golden power biscuit in Rwanda

Certain varieties of sweet potato, especially orange-fleshed, are being promoted as part of the strategy to combat vitamin A deficiency in children and pregnant mothers. However, the consumption of sweet potato is more widespread in rural households where it is mainly boiled or eaten raw. The lack of value addition excludes majority of urban and higher income consumers who consider sweet potato an inferior product. At the same time low income urban households that would be interested in consuming sweet potatoes are not able to receive regular supplies from the rural producing areas due to perishability and bulkiness of the produce. This study examines consumer perceptions and demand for value-added biofortified biscuit derived from the vitamin A-rich orange fleshed sweet potato in Rwanda. Specifically, it assesses consumer perceptions and preference for biofortified biscuit, consumer willingness to pay for biofortified biscuit and consumers’ rating of the biofortified biscuit. It uses data from 1085 consumers stratified by income levels drawn from consumers in several urban markets of Rwanda. The study finds very favorable rating of the taste, color, packaging, looks, and sweetness for the biofortified biscuit. It also finds higher willingness to pay (WTP) for the biofortified biscuit among consumers from low and low/middle income groups. However, the study finds mixed results of WTP for the biofortifed sweet potato among consumers in the high income neigborhoods. Also, contrary to expectations, the study finds no evidence that knowledge of vitamin A increases consumer rating for the biofortified biscuit, suggesting that the promotion campaigns did not change the way consumers perceive the biofortified sweet potato, perhaps due to the way the campaign was designed. The study concludes that the biofortified biscuit is currently more acceptable among the low and low/middle end income categories probably because of greater promotion at these levels. However, it has a high potential for the high amd medium income groups as evident from the high rating it received among these groups. The paper discusses the implications of these findings and suggests a need for more detailed studies and indepth quantitative analysis of consumer perceptions and WTP for orange-fleshed sweet potato.Key words: Consumers, demand, biofortified biscuits, Rwand

Farmers’ perceptions of orange-fleshed sweetpotato: Do common beliefs about sweetpotato production and consumption really matter?

Efforts to combat vitamin A deficiency in developing countries have focused on the promotion of growing and consuming orange-fleshed sweetpotato (OFSP), among other crops. Past studies have found increased intake and even incomes among households that have been reached with information about nutritional benefits of OFSP. Consequently, efforts to scale up the production and consumption of OFSP are on-going in several African countries where vitamin A deficiency is a major problem. However, to date, few studies have systematically examined farmers’ perceptions and attitudes towards some of the attributes of OFSP. This paper interrogates some of the beliefs about the production and consumption of sweetpotato in general, and OFSP, in particular. It uses data generated using multi-stage sampling technique and involving 732 households in the Lake zone of Tanzania. The households were stratified into project participants (the intervention group) and non-participants (the control group). Within each household, data were collected from a male or female adult member (usually spouses) through personal interviews. Overall, 455 project participants and 277 non-participants were interviewed. This study uses both descriptive and exploratory factor analysis to assess some common beliefs about sweetpotato production and consumption. Contrary to the common beliefs, the study finds that sweetpotato is an important food crop to producing households, and that the common negative beliefs about sweetpotato production and consumption are not widely held. This study, therefore, recommends the need to upscale and out-scale efforts to sensitize farmers about the nutritional benefits of growing and consuming OFSP to counter the common negative beliefs about sweetpotato. In particular, educating farmers on the health effects of inadequate intake of Vitamin A and the importance of OFSP as its source can greatly influence their perceptions about OFSP. Further, there is need to increase efforts at breeding aimed at supplying the multiple desirable table and postharvest attributes of orange-fleshed sweetpotato, in addition to focusing on agronomic traits. For sub-Saharan Africa, such attributes include taste, storability of the tubers, dry matter content, and sugar content.Keywords: Sweetpotato, attributes, nutritional benefits, common beliefs, farmer perceptions, Tanzani

Turbulence and galactic structure

Interstellar turbulence is driven over a wide range of scales by processes including spiral arm instabilities and supernovae, and it affects the rate and morphology of star formation, energy dissipation, and angular momentum transfer in galaxy disks. Star formation is initiated on large scales by gravitational instabilities which control the overall rate through the long dynamical time corresponding to the average ISM density. Stars form at much higher densities than average, however, and at much faster rates locally, so the slow average rate arises because the fraction of the gas mass that forms stars at any one time is low, ~10^{-4}. This low fraction is determined by turbulence compression, and is apparently independent of specific cloud formation processes which all operate at lower densities. Turbulence compression also accounts for the formation of most stars in clusters, along with the cluster mass spectrum, and it gives a hierarchical distribution to the positions of these clusters and to star-forming regions in general. Turbulent motions appear to be very fast in irregular galaxies at high redshift, possibly having speeds equal to several tenths of the rotation speed in view of the morphology of chain galaxies and their face-on counterparts. The origin of this turbulence is not evident, but some of it could come from accretion onto the disk. Such high turbulence could help drive an early epoch of gas inflow through viscous torques in galaxies where spiral arms and bars are weak. Such evolution may lead to bulge or bar formation, or to bar re-formation if a previous bar dissolved. We show evidence that the bar fraction is about constant with redshift out to z~1, and model the formation and destruction rates of bars required to achieve this constancy.Comment: in: Penetrating Bars through Masks of Cosmic Dust: The Hubble Tuning Fork strikes a New Note, Eds., K. Freeman, D. Block, I. Puerari, R. Groess, Dordrecht: Kluwer, in press (presented at a conference in South Africa, June 7-12, 2004). 19 pgs, 5 figure

A step too far? Making health equity interventions in Namibia more sufficient

BACKGROUND: Equality of health status is the health equity goal being pursued in developed countries and advocated by development agencies such as WHO and The Rockefeller Foundation for developing countries also. Other concepts of fair distribution of health such as equity of access to medical care may not be sufficient to equalise health outcomes but, nevertheless, they may be more practical and effective in advancing health equity in developing countries. METHODS: A framework for relating health equity goals to development strategies allowing progressive redistribution of primary health care resources towards the more deprived communities is formulated. The framework is applied to the development of primary health care in post-independence Namibia. RESULTS: In Namibia health equity has been advanced through the progressive application of health equity goals of equal distribution of primary care resources per head, equality of access for equal met need and equality of utilisation for equal need. For practical and efficiency reasons it is unlikely that health equity would have been advanced further or more effectively by attempting to implement the goal of equality of health status. CONCLUSION: The goal of equality of health status may not be appropriate in many developing country situations. A stepwise approach based on progressive redistribution of medical services and resources may be more appropriate. This conclusion challenges the views of health economists who emphasise the need to select a single health equality goal and of development agencies which stress that equality of health status is the most important dimension of health equity

Syntaxin 16 is a master recruitment factor for cytokinesis

Recently it was shown that both recycling endosome and endosomal sorting complex required for transport (ESCRT) components are required for cytokinesis, in which they are believed to act in a sequential manner to bring about secondary ingression and abscission, respectively. However, it is not clear how either of these complexes is targeted to the midbody and whether their delivery is coordinated. The trafficking of membrane vesicles between different intracellular organelles involves the formation of soluble N-ethylmalei­mide–sensitive factor attachment protein receptor (SNARE) complexes. Although membrane traffic is known to play an important role in cytokinesis, the contribution and identity of intracellular SNAREs to cytokinesis remain unclear. Here we demonstrate that syntaxin 16 is a key regulator of cytokinesis, as it is required for recruitment of both recycling endosome–associated Exocyst and ESCRT machinery during late telophase, and therefore that these two distinct facets of cytokinesis are inextricably linked

Telepresence and the Role of the Senses

The telepresence experience can be evoked in a number of ways. A well-known example is a player of videogames who reports about a telepresence experience, a subjective experience of being in one place or environment, even when physically situated in another place. In this paper we set the phenomenon of telepresence into a theoretical framework. As people react subjectively to stimuli from telepresence, empirical studies can give more evidence about the phenomenon. Thus, our contribution is to bridge the theoretical with the empirical. We discuss theories of perception with an emphasis on Heidegger, Merleau-Ponty and Gibson, the role of the senses and the Spinozian belief procedure. The aim is to contribute to our understanding of this phenomenon. A telepresence-study that included the affordance concept is used to empirically study how players report sense-reactions to virtual sightseeing in two cities. We investigate and explore the interplay of the philosophical and the empirical. The findings indicate that it is not only the visual sense that plays a role in this experience, but all senses

Star forming dwarf galaxies

Star forming dwarf galaxies (SFDGs) have a high gas content and low metallicities, reminiscent of the basic entities in hierarchical galaxy formation scenarios. In the young universe they probably also played a major role in the cosmic reionization. Their abundant presence in the local volume and their youthful character make them ideal objects for detailed studies of the initial stellar mass function (IMF), fundamental star formation processes and its feedback to the interstellar medium. Occasionally we witness SFDGs involved in extreme starbursts, giving rise to strongly elevated production of super star clusters and global superwinds, mechanisms yet to be explored in more detail. SFDGs is the initial state of all dwarf galaxies and the relation to the environment provides us with a key to how different types of dwarf galaxies are emerging. In this review we will put the emphasis on the exotic starburst phase, as it seems less important for present day galaxy evolution but perhaps fundamental in the initial phase of galaxy formation.Comment: To appear in JENAM Symposium "Dwarf Galaxies: Keys to Galaxy Formation and Evolution", P. Papaderos, G. Hensler, S. Recchi (eds.). Lisbon, September 2010, Springer Verlag, in pres

Triggered optical coherence tomography for capturing rapid periodic motion

Quantitative cross-sectional imaging of vocal folds during phonation is potentially useful for diagnosis and treatments of laryngeal disorders. Optical coherence tomography (OCT) is a powerful technique, but its relatively low frame rates makes it challenging to visualize rapidly vibrating tissues. Here, we demonstrate a novel method based on triggered laser scanning to capture 4-dimensional (4D) images of samples in motu at audio frequencies over 100 Hz. As proof-of-concept experiments, we applied this technique to imaging the oscillations of biopolymer gels on acoustic vibrators and aerodynamically driven vibrations of the vocal fold in an ex vivo calf larynx model. Our results suggest that triggered 4D OCT may be useful in understanding and assessing the function of vocal folds and developing novel treatments in research and clinical settings

Physiological Stress and Refuge Behavior by African Elephants

Physiological stress responses allow individuals to adapt to changes in their status or surroundings, but chronic exposure to stressors could have detrimental effects. Increased stress hormone secretion leads to short-term escape behavior; however, no studies have assessed the potential of longer-term escape behavior, when individuals are in a chronic physiological state. Such refuge behavior is likely to take two forms, where an individual or population restricts its space use patterns spatially (spatial refuge hypothesis), or alters its use of space temporally (temporal refuge hypothesis). We tested the spatial and temporal refuge hypotheses by comparing space use patterns among three African elephant populations maintaining different fecal glucocorticoid metabolite (FGM) concentrations. In support of the spatial refuge hypothesis, the elephant population that maintained elevated FGM concentrations (iSimangaliso) used 20% less of its reserve than did an elephant population with lower FGM concentrations (Pilanesberg) in a reserve of similar size, and 43% less than elephants in the smaller Phinda reserve. We found mixed support for the temporal refuge hypothesis; home range sizes in the iSimangaliso population did not differ by day compared to nighttime, but elephants used areas within their home ranges differently between day and night. Elephants in all three reserves generally selected forest and woodland habitats over grasslands, but elephants in iSimangaliso selected exotic forest plantations over native habitat types. Our findings suggest that chronic stress is associated with restricted space use and altered habitat preferences that resemble a facultative refuge behavioral response. Elephants can maintain elevated FGM levels for ≥6 years following translocation, during which they exhibit refuge behavior that is likely a result of human disturbance and habitat conditions. Wildlife managers planning to translocate animals, or to initiate other management activities that could result in chronic stress responses, should consider the potential for, and consequences of, refuge behavior