2,620 research outputs found
Cytoskeletal turnover and Myosin contractility drive cell autonomous oscillations in a model of Drosophila Dorsal Closure
Oscillatory behaviour in force-generating systems is a pervasive phenomenon
in cell biology. In this work, we investigate how oscillations in the
actomyosin cytoskeleton drive cell shape changes during the process of Dorsal
Closure, a morphogenetic event in Drosophila embryo development whereby
epidermal continuity is generated through the pulsatile apical area reduction
of cells constituting the amnioserosa (AS) tissue. We present a theoretical
model of AS cell dynamics by which the oscillatory behaviour arises due to a
coupling between active Myosin-driven forces, actin turnover and cell
deformation. Oscillations in our model are cell-autonomous and are modulated by
neighbour coupling, and our model accurately reproduces the oscillatory
dynamics of AS cells and their amplitude and frequency evolution. A key
prediction arising from our model is that the rate of actin turnover and Myosin
contractile force must increase during DC in order to reproduce the decrease in
amplitude and period of cell area oscillations observed in vivo. This
prediction opens up new ways to think about the molecular underpinnings of AS
cell oscillations and their link to net tissue contraction and suggests the
form of future experimental measurements.Comment: 17 pages, 6 figures; added references, modified and corrected Figs. 1
and 3, corrected typos, expanded discussio
Local Government Cybersecurity: How Michigan Counties Cope with Cyber Threats
In the age of global interconnectedness, we can all be equally affected by cyberattacks. Given the evolving nature of threat landscapes, comprehensive and preemptive practices are needed now more than ever to keep local government and citizen data secure. According to Recorded Future, in 2019, local U.S. government infrastructure was targeted by ransomware attacks 100 times. Cyber threats to local government systems have been increasing exponentially over the last several years, and the frequency of attacks will only continue to grow. Although cyberattacks on local government entities are rising every year, the challenges county IT departments face in combating the thousands of yearly attacks remains largely unexamined. This research study aims to understand how Michigan counties are currently protecting their IT systems, define the challenges they face in improving their cybersecurity posture, and address the potential improvements regarding current cybersecurity practices. This thesis addresses these goals through semi-structured interviews and a post-interview questionnaire with local government IT leaders across the State of Michigan. The results of this research study found challenges local Michigan governments face in enhancing their county's culture of cybersecurity, operating with limited funding and support, and inability to properly utilize state resources due to limited staffing needed to operationalize. A surprising finding was learning how essential communication and relationship building are to cybersecurity and how these relationships impact the culture of cybersecurity in an organization. By identifying these challenges, policymakers can introduce evidence-based policies that will address the essential needs of local Michigan counties and provide actionable and implementable solutions. Additionally, it will enable researchers and cybersecurity professionals to develop recommendations and mitigating solutions to improve local Michigan government cybersecurity.Master of Science in InformationSchool of Informationhttp://deepblue.lib.umich.edu/bitstream/2027.42/168552/1/20210511_Duque,Marilu_Final_MTOP_Thesis.pd
Fermion mass hierarchy and non-hierarchical mass ratios in SU(5) x U(1)_F
We consider a SU(5) x U(1)_F GUT-flavor model in which the number of effects
that determine the charged fermions Yukawa matrices is much larger than the
number of observables, resulting in a hierarchical fermion spectrum with no
particular regularities. The GUT-flavor symmetry is broken by flavons in the
adjoint of SU(5), realizing a variant of the Froggatt-Nielsen mechanism that
gives rise to a large number of effective operators. By assuming a common mass
for the heavy fields and universality of the fundamental Yukawa couplings, we
reduce the number of free parameters to one. The observed fermion mass spectrum
is reproduced thanks to selection rules that discriminate among various
contributions. Bottom-tau Yukawa unification is preserved at leading order, but
there is no unification for the first two families. Interestingly, U(1)_F
charges alone do not determine the hierarchy, and can only give upper bounds on
the parametric suppression of the Yukawa operators.Comment: 14 pages, one figure. Few typos correcte
Long-distance structure of the X(3872)
We investigate heavy quark symmetries for heavy meson hadronic molecules, and
explore the consequences of assuming the X(3872) and as an
isoscalar and an isovector hadronic molecules,
respectively. The symmetry allows to predict new hadronic molecules, in
particular we find an isoscalar bound state with a mass
about 10580 MeV and the isovector charmonium partners of the and
the states. Next, we study the
three body decay. This decay mode is more sensitive to the long-distance
structure of the X(3872) resonance than its and
decays, which are mainly controlled by the short distance part of the X(3872)
molecular wave function. We discuss the final state
interactions, which in some situations become quite important. Indeed in these
cases, a precise measurement of this partial decay width could provide precise
information on the interaction strength between the charm
mesons.Comment: Talk presented at the "XI International Conference on Hyperons, Charm
and Beauty Hadrons (BEACH 2014)", Birmingham (U.K.), July 201
From food waste to volatile fatty acids towards a circular economy
The food industrial sector generates large amounts of waste, which are often used for animal feed, for agriculture or landfilled. However, these wastes have a very reach composition in carbon and other compounds, which make them very attractive for valorization through biotechnological processes. Added value compounds, such as volatile fatty acids (VFAs), can be produced by anaerobic fermentation using pure cultures or mixed microbial cultures and food waste as carbon source. Research on valuable applications for VFAs, such as polyhydroxyalkanoates, bioenergy or biological nutrient removal, towards a circular economy is emerging. This enhances the sustainability and the economic value of food waste. This chapter reviews the various types of food waste used for VFAs production using mixed microbial cultures, the anaerobic processes, involved and the main applications for the produced VFAs. The main parameters affecting VFAs production are also discussed.publishersversionpublishe
Voluntary food sharing in pinyon jays: The role of reciprocity and dominance
Food sharing offers a clear example of prosocial behavior, in which one individual’s actions benefit another. Researchers have proposed a range of hypotheses that explain why food sharing may occur among unrelated individuals. Two such hypotheses, reciprocity and dominance, have been tested in many species, including fish, corvids, rats, bats, and primates, showing that (1) recipients sometimes reciprocate sharing back to previous donors and (2) dominant individuals share more than subordinates. Although primates dominate the study of prosocial behavior, active donation of food is actually quite rare in primates. In contrast, several corvid species spontaneously share food much more frequently. Here, we explored the role of reciprocity and dominance in spontaneous food sharing among male pinyon jays (Gymnorhinus cyanocephalus); a North American corvid species that exhibits high levels of social complexity. Unlike much of the previous work, we tested prosocial behavior among unrelated, non-pair bonded adults. We observed high levels of active sharing, and donors showed clear preferences with whom they shared. We found no evidence that pinyon jays reciprocated shares in either the short or long term. This was true for both sharing within-dyads (direct reciprocity) and sharing irrespective of most recent partner identity (generalized reciprocity). However, dominance influenced sharing in one of our groups, with dominant individuals sharing more than subordinates. This study highlights corvids as a fruitful model for the study of the proximate mechanisms underlying naturally occurring prosocial behaviors
Voluntary food sharing in pinyon jays: The role of reciprocity and dominance
Food sharing offers a clear example of prosocial behavior, in which one individual’s actions benefit another. Researchers have proposed a range of hypotheses that explain why food sharing may occur among unrelated individuals. Two such hypotheses, reciprocity and dominance, have been tested in many species, including fish, corvids, rats, bats, and primates, showing that (1) recipients sometimes reciprocate sharing back to previous donors and (2) dominant individuals share more than subordinates. Although primates dominate the study of prosocial behavior, active donation of food is actually quite rare in primates. In contrast, several corvid species spontaneously share food much more frequently. Here, we explored the role of reciprocity and dominance in spontaneous food sharing among male pinyon jays (Gymnorhinus cyanocephalus); a North American corvid species that exhibits high levels of social complexity. Unlike much of the previous work, we tested prosocial behavior among unrelated, non-pair bonded adults. We observed high levels of active sharing, and donors showed clear preferences with whom they shared. We found no evidence that pinyon jays reciprocated shares in either the short or long term. This was true for both sharing within-dyads (direct reciprocity) and sharing irrespective of most recent partner identity (generalized reciprocity). However, dominance influenced sharing in one of our groups, with dominant individuals sharing more than subordinates. This study highlights corvids as a fruitful model for the study of the proximate mechanisms underlying naturally occurring prosocial behaviors
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