3,847 research outputs found
Address resolution protocol optimization
This paper proposes an improved Address Resolution Protocol (ARP) for Ethernet-based networks. In the proposed alternative method, the ARP request packets are not broadcasted but instead unicasted to an ARP server which will have all the mappings of all the hosts connected to the network. This significantly reduces ARP signaling and processing overhead. The ARP server obtains the mappings through a novel passive method that does not introduce additional overhead in the network. Furthermore, the use of the ARP server makes it much easier to secure the network against certain attacks like ARP poisoning
Long time Solutions for a Burgers-Hilbert Equation via a Modified Energy Method
We consider an initial value problem for a quadratically nonlinear inviscid
Burgers-Hilbert equation that models the motion of vorticity discontinuities.
We use a modified energy method to prove the existence of small, smooth
solutions over cubically nonlinear time-scales
The return of the Andromedids meteor shower
The Andromedid meteor shower underwent spectacular outbursts in 1872 and
1885, producing thousands of visual meteors per hour and described as `stars
fell like rain' in Chinese records of the time. The shower originates from
comet 3D/Biela whose disintegration in the mid-1800's is linked to the
outbursts, but the shower has been weak or absent since the late 19th Century.
This shower returned in December 2011 with a zenithal hourly rate of
approximately 50, the strongest return in over a hundred years. Some 122
probable Andromedid orbits were detected by the Canadian Meteor Orbit Radar.
The shower outburst occurred during 2011 Dec 3-5. The radiant at RA
+ and Dec + is typical of the `classical' Andromedids of
the early 1800's, whose radiant was actually in Cassiopeia. The orbital
elements indicate that the material involved was released before 3D/Biela's
breakup prior to 1846. The observed shower in 2011 had a slow geocentric speed
(16 km s) and was comprised of small particles: the mean measured mass
from the radar is kg corresponding to radii of 0.5 mm at
a bulk density of 1000 kg/m.
Numerical simulations of the parent comet indicate that the meteoroids of the
2011 return of the Andromedids shower were primarily ejected during 3D/Biela's
1649 perihelion passage. The orbital characteristics, radiant, timing as well
as the absence of large particles in the streamlet are all consistent with
simulations. Predictions are made regarding other appearances of the shower in
the years 2000-2047 based on our numerical model. We note that the details of
the 2011 return can, in principle, be used to better constrain the orbit of
3D/Biela prior to the comets first recorded return in 1772.Comment: submitted to the Astronomical Journal Sep 22 201
Developing community-based engagement in Smart Cities: A design-computational thinking approach
Smart Cities development has progressed rapidly
with Internet of Things (IoT), ambient intelligence and
increasingly, crowdsourcing. Engaging the community thus
plays a key role in developing meaningful communal growth
along with other stakeholders. This paper briefly presents a
pilot study on developing computational perspectives for
community-based engagement and innovations in Smart
Cities for the young and thereafter, to explore possibilities of engaging seniors in self and community development, and the young and old in community-based engagement and possibly in the future, the development of viable values-based innovations in information systems
Learning e-commerce web design engineering: Towards discovery of service innovational opportunities
Graduates are expected to be skilled across disciplines
and provide holistic solutions. Hence, scaffolding is crucial as transfer of learning does not occur naturally and teaching learning strategies found to be effective for experts may not be adopted similarly for novice learners. We hypothesize that if we can help students to model in relation to the ecosystem, they should be able to identify or discover opportunities, strategically assess technologies and create new innovations and interactions
for e-commerce Websites. For goal-based scaffolding, we use
technology-assisted design thinking, embedded formative
assessments. We study more effective ways to develop: a) skills useful to the design and development of sustainable Web systems and services and possibly sustainable smart services in the future by relating business to technology and impacts on society; b) epistemic agency for lifelong learning
Adverse Effects of Perinatal Nicotine Exposure on Reproductive Outcomes
Nicotine exposure during pregnancy through cigarette smoking, nicotine replacement therapies or e-cigarette use continues to be awidespread public health problem, impacting both fetal and postnatal health. Yet, at this time, there remains limited data regarding the safety and efficacy in using these nicotine products during pregnancy. Notably, reports assessing the effect of nicotine exposure on postnatal health outcomes in humans, including reproductive health, are severely lacking. Our current understanding regarding the consequences of nicotine exposure during pregnancy is limited to a few animal studies, which do not comprehensively address the underlying cellular mechanisms involved. This paper aims to critically review the current knowledge from human and animal studies regarding the direct and indirect effects (e.g., obesity) of maternal nicotine exposure, regardless of its source, on reproductive outcomes in pregnancy and postnatal life. Furthermore, this review highlights several key cellular mechanisms involved in these adverse reproductive deficits including oxidative stress, inflammation, and endoplasmic reticulum (ER) stress. By understanding the interplay of the cellular mechanisms involved, further strategies could be developed to prevent the reproductive abnormalities resulting from exposure to nicotine in utero and influence informed clinical guidelines for pregnant women
Energy-Efficient Heterogeneous Cellular Networks with Spectrum Underlay and Overlay Access
In this paper, we provide joint subcarrier assignment and power allocation
schemes for quality-of-service (QoS)-constrained energy-efficiency (EE)
optimization in the downlink of an orthogonal frequency division multiple
access (OFDMA)-based two-tier heterogeneous cellular network (HCN). Considering
underlay transmission, where spectrum-efficiency (SE) is fully exploited, the
EE solution involves tackling a complex mixed-combinatorial and non-convex
optimization problem. With appropriate decomposition of the original problem
and leveraging on the quasi-concavity of the EE function, we propose a
dual-layer resource allocation approach and provide a complete solution using
difference-of-two-concave-functions approximation, successive convex
approximation, and gradient-search methods. On the other hand, the inherent
inter-tier interference from spectrum underlay access may degrade EE
particularly under dense small-cell deployment and large bandwidth utilization.
We therefore develop a novel resource allocation approach based on the concepts
of spectrum overlay access and resource efficiency (RE) (normalized EE-SE
trade-off). Specifically, the optimization procedure is separated in this case
such that the macro-cell optimal RE and corresponding bandwidth is first
determined, then the EE of small-cells utilizing the remaining spectrum is
maximized. Simulation results confirm the theoretical findings and demonstrate
that the proposed resource allocation schemes can approach the optimal EE with
each strategy being superior under certain system settings
Nicotine Directly Induces Endoplasmic Reticulum Stress Response in Rat Placental Trophoblast Giant Cells
Nicotine exposure during pregnancy leads to placental insufficiency impairing both fetal and neonatal development. Previous studies from our laboratory have demonstrated that in rats,nicotine augmented endoplasmic reticulum (ER) stress in association with placental insufficiency, however, the underlying mechanisms remain elusive. Therefore, we sought to investigate the possible direct effect of nicotine on ER stress in Rcho-1 rat placental trophoblastgiant (TG) cells during differentiation. Protein and/or mRNA expression of markers involved in ER stress (e.g., phosphorylated PERK, eIF2α, CHOP, BiP/GRP78) and trophoblast giant cell differentiation and function (e.g., Pl-1, Pgf, Hsd11b1, and Hsd11b2) were quantified via Western blot or Real-Time PCR. Nicotine treatment led to dose-dependent increases in the phosphorylation of PERK[Thr981] and eIF2α[Ser51], whereas pre-treatment with a nicotinic acetylcholine receptor (nAChR) antagonist (mecamylamine hydrochloride) blocked the induction of PERK phosphorylation, verifying the direct involvement of nicotine and nAChR binding. We next investigated select target genes known to play essential roles in placental TG cell differentiation and function (Pl-1, Pgf, Hsd11b1, and Hsd11b2), and found that nicotine significantly augmented the mRNA levels of Hsd11b1 in a dose-dependent manner. Furthermore, using Tauroursodeoxycholic acid (TUDCA), a safe bile acid known to improve protein chaperoning and folding, we were able to prevent nicotine-induced increases in both PERK phosphorylation and Hsd11b1 mRNA levels, revealing a potential novel therapeutic approach to reverse the deleterious effects of nicotine exposure in pregnancy. Collectively, these results implicate that nicotine, acting through its receptor, can directly augment ER stress and impair placental function
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