117 research outputs found
IEEE 802.15.4e: a Survey
Several studies have highlighted that the IEEE 802.15.4 standard presents a number of limitations such as low reliability, unbounded packet delays and no protection against interference/fading, that prevent its adoption in applications with stringent requirements in terms of reliability and latency. Recently, the IEEE has released the 802.15.4e amendment that introduces a number of enhancements/modifications to the MAC layer of the original standard in order to overcome such limitations. In this paper we provide a clear and structured overview of all the new 802.15.4e mechanisms. After a general introduction to the 802.15.4e standard, we describe the details of the main 802.15.4e MAC behavior modes, namely Time Slotted Channel Hopping (TSCH), Deterministic and Synchronous Multi-channel Extension (DSME), and Low Latency Deterministic Network (LLDN). For each of them, we provide a detailed description and highlight the main features and possible application domains. Also, we survey the current literature and summarize open research issues
A Localized Slot Allocation Algorithm for Wireless Sensor Networks
While energy efficiency is typically considered the
major concern in wireless sensor networks (WSNs), many
real-life applications also require reliability, timeliness, and
scalability. In such scenarios, Time Division Multiple Access
(TDMA) is typically used for data communication, as it avoids
collisions and provides predictable latency and minimum
energy consumption. TDMA requires a slot scheduling
algorithm to allocate transmission slots to sensor nodes. In
this paper, we propose a decentralized slot allocation
algorithm which is localized and self adaptive, i.e., each node
selects its slot(s) and adapts its behavior only basing on
locally-available information. We derive analytically the time
taken by the algorithm and the average energy consumed by
the network to achieve a complete schedule. We also show
that our solution performs significantly better than another
previous similar algorithm
Just-in-Time Adaptive Algorithm for Optimal Parameter Setting in 802.15.4 WSNs
Recent studies have shown that the IEEE 802.15.4 MAC protocol suffers from severe limitations, in terms
of reliability and energy efficiency, when the CSMA/CA parameter setting is not appropriate. However,
selecting the optimal setting that guarantees the application reliability requirements, with minimum
energy consumption, is not a trivial task in wireless sensor networks, especially when the operating
conditions change over time. In this paper we propose a Just-in-Time LEarning-based Adaptive Parameter
tuning (JIT-LEAP) algorithm that adapts the CSMA/CA parameter setting to the time-varying operating
conditions by also exploiting the past history to find the most appropriate setting for the current
conditions. Following the approach of active adaptive algorithms, the adaptation mechanism of JIT-LEAP
is triggered by a change detection test only when needed (i.e., in response to a change in the operating
conditions). Simulation results show that the proposed algorithm outperforms other similar algorithms,
both in stationary and dynamic scenarios
Strategies for Optimal MAC Parameter Setting in IEEE 802.15.4 Wireless Sensor Networks: a Performance Comparison
Recent studies have shown that the IEEE 802.15.4
MAC protocol may suffer from severe limitations in terms of
reliability and energy efficiency if a non appropriate
parameter setting is used. Hence, a number of solutions have
been proposed to select the optimal parameter setting to
provide reliability with minimum energy consumption. In this
paper we compare, by simulation, three different algorithms
that take different approaches to the problem, namely offline
computation, model-based adaptation, and measurement-based
adaptation. We show that adaptive algorithms perform well,
however the model-based adaptive approach has some
limitations that make it unsuitable in practical scenarios,
where operating conditions may vary over time and
transmission errors cannot be neglected. Instead, the
measurement-based adaptive approach is flexible and
effectiv
Standard model anomalies: Lepton flavour non-universality and lepton g-2
We critically analyze the body of results that hints to the existence of New
Physics from possible violations of lepton universality observed by the LHCb
experiment in the ratios and to the lepton
anomalies. The analysis begins with a theoretical, in depth, study of the
ratios and as well as the process . Here we consider the impact of complex Wilson coefficients and
derive constraints on their imaginary and real parts. We then move to a
comprehensive comparison with experimental results. We show that, by fitting a
single Wilson coefficient, the deviations from the Standard Model are at the
level when including only the hadronic insensitive observables
while it increases to when including also the hadronic sensitive
ones. When switching on all relevant Wilson coefficients and combining both
hadronic sensitive and insensitive data into the fit, the deviation from the
Standard Model peaks at 7.2 and decreases at the level if
we assume that the central values of and are taken to be
unity. We further estimate the non-perturbative long distance hadronic
contributions and show that their inclusion still requires New Physics to fit
the data. We then introduce the lepton anomalies results. Different
theoretical models are considered that can explain the discrepancies from the
Standard Model. In the final part of our work we estimate the impact of the
forthcoming data from LHCb (coming from LHC Run3) and Belle II, when it will
have accumulated about
Occult HCV Infection: An Unexpected Finding in a Population Unselected for Hepatic Disease
BACKGROUND:Occult Hepatitis C virus (HCV) infection is a new pathological entity characterized by presence of liver disease and absence or very low levels of detectable HCV-RNA in serum. Abnormal values of liver enzymes and presence of replicative HCV-RNA in peripheral blood mononuclear cells are also observed. Aim of the study was to evaluate occult HCV occurrence in a population unselected for hepatic disease. METHODOLOGY/PRINCIPAL FINDINGS:We chose from previous epidemiological studies three series of subjects (n = 276, age range 40-65 years) unselected for hepatic disease. These subjects were tested for the presence of HCV antibodies and HCV-RNA in plasma and in the peripheral blood mononuclear cells (PBMCs) by using commercial systems. All subjects tested negative for HCV antibodies and plasma HCV-RNA and showed normal levels of liver enzymes; 9/276 patients (3.3%) were positive for HCV-RNA in PBMCs, identifying a subset of subjects with potential occult HCV infection. We could determine the HCV type for 8 of the 9 patients finding type 1a (3 patients), type 1b (2 patients), and type 2a (3 patients). CONCLUSIONS:The results of this study show evidence that occult HCV infection may occur in a population unselected for hepatic disease. A potential risk of HCV infection spread by subjects harbouring occult HCV infection should be considered. Design of prospective studies focusing on the frequency of infection in the general population and on the clinical evolution of occult HCV infection will be needed to verify this unexpected finding
Dermatome mapping test in the analysis of anatomo-clinical correlations after inguinal hernia repair
Abstract
Background: Nerve identification is recommended in inguinal hernia repair to reduce or avoid postoperative pain.
The aim of this prospective observational study was to identify nerve prevalence and find a correlation between neuroanatomy
and chronic neuropathic postoperative inguinal pain (CPIP) after 6 months.
Material: A total of 115 patients, who underwent inguinal hernia mesh repair (Lichtenstein tension-free mesh
repair) between July 2018 and January 2019, were included in this prospective observational study. The mean age
and BMI respectively resulted 64 years and 25.8 with minimal inverse distribution of BMI with respect to age. Most
of the hernias were direct (59.1%) and of medium dimension (47.8%). Furthermore, these patients were undergoing
Dermatome Mapping Test in preoperatively and postoperatively 6 months evaluation.
Results: Identification rates of the iliohypogastric (IH), ilioinguinal (II) and genitofemoral (GF) nerves were 72.2%,
82.6% and 48.7% respectively. In the analysis of nerve prevalence according to BMI, the IH was statistically significant
higher in patients with BMI < 25 than BMI ≥ 25 P (< 0.05). After inguinal hernia mesh repair, 8 patients (6.9%) had
chronic postoperative neuropathic inguinal pain after 6 months. The CPIP prevailed at II/GF dermatome. The relation
between the identification/neurectomy of the II nerve and chronic postoperative inguinal pain after 6 months was
not significant (P = 0.542).
Conclusion: The anatomy of inguinal nerve is very heterogeneous and for this reason an accurate knowledge of
these variations is needed during the open mesh repair of inguinal hernias. The new results of our analysis is the statistically
significant higher IH nerve prevalence in patients with BMI < 25; probably the identification of inguinal nerve
is more complex in obese patients. In the chronic postoperative inguinal pain, the II nerve may have a predominant
role in determining postoperative long-term symptoms. Dermatome Mapping Test in an easy and safe method for
preoperative and postoperative 6 months evaluation of groin pain. The most important evidence of our analysis is
that the prevalence of chronic pain is higher when the nerves were not identified.
Keywords: Inguinal hernia, Inguinal nerves, Nerve identification, Pain, Follow-up
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Survival analysis of a multicentre, randomized phase 3 study on the optimization of the combination of bevacizumab with FOLFOX/OXXEL in patients with metastatic colorectal cancer (mCRC)
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