388 research outputs found
Outage Probability and Outage-Based Robust Beamforming for MIMO Interference Channels with Imperfect Channel State Information
In this paper, the outage probability and outage-based beam design for
multiple-input multiple-output (MIMO) interference channels are considered.
First, closed-form expressions for the outage probability in MIMO interference
channels are derived under the assumption of Gaussian-distributed channel state
information (CSI) error, and the asymptotic behavior of the outage probability
as a function of several system parameters is examined by using the Chernoff
bound. It is shown that the outage probability decreases exponentially with
respect to the quality of CSI measured by the inverse of the mean square error
of CSI. Second, based on the derived outage probability expressions, an
iterative beam design algorithm for maximizing the sum outage rate is proposed.
Numerical results show that the proposed beam design algorithm yields better
sum outage rate performance than conventional algorithms such as interference
alignment developed under the assumption of perfect CSI.Comment: 41 pages, 14 figures. accepted to IEEE Transactions on Wireless
Communication
New Classes of Distributed Time Complexity
A number of recent papers -- e.g. Brandt et al. (STOC 2016), Chang et al.
(FOCS 2016), Ghaffari & Su (SODA 2017), Brandt et al. (PODC 2017), and Chang &
Pettie (FOCS 2017) -- have advanced our understanding of one of the most
fundamental questions in theory of distributed computing: what are the possible
time complexity classes of LCL problems in the LOCAL model? In essence, we have
a graph problem in which a solution can be verified by checking all
radius- neighbourhoods, and the question is what is the smallest such
that a solution can be computed so that each node chooses its own output based
on its radius- neighbourhood. Here is the distributed time complexity of
.
The time complexity classes for deterministic algorithms in bounded-degree
graphs that are known to exist by prior work are , , , , and . It is also known
that there are two gaps: one between and , and
another between and . It has been conjectured
that many more gaps exist, and that the overall time hierarchy is relatively
simple -- indeed, this is known to be the case in restricted graph families
such as cycles and grids.
We show that the picture is much more diverse than previously expected. We
present a general technique for engineering LCL problems with numerous
different deterministic time complexities, including
for any , for any , and
for any in the high end of the complexity
spectrum, and for any ,
for any , and
for any in the low end; here
is a positive rational number
Advantages and challenges of using capture-the-flag games in cyber security education
Abstract. The world around us is digitalising fast and internet is almost everywhere, which makes cyber security an inevitable part of our lives. This thesis explored if capture-the-flag (CTF) games are viable solution to teaching cyber security. Research method used was a narrative literature review. 16 academic sources were reviewed, nine of which used quantitative research methods.
Prior research showed that capture-the-flag games had a positive impact on participants’ motivation and engagement levels. In some studies, capture-the-flag games were found to lead to statistically better learning results and better understanding of computer security. Other resulting advantages were better practical knowledge in cyber security, increased grades and increased confidence in cyber security skills.
Organising such games was found to be a challenging job and consequently, knowledge is required from both organisers and participants of capture-the-flag games. Capture-the-flag game environments are complex and support staff is needed in organising such games. Designing the challenges to be appropriately challenging was found to be a difficult task and a related problem was challenge avoidance. Quality assurance was found to be an important, but often overlooked part of the design process.
In some papers, plagiarism was mentioned being a trouble. Automated approval of flag submissions in the games could lead to students illicitly sharing flags. Besides plagiarism, other ethical implications of teaching offensive computer security methods were a concern to many authors, but no quantitative research on this topic has so far been conducted
In vitro inhibitory activities of the extract of Hibiscus sabdariffa L. (family malvaceae) on selected cytochrome p450 isoforms
Literature is scanty on the interaction potential of Hibiscus sabdariffa L., plant extract with other drugs and the affected targets. This study was conducted to investigate the cytochrome P450 (CYP) isoforms that are inhibited by the extract of Hibiscus sabdariffa L. in vitro. The inhibition towards the major drug metabolizing CYP isoforms by the plantextract were estimated in human liver microsomal incubations, by monitoring the CYP-specific model reactions through previously validated N-in-one assay method. The ethanolic extract of Hibiscus sabdariffa showed inhibitory activities against nine selected CYP isoforms: CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 andCYP3A4. The concentrations of the extract which produced 50% inhibition of the CYP isoforms ranged from 306 ìg/ml to 1660 ìg/ml, and the degree of inhibition based on the IC50 values for each CYP isoform was in the following order: CYP1A2 > CYP2C8 > CYP2D6 > CYP2B6 > CYP2E1 > CYP2C19 > CYP3A4 >> CYP2C9 >> CYP2A6. Ethanolic extract of Hibiscus sabdariffa caused inhibition of CYP isoforms in vitro. These observed inhibitions may not cause clinically significant herb-drug interactions; however, caution may need to be taken in co-administering the water extract of Hibiscus sabdariffa with other drugs until clinical studies are available to further clarify these findings.Key words: Cytochrome P450, Hibiscus sabdariffa, Herb-drug interaction, Anthocyanin, N-in-one assay
Crural Index and extensive atherosclerosis of crural vessels are associated with long-term cardiovascular mortality in patients with symptomatic peripheral artery disease
Background and aims: Limited data exist on the association of the anatomical distribution of atherosclerotic lesions and the extent of atherosclerosis at defined arterial segments with life expectancy. We recently presented a new classification of the extent of atherosclerosis in crural vessels and showed that Crural Index (CIx) was associated with mid-term survival of symptomatic peripheral artery disease (PAD) patients. This study evaluates the significance of the extent of crural atherosclerosis on long-term cardiovascular mortality. Methods: 887 consecutive patients with PAD, admitted for digital subtraction angiography (DSA) at Turku University Hospital Department of Vascular Surgery (Turku, Finland) between January 1st, 2009 and July 30th, 2011, were retrospectively analysed. Each crural angiographic image was graded according to CIx criteria. Aorto-iliac and femoro-popliteal arterial segments were similarly graded according to modified TASC II criteria. CIx was used as the categorical variable for the extent of atherosclerosis in crural vessels for survival analysis. Survival was also evaluated with respect to which arterial segment was most severely affected. Causes of death were provided by the Cause of Death Registry of Statistics Finland, updated on January 23rd, 2017. Results: Altogether, 408 (46%) patients died during follow-up. The majority of deaths were due to cardiovascular causes (n = 246, 60%). Cardiovascular mortality was strongly associated with a high CIx (CIx III (Hazard ratio (HR) 2.16, Confidence interval (CI) 95% 1.23-3.80, p = 0.007)) and CIx IV (HR 3.513, 95% CI 1.93-4.565, p <0.001), as compared to CIx 0. In patients having the crural segment as the most severely affected arterial segment, cardiovascular mortality was significantly increased (HR 2.321, 95% CI 1.45-3.73, p <0.001), as was overall mortality (HR 2.177, 95% CI 1.53-3.10, p <0.001). Conclusions: High Crural Index and extensive crural vessel atherosclerosis are associated with long-term cardiovascular mortality, and both may serve as useful indicators of survival among patients with symptomatic PAD. (c) 2017 Elsevier B.V. All rights reserved.Peer reviewe
Clinical Alarms in a Gynaecological Surgical Unit: A Retrospective Data Analysis
Alarm fatigue refers to the desensitisation of medical staff to patient monitor clinical alarms, which may lead to slower response time or total ignorance of alarms and thereby affects patient safety. The reasons behind alarm fatigue are complex; the main contributing factors include the high number of alarms and the poor positive predictive value of alarms. The study was performed in the Surgery and Anaesthesia Unit of the Women’s Hospital, Helsinki, by collecting data from patient monitoring device clinical alarms and patient characteristics from surgical operations. We descriptively analysed the data and statistically analysed the differences in alarm types between weekdays and weekends, using chi-squared, for a total of eight monitors with 562 patients. The most common operational procedure was caesarean section, of which 149 were performed (15.7%). Statistically significant differences existed in alarm types and procedures between weekdays and weekends. The number of alarms produced was 11.7 per patient. In total, 4698 (71.5%) alarms were technical and 1873 (28.5%) were physiological. The most common physiological alarm type was low pulse oximetry, with a total of 437 (23.3%). Of all the alarms, the number of alarms either acknowledged or silenced was 1234 (18.8%). A notable phenomenon in the study unit was alarm fatigue. Greater customisation of patient monitors for different settings is needed to reduce the number of alarms that do not have clinical significance
Cerebral Dopamine Neurotrophic Factor Diffuses Around the Brainstem and Does Not Undergo Anterograde Transport After Injection to the Substantia Nigra
Cerebral dopamine neurotrophic factor (CDNF) has shown therapeutic potential in rodent and non-human primate models of Parkinson's disease by protecting the dopamine neurons from degeneration and even restoring their phenotype and function. Previously, neurorestorative efficacy of CDNF in the 6-hydroxydopamine (6-OHDA) model of Parkinson's disease as well as diffusion of the protein in the striatum (STR) has been demonstrated and studied. Here, experiments were performed to characterize the diffusion and transport of supra-nigral CDNF in non-lesioned rats. We injected recombinant human CDNF to the substantia nigra (SN) of naive male Wistar rats and analyzed the brains 2, 6, and 24 h after injections. We performed immunohistochemical stainings using an antibody specific to human CDNF and radioactivity measurements after injecting iodinated CDNF. Unlike the previously reported striatonigral retrograde transport seen after striatal injection, active anterograde transport of CDNF to the STR could not be detected after nigral injection. There was, however, clear diffusion of CDNF to the brain areas surrounding the SN, and CDNF colocalized with tyrosine hydroxylase (TH)-positive neurons. Overall, our results provide insight on how CDNF injected to the SN may act in this region of the brain.Peer reviewe
Devon: Deformable Volume Network for Learning Optical Flow
State-of-the-art neural network models estimate large displacement optical
flow in multi-resolution and use warping to propagate the estimation between
two resolutions. Despite their impressive results, it is known that there are
two problems with the approach. First, the multi-resolution estimation of
optical flow fails in situations where small objects move fast. Second, warping
creates artifacts when occlusion or dis-occlusion happens. In this paper, we
propose a new neural network module, Deformable Cost Volume, which alleviates
the two problems. Based on this module, we designed the Deformable Volume
Network (Devon) which can estimate multi-scale optical flow in a single high
resolution. Experiments show Devon is more suitable in handling small objects
moving fast and achieves comparable results to the state-of-the-art methods in
public benchmarks
Mesencephalic Astrocyte-Derived Neurotrophic Factor (MANF) Elevates Stimulus-Evoked Release of Dopamine in Freely-Moving Rats
Neurotrophic factors (NTFs) hold potential as disease-modifying therapies for neurodegenerative disorders like Parkinson's disease. Glial cell line-derived neurotrophic factor (GDNF), cerebral dopamine neurotrophic factor (CDNF), and mesencephalic astrocyte-derived neurotrophic factor (MANF) have shown neuroprotective and restorative effects on nigral dopaminergic neurons in various animal models of Parkinson's disease. To date, however, their effects on brain neurochemistry have not been compared using in vivo microdialysis. We measured extracellular concentration of dopamine and activity of dopamine neurochemistry-regulating enzymes in the nigrostriatal system of rat brain. NTFs were unilaterally injected into the striatum of intact Wistar rats. Brain microdialysis experiments were performed 1 and 3 weeks later in freely-moving animals. One week after the treatment, we observed enhanced stimulus-evoked release of dopamine in the striatum of MANF-treated rats, but not in rats treated with GDNF or CDNF. MANF also increased dopamine turnover. Although GDNF did not affect the extracellular level of dopamine, we found significantly elevated tyrosine hydroxylase (TH) and catechol-O-methyltransferase (COMT) activity and decreased monoamine oxidase A (MAO-A) activity in striatal tissue samples 1 week after GDNF injection. The results show that GDNF, CDNF, and MANF have divergent effects on dopaminergic neurotransmission, as well as on dopamine synthetizing and metabolizing enzymes. Although the cellular mechanisms remain to be clarified, knowing the biological effects of exogenously administrated NTFs in intact brain is an important step towards developing novel neurotrophic treatments for degenerative brain diseases.Peer reviewe
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