25 research outputs found
Exploiting Device-to-Device Communications to Enhance Spatial Reuse for Popular Content Downloading in Directional mmWave Small Cells
With the explosive growth of mobile demand, small cells in millimeter wave
(mmWave) bands underlying the macrocell networks have attracted intense
interest from both academia and industry. MmWave communications in the 60 GHz
band are able to utilize the huge unlicensed bandwidth to provide multiple Gbps
transmission rates. In this case, device-to-device (D2D) communications in
mmWave bands should be fully exploited due to no interference with the
macrocell networks and higher achievable transmission rates. In addition, due
to less interference by directional transmission, multiple links including D2D
links can be scheduled for concurrent transmissions (spatial reuse). With the
popularity of content-based mobile applications, popular content downloading in
the small cells needs to be optimized to improve network performance and
enhance user experience. In this paper, we develop an efficient scheduling
scheme for popular content downloading in mmWave small cells, termed PCDS
(popular content downloading scheduling), where both D2D communications in
close proximity and concurrent transmissions are exploited to improve
transmission efficiency. In PCDS, a transmission path selection algorithm is
designed to establish multi-hop transmission paths for users, aiming at better
utilization of D2D communications and concurrent transmissions. After
transmission path selection, a concurrent transmission scheduling algorithm is
designed to maximize the spatial reuse gain. Through extensive simulations
under various traffic patterns, we demonstrate PCDS achieves near-optimal
performance in terms of delay and throughput, and also superior performance
compared with other existing protocols, especially under heavy load.Comment: 12 pages, to appear in IEEE Transactions on Vehicular Technolog
A Two-Level Game Theory Approach for Joint Relay Selection and Resource Allocation in Network Coding Assisted D2D Communications
Device-to-device (D2D) communication, which enables direct transmissions between mobile devices to improve spectrum efficiency, is one of the preferable candidate technologies for the next generation cellular network. Network coding, on the other hand, is widely used to improve throughput in ad hoc networks. Thus, the performance of D2D communications in cellular networks can potentially benefit from network coding. Aiming to improve the achievable capacity of D2D communications, we propose a system with inter-session network coding enabled to assist D2D transmissions. We formulate the joint problem of relay selection and resource allocation in network coding assisted D2D communications, and obtain the overall capacity of the network under complex interference conditions as a function of the relay selection and resource allocation. To solve the formulated problem, we propose a two-level decentralized approach termed NC-D2D, which solves the relay selection and resource allocation problems alternatively to obtain stable solutions for these two problems. Specifically, a coalition formation game associates relays with D2D pairs to enable network coding aided transmissions, and a greedy algorithm based game allocates limited cellular resources to D2D pairs and relays in NC-D2D, respectively. The performances of the proposed scheme is evaluated through extensive simulations to prove its superiority
Two-dimensional anisotropic Dirac materials PtN4C2 and Pt2N8C6 with quantum spin and valley Hall effects
We propose two novel two-dimensional topological Dirac materials, planar
PtN4C2 and Pt2N8C6, which exhibit graphene-like electronic structures with
linearly dispersive Dirac-cone states exactly at the Fermi level. Moreover, the
Dirac cone is anisotropic, resulting in anisotropic Fermi velocities and making
it possible to realize orientation-dependent quantum devices. Using the
first-principles electronic structure calculations, we have systemically
studied the structural, electronic, and topological properties. We find that
spin-orbit coupling opens a sizable topological band gap so that the materials
can be classified as quantum spin Hall insulators as well as quantum valley
Hall insulators. Helical edge states that reside in the insulating band gap
connecting the bulk conduction and valence bands are observed. Our work not
only expands the Dirac cone material family, but also provides a new avenue to
searching for more two-dimensional topological quantum spin and valley Hall
insulators.Comment: 6 pages, 4 figure
Apoptosis signal-regulating kinase 1 (Ask1) deficiency alleviates MPP+-induced impairment of evoked dopamine release in the mouse hippocampus
The dopaminergic system is susceptible to dysfunction in numerous neurological diseases, including Parkinson’s disease (PD). In addition to motor symptoms, some PD patients may experience non-motor symptoms, including cognitive and memory deficits. A possible explanation for their manifestation is a disturbed pattern of dopamine release in brain regions involved in learning and memory, such as the hippocampus. Therefore, investigating neuropathological alterations in dopamine release prior to neurodegeneration is imperative. This study aimed to characterize evoked hippocampal dopamine release and assess the impact of the neurotoxin MPP+ using a genetically encoded dopamine sensor and gene expression analysis. Additionally, considering the potential neuroprotective attributes demonstrated by apoptosis signal-regulating kinase 1 (Ask1) in various animal-disease-like models, the study also aimed to determine whether Ask1 knockdown restores MPP+-altered dopamine release in acute hippocampal slices. We applied variations of low- and high-frequency stimulation to evoke dopamine release within different hippocampal regions and discovered that acute application of MPP+ reduced the amount of dopamine released and hindered the recovery of dopamine release after repeated stimulation. In addition, we observed that Ask1 deficiency attenuated the detrimental effects of MPP+ on the recovery of dopamine release after repeated stimulation. RNA sequencing analysis indicated that genes associated with the synaptic pathways are involved in response to MPP+ exposure. Notably, Ask1 deficiency was found to downregulate the expression of Slc5a7, a gene encoding a sodium-dependent high-affinity choline transporter that regulates acetylcholine levels. Respective follow-up experiments indicated that Slc5a7 plays a role in Ask1 deficiency-mediated protection against MPP+ neurotoxicity. In addition, increasing acetylcholine levels using an acetylcholinesterase inhibitor could exacerbate the toxicity of MPP+. In conclusion, our data imply that the modulation of the dopamine-acetylcholine balance may be a crucial mechanism of action underlying the neuroprotective effects of Ask1 deficiency in PD
Effect of magnesium sulfate on cerebral vasospasm in the treatment of aneurysmal subarachnoid hemorrhage: a systematic review and meta-analysis
IntroductionThe use of magnesium sulfate for treating aneurysmal subarachnoid hemorrhage (aSAH) has shown inconsistent results across studies. To assess the impact of magnesium sulfate on outcomes after aSAH, we conducted a systematic review and meta-analysis of relevant randomized controlled trials.MethodsPubMed, Embase, and the Cochrane Library were searched for relevant literature on magnesium sulfate for aSAH from database inception to March 20, 2023. The primary outcome was cerebral vasospasm (CV), and secondary outcomes included delayed cerebral ischemia (DCI), secondary cerebral infarction, rebleeding, neurological dysfunction, and mortality.ResultsOf the 558 identified studies, 16 comprising 3,503 patients were eligible and included in the analysis. Compared with control groups (saline or standard treatment), significant differences were reported in outcomes of CV [odds ratio (OR) = 0.61, p = 0.04, 95% confidence interval (CI) (0.37–0.99)], DCI [OR = 0.57, p = 0.01, 95% CI (0.37–0.88)], secondary cerebral infarction [OR = 0.49, p = 0.01, 95% CI (0.27–0.87)] and neurological dysfunction [OR = 0.55, p = 0.04, 95% CI (0.32–0.96)] after magnesium sulfate administration, with no significant differences detected in mortality [OR = 0.92, p = 0.47, 95% CI (0.73–1.15)] and rebleeding [OR = 0.68, p = 0.55, 95% CI (0.19–2.40)] between the two groups.ConclusionThe superiority of magnesium sulfate over standard treatments for CV, DCI, secondary cerebral infarction, and neurological dysfunction in patients with aSAH was demonstrated. Further randomized trials are warranted to validate these findings with increased sample sizes