Low Transmission Probability Research Articles

The contagion model with social dependency

Empirical evidence demonstrates that contagion relies on social relationships, and the level of social dependency varies for different contagious entities (e.g., diseases or information). To unravel the influence of social dependency on the contagion dynamics, we introduce a social dependency coefficient and present a contagion model with the memory of non-redundant influence on complex networks, which bridges the simple and complex contagions. In this model, individuals exist in one of three states: susceptible, infected, or recovered. Susceptible individuals become infected when the cumulative non-redundant effects they have received (represented by a belief function) exceed their thresholds. By percolation method and mean-field theory, we find that low social dependency can expand the size of final recovered population, yet this effect is not continuous. Specifically, the level of social dependency can be categorized into three intervals based on the critical transmission probability. In the low-dependency interval, contagious entities can spread widely at a low transmission probability. In the medium dependency interval, the critical transmission probability increases stepwise with the social dependency. In the high-dependency interval, the population is free from large outbreaks of contagion at any transmission probability. Besides, the results are not qualitatively affected by the heterogeneous network structure and the theoretical predictions are consistent with the simulation results.

Coronavirus and Sexual Transmission: A Systematic Review

Introduction: Severe Acute Respiratory Syndrome Coronavirus-2 (SARS) was first identified in December 2019 in Wuhan, China. Although the respiratory system is infected in this disease, other tissues are prone to coronavirus attack so that the male reproductive system is another target for the virus causing sexual transmission of coronavirus. This study systematically examined the results of studies conducted on COVID-19 and possible sexual transmission of this virus. Method: This was a systematic review study in which the articles and papers were collected by using some keywords such as COVID-19, Semen, Novel Coronavirus, SARS-COV-2, ACE2, and Male Infertility searching through databases (PubMed, Web of Science, Scopus, Google Scholar) using OR and AND operators from December 2019 to November 2020. Finally, 13 papers as eligible articles were studied. Findings: The collected papers were reviewed, and ultimately 13 papers were entered into this study. According to current studies, the Angiotensin-converting enzyme (ACE2), which is found abundantly in testicles can perform as a cellular receptor for SARS-COV-2. This finding is the foundation of this hypothesis that human testis and semen can be infected by SARS-COV-2. In particular, a study showed that SARS-COV-2 might be detected in semen of patients with COVID-19 while other studies found no viral RNA in testicular biopsy tissue. Furthermore, some studies concluded that this virus, even in the acute phase, could not infect testicles or the male genital system. Accordingly, no evidence confirms that this virus can be transmitted through male genital organs. Conclusion: Although this virus has not been detected in semen fluid and it has not been sexually transmitted, one study found this virus in semen of coronavirus-infected patients and introduced its possible sexual transmission. Therefore, there is a low probability of sexual transmission of coronavirus.

Surface sampling for SARS-CoV-2 RNA in workplace outbreak settings in the UK, 2021-22.

To utilise environmental surface sampling to evaluate areas of SARS-CoV-2 contamination within workplaces to identify trends and improve local COVID-control measures. Surface sampling was undertaken at 12 workplaces that experienced a cluster of COVID-19 cases in the workforce between March 2021 and March 2022. 7.4% (61/829) of samples collected were positive for SARS-CoV-2 RNA by qPCR with only 1.8% (15/829) of samples identified with crossing threshold (Ct) values below 35.0. No sample returned whole genome sequence inferring RNA detected was degraded. Few workplace surface samples were positive for SARS-CoV-2 RNA and positive samples typically contained low levels of nucleic acid. Although these data may infer a low probability of fomite transmission within the workplace, Ct values may have been lower at the time of contamination. Workplace environmental sampling identified lapses in COVID-control measures within individual sites and showed trends through the pandemic.

Triggering of an Epidemic Outbreak via Long-Range Atmospheric Transport of Bio-Aerosols—Application to a Hypothetical Case for COVID-19

In the present work, we investigate the possibility that long-range airborne transport of infectious aerosols could initiate an epidemic outbreak at distances downwind beyond one hundred kilometers. For this, we have developed a simple atmospheric transport box model, which, for a hypothetical case of a COVID-19 outbreak, was compared to a more sophisticated three-dimensional transport-dispersion model (HYSPLIT) calculation. Coupled with an extended Wells–Riley description of infection airborne spread, it shows that the very low probability of outdoor transmission can be compensated for by high numbers and densities of infected and susceptible people in the source upwind and in the target downwind, respectively, such as occur in large urban areas. This may result in the creation of a few primary cases. It is worth pointing out that the probability of being infected remains very small at the individual level. Therefore, this process alone, which depends on population sizes, geography, seasonality, and meteorology, can only “trigger” an epidemic, which could then spread via the standard infection routes.

Emission rate of electron transport through a quantum point contact

Electron emissions in mesoscopic conductors are inherently correlated due to the Pauli exclusion principle. In this paper, we show that the correlation can be read from the electron emission rate. To demonstrate this, we concentrate on the electron emission in a single-channel quantum point contact (QPC). The emission can be driven by either a dc bias voltage or an unit-charged Lorentzian voltage pulse. In the case of dc bias voltage, the correlation is pronounced at both short and long times. The long-time correlation can be effectively suppressed by increasing the electron temperature and/or decreasing the transmission probability of the QPC. In contrast, the short-time correlation is much robust. As a consequence, the emission at high temperatures and/or low transmission probabilities can be treated as a Poisson process at long times, but follows a non-Poisson renewal statistics at short times. In the case of Lorentzian pulse, the correlation is much sensitive to the electron temperature. As the electron temperature increases, the electron emission evolves gradually from a non-renewal process at low temperatures to a time-dependent Poisson process at high temperatures.

The Use of Fish Skin (Tilapia) in Burn Patients as a New Therapy Under Study

Tilapia skin is an attractive and viable option for the treatment of second and third degree burns in patients. Several studies have shown that tilapia skin has antibacterial and anti-inflammatory properties that promote wound healing and reduce pain and inflammation in burn patients. In addition, tilapia skin is readily available, inexpensive and has a low probability of disease transmission. Compared to other treatment options, such as skin grafts, tilapia skin has a high success rate in promoting wound healing. More research is needed to fully establish the efficacy and safety of tilapia skin in the treatment of burns, but the current results are promising and suggest that tilapia skin may be a viable and cost-effective option for burn treatment.

Backhaul Capacity-Intent Interference Easing for Sum Rate Improving in 6G Cellular Internet of Things

A mmWave-enabled integrated access backhaul (IAB) network for the 6G cellular Internet of Things (IoT) is necessary to handle the escalating wideband communications needs. A decreased sum rate and low successful transmission probability were the results of the mmWave-enabled IAB network's significant interference problems between access links and differentiated small-cell base stations' backhaul capacities. This article suggests the Q-learn JUP algorithm, which stands for joint user equipment association and power allocation. In order to establish the UA and PA problem, we first investigate how the SBSs-UE association and transmit power are related. Second, using the interference and backhaul burden as the state, UA and PA as the action, and the overall sum rate increment as the reward function of Q-learning, we determine the best joint optimization framework through off-line training. In order to lessen interference and backhaul load, a new backhaul capacity and cautious matching approach utility function has also been designed. Simulation results demonstrate that, in contrast to existing algorithms, the proposed algorithm may vastly enhance the network sum rate and successful transmission probability.

Analytical models for phonon mean free path in polycrystalline nanostructures based on mean square displacement

In this study, a numerical simulation method and analytical models for predicting the boundary scattering mean free path (MFP) of phonons in polycrystalline nanostructures are developed. The grain morphologies are assumed to be approximately equiaxed, i.e., forbidding needle-like or pancake-like morphologies. Adapting a technique from rarefied gas dynamics, the method evaluates the MFP from the mean square displacements of phonons that experience random motion and interface collisions in nanostructures. We confirm that the MFP in simple cubic polycrystalline nanostructures obtained by the simulations agrees with that reported in a previous study; this result supports the validity of the method. Two analytical models for high and low interfacial transmission probabilities at the crystal interfaces are also derived by considering the mean square displacements. We find that the grain-boundary intercept length distribution of polycrystalline structures is an essential parameter for determining this boundary scattering MFP. These analytical models reproduce the MFPs in simple cubic and Voronoi diagram polycrystalline nanostructures calculated by the numerical simulations. This result indicates that the boundary scattering MFP of phonons in polycrystalline nanostructures can be obtained once the intercept length distribution is evaluated, without any additional numerical simulations.

Canine Distemper Virus (CDV) – The COVID-19 of the Wild Cats

In the year 1994, the Serengeti lion population was decimated by a canine distemper disease outbreak. Retrospective investigations showed that this host population had already been in contact with the pathogen in 1981 without any detected sign of disease. As an alternative to the virus mutation hypothesis to explain this difference in virulences observed in 1981 and 1994, we propose a novel mechanism of disease emergence based on variation in population immunity. We use a stochastic model to show that stochastic fluctuations in pathogen circulation, owing to a low probability of virus transmission from its reservoir to the target host and thereby resulting in variations in the global immunity level of the target host population, can explain the observations made in Serengeti. This mechanism may also be involved in other infectious disease emergences or re-emergences.

Evaluating the presence of SARS-CoV-2 RNA in the particulate matters during the peak of COVID-19 in Padua, northern Italy

The airborne transmission of SARS-CoV-2, the etiologic agent of the current COVID-19 pandemic, has been hypothesized as one of the primary routes of transmission. Current data suggest a low probability of airborne transmission of the virus in open environments and a higher probability in closed ones, particularly in hospitals or quarantine facilities. However, the potential diffusion of the virus in open environments, especially using particulate matter (PM) as a transport carrier, generated concern in the exposed populations. Several authors found a correlation between the exceeding of the PM10 concentration limits in some Italian cities and the prevalence of Covid-19 cases detected in those areas. This study investigated the potential presence of SARS-COV-2 RNA on a representative series of PM samples collected in the province of Padua in Northeastern Italy during the first wave of COVID pandemic. Forty-four samples of PM2.5 and PM10 were collected between February 24 and March 9, 2020 and analyzed with RT-qPCR for SARS-CoV-2 RNA. The experimental results did not indicate the presence of SARS-CoV-2 RNA in the outdoor PMs, thus confirming the low probability of virus airborne transmission through PM.

Improving the Throughput in Lightly Disturbed IEEE 802.11 DCF Saturated Network Using the Fragmentation Mechanism Under Basic Access Mode

The IEEE 802.11 is the most dominating protocol in the wireless local area networks and in which, the fundamental mechanism to access the channel is called distributed coordination function (DCF). As this mechanism is random, the calculation of the performance metrics for IEEE 802.11 networks is focused on the determination of probabilities such as collision probability and successful transmission probability. Recently, there are performance studies in the literature are based on the mathematical models developed using the Markov chains, which model the DCF mechanism with fragmentation in IEEE 802.11 network under imperfect channel. Yet, these models suffer with high collision probability and low successful transmission probability and as a result, the transmission with fragmentation is not recommended at all in the IEEE 802.11 basic DCF networks when the bit error rate is low $$\left( {BER < 5 \times 10^{ - 5} } \right)$$ . In order to solve this, a new analytical model of the basic DCF mechanism with fragmentation is presented in this paper to accurately evaluate throughput metric in the lightly disturbed IEEE 802.11 network at $$BER = 10^{ - 5}$$ under saturated traffic. Analytical results show that our model significantly improves the throughput of the IEEE 802.11 DCF network compared with existing model and hence, provides a higher throughput than that is improved with the request to send/clear to send (RTS/CTS) mode, regardless to network size.

The relativistic tunneling flight time may be superluminal, but it does not imply superluminal signaling

Wavepacket tunneling, in the relativistic limit, is studied via solutions to the Dirac equation for a square barrier potential. Specifically, the arrival time distribution (the time-dependent flux) is computed for wavepackets initiated far away from the barrier, and whose momentum is well below the threshold for above-barrier transmission. The resulting distributions exhibit peaks at shorter times than those of photons with the same initial wavepacket transmitting through a vacuum. However, this apparent superluminality in time is accompanied by very low transmission probabilities. We discuss these observations, and related observations by other authors, in the context of published objections to the notion that tunneling can be superluminal in time. We find that many of these objections are not consistent with our observations, and conclude that post-selected (for transmission) distributions of arrival times can be superluminal. However, the low probability of tunneling means a photon will most likely be seen first and therefore the superluminality does not imply superluminal signaling.

Secondary attack rate of COVID-19 in household contacts: a systematic review.

Objective COVID-19 is a novel virus with continuously evolving transmission trends. Contact tracing and quarantining of positive cases are chief strategies of disease control that has been accepted globally. Though scientific knowledge regarding household transmission of the COVID-19 through contact of positive case is sparse. Current systematic review was planned to assess global statistics and characteristics of household secondary attack rate (SAR) of COVID-19. Methods Eligible articles were retrieved through search of – MEDLINE, SCOPUS and EMBASE for the period December 2019 to June 15th 2020. Search terms were developed to identify articles reporting household SARs in various countries. After initial screening of 326 articles, 13 eligible studies were included in the final evidence synthesis. Results We found that SAR varies widely across countries with lowest reported rate as 4.6% and highest as 49.56%. The rates were unaffected by confounders such as population of the country, lockdown status and geographic location. Review suggested greater vulnerability of spouse and elderly population for secondary transmission than other household members. It was also observed that quarantining and isolation are most effective strategies for prevention of the secondary transmission of the disease. Symptomatic status of the index case emerged to be a critical factor, with very low transmission probability during asymptomatic phase. Conclusion Present review findings recommend that adequate measures should be provided to protect the vulnerable population as only case tracing and quarantining might be insufficient. It should be combined with advisory for limiting household contacts and active surveillance for symptom onset.

Concordance between epidemiological evaluation of probability of transmission and whole genome sequence relatedness among hospitalized patients acquiring Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae

ObjectivesWe aimed to evaluate the concordance between epidemiologically determined transmission and genetic linkage of Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-Kp). MethodsWe included consecutive KPC-Kp carriers between December 2016 and April 2017 in a hospital endemic for KPC-Kp. We assessed epidemiological relatedness between patients by prospective investigations by the infection control team. The probability of epidemiological relatedness was classified into four groups: no suspected transmission, low, moderate and high probability of transmission. Whole-genome sequencing of isolates was performed. Genetic linkage between KPC-Kp isolates was expressed by distance between isolates in single nucleotide polymorphisms (SNPs). We established an SNP cut-off defining a different strain based on the reconstructed phylogenetic tree. We compared the epidemiological and genetic linkage of all isolates from all patients. ResultsThe study included 25 KPC-Kp carriers with 49 isolates. SNP variance was available for 1129 crossed patient-isolate pairs. Genomic linkage, based on a cut-off of 80 SNPs to define related isolates, was found in 115/708 (16.2%) of isolates with no transmission suspected epidemiologically, 27/319 (8.5%) of low, 11/26 (42.3%) of moderate and 64/76 (84.2%) of high epidemiological transmission risk determination (p < 0.001 for trend). Similar results and significant trends were shown on sensitivity analyses using a lower SNP cut-off (six SNPs) and patient-isolate unique pairs, analysing the first isolate from each patient. ConclusionsWhile significant concordance between epidemiological and genomic transmission patterns was found, epidemiological investigations of transmission are limited by the possibility of unidentified transmissions or over-estimation of associations. Genetic linkage analysis is an important aid to epidemiological transmission assessment.

Chiral tunneling oscillations based on Weyl semimetals

Chiral tunneling oscillations are investigated by modulations of a double potential barrier based on Weyl semimetals . Analytical results are directly derived from transfer matrix constituted by the parametric controls, which range to the incoming energy, incident angle, width and strength of the potential barriers. Referring to the analytical analysis and numerical simulations, the transmission and conductance resonances effected by the double potential barrier can be clearly obtained and understood. Specially, modulations of the chiral tunneling show that resonant oscillations emerge in serial high incident energies, and platforms of low transmission probability come into existence due to propagations of the imaginary wave vectors.

Link between the numbers of particles and variants founding new HIV-1 infections depends on the timing of transmission.

Understanding which HIV-1 variants are most likely to be transmitted is important for vaccine design and predicting virus evolution. Since most infections are founded by single variants, it has been suggested that selection at transmission has a key role in governing which variants are transmitted. We show that the composition of the viral population within the donor at the time of transmission is also important. To support this argument, we developed a probabilistic model describing HIV-1 transmission in an untreated population, and parameterised the model using both within-host next generation sequencing data and population-level epidemiological data on heterosexual transmission. The most basic HIV-1 transmission models cannot explain simultaneously the low probability of transmission and the non-negligible proportion of infections founded by multiple variants. In our model, transmission can only occur when environmental conditions are appropriate (e.g. abrasions are present in the genital tract of the potential recipient), allowing these observations to be reconciled. As well as reproducing features of transmission in real populations, our model demonstrates that, contrary to expectation, there is not a simple link between the number of viral variants and the number of viral particles founding each new infection. These quantities depend on the timing of transmission, and infections can be founded with small numbers of variants yet large numbers of particles. Including selection, or a bias towards early transmission (e.g. due to treatment), acts to enhance this conclusion. In addition, we find that infections initiated by multiple variants are most likely to have derived from donors with intermediate set-point viral loads, and not from individuals with high set-point viral loads as might be expected. We therefore emphasise the importance of considering viral diversity in donors, and the timings of transmissions, when trying to discern the complex factors governing single or multiple variant transmission.

Real-time first-principles simulations of thermionic emission from N-doped diamond surfaces

We investigate thermionic emission from N-doped C(100) surfaces terminated with H or Li atoms using finite-temperature real-time density functional theory simulations. The current–temperature characteristics are found to follow the Richardson–Dushman (RD) equation, which was derived from a semiclassical theory. However, the Richardson constants are two orders of magnitude smaller than the ideal values from the RD theory. This considerable reduction is attributed primarily to the extremely low transmission probability of electrons from the surfaces toward the vacuum. The present method enables straightforward evaluation of the ideal efficiency of a thermionic energy converter.

Behaviors, movements, and transmission of droplet-mediated respiratory diseases during transcontinental airline flights

With over 3 billion airline passengers annually, the inflight transmission of infectious diseases is an important global health concern. Over a dozen cases of inflight transmission of serious infections have been documented, and air travel can serve as a conduit for the rapid spread of newly emerging infections and pandemics. Despite sensational media stories and anecdotes, the risks of transmission of respiratory viruses in an airplane cabin are unknown. Movements of passengers and crew may facilitate disease transmission. On 10 transcontinental US flights, we chronicled behaviors and movements of individuals in the economy cabin on single-aisle aircraft. We simulated transmission during flight based on these data. Our results indicate there is low probability of direct transmission to passengers not seated in close proximity to an infectious passenger. This data-driven, dynamic network transmission model of droplet-mediated respiratory disease is unique. To measure the true pathogen burden, our team collected 229 environmental samples during the flights. Although eight flights were during Influenza season, all qPCR assays for 18 common respiratory viruses were negative.

Theoretical simulation of negative differential transconductance in lateral quantum well nMOS devices

We present a theoretical study of the negative differential transconductance (NDT) recently observed in the lateral-quantum-well Si n-channel field-effect transistors [J. Appl. Phys. 118, 124505 (2015)]. In these devices, p+ doping extensions are introduced at the source-channel and drain-channel junctions, thus creating two potential barriers that define the quantum well across whose quasi-bound states resonant/sequential tunneling may occur. Our study, based on the quantum transmitting boundary method, predicts the presence of a sharp NDT in devices with a nominal gate length of 10-to-20 nm at low temperatures (∼10 K). At higher temperatures, the NDT weakens and disappears altogether as a result of increasing thermionic emission over the p+ potential barriers. In larger devices (with a gate length of 30 nm or longer), the NDT cannot be observed because of the low transmission probability and small energetic spacing (smaller than kBT) of the quasi-bound states in the quantum well. We speculate that the inability of the model to predict the NDT observed in 40 nm gate-length devices may be due to an insufficiently accurate knowledge of the actual doping profiles. On the other hand, our study shows that NDT suitable for novel logic applications may be obtained at room temperature in devices of the current or near-future generation (sub-10 nm node), provided an optimal design can be found that minimizes the thermionic emission (requiring high p+ potential-barriers) and punch-through (that meets the opposite requirement of potential-barriers low enough to favor the tunneling current).

Host contact and shedding patterns clarify variation in pathogen exposure and transmission in threatened tortoiseGopherus agassizii: implications for disease modelling and management

Most directly transmitted infections require some form of close contact between infectious and susceptible hosts to spread. Often disease models assume contacts are equal and use mean field estimates of transmission probability for all interactions with infectious hosts. Such methods may inaccurately describe transmission when interactions differ substantially in their ability to cause infection. Understanding this variation in transmission risk may be critical to properly model and manage some infectious diseases. In this study, we investigate how varying exposure and transmission may be key to understanding disease dynamics in the threatened desert tortoise Gopherus agassizii. We created heterogeneity in Mycoplasma agassizii exposure (the putative bacterial agent of a respiratory disease) by varying the duration of interactions between naturally infected and uninfected captive desert tortoises. Using qPCR, we identified new infections and compared models of transmission probability as a function of contact duration and pathogen load. We then examined the contact patterns of a wild tortoise population using proximity loggers to identify heterogeneity in contact duration. The top-ranked model predicting M.agassizii transmission included a dose term defined as the product of the number of days in proximity to an infected host and the infection level of that host. Models predicted low transmission probability for short interactions, unless the infectious host had a high load of M.agassizii: such hosts were predicted to transmit infection at higher rates with any amount of contact. We observed predominantly short-lived interactions in a free-ranging tortoise population and thus, expect transmission patterns in this population to vary considerably with the frequency and duration of high infection levels. Mean field models may misrepresent natural transmission patterns in this and other populations depending on the distribution of high-risk contact and shedding events. Rapid outbreaks in generally solitary species may result from changes to their naturally low-risk contact patterns or due to increases in the frequency of severe infections or super-shedding events - population characteristics that should be further investigated to develop effective management strategies.