Reducing NOx Emissions of Cargo Handling Equipment (CHE) with Humid Air Systems

The authors designed and tested a humid air system (HAS) for reducing NOx emissions of an LPG-powered forklift. The HAS uses distilled water and heat from the exhaust to generate steam that is injected into the intake air of the engine to increase humidity and thus achieve NOx reduction. Field tests with HAS have shown 2.2 ppm of NOx reduction with each percent increase in humidity of the intake air. A provisional patent based on the developed system has been filed

Oscillatory Flow Driven by Cavity

Flows past a cavity are known to exhibit an oscillatory behavior with an amplitude and frequency dependent on the incoming flow properties and the geometry of the cavity. Experiments and numerical analyses have been performed to determine the effects of a flow passing through an axisymmetric cavity and discharging into a transverse freestream. The study focuses on the mechanisms involved in the generation of pulsatile flow and its influences on a jet in crossflow. Flow characteristics through the cavity and the jet in crossflow interaction were analyzed using the computational fluid dynamics software Siemens Star-CCM+. The experimental analysis utilized a Laser Doppler Velocimetry (LDV) system for measurements of velocity profiles to determine the oscillatory jet flow properties as well at the oscillation frequency. Cavity dimensions with a Length to Depth ratio of 2 was used with an incoming flow mean velocity of 50 m/s resulting in a turbulent jet with a Reynolds number of approximately 33,600. The flow through the cavity emitted an oscillatory flow at 66.68 Hz determined by a Power Spectral Density plot. The oscillatory flow in cross flow exhibited a lower jet trajectory when compared to a steady jet in crossflow and indicates increased vorticity production within the jet, supporting flow recovery immediately downstream of the jet. The passive approach of generating an oscillatory jet in crossflow can aid in mixing of the two flows. Also included in the study is an application of the cavity driven oscillatory flow as it pertains to the upper respiratory system

Virus Control Aboard a Commuter Bus

A major health concern for public transit users is exposure to viruses from other passengers. This numerical study examines virus containment aboard a public bus with changes to the bus ventilation system. The virus was modeled as a 2.5 µm round solid particle released from the mouth of the infectious passenger at a rate of 21 particles per second at a mouth velocity of 0.278 m/sec. The air delivery to the cabin was two linear ceiling slots spanning the length of the bus delivering 59.38 m3/min (2,097 CFM) of air at a mean velocity of 1 m/sec. Two different axial and vertical linear exhaust slots placed on the side walls were investigated to examine how they affected virus containment and spread to the other parts of the cabin. Simulations were performed for both cases of the bus in transit and at the bus stop when the drop-off door was opened. Results indicate during transit that virus spread was contained to passengers sitting immediately in front of and behind the infectious passenger and the level of virus concentration could merit an increased risk of infection with increased virus residence time. However, augmented air mixing was observed between inside and outside air during the passenger drop-off with viruses spread to the front and back of the bus with reduced concentration and risk of infection. Analytical analyses of the risk of infection using the Wells-Riley equation were performed for the bus ventilation using 100% recirculating air without filtration, and 50% and 100% fresh air ventilation. Results indicate a high risk of infection when recirculating air is used, but the risk is reduced significantly with 50% and 100% fresh air ventilation. These results are critical to informing bus manufacturers, transit agencies, planners, and public transportation users about the potential of virus containment using a new ventilation system

Numerical Investigations of Virus Transport Aboard a Commuter Bus

The authors performed unsteady numerical simulations of virus/particle transport released from a hypothetical passenger aboard a commuter bus. The bus model was sized according to a typical city bus used to transport passengers within the city of Long Beach in California. The simulations were performed for the bus in transit and when the bus was at a bus stop opening the middle doors for 30 seconds for passenger boarding and drop off. The infected passenger was sitting in an aisle seat in the middle of the bus, releasing 1267 particles (viruses)/min. The bus ventilation system released air from two linear slots in the ceiling at 2097 cubic feet per minute (CFM) and the air was exhausted at the back of the bus. Results indicated high exposure for passengers sitting behind the infectious during the bus transit. With air exchange outside during the bus stop, particles were spread to seats in front of the infectious passenger, thus increasing the risk of infection for the passengers sitting in front of the infectious person. With higher exposure time, the risk of infection is increased. One of the most important factors in assessing infection risk of respiratory diseases is the spatial distribution of the airborne pathogens. The deposition of the particles/viruses within the human respiratory system depends on the size, shape, and weight of the virus, the morphology of the respiratory tract, as well as the subject’s breathing pattern. For the current investigation, the viruses are modeled as solid particles of fixed size. While the results provide details of particles transport within a bus along with the probable risk of infection for a short duration, however, these results should be taken as preliminary as there are other significant factors such as the virus’s survival rate, the size distribution of the virus, and the space ventilation rate and mixing that contribute to the risk of infection and have not been taken into account in this investigation

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Subsonic venturi interaction in a cross flow

Numerical and experimental investigations were performed on a venturi discharging into a cross flow. The numerical analysis consists of a non-uniform meshed model, solved using CD-Adapco Star CCM+ commercial software with K-&egr; and K-ω turbulence models. The analysis consisted of two different configurations; the venturi is flush with the tunnel's bottom wall and with a 15.24 cm extension tube of the same diameter installed between the venturi and bottom wall. The experimental investigations were carried in an open-circuit wind tunnel with a single hot wire sensor at the Center for Energy and Environmental Research and Services (CEERS) facility without the extension tube in place. Momentum Ratios, r, were set at 50%, 75% and 100% for the numerical analysis and 50%, 85% and 100% for the experimental investigations. Results indicate that no flow separation of recirculation occurred in the venturi or extension tube

Hypoglycemia is associated with increased risk for brain injury and adverse neurodevelopmental outcome in neonates at risk for encephalopathy.

ObjectiveTo investigate the contribution of hypoglycemia in the first 24 hours after birth to brain injury in term newborns at risk for neonatal encephalopathy.Study designA prospective cohort of 94 term neonates born between 1994 and 2010 with early postnatal brain magnetic resonance imaging studies were analyzed for regions of brain injury. Neurodevelopmental outcome was assessed at 1 year of age.ResultsHypoglycemia (glucose <46 mg/dL) in the first 24 hours after birth was detected in 16% of the cohort. Adjusting for potential confounders of early perinatal distress and need for resuscitation, neonatal hypoglycemia was associated with a 3.72-fold increased odds of corticospinal tract injury (P=.047). Hypoglycemia was also associated with 4.82-fold increased odds of 1-point worsened neuromotor score (P=.038) and a 15-point lower cognitive and language score on the Bayley Scales of Infant Development (P=.015).ConclusionNeonatal hypoglycemia is associated with additional risks in the setting of neonatal encephalopathy with increased corticospinal tract injury and adverse motor and cognitive outcomes