Chris Ng - Academia.edu (original) (raw)

Papers by Chris Ng

2018 IEEE 5G World Forum (5GWF), 2018

Hybrid beamforming via large antenna arrays has shown a great potential for increasing data rate ... more Hybrid beamforming via large antenna arrays has shown a great potential for increasing data rate in cellular networks by delivering multiple data streams simultaneously. In this paper, several beamforming design algorithms are proposed based on the long-term channel information for macro-cellular environments where the base station is equipped with a massive phased array under per-antenna power constraint. Using an adaptive scheme, beamforming vectors are updated whenever the long-term channel information changes. First, the problem is studied when the base station has a single RF chain (single-beam scenario). Semi-definite relaxation (SDR) with randomization is used to solve the problem. As a second approach, a lowcomplexity heuristic beam composition algorithm is proposed which performs very close to the upper-bound obtained by SDR. Next, the problem is studied for a generic number of RF chains (multi-beam scenario) where the Gradient Projection method is used to obtain local solutions. Numerical results reveal that using massive antenna arrays with optimized beamforming vectors can lead to 5X network throughput improvement over systems with conventional antennas.

Environmental Health and Preventive Medicine, 2017

Background: The objective is to examine the association between AD and the daily number of medica... more Background: The objective is to examine the association between AD and the daily number of medical consultations for pollinosis in Fukuoka City. Methods: We analyzed 65,488 daily medical consultations for pollinosis from 4 clinics in Fukuoka City from February to April, 1989-2012. Time-series analyses were performed to estimate the clinic-specific relative risk (RR) of clinical pollinosis associated with AD, adjusting for airborne pollen, suspended particulate matter (SPM), meteorological and temporal factors. Delayed effects were considered. The association with SPM was also examined given its relationship with AD. The clinic-specific RRs were combined using meta-analytic technique. Results: AD on the same day (lag 0) and the previous 3 to 5 days (lags 3, 4, and 5) was positively associated with the risk of medical consultations for pollinosis. Clinic visits were 21.5% (95% confidence interval 3.1%-43.1%) higher when there was an AD event (across lags 0-5). The association with SPM showed comparable lag structure, but with smaller effect estimates. When stratified by the occurrence of AD, the estimated risk increases associated with SPM did not differ between the AD-affected and AD-free days. Conclusion: AD is associated with an increased risk of medical consultations for pollinosis in spring. More research is needed to elucidate the roles of air particles with different sizes.

Environmental Health and Preventive Medicine, 2017

Background: The objective is to examine the association between AD and the daily number of medica... more Background: The objective is to examine the association between AD and the daily number of medical consultations for pollinosis in Fukuoka City. Methods: We analyzed 65,488 daily medical consultations for pollinosis from 4 clinics in Fukuoka City from February to April, 1989-2012. Time-series analyses were performed to estimate the clinic-specific relative risk (RR) of clinical pollinosis associated with AD, adjusting for airborne pollen, suspended particulate matter (SPM), meteorological and temporal factors. Delayed effects were considered. The association with SPM was also examined given its relationship with AD. The clinic-specific RRs were combined using meta-analytic technique. Results: AD on the same day (lag 0) and the previous 3 to 5 days (lags 3, 4, and 5) was positively associated with the risk of medical consultations for pollinosis. Clinic visits were 21.5% (95% confidence interval 3.1%-43.1%) higher when there was an AD event (across lags 0-5). The association with SPM showed comparable lag structure, but with smaller effect estimates. When stratified by the occurrence of AD, the estimated risk increases associated with SPM did not differ between the AD-affected and AD-free days. Conclusion: AD is associated with an increased risk of medical consultations for pollinosis in spring. More research is needed to elucidate the roles of air particles with different sizes.

2006 IEEE Information Theory Workshop

We compare the rates of one-shot and iterative conferencing in a cooperative Gaussian relay chann... more We compare the rates of one-shot and iterative conferencing in a cooperative Gaussian relay channel. The relay and receiver cooperate via a conference, as introduced by Willems, in which they exchange a series of communications over orthogonal links. Under one-shot conferencing, decode-and-forward (DF) is capacity-achieving when the relay has a strong channel. On the other hand, Wyner-Ziv compress-and-forward (CF) approaches the cut-set bound when the conference link capacity is large. To contrast with one-shot conferencing, we consider a two-round iterative conference scheme; it comprises CF in the first round, and DF in the second. When the relay has a weak channel, the iterative scheme is disadvantageous. However, when the relay channel is strong, iterative cooperation, with optimal allocation of conferencing resources, outperforms one-shot cooperation provided that the conference link capacity is large. When precise allocation of conferencing resources is not possible, we consider iterative cooperation with symmetric conference links, and show that the iterative scheme still surpasses one-shot cooperation, albeit under more restricted conditions.

Proceedings. International Symposium on Information Theory, 2005. ISIT 2005.

Capacity gain from transmitter and receiver cooperation are compared in a relay network where the... more Capacity gain from transmitter and receiver cooperation are compared in a relay network where the cooperating nodes are close together. When all nodes have equal average transmit power along with full channel state information (CSI), it is proved that transmitter cooperation outperforms receiver cooperation, whereas the opposite is true when power is optimally allocated among the nodes but only receiver phase CSI is available. In addition, when the nodes have equal average power with receiver phase CSI only, cooperation is shown to offer no capacity improvement over a non-cooperative scheme with the same average network power. When the system is under optimal power allocation with full CSI, the decode-and-forward transmitter cooperation rate is close to its cut-set capacity upper bound, and outperforms compress-and-forward receiver cooperation. Moreover, it is shown that full CSI is essential in transmitter cooperation, while optimal power allocation is essential in receiver cooperation.

Atmosphere

The high level of ambient particulate matter in many developing countries constitutes a major hea... more The high level of ambient particulate matter in many developing countries constitutes a major health burden, but evidence on its impact on children’s health is still limited in these regions. We conducted a time-stratified case-crossover analysis to quantify the short-term association between fine particulate matter (PM2.5) and hospital admissions due to acute respiratory infections (ARI) among children in Bhaktapur district, Nepal, and to investigate the potential modification of the effect by nutritional characteristic. We analyzed 258 children admitted to the pediatric hospital for ARI between February 2014 to February 2015. We observed evidence of increased risk on the same (lag 0) and preceding day (lag 1). The cumulative estimate of their average (lag 01) suggested each 10 μg/m3 increase in PM2.5 was associated with a relative risk (RR) of 1.16 (95% confidence interval [CI]: 1.02–1.31). The strongest evidence from a stratified analysis of three categories of weights was observ...

2020 IEEE 3rd 5G World Forum (5GWF), 2020

Using a single rectangular antenna panel enhances cellular capacity via vertical beamforming (e.g... more Using a single rectangular antenna panel enhances cellular capacity via vertical beamforming (e.g. “Full Dimension MIMO”) but may impact diversity gain. We compare the receive diversity performance of several single-panel signal processing techniques, including: subarrays (with wide or narrow beamwidths), pattern diversity (with various a priori azimuth offset beam steering), and Maximum Ratio Combining. Spatial fading correlation is obtained from the 3GPP TR 25.996 model. We assume a hybrid analog-digital beamformer and derive the SNR for any analog beamformer followed by an MRC digital stage. This allows us to apply various beamforming strategies to the antenna subarrays and determine if there is a benefit. In a simple azimuth-only, single user simulation we find:4R (i.e. 4 outputs) subarrays with narrow steered beams approaches the performance of 8RMRC, while a 4 dB shortfall is found for widebeam subarrays relative to MRC; and pattern diversity is competitive with widebeam subar...

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)

In this work we discuss ongoing development of a hybrid fiber/copper data and timing infrastructu... more In this work we discuss ongoing development of a hybrid fiber/copper data and timing infrastructure for the future IceCube-Gen2 detector. The IceCube Neutrino Observatory is a kilometer-scale detector operating with 86 strings of modules. These modules communicate utilizing a custom protocol to mitigate the signaling challenges of long distance copper cables. Moving past the limitations of a copper-based backbone will allow larger future IceCube detectors with extremely precise timing and a large margin of excess throughput to accommodate innovative future modules. To this end, the upcoming IceCube Upgrade offers an opportunity to deploy a pathfinder for the new fiber optic infrastructure, called the Fiber Test System. This design draws on experience from AMANDA and IceCube and incorporates recently matured technologies such as ruggedized fibers and White Rabbit timing to deliver robust and high-performance data and timing transfer.

2018 IEEE 5G World Forum (5GWF)

Massive multiple-input and multiple-output (MIMO) has been the subject of interest in both indust... more Massive multiple-input and multiple-output (MIMO) has been the subject of interest in both industry and academia for the past few years. Massive MIMO refers to the use of a large number of antennas typically at the base station (BS) to serve multiple user equipment (UE) simultaneously to deliver reliable and high data throughput. Two basic architectures have been considered in the literature. First is a full digital massive MIMO where all the beamforming and precoding is performed digitally in baseband and a radio frequency (RF) chain is required for every antenna element. In the second architecture referred to as hybrid massive MIMO, beamforming and precoding are done in two stages, digital precoding over fewer digital ports followed by analog beamforming across large number of antenna elements. In this paper, we provide a comparison of implementation challenges for each approach. We introduce the High Definition Active Antenna System (HDAAS), a novel scalable architecture to implement a hybrid Massive MIMO system. This design philosophy is used to build BeamCraft500, which we believe is a first commercial hybrid 3D beamforming system operating at 2 GHz. We also present results from one of the field trials in a live LTE network that validate the stability and performance of the system under real world conditions.

International Journal of Environmental Research and Public Health

The acute effect of temperature on asthma morbidity in Bangladesh is not well understood. As clim... more The acute effect of temperature on asthma morbidity in Bangladesh is not well understood. As climate varies extensively in different parts of the world, the relation between temperature and asthma might also differ. We investigated the association between temperature and asthma-related hospital visits in the tropical city of Dhaka. We analyzed information from a total of 5989 asthma patients who received ambulatory care in the form of nebulized medication at the National Asthma Center in Mohakhali, Dhaka from February to November 2013. A time-stratified case-crossover study was conducted to estimate the effect of daily temperature, with consideration of delayed effects and possible confounders such as relative humidity and political strikes. An inverse association was observed between temperature and the number of hospital visits. The effect was delayed for approximately a week. A degree centigrade decrease in mean temperature (averaged across lags 0-6) was associated with an increa...

Orthopaedic Journal of Sports Medicine

Background: Prearthritic hip disorders (PAHD), such as femoroacetabular impingement (FAI), acetab... more Background: Prearthritic hip disorders (PAHD), such as femoroacetabular impingement (FAI), acetabular dysplasia, and acetabular labral tears, are a common cause of pain and dysfunction in adolescent and young adult athletes, and optimal patient-specific treatment has not been defined. Operative management is often recommended, but conservative management may be a reasonable approach for some athletes. Purpose: To identify (1) the relative rate of progression to surgery in self-reported competitive athletes versus nonathletes with PAHD and (2) baseline demographic, pain, and functional differences between athletes who proceeded versus those who did not proceed to surgery within 1 year of evaluation. Study Design: Cohort study; Level of evidence, 3. Methods: An electronic medical record review was performed of middle school, high school, and college patients who were evaluated for PAHD at a single tertiary-care academic medical center between June 22, 2015, and May 1, 2018. Extracted ...

genesis

REDOX mechanisms that induce biosynthesis of the reactive oxygen species (ROS) have attracted con... more REDOX mechanisms that induce biosynthesis of the reactive oxygen species (ROS) have attracted considerable attention due to both the deleterious and beneficial responses elicited by the reactive radical. In several organisms including Drosophila melanogaster, modulation of ROS activity is thought to be crucial for the maintenance of cell fates in developmental contexts. Interestingly, REDOX mechanisms have been shown to be involved in maintaining progenitor fate of stem cells as well as their proliferation and differentiation. Here, we have explored the possible functions of ROS during proper specification and developmental progression of embryonic primordial germ cells (PGCs). Indicating its potential involvement in these processes, ROS can be detected in the embryonic PGCs and the surrounding somatic cells from very early stages of embryogenesis. Using both “loss” and “gain” of function mutations in two different components of the REDOX pathway, we show that ROS levels are likely to be critical in maintaining germ cell behavior, including their directed migration. Altering the activity of a putative regulator of ROS also adversely influences the ability of PGCs to adhere to one another in cellular blastoderm embryos, suggesting potential involvement of this pathway in orchestrating different phases of germ cell migration.

2018 52nd Asilomar Conference on Signals, Systems, and Computers, Oct 1, 2018

Hybrid Massive MIMO reduces implementation complexity but only supports beamforming coefficients ... more Hybrid Massive MIMO reduces implementation complexity but only supports beamforming coefficients that are common across all subbands. However, in macro cellular where the channel has limited degrees of freedom, the longterm component of the channel can be decomposed into a set of subband-independent beamforming basis functions referred to as eigenbeams. A Coherent Hybrid Massive MIMO system can form arbitrary linear combinations of the eigenbeams at every subband to mimic Digital Massive MIMO beamforming as observed across all locations in the cell.

IEEE Signal Processing Letters

This letter provides a theoretical analysis for the static beamforming problem when the base stat... more This letter provides a theoretical analysis for the static beamforming problem when the base station is equipped with two antennas. It is assumed that the base station cannot change the beamforming vector dynamically due to hardware restrictions. The objective is to find the static beamforming vector that maximizes network utility when long-term information about the user location is available. Non-linear optimization techniques are used to find the solution of the problem for two different network utility functions: average SNR and average rate. Numerical results are provided to support the analysis.

PLoS neglected tropical diseases, Apr 1, 2018

Leptospirosis is a worldwide bacterial zoonosis. Outbreaks of leptospirosis after heavy rainfall ... more Leptospirosis is a worldwide bacterial zoonosis. Outbreaks of leptospirosis after heavy rainfall and flooding have been reported. However, few studies have formally quantified the effect of weather factors on leptospirosis incidence. We estimated the association between rainfall and leptospirosis cases in an urban setting in Manila, the Philippines, and examined the potential intermediate role of floods in this association. Relationships between rainfall and the weekly number of hospital admissions due to leptospirosis from 2001 to 2012 were analyzed using a distributed lag non-linear model in a quasi-Poisson regression framework, controlling for seasonally varying factors other than rainfall. The role of floods on the rainfall-leptospirosis relationship was examined using an indicator. We reported relative risks (RRs) by rainfall category based on the flood warning system in the country. The risk of post-rainfall leptospirosis peaked at a lag of 2 weeks (using 0 cm/week rainfall as...

Environmental health perspectives, Mar 6, 2018

There is growing evidence suggesting an association between air pollution and suicide. However, p... more There is growing evidence suggesting an association between air pollution and suicide. However, previous findings varied depending on the type of air pollutant and study location. We examined the association between air pollutants and suicide in 10 large cities in South Korea, Japan, and Taiwan. We used a two-stage meta-analysis. First, we conducted a time-stratified case-crossover analysis to estimate the short-term association between nitrogen dioxide (NO), sulfur dioxide (SO), and particulate matter [aerodynamic diameter ≤10μm (PM), aerodynamic diameter ≤2.5μm (PM), and PM] and suicide, adjusted for weather factors, day-of-week, long-term time trends, and season. Then, we conducted a meta-analysis to combine the city-specific effect estimates for NO, SO, and PM across 10 cities and for PM and PM across 3 cities. We first fitted single-pollutant models, followed by two-pollutant models to examine the robustness of the associations. Higher risk of suicide was associated with higher...

Environmental Health Perspectives

BACKGROUND: In March 2011, the Great East Japan Earthquake devastated several power stations and ... more BACKGROUND: In March 2011, the Great East Japan Earthquake devastated several power stations and caused severe electricity shortages. This accident was followed by the implementation of policies to reduce summer electricity consumption in the affected areas, for example, by limiting airconditioning (AC) use. This provided a natural experimental scenario to investigate if these policies were associated with an increase in heat-related mortality. OBJECTIVES: We examined whether the reduced electricity consumption in warm season modified heat-related mortality from 2008 to 2012. METHODS: We conducted prefecture-specific interrupted time-series (ITS) analyses to compare temperature-mortality associations before and after the earthquake, and used meta-analysis to generate combined effect estimates for the most affected and less affected areas (prefectures with >10% or ≤10% reductions in electricity consumption, respectively). We then examined whether the temperature-mortality association in Tokyo, one of the most affected areas, was modified by the percent reduction in electricity consumption relative to expected consumption for comparable days before the earthquake. RESULTS: Contrary to expectations, we estimated a 5-9% reduction in all-cause heat-related mortality after the earthquake in the 15 prefectures with the greatest reduction in electricity consumption, and little change in the other prefectures. However, the percent reduction in observed vs. expected daily electricity consumption after the earthquake did not significantly modify daily heat-related mortality in Tokyo. CONCLUSIONS: In the prefectures with the greatest reductions in electricity consumption, heat-related mortality decreased rather than increased following the Great East Japan Earthquake. Additional research is needed to determine whether this finding holds for other populations and regions, and to clarify its implications for policies to reduce the consequences of climate change on health.

Schizophrenia bulletin, Jan 22, 2017

The ability to follow spoken instructions is important to everyday functioning but has seldom bee... more The ability to follow spoken instructions is important to everyday functioning but has seldom been studied in patients with schizophrenia (SZ). Recent evidence suggests that action-based processing may facilitate the ability to follow instructions, which relies largely on working memory. In this study, we tested the hypothesis that SZ patients may also benefit from action-based advantages in following instructions. Forty-eight clinically stable SZ patients and 48 demographic- and IQ-matched controls completed a following spoken instruction span task involving varied encoding and recall conditions. While SZ patients were impaired in the overall performance of following spoken instructions, this deficit could be attributed to working memory impairment. More importantly, SZ patients showed action-based advantages both at the encoding and retrieval stage to the same extent as healthy controls. Specifically, both healthy controls and SZ patients showed improved memory performance when th...

Journal of pain and symptom management, Jan 21, 2017

The Expanded Prostate Cancer Index Composite (EPIC) instrument was designed to assess a range of ... more The Expanded Prostate Cancer Index Composite (EPIC) instrument was designed to assess a range of health-related quality of life issues specifically relevant to patients with prostate cancer. This study examined the validity and reliability of Chinese versions of the 26-item EPIC and of the 16-item EPIC for clinical practice (EPIC-CP) in Chinese patients with prostate cancer. A Chinese version of the 26-item EPIC and the 16-item EPIC-CP were self-completed by 252 Chinese patients with prostate cancer who were recruited from three community-based cancer service centres. Confirmatory factors analysis (CFA) assessed the factor structures of the EPIC and the EPIC-CP. Internal consistency and construct and clinical validities of the factor structures were assessed. CFA revealed the original factor structure of both EPIC-26 and EPIC-CP showed good fit to this sample. A correlated model was superior to a hierarchical model in both EPIC-26 and EPIC-CP supporting the utility of the domain sco...

2018 IEEE 5G World Forum (5GWF), 2018

Hybrid beamforming via large antenna arrays has shown a great potential for increasing data rate ... more Hybrid beamforming via large antenna arrays has shown a great potential for increasing data rate in cellular networks by delivering multiple data streams simultaneously. In this paper, several beamforming design algorithms are proposed based on the long-term channel information for macro-cellular environments where the base station is equipped with a massive phased array under per-antenna power constraint. Using an adaptive scheme, beamforming vectors are updated whenever the long-term channel information changes. First, the problem is studied when the base station has a single RF chain (single-beam scenario). Semi-definite relaxation (SDR) with randomization is used to solve the problem. As a second approach, a lowcomplexity heuristic beam composition algorithm is proposed which performs very close to the upper-bound obtained by SDR. Next, the problem is studied for a generic number of RF chains (multi-beam scenario) where the Gradient Projection method is used to obtain local solutions. Numerical results reveal that using massive antenna arrays with optimized beamforming vectors can lead to 5X network throughput improvement over systems with conventional antennas.

Environmental Health and Preventive Medicine, 2017

Background: The objective is to examine the association between AD and the daily number of medica... more Background: The objective is to examine the association between AD and the daily number of medical consultations for pollinosis in Fukuoka City. Methods: We analyzed 65,488 daily medical consultations for pollinosis from 4 clinics in Fukuoka City from February to April, 1989-2012. Time-series analyses were performed to estimate the clinic-specific relative risk (RR) of clinical pollinosis associated with AD, adjusting for airborne pollen, suspended particulate matter (SPM), meteorological and temporal factors. Delayed effects were considered. The association with SPM was also examined given its relationship with AD. The clinic-specific RRs were combined using meta-analytic technique. Results: AD on the same day (lag 0) and the previous 3 to 5 days (lags 3, 4, and 5) was positively associated with the risk of medical consultations for pollinosis. Clinic visits were 21.5% (95% confidence interval 3.1%-43.1%) higher when there was an AD event (across lags 0-5). The association with SPM showed comparable lag structure, but with smaller effect estimates. When stratified by the occurrence of AD, the estimated risk increases associated with SPM did not differ between the AD-affected and AD-free days. Conclusion: AD is associated with an increased risk of medical consultations for pollinosis in spring. More research is needed to elucidate the roles of air particles with different sizes.

Environmental Health and Preventive Medicine, 2017

Background: The objective is to examine the association between AD and the daily number of medica... more Background: The objective is to examine the association between AD and the daily number of medical consultations for pollinosis in Fukuoka City. Methods: We analyzed 65,488 daily medical consultations for pollinosis from 4 clinics in Fukuoka City from February to April, 1989-2012. Time-series analyses were performed to estimate the clinic-specific relative risk (RR) of clinical pollinosis associated with AD, adjusting for airborne pollen, suspended particulate matter (SPM), meteorological and temporal factors. Delayed effects were considered. The association with SPM was also examined given its relationship with AD. The clinic-specific RRs were combined using meta-analytic technique. Results: AD on the same day (lag 0) and the previous 3 to 5 days (lags 3, 4, and 5) was positively associated with the risk of medical consultations for pollinosis. Clinic visits were 21.5% (95% confidence interval 3.1%-43.1%) higher when there was an AD event (across lags 0-5). The association with SPM showed comparable lag structure, but with smaller effect estimates. When stratified by the occurrence of AD, the estimated risk increases associated with SPM did not differ between the AD-affected and AD-free days. Conclusion: AD is associated with an increased risk of medical consultations for pollinosis in spring. More research is needed to elucidate the roles of air particles with different sizes.

2006 IEEE Information Theory Workshop

We compare the rates of one-shot and iterative conferencing in a cooperative Gaussian relay chann... more We compare the rates of one-shot and iterative conferencing in a cooperative Gaussian relay channel. The relay and receiver cooperate via a conference, as introduced by Willems, in which they exchange a series of communications over orthogonal links. Under one-shot conferencing, decode-and-forward (DF) is capacity-achieving when the relay has a strong channel. On the other hand, Wyner-Ziv compress-and-forward (CF) approaches the cut-set bound when the conference link capacity is large. To contrast with one-shot conferencing, we consider a two-round iterative conference scheme; it comprises CF in the first round, and DF in the second. When the relay has a weak channel, the iterative scheme is disadvantageous. However, when the relay channel is strong, iterative cooperation, with optimal allocation of conferencing resources, outperforms one-shot cooperation provided that the conference link capacity is large. When precise allocation of conferencing resources is not possible, we consider iterative cooperation with symmetric conference links, and show that the iterative scheme still surpasses one-shot cooperation, albeit under more restricted conditions.

Proceedings. International Symposium on Information Theory, 2005. ISIT 2005.

Capacity gain from transmitter and receiver cooperation are compared in a relay network where the... more Capacity gain from transmitter and receiver cooperation are compared in a relay network where the cooperating nodes are close together. When all nodes have equal average transmit power along with full channel state information (CSI), it is proved that transmitter cooperation outperforms receiver cooperation, whereas the opposite is true when power is optimally allocated among the nodes but only receiver phase CSI is available. In addition, when the nodes have equal average power with receiver phase CSI only, cooperation is shown to offer no capacity improvement over a non-cooperative scheme with the same average network power. When the system is under optimal power allocation with full CSI, the decode-and-forward transmitter cooperation rate is close to its cut-set capacity upper bound, and outperforms compress-and-forward receiver cooperation. Moreover, it is shown that full CSI is essential in transmitter cooperation, while optimal power allocation is essential in receiver cooperation.

Atmosphere

The high level of ambient particulate matter in many developing countries constitutes a major hea... more The high level of ambient particulate matter in many developing countries constitutes a major health burden, but evidence on its impact on children’s health is still limited in these regions. We conducted a time-stratified case-crossover analysis to quantify the short-term association between fine particulate matter (PM2.5) and hospital admissions due to acute respiratory infections (ARI) among children in Bhaktapur district, Nepal, and to investigate the potential modification of the effect by nutritional characteristic. We analyzed 258 children admitted to the pediatric hospital for ARI between February 2014 to February 2015. We observed evidence of increased risk on the same (lag 0) and preceding day (lag 1). The cumulative estimate of their average (lag 01) suggested each 10 μg/m3 increase in PM2.5 was associated with a relative risk (RR) of 1.16 (95% confidence interval [CI]: 1.02–1.31). The strongest evidence from a stratified analysis of three categories of weights was observ...

2020 IEEE 3rd 5G World Forum (5GWF), 2020

Using a single rectangular antenna panel enhances cellular capacity via vertical beamforming (e.g... more Using a single rectangular antenna panel enhances cellular capacity via vertical beamforming (e.g. “Full Dimension MIMO”) but may impact diversity gain. We compare the receive diversity performance of several single-panel signal processing techniques, including: subarrays (with wide or narrow beamwidths), pattern diversity (with various a priori azimuth offset beam steering), and Maximum Ratio Combining. Spatial fading correlation is obtained from the 3GPP TR 25.996 model. We assume a hybrid analog-digital beamformer and derive the SNR for any analog beamformer followed by an MRC digital stage. This allows us to apply various beamforming strategies to the antenna subarrays and determine if there is a benefit. In a simple azimuth-only, single user simulation we find:4R (i.e. 4 outputs) subarrays with narrow steered beams approaches the performance of 8RMRC, while a 4 dB shortfall is found for widebeam subarrays relative to MRC; and pattern diversity is competitive with widebeam subar...

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)

In this work we discuss ongoing development of a hybrid fiber/copper data and timing infrastructu... more In this work we discuss ongoing development of a hybrid fiber/copper data and timing infrastructure for the future IceCube-Gen2 detector. The IceCube Neutrino Observatory is a kilometer-scale detector operating with 86 strings of modules. These modules communicate utilizing a custom protocol to mitigate the signaling challenges of long distance copper cables. Moving past the limitations of a copper-based backbone will allow larger future IceCube detectors with extremely precise timing and a large margin of excess throughput to accommodate innovative future modules. To this end, the upcoming IceCube Upgrade offers an opportunity to deploy a pathfinder for the new fiber optic infrastructure, called the Fiber Test System. This design draws on experience from AMANDA and IceCube and incorporates recently matured technologies such as ruggedized fibers and White Rabbit timing to deliver robust and high-performance data and timing transfer.

2018 IEEE 5G World Forum (5GWF)

Massive multiple-input and multiple-output (MIMO) has been the subject of interest in both indust... more Massive multiple-input and multiple-output (MIMO) has been the subject of interest in both industry and academia for the past few years. Massive MIMO refers to the use of a large number of antennas typically at the base station (BS) to serve multiple user equipment (UE) simultaneously to deliver reliable and high data throughput. Two basic architectures have been considered in the literature. First is a full digital massive MIMO where all the beamforming and precoding is performed digitally in baseband and a radio frequency (RF) chain is required for every antenna element. In the second architecture referred to as hybrid massive MIMO, beamforming and precoding are done in two stages, digital precoding over fewer digital ports followed by analog beamforming across large number of antenna elements. In this paper, we provide a comparison of implementation challenges for each approach. We introduce the High Definition Active Antenna System (HDAAS), a novel scalable architecture to implement a hybrid Massive MIMO system. This design philosophy is used to build BeamCraft500, which we believe is a first commercial hybrid 3D beamforming system operating at 2 GHz. We also present results from one of the field trials in a live LTE network that validate the stability and performance of the system under real world conditions.

International Journal of Environmental Research and Public Health

The acute effect of temperature on asthma morbidity in Bangladesh is not well understood. As clim... more The acute effect of temperature on asthma morbidity in Bangladesh is not well understood. As climate varies extensively in different parts of the world, the relation between temperature and asthma might also differ. We investigated the association between temperature and asthma-related hospital visits in the tropical city of Dhaka. We analyzed information from a total of 5989 asthma patients who received ambulatory care in the form of nebulized medication at the National Asthma Center in Mohakhali, Dhaka from February to November 2013. A time-stratified case-crossover study was conducted to estimate the effect of daily temperature, with consideration of delayed effects and possible confounders such as relative humidity and political strikes. An inverse association was observed between temperature and the number of hospital visits. The effect was delayed for approximately a week. A degree centigrade decrease in mean temperature (averaged across lags 0-6) was associated with an increa...

Orthopaedic Journal of Sports Medicine

Background: Prearthritic hip disorders (PAHD), such as femoroacetabular impingement (FAI), acetab... more Background: Prearthritic hip disorders (PAHD), such as femoroacetabular impingement (FAI), acetabular dysplasia, and acetabular labral tears, are a common cause of pain and dysfunction in adolescent and young adult athletes, and optimal patient-specific treatment has not been defined. Operative management is often recommended, but conservative management may be a reasonable approach for some athletes. Purpose: To identify (1) the relative rate of progression to surgery in self-reported competitive athletes versus nonathletes with PAHD and (2) baseline demographic, pain, and functional differences between athletes who proceeded versus those who did not proceed to surgery within 1 year of evaluation. Study Design: Cohort study; Level of evidence, 3. Methods: An electronic medical record review was performed of middle school, high school, and college patients who were evaluated for PAHD at a single tertiary-care academic medical center between June 22, 2015, and May 1, 2018. Extracted ...

genesis

REDOX mechanisms that induce biosynthesis of the reactive oxygen species (ROS) have attracted con... more REDOX mechanisms that induce biosynthesis of the reactive oxygen species (ROS) have attracted considerable attention due to both the deleterious and beneficial responses elicited by the reactive radical. In several organisms including Drosophila melanogaster, modulation of ROS activity is thought to be crucial for the maintenance of cell fates in developmental contexts. Interestingly, REDOX mechanisms have been shown to be involved in maintaining progenitor fate of stem cells as well as their proliferation and differentiation. Here, we have explored the possible functions of ROS during proper specification and developmental progression of embryonic primordial germ cells (PGCs). Indicating its potential involvement in these processes, ROS can be detected in the embryonic PGCs and the surrounding somatic cells from very early stages of embryogenesis. Using both “loss” and “gain” of function mutations in two different components of the REDOX pathway, we show that ROS levels are likely to be critical in maintaining germ cell behavior, including their directed migration. Altering the activity of a putative regulator of ROS also adversely influences the ability of PGCs to adhere to one another in cellular blastoderm embryos, suggesting potential involvement of this pathway in orchestrating different phases of germ cell migration.

2018 52nd Asilomar Conference on Signals, Systems, and Computers, Oct 1, 2018

Hybrid Massive MIMO reduces implementation complexity but only supports beamforming coefficients ... more Hybrid Massive MIMO reduces implementation complexity but only supports beamforming coefficients that are common across all subbands. However, in macro cellular where the channel has limited degrees of freedom, the longterm component of the channel can be decomposed into a set of subband-independent beamforming basis functions referred to as eigenbeams. A Coherent Hybrid Massive MIMO system can form arbitrary linear combinations of the eigenbeams at every subband to mimic Digital Massive MIMO beamforming as observed across all locations in the cell.

IEEE Signal Processing Letters

This letter provides a theoretical analysis for the static beamforming problem when the base stat... more This letter provides a theoretical analysis for the static beamforming problem when the base station is equipped with two antennas. It is assumed that the base station cannot change the beamforming vector dynamically due to hardware restrictions. The objective is to find the static beamforming vector that maximizes network utility when long-term information about the user location is available. Non-linear optimization techniques are used to find the solution of the problem for two different network utility functions: average SNR and average rate. Numerical results are provided to support the analysis.

PLoS neglected tropical diseases, Apr 1, 2018

Leptospirosis is a worldwide bacterial zoonosis. Outbreaks of leptospirosis after heavy rainfall ... more Leptospirosis is a worldwide bacterial zoonosis. Outbreaks of leptospirosis after heavy rainfall and flooding have been reported. However, few studies have formally quantified the effect of weather factors on leptospirosis incidence. We estimated the association between rainfall and leptospirosis cases in an urban setting in Manila, the Philippines, and examined the potential intermediate role of floods in this association. Relationships between rainfall and the weekly number of hospital admissions due to leptospirosis from 2001 to 2012 were analyzed using a distributed lag non-linear model in a quasi-Poisson regression framework, controlling for seasonally varying factors other than rainfall. The role of floods on the rainfall-leptospirosis relationship was examined using an indicator. We reported relative risks (RRs) by rainfall category based on the flood warning system in the country. The risk of post-rainfall leptospirosis peaked at a lag of 2 weeks (using 0 cm/week rainfall as...

Environmental health perspectives, Mar 6, 2018

There is growing evidence suggesting an association between air pollution and suicide. However, p... more There is growing evidence suggesting an association between air pollution and suicide. However, previous findings varied depending on the type of air pollutant and study location. We examined the association between air pollutants and suicide in 10 large cities in South Korea, Japan, and Taiwan. We used a two-stage meta-analysis. First, we conducted a time-stratified case-crossover analysis to estimate the short-term association between nitrogen dioxide (NO), sulfur dioxide (SO), and particulate matter [aerodynamic diameter ≤10μm (PM), aerodynamic diameter ≤2.5μm (PM), and PM] and suicide, adjusted for weather factors, day-of-week, long-term time trends, and season. Then, we conducted a meta-analysis to combine the city-specific effect estimates for NO, SO, and PM across 10 cities and for PM and PM across 3 cities. We first fitted single-pollutant models, followed by two-pollutant models to examine the robustness of the associations. Higher risk of suicide was associated with higher...

Environmental Health Perspectives

BACKGROUND: In March 2011, the Great East Japan Earthquake devastated several power stations and ... more BACKGROUND: In March 2011, the Great East Japan Earthquake devastated several power stations and caused severe electricity shortages. This accident was followed by the implementation of policies to reduce summer electricity consumption in the affected areas, for example, by limiting airconditioning (AC) use. This provided a natural experimental scenario to investigate if these policies were associated with an increase in heat-related mortality. OBJECTIVES: We examined whether the reduced electricity consumption in warm season modified heat-related mortality from 2008 to 2012. METHODS: We conducted prefecture-specific interrupted time-series (ITS) analyses to compare temperature-mortality associations before and after the earthquake, and used meta-analysis to generate combined effect estimates for the most affected and less affected areas (prefectures with >10% or ≤10% reductions in electricity consumption, respectively). We then examined whether the temperature-mortality association in Tokyo, one of the most affected areas, was modified by the percent reduction in electricity consumption relative to expected consumption for comparable days before the earthquake. RESULTS: Contrary to expectations, we estimated a 5-9% reduction in all-cause heat-related mortality after the earthquake in the 15 prefectures with the greatest reduction in electricity consumption, and little change in the other prefectures. However, the percent reduction in observed vs. expected daily electricity consumption after the earthquake did not significantly modify daily heat-related mortality in Tokyo. CONCLUSIONS: In the prefectures with the greatest reductions in electricity consumption, heat-related mortality decreased rather than increased following the Great East Japan Earthquake. Additional research is needed to determine whether this finding holds for other populations and regions, and to clarify its implications for policies to reduce the consequences of climate change on health.

Schizophrenia bulletin, Jan 22, 2017

The ability to follow spoken instructions is important to everyday functioning but has seldom bee... more The ability to follow spoken instructions is important to everyday functioning but has seldom been studied in patients with schizophrenia (SZ). Recent evidence suggests that action-based processing may facilitate the ability to follow instructions, which relies largely on working memory. In this study, we tested the hypothesis that SZ patients may also benefit from action-based advantages in following instructions. Forty-eight clinically stable SZ patients and 48 demographic- and IQ-matched controls completed a following spoken instruction span task involving varied encoding and recall conditions. While SZ patients were impaired in the overall performance of following spoken instructions, this deficit could be attributed to working memory impairment. More importantly, SZ patients showed action-based advantages both at the encoding and retrieval stage to the same extent as healthy controls. Specifically, both healthy controls and SZ patients showed improved memory performance when th...

Journal of pain and symptom management, Jan 21, 2017

The Expanded Prostate Cancer Index Composite (EPIC) instrument was designed to assess a range of ... more The Expanded Prostate Cancer Index Composite (EPIC) instrument was designed to assess a range of health-related quality of life issues specifically relevant to patients with prostate cancer. This study examined the validity and reliability of Chinese versions of the 26-item EPIC and of the 16-item EPIC for clinical practice (EPIC-CP) in Chinese patients with prostate cancer. A Chinese version of the 26-item EPIC and the 16-item EPIC-CP were self-completed by 252 Chinese patients with prostate cancer who were recruited from three community-based cancer service centres. Confirmatory factors analysis (CFA) assessed the factor structures of the EPIC and the EPIC-CP. Internal consistency and construct and clinical validities of the factor structures were assessed. CFA revealed the original factor structure of both EPIC-26 and EPIC-CP showed good fit to this sample. A correlated model was superior to a hierarchical model in both EPIC-26 and EPIC-CP supporting the utility of the domain sco...