phuong cao - Academia.edu (original) (raw)

Papers by phuong cao

Research paper thumbnail of Precoding Design for Massive MIMO Systems with Sub-connected Architecture and Per-antenna Power Constraints

This paper provides the necessary conditions to design precoding matrices for massive MIMO system... more This paper provides the necessary conditions to design precoding matrices for massive MIMO systems with a sub-connected architecture, RF power constraints and per-antenna power constraints. The sys ...

Research paper thumbnail of Platelets: An Efficient Depot for Generation and Distribution of Lysosomal Idua in Enzyme-Deficient MPS I Mice

Blood, 2012

3157 Proviral integration into hematopoietic stem cells (HSC) by lentivirus vector (LV)-mediated ... more 3157 Proviral integration into hematopoietic stem cells (HSC) by lentivirus vector (LV)-mediated gene transfer can provide the benefit of life-long therapeutic effect, yet it can also bring the risk of insertional oncogenesis. Platelets are terminally differentiated, enucleated cells full of secretory granules. Restricting transgene expression to platelets may reduce the risk for activating oncogenes in HSCs and most of their progeny, and take advantage of their rapid turnover and professional secretion function. In this study, we evaluated the feasibility of employing megakaryocyte-platelet as a depot for the over-expression and release of alpha-L-iduronidase (IDUA), the lysosomal enzyme deficient in patients with Mucopolysaccharidosis type I (MPS I, or Hurler Syndrome). Utilizing a human megakaryocytic DAMI cell line, we found that a hybrid human ankyrin-1 promoter (K) containing ALAS2 intron 8 enhancer and HS40 core element from human alpha LCR could introduce robust intracellula...

Research paper thumbnail of Optimal Transmit Strategies for Gaussian MISO Wiretap Channels

IEEE Transactions on Information Forensics and Security, 2019

This paper studies the optimal tradeoff between secrecy and non-secrecy rates of the MISO wiretap... more This paper studies the optimal tradeoff between secrecy and non-secrecy rates of the MISO wiretap channels for different power constraint settings: sum power constraint only, per-antenna power constraints only and joint sum and perantenna power constraints. The problem is motivated by the fact that channel capacity and secrecy capacity are generally achieved by different transmit strategies. First, a necessary and sufficient condition to ensure a positive secrecy capacity is shown. The optimal tradeoff between secrecy rate and transmission rate is characterized by a weighted rate sum maximization problem. Since this problem is not necessarily convex, equivalent problem formulations are introduced to derive the optimal transmit strategies. Under sum power constraint only, a closedform solution is provided. Under per-antenna power constraints, necessary conditions to find the optimal power allocation are provided. Sufficient conditions are provided for the special case of two transmit antennas. For the special case of parallel channels, the optimal transmit strategies can deduced from an equivalent point-to-point channel problem. Lastly, the theoretical results are illustrated by numerical simulations.

Research paper thumbnail of Optimal Transmit Strategy for MISO Channels With Joint Sum and Per-Antenna Power Constraints

IEEE Transactions on Signal Processing, 2016

In this paper, we study an optimal transmit strategy for multiple-input single-output (MISO) Gaus... more In this paper, we study an optimal transmit strategy for multiple-input single-output (MISO) Gaussian channels with joint sum and per-antenna power constraints. We study in detail the interesting case where the sum of the per-antenna power constraints is larger than sum power constraint. A closed-form characterization of an optimal beamforming strategy is derived. It is shown that we can always find an optimal beamforming transmit strategy that allocates the maximal sum power with phases matched to the complex channel coefficients. The main result is a simple recursive algorithm to compute the optimal power allocation. Whenever the optimal power allocation of the corresponding problem with sum power constraint only exceeds per-antenna power constraints, it is optimal to allocate maximal per-antenna power to those antennas to satisfy the per-antenna power constraints. The remaining power is divided amongst the other antennas whose optimal allocation follows from a reduced joint sum and per-antenna power constraints problem of smaller channel coefficient dimension and reduced sum power constraint. Finally, the theoretical results are illustrated by numerical examples.

Research paper thumbnail of Getting the Most: Enhancing Efficacy by Promoting Erythropoiesis and Thrombopoiesis after Gene Therapy in Mice with Hurler Syndrome

Molecular Therapy - Methods & Clinical Development, 2018

Novel strategies are needed to solve the conundrum of achieving clinical efficacy with high vecto... more Novel strategies are needed to solve the conundrum of achieving clinical efficacy with high vector copy numbers (VCNs) in hematopoietic stem cells (HSCs) while attempting to minimize the potential risk of oncogenesis in lentiviral vector (LV)-mediated gene therapy clinical trials. We previously reported the benefits of reprogramming erythroid-megakaryocytic (EMK) cells for high-level lysosomal enzyme production with less risk of activating oncogenes in HSCs. Herein, using a murine model of mucopolysaccharidosis type I (MPS I) with a deficiency of a-L-iduronidase (IDUA), we sought to determine the transgene minimum effective doses (MEDs) in major organs, and if a transient increase of IDUA-containing red blood cells and platelets by repeated phlebotomy would provide further therapeutic benefits in diseased mice after EMK-restricted LV-mediated gene therapy. The MEDs for complete metabolic correction ranged from 0.1 to 2 VCNs in major visceral organs, which were dramatically reduced to 0.005-0.1 VCN by one cycle of stress induction and were associated with a further reduction of pathological deficits in mice with 0.005 VCN. This work provides a proof of concept that transiently stimulating erythropoiesis and thrombopoiesis can further improve therapeutic benefits in HSC-mediated gene therapy for MPS I, a repeatable and reversible approach to enhance clinical efficacy in the treatment of lysosomal storage diseases.

Research paper thumbnail of On the energy efficiency in multi-user multi-relay coded network

2016 23rd International Conference on Telecommunications (ICT), 2016

In this paper, the energy efficiency (EE) of a cooperative diversity system with maximum diversit... more In this paper, the energy efficiency (EE) of a cooperative diversity system with maximum diversity network coding (MDNC) is studied. In the considered system, channel state information (CSI) is only available at the receivers for all the channels. We formulate the problem of maximizing the EE under the constraint on the outage probability. The problem is NP-hard due to the non-convexity of the outage probability function and the nonlinear fractional structure of the introduced EE. To solve the optimization problem efficiently, first, the outage probability function is tightly approximated as a log-convex form in the high signal-tonoise ratio (SNR) region. Further, based on the fractional programming, we transform the introduced EE into a subtractive-form, which is proved to be a convex form. The tradeoff between outage probability and EE is given. The results show that our power allocation (PA) policy can substantially increase the EE. We show that EE can be increased if more relays forward the messages. Additionally, we also investigate the effect of the relay locations on the EE and demonstrate that the increase in the transmission distance in the first hop causes the loss of the EE. The loss can be reduced by our PA policy.

Research paper thumbnail of Secreted Luciferase for In Vivo Evaluation of Systemic Protein Delivery in Mice

Molecular Biotechnology, 2012

A naturally secreted Gaussia luciferase (Gluc) has been utilized as a reporter for bioluminescenc... more A naturally secreted Gaussia luciferase (Gluc) has been utilized as a reporter for bioluminescence imaging (BLI) evaluation. However, the potential application of Gluc for in vivo monitoring of systemic protein delivery, as well as its natural biodistribution, has not been studied. To examine Gluc secretion and uptake profile, we injected Gluc-encoding plasmids into mice by hydrodynamic tail-vein injection. Whole-body BLI showed that imaging quantification obtained at pawpad was directly correlated to blood Gluc activities. When gene expression was restricted to the liver by the use of a hepatic promoter, in vivo Gluc biodistribution analysis revealed the kidney/bladder, stomach/intestine and lung as the major uptake organs. Three-dimensional BLI identified liver/stomach and lung as the main internal luminescent sources, demonstrating the feasibility of detecting major uptake organs in live animals by 3D BLI with high background signals in circulation. Notably, Gluc levels in capillary-depleted brain samples from Gluc-injected mice were comparable to controls, suggesting Gluc may not cross the blood-brain barrier. Gluc uptake kinetics and intracellular half-life were assessed in various types of cell lines, implicating the involvement of non-specific pinocytosis. These results suggest that Gluc-based system may provide a useful tool for in vivo evaluation of protein/agent biodistribution following systemic delivery.

Research paper thumbnail of Precoding Design for Massive MIMO Systems with Sub-connected Architecture and Per-antenna Power Constraints

This paper provides the necessary conditions to design precoding matrices for massive MIMO system... more This paper provides the necessary conditions to design precoding matrices for massive MIMO systems with a sub-connected architecture, RF power constraints and per-antenna power constraints. The sys ...

Research paper thumbnail of Platelets: An Efficient Depot for Generation and Distribution of Lysosomal Idua in Enzyme-Deficient MPS I Mice

Blood, 2012

3157 Proviral integration into hematopoietic stem cells (HSC) by lentivirus vector (LV)-mediated ... more 3157 Proviral integration into hematopoietic stem cells (HSC) by lentivirus vector (LV)-mediated gene transfer can provide the benefit of life-long therapeutic effect, yet it can also bring the risk of insertional oncogenesis. Platelets are terminally differentiated, enucleated cells full of secretory granules. Restricting transgene expression to platelets may reduce the risk for activating oncogenes in HSCs and most of their progeny, and take advantage of their rapid turnover and professional secretion function. In this study, we evaluated the feasibility of employing megakaryocyte-platelet as a depot for the over-expression and release of alpha-L-iduronidase (IDUA), the lysosomal enzyme deficient in patients with Mucopolysaccharidosis type I (MPS I, or Hurler Syndrome). Utilizing a human megakaryocytic DAMI cell line, we found that a hybrid human ankyrin-1 promoter (K) containing ALAS2 intron 8 enhancer and HS40 core element from human alpha LCR could introduce robust intracellula...

Research paper thumbnail of Optimal Transmit Strategies for Gaussian MISO Wiretap Channels

IEEE Transactions on Information Forensics and Security, 2019

This paper studies the optimal tradeoff between secrecy and non-secrecy rates of the MISO wiretap... more This paper studies the optimal tradeoff between secrecy and non-secrecy rates of the MISO wiretap channels for different power constraint settings: sum power constraint only, per-antenna power constraints only and joint sum and perantenna power constraints. The problem is motivated by the fact that channel capacity and secrecy capacity are generally achieved by different transmit strategies. First, a necessary and sufficient condition to ensure a positive secrecy capacity is shown. The optimal tradeoff between secrecy rate and transmission rate is characterized by a weighted rate sum maximization problem. Since this problem is not necessarily convex, equivalent problem formulations are introduced to derive the optimal transmit strategies. Under sum power constraint only, a closedform solution is provided. Under per-antenna power constraints, necessary conditions to find the optimal power allocation are provided. Sufficient conditions are provided for the special case of two transmit antennas. For the special case of parallel channels, the optimal transmit strategies can deduced from an equivalent point-to-point channel problem. Lastly, the theoretical results are illustrated by numerical simulations.

Research paper thumbnail of Optimal Transmit Strategy for MISO Channels With Joint Sum and Per-Antenna Power Constraints

IEEE Transactions on Signal Processing, 2016

In this paper, we study an optimal transmit strategy for multiple-input single-output (MISO) Gaus... more In this paper, we study an optimal transmit strategy for multiple-input single-output (MISO) Gaussian channels with joint sum and per-antenna power constraints. We study in detail the interesting case where the sum of the per-antenna power constraints is larger than sum power constraint. A closed-form characterization of an optimal beamforming strategy is derived. It is shown that we can always find an optimal beamforming transmit strategy that allocates the maximal sum power with phases matched to the complex channel coefficients. The main result is a simple recursive algorithm to compute the optimal power allocation. Whenever the optimal power allocation of the corresponding problem with sum power constraint only exceeds per-antenna power constraints, it is optimal to allocate maximal per-antenna power to those antennas to satisfy the per-antenna power constraints. The remaining power is divided amongst the other antennas whose optimal allocation follows from a reduced joint sum and per-antenna power constraints problem of smaller channel coefficient dimension and reduced sum power constraint. Finally, the theoretical results are illustrated by numerical examples.

Research paper thumbnail of Getting the Most: Enhancing Efficacy by Promoting Erythropoiesis and Thrombopoiesis after Gene Therapy in Mice with Hurler Syndrome

Molecular Therapy - Methods & Clinical Development, 2018

Novel strategies are needed to solve the conundrum of achieving clinical efficacy with high vecto... more Novel strategies are needed to solve the conundrum of achieving clinical efficacy with high vector copy numbers (VCNs) in hematopoietic stem cells (HSCs) while attempting to minimize the potential risk of oncogenesis in lentiviral vector (LV)-mediated gene therapy clinical trials. We previously reported the benefits of reprogramming erythroid-megakaryocytic (EMK) cells for high-level lysosomal enzyme production with less risk of activating oncogenes in HSCs. Herein, using a murine model of mucopolysaccharidosis type I (MPS I) with a deficiency of a-L-iduronidase (IDUA), we sought to determine the transgene minimum effective doses (MEDs) in major organs, and if a transient increase of IDUA-containing red blood cells and platelets by repeated phlebotomy would provide further therapeutic benefits in diseased mice after EMK-restricted LV-mediated gene therapy. The MEDs for complete metabolic correction ranged from 0.1 to 2 VCNs in major visceral organs, which were dramatically reduced to 0.005-0.1 VCN by one cycle of stress induction and were associated with a further reduction of pathological deficits in mice with 0.005 VCN. This work provides a proof of concept that transiently stimulating erythropoiesis and thrombopoiesis can further improve therapeutic benefits in HSC-mediated gene therapy for MPS I, a repeatable and reversible approach to enhance clinical efficacy in the treatment of lysosomal storage diseases.

Research paper thumbnail of On the energy efficiency in multi-user multi-relay coded network

2016 23rd International Conference on Telecommunications (ICT), 2016

In this paper, the energy efficiency (EE) of a cooperative diversity system with maximum diversit... more In this paper, the energy efficiency (EE) of a cooperative diversity system with maximum diversity network coding (MDNC) is studied. In the considered system, channel state information (CSI) is only available at the receivers for all the channels. We formulate the problem of maximizing the EE under the constraint on the outage probability. The problem is NP-hard due to the non-convexity of the outage probability function and the nonlinear fractional structure of the introduced EE. To solve the optimization problem efficiently, first, the outage probability function is tightly approximated as a log-convex form in the high signal-tonoise ratio (SNR) region. Further, based on the fractional programming, we transform the introduced EE into a subtractive-form, which is proved to be a convex form. The tradeoff between outage probability and EE is given. The results show that our power allocation (PA) policy can substantially increase the EE. We show that EE can be increased if more relays forward the messages. Additionally, we also investigate the effect of the relay locations on the EE and demonstrate that the increase in the transmission distance in the first hop causes the loss of the EE. The loss can be reduced by our PA policy.

Research paper thumbnail of Secreted Luciferase for In Vivo Evaluation of Systemic Protein Delivery in Mice

Molecular Biotechnology, 2012

A naturally secreted Gaussia luciferase (Gluc) has been utilized as a reporter for bioluminescenc... more A naturally secreted Gaussia luciferase (Gluc) has been utilized as a reporter for bioluminescence imaging (BLI) evaluation. However, the potential application of Gluc for in vivo monitoring of systemic protein delivery, as well as its natural biodistribution, has not been studied. To examine Gluc secretion and uptake profile, we injected Gluc-encoding plasmids into mice by hydrodynamic tail-vein injection. Whole-body BLI showed that imaging quantification obtained at pawpad was directly correlated to blood Gluc activities. When gene expression was restricted to the liver by the use of a hepatic promoter, in vivo Gluc biodistribution analysis revealed the kidney/bladder, stomach/intestine and lung as the major uptake organs. Three-dimensional BLI identified liver/stomach and lung as the main internal luminescent sources, demonstrating the feasibility of detecting major uptake organs in live animals by 3D BLI with high background signals in circulation. Notably, Gluc levels in capillary-depleted brain samples from Gluc-injected mice were comparable to controls, suggesting Gluc may not cross the blood-brain barrier. Gluc uptake kinetics and intracellular half-life were assessed in various types of cell lines, implicating the involvement of non-specific pinocytosis. These results suggest that Gluc-based system may provide a useful tool for in vivo evaluation of protein/agent biodistribution following systemic delivery.