1,552 research outputs found
Optimal Transmit Covariance for Ergodic MIMO Channels
In this paper we consider the computation of channel capacity for ergodic
multiple-input multiple-output channels with additive white Gaussian noise. Two
scenarios are considered. Firstly, a time-varying channel is considered in
which both the transmitter and the receiver have knowledge of the channel
realization. The optimal transmission strategy is water-filling over space and
time. It is shown that this may be achieved in a causal, indeed instantaneous
fashion. In the second scenario, only the receiver has perfect knowledge of the
channel realization, while the transmitter has knowledge of the channel gain
probability law. In this case we determine an optimality condition on the input
covariance for ergodic Gaussian vector channels with arbitrary channel
distribution under the condition that the channel gains are independent of the
transmit signal. Using this optimality condition, we find an iterative
algorithm for numerical computation of optimal input covariance matrices.
Applications to correlated Rayleigh and Ricean channels are given.Comment: 22 pages, 14 figures, Submitted to IEEE Transactions on Information
Theor
CRIMINAL LAW—MIRRORING THE TRIAL: MAKING SENSE OF THE LAW OF CLOSING ARGUMENT IN CRIMINAL CASES
The law of closing arguments in criminal cases has proven to be a minefield for prosecutors and judges. Whereas criminal convictions can be overturned because of improper argument by the government, acquittals obtained through improper argument by defense counsel cannot be reviewed because of the Double Jeopardy clause. Two rules, the prohibition against vouching and the proscription against the expression of personal opinions, have proven to be very difficult to apply in a coherent manner, to the point that argument about the credibility of witnesses has been prohibited in some jurisdictions. Jury nullification arguments by the defense tend to creep into a criminal trial during summation, and they present a difficult dilemma for the ethical prosecutor. Sometimes error in closing argument occurs when the prosecutor attempts to respond to appeals for jury nullification, that is, for a verdict outside the law and the evidence presented in the courtroom. An effective means of policing closing arguments and of preventing jury nullification would be a rule that requires closing arguments to mirror the trial. This “mirroring” principle means that the scope of closing argument should be the same as the scope of the facts and law presented during the trial. This principle would set out logical boundaries of proper and improper argument, and it would help trial judges identify and thwart pleas for jury nullification
Zebrafish Model of MLL-Rearranged Acute Myeloid Leukemia
Background: Acute myeloid leukemia (AML) is the second most common type of leukemia. Standard treatment includes chemotherapy as well as stem cell transplantation, but for aging patients and those with impaired immune function these rigorous therapies are not always possible. Furthermore, AML patients harboring a chromosomal rearrangement involving Multiple Lineage Leukemia (MLL) exhibit far worse prognoses than patients without. Given these circumstances new therapies must be developed.
Methods: Danio rerio (zebrafish) has emerged as a powerful model organism for investigating human blood malignancies due to the conservation of hematopoiesis between humans and zebrafish. We developed a transient transgenic model exhibiting AML characteristics by microinjecting single-cell zebrafish embryos with a tissue specific MLL-ENL expression construct.
Results: We found that the expression of MLL-ENL induced a clustered expansion of MLL+ and pu.1+ myeloid cells on the yolk sac at 48 and 72 hours post fertilization (hpf). To characterize our transient AML model, we treated MLL-ENL expressing embryos with either one of or a combination of two drugs that are currently being used in human AML drug trials, Venetoclax and Flavopiridol. We found that treatment with either drug reduced the myeloid expansion induced by the expression of MLL-ENL, and that co-treatment reduced the observed myeloid expansion even further.
Conclusions: Although further analysis is required, these data suggest that we successfully developed a transient transgenic AML model in zebrafish. Furthermore, these data suggest that Venetoclax and Flavopiridol co-treatment could yield better outcomes for AML patients than treatment with either drug individually.https://scholarscompass.vcu.edu/gradposters/1112/thumbnail.jp
Performance Analysis of MIMO-MRC in Double-Correlated Rayleigh Environments
We consider multiple-input multiple-output (MIMO) transmit beamforming
systems with maximum ratio combining (MRC) receivers. The operating environment
is Rayleigh-fading with both transmit and receive spatial correlation. We
present exact expressions for the probability density function (p.d.f.) of the
output signal-to-noise ratio (SNR), as well as the system outage probability.
The results are based on explicit closed-form expressions which we derive for
the p.d.f. and c.d.f. of the maximum eigenvalue of double-correlated complex
Wishart matrices. For systems with two antennas at either the transmitter or
the receiver, we also derive exact closed-form expressions for the symbol error
rate (SER). The new expressions are used to prove that MIMO-MRC achieves the
maximum available spatial diversity order, and to demonstrate the effect of
spatial correlation. The analysis is validated through comparison with
Monte-Carlo simulations.Comment: 25 pages. Submitted to the IEEE Transactions on Communication
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