83 research outputs found
Coordinated Shared Spectrum Precoding with Distributed CSIT
In this paper, the operation of a Licensed Shared Access (LSA) system is
investigated, considering downlink communication. The system comprises of a
Multiple-Input-Single-Output (MISO) incumbent transmitter (TX) - receiver (RX)
pair, which offers a spectrum sharing opportunity to a MISO licensee TX-RX
pair. Our main contribution is the design of a coordinated transmission scheme,
inspired by the underlay Cognitive Radio (CR) approach, with the aim of
maximizing the average rate of the licensee, subject to an average rate
constraint for the incumbent. In contrast to most prior works on underlay CR,
the coordination of the two TXs takes place under a realistic Channel State
Information (CSI) scenario, where each TX has sole access to the instantaneous
direct channel of its served terminal. Such a CSI knowledge setting brings
about a formulation based on the theory of Team Decisions, whereby the TXs aim
at optimizing a common objective given the same constraint set, on the basis of
individual channel information. Consequently, a novel set of applicable
precoding schemes is proposed. Relying on statistical coordination criteria,
the two TXs cooperate in the lack of any instantaneous CSI exchange. We verify
by simulations that our novel coordinated precoding scheme outperforms the
standard underlay CR approach
Joint Sensing and Reception Design of SIMO Hybrid Cognitive Radio Systems
In this paper, the problem of joint design of Spectrum Sensing (SS) and
receive beamforming (BF), with reference to a Cognitive Radio (CR) system, is
considered. The aim of the proposed design is the maximization of the
achievable average uplink rate of a Secondary User (SU), subject to an
outage-based Quality-of-Service (QoS) constraint for primary communication. A
hybrid CR system approach is studied, according to which, the system either
operates as an interweave (i.e., opportunistic) or as an underlay (i.e.,
spectrum sharing) CR system, based on SS results. A realistic Channel State
Information (CSI) framework is assumed, according to which, the direct channel
links are known by the multiple antenna receivers (RXs), while, merely
statistical (covariance) information is available for the interference links. A
new, closed form approximation is derived for the outage probability of primary
communication, and the problem of rate-optimal selection of SS parameters and
receive beamformers is addressed for hybrid, interweave and underlay CR
systems. It is proven that our proposed system design outperforms both underlay
and interweave CR systems for a range of system scenarios
The diagnostic and prognostic potential of the EGFR/MUC4/MMP9 axis in glioma patients
Glioblastoma is the most aggressive form of brain cancer, presenting poor prognosis despite current advances in treatment. There is therefore an urgent need for novel biomarkers and therapeutic targets. Interactions between mucin 4 (MUC4) and the epidermal growth factor receptor (EGFR) are involved in carcinogenesis, and may lead to matrix metalloproteinase-9 (MMP9) overexpression, exacerbating cancer cell invasiveness. In this study, the role of MUC4, MMP9, and EGFR in the progression and clinical outcome of glioma patients was investigated. Immunohistochemistry (IHC) and immunofluorescence (IF) in fixed tissue samples of glioma patients were used to evaluate the expression and localization of EGFR, MMP9, and MUC4. Kaplan–Meier survival analysis was also performed to test the prognostic utility of the proteins for glioma patients. The protein levels were assessed with enzyme-linked immunosorbent assay (ELISA) in serum of glioma patients, to further investigate their potential as non-invasive serum biomarkers. We demonstrated that MUC4 and MMP9 are both significantly upregulated during glioma progression. Moreover, MUC4 is co-expressed with MMP9 and EGFR in the proliferative microvasculature of glioblastoma, suggesting a potential role for MUC4 in microvascular proliferation and angiogenesis. The combined high expression of MUC4/MMP9, and MUC4/MMP9/EGFR was associated with poor overall survival (OS). Finally, MMP9 mean protein level was significantly higher in the serum of glioblastoma compared with grade III glioma patients, whereas MUC4 mean protein level was minimally elevated in higher glioma grades (III and IV) compared with control. Our results suggest that MUC4, along with MMP9, might account for glioblastoma progression, representing potential therapeutic targets, and suggesting the ‘MUC4/MMP9/EGFR axis’ may play a vital role in glioblastoma diagnostics
Case of a sigmoid colon cancer with metachronous metastases to the mesorectum and the abdominal wall
<p>Abstract</p> <p>Backround</p> <p>Sigmoid colon cancer metachronous metastases commonly occur in the liver and lungs with sporadic reports also to the spleen, stomach, thyroid gland, abdominal wall and upper urinary tract. This is a rare case of metachronous metastases invading the mesorectum and the abdominal wall.</p> <p>Case presentation</p> <p>A 72-year-old female underwent sigmoidectomy for stage I (T2N0 M0) sigmoid colon cancer in May 2008. In June 2009, an abdominal computed tomography scan revealed a tumor 2 cm in size at the lower anterior mesorectum and a second mass 2 cm in size at the anterior abdominal wall midline. Total colonoscopy showed no mucosal lesion. The serum carcinoembryonic antigen level was normal. A biopsy of the mesorectum tumor showed similar histologic characteristics with the primary tumor. Since no other site of recurrence was identified, an abdominoperineal resection was attempted. During the operation and after the removal of the incision recurrence, sinus bradycardia and signs of myocardial ischemia were noticed. A loop transverse colostomy was immediately perfomed and the operation was terminated. Postoperative cardiologic examination revealed an acute myocardium infract. Chemo-radiation of the mesorectum tumor and re-evaluation for surgical excision was decided.</p> <p>Conclusion</p> <p>Metachronous metastasis of the mesorectum from sigmoid colon cancer is extremely rare. Although patterns of lymphatic spread from rectal cancer to sigmoid colon have recently been demonstrated, there is no evidence of metachronous mesorectum invasion from sigmoid colon cancer. This could be the issue for future trials.</p
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