Modulation-mode and power-assignment for SVD-and GMD-assisted downlink MIMO systems

Multiuser multiple-input multiple-output (MIMO) downlink (DL) transmission schemes experience both multiuser interference (MUI) as well as inter-antenna interference. However, instead of treating all the users jointly as in zero-forcing (ZF) multiuser transmission techniques, the investigated singular value decomposition (SVD) and geometric mean decomposition (GMD) assisted DL multiuser MIMO systems take the individual user's channel characteristics into account. The performed joint optimization of the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power shows that not necessarily all user-specific MIMO layers have to be activated in order to minimize the overall BER under the constraint of a fixed data throughpu

Performance Analysis of SVD-assisted Downlink Multiuser MIMO Systems

Multiuser multiple-input multiple-output (MIMO) downlink (DL) transmission schemes experience both multiuser interference as well as inter-antenna interference. Instead of treating all the users jointly as in zero-forcing (ZF) multiuser transmission techniques, the investigated singular value decomposition (SVD) assisted DL multiuser MIMO system takes the individual user’s channel characteristics into account. This translates to a choice of modulation constellation and transmitter power and, in our proposed system, to a choice of number of activated user-specific MIMO layers. The performed joint optimization of the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power shows that not necessarily all user-specific MIMO layers has to be activated in both frequency-selective and non-frequency selective MIMO channels in order to minimize the overall BER under the constraint of a given fixed data throughput

Impact of the closure of Berlin-Tegel Airport on ultrafine particle number concentrations on the airfield

Airports contribute substantially to ultrafine particle (UFP; <100 nm) concentrations on a local scale. These UFPs, which derive mainly from combustion processes, are generated during take-off and landing of aircraft, during aircraft movements on the tarmac, when engines and turbines are started, and by vehicles transporting goods and people on the airfield. UFPs are considered particularly harmful to human health as their small size enables them to pass far into the human body. This study investigates the extent to which particle number concentrations (PNCs) sized 7–2,000 nm respond to the cessation of air traffic due to the closure of a major airport. PNCs and wind data were monitored with a 5 s resolution at one location on the airfield of Berlin-Tegel Airport (TXL). The station was located 600 –640 m east of the runways and thus downwind of the runways for the predominant wind direction. Observations took place 24 h per day every day for about 3 weeks before and 3 weeks after the closure of the airport. During the measurement campaign, a total of 2,507 take-offs and landings took place. Including all wind directions, this study shows 30 %–40% lower PNCs on average, 2.5-fold lower maximum values as well as a 3-fold lower PNC spread after the closure of the airport. These differences are evident only during the day with active flight operations, and not during the nighttime flight ban. Downwind of the airfield, differences are even higher. After the closure of the airport, average PNCs drop by 70%, maxima by 85%, and variability is reduced by almost 90%. 70% lower and 30% less frequent PNC peaks occur downwind of the airport after flight operations are discontinued. This unique natural experiment allows for relatively clear conclusions about the relevance of airport operations on PNCs in the airfield area. The measurements carried out before and after the closure allow a direct comparison of the PNCs during airport operations and without any. Thus, our study reveals the change in UFP concentration that can be achieved through a reduction in flight operations.Peer Reviewe

Modulation-mode assignment in SVD-assisted multiuser MIMO-OFDM systems

In order to comply with the demand on increasing available data rates in particular in wireless technologies, systems with multiple transmit and receive antennas, also called MIMO (multiple-input multiple-output) systems, have become indispensable for future generations of wireless systems. Due to the strongly increasing demand in high-data rate transmission systems, frequency non-selective MIMO links have reached a state of maturity and frequency selective MIMO links are in the focus of interest. In this field, the combination of MIMO transmission and OFDM (orthogonal frequency division multiplexing) can be considered as an essential part of fulfilling the requirements of future generations of wireless systems. However, single-user scenarios have reached a state of maturity. By contrast multiple users’ scenarios require substantial further research, where in comparison to ZF (zero-forcing) multiuser transmission techniques, the individual user’s channel characteristics are taken into consideration in this contribution. The performed joint optimization of the number of activated MIMO layers and the number of transmitted bits per subcarrier along with the appropriate allocation of the transmit power shows that not necessarily all user-specific MIMO layers per subcarrier have to be activated in order to minimize the overall BER under the constraint of a given fixed data throughput

Modulation-mode Assignment for SVD-assisted Multiuser MIMO Systems with Correlation.

Multiuser multiple-input multiple-output (MIMO) downlink (DL) transmission schemes experience both multiuser interference as well as inter-antenna interference. The singular value decomposition provides an appropriate mean to process channel information and allows us to take the individual user’s channel characteristics into account rather than treating all users channels jointly as in zero-forcing (ZF) multiuser transmission techniques. However, uncorrelated MIMO channels has attracted a lot of attention and reached a state of maturity. By contrast, the performance analysis in the presence of antenna fading correlation, which decreases the channel capacity, requires substantial further research. The joint optimization of the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power shows that not necessarily all user-specific MIMO layers has to be activated in order to minimize the overall BER under the constraint of a given fixed data throughput

DataSheet1_Impact of the closure of Berlin-Tegel Airport on ultrafine particle number concentrations on the airfield.pdf

Airports contribute substantially to ultrafine particle (UFP; <100 nm) concentrations on a local scale. These UFPs, which derive mainly from combustion processes, are generated during take-off and landing of aircraft, during aircraft movements on the tarmac, when engines and turbines are started, and by vehicles transporting goods and people on the airfield. UFPs are considered particularly harmful to human health as their small size enables them to pass far into the human body. This study investigates the extent to which particle number concentrations (PNCs) sized 7–2,000 nm respond to the cessation of air traffic due to the closure of a major airport. PNCs and wind data were monitored with a 5 s resolution at one location on the airfield of Berlin-Tegel Airport (TXL). The station was located 600 –640 m east of the runways and thus downwind of the runways for the predominant wind direction. Observations took place 24 h per day every day for about 3 weeks before and 3 weeks after the closure of the airport. During the measurement campaign, a total of 2,507 take-offs and landings took place. Including all wind directions, this study shows 30 %–40% lower PNCs on average, 2.5-fold lower maximum values as well as a 3-fold lower PNC spread after the closure of the airport. These differences are evident only during the day with active flight operations, and not during the nighttime flight ban. Downwind of the airfield, differences are even higher. After the closure of the airport, average PNCs drop by 70%, maxima by 85%, and variability is reduced by almost 90%. 70% lower and 30% less frequent PNC peaks occur downwind of the airport after flight operations are discontinued. This unique natural experiment allows for relatively clear conclusions about the relevance of airport operations on PNCs in the airfield area. The measurements carried out before and after the closure allow a direct comparison of the PNCs during airport operations and without any. Thus, our study reveals the change in UFP concentration that can be achieved through a reduction in flight operations. </p

Clinical impact of duodenal pancreatic heterotopia – Is there a need for surgical treatment?

Background Pancreatic heterotopia (PH) is defined as ectopic pancreatic tissue outside the normal pancreas and its vasculature and duct system. Most frequently, PH is detected incidentally by histopathological examination. The aim of the present study was to analyze a large single-center series of duodenal PH with respect to the clinical presentation. Methods A prospective pancreatic database was retrospectively analyzed for cases of PH of the duodenum. All pancreatic and duodenal resections performed between January 2000 and October 2015 were included and screened for histopathologically proven duodenal PH. PH was classified according to Heinrich’s classification (Type I acini, ducts, and islet cells; Type II acini and ducts; Type III only ducts). Results A total of 1274 pancreatic and duodenal resections were performed within the study period, and 67 cases of PH (5.3%) were identified. The respective patients were predominantly male (72%) and either underwent pancreatoduodenectomy (n = 60); a limited pancreas resection with partial duodenal resection (n = 4); distal pancreatectomy with partial duodenal resection (n = 1); total pancreatectomy (n = 1); or enucleation (n = 1). Whereas 65 patients (83.5%) were asymptomatic, 11 patients (18.4%) presented with symptoms related to PH (most frequently with abdominal pain [72%] and duodenal obstruction [55%]). Of those, seven patients (63.6%) had chronic pancreatitis in the heterotopic pancreas. The risk of malignant transformation into adenocarcinoma was 2.9%. Conclusions PH is found in approximately 5% of pancreatic or duodenal resections and is generally asymptomatic. Chronic pancreatitis is not uncommon in heterotopic pancreatic tissue, and even there is a risk of malignant transformation. PH should be considered for the differential diagnosis of duodenal lesions and surgery should be considered, especially in symptomatic cases

Synthetic Lethality Screen Identifies RPS6KA2 as Modifier of Epidermal Growth Factor Receptor Activity in Pancreatic Cancer

Pancreatic cancer is characterized by a high degree of resistance to chemotherapy. Epidermal growth factor receptor (EGFR) inhibition using the small-molecule inhibitor erlotinib was shown to provide a small survival benefit in a subgroup of patients. To identify kinases whose inhibition acts synergistically with erlotinib, we employed a kinome-wide small-interfering RNA (siRNA)-based loss-of-function screen in the presence of erlotinib. Of 779 tested kinases, we identified several targets whose inhibition acted synergistically lethal with EGFR inhibition by erlotinib, among them the S6 kinase ribosomal protein S6 kinase 2 (RPS6KA2)/ribosomal S6 kinase 3. Activated RPS6KA2 was expressed in approximately 40% of 123 human pancreatic cancer tissues. RPS6KA2 was shown to act downstream of EGFR/RAS/mitogen-activated protein kinase kinase (MEK)/extracellular-signal regulated kinase (ERK) signaling and was activated by EGF independently of the presence of KRAS mutations. Knockdown of RPS6KA2 by siRNA led to increased apoptosis only in the presence of erlotinib, whereas RPS6KA2 activation or overexpression rescued from erlotinib- and gemcitabine-induced apoptosis. This effect was at least in part mediated by downstream activation of ribosomal protein S6. Genetic as well as pharmacological inhibition of RPS6KA2 by the inhibitor BI-D1870 acted synergistically with erlotinib. By applying this synergistic lethality screen using a kinome-wide RNA interference-library approach, we identified RPS6KA2 as potential drug target whose inhibition synergistically enhanced the effect of erlotinib on tumor cell survival. This kinase therefore represents a promising drug candidate suitable for the development of novel inhibitors for pancreatic cancer therapy

Acellularization-induced changes in tensile properties are organ specific: an in-vitro mechanical and structural analysis of porcine soft tissues

Introduction: Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and methods: Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens. Results: Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A loss of the epidermal layer and decreased fibronectin content was present in the skin. Discussion: Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin