Improved Group multiuser detection with multiple receive antennas in the presence of improper multi-access interference

We consider the transmission of K binary phase-shift keying signals over M diversity channels through a rich scattering environment. Improved group detection rules are proposed to mitigate the effect of the improper multiaccess interference, and an enhancement of the system receive diversity order is shown to be obtained. For example, it is demonstrated that a further gain of |g~|/2 per group is obtained compared with conventional group detection, where |g~| is the interfering group size. In addition, when there is only one antenna per group, the considered receiver with the improved detection rules is equivalent to the decorrelator. In this case, it is shown that (K-1) interferers can be ed out, and that an M-(K-1/2) receive diversity order is achieved, compared with only M-/sup 2/K+1 with the conventional detection rules. Numerical results will further put in evidence such gains.     

Receive antenna selection for closely-spaced antennas with mutual coupling

We investigate the achievable rate of receive antenna selection MIMO systems in the presence of mutual coupling and spatial correlation. For that, we assume the antenna array to consist of dipole antennas placed side-by-side in a linear pattern and in a very limited physical space. In a first step, we will assume perfect channel state information at the receiver side only and a negligible training overhead compared with the payload. We will demonstrate that in contrast to what might be expected based on results for cases without mutual coupling, MIMO receive antenna selection can achieve higher data rates than the system using all antennas provided that the total number of receive antennas is larger than a critical value that we will further discuss. We then propose an optimal antenna selection processing that ensures rate maximization regardless of the number of antennas used. In a later step, we will address the impact of training overhead on the system achievable rate when the training overhead is considerable. We will show that such a rate is reduced dramatically due to the large amount of training overhead arising from the presence of mutual coupling. To overcome this problem, we will thus propose a novel channel estimation method, which reduces the training overhead greatly and improves the system achievable rate performance.     

A quasi-orthogonal group space-time architecture to achieve a better diversity-multiplexing tradeoff

Most existing MIMO (multiput-input multiput-output) schemes optimize only either the diversity gain or the multiplexing gain. To obtain a good tradeoff between these two, the quasi-orthogonal group space-time (QoGST) architecture is proposed, wherein the transmit stream is subgrouped but encoded via an inter-group space-time block encoder, with group interference suppression at the receiver. This paper also considers another combined space-time coding and layered space-time architecture, which we refer to as group layered space-time (GLST), where space-time block coding is employed within each group. Under the assumption of Rayleigh fading and a prior perfect channel state information at the receiver, a performance analysis will demonstrate that both QoGST and GLST can achieve a good diversity-multiplexing tradeoff. QoGST is even superior to GLST. Simulation results will validate our analysis and further show that compared to the existent layered space-time block code (LSTBC) scheme, both QoGST and GLST can achieve a significant performance gain     

Characterization of the Absorption of Theophylline From Immediate- and Controlled-Release Dosage Forms With a Numerical Approach Using the In Vitro Dissolution-Permeation Process Using Caco-2 Cells

After oral administration, drug absorption rate is recognized to be dependent on two major factors: dissolution and intestinal cells permeability. Caco-2 monolayer cells have been largely used as a permeation study model. In this study, a numerical approach funded on an exponential first-order time relationship was tested to compare immediate- and controlled-release tablets of theophylline using a dissolution-permeation system. The dissolution performance using USP II paddle apparatus was coupled to the permeability studies investigated in Caco-2 cell monolayers. The dissolved samples were taken at different times; their pH and osmolarity were adjusted to render them suitable to Caco-2 permeability studies (osmolarity = 300 mosm, pH = 7.4). The experimental data show that the dissolution fits the exponential first-order relationship rate. The permeability values were in a range of 4.45 10^- 6-5.28 10^- 6 cm/s, and percentages of absorbed drug dose were dependent on the fraction initially present in the donor compartment, indicating that absorption of theophylline was dissolution rate limited. Plotting experimental absorbed fractions (F_a) against experimental dissolved fractions (F_d) show that permeation is the rate-limiting step in drug absorption process in the extended release form of theophylline. Our results demonstrate a general agreement between observed F_a/F_d relationships and theoretical F_a/F_d relationships obtained with our approach funded on dissolution and permeation behavior. We concluded that the couple dissolution-caco-2 system could be a useful tool to characterize intestinal permeation for a new formulation of a drug compared with the conventional one.     

Relationship between small dam efficiency and gully erodibility of the lithologic formations covering their watershed

Soil conservation strategy in the semi-arid areas of central Tunisia has focused on the construction of numerous hill reservoirs. However, limited rainfall combined with severe soil erosion is jeopardizing the usefulness of hill reservoirs such that there is an urgent need to undertake further studies into the location and efficiency of small dams. The paper reports investigations into the relationship between location of the dam and the underlying lithology of the catchment areas with the dam efficiency. A gully erodibility factor has been proposed for nine groups of lithological formations identified and a watershed lithologic number was computed as the product of seven watersheds for which 1:50,000 scale lithological maps were available. A significant linear relationship was determined between the watershed lithologic number and the efficiency of the small dams, indicating that an accurate lithological survey prior to small dam planning can be used to indicate the dam's likely efficiency and to plan any necessary soil and water conservation works in the catchment areas.     

Optimal diversity-multiplexing tradeoff with group detection for MIMO systems

It is well known that multiple-input multiple-output (MIMO) systems provide two types of gains: diversity gains and spatial multiplexing gains. Recently, a tradeoff function of these two gains has been derived for a point-to-point MIMO system when optimal detection is used. In this paper, we extend the previous work to a more general MIMO system, where the transmitted data is coded in groups. Group detection is applied at the receiver to retrieve the data. It consists of a zero-forcing decorrelation that separates the groups, followed by a joint detection for each of the groups. Two receiver structures are considered in this paper; namely, group zero forcing (GZF) and group successive interference cancellation (GSIC). We assess the diversity-multiplexing tradeoff function of each of these receivers over a richly scattered Rayleigh fading channel. Three rate-allocation algorithms will be considered here; namely, equal rate, group-size proportional rate, and optimal-rate allocation. An explicit expression of the system tradeoff will be derived for both receivers with these three rate allocations. The obtained results will first be optimized over all possible group partitions for a given number of groups. Next, the number of groups will be varied to further optimize the system-tradeoff performance. An overall optimum tradeoff for a general MIMO system with group detection will then be obtained. Numerical results will indicate that optimum performance can be approached with very-low-complexity schemes for a wide range of data rates. It will be also demonstrated that group detection bridges the gap between the traditional decorrelator and the optimal receiver tradeoff performances.     

Acute intestinal obstruction and pregnancy. Apropos of 3 cases

The axillary artery has been successfully cannulated in critically ill adult and paediatric patients. There is little information about experience with this technique in neonates. We report the use of axillary cannulation in 62 mechanically ventilated neonates with birth weight from 750 to 3800 g (mean 1950 g). The axillary artery was catheterized with 24 or 22 gauge teflon catheters by means of the catheter-over-a-needle technique. Arterial access was used for blood pressure monitoring, blood sampling and in seven cases for blood removal during exchange transfusions. Cannulae were removed when the fraction of inspired oxygen (FIO2) was less than 0.3. During cannulation capillary refill, radial artery pulse and neurological status of the arm were checked daily. The mean period of cannulation was 4.1 days (1-10 days). During cannulation and after catheter removal there were no complications related to the chosen vessel e.g. no change in the skin colour, skin warmth, capillary refill and the quality of the radial pulse. No changes in the motor activity of the limb on the cannulated side were observed. CONCLUSION: Axillary artery cannulation is a useful alternative for establishing an arterial access in ventilated neonates. Further studies are needed to evaluate the long-term consequences of this technique.     

Characterization of the absorption of theophylline from immediate- and controlled-release dosage forms with a numerical approach using the in vitro dissolution-permeation process using caco-2 cells

After oral administration, drug absorption rate is recognized to be dependent on two major factors: dissolution and intestinal cells permeability. Caco-2 monolayer cells have been largely used as a permeation study model. In this study, a numerical approach funded on an exponential first-order time relationship was tested to compare immediate- and controlled-release tablets of theophylline using a dissolution-permeation system. The dissolution performance using USP II paddle apparatus was coupled to the permeability studies investigated in Caco-2 cell monolayers. The dissolved samples were taken at different times; their pH and osmolarity were adjusted to render them suitable to Caco-2 permeability studies (osmolarity = 300 mosm, pH = 7.4). The experimental data show that the dissolution fits the exponential first-order relationship rate. The permeability values were in a range of 4.45 10(- 6)-5.28 10(- 6) cm/s, and percentages of absorbed drug dose were dependent on the fraction initially present in the donor compartment, indicating that absorption of theophylline was dissolution rate limited. Plotting experimental absorbed fractions (F(a)) against experimental dissolved fractions (F(d)) show that permeation is the rate-limiting step in drug absorption process in the extended release form of theophylline. Our results demonstrate a general agreement between observed F(a)/F(d) relationships and theoretical F(a)/F(d) relationships obtained with our approach funded on dissolution and permeation behavior. We concluded that the couple dissolution-caco-2 system could be a useful tool to characterize intestinal permeation for a new formulation of a drug compared with the conventional one.     

Indication of medical abortion in cases of fetal abnormalities diagnosed in utero

OBJECTIVE: To search the novel gene related to human hepatoma. METHODS: Northern blot analysis was used to isolate from EST (expressed sequence tags) clones a cDNA fragment differentially expressed in hepatocellular carcinoma versus its surrounding noncancerous hepatic tissue. Human fetal liver cDNA library was screened with EST fragment probe. RESULTS: Northern blot analysis showed that EST clone F9391 expressed at high level in all the 6 hepatocellular carcinoma samples but low level in the surrounding noncancerous hepatic tissues and 2 normal liver tissues. In further screening of human fetal liver cDNA library, we obtained a positive clone named FL6. Nucleotide sequencing indicated that FL6 contained 1464 base pairs and the matched DNA sequence was not found in the gene data bases (EMBL 96.6). Northern blot analysis of various fetus tissues with FL6 probe showed a high level expression in lung, small intestine, skin and placenta, middle level expression in liver, stomach, colon and muscle but low level expression in brain, thyroid, thymus, heart, kidney, pancreas and bladder. CONCLUSION: The results suggested that FL6 gene related to cell proliferation and may play an important role in the process of oncogenesis.