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To get channel state information (CSI) at a base station (BS), most of researches on massive multiple-input multiple-output (MIMO) systems consider time division duplexing (TDD) to get benefit from the uplink and downlink channel reciprocity. Even in TDD, however, the BS still needs to transmit downlink training signals, which are referred to as channel state information reference signals (CSI-RSs) in the 3GPP standard, to support spatial multiplexing in practice. This is because there are many cases that the number of transmit antennas is less than the number of receive antennas at a user equipment (UE) due to power consumption and circuit complexity issues. Because of this mismatch, uplink sounding reference signals (SRSs) from the UE are not enough for the BS to obtain full downlink MIMO CSI. Therefore, after receiving the downlink CSI-RSs, the UE needs to feedback quantized CSI to the BS using a pre-defined codebook to support spatial multiplexing. In this paper, possible approaches to reconstruct full downlink MIMO CSI at the BS are proposed by exploiting both the SRS and quantized downlink CSI considering practical antenna structures with reduced downlink CSI-RS overhead. Numerical results show that the spectral efficiencies by spatial multiplexing based on the proposed downlink MIMO CSI reconstruction techniques outperform the conventional methods solely based on the quantized CSI. [ABSTRACT FROM AUTHOR]

Hybrid precoding is used in millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems instead of full digital precoding to reduce the cost and power consumption. Conventional hybrid precoding however requires complex channel estimation before beamforming. In this paper, we propose a low complexity low-cost channel estimation-free deep direct beamforming method composed of two basic steps-beam impulse and beamforming for time division duplex (TDD). This method is built upon randomized singular value decomposition (RSVD) and can directly complete the process of beamforming. Furthermore, a realistic dataset of mmWave channel-DeepMIMO is adopted to evaluate and determine the practicability of this method. The simulation results demonstrate that the proposed deep direct beamforming achieves high performance while its complexity and power consumption are very low. Compared with other methods without perfect channel status information (CSI), the proposed method costs less and requires lower computational resources while achieves higher spectral efficiency. Furthermore, the RSVD can be easily combined with conventional beamforming methods hence the proposed method is easily extendable to other applications. [ABSTRACT FROM AUTHOR]

There is a great need for innovative new medicines to treat unmet medical needs. The discovery and development of innovative new medicines is extremely difficult, costly, and inefficient. In the last decade, phenotypic drug discovery (PDD) was reintroduced as a strategy to provide first-in-class medicines. PDD uses empirical, target-agnostic lead generation to identify pharmacologically active molecules and novel therapeutics which work through unprecedented drug mechanisms. The economic and scientific value of PDD is exemplified through game-changing medicines for hepatitis C virus, spinal muscular atrophy, and cystic fibrosis. In this short review, recent advances are noted for the implementation and de-risking of PDD (for compound library selection, biomarker development, mechanism identification, and safety studies) and the potential for artificial intelligence. A significant barrier in the decision to implement PDD is balancing the potential impact of a novel mechanism of drug action with an under-defined scientific path forward, with the desire to provide infrastructure and metrics to optimize return on investment, which a known mechanism provides. A means to address this knowledge gap in the future is to empower precompetitive research utilizing the empirical concepts of PDD to identify new mechanisms and pharmacologically active compounds.

A wideband antenna design with double negative metamaterial (DNG) has been designed and evaluated for 4 G and 5 G applications. The antenna design is investigated for wideband operations for 5 G NR (New Radio) n78 band and TDD LTE (Long Term Evolution) bands from LTE band no. 33 to 43. The design is ruled out for size miniaturisation and wide bandwidth using a radiating-folded dipole. The radiating elements can be tuned to adapt to different configurations using controlling parameters. Moreover, the antenna designed is also investigated for SAR, gain, polarisation and efficiency using metamaterial integration. CST microwave studio is used for designing and analysis of the design and the results are validated for the fabricated prototype. The measured and simulated results are in good agreement with each other and proofs to be a good design for 4 G and 5 G communications. [ABSTRACT FROM AUTHOR]

Test-driven development (TDD) is a popular design approach used by the developers with testing being the important software development driving factor. On the other hand, mutation testing is considered one of the most effective testing techniques. However, there is not so much research on combining these two techniques together. In this paper, we propose a novel, hybrid approach called TDD+M which combines test-driven development process together with the mutation approach. The aim was to check whether this modified approach allows the developers to write a better quality code. We verify our approach by conducting a controlled experiment and we show that it achieves better results than the sole TDD technique. The experiment involved 22 computer science students split into eight groups. Four groups (TDD+M) were using our approach, the other four (TDD) – a normal TDD process. We performed a cross-experiment by measuring the code coverage and mutation coverage for each combination (code of group X, tests from group Y). The TDD+M tests achieved better coverage on the code from TDD groups than the TDD tests on their own code (53.3% vs. 33.5% statement coverage and 64.9% vs. 37.5% mutation coverage). The TDD+M tests also found more post-release defects in the TDD code than TDD tests in the TDD+M code. The experiment showed that adding mutation into the TDD process allows the developers to provide better, stronger tests and to write a better quality code. [ABSTRACT FROM AUTHOR]

Software engineering (SE) experiments suffer from threats to validity that may impact their results. Replication allows researchers building on top of previous experiments' weaknesses and increasing the reliability of the findings. Illustrating the benefits of replication to increase the reliability of the findings and uncover moderator variables. We replicate an experiment on test-driven development (TDD) and address some of its threats to validity and those of a previous replication. We compare the replications' results and hypothesize on plausible moderators impacting results. Differences across TDD replications' results might be due to the operationalization of the response variables, the allocation of subjects to treatments, the allowance to work outside the laboratory, the provision of stubs, or the task. Replications allow examining the robustness of the findings, hypothesizing on plausible moderators influencing results, and strengthening the evidence obtained. [ABSTRACT FROM AUTHOR]

Thanks to the digitization and softwarization of radio communication, the development cycle of new radio technologies can be significantly accelerated by prototyping on software-defined radio (SDR) platforms. However, a slow turnaround time (TT) of the front-end of an SDR for switching from receiving mode to transmitting mode or vice versa, are jeopardizing the prototyping of wireless protocols, standards, or systems with stringent latency requirements. In this paper, a novel solution called BaseBand processing unit operating in Half Duplex mode and analog Radio Frequency front-end operating in Full Duplex mode, BBHD-RFFD, is presented to reduce the TT on SDR. A prototype is realized on the widely adopted AD9361 radio frequency frontend to prove the validity of the proposed solution. Experiments unveil that for any type of application, the TT in time division duplex (TDD) operation mode can be reduced to zero by the BBHD-RFFD approach, with negligible impact on the communication system in terms of receiver sensitivity. The impact is measured for an in-house IEEE 802.15.4 compliant transceiver. When compared against the conventional TDD approach, only a 7.5-dB degradation is observed with the BBHD-RFFD approach. The measured sensitivity of -91 dBm is still well above the minimum level (i.e., -85 dBm at 2.4 GHz) defined by the IEEE 802.15.4 standard.

Techniques for quality assurance have to deal with the complexity of software systems and the high probabilities of new errors appearing in any stage of the software life cycle. Software testing is a widely used approach but, due to the costs involved in this process, development teams often debate its applicability in their projects. In the endeavor to reduce the complexity of this process, this study presents an approach for software development based in Test-Driven Development (TDD) supported by Model-Based Testing (MBT) tools to allow automatic test-case generation. The approach, called MoFQA (Model-First Quality Assurance), consists of two main aspects: i) a method to drive software development based on testing techniques which defines steps and recom-mended practices; and, ii) a tool-set to allow clients and stakeholders to model system requirements, testers to create models that represent unit and abstract tests, and transformation tools used to generate executable tests. The tools that MoFQA provides are focusing on web applications. In order to validate the MoFQA tools, two validation experiences are presented.

W artykule przedstawiono jeden z problemów występujących podczas korzystania ze standardu C++14 wraz z biblioteką Google Mock. Na podstawie wprowadzonego problemu omówiono możliwe rozwiązania, a także zaprezentowano poprawiony schemat dla podejścia TDD.

Channel estimation is an essential component, in which channel state information playing very important role in wireless communications. But acquiring CSI in practice is a challenging issue for massive MIMO systems. To reduce the over burden for obtaining channel impulse response of huge Multi input multi output system channel reciprocity in TDD domain is suggested, because the forward link channel data can be derived from the reverse link signal without any feedback involvement. Because of mismatches at uplink, downlink channels maintaining reciprocity in TDD systems is impractical. We study the impact of multiplicative reciprocity error for precoders (Zero forcing, MMSE and MRT) performance along with channel estimation error. In this paper effect of RF mismatches impact on linear precoders is analyzed and simulated in terms of SINR versus SNR under additive white Gaussian noise. [ABSTRACT FROM AUTHOR]

In time-division duplexing (TDD) massive multiple-input multiple-output (MIMO) systems, the reciprocity between the downlink (DL) and the uplink (UL) channels can be utilized to infer the DL channel state information (CSI) with the acquired uplink (UL) CSI. However, the end-to-end UL and DL channel reciprocity are broken when there are mismatches in the radio frequency (RF) analog circuits among different antennas at the base station (BS). Without accurate calibration, there will be severe system performance degradation. This paper studies the internal self-calibration scheme to recover all the unknown full calibration coefficients when different BS antennas are interconnected via hardware transmission lines. On the one hand, we derive the calibration performance for an arbitrary interconnection network in closed-form and obtain closed-form Cramer-Rao lower bound (CRLB) expressions when $(M-1)$ transmission lines are consumed and $M$ denotes the total number of BS antennas. On the other hand, we prove that the star interconnection network is optimal for internal full self-calibration due to its lowest CRLB. Numerical simulation are carried out to verify our theoretical analyses and results. [ABSTRACT FROM AUTHOR]

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Competing Interests: Jeffrey A. Klein owns HK Surgical, Inc (a surgical supply and equipment company that develops infiltration pumps that can be used for Tumescent Drug Delivery). Jeffrey A. Klein and Paytra A. Klein have patents regarding Tumescent Drug Delivery.

Using skin patches to deliver drugs is dependable and doesn't have the same issues as permeation enhancers, which help drugs get through the skin but struggle because of the skin's natural barrier. Strategies are required to increase topical bioavailability to enhance drug absorption. Natural compounds offer a promising solution by temporarily reducing skin barrier resistance and improving drug absorption. Natural substances allow a wider variety of medications to be distributed through the stratum corneum, offering a dependable approach to enhancing transdermal drug delivery. Natural substances have distinct advantages as permeability enhancers. They are pharmacologically effective and safe, inactive, non-allergenic, and non-irritating. These characteristics ensure their suitability for use without causing adverse effects. Natural compounds are readily available and well tolerated by the body. Studies investigating the structure-activity relationship of natural chemicals have demonstrated significant enhancer effects. By understanding the connection between chemical composition and enhancer activity, researchers can identify effective natural compounds for improving drug penetration. In conclusion, current research focuses on utilizing natural compounds as permeability enhancers in transdermal therapy systems. These substances offer safety, non-toxicity, pharmacological inactivity, and non-irritation. Through structure-activity relationship investigations, promising advancements have been made in enhancing drug delivery. Using natural compounds holds enormous potential for improving the penetration of trans-dermally delivered medications., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

In this paper, we propose a method to reuse the cyclic-prefix (CP) intervals of an ongoing OFDM link, by another link, without degrading the OFDM link performance. We label the link that reuses the CP-intervals as CPLink, as they use only the CP-intervals of the ongoing link labeled, MainLink. We leverage the fact that the most commonly used OFDM receivers discard the samples in CP-intervals to design the CPLink that ensures below-noise-floor interference at every MainLink-receiver. The key contribution in this paper is the design and study of zero-knowledge CPLink, in which the CPLink-transmitter ensures below-noise-floor interference at every MainLink-receiver with no knowledge about the locations or the number of MainLink-receivers. We analytically show that the zero-knowledge CPLink capacity is positive. For LTE frame structure with 20-MHz bandwidth and 2-km cell-radius, we evaluate the CPLink for two kinds of CPLink-receivers: full-duplex base-station and a half-duplex device. Even for the cell-edge CPLink-transmitters, full-duplex zero-knowledge CPLink data rates can be up to 20 Mbps (60 Mbps) when the CP duration is ~7% (25%) of the data-symbol duration. The half-duplex CPLink rate is 5–40 Mbps when the CPLink-transmitter is within 250 m of CPLink-receiver. CPLink capacity is found to increase near-linearly with the CP duration, thus mitigating CP overhead. [ABSTRACT FROM AUTHOR]

One of the biggest challenges in operating massive multiple-input multiple-output systems is the acquisition of accurate channel state information at the transmitter. To take up this challenge, time division duplex is more favorable thanks to its channel reciprocity between downlink and uplink. However, while the propagation channel over the air is reciprocal, the radio-frequency front-ends in the transceivers are not. Therefore, calibration is required to compensate the RF hardware asymmetry. Although various over-the-air calibration methods exist to address the above problem, this paper offers a unified representation of these algorithms, providing a higher level view on the calibration problem, and introduces innovations on calibration methods. We present a novel family of calibration methods, based on antenna grouping, which improves accuracy and speeds up the calibration process compared to existing methods. We then provide the Cramér–Rao bound as the performance evaluation benchmark and compare maximum likelihood and least squares estimators. We also differentiate between the coherent and non-coherent accumulation of calibration measurements, and point out that enabling non-coherent accumulation allows the training to be spread in time, minimizing the impact to the data service. Overall, these results have special value in allowing the design of reciprocity calibration techniques that are both accurate and resource-effective. [ABSTRACT FROM AUTHOR]

In this study, the scaling laws of optimal training lengths were investigated for time-division duplexing massive multiple-input multiple-output systems. First, the generalized asymptotic achievable rate was derived by taking into account both uplink and downlink training. From the general form, the achievable rates of zero-forcing (ZF) and matched filter (MF) precoders are directly obtained by using the mean and variance of the effective channel. Then, we analyzed the rate gaps of ZF and MF with respect to uplink and downlink training, respectively. According to the analysis of rate gaps, it is shown that the achievable rates are more dominated by the uplink training than downlink training for both ZF and MF. The joint optimization problem for training lengths maximizing the spectral efficiency is formulated as a function of rate gaps. To study the scaling of optimal training lengths with the system parameters, we derived the optimal training lengths as a closed-form expression by using an approximation for the logarithm function. From the analysis, it is shown that the optimal training lengths decrease as the number of antennas increases, and increase as the coherence block length increases. In addition, the optimal training lengths increase as the transmit power increases for ZF, whereas it does not change for MF. Finally, we investigated the superior region for noncoherent detection (which means only statistical information is used for demodulation without downlink training) with the system parameters by comparing the spectral efficiency with and without downlink training. [ABSTRACT FROM AUTHOR]

Purpose: To report embolization of the thoracic duct by direct injection of N-butyl-2-cyanoacrylate (NBCA) glue via a puncture needle.Materials and Methods: Two cases of high output chylothorax were successfully treated with direct injection of N-butyl-2-cyanoacrylate (NBCA) glue via a puncture needle. In them, conventional thoracic duct embolization (TDE) was attempted, but the cisterna chyli was absent on intranodal lymphangiography, and probably for this reason catheterization of the thoracic duct was unsuccessful. Contrast material injection via a puncture needle, however, clearly showed a leak from the thoracic duct, prompting us to attempt embolization of the thoracic duct by direct injection of NBCA glue via the needle.Results: Thoracic duct embolization by direct injection of NBCA glue via a puncture needle was technically successful in both patients. No minor or major complication occurred. Both patients disappeared chylothorax after this treatment.Conclusion: This embolization method can be useful for treatment of chylothorax when conventional TDE is not achievable. [ABSTRACT FROM AUTHOR]

Downlink beamforming in Massive multiple-input and multiple-output (MIMO) either relies on uplink pilot measurements—exploiting reciprocity and time-division duplexing operation, or on the use of a predetermined grid of beams with user equipments reporting their preferred beams, mostly in frequency-division duplexing operation. Massive MIMO in its originally conceived form uses the first strategy, with uplink pilots, whereas there is currently significant commercial interest in the second, grid-of-beams. It has been analytically shown that with isotropic scattering (independent Rayleigh fading) the first approach outperforms the second. Nevertheless, there remains controversy regarding their relative performance in practical channels. In this contribution, the performances of these two strategies are compared using measured channel data at 2.6 GHz. [ABSTRACT FROM PUBLISHER]