How Many Lymph Nodes Are Enough? Assessing the Adequacy of Lymph Node Yield for Staging in Favorable Histology Wilms Tumor

© 2019 Elsevier Inc. Purpose: Current investigational priorities in the treatment of favorable histology Wilms tumor (FHWT) center on accurate staging and risk-stratification. The extent of lymph node (LN) sampling has not been clearly defined; its importance cannot be overstated as it guides adjuvant therapy. The identification of a minimum LN yield to minimize the risk of harboring occult metastatic disease could help development of surgical guidelines. This study focuses on using the beta-binomial distribution to estimate the risk of occult metastatic disease in patients with FHWT. Materials & methods: The National Cancer Database was queried for patients with unilateral FHWT from 2004 to 2013. Data were used to characterize nodal positivity for patients who underwent surgery and had ≥ 1 positive LN and ≥ 2 LNs examined. The probability of missing a positive LN (i.e., false negative) for a given LN yield was calculated using an empirical estimation and the beta-binomial model. Patients were then stratified by tumor size. Results: 422 patients met study criteria. To limit the chance of missing a positive LN to ≤ 10%, the empirical estimation and beta-binomial model estimated that 6 and 10 LNs needed to be sampled, respectively. Tumor size did not influence the result. Internal validation showed little variation to maintain a false negative rate ≤ 10%. Conclusions: Using mathematical modeling, it appears that the desired LN yield in FHWT to reduce the risk of false-negative LN sampling to ≤ 10% is between 6 and 10. The current analysis represents an objective attempt to determine the desired surgical approach to LN sampling to accurately stage patients with FHWT. Level of evidence: I

Wireless Communication onboard Spacecraft: Draadloze Communicatie aan boord van Ruimtevaartuigen

This dissertation focuses on intra-spacecraft wireless communication as a solution for reducing the spacecraft onboard harness. Despite outstanding advances in aerospace industry, the cost of accessing space is still very high and the amount of engineering work required for spacecraft design and development is enormous. The key elements which increase the development and launch cost of a spacecraft are size, mass, and the necessity of a tailored design for each mission. Studies show that the contribution of onboard harness to spacecraft mass is about 6% to 10%. Any effort to reduce harness can directly result in reducing the launch cost and arriving to a more modular and flexible design.This thesis aims to answer the following questions:1. What are the problems of onboard wired standards and what are the benefits and characteristics of wireless network onboard spacecraft?2. Which spacecraft subsystems could benefit most from a wireless onboard communication paradigm?3. What is the major challenge regarding employing a wireless standard onboard a spacecraft?4. How can we solve the identified system level design challenge?To answer these questions, this dissertation reviews the existing wired spacecraft data bus standards and major commercial off the shelf (COTS) wireless communication solutions to identify and characterize their architectures. These wireless standards are Wi-Fi, Bluetooth and ZigBee. Categorizing different onboard data types aids to identify a suitable COTS wireless communication solution for each application category. Specifically, sensors of attitude determination and control system (ADCS) can greatly benefit from a low power and low data rate wireless communication solution such as ZigBee, however, the major challenge is conserving energy on the sensors to enable a wireless architecture and achieve an adequate battery life without compromising the system performance. This dissertation proposes two onboard energy managers based on sensor scheduling schemes to tackle the energy conservation challenge. These solutions are tailored to ADCS and aim to reduce the overall ADCS energy consumption without affecting the required accuracy of attitude determination. Both energy managers use similar design elements and decision making algorithms while one of them presents a centralized scheme and the other one employs a decentralized architecture. A unique characteristic of these designs is that the energy management solution is fully integrated with the onboard attitude determination system of the spacecraft. Simulation results show that enabling the energy managers result in total energy saving between 20.9% to 51% (depending on the scenario) without compromoising accuracy of attitude determination.Space Systems Egineerin

Bacterial cytoskeletal filaments: Towards a DNA segregation system for a synthetic cell

The past decades have seen the rapid development of many aspects of synthetic biology. For example, attempts to build synthetic cells under controlled conditions in the laboratory have led to significant achievements. Following a bottom-up approach, scientists aim at building a self-reproducing synthetic cell with a minimum number of biological modules. A functional synthetic cell should accomplish at least four processes during one cycle: growth,DNAreplication,DNA segregation, and division. DNA segregation, as a vital step in the life cycle of a synthetic cell, is in focus in this thesis. Segregation of replicated DNA in eukaryotes depends highly on microtubules. Microtubules are protein polymers which form cylindrical tubes, a dynamic structure with which they can exert both pulling and pushing forces. During cell division, microtubules form a spindle-like structure, named the mitotic spindle. Microtubules in the mitotic spindle apparatus attach to the replicated chromosomes through kinetochores and exert pulling forces to separate the sister chromosomes and place them in the newly born daughter cells. These hollow tubes can grow in the presence of GTPbound tubulin dimers. When all the GTP-tubulin subunits at the end of a filament turned into GDP-tubulin, themicrotubule exhibits a transition to shrinkage. While the addition of GTP-tubulin to the end of microtubulesmay cause pushing forces, shrinking microtubules are able to exert pulling forces with the help of microtubule adapter proteins. The random transitions between growth and shrinkage of a microtubule is called dynamic instability and has been studied throughout decades. DNA segregation components of a synthetic cell should preferably be fully expressible in a cell-free manner which employs reconstituted transcription-translation factors. Although mitosis in eukaryotes is the best-studied DNA segregation system to date, microtubules are unsuitable for cell-free expression due to their complex chaperondependent folding as well as essential post-translational modifications. Interesting alternatives for DNA segregation in synthetic cells are provided by bacterial segregation systems. An active bacterial segregation system is ideally composed of three elements: a cytomotive NTPase filament, a connecting or adapter protein, and a centromere-like DNA sequence. This thesis will examine various bacterial cytoskeletal filaments with a central focus on their suitability for building a DNA segregation systemfor synthetic cells...BN/Bionanoscienc

A comparative analysis of project management and systems engineering techniques in CubeSat projects

Space EngineeringAerospace Engineerin

An attitude determination system suitable for a spacecraft

Delft University of Technolog

Spatially Correct Rate-Constrained Noise Reduction For Binaural Hearing Aids in Wireless Acoustic Sensor Networks

Compared to monaural hearing aids (HAs), binaural hearing aid systems, in which there is a communication link between the two devices, have improved noise reduction capabilities and the ability to preserve binaural spatial information. However, the limited HA battery lifetime puts constraints on the amount of information that can be shared between the two devices. In other words, the rate of transmission between the devices is an important constraint that needs to be considered, while preserving the spatial information. In this article, a linearly constrained noise reduction problem is proposed, which jointly finds the optimal rate allocation and the optimal estimation (beamforming) weights across all sensors and frequencies, while preserving the binaural spatial cues of point sources. The proposed method considers a rate constraint together with linear constraints to preserve the binaural spatial cues of point sources. Minimizing the mean square error on the estimated target speech at the left and the right side beamformers, the optimal weights are found to be rate-constrained linearly constrained minimum variance (LCMV) filters, and the optimal rates are found to be the solutions to a set of reverse water filling problems. The performance of the proposed method is evaluated using the averaged binaural signal-to-noise ratio (SNR), the interaural level difference (ILD) error and the interaural time difference (ITD) error. The results show that the proposed method outperforms spatially correct noise reduction approaches that use naive/random rate allocation strategies.Circuits and System

Rate-constrained noise reduction in wireless acoustic sensor networks

Wireless acoustic sensor networks (WASNs) can be used for centralized multi-microphone noise reduction, where the processing is done in a fusion center (FC). To perform the noise reduction, the data needs to be transmitted to the FC. Considering the limited battery life of the devices in a WASN, the total data rate at which the FC can communicate with the different network devices should be constrained. In this article, we propose a rate-constrained multi-microphone noise reduction algorithm, which jointly finds the best rate allocation and estimation weights for the microphones across all frequencies. The optimal linear estimators are found to be the quantized Wiener filters, and the rates are the solutions to a filter-dependent reverse water-filling problem. The performance of the proposed framework is evaluated using simulations in terms of mean square error and predicted speech intelligibility. The results show that the proposed method is very close in performance to that of the existing optimal method based on discrete optimization. However, the proposed approach can do this at a much lower complexity, while the existing optimal reference method needs a non-tractable exhaustive search to find the best rate allocation across microphones.Accepted author manuscriptCircuits and System

On the Impact of Quantization on Binaural MVDR Beamforming

Multi-microphone noise reduction algorithms in binaural hearing aids which cooperate through a wireless link have the potential to become of great importance in future hearing aid systems. However, limited transmission capacity of such devices necessitates the data compression of signals transmitted from one hearing aid to the contralateral one. In this paper we study the impact of quantization as a data compression scheme on the performance of the multi-microphone noise reduction algorithms. Using the binaural minimum variance distortionless response (BMVDR) beamformer as an illustration, we propose a quantization aware beamforming scheme which uses a modified cross power spectral density (CPSD) of the system noise including the quantization noise (QN). Moreover, several assumptions on the QN are investigated in the proposed method. Based on the output SNR, we compare different variations of the proposed method with the conventional BMVDR beamformer. The results confirm the improved performance of the proposed method.Circuits and System

Experimental analysis for the dynamic initiation mechanism of debris flows

Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dynamic triaxial tests. A series of static and dynamic triaxial tests were conducted on samples in the lab. The samples were prepared according to different grain size distribution, degree of saturation and earthquake magnitudes. The relations of dynamic shear strength, degree of saturation, and number of cycles are summarized through analyzing experimental results. The findings show that the gravelly soil with a wide and continuous gradation has a critical degree of saturation of approximately 87%, above which debris flows will be triggered by rainfall, while the debris flow will be triggered at a critical degree of saturation of about 73% under the effect of rainfall and earthquake (M > 6.5). Debris flow initiation is developed in the humidification process, and the earthquake provides energy for triggering debris flows. Debris flows are more likely to be triggered at the relatively low saturation under dynamic loading than under static loading. The resistance of debris flow triggering relies more on internal frication angle than soil cohesion under the effect of rainfall and earthquake. The conclusions provide an experimental analysis method for dynamic initiation mechanism of debris flows

Tehran environmental and neurodevelopmental disorders (TEND) cohort study: Phase I, feasibility assessment

Purpose: To advance knowledge about childhood neurodevelopmental disorders and study their environmental determinants, we conducted a study in Tehran, Iran to assess the feasibility of prospective birth cohort study. Methods: We evaluated participation of pregnant women, feasibility of sampling biological material, and health care services availability in Tehran in four steps: (1) first trimester of pregnancy; (2) third trimester of pregnancy; (3) at delivery; and (4) two to three months after delivery. We collected related data through questionnaires, also various biological samples were obtained from mothers (blood, urine, milk and nails�hands and feet) and newborns (umbilical cord blood, meconium, and urine samples) from February 2016 to October 2017. Results: overall 838 eligible pregnant women were approached. The participation rate was 206(25) in our study and about 185(90) of subjects were recruited in hospitals. Out of 206 participants in the first trimester, blood, urine, hand nail, and foot nail samples were collected from 206(100),193(93), 205(99), and 205(99), respectively. These values dropped to 65(54), 83(69), 84(70), and 84(70) for the remaining participants 120(58) in the third trimester, respectively. Also, we gathered milk samples from 125(60) of mothers at two to three months after delivery. Conclusion: Our findings suggest that hospitals were better places for recruitment of subjects in a birth cohort in Tehran. We further concluded that birth cohort study recruitment can be improved by choosing appropriate gestational ages. Obtaining the newborn�s urine, meconium, and umbilical cord blood were challenging procedures and require good collaboration between hospital staff and researchers. © 2020, Springer Nature Switzerland AG