High-Speed Analog-to-Digital Converters for Broadband Applications

Flash Analog-to-Digital Converters (ADCs), targeting optical communication standards, have been reported in SiGe BiCMOS technology. CMOS implementation of such designs faces two challenges. The first is to achieve a high sampling speed, given the lower gain-bandwidth (lower ft) of CMOS technology. The second challenge is to handle the wide bandwidth of the input signal with a certain accuracy. Although the first problem can be relaxed by using the time-interleaved architecture, the second problem remains as a main obstacle to CMOS implementation. As a result, the feasibility of the CMOS implementation of ADCs for such applications, or other wide band applications, depends primarily on achieving a very small input capacitance (large bandwidth) at the desired accuracy. In the flash architecture, the input capacitance is traded off for the achievable accuracy. This tradeoff becomes tighter with technology scaling. An effective way to ease this tradeoff is to use resistive offset averaging. This permits the use of smaller area transistors, leading to a reduction in the ADC input capacitance. In addition, interpolation can be used to decrease the input capacitance of flash ADCs. In an interpolating architecture, the number of ADC input preamplifiers is reduced significantly, and a resistor network interpolates the missing zero-crossings needed for an N-bit conversion. The resistive network also averages out the preamplifiers offsets. Consequently, an interpolating network works also as an averaging network. The resistor network used for averaging or interpolation causes a systematic non-linearity at the ADC transfer characteristics edges. The common solution to this problem is to extend the preamplifiers array beyond the input signal voltage range by using dummy preamplifiers. However, this demands a corresponding extension of the flash ADC reference-voltage resistor ladder. Since the voltage headroom of the reference ladder is considered to be a main bottleneck in the implementation of flash ADCs in deep-submicron technologies with reduced supply voltage, extending the reference voltage beyond the input voltage range is highly undesirable. The principal objective of this thesis is to develop a new circuit technique to enhance the bandwidth-accuracy product of flash ADCs. Thus, first, a rigorous analysis of flash ADC architectures accuracy-bandwidth tradeoff is presented. It is demonstrated that the interpolating architecture achieves a superior accuracy compared to that of a full flash architecture for the same input capacitance, and hence would lead to a higher bandwidth-accuracy product, especially in deep-submicron technologies that use low power supplies. Also, the gain obtained, when interpolation is employed, is quantified. In addition, the limitations of a previous claim, which suggests that an interpolating architecture is equivalent to an averaging full flash architecture that trades off accuracy for the input capacitance, is presented. Secondly, a termination technique for the averaging/interpolation network of flash ADC preamplifiers is devised. The proposed technique maintains the linearity of the ADC at the transfer characteristics edges and cancels out the over-range voltage, consumed by the dummy preamplifiers. This makes flash ADCs more amenable for integration in deep-submicron CMOS technologies. In addition, the elimination of this over-range voltage allows a larger least-significant bit. As a result, a higher input referred offset is tolerated, and a significant reductions in the ADC input capacitance and power dissipation are achieved at the same accuracy. Unlike a previous solution, the proposed technique does not introduce negative transconductance at flash ADC preamplifiers array edges. As a result, the offset averaging technique can be used efficiently. To prove the resulting saving in the ADC input capacitance and power dissipation that is attained by the proposed termination technique, a 6-bit 1.6-GS/s flash ADC test chip is designed and implemented in 0.13-$\mu$m CMOS technology. The ADC consumes 180 mW from a 1.5-V supply and achieves a Signal-to-Noise-plus-Distortion Ratio (SNDR) of 34.5 dB and 30 dB at 50-MHz and 1450-MHz input signal frequency, respectively. The measured peak Integral-Non-Linearity (INL) and Differential-Non-Linearity (DNL) are 0.42 LSB and 0.49 LSB, respectively

Private equity and venture capital in emerging markets : a case study of Egypt and the MENA region

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2009."September 2009." Cataloged from PDF version of thesis.Includes bibliographical references (p. 229-241).Private equity and venture capital investments in emerging markets grew significantly over the past five years (2003-2008), both in absolute and relative terms. In this study, we examine the industry's role in emerging markets, in terms of key actors, business processes, and impact on portfolio companies. We use a case study of private equity and venture capital in Egypt, and the Middle East and North Africa region. We focus on two key questions: (i) Why did private equity activities grow so much and so fast in Egypt?; (ii) What is the impact of private equity firms on their portfolio companies? And what are the broader economic development implications for the country? In addition to a number of global and macroeconomic trends that created a positive environment for private equity investments, we identify two key factors behind the industry's success in Egypt: first, the industry is dominated by local firms that rely on a mix of local knowledge and expatriate expertise, and have developed key competencies that provided them with a strong competitive advantage and enabled their growth. Second, these firms, while adopting global best practices in the industry, have adapted their business model and practices to the local market needs. In terms of their impact, we found that in most transactions, private equity firms acted as a catalyst for initiating, consolidating, professionalizing, growing and globalizing their portfolio companies, and in doing so, they increased their competitiveness and expanded their operations in regional and global markets.(cont.) Based on these findings, we argue that private equity firms in emerging markets are providing a new type of "financial entrepreneurship" that is increasingly playing a positive role in economic development.by Ayman Ismail.Ph.D

A distributed system architecture for spatial data management to support engineering modeling

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1999.Includes bibliographical references (leaves 48-50).This research seeks ways to manage the process of analysis and synthesis of geographic data to support collaboration among researchers, planners, and engineers working on a spatial problem. This question is addressed on two levels. The first level examines the abstraction and representation of the analysis process, using the Unified Modeling Language. The second level examines the distributed environment that enables such collaboration, and proposes a three-tier distributed system architecture. The interdisciplinary Urban Respiration project provides a context and examples illustrating the need for such design. A prototype application is developed to test and understand the applicability of the proposed designs.by Ayman Ismail.M.C.P

A NEW SMALL POTATO PLANTER FOR EGYPTIAN AGRICULTURE

Reducing the tuber period for potato plants by planting previously grown sprouts is a new technique. Applying this new agricultural methodology requires modification of the potato planter. The theoretical analysis was carried out to obtain information that can help avoid tuber damage during feeding and until it exits the feeding system. Starting from these considerations, a new potato planter with a spoon-based feeding system was designed and built. The tests conducted verified that the new system performed well when dividing tuber pieces into rows: considering the best growth spacing for potatoes is 20÷30 cm, the new system has a 68% distribution versus the 50,62 % of the old one. The tubers' spacing in rows are evaluated based on tuber voids and tuber doubles. The results show that there is no difference between the two systems' configurations, while a general consideration about our machine is that it is better at managing small tuber pieces. The void ratios are largely valid within the range of 0.4 up to 0.8 m/s of planted speeds; moreover, the results revealed that the tuber doubles decrease by increasing planting speed and vice versa with tuber voids. The quality of the potatoes planted is evaluated using the Shatter Index (SI %), which shows how the new configuration is more delicate with the tuber pieces (1.5 % against 17.5 % at 10 rpm or 46 % against 94 % at rpm 20). The new configuration could be an interesting improvement for potato quality and Egyptian potato production

A Proposed Model for Predicting Employee Turnover of Information Technology Specialists Using Data Mining Techniques

This article proposes a data mining framework to predict the significant explanations of employee turn-over problems. Using Support vector machine, decision tree, deep learning, random forest, and other classification algorithms, the authors propose features prediction framework to determine the influencing factors of employee turn-over problem. The proposed framework categorizes a set of historical behavior such as years at company, over time, performance rating, years since last promotion, and total working years. The proposed framework also classifies demographics features such as Age, Monthly Income, and Distance from Home, Marital Status, Education, and Gender. It also uses attitudinal employee characteristics to determine the reasons for employee turnover in the information technology sector. It has been found that the monthly rate, overtime, and employee age are the most significant factors which cause employee turnover

Distributed GIS for Monitoring and Modeling Urban Air Quality

The progress of technology has made the measurement of air quality and the simulation of complex air pollution models both feasible and cost-effective. However, there is a long way to go in terms of facilitating widespread access to the data and models, and linking the monitoring of trace gases with specific urban activities and land use that might be controllable. As part of a NASA-funded project, we are working with scientists and engineers to design and test a distributed GIS infrastructure for studying such "urban respiration" phenomena. Measurements of trace gases within a metropolitan area (from mobile and fixed instruments) are geo-referenced, time-stamped, and stored in a relational database server (Oracle). GIS services (using ArcInfo and ArcView) are connected to the database so that subsets of the trace gas measurements can be extracted and converted on-the-fly into GIS data layers. These subsets (by location, date, and time-of-day) can be displayed and cross-referenced with other layers such as weather conditions, land use and cover, topography, hydrography, demography, and congestion levels of road networks. A web-based interface (using ArcView Internet Map Server) allows research team members at different locations to query, visualize, and process the cross-referenced data layers in order to generate surface level estimates of initial conditions for use in the air quality models.NAS

Radon Calibration System

In this chapter, an irradiation radon system was explained in detail. This system is based on soil gas as a natural radon source. The radon system was used to determine both the calibration factor of the radon detector and the equilibrium factor between radon and its short-lived daughters. Also, the calibration factor has been calculated theoretically and experimentally. The effect of humidity upon the calibration factor has been investigated. The diffusion of radon through polyethylene membrane has been determined using new nuclear method. This method depends upon the physical decay of radon

Gut and genital tract microbiomes: Dysbiosis and link to gynecological disorders

Every year, millions of women are affected by genital tract disorders, such as bacterial vaginosis (BV), endometrial cancer, polycystic ovary syndrome (PCOS), endometriosis, and uterine fibroids (UFs). These disorders pose a significant economic burden on healthcare systems and have serious implications for health and fertility outcomes. This review explores the relationships between gut, vaginal, and uterine dysbiosis and the pathogenesis of various diseases of the female genital tract. In recent years, reproductive health clinicians and scientists have focused on the microbiome to investigate its role in the pathogenesis and prevention of such diseases. Recent studies of the gut, vaginal, and uterine microbiomes have identified patterns in bacterial composition and changes across individuals’ lives associated with specific healthy and diseased states, particularly regarding the effects of the estrogen–gut microbiome axis on estrogen-driven disorders (such as endometrial cancer, endometriosis, and UFs) and disorders associated with estrogen deficiency (such as PCOS). Furthermore, this review discusses the contribution of vitamin D deficiency to gut dysbiosis and altered estrogen metabolism as well as how these changes play key roles in the pathogenesis of UFs. More research on the microbiome influences on reproductive health and fertility is vital

Knowledge, attitude and practice of long acting reversible hormonal contraception (LARHC) among women in urban upper Egypt

Background: The current study aims to assess the knowledge, attitude and practice of long acting reversible hormonal contraception (LARHC) among women in urban upper Egypt.Methods: A cross sectional study which included 902 married women, in the reproductive age, attending the outpatient clinics (Gynecology and family planning) of: 1-Assiut University Maternity Hospital, 2- Sohag University Hospital, and 3-Gehina General Hospital (MOH hospital) with current or previous use of any method of LARHC methods. A Questionnaire file was designed to assay knowledge attitude and practice of clients towards contraceptive methods. All data collected from clients reviewed separately to assess knowledge, attitude and practice of women towards contraceptive methods.Results: The most popular contraceptive method is COCs followed by IUD then DMPA. 99% of studied sample heard with good description about different types of LARHC. 54.9% of studied sample most popular/famous LARHC DMPA, most sources of information on LARHC were, Hospital, Relative/friends and health workers. 94.24% of the studied sample were in favor to use of LARHC, 94.2% of them agree to take a space between births, about 55.4% of them were health child and 61% comfortable lifestyle benefit from birth spacing, 33% of studied sample were maternal health, 68% of them were think/prefer to use implants, 64.5% of them didn’t pregnant while breastfeeding. 11% of sample women never used any contraception before and most reasons for not using contraception are fear of side effects, desire for more children, irregular sexual relationship, and husband opposition. Only 16.6 % of studied sample used LARHC before and most of them used DMPA, however 3 women who used DMPA get pregnant while using it.Conclusions: There is a good level of knowledge between upper Egypt women about LARHC methods

Enhanced Antifibrinolytic Efficacy of a Plasmin-Specific Kunitz-Inhibitor (60-Residue Y11T/L17R with C-Terminal IEK) of Human Tissue Factor Pathway Inhibitor Type-2 Domain1

Current antifibrinolytic agents reduce blood loss by inhibiting plasmin active sites (e.g., aprotinin) or by preventing plasminogen/tissue plasminogen activator (tPA) binding to fibrin clots (e.g., ε-aminocaproic acid and tranexamic acid); however, they have adverse side effects. Here, we expressed 60-residue (NH2NAE . . . IEKCOOH) Kunitz domain1 (KD1) mutants of human tissue factor pathway inhibitor type-2 that inhibit plasmin as well as plasminogen activation. A single (KD1-L17R-KCOOH) and a double mutant (KD1-Y11T/L17R- KCOOH) were expressed in Escherichia coli as His-tagged constructs, each with enterokinase cleavage sites. KD1-Y11T/L17R-KCOOH was also expressed in Pichia pastoris. KD1-Y11T/L17R-KCOOH inhibited plasmin comparably to aprotinin and bound to the kringle domains of plasminogen/plasmin and tPA with Kd of ~50 nM and ~35 nM, respectively. Importantly, compared to aprotinin, KD1-L17R-KCOOH and KD1-Y11T/L17R-KCOOH did not inhibit kallikrein. Moreover, the antifibrinolytic potential of KD1-Y11T/L17R-KCOOH was better than that of KD1-L17R-KCOOH and similar to that of aprotinin in plasma clot-lysis assays. In thromboelastography experiments, KD1-Y11T/L17R-KCOOH was shown to inhibit fibrinolysis in a dose dependent manner and was comparable to aprotinin at a higher concentration. Further, KD1-Y11T/L17R-KCOOH did not induce cytotoxicity in primary human endothelial cells or fibroblasts. We conclude that KD1-Y11T/L17R-KCOOH is comparable to aprotinin, the most potent known inhibitor of plasmin and can be produced in large amounts using Pichia