Architectures for RF Frequency synthesizers

Frequency synthesizers are an essential building block of RF communication products. They can be found in traditional consumer products, in personal communication systems, and in optical communication equipment. Since frequency synthesizers are used in many different applications, different performance aspects may need to be considered in each case. The main body of the text describes a conceptual framework for analyzing the performance of PLL frequency synthesizers, and presents optimization procedures for the different performance aspects. The analysis of the PLL properties is performed with the use of the open-loop bandwidth and phase margin concepts, to enable the influence of higher-order poles to be taken into account from the beginning of the design process. The theoretical system analysis is complemented by descriptions of innovative system and building block architectures, by circuit implementations in bipolar and CMOS technologies, and by measurement results. Architectures for RF Frequency Synthesizers contains basic information for the beginner as well as in-depth knowledge for the experienced designer. It is widely illustrated with practical design examples used in industrial products.\ud Written for:\ud Electrical and electronic engineer

Sensitivity of cupuassu (Theobroma grandiflorum (Wiild. ex Spreng.) Schum.) seeds to desiccation.

Abstract 220

Low-Jitter Clock Multiplication: a Comparioson between PLLs and DLLs

This paper shows that, for a given power budget, a practical phase-locked loop (PLL)-based clock multiplier generates less jitter than a delay-locked loop (DLL) equivalent. This is due to the fact that the delay cells in a PLL ring-oscillator can consume more power per cell than their counterparts in the DLL. We can show that this effect is stronger than the notorious jitter accumulation effect that occurs in the voltage-controlled oscillator (VCO) of a PLL. First, an analysis of the stochastic-output jitter of the architectures, due to the most important noise sources, is presented. Then, another important source of jitter in a DLL-based clock multiplier is treated, namely the stochastic mismatch in the delay cells which compose the DLL voltage-controlled delay line (VCDL). An analysis is presented that relates the stochastic spread of the delay of the cells to the output jitter of the clock multiplier. A circuit design technique, called impedance level scaling, is then presented which allows the designer to optimize the noise and mismatch behavior of a circuit, independently from other specifications such as speed and linearity. Applying this technique on a delay cell design yields a direct tradeoff between noise induced jitter and power usage, and between stochastic mismatch induced jitter and power usage

Application and validation of the notch master curve in medium and high strength structural steels

This paper applies and validates the Notch master curve in two ferritic steels with medium (steel S460M) and high (steel S690Q) strength. The Notch master curve is an engineering tool that allows the fracture resistance of notched ferritic steels operating within their corresponding ductile-to-brittle transition zone to be estimated. It combines the Master curve and the Theory of critical distances in order to take into account the temperature and the notch effect respectively, assuming that both effects are independent. The results, derived from 168 fracture tests on notched specimens, demonstrate the capability of the Notch master curve for the prediction of the fracture resistance of medium and high strength ferritic steels operating within their ductile-to-brittle transition zone and containing notches

The Notch Master Curve: A proposal of Master Curve for ferritic–pearlitic steels in notched conditions

This paper presents a model for the prediction of the apparent fracture toughness of ferritic–pearlitic steels in notched conditions and operating at temperatures corresponding to their ductile-to-brittle transition zone. The model, here named the Notch-Master Curve, is based on the combination of the Master Curve of the material in cracked conditions and the notch corrections provided by the Theory of Critical Distances. In order to validate the model, the fracture resistance results obtained in 168 tests performed on CT specimens (84 for each material) are presented. These tests were carried out, for each material, in specimens with six different notch radii, from 0 mm up to 2.0 mm, and at three different temperatures within their corresponding ductile-to-brittle transition zone. It has been observed that the model provides good predictions of the fracture resistance in notched conditions for the two materials analysed

Sensitivity of seed to desiccation in cupuassu (Theobroma grandiflorum (Willd. ex Spreng.) K. Schum. - Sterculiaceae.

A resposta das sementes à redução do grau de umidade determinará se as mesmas poderão ser armazenadas pelos métodos convencionais. Verificou-se o efeito do dessecamento na germinação e no vigor de sementes de cupuaçu (Theobroma grandiflorum (Willd. ex Spreng.) K. Schum.), uma espécie frutífera tropical. Os seguintes teores de água foram avaliados: 57,1%, 53,7%, 49,8%, 46,5%, 41,4%, 35,4%, 28,3%, 23,2%, 17,4%, 15,5% e 14,6%. A secagem das sementes até 41,4% de água não afeta a germinação e o vigor, porém, a velocidade de emergência foi reduzida quando o teor de água das sementes atinge 41,4%. Abaixo de 35,4% uma redução na qualidade das sementes foi detectada, a qual foi mais acentuada abaixo de 28,3%. Quando o teor de água das sementes foi de 14,6% a deterioração foi máxima. A sensibilidade de sementes de cupuaçu a redução do grau de umidade sugere que no armazenamento o teor de água das sementes deve ser mantido em valor superior a 41%

Health outcomes in patients using no-prescription online pharmacies to purchase prescription drugs

BACKGROUND: Many prescription drugs are freely available for purchase on the Internet without a legitimate prescription from a physician. OBJECTIVE: This study focused on the motivations for using no-prescription online pharmacies (NPOPs) to purchase prescription drugs rather than using the traditional doctor-patient-pharmacy model. We also studied whether users of NPOP-purchased drugs had poorer health outcomes than those who obtain the same drug through legitimate health care channels. METHODS: We selected tramadol as a representative drug to address our objective because it is widely prescribed as an unscheduled opioid analgesic and can easily be purchased from NPOPs. Using search engine marketing (SEM), we placed advertisements on search result pages stemming from the keyword “tramadol” and related terms and phrases. Participants, who either used the traditional doctor-patient-pharmacy model to obtain tramadol (traditional users, n=349) or purchased it on the Web without a prescription from their local doctor (ie, nontraditional users, n=96), were then asked to complete an online survey. RESULTS: Respondents in both groups were primarily white, female, and in their mid-forties (nontraditional users) to upper forties (traditional users). Nearly all nontraditional users indicated that their tramadol use was motivated by a need to treat pain (95%, 91/96) that they perceived was not managed appropriately through legitimate health care channels. A majority of nontraditional users (55%, 41/75) indicated they used NPOPs because they did not have access to sufficient doses of tramadol to relieve pain. In addition, 29% (22/75) of nontraditional users indicated that the NPOPs were a far cheaper alternative than seeing a physician, paying for an office visit, and filling a prescription at a local pharmacy, which is often at noninsured rates for those who lack medical insurance (37%, 35/96, of NPOP users). The remainder of participants (16%, 12/96) cited other motivations (eg, anonymity) for using NPOPs. In terms of health outcomes, nontraditional users experienced a significantly (P<.01) greater number and severity of adverse events, including life-threatening seizures: 7% (7/96) of nontraditional users reported seizures, while none of the traditional users reported seizures. CONCLUSIONS: Although online pharmacies can offer distinct advantages in terms of convenience and cost, users of these “rogue” pharmacies that offer drugs with no prescription or doctor supervision do so at great risk to their health, as evidenced by much higher rates of adverse events. The most logical explanation for these findings is that the lack of physician oversight of dosage schedules, contraindicated conditions, and concomitant medications, were responsible for the increased intensity and frequency of adverse events in the nontraditional users. Although we only examined tramadol, it is logical to postulate that similar results would be observed with dozens of equally accessible prescription drugs. As such, the geometric growth in the use of online pharmacies around the world should prompt intense medical and regulatory discussion about their role in the provision of medical care

Nutraceutical approach to Non-alcoholic fatty liver disease (NAFLD): the available clinical evidence.

Non-alcoholic fatty liver disease (NAFLD) is a clinical condition characterized by lipid infiltration of the liver, highly prevalent in the general population affecting 25% of adults, with a doubled prevalence in diabetic and obese patients. Almost 1/3 of NAFLD evolves in Non-Alcoholic SteatoHepatitis (NASH), and this can lead to fibrosis and cirrhosis of the liver. However, the main causes of mortality of patients with NAFLD are cardiovascular diseases. At present, there are no specific drugs approved on the market for the treatment of NAFLD, and the treatment is essentially based on optimization of lifestyle. However, some nutraceuticals could contribute to the improvement of lipid infiltration of the liver and of the related anthropometric, haemodynamic, and/or biochemical parameters. The aim of this paper is to review the available clinical data on the effect of nutraceuticals on NAFLD and NAFLD-related parameters. Relatively few nutraceutical molecules have been adequately studied for their effects on NAFLD. Among these, we have analysed in detail the effects of silymarin, vitamin E, vitamin D, polyunsaturated fatty acids of the omega-3 series, astaxanthin, coenzyme Q10, berberine, curcumin, resveratrol, extracts of Salvia milthiorriza, and probiotics. In conclusion, Silymarin, vitamin E and vitamin D, polyunsaturated fatty acids of the omega-3 series, coenzyme Q10, berberine and curcumin, if well dosed and administered for medium\u2013long periods, and associated to lifestyle changes, could exert positive effects on NAFLD and NAFLD-related parameters. View Full-Tex