9.1 INTRODUCTION

In the preceding chapter, we intensively discussed the concept of negative feedback and its effects on amplifiers in detail. In the present chapter, the effect of feedback will be discussed in the context of working and analysis of oscillator circuits to generate sinusoidal and non-sinusoidal pulses and waveforms. The basic concept of oscillator differs from that of an amplifier. An amplifier amplifies a given AC input signal by using the DC power supply VCC and resistive networks to provide proper bias and stability with the aid of negative/degenerative feedback so as to stabilize gain and enhance bandwidth of operation. As completely opposed to this, an oscillator circuit needs no input AC signal. The power supply DC input VCC helps in picking up noise signals from its wide frequency spectrum, which due to regenerative/positive feedback networks and amplifier, gets sustained in the oscillatory circuit. Hence DC input gets converted into AC output. Thus, an oscillator can also be referred to as AC-DC converter. The working of an oscillator is exactly opposite to rectifier; hence it can be called an ‘inverter’. But it should be well understood that an oscillator does not create energy, instead it converts unidirectional current drawn from DC source into alternating current of desired frequency. Hence, the oscillator can be broadly defined as an amplifier with positive feedback. The difference between amplifier and oscillator is explained in the block diagram of Figure 9.1(a).

9.2 CLASSIFICATION OF OSCILLATORS

Oscillators can be broadly classified using following two aspects,

• a) Classification based on design principle

• b) Classification based on frequency of oscillation

a) Figure 9.2 shows the detailed family tree of various types of oscillators based on the design principle.

From Figure 9.2, based on the design principle, commonly used oscillators can be broadly classified as harmonic and relaxation oscillators. Harmonic oscillators generate sinusoidal waveforms, whereas relaxation oscillators generate pulse/rectangular/sawtooth waveforms. The basic tuning circuit for harmonic oscillators can be made of combination of L-C networks, which are suitable for generating RF (radio frequency) oscillations from 720 KHz up to hundreds of MHz, whereas R-C networks are suitable for generating AF (Audio Frequency) oscillations in the range of 20 Hz–20 KHz. The detailed description of each of the oscillator is performed in subsection 9.5 and 9.6.

In Chapter 3 we described how MNEs competing in today's global competitive environment are required to build layers of competitive advantage – the ability to capture global-scale efficiencies, local market responsiveness, and worldwide learning capability. As many of these companies found ways to match one another in the more familiar attributes of global-scale efficiency and local responsiveness, they had to find new ways to gain competitive advantage. In this process, competitive battles among leading-edge MNEs (particularly those in knowledge-intensive industries such as telecommunications, biotechnology, pharmaceuticals, etc.) have shifted to their ability to link and leverage their worldwide resources and capabilities to develop and diffuse innovation.

The trend is reflected in the fact that R…D expenditure globally more than doubled in real terms between 1992 and 2010. Unsurprisingly, worldwide patent applications grew from 922,000 in 1985 to almost 2million in 2010. In the same period, trademark applications also increased world wide from about 1million in 1985 to 3.6million in 2010.

The Glaucophyta include those algae that have endosymbiotic cyanobacteria in the cytoplasm instead of chloroplasts. Because of the nature of their symbiotic association, they are thought to represent unsuccessful intermediates in the evolution of the chloroplast.

The pigments of the Glaucophyta are similar to those of the Cyanophyceae: both chlorophyll a and the phycobiliproteins are present; however, two of the cyanobacterial carotenoids, myxoxanthophyll and echinenone, are absent (Chapman, 1966).

Although similar to cyanobacteria, the cyanelles should be regarded as organelles rather than endosymbiotic cyanobacteria (Helmchen et al., 1995; McFadden, 2001). Cyanobacteria have over 3000 genes whereas cyanelles have about the same number of genes as plastids (about 200 genes). It is clear the cyanelle (and plastid) genomes have undergone substantial reduction during endosymbiosis. Many of the missing genes eventually relocated to the nucleus, while other genes were lost – made redundant in the cyanelles’ new role as an endosymbiont. For example, cyanobacteria have a respiratory electron-chain whereas plastids do not, the respiratory electronchain is coded by the nucleus in eukaryotic algae.

The organisms in the Glaucophyta are very old; McFadden (2001) calls them the coelocanths of endosymbiosis. The Glaucophyta probably branched off the evolutionary tree before the divergence of red and green algae from one another (Keeling, 2004).

The fact that in such syncyanoses one is dealing with composite organisms that exhibit features altogether new and no longer characteristic of either partner alone, led Skuja in 1954 to establish the phylum Glaucophyta. It must be appreciated that the organisms in the phylum represent a very old group, and that, when evolving, they were very plastic and undergoing a great deal of change in the attempt to reach the relatively stable level of a cell with a chloroplast. Such a dynamic group was formed consisting of a large number of organisms not well suited to compete with their more highly developed progeny. Such a situation led to the demise of many of the original members of the Glaucophyta, resulting in the existence today of few extant members of the group.

The Bacillariophyceae or the diatoms probably evolved from a scaly member of the Chrysophyceae (similar to the organisms in the Parmales) or Bolidophyceae (Guillou et al., 1999 ; Medlin, 2016) around the Devonian–Carboniferous transition (360 Ma)(Brown, 2010). The diatoms are unicellular, sometimes colonial, algae found in almost every aquatic habitat as free-living photosynthetic autotrophs, colorless heterotrophs, or photosynthetic symbiotes (Schmaljohann and Rottger, 1978). They may occur as plankton or periphyton, with most brownish-green films on substrates such as rocks or aquatic plants being composed of attached diatoms. The cells are surrounded by a rigid two-part boxlike cell wall composed of silica, called the frustule. The chloroplasts contain chlorophylls a, c 1, and c 2 with the major carotenoid being the goldenbrown fucoxanthin, which gives the cells their characteristic color.

In discussing diatoms and silica, there is often confusion over terminology in regard to silicon. Silicon is the element. Silica is a short convenient designation for silicon dioxide (SiO 2) in all of its crystalline, amorphous, and hydrated or hydroxylated forms. Silicate is any of the ionized forms of monosilicic acid [Si(OH) 4] (Iler, 1979).

Cell Structure

The two-part frustule surrounds protoplasm that has a more or less central nucleus suspended in a system of protoplasmic threads. The chloroplasts occupy most of the cell usually as two parietal plastids although sometimes as numerous discoid plastids. The storage product, chrysolaminarin, occurs in vesicles in the protoplasm.

Cell Wall

The characteristic feature of the Bacillariophyceae is their ability to secrete an external wall composed of silica, the frustule. It is constructed of two almost equal halves, the smaller fitting into the larger like a Petri dish (Figs. 17.1, 17.8, 17.9, 17.34). The outer of the two half-walls is the epitheca and the inner the hypotheca. Each theca is composed of two parts, the valve, a more or less flattened plate, and the connecting band, attached to the edge of the valve. The two connecting bands, one attached to each valve, are called the girdle (von Stosch, 1975). Sometimes the connecting bands themselves are called girdle bands (Fig. 17.34).

Euglenoid flagellates occur in most freshwater habitats: puddles, ditches, ponds, streams, lakes, and rivers, particularly waters contaminated by animal pollution or decaying organic matter (Buetow, 1968). Usually larger bodies of purer water, such as rivers, lakes, and reservoirs, have sparser populations of less common euglenoids as planktonic organisms. Marine euglenoids are more common than supposed, with Eutreptia, Eutreptiella (Figs. 6.8, 6.11(c)), and Klebsiella occurring exclusively in marine or brackish water, and many other genera having one or a few marine species. These occur in the open sea, in tidal zones among seaweeds, and as sand inhabitants on beaches. Brackish species of Euglena (Figs. 6.1, 6.2, 6.4, 6.11(a)) often color estuarine mud flats green when light intensity is low, the green color disappearing in full sunlight as the euglenoids creep away from the surface. There are also several parasitic euglenoid flagellates, mostly species of Khawkinea, Euglenamorpha, and Hegneria.

Euglenoids are characterized by chlorophylls a and b, one membrane of chloroplast endoplasmic reticulum, a mesokaryotic nucleus, flagella with fibrillar hairs in one row, no sexual reproduction, and paramylon or chrysolaminarin as the storage product in the cytoplasm.

Euglenoid cells have two basal bodies and one or two emergent flagella (Fig. 6.2). The flagella are similar to those of trypanosomes in having a paraxonemal rod (paraxial rod) that runs the length of the flagellum inside the flagellar membrane (Ngo and Bouck, 1998 ; Bastin and Gull, 1999 ; Talke and Preisfeld, 2002). The paraflagellar rod is composed of two major proteins forming an elongated alpha-helical stalk that parallels the axoneme. The one emergent flagellum in Euglena has helically arranged fibrillar hairs (no microtubules) attached along the length of the flagellar membrane. The fibrillar hairs are of two lengths: there is a single helical row of long (3 μm) hairs and two helical rows of short (1.5 μm) hairs in Euglena (Bouck et al., 1978). Other genera have flagella similar to Euglena (Hilenski and Walne, 1985). There are two basic types of flagellar movement in the class.

These golden-brown algae are characterized by tentacles or rhizopodia on basically amoeboid vegetative cells (Moestrup, 1995 ; Preisig, 1995). Amoeboid cells are relatively rare among the algae, being mostly restricted to the Dictyochophyceae and the Xanthophyceae (Hibberd and Chretiennot-Dinet, 1979). The algae in the Dictyochophyceae have been previously classified in the Chrysophyceae, although molecular evidence shows them to be most closely related to the Pelagophyceae (Cavalier-Smith et al., 1995) or Eustigmatophyceae (Daugbjerg and Andersen, 1997).

Classification

The Dictyochophyceae can be divided into three orders (Preisig, 1995).

Rhizochromulinales

This order contains the more primitive organisms in the order (O'Kelly and Wujek, 1995). Rhizochromulina (Fig. 14.1(a), (b)) has amoeboid non-flagellated vegetative cells with many finebeaded filipodia and a single golden-brown chloroplast (Hibberd and Chretiennot-Dinet, 1979). The fusiform zoospore has a single tinsel flagellum with a second basal body in the protoplasm (Fig. 14.1(b)). Chrysoamoeba (Fig. 14.1(d)) lives as a solitary amoeba for the greater part of its life cycle, transforming into swimming cells with a single long flagellum only for short periods. In Phaeaster (Fig. 14.1(c)), the anterior portion of the cell is drawn out into rhizopodia.

Pedinellales

The pedinellids are unique in containing genera that are phototrophic (Apedinella (Fig. 14.2(c)), Pseudopedinella), mixotrophic (able to photosynthesize and take up organic compounds) (Pedinella) (Fig. 14.2(a), (b)), and phagotrophic (Pteridomonas, Ciliophrys). The phagotrophic genera have vestigial chloroplasts and evolved from genera with chloroplasts (Sekiguchi et al., 2002). The organisms in this order have three interconnected microtubules (triads) that course from the nuclear envelope through tentacles (if they are present) to the plasma membrane (Fig. 14.2(a)) (Daugbjerg, 1996).

It is with pleasure that I write a foreword to this timely exposition and analysis of the system of environmental law as a whole, and as it stands after the Rio Conference. If it seems a little bold to call environmental law a ‘system’, it is assuredly not so bold as it would have been before the publication of Philippe Sands’ important work. A main purpose of academic writing should be to perceive and portray patterns and relations in a body of legal rules so as to make it manageable, teachable, comprehensible and usable. The present work succeeds in doing this to a remarkable degree.

The author's statement that environmental law has a ‘longer history than some might suggest’ might be thought to border on understatement. When something is taken up as a modish ‘concern’, there is often a strong temptation to think of it as a discovery by a newly enlightened generation. It is, therefore, a useful antidote to be reminded that, of the two pioneering decisions, both still leading and much-cited cases, one was the Bering Sea arbitration, of a century ago, and the other, the Trail Smelter arbitration, of half a century ago. Nevertheless, the present-day need for law to protect the environment and to preserve resources is of a scale and urgency far beyond the imagining of the early pioneers.

Seeing these questions, however, in a proper historical perspective does help to warn against the dangers of treating environmental law as a specialisation, which can be made a separate study; or, on the other hand, of regarding environmental law – and here I borrow Philippe's words – as a ‘marginal part of the existing legal order’. A perusal of this book will readily reveal to the reader the fallacy of both of these attitudes. Part I of the book – which is entitled ‘The Legal and Institutional Framework’ – comprises illuminating treatments of such basic subjects of international law as the legal nature of states, international organisations, non-governmental organisations, treaties and other international acts such as resolutions of the General Assembly and other international bodies, EC regulations and directives, the nature and uses of customary law, the general principles of law, and general problems of compliance, implementation and enforcement, and dispute settlement.

Almost every undergraduate engineering discipline starting from electronics, electrical, computer science, instrumentation engineering, information technology, mechanical engineering, biotechnology etc. requires a solid foundation in basic electronics which comprises a study of fundamental devices like diodes, transistors and their applications in designing amplifiers, switching/logic circuits etc. While for some disciplines, a basic understanding might be sufficient, for other disciplines like electronics, electrical etc., this course acts as an important building block in the curriculum. Moreover, for various advanced courses like analog electronics, digital circuits and VLSI, in-depth understanding of basic electronics is a prerequisite. This book is written keeping both these aspects in mind and as a result it will serve undergraduate students of various engineering disciplines. In addition, it can also cater to the needs of college and university students belonging to disciplines like physics, electronics, and also in electronics courses in polytechnics. A competent electronics engineer, even in the modern era of integrated-circuit based design, needs a thorough and solid understanding of the basic concepts of semiconductors and a firm grasp of fundamental devices like diodes and various kind of transistors. This book attempts a perfect balance between housing all the basic concepts in accordance with the syllabi of leading institutes and universities and a thorough understanding required for future courses. In solid state electronics and analog electronics, which normally appears at a later stage of the undergraduate electronics curriculum, the approach is significantly different: while solid state electronics provides more emphasis on device physics and detailed understanding, analog electronics concentrates more on the applications, where the device is generally treated as a black box. Even though these two advanced courses are mutually dependent on each other, there exists a significant gap between the two approaches and undergraduate students face real difficulties in making a correlation and correspondence between them. This book attempts to minimize this gap between the different approaches to solid state devices and analog circuits. Special care has been taken to explain all the semiconductor devices in this book from both, physical and circuit approaches. To facilitate this, extra stress is given in chapters 2 and 3 while discussing crystal structures and the p-n junctions.

Algae are organisms that have plastids, or organisms that are derived from cells whose ancestors possessed plastids. Until 1994, it was thought that the apicomplexa did not have plastids (and consequently were not covered in phycology textbooks). Then it was shown that a known organelle in many apicomplexa was actually a reduced colorless plastid called an apicoplast with a genome reduced to 35 kb (Fig. 8.1) (Wilson, 1993 ; Wilson et al., 1994 ; Parsons et al., 2009 ; McFadden, 2011). Molecular studies have shown that the apicoplast and dinoflagellate plastids are related and originated from red algae by a single endosymbiotic event that occurred relatively early in eukaryotic evolution (Fast et al., 2001 ; Janouskovec et al., 2010). Chromera velia has chlorophyll a, is photosynthetic, and is a relative of the apicomplexa with similar cell structure (Janouskovec et al., 2010 ; Obornek et al., 2011).

The discovery of the apicoplast generated considerable interest since most apicomplexans are unicellular endoparasites that cause some of the most significant tropical diseases (Foth and McFadden, 2003). Malaria in humans is produced by the apicomplexan Plasmodium. About 300 million people are infected with malaria, leading to one million deaths annually (Ralph et al., 2004). Apicomplexans cause other serious diseases in livestock and humans, such as cryptosporidiosis, babesiosis (Texas cattle fever), theileriosis (East Coast fever), and toxoplasmosis. The realization that these endoparasites were once algae raised hopes that the apicoplast might be a drug target for two reasons (Goodman and McFadden, 2014). The first is that the apicoplast is essential for the survival of Plasmodium and Toxoplasma. The second is that drugs effective against prokaryotic organisms might be effective against the apicoplast since all plastids originally evolved from endosymbiotic prokaryotic cyanobacteria. Apicomplexans are absolutely dependent on the apicoplast, which has led to speculation that this curious organelle is a potential “Achilles heel” of parasites, such as Plasmodium.

The apicomplexan have functional mitochondria. However, the apicomplexan mitochondria are unconventional in that the majority of cellular ATP is synthesized through glycolysis and lactic acid production and there is no evience of mitochondrial acetyl CoA (Butterfield et al., 2013).

11.1 INTRODUCTION TO THYRISTOR

Thyristors are able to switch large levels of power and are used in a wide variety of different applications. Thyristors find use in low-power electronics, where they are used in many circuits ranging from light dimmers to power supply over voltage protection. The idea of thyristor was first described by William Shockley in 1950. It was referred to as a bipolar transistor with a p-n hook collector. The mechanism for the operation was analysed further in 1952 by Jewell James Ebers and in 1956 John L. Moll investigated the switching mechanism of the thyristor.

The first silicon-controlled rectifiers became available in the early 1960s when it started to gain a significant level of popularity for power switching. It is a multilayered semiconductor device which requires a gate signal to turn it ‘ON’. Once it is turned ‘ON’, it behaves like a rectifying diode. Thus, the name silicon-controlled rectifier is justified by its working principle. In fact, the circuit symbol for the thyristor suggests that this device acts like a controlled rectifying diode.

Four layers are formed by alternating n-type and p-type semiconductor materials. Consequently, there are three p-n junctions formed in the device. It is a bistable device. The three terminals of this device are anode (A), cathode (K) and gate (G). The gate (G) terminal is the control terminal of the device. The circuit symbol is shown in the Figure 11.1.The current flowing through the device is controlled by electrical signal applied to the gate (G) terminal. The anode (A) and cathode (K) are the power terminals of the device which can handle large applied voltage and conduct the major current through thyristor. For example, when the device is connected in series with load circuit, the load current will flow through the device from anode (A) to cathode (K) but this load current will be controlled by the gate (G) signal applied to the device externally.

11.2 CONSTRUCTION: REALIZATION USING TRANSISTORS

Unlike the normal p-n junction diode, which is a two-layer semiconductor device, or the transistor, a three layer (p-n-p or n-p-n) device, the Thyristor is a four-layer (p-n-p-n) semiconductor device that contains three p-n junctions in series, as shown in Figure 11.2.

This book focuses on the management challenges associated with developing the strategies, building the organizations, and managing the operations of companies whose activities stretch across national boundaries. Clearly, operating in an international rather than a domestic arena presents managers with many new opportunities. Having worldwide operations not only gives a company access to new markets and low-cost resources, it also opens up new sources of information and knowledge, and broadens the options for strategic moves the company might make in competing with its domestic and international rivals. However, with all these new opportunities come the challenges of managing strategy, organization, and operations that are innately more complex, diverse, and uncertain.

Our starting point is to focus on the dominant vehicle of internationalization, the MNE, and briefly review its role and influence in the global economy. Only after understanding the origins, interests, and objectives of this key actor will we be in a position to explore the strategies it pursues and the organization it develops to achieve them.

In this chapter, we introduce the MNE by defining its key characteristics, discussing its origins, interests, and objectives, and reviewing its major role and influence in the global economy. We then describe the motivations that drive these companies abroad, the means they adopt to expand internationally, and the mentalities of management that shape the strategies MNEs pursue and the organizations they develop to achieve them.