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Infiltration was a widespread phenomenon, as former mujahidin set up their own bands or operated on ‘contract’ for Arab military intelligence services, but neither they nor Husayni attempted to construct modem political organizations on that basis. Egypt was the first country to conclude an armistice agreement with Israel, and, like Jordan, was anxious to avoid further conflict after 1949. The Egyptian command then placed a section of the police under another officer, ʻAbd-al-'Azim al-Saharti, to guard public installations in Gaza. Unlike the border police, the Saharti battalion, as it came to be known, was attached to the military governor's office. This caused considerable resentment among the Palestinian personnel, who took this to indicate a lower status. Palestinian anger at Israeli reprisals and Egyptian restrictions erupted in March, as demonstrators took to the streets of Gaza to demand conscription and the distribution of arms to the local population.

This chapter focuses on Dr. Juan Negrín, the minister of finance, and Julio Alvarez del Vayo, the foreign minister, as the central figures in the Communists' influence over the government. Alvarez del Vayo in particular was a trusted adviser to Largo Caballero during the early months of the Civil War. Alvarez del Vayo would later help the Communists implement their strategy of infiltration and domination in the early stages of the Civil War. Despite his contributions, however, the main instrument in bringing their plans to fruition in its final stages was Dr. Negrín, who even after fifty years remains the most controversial figure of the war.

A child’s future perceptions and expectations are likely to be conditioned by early experiences of dental treatment. Just under half of all children report low to moderate general dental anxiety, and 10–20% report high levels of dental anxiety. Montiero et al. (2014) indicate that the prevalence of needle phobia may be as high as 19% in 4- to 6-year-olds. Davidovich et al. (2015) reflected that, for general practitioners and specialists alike, Local anaesthetic (LA) injection for an anxious child was the most stressful procedure regardless of the operator’s age, gender, or years of professional experience. Despite impressive reductions in caries in children in recent years, there still exists a social gradient with inequalities in experience of dental disease, and there remains a significant cohort of children for whom extractions and restoration of teeth are necessary. Aside from emerging restorative strategies that do not require LA (e.g. atraumatic restorative technique or placement of preformed metal crowns using the Hall technique), effective and acceptable delivery of LA remains an important tool to enable successful operative dental treatment to be carried out comfortably for child patients. Effective surface anaesthesia prior to injection is very important as a child’s initial experience of LA techniques may influence their future perceptions and help in establishing trust. Cooling tissues prior to injection has been described but is rarely used, and surface anaesthesia is generally achieved with intra-oral topical agents. Although the main use of topical agents is as a pre-injection treatment, they have been used as the sole means of anaesthesia for some procedures including the extraction of mobile primary teeth. It is possible to achieve a depth of 2–3mm of anaesthesia if topical agents are used correctly: • the area of application should be dried • topical anaesthetic agent should be applied over a limited area • the anaesthetic agent should be applied for sufficient time. In the UK 5% lidocaine (lignocaine) and 18–20% (17.9%) benzocaine gels are the most commonly used agents. Benzocaine topical anaesthetic gel is not recommended for use on children under 2 years old because of an increased risk of methaemoglobinaemia.

Palestinian nationalists maintained that Arab refugees who were uprooted during the 1948 hostilities had the right to return to their homes. Infiltration was one of the most acute challenges faced by the young state of Israel. Some infiltrators were out to kill and avenge as well as to act as spies. Others were motivated by destitution. Some of them lived by robbery and theft in the country that had arisen on the ruins of their villages, and others worked as smugglers. Arabs who crossed the border with the intention of remaining in the country jeopardized Israel's demographic balance, and smugglers undercut the country's sovereignty within its borders. It is hardly surprising, then, that the battle against infiltration, both defensive and offensive, was the focal point of Israel Defense Forces operations; the police force and military government also worked hard against it. There were collaborators with Arab intelligence organizations who conveyed information about Israel over the border, nationalists who sheltered infiltrators, and informers who turned them in.

Tackling haematology is never easy. Revision can be a struggle, as it may not always be obvious which topic areas will be directly relevant to clin­ical practice. We still, however, benefit from an understanding of these areas and an appreciation of how to do and interpret the basics and when more expertise is required. Sometimes the answers require a trip right back to the stem cell. A junior doctor’s most frequent contact with haematology is in interpreting a full blood count. In this task, the core skills of the chapter come to the fore— in response to an anaemia, we should be able to explore the possibilities of iron deficiency, vitamin deficiency, and haem­olysis. On seeing a thrombocytopenia or an abnormal clotting profile, we should be able to make a clinical assessment and perform further appropriate tests, with a view to suggesting differential diagnoses. The questions in this chapter aim to build confidence in these tasks. There is a lot more to haematology, however, than a blood count. As a junior doctor, there will be regular practical challenges such as pre­scribing and altering anticoagulation therapy, overseeing the safe delivery of a blood transfusion, and managing acute situations such as sickle- cell crises. The way forward is to be able to master these basics and start to see the bigger picture. This means developing a feel for the more subtle symptoms and signs of haematological disease and becoming proactive in the face of abnormal blood results. As with all of the chapters in this book, it is a way of thinking that is crucial— one that allows confident management of common situations and recognition of potentially catastrophic conditions, but also one that encourages creativity and initiative. When faced with a clinical conun­drum, we should have the knowledge and confidence to ask appropri­ately: ‘Is the answer in the blood?’

This chapter examines the pathophysiological mechanisms of pain associated with respiratory disease, focusing on the chest wall, diaphragm, and mediastinal pain, and with brachial plexopathy. It explains that thoracic pain can be nociceptive, neuropathic, or mixed, and that pain may arise from the thoracic viscera, muscles, bony cage, or skin or nerve structures. Thoracic pains are mainly caused by tumour, trauma, infection, or inflammation and there are difficult pain syndromes that arise with postherpetic neuralgia, pleural involvement, mediastinal disease, and brachial plexus infiltration.

Soil texture can be defined as the size and proportion of the soil particles—sand, silt, and clay—that are present in a soil. . . . Sand is the largest—from 0.05 to 2mm—and considered coarse texture; consists of angular spheres or cubes. Silt is intermediate—from 0.002 to 0.05mm—and considered medium texture; consists of properties between sand and clay. Clay is the smallest, being less than 0.002mm, and considered fine texture; appears as plate-like or flakes. . . . Any individual soil can be placed on the soil textural diagram when relative amounts of sand, silt, and clay are specified. As a general rule, the type of soil can be determined by feel when squeezed between the fingers. If the soil feels harsh and gritty it would be classified as a sandy soil. One that feels smooth and not sticky or plastic would be a silt soil, and one that is sticky or plastic would be a clay. Another way to distinguish between soils is their ability to form a ribbon. Soils that will not form a ribbon are sands. Those that form a fragile ribbon are loams; those that easily form a thick ribbon are clay loams; and those that easily form a long, thin, flexible ribbon are clays. . . . To be classified a sand, the soil must have more than 45% sand. To be classified a clay, the soil must have more than 20% clay. Loam is a mixture of sand, silt, and clay in about equal proportions. It is considered “ideal” for growing plants. . . . Weight of the soil solids is called “particle density.” For most common mineral soils (soils in which organic matter is usually less than 20%), particle density is about 2.65 g/cm3. Organic soils (where organic matter is greater than 20%) are usually about half as heavy, with particle density between 1.1 to 1.4 g/cm3. This measurement would be an important factor to consider if much material was to be transported for topsoiling.

Inherent properties of a soil determine the extent to which that soil will erode. These properties are soil texture, soil structure, soil permeability, and the amount of soil organic matter. Soil texture consists of a mixture of soil particle sizes of sand, silt, and clay. Soil texture is also related to water movement into the soil [infiltration] and water movement through a soil (permeability). Sand grains are large and difficult to move; however, they are easily detached. Clay particles often stick together and therefore are difficult to detach; however, once detached the clays remain suspended and are easily carried and separated from the original soil mass by water. Silt is intermediate in size between sand and clay, but silt is both easily detached and easily transported. Thus, any soil that has large amounts of silt will erode easily. Infiltration. Water moves into and within a soil through the large macropores and only a very limited amount in the small micropores. Sandy soils have many large pores allowing water to move into the soils by infiltration. Conversely, clay soils have many microspores through which water passes only very slowly. Therefore, during a moderate storm, runoff and erosion would be greater from a soil with more fine textured clays than from a soil where coarse texture dominates. Permeability. Once water enters a soil, it flows within the soil. The extent of internal movement of water in a soil is the permeability of that soil. A soil aggregate is a soil granule or soil crumb consisting of a number of soil grains, that is, silt or clay, held together by a cementing substance. Aggregation is the condition of a soil having many individual aggregates. Soils that have many large stable aggregate are more permeable and are difficult to detach and erode. An aggregate has stability when it is not broken easily by water. Soil aggregates help keep the soil receptive to rapid infiltration of water and keep water from moving over the soil and eroding it.

Erosion can be controlled by four main means, that is, improving soil structure, covering soil with plants, covering soil with mulch, and using special structures. Soil structure is related to the soil tilth, or physical condition of a soil, with respect to ease of tillage or workability as shown by the fitness of a soil as a seedbed and the ease of root penetration. Other terms relating to soil structure improvement are soil aggregation and the formation of aggregates. Aggregates form when a cementing substance is present in a soil. The most important cementing substances in soil are soil polysaccharides and soil polyuronides produced as by-products from microorganisms during decomposition of organic matter. Other less important cementing substances in soil include clays, Ca, and Fe. Formation of aggregates results in improved water infiltration with reduction in erosion. Decomposition of organic matter in soils can be shown as an equation: . . . Plant and animal remains + O2 + soil microorganisms → CO2 + H2O + elements + humus + synthates + energy . . . The decomposition process has the following features: . . . 1. Oxygen is required; thus soil aeration is important. Anytime a soil is stirred or mixed by cultivation, spading, plowing, some organic matter decomposition occurs. 2. Readily available decomposable organic material is required for the microbes to work on. Green organic material, such as grass clippings, is an excellent substrate. 3. Many different types of soil microorganisms are involved in this process. Decomposition is more rapid in soils at pH 7 (neutral). 4. A product of organic decomposition is humus. Humus has many desirable features that improve a soil for plant growth. 5. Plant or animal remains are not effective in soil aggregation until they begin to decompose. 6. The more rapid the decomposition, the greater effect of soil aggregation. . . . Microbial synthates consist of polymers called “polysaccharides” and “polyuronides.” A polymer is a long-chain compound made up of single monomer units hooked together acting as a unit. The term “poly” means “many” and “saccharide” means “sugar.”

Hydrological processes exert strong control over biological and climatic processes in every ecosystem. They are particularly important in the boreal zone, where the average annual temperatures of the air and soil are relatively near the phase-change temperature of water (Chapter 4). Boreal hydrology is strongly controlled by processes related to freezing and thawing, particularly the presence or absence of permafrost. Flow in watersheds underlain by extensive permafrost is limited to the near-surface active layer and to small springs that connect the surface with the subpermafrost groundwater. Ice-rich permafrost, near the soil surface, impedes infiltration, resulting in soils that vary in moisture content from wet to saturated. Interior Alaska has a continental climate with relatively low precipitation (Chapter 4). Soils are typically aeolian or alluvial (Chapter 3). Consequently, in the absence of permafrost, infiltration is relatively high, yielding dry surface soils. In this way, discontinuous permafrost distribution magnifies the differences in soil moisture that might normally occur along topographic gradients. Hydrological processes in the boreal forest are unique due to highly organic soils with a porous organic mat on the surface, short thaw season, and warm summer and cold winter temperatures. The surface organic layer tends to be much thicker on north-facing slopes and in valley bottoms than on south-facing slopes and ridges, reflecting primarily the distribution of permafrost. Soils are cooler and wetter above permafrost, which retards decomposition, resulting in organic matter accumulation (Chapter 15). The markedly different material properties of the soil layers also influence hydrology. The highly porous near-surface soils allow rapid infiltration and, on hillsides, downslope drainage. The organic layer also has a relatively low thermal conductivity, resulting in slow thaw below thick organic layers. The thick organic layer limits the depth of thaw each summer to about 50–100 cm above permafrost (i.e., the active layer). As the active layer thaws, the hydraulic properties change. For example, the moisture-holding capacity increases, and additional subsurface layers become available for lateral flow. The mosaic of Alaskan vegetation depends not only on disturbance history (Chapter 7) but also on hydrology (Chapter 6).

Many of the principles guiding stochastic analysis of flow and transport processes in the vadose zone are those which we also employ in the saturated zone, and which we have explored in earlier chapters. However, there are important considerations and simplifications to be made, given the nature of the flow and of the governing equations, which we explore here and in chapter 12. The governing equation for water flow in variably saturated porous media at the smallest scale where Darcy’s law is applicable (i.e., no need for upscaling of parameters) is Richards’ equation (cf. Yeh, 1998)

This chapter is an extension of our discussion on transport in chapters 7 to 10. Our goal here is to explore a few aspects of the transport problem which are unique to variably saturated soils. The heterogeneity of soils affects transport of solutes in the vadose zone in different ways. It leads to irregular and hard-to-predict spreading of the solutes. The solutes may be channeled through highly conductive flow channels where diffusion plays only a minor role. This may lead to concentrations which are high and travel times which are fast compared to what one may anticipate by assuming that the medium is homogeneous. Evidence for such behavior was found in field experiments (cf. Wierenga et al., 1991; Ellsworth et al., 1991; Ritsema et al., 1998; Sassner et al., 1994) and in large-scale laboratory experiments (Dagan et al., 1991). Hence, the effects of heterogeneity must be recognized and modeled. The effects of heterogeneity can be modeled by employing the stochastic concepts discussed in earlier chapters. The approach for modeling contaminant transport which is the least restrictive in terms of assumptions introduced is the MC simulation. This approach will be reviewed briefly in section 12.1. Modeling of the mean concentration along our discussion in chapter 8 is computationally less demanding compared to MC simulations, yet is less informative since the concentration in the field can hardly be expected to be equal to its expected value. Applications along that line are limited since deriving the macrodispersion coefficients needed for such an undertaking is difficult. Nonetheless, we shall discussed this approach in section 12.2, for the insight into the transport processes it provides. A few simple models are available for gravitational flow through shallow depths. These methods are of course limited in applications, yet they are less demanding in terms of data requirements and the computational efforts involved. Such methods are the focus of the last section in this chapter. The concept of MC simulation was discussed in earlier chapters.

The hydrologic cycle has received considerable attention in recent years with particular interest in the dynamics of land–atmosphere exchanges as it relates to global climate change and the need for more accurate numbers in global circulation models (GCMs). Recent advance in remote sensing and operational weather forecasts have significantly improved the ability to monitor the hydrologic cycle over broad regions (Vörösmarty and Peterson, 2000). The application of hydrologic models in understanding interactions between the watersheds and estuaries is critical when examining seasonal changes in the biogeochemical cycles of estuaries. Water is the most abundant substance on the Earth’s surface with liquid water covering approximately 70% of the Earth. Most of the water (96%) in the reservoir on the Earth’s surface is in the global ocean. The remaining water, predominantly stored in the form of ice in polar regions, is distributed throughout the continents and atmosphere—estuaries represent a very small fraction of this total reservoir as a subcomponent of rivers. Water is moving continuously through these reservoirs. For example, there is a greater amount of evaporation than precipitation over the oceans; this imbalance is compensated by inputs from continental runoff. The most prolific surface runoff to the oceans is from rivers which discharge approximately 37,500 km3 y−1 (Shiklomanov and Sokolov, 1983). The 10 most significant rivers, in rank of water discharge, account for approximately 30% of the total discharge to the oceans (Milliman and Meade, 1983; Meade, 1996). The most significant source of evaporation to the global hydrologic cycle occurs over the oceans; this occurs nonuniformly and is well correlated with latitudinal gradients of incident radiation and temperature. The flow of water from the atmosphere to the ocean and continents occurs in the form of rain, snow, and ice. Average turnover times of water in these reservoirs can range from 2640 y in the oceans to 8.2 d (days) in the atmosphere (Henshaw et al., 2000; table 3.1). The aqueous constituents of organic materials, such as overall biomass, have an even shorter turnover time (5.3 d). These differences in turnover rate are critical in controlling rates of biogeochemical processes in aquatic systems.