Highlights

Abstract

Keywords

Abbreviations

1. Introduction

2. Iron

3. Antioxidants

4. Vitamin D

5. Calcium

6. Discussion/conclusion

CRediT authorship contribution statement

Declaration of competing interest

References

Abstract

Optimising nutrition intake is a key component for supporting athletic performance and supporting adaption to training. Athletes often use micronutrient supplements in order to correct vitamin and mineral deficiencies, improve immune function, enhance recovery and or to optimise their performance. The aim of this review was to investigate the recent literature regarding micronutrients (specifically iron, vitamin C, vitamin E, vitamin D, calcium) and their effects on physical performance. Over the past ten years, several studies have investigated the impacts of these micronutrients on aspects of athletic performance, and several reviews have aimed to provide an overview of current use and effectiveness. Currently the balance of the literature suggests that micronutrient supplementation in well-nourished athletes does not enhance physical performance. Excessive intake of dietary supplements may impair the body’s physiological responses to exercise that supports adaptation to training stress. In some cases, micronutrient supplementation is warranted, for example, with a diagnosed deficiency, when energy intake is compromised, or when training and competing at altitude, however these micronutrients should be prescribed by a medical professional. Athletes are encouraged to obtain adequate micronutrients from a wellbalanced and varied dietary intake.

1. Introduction The foundations of sport performance are training and nutrition/diet of the athlete, with nutritional strategies providing a supportive role in enhancing training adaption (Stellingwerff et al., 2019). In line with the evolution of methods to optimise training through various training prescriptions, there has been a concurrent evolution in nutrition strategies for athletes. Current nutritional consensus statements promote the periodisation of nutritional intake to optimise the adaptation from the training programme prescribed to the athlete (Stellingwerff et al., 2019). The theory of nutritional periodisation is planned energetic and macronutrient strategies to target the individual exercise sessions and overall training programme to aid in obtaining long term performance gains in athletes (Jeukendrup, 2017). Strategies of nutritional periodisation include manipulating carbohydrate and fat intake to upregulate key signalling pathways in the skeletal muscle and promote mitochondrial biogenesis, angiogenesis and increased lipid oxidation (Hansen et al., 2005; Hulston et al., 2010; Morton et al., 2009) or optimising protein intake to support hypertrophic responses in skeletal muscle (Stellingwerff et al., 2019). However, numerous metabolic processes and reactions involved in energy extraction from macronutrients, oxygen delivery and transfer, tissue repair, and growth and development are dependent on essential vitamins and minerals (Volpe, 2007).

Micronutrients are essential for life and include; vitamins which are organic compounds that support health, growth and reproduction and are needed in small amounts to prevent clinical deficiencies and declines in health (Fogelholm, 2015). A key feature of most vitamins is that the human body is unable to synthesise them (Fogelholm, 2015), therefore they must be obtained from dietary intake. Vitamins are classified based on their in vivo solubility, with A, D, E and K classified as fat-soluble and vitamins B and C classified as water soluble (Fogelholm, 2015). Minerals are inorganic substances that support physiological functioning (Fogelholm, 2015). The daily physiological requirements determine the mineral classifications, hence ~100 mg⋅day− 1 of macrominerals (sodium, potassium, calcium, phosphorus and magnesium) and ~20 mg⋅day− 1 of trace elements (iron, zinc, copper, chromium and selenium) are required by healthy individuals (Fogelholm, 2015).

1- Introduction

2- Materials and methods

3- Results

4- Discussion

References

Abstract

Photosynthesis is an important driver of calcium carbonate deposition on tropical coral reefs largely due to the symbiosis of numerous invertebrates with photosynthetic dinoflagellates in the family Symbiodiniaceae. In bioeroding sponges, however, similar symbioses appear to support the decalcification of carbonate substrates. Compared to its role in calcification, the relative importance of photosynthesis to decalcification processes is less known. Here, the daytime and night-time chemical bioerosion rates of the common Indo-Pacific sponge Cliona orientalis were examined under varying levels of photosynthetic activity and/or varying abundances of intracellular dinoflagellates. Photosynthesis was manipulated either by preconditioning the sponges with the photosynthetic inhibitor diuron (DCMU), or by exposing them to short-term heat stress to achieve bleaching (loss of symbionts). DCMU reduced symbiont numbers and diminished their ability to evolve oxygen. Thermal stress caused a significantly greater loss of symbionts, but photosynthesis was less inhibited. In both cases, decreases in photosynthetic activity and symbiont densities led to proportionately lowered daytime chemical bioerosion rates. Moreover, increased rates of night-time bioerosion were linked to greater daytime rates of photosynthesis, rather than to the night-time respiration of the sponge holobiont. Our findings support the conclusion that photosynthetic products (photosynthates) and/or by-products (oxygen) stimulate sponge bioerosion. This work further reveals the importance of symbionts in the ecology of such sponges and in their ability to sustain high bioerosion activity in otherwise nutrient-poor ecosystems.

Introduction

Tropical coral reefs thrive in shallow clear waters where sunlight powers productive and diverse food chains. Symbioses between invertebrates and a variety of photosynthetic microorganisms enable high rates of productivity on reefs despite low environmental concentrations of inorganic nutrients (Muscatine and Porter, 1977; Seckbach, 2004; Yellowlees et al., 2008). The evolutionary success that results from hosting phototrophic microbes such as dinoflagellates, diatoms, chlorophytes, rhodophytes, or cyanobacteria is seen in a wide range of diverse invertebrates belonging to taxa such as Cnidaria, Mollusca, Foraminifera, Platyhelminthes, and Porifera (Trench, 1993; Stat et al., 2006; Lipps and Stanley, 2016). Presently almost 200 sponge species (Porifera) are known to host microbial photosynthetic symbionts (“photosymbiotic” sponges), which may contribute to the nutrition and health of the sponge (e.g. Wilkinson, 1987; Hill et al., 2011; Thacker and Freeman, 2012). Sponge species that receive substantial contributions in this way are often named “phototrophic” after the nutritional mode of their symbionts, or “mixotrophic” given that they also depend on filter-feeding by specialized food-trapping sponge cells. The nutrition of sponges is often further supplemented by inputs from intimate associations formed with heterotrophic bacterial populations of varying density and diversity (e.g. Hentschel et al., 2003; Taylor et al., 2007).

The rheological behavior of low-calcium fly ash suspensions in activating solutions of colloidal silica and alkali hydroxide is investigated. The study is aimed at relating the rheological behavior of alkali-silicate activated low-calcium fly ash (AAF) suspensions with Portland cement paste suspensions. The yield stress and the viscosity of the AAF suspensions increase with the alkalinity of the colloidal solution, which is due to changes in the surface charges on fly ash particles with the change in the ionic medium. Increasing the alkalinity results in a less negative zeta potential of fly ash in the alkaline solution of colloidal silica and an increase in the yield srtess of the AAF suspension. The thixotropic behavior in AAF suspensions is associated with structure breakdown to a finely dispersed suspension of particles produced by shearing. Energy measurements indicate a very slow change in the internal particle structure with age at room temperature. A comparison of AAF suspensions is presented with suspensions of Portland cement in water, which are proportioned for similar physical flow characteristics and yield stress. AAF suspensions have a larger solid fraction than the cement suspensions in water of comparable yield stress. The zeta potential of cement particles in water is less negative when compared to fly ash in alkaline-silicate solutions. The AAF suspensions of comparable yield stress exhibit a significantly higher viscosity than the cement suspensions in water. Cement paste and AAF suspensions exhibit a rate dependent yield response. Cement paste suspensions exhibit a threshold strain rate for minimum yield stress. In AAF suspensions there is a continuous decrease in the yield stress at lower strain rates. The thixotropic behavior in cement paste is influenced by chemical ageing which produces a rapid recovery of yield stress. In comparison, there is very little ageing at room temperature in the AAF suspensions and a very slow recovery of yield stress after shearing.

Introduction

Concrete is one of the most used construction material, and it is conventionally made using a binder consisting of cement and water. Concrete is a particulate composite material, with aggregate inclusions in a cement paste matrix. The suspension of cement paste in water is referred to as cement paste suspension and it provides fluidity to concrete. Chemical ageing produced by the hydration reaction between cement and water produces a continuous evolution in the rheological behavior of a cement paste suspension, leading ultimately to a change in the state of the material from a fluid to a solid (Subramaniam and Wang, 2010; Wang and Subramaniam, 2011). Cement paste is a non-Newtonian, shear thinning suspension which within a finite yield stress (Lootens et al., 2004; Chateau et al., 2008; Tattersall and Banfill, 1983). The rheological behavior of cement paste suspensions is well understood, and this knowledge is used to produce concrete with different flow behaviors, for diverse applications. The production of concrete with different characteristics, and for different applications such as pumping, self-levelling flow and layer deposition have been achieved by controlling the rheology of cement paste suspensions (Deng et al., 2007; Kim et al., 2017; Choi et al., 2016; Van Zijl et al., 2016; Perrot et al., 2012; Nair and Ferron, 2016; Li et al., 2002).

This study sets out to harvest microalgae through auto-flocculation by manipulating the interactive effect of calcium, phosphate, and polysaccharides (PSAs). The harvesting efficiency (H.E) of 91 ± 2.7% was achieved for Ettlia sp. through auto-flocculation. The H.E was attributed to the chelation of calcium and PSAs present in microalgae medium. In the absence of PSAs, the H.E reduced to 64 ± 05% only. The addition of phosphate (34 ± 0.13 mg L
1 ) increased the H.E to 73 ± 1.5%. Zeta-potential measurements showed that the harvesting was induced by charge neutralization and inter-particle bridging. The PSAsbased auto-flocculation was tested for Chlorella sp. too but it turned out the H.E of 51 ± 1.3% only. The flocculation did not take place when the co-harvesting of Ettlia sp. and Chlorella sp. was carried out. It is concluded that each microalgae specie shows different auto-flocculation mechanism due to variation in their PSAs characteristics. It triggers up the need for setting up a distinct protocol for different microalgae species to assess their auto-flocculation potential.

Introduction

Harvesting or dewatering is a critical step of microalgae bioprocessing (Gejji and Fernando, 2018; Pradhan et al., 2019). Harvesting accounts for 20e30% of the total cost of microalgae bioprocessing (Sahoo et al., 2017a; Yoo et al., 2013). So far, various methods for microalgae harvesting including centrifugation, dissolved air flotation, and filtration have been developed; however, none of them is cost-effective yet (Sahoo et al., 2017b). To address this challenge, auto-flocculation has been recognized as an alternative method for microalgae harvest (Raheem et al., 2018). Autoflocculation is a cheap and efficient method (Lai et al., 2016; Mathimani et al., 2018; Wang et al., 2018). It demands less resource input than any other method of microalgae harvest (Ding et al., 2017; Jimenez et al., 2017 ). Auto-flocculation is based on the principle of the well-known chemical flocculation process; however, it does not involve the addition of expensive chemicals. Autoflocculation is mainly driven by the interaction of polysaccharides (PSAs), calcium, and phosphate (Tran et al., 2017; Ummalyma et al., 2017; Vandamme et al., 2012). PSAs are the form of polymeric carbohydrates, which are produced by microalgae under specific cultivation conditions. PSAs are composed of glucose, arabinose, galactose, xylose, mannose, and fructose. Each sugar group has a different role in cell metabolism. For example, arabinose controls cell aggregation properties, and galactose is responsible for providing energy. It is widely known that microalgae produce PSAs under light and nutrients stress condition. The yield and the characteristics of PSAs depend on the microalgal species (Lee et al., 2016; Vandamme et al., 2012).

The market for air-cooled condensers (ACCs) for power generation applications has increased during the past decade due to growing water use restrictions on power plants. While ACCs are very good at reducing power plant water withdraw, this benefit is associated with a drawback caused by the steam condenser’s operating temperature being dependent on the ambient air temperature.[1] On very hot days, the condenser temperature can rise above its design condition, increasing the backpressure experienced by the low-pressure (LP) turbine and limiting its power output. Because of this, net unit heat rate would increase, resulting in an increase in fuel consumption in order to meet demand. This problem is exasperated if the ACCs have not been adequately sized to maintain performance on the hottest days in order to reduce their size and associated capital costs. One approach to supplement the performance of an ACC is to utilize a phase change material (PCM), which can be frozen at night and melted during the day, with the melting process removing heat from the condensate. The proposed PCM-based supplemental cooling system is presented in Figure 1. This system can either be used in series with an existing ACC or be sized to entirely replace it. In this concept, heat is transferred into the PCM through a pipe connecting the PCM-filled trays. At night, this same pipe is used to transfer heat out of the PCM and into the air through fins at the top of the system. The selection of a suitable PCM is critical to the success of the proposed enhanced ACC system, as it must meet several key criteria. First, the PCM must melt and freeze at a temperature between the nighttime temperature and the target condensate temperature. A melt/freeze temperature around 30 °C is a reasonable value, since it meets the cooling requirements for plants in regions where nighttime temperatures fall to around 20 °C. PCM cost is also critical as the expected quantity required for a full-scale system is considerable. The PCM should also have a high energy storage density, be non-hazardous and non-flammable, and maintain its performance during thousands of freezing and melting cycles. There are two major classifications of PCMs, organic PCMs, such as paraffin waxes and fatty acids; and inorganic PCMs, which are primarily hydrated salts.[2–4] Organic PCMs offer the benefits of high energy storage capacity, little degradation after many operating cycles and minimal corrosiveness. Inorganic PCMs are typically an order of magnitude less expensive than organics, offer high energy storage capacities, and are non-flammable.[5] Some known issues with inorganic PCMs are that they can degrade over time, they tend to be highly corrosive, and they typically require additives to prevent supercooling. However, since PCM cost is a first consideration for this proposed system, inorganic PCMs are considered to be the first choice.

It is well-established that contraction of the heart is controlled by changes of cytoplasmic calcium concentration ([Ca2+]i). [Ca2+]i must be high enough in systole to activate the contractile proteins in order to pump blood out of the heart. Equally importantly, it must fall during diastole to low enough levels that the muscle of the heart relaxes so that the chambers can refill with blood. The aim of this article is to discuss factors responsible for both the rise and fall of [Ca2+]i . The importance of calcium in contraction of the heart was originally demonstrated by Sydney Ringer (Ringer, 1883). I have recently described both the serendipitous nature of his discovery and the manner in which it was published (Eisner, 2014). In the subsequent 130 years it has become clear that changes of intracellular calcium concentration ([Ca2+]i) regulate the function of virtually all organs. It took, however, almost one hundred years after Ringer’s discovery to measure directly the transient elevation of [Ca2+]i (the calcium transient) which underlies cardiac contraction (Allen & Blinks, 1978; Allen & Kurihara, 1980). Calcium versus other signalling modalities. Calcium has its actions by binding to proteins and thereby changing their shape and properties (Fig. 1A). In the case of striated muscle, calcium binds to troponin and the resulting movement of tropomyosin allows actin and myosin to interact. There are, of course, many other ways to alter the properties of proteins including phosphorylation and nitrosylation. This immediately raises the question of what are the advantages and disadvantages of using calcium as opposed to other ways of modifying protein structure? One great advantage of calcium is its speed of action. [Ca2+]i rises and Ca2+ ions bind to troponin very quickly and. In cardiac muscle contraction can be 50% complete within 200 ms (Fig 1A). In contrast regulation by phosphorylation is much slower. Fig 1B shows the effects of beta adrenergic stimulation on the Ca current. This takes about 20 s to be 50% complete (Frace et al., 1993). This slower timescale is due to the many steps involved; agonist binding to the receptor, generation of cyclic AMP, and, finally, the activation of protein kinase A which then phosphorylates the L-type channel. Although signalling by phosphorylation is slower than that by Ca2+, it has the advantage that it can be regulated in a much more subtle way. Specific phosphodiesterases can break down cAMP and various regulators affect the activities of the kinases and phosphatases. Another significant advantage of control by phosphorylation is that it can be reversed simply by dephoshorylation. In contrast, Ca2+ ions cannot be destroyed. The only way to reverse Ca2+ binding is to pump the Ca2+ across a membrane either out of the cell or into an intracellular store. Put simply, Ca2+ must be recycled and many of the results and conclusions of the remainder of this review follow from this.

Despite a considerable amount of research to find alternatives to heavy metals (commonly defined as metals both heavier than 5 g/cm3 and toxic at low concentrations) (Ricco et al. 2015), they still find ever increasing usage in modern products, including batteries, pesticides, paints, and electronics. Consequently, the rising presence of heavy metal waste in the environment provides a potential and possibly increasing risk of prolonged health problems to humans and other living species. For example, lead poisoning can severely affect central nervous systems (Okoye et al. 2010); cadmium compounds are likely human carcinogens, longterm exposure may cause fragile bones, kidney damage, and even death (Boparai et al. 2011; Srivastava et al. 2006); symptoms of copper poisoning include nausea, vomiting, and death (Fu and Wang 2011). These problems are exacerbated by the fact that heavy metals are usually not easily removed from the biosphere but instead tend to accumulate in living organisms (Annadurai et al. 2003; Fu and Wang 2011; Reed and Matsumoto 1993), making the problem of heavy metal contamination more severe. Therefore, simple and effective treatments for water contaminated with heavy metals have received continuous attention (Fu and Wang 2011). Existing methods for heavy metal removal from water include chemical precipitation (Charerntanyarak 1999; Matlock et al. 2002), ion exchange (Tavakoli et al. 2017; Wang et al. 2014), membrane filtration (Al-Rashdi et al. 2013; Blöcher et al. 2003), and adsorption (Celis et al. 2000; Ho et al. 1996). Among these technologies, adsorption is one of the most promising methods, as it is generally passive and relatively facile. Recently, several types of adsorbents have been reported for removing heavy metals from water, including carbon nanotubes (Stafiej and Pyrzynska 2007), activated carbon (Amuda et al. 2007; Kobya et al. 2005), zeolites (Erdem et al. 2004), metal-organic frameworks (MOFs) (Ricco et al. 2015), nanosized metal oxides (Hua et al. 2012; Wang et al. 2010a), and resins (Lin et al. 2000). Among these adsorbents (Table 1), nano-adsorbents such as carbon nanotubes, MOFs, or metal oxide nanomaterials show a high capacity for adsorbing metal ions from aqueous solution due to their high surface areas; however, these adsorbents can be expensive and difficult to prepare (Gupta et al. 2011). Therefore, there is a pressing need for adsorbents that are cost-effective, abundant, easy to prepare, biocompatible, and capable of efficiently removing heavy metals, that is, absorption that is fast and extensive.

Periapical lesion results from serious inflammatory response to microorganisms around the tooth root and the root canal [1]. Periapical lesions could perforate into the oral cavity affecting hard tissue or maxillary sinus. The infection around the root and tooth leads to bone resorption caused by local osteomyelitis [2]. Furthermore, cellulitis in soft tissue causing swelling in the face is a common symptom of severe local jawbone osteomyelitis. Traumatic injuries of teeth can cause granuloma or cysts associated with periapical lesions. Granulomas are composed usually of solid soft tissue, while cysts are semisolid tissue surrounded by epithelium [3]. Radiographs show lesions structure as unilocular, lucent, round, or pear shaped contoured by a thin rim of cortical bone [4]. The incidence of cysts formation is between 6 and 55% in small lesions and a 100% with lesions larger than 20 mm [2]. On the other hand, granulomas occurrence ranges between 9.3 and 87.1%, where abscesses formation rate is between 28.7 and 70.07% [4]. Epithelial proliferation and other molecular mechanisms can cause lesion formation. Nonetheless, by-products of microorganisms, which lead to osmotic fluid accumulation in the lumen, are the most common cause of periapical lesions [5]. Therefore, eliminating microorganisms can release the hydrostatic pressure resulting from osmotic fluid and minimize the effect of periapical lesions on the tooth. Management of infection-caused periapical lesions is a two-step process. Firstly, antibacterial treatment is performed using antibiotics (e.g., metronidazole, ciprofloxacin, and minocycline), chemical irrigation, and disinfectants (i.e., calcium hydroxide). Despite its wide use as disinfectant of the root canal system, calcium hydroxide is not effective as root canal dressing [2, 6, 7]. Secondly, releasing the hydrostatic pressure is detrimental and can be achieved by decompression, aspiration, and aspiration irrigation [8–10].