BMC Medicine Blood pressure demographics: nature or nurture ... ... genes or environment? Hypertensionprevalencegeneticenvironmentpsychosocial factors

Joseph Tomson email@example.com
Address: University Department of Medicine
City Hospital
B18 7QHBirminghamEngland, UK

Gregory Yh Lip
Address: University Department of Medicine
City Hospital
B18 7QHBirminghamEngland, UK

BMC Medicine Blood pressure demographics: nature or nurture ... ... genes or environment? Hypertensionprevalencegeneticenvironmentpsychosocial factors
10.1186/1741-7015-3-3BioMed Central Page 1 of 4 (page number not for citation purposes) Commentary * Corresponding author
Hypertension is a growing worldwide problem associated with an increased risk of cardiovascular morbidity and mortality. However, the rates of prevalence of hypertension are higher in some populations than others. Although ethnic and genetic factors have been implied in the past to explain this, the environmental influence and psychosocial factors may play a more important role than is widely accepted. Examining the non-genetic influences in future hypertension research may be necessary in order to clearly define the local blood pressure demographics and the global hypertensive disease burden.

Hypertension is a common problem, with a consistent and continuous risk of cardiovascular disease and stroke associated with rising blood pressure levels [1]. Furthermore, effective treatment of blood pressures has been shown to cause reductions in morbidity and mortality from cardiovascular disease and stroke. The modern management of hypertension is even more complex, with the emergence of newer therapies, ageing populations and new clinical trial evidence, as well as the need for multiple agents to achieve target blood pressures, which are much lower than they used to be in the past [1].

The consequences of poor blood pressure control are huge. As high blood pressure is the most important risk factor for cardiovascular disease, it has been calculated that by achieving the target of 140 mmHg, there would be a reduction of 28-44% in stroke and 20-35% in ischaemic heart disease depending on the age. This would prevent approximately 21400 stroke deaths and 41400 ischaemic heart disease deaths each year -and these translate to approximately 42800 strokes and 82800 ischaemic heart diseases saved, making a total of 125600 events saved per year in the United Kingdom alone [2]. Even white coat hypertension is by no means a benign condition [3]. By 2020, the world population would be an estimated 7.8 billion people and hypertension currently is 'estimated' to affect about 1 billion worldwide -this figure will be rising. The growing numbers and the lack of concerted effort to tackle the burden of hypertension makes depressing reading.

Nonetheless, what is more intriguing and perhaps still not fully explained, is why some populations seem to have a much higher population prevalence of hypertension as compared to others. For instance, the prevalence and incidence of hypertension differs between the non-westernised and westernised populations. Even within the western world, the Afro-Caribbean or African-American black population has a higher prevalence of hypertension and target organ damage related to it, as compared to white Europeans or Americans [4]. Differences also exist within the same region, for example, with people of Eastern European origins having a higher prevalence of hypertension compared to elsewhere in Europe [5]. Understanding the reason(s) behind these geographical and ethnic differences would help devise effective measures in primary prevention.

Cooper et al [6], writing in BMC Medicine, address the issue of whether there is a truly genetic predisposition or perhaps an environmental influence is to blame for higher rates of prevalence of hypertension seen in some of these ethnic populations. In a well-designed pooled analysis, incorporating eight studies involving 8 white and 3 black populations from the North American, European and African populations -a dataset of nearly 85,000 patients -Cooper et al [6] examined patterns of blood pressure distribution in the different ethnic groups across three continents. They found a wide variation in hypertension prevalence among white and black racial groups, and the rates among blacks were not unusually high when viewed internationally. They therefore suggest that the impact of environmental factors among black and white populations may have been under-appreciated. Specifically, and perhaps contrary to expectations, the prevalence of hypertension was lower amongst the white peoples in Northern America and Canada, as compared to Europe.

Does this take us back to the drawing board? Perhaps environmental factors do play a more major role in developing hypertension than is widely accepted. Indeed, does urbanisation per se together with the unhealthy lifestyle and diet in the western world increase the risk of hypertension, compared to the rural, 'low stress', healthier lifestyle and dietary habits in Africa? Perhaps the genotype of black subjects was not idealised for the 'pro-hypertension' environment of the western world, leading to the greater risk of developing hypertension amongst blacks in the western world. This 'genetic predisposition' of certain ethnic groups, coupled with the 'wrong' environment, leads to an unhealthy combination that predisposes to cardiovascular disease [7]. However, the sociological definition of an ethnic group would be "people of the same race or nationality who share a common and distinctive culture", as it is impossible to consistently classify people by race. Genetic analyses have found more genetic variation within one ethnic group than between one group and another [8]. Therefore, race or ethnicity may appear to be more defined by customs, traditions, language and history than purely by genotype alone. Indeed, classification of race or ethnicity or skin colour, for example, is pretty subjective, imprecise and unreliable. Evidence for this exists in the differences in coronary risk factors in Indians, Paki-stani and Bangladeshi populations in a British city, eventhough together these people might have been classed as 'Indo-Asian' but are clearly different [9]. Similarly, a Scottish Highland crofter is quite different from a Swede businessman, who would again be quite different from a Greek fisherman, although all would be ethnically classified as 'white caucasian'.

Can this 'wrong genotype in the wrong environment' hypothesis be applied to hypertension in black African-Americans? Efforts have already been made to understand the reasons behind the higher prevalence of hypertension in African Americans, with the underlying assumption that there may a genetically determined predisposition as compared to their white counterparts; however, no convincing data are available [10]. This may be because multiple genes determine human hypertension, at least in the vast majority of cases [11], and genetic factors have not been able to fully account for the differences in blood pressure prevalence between ethnic groups. Furthermore, elsewhere, black populations migrating to countries like UK have been shown to have similar blood pressures compared to the white UK population [12].

Numerous potential explanations for the higher prevalence of hypertension in blacks have been proposed. Genetic mechanisms have been used to explain familial aggregation of hypertension in Jamaican blacks and the intra-class correlation of systolic blood pressures amongst black twins [13,14]. Low renin levels noted in the USA black population have been hypothesised to be the result of a genetic 'maladaptation' which though benefited their earlier black ancestors to survive the torment of a transatlantic voyage under slavery, later turned out to be detrimental to survival due to the resultant avid salt retention [15]. Indeed, increased sodium sensitivity, abnormalities in sodium transport, increased vascular responsiveness to pressor stimuli, association between stresses of low socioeconomic status and hypertension, and insulin resistance have also been suggested. Furthermore, ethnic differences in response to anti-hypertensive therapy are also well documented [4], with a potent effects of diuretics and calcium antagonists in black patients, compared to a relatively poor response to beta blockers and drugs that act on the renin-angiotensin system (such as the ACE inhibitors and angiotensin receptor blockers).

Notwithstanding the shortcomings of a retrospective, pooled study, with varying criteria for inclusion, and the intra-, inter-and cross-study observational errors, Cooper et al [6] have shown that the burden of hypertension seems to be more amongst the white population in Europe and that the global rates of hypertension amongst the black population are less in comparison. This study therefore sets the stage for a closer examination of data across geographic areas and calls for more stringent, standardised and possibly nationalised surveillance of blood pressure trends. If nothing else, the data suggests that inferences from cross-sectional studies done in certain geographic areas of a differing socio-economic stature cannot be extrapolated as logical benchmarks for other areas. Unintentionally perhaps, it beckons 'the scientist' to take a second look into the effect of other non-genetic mechanisms to explain the paradoxical findings. Surely more studies of a larger size are needed to confirm these implications.

Evidence that environmental and particularly psychosocial factors are important in the development of hypertension also comes from a series of epidemiological studies conducted in the early part of the last century, which have shown that urbanisation and adoption of a westernised life style leads to blood pressure rises. Many of these studies have been conducted in Africa, where the rural populace has a relatively low prevalence of hypertension. For example, primitive black populations living in more frugal circumstances in rural Africa have been shown to have low blood pressures. Evidence suggests that there are some populations that exist who are naïve to hypertension and related morbidity. Interestingly, their blood pressures hardly rise with increasing age, a common response to age in many other (urbanised?) communities [16][17][18]. The most important characterising feature of these populations were that, their lifestyle was traditional and they had not adopted or been under the influence of beliefs, customs or practices of another culture alien to theirs; the so-called 'unacculturated societies', with a close resemblance to the 'hunter-gatherer' lifestyle of primitive man. The other interesting feature observed was the constancy of electrolyte intake in the diet in these populations, which was in sharp contrast to the more 'developed' Western populations [19].

Migration, not withstanding the complexity of the studies in these populations, has been shown to significantly affect blood pressures. A study examining the migrant islanders into New Zealand showed raised population blood pressures, as well as an increased slope of the ageblood pressure relationship [20]. The Kenyan Luo migration study examined migration of rural tribes to the capital city Nairobi, also found that urbanised populations had higher mean blood pressures [21]. Chronic and excessive alcohol ingestion may also adversely affect blood pressure [22]. The relationship of hypertension with obesity has been demonstrated but weight loss seemed to have more pronounced blood pressure reductions in whites rather than blacks.

The issue of the influence of colour of the skin to blood pressures is even more complex. On the one hand, studies in America have shown relationship between the dark skin and blood pressures, leading to some suggesting that the link is genetic. In contrast, some argue that it is a manifestation of the stress and social pressure of having a dark skin that causes this. In Cuba, for example, where communist principles are considered to have broken the racial barriers, the ethnic differences in blood pressures were shown to be small, supporting the latter argument [23]. In addition, there may even be an effect of neighbourhoods or the social environment on blood pressure and cardiovascular disease [24,25].

Thus, the process by which a society becomes more economically advanced or "developed" seems to be associated closely with rates of hypertension prevalence. Indeed, lifestyle and dietary changes related to the so-called "development" seem linked to the prevalence of hypertension. In the INTERHEART population case-control study [26], which was an investigation into the association of psychosocial risk factors in patients with acute myocardial infarction, examining 11119 cases and 13648 controls from 52 countries, demonstrated higher prevalence of all four 'stress factors' (stress at home, at work, financial stress and major life events) in these patients, with consistency across regions, ethnicity and gender. Though data implicating stress as being contributory to the development of high blood pressures are limited and perhaps even hard to establish, a causal relationship between stress and developing high blood pressure does not appear to be an illogical assumption.

There remain many uncertainties to the relative importance and contribution of environmental versus genetic influences on the development of blood pressure -there is more than likely an influence from both. However, there is now evidence to necessitate increased attention in examining the non-genetic influences on blood pressure, a neglected area of hypertensive research but perhaps a goldmine for establishing causal influences. As stated earlier, the future of hypertension research should focus on more standardised and comparable protocols, with comparable designs in data collection. Multi-centric data collection with a view to establishing local or national blood pressure demographics is crucial for the formal assessment of the global hypertension burden and the implementation of cost-effective primary preventive measures.
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Society: Guidelines for management of hypertension: report of the fourth working party of the British Hypertension Society, 2004-BHS IV. B Willaims, N R Poulter, M J Brown, M Davis, G T Mcinnes, J F Potter, P S Sever, Mcg Thom, S , British Hypertension, J Hum Hypertens. 183Willaims B, Poulter NR, Brown MJ, Davis M, McInnes GT, Potter JF, Sever PS, McG Thom S, British Hypertension Society: Guidelines for management of hypertension: report of the fourth work- ing party of the British Hypertension Society, 2004-BHS IV. J Hum Hypertens 2004, 18(3):139-85.

Cost of poor pressure control in the UK: 62000 unnecessary deaths per year. F J He, G A Macgregor, J Human Hypertens. 17He FJ, MacGregor GA: Cost of poor pressure control in the UK: 62000 unnecessary deaths per year. J Human Hypertens 2003, 17:455-457.

White coat hypertension is a cardiovascular risk factor: a 10-year followup study. P H Gustavsen, A Hoegholm, L E Bang, K S Kristensen, J Hum Hypertens. 1712Gustavsen PH, Hoegholm A, Bang LE, Kristensen KS: White coat hypertension is a cardiovascular risk factor: a 10-year follow- up study. J Hum Hypertens 2003, 17(12):811-7.

Ethnic differences in hypertension and blood pressure control in the UK. QJM. D A Lane, Gyh Lip, 94Lane DA, Lip GYH: Ethnic differences in hypertension and blood pressure control in the UK. QJM 2001, 94(7):391-6.

The coming epidemic: hypertension in rural Kyrgyzstan, Central Asia. J Hum Hypertens in press. J H Young, P Parler, B Bristol, M J Klag, Young JH, Parler P, Bristol B, Klag MJ: The coming epidemic: hypertension in rural Kyrgyzstan, Central Asia. J Hum Hyper- tens in press. 2004 Oct 21

An International Comparative Study of Blood Pressure in Populations of European vs. African Descent. R S Cooper, K Wolf-Maier, A Luke, A Adeyemo, J R Banegas, T Forrester, S Giampaoli, M Joffres, M Kastarinen, P Primatesta, B Stegmayr, M Thamm, BMC Med. 32Cooper RS, Wolf-Maier K, Luke A, Adeyemo A, Banegas JR, For- rester T, Giampaoli S, Joffres M, Kastarinen M, Primatesta P, Stegmayr B, Thamm M: An International Comparative Study of Blood Pressure in Populations of European vs. African Descent. BMC Med 3:2.

Coronary risk factors in people from the Indian subcontinent living in west London and their siblings in India. D Bhatnagar, I S Anand, P N Durrington, D J Patel, G S Wander, M I Mackness, F Creed, B Tomenson, Y Chandrashekhar, M Winterbotham, Lancet. 3458947Bhatnagar D, Anand IS, Durrington PN, Patel DJ, Wander GS, Mack- ness MI, Creed F, Tomenson B, Chandrashekhar Y, Winterbotham M, et al.: Coronary risk factors in people from the Indian subcon- tinent living in west London and their siblings in India. Lancet 345(8947):405-9. 1995 Feb 18

The apportionment of human diversity. R C Lewontin, Evol Biol. 6Lewontin RC: The apportionment of human diversity. Evol Biol 1972, 6:381-398.

Heterogeneity of coronary heart disease risk factors in Indian, Pakistani, Bangladeshi, and European origin populations: cross sectional study. R Bhopal, N Unwin, M White, J Yallop, L Walker, K G Alberti, BMJ. 3197204Bhopal R, Unwin N, White M, Yallop J, Walker L, Alberti KG, et al.: Heterogeneity of coronary heart disease risk factors in Indian, Pakistani, Bangladeshi, and European origin popula- tions: cross sectional study. BMJ 1999, 319(7204):215-20.

Hypertension in blacks. R Cooper, C Rotimi, Am J Hypertens. 10Cooper R, Rotimi C: Hypertension in blacks. Am J Hypertens 1997, 10:804-812.

Genes and hypertension. E A Garcia, S Newhouse, M J Caulfield, P B Munroe, Curr Pharm Des. 921Garcia EA, Newhouse S, Caulfield MJ, Munroe PB: Genes and hypertension. Curr Pharm Des 2003, 9(21):1679-89.

Similarity of blood pressure in blacks, whites and Asians in England: The Birmingham Factory study. J K Cruickshank, Shd Jackson, D G Beevers, L T Bannan, M Beevers, V L Stewart, J Hypertension. 3Cruickshank JK, Jackson SHD, Beevers DG, Bannan LT, Beevers M, Stewart VL: Similarity of blood pressure in blacks, whites and Asians in England: The Birmingham Factory study. J Hyperten- sion 1985, 3:365-371.

Factors influencing arterial blood pressures in the general population in Jamaica. W E Miall, E H Kass, J Ling, E L Stuart, BMJ. 1962Miall WE, Kass EH, Ling J, Stuart EL: Factors influencing arterial blood pressures in the general population in Jamaica. BMJ 1962, 2:497-506.

Blood pressure in blacks. Twin studies in Barbados. C E Grim, T W Wilson, G D Nicholson, T A Hassel, H S Fraser, C M Grim, D M Wilson, Hypertension. 15Grim CE, Wilson TW, Nicholson GD, Hassel TA, Fraser HS, Grim CM, Wilson DM: Blood pressure in blacks. Twin studies in Bar- bados. Hypertension 1990, 15:803-809.

Biohistory of slavery and blood pressure differences in blacks today. A hypothesis. T W Wilson, C E Grim, Hypertension. 17suppl IWilson TW, Grim CE: Biohistory of slavery and blood pressure differences in blacks today. A hypothesis. Hypertension 1991, 17(suppl I):I 122-I 128.

Blood pressure and associated factors in a rural Kenyan community. N R Poulter, K T Khaw, Bec Hopwood, M Mugambi, W S Peart, G Rose, Hypertension. 6Poulter NR, Khaw KT, Hopwood BEC, Mugambi M, Peart WS, Rose G: Blood pressure and associated factors in a rural Kenyan community. Hypertension 1984, 6:810-813.

Cardiovascular disease in the Masai. G V Mann, Shafer Rd, R S Anderson, H H Stanstead, J Atherosclerosis Res. 4Mann GV, Shafer Rd, Anderson RS, Stanstead HH: Cardiovascular disease in the Masai. J Atherosclerosis Res 1964, 4:289-312.

Cardiovascular disease in African pygmies. G V Mann, A A Roels, D L Price, J M Merrill, J Chron Dis. 15Mann GV, Roels AA, Price DL, Merrill JM: Cardiovascular disease in African pygmies. J Chron Dis 1962, 15:341-371.

Salt and blood pressure in various populations. N Poulter, K T Khaw, Bec Hopwood, M Mugambi, W S Peart, P S Sever, J Cardiovasc Pharmacol. 6Poulter N, Khaw KT, Hopwood BEC, Mugambi M, Peart WS, Sever PS: Salt and blood pressure in various populations. J Cardiovasc Pharmacol 1984, 6:S197-S203.

Blood pressure and social interaction and Tokelau and migrants in New Zealand. R Beaglehole, C E Salmond, A Hooper, J Huntsman, J M Stanhope, J C Cassel, Iam Prior, J Chron Dis. 30Beaglehole R, Salmond CE, Hooper A, Huntsman J, Stanhope JM, Cas- sel JC, Prior IAM: Blood pressure and social interaction and Tokelau and migrants in New Zealand. J Chron Dis 1977, 30:803-812.

The Kenyan Luo migration study: Observations on the initiation of a rise in blood pressure. N R Poulter, K T Khaw, B E Hopwood, BMJ. 300Poulter NR, Khaw KT, Hopwood BE, et al.: The Kenyan Luo migration study: Observations on the initiation of a rise in blood pressure. BMJ 1990, 300:967-972.

Alcohol, hypertension, coronary disease and stroke. G Y Lip, D G Beevers, Clin Exp Pharmacol Physiol. 223Lip GY, Beevers DG: Alcohol, hypertension, coronary disease and stroke. Clin Exp Pharmacol Physiol 1995, 22(3):189-94.

Hypertension in Cuba: Evidence of a narrow African-white difference. P O Ordunez-Garcia, A D Espinosa-Brito, R S Cooper, J Hum Hypertens. 12Ordunez-Garcia PO, Espinosa-Brito AD, Cooper RS, et al.: Hyper- tension in Cuba: Evidence of a narrow African-white differ- ence. J Hum Hypertens 1998, 12:111-116.

Socioecological stressor areas and African-white blood pressure: Detroit. E Harburg, J C Erfurt, C Chape, J Chronic Dis. 26Harburg E, Erfurt JC, Chape C, et al.: Socioecological stressor areas and African-white blood pressure: Detroit. J Chronic Dis 1973, 26:595-611.

Neighbourhood environments and coronary heart disease: A multilevel analysis. A V Diez-Roux, F J Nieto, C Muntaner, Am J Epidemiol. 146Diez-Roux AV, Nieto FJ, Muntaner C, et al.: Neighbourhood envi- ronments and coronary heart disease: A multilevel analysis. Am J Epidemiol 1997, 146:48-63.

Association of psychosocial risk factors with risk of acute myocardial infarction in 11119 cases and 13648 controls from 52 countries (the INTERHEART study): case-control study. A Rosengren, S Hawken, S Ounpuu, K Sliwa, M Zubaid, W A Almahmeed, K N Blackett, C Sitthi-Amorn, H Sato, S Yusuf, Lancet. 3649438Rosengren A, Hawken S, Ounpuu S, Sliwa K, Zubaid M, Almahmeed WA, Blackett KN, Sitthi-amorn C, Sato H, Yusuf S, INTERHEART investigators: Association of psychosocial risk factors with risk of acute myocardial infarction in 11119 cases and 13648 con- trols from 52 countries (the INTERHEART study): case-con- trol study. Lancet 2004, 364(9438):953-62.


Peculiarities of Surface Interaction of Al+REM Alloys with Air and Water
2017

N A Popov
Institute of Solid State Chemistry
Ural Branch of RAS
Russia

L A Akashev
Institute of Solid State Chemistry
Ural Branch of RAS
Russia

V G Shevchenko
Institute of Solid State Chemistry
Ural Branch of RAS
Russia

I G Grigorov
Institute of Solid State Chemistry
Ural Branch of RAS
Russia

Peculiarities of Surface Interaction of Al+REM Alloys with Air and Water

Universal Journal of Physics and Application
114201710.13189/ujpa.2017.110402Aluminium-rare Earths AlloysEllipsometryOxide Film Growth
The effect of the phase and chemical composition of aluminium+rare earth metal (1-2.5%R, ~22%R) polycrystalline alloys (Al+REM) on the rate of their surface film growth in air (at temperatures 400, 500, 600°C) and in water (~100 °C) was studied. It is shown that in the temperature range 500-600°C the oxidation of 1-2.5%R alloys in air is enhanced due to the increasing amount of REM oxide phases and crystallization of amorphous Al 2 O 3 . Al+1at.%Yb alloy shows the lowest oxidation stability in this temperature range owing to the formation of the greatest amount of REM oxides. Oxidation of Al+REM (~22%R) alloys in air begins at a temperature below 400°C. Their oxidation rate depends on the type and amount of dopant metal and the phase composition: the presence of REM-rich intermetallics in the alloy dramatically increases its reactivity. It is established that in the interaction of Al+REM alloys with boiling water, the active reacting phase is aluminum.

Introduction

Aluminum alloys with rare earth metals (REM) find wide application in electrical engineering. Small amounts (up to at.5%) of transition (Zr) or rare-earth metal (Sc, Y and lanthanides) dopants increase the strength of aluminum applied in high-strength power lines. Due to low solubility of these metals in aluminum, its electrical conductivity is preserved. The finely dispersed phase of intermetallic compounds Al 11 R 3 (Al 3 R) formed in the aluminum alloy increases its strength almost twice [1]. Additives reinforcing aluminum (for example, copper in duralumin) often impair its resistance to corrosion. One of the reasons of this is a variation in the chemical composition and structure of the passivating oxide films. Therefore, the study of the protective properties of oxide films of aluminum alloys is not less important than the study of their strength and electrical properties. The information about the properties of protective passivating oxide films at elevated temperatures can be used for the development of new high-temperature (up to 300°C) uninsulated wires and wires operating at elevated humidity.

Besides, the prospects of using rare-earth metals as alloying additions increasing the oxidation rate of aluminum powder in rocket propellants were shown by authors of works [2,3]. Small additions of rare earth metals improve the burning rate and other impulse characteristics of disperse aluminum by reducing the protective properties of its oxide film. Because of this, it is important to study the effect of rare earth additives on the thermokinetic characteristics of aluminum, including cracking of the barrier layer of oxidation products on the metal surface.

Experimental Section

To determine the quantitative effect of the chemical and phase composition of alloys on the intensity of their interaction with reactive media (air, water), two groups of alloys were synthesized: alloys close to eutectics (Al+1-2,5%R) and alloys with chemical composition close to aluminum in intermetallides Al 11 R 3 (~22%R). All samples were synthesized by melting in a vacuum furnace in helium environment (high purity grade) at 1500°C followed by cooling in alundum crucibles. The composition of the alloys was refined by mass spectrometry (Spectromass 2000) and X-ray fluorescence spectroscopy (XRF-1800). The investigated sample surface was the top plane polished mechanically. The alloys were polished by diamond pastes applied on soft fabrics until a specular reflection was obtained (surface roughness was Ra = 0.047-0.051μm. Then the samples were washed thoroughly with alcohol and acetone with additional annealing in vacuum (~0,01 Pa) at 300°C for 1 h. The alloys were oxidized in air in a muffle furnace at temperatures of 400, 500 and 600°C. In all the experiments, the oxidation of alloys took place stepwise at the same temperature at 5, 10, 15 etc. min. intervals with windows for measurements. The interaction of water with the surface of Al+REM alloys was realized by immersing the samples in boiling distilled water at 100°C with the same intervals for ellipsometric measurements in air.

The ellipsometric parameters Δ and ѱ were measured by the compensating (zero) method with a one-wave ellipsometer LEF-3M (λ = 0.6328μm) after the samples were cooled in air to room temperature. Thereby the time dependence of the ellipsometric parameters of the examined surface in quasi-isothermal conditions was obtained.

To determine the kinetics of surface film growth (thickness against time), at first the optical constants (n, k) of the alloys and their natural passivation films were found. For this purpose, we used the ellipsometric immersion method [4,5]. The immersion liquids were anise oil (n = 1.5) and alcohol (n = 1.364). Table 1 lists the refractive indices (n 2 ) and extinction coefficients (k 2 ) of pure aluminum, alloys of intermetallic and eutectic compositions, as well as of their natural oxide films (n 1 , k 1 ) with the initial thickness d. It is seen that the thickness of the oxide layer on the alloys is always higher than on pure aluminum. Besides, the optical constants of substrates for the two groups of alloys differ considerably from each other due to different phase composition.    Figure 1(a,b) presents the temperature and time dependences of the thickness growth of oxide films as oxidation products. The thickness of the oxide film on the Al+1-2.5%R alloys is higher than on pure Al and increases with temperature. There are several stages at each temperature. The oxidation of the Al+1-2.5%R alloys at 400°C (Fig.1a) for 15 min is characterized by thermal desorption of water molecules and carbonates adsorbed from air. During long-term annealing, the increase in the oxide thickness is less than 4 nm per hour. When the temperature is raised to 500°C, a more active growth of the oxide film is observed. Thermal desorption takes less than 5 min, therefore it is not marked on the curves. After 1 h exposure at 500°C and 600°C ( fig.1b), the greatest increase in the film thickness was observed for the alloy with ytterbium (1%Yb). At 600°C, during the first 25 minutes of exposure, a sharp increase in the oxide film thickness takes place for the majority of Al + 1-2.5at.% R alloys (Fig. 1b).

Results and Discussion

Thermal Oxidation of the Alloys in Air

Detailed analysis of the curves shows that the sharp thickness growth is due to crystallization of the natural (amorphous) aluminum oxide film in γ-Al 2 O 3 . Aluminum oxide is a predominant component of the examined oxide films; it crystallizes forming grain boundaries that give way to oxygen particles to the alloy surface. According to different literature data [6][7][8][9][10][11][12], the temperature of the phase transformation of aluminum oxide falls within the range of 475-550 °C. Figures 2, 3 show the literature data proving that in the temperature interval 475-550°C, on the surface of bulk [6] and finely-dispersed aluminum [12], the amorphous surface oxide film transforms into a crystalline gamma modification.  The active thickness growth of the oxide film on Al+1%Yb alloy (Figure 1a,b) can be explained as follows: in addition to crystallization of amorphous Al 2 O 3 , individual oxide phases R x O y are formed in the films at these temperatures. The formation of R x O y phases affects the continuity and overall thickness of the oxide film in the same way. This is particularly evident in the case of Yb oxides during oxidation of Al+1%Yb alloy. In ref 10, the study of ytterbium powder oxidation in air revealed that three oxide phases are present at once in the powder in a wide temperature range (from 250 to 650°C and higher): lower oxide YbO crystallizing in fcc structure (unlike lower oxides of other rare-earth metals formed in the bcc lattice), orthorhombic Yb 3 O 4 found in the interval 300-650°C, and sesquioxide bcc oxide Yb 2 O 3 (>400°C).

Thus, in the temperatures interval 550-600°C the multiphase oxide film may contain at once three stoichiometric oxide phases (Figure 4), which was also confirmed by the maxima on the thermogravimetric curves [3].

Analysis of the available literature data [13][14][15] and our experimental findings shows that in the investigated temperature range, the oxidation of other rare earth metals (lanthanides) is accompanied by the formation of maximum two stoichiometric oxide phases ( Figure 4) Oxidation of the alloys with a high content of REM (~22 at.%R) begins at lower temperatures (400°C) (Fig. 5). The time dependences of the films thicknesses contain the curves for the alloys with large and small additions of REM at 400°C and 500°C. It is seen that the increase in temperature by 100 degrees leads to 2-3 times enhancement of the oxide film thickness. At 600°C, after 5 min exposure in the furnace, a strong interference of the reflected beam is observed for the surface of intermetallic compounds, which is associated with a dramatic thickening of the oxide film.   Analysis of the equilibrium diagrams [13] and micrographs of the alloy surface showed that the film growth rate depends on the phase composition of the alloy. The main phase in the structure of Al+1-2.5%R alloys ( Figure 6) is aluminum (rare earth metals have a very low solubility in aluminum). The rare earth metal is present in the structure of these alloys in the form of intermetallic inclusions.

The structures of the alloys with a high content of REM differ from each other. So, in the structure of Al+21.5%La and Al+22.4%Sm alloys (Figure 7 a, d), grains of intermetallic compounds dominate (hypereutectic region of the diagram) -these phases have the greatest affinity for atmospheric oxygen. Therefore, the film thickness on their surface is considerably higher ( Figure 5).

On the phase diagram, the alloys Al+22.8%Pr (Figure 7b) and Al+22.5%Nd are exclusively in the region of intermetallic compounds, as seen from their structure. The thickness of their oxide films will be slightly higher than in the hypereutectic region. When the rare earth metal content increases further as in the Al+28.9%Ce alloy, the alloy enters into the two-phase region Al 3 R -Al 2 R. Due to the presence of Al 2 Ce phase, the Al+28.9%Ce alloy exhibits a high activity during thermal oxidation in air ( Figure 5). Thus, it is seen that the presence of REM-rich phases dramatically increases the oxidation rate of Al+R alloys.

Interaction with Boiling Water

The opposite character of interaction was observed in the study of the interaction of Al+REM surface with boiling water. According to the IR spectroscopy and X-ray analysis results, the main product of the reaction on the Al and Al+REM alloys surface in these conditions is the AlOOH hydroxide film. The thicknesses were calculated from the ellipsometric parameters Δ and ѱ on the basis of the two-layer model: substrate -oxide film -hydroxide film (n=1.56). Figure 8 shows the time dependence of the surface film thickness growth. It is seen that the rate of the formation of reaction products on the surface of pure aluminum and Al+1-2.5%R alloys is higher than on the surface of intermetallic compounds. Small additions of REM in aluminum affect little the thickness of films produced in these conditions on its surface. The ellipsometric parameters at the initial stages of interaction (1-3 min) are described well by a two-layer model with an inhomogeneous (porous) film of the upper layer of aluminum hydroxide. At further boiling, the layer is compacted, as a result of which it grows already at a slower rate. After 65 min interaction with distilled water, the film thickness on aluminum reaches 270 nm, while on the Al+1-2.5%R alloys it is slightly smaller. As can be seen, after 65 min boiling the formation of films on the alloys is not completed. For Al+~22%R alloys, the interaction takes place at a much lower rate due to a significantly smaller content of aluminum metal (solid solution) in the bulk and on the surface of these alloys. The films on their surface turned out to be 2.5 times thinner during this period of time, thus there was no noticeable film growth (Figure 8).

The presence of a porous film formed on the surface of eutectic alloys and pure aluminum after 1-3 min boiling in distilled water was confirmed by atomic force microscopy.

As seen in Figure 9, a raised roughness is detected on the aluminum surface after 1.5 min interaction (average roughness Ra = ~ 12.7 nm), which may be indicative of a porous structure of aluminum hydroxide on the surface at the initial stage of interaction. The stripes are the traces of pre-mechanical polishing of the surface. The sample of aluminum intermetallic with praseodymium (Fig. 9b) has a much smaller average roughness Ra = ~6.3nm under these conditions.

Note that before and after 1.5 min interaction the Al+~ 22at.%R alloys visually retain their mirror surface. The surface of aluminum and Al+1-2.5%R quickly gets cloudy.

The alloy powders prepared by mechanical grinding of monolithic ingots in a mortar and by screening on laboratory sieves (diameter of grains <63μm) were boiled for 65 min under the same conditions. Figure 10 shows the IR spectra of the powders obtained for all the investigated alloys. The intensity of the absorption bands is weak because of low dispersion. However, on the spectra of Al+1-2.5at%R powders one can identify the absorption bands corresponding to stretching, deformation and libration vibrations of OH-bonds in aluminum hydroxide (3433 cm -1 , 1631 cm -1 , 1078 cm -1 , respectively). In all the IR spectra of Al+~22%R alloys, the absorbtion band at 1078cm -1 is faint or absent, which is indicative of a small amount of hydroxide forming the surface film. Proceeding from the surface morphology of the samples, it can be supposed that metallic aluminum in these alloys in water at 100°C is the main reactive phase, and when its content in the bulk and on the alloy surface decreases, the amount of hydroxide forming the surface film lowers.

Conclusions

The peculiarities of the surface interaction of Al+REM alloys with oxygen at 400, 500, and 600°C and with boiling water were studied. For Al+1-2.5%R alloys, in the temperature range from 500 to 600°C oxidation in air is enhanced due to the increasing amount of R x O y oxide phases and crystallization of amorphous Al 2 O 3 inside the surface film. The Al+1%Yb alloy has the lowest oxidation stability in this temperature range owing to the formation of the greatest amount of REM oxides.

The oxidation of Al+~22%R alloy in air begins at a temperature below 400°C. The oxidation rate depends on the type and amount of the alloying metal and the phase composition: the presence of REM-rich phase dramatically increases the oxidation rate of Al+R alloys.

It is found that in the interaction of Al+REM alloys with boiling water, the active reacting phase is pure aluminum.

Figure 1 .
1Temperature and time dependences of the oxide film thickness growth on Al+1-2.5%R alloys at 400, 500 (a), and 600°С (b) in air

Figure 2 .
2The growth of oxide film on bulk Al as a function of temperature[6]

Figure 3 .
3XRD diagram of aluminum nanopowder samples annealed in air for 1.5 h at 350°C and 550°C[12]

Figure 4 .Figure 5 .
45XRD diagrams of ytterbium powder at different temperatures [Time dependence of the thickness of oxide films on aluminum alloys Al + ~ 22at.%R at 400 (a) and 500°C (b) in air.

Figure 6 .
6The micrographs of the surfaces of Al+1-2.5at.%R alloys: а) Al+2.57at.%La; b) Al+2.57at.%Ce; c) Al+2.54at.%Pr; d) Al+1.5at.%Sm

Figure 7 .
7The micrographs of the surfaces of Al+~22at.%R alloys: а) Al+21.5 at.%La, b) Al+28.9 at.%Ce, c) Al+22.8 at.%Pr, d)Al+22.4 at.%Sm

Figure 8 .
8The time dependence of thicknesses of oxide-hydroxide films on Al and Al+REM alloys during interaction with distilled water at 100°C.

Figure 9 .
9a) AFM picture of aluminum surface after 1.5 min interaction with water. b) AFM photograph of the surface of the intermetallic compound Al + 22.8at.% Pr after 1.5 min interaction with water (the stripes are polishing defects).

Figure 10 .
10The infrared transmission spectra of powders of Al+REM alloys after 65 min contact with boiling water

Table 1 .
1Chemical composition and optical constants of Al+REM alloysalloy (substrate)
Natural passivating film

n2
k2
n1
k1
d, nm

Al
1.65
6.5
1.6
0-0.05
4-6

Аl+2.5La
2.84
7.06
1.7
0-0.3
7-10

Аl+2.5Се
2.99
7.04
1.75
0-0.3
5.5-8

Аl+2.5Рr
2.54
6.69
1.66
0-0.6
6-9

Аl+1.5Sm
2.46
6.7
1.67
0-0.46
6.5-8

Al+2.0Gd
2.45
6.67
1.7
0-0.2
6-8,5

Al+1.7Tb
2.24
6.36
1.61
0-0.25
7-8

Al+1.8Ho
2.34
6.57
1.61
0-0.3
6-9

Al+2.5Dy
2.73
5.67
1.65
0-0.3
4.5-6

Al+1.0Er
2.96
6.19
1.65
0-0.3
6.5-8,5

Al+2.3Eu
2.33
6.35
1.64
0-0.05
5-6.6

Al+1.0Yb
2.30
6.24
1.6
0-0.19
5-8

Al+1.0Lu
2.25
7.25
1.69
0-0.2
7.5-9.5

Al+21.5La
3.55
4.58
1.724
0-0.3
6-7

Al+28.9Ce
4.39
4.66
1.9
0-0.5
9.6-10

Al+22.8Pr
3.62
4.27
1.784
0-0.11
6-7

Al+22.5Nd
3.9
4.42
1.9
0-0.6
6.5-7

Al+22.4Sm
3.61
4.59
1.735
0-0.09
7-8

. So, oxides of elements from Nd to Lu are usually formed as higher R 2 O 3 oxide (typical valence of REM is 3+) having a bcc lattice. In the case of La, Ce, Pr, the following structural phase transitions are possible: La (bcc La 2 O 3 ). Thus, it is shown that the main reason of increasing the oхidation rate of Al+1-2.5%R alloys at t> 500°C is the growth of interfaces of individual oxides.hcp La 2 O 3 ),

Ce (bcc Ce 2 O 3
fcc CeO 2 ), Pr (bcc Pr 2 O 3
hcp
Pr 2 O 3

. I Matveeva, N Dovzhenko, S Sidelnikov, et al.Matveeva, I., Dovzhenko, N., Sidelnikov, S. [et al.].

Development and Research of New Aluminium Alloys with Transition and Rare-Earth Metals and Equipment for Production of Wire for Electrotechnical Applications by Methods of Combined Processing. Proceed. of the symposia «Light metals. John Wiley & Sons IncNew JerseyDevelopment and Research of New Aluminium Alloys with Transition and Rare-Earth Metals and Equipment for Production of Wire for Electrotechnical Applications by Methods of Combined Processing. Proceed. of the symposia «Light metals 2013». -New Jersey: John Wiley & Sons Inc., 2013, 443-447.

Effect of alloying on the kinetics and mechanism of oxidation of powdered aluminum-based alloys with rare-and alkaline-earth metals, Combustion, Explosion, and Shock Waves. V G Shevchenko, V.G. Shevchenko, Effect of alloying on the kinetics and mechanism of oxidation of powdered aluminum-based alloys with rare-and alkaline-earth metals, Combustion, Explosion, and Shock Waves. -2011. -V. (47) № 2. -P. 166-173.

Physicochemistry of activation of dispersed systems based on aluminum UrO RAN: Ekaterinburg. V I Kononenko, V G Shevchenko, in RussianKononenko, V.I., Shevchenko, V.G. Physicochemistry of activation of dispersed systems based on aluminum UrO RAN: Ekaterinburg, 2006. (in Russian)

Ellipsometry of thin transparent films on aluminum. Optika i spektroskopiya. G А Egorova, Е V Potapov, А V Rakov, 41in RussianEgorova, G.А., Potapov, Е.V., Rakov А.V. Ellipsometry of thin transparent films on aluminum. Optika i spektroskopiya. 1976, 41(4), 643-647 (in Russian).

Ellipsometry of subthin transparent films. Optika i spektroskopiya. G А Egorova, N S Ivanova, Е V Potapov, А V Rakov, 36in RussianEgorova, G.А., Ivanova, N.S., Potapov, Е.V., Rakov, А.V. Ellipsometry of subthin transparent films. Optika i spektroskopiya. 1974, 36 (4), 773-776 (in Russian).

Corrosion of aluminium. C Vargel, ElsevierNetherlandsVargel, C. Corrosion of aluminium; Elsevier: Netherlands, 2004.

Natural and thermally oxide films on aluminum. M S Hunter, P Fowle, J. Electrochem. Soc. 103Hunter, M.S., Fowle, P. Natural and thermally oxide films on aluminum. J. Electrochem. Soc. 1956, 103. 482-485.

Determination of barrier layer thickness of anodic oxide coatings. M S Hunter, P Fowle, J. Electrochem. Soc. 101Hunter, M.S., Fowle, P. Determination of barrier layer thickness of anodic oxide coatings. J. Electrochem. Soc. 1954, 101. 481-485.

Effect of polymorphic phase transformations in Al 2 O 3 film on oxidation kinetics of aluminum powders. M A Trunov, M Schoenitz, X Zhu, E L Dreizin, Combust and Flame. 1404Trunov, M. A., Schoenitz, M., Zhu, X., Dreizin, E.L. Effect of polymorphic phase transformations in Al 2 O 3 film on oxidation kinetics of aluminum powders. Combust and Flame. 2005, 140 (4), 310-318.

The kinetics of oxidation of aluminum electroexplosive nanopowders during heating in air. A V Korshunov, A P Ilyin, N I Radishevskaya, T P Morozova, Rus. J of Phys. Chem A. 849Korshunov, A. V., Ilyin, A. P., Radishevskaya, N. I., Morozova, T. P. The kinetics of oxidation of aluminum electroexplosive nanopowders during heating in air. Rus. J of Phys. Chem A, 2010, 84 (9), 1576-1584.

Growth kinetics and mechanisms of aluminum-oxide films formed by thermal oxidation of aluminum. L P H Jeurgens, W G Sloof, F D Tichelaar, E J Mittemeijer, J. Appl. Phys. 1649Jeurgens, L. P. H., Sloof, W. G., Tichelaar, F. D., Mittemeijer, E. J. Growth kinetics and mechanisms of aluminum-oxide films formed by thermal oxidation of aluminum, J. Appl. Phys., 2002, 92, 1649.

Effect of the state of oxide-hydroxide shell on the reactivity of aluminum nanoparticles, Proceed. of the Tomsk polytech. А V Korshunov, А P Ilyin, 312in RussianKorshunov, А.V., Ilyin, А.P. Effect of the state of oxide-hydroxide shell on the reactivity of aluminum nanoparticles, Proceed. of the Tomsk polytech. univ., 2008. 312(3), 11-15 (in Russian).

Desk Handbook: Phase Diagrams for Binary Alloys. H Okamoto, OhioOkamoto, H. Desk Handbook: Phase Diagrams for Binary Alloys; ASM International: Ohio, 1996.

Polymorphism of oxides of rare-earth elements. V B Glushkova, Nauka: Leningrad. in RussianGlushkova, V.B. Polymorphism of oxides of rare-earth elements; Nauka: Leningrad, 1967 (in Russian).

K A Gschneidner, Eyring L. Handbook on the Physics and Chemistry of Rare Earths. North-Holland Publishing Company3Gschneidner, K.A.; Eyring L. Handbook on the Physics and Chemistry of Rare Earths, Vol.3,4; North-Holland Publishing Company, 1979.


IT and tourism: still a hot topic, but do not forget IT 1 e-Tourism and a short history (without numbers) In accordance with Werthner and Klein (1999), we base our discussion on the following definition of e-tourism: e-tourism denotes the analysis, design, imple- mentation and application of IT/e-commerce solutions in the travel and tourism
0123456789. 2018

Julia Neidhardt firstname.lastname@example.com
Faculty of Informatics
TU Wien
Favoritenstrasse 9-11/194-041040ViennaAustria

Hannes Werthner
Faculty of Informatics
TU Wien
Favoritenstrasse 9-11/194-041040ViennaAustria

Julia Neidhardt
Faculty of Informatics
TU Wien
Favoritenstrasse 9-11/194-041040ViennaAustria

IT and tourism: still a hot topic, but do not forget IT 1 e-Tourism and a short history (without numbers) In accordance with Werthner and Klein (1999), we base our discussion on the following definition of e-tourism: e-tourism denotes the analysis, design, imple- mentation and application of IT/e-commerce solutions in the travel and tourism

Information Technology & Tourism
200123456789. 201810.1007/s40558-018-0115-xReceived: 24 June 2018 / Accepted: 3 August 2018 /1 3 VIEWPOINTe-Tourism · Information technology · Computer science · IT-based innovation · Tourism research
More and more aspects of our life "move" to the Web. The Web and the Internet, as the underlying information infrastructure and "machine", can be considered as a mirror of the "real" physical world. However, the Web is not only reflecting this world, it is obviously also transforming it, where it is increasingly hard to distinguish between the physical and the virtual. It acts both as an enabler and driver of new, technical, economic and societal developments. With recent achievements in areas such as machine learning, Internet of Things or artificial intelligence (or rather intelligent assistance-a probably more appropriate term), we see the power of computer science. In this short comment, we argue that IT and tourism is still a hot topic, also or especially from a scientific point of view. However, from this latter point of view this might change, and we claim that, in order to prevent the field from becoming insignificant, more emphasis must be put on technical and formal aspects of science. We do not know the future, we are not "futurologists" (In a marketing note of an innovation and technology conference, the organizers even wanted to provide a look beyond the future-we have no idea how this nonsense could be done!), but we take the freedom to highlight some issues, which we consider to be important-in particular since one of the authors has a background of driving the field for nearly 30 years.

e-Tourism and a short history (without numbers)

In accordance with Werthner and Klein (1999), we base our discussion on the following definition of e-tourism: e-tourism denotes the analysis, design, implementation and application of IT/e-commerce solutions in the travel and tourism 1 3 industry, as well as the analysis (of the impact) of the respective technical/economic processes and market structures. This non-normative definition contains a constructive and an analytical part, needing a mixture of methods coming from engineering, mathematics and science.

One of the authors was almost thrown out of the room when telling the industry that IT would become THE factor of their business in 1994. But, IT has radically changed the industry; one might also say, IT created a new industry. Today, we have a well-developed business landscape in tourism, where we moved from simple Websites to partnerships and to IT-based business networks, leading to a so-called "informatization" of the entire value chain. In addition, since e-commerce favors, in tendency, consumers, we moved from a "customer focused" to a "customer driven" industry, which becomes obvious when looking at online communities or social media sites and their respective power. Moreover, online services became commodities, with an ongoing deconstruction of the value chain. This means, that nowadays you do not need to develop yourselves all your IT services; you just use pre-existing ones on the Web, which provide standard interfaces. In this complex mix of partnering and evolving IT structure, the emphasis moved (or should have moved) from process re-engineering, to network engineering, which implies that in complex network structures of companies and services, enterprises have to focus more on their value contribution (asking, what is their respective added value) and not so much on efficiency. This might be a little bit provocative, but otherwise they run into the risk to produce very efficiently things, which nobody needs. At the same time, we see an enormous trend towards concentration, where the winner takes it all. In some sense, the development of the Web can be seen as an evolution that lead to both order (i.e. highly centralized) and disorder (i.e. permanent appearance of new services and technologies).

A second general phenomenon worth mentioning might be characterized as a transparency paradox: more and more information leads to increasing and decreasing transparency at the same time. On the one hand, all this information is available and can be accessed. On the other hand, the amount of available information is likely to lead to information overload, where it might be hard for the users to find what they are actually looking for. Search tools and recommender systems are available and can help to address this problem, but users typically do not know how these systems exactly work and what data they exploit. All of this is increasingly leading to a feeling of insecurity and related problems of trust.

Finally, IT-based newcomers were driving innovation with their fast imitation of business models and technology, whereas traditional market players had problems with service innovation, business models and technology development. These newcomers became very fast the new and now stronger middlemen (compared to pre-Web times). In the two-sided market, where suppliers sponsored consumers (consumers pay with their data), the network effect favored this development. Fragmented supplier markets, constituted mainly by SMEs, could not compete with the new players. In addition, these new companies primarily focused on the market (transaction) and not on the product itself. They conquered the consumers very fast, providing the necessary information and trust functions in an information asymmetric market. The initial hope of the start time of the 1990s of direct distribution and a direct link from suppliers to consumers was not fulfilled (or even worsened?).

This reads like a history of e-commerce, but it is one of e-tourism. The reason is that e-tourism was at the forefront of the general development (and still is) due to its inherent features (Werthner and Ricci 2004).

Current situation and dominance of platforms

The travel and tourism industry is still a major application area for IT, with many technical innovations including recommender systems, emotional computing, group decisions, social media and analytics. However, currently the most important aspect is probably the dominance of IT-based platform businesses. For example, this is also true for the sharing economy, which has been emerging very fast. It has to be pointed out that, with respect to the sharing economy, first and major examples can be located in tourism and mobility as well, namely, Airbnb and Uber. This underlines the up-to-date importance of this industry sector.

IT-based innovations, also in the tourism market, are often connected with socalled platform strategies. Such platforms offer technologies and services for a broad ecosystem of users and companies (Cusumano 2010a). External innovations create these ecosystems around the platform (Cusumano 2008). Functionalities are provided by partners or competitors, which also use these services at the same time.

The platform operator provides the basic functionality and opens the platform to enable external innovation. This presents a competitive advantage over so-called pure product solutions that have to constantly implement and integrate their own services and innovations. Platforms have to meet two conditions: first, there must be at least one open technical interface as "a system of use" and second, it has to be easy to get and stay connected. Switching costs and bundling form a strategically important part of platforms by attracting users to their platforms and by offering many different features for one low price and retain users by making it technically difficult to move to another platform (Cusumano 2010b). Obviously, the value of a platform increases with the number of participating companies and/or users.

Tourism, illustrated by the history of e-tourism, is an excellent example for such innovation approaches. Take Online Travel Agencies (OTA), for example: they will continue to grow, with a monopolistic tendency. Due to positive network effects in the two-sided market, the already strong platforms will become stronger with every additional input (e.g., hotels, customers, reviews, etc.). The more hotels rely on the different platforms and distribute their rooms through them, the greater the market power of the latter. Owing to the competition and the importance of the OTAs, providers are forced onto such platforms. Comparison-based on only a few parameters-eases the cognitive load of customers, with the negative consequence of lowered prices for the service providers. Similar considerations are valid for search engines or social media sites. The activities on these sites increase the expenses of the service providers and strengthen the network effects of the platforms. This creates a paradoxical spiral: the expenditures of the service provider increase to the same extent as their dependence on the latter, including higher costs. The spiral is like a vicious circle: The more effort is made by suppliers, the weaker becomes their position with regard to these "central" organizations.

It is an ironic fact that tourist destinations would nearly perfectly meet the prerequisites for an industry service platform. They already have the required regional/ national ecosystem (i.e., users, service providers, complementary services and products, content, advertisers and channel partners) to form a successful platform. There is a kind of a structural equivalence of a Web network/platform strategy and a destination's cooperation strategy. This is also valid for the cooperation with other industries which is especially important, since tourists look for a bundle of comprehensive tourism experiences, not only for hotels or individual activities. Finally, such a platform would enable the bundling of know-how, and the gathering of data for the analysis of consumer behavioral or product development. And it would ease the participation in a wider innovation process. However, this opportunity has not been taken by the destinations (Calatrava Moreno et al. 2015).

e-Tourism as a scientific field

With respect to research topics in e-tourism, several reviews of scientific contributions of the previous 10-20 years were published, such as (Buhalis and Law 2008) or (Wang et al. 2010), with similar results. From a historical perspective, three main general topics were identified including: (1) consumers and demand dimension including changes of travel behavior due to the Web, information search as relevant part of the purchase decision, the emergence of Web 2.0 bringing together online social networks and tourism, choice overload and recommender systems/personalization as countermeasure; (2) more IT and technological issues including interoperability, ontologies and Semantic Web, multimedia and virtual reality, mobile and wireless technologies, Web design and accessibility and ambient intelligence (now called IoT); and (3) industry and business functions including strategic and operational dimensions, competitiveness, marketing and distribution and adoption. Particularly in the early days, research rather focused on technical issues and on showing how to automate processes through IT. However, this has been gradually changing, and social sciences and marketing aspects have been gaining more and more importance in e-tourism journals. Similarly, with respect to the methodological approach, the field moved away from engineering and system design with its constructive approach to empirical studies, case studies and, recently, data driven approaches. (In this context, it is interesting that one of the authors of this commentary gave a keynote on data science, network science and service science already at ENTER 2006.) In recent years, the number of quantitative papers is rising, as is their quality. The availability of data and tools, which has an impact on the way social sciences work in general (Lazer et al. 2009), might be a reason. However, it is worth pointing out that research in the e-tourism field still mainly relies on data acquired by questionnaires and surveys rather than open data or large-scale Web-based data, as a survey of used data sources of all publications in the ENTER 2017 proceedings suggests (Sertkan 2018).

A critical issue is that rather few articles on tourism applications can be found in pure computer science journals. In those articles that exist and where tourism serves as an application domain, the specific features of the field, which are particularly challenging, or the potential of the domain are typically not mentioned. Another observation indicates that with respect to strategies, the field moves from the macro level to the micro level, i.e., the focus is on adoption and/or marketing for individual enterprises, which involves the danger of losing the big picture at the macro and strategic industry scale. However, this point of view would be required to cover the aspects of platform strategies, power relationships or structural changes in a complex market, the latter having been a hot topic in the early days of e-tourism.

Finally, the e-tourism topic is spreading to (nearly) all tourism and hospitality research journals, with a clear focus on organizational, business, or marketing issues, losing the close relation to computer science. Or put differently, it is about observing adoption, and not on designing and implementing new solutions. A similar pattern can be observed at the conference side, where more and more industry e-tourism conferences are organized, with little scientific base at all-where tourism researchers-to put in a provocative way-take the loud marketing claims of IT and e-commerce companies as granted. With respect to both phenomena, the spread to tourism journals as well as the rise of industry driven e-tourism conferences, a strong scientific e-tourism base would be needed.

Invariants and important issues for the future

We like to remember that the tourism product as well as the tourism industry have special, inherent features, which emphasize the important relationship between IT and tourism (Werthner and Klein 1999). As a consequence, travel and tourism can be regarded as a critical test and application field for computer science, which, in turn, is enabling new services, products and co-operations for the tourism domain.

The special features of the tourism product include that it is an experience good, thus information based, and that it is-normally-an aggregated product, consisting of legally, economically and geographically distributed parts. Thus, integration of different players-with different business rules and objectives-on the fly is required. Consequently, the (virtual or physical) intermediary or product aggregator/ assembler (who might also be the user) has a specific role. A rather tricky issue is that the tourism product is defined by the tourist. Nearly every product can become a tourism product, when it is consumed by the tourist. Thus, from a computer science point of view, domain models have to cover the "entire world". Finally, it is an emotional and personality-based product that is associated with fun and that is driving inspiration and behavior. Thus, these non-rational components impose specific challenges for interfaces as well as for decision-making, recommender and highly personalized persuasion systems (which will pop up soon).

From the computer science point of view we highlight only some recent developments, e.g., Internet of Things and related disappearing interfaces, where IT is everywhere at any time. This calls for new forms of distributed computing with little latency, bringing us into the field of edge computing. IoT requires new search and recommender approaches that move away from textual search using the terminology of the suppliers to emotional, implicit, and sensor-based approaches. Also in this field promising application cases very often come from the tourism domain. Another important area is machine learning and/or artificial intelligence, where here we do not discuss the important difference between both. Referring to AI, a really interesting "project" would be a Turing test, tailored to the tourism domain. 1 Just these two examples, combined with the specific features of the domain, show that, if one wants to interfere and influence this development with accelerating technology cycles, more emphasis on a computer science approach (with its formal and engineering leg) is needed-if one does not just want to observe. This is not a contradiction to the need for interdisciplinary research, when looking at the evolving complexity with respect to processes, structures and technology. Here we would like to point to the JITT research agenda , which summarizes in an integrative and consistent form the open and most promising research issues in e-tourism, classified according to the concept of digital infrastructure with its five different layers, i.e., (1) individual, (2) group/social, (3) enterprise/corporation, (4) networks/industry, and, finally, (5) governmental/policy.

Conclusions

When looking at the tourism industry, it is obvious that IT has changed nearly everything; as it has also changed the tourism research field, with all its publications and meetings outlets. However, what we see is the diminishing role of IT-based and computer science-focused research in e-tourism research. Here, in scientific journals and at conferences, this topic is becoming increasingly rare. We would like to stress that computer science is central. Or stated otherwise: technology is not everything, but without it everything might be nothing, Secondly, on a macro level IT-based innovation led to platforms and by and by to a monopolistic market structure. Thus, the focus-in the observational fieldshould not only be at the micro level, but by exploiting more and more large-scale data, at the macro level. We should not forget the "big picture".

The travel and tourism industry shows very well the metamorphosis of IT and its pervasiveness. Clearly, we will see further technology waves (as in the past). The journey has not ended. However, we should not only observe the journey, but contribute to its design and construction!
 Imagine, for example, a specific Turing test, mimicking a Travel Agent's counseling session, organized by JITT or IFITT. Research groups compete world-wide for the 500,000 Euro Price, sponsored by e-commerce and e-tourism companies, for passing as first the (probably slightly reduced and modified) Turing test.
Acknowledgements Open access funding provided by TU Wien (TUW).Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Progress in information technology and tourism management: 20 years on and 10 years after the Internet-The state of eTourism research. D Buhalis, R Law, Tour Manag. 294Buhalis D, Law R (2008) Progress in information technology and tourism management: 20 years on and 10 years after the Internet-The state of eTourism research. Tour Manag 29(4):609-623

Strategic e-tourism alternatives for destinations. Calatrava Moreno, Mdc Hörhager, G Schuster, R Werthner, H , Information and communication technologies in tourism 2015. ChamSpringerCalatrava Moreno MDC, Hörhager G, Schuster R, Werthner H (2015) Strategic e-tourism alternatives for destinations. In: Information and communication technologies in tourism 2015 (pp 405-417), Springer, Cham

Technology strategy and management The puzzle of Apple. M Cusumano, Commun ACM. 519Cusumano M (2008) Technology strategy and management The puzzle of Apple. Commun ACM 51(9):22-24

Staying power: six enduring principles for managing strategy and innovation in an uncertain world (lessons from Microsoft, Apple, Intel, Google, Toyota and more) (Clarendon lectures in management studies). M A Cusumano, Oxford University PressOxfordCusumano MA (2010a) Staying power: six enduring principles for managing strategy and innovation in an uncertain world (lessons from Microsoft, Apple, Intel, Google, Toyota and more) (Clarendon lectures in management studies). Oxford University Press, Oxford, pp 22-30

Technology strategy and management: the evolution of platform thinking. M A Cusumano, Commun ACM. 531Cusumano MA (2010b) Technology strategy and management: the evolution of platform thinking. Com- mun ACM 53(1):32-34

Life in the network: the coming age of computational social science. D Lazer, A S Pentland, L Adamic, S Aral, A L Barabasi, D Brewer, N Christakis, N Contractor, J Fower, M Gutmann, T Jebara, G King, M Macy, D Roy, M Van Alstyne, Science. 3235915721Lazer D, Pentland AS, Adamic L, Aral S, Barabasi AL, Brewer D, Christakis N, Contractor N, Fower J, Gutmann M, Jebara T, King G, Macy M, Roy D, Van Alstyne M (2009) Life in the network: the coming age of computational social science. Science (New York, NY) 323(5915):721

The journal of information technology and tourism: a content analysis of the past 10 years. M ; Tu Wien Sertkan, D Wang, D R Fesenmaier, H Werthner, K Wöber, Inf Technol Tour. 121Master's ThesisClassifying and mapping e-tourism datasetsSertkan M (2018) Classifying and mapping e-tourism datasets. Master's Thesis, TU Wien Wang D, Fesenmaier DR, Werthner H, Wöber K (2010) The journal of information technology and tour- ism: a content analysis of the past 10 years. Inf Technol Tour 12(1):3-16

Information technology and tourism: a challenging relationship. H Werthner, S Klein, Commun ACM. 4712SpringerE-commerce and tourismWerthner H, Klein S (1999) Information technology and tourism: a challenging relationship. Springer, Wien Werthner H, Ricci F (2004) E-commerce and tourism. Commun ACM 47(12):101-105

. H Werthner, A Alzua-Sorzabal, L Cantoni, A Dickinger, U Gretzel, D Jannach, J Neidhardt, B Pröll, F Ricci, M Scaglione, B Stangl, O Stock, M Zanker, Future research issues in it and tourism. Inf Technol Tour. 151Werthner H, Alzua-Sorzabal A, Cantoni L, Dickinger A, Gretzel U, Jannach D, Neidhardt J, Pröll B, Ricci F, Scaglione M, Stangl B, Stock O, Zanker M (2015) Future research issues in it and tourism. Inf Technol Tour 15(1):1-15