Vol.10 issue 1 2020

“Ask-Me-Anything” Interview with Klaus Roth

 Views on Life, the World and Everything, Vol.10 issue 1 2020  Comments Off on “Ask-Me-Anything” Interview with Klaus Roth
Jul 142020

Klaus Roth[1] is an emeritus professor at the Freie Universität Berlin where he studied chemistry from 1964 – 1969 and completed his dissertation in 1973. After a post-doctoral stay at the Institute for Medical Research in Mill Hill, London from 1979 – 1980, he completed his habilitation at the Freie Universität Berlin in 1981. Between 1986 – 1988, he held a position as a visiting professor at the University of California in San Francisco, after which he returned to his home university as an extraordinary professor and became a full professor in 2000. During his research career, he dealt with many aspects of NMR spectroscopy but also popular science.

Klaus Roth publishes regularly in “Chemie in unserer Zeit” about the significance of chemistry in everyday life. You can find some of his articles on www.chemistryviews.org. On Nov. 28th, 2019 we invited him once again to have a talk at the university in Mainz about the chemistry of the hangover. For that occasion, students and researchers from our university were invited to send us questions from any kind of topic that we asked him together with the Young Chemists Form of Mainz in an “Ask-Me-Anything” interview. Here we present the “best-of” selection.


JUnQ: Which value has symmetry in your life?

Klaus Roth: Some say symmetry is the mathematical form of beauty. But I counter with a saying from northern Germany “Beten scheef hett Gott leev!” which means “God likes it a little crooked”. A little asymmetry can be charming. Of course, as an organic chemist, I had to deal with chirality and optical activity a lot.

JUnQ: What is your favorite molecule?

Klaus Roth: My favorite molecule is a chelate complex with an organic ligand, DTPA (diethylenetriaminepentaacetic acid), and a gadolinium center. It is used in nuclear resonance imagining as a contrast agent. It is not toxic and is injected intravenously in an amount of up to two grams. I have been involved in developments on this topic during my stay in San Francisco and together with the Schering AG.

JUnQ: Which historic moment in science would you like to have witnessed or even have been involved with?

Klaus Roth: Very hard to tell because there have been so many. You might find this strange, but I think very highly about the role of physics in the 1910s and 1920s. It practically turned the conception of the world and physics upside down once more every year. Just think of quantum mechanics and the discoveries of Max Planck and classic electrodynamics, that seemed to coexist incompatibly before. I guess these were exciting times!

JUnQ: Do you do any sports?

Klaus Roth: Since I am living in Berlin-Köpenick, getting in touch with soccer is inevitable (Union Berlin is my club!). I like doing sports myself and can’t imagine living without it. I am a passionate tennis player, although I’m not very good.

JUnQ: How can we imagine the young Klaus Roth, and who were your role models?

Klaus Roth: Well, I’d say just like the old one. I think I kept my essential character traits and still feel young, at least mentally. I never had a particular role model, but I have always had lecturers from whom I have learned how to do it and also how not to do it.

JUnQ: Did you always want to be a chemist?

Klaus Roth: (laughs) When I was a kid, I wanted to be a pastry chef. Amazing job! I am mad about eating cakes. Making all those pastries and pies was a dream. Then I ended up being a chemist, which is nice too. Alas, you can’t eat what you have produced.

JUnQ: What is the most drastic experience from your student days?

Klaus Roth: I remember that I nearly failed because of one experiment in quantitative analytics training. It was the analysis of the separation of sodium and potassium, and I had to repeat it seven times because I never obtained the right results. And everyone else was faster. That is the most horrible memory that I have from my inorganic practicum.

During the research on my diploma thesis, on the other hand, having the final product with the clean mass and NMR spectra in hand was a very uplifting moment, and I knew: this is my profession!

JUnQ: Which achievement in your life makes you most proud?

Klaus Roth: Being a father is the best thing I have achieved in my life. Everything else is not that important.

JUnQ: Imagine someone makes a movie about your life, who would play your part?

Klaus Roth: I cannot imagine that anyone would ever be interested in making a movie about that. But then, it absolutely must be George Clooney, of course.

JUnQ: With whom do you want to have a drink?

Klaus Roth: I guess it would be Hieronymus Bosch. He made some fantastic paintings, and I’d like to know where he got his inspiration from.

JUnQ: Which one of your talk topics is your favorite?

Klaus Roth: That’s hard to tell because I like every one of them. Perhaps, what’s most important to me has rarely been requested yet. It is the story of a young biochemist in Freiburg, Germany (in the 1930s), who’s world drastically changed within half a year. He was first praised as a rising star and later in his life even became a Nobel prize winner. Then he was sort of expelled because of his Jewish ancestry and left the institute in a rush with just the words: “I need to catch the 11 o’clock train.” His name was Hans Krebs, the co-discoverer of the citric acid cycle in England. After the war, he was the first one to take care of the reintegration of German scientists into the scientific community. An exceptional man! Unfortunately, this question did not yet attract much interest except in Freiburg.

JUnQ: How should our publication philosophy change, and how should the scientific community treat null and negative results?

Klaus Roth: Peer-reviewed journals should persist. Despite all the disadvantages and extra work that it implicates, it’s the best we have. Of course, online access to information and journals is a vital improvement compared to the dull library research of the past. Today it’s much more efficient. Negative results have always been neglected in the publications. But this is what JUnQ is trying to work against.

JUnQ: How do we approach more people outside of chemistry?

Klaus Roth: Chemists tend to think that they have a negative image in society. On the contrary, a research study from the Royal Chemical Society showed that we have a far better reputation. We are respected but don’t recognize it. What people expect from us is more communication and clarification in a language that they understand. This is not taught by universities. I think every Ph.D. student should be able to describe their projects to their grandparents within two minutes in such a way that they say: “Gosh! You are doing an impressive job!”. We need to train this because people are not ignorant per se. We simply should use an easier language to convey our passion.

JUnQ: How do we solve the problem of climate change?

Klaus Roth: It’s not possible to answer this in just a few words. In any case, something must happen soon. It is, of course, reasonable to apply strict measures. But in the long term, the industry of a solitary country will decay or at least suffer. Without international cooperation and support from the Great Powers, it won’t be possible. Right now, I’m very pessimistic, and I don’t know what else must happen before everyone sits down at one table to talk.

JUnQ: Which food should we better not eat anymore?

Klaus Roth: In my opinion, food that you can buy in the supermarket, which is already processed and packed in aluminum, just to be fried or warmed up again – like roast potatoes, for example. It is no wonder that they contain preservatives. How else could they stay on the shelves for months? They are easy to make at home and taste much better. Those convenient foods should be evaluated by how much more sense it would make and money one would save by preparing them at home.

JUnQ: Imagine that Elon Musk invites you on a trip to the moon. Would you accept the invitation?

Klaus Roth: Now? Since I have seen the spatial conditions on those space crafts, I’d say most certainly not! Apart from that, the chemistry on the moon is definitively too inorganic.

But looking at our planet from so far away – I remember one picture from one of those voyager missions where the earth was just a tiny spot in the empty space – makes us appear to be much more irrelevant than we value ourselves. I think people should be less occupied with themselves.

JUnQ: What is your favorite conspiracy theory?

Klaus Roth: Perhaps it is the anti-vaccination movement. To me, the whole discussion is incomprehensible. Just look at the statistics. It’s a shame that the anti-vaxxers profit from those who take the vaccines. Nowadays, people don’t consider hard facts anymore because their life has become too easy. They don’t know what it means to be infected and seriously ill because most of us are vaccinated against whooping cough, rubella, smallpox, and so on. Nobody worries about their physical health anymore.

JUnQ: What’s your best advice for young chemists at the beginning of their careers?

Klaus Roth: Most important: be well prepared for your job interview but be yourself. Read a newspaper daily, go to the theater, and try not to be a geek.

JUnQ: What’s your universal message to every scientist in the world?

Klaus Roth: Peace and Cheers!

JUnQ: Thank you very much for the interview!

We would also like to thank the YCF team for their support!

— Tatjana Dänzer

[1] klaus.roth@fu-berlin.de

Why do your pipes sometimes bang when you turn off your faucet?

 Question of the Month, Vol.10 issue 1 2020  Comments Off on Why do your pipes sometimes bang when you turn off your faucet?
Jul 132020

2 You might have encountered the phenomenon: You have a faucet running, for instance, while filling your bathtub, and quite a bit of water is flowing out. Then you want to stop the flow and quickly turn the valve to block the water. Suddenly, in the very moment you close the valve, you hear a banging sound in the walls around you. Sometimes it is rather quiet, sometimes it can be scarily loud. But what is actually causing the sounds and is it something you should worry about?

It turns out that the answer to this question is one of the most relevant design considerations for civil engineering.1,2 It all roots in a fundamental property of liquids: not being compressible. You may have noticed that a balloon filled with air can be compressed quite a bit while one filled with water only changes shape and cannot be made smaller. This very principle is the core of hydraulics, i.e. using the volume of a liquid like water or oil to transfer force in a system.

Maybe you are wondering now how this affects your pipes, considering that the volume of the pipe always stays the same. Nobody (hopefully) compresses the pipes in your walls. There is, however, also another important aspect to a liquid: its momentum. Once a liquid starts to move through a pipe it builds momentum just like a car or a train build momentum when they move (see Fig. 1). As long as the flow can continue undisturbed no ill effects occur and similarly, nothing happens if the flow is slowly brought to a halt by gradually closing the valve. To stay in our analogy, this would correspond to a train of cars slowing down when a road gradually narrows from two lanes to one and eventually to a road blockage.

Figure 1: Analogy of moving water and a train of cars. When the water is still, no momentum is stored in the system. Once the water moves, a significant amount of inertia can be present in the flow and if that flow is suddenly restricted by something (like a valve), the entire inertia must be transferred to the environment. That is the walls of the pipe and the valve itself. ©JUnQ.

The interesting effects happen when we force the flow of liquid to stop suddenly with a valve, essentially causing an accident on our road that causes all the cars to slam into the blockage. In this case, a rather large amount of inertia must be dissipated into the valve and the walls of the pipe causing a large pressure spike. If the pipe can move like a free garden hose (e.g. old pipes that are not properly fixed) this can lead to a sudden jerk and might loosen connections. The story is not so easy, though, for pipes that are fixed in your walls or buried beneath streets: those usually cannot move. As a result, the full force of the pressure acts on the valve and the walls of the pipe – causing the banging sound in your bathroom. The effect is officially called ‘water hammer’.3

But before you start wondering now if your pipes will one day burst and start flooding your apartment: civil engineering has developed a series of safety measured to prevent this from happening in our daily life. To understand how, it is important to know that the pressure spike caused by the sudden restriction in water flow is directly related to the flow rate. In our car analogy this would correspond to the relation between the number of lanes on the road and the number of cars that have to pass through a road segment at any given time. Together this dictates the speed the cars are traveling with and their cumulative inertia. In simple words: fast-moving cars on a narrow street do have a much harder time to slow down than a larger number of slower cars. Therefore, many supply pipes have large diameters, causing the water to flow slowly and thus avoiding the pressure spikes if the flow is restricted by one of the recipients. Additionally, air or spring-loaded pressure relief valves can engage to dissipate a dangerous spike without causing damage and water suppliers usually have build-in safety measures to make sure pumps are not starting up too quickly.

All in all, you usually do not have to worry about a slight banging sound caused by quickly closing a faucet, even though you should avoid it if possible. However, if it is loud or suddenly starts to appear you should be careful to reduce the wear and tear of your pipes or directly ask a pumper. A neat little starting point is Ref. [1]. Anyway, next time you use your sink or shower, think maybe of all the civil engineering that is necessary to let you shower or take a bath anytime at will.

Kai Litzius

Disclaimer: This article is meant to give an introduction into the physics behind the water hammer. In doubt always ask a specialist if your piping needs to be repaired.

Read more:

[3]A similar effect occurs with steam, the so-called ‘steam hammer’, which is an exceptionally dangerous phenomenon that can lead to steam pipes exploding once too much steam condenses and the condensate gets accelerated through the pipe. See also here for a great explanation: https://www.youtube.com/watch?v=JyvoN1hIqRo

Gödel’s theorem and traffic development

 Question of the Month, Vol.10 issue 1 2020  Comments Off on Gödel’s theorem and traffic development
Mar 102020

Traffic development

Absolute nothingness ( Śūnyata ) is one of the most exciting notions in Buddhism. Essentially, it cannot be interpreted anyhow but can be thought of as Ultimate Reality[1]. In Mediterranean tradition, ancient cosmologists introduced another term that sounds more familiar – The Chaos. It was associated with the infinite ocean and expressed an initial state of cosmos in potentia[2]. Not to get numb by the immensity of this semantic unit, we can consider chaos as noise having an infinite spectrum of all conceivable frequencies. And through interaction with external conditions, certain modes manage to become more pronounced as, for example, in the process of stimulated emission build-up in the laser[3] or during the process of natural selection in the theory of evolution.[4]

Traffic development

In the context of road traffic development, we can define the situation in ancient times as the initial chaotic state. As there were no roads as such, the traffic was chaotic. With the evolution of horse-drawn transport, the road map was developing. However, the roads were still only directions along which one could get from one place to another.

The situation changed when engine cars jolted the slow and stagnant horse traffic. Between the man and the road there was no middle link anymore that could choose a better way within the given direction on its own. Nonetheless, engine-drawn transport had an obvious advantage of higher achievable speed. In turn, the desire to move faster and faster required less scattering at the surface roughness, which inevitably resulted in roads getting smoother, i.e., less chaotic. In the meantime, the assembly line was progressing drastically and both factors lead to a dense cloud of potentially fast cars. But people were still scratching their heads why the average speed of the road traffic was not increasing. After a while, they figured out who is to blame in the residual scattering – the interaction of the drivers themselves with each other. With the absence of any predefined rules, everyone had to slow down and likely change the direction to avoid physical interaction with another participant of the traffic. Thus, the necessity of the traffic regulations was obvious.

The first “Convention with respect to the international circulation of motor vehicles” was signed in Paris in 1909[5]. Among others, it contained the sign depicted in Fig. 1, which indicated the road intersection. And naturally, originating from the ship traffic, the habitual priority-to-the-right rule was established to regulate the right-of-way for two vehicles with intersecting directions. Later a set of traffic regulations was complemented with priority signs and traffic lights.

Gödel’s theorems

In 1930 Kurt Gödel presented two theorems reflecting insuperable limitations of formal arithmetics. These theorems had a direct relation to the second problem from Hilbert’s list asking for the proof that arithmetics is consistent.[7] The first Gödel’s theorem (in Rosser form) states that within any consistent formal system S, one can come up with expression A that can be neither proved nor disproved[8]. In other words, the axiomatic system S is incomplete. Hao Wang published in his Logical Journey[9] the full text that Gödel had written about his discovery of the incompleteness theorems:

“In the summer of 1930 I began to study the consistency problem of classical analysis. It is mysterious why Hilbert wanted to prove directly the consistency of analysis by finitary methods. I saw two distinguishable problems: to prove the consistency of number theory by finitary number theory and to prove the consistency of analysis by number theory <…> Since the domain of finitary number theory was not well-defined, I began by tackling the second half <…> I represented real numbers by predicates in number theory <…> and found that I had to use the concept of truth (for number theory) to verify the axioms of analysis. By an enumeration of symbols, sentences and proofs within the given system, I quickly discovered that the concept of arithmetic truth cannot be defined in arithmetic. If it were possible to define truth in the system itself, we would have something like the liar paradox, showing the system to be inconsistent <…> Note that this argument can be formalized to show the existence of undecidable propositions without giving any individual instances. (If there were no undecidable propositions, all (and only) true propositions would be provable within the syosmos in potestem. But then we would have a contradiction.) <…> In contrast to truth, provability in a given formal system is an explicit combinatorial property of certain sentences of the system, which is formally specifiable by suitable elementary means…”

Traffic regulations in the context of the 1st Gödel’s theorem

We can consider any set of interrelated rules, including traffic regulations, as a formal axiomatic system where each axiom is not subject to prove and serves as a basis for further deriving the formulas and theorems (or behavior in a traffic situation). Clearly, the traffic regulations are consistent because otherwise, the number of car crashes would be much higher. Hence, according to the 1st Gödel’s theorem, the system is incomplete. This means that there would always exist a situation, which cannot be resolved regardless of the number of regulations (axioms) contained in the system.

The example of such a situation can be observed on the road intersection regulated by priority-to-the-right rule depicted in Fig. 2. Here four vehicles coming from every direction want to pass this intersection each going straight. There is no way to resolve this situation (to derive the formula) within the traffic regulations system and the drivers in every certain situation are supposed to make the decision: who has the priority.

We can incrementally enhance our axiomatic system by introducing another rule to resolve such a dead-end situation. A rule that gives priority to go first, say, to a red car. Again, four red cars on the same road crossing end up with the same confusion. As long as we add the rules (axioms) into the system enumerably, which is the case for the traffic regulations, such situations will always appear. Introducing the priority signs, constant or variable in time, like traffic lights, or topological road junctions (see Fig. 3) can only decrease the probability of this situation emerging.

Nowadays, most of the intersections are controlled (or topologically resolved). And let’s assume that the preposterous situation with four red cars trying to figure out the right-of-way on the uncontrolled intersection hasn’t happened up to the moment in our complex but finite system of road traffic. Hence, the drivers’ behavior seems to be fully governed with the traffic regulations. However, there still is a possibility of an unresolvable situation, namely, if one comes up with an expression: “I’m not going to obey the rules. For the axiomatic system of traffic regulations, this expression serves as a “liar paradox” and cannot be resolved. Thus people had to come up with the penalty system for acceptable performance of the traffic regulations. But again, it is impossible to nullify the probability of such a situation emerging.

Instead of conclusion

The aim of this text was not to establish a solid theory in either mathematics or law, and the presented examples may not be in strict compliance with the described statements. However, the author finds entertaining the fact that there are bridges between different islands of knowledge accumulated by mankind over the infinite ocean of the unknown.

— Sergei Sobolev

Read more:
[1] D. Mathers, M. Miller, O. Ando. Self and No-Self: Continuing the Dialogue Between Buddhism and Psychotherapy. 2013 Routledge
[2] http://www.plato.spbu.ru/TEXTS/lebedev/1/ferekid.htm
[3] W. Koechner. Solid-State Laser Engineering, 2006 Springer
[4] C. Darwin. The origin of species by means of natural selection; or, the preservation of favoured races in the struggle for life. 1859 London
[5] Convention with Respect to the International Circulation of Motor Vehicles. The American Journal of International Law Vol. 4, No. 4, Supplement: Official Documents (Oct., 1910), pp. 316-328
[6] https://upload.wikimedia.org/wikipedia/commons/f/f2/1909_Paris_Convention_road_signs.jpg
[7] D. Hilbert. “Mathematical Problems”. Bulletin of the American Mathematical Society. 8 (10): 437–479, 1902.
[8] Introduction to metamathematics. S. Kleene, 1952 D. Van Nostrand Company, Inc.
[9] H. Wang. A Logical Journey. From Gödel to Philosophy. 1996 The MIT Press.
[10] https://www.archdaily.com/64354/pearl-river-necklace-nl-architects/

How Beneficial is Camel Urine for Human Health?

 Question of the Month, Vol.10 issue 1 2020  Comments Off on How Beneficial is Camel Urine for Human Health?
Jan 122020

Just the thought of getting in touch with or even ingesting urine repels many people. But medical treatment with urine – also called urotherapy – has been a valuable approach in the traditional medicine of many cultures over the last centuries. Usually, endogenous urine is used but animals are also popular sources. The utilization of urine in conventional medicine is not uncommon too. Urokinase, for example, can be isolated from (human) urine and is an important thrombolytic agent.[1] The drug Premarin®, which is used for hormone treatment, contains estrogens that are extracted from the urine of pregnant mares.[2]

Besides milk, camel (i. e. camelus dromedarius) urine plays a special role for desert dwelling people like the Bedouin. Its use was advised by Prophet Mohammed, thus it has found its way into the Islamic prophetic medicine.[3] Apparently, this body liquid cures diseases like tuberculosis, hepatitis, digestion problems, impotence, hemorrhoids, and flatulence, just to name a few. In 2013, one liter of urine from a virgin camel was worth about 15 € (ca 20 USD) in Yemen, where it is not only used for universal medical treatment but also as a cosmetic product for skin and hair care.[4]

src="Dromadaire4478.jpg" alt="Journal of Unsolved Questions (JUnQ): A Moroccan dromedary camel ‒ a favored livestock of Bedouin people. It's urine is said to be medicative."
A Moroccan dromedary camel ‒ a favored livestock of Bedouin people.[5] (public domain – wikimedia commons)

Conventional medicine offers plenty of pharmaceutical cancer treatments which are a blessing and a curse for the patients at the same time. Besides the tedious and exhaustive treatment, patients are confronted with severe side-effects including nausea, fatigue, hair loss, inflammation, and temporary immunodeficiency. The demand for alternatives that are at the same time highly effective, easy to use, mild, and in the best case based on renewable resources is therefore very high.

Camel urine has long been claimed to be an efficient cancer treatment but detailed research on its actual potency and effect on human health is scarce. The soothing effect of pure camel urine on digestive problems can sufficiently be explained through its relatively high content of electrolytes like sodium and zinc as found by Al-Attas, in 2009 – a result that certainly might be achieved just as well by drinking a bouillon.[6] Kohrshid et al. were the first to show an inhibiting effect of lyophilized camel urine on carcinoma cells in animals.[7] In 2011, Alhaider et al. found that treatment of murine hepatoma cells (Hepa 1c1c7, i. e. liver cells) with camel urine inhibited the induction of Cyp 1a1 (a well-known cancer-activator) gene expression by TCDD, a potent Cyp 1a1 inducer and a known carcinogen. Among virgin, pregnant, and lactating camels, the virgin’s urine was found to be most potent while the urine of pregnant camels showed the least potency.[8] One year later, Khorsihd et al. showed that the potency of camel urine to reduce a specific type of lung cancer cells (A549) is somewhat dependent on the breed (Majaheem urine was found to be more effective than Magateer urine) and the age of the camels. The depletion of the cancer cells ranged between 85‒93% of the starting cell number.[9,10] The bioactive subfraction PMF which is believed to be responsible for these effects is obtained from lyophilized camel urine (in literature frequently called PM701).[10] Clinical trials on the oral uptake of PM701 fractions showed no negative effects on human health so far.[11] Apparently, the urine contains a high amount of antibodies of such a small size, that they can be easily absorbed by the patient’s digestive system.[12] Other experiments also show antimicrobial effects of camel urine on bacteria and fungi.[13] Aiming at the environmentally friendly substitution of synthetic agents which are usually obtained from complex multistep reactions this approach is most honorable. It is exciting to see that a waste product has the potential to cure severe diseases although much more research must be done on this subject to clearly verify the efficacy. After all, urine is an excretion that contains various less beneficial digestive metabolites, and even toxins that the body wants to get rid of and indisputable evidence for the efficacy and safety of the PM701 fractions are vital.

For those people who are curious enough to try camel urine for whatever reason but are too disgusted by the idea to drink it pure, a solution might be on the way: there are capsules of PM701, or PMF respectively, but they are not yet available on the market.[10] Another alternative might be camel milk which sounds much more enjoyable and is supposed to be a medicine just as magical as camel urine. It is said to “reduce blood sugar […] solve the problems of autism in children, enhance the immunity of the body…” and many more.[14] Alas, some bad news comes from the World Health Organization (WHO) concerning the use of camel milk and urine: shortly after the Middle East respiratory syndrome coronavirus (MERS-CoV) outbreak in Saudi Arabia in the year 2012 dromedary camels were found to be zoonotic transmitters, meaning that the virus is rapidly transferred from animals to humans – just as we experience right now with the latest outbreak of a coronavirus (COVID-19).[15] As a consequence the WHO advises to avoid contact with camels or consuming raw camel milk and urine.[16] This surely dampens the enthusiasm to utilize camel urine and we might have to wait a few years more for some groundbreaking results in cancer research.

‒ Tatjana Dänzer


[1] “Abstracts of Papers Read”. American Journal of Physiology. Legacy Content., 1952, 171, 704–781.
[2] D. Brügger, „Hormone aus Stutenharn“, pharma-kritik, 2019, Nr. 5/6/1997.
[3] Alhaidar, A., Gader, A. G. M. A., Mousa, S. A., The Journal of Alternative and Complementary Medicine, 2011, 17, 803‒808.
[4] https://www.vice.com/en_us/article/4w7gvn/drinking-camel-urine-in-yemen-fob-000300-v20n8.
[5] https://upload.wikimedia.org/wikipedia/commons/4/40/Dromadaire4478.jpg
[6] Al-Attas, A. S., Arab J. Nucl. Sci. Appl., 2009, 42, 59–67.
[7] Khorshid F., International Journal of Pharmacology, 2008, 4, 443‒451
[8] Alhaidar, A. A.; El Gendy, M. A. M.; Korashy, H. M.; El-Kadi, A. O. S., Journal of Ethnopharmacology, 2011, 133, 184–190.
[9] Alghamdi, Z.; Khorshid, F., Journal of Natural Sciences Research, 2012, 2, 9‒16.
[10] Khorshid, F. A., 2009, US 20090297622.
[11] Khorshid, F. A., Alshazly, H., Al Jefery, A., Osman, M. A.-M., Journal of Pharmacology and Toxicology 2010, 5, 91‒97.
[12] Hamers-Casterman, C.; Atarhouch, T.; Muyldermans, S.; Robinson, G., Hammers, C.; Songa, E. B.; Bendahman, N. and Hammers, R., Nature, 1993, 363, 446‒448.
[13] Mostafa, M. S.; Dwedar, R. A., British Journal of Pharmaceutical Research, 2016, 13, 1‒6.
[14] Hammam, A. R. A., Emirates Journal of Food and Agriculture, 2019, 31, 148‒152.
[15] https://www.eurosurveillance.org/content/10.2807/1560-7917.ES2014.19.16.20781.
[16] https://www.who.int/csr/don/08-january-2020-mers-uae/en/.