8. Share-based payments (Details 7) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Dividend yield
Minimum [Member]
Volatility	102.00%	108.00%
Risk-free interest rate	1.70%	0.50%
Expected life (years)	0 years	2 months 12 days
Maximum [Member]
Volatility	119.00%	199.00%
Risk-free interest rate	2.70%	1.80%
Expected life (years)	1 year 3 months 19 days	1 year 8 months 12 days
Service and performance conditions [Member]
Volatility
Risk-free interest rate
Expected life (years)		3 years
Dividend yield
Service and performance conditions [Member] \| Minimum [Member]
Volatility		141.00%
Risk-free interest rate		1.50%
Service and performance conditions [Member] \| Maximum [Member]
Volatility		144.00%
Risk-free interest rate		1.60%

The estimated amount of dividends to be paid to holders of the underlying shares (expected dividends) over the option's term. Dividends are taken into account because payment of dividends to shareholders reduces the fair value of the underlying shares, and option holders generally do not receive dividends.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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