Assume there is 0 contracts open and 2 traders, and a new futures contract expiring in 7 days opens. You can "create" a contract by putting a limit sell order in the orderbook at a given price. If someone market buys that limit order, an open contract is created between you and the other trader. This is how you can go from a position of 0 to a negative exposure just by selling a contract.
With BitVC and OKCoin you can hold simultaneous long and short positions on the same contract. In BitMEX you can not. Technically it makes no sense to hold opposite simultaneous positions because it just cancels each other out. You may as well just close the position instead. There are some who still prefer, for psychological reasons, to use this and wrongly call it a "hedge", but really you're better off saving the trading fees and just getting out of a position if your outlook on a trade has changed.

that receive different proportions of the interest and principal distributions from a pool of mortgage assets. The Funds will only invest in SMBS whose mortgage assets are U.S. government obligations. A common type of SMBS will be structured so that one class receives some of the interest and most of the principal from the mortgage assets, while the other class receives most of the interest and the remainder of the principal. If the underlying mortgage assets experience greater than anticipated prepayments of principal, each Fund may fail to fully recoup its initial investment in these securities. The market value of any class that consists primarily or entirely of principal payments generally is unusually volatile in response to changes in interest rates.
State the general effect of any contract, arrangements or statute under which any director, officer, underwriter or affiliated person of the registrant is insured or indemnified against any liability incurred in their official capacity, other than insurance provided by any director, officer, affiliated person, or underwriter for their own protection.
Bitcoin is a relatively new type of currency—a digital or cryptocurrency secured through cryptography, or codes that can’t be read without a key. Traditional currencies are made up of paper bills and coins. Unlike traditional currencies, the bitcoin is not issued by any central government. Rather, a computer algorithm determines how many bitcoins are produced and added to the economy. This is much different than a traditional currency, where central banks typically determine how much money to print.
In general, a foreign corporation that is not engaged in and is not treated as engaged in a U.S. trade or business is nonetheless subject to tax at a flat rate of 30% (or lower tax treaty rate), generally payable through withholding, on the gross amount of certain U.S.-source income that is not effectively connected with a U.S. trade or business. There is presently no tax treaty in force between the United States and the jurisdiction in which any Subsidiary is (or would be) resident that would reduce this rate of withholding tax. Income subject to such a flat tax is of a fixed or determinable annual or periodic nature and includes dividends and interest income. Certain types of income are specifically exempted from the 30% tax and thus withholding is not required on payments of such income to a foreign corporation. The 30% tax generally does not apply to capital gains (whether long-term or short-term) or to interest paid to a foreign corporation on its deposits with U.S. banks. The 30% tax also does not apply to interest which qualifies as “portfolio interest.” Very generally, the term portfolio interest includes U.S.-source interest (including OID) on an obligation in registered form, and with respect to which the person, who would otherwise be required to deduct and withhold the 30% tax, received the required statement that the beneficial owner of the obligation is not a U.S. person within the meaning of the Code.
participating in a distribution (as opposed to engaging in ordinary secondary market transactions), and thus dealing with the Fund’s shares as part of an “unsold allotment” within the meaning of Section 4(3)(C) of the Securities Act, will be unable to take advantage of the prospectus delivery exemption provided by Section 4(3) of the Securities Act.
The Funds may invest in forward currency contracts for investment or risk management purposes. A forward currency contract is an obligation to buy or sell a specific currency at a future date, which may be any fixed number of days from the date of the contract agreed upon by the parties, at a price set at the time of the contract. These contracts are entered into on the interbank market conducted directly between currency traders (usually large commercial banks) and their customers. Forward currency contracts may be structured for cash settlement, rather than physical delivery.

Sections 1471-1474 of the Code and the U.S. Treasury and IRS guidance issued thereunder (collectively, “FATCA”) generally require a Fund to obtain information sufficient to identify the status of each of its shareholders under FATCA or under an applicable intergovernmental agreement (an “IGA”). If a shareholder fails to provide this information or otherwise fails to comply with FATCA or an IGA, a Fund or its agent may be required to withhold under FATCA at a rate of 30% with respect to that shareholder on ordinary dividends it pays to such shareholder and 30% of the gross proceeds of share redemptions or exchanges and certain Capital Gain Dividends it pays to such shareholder after December 31, 2018. If a payment by a Fund is subject to FATCA withholding, the Fund or its agent is required to withhold even if such payment would otherwise be exempt from withholding under the rules applicable to foreign shareholders described above (e.g., Capital Gain Dividends, short-term capital gain dividends, and interest-related dividends).

The Funds may invest in foreign issuers, securities traded principally in securities markets outside the United States, U.S.-traded securities of foreign issuers and/or securities denominated in foreign currencies (together “foreign securities”). Also, each Fund may seek exposure to foreign securities by investing in Depositary Receipts (discussed below). Foreign securities may involve special risks due to foreign economic, political and legal developments, including unfavorable changes in currency exchange rates, exchange control regulation (including currency blockage), expropriation or nationalization of assets, confiscatory taxation, taxation of income earned in foreign nations, withholding of portions of interest and dividends in certain countries and the possible difficulty of obtaining and enforcing judgments against foreign entities. Default in foreign government securities, political or social instability or diplomatic developments could affect investments in securities of issuers in foreign nations. In addition, in many countries there is less publicly available information about issuers than is available in reports about issuers in the United States. Foreign companies are not generally subject to uniform accounting, auditing and financial reporting standards, and auditing practices and requirements may differ from those applicable to U.S. companies. Further, the growing interconnectivity of global economies and financial markets has increased the possibilities that conditions in any one country or region could have an adverse impact on issuers of securities in a different country or region.
To illustrate the point, recall that futures markets are just counterparty contracts. Let's say I want to SHORT the market and profit off a decline in BTC/USD. If I put an order to sell Weekly futures contract at $400, and someone buys that offer, then we have created a futures contract. If it goes down, I profit and he loses, if it goes up, he profits and I lose. However, what if price goes down really fast, and my counterparty only had a little margin backing his position? Well, he gets margin-called when it goes down enough, and the system takes his contract and forces it to be sold to a different counterparty that wants to take the LONG side of my contract.

The biggest problem of the Blockchain is its reliance on miners. This is exactly why the cryptocurrency called IOTA (the Internet of Thigs Application) was created in 2016. IOTA also battles increasing transaction fees and network scalability. IOTA’s blockchain is called Tangle. It is a blockchain with no blocks and no chains. In this system, the users themselves are responsible for validating transactions. This means there’s no need for approval from miners; so users enjoy a fee-free transaction and an increased process speed.

Bitcoin and other cryptocurrencies have evolved from a playful experiment among technical experts to an established and growing branch of the global financial industry. This means that the times in which cryptocurrency traders and investors only concerned themselves with straightforward buying and selling are over. Derivatives are now entering the picture.