The filing for a mixed shelf offering is a significant financial move for Nephros, indicating potential for future growth or debt management. The positive or negative impact on the stock price in the short term will largely depend on investor perception of the company's strategy for using the raised funds. If investors believe the funds will be used effectively for growth or to improve the balance sheet, the stock could see a positive impact. However, the issuance of new securities could also dilute existing shareholders, which is a factor to consider.