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BOSTON ( TheStreet) -- The following companies have market capitalizations between $50 million and $500 million and "buy"-ratings from our proprietary quantitative model, which considers more than 60 factors. They are ordered by their potential to gain.

PetMed Express ( PETS) sells medication and health products for dogs, cats and horses.

The numbers: Fiscal first-quarter revenue increased 13% to $77 million. Net income grew 22% to $8.1 million and earnings per share climbed 29% to 36 cents, helped by a lower share count. Its operating margin increased from 14% to 16% and its net margin passed 10%. The company has no debt and a quick ratio of 3.7, which indicates outstanding liquidity.

The stock: PetMed is up 3% this year, underperforming the Dow Jones Industrial Average and S&P 500 Index. The stock trades at a fair price-to-earnings ratio of 17 and doesn't pay dividends.

Applied Signal Technology ( APSG) provides intelligence, surveillance and reconnaissance solutions for the defense and homeland security markets.

The numbers: Fiscal second-quarter revenue increased 18% to $54 million as earnings doubled to $4 million, or 31 cents per share. Its operating margin climbed to 12% and its net margin rose to 8%. The company has an ideal financial position, with just $4 million of debt and $55 million of cash, amounting to a quick ratio of 4.6 and a debt-to-equity ratio just above zero.

The stock: Applied Signal Technology has advanced 32% this year, outperforming major U.S. indices. The stock trades at an expensive price-to-earnings ratio of 25 and offers a lackluster 2.1% dividend yield.

Aaon ( AAON) sells air-conditioning and heating equipment in the U.S. and Canada.

The numbers: First-quarter revenue decreased 2% to $64 million, but net income rose 5% to $6.7 million and earnings per share jumped 11% to 39 cents, boosted by a lower share count. Its operating margin increased from 14% to 16% and its net margin climbed to 11%. A quick ratio of 1.2 demonstrates Aaon's strong liquidity position. The company has minimal debt.

The stock: Aaon has dropped 3% this year, lagging major U.S. indices. The stock trades at a cheap price-to-earnings ratio of 12 and offers a weak 1.8% dividend yield.

Balchem ( BCPC) sells specialty ingredients for food, animal feed and pharmaceuticals.

The numbers: Second-quarter revenue declined 16% to $53 million, but net income surged 45% to $6.9 million, or 36 cents. Its operating margin increased from 12% to 19% and its net margin advanced from 8% to 13%. Balchem has boosted cash reserves tenfold to $27 million from the year-earlier quarter. A quick ratio of 1.9 indicates a strong liquidity position and just $6.8 million of long-term obligations reflects modest leverage.

The stock: Balchem is up 7% this year, beating the Dow, but underperforming the S&P 500. The stock trades at an expensive price-to-earnings ratio of 24 and offers a dividend yield less than 1%.

Bio-Reference Laboratories ( BRLI) provides clinical lab testing services in the New York area.

The numbers: Fiscal second-quarter earnings grew 35% to $4.6 million, or 33 cents, as revenue advanced 16% to $87 million. Its operating margin increased from 8% to 10% and its net margin inched past 5%. The company has an admirable financial position, with $13 million of cash reserves, amounting to a quick ratio of 1.8, and a debt-to-equity ratio of just 0.3.

The stock: Bio-Reference is up 14% this year, outpacing the Dow and S&P 500. The stock trades at a costly price-to-earnings ratio of 23 and doesn't pay dividends.

-- Reported by Jake Lynch in Boston.

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