721 research outputs found
Streaming Codes for Channels with Burst and Isolated Erasures
We study low-delay error correction codes for streaming recovery over a class
of packet-erasure channels that introduce both burst-erasures and isolated
erasures. We propose a simple, yet effective class of codes whose parameters
can be tuned to obtain a tradeoff between the capability to correct burst and
isolated erasures. Our construction generalizes previously proposed low-delay
codes which are effective only against burst erasures. We establish an
information theoretic upper bound on the capability of any code to
simultaneously correct burst and isolated erasures and show that our proposed
constructions meet the upper bound in some special cases. We discuss the
operational significance of column-distance and column-span metrics and
establish that the rate 1/2 codes discovered by Martinian and Sundberg [IT
Trans.\, 2004] through a computer search indeed attain the optimal
column-distance and column-span tradeoff. Numerical simulations over a
Gilbert-Elliott channel model and a Fritchman model show significant
performance gains over previously proposed low-delay codes and random linear
codes for certain range of channel parameters
An Abdominal Aortic Aneurysm, Intramural Thrombus and Moderate Leak in an Asian Man Presenting with Acute Gastroenteritis
Introduction: Missing a leaking abdominal aortic aneurysm (AAA) is common in medical practice because few at-risk patients have a history
of AAA and many have an unusual presentation.
Background: AAA is less common among Asians than white Caucasians of the same age. Our patient had no significant risk factors apart from
age and sex and had an unusual presentation.
Patient and Methods: A 67-year-old Asian man presented to the emergency room (ER) with a 1-day history of nausea, vomiting, diarrhoea,
fever and abdominal pain. He was febrile, dehydrated. and had marked tenderness at the right iliac fossa. Laboratory findings suggested
bacterial gastroenteritis but this did not explain the localized tenderness at the right iliac fossa.
Result and Discussion: A CT scan of the abdomen revealed an AAA arising above the origins of the renal arteries, an intramural thrombus,
a retroperitoneal haematoma and a leak extending to the right iliac fossa. The patient was transferred to another hospital and underwent
exploratory laparotomy, surgical repair of the aneurysm, and aortobi-iliac grafting with removal of the thrombus. The patient was discharged
in good shape 3 weeks after surgery. Without the CT scan of the abdomen, the AAA could have been missed and the patient treated for
severe gastroenteriti
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