On a barrier height problem for RNA branching.

The branching of an RNA molecule is an important structural characteristic yet difficult to predict correctly, especially for longer sequences. Using plane trees as a combinatorial model for RNA folding, we consider the thermodynamic cost, known as the barrier height, of transitioning between branching configurations. Using branching skew as a coarse energy approximation, we characterize various types of paths in the discrete configuration landscape. In particular, we give sufficient conditions for a path to have both minimal length and minimal branching skew. The proofs offer some biological insights, notably the potential importance of both hairpin stability and domain architecture to higher resolution RNA barrier height analyses.

Epstein-Barr Virus-Associated Atraumatic Spleen Laceration Presenting with Neck and Shoulder Pain.

BACKGROUND: Infectious mononucleosis, caused by the Epstein-Barr virus (EBV), is a common infection with worldwide distribution; more than 90% of people have been infected by adulthood. One of the most feared, albeit rare, complications, occurring in less than 0.5% of those infected, is splenic injury or rupture. CASE REPORT: A febrile 15-year-old male presented to the emergency department with the chief compliant of headache, neck pain, and upper shoulder pain. He did not recall any specific traumatic injury. His abdomen was soft, nondistended, and was tender in the right and left lower quadrants. Right lower quadrant ultrasound demonstrated non-visualization of the appendix, moderate right lower quadrant free fluid, and positive McBurney's sign. CT of the abdomen and pelvis was ordered, which demonstrated moderate splenomegaly, with findings compatible with laceration through the anterior aspect of the spleen, with moderate hemoperitoneum. Monospot was negative and EBV panel demonstrated IGG negative, IGM positive, and, IGG negative. The patient was transferred to interventional radiology for a splenic angiogram and proximal splenic artery embolization. The angiogram demonstrated grade 3 laceration with moderate hemoperitoneum and no active extravasation or evidence of pseudoaneurysm. The patient was admitted and made a prompt recovery without any other sequelae. CONCLUSIONS: The presentation of splenic injury or rupture can vary; the patient may complain of abdominal pain or left upper quadrant pain, may exhibit referred left shoulder pain when the LUQ is palpated (Kehr's Sign), or may exhibit hemodynamic instability. Given the spectrum of non-specific symptoms, diagnosing EBV-induced splenic laceration can be difficult.

Identification of protected avian species using a single feather barb.

We report on the unambiguous identification of protected avian species from as little as one barb of a feather. Many avian species are protected by international agreements and national legislation, yet they are traded illegally because of their high value. Two sections of the avian mitochondrial genome were chosen to identify bird species, being a 561-bp section of ND2 gene and a 921-bp section of the ND5 gene. Two different DNA extraction methods were compared for their ability to reliably isolate sufficient DNA to be detected in a subsequent PCR. Using a commercial kit supplied by QIAGEN, a complete sequence was obtained from one barb for the ND2 gene, whereas two barbs were required to reliably sequence the 921-bp section of the ND5 gene. The process worked on all species tested using feathers from archival museum specimens, resulted in minimal damage to the specimen and can readily be adopted by a forensic science laboratory.

A parametric study on the synthesis of carbon nanotubes through arc-discharge in water.

A parametric study was carried out on a novel carbon nanotube (CNT) synthesis using 'arc-discharge in solution' (ADS). The carbon nanostructure yield as a function of time, the rate of erosion of the anode, and the rate of deposition of carbonaceous materials on the cathode electrode were investigated. Amperage dependent normalized kinetic parameters were evaluated. The production rate of carbon nanostructures including CNTs at 75 A is as high as 5.89 ± 0.28 g min(-1). Thermogravimetric analysis and x-ray diffraction studies reveal high purity of the carbon nanostructures collected from water and have a very good agreement with electron microscopy analyses. Very high surface area of the pristine multiwalled CNTs and nanostructures (84 ± 3.5 m(2) g(-1)) was measured using BET. The dynamic light scattering (DLS) analysis shows further agreement with the amperage dependent studies.