The electrical conductance, thermal conductance, thermal power and figure of merit (ZT) of semiconductor quantum dots (QDs) embedded into an insulator matrix connected with metallic electrodes are theoretically investigated in the Coulomb blockade regime. The multilevel Anderson model is used to simulate the multiple QDs junction system. The charge and heat currents in the sequential tunneling process are calculated by the Keldysh Green function technique. In the linear response regime the ZT values are still very impressive in the small tunneling rates case, although the effect of electron Coulomb interaction on ZT is significant. In the nonlinear response regime, we have demonstrated that the thermal rectification behavior can be observed for the coupled QDs system, where the very strong asymmetrical coupling between the dots and electrodes , large energy level separation between dots and strong interdot Coulomb interactions are required.
Accidental ingestion of foreign bodies and its management is a common problem seen more in the pediatric population than in adults. A review of the literature suggests that endoscopic removal of foreign bodies is curative for objects located in the cricopharynx or upper esophagus. Foreign bodies passed into the stomach can usually be observed for development of symptoms, because 80% of them would be spontaneously passed.However, ingestion of metallic foreign bodies involving coins or button-type batteries may require an aggressive approach. A few cases of intestinal obstruction due to magnet ingestion have been reported in Japan, China, and Korea where magnets are used for treatment in traditional medicine.1-5 When more than one magnet is ingested they can be attracted to each other through the intestinal wall, causing necrosis and intestinal perforation or fistula, so they should be removed while they are still accessible with endoscope.We report a case for the first time in the United States of intestinal obstruction and fistula formation due to ingestion of more than one magnet. We feel that early endoscopic removal of magnets or a magnet along with a magnetic foreign body is safe and should be the choice of management. The author proposes an algorithm for management of foreign body ingestion focusing on early retrieval of magnetic foreign bodies.
CaseAn 11-year old boy presented with a three-week history of nausea, vomiting, and burning epigastric pain. He had been treated for Streptococcus A pharyngitis by his pediatrician and had been seen in the emergency department previously with a negative work-up. At admission, vital signs were stable but the patient was visibly uncomfortable, lying on his left side with bilateral lower extremities flexed. Physical examination revealed abdominal tenderness with light palpation and decreased bowel sounds in the right and left lower quadrants. Leukocyte count was 13,900/mm 3 , hemoglobin and hematocrit were slightly elevated, and all other laboratory findings were within normal limits. Radiograph and CT scan of abdomen and pelvis confirmed the presence of two foreign bodies in the pelvis with bowel obstruction (Figures 1 and 2). After multiple rounds of questioning, the patient revealed that he had swallowed two magnets from a toy approximately 1 month before. A surgical consult was called that resulted in an exploratory laparotomy. Operative report of our patient describes fistulae formation at ileoileal level involving a "U" turn region of ileum and proximal jejunum and distal ileum that fistulized through the mesentery of terminal ileum. The procedure involved division, debridement to healthy bowel and closure of jejunoileal fistula, enterotomy for foreign body removal, and reinforcement at ileoileal fistula after division. The specimens were examined by the pathologist and confirmed to be consistent with fis-
A multi-level Anderson model is employed to simulate the system of a nanostructure tunnel junction with any number of one-particle energy levels. The tunneling current, including both shelltunneling and shell-filling cases, is theoretically investigated via the nonequilibrium Green's function method. We obtain a closed form for the spectral function, which is used to analyze the complicated tunneling current spectra of a quantum dot or molecule embedded in a double-barrier junction. We also show that negative differential conductance can be observed in a quantum dot tunnel junction when the Coulomb interactions with neighboring quantum dots are taken into account.In the last decade, the tunneling current spectra of nanostructure junctions such as single-electron transistors (SETs) 1−2 and molecule transistors (MTs) 3−5 have been extensively studied due to their important applications in quantum computing, quantum communication, and ultrahigh-density IC circuits. Although the singleparticle energy levels of such systems can be obtained by ab inito or semiempirical methods 6−10 , it is still difficult to model the full tunneling current spectra due to the presence of Coulomb blockade and the uncertainty in dot shape, size and position.
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