Uncertainty quantification in atomistic simulations of silicon using interatomic potentials.

Atomistic simulations often rely on interatomic potentials to access greater time and length scales than those accessible to first-principles methods, such as density functional theory. However, since a parameterized potential typically cannot reproduce the true potential energy surface of a given system, we should expect a decrease in accuracy and increase in error in quantities of interest calculated from these simulations. Quantifying the uncertainty on the outputs of atomistic simulations is thus an important, necessary step so that there is confidence in the results and available metrics to explore improvements in said simulations. Here, we address this research question by forming ensembles of atomic cluster expansion potentials, and using conformal prediction with ab initio training data to provide meaningful, calibrated error bars on several quantities of interest for silicon: the bulk modulus, elastic constants, relaxed vacancy formation energy, and the vacancy migration barrier. We evaluate the effects on uncertainty bounds using a range of different potentials and training sets.

Transfemoral extraction of an intracardiac bullet embolus.

Missiles may reach the heart via direct penetration of the thoracic cavity or indirectly by means of the venous circulation. Often the hemodynamic stability of the patient dictates the approach that is used not only to retrieve the projectile but also to repair associated life-threatening injuries. The case of a 40-year-old man with an intracardiac missile after a gunshot wound to the right gluteal area is presented along with the transfemoral technique used to recover an intracardiac projectile. This approach may be used instead of thoracotomy for missile extraction in stable patients.

Complication of the retroperitoneal approach: intercostal abdominal hernia.

The left thoracoabdominal incision with retroperitoneal dissection offers excellent exposure of the abdominal and thoracic aorta. Disadvantages to this approach include inadequate access to the right ileofemoral arterial segments and the right renal artery. Additional difficulties with this approach include flank bulges, hernias, and neuropathy. We present a case of an incisional hernia at the tenth interspace with subsequent herniation of the left colon through this defect. CT defined the extent of this defect and ruled out other significant pathology. The patient underwent an uneventful herniorrhaphy. Abdominal-intercostal hernias have not been previously reported in association with the retroperitoneal aortic repair.

Complications of isolated bilateral iliac artery aneurysms.

Isolated iliac artery aneurysms occur infrequently. They comprise about 2 per cent of all abdominal aneurysms. Most patients are symptomatic at the time of presentation. The average diameter is 5.7 cm at diagnosis. We report the acutely symptomatic presentation of a 76-year-old African-American man with 7- and 9-cm bilateral common iliac and a right hypogastic artery aneurysms. Aneurysmorrhaphy was complicated by pelvic ischemia. Colonoscopy and arteriography were used postoperatively to evaluate the extent of his worsening gluteal ischemia. Restoration of pelvic blood flow corrected his gluteal ischemia.

The antiphospholipid symdrome in a teenage with miscarriages, thromboses, and diabetes mellitus.

The antiphospholipid syndrome has been associated with many clinical conditions since its description by GRV Hughes in 1983. The linkage to Type 1 diabetes mellitus has not been established. There have been no reports of deep venous thrombosis in association with antiphospholipid syndrome and diabetes mellitus. We present the case of an African-American teenager with multiple miscarriages, diabetic ketoacidosis, deep venous thromboses, and elevated immunoglobulin M and G anticardiolipin antibodies. We urge that clinicians consider testing for antiphospholipid antibodies when diabetic patients present with multiple miscarriages or deep venous thrombosis.

Proviral load and immune markers associated with human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in Peru.

Human T-lymphotropic virus type 1 (HTLV-1) is the aetiological agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The objective of this study is to identify which ex vivo and in vivo markers are associated independently with HAM/TSP in a Peruvian population. Eighty-one subjects (33 men/48 women) were enrolled: 35 presented with HAM/TSP, 33 were asymptomatic HTLV-1 carriers (ACs) and 13 were HTLV-1-seronegative controls (SCs). Ex vivo markers included T cell proliferation and Th1 [interferon (IFN)-gamma], Th2 [interleukin (IL)-4, IL-5], proinflammatory [tumour necrosis factor (TNF)-alpha] and anti-inflammatory (IL-10) cytokine production in non-stimulated peripheral blood mononuclear cell (PBMC) cultures. In vivo CD4(+) T cell count, markers of Th1 [interferon-inducible protein (IP)-10] and Th2 (sCD30) activity in plasma and HTLV-1 proviral load in PBMCs were also evaluated. In univariate analysis, several markers, including T cell proliferation, IFN-gamma, IP-10, sCD30 and proviral load were associated with HAM/TSP, but in a multiple logistic regression analysis only the proviral load remained associated significantly with disease manifestation [adjusted OR 9.10 (1.24-66.91)]. Our findings suggest that HAM/TSP is associated primarily with proviral load, whereas the observed association with some immune markers seems secondary.

Mycotic aortic aneurysm in a patient with Tolosa-Hunt syndrome.

Mycotic aneurysms have been associated with many clinical conditions. A tender pulsatile abdominal mass in association with fever, chills, and unrelenting back pain is suggestive of a leaking mycotic aneurysm. However, the extracranial manifestations of Tolosa-Hunt syndrome (THS) may mimic several of these symptoms. We report the case of a woman who was successfully treated with high-dose steroids for THS. Two months later, she was admitted to another hospital with rigors and unremitting back and abdominal pain. CT-guided aspiration of an L5-S1 paravertebral mass was done. The aspirate and blood cultures grew Staphylococcus aureus. Intravenous antibiotics and analgesics were administered with good relief. A month after discharge from that hospital, she was admitted to our hospital with classic signs and symptoms of a leaking mycotic aneurysm. She was treated surgically and has remained asymptomatic for 21 months. Tolosa-Hunt syndrome associated with mycotic aortic aneurysms has not been previously reported.

Transaortic endarterectomy of renal visceral artery lesions in association with infrarenal aortic surgery.

The complexity of infrarenal aortic reconstruction increases when bypass grafts to revascularize associated renal and visceral arteries are needed. Lesions in these vessels, however, are usually limited to their aortic orifices and therefore are amenable to retroperitoneal transaortic endarterectomy. A combined infrarenal aortic reconstruction and transaortic endarterectomy of the renal/visceral vessels was used in 18 (16%) of 120 patients undergoing elective infrarenal aortic reconstruction over a 2-year-period. Transaortic endarterectomy was performed primarily for renal preservation in 11 patients with bilateral, high-grade renal artery stenoses and abnormal renal function (serum creatinine greater than or equal to 1.9 mg/dl). In seven patients transaortic endarterectomy was performed as a secondary procedure during the course of complex reconstruction of aneurysmal or occlusive aortic disease. Mean serum creatinine, which was elevated preoperatively in 14 (78%) patients (3.3 mg/dl), decreased significantly after the operation (2.0 mg/dl, p less than 0.01). A single death occurred in the 18 patients undergoing transaortic endarterectomy. Renal function preservation can be achieved by renal revascularization in patients with bilateral renal artery stenoses and decreased renal function. The retroperitoneal approach to aortic reconstruction and the use of transaortic endarterectomy allows correction of most renal/visceral vessel involvement in complex aortic revascularization procedures.

The value of computed tomography in the management of symptomatic abdominal aortic aneurysms.

The use of computed tomographic (CT) scanning in the diagnosis of ruptured abdominal aortic aneurysm is controversial because the delay created by the procedure, it has been argued, may increase overall mortality. However, if emergency surgery can be avoided in the medically compromised patient, surgical results may improve. To assess the value of CT scanning, we studied the 1983 to 1988 records of 65 hemodynamically stable patients with abdominal aortic aneurysms, who underwent diagnostic CT scanning for acute abdominal or back pain. Twenty-one patients had a history of severe cardiac, renal, or pulmonary disease. The average duration of the examination was 63 minutes; no episodes of hypotension occurred. Subsequently, 17 of 18 patients with ruptured aneurysms had emergency surgery, with 31% morbidity and 29% mortality. Of 44 patients found to have nonruptured aneurysms, 13 had other causes for their pain, nine were not considered surgical candidates, and 24 had elective aneurysmectomies, with 8% morbidity and 0% mortality. In three patients CT scanning excluded the diagnosis of aneurysm. Additional information provided by CT scanning enhanced the safety of the perioperative management of four patients with rupture and 14 without. In conclusion, the delay imposed by obtaining a preoperative CT scan in patients with possible ruptured aneurysm did not adversely affect patient outcome, and the information obtained from it aided significantly in both preoperative and intraoperative management.

Mesenteric blood flow in patients with diabetic neuropathy.

We examined flow velocities in the superior mesenteric artery and celiac artery in normal controls (group C, n = 11), diabetic patients (group D, n = 8), and diabetic patients with clinically evident autonomic neuropathy (group DN, n = 6) to further define the usefulness of duplex examination in the evaluation of the mesenteric circulation in normal and disease states. By use of a 3 MHz duplex scanner, peak systolic velocity, peak diastolic forward velocity, end-diastolic forward velocity, and peak diastolic reverse velocity were measured in centimeters per second before and after a standardized meal. The vessels' diameters in centimeters were also measured. After the meal peak diastolic reverse velocity disappeared in all patients. The average vessel diameter in the superior mesenteric artery (0.7 cm) and celiac artery (0.8 cm) did not change. Flow velocities in the celiac artery were not significantly altered by the meal. In the control group, peak systolic velocity in the superior mesenteric artery increased 38%, peak diastolic forward velocity rose 66%, and end-diastolic forward velocity increased by 70%. In the diabetic nonneuropathic group the changes were 15%, 98%, and 100%, respectively. These changes were statistically significant (p less than 0.01). On the other hand, the patients with diabetic autonomic neuropathy presenting a picture of gastroparesis did not exhibit the expected increases in postprandial velocities. Moreover, this alteration in blood flow velocity, although similar to that encountered in patients with intestinal angina, did not appear to be due to occlusive arterial disease on the basis of clinical examination and B-mode scanning.