Molecular Dynamics Study of the Aggregation Behavior of N,N,N',N'-Tetraoctyl Diglycolamide.

Liquid-liquid extraction is a commonly used technique to separate metals and is a process that has particular relevance to the nuclear industry. There has been a drive to use environmentally friendly ligands composed only of carbon, hydrogen, nitrogen, and oxygen. One example is the i-SANEX process that has been developed to separate minor actinides from spent nuclear fuel. The underlying science of such processes, is, however, both complex and intriguing. Recent research indicates that the liquid phases involved are frequently structured fluids with a hierarchical organization of aggregates. Effective flow-sheet modeling of such processes is likely to benefit from the knowledge of the fundamental properties of these phases. As a stepping stone toward this, we have performed molecular dynamics simulations on a metal free i-SANEX system composed of the ligand N,N,N',N'-tetraoctyl diglycolamide (TODGA), diluent hydrogenated tetrapropylene (TPH), and polar species water and nitric acid. We have also studied the effects of adding n-octanol and swapping TPH for n-dodecane. It would seem sensible to understand this simpler system before introducing metal complexes. Such an understanding would ideally arise from studying the system's properties over a wide range of compositions. The large number of components, however, precludes a comprehensive scan of compositions, so we have chosen to study a fixed concentration of TODGA while varying the concentrations of water and nitric acid over a substantial range. Reverse aggregates are observed, with polar species in the interior in contact with the polar portions of the TODGA molecules and the organic diluent on the exterior in contact with the TODGA alkyl chains. These aggregates are irregular in shape and grow in size as the amount of water and nitric acid increases. At a sufficiently high polar content, a single extended cluster forms corresponding to the third phase formation. No well-defined bonding motifs were observed between the polar species and TODGA. The cluster size distribution fits an isodesmic model, where the Gibbs energy change of adding a TODGA molecule to a cluster ranges between 4.5 and 7.0 kJ mol-1, depending on the system composition. The addition of n-octanol was found to reduce the degree of aggregation, with n-octanol acting as a co-surfactant. Exchanging the diluent TPH for n-dodecane also decreased the aggregation. We present evidence that this is due to the greater penetration of n-dodecane into the reverse aggregates. It is known, however, that the propensity for the third phase formation is greater with n-dodecane as the diluent than is the case with TPH, but we argue that these two results are not contradictory. This research casts light on the driving forces for aggregation, informs process engineers as to what species are present, and indicates that flow-sheet liquid-liquid extraction modeling might benefit by incorporating an isodesmic aggregation approach.

Palliative care access in the elderly metastatic breast cancer population: obstacles and opportunities.

Metastatic breast cancer in the elderly encompasses a group of patients with worse cancer-specific survival and more barriers to care than their non-elderly counterparts. Metastatic breast cancer has a longer natural history than many other common metastatic solid tumors. Palliative care access in this group is thus affected by increased need from (I) more aggressive disease status with more severe symptoms, (II) increased barriers to care, (III) more patients living with the disease than other metastatic solid tumors, and (IV) increased incidence of breast cancer as compared to other solid tumors. This review outlines the rationale for outpatient palliative care, the needs for this specific population of cancer patients, and the barriers that the medical community faces in providing palliative care access for these patients.

Novel computed tomographic chest metrics to detect pulmonary hypertension.

BACKGROUND: Early diagnosis of pulmonary hypertension (PH) can potentially improve survival and quality of life. Detecting PH using echocardiography is often insensitive in subjects with lung fibrosis or hyperinflation. Right heart catheterization (RHC) for the diagnosis of PH adds risk and expense due to its invasive nature. Pre-defined measurements utilizing computed tomography (CT) of the chest may be an alternative non-invasive method of detecting PH. METHODS: This study retrospectively reviewed 101 acutely hospitalized inpatients with heterogeneous diagnoses, who consecutively underwent CT chest and RHC during the same admission. Two separate teams, each consisting of a radiologist and pulmonologist, blinded to clinical and RHC data, individually reviewed the chest CT's. RESULTS: Multiple regression analyses controlling for age, sex, ascending aortic diameter, body surface area, thoracic diameter and pulmonary wedge pressure showed that a main pulmonary artery (PA) diameter ≥29 mm (odds ratio (OR)=4.8), right descending PA diameter ≥19 mm (OR=7.0), true right descending PA diameter ≥16 mm (OR=4.1), true left descending PA diameter ≥21 mm (OR=15.5), right ventricular (RV) free wall ≥6 mm (OR=30.5), RV wall/left ventricular (LV) wall ratio ≥0.32 (OR=8.8), RV/LV lumen ratio ≥1.28 (OR=28.8), main PA/ascending aorta ratio ≥0.84 (OR=6.0) and main PA/descending aorta ratio ≥1.29 (OR=5.7) were significant predictors of PH in this population of hospitalized patients. CONCLUSION: This combination of easily measured CT-based metrics may, upon confirmatory studies, aid in the non-invasive detection of PH and hence in the determination of RHC candidacy in acutely hospitalized patients.

Acute fracture of the os trigonum.

A 21-year-old man presented with ankle pain after a motor vehicle accident. Imaging revealed an acute fracture of the os trigonum in addition to multiple, other lower-extremity fractures. In this case, the fracture of the os trigonum was a result of a significant traumatic injury. Thus, the presence of this fracture in an acute setting should prompt a search for other associated fractures.

The efficacy of B-type natriuretic peptide for early identification of blood loss in traumatic injury.

BACKGROUND: Because B-type natriuretic peptide (BNP) secretion has a direct linear correlation with intravascular volume status, it was assessed as an initial marker for blood loss (BL) in polytrauma patients. METHODS: Hemodynamically unstable trauma patients between 18 and 45 years had serial BNP levels and hemoglobin (Hgb) levels obtained on admission, at 8 and 24 hours, and every morning during resuscitation. RESULTS: The 14 patients were categorized into 2 groups based on the 24-hour trend in Hgb levels: clinically significant blood loss (Hgb decrease >3 g/dL) or no clinical blood loss (Hgb decrease <3 g/dL). On admission, the 5 patients in the no blood loss group had normal BNP levels, whereas the 9 patients in the BL group had below-normal BNP levels. Because patients in the BL category were resuscitated, their BNP levels normalized. CONCLUSIONS: BNP levels below normal are indicative of intravascular volume loss in traumatically injured patients.