Ke-Feng Wang

Background: 30-day readmission after ischemic stroke is an important health quality of care metric, but little is known about potential race-ethnic disparities for this outcome. We examined 30-day rates and causes for readmission among Medicare beneficiaries in the NINDS-funded Florida-Puerto Rico Collaboration to Reduce Stroke Disparities (CReSD) Study. Methods: We examined 30-day all-cause readmission for Medicare fee-for-service beneficiaries treated for ischemic stroke (ICD-9 433,434, 436) in FL CReSD hospitals from 2010-2013. We fit a Cox proportional hazards model that censored for death and adjusted for age, sex, and comorbidities to assess race-ethnic differences in readmission, and identified reasons for readmissions. Results: Among 16,952 unique ischemic stroke patients (54% women, 75% white, 8% black, 15% Hispanic), all-cause 30-day readmission was 15%. Readmission rates were 17.2% for Blacks, 16.7% for Hispanics, 14.4% for Whites, and 14.7% for Others (p=0.003). There was a median of 11 days between discharge and first readmission. In risk-adjusted analyses, there was no significant difference in 30-day readmission for Blacks (hazard ratio 1.15, 95% confidence interval 0.99-1.33), Hispanics (1.00, 0.90-1.13), and those of other race (0.91, 0.71-1.16) compared to Whites. Nearly 1 in 4 readmissions were attributable to an acute cerebrovascular event: 16.6% ischemic stroke or transient ischemic attack, 1.5% hemorrhagic stroke, and 5.2% cerebral artery intervention (carotid endarterectomy or stenting, endovascular). Interventions were more common among Whites (6.0%) and those of other race (7.5%) than among Blacks (1.8%) and Hispanics (3.8%; p=0.029). Readmission due to pneumonia or urinary tract infection was 8.2%. Conclusions: Readmissions varied by race/ethnicity, but generally occurred within two weeks of hospital discharge. Our results underscore the importance of post-discharge transition of care and the need for better secondary stroke prevention strategies early after ischemic stroke. Implementation of effective transition of care after acute stroke hospitalization may reduce potentially preventable readmissions, particularly among minority populations.

We report the electronic structure, electric and thermal transport properties of Ru_1−xIr_xSe₂ (x ≤ 0.2). RuSe₂ is a semiconductor that crystallizes in a cubic pyrite unit cell. The Seebeck coefficient of RuSe₂ exceeds −200 μV/K around 730 K. Ir substitution results in the suppression of the resistivity and the Seebeck coefficient, suggesting the removal of the peaks in density of states near the Fermi level. Ru_0.8Ir_0.2Se₂ shows a semiconductor-metal crossover at about 30 K. The magnetic field restores the semiconducting behavior. Our results indicate the importance of the electronic correlations in enhanced thermoelectricity of RuSb₂.

The magnetic field response of the transport properties of novel materials and then the large magnetoresistance effects are of broad importance in both science and application. We report large transverse magnetoreistance (the magnetoresistant ratio ~ 1.3 × 105% in 2 K and 9 T field, and 4.3 × 106% in 0.4 K and 32 T field, without saturation) and field-induced metal-semiconductor-like transition, in NbSb2 single crystal. Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane. The sign reversal of the Hall resistivity and Seebeck coefficient in the field, plus the electronic structure reveal the coexistence of a small number of holes with very high mobility and a large number of electrons with low mobility. The large MR is attributed to the change of the Fermi surface induced by the magnetic field which is related to the Dirac-like point, in addition to orbital MR expected for high mobility metals.

Patients with stage IE/IIE natural killer T (NK/T) cell lymphomas have discrepant survival outcome. This study aims to establish a prognostic model based on the pretreatment platelet lymphocyte ratio (PLR) specifically for localized extranodal NK/T cell lymphoma to guide the therapy. We retrospectively analyzed the data of 252 patients with early-stage upper aerodigestive tract NK/T cell lymphoma. The 5-year overall survival rate in 252 patients was 67.1 %. Prognostic factors for survival were female (P = 0.025; relative risk, 0.51; 95 % CI 0.28–0.92), older age (P = 0.000; relative risk, 3.34; 95 % CI 1.94–5.75), stage II(P = 0.020; relative risk, 1.79; 95 % CI 1.10–2.91), lactate dehydrogenase (LDH) level (P = 0.009; relative risk, 2.00; 95 % CI 1.19–3.35), and PLR (P = 0.020; relative risk, 1.77; 95 % CI 1.10–2.87). Based on these five parameters, we identified three different risk groups: group 1(106 cases, 43.4 %), no or one adverse factor; group 2(85 cases, 34.8 %), two factors; group 3(53 cases, 21.7 %), three to five factors. Five-year overall survival was 83.3 % for group 1, 62.2 % for group 2, and 43.1 % for group 3 (P = 0.000). Compared with International Prognostic Index and Korean Prognostic Index, the new model has a better prognostic discrimination for the patients of stage IE/IIE upper aerodigestive tract NK/T cell lymphoma. The PLR-based prognosis model is useful to stratify patients with localized extranodal NK/T cell lymphoma into different risk groups and guide the treatment modalities selection.

Optimal chemotherapy regimen for Extranodal natural killer/T-cell lymphoma (ENKTL) has not yet been defined. We retrospectively compared the outcome of 93 patients newly diagnosed with stage IE to IIE ENKTL who received gemcitabine, oxaliplatin and L-asparaginase (GELOX) (n = 40) or etoposide, vincristine, doxorubicin, cyclophosphamide and prednisone (EPOCH) (n = 53) as induction chemotherapy. After induction chemotherapy, the complete response (CR) rate and overall response rate (ORR) for the GELOX group were higher than those for the EPOCH group (70.0% vs. 41.5%, p = 0.007 for CR; 87.5% vs. 67.9%, p = 0.047 for ORR). The GELOX regimen resulted in significantly superior 5-year progression-free survival (PFS) (79.0% vs. 46.5%, p = 0.005) and overall survival (OS) rates (78.9% vs. 50.4%, p = 0.003). Toxicity of both regimens was acceptable. The GELOX regimen produces a better long outcome with less toxicity than the EPOCH regimen for patients with early stage ENKTL.

We have synthesized K0.95(1)Ni1.86(2)Se2 single crystals. The single crystals contain K and Ni deficiencies not observed in KNi2Se2 polycrystals. Unlike KNi2Se2 polycrystals, the superconductivity is absent in single crystals. The detailed physical property study indicates that the K0.95Ni1.86Se2 single crystals exhibit heavy-fermion-like characteristics. The transition to a heavy fermion state below T ~ 30 K results in an enhancement of the electron-like carrier density whereas the magnetic susceptibility shows little anisotropy and suggests the presence of both itinerant and localized Ni orbitals.

We report electrical and thermal transport properties of Mn-based material BaMn₂Bi₂ with ThCr₂Si₂ structure. The resistivity of the antiferromagnetic BaMn₂Bi₂ shows a metal-semiconductor transition at ∼80 K with decreasing temperature. Correspondingly, the thermopower S shows a peak at the same temperature, approaching 150 μV/K. With increasing temperature, S decreases to about 125 μV/K at the room temperature. The magnetic field enhances the peak value to 210 μV/K. The Hall resistivity reveals an abrupt change of the carrier density close to the metal-semiconductor transition temperature.