Migration of aluminum atoms in the transformation of γ− to θ−alumina

2002 MRS Spring Proceedings, 731, pp. W3.6.1 - W3.6.6.γ− and θ−alumina are two metastable phases of aluminum oxide observed along the thermal dehydration sequence of boehmite before conversion to the final product α−alumina. The transformation from γ− to θ−alumina was studied by using Al16O24 cells. Motion of some Al atoms from their γ−alumina positions to new positions and no O motions result in an approximate structure that, upon relaxation by first-principles calculations, becomes the known θ−alumina structure. Total-energy calculations along the paths of the atomic motions have been used to map out transformation pathways. The model accurately predicts experimentally observed domain boundaries in θ−alumina and the γ− to θ−alumina conversion rate

High-Dose Therapy and Autologous Hematopoietic Cell Transplantation in Peripheral T Cell Lymphoma (PTCL): Analysis of Prognostic Factors

Patients with peripheral T cell lymphoma (PTCL) have a poor prognosis with current treatment approaches. We examined the outcomes of high-dose therapy (HDT) and autologous hematopoietic cell transplant (AHCT) on the treatment of PTCL and the impact of patient/disease features on long-term outcome. Sixty-seven patients with PTCL–not otherwise specified (n = 30), anaplastic large cell lymphoma (n = 30), and angioimmunoblastic T cell lymphoma (n = 7) underwent HDT/AHCT at the City of Hope. The median age was 48 years (range: 5-78). Twelve were transplanted in first complete remission (1CR)/partial remission (PR) and 55 with relapsed or induction failure disease (RL/IF). With a median follow-up for surviving patients of 65.8 months (range: 24.5-216.0) the 5-year overall survival (OS) and progression-free survival (PFS) were 54% and 40%, respectively. The 5-year PFS was 75% for 1CR/PR compared to 32% for RL/IF patients (P = .01). When the Prognostic Index for PTCL unspecified (PIT) was applied at the time of transplant, patients in the PIT 3-4 group had 5-year PFS of only 8%. These results show that HDT/AHCT can improve long-term disease control in relapsed/refractory PTCL and that HDT/AHCT should ideally be applied either during 1CR/PR, or as part of upfront treatment. More effective and novel therapies are needed for patients with high-risk disease (PIT 3-4 factors) and allogeneic HCT should be explored in these patients

Endothelial cell Bcl‐2 and lymph node metastasis in patients with oral squamous cell carcinoma

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90040/1/j.1600-0714.2011.01081.x.pd

Phase transformation mechanism between γ- and θ-alumina

【英文摘要】γ-alumina transforms to θ-alumina and finally to α-alumina in the sequence of thermal dehydration of boehmite. We report a detailed theoretical investigation of the γ- to θ-alumina transformation based on first-principles density-functional calculations. Although the unit cells of cubic γ-alumina and monoclinic θ-alumina look quite different, we have identified cells for both the polytypes (with the composition Al16O24) that look very similar and can be continuously transformed one to another. The transformation may be described by a set of aluminum atom migrations between different interstitials while the oxygen atoms remain fixed. Total-energy calculations along the paths of the atomic migrations have been used to map out possible transformation pathways. The calculated conversion rate accurately predicts the experimentally measured transformation temperature. The deduced orientation relationships between the γ- and θ-alumina forms also agree with experimental observations. The formation of several different interfaces observed in domain boundaries of θ-alumina may correspond to different migration paths of the aluminum atoms in neighboring domains during the γ- to θ-alumina phase transition

Phase transformation mechanism between γ- and θ-alumina

Physical Review B, 67: pp. 224104-1 - 224104-10.y-alumina transforms to θ-alumina and finally to a-alumina in the sequence of thermal dehydration of boehmite. We report a detailed theoretical investigation of the y- to θ-alumina transformation based on first principles density-functional calculations. Although the unit cells of cubic y-alumina and monoclinic θ-alumina look quite different, we have identified cells for both the polytypes (with the composition Al16O24) that look very similar and can be continuously transformed one to another. The transformation may be described by a set of aluminum atom migrations between different interstitials while the oxygen atoms remain fixed. Total-energy calculations along the paths of the atomic migrations have been used to map out possible transformation pathways. The calculated conversion rate accurately predicts the experimentally measured transformation temperature. The deduced orientation relationships between the y- and θ-alumina forms also agree with experimental observations. The formation of several different interfaces observed in domain boundaries of u-alumina may correspond to different migration paths of the aluminum atoms in neighboring domains during the y- to θ-alumina phase transition

Atomic scale mechanism of the transformation of γ-alumina to θ-alumina

Physical Review Letters, 89: pp. 235501-1 - 235501-4.y-alumina is known to transform to θ-alumina and finally to a-alumina upon thermal treatment with a catastrophic loss of porosity and catalytic activity. First-principles calculations were performed to investigate the atomic scale mechanism of the y- to θ-alumina transformation. The transformation pathways between the two different forms have been mapped out and identified as a sequence of Al cation migrations. Different possible Al migration paths may be responsible for the experimentally observed formation of domains and twins in θ-alumina. The estimated temperature dependence of the conversion rate is in excellent agreement with the experimental transformation temperature

A Reliable Energy-Efficient Multi-Level Routing Algorithm for Wireless Sensor Networks Using Fuzzy Petri Nets

A reliable energy-efficient multi-level routing algorithm in wireless sensor networks is proposed. The proposed algorithm considers the residual energy, number of the neighbors and centrality of each node for cluster formation, which is critical for well-balanced energy dissipation of the network. In the algorithm, a knowledge-based inference approach using fuzzy Petri nets is employed to select cluster heads, and then the fuzzy reasoning mechanism is used to compute the degree of reliability in the route sprouting tree from cluster heads to the base station. Finally, the most reliable route among the cluster heads can be constructed. The algorithm not only balances the energy load of each node but also provides global reliability for the whole network. Simulation results demonstrate that the proposed algorithm effectively prolongs the network lifetime and reduces the energy consumption

Particle export from the upper ocean over the continental shelf of the west Antarctic Peninsula: A long-term record, 1992–2007

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 2118-2131, doi:10.1016/j.dsr2.2008.04.028.Includes supplemental materialsWe report on results of a long-term (1993-2007) time series sediment trap moored at 170 m to the west of the Antarctic Peninsula in the mid-continental shelf region (350 m depth; 64º30’ S, 66º00’ W). This is a region characterized by late spring-summer diatom blooms, moderately high seasonal primary productivity (50-150 mmol C m-2 d-1 in December-February) and high phytoplankton and krill biomass in the seasonal sea ice zone. The mass flux ranged from near 0 to over 1 g m-2 d-1 and was near 0 to >30% organic carbon (mean 8%). Sedimentation from the upper ocean as estimated by the trap collections at 170 m exhibited strong seasonality with high fluxes (1-10 mmol C m-2 d-1) in November-March following ice retreat and very low fluxes (<0.001 mmol C m-2 d-1) during the Austral winter and under sea ice cover. An average of 85% of the annual export of 212 mmol C m-2 occurred during the seasonal peak flux episodes. Over the trap record, the annual peak flux episode has tended to occur later in the Austral summer, advancing by about 40 days since 1993. The time-integrated sedimentation during the peak flux episode was <1 – 50% of the SeaWiFS-estimated primary production (mean 4%) at the trap site over the period 1998-2006. The elemental composition of material captured in the traps had an average C:N:P of 212:28:1, greater than the canonical Redfield values. High C:P ratios (400- 600) corresponded with the annual flux peak, indicating preferential loss of P from the sinking particles in the summer, ice-free period. The composition of the exported material more closely approximated the Redfield composition during the low-flux, winter period.This research was supported by NSF Grants OPP 9011927, 9632763 and 0217282 for the Palmer Long Term Ecological Research project

Automated Assessment of Pavlovian Conditioned Freezing and Shock Reactivity in Mice Using the Video Freeze System

The Pavlovian conditioned freezing paradigm has become a prominent mouse and rat model of learning and memory, as well as of pathological fear. Due to its efficiency, reproducibility and well-defined neurobiology, the paradigm has become widely adopted in large-scale genetic and pharmacological screens. However, one major shortcoming of the use of freezing behavior has been that it has required the use of tedious hand scoring, or a variety of proprietary automated methods that are often poorly validated or difficult to obtain and implement. Here we report an extensive validation of the Video Freeze system in mice, a “turn-key” all-inclusive system for fear conditioning in small animals. Using digital video and near-infrared lighting, the system achieved outstanding performance in scoring both freezing and movement. Given the large-scale adoption of the conditioned freezing paradigm, we encourage similar validation of other automated systems for scoring freezing, or other behaviors

Peer Smoking, Other Peer Attributes, and Adolescent Cigarette Smoking: A Social Network Analysis

Peer attributes other than smoking have received little attention in the research on adolescent smoking, even though the developmental literature suggests the importance of multiple dimensions of adolescent friendships and peer relations. Social network analysis was used to measure the structure of peer relations (i.e., indicators of having friends, friendship quality, and status among peers) and peer smoking (i.e., friend and school smoking). We used three-level hierarchical growth models to examine the contribution of each time varying peer variable to individual trajectories of smoking from age 11 to 17 while controlling for the other variables and we tested interactions between the peer structure and peer smoking variables. Data were collected over five waves of assessment from a longitudinal sample of 6,579 students in three school districts. Findings suggest a greater complexity in the peer context of smoking than previously recognized