Driving, aging, and traumatic brain injury: Integrating findings from the literature.

Objective: In order to address the potential compounded risk in the population of aging traumatic brain injury (TBI) survivors who continue to drive, the authors synthesized literatures regarding the impact of aging or TBI on driving. Study Design: PubMed searches were conducted utilizing combinations of the following terms: driving, aging, elderly, TBI, cognition, seizures, vision, hearing, rehabilitation, sleep, fatigue, and assessment. Additional sources were also identified from the bibliographies of articles obtained and the Transportation Research Information Service electronic database. Clinically relevant human studies written in English were reviewed. Results: Using a conceptual framework developed by W. H. Brouwer and F. K. Withaar (1997), the authors of the current review highlight driving-related obstacles for TBI survivors and aging adults and suggest that individuals aging with TBI may be at increased risk for driving-related problems. Implications: Areas for clinical consideration include seizures, sleepiness and fatigue, vision, cognition, driving assessment, and caregiver involvement. The need for further study of postacute driving assessment and rehabilitation is highlighted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chronic myelogenous leukemia: molecular and cellular aspects

Chronic myelogenous leukemia (CML) originates in a pluripotent hematopoietic stem cell of the bone marrow and is characterized by greatly increased numbers of granulocytes in the blood. Myeloid and other hematopoietic cell lineages are involved in the process of clonal proliferation and differentiation. After a period of 4-6 years the disease progresses to acute-stage leukemia. On the cellular level, CML is associated with a specific chromosome abnormality, the t(9; 22) reciprocal translocation that forms the Philadelphia (Ph) chromosome. The Ph chromosome is the result of a molecular rearrangement between the c-ABL proto-oncogene on chromosome 9 and the BCR (breakpoint cluster region) gene on chromosome 22. Most of ABL is linked with a truncated BCR. The BCR/ABL fusion gene codes for an 8-kb mRNA and a novel 210-kDa protein which has higher and aberrant tyrosine kinase activity than the normal c-ABL-coded counterpart. Phosphorylation of a number of substrates such as GAP, GRB-2, SHC, FES, CRKL, and paxillin is considered a decisive step in transformation. An etiological connection between BCR/ABL and leukemia is indicated by the observation that transgenic mice bearing a BCR/ABL DNA construct develop leukemia of B, T, and myeloid cell origin. CML cells proliferate and expand in an almost unlimited manner. Adhesion defects in bone marrow stromal cells have been proposed to explain the increased number of leukemic cells in the peripheral blood. However, findings of our laboratory have shown that the BCR/ABL chimeric protein that is expressed in transfected cells may, under certain conditions, also increase the adhesion to fibronectin via enhanced expression of integrin. Our previous immunocytological studies on the expression of beta1 and beta2 integrins have found no qualitative differences between normal and CML hematopoietic cells in vitro. Even long-term-cultured CML bone marrow or blood cells continuously express those adhesion molecules that are characteristic of the cytological type. Recent experiments indicate that certain early CML progenitors may adhere to the stromal layer in vitro similarly to their normal counterparts. They cannot be completely removed by long-term culture on allogeneic stromal cells. At present, the only curative therapy is transplantation of allogeneic hematopoietic stem cells. Based on the molecular and cellular state of knowledge of CML, new therapies are being developed. BCR/ABL antisense oligonucleotides, inhibitors of tyrosine kinase, peptide-specific adoptive immunotherapy or peptide vaccination, and restoration of hematopoiesis by autologous stem cell transplantation following CML cell purging are examples of important approaches to improving CML treatment.     

Analysis of the short-term DC-current gain variation during highcurrent density-low temperature stress of AlGaAs/GaAs heterojunctionbipolar transistors

Improving the reliability of AlGaAs/GaAs heterojunction bipolar transistors (HBT's) is one of the major issues in order to exploit their performance in future microwave systems at higher power and current densities. In this work, we show the following: (1) under very high current density (Jc>3×10⁴ A/cm²) the DC-current gain (B) of HBT's exhibits principally two effects: an increase (burn-in) or a decrease (degradation). Burn-in and degradation are initiated by different junction temperatures. No remarkable change of B is observed if Jc is lower than 2×10⁴ A/cm² . (2) Linear dependences on the collector current density and activation energies of about 0.4 eV are extracted both for burn-in and degradation. (3) By comparing devices fabricated on epitaxial layers with different DC-current gains a correlation between the value of B and the observed phenomena (i.e., burn in and degradation) is found. (4) Consequently, we discuss the roles of the extrinsic base surface, base-emitter junction, and material quality. Based on the measured data, we propose a hydrogen-related mechanism, which allows us to explain the observed degradation mode     

Driving errors of learner teens: Frequency,nature and their association with practice

Background

Despite demonstrating basic vehicle operations skills sufficient to pass a state licensing test, novice teen drivers demonstrate several deficits in tactical driving skills during the first several months of independent driving. Improving our knowledge of the types of errors made by teen permit holders early in the learning process would assist in the development of novel approaches to driver training and resources for parent supervision.

Methods

The purpose of the current analysis was to describe driving performance errors made by teens during the permit period, and to determine if there were differences in the frequency and type of errors made by teens: (1) in comparison to licensed, safe, and experienced adult drivers; (2) by teen and parent-supervisor characteristics; and (3) by teen-reported quantity of practice driving. Data for this analysis were combined from two studies: (1) the control group of teens in a randomized clinical trial evaluating an intervention to improve parent-supervised practice driving (n = 89 parent-teen dyads) and (2) a sample of 37 adult drivers (mean age 44.2 years), recruited and screened as an experienced and competent reference standard in a validation study of an on-road driving assessment for teens (tODA). Three measures of performance: drive termination (i.e., the assessment was discontinued for safety reasons), safety-relevant critical errors, and vehicle operation errors were evaluated at the approximate mid-point (12 weeks) and end (24 weeks) of the learner phase. Differences in driver performance were compared using the Wilcoxon rank sum test for continuous variables and Pearson's Chi-square test for categorical variables.

Results

10.4% of teens had their early assessment terminated for safety reasons and 15.4% had their late assessment terminated, compared to no adults. These teens reported substantially fewer behind the wheel practice hours compared with teens that did not have their assessments terminated: tODA_early (9.0 vs. 20.0, p < 0.001) and tODA_late (19.0 vs. 58.3, p < 0.001). With respect to critical driving errors, 55% of teens committed a total of 85 critical errors (range of 1–5 errors per driver) on the early tODA; by comparison, only one adult committed a critical error (p < 0.001). On the late tODA, 54% of teens committed 67 critical errors (range of 1–8 errors per driver) compared with only one adult (p < 0.001). No differences in teen or parent gender, parent/teen relationship type or parent prior experience teaching a teen to drive were observed between teens who committed a critical error on either route and teens that committed no critical errors. A borderline association between median teen-reported practice quantity and critical error commission was observed for the late tODA. The overall median proportion of vehicle operation errors for teens was higher than that of adults on both assessments, though median error proportions were less than 10% for both teens and adults.

Conclusion

In comparison to a group of experienced adult drivers, a substantially higher proportion of learner teens committed safety-relevant critical driving errors at both time points of assessment. These findings, as well as the associations between practice quantity and the driving performance outcomes studied suggest that further research is needed to better understand how teens might effectively learn skills necessary for safe independent driving while they are still under supervised conditions.     

The Application of a Digital Computer to the Control and Monitoring of a Proton Linear Accelerator

Preliminary design studies have been carried out on the control system for an 800-Mev proton linear accelerator based on the use of an on-line digital computer as the main controlling element. The accelerator system is divided into fifty-two subsections or modules. A module has complete control of all the equipment associated with it. Selected data and monitoring signals are transmitted on a time-shared basis to a central control computer. The functions which the computer performs in the control of the accelerator may be classified into Operational Control, Operational Supervision, and Data Monitoring and Handling. The operator gives instructions to the computer through interrupt lines. Commands to the modules and displays for the operator time-share a common channel in the computer output system. Synchronization of the input and output data flow is controlled by the computer through a timing unit. A comparison has been made of the computer-based control system with a possible alternate system which does not use a computer. The computer replaces much of the control and data handling equipment required by the alternate system. As a result, the costs of the two systems are comparable. However, the computer-based system is preferable since it has many functional advantages over the alternate system.