Seeded growth of highly luminescent CdSe/CdS nanoheterostructures with rod and tetrapod morphologies

We have demonstrated that seeded growth of nanocrystals offers a convenient way to design nanoheterostructures with complex shapes and morphologies by changing the crystalline structure of the seed. By using CdSe nanocrystals with wurtzite and zinc blende structure as seeds for growth of CdS nanorods, we synthesized CdSe/CdS heterostructure nanorods and nanotetrapods, respectively. Both of these structures showed excellent luminescent properties, combining high photoluminescence efficiency (approximately 80 and approximately 50% for nanorods and nanotetrapods, correspondingly), giant extinction coefficients (approximately 2 x 10(7) and approximately 1.5 x 10(8) M(-1) cm(-1) at 350 nm for nanorods and nanotetrapods, correspondingly), and efficient energy transfer from the CdS arms into the emitting CdSe core.     

Design issues for adaptive control charts

Adaptive control charts allow the components of the quality‐monitoring scheme to vary in order to obtain improved performance over non‐adaptive control charts. Research has centered on components such as the sample size, time between samples, warning limits, and control limits and has recommended a variety of schemes, many of which are optimal in some sense. In practice, there are many other adaptive schemes that are near optimal, which will still yield considerable improvement over non‐adaptive control charts. In addition, the impact of parameter estimation on adaptive control chart performance must be taken into consideration. Based on the simulation results shown here, adaptive control charts should only be used for mature processes, where a sufficient amount of Phase I data have been obtained to ensure that the estimated control limits are accurate. When evaluating control chart performance, we consider initial state performance measures for simplicity and note that the conclusions obtained here apply to steady‐state performance measures. The evaluation of performance measures is easily handled by the Markov chain approach detailed in the Appendix. Copyright © 2008 John Wiley & Sons, Ltd.     

Structure–Property Relationships in Lanthanide‐Doped Upconverting Nanocrystals: Recent Advances in Understanding Core–Shell Structures

The production of upconverting nanostructures with tailored optical properties is of major technological interest, and rapid progress toward the realization of such production has been made in recent years. Ultimately, accurate understanding of nanostructure organization will lead to design rules for accurately tailoring optical properties. Here, the context of open questions still of general importance to the upconversion and nanocrystal communities is presented, with a particular emphasis on the structure–property relationships of core–shell upconverting nanocrystals. Although the optical properties of the latter have been thoroughly investigated, little is known regarding their atomic‐scale organization. Indeed, solving the atomic‐scale structure of such nanomaterials is challenging because of their intrinsic nonperiodic nature. Familiar concepts of crystallography are no longer appropriate; chemical and structural modulation waves must be introduced. To reveal the exact core–shell structures, innovative characterization techniques need to be applied and developed, as discussed herein. The continued development and application of structural characterization techniques will be vital to consolidate the currently incomplete link between atomic‐scale structure and upconversion properties. This will ultimately provide a valuable contribution to the emerging detailed guidelines on how to better design upconverting nanostructures to achieve given optical properties in terms of efficiency, absorption, spectral emission, and dynamics.     

Ventilation in the patient with unilateral lung disease

Severe ULD presents a challenge in ventilator management because of the marked asymmetry in the mechanics of the two lungs. The asymmetry may result from significant decreases or increases in the compliance of the involved lung. Traditional ventilator support may fail to produce adequate gas exchange in these situations and has the potential to cause further deterioration. Fortunately, conventional techniques can be safely and effectively applied in the majority of cases without having to resort to less familiar and potentially hazardous forms of support. In those circumstances when conventional ventilation is unsuccessful in restoring adequate gas exchange, lateral positioning and ILV have proved effective at improving and maintaining gas exchange. Controlled trials to guide clinical decision making are lacking. In patients who have processes associated with decreased compliance in the involved lung, lateral positioning may be a simple method of improving gas exchange but is associated with many practical limitations. ILV in these patients is frequently successful when differential PEEP is applied with the higher pressure to the involved lung. In patients in whom the pathology results in distribution of ventilation favoring the involved lung, particularly BPF, ILV can be used to supply adequate support while minimizing flow through the fistula and allowing it to close. The application of these techniques should be undertaken with an understanding of the pathophysiology of the underlying process; the reported experience with these techniques, including indications and successfully applied methods; and the potential problems encountered with their use. Fortunately, these modalities are infrequently required, but they provide a critical means of support when conventional techniques fail.     

Using Dissertations to Examine Potential Bias in Child and Adolescent Clinical Trials.

The major youth psychotherapy meta-analyses have relied on published studies, which may have led to biased effect size estimates. To examine this possibility, the authors compared 121 dissertations with 134 published studies and found the following: (a) few differences on individual methodological variables, but, overall, stronger methodology in dissertations; (b) no differences in the steps taken to ensure treatment integrity; and (c) a mean dissertation effect size less than half that of published studies. The effect size difference remained robust across tests controlling for all reliable method differences. The findings suggest that dissertations are so strong, both methodologically and clinically, that they warrant inclusion in child psychotherapy meta-analyses and that previous meta-analyses, by excluding them, may have overestimated treatment effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive–behavioral therapy versus usual clinical care for youth depression: An initial test of transportability to community clinics and clinicians.

Community clinic therapists were randomized to (a) brief training and supervision in cognitive–behavioral therapy (CBT) for youth depression or (b) usual care (UC). The therapists treated 57 youths (56% girls), ages 8–15, of whom 33% were Caucasian, 26% were African American, and 26% were Latino/Latina. Most youths were from low-income families and all had Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) depressive disorders (plus multiple comorbidities). All youths were randomized to CBT or UC and treated until normal termination. Session coding showed more use of CBT by CBT therapists and more psychodynamic and family approaches by UC therapists. At posttreatment, depression symptom measures were at subclinical levels, and 75% of youths had no remaining depressive disorder, but CBT and UC groups did not differ on these outcomes. However, compared with UC, CBT was (a) briefer (24 vs. 39 weeks), (b) superior in parent-rated therapeutic alliance, (c) less likely to require additional services (including all psychotropics combined and depression medication in particular), and (d) less costly. The findings showed advantages for CBT in parent engagement, reduced use of medication and other services, overall cost, and possibly speed of improvement—a hypothesis that warrants testing in future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High aspect ratio meso-scale parts enabled by wire micro-EDM

Micro-electro discharge machining (EDM) is a subtractive meso-scale machining process. The Agie Excellence 2F wire micro EDM is capable of machining with a 25 micron diameter wire electrode and positioning the work piece to within ±1.5 microns. The over-burn gap can be controlled to within 3 microns to obtain a minimum feature radius of about 16 microns while achieving submicron surface finish and an imperceptible recast layer. For example, meso-scale gears that require vertical sidewalls and contour tolerances to within 3 microns can be wire EDMed into a variety of conductive materials. Material instabilities can affect the dimensional precision of machined meso-scale parts by material relaxation during the machining process. A study is done to investigate the machining performance of the wire micro EDM process by machining a high aspect ratio meso-scale part into a variety of metals (e.g. 304L stainless steel, Nitronic 60 Austentic Stainless, Beryllium Copper, and Titanium). Machining performance parameters such as, profile tolerance, perpendicularity, and repeatability are compared for the different materials. Pertinent inspection methods desirable for meso-scale quality assurance tasks are also evaluated. Sandia National Laboratories is developing meso-scale electro-mechanical components and has an interest in the assembly implications of piece parts fabricated by various meso-scale manufacturing processes. Although the wire EDM process is typically used to fabricate 2½ dimensional features, these features can be machined into a 3 dimensional part having other features such as hubs and chamfers to facilitate assembly.     

The effects of n-6 polyunsaturated fatty acids on the expression of nm-23 in human cancer cells

Over an interval of approximately six months beginning in October 1993, most haemophilia A patients in Canada were switched from a plasma-derived intermediate-purity factor VIII concentrate (i.p. VIII) to a recombinant factor VIII (rVIII). In order to determine the consequence of this change in therapy on progression of HIV infection, we gathered surveillance data on clinical status and CD4 and CD8 cell counts in those patients who were HIV seropositive at the time of switching concentrates. Data were recorded at the time of switchover, annually for 2 years thereafter, and retrospectively at a point 1 year prior to the switch. CD4 cells fell significantly over the study period. Multiple direct comparisons revealed that this decline was restricted to the time intervals which included the final year in which patients received intermediate-purity factor VIII concentrate (i.p. VIII). In the 2 year interval in which rVIII was used exclusively, there was a nonsignificant fall in CD4 cells. Changes in CD4 cells did not correlate with the intensity of exposure to either i.p.VIII or rVIII. CD8 cells did not fall significantly over the study period. There was no obvious reduction in the incidence of death or clinical progression over the 2 years in which rVIII was used. However, we are hopeful that the stabilizing trend in CD4 cell counts which followed the introduction of rVIII will be predictive of corresponding clinical stabilization over the coming years.     

A computational study of sulfur bridged cyclooctatetraenophanes

Calculations of several thiacyclooctatetraenophanes predicted, as part of their overall geometry, substantial flattening of the cyclooctatetraene (COT) structures relative to the tub conformation generally associated with the COT molecule. The COT structures were approximately parallel to each other and the interplanar distances were predicted to be within 2.787-2.803 angstrom at the DFT/UB3YLP level of calculation. DFT/UB3LYP optimized geometries afforded significant delocalization of the COT structures in each of the thiacyclooctatetraenophanes. Hartree-Fock (HF) methods and the semi-empirical Austin Model 1 (AM1) method deviated significantly from the DFT/UB3LYP optimized geometries. Cyclooctatetraenes can undergo reversible sizing by oxidation and reduction reactions to form the aromatic dication and aromatic dianion, respectively, which could then be used to prepare molecular backbones for polymeric organometallic molecular wires. The number of bridges and the introduction of the sulfur atom have been investigated to provide disparate synthetic routes.