Direct atom-by-atom chemical identification of nanostructures and defects of topological insulators

We present a direct atom-by-atom chemical identification of the nanostructures and defects of topological insulators (TIs) with a state-of-the-art atomic mapping technology. Combining this technique and density function theory calculations, we identify and explain the layer chemistry evolution of Bi(2)Te(3–x)Se(x) ternary TIs. We also reveal a long neglected but crucially important extended defect found to be universally present in Bi(2)Te(3) films, the seven-layer Bi(3)Te(4) nanolamella acceptors. Intriguingly, this defect is found to locally pull down the conduction band, leading to local n-type conductivity, despite being an acceptor which pins the Fermi energy near the valence band maximum. This nanolamella may explain inconsistencies in measured conduction type as well as open up a new route to manipulate bulk carrier concentration. Our work may pave the way to more thoroughly understand and tailor the nature of the bulk, as well as secure controllable bulk states for future applications in quantum computing and dissipationless devices.

Influence of active recovery on professional rugby union player's ability to harness postactivation potentiation

AIM

After postactivation potentiation (PAP) has been induced, current research recommends that, on average, an 8 minute passive recovery period is applied before engaging in subsequent dynamic exercise. However, given the importance of maximizing time usage during the warm-up of elite athletes, it is likely that further exercise would be incorporated into this time frame. This study aimed to examine the effects of passive and active recovery on the ability to utilize PAP.

METHODS

In a randomised and counter balanced design, 36 professional rugby union players completed two experimental trials involving a baseline countermovement jump (CMJ), followed by a PAP stimulus (3 x 3 repetitions at 87% of 1-RM back squat) and CMJ retesting after 8 minutes of passive or active recovery. The active recovery involved subjects performing ballistic bench throws (1 x 3 repetitions at 30% 1-RM bench press) 4 minutes after the lower body PAP stimulus. Data presented as mean±SD.

RESULTS

Baseline peak power output (PPO) was not different between conditions (P=0.61). CMJ PPO increased from baseline under both conditions, however the delta (mean±SD; passive +161±127 vs. active +116±44 W; P=0.03) and % change (passive 3.3±2.8 vs. active 2.3±0.9 %; P=0.03) in PPO was greater after the passive recovery, when compared to the active recovery.

CONCLUSION

In conclusion, the passive and active recovery periods both led to increases in lower-body PPO, nevertheless, the passive recovery elicited the greatest performance changes. However, the active recovery is a more practical option for athletes, as it maximizes time usage during warm-up.

Regulating energy transfer of excited carriers and the case for excitation-induced hydrogen dissociation on hydrogenated graphene

Understanding and controlling of excited carrier dynamics is of fundamental and practical importance, particularly in photochemistry and solar energy applications. However, theory of energy relaxation of excited carriers is still in its early stage. Here, using ab initio molecular dynamics (MD) coupled with time-dependent density functional theory, we show a coverage-dependent energy transfer of photoexcited carriers in hydrogenated graphene, giving rise to distinctively different ion dynamics. Graphene with sparsely populated H is difficult to dissociate due to inefficient transfer of the excitation energy into kinetic energy of the H. In contrast, H can easily desorb from fully hydrogenated graphane. The key is to bring down the H antibonding state to the conduction band minimum as the band gap increases. These results can be contrasted to those of standard ground-state MD that predict H in the sparse case should be much less stable than that in fully hydrogenated graphane. Our findings thus signify the importance of carrying out explicit electronic dynamics in excited-state simulations.

Limits on passivating defects in semiconductors: the case of Si edge dislocations

By minimizing the free energy while constraining dopant density, we derive a universal curve that relates the formation energy (E(form)) of doping and the efficiency of defect passivation in terms of segregation of dopants at defect sites. The universal curve takes the simple form of a Fermi-Dirac distribution. Our imposed constraint defines a chemical potential that assumes the role of "Fermi energy," which sets the thermodynamic limit on the E(form) required to overcome the effect of entropy such that dopant segregation at defects in semiconductors can occur. Using Si edge dislocation as an example, we show by first-principles calculations how to map the experimentally measurable passivation efficiency to our calculated E(form) by using the universal curve for typical n- and p-type substitutional dopants. We show that n-type dopants are ineffective. Among p-type dopants, B can satisfy the thermodynamic limit while improving electronic properties.

A study of naturally occurring cases of ovine foot abscess in New Zealand

A study was made of various aspects of 53 naturally occurring cases of foot abscess in sheep in New Zealand. Radiographic techniques were used to follow the progress of the lesion and from this it was concluded that foot abscess could be defined as an infection of the distal interphalangeal joint. The term foot abscess was considered preferable to the term "infective bulbar necrosis". The attack rate of foot abscess was reported to be higher for rams than for ewes and the condition was less prevalent during summer. Once infection was established in the distal interphalangeal joint a relatively uniform and thus predictable series of events took place that inevitably resulted in some permanent damage and deformity to the digit. If rupture of the axial collateral ligaments occurred, the joint became unstable and the degree of permanent deformity was greater. Treatment with antibiotics did not appear to markedly affect the progress of the lesion or the outcome, once infection had become established in the joint. Although the prognosis for complete recovery was poor, in most cases the foot healed sufficiently after a period of about two months to allow the animal to walk normally.

Hole-mediated hydrogen spillover mechanism in metal-organic frameworks

Hydrogen spillover on carbon-based systems has been proposed as a viable alternative for room-temperature storage. Given the strength of the C-H bonds, however, it is unclear if spillover indeed takes place in such materials. We performed a first-principles study of H spillover on IRMOF-1. Spillover becomes thermodynamically stable only at high H coverage with a calculated Gibbs free energy of -14  kJ/mol at ambient condition. In general, however, spillover may not proceed due to high-energy states at lower H coverage. We propose that hole doping can substantially lower the energies as well as barriers to enable spillover at ambient conditions.

Histological differentiation of skin toxicity between cetuximab, erlotinib and panitumumab (single ErbB1) and lapatinib (dual ErbB1/2) epidermal growth factor receptor inhibitors

e20617

Background: Epidermal growth factor receptor inhibition by monoclonal antibodies and tyrosine kinase inhibitors has demonstrated activity in solid tumors. However, blockade of EGFR in skin results in disabling skin toxicity that may lead to therapeutic dose modification or interruption. This study compares cutaneous histological alterations among four EGFR inhibitors (EGFRIs): cetuximab (C), erlotinib (E), lapatinib (L) and panitumumab (P). Methods: Punch skin biopsies from patients with papulopustular rash were collected from 8 patients per each EGFRI (n=32). Two dermatopathologists performed independent blinded assessment of epidermis, dermis, follicle and inflammatory infiltrates. Histologic features were rated as 0 (absent) or 1 (present), with the exception of dyskeratosis, rated from 0 (absent) to 2 (severe) and infiltrate, rated from 0 (absent) to 3 (most prominent). Where variation occurred, scores were reconciled and combined for analysis. Results: Epidermal atrophy was observed for C, E, L and P (range 0–1, median 1, 1, 0, 0.5, respectively) and neutrophilic follicular infiltrate was observed for C, E, L and P (range 0–3, median 0.5, 3, 0, 3, respectively). Neutrophilic dermal infiltrate (range 0–3) and follicular neutrophilic pustules (range 0–1) were most prevalent in P (median 0.5), whereas the median for C, E and L was 0. A mononuclear dermal infiltrate (range 0–3) was least prevalent with C (median 0) while E, L and P had a median of 0.5. Concretions (range 0–1) were most prevalent for E (median 1), whereas the median for C, L and P was 0. Conclusions: Lapatinib, a dual ErbB1/2 inhibitor, induced the least structural disarray and inflammation in the skin as measured by median scores for epidermal atrophy, neutrophilic dermal and follicular infiltrates, neutrophilic pustules and lack of bacterial concretions. These histological data confirm a more benign pattern of rash with lapatinib compared to single ErbB1 inhibitors.

[Table: see text]

The human CD94 gene encodes multiple, expressible transcripts including a new partner of NKG2A/B

CD94/NKG2A is an inhibitory receptor expressed by natural killer (NK) cells and a subset of CD8+ T cells. Ligation of CD94/NKG2A by its ligand HLA-E results in tyrosine phosphorylation of the NKG2A immunoreceptor tyrosine-based inhibitory motifs, and recruitment and activation of the SH2 domain-bearing tyrosine phosphatase-1, which in turn suppresses activation signals. The nkg2a gene encodes two isoforms, NKG2A and NKG2B, with the latter lacking the stem region. We identified three new alternative transcripts of the cd94 gene in addition to the originally described canonical CD94Full. One of the transcripts, termed CD94-T4, lacks the portion that encodes the stem region. CD94-T4 associates with both NKG2A and NKG2B, but preferentially associates with the latter. This is probably due to the absence of a stem region in both CD94-T4 and NKG2B. CD94-T4/NKG2B is capable of binding HLA-E and, when expressed in E6-1 Jurkat T cells, inhibits TCR mediated signals, demonstrating that this heterodimer is functional. Coevolution of stemless isoforms of CD94 and NKG2A that preferentially pair with each other to produce a functional heterodimer indicates that this may be more than a serendipitous event. CD94-T4/NKG2B may contribute to the plasticity of the NK immunological synapse by insuring an adequate inhibitory signal.

Family history of haematopoietic malignancies and non-Hodgkin's lymphoma risk in the California Teachers Study

Family history of haematopoietic malignancies appears to be a risk factor for non-Hodgkin's lymphoma (NHL), but whether risk varies by family member's gender is unclear. Among 121 216 women participating in the prospective California Teachers Study, NHL risk varied by type of haematopoietic malignancy and gender of the relative.

Prognosis in BRCA1, BRCA2 associated breast cancer (BC): a prospective Breast Cancer Family Registry (BCFR) international population-based cohort study

Abstract #2072

Hereditary BC occurs at a younger age and is associated with more adverse tumor-related features than sporadic breast cancer (BC) (defined here as BC in those with no 1st or 2nd degree family history of breast or ovarian cancer). Using pre-specified criteria, we assembled a population-based cohort of newly diagnosed BC at 3 centers: Ontario, Canada (1996-98), San Francisco Bay area, USA (1995-2000), Melbourne/Sydney, Australia (1991-1998). Medical information was obtained from medical records; women were followed prospectively for recurrence, new cancers and death. Pathology data were obtained from central review or pathology reports. BRCA1 and BRCA2 mutation testing was performed on 77% and 70% of cases, respectively (sporadic BC cases were not tested at 2 centers). Hereditary and sporadic BC cases were compared using Cox proportional hazards (stratified by center). 3215 eligible cases were enrolled in the BCFR, with a mean age at diagnosis of 46.9 years. Median follow-up was 7.61 years; 565 women had distant recurrences and 547 died. There were 92 cases with BRCA1 and 72 with BRCA2 mutations; 1549 (48.2%) had sporadic BC; the remainder had familial BC as defined above. BRCA1 mutations were associated with young age, estrogen and progesterone receptor (ER and PgR) negativity and high grade; BRCA2 mutations were associated with node positivity and high grade. Distant disease-free survival (DDFS) and overall survival (OS) did not differ significantly between BRCA1 carriers and sporadic cases in univariate or multivariate analyses. DDFS and OS were worse in BRCA2 carriers than in sporadic cases (HR 1.6, p=0.04 and HR 1.8, p=0.01, respectively) in univariate analyses but not in multivariate analyses (DDFS HR 1.0, p=0.98; OS HR 1.13, p=0.61). The small group of BRCA2 carriers who did not receive adjuvant chemotherapy had a significantly worse OS (multivariate HR 3.63, p = 0.005). Furthermore, BRCA2 carriers who received adjuvant tamoxifen had significantly worse OS than women with sporadic BC (HR=2.0, p=0.03). We conclude that BRCA1 and BRCA2 mutations do not independently impact DDFS or OS. Significantly worse outcomes were seen in BRCA2 carrier subgroups defined by adjuvant treatment; this requires further investigation and may have implications for clinical practice.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2072.

Reliability and validity of the revised Triple C: Checklist of Communicative Competencies for adults with severe and multiple disabilities

AIMS

Few tools are available to assess the communication skills of adults with severe and multiple disabilities functioning at unintentional to early symbolic levels. An exception is the Triple C: Checklist of Communicative Competencies. In this study, aspects of support worker and clinician agreement, internal consistency and construct validity of a revised version of the Triple C were explored.

METHOD

Triple C checklists were completed for 72 adults with severe intellectual disabilities (ID) by 118 support workers and stages were assigned by the researchers. Two support workers completed checklists for each of 68 adults with ID. Three researchers also conducted direct observations of 20 adults with ID.

RESULTS

The average support worker agreement for items across the five stages of the Triple C ranged from 81% to 87%; agreement for stage assignment based on first and second support worker checklists was moderate to high (k = 0.63). Internal consistency was high (KR20 = 0.97); the stages were found to tap one factor (accounting for approximately 74% of variance), interpreted to be unintentional to early symbolic communication. Agreements between stages based on researcher observations and support worker-completed checklists were 35% and 71% across first and second support workers.

CONCLUSION

The revised Triple C provides a reliable means of gathering data on which to determine the communication skills of adults with severe and multiple disabilities. The results support a collaborative use of the Triple C, such that a speech-language pathologist or other communication specialist works with a support worker to ensure understanding of the skills observed and development of appropriate intervention strategies.

Calculations for displacive ω-phase transformations in Ti-Al alloys with Nb additions at finite temperature

We examine by means of first-principles calculations the bcc-like (bcc: body centered cubic) to ω-like phase transformations in Ti-Al alloys with Nb additions at finite temperature. To simulate the alloy we use different discrete atomic configurations in a six atom unit cell of the stoichiometry Ti(3)Al(2)Nb. Calculated ground state energies show an instability in the ternary Ti(3)Al(2)Nb alloy against the ω structure type atomic displacement. To better understand the role of entropy in the stability/instability of these systems, the first-principles calculations are extended to finite temperature by including various contributions to the free energy. In particular, the vibrational free energy is calculated within a quasiharmonic approximation. It is shown that the bcc structure is stabilized by the contribution of the low energy modes to the lattice entropy against ω type atomic displacements. We find that configurational entropy plays a major role in the ω to B8(2) transformation. Calculated lattice parameters and transition temperatures are found to be in excellent agreement with experiment.