Binding and interlayer force in the near-contact region of two graphite slabs: experiment and theory

Via a novel experiment, Liu \emph{et al.} [Phys. Rev. B, {\bf 85}, 205418 (2012)] estimated the graphite binding energy, specifically the cleavage energy, an important physical property of bulk graphite. We re-examine the data analysis and note that within the standard Lennard-Jones model employed, there are difficulties in achieving internal consistency in the reproduction of the graphite elastic properties. By employing similar models which guarantee consistency with the elastic constant, we find a wide range of model dependent binding energy values from the same experimental data. We attribute some of the difficulty in the determination of the binding energy to: i) limited theoretical understanding of the van der Waals dispersion of graphite cleavage, ii) the mis-match between the strong bending stiffness of the graphite-SiO$_2$ cantilever and the weak asymptotic inter-layer forces that are integrated over to produce the binding energy. We find, however, that the data does support determination of a maximum inter-layer force that is relatively model independent. We conclude that the peak force per unit area is $1.1 \pm 0.15$GPa for cleavage, and occurs at an inter-layer spacing of $0.377\pm 0.013$nm

Statistical Origin of Constituent-Quark Scaling in the QGP hadronization

Nonextensive statistics in a Blast-Wave model (TBW) is implemented to describe the identified hadron production in relativistic p+p and nucleus-nucleus collisions. Incorporating the core and corona components within the TBW formalism allows us to describe simultaneously some of the major observations in hadronic observables at the Relativistic Heavy-Ion Collider (RHIC): the Number of Constituent Quark Scaling (NCQ), the large radial and elliptic flow, the effect of gluon saturation and the suppression of hadron production at high transverse momentum (pT) due to jet quenching. In this formalism, the NCQ scaling at RHIC appears as a consequence of non-equilibrium process. Our study also provides concise reference distributions with a least chi2 fit of the available experimental data for future experiments and models.Comment: 4 pages, 3 figures; added two tables, explained a little bit more on TBW_p

General Relativistic Dynamics of Irrotational Dust: Cosmological Implications

The non--linear dynamics of cosmological perturbations of an irrotational collisionless fluid is analyzed within General Relativity. Relativistic and Newtonian solutions are compared, stressing the different role of boundary conditions in the two theories. Cosmological implications of relativistic effects, already present at second order in perturbation theory, are studied and the dynamical role of the magnetic part of the Weyl tensor is elucidated.Comment: 12 pages , DFPD 93/A/6

Layer-dependent anisotropic electronic structure of freestanding quasi-two dimensional MoS2

The anisotropy of the electronic transition is an important physical property not only determining the materials' optical property, but also revealing the underlying character of the electronic states involved. Here we used momentum-resolved electron energy-loss spectroscopy to study the evolution of the anisotropy of the electronic transition involving the low energy valence electrons in the free-standing MoS2 systems as the layer thickness was reduced to monolayer. We used the orientation and the spectral-density analysis to show that indirect to direct band-gap transition is accompanied by a three- to two-dimensional anisotropy cross-over. The result provides a logical explanation for the large sensitivity of indirect transition to the change of thickness compared with that for direct transition. By tracking the energy of indirect transition, we also revealed the asymmetric response of the valence band and conduction band to the quantum confinement effect. Our results have implication for future optoelectronic applications of atomic thin MoS2

Quantum Size Effects on the Chemical Sensing Performance of Two-Dimensional Semiconductors

We investigate the role of quantum confinement on the performance of gas sensors based on two-dimensional InAs membranes. Pd-decorated InAs membranes configured as H2 sensors are shown to exhibit strong thickness dependence, with ~100x enhancement in the sensor response as the thickness is reduced from 48 to 8 nm. Through detailed experiments and modeling, the thickness scaling trend is attributed to the quantization of electrons which favorably alters both the position and the transport properties of charge carriers; thus making them more susceptible to surface phenomena

Current Neonatal Skin Care Practices in Four African Sites

Data for this study on skin care practices and emollient use in four African sites were collected using in-depth interviews, focus-group discussions and observations. Respondents were mothers, grandmothers, fathers, health workers, birth attendants and people selling skin-care products. Analysis included content and framework analyses.Emollient use was a normative practice in all sites, with frequent application from an early age in most sites. There were variations in the type of emollients used, but reasons for use were similar and included improving the skin, keeping the baby warm, softening/strengthening the joints/bones, shaping the baby, ensuring flexibility and encouraging growth and weight gain. Factors that influenced emollient choice varied and included social pressure, cost, availability and deep-rooted traditional norms. Massage associated with application was strong and potentially damaging to the skin in some sites.Given the widespread use of emollients, the repeated exposure of newborns in the first month of life and the potential impact of emollients on mortality, trials such as those that have been conducted in Asia are needed in a range of African settings

Staff Time and Motion Assessment for Administration of Erythropoiesis-Stimulating Agents: A Two-Phase Pilot Study in Clinical Oncology Practices

BACKGROUND: Erythropoiesis-stimulating agents (ESAs) are used for the management of anaemia in patients with non-myeloid malignancies where anaemia is due to the effect of concomitant myelosuppressive chemotherapy. Assessing the impact of different ESA dosing regimens on office staff time and projected labour costs is an important component of understanding the potential for optimization of oncology practice efficiencies. OBJECTIVES: A two-phase study was conducted to evaluate staff time and labour costs directly associated with ESA administration in real-world oncology practice settings among cancer patients undergoing chemotherapy. The objective of Phase 1 was to determine the mean staff time required for the process of ESA administration in patients with anaemia due to concomitantly administered chemotherapy. The objective of Phase 2 was to quantify and compare the mean staff time and mean labour costs of ESA administered once weekly (qw) with ESA once every 3 weeks (q3w) over an entire course of chemotherapy. METHODS: Phase 1 was a prospective, cross-sectional time and motion study conducted in six private oncology practices in the US based on nine steps associated with ESA administration. Using findings from Phase 1, Phase 2 was conducted as a retrospective chart review to collect data on the number and types of visits in two private oncology practices for patients receiving a complete course of myelosuppressive chemotherapy. RESULTS: In Phase 1, the mean total time that clinic staff spent on ESA administration was 23.2 min for patient visits that included chemotherapy administration (n(chemo) = 37) and 21.5 min when only ESA was administered (n(ESAonly) = 36). In Phase 2, the mean duration of treatment was significantly longer for q3w than qw (53.84 days for qw vs. 113.38 for q3w, p < 0.0001); thus, analyses were adjusted using analysis of covariance (ANCOVA) for episode duration for between-group comparisons. Following adjustment by ANCOVA, qw darbepoetin alfa (DA) patients (n(qw) = 83) required more staff time for ESA + chemotherapy visits and ESA-only visits than q3w patients (n(q3w) = 118) over a course of chemotherapy. Overall, mean total staff time expended per chemotherapy course was greater for patients receiving qw versus q3w DA. Weekly DA dosing was associated with greater projected mean labour costs ($US38.16 vs.$US31.20 [average for 2007–2010]). CONCLUSIONS: The results from this real-world study demonstrate that oncology practices can attain staff time and labour costs savings through the use of q3w ESA. The degree of savings depends on the individual oncology practice’s staffing model and ESA administration processes, including those that allow for optimized synchronization of patient visits for ESA and chemotherapy administration. These findings indicate that additional research using standard ESA administration protocols for longer periods of time with a larger number of oncology practices and patients should be conducted to confirm these findings

In situ interface engineering for probing the limit of quantum dot photovoltaic devices.

Quantum dot (QD) photovoltaic devices are attractive for their low-cost synthesis, tunable band gap and potentially high power conversion efficiency (PCE). However, the experimentally achieved efficiency to date remains far from ideal. Here, we report an in-situ fabrication and investigation of single TiO2-nanowire/CdSe-QD heterojunction solar cell (QDHSC) using a custom-designed photoelectric transmission electron microscope (TEM) holder. A mobile counter electrode is used to precisely tune the interface area for in situ photoelectrical measurements, which reveals a strong interface area dependent PCE. Theoretical simulations show that the simplified single nanowire solar cell structure can minimize the interface area and associated charge scattering to enable an efficient charge collection. Additionally, the optical antenna effect of nanowire-based QDHSCs can further enhance the absorption and boost the PCE. This study establishes a robust 'nanolab' platform in a TEM for in situ photoelectrical studies and provides valuable insight into the interfacial effects in nanoscale solar cells

Oscillatory tunnel magnetoresistance in double barrier magnetic tunnel junctions

We report an unconventional oscillatory tunnel magnetoresistance as a function of the applied bias in double barrier magnetic tunnel junctions that were made of two Al2O3 barriers sandwiched by three ferromagnetic layers. When the center ferromagnetic layer is aligned antiparallel to the top and bottom magnetic layers, a distinct magnetoresistance oscillation appears with respect to the increase of the bias voltage at 4.2 K and at room temperature. The period of the oscillation is about 1.6 mV

"Why not bathe the baby today?": A qualitative study of thermal care beliefs and practices in four African sites

BACKGROUND: Recommendations for care in the first week of a newborn's life include thermal care practices such as drying and wrapping, skin to skin contact, immediate breastfeeding and delayed bathing. This paper examines beliefs and practices related to neonatal thermal care in three African countries. METHODS: Data were collected in the same way in each site and included 16-20 narrative interviews with recent mothers, eight observations of neonatal bathing, and in-depth interviews with 12-16 mothers, 9-12 grandmothers, eight health workers and 0-12 birth attendants in each site. RESULTS: We found similarities across sites in relation to understanding the importance of warmth, a lack of opportunities for skin to skin care, beliefs about the importance of several baths per day and beliefs that the Vernix caseosa was related to poor maternal behaviours. There was variation between sites in beliefs and practices around wrapping and drying after delivery, and the timing of the first bath with recent behavior change in some sites. There was near universal early bathing of babies in both Nigerian sites. This was linked to a deep-rooted belief about body odour. When asked about keeping the baby warm, respondents across the sites rarely mentioned recommended thermal care practices, suggesting that these are not perceived as salient. CONCLUSION: More effort is needed to promote appropriate thermal care practices both in facilities and at home. Programmers should be aware that changing deep rooted practices, such as early bathing in Nigeria, may take time and should utilize the current beliefs in the importance of neonatal warmth to facilitate behaviour change