Relating 3D Geometry and Photoelectrochemical Activity of WO3-loaded n-Si Nanowires: Design Rules for Photoelectrodes

Nanostructured electrodes for photoelectrochemical (PEC) applications, such as water splitting, have rather low photocurrent density regarding their highly enlarged surface area compared to plain electrodes. This demands for further understanding of the relation between the 3D geometry and the PEC activity. To this end, we fabricate WO3/Si nanowire array photoanodes with various nanowire lengths (1.3 µm, 2.7 µm, 3.2 µm and 3.8 µm) and different WO3 thicknesses (10 nm, 30 nm and 50 nm) using wet chemical etching for nanostructuring of Si and atomic layer deposition for the deposition of WO3. It is found that by increasing the etching time, the nanowires become longer and the top surface area decreases. The photocurrent density first increases and then decreases with increasing Si etching time. This behaviour can be explained by different and opposite effects regarding absorption, geometry and materials specific properties. Particularly, the decrease of the photocurrent density can be due to: First, the longer the nanowires the heavier the recombination of the photogenerated carriers. Second, the long-time Si etching results in a loss of top part of the nanowire arrays. Because of shadowing, the WO3 located at the top part of the nanowires is more effective than that at the bottom part for the WO3/Si nanowire arrays and therefore the photocurrent is decreased. It reveals a trade-off between the top part surface area and the length of the nanowires. This study contributes to a better understand of the relation between the geometry of nanostructures and the performance of PEC electrodes.</p

How does the substrate affect the Raman and excited state spectra of a carbon nanotube?

We study the optical properties of a single, semiconducting single-walled carbon nanotube (CNT) that is partially suspended across a trench and partially supported by a SiO2-substrate. By tuning the laser excitation energy across the E33 excitonic resonance of the suspended CNT segment, the scattering intensities of the principal Raman transitions, the radial breathing mode (RBM), the G-mode and the D-mode show strong resonance enhancement of up to three orders of magnitude. In the supported part of the CNT, despite a loss of Raman scattering intensity of up to two orders of magnitude, we recover the E33 excitonic resonance suffering a substrate-induced red shift of 50 meV. The peak intensity ratio between G-band and D-band is highly sensitive to the presence of the substrate and varies by one order of magnitude, demonstrating the much higher defect density in the supported CNT segments. By comparing the E33 resonance spectra measured by Raman excitation spectroscopy and photoluminescence (PL) excitation spectroscopy in the suspended CNT segment, we observe that the peak energy in the PL excitation spectrum is red-shifted by 40 meV. This shift is associated with the energy difference between the localized exciton dominating the PL excitation spectrum and the free exciton giving rise to the Raman excitation spectrum. High-resolution Raman spectra reveal substrate-induced symmetry breaking, as evidenced by the appearance of additional peaks in the strongly broadened Raman G band. Laser-induced line shifts of RBM and G band measured on the suspended CNT segment are both linear as a function of the laser excitation power. Stokes/anti-Stokes measurements, however, reveal an increase of the G phonon population while the RBM phonon population is rather independent of the laser excitation power.Comment: Revised manuscript, 20 pages, 8 figure

Macroscopic quantum phenomena in Josephson structures

The Josephson effect is a probe with unparalleled capabilities for the study of a variety of macroscopic quantum phenomena. This is a survey of important achievements and challenging trends, in particular macroscopic quantum tunneling and energy level quantization. We focus on high-T-C superconducting structures and recent research on nanostructures

The Origin of High Activity of Amorphous MoS2 in the Hydrogen Evolution Reaction

Molybdenum disulfide (MoS2) and related transition metal chalcogenides can replace expensive precious metal catalysts such as Pt for the hydrogen evolution reaction (HER). The relations between the nanoscale properties and HER activity of well‐controlled 2H and Li‐promoted 1T phases of MoS2, as well as an amorphous MoS2 phase, have been investigated and a detailed comparison is made on Mo−S and Mo−Mo bond analysis under operando HER conditions, which reveals a similar bond structure in 1T and amorphous MoS2 phases as a key feature in explaining their increased HER activity. Whereas the distinct bond structure in 1T phase MoS2 is caused by Li+ intercalation and disappears under harsh HER conditions, amorphous MoS2 maintains its intrinsic short Mo−Mo bond feature and, with that, its high HER activity. Quantum‐chemical calculations indicate similar electronic structures of small MoS2 clusters serving as models for amorphous MoS2 and the 1T phase MoS2, showing similar Gibbs free energies for hydrogen adsorption (ΔGH*) and metallic character

Mindfulness based interventions in multiple sclerosis: a systematic review

&lt;b&gt;Background&lt;/b&gt; Multiple sclerosis (MS) is a stressful condition; depression, anxiety, pain and fatigue are all common problems. Mindfulness based interventions (MBIs) mitigate stress and prevent relapse in depression and are increasingly being used in healthcare. However, there are currently no systematic reviews of MBIs in people with MS. This review aims to evaluate the effectiveness of MBIs in people with MS.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Methods&lt;/b&gt; Systematic searches were carried out in seven major databases, using both subject headings and key words. Papers were screened, data extracted, quality appraised, and analysed by two reviewers independently, using predefined criteria. Study quality was assessed using the Cochrane Collaboration risk of bias tool. Perceived stress was the primary outcome. Secondary outcomes include mental health, physical health, quality of life, and health service utilisation. Statistical meta-analysis was not possible. Disagreements were adjudicated by a third party reviewer.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Results&lt;/b&gt; Three studies (n = 183 participants) were included in the final analysis. The studies were undertaken in Wales (n = 16, randomised controlled trial - (RCT)), Switzerland (n = 150, RCT), and the United States (n = 17, controlled trial). 146 (80%) participants were female; mean age (SD) was 48.6 (9.4) years. Relapsing remitting MS was the main diagnostic category (n = 123, 67%); 43 (26%) had secondary progressive disease; and the remainder were unspecified. MBIs lasted 6–8 weeks; attrition rates were variable (5-43%); all employed pre- post- measures; two had longer follow up; one at 3, and one at 6 months. Socio-economic status of participants was not made explicit; health service utilisation and costs were not reported. No study reported on perceived stress. All studies reported quality of life (QOL), mental health (anxiety and depression), physical (fatigue, standing balance, pain), and psychosocial measures. Statistically significant beneficial effects relating to QOL, mental health, and selected physical health measures were sustained at 3- and 6- month follow up.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Conclusion&lt;/b&gt; From the limited data available, MBIs may benefit some MS patients in terms of QOL, mental health, and some physical health measures. Further studies are needed to clarify how MBIs might best serve the MS population.&lt;p&gt;&lt;/p&gt

Homeomorphic Embedding for Online Termination of Symbolic Methods

Well-quasi orders in general, and homeomorphic embedding in particular, have gained popularity to ensure the termination of techniques for program analysis, specialisation, transformation, and verification. In this paper we survey and discuss this use of homeomorphic embedding and clarify the advantages of such an approach over one using well-founded orders. We also discuss various extensions of the homeomorphic embedding relation. We conclude with a study of homeomorphic embedding in the context of metaprogramming, presenting some new (positive and negative) results and open problems

Expression of the RNA helicase DDX3 and the hypoxia response in breast cancer

&lt;p&gt;Aims: DDX3 is an RNA helicase that has antiapoptotic properties, and promotes proliferation and transformation. In addition, DDX3 was shown to be a direct downstream target of HIF-1α (the master regulatory of the hypoxia response) in breast cancer cell lines. However, the relation between DDX3 and hypoxia has not been addressed in human tumors. In this paper, we studied the relation between DDX3 and the hypoxic responsive proteins in human breast cancer.&lt;/p&gt; &lt;p&gt;Methods and Results: DDX3 expression was investigated by immunohistochemistry in breast cancer in comparison with hypoxia related proteins HIF-1α, GLUT1, CAIX, EGFR, HER2, Akt1, FOXO4, p53, ERα, COMMD1, FER kinase, PIN1, E-cadherin, p21, p27, Transferrin receptor, FOXO3A, c-Met and Notch1. DDX3 was overexpressed in 127 of 366 breast cancer patients, and was correlated with overexpression of HIF-1α and its downstream genes CAIX and GLUT1. Moreover, DDX3 expression correlated with hypoxia-related proteins EGFR, HER2, FOXO4, ERα and c-Met in a HIF-1α dependent fashion, and with COMMD1, FER kinase, Akt1, E-cadherin, TfR and FOXO3A independent of HIF-1α.&lt;/p&gt; &lt;p&gt;Conclusions: In invasive breast cancer, expression of DDX3 was correlated with overexpression of HIF-1α and many other hypoxia related proteins, pointing to a distinct role for DDX3 under hypoxic conditions and supporting the oncogenic role of DDX3 which could have clinical implication for current development of DDX3 inhibitors.&lt;/p&gt

Association of Vitamin B12 Deficiency with Fatigue and Depression after Lacunar Stroke

Background: In lacunar stroke patients vitamin B12 deficiency is often found and a relationship with the degree of periventricular white matter lesions (pWMLs) is suggested. Given the known relationships between WMLs and depression and between depression and fatigue after stroke, we studied both depression and fatigue in lacunar stroke patients with and without vitamin B12 deficiency. Methods: In 40 first-ever lacunar stroke patients vitamin B12 levels were determined and self-report questionnaires for fatigue and depression were completed three months after stroke. Results: Lacunar stroke patients with vitamin B12 deficiency (N = 13) reported significantly more fatigue (90.7 versus 59.4; p =.001) and depressive symptoms (6.62 versus 3.89; p,.05) than those without (N = 27). In regression analyses, vitamin B12 deficiency was significantly and independently associated with the presence of severe fatigue and clinically significant depression. Conclusions: Our preliminary results suggest a relationship between vitamin B12 deficiency and increased levels of fatigue and depression in lacunar stroke patients. If these findings could be replicated in a larger and general stroke sample, thi