Continued monitoring of LMXBs with the Faulkes Telescopes

The Faulkes Telescope Project is an educational and research arm of the Las Cumbres Observatory Global Telescope Network (LCOGTN). It has two 2-metre robotic telescopes, located at Haleakala on Maui (FT North) and Siding Spring in Australia (FT South). It is planned for these telescopes to be complemented by a research network of eighteen 1-metre telescopes, along with an educational network of twenty-eight 0.4-metre telescopes, providing 24 hour coverage of both northern and southern hemispheres. We have been conducting a monitoring project of 13 low-mass X-ray binaries (LMXBs) using FT North since early 2006. The introduction of FT South has allowed us to extend this to monitor a total of 30 LMXBs (see target list, Section 4). New instrumentation will allow us to expand this project to include both infrared wavelengths (z and y band) and spectroscopy. Brighter targets (~ 16 - 18 mag.) are imaged weekly in V, R and i’ bands (SNR ~ 50), while fainter ones (> 18 mag.) are observed only in i’ band (SNR ~ 20). We alter this cadence in response to our own analysis or Astronomers Telegrams (ATels)

First-passage theory of exciton population loss in single-walled carbon nanotubes reveals micron-scale intrinsic diffusion lengths

One-dimensional crystals have long range translational invariance which manifests as long exciton diffusion lengths, but such intrinsic properties are often obscured by environmental perturbations. We use a first-passage approach to model single-walled carbon nanotube (SWCNT) exciton dynamics (including exciton-exciton annihilation and end effects) and compare it to results from both continuous-wave and multi-pulse ultrafast excitation experiments to extract intrinsic SWCNT properties. Excitons in suspended SWCNTs experience macroscopic diffusion lengths, on the order of the SWCNT length, (1.3-4.7 um) in sharp contrast to encapsulated samples. For these pristine samples, our model reveals intrinsic lifetimes (350-750 ps), diffusion constants (130-350 cm^2/s), and absorption cross-sections (2.1-3.6 X 10^-17 cm^2/atom) among the highest previously reported.and diffusion lengths for SWCNTs.Comment: 6 pages, 3 figure

The chemical vapour deposition of MoTe2 thin films and their applications

The isolation of graphene, a single layer of graphite, in 2004 highlighted the important role dimensionality plays in determining the properties of materials. This discovery led to attention being focused on other types of two-dimensional materials, in particular the family of compounds known as the transition metal dichalcogenides (TMDCs). The chemical and structural diversity of the TMDCs means they exhibit many exotic properties that make them interesting for both fundamental science and suitable for many applications. Of the TMDCs, perhaps one of the most interesting is molybdenum ditelluride. MoTe2 can exist in two polymorphs, one of which is semiconducting and the other metallic and their properties vary depending on their thickness. This polymorphism also presents a challenge towards the synthesis of phase pure MoTe2 films by chemical vapour deposition (CVD), a method which shows promise for being able to produce these materials at scale and with high throughput. Both polymorphs tend to exist at the typical deposition temperatures used and as such are in competition with each other. This work sought to develop a CVD set up that can retain control over the phase and thickness of the MoTe2 product films. Following the determination of conditions that allowed for the deposition of 2H- and 1T’-MoTe2, the films were characterised extensively with a variety of techniques to ensure that they were indeed phase pure. Subsequently, films of both phases with a variety of thicknesses were produced, highlighting the ability of the CVD method to accurately control the thickness and phase of MoTe2. The method also allowed for the simultaneous deposition of 1T’- and 2H-MoTe2 on the same substrate by taking advantage of the type of precursor layer used. The CVD grown films of MoTe2 were then trialled in two different applications. Firstly, as electrocatalytic films for the production of hydrogen from water, where the impact of the phase and film thickness on the catalytic activity was studied. Secondly, 1T’-MoTe2 was applied as a surface enhanced Raman spectroscopy substrate. A preliminary study was conducted using a model analyte, rhodamine 6G, with the intention of confirming the activity of the 1T’-phase and performing brief thickness dependent measurements. Subsequently a thorough study was conducted using a clinically relevant biomolecule, β-sitosterol, as an analyte. This highlighted the potential applications of the TMDCs as SERS substrates with the achieved limit of detection of 10-9 M being one of the lowest reported so far for sterol-like lipophilic molecules. Furthermore, the mechanism of Raman enhancement was determined to be related to the formation of a surface complex between the analyte and 1T’-film, which was then characterised extensively. Finally, the Mo3Sb7-xTex (where x = 0, 1, 1.6 and 2) group of compounds were synthesised and investigated. These materials offer an interesting opportunity to see how varying the tellurium amount impacts their performance as hydrogen evolution catalysts. It was found that increasing the amount of tellurium led to increased catalytic performance as well as improving the stability of the materials. Efforts were made to utilise the previously developed CVD system to try and deposit thin films of Mo3Sb7 and Mo3Sb5.4Te1.6 as there are no literature reports of this being achieved. This was somewhat successful but overall hampered by the difficulty in characterising the product films

Vitamin D supplementation does not improve human skeletal muscle contractile properties in insufficient young males

Vitamin D may be a regulator of skeletal muscle function, although human trials investigating this hypothesis are limited to predominantly elderly populations. We aimed to assess the effect of oral vitamin D3 in healthy young males upon skeletal muscle function

Determination of ubiquitin fitness landscapes under different chemical stresses in a classroom setting

Ubiquitin is essential for eukaryotic life and varies in only 3 amino acid positions between yeast and humans. However, recent deep sequencing studies indicate that ubiquitin is highly tolerant to single mutations. We hypothesized that this tolerance would be reduced by chemically induced physiologic perturbations. To test this hypothesis, a class of first year UCSF graduate students employed deep mutational scanning to determine the fitness landscape of all possible single residue mutations in the presence of five different small molecule perturbations. These perturbations uncover \u27shared sensitized positions\u27 localized to areas around the hydrophobic patch and the C-terminus. In addition, we identified perturbation specific effects such as a sensitization of His68 in HU and a tolerance to mutation at Lys63 in DTT. Our data show how chemical stresses can reduce buffering effects in the ubiquitin proteasome system. Finally, this study demonstrates the potential of lab-based interdisciplinary graduate curriculum

Effect of carbohydrate feeding on the bone metabolic response to running

Bone resorption is increased after running, with no change in bone formation. Feeding during exercise might attenuate this increase, preventing associated problems for bone. This study investigated the immediate and short-term bone metabolic responses to carbohydrate (CHO) feeding during treadmill running. Ten men completed two 7-day trials, once being fed CHO (8% glucose immediately before, every 20 min during, and immediately after exercise at a rate of 0.7 g CHO·kg body mass-1·h-1) and once being fed placebo (PBO). On day 4 of each trial, participants completed a 120-min treadmill run at 70% of maximal oxygen consumption (VO2 max). Blood was taken at baseline (BASE), immediately after exercise (EE), after 60 (R1) and 120 (R2) min of recovery, and on three follow-up days (FU1-FU3). Markers of bone resorption [COOH-terminal telopeptide region of collagen type 1 (β-CTX)] and formation [NH2-terminal propeptides of procollagen type 1 (P1NP)] were measured, along with osteocalcin (OC), parathyroid hormone (PTH), albumin-adjusted calcium (ACa), phosphate, glucagon-like peptide-2 (GLP-2), interleukin-6 (IL-6), insulin, cortisol, leptin, and osteoprotogerin (OPG). Area under the curve was calculated in terms of the immediate (BASE, EE, R1, and R2) and short-term (BASE, FU1, FU2, and FU3) responses to exercise. β-CTX, P1NP, and IL-6 responses to exercise were significantly lower in the immediate postexercise period with CHO feeding compared with PBO (β-CTX: P=0.028; P1NP: P=0.021; IL-6: P=0.036), although there was no difference in the short-term response (β-CTX: P=0.856; P1NP: P=0.721; IL-6: P=0.327). No other variable was significantly affected by CHO feeding during exercise. We conclude that CHO feeding during exercise attenuated the β-CTX and P1NP responses in the hours but not days following exercise, indicating an acute effect of CHO feeding on bone turnover

The investigation of Mo3Sb7 and Mo3Sb7-xTex as electrocatalysts for the hydrogen evolution reaction

Proton exchange membrane electrolysers are considered one of the most promising devices for storing the excess, intermittent energy generated by renewable sources through water electrolysis. Hydrogen production by electrolysis is currently facilitated by expensive noble metals that act as electrocatalysts. Therefore, the future development of the hydrogen evolution reaction (HER) relies on sourcing relatively inexpensive materials that can act as alternative catalysts to noble metals. Herein, we explore the catalytic activity of Mo3Sb7 towards the HER and the effect that tellurium doping has on the system. Mo3Sb7 showed a large overpotential of 570 mV at a current density of 10 mA cm-2. However, the replacement of Sb with Te increased the stability of the catalyst and in the case of Mo3Sb5.4Te1.6 reduced the overpotential required to achieve 10 mA cm-2 to 511 mV. This improvement in performance is also mirrored in the Tafel slopes of the materials with Mo3Sb5.4Te1.6 having a Tafel slope of 136.2 ± 0.5 mV dec-1 compared to 167.5 ± 0.6 mV dec-1 exhibited by Mo3Sb7. Although the three compounds tested are suboptimal HER catalysts, compared to state-of-the-art materials, they nevertheless provide an interesting system to observe the effects of tellurium doping on the catalytic performance

Population screening for colorectal cancer means getting FIT:the past, present, and future of colorectal cancer screening using the fecal immunochemical test for hemoglobin (FIT)

Fecal immunochemical tests for hemoglobin (FIT) are changing the manner in which colorectal cancer (CRC) is screened. Although these tests are being performed worldwide, why is this test different from its predecessors? What evidence supports its adoption? How can this evidence best be used? This review addresses these questions and provides an understanding of FIT theory and practices to expedite international efforts to implement the use of FIT in CRC screening