47 research outputs found
Generation of photovoltage in graphene on a femtosecond time scale through efficient carrier heating
Graphene is a promising material for ultrafast and broadband photodetection.
Earlier studies addressed the general operation of graphene-based
photo-thermoelectric devices, and the switching speed, which is limited by the
charge carrier cooling time, on the order of picoseconds. However, the
generation of the photovoltage could occur at a much faster time scale, as it
is associated with the carrier heating time. Here, we measure the photovoltage
generation time and find it to be faster than 50 femtoseconds. As a
proof-of-principle application of this ultrafast photodetector, we use graphene
to directly measure, electrically, the pulse duration of a sub-50 femtosecond
laser pulse. The observation that carrier heating is ultrafast suggests that
energy from absorbed photons can be efficiently transferred to carrier heat. To
study this, we examine the spectral response and find a constant spectral
responsivity between 500 and 1500 nm. This is consistent with efficient
electron heating. These results are promising for ultrafast femtosecond and
broadband photodetector applications.Comment: 6 pages, 4 figure
Improving the Prognostic Ability through Better Use of Standard Clinical Data - The Nottingham Prognostic Index as an Example
Background Prognostic factors and prognostic models play a key role in medical
research and patient management. The Nottingham Prognostic Index (NPI) is a
well-established prognostic classification scheme for patients with breast
cancer. In a very simple way, it combines the information from tumor size,
lymph node stage and tumor grade. For the resulting index cutpoints are
proposed to classify it into three to six groups with different prognosis. As
not all prognostic information from the three and other standard factors is
used, we will consider improvement of the prognostic ability using suitable
analysis approaches. Methods and Findings Reanalyzing overall survival data of
1560 patients from a clinical database by using multivariable fractional
polynomials and further modern statistical methods we illustrate suitable
multivariable modelling and methods to derive and assess the prognostic
ability of an index. Using a REMARK type profile we summarize relevant steps
of the analysis. Adding the information from hormonal receptor status and
using the full information from the three NPI components, specifically
concerning the number of positive lymph nodes, an extended NPI with improved
prognostic ability is derived. Conclusions The prognostic ability of even one
of the best established prognostic index in medicine can be improved by using
suitable statistical methodology to extract the full information from standard
clinical data. This extended version of the NPI can serve as a benchmark to
assess the added value of new information, ranging from a new single clinical
marker to a derived index from omics data. An established benchmark would also
help to harmonize the statistical analyses of such studies and protect against
the propagation of many false promises concerning the prognostic value of new
measurements. Statistical methods used are generally available and can be used
for similar analyses in other diseases
Exercise and the Prevention of Oesophageal Cancer (EPOC) study protocol: a randomized controlled trial of exercise versus stretching in males with Barrett's oesophagus
<p>Abstract</p> <p>Background</p> <p>Chronic gastro-oesophageal reflux disease and excessive body fat are considered principal causes of Barrett's oesophagus (a metaplastic change in the cells lining the oesophagus) and its neoplastic progression, oesophageal adenocarcinoma. Metabolic disturbances including altered levels of obesity-related cytokines, chronic inflammation and insulin resistance have also been associated with oesophageal cancer development, especially in males. Physical activity may have the potential to abrogate metabolic disturbances in males with Barrett's oesophagus and elicit beneficial reductions in body fat and gastro-oesophageal reflux symptoms. Thus, exercise may be an effective intervention in reducing oesophageal adenocarcinoma risk. However, to date this hypothesis remains untested.</p> <p>The 'Exercise and the Prevention of Oesophageal Cancer Study' will determine whether 24 weeks of exercise training will lead to alterations in risk factors or biomarkers for oesophageal adenocarcinoma in males with Barrett's oesophagus. Our primary outcomes are serum concentrations of leptin, adiponectin, tumour necrosis factor-alpha, C-reactive protein and interleukin-6 as well as insulin resistance. Body composition, gastro-oesophageal reflux disease symptoms, cardiovascular fitness and muscular strength will also be assessed as secondary outcomes.</p> <p>Methods/Design</p> <p>A randomized controlled trial of 80 overweight or obese, inactive males with Barrett's oesophagus will be conducted in Brisbane, Australia. Participants will be randomized to an intervention arm (60 minutes of moderate-intensity aerobic and resistance training, five days per week) or a control arm (45 minutes of stretching, five days per week) for 24 weeks. Primary and secondary endpoints will be measured at baseline (week 0), midpoint (week 12) and at the end of the intervention (week 24).</p> <p>Discussion</p> <p>Due to the increasing incidence and very high mortality associated with oesophageal adenocarcinoma, interventions effective in preventing the progression of Barrett's oesophagus are urgently needed. We propose that exercise may be successful in reducing oesophageal adenocarcinoma risk. This primary prevention trial will also provide information on whether the protective association between physical activity and cancer is causal.</p> <p>Trial Registration</p> <p>ACTRN12609000401257</p
Mathematical modelling of clostridial acetone-butanol-ethanol fermentation
Clostridial acetone-butanol-ethanol (ABE) fermentation features a remarkable shift in the cellular metabolic activity from acid formation, acidogenesis, to the production of industrial-relevant solvents, solventogensis. In recent decades, mathematical models have been employed to elucidate the complex interlinked regulation and conditions that determine these two distinct metabolic states and govern the transition between them. In this review, we discuss these models with a focus on the mechanisms controlling intra- and extracellular changes between acidogenesis and solventogenesis. In particular, we critically evaluate underlying model assumptions and predictions in the light of current experimental knowledge. Towards this end, we briefly introduce key ideas and assumptions applied in the discussed modelling approaches, but waive a comprehensive mathematical presentation. We distinguish between structural and dynamical models, which will be discussed in their chronological order to illustrate how new biological information facilitates the ‘evolution’ of mathematical models. Mathematical models and their analysis have significantly contributed to our knowledge of ABE fermentation and the underlying regulatory network which spans all levels of biological organization. However, the ties between the different levels of cellular regulation are not well understood. Furthermore, contradictory experimental and theoretical results challenge our current notion of ABE metabolic network structure. Thus, clostridial ABE fermentation still poses theoretical as well as experimental challenges which are best approached in close collaboration between modellers and experimentalists
Nicotinic acetylcholine receptors in attention circuitry: the role of layer VI neurons of prefrontal cortex
Patterns of relapse in older women diagnosed with estrogen receptor (ER)–positive early-stage breast cancer (BC) treated with lumpectomy without adjuvant endocrine therapy (ET)
Direct comparison of three different mathematical models in two independent datasets of EUSOMA certified centers to predict recurrence and survival in estrogen receptor-positive breast cancer: impact on clinical practice
Hot carrier multiplication on graphene/TiO2 Schottky nanodiodes
Carrier multiplication (i.e. generation of multiple electron–hole pairs from a single high-energy electron, CM) in graphene has been extensively studied both theoretically and experimentally, but direct application of hot carrier multiplication in graphene has not been reported. Here, taking advantage of efficient CM in graphene, we fabricated graphene/TiO(2) Schottky nanodiodes and found CM-driven enhancement of quantum efficiency. The unusual photocurrent behavior was observed and directly compared with Fowler’s law for photoemission on metals. The Fowler’s law exponent for the graphene-based nanodiode is almost twice that of a thin gold film based diode; the graphene-based nanodiode also has a weak dependence on light intensity—both are significant evidence for CM in graphene. Furthermore, doping in graphene significantly modifies the quantum efficiency by changing the Schottky barrier. The CM phenomenon observed on the graphene/TiO(2) nanodiodes can lead to intriguing applications of viable graphene-based light harvesting