Rayleigh-B\'{e}nard convection in a homeotropically aligned nematic liquid crystal

We report experimental results for convection near onset in a thin layer of a homeotropically aligned nematic liquid crystal heated from below as a function of the temperature difference $\Delta T$ and the applied vertical magnetic field $H$ and compare them with theoretical calculations. The experiments cover the field range 8 \alt h \equiv H/ H_{F} \alt 80 ($H_F =$ is the Fr\'eedericksz field). For $h$ less than a codimension-two field $h_{ct} \simeq 46$ the bifurcation is subcritical and oscillatory, with travelling- and standing-wave transients. Beyond $h_{ct}$ the bifurcation is stationary and subcritical until a tricritical field $h_t= 57.2$ is reached, beyond which it is supercritical. The bifurcation sequence as a function of $h$ found in the experiment confirms the qualitative aspects of the theoretical predictions. However, the value of $h_{ct}$ is about 10% higher than the predicted value and the results for $k_c$ are systematically below the theory by about 2% at small $h$ and by as much as 7% near $h_{ct}$. At $h_{ct}$, $k_c$ is continuous within the experimental resolution whereas the theory indicates a 7% discontinuity. The theoretical tricritical field $h_t^{th} = 51$ is somewhat below the experimental one. The fully developed flow above $R_c$ for $h < h_{ct}$ is chaotic. For $h_{ct} < h < h_t$ the subcritical stationary bifurcation also leads to a chaotic state. The chaotic states persist upon reducing the Rayleigh number below $R_c$, i.e. the bifurcation is hysteretic. Above the tricritical field $h_t$, we find a bifurcation to a time independent pattern which within our resolution is non-hysteretic.Comment: 15 pages incl. 23 eps figure

Perspective: The first ten years of broadband chirped pulse Fourier transform microwave spectroscopy

Since its invention in 2006, the broadband chirped pulse Fourier transform spectrometer has transformed the field of microwave spectroscopy. The technique enables the collection of a ≥10 GHz bandwidth spectrum in a single shot of the spectrometer, which allows broadband, high-resolution microwave spectra to be acquired several orders of magnitude faster than what was previously possible. We discuss the advantages and challenges associated with the technique and look back on the first ten years of chirped pulse Fourier transform spectroscopy. In addition to enabling faster-than-ever structure determination of increasingly complex species, the technique has given rise to an assortment of entirely new classes of experiments, ranging from chiral sensing by three-wave mixing to microwave detection of multichannel reaction kinetics. However, this is only the beginning. Future generations of microwave experiments will make increasingly creative use of frequency-agile pulse sequences for the coherent manipulation and interrogation of molecular dynamics.United States. Dept. of Energy. Office of Basic Energy Sciences. Chemical Sciences, Geosciences, & Biosciences Division (Grant DE-FG0287ER13671)National Science Foundation (U.S.) (Grant CHE-1361865)Petroleum Research Fund (Grant 50650-ND6

Measuring electrophysiological connectivity by power envelope correlation: a technical review on MEG methods

The human brain can be divided into multiple areas, each responsible for different aspects of behaviour. Healthy brain function relies upon efficient connectivity between these areas and, in recent years, neuroimaging has been revolutionised by an ability to estimate this connectivity. In this paper we discuss measurement of network connectivity using magnetoencephalography (MEG), a technique capable of imaging electrophysiological brain activity with good (~5mm) spatial resolution and excellent (~1ms) temporal resolution. The rich information content of MEG facilitates many disparate measures of connectivity between spatially separate regions and in this paper we discuss a single metric known as power envelope correlation. We review in detail the methodology required to measure power envelope correlation including i) projection of MEG data into source space, ii) removing confounds introduced by the MEG inverse problem and iii) estimation of connectivity itself. In this way, we aim to provide researchers with a description of the key steps required to assess envelope based functional networks, which are thought to represent an intrinsic mode of coupling in the human brain. We highlight the principal findings of the techniques discussed, and furthermore, we show evidence that this method can probe how the brain forms and dissolves multiple transient networks on a rapid timescale in order to support current processing demand. Overall, power envelope correlation offers a unique and verifiable means to gain novel insights into network coordination and is proving to be of significant value in elucidating the neural dynamics of the human connectome in health and disease

Mechanisms by which sialylated milk oligosaccharides impact bone biology in a gnotobiotic mouse model of infant undernutrition

Undernutrition in children is a pressing global health problem, manifested in part by impaired linear growth (stunting). Current nutritional interventions have been largely ineffective in overcoming stunting, emphasizing the need to obtain better understanding of its underlying causes. Treating Bangladeshi children with severe acute malnutrition with therapeutic foods reduced plasma levels of a biomarker of osteoclastic activity without affecting biomarkers of osteoblastic activity or improving their severe stunting. To characterize interactions among the gut microbiota, human milk oligosaccharides (HMOs), and osteoclast and osteoblast biology, young germ-free mice were colonized with cultured bacterial strains from a 6-mo-old stunted infant and fed a diet mimicking that consumed by the donor population. Adding purified bovine sialylated milk oligosaccharides (S-BMO) with structures similar to those in human milk to this diet increased femoral trabecular bone volume and cortical thickness, reduced osteoclasts and their bone marrow progenitors, and altered regulators of osteoclastogenesis and mediators of Th2 responses. Comparisons of germ-free and colonized mice revealed S-BMO-dependent and microbiota-dependent increases in cecal levels of succinate, increased numbers of small intestinal tuft cells, and evidence for activation of a succinate-induced tuft cell signaling pathway linked to Th2 immune responses. A prominent fucosylated HMO, 2'-fucosyllactose, failed to elicit these changes in bone biology, highlighting the structural specificity of the S-BMO effects. These results underscore the need to further characterize the balance between, and determinants of, osteoclastic and osteoblastic activity in stunted infants/children, and suggest that certain milk oligosaccharides may have therapeutic utility in this setting

Smelling the past: a case study for identification, analysis and archival of historic pot-pourri as a heritage smell

Our interaction with heritage objects and spaces is very often limited to a visual experience. However, our perception is multisensory, whether deliberate or not; olfactory stimuli can significantly affect our experience of the world, including cultural heritage. Little is known about the smells of the past, and the olfactory properties of heritage objects and places are not systematically preserved and protected. This work presents scientific analysis of a potpourri identified as historic, by sampling and identification of volatile organic compounds using thermal desorption – gas chromatography with time-of-flight mass spectrometric detection (TD-GC-TOF-MS). The odour of the potpourri was also characterised using GC with olfactometric detection and evaluated by a sensory panel. The chemical and sensory information was used to create a historic potpourri odour wheel, as a conservation tool for archival and public engagement purposes

'Like building a plane and flying it all in one go': an interview study of infection prevention and control in Australian general practice during the first 2 years of the SARS-CoV-2 pandemic.

OBJECTIVES: General practitioners (GPs) and their staff have been at the frontline of the SARS-CoV-2 pandemic in Australia. However, their experiences of responding to and managing the risks of viral transmission within their facilities are poorly described. The aim of this study was to describe the experiences, and infection prevention and control (IPC) strategies adopted by general practices, including enablers of and challenges to implementation, to contribute to our understanding of the pandemic response in this critical sector. DESIGN: Semistructured interviews were conducted in person, by telephone or online video conferencing software, between November 2020 and August 2021. PARTICIPANTS: Twenty general practice personnel working in New South Wales, Australia, including nine GPs, one general practice registrar, four registered nurses, one nurse practitioner, two practice managers and two receptionists. RESULTS: Participants described implementing wide-ranging repertoires of IPC strategies-including telehealth, screening of patients and staff, altered clinic layouts and portable outdoor shelters, in addition to appropriate use of personal protective equipment (PPE)-to manage the demands of the SARS-CoV-2 pandemic. Strategies were proactive, influenced by the varied contexts of different practices and the needs and preferences of individual GPs as well as responsive to local, state and national requirements, which changed frequently as the pandemic evolved. CONCLUSIONS: Using the 'hierarchy of controls' as a framework for analysis, we found that the different strategies adopted in general practice often functioned in concert with one another. Most strategies, particularly administrative and PPE controls, were subjected to human variability and so were less reliable from a human factors perspective. However, our findings highlight the creativity, resilience and resourcefulness of general practice staff in developing, implementing and adapting their IPC strategies amidst constantly changing pandemic conditions

Understanding the needs and preferences for cancer care among First Nations people: an integrative review.

This systematic review aimed to identify the needs and preferences for cancer care services among Australian First Nations people. An integrative review was conducted. A wide range of search terms were used to increase the sensitivity and specificity of the searches in electronic databases. Methodological quality assessment, data extraction, was conducted independently by two reviewers, and a narrative synthesis was conducted. Forty‐two studies were included. A total of 2965 Australian First Nations adults, both men and women of various ages across the lifespan, were represented; no First Nations children affected by cancer were represented in the studies. Three themes emerged which included: (1) discrimination, racism and trauma, resulting from colonization, directly impacted First National people's cancer care experience; (2) cultural ways of knowing, being and doing are fundamental to how First Nations people engage with cancer care services; and (3) First Nations people need culturally safe person‐centred cancer care services that address practical needs. Most participants represented in this review experienced discrimination, racism and trauma, resulting from colonization, which directly negatively impacted Aboriginal peoples' cancer care experience. While the Optimal Cancer Pathway (OCP) was launched in Australia several years ago, people with cancer may continue to experience distressing unmet care needs. Our team includes both First Nations people, non‐First Nations researchers and healthcare professionals with expertise in cancer care. The researchers employed decolonizing restorative approaches to ensure voice, respect, accountability and reciprocity in this review work. Members of the multidisciplinary team including nurses and policymakers should reflect on these findings, ensure that they have up‐to‐date cultural safety training and stand together with Indigenous and non‐Indigenous cancer leaders to take proactive steps to stamp out and dismantle oppression in health, and safely implement the OCP