We report on stimulated Raman scattering in an approximately 1-meter-long hollow-core photonic crystal fiber filled with hydrogen gas under pressure. Light was guided and confined in the ...15-micrometer-diameter hollow core by a two-dimensional photonic bandgap. Using a pulsed laser source (pulse duration, 6 nanoseconds; wavelength, 532 nanometers), the threshold for Stokes (longer wavelength) generation was observed at pulse energies as low as 800 ± 200 nanojoules, followed by a coherent anti-Stokes (shorter wavelength) generation threshold at 3.4 ± 0.7 microjoules. The pump-to-Stokes conversion efficiency was 30 ± 3% at a pulse energy of only 4.5 microjoules. These energies are almost two orders of magnitude lower than any other reported energy, moving gas-based nonlinear optics to previously inaccessible parameter regimes of high intensity and long interaction length.
Cells exposed to extreme physicochemical or mechanical stimuli die in an uncontrollable manner, as a result of their immediate structural breakdown. Such an unavoidable variant of cellular demise is ...generally referred to as 'accidental cell death' (ACD). In most settings, however, cell death is initiated by a genetically encoded apparatus, correlating with the fact that its course can be altered by pharmacologic or genetic interventions. 'Regulated cell death' (RCD) can occur as part of physiologic programs or can be activated once adaptive responses to perturbations of the extracellular or intracellular microenvironment fail. The biochemical phenomena that accompany RCD may be harnessed to classify it into a few subtypes, which often (but not always) exhibit stereotyped morphologic features. Nonetheless, efficiently inhibiting the processes that are commonly thought to cause RCD, such as the activation of executioner caspases in the course of apoptosis, does not exert true cytoprotective effects in the mammalian system, but simply alters the kinetics of cellular demise as it shifts its morphologic and biochemical correlates. Conversely, bona fide cytoprotection can be achieved by inhibiting the transduction of lethal signals in the early phases of the process, when adaptive responses are still operational. Thus, the mechanisms that truly execute RCD may be less understood, less inhibitable and perhaps more homogeneous than previously thought. Here, the Nomenclature Committee on Cell Death formulates a set of recommendations to help scientists and researchers to discriminate between essential and accessory aspects of cell death.
This handbook presents a much-needed and comprehensive exploration of the rapidly growing fields of animal welfare and law. In recent years there has been increasing attention paid to our complex, ...multifaceted relationships with other animals, and in particular, the depth and breadth of various societal uses of animals. This has led to a reconsideration of their moral and social status, which has sometimes challenged the interests of those who use animals. In such a contested domain, sound evidence and reasoning become particularly important. Through firm commitment to such principles, this book explores the biological foundations for the moral consideration of animals and for evolving conceptualisations of animal welfare. It reviews in detail the welfare concerns associated with numerous forms of animal use. The inclusion of key recent developments such as climate change, pandemics, and antimicrobial resistance, ensures this text is among the most current in its field. The ethical implications of the various uses of animals by society are considered, and chapters provide important recommendations for reforms of practice, law, or policy. The status of animal law internationally, and in major world regions, is reviewed. Finally, the book considers human behavioural change and strategies for improving stakeholder communication and education. The handbook is essential reading for students and scholars of animal welfare, animal law and animal ethics everywhere, and for policy-makers and other professionals working in the animal welfare sector.
We report on visibly white supercontinuum generation in photonic crystal fibers using a sub ns pump source at 1064 nm. The spectra extend from below 400 nm to 2450 nm, some 50 nm further into the ...blue than previously reported spectra. The extra bandwidth which is achieved by a simple modification to the fiber structure gives a higher apparent color temperature and a truly "white" visual appearance. The mechanism for the generation of the deeper blue to ultraviolet frequencies is outlined and our modified fiber is compared with fibers which have been conventionally used for supercontinuum generation.
Single-Mode Photonic Band Gap Guidance of Light in Air Cregan, R. F.; Mangan, B. J.; Knight, J. C. ...
Science (American Association for the Advancement of Science),
09/1999, Letnik:
285, Številka:
5433
Journal Article
Recenzirano
The confinement of light within a hollow core (a large air hole) in a silica-air photonic crystal fiber is demonstrated. Only certain wavelength bands are confined and guided down the fiber, each ...band corresponding to the presence of a full two-dimensional band gap in the photonic crystal cladding. Singlemode vacuum waveguides have a multitude of potential applications from ultrahigh-power transmission to the guiding of cold atoms.
We report the fabrication of photonic crystal fibers with a continuously-decreasing zero-dispersion wavelength along their length. These tapered fibers are designed to extend the generation of ...supercontinuum spectra from the visible into the ultraviolet. We report on their performance when pumped with both nanosecond and picosecond sources at 1.064 microm. The supercontinuum spectra have a spectral width (measured at the 10 dB points) extending from 0.372 microm to beyond 1.75 microm. In an optimal configuration a flat (3 dB) spectrum from 395 to 850 nm, with a minimum spectral power density of 2 mW/nm was achieved, with a total continuum output power of 3.5 W. We believe that the shortest wavelengths were generated by cascaded four-wave mixing: the continuous decrease of the zero dispersion wavelength along the fiber length enables the phase-matching condition to be satisfied for a wide range of wavelengths into the ultraviolet, while simultaneously increasing the nonlinear coefficient of the fiber.
An effective and pain-free killing method is required to achieve the goal of euthanasia, a “good death”. Overdose of sodium pentobarbital (PB) by intraperitoneal (IP) injection is a widely accepted ...technique in laboratory rats, but questions remain regarding pain associated with administration. As PB rapidly causes sedation and loss of consciousness, most studies have relied on indirect evidence of pain. The objective of this study was to assess pain associated with IP PB using an appropriate vehicle control. Adult male and female Sprague Dawley (SD) and female Wistar rats (N = 84) were block randomised by sex and strain to receive one of three treatments: 1) 800 mg/kg PB (pH 11), 2) saline or 3) vehicle controls (pH 11 or 12.5). Behavior (Rat Grimace Scale (RGS), writhing, back arching) was evaluated at baseline, before loss of righting reflex (LORR, PB group), and at 80s, 151s and 10 min post-injection (PI; saline and vehicle control groups). In the PB group, mean time to LORR was 78 ± 7.9 seconds. In the vehicle control groups, RGS scores were increased at 151s PI (SD: p = 0.0002, 95%CI 0.73 to 0.20) from baseline, as was relative frequency of writhing (SD: p < 0.0001; Wistar; p = 0.0004). RGS scores remained elevated 10 mins PI (SD: p = 0.0005, 95%CI 0.71 to 0.18; Wistar: p = 0.0234, 95%CI 0.91 to 0.07) but the relative frequency of writhing did not (p > 0.999). The RGS scores and the relative frequency of writhing remained low in the PB and saline groups (p > 0.05). These results show that, vehicle controls for IP PB result in signs associated with pain, pain may not be experienced following IP PB when LORR occurs quickly, and that the effects of PB limit behavioral pain assessments.
Gas-phase materials are used in a variety of laser-based applications-for example, in high-precision frequency measurement, quantum optics and nonlinear optics. Their full potential has however not ...been realized because of the lack of a suitable technology for creating gas cells that can guide light over long lengths in a single transverse mode while still offering a high level of integration in a practical and compact set-up or device. As a result, solid-phase materials are still often favoured, even when their performance compares unfavourably with gas-phase systems. Here we report the development of all-fibre gas cells that meet these challenges. Our structures are based on gas-filled hollow-core photonic crystal fibres, in which we have recently demonstrated substantially enhanced stimulated Raman scattering, and which exhibit high performance, excellent long-term pressure stability and ease of use. To illustrate the practical potential of these structures, we report two different devices: a hydrogen-filled cell for efficient generation of rotational Raman scattering using only quasi-continuous-wave laser pulses; and acetylene-filled cells, which we use for absolute frequency-locking of diode lasers with very high signal-to-noise ratios. The stable performance of these compact gas-phase devices could permit, for example, gas-phase laser devices incorporated in a 'credit card' or even in a laser pointer.
Postpartum depression (PPD) affects approximately 13% of women and has a negative impact on mother and infant, hence reliable biological tests for early detection of PPD are essential. We aimed to ...identify robust predictive biomarkers for PPD using peripheral blood gene expression profiles in a hypothesis-free genome-wide study in a high-risk, longitudinal cohort.
We performed a genome-wide association study in a longitudinal discovery cohort comprising 62 women with psychopathology. Gene expression and hormones were measured in the first and third pregnancy trimesters and early postpartum (201 samples). The replication cohort comprised 24 women with third pregnancy trimester gene expression measures. Gene expression was measured on Illumina-Human HT12 v4 microarrays. Plasma estradiol and estriol were measured. Statistical analysis was performed in R.
We identified 116 transcripts differentially expressed between the PPD and euthymic women during the third trimester that allowed prediction of PPD with an accuracy of 88% in both discovery and replication cohorts. Within these transcripts, significant enrichment of transcripts implicated that estrogen signaling was observed and such enrichment was also evident when analysing published gene expression data predicting PPD from a non-risk cohort. While plasma estrogen levels were not different across groups, women with PPD displayed an increased sensitivity to estrogen signaling, confirming the previously proposed hypothesis of increased sex-steroid sensitivity as a susceptibility factor for PPD.
These results suggest that PPD can be robustly predicted in currently euthymic women as early as the third trimester and these findings have implications for predictive testing of high-risk women and prevention and treatment for PPD.
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