Probing Majorana neutrinos with double-β decay

A discovery that neutrinos are Majorana fermions would have profound implications for particle physics and cosmology. The Majorana character of neutrinos would make possible the neutrinoless double-β (0νββ) decay, a matter-creating process without the balancing emission of antimatter. The GERDA Collaboration searches for the 0νββ decay of ⁷⁶Ge by operating bare germanium detectors in an active liquid argon shield. With a total exposure of 82.4 kg⋅year, we observe no signal and derive a lower half-life limit of T _1/2 > 0.9 × 10²⁶ years (90% C.L.). Our T _1/2 sensitivity, assuming no signal, is 1.1 × 10²⁶ years. Combining the latter with those from other 0νββ decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 to 0.16 electron volts.

Proton-driven plasma wakefield acceleration in AWAKE

In this article, we briefly summarize the experiments performed during the first run of the Advanced Wakefield Experiment, AWAKE, at CERN (European Organization for Nuclear Research). The final goal of AWAKE Run 1 (2013-2018) was to demonstrate that 10-20 MeV electrons can be accelerated to GeV energies in a plasma wakefield driven by a highly relativistic self-modulated proton bunch. We describe the experiment, outline the measurement concept and present first results. Last, we outline our plans for the future. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities

We give direct experimental evidence for the observation of the full transverse self-modulation of a long, relativistic proton bunch propagating through a dense plasma. The bunch exits the plasma with a periodic density modulation resulting from radial wakefield effects. We show that the modulation is seeded by a relativistic ionization front created using an intense laser pulse copropagating with the proton bunch. The modulation extends over the length of the proton bunch following the seed point. By varying the plasma density over one order of magnitude, we show that the modulation frequency scales with the expected dependence on the plasma density, i.e., it is equal to the plasma frequency, as expected from theory.

Experimental Observation of Plasma Wakefield Growth Driven by the Seeded Self-Modulation of a Proton Bunch

We measure the effects of transverse wakefields driven by a relativistic proton bunch in plasma with densities of 2.1×10^{14} and 7.7×10^{14}  electrons/cm^{3}. We show that these wakefields periodically defocus the proton bunch itself, consistently with the development of the seeded self-modulation process. We show that the defocusing increases both along the bunch and along the plasma by using time resolved and time-integrated measurements of the proton bunch transverse distribution. We evaluate the transverse wakefield amplitudes and show that they exceed their seed value (<15  MV/m) and reach over 300  MV/m. All these results confirm the development of the seeded self-modulation process, a necessary condition for external injection of low energy and acceleration of electrons to multi-GeV energy levels.

Mechanisms Underlying Overactive Bladder and Interstitial Cystitis/Painful Bladder Syndrome

The bladder is innervated by extrinsic afferents that project into the dorsal horn of the spinal cord, providing sensory input to the micturition centers within the central nervous system. Under normal conditions, the continuous activation of these neurons during bladder distension goes mostly unnoticed. However, for patients with chronic urological disorders such as overactive bladder syndrome (OAB) and interstitial cystitis/painful bladder syndrome (IC/PBS), exaggerated bladder sensation and altered bladder function are common debilitating symptoms. Whilst considered to be separate pathological entities, there is now significant clinical and pre-clinical evidence that both OAB and IC/PBS are related to structural, synaptic, or intrinsic changes in the complex signaling pathways that mediate bladder sensation. This review discusses how urothelial dysfunction, bladder permeability, inflammation, and cross-organ sensitisation between visceral organs can regulate this neuroplasticity. Furthermore, we discuss how the emotional affective component of pain processing, involving dysregulation of the HPA axis and maladaptation to stress, anxiety and depression, can exacerbate aberrant bladder sensation and urological dysfunction. This review reveals the complex nature of urological disorders, highlighting numerous interconnected mechanisms in their pathogenesis. To find appropriate therapeutic treatments for these disorders, it is first essential to understand the mechanisms responsible, incorporating research from every level of the sensory pathway, from bladder to brain.

Acceleration of electrons in the plasma wakefield of a proton bunch

High-energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. To increase the energy of the particles or to reduce the size of the accelerator, new acceleration schemes need to be developed. Plasma wakefield acceleration^1–5, in which the electrons in a plasma are excited, leading to strong electric fields (so called ‘wakefields’), is one such promising acceleration technique. Experiments have shown that an intense laser pulse^6–9 or electron bunch^10,11 traversing a plasma can drive electric fields of tens of gigavolts per metre and above—well beyond those achieved in conventional radio-frequency accelerators (about 0.1 gigavolt per metre). However, the low stored energy of laser pulses and electron bunches means that multiple acceleration stages are needed to reach very high particle energies^5,12. The use of proton bunches is compelling because they have the potential to drive wakefields and to accelerate electrons to high energy in a single acceleration stage¹³. Long, thin proton bunches can be used because they undergo a process called self-modulation^14–16, a particle–plasma interaction that splits the bunch longitudinally into a series of high-density microbunches, which then act resonantly to create large wakefields. The Advanced Wakefield (AWAKE) experiment at CERN^17–19 uses high-intensity proton bunches—in which each proton has an energy of 400 gigaelectronvolts, resulting in a total bunch energy of 19 kilojoules—to drive a wakefield in a ten-metre-long plasma. Electron bunches are then injected into this wakefield. Here we present measurements of electrons accelerated up to two gigaelectronvolts at the AWAKE experiment, in a demonstration of proton-driven plasma wakefield acceleration. Measurements were conducted under various plasma conditions and the acceleration was found to be consistent and reliable. The potential for this scheme to produce very high-energy electron bunches in a single accelerating stage²⁰ means that our results are an important step towards the development of future high-energy particle accelerators^21,22.

Electron acceleration to very high energies is achieved in a single step by injecting electrons into a ‘wake’ of charge created in a 10-metre-long plasma by speeding long proton bunches.

DIBI, a polymeric hydroxypyridinone iron chelator, reduces ocular inflammation in local and systemic endotoxin-induced uveitis

BACKGROUND/OBJECTIVE

Non-infectious uveitis is an inflammatory disease of the eye commonly treated by corticosteroids, though important side effects may result. A main mediator of inflammation are oxygen free radicals generated in iron-dependent pathways. As such, we investigated the efficacy of a novel iron chelator, DIBI, as an anti-inflammatory agent in local and systemic models of endotoxin induced uveitis (EIU).

METHODS

Firstly, the effects of DIBI in systemic EIU in Lewis rats were established. 2 hours post intravenous LPS or LPS/DIBI injections, leukocyte activation and functional capillary density (FCD) were examined using intravital microscopy (IVM) of the iridial microcirculation. Secondly, the toxicity of DIBI was evaluated in BALB/C mice for both acute and chronic dosages through gross ocular examination, intraocular pressure measurements and hematoxylin-eosin staining of ocular tissue. Lastly, three groups of BALB/C mice, control, LPS or DIBI + LPS, were studied to evaluate the effectiveness of DIBI in treating local EIU. Five hours post-local intravitreal (i.v) injection, leukocyte activation and capillary density were examined via IVM.

RESULTS

Treatment of systemic EIU with DIBI resulted in a reduction of leukocyte activation and FCD improvement within the iridial microcirculation. Toxicity studies suggested that acute and chronic DIBI administration had no adverse effects in the eye. In the local EIU model, DIBI was shown to reduce leukocyte activation and restored the FCD/DCD ratio, providing evidence for its anti-inflammatory properties.

CONCLUSIONS

Our study has provided evidence that DIBI has anti-inflammatory effects in experimental uveitis. Additionally, no local ocular toxicity was observed.

Improved Limit on Neutrinoless Double-β Decay of ^{76}Ge from GERDA Phase II

The GERDA experiment searches for the lepton-number-violating neutrinoless double-β decay of ^{76}Ge (^{76}Ge→^{76}Se+2e^{-}) operating bare Ge diodes with an enriched ^{76}Ge fraction in liquid argon. The exposure for broad-energy germanium type (BEGe) detectors is increased threefold with respect to our previous data release. The BEGe detectors feature an excellent background suppression from the analysis of the time profile of the detector signals. In the analysis window a background level of 1.0_{-0.4}^{+0.6}×10^{-3}  counts/(keV kg yr) has been achieved; if normalized to the energy resolution this is the lowest ever achieved in any 0νββ experiment. No signal is observed and a new 90% C.L. lower limit for the half-life of 8.0×10^{25}  yr is placed when combining with our previous data. The expected median sensitivity assuming no signal is 5.8×10^{25}  yr.

Voltage-gated sodium channels: (NaV )igating the field to determine their contribution to visceral nociception

Chronic visceral pain, altered motility and bladder dysfunction are common, yet poorly managed symptoms of functional and inflammatory disorders of the gastrointestinal and urinary tracts. Recently, numerous human channelopathies of the voltage-gated sodium (NaV ) channel family have been identified, which induce either painful neuropathies, an insensitivity to pain, or alterations in smooth muscle function. The identification of these disorders, in addition to the recent utilisation of genetically modified NaV mice and specific NaV channel modulators, has shed new light on how NaV channels contribute to the function of neuronal and non-neuronal tissues within the gastrointestinal tract and bladder. Here we review the current pre-clinical and clinical evidence to reveal how the nine NaV channel family members (NaV 1.1-NaV 1.9) contribute to abdominal visceral function in normal and disease states.

Multiple sodium channel isoforms mediate the pathological effects of Pacific ciguatoxin-1

Human intoxication with the seafood poison ciguatoxin, a dinoflagellate polyether that activates voltage-gated sodium channels (Na_V), causes ciguatera, a disease characterised by gastrointestinal and neurological disturbances. We assessed the activity of the most potent congener, Pacific ciguatoxin-1 (P-CTX-1), on Na_V1.1–1.9 using imaging and electrophysiological approaches. Although P-CTX-1 is essentially a non-selective Na_V toxin and shifted the voltage-dependence of activation to more hyperpolarising potentials at all Na_V subtypes, an increase in the inactivation time constant was observed only at Na_V1.8, while the slope factor of the conductance-voltage curves was significantly increased for Na_V1.7 and peak current was significantly increased for Na_V1.6. Accordingly, P-CTX-1-induced visceral and cutaneous pain behaviours were significantly decreased after pharmacological inhibition of Na_V1.8 and the tetrodotoxin-sensitive isoforms Na_V1.7 and Na_V1.6, respectively. The contribution of these isoforms to excitability of peripheral C- and A-fibre sensory neurons, confirmed using murine skin and visceral single-fibre recordings, reflects the expression pattern of Na_V isoforms in peripheral sensory neurons and their contribution to membrane depolarisation, action potential initiation and propagation.

GHz modulation detection using a streak camera: Suitability of streak cameras in the AWAKE experiment

Using frequency mixing, a modulated light pulse of ns duration is created. We show that, with a ps-resolution streak camera that is usually used for single short pulse measurements, we can detect via an FFT detection approach up to 450 GHz modulation in a pulse in a single measurement. This work is performed in the context of the AWAKE plasma wakefield experiment where modulation frequencies in the range of 80-280 GHz are expected.

PD-1 expression by canine T cells and functional effects of PD-1 blockade

The co-inhibitory checkpoint molecule programmed death receptor 1 (PD-1) can trigger T cell functional exhaustion upon binding to its ligand PD-L1 expressed on tumour cells or macrophages. PD-1 blocking antibodies have generated remarkable results in human cancer patients, including inducing durable responses in a number of advanced cancers. Therefore, monoclonal antibodies specific for canine PD-1 were assessed for T cell binding and induction of functional activation. A total of 5-10% of CD4 T cells and 20-25% of CD8 T cells from healthy dogs expressed PD-1, and PD-1 expression was upregulated on T cells from dogs with cancer. Functionally, PD-1 antibodies significantly enhanced T-cell activation, as assessed by proliferation and interferon-gamma (IFN-γ) production. PD-1 antibodies also reversed T-cell suppression induced by canine soluble PD-L1 and by tumour cells and tumour explant fragments. These findings indicate that PD-1 antibodies have potential for use in cancer immunotherapy in dogs.

Immune regulation of canine tumour and macrophage PD-L1 expression

Expression of programmed cell death receptor ligand 1 (PD-L1) on tumor cells has been associated with immune escape in human and murine cancers, but little is known regarding the immune regulation of PD-L1 expression by tumor cells and tumor-infiltrating macrophages in dogs. Therefore, 14 canine tumor cell lines, as well as primary cultures of canine monocytes and macrophages, were evaluated for constitutive PD-L1 expression and for responsiveness to immune stimuli. We found that PD-L1 was expressed constitutively on all canine tumor cell lines evaluated, although the levels of basal expression were very variable. Significant upregulation of PD-L1 expression by all tumor cell lines was observed following IFN-γ exposure and by exposure to a TLR3 ligand. Canine monocytes and monocyte-derived macrophages did not express PD-L1 constitutively, but did significantly upregulate expression following treatment with IFN-γ. These findings suggest that most canine tumors express PD-L1 constitutively and that both innate and adaptive immune stimuli can further upregulate PD-L1 expression. Therefore the upregulation of PD-L1 expression by tumor cells and by tumor-infiltrating macrophages in response to cytokines such as IFN-γ may represent an important mechanism of tumor-mediated T-cell suppression in dogs as well as in humans.

Results on neutrinoless double-β decay of 76Ge from phase I of the GERDA experiment

Neutrinoless double beta decay is a process that violates lepton number conservation. It is predicted to occur in extensions of the standard model of particle physics. This Letter reports the results from phase I of the Germanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope (76)Ge. Data considered in the present analysis have been collected between November 2011 and May 2013 with a total exposure of 21.6 kg yr. A blind analysis is performed. The background index is about 1 × 10(-2) counts/(keV kg yr) after pulse shape discrimination. No signal is observed and a lower limit is derived for the half-life of neutrinoless double beta decay of (76)Ge, T(1/2)(0ν) >2.1 × 10(25) yr (90% C.L.). The combination with the results from the previous experiments with (76)Ge yields T(1/2)(0ν)>3.0 × 10(25) yr (90% C.L.).

Exploring fecal indicator bacteria in a constructed stormwater wetland

Microbial pollution in surface waters is a concern throughout the world, with both public health and economic implications. One contributing source to such pollution is stormwater runoff, often treated using various types of stormwater control measures. However, relatively little is known regarding microbe sequestration in constructed stormwater wetlands (CSWs), one type of commonly installed stormwater control measure. In this study, indicator bacteria concentrations in both the water and sediment of a CSW were evaluated at multiple locations. Results suggested that fecal coliform concentrations in stormwater runoff decrease through the system, with relatively consistent concentrations noted throughout the second half of the wetland. This potentially indicates a baseline concentration of fecal coliform is present due to internal processes such as animal activity and microbial persistence. However, wetland sediments showed little E. coli present during most sampling events, with minimal patterns existing with respect to sediment sampling location. CSW designs should promote optimization of hydraulic retention time and minimization of stormwater velocities to promote sedimentation and degradation of microbes by way of wetland treatment functions.

Inclusive K(S);(0)K(S);(0) resonance production in ep collisions at HERA

Inclusive K_{S};{0}K_{S};{0} production in ep collisions at the DESY ep collider HERA was studied with the ZEUS detector using an integrated luminosity of 0.5 fb;{-1}. Enhancements in the mass spectrum were observed and are attributed to the production of f_{2}(1270)/a_{2};{0}(1320), f_{2};{'}(1525) and f_{0}(1710). Masses and widths were obtained using a fit which takes into account theoretical predictions based on SU(3) symmetry arguments, and are consistent with the Particle Data Group values. The f_{0}(1710) state, which has a mass consistent with a glueball candidate, was observed with a statistical significance of 5 standard deviations. However, if this state is the same as that seen in gammagamma-->K_{S};{0}K_{S};{0}, it is unlikely to be a pure glueball state.

Phytate and phytase: consequences for protein utilisation

The excretion of large amounts of P in effluent from intensive pig and poultry units is indicative of the poor availability of phytate-bound P in plant-derived feed ingredients. This environmental problem prompted the development and acceptance of microbial phytase feed enzymes for single-stomached animals. Their introduction led to an increasing recognition that phytate may have adverse effects on protein utilisation in addition to P. Consequently, the nutritional relevance of protein–phytate interactions for pigs and poultry is considered in the present review. Since the current understanding of the effects of protein–phytate interactions comes mainly from responses obtained to added phytase, literature on the influence of microbial phytases on amino acid digestibility and utilisation is summarised, followed by a discussion of possible mechanisms contributing to the negative effects of phytate. However, the rationale for the protein responses to added phytase remains largely speculative, and several modes of action are probably involved. It may be that the release of protein from protein–phytate complexes occurring naturally in feed ingredients, the prevention of formation of binary and ternary protein–phytate complexes within the gut, the alleviation of the negative impact of phytate on digestive enzymes and the reduction in endogenous amino acid losses are all contributing factors. A better understanding of the mechanisms of protein–phytate interactions and the modes of action of exogenous phytase enzymes is clearly desirable. Studies are also needed to identify and quantify the factors that contribute to the variable amino acid responses to added phytase. It appears that the relative solubilities of phytate salts and proteins from different feed ingredients and their effects on the extent of protein–phytate complex formation, coupled with variations in the effectiveness of phytase in different dietary contexts, may be the major factors responsible.