Ultrafast electron localization and screening in a transition metal dichalcogenide

The coupling of light to electrical charge carriers in semiconductors is the foundation of many technological applications. Attosecond transient absorption spectroscopy measures simultaneously how excited electrons and the vacancies they leave behind dynamically react to the applied optical fields. In compound semiconductors, these dynamics can be probed via any of their atomic constituents with core-level transitions into valence and conduction band. Typically, the atomic species forming the compound contribute comparably to the relevant electronic properties of the material. One therefore expects to observe similar dynamics, irrespective of the choice of atomic species via which it is probed. Here, we show in the two-dimensional transition metal dichalcogenide semiconductor MoSe₂, that through a selenium-based core-level transition we observe charge carriers acting independently from each other, while when probed through molybdenum, the collective, many-body motion of the carriers dominates. Such unexpectedly contrasting behavior can be explained by a strong localization of electrons around molybdenum atoms following absorption of light, which modifies the local fields acting on the carriers. We show that similar behavior in elemental titanium metal [M. Volkov et al., Nat. Phys. 15, 1145-1149 (2019)] carries over to transition metal-containing compounds and is expected to play an essential role for a wide range of such materials. Knowledge of independent particle and collective response is essential for fully understanding these materials.

Negative refraction in hyperbolic hetero-bicrystals

We visualized negative refraction of phonon polaritons, which occurs at the interface between two natural crystals. The polaritons-hybrids of infrared photons and lattice vibrations-form collimated rays that display negative refraction when passing through a planar interface between the two hyperbolic van der Waals materials: molybdenum oxide (MoO₃) and isotopically pure hexagonal boron nitride (h¹¹BN). At a special frequency ω₀, these rays can circulate along closed diamond-shaped trajectories. We have shown that polariton eigenmodes display regions of both positive and negative dispersion interrupted by multiple gaps that result from polaritonic-level repulsion and strong coupling.

A particulate blood analogue based on artificial viscoelastic blood plasma and RBC-like microparticles at a concentration matching the human haematocrit

There has been enormous interest in the production of fluids with rheological properties similar to those of real blood over the last few years. Application fields range from biomicrofluidics (microscale) to forensic science (macroscale). The inclusion of flexible microparticles in blood analogue fluids has been demonstrated to be essential in order to reproduce the behaviour of blood flow in these fields. Here, we describe a protocol to produce a whole human blood analogue composed of a proposed plasma analogue and flexible spherical microparticles that mimic the key structural attributes of RBCs (size and mechanical properties), at a concentration matching the human haematocrit (∼42% by volume). Polydimethylsiloxane (PDMS) flexible microparticles were used to mimic RBCs, whose capability to deform is tunable by means of the mixing ratio of the PDMS precursor. Their flow through glass micronozzles allowed us to find the appropriate mixing ratio of PDMS to have approximately the same Young's modulus (E) as that exhibited by real RBCs. Shear and extensional rheology and microrheology techniques were used to match the properties exhibited by human plasma and whole blood at body temperature (37 °C). Finally, we study the flow of our proposed fluid through a microfluidic channel, showing the in vitro reproduction of the multiphase flow effects taking place in the human microcirculatory system, such as the cell-free layer (CFL) and the Fåhræus-Lindqvist effect. A macroscale application in the field of forensic science is also presented, concerning the impact of our blood analogue droplets on a solid surface for bloodstain pattern analysis.

The 2021 ultrafast spectroscopic probes of condensed matter roadmap

In the 60 years since the invention of the laser, the scientific community has developed numerous fields of research based on these bright, coherent light sources, including the areas of imaging, spectroscopy, materials processing and communications. Ultrafast spectroscopy and imaging techniques are at the forefront of research into the light-matter interaction at the shortest times accessible to experiments, ranging from a few attoseconds to nanoseconds. Light pulses provide a crucial probe of the dynamical motion of charges, spins, and atoms on picosecond, femtosecond, and down to attosecond timescales, none of which are accessible even with the fastest electronic devices. Furthermore, strong light pulses can drive materials into unusual phases, with exotic properties. In this roadmap we describe the current state-of-the-art in experimental and theoretical studies of condensed matter using ultrafast probes. In each contribution, the authors also use their extensive knowledge to highlight challenges and predict future trends.

Programmable hyperbolic polaritons in van der Waals semiconductors

Collective electronic modes or lattice vibrations usually prohibit propagation of electromagnetic radiation through the bulk of common materials over a frequency range associated with these oscillations. However, this textbook tenet does not necessarily apply to layered crystals. Highly anisotropic materials often display nonintuitive optical properties and can permit propagation of subdiffractional waveguide modes, with hyperbolic dispersion, throughout their bulk. Here, we report on the observation of optically induced electronic hyperbolicity in the layered transition metal dichalcogenide tungsten diselenide (WSe₂). We used photoexcitation to inject electron-hole pairs in WSe₂ and then visualized, by transient nanoimaging, the hyperbolic rays that traveled along conical trajectories inside of the crystal. We establish here the signatures of programmable hyperbolic electrodynamics and assess the role of quantum transitions of excitons within the Rydberg series in the observed polaritonic response.

Dose-dependent beneficial effects of citrulline supplementation in short bowel syndrome in rats

OBJECTIVES

Supplementing diet with citrulline has proved an efficient means of preserving nitrogen balance and improving nutritional status after massive intestinal resection. The aim of this study was to model the action of citrulline in gut-resected rats using a dose-ranging study focused on skeletal muscle nitrogen homeostasis.

METHODS

Forty-six rats were randomly assigned to one of the following groups: citrulline 0.5 g·kg·d^-1 (n = 9), citrulline 1 g·kg·d^-1 (n = 7), citrulline 2.5 g·kg·d^-1 (n = 8), citrulline 5 g·kg·d^-1 (n = 8), control (n = 6), and sham (n = 8). The sham group underwent transection and the other groups underwent resection of 80% of the small intestine. All rats were then fed enteral nutrition (EN; all diets were isocaloric and isonitrogenous). After 10 d, the rats were sacrificed to measure and analyze animal weight; duodenum, jejunum, and ileum weight; and muscle trophicity. Protein fractional synthesis rate (FSR) and mammalian target of rapamycin complex (mTORC)1 activation were measured in the tibialis muscle.

RESULTS

There was a significant dose-dependent association between rat weight and citrulline dose up to 2.5 g·kg·d^-1 (P = 0.004). There was a significant improvement in tibialis weight correlated to plasma citrulline. Net protein FSR in the tibialis tended to be greater after resection and tended to return to baseline after citrulline supplementation. Citrulline supplementation significantly decreased the activated phosphorylated forms of S6 K1 (P = 0.003) and S6 RP (P = 0.003), with a significant positive association between myofibrillar FSR and activation of S6 K1 (r = 0.614; P = 0.02) and S6 RP (r = 0.601; P = 0.023). Jejunum weight was significantly positively correlated with plasma citrulline (r = 0.319; P = 0.0345).

CONCLUSION

Citrulline promotes body weight gain, preserves muscle trophicity, and enhances intestinal adaptation in a dose-dependent manner in a model of resected rats.

Measuring farmers' attitude towards breeding tools: the Livestock Breeding Attitude Scale

Under-use of genetic improvement tools and low participation in breeding programmes are key drivers of breeding programmes under-performance. Both aspects are heavily influenced by farmers attitudes which, to date, have not been analysed in an objective and systematic manner. A key factor constraining the implementation of attitudinal studies towards livestock breeding tools is the lack of a reference scale for measuring attitudes. In this research, we provide the livestock breeding sector with such a reference measure. We developed the scale following the standardized psychometric methodologies and statistical tools. Then, as a case study, we used the scale to explore the attitudes of beef and dairy sheep farmers in Australia, New Zealand and Spain and analysed farmer and farming system factors related to those attitudes. Fourteen sheep and beef breed associations facilitated the implementation of a survey of 547 farmers, generating data that was used for the scale evaluation. The relationship between attitudinal factors and farmer and farming system factors was analysed using generalized linear models across and within breeds. The results suggest that the 8-item definitive scale we have developed is appropriate to measure farmer attitudes. We found that attitudes towards genetic improvement tools have two components; i) traditional selection and ii) genetic and genomic selection combined. This means that positive attitudes towards traditional phenotypic selection do not necessarily imply a negative attitude towards genetic and genomic selection tools. Farmer attitudes varied greatly not only across the studied breeds, species and countries, but also within them. High-educated farmers of business-oriented farms tend to have the most negative attitude towards traditional selection. However, attitudes towards genetic and genomic selection tools could not be linked to these factors. Finally, we found that the breed raised had a large effect on farmer attitude. These findings may help in the evolution of breeding programmes by identifying both the farmers most inclined to uptake breeding innovations in the early stages of its establishment and the farmers who would be more reluctant to participate in such programmes, thus informing where to focus extension efforts.

Common and distinct neural representations of aversive somatic and visceral stimulation in healthy individuals

Different pain types may be encoded in different brain circuits. Here, we examine similarities and differences in brain processing of visceral and somatic pain. We analyze data from seven fMRI studies (N = 165) and five types of pain and discomfort (esophageal, gastric, and rectal distension, cutaneous thermal stimulation, and vulvar pressure) to establish and validate generalizable pain representations. We first evaluate an established multivariate brain measure, the Neurologic Pain Signature (NPS), as a common nociceptive pain system across pain types. Then, we develop a multivariate classifier to distinguish visceral from somatic pain. The NPS responds robustly in 98% of participants across pain types, correlates with perceived intensity of visceral pain and discomfort, and shows specificity to pain when compared with cognitive and affective conditions from twelve additional studies (N = 180). Pre-defined signatures for non-pain negative affect do not respond to visceral pain. The visceral versus the somatic classifier reliably distinguishes somatic (thermal) from visceral (rectal) stimulation in both cross-validation and independent cohorts. Other pain types reflect mixtures of somatic and visceral patterns. These results validate the NPS as measuring a common core nociceptive pain system across pain types, and provide a new classifier for visceral versus somatic pain.

Light-Induced Renormalization of the Dirac Quasiparticles in the Nodal-Line Semimetal ZrSiSe

In nodal-line semimetals, linearly dispersing states form Dirac loops in the reciprocal space with a high degree of electron-hole symmetry and a reduced density of states near the Fermi level. The result is reduced electronic screening and enhanced correlations between Dirac quasiparticles. Here we investigate the electronic structure of ZrSiSe, by combining time- and angle-resolved photoelectron spectroscopy with ab initio density functional theory (DFT) complemented by an extended Hubbard model (DFT+U+V) and by time-dependent DFT+U+V. We show that electronic correlations are reduced on an ultrashort timescale by optical excitation of high-energy electrons-hole pairs, which transiently screen the Coulomb interaction. Our findings demonstrate an all-optical method for engineering the band structure of a quantum material.

Attosecond timing of the dynamical Franz–Keldysh effect

To what extent do intra- or inter-band transitions dominate the optical response of dielectrics when pumped by a few-cycle near-infrared transient electric field? In order to find an answer to this question we investigate the dynamical Franz–Keldysh effect in polycrystalline diamond and discuss in detail the attosecond delay of the induced electron dynamics with regard to the driving transient electric field while the peak intensity is varied between 1 × 1012 and 10 × 1012 W cm−2. We found that the main oscillating feature in transient absorption at 43 eV is in phase with the electric field of the pump, to within 49 ± 78 as. However, the phase delay shows a slightly asymmetric V-shaped linear energy dispersion with a rate of about 200 as eV–1. Theoretical calculations within the dipole approximation reproduce the data and allow us to conclude that intra-band motion dominates under our experimental conditions.

Comparative study of preterm infants fed new and existing human milk fortifiers showed favourable markers of gastrointestinal status

Aim

This study examined the influence of different human milk fortifiers on biomarkers of gastrointestinal immaturity and inflammation in preterm infants.

Methods

We report secondary outcomes from a controlled, double‐blind, randomised, parallel group study conducted from 2011 to 2014 in neonatal intensive care units at 11 metropolitan hospitals in France, Belgium, Germany, Switzerland and Italy. Preterm infants born at up to 32 weeks or weighing up to 1500 g were randomised to a new powdered human milk fortifier (n = 77) or a control fortifier (n = 76) for a minimum of 21 days. We analysed faecal markers of gut inflammation, namely alpha‐1 antitrypsin and calprotectin, and maturity, namely elastase‐1.

Results

Faecal alpha‐1 antitrypsin was slightly lower in the new than control fortifier group after 21 days of full enteral feeding, with a geometric mean and standard deviation of 1.52 ± 1.32 vs 1.82 ± 1.44 mg/g stools (P = .01). There was no significant difference in faecal calprotectin (median [Q1‐Q3] of 296 [136‐565] μg/g stools in both groups combined at study day 21). Faecal elastase‐1 was lower in the new fortifier than control fortifier group (202.5 ± 1.6 vs 257.7 ± 1.5 μg/g stools, P = .016).

Conclusion

Mean values for each parameter were within the ranges in healthy term infants, indicating favourable markers of gastrointestinal status in both groups. In addition, for faecal calprotectin, the relatively high concentration observed in preterm infants fed fortified human milk suggests that the threshold level for detecting necrotising enterocolitis should be revised.

A rural-urban latitudinal study of the distributions of Culex quinquefasciatus and Culex pipiens bioforms in their southernmost sympatric fringe

Mosquitoes grouped in the complex Culex pipiens L. (Diptera: Culicidae) are important vectors of medical and veterinary diseases. In the South American sympatric region, Cx. pipiens and Culex quinquefasciatus Say coexist and potentially hybridize. To identify key drivers of their geographical distribution, mosquito immatures were collected from flower vases of eight urban/rural cemetery pairs within a 5° latitudinal transect along Buenos Aires Province, Argentina. The specimens were identified by molecular methods and their relative proportion modelled as a function of environmental variables. At the beginning of the warm season, northern and southern cemeteries presented exclusively Cx. quinquefasciatus and Cx. pipiens, respectively, with different proportions of both at mid latitudes. By the end of the summer, Cx. quinquefasciatus was present throughout the study area, exclusively in 11 of the 16 cemeteries both rural and urban, whereas Cx. pipiens was predominant only in the southernmost pair. Mean annual temperature, photoperiod variability and time of the season were key drivers of their distributions. All specimens of Cx. pipiens were identified as form molestus and no hybrids were recognized. The reported distribution patterns and the potential absence of Cx. pipiens f. pipiens and hybrids are discussed, along with their implications in disease transmission.

One-dimensional flat bands in twisted bilayer germanium selenide

Experimental advances in the fabrication and characterization of few-layer materials stacked at a relative twist of small angle have recently shown the emergence of flat energy bands. As a consequence electron interactions become relevant, providing inroads into the physics of strongly correlated two-dimensional systems. Here, we demonstrate by combining large scale ab initio simulations with numerically exact strong correlation approaches that an effective one-dimensional system emerges upon stacking two twisted sheets of GeSe, in marked contrast to all moiré systems studied so far. This not only allows to study the necessarily collective nature of excitations in one dimension, but can also serve as a promising platform to scrutinize the crossover from two to one dimension in a controlled setup by varying the twist angle, which provides an intriguing benchmark with respect to theory. We thus establish twisted bilayer GeSe as an intriguing inroad into the strongly correlated physics of lowdimensional systems.

Time-Dependent Magnons from First Principles

We propose an efficient and non-perturbative scheme to compute magnetic excitations for extended systems employing the framework of time-dependent density functional theory. Within our approach, we drive the system out of equilibrium using an ultrashort magnetic kick perpendicular to the ground-state magnetization of the material. The dynamical properties of the system are obtained by propagating the time-dependent Kohn–Sham equations in real time, and the analysis of the time-dependent magnetization reveals the transverse magnetic excitation spectrum of the magnet. We illustrate the performance of the method by computing the magnetization dynamics, obtained from a real-time propagation, for iron, cobalt, and nickel and compare them to known results obtained using the linear-response formulation of time-dependent density functional theory. Moreover, we point out that our time-dependent approach is not limited to the linear-response regime, and we present the first results for nonlinear magnetic excitations from first principles in iron.

Splenic infarction associated with transient anti-prothrombin antibodies is a rare manifestation of acute Mycoplasma pneumoniae infection

We report the first paediatric case of splenic infarction following acute Mycoplasma pneumoniae infection with induction of anti-prothrombin (aPT) antibodies. A 12-year-old boy was admitted to the paediatric emergency department for a left pleuropneumonia and a splenic infarction. aPT antibodies were transitorily detected. The patient recovered fully after antibiotic therapy and a 3-month course of anticoagulation treatment. Antiphospholipid (aPL) antibodies induced by acute infections have already been reported but cases of clinically relevant thrombosis remain rare. The pathogenicity of aPT antibodies is discussed here. We hypothesize that these antibodies were involved in this symptomatic hypercoagulable state.

Polarization-state-resolved high-harmonic spectroscopy of solids

Attosecond metrology sensitive to sub-optical-cycle electronic and structural dynamics is opening up new avenues for ultrafast spectroscopy of condensed matter. Using intense lightwaves to precisely control the fast carrier dynamics in crystals holds great promise for next-generation petahertz electronics and devices. The carrier dynamics can produce high-order harmonics of the driving field extending up into the extreme-ultraviolet region. Here, we introduce polarization-state-resolved high-harmonic spectroscopy of solids, which provides deeper insights into both electronic and structural sub-cycle dynamics. Performing high-harmonic generation measurements from silicon and quartz, we demonstrate that the polarization states of the harmonics are not only determined by crystal symmetries, but can be dynamically controlled, as a consequence of the intertwined interband and intraband electronic dynamics. We exploit this symmetry-dynamics duality to efficiently generate coherent circularly polarized harmonics from elliptically polarized pulses. Our experimental results are supported by ab-initio simulations, providing evidence for the microscopic origin of the phenomenon.

High-harmonic generation in solids is related to the carrier dynamics and can be used to probe dynamic processes. Here, Klemke et al. show that the polarization states of high harmonics generated from silicon and quartz are determined by the crystal symmetries but can also be dynamically controlled.

Local adsorption structure and bonding of porphine on Cu(111) before and after self-metalation

We have experimentally determined the lateral registry and geometric structure of free-base porphine (2H-P) and copper-metalated porphine (Cu-P) adsorbed on Cu(111), by means of energy-scanned photoelectron diffraction (PhD), and compared the experimental results to density functional theory (DFT) calculations that included van der Waals corrections within the Tkatchenko-Scheffler approach. Both 2H-P and Cu-P adsorb with their center above a surface bridge site. Consistency is obtained between the experimental and DFT-predicted structural models, with a characteristic change in the corrugation of the four N atoms of the molecule's macrocycle following metalation. Interestingly, comparison with previously published data for cobalt porphine adsorbed on the same surface evidences a distinct increase in the average height of the N atoms above the surface through the series 2H-P, Cu-P, and cobalt porphine. Such an increase strikingly anti-correlates the DFT-predicted adsorption strength, with 2H-P having the smallest adsorption height despite the weakest calculated adsorption energy. In addition, our findings suggest that for these macrocyclic compounds, substrate-to-molecule charge transfer and adsorption strength may not be univocally correlated.

Normal serum ApoB48 and red cells vitamin E concentrations after supplementation in a novel compound heterozygous case of abetalipoproteinemia

BACKGROUND AND AIMS

Abetalipoproteinemia (ABL) is a rare recessive monogenic disease due to MTTP (microsomal triglyceride transfer protein) mutations leading to the absence of plasma apoB-containing lipoproteins. Here we characterize a new ABL case with usual clinical phenotype, hypocholesterolemia, hypotriglyceridemia but normal serum apolipoprotein B48 (apoB48) and red blood cell vitamin E concentrations.

METHODS

Histology and MTP activity measurements were performed on intestinal biopsies. Mutations in MTTP were identified by Sanger sequencing, quantitative digital droplet and long-range PCR. Functional consequences of the variants were studied in vitro using a minigene splicing assay, measurement of MTP activity and apoB48 secretion.

RESULTS

Intestinal steatosis and the absence of measurable lipid transfer activity in intestinal protein extract supported the diagnosis of ABL. A novel MTTP c.1868G>T variant inherited from the patient's father was identified. This variant gives rise to three mRNA transcripts: one normally spliced, found at a low frequency in intestinal biopsy, carrying the p.(Arg623Leu) missense variant, producing in vitro 65% of normal MTP activity and apoB48 secretion, and two abnormally spliced transcripts resulting in a non-functional MTP protein. Digital droplet PCR and long-range sequencing revealed a previously described c.1067+1217_1141del allele inherited from the mother, removing exon 10. Thus, the patient is compound heterozygous for two dysfunctional MTTP alleles. The p.(Arg623Leu) variant may maintain residual secretion of apoB48.

CONCLUSIONS

Complex cases of primary dyslipidemia require the use of a cascade of different methodologies to establish the diagnosis in patients with non-classical biological phenotypes and provide better knowledge on the regulation of lipid metabolism.

Cavity quantum-electrodynamical polaritonically enhanced electron-phonon coupling and its influence on superconductivity

So far, laser control of solids has been mainly discussed in the context of strong classical nonlinear light-matter coupling in a pump-probe framework. Here, we propose a quantum-electrodynamical setting to address the coupling of a low-dimensional quantum material to quantized electromagnetic fields in quantum cavities. Using a protoypical model system describing FeSe/SrTiO3 with electron-phonon long-range forward scattering, we study how the formation of phonon polaritons at the two-dimensional interface of the material modifies effective couplings and superconducting properties in a Migdal-Eliashberg simulation. We find that through highly polarizable dipolar phonons, large cavity-enhanced electron-phonon couplings are possible, but superconductivity is not enhanced for the forward-scattering pairing mechanism due to the interplay between coupling enhancement and mode softening. Our results demonstrate that quantum cavities enable the engineering of fundamental couplings in solids, paving the way for unprecedented control of material properties.

Transient Charge and Energy Flow in the Wide-Band Limit

The wide-band limit is a commonly used approximation to analyze transport through nanoscale devices. In this work we investigate its applicability to the study of charge and heat transport through molecular break junctions exposed to voltage biases and temperature gradients. We find by comparative simulations that while the wide-band-limit approximation faithfully describes the long-time charge and heat transport, it fails to characterize the short-time behavior of the junction. In particular, we show that the charge current flowing through the device shows a discontinuity when a temperature gradient is applied, while the energy flow is discontinuous when a voltage bias is switched on and even diverges when the junction is exposed to both a temperature gradient and a voltage bias. We provide an explanation for this pathological behavior and propose two possible solutions to this problem.

Heterogeneous distribution of Culex pipiens, Culex quinquefasciatus and their hybrids along the urbanisation gradient

The mosquitoes of the Culex pipiens complex, hereafter referred to as the Pipiens Assemblage, are vectors of arbovirus of worldwide concern including West Nile and St. Louis encephalitis. Given their distinct eco-physiology and vectorial capacity, accurate specimen identification and insight in the environmental drivers of their distribution are essential for the understanding of disease transmission patterns. Using a PCR-based identification protocol, we characterized the spatial distribution of Cx. pipiens, Cx. quinquefasciatus and their hybrids developing in used tyres located within the overlapping region in South America as a function of different estimators of the urbanisation gradient. Out of 84 samples collected from tyre piles of 20 sites, we identified 369 larvae which corresponded predominantly to Cx. quinquefasciatus (76.4% of immatures) all along the gradient but more frequent at the urban end. Cx. pipiens (21.4%) was more conspicuous at the low urbanised end but was also present in highly urbanised sites, whereas hybrids were collected in very low numbers (2.2%). The urbanisation estimator best associated with the heterogeneous occurrence of the Pipiens Assemblage members was the proportion of impervious surface 1km around each tyre pile, which explained 41.7% of the variability in the data, followed closely by the distance to the Capital City (38.3%). Cumulative annual precipitation, population number in a 1km radius around each pile and distance to the de la Plata River were significantly associated with the distribution of the Pipiens Assemblage at lower explanation percentages (20-23%). A thorough understanding of the ecological basis and environmental associations of the distribution of Pipiens Assemblage members will enable forecasting population trends in changing environments to develop effective control measures for mosquitoes and the diseases they transmit.

Momentum-Resolved View of Electron-Phonon Coupling in Multilayer WSe_{2}

We investigate the interactions of photoexcited carriers with lattice vibrations in thin films of the layered transition metal dichalcogenide (TMDC) WSe_{2}. Employing femtosecond electron diffraction with monocrystalline samples and first-principles density functional theory calculations, we obtain a momentum-resolved picture of the energy transfer from excited electrons to phonons. The measured momentum-dependent phonon population dynamics are compared to first-principles calculations of the phonon linewidth and can be rationalized in terms of electronic phase-space arguments. The relaxation of excited states in the conduction band is dominated by intervalley scattering between Σ valleys and the emission of zone boundary phonons. Transiently, the momentum-dependent electron-phonon coupling leads to a nonthermal phonon distribution, which, on longer time scales, relaxes to a thermal distribution via electron-phonon and phonon-phonon collisions. Our results constitute a basis for monitoring and predicting out of equilibrium electrical and thermal transport properties for nanoscale applications of TMDCs.

[Nasogastric rehydration for treating children with gastroenteritis]

INTRODUCTION

When oral rehydration is not feasible, enteral rehydration via the nasogastric route has been the ESPGHAN recommended method of rehydration since 2008, rather than intravenous rehydration (IVR), for children with acute gastroenteritis. However, these recommendations are rarely followed in France. Since 2011, in case of failure of oral rehydration, enteral rehydration has been used as a first-line therapy in the Children's Emergency Department at the Grenoble-Alpes University Hospital.

PURPOSE

The aims of the study were to compare the length of the hospital stay, the duration of initial rehydration, and the incidence of complications and failure with the use of enteral nasogastric versus intravenous rehydration.

METHODS

This study compared two cohorts of children (<3 years of age) with mild-to-moderate dehydration caused by acute gastroenteritis and failure of rehydration via the oral route. The first group (winter 2010-2011) was managed according to the previous protocol (intravenous rehydration). The second group (winter 2011-2012) was managed according the new protocol (nasogastric tube rehydration [NGR]). The rest of the gastroenteritis management was identical in both groups.

RESULTS

A total of 132 children were included, 65 were treated with nasogastric tube rehydration (NGR) and 67 with intravenous rehydration. There was a significant reduction in the duration of hospitalization in the post-emergency unit in the NGR group: 23.6h vs 40.1h (P<0.05). The duration of initial rehydration was also significantly reduced (10.5h vs 22.0h). There was no significant difference regarding serious adverse events. However, the NGR group presented more mild adverse events (22 vs 7, P<0.05) and more treatment failures (15.3% vs 3%, P=0.013).

CONCLUSION

Nasogastric rehydration reduces the duration of rehydration and the length of the hospital stay without increasing the incidence of serious adverse events for dehydrated children hospitalized for acute gastroenteritis.

Prevalence and Phylogenetic Analysis of Bartonella Species of Wild Carnivores and Their Fleas in Northwestern Mexico

The host-parasite-vector relationship of Bartonella spp. system in wild carnivores and their fleas from northwestern Mexico was investigated. Sixty-six carnivores belonging to eight species were sampled, and 285 fleas belonging to three species were collected during spring (April-May) and fall (October-November) seasons. We detected Bartonella species in 7 carnivores (10.6%) and 27 fleas (9.5%) through either blood culture or PCR. Of the 27 Bartonella-positive fleas, twenty-two were Pulex simulans, three were Pulex irritans and one was Echidnophaga gallinacea. The gltA gene and ITS region sequences alignment revealed six and eight genetic variants of Bartonella spp., respectively. These variants were clustered into Bartonella rochalimae, Bartonella vinsonii subsp. berkhoffii and another genotype, which likely represents a novel species of Bartonella spp. Although experimental infection studies are required to prove the vector role of P. simulans, our results suggest that this flea may play an important role in the Bartonella transmission. The results indicated possible host-specific relationships between Bartonella genotypes and the families of the carnivores, but further studies are needed to verify this finding. The presence of zoonotic species of Bartonella spp. in wild carnivores raises the issue of their potential risk for humans in fragmented ecosystems.

FOTROCAN Delphi consensus statement regarding the prevention and treatment of cancer-associated thrombosis in areas of uncertainty and low quality of evidence

INTRODUCTION

Decision-making in cancer-related venous thromboembolism (VTE) is often founded on scant lines of evidence and weak recommendations. The aim of this work is to evaluate the percentage of agreement surrounding a series of statements about complex, clinically relevant, and highly uncertain aspects to formulate explicit action guidelines.

MATERIALS AND METHODS

Opinions were based on a structured questionnaire with appropriate scores and were agreed upon using a Delphi method. Questions were selected based on a list of recommendations with low evidence from the Spanish Society of Oncology Clinical Guideline for Thrombosis. The questionnaire was completed in two iterations by a multidisciplinary panel of experts in thrombosis.

RESULTS

Of the 123 statements analyzed, the panel concurred on 22 (17%) and another 81 (65%) were agreed on by qualified majority, including important aspects of long-term and prolonged anticoagulation, major bleeding and rethrombosis management, treatment in special situations, catheter-related thrombosis and thromboprophylaxis. Among them, the panelists agreed the incidental events should be equated to symptomatic ones, long-term and extended use of full-dose low-molecular weight heparin, and concluded that the Khorana score is not sensitive enough to uphold an effective thromboprophylaxis strategy.

CONCLUSION

Though the level of consensus varied depending on the scenario presented, overall, the iterative process achieved broad agreement as to the general treatment principles of cancer-associated VTE. Clinical validation of these statements in genuine practice conditions would be useful.

Diagnosis Accuracy of Transcutaneous Bilirubinometry in Very Preterm Newborns

BACKGROUND

Transcutaneous bilirubin (TcB) is a validated test for systematic screening of neonatal hyperbilirubinemia and monitoring term and near-term infants under phototherapy.

OBJECTIVES

To evaluate TcB diagnostic accuracy for very preterm neonates.

METHODS

Total serum bilirubin (TSB) and TcB measurements were performed prospectively in a multicenter sample of newborns <30 weeks of gestational age (GA). TcB sensitivity, specificity, predictive values, and likelihood ratios for the detection of neonates requiring phototherapy were calculated over the first 15 days of life, with or without phototherapy, with the expectation of achieving a detection rate of hyperbilirubinemia of over 95%. The potential influence of neonatal characteristics on the discordance between TcB and TSB in very preterm newborns was analyzed using multivariate multilevel logistic regression analyses.

RESULTS

Altogether, 481 measurements were analyzed in 167 preterm patients. Mean GA was 27.6 ± 1.6 weeks. The rates of newborns requiring phototherapy were 52% in the first 3 days, 16% from the 4th to the 7th day, and 2% during the second week. Diagnostic performance was similar among babies with or without phototherapy. TcB sensitivity decreased over time from 100% (93.9-100.0) to 50% (1.3-98.7). Specificity showed an inverse evolution from 14.8% (7.0-26.2) to 80.7% (72.2-89.2). The best performance was that of negative predictive values which varied from 95.5 to 100.0. False negatives were rare throughout the study (0.8% of measurements). In a multivariate analysis, the only factor significantly influencing discordance between TcB and TSB was postnatal age. We did not find any impact of GA and skin color.

CONCLUSION

Among very preterm babies, TcB measurements might be useful for screening for neonatal jaundice in the first 2 weeks of life. In case of a TcB value below the phototherapy threshold, invasive TSB quantification could be unnecessary, with potential avoidance of blood drawing.

Generation and Evolution of Spin-, Valley-, and Layer-Polarized Excited Carriers in Inversion-Symmetric WSe_{2}

We report the spin-selective optical excitation of carriers in inversion-symmetric bulk samples of the transition metal dichalcogenide (TMDC) WSe_{2}. Employing time- and angle-resolved photoelectron spectroscopy (trARPES) and complementary time-dependent density functional theory (TDDFT), we observe spin-, valley-, and layer-polarized excited state populations upon excitation with circularly polarized pump pulses, followed by ultrafast (<100  fs) scattering of carriers towards the global minimum of the conduction band. TDDFT reveals the character of the conduction band, into which electrons are initially excited, to be two-dimensional and localized within individual layers, whereas at the minimum of the conduction band, states have a three-dimensional character, facilitating interlayer charge transfer. These results establish the optical control of coupled spin-, valley-, and layer-polarized states in centrosymmetric materials with locally broken symmetries and suggest the suitability of TMDC multilayer and heterostructure materials for valleytronic and spintronic device concepts.

Brain responses to uncertainty about upcoming rectal discomfort in quiescent Crohn's disease - a fMRI study

BACKGROUND

Patients with Crohn's disease (CD) in remission are exposed to chronic psychological distress, due to the constant risk of relapse. This permanent situation of anticipation and uncertainty can lead to anxiety, which may, in turn, trigger relapse. We aimed to investigate the effects of uncertainty on behavioral and brain responses to anticipation of visceral discomfort in quiescent CD patients.

METHODS

Barostat-controlled rectal distensions were preceded by cued uncertain or certain anticipation in nine CD patients and nine matched healthy volunteers. Brain responses obtained before distension across the different anticipation conditions in regions of interest (ROI) involved in (anticipation of) pain were measured using functional magnetic resonance imaging and compared between CD and controls. The association between anxiety-related psychological variables and cerebral anticipatory activity was tested.

KEY RESULTS

During uncertainty, CD patients had significantly stronger activations than controls in the cingulate cortex, insula, amygdala, and thalamus with trends in the hippocampus, prefrontal, and secondary somatosensory cortex. In patients, brain responses to uncertainty in the majority of ROI correlated positively with gastrointestinal symptom-specific anxiety, trait-anxiety, and intolerance of uncertainty.

CONCLUSIONS & INFERENCES

In a context of uncertainty regarding occurrence of uncomfortable visceral sensations, CD is associated with excessive reactivity in brain regions known to be involved in sensory, cognitive and emotional aspects of pain processing and modulation, and threat appraisal. Our findings contribute to a better understanding of the role of emotional and cognitive processes in CD. This may, in turn, lead to the development of new (psycho)therapeutic approaches for management of symptoms and related anxiety.

[Collagenous gastritis and colitis in a 10-year-old girl]

There are few data in the literature on microscopic gastritis and colitis in the pediatric population. The diagnosis is often made after the occurrence of complications. We report the case of a 10.5 year-old girl for whom the diagnosis was made several years after the initial symptoms. Test for infections, inflammation, and auto-immunity yielded normal results. Upper endoscopy and colonoscopy revealed an abnormal mucosa. However, histology showed microscopic inflammation and fibrotic lesions in the lamina propria, and a thick subepithelial collagenous band. This led to the diagnosis of collagenous gastritis and colitis. Budesonide treatment resulted in the cessation of diarrhea and significant weight gain. Treatment by oral budesonide indeed seems to be highly effective but relapses are frequent when the treatment is stopped. This case shows the importance of being vigilant regarding transit disorders with impact on growth kinetics. Upper endoscopy and colonoscopy need to be carried out when children have organic diarrhea with normal blood tests.

Characterization and isolation of immature neurons of the adult mouse piriform cortex

Physiological studies indicate that the piriform or primary olfactory cortex of adult mammals exhibits a high degree of synaptic plasticity. Interestingly, a subpopulation of cells in the layer II of the adult piriform cortex expresses neurodevelopmental markers, such as the polysialylated form of neural cell adhesion molecule (PSA-NCAM) or doublecortin (DCX). This study analyzes the nature, origin, and potential function of these poorly understood cells in mice. As previously described in rats, most of the PSA-NCAM expressing cells in layer II could be morphologically classified as tangled cells and only a small proportion of larger cells could be considered semilunar-pyramidal transitional neurons. Most were also immunoreactive for DCX, confirming their immature nature. In agreement with this, detection of PSA-NCAM combined with that of different cell lineage-specific antigens revealed that most PSA-NCAM positive cells did not co-express markers of glial cells or mature neurons. Their time of origin was evaluated by birthdating experiments with halogenated nucleosides performed at different developmental stages and in adulthood. We found that virtually all cells in this paleocortical region, including PSA-NCAM-positive cells, are born during fetal development. In addition, proliferation analyses in adult mice revealed that very few cells were cycling in layer II of the piriform cortex and that none of them was PSA-NCAM-positive. Moreover, we have established conditions to isolate and culture these immature neurons in the adult piriform cortex layer II. We find that although they can survive under certain conditions, they do not proliferate in vitro either. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 748-763, 2016.

Uncertainty in anticipation of uncomfortable rectal distension is modulated by the autonomic nervous system--a fMRI study in healthy volunteers

The human brain responds both before and during the application of aversive stimuli. Anticipation allows the organism to prepare its nociceptive system to respond adequately to the subsequent stimulus. The context in which an uncomfortable stimulus is experienced may also influence neural processing. Uncertainty of occurrence, timing and intensity of an aversive event may lead to increased anticipatory anxiety, fear, physiological arousal and sensory perception. We aimed to identify, in healthy volunteers, the effects of uncertainty in the anticipation of uncomfortable rectal distension, and the impact of the autonomic nervous system (ANS) activity and anxiety-related psychological variables on neural mechanisms of anticipation of rectal distension using fMRI. Barostat-controlled uncomfortable rectal distensions were preceded by cued uncertain or certain anticipation in 15 healthy volunteers in a fMRI protocol at 3T. Electrocardiographic data were concurrently registered by MR scanner. The low frequency (LF)-component of the heart rate variability (HRV) time-series was extracted and inserted as a regressor in the fMRI model ('LF-HRV model'). The impact of ANS activity was analyzed by comparing the fMRI signal in the 'standard model' and in the 'LF-HRV model' across the different anticipation and distension conditions. The scores of the psychological questionnaires and the rating of perceived anticipatory anxiety were included as covariates in the fMRI data analysis. Our experiments led to the following key findings: 1) the subgenual anterior cingulate cortex (sgACC) is the only activation site that relates to uncertainty in healthy volunteers and is directly correlated to individual questionnaire score for pain-related anxiety; 2) uncertain anticipation of rectal distension involved several relevant brain regions, namely activation of sgACC and medial prefrontal cortex and deactivation of amygdala, insula, thalamus, secondary somatosensory cortex, supplementary motor area and cerebellum; 3) most of the brain activity during anticipation, but not distension, is associated with activity of the central autonomic network. This approach could be applied to study the ANS impact on brain activity in various pathological conditions, namely in patients with chronic digestive conditions characterized by visceral discomfort and ANS imbalance such as irritable bowel syndrome or inflammatory bowel diseases.