Scale-free movement patterns in termites emerge from social interactions and preferential attachments

As the number or density of interacting individuals in a social group increases, a transition can develop from uncorrelated and disordered behavior of the individuals to a collective coherent pattern. We expand this observation by exploring the fine details of termite movement patterns to demonstrate that the value of the scaling exponent μ of a power law describing the Lévy walk of an individual is modified collectively as the density of animals in the group changes. This effect is absent when termites interact with inert obstacles. We also show that the network of encounters and interactions among specific individuals is selective, resembling a preferential attachment mechanism that is important for social networking. Our data strongly suggest that preferential attachments, a phenomenon not reported previously, and favorite interactions with a limited number of acquaintances are responsible for the generation of Lévy movement patterns in these social insects.

Global behavioral traits in social insects represent a trade-off between individual and collective actions. In termites, where neuter individuals (workers and soldiers) are blind, short-range local interactions among conspecifics are known to generate large-scale spatial and temporal patterns of organization including sophisticated nest mounds, tunneling systems, soil patterns, and worker survival and foraging strategies (1–7). At the heart of collective social patterns are individual behaviors that are amplified or modified in a process known as social facilitation. In recent years, it has become important to study the details of the individual basis of termite behavior to better understand socially facilitated patterns arising at a large scale (5, 8).Regarding foraging and spatial exploration, it is well known that individual termite workers forage inside underground or wood-carved tunnels with a few examples of species foraging in the open (9). Laboratory observations have established that individual termite spatial exploration is highly directional with distances traveled following self-similar scale-free patterns (10) in a way that resembles passive floaters in near-chaos turbulent fluids, prompting the idea that generic physical phenomena may be at play. In ants, another social group, it was observed that density-dependent interactions among workers are responsible for a transition from chaos to periodic patterns of activity (11, 12), while in the gregarious locust a critical transition was observed in the coherence of the collective movement patterns when the size of the group was increased (13).Lévy walks (LW) are random walks composed of clusters of multiple short steps with longer steps between them. This pattern is repeated across all scales with the resulting clusters creating fractal patterns that have no characteristic scale. Because there is no characteristic scale, the overall length of LW is dominated by the longest step taken and, while the step-length variance grows over time, it nonetheless remains finite even when unbounded by biological and ecological considerations. The hallmark of Lévy walks is a distribution of step lengths, l, with a heavy power-law tail as described by the formula f(l)∼l−μ, where ∼ means “distributed as” and μ is the scaling exponent with 1 < μ < 3 as a condition which ensures that the distribution can be normalized with probabilities that sum to unity and is characterized by a divergent variance. When μ is close to 1, movements are close to being ballistic and when μ < 3, they are effectively Brownian (scale finite rather than scale-free). It has been hypothesized that LW may be an efficient way of exploring space when searching (14–17). It is now well established that many social insects including bumblebees (18), honeybees (19), ants (20), and termites (10) perform LW when engaged in foraging activities. LW have also been identified in swarming bacteria (21) and in spider monkeys (22) which live in social groups. Similarly, theoretical studies have shown how LW might arise in systems composed of interacting individuals (23). However, most of the experimental studies in these insects—and in other animals in general—have focused on individuals acting in the absence of interactions with conspecifics. Here we report on an experimental study—with strong theoretical support—of collective patterns where the aim is to explore in detail how social interactions influence the motion mode of individuals in a social context. For this we discuss three complementary experimental designs, each aimed at exploring different aspects of interacting termite motion. The experiments detailed below are 1) social interactions and collective motion, 2) motion with passive obstacles, and 3) annular constrained motion. We also develop computer simulations to uncover the possible mechanism involved in the generation of LW from collective behaviors.     

Stochastic coordination of multiple actuators reduces latency and improves chemotactic response in bacteria

Individual neuronal, signal transduction, and regulatory pathways often control multiple stochastic downstream actuators, which raises the question of how coordinated response to a single input can be achieved when individual actuators fluctuate independently. In Escherichia coli, the bacterial chemotaxis pathway controls the activity of multiple flagellar motors to generate the run-and-tumble motion of the cell. High-resolution microscopy experiments have identified the key conformational changes adopted by individual flagella during this process. By incorporating these observations into a stochastic model of the flagellar bundle, we demonstrate that the presence of multiple motors imposes a trade-off on chemotactic performance. Multiple motors reduce the latency of the response below the time scale of the stochastic switching of a single motor, which improves performance on steep gradients of attractants. However, the uncoordinated switching of multiple motors interrupts and shortens cell runs, which thereby reduces signal detection and performance on shallow gradients. Remarkably, when slow fluctuations generated by the adaptation mechanism of the chemotaxis system are incorporated in the model at levels measured in experiments, the chemotactic sensitivity and performance in shallow gradients is partially restored with marginal effects for steep gradients. The noise is beneficial because it simultaneously generates long events in the statistics of individual motors and coordinates the motors to generate a long tail in the run length distribution of the cell. Occasional long runs are known to enhance exploration of random walkers. Here we show that they have the additional benefit of enhancing the sensitivity of the bacterium to very shallow gradients.     

Fréedericksz Transitions in 6CB Based Ferronematics—Effect of Magnetic Nanoparticles Size and Concentration

In this paper, results acquired from capacitance measurements performed on composites based on nematic liquid crystal 4-cyano-4′-hexylbiphenyl (6CB) and spherical iron oxide nanoparticles of various sizes are presented. Electric and magnetic Fréedericksz transitions, as well as structural transitions in combined electric and magnetic fields, were investigated. The obtained results showed the lowering of the threshold magnetic field with an increase in the volume concentration of nanoparticles. Estimations based on results obtained from measurements suggest soft anchoring between liquid crystal director and nanoparticles magnetization vector.     

COVID-19: A year later: Suboptimal prenatal screening of Chlamydia trachomatis and Neisseria gonorrhoeae infections in a Montréal birthing and tertiary care centre: A retrospective cohort study

BackgroundThe Canadian Paediatric Society no longer recommends the use of universal ocular prophylaxis with erythromycin ointment to prevent ophthalmia neonatorum. Screening for Chlamydia trachomatis and Neisseria gonorrhoeae in all pregnant women is considered the most effective way of preventing vertical transmission and ophthalmia neonatorum.ObjectiveThe aims of this study were to assess prenatal screening rates of C. trachomatis and N. gonorrhoeae and to compare sociodemographic factors between those screened and those not screened.MethodsThe list of all women who delivered at a tertiary care hospital in Montréal, Québec, between April 2015 and March 2016, was cross-referenced with the list of samples tested for C. trachomatis and N. gonorrhoeae. Maternal medical records were reviewed for demographic, prenatal and diagnostic information.ResultsOf 2,688 mothers, 2,245 women were screened at least once, but only 2,206 women had at least one valid C. trachomatis and N. gonorrhoeae result the day of delivery (82.1%; 95% CI: 80.6%–83.5%). Infection was detected in 46/2,206 (2.1%) screened women: 42 had C. trachomatis infection, two had N. gonorrhoeae infection and two were co-infected. C. trachomatis infection was more frequent in women younger than 25 years (9.8%; 95% CI: 6.7%–13.8%) than in older women (0.8%; 95% CI: 0.4%–1.3%; p<0.001). Each increase in parity decreased the probability of being tested (adjusted odds ratio=0.89; 95% CI: 0.80%–0.97%; p=0.01). Of those with an initial negative test result, 35/267 (13.1%; 95% CI: 9.3%–17.8%) of women younger than 25 years and 122/1,863 (6.6%; 95% CI: 5.5%–7.8%; p<0.001) of women aged 25 years and older were retested. Subsequent infection was detected in 4/35 (11%) women, all younger than 25.ConclusionSuboptimal screening rates for C. trachomatis and N. gonorrhoeae suggest that current universal ocular prophylaxis cannot be discontinued. Repeating universal screening should be considered, especially among those younger than 25 years.     

Modeling the effects of strain diversity and mechanisms of strain competition on the potential performance of new tuberculosis vaccines

While bacillus Calmette-Guérin vaccination plays an important role in reducing the morbidity of tuberculosis (TB) infection during childhood, new tuberculosis vaccines are necessary to disrupt the transmission of disease and improve global control of this pathogen. Growing evidence of the presence of meaningful Mycobacterium tuberculosis strain diversity, coupled with the possibility that new vaccines may differentially protect against infection or disease with circulating M. tuberculosis strains, suggest that these vaccines may have complicated effects on disease dynamics. We use a mathematical model to explore the potential effects of strain diversity on the performance of vaccines and find that vaccines offer great promise for improving tuberculosis control, but the expected benefits of mass vaccination will be eroded if strain replacement with M. tuberculosis variants that are not effectively targeted by vaccines occurs. Determining the likelihood of strain replacement will require additional knowledge of the strain specificities of current vaccine candidates, and an improved understanding of the mechanisms of strain interaction, which are responsible for maintaining the diversity of M. tuberculosis within communities.     

First Nations Health: Supporting health equity for First Nations,Inuit and Métis peoples

The National Collaborating Centre for Indigenous Health (NCCIH) is unique among the National Collaborating Centres as the only centre focused on the health of a population. In this fifth article of the Canada Communicable Disease Report’s series on the National Collaborating Centres and their contribution to Canada’s public health response to the coronavirus disease 2019 (COVID-19) pandemic, we describe the work of the NCCIH. We begin with a brief overview of the NCCIH’s mandate and priority areas, describing how it works, who it serves and how it has remained flexible and responsive to evolving Indigenous public health needs. Key knowledge translation and exchange activities undertaken by the NCCIH to address COVID-19 misinformation and to support the timely use of Indigenous-informed evidence and knowledge in public health decision-making during the pandemic are also discussed, with a focus on acting on lessons learned moving forward.     

Atmospheric record in the Hadean Eon from multiple sulfur isotope measurements in Nuvvuagittuq Greenstone Belt (Nunavik,Quebec)

Mass-independent fractionation of sulfur isotopes (S-MIF) results from photochemical reactions involving short-wavelength UV light. The presence of these anomalies in Archean sediments [(4–2.5 billion years ago, (Ga)] implies that the early atmosphere was free of the appropriate UV absorbers, of which ozone is the most important in the modern atmosphere. Consequently, S-MIF is considered some of the strongest evidence for the lack of free atmospheric oxygen before 2.4 Ga. Although temporal variations in the S-MIF record are thought to depend on changes in the abundances of gas and aerosol species, our limited understanding of photochemical mechanisms complicates interpretation of the S-MIF record in terms of atmospheric composition. Multiple sulfur isotope compositions (δ³³S, δ³⁴S, and δ³⁶S) of the >3.8 billion-year-old Nuvvuagittuq Greenstone Belt (Ungava peninsula) have been investigated to track the early origins of S-MIF. Anomalous S-isotope compositions (Δ³³S up to +2.2‰) confirm a sedimentary origin of sulfide-bearing banded iron and silica-rich formations. Sharp isotopic transitions across sedimentary/igneous lithological boundaries indicate that primary surficial S-isotope compositions have been preserved despite a complicated metamorphic history. Furthermore, Nuvvuagittuq metasediments recorded coupled variations in ³³S/³²S, ³⁴S/³²S, and ³⁶S/³²S that are statistically indistinguishable from those identified several times later in the Archean. The recurrence of the same S-isotope pattern at both ends of the Archean Eon is unexpected, given the complex atmospheric, geological, and biological pathways involved in producing and preserving this fractionation. It implies that, within 0.8 billion years of Earth’s formation, a common mechanism for S-MIF production was established in the atmosphere.Multiple sulfur isotopes have become the tool of choice for probing atmospheric evolution during the first 2.5 billion years of Earth history. In particular, mass-independent fractionation of sulfur isotopes (S-MIF) (1) is a characteristic feature of the geologic record before 2.32 gigayears ago (Ga) (2), after which S-MIF is almost completely lacking (3). Photochemistry in a low-O₂ atmosphere is often considered as the dominant cause of S-MIF (1), and models for production and preservation of S-MIF anomalies suggest that an increase in O₂ beyond ∼10⁻⁵ times present atmospheric level (PAL) (4) would quench the production of S-MIF signals in the geological record. While the abrupt nature of the Archean/Proterozoic transition reflects a high-sensitivity response to atmospheric O₂, the temporal variability of the S-MIF record before about 2.45 Ga indicates a complex interplay among atmospheric composition (5–8), magnitude (9) and oxidation state (10) of sulfur fluxes into the atmosphere, accessible photochemical pathways (11), microbial sulfur cycling in the surface environment (10), and atmospheric solar flux (12). Despite the broad range of geologic and biologic controls that apparently influence the S-isotopic record, first-order isotopic patterns are present that span wide intervals in time and are shared among a variety of rock-forming environments.High-resolution measurements on Neoarchean samples (2.5–2.8 Ga) (13, 14) have provided evidence for temporal variation of the multiple S-isotopic signal reflecting changes in the relative proportions of atmospheric gases of volcanogenic and biogenic origin. The S-isotopic signal then appears as a robust metric of atmospheric composition that reflects both the photolytic reactions involving S-bearing phases and their transfer to the sediments. The present study focuses on the origins and extent of this atmospheric memory in the sedimentary record. To probe the sensitivity of early Archean photochemical processes to major surface perturbations, including emergence of dominant biogenic elemental cycling, intense volcanic activity, bombardment of Earth’s surface by bolides, and evolution of the solar flux, we examined the multiple sulfur isotope record in some of the oldest metasediments found on Earth. The samples were collected in the >3.8-Ga Nuvvuagittuq Greenstone Belt (NGB) (15) located on the eastern coast of Hudson Bay (Ungava Penninsula, Northeastern Superior Province of Canada).     

Structural and Magnetic Properties of Inverse-Heusler Mn2FeSi Alloy Powder Prepared by Ball Milling

Ternary Mn₂FeSi alloy was synthesized from pure elemental powders by mechanical alloying, using a high-energy planetary ball mill. The formation of an inverse-Heusler phase after 168 h of milling and subsequent annealing at 1173 K for 1.5 h was confirmed by X-ray diffraction. The diffractogram analysis yielded XA structure and the lattice parameter 0.5677 nm in a good agreement with the theoretically obtained value of 0.560 nm. The final powder was formed by particles of irregular shape and median diameter D50 of 3.8 μm and their agglomerates. The chemical analysis resulted in the mean composition of 49.0 at.% Mn, 25.6 at.% Fe and 25.4 at.% Si. At room temperature, the prepared samples featured a heterogeneous magnetic structure consisting of dominant paramagnetic phase confirmed by Mössbauer spectrometry and a weak ferro-/ferrimagnetic contribution detected by magnetization curves. From the field-cooled and zero-field-cooled curves the Néel temperature of 67 K was determined.     

The Technology Transfer from Europe to China in the 17th–18th Centuries: Non-Invasive On-Site XRF and Raman Analyses of Chinese Qing Dynasty Enameled Masterpieces Made Using European Ingredients/Recipes

Two masterpieces of the Qing Dynasty (1644–1912 CE), one in gilded brass (incense burner) decorated with cloisonné enamels stylistically attributed to the end of the Kangxi Emperor’s reign, the other in gold (ewer offered by Napoleon III to the Empress as a birthday present), decorated with both cloisonné and painted enamels bearing the mark of the Qianlong Emperor, were non-invasively studied by optical microscopy, Raman microspectroscopy and X-ray microfluorescence spectroscopy (point measurements and mapping) implemented on-site with mobile instruments. The elemental compositions of the metal substrates and enamels are compared. XRF point measurements and mappings support the identification of the coloring phases and elements obtained by Raman microspectroscopy. Attention was paid to the white (opacifier), blue, yellow, green, and red areas. The demonstration of arsenic-based phases (e.g., lead arsenate apatite) in the blue areas of the ewer, free of manganese, proves the use of cobalt imported from Europe. The high level of potassium confirms the use of smalt as the cobalt source. On the other hand, the significant manganese level indicates the use of Asian cobalt ores for the enamels of the incense burner. The very limited use of the lead pyrochlore pigment (European Naples yellow recipes) in the yellow and soft green cloisonné enamels of the Kangxi incense burner, as well as the use of traditional Chinese recipes for other colors (white, turquoise, dark green, red), reinforces the pioneering character of this object in technical terms at the 17th–18th century turn. The low level of lead in the cloisonné enamels of the incense burner may also be related to the use of European recipes. On the contrary, the Qianlong ewer displays all the enameling techniques imported from Europe to obtain a painted decoration of exceptional quality with the use of complex lead pyrochlore pigments, with or without addition of zinc, as well as cassiterite opacifier.     

The effects of intravascular photobiomodulation on sleep disturbance caused by Guillain-Barré syndrome after Astrazeneca vaccine inoculation: Case report and literature review

Rationale:Sleep disturbance is commonly noted after Guillain-Barré syndrome (GBS) and is often caused by persistent discomfort after disease survival. Intravascular laser irradiation of blood (ILIB) has been shown to be effective in pain modulation owing to the influence of nociceptive signals in the peripheral nervous system. We investigated the application of ILIB on post-Oxford –AstraZeneca vaccination GBS and evaluated its effect on sleep quality.Patient concerns:A 48-year-old woman was subsequently diagnosed with GBS after Oxford–AstraZeneca vaccination. The patient was discharged after a 5-day course of intravenous immunoglobulin administration. However, 1 week after discharge, the previously relieved symptoms flared with accompanying sleep disturbance.Diagnosis and interventions:The patient was diagnosed with post-vaccination GBS, and persistent pain and sleep disturbances persisted after disease survival. ILIB was performed.Outcomes:We used the Pittsburgh Sleep Quality Index before and after intravascular laser irradiation. There was a marked improvement in the sleep duration, efficiency, and overall sleep quality. The initial score was 12 out of 21 and the final score was 7 out of 21.Lessons:We found that ILIB was effective in pain modulation in post-vaccination GBS and significantly improved sleep quality.     

Microbubbles Remove Listeria monocytogenes from the Surface of Stainless Steel,Cucumber, and Avocado

Fresh produce may be contaminated by bacterial pathogens, including Listeria monocytogenes, during harvesting, packaging, or transporting. A low-intensity cavitation process with air being injected into water was studied to determine the microbubbles’ efficiency when detaching L. monocytogenes from stainless steel and the surface of fresh cucumber and avocado. Stainless steel coupons (1″ × 2″), cucumber, and avocado surfaces were inoculated with L. monocytogenes (LCDC strain). After 1, 24 or 48 h, loosely attached cells were washed off, and inoculated areas were targeted by microbubbles (~0.1–0.5 mm dia.) through a bubble diffuser (1.0 L air/min) for 1, 2, 5, or 10 min. For steel, L. monocytogenes (48 h drying) detachment peaked at 2.95 mean log reduction after 10 min of microbubbles when compared to a no-bubble treatment. After 48 h pathogen drying, cucumbers treated for 10 min showed a 1.78 mean log reduction of L. monocytogenes. For avocados, L. monocytogenes (24 h drying) detachment peaked at 1.65 log reduction after 10 min of microbubbles. Microbubble applications may be an effective, economical, and environmentally friendly way to remove L. monocytogenes, and possibly other bacterial pathogens, from food contact surfaces and the surfaces of whole, intact fresh produce.     

Hyaluronic acid gel ( Juvéderm?) preparations in the treatment of facial wrinkles and folds

Soft tissue augmentation with temporary dermal fillers is a continuously growing field, supported by the ongoing development and advances in technology and biocompatibility of the products marketed. The longer lasting, less immunogenic and thus more convenient hyaluronic acid (HA) fillers are encompassing by far the biggest share of the temporary dermal filler market. Since the approval of the first HA filler, Restylane^®, there are at least 10 HA fillers that have been approved by the FDA. Not all of the approved HA fillers are available on the market, and many more are coming. The Juvéderm^™ product line (Allergan, Irvine, CA), consisting of Juvéderm^™ Plus and Juvéderm^™ Ultra Plus, was approved by the FDA in 2006. Juvéderm^™ is a bacterium-derived nonanimal stabilized HA. Juvéderm^™ Ultra and Ultra Plus are smooth, malleable gels with a homologous consistency that use a new technology called “Hylacross^™ technology”. They have a high concentration of cross-linked HAs, which accounts for its longevity. Juvéderm^™ Ultra Plus is used for volumizing and correcting deeper folds, whereas Juvéderm^™ Ultra is best for contouring and volumizing medium depth facial wrinkles and lip augmentation. Various studies have shown the superiority of the HA filler products compared with collagen fillers for duration, volume needed, and patient satisfaction. Restylane^®, Perlane^®, and Juvéderm^™ are currently the most popular dermal fillers used in the United States.     

Clinical predictors and outcome of hypoxaemia among under-five diarrhoeal children with or without pneumonia in an urban hospital, Dhaka, Bangladesh

Objective To explore the predictors and outcome of hypoxaemia in children under 5 years of age who were hospitalized for the management of diarrhoea in Dhaka, where comorbidities are common. Methods In a prospective cohort study, we enrolled all children <5 years of age admitted to the special care ward (SCW) of the Dhaka Hospital of ICDDR,B from September to December 2007. Those who presented with hypoxaemia (SpO₂ < 90%) constituted the study group, and those without hypoxaemia formed the comparison group. Results A total of 258 children were enrolled, all had diarrhoea. Of the total, 198 (77%) had pneumonia and 106 (41%) had severe malnutrition (Z‐score of weight for age of the median of the National Centre for Health Statistics), 119 (46%) had hypoxaemia and 138 children did not have hypoxaemia at the time of admission. Children with hypoxaemia had a higher probability of a fatal outcome (21%vs. 4%; P < 0.001). Using logistic regression analysis, the independent predictors of hypoxaemia at the time of presentation were lower chest wall indrawing [OR 6.91, 95% confidence intervals (CI) 3.66–13.08, P < 0.001], nasal flaring (OR 3.22, 95% CI 1.45–7.17, P = 0.004) and severe sepsis (OR 4.48, 95% CI 1.62–12.42, P = 0.004). Conclusion In this seriously ill population of children with diarrhoea and comorbidities, hypoxaemia was associated with high case–fatality rates. Independent clinical predictors of hypoxaemia in this population, identifiable at the time of admission, were lower chest wall indrawing, nasal flaring and the clinical syndrome of severe sepsis.     

Significant Near-Field Enhancement over Large Volumes around Metal Nanorods via Strong Coupling of Surface Lattice Resonances and Fabry–Pérot Resonance

Metal nanoparticles supporting plasmons are widely used to enhance electromagnetic fields, resulting in strong light–matter interactions at the nanoscale in a diverse range of applications. Recently, it has been shown that when metal nanorods are periodically arranged with proper lattice periods, surface lattice resonances (SLRs) can be excited and near fields can be greatly enhanced over extended volumes. In this work, we report significant near field enhancement over even larger volumes by placing the metal nanorod array within a Fabry–Pérot (F-P) microcavity. Simulation results show that by taking advantage of strong coupling between the SLR and the photonic F-P resonances, the electric field intensity of the bonding split mode can be enhanced by up to 1935 times, which is about three times of the enhancement of the SLR, and the greatly enhanced field can extend over most of the F-P microcavity. We further show that the F-P resonances of both odd and even orders can strongly couple to the SLR by varying the nanorods position from the middle of the microcavity. We expect that the proposed plasmonic-photonic coupling system will find promising applications in nanolasers, nonlinear optics and sensing.     

Morphological and Optical Characterization of Colored Nanotubular Anodic Titanium Oxide Made in an Ethanol-Based Electrolyte

In this paper, the possibility of color controlling anodic titanium oxide by changing anodizing conditions of titanium in an ethanol-based electrolyte is demonstrated. Colored anodic titanium oxide was fabricated in an ethanol-based electrolyte containing 0.3 M ammonium fluoride and various amounts of deionized water (2, 3.5, 5, or 10 vol%), at voltages that varied from 30 to 60 V and at a constant anodization temperature of 20 °C. Morphological characterization of oxide layers was established with the use of a scanning electron microscope. Optical characterization was determined by measuring diffusion reflectance and calculating theoretical colors. The resulting anodic oxides in all tested conditions had nanotubular morphology and a thickness of up to hundreds of nanometers. For electrolytes with 3.5, 5, and 10 vol% water content, the anodic oxide layer thickness increased with the applied potential increase. The anodic titanium oxide nanotube diameters and the oxide thickness of samples produced in an electrolyte with 2 vol% water content were independent of applied voltage and remained constant within the error range of all tested potentials. Moreover, the color of anodic titanium oxide produced in an electrolyte with 2 vol% of water was blue and was independent from applied voltage, while the color of samples from other electrolyte compositions changed with applied voltage. For samples produced in selected conditions, iridescence was observed. It was proposed that the observed structural color of anodic titanium oxide results from the synergy effect of nanotube diameter and oxide thickness.