Super-Poissonian Light Statistics from Individual Silicon Vacancy Centers Coupled to a Laser-Written Diamond Waveguide.

Modifying light fields at the single-photon level is a key challenge for upcoming quantum technologies and can be realized in a scalable manner through integrated quantum photonics. Laser-written diamond photonics offers 3D fabrication capabilities and large mode-field diameters matched to fiber optic technology, though limiting the cooperativity at the single-emitter level. To realize large coupling efficiencies, we combine excitation of single shallow-implanted silicon vacancy centers via high numerical aperture optics with detection assisted by laser-written type-II waveguides. We demonstrate single-emitter extinction measurements with a cooperativity of 0.0050 and a relative beta factor of 13%. The transmission of resonant photons reveals single-photon subtraction from a quasi-coherent field resulting in super-Poissonian light statistics. Our architecture enables light field engineering in an integrated design on the single quantum level although the intrinsic cooperativity is low. Laser-written structures can be fabricated in three dimensions and with a natural connectivity to optical fiber arrays.

Health Care Students' Perspectives on Artificial Intelligence: Countrywide Survey in Canada.

BACKGROUND: Artificial intelligence (AI) is no longer a futuristic concept; it is increasingly being integrated into health care. As studies on attitudes toward AI have primarily focused on physicians, there is a need to assess the perspectives of students across health care disciplines to inform future curriculum development. OBJECTIVE: This study aims to explore and identify gaps in the knowledge that Canadian health care students have regarding AI, capture how health care students in different fields differ in their knowledge and perspectives on AI, and present student-identified ways that AI literacy may be incorporated into the health care curriculum. METHODS: The survey was developed from a narrative literature review of topics in attitudinal surveys on AI. The final survey comprised 15 items, including multiple-choice questions, pick-group-rank questions, 11-point Likert scale items, slider scale questions, and narrative questions. We used snowball and convenience sampling methods by distributing an email with a description and a link to the web-based survey to representatives from 18 Canadian schools. RESULTS: A total of 2167 students across 10 different health professions from 18 universities across Canada responded to the survey. Overall, 78.77% (1707/2167) predicted that AI technology would affect their careers within the coming decade and 74.5% (1595/2167) reported a positive outlook toward the emerging role of AI in their respective fields. Attitudes toward AI varied by discipline. Students, even those opposed to AI, identified the need to incorporate a basic understanding of AI into their curricula. CONCLUSIONS: We performed a nationwide survey of health care students across 10 different health professions in Canada. The findings would inform student-identified topics within AI and their preferred delivery formats, which would advance education across different health care professions.

Morphological Study of Nanostructures Induced by Direct Femtosecond Laser Ablation on Diamond.

High spatial frequency laser induced periodic surface structure (HSFL) morphology induced by femtosecond laser with 230 fs pulse duration, 250 kHz repetition rate at 1030 nm wavelength on CVD diamond surface is investigated and discussed. The spatial modification was characterized and analyzed by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and 2D-Fast Fourier Transform (2D-FFT). We studied the effect of pulse number and laser power on the spatial development of nanostructures, and also deduced the impact of thermal accumulation effect on their morphology. A generalized plasmonic model has been used to follow the optical evolution of the irradiated surface and to determine the periodic value of the nanostructures. We suggest that non-thermal melting and plasmonic excitation are the main processes responsible for the formation of HSFL-type nanostructures.

Micro-Hole Generation by High-Energy Pulsed Bessel Beams in Different Transparent Materials.

Micro-drilling transparent dielectric materials by using non-diffracting beams impinging orthogonally to the sample can be performed without scanning the beam position along the sample thickness. In this work, the laser micromachining process, based on the combination of picosecond pulsed Bessel beams with the trepanning technique, is applied to different transparent materials. We show the possibility to create through-apertures with diameter on the order of tens of micrometers, on dielectric samples with different thermal and mechanical characteristics as well as different thicknesses ranging from two hundred to five hundred micrometers. Advantages and drawbacks of the application of this technique to different materials such as glass, polymer, or diamond are highlighted by analyzing the features, the morphology, and the aspect-ratio of the through-holes generated. Alternative Bessel beam drilling configurations, and the possibility of optimization of the quality of the aperture at the output sample/air interface is also discussed in the case of glass.

A dynamic role for dopamine receptors in the control of mammalian spinal networks.

Dopamine is well known to regulate movement through the differential control of direct and indirect pathways in the striatum that express D1 and D2 receptors respectively. The spinal cord also expresses all dopamine receptors; however, how the specific receptors regulate spinal network output in mammals is poorly understood. We explore the receptor-specific mechanisms that underlie dopaminergic control of spinal network output of neonatal mice during changes in spinal network excitability. During spontaneous activity, which is a characteristic of developing spinal networks operating in a low excitability state, we found that dopamine is primarily inhibitory. We uncover an excitatory D1-mediated effect of dopamine on motoneurons and network output that also involves co-activation with D2 receptors. Critically, these excitatory actions require higher concentrations of dopamine; however, analysis of dopamine concentrations of neonates indicates that endogenous levels of spinal dopamine are low. Because endogenous levels of spinal dopamine are low, this excitatory dopaminergic pathway is likely physiologically-silent at this stage in development. In contrast, the inhibitory effect of dopamine, at low physiological concentrations is mediated by parallel activation of D2, D3, D4 and α2 receptors which is reproduced when endogenous dopamine levels are increased by blocking dopamine reuptake and metabolism. We provide evidence in support of dedicated spinal network components that are controlled by excitatory D1 and inhibitory D2 receptors that is reminiscent of the classic dopaminergic indirect and direct pathway within the striatum. These results indicate that network state is an important factor that dictates receptor-specific and therefore dose-dependent control of neuromodulators on spinal network output and advances our understanding of how neuromodulators regulate neural networks under dynamically changing excitability.

The Effects of a Ketogenic Diet on Sensorimotor Function in a Thoracolumbar Mouse Spinal Cord Injury Model.

Spinal cord injury and peripheral nerve injuries are traumatic events that greatly impact quality of life. One factor that is being explored throughout patient care is the idea of diet and the role it has on patient outcomes. But the effects of diet following neurotrauma need to be carefully explored in animal models to ensure that they have beneficial effects. The ketogenic diet provides sufficient daily caloric requirements while being potentially neuroprotective and analgesic. In this study, animals were fed a high-fat, low-carbohydrate diet that led to a high concentration of blood ketone that was sustained for as long as the animals were on the diet. Mice fed a ketogenic diet had significantly lower levels of tyrosine and tryptophan, but the levels of other monoamines within the spinal cord remained similar to those of control mice. Mice were fed a standard or ketogenic diet for 7 d before and 28 d following the injury. Our results show that mice hemisected over the T10-T11 vertebrae showed no beneficial effects of being on a ketogenic diet over a 28 d recovery period. Similarly, ligation of the common peroneal and tibial nerve showed no differences between mice fed normal or ketogenic diets. Tests included von Frey, open field, and ladder-rung crossing. We add to existing literature showing protective effects of the ketogenic diet in forelimb injuries by focusing on neurotrauma in the hindlimbs. The results suggest that ketogenic diets need to be assessed based on the type and location of neurotrauma.

Macrophages and Associated Ligands in the Aged Injured Nerve: A Defective Dynamic That Contributes to Reduced Axonal Regrowth.

The regenerative capacity of injured peripheral nerves is diminished with aging. To identify factors that contribute to this impairment, we compared the immune cell response in young vs. aged animals following nerve injury. First, we confirmed that macrophage accumulation is delayed in aged injured nerves which is due to defects in monocyte migration as a result of defects in site-specific recruitment signals in the aged nerve. Interestingly, impairment in both macrophage accumulation and functional recovery could be overcome by transplanting bone marrow from aged animals into young mice. That is, upon exposure to a youthful environment, monocytes/macrophages originating from the aged bone marrow behaved similarly to young cells. Transcriptional profiling of aged macrophages following nerve injury revealed that both pro- and anti-inflammatory genes were largely downregulated in aged compared to young macrophages. One ligand of particular interest was macrophage-associated secreted protein (MCP1), which exhibited a potent role in regulating aged axonal regrowth in vitro. Given that macrophage-derived MCP1 is significantly diminished in the aged injured nerve, our data suggest that age-associated defects in MCP1 signaling could contribute to the regenerative deficits that occur in the aged nervous system.

Laser-Inscribed Diamond Waveguide Resonantly Coupled to Diamond Microsphere.

An all-diamond photonic circuit was implemented by integrating a diamond microsphere with a femtosecond-laser-written bulk diamond waveguide. The near surface waveguide was fabricated by exploiting the Type II fabrication method to achieve stress-induced waveguiding. Transverse electrically and transverse magnetically polarized light from a tunable laser operating in the near-infrared region was injected into the diamond waveguide, which when coupled to the diamond microsphere showed whispering-gallery modes with a spacing of 0.33 nm and high-quality factors of 105. By carefully engineering these high-quality factor resonances, and further exploiting the properties of existing nitrogen-vacancy centers in diamond microspheres and diamond waveguides in such configurations, it should be possible to realize filtering, sensing and nonlinear optical applications in integrated diamond photonics.

Orexinergic Modulation of Spinal Motor Activity in the Neonatal Mouse Spinal Cord.

The role of orexin during development, and especially in terms of spinal cord function, is not well understood. It is for this reason that we focused on the network actions of orexin during the first week of development. We found that orexinergic fibers were present in the lumbar spinal cord of postnatal day 0 (P0) to P3 mice. The fibers were expressed mainly in the dorsal horn, but occasional fibers were observed in the ventral horn. Both orexin (OX) A and OXB increased the motoneurons (MNs) tonic neurogram discharge. However, only OXA was found to significantly increase spontaneous bursting activity and the frequency of fictive locomotor bursts. We show that OXA is able to act directly on MNs. To test the contribution of the recurrent MN collaterals, we blocked the nicotinic cholinergic drive and observed that OXA retained its ability to increase fictive locomotor activity. Additionally, we recorded neurograms from ventral lateral funiculi, where OXA had no effect on population discharge. These effects were also confirmed by recording from descending commissural interneurons via patch recordings. The loci of the effects of OXA were further investigated in a dorsal horn-removed preparation where OXA also shows an increase in the discharge from ventral root neurograms but no increase in the frequency of spontaneous or fictive locomotion burst activity. In summary, multiple lines of evidence from our work demonstrate the robust effects of orexins on spinal cord networks and MNs at the time of birth.

Optogenetic Activation of A11 Region Increases Motor Activity.

Limbic brain regions drive goal-directed behaviors. These behaviors often require dynamic motor responses, but the functional connectome of limbic structures in the diencephalon that control locomotion is not well known. The A11 region, within the posterior diencephalon has been postulated to contribute to motor function and control of pain. Here we show that the A11 region initiates movement. Photostimulation of channelrhodopsin 2 (ChR2) transfected neurons in A11 slice preparations showed that neurons could follow stimulation at frequencies of 20 Hz. Our data show that photostimulation of ChR2 transfected neurons in the A11 region enhances motor activity often leading to locomotion. Using vGluT2-reporter and vGAT-reporter mice we show that the A11 tyrosine hydroxylase positive (TH) dopaminergic neurons are vGluT2 and vGAT negative. We find that in addition to dopaminergic neurons within the A11 region, there is another neuronal subtype which expresses the monoenzymatic aromatic L-amino acid decarboxylase (AADC), but not TH, a key enzyme involved in the synthesis of catecholamines including dopamine. This monoaminergic-based motor circuit may be involved in the control of motor behavior as part of a broader diencephalic motor region.

Laser surface structuring of diamond with ultrashort Bessel beams.

We investigate the effect of ultrafast laser surface machining on a monocrystalline synthetic diamond sample by means of pulsed Bessel beams. We discuss the differences of the trench-like microstructures generated in various experimental conditions, by varying the beam cone angle, the energy and pulse duration, and we present a brief comparison of the results with those obtained with the same technique on a sapphire sample. In diamond, we obtain V-shaped trenches whose surface width varies with the cone angle, and which are featured by micrometer sized channels having depths in the range of 10-20 µm. By laser writing crossed trenches we are also able to create and tailor on the diamond surface pillar-like or tip-like microstructures potentially interesting for large surface functionalization, cells capturing and biosensing.

Silicon microsphere whispering gallery modes excited by femtosecond-laser-inscribed glass waveguides.

We report on the coupling of whispering gallery modes in a 500-µm-radius silicon microsphere to a femtosecond-laser-inscribed glass optical waveguide. The shallow glass waveguide with a large mode field diameter in the near-infrared is written at a depth of 25 µm below the glass surface, resulting in a high excitation impact parameter of 525 µm for the microsphere. The excited whispering gallery modes of the silicon microsphere have quality factors of approximately 105 in the 90° elastic scattering and 0° transmission. Integration of such spherical silicon microresonators on femtosecond-laser-inscribed glass waveguides is promising for photonic communication, computation, and sensing applications.

Optical NP problem solver on laser-written waveguide platform.

Cognitive photonic networks are researched to efficiently solve computationally hard problems. Flexible fabrication techniques for the implementation of such networks into compact and scalable chips are desirable for the study of new optical computing schemes and algorithm optimization. Here we demonstrate a femtosecond laser-written optical oracle based on cascaded directional couplers in glass, for the solution of the Hamiltonian path problem. By interrogating the integrated photonic chip with ultrashort laser pulses, we were able to distinguish the different paths traveled by light pulses, and thus infer the existence or the absence of the Hamiltonian path in the network by using an optical correlator. This work proves that graph theory problems may be easily implemented in integrated photonic networks, down scaling the net size and speeding up execution times.

Laser-Inscribed Glass Microfluidic Device for Non-Mixing Flow of Miscible Solvents.

In recent years, there has been significant research on integrated microfluidic devices. Microfluidics offer an advantageous platform for the parallel laminar flow of adjacent solvents of potential use in modern chemistry and biology. To reach that aim, we worked towards the realization of a buried microfluidic Lab-on-a-Chip which enables the separation of the two components by exploiting the non-mixing properties of laminar flow. To fabricate the aforementioned chip, we employed a femtosecond laser irradiation technique followed by chemical etching. To optimize the configuration of the chip, several geometrical and structural parameters were taken into account. The diffusive mass transfer between the two fluids was estimated and the optimal chip configuration for low diffusion rate of the components was defined.

AlphaB-crystallin regulates remyelination after peripheral nerve injury.

AlphaB-crystallin (αBC) is a small heat shock protein that is constitutively expressed by peripheral nervous system (PNS) axons and Schwann cells. To determine what role this crystallin plays after peripheral nerve damage, we found that loss of αBC impaired remyelination, which correlated with a reduced presence of myelinating Schwann cells and increased numbers of nonmyelinating Schwann cells. The heat shock protein also seems to regulate the cross-talk between Schwann cells and axons, because expected changes in neuregulin levels and ErbB2 receptor expression after PNS injury were disrupted in the absence of αBC. Such dysregulations led to defects in conduction velocity and motor and sensory functions that could be rescued with therapeutic application of the heat shock protein in vivo. Altogether, these findings show that αBC plays an important role in regulating Wallerian degeneration and remyelination after PNS injury.

Diamond photonics platform enabled by femtosecond laser writing.

Diamond is a promising platform for sensing and quantum processing owing to the remarkable properties of the nitrogen-vacancy (NV) impurity. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532 nm laser light, even at room temperature. The NV's states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, still lacking is an efficient photonic fabrication method for diamond akin to the photolithographic methods that have revolutionized silicon photonics. Here, we report the first demonstration of three dimensional buried optical waveguides in diamond, inscribed by focused femtosecond high repetition rate laser pulses. Within the waveguides, high quality NV properties are observed, making them promising for integrated magnetometer or quantum information systems on a diamond chip.

Optical realization of the dissipative quantum oscillator.

An optical realization of the damped quantum oscillator, based on transverse light dynamics in an optical resonator with slowly-moving mirrors, is theoretically suggested. The optical resonator setting provides a simple implementation of the time-dependent Caldirola-Kanai Hamiltonian of the dissipative quantum oscillator and enables the visualization of the effects of damped oscillations in the classical (ray optics) limit and wave packet collapse in the quantum (wave optics) regime.

Enhancing adult nerve regeneration through the knockdown of retinoblastoma protein.

Tumour suppressor pathways may offer novel targets capable of altering the plasticity of post-mitotic adult neurons. Here we describe a role for the retinoblastoma (Rb) protein, widely expressed in adult sensory neurons and their axons, during regeneration. In adult sensory neurons, Rb short interfering RNA (siRNA) knockdown or Rb1 deletion in vitro enhances neurite outgrowth and branching. Plasticity is achieved in part through upregulation of neuronal PPARυ; its antagonism inhibits Rb siRNA plasticity, whereas a PPARυ agonist increases growth. In an in vivo regenerative paradigm following complete peripheral nerve trunk transection, direct delivery of Rb siRNA prompts increased outgrowth of axons from proximal stumps and entrains Schwann cells to accompany them for greater distances. Similarly, Rb siRNA delivery following a nerve crush improves behavioural indices of motor and sensory recovery in mice. The overall findings indicate that inhibition of tumour suppressor molecules has a role to play in promoting adult neuron regeneration.

Three-dimensional structural niches engineered via two-photon laser polymerization promote stem cell homing.

A strategy to modulate the behavior of stem cells in culture is to mimic structural aspects of the native cell/extracellular matrix interaction. We applied femtosecond laser two-photon polymerization (2PP) to fabricate three-dimensional (3-D) microscaffolds, or "niches", using a hybrid organic-inorganic photoresist called SZ2080. The niches, of sizes fitting in a volume of 100×100×100 µm(3), were made by an external containment grid of horizontal parallel elements and by an internal 3-D lattice. We developed two niche heights, 20 and 80-100 µm, and four lattice pore dimensions (10, 20, 30 µm and graded). We used primary rat mesenchymal stem cells (MSCs) to study cell viability, migration and proliferation in the niches, up to 6 culture days. MSCs preferentially stayed on/in the structures once they ran into them through random migration from the surrounding flat surface, invaded those with a lattice pore dimension greater than 10 µm, and adhered to the internal lattice while the cell nuclei acquired a roundish morphology. In the niches, the highest MSC density was found in those areas where proliferation was observed, corresponding to the regions where the scaffold surface density available for cell adhesion was highest. The microgeometry inducing the highest cell density was 20 µm high with graded pores, in which cell invasion was favored in the central region of large porosity and cell adhesion was favored in the lateral regions of high scaffold surface density. Cell density in the niches, 17±6 cells/(100×100 µm(2)), did not significantly differ from that of the flat surface colonies. This implies that MSCs spontaneously homed and established colonies within the 3-D niches. This study brings to light the crucial role played by the niche 3-D geometry on MSC colonization in culture, with potential implications for the design of biomaterial scaffolds for synthetic niche engineering.

A new perfluoropolyether-based hydrophobic and chemically resistant photoresist structured by two-photon polymerization.

Two-photon polymerization technology has been used to fabricate submicrometer three-dimensional (3D) structures using a new polyfunctional perfluoropolyether-based resist, which is a polymer intrinsically hydrophobic and chemically resistant. The fluorinated resist was designed and synthesized in this work and successfully employed to fabricate woodpile structures in various experimental conditions. This is the first demonstration of the capability to fabricate hydrophobic and chemically resistant 3D structures with submicrometer resolution and arbitrary geometry.