Collective spin waves in RKKY interlayer-coupled Ni80Fe20/Ru/Ni80Fe20nanowire arrays.

We report on a comprehensive investigation of collective spin waves in Ruderman-Kittel-Kasuya-Yosida (RKKY) interlayer-coupled Ni80Fe20(10 nm)/Ru(1.0 nm)/ Ni80Fe20(10 nm) nanowire (NW) arrays. We employed Brillouin light scattering to probe the field- and wavevector-dependences of the spin-wave frequency spectra. The acquired data were subsequently analyzed and interpreted within the framework of a microscopic Hamiltonian-based method, enabling a detailed understanding of the observed spin-wave behavior. We observed the propagation of Bloch-type collective spin waves within the arrays, characterized by distinct magnonic bandwidths that stem from the combined influence of RKKY interlayer and inter-NW dynamical dipolar interactions.

Theory for magnetic impurity modes in two-dimensional van der Waals ferromagnetic films.

A spin-wave analysis is developed to calculate the energies of the localized excitations occurring in two-dimensional ferromagnetic van der Waals monolayers when a substitutional magnetic impurity is introduced. The magnetic ions lie on a bipartite honeycomb lattice (similar to that for graphene) and the theory includes the effects of both Ising anisotropy and single-ion anisotropy to stabilize the magnetic ordering perpendicular to the atomic plane at low temperatures. A Dyson-equation formalism, together with the spin-dependent Green's functions derived for van der Waals monolayers, is employed to evaluate the existence conditions and energies for the impurity modes, which lie above the band of spin-wave states of the pure host material. For realistic parameter values it is found that typically two impurity modes may exist, depending on the spin quantum number for the magnetic impurity atom. Numerical applications are made to CrI3and Cr2Ge2Te6as the host materials.

Spin Waves in Ferromagnetic Nanorings with Interfacial Dzyaloshinskii-Moriya Interactions: II. Directional Effects.

A theory is presented to study the effect of interfacial Dzyaloshinskii-Moriya interactions (DMIs) on the static and dynamic magnetic properties in single-layered ferromagnetic nanorings. A microscopic (Hamiltonian-based) approach is used that also includes the antisymmetric DMI besides the competing symmetric (bilinear) exchange interactions, magnetic dipole-dipole interactions, and an applied magnetic field. Here, the axial vector of the DMI is taken to be in the plane of the nanoring (by contrast with earlier studies) and we explore cases where it is either parallel or perpendicular to the in-plane magnetic field. Significantly, with this orientation for the DMI axial vector, the inhomogeneous static magnetization is tilted to have a component perpendicular to the plane giving a surface texture. This effect is studied in both the low-field vortex and high-field onion states. There is a consequent modification to the discrete set of spin-wave modes in both states through their frequencies and spatial amplitudes. We present combined analytical and numerical results for the static properties and dynamical magnetization in ferromagnetic nanorings, including the variation with applied field.

Impact of Pediatric Dental Resident Availability in the Pediatric Emergency Department.

OBJECTIVE: The purpose of this study is to describe the impact of Delaware's first pediatric dental residency program on treatment of patients presenting to the pediatric emergency department (PED). METHODS: Charts were reviewed for patients presenting to the PED with a dental chief complaint over a 9-month period with a comparison period. Chief complaint, diagnosis, treatment interventions, disposition, and demographic information were included. χ 2 , Fisher exact, and Student t tests with a P value less than 0.05 were regarded as significant. RESULTS: A total of 432 patients met inclusion criteria; 197 before dental residency commencement and 235 after residency commencement. Dental consultation significantly increased (56% vs 7%, P < 0.01) between the study periods. There were no statistically significant differences in sex, race, insurance type, admissions, or proportion of presentations of trauma or infection between the study periods. Dental residents provided in-person evaluation for 40% of patients. The proportion of patients receiving dental intervention increased significantly postresidency period (57% vs 47%, P = 0.04). Pediatric emergency department extractions and splints both occurred in a significantly larger portion of patients after the start of the residency program (17% vs 1% and 5% vs 0%, P < 0.01). A higher proportion of patients with dental complaints received procedural sedation in the PED after residency (13% vs 2%, P < 0.01). CONCLUSIONS: Pediatric dental resident availability in the PED significantly increased dental consultation and intervention. A significantly higher percentage of PED patients received definitive treatment at point of service without requiring referral to another facility.

Oral Complaint Visits to the Pediatric Emergency Department During the COVID-19 Pandemic.

OBJECTIVE: We aimed to describe differences in orofacial complaints presenting to a pediatric emergency department (PED) during the COVID-19 pandemic as compared to those presenting prior to the pandemic. STUDY DESIGN: A retrospective review was conducted in the PED from March 16, 2020, to August 16, 2020, and compared with the prior year. RESULTS: Despite a 41% reduction in total PED visits, oral visits as a percentage of PED volume increased (3% vs 2%) P < 0.01) during the pandemic. More children with dental complaints required intervention during the pandemic (48% vs 30%, P < 0.001) including extractions and splinting (15% vs 1%, P < 0.001). Compared with pre-pandemic, proportion of tooth infections increased (68% vs 40%, P < 0.001), while oral ulcers decreased (19% vs 47%, P < 0.001). CONCLUSION: Pediatric emergency department presentation decreased during the pandemic, but patients requiring interventions increased. This may reflect hesitation in seeking treatment, outpatient facility closures, and increased acuity at the time of PED presentation due to delays in seeking care.

Dipole-exchange spin waves in two-dimensional van der Waals ferromagnetic films and stripes.

A spin-wave (SW) theory that includes the long-range dipole-dipole interactions is presented for monolayers of van der Waals (vdW) ferromagnets for which the magnetic ions lie on a two-dimensional honeycomb lattice. The dipolar interactions provide an additional anisotropy in these materials, along with the Ising exchange interaction and/or single-ion anisotropies that typically stabilize the two-dimensional magnetic ordering. Analytical results for the linearized SW energies are obtained for the ferromagnets in two geometries: complete films and finite-width stripes (or ribbons). In both cases it is found that the inclusion of the dipole-dipole interactions leads to a shift and sometimes a splitting of the magnetic modes in the vdW structure. Also, in the latter case, where the edges are assumed to be along the zigzag lattice directions, the dipole-dipole interactions are found to play a role, as well as the exchange interactions, in modifying the localized edge SWs. Numerical examples are given, including applications to the ferromagnet CrI3.

Postoperative Bleeding Complications after Stainless Steel Crown Placement: A Case Series.

Stainless steel crown (SSC) placement is a common pediatric restorative treatment, generally completed with minimal complications. Discussed in this case series are two patients who presented to the emergency department (ED) with moderate oral bleeding persisting more than 12 hours after oral rehabilitation under general anesthesia. Bleeding incidence after pediatric oral rehabilitation has been found to range from 20% to 40%, with most being considered mild and significantly associated with extractions. There is limited documentation regarding moderate, persistent postoperative bleeding associated with placement of preformed metal crowns. The objective of this paper is to raise awareness of postoperative bleeding following SSC placement, discuss probable causes to minimize complications in the future, and discuss the local measures that were used to obtain hemostasis.

Quantum statistics and squeezing for a microwave-driven interacting magnon system.

Theoretical studies are reported for the statistical properties of a microwave-driven interacting magnon system. Both the magnetic dipole-dipole and the exchange interactions are included and the theory is developed for the case of parallel pumping allowing for the inclusion of the nonlinear processes due to the four-magnon interactions. The method of second quantization is used to transform the total Hamiltonian from spin operators to boson creation and annihilation operators. By using the coherent magnon state representation we have studied the magnon occupation number and the statistical behavior of the system. In particular, it is shown that the nonlinearities introduced by the parallel pumping field and the four-magnon interactions lead to non-classical quantum statistical properties of the system, such as magnon squeezing. Also control of the collapse-and-revival phenomena for the time evolution of the average magnon number is demonstrated by varying the parallel pumping amplitude and the four-magnon coupling.

Spin-wave instabilities of ferromagnetic nanowire stripes under parallel pumping.

A microscopic (or Hamiltonian-based) theory is presented for the spin-wave instability thresholds in ferromagnetic nanowires under conditions of parallel pumping with a microwave field. A dipole-exchange Hamiltonian is employed in which the external magnetic field is either longitudinal or transverse to the length of the nanowire. This contrasts with most previous work on nonlinear spin waves which concentrate on situations where a macroscopic (or continuum) theory is appropriate. In nanowire stripes with lateral dimensions of order 100 nm or less, the quantization of the eigenmodes becomes modified due to strong spatial confinement and edge effects, making it appropriate to employ a microscopic dipole-exchange approach analogous to that used recently for ultrathin films. Numerical applications are presented for the dependence of the threshold microwave field amplitude for instability on the static applied field (the analog of the butterfly curves). The cases of longitudinal and transverse applied fields are found to lead to distinctly different behaviors, which are illustrated using EuS and permalloy as materials with different ratios of dipolar to exchange interactions. Structural effects due to the discrete spin-wave branches lead to structural aspects of the butterfly curves that are significantly modified compared with those for ultrathin films due to the edge modes in the nanowires.

Spectroscopic, computational modeling and cytotoxicity of a series of meso-phenyl and meso-thienyl-BODIPYs.

A series of twenty-two BODIPY compounds were synthesized, containing various meso-phenyl and meso-thienyl groups, and their spectroscopic and structural properties were investigated using both experimental and computational methods. Further functionalization of the BODIPY framework via iodination at the 2,6-pyrrolic positions was explored in order to determine the effect of these heavy atoms on the photophysical and cytotoxicity of the meso-aryl-BODIPYs. BODIPYs bearing meso-thienyl substituents showed the largest red-shifted absorptions and emissions and reduced fluorescence quantum yields. The phototoxicity of the BODIPYs in human carcinoma HEp2 cells depends on both the presence of iodines and the nature of the meso-aryl groups. Six of the eleven 2,6-diiodo-BODIPYs investigated showed at least a sevenfold enhancement in phototoxicity (IC50 = 3.5-28 µM at 1.5 J/cm(2)) compared with the non-iodinated BODIPYs, while the others showed no cytotoxicity, while their singlet oxygen quantum yields ranged from 0.02 to 0.76. Among the series investigated, BODIPYs 2a and 4a bearing electron-donating meso-dimethoxyphenyl substituents showed the highest phototoxicity and dark/phototoxicity ratio, and are therefore the most promising for application in PDT.

Evaluation of the spatter-reduction effectiveness of two dry-field isolation techniques.

BACKGROUND: The authors conducted a study to compare the effectiveness of two dry-field isolation techniques with that of a control technique (no isolation) in reducing spatter from a dental operative site. METHODS: The authors designed a benchtop experiment to evaluate spatter patterns after performing simulated occlusal surface preparations on three typodont teeth in a dental manikin. Fluorescein dye served as the marker to enable visualization of the spatter distribution. The authors compared the effectiveness of a nonisolated control consisting of high-volume evacuation (HVE) alone with that of two dry-field isolation techniques: a dental dam with HVE and the Isolite system (Isolite Systems, Santa Barbara, Calif). RESULTS: The authors performed a two-way analysis of variance. Both the Isolite device and the dental dam with HVE exhibited a significant decrease in the number of contaminated squares (P < .001) compared with that for the nonisolated control. In addition, overall, the results showed no statistically significant difference between the Isolite system and the dental dam with HVE (P = .126). CONCLUSIONS: The study results showed that use of a dental dam with HVE or the Isolite system significantly reduced spatter overall compared with use of HVE alone. CLINICAL IMPLICATIONS: Isolation with a dental dam and HVE or with the Isolite system appears to aid in the reduction of spatter during operative dental procedures, potentially reducing exposure to oral pathogens.

An effective nonchemical treatment for head lice: a lot of hot air.

OBJECTIVES: Head lice (Pediculus humanus capitis) are a major irritant to children and their parents around the world. Each year millions of children are infested with head lice, a condition known as pediculosis, which is responsible for tens of millions of lost school days. Head lice have evolved resistance to many of the currently used pediculicides; therefore, an effective new treatment for head lice is needed. In this study we examined the effectiveness of several methods that use hot air to kill head lice and their eggs. METHODS: We tested 6 different treatment methods on a total of 169 infested individuals. Each method delivers hot air to the scalp in a different way. We evaluated how well these methods kill lice and their eggs in situ. We also performed follow-up inspections to evaluate whether the sixth, most successful, method can cure head louse infestations. RESULTS: All 6 methods resulted in high egg mortality (> or = 88%), but they showed more-variable success in killing hatched lice. The most successful method, which used a custom-built machine called the LouseBuster, resulted in nearly 100% mortality of eggs and 80% mortality of hatched lice. The LouseBuster was effective in killing lice and their eggs when operated at a comfortable temperature, slightly cooler than a standard blow-dryer. Virtually all subjects were cured of head lice when examined 1 week after treatment with the LouseBuster. There were no adverse effects of treatment. CONCLUSIONS: Our findings demonstrate that one 30-minute application of hot air has the potential to eradicate head lice infestations. In summary, hot air is an effective, safe treatment and one to which lice are unlikely to evolve resistance.

Segregation of the photosystems in higher plant thylakoids and short- and long-term regulation by a mesoscopic approach.

In this paper we consider the relationship between the lateral segregation of photosystems I and II in the grana and characteristics of the short- and long-term regulation in thylakoids following the mesoscopic approach. Our study is thermodynamic; it is based on the Flory-Huggins theory for binary mixtures and the McMillan-Mayer theory of heterogeneous solutions. We demonstrate that state transitions promote rearrangement of photosystems by either favoring their mixing after LHCII phosphorylation or enhancing their segregation after LHCII dephosphorylation. This regulation influences the entire system properties locally. We also demonstrate that the variations of the photosystem ratio promote rearrangement of the photosystems preserving their segregation. This regulation influences the entire system properties globally. The studies presented are another indication of the importance of the segregation of the photosystems in the grana thylakoids of higher plants. Segregation of PSIs and PSIIs is a signature of the spinodal decomposition, which is a fine regulatory mechanism, related to both the short- and long-term adaptations of the photosynthetic apparatus in higher plant thylakoids.

Segregation of the photosystems in thylakoids depends on their size.

Lateral segregation of two types of photosystems in thylakoid membranes of green plants is one of the key factors that provide the stability and fine-tuning of the light quanta supply by pigment proteins and non-cyclic electron transport. Due to this specific feature of the membrane structural organization, the photosynthetic units function in the green plants with optimal performance. In this report a mesoscopic theory is outlined to address the physical aspects of segregation phenomenon. Results of theoretical studies and computer simulations suggest that charge mismatch and the size difference between two photosystems in grana are most responsible for their lateral segregation, which is driven by the screened electrostatic and lipid-induced interactions. Comparative simulations of photosystems of different sizes show the crucial dependence of their ordering on a geometrical parameter. It seems that the size effect alone may prevent photosystems from segregated arrangement in cyanobacterial thylakoids.

Lateral heterogeneity of photosystems in thylakoid membranes studied by Brownian dynamics simulations.

The aggregation and segregation of photosystems in higher plant thylakoid membranes as stromal cation-induced phenomena are studied by the Brownian dynamics method. A theoretical model of photosystems lateral movement within the membrane plane is developed, assuming their pairwise effective potential interaction in aqueous and lipid media and their diffusion. Along with the screened electrostatic repulsive interaction the model accounts for the van der Waals-type, elastic, and lipid-induced attractive forces between photosystems of different sizes and charges. Simulations with a priori estimated parameters demonstrate that all three studied repulsion-attraction alternatives might favor the local segregation of photosystems under physiologically reasonable conditions. However, only the lipid-induced potential combined with the size-corrected screened Coulomb interaction provides the segregated configurations with photosystems II localized in the central part of the grana-size simulation cell and photosystems I occupying its margins, as observed experimentally. Mapping of thermodynamic states reveals that the coexistence curves between isotropic and aggregated phases are the sigmoidlike functions regardless of the effective potential type. It correlates with measurements of the chlorophyll content of thylakoid fragments. Also the universality of the phase curves characterizes the aggregation and segregation of photosystems as order-disorder phase transitions with the Debye radius as a governing parameter.

Polaritons in hollow cylinders in the presence of a dc magnetic field.

We study the effects of a dc external magnetic field on the polaritons propagating in hollow dielectric cylinders, taking into account the retardation effects. In solving Maxwell's equations we show that only the TM modes can propagate in these systems, and we obtain the dispersion relation of the confined-surface-polariton modes. The effects of geometric parameters and the external magnetic field on the propagation of surface-polariton modes are also analyzed and show significant influence on the behavior of the modes. Numerical results are presented for the dispersion relation of surface polaritons with GaAs as the optically active medium.