Nanocavity-Mediated Purcell Enhancement of Er in TiO2 Thin Films Grown via Atomic Layer Deposition

The use of trivalent erbium (Er3+), typically embedded as an atomic defect in the solid-state, has widespread adoption as a dopant in telecommunication devices and shows promise as a spin-based quantum memory for quantum communication. In particular, its natural telecom C-band optical transition and spin-photon interface make it an ideal candidate for integration into existing optical fiber networks without the need for quantum frequency conversion. However, successful scaling requires a host material with few intrinsic nuclear spins, compatibility with semiconductor foundry processes, and straightforward integration with silicon photonics. Here, we present Er-doped titanium dioxide (TiO2) thin film growth on silicon substrates using a foundry-scalable atomic layer deposition process with a wide range of doping controls over the Er concentration. Even though the as-grown films are amorphous after oxygen annealing, they exhibit relatively large crystalline grains, and the embedded Er ions exhibit the characteristic optical emission spectrum from anatase TiO2. Critically, this growth and annealing process maintains the low surface roughness required for nanophotonic integration. Finally, we interface Er ensembles with high quality factor Si nanophotonic cavities via evanescent coupling and demonstrate a large Purcell enhancement (≈300) of their optical lifetime. Our findings demonstrate a low-temperature, nondestructive, and substrate-independent process for integrating Er-doped materials with silicon photonics. At high doping densities this platform can enable integrated photonic components such as on-chip amplifiers and lasers, while dilute concentrations can realize single ion quantum memories.

Magnon-mediated qubit coupling determined via dissipation measurements

Controlled interaction between localized and delocalized solid-state spin systems offers a compelling platform for on-chip quantum information processing with quantum spintronics. Hybrid quantum systems (HQSs) of localized nitrogen-vacancy (NV) centers in diamond and delocalized magnon modes in ferrimagnets-systems with naturally commensurate energies-have recently attracted significant attention, especially for interconnecting isolated spin qubits at length-scales far beyond those set by the dipolar coupling. However, despite extensive theoretical efforts, there is a lack of experimental characterization of the magnon-mediated interaction between NV centers, which is necessary to develop such hybrid quantum architectures. Here, we experimentally determine the magnon-mediated NV-NV coupling from the magnon-induced self-energy of NV centers. Our results are quantitatively consistent with a model in which the NV center is coupled to magnons by dipolar interactions. This work provides a versatile tool to characterize HQSs in the absence of strong coupling, informing future efforts to engineer entangled solid-state systems.

Purcell Enhancement of Erbium Ions in TiO2 on Silicon Nanocavities

Isolated solid-state atomic defects with telecom optical transitions are ideal quantum photon emitters and spin qubits for applications in long-distance quantum communication networks. Prototypical telecom defects, such as erbium, suffer from poor photon emission rates, requiring photonic enhancement using resonant optical cavities. Moreover, many of the traditional hosts for erbium ions are not amenable to direct incorporation with existing integrated photonics platforms, limiting scalable fabrication of qubit-based devices. Here, we present a scalable approach toward CMOS-compatible telecom qubits by using erbium-doped titanium dioxide thin films grown atop silicon-on-insulator substrates. From this heterostructure, we have fabricated one-dimensional photonic crystal cavities demonstrating quality factors in excess of 5 × 10⁴ and corresponding Purcell-enhanced optical emission rates of the erbium ensembles in excess of 200. This easily fabricated materials platform represents an important step toward realizing telecom quantum memories in a scalable qubit architecture compatible with mature silicon technologies.

Raman Linewidth Contributions from Four-Phonon and Electron-Phonon Interactions in Graphene

The Raman peak position and linewidth provide insight into phonon anharmonicity and electron-phonon interactions in materials. For monolayer graphene, prior first-principles calculations have yielded decreasing linewidth with increasing temperature, which is opposite to measurement results. Here, we explicitly consider four-phonon anharmonicity, phonon renormalization, and electron-phonon coupling, and find all to be important to successfully explain both the G peak frequency shift and linewidths in our suspended graphene sample over a wide temperature range. Four-phonon scattering contributes a prominent linewidth that increases with temperature, while temperature dependence from electron-phonon interactions is found to be reversed above a doping threshold (ℏω_{G}/2, with ω_{G} being the frequency of the G phonon).

Preliminary experience with the percutaneous embolization of juvenile angiofibromas using only ethylene-vinyl alcohol copolymer (Onyx) for preoperative devascularization prior to surgical resection

BACKGROUND AND PURPOSE

Juvenile angiofibromas are hypervascular tumors that may benefit from preoperative devascularization to reduce intraoperative blood loss. Our purpose was to evaluate the extent of angiographic devascularization and intraoperative blood loss by using only Onyx for percutaneous juvenile angiofibroma tumor embolization.

MATERIALS AND METHODS

We reviewed the clinical records and preoperative and postoperative imaging studies of a consecutive series of 9 patients with juvenile angiofibromas who were treated with preoperative embolization with direct percutaneous injection of Onyx followed by resection from a standard open surgical or endoscopic approach.

RESULTS

Two Fisch type I, 1 Fisch type II, 5 Fisch type IIIa, and 1 Fisch type IVa tumor were treated. Complete devascularization was achieved in all cases percutaneously with only Onyx. There were no complications. The average intraoperative blood loss was 567.7 mL (range, 10-1700 mL). An average of 2.2 needles (range, 1-5 needles) was placed into the tumor. An average of 14.6 mL of Onyx (range, 2-25 mL) was injected into each tumor. Four Fisch type IIIa tumors were removed completely from only an ENE approach.

CONCLUSIONS

Presurgical direct percutaneous embolization of a juvenile angiofibroma with only EVOH before surgical resection is safe and feasible. Our preliminary experience suggests that Onyx may offer a higher degree of devascularization compared with other embolic agents. This may facilitate an easier surgical resection with lower blood loss.

Usefulness of percutaneously injected ethylene-vinyl alcohol copolymer in conjunction with standard endovascular embolization techniques for preoperative devascularization of hypervascular head and neck tumors: technique, initial experience, and correlation with surgical observations

BACKGROUND AND PURPOSE

Few reports have described the embolization of head and neck lesions by using direct percutaneous techniques. We report our preliminary experience in the direct percutaneous embolization of hypervascular head and neck tumors by using Onyx in conjunction with standard endovascular embolization techniques. We describe the technical aspects of the procedure and its efficacy in reducing intraoperative blood loss.

MATERIALS AND METHODS

We retrospectively studied 14 patients (3 females and 11 males; mean age, 33.4 years; range, 11-56 years) with 15 hypervascular tumors of the head and neck that underwent direct percutaneous embolization with Onyx in conjunction with particulate embolization. Nine paragangliomas and 6 JNAs underwent treatment. Documented blood loss was obtained from operative reports in these 15 patients with surgical resection performed 24-48 hours after the embolization.

RESULTS

Intratumoral penetration with progressive blood flow stasis was achieved during each injection. A mean of 3.1 needles (20-gauge, 3.5-inch spinal needle) were placed percutaneously into the lesion (range, 1-6). The mean intraoperative blood loss was 780 mL (range, <50-2200 mL). Near total angiographic devascularization was achieved in 13 of 15 tumors. There were no local complications or neurologic deficits from the percutaneous access or embolization of these hypervascular tumors.

CONCLUSIONS

In this study, the use of percutaneous injected Onyx in conjunction with standard endovascular embolization techniques in patients with hypervascular head and neck tumors seemed to enhance the ability to devascularize these tumors before operative removal.

Effects of intraventricular infusion of vascular endothelial growth factor on cerebral blood flow, edema, and infarct volume

BACKGROUND

Therapeutic cerebral angiogenesis, utilizing angiogenic factors to enhance collateral vessel formation within the central nervous system, is a potential method for cerebral revascularization. A prior dose-response study determined that intracerebroventricular infusion of vascular endothelial growth factor (VEGF) increases vascular density with minimal associated brain edema at a concentration of 5 microg/ml. The purpose of this study was to assess effects of intracerebroventricular infusion of VEGF (5 microg/ml) on cerebral blood flow, infarct volume, and brain edema after ischemia.

METHODS

Recombinant human VEGF(165) was infused into the right lateral ventricle of rats with an osmotic minipump at a rate of 1 microl/hr for 7 days. Control animals received vehicle only. Ischemia was produced by transient (2 hours) middle cerebral artery occlusion (MCAO). After MCAO, cerebral blood flow was determined with the indicator fractionation technique: infarct volume was assessed with 2,3,5-triphenlytetrazolium chloride staining, and brain edema was determined by measuring brain water content.

FINDINGS

Cerebral blood flow was not significantly different in animals treated with VEGF compared to controls. There was a significant reduction in total infarct volume after temporary MCAO in VEGF-treated animals compared to controls (163+/-37 mm(3) vs. 309+/-54 mm(3), P<0.05). Brain water content after transient MCAO was also significantly reduced in VEGF-treated animals compared to controls (80.9+/-0.7% vs. 83.3+/-0.6%, P<0.05).

INTERPRETATION

Intracerebroventricular infusion of VEGF(165) (5 microg/ml) decreases infarct volume and brain edema after temporary MCAO without a significant increase in cerebral blood flow. These results indicate that VEGF may have a direct neuroprotective effect in cerebral ischemia.

Eosinophilia in the neonatal intensive care unit

Although common in the neonatal intensive care unit, eosinophilia is often overlooked or ignored. The latter might be, at least in part, because evaluating the neonate with eosinophilia can be a complex process. This article reviews the physiologic features of eosinophilia, reference ranges, and clinical conditions associated with eosinophilia in the neonate. Recommendations for the evaluation of the neonate with eosinophilia are presented.

Granulocyte-macrophage colony-stimulating factor and interleukin-5 concentrations in premature neonates with eosinophilia

OBJECTIVE

Eosinophilia is common among premature neonates, but little is known about the cytokines responsible for influencing its onset in neonates. In adults and transgenic mice, granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-5 (IL-5) influence the development of eosinophilia. We sought to prospectively determine whether these cytokines correlated with the development of eosinophilia in premature infants.

STUDY DESIGN

We measured the absolute eosinophil count (AEC) and serial serum concentrations of GM-CSF and IL-5 in premature neonates with eosinophilia.

RESULTS

Among 201 premature neonates, 21 had an eosinophil count of > 700/microliter (occurrence, 10.5%). Of these 21 neonates, 4 had mild (700/microliter to 999/microliter), 13 had moderate (1000/microliter to 2999/microliter), and 4 had severe (> 3000/microliter) eosinophilia. No differences in gestational age or age at onset of eosinophilia were observed between the groups, but the duration of eosinophilia was less with mild than with moderate or severe eosinophilia. A total of 20 of the 21 patients had an infection or necrotizing enterocolitis diagnosed within 48 hours of the onset of eosinophilia. In patients with mild and moderate eosinophilia, serial GM-CSF and IL-5 concentrations were below the lowest enzyme-linked immunosorbent assay standard. There was no correlation between AEC and GM-CSF or IL-5 concentration in these infants. However, in one patient with severe eosinophilia, two distinct elevations in IL-5 were noted (34.6 and 46.0 pg/ml); each peak occurred 7 to 8 days before a peak in eosinophil count.

CONCLUSION

Eosinophilia is relatively common, and in those neonates with the highest AECs, the duration of eosinophilia can last for > 6 weeks. The majority of cases of eosinophilia occurred in temporal proximity to an infectious illness or necrotizing enterocolitis. Serum concentrations of IL-5 were elevated in only one of our patients with severe eosinophilia.

N-acetylaspartylglutamate selectively activates mGluR3 receptors in transfected cells

In previous studies, we demonstrated that the neuropeptide, N-acetylaspartylglutamate (NAAG), meets the traditional criteria for a neurotransmitter and selectively activates metabotropic glutamate receptor mGluR2 or mGluR3 in cultured cerebellar granule cells and glia. Sequence homology and pharmacological data suggest that these two receptors are highly related structurally and functionally. To define more rigorously the receptor specificity of NAAG, cloned rat cDNAs for mGluR1-6 were transiently or stably transfected into Chinese hamster ovary cells and human embryonic kidney cells and assayed for their second messenger responses to the two endogenous neurotransmitters, glutamate and NAAG, as well as to metabotropic receptor agonists, trans-1-aminocyclopentane-1,3-dicarboxylate (trans-ACPD) and L-2-amino-4-phosphonobutyrate (L-AP4). Despite the high degree of relatedness of mGluR2 and mGluR3, NAAG selectively activated the mGluR3 receptor. NAAG activated neither mGluR2 nor mGluR1, mGluR4, mGluR5, or mGluR6. The mGluR agonist, trans-ACPD, activated each of the transfected receptors, whereas L-AP4 activated mGluR4 and mGluR6, consistent with the published selectivity of these agonists. Hybrid cDNA constructs of the extracellular domains of mGluR2 and mGluR3 were independently fused with the transmembrane and cytoplasmic domain of mGluR1a. This latter receptor domain is coupled to phosphoinositol turnover, and its activation increases intracellular calcium. The cells transfected with these chimeric receptors responded to activation by glutamate and trans-ACPD with increases in intracellular calcium. NAAG activated the chimeric receptor that contained the extracellular domain of mGluR3 and did not activate the mGluR2 chimera.

Haplotype distribution of the human phenylalanine hydroxylase locus in Scotland and Switzerland

RFLP haplotypes at the phenylalanine hydroxylase (PAH) locus were determined in 45 nuclear Caucasian families from Switzerland and Scotland. The RFLPs at the PAH locus are highly informative, and prenatal diagnosis is possible in 85% of the families studied. The data were combined with the profiles previously observed in the Danish population, in order to study the variation in RFLP haplotype distribution among European populations. A total of 22 different haplotypes were observed in Denmark, Switzerland, and Scotland. Fifteen and 19 haplotypes are associated with the normal (non-PKU) and with the mutant chromosomes, respectively. The haplotype distribution and the allele frequency of normal chromosomes remain constant between Denmark, Switzerland, and Scotland. However, both the haplotype distribution and allele frequencies of mutant chromosomes show significant variation between the three countries. Our results suggest there may be additional mutations in the PAH gene that cause PKU.

Correlation between polymorphic DNA haplotypes at phenylalanine hydroxylase locus and clinical phenotypes of phenylketonuria

Eight polymorphic sites for seven restriction endonucleases have been reported at the human phenylalanine hydroxylase locus. The composite profile of the presence or absence for each of the eight polymorphic sites within an allele defines the haplotype of the corresponding allele. Twelve such haplotypes associated with normal and mutant phenylalanine hydroxylase alleles have been identified in 33 Danish families with children with phenylketonuria. Of the 66 mutant alleles analyzed, 59 (89%) were associated with only four haplotypes. The identification of individual phenylalanine hydroxylase alleles by haplotype analysis enables correlation of the hyperphenylalaninemic phenotypes of the patients with their genotypes. Patients who were either homozygous or heterozygous for the mutant alleles of haplotypes 2 and 3 had a severe clinical course. Patients who had a mutant allele of either haplotype 1 or 4 usually had a less severe clinical phenotype. The recent demonstration that the mutation responsible for classic phenylketonuria associated with haplotype 3 is not present in mutant alleles of other haplotypes provides unambiguous evidence that there are multiple mutations in the phenylalanine hydroxylase gene and supports the hypothesis that different combinations of mutant alleles may be responsible for the clinical diversity of phenylketonuria.