Momentum-resolved electronic structure and band offsets in an epitaxial NbN/GaN superconductor/semiconductor heterojunction.

The electronic structure of heterointerfaces is a pivotal factor for their device functionality. We use soft x-ray angle-resolved photoelectron spectroscopy to directly measure the momentum-resolved electronic band structures on both sides of the Schottky heterointerface formed by epitaxial films of the superconducting NbN on semiconducting GaN, and determine their momentum-dependent interfacial band offset as well as the band-bending profile. We find, in particular, that the Fermi states in NbN are well separated in energy and momentum from the states in GaN, excluding any notable electronic cross-talk of the superconducting states in NbN to GaN. We support the experimental findings with first-principles calculations for bulk NbN and GaN. The Schottky barrier height obtained from photoemission is corroborated by electronic transport and optical measurements. The momentum-resolved understanding of electronic properties of interfaces elucidated in our work opens up new frontiers for the quantum materials where interfacial states play a defining role.

Is contrast sensitivity a physiological marker in attention-deficit hyperactivity disorder?

Attention-deficit hyperactivity disorder (ADHD) is one of the most common childhood-onset psychiatric disorders. Although the etiology is complex and has not yet been clarified, dopamine is thought to play a role in the etiology. Methylphenidate (MPH) is a psychostimulant drug used as first-line treatment for ADHD and it inhibits dopamine and norepinephrine reuptake transporters. Dopamine also has an effect on retina and contrast sensitivity. Despite evidence indicating the effects of dopamine on contrast sensitivity, the results of studies examining contrast sensitivity in ADHD patients are inconsistent. Also, no studies have been encountered examining the possible effect of MPH on contrast sensitivity. The hypotheses of this study are that children with ADHD who have not used MPH will have lower contrast sensitivity levels than the members of the control group, that contrast sensitivity levels increase after the use of MPH, and that contrast sensitivity is a potential physiological marker for ADHD. The study was conducted with 30 children with ADHD and 30 children without ADHD. Psychiatric evaluations of the participants were conducted with the Schedule for Affective Disorders and Schizophrenia for School Age Children-Present and Lifetime-Turkish version, Conner's Parent Rating Scale-Revised Short form and the Turgay DSM-IV-based Child and Adolescent Behavioral Disorders Screening and Rating Scale. Photopic contrast sensitivity was measured using the Functional Acuity Contrast Test (FACT). Results showed that FACT mean values of the control group were significantly higher than those of the ADHD group (pre-treatment) in all spatial frequencies. In four spatial frequencies (CPD 1.5, 3, 12 and 18), the FACT mean values of the control group were significantly higher than the ADHD group (during the OROS-MPH treatment). At all spatial frequencies, the mean values of the ADHD group during the OROS-MPH treatment were significantly higher than before the OROS-MPH treatment. In conclusion, the present study showed that contrast sensitivity is low in children with ADHD and increases significantly after OROS-MPH medication, but still did not reach the levels of the children without ADHD. Our findings suggest that contrast sensitivity may be a potential physiological marker in ADHD.

Realization of Epitaxial Thin Films of the Topological Crystalline Insulator Sr3 SnO.

Topological materials are derived from the interplay between symmetry and topology. Advances in topological band theories have led to the prediction that the antiperovskite oxide Sr3 SnO is a topological crystalline insulator, a new electronic phase of matter where the conductivity in its (001) crystallographic planes is protected by crystallographic point group symmetries. Realization of this material, however, is challenging. Guided by thermodynamic calculations, a deposition approach is designed and implemented to achieve the adsorption-controlled growth of epitaxial Sr3 SnO single-crystal films by molecular-beam epitaxy (MBE). In situ transport and angle-resolved photoemission spectroscopy measurements reveal the metallic and electronic structure of the as-grown samples. Compared with conventional MBE, the used synthesis route results in superior sample quality and is readily adapted to other topological systems with antiperovskite structures. The successful realization of thin films of Sr3 SnO opens opportunities to manipulate topological states by tuning symmetries via strain engineering and heterostructuring.

Measurement of Contrast Sensitivity in Patients with Behçet's Disease without Ocular Involvement.

PURPOSE: To evaluate contrast sensitivity in patients with Behçet's disease (BD) without ocular involvement. METHODS: The study group was composed of 47 BD patients (20 to 50 years of age) who did not have ocular involvement. The control group was composed of 47 normal volunteers who were similar to the study group in terms of age and gender. No participants in this study had any ocular or systemic pathologies except for BD. The contrast sensitivity measurements were performed using the Functional Acuity Contrast Test under photopic conditions, and the results were compared between the two groups. RESULTS: The mean age of the BD patients and control subjects was 34.5 ± 9.7 and 33.2 ± 7.6 years, respectively. The mean disease duration of the BD patients was 5.5 ± 6.4 years. There was a statistically significant decrease at five spatial frequencies (A, 1.5; B, 3; C, 6; D, 2; and E, 18 cycles per degree) in patients with BD compared with control subjects (p < 0.001, p = 0.004, p = 0.002, p < 0.001, and p = 0.001, respectively). CONCLUSIONS: The contrast sensitivity of BD patients without ocular involvement was lower than that of the control group. Further studies seem mandatory to confirm our results.

Duane Retraction Syndrome: Clinical Features and a Case Group-Specific Surgical Approach.

PURPOSE: To describe the clinical features of patients with Duane retraction syndrome (DRS) and evaluate the outcomes of surgical approaches based on the characteristics of each patient. METHODS: The records of 38 Caucasian subjects with DRS were retrospectively reviewed. The patients were classified as type I, II, or III based on the Huber Classification. Ten patients underwent unilateral medial rectus (MR) recession due to abnormal head posture (AHP) and/or esotropia. Four patients underwent Y-splitting and recession of the lateral rectus (LR) with MR recession due to AHP and/or esotropia, upshoot, and globe retraction. RESULTS: There was a preponderance of unilaterality, female gender, left eye, type I, orthotropia, upshoot, and low refractive error. All patients demonstrated globe retraction and fissure narrowing. AHP was only present in unilateral cases. Nine patients had amblyopia. More than half of the patients over 5 years of age had decreased stereopsis. MR recession decreased AHP to less than 8° in all patients. Y-splitting and recession of the LR eliminated upshoot in all four patients. One patient who underwent an 8-mm MR recession demonstrated -2 adduction limitation. CONCLUSIONS: The DRS patients in our study demonstrated features that are consistent with previous reports in the literature. This study emphasizes the need to consider disease classification in the surgical management of DRS patients.

Measurement of Contrast Sensitivity in Patients with Behçet's Disease without Ocular Involvement

PURPOSE: To evaluate contrast sensitivity in patients with Behçet's disease (BD) without ocular involvement. METHODS: The study group was composed of 47 BD patients (20 to 50 years of age) who did not have ocular involvement. The control group was composed of 47 normal volunteers who were similar to the study group in terms of age and gender. No participants in this study had any ocular or systemic pathologies except for BD. The contrast sensitivity measurements were performed using the Functional Acuity Contrast Test under photopic conditions, and the results were compared between the two groups. RESULTS: The mean age of the BD patients and control subjects was 34.5 ± 9.7 and 33.2 ± 7.6 years, respectively. The mean disease duration of the BD patients was 5.5 ± 6.4 years. There was a statistically significant decrease at five spatial frequencies (A, 1.5; B, 3; C, 6; D, 2; and E, 18 cycles per degree) in patients with BD compared with control subjects (p < 0.001, p = 0.004, p = 0.002, p < 0.001, and p = 0.001, respectively). CONCLUSIONS: The contrast sensitivity of BD patients without ocular involvement was lower than that of the control group. Further studies seem mandatory to confirm our results.

Insights into the Structure of Liquid Water from Nuclear Quantum Effects on the Density and Compressibility of Ice Polymorphs.

Nuclear quantum effects lead to an anomalous shift of the volume of hexagonal ice; heavy ice has a larger volume than light ice. Furthermore, this anomaly in ice increases with temperature and persists in liquid water up to the boiling point. To gain more insight, we study nuclear quantum effects on the density and compressibility of several ice-like structures and crystalline ice phases. By calculating the anisotropic contributions to the stain tensor, we analyze how the compressibility changes along different directions in hexagonal ice, and find that hexagonal ice is softer along the x- y plane than the z-direction. Furthermore, by performing ab initio density functional theory calculations with a van der Waals functional and with the quasiharmonic approximation, we find an anomalous isotope effect in the bulk modulus of hexagonal ice: heavy ice has a smaller bulk modulus than light ice. In agreement with the experiments, we also obtain an anomalous isotope effect for clathrate hydrate structure I. For the rest of the ice polymorphs, the isotope effect is (i) anomalous for ice IX, Ih, Ic, clathrate, and low density liquid-like (LDL-like) amorphous ice; (ii) normal at T = 0 K and becomes anomalous with increasing temperature for ice IX, II, high density liquid-like (HDL-like) amorphous ices, and ice XV; and (iii) normal for ice VIII up to the melting point. There is a transition from an anomalous isotope effect to a normal isotope effect for both the volume and bulk modulus, as the density (compressibility) of the structures increases (decreases). This result can explain the anomalous isotope effect in liquid water: as the compressibility decreases from the melting point to the compressibility minimum temperature, the difference between the volumes of the heavy and light water rapidly decreases, but the effect stays anomalous up to the boiling temperature as the hydrogen bond network is never completely broken by fully filling all of the interstitial sites.

Nontraumatic Descemet Membrane Detachment with Tear in Osteogenesis Imperfecta.

We report the first case of unilateral spontaneous Descemet membrane detachment (DMD) with tear occurring in a patient with osteogenesis imperfecta (OI). A 20-year-old male patient with OI presented with a history of recent primary repair (2 weeks prior) of left globe rupture following local finger trauma to the left eye. The patient had no history of other ocular surgery or trauma. The examination revealed a best corrected visual acuity of 20/40 in the right and no light perception in the left eye. Slit-lamp examination showed an oval giant Descemet tear extending from the 12 o'clock to the 5 o'clock area and a large DMD involving the upper and nasal quadrants in the right cornea. It was thought that monitoring the patient without intervention and only considering a surgical procedure if the disorder progressed was the best option, taking into account the patient's reasonable visual acuity and the risks of keratoplasty. The dimensions of the DMD and tear had remained the same at 1-year follow-up period. We believe that follow-up without intervention should be considered for non-progressive DMD with a giant tear if the patient has a single functional eye.