Colossal optical anisotropy from atomic-scale modulations

In modern optics, materials with large birefringence ({\Delta}n, where n is the refractive index) are sought after for polarization control (e.g. in wave plates, polarizing beam splitters, etc.), nonlinear optics and quantum optics (e.g. for phase matching and production of entangled photons), micromanipulation, and as a platform for unconventional light-matter coupling, such as Dyakonov-like surface polaritons and hyperbolic phonon polaritons. Layered "van der Waals" materials, with strong intra-layer bonding and weak inter-layer bonding, can feature some of the largest optical anisotropy; however, their use in most optical systems is limited because their optic axis is out of the plane of the layers and the layers are weakly attached, making the anisotropy hard to access. Here, we demonstrate that a bulk crystal with subtle periodic modulations in its structure -- Sr9/8TiS3 -- is transparent and positive-uniaxial, with extraordinary index n_e = 4.5 and ordinary index n_o = 2.4 in the mid- to far-infrared. The excess Sr, compared to stoichiometric SrTiS3, results in the formation of TiS6 trigonal-prismatic units that break the infinite chains of face-shared TiS6 octahedra in SrTiS3 into periodic blocks of five TiS6 octahedral units. The additional electrons introduced by the excess Sr subsequently occupy the TiS6 octahedral blocks to form highly oriented and polarizable electron clouds, which selectively boost the extraordinary index n_e and result in record birefringence ({\Delta}n > 2.1 with low loss). The connection between subtle structural modulations and large changes in refractive index suggests new categories of anisotropic materials and also tunable optical materials with large refractive-index modulation and low optical losses.Comment: Main text + supplementar

Giant Modulation of Refractive Index from Correlated Disorder

Correlated disorder has been shown to enhance and modulate magnetic, electrical, dipolar, electrochemical and mechanical properties of materials. However, the possibility of obtaining novel optical and opto-electronic properties from such correlated disorder remains an open question. Here, we show unambiguous evidence of correlated disorder in the form of anisotropic, sub-angstrom-scale atomic displacements modulating the refractive index tensor and resulting in the giant optical anisotropy observed in BaTiS3, a quasi-one-dimensional hexagonal chalcogenide. Single crystal X-ray diffraction studies reveal the presence of antipolar displacements of Ti atoms within adjacent TiS6 chains along the c-axis, and three-fold degenerate Ti displacements in the a-b plane. 47/49Ti solid-state NMR provides additional evidence for those Ti displacements in the form of a three-horned NMR lineshape resulting from low symmetry local environment around Ti atoms. We used scanning transmission electron microscopy to directly observe the globally disordered Ti a-b plane displacements and find them to be ordered locally over a few unit cells. First-principles calculations show that the Ti a-b plane displacements selectively reduce the refractive index along the ab-plane, while having minimal impact on the refractive index along the chain direction, thus resulting in a giant enhancement in the optical anisotropy. By showing a strong connection between correlated disorder and the optical response in BaTiS3, this study opens a pathway for designing optical materials with high refractive index and functionalities such as a large optical anisotropy and nonlinearity.Comment: 24 pages, 3 figure

Effects of deposition parameters on cumulative energy demand for Cold Metal Transfer additive manufacturing processes

This paper proposes a methodology that can be used to assess the effects of variations in the process parame- ters on the energy consumption of a Cold Metal Transfer (CMT) additive manufacturing process. The analysis was carried out at the process level and then extended to cradle-to-gate system boundaries. A thin-walled component was considered as a demonstrative case study. The results demonstrate that any variation in deposition process parameters (namely, the wire feed speed and the travel speed) affects not only the energy requirements related to the deposition process itself, but also the material deposition efficiency and the cra- dle-to-gate cumulative energy demand

Clinical psychology in school and educational settings: Emerging trends

Background: First clinical services in psychology have been established for educational purposes when Witmer founded its Psychological Clinic. Over the years, the educational dimension played a significant role in the development of new evaluation methods and intervention strategies for the pursuit of positive mental health. The present review aims to capture developments that have been considered emerging applications of clinical psychology in school and educational settings. Methods: We conducted a search of the literature on Scopus, PubMed and Web of Science. The following search terms were used and combined: "clinical", "psychology", "educational", and "school". Results: A total of 18 research articles were included and analyzed in the current review. A number of studies showed that school-based positive psychology interventions were effective not only in reducing symptoms of psychological distress (somatization, depression, and anxiety) but also in increasing levels of positive mental health (a sense of individual growth, self-esteem, self-efficacy and optimism). As to studies on evaluation methods, the WHO-5 and the psychological well-being subscale from the Kellner Symptom Questionnaire were found to be clinically valid self-rating scales for the assessment of positive mental health in children and adolescents. Conclusion: Studies demonstrated that promoting positive mental health is more beneficial in the long term than simply treating symptoms of psychological distress. In clinical psychology, time has come to move from a traditional psychopathology-based perspective to a positive clinical approach to be used for innovative interventions and assessment strategies in school and educational settings

Facial basal cell carcinomas treated with hypo-fractionated radiotherapy: A retrospective analysis in 117 elderly patients

A study on the treatment of facial basal cell carcinoma of the elderly with hypo-fractotionated radiotherap

Necrosis score, surgical time, and transfused blood volume in patients treated with preoperative embolization of intracranial meningiomas. Analysis of a single-centre experience and a review of literature

Several authors have demonstrated that preoperative embolization of meningiomas reduces blood loss during surgery. However, preoperative embolization is still under debate. Aim of this study is the retrospective evaluation of necrosis score, surgical time, and transfused blood volume, on patients affected by intracranial meningiomas treated with preoperative embolization before surgery, compared with a control group treated only with surgery.Twenty-eight patients with meningiomas were subjected to a preoperative embolization with polyvinyl alcohol (PVA). These patients were divided into two groups: group 1, patients with preoperative embolization performed at least 7 days before surgery; and group 2, patients with preoperative embolization performed less than 7 days before surgery. A statistical evaluation was made by comparing necrosis score, surgical time, and transfused blood volume of these groups. Then, we compared these parameters also with group 3, which included patients with surgically treated meningioma who did not undergo preoperative embolization.Surgery time and transfused blood volume were significantly lower in patients who had been embolized at least 7 days before definitive surgery. Furthermore, large confluent areas of necrosis were significantly more frequent in patients with a larger time span between embolization and surgery.Preoperative embolization with PVA in patients with intracranial meningiomas is safe and effective, as it reduces the volume of transfused blood during surgical operation. However, patients should undergo surgery at least 7 days after embolization, as a shorter time interval has been correlated with a longer surgical time and a higher transfused blood volume

Stereotactic Body Radiation Therapy With Simultaneous Integrated Boost in Patients With Spinal Metastases

Stereotactic body radiation therapy in patients with spine metastases maximizes local tumor control and preserves neurologic function. A novel approach could be the use of stereotactic body radiation therapy with simultaneous integrated boost delivering modality. The aim of the present study is to report our experience in the treatment of spine metastases using a frameless radiosurgery system delivering stereotactic body radiation therapy-simultaneous integrated boost technique. The primary endpoints were the pain control and the time to local progression; the secondary ones were the overall survival and toxicity. A total of 20 patients with spine metastases and 22 metastatic sites were treated in our center with stereotactic body radiation therapy-simultaneous integrated boost between December 2007 and July 2018. Stereotactic body radiation therapy-simultaneous integrated boost treatments were delivered doses of 8 to 10 Gy in 1 fraction to isodose line of 50%. The median follow-up was 35 months (range: 12-110). The median time to local progression for all patients was not reached and the actuarial 1-, 2-, and 3-years local free progression rate was 86.36%. In 17 of 20 patients, a complete pain remission was observed and 3 of 20 patients had a partial pain remission (complete pain remission + partial pain remission: 100%). The median overall survival was 38 months (range 12-83). None of the patients experienced neither radiation adverse events (grade 1-4) nor reported pain flair reaction. None of the patients included in our series experienced vertebral compression fracture. Spine radiosurgery with stereotactic body radiation therapy-simultaneous integrated boost is safe. The use of this modality in spine metastases patients provides an excellent local control