Topological insulator BSTS as a broadband switchable metamaterial

The development of metamaterials into a viable platform for nanophotonic applications, data processing circuits, sensors, etc. requires identification of new plasmonic materials to overcome the limitations of noble metals, in particular their high losses. Here we describe a class of topological insulator materials which support broadband plasmonic response and possess extremely appealing photonic properties ranging from mid-IR to UV. Bi1.5Sb0.5Te1.8Se1.2 (BSTS) is a bulk insulator with robust conducting surface states protected by time-reversal symmetry, due to the strong spin-orbit coupling. BSTS single crystals were synthesized by melting high-purity Bi, Sb, Te and Se powders at 950°C in an evacuated quartz tube. The temperature was then gradually decreased to room temperature over a span of three weeks. The resulting crystals were then cleaved along the (100) family of planes to a thickness of ~0.5 mm. BSTS dielectric constants were derived by ellipsometric measurements and appear to be in excellent agreement with first principle DFT calculations. Unlike common direct or indirect bandgap semiconductors, the anomalous dispersion region falls in the visible part of the spectrum, leading to negative values of the permittivity. This behavior of the optical response is attributed to a combination of bulk interband transitions and surface contribution of the topologically protected states. To prove metallic behavior of BSTS, we fabricated metamaterials and gratings on crystal flakes and registered strong plasmonic response from UV to NIR. The coexistence of plasmonic response of the topological surface with dielectric properties of the semiconducting bulk enables ultrafast (t>100 fs) and broadband (to mid-IR) photo-modulation of the optical response. These findings show the potential of topological insulators as a platform for high-frequency switchable plasmonic metamaterials

The hand of Homo naledi

A nearly complete right hand of an adult hominin was recovered from the Rising Star cave system, South Africa. Based on associated hominin material, the bones of this hand are attributed to Homo naledi. This hand reveals a long, robust thumb and derived wrist morphology that is shared with Neandertals and modern humans, and considered adaptive for intensified manual manipulation. However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during locomotor climbing and suspension. These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi

Comparative study of functional outcome analysis and extent of paraspinal muscle damage between lumbar spinous process splitting decompression and conventional midline decompression for lumbar canal stenosis

INTRODUCTION Lumbar spinal canal stenosis is a clinical syndrome of back or leg pain with characteristic provocative and palliative features, which occurs due to narrowing of spinal canal, nerve root canal and the intervertebral foramen. Lumbar spinal canal stenosis has been regarded as “the forgotten spinal disease” for more than 100 years. This neglect occurred because of the association between herniated intervertebral discs and sciatica received most of the attention after it was discovered by Mixter and Barr in 1934. However, Lumbar spinal canal stenosis was not widely understood until Verbiest in 1954 described the classic finding of this syndrome. It occurs in middle aged and older adults with back pain and lower extremity pain precipitated by standing and walking and aggravated by hyperextension. The secondary degenerative changes that further narrow the lumbar spinal canal precipitated symptoms. Lumbar spinal canal stenosis now is an accepted clinical entity. The degenerative lumbar spinal canal stenosis is due to thickening of interspinous ligament, ligamentum flavum and facet joint hypertrophy. Lumbar spinal canal stenosis cause signs of intermittent neurogenic claudication, and it can lead to decreased quality of life. Conservative measures provide relief from symptoms for a shorter period only, but finally surgical decompression of the neurovascular structures will be needed. AIM OF THE STUDY: This prospective Randomised Control Study compares the the functional outcome and extent of paraspinal muscle damage between Lumbar spinous process splitting decompression (LSPSD) and Conventional Midline Decompression(CMD) by laminectomy surgical approaches in degenerative lumbar canal stenosis and their aim was whether 1) Lumbar spinous process splitting decompression (LSPSD ) approach provide sufficient decompression. 2) Preserve posterior musculoligamentous complex and reduces associated morbidity. MATERIALS AND METHODS : This randomized prospective control study was approved by the medical ethics committee of the Institutional Review Board in our hospital. Patients meeting the following inclusion criteria were enrolled for the study after obtaining written informed consent. 20 patients with degenerative lumbar canal stenosis are randomly divided into two groups and recruited into the study based on the following criterias INCLUSUION CRITERIA: Degenerative LCS affecting 3 or less levels, -Typical neurogenic claudication symptoms, - Magnetic resonance image demonstrating good clinical correlation, - Failure of conservative methods of treatment for a minimum period of 6 months. EXCLUSION CRITERIA: -Spondylolisthesis with slip grade 2 or greater (Meyerding grade). - Instability at the level of stenosis (as defined by >3-mm translation or >10° angular change on flexion extension lateral radiographs) - Associated symptomatic cervical or thoracic stenosis. - Multiple level canal stenosis. -Spinal canal stenosis due to congenital, traumatic , iatrogenic causes. - Presence of spinal disorders( ankylosing spondylitis, neoplasm ) - Comorbidities ( such as cardiopulmonary insufficiency, peripheral neuropathy, peripheral vascular disease, prior lumbar spine surgery, and severe hip or knee disease). RESULTS: 20 patients were followed up for 6-18 months with mean average follow up of 11.4 months. Data of 10 patients (5 men and 5 women) in the lumbar spinous process splitting decompression group and 10 patients (4 men and 6 women) in the Conventional Midline Decompression group were included in the final analysis. The mean age was 58.9 (range 54-65) yrs for the lumbar spinous process splitting decompression group and 60.4 (range 55-65) yrs for Conventional Midline Decompression group. Mean number of decompressed levels were 1.30 for Conventional Midline Decompression group and 1.20 for lumbar spinous process splitting decompression. CONCLUSION: In our study, Lumbar Spinous Process Splitting Decompression provides minimal exposure for decompression in lumbar canal stenosis while preserving musculoligamentous attachments of the posterior elements of spine and good postoperative results after one year with favourable outcomes of atleast 70% on the Japanese orthopaedic association score and Neurogenic claudication outcome score. With both these surgical techniques, a significant improvement in the outcome after surgical decompression could be demonstrated. There was no significant difference between the Lumbar Spinous Process Splitting decompression and Midline decompression by laminectomy techniques regarding the later outcome. But Lumbar Spinous Process Splitting decompressive approach is not suitable for cases with bilateral intervertebral disc protrusion and bilateral fac et joint arthritis with hypertrophy causing degenerative lumbar canal stenosis and foraminal stenosis

A multi-biometric iris recognition system based on a deep learning approach

YesMultimodal biometric systems have been widely applied in many real-world applications due to its ability to deal with a number of significant limitations of unimodal biometric systems, including sensitivity to noise, population coverage, intra-class variability, non-universality, and vulnerability to spoofing. In this paper, an efficient and real-time multimodal biometric system is proposed based on building deep learning representations for images of both the right and left irises of a person, and fusing the results obtained using a ranking-level fusion method. The trained deep learning system proposed is called IrisConvNet whose architecture is based on a combination of Convolutional Neural Network (CNN) and Softmax classifier to extract discriminative features from the input image without any domain knowledge where the input image represents the localized iris region and then classify it into one of N classes. In this work, a discriminative CNN training scheme based on a combination of back-propagation algorithm and mini-batch AdaGrad optimization method is proposed for weights updating and learning rate adaptation, respectively. In addition, other training strategies (e.g., dropout method, data augmentation) are also proposed in order to evaluate different CNN architectures. The performance of the proposed system is tested on three public datasets collected under different conditions: SDUMLA-HMT, CASIA-Iris- V3 Interval and IITD iris databases. The results obtained from the proposed system outperform other state-of-the-art of approaches (e.g., Wavelet transform, Scattering transform, Local Binary Pattern and PCA) by achieving a Rank-1 identification rate of 100% on all the employed databases and a recognition time less than one second per person

Structural hierarchies define toughness and defect-tolerance despite simple and mechanically inferior brittle building blocks

Mineralized biological materials such as bone, sea sponges or diatoms provide load-bearing and armor functions and universally feature structural hierarchies from nano to macro. Here we report a systematic investigation of the effect of hierarchical structures on toughness and defect-tolerance based on a single and mechanically inferior brittle base material, silica, using a bottom-up approach rooted in atomistic modeling. Our analysis reveals drastic changes in the material crack-propagation resistance (R-curve) solely due to the introduction of hierarchical structures that also result in a vastly increased toughness and defect-tolerance, enabling stable crack propagation over an extensive range of crack sizes. Over a range of up to four hierarchy levels, we find an exponential increase in the defect-tolerance approaching hundred micrometers without introducing additional mechanisms or materials. This presents a significant departure from the defect-tolerance of the base material, silica, which is brittle and highly sensitive even to extremely small nanometer-scale defects

Mathematical model for predicting solidification and cooling of steel inside mould and in air

A two-dimensional mathematical model has been developed to describe the solidification and cooling of steel inside the mould after teeming and in the air after stripping. Partial differential equations describing the processes have been discretized using control volume approach. The discretization equations obtained are of Tri-diagonal matrix form, which have been solved using well known Tri-diagonal matrix algorithm (TDMA) and Alternate direction implicit (ADI) solver. The model has been validated by measuring surface temperatures of mould and ingot using Infrared thermo-vision scanner. This is then used to compute charging temperature and solidification status of ingot as function of track time and type of ingot

Three-dimensional geometric morphometrics of thorax-pelvis covariation and its potential for predicting the thorax morphology: A case study on Kebara 2 Neandertal

The skeletal torso is a complex structure of outstanding importance in understanding human body shape evolution, but reconstruction usually entails an element of subjectivity as researchers apply their own anatomical expertise to the process. Among different fossil reconstruction methods, 3D geometric morphometric techniques have been increasingly used in the last decades. Two-block partial least squares analysis has shown great potential for predicting missing elements by exploiting the covariation between two structures (blocks) in a reference sample: one block can be predicted from the other one based on the strength of covariation between blocks. The first aim of this study is to test whether this predictive approach can be used for predicting thorax morphologies from pelvis morphologies within adult Homo sapiens reference samples with known covariation between the thorax and the pelvis. The second aim is to apply this method to Kebara 2 Neandertal (Israel, ∼60 ka) to predict its thorax morphology using two different pelvis reconstructions as predictors. We measured 134 true landmarks, 720 curve semilandmarks, and 160 surface semilandmarks on 60 3D virtual torso models segmented from CT scans. We conducted three two-block partial least squares analyses between the thorax (block 1) and the pelvis (block 2) based on the H. sapiens reference samples after performing generalized Procrustes superimposition on each block separately. Comparisons of these predictions in full shape space by means of Procrustes distances show that the male-only predictive model yields the most reliable predictions within modern humans. In addition, Kebara 2 thorax predictions based on this model concur with the thorax morphology proposed for Neandertals. The method presented here does not aim to replace other techniques, but to rather complement them through quantitative prediction of a virtual 'scaffold' to articulate the thoracic fossil elements, thus extending the potential of missing data estimation beyond the methods proposed in previous works

A hominin first rib discovered at the Sterkfontein Caves, South Africa.

First ribs - the first or most superior ribs in the thorax - are rare in the hominin fossil record, and when found, have the potential to provide information regarding the upper thorax shape of extinct hominins. Here, we describe a partial first rib from Member 4 of the Sterkfontein Caves, South Africa. The rib shaft is broken away, so only the head and neck are preserved. The rib is small, falling closest to small-bodied Australopithecus first ribs (AL 288-1 and MH1). Given that it was recovered near the StW 318 femur excavation, which also represents a small individual, we suggest that the two may be associated. Three-dimensional geometric morphometric analyses were used to quantify the rib fragment morphology and compare it to extant hominoid and other fossil hominin ribs. While only the proximal end is preserved, our analyses show that South African Australopithecus share derived features of the proximal first rib more closely resembling A. afarensis and later hominins than great apes.NCS2016

Suppression of uPAR Retards Radiation-Induced Invasion and Migration Mediated by Integrin β1/FAK Signaling in Medulloblastoma

Despite effective radiotherapy for the initial stages of cancer, several studies have reported the recurrence of various cancers, including medulloblastoma. Here, we attempt to capitalize on the radiation-induced aggressive behavior of medulloblastoma cells by comparing the extracellular protease activity and the expression pattern of molecules, known to be involved in cell adhesion, migration and invasion, between non-irradiated and irradiated cells.We identified an increase in invasion and migration of irradiated compared to non-irradiated medulloblastoma cells. RT-PCR analysis confirmed increased expression of uPA, uPAR, focal adhesion kinase (FAK), N-Cadherin and integrin subunits (e.g., α3, α5 and β1) in irradiated cells. Furthermore, we noticed a ∼2-fold increase in tyrosine phosphorylation of FAK in irradiated cells. Immunoprecipitation studies confirmed increased interaction of integrin β1 and FAK in irradiated cells. In addition, our results show that overexpression of uPAR in cancer cells can mimic radiation-induced activation of FAK signaling. Moreover, by inhibiting FAK phosphorylation, we were able to reduce the radiation-induced invasiveness of the cancer cells. In this vein, we studied the effect of siRNA-mediated knockdown of uPAR on cell migration and adhesion in irradiated and non-irradiated medulloblastoma cells. Downregulation of uPAR reduced the radiation-induced adhesion, migration and invasion of the irradiated cells, primarily by inhibiting phosphorylation of FAK, Paxillin and Rac-1/Cdc42. As observed from the immunoprecipitation studies, uPAR knockdown reduced interaction among the focal adhesion molecules, such as FAK, Paxillin and p130Cas, which are known to play key roles in cancer metastasis. Pretreatment with uPAR shRNA expressing construct reduced uPAR and phospho FAK expression levels in pre-established medulloblastoma in nude mice.