Stabilized Wide Bandgap MAPbBr\u3csub\u3ex\u3c/sub\u3eI\u3csub\u3e3– x\u3c/sub\u3e Perovskite by Enhanced Grain Size and Improved Crystallinity

Methylammonium lead trihalide perovskite (MAPbX3, where MA is methylammonium, and X is a halide)-based solar cells have been intensively investigated recently, with the demonstrated certified solar power conversion efficiency (PCE) exceeding 20%. To further boost the PCE to beyond the Schockley–Queisser limit, tandem structured solar cells have been investigated based on integrating MAPbX3 and low bandgap solar cells. However, the efficiency of the two-terminal integrated perovskite-silicon tandem cells is still low. The best reported efficiency of 13.7% for this type of tandem cells is far smaller than the individual cells yet, partially due to the limited performance of the mixed-halide perovskite MAPbBrxI 3– x solar cell employed in this structure. The mixed-halide perovskite MAPbBrx I3– x is still one of the most promising candidates as the wide-bandgap light absorber for the tandem application to match the bandgap of silicon, considering its continuously tunable bandgap from 1.6 eV to 2.3 eV with different bromide incorporation ratio. However, the application of MAPb-Brx I3– x based solar cells has been reported to confront with one big challenge of intrinsic light instability. The MAPbBrx I3– x materials on mesoporous scaffold were shown to be unstable under illumination with a photo-excited phase-separation into two phases, one iodine-rich phase and one iodine-poor phase. The lower bandgap phase thus acts as the charge traps, which was hypothesized to be responsible to the severely reduced device open circuit voltage and device PCE for the mixed-halide perovskite devices

A Roughness Study of Ytterbium-Doped Potassium Yttrium Tungstate (YB: KYW) Thin-Disk Femtosecond Ablated Dentin

Introduction: The aim of this study was to evaluate the morphological changes and quantitatively assess the roughness of dentin after the ablation with a Ytterbium-Doped Potassium Yttrium Tungstate (YB: KYW) thin-disk femtosecond pulsed laser of different fluences, scanning speeds and scanning distances.Method: Twelve extracted human premolars were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick with a cutting machine. The dentin samples were fixed on a stage at focus plane. The laser beam was irradiated onto the samples through a galvanometric scanning system, so rectangular movement could be achieved. After ablation, the samples were examined with a scanning electron microscope and laser three-dimensional profile measurement microscope for morphology and roughness study.With increasing laser fluence, dentin samples exhibited more melting and resolidification of dentin as well as debris-like structure and occluded parts of dentinal tubules.Results: When at the scanning speed of 2400mm/s and scanning distance of 24μm, the surface roughness of dentin ablated with femtosecond pulsed laser decreased significantly and varied between values of dentin surface roughness grinded with two kinds of diamond burs with different grits. When at the scanning speed of 1200mm/s and scanning distance of 12μm, the surface roughness decreased slightly, and the surface roughness of dentin ablated with femtosecond pulsed laser was almost equal to that grinded with a low grit diamond bur.Conclusion: This study showed that increased laser influence may lead to more collateral damage and lower dentin surface roughness, while scanning speed and scanning distance were also negatively correlated with surface roughness. Adequate parameters should be chosen to achieve therapeutic benefits, and different parameters can result in diverse ablation results

Comparative Study of Various Approximations to the Covariance Matrix in Template Attacks

Template attacks have been shown to be among the strongest attacks when it comes to side–channel attacks. An essential ingredient there is to calculate the inverse of a covariance matrix. In this paper we make a comparative study of the effectiveness of some 24 different variants of template attacks based on different approximations of this covariance matrix. As an example, we have chosen a recent smart card where the plain text, cipher text, as well as the key leak strongly. Some of the more commonly chosen approximations to the covariance matrix turn out to be not very effective, whilst others are

Ciphertext and Plaintext Leakage Reveals the Entire TDES Key

SCA(Side-channel analysis) is a well-known method to recover the sensitive data stored in security products. Meanwhile numerous countermeasures for hardware implementation of cryptographic algorithms are proposed to protect the internal data against this attack fortunately. However, some designs are not aware that the protection of the plaintext and ciphertext is also crucial. In this work, we attack an implementation TDES(triple DES) by taking advantage of such leakages detected in a widely used commercial product which is based on the hardware platform that passed the EAL5+ certification. In particular, we guess entire DES keys to construct hypotheses for the intermediate outputs in a TDES calculation. The time cost for this approach is nearly $\frac{1}{2^{32}}$ of that by a brute force. Furthermore, if in addition leakage about the key becomes available, the attack costs become practical. That is, reducing the key entropy of every DES key to $2^{28}$ allows an enumeration of the entire TDES in 21.6 hours

Crystallization and preliminary X-ray diffraction studies of guanidinoacetate methyltransferase from rat liver

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0907444999010318.Guanidinoacetate methyltransferase is the enzyme which catalyzes the last step of creatine biosynthesis. The enzyme is found ubiquitously and in abundance in the livers of all vertebrates. Recombinant rat-liver guanidinoacetate methyltransferase has been crystallized with guanidinoacetate and S-adenosylhomocysteine. The crystals belong to the monoclinic space group P21, with unit-cell parameters a = 54.8, b = 162.5, c = 56.1 Å, [beta] = 96.8 (1)° at 93 K, and typically diffract beyond 2.8 Å

Clinical manifestations and imaging and pathological features of giant cell angioblastoma: Report of four cases and literature review

Giant cell angioblastoma is a relatively rare vasogenic tumour. To date, studies on its clinical manifestations, imaging characteristics, pathological features, and prognosis are extremely limited and unknown, with only a few cases recorded. In this study, four cases of giant cell angioblastoma confirmed by pathological examination were reported to improve our understanding and deep exploration of the tumour spectrum. All cases in our study were male, including two adults and two boys. The lesions were located in the lower segment of the femur, medial condyle of the femur, knee joint, and popliteal fossa. Regarding the imaging characteristics, two patients with lesions in bone showed bone destruction, while the other two had lesions that invaded soft tissues, showing irregular, abnormal signal shadows and obvious enhancement. Histopathological analysis revealed that the nodular tumour tissue was mainly composed of oval and spindle cells, with varying numbers of osteoclast-like multinucleated giant cells, and the interstitial tissues were often filled with blood vessels of different sizes. The immunophenotype demonstrates that endothelial cells of small vessels in nodules expressed CD31, SMA, and ERG, while osteoclast-like multinucleated giant cells and histiocytes expressed CD68 and CD163, and the surrounding cells expressed SMA. All four patients were treated with surgical resection. One of them relapsed 1 month after surgery and received a second surgical resection. No distant metastasis or death occurred during the follow-up period. This study indicates that giant cell angioblastoma is a local invasive vascular tumour that can develop both in children and adults with skin, mucous membrane, soft tissue, and bone involvement. Imaging characteristics show bone destruction and irregular, abnormal signal shadows; in addition, obvious pathological morphological features can be observed. Currently, the treatment is mainly surgical resection, and interferons may be used as adjuvant chemotherapy

AB-SIFA: SIFA with Adjacent-Byte Model

Statistical Ineffective Fault Attack (SIFA) has been a threat for implementa-tions of symmetric cryptographic primitives. Unlike Differential Fault At-tacks (DFA) which takes both correct and faulty ciphertexts, SIFA can re-cover the secret key with only correct ciphertexts. The classic SIFA is only effective on fault models with non-uniform distribution of intermediate val-ue. In this paper, we present a new fault model named adjacent-byte model, which describes a non-uniform distribution of relationship between two bytes (i.e. exclusive-or). To the best of our knowledge, it is the first time that this fault model has been proposed. We also show that the adjacent-byte faults can be induced by different fault sources and easy to reproduce. Then a new SIFA attack method called AB-SIFA on symmetric cryptography is proposed. We demonstrate the effectiveness of this new attack by simulating the attack. Finally, our attacks are applied to a software implementations of AES-128 with redundant countermeasure and a hardware AES co-processor, utilizing voltage glitches and clock glitches