Benzodithiophene Hole‐Transporting Materials for Efficient Tin‐Based Perovskite Solar Cells

Developing efficient interfacial hole transporting materials (HTMs) is crucial for achieving high‐performance Pb‐free Sn‐based halide perovskite solar cells (PSCs). Here, a new series of benzodithiophene (BDT)‐based organic small molecules containing tetra‐ and di‐triphenyl amine donors prepared via a straightforward and scalable synthetic route is reported. The thermal, optical, and electrochemical properties of two BDT‐based molecules are shown to be structurally and energetically suitable to serve as HTMs for Sn‐based PSCs. It is reported here that ethylenediammonium/formamidinium tin iodide solar cells using BDT‐based HTMs deliver a champion power conversion efficiency up to 7.59%, outperforming analogous reference solar cells using traditional and expensive HTMs. Thus, these BDT‐based molecules are promising candidates as HTMs for the fabrication of high‐performance Sn‐based PSCs.     

Worst case Cramer-Rao bounds for parametric estimation ofsuperimposed signals with applications

The problem of parameter estimation of superimposed signals in white Gaussian noise is considered. The effect of the correlation structure of the signals on the Cramer-Rao bounds is studied for both the single and multiple experiment cases. The best and worst conditions are found using various criteria. The results are applied to the example of parameter estimation of superimposed sinusoids, or plane-wave direction finding in white Gaussian noise, and best and worst conditions on the correlation structure and relative phase of the sinusoids are found. This provides useful information on the limits of the resolvability of sinusoid signals in time series analysis or of plane waves in array processing. The conditions are also useful for designing worst-case simulation studies of estimation algorithms, and for the design of minimax signal acquisition and estimation procedures, as demonstrated by an example     

Characteristics of Er-doped Al2O3 thin filmsdeposited by reactive co-sputtering

Er-doped Al₂O₃ thin films have been deposited by reactive co-sputtering onto thermally oxidized Si-wafers. The deposition process has been optimized with respect to the requirements originating from the application of these multilayer structures as integrated optical amplifiers for the third telecom window, i.e., the wavelength range 1.52-1.55 μm. The films obtained at a substrate temperature of only 400°C are amorphous and show a homogenous structure, without columns or grains. For slabguides, background losses smaller than 0.25 dB/cm have been obtained, even without any annealing. A relatively broad luminescence band, having an FWHM of ~55 nm around the 1.533-μm wavelength, has been measured. From gain versus pumping power curves, an upconversion coefficient lower then 20·10^-25 m³/s has been derived, being half of the values reported up to now in the literature. Simulations based on experimentally determined material parameters and assuming a channel attenuation of 0.5 dB/cm indicate, for 0.24 at.% Er channel devices with an optimal channel length of 7.7 cm, an amplification of 8 dB at 1.533 μm for a pump wavelength of 1.48 μm, and a pump power of only 8.7 mW     

An efficient algorithm for superresolution in medium field imaging

In this paper, we study the problem of reconstruction of a high-resolution (HR) image from several blurred low-resolution (LR) image frames in medium field. The image frames consist of blurred, decimated, and noisy versions of a HR image. The HR image is modeled as a Markov random field (MRF), and a maximum a posteriori (MAP) estimation technique is used for the restoration. We show that with the periodic boundary condition, a HR image can be restored efficiently by using fast Fourier transforms. We also apply the preconditioned conjugate gradient method to restore HR images in the aperiodic boundary condition. Computer simulations are given to illustrate the effectiveness of the proposed approach. This research was conducted with support from the Army Research Office Grant DAAD 19-03-1-0261 and the National Science Foundation Grant CCF-0429481. Research supported in part by RGC Grant Nos. 7130/02P, 7046/03P, 7035/04P and 7035/04P and FRG/04-05/II-51.     

Group Study of Simulated Driving fMRI Data by Multiset Canonical Correlation Analysis

In this work, we apply a novel statistical method, multiset canonical correlation analysis (M-CCA), to study a group of functional magnetic resonance imaging (fMRI) datasets acquired during simulated driving task. The M-CCA method jointly decomposes fMRI datasets from different subjects/sessions into brain activation maps and their associated time courses, such that the correlation in each group of estimated activation maps across datasets is maximized. Therefore, the functional activations across all datasets are extracted in the order of consistency across different dataset. On the other hand, M-CCA preserves the uniqueness of the functional maps estimated from each dataset by avoiding concatenation of different datasets in the analysis. Hence, the cross-dataset variation of the functional activations can be used to test the hypothesis of functional-behavioral association. In this work, we study 120 simulated driving fMRI datasets and identify parietal-occipital regions and frontal lobe as the most consistently engaged areas across all the subjects and sessions during simulated driving. The functional-behavioral association study indicates that all the estimated brain activations are significantly correlated with the steering operation during the driving task. M-CCA thus provides a new approach to investigate the complex relationship between the brain functions and multiple behavioral variables, especially in naturalistic tasks as demonstrated by the simulated driving study.     

Advanced wood-frame construction details in Canada

This paper investigates how durability, energy efficiency and indoor air quality can be improved through proper detailing. The energy implications of air-tight construction are evaluated for terrace and semi-detached houses.     

Fast blue, a fluorescent tracer in glioma cell culture, affects cell proliferation and motility

The azo-dye, Fast Blue (FB), initially employed for retrograde neuronal tracing is increasingly used in cell invasion and migration studies to detect living cells in monolayer and glioma tumor cell spheroid models. As yet, it is assumed that a cell stained with a tracker dye retains the characteristics of the original cell. The following experiments compared the adhesion, migration and proliferation properties of the cell lines U373 and GaMG with and without FB staining. FB staining reduced cell adhesion (P < 0.01) and proliferative activity (P < 0.01) and also had a significant inhibitory effect on cell migration (P < 0.001). From the results presented it follows that FB staining markedly influences basic cell characteristics.     

Large parallel machines can be extremely slow for small problems

We consider concurrent-write PRAMs with a large number of processors of unlimited computational power and an infinite shared memory. Our adversary chooses a small number of our processors and gives them a 0–1 input sequence (each chosen processor gets a bit, and each bit is given to one processor). The chosen processors are required to compute thePARITY of their input, while the others do not take part in the computation. Ifat most q processors are chosen andq ≤1/2 log logn, then we show that computing PARITY needsq steps in the worst case. On the other hand, there exists an algorithm which computes PARITY inq steps (for anyq <n) in this model, thus our result is sharp. Surprisingly, if our adversary choosesexactly q of our processors, then they can compute PARITY in [q/2] + 2 steps, and in this case we show that it needs at least [q2] steps. Our result implies that large parallel machines which are efficient when only a small number of their processors are active cannot be constructed. On the other hand, a result of Ajtai and Ben-Or [1] shows that if we haven input bits which contain at most polylogn 1's and polynomially many processors which are all allowed to work, then thePARITY can be solved inconstant time.     

An unusual presentation of multiple congenital melanocytic nevi with a limb distribution

We report a newborn in whom multiple small congenital melanocytic nevi (MN) were noted on the right side involving the scapular area, shoulder, upper arm and forearm. Such a limb distribution of small congenital MN has never been reported in the literature.     

Lost in translation: theory and practice in cryptography

The perils of using encryption without authentication or integrity protection are well known in the cryptographic research community. Yet its exactly the mandatory support for unauthenticated encryption that forms the basis of a serious security flaw in an IPsec implementation we recently discovered. In response, the UK's equivalent to CERT, the National Infrastructure Coordination Centre published a vulnerability advisory about the flaw. Vendors also issued updated recommendations to customers, and we saw a flurry of discussion on Slash-dot and the sci.crypt newsgroup. In the aftermath, we asked ourselves, how did this happen?.