Password memorability and security: empirical results

Users rarely choose passwords that are both hard to guess and easy to remember. To determine how to help users choose good passwords, the authors performed a controlled trial of the effects of giving users different kinds of advice. Some of their results challenge the established wisdom.     

包含负荷及系统动态的电力系统电压稳定仿真

本文提出一种对系统电压稳定进行详细仿真的方法，此方法考虑了系统及负荷动态的影响，诸如系统干扰、电动机力矩及滑差，变压器抽头的的换接、坚持Ｐ、Ｑ需要的负荷、抑制励磁以防止发电机过热，以及有电压偏移负反馈的ＳＶＣ等。由于是高阶次的非线性全模，作者采用一种既精确又快速的方法来进行积分，还应用了一种毋需经过亢介次矩阵求逆就可便捷地求解亢介次Ｊａｃｏｂｉ阵的方法。     

Viscoelastic properties and morphology of sulfonated poly(styrene-b-ethylene/butylene-b-styrene) block copolymers (sBCP), and sBCP/[silicate] nanostructured materials

Self-assembled organic/inorganic hybrid materials were created via domain targeted sol-gel reactions of tetraethylorthosilicate in solution with sulfonated poly(styrene-b-[ethylene-co-butylene]-b-styrene) (sSEBS) copolymers. Dynamic mechanical analyses (DMA) of these hybrid materials suggest that the silicate component preferentially incorporates within the sulfonated polystyrene (PS) domains. An irreversible order-order transition (OOT) for unmodified SEBS, sSEBS, and the organic/inorganic hybrids was identified using DMA in shear mode. The OOT temperature increases with sulfonation as well as by adding a silicate phase by the sol-gel process. The DMA results imply a morphological shift with sulfonation, and reflect modified interactions within and between phases. Atomic force microscopy (AFM) indicated a shift from hexagonally packed cylinders in unmodified SEBS to a lamellar morphology in the sulfonated materials, but silicate incorporation did not affect the morphology or domain dimensions. The latter result is evidence for sol-gel polymerization templating in a self-assembly process. The phase-separated morphology is stable up to the degradation temperature of the polymer and thermogravimetric analysis revealed that the degradation temperature is unaffected by silicate incorporation. Small angle X-ray scattering data are in harmony with the structures revealed by AFM in terms of degree of order and scale of features. These results are largely rationalized in terms of chain mobility restrictions due to hydrogen-bonding interactions between different sulfonated PS blocks, an increase in the PS-ethylene/butylene block mixing parameter, increased interfacial surface tension and chain restrictions posed by inserted silicate nanostructures in the case of the hybrid materials.     

A preliminary assessment of high speed tool steels manufactured from powder for rolling bearing materials

High speed tool steels manufactured from powder were assessed under arduous conditions of rolling contact and compared with conventional materials using an accelerated service simulation test. Metallographic investigations revealed factors influencing performance. Material manufactured from powder was generally found to be inferior to vacuum-remelted material due to poor structure, porosity, high interstitial nitrogen content and other manufacturing variables. Sound homogeneous material with uniform fine carbide distribution and gas content comparable with those of conventionally cast material appears potentially suitable for rolling bearings. The improved performance at elevated temperature may be due to metallographic changes, deleterious interstitial nitrogen content being reduced by a precipitation process.     

A neural-network technique for the retrieval of atmospheric temperature and moisture profiles from high spectral resolution sounding data

A novel statistical method for the retrieval of atmospheric temperature and moisture profiles has been developed and evaluated with simulated clear-air and observed partially cloudy sounding data from the Atmospheric InfraRed Sounder (AIRS) and the Advanced Microwave Sounding Unit (AMSU). The algorithm is implemented in two stages. First, a projected principal components (PPC) transform is used to reduce the dimensionality of and optimally extract geophysical profile information from the cloud-cleared infrared radiance data. Second, a multilayer feedforward neural network (NN) is used to estimate the desired geophysical parameters from the PPCs. For the first time, NN temperature and moisture retrievals are presented using actual microwave and hyperspectral infrared observations of cloudy atmospheres, over both ocean and land (with variable terrain elevation), and at all sensor scan angles. The performance of the NN retrieval method (henceforth referred to as the PPC/NN method) was evaluated using global Earth Observing System Aqua orbits colocated with European Center for Medium-range Weather Forecasting fields for seven days throughout 2002 and 2003. Over 350,000 partially cloudy footprints were used in the study, and retrieval performance was compared with the AIRS Science Team Level-2 retrieval algorithm (version 3). Performance compares favorably with that obtained with simulated clear-air observations from the NOAA88b radiosonde set of approximately 7500 profiles. The PPC/NN method requires significantly less computation than traditional variational retrieval methods, while achieving comparable performance.     

Sandtray therapy with a 24-year-old woman in the residual phase of schizophrenia.

Sandtray therapy is a clinical tool for helping a client express and understand his or her unconscious dynamics. It utilizes a sandtray and anywhere from a few hundred to a few thousand figurines in the room for the client to select from. These figurines cover a wide range of people, situations, and objects, from the most ordinary to the mythical. The client makes a story in the sand, which the client and therapist then discuss. It is standard therapeutic wisdom that one should not use techniques involving fantasy with psychotic clients since it is typically too hard for both them and the clinician to contain those fantasies in a healthy manner. Although this is very often true, the authors offer an example of how they were able to use sandtray to great therapeutic advantage with a schizophrenic client in the residual phase of schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diffusion of liquids into semicrystalline polyethylene

Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) and microimaging experiments have been performed to study the diffusion of liquid alkanes into a variety of semicrystalline polyethylene (PE) samples. The results highlight the importance of the crystalline phase in controlling the diffusion process in terms of both the geometric impedance imposed by the presence of impenetrable crystals and their effect on the mobility of the polymer chains comprising the amorphous material through which the penetrants migrate.     

The role of N-glycosylation for functional expression of the human platelet-activating factor receptor. Glycosylation is required for efficient membrane trafficking

Streptococcus pneumoniae has been shown to utilize the platelet activating factor receptor for binding and invasion of host cells (Cundell, D. R., Gerard, N. P., Gerard, C., Idanpaan-Heikkila, I., and Tuomanen, E. I. (1995) Nature, in press). Because bacterial binding is in part carbohydrate dependent, and the human platelet-activating factor (PAF) receptor bears a single N-linked glycosylation sequence in the second extracellular loop, we undertook studies to determine the role of this epitope in PAF receptor function. Binding of pneumococci to COS cells transfected with the human PAF receptor is greatly reduced for a receptor mutant that bears no N-linked glycosylation site. Immunohistochemical and binding analyses show decreased expression of the non-glycosylated molecule on the cell membrane relative to the wild type receptor; however, metabolic labeling and immunopurification indicate it is synthesized intracellularly at a level similar to the native molecule. A mutant receptor encoding a functional glycosylation site at the NH2 terminus is better expressed at the cell surface compared with the non-glycosylated form, indicating that trafficking to the cell surface is facilitated by glycosylation, but its location is relatively unimportant. The binding affinity for PAF is not significantly effected by the presence or location of the carbohydrate, and variations in cell surface expression have little influence on signal transduction, as the non-glycosylated PAF receptor is equally effective for activation of phospholipase C as the native molecule. These data are supportive of pneumococcal binding on protein moiety(ies) of the PAF receptor and indicate that N-glycosylation facilitates expression of the protein on the cell membrane.     

Aristolochic acids, aristolactam alkaloids and amides from Aristolochia kankauensis

Fourteen aristolochic acid derivatives: ariskanins A-E, 3-hydroxy-4-methoxy-10-nitrophenanthrene-1-carboxylic acid methyl ester, aristolochic acid-II methyl ester, aristolochic acid-IV methyl ester, aristolochic acid-C, -I, -II, -III, -IV, -IVa; nine aristolactam alkaloids: aristolactam, aristolactam-AII, -BIII, -AIII, -III, cepharanone-A, 9-methoxy-aristolactam-I, aristolactam-N-beta-D-glucoside and aristolactam-C-N-beta-D-glucoside; a 4,5-dioxoaporphine alkaloid: cepharadione-A, together with 12 other compounds: methyl-p-coumarate, N-trans-feruloyltyramine, N-cis-feruloyltyramine, methyl vanillate, methyl paraben, allantoin, an octadecyl- and eicosyl ferulate mixture, cis- and trans-p-coumaric acid, N-p-coumaroyltyramine, N-p-cis-coumaroyltyramine, methyl ferulate and isorhamnetin-3-O-rutinoside were isolated and characterized from the fresh root and stem of Aristolochia kankauensis. Their structures were elucidated by spectral and chemical methods. Among them, ariskanins-A-E and N-p-cis-coumaroyltyramine are reported for the first time from a natural source. The cytotoxicity and antiplatelet activity of the compounds isolated are also discussed.     

Dosimetric analysis of chimeric monoclonal antibody cMOv18 IgG in ovarian carcinoma patients after intraperitoneal and intravenous administration

In this study the potential of intraperitoneal (i.p.) and intravenous (i.v.) administration of chimeric iodine-131-labelled MOv18 IgG for radioimmunotherapy was determined. The dosimetry associated with both routes of administration of cMOv18 IgG was studied in patients. Eight patients suspected of having ovarian carcinoma received 150 MBq 131I-cMOv18 IgG i.p. Blood and urine were collected and serial gamma camera images were acquired. Another group of four patients received 7.5 MBq 131I-cMOv18 IgG i.v. For all patients, tissue biopsies were obtained at surgery. Activity in the blood after i.p. administration was described by a bi-exponential curve with a mean uptake and elimination half-life of 6.9+/-3.2 h and 160+/-45 h, respectively. For i.v. infusion the mean half-life for the elimination phase was 103+/-12 h. Cumulative excretion in the urine was 17%+/-3% ID and 21%+/-7% ID in 96 h for i.p. and i.v. administration, respectively. Scintigraphic images after i.p. administration showed accumulation in ovarian cancer lesions, while all other tissues showed decreasing activity with time. Tumour uptake determined in the ovarian cancer tissue specimens ranged from 3.4% to 12.3% ID/kg for i.p. administration and from 3.6% to 5.4% ID/kg for i.v. administration. Dosimetric analysis of the data indicated that 1.7-4.3 mGy/MBq and 1.7-2.2 mGy/MBq can be guided to solid or ascites cells after i.p. and i.v. administration, respectively. Assuming that an absorbed dose to the bone marrow of 2 Gy will be dose limiting, a total activity of 4.1 GBq 131I-cMOv18 IgG can be administered safely via the i.p. route and 3.5 GBq via the i.v. route. At this maximal tolerated dose, a maximum absorbed dose to 1-g tumours in the peritoneal cavity of 18 and 8 Gy can be reached after i.p. and i.v. administration, respectively. For the i. p. route of administration, dose estimates for the tumour are even higher when the electron dose of the peritoneal activity is also taken into account: total doses to the tumour of 30 Gy and 22 Gy will be absorbed at the tumour surface and at 0.2 mm depth, respectively. In conclusion, therapeutic tumour doses can be achieved with 131I-cMOv18 IgG in patients with intraperitoneal ovarian cancer lesions with no normal organ toxicity. The i.p. route of administration seems to be preferable to i.v. administration.