Annealing-induced interfacial toughening using a molecular nanolayer

Self-assembled molecular nanolayers (MNLs) composed of short organic chains and terminated with desired functional groups are attractive for modifying surface properties for a variety of applications. For example, organosilane MNLs are used as lubricants, in nanolithography, for corrosion protection and in the crystallization of biominerals. Recent work has explored uses of MNLs at thin-film interfaces, both as active components in molecular devices, and as passive layers, inhibiting interfacial diffusion, promoting adhesion and toughening brittle nanoporous structures. The relatively low stability of MNLs on surfaces at temperatures above 350-400 degrees C (refs 12, 13), as a result of desorption or degradation, limits the use of surface MNLs in high-temperature applications. Here we harness MNLs at thin-film interfaces at temperatures higher than the MNL desorption temperature to fortify copper-dielectric interfaces relevant to wiring in micro- and nano-electronic devices. Annealing Cu/MNL/SiO2 structures at 400-700 degrees C results in interfaces that are five times tougher than pristine Cu/SiO2 structures, yielding values exceeding approximately 20 J m(-2). Previously, similarly high toughness values have only been obtained using micrometre-thick interfacial layers. Electron spectroscopy of fracture surfaces and density functional theory modelling of molecular stretching and fracture show that toughening arises from thermally activated interfacial siloxane bridging that enables the MNL to be strongly linked to both the adjacent layers at the interface, and suppresses MNL desorption. We anticipate that our findings will open up opportunities for molecular-level tailoring of a variety of interfacial properties, at processing temperatures higher than previously envisaged, for applications where microlayers are not a viable option-such as in nanodevices or in thermally resistant molecular-inorganic hybrid devices.     

The growth plate’s response to load is partially mediated by mechano-sensing via the chondrocytic primary cilium

Mechanical load plays a significant role in bone and growth-plate development. Chondrocytes sense and respond to mechanical stimulation; however, the mechanisms by which those signals exert their effects are not fully understood. The primary cilium has been identified as a mechano-sensor in several cell types, including renal epithelial cells and endothelium, and accumulating evidence connects it to mechano-transduction in chondrocytes. In the growth plate, the primary cilium is involved in several regulatory pathways, such as the non-canonical Wnt and Indian Hedgehog. Moreover, it mediates cell shape, orientation, growth, and differentiation in the growth plate. In this work, we show that mechanical load enhances ciliogenesis in the growth plate. This leads to alterations in the expression and localization of key members of the Ihh-PTHrP loop resulting in decreased proliferation and an abnormal switch from proliferation to differentiation, together with abnormal chondrocyte morphology and organization. Moreover, we use the chondrogenic cell line ATDC5, a model for growth-plate chondrocytes, to understand the mechanisms mediating the participation of the primary cilium, and in particular KIF3A, in the cell’s response to mechanical stimulation. We show that this key component of the cilium mediates gene expression in response to mechanical stimulation.     

任务导向与员工导向:一项关于国营企业和中外合资企业领导风格的比较研究

文章对中国国营企业和中外合资企业的领导风格进行了比较研究。采用一种在西方广泛使用的测量领导风格的调查问卷,对410名国营企业和中外合资企业的员工进行了问卷调查。这些问卷的统计分析结果显示出两种不同的领导风格：“任务导向”和“员工导向”。国营企业有着更强有力的“任务导向的领导”,而中外合资企业存在着更强有力的“员工导向的领导”。     

Hypotrichosis simplex of the scalp is associated with nonsense mutations in CDSN encoding corneodesmosin

We have identified nonsense mutations in the gene CDSN (encoding corneodesmosin) in three families suffering from hypotrichosis simplex of the scalp (HSS; OMIM 146520). CDSN, a glycoprotein expressed in the epidermis and inner root sheath (IRS) of hair follicles, is a keratinocyte adhesion molecule. Truncated CDSN aggregates were detected in the superficial dermis and at the periphery of hair follicles. Our findings suggest that CDSN is important in normal scalp hair physiology.     

Towards Disaggregate Dynamic Travel Forecasting Models

The authors argue that travel forecasting models should be dynamic and disaggregate in their representation of demand, supply, and supply-demand interactions, and propose a framework for such models. The proposed framework consists of disaggregate activity-based representation of travel choices of individual motorists on the demand side integrated with disaggregate dynamic modeling of network performance, through vehicle-based traffic simulation models on the supply side. The demand model generates individual members of the population and assigns to them socioeconomic characteristics. The generated motorists maintain these characteristics when they are loaded on the network by the supply model. In an equilibrium setting, the framework lends itself to a fixed-point formulation to represent and resolve demand-supply interactions. The paper discusses some of the remaining development challenges and presents an example of an existing travel forecasting model system that incorporates many of the proposed elements.     

Introduction to the special issue on mathematics and algorithms in computer-aided manufacturing, engineering, and numerical control

Sixty years have passed since numerical control of machine tools was first demonstrated at MIT. Since then, rapid developments in advanced manufacturing technology have posed new challenges and requirements, among them faster machining （high-speed machining）, higher feed-rates, more accurate parts and better surface finish. Not only are sophisticated computer- enabling technologies needed to cope with these challenges, but also significantly improved and more sophisticated mathematical tools. These emerging challenges and requirements under- score the growing importance of mathematical methods and algorithms. On the other hand, new challenges, optimization functions and constraints, arising in the field of advanced man- ufacturing have also stimulated the development of new branches of industrial and applied mathematics. Mathematics and Algorithms for Computer-Aided Manufacturing, Engineering and Numerical Control （MAMENC） is an annual workshop organized by the National Cen- ter for Mathematics and Interdisciplinary Sciences of China （NCMIS）. The workshop＇s topics focus on how mathematical methods and algorithms interact with computer-aided manufac- turing, computer-aided engineering and computer numerical control. MAMENC 2012 is the second workshop in the series. The first was held in Beijing in 2011, and the proceedings were published in the September 2012 issue （number 3） of the Mathematics in Computer Science journal under the title Special Focus on Mathematics and Algorithms for CAM and CNC.     

Defective planar cell polarity in polycystic kidney disease

Morphogenesis involves coordinated proliferation, differentiation and spatial distribution of cells. We show that lengthening of renal tubules is associated with mitotic orientation of cells along the tubule axis, demonstrating intrinsic planar cell polarization, and we demonstrate that mitotic orientations are significantly distorted in rodent polycystic kidney models. These results suggest that oriented cell division dictates the maintenance of constant tubule diameter during tubular lengthening and that defects in this process trigger renal tubular enlargement and cyst formation.     

Heterozygous mutations of the kinesin KIF21A in congenital fibrosis of the extraocular muscles type 1 (CFEOM1)

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1; OMIM #135700) is an autosomal dominant strabismus disorder associated with defects of the oculomotor nerve. We show that individuals with CFEOM1 harbor heterozygous missense mutations in a kinesin motor protein encoded by KIF21A. We identified six different mutations in 44 of 45 probands. The primary mutational hotspots are in the stalk domain, highlighting an important new role for KIF21A and its stalk in the formation of the oculomotor axis.