The Line Formation with Alumina Powders in Drop on Demand Three Dimensional Printing

Three Dimensional Printing (3DP) is a Droplet-Based Manufacturing (DBM) process, in which powdered materials are deposited in layers and selectively joined with binder from an ink-jet style printhead. Unbound powder is removed upon process completion, leaving a three dimensional part. With this technology, functional parts or moulds (rapid tooling) can be created directly from a CAD file. Drop on Demand (DoD) is an emerging inkjet technology in 3DP, but it seems that the interaction between drops and powder grains cannot be explained with the available Continuous Jet (CJ) models. In this paper, an experimental theory describing the main physical phenomena involved is proposed. The role of the powder mobility is stressed and documented by pictures and observations coming from a systematic experimentation exploring a multidimensional variable space. A simple mathematical model to predict the line size and density is also proposed

Evaluation of Surface State Mediated Charge Recombination in Anatase and Rutile TiO2

In nanostructured thin films, photogenerated charge carriers can access the surface more easily than in dense films and thus react more readily. However, the high surface area of these films has also been associated with enhanced recombination losses via surface states. We herein use transient absorption spectroscopy to compare the ultrafast charge carrier kinetics in dense and nanostructured TiO2 films for its two most widely used polymorphs: anatase and rutile. We find that nanostructuring does not enhance recombination rates on ultrafast timescales, indicating that surface state mediated recombination is not a key loss pathway for either TiO2 polymorph. Rutile shows faster, and less intensity-dependent recombination than anatase, which we assign to its higher doping density. For both polymorphs, we conclude that bulk rather than surface recombination is the primary determinant of charge carrier lifetime

The Problem of Inertia in Friedmann Universes

In this paper we study the origin of inertia in a curved spacetime, particularly the spatially flat, open and closed Friedmann universes. This is done using Sciama's law of inertial induction, which is based on Mach's principle, and expresses the analogy between the retarded far fields of electrodynamics and those of gravitation. After obtaining covariant expressions for electromagnetic fields due to an accelerating point charge in Friedmann models, we adopt Sciama's law to obtain the inertial force on an accelerating mass $m$ by integrating over the contributions from all the matter in the universe. The resulting inertial force has the form $F = -kma$, where $k < 1$ depends on the choice of the cosmological parameters such as $\Omega_{M}$, $\Omega_{\Lambda}$, and $\Omega_{R}$ and is also red-shift dependent.Comment: 10 page

A Silver Lining? Impact of Commodity Price Fall on Good Governance in Sierra Leone

From 2002 to 2013, resource-rich countries in Africa enjoyed the benefits of a commodity boom, using increased revenues to embark on major infrastructure projects in roads, rail, ports, and housing. But when commodity prices fell starting in 2011 (see figure below), public sector revenues took a major hit with private sector companies scaling back operations, delaying investment decisions and suspending unprofitable operations. Especially as the number and size of investments in the sector contracted, Governments felt increased pressure to collect, manage and spend those revenues more efficiently. As a result, the fall in commodity prices and mounting economic pressure actually led to opportunities to improve governance of the extractives sector. The result in a number of resource-rich countries has been efforts to improve laws and increase focus on implementing existing laws. There is evidence of some success in reducing corruption in the sector

Practice pointer: Using the new UK-WHO growth charts

The new UK growth charts for children aged 0-4 years (designed using data from the new WHO standards) describe the optimal pattern of growth for all children, rather than the prevailing pattern in the UK (as with previous charts). The new charts are suitable for all ethnic groups and set breast feeding as the norm. UK children match the new charts well for length and height, but after age 6 months fewer children will be below the 2nd centile for weight or show weight faltering, and more will be above the 98th centile. The new charts look different: they have a separate preterm section, no lines between 0 and 2 weeks, and the 50th percentile is no longer emphasised. The charts give clear instructions on gestational correction, and there is a new chart for infants born before 32 weeks’ gestation. The instructions advise on when and how to measure and when a measurement or growth pattern is outside the normal range. The charts include a “look-up” tool for determining the body mass index centile from height and weight centiles without calculation and aid for predicting adult height. The charts and supporting educational materials can be downloaded from www.growthcharts.rcpch.ac.u

A Riemann-Hilbert Problem for an Energy Dependent Schr\"odinger Operator

\We consider an inverse scattering problem for Schr\"odinger operators with energy dependent potentials. The inverse problem is formulated as a Riemann-Hilbert problem on a Riemann surface. A vanishing lemma is proved for two distinct symmetry classes. As an application we prove global existence theorems for the two distinct systems of partial differential equations $u_t+(u^2/2+w)_x=0, w_t\pm u_{xxx}+(uw)_x=0$ for suitably restricted, complementary classes of initial data

Use of the Physician Orders for Scope of Treatment Program in Indiana Nursing Homes

OBJECTIVES: To assess the use of the Indiana Physician Orders for Scope of Treatment (POST) form to record nursing home (NH) resident treatment preferences and associated practices. DESIGN: Survey. SETTING: Indiana NHs. PARTICIPANTS: Staff responsible for advance care planning in 535 NHs. MEASUREMENTS: Survey about use of the Indiana POST, related policies, and educational activities. METHODS: NHs were contacted by telephone or email. Nonresponders were sent a brief postcard survey. RESULTS: Ninety-one percent (n=486) of Indiana NHs participated, and 79% had experience with POST. Of the 65% of NHs that complete POST with residents, 46% reported that half or more residents had a POST form. POST was most often completed at the time of admission (68%). Only 52% of participants were aware of an existing facility policy regarding use of POST; 80% reported general staff education on POST. In the 172 NHs not using POST, reasons for not using it included unfamiliarity with the tool (23%) and lack of facility policies (21%). CONCLUSION: Almost 3 years after a grassroots campaign to introduce the voluntary Indiana POST program, a majority of NHs were using POST to support resident care. Areas for improvement include creating policies on POST for all NHs, training staff on POST conversations, and considering processes that may enhance the POST conversation, such as finding an optimal time to engage in conversations about treatment preferences other than a potentially rushed admission process

Elastic cavitation, tube hollowing, and differential growth in plants and biological tissues

Elastic cavitation is a well-known physical process by which elastic materials under stress can open cavities. Usually, cavitation is induced by applied loads on the elastic body. However, growing materials may generate stresses in the absence of applied loads and could induce cavity opening. Here, we demonstrate the possibility of spontaneous growth-induced cavitation in elastic materials and consider the implications of this phenomenon to biological tissues and in particular to the problem of schizogenous aerenchyma formation

Slurry-Based 3DP and Fine Ceramic Components

Slurry-based 3DPTM (S-3DPÔ) is a solid freeform fabrication technique developed at MIT for production of fine ceramic components with complex geometries and fired densities in excess of 99% of theoretical density. Current research involves identification of the factors controlling minimum feature size in S-3DPTM. The ink-jet printed binder droplet size is the primary factor controlling the minimum feature dimension when deposited on the powder layers. For a given droplet size, however, a balance between spreading of the binder solution on the surface of the S3DPTM powderbed and infiltration determine the feature size, while interactions between the polymeric binder and the powder surface (polymer adsorption) control the minimum feature cross-section. Droplet-on-demand printing of the binder solution has been introduced to improve resolution, decreasing the minimum feature width from 300 mm to less than 150 mm.Mechanical Engineerin

Vectorial Loading of Processive Motor Proteins: Implementing a Landscape Picture

Individual processive molecular motors, of which conventional kinesin is the most studied quantitatively, move along polar molecular tracks and, by exerting a force ${\bm F} = (F_x,F_y,F_z)$ on a tether, drag cellular cargoes, {\em in vivo}, or spherical beads, {\em in vitro}, taking up to hundreds of nanometer-scale steps. From observations of velocities and the dispersion of displacements with time, under measured forces and controlled fuel supply (typically ATP), one may hope to obtain insight into the molecular motions undergone in the individual steps. In the simplest situation, the load force ${\bm F}$ may be regarded as a scalar resisting force, $F_x < 0$, acting parallel to the track: however, experiments, originally by Gittes {\em et al.} (1996), have imposed perpendicular (or vertical) loads, $F_z > 0$, while more recently Block and coworkers (2002, 2003) and Carter and Cross (2005) have studied {\em assisting} (or reverse) loads, $F_x > 0$, and also sideways (or transverse) loads $F_y \neq 0$