Characterizing block graphs in terms of their vertex-induced partitions

Block graphs are a generalization of trees that arise in areas such as metric graph theory, molecular graphs, and phylogenetics. Given a finite connected simple graph $G=(V,E)$ with vertex set $V$ and edge set $E\subseteq \binom{V}{2}$, we will show that the (necessarily unique) smallest block graph with vertex set $V$ whose edge set contains $E$ is uniquely determined by the $V$-indexed family \Pp_G =\big(\pi_v)_{v \in V} of the partitions $\pi_v$ of the set $V$ into the set of connected components of the graph $(V,\{e\in E: v\notin e\})$. Moreover, we show that an arbitrary $V$-indexed family \Pp=(\p_v)_{v \in V} of partitions \p_v of the set $V$ is of the form \Pp=\Pp_G for some connected simple graph $G=(V,E)$ with vertex set $V$ as above if and only if, for any two distinct elements $u,v\in V$, the union of the set in \p_v that contains $u$ and the set in \p_u that contains $v$ coincides with the set $V$, and \{v\}\in \p_v holds for all $v \in V$. As well as being of inherent interest to the theory of block graphs,these facts are also useful in the analysis of compatible decompositions of finite metric spaces

The effect of temperature on the Fischer-Tropsch selectivity and further mechanistic insights

Includes bibliographical references (p. 133-145).Concern’s that the world’s energy supply will not be able to keep pace with rising energy demands, have surfaced periodically for much of the petrochemical industry’s nearly 150 year history, but each time the industry has responded with technological advances and innovations to satisfy the global energy needs. Future advances will most likely include the enhanced recovery of conventional oil, the production of extra-heavy oil / tar sands and the utilization of alternative energy production technologies (technologies other than crude oil refining). The Fischer-Tropsch Synthesis (FTS) discovered in 1923 by Fischer and Tropsch, is one of these alternative fuel production technologies and can briefly be defined as the means used to convert synthesis gas containing hydrogen and carbon monoxide over a group VIII metal catalyst to hydrocarbon products and water. Given the vast product spectrum possible for the FTS (paraffins, olefins, alcohols, carbonyls, acids and aromatics), a great deal of controversy still exists as to the chemical identity of the monomeric building block and the propagation of the hydrocarbon chain on the catalyst surface [van Dijk., 2001]. Several mechanisms have been published with the four most popular (alkyl, alkenyl, enol and CO-insertion), recently reviewed by Claeys and van Steen (2004). It must however, be appreciated that given the complexity of the FT reaction it is generally accepted that more than one mechanism may operate on the catalyst surface at any one time. Furthermore, process parameters such as temperature, total pressure, partial pressure, hydrogen to carbon monoxide ratio, space velocity and residence time all have an influence on the FT product selectivity. Because of this it becomes exceptionally complicated to determine the effects of just one parameter while taking the effects of the additional parameters into account

A very high speed lossless compression/decompression chip set

A chip is described that will perform lossless compression and decompression using the Rice Algorithm. The chip set is designed to compress and decompress source data in real time for many applications. The encoder is designed to code at 20 M samples/second at MIL specifications. That corresponds to 280 Mbits/second at maximum quantization or approximately 500 Mbits/second under nominal conditions. The decoder is designed to decode at 10 M samples/second at industrial specifications. A wide range of quantization levels is allowed (4...14 bits) and both nearest neighbor prediction and external prediction are supported. When the pre and post processors are bypassed, the chip set performs high speed entropy coding and decoding. This frees the chip set from being tied to one modeling technique or specific application. Both the encoder and decoder are being fabricated in a 1.0 micron CMOS process that has been tested to survive 1 megarad of total radiation dosage. The CMOS chips are small, only 5 mm on a side, and both are estimated to consume less than 1/4 of a Watt of power while operating at maximum frequency

Hyperbolic Bridged Graphs

AbstractGiven a connected graph G, we take, as usual, the distance xy between any two verticesx , y of G to be the length of some geodesic between x and y. The graph G is said to be δ - hyperbolic, for some δ≥ 0, if for all vertices x,y , u, v in G the inequality xy+uv ≤max{ xu+ yv,xv + yu } + δholds, and G isbridged if it contains no finite isometric cycles of length four or more. In this paper, we will show that a finite connected bridged graph is 1-hyperbolic if and only if it does not contain any of a list of six graphs as an isometric subgraph

A secretory kinase complex regulates extracellular protein phosphorylation.

Although numerous extracellular phosphoproteins have been identified, the protein kinases within the secretory pathway have only recently been discovered, and their regulation is virtually unexplored. Fam20C is the physiological Golgi casein kinase, which phosphorylates many secreted proteins and is critical for proper biomineralization. Fam20A, a Fam20C paralog, is essential for enamel formation, but the biochemical function of Fam20A is unknown. Here we show that Fam20A potentiates Fam20C kinase activity and promotes the phosphorylation of enamel matrix proteins in vitro and in cells. Mechanistically, Fam20A is a pseudokinase that forms a functional complex with Fam20C, and this complex enhances extracellular protein phosphorylation within the secretory pathway. Our findings shed light on the molecular mechanism by which Fam20C and Fam20A collaborate to control enamel formation, and provide the first insight into the regulation of secretory pathway phosphorylation

An Overview of MODIS On-orbit Operation, Calibration, and Lessons

Two nearly identical copies of the Moderate Resolution Imaging Spectroradiometer (MODIS) have successfully operated onboard the Terra and Aqua spacecraft for more than II years and 9 years since their launch in December 1999 and May 2002, respectively. MODIS is a key instrument for the NASA's Earth Observing System (EOS) missions. MODIS observations have produced an unprecedented amount and a broad range of data products and significantly benefited the science and user community. Its follow-on instrument, the Visible/Infrared Imager Radiometer Suite (VIIRS) on-board the NPOESS Preparatory Project (NPP) spacecraft, is currently scheduled for launch in late October, 2011. The NPP serves as a bridge mission between EOS and the Joint Polar Satellite System (JPSS). MODIS collects data in 36 spectral bands, covering spectral regions from visible (VIS) to long-wave infrared (L WIR), and at three different spatial resolutions. Because of its stringent design requirements, MODIS was built with a complete set of onboard calibrators, including a solar diffuser (SO), a solar diffuser stability monitor (SDSM), a blackbody (BB), a spectroradiometric calibration assembly (SRCA), and a space view (SV) port. Except for tbe SRCA, VIlRS carries the same set of onboard calibrators as MODIS. The SD/SDSM system is used together to calibrate tbe reflective solar bands (RSB). The BB is designed for the thermal emissive bands (TEB) calibration. Similar to Terra and Aqua MODIS, VIlRS will also make regular lunar observations to monitor RSB radiometric calibration stability. In this paper, we provide an overview of MODIS on-orbit operation and calibration activities and present issues identified and lessons learned from mission-long instrument operations and implementation of various calibration and characterization strategies. Examples of both Terra and Aqua MODIS instrument on-orbit performance, including their similarities and unique characteristics, are discussed in tbe context of what might be expected from and benefited to tbe NPP VIlRS operation and calibration. It is anticipated that MODIS experience and lessons will also provide valuable information for other earth observing missions/sensors

The Liberating Consequences of Creative Work: How a Creative Outlet Lifts the Physical Burden of Secrecy

A newly emerging stream of research suggests creativity can be fruitfully explored, not as an outcome variable, but as a contributor to the general cognitive and behavioral responding of the individual. In this paper, we extend this nascent area of research on the consequences of creativity by showing that working on a creative task can contribute to feelings of liberation— feelings that can help people to overcome psychological burdens. We illustrate the liberating effects of creativity by integrating the embodied cognition literature with recent research showing that keeping a secret is experienced as a psychological and physical burden. While secrecy is metaphorically related to physical burden, creativity is metaphorically associated with freedom to “think outside the box” and explore beyond normal constraints. Thus, we predict permission to be creative may actually feel liberating and feelings of liberation may, in turn, lift the physical burden of keeping a big secret. The results of three studies supported our prediction and suggest that the opportunity to be creative may be a way for people to unburden without directly revealing secrets that could cause shame and embarrassment. We discuss the implications of our results for future research on the psychological consequences of performing creative work