Instance and Output Optimal Parallel Algorithms for Acyclic Joins

Massively parallel join algorithms have received much attention in recent years, while most prior work has focused on worst-optimal algorithms. However, the worst-case optimality of these join algorithms relies on hard instances having very large output sizes, which rarely appear in practice. A stronger notion of optimality is {\em output-optimal}, which requires an algorithm to be optimal within the class of all instances sharing the same input and output size. An even stronger optimality is {\em instance-optimal}, i.e., the algorithm is optimal on every single instance, but this may not always be achievable. In the traditional RAM model of computation, the classical Yannakakis algorithm is instance-optimal on any acyclic join. But in the massively parallel computation (MPC) model, the situation becomes much more complicated. We first show that for the class of r-hierarchical joins, instance-optimality can still be achieved in the MPC model. Then, we give a new MPC algorithm for an arbitrary acyclic join with load O ({\IN \over p} + {\sqrt{\IN \cdot \OUT} \over p}), where \IN,\OUT are the input and output sizes of the join, and $p$ is the number of servers in the MPC model. This improves the MPC version of the Yannakakis algorithm by an O (\sqrt{\OUT \over \IN} ) factor. Furthermore, we show that this is output-optimal when \OUT = O(p \cdot \IN), for every acyclic but non-r-hierarchical join. Finally, we give the first output-sensitive lower bound for the triangle join in the MPC model, showing that it is inherently more difficult than acyclic joins

A practical approach to managing patients with HCV infection.

Hepatitis C virus (HCV) infection is a major worldwide public health concern. It is a common cause of chronic liver disease and hepatocellular carcinoma. HCV antibody and HCV RNA testing are available diagnostic studies that offer high degree of accuracy. Current standard therapy includes a combination of pegylated interferon and ribavirin. Response rate is approximately 40% for genotype 1 and 80% for genotypes 2 and 3, respectively. Successful treatment can stop the progression of chronic liver disease, reduce the need for liver transplantation, and possibly decrease the risk for Hepatocellular carcinoma (HCC). Evaluating for potential treatment candidacy is an important initial step in the management of chronic HCV infection as not all individuals may need or qualify for the treatment. Understanding the natural history, the different diagnostic modalities, the current therapeutic options and, the treatment response and adverse effect profiles can help the practitioners better manage chronic HCV infection

A reception study of machine translated subtitles for MOOCs

As MOOCs (Massive Open Online Courses) grow rapidly around the world, the language barrier is becoming a serious issue. Removing this obstacle by creating translated subtitles is an indispensable part of developing MOOCs and improving accessibility. Given the large quantity of MOOCs available worldwide and the considerable demand for them, machine translation (MT) appears to offer an alternative or complementary translation solution, thus providing the motivation for this research. The main goal of this research is to test the impact machine translated subtitles have on Chinese viewers’ reception of MOOC content. More specifically, the author is interested in whether there is any difference between viewers’ reception of raw machine translated subtitles as opposed to fully post-edited machine translated subtitles and human translated subtitles. Reception is operationalized by adapting Gambier's (2007) model, which divides ‘reception’ into ‘the three Rs’: (i) response, (ii) reaction and (iii) repercussion. Response refers to the initial physical response of a viewer to an audio-visual stimulus, in this case the subtitle and the rest of the image. Reaction involves the cognitive follow-on from initial response, and is linked to how much effort is involved in processing the subtitling stimulus and what is understood by the viewer. Repercussion refers to attitudinal and sociocultural dimensions of AVT consumption. The research contains a pilot study and a main experiment. Mixed methods of eye-tracking, questionnaires, translation quality assessment and frequency analysis were adopted. Over 60 native Chinese speakers were recruited as participants for this research. They were divided into three groups, those who read subtitles created by raw MT, post-edited MT (PE) and human translation (HT). Results show that most participants had a positive attitude towards the subtitles regardless of their type. Participants who were offered PE subtitles scored the best overall on the selected reception metrics. Participants who were offered HT subtitles performed the worst in some of the selected reception metrics

Enhancement of ion transmission and reduction of background and interferences in inductively coupled plasma mass spectrometry

A new inductively coupled plasma-mass spectrometer (ICP-MS) with four stages of differential pumping is described. The relatively large sampling orifice (1.31 mm diam.) improves signals for metal ions and resists plugging from deposited solids. The ion lens deflects ions off center and then back on center into the differential pumping orifice; there is no photon stop in the center of the beam. Calculations of ion trajectories with SIMION show that only those ions that leave the skimmer on center are transmitted, whereas most other lenses used in ICP-MS transmit only ions that leave the skimmer off axis. The performance of a Channeltron electron multiplier is compared to that of a Daly detector. Both detectors yield similar sensitivities of ~10[superscript]6 counts s[superscript]-1 per ppm and detection limits of ~1 pptr. The background with a Channeltron electron multiplier is only 0.4 counts s[superscript]-1 and is only slightly higher than the dark current count rate. The background with the Daly detector is 4 counts s[superscript]-1, which represents a substantial improvement over the background obtained in previous use of the Daly detector with ICP-MS;This new ICP-MS yields very low levels of many troublesome polyatomic ions such as ArO[superscript]+, ArN[superscript]+, Ar[subscript]2[superscript]+, ClO[superscript]+, and ArCl[superscript]+. The signals from refractory metal oxide ions are ~1% of the corresponding metal ion signals, which is typical of most ICP-MS devices. Grounding the first electrode of the ion lens greatly reduces the severity of matrix effects to [subscript]sp~\u3c20% loss in signal for Co[superscript]+, Y[superscript]+ or Cs[superscript]+ in the presence of 10 mM Sr, Tm or Pb. This latter lens setting causes only a modest loss (30%) in sensitivity for analyte elements compared to the best sensitivity obtainable by biassing the first lens;Conventionally, the metal cones through which the ions are extracted are connected to ground potential. Floating one or both of these cones at various potentials can improve the ion transmission by a factor of at least four to six. The net result is better sensitivity and higher ion beam intensity than are obtained with a grounded skimmer and sampler. (Abstract shortened with permission of author.

Organizational Changes of the Daughter Basal Complex during the Parasite Replication of Toxoplasma gondii

The apicomplexans are a large group of parasitic protozoa, many of which are important human and animal pathogens, including Plasmodium falciparum and Toxoplasma gondii. These parasites cause disease only when they replicate, and their replication is critically dependent on the proper assembly of the parasite cytoskeletons during cell division. In addition to their importance in pathogenesis, the apicomplexan parasite cytoskeletons are spectacular structures. Therefore, understanding the cytoskeletal biogenesis of these parasites is important not only for parasitology but also of general interest to broader cell biology. Previously, we found that the basal end of T. gondii contains a novel cytoskeletal assembly, the basal complex, a cytoskeletal compartment constructed in concert with the daughter cortical cytoskeleton during cell division. This study focuses on key events during the biogenesis of the basal complex using high resolution light microscopy, and reveals that daughter basal complexes are established around the duplicated centrioles independently of the structural integrity of the daughter cortical cytoskeleton, and that they are dynamic “caps” at the growing ends of the daughters. Compartmentation and polarization of the basal complex is first revealed at a late stage of cell division upon the recruitment of an EF-hand containing calcium binding protein, TgCentrin2. This correlates with the constriction of the basal complex, a process that can be artificially induced by increasing cellular calcium concentration. The basal complex is therefore likely to be a new kind of centrin-based contractile apparatus