On Conceptually Simple Algorithms for Variants of Online Bipartite Matching

We present a series of results regarding conceptually simple algorithms for bipartite matching in various online and related models. We first consider a deterministic adversarial model. The best approximation ratio possible for a one-pass deterministic online algorithm is $1/2$, which is achieved by any greedy algorithm. D\"urr et al. recently presented a $2$-pass algorithm called Category-Advice that achieves approximation ratio $3/5$. We extend their algorithm to multiple passes. We prove the exact approximation ratio for the $k$-pass Category-Advice algorithm for all $k \ge 1$, and show that the approximation ratio converges to the inverse of the golden ratio $2/(1+\sqrt{5}) \approx 0.618$ as $k$ goes to infinity. The convergence is extremely fast --- the $5$-pass Category-Advice algorithm is already within $0.01\%$ of the inverse of the golden ratio. We then consider a natural greedy algorithm in the online stochastic IID model---MinDegree. This algorithm is an online version of a well-known and extensively studied offline algorithm MinGreedy. We show that MinDegree cannot achieve an approximation ratio better than $1-1/e$, which is guaranteed by any consistent greedy algorithm in the known IID model. Finally, following the work in Besser and Poloczek, we depart from an adversarial or stochastic ordering and investigate a natural randomized algorithm (MinRanking) in the priority model. Although the priority model allows the algorithm to choose the input ordering in a general but well defined way, this natural algorithm cannot obtain the approximation of the Ranking algorithm in the ROM model

Climate Change and invasibility of the Antarctic benthos

Benthic communities living in shallow-shelf habitats in Antarctica (<100-m depth) are archaic in their structure and function. Modern predators, including fast-moving, durophagous (skeleton-crushing) bony fish, sharks, and crabs, are rare or absent; slow-moving invertebrates are the top predators; and epifaunal suspension feeders dominate many soft substratum communities. Cooling temperatures beginning in the late Eocene excluded durophagous predators, ultimately resulting in the endemic living fauna and its unique food-web structure. Although the Southern Ocean is oceanographically isolated, the barriers to biological invasion are primarily physiological rather than geographic. Cold temperatures impose limits to performance that exclude modern predators. Global warming is now removing those physiological barriers, and crabs are reinvading Antarctica. As sea temperatures continue to rise, the invasion of durophagous predators will modernize the shelf benthos and erode the indigenous character of marine life in Antarctica

"I am your mother and your father!": In vitro derived gametes and the ethics of solo reproduction

In this paper, we will discuss the prospect of human reproduction achieved with gametes originating from only one person. According to statements by a minority of scientists working on the generation of gametes in vitro, it may become possible to create eggs from men’s non-reproductive cells and sperm from women’s. This would enable, at least in principle, the creation of an embryo from cells obtained from only one individual: ‘solo reproduction’. We will consider what might motivate people to reproduce in this way, and the implications that solo reproduction might have for ethics and policy. We suggest that such an innovation is unlikely to revolutionise reproduction and parenting. Indeed, in some respects it is less revolutionary than in vitro fertilisation as a whole. Furthermore, we show that solo reproduction with in vitro created gametes is not necessarily any more ethically problematic than gamete donation—and probably less so. Where appropriate, we draw parallels with the debate surrounding reproductive cloning. We note that solo reproduction may serve to perpetuate reductive geneticised accounts of reproduction, and that this may indeed be ethically questionable. However, in this it is not unique among other technologies of assisted reproduction, many of which focus on genetic transmission. It is for this reason that a ban on solo reproduction might be inconsistent with continuing to permit other kinds of reproduction that also bear the potential to strengthen attachment to a geneticised account of reproduction. Our claim is that there are at least as good reasons to pursue research towards enabling solo reproduction, and eventually to introduce solo reproduction as an option for fertility treatment, as there are to do so for other infertility related purposes

Changing Patterns of Microhabitat Utilization by the Threespot Damselfish, Stegastes planifrons, on Caribbean Reefs

Background: The threespot damselfish, Stegastes planifrons (Cuvier), is important in mediating interactions among corals, algae, and herbivores on Caribbean coral reefs. The preferred microhabitat of S. planifrons is thickets of the branching staghorn coral Acropora cervicornis. Within the past few decades, mass mortality of A. cervicornis from white-band disease and other factors has rendered this coral a minor ecological component throughout most of its range. Methodology/Principal Findings: Survey data from Jamaica (heavily fished), Florida and the Bahamas (moderately fished), the Cayman Islands (lightly to moderately fished), and Belize (lightly fished) indicate that distributional patterns of S. planifrons are positively correlated with live coral cover and topographic complexity. Our results suggest that speciesspecific microhabitat preferences and the availability of topographically complex microhabitats are more important than the abundance of predatory fish as proximal controls on S. planifrons distribution and abundance. Conclusions/Significance: The loss of the primary microhabitat of S. planifrons—A. cervicornis—has forced a shift in the distribution and recruitment of these damselfish onto remaining high-structured corals, especially the Montastraea annulari

Temporary exclusion of ill children from childcare centres in Switzerland: practice, problems and potential solutions.

BACKGROUND: In childcare centres, temporary exclusion of ill children, if their illness poses a risk of spread of harmful diseases to others, is a central approach to fight disease transmission. However, not all ill children need to be excluded. Previous studies suggested that childcare centre staff have difficulties in deciding whether or not to exclude an ill child, even when official ill-child guidelines are used. We aimed to describe, quantify and analyse these ambiguities and discuss potential solutions. METHODS: For this cross-sectional study, we sent postal surveys to 488 childcare centre directors in the Swiss Canton of Zurich, where no official ill-child guideline is in place. We asked for exclusion criteria for ill children and ambiguities faced when dealing with ill children. We checked whether existing guidelines provided solutions to the ambiguities identified. RESULTS: 249/488 (51%) directors responded to the survey. The most common exclusion criteria were fever (87.4%) and contagiousness (52.2%). Ambiguities were mostly caused by conjunctivitis (23.7%) and use of antipyretic drugs (22.9%). Roughly one third of the ambiguities identified could have been resolved with existing guidelines, another third if existing guidelines contained additional information. For the last third, clear written directives are difficult to formulate. CONCLUSIONS: Written recommendations may help to clarify when an ill child should temporarily be excluded. However, such a guideline should cover the topics antipyretic drugs and teething and have room for modification to local circumstances. Collaboration with a paediatrician may be of additional benefit

The safety of over-the-counter niacin. A randomized placebo-controlled trial [ISRCTN18054903]

BACKGROUND: Niacin is widely available over the counter (OTC). We sought to determine the safety of 500 mg immediate release niacin, when healthy individuals use them as directed. METHODS: 51 female and 17 male healthy volunteers (mean age 27 years SD 4.4) participated in a randomized placebo-controlled blinded trial of a single dose of an OTC, immediate-release niacin 500 mg (n = 33), or a single dose of placebo (n = 35) on an empty stomach. The outcomes measured were self-reported incidence of flushing and other adverse effects. RESULTS: 33 volunteers on niacin (100%) and 1 volunteer on placebo (3%) flushed (relative risk 35, 95% confidence interval (CI) 6.8–194.7). Mean time to flushing on niacin was 18.2 min (95% CI: 12.7–23.6); mean duration of flushing was 75.4 min (95% CI: 62.5–88.2). Other adverse effects occurred commonly in the niacin group: chills (51.5% vs. 0%, P < .0001), generalized pruritus (75% vs. 0%, P = <.001), gastrointestinal upset (30% vs. 3%, P = .005), and cutaneous tingling (30% vs. 0%, P = <.001). Six participants did not tolerate the adverse effects of niacin and 3 required medical attention. CONCLUSION: Clinicians counseling patients about niacin should alert patients not only about flushing but also about gastrointestinal symptoms, the most severe in this study. They should not trust that patients would receive information about these side effects or their prevention (with aspirin) from the OTC packet insert

Evaluating Patterns of a White-Band Disease (WBD) Outbreak in Acropora palmata Using Spatial Analysis: A Comparison of Transect and Colony Clustering

. Likewise, there is little known about the spatiality of outbreaks. We examined the spatial patterns of WBD during a 2004 outbreak at Buck Island Reef National Monument in the US Virgin Islands. colonies with and without WBD.As the search for causation continues, surveillance and proper documentation of the spatial patterns may inform etiology, and at the same time assist reef managers in allocating resources to tracking the disease. Our results indicate that the spatial scale of data collected can drastically affect the calculation of prevalence and spatial distribution of WBD outbreaks. Specifically, we illustrate that higher resolution sampling resulted in more realistic disease estimates. This should assist in selecting appropriate sampling designs for future outbreak investigations. The spatial techniques used here can be used to facilitate other coral disease studies, as well as, improve reef conservation and management

Adults with corrected oesophageal atresia: is oesophageal function associated with complaints and/or quality of life?

The aim of this study was to evaluate oesophageal function after correction of oesophageal atresia in adults, and to investigate the association between complaints, oesophageal function and quality of life (QoL). Twenty-five adults were included who participated in previous follow-up studies, during which complaints of dysphagia and gastro-oesophageal reflux (GOR), results of upper gastrointestinal endoscopy, oesophageal biopsies and QoL had been collected. Manometry was performed in 20 patients, 24 h pH-measurements were performed in 21 patients. pH-values (sample time 5 s) were calculated using criteria of Johnson and DeMeester. Associations were tested with ANOVA and χ2-tests. Ten patients (48%) reported complaints of dysphagia, seven (33%) of GOR. The amplitude of oesophageal contractions was low (<15 mmHg) in four patients (20%). pH-measurements showed pathological reflux in three patients (14%). Patients reporting dysphagia more often had disturbed motility (P = 0.011), and lower scores on the domains “general health perceptions” (SF-36) (P = 0.026), “standardised physical component” (SF-36) (P = 0.013), and “physical well-being” (GIQLI) (0.047). No other associations were found. This study shows a high percentage of oesophageal motility disturbances and a moderate percentage of GOR after correction of oesophageal atresia. Patients reporting dysphagia, whom more often had disturbed motility, seemed to be affected by these symptoms in their QoL

Polyantigenic Interferon-γ Responses Are Associated with Protection from TB among HIV-Infected Adults with Childhood BCG Immunization

Surrogate immunologic markers for natural and vaccine-mediated protection against tuberculosis (TB) have not been identified. HIV-infected adults with childhood BCG immunization entering the placebo arm of the DarDar TB vaccine trial in Dar es Salaam, Tanzania, were assessed for interferon gamma (IFN-γ) responses to three mycobacterial antigen preparations--secreted Mycobacterium tuberculosis antigens 85 (Ag85), early secretory antigenic target 6 (ESAT-6) and polyantigenic whole cell lysate (WCL). We investigated the association between the number of detectable IFN-γ responses at baseline and the subsequent risk of HIV-associated TB. During a median follow-up of 3.3 years, 92 (9.4%) of 979 placebo recipients developed TB. The incidence of TB was 14% in subjects with no detectable baseline IFN-γ responses vs. 8% in subjects with response to polyantigenic WCL (P = 0.028). Concomitant responses to secreted antigens were associated with further reduction in the incidence of HIV-associated TB. Overall the percentage of subjects with 0, 1, 2 and 3 baseline IFN-γ responses to mycobacterial preparations who developed HIV-associated TB was 14%, 8%, 7% and 4%, respectively (P = 0.004). In a multivariate Cox regression model, the hazard of developing HIV-associated TB was 46% lower with each increment in the number of detectable baseline IFN-γ responses (P<0.001). Among HIV-infected adults who received BCG in childhood and live in a TB-endemic country, polyantigenic IFN-γ responses are associated with decreased risk of subsequent HIV-associated TB. ClinicalTrials.gov NCT0052195

Natural Disease Resistance in Threatened Staghorn Corals

Disease epidemics have caused extensive damage to tropical coral reefs and to the reef-building corals themselves, yet nothing is known about the abilities of the coral host to resist disease infection. Understanding the potential for natural disease resistance in corals is critically important, especially in the Caribbean where the two ecologically dominant shallow-water corals, Acropora cervicornis and A. palmata, have suffered an unprecedented mass die-off due to White Band Disease (WBD), and are now listed as threatened under the US Threatened Species Act and as critically endangered under the IUCN Red List criteria. Here we examine the potential for natural resistance to WBD in the staghorn coral Acropora cervicornis by combining microsatellite genotype information with in situ transmission assays and field monitoring of WBD on tagged genotypes. We show that six percent of staghorn coral genotypes (3 out of 49) are resistant to WBD. This natural resistance to WBD in staghorn corals represents the first evidence of host disease resistance in scleractinian corals and demonstrates that staghorn corals have an innate ability to resist WBD infection. These resistant staghorn coral genotypes may explain why pockets of Acropora have been able to survive the WBD epidemic. Understanding disease resistance in these corals may be the critical link to restoring populations of these once dominant corals throughout their range