Experimental Demonstration of an Allee Effect in Microbial Populations

Microbial populations can be dispersal limited. However, microorganisms that successfully disperse into physiologically ideal environments are not guaranteed to establish. This observation contradicts the Baas-Becking tenet: ‘Everything is everywhere, but the environment selects’. Allee effects, which manifest in the relationship between initial population density and probability of establishment, could explain this observation. Here, we experimentally demonstrate that small populations of Vibrio fischeri are subject to an intrinsic demographic Allee effect. Populations subjected to predationby the bacterivore Cafeteria roenbergensis display both intrinsic and extrinsic demographic Allee effects. The estimated critical threshold required to escape positive densitydependence is around 5, 20 or 90 cells ml-1 under conditions of high carbon resources, low carbon resources or low carbon resources with predation, respectively. Thiswork builds on the foundations ofmodern microbial ecology, demonstrating that mechanisms controlling macroorganisms apply to microorganisms, and provides a statistical method to detect Allee effects in data

Heterospecific Anural Eavesdropping Cues

The ability to communicate within species is a trait utilized by every organism. Using cues conspecifically creates a better chance of survival for other members of the species and increases fitness overall. However, using cues heterospecifically also poses a great advantage as animals can eavesdrop on cues released by another species. Previous studies have recorded that eavesdropping is beneficial to prey species, such as squirrels reacting to bird calls and tadpoles reacting to visual and chemical cues to avoid predation. We asked how one local and one exotic species of frog would respond to cues emitted by another local species of frog, especially considering that the exotic frog has no natural predators. We hypothesized that Pseudacis cadaverina will react to the chemical cues released by an agitated Psuedacris regilla while Dendrobates tinctorius will not. For this experiment, data were collected on the reactions of the two species to P. regilla cues. The data was found to be non-normal and non-parametric, therefore a Wilcox test was run to determine if the control and experimental frogs had differing responses. We expected the control frogs to have no reaction since there should not have been a cue to respond to, but the p-values acquired for P. cadaverina, and D. tinctorius were less than .01. This could suggest our experimental design was flawed although the two species do appear to have different responses to the cues. Understanding how animals communicate and respond to potential danger can inform how we can best conserve these species

Development and testing of a measure designed to assess the quality of care transitions

BACKGROUND: To improve the quality of care delivered to older persons receiving care across multiple settings, interventions are needed. However, the absence of a patient-centred measure specifically designed to assess this care has constrained innovation. OBJECTIVE: To develop a rigorously designed and tested measure, the Care Transition Measure (CTM). SETTING: A large, integrated managed care organisation in Colorado with approximately 55,000 members over the age of 65 years. PARTICIPANTS: Patients 65 years and older who were recently discharged from hospital and received subsequent skilled nursing care in a facility or in the home. METHODS: Six focus groups of older persons and their caregivers (n=49) were established. Standard qualitative analytic techniques were applied to written transcripts and four key domains were identified: (1) information transfer; (2) patient and caregiver preparation; (3) self-management support; and (4) empowerment to assert preferences. Specific CTM items were developed, pilot tested, and refined. Psychometric testing, conducted in a different population but selected using the same entry criteria (n=60), included content and construct validity, intra-item variation, and floor/ceiling properties. RESULTS: Older patients and clinicians found the measure to be highly relevant and comprehensive (i.e. content validity). Construct validity was assessed by comparing items from the CTM to selected items from a measure developed by Hendriks and colleagues (Medical Care 2001; 39(3): 270–283). Inter-item Spearman correlations ranged 0.388–0.594. No significant floor or ceiling effects were detected. CONCLUSIONS: The CTM was developed with substantial input from older patients and their caregivers. Psychometric testing suggested that the measure was valid. The CTM may serve to fill an important gap in health system performance evaluation by measuring the quality of care delivered across settings

Cardiac resynchronization therapy restores optimal atrioventricular mechanical timing in heart failure patients with ventricular conduction delay

AbstractObjectivesWe characterized the relationship between systolic ventricular function and left ventricular (LV) end-diastolic pressure (LVEDP) in patients with heart failure (HF) and baseline asynchrony during ventricular stimulation.BackgroundThe role of preload in the systolic performance improvement that can be obtained in HF patients with LV stimulation is uncertain.MethodsWe measured the maximum rate of increase of LV pressure, LVEDP, aortic pulse pressure (PP) and the atrioventricular mechanical latency (AVL) between left atrial systole and LV pressure onset in 39 patients with HF. Two subgroups were identified: “responder” if PP improved, or “nonresponder.”ResultsMaximum hemodynamic improvement occurred at an atrioventricular (AV) delay that did not decrease LVEDP. Left ventricular and biventricular (BV) stimulation increased systolic hemodynamics significantly, despite no significant increase in LVEDP. All parameters decreased when the LVEDP was decreased by shorter AV delay. Left ventricular and BV stimulation provided better hemodynamics than right ventricular (RV) stimulation. For the nonresponder subgroup, systolic hemodynamics only worsened during AV delay shortening. For the responder subgroup, optimum PP was achieved when AVL was near zero.ConclusionsRestoration of optimal left atrial-ventricular mechanical timing partly contributes to the hemodynamic improvements observed in this patient subgroup. However, preload alone cannot explain the differences seen between RV and BV stimulation and the contradictory PP decreases even at maximal preload in the nonresponder subgroup. These results may be explained by a site-dependent mechanism such as the degree of ventricular synchrony. Caution should be taken in these patients when optimizing AV delays using echocardiography techniques that focus on LV inflow

Social contexts of remission from DSM-5 alcohol use disorder in a high-risk sample

BACKGROUND: Measures of social context, such as marriage and religious participation, are associated with remission from alcohol use disorders (AUDs) in population-based and treatment samples, but whether these associations hold among individuals at high familial risk for AUD is unknown. This study tests associations of measures of social context and treatment with different types of remission from DSM-5 AUD in a high-risk sample. METHODS: Subjects were 686 relatives of probands (85.7% first-degree) who participated in a high-risk family study of alcohol dependence. All subjects met criteria for AUD at baseline and were re-interviewed 5 years later. Follow-up status was categorized as persistent AUD, high-risk drinking, remitted low-risk drinking, and abstinence. Social context measures were defined as stable or changing from baseline to follow-up, and their bivariate and multivariate associations with follow-up status were tested. RESULTS: At follow-up, 62.8% of subjects had persistent AUD, 6.4% were high-risk drinkers, 22.2% were remitted low-risk drinkers, and 8.6% were abstinent. Birth of first child during the interval was the only measure of social context associated with remitted low-risk drinking and was significant for women only. Abstinent remission was characterized by being stably separated or divorced for women, new marriage for both sexes, experiencing low levels of family support and high levels of friend support, and receiving treatment. High-risk drinkers were more likely than individuals with persistent AUD to have a stable number of children and to have been recently unemployed. CONCLUSIONS: The social contexts accompanying different types of remission in this high-risk sample resemble those found in population-based and clinical samples. Low-risk drinkers resemble natural remitters from population-based samples who change their drinking habits with life transitions. Abstainers resemble clinical samples in marital context, support from friends, and treatment. High-risk drinkers appear to continue to experience negative consequences of heavy drinking

Superheating fields of superconductors: Asymptotic analysis and numerical results

The superheated Meissner state in type-I superconductors is studied both analytically and numerically within the framework of Ginzburg-Landau theory. Using the method of matched asymptotic expansions we have developed a systematic expansion for the solutions of the Ginzburg-Landau equations in the limit of small $\kappa$, and have determined the maximum superheating field $H_{\rm sh}$ for the existence of the metastable, superheated Meissner state as an expansion in powers of $\kappa^{1/2}$. Our numerical solutions of these equations agree quite well with the asymptotic solutions for $\kappa<0.5$. The same asymptotic methods are also used to study the stability of the solutions, as well as a modified version of the Ginzburg-Landau equations which incorporates nonlocal electrodynamics. Finally, we compare our numerical results for the superheating field for large-$\kappa$ against recent asymptotic results for large-$\kappa$, and again find a close agreement. Our results demonstrate the efficacy of the method of matched asymptotic expansions for dealing with problems in inhomogeneous superconductivity involving boundary layers.Comment: 14 pages, 8 uuencoded figures, Revtex 3.

A Survey of Patients with Inflatable Penile Prostheses: Assessment of Timing and Frequency of Intercourse and Analysis of Implant Durability

Introduction.  This study was conducted to determine how long after inflatable penile prosthesis (IPP) surgery patients attempt sexual intercourse and the frequency of subsequent relations. We also examined survival‐related factors for the AMS 700 CX, Mentor Alpha 1, and Mentor Alpha Narrow Base. Aims.  The aim was to survey men who received IPPs and collect information about their return to sexual function and frequency of use, and to assess the resilience of their devices. Methods.  Phase I involved retrospective chart review of 1,298 virgin IPP surgeries performed by one surgical team from January 1992 to December 1998. Phase II included 330 subjects selected by stratified, systematic, random sampling from phase I patients. Data were collected by computer‐assisted telephone interview, using a 27‐question survey. All patients had been instructed to wait 4 weeks before using the implant and were taught how to inflate/deflate their prostheses at the 4‐week postsurgical visits. Main Outcome Measures.  The survey examines the length of time after surgery for men to resume sexual function. In the same study, information was garnered about mechanical durability of the device. Results.  Among phase I subjects, the 5‐year survival rate was 83% (N = 1,069) for IPP revision for any reason. Of the 330 phase II subjects, 248 (75%) were successfully contacted; 199 (80%) responded to the full survey and 49 (20%) responded to selected parts of the survey. Sexual intercourse was resumed postoperatively at 1–4 weeks for 41% (78/190), at 5–6 weeks for 31% (59/190), at 7–8 weeks for 16% (30/190), and at >8 weeks for 12% (23/190) of the patients. More than 60% of patients reported using their IPP at least once weekly. Conclusion.  The three‐piece IPP has excellent 5‐year survival rates. Most patients return to sexual activity relatively quickly, with high frequency of usage of their prostheses. Henry GD, Brinkman MJ, Mead SF, Delk JR II, Cleves MA, Jennermann C, Wilson SK, and Kramer AC. A survey of patients with inflatable penile prostheses: Assessment of timing and frequency of intercourse and analysis of implant durability. J Sex Med 2012;9:1715–1721.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92055/1/j.1743-6109.2012.02729.x.pd

Planning tiger recovery: Understanding intraspecific variation for effective conservation

Although significantly more money is spent on the conservation of tigers than on any other threatened species, today only 3200 to 3600 tigers roam the forests of Asia, occupying only 7% of their historical range. Despite the global significance of and interest in tiger conservation, global approaches to plan tiger recovery are partly impeded by the lack of a consensus on the number of tiger subspecies or management units, because a comprehensive analysis of tiger variation is lacking. We analyzed variation among all nine putative tiger subspecies, using extensive data sets of several traits [morphological (craniodental and pelage), ecological, molecular]. Our analyses revealed little variation and large overlaps in each trait among putative subspecies, and molecular data showed extremely low diversity because of a severe Late Pleistocene population decline. Our results support recognition of only two subspecies: the Sunda tiger, Panthera tigris sondaica, and the continental tiger, Panthera tigris tigris, which consists of two (northern and southern) management units. Conservation management programs, such as captive breeding, reintroduction initiatives, or trans-boundary projects, rely on a durable, consistent characterization of subspecies as taxonomic units, defined by robust multiple lines of scientific evidence rather than single traits or ad hoc descriptions of one or few specimens. Our multiple-trait data set supports a fundamental rethinking of the conventional tiger taxonomy paradigm, which will have profound implications for the management of in situ and ex situ tiger populations and boost conservation efforts by facilitating a pragmatic approach to tiger conservation management worldwid