Vietoris-Rips and Cech Complexes of Metric Gluings

We study Vietoris-Rips and Cech complexes of metric wedge sums and metric gluings. We show that the Vietoris-Rips (resp. Cech) complex of a wedge sum, equipped with a natural metric, is homotopy equivalent to the wedge sum of the Vietoris-Rips (resp. Cech) complexes. We also provide generalizations for certain metric gluings, i.e. when two metric spaces are glued together along a common isometric subset. As our main example, we deduce the homotopy type of the Vietoris-Rips complex of two metric graphs glued together along a sufficiently short path. As a result, we can describe the persistent homology, in all homological dimensions, of the Vietoris-Rips complexes of a wide class of metric graphs

Scale effect concerning hydraulic quasi-stationary oscillations on a turbine model and test circuit

For the continuation of the study undertaken during the Amsterdam Symposium and within the framework of the "Work Group on the Behavior of Hydraulic Machinery under steady oscillatory conditions" the authors have the following objectives: - comparison between the experimental responses of the circuit to a piston machine excitation and the calculated responses by the impedance method; - comparison between the experimental responses of the circuit to a piston machine excitation and the responses to excitation produced by the flow at partial load; - conditions under which a pulsation phenomenon occurs at high loads. The first aim is achieved but yet under restrictive conditions. The second investigation shows that the scale effects of fluctuations versus/test head have the same tendencies as the frequency responses of the circuit but that the occurence of cavitation deeply changes such responses. Finally, the occurence of pulsations at high loads is closely related to the axisymmetric vapor amount in the draft tube and the pulsation frequency also varies with the characteristics of this vapor amount

Factors associated with HIV voluntary disclosure of people living with HIV to their steady sexual partner in the Democratic Republic of the Congo: results from a community-based participatory research

Introduction: HIV disclosure to a steady sexual partner (SSP) is important both in preventing HIV transmission and improving the quality of life of people living with HIV (PLHIV). “Its determinants have been poorly investigated in the Democratic Republic of the Congo.” The study objective was to determine factors independently associated with voluntary disclosure to one's SSP in PLHIV receiving services from a Congolese community-based organization (CBO). Methods: a community-based participatory research was performed and 300 PLHIV were interviewed by members of the CBO, using a standardized questionnaire. A multivariate logistic regression was used to determine the variables independently associated with disclosure. Results: in this sample, 79 of the 127 participants (62%) included in the analysis declared having voluntarily disclosed their serostatus to their SSP. Declaring to be in a relationship (Odds Ratio (95% Confidence Interval): 4.2 (1.4-12.6)), having tested for HIV because of symptoms (2.5 (1.0-6.4)), having taken the test on one's own initiative (3.2 (1.3-8.0)), having felt sympathy and indifference from people when disclosing (6.0 (1.4-26.9) and 5.0 (1.1-22.8), respectively) as well as having a higher score of the "regular discussion about daily life with HIV" index (1.7 (1.1-2.5)) were significantly associated with disclosure to one's SSP. Conclusion: several individual and contextual factors were associated with voluntary disclosure to SSP in this study, highlighting the complex nature of the disclosure process. Interventions encouraging disclosure should be designed "so as to adapt to one's personal life with HIV as well as psychosocial environment"

Extracellular Bacterial Pathogen Induces Host Cell Surface Reorganization to Resist Shear Stress

Bacterial infections targeting the bloodstream lead to a wide array of devastating diseases such as septic shock and meningitis. To study this crucial type of infection, its specific environment needs to be taken into account, in particular the mechanical forces generated by the blood flow. In a previous study using Neisseria meningitidis as a model, we observed that bacterial microcolonies forming on the endothelial cell surface in the vessel lumen are remarkably resistant to mechanical stress. The present study aims to identify the molecular basis of this resistance. N. meningitidis forms aggregates independently of host cells, yet we demonstrate here that cohesive forces involved in these bacterial aggregates are not sufficient to explain the stability of colonies on cell surfaces. Results imply that host cell attributes enhance microcolony cohesion. Microcolonies on the cell surface induce a cellular response consisting of numerous cellular protrusions similar to filopodia that come in close contact with all the bacteria in the microcolony. Consistent with a role of this cellular response, host cell lipid microdomain disruption simultaneously inhibited this response and rendered microcolonies sensitive to blood flow–generated drag forces. We then identified, by a genetic approach, the type IV pili component PilV as a triggering factor of plasma membrane reorganization, and consistently found that microcolonies formed by a pilV mutant are highly sensitive to shear stress. Our study shows that bacteria manipulate host cell functions to reorganize the host cell surface to form filopodia-like structures that enhance the cohesion of the microcolonies and therefore blood vessel colonization under the harsh conditions of the bloodstream

Pancreatic Fistula Following Pancreaticoduodenectomy: Clinical Predictors and Patient Outcomes

Pancreatic fistula continues to be a common complication following PD. This study seeks to identify clinical factors which may predict pancreatic fistula (PF) and evaluate the effect of PF on outcomes following pancreaticoduodenectomy (PD). We performed a retrospective analysis of a clinical database at an academic tertiary care hospital with a high volume of pancreatic surgery. Five hundred ten consecutive patients underwent PD, and PF occurred in 46 patients (9%). Perioperative mortality of patients with PF was 0%. Forty-five of 46 PF (98%) closed without reoperation with a mean time to closure of 34 days. Patients who developed PF showed a higher incidence of wound infection, intra-abdominal abscess, need for reoperation, and hospital length of stay. Multivariate analysis demonstrated an invaginated pancreatic anastomosis and closed suction intraperitoneal drainage were associated with PF whereas a diagnosis of chronic pancreatitis and endoscopic stenting conferred protection. Development of PF following PD in this series was predicted by gender, preoperative stenting, pancreatic anastomotic technique, and pancreas pathology. Outcomes in patients with PF are remarkable for a higher rate of septic complications, longer hospital stays, but in this study, no increased mortality

A Fiji multi-coral δ¹⁸O composite approach to obtaining a more accurate reconstruction of the last two-centuries of the ocean-climate variability...

The limited availability of oceanographic data in the tropical Pacific Ocean prior to the satellite era makes coral-based climate reconstructions a key tool for extending the instrumental record back in time, thereby providing a much needed test for climate models and projections. We have generated a unique regional network consisting of five Porites coral δ¹⁸O time series from different locations in the Fijian archipelago. Our results indicate that using a minimum of three Porites coral δ¹⁸O records from Fiji is statistically sufficient to obtain a reliable signal for climate reconstruction, and that application of an approach used in tree ring studies is a suitable tool to determine this number. The coral δ¹⁸O composite indicates that while sea surface temperature (SST) variability is the primary driver of seasonal δ¹⁸O variability in these Fiji corals, annual average coral δ¹⁸O is more closely correlated to sea surface salinity (SSS) as previously reported. Our results highlight the importance of water mass advection in controlling Fiji coral δ¹⁸O and salinity variability at interannual and decadal time scales despite being located in the heavy rainfall region of the South Pacific Convergence Zone (SPCZ). The Fiji δ¹⁸O composite presents a secular freshening and warming trend since the 1850s coupled with changes in both interannual (IA) and decadal/interdecadal (D/I) variance. The changes in IA and D/I variance suggest a re-organization of climatic variability in the SPCZ region beginning in the late 1800s to period of a more dominant interannual variability, which could correspond to a southeast expansion of the SPCZ

High Risk of Acute Kidney Failure in Kidney Transplant Recipients Early after Bariatric Surgery

Bariatric surgery is routinely proposed to patients suffering from obesity including kidney transplant recipients. In this specific population, bariatric surgery has a positive impact in long-term outcomes in terms of patient and graft survival. We report here the cases of 4 patients with five post-kidney transplantation bariatric surgeries who experimented acute renal injury early after surgery. Creatinine rising occurred between day 14 and day 20 after surgery. In all cases, it was due to dehydration leading to a pre-renal acute renal failure. The specific care of kidney transplanted patients is discussed: single kidney associated with pre-existing altered kidney function associated with concomitant use of nephrotoxic drugs. Specific education intervention before surgery associated with careful early management of hydration after surgery is mandatory for these patients

The genetic landscape and clinical spectrum of nephronophthisis and related ciliopathies

Nephronophthisis (NPH) is an autosomal-recessive ciliopathy representing one of the most frequent causes of kidney failure in childhood characterized by a broad clinical and genetic heterogeneity. Applied to one of the worldwide largest cohorts of patients with NPH, genetic analysis encompassing targeted and whole exome sequencing identified disease-causing variants in 600 patients from 496 families with a detection rate of 71%. Of 788 pathogenic variants, 40 known ciliopathy genes were identified. However, the majority of patients (53%) bore biallelic pathogenic variants in NPHP1. NPH-causing gene alterations affected all ciliary modules defined by structural and/or functional subdomains. Seventy six percent of these patients had progressed to kidney failure, of which 18% had an infantile form (under five years) and harbored variants affecting the Inversin compartment or intraflagellar transport complex A. Forty eight percent of patients showed a juvenile (5-15 years) and 34% a late-onset disease (over 15 years), the latter mostly carrying variants belonging to the Transition Zone module. Furthermore, while more than 85% of patients with an infantile form presented with extra-kidney manifestations, it only concerned half of juvenile and late onset cases. Eye involvement represented a predominant feature, followed by cerebellar hypoplasia and other brain abnormalities, liver and skeletal defects. The phenotypic variability was in a large part associated with mutation types, genes and corresponding ciliary modules with hypomorphic variants in ciliary genes playing a role in early steps of ciliogenesis associated with juvenile-to-late onset NPH forms. Thus, our data confirm a considerable proportion of late-onset NPH suggesting an underdiagnosis in adult chronic kidney disease