Network Geometry and Complexity Mulder, Daan; Bianconi, Ginestra
Journal of statistical physics,
11/2018, Letnik:
173, Številka:
3-4
Journal Article
Recenzirano
Odprti dostop
Higher order networks are able to characterize data as different as functional brain networks, protein interaction networks and social networks beyond the framework of pairwise interactions. Most ...notably higher order networks include simplicial complexes formed not only by nodes and links but also by triangles, tetrahedra, etc. More in general, higher-order networks can be cell-complexes formed by gluing convex polytopes along their faces. Interestingly, higher order networks have a natural geometric interpretation and therefore constitute a natural way to explore the discrete network geometry of complex networks. Here we investigate the rich interplay between emergent network geometry of higher order networks and their complexity in the framework of a non-equilibrium model called Network Geometry with Flavor. This model, originally proposed for capturing the evolution of simplicial complexes, is here extended to cell-complexes formed by subsequently gluing different copies of an arbitrary regular polytope. We reveal the interplay between complexity and geometry of the higher order networks generated by the model by studying the emergent community structure and the degree distribution as a function of the regular polytope forming its building blocks. Additionally, we discuss the underlying hyperbolic nature of the emergent geometry and we relate the spectral dimension of the higher-order network to the dimension and nature of its building blocks.
In clinically localized high-risk prostate cancer patients, sentinel lymph node biopsy–based selection of men with occult nodal metastases for whole pelvis radiotherapy is associated with favorable ...oncological outcomes as compared with imaging-based prostate-only radiotherapy.
Accurate identification of men who harbor nodal metastases is necessary to select patients who most likely benefit from whole pelvis radiotherapy (WPRT). Limited sensitivity of diagnostic imaging approaches for the detection of nodal micrometastases has led to the exploration of the sentinel lymph node biopsy (SLNB).
To evaluate whether SLNB can be used as a tool to select pathologically node-positive patients who likely benefit from WPRT.
We included 528 clinically node-negative primary prostate cancer (PCa) patients with an estimated nodal risk of >5% treated between 2007 and 2018.
A total of 267 patients were directly treated with prostate-only radiotherapy (PORT; non-SLNB group), while 261 patients underwent SLNB to remove lymph nodes directly draining from the primary tumor prior to radiotherapy (SLNB group); pN0 patients were treated with PORT, while pN1 patients were offered WPRT.
Biochemical recurrence–free survival (BCRFS) and radiological recurrence-free survival (RRFS) were compared using propensity score weighted (PSW) Cox proportional hazard models.
The median follow-up was 71 mo. Occult nodal metastases were found in 97 (37%) SLNB patients (median metastasis size: 2 mm). Adjusted 7-yr BCRFS rates were 81% (95% confidence interval CI 77–86%) in the SLNB group and 49% (95% CI 43–56%) in the non-SLNB group. The corresponding adjusted 7-yr RRFS rates were 83% (95% CI 78–87%) and 52% (95% CI 46–59%), respectively. In the PSW multivariable Cox regression analysis, SLNB was associated with improved BCRFS (hazard ratio HR 0.38, 95% CI 0.25–0.59, p < 0.001) and RRFS (HR 0.44, 95% CI 0.28–0.69, p < 0.001). Limitations include the bias inherent to the study’s retrospective nature.
SLNB-based selection of pN1 PCa patients for WPRT was associated with significantly improved BCRFS and RRFS compared with (conventional) imaging-based PORT.
Sentinel node biopsy can be used to select patients who will benefit from the addition of pelvis radiotherapy. This strategy results in a longer duration of prostate-specific antigen control and a lower risk of radiological recurrence.
Abstract Objective: To assess the impact of HIV-1 infection on mortality over five years in a rural Ugandan population. Design: Longitudinal cohort study followed up annually by a house to house ...census and medical survey. Setting: Rural population in south west Uganda. Subjects: About 10 000 people from 15 villages who were enrolled in 1989–90 or later. Main outcome measures: Number of deaths from all causes, death rates, mortality fraction attributable to HIV-1 infection. Results: Of 9777 people resident in the study area in 1989-90, 8833 (90%) had an unambiguous result on testing for HIV-1 antibody; throughout the period of follow up adult seroprevalence was about 8%. During 35 083 person years of follow up, 459 deaths occurred, 273 in seronegative subjects and 186 in seropositive subjects, corresponding to standardised death rates of 8.1 and 129.3 per 1000 person years. Standardised death rates for adults were 10.4 (95% confidence interval 9.0 to 11.8) and 114.0 (93.2 to 134.8) per 1000 person years respectively. The mortality fraction attributable to HIV-1 infection was 41% for adults and was in excess of 70% for men aged 25–44 and women aged 20–44 years. Median survival from time of enrolment was less than three years in subjects aged 55 years or more who were infected with HIV-1. Life expectancy from birth in the total population resident at any time was estimated to be 42.5 years (41.4 years in men; 43.5 years in women), which compares with 58.3 years (56.5 years in men; 60.5 years in women) in people known to be seronegative. Conclusions: These data confirm that in a rural African population HIV-1 infection is associated with high death rates and a substantial reduction in life expectancy. Key messages Comparatively few data exist on mortality associated with HIV-1 in sub-Saharan Africa Adults positive for HIV-1 in a rural Ugandan population with a prevalence of infection of 8% were more than 10 times more likely to die over a 5 year period than those negative for HIV-1 Over 40% of all deaths in adults were attributable to HIV-1 infection, the percentage in young adults aged 25–44 being in excess of 70% Life expectancy is estimated to have declined from 58.6 to 42.5 years as a consequence of the AIDS epidemic
The majority of people infected with HIV-1 live in Africa, yet little is known about the natural history of the disease in that continent. We studied survival times, disease progression, and ...AIDS-defining disorders, according to the proposed WHO staging system, in a population-based, rural cohort in Uganda.
In 1990 we recruited a random sample of people already infected with HIV-1 (as prevalent cases) detected during the initial survey round of a general-population study to form a natural-history cohort. Individuals from the general-population cohort who seroconverted between 1990 and 1995 (incident cases) were also invited to enrol. Participants were seen routinely every 3 months and when they were iII.
By the end of 1995, 93 prevalent cases and 86 incident cases had been enrolled. Four patients in the prevalent group were in stage 4 (AIDS) at the initial visit. During the next 5 years, 37 prevalent cases progressed to AIDS. Seven incident cases progressed to AIDS and the cumulative progression to AIDS at 1, 3, and 5 years after seroconversion was 2%, 6%, and 22%, respectively. The cumulative probability of AIDS at 4 years from entering stages 1, 2, and 3 was 11%, 33%, and 58%, respectively. There were 47 deaths among prevalent cases and seven among incident cases during follow-up. The cumulative mortality 4 years after patients entered stages 1, 2, 3, and 4 was 9%, 33%, 56%, and 86%, respectively. The median survival after the onset of AIDS was 9·3 months.
Our results are important for the setting of priorities and rationalisation of treatment availability in countries with poor resources. We found that progression rates to AIDS are similar to those in developed countries for homosexual cohorts and greater than for cohorts infected by other modes of transmission. However, we have found that the rates of all-cause mortality are much higher and the progression times to death are shorter than in developed countries.
Background In general, information on the causes of adult deaths in developing countries is scarce. More specifically, relatively little is known about the effect of HIV-1 associated disease on adult ...mortality in general populations. In this study we have used a verbal autopsy technique to ascertain whether adult deaths were associated with HIV-1 In a rural population with a prevalence of HIV-1 infection of 8%, and used HIV-1 antibody status to validate the verbal autopsy findings. Methods All adult deaths in the population cohort that occurred between December 1990 and November 1993 were identified through a monthly death registration system. Approximately 2 months after death, a relative of the deceased was interviewed by a trained nurse, and questionnaires were assessed by at least two independent clinicians; all were unaware of the HIV serostatus of the deceased. Results A total of 155 adult deaths was assessed, i e. 53% of all recorded adult deaths. Of those assessed half were HIV-1 positive. In all 47% of deaths were classified as HIV-related. The overall specificity and positive predictive value of the verbal autopsy tool were both 92% in those aged 13–44 years (83 adults) the corresponding values were 85% and 95% respectively. The verbal autopsy estimated HIV-1 attributable mortality fraction was similar to the calculated fraction based on prospective data. Conclusions The results of this study suggest that verbal autopsy studies may assist in providing data on HIV-associated mortality in general populations and may be useful as surveillance tools.
Kengeya-Kayondo J-F (MRC UK Programme on AIDS in Uganda, Uganda Virus Research Institute, PO Box 49, Entebbe, Uganda), Kamali A, Nunn A J, Ruberantwari A, Wagner H-U H and Mulder D W. Incidence of ...HIV-1 Infection in adults and sodo-demographic characteristics of seroconverters in a rural population in Uganda: 1990–1994. International Journal of Epidemiology 1996; 25: 1077–1082. Background To evaluate HIV-1 incidence among adults and socio-demographic risk factors in a rural population in Uganda, a prospective cohort study was carried out. Methods All consenting adult residents in a cluster of 15 neighbouring villages of the Masaka District of south-west Uganda have been participating in annual socio-demographic and seroJogical surveys since November 1989. Those who had a negative serostatus when they were first tested and had at least one serostatus assessment during the 4 years of follow-up (1990–1994) have been evaluated for HIV-1 seroconversion. Incidence rates have been calculated per 1000 person-years of observation and socio-demographic characteristics assessed for association with recent seroconversion. Results At the baseline survey, of 4175 adults with assessable serostatus (79% of all censused adults), 342 (8.2%) were seroposltive. During 12 588.2 person-years of follow-up 89 seroconversions were identified corresponding to an incidence rate of 7.1 (95% Ct : 5.6–8.5). Overall rates were highest in females aged 20–24 years (15.2) and in males aged 20–44 years (11.6). There was a significant interaction between age and sex; the ratio of the rate in females to that in males decreased from 3.3: 1 to 0.5: 1 with increasing age. Rates for males aged ≥20 years were four times higher than those for younger males. Other significant socio-demographic correlates with risk included not belonging to the majority tribe, non-Muslim religion and length of stay on compound of less than 10 years. Incidence rates did not show any clear trends with time. Conclusion These findings further emphasize the need for targeted interventions.
This study was conducted in order to understand how women in rural Uganda recognise malaria, their treatment-seeking behaviour when malaria is suspected and how the perception of cause may influence ...this behaviour. Focus group discussions and semi-structured interviews were held with women selected from the general population and from women attending health clinics for both preventive and curative services. The main finding of this study was that the word used for malaria in the local language, omusujja, covered a broad symptom complex which did not consistently correspond to the clinical case definition of malaria. Since there was no specific word for 'malaria', the study was broadened to encompass omusujja. The women reported that omusujja was an important health problem which had various causes, including poor diet, environmental conditions, and the bites of mosquitoes. The symptoms associated with omusujja were quite varied and ranged from generally 'feeling unwell' to a specific fever diagnosis (usually in children) of 'a rise in body temperature'. Women recognised that omusujja posed a particular threat to pregnant women. Preventive actions recommended by the women were in line with their perceptions of cause. The respondents usually mentioned the use of herbs as the first treatment action, followed by the purchase of tablets from shops, with the final recourse being the formal health sector if the previous actions had not effected a cure.
To investigate the combined effects of HIV infection and silicosis on mycobacterial disease.
A retrospective cohort of 1374 HIV-positive and 2648 HIV-negative miners who attended a South African gold ...mining hospital and primary health clinics.
Miners who had been tested for HIV, with consent, at primary health clinics during 1991-1996, predominantly because of a symptomatic sexually transmitted disease.
Tuberculosis (TB) incidence was 4.9 and 1.1 per 100 person-years in HIV-positive and HIV-negative miners respectively. The incidence of Mycobacterium kansasii disease was also high (0.32 and 0.10 per 100 person-years, respectively). Silicosis was highly prevalent, implying inadequate dust control, and was a significant TB risk factor among both HIV-positive and HIV-negative men (adjusted incidence rate ratios 1.4-2.5 according to radiological severity). The data were consistent with the risks of silicosis and HIV combining multiplicatively, but did not fit an additive model. The incidence of HIV-associated TB increased significantly during the study, with no corresponding change in HIV-negative rates, to reach 16.1 per 100 person-years among HIV-positive silicotics.
The risks of silicosis and HIV infection combine multiplicatively, so that TB remains as much a silica-related occupational disease in HIV-positive as in HIV-negative miners, and HIV-positive silicotics have considerably higher TB incidence rates than those reported from other HIV-positive Africans. The increasing impact of HIV over time may indicate epidemic TB transmission with rapid disease development in HIV-infected miners. Similar but currently unrecognized interactions may be contributing to TB control problems in other industrializing countries affected by the HIV epidemic.
Higher order networks are able to characterize data as different as functional brain networks, protein interaction networks and social networks beyond the framework of pairwise interactions. Most ...notably higher order networks include simplicial complexes formed not only by nodes and links but also by triangles, tetrahedra, etc. More in general, higher-order networks can be cell-complexes formed by gluing convex polytopes along their faces. Interestingly, higher order networks have a natural geometric interpretation and therefore constitute a natural way to explore the discrete network geometry of complex networks. Here we investigate the rich interplay between emergent network geometry of higher order networks and their complexity in the framework of a non-equilibrium model called Network Geometry with Flavor. This model, originally proposed for capturing the evolution of simplicial complexes, is here extended to cell-complexes formed by subsequently gluing different copies of an arbitrary regular polytope. We reveal the interplay between complexity and geometry of the higher order networks generated by the model by studying the emergent community structure and the degree distribution as a function of the regular polytope forming its building blocks. Additionally we discuss the underlying hyperbolic nature of the emergent geometry and we relate the spectral dimension of the higher-order network to the dimension and nature of its building blocks.
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