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Human mobility impacts many aspects of a city, from its spatial structure 1 – 3 to its response to an epidemic 4 – 7 . It is also ultimately key to social interactions 8 , innovation 9 , 10 and productivity 11 . However, our quantitative understanding of the aggregate movements of individuals remains incomplete. Existing models—such as the gravity law 12 , 13 or the radiation model 14 —concentrate on the purely spatial dependence of mobility flows and do not capture the varying frequencies of recurrent visits to the same locations. Here we reveal a simple and robust scaling law that captures the temporal and spatial spectrum of population movement on the basis of large-scale mobility data from diverse cities around the globe. According to this law, the number of visitors to any location decreases as the inverse square of the product of their visiting frequency and travel distance. We further show that the spatio-temporal flows to different locations give rise to prominent spatial clusters with an area distribution that follows Zipf’s law 15 . Finally, we build an individual mobility model based on exploration and preferential return to provide a mechanistic explanation for the discovered scaling law and the emerging spatial structure. Our findings corroborate long-standing conjectures in human geography (such as central place theory 16 and Weber’s theory of emergent optimality 10 ) and allow for predictions of recurrent flows, providing a basis for applications in urban planning, traffic engineering and the mitigation of epidemic diseases. Using large-scale mobility data from diverse cities around the globe, a simple and robust scaling law that captures the temporal and spatial range of population movement is revealed.

Identifying changes in the spatial structure of cities is a prerequisite for the development and validation of adequate planning strategies. Nevertheless, current methods of measurement are becoming ever more challenged by the highly diverse and intertwined ways of how people actually make use of urban space. Here, we propose a new quantitative measure for the centrality of locations, taking into account not only the numbers of people attracted to different locations, but also the diversity of the activities they are engaged in. This 'centrality index' allows for the identification of functional urban centres and for a systematic tracking of their relative importance over time, thus contributing to our understanding of polycentricity. We demonstrate the proposed index using travel survey data in Singapore for different years between 1997 and 2012. It is shown that, on the one hand, the city-state has been developing rapidly towards a polycentric urban form that compares rather closely with the official urban development plan. On the other hand, however, the downtown core has strongly gained in its importance, and this can be partly attributed to the recent extension of the public transit system.

•Analytical differentiation between cyclopropylfentanyl and crotonylfentanyl.•Quantitative postmortem values for cyclopropylfentanyl in different matrices.•Significant postmortem redistribution found for cyclopropylfentanyl. A growing number of fatal overdoses involving opioid drugs, in particular involving fentanyl and its analogues, pose an immense threat to public health. Postmortem casework of forensic toxicologists in such cases is challenging, as data on pharmacodynamic and pharmacokinetic properties as well as reference values for acute toxicities and data on potential postmortem redistribution (PMR) mechanisms often do not exist. A fatal case involving cyclopropylfentanyl was investigated at the Zurich Institute of Forensic Medicine and the Zurich Forensic Science Institute; an unknown powder found at the scene was reliably identified as cyclopropylfentanyl by gas chromatography-infrared spectroscopy (GC-IR). Femoral blood samples were collected at two time points after death; 11h postmortem (t1) and during the medico-legal autopsy 29h after death (t2). At the autopsy, additional samples from the heart blood, urine and gastric content were collected. Cyclopropylfentanyl was quantified using a validated liquid chromatography-tandem mass spectrometric (LC–MS/MS) method. Femoral blood concentration of cyclopropylfentanyl at autopsy was 19.8ng/mL (t1=15.7ng/mL; heart blood concentration at autopsy=52.4ng/mL). In the light of the current literature and under the exclusion that no other morphological findings could explain the cause of death, contribution of cyclopropylfentanyl to death was proposed (polydrug use). Significant postmortem concentration increases of cyclopropylfentanyl in femoral blood during 18h after the first sampling were observed, thus indicating a relevant potential to undergo PMR. A central-to-peripheral blood concentration ratio of 2.6 supports this. Consequently, the current case suggests that postmortem cyclopropylfentanyl concentration should always be interpreted with care.

As cities grow, certain neighborhoods experience a particularly high demand for housing, resulting in escalating rents. Despite far-reaching socioeconomic consequences, it remains difficult to predict when and where urban neighborhoods will face such changes. To tackle this challenge, we adapt the concept of ‘bioindicators’, borrowed from ecology, to the urban context. The objective is to use an ‘indicator group’ of people to assess the quality of a complex environment and its changes over time. Specifically, we analyze 92 million geolocated Twitter records across five US cities, allowing us to derive socio-economic user profiles based on individual movement patterns. As a proof-of-concept, we define users with a ‘high-income-profile’ as an indicator group and show that their visitation patterns are a suitable indicator for expected future rent increases in different neighborhoods. The concept of indicator groups highlights the potential of closely monitoring only a specific subset of the population, rather than the population as a whole. If the indicator group is defined appropriately for the phenomenon of interest, this approach can yield early predictions while simultaneously reducing the amount of data that needs to be collected and analyzed.

Accurate population flow prediction is essential for urban planning, transportation management, and public health. Yet existing methods face key limitations: traditional models rely on static spatial assumptions, deep learning models struggle with cross-city generalization, and Large Language Models (LLMs) incur high computational costs while failing to capture spatial structure. Moreover, many approaches sacrifice resolution by clustering Points of Interest (POIs) or restricting coverage to subregions, limiting their utility for city-wide analytics. We introduce UrbanPulse, a scalable deep learning framework that delivers ultra-fine-grained, city-wide OD flow predictions by treating each POI as an individual node. It combines a temporal graph convolutional encoder with a transformer-based decoder to model multi-scale spatiotemporal dependencies. To ensure robust generalization across urban contexts, UrbanPulse employs a three-stage transfer learning strategy: pretraining on large-scale urban graphs, cold-start adaptation, and reinforcement learning fine-tuning.Evaluated on over 103 million cleaned GPS records from three metropolitan areas in California, UrbanPulse achieves state-of-the-art accuracy and scalability. Through efficient transfer learning, UrbanPulse takes a key step toward making high-resolution, AI-powered urban forecasting deployable in practice across diverse cities.

Deep brain stimulation (DBS) to different sites allows interfering with dysfunctional network function implicated in major depression. Because a prominent clinical feature of depression is anhedonia—the inability to experience pleasure from previously pleasurable activities—and because there is clear evidence of dysfunctions of the reward system in depression, DBS to the nucleus accumbens might offer a new possibility to target depressive symptomatology in otherwise treatment-resistant depression. Three patients suffering from extremely resistant forms of depression, who did not respond to pharmacotherapy, psychotherapy, and electroconvulsive therapy, were implanted with bilateral DBS electrodes in the nucleus accumbens. Stimulation parameters were modified in a double-blind manner, and clinical ratings were assessed at each modification. Additionally, brain metabolism was assessed 1 week before and 1 week after stimulation onset. Clinical ratings improved in all three patients when the stimulator was on, and worsened in all three patients when the stimulator was turned off. Effects were observable immediately, and no side effects occurred in any of the patients. Using FDG-PET, significant changes in brain metabolism as a function of the stimulation in fronto–striatal networks were observed. No unwanted effects of DBS other than those directly related to the surgical procedure (eg pain at sites of implantation) were observed. Dysfunctions of the reward system—in which the nucleus accumbens is a key structure—are implicated in the neurobiology of major depression and might be responsible for impaired reward processing, as evidenced by the symptom of anhedonia. These preliminary findings suggest that DBS to the nucleus accumbens might be a hypothesis-guided approach for refractory major depression.

Aim Species capable of vigorous growth under a wide range of environmental conditions should have a higher chance of becoming invasive after introduction into new regions. High performance across environments can be achieved either by constitutively expressed traits that allow for high resource uptake under different environmental conditions or by adaptive plasticity of traits. Here we test whether invasive and non-invasive species differ in presumably adaptive plasticity. Location Europe (for native species); the rest of the world and North America in particular (for alien species). Methods We selected 14 congeneric pairs of European herbaceous species that have all been introduced elsewhere. One species of each pair is highly invasive elsewhere in the world, particularly so in North America, whereas the other species has not become invasive or has spread only to a limited degree. We grew native plant material of the 28 species under shaded and non-shaded conditions in a common garden experiment, and measured biomass production and morphological traits that are frequently related to shade tolerance and avoidance. Results Invasive species had higher shoot-root ratios, tended to have longer leaf-blades, and produced more biomass than congeneric non-invasive species both under shaded and non-shaded conditions. Plants responded to shading by increasing shoot-root ratios and specific leaf area. Surprisingly, these shade-induced responses, which are widely considered to be adaptive, did not differ between invasive and non-invasive species. Main conclusions We conclude that high biomass production across different light environments pre-adapts species to become invasive, and that this is not mediated by plasticities of the morphological traits that we measured.

To understand prerequisites of biological invasions, it is imperative to know whether species have traits that pre-adapt them to become invasive elsewhere. However, few experimental studies have explicitly tested this by comparing traits between invasive and noninvasive species in their native range instead of in the nonnative range. We used native plant material of 14 European congeneric pairs of herbaceous species that were all introduced to North America, and of which one species per pair is invasive. In our germination and common garden experiment with and without fertilizer addition, the invasive species germinated faster, produced more biomass and had a higher proportion of flowering plants than the noninvasive congeners. Our results indicate that species traits, which lead to a high plant performance in the native range, can confer pre-adaptation to become invasive. We suggest that such traits may be especially relevant for use in risk-assessment protocols before introduction elsewhere.

Because of species selectivity, HIV research is largely restricted to in vitro or clinical studies, both limited in their ability to rapidly assess new strategies to fight the virus. To prospectively study some aspects of HIV in vivo , immunodeficient mice, transplanted with either human peripheral blood leukocytes or human fetal tissues, have been developed. Although these are susceptible to HIV infection, xenoreactivity, and short infection spans, resource and ethical constraints, as well as biased HIV coreceptor tropic strain infection, pose substantial problems in their use. Rag2 −/− γ c −/− mice, transplanted as newborns with human CD34 + cells, were recently shown to develop human B, T, and dendritic cells, constituting lymphoid organs in situ . Here we tested these mice as a model system for HIV-1 infection. HIV RNA levels peaked to up to 2 × 10 6 copies per milliliter of plasma early after infection, and viremia was observed for up to 190 days, the longest time followed. A marked relative CD4 + T cell depletion in peripheral blood occurred in CXCR4-tropic strain-infected mice, whereas this was less pronounced in CCR5-tropic strain-infected animals. Thymus infection was almost exclusively observed in CXCR4-tropic strain-infected mice, whereas spleen and lymph node HIV infection occurred irrespective of coreceptor selectivity, consistent with respective coreceptor expression on human CD4 + T cells. Thus, this straightforward to generate and cost-effective in vivo model closely resembles HIV infection in man and therefore should be valuable to study virus-induced pathology and to rapidly evaluate new approaches aiming to prevent or treat HIV infection.

This report describes the successful treatment of a patient suffering from an episode of drug-resistant major depression using magnetic seizure therapy (MST). The patient suffered from recurrent major depression since adolescence. MST is a novel brain stimulation method using transcranial magnetic stimulation at convulsive parameters in order to induce therapeutic seizures under general anesthesia in the same setting used for electroconvulsive therapy (ECT). The first use of therapeutic magnetic seizure induction in a psychiatric patient took place at the University Hospital in Bern, Switzerland, in May 2000. Results of a recent randomized, within-subject, double-masked trial comparing ECT and MST in 10 patients indicate that MST appears to have less subjective and objective side effects, is associated with faster recovery of orientation, and is superior to ECT on measures of attention, retrograde amnesia, and category fluency. ECT has an unparalleled and well-documented efficacy in severe depression but is associated with cognitive side effects. MST is currently under study in several centers with respect to its antidepressant efficacy. We report here on the treatment of a patient with refractory major depression (DSM IV-R), who underwent a series of 12 sessions of MST in an inpatient setting. Baseline Hamilton Depression Rating Scale (HRSD-21) of 33 and Beck Depression Inventory (BDI) of 40 decreased to 6 and 11 respectively, 1 week after completion of the MST trial. Measures of cognitive functions support the hypothesis that MST is associated with a less severe profile of cognitive side effects. [ 99m Tc]-HMPAO SPECT studies (baseline and 4 days after the completion of the MST trial) point to a raise of blood flow at baseline in the left fronto-parietal region and the brainstem. Our preliminary data support the prospect of antidepressant efficacy of MST and point to a benign cognitive side-effect profile in a patient suffering from severe treatment-resistant major depression.