Substantial Time Delay Research Articles

Comparative analysis of new mScarlet-based red fluorescent tags in Caenorhabditis elegans.

One problem that has hampered the use of red fluorescent proteins in the fast-developing nematode Caenorhabditis elegans has been the substantial time delay in maturation of several generations of red fluorophores. The recently described mScarlet-I3 protein has properties that may overcome this limitation. We compare here the brightness and onset of expression of CRISPR/Cas9 genome-engineered mScarlet, mScarlet3, mScarlet-I3, and GFP reporter knock-ins. Comparing the onset and brightness of expression of reporter alleles of C. elegans golg-4, encoding a broadly expressed Golgi resident protein, we found that the onset of detection of mScarlet-I3 in the embryo is several hours earlier than older versions of mScarlet and comparable to GFP. These findings were further supported by comparing mScarlet-I3 and GFP reporter alleles for pks-1, a gene expressed in the CAN neuron and cells of the alimentary system, as well as reporter alleles for the pan-neuronal, nuclear marker unc-75. Hence, the relative properties of mScarlet-I3 and GFP do not depend on cellular or subcellular context. In all cases, mScarlet-I3 reporters also show improved signal-to-noise ratio compared to GFP.

Comparative analysis of new, mScarlet-based red fluorescent tags in Caenorhabditis elegans.

One problem that has hampered the use of red fluorescent proteins in the fast-developing nematode C. elegans has been the substantial time delay in maturation of several generations of red fluorophores. The recently described mScarlet-I3 protein has properties that may overcome this limitation. We compare here the brightness and maturation time of CRISPR/Cas9 genome-engineered mScarlet, mScarlet3, mScarlet-I3 and GFP reporter knock-ins. Comparing the onset and brightness of expression of reporter alleles of C. elegans golg-4, encoding a broadly expressed Golgi resident protein, we found that the onset of detection of mScarlet-I3 in the embryo is several hours earlier than older versions of mScarlet and comparable to GFP. These findings were further supported by comparing mScarlet-I3 and GFP reporter alleles for pks-1, a gene expressed in the CAN neuron and cells of the alimentary system, as well as reporter alleles for the panneuronal, nuclear marker unc-75. Hence, the relative properties of mScarlet-I3 and GFP do not depend on cellular or subcellular context. In all cases, mScarlet-I3 reporters also show improved signal-to-noise ratio compared to GFP.

Spiking neural networks with consistent mapping relations allow high-accuracy inference

Spike-based neuromorphic hardware has demonstrated substantial potential in low energy consumption and efficient inference. However, the direct training of deep spiking neural networks is challenging, and conversion-based methods still require substantial time delay owing to unresolved conversion errors. We determine that the primary source of the conversion errors stems from the inconsistency between the mapping relationship of traditional activation functions and the input-output dynamics of spike neurons. To counter this, we introduce the Consistent ANN-SNN Conversion (CASC) framework. It includes the Consistent IF (CIF) neuron model, specifically contrived to minimize the influence of the stable point's upper bound, and the wake-sleep conversion (WSC) method, synergistically ensuring the uniformity of neuron behavior. This method theoretically achieves a loss-free conversion, markedly diminishing time delays and improving inference performance in extensive classification and object detection tasks. Our approach offers a viable pathway toward more efficient and effective neuromorphic systems.

An automated online field instrument to quantify the oxidative potential of aerosol particles via ascorbic acid oxidation

Abstract. Large-scale epidemiological studies have consistently shown that exposure to ambient particulate matter (PM) is responsible for a variety of adverse health effects. However, the specific physical and chemical properties of particles that are responsible for the observed health effects, as well as the underlying mechanisms of particle toxicity upon exposure, remain largely uncertain. Studies have widely suggested that the oxidative potential (OP) of aerosol particles is a key metric to quantify particle toxicity. OP is defined as the ability of aerosol particle components to produce reactive oxidative species (ROSs) and deplete antioxidants in vivo. Traditional methods for measuring OP using acellular assays largely rely on analyzing PM collected in filters offline. This is labor intensive and involves a substantial time delay between particle collection and OP analysis. It therefore likely underestimates particle OP because many reactive chemical components which contribute to OP are short-lived and therefore degrade prior to offline analysis. Thus, new techniques are required to provide a robust and rapid quantification of particle OP, capturing the chemistry of oxidizing and short-lived, highly reactive aerosol components and their concentration dynamics in the atmosphere. To address these measurement shortcomings, we developed a portable online instrument that directly samples particles into an ascorbic acid-based assay under physiologically relevant conditions of pH 6.8 and 37 ∘C, providing continuous, accurate OP measurements with a high time resolution (5 min). The instrument runs autonomously for up to 3 d and has a detection limit of about 5 µg m−3 in an urban environment, which allows the characterization of particle OP even in low-pollution areas.

The energetics of rapid cellular mechanotransduction

Cells throughout the human body detect mechanical forces. While it is known that the rapid (millisecond) detection of mechanical forces is mediated by force-gated ion channels, a detailed quantitative understanding of cells as sensors of mechanical energy is still lacking. Here, we combine atomic force microscopy with patch-clamp electrophysiology to determine the physical limits of cells expressing the force-gated ion channels (FGICs) Piezo1, Piezo2, TREK1, and TRAAK. We find that, depending on the ion channel expressed, cells can function either as proportional or nonlinear transducers of mechanical energy and detect mechanical energies as little as ~100 fJ, with a resolution of up to ~1 fJ. These specific energetic values depend on cell size, channel density, and cytoskeletal architecture. We also make the surprising discovery that cells can transduce forces either nearly instantaneously (<1 ms) or with a substantial time delay (~10 ms). Using a chimeric experimental approach and simulations, we show how such delays can emerge from channel-intrinsic properties and the slow diffusion of tension in the membrane. Overall, our experiments reveal the capabilities and limits of cellular mechanosensing and provide insights into molecular mechanisms that different cell types may employ to specialize for their distinct physiological roles.

The energetics of rapid cellular mechanotransduction.

Cells throughout the human body detect mechanical forces. While it is known that the rapid (millisecond) detection of mechanical forces is mediated by force-gated ion channels, a detailed quantitative understanding of cells as sensors of mechanical energy is still lacking. Here, we combine atomic force microscopy with patch-clamp electrophysiology to determine the physical limits of cells expressing the force-gated ion channels Piezo1, Piezo2, TREK1, and TRAAK. We find that, depending on the ion channel expressed, cells can function either as proportional or nonlinear transducers of mechanical energy, detect mechanical energies as little as ∼100 fJ, and with a resolution of up to ∼1 fJ. These specific energetic values depend on cell size, channel density, and cytoskeletal architecture. We also make the surprising discovery that cells can transduce forces either nearly instantaneously (<1ms), or with substantial time delay (∼10 ms). Using a chimeric experimental approach and simulations we show how such delays can emerge from channel-intrinsic properties and the slow diffusion of tension in the membrane. Overall, our experiments reveal the capabilities and limits of cellular mechanosensing and provide insights into molecular mechanisms that different cell types may employ to specialize for their distinct physiological roles.

New Biomarkers in Early Diagnosis of Acute Kidney Injury in Children

Acute Kidney Injury (AKI) is a common condition with a high risk of mortality and morbidity, so, early diagnosis and management of AKI is very important in clinical practice. Despite significant progress in the management of AKI, it still carries high morbidity and mortality. BUN and serum creatinine are not very sensitive nor specific for the diagnosis of AKI because they are affected by many renal and non-renal factors that are independent of kidney injury or kidney function and change significantly only after significant kidney injury and with a substantial time delay. Detection of biomarkers of AKI made predominantly by the injured kidney tissue are essential for the early diagnosis of AKI. An ideal biomarker should be one that could be easily measured, with no interference with other biologic variables, and be able to clarify early phases of kidney damage. The most common biomarkers studied are Neutrophil Gelatinase-Associated Lipocalin (NGAL), Interleukin-18 (IL-18), Kidney Injury Molecule-1 (KIM-1), Cystatin-C, L type Fatty Acid-Binding Protein (L-FABP), N-Acetyl-β-D Glucosaminidase (NAG), netrin-1, vanin-1, and Monocyte Chemoattractant Protein-1 (MCP-1) and calprotectin.

Investigation of dynamical stability of vehicle lateral motion control system with feedback delay

<p indent="0mm">Time delay is one of the key factors damaging the driving safety in a vehicle lateral motion control system. This paper establishes a nonlinear vehicle model considering yaw and lateral motion, and two types of nonlinear steering characteristics and motion stability conditions are analyzed using handling diagrams. Next, a PD-based active yaw moment controller with time delay is applied to construct a complete hybrid vehicle system with delayed control. Firstly, the effect of time delay on the general stability and stability boundary of the vehicle system is studied using the location of the characteristic roots and the frequency domain method, wherein the results indicate that the lateral stability of the vehicle is significantly weakened under time delay, and the instability boundary can be reached under a substantial time delay. Furthermore, the optimization factor characterizing the system decay rate is introduced, and the optimization method for the control parameter of the vehicle lateral system is designed. The stability region is optimally divided to select the optimal control gain set under some delay. The optimization is compared and verified based on the steady-state simulation and dynamic test, and the results validate its effectiveness in improving the lateral stability and suppressing the effect of time delay, wherein the optimized dynamic responses of the system follow the target trajectory. Based on the relations between the optimization factor and vehicle characteristics, the critical maximum of the optimization factor is proposed as the quantitative index to evaluate the vehicle lateral stability under time delay, where its general parametric expressions are derived by exploring two types of critical instability conditions. Finally, the effectiveness and efficiency of the index in quantifying the delayed system stability and predicting the time-delay boundary of instability are sufficiently verified in steady-state and dynamic simulation.

Control Scheme for Rapidly Responding Register Controller Using Response Acceleration Input in Industrial Roll-To-Roll Manufacturing Systems

A roll-to-roll (R2R) manufacturing system has been considered the most suitable candidate for commercializing flexible electronic devices owing to its large-area and mass-production characteristics. A high-precision register control should be ensured when fabricating devices using the R2R system. Contrary to conventional manufacturing systems that are applied to rigid materials, the control target in an R2R system is a flexible film that can lead to a substantial time delay in the control response and degrade the register control performance. This article proposes a novel control scheme, namely response acceleration input, to provide a rapid response in the register control of flexible substrates. Mathematical models to achieve the proposed scheme were developed. A register control system based on the developed models was designed, followed by experimental verifications using an industrial-scale R2R system. The results show that the register error is successively controlled below ±10 µm with a high yield of over 80% for 1800 s. We believe that the proposed control strategy can realize a high-precision register control below ±10 µm in industrial-scale R2R manufacturing systems, thus enabling the commercialization of multilayered, flexible electronic devices.

Detection of Endometrial Nerve Fibres in the Diagnosis of Endometriosis: A Case-control Study

Introduction: Due to non-availability of a good non-invasive or semi-invasive test for diagnosing endometriosis, there is a substantial time delay between the onset of symptoms and surgically confirmed endometriosis. Development of a simple non-invasive or semi-invasive diagnostic method can greatly help to reduce this delay and prevent severe morbidity in minimal to mild endometriosis which cannot be diagnosed clinically or by ultrasonography. Aim: To evaluate the role of nerve fibre detection in endometrial biopsy for diagnosing endometriosis Materials and Methods: In this observational study, detection of endometrial nerve fibres in endometrial biopsy in women undergoing laparoscopy/laparotomy for pelvic pain or infertility was done using polyclonal rabbit anti-protein gene product 9.5 (Dako, Australia). The results were compared between women who has laparoscopic/laparotomy visualisation of endometriotic lesions with those who don't have endometriotic lesions. Women with visual evidence of endometriosis in laparoscopy/laparotomy were taken as cases (n=32). Women without evidence of endometriosis in laparoscopy/laparotomy were taken as controls (n=29). Presence of endometrial nerve fibre was compared between women with and without evidence of endometriosis. Presence of endometrial nerve fibres and its association with painful symptoms, history of hormonal therapy, endometrial histopathology and stages of endometriosis was analysed. Results: Endometrial nerve fibres were detected in the functional layer in 21.8% of the endometriosis patients and no nerve fibres were detected in the control group. There was no significant association between endometrial nerve fibres in endometriosis and presentation of painful symptoms, history of hormonal therapy, endometrial histopathology and stages of endometriosis. Sensitivity of detecting endometriosis by the presence of nerve fibres in endometrial nerve biopsy specimen was 21.8% and specificity was 100%. Conclusion: Endometrial nerve fibre assessment for identifying endometriosis in women undergoing laparoscopy/laparotomy using routine endometrial sampling and immunohistochemical analysis was found not to be sensitive for the diagnosis of endometriosis.

Stakeholder views of the practical and cultural barriers to epilepsy care in Uganda

ObjectiveEpilepsy is one of the most prevalent, treatable neurological diseases globally. In sub-Saharan Africa, people with epilepsy (PWE) frequently seek treatment from traditional or pastoral healers, who are more accessible than biomedical care providers. This often contributes to the substantial time delay in obtaining adequate biomedical care for these patients. In Uganda, the few biomedical providers who can treat epilepsy cannot meet the great need for epilepsy care. Additionally, patients are often hesitant to seek biomedical care, often preferring the easily accessible and trusted sociocultural treatment options. This study sought to elucidate the barriers to biomedical care for PWE as well as identify potential solutions to overcome these barriers from various stakeholder perspectives. MethodsThis study used qualitative research methods. Semistructured interviews and focus group discussions were conducted with four major stakeholder groups: PWE or family members of PWE, neurologists and psychiatrists, traditional healers, and pastoral healers. All interviews and focus group discussions that were in English were audio recorded and transcribed verbatim. Those that were not in English were translated live and audio recorded. A translator later translated the non-English portion of audio recording to ensure proper interpretation. Two independent coders coded the dataset and conducted an inter-rater reliability (IRR) assessment to ensure reliable coding of the data. Thematic analysis was then performed to discern themes from the data and compare nuances between each of the study design groups. ResultsParticipants discussed several different causes of epilepsy ranging from spiritual to biological causes, often incorporating elements of both. Commonly endorsed spiritual causes of epilepsy included witchcraft and ancestral spirits. Commonly endorsed biological causes included genetics, fever, malaria, and brain injury. For patients and families, beliefs about the cause of epilepsy often played a role in whom they chose to seek treatment from. Three major barriers to biomedical care were discussed: practical barriers, medical infrastructure barriers, and barriers related to stigma. Practical barriers related to issues such as transportation, cost of medical care, and distance to the nearest healthcare facility. Under medical infrastructure, drug stock-outs and lack of access to antiepileptic drugs (AEDs) were the most consistent problems stated among patients. Stigma was heavily discussed and brought up by nearly every participant. Additionally, three significant solutions to improving epilepsy care in Uganda were highlighted by participants: collaboration among treatment providers, community sensitization efforts to address stigma, and building medical infrastructure. Within building infrastructure, all participant types, except traditional healers, proposed the development of an epilepsy clinic designed to specifically treat epilepsy. ConclusionsBased on these findings, there are four critical interventions that should be considered for improving epilepsy care in Uganda: the creation of dedicated epilepsy clinics, infrastructure strengthening to address medication stock-outs, community outreach programs for sensitization, and collaboration between biomedical providers and traditional healers.This article is part of the Special Issue “The Intersection of Culture, Resources, and Disease: Epilepsy Care in Uganda”

Extinction debt across three taxa in well-connected calcareous grasslands

The biodiversity in calcareous grasslands suffered from severe habitat loss due to land-use intensification and abandonment across Europe. Although these grasslands are now protected under the EU Habitats Directive, many species in the remaining habitat patches are still declining. Recent studies suggest that species across different taxa may become extinct with a substantial time delay, even without further habitat loss. Consequently, there might be an extinction debt, which poses a major challenge for conservation. Here, we analysed the response of plant, grasshopper and butterfly species richness in calcareous grasslands to habitat fragmentation over the last five decades. In this study, habitat area and connectivity have undergone a marked decline between 1970 and 1990 but have only slightly declined during the last three decades. Despite this, the current richness of specialist and generalist species among plants and butterflies was equally or better explained by past than present landscape conditions. This finding indicates the existence of an extinction debt in both taxa in the still well-connected grasslands of the study area. We conclude that increased conservation measures since the 1990s have favoured species persistence, despite severe habitat loss in the more distant past. By contrast, grasshopper diversity weakly responded to habitat area and connectivity; rather it is likely to depend mainly on habitat quality. To inhibit future extinctions, it is crucial to maintain large-scale patches by traditional land-use practices (i.e. rough grazing or mowing once a year), as well as restore former habitat to facilitate species dispersal in fragmented landscapes.

PSY32 DELAY IN DIAGNOSIS OF PRIMARY LYMPHOEDEMA AND ITS IMPACT ON QUALITY OF LIFE: A SYSTEMATIC REVIEW

Currently in the United Kingdom, there is no standardised education for healthcare professionals on primary lymphoedema. Therefore the condition is often under or misdiagnosed. Early diagnosis and treatment reduces its psychological and social impact and delays disease progression and the onset of complications. A systematic review (SR) was conducted to assess the reported time between the onset of symptoms and diagnosis and the impact of a delayed diagnosis on quality of life (QoL) in patients with primary lymphoedema. Electronic databases (Medline, Embase, Cochrane) were interrogated in May 2019 to identify English-language studies reporting the time between onset of symptoms and final diagnosis in patients (all ages) with primary lymphoedema. Data reporting the impact of delay on QoL outcomes were also captured. Studies reporting syndromes with clinical presenting features unrelated to lymphoedema were excluded. The database search identified 2,869 citations of which 29 publications met the pre-defined inclusion criteria. In paediatric studies, the time from symptom onset to lymphoedema diagnosis ranged from 0-12 years (reported in 15 studies). In adults the time to diagnosis ranged from 3-50 years (14 studies) with the majority of studies (11/14 studies) reporting a delay of >14 years before an initial diagnosis was obtained. QoL data were captured qualitatively in three studies (2 paediatric and 1 adult) with all reporting that delayed diagnosis was associated with psychological stress in patients or relatives. This SR provides a comprehensive review of the current evidence base and although there is a paucity of adequately powered studies, data are suggestive of a substantial time delay between symptom onset and diagnosis which impacts negatively on QoL. Further data are required to address this evidence gap and additional education of healthcare professionals may help avoid clinical, psychological, and cost implications of a delay or misdiagnosis of primary lymphoedema.

Time of administration of rabies immunoglobulins and adequacy of antibody response upon post-exposure prophylaxis: a descriptive retrospective study in Belgium

ABSTRACT Background: Data on rabies post-exposure prophylaxis (PEP) and the use of human rabies immunoglobulins (HRIG) in Belgium are scarce. The main objective of this study was to evaluate the timely administration of HRIG after rabies exposure. The secondary objective was to evaluate the adequate antibody response following PEP. Methods: We reviewed all medical records from July 2017 to June 2018 of patients seeking care at, or referred to, the Institute of Tropical Medicine and the University Hospital, Antwerp for the administration of human rabies immunoglobulins following potential rabies exposure abroad or in Belgium. A timely response was defined as starting HRIG with a delay of ≤48 h and rabies vaccination in the first 7 days after exposure. Adequate antibody response was defined as a titer of >5.0 IU/mL in case of bat-related exposure and >3.0 IU/mL in case of exposure to other animals. Titers were measured 10 days after the last PEP vaccine dose, using the rapid fluorescent focus inhibition test (RFFIT). Results: Of the 92 cases treated with HRIG, 75 were evaluated. The majority of injuries were acquired in Asia (n = 26,34%) and in Western Europe (n = 18, 24%), of which 17 in Belgium. The five most frequently recorded countries overseas were Indonesia (n = 13), Thailand (n = 7), Morocco (n = 4), Peru (n = 3) and Costa Rica (n = 3). Administration of immunoglobulins was related to injuries by dogs (36%), monkeys (25%) or bats (22%). A timely response was observed in 16 (21,33%) and in 55 (73,33%) of subjects receiving HRIG (≤48 h) or rabies vaccine (<7days) respectively. The mean time between exposure and the first administered dose of rabies vaccine and HRIG was 7.7 and 8.7 days, respectively. The mean delay for HRIG administration was 9.6 days and 6 days for abroad and inland risks, respectively. In 15 of 16 (94%) bat-related cases the antibody titer after full PEP was >5.0 IU/ml. In 38 of 47 (81%) cases related to other animals the RFFIT titer was >3.0 IU/ml. All low-responders received additional rabies injections. Conclusion: This study showed a substantial time delay between the animal-related risk and the administration of HRIG, in particular when the injury occurred abroad. More targeted communication about the risks of rabies and preventable measures may reduce this delay. Furthermore, the antibody response was inadequate in some cases following full PEP administration according to the Belgian recommendation.

Peculiarities in Transmission (Reflection) of Ultrashort Resonant Laser Pulses by a Thin Semiconductor Film in the Conditions of Exciton and Biexciton Excitation

We have studied the nonstationary transmission of two ultrashort laser pulses incident on a thin film. The radiation frequency of one of these pulses is in resonance with the two-photon transition from the ground state of the crystal to the biexciton state, while the other pulse coherently mixes the exciton and biexciton states, leading to strong renormalization of the energy spectrum of the crystal. We have obtained a system of nonlinear equations describing the time evolution of the exciton and biexciton amplitudes and the fields of three pulses transmitted through the film. We have analyzed the effect of amplitudes and widths of incident pulsed and of the time delay between them on the peculiarities of film transmission of these pulses. We have predicted the effect of a substantial time delay in the generation of the pulse transmitted through the film relative to the incident pulse, which is in resonance with the exciton–biexciton transition frequency. The possibility of generation of a precursor, viz., a pulse transmitted through the film sooner than the peak of the incident pulse reaches the film, as well as possibility of generation of a reflected pulse in the absence of the incident pulse, has been proven.

Supernovae Ia in 2017: a long time delay from merger/accretion to explosion

I use recent observational and theoretical studies of type Ia supernovae (SNe Ia) to further constrain the viable SN Ia scenarios and to argue that there must be a substantial time delay between the end of the merger of the white dwarf (WD) with a companion or the end of mass accretion on to the WD and its terminal explosion.This merger/accretion to explosion delay (MED) is required to allow the binary system to lead to a more or less spherical explosion and to prevent a pre-explosion ionizing radiation. Considering these recent results and the required MED, I conclude that the core degenerate scenario is somewhat more favorable over the other scenarios, followed by the double degenerate scenario. Although the single degenerate scenario is viable as well, it is less likely to account for common (normal) SN Ia. As all scenarios require substantial MED, the MED has turned from a disadvantage of the core degenerate scenario to a challenge that theory should overcome. I hope that the requirement for a MED will stimulate the discussion of the different SN Ia scenarios and the comparison of the scenarios to each other.

Time Delays in Transdermal Alcohol Concentrations Relative to Breath Alcohol Concentrations.

Monitors of transdermal alcohol concentration (TAC) provide an objective measurement of alcohol consumption that is less invasive than measurements in blood, breath or urine; however, there is a substantial time delay in the onset of TAC compared to blood or breath alcohol concentrations (BrACs). The current study examined the characteristics of the delay between peak TAC and peak BrAC. Data was aggregated from three experimental laboratory studies (N=61; 32 men, 29 women) in which participants wore a TAC monitor and BrAC was monitored while drinking one, two, three, four and five beers in the laboratory. Analyses examined the sex- and dose-related differences in peak BrAC and TAC, the time-to-peak BrAC and TAC, and time lag between the peak BrAC and TAC values. The times-to-peak were an increasing function of the number of beers consumed. At each level of beer consumption the peak TAC averaged lower than peak BrAC and times-to-peak TAC were longer than for BrAC. The time-to-peak BrAC and TAC was longer for women than men. The congruence between peak TAC and BrAC increased as a function of the beers consumed. No sex difference in the time lag between peak BrAC and TAC was detected. The congruence between TAC and BrAC and time lags between TAC and BrAC are related to the number of beers consumed. Peak values of TAC and BrAC became more congruent with higher doses but the time lag increased as a function of the amount of alcohol consumed. The time delay (or lag) and congruence between transdermal vs. BrACs increases as the number of beers increases. Though sex differences are evident in peak transdermal and BrACs, no sex differences were evident in the time lag and the congruence between transdermal and breath alcohol concentrations.

CLINICAL CASE OF THROMBOLYTIC THERAPY OF RECURRENT ST-SEGMENT ELEVATION MYOCARDIAL INFARCTION IN PATIENT WITH LONG HISTORY OF ISCHEMIC HEART DISEASE

Presented case report demonstrates the efficacy and safety of hospital use of thrombolytic agent Fortelizin in pharmaco-invasive strategy for the treatment of a patient with acute myocardial infarction and with a long history of ischemic heart disease and long-term dynamics of the verified angiographic progression of coronary atherosclerosis. Hospital thrombolytic therapy with Fortelizin was vital alternative in case of a substantial time delay in mechanical reperfusion of the myocardium.

The legacy of deer overabundance: long-term delays in herbaceous understory recovery

Decades of white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) overpopulation have dramatically homogenized forests across much of the eastern United States, creating depauperate forest understory communities. The rate at which these communities recover once deer browsing has been reduced remains an open question. We evaluate overbrowsing legacy effects by examining how forest herbaceous layers respond in terms of biodiversity, density, and community composition over 11 years using exclosures and control plots within a mature beech–maple forest. Although little recovery occurred in the first 5 years, total density and preferred browse density rebounded substantially during the final years of the study. Although community composition began to diverge between exclosure and control plots after 5 years, diversity failed to recover even after 11 years of excluding browsers. Our findings show that vulnerable species can increase after excluding browsers but only if those species were initially present. Biodiversity recovery may be extremely slow because preferred browse species have been nearly extirpated from many forests and thus are unable to recruit into refugia. We empirically demonstrate the extent of the ghost of herbivory past or legacy effect of browsing, i.e., the substantial time delay between herbivore abatement and community response after decades of high deer densities.

A new framework for modeling decisions about changing information: The Piecewise Linear Ballistic Accumulator model

In the real world, decision making processes must be able to integrate non-stationary information that changes systematically while the decision is in progress. Although theories of decision making have traditionally been applied to paradigms with stationary information, non-stationary stimuli are now of increasing theoretical interest. We use a random-dot motion paradigm along with cognitive modeling to investigate how the decision process is updated when a stimulus changes. Participants viewed a cloud of moving dots, where the motion switched directions midway through some trials, and were asked to determine the direction of motion. Behavioral results revealed a strong delay effect: after presentation of the initial motion direction there is a substantial time delay before the changed motion information is integrated into the decision process. To further investigate the underlying changes in the decision process, we developed a Piecewise Linear Ballistic Accumulator model (PLBA). The PLBA is efficient to simulate, enabling it to be fit to participant choice and response-time distribution data in a hierarchal modeling framework using a non-parametric approximate Bayesian algorithm. Consistent with behavioral results, PLBA fits confirmed the presence of a long delay between presentation and integration of new stimulus information, but did not support increased response caution in reaction to the change. We also found the decision process was not veridical, as symmetric stimulus change had an asymmetric effect on the rate of evidence accumulation. Thus, the perceptual decision process was slow to react to, and underestimated, new contrary motion information.