Unique Thresholds Research Articles

Optimal Timing of Palatoplasty in Infants With Comorbidities.

Ideal timing of palatoplasty continues to be debated given that early repair is thought to improve speech and hearing, whereas delayed repair is associated with less midface growth disruption. The purpose of this study is to elucidate optimal timing of palatoplasty in patients with comorbidities to mitigate perioperative complications. Retrospective cohort study. Hospitals participating in the American College of Surgeons National Surgical Quality Improvement Program Pediatric. Palatoplasty performed for children younger than the age of 2 years with comorbidities. Medical/surgical complications, reoperations, readmissions within 30 days postoperatively. Patients with comorbidities having Veau I or II cleft palate were associated with significantly decreased risk of adverse events when performing palatoplasty after 125 days of age (P < .001). Patients with comorbidities having Veau III cleft palate were associated with significantly decreased risk of adverse events when performing palatoplasty after 225 days of age (P = .010). Patients with comorbidities having Veau IV cleft palate were associated with significantly decreased risk of adverse events when performing palatoplasty after 250 days of age (P = .045). Infants with comorbidities having progressively increasing Veau classification demonstrate unique age-dependent perioperative thresholds, such that more extensive phenotypes are associated with better perioperative outcomes with older age at time of cleft palate repair.

Three probabilistic metrics for adequacy assessment of the Pacific Northwest power system

All regional power system entities within the bulk assessment areas in North America calculate and report probabilistic adequacy metrics that measure projected shortfall duration and magnitude to the North American Electric Reliability Corporation (NERC). While no maximum thresholds have been defined for either metric to be used as an adequacy standard, it is possible that such thresholds could be defined sometime in the future as planners gain a better understanding of the risks associated with each metric and how they interact. Therefore, it is prudent to know whether setting a threshold for one metric automatically leads to an equivalent and predictable threshold for the other. To answer this question, this paper examines mathematical relationships among these two metrics and a third metric (that measures the projected shortfall frequency) for the Pacific Northwest power supply. Results from a Monte Carlo simulation model show that although in special cases the threshold for one metric can be used to calculate unique thresholds for the other two, in general this is not the case. Hence, if these metrics are to be used to define an adequacy standard for the Northwest, threshold values for all three metrics should be defined independently.

Thermoeffector threshold plasticity: The impact of thermal pre-conditioning on sudomotor, cutaneous vasomotor and thermogenic thresholds.

To better understand the relationships between changes in body temperature and displacements of the thermoeffector thresholds (critical temperatures), the passive cooling (and heating) of pre-heated (and pre-cooled) individuals was investigated. Such experiments are necessary to understand the inter-dependence of those thresholds, and may possibly yield human evidence for the existence of separate central controllers. Eight males participated in four trials; two when normothermic, one following pre-experimental heating and the fourth following pre-cooling. Subjects were exposed to passive, whole-body cooling and heating when normothermic (the control trials), and again following pre-heating and pre-cooling (respectively). Cutaneous vasomotor, thermogenic, as well as precursor and discharged sudomotor thresholds from different body segments were compared across those dynamic thermal states. Following pre-heating, the critical mean body temperatures for vasoconstriction (0.37 °C ± 0.10) and thermogenesis (0.67 °C ± 0.20) were significantly elevated during passive cooling, relative to the corresponding control trial (both P < 0.05). When passive heating followed pre-cooling, the thresholds for vasodilatation were reduced (0.37 °C ± 0.07; P < 0.05). Conversely, but with the exception of forehead precursor sweating, the sudomotor thresholds were elevated (averaging 0.16 °C ± 0.02; P < 0.05). Most thermoeffectors revealed unique and adjustable activation thresholds, with the threshold displacements for thermogenesis and vasomotion appearing to be linked to the change in mean body temperature. Following pre-cooling, the critical temperatures for vasodilatation and sudomotor activation varied independently, with the exception of forehead precursor sweating. Collectively, those observations are consistent with the presence of independent central controllers for thermally dependent vasomotor and sudomotor responses, and perhaps also for shivering thermogenesis.

Mild Intraocular Pressure Elevation in Mice Reveals Distinct Retinal Ganglion Cell Functional Thresholds and Pressure-Dependent Properties.

Elevation of intraocular pressure (IOP) causes retinal ganglion cell (RGC) dysfunction and death and is a major risk factor for glaucoma. We used a bead injection technique to increase IOP in mice of both genders by an average of ∼3 mmHg for 2 weeks. This level of IOP elevation was lower than that achieved in other studies, which allowed for the study of subtle IOP effects. We used multielectrode array recordings to determine the cellular responses of RGCs exposed to this mild degree of IOP elevation. We found that RGC photopic receptive field (RF) center size and whole-field RGC firing rates were unaffected by IOP elevation. In contrast, we found that the temporal properties of RGC photopic responses in the RF center were accelerated, particularly in ON sustained cells. We also detected a loss of antagonistic surround in several RGC subtypes. Finally, spontaneous firing rate, interspike interval variance, and contrast sensitivity were altered according to the magnitude of IOP exposure and also displayed an IOP-dependent effect. Together, these results suggest that individual RGC physiologic parameters have unique IOP-related functional thresholds that exist concurrently and change following IOP elevation according to specific patterns. Furthermore, even subtle IOP elevation can impart profound changes in RGC function, which in some cases may occur in an IOP-dependent manner. This system of overlapping functional thresholds likely underlies the complex effects of elevated IOP on the retina.SIGNIFICANCE STATEMENT Retinal ganglion cells (RGCs) are the obligate output neurons of the retina and are injured by elevated intraocular pressure (IOP) in diseases such as glaucoma. In this study, a subtle elevation of IOP in mice for 2 weeks revealed distinct IOP-related functional thresholds for specific RGC physiologic parameters and sometimes showed an IOP-dependent effect. These data suggest that overlapping IOP-related thresholds and response profiles exist simultaneously in RGCs and throughout the retina. These overlapping thresholds likely explain the range of RGC responses that occur following IOP elevation and highlight the wide capacity of neurons to respond in a diseased state.

Condensin ATPase motifs contribute differentially to the maintenance of chromosome morphology and genome stability.

Effective transfer of genetic information during cell division requires a major reorganization of chromosome structure. This process is triggered by condensin, a conserved pentameric ATPase essential for chromosome condensation. How condensin harnesses the energy of ATP hydrolysis to promote chromatin reorganization is unknown. To address this issue, we performed a genetic screen specifically focused on the ATPase domain of Smc4, a core subunit of condensin. Our screen identified mutational hotspots that impair condensin’s ability to condense chromosomes to various degrees. These mutations have distinct effects on viability, genome stability, and chromosome morphology, revealing unique thresholds for condensin enzymatic activity in the execution of its cellular functions. Biochemical analyses indicate that inactivation of Smc4 ATPase activity can result in cell lethality because it favors a specific configuration of condensin that locks ATP in the enzyme. Together, our results provide critical insights into the mechanism used by condensin to harness the energy of ATP hydrolysis for the compaction of chromatin.

Sensor-less on-line chatter detection in turning process based on phase monitoring using power factor theory

This paper presents a sensor-less on-line chatter detection method for a turning process by introducing a mechanical energy factor (MEF) and a mechanical power factor (MPF). The MEF and MPF serve as indexes for self-excited chatter and forced chatter, respectively. The indexes are based on the power-factor theory, which generally represents the electrical-power efficiency as having a correlation with the phase difference between the current and the voltage. By applying this theory to a mechanical system, the MEF and MPF can be employed to monitor the phase difference between the cutting force and the displacement/velocity of the tool system, respectively. By monitoring the phase difference, chatter vibration can be detected in time domain with a high response and small number of computations. The MEF and MPF can be calculated without using additional external sensors employing the sensor-less cutting-force estimation technique based on the disturbance observer. The monitoring performance of the proposed method was evaluated through several outside turning tests with a prototype precision lathe. The results showed that both the self-excited and forced chatters were successfully detected with unique thresholds, which did not depend on the cutting condition or the workpiece material.

Regression-based three-way recommendation

Recommender systems employ recommendation algorithms to predict users’ preferences to items. These preferences are often represented as numerical ratings. However, existing recommender systems seldom suggest the appropriate behavior together with the numerical prediction, nor do they consider various types of costs in the recommendation process. In this paper, we propose a regression-based three-way recommender system that aims to minimize the average cost by adjusting the thresholds for different behaviors. This is undertaken using a step-by-step approach, starting with simple problems and progressing to more complex ones. First, we employ memory-based regression approaches for binary recommendation to minimize the loss. Next, we consider misclassification costs and adjust the approaches to minimize the average cost. Finally, we introduce coupon distribution action with promotion cost, and propose two optimal threshold-determination approaches based on the three-way decision model. From the viewpoint of granular computing, a three-way decision is a good tradeoff between the numerical rating and binary recommendation. Experimental results on the well-known MovieLens data set show that threshold settings are critical to the performance of the recommender, and that our approaches can compute unique optimal thresholds.

Rainfall thresholds for the occurrence of debris flows in the Jiangjia Gully, Yunnan Province, China

The Jiangjia Gully (JJG), Yunnan Province, China, is one of several debris flow gullies that characterize the topography of mountainous areas in China. Rainfall-triggered debris flows are frequent in the JJG. In order to model and predict these debris flow occurrences, we analyzed precipitation parameters (including intensity–duration thresholds and rainfall event–duration thresholds) that triggered past debris flow events in the JJG. Since the JJG is unique, any model used for predicting debris flows in this gully must be developed using data from only this gully. Furthermore, the effects of normalized precipitation and antecedent precipitation on debris flows in the JJG were considered. Debris flow data and precipitation data were compiled from 47 debris flow events in 1993, 1994, 1998–2001, 2004 and 2006 in JJG. All of these debris flows were triggered following a precipitation event with a duration of 6h or less, with most of the precipitation events exhibiting a duration of 3 to 6h. Only three rainfall events with a duration of less than 1h and average intensity between 1.0 and 42.0mm/h produced debris flows. The 90%, 70% and 50% probability curves for debris flow events were then constructed. Intensity–duration (I–D) and rainfall event–duration (RE–D) thresholds were then used for debris flow modeling based on preliminary tests and comparisons. Antecedent precipitation was found not to be a significant factor in triggering debris flows in the JJG; however, intraday precipitation played a significant role. Normalized precipitation threshold curves from adjacent areas were not well-correlated with the patterns observed in the JJG. Determination of unique thresholds for each gully is necessary for developing an effective prediction system.

Differential fiber-specific block of nerve conduction in mammalian peripheral nerves using kilohertz electrical stimulation.

Kilohertz electrical stimulation (KES) has been shown to induce repeatable and reversible nerve conduction block in animal models. In this study, we characterized the ability of KES stimuli to selectively block specific components of stimulated nerve activity using in vivo preparations of the rat sciatic and vagus nerves. KES stimuli in the frequency range of 5-70 kHz and amplitudes of 0.1-3.0 mA were applied. Compound action potentials were evoked using either electrical or sensory stimulation, and block of components was assessed through direct nerve recordings and muscle force measurements. Distinct observable components of the compound action potential had unique conduction block thresholds as a function of frequency of KES. The fast component, which includes motor activity, had a monotonically increasing block threshold as a function of the KES frequency. The slow component, which includes sensory activity, showed a nonmonotonic block threshold relationship with increasing KES frequency. The distinct trends with frequency of the two components enabled selective block of one component with an appropriate choice of frequency and amplitude. These trends in threshold of the two components were similar when studying electrical stimulation and responses of the sciatic nerve, electrical stimulation and responses of the vagus nerve, and sensorimotor stimulation and responses of the sciatic nerve. This differential blocking effect of KES on specific fibers can extend the applications of KES conduction block to selective block and stimulation of neural signals for neuromodulation as well as selective control of neural circuits underlying sensorimotor function.

Anthropometric markers for detection of the metabolic syndrome in adolescents

ObjectivesThis study aimed to estimate, in a large group of Algerian adolescents, the prevalence of the metabolic syndrome (MetS), using four definitions (by Cook, De Ferranti, Viner and the IDF), and to test the validity of unique thresholds of waist circumference, waist/height ratio and BMI in screening for the MetS regardless of the definition used. Subjects and methodsA total of 1100 adolescent students, aged 12–18 y, were randomly selected from schools and classrooms in the city of Constantine; all had anthropometric measurements taken and 989 had blood tests. ResultsPrevalences of the MetS were: 2.6% for boys and 0.6% for girls by the Cook definition; 4.0% for boys and 2.0% for girls by the De Ferranti definition; 0.7% for boys and 0% for girls by the Viner definition; and 1.3% for boys and 0.5% for girls by the 2007 IDF definition. Prevalences ranged from 3.7% to 13.0% in obese adolescents. Unique thresholds, independent of gender, age and height, of 80cm for waist circumference, 0.50 for waist/height ratio and 25kg/m2 for BMI had sensitivities of 72–100%, 67–100% and 72–100%, respectively, and specificities of 74–78%, 74–86% and 74–78%, respectively, depending on the MetS definition used. ConclusionThe MetS is present in Algerian adolescents and the prevalence is especially high in obese young people. Our thresholds for waist circumference, waist/height ratio and BMI for screening for the MetS should now be tested in other adolescent populations.

Risk-integrated cash flow forecasting for overseas construction projects

Construction firms have long attempted to forecast a project cash flow at the initial stage of a project, which is closely related to the payment conditions and financing schedules. There are, however, diverse risk factors influencing project cash flow, in particular for the domain of international projects, which often fluctuate because of a myriad of external as well as internal uncertainties. In this research, risk factors that impact the soundness of cash flow are classified into two categories: financial risks and project-specific risks. The former refers to the external economic conditions such as exchange rate, cost escalation, and interest rate which can be analyzed through a probabilistic financial algorithm. Then, the project-specific risks such as host country’s geotechnical conditions, weather and climate differences, and resource delivery conditions are further assessed through utility curves to represent the firm’s unique risk perceptions and thresholds to the amount of risk exposures. Results of cash flow forecasts by the proposed approach are compared with the actual cash flow of a retrospective case project. It is found that construction firms better decide on a decent level of cash contingency and the probable net-profit at completion by the adoption of the proposed approach.

Neuropharmacological specificity of brain structures involved in soman-induced seizures

Pharmacological control of seizure activity following nerve agent exposure is critical in reducing neuropathology and improving survival in casualties. Three classes of drugs, anticholinergics, benzodiazepines and excitatory amino acid (EAA) antagonists, have been shown to be effective at moderating nerve agent-induced seizures. However, little is known about which brain structures are involved in producing the anticonvulsant response. This study evaluated drugs from each class, injected directly into one of three specific brain structures, the perirhinal cortex, the entorhinal cortex, or the mediodorsal thalamus, for their ability to modulate seizures induced by the nerve agent soman. The drugs evaluated were the anticholinergic scopolamine, the benzodiazepine midazolam, and the EAA antagonist MK-801. For each drug treatment in each brain area, anticonvulsant ED50 values were calculated using an up-down dosing procedure over successive animals. There was no statistical difference in the anticonvulsant ED50 values for scopolamine and MK-801 in the perirhinal and entorhinal cortices. MK-801 pretreatment in the mediodorsal thalamus had a significantly lower anticonvulsant ED50 value than any other treatment/injection site combination. Midazolam required significantly higher doses than scopolamine and MK-801 in the perirhinal and entorhinal cortices to produce an anticonvulsant response and was ineffective in the mediodorsal thalamus. These findings support the contention that specific neuroanatomical pathways are activated during nerve agent-induced seizures and that the discrete brain structures involved have unique pharmacological thresholds for producing an anticonvulsant response. This study is also the first to show the involvement of the mediodorsal thalamus in the control of nerve agent-induced seizures.

Influence of Near Threshold Visual Distractors on Perceptual Detection and Reaching Movements

Providing evidence against a dissociation between conscious vision for perception and unconscious vision for action, recent studies have suggested that perceptual and motor decisions are based on a unique signal but distinct decisional thresholds. The aim of the present study was to provide a direct test of this assumption in a perceptual-motor dual task involving arm movements. In 300 trials, 10 participants performed speeded pointing movements toward a highly visible target located at 10° from the fixation point and ± 45° from the body midline. The target was preceded by one or two close to threshold distractor(s) (80 ms stimulus onset asynchrony) presented ± 30° according to the target location. After each pointing movement, participants judged whether the distractor was present or not on either side of the target. Results showed a robust reaction time facilitation effect and a deviation toward the distractor when the distractor was both present and consciously perceived (Hit). A small reaction time facilitation was also observed when two distractors were physically present but undetected (double-miss)--this facilitation being highly correlated with the physical contrast of the distractors. These results are compatible with the theory proposing that perceptual and motor decisions are based on a common signal but emerge from a contrast dependent fixed threshold for motor responses and a variable context dependent criterion for perceptual responses. This paper thus extends to arm movement control previous findings related to oculomotor control.

Enumerative and Binomial Sequential Sampling Plans for the Multicolored Asian Lady Beetle (Coleoptera: Coccinellidae) in Wine Grapes

To develop a practical integrated pest management (IPM) system for the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), in wine grapes, we assessed the spatial distribution of H. axyridis and developed eight sampling plans to estimate adult density or infestation level in grape clusters. We used 49 data sets collected from commercial vineyards in 2004 and 2005, in Minnesota and Wisconsin. Enumerative plans were developed using two precision levels (0.10 and 0.25); the six binomial plans reflected six unique action thresholds (3, 7, 12, 18, 22, and 31% of cluster samples infested with at least one H. axyridis). The spatial distribution of H. axyridis in wine grapes was aggregated, independent of cultivar and year, but it was more randomly distributed as mean density declined. The average sample number (ASN) for each sampling plan was determined using resampling software. For research purposes, an enumerative plan with a precision level of 0.10 (SE/X) resulted in a mean ASN of 546 clusters. For IPM applications, the enumerative plan with a precision level of 0.25 resulted in a mean ASN of 180 clusters. In contrast, the binomial plans resulted in much lower ASNs and provided high probabilities of arriving at correct "treat or no-treat" decisions, making these plans more efficient for IPM applications. For a tally threshold of one adult per cluster, the operating characteristic curves for the six action thresholds provided binomial sequential sampling plans with mean ASNs of only 19-26 clusters, and probabilities of making correct decisions between 83 and 96%. The benefits of the binomial sampling plans are discussed within the context of improving IPM programs for wine grapes.

The threshold pattern of calcineurin-dependent gene expression is altered by loss of the endogenous inhibitor calcipressin.

Calcineurin links calcium signaling to transcriptional responses in the immune, nervous and cardiovascular systems. To determine the function of the calcipressins, a family of putative calcineurin inhibitors, we assessed the calcineurin-dependent process of T cell activation in mice engineered to lack the gene encoding calcipressin 1 (Csp1). Csp1 regulated calcineurin in vivo, and genes triggered in an immune response had unique transactivation thresholds for T cell receptor stimulation. In the absence of Csp1, the apparent transactivation thresholds for all these genes were shifted because of enhanced calcineurin activity. This unbridled calcineurin activity drove Fas ligand expression, which normally requires high T cell receptor stimulation and results in the premature death of T helper type 1 cells. Thus, calcipressins modulate the pattern of calcineurin-dependent transcription, and may influence calcineurin activity beyond calcium to integrate a broad array of signals into the cellular response.

Colour and polarity contributions to global motion perception.

The influence of the image segmentation cues based on colour and polarity on a motion coherence task were examined. In line with previous reports, when the signal and noise were given unique identities thresholds were much lower than when they were the same, suggesting a strong influence of segmentation. In another paradigm extra noise elements that differed in colour or polarity interfered despite this perceptual segmentation. We suggest that the results when signal and noise have unique identities are attributable to the subjects' ability to attend to a particular location(s) in space. When this strategy was eliminated by presenting the stimuli in the near-periphery or very briefly the effect of the colour or polarity information disappears.

Dipole-allowed transitions in collisions of charged particles and Rydberg atoms: method of virtual quanta in low velocity collisions

Experiments involving collisions between charged particles and Na Rydberg atoms have been undertaken to study the projectile-velocity dependence of collisionally induced dipole-allowed transitions. Measurements being carried out in this laboratory, involving H +, H 2 +, He +, Ne +, and e − projectiles incident on Na(30s) and Na(29d), cover the reduced projectile velocity range from 1.7 to 200 times the mean orbital velocity of the excited electron. Absolute cross sections for the dipole-allowed transitions, 30s to 30p and 29d to 30p, have been measured and exhibit pronounced and unique projectile-velocity dependent thresholds. The Weizsäcker-Williams method of virtual quanta has been extended to include low projectile velocities and is found to be in good agreement with the observed projectile-velocity dependent dipole-allowed thresholds.

Vasomotor thresholds in the squirrel monkey: effects of central and peripheral temperature.

Six squirrel monkeys (Saimiri sciureus) participated in two ex,eriments examining how central (preoptic/anterior hypothalamic, Tpo) and peripheral (ambient, Ta, or mean skin, Tsk) temperatures influence peripheral vasomotion. In the first experiment, four monkeys with unilateral preoptic thermodes were exposed to a wide range of central (23 degrees C less than Tpo less than 44 degrees C) and peripheral (10 degrees C less than Ta less than 38 degrees C) temperatures. Results indicated that the skin of both tail and foot vasodilates at discrete but unique Ta thresholds (Tpo congruent to 39 degrees C) and that raising Tpo lowers these thresholds. In the second experiment, results from two monkeys implanted with bilateral thermodes surrounding the preoptic area replicated those of experiment 1. Subsequent tests with these two monkeys on the quantitative interaction between central and peripheral temperatures indicated that the dilation threshold is approximately a linear function of Tpo and Tsk. These effects are related to the interaction between central and peripheral inputs to the thermoregulatory system.