Unit Distance Research Articles

Prayer paper production facility layout redesign using systematic layout planning method and CRAFT

Abstract. The facility layout is a strategic design that is used for a long time. All manufacturing industries must pay attention to the right layout to increase the productivity of the industry. A prayer paper manufacturing industry located in the Tanjung Morawa area, Medan has an error in the placement of raw materials and the placement of production machines, so that the distance from the temporary warehouse to the printing and cutting work stations is far apart, causing high material handling costs. Seeing these problems, research was carried out to improve the layout of the facilities and redesign. The method used for this research is Systematic Layout Planning (SLP), which is one of the methods used to regulate a workplace in a factory by using two areas with high frequency and logical relationships with each other. And the Computerized Relative Allocation of Facilities Technique (CRAFT) Algorithm is a repair program, which is a program that looks for optimal design by making gradual improvements to the layout. CRAFT evaluates the layout by interchanging departmental locations. Inputs required for the CRAFT algorithm include initial layout, data flow or frequency of movement, cost data per unit distance, and the number of departments that do not change or remain. The CRAFT method is usually applied using Quantitative Systems (QS) software. By comparing the layout between SLP and CRAFT, the optimal result is obtained using the SLP method by reducing the distance between departments by 1.407 meters or a distance efficiency of 39.91%.

Thermodynamics of Animal Locomotion.

Muscles are biological actuators extensively studied in the frame of Hill's classic empirical model as isolated biomechanical entities, which hardly applies to a living organism subjected to physiological and environmental constraints. Here we elucidate the overarching principle of a living muscle action for locomotion, considering it from the thermodynamic viewpoint as an assembly of actuators (muscle units) connected in parallel, operating via chemical-to-mechanical energy conversion under mixed (potential and flux) boundary conditions. Introducing the energy cost of effort as the generalization of the well-known oxygen cost of transport in the frame of our compact locally linear nonequilibrium thermodynamics model, we analyze oxygen consumption measurement data from a documented experiment on energy cost management and optimization by horses moving at three different gaits. Horses adapt to a particular gait by mobilizing a nearly constant number of muscle units minimizing waste production per unit distance covered; this number significantly changes during transition between gaits. The mechanical function of the animal is therefore determined both by its own thermodynamic characteristics and by the metabolic operating point of the locomotor system.

Attenuating gradient of residual stratigraphic pressure and its controls on hydrocarbon migration and accumulation

Abnormal stratigraphic pressure is highly significant for hydrocarbon migration and accumulation for the exploration and exploitation of exploratory fields. However, the relationship between abnormal pressure and hydrocarbon migration processes is difficult to characterize quantitatively. In this paper, a new parameter, the attenuating gradient of residual pressure (AGRP), which is defined as the variation in residual stratigraphic pressure over a unit distance in a certain direction, is introduced to characterize hydrocarbon migration forced by residual pressure and hydrocarbon accumulation influenced by fault seals in the Huimin Depression, Bohai Bay Basin. The AGRP against the geological background can be calculated by the formation pressure of the source region by equivalent depth method using well log data (sonic travel time/velocity and resistivity) formation pressure of hydrocarbon reservoirs by drill stem tests of 32 exploration wells. For the Huimin Depression, the calculation results of the third member of the Paleogene Shahejie Formation (Es3) reservoir interval show that the northern tectonic uplift belt (NTUB) and parts of the central deep sag zone (CDSZ) and southern slope belt (SSB) are characterized by stepped distributions of high AGRP values ranging from 1.2 to 2.5 MPa/km with developed faults. The other parts of the Huimin Depression are characterized by continuously distributed low AGRP values from 0.5 to 1.0 MPa/km. The AGRP is effective for characterizing and evaluating hydrocarbon migration and accumulation in structural hydrocarbon traps with AGRP values higher than 1.0 MPa/km, which indicates that these reservoirs are dominated by residual pressure as the main driving force. For these traps, oil and gas tend to migrate to the high-AGRP areas, which indicates a large driving force by residual pressure. Furthermore, the stepped distribution of the AGRP suggests a well-sealed fault and hence good preservation conditions for hydrocarbon accumulation. This study shows that the AGRP can characterize hydrocarbon migration and accumulation more precisely and hence provide guidance for petroleum exploration and exploitation, especially in rift petroliferous basins with abnormal pressure and developed faults.

Antixenosis, tolerance and genetic analysis of some rice landraces for resistance to Nilaparvata lugens (Stål.)

• Six rice landraces of West Bengal exhibited a high level of resistance to BPH. • Phenotypic reactions of the resistant landraces were equivalent to Ptb33. • Genetic diversity was observed within the landraces with similar phenotypic expression. • Resistant landraces can be used in resistance breeding programme to develop BPH resistant varieties. Twenty-six rice landraces from West Bengal, India were evaluated for antixenosis and tolerance against brown planthopper (BPH) biotype 4 at the Bidhan Chandra Krishi Viswavidyalaya (BCKV), West Bengal. High levels of resistance were observed in six landraces, namely Badshabhog, Gamra, Haldichuri, Janglijata, Kalabhat and Khara. These phenotypically resistant rice landraces including Ptb33 exhibited lowest feeding rate, fecundity, nymphal and adult preference, survival, plant dry weight loss per mg of BPH dry weight produced (PDWL), and higher functional plant loss index (FPLI), more days to wilt and unhatched eggs compared with the susceptible check Swarna. All the landraces were classified into four major clusters at 10 unit distance by the scale of similarity during genetic diversity analysis through 21 gene-linked SSR markers of BPH resistance. Some phenotypically resistant landraces were gathered under the major cluster I indicating their analogous genetic history, while some were grouped with susceptible landraces exhibiting their genetic variation. The resistant landraces can be used as potential donors in the breeding programme for the development of rice varieties with resistance to BPH.

A model for calculating the mechanical demands of overground running

ABSTRACT An energy-based approach to quantifying the mechanical demands of overground, constant velocity and/or intermittent running patterns is presented. Total mechanical work done (Wtotal ) is determined from the sum of the four sub components: work done to accelerate the centre of mass horizontally (Whor ), vertically (Wvert ), to overcome air resistance (Wair ) and to swing the limbs (Wlimbs ). These components are determined from established relationships between running velocity and running kinematics; and the application of work-energy theorem. The model was applied to constant velocity running (2–9 m/s), a hard acceleration event and a hard deceleration event. The estimated Wtotal and each sub component were presented as mechanical demand (work per unit distance) and power (work per unit time), for each running pattern. The analyses demonstrate the model is able to produce estimates that: 1) are principally determined by the absolute running velocity and/or acceleration; and 2) can be attributed to different mechanical demands given the nature of the running bout. Notably, the proposed model is responsive to varied running patterns, producing data that are consistent with established human locomotion theory; demonstrating sound construct validity. Notwithstanding several assumptions, the model may be applied to quantify overground running demands on flat surfaces.

Synthetic observations of spiral arm tracers of a simulated Milky Way analog

Context.The Faraday rotation measure (RM) is often used to study the magnetic field strength and orientation within the ionized medium of the Milky Way. Recent observations indicate an RM magnitude in the spiral arms that exceeds the commonly assumed range. This raises the question of how and under what conditions spiral arms create such strong Faraday rotation.Aims.We investigate the effect of spiral arms on Galactic Faraday rotation through shock compression of the interstellar medium. It has recently been suggested that the Sagittarius spiral arm creates a strong peak in Faraday rotation where the line of sight is tangent to the arm, and that enhanced Faraday rotation follows along side lines which intersect the arm. Here our aim is to understand the physical conditions that may give rise to this effect and the role of viewing geometry.Methods.We apply a magnetohydrodynamic simulation of the multi-phase interstellar medium in a Milky Way-type spiral galaxy disk in combination with radiative transfer in order to evaluate different tracers of spiral arm structures. For observers embedded in the disk, dust intensity, synchrotron emission, and the kinematics of molecular gas observations are derived to identify which spiral arm tangents are observable. Faraday rotation measures are calculated through the disk and evaluated in the context of different observer positions. The observer’s perspectives are related to the parameters of the local bubbles surrounding the observer and their contribution to the total Faraday rotation measure along the line of sight.Results.We reproduce a scattering of tangent points for the different tracers of about 6° per spiral arm similar to the Milky Way. For the RM, the model shows that compression of the interstellar medium and associated amplification of the magnetic field in spiral arms enhances Faraday rotation by a few hundred rad m−2in addition to the mean contribution of the disk. The arm–interarm contrast in Faraday rotation per unit distance along the line of sight is approximately ~10 in the inner Galaxy, fading to ~2 in the outer Galaxy in tandem with the waning contrast of other tracers of spiral arms. We identify a shark fin pattern in the RM Milky Way observations and in the synthetic data that is characteristic for a galaxy with spiral arms.

Model Prediction and Rule Based Energy Management Strategy for a Plug-in Hybrid Electric Vehicle With Hybrid Energy Storage System

This article presents an energy management strategy (EMS) design and optimization approach for a plug-in hybrid electric vehicle (PHEV) with a hybrid energy storage system (HESS) which contains a Li–Ti–O battery pack and a Ni–Co–Mn battery pack. The EMS shares power flows within the hybrid powertrain, and it employs a dual fuzzy logical controller whose inputs are predictions for PHEV powertrain states. An elitist nondominant genetic algorithm using a model in loop simulation approach as fitness functions is implemented to multiobjective optimization for the EMS under worldwide light-duty test cycles. The optimal objectives are improving PHEV mileage, minimizing battery packs capacity fades, reducing HESS degradation inconsistency, and minimizing driving cost unit distance. A hardware in loop test bench has been established to verify EMS performances in embedded systems. The test results under new European driving cycles demonstrate that optimized EMSs remain appropriate for different driving cycles and their performances are close to dynamic programming based offline optimal solutions. Due to the contributions of both the HESS and the optimized EMS, the PHEV energy efficiency has been improved by 1.6%–2.5% and the PHEV energy storage system cycle life can be improved by 159%–203%.

Tools for addressing transport inequality: A novel variant of accessibility measurement

Accessibility is widely thought the most appropriate reference point when assessing transport inequality, a fundamental consideration of the liveable city. But definitions of accessibility vary and often either trivialise or overcomplicate the concept, with the result that decision makers lack a representation of it that is sufficiently accurate and at the same time sufficiently straightforward. A response is offered in this paper: the Index of Personal Travel Impact (IPTI). IPTI is an estimate at the individual level of the relative impact of desired travel, reflecting the time taken and real financial effect, and is expressed as an amount per unit distance. It is calculated using the journeys an individual would like to make (as opposed to those they actually make or those that an authority might assume “important”) and reflects the specific characteristics of the individual (e.g. car availability or mobility impairment) and of the journey (e.g. the need to arrive by a given time). It therefore serves as a good individual-level representation of the relative ease/difficulty of travelling.The rationale for IPTI's formulation is described in detail and the measure's strengths and weaknesses discussed. The practical feasibility of calculating IPTI is explored through description of a small pilot which produced encouraging results, and through a discussion of the potential efficiencies offered by the increasing availability of large data sources and online journey-planning tools. IPTI's potential applications are then discussed: first, it could provide an intelligible way of demonstrating the differing extent to which people face mobility barriers, which could be useful where an attempt is being made to address inequality. Second, IPTI could inform the appraisal process by showing the distributional effects of a given scheme upon individuals' relative capacity to travel. The paper concludes with recommendations for further research.

A universal partition result for infinite homogeneous [formula omitted]-free and related graphs

We study new partition properties of infinite Kn-free graphs. First, we investigate the number bpi(G,m) introduced by A. Aranda et al. (denoted there by r(G,m)) : the minimal r so that for any partition of G into r classes of equal size, there exists an independent set which meets at least m classes in size |G|. In the case of Henson’s countable universal Kn-free graph Hn, we express bpi(Hnm) by well-known Ramsey-numbers for finite digraphs. In particular we answer a conjecture of Thomassé (2000) by showing that indeed bpi(Hn,2)=2 for all n⩾3. Furthermore, we bound and in some cases determine bpi(G,m) for certain geometric graphs, including shift graphs, unit distance graphs and orthogonality graphs.Second, we prove a new universal partition property for Hn. Given a finite bipartite graph G on classes A,B, we show that for any balanced 2-colouring of Hn there is an induced copy of G in Hn so that the images of A and B are monochromatic of distinct colours. We end our paper with further open problems.

The effects of transportation system improvements on urban performances with heterogeneous residents

Through developing a spatial equilibrium model for a linear monocentric city with a bi-modal traffic corridor (i.e., highway and public transit), this paper examines the effects of transportation improvements (including the decreases of the fixed travel cost, the travel time and monetary cost per unit distance) on urban spatial structure and the utilities of the two resident classes, namely car-available-residents (CARs) and car-unavailable-residents (CURs). As a result, it is demonstrated that the city size increases with the improvements of vehicle-highway system and the degree of CARs’ travel mode choice rationality, but the improvement of public transit may produce a shrinkage rather than an expansion in city size. From the aspect of utility, both CARs and CURs benefit from the improvement of vehicle-highway system; however, the improvement of public transit might have an adverse effect on the utility of CARs. These findings would provide valuable reference for the future transportation and urban planning.

Travel Time Variability and Congestion Assessment for Origin–Destination Clusters through the Experience of Mobility Companies

Reliability is a measure of network performance that reflects the ability of the network to provide predictable travel times. Deviations from planned travel times can increase travel costs for users. To improve the system's performance, it is crucial to identify sources of unreliability, particularly the location on the network of unreliable performance. The large amount of travel time data recorded by Transportation Network Providers (TNPs) in recent years has enabled researchers to study the performance of entire networks. In this study, a real-world dataset provided by TNPs in Chicago is used to determine time of day, and day of week distribution of travel time per unit distance for origin–destination (OD) pairs. Eight measures of reliability are calculated for OD pairs in the network. Standard deviation (SD), planning time index (PTI), and on-time measure (PR) are used for a network-wide comparison of reliability performance. K-means clustering is performed on more than 21.3 million trips to divide 3,450 eligible OD pairs in the Chicago network into three groups with low, medium, and high intensity of each reliability metric. Lastly, metrics in each cluster of SD, PTI, and PR are compared. The results show that ranking PTI and PR is not sufficient for identifying unreliable/congested OD pairs in the network. Approaches for comparing reliability performance over different periods of the day for the same segment and over different segments in the network are discussed, along with network-wide measures of reliability.

Beam Quality Measurement and Verification in Radiation Therapy

The aim of all radiotherapy treatment is to precisely deliver a prescribed dose of radiation to a tumour volume while simultaneously sparing the organs at risk (OARs) surrounding this tumour. Radiation therapy has evolved and the method of radiation generation varies, ranging from the controlled emission of gamma rays from a Cobalt 60 source to the production of particles such as; photons, electrons and protons produced in linear accelerators. The high energy photons employed during tumour treatment can interact with components of the gantry such as lead jaws, and produce particles that may contaminate the treatment beam. These contaminants are produced through various interactions with the photons and the absorbing medium such as; Compton Interaction, Photoelectric Effect and Pair Production. Photons have more penetrating power than charged particles of similar energy, and as they traverse a medium there is energy transformation to electron energy(1). The prospect of an interaction per unit distance travelled is denoted by the principle N= N_0 e^(-μx), where μ is dependent on the energy of the photon and the materials through which it travels(2). The aim of this paper is to conduct beam quality measurements and verification for treatment plan quality assurance in radiation therapy. An IBA Pharma type ion chamber (FC65-G) and electrometer (IBA Dose 2) were used to obtain ionization charges for an 18MV and a 6MV photon beam from a C-Series linear accelerator. These measurements were taken using a 1D water phantom, dimensions 40cm* 35cm*34.5 cm at a source to detector distance (SDD) of 100cm with the chamber 10cm beneath the water surface. The “K” (quality conversion factor) was calculated using the TPR20, 10 method. Two sets of measurements were taken at a depth of 20 cm and 10 cm beneath the water surface at a source to detector distance of 100cm. Three measurements were taken for both photon energies at polarities of +300, -300 and +100 on the electrometer. Ka values were calculated using the TPR20, 10 principles outlined in the TRS 135 protocol. The Ka value for the 6MV photon was determined to be 0.996 Gy while that for the 18MV was 0.973 Gy. These Ka values were then used to determine the tabulated percentage depth dose (PDD) for the photon energies. The tabulated PDD’s were 0.665 and 0.788 for the 6MV and 18MV beam respectively. From equation 2, Dw (10cm) for 6MV photon was calculated to be 0.68 Gy and that for the 18 MV photon was 0.81 Gy. The absorbed dose of the treatment unit at Dmax (Eq. 3) was calculated to be; (18MV) 1.03 Gy and (6MV) 1.03 Gy

Sendov’s Conjecture: A Note on a Paper of Dégot

Sendov’s conjecture states that if all the zeroes of a complex polynomial P(z) of degree at least two lie in the unit disk, then within a unit distance of each zero lies a critical point of P(z). In a paper that appeared in 2014, Degot proved that, for each a ∈ (0, 1), there exists an integer N such that for any polynomial P(z) with degree greater than N, if P(a) = 0 and all zeroes lie inside the unit disk, the disk |z − a| ≤ 1 contains a critical point of P(z). Based on this result, we derive an explicit formula N(a) for each a ∈ (0, 1) and, consequently obtain a uniform bound N for all a ∈ [α, β] where 0 < α < β < 1. This (partially) addresses the questions posed in Degot’s paper.

Effect of terrain relief on the transport cost on road of biomass raw materials: Energy conservation study of 9 cities and counties in China

Transport cost on road is an important limiting factor in the development of biomass energy. At present, transport cost on road is typically calculated using the average slope derived from the elevational difference between two points on a 2D road network, but this method ignores terrain relief, which is an important factor that influences road slope and vehicle fuel consumption. This study explores the effect of terrain relief on transport cost on road to provide data support for the optimization of transportation routes for biomass raw materials. By setting sample points at different intervals along a transportation route to accommodate different reliefs, the results showed that terrain relief was positively correlated with the unit distance transport cost on road by truck of biomass raw materials. When the sample interval was less than 500 m, the unit distance transport cost on road decreased rapidly with an increase in sample interval, and the rate of decline in hilly areas was greater than that in plains areas. When the sample interval was greater than 500 m, the unit distance transport cost on road decreased slowly and approached a stable level as the sample interval increased. In hilly areas, the transport cost on road of biomass raw materials and the relief effect were greater than those in plains areas. Therefore, when calculating the transport cost on road of biomass raw materials, we recommend using sample intervals less than 500 m to achieve a more accurate calculation and maintain a relatively small calculation load.

Oxygen cost of over-ground walking in persons with mild-to-moderate Parkinson’s disease

BackgroundOxygen (O2) cost of walking is a physiological marker of walking dysfunction and reflects the amount of O2 consumed per kilogram of body weight per unit distance walked. The onset of walking dysfunction (i.e., reduced walking speed and shorter stride length) is commonly observed in Parkinson’s disease (PD), even in the early stages of the disease. However, the O2 cost of walking has not been assessed in persons with PD. Research questionDoes O2 cost of walking differ between persons with PD and controls matched by age and sex? MethodsThe sample included 31 persons with mild-to-moderate PD (Hoehn and Yahr stages 2–3) and 31 age- and sex-matched controls in this cross-sectional study. O2 consumption (VO2) was measured using a portable indirect calorimetry system during a 6-min period of over-ground walking at a normal comfortable speed, and the O2 cost of walking was calculated based on the ratio of net relative VO2 (ml kg−1 min−1) and speed (m min−1). ResultsThere were no differences in resting VO2, steady-state VO2, and over-ground walking speed between persons with PD and controls (p > 0.05). There was a significant difference in the O2 cost of walking between persons with PD and healthy controls (p < 0.01) such that persons with PD had a higher O2 cost of walking. The mean(SD) O2 cost of walking for persons with PD was 0.179 (0.038) ml kg−1 m−1, and the O2 cost of walking for healthy controls was 0.153 (0.024) ml kg−1 m−1. SignificancePersons with PD demonstrated a higher O2 cost of walking compared with controls, and this may reflect worse walking economy in PD. The possibility of worse walking economy under free-living conditions may result in reduced community ambulation and participation.

Medial knee cartilage is unlikely to withstand a lifetime of running without positive adaptation: a theoretical biomechanical model of failure phenomena.

Runners on average do not have a high risk of developing knee osteoarthritis, even though running places very high loads on the knee joint. Here we used gait analysis, musculoskeletal modeling, and a discrete-element model of knee contact mechanics to estimate strains of the medial knee cartilage in walking and running in 22 young adults (age 23 ± 3 years). A phenomenological model of cartilage damage, repair, and adaptation in response to these strains then estimated the failure probability of the medial knee cartilage over an adult lifespan (age 23–83 years) for 6 km/day of walking vs. walking and running 3 km/day each. With no running, by age 55 the cumulative probability of medial knee cartilage failure averaged 36% without repair and 13% with repair, similar to reports on incidence of knee osteoarthritis in non-obese adults with no knee injuries, but the probability for running was very high without repair or adaptation (98%) and remained high after including repair (95%). Adaptation of the cartilage compressive modulus, cartilage thickness, and the tibiofemoral bone congruence in response to running (+1.15 standard deviations of their baseline values) was necessary for the failure probability of walking and running 3 km/day each to equal the failure probability of walking 6 km/day. The model results suggest two conclusions for further testing: (i) unlike previous findings on the load per unit distance, damage per unit distance on the medial knee cartilage is greater in running vs. walking, refuting the “cumulative load” hypothesis for long-term joint health; (ii) medial knee cartilage is unlikely to withstand a lifetime of mechanical loading from running without a natural adaptation process, supporting the “cartilage conditioning” hypothesis for long-term joint health.

An estimation method for the fuel burn and other performance characteristics of civil transport aircraft in the cruise. Part 1 fundamental quantities and governing relations for a general atmosphere

AbstractThis paper is one of a series addressing the need for simple, yet accurate, methods for the estimation of cruise fuel burn and other important aircraft performance parameters. Here, a previously published, constant Reynolds number model for turbofan-powered, civil transport aircraft is extended to include Reynolds number effects. Provided the variation of temperature with pressure is known, the method is applicable to flight in any atmospheric conditions. For a given aircraft, cruising in a given atmosphere, there is a single Mach number and Flight Level pair, at which the fuel burn per unit distance travelled through the air has an absolute minimum value. Both these quantities depend upon the Reynolds number, which, in turn, depends upon the aircraft weight and the atmospheric vertical temperature profile. Simple, explicit expressions are developed for all parameters at the optimum condition. These are shown to be in close agreement with numerical solutions of the governing equations. It is found that typical operational mass and temperature profile variations can change cruise fuel burn rate by several percent. In the International Standard Atmosphere, when the speed and altitude deviate from their optimum values, the fuel burn penalty is reduced slightly relative to the constant Reynolds number case. By way of example, the method is used to estimate the minimum fuel, speed-versus-height trajectory for cruise in a realistic atmosphere.For each aircraft, cruise fuel burn is found to be governed by six independent parameters. All are constants. Two are simple, involving only size and weight, whereas four are complex and must be determined by either theoretical, or empirical, means. The estimation of these quantities will be considered in Part 2.

Monochromatic equilateral triangles in the unit distance graph

Let $\chi_{\Delta}(\mathbb{R}^{n})$ denote the minimum number of colors needed to color $\mathbb{R}^{n}$ so that there will not be a monochromatic equilateral triangle with side length $1$. Using the slice rank method, we reprove a result of Frankl and Rodl, and show that $\chi_{\Delta}\left(\mathbb{R}^{n}\right)$ grows exponentially with $n$. This technique substantially improves upon the best known quantitative lower bounds for $\chi_{\Delta}\left(\mathbb{R}^{n}\right)$, and we obtain \[ \chi_{\Delta}\left(\mathbb{R}^{n}\right)>(1.01446+o(1))^{n}. \]

Band-Limited Chirp-Evoked Compound Action Potential in Guinea Pig: Comprehensive Neural Measure for Cochlear Implantation Monitoring.

Patients with severely impaired high-frequency hearing and sufficient residual low-frequency hearing can be provided with a cochlear implant (CI), thereby facilitating ipsilateral electric and acoustic stimulation with established advantages over electric stimulation alone. However, partial or complete hearing loss often occurred after implantation due to, inter alia, acute mechanical trauma to cochlear structures during electrode insertion. Possibilities of intraoperative monitoring using electrocochleography (ECochG) have recently been studied in CI patients, primarily using the ongoing response to low-frequency tone bursts consisting of the cochlear microphonic (CM) and the auditory nerve neurophonic. By contrast, the transient neural response to tone bursts, that is, compound action potential (CAP), was generally less detectable or less sensitive as a monitoring measure, thus falling short of providing useful contribution to electrocochleography analysis. In this study, we investigate using chirps to evoke more robust CAP responses in a limited frequency band by synchronizing neural firing, and thereby improving CAP sensitivity to mechanical trauma in a guinea pig model of cochlear implantation. Stimuli were band-limited between 100 Hz and 10 kHz to investigate their frequency range selectivity as a preliminary model for low-frequency hearing. They were constructed by adding a harmonic series either with zero phase delay (click) or by adjusting the phase delay at a rate that is inversely related to a traveling wave delay model (chirp), with three different parameters to examine level-dependent delay compression. The amplitude spectrum was thus identical between stimuli with differences only in phase. In Experiment 1, we compared input-output functions recorded at the round window in normal-hearing guinea pigs and implemented a high-pass noise masking paradigm to infer neural contribution to the CAP. In Experiment 2, guinea pigs were implanted with a custom-built CI electrode using a motorized micromanipulator. Acute mechanical trauma was simulated during the electrode insertion. At each insertion step, CAP and CM responses were measured at the round window for the following stimuli: broad-band click, band-limited click, and band-limited chirps (3 parameters), and tone bursts at frequencies 1, 2, 4, and 8 kHz. Chirps compared with the equal-band click showed significantly lower thresholds and steeper slopes of sigmoid-fitted input-output functions. The shorter chirp evoked significantly larger amplitudes than click when compared at equal sensation level. However, the click evoked larger amplitudes than chirps at higher levels and correspondingly achieved larger saturation amplitudes. The results of the high-pass noise masking paradigm suggest that chirps could efficiently synchronize neural firing in their targeted frequency band, while the click recruited more basal fibers outside its limited band. Finally, monitoring sensitivity during electrode insertion, defined as relative amplitude change per unit distance, was higher for chirp-evoked CAP and tone burst-evoked CM, but smaller for CAP responses evoked by clicks or tone bursts. The chirp was shown to be an efficient stimulus in synchronizing neural firing for a limited frequency band in the guinea pig model. This study provides a proof of principle for using chirp-evoked CAP as a comprehensive neural measure in CI patients with residual hearing.

Easier polar plunge for penguins

Ecology In polar regions affected by a warming climate, it is increasingly important to understand what effect yearly variations in sea ice have on animal foraging and reproductive success. Watanabe et al. instrumented 175 Adelie penguins—a sentinel species for Southern Ocean ecosystems—with activity monitors and video cameras during four Antarctic field seasons with variable amounts of ice. During ice-free years, penguins traveled more by swimming rather than walking, lowering their energetic cost per unit distance traveled. Forage area increased in ice-free years, and more krill were captured per unit dive time, increasing foraging efficiency, growth rates, and breeding success. Adelie penguin populations in the continental Antarctic region are thus likely to grow in the coming decades as sea ice declines. Sci. Adv. 10.1126/sciadv.aba4828 (2020).