Distant Return Research Articles

The ordering of historical returns and the cross-section of subsequent returns

Abstract We show that the ordering of historical stock returns significantly predicts the cross-section of subsequent returns. More specifically, stocks with comparably high recent and low distant returns experience low subsequent returns and vice versa. Our new measure of chronological return ordering yields significant decile return spreads after accounting for a wide range of asset pricing factors. This finding holds for both a monthly and an annual formation period and is valid beyond micro-structure, reversal, and momentum effects. Further analyses on limits to arbitrage, investor attention, and informed option trading support a mispricing-based explanation for parts of the documented return predictability.

How War Changes Land: Soil Fertility, Unexploded Bombs, and the Underdevelopment of Cambodia

AbstractHow does past political violence impact subsequent development and practices, long beyond the life of the regime that perpetrated violence? Prior research focuses on physical destruction without much attention to weapons left behind in conflict zones. I contend that unexploded ordnance create direct and imminent threats to rural livelihoods. Individuals respond by shortening time horizons and avoiding investment in activities for which there is an immediate security cost but a distant return. Short‐term adjustments in agricultural methods accumulate to long‐term underdevelopment and poverty. In Cambodia, I find that the historic bombing of high‐fertility land, where impact fuses hit soft ground and were more likely to fail, reduces contemporary household production and welfare. Counterintuitively, the most fertile land becomes the least productive. This reversal of fortune qualifies the presumption that post‐war economies will eventually converge back to steady‐state growth.

The application of plant biotechnology in seed industry in the developing countries.

The indigenous seed industry in most developing countries comprises of small and medium scale seed industry. This is supplemented by satellite research laboratories and sales & marketing units of the large trans-national companies. From the angle of application of plant biotechnology, some of the factors playing a decisive role for the indigenous small and medium scale seed industry include quick delivery of results, readily available technologies, minimal risk in investment, proven technologies and minimal financial resources. The large scale trans-national seed companies on the other hand have the investment potential for capital-intensive research and novel research with distant returns. The academia in both, the developing and the developed countries tend to be driven more by novel research having publication potential rather than by application value. Such a situation presents the indigenous small and medium scale seed industry in the developing nations with a unique challenge of having to do with a technical work force who have a gap in training and application and to deliver with limited capital resources. This talk will cover an overview of plant biotechnology. An attempt will be made to present the actual seed industry situation in the developing countries. Plant biotechnology will be sectioned into various areas of application, of which the small and medium scale seed industry is one. The areas of strength and weakness will be discussed. With the advent of low cost sequencers, the molecular-breeding scenario is likely to change at all levels. A paradigm shift in challenges from infrastructure to analytics is expected. Discovery research versus applied research will be discussed. The clarity shed on the applications of plant biotechnology in developing countries should be a handy tool for the aspiring plant biotech professionals, seed industry in the developing countries and for the governmental policy makers.

Casing integrity mapping using top-casing electrodes and surface-based electromagnetic fields

Wellbore integrity is of paramount importance to subsurface resource extraction, energy storage, and hazardous waste disposal. We have developed a simple noninvasive technology for casing integrity screening, based on the continuity of electrical current flow. Applying low-frequency current to a wellhead, with a distant return electrode, produces a casing current dependent on the background formation and the properties and depth extent of the well casing. These currents in turn generate surface electrical fields that can be captured in a radial profile and can be used to analyze properties of the well casing. Numerical modeling results reveal a strong relation of the electric field to the casing properties and depth extent of the well. A small breakage in the casing produces a profile coincident to a cased well with a completion depth above the break. A corroded patch, in which the casing conductivity is reduced, also alters the field profiles, and its depth may be estimated by comparing to the profile expected from the well completion diagrams. The electric field profiles are also strongly dependent on background resistivity distributions and on whether the well was drilled using water- or oil-based drilling fluids. We validate the proof of concept in a field experiment, in which we apply currents at the wellheads of two adjacent wells with different casing lengths in an area of known background resistivity. The two profiles are similar in appearance but are offset in amplitude by more than a factor of five, consistent with the theoretical analysis and the 3D modeling results. These results demonstrate that our approach has promise for mapping the general casing condition without well intervention. This approach can be a practical and effective tool for rapidly screening several wells before expensive logging-based technologies are used for casing inspection in detail.

Epiretinal stimulation with local returns enhances selectivity at cellular resolution

Objective. Epiretinal prostheses are designed to restore vision in people blinded by photoreceptor degenerative diseases, by directly activating retinal ganglion cells (RGCs) using an electrode array implanted on the retina. In present-day clinical devices, current spread from the stimulating electrode to a distant return electrode often results in the activation of many cells, potentially limiting the quality of artificial vision. In the laboratory, epiretinal activation of RGCs with cellular resolution has been demonstrated with small electrodes, but distant returns may still cause undesirable current spread. Here, the ability of local return stimulation to improve the selective activation of RGCs at cellular resolution was evaluated. Approach. A custom multi-electrode array (512 electrodes, 10 μm diameter, 60 μm pitch) was used to simultaneously stimulate and record from RGCs in isolated primate retina. Stimulation near the RGC soma with a single electrode and a distant return was compared to stimulation in which the return was provided by six neighboring electrodes. Main results. Local return stimulation enhanced the capability to activate cells near the central electrode (<30 μm) while avoiding cells farther away (>30 μm). This resulted in an improved ability to selectively activate ON and OFF cells, including cells encoding immediately adjacent regions in the visual field. Significance. These results suggest that a device that restricts the electric field through local returns could optimize activation of neurons at cellular resolution, improving the quality of artificial vision.

Uncovering Trend Rules

Trend rules are widely used to infer whether financial markets show upward or downward movement. By taking suitable long or short positions, one can profit from a continuation of these movements. Conventionally, trend rules are based on moving averages (MAs) of prices rather than returns, which obscures how much weight is assigned to different historical time periods. In this article, the authors show how to uncover the underlying historical return weights of price MAs and combinations of price MAs. This leads to surprising and useful insights about popular trend rules—for example, that some trend rules have inverted information decay (i.e., distant returns have more weight than recent ones) or hidden mean-reversion patterns. This opens the possibility for improving the trend rule by analyzing the added value of the mean-reversion segment. Because of the increased transparency and flexibility, they advocate designing trend rules in terms of returns instead of prices.

Uncovering Trend Rules

Trend rules are widely used to infer whether financial markets show an upward or downward trend. By taking suitable long or short positions, one can profit from a continuation of these trends. Conventionally, trend rules are based on moving averages (MAs) of prices rather than returns, which obscures how much weight is assigned to different historical time periods. In this paper, we show how to uncover the underlying historical weighting schemes of price MAs and combinations of price MAs. This leads to surprising and useful insights about popular trend rules, for example that some trend rules have inverted information decay (i.e., distant returns have more weight than recent ones) or hidden mean-reversion patterns. This opens the possibility for improving the trend rule by analyzing the added value of the mean reversion part. We advocate designing trend rules in terms of returns instead of prices, as they offer more flexibility and allow for adjusting trend rules to autocorrelation patterns in returns.

3D finite element modeling of epiretinal stimulation: Impact of prosthetic electrode size and distance from the retina.

A novel 3-dimensional (3D) finite element model was established to systematically investigate the impact of the diameter (Φ) of disc electrodes and the electrode-to-retina distance on the effectiveness of stimulation. The 3D finite element model was established based on a disc platinum stimulating electrode and a 6-layered retinal structure. The ground electrode was placed in the extraocular space in direct attachment with sclera and treated as a distant return electrode. An established criterion of electric-field strength of 1000 Vm-1 was adopted as the activation threshold for RGCs. The threshold current (TC) increased linearly with increasing Φ and electrode-to-retina distance and remained almost unchanged with further increases in diameter. However, the threshold charge density (TCD) increased dramatically with decreasing electrode diameter. TCD exceeded the electrode safety limit for an electrode diameter of 50 µm at an electrode-to-retina distance of 50 to 200 μm. The electric field distributions illustrated that smaller electrode diameters and shorter electrode-to-retina distances were preferred due to more localized excitation of RGC area under stimulation of different threshold currents in terms of varied electrode size and electrode-to-retina distances. Under the condition of same-amplitude current stimulation, a large electrode exhibited an improved potential spatial selectivity at large electrode-to-retina distances. Modeling results were consistent with those reported in animal electrophysiological experiments and clinical trials, validating the 3D finite element model of epiretinal stimulation. The computational model proved to be useful in optimizing the design of an epiretinal stimulating electrode for prosthesis.

Performance optimization of current focusing and virtual electrode strategies in retinal implants

The electrode configuration in an implanted visual prosthesis array affects the spatial electric field distribution within the retina, contributing to current focusing and virtual electrode (VE) stimulation strategies. In this paper, a finite element model incorporating various electrode configurations was used to study the interaction between electrode size and electrode-to-cell distance in current focusing and VE stimulation paradigms. The electrode array unit comprises an active electrode, six flanking return electrodes and a distant monopolar return. A quasi-monopolar (QMP) fraction is defined as the proportion of current which can be preferentially returned through the distant return, in comparison with the more adjacent flanking electrodes. The simulation results indicate that current focusing and VE strategies can be optimized by tuning the QMP fraction. The QMP fraction is adjusted to optimize the electric field spread based on retinal ganglion cell (RGC) density in the degenerate retina, thereby offsetting the effect of inhomogeneous distribution of surviving RGCs and leading to a uniform stimulation paradigm across electrodes. Importantly, there is negligible difference in functional performance across electrode configurations for distances less than the electrode diameter, implying that the stimulation mode does not significantly affect activation threshold or activated retinal area for electrode diameters greater than the retinal thickness. Furthermore, the QMP fraction has a significant effect on VE performance, defined by activation threshold and activated retinal area, when threshold current is evenly divided between two adjacent active electrodes.

Quasi-monopolar electrical stimulation of the retina: a computational modelling study

Objective. In this study we investigated the feasibility of quasi-monopolar (QMP) electrical stimulation for retinal implant devices, using a computational model of the retinal ganglion cell layer. Approach. When used with hexagonally arrayed multiple electrodes, QMP stimulation is a hybrid of hexapolar and conventional monopolar stimulus modes. In hexapolar mode, each active electrode is surrounded by six guards which collectively return the stimulus current, whereas in monopolar mode the injected stimulus current is returned through a distant return electrode. The QMP paradigm, on the other hand, distributes the return current between the guard electrodes as well as the distant return. The electrodes tested were 25, 50 and 100 µm in diameter, with hexagonally arranged centre-to-centre spacing of either double or quadruple this diameter. Main results. Simulation results indicated that electrode size had minimal effects on subretinal threshold currents, whilst electrode configuration and centre-to-centre spacing played major roles in determining thresholds and spatial activation patterns. Threshold charge densities for 50 and 100 µm electrodes were generally within the safe limit. Significance. We found that QMP stimulation offers greater advantages compared to monopolar and hexapolar stimulation, in that it combines the low thresholds of monopolar stimulation with the localized spatial activation achieved with hexapolar electrodes during parallel stimulation.

Optimized multi-electrode stimulation increases focality and intensity at target

Transcranial direct current stimulation (tDCS) provides a non-invasive tool to elicit neuromodulation by delivering current through electrodes placed on the scalp. The present clinical paradigm uses two relatively large electrodes to inject current through the head resulting in electric fields that are broadly distributed over large regions of the brain. In this paper, we present a method that uses multiple small electrodes (i.e. 1.2 cm diameter) and systematically optimize the applied currents to achieve effective and targeted stimulation while ensuring safety of stimulation. We found a fundamental trade-off between achievable intensity (at the target) and focality, and algorithms to optimize both measures are presented. When compared with large pad-electrodes (approximated here by a set of small electrodes covering 25cm2), the proposed approach achieves electric fields which exhibit simultaneously greater focality (80% improvement) and higher target intensity (98% improvement) at cortical targets using the same total current applied. These improvements illustrate the previously unrecognized and non-trivial dependence of the optimal electrode configuration on the desired electric field orientation and the maximum total current (due to safety). Similarly, by exploiting idiosyncratic details of brain anatomy, the optimization approach significantly improves upon prior un-optimized approaches using small electrodes. The analysis also reveals the optimal use of conventional bipolar montages: maximally intense tangential fields are attained with the two electrodes placed at a considerable distance from the target along the direction of the desired field; when radial fields are desired, the maximum-intensity configuration consists of an electrode placed directly over the target with a distant return electrode. To summarize, if a target location and stimulation orientation can be defined by the clinician, then the proposed technique is superior in terms of both focality and intensity as compared to previous solutions and is thus expected to translate into improved patient safety and increased clinical efficacy.

Journeys and Spaces in Shakespeare's Romances

Structurally Shakespeare's romances including Pericles, Cymbeline. The Winter's Tale and The Tempest show a common movement or pattern of separation, wandering, and reunion derived from the chivalric romance. Also they represent the pattern of pastoral romance of exile from court, pastoral sojourn, and return to court. Therefore, most of characters in his romances can be seen as travellers or wanderers who leave their own native places, experience a variety of ups and downs in the exotic and distant locations and return to their homes. Seen from the aspect of time, the major characters' life journeys in the romances exhibit a tragicomic pattern in which the catastrophic movement down into terrible disorder is followed by the anastrophic movement up to stability. The pattern also represents the cyclic movement from order and harmony through chaos, disorder, and then back to order and harmony. In addition, their tragicomic life journeys are depicted as recurrent actions in successive generations ranging from father to daughter or son. Also the continuous familial disintegration reflects the repeated past as history. Hence, such life journeys portray a world of archetypal order in which the recurrent tragicomic cycle ultimately shapes human beings' existence. The cycle is also closely related to the cosmic rhythms such as the seasonal change from spring through winter and then back to spring or the ever-changing sea showing the recurrent rhythms of instability and stability. From the angle of space, characters' journeys in all the four plays show the movement of exile from court, recreative sojourn in the country or exotic places, and triumphant return to court. Then, each world of court and country is described as an imperfect or real world, which has both positive and negative things, not the ideal world of the Golden Age in the Arcadian romance. The courts or palaces are shown as the most destructive and tragic place in the beginning of journey, but in the final scene, they are changed into the most harmonious and restorative world. Hence, through characters' life journeys, the court worlds shows the extremes of hell and paradise, winter and spring, and exile and return. The country or pastoral worlds symbolizing the mutual concord and love, compared with the court society of disintegration and separation, are also represented as an imperfect reality, that is, the distant and exotic places in Pericles, the Welsh mountains in Cymbeline, the Bohemian countryside in The Winter's Tale, and the enchanted island in The Tempest are seen as an uneasy haven lack of permanent stability and rest. Through the time and space journeys of major characters in Shakespeare's romances we can read the archetypal order of our human beings' life journeys beyond history, which repeats the cycle of loss and recovery, separation and reunion, failure and success. The journeys also reflect the cosmic rhythms of daily change from night to day, seasonal from winter to spring or historical from chaos to harmony.

Polypectomy devices

Polypectomy devices

Endoscopy in patients with implanted electronic devices

Endoscopy in patients with implanted electronic devices

AC transport current loss in a coated superconductor in the Bean model

A new and straightforward calculation is made of the loss in a very thin superconducting strip of rectangular cross-section (e.g. the coating on a coated superconductor) carrying ac transport current in zero applied magnetic field, with a similar strip acting as the return path. The computation is made assuming only that the strip is composed of uniform material which obeys Maxwell’s equations and the Bean model. An important consequence of the Bean model is the existence of a field-free region about the middle of the superconductor cross-section. The present loss calculation is novel in two respects: (1) It uses for the first time an actual computation of the shape of the field-free region rather than using qualitative assumptions, and (2) it uses a new approach for making the loss calculation, based on a rigorous solution of Maxwell’s equations for this problem. The rigorous solution correctly treats the problem as three-dimensional, having a time-dependent charge on the surface of the superconductor, and having the electric field described by both a vector and a scalar potential. Loss computations are made for the ratio of peak current to critical current in the approximate range of one-half to one, where within this range the loss decreases by about two powers of 10. The most important result coming out of the present calculation (made for the case of a distant return path large compared with the conductor cross-section dimensions but small compared with the length of the conductor), is a confirmation of Norris’s previously estimated loss expression which he obtained in a different way.

A comprehensive 2-D inductance modeling approach for VLSI interconnects: frequency-dependent extraction and compact circuit model synthesis

Although three-dimensional (3-D) partial inductance modeling costs have decreased with stable, sparse approximations of the inductance matrix and its inverse, 3-D models are still intractable when applied to full chip timing or crosstalk analysis. The 3-D partial inductance matrix (or its inverse) is too large to be extracted or simulated when power-grid cross-sections are made wide to capture proximity effect and wires are discretized finely to capture skin effect. Fortunately, 3-D inductance models are unnecessary in VLSI interconnect analysis. Because return currents follow interconnect wires, long interconnect wires can be accurately modeled as two-dimensional (2-D) transmission lines and frequency-dependent loop impedances extracted using 2-D methods . Furthermore, this frequency dependence can be approximated with compact circuit models for both uncoupled and coupled lines. Three-dimensional inductance models are only necessary to handle worst case effects such as simultaneous switching in the end regions. This paper begins by explaining and defending the 2-D modeling approach. It then extends the extraction algorithm to efficiently include distant return paths. Finally, a novel synthesis technique is described that approximates the frequency-dependent series impedance of VLSI interconnects with compact circuit models suitable for timing and noise analysis.

Inverting, imaging, and mapping ocean-basin reverberation onto high-resolution bathymetry

The objective of this paper is to determine the relationship between low-frequency ocean-basin reverberation and bathymetry. Long-range reverberation data acquired on the western flank of the Mid-Atlantic Ridge (MAR) are mapped onto high-resolution bathymetry. Since reverberation was measured via horizontally towed line array, there is a ‘‘right–left’’ ambiguity about the array’s axis and a decrease in resolution for off broadside beams and more distant returns. These ambiguities make an objective correlation between reverberation and bathymetry difficult. Therefore, an optimization procedure has been applied for eliminating the right–left ambiguity and maximizing resolution by simultaneously inverting data taken with differing array locations and orientations. Combined with range-dependent propagation modeling, the images show that distant reverberation is significant when the intermediate propagation path is free from bottom interaction. Since the experiment site is primarily bottom-limited, such paths are not abundant, and a sparse azimuthal distribution of strong returns at convergence zone intervals is often found. In general, strong returns coincide with prominent bathymetric features, such as abyssal hillsides. However, such correlations must be made judiciously because the azimuthal resolution of distant returns is often on the order of the width and separation between ridges in the MAR’s continuously rugged bathymetry.

System for detecting substructure microfracture and methods therefor

Bursts of signals at different frequencies are induced into substructure, adjacent a borehole. The return signals from each burst of signals are normalized to compensate for the attenuation, experienced by more distant return signals. The peak amplitudes of return signals, above a selected level, are cut off, and an average signal is produced from the normalized amplitude-limited return signals of each burst. The averaged signals of the return signals of all the signal bursts at the different frequencies are processed, to provide a combined signal, whose amplitude is related to the microfracture density of the substructure adjacent the borehole.

Comportement de l'espèce “Salmo trutta” dans le bassin de la Seine. Suite et fin

Since a certain time, it is observed, in the spring, in Low Seine, that Salmonidae are coming together. These concentrations concern yearling subjects. Besides, a certain number of adult fisches, marked in Ile de France in 1961-1962-1963, have been captured downstream very far from their introduction point. Because of the investments supported by fishmen for restocking the rivers as well with immediately catchable trouts than with fry and young trouts, it became necessary to try to understand the reasons of the runnings down that has been recorded and to calculate their importance. These investigations have been carried out by a systematic marking of the fishes organized on the whole of the four great hydrographic Regions of the River Seine :— Bassin of the Upper Marne ;— Bassins of the Upper Seine and Upper Aube ;— Bassin of the Upper Aisne. On the 31th October 1967, on 30.030 marked subjects, 3.138 have been caught and recorded. On these 3.138 subjects, 3.049 had not left the Bassin into which they had been introduced. The general mark-returns percentage, reaches 10,15% and the percentage of the distant returns is 3,06‰ The highest returns percentage is this of the Upper Bassin of the River Aisne, where, locally, 34,80% of the marked fishes have been captured. But it can be noted a running down rate in Lower Seine and in the sea of 2,94‰ for the Upper Marne; 2,20‰ for the River Aube and the Upper Seine and 4,71‰ for the Ile de France. The highest removing is this of a trout introduced in Ardennes Country and which has been caught at Dunkerque Harbourgh after a travel of 805 kilometers, 530 of wihch made in fresh water. Investigations by marking have been completed by biometrical studies carried out on samples drawn of Lower Seine, at the time of the big concentrations of the winter end. A certain number of constatations derives from it :— There are groups of fishes which are inclined to run down-stream, more than the others— The exotic peninsular (Danish) stocks gives a higher rate of migratories than the native continental stocks.— Some fishes have irregular removings, either upstream or downstream, to search a more propicious environment.— The breeders are going more or less far to search proper spawning places.— The native populations are very sedentary, if they lives in a stable and inviolate environment.— The concentrations of fishes in Low-Seine includes, vith the same silverwhite skin :— Salmo trutta fario ;— Salmo trutta gairdneri ;— and Salmo salar.But, it is not possible, to make a discrimination between Salmo trutta fario (dulcaquicola) ; and Salmo trutta fario (marina). The migrator fishes of the species changes their skin at the time of the physiological motivation and it can be found all the possible links between the sea-trout and the streamtrout.

Migrating Behaviour of Sea-Running Salvelinus fontinalis

This trout in Moser river, Nova Scotia, descends to the sea in April and May, with risin, temperature. Falling temperature lessens or stops descent, causing some to return upstream. The smallest showed straying in 1940 to other streams several miles distant and smaller percentage return to river than for other sizes. Return was related to freshets in the main river, rather than in tributary of origin. Homing to latter was definite, but only partial, and apparently lessened by winter sojourn elsewhere. Period of absence in sea ranged from 42 to 84 days.