Evidence For Symmetry Research Articles

Exchange rate movements and trade balance in developing economies: Evidence of symmetry and country-specific asymmetries

The impact of exchange rate (ER) movements on the trade balance has been extensively debated in the literature, with conflicting views on the nature and magnitude of this effect. This paper investigates the relationship between ER movements and trade balance in developing economies, with a specific focus on bilateral analysis involving Pakistan. Employing the Nonlinear Autoregressive Distributed Lag (NARDL) model, our results reveal a symmetric relationship between positive and negative ER changes and the trade balance, showing significant long-term and short-term effects across the panel of developing economies. However, country-specific asymmetries are observed, especially in the cases of India and China, and are more pronounced in each bilateral analysis, whether in the short run or long run. The study findings highlight the critical importance of maintaining a stable exchange rate policy, which can provide policymakers with precise insights into the money market and the broader economy while preventing high volatility and continuous depreciation of domestic currencies. Such measures can mitigate the long-term adverse effects of ER movements on trade agreements. The study offers valuable insights for policymakers and investors in developing economies, aiding them in making informed decisions about exchange rate policies.

Antitumor drugs effect on the stability of double-stranded DNA: steered molecular dynamics analysis

Denaturation of the DNA double helix inside the cell is essential for cellular processes such as replication and transcription for the growth of the cells. However, the growth of unwanted cells, which are responsible for cancerous kind of disease, is one of the biggest challenges of modern therapeutics. DNA cross-linking agents may kill cancer cells by damaging their DNA and stopping them from dividing. In the present study, we have carried out steered molecular dynamics simulations to study the effects of rupture and unzipping forces on the stability of dsDNA in the absence and presence of covalently bonded drugs. We have found that the stability of dsDNA increases strongly in the presence of covalently bonded drugs. The microscopic study of disruption of hydrogen-bonds associated with base-pairs of the dsDNA and the study of the variation of stacking overlap parameters gives evidence of symmetry during the rupture and asymmetry in the unzip event. The significance of the mechanism of force-induced melting study of the dsDNA in the absence and presence of antitumor drugs might have a biological relevance as it provides a pathway to open the double helix in a specific position and may help for the pharmaceutical design of drugs. Communicated by Ramaswamy H. Sarma

Direct Evidence of Symmetry between Bilateral Human Corneas in Biomechanical Properties: A Comparison Study with Fresh Corneal Tissue

Purpose. To investigate the difference between the eyes from the same human with respect to the biomechanical properties of fresh corneal tissues and investigate the assumption of similarity of the corneal biomechanical properties between the eyes. Methods. Strip specimens extracted through a small incision lenticule extraction (SMILE) surgery were tested using a uniaxial tensile test. The specimens were extracted vertically. Low-strain tangent modulus (LSTM), high-strain tangent modulus (HSTM), and tensile strength (σb) were the biomechanical parameters used in the comparison of the eyes from the same human. Results. Ninety corneal specimens from 45 persons were included in this study. The LSTM of the left and right eyes were 1.34 ± 0.52 and 1.37 ± 0.46 MPa, while the HSTM were 50.53 ± 7.51 and 49.41 ± 7.01 MPa, respectively. There was no significant difference between the eyes in terms of LSTM, HSTM, andσbP=0.813, 0.335, and 0.605, resp.. The LSTM and HSTM were significantly correlated with the spherical equivalent (SE) (P≤0.01, P=0.001, resp.). Conclusions. The assumption that the corneal biomechanical properties of the eyes from the same human are similar has been confirmed for the first time using fresh human corneal tissue. This finding may be useful in further biomechanical studies.

Evidence for Symmetry Breaking in the Ground State of the Si(111)‐7 × 7: The Origin of Its Metal–Insulator Transition

Evidence for Symmetry Breaking in the Ground State of the Si(111)‐7 × 7: The Origin of Its Metal–Insulator Transition

Neurobiology of developmental dyslexia: Part 1: A review of evidence from autopsy and structural neuro-imaging studies

Developmental dyslexia (DD) is a language-based neurological disorder which impairs readingability but does not result from low intelligence,lack of motivation, sensory impairment, or inadequate instruction. Although the neurological basisof dyslexia has long been assumed, the exact natureof the altered brain structure associated with DD remains unknown and has been a subject of autopsyand neuro-imaging research. Autopsy studies provide consistent evidence of symmetry of the planum temporale (PT), thalamus and cortical malformations, whereas results from structural imaging studies such as computed tomography (CT) and magnetic resonance imaging (MRI) are inconsistent. To address the possible etiology of DD, this paper reviews evidence from autopsy and structural imaging studies on developmental dyslexia and discusses possible methodological sources of some inconsistent results. The role of the optometrist in the multidisciplinary management of dyslexia is highlighted. (S Afr Optom 2011 70(4) 191-202)

Associative symmetry by pigeons after few-exemplar training.

The present experiment investigated whether pigeons can show associative symmetry on a two-alternative matching-to-sample procedure. The procedure consisted of a within-subject sequence of training and testing with reinforcement, and it provided (a) exemplars of symmetrical responding, and (b) all prerequisite discriminations among test samples and comparisons. After pigeons had learned two arbitrary-matching tasks (A-B and C-D), they were given a reinforced symmetry test for half of the baseline relations (B1-A1 and D1-C1). To control for the effects of reinforcement during testing, two novel, nonsymmetrical responses were concurrently reinforced using the other baseline stimuli (D2-A2 and B2-C2). Pigeons matched at chance on both types of relations, thus indicating no evidence for symmetry. These symmetrical and nonsymmetrical relations were then directly trained in order to provide exemplars of symmetry and all prerequisite discriminations for a second test. The symmetrical test relations were now B2-A2 and D2-C2 and the nonsymmetrical relations were D1-A1 and B1-C1. On this test, 1 pigeon showed clear evidence of symmetry, 2 pigeons showed weak evidence, and 1 pigeon showed no evidence. The previous training of all prerequisite discriminations among stimuli, and the within-subject control for testing with reinforcement seem to have set favorable conditions for the emergence of symmetry in nonhumans. However, the variability across subjects shows that methodological variables still remain to be controlled.

Evidence for symmetry in the elementary process of bidirectional torque generation by the bacterial flagellar motor

The bacterial flagellar motor can rotate in both counterclockwise (CCW) and clockwise (CW) directions. It has been shown that the sodium ion-driven chimeric flagellar motor rotates with 26 steps per revolution, which corresponds to the number of FliG subunits that form part of the rotor ring, but the size of the backward step is smaller than the forward one. Here we report that the proton-driven flagellar motor of Salmonella also rotates with 26 steps per revolution but symmetrical in both CCW and CW directions with occasional smaller backward steps in both directions. Occasional shift in the stepping positions is also observed, suggesting the frequent exchange of stators in one of the 11-12 possible anchoring positions around the rotor. These observations indicate that the elementary process of torque generation by the cyclic association/dissociation of the stator with every FliG subunit along the circumference of the rotor is symmetric in CCW and CW rotation even though the structure of FliG is highly asymmetric and suggests a 180° rotation of a FliG domain for the rotor-stator interaction to reverse the direction of rotation.

Symmetry of evidence without evidence of symmetry

The de Finetti Theorem is a cornerstone of the Bayesian approach. Bernardo (1996, p. 5) writes that its “message is very clear: if a sequence of observations is judged to be exchangeable, then any subset of them must be regarded as a random sample from some model, and there exists a prior distribution on the parameter of such model, hence requiring a Bayesian approach.” We argue that although exchangeability, interpreted as symmetry of evidence, is a weak assumption, when combined with subjective expected utility theory, it also implies complete confidence that experiments are identical. When evidence is sparse and there is little evidence of symmetry, this implication of de Finetti’s hypotheses is not intuitive. This motivates our adoption of multiple-priors utility as the benchmark model of preference. We provide two alternative generalizations of the de Finetti Theorem for this framework. A model of updating is also provided.

The Associations Between the Dominant and Nondominant Peak External Knee Adductor Moments During Gait in Healthy Subjects: Evidence for Symmetry

Teichtahl AJ, Wluka AE, Morris ME, Davis SR, Cicuttini FM. The associations between the dominant and nondominant peak external knee adductor moments during gait in healthy subjects: evidence for symmetry. Objectives There is growing interest in the role of the knee adduction moment in the pathogenesis of knee pain and osteoarthritis. It is unclear whether the knee adduction moment is similar between the dominant and nondominant legs during locomotion. This study examined whether asymmetry exists in the peak knee adductor moments during gait in healthy adults. Design Cross-sectional study. Setting Musculoskeletal Research Centre, La Trobe University, Melbourne, Victoria, Australia. Participants Three-dimensional Vicon gait analyses were performed for 17 healthy men and women. Interventions Not applicable. Main Outcome Measures The external dominant and nondominant peak knee adduction moments during early and late stance were analyzed to determine whether any significant differences occurred between limbs. Results Peak knee adductor moments for dominant and nondominant limbs were significantly correlated during early ( R=0.61, P=0.009) and late ( R=0.72, P=0.001) stance. After adjustment for age and sex, there was an associated 0.58 ( P=0.030) and 0.98 ( P=0.009) unit increase in the peak knee adduction moment in the nondominant leg, for every 1 unit increase in the dominant leg during the early and late stance phases of gait, respectively. Further evidence for symmetry was provided by the symmetry index, which was 0.04% and 0.62% for early and late stance, respectively. Conclusions In healthy subjects, the magnitude of the dominant limb peak external knee adduction moments during stance, and in particular late stance, appears representative of the magnitude of the moment in the nondominant limb. These findings imply symmetry between these moments and may have important implications when collecting data for limb analyses among healthy subjects. Whether gait symmetry protects against the onset of unilateral (or increases the risk for bilateral) pathological joint changes will need to be confirmed longitudinally.

Flexibility of Household Structure

Using data I collected in Africa, this paper examines a household's decision to adjust its size through child fostering, an institution where biological parents temporarily send children to live with other families. Households experiencing negative idiosyncratic income shocks, child gender imbalances, located further from primary schools, or with more good quality network members (fewer subsistence farmers and unmarried individuals and more educated members) are significantly more likely to send a child. Results reject an overall symmetric fostering model across senders and receivers, but evidence of symmetry is found when the test is restricted to exogenous income shocks and gender imbalances.

Flexibility of Household Structure: Child Fostering Decisions in Burkina Faso

Using data I collected in Africa, this paper examines a household's decision to adjust its size through child fostering, an institution where biological parents temporarily send children to live with other families. Households experiencing negative idiosyncratic income shocks, child gender imbalances, located further from primary schools, or with more "good" quality network members (fewer subsistence farmers and unmarried individuals and more educated members) are significantly more likely to send a child. Results reject an overall symmetric fostering model across senders and receivers, but evidence of symmetry is found when the test is restricted to exogenous income shocks and gender imbalances.

ASSOCIATIVE SYMMETRY, ANTISYMMETRY, AND A THEORY OF PIGEONS' EQUIVALENCE‐CLASS FORMATION

Five experiments assessed associative symmetry in pigeons. In Experiments 1A, 1B and 2, pigeons learned two-alternative symbolic matching with identical sample- and comparison-response requirements and with matching stimuli appearing in all possible locations. Despite controlling for the nature of the functional stimuli and insuring all requisite discriminations, there was little or no evidence for symmetry. By contrast, Experiment 3 demonstrated symmetry in successive (go/no-go) matching, replicating the findings of Frank and Wasserman (2005). In view of these results, I propose that in successive matching, (1) the functional stimuli are stimulus-temporal location compounds, (2) continual nonreinforcement of some sample-comparison combinationsjuxtaposed with reinforcement of other combinations throughout training facilitates stimulus class formation, (3) classes consist of the elements of the reinforced combinations, and (4) common elements produce class merger. The theory predicts that particular sets of training relations should yield "antisymmetry": Pigeons should respond more to a reversal of the nonreinforced symbolic baseline relations than to a reversal of the reinforced relations. Experiment 4 confirmed this counterintuitive prediction. These results and other theoretical implications support the idea that equivalence relations are a natural consequence of reinforcement contingencies.

Investigating business cycle asymmetry for the G7 countries: Evidence from over a century of data

In this paper we test for asymmetric behaviour of business cycles for the G7 countries, using the entropy-based test for asymmetry suggested by Racine and Maasoumi [Racine, J.S., & Maasoumi, E. (in press-a). A versatile and robust metric entropy test of time-reversibility, and other hypotheses, Journal of Econometrics; Racine, J.S., & Maasoumi, E. (in press-b). A robust entropy based test for asymmetry. Econometric Reviews.]. We find overwhelming evidence of symmetry. In only 14% of the cases, we find some evidence of asymmetric behaviour of GDP and per capita GDP. More importantly, the period marked by the flexible exchange rate regime, over which much of the empirical work for the G7 countries has been conducted, evidence suggests that the two GDP series are symmetric.

A Discrete-State Continuous-Time Model of Financial Transactions Prices and Times

Financial transaction prices typically lie on a discrete grid of values and arrive at random times. This paper proposes an econometric model with this structure. The distribution of each price change is a multinomial, conditional on past information and the time interval between the transactions. The proposed autoregressive conditional multinomial (ACM) model is not restricted to be Markov or symmetric in response to shocks; however, such restrictions can be imposed. The duration between trades is modeled as an autoregressive conditional duration (ACD) model following Engle and Russell (1998). Maximum likelihood estimation and testing procedures are developed. The model is estimated with 12 months of tick data on a moderately frequently traded NYSE stock, Airgas. The preferred model is estimated, with three lags for the ACM model and two lags for the ACD model. Both price returns and squared returns influence future durations and present and past durations affect price movements. The model exhibits reversals in transaction prices in the short run due to bid–ask bounce and clustering of large moves of either sign in the longer run. Evidence of symmetry in the dynamics of prices is seen, but the response to durations is clearly nonsymmetric. It is found that the volatility per second of trades is highest for short-duration trades and that expected returns are lower for longer-duration trades.

The Effect of Radiation on Pedicled TRAM Flap Breast Reconstruction: Outcomes and Implications

The purpose of this study was to examine the effect of postreconstruction radiation therapy on patients undergoing pedicled TRAM flap breast reconstruction. Post-TRAM radiation patients were compared with patients who received pre-TRAM radiation and a control TRAM-only group who received no radiation. Overall aesthetic appearance, evidence of symmetry, flap contracture, and hyperpigmentation were assessed by blinded reviewers. A total of 171 pedicled TRAM reconstructions were performed in 150 patients. Total flap complications were seen in 49.5 percent of the control patients, 57.1 percent of pre-TRAM radiation patients, and 50 percent of post-TRAM radiation patients but were not statistically different. The complete flap necrosis rate was 0.6 percent and the partial flap necrosis rate was 7.6 percent, again with no statistical differences among the groups. Donor-site complications occurred in approximately one third of patients in each of the groups. Deep venous thrombosis and pulmonary embolus each occurred once and only in the post-TRAM radiation group. In terms of overall aesthetic outcome, symmetry, and contracture, the control group consistently rated better than the pre-TRAM (p = 0.021, p = 0.03, p = 0.03, respectively) and the post-TRAM (p = 0.0001, p = 0.0001, and p =0.0001, respectively) radiation groups. The control group also had clinically and statistically significant less hyperpigmentation than the post-TRAM radiation group (p = 0.0002). In contrast, irradiated postreconstruction patients had scores, including aesthetic outcome, symmetry, and contracture, worse than those of irradiated prereconstruction patients. When these two groups were compared with each other, except for contracture, no statistical significance, because of a small patient sample, was found. Neither preoperative nor postoperative radiation increased the risk for flap or donor-site complications. In contrast, radiation of any type did affect aesthetic appearance, symmetry, contracture, and hyperpigmentation. The authors recommend that TRAM flap breast reconstruction be postponed in those patients known or expected to receive postmastectomy radiation.

Evidence of Symmetry in price behaviour

Evidence has been found of a relationship between gradients of consecutive bull and bear markets. The gradient of a major resistance trend line of a bear market can be derived from the resistance line of the preceding bull market. Similarly, a major support line of a bull market can be derived from a support line of the previous bear market. This phenomenon reveals a symmetrical relationship between the gradients of the resistance or support lines on either side of a trend reversal, i.e. of consecutive bull and bear trends.The relationship is inverse, as the gradient of the derived line is of opposite sign to that of the primary line. The magnitude of the new inverted gradient may be equal to that of the primary line, or it could differ by some multiple of the Fibonacci ratio.In practice, this relationship can be used to anticipate where a key reversal could occur during a new bull or bear market.The existence of a method to anticipate major reversals is of value for technical analysis, and is also likely to put new life into the debate on the Random Walk Hypothesis.

Evidence for symmetry in the phytochrome subunit

PHYTOCHROME is a chromoprotein that has been shown to initiate and control major developmental responses of plants to light1. It has two spectrally different forms that can be reversibly interconverted by light, as indicated: The spectral properties of phytochrome are sensitive to changes in the microenvironment of the covalently bound chromophore(s). Relatively mild denaturing treatments, such as incubation at 25 °C for over an hour2 and dehydration3, result in a significant loss of photoreversibility. In view of this susceptibility to spectral denaturation, it is remarkable that phytochrome can be proteolytically degraded to a molecular weight (MW) of 60,000, or half its native subunit size, without exhibiting any loss of photoreversibility or even any blue shift in its peak absorbance as Pr4. The additional fact that further proteolysis of phytochrome to 40,000 MW drastically reduces photoreversibility5 suggests that the 60,000 MW fragment has a sequence and configuration that are both sufficient and necessary to preserve photoreversibility. It is not clear whether this fragment is the product of one or more centrally located cleavages of the native subunit to yield two pieces of MW near 60,000 per native subunit or whether it is the product of extensive proteolysis which yields a single 60,000 MW fragment per native subunit. We have compared the amino acid composition and the peptide map of the proteolytically-derived 60,000 MW fragment with those of the native 120,000 MW subunit. Our results strongly support the conclusion that the native 120,000 MW subunit is composed of two halves with nearly identical sequences.