Xie Model Research Articles

A study protocol of external validation of eight COVID-19 prognostic models for predicting mortality risk in older populations in a hospital, primary care, and nursing home setting

BackgroundThe COVID-19 pandemic has a large impact worldwide and is known to particularly affect the older population. This paper outlines the protocol for external validation of prognostic models predicting mortality risk after presentation with COVID-19 in the older population. These prognostic models were originally developed in an adult population and will be validated in an older population (≥ 70 years of age) in three healthcare settings: the hospital setting, the primary care setting, and the nursing home setting.MethodsBased on a living systematic review of COVID-19 prediction models, we identified eight prognostic models predicting the risk of mortality in adults with a COVID-19 infection (five COVID-19 specific models: GAL-COVID-19 mortality, 4C Mortality Score, NEWS2 + model, Xie model, and Wang clinical model and three pre-existing prognostic scores: APACHE-II, CURB65, SOFA). These eight models will be validated in six different cohorts of the Dutch older population (three hospital cohorts, two primary care cohorts, and a nursing home cohort). All prognostic models will be validated in a hospital setting while the GAL-COVID-19 mortality model will be validated in hospital, primary care, and nursing home settings. The study will include individuals ≥ 70 years of age with a highly suspected or PCR-confirmed COVID-19 infection from March 2020 to December 2020 (and up to December 2021 in a sensitivity analysis). The predictive performance will be evaluated in terms of discrimination, calibration, and decision curves for each of the prognostic models in each cohort individually. For prognostic models with indications of miscalibration, an intercept update will be performed after which predictive performance will be re-evaluated.DiscussionInsight into the performance of existing prognostic models in one of the most vulnerable populations clarifies the extent to which tailoring of COVID-19 prognostic models is needed when models are applied to the older population. Such insight will be important for possible future waves of the COVID-19 pandemic or future pandemics.

On the Physical Layer Security Peculiarities of Wireless Communications in the Presence of the Beaulieu-Xie Shadowed Fading

The article presents an analysis of the physical layer security of a wireless communication system functioning in the presence of multipath fading and a wiretap. Under the assumption of the equal propagation conditions (both for the legitimate receiver and the eavesdropper) described by the shadowed Beaulieu–Xie model, a closed-form expression for the secrecy outage probability was derived. The correctness of the obtained expression was numerically verified via comparison with the direct numerical integration. The truncated version of the obtained expression was analyzed for various channel parameters to establish the requirements for numerically efficient implementation (in terms of the number of summands delivering the desired precision). An in-depth study of the secrecy outage probability dependence from all the possible channel parameters for different fading scenarios was performed, including heavy fading and light fading, with and without strong dominant and multipath components. The performed research demonstrated the existence of the secrecy outage probability non-uniqueness with the respect to the average signal-to-noise ratio in the main channel and the relative distance between the legitimate and wiretap receivers.

Regional performance variation in external validation of four prediction models for severity of COVID-19 at hospital admission: An observational multi-centre cohort study.

BackgroundPrediction models should be externally validated to assess their performance before implementation. Several prediction models for coronavirus disease-19 (COVID-19) have been published. This observational cohort study aimed to validate published models of severity for hospitalized patients with COVID-19 using clinical and laboratory predictors.MethodsPrediction models fitting relevant inclusion criteria were chosen for validation. The outcome was either mortality or a composite outcome of mortality and ICU admission (severe disease). 1295 patients admitted with symptoms of COVID-19 at Kings Cross Hospital (KCH) in London, United Kingdom, and 307 patients at Oslo University Hospital (OUH) in Oslo, Norway were included. The performance of the models was assessed in terms of discrimination and calibration.ResultsWe identified two models for prediction of mortality (referred to as Xie and Zhang1) and two models for prediction of severe disease (Allenbach and Zhang2). The performance of the models was variable. For prediction of mortality Xie had good discrimination at OUH with an area under the receiver-operating characteristic (AUROC) 0.87 [95% confidence interval (CI) 0.79–0.95] and acceptable discrimination at KCH, AUROC 0.79 [0.76–0.82]. In prediction of severe disease, Allenbach had acceptable discrimination (OUH AUROC 0.81 [0.74–0.88] and KCH AUROC 0.72 [0.68–0.75]). The Zhang models had moderate to poor discrimination. Initial calibration was poor for all models but improved with recalibration.ConclusionsThe performance of the four prediction models was variable. The Xie model had the best discrimination for mortality, while the Allenbach model had acceptable results for prediction of severe disease.

Applicability of two satellite-based precipitation products for assessing rainfall erosivity in China

Soil erosion has become one of the most serious environmental problems worldwide, and rainfall is considered a crucial factor in water erosion. Rainfall erosivity is defined as the ability of precipitation to trigger soil erosion. The accurate assessment of rainfall erosivity is essential before taking appropriate measures to stop or slow down water erosion. In this study, we calculated the rainfall erosivity in China using the Xie model and two satellite-based precipitation products (SPPs). Gauge-based data from 2417 stations in China were used for a comparison of the results. We also proposed a procedure to assess the performance of the two SPPs using four statistical metrics and provided recommendations for different sub-regions at different time scales. The results showed that the annual rainfall erosivity based on the IMERG-F and TMPA 3B42-V7 products and the in situ gauge stations were 2014, 1954, and 2138 MJ·mm/(hm2·h·yr), respectively. The spatial correlation between IMERG-F and situ gauge stations is 0.944 and that between the TMPA 3B42-V7 product and situ gauge stations is 0.909. The variation trends of the two were highly similar to those of the gauge-based rainfall erosivity at all time scales. The TMPA 3B42-V7 product is recommended for estimating rainfall erosivity in Haihe River Basin and Huaihe River Basin at monthly scale, in Haihe River Basin and China at seasonal scale, in the Haihe River Basin, Huaihe River Basin, Yellow River Basin at annual scale; while the IMERG-F is recommended for the remaining regions except Continental Basins at the three time scales. Generally, the IMERG-F has broader applicability than the TMPA 3B42-V7 product for estimating rainfall erosivity in China. The results of this study provide a reference for selecting suitable SPPs for rainfall erosivity estimates.

An Adapted Chronic Constriction Injury of the Sciatic Nerve Produces Sensory, Affective, and Cognitive Impairments: A Peripheral Mononeuropathy Model for the Study of Comorbid Neuropsychiatric Disorders Associated with Neuropathic Pain in Rats.

Chronic constriction injury (CCI) is a model of neuropathic pain induced by four loose ligatures around the sciatic nerve. This work aimed to investigate the sensory, affective, cognitive, and motor changes induced by an adaptation of the CCI model by applying a single ligature around the sciatic nerve. Mechanical allodynia was measured from day 1 to day 28 postsurgery by the von Frey test. The beam walking test (BWT) was conducted weekly until 28 days after surgery.Anxiety- and depression-like behaviors, and cognitive performance were assessed through the open field (OF), forced swimming (FS), and novel object recognition (NOR) tests, respectively, 21 days after surgery. The two CCI models, both Bennett and Xie's model (four ligatures of the sciatic nerve) and a modification of it (one ligature), induced mechanical allodynia, increased immobility in the FS, and reduced recognition index in the NOR. The exploratory behavior and time spent in the central part of the arena decreased, while the defensive behavior increased in the OF. The animals subjected to the two CCI models showed motor alterations in the BWT; however, autotomy was observed only in the group with four ligatures and not in the group with a single ligature. Overall these results demonstrate that our adapted CCI model, using a single ligature around the sciatic nerve, induces sensory, affective, cognitive, and motor alterations comparable to the CCI model with four ligatures without generating autotomy. This adaptation to the CCI model may therefore represent an appropriate and more easily performed model for inducing neuropathic pain and study underlying mechanisms and effective treatments.

Reexamination of the Xie model and spatiotemporal variability in rainfall erosivity in mainland China from 1960 to 2018

Soil erosion has become one of the most serious global environmental and ecological crises. Rainfall erosivity measures the potential ability of precipitation to trigger soil erosion. This study estimated the degree of rainfall erosivity in mainland China from 1960 to 2018 using the Xie model and analyzed its spatiotemporal variability. The accuracy of the Xie model was reexamined and further verified with the use of data from densely distributed stations by comparing it with two typical daily models and an hourly model. The relationships between changes in rainfall erosivity and soil erosion were also discussed. Results showed that annual rainfall erosivity in mainland China ranged from 2 to 23,129 MJ⋅mm/(hm2⋅h⋅a) and decreased gradually from southeast to northwest. Annual rainfall erosivity also showed a significant increasing trend (P < 0.05) with a mean value of 3738 MJ⋅mm/(hm2⋅h⋅a) and a growth rate of 8 MJ·mm/((hm2·h·a)·a). The significant breakpoint (P < 0.05) occurred in 2002. Multiple oscillation periods were identified, but 3.5 years was identified as the main oscillation period. The Xie model was shown to be more accurate for estimating rainfall erosivity in mainland China because of its simple formula, which reduces computing time and the effort needed to make calculations. Therefore, the Xie model provides a robust daily model that could be widely used in mainland China. Although annual precipitation has reduced, the increasing concentration and intensity of precipitation appears to be the primary reason underlying the increase in rainfall erosivity. Efficient, economic, and environmental measures need to be taken to address some of the challenges of soil conservation in mainland China.

Indomethacin attenuates mechanical allodynia during the organization but not the maintenance of the peripheral neuropathic pain induced by nervus ischiadicus chronic constriction injury.

The neurochemical mechanisms underlying neuropathic pain (NP) are related to peripheral and central sensitization caused by the release of inflammatory mediators in the peripheral damaged tissue and ectopic discharges from the injured nerve, leading to a hyperexcitable state of spinal dorsal horn neurons. The aim of this work was to clarify the role played by cyclooxygenase (COX) in the lesioned peripheral nerve in the development and maintenance of NP by evaluating at which moment the non-steroidal anti-inflammatory drug indomethacin, a non-selective COX inhibitor, attenuated mechanical allodynia after placing one loose ligature around the nervus ischiadicus, an adaptation of Bennett and Xie's model in rodents. NP was induced in male Wistar rats by subjecting them to chronic constriction injury (CCI) of the nervus ischiadicus, placing one loose ligature around the peripheral nerve, and a sham surgery (without CCI) was used as control. Indomethacin (2 mg/kg) or vehicle was intraperitoneally and acutely administered in each group of rats and at different time windows (1, 2, 4, 7, 14, 21, and 28 days) after the CCI or sham surgical procedures, followed by von Frey's test for 30 min. The data showed that indomethacin decreased the mechanical allodynia threshold of rats on the first, second, and fourth days after CCI (P<0.05). These findings suggested that inflammatory mechanisms are involved in the induction of NP and that COX-1 and COX-2 are involved in the induction but not in the maintenance of NP.

Effect of hangebyakujutsutemmato on pregabalin‐induced dizziness in a rat model of neuropathic pain

ABSTRACTAimThis study investigated the efficacy of hangebyakujutsutemmato (HBT) in alleviating disturbances of equilibrium using a rat pregabalin model of neuropathic pain with dizziness. Pregabalin is effective for treating neuropathic pain, but some patients cannot tolerate continued treatment owing to dizziness resulting from pregabalin, especially shortly after beginning treatment. HBT is a Japanese kampo medicine that is used to treat dizziness.MethodsRats with chronic constriction injury of the sciatic nerve (Bennett and Xie model) underwent the beam balance test to evaluate their sense of equilibrium. The animals were divided into four groups, as follows: pregabalin (50 mg/kg) + HBT (1 g/kg; PH), n = 8; pregabalin (50 mg/kg; P), n = 8; HBT (1 g/kg; H), n = 8; and water (N), n = 8. Pregabalin and HBT treatments were initiated 9 days following injury.ResultsOn postoperative day 10 (POD10), the day after starting drug treatment, there was a significant difference in the crossing time between PH and P (P &lt; 0.01). The crossing time in group P recovered to a level similar to the other groups on POD16.ConclusionHBT alleviated the disturbance of equilibrium resulting from pregabalin in a rat model of neuropathic pain. This suggests that HBT may also alleviate dizziness and/or accelerate recovery from dizziness due to pregabalin treatment in humans.

A New Methodological Approach for Studying Intergenerational Mobility with an Application to Swiss Data

Despite the widespread interest in the topic and a vast international literature, very little is known about the development of intergenerational mobility in Switzerland. Based on a new harmonized database for Switzerland (comprising various surveys such as different waves of the ISSP, EVS, and the ESS), we provide a systematic account of changes in the link between social origin and destination over time (covering birth cohorts from around 1935 to 1980). We analyze effects of parental education and class on own educational achievement and social class for both men and women, using a refined variant of the methodological approach proposed by Jann and Combet (2012). The approach is based on the concept of proportional reduction of error (PRE) and features a number of advantages over more traditional approaches. For example, it provides smooth estimates of changes in social mobility that have a clear interpretation and it can easily incorporate control variables and multiple dimensions of parental characteristics. To evaluate the validity of our approach, we employ the oft-used log-multiplicative layer effect (a.k.a Unidiff) model (Xie 1992, Erikson and Goldthorpe 1992) as a benchmark. Results indicate that our approach performs well and produces qualitatively similar findings as Xie's model. For both men and women, effects of social origin initially decreased, but then, towards the end of the observation period, increased again. This u-shaped pattern, which can be observed with respect to both education and class, appears to be more pronounced for women than for men.

An improved experimental model for peripheral neuropathy in rats

A modification of the Bennett and Xie chronic constriction injury model of peripheral painful neuropathy was developed in rats. Under tribromoethanol anesthesia, a single ligature with 100% cotton glace thread was placed around the right sciatic nerve proximal to its trifurcation. The change in the hind paw reflex threshold after mechanical stimulation observed with this modified model was compared to the change in threshold observed in rats subjected to the Bennett and Xie or the Kim and Chung spinal ligation models. The mechanical threshold was measured with an automated electronic von Frey apparatus 0, 2, 7, and 14 days after surgery, and this threshold was compared to that measured in sham rats. All injury models produced significant hyperalgesia in the operated hind limb. The modified model produced mean ± SD thresholds in g (19.98 ± 3.08, 14.98 ± 1.86, and 13.80 ± 1.00 at 2, 7, and 14 days after surgery, respectively) similar to those obtained with the spinal ligation model (20.03 ± 1.99, 13.46 ± 2.55, and 12.46 ± 2.38 at 2, 7, and 14 days after surgery, respectively), but less variable when compared to the Bennett and Xie model (21.20 ± 8.06, 18.61 ± 7.69, and 18.76 ± 6.46 at 2, 7, and 14 days after surgery, respectively). The modified method required less surgical skill than the spinal nerve ligation model.

Price Convergence and Forecasting Returns by V/P Ratio: Evidences from TSE

Aims: This study investigates the convergence of prices to fundamental value of stocks to deepen the insights of investors about the market mechanisms. The paper checks the value relevance of accounting and financial reporting information and addresses the usefulness of V/P ratio as a good predictor of stock returns which can be exploited by analysts. Study Design: The study design consist of the following steps: Fundamental value estimation, Calculating the V/P ratio, Classification of the sample based on Johnson and Xie Model (2004), Normal and abnormal return calculation, Factorial correlation analysis. Place and Duration of Study: The society consists of all the firms accepted in TSE from 2002 through 2010 which the sample (consist of 87 firms) has been selected by some restrictions. Methodology: This paper introduces the concept of Convergence of prices to fundamental based on Johnson & Xie model (2004) and tests its predicting ability. This is an applied research utilizing correlation and regression methods to describe the variables and the relations. Results: The Findings support the prediction ability of V/P ratio with respect to long-run normal and abnormal returns. Also, the results show the return accumulation in price convergence subgroup of sample; say that the primary source of this abnormal return is the convergence of prices to fundamental values of stocks. The correlation between accounting and financial reporting information with market prices has been evident, too. Conclusion: The results support the value relevance of accounting book values for fundamental value estimations and the prediction ability of V/P ratio especially in long-run Research Article Moradi; JSRR, Article no. JSRR.2013.027

Effect of aging on the substance P receptor, NK–1, in the spinal cord of rats with peripheral nerve injury

Substance P (SP) levels in the spinal cords of very old rats are less than the levels in younger rats (Bergman et al., 1996). After injury to a peripheral nerve in young rats, immunoreactivity (ir) to the SP receptor, NK–1 (neurokinin-1), increases in the spinal cord ipsilateral to the injury and the increases are correlated with the development of thermal hyperalgesia (Goff et al., 1998). Thus we postulated that aged rats might display an increased sensitivity to thermal stimulation before peripheral nerve injury and that they might respond differently to injury than do younger rats. To test this hypothesis, we used the Bennett and Xie model (1988) of chronic constriction injury (CCI) to the sciatic nerve to induce a neuropathic pain condition. We investigated the effect of age on changes in NK-1 ir in superficial layers of the dorsal horn and on numbers of NK ir cells in deeper laminae at the L4-L5 levels of the spinal cord after CCI. NK-1 receptors were tagged immunohistochemically and their distribution quantified by use of computer-assisted image analysis. NK-1 ir changes were related to alterations in thermal and tactile sensitivity that developed after CCI in young, mature and aged (4-6, 14-16, and 24-26 months) Fischer F344 BNF1 hybrid rats. No differences in thermal or tactile sensitivity of young and aged rats were seen in the absence of nerve injury. After injury, aged rats developed thermal hyperalgesia and tactile allodynia more slowly than did the younger rats. NK-1 receptor ir and numbers of NK-1 ir cells in the dorsal horn increased with time post-injury in all three groups. NK-1 ir increases were correlated with the development of thermal hyperalgesia in those rats that displayed hyperalgesia. However, some rats developed an increased threshold to thermal stimuli (analgesia) and that also was correlated with increases in NK-1 ir. Thus NK-1 ir extent, while correlated with thermal sensitivity in the absence of injury, is not a specific marker for disturbances in one particular sensory modality; rather it increases with peripheral nerve injury per se.

Changes in Spinal Serotonin Turnover Mediate Age-Related Differences in the Behavioral Manifestations of Peripheral Nerve Injury

The Bennett and Xie model of peripheral nerve injury was used to study the effects of aging on the onset and progression of sciatic nerve ligation (SNL)-induced thermal hyperalgesia and tactile-evoked allodynia in young, mature, and aged Fischer 344 FBNF1 male rats (4–6, 14–16, and 24–26 months old, respectively). A plantar analgesia meter and calibrated von Frey pressure filaments were employed as the analgesiometric assays. In the absence of nerve injury, aged rats were found to be more sensitive than younger animals to noxious thermal stimuli. Following the SNL surgery, thermal hyperalgesia was observed in all three age groups within 3 days. On post-SNL day 35, the paw-withdrawal latency values of the young and mature animals returned to presurgical baseline levels, while the aged rats continued to exhibit thermal hyperalgesia. Tactile-evoked allodynia was apparent within 3 days following peripheral nerve injury in the oldest cohort, but was delayed in the younger animals. On post-SNL days 0 (control), 3, 21, and 35, young, mature, and aged rats were sacrificed and high-performance liquid chromatography and electrochemical detection (HPLC/ECD) methods were used for neurochemical analyses of spinal serotonin (5-HT), norepinephrine (NE), and 5-hydroxyindoleacetic acid (5-HIAA). Spinal 5-HT and NE levels were not significantly altered by the aging process, nor were they affected by peripheral nerve injury. However, spinal 5-HT turnover from the aged animals was greater than that detected in spinal tissue from the younger counterparts. Differences in spinal 5-HT turnover may contribute to age-related variability in spinal nociceptive processing.

Possible analgesic effect of vigabatrin in animal experimental chronic neuropathic pain.

Since anticonvulsants have been used for treating neuralgias, an interest has arisen to experimentally test vigabatrin for its gabaergic mechanism of action. For this, 41 Wistar rats were used, and in 25 of them a constrictive sciatic neuropathy was induced (Bennet & Xie model). For testing pain symptoms, spontaneous (scratching) and evoked behaviors to noxious (46 degrees C) and non-noxious (40 degrees C) thermal stimuli were quantified. Moreover, a comparative pharmacological study of vigabatrin with other analgesic anticonvulsant drugs was also performed. The results showed a possible dose-dependent analgesic effect of vigabatrin (gamma-vinyl-GABA) on experimental neuropathic pain, as shown by the significant (p < 0.05) decreasing effect of vigabatrin on scratching and by its significant (p < 0.05) increasing effect on the latency of the right hindpaw withdrawal of the animals to noxious thermal stimulus. This was corroborated by similar findings with analgesic anticonvulsants (carbamazepine, phenytoin and valproic acid). This possible and not yet described analgesic effect of vigabatrin seems not to be opioid mediated.

Role of Nitric Oxide in the Development of Thermal Hyperesthesia Induced by Sciatic Nerve Constriction Injury in the Rat

Nitric oxide (NO) has been shown to be involved in mediating nociceptive information transmission in the spinal cord. It is known that the N-methyl-D-aspartate receptor plays an important role in the development of the spinal facilitation evoked by a protracted small afferent input and that this effect is mediated at least in part by NO. Recently, it has been found that N-methyl-D-aspartate receptor-mediated spinal facilitation is crucial in the development of thermal hyperesthesia evoked by a nerve constriction injury. In the current study, we investigated the role of NO in the development of thermal hyperesthesia after a nerve constriction injury. The Bennett and Xie model (four loose chromic gut ligations around the rat sciatic nerve) was used to examine the development of thermal hyperesthesia. An NO synthase inhibitor (N omega-nitro-L-arginine or N omega-nitro-L-arginine methyl ester hydrochloride), rat hemoglobin, or L-arginine was administered intrathecally 10 min before the nerve injury (pretreatment study) or 15 min after the nerve injury (posttreatment study). Pretreatment but not posttreatment administration of NO synthase inhibitor significantly delayed the development of thermal hyperesthesia. The effect of NO synthase inhibitor was reversed by the coadministration of L-arginine but not by the coadministration of D-arginine. Pretreatment with rat hemoglobin also delayed the development of thermal hyperesthesia. L-Arginine itself had no effect on the development of thermal hyperesthesia. NO may play an important role in the development of N-methyl-D-aspartate receptor-mediated spinal facilitation after a nerve constriction injury.