1,003 research outputs found
Forecasting unstable processes
Previous analysis on forecasting theory either assume knowing the true
parameters or assume the stationarity of the series. Not much are known on the
forecasting theory for nonstationary process with estimated parameters. This
paper investigates the recursive least square forecast for stationary and
nonstationary processes with unit roots. We first prove that the accumulated
forecast mean square error can be decomposed into two components, one of which
arises from estimation uncertainty and the other from the disturbance term. The
former, of the order of , is of second order importance to the latter
term, of the order T. However, since the latter is common for all predictors,
it is the former that determines the property of each predictor. Our theorem
implies that the improvement of forecasting precision is of the order of
when existence of unit root is properly detected and taken into
account. Also, our theorem leads to a new proof of strong consistency of
predictive least squares in model selection and a new test of unit root where
no regression is needed. The simulation results confirm our theoretical
findings. In addition, we find that while mis-specification of AR order and
under-specification of the number of unit root have marginal impact on
forecasting precision, over-specification of the number of unit root strongly
deteriorates the quality of long term forecast. As for the empirical study
using Taiwanese data, the results are mixed. Adaptive forecast and imposing
unit root improve forecast precision for some cases but deteriorate forecasting
precision for other cases.Comment: Published at http://dx.doi.org/10.1214/074921706000000969 in the IMS
Lecture Notes Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
Physiological Electrical Signals Promote Chain Migration of Neuroblasts by Up-Regulating P2Y1 Purinergic Receptors and Enhancing Cell Adhesion
Acknowledgments This work was supported by a grant from NHS Grampian. Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are creditedPeer reviewedPublisher PD
Investigation of Landslides and Debris Flows in Tachia Watershed Between Maan Dam and Techi Dam
The Chi-Chi earthquake and subsequent typhoon events induced severe landslides and debris flows in the watershed of Tachia river. It inflicted severe damage to the power generation facilities and highway links. For the rehabilitation planning, quantitative assessment of landslides, debris flows and river deposits were conducted by using aerial photos and satellite images obtained at six stages of earthquake and typhoon events. The future trends of landslide and debris flow were also investigated by using empirical models. The long-term deposition or scouring was also conducted by numerical simulation. The results show that over 50,000,000 to 70,000,000m3 of sliding volume were induced in the Chi-Chi earthquake and subsequent typhoon events during 1999 to 2005. By conservative estimation, 60% of the debris still remain in the watershed, which will cause silting of the main river channel in the future. The deposition in the main river channel will increase with decreasing rate in the future, and river channel scouring is not expected to occur in the future 20 to 30 years
Toward optimal multistep forecasts in non-stationary autoregressions
This paper investigates multistep prediction errors for non-stationary
autoregressive processes with both model order and true parameters unknown. We
give asymptotic expressions for the multistep mean squared prediction errors
and accumulated prediction errors of two important methods, plug-in and direct
prediction. These expressions not only characterize how the prediction errors
are influenced by the model orders, prediction methods, values of parameters
and unit roots, but also inspire us to construct some new predictor selection
criteria that can ultimately choose the best combination of the model order and
prediction method with probability 1. Finally, simulation analysis confirms the
satisfactory finite sample performance of the newly proposed criteria.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ165 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
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Investigations of urethral sphincter activity in mice with bladder hyperalgesia before and after drug administration of gabapentin.
PurposeThis study investigated the effect of gabapentin on lower urinary tract dysfunction focusing on urethral activities and cystitis-induced hyperalgesia in a mouse model of painful bladder syndrome/interstitial cystitis (PBS/IC). The electromyography (EMG) of external urethral sphincter (EUS) was difficult to obtain, but contained useful information to examine the drug effect in mice.MethodsFemale C57BL/6J mice were intraperitoneally (ip) administration with either saline or 200 mg/kg of cyclophosphamide (CYP) 48 h before experimental evaluation. Cystitis mice were treated with administration of gabapentin (25 or 50 mg/kg, ip). Cystometry and EUS EMG were obtained and analyzed during continuous bladder infusion. The visceral pain-related visceromotor reflex (VMR) was recorded in response to isotonic bladder distension.ResultsCystitis mice showed shorter inter-contraction intervals and increased occurrence of non-voiding contractions during bladder infusion, with increased VMR during isotonic bladder distension, indicating cystitis-induced bladder hyperalgesia. Gabapentin (50 mg/kg) suppressed effects of CYP on cystometry, but not on EUS EMG activity, during bladder infusion. The effect on urodynamic recordings lasted 4 h. VMR was significantly reduced by gabapentin.ConclusionsThe present study showed that CYP-induced cystitis in mice is a model of visceral hyperalgesia affecting detrusor contractions, not urethral activations. The technique of using EUS EMG to evaluate the drug effects on urethral activities is novel and useful for future investigations. Gabapentin can be as a potential treatment for detrusor overactivity and PBS/IC
The prognostic factors for locally advanced cervical cancer patients treated by intensity-modulated radiation therapy with concurrent chemotherapy
Background/PurposeTo identify the prognostic factors for locally advanced cervical cancer patients treated by intensity-modulated radiotherapy (IMRT) and concurrent cisplatin-based chemotherapy.MethodsA total of 125 patients with stage IB2āIII cervical carcinoma were treated with IMRT and concurrent cisplatin-based chemotherapy, plus high dose rate (HDR) brachytherapy between January 2004 and November 2010, in our institution. All patients received external irradiation of 45ā54Ā Gy with the IMRT technique and concurrent cisplatin-based chemotherapy monthly or weekly. HDR brachytherapy of 20ā30.5Ā Gy was prescribed to point A, as a local boost. Prognostic factors including age, histology, stage, lymph nodes metastasis, pretreatment hemoglobin level, serum squamous cell carcinoma antigen (serum SCC-Ag), chemotherapy regimens and the cumulative dose of weekly cisplatin, were analyzed. The endpoints were overall survival (OS), local failure-free survival (LFFS) and disease-free survival (DFS).ResultsThe median follow-up time was 42 months. The 4-year OS, LFFS and DFS were 73.8%, 77.9% and 67.2%, respectively. Four (3.2%) patients developed ā„grade 3 acute gastrointestinal (GI) toxicity and 29 (23.2%) patients developed ā„grade 3 acute hematological toxicity. Five (4.0%) patients developed ā„grade 3 late GI toxicity and seven (5.6%) patients developed ā„grade 3 late genitourinary system toxicity. On univariate analysis, adenocarcinoma was a poor prognostic factor for OS (pĀ =Ā 0.05), LFFS (pĀ =Ā 0.01) and DFS (pĀ =Ā 0.006). Patients with lymph nodesĀ metastasis at diagnosis had worse OS (pĀ =Ā 0.02). The high cumulative dose of cisplatin (>180Ā mg/m2) had better OS (pĀ =Ā 0.03) and tended to have better survival on LFFS (pĀ =Ā 0.13) and DFS (pĀ =Ā 0.10). On multivariate analysis, adenocarcinoma was a significant independent prognostic factor for OS (pĀ =Ā 0.001), LFFS (pĀ =Ā 0.005) and DFS (pĀ <Ā 0.001). Initial lymph nodes metastasis was an independent predictor of OS (pĀ =Ā 0.013). Cumulative dose of weekly cisplatin significantly affected OS (pĀ =Ā 0.041), and high cumulative dose of cisplatin tended to have better LFFS (pĀ =Ā 0.083). Higher pretreatment hemoglobin level had better LFFS (pĀ =Ā 0.034).ConclusionAdenocarcinoma and lymph nodes metastases were poor prognostic factors for patients with locally advanced cervical cancer. Lower pretreatment hemoglobin level had poorer local control. Chemotherapy with a high cumulative dose of cisplatin tended to result in better survival
Association of p53 Codon 72 Polymorphism with Risk of Hypopharyngeal Squamous Cell Carcinoma in Taiwan
Backgroundp53 polymorphism at codon 72 is a known risk marker for various malignancies, but it has not been studied in hypopharyngeal cancer. This study investigated the genotype distribution of p53 codon 72 polymorphism in hypopharyngeal cancer patients and non-cancer controls matched for age, gender, alcohol consumption and smoking habit.MethodsGenomic DNA was extracted from peripheral blood cells of 53 patients with hypopharyngeal cancer and 53 non-cancer controls. Codon 72 polymorphism of p53 was identified by polymerase chain reaction-restriction fragment length polymorphism.ResultsPatients with hypopharyngeal cancer had higher frequencies of Pro/Pro (26.4% vs. 13.2%) and Pro/Arg (51.0% vs. 45.3%) but lower frequencies of Arg/Arg (22.6% vs. 45.1%) compared to controls. Compared to Arg/Arg genotypes, Pro/Pro genotypes had a relative risk of hypopharyngeal cancer of 3.667 (95% confidence interval, 1.16-11.56; p = 0.03). As a group, patients with Pro/Pro or Arg/Pro who were carriers of the Pro allele had a higher relative risk of hypopharyngeal cancer compared to Arg homozygous carriers (odds ratio, 2.415; 95% confidence interval, 1.04-5.64; p = 0.04).ConclusionThis study demonstrated that p53 codon 72 Pro homozygosity is associated with a higher risk of developing hypopharyngeal cancer
Comparison of clinical outcomes and toxicity in endometrial cancer patients treated with adjuvant intensity-modulated radiation therapy or conventional radiotherapy
PurposeTo evaluate the treatment outcomes and toxicity in endometrial cancer patients treated with hysterectomy and adjuvant intensity-modulated radiation therapy (IMRT) or conventional radiotherapy (CRT).MethodsThere were 101 patients with stage IA-IIIC2 endometrial carcinoma treated with hysterectomy and adjuvant radiotherapy. In total, 36 patients received adjuvant CRT and 65 were treated with adjuvant IMRT. The endpoints were overall survival, local failure-free survival, and disease-free survival. Patients were assessed for acute toxicity weekly according to the Common Terminology Criteria for Adverse Events version 3.0. Late toxicity was evaluated according to the Radiation Therapy Oncology Group and the European Organization for Research and Treatment of Cancer Late Radiation Morbidity Scoring Schema.ResultsThe 5-year overall survival, local failure-free survival, and disease-free survival for the CRT group and the IMRT group were 82.9% versus 93.5% (pĀ =Ā 0.26), 93.7% versus 89.3% (pĀ =Ā 0.68), and 88.0% versus 82.8% (pĀ =Ā 0.83), respectively. Four (11.1%) patients had Grade 3 or greater acute gastrointestinal (GI) toxicity and three (8.3%) patients had Grade 3 or greater acute genitourinary (GU) toxicity in the CRT group, whereas four (6.2%) patients had Grade 3 or greater acute GI toxicity in the IMRT group and no patient had severe GU toxicity. There was one (2.8%) patient who had Grade 3 or greater late GI toxicity and one (2.8%) patient had Grade 3 or greater late GU toxicity in the CRT group, whereas no patient had severe GI or GU toxicity in the IMRT group.ConclusionAdjuvant IMRT for endometrial cancer patients had comparable clinical outcomes with CRT and had less acute and late toxicity
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