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Current developments in signal processing are allowing for enhanced seismic illustrations and investigation of subsurface structures. Recently, Empirical Mode Decomposition (EMD) and Continuous Wavelet Transformation (CWT) have been introduced to extract various features from a time series dataset. In this investigation, seismic signal with 10% Gaussian noise is transformed into sub-signals by EMD analysis to improve the Signal-to-Noise Ratio (SNR). Then, CWT is implemented for each sub-signal to identify the exact locations of seismic reflections. The main objective of this study is to utilize the EMD as a noise filter in the time-domain and CWT to recognize the anomalous zone in each sub-signal. Based on the results of EMD and CWT, the true representation of a seismic signal with minimum noise in the time domain has been achieved. The successful integration of EMD and CWT is achieved in terms of the identification of true seismic reflections as localized anomalous zones at 0.8 sec, 1 sec, and 1.07 sec.

Rock physics has proven its credibility for the quantitative seismic interpretation of reservoir and reservoir characterization. In this study, we implemented K-means clustering to group data points more objectively and without prior misconceptions into clusters. Furthermore, we used the grouping suggested by the algorithm for our study. We integrated rock physics and K-means cluster analysis to determine a possible hydrocarbon reservoir using three well logs data. Initially, K-means clustering was implemented on density logs and based on the arithmetic mean of each density log cluster, sandstone and shale-dominant parts were identified and separated. Then, rock physics parameters were computed for the sandstone-dominant part of the well logs. Based on the cross-plots of Lame’s constants with density product, and Lame’s constants ratio, additional lithology discrimination was done for the identification of a clean gas-sand zone. In the clean gas-sand zone, two different pore fluids zones were identified based on Vp/Vs ratio, Poisson ratio, P- and S-wave impedances. Finally, statistical analysis was carried out to observe the underlying frequency distribution of rock physics parameters. The integration of cluster analysis and rock physics gave us significant information about the presence of different fluids and the existence of a potential hydrocarbon reservoir.

Continuous wavelet transformation (CWT) as a new mathematical tool has provided deep insights for the identification of localized anomalous zone in the time series data set. In this study, a three-layer geological model is investigated by CWT to locate seismic reflections temporally and spatially. This model consists of three layers, where the third layers of the anticline structure are assumed to act as a pure sandstone hydrocarbon reservoir with 10% porosity. The equation of Gassmann has been implemented for the pore fluid substitution in the reservoir. Synthetic seismic data are generated for the three-layer geological model. Due to the presence of noise, it is always difficult to interpret seismic data. But, CWT has the ability of noise reduction, improving the visualization of a data set and locating the anomalies in terms of scalogram and 3D CWT coefficients. Synthetic seismic data of the geological structure are transformed by CWT. The successful transformation of P-wave velocity, synthetic seismic data and acoustic impedance inversion provided evidence to distinguish different interfaces accurately. CWT has successfully located seismic reflections by localizing high-energy spectrum within the cone of influence. Three high-energy spectrums have been identified at 0.8 s, 1 s and 1.07 s, and it exactly matches the seismic data and three-layer geological model.

We proposed a new full waveform inversion (FWI) method, namely full waveform inversion of the second-order time integral wavefield, by enhancing low-frequency components of seismic data with a second-order time integration of seismic wavefield, which can efficiently reduce the initial model dependence of FWI. According to the propagation equation of scattering wavefield in scattering theory, we derived a propagation equation for the scattering wavefield with second-order time integral, and used the leading order Born approximation for the linearization of the propagation equation. Based on the propagation equation for the scattering wavefield with second-order time integral, using the scattering wavefield to invert for the distribution of scattering sources in subsurface, and using wavefield modeling to construct the incident wavefield, and according to the linear relationship between the scattering wavefield and the incident wavefield and velocity perturbation in the linear propagation equation for the scattering wavefield with second-order time integral, we applied a formula similar to the imaging formula of migration to obtain the estimation of velocity perturbation, and established an iterative inversion method for the full waveform inversion of second-order integral wavefield. Applying the inversion result of full waveform inversion of second-order integral wavefield as the initial velocity model for the conventional FWI can efficiently reduce the initial model dependence of FWI. Numerical tests using synthetic data of the Marmousi model demonstrated the validity and feasibility of the proposed method. The final results of the new method can deliver much improved results than the conventional FWI. Furthermore, to test the independence from the seismic frequency-band, we use a low-cut source wavelet (cut from 4Hz below) to generate the synthetic data. The inversion results by our new method show no appreciable difference from the full-band source results.

Least-squares migration is a linear seismic inversion method which is established based on the linear relationship between seismic reflection data and underground reflection. Compared with conventional imaging technique, it has better performance in preserving amplitude. This paper presents an one-way wave equation least-squares migration based on illumination compensation. Firstly, we use the stable Born approximation generalized screen one-way wave-field propagator to construct the linear operator between reflected seismic data and underground reflection. Then we use the linear optimization method to solve the linear inverse problem of the least-squares migration. In the process of solving the optimization problems iteratively, we employ the seismic wave illumination as a preconditioned operator of the iterative inversion, so as to accelerate the convergence of iteration. During the one-way wave propagation, we consider the transmission effect arising from velocity interface, and substitute monopole source for the dipole source in conventional migration. Applying the method proposed in this paper to the layered theory model and the Marmosi model achieved ideal results.

In this paper, we summarize the influence of the Hessian operator in seismic inversion methods and review the mathematical and physical meanings of the Hessian operator in the seismic inversion imaging. The Hessian operator is the second derivation of the misfit function to the seismic model parameters. Its Green's function formulation under the acoustic wave approximation shows that the Hessian operator reflects the effects of the seismic acquisition system and wavelet frequency band during the projection of information from the data spaces to the model space. We propose two pseudo-Hessian forms for the least-squares migration and the full waveform inversion separately. The application of the plane-wave Hessian operator can lead to an amplitude-preserved migration result. The sub-offset Hessian can be used to the full waveform inversion to enhance the efficiency of inversion. At last, we discuss and evaluate the Hessian operator in seismic inversion imaging.

We present five patients of epilepsy in which seizures were triggered by playing or watching the traditional Chinese gambling game “Mah-Jong.” One patient also experienced seizures while playing a computer version of the Mah-Jong game. This condition appeared to have a predominance of males (80%) and middle-aged onset (39.4 years). Four patients had generalized tonic-clonic seizures and one patient had partial seizures with secondary generalization. No spontaneous seizure occurred in these patients. Three patients had been receiving antiepileptic drug therapy, but without effective control over their seizures. Mah-Jong-induced epilepsy is a very peculiar form of complex reflex epilepsy that involves the higher mental activities. This phenomenon may consist of distinct pathophysiologic mechanisms from other reflex epilepsy induced by thinking and spatial tasks in idiopathic generalized epilepsies. This unusual reflex epilepsy is relatively benign in nature and antiepileptic drug therapy has uncertain benefits. It may be necessary to avoid playing the Mah-Jong game in order to prevent seizures.

In this study, 116 patients, at least 1 month of age but younger than 5 years, were identified with culture-proven bacterial meningitis. A comparison was made between the clinical data of the patients with and without seizures during hospitalization. Seizures during acute bacterial meningitis accounted for 47% (55/116) of the episodes. Time interval between the onset of bacterial meningitis and that of seizures was 1 to 20 days (mean, 4 days). Twelve of these 55 patients had one or more afebrile seizures after completing the treatment. At follow-up of at least 1 year after completing treatment, 26 patients had good outcomes, whereas the other 29 patients had poor outcomes. A strong correlation between the findings of abnormalities through neuroimaging and the occurrence of seizures during hospitalization was observed. The long-term outcomes of patients with infantile and childhood bacterial meningitis, who had seizures during the acute phase of bacterial meningitis, were worse than the outcomes of those who did not have such seizures. No child developed late seizures unless there were acute seizures. Factors associated with seizures during acute bacterial meningitis include disturbed consciousness on admission, abnormal neuroimaging findings, and low glucose and high concentration of total proteins in cerebrospinal fluid.

This 16-year (1986-2001) retrospective study enrolled 80 infantile patients (aged, 30-365 days old) with culture-proven bacterial meningitis. The most prevalent pathogens were Salmonellaspecies, Streptococcus (S.) agalactiae, Escherichia (E.) coli, and Haemophilus (H.) influenzae, accounting for about 59% of the episodes. Meningitis caused by Salmonella species, E. coli and H. influenzae occurs more often in the older infants, while that caused by S. agalactiae occurs more often in young infants. Our study revealed a decrease in the proportion of Salmonella meningitis from 27% in the first 8 years to 9% in the second 8 years with E. coli replacing Salmonella species as the leading pathogen of this disease during the second period. Overall mortality rate for both periods of time was 11%. However, if we take those with undesirable poor outcomes into account, 43% of patients could be considered treatment failures. The study also reveals a high prevalence of neurological complications when this disease is caused by H. influenzae, S. pneumoniae, and Salmonella species. Stepwise logistic regression analysis revealed that only initial changing levels of consciousness (P = 0.006) were independently associated with treatment failure. The most frequent neurological complications associated with this disease included subdural empyema, hydrocephalus, cerebral infarctions, and seizures. Because therapeutic regimens may require attention to the eradication of bacterial pathogen but also the neurological complications, early diagnosis and choice of appropriate antibiotics are essential to increasing the possibility of survival.

To determine the clinical features, prognostic factors, and therapeutic results of Guillain-Barre syndrome (GBS) in order to improve the therapeutic strategy for this disease. We retrospectively reviewed the electrodiagnostic study and medical records of patients with GBS admitted to Chang Gung Memorial Hospital, Kaohsiung, between January 1986 and December 2000. Outcomes and prognosis were followed-up after 1 year. Ninety-six patients were enrolled in this study. According to the clinical and electrophysiological findings, 77 patients were acute inflammatory demyelinating polyradiculoneuropathy, seven were Miller Fisher syndrome, and six were axonal forms, and six were unclassified. At a follow-up of 1 year, 61 patients (64%) recovered, 30 (31%) had residua and five (5%) died. Amongst these 30 had residua, including unassisted gait in 19, assisted gait in four, and wheel/bed bound in seven. According to the statistical analysis, disabilities at the nadir (P < 0.0001) and at admission (P = 0.014) were significant prognostic factors. Variables used for the stepwise logistic regression, and the results revealed that after analysis for all the above variables, only disability at the nadir (P < 0.0001) was independently associated with the treatment failure rate. Our study revealed 27% of cases in need of respiratory support during hospitalization, and 5% of hospital-treated patients die from the complications. Furthermore, 31% had residua at a follow-up of 1 year or more. If prognostic factors are considered, disability at the nadir during hospitalization demonstrates consistently poor therapeutic outcomes. Therefore, early diagnosis, choice of appropriate treatment, and preventing complications during acute stages are essential to maximize the potential for survival.

Common etiologies of acute acquired cerebellar ataxia include cerebrovascular diseases, toxin or drugs, infections/para-infections, and autoimmune diseases. It is a rare manifestation of Sjögren's syndrome, which is a common autoimmune disease but is often missed as a differential diagnosis.This is a report of a patient with acute onset cerebellar ataxia for one month. She also had massive neck lymphadenopathy. After a series of studies and the exclusion of other common causes of acute cerebellar ataxia, she was diagnosed as having Sjögren's syndrome. Patients with Sjögren's syndrome have higher risk for lymphoma, which leads to poorer prognosis. After lymph node biopsy, the patient was proven to have sinus histiocytosis, which is another rare finding in Sjögren's syndrome.For patients with acute acquired cerebellar ataxia, immune-mediated cerebellar ataxia should be an important differential diagnosis aside from the more common causes like stroke or drugs.