Electro-osmotic flow through a two-dimensional screen-pump filter.

The electro-osmotic flow driven by a screen pump, composed of a line array of evenly spaced identical rectangular solid blocks, is investigated under the Debye-Hückel approximation. The geometry of the screen pump is determined by the spacing and aspect ratio of the solid blocks. A constant surface zeta potential is assumed on the block surface. The method of eigenfunction series expansion is applied to solve analytically for the applied electric field, electric charge potential in the fluid, and flow field. Because of the low Reynolds number, Stokes equations are applied for the flow. The analytic result is first confirmed by comparing with the exact solution of the electro-osmotic flow in an infinite channel. Then different geometries of the screen pump and the effect of the electrokinetic width are computed for their influence on the flow rate. Recirculating eddies and reversing flow are found even though the applied electric driving field is unidirectional.

Unsteady electroosmosis in a microchannel with Poisson-Boltzmann charge distribution.

The present study is concerned with unsteady electroosmotic flow (EOF) in a microchannel with the electric charge distribution described by the Poisson-Boltzmann (PB) equation. The nonlinear PB equation is solved by a systematic perturbation with respect to the parameter λ which measures the strength of the wall zeta potential relative to the thermal potential. In the small λ limits (λ<<1), we recover the linearized PB equation - the Debye-Hückel approximation. The solutions obtained by using only three terms in the perturbation series are shown to be accurate with errors <1% for λ up to 2. The accurate solution to the PB equation is then used to solve the electrokinetic fluid transport equation for two types of unsteady flow: transient flow driven by a suddenly applied voltage and oscillatory flow driven by a time-harmonic voltage. The solution for the transient flow has important implications on EOF as an effective means for transporting electrolytes in microchannels with various electrokinetic widths. On the other hand, the solution for the oscillatory flow is shown to have important physical implications on EOF in mixing electrolytes in terms of the amplitude and phase of the resulting time-harmonic EOF rate, which depends on the applied frequency and the electrokinetic width of the microchannel as well as on the parameter λ.

Starting electroosmotic flow in an annulus and in a rectangular channel.

The initial electroosmotic flow through a small pore or microchannel with annular or rectangular cross section is studied under the Debye-Hückel approximation. Analytical series solutions and their asymptotic behavior for small and large non-dimensional electrokinetic widths are found for these two basic cases. The explicit and accurate solutions are particularly useful for examining various geometric/physical effects on the transient time scales and the flow rates for the transient states. The steady flow rate of the smaller channel may be disproportionately smaller than a reference channel if the electric double layer is thick, but will be in close proportion to the area ratio if the electric double layer is thin. A smaller channel compared to a reference channel has a shorter transient time scale, and the transient flow has characters very different from the steady state if the electric double layer is thin. The total transient flow rate of several smaller pores or channels may exceed largely that of a single large pore or channel with the same total cross section on the transient time scale of the smaller channels. The results have important implications on liquid transport in micropores or channels by pulse voltages or more general time-varying voltages.

EOF using the Ritz method: application to superelliptic microchannels.

An efficient Ritz method is developed from the variational principle to solve the Poisson-Boltzmann equation under the Debye-Hückel approximation for studying the EOF in microchannels. The method is applied to the family of superelliptic cross sections which includes the elliptic channel and the rectangular channel as limiting cases. Several accurate tables presented are useful for design of electroosmotic channels, especially rectangular channels with rounded corners. It is shown how the flow rate Q is a sophisticated consequence of the nondimensional electrokinetic width K, the aspect ratio b as well as the superelliptic exponent n.

Analysis of surface plasmon modes and band structures for plasmonic crystals in one and two dimensions.

In this study, we employ the interfacial operator approach to compute surface plasmon modes as well as band structures (including longitudinal modes) for plasmonic crystals in one and two dimensions. In particular, we consider the free-electron model for the metal. It is shown that the localized feature of surface plasmon modes can be resolved near the interface by introducing interfacial variables. For a one-dimensional array of metal, convergence of two branches of surface plasmon modes is studied by varying the filling fraction of the metal. For two-dimensional metallic structures, band flattening, band broadening, and plasmonic band gaps are observed and discussed. The highly degenerate nature and infinite number of surface plasmon modes can be explained by employing the Rayleigh quotient for the TE modes. The cutoff behavior in the TM modes is made clear by considering the energy density of the electromagnetic fields. The transverse electric fields, surface charges, and polarization currents are visualized to help understand various properties of surface plasmon modes. Moreover, the effect of plasma frequency and the transition from dispersive metals to perfect conductors are also explored. Finally, the contribution of Drude damping is considered by perturbation analysis.

Large full band gaps for photonic crystals in two dimensions computed by an inverse method with multigrid acceleration.

In this study, two fast and accurate methods of inverse iteration with multigrid acceleration are developed to compute band structures of photonic crystals of general shape. In particular, we report two-dimensional photonic crystals of silicon air with an optimal full band gap of gap-midgap ratio Deltaomega/omega(mid)=0.2421, which is 30% larger than ever reported in the literature. The crystals consist of a hexagonal array of circular columns, each connected to its nearest neighbors by slender rectangular rods. A systematic study with respect to the geometric parameters of the photonic crystals was made possible with the present method in drawing a three-dimensional band-gap diagram with reasonable computing time.

Solvable model in renormalization group analysis for effective eddy viscosity.

This study presents a solvable model in renormalization group analysis for the effective eddy viscosity. It is found fruitful to take a simple hypothesis that large-scale eddies are statistically independent of those of smaller scales. A limiting operation of renormalization group analysis yields an inhomogeneous ordinary differential equation for the invariant effective eddy viscosity. The closed-form solution of the equation facilitates derivations of an expression of the Kolmogorov constant C(K) and of the Smagorinsky model for large-eddy simulation of turbulent flow. The Smagorinsky constant C(S) is proportional to C(3/4)(K). In particular, we shall illustrate that the value of C(K) ranges from 1.35 to 2.06, which is in close agreement with the generally accepted experimental values (1.2 approximately 2.2).

Biodegradation of carbonate apatite/collagen composite membrane and its controlled release of carbonate apatite.

The aim of this study was to investigate the biodegradation of carbonate apatite (CO(3)Ap)/collagen composite membrane as a new guided tissue regeneration membrane in vivo and to estimate its controlled release of CO(3)Ap in vitro. To control the biodegradation of the guided tissue regeneration membrane and to promote hard tissue regeneration in the periodontal region, we added CO(3)Ap into the collagen membrane. To investigate the biodegradation of CO(3)Ap/collagen composite membranes, the prepared membranes (CO(3)Ap:0, 10 wt %) were cut into 5 x 5 x 0.1 mm and subcutaneously implanted into the backside of male rats under general anesthesia. The explanted membranes were investigated histologically. To estimate their controlled release of CO(3)Ap in vitro, the membranes (CO(3)Ap 0-10 wt %, 5 x 5 x 0.1 mm) were immersed into collagenase solution and compulsorily dissolved for 48 h. Histological results suggested that the membrane had a good biocompatibility and the biodegradable period was shortened with the presence of CO(3)Ap. In the solubility experiments of the membrane, eluted Ca concentrations gradually increased with total dependence on the dissolution of the collagen membrane. Our study demonstrated that the biodegradation time can be controlled by CO(3)Ap contents in the membrane and CO(3)Ap could be released from the membrane with the biodegradation period.

Genomic deletion and p53 inactivation in cervical carcinoma.

The tumor-suppressor gene p53 acts as "the guardian of the genome", sensing DNA damage and initiating protective responses. To examine the hypothesis that p53 abnormality leads to increased genomic alterations in primary tumor cells, our study utilized 51 primary tumors of cervical carcinoma and 10 microsatellite markers. These markers were mapped to the short arms of chromosomes 3 and 5, covering the regions 3p13-25 and 5p15.1-15.3. Genomic deletion on 3p and 5p was correlated with genetic or epigenetic p53 inactivation pathways, including p53 mutation, genetic deletion of p53 and cervical infection with human papillomavirus. The proportion of abnormal p53 was found to be significantly higher in the cases exhibiting loss of heterozygosity (LOH) on 5p (p < 0.001), supporting the hypothesis of the presence of a p53-dependent pathway to cervical tumorigenesis. In contrast, however, LOH on 3p was found to be independent of p53 inactivation. A common deletion region, 3p22-24, was identified in 44% of informative cases, and genomic loss at this specific region was correlated with early tumorigenic onset and poor grade of tumor differentiation. Diversity within the patterns of genomic alteration in the same form of cancer suggests different sets of risk/tumorigenic profiles, molecular pathogenesis, as well as prognosis and outcome.

Diuretic renography findings in enterovesical fistula.

A 73-year-old male presented with a 2 week history of gross haematuria and faecal material in the urine. Bone scan for cancer work-up showed 99T(cm)-MDP radioactivity accumulation in the transverse and descending colon. A 99T(cm)-DTPA diuretic renogram was arranged to study renal function and to determine the location of the enterovesical fistula. Diuretic renography demonstrated extraurinary tract radioactivity in the sigmoid colon in the early images, extending to the descending and transverse colon in the subsequent dynamic images. A sigmoid colon adenocarcinoma with bladder wall invasion and fistula formation was confirmed at surgical operation. The impressive dynamic diuretic renography study in this patient was helpful in determining the location of the fistula and in planning surgical management.

Hepatobiliary imaging of functional and morphological changes following hepatic arterial embolization in hepatocellular carcinoma.

UNLABELLED: Hepatic arterial embolization (HAE) is the treatment of choice for inoperable hepatocellular carcinoma. There are functional changes following HAE in the tumor and in the adjoining normal liver and biliary structures. We sought to determine if a 99mTc-HIDA hepatobiliary scan could evaluate the morphological and functional changes of the liver and biliary systems in patients with hepatocellular carcinoma undergoing HAE. METHODS: Patients with hepatoma were evaluated by 99mTc-HIDA hepatobiliary scans before and after HAE. RESULTS: Ten patients with histologically proven hepatomas had 44 99mTc-HIDA scans over a 319-mo period. Liver uptake was good in all patients, none developed hepatic failure. Liver tumors were detected in five of the eight studies done before the first HAE. The HIDA scan failed to locate the tumor throughout the whole study period in only one patient. Two patients showed evidence of tumor uptake of the HIDA agent. In one of these two patients the hot uptake disappeared after the HAE but reappeared after tumor recurrence. Gallbladder filling time and contractility worsened in all eight patients the day after embolization. On the HIDA scans, the gallbladder was not visualized in three of four patients who survived longer than 40 mo after HAE. Bile stasis in the left intrahepatic duct was found in six of the eight patients who survived longer than 8 mo after HAE. CONCLUSIONS: Biliary complications were common in patients who received HAE, and HIDA scans may be useful for evaluating the biliary system and hot uptake in hepatocellular carcinoma in candidates for HAE.

Survival impact of lymph node metastasis in TNM stage III carcinoma of the colon and rectum.

BACKGROUND: Node-positive (TNM stage III) adenocarcinoma of the colon and rectum consists of tumors with a widely variable prognosis. To predict the outcome of patients with stage III carcinoma, we assessed the survival impact of the number and level of lymph node metastasis and other clinicopathological variables. STUDY DESIGN: A retrospective study was performed on 538 patients with stage III carcinoma of the colon and rectum who underwent curative resection at Chang Gung Memorial Hospital between 1980 and 1989. Ten or more lymph nodes in each resected specimen were identified microscopically. Multivariate analysis was used to determine the independent variables. RESULTS: The relative survival rates at five and ten years were 52 and 42 percent, respectively. Tumor morphology, depth or tumor penetration, histologic grade, and the status (number and level) of nodal involvement were significant in the univariate analyses. Only grade and nodal status remained significant in the multivariate analysis. Based on the nodal status, these patients were separated into three groups: stage IIIA (one to three positive nodes and absence of pN3 metastasis), IIIB (four to nine nodes and absence of pN3), and IIIC (ten or more nodes or presence of pN3). The five-year survival rates for patients with stages IIIA, IIIB, and IIIC disease were 69, 44, and 29 percent, respectively. Compared with patients with stage IIIA disease, the odds of death for patients with stages IIIB and IIIC carcinoma were 2.1 (95 percent confidence interval: 1.5 to 2.8, p = 0.0001) and 3.3 (95 percent confidence interval 2.4 to 4.5, p = 0.001), respectively. CONCLUSIONS: We suggest that stage III adenocarcinoma of the colon and rectum be divided into three substages: IIIA (one to three positive nodes and absence of pN3 metastasis), IIIB (four to nine nodes and absence of pN3), and IIIC (ten or more positive nodes or presence of pN3.

Ultrasonically-guided needle aspiration with preparation of cell blocks in the diagnosis of liver tumors.

To evaluate the diagnostic value of a method combining ultrasonically-guided Chiba needle aspiration and histological block preparation of aspiration specimen, 50 consecutive patients with histologically confirmed focal or diffuse lesion of the liver were studied. In addition to conventional aspiration cytology, the aspiration specimen was mixed 1:1 by volume with 95% alcohol and centrifuged. The precipitated specimen was then embedded in paraplast. Serial sections were obtained and stained with hematoxylin and eosin (H & E) technique. The diagnostic specificity and positive predictive value of the cell block technique in diagnosing hepatic malignancies were both 100%, as was those of aspiration cytology. The diagnostic sensitivity and overall accuracy of cell blocks were significantly better than those of aspiration cytology (89.5% vs. 63.2%, P < 0.01; and 92.0% vs. 72.0%, P < 0.01). The negative predictive value of cell blocks was also better than that of aspiration cytology, but the difference was not statistically significant (75.0% vs. 46.2%, P > 0.05). In terms of cellular differentiation, the accuracy of the diagnosis of cell blocks was 78.6% (22/28) in hepatoma; 80.0% (4/5) in metastatic adenocarcinoma and 100.0% (1/1) in small cell carcinoma. No complications were encountered in any of the patients. The results suggest that the preparation of cell blocks of the aspiration specimen is a reliable and accurate method for the diagnosis of hepatic malignancies. This method also elevates the diagnosis of the aspiration specimen from the cytological to the histopathological level.

Postoperative adjuvant radiotherapy in Astler-Coller stages B2 and C rectal cancer.

Between 1979 and 1983, 127 patients with Stages B2 or C rectal cancer treated with surgery plus postoperative adjuvant radiotherapy (RT group) and 122 patients treated with surgery alone (S group) were compared to evaluate the effect of postoperative radiotherapy on survival and disease recurrence. Each group was stratified into subgroups according to stage and tumor differentiation as follows: Subgroups BW (Stage B2 and well-differentiated tumor), BM (Stage B2 and moderately differentiated tumor), CW (Stage C and well-differentiated tumor), CM (Stage C and moderately differentiated tumor), and P (poorly differentiated tumor). Ninety-five percent of the patients were followed until death or, if alive, to five years after surgery. Postoperative radiotherapy was associated with a reduced five-year survival rate in Subgroup BW (67 vs. 87 percent; P = 0.02). In the remaining subgroups of the RT group, there was a statistically insignificant trend toward a worse survival rate (56 vs. 65 percent, 47 vs. 64 percent, 41 vs. 46 percent, and 50 vs. 36 percent for Subgroups BM, CW, CM, and P, respectively). The local failure rates for the S group and RT group were 10 vs. 23 percent (P = 0.15) in Subgroup BW, 32 vs. 21 percent (P = 0.4) in Subgroup BM, 24 vs. 25 percent (P = 0.6) in Subgroup CW, and 18 vs. 18 percent (P = 0.6) in Subgroup CM, respectively. Eight percent (9/127) had severe or life-threatening radiation-related complications. Postoperative adjuvant radiotherapy alone did not improve the survival of patients with Stages B2 or C rectal cancers. It may have led to worsened survival in the subgroup of patients with well-differentiated Stage B2 rectal cancer.

Liver biochemical tests and dengue fever.

The impact of dengue on liver function was studied by biochemical tests on 125 male and 145 female patients diagnosed with this disease during an outbreak that extended from November 1987 to December 1988. Abnormal levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), bilirubin, alkaline phosphatase, and gamma-glutamyl transpeptidase (G-GT) were observed in 93.3%, 82.2%, 7.2%, 16.3% and 83.0% of the patients, respectively. The elevation of transaminases was mild to moderate in most cases, but was 10-fold greater than the normal upper limit for AST and ALT in 11.1% and 7.4% of the patients, respectively. Initially, the level of AST was greater than that of ALT, increasing to maximum levels nine days after the onset of symptoms, then decreasing to normal levels within two weeks. Results of the biochemical tests did not differ significantly between the cases with and without hepatitis B or hepatitis C virus infection, but significantly higher elevations of AST, ALT, and G-GT were observed in patients with episodes of bleeding. Liver biopsies of two patients showed features of lobular hepatitis. Of the five fatal cases, three died of hepatic failure. It is concluded that dengue fever may cause hepatic injury and transaminase elevation similar to that in patients with conventional viral hepatitis. In epidemic or endemic areas, dengue fever infection should be considered in the differential diagnosis of hepatitis.

The prognostic factors of severe amebic liver abscess: a retrospective study of 125 cases.

One hundred twenty-five cases of amebic liver abscess were diagnosed at Chang Gung Memorial Hospital in Taiwan from January 1981 to December 1989. An analysis of possible prognostic factors for severe amebic liver abscess was done retrospectively. The majority of the patients came from the southern part of Taiwan. Severe amebic liver abscess was defined as the rupture of an abscess that was resistant to 72 hr of medical treatment, or complicated by secondary bacterial infection. The results showed significant differences between patients with severe liver abscess and those with more moderate forms of amebic liver abscess in indices such as jaundice, hemoglobin and serum bilirubin levels, and dyspnea, as well as in pulmonary changes (right diaphragm elevation, right pleural effusion) seen on chest radiographs. Those patients with diabetes mellitus also had greater evidence of severe liver abscess. Moderate cases that were treated with amebicides showed excellent responses (no mortality). Severe cases required, in addition to amebicide therapy, either percutaneous or surgical drainage of pus, especially in those patients with ruptured abscesses. Those patients with abscesses that ruptured into the thoracic cavity were treated by either thoracostomy or needle aspiration, and all were cured. Three patients died of abscess rupture into the abdominal cavity, associated with secondary bacterial infection. The overall mortality rate was 2.4%. These symptoms and signs of severe liver abscess are indicators of the need for intensive treatment such as aspiration or surgical drainage.

Prognostic factors in management of traumatic perforation of colon and rectum.

A retrospective analysis was made of the prognostic factors and management of traumatic perforation of the colon and rectum in 80 patients during the period of 1980 to 1988 at Chang Gung Memorial Hospital. The total mortality was 11%. Morbidity was 18% among the survivors. The mortality was higher in patients with old age (50% for those over 60 years old), delayed operation (50% for a delay of more than 72 hours), poor nutrition (57%), shock condition before or during operation (50%), severe abdominal fecal contamination (35%) and associated abdominal injury. We conclude that the surgical procedures for traumatic perforation of colon and rectum performed depend upon the patient's condition. The prognostic factors in patients with traumatic perforation are patient's age, timing of operation, degree of abdominal fecal contamination, injury to other abdominal organs and general condition such as nutrition and shock.

The role of lasers in hemorrhoidectomy.

Eighty-eight patients who received treatment for hemorrhoids were randomized into two groups. Group A received the Nd-YAG laser phototherapy for internal hemorrhoid combined with the CO2 laser for external hemorrhoid. Group B was treated with closed Ferguson hemorrhoidectomy. The need of narcotic injections for pain relief was 11 percent in group A vs. 56 percent in group B (P less than 0.001). The incidence of postoperative urinary retention was 7 percent in group A, vs. 39 percent in group B (P less than 0.05). No enema was required postoperatively in group A, vs. 9 percent in group B; 84 percent of the patients in group A were discharged on the second postoperative day, vs. 83 percent of the patients in group B discharged on the fifth postoperative day. The cost was 20 percent less in the former group. The overall complications in both groups were insignificant in difference, except prolonged wound healing in group A was noted. One year follow-up showed satisfactory results. Laser treatment is considered one of the alternatives to conventional treatment, but the surgeon needs to be aware of laser hazards.

Leiomyoma of the ovary--a case report.

Primary ovarian leiomyoma is rare. About 40 cases have been reported in the literature. A case report of leiomyoma of ovary and the literature review was presented.

Sonographic demonstration of free air in perforated peptic ulcers: comparison of sonography with radiography.

Abdominal sonography was performed in 283 patients with acute abdominal pain. Of these patients, 10 were diagnosed as having an acute perforated peptic ulcer (PPU) and 2 were diagnosed as having a sealed-off PPU. Sonographic findings of acute PPU are summarized. The presence of an interference echo with the shifting phenomenon is a very strong indication of the presence of free air in the abdominal cavity. Using these sonographic criteria, intraperitoneal free air was diagnosed as 9/10 patients with PPU in comparison to 8/10 by abdominal and chest radiographs. Two patients with sonographic evidence of free air, but negative X-ray studies, were later found to have free air in the subsequent radiographic studies. These findings suggest that sonography is highly sensitive in the small number of patients in whom air is found. Sonographic studies also have the advantage of detecting other changes associated with PPU, such as fluid accumulation, inflammatory mass, and thickening of the gallbladder.