Development of an Explicit Symplectic Scheme that Optimizes the Dispersion-Relation Equation of the Maxwell's Equations

In this paper an explicit finite-difference time-domain scheme for solving the Maxwell's equations in non-staggered grids is presented. The proposed scheme for solving the Faraday's and Ampère's equations in a theoretical manner is aimed to preserve discrete zero-divergence for the electric and magnetic fields. The inherent local conservation laws in Maxwell's equations are also preserved discretely all the time using the explicit second-order accurate symplectic partitioned Runge-Kutta scheme. The remaining spatial derivative terms in the semi-discretized Faraday's and Ampère's equations are then discretized to provide an accurate mathematical dispersion relation equation that governs the numerical angular frequency and the wavenumbers in two space dimensions. To achieve the goal of getting the best dispersive characteristics, we propose a fourth-order accurate space centered scheme which minimizes the difference between the exact and numerical dispersion relation equations. Through the computational exercises, the proposed dual-preserving solver is computationally demonstrated to be efficient for use to predict the long-term accurate Maxwell's solutions.     

Preoperative ketamine improves postoperative analgesia after gynecologic laparoscopic surgery

In this study, we evaluated the preemptive effect of a small dose of ketamine on postoperative wound pain. In a randomized, double-blinded, controlled trial, we compared the analgesic requirement in patients receiving preincision ketamine with ketamine after skin closure or placebo after gynecologic laparoscopic surgery. One-hundred-thirty-five patients were randomly assigned to receive preincision or postoperative ketamine 0.15 mg/kg or saline IV. Anesthetic technique was standardized. Patients were interviewed regularly up to 4 wk after surgery. Pain score, morphine consumption, side effects, and quality of recovery score were recorded. Patients receiving preincision ketamine had a lower pain score in the first 6 h after operation compared with the postoperative (P = 0.001) or placebo groups (P < 0.001). The mean (95% confidence intervals) time to first request for analgesia in the preincision group, 1.8 h (1.4-2.1), was longer than the postoperative group, 1.2 h (0.9-1.5; P < 0.001), or the placebo group, 0.7 h (0.4-0.9; P < 0.001). The mean +/- SD morphine consumption in the preincision group, 1.5 +/- 2.0 mg, was less than that in the postoperative group, 2.9 +/- 3.1 mg (P = 0.04) and the placebo group, 3.4 +/- 2.7 mg (P = 0.003). There was no significant difference among groups with respect to hemodynamic variables or side effects. No patient complained of hallucinations or nightmares. We conclude that a small dose of ketamine is not only safe, but it also provides preemptive analgesia in patients undergoing gynecologic laparoscopic surgery. IMPLICATIONS: In women undergoing laparoscopic gynecologic surgery, a small preoperative dose of ketamine (0.15 mg/kg) produced preemptive analgesia. There were no significant hemodynamic and psychological side effects with this dose.     

Ex vivo comparative study using the Endolifter® as a traction device for enhancing submucosal visualization during endoscopic submucosal dissection

Background

Endoscopic submucosal dissection (ESD) is a technically demanding procedure, and exposure of the submucosa depends on the action of gravity and submucosal injection. The aim of the study was to investigate the effectiveness of the Endolifter^® as a traction device for enhancing submucosal visualization during ESD.

Methods

This was a prospective ex vivo comparative study conducted between September 2010 and March 2011 in the Prince of Wales Hospital. Consecutive ESDs were performed by four experienced endoscopists in an ex vivo ESD model with or without the Endolifter^®. The Endolifter^® allows simultaneous grasping, retracting and lifting of the mucosa during ESD, resulting in exposure of the submucosa. Each of the procedures were recorded and reviewed later by two independent assessors. The outcome measures included the proportion of time that the submucosa was visualized during the procedures (SM ratio), procedural times, perforation rates, amount of submucosal injections, and the difficulty of the procedure.

Results

Forty-eight gastric ESD procedures were performed on the model. The SM ratio was higher in the Endolifter^® group (P = 0.007), particularly for lesions located at the antrum (P < 0.001). The time required for submucosal dissection and the total procedural time were also less in the Endolifter^® group. The endoscopists rated the ESD procedures in the Endolifter^® group as less difficult (P = 0.033).

Conclusions

The Endolifter^® improved submucosal visualization during gastric ESD and reduces the difficulty of performing the procedures. The device may improve the ease of performing ESD in low-volume centers or large mucosal lesions.     

Endogenous tyrosine hydroxylase activity in the developing chick heart: a possible source of extraneuronal catecholamines

The source of catecholamines in the developing chick heart was investigated by using catecholamine assays and tyrosine hydroxylase assays on hearts from normal and chemically-sympathectomized chick embryos. A biochemical index of sympathetic nerve development in the heart was obtained by monitoring the ability of sympathetic nerves in the atria to take up [3H]-norepinephrine in vitro. Specific neuronal uptake of [3H]-norepinephrine in atria was first detected on incubation day 11 and increased throughout the incubation period. High performance liquid chromatography with electrochemical detection was used to measure the norepinephrine concentration and content of embryonic hearts. The cardiac norepinephrine concentration fluctuated throughout the incubation period but was particularly low (0.01 +/- 0.005 ng/mg wet wt) on incubation days 10 to 13, coincident with the arrival of sympathetic nerves in the heart. The highest norepinephrine concentration was measured on incubation day 7 (2.09 +/- 0.50 ng/mg wet wt) prior to the arrival of sympathetic nerves in the heart. Sympathetic nerve axotomy produced by chronic treatment with 6-hydroxydopamine reduced [3H]-norepinephrine uptake in atria and norepinephrine concentration in whole hearts on incubation day 20 to 33 and 47% of control, respectively. Tyrosine hydroxylase activity was detected in normal hearts on incubation day 7, 3 to 4 days before the heart is innervated by sympathetic nerves. Tyrosine hydroxylase activity persisted in the heart on incubation day 20, despite treatment with 6-hydroxydopamine on incubation days 13 to 19. The tyrosine hydroxylase activity in 6-hydroxydopamine lesioned hearts was not significantly different from saline-treated controls. This data indicates that tyrosine hydroxylase activity is present in the immature chick heart prior to the arrival of sympathetic innervation and following chemical sympathectomy; hence, an extraneuronal source of tyrosine hydroxylase, the rate limiting enzyme for catecholamine biosynthesis, exists in the embryonic chick heart.     

Can the self-selection of aerobic exercise be used in individuals with different cardiorespiratory fitness levels?

Sport Sciences for Health - To compare the intensity and duration self-selected by participants with higher and lower cardiorespiratory fitness to that recommended by the American College of Sports...     

Axillary lymph node status,but not tumor size,predicts locoregional recurrence and overall survival after mastectomy for breast cancer

OBJECTIVE: To assess the significance of axillary lymph node status and tumor size for predicting locoregional recurrence (LRR) and overall survival after mastectomy for breast cancer and to discuss the utility of postmastectomy radiation therapy. SUMMARY BACKGROUND DATA: Patients with locally advanced breast cancer require multimodality treatment combining chemotherapy (and/or hormonal therapy), surgery, and radiation. Randomized trials have demonstrated that postmastectomy radiation reduces LRR, but no overall survival benefit has been established. METHODS: Criteria for accrual to the Alabama Breast Cancer Project (1975-1978) were female gender and T2-3 breast cancer with M0 status. Patients underwent a radical or a modified radical mastectomy. Node-positive patients received adjuvant cyclophosphamide, methotrexate, and fluorouracil chemotherapy or adjuvant melphalan. Patients were evaluated for LRR and overall survival based on the number of positive axillary lymph nodes and (in N0 patients) pathologic tumor size. Significance was determined using chi-square analysis. Survival curves were generated using the Kaplan-Meier method and were compared by log-rank analysis. RESULTS: After median follow-up of 15 years, neither type of surgery nor chemotherapy was shown to affect locoregional disease-free or overall survival. LRR rates were higher and overall survival rates were lower in patients with nodal involvement, while tumor size was not shown to significantly affect these rates. CONCLUSIONS: Patients with axillary lymph node metastases may benefit from postmastectomy radiation, but the use of postmastectomy radiation in N0 patients is not supported when it is based on tumor size alone.     

Results of long-term follow-up for transanal excision for rectal cancer

Low anterior resection and abdominoperineal resection are the surgical techniques used most frequently in the treatment of rectal cancer. It is our hypothesis that selected patients with early T stage, well or moderate grade of differentiation, and small tumor size are good candidates for transanal excision in terms of minimal morbidity, low recurrence rate, and sphincter preservation. From January 1993 until August 2001 30 patients underwent transanal excision; three patients were excluded because they had histology other than adenocarcinoma. Factors analyzed included those related to the patient [age (years), gender, race, body mass index, and anal tone], tumor [size (cm), distance from the anal verge (cm), differentiation, and American Joint Committee on Cancer stage], and additional treatment. Median follow-up of the group was 40.7 months (range 0.6-99) and the primary end points were local and distant recurrence. Data are presented as mean (range). The median age of the group was 58.9 years (range 27-94); 52 per cent were female and 48 per cent were male. The mean body mass index was 25.9 (range 22.7-36.7). Preoperatively 81, 11, and 4 per cent of the patients had stage I, II, and III/IV cancer, respectively. Preoperative size of the tumor was 2.0 cm (1-3 cm), and distance from the anal verge was 5.0 cm (3-15 cm). Blood loss was 50 cm3 (5-200 cm3), and there were no operative complications. Tumor differentiation levels were well (37%) and moderate (63%). All patients had negative margins. Additional treatment consisted of radiation therapy in seven patients (six postoperative and one preoperative). Chemotherapy was given to seven patients (six postoperative and one preoperative). The local recurrence rate was 7.4 per cent (two patients), and 3.7 per cent recurred distantly (one patient). Transanal excision of low rectal cancer in selected patients is an acceptable alternative to formal resection. Important selection criteria include early T stage, well or moderate differentiation, relatively small tumor size, and negative microscopic margins. The roles of radiation and chemotherapy remain controversial.     

Breast tomosynthesis and digital mammography: a comparison of breast cancer visibility and BIRADS classification in a population of cancers with subtle mammographic findings

The main purpose was to compare breast cancer visibility in one-view breast tomosynthesis (BT) to cancer visibility in one- or two-view digital mammography (DM). Thirty-six patients were selected on the basis of subtle signs of breast cancer on DM. One-view BT was performed with the same compression angle as the DM image in which the finding was least/not visible. On BT, 25 projections images were acquired over an angular range of 50 degrees, with double the dose of one-view DM. Two expert breast imagers classified one- and two-view DM, and BT findings for cancer visibility and BIRADS cancer probability in a non-blinded consensus study. Forty breast cancers were found in 37 breasts. The cancers were rated more visible on BT compared to one-view and two-view DM in 22 and 11 cases, respectively, (p < 0.01 for both comparisons). Comparing one-view DM to one-view BT, 21 patients were upgraded on BIRADS classification (p < 0.01). Comparing two-view DM to one-view BT, 12 patients were upgraded on BIRADS classification (p < 0.01). The results indicate that the cancer visibility on BT is superior to DM, which suggests that BT may have a higher sensitivity for breast cancer detection.     

Sulfonylurea-sensitive K(+) transport is involved in Cl(-) secretion and cyst trowth by cultured ADPKD cells

Transepithelial chloride and fluid secretion by many types of epithelia involves activation of a conductive K(+) pathway that serves to support the electrochemical driving force for Cl(-) secretion. This study sought to determine if such a pathway is involved in Cl(-) and fluid secretion by the cystic epithelia in autosomal dominant polycystic kidney disease (ADPKD). Primary cultures of cells derived from the cysts of patients with ADPKD were used. Confluent monolayers of these cells, mounted in Ussing chambers, were stimulated to secrete Cl(-) by application of the adenylyl cyclase agonist, forskolin. The effects of various K(+) channel blockers on the increase in short-circuit current (I(sc)) generated by active Cl(-) secretion were determined. Charybdotoxin, an inhibitor of Ca(2+)-sensitive K(+) channels exerted no effect. Similarly, the chromanole 293B, an inhibitor of cAMP-induced K(+) conductance, exerted no effect on cAMP-dependent anion secretion. Glibenclamide, an inhibitor of ATP-sensitive K(+) channels and the cystic fibrosis transmembrane conductance regulator (CFTR), modestly inhibited the forskolin-stimulated current when applied to the apical surface of the monolayers, suggesting a relatively weak effect on CFTR. Basolateral application of glibenclamide inhibited I(sc) to a greater extent. This latter effect may be due to inhibition of a K(+)-conductive transport step. Glibenclamide exerted little effect on the I(sc) of nonstimulated monolayers. Cyst growth in ADPKD is driven by cell proliferation and Cl(-) and fluid secretion. The effect of glibenclamide on the growth of cysts formed within a collagen gel by cultured ADPKD cells was tested. Addition of glibenclamide to the media bathing the cysts inhibited their growth. Glibenclamide also blocked the formation of cysts when it was added to the media at the time the cells were seeded within the collagen gel. Glibenclamide was also found to inhibit the proliferation of ADPKD cells. RT-PCR analysis demonstrated that the ATP-sensitive K(+) channel, K(ir) 6.2, is expressed in cultured ADPKD cells and in normal human kidney. These results suggest that ATP-sensitive K(+) channel blockers should be investigated as possible therapeutic agents to inhibit cyst growth in ADPKD.     

Arteriovenous malformation mimicking a renal-cell carcinoma

We describe a renal arteriovenous malformation in a patient with a 1-month history of flank pain. Imaging studies were interpreted as being consistent with renal-cell carcinoma. However, Doppler ultrasonography demonstrated turbulent blood flow, and selective renal angiography confirmed the diagnosis of an arteriovenous malformation. Embolization relieved the pain. This case calls attention to the need to consider arteriovenous malformations in the differential diagnosis of central homogenously enhancing renal lesions.