Polarization-division multiplexing based on the nonlinear Fourier transform.

Polarization-division multiplexed (PDM) transmission based on the nonlinear Fourier transform (NFT) is proposed for optical fiber communication. The NFT algorithms are generalized from the scalar nonlinear Schrödinger equation for one polarization to the Manakov system for two polarizations. The transmission performance of the PDM nonlinear frequency-division multiplexing (NFDM) and PDM orthogonal frequency-division multiplexing (OFDM) are determined. It is shown that the transmission performance in terms of Q-factor is approximately the same in PDM-NFDM and single polarization NFDM at twice the data rate and that the polarization-mode dispersion does not seriously degrade system performance. Compared with PDM-OFDM, PDM-NFDM achieves a Q-factor gain of 6.4 dB. The theory can be generalized to multi-mode fibers in the strong coupling regime, paving the way for the application of the NFT to address the nonlinear effects in space-division multiplexing.

A micromechanical comparison of human and porcine skin before and after preservation by freezing for medical device development.

Collecting human skin samples for medical research, including developing microneedle-based medical devices, is challenging and time-consuming. Researchers rely on human skin substitutes and skin preservation techniques, such as freezing, to overcome the lack of skin availability. Porcine skin is considered the best substitute to human skin, but their mechanical resemblance has not been fully validated. We provide a direct mechanical comparison between human and porcine skin samples using a conventional mechano-analytical technique (microindentation) and a medical application (microneedle insertion), at 35% and 100% relative humidity. Human and porcine skin samples were tested immediately after surgical excision from subjects, and after one freeze-thaw cycle at -80 °C to assess the impact of freezing on their mechanical properties. The mechanical properties of fresh human and porcine skin (especially of the stratum corneum) were found to be different for bulk measurements using microindentation; and both types of skin were mechanically affected by freezing. Localized in-plane mechanical properties of skin during microneedle insertion appeared to be more comparable between human and porcine skin samples than their bulk out-of-plane mechanical properties. The results from this study serve as a reference for future mechanical tests conducted with frozen human skin and/or porcine skin as a human skin substitute.

Comparison of human and porcine gastric clasp and sling fiber contraction by M2 and M3 muscarinic receptors.

To compare the gastroesophageal junction of the human with the pig, M(2) and M(3) receptor densities and the potencies of M(2) and M(3) muscarinic receptor subtype selective antagonists were determined in gastric clasp and sling smooth muscle fibers. Total muscarinic and M(2) receptors are higher in pig than human clasp and sling fibers. M(3) receptors are higher in human compared with pig sling fibers but lower in human compared with pig clasp fibers. Clasp fibers have fewer M(3) receptors than sling fibers in both humans and pigs. Similar to human clasp fibers, pig clasp fibers contract significantly less than pig sling fibers. Analysis of the methoctramine Schild plot suggests that M(2) receptors are involved in mediating contraction in pig clasp and sling fibers. Darifenacin potency suggests that M(3) receptors mediate contraction in pig sling fibers and that M(2) and M(3) receptors mediate contraction in pig clasp fibers. Taken together, the data suggest that both M(2) and M(3) muscarinic receptors mediate the contraction in both pig clasp and sling fibers similar to human clasp and sling fibers.

Minimally invasive measurement of esophageal variceal pressure and wall tension (with video).

BACKGROUND: There is no simple method to measure intravariceal pressure in patients with esophageal varices. OBJECTIVE: Our purpose was to develop a new noninvasive technique to measure resting intravariceal pressure and wall tension. DESIGN: A model was developed. A long balloon (varix) was fitted inside an airtight cylinder (esophagus). Fluid ran through the model varices to maintain 5 different constant pressures. An endoscope was placed in the model esophagus, and pressure was increased by air insufflation. The endoscopy and pressure readings from the esophagus and varix were recorded continuously until variceal collapse. SETTING: Patient studies were done in an endoscopy suite with the patient under fentanyl and midazolam sedation. PATIENTS: Esophageal pressure was measured during air insufflation in patients with varices until the varices collapsed. EUS was used to measure radius and wall thickness to calculate wall tension. RESULTS: In the varix model, the mean (SD) intraluminal esophageal pressures at variceal flattening for the model varices at 5, 10, 15, 20, and 25 mm Hg were 5.69 (0.34), 11 (0.32), 15.72 (0.51), 21.55 (0.63), and 25.8 (0.14) mm Hg. The correlation between actual and measured variceal pressure in the model at variceal flattening was r = 0.98. In the patients, a total of 10 varices in 3 patients were evaluated. The mean (SD) for the varices in each subject was 12.16 (2.4), 23.2 (1.3), and 6.5 (2.2) mm Hg for subjects 1, 2, and 3, respectively. CONCLUSION: Standard endoscopy with air insufflation and manometry can be used as an accurate, simple, and reproducible method to measure intravariceal pressure.

Quantitation of the contractile response mediated by two receptors: M2 and M3 muscarinic receptor-mediated contractions of human gastroesophageal smooth muscle.

Although muscarinic receptors are known to mediate tonic contraction of human gastrointestinal tract smooth muscle, the receptor subtypes that mediate the tonic contractions are not entirely clear. Whole human stomachs with attached esophagus were procured from organ transplant donors. Cholinergic contractile responses of clasp, sling, lower esophageal circular (LEC), midesophageal circular (MEC), and midesophageal longitudinal (MEL) muscle strips were determined. Sling fibers contracted greater than the other fibers. Total, M(2) and M(3) muscarinic receptor density was determined for each of these dissections by immunoprecipitation. M(2) receptor density is greatest in the sling fibers, followed by clasp, LEC, MEC, and then MEL, whereas M(3) density is greatest in LEC, followed by MEL, MEC, sling, and then clasp. The potency of subtype-selective antagonists to inhibit bethanechol-induced contraction was calculated by Schild analysis to determine which muscarinic receptor subtypes contribute to contraction. The results suggest both M(2) and M(3) receptors mediate contraction in clasp and sling fibers. Thus, this type of analysis in which multiple receptors mediate the contractile response is inappropriate, and an analysis method relating dual occupation of M(2) and M(3) receptors to contraction is presented. Using this new method of analysis, it was found that the M(2) muscarinic receptor plays a greater role in mediating contraction of clasp and sling fibers than in LEC, MEC, and MEL muscles in which the M(3) receptor predominantly mediates contraction.

High prevalence of penicillin resistance and comparative in vitro activity of various antibiotics in clinical isolates of streptococcus pneumoniae isolated in the Province of Hainaut during winter 2004.

A total of 154 isolates of Streptococcus pneumoniae obtained from 8 different centres in the province of Hainaut were included in this study. The susceptibilities to penicillin, amoxicillin, cefuroxime, ciprofloxacin, moxifloxacin, erythromycin and tetracycline were determined by a microdilution technique following NCCLS recommendations. Decreased susceptibility to penicillin was 32.5% (23.4% intermediate and 9.1% high-level). The other insusceptibility rates were as follows: amoxicillin 1.9% [0% Resistance (R)], cefuroxime 23.4% (R 22.1%), ciprofloxacin 9.1% (R 1.3%), erythromycin 39.6% (R 38.3%), and tetracycline 31.8% (R 30.5%). No decreased susceptibility was found for moxifloxacin. MICs of amoxicillin, cefuroxime, erythromycin and tetracycline rose with those of penicillin for penicillin-insusceptible isolates. Most penicillin-insusceptible isolates remained fully susceptible to amoxicillin (94%), while moxifloxacin and ciprofloxacin kept an activity on 100% and 92% of these isolates respectively. Phenotypes with triple or quadruple insusceptibility were present in 31.2% of the isolates. Penicillin-insusceptible isolates showed a co-insusceptibility of 36.7% to erythromycin, 30.0% to tetracycline and 3.3% to ciprofloxacin.

Analysis of inconclusive breast FNA by triple test.

OBJECTIVE: To evaluate the efficiency of triple test for non-diagnostic (inconclusive and inadequate) FNAs of palpable breast lesions and to compare our results with the literature. METHODS: A retrospective analysis was done on cases that were having cyto-histological correlation with clinical and radiological follow up. Out of 446 FNAs performed at our institute during the period of 15 years, only 16 cases were discovered fulfilling the above criteria and these were reviewed blindly and scored. The triple test was applied to each case. Each component of the triple test was assigned 1, 2, or 3 points for a benign, suspicious, or malignant result, respectively, yielding a total triple test score (TTS) of these 16 cases. RESULTS: Three out of 16 specimens were unsatisfactory and rest 13 cases inconclusive (i.e., suspicious) cytologically, diagnosed as having scant atypical cells. All malignant cases scored above 6 except one case that scored 5. The two benign cases scored 1 and 3. On histological follow up 2 of the unsatisfactory cases turned out as fibroadenoma (scored 1 and 3) and one as malignant (scored 5). Among inconclusive cases all turned out to be malignant on histological follow up (all scored 6 and above). High clinical suspicion was present in all 14 cases that were proved malignant in histological follow up. Radiological diagnosis of malignancy was present in 11 of 14 malignant cases, suspicious in two malignant cases and in 1 of 2 fibroadenoma cases. All cases underwent surgical removal of the mass as a result of clinical or radiological suspicion. CONCLUSION: Triple test can reliably guide the evaluation and treatment of palpable breast masses. Masses that score 6 points or higher are malignant and should undergo definitive therapy; masses that score 4 points or lower are benign and may be clinically followed up. Only those masses that score 5 points require open biopsy. Our results were in concordance with other larger studies published in the literature. We recommend utilizing the three diagnostic parameters of cytology, clinical findings and radiology, the triple test, to achieve the best diagnostic accuracy in breast FNAs and patient management.

Gallbladder pathologies and cholelithiasis.

OBJECTIVE: Cholecystectomy, mostly due to cholelithiasis is one of the most common surgical procedures utilizing a significant amount of healthcare resources. As there are a huge number of cases, for example approximately 300 cases per year in our region, outlines this commonly encountered lesion should be recorded. Also, in an attempt to delineate the outline of the pattern, age and sex distribution of gallbladder diseases in the whole Kingdom, a comparative analysis is also included in this study with 7 other studies published from different parts of the Kingdom. METHODS: Our study consisted of 740 consecutive gallbladder cholecyctectomies mostly for cholelithiasis received in a time frame of 3.5 years (for example between January 1997 through to May 2000) by the Department of Histopathology retrieved from the records of the laboratory. The outline of main gallbladder pathologies was tabulated. The number of gallbladders received with stones was also calculated. Age and sex distribution for gallbladder pathology and gallstones was also tabulated. RESULTS: There were 131 males (18%) and 609 (82%) females, with a female ratio male 4.6:1. Benign lesions comprised 99% (mean age 36), mostly chronic cholecyctitis (97%) and acute cholecystitis which constituted 15 cases only (2%), malignant lesions comprised only 7 cases for example 1% of all lesions (mean age 65). CONCLUSION: Gallbladder pathologies are very common and similar results have been obtained from other studies by comparative analysis. The mean cholecystectomy rates in the Kingdom totalled approximately 10%, mean age for all cholecystectomy diseases in both sexes equalled 37.05. The mean age for males was 42.26, females 37.25 and their ratio was 44.5:1.

Morphological profile of testicular biopsies associated with infertility.

OBJECTIVE: Based on testicular biopsies examined at King Abdulaziz University Hospital, Jeddah, Kingdom of Saudi Arabia, the goal of this retrospective study is identification and systemization of the histopathological patterns of testicular biopsies received especially for investigating male infertility and further more to compare the findings of our study with similar studies in the literature. METHODS: Our study group consisted of 164 testicular biopsies, which were examined in the Department of Histopathology at King Abdulaziz University Hospital in Jeddah, over a period of 10 years. The data was retrieved and analyzed and the available histopathological results were grouped into 8 different morphological categories. RESULTS: The findings of the biopsies associated with infertility were complied as follows: 45 (27%) showed normal spermatogenesis of which 15% showed active spermatogenesis associated with duct obstruction, 41 (25%) with hypospermatogenesis, 39 (24%) showed end stage tubular sclerosis with interstitial fibrosis, 27 (16.5%) with germ cell aplasia (with or without focal spermatogenesis), 11 (7%) biopsies showed maturation arrest and only on biopsy were associated with karyotpic abnormalities. CONCLUSION: A higher percentage of hypospermatogenesis and end stage tubular sclerosis with interstitial fibrosis was noticed in this study when compared with the other studies reported from Saudi Arabia. A high percentage (27%) of the biopsies show normal spermatogenesis with or without duct obstruction.

Uses of internet technology in clinical practice.

The practice of medicine has extended itself to vast areas and requires active clinicians to systematize and organize their workload through the use of the most up-to-date digital and computer communication technologies. Computerization and worldwide accessibility of information has especially provided great assistance in this regard. The explosive growth of medical information increases the need for the use of these new methods of organizing and accessing data. This article briefly summarizes a few of the vital tools that internet technology has provided clinical practice, with the aid of basic concepts of internet, database systems, hospital systems and data security and reliability.

Profile of female breast lesions in Saudi Arabia.

OBJECTIVE: To evaluate the outline and pattern of male and female breast diseases in Saudi Arabia. METHODS: The study consisted of 953 consecutive female breast biopsies and mastectomies. Information on these cases were retrieved from the records of the laboratory. Outline of breast lesions were tabulated and classified into inflammatory, benign and malignant lesions. RESULTS: Benign lesions comprised 55.24% of all lesions (mean age 31.7), most commonly reported being fibroadenoma 46.9%, fibrocystic disease 23.25% and fibroadenosis 14.5%. Malignant lesion comprised 31.5% of all lesions (mean age 49.19), most commonly reported being ductal carcinoma 80% and lobular carcinoma 5.5%. Inflammatory lesions comprised of 10.1% of all lesions (mean age 29.56), most commonly reported lesion being chronic mastitis 30% and ducectasia 17.6%. CONCLUSION: The rates for female breast diseases varied in different studies but benign fibroadenoma was the most common breast lesion followed by ductal carcinoma. The mean age for malignant lesions in seven different studies was 44.18 years.

Evidence-based medicine.

Evidence-based medicine is one of the recently born explosively growing important issues, whose philosophical origins extend back to mid-19th century and remains a hot topic for clinicians, public health practioners, purchasers, planners, and the public. Evidence-based health care has extended the application of the prinicples of evidence-based medicine to all professions associated with health care, including purchasing and management. So it is important for the up and coming young doctors and clinicians, and even other health care professions, to gain knowledge of critical appraisal and experience in the practice of evidence-based health care. This article gives a brief description of what evidence-based medicine is and how to practice evidence-based medicine and enlists some useful Internet sites that can provide assistance in understanding the subject in even greater detail.

Analysis of false positive and false negative cytological diagnosis of breast lesions.

OBJECTIVE: To study the reasons for interpretive errors in false negative and false positive diagnosis of breast carcinoma on fine needle aspiration cytology material. METHODS: We reviewed only those cases in which cytohistological discrepancies were found, where the cytologic material was abnormal and to some extent misinterpreted or both. RESULTS: There was only one false negative case (false negative fraction 0.32%) proved histologically as ductal carcinoma and four false positive cases (false positive fraction 1.2%); 2 fibroadenoma; 1 fibrocystic disease; and 1 stromal fibrosis. Smears of the two false positive fibroadenoma cases showed very high cellularity, overcrowded clusters and frequent stripped nuclei. The fibrocystic case showed tight clusters of apocrine cells and sheets of loosely aggregated macrophages that were over interpreted. Smears of the false negative ductal carcinoma was hypocellular overall, and the cells showed minimal nuclear pleomorphism. CONCLUSION: Overcrowded clusters and hypercellular smears should be carefully assessed for uniformity of cells and detailed nuclear and cytomorphological features. If the full-blown malignant cytomorphological changes are not visible, a diagnosis of suspicious or inconclusive should be made and frozen section recommended before surgery. Hypocellularity and relatively nuclear monomorphism are the reasons for failure to diagnose malignant breast lesions. Careful attention should be paid to extreme nuclear monomorphism and absence of naked bipolar cells. A cytologically atypical or suspicious diagnosis together with positive radiological and clinical findings should suggest a diagnosis of malignancy.

Evidence-based medicine.

Evidence-based medicine is one of the recently born explosively growing important issues, whose philosophical origins extend back to mid-19th century and remains a hot topic for clinicians, public health practioners, purchasers, planners, and the public. Evidence-based health care has extended the application of the prinicples of evidence-based medicine to all professions associated with health care, including purchasing and management. So it is important for the up and coming young doctors and clinicians, and even other health care professions, to gain knowledge of critical appraisal and experience in the practice of evidence-based health care. This article gives a brief description of what evidence-based medicine is and how to practice evidence-based medicine and enlists some useful Internet sites that can provide assistance in understanding the subject in even greater detail.