Polarization gaps in spiral photonic crystals

We studied the optical properties of a dielectric photonic crystal structure with spirals arranged in a hexagonal lattice. The dielectric constant of the material was 9 and the filling ratio was 15.2%. We found that this kind of structure exhibits a significant polarization gap in the light that was incident along the axis of the spirals. The eigenmodes inside the polarization gap were predominantly right-hand (left-hand) polarized depending on the whether if the spirals are left-handed (right-handed). We calculated the transmission spectrum of a slab of such a structure and it matches well with the analysis of the eigenmodes.

Chiral microstructures (spirals) fabrication by holographic lithography

We present an optical interference model to create chiral microstructures (spirals) and its realization in photoresist using holographic lithography. The model is based on the interference of six equally-spaced circumpolar linear polarized side beams and a circular polarized central beam. The pitch and separation of the spirals can be varied by changing the angle between the side beams and the central beam. The realization of the model is carried out using the 325 nm line of a He-Cd laser and spirals of sub-micron size are fabricated in photoresist.

Delay in diagnosis and its effect on outcome in head and neck cancer

We examined the records of two cohorts of patients who were seen from 1960 to 1999 with a diagnosis of squamous cell carcinoma (SCC) of the mouth and throat, one series being retrospective (n=400) and the other prospective (n=213) to find out about delays in diagnosis. The median delay in both cohorts was 3 months and the patients were responsible for the delay in most cases (n=319, 81% and n=160, 78%, respectively). Half the patients in each cohort had delayed diagnoses (n=217, 54% and n=119, 56%, respectively) and similar percentages (n=110, 53% and n=172, 47%) presented with advanced disease (stage III or IV). These were not the same patients for there was no correlation between delay and stage or survival. Logistic regression analysis showed that non-white race (p=0.01) and high-grade histology (p=0.002) predicted advanced disease. The proportion of patients presenting with advanced disease had not changed in 40 years despite public education. We suggest that some tumours may be silent and that initial symptoms do not reliably predict early disease.

Major pulmonary embolism treated with a rheolytic thrombectomy catheter

The current treatment of massive pulmonary embolism (PE) has been either thrombolysis or surgical embolectomy. Recently, percutaneous rheolytic thrombectomy has emerged as an alternative treatment in patients with contraindications to thrombolysis. We describe a 45-year-old woman who developed major PE post-operatively, who was treated successfully with the AngioJet system. The principles of percutaneous rheolytic thrombectomy, its effectiveness and potential complications are discussed.

Primary care of patients with sexually transmitted diseases or genitourinary symptoms in Hong Kong

OBJECTIVES

To determine the adequacy of care received from general practitioners by patients with sexually transmitted diseases or genitourinary symptoms.

DESIGN

Prospective study.

SETTING

Hong Kong.

PARTICIPANTS

Diagnoses and drug data obtained from logbooks submitted by doctors studying for the Diploma in Family Medicine and candidates for Fellowship examinations between 1999 and 2002.

MAIN OUTCOME MEASURES

Diagnosis or symptom of a sexually transmitted disease and prescribed treatment.

RESULTS

Sexually transmitted diseases and genitourinary symptoms accounted for 1.1% of the workload of these community doctors in Hong Kong. The majority of patients were young adult males. The overall standard of treatment was inadequate: both multi-pharmacy and inappropriate treatment was common; in up to 30% of cases, doctors ignored local or international guidelines.

CONCLUSION

Primary care doctors play an important role in the diagnosis and management of sexually transmitted diseases or genitourinary symptoms in Hong Kong. A high index of suspicion should be maintained and continuing education made available if doctors are to provide an equally high standard of care.

Motor development of very low birthweight infants with chronic lung disease - a comparative study

INTRODUCTION

To determine whether chronic lung disease (CLD) influences specific aspects of motor development in infancy.

MATERIALS AND METHODS

Twenty-nine very low birthweight infants with CLD at 36 weeks' post-conceptional age and 31 infants without CLD were evaluated at 8 months' and 24 months' corrected age using the Neurosensory Motor Development Assessment. Perinatal and neonatal characteristics of the infants with CLD and control infants were compared using the chi-square test for categorical variables and Student's t-test for continuous variables. The relationship between CLD and adverse outcome was measured by the odds ratio (OR) and its 95% confidence interval (CI).

RESULTS

The overall developmental scores of the CLD infants were significantly different compared with control infants at 8 months. By 2 years of age, both groups of infants showed marked improvement in motor performance. However, differences persisted in the area of postural balance and sensory motor skills. Taking periventricular haemorrhage and periventricular leukomalacia into consideration, CLD contributed significantly to the occurrence of motor dysfunction at 8 months of age [odds ratio (OR), 7.4; 95% confidence interval (CI), 2.1 to 26.5]. The impact of CLD on motor development remained substantial, though not statistically significant (OR, 3.7; 95% CI, 0.4 to 37.9) at 2 years of age.

CONCLUSION

CLD has a definite effect on motor development. The pathologic influence of CLD on motor development remains speculative but results of this study emphasise the need for careful neurodevelopmental follow-up of infants with CLD, whether or not these infants suffer intraventricular haemorrhage or periventricular leukomalacia.

Alginate as an auxiliary bacterial membrane: binding of membrane-active peptides by polysaccharides*

The chronicity of Pseudomonas aeruginosa infections in cystic fibrosis (CF) patients is characterized by overproduction of the exopolysaccharide alginate, in which biofilm bacteria are embedded. Alginate apparently contributes to the antibiotic resistance of bacteria in this form by acting as a diffusion barrier to positively charged antimicrobial agents. We have been investigating cationic antimicrobial peptides (CAPs) (prototypic sequence: KKAAAXAAAAAXAAWAAXAAAKKKK-NH(2), where X is any of the 20 commonly occurring amino acids) that were originally designed as transmembrane mimetic peptides. Peptides of this group above a specific hydrophobicity threshold insert spontaneously into membranes and have antibacterial activity at micromolar concentrations. While investigating the molecular basis of biofilm resistance to peptides, we found that the anionic alginate polysaccharide induces conformational changes in the most hydrophobic of these peptides typically associated with insertion of such peptides into membrane environments [Chan et al., J. Biol. Chem. (2004) vol. 279, pp. 38749-38754]. Through a combination of experiments measuring release of the fluorescent dye calcein from phospholipid vesicles, peptide interactions with vesicles in the presence and absence of alginate, and affinity of peptides for alginate as a function of net peptide core hydrophobicity, we show here that alginate offers a microenvironment that provides a protective mechanism for the encased bacteria by both binding and promoting the self-association of the CAPs. The overall results indicate that hydrophilic alginate polymers contain a significant hydrophobic compartment, and behave as an 'auxiliary membrane' for bacteria, thus identifying a unique protective role for biofilm exopolysaccharide matrices.

Crystals of the carotenoid protein from Arthrospira maxima containing uniformly oriented pigment molecules

Crystals of a carotenoid protein from the cyanobacterium Arthrospira maxima have been grown in space group C2 with unit-cell dimensions a = 219.6, b = 40.3, c = 75.5 A and beta = 95.5 degrees. The crystals diffract X-rays to 2.3 A resolution and display unusual optical properties in polarized light that suggest that all of the carotenoid molecules in the crystals are oriented similarly. A slight increase in the concentration of a crystallization additive in the mother liquor induces macroscopic twinning, which is also visible when the crystals are illuminated with polarized light.

Tissue deformation and shape models in image-guided interventions: a discussion paper

This paper promotes the concept of active models in image-guided interventions. We outline the limitations of the rigid body assumption in image-guided interventions and describe how intraoperative imaging provides a rich source of information on spatial location of anatomical structures and therapy devices, allowing a preoperative plan to be updated during an intervention. Soft tissue deformation and variation from an atlas to a particular individual can both be determined using non-rigid registration. Established methods using free-form deformations have a very large number of degrees of freedom. Three examples of deformable models--motion models, biomechanical models and statistical shape models--are used to illustrate how prior information can be used to restrict the number of degrees of freedom of the registration algorithm and thus provide active models for image-guided interventions. We provide preliminary results from applications for each type of model.

Australian consumers are sceptical about but influenced by claims about fat on food labels

OBJECTIVES

To explore the beliefs and attitudes of Australian consumers to claims about fat made on the labels of packaged food.

DESIGN

Content analysis of transcripts from focus group discussions.

SUBJECTS

A total of 26 female and 10 male participants aged 20-80 y, recruited by advertisement into six focus groups, stratified by age, sex and health status.

RESULTS

Awareness of claims about fat was high in this sample of Australians and participants admitted that they influenced their purchase decisions. The most preferred form of claim was 'X% fat free'. Claims were considered most useful on foods that were high in fat. There was considerable scepticism about all nutrient claims, and consumers preferred to check claims about fat against the values in the nutrition information panel. Many claims were seen as advertising that could be misleading, deceptive or confusing. While claims about fat might prompt product trial, factors such as price, taste, naturalness, as well as other nutritional factors, also influenced purchase decisions. Some consumers believe low fat claims encourage over consumption of foods.

CONCLUSIONS

Changes to regulations governing nutrition claims on food labels should be made to enhance their credibility and support their role in assisting consumers to make healthier food choices.

Laparoscopic drainage of pancreatic pseudocysts

BACKGROUND

Laparoscopic drainage of pancreatic pseudocysts (PPs) has been used in selected cases. The aim of this study is to analyze our results with the laparoscopic technique and to compare them with those of a cohort of patients treated by open surgery during the same time period.

PATIENTS AND METHODS

Ten patients underwent laparoscopic drainage of PPs during a 7-year period [laparoscopic group (LG)]. The type of drainage was chosen according to the size and location of the PP. Demography, surgical details, results, and complications were analyzed and contrasted with those of 6 patients who underwent open drainage [open group (OG)].

RESULTS

All patients presented with mature PPs developed after a documented episode of acute pancreatitis. Mean age of the LG was 42 years (six males and four females). In the OG, mean age was 36 years (five males and one female). Etiology of the pancreatitis was alcoholic in eight patients, biliary in five, toxic in two, and associated with systemic lupus erythematous in one. Laparoscopic procedures included Roux-en-Y cystojejunostomy in four patients, extraluminal cystogastrostomy in four, and intraluminal cystogastrostomy in two. There were no conversions. In the OG, cystogastrostomy was performed in three patients and Roux-en-Y cystojejunostomy in three. One patient in the LG developed upper gastrointestinal bleeding the day after surgery that resolved uneventfully, one patient presented a postoperative abscess that required open drainage, and one patient presented a residual pseudocyst that was treated by endoscopy. Morbidity in the OG included a small bowel obstruction secondary to an internal hernia that required reoperation, pneumonia, and a residual pseudocyst that was treated conservatively in one patient each. At a median follow-up of 22 months (range, 1-72) all patients were asymptomatic with no evidence of recurrent disease by computed tomography scan.

CONCLUSION

Laparoscopic drainage of PPs is feasible, safe, and effective. Results are similar to those obtained using the open technique.

The pattern of distribution of selected ATP-sensitive P2 receptor subtypes in normal rat kidney: an immunohistological study

Using immunohistological techniques and available polyclonal antibodies, we have identified several ATP-sensitive P2 receptor subtypes in specific structures of the normal rat kidney. Of the P2 receptor subtypes examined, P2X1, P2X2 and P2Y1 receptors were found in the smooth muscle layer of intrarenal vessels. The P2Y1 receptor was also found on glomerular mesangial cells, the brush border membrane of the proximal straight tubule and on peritubular fibroblasts. In the cortex, P2Y4 receptors were found on the tubule epithelium of the proximal convoluted tubule, and P2Y2 receptors on glomerular epithelial cells (podocytes). P2X4 and P2X6 receptors were present throughout the renal tubule epithelium from the proximal tubule to the collecting duct. P2X5 receptors were expressed on medullary collecting duct cells and the apical membrane of the S3 segment of the proximal tubule. Possible functions of these receptor subtypes in normal rat kidney are discussed.

Antibody response to the human stress protein BiP in rheumatoid arthritis

OBJECTIVES

The human stress protein BiP (immunoglobulin binding protein) has been implicated in the pathogenesis of rheumatoid arthritis (RA) since BiP was found to stimulate synovial T-cell proliferation and anti-BiP antibodies are present in the serum of RA patients. The aim of this study was the development of a rapid and reproducible enzyme-linked immunosorbent assay (ELISA) to determine the specificity and sensitivity of anti-BiP antibodies in RA.

METHODS

An ELISA was developed that detected antibodies to BiP. The prevalence of anti-BiP antibodies was determined in sera from patients with early and established RA, sera antedating the onset of RA and sera from patients with other inflammatory and autoimmune diseases and healthy controls.

RESULTS

We have confirmed the increased prevalence of antibodies to BiP in the sera of a large cohort of patients with established RA (specificity 71% and sensitivity 73%) and early RA (specificity 65% and sensitivity 66%). In pre-disease sera, median 2.5 yr (interquartile range 1.1-4.7) before symptoms of joint disease, the sensitivity for anti-BiP antibodies was 45% and the specificity was 65% for the development of RA.

CONCLUSION

Antibodies to BiP are found in the sera of patients with RA and in sera antedating the onset of RA.

Drug-eluting stents: the end of restenosis?

One of the major advancements in interventional cardiology has been the introduction of drug-eluting stents (DES). By incorporating anti-proliferative agents onto the surface of the stent, neointimal hyperplasia occurring within the stent, which is the main cause of in-stent restenosis (ISR), is markedly reduced. Stents coated with agents, like sirolimus or paclitaxel, when compared to bare metal stents (BMS), had shown remarkable reduction in binary restenosis and target vessel revascularisation (TVR) rates in large randomised clinical trials. The final hurdle of percutaneous coronary intervention (PCI) seems to have been overcome. However, there are still many uncertainties that need to be clarified. The long-term safety of DES remains a major concern; in particular, stent thrombosis and incomplete stent apposition. In the real world, there is a tendency to implant DES in smaller vessels, longer lesions, and complex lesions, as these are high risk for ISR and would yield the greatest benefit. Whether the excellent results of clinical trials of DES can be replicated in these more complex lesions is still unknown and awaits further studies. Although early experience with DES in complex lesions had shown improved results, a higher number of ISR were seen. Finally, the high cost of these devices has precluded their use in all patients undergoing PCI and deliberation among healthcare policy-makers on who should receive DES has centred not only on financial, but also legal and ethical issues. As DES has not completely eliminated ISR and not all patients can afford DES, ISR may survive the initial assault of DES, albeit considerably less in number, for now.

Use of an electronic barcode system for patient identification during blood transfusion: 3-year experience in a regional hospital

OBJECTIVE

To evaluate the use of an electronic barcode system for patient identification during blood transfusion.

DESIGN

Retrospective study.

SETTING

Regional hospital, Hong Kong.

PATIENTS

For all patients requiring blood transfusion between May 1999 and April 2002, with the exception of patients in the psychiatric wards and the accident and emergency department, a portable, hand-held scan-and-print electronic device was used to verify and document patients' identity at two critical points of transfusion: blood sampling for the compatibility test and blood administration.

MAIN OUTCOME MEASURES

Scope of use of the electronic device, cost, effectiveness, staff compliance, problems and solution for improvement.

RESULTS

In the first 3 years of hospital-wide use of the new device, no incidents of blood transfusion to wrong patients, or wrong labelling of blood samples, occurred with 41,00 blood sampling procedures and administration of 27 000 units of blood. Blood sampling took 6 minutes to complete with the use of the electronic device-similar to that taken by the conventional second-checker system. Among hospital staff, the compliance rate of using the new device approached 90%. Battery problems occurred in 12% of episodes of use of the device.

CONCLUSIONS

The electronic barcode system was effective in reducing human error related to bedside transfusion procedures. The future goal is to tailor-make a more efficient device with additional functions.

Phenotypic and functional differences between human saphenous vein (HSVEC) and umbilical vein (HUVEC) endothelial cells

The vascular endothelial cell (EC) plays an essential role in the pathogenesis of inflammation, transplant rejection and tumour metastasis. Most research on vascular ECs uses human umbilical vein endothelial cells (HUVECs). However, HUVECs are derived from immune-naive foetal tissue, and show significant functional differences from adult vascular endothelium. In this paper, we characterise an alternative model based on human saphenous vein ECs (HSVECs), describe their culture conditions and provide a detailed functional comparison with HUVECs. Compared with HUVECs, HSVECs show an increased sensitivity to ox-LDL and a reduced response to cytokines, as indicated by adhesion molecule expression as well as leukocyte adhesion and transmigration. With respect to their ability to present antigen, HSVECs have a higher level of HLA-DR, CD40 and ICOS-L following cytokine stimulation. In addition, HSVECs upregulate the costimulatory ligand CD80 (B7.1) following CD40 ligation, and support allogeneic T cell proliferation, while HUVECs fail to express CD80. Due to differential expression of adhesion molecules, poorly differentiated tumour cell lines also showed more adhesion to HSVECs than to HUVECs. These results indicate that HSVECs have advantages over HUVECs for studying adult vascular endothelial pathology in vitro.

Tolerance mechanisms and recent progress

There has been tremendous progress in our understanding of the mechanisms mediating allograft tolerance, which have been revealed to be far more complex and regulated than hitherto suspected. New results have enriched our understanding of the relative contributions of the direct and indirect pathways to immunity and tolerance over time. The role of central tolerance has been expanded with the surprising discovery of "ectopic" or "promiscuous" antigens expressed by medullary thymic epithelial cells, and the function of the thymus in generating naturally occurring CD4+ CD25+ regulatory T cells. In the periphery, it is increasingly appreciated that tolerance is a highly active process, with tolerogenic dendritic cells and regulatory T cells being the major players. However, the challenge of understanding the complex interactions regulating the dynamic balance between immunity and tolerance are formidable, and new tools from the more formal disciplines of nonlinear dynamics and systems engineering may help provide insight. Although many hurdles remain, the progress in elucidating the basic mechanisms of tolerance is rapidly being translated into clinical trials and provides grounds for optimism that clinical tolerance will eventually become a reality.

Effects of active fiber length on the tunability of erbium-doped fiber ring lasers

We numerically investigate the effects of the active fiber length on the tunability of erbium-doped fiber ring lasers for the cases of with and without pair-induced quenching (PIQ). The numerical results are confirmed by experiments. We have found that the tuning range shifts from C-band to L-band with an increase in the active fiber length. A maximum tuning range of over 100 nm, covering both the C- and L-band, can be achieved with an optimized active fiber length. It is also found that the PIQ is favorable for Lband lasing though it reduces the output power and degrades the power flatness. Using these findings, a novel method employing active fiber length switching is proposed to extend the tuning range of the laser, which is only limited by the free spectral range (FSR) of the tunable filter. A large tuning range of 102 nm is obtained using a tunable fiber Fabry-Perot filter with an FSR of 75 nm.