Direct thermo-optical tuning of silicon microresonators for the mid-infrared

We use light from a visible laser diode to directly tune silicon-on-chip microresonators by thermo-optical effect. We show that this direct tuning is local, non invasive and has a much smaller time constant than global temperature tuning methods. Such an approach could prove to be highly effective for Kerr comb generation in microresonators pumped by quantum cascade lasers, which cannot be easily tuned to achieve comb generation and soliton-mode locked states.

Reverse Phase HPLC Analysis of Commercial Surfactants used as Melt Additives

Reverse phase HPLC (High Performance Liquid Chromatography) was used to analyze the length distribution of polyoxyethylene (POE) chains in commercial surfactants that can be used as melt additives for hydrophilic polypropylene surface modification. Ten nonionic surfactants including ethoxylated alcohols, nonyl phenols and amines, PEG esters, and mono glycerides were investigated. HPLC methods described herein are capable of analyzing ethoxylated nonionic surfactants and offer the advantage of separating the components in surfactants according to both the hydrophobe and hydrophile chain length. Moreover, the method is rapid and gradient elution allows for good baseline separation of the several components in the additives.

Modelling the transmission dynamics of acute haemorrhagic conjunctivitis: application to the 2003 outbreak in Mexico

We model an outbreak of acute haemorrhagic conjunctivitis (AHC) using a simple epidemic model that includes susceptible, infectious, reported, and recovered classes. The model's framework considers the impact of underreporting and behaviour changes on the transmission rate and is applied to a recent epidemic of AHC in Mexico, using a fit to the cumulative number of cases to estimate model parameters, which agree with those derived from clinical studies. The model predicts a 'mean time from symptomatic onset to diagnosis' of 1.43 days (95 per cent CI: 1-2.5) and that the final size of the Mexican epidemic was underreported by 39 per cent. We estimate that a primary infectious case generates approximately 3 secondary cases (R0* = 2.64, SD 0.65). We explore the impact of interventions on the final epidemic size, and estimate a 36 per cent reduction in the transmission rate due to behaviour changes. The effectiveness of the behaviour changes in slowing the epidemic is evident at 21.90 (SD 0.19) days after the first reported case. Results therefore support current public health policy including expeditious announcement of the outbreak and public health information press releases that instruct individuals on avoiding contagion and encourage them to seek diagnosis in hospital clinics.

An age-structured epidemic model of rotavirus with vaccination

The recent approval of a rotavirus vaccine in Mexico motivates this study on the potential impact of the use of such a vaccine on rotavirus prevention and control. An age-structured model that describes the rotavirus transmission dynamics of infections is introduced. Conditions that guarantee the local and global stability analysis of the disease-free steady state distribution as well as the existence of an endemic steady state distribution are established. The impact of maternal antibodies on the implementation of vaccine is evaluated. Model results are used to identify optimal age-dependent vaccination strategies. A convergent numerical scheme for the model is introduced but not implemented. This paper is dedicated to Prof. K. P. Hadeler, who continues to push the frontier of knowledge in mathematical biology.

Short-pulse carbon dioxide laser resurfacing in the treatment of rhytides and scars. A clinical and histopathological study

BACKGROUND

Previous studies have shown the efficacy of short-pulse carbon dioxide (CO2) lasers in the treatment of rhytides and scars. To date, there have been few studies examining the histological aspects of these treatments.

OBJECTIVE

The purpose of this study was to perform a prospective clinical and histopathological study of CO2 laser resurfacing for improvement of facial rhytides and scars.

METHODS

A total of 23 patients were studied. Clinical improvement was evaluated both pre- and postoperatively using photographs and optical profilometry. Skin biopsies of rhytides were also obtained.

RESULTS

Postoperatively, rhytides and scars both demonstrated significant increases in clinical improvement scores. Results from optical profilometry studies reflected these results. Skin biopsies from rhytides posttreatment demonstrated increases in collagen layer thickness. Improvement was sustained as late as 1 year following treatment.

CONCLUSIONS

Histopathological studies suggest improvement of rhytides and scars by CO2 laser resurfacing may be attributed to new collagen formation following treatment.

Axial and peripheral bone density and nutrient intakes of postmenopausal vegetarian and omnivorous women

The study investigated whether differences exist between postmenopausal Caucasian vegetarian and omnivorous women regarding trabecular and cortical bone density measured with single- and dual-photon absorptiometry. Anthropometric measurements, blood and urine samples, and food intakes of the twenty-eight matched pairs were also compared. The Wilcoxon signed-rank test indicated no significant differences in bone measurements between vegetarians and omnivores at any sites except the skull. The vegetarians' serum globulin and total protein measured higher. Urine calcium and creatinine were similar between the groups. The vegetarians consumed greater quantities of carbohydrate, fiber, magnesium, ascorbic acid, copper, and energy as percent carbohydrate, and lower quantities of protein, niacin, alcohol, vitamin B-12, cholesterol, and energy as percent protein. Despite several differences in dietary intakes, the results indicate that neither cortical nor trabecular bone density in these postmenopausal women was affected by a lactoovovegetarian diet.