Biomedical subjects

T Will

Publications and source records attributed to T Will.

6 recordsLinked to original sources

PubMed2002

Distribution of sunscreens on skin.

The effectiveness of sunscreens was originally achieved by incorporation of soluble organic UV absorbers such as cinnamates and others into cosmetic formulations. Determinations of the sun protection factor (SPF) of emulsions containing different organic UV absorbers clearly indicate that the efficacy depends on the absorption characteristics of each single UV filter substance. Nowadays, micronised pigments such as titanium dioxide or zinc oxide have also been found to be protective against harmful UV rays. Our investigations using optical and electron microscopy proved that neither surface characteristics, particle size nor shape of the micronised pigments result in any dermal absorption of this substance. Micronised titanium dioxide is solely deposited on the outermost surface of the stratum corneum and cannot be detected in deeper stratum corneum layers, the human epidermis and dermis.

Administration, Topical↗

PubMed2001

The human stratum corneum layer: an effective barrier against dermal uptake of different forms of topically applied micronised titanium dioxide.

Electron microscopy visualisation and light microscopic investigations of three different application forms of titanium dioxide proved that neither surface characteristics, particle size nor shape of the micronised titanium dioxide result in any dermal absorption of this substance: Micronised titanium dioxide is solely deposited on the outermost surface of the stratum corneum and cannot be detected in deeper stratum corneum layers, the human epidermis and dermis.

Administration, Topical↗

PubMed2000

Penetration pathways of fluorescent dyes in human hair fibres investigated by scanning near-field optical microscopy.

Thin cross-sections of human hairs were investigated by scanning near-field optical microscopy (SNOM) and confocal laser scanning microscopy (CLSM) after penetration of a fluorescent dye. The same samples were measured with both techniques to compare the observed structures. The images obtained from the two methods show nearly identical structures representing pathways of the dye molecules in hairs. The SNOM images provide a higher resolution than the CLSM images. Therefore, SNOM is believed to be a suitable method for investigations at a resolution of 100 nm on penetration pathways of fluorescent dyes such as the cell membrane complex pathway in cross-sections of hairs.

Fluorescent Dyes↗

PubMed2000

An iterative method for faster sum-of-pairs multiple sequence alignment.

MOTIVATION: Multiple sequence alignment is an important tool in computational biology. In order to solve the task of computing multiple alignments in affordable time, the most commonly used multiple alignment methods have to use heuristics. Nevertheless, the computation of optimal multiple alignments is important in its own right, and it provides a means of evaluating heuristic approaches or serves as a subprocedure of heuristic alignment methods. RESULTS: We present an algorithm that uses the divide-and-conquer alignment approach together with recent results on search space reduction to speed up the computation of multiple sequence alignments. The method is adaptive in that depending on the time one wants to spend on the alignment, a better, up to optimal alignment can be obtained. To speed up the computation in the optimal alignment step, we apply the alpha(*) algorithm which leads to a procedure provably more efficient than previous exact algorithms. We also describe our implementation of the algorithm and present results showing the effectiveness and limitations of the procedure.

Algorithms↗

PubMed1999

[Early decline in an epidemic: evolution of the prevalences of HIV, hepatitis B, hepatitis C and aminotransferases in intravenous drug abusers in Strasbourg between 1980 and 1990].

OBJECTIVE: In order to study the prevalence of hepatitis B and C as well as HIV virus and disruptive factors of aminotransferase enzyme among intravenous drug users. METHOD: We conducted retrospective study of 169 patients who were hospitalised in a clinic where they were weaned from drug use between 1980 and 1990. RESULTS: The prevalence of HIV is 13.2%, and that of hepatitis B is 67.5%. When comparing the years 1980-1987 and 1987-1990, we noticed that the prevalence of HIV drops from 25.9% to 7.8% (p = 0.006), and that of hepatitis B from 75.9% to 60% (p = 0.027). Since November 1989, we were able to detect hepatitis C virus on a regular basis, and it showed a prevalence of 67.4%. The prevalence of aminotransferase enzyme disorders is 52.7%. CONCLUSION: We compare these results with those of other material on the same subject and we discuss various ideas to explain the unexpected decrease of HIV prevalence.

Adult↗

PubMed1997

Nanofabrication of Small Copper Clusters on Gold(111) Electrodes by a Scanning Tunneling Microscope

The use of scanning tunneling microscopy in an electrochemical environment as a tool for the nanoscale modification of gold electrodes was demonstrated. Small copper clusters, typically two to four atomic layers in height, were precisely positioned on a gold(111) electrode by a process in which copper was first deposited onto the tip of the scanning tunneling microscope, which then acted as a reservoir from which copper could be transferred to the surface during an appropriate approach of the tip to the surface. Tip approach and position were controlled externally by a microprocessor unit, allowing the fabrication of various patterns, cluster arrays, and "conducting wires" in a very flexible and convenient manner.

Journal Article↗