Influence of the Mold Temperature and Part Thickness on the Replication Quality and Molecular Orientation in Compression Injection Molding of Polystyrene

It is well known that the process of injection molding with dynamic mold temperature control leads to a good replication quality of high aspect ratio microstructures. However, the inhomogeneous pressure distribution during the holding pressure phase results in an anisotropy of the component properties, low dimensional accuracy and, especially with optical polymers, in undesired stress birefringence. The anisotropy is based on the orientation of the molecular chains in the flow direction, which can be reduced by an injection-compression molding (ICM) process. In order to use the synergy from both processes, an injection-compression molding process with dynamic mold temperature control can be utilized. Within the scope of this investigation, the new process was reproduced by an ICM process at elevated mold temperature (ICM_EMT) and compared with injection molding (IM) with regard to molding accuracy and optical properties in dependence of component thickness and mold temperature. In order to evaluate the molding accuracy, the roughness of a wire-eroded microstructure on the cavity surface was measured. To determine the degree of orientation, the optical properties considered were the transmission and the path difference. It was shown that the adapted ICM process was able to achieve a high degree of replication accuracy with a low degree of orientation, especially for thin-walled components. ICM at elevated mold temperature reduced the path difference in the components with the lowest wall thickness by a factor of two while at the same time optimizing the replication of the microstructure. This could also be confirmed by transmission measurements.

Optoacoustic inversion via convolution kernel reconstruction in the paraxial approximation and beyond

In this article we address the numeric inversion of optoacoustic signals to initial stress profiles. Therefore we study a Volterra integral equation of the second kind that describes the shape transformation of propagating stress waves in the paraxial approximation of the underlying wave-equation. Expanding the optoacoustic convolution kernel in terms of a Fourier-series, a best fit to a pair of observed near-field and far-field signals allows to obtain a sequence of expansion coefficients that describe a given "apparative" setup. The resulting effective kernel is used to solve the optoacoustic source reconstruction problem using a Picard-Lindelöf correction scheme. We verify the validity of the proposed inversion protocol for synthetic input signals and explore the feasibility of our approach to also account for the shape transformation of signals beyond the paraxial approximation including the inversion of experimental data stemming from measurements on melanin doped PVA hydrogel tissue phantoms.

[Instillation therapies for urothelial carcinoma of the upper urinary tract]

Traditionally, urothelial carcinoma of the upper urinary tract was a clear indication for radical nephroureterectomy with bladder cuff excision. It has been shown that in well-selected patients and depending on tumor stage, a kidney-sparing approach can be pursued with good oncological outcome and equivalent to the radical approach. The prevention of local and bladder recurrences is an important factor. Instillation therapies with bacillus Calmette-Guérin and/or mitomycin C have been successfully used to this end. Due to the low incidence of upper tract urothelial cancer and due to the usually retrospective nature of existing literature, however, data is limited. In this article, we provide a review of the indication, technical execution and results of instillation therapies of the upper urinary tract.

Direct Text Entry in Electronic Progress Notes

Objectives: It is not uncommon that the introduction of a new technology fixes old problems while introducing new ones. The Veterans Administration recently implemented a comprehensive electronic medical record system (CPRS) to support provider order entry. Progress notes are entered directly by clinicians, primarily through keyboard input. Due to concerns that there may be significant, invisible disruptions to information flow, this study was conducted to formally examine the incidence and characteristics of input errors in the electronic patient record.

Methods: Sixty patient charts were randomly selected from all 2,301 inpatient admissions during a 5-month period. A panel of clinicians with informatics backgrounds developed the review criteria. After establishing inter-rater reliability, two raters independently reviewed 1,891 notes for copying, copying errors, inconsistent text, inappropriate object insertion and signature issues.

Results: Overall, 60% of patients reviewed had one or more input-related errors averaging 7.8 errors per patient. About 20% of notes showed evidence of copying, with an average of 1.01 error per copied note. Copying another clinician’s note and making changes had the highest risk of error. Templating resulted in large amounts of blank spaces. Overall, MDs make more errors than other clinicians even after controlling for the number of notes.

Conclusions: Moving towards a more progressive model for the electronic medical record, where actions are recorded only once, history and physical information is encoded for use later, and note generation is organized around problems, would greatly minimize the potential for error.

Development of a combined OCT-Raman probe for the prospective in vivo clinical melanoma skin cancer screening

A combined optical coherence tomography (OCT)-Raman probe was designed and built into a spectral domain OCT head, and its performance was evaluated and compared to the most common Raman probe setups, based on a fiber bundle and confocal free space optics. Due to the use of the full field of view of an OCT scanning lens, the combined probe has a superior performance within maximum permissible exposure limits, compared to the other two probes. Skin Raman spectra, recorded in vivo, further prove the feasibility of the OCT-Raman probe for the future in vivo clinical applications in skin cancer screening.

Effective one-dimensional approach to the source reconstruction problem of three-dimensional inverse optoacoustics

The direct problem of optoacoustic signal generation in biological media consists of solving an inhomogeneous three-dimensional (3D) wave equation for an initial acoustic stress profile. In contrast, the more defiant inverse problem requires the reconstruction of the initial stress profile from a proper set of observed signals. In this article, we consider an effectively 1D approach, based on the assumption of a Gaussian transverse irradiation source profile and plane acoustic waves, in which the effects of acoustic diffraction are described in terms of a linear integral equation. The respective inverse problem along the beam axis can be cast into a Volterra integral equation of the second kind for which we explore here efficient numerical schemes in order to reconstruct initial stress profiles from observed signals, constituting a methodical progress of computational aspects of optoacoustics. In this regard, we explore the validity as well as the limits of the inversion scheme via numerical experiments, with parameters geared toward actual optoacoustic problem instances. The considered inversion input consists of synthetic data, obtained in terms of the effectively 1D approach, and, more generally, a solution of the 3D optoacoustic wave equation. Finally, we also analyze the effect of noise and different detector-to-sample distances on the optoacoustic signal and the reconstructed pressure profiles.

Effect of antiseptic irrigation on infection rates of traumatic soft tissue wounds: a longitudinal cohort study

OBJECTIVE

Acute traumatic wounds are contaminated with bacteria and therefore an infection risk. Antiseptic wound irrigation before surgical intervention is routinely performed for contaminated wounds. However, a broad variety of different irrigation solutions are in use. The aim of this retrospective, non-randomised, controlled longitudinal cohort study was to assess the preventive effect of four different irrigation solutions before surgical treatment, on wound infection in traumatic soft tissue wounds.

METHOD

Over a period of three decades, the prophylactic application of wound irrigation was studied in patients with contaminated traumatic wounds requiring surgical treatment, with or without primary wound closure. The main outcome measure was development of wound infection. From 1974-1983, either 0.04 % polihexanide (PHMB), 1 % povidone-iodine (PVP-I), 4 % hydrogen peroxide, or undiluted Ringer's solution were concurrently in use. From 1984-1996, only 0.04 % PHMB or 1 % PVP-I were applied. From 1997, 0.04 % PHMB was used until the end of the study period in 2005.

RESULTS

The combined rate for superficial and deep wound infection was 1.7 % in the 0.04 % PHMB group (n=3264), 4.8 % in the 1 % PVP-I group (n=2552), 5.9 % in the Ringer's group (n=645), and 11.7 % in the 4 % hydrogen peroxide group (n=643). Compared with all other treatment arms, PHMB showed the highest efficacy in preventing infection in traumatic soft tissue wounds (p<0.001). However, compared with PVP-I, the difference was only significant for superficial infections.

CONCLUSION

The large patient numbers in this study demonstrated a robust superiority of 0.04 % PHMB to prevent infection in traumatic soft tissue wounds. These retrospective results may further provide important information as the basis for power calculations for the urgently needed prospective clinical trials in the evolving field of wound antisepsis.

Detection, numerical simulation and approximate inversion of optoacoustic signals generated in multi-layered PVA hydrogel based tissue phantoms

Optoacoustic (OA) measurements can not only be used for imaging purposes but as a more general tool to "sense" physical characteristics of biological tissue, such as geometric features and intrinsic optical properties. In order to pave the way for a systematic model-guided analysis of complex objects we devised numerical simulations in accordance with the experimental measurements. We validate our computational approach with experimental results observed for layered polyvinyl alcohol hydrogel samples, using melanin as the absorbing agent. Experimentally, we characterize the acoustic signal observed by a piezoelectric detector in the acoustic far-field in backward mode and we discuss the implication of acoustic diffraction on our measurements. We further attempt an inversion of an OA signal in the far-field approximation.

Synthesis of Control Systems for Manipulators Using Multivariable Robust Servomechanism Theory

This paper describes a framework for synthesizing control laws for manipulators based on robust servomechanism theory for multivariable linear systems. This framework takes into account the coupled and nonlinear nature of the differen tial equations describing the manipulator as well as the fact that the inputs and outputs are subject to large excursions.

The robust servomechanism theory is applied to the linear system that results when the overall, nonlinear, dynamic system is split, in the standard manner, into a nominal sys tem and a (linear) system linearized about the nominal. A control law for the linear system is then derived on the basis of linear quadratic regulator theory. To ensure good dynamic response, the implicit model-following technique is used to choose the weights in the resulting performance index.

The theory is then applied to design a control law for a two-degree-of-freedom spatial manipulator following a pre scribed trajectory. The effect of changing the speed and iner tias of the manipulator on the gains prescribed by the control law is also discussed.