Sensitivity of temperature-based time since death estimation on measurement location.

Rectal temperature measurement (RTM) from crime scenes is an important parameter for temperature-based time of death estimation (TDE). Various influential variables exist in TDE methods like the uncertainty in thermal and environmental parameters. Although RTM depends in particular on the location of measurement position, this relationship has never been investigated separately. The presented study fills this gap using Finite Element (FE) simulations of body cooling. A manually meshed coarse human FE model and an FE geometry model developed from the CT scan of a male corpse are used for TDE sensitivity analysis. The coarse model is considered with and without a support structure of moist soil. As there is no clear definition of ideal rectal temperature measurement location for TDE, possible variations in RTM location (RTML) are considered based on anatomy and forensic practice. The maximum variation of TDE caused by RTML changes is investigated via FE simulation. Moreover, the influence of ambient temperature, of FE model change and of the models positioning on a wet soil underground are also discussed. As a general outcome, we notice that maximum TDE deviations of up to ca. 2-3 h due to RTML deviations have to be expected. The direction of maximum influence of RTML change on TDE generally was on the line caudal to cranial.

Biomechanical approach for the assessment of contacts with deformable objects.

Forensic and biomechanical assessment in case of blunt force trauma can be a challenging task especially when deformable striking objects are used. Evaluations solely based on empirical knowledge can lead to misjudgments. Semi-quantitative and quantitative investigations give the forensic assessment a scientific basis comprising experimental and calculation methods. Based on a real case where a car wheel was used as a striking object, our work presents a simple test setup for contact force estimation in head contacts with deformable contact partners. Our approach combines experimental measurements using a single accelerometer and calculations applying the conservation of linear momentum and Newton's second law. Both experimental and calculation results are discussed in terms of validity, reproducibility, and plausibility. With regard to our case, we can conclude that the injury pattern without skull fractures does not confound multiple strikes with a wheel. Skull fractures and potential fatal injuries had not to be expected assuming a head-carcass contact in case of a non-supported head. The approach presented can be applied to any case where deformable or uncommon blunt objects are used.

Influence of striking technique on maximum striking velocities-experimental and statistical investigation.

Forensic experts often have to assess injury and fatality risks in the context of violent blunt force trauma. Maximum striking velocities in one- and two-handed strikes with a rod-like implement can be of particular interest. Current literature lacks studies addressing this problem. The purpose of this study was therefore to measure and analyse maximum striking velocities in one-handed and two-handed strikes in female and male volunteers. We hypothesised higher striking velocities in two-handed strikes compared to one-handed strikes. Fifty volunteers performed one- and two-handed strikes from top to bottom using a steel rod of 65 cm length and 1000 g weight. A Qualisys™ Motion Analysis system registered displacements of reflecting markers fixed to the rod as well as to the volunteer's body. In one-handed strikes, the mean maximum striking velocity was 17.2 m/s in the female sample and 23.9 m/s in the male sample. Statistically not significantly different maximum striking velocities were found in two-handed strikes with mean values of 18.3 m/s in the female sample and 24.2 m/s in the male sample. Female and male volunteers also yielded similar mean maximum striking velocities in two-handed strikes comparing 'overhead' and 'overshoulder' striking techniques. In conclusion, the striking technique did not relevantly influence maximum striking velocities in our setup.

Improving stomach content based death time determination by maximum probability estimation.

Stomach content based death time estimation (SCE), is a well-known technique in forensic sciences. Among more qualitatively oriented approaches the content percentage based method SCE by Tröger, Baur and Spann yields quantitative results and gives stochastic error measures for its outputs. This is possible since the methods estimator, which we call transformed expectation estimator (TEE) as well as the probability distribution of the time between last meal and death are determined numerically, though in SCE the estimator and confidence intervals are presented graphically only. Our articles outcomes are.

Maximum striking velocities in strikes with steel rods-the influence of rod length, rod mass and volunteer parameters.

In blunt force trauma to the head caused by attacks with blunt instruments, contact forces can be estimated based on the conservation of momentum if impact velocities are known. The aims of this work were to measure maximum striking velocities and to examine the influence of rod parameters such as rod mass and length as well as volunteer parameters such as sex, age, body height, body mass, body mass index and the average amount of physical exercise. Steel rods with masses of 500, 1000 and 1500 g as well as lengths of 40, 65 and 90 cm were exemplarily tested as blunt instruments. Twenty-nine men and 22 women participated in this study. Each volunteer performed several vertical strikes with the steel rods onto a passive immobile target. Maximum striking velocities were measured by means of a Qualisys motion capture system using high-speed cameras and infrared light. Male volunteers achieved maximum striking velocities between 14.0 and 35.5 m/s whereas female volunteers achieved values between 10.4 and 28.3 m/s. Results show that maximum striking velocities increased with smaller rod masses and less consistently with higher rod lengths. Statistically significant influences were found in the volunteers' sex and average amount of physical exercise.

Influence of hypo- and hyperthermia on death time estimation - A simulation study.

Numerous physiological and pathological mechanisms can cause elevated or lowered body core temperatures. Deviations from the physiological level of about 37°C can influence temperature based death time estimations. However, it has not been investigated by means of thermodynamics, to which extent hypo- and hyperthermia bias death time estimates. Using numerical simulation, the present study investigates the errors inherent in temperature based death time estimation in case of elevated or lowered body core temperatures before death. The most considerable errors with regard to the normothermic model occur in the first few hours post-mortem. With decreasing body core temperature and increasing post-mortem time the error diminishes and stagnates at a nearly constant level.

Calibration and parameter variation using a finite element model for death time estimation: The influence of the substrate.

The most established method for temperature based death time estimation is based on an empirical double exponential model. New physically based approaches using numerical simulation techniques are subject of current research. A major advantage of such models is the possibility to incorporate non-standard boundary conditions. The aim of this study was to investigate the influence of the substrate on the cooling rate of a body in the early postmortem phase. A finite element model was used for parameter variation in terms of different substrate materials. Simulation results showed a considerable influence of substrate material on the postmortem cooling rate of a body. From a thermodynamical point of view, comparability between measurements on a steel trolley and real cooling scenarios with common substrates like normal floors, asphalt or soil remains questionable. It could be shown that not only the type of substrate but also its composition can have a considerable influence on the postmortem body cooling rate.

Do multiple temperature measurements improve temperature-based death time estimation? The information degradation inequality.

The accuracy of the input parameter values limits the accuracy of the output values in forensic temperature-based death time estimation (TDE) like in many scientific methods. A standard strategy to overcome this problem is to perform multiple measurements of the input parameter values, but such approaches are subject to noise accumulation and stochastic dependencies. A quantitative mathematical analysis of advantages as well as disadvantages of multiple measurements approaches (MMAs) was performed. The results are A general stochastic model of MMA. The information degradation inequality quantifying gains and losses of MMAs. Example calculations of the information degradation inequality for the following two MMAs relevant to TDE: o Multiple successive rectal temperature measurements o Multiple synchronous body layer temperature measurements Neither multiple successive rectal temperature measurements nor multiple synchronous body layer temperature measurements seem to significantly improve death time estimation. MMAs are superior to the single measurement approach only in the very early body cooling phase.

Clinical two-photon microendoscopy.

Two-photon medical imaging has found its way into dermatology as an excellent method for noninvasive skin cancer detection without need of contrast agents as well as for in situ drug screening of topically-applied cosmetical and pharmaceutical components. There is an increasing demand to apply the multiphoton technology also for deep-tissue skin imaging as well as for intracorporal imaging. We report on the first clinical use of multiphoton endoscopes, in particular of a miniaturized rigid two-photon GRIN lens endoscope. The microendoscope was attached to the multiphoton tomograph DermaInspect and employed to detect the extracellular matrix proteins collagen and elastin in the human dermis of volunteers and patients with ulcera by in vivo second harmonic generation and in vivo two-photon autofluorescence.

Absorption spectroscopy of three-dimensional bacteriorhodopsin crystals at cryogenic temperatures: effects of altered hydration.

A comparative study of absorption spectroscopy at 100 K has been performed on three-dimensional crystals of bacteriorhodopsin extracted from a lipidic cubic phase and on native purple membrane. A modified microspectrophotometer has been designed which yields absorption data with a high signal-to-noise ratio and remarkable reproducibility. Excellent agreement of the absorption spectra of the three-dimensional crystals and the purple membrane is observed provided that a rigorous crystal-handling procedure is followed. This result supports the equivalence of the protein structure in both the cubic phase crystals and the native purple membrane. On the other hand, it is shown that dramatic deviations of the crystal spectrum can be induced by minor changes in the extraction method. Exposure to air at room temperature can lead within a short time to an irreversible dehydration manifested by a distinct species with an absorption maximum at 500 nm. Exposure of the crystals to a buffer with lower ionic strength than the crystallization solution produces a different spectral form with an absorption maximum at 477 nm, which was assigned to a distorted protein conformation induced by osmotic stress. The extreme sensitivity of these crystals to experimental conditions is relevant for X-ray structural studies, in particular as different experimental treatments are implemented to trap the intermediates of the protein's photocycle.

Insights into excited-state and isomerization dynamics of bacteriorhodopsin from ultrafast transient UV absorption.

A visible-pump/UV-probe transient absorption is used to characterize the ultrafast dynamics of bacteriorhodopsin with 80-fs time resolution. We identify three spectral components in the 265- to 310-nm region, related to the all-trans retinal, tryptophan (Trp)-86 and the isomerized photoproduct, allowing us to map the dynamics from reactants to products, along with the response of Trp amino acids. The signal of the photoproduct appears with a time delay of approximately 250 fs and is characterized by a steep rise ( approximately 150 fs), followed by additional rise and decay components, with time scales characteristic of the J intermediate. The delayed onset and the steep rise point to an impulsive formation of a transition state on the way to isomerization. We argue that this impulsive formation results from a splitting of a wave packet of torsional modes on the potential surface at the branching between the all-trans and the cis forms. Parallel to these dynamics, the signal caused by Trp response rises in approximately 200 fs, because of the translocation of charge along the conjugate chain, and possible mechanisms are presented, which trigger isomerization.

Probing the ultrafast charge translocation of photoexcited retinal in bacteriorhodopsin.

The ultrafast evolution of the electric field within bacteriorhodopsin was measured by monitoring the absorption changes of a tryptophan residue after excitation of retinal. The Trp absorption decreases within the first 200 femtoseconds and then recovers on time scales typical for retinal isomerization and vibrational relaxation. A model of excitonic coupling between retinal and tryptophans shows that the signal reflects a gradual rise of the retinal difference dipole moment, which precedes and probably drives isomerization. The results suggest an intimate connection between the progressive dipole moment change and the retinal skeletal changes reported over the same time scale.

Femtosecond and picosecond fluorescence of native bacteriorhodopsin and a nonisomerizing analog.

The spectrally and temporally resolved fluorescence properties of native bacteriorhodopsin (bR) and bR reconstituted with a nonisomerizing analog of the retinal Schiff base (bR5.12) are examined. The first attempt to experimentally monitor the excited state relaxation processes in both type of pigments using ultrafast fluorescence spectroscopy is reported. The fluorescence is emitted from retinal molecules in an all-trans configuration. Substantial energy relaxation involves very fast intramolecular and intermolecular vibrational modes and these are shown to occur on a time scale faster than isomerization. The possible contribution of dielectric interaction between the retinal Schiff base and the protein environment for the excited state energy relaxation is discussed.

Spectral and kinetic fluorescence properties of native and nonisomerizing retinal in bacteriorhodopsin.

Steady-state and picosecond (ps) fluorescence studies of wild-type bacteriorhodopsin (wt-bR) and of a nonisomerizing analog locked in the all-trans configuration have been performed. Extending earlier work done by femtosecond absorption spectroscopy, we observe a strong similarity between both proteins in both fluorescence spectra and Stokes shift thus confirming the previous result that the fluorescent state I460 of the native bR proteins is in the all-trans configuration. Comparison of the spectra of fluorescence and stimulated emission of the locked pigments indicates the presence of an excited-state absorption situated around 750 nm. Upon increase of the excitation energy, the time-integrated fluorescence shows an interesting weak blue shift, which is identical for both pigments. Finally, we discuss the primary structural processes in retinal and in the protein that lead to the sub-100 fs formation of I460 and in particular to the considerable Stokes shift.

[Hemodynamic reactions in the area supplied by the middle cerebral artery in post-puncture headache]. / Hämodynamische Reaktionen im Stromgebiet der A. cerebri media bei postpunktionellen Kopfschmerzen.

We used transcranial Doppler ultrasonography to investigate whether a change in hemodynamics in the major arteries of the brain base occurred after diagnostic lumbar puncture. On the day before diagnostic lumbar puncture the flow in the right and left middle cerebral artery was measured in 36 patients using transcranial Doppler ultrasonography. 48 hours after lumbar puncture a second ultrasound examination was performed. We found that only patients with post-lumbar puncture headache (PLPS) showed a significant reduction in the flow of the right middle cerebral artery (p less than or equal to .05). These findings support the puncture-hole-seepage theory as pathogenetic principle of PLPS.

Changes in cerebral haemodynamics in cases of post-lumbar puncture headache: a prospective transcranial Doppler ultrasound study.

We used transcranial Doppler ultrasonography in 45 patients to investigate if changes in haemodynamics in the major arteries of the brain base occurred after lumbar puncture and whether or not patients with or without post-lumbar puncture headache differ with respect to their cerebral haemodynamic parameters before and after lumbar puncture. Before lumbar puncture, patients with post-lumbar puncture headache differed from patients without post-lumbar puncture headache in that they showed significantly higher flow velocities and significant asymmetry of flow velocities with lateralization to the right (p less than or equal to 0.05). Patients without post-lumbar puncture headache, on the other hand, showed non-significant flow velocity lateralization to the left. Forty-eight hours after lumbar puncture, both groups demonstrated symmetrical flow velocities. In addition, only patients with post-lumbar puncture headache showed a significant reduction in the flow velocity of the right middle cerebral artery (p less than or equal to 0.05). These findings suggest that it is not only absolute flow velocity that plays a part in the event of headache, the interhemispheric relation of cerebral haemodynamics also plays a fundamental role.