ANGULAR DISTRIBUTION IN PHOTODISSOCIATION OF ORIENTED POLYATOMIC MOLECULES

This paper presents a general formula for the angular distribution in the direct photo-dissociation of polyatomic molecules, in which the asymmetry of the parent and fragmentmolecules, the polarization of the radiation field, the number of photons absorbed, the tran-sition dipole moment orientation, and the recoil direction have been explicitly considered.

Assessing the thermal stability of toolmarks casting materials through optical comparison microscopy,virtual comparison microscopy and quantitative similarity scores

Toolmarks,particularly those found on bulky,inaccessible or immovable items,can be recovered by casting.To allow for subsequent comparative examinations,the casting material,typically polysiloxanes or silicones,must be able to capture and preserve fine details within a toolmark accurately.To study the stability of such details after exposure to heat,toolmark casts were heated at either 60°C for 2 h,or 90°C for 1 h.These casts were subsequently compared to casts that had not been exposed to heat,using traditional optical comparison microscopy,as well as virtual comparison microscopy.Digitised toolmark signatures were also extracted from the casts and compared pairwise to obtain quantitative similarity scores based on cross-correlation,consecutive matching striae and Mann-Whitney U-statistic.Our results show that the fine surface details captured on all four commercial toolmark casting materials tested herein remained stable after exposure to heat.This study shows that the above heating protocols are viable viral inactivation methods for toolmark casts that are potentially contaminated with human coronaviruses,such as SARS-CoV-2.Our findings also apply to other scenarios,such as for casts that were left in a vehicle parked under the sun.

Forensic examination of plastic drinking straws based on their physical characteristics and manufacturing marks

This work highlights the evidential value of examining plastic drinking straws to establish linkages between multiple sources for forensic intelligence,investigative or prosecution pur-poses.Plastic drinking straws are commonly encountered in drug cases,either as inhalational paraphernalia or as packaging material.However,to the best of our knowledge,systematic studies on the evidential value of straws have not previously been carried out.In this study,over 80 packets of clear and colourless straws—most of which were visually similar—were purchased from various commercial outlets in Singapore.Some physical characteristics(viz.,polarizing patterns,thickness,circumference and mass per unit length)and the manufactur-ing marks of these straws were examined to assess their potentials for discriminating straws from different packets.Comparison of polarizing patterns yielded a discrimination of approximately 69%,while thickness,circumference,and mass per unit length measurements resulted in lower discriminations.Comparison microscopy of manufacturing marks was found to be the most discriminating among all techniques employed herein,with a discrimination of about 95%,even among straws with similar polarizing patterns.