On dispersion curve coloring for mechanical metafilters.

This paper formalizes smooth curve coloring (i.e., curve identification) in the presence of curve intersections as an optimization problem, and investigates theoretically properties of its optimal solution. Moreover, it presents a novel automatic technique for solving such a problem. Formally, the proposed algorithm aims at minimizing the summation of the total variations over a given interval of the first derivatives of all the labeled curves, written as functions of a scalar parameter. The algorithm is based on a first-order finite difference approximation of the curves and a sequence of prediction/correction steps. At each step, the predicted points are attributed to the subsequently observed points of the curves by solving an Euclidean bipartite matching subproblem. A comparison with a more computationally expensive dynamic programming technique is presented. The proposed algorithm is applied with success to elastic periodic metamaterials for the realization of high-performance mechanical metafilters. Its output is shown to be in excellent agreement with desirable smoothness and periodicity properties of the metafilter dispersion curves. Possible developments, including those based on machine-learning techniques, are pointed out.

Vascular lesions simulating bruising.

Careful examination of the skin and soft tissues is a routine part of the forensic autopsy to identify and characterise traumatic lesions. Three cases are reported where benign vascular lesions presented as bruises. In case 1, a 44-year-old man with a history of epilepsy was found dead on the floor. Dissection of the neck revealed a haemorrhagic area 15 mm × 1.5 mm, deep to the left thyrohyoid muscle. In case 2, an 87-year-old man was found dead with a plastic bag over his head attached to an opened cylinder of nitrogen gas. On the mucosal surface of his upper lip, there was an apparent 5 mm blue/purple bruise. In case 3, examination of the back of a 16-month-old girl revealed an apparent 15 mm bruise. Histological examination of all three lesions revealed benign vascular lesions. In the absence of microscopy, these lesions would have been considered traumatic in origin, raising the possibility of inflicted trauma.

Histological Changes in the Thyroid Gland in Cases of Infant and Early Childhood Asphyxia-A Preliminary Study.

A retrospective blinded study of thyroid gland histology was undertaken in 50 infants and young children aged from 1 to 24 months. Deaths were due to (i) suffocation (N = 7), hanging (4), wedging (3), and chest and/or neck compression (4), and (ii) SIDS (20), noncervical trauma (7), organic disease, (4) and drug toxicity (1). In the asphyxia group (N = 18), thyroid gland congestion ranged from 0 to 3+ with 39% of cases (7/18) having moderate/marked congestion. In three cases, focal aggregates of red blood cells (blood islands) were observed within the intrafollicular colloid. These deaths involved chest compression, chest and/or neck compression, and crush asphyxia in a vehicle accident, and all had facial petechiae. Only 22% of the 32 control cases (7/32) had moderate/marked congestion with no blood islands being identified (p < 0.05). Blood islands within the thyroid gland may be caused by congestion associated with crushing or compression and may provide supportive evidence for this diagnosis.

Incidence of Low Body Mass Index in the Elderly in Forensic Cases-A Possible Marker for Frailty Syndrome?

Diagnosing frailty syndrome at autopsy may be difficult if no adequate clinical history is provided. As low body mass index (BMI) may be associated with frailty in the elderly, the following study was undertaken to determine the percentage of medicolegal cases with BMIs < 18.5 in decedents aged over 75 years. Review was undertaken over three time periods: January to December 1986, January to December 2006, and January to December 2012. In 1986, 16% (15 of 93) of individuals aged ≥75 years had BMIs < 18.5, in 2006, 15% (50 of 336), and in 2012, 13% (35 of 274). In no case was frailty syndrome mentioned. This study demonstrates that frailty syndrome appears to be an underappreciated diagnosis in forensic practice despite a significant percentage of elderly decedents (13-16% over a 27-year period) having low BMIs. Prospective assessment of this group is required to determine the incidence and contribution to mortality of frailty syndrome in a forensic context.

An audit of the contribution to post-mortem examination diagnosis of individual analyte results obtained from biochemical analysis of the vitreous.

Biochemical analysis of the vitreous humor from the eye is an accepted accessory test for post-mortem investigation of cause of death. Modern biochemical analyzers allow testing of a range of analytes from a sample. However, it is not clear which analytes should be requested in order to prevent unnecessary testing (and expense). The means and standard deviation of the values obtained from analysis of the vitreous humor for sodium, potassium, chloride, osmolality, glucose, ketones (ß-hydroxybutyrate), creatinine, urea, calcium, lactate, and ammonia were calculated from which the contribution of each analyte was reviewed in the context of post-mortem findings and final cause of death. For sodium 32 cases were regarded as high (more than one standard deviation above the mean), from which 9 contributed to post-mortem diagnosis [drowning (4), heat related death (2), diabetic hyperglycemia (2), and dehydration (1)], but 25 low values (greater than one standard deviation below the mean) made no contribution. For chloride 29 high values contributed to 4 cases--3 drowning and 1 heat-related, but these were all previously identified by a high sodium level. There were 29 high and 35 low potassium values, none of which contributed to determining the final cause of death. Of 22 high values of creatinine, 12 contributed to a diagnosis of renal failure. From 32 high values of urea, 18 contributed to 16 cases of renal failure (2 associated with diabetic hyperglycemia), 1 heat-related death, and one case with dehydration. Osmolarity contributed to 12 cases (5 heat-related, 4 diabetes, 2 renal failure, and 1 dehydration) from 36 high values. There was no contribution from 32 high values and 19 low values of calcium and there was no contribution from 4 high and 2 low values of ammonia. There were 11 high values of glucose, which contributed to the diagnosis of 6 cases of diabetic hyperglycemia and 21 high ketone levels contributed to 8 cases: 4 diabetic ketosis, 3 hypothermia, 3 ketosis of unknown cause, and 2 alcohol related deaths. A high lactate was identified in 25 cases, which contributed to 1 case with a diagnosis of metformin toxicity (1), but none of the 22 low lactate values contributed. The results of this audit have been used to reduce vitreous biochemistry test requests for sodium, osmolality, glucose, ketones, urea, and creatinine in most cases. Critical appraisal of each part of the post-mortem process should be undertaken to provide evidence to justify any investigative methods used in an autopsy.

The effect of decalcifying solutions on hemosiderin staining.

To determine whether routine decalcification may reduce the amount of stainable iron that is visible on tissue sections, samples of liver and lung tissue with excessive iron stores were placed in three standard decalcifying solutions (i) formic acid [33%], formaldehyde [4%], and NaCl [0.85%]; (ii) formic acid [30%], formaldehyde [4%], and water; and (iii) nitric acid [5%] for 24, 48, 72, and 96 h. After exposure to the decalcifying solutions, the tissues were stained with Perls stain. The slides were examined blind and the intensity of iron staining was scored semiquantitatively from 0 to 3+. The trend in all samples over the course of the experiment (96 h) was for reduction in the intensity of hemosiderin staining. As the amount of stainable hemosiderin in tissues may be significantly altered by decalcification, the absence of hemosiderin in tissues adjacent to a fracture site does not necessarily indicate that the injury was acute.

Significant increases in body mass indexes (BMI) in an adult autopsy population from 1986 to 2006--implications for modern forensic practice.

A study was undertaken of two coronial autopsy populations aged >or= 17 years in Adelaide, South Australia in 1986 and in 2006 to determine whether there had been any increase in body mass index over the intervening 21 years. In 1986 there were 689 cases; M:F=2.8:1. The average BMI was 25.1, with a range from 12.5 to 55.5. 47% of cases had a normal BMI (18.5-24.9), 14.8% were obese (BMI >or= 30), with a subset of 1.3% of cases classified as morbidly obese (BMI >or= 40). In 2006 there were 1176 cases; M:F=1.9:1. The average BMI was 27.1 with a range from 10.5 to 80.6. 32.1% of cases had a normal BMI, 27.2% were obese, with a subset of 4.8% of cases classified as morbidly obese. This study has confirmed that there has been a marked relative and absolute increase in numbers of obese individuals undergoing coronial post-mortem examinations in South Australia, with 218 more autopsies in 2006 involving obese bodies, including 47 more cases where morbid obesity was documented. This trend is undoubtedly occurring in other countries. Significant problems exist in trying to handle obese and particularly morbidly obese individuals in mortuaries designed for bodies with normal BMIs. Lifting, transport, transfer, storage and autopsy dissection are all difficult. Obesity enhances putrefaction that further complicates handling. Unless mortuaries are modified to deal with the increasing numbers of morbidly obese individuals, with reinforced and robust equipment including lifting hoists, the autopsy examination of such cases may be compromised, and staff will be confronted with ongoing and increasing risk of injury.