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P M Reis

Publications and source records attributed to P M Reis.

6 recordsLinked to original sources
PubMed2006

Crystallization of a quasi-two-dimensional granular fluid.

We experimentally investigate the crystallization of a uniformly heated quasi-2D granular fluid as a function of the filling fraction. Our experimental results for the Lindemann melting criterion, the radial distribution function, the bond order parameter, and the statistics of topological changes at the particle level are the same as those found in simulations of equilibrium hard disks. This direct mapping suggests that the study of equilibrium systems can be effectively applied to study nonequilibrium steady states such as those found in our driven and dissipative granular system.

Journal Article↗
PubMed2005

Cracks in thin sheets: when geometry rules the fracture path.

We study the propagation of brittle fractures coupled to large out-of-plane bending, as when a brittle elastic thin sheet is cut by a moving object. Taking into account the separation of the film's bending and stretching energies and using fracture theory we show that such cracks propagate according to a simple set of geometrical rules in the limit of small thickness. In particular, this provides some insight into the geometrical origin of the oscillatory fracture patterns reported in two recent experiments. Numerical integration of our geometrical rules accurately reproduces both the shape of the fracture pattern and the detailed time evolution of the propagation of the crack tip, for various geometries of the cutting object.

Journal Article↗
PubMed2000

Abruptio placentae after auto accidents. A case-control study.

OBJECTIVE: To compare accident and injury characteristics in pregnant women with and without abruptio placentae involved in auto accidents (AAs). STUDY DESIGN: A retrospective, case-control study involving 12 pregnant women (16-39 weeks) with a diagnosis of abruptio placentae after AAs and 12 control subjects matched for gestational age (+/- 2 weeks) involved in AAs without abruptio placentae from 1988 through 1997. Numerous variables were compared, including restraint system use, estimated speed of the collision, injury severity score (ISS), clinical findings and patient position in the vehicle. Patient complaints and physical examination on admission were also recorded, and obstetric and neonatal outcomes were compared. Statistical analysis was performed using the independent sample t, Mann-Whitney and Fisher's exact tests, when appropriate. RESULTS: There was no significant difference in the frequency of unrestrained subjects or position in the vehicle between cases and controls. Estimated speed of the vehicle at the time of collision was significantly higher in the abruptio placentae group (> 30 mph, 92% vs. 50%, P = .03), as was the mean ISS code (20 [SD 12.71] vs. 4 [SD 5.13], P < .001). Abdominal pain and vaginal bleeding were seen more frequently in women with abruptio placentae as compared to controls (58% vs. 25% and 33% vs. 0, respectively). Patients with abruptio placentae had a higher incidence of preterm delivery (mean gestational age at delivery = 29 weeks [SD 7.99] vs. 36 weeks [SD 7.21], P = .008) and stillbirth (57% vs. 0%, P = .002) and lower mean birth weight (1,924 g [SD 931] vs. 3,069 g [SD 450], P = .003). There was no significant difference in cesarean section rates between the groups (58% vs. 30%, P = .23). There was no difference in the two groups in placental location on ultrasonography. CONCLUSION: Pregnant women who were involved in severe accidents (i.e., higher speed or ISS) were more likely to suffer abruptio placentae. In severe accidents, proper restraints were frequently not used. Because of the severity of these accidents, current restraint systems may not be sufficient to prevent abruptio placentae even with proper restraint use. Efforts toward designing new restraint systems for pregnant women should be encouraged.

Abruptio Placentae↗
PubMed1999

Outcome of infants with hypoplastic left heart and Turner syndromes.

OBJECTIVE: To report the obstetric and neonatal outcomes of ten infants with hypoplastic left heart syndrome in association with Turner syndrome. METHODS: The Pediatric Cardiovascular Surgery database at the University of Michigan was searched from 1990 to 1997, and obstetric and neonatal records of neonates with hypoplastic left heart syndrome and Turner syndrome were reviewed. RESULTS: There were 406 cases of hypoplastic left heart syndrome admitted during 8 years, of which ten (2.5%) also had Turner syndrome. Nine infants were delivered at term and one at 36 weeks. The mean (+/- standard deviation [SD]) gestational age at delivery was 38 +/- 1.2 weeks, and mean (+/-SD) birth weight was 2991 +/- 438 g. Delivery was vaginal in all cases, and no infant had an Apgar score at 5 minutes less than 7. Karyotype was 45, X in seven cases, and 45, X mosaic in three. Most infants had dysmorphic features at birth. All ten infants had first-stage reconstruction surgery for hypoplastic left heart syndrome. Only two survived and underwent second-stage palliation; both are alive currently, although with significant medical problems. CONCLUSION: For infants with hypoplastic left heart and Turner syndromes, regular obstetric management appears appropriate. Although staged reconstruction surgery has improved survival for neonates with isolated hypoplastic left heart syndrome, for those with Turner syndrome, survival appears markedly reduced.

Female↗
PubMed1998

Obstetric management of 219 infants with hypoplastic left heart syndrome.

OBJECTIVE: The objective of this study was to describe the obstetric parameters from 219 deliveries of infants with hypoplastic left heart syndrome. STUDY DESIGN: The Pediatric Cardiovascular Surgery Database at the University of Michigan was searched, and cases of neonates with the diagnosis of hypoplastic left heart syndrome were found. Obstetric records were then reviewed. RESULTS: One hundred sixty-one infants (74%) were delivered vaginally and 58 (26%) were delivered by the cesarean route. The mean gestational age at delivery was 38.9 weeks. Mean Apgar scores at 1 and 5 minutes were 7 and 8, respectively. Ninety percent were delivered at term and 10% were delivered before 37 weeks. The diagnosis of hypoplastic left heart syndrome was made antenatally in 82 cases (37%) and neonatally in 137 cases (63%). In the antenatal group the mean gestational age at diagnosis was 27 weeks. Karyotype analysis was performed in 32 of all cases (15%), with 8 fetuses revealing an abnormal karyotype. Seven cases were 45,X and 1 was trisomy 21. CONCLUSION: Staged reconstruction surgery has markedly improved survival for neonates born with isolated hypoplastic left heart syndrome. Our review suggests that, aside from determining the karyotype, no further obstetric interventions seem warranted. While awaiting spontaneous labor at term, the planned mode of delivery should be vaginal, with cesarean delivery performed for routine obstetric indications only.

Adolescent↗