Effects of target properties on the formation of lunar impact craters in the simple-to-complex transition

Thesis (Ph.D.) University of Alaska Fairbanks, 2019The transition from simple to complex crater morphology in impact craters with increase in crater size has been modelled and observed in planetary bodies across the Solar System. The transition diameter depends upon the strength and gravity of the planetary body. On the Moon, this transition takes place over a diameter range of several kilometers. This range spans a diversity of crater morphologies including simple, transitional and complex craters. The diameter range of 15 20 km falls within the lunar simple-to-complex transition. All other impactor properties held constant, the 15-20 km range corresponds to a factor of three in the magnitude of impact kinetic energy. I conducted detailed geologic investigation of 244 well-preserved craters in this diameter range to elucidate the root causes of morphological variations. I used panchromatic data for observing crater and surface morphology, Digital Elevation Models (DEMs) for evaluating crater morphometry and topographic variation of pre-impact terrain, near-infrared (NIR) bands for determining the composition of crater cavity and surrounding terrain, thermal infrared bands for examining rock abundance, and Synthetic Aperture Radar (SAR) data for detecting impact melt deposits. The results of my investigation indicate that the morphological differences are primarily governed by target properties. Simple craters are confined to the highlands, and the mare are more abundant in complex craters. The mare are composed of solidified basaltic lava flows interlayered with regolith. The layering creates vertical strength heterogeneities that drive the destabilization of the transient cavity and its collapse, causing the transition to complex craters at smaller diameters in the mare. The non-layered highlands are more vertically homogeneous in strength and therefore favor simple crater formation. Eight atypically deep simple craters were identified in the highlands near the mare highlands boundaries, the most porous terrains on the lunar surface. After detailed examination of these craters in comparison to their normal-depth counterparts, I conclude that part of the energy from impact on porous target was spent in target compaction. The higher the porosity of the target, the deeper the crater and greater its volume, due to increased compaction. That only some of the craters in the high porosity terrains are deep suggests that those craters are on locally extreme-high porosity patches. However, an unusual impactor property, such as a high velocity impact, a high density impactor, or a near-vertical impact may also be a contributor. The simple craters in the highlands were observed to be located on flat or gradually sloping surfaces or degraded rims and terraces of pre-existing craters. Most craters with localized slumps superpose sharp topographic breaks such as well-developed rims and terraces of pre-existing craters. However, the topographic settings of 35% of the craters with localized slumps appeared to be similar to that of the simple craters. More detailed topographic study of the pre-impact terrains of these two morphologies revealed that the pre-impact terrains of 35% of the craters with localized slumps are gradually sloping or have subtle topographic breaks. Both sharp and subtle breaks are characterized with similar sloping directions as the adjacent craters' walls, which led to over steepening of the transient cavity walls around this part of the rim and their collapse, thereby causing the accumulation of localized slumped material. Several simple craters were also identified to have formed on pre-impact topographic breaks. However, the simple craters' walls that superpose these breaks were observed to be sloping in directions opposite to that of the breaks. So the ejecta around these walls was deposited along the break slopes, and thus syn-impact mass wasting occurred external (and not internal) to the crater cavity.Chapter 1 Introduction -- 1.1 Chapter 2: Geologic analyses of the causes of morphological variations in lunar craters within the simple-to-complex transition -- 1.2 Chapter 3: Geologic investigation of deep simple craters in the lunar simple-to complex transition -- 1.3 Chapter 4: Influence of target properties on wall slumping in lunar craters within the simple-to-complex transition -- 1.4 References. Chapter 2: Geologic analyses of the causes of morphological variations in lunar craters within the simple-to-complex transition -- Abstract -- 2.1 Introduction -- 2.1.1 Lunar simple-to-complex impact crater transition -- 2.1.2 Objectives -- 2.2 Methods and data -- 2.2.1 Morphological characterization -- 2.2.2 Close-proximity analyses -- 2.2.3 Data sets used -- 2.3 Results -- 2.3.1 Morphological characterization -- 2.3.1.1 Simple crater -- 2.3.1.2 Crater with localized slumps -- 2.3.1.3 Crater with localized slumps and terraces -- 2.3.1.4 Crater with localized slumps and central uplift -- 2.3.1.5 Crater with localized slumps, terraces, and central uplift -- 2.3.1.6 Floor-fractured crater -- 2.3.1.7 Concentric crater -- 2.3.2 Highlands versus mare craters -- 2.3.3 Close-proximity craters -- 2.4 Discussion -- 2.4.1 Mare-highlands differences -- 2.4.2 Unusually deep craters -- 2.4.2.1 Impact into a high-porosity target -- 2.4.2.2 The highlands are more coherent in these locations and less susceptible to minor slumping of the transient cavity -- 2.4.3 Potential impactor-caused variations -- 2.4.4 Comparison with other planets -- 2.5 Conclusions -- 2.6 Acknowledgments -- 2.7 References -- Appendix A. Chapter 3: Geologic investigation of deep simple craters in the lunar simple-to-complex transition -- Abstract -- 3.1 Introduction -- 3.1.1 Deep simple craters -- 3.1.2 Objectives -- 3.1.2.1 Greater compaction of target with increase in porosity results in larger crater depths -- 3.1.2.2 The highlands are more coherent in these locations and more resistant to minor slumping of the transient cavity -- 3.2 Methods and data sets -- 3.2.1 Crater depths from SLDEM and LOLA tracks -- 3.2.2 Depths of proximity craters -- 3.2.3 Trends in crater morphometry -- 3.2.4 impact melt deposits -- 3.2.5 Visual examinations of crater cavities -- 3.3 Results -- 3.3.1 Crater depths from SLDEM and LOLA tracks -- 3.3.2 Depths of proximity craters -- 3.3.3 Trends in crater morphometry -- 3.3.3.1 Association of crater depth with porosity -- 3.3.3.2 Rim height -- 3.3.3.3 Wall slope -- 3.3.3.4 Floor size -- 3.3.3.5 Cavity profiles -- 3.3.3.6 Ejecta-cavity volume ratio -- 3.3.4 Impact melt deposits -- 3.3.5 Visual examinations of crater cavities -- 3.4 Discussion -- 3.4.1 Greater compaction of target with increase in porosity results in larger crater depths -- 3.4.2 The highlands are more coherent in these locations and more resistant to minor slumping of the transient cavity -- 3.5 Conclusions -- 3.6 Acknowledgements -- 3.7 References -- Appendix B. Chapter 4: Influence of target properties on wall slumping in lunar craters within the simple-to-complex transition -- Abstract -- 4.1 Introduction -- 4.1.1 Wall slumping -- 4.1.2 Objectives -- 4.1.2.1 Localized slumping occurred post-crater formation -- 4.1.2.2 Localized slumping occurred on weaker target -- 4.1.2.3 Impact cratering on a slope causes the localized slumping -- 4.2 Methods and data sets -- 4.2.1 Testing hypothesis 1: Comparison of crater densities on slumps and ejecta units of craters with localized slumps -- 4.2.2 Testing hypothesis 2: Frequencies of proximal simple craters and craters with localized slumps -- 4.2.3 Testing hypothesis 3: Topographic variation in pre-impact terrains of the simple craters and craters with localized slumps along with rim circularity -- 4.3 Results -- 4.3.1 Comparison of crater densities on slumps and ejecta units of craters with localized slumps -- 4.3.2 Frequencies of proximal simple craters and craters with localized slumps -- 4.3.3 Topographic variation in pre-impact terrains of the simple craters and craters with localized slumps along with rim circularity -- 4.4 Discussion -- 4.5 Conclusions -- 4.6 Acknowledgements -- 4.7 References -- Appendix C. Chapter 5: Conclusion -- 5.1 Target properties -- 5.2 Impactor properties

Association between clinical diagnosis of foetal distress with umbilical artery acidaemia at birth in women undergoing caesarean section for foetal distress

Background: The risks of maternal morbidity and mortality associated with a caesarean section may not be reasonably justified by the degree of neonatal compromise at birth associated with caesarean section done for clinically diagnosed foetal distress. The aim was to study the association of clinical diagnosis of non-reassuring foetal status with umbilical artery acidaemia at birth in women undergoing caesarean section for foetal distress and to evaluate outcomes in neonates born by caesarean section performed for foetal distress.Methods: Prospective observational study of all the women undergoing emergency caesarean section for foetal distress at a tertiary care teaching facility over 2 months. Criteria for diagnosis of foetal distress were thick meconium stained liquor only or foetal heart rate abnormality with or without meconium stained liquor. Testing for pH was done on arterial blood drawn from umbilical cord at the time of birth. Acidaemia was defined as cord blood pH less than 7.2.  Severe acidaemia was defined as cord blood pH less than 7.0.Results: Cord blood pH was analysed in 110 caesareans done for foetal distress. Incidence of neonatal acidaemia at birth in study population was 53.6%.Conclusions: Much lower incidence of actual acidaemia and low Apgar scores in neonates born by caesarean section done for clinical diagnosis of foetal distress than previously reported indicate the need for more stringent criteria and more objective tests for diagnosis of foetal distress

A study to evaluate gestational age with the help of placental thickness

Background: To assess relationship of placental thickness with gestational age.Methods: The study was conducted on 754 normal antenatal patients, of all gestational ages attending the out patient department of Dhiraj hospital from October 2012 to March 2013. USG was done by using Philips HD 7machine with a 3.75 MHz sector probe. After estimating the fetal age by CRL, BPD, HC, AC, and FL, the placental thickness with standard deviation was calculated for all gestational ages.Results: It was observed that the placental thickness gradually increased from 15 mm at 11 weeks of gestation to 36.3 mm at 39 weeks. From the 22nd week to the 35th week of gestation the placental thickness coincide almost exactly with the gestational age in weeks.Conclusion: Placental thickness is a good parameter for estimation of gestational age especially in the late second trimester and early third trimester.

Study of route of hysterectomy

Background: The objective is to study complication rate, advantages and outcome of different route of hysterectomy.Methods: A prospective study of 175 women over a period of 1 year i.e. from 01/01/2011 to 31/12/2011 SSG hospital, Vadodara. Depending on the patient profile, experience of surgeon optimum route of hysterectomy was decided.Results mean operating time in AH group was 68.4±14.4min, which was 80±10.3min, 115.8±40.6min and 148.8±25.5min in NDVH, LAVH and TLH group respectively. TLH was performed by consultants. Febrile morbidity was significantly high in AH (23%). Bladder and ureteral injuries were seen in 4% and 3% cases of NDVH and AH group. Wound complications were seen in AH (10%), whereas vault complications were higher in TLH. The hospital stay was shortest in TLH. Women with TLH had early ambulation, early resumption to normal diet, early return to routine work and better sexual function.Conclusions: Women with excessively enlarged uteri, significant pelvic pathology, or cancer are obvious candidates for AH. On the other hand, VH is frequently chosen for the small uterus in a multiparous woman with a large pelvis and no prior pelvic inflammatory disease or surgery. Although TLH, LAVH have significantly lower complication rate than AH, but overall cost is higher owing to the high operating room charges. The final selection of hysterectomy route should be based on surgeon’s experience and indication for surgery

A prospective study of the incidence and outcomes of eclampsia in a tertiary care hospital and teaching institute in India

Background: Eclampsia is a common cause of maternal and foetal morbidity and mortality in India and the rest of the world accounting for nearly 10% of all maternal deaths. However, there is a relative scarcity of outcome data for patients with eclampsia in India. Our goal was to estimate the incidence of eclampsia, the maternal and foetal outcomes of patients presenting with eclampsia, and predictors of clinical outcomes in these patients. Objective of this study was to estimate the incidence of eclampsia in patients who delivered at a single tertiary care institution over a 2-year period and to study the maternal and perinatal outcomes in those patients.Methods: Prospective cohort study conducted from September 2008 to August 2010 on all patients with eclampsia admitted during the study period at Lok Nayak Hospital, New Delhi, India.Results: The incidence of eclampsia among total deliveries was 0.45%.  About 97% of these patients received parenteral magnesium sulphate as the primary anticonvulsant therapy. Caesarean section was performed in 22.7% and majorities were done for foetal distress. Maternal complications were encountered among 17% of patients. There were 2 maternal deaths (2.3%), 13 stillbirths (14.1%) and 7 early neonatal deaths (7.9%).Conclusions: The incidence of eclampsia among all deliveries over a 2-year period at a tertiary care centre in India was 0.45%. Parenteral magnesium sulphate was effective in the vast majority of these patients in controlling the seizures. Further studies to evaluate whether early registration for antepartum care improves maternal and foetal outcomes in patients with eclampsia are warranted

Bianchijevi modeli tipa I u Lyrinoj geometriji s magnetiziranom krutom tekućinom

Bianchi type-I magnetized cosmological models with time-dependent gauge function β for stiff fluid distribution within the framework of Lyra geometry are investigated. To get the deterministic model of the universe, we have assumed that eigenvalue (σ 1 1 ) of shear tensor (σ j i ) is proportional to the expansion (θ). This leads to A = (BC) n where A, B and C are metric potentials. The physical and geometrical aspects of the models and singularities in the models are discussed.Istražujemo Bianchijeve kozmološke modele s vremenski-ovisnom baždarnom funkcijom β za krutu tekućinsku raspodjelu u okviru Lyrine geometrije. Radi postizanja određenja u modelima, pretpostavljamo da je svojstvena vrijednost (σ 1 1 ) tenzora smicanja (σ j i ) razmjerna širenju (θ). To vodi na A = (BC) n gdje su A, B and C metrički potencijali. Raspravljamo također fizičke i geometrijske značajke modela i singularnosti

Oral and vaginal route of misoprostol for induction of labour: a comparative study

Background: Induction of labour can be defined as “Artificial initiation of uterine contractions before the onset of spontaneous labour, after the period of viability, by any methods, for purpose of vaginal delivery.” The key factor for a successful induction is the status of cervix, its form, consistency and dilatation which is determined by the Bishop score. In case of unfavourable cervix or in the pregnancies remote from the term; prostaglandins are more effective than any other method of induction. Introduction of misoprostol, PGE1 analogue, for the induction of labour in 1993 and its approval for clinical use by ACOG (American College of Obstetrics and Gynecology) in 1999 has been the most significant advancement. It is the latest drug for induction of labour which is cheap and stable at room temperature and is being used worldwide in different doses and by various routes. We compared the most commonly preferred two routes; vaginal and oral in terms of success of induction and noted the adverse events and side effects in both routes.Methods: This was a prospective comparative study carried out at SBKSMIRC (Shrimati Bhikhiben Kanjibhai Shah Medical Institute and Research Centre), Dhiraj general hospital, Vadodara, Gujarat, 200 patients who required induction of labour were recruited after applying inclusion and exclusion criteria and were randomly divided in two groups- Group A meant to receive 50µg oral misoprostol, Group B - meant to receive 25µg vaginal misoprostol repeated 4 hourly up to maximum of five doses. Progress of labour was charted on the partograph. The mean induction delivery interval, mode of delivery, maternal and neonatal outcomes and complications were observed.Results: The mean induction to delivery interval was significantly less in vaginal group than oral (23.3±12.4 hours in oral vs. 17.3±10 hours in vaginal). Vaginal delivery and cesarean section rates were comparable in both groups (76% in Group A vs. 72% in Group B for vaginal delivery, 18% vs. 20% for Cesarean section, respectively). 58% patients in Group A required more than two doses as compared to 39% in group B, though the difference was statistically not significant. Significant number of patients required added oxytocin administration in Group A (72%). No major complications or adverse events were observed. Neonatal hyperbilirubinemia was seen more in Group A.Conclusions: Both Oral misoprostol in a dose of 50μg and vaginal misoprostol 25 μg every four hours, to a maximum of five doses, have the potential to induce labour safely and effectively. The vaginal route however is beneficial in effecting delivery in lesser time with few numbers of doses as compared to oral route

Clinical study of IUGR cases and correlation of Doppler parameters with perinatal outcome

Background: Early detection and timely intervention in IUGR babies can significantly improve perinatal outcome. Bio physical profile and non stress test have been the common modalities used for foetal surveillance but neither of these is accurate in predicting poor perinatal outcome. With the advent of Doppler, it has become much easier to pick up IUGR cases early and with high reproducibility and efficacy for perinatal outcome. Objectives of this study were 1) to correlate clinical findings in IUGR with colour Doppler and perinatal outcome 2) to study prognostic efficacy of Doppler parameters in early detection of foetal compromise.Methods: Sixty singleton pregnancies diagnosed to have IUGR beyond 30 weeks gestation were included in the study and were examined and followed clinically as well as with Doppler findings till delivery. Prognostic efficacy (sensitivity, specificity, positive and negative predictive values) of umbilical artery and middle cerebral artery waveforms were studied using percentage.Results: The sensitivity and specificity of MCA PI (78%, 93%) as an indicator for extent of foetal compromise in IUGR was highest, though ratios such as MCA PI/UA PI as well as UA SD (>3) were comparably specific predictors for poor perinatal outcome. Absent and reverse end diastolic flow in umbilical artery is associated with definite poor perinatal outcome in terms of mortality. Clinical examination as well as ultrasound biometry has limited accuracy in determining appropriate time of intervention in growth restricted foetuses. Non reactive non stress test was shown to have positive predictive value of only 24% with false positive rate of 75%.Conclusions: Colour Doppler study is a simple, quick, non invasive procedure and multiple vessel study has high accuracy among the other tests for ante partum foetal surveillance

Pain relief in labour: tramadol versus pentazocine

Background: The present study was undertaken to compare the effect of 100 mg intramuscular tramadol to 30 mg intramuscular Pentazocine for labour analgesia.Methods: A total of 60 cases with 37-40 weeks pregnancy in labour, without any foetal or maternal complications were selected. Out of them Inj. Tramadol was given to 30 cases while rest of the 30 patients received injection Pentazocine.Results: In Tramadol group pain relief was observed in 80% cases, effect started as early as 7-8 min and continued for 2.13 hrs. While in Pentazocine group pain relief was observed in only 60% cases with delayed onset (15-16 min), effect lasted for 2.67 hrs. Maternal and foetal complications were slightly more in Pentazocine group.Conclusions: Tramadol is an effective and safe labour analgesic, producing moderate to satisfactory. Besides it also significantly shortens the duration of labour

Role of obstetrician and gynecologist in diagnosis and management of breast lump

Background: This study of last three years undertaken to determine the types of breast lumps as seen by an obstetrician and gynecologist and to determine the high risk factors for diagnosing malignant breast lump and guide patient for early and proper management.Methods: The diagnostic triad of clinical examination, FNAC and mammography was used to help detect a malignant mass.Results: Out of 202 cases, 162 were of benign breast lump and 40 of malignant breast lump. Age and family history were the most important risk factors. Other risk factors were nulliparity, first child after 30 years of age and postmenopausal age. Fibroadenoma was the most common benign tumor usually occurring at a younger age. Of the 40cases of malignant breast lump, only 45% were detected early.Conclusion: All gynecologist should examine patient’s reproductive organs as well breast and also learn patient - how to examine breast herself regularly. Thus all obstetrician and gynecologist should participate in the breast cancer screening and help detect this malignancy in its early stage