Ab initio study on the magneto-structural properties of MnAs

The magnetic and structural properties of MnAs are studied with ab initio methods, and by mapping total energies onto a Heisenberg model. The stability of the different phases is found to depend mainly on the volume and on the amount of magnetic order, confirming previous experimental findings and phenomenological models. It is generally found that for large lattice constants the ferromagnetic state is favored, whereas for small lattice constants different antiferromagnetic states can be stabilized. In the ferromagnetic state the structure with minimal energy is always hexagonal, whereas it becomes orthorhombically distorted if there is an antiferromagnetic component in the hexagonal plane. For the paramagnetic state the stable cell is found to be orthorhombic up to a critical lattice constant of about 3.7 Angstrom, above which it remains hexagonal. This leads to the second order structural phase transition between paramagnetic states at about 400 K, where the lattice parameter increases above this critical value with rising temperature due to the thermal expansion. For the paramagnetic state an analytic approximation for the magnitude of the orthorhombic distortion as a function of the lattice constant is given. Within the mean field approximation the dependence of the Curie temperature on the volume and on the orthorhombic distortion is calculated. For orthorhombically distorted cells the Curie temperature is much smaller than for hexagonal cells. This is mainly due to the fact that some of the exchange coupling constants in the hexagonal plane become negative for distorted cells. With these results a description of the susceptibility as function of temperature is given

Finite Sized Atomistic Simulations of Screw Dislocations

The interaction of screw dislocations with an applied stress is studied using atomistic simulations in conjunction with a continuum treatment of the role played by the far field boundary condition. A finite cell of atoms is used to consider the response of dislocations to an applied stress and this introduces an additional force on the dislocation due to the presence of the boundary. Continuum mechanics is used to calculate the boundary force which is subsequently accounted for in the equilibrium condition for the dislocation. Using this formulation, the lattice resistance curve and the associated Peierls stress are calculated for screw dislocations in several close packed metals. As a concrete example of the boundary force method, we compute the bow out of a pinned screw dislocation; the line-tension of the dislocation is calculated from the results of the atomistic simulations using a variational principle that explicitly accounts for the boundary force.Comment: LaTex, 20 pages, 11 figure

Ab Initio Study of Screw Dislocations in Mo and Ta: A new picture of plasticity in bcc transition metals

We report the first ab initio density-functional study of screw dislocations cores in the bcc transition metals Mo and Ta. Our results suggest a new picture of bcc plasticity with symmetric and compact dislocation cores, contrary to the presently accepted picture based on continuum and interatomic potentials. Core energy scales in this new picture are in much better agreement with the Peierls energy barriers to dislocation motion suggested by experiments.Comment: 3 figures, 3 table

Hysteroscopic Sterilization Device Follow-Up Rate: Hysterosalpingogram Versus Transvaginal Ultrasound

Study Objective To assess if follow-up confirmation testing 3 months after hysteroscopic sterilization with the Essure device improved with recommendation for transvaginal ultrasound (TVUS) versus hysterosalpingogram (HSG). Design Retrospective, observational case-controlled cohort study (Canadian Task Force classification II-2) Setting Two physician private practice in Evansville, Indiana Patients Compliance rates for a TVUS confirmation test on 100 women who underwent hysteroscopic sterilization compared to a previously published cohort of 1004 women who were scheduled to undergo HSG confirmation test. Intervention Acquisition of 3 month confirmation testing after Essure hysteroscopic sterilization Measurement and Main Results All women who underwent Essure hysteroscopic sterilization with recommendation for TVUS confirmation testing between July 2015 and January 2017 were compared to a previously published cohort of 1004 patients with recommendation for HSG confirmation testing (HSG cohort). In addition, an HSG subgroup cohort (HSG subgroup) similar in size and closest chronology to the TVUS cohort was drawn from the original 1004 patients and analyzed for HSG follow-up. Records for all patients were reviewed for demographic, procedural, confirmation testing, and outcome data. One hundred patients were identified with successful Essure device placement and a recommendation for TVUS confirmation testing. Eighty-eight (88.0%) patients returned for TVUS at 3 months. In the HSG cohort, 1004 successful Essure devices were placed and 778 patients returned for the recommended HSG follow-up (77.5%). There was a significantly higher follow-up rate for TVUS compared to the HSG cohort (88.0% vs 77.5%, p = 0.008). In the HSG subgroup, 184 patients were identified and 133 patients presented for HSG follow-up (72.3%) indicating a significantly higher follow-up rate in the TVUS cohort (88.0% vs 72.3%, p = 0.001). No pregnancies after any confirmation testing were noted. Conclusion Confirmation testing with transvaginal ultrasound rather than hysterosalpingogram 3 months after Essure device placement results in increased patient compliance that may lead to improved patient outcomes with reduction of unintended pregnancy

Influence of religiosity on the quality of life and on pain intensity in chronic pancreatitis patients after neurolytic celiac plexus block:Case-controlled study

The quality of life in patients with chronic pancreatitis (CP) is reduced due to their suffering of high levels of pain. It has been presented that quality of life can also be linked to religiosity and/or spirituality. The aim of this study is to assess the influence of religious practices on the quality of life and on the subjective level of pain in CP patients. Ninety-two patients (37 women and 55 men) with chronic pancreatitis were treated invasively for pain with neurolytic celiac plexus block (NCPB). The religiosity of the patients was recorded and served as a dichotomizer. Group 1 was for patients who claimed to have no contact with the church or to have very sporadic contact (N = 35 patients). Group 2 was for patients who claimed to have deep faith and were regular participants at church activities (N = 57 patients). Visual analogue scale was used to assess pain, while the quality of life was measured by using QLQ C-30 questionnaire adapted for chronic pancreatitis patients in Polish population. The patients were assessed prior to the pain-relieving intervention and subsequently 2 and 8 weeks after it. The intensity of pain was reduced in both groups significantly after performing the NCPB. Patients who declared a deep faith reported higher level of pain on the VAS scale prior to intervention than non-religious patients. Quality of life in both groups of patients significantly improved after NCPB. Following NCPB, global quality of life in patients who declared higher religiosity/church attendance was significantly higher (79.88) than for those patients who have no contact or sporadic contact with the church (44.21, P < 0.05). NCPB resulted in significant reduction of pain and increase in quality of life in both groups of patients with CP. Nevertheless, in the group declaring higher religiosity/church attendance, reported pain was higher, but, despite that, quality of life better. It may be concluded that religious practices might serve as an additional factor improving quality of life and coping in patients suffering from chronic pancreatitis. Keywords Chronic pancreatitis Pain Coping Religiosity Neurolytic coeliac plexus block NCPB Spiritualit