Search for Boosted Dark Matter in COSINE-100

We search for energetic electron recoil signals induced by boosted dark matter (BDM) from the galactic center using the COSINE-100 array of NaI(Tl) crystal detectors at the Yangyang Underground Laboratory. The signal would be an excess of events with energies above 4 MeV over the well-understood background. Because no excess of events are observed in a 97.7  kg·yr exposure, we set limits on BDM interactions under a variety of hypotheses. Notably, we explored the dark photon parameter space, leading to competitive limits compared to direct dark photon search experiments, particularly for dark photon masses below 4 MeV and considering the invisible decay mode. Furthermore, by comparing our results with a previous BDM search conducted by the Super-Kamionkande experiment, we found that the COSINE-100 detector has advantages in searching for low-mass dark matter. This analysis demonstrates the potential of the COSINE-100 detector to search for MeV electron recoil signals produced by the dark sector particle interactions.

Comparison of the Mean Cross-sectional Area of the Median Nerve between Pregnant and Non-Pregnant Women Using Ultrasonography in a Tertiary Level Hospital, Nepal

Background The median nerve is subjected to compression in the carpal tunnel giving rise to a constellation of symptoms known as carpal tunnel syndrome. It is the most frequent form of peripheral entrapment neuropathies and is most prevalent in the middle age females. The most common cause of this syndrome is idiopathic. One of the known secondary causes is pregnancy. Objective To compare the mean cross sectional area of median nerve using ultrasound in pregnant and non-pregnant females at carpal tunnel inlet and its variations with different trimesters. Method The study was conducted during a period of one year (October 2014 to September 2015). A total of 204 participants were evaluated among which 102 were nonpregnant and 102 were pregnant. Among the 102 pregnant participants, 34 females each were in the first, second, and third trimesters. A convenience sampling technique was used for the selection of the participants. The mean cross-sectional area of the median nerve was calculated in both of these groups in both hands by using the direct method. The mean cross-sectional area of non-pregnant female was used as the reference value to which that of pregnant female were compared. Data obtained were compiled and analyzed using Statistical Package for Social Sciences Version 16. Result The overall mean cross-sectional area of the median nerve in non-pregnant females was 6.76 ± 1.05 mm2 and in pregnant females was 6.84 ± 1.09 mm. No statistically significant difference was noted in the mean cross-sectional area of the median nerve in either hand in both pregnant and non-pregnant females. No statistically significant difference was noted in the overall mean cross-sectional area between the non-pregnant and pregnant females. There was no significant difference in the mean cross-sectional area within the different trimesters in both hands on intergroup comparisons. Conclusion Ultrasound examination of the median nerve and measurement of its crosssectional area is a useful diagnostic tool in the evaluation of carpal tunnel syndrome. Ultrasound has the advantage of easy availability, low cost, quick scan time, able to scan a long segment of nerve and examine the structures in both static and dynamic states. Besides, it also helps in the identification of various anatomic variants and pathologies within or adjacent to carpal tunnel.

Isolation and Intensive Care (ICU) Service, Surge Capacity and Pandemic Training in Government Designated COVID-19 Clinics and Hospitals of Nepal

Background The coronavirus pandemic preparedness and response activities began in Nepal after the detection of the first case on 24 January 2020. Highest daily case record in June 2020 was 671, but it reached above 5,000 in October 2020. Objective This study assessed preparedness and response status of government designated COVID-19 clinics and various level hospitals. Method A web-based survey was conducted among government designated COVID-19 clinics and Level hospitals in June 2020. The Medical Operations Division of the COVID-19 Crisis Management Center (CCMC) retained contact list of focal person in each facility for regular updates. Forty-nine out of 125 clinics and all level hospitals (five Level-1, 12 Level-2, three Level-3) provided responses. Result There were 25 or less isolation beds in the majority of COVID-19 clinics (83.7%) and Level-1 hospitals (60%), whereas the majority of Level-2 (92%) and Level-3 hospitals (67%) had arranged >25 beds. Only five clinics, one Level-1 hospital, six Level-2 and two Level-3 hospitals had a surge capacity of additional 20 or more isolation beds. Only one-fourth of the designated health facilities had arranged separate isolation facility for vulnerable population. Majority of the designated clinics and Level-1 hospitals had five or less functional ICU beds and functional ventilators. Very few Level-2 hospitals had > 10 ICU beds and > 10 ventilators. Healthcare workers in the majority of facilities were trained on donning/doffing, hand washing, swab collection, and healthcare waste management, but, a very few received formal training on patient transport, dead body management, epidemic drill, and critical care. Conclusion This study revealed insufficient preparation in COVID-19 facilities during the initial phase of pandemic. The findings were utilized by the government stakeholders at central, provincial and local levels for scaling up surge capacity and improving health services at the time of case surge. As the pandemic itself is a dynamic process, periodic assessments are needed to gauze preparedness and response during different phases of disease outbreak.

Childhood Mesenteric Adenitis -The Spectrum of Findings

Background Mesenteric adenitis in children (≤ 18 years) can present with varied findings often causing a diagnostic confusion. In children, considering the inadequacies in history and physical examination, an accurate clinic-radiological diagnosis backed up with laboratory data as indicated becomes important to avoid misdiagnosis and futile interventions. Objective To study the profile of children evaluated for acute abdominal pain and diagnosed as mesenteric adenitis. Method A retrospective review of children with abdominal symptoms, diagnosed to have mesenteric adenitis between January 2018 and December 2020. Result A total of 85 patients (63 males, 22 females) were identified presenting at mean age of 6 years (range 4 months-16 years). Primary Mesenteric Adenitis (PA) was found in 62, Secondary Mesenteric Adenitis (SA) in 11 and Complicated Primary Mesenteric Adenitis (CPA) was identified in 12. All with PA responded well to supportive care. Those with SA were treated for the primary cause and the ones with Complicated Primary Mesenteric Adenitis were managed by treating the complication. All had a favorable outcome. Conclusion When managing a child with abdominal pain, mesenteric adenitis should be considered. Once clinically suspected, tailored management approach results in fruitful outcome.

Search for a Dark Matter-Induced Annual Modulation Signal in NaI(Tl) with the COSINE-100 Experiment

We present new constraints on the dark matter-induced annual modulation signal using 1.7 years of COSINE-100 data with a total exposure of 97.7 kg yr. The COSINE-100 experiment, consisting of 106 kg of NaI(Tl) target material, is designed to carry out a model-independent test of DAMA/LIBRA's claim of WIMP discovery by searching for the same annual modulation signal using the same NaI(Tl) target. The crystal data show a 2.7  cpd/kg/keV background rate on average in the 2-6 keV energy region of interest. Using a χ-squared minimization method we observe best fit values for modulation amplitude and phase of 0.0092±0.0067  cpd/kg/keV and 127.2±45.9  d, respectively.

First Direct Search for Inelastic Boosted Dark Matter with COSINE-100

A search for inelastic boosted dark matter (IBDM) using the COSINE-100 detector with 59.5 days of data is presented. This relativistic dark matter is theorized to interact with the target material through inelastic scattering with electrons, creating a heavier state that subsequently produces standard model particles, such as an electron-positron pair. In this study, we search for this electron-positron pair in coincidence with the initially scattered electron as a signature for an IBDM interaction. No excess over the predicted background event rate is observed. Therefore, we present limits on IBDM interactions under various hypotheses, one of which allows us to explore an area of the dark photon parameter space that has not yet been covered by other experiments. This is the first experimental search for IBDM using a terrestrial detector.

Background model for the NaI(Tl) crystals in COSINE-100

The COSINE-100 dark matter search experiment is an array of NaI(Tl) crystal detectors located in the Yangyang Underground Laboratory (Y2L). To understand measured backgrounds in the NaI(Tl) crystals we have performed Monte Carlo simulations using the Geant4 toolkit and developed background models for each crystal that consider contributions from both internal and external sources, including cosmogenic nuclides. The background models are based on comparisons of measurement data with Monte Carlo simulations that are guided by a campaign of material assays and are used to evaluate backgrounds and identify their sources. The average background level for the six crystals (70 kg total mass) that are studied is 3.5 counts/day/keV/kg in the (2-6) keV energy interval. The dominant contributors in this energy region are found to be 210 Pb and 3 H.