Search for: All records

Abstract The impact of latitudinal variations in the Intertropical Convergence Zone (ITCZ) on northern Andean hydroclimate during the Medieval Climate Anomaly (MCA; 950–1,150 CE) and Little Ice Age (LIA; 1,300–1,850 CE) is uncertain. Synthesis of two new lacustrine paleoclimate records from the Eastern Colombian Andes with existing circum‐Andean records shows that effective moisture anomalies were synchronous and in phase across the tropical Andes during the last millennium. During the MCA, when the ITCZ was shifted northward, topographically controlled responses in the northern Andes to vigorous atmospheric convection resulted in low precipitation and high evaporation, while precipitation was also reduced in the southern tropical Andes. During the LIA, precipitation decreased in the northern Andes as the ITCZ migrated southward but was offset by cooling that lowered evaporation, establishing high effective moisture. In the southern tropical Andes, the southward ITCZ position simultaneously strengthened precipitation, increasing effective moisture. MCA‐like responses to continued warming trends could similarly reduce northern Andean precipitation while increasing evaporation, thereby lowering effective moisture and possibly reducing water resource availability. 

Teacher turnover in science and mathematics is a significant and consistent challenge for K-12 education in the U.S. This paper provides: (a) an investigation of the relationship between teacher retention and several social and motivational factors; and (b) a comparison of Master Teaching Fellows (MTF) and non-MTF teachers in terms of their retention and social and motivational factors. Teachers are classified into three retention categories: (a) stayers, (b) shifters, and (c) leavers. Social and motivational factors included teaching self-efficacy, diversity dispositions, leadership skills, principal autonomy support, teacher-school fit (adapted from person-organization fit literature), and social networks related to teaching and education. Study 1 included about 250 science and math teachers from the gulf coast region of Texas. Study 2 included 167 science and math teachers across the country. Teachers completed a survey in the summer and fall of 2021. For study 1, multinomial logistics regression analyses indicate: (a) leavers have significantly higher levels of self-efficacy; and (b) shifters have significantly higher levels of leadership skills and lower levels of teacher-school fit. The second study findings indicate: (a) MTFs’ teacher leadership network and teaching self-efficacy are significantly greater than that of non-MTFs’; and (b) MTFs significantly tend to shift to a leadership position than non-MTFs do. 

Teacher turnover i science and mathematics is a significant and consistent challenge for K-12 education in the U.S. This paper provides: (a) an investigation of the relationship between teacher retention and several social and motivational factors; and (b) a comparison of Master Teaching Fellows (MTF) and non-MTF teachers in terms of their retention and social and motivational factors. Teachers are classified into three retention categories: (a) stayers, (b) shifters, and (c) leavers. Social and motivational factors included teaching self-efficacy, diversity dispositions, leadership skills, principal autonomy support, teachers-school fit (adapted from person-organization fit literature), and social networks related to teaching and education. Study 1 included about 250 science and math teachers from the gulf coast region of Texas. Study 2 included 167 science and math teachers across the country. Teachers completed a survey in the summer and fall of 2021. For study 1, multinomial logistics regression analyses indicate: (a) leavers have significantly higher levels of self-efficacy; and (b) shifters have significantly higher levels of leadership skills and lower levels of teacher-school fit. The second study findings indicate: (a) MTFs' teacher leadership network and teaching self-efficacy are significantly greater than that of non-MTFs'; and (b) MTFs significantly tend to shift to a leadership position than non-MTFs do. 

Abstract We present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19, during the LIGO–Virgo–KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered ∼14% of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz, where we assume the gravitational-wave emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy 1 × 10⁻⁴M_⊙c²and luminosity 2.6 × 10⁻⁴M_⊙c²s⁻¹for a source emitting at 82 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.08, at frequencies above 1200 Hz, surpassing past results.