An Experience in Mentoring: Shaping Young Mathematical Minds

The Math PLUS program is a partnership between Linfield College and a local middle school which seeks to encourage more mathematics in local and regional science fairs. Linfield students are paired with middle school students to mentor science fair projects that are required to have a mathematical focus. We briefly discuss an overview of the program—its goals, structure and execution—before touching on our personal experiences as mentors for Yamhill-Carlton Intermediate School students. We also provide suggestions for improvements for those looking to implement similar programs at their own institution. The program is funded by a Dolciani Mathematics Enrichment Grant

Heavy Backpack Load Carriage Affects the Median Nerve

First responder and military personal often carry heavy backpacks of over 30% body weight when loaded with equipment. Use of the hands may be impaired by the compression of backpack straps on the nerves of the upper limb. PURPOSE: The aim of the study is to characterize the effects of walking with backpack load on upper limb function by examining changes in nerve conduction resulting from compression of the brachial plexus by backpack straps. We hypothesized that nerve conduction would be decreased in amplitude of the action potential and timing would be delayed after walking while carrying a 30% body weight load in a backpack. METHODS: 27 participants (12 female, 15 male; mean ± SD of 23.0 ± 4.8 yrs, 174.1 ± 10.5 cm height; 78.1 ± 14.9 kg mass, 27 right handed) were measured for motor and sensory nerve conduction using a Natus Neurodiagnostic System to stimulate and record median nerve conduction for the dominant upper limb. The median nerve was stimulated at the wrist for the sensory measures and at the elbow and axilla for motor nerve measurements. Participants walked on a treadmill for 20 minutes at 1.1 m/s while carrying a load of 30% bodyweight in a military-style external frame backpack with hip belt. Measurements were taken before participants donned the backpack (PRE) and immediately after walking while participants were still wearing the backpack (POST). Amplitude and latency of action potentials were recorded. Paired t tests were used to compare PRE and POST values of nerve conduction. RESULTS: Sensory nerve conduction showed significant changes (p=0.040) with a decrease in baseline-to-peak amplitude from 46.6 ± 16.2 µV PRE to 40.8 ± 13.2 µV POST. Latency of the motor nerve action potential was significantly increased (p=0.013) from a mean of 7.46 ± 0.71ms PRE to 7.60 ± 0.86 ms POST when stimulated at the elbow. Stimulation at the axilla also demonstrated significantly increased motor latency (p=0.037) from a mean of 9.36 ± 0.91 ms PRE to 9.49 ± 1.04 ms POST. CONCLUSION: Walking for 20 minutes while carrying a backpack loaded to 30% body weight affected nerve conduction for the median nerve. The increase in latency and decrease in amplitude of nerve conduction after a short bout of walking could potentially affect use of the hand and finger muscles and consequently affect manual task performance

Bald-faced bullshit and authoritarian political speech: Making sense of Johnson and Trump

Donald Trump and Boris Johnson are notoriously uninterested in truthtelling. They also often appear uninterested even in constructing plausible falsehoods. What stands out above all is the brazenness and frequency with which they repeat known falsehoods. In spite of this, they are not always greeted with incredulity. Indeed, Republicans continue to express trust in Donald Trump in remarkable numbers. The only way to properly make sense of what Trump and Johnson are doing, we argue, is to give a greater role to audience relativity - and in some cases, audience participation - in notions like bullshitting and bald-faced lying. In this paper, we develop a new understanding of bullshitting, one that includes bald-faced lying, and recognizes that different communicative acts may be directed at different audiences with a single utterance. In addition, we argue for recognition of the category of bald-faced bullshitting, a particular speciality of both Trump and Johnson, and one especially useful to authoritarian leaders

Implicit Bias and Reform Efforts in Philosophy: a Defence

This paper takes as its focus efforts to address particular aspects of sexist oppression and its intersections, in a particular field: it discusses reform efforts in philosophy. In recent years, there has been a growing international movement to change the way that our profession functions and is structured, in order to make it more welcoming for members of marginalized groups. One especially prominent and successful form of justification for these reform efforts has drawn on empirical data regarding implicit biases and their effects. Here, we address two concerns about these empirical data. First, critics have for some time argued that the studies drawn upon cannot give us an accurate picture of the workings of prejudice, because they ignore the intersectional nature of these phenomena. More recently, concerns have been raised about the empirical data supporting the nature and existence of implicit bias. Each of these concerns, but perhaps more commonly the latter, are thought by some to undermine reform efforts in philosophy. In this paper, we take a three- pronged approach to these claims. First, we show that the reforms can be motivated quite independently of the implicit bias data, and that many of these reforms are in fact very well suited to dealing with intersectional worries. Next, we show that in fact the empirical concerns about the implicit bias data are not nearly as problematic as some have thought. Finally, we argue that while the intersectional concerns are an immensely valuable criticism of early work on implicit bias, more recent work is starting to address these worries

The Effects of Heavy Backpack Carriage on Hand Strength

Force production in upper limb muscles could be affected following exercise that involves carrying a heavy backpack load. In lower limb muscles, previous study has demonstrated that there is muscle force depression after several different regimens of metabolically and mechanically demanding exercise. PURPOSE: The aim of this study is to examine pinch strength after exercising while carrying a heavy backpack with straps that compress the nerves and blood vessels of the upper limb. We hypothesized that backpack load carriage at 15% body weight and 30% body weight will lead to changes in upper limb lateral pinch strength as compared to a no-load condition. METHODS: To date, eleven participants (5 female, 6 male; mean ± SD of 25.8 ± 6.3 yrs, 81.9 ± 18 kg mass, 11 right handed) have completed 3 load conditions on separate days: 1) no backpack, 2) 15% body weight (BW) backpack, and 3) 30% BW backpack. Load condition order was randomized. Maximum lateral pinch strength was measured bilaterally using a pinch dynamometer before and after participants walked on a treadmill at 1.1 m/s for 30 minutes for each load condition. Pinch strength was measured every 5 minutes for 30 minutes after exercise. RMANOVA with Bonferroni post-hoc testing was used to compare among backpack conditions and among timepoints. RESULTS: Mean pinch strength on the dominant hand before backpack carriage was 10.8 ± 2.7 kg for male participants and 8.0 ± 1.2 kg for female participants. Pinch strength on the non-dominant hand before load carriage averaged 9.9 ± 1.7 kg for male participants and 7.5 ± 1.0 kg for female participants. Mean pinch strength on the dominant hand after 30% BW backpack carriage ranged from 10.6-10.9 kg for male participants and from 7.8 - 8.3 kg for female participants. There were no significant differences in pinch strength on either hand when comparing among backpack load conditions or timepoints for male or female participants. CONCLUSION: The compression of backpack straps and the exercise of walking with a backpack load did not affect pinch strength in the first 30 minutes after backpack carriage

Thermodynamic analysis of an entropically driven, high affinity nanobody-HIV p24 interaction

Protein-protein interactions are fundamental to life processes. Complementary computational, structural and biophysical studies of these interactions enable the forces behind their specificity and strength to be understood. Antibody fragments such as single-chain antibodies have the specificity and affinity of full antibodies but a fraction of their size, expediting whole molecule studies and distal effects without exceeding the computational capacity of modelling systems. We previously reported the crystal structure of a high affinity nanobody 59H10 bound to HIV-1 capsid protein p24, and deduced key interactions using all-atom molecular dynamics (MD) simulations. We studied the properties of closely-related medium (37E7) and low (48G11) affinity nanobodies, to understand how changes of three (37E7) or one (48G11) amino acids impacted these interactions, however, the contributions of enthalpy and entropy were not quantified. Here, we report the use of qualitative and quantitative experimental and in silico approaches to separate the contributions of enthalpy and entropy. We used complementary circular dichroism spectroscopy and molecular dynamics simulations to qualitatively delineate changes between nanobodies in isolation and complexed with p24. Using quantitative techniques such as isothermal titration calorimetry alongside WaterMap and Free Energy Perturbation protocols, we found the difference between high (59H10) and medium (37E7) affinity nanobodies on binding to HIV-1 p24 is entropically driven, accounted for by the release of unstable waters from the hydrophobic surface of 59H10. Our results provide an exemplar of the utility of parallel in vitro and in silico studies and highlight that differences in entropic interactions between amino acids and water molecules are sufficient to drive orders of magnitude differences in affinity

A tetraspecific VHH-based neutralizing antibody modifies disease outcome in three animal models of Clostridium difficile infection

Clostridium difficile infection (CDI), a leading cause of nosocomial infection, is a serious disease in North America, Europe, and Asia. CDI varies greatly from asymptomatic carriage to life-threatening diarrhea, toxic megacolon, and toxemia. The incidence of community-acquired infection has increased due to the emergence of hypervirulent antibiotic-resistant strains. These new strains contribute to the frequent occurrence of disease relapse, complicating treatment, increasing hospital stays, and increasing morbidity and mortality among patients. Therefore, it is critical to develop new therapeutic approaches that bypass the development of antimicrobial resistance and avoid disruption of gut microflora. Here, we describe the construction of a single heteromultimeric VHH-based neutralizing agent (VNA) that targets the two primary virulence factors of Clostridium difficile, toxins A (TcdA) and B (TcdB). Designated VNA2-Tcd, this agent has subnanomolar toxin neutralization potencies for both C. difficile toxins in cell assays. When given systemically by parenteral administration, VNA2-Tcd protected against CDI in gnotobiotic piglets and mice and to a lesser extent in hamsters. Protection from CDI was also observed in gnotobiotic piglets treated by gene therapy with an adenovirus that promoted the expression of VNA2-Tcd

Fisiología y atributos de calidad de la guayaba “pera” (Psidium guajava cv.) en postcosecha

El objetivo de este trabajo fue evaluar la fisiología de la madurez en frutos de guayaba “pera” (Psidium guajava cv.) cosechados al norte del departamento del Huila en Colombia, recolectados en tres estados de madurez, y mantenidos en dos condiciones de almacenamiento. Se evaluaron los índices de madurez hasta el momento de consumo.La pérdida de peso presentó una tendencia lineal y la firmeza una tendencia logarítmica; el contenido de sólidos solubles se incrementó y el contenido de ácido cítrico disminuyó; la tasa respiratoria en condiciones ambientales osciló entre  60 y 100 mL CO2 • kg-1 • h-1 y la crisis climatérica inició a las 50 horas, mientras que en almacenamiento refrigerado se presentó entre  las 75 y 90 horas, produciendo entre 15 y 20 mL CO2 • kg-1 • h-1.