ABSTRACT
It is intriguing how the Hammett equation enables control of chemical reactivity throughout chemical space by separating the effect of substituents from chemical process variables, such as reaction mechanism, solvent, or temperature. We generalize Hammett's original approach to predict potential energies of activation in non aromatic molecular scaffolds with multiple substituents. We use global regression to optimize Hammett parameters ρ and σ in two experimental datasets (rate constants for benzylbromides reacting with thiols and ammonium salt decomposition), as well as in a synthetic dataset consisting of computational activation energies of â¼2400 SN2 reactions, with various nucleophiles and leaving groups (-H, -F, -Cl, -Br) and functional groups (-H, -NO2, -CN, -NH3, -CH3). Individual substituents contribute additively to molecular σ with a unique regression term, which quantifies the inductive effect. The position dependence of substituents can be modeled by a distance decaying factor for SN2. Use of the Hammett equation as a base-line model for Δ-machine learning models of the activation energy in chemical space results in substantially improved learning curves reaching low prediction errors for small training sets.
ABSTRACT
Pancreatic cancer remains an aggressive disease, with a poor prognosis and a high risk of incurring into cachexia. Supportive care, such as exercise, nutritional and psychological support, may be effective in reducing functional loss, psychological distress and improving nutritional status. We report the effect of 12 weeks of multimodal lifestyle intervention in a 55-year-old female, diagnosed with unresectable body/tail pancreatic cancer and metastasis in the liver, bone, lymph node and lung, to counteract cachexia. The multimodal program resulted safe and feasible. Over 12 weeks, considerable improvements were found in body weight, health-related physical fitness, nutritional status, distress scores, anxiety and depression levels. These findings highlight the potential role of integrated supportive interventions to manage metastatic cancer and cancer-induced cachexia.
ABSTRACT
We report the electronic, magnetic and transport properties of a prototypical antiferromagnetic (AFM) spintronic device. We chose Cr as the active layer because it is the only room-temperature AFM elemental metal. We sandwiched Cr between two non-magnetic metals (Pt or Au) with large spin-orbit coupling. We also inserted a buffer layer of insulating MgO to mimic the structure and finite resistivity of a real device. We found that, while spin-orbit has a negligible effect on the current flowing through the device, the MgO layer plays a crucial role. Its effect is to decouple the Cr magnetic moment from Pt (or Au) and to develop an overall spin magnetization. We have also calculated the spin-polarized ballistic conductance of the device within the Büttikerâ»Landauer framework, and we have found that for small applied bias our Pt/Cr/MgO/Pt device presents a spin polarization of the current amounting to ≃25%.
