Adult neurogenesis and specific replacement of interneuron subtypes in the mouse main olfactory bulb

Background  

New neurons are generated in the adult brain from stem cells found in the subventricular zone (SVZ). These cells proliferate in the SVZ, generating neuroblasts which then migrate to the main olfactory bulb (MOB), ending their migration in the glomerular layer (GLL) and the granule cell layer (GCL) of the MOB. Neuronal populations in these layers undergo turnover throughout life, but whether all neuronal subtypes found in these areas are replaced and when neurons begin to express subtype-specific markers is not known.     

ZSM‐5 Zeolite Nanosheets with Improved Catalytic Activity Synthesized Using a New Class of Structure‐Directing Agents

A new series of multiquaternary ammonium structure‐directing agents, based on 1,4‐diazabicyclo[2.2.2]octane, was prepared. ZSM‐5 zeolites with nanosheet morphology (10 nm crystal thickness) were synthesized under hydrothermal conditions using multiquaternary ammonium surfactants as the zeolite structure‐generating agents. Both wide‐angle and small‐angle diffraction patterns were obtained using only a suitable structure‐directing agent under a specific zeolite synthesis composition. A mechanism of zeolite formation is proposed based on the results obtained from various physicochemical characterizations. ZSM‐5 materials were investigated in catalytic reactions requiring medium to strong acidity, which are important for the synthesis of a wide range of industrially important fine and specialty chemicals. The catalytic activity of ZSM‐5 materials was compared with that of the conventional ZSM‐5 and amorphous mesoporous aluminosilicate Al‐MCM‐41. The synthesis strategy of the present investigation using the new series of structure‐directing agents could be extended for the synthesis of other related zeolites or other porous materials in the future. Zeolite with a structural feature as small as the size of a unit cell (5–10 nm) with hierarchically ordered porous structure would be very promising for catalysis.     

Longitudinal 3D Blood Flow Distribution Provided by Diffuse Correlation Tomography during Bone Healing in a Murine Fracture Model

Noninvasive monitoring of vascularization can potentially diagnose impaired bone healing earlier than current radiographic methods. In this study, a noncontact diffuse correlation tomography (DCT) technique was employed to measure longitudinal blood flow changes during bone healing in a murine femoral fracture model. The three-dimensional distribution of the relative blood flow was quantified from one day pre-fracture to 48 days post-fracture. For three mice, frequent DCT measurements were performed every other day for one week after fracture, and then weekly thereafter. A decrease in blood flow was observed in the bone fracture region at one day post-fracture, followed by a monotonic increase in blood flow beyond the pre-injury baseline until five to seven days post-fracture. For the remaining 12 mice, only weekly DCT measurements were performed. Data collected on a weekly basis show the blood flow for most mice was elevated above baseline during the first two post-fracture weeks, followed by a subsequent decrease. Torsional strength of the excised femurs was measured for all 15 mice after 7 weeks of healing. A metric based on the early blood flow changes shows a statistically significant difference between the high strength group and the low strength group.     

Multi-criteria logistics modeling for military humanitarian assistance and disaster relief aerial delivery operations

Given that it is not always feasible to reach an affected area via land or sea within the first week following a natural disaster, aerial delivery provides the primary means to rapidly supply the affected population. Further, it is often the case that high density delivery of humanitarian aid supplies are taken over by non-friendly groups within the affected population. By using direct airdrop systems to deliver large quantities of individually wrapped food and water items, dispersion among the affected disaster relief population will occur more quickly. In this paper, we proffer a multiple criteria decision analysis (MCDA) framework to optimize the military humanitarian assistance/disaster relief (HA/DR) aerial delivery supply chain network. The model uses stochastic, mixed-integer, weighted goal programming to optimize network design, logistics costs, staging locations, procurement amounts, and inventory levels. The MCDA framework enables decision-makers to explore the trade-offs between military HA/DR aerial delivery supply chain efficiency and responsiveness, while optimizing across a wide range of real-world, probabilistic scenarios to account for the inherent uncertainty in the location of global humanitarian disasters as well as the amount of demand to be met.     

Effect of Substituents and Dopants on the Structure–Property Relationship of Poly(Aniline)—A Comparative Study

Effects of substituents and dopants on the structure–property relationships of poly(aniline) (PANI)-type homopolymers are analyzed. The gravimetric method was used for the estimation of rate of polymerization (R_p). FTIR spectroscopy was used for the calculation of relative intensities (RI) of benzenoid (RI_[B/CH]), quinonoid (RI_[Q/CH]), and their internal conversion (RI_[B/Q]). Thermogravimetric analysis (TGA) characterized the thermal stability of PANIs. A standard four probe method was employed for the conductivity measurements. The results are analyzed and critically compared.     

Four complementary theoretical approaches for the analysis of NMR paramagnetic relaxation

Four theoretical and computational approaches used at the University of Michigan to analyze NMR paramagnetic relaxation enhancement (NMR-PRE) are described. The primary objective of the theory is to describe the relationship of the NMR-PRE phenomenon to the electron spin hamiltonian and the spin energy level structure when zero field splitting interactions are significant. Four formulations of theory are discussed: (1) spin dynamics simulation; (2) the laboratory frame "constant H(S)" formulation; (3) the Molecular Frame "constant H(S)" formulation; and (4) the zfs-limit "constant H(S)" formulation. No single theoretical approach describes all important aspects of the relaxation mechanism in a fully satisfactory way. We use the four formulations in a complementary manner to provide as complete a picture of the relaxation mechanism as possible. We also discuss the integration of NMR-PRE theory and recently developed theory of electron spin relaxation which accounts for effects of the permanent zfs hamiltonian.     

Temporal onset-order discrimination through the tactual sense

Tactual temporal-onset order thresholds were measured for two sinusoidal vibrations of different frequencies delivered to two separate locations (thumb and index finger) of a multi-finger tactual stimulating device. The frequency delivered to the thumb was fixed at 50 Hz and that to the index finger at 250 Hz. The amplitude and duration of each of the two sinusoidal vibrations were roved independently from trial to trial in a 1-interval, 2AFC procedure. Performance, measured as a function of stimulus-onset asynchrony (SOA), indicated that the temporal-onset-order threshold averaged 34 ms across four subjects. The data were further classified into subsets according to both the amplitude and duration of the two stimuli in each trial of the roving-discrimination paradigm. The results indicated that the amplitude differences of the two stimuli in each trial had a substantial effect on onset-order discrimination, while duration differences generally had little effect. The effects of amplitude differences are explained qualitatively in terms of amplitude latency relationships and stimulus interactions such as temporal masking. Overall, the results not only contribute to an enhanced understanding of the temporal sensitivity of the tactual system but also provide guidelines for the design of tactual aids for hearing-impaired persons.     

The first direct evaluation of the two-active site mechanism for chitin synthase

Chitin synthase polymerizes UDP-GlcNAc to form chitin (poly-beta(1,4)-GlcNAc) and is essential for fungal cell wall biosynthesis. The alternating orientation of the GlcNAc residues within the chitin chain has led to the proposal that chitin synthase possesses two active sites. We report the results of the first direct test of this possibility. Two simple uridine-derived dimeric inhibitors are shown to exhibit 10-fold greater inhibition than a monomeric control, consistent with the presence of two active sites. This observation has important implications for the development of antifungal agents, as well as the understanding of polymerizing glycosyltransferases.     

Arrested chloride abstraction from trans-RuCl2(DMeOPrPE)2 with TlPF6; formation of a 1-D coordination polymer having unusual octahedral coordination around thallium(I)

An "arrested" chloride abstraction occurs in the reaction of trans-RuCl(2)(DMeOPrPE)(2) with TlPF(6); the product is a 1-D coordination polymer in which the Tl(I) centers have an unusual octahedral coordination geometry with a stereochemically active 6s(2) lone pair.