Fabrication of Metal-Silicon Nanostructures by Reactive Laser Ablation in Liquid

Metal-silicon nanostructures are a growing area of research due to their applications in multiple fields such as biosensing and catalysis. In addition, silicon can provide strong support effects to metal nanoparticles while being more cost effective than traditionally used supports, like titania. Traditional wet-chemical methods are capable of synthesizing metal-silicon nanostructures with a variety of composition and nanoparticle shapes, but they often require high temperatures, toxic solvents, strong reducing agents, or need capping agents added to stabilize the nanoparticles. Laser processing is an emerging technique capable of synthesizing metal-silicon composite surfaces that offers a faster, simpler, and greener synthesis route to these structures. Reactive laser ablation in liquid (RLAL) is a single-step process that can be considered both a “top-down” and “bottom-up” approach. It combines pulsed laser ablation in liquid (PLAL) and laser reduction in liquid (LRL) by ablating a solid target in a metal salt solution. RLAL has been studied previously for synthesizing silver-silicon nanostructured surfaces for use in SERS. However, little is known about the chemical composition of these laser-processed surfaces and the reaction mechanisms leading to their formation are poorly understood. In this work, we synthesized and characterized various silicon-metal nanostructures through femtosecond-RLAL (fs-RLAL). Furthermore, we discuss the relationship between the pH of the precursor solution, processing silicon simultaneously or sequentially, the concentration of the precursor solution, and sample translation rate on the resulting metal-silicon nanostructured surfaces. First, silicon wafers were immersed in pH-controlled solutions of KAuCl4 and Cu(NO3)2, then processed with ultrashort laser pulses. For both copper and gold, two syntheses were compared: (1) simultaneous deposition, wherein a silicon wafer was laser-processed in aqueous metal salt solution, and (2) sequential deposition, wherein the silicon wafer was laser-processed in water and then exposed to aqueous metal salt solution. Gold deposition on the silicon wafers was found to xv depend upon the pH of the precursor solution: near-neutral solutions (pH ~6.3) resulted in much higher gold deposition than acidic or basic solutions. X-ray photoelectron spectroscopy and depth profiling showed the existence of both gold (Au0) and gold-silicide (AuxSi) phases on the surfaces of simultaneous and sequential samples. For copper, only simultaneous deposition resulted in high Cu loading and cubic Cu NPs deposited on the surface. Solution pH near ~6.8 maximized Cu deposition. When Cu(NO3)2 concentration was varied, it affected the Cu NP shape, but not Cu loading. When sample translation rate was varied, the Cu NP size and Cu loading was affected. Silver and various alloy combinations were used in the fs-RLAL synthesis to determine if silver or alloys could be deposited onto the silicon nanostructures. Silver deposition was greatly enhanced by slowing the sample translation rate and utilizing NH3 as the base instead of KOH resulted in smaller Ag NPs. This synthesis method was unable to efficiently synthesize alloy structures on silicon, but initial data suggests that the addition of a second metal into the synthesis invokes a galvanic replacement type effect, enhancing deposition of the metal with the higher reduction potential. We propose mechanisms that explain the observed gold penetration depth and its deposition dependence on solution pH, the morphology of cubic Cu NPs deposited on silicon and their dependence on various parameters, the deposition of silver, as well as the sacrificial nature of using additional metals in RLAL. The mechanistic understanding gained in this work may have use for synthesizing a variety of metal-silicon composite surfaces through laser processing to prepare functional materials such as catalysts and surface-enhanced Raman spectroscopy substrates

A common role for astrocytes in rhythmic behaviours?

Authors acknowledge the Motor Neurone Disease (MND) Association UK (Miles/Apr18/863-791) and the Biotechnology and Biological Sciences Research Council (BBSRC; BB/M021793/1) for their funding and support.Astrocytes are a functionally diverse form of glial cell involved in various aspects of nervous system infrastructure, from the metabolic and structural support of neurons to direct neuromodulation of synaptic activity. Investigating how astrocytes behave in functionally related circuits may help us understand whether there is any conserved logic to the role of astrocytes within neuronal networks. Astrocytes are implicated as key neuromodulatory cells within neural circuits that control a number of rhythmic behaviours such as breathing, locomotion and circadian sleep-wake cycles. In this review, we examine the evidence that astrocytes are directly involved in the regulation of the neural circuits underlying six different rhythmic behaviours: locomotion, breathing, chewing, gastrointestinal motility, circadian sleep-wake cycles and oscillatory feeding behaviour. We discuss how astrocytes are integrated into the neuronal networks that regulate these behaviours, and identify the potential gliotransmission signalling mechanisms involved. From reviewing the evidence of astrocytic involvement in a range of rhythmic behaviours, we reveal a heterogenous array of gliotransmission mechanisms, which help to regulate neuronal networks. However, we also observe an intriguing thread of commonality, in the form of purinergic gliotransmission, which is frequently utilised to facilitate feedback inhibition within rhythmic networks to constrain a given behaviour within its operational range.PostprintPeer reviewe

Innovative strategies for the reception of asylum seekers and refugees in European cities: Multi-level governance, multi-sector urban networks and local engagement

Cities are taking a prominent role in solving global challenges, with a ‘new localism’ inviting a reorientation of power from nation-states downwards, outwards and globally. This special issue explores this phenomenon through extending the existing analyses of multi-level governance and the ‘local turn’ to the underexplored area of asylum seeker and refugee reception in European cities. The special issue draws on research in European cities where new strategies were piloted especially in the wake of ‘the refugee crisis’ from 2015, consolidating the ‘local turn’ evident in immigration and integration policy-making. The collection is in two parts: the first part explores innovation in local governance of asylum seeker reception. Here, case studies demonstrate how cities responded through forging new alliances both vertically and (especially) horizontally in networks within and between cities. The second part explores innovation in practice, analysing novel initiatives premised on local engagement and inclusivity of newcomers within the social fabric of the city. This editorial paper draws out the wider lessons of efforts from this comparative exploration of attempts to rethink asylum seeker and refugee reception at the local level

M-type potassium currents differentially affect activation of motoneuron subtypes and tune recruitment gain

Funding: Royal Society: NIF/R1/180091; Wellcome Trust: 204821/Z/16/Z; Canadian Institute for Health Research: 202012MFE – 459188 – 297534.The size principle is a key mechanism governing the orderly recruitment of motor units and is believed to be dependent on passive properties of the constituent motoneurons. However, motoneurons are endowed with voltage-sensitive ion channels that create non-linearities in their input-output functions. Here we describe a role for the M-type potassium current, conducted by KCNQ channels, in the control of motoneuron recruitment in mice. Motoneurons were studied with whole-cell patch clamp electrophysiology in transverse spinal slices and identified based on delayed (fast) and immediate (slow) onsets of repetitive firing. M-currents were larger in delayed compared to immediate firing motoneurons, which was not reflected by variations in the presence of Kv7.2 or Kv7.3 subunits. Instead, a more depolarized spike threshold in delayed-firing motoneurons afforded a greater proportion of the total M-current to become activated within the subthreshold voltage range, which translated to a greater influence on their recruitment with little influence on their firing rates. Pharmacological activation of M-currents also influenced motoneuron recruitment at the population level, producing a rightward shift in the recruitment curve of monosynaptic reflexes within isolated mouse spinal cords. These results demonstrate a prominent role for M-type potassium currents in regulating the function of motor units, which occurs primarily through the differential control of motoneuron subtype recruitment. More generally, these findings highlight the importance of active properties mediated by voltage-sensitive ion channels in the differential control of motoneuron recruitment, which is a key mechanism for the gradation of muscle force.Publisher PDFPeer reviewe

Comparing March and May Calving Systems in the Nebraska Sandhills

Three production years for March and May calving, Red Angus- based cows and their off spring from the Gudmundsen Sandhills Laboratory (GSL), Whitman, NE, were evaluated. Steer progeny were evaluated through harvest and carcass data collected. Calf birth body weight (BW) and breeding BW were greater for May calves vs. March; however, adjusted weaning BW was greater for March calves. Pregnancy rates, weaning rates, calving interval, calving difficulty, and calf vigor were similar between calving systems. Udder score was greater for March cows. Compared with March calf- fed steers, May calf- fed steers had greater hot carcass weight (HCW), longissimus muscle area (LMA), marbling, and backfat. May yearlings had greater HCW, LMA, marbling, and backfat compared with March calf- feds. In the Sandhills, a May calving system can increase production while reducing total herd inputs when compared to a March calving system

Modulation of spinal motor networks by astrocyte-derived adenosine is dependent on D1-like dopamine receptor signalling

D.A. was supported by funds from a Wellcome Trust Institutional Strategic Support Fund grant. G.B.M. and M.J.B. received support from Biotechnology and Biological Science Research Grant BB/M021793/1.Astrocytes modulate many neuronal networks, including spinal networks responsible for the generation of locomotor behavior. Astrocytic modulation of spinal motor circuits involves release of ATP from astrocytes, hydrolysis of ATP to adenosine, and subsequent activation of neuronal A1 adenosine receptors (A1Rs). The net effect of this pathway is a reduction in the frequency of locomotor-related activity. Recently, it was proposed that A1Rs modulate burst frequency by blocking the D1-like dopamine receptor (D1LR) signaling pathway; however, adenosine also modulates ventral horn circuits by dopamine-independent pathways. Here, we demonstrate that adenosine produced upon astrocytic stimulation modulates locomotor-related activity by counteracting the excitatory effects of D1LR signaling and does not act by previously described dopamine-independent pathways. In spinal cord preparations from postnatal mice, a D1LR agonist, SKF 38393, increased the frequency of locomotor-related bursting induced by 5-hydroxytryptamine and N-methyl-d-aspartate. Bath-applied adenosine reduced burst frequency only in the presence of SKF 38393, as did adenosine produced after activation of protease-activated receptor-1 to stimulate astrocytes. Furthermore, the A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine enhanced burst frequency only in the presence of SKF 38393, indicating that endogenous adenosine produced by astrocytes during network activity also acts by modulating D1LR signaling. Finally, modulation of bursting by adenosine released upon stimulation of astrocytes was blocked by protein kinase inhibitor-(14–22) amide, a protein kinase A (PKA) inhibitor, consistent with A1R-mediated antagonism of the D1LR/adenylyl cyclase/PKA pathway. Together, these findings support a novel, astrocytic mechanism of metamodulation within the mammalian spinal cord, highlighting the complexity of the molecular interactions that specify motor output.Publisher PDFPeer reviewe

The significance of 'the visit' in an English category-B prison: Views from prisoners, prisoners' families and prison staff

A number of claims have been made regarding the importance of prisoners staying in touch with their family through prison visits, firstly from a humanitarian perspective of enabling family members to see each other, but also regarding the impact of maintaining family ties for successful rehabilitation, reintegration into society and reduced re-offending. This growing evidence base has resulted in increased support by the Prison Service for encouraging the family unit to remain intact during a prisoner’s incarceration. Despite its importance however, there has been a distinct lack of research examining the dynamics of families visiting relatives in prison. This paper explores perceptions of the same event – the visit – from the families’, prisoners’ and prison staffs' viewpoints in a category-B local prison in England. Qualitative data was collected with 30 prisoners’ families, 16 prisoners and 14 prison staff, as part of a broader evaluation of the visitors’ centre. The findings suggest that the three parties frame their perspective of visiting very differently. Prisoners’ families often see visits as an emotional minefield fraught with practical difficulties. Prisoners can view the visit as the highlight of their time in prison and often have many complaints about how visits are handled. Finally, prison staff see visits as potential security breaches and a major organisational operation. The paper addresses the current gap in our understanding of the prison visit and has implications for the Prison Service and wider social policy

Stratigraphy of the Dubuque Formation (Upper Ordovician) in Iowa

The Dubuque Formation of Upper Ordovician age crops out in the Upper Mississippi Valley. It comprises interbedded carbonate and argillaceous rocks that are approximately 35 feet thick in Iowa and Illinois, but thicken to a maximum of approximately 45 feet in southern Minnesota. Three proposed informal subdivisions: Frankville, Luana, and Littleport beds, are differentiated on the basis of bed surface topography ranging upward from nearly planar beds in the Frankville to prominently undulose surfaces in the Littleport beds. The Frankville beds represent a transition from the massive dolomite of the underlying Stewartville Member of the Wise Lake Formation to the overlying interbedded carbonate rocks and shale of the upper Dubuque. The base of the Dubuque Formation in Iowa and Minnesota is placed at a prominent, approximately 8 inch thick, carbonate bed at the base of the Frankville beds. This \u27\u27marker bed\u27\u27 provides a more precise datum for lithostratigraphic correlation than the lowest prominent shale parting employed by previous workers to identify the base of the Dubuque