Graphene sheets are a highly radiation-resistant material for prospective nuclear applications and nanoscale defect engineering. However, the precise mechanism of graphene radiation hardness has remained elusive. In this paper, we study the origin and nature of defects induced by gamma radiation in a graphene rolled-up plane. In order to reduce the environmental influence on graphene and reveal the small effects of gamma rays, we have synthesized a novel graphene-based nanocomposite material containing a bilayer of highly aligned carbon nanotube assemblies that have been decorated by organometallic compounds and suspended on nanoporous Al A” (“B”) graphene sublattice, together with the closest neighboring carbon atoms residing in a trigonal “B” (“A”) graphene sublattice, may function as information bits “0” (“1”) in new-generation nanoscale memory arrays [Applications of graphene-like materials are highly anticipated due to extreme mobility of their charge carriers ,2,3. Amo-healing . Grapheny arrays . The proy arrays .The understanding of the interactions between energetic particle beams and solids allows us to predict the behavior of three-dimensional (3D) systems under energetic particle beam irradiation, which occurs as a result of projectile–nuclei collisions, leading to the loss of the atom’s structural integrity and the formation of an ion and a charged vacancy. In contrast, vacancies induced by beta and ion radiation in graphene form neutral clusters ,9,17. Thoseconds . Such hi08 A/cm2  or less 08 A/cm2 , respectOne of the mechanisms of 2D radiation damage is the 3D mechanism of a knock-on atom , which iAt present, the 2D mechanism of defect production, which is called interatomic Coulombic decay (ICD), is considered the prevalent mechanism of X-ray scattering in graphene ,31 becauHowever, competing with the Hartree self-consistent field, the Fock exchange impedes the repulsion process  exist in the graphene flat bands, where the VHSs are pushed to the Fermi level lectrons ,44. Surplectrons . The devenergies . This hienergies .The stability of graphene under gamma-ray irradiation can be caused by interactions between the gamma quanta and pseudo-Majorana-type pairs of correlated graphene charge carriers, as sharp increases in the conductivity of rolled-up-graphene have been observed just after gamma-ray exposure at sufficiently low fluence ,49. When013 cm−2 .Thus, the pseudo-Majorana quasiparticles, which comprise configurations of the Dirac fermion pair, can be candidates to play the role of repulsively bound states. Signatures of Majorana excitation were observed for graphene in . The disIn this paper, we use the pseudo-Majorana graphene model to explain how ionizing radiation interacts with nanostructures based on graphene.The electronic structure of a graphene monolayer is strongly influenced by the environment. Since both the environment and graphene sample are exposed to radiation and the experimental conditions and samples are not identical, it is very difficult to detect the weak contribution of radiation damage to the change in the intensity of graphene Raman bands due to the significant influence of the environment . The envIn this work, to eliminate environmental influences, we fabricate bilayers of highly aligned carbon nanotube assemblies that are decorated by organometallic compounds and suspended on nanoporous AlThe goal of the paper is to reveal and explain the mechanisms responsible for producing high-energy free vortex–antivortex pairs in the electron density of graphene through the breaking of hexagonal symmetry upon impact with a low-intensity gamma beam. To achieve this, we use the pseudo-Majorana graphene model. We propose that the radiation hardness of graphene stems from the production of topological defects.Few-walled CNTs (FWCNTs) with a diameter of 2.5 nm and a length of ∼5–10 g manner . As a prA standard low-intensive source of ionizing radiation (IRS) L = 25, 50 mm length. The scheme of irradiation is shown in k is the percentage of the emitted photons per one decay (quantum yield), Here, .2 years . A sampladiation . HoweverU changed from 100 to 1000 V; after 20 min of warming, the voltage instability did not exceed 0.05% for 5 h of continuous apparatus operation; the admissible current of the PEM power supply was not less than 5 mA; the input resistance of the main amplifier was 15 kOm; the amplifier gain changed from 1 to 100 smoothly or stepwise; the transformable signal range was 0 to 10 V; the signal polarity was arbitrary ; the signal-front duration was no more than 0.3 An analysis of the transmitted gamma rays was performed using the lab-quality radiation spectrometric equipment in the “Nuclear Physics”  training laboratory. A thallium-activated sodium iodide scintillation crystal NaI(Tl)  was utilized as a detector crystal. The technical characteristics of the radiation spectrometer were as follows. The photoelectric-multiplier (PEM) supply voltage E: b asc are the electron mass and the speed of light, respectively.The number nels see f. The nuK-shells in the atoms of the lead collimator. The photopeak appears at the energy of the original The response functions of the detector shown in  crystal .The normalized full-energy peak of the n 0.997) . Thus, tPreliminary, inverse micelles of stearic acid with the FWCNTs inside were obtained by mixing the stearic acid and FWCNTs in hexane by ultrasound treatment. Then, two or three carbon nanotube monolayers fabricated from these micellar FWCNTs using the LB technique were deposited on a Si support or suspended on 10 nm pores in anodic aluminum oxide (AOA). The highly ordered aligned carbon nanotube LB assemblies decorated with a 5-monolayer film of nanocyclic organometallic complexes, Fe(II)DTP, were deposited on the Si surface or suspended on an interdigital structure of aluminum electrodes, on the surface of which, the nanoporous AOA layer was previously formed as an insulator coating. The Fe(II)DTP film was fabricated using the LB technique. The interdigital electrode structure was deposited on glass-ceramic support such as pyroceramics .Microdiffraction patterns and TEM images were obtained using a transmission electron microscope JEM-100CX  at an accelerating voltage of 100 kV. The samples were previously deposited on a copper grid with a formvar polymer coating or 19 nm porous AOA membranes from the direction of the AOA barrier layer.Spectral studies in the visible range were carried out using a confocal micro-Raman spectrometer Nanofinder HE  with lasers operating at wavelengths of 355 , 473 (diode pumped solid state (DPSS) laser), and 532 (DPSS laser) nm, with power in the range of 0.0001 to 20 mW. The spectra were recorded in back-scattering geometry under a ×50 objective at room temperature. Nanoporous AOA membranes with a pore diameter of 10 nm and Si supports were utilized in the Raman spectroscopic studies.The nanostructured composite material is shown schematically in The TEM images of the original carboxylated FWCNTs are shown in ely, see b. The va formula :(6)ωRBM=Let us estimate  formula :(7)dCNT=D), 2443.19  onto the graphene plane decreases DTP-decorated bilayer become weakly intense  see c. The DiV(r) see b. The shling see c, left. ases see c, middleases see b, the inThe CNT bilayer and three-monolayer CNT LB films would produce two related microdiffraction spots corresponding to the SWCNTs of opposite chirality (whose axes are in opposite directions), or the diffraction spots associated with a range of CNT chiral angles would form arcs. The arrangement of the microdiffraction reflections shown in  formula:Rt=12 in a T-shape configuration. An atomic chain with two topological defects at the ends implements a pseudo-Majorana particle [The Zak phase of the graphene charge carriers entering the pseudo-Majorana configuration is non-zero. The charge carriers, whose non-Abelian Zak phase multiples of particle ,67. The One of the two eigenvalues of the Majorana mass term entering the Hamiltonian of the pseudo-Majorana fermion turns out to be zero. Therefore, one of the pseudo-Majorana particles is composed of two chiral vortex defects, the second one is composed of two nonchiral vortices, and only one vortex is chiral for the third pseudo-Majorana mode. Since the flavor is associated with the chirality, let us call the pseudo-Majorana differently flavored modes the chiral, semichiral, and nonchiral pseudo-Majorana particles Thus, the pseudo-Majorana fermion graphene model is a topological semimetal. Resulting in the eight subreplicas of the graphene bands, the SOC is capable of competing with the hexagonal symmetry at large energies in the flat bands only. When the pseudo-cubic symmetry holds, the electron-hole symmetry for every graphene band is broken separately, and, correspondingly, the bound vortical and antivortical pseudo-Majorana fermions, forming electrons and holes, which are deconfined by large SOC. These free deconfined pseudo-Majorana particles exist in a very narrow energy range because they reside in the flat area of the graphene bands. Since the velocity The gamma quantum resides in the order of The model of the interactions of the photons and the electron density by the Compton mechanism is presented in The rotating electric field of the circularly polarized gamma radiation quanta twists the electron density around the vortex cores located at the sites of the hexagonal lattice. The high-energy gamma radiation quantum is able to excite a huge number of low-energy electrons in the flat regions of the graphene band structure. The flat electronic bands, Using the calculation results presented in Let us estimate the current of the topologically nontrivial graphene charge carriers and make a comparison with a current for the pseudo-Dirac fermion graphene model. To do this, let us use the Heisenberg uncertainty principle iΔpi≥ℏ/2  to find N using the following energy condition Here,  carrier . Here, pLet us choose the energy limits from 0 to 0.02 eV in Expression  because K because when bypassing the lattice site, the topologically nontrivial graphene charge carriers with the cyclic group The Majorana vortex moves as a whole because it resides in the graphene valley only with the wave number After changing Here, k is the 3-vector with the following components: Here, Property , one obtTaking into account that Equation  into EquEquation  gives thThe theoretically predicted value  of the sd scales .The energy losses of K→′) see c. Corresband see c. After Here, the total number of electrons coincides with the total number of holes Thus, an electron-hole pair avalanche is produced due to the confinement of the Majorana fermions in the flavorless Dirac configurations. The prediction of the low-energy electron avalanche explains the appearance of the large number of low-energy electrons (0–10-eV electrons) that are experimentally observed in the irradiated graphene samples . The vorWe justify the pseudo-Majorana nature of graphene fermions through our experimental results.Hereafter, experimental evidence is presented to show that pseudo-Majorana vortical fermions exist on the defects induced by the gamma-ray irradiation of the graphene plane.A, Let us analyze the carbon nanotube bilayer effects on the incoming If one interprets e result  would prAfter placing the electromagnetic radiation bilayer absorber into the collimator, three additional peaks appear in the trahlung . The thrThe spectra When comparing the single Compton continuums in the radiation spectra for the detector with and without the sample, we conclude that the growth in the number of photons scattered at the scattering angle mple see c. In accr energy . TherefoThe semimetal graphene hosts bound electrons (electrons in steady states) and, correspondingly, the uncharged photons cannot influence the graphene surface through the Coulomb force. The effects of the gamma-ray irradiation of the bilayer reveal that there is a Compton mechanism of the interaction of gamma rays with graphene. This mechanism does not involve free electrons, but the free electrons appear after the radiation-induced creation of vortical defects in graphene.Now, let us estimate the variation in the energy deposition in the channels after the installation of the sample in the collimator. To achieve this, let us select groups of channels so that six and more credible events are recorded in each channel of the groups see d. Let usAccording to the data shown in vely see . The locThus, the positive shifts mean that the increased number of photons with higher energies are registered by the detector. Since other energy loss peaks of characteristic X-ray photons do not appear in the radiation spectrum, the collisions with the gamma ray do not lead to the ionization of the bilayer.In this section, we discuss the proposed mechanism of the interaction of the rolled-up graphene with the gamma radiation, which is particularly relevant in light of the experimental facts reported above.When swirling an electron density in the graphene plane by the rotating electric field, the gamma quantum creates a feather of a vortex, whose core resides in the Dirac point. The characteristics of these topologically nontrivial radiation-induced defects are non-Abelian and the pseudo-Majorana quasiparticle fermion excitations reside on the defects see . This memple see d–e. The The graphene pseudo-Majorana fermions are massless at the Dirac point the mass .The massless pseudo-Majorana fermions move collisionless in the graphene plane by virtue of the laws of conservation of helicity and topological charge. Correspondingly, they live until the pairs of bound pseudo-Majorana fermions with zero topological charge are formed. Since the lifetime The nonchiral vortices with the non-zero pseudo-Majorana mass stop and then remain in a resting state until the disintegration proceeds. The de-excitation of the semichiral pseudo-Majorana fermion  keV see e.The right and left twisted vortices entering the nonchiral pseudo-Majorana fermion, −2Eb see e.As a result, based on the experimental data, one can estimate the energy, Placed outside the sites of the pseudo-cubic lattice, the Majorana vortices in flavor pull carbon atoms in a circular motion and, correspondingly, three differently flavored ordered sets of circular apertures appear as the electron density, and carbon atoms are absent in the sites of the pseudo-cubic lattice. The incident gamma rays undergo Fraunhofer diffraction on these voids. The presence of the three radiation spectrum bands undergoing the giant shifts DTP Raman spectrum shown in red in Thus, the mechanism of interaction of laser radiation and graphene stems from the existence of the pseudo-Majorana mode.The photons are not electrically charged, and, correspondingly, do not produce charge carrier currents. However, these currents can be created by an electron beam that pushes electrons out of the lattice sites, electrically polarizing the graphene crystal cell. The analysis of the electron structure of the graphene surface using TEM demonstrates that the electric field of the 100 keV electron beam oblique to the aligned CNT assemblies “negatively dopes” the graphene plane. These “negatively doped patches” are visualized as an “electron-dense layer”. The apparent CNT diameter (1.9 nm) increases 2.5 times in comparison to the size of the nanotube cross-section (0.761 nm) due to this “doping” see b,c. On tThe high-energy vortex of the pseudo-Majorana fermion flow in flavor is capable of carrying electrically neutral carbon atoms that are pulled into the vortex funnels away from their locations in the hexagonal lattice. Since the antivortices entering these pseudo-Majorana fermions remain in the lattice sites where the atoms previously resided, a cluster of vacancies that are electrically neutral but different in flavor is formed. Meanwhile, the flows of the vortices belonging to these Majorana fermions carry away electrically neutral carbon atoms (see the model shown in Thus, by changing the direction of the wave vector, the diffraction effectively increases the number of trapped photons. The longer-wave bremsstrahlung photons that are deflected at very large angles are capable of going around an obstacle of such sizes as the vacancy in flavor. The intensity of the “Brem” peak decreases by a factor of two due to the interference of the bremsstrahlung photons. The flavored vortices carrying out the electrically neutral carbon atoms are in a quasi-steady state by virtue of the law of conservation of the topological charge. The topological charge of the radiation-induced defect of the “vacancy in flavor” can be neutralized only by the vortex bringing the carried-away topological charge and knock-on carbon atom to the vacancy; after that, the radiation damage disappears.This discovery, together with the contraction of the Compton contribution and the possibility of reducing the sizes for both the crystal and radiation shield, allows for the development of inexpensive detectors with higher collection efficiency. The presence of the electron-hole avalanche impedes the creation of defects in the detector crystal at exposure, and, correspondingly, can facilitate the increase in the operating lifetime of the detector crystal. Our findings open up prospects for a dramatic improvement in the sensitivity of modern detectors.The experimental evidence shows that very high energetic vortex electron density structures can reside in monolayer graphene. A very large number of the vortex structure branches hosted by the flattenings of graphene bands behave as a whole. Pairs of topologically nontrivial vortical and antivortical defects are created in rolled-up graphene planes irradiated by the 661.7-keV gamma quanta. The high-energy graphene vortex–antivortex pairs are pseudo-Majorana fermions.We provide the mechanism responsible for graphene radiation hardness, according to which gamma rays can escape from the detector crystal–CNT bilayer system due to the production of irradiation defect pairs. When creating neutral radiation-induced vacancies We theoretically predict and experimentally demonstrate that the Fraunhofer diffraction of the gamma quanta on the vortex of the pseudo-cubic crystal lattice with non-occupied sites and the Fraunhofer diffraction of the backscatter and bremsstrahlung Finally, the incorporation of the suspended metallic carbon nanotube assemblies into the collimator greatly increases the beam-energy deposition in the crystal detector and radiation shield due to the electron-hole avalanche that occurs in the disintegrated Majorana fermion’s confinement decay channel. Through our research, we have found that the detection of ionizing radiation with very low levels that are below the detection limit of conventional detectors can be achieved via the measurement of the conductivity change of thin films, which allows us to determine the presence of radiation.


Composites of LiBH4-catalysts were prepared by melt infiltration and investigated by X-ray diffraction, TEM, STEM-EDS and TPD. The role of ferrite additives, metal precursor treatment  and the effect on hydrogen storage parameters are discussed. The thermodynamic parameters for the most promising composite LiBH4-graphene-NiFe2O4 (Ar) were investigated by Kissinger plot method, revealing an EA = 127 kJ/mol, significantly lower than that of neat LiBH4 (170 kJ/mol). The reversible H2 content of LiBH4-graphene-NiFe2O4 (Ar) after 5 a/d cycles was ~6.14 wt%, in line with DOE’s target of 5.5 wt% storage capacity, while exhibiting the lowest desorption temperature peak of 349 °C. The composites with catalysts treated in Ar have lower desorption temperature due to better catalyst dispersion than using H2/Ar.Featuring a high hydrogen storage content of up to 20 wt%, complex metal borohydrides remain promising solid state hydrogen storage materials, with the real prospect of reversible behavior for a zero–emission economy. However, the thermodynamic barriers and sluggish kinetics are still barriers to overcome. In this context, nanoconfinement has provided a reliable method to improve the behavior of hydrogen storage materials. The present work describes the thermodynamic and kinetic enhancements of LiBH The safe and effective production, storage and transport of hydrogen energy remains a current challenge. Among potential hydrogen sources, solid-state hydrogen storage materials such as simple and complex metal hydrides have been extensively investigated over the past few decades . A serieWhen nanoconfined in the pores of a proper scaffold, the behavior of borohydrides and alanates features marked improvements over their pristine counterparts ,2. On on3O4 [A key step in engineering competent nanocomposites for energy storage is to ensure the active hydrogen storage material is confined uniformly at the nanoscale, so that there are no outer-host processes like crystal growth which would adversely affect the hydrogen storage performance. The majority of previously-reported works deal with confinement of complex hydrides in previously-prepared hosts, which impairs some degree of inhomogeneity. Many nanoporous substrates were used as scaffolds: 2D-structured silica, carbon, carbon nanobowls, mesoporous carbon, and graphene . Graphen4 [4)2 [4 [4 for instance, without the additional support of a porous scaffold [2B12H12 and possibly other crystallographic forms of LiBH4 as well [2O4 and NiFe2O4 have been investigated as catalysts for complex hydrides, especially for complex hydrides like lithium borohydride LiBH4 [4 [4 [Among investigated species nanoconfined in porous scaffolds are LiBH4 ,13,14,154 [4)2 , or LiAl [4)2 [4 . There ascaffold . Variousscaffold , extensiscaffold  and extescaffold . These i as well . Other a as well . Modern  as well . Other m as well ,26. Othe as well , while Cde LiBH4  and alkaLiBH4 [4 ,30 and NH4 [4 [4 .2O4, CoFe2O4) starting from a stoichiometric mixture of corresponding metal nitrates. The thermal decomposition of metal precursors was carried out under two different conditions: in Ar flow or H2/Ar flow. A comparison of catalyst morphology revealed that the Ar flow treatment leads to a better catalyst dispersion inside graphene nanosheets, hence producing a more potent catalyst. Additionally, the in-situ production of MFe2O4  stems from a bottom-up approach that would ensure homogeneous catalyst dispersion and a more controllable kinetic behavior of confined hydride species. The different gas flow approaches (inert–Ar or reducing H2/Ar) allowed further evaluation of metal ferrites  and intermetallics/alloys . In all investigated cases, the ferrite catalysts showed enhanced kinetic behavior of the LiBH4@catalyst nanocomposites, and superior to the intermetallic catalysts obtained under reducing conditions, providing a useful starting point for further investigation of in-situ generated ferrite catalysts for hydrogen production.However, oftentimes the activity of nanosized catalysts dispersed in porous scaffolds yields results which are hard to predict and moreover, even differ between various research groups. A possible reason is that, even though the chemical nature of the catalyst may be similar, its dispersion within the scaffold is not homogeneous and even the chemical composition of the catalyst can be altered during HEBM . In the current work, we address the inhomogeneity issue of the catalyst dispersion inside graphene 2D sheets by an in-situ catalyst preparation , graphene nanoplatelets , iron (III) nitrate nonahydrate, Fe(NO3)3⋅9H2O, , nickel (II) nitrate hexahydrate Ni(NO3)2⋅6H2O , cobalt (II) nitrate hexahydrate Co(NO3)2⋅6H2O , absolute ethanol . The catalysts based on cobalt ferrite and nickel ferrite supported on graphene were prepared and used as supports for subsequent LiBH4 melt impregnation. Stoichiometric amounts of Fe(NO3)3⋅9H2O and Ni(NO3)2⋅6H2O or Co(NO3)2⋅6H2O corresponding to the final loading of graphene with either 15 wt% of NiFe2O4 or CoFe2O4 have been impregnated by incipient wetness method (in 5–7 impregnation steps) from absolute ethanol solutions of corresponding nitrates. The concentrations of the solutions were 0.045 M ethanol solutions of Ni(NO3)2.6H2O or Co(NO3)2.6H2O, and 0.09 M for Fe(NO3)3.9H2O, and were used in stoichiometric amount to yield MFe2O4 . The impregnated samples were subjected to thermal treatments either in Argon (Ar) or 5% Hydrogen in Argon (further noted in the text as: H2Ar) gas flow . The CoFe2O4/graphene and NiFe2O4/graphene catalysts synthesized in Ar or H2Ar gas flow were mixed with LiBH4 in the mass ratio 1:1 by prolonged time grinding under dry inert atmosphere using pestle and mortar. Afterwards they were hydrogenated at 300 °C in hydrogen gas with 99.9999% purity under 80 atm H2 pressure. This temperature was above the melting point of LiBH4 (270 °C) allowing an intimate mixing between lithium borohydride and the supported catalysts. The samples processing was carried out in MBraun LabStar  glove box under purified re-circulated Argon  during all stages of sample manipulation. X-Ray diffraction investigation was performed using D-8 Advance Bruker diffractometer  with Cu K-alpha radiation. During X-ray diffraction measurements the samples were covered with polymeric foil in order to avoid oxidation. TEM images were obtained with JEM-2100 analytical transmission electron microscope  operated at 200 kV endowed with dispersive X-ray spectrometer. For TEM measurements, the samples were dispersed in hexane using high power device  and afterwards were deposited on grids by drying the hexane. A commercially available Sievert volumetric apparatus  was used for hydrogen absorption and desorption measurements at a particular temperature or with a temperature ramp rate .Starting materials for samples preparations were: lithium borohydride, LiBH4-graphene, (ii) LiBH4-, (iii) LiBH4-, (iv) LiBH4- (v) LiBH4-. The catalysts contain 15 wt% NiFe2O4 or CoFe2O4 dispersed on graphene.Five composite samples were prepared and investigated in the present work: (i) LiBH2O4/graphene (treated in H2Ar flow) as CFO-G-H2Ar, (B) 15 wt% NiFe2O4/graphene (treated in H2Ar flow) as NFO-G-H2Ar, (C) 15 wt% CoFe2O4/graphene (treated in Ar flow) as CFO-G-Ar, and (D) 15 wt% NiFe2O4/graphene (treated in Ar flow) as NFO-G-Ar. The XRD patterns of the catalysts synthesized in the present work are depicted in 2O4 (ICDD file 04-005-6361) and FeNi (ICDD file 04-021-6318). The formation of FeNi is supported by the reducing effect of the carbon matrix. By contrast, the sample CFO-G-Ar contains mainly CoFe2O4 (ICDD file 00-066-0244), but also small amounts of carbide phases Fe3C (ICDD file 04-008-9572) and Co3C (ICDD file 04-003-4355). Regarding the samples treated under reducing flux (H2Ar), the ferrite phase MFe2O4  is no longer visible in XRD diffractogram, and full reduction to metallic alloy/intermetallic MFex  can be observed. The sample NFO-G-H2Ar contains only FeNi and Fe-bcc, besides the main contribution from graphene. As previously mentioned in the literature, the hydrogenation of NiFe2O4 leads to the formation of FeNi and Fe and this observation holds true for reduction of nanoconfined nickel ferrite in the particular case when using a graphene support matrix. In the case of CoFe2O4 the treatment in H2 or H2Ar (hydrogen + argon) mixture generates CoFe2 (ICDD file 04-016-4643). Hence, the sample CFO-G-H2Ar contains only CoFe2 besides the main graphene contribution. The XRD peaks corresponding to NiFe2O4, CoFe2O4, FeNi and Fe are relatively wide, suggesting grains in the nanometric range. For clarity, a summary of phase identification of these catalyzed graphene supports can be found in the For simplicity, in the following notations were used: (A) 15 wt% CoFe4 mixed with CoFe2O4 and NiFe2O4 catalysts supported on graphene. The samples were extracted after five cycles of hydrogen absorption/desorption being in final re-hydrogenated (absorbed) state. During measurements the samples were covered with polymeric foil in order to avoid oxidation. The peaks from from 2Θ of about 22° and 36° belong to this foil. Expectedly, the dominant contribution from the XRD pattern belongs to graphene. Additionally, in the sample LiBH4-G were evidenced not only the peaks of LiBH4 (ICDD file 01-084-8599) but also an important contribution from Li3BO3 (ICDD file 00-018-0718) as effect of surface oxidation. After hydrogen absorbtion/desorption cycles, LiBH4 interacts with the ferrites or intermetallics contained in the samples, forming borides. FeB (ICDD file 04-004-2772) and Fe2B (ICDD file 04-002-9005) appeared in all samples which contain supported catalysts. The samples LiBH4-CFO-Ar and LiBH4-CFO-H2Ar contain also CoB (ICDD file 04-004-2683) whereas samples LiBH4-NFO-Ar and LiBH4-NFO-H2Ar present also NiB (ICDD file 01-074-1207), besides iron borides, LiBH4 and Li3BO3. The borides peak are broad, clearly indicating very small grains. A summary of the phase identification of used catalyst (after 5 a/d cycles) is presented for clarity also in 4-G, LiBH4-NFO-G-Ar, LiBH4-NFO-G-H2Ar, LiBH4-CFO-G-Ar depict large sheets of graphene, with lateral dimensions of a few microns. The selected area diffraction patterns (SAED) of all 4 samples reveal the presence of graphene (rings corresponding to graphite interplanar distances were identified). Also the spots corresponding to LiBH4 were detected. TEM images at higher magnification revealed elongated crystalline zones with 7–14 nm thickness  and have irregular shapes. In samples LiBH4-NFO-G-Ar and LiBH4-CFO-G-Ar the nanoparticles are well separated, although they seem to be more uniformly distributed in LiBH4-CFO-G-Ar. The sample LiBH4-NFO-G-H2Ar contains nanoparticles more likely to form large clusters with high particles densities, while in other areas these clusters are absent. Their composition was confirmed by the EDS mapping to be: Fe-Ni , and Fe-Co (for LiBH4-CFO-G-Ar), with slightly higher iron concentration.STEM-EDS measurements for samples LiBHO-G-H2Ar  proved tInvestigation of hydrogen desorption behavior using temperature ramp rate of 2 °C/min  was performed using AMC Sievert volumetric apparatus . The samples were manipulated in inert and dry atmosphere in glove box and transferred in the sample holder of AMC apparatus using the same facility. The samples were first degassed in vacuum at about 100 °C, but temperatures above 150 °C have been avoided during degassing due to the risk of hydrogen desorption before the envisaged release measurement for as–prepared samples. Hydrogen desorption measurements with temperature ramp rate (TPD) were performed both for first desorption A when tB.4 decomposition into LiH and B is 13.8 wt% H2 [2 was normalized to this value. LiBH4 without graphene or catalyst addition released a normalized value of only 0.25 for desorption measurement with 2 °C/min up to 450 °C. For subsequent desorption, the sample was loaded with H2 after each hydrogen desorption at 450 °C and 80 atm H2 for prolonged time (24 h) in order to ensure that the sample reached the maximum level of absorbed hydrogen. One can observe that even though the first LiBH4-G decomposition is th e fastest among all samples, the same sample behaves worst at the saturated behavior after 5 a/d cycles. This confirmed the catalytic role of NiFe2O4 and CoFe2O4 addition to graphene, which improves the hydrogen desorption process. Hydrogen desorption with temperature ramp rate of 2 °C/min up to 450 °C is not enough to release all the hydrogen from samples. In order to achieve this goal, the desorption was allowed longer time at the final temperature of 450 °C. The corresponding desorption kinetics curves were provided in electronic The theoretical maximum value of hydrogen amount released during LiBHUsing the TPD from 4-graphene sample that proved the advantages of doping graphene with cobalt or nickel ferrite in order to improve hydrogen desorption kinetics of LiBH4. In 4-NFO sample compared with LiBH4-CFO sample for catalysts treated both in Ar and H2Ar flow.As depicted in 4. On the other hand, LiBH4 mixed with catalysts heat treated in Ar flow have lower desorption peak temperature than their counterparts annealed in H2Ar flow both for cobalt and nickel ferrite supported on graphene. One should recall from STEM-EDS  is the lowest among all samples. For this sample, TPD measurements were performed with different temperature ramp rate of 1 K/min, 2 K/min, 4 K/min and 7 K/min up to 450 °C  flow at 620 °C. The composites LiBH4-catalysts were prepared by prolonged mixing under protective atmosphere followed by melt infiltration under hydrogen pressure. Dehydrogenation measurements confirmed that both Ni- and Co-ferrite catalyzed graphene nanocomposites show faster desorption kinetics than pristine graphene. LiBH4-(NiFe2O4/graphene) using nickel ferrite catalyst synthesized in Ar flow has the lowest desorption temperature peak of 349 °C, whereas the same composition, but using treatment in H2/Ar, presents the highest reversible storing capacity of 6.14 wt% H2. The Kissinger plot for LiBH4-(NiFe2O4/graphene/Ar) revealed an activation energy of 127 kJ/mol. The kinetic improvement can be traced to the Fe, Ni and Co borides formed during hydrogenation. The composites with catalysts treated in Ar have lower desorption temperature due to better catalyst dispersion than using H2/Ar, when catalyst clustering was observed by STEM-EDS measurements. The Ni–ferrite NiFe2O4 was more effective than Co–ferrite CoFe2O4 in lowering the decomposition temperature of catalyzed LiBH4 composites, and also more effective than metal borides and carbides identified in the reaction mixture as potential catalysts. Additionally, the current work highlights the role of metal ferrites, metal boride and carbide phases acting as hydrogenation catalysts, providing useful information on the actual state of catalytic sites during cycling. Considering the promising results exhibited by graphene-supported MFe2O4 , the ferrite–based supports will be further investigated in catalytic de–/rehydrogenation studies of other complex hydrides and RHCs.The present work investigated the improved efficiency of LiBH


Syringe service programs (SSPs) deliver critical harm reduction services to people who inject drugs (PWID). Some SSPs in New York State received enhanced funding to provide additional services to combat opioid overdose fatalities. These SSPs, known as Drug User Health Hubs, provide buprenorphine for the treatment of opioid use disorder and other health-related services in addition to their syringe services. While the COVID-19 pandemic posed widespread challenges to the delivery of health services nationwide, the effect of the pandemic on SSPs uniquely impacts PWID. This study examines the impact of COVID-19 on service delivery of Drug User Health Hubs and stand-alone SSPs in New York State.Between July 2020 and September 2020, we performed eleven semi-structured virtual interviews with staff from three Health Hub SSPs and three stand-alone SSPs. The interviews explored the effect of the COVID-19 pandemic on SSPs and their clients as well as the changes implemented in response. Interviews were recorded and transcribed. We performed content analysis to identify emerging themes from the data.Due to the COVID-19 pandemic, some SSPs temporarily shut down while others limited their hours of operation. SSPs modified their service delivery to maintain syringe services and naloxone distribution over other services such as STI and HCV testing. They virtualized components of their services, including telemedicine for the provision of buprenorphine. While SSPs found virtualization to be important for maintaining their services, it negatively impacted the intimate nature of client interactions. Participants also described the impact of the pandemic on the well-being of PWID, including isolation, worsened mental health challenges, and increased drug overdoses.In response to the COVID-19 pandemic, SSPs demonstrated innovation, adaptability, and togetherness. Despite the challenges posed by the pandemic, SSPs continued to be key players in maintaining access to sterile supplies, buprenorphine, and other services for PWID. In addition to adapting to COVID-19 restrictions, they also responded to the dynamic needs of their clients. Sustainable funding and recognition of the critical role of SSPs in supporting PWID can help to improve outcomes for PWID. Syringe Service Programs (SSPs) play a crucial role in delivering critical services to people who inject drugs (PWID). While diverse in their structures and delivery models, SSPs are community-based programs grounded in harm reduction principles and community advocacy. In addition to syringe services, SSPs typically offer additional services for PWID including opioid overdose education, naloxone distribution, HIV and hepatitis C (HCV) testing, and linkage to medical care , 2. TherThe COVID-19 pandemic has had a significant impact on health delivery nationwide. New York was an early epicenter of the COVID-19 pandemic. In March of 2020, New York State declared a state of emergency due to the rapidly increasing incidence of COVID-19, followed by an executive order mandating the closure of all non-essential businesses and offices . With 20In New York State, some SSPs were funded to implement additional programming targeted toward reducing opioid overdose fatalities. These SSPs, called Drug User Health Hubs , provide typical harm reduction services, and also provide on-site buprenorphine for MOUD. Few SSPs offer on-site buprenorphine in the United States , therefoGiven the critical role that SSPs play in their communities, COVID-mediated changes in service delivery at SSPs had the capacity to worsen access to care and health outcomes for PWID, but also to mitigate the harm being caused by the pandemic. As a part of an ongoing evaluation of the Drug User Health Hub program, this study aims to understand how the COVID-19 pandemic affected service delivery at Health Hubs and other SSPs in New York State in 2020.The methods of this study are reported according to the Consolidated Criteria for Reporting Qualitative Research (COREQ) checklist . The resThis qualitative study is embedded in a larger evaluation study of the Health Hubs program. In that study, Health Hubs implementation is being examined and outcomes are being compared between Health Hubs and “stand-alone” SSPs. Both Health Hubs and stand-alone SSPs are located in New York State and provide essential syringe services and other harm reduction services. Health Hubs provide additional services including buprenorphine treatment.Participants included key management staff from 3 Health Hubs and 3 stand-alone SSPs in New York State. All of the programs participating in the study are part of larger multi-site programs with one site from each program participating in the study, except for program 3, which had two separate sites participating Table . One to We conducted eleven semi-structured interviews of staff from Health Hubs and stand-alone SSPs. Interviews were conducted over WebEx video-conference software between July and September 2020 and ranged from 80 to 110 min in length. Interviews were recorded and transcribed. Each interview consisted of two interviewers and one respondent. Interview guides examined multiple domains related to Health Hub and syringe services program implementation. Analyses in this manuscript focus on responses about the COVID-19 pandemic and (1) staffing and capacity of programs (2) service offerings and changes, (3) strategies and adaptations to maintain service delivery, (4) well-being of program clients. Participants were not compensated for the interviews.COVID-19, Telemedicine, Buprenorphine Access, HIV/HCV testing, Outreach, and other themes from prior studies. Additional codes were added inductively as they emerged from the data. New codes that emerged from this data included: isolation, drug supply, overdose, staff mental health, remote work, PPE and Social Distancing, and others. Researchers discussed themes that emerged across categories and converged related codes into themes, then refined them through continued discussion.Interviews were coded using content analysis after data collection was completed . Two uniThe results encompass findings from both Health Hub SSPs and stand-alone SSPs unless specified.Three major domains emerged from the data, each containing 3–5 separate themes: (1) operational changes resulting from the pandemic, (2) changes to the individual services delivered, and (3) the effect of the pandemic on the well-being of SSP clients.Because we had kind of a halt in reimbursement from New York State, we did have to furlough several staff… We just weren't getting money in enough to be able to continue to pay people. So we went a month. We furloughed people starting July 4, and July 6 that faucet turned and things kind of flowed back into the agency… But that month, that 30 days, was tough. It was figuring out what we needed to do and really just maintaining the programs as best we could with the staff. (B)During the COVID-19 pandemic in 2020, some SSPs temporarily closed while others reduced their hours of operation as directed by state guidelines. However, one program that had been operating under a limited schedule emphasized the desire to continue to perform essential tasks: “Even if the governor would’ve not let us come in…we were starting to get busier so we were actually gonna start reviewing and seeing if we can just go back to our normal schedule. (A)” Due to the pandemic’s effect on funding, one program described furloughing a number of its staff during the pandemic and the significant impact this had on their ability to maintain services:Designation as an ‘Essential Service’ became an important lifeline for SSPs, allowing programs to keep staff onboard and continue to service their target population.During the early pandemic, SSPs rapidly made operational changes to their programs in an effort to keep clients and staff safe and comply with government guidelines. They described periods of uncertainty, during which they were unsure of which types of operational changes would need to take place and for how long these changes would last: “You know it's been tough on staff, because there's so many changes just because no one knows. You know the distance guidelines comes out every day and we have to change things up, but they've [the staff] been so adaptable and you know almost like kind of brought us together more. (F)”.This period was also characterized by confusion about how to fulfill both minor and major tasks given the rapidly evolving environment. For one program, common tasks like placing referrals became more complicated with the new work environment: “I know like our department of human services and stuff, it was like, the door was locked and the way people had to access it were in ways that just weren't realistic. Oh, you can scan this paperwork. And you're like, who has a scanner? I don't know. Maybe my kid has a scanner or something. I don't necessarily think I have a scanner. (C)” Another program described their attempts to cope with the changing environment: “You know, the way we're operating right now, it's literally 1 week at a time of how we're doing things, how things are changing, what the agency has decided is a priority versus what the agency has decided to no longer be a priority. (F)”.When we shut down, it was literally from one day to the next. We were in the office one day. The next day, nobody goes to the office… That was hard for me to swallow because typically, if we're going to close for the holidays… we give a well-advanced notice to our participants. We make sure they have enough supplies. We make sure that, you know, we link them to any services that they may need or they think they may need while we're closed. We weren't able to do that. We weren't able to give our participants any notices. (B)SSPs were unable to prepare their clients for changes in access due to rapidly changing restrictions. Whereas prior closures would have been communicated to clients and to the community beforehand, the uncertainty from the COVID-19 pandemic made it difficult for programs to appropriately alert their clients of shutdowns or closures.:In response to the COVID-19 pandemic, programs implemented social distancing, symptom screening, and personal protective equipment (PPE) policies. However, SSPs found it to be “a huge battle trying to get PPE (B)” during the early pandemic for both staff and clients. For some programs, this was a significant barrier to maintaining full operations or resumption of services. SSPs overcame this barrier through support from the community and other partners. Several programs reported receiving masks, other PPE, or hand sanitizers as donations from businesses in the community or local agencies. One program describes having insufficient access to hand sanitizer but received enough donations of PPE to distribute these supplies to clients: “We unfortunately do not have access to hand sanitizer to give them. Because these are hot commodities these days. But we've been able to get donations from a lotta local agencies and we provide reusable masks to all of our clients who need them. (A)”.In order to adhere to social distancing guidelines during the pandemic, SSPs also made changes to their physical spaces. Such changes included providing services outdoors where possible, performing transactions through windows, reorganizing office spaces, and closing down spaces where clients typically gather such as lobbies and lounges.These changes affected the intimate nature of their interactions with clients typical of SSPs. Staff described the physical environment after COVID changes as less personal and more clinical and transactional, contradicting the normally casual and welcoming environment that characterizes SSPs: “It's a lot less homey and a lot more clinical than we would like, but we understand right now, that's just how it has to be, that we don't want to have a lot of things out that we have to sanitize and we have to keep things moving, that we can't have benches out for people to hang out on and have the TV on and stuff. (C)”.All the Health Hubs included in this study provided buprenorphine in addition to their services as SSPs. During the pandemic, Health Hubs were able to continue providing buprenorphine though rapid implementation of telemedicine. Programs utilized phone calls and video conferencing software to provide buprenorphine: “Our nurse practitioners in the support staff that help with the low-threshold buprenorphine stuff from a hub program standpoint, were really I think excited to be able to do appointments by telephone, and like video calling type of things at first March, April in the early part of the pandemic. (D)”.The SSPs generally found these telemedicine programs to be successful: “I mean, it was really great during, like, the peak of our crisis… Because it offered the opportunity for our provider to still connect with our patients, and it didn't require patients to come in, it included the opportunity to engage or do inductions with new patients, and it was really seamless and easy. (E)” Some Health Hubs provided phones on-site to ensure that patients could engage in telemedicine regardless of personal phone access. Program staff described telehealth as a platform that they would like to continue after the end of the pandemic.We’ve only had the low-threshold buprenorphine stuff going for a few years here, but it seems like part of what makes that program work is that the rapport and the trust of the connection between that staff and the people that are taking part in the program. And it just was cool to still be able to prescribe the medication and make some connection with them, but telehealth doesn’t capture the interaction as well as in-person one does, so that’s been a struggle. (D)While SSP staff found telemedicine to be seamless on their end, they felt that provider-patient interactions were not as strong as they had been in-person.But for a while we weren't doing the rapid testing… It was more like we slipped more into doing the syringes, Narcan. So, that kind of affected it just because we were trying to make sure that we were socially distant, for their sake and for our sakes. And we were also trying to be mindful about how long we would spend with a patient as well. So, we didn't want to sit down and do like an intervention that was going to take a half-hour or something. So, that was a piece. We really pulled into some of the very, very core services for a while. (C)The pandemic required programs to rapidly adjust their service delivery given the new COVID prevention policies and the reduced capacities of many SSPs. SSPs halted their HIV and HCV testing, while developing innovative strategies to ensure that buprenorphine, syringe services, and naloxone distribution continued. One explanation for the de-prioritization of HIV testing and other rapid testing was that these services were too difficult to perform within the limitations of COVID-19 social distancing policies. Additionally, HIV and STI testing were not perceived to be as urgent as their ‘core services’ which include syringe services and naloxone distribution. For one SSP, they considered how counseling patients after a positive rapid test would be difficult given the constraints of COVID.Pretty much we were doing all services remotely. Even with HIV testing, we were actually mailing out the home HIV test kits so that people who felt they were at risk could still test themselves. We would do a pretest screening where we would talk about, "What are you concerned about? What are some of the reasons? Do you have concerns and that's why you're asking for one?" (B).While most centers halted HIV/STI testing, one program implemented a delivery system to address the challenges of infectious disease testing during the pandemic.Due to the pandemic, some SSPs pulled back their mobile vans and closed down storefronts. In order to maintain syringe distribution, they developed alternative systems such as collaboration with local pharmacies, delivery systems, and special arrangements. One center developed a new text message system to facilitate syringe delivery to their clients. While syringe deliveries were a novel COVID innovation for some programs, SSPs considered continuing the system given its efficiency and wider reach: “More specifically in terms of syringe exchanges, we are leaning toward, ‘Does it make sense to keep the mobile units when we built this sort of really efficient system of doing deliveries, and then folks may be on the peer delivery syringe model’—which allows us, really, to reach more people. (E)”.In order to make transactions safer for clients and staff, one program described pre-packaging their supplies to minimize COVID exposure: “We've pre-packaged more things than we used to. I'm not quite sure if we're going to hold on to that or not, but we thought that because of COVID, that the faster we could do the [syringe] exchange the better. (C)” This SSP also packaged other harm reduction supplies and PPE, such as cookers, cotton, and gloves, in order to streamline their interactions with clients.During the pandemic, SSPs were providing more syringes to clients than before the pandemic. They attributed this to an increased demand in syringe services stemming from the anticipation of future closures or reduced availability of syringe services. Programs also believed there to be more secondary exchange of sterile supplies occurring during the pandemic, with some clients not presenting to SSPs due to barriers of the pandemic. SSPs preemptively increased their supply of syringes and other harm reduction supplies  given their own uncertainty of what operational changes could lie ahead: “We started loading clients up with 300 syringes at a time—especially early-on when we anticipated that we could close entirely. And we weren't going to have access to anything. So we gave out a few Narcan kits, those types of things, extra Fentanyl test strips. (E)”.A lot of our clients didn't know. They had no idea what was going on. Because if you don't have access to social media, if you're not kind of running in a circle where people are talking about this, how would you know? And it was really upsetting to know how many people weren't informed. So while we don't provide COVID-specific services, we have been, since that time, providing information to our clients about COVID and about these hygiene practices that can help folks. (A)As the needs of PWID evolved during the pandemic, SSPs adapted to meet them. One way that SSPs helped to meet emerging needs was by becoming a source of COVID-related information for their clients. Programs believed that their clients tended to be more vulnerable, having less access to digital information-sharing platforms such as social media and television news. Therefore, some clients first learned of the pandemic via their interactions with SSP staff. Programs soon took on the role of providing COVID information, including harm reduction related information, as well as dispelling misinformation about the pandemic.Additionally, as COVID worsened pre-existing barriers for their target population such as food and shelter, SSPs helped to meet these needs by providing grocery vouchers, shelter referrals, hygiene kits and PPE. One center described providing gift cards in addition to grocery vouchers: “And then because of COVID, we've been able to give folks our food vouchers, those gift cards… We're able to give people that. And our clients are really thankful for that. Because food stamps don't cover hygiene products, right?… Every client gets one per month… And how thankful they've been. Because they've never had that service on the van before (A).”So very quickly we were able to set up Zoom meetings, Zoom support groups that people could come to, even one-on-one. So to be able to really continue with the service delivery was something that was really important not only to the administration here, but also to our staff. They didn't want to leave their clients isolated and alone 'cause they knew that things could get much worse if that was the case. They really wanted to make sure that those services continued in whatever way we could. (B)In addition to providing buprenorphine via telemedicine, SSPs made efforts to virtualize other aspects of their service delivery as well. Programs provided virtual Narcan trainings, virtual harm reduction counseling, and held other virtual groups. Virtualization allowed SSPs to maintain their outreach programs, community education, and social check-ins for both staff and clients.SSPs found virtual platforms to be an effective way of delivering services, with many SSPs intending to maintain a virtual option for their clients.After a while, our patients started to ask about when they could come in. They wanted to see our provider… I've heard that trend…particularly around, like, recovery groups and peer recovery, like, everybody's zoomed out. Like, you know, there's only so many, like, Zoom meetings that you can go to; people miss, like, that face-to-face connectivity and – and we've started to see that. (E)Barriers for some patients included poor access to Wi-Fi or smart devices, and technology illiteracy: “We are doing our opioid overdose prevention community training via Zoom. Our nutrition health education program, a lot of those clients are older, and so they were having trouble with logging onto Zoom and that type of thing (B).” Additionally, while virtual platforms were critical for maintaining service delivery for SSPs, they could not provide the level of intimacy and connection that in-person interactions provided. One program worried that with telehealth and other virtual models, they were not maintaining “enough of a connection with the population. (D)” Another SSP described how ‘zoom fatigue’ impacted their care delivery:And I'm watching the repercussions of us closing due to COVID on TV. And, you know, that was very difficult for me to watch. And, I mean, I can imagine it was even more difficult for the participants… For some people, their only outlet for them – their only human connection for them is to come down to the exchange... Some people will come down, and they'll spend their half-hour, hour – in some cases, two hours – just wanting to talk; just wanting to connect with another human being. And since we built that trust and that relationship with most of our participants, you know, they know that they always have that...to closing down and then pretty much taking that away from them really impacted them. It really impacted them. (B).While changes such as virtualization and closure of waiting rooms and gathering spaces were necessitated by the COVID pandemic, these changes meant less human connection and less time spent with clients. The population serviced by SSPs is particularly sensitive to the removal of safe spaces, given the stigma they experience within the larger society. For many clients, the closure of SSPs meant fewer safe spaces for PWID and more social isolation. SSPs felt that the closing of their physical spaces negatively impacted the mental well-being of their clients:During the COVID pandemic, social isolation, anxiety, and loss of social assistance negatively impacted the mental health of SSP clients. Programs felt that their client population was particularly affected by the social isolation that many people experienced during the pandemic. One staff member recounted how during the pandemic, “many individuals from recovered communities or substance use community became isolated. (E)” Another program described how this social isolation was compounded by the loss that PWID experienced during the pandemic: “And, you know, it made us a little sad. It did. It made me personally sad because when I saw the—I saw what was missing, and I saw that loneliness and that…and I saw, you know—and we heard—a lot of reports of their friends, their sisters, their mothers, their fathers overdosing and dying during that period. You know? (A)”.SSPs described the stress and anxiety that their clients experienced during the pandemic. This stemmed from worsened social conditions and loss of social assistance, such as the closing of food pantries and difficulty accessing housing referrals: “When everything started closing down I think we started seeing—I mean, I think it was emotionally hurting our staff to see this, where they started closing food pantries, soup kitchens. And it was like everybody's like, ‘Well, COVID is happening so I'll close,’ but not really noticing how much that would impact so many of our clients, our community (A)”.Programs worried about the increased overdoses in their communities during the COVID-19 pandemic. The rise in overdoses came at a time of limited access to clean syringes and supplies and worsened social conditions. Programs learned of these overdoses through anecdote from their clients, publicly shared information, and data-sharing collaborations with local stakeholders. These collaborations include taskforces for overdose prevention, police departments, emergency departments, county health departments, housing programs, and other community stakeholders.And there were situations where like I’ll remember one in late May… Three individuals died in a house, and what was obtained at the scene, you know, was a mixture of cocaine and fentanyl. And that matched some of these anecdotes that we had heard that people whose primary drug of choice was cocaine were falling out. Falling out in the way that one would from fentanyl. And of course those are people that didn’t tend to have like lots of Narcan on hand, didn’t tend to be people who had fentanyl test strips. (D)The pandemic may have shifted the drug supply such that clients were accessing different drugs from different and unfamiliar suppliers. One proposed reason for increased overdoses in the community was fentanyl in the stimulant drug supply:A lot of people have said of course the isolation – a big thing that we talk about is: never use alone. But when you're in a situation, you have to use alone. You're using alone. What happens then? … There've been so many talks about what it is. There're some people that just feel that isolation, that depression, and that increase, that mental health piece, and there's been an increase [in overdoses] because of that. (A)Another proposed reason for more overdoses was an increase in substance use during the pandemic as a result of increased psychological stressors: “We've seen a lot more of that, like, this hopelessness, that I think drives some people's risky behavior. (E)” Finally, increased rates of solitary drug use, as a result of COVID-mediated social isolation, was also identified as a potential factor in increased overdoses in the community:This study investigated the impact of the COVID-19 pandemic on stand-alone SSPs and Drug User Health Hub SSPs during the summer of 2020 in New York State. The response of these SSPs to the COVID-19 pandemic was characterized by innovation, adaptability, and togetherness. SSPs adjusted all aspects of their programming including the spatial organization, the syringe service delivery model, and the treatment model for buprenorphine. They modified their systems to maintain the services they deemed feasible and most important, while minimizing COVID exposure to their clients and staff. They also took on new roles and provided additional services, such as providing COVID information and PPE, as the needs of their clients changed. Despite the emotional toll that the COVID-19 pandemic had on staff members, and structural challenges they experienced with funding and staffing, these SSPs demonstrated resilience as most recovered and reopened services to maintain service delivery.Throughout the pandemic, SSPs maintained a sense of togetherness, a value that has been principal to the harm reduction community since prior to the COVID-19 pandemic. SSPs, which tend to operate on a small and more local scale, worked with other community stakeholders to share information regarding how COVID was impacting their community. They also leaned on their community for donations of PPE and other resources. Likewise, their clients looked to SSPs for COVID-related information and distribution of PPE, in addition to their SSP services. Importantly, they continued to prioritize engagement with their clients, via actions such as scheduling virtual check-ins and calls with clients.While Drug User Health Hub SSPs offer a more comprehensive set of prevention and clinical services compared to the typical SSP, their primary services remain rooted in syringe and naloxone distribution. Despite the medical aspect of Health Hub service capabilities, both Health Hub SSPs and stand-alone SSPs prioritized syringe services and naloxone over services such as HIV and STI testing that could not be easily offered via telehealth during COVID-19. These findings are in line with other qualitative findings from SSPs in the United States , 15, 20.SSPs were automatically designated as an “Essential Service’ in the state of New York , allowinThe Health Hubs that provided buprenorphine were able to implement telemedicine, which has been noted elsewhere as a potential tool for improving access to buprenorphine initiation during the COVID-19 pandemic . NationaA unique finding of this study was how virtualization affected interactions between SSPs and their clients. SSPs commented that virtualization eroded the intimate nature of interactions between SSP staff and their clients during the pandemic. Given the negative health experiences of PWID with healthcare providers , 34, rapRecent data from the Centers for Disease Control and Prevention (CDC) indicate a devastating increase in drug overdose deaths during the April 2020 to April 2021 period compared to the corresponding prior 12-month period . FindingThis study has several limitations. One limitation is that the findings are based on a selected sample of SSPs in a state that was severely affected by COVID-19 early in the pandemic. In particular, our sample includes Drug User Health Hub SSPs which have augmented funding to provide additional services. This is advantageous because these programs tended to have a broader spectrum of activity, including providing buprenorphine, which enriches the existing literature. However, some findings may not represent those of other SSPs. Additionally, this study does not include the direct perspectives of PWID, as client interviews were not included in the larger evaluation study that this project is embedded within. Another limitation is the cross-sectional nature of data collection. As the pandemic progressed and we learned more about COVID-19, SSPs likely continued to evolve. Our findings apply to the earliest months of the pandemic, and as policy responses adapted to changes in COVID incidence and severity, a number of changes to SSP operations that we observed may have reverted to their previous practice. However, this early data is helpful for informing a suitable emergency preparedness approach for SSPs and PWID in future.This study adds to the literature describing the impact of COVID-19 and related restrictions on SSPs, while uniquely identifying themes that are relevant to SSPs providing an expanded array of services, including buprenorphine. During the height of the pandemic in New York State, SSPs were key players in maintaining access to sterile injection supplies and helped to maintain access to MOUD. Disruptions in their services have the potential to significantly worsen outcomes for PWID. With the persistence of the COVID-19 pandemic for 3 years, providing sustainable funding for SSPs and recognition of SSPs as critical and ‘essential’ community partners in ending the opioid epidemic can improve outcomes for PWID.


Drawing on a theoretical expression previously derived for general semiconductor substrates, we examine the surface-enhancement of the Raman signal (SERS) when the substrate is chosen to be monolayer graphene. The underlying theory involves vibronic coupling, originally proposed by Herzberg and Teller. Vibronic coupling of the allowed molecular transitions with the charge-transfer transitions between the molecule and the substrate has been shown to be responsible for the SERS enhancement in semiconductor substrates. We then examine such an expression for the Raman enhancement in monolayer graphene, which is dependent on the square of the derivative of the density of states of the graphene. On integration, we find that the discontinuity of the density-of-states function leads to a singularity in the SERS intensity. Knowledge of the location of this resonance allows us to maximize the Raman intensity by careful alignment of the doping level of the graphene substrate with the charge-transfer transition. These remarkable enhancements were sufficiently sensitive to enable detection of a single molecule [It has been observed that when a molecule is oriented close to the surface of a metallic nanoparticle such as Ag and Au, the intensity of the Raman spectrum  is often enhanced by many orders of magnitude . This armolecule . These imolecule . Such ch3 , and onechanism .In this work, we will apply the theory of SERS to the adoption of graphene substrates. Graphene has many special properties, which encourage widespread use for many applications. Numerous attempts have been made to take advantage of these properties ,13,14,15α) could be written:A term involves Franck–Condon sums, and the B, C terms represent the inclusion of Herzberg–Teller coupling. Since then, this formalism has been extended to surface-enhanced Raman spectroscopy [m) and charge-transfer (CT) optical transitions are coupled by a Herzberg–Teller coupling constant (m-CTh). Whenever the CT transitions involved are from a level in the molecule to a band in the semiconductor (in this case the B-term), we may replace the sum over all states with an integral over the semiconductor levels such that:More than 50 years ago, Albrecht  derived troscopy , in whicIn this formulation:mμ, CTμ, and m-CTh represent the electronic transition moment of the molecule (mμ), the charge-transfer transition moment (CTμ), and the Herzberg–Teller coupling constant (m-CTh), respectively. Q is the displacement of any chosen molecular normal mode between the ground state vibrational levels , and CTγ is the band-width of the charge-transfer transition [ρ is the density of semiconductor levels. Integrating by parts  function. For convenience, H may be chosen symmetrically such that H(x) = +1 for x > 0, and −1 for x < 0.The density-of-states function for graphene in the vicinity of the graphene Dirac point ,19 Figu is:(4)ρ(δ (We use the fact that the derivative of the Heaviside function is simply the Dirac It is common for the Dirac point  to be chCT) band. Evaluating the integral (6), we obtain:We may call this the charge transfer , upon tmω (the molecular resonance) is represented by an arrow connecting an occupied level of the ground state (I) to an excited state (K) transition in the molecule. The Herzberg–Teller effect involves vibronic coupling between this  molecular transition and one of the two possible charge-transfer transitions CTω. Transitions either from the ground state of the molecule to one of the empty levels of graphene (B-term) or from the highest filled level of graphene to an unfilled excited level of the molecule (C-term) are represented by CTω. Only the former is shown in CTω). A similar result is found for the analogous derivation for the C term, which we will not repeat.This is illustrated in n-) doping level of the graphene monolayer should therefore be set at −0.11 eV. This illustrates the value of obtaining good excitation profiles of molecules of interest on graphene as a function of doping level.As an example, let us take the molecule copper phthalocyanine (CuPc) on a monolayer of graphene. This system is illustrated in derivative becomes large. Near a singularity in this function, we predict a very large increase. Such a singularity occurs due to a discontinuity in the density-of-states function itself. In monolayer graphene there is such a discontinuity near the Dirac point. In F = 0. Such considerations point us in the direction of predicting the conditions needed to optimize the SERS intensity. We can often obtain information concerning the density-of-states function or its derivative by measuring the appropriate excitation profiles.We have now illustrated the value of knowing the density-of-states function of an organic semiconductor. The SERS intensity depends crucially on the derivative of the density of states as a function of energy, and consequently, wherever this 1g) displayed a maximum at 475 nm (2.61 eV), while the non-totally symmetric modes (b2g) peaked at 605 nm (2.05 eV). Ling et al. [There are several examinations of density-of-states functions using the molecule CuPc . One study  utilizedg et al. ,24 have g et al. .


As a result, our experiments and ab initio calculations show that cytochrome c retains itsgas-phase folded structure when it collides onto freestanding single-layergraphene at low energies (∼20 meV/atom). The molecule-on-trampoline dynamics, expected to be operative on many freestanding atomic membranes,enable reliable means to transfer gas-phase macromolecular structuresonto freestanding surfaces for their single-molecule imaging, complementingmany bioanalytical techniques.Molecule–surfacecollisions are known to initiate dynamicsthat lead to products inaccessible by thermal chemistry. These collisiondynamics, however, have mostly been examined on bulk surfaces, leavingvast opportunities unexplored for molecular collisions on nanostructures,especially on those that exhibit mechanical properties radically differentfrom those of their bulk counterparts. Probing energy-dependent dynamicson nanostructures, particularly for large molecules, has been challengingdue to their fast time scales and high structural complexity. Here,by examining the dynamics of a protein impinging on a freestanding,single-atom-thick membrane, we discover  Efficient molecule-to-surfaceenergy transfer in the landingof proteins on freestanding graphene preserves their gas-phase foldingstate on the surface, enabling them to be imaged one at a time. Molecular collisionis one of the simplest ways for a moleculeto obtain enough energy to initiate chemical reactions or conformationalswitches. Examining how energy flows in a molecule during its collisionevent is critical to understand—and eventually control—theoutcome of any molecular collisions.7 bottom-up material fabrication,10 mechanochemistry,12 astrochemistry,8 and macromolecular structure characterization.17 Intricate details of molecule–surface collisions have beenrevealed by molecule–surface scattering experiments in vacuo(13 These studies highlight a unique feature ofmolecule–surface collision which promptly (sub-picoseconds)converts molecular translational energy toward the surface (T) to molecular vibrational energy associated with soft,flexible modes of the molecule (Vmol).Such a prompt energy transfer has been shown to lead to collisionoutcomes that are thermally inaccessible, such as conformational changes18 , mechanochemicalreactions,11 and molecular fragmentation16 (large Vmol transferred), thereby offeringa means to manipulate molecular structures.Molecule–surfacecollisions are especially important dueto the ubiquity of molecule–surface interactions in many areasof chemistry such as heterogeneous catalysis,T → Vmol energy transfer in molecule–surface collision,which would preserve the nuclear and electronic state of gas-phasemolecules when they are deposited on a surface in vacuo. Success in such undertaking will enable gas-phase molecular speciesto be preserved and immobilized on surfaces and structurally characterizedone molecule at a time by single-molecule microscopy methods, suchas electron microscopy21 or scanning probe microscopy techniques.22 These new capabilities will unlock new frontiersin both single-molecule microscopy and native mass spectroscopy, asit enables single-molecule visualization of any molecular speciesrelevant to chemistry and biology that can be isolated from the solutionphase by native electrospray. Such a combination has been shown formacromolecules by successful soft deposition and direct observationof folded proteins on a surface, ranging from small proteins (∼12kDa) to large multiunit protein complexes (∼800 kDa).25An important frontierin molecule–surface collision dynamicsis the quest to minimize T) away from the molecular internal coordinates in molecule–surfacecollision. One ideal destination for the energy is the surface, sinceit possesses a large number of soft vibrational/phonon modes (Vsurf), well suited to absorb the translationalenergy of the incident molecule. Collision dynamics dominated by T → Vsurf energy transferwould minimize the energy transferred to the internal coordinatesof the molecule and preserve the gas-phase molecular structure onsurface that can be subsequently characterized by many surface-basedmicroscopy techniques.22 Given that the translational energy (T) would flowto the softest mode between the collision partners,27 be that mode residing in the molecule or the surface, replacing T → Vmol by T → Vsurf requires the surfaceto possess softer vibrational modes than the incident molecule. Thisrequirement has been fulfilled in previous studies by noble-gas29 or organic adlayers32 on bulk surfaces, which cushion the impact of incidentmolecules on surfaces.34Realizingthe full potential of this vision calls for strategiesto divert the flow of molecular translational energy  proteins, which preserves the gas-phase folding state of cyt con the surface. Ions of cyt c were generated by nanoelectrospray36 (nESI) and soft-landed on graphene in vacuo byan electrospray ion beam deposition (ESIBD) technique,37 whereupon the adsorbed cyt c structure was imaged one molecule ata time by low-energy electron holography21 (LEEH). We corroborate our experimental findings by simulating thecollision dynamics of the cyt c on graphene using ab initio molecular dynamics (AIMD) implemented in density functional theory(DFT). Our simulation shows the dominance of T → Vsurf dynamics in the landing of molecules onthe freestanding atomic membrane, where Vsurf is the soft acoustic vibrations of graphene. The efficient proteinto graphene energy transfer preserves the gas-phase folding stateof the protein on the surface, as observed in the experiment. The T → Vsurf dynamics ona freestanding atomic membrane, here termed molecule-on-trampoline dynamics, are expected to be operative in the encounter of rigidmolecules with many freestanding 2D materials,38 such as graphene oxide, hexagonal boron nitride, metalchalcogenides (e.g. MoS2), etc. We focus our present workon graphene due to its widespread use across scientific disciplinesthat span from fundamental physics39 tostructural biology.40 Our work shows thepotential of the tandem combination of nESI + ESIBD + LEEH on grapheneto reveal, at the single-molecule level, folded structures of molecularspecies generated from the native mass spectroscopy techniques.Here we point out that freestanding atomic membranes, suchas single-layergraphene (SLG), possess a soft “trampoline” mode thatfulfills the requirement for 7+) were collided normal to a freestanding graphene held at room temperature.The proteins were collided at a selected energy of 35 eV collisionenergy (i.e. 5 eV/charge), previously shown to preserve the chemicalstructures of incident molecules on surfaces.41 The proteins adsorbed on graphene were subsequently imaged as singlemolecules using LEEH to reveal their structures, as inferred fromtheir observed sizes and shapes.2 wasfound to agree with the size of folded cyt c measured in the gas phaseby ion-mobility experiments42 (∼14nm2). Given the low energy involved in the landing event,13 the folding state of the adsorbed cyt c is expectedto be similar to its gas-phase folded structure, consistent with theprevious protein landing studies on graphene.21The cyt c protein soft-landed on graphene was observedby LEEHas a folded protein 1b. The o7+ protein ion ontoa freestanding graphene, whereby the protein possesses a 35 eV translationalenergy toward the graphene. We approximate the gas-phase structureof cyt c7+ ion by relaxing the crystal structure of cytc (PDB ID 1HRC) in the gas phase with a net charge of +7. Our calculation givesa gas-phase cyt c structure that has a near-identical three-dimensionalstructure to its crystal structure, with the most significant changesbeing localized at the protein–vacuum interface. These structuralchanges are caused by the formation of salt bridges and hydrogen bondsamong the side chains of the amino acids at the protein–vacuuminterface, thereby confirming the “side chain collapse”in the literature46 at the ab initio level  that agrees well with its measured experimental value42 (∼14 nm2). The slight differencebetween theory and experimental cross sections may be attributed tothe finite temperature effects, such as cyt c structural dynamicsat ∼300 K, that have yet to be included in present DFT calculations.We corroborate our findings by investigating the structuralchangesin the protein when it lands from the gas-phase onto the surface,using AIMD calculations at the level of DFT. We model the landingevent by colliding a gas-phase cyt cio level 2a, inset1HRC) with the most significantchanges located at the omega loops of the protein   2a. Our fab initio calculations on the entire proteinshed light into the electronic structure of cyt c on graphene, revealingits density of states and its binding mechanism to the surface. –12 perincident electron was observed; see + + 2e) and cause molecular dissociations,52 the apparentimmunity of proteins on graphene toward electron-induced dissociationsindicates an efficient hole removal from the protein. This efficienthole transfer mechanism is understood to originate from the largeelectronic transition probability between the protein and graphene,enabled by the strong electronic state overlap between them—acommon feature for molecules adsorbed on conductive surfaces.53 For molecules adsorbed on metal surfaces,55 the lifetime of transient charges trapped in the molecules was measuredto be below 5 fs—a time scale that is too short for any molecularbonds to significantly stretch to cause any chemical reactions, whichtypically requires tens or hundreds of femtoseconds.56 This insight highlights the importance of fast electronicrelaxation in suppressing electron-induced reactive events in adsorbedmolecules.Our Figure S1), which shows the nonoverlapbetween unoccupied cyt c states and the water electronic states betweenthe Fermi level to ∼3 eV above the Fermi level . The nonoverlap implies that electrons can be trapped onthese “unprotected” states to cause molecular dissociations,since these trapped charges can only be removed by slow nuclear dynamics(e.g. a Grothuss-like mechanism57) as opposedto fast electronic dynamics. Our comparison thereby highlights theimportance of protein contact to a conductive medium (e.g. graphene)in providing fast electronic de-excitation pathways for the protein.We contrast the cyt c-graphene pDOS to that for hydratedcyt cS1, which2 geometry. Our calculations estimate the cyt c–graphene bindingenergy to be ∼33 eV, originating primarily from electrostaticinteractions (77%) and secondarily from van der Waals interactions(23%). The dominant electrostatic cyt c–graphene interactionis understood to arise from the net positive cyt c (+3.2e) accumulatinga pool of electrons on the underlying graphene (−3.2e) thatleads to a charge–image charge interaction between cyt c andgraphene  interactions, as revealed by our calculation thatshows that every C atom on the graphene retains its C-spgraphene 2c.The pFigure S3a), similar to the previouslyreported “proteinquake” collective oscillation in aprotein.59 This oscillation subsequently is followedby a slight compression (∼10%) and decompression of the entireprotein prior to its stable adsorption on graphene .We now detail the mechanism that connects the initial, gas-phaseprotein structure to the final, adsorbed protein structure. Figures S3a and 4a) and reactivelanding regimes . In the low-energy regime, the gained vibrational energyis insufficient to cause major conformational changes, as shown bythe similar protein folding between the final adsorbed structure andthe crystal structure  technique16 that uses a high-energy collision of macromolecules on surfacesto induce their fragmentations for macromolecular structure characterization.The protein compression evidences the conversion of its moleculartranslational energy toward its molecular vibrational energy. Specifically,the most flexible, collective vibrational modes of the protein areexcited upon landing, whose magnitude dictates the extent of structuralchange in the protein upon its landing on surface. We verify thisclaim by comparing AIMD calculations of cyt c at soft landing . T) is convertedlargely to the surface vibrational energy (Vsurf) (77%) and, to a lesser extent, to the molecular vibrationalenergy (Vmol) (19%). These results arein stark contrast to that for molecular landing on bulk surfaces,18 whereby T is converted primarily to Vmol (34%), and secondarily to Vsurf (23%). The different energy transfer dynamics on hard, bulk surfaces and soft, freestanding grapheneecho the previously reported experiments32 and calculations33 of peptides scatteringon hard, fluorinated self-assembled monolayers (SAMs)and soft, hydrocarbon SAMs. We additionally notethat these dynamics also minimize the T →Rmol energy transfer , which suggests that the observed molecular orientationon the surface would be largely similar to the orientation of thegas-phase molecule prior to its landing. Protein rotations only becomesignificant in the collision dynamics at very low collision energy,such as at 3.5 eV , becausethe slowly moving protein has ample time to experience the attractiveforces from the surfaces that reorients the protein throughout itssurface collision .An energy analysis of protein landing on graphene reveals the dominanceof  feature S5. FigurT → Vsurf in a protein–graphenecollision evidencesa coupling between incident protein translation and graphene vibration.Specifically, our calculations show the collision exciting the out-of-plane,soft “trampoline” vibrational mode in graphene, whosefundamental is measured to be in megahertz62 due to the low mass and the freestanding state of graphene. Theprotein–graphene collision generates a soliton-like, travelingtransverse wavepacket in the graphene (63 or an elastic deformation wave64), understood to be the superposition of various out-of-planemodes of freestanding graphene. At short time scales (approximatelypicoseconds) covered by our AIMD calculations, our result shows thatthe soliton travels as fast as 3–4 nm/ps, in agreement withpreviously computed values.65 At long timescales (approximately nanoseconds to approximately milliseconds),we expect the soliton to gradually disperse into various out-of-planemodes of the graphene,66 as its kineticenergy equipartitions to all degrees of freedom in the graphene. Thesoliton dynamics highlight the fast protein-to-surface energy dissipationchannel for the protein translational energy, which enables the preservationof protein folded states when they land on freestanding surfaces.These molecule-on-trampoline dynamics are expectedto be general in the collision of rigid molecules with many freestanding2D materials, which opens up new research opportunities at the intersectionof reaction dynamics, macromolecular chemistry, nanoelectromechanical(NEMS) resonators,67 and 2D materials research.One interesting avenue is to examine the scaling behavior of thesedynamics across different projectile sizes, starting from a smallmolecule (e.g. amino acid) to a large macromolecular complex (e.g.membrane proteins in a micelle), and to examine whether their surfaceencounters could be discerned by transient electrical transport measurements.68The dominance of graphene 4b  and +8  cyt c ions and subsequently deposited on a freestandingsingle-layer graphene (SLG) held at room temperature under ultrahighvacuum (P < 10–10 mbar). Theprotein–graphene collision energy was controlled by applyinga selected voltage to decelerate the incident protein ion. After thedeposition, the graphene sample was transferred in vacuo to a low-energy electron holography (LEEH) instrument, operatedat room temperature under ultrahigh vacuum (P <10–10 mbar). Low-energy electrons between 50 and150 eV were used in LEEH imaging with a dose estimated at ∼10nA per 50 nm2. Illuminating a protein for ∼1 s wassufficient to record a high-quality hologram, which was subsequentlyreconstructed using the previously described method21 to reveal the real-space image of the adsorbed protein.Cytochrome c (cyt c) was dissolved in a 200 mMammonium acetate solution and desalted twice (Bio-Rad BioSpin P6 column)to give a cyt c spray solution (1.5 mg/mL). The solution was loadedto a metal-coated nanoelectrospray glass emitter and sprayed at 1.0–1.5kV to a 80 °C capillary inlet to prevent denaturation of theprotein. No unexpected or unusually high safety hazards were encountered.Using an electrospray ion beam deposition (ESIBD) setup, describedin detail elsewhere,11 electrons had been scattered on the protein.Given that no inelastic event was observed, our data thereby set an upper limit for any inelasticevent probability to be ∼3 × 10–12 eventper electron.The cyt c protein shown in Ab initio calculations at thelevel of density functional theory (DFT) as implemented in the codeOpenMX71 (version 3.9.2) was used to model the experiment.The code employed norm-conserving pseudopotentials, pseudoatomic localizedbasis functions, periodic boundary conditions, and van der Waals correctionusing Grimme’s DFT-D3 method.72 Ourcalculations employed a cutoff energy of 300 Ry, an electronic temperatureof 300 K, and a supercell with dimensions of 51.33 Å (X axis), 49.39 Å (Y axis), and 50.00Å (Z axis). All calculations sampled only thegamma point of the k-mesh and used an electronicconvergence criterion of 4 × 10–8 hartree,employing the divide-conquer with localized natural orbitals (DC-LNO)method.73 The graphene was modeled by 960C atoms, and the cyt c was modeled with a total of 1744 atoms as C558H878O155N148FeS4. The relaxation calculations were performed until the forces inall atoms were below 4 × 10–4 hartree/bohr.Charge analyses of the relaxed structures were performed using a Baderanalysis.74 Visualization of the molecularstructures was performed using the ChimeraX software.76N), volume (V), and energy (E). The MD calculations were performed with a 0.5 fs timestep, which gave a negligible total energy drift of as low as ∼2meV/ps per atom. The initial state of the MD placed a gas-phase relaxedcyt c ∼7 Å above the graphene. All atoms were subsequentlyinitialized with random velocities sampled from the Boltzmann distributionat room temperature (298 K). The thermalization of these velocitiesis evident in the first few femtoseconds at the start of the trajectory,shown in the Evib,mol and Evib,surf of Figure S5a. On top of thesevelocities, all atoms in cyt c receive a constant velocity towardthe graphene that corresponded to the translational energy of theprotein toward the graphene of either 35 or 350 eV. In the MD calculations,all of the C atoms of the graphene were free to move, causing theact of restoring force in the graphene “trampoline”onto the protein to be unaccounted for in the MD calculations. However,these forces, estimated to be ∼0.3–0.6 nN from ref  and therebywere not expected to be the major factor in the landing dynamics ofthe protein on graphene.Born–Oppenheimer MD calculations were performed asa microcanonical ensemble that preserved the total number of atoms(from ref , were mi