Water is the dominantliquid on Earth. Despite this, the main focusof supramolecular chemistry research has been on binding and assemblyevents in organic solvents. This arose because it is more straightforwardto synthesize organic-media-soluble hosts and because of the relativesimplicity of organic solvents compared to water. Nature, however,relies on water as a solvent, and spurred by this fact, supramolecularchemists have recently been making forays into the aqueous domainto understand water-mediated non-covalent interactions. These studiescan benefit from the substantial understanding of the hydrophobiceffect and electrostatic interactions developed by physical chemists.Nearly 20 years ago, the Gibb group first synthesized a class of water-solublehost molecules, the deep-cavity cavitands, that possess non-polarpockets that readily bind non-polar moieties in aqueous solution andare capable of assembling into a wide range of complexes with distinctstoichiometries. As such, these amphipathic host species are idealplatforms for studying the role of negatively curved features on guestcomplexation and the structural requirements for guided assembly processesdriven by the hydrophobic effect. Here we review the collaborativeexperimental and computational investigations between Gibb and Ashbaughover the past 10 years exploring questions including the following:How does water wet/solvate the non-polar surfaces of non-polar pockets?How does this wetting control the binding of non-polar guests? Howdoes wetting affect the binding of anionic species? How does the natureand size of a guest size impact the assembly of cavitand hosts intomultimeric capsular complexes? What are the conformational motifsof guests packed within the confines of capsular complexes? How mightthe electrostatic environment engendered by hosts impact the propertiesand reactivity of internalized guests? Solvation of the pocket is ofconsiderable interest because of the many open questions surroundingthe hydration of tight “nooks and crannies” on the surfaceof proteins and other biomacromolecules, and correspondingly how hydrationcan drive function.A slightly adapted synthesis led to the so-calledocta-acid 2, 1, the fie formed1, but ho11 Thisprediction is the direct result of the statistical mechanically exact“wall theorem” that dictates the density of the solventin contact with a hard wall is determined by the ratio of the bulkpressure divided by the ideal gas law prediction or the solvent pressureusing the actual solvent density, amounting to contact densities over1000 times smaller than the bulk solvent for liquids at coexistence.Huang and Chandler subsequently predicted that turning on ubiquitousvan der Waals attractions can collapse the vapor layer in contactwith the wall.12 This predicted dewettingphenomenon is thought to play a major role in driving the interactionsbetween hydrophobic surfaces in water, giving rise to interfacialforces between dewetted surfaces that drive them together.16 Simulations performed by Berne and co-workers have demonstrateddewetting as playing a role in the final steps of protein folding17 and in the formation of quarternary structurein protein assemblies,18 while simulationsby Hummer and co-workers have found that dewetting of protein surfacesand internalized cavities can play a role in their function.21 Ashbaugh demonstrated the dewetting of hard spheres anticipatedby Stillinger and showed its connections with the bulk interfacialtension of the liquid/vapor interface.26 Moreover, Ashbaugh has shown from simulations thatattractive interactions do indeed suppress surface dewetting.27 Sarupria and Garde have subsequently found that, while van der Waalsattractions enable rewetting of non-polar surfaces, solvent densityfluctuations at those surfaces closely resemble those in the vaporhighlighting water’s apprehension with hydrating extended hydrophobicdomains.28In 1973, Stillinger predicted that waterwill pull away from anddewet the surface of a nonattractive, hard sphere solute in aqueoussolution as it grows in size, leaving only the whisper of a vapor-likelayer in contact with the solute.31 in agreement with Sarupria and Garde’s results regardingdensity fluctuations.28 In Setny’ssimulations, the approach of a ligand to the pocket induced the freeenergy landscape of water to become bimodal, vacillating between awet “liquid-like” and dry “vapor-like”state. Upon ligand binding, water was displaced from the pocket andthe dewetted state became dominant. This dewetting-mediated binding,or triggered dissociative mechanism of guest exchange, was found tobe driven by a favorable association enthalpy resulting from watersgaining attractive interaction upon release from the pocket. The entropyof association, on the other hand, opposed ligand binding. This dewettingdriven interaction in water is distinct from that which typicallycomes to mind when discussing processes driven by the hydrophobiceffect, i.e., that central to such phenomena is an entropic releaseof unfavorably structured water in the hydration shell of non-polarmoieties in solution. Such processes are often termed as being drivenby the classic hydrophobic effect. In contrast, host–guestbinding processes in water are typically enthalpically driven associationsand are frequently described as being driven by the nonclassical hydrophobiceffect. This phenomenon has been experimentally observed for guestsbinding to proteins and host–guest species in water, supportingthese simulation observations.34 Nau and co-workers have founda strong correlation between the number of hydrogen bonds water forfeitswhen it enters a non-polar confinement, as determined from simulationand experimental guest binding constants,36 although this hypothesis does not account for the bimodal equilibriumbetween wet and dry states observed by Setny. Nevertheless, takentogether, these observations suggest complexations with non-polarpockets are distinct from the classic picture of hydrophobic association.37A majority of simulationstudies of hydrophobic hydration havefocused on convex, positively curved surfaces akin to the shape ofsmall solutes, rather than on concave, negatively curved surfacessuch as those found in protein binding sites and the hosts discussedhere. An important exception to this are the simulations by Setnyand co-workers of an idealized, hemispherical non-polar pocket inwater. They found that water freely fluctuates between all possiblehydration states from zero to 10 waters in the pocket,38 this collaboration has expanded to examine awide range of issues, including the following: wetting/dewetting ofcavitand pockets in water; assembly of cavitands and alkanes intoa wide range of complexes that depend on the functionalization ofthe host portals and length of the encapsulated guests; packing ofguests within host complexes; anion binding to host pockets at theroot of salting-in Hoffmeister effects; and the encapsulated guestreaction catalysis driven by the electrostatic environment engenderedby the host. Below, we detail the major experimental observationsmade regarding cavitand host–guest interactions in water bythe Gibb group and the molecular insights gained from complementarycomputational work performed by the Ashbaugh group. We conclude withan outlook toward possible future directions for this mutually enrichingcollaboration.Finding mutual research interests in hydrophobicity-drivencomplexationand assembly phenomena in aqueous solution, Ashbaugh and Gibb establisheda computational and experimental collaboration on the formation andproperties of supramolecular complexes of deep-cavity cavitands inwater. The range of cavitand hosts available e.g., 1 and the39 of host 2 in aqueous solution foundthat approximately four waters on average reside within the cavitandcompletely filling the non-polar pocket. The probability distributionof observing n waters in the pocket fluctuates from0 to 8 waters, with transitions between occupation states occurringon ps time scales states compared to either host 2 or host 3. Analogously, exo-octa acid  bind exothermically to thehydrophobic pockets of 2 and 4, despitethe two hosts being at least nominally, if not literally, octa-anionic.43A natural question following from these observationsis, what isthe impact of host pocket drying on cavitand–guest association?Concomitant isothermal titration calorimetry (ITC) experiments examinedthe thermodynamics of binding of a series of sodium alkanoates, from 45 When sandwiched between two flat, non-polar surfaces, water willspontaneously evacuate the slit as a result of capillary forces oncethe separation between surfaces falls below a critical distance.15 The driving force for drying can be exacerbated for negatively curvedpits and depressions, as in the case of hosts such as cavitands, cyclodextrins,and cucurbiturils.47 Examination of the water occupation probabilitiesof the pockets of 2 and 4 from simulationfinds that the distribution is bimodal . Second, typical methods for guestbinding analysis, e.g., NMR spectroscopy, are not routinely set upfor high-pressure work. Even if that is the case, modern instrumentationis normally only rated to approximately 14 bar of overpressure.To investigate the thermodynamic nature of the observedcavitanddewetting transition, we expanded our simulation study to examinethe hydration of a wider range of host rim functionalizations overpressures ranging from −500 to 2500 bar.2 and 4, we studied in silico cavitands with one, two, and three methyl groupsplaced at the endo-position. At atmospheric pressure,we found that the probability of observing the dry state (n = 0) grows systematically with the number of endo-methyl groups, while the wet-state (n ≈4) probability decreases with increasing endo-methylportal functionalization. In all hosts, we consistently observed aprobability minimum at n = 1 between the dry andwet states. Wetting/dewetting of all of the cavitand pockets couldsubsequently be tuned by varying the hydrostatic pressure, with drystates favored with decreasing pressure (or tension in the case ofnegative pressure) and wet states favored with increasing pressure.Over the entire range of pressures examined, the dry and wet stateswere separated by a probability minimum at n = 1.Based on these observations, we concluded that the hydration of thecavitands corresponded to a two-state-like transition between a dryand wet state. We subsequently developed a capillary evaporation modelthat quantitatively described the filling of cavitand pockets withwater as a function of pressure. Within the context of this model,the role of an endo-methyl group is to shift theeffective pressure within the host pocket to lower pressures in proportionto their increasing number, thereby stabilizing the dry state. Thiswork highlighted the potential importance of considering pressureeffects in water-mediated host–guest association.In addition to hosts 2 and steroid guests.3 Proton couplingsmeasured via nuclear Overhauser effect 1H NMR (NOESY NMR)indicate that the rims of two cavitands face one another, forminga capsular assembly with the guest buried within the inner space ofthe capsule. If the steroid guest is too long or too wide, for example,cholesterol, the capsular assemblies are unable to fully form. Asa result of the two “hemispheres” being unable to clampdown on one another, the complexes have reduced thermodynamic andkinetic stability. A highly preorganized guest is not necessary forcapsule formation. For example, simple alkenes form extended or J-and U-shaped “hairpin” motifs within the capsule dependingon the length of the guest.49 Indeed, even propaneand n-butane can trigger capsule formation. Here,with these small guests, two alkanes are encapsulated to form 2:2host–guest complexes. As might be anticipated, guest size iskey to the thermodynamic and kinetic stability of the complexes; somuch so that capsule formation can be used to sequester a strongerbinding alkane from the gas phase to affect the separation of hydrocarbongases.50Cavitand hosts readily scavenge amphiphilicand anionic speciesto form 1:1 complexes. In the resulting complexes, the portal regionof the host–guest complex remains relatively hydrophilic becauseof the charged headgroup of the amphiphile or charged anionic guest.However, in cases where the guest is devoid of any polar moiety, theportal region of the pocket remains relatively non-polar and the complexcan assemble into a capsule. The simplest example of such an assemblyis the 2:1 host–guest complexes formed between 2 and 4 with n-alkanes showeddistinct assembly patterns with increasing guest chain length  which measuresthe diffusion coefficient (and therefore hydrodynamic volume via theStokes–Einstein equation) of the assembly by the applicationof gradient radio-frequency pulse. Methane (C1), for instance,readily binds to host 4 to form a 1:1 complex, whileit does not evidently associate with 2. This observationis consistent with host 4 forming stronger complexeswith hydrophobes as a result of the comparative ease water is displacedfrom its pocket.40 The next homologue,ethane (C2), forms 1:1 complexes with both hosts.51 Host 2 forms dimeric complexeswith further increases in the guest size beginning with C3, as indicated by the drop in the diffusion coefficient of the complexby a factor of 1.25 3–C8 form 2:2 complexes with 2. However, betweenC8 and C9, the assembly with 2 switchesfrom 2:2 to 2:1 complexes. This 2:1 stoichiometry persists from C9 to C26, the longest guest examined experimentally.52 Similar to host 2, 4 forms 2:2 complexes for alkanes from C3 to C6.51 The assembly state, however, revertsback to monomeric 1:1 complexes for C7 and C8 before switching to dimeric 2:1 complexes for guests from C9 to C14. Even larger tetrameric and hexameric complexescan be formed by host 4 with even longer alkane guests,as discussed further below.A systematic experimentalstudy of the association of hosts n length 3a.51 ExpA) toform 1:1, 2:1, and 2:2 complexes areKXY:, is hampered by the vanishingly low solubilitiesof n-alkanes in aqueous solution. This precludeshost–guest titration experiments used to determine affinitiesby monitoring the amount of host–guest complex as a functionof host–guest ratio. Relatedly, even in the cases where host–guestaffinities can be measured from the host–guest ratio, the vanishinglysmall solubility of the guest again precludes experimental evaluation;only the host–guest complex is typically observed at equilibrium.The alkane guest solubilities and the association free energies betweendistinct host and guest species following the proposed reaction network,however, can be evaluated from molecular simulations to gain insightinto the non-monotonic assembly patterns of host 4 comparedto 2.53 Specifically, pairwiseassociation free energies for forming each complex, ΔGXY:, can be evaluated following the proposed reaction scheme from thepotentials of mean force (PMFs) between hosts and guests in wateralong specified reaction trajectories using molecular simulations.A PMF corresponds to the free energy of a system with two of its components,hosts and guests, at a specified position and orientation relativeto them being infinitely far away from one another. The pairwise associationfree energies were evaluated from the minima in the PMF free energiesfor bringing hosts, guests, and host–guest complexes togetheraligned along the rotational axes of symmetry of the cavitands.The distribution of hostsand guests between distinct complexescan be rationalized via a reaction network model. The set of reactionsdescribing host assembly with alkane guests  than that of host 2, attributable to host 4 being drier than host 2.40 The 2:1 association free energies.58 These distinct assemblypathways can ultimately be attributed to the steric interactions betweenthe endo-methyl groups of the cavitand subunits whichdecrease with the larger assemblies as the bite angle between anytwo adjacent cavitands increases.Experimentally, the stoichiometries of the assembliesformed betweenhosts 2, two-dimensional 1H–1H correlation NMR spectroscopy (COSYNMR) was performed in the solution state. It was previously determinedby Rebek and co-workers that the change in chemical shift  of the guest proton signals between the free and bound statescan indicate how deep a proton of a guest lies in a conical cavitysuch as velcrands and deep-cavity cavitands.60 The difference and signal anisotropy in the bound state is broughtabout by the structure of the cavitand itself; walls composed of πsystems physically and magnetically shield the guest from the externalmagnetic field causing a spread of signals.63 Sections ofthe guest that are deeper in the cavity have larger negative Δδshifts than those guest protons that are closer to the equator ofthe capsule, and thus the portal of the cavitand. These experimentsreveal that for C9–C16 the guest assumesa conformation such that the terminal methyl protons are deep in thepocket of the opposing cavitands, with the intervening methylenesprogressively compressed within the equatorial region of the capsuleand the guest in part adopting a motif that ranges from fully extendedin C9–C11 where all gauche interactions are minimized to a form akin to a compressed α-helixin C12–C16. In contrast, because of thelimited compressibility of the guests within the capsule, guests C17–C23 are forced to adopt a hairpin (orJ/U-shaped) motif in the capsule: one end of the molecule residesin the depths of one pocket, while the other end lies in the vicinityof the equatorial region, and the end of the other pocket containsthe turn. From C24 to C26, the guest motif againswitches—both methyl groups again reside deep in the interiorpoles of the capsule, while the intervening methylenes coil to adopta disk-shaped conformation to give the guest an overall spinning-top-likeform. In such cases, the central methylene groups of the guest can“hemorrhage” out of the equator of the capsule and beexposed to free solution. These different ways that guests can packwithin the dimeric capsule can be taken advantage of to control thechemical properties of bound guests. For example, it has been shownthat the bound guest motif can greatly influence the acidity and rateof cyclization of internalized guests (see below).64To experimentally probe the conformational motifsof guests packedwithin dimeric capsules of host 65 was conducted to determine if the predictedsuccessionof bound guest conformational motifs conformed to those inferred byNMR spectroscopy and to interpret the role of guest packing withinthe interiors of host capsules on determining the resultant guestconformations observed. Given the restricted environment within whichguests are confined, simple molecular simulations at a fixed temperaturemay not be able to sample the ensemble of potentially available conformers.To attempt to overcome this difficulty, alkanes from C9 to C25 were initially simulated within a host 2 capsule in a vacuum using replica exchange molecular dynamics tosample conformations over a broad temperature range to hopefully overcomefree energy barriers between the initial and equilibrium guest conformations.In these solventless simulations, the capsules were held closed usingharmonic restraints. Following this equilibration phase, the host–guestcomplexes were placed in aqueous solution, the harmonic restraintsremoved, and long simulations performed to allow the conformationallyequilibrated guests to relax and explore conformations in the unrestrained,hydrated conformations.A complementary molecular simulation investigation25 so thatthe turn in the spinning-top motif pries the two cavitands apart andpartially herniates from the capsule. This observation highlightsthe importance of relieving the harmonic restraints from our vacuumequilibration simulations to properly capture the guest conformation.These conformational motifs systematically follow one another withincreasing alkane length, as can be seen in the succession of thedominant conformations observed from C9 to C25. While the agreement with experiment is excellent, we find thatthe simulations do predict the transition from the hairpin to spinning-topmotifs for shorter chains (between C19 and C20) than experiment (between C23 and C24). Nevertheless,shifts in the 1H-NMR chemical shifts of the alkane protonsupon transfer from solution to the host environment predicted by gaugeinvariant atomic orbital66 calculationsperformed using Gaussian67 on the dominantsimulation conformations reported in 65 These simulations subsequentlysupport the experimentally inferred progression of guest conformersencapsulated within host 2 dimers.As inferred from NMR spectroscopy, oursimulations found that thedominant guest conformations progressed from an extended, to helical,to hairpin, to spinning-top motif with increasing chain length 5a. These9 to C25, ΔGnn+1→. For the shortest chains considered, from C9 toC12, the free energy increment was found to be negativeand constant, with ΔGnn+1→ ≈ −7kJ mol–1. This is consistent with those guests bothfavoring transfer into the capsular environment and adopting the sameextended conformational motif. Between C12 and C16, the extensional free energy increment consistently increased by+2 kJ mol–1 with increasing chain length, such thatfor C16 and C17 the free energy ultimately becomespositive with ΔG16→17 = 2.5kJ mol–1, comparable to the thermal energy RT. The increase in the free energy over this chain lengthregime results from the guests adopting an increasing fraction of gauche dihedral conformations in the helical motif thatare energetically more unfavorable than the trans conformation that dominates the extended motif. As suggested bythe 1:1 complexation free energies reported in 2 pocketis comparable to a C6 chain. It therefore makes sense thatthe transition to the helical motif initiates with C12 atwhich point the guest spans the length of the dimeric capsule. Theincrease in the extensional free energy is then analogous to the compressionof a spring as the host capsule attempts to accommodate guests ofincreasing length. Once the extensional free energy becomes positive,the guest adopts the hairpin motif to minimize the gauche strain along the entire length of the chain and localize the unfavorable gauche conformations at the hairpin turn. Resultantly, theextensional free energy between C17 and C20 isapproximately constant and positive, equal to the ΔG16→17 increment. Eventually, beginning with C20, the guest fills the inner space of the capsule and wedgesthe two cavitands apart, herniating the guest  to dimeric, capsular complexes (C3–C14), this trend does not completely apply to 4. The DOSY spectra of guests C1, C2, C7, and C8 all indicate the formation of monomeric1:1 complexes. Guests C9–C14, on theother hand, were determined to complex to dimers of 4, whereby the hydrophobic surface of the guest is completely encapsulated.An expansion of the complex is seen as the guest size increases toC12–C14: the guest becomes large enoughthat the void space is not only completely filled, but also the twohalves of the capsule are pushed farther apart in order to accommodatethe increase in guest volume. Guest C5 presented an anomalysuch that it formed a 2:2 complex. This phenomenon can be explainedby the fact that dimerization of 4 leads to a less stablecapsule than that formed by 2. As a result, the capsuleis more particular about how guests bind. Thus, small (C1 and C2) and medium sized guests (C7 and C8) form 1:1 complexes because their respective 2:2 and 2:1host–guest complexes would contain too much empty inner space.Contrastingly, the C5 guest, and C9 and biggerguests, can nicely fill the capsule containing two guests or one guest,respectively. Intermediary guest lengths, i.e., C3, C4, and C6, however, are caught between these twopossibilities. As a result, each guest exists as a dynamic equilibriumof 1:1 and 2:2 host–guest complexes.The narrower portal of host n-alkanes, TEMOA 4 wasfound to form 4:2 and 6:3 host–guest complexes.58 Thus, using 1H and diffusion NMRexperiments, it was shown that, whereas C14 formed thedimeric complex, C17 formed the tetrameric 4:2 speciesand C24 the hexameric 6:3 host–guest complex. Ananalysis of the inner space of these larger complexes noted that bothwere more capacious than simply double or triple the volume of thedimeric capsule. The inner volume of the tetrameric capsule is equalto four cavitand volumes, plus a central pseudotetrahedral volumeenclosed by the cavitands, whereas the hexameric capsule has a totalvolume of six cavitand volumes plus a core, pseudocubic defined bythe hexahedral arrangement of the cavitands (see below). This workdid not definitely identify the driving forces for the tetramericand hexameric assemblies, but as OA 2 does not form tetramericand hexameric assemblies, it is evident that the four endo-methyls of TEMOA 4 are key. As noted above, the biteangles between adjacent cavitands in the dimer, tetramer, and hexamerare approximately 0, 70, and 90°, respectively, and models suggestthat angles greater than approximately 30° reduce the stericclashes between rim methyl groups in opposing cavitands that are prevalentin the dimer interface. As a result, whereas OA 2 hasa predisposition to form a dimeric capsule, TEMOA 4 ismore predisposed to form higher assemblies when guests are suitablylarge enough to fill the inner space.With bigger 4 was amenable todirect simulations of the interactions betweenguest and host subunits, the number of species coming together toform tetramers (4 hosts and 2 guests) and hexamers (6 hosts and 3guests) complicates reduction of multimer formation into simple pairwiseprocesses  and intersects that into the dimer between C14 and C15, after which transfer into the tetrameris favored. Eventually, the transfer free energy into the tetramerreaches a plateau, after which the transfer free energy into the hexamercrosses that of the tetramer between C18 and C19 to become the favored complex morphology.The guest transfer freeenergies determined from simulation reportedin While the guest–transferfree energies show clear preferencesfor complexes with increasing numbers of hosts with increasing chainlength, the chain lengths for which the transfer free energies betweensuccessive complexes size cross one another are shorter than experimentallyobserved ,we showed that moving the carboxylate groups at the rim of 2 closer to the portal of the weakly solvated cavity, i.e., exo-octa acid 5, changes the binding propertiesof the host.71 In the case of 2, unexpectedly, negatively charged guests bound slightly more stronglythan positively charged ones. This was reversed in the case of exo-octa acid 5. Here, positively charged guestsbound more strongly than negatively charged ones. However, this differencewas only 70% of what might be expected from Coulombic (ion–ion)considerations. Moreover, for the four negatively and four positivelycharged guests examined, binding to exo-OA 5 was always weaker than that to OA 2. We alsoused molecular dynamics simulations to show that, because of the proximityof the negative charges in exo-OA 5,its pocket had a higher desolvation penalty.41 Thus, both direct ion–ion interactions between host and guestand indirect ion–dipole interactions (between host and water)affect guest affinity. Further molecular dynamics simulations alsopointed to changes in water hydrogen bonding as a complex is formed;hence, we believe that differences in guest affinity between the twohosts may also involve the asymmetry of how groups of opposite chargeare solvated. Further work on these types of systems is required toparse out all of the factors controlling guest affinity.A large fraction of the time and costof drug development involveshit screening, lead optimization, and primary assays. This monetaryand temporal cost would be significantly lowered if it were possibleto predict high-affinity ligands for targets. The statistical assessmentof the modeling of proteins and ligands (SAMPL) challenges are a setof collaborative analysis–computation experiments designedto improve the predictive power of computational drug design.2 can bind charge-diffuse anions.Modeling with the Rick group demonstrated that anions such as I–, PF6–, and ClO4– were bound in partially hydrated states .74 Thus, despite that both the host and the guest are formally anionic,complexation is exothermic. On the other hand, smaller anions suchas Cl– that are more strongly solvated do not bind.Host–anion interactions in the complex cannot compete withthe strong water–anion interactions of the free ion.Evidently, the key to anion binding is a weak andflexible solvationshell. Thus, measurements of complexation thermodynamics using ITCshowed that the binding free energies of these salting-in anions areenthalpically favored but entropically penalized  and ReO4– (Ka4/Ka2 = 7.2). The most likely explanation for this is that the dryer pocketof 4 means that anions do not have to compete with waterto bind. Indeed, calculations of the electrostatic fields exertedby the charges of both hosts found them to be indistinguishable, pointingtoward solvation differences between the two hosts playing a controllingrole.76 However, exceptions to cavitand 4 being a better host seem to present some questions. Forexample, the hydration free energies of ClO4– and ReO4– are very similar,77 yet in contrast to the date for the latter,the former bound more weakly to host 4 than to host 2. Clearly other factors must be in play. We suspect thatanother key factor is the size and symmetry of the ideal solvationshell around an anion. If two anions are similar in size and havesimilar overall solvation free energies, then the difference in hostaffinity may be caused by the ability (or inability) of the host toalso accommodate the three or four waters of solvation that necessarilymust accompany the bound anion.Compared to OA 79 water-sensitive gold-catalyzed reactionscan be performed,80 and proton-mediatedterpene cyclizations can be achieved—all in water84 and within the hydrophobic interior of synthetic supramolecularassemblies. Contributing to this growing field, the binding of cyclableα,ω-difunctionalized alkyl chains into dimeric capsulesof 2 has been explored.85 Thealkyl chain guests were composed of α,ω-thioalkyl bromides,which in free solution form polymer rather than cyclize to form thecorresponding thioether. However, trapped within the inner space ofthe capsules, an individual guest cannot take part in polymerization.Rather, the forced proximity of the nucleophilic thiol and electrophilicmethylene halide (−CH2X) promotes intramolecularcyclization.Synthetic cavities with weakly solvatedpockets have been of particularresearch interest of late, particularly those that exhibit protectiveproperties for bound guests or function as catalysts that have thepotential to mimic enzymes. Among a whole host of possibilities, reactivereagents like white phosphorus can be encapsulated in a supramolecularcage,2 and a positively charged analogue assembled from the dimerizationof so-called positand 6 (14) underwent fast cyclization. In contrast, shorterguests  that bound in an extended motif in whicheach end of the capsule was occupied by one of the termini of theguest underwent a very slow reaction. Reaction rates that differedby 3 orders of magnitude were seen for these two lengths of guests.Interestingly, intermediate reaction rates were observed for verylong guests. These too adopted J-motifs within the capsule, but thelimited remaining free space within the capsule attenuated cyclizationrates considerably. Thus, the capsules demonstrated excellent selectivityfor cyclizing guests of lengths C14–C16.To probe the effect of guest packing and host electrostaticpotentialfield, the Gibb group investigated the cyclization of α,ω-thioalkylbromides of different lengths within a capsule formed by OA sitand 6 1. With r12 guest was over 3 orders of magnitude shorter inthe capsule formed by 6. An Eyring analysis revealedthat both intermediate sized guests and reaction in the capsule formedby 6 were favored by lower enthalpies of cyclization.When rates of cyclization in the positive and negativelychargedcapsules were compared, it was evident that the transition state tocyclization possessed considerable negative charge. Thus, the half-lifeof a CKa of simply long-chain thiol guests within the same two capsules revealedthree factors that controlled the acidity of a thiol guest. In orderof decreasing importance, these were the following: guest motif, hostcharge, and the nature of the host counterion or exogenous salts insolution. Briefly, when the guest adopted a J-motif in which the thiolheadgroup was located at the equatorial region of the capsule, thepKa was lowered by up to five units relativeto guests that adopted extended conformations where the thiol groupwas deeply buried. As there were only small differences in the electrostaticpotential field at these two points of the inner space (see below),partial solvation of the equatorial located thiol was presumed tobe key to making these thiol complexes more acidic. With regard tothe nature of the capsule, pKa valueswere generally between one and three units lower within the host 6 capsule. It is understood that these two factors—motifof guest and nature of capsule—contributed to the spontaneouscyclization of the C14 α,ω-thioalkyl bromide(J-motif) within the positive capsule; a low pKa meant the guest spontaneously deprotonated (and cyclized),whereas, with the other host–guest combinations, the additionof excess base was required to initiate reaction. Finally, it wasfound that the nature of exogenous salts also affected the pKa of bound guests. Salts in which one of theions could exchange with the counterion of the capsule and condenseon its surface raised the pKa of the boundguest by attenuating the electrostatic potential field of the host.A follow-up report examining the p2 and 6 on promoting the cyclizationof the guests  smeared across its surfacearea (δq (= –1e) is the charge on the guest within the capsule, q– (= –16 e) and q+ (= +16 e) are the net charges on the anionicand cationic capsules, respectively, ε (= 80 for water)is the dielectric constant of the solvent, R (= 12Å) is the effective Born diameter of the host capsules (assumedhere to be given by the mean isotropic radii in G+–* = 17.2kJ mol–1, which is in reasonable quantitative agreementwith the pKa shifts of the alkylthiolbetween the anionic and cationic capsule environments and the ∼103-fold increase in the thioalkyl bromides cyclization reactionrate increase that passes through an anionic intermediate. While theagreement between experiment and theory is surprising given the approximationsmade to arrive at Returning to the cyclization of α,ω-thioalkyl bromideguests within the capsule, complementary potential calculations wereperformed to probe the role of electrostatic interactions within capsulesof hosts e guests 8b. Unsur capsule 8c. In thacearea 8c. This88 the forays of supramolecular chemists from organic mediainto aqueous solutions represent a rich field of opportunity for syntheticand physical chemists to collaboratively explore, bringing to beara deep understanding of experimental host–guest interactionsand theoretical insights into the role of the solvent on driving association.While our initial collaboration focused on using simulations to tryto understand prior experimental observations, such as understandingthe conformational motifs of guests within capsules and the non-monotonicassembly patterns of host–guest complexes, more recent workhas seen simulation predictions drive the experimental efforts, aswas the case for our study of the wetting/drying of cavitand pocketsand its impact on host–guest association. As the collaborationhas matured, both experimental and theoretical questions have drivenricher questions regarding host–guest complexation phenomenain aqueous solutions. Ongoing research questions we are exploringinclude the following: What is the impact of polarizability on drivinganion binding to cavitand hosts? What is the extent to which the describedelectrostatic potential field of capsules can affect reactivity ingeneral? How might co-nonsolvency and macromolecular crowding impactcomplex formation for weakly interacting cavitands? What role mightpressure play on moderating association? Answering these and othersuch questions has the potential to expand our molecular-level understandingof different non-covalent interactions in water, point to new technologiessuch as sensors or purifiers that rely on the orchestration of theseforces, as well as shine light on the function of biological systems.As water is the solvent of life, and therefore the greenest of media,the opportunities are boundless.The essence of a successful collaboration is the ability of researchersto come together to address problems from different points of viewto arrive at new insights that could not have been arrived at alone.As recently discussed in a review by Cremer et al.,


The vast majority (88.5%) recognized at least one antibiotic resistance term; however, 53.2% believed that antibiotic resistance is a problem in other nations. The participants in this study reported using antibiotics incorrectly, believing that they were treating sore throats, colds, and flu. The participants were well aware of antibiotic resistance solutions and their consequences on health. Age, education, health literacy, and antibiotic knowledge were found to be substantially (p < 0.05) associated with greater awareness of antibiotic resistance. The findings highlight the need for antimicrobial resistance education campaigns, health literacy, and antibiotic stewardship initiatives.Multi-drug-resistant (MDR) organisms pose a global threat to modern medicine, which has grown as a result of irrational antibiotic use and misuse. This study aimed to assess general public knowledge in Jordan and awareness of antibiotics and antibiotic resistance during the COVID-19 pandemic. A cross-sectional study was carried out utilizing the WHO multicountry public awareness survey. The study population was composed mainly of social media users, and a total of 1213 participants completed the online survey. According to the findings, more than half of the participants were well versed in antibiotic use and resistance. Those with adequate health literacy were found to better understand antibiotics (OR = 1.37,  The emergence of multi-drug-resistant (MDR) organisms has posed a global challenge to modern medicine since the discovery of antibiotics. Antibiotic resistance occurs naturally, but unsustainable antibiotic use and misuse have expedited the process, putting humanity’s well-being in danger ,2,3. An n = 856; 70.6%). Almost one-third of the participants (35.4%) were between the ages of 25 and 34, and the vast majority lived in cities (61.1%). Around half of the participants (54.9%) were educated with a bachelor’s degree, and less than one-third (28.3%) were employed in the medical field. Additional sociodemographic factors are listed in The study included 1213 participants, the majority of whom were females , “2 = most of the time” , “3 = sometimes” , “4 = rarely” , and “5 = never” . The findings of this study indicated that nearly two-thirds (62.6%) of the participants possessed adequate health literacy, while 37.4% had inadequate health literacy. With the exception of education level, health literacy levels were comparable across groups. Consistent with previous research . Th. Thp < 0ormality . Levene’


IgG4-related disease (IgG4-RD) includes a group of immune-mediated diseases histologically characterized by lymphoplasmacytic infiltrate with a prevalence of IgG4-positive plasma cells, storiform fibrosis and obliterative phlebitis. Autoimmune pancreatitis, sialadenitis, dacryoadenitis and retroperitoneal fibrosis are the most frequent manifestations. IgG4-related sialadenitis usually affects submandibular glands and is very rare in children.Here we report the case of IgG4-related sialadenitis in a six-year-old patient previously diagnosed as juvenile recurrent parotitis.A six-year-old patient was referred to our Centre for left parotid swelling of 4 × 3 cm, that was tender, soft in consistency, with overlying red and warm skin. His general condition was good but he was subfebrile; general examination revealed mild enlargement of left cervical lymph nodes. In the last 2 years he had had five episodes of parotitis, diagnosed by another pediatric Center as juvenile recurrent parotitis.On ultrasound examination the left parotid gland appeared enlarged, inhomogeneous, with a colliquative intraparotid lymph node and no evidence of sialolithiasis. Laboratory tests showed an increase of white blood cells and anti-VCA IgM and IgG positivity, with anti-EBNA e anti-EA I negativity.The patient was initially treated with oral antibiotics, but after 10 days the parotid became fluctuating, requiring surgical biopsy and drainage. Postoperative course was regular, with complete remission under oral antibiotic and steroid therapy. Microbiological tests, including cultures for aerobic and anaerobic bacteria, mycobacteria and Bartonella, were negative.Surprisingly, histology showed marked fibrosis and histiocytic and lymphoplasmacellular infiltrate with polyclonal plasma cells mostly expressing IgG4 immunoglobulins. Thus, the diagnosis of IgG4 related chronic sialadenitis in recurrent parotitis and recent EBV infection was made.IgG4-related sialadenitis is very unusual in children. Histology plays a key role in diagnosis, considering that up to 30% of patients have normal serum IgG4 levels, as shown in our case.The lack of previous histological data makes it impossible to attribute our patient’s previous episodes of parotitis to IgG4-RD, though it is a very consistent possibility. IgG4-related disease (IgG4-RD) emerged over the last two decades as an immune-mediated condition that unifies multiple fibro-inflammatory single-organ diseases previously considered as separate entities , 2. A siDiagnosis is based on clinical, serologic and typical histological findings. IgG4-RD histology shows a lymphoplasmacytic infiltrate with a prevalence of IgG4-positive plasma cells, storiform fibrosis and obliterative phlebitis , 4. The The pathogenesis is immune-mediated, with a central role of T-lymphocytes, whereas IgG4 do not seem responsible for the tissue damage , 8.Autoimmune pancreatitis, sialadenitis, dacryoadenitis and retroperitoneal fibrosis are the most frequent manifestations of IgG4-RD. IgG4-related sialadenitis usually involves submandibular glands, whereas parotid glands are rarely affected , 10.The natural history, without treatment, is the evolution towards advanced fibrosis, atrophy and loss of function. In the case of IgG4-related sialadenitis, xerostomia is a common evolution of the disease.Immunosuppressive treatment is the mainstem of therapy. Steroids, usually prednisone, are commonly used as first-line agents, with good response rates. Methotrexate, azathioprine and mycophenolate have been used in relapsed-resistant cases –13. RituIgG4-related sialadenitis usually affects submandibular glands and is very rare in children –17.Here we report the unexpected case of IgG4-related sialadenitis in a 6 years old patient previously diagnosed as juvenile recurrent parotitis.A six-year-old Caucasian patient was referred to our Centre for left parotid swelling.His family history was negative for autoimmune diseases. In the last 2 years, his past history showed five episodes of parotitis that have been investigated by a regional Children’s Hospital. Once immunological and rheumatological pathologies were excluded, a diagnosis of juvenile recurrent parotitis was made. Careful oral hygiene and periodic otorhinolaryngological follow up were recommended.General examination showed good general condition, T 37.5 °C, a parotid swelling of about 4 × 3 cm that was tender, soft in consistency with red and warm overlying skin, and a mild enlargement of left cervical lymph nodes (maximum 2 cm).White blood cells (WBC) were 14,400/fL with 57% neutrophils, hemoglobin and platelet counts were normal. C-reactive protein, procalcitonin, electrolytes, glucose, creatinine, transaminases were normal, as well as amylase and lipase. Serology for Ebstein Barr virus (EBV) tested positive for IgM and IgG anti-VCA , with negative anti-EBNA IgG e anti-EA IgG. Serologies for Cytomegalovirus (CMV), Bartonella, Toxoplasma, Mantoux TST and Quantiferon-TB were negative. Serum IgG, IgA, IgM levels were normal  as well as serum IgG1, IgG2, IgG3, IgG4 , whereas IgE level was high (752 kU/L). The left parotid gland appeared enlarged and inhomogeneous to ultrasound examination, with a colliquative intraparotid lymph node and an associated mild left latero-cervical lymphadenopathy. There was no evidence of sialolithiasis.The patient was first treated with ceftriaxone, then, after consultation with the infectious disease specialist, with cefixime and azithromycin. Despite antibiotic therapy, though, in 10 days the parotid gland became fluctuant, requiring surgical drainage and biopsy , mostly expressing class G immunoglobulins. The IgG4 subclass meanly represented 50–60% of the total IgG, reaching up to 100 plasma cells/high-power field (HPF) in specific areas.  was negative.Thus, the final diagnosis was IgG4-related chronic sclerosing sialadenitis in recurrent parotitis and recent EBV infection.The patient is now under strict follow up, and screening for other IgG4-related clinical manifestations is currently negative. Serum IgG, IgM, IgA are normal, as lymphocyte subpopulations. Antinuclear antibodies (ANA), anti Ro/SSA, anti-La/SSB, anti-double stranded DNA (anti-dsDNA Ab) are negative. FT3, FT4, TSH are normal. Anti-EBNA IgG antibodies are now positive (239 U/mL), as well as anti-VCA IgG (42 U/mL). Anti-VCA IgM are negative.One year after hospitalization, the patient only had two other mild episodes of tender swelling of the left parotid gland with normal blood tests, successfully treated with a short course of amoxicillin and betamethasone, without adverse events. Considering the prompt clinical response, no long-term steroid therapy was proposed so far.The parotid gland, though, persists enlarged (AP diameter 15 mm) with marked inhomogeneity at US examination.The consensus statement  for histAccording to Despande et al., our patient was classified as “histologically highly suggestive” . We did not observe storiform fibrosis nor obliterative phlebitis, rarely described in IgG4-related parotitis .As mentioned before, our patient had had four previous episodes of parotitis, formerly diagnosed as “juvenile recurrent parotitis”. The lack of previous histological data makes it impossible to disprove this diagnosis and attribute those episodes to IgG4-RD instead, though it is a very consistent possibility.Juvenile recurrent parotitis, in fact, is a recurrent non-obstructive and non-suppurative parotid inflammation. The highest incidence is between 3 and 6 years of age, spontaneously disappearing in the second decade of life –21. VariA very confounding feature of our case was the parotid gland appearance. The tender consistency with red and warm skin seemed more consistent with an infectious etiology at first examination, especially when compared to typical aspects of IgG4-related sialadenitis, which is elastic or firm, painless and persistent. In the hypothesis of a reactive infectious form, antibiotics were initially prescribed. Negative bacteriological and cultural examinations do not rule out the possible bacterial superinfection, as they were performed on the bioptical specimen, after 10 days of antibiotic therapy.During the follow-up, the persistent enlargement of the left parotid with marked ecostructural inhomogeneity suggests a chronic process, with episodic reactivations, controlled on demand by corticosteroid therapy.For what concerns laboratory tests, serum IgG4 were normal in our case, as described in a minority (30%) of cases , 25–27, Strehl JD et al  publisheLiterature data show a relationship between EBV infection and increased IgG4 production. Takeuchi et al. observed an increase in EBV-infected cells in patients with IgG4-related lymphadenopathy by in situ hybridization . Nagata In our case, the laboratory demonstrated an acute/recent EBV infection. However, the negativity of the in situ hybridization for EBV leads us to believe that a causal link between EBV infection and the histological picture is unlikely.The lack of previous histological data makes it impossible to attribute our patient’s past episodes of parotitis to IgG4-RD, though it is a very consistent possibility. The present case, instead, fulfills the current histologic diagnostic criteria for IgG4-RD.The histological finding was quite unexpected, as IgG4-related disease is rare in children, but it underlines once more the key role of the pathologist in the differential diagnosis of lymphadenopathies and masses of head and neck area.Our findings are relevant for pediatricians to make a correct diagnosis and to set up an appropriate follow up.EBV virus:S-anti VCA IgM U/mL < 20 negative, 20–40 doubtful, > 40 positive.S-anti VCA IgG U/mL < 20 negative, ≥20 positive.S-anti EBNA IgG U/mL < 5 negative, 5–20 doubtful, ≥20 positive.S-anti EA IgG U/mL < 10 negative, 10–40 doubtful, > 40 positive.Immunoglobulins, 6 years:S-IgG 5.6–1.5 g/L.S-IgA 0.5–2.2 g/L.S-IgM 0.3–1.2 g/L.S-IgG1 400–1000 mg/dL.S-IgG2 80–250 mg/dL.S IgG3 20–96 mg/dL.S-IgG4 3–108 mg/dL.S-IgE < 100 kUI/L.


In the present study, the improvement of mechanical properties of conventional concretes using carbon nanoparticles is investigated. More precisely, carbon nanotubes are added to a pristine concrete matrix, and the mechanical properties of the resulting structure are investigated using the molecular dynamics (MD) method. Some parameters such as the mechanical behavior of the concrete matrix structure, the validation of the computational method, and the mechanical behavior of the concrete matrix structure with carbon nanotube are also examined. Also, physical quantities such as a stress–strain diagram, Poisson's coefficient, Young's modulus, and final strength are calculated and reported for atomic samples under external tension. From a numerical point of view, the quantities of Young's modulus and final strength are converged to 35 GPa and 35.38 MPa after the completion of computer simulations. This indicates the appropriate effect of carbon nanotubes in improving the mechanical behavior of concrete and the efficiency of molecular dynamics method in expressing the mechanical behavior of atomic structures such as concrete, carbon nanotubes and composite structures derived from raw materials is expressed that can be considered in industrial and construction cases. Sometimes to change some of the concrete properties, when mixing materials, the amount of additives is added to it. These additives can also be in nanoscale. The nature of nanotechnology means working at the molecular and atomic levels in the dimensions of 1–100 nm4. Nanotechnology is used to intervene and fabricate the arrangement of devices, materials, and particles for greater efficiency5. Carbon nanotubes are one of the most important and widely used carbon structures. In addition to being very strong, carbon nanotubes also have good flexibility. From an atomic point of view, carbon nanotubes are cylindrical molecules with open or closed ends. In general, carbon nanotubes can be divided into three general categories: zig-zag carbon nanotubes, chiral carbon nanotubes and armchair carbon nanotubes7. Armchair carbon nanotubes share electrical properties similar to metals. Existence armchair carbon nanotubes in concrete increase the flexural and tensile compressive strength. In the construction industry, the presence of carbon nanotubes in concrete increases the strength and prevents the penetration of cracks8. In a computational study, Wu et al.9 simulated the mechanical behavior of a concrete sample. In this research, the molecular dynamics method and LAMMPS software were used for this purpose so that the field of selected forces in this work was selected as Compass, UFF, and Dreiding, and the results of each potential were compared with experimental results. The results of molecular dynamics simulations showed the high accuracy of all three force fields in predicting the mechanical properties of concrete structures. Yu et al.10 investigated the mechanical properties of concrete using the coarse-grained method. In this study, concrete particles were considered as disk-type particles, and the Gay-Bourne force field was used to predict their mechanical properties. The results of the research were in good agreement with the experimental results. Tavakoli et al.11 studied the mechanical properties of different phases of concrete and determined its properties by examining concrete with atomic precision and simulating it with nanometer dimensions. In this study, eight different force fields were used to perform simulation MD instruments, and mechanical factors such as Young's modulus, shear modulus, compressibility, and final strength of atomic structures were calculated and reported. Titscher et al.12 designed high-density concrete using molecular dynamics simulation. In this computational work, they studied the mechanical properties of condensed concrete structure and showed that this secondary structure has promising mechanical properties. Zhou et al.13 simulated concrete with a polymer chain. They reported the samples' mechanical properties by examining the interaction between concrete and simulated polymer chains so that the mechanical and thermodynamic results of this group showed an improvement in mechanical behavior and increased strength of the simulated structure. Hassan et al.14 added single-walled carbon nanotubes to conventional concrete samples. By examining the mechanical factors such as the strength of the nanocomposite, they reported the amount of improvement in the mechanical performance of this structure compared to the concrete matrix. Manzur et al.15 added multilayer carbon nanotubes into the concrete matrix. By adding multi-walled carbon nanotubes into the concrete matrix, the improvement of the mechanical properties of the obtained material was proved. Carriço et al.16 added multi-walled carbon nanotubes to the concrete sample. By adding carbon nanotubes with a weight ratio of 0.05–0.1%, they estimated the chemical stability and mechanical strength of these structures at 21–25%. By adding carbon nanotubes with mass ratios of 0.2%, 0.4%, and 0.6% to the concrete structure, Evangelista et al.17 investigated the change in mechanical properties of these structures. The results of the mechanical experiments show that the maximum improvement in the mechanical properties of the nanocomposition created for 0.4% of carbon nanotubes added. With the help of carbon nanotubes and carbon nanofibers, Danoglidis et al.18 proposed a new method to improve the mechanical properties of concrete samples. In this experimental study, they increased the amount of modulus of nanocomposites by adding carbon nanostructures. In addition to the molecular dynamics method, there are other methods for studying micro- and nano-scale currents21.Concrete is a broad concept that refers to any material or compound that is composed of a cementations adhesive. Concrete can be made from different types of cement as well as sulfur, additives, polymers, fibers, etc. Also, heat, water vapor, vacuum, hydraulic pressures, and various compressors may be used in its construction22. The MD simulations tend to have high strain rates and the mechanical parameters are strain rate dependent23. In this research, parameters such as the temperature of the simulated system, the total energy of the simulated system, the mechanical behavior of the concrete matrix structure, the validation of the computational method, and the concrete matrix structure's mechanical behavior carbon nanotube were studied. Initially, in this study, a matrix of concrete containing the atoms of calcium, hydrogen, oxygen, and silicon is created inside the simulation box. In the next step, carbon nanotubes with different types  are simulated. In the third step, the composition of the concrete matrix with carbon nanotubes is determined with certain ratios and then the final atomic system is equilibrated at initial temperature as initial condition. The simulations of this research are performed in two general steps of equilibration of atomic structures and mechanical testing of pure concrete structure and reinforced concrete with carbon nanotubes. The first part of the simulated structures is done in 1,000,000 time steps and in the second stage the simulation process continues until the complete stress–strain diagram of the structure is obtained. To be more precise, in the calculations which performed in this research, the results reported in each of the simulation steps are sampled once every 10,000 time steps, so that the each time step is considered equal to 1 fs (Δt = 1 fs). An example of a simulated primary concrete structure with present atoms in the concrete structure is shown in Fig. In this paper, the computer simulations and molecular dynamics method are used. To apply the molecular dynamics method in the present study, LAMMPS software is used 27.In molecular dynamics simulation, each atom's acceleration in the system can be determined by having the force applied to each atom. Then, by integrating the equation of motion, the path of motion of the particles, which describes the location, speed, and acceleration of each particle, is determined over time. Thus the evolution of the path of motion over time will be determined. In the next step, using the path of movement, the average values of the properties can be determined. In the molecular dynamics method, all calculations are performed according to Newton's equations, and in the simulation, Newton's second law formulation is used as below equationi is the total force in simulated structures, ri/vi is position/velocity of atoms, and mi represents the atomic mass. Computationally, The velocity-Verlet algorithm is used to integrate Newton's law equation28.In this equation, F29:In MD simulations, force-fields have high importance to describe physical behavior of atomic systems. Here, the Lennard–Jones potential function is used to describe the interactions between concrete particles as well as the interactions between carbon nanotube particles and concrete. The most common relationship for the Lennard–Jones potential function is as followsε is the depth of the well, σ is the distance at which the potential value becomes zero, and r is the distance of the particles from each other. Also, rc is cut-off radius in Eq.  Equilibration process of atomic structures: Firstly, the pristine/reinforced concrete matrix was simulated for 1,000,000 time steps. In this step, Nose–Hoover thermostat was used to equilibrate of atomic system temperature at T0 = 300 K as initial condition. Temperature damping ratio in this step is equal 0.01. For equilibrium process detecting, physical parameters such as temperature and total energy were reported.Step B) Mechanical behavior of atomic structures: Next, the mechanical deforming and pullout process was implemented to pristine/reinforced matrix by using the NVE ensemble for 10,000 time steps. After the tensile and pullout tests, physical parameters such as stress–strain curve, Young’s modulus, ultimate strength, and interaction energy were reported to describe the mechanical behavior of pristine/reinforced concrete matrixes.In the first step of this research, the structure of concrete is simulated, and the thermodynamic equilibrium in this structure is investigated. To investigating the thermodynamic equilibrium in this atomic structure, physical properties such as the temperature of the simulated system and the energy of the whole simulated system are studied. According to the calculation method, the diagrams corresponding to the temperature and energy of the whole structure are shown in Figs. −1 strain rate with Δt=1 fs and with NVE ensemble used in z direction. This atomic deformation process implemented to all regions of atomic sample and all atoms of modeled matrix deformed in each computational steps.In this part of the research, and after ensuring the correctness of the simulations performed in the field of modeling atomic structures using LAMMPS software, we calculate the mechanical properties of the simulated concrete sample using the molecular dynamics method. The basis for calculating the mechanical properties in the simulation is the use of the loading method and deforms order in LAMMPS software, in which the stress-strain diagram is calculated, and mechanical information is extracted by creating tension in the simulated structure. In this method, the structure's initial length is calculated according to the number of atoms present in the simulation. Then, by stretching the structure in the next moments using the structure's instantaneous length in the strain formula, the strain value is calculated. Also, the stress-strain diagram of the simulated structure is calculated. The mechanical traction process created in the simulated atomic structures is shown in Fig. 34. From a numerical point of view, the maximum stress tolerance by different concrete samples is in the range of 20–40 MPa. All calculations and reports made in this section are done in standard conditions. This indicates the efficiency of the molecular dynamics method in simulating the mechanical properties of atomic structures such as a concrete matrix. From a physical and technical point of view, the appropriate results obtained in this study are simulated due to the appropriate selection of interatomic interactions in structures and also the allocation of suitable atomic positions for different atoms in the concrete structure, which shows the exact method of atomic modeling. From a mechanical point of view, the linear region in the stress-strain diagram contains important information such as Young's modulus of the atomic structure is simulated so that by calculating the slope of the stress-strain diagram drawn in the linear region, it is possible to calculate Young's modulus by simulation. The numerical value of Young's modulus calculated for concrete was 30 GPa . In these MD simulations, the periodic condition from the xy plane change to fix one and fixing the concrete structures at the back region of the CNT for 10 Å depth. The nanotube was pull out along the z axis for 10000 time steps, while the interaction energy between two atomic structures computed throughout the pullout procedure as depicted in Fig. The amount of temperature in atomic structures tends to 300 K, which indicates the temperature equilibrium in the simulated atomic structures.The convergence of total energy in a negative value indicates that the potential energy of the atomic structure is greater than its kinetic energy, and as a result, the higher potential energy than the kinetic energy of the concrete structure indicates its physical equilibrium and mechanical stability.Young’s modulus was determined by simulation using a stress–strain diagram. The numerical value of the calculated Young's modulus for concrete was 30 GPa.x and y- directions, it is possible to calculate Poisson's coefficient in the atomic structure of concrete. The numerical value of this quantity was calculated to be 0.15.By creating a deformation in the structure of the concrete sample in the The addition of carbon nanotubes with a zig-zag edge has the greatest effect on the mechanical behavior of concrete samples because carbon atoms in the structure of carbon nanotubes with a zig-zag edge have a stronger adsorption interaction than chiral and armchair samples.In this study, using computer simulations, the mechanical properties of the improved concrete matrix were investigated using the addition of carbon nanotubes. The simulations performed in this study were of the molecular dynamics type, which was performed using LAMMPS software. The results of this research can be expressed as follows:


There was a significant increase of resistance to amoxicillin with clavulanic acid (p = 0.001), gentamicin (p = 0.017) and ceftazidime (p = 0.0005). According to the CART method, we managed to estimate C-reactive protein (CRP), procalcitonin (PCT) and white blood cell (WBC) values, in which antibiotic sensitivity was observed. In children with CRP > 97.91 mg/L, there was a high percentage of sensitive cases to amoxicillin with clavulanic acid (87.5%). Values of WBC above 14.45 K/µL were associated with E. coli more sensitivity to ampicillin. 100% of children with CRP > 0.42 mg/L and PCT ≤ 6.92 ng/mL had confirmed sensitivity to cefuroxime. Concerning sensitivity to gentamicin, the most optimal cut-off point of WBC was >7.80 K/µL, while in the case of nitrofurantoin, it was CRP value > 0.11 mg/L (which was presented in 98.50% of children). These results may guide us with antibiotic therapy and help to inhibit increasing antibiotic resistance.The study was conducted to analyze urinary tract infections (UTI) in children by considering epidemiology and antibiotic resistance patterns of pathogens in accordance with inflammatory parameters. The research included 525 patients who demonstrated 627 episodes of UTI. The increasing resistance of bacteria was observed over the years covered by the study ( Urinary tract infections (UTI) are known as one of the most common bacterial diseases in children (after respiratory tract infections). Furthermore, they are often the cause of infant and toddler hospitalization . Proper Due to conditions present in childhood age, such as short urethra, possibility of contamination with fecal bacteria, higher incidence of congenital defects and continuous development of human organ systems (including the immune system), the child’s organism is more likely to develop UTI than an adult’s. UTI occurs in 2–8% of children. Infections of this system affect 0.1–1% of full–term newborns , while iIn early infancy , the male sex is more predisposed to UTI due to higher incidence of CAKUT , whereas in adolescence, infections are more common in girls ,7. The iEscherichia coli, which is responsible for about 90% of infections [Pseudomonas aeruginosa, Klebsiella pneumoniae and Enterobacter spp. [Pseudomonas aeruginosa, due to its properties, is a common cause of recurrent UTI.The most dominant etiological factor of UTI is fections ,9,10. Prter spp. ,12. PseuIncidence of UTI is more frequent in groups of children with risk factors, including anomalies of urinary tract  and dysfunctional elimination syndrome ,14.The discovery of first antibiotic (penicillin) is one of the biggest achievements of medicine. Over the decades, it has helped to save millions of human lives. However, the common use of antibiotics reduced the effectiveness of this type of treatment. Klein et al.  analyzedEscherichia coli is systematically increasing. The study showed the increase of resistance from 7.2% in the years from 1950–1959 to 63.6% in the years from 2000–2002.It is known that the process of acquiring resistance is a natural example of evolution in response to usage of antibiotics. Unfortunately, irrational antibiotic therapy accelerates this trend. Tadesse et al. , conductLaboratory tests that can be helpful in making a diagnosis are markers of inflammation, e.g., elevated concentration of C-reactive protein–CRP. High CRP values are frequently found in patients with upper urinary tract infection and CRP testing has been shown to be useful in differentiating upper and lower UTI . Raised The main aim of the study was to analyze antibiotic resistance trends over the years. We also assessed inflammatory parameters’ association with patients’ responsiveness to prescribed drugs and if it is possible to plan empiric therapy on the basis of inflammatory markers levels.The retrospective study was conducted in 525 children hospitalized in the Department of Pediatrics and Nephrology  from 2010–2017, in which we observed 627 episodes of UTI. The inclusion criterion for the study group was a positive urine culture with accompanying clinical symptoms . The exclusion criteria were insignificant bacteriuria, leukocyturia with negative urine culture (except cases with administered outpatient antibiotic therapy). From among the performed microbiological tests, a significant growth of bacteria was obtained in 590 cases. Initially, 711 cases of UTI were included in the preliminary analysis. After excluding cases that did not meet the inclusion criteria or were not eligible for the study due to the exclusion criteria, the final analysis contained 627 episodes of UTI (398 in girls and 229 in boys). 318 episodes were febrile UTIs; patients without fever were hospitalized due to other symptoms, such as vomiting or severe abdominal pain. Twenty-nine of excluded cases were asymptomatic bacteriuria. Patients with history of recurrent UTIs and with VUR grade III–V were on chemoprohylaxis (110 girls and 51 boys). Renal scars and features of nephropathy were assessed in 51 cases by performing DMSA (as a feature of nephropathy (most often reflux nephropathy), a hypofunction of kidney determined as the split kidney function <30% shown on DMSA). Participants were aged between 7 days old and almost 18 years old . The anthropometric measurements and laboratory tests were carried out at the time of admission to the hospital. In every patient, blood laboratory tests were performed, which included white blood count (WBC), C-reactive protein and procalcitonin (PCT). Blood count was examined from K-EDTA blood , however CRP and PCT concentrations were measured in serum with a clot activator . Urine samples for urinalysis and urine culture were collected by clean–catch of midstream urine or catheterization, also in infants (the method of clean–catch of midstream urine was used in cases when parents refused to consent catheterization). The use of a urine bag was only permitted for urinalysis. After bacteria growth in the urine culture, the antibiograms were marked in order to assess sensitivity of microbes to commonly used antibiotics .p < 0.05 was used. For the analyzed numerical features, in each of the estimated group, the normality of the distribution was assessed using the Shapiro-Wilk test. Due to the lack of normal distribution the studied groups were compared with the non-parametric Mann-Whitney U test. Additionally, the non-parametric Pearson’s Chi-square test of independence was used to assess the relationship between categorical features. The method of classification and regression trees (CART) was used to establish the optimal cut–off point for inflammatory markers, which allow to classify cases as sensitive or resistant to analyzed antibiotics.The research results were statistically analyzed using the Statistica 13.3 computer program . In the analyzes and tests, the significance level of The study was carried out after agreement of the Bioethics Committee of the Medical University of Bialystok (R-I-002/104/2018).The study included a total of 525 children hospitalized in the Department of Pediatrics and Nephrology  due to UTI in years 2010–2017. Girls constituted 63.1% (331) of children covered by the study, while boys—36.9% (194). Demographic and clinical parameters of participants are shown in p < 0.001). The analysis showed that girls have greater body weight than boys (p < 0.001), but there was no significant difference in BMI values (p = 0.12). Comparisons of concentrations of inflammatory markers showed significantly higher values of WBC in males (p = 0.009). Values of CRP and PCT did not differ significantly (p > 0.05). The diagram in The youngest patient developed UTI in the first week of life, while the oldest patient was 17 years and 11 months old. The median age was 2.08 years old. The age of patients with UTI differ significantly between males and females (p = 0.06).In the study group, 147 patients had a history of recurrent UTIs—girls constituted 69.4% (102) and boys—30.6% (45). The recurrent UTIs were observed in 30.8% of girls and in 23.2% of boys. There was no significant dependence of sex on recurrent UTIs incidence . In boys, a high-grade VUR was observed more often (48.4%) than in girls (24.6%).In Renal scintigraphy (DMSA) was performed in 51 patients to assess kidney function. In 31.4% of cases features of nephropathy were found, while in 19.6%, there were renal scars.The diagram in Escherichia coli (72.7%). Other microbes found in the study were Pseudomonas aeruginosa (5.8%), Proteus mirabilis (5.8%) and Klebsiella pneumonia (3.9%); each of the rest of bacteria represented less than 2% of the total.In Escherichia coli in boys than in girls (64.8% vs. 77.3% in whole examined group), similar to the ESBL strain of this bacteria (1.4% vs. 2.2% in whole examined group). Other microbes accounted for a greater percentage in males than females .The increasing resistance of bacteria was observed in antibiograms of the urine cultures, shown in E. coli (p = 0.0002), K. pneumoniae (p = 0.004) and P.mirabilis (p = 0.006).The diagrams in Escherichia coli, the highest percentage of resistance was found in ampicillin (47.2%) and amoxicillin with clavulanic acid (24.8%). Pseudomonas aeruginosa was characterized by a high percentage of resistance to ticarcillin with clavulanic acid (42.9%). It is necessary to mention that sensitivity to this antibiotic was estimated on the basis of only seven antibiograms. Klebsiella pneumoniae was most resistant to amoxicillin with clavulanic acid (69.2%); however, Proteus mirabilis was most resistant to cotrimoxazole (33.3%).Comparisons of sensitivity of the most dominant bacteria to antibiotics are presented in E. coli were analyzed. Other etiological factors were not assessed due to the insufficient number of cases, which did not allow for obtaining reliable results. The percentage of antibiotic resistance were higher in UTI episodes in children with VUR (p = 0.002). Antibiotic resistance was observed a little more often in cases of recurrent UTI (9.93%) than in non-recurrent UTI (9.04%), but there was no statistical significance (p = 0.37). Additionally, assessment of antibiotic resistance in children on chemoprophylaxis was performed. Resistant E. coli was observed more often in children on chemoprophylaxis (p < 0.001).Considering risk factors of UTI, such as VUR and recurrence of infections, the association between the presence of them and antibiotic resistance was assessed . Only epp = 0.001), gentamicin (p = 0.017) and ceftazidime (p = 0.0005). The only drug where decreasing resistance was observed was nitrofurantoin (p = 0.032).The diagrams in Escherichia coli to commonly used antibiotics. In the analysis, there were found to be significantly lower values of WBC in patients with Escherichia coli resistant to ampicillin (p = 0.04), cefuroxime (p = 0.007) and nitrofurantoin (p = 0.0045) beside sensitive ones. In the case of CRP, higher concentrations were observed in participants with E. coli sensitive to cefuroxime (p = 0.045) and nitrofurantoin (p = 0.02). There was no significant difference in analyzed values of PCT in the case of any antibiotic. It was not possible to evaluate statistical significance of PCT difference for nitrofurantoin because of no PCT test in patients with E. coli resistance to this antibiotic. However, for ceftazidime, too few resistant samples to carry out the analysis were observed.Further tests were carried out to identify differences in values of inflammatory markers between resistant and sensitive Taking into consideration resistance to amoxicillin with clavulanic acid, the CART tree showed differences in CRP and PCT concentrations . In chilE. coli expected to be more sensitive to ampicillin. On the other hand, CRP in the CART was also taken into consideration. In participants with WBC > 14.45 K/µL, patients with CRP in the range of 43.91–123.47 mg/L were classified as patients with higher risk of resistance to ampicillin than children with CRP > 123.47 mg/L. Considering PCT concentration in this tree, children with WBC below or equal 14.45 K/µland with PCT ≤ 0.08 ng/mL were at high risk of resistance to ampicillin (75.0% of samples). However, it is important to notice that there were only eight cases in this tree node. A similar situation took place in children with CRP values between 43.91 mg/L and 123.47 mg/L; patients with a concentration of PCT ≤ 0.28 ng/mL were at higher risk of resistance to ampicillin (85.71% of children). However, this tree node was also presented with small number of cases.E.coli. 100% of children with CRP > 0.42 mg/land PCT ≤ 6.92 ng/mL had confirmed sensitivity to cefuroxime in antibiograms . In the study by Orellana et al. [p = 0.001) and, contrary to our results, in boys. In the research study by Swerkersson et al. [p < 0.01), what was also obtained in our study.The other risk factors, which were included in our analysis, were anatomical and functional disorders of the urinary tract. The most common abnormality is VUR. In our study, VUR was diagnosed in 18.4% of girls and in 16% of boys. There was a correlation between grade of VUR and gender of patients–boys were statistically more likely to have high-grade VUR than girls  and the presence of leukocyturia in urinalysis are necessary to reach a UTI diagnosis. In our analysis, pyuria was found in 78.8% of urine samples. In the remaining 21.2% of samples, in 34 cases there was outpatient antibiotic therapy administered . In most of the remaining cases, lack of leukocyturia was concerned in infants and children < 2 years old who hadyet to complete toilet training. Therefore, urine is not kept in the bladder long enough to detect pyuria in the urinalysis in children at this age. Kim et al.  conducteEscherichia coli, which varies between 53% and 87% [Klebsiella pneumoniae (7–36.2%), Proteus mirabilis (3.0–3.49%) and Pseudomonas aeruginosa (2.3–7.57%). Our study also identified E. coli as the most dominant UTI etiological factor (72.7%). Contrary to presented studies, we observed the lower percentage in UTIs caused by K. pneumoniae (3.9%) and greater number of cases with P. mirabilis etiology (5.8%), which may be correlated with no tradition of boys’ circumcising in Poland and consequently with the presence of foreskin. The same studies took into consideration variability of antibiotic susceptibility. The antibiotic with the greatest percentage of resistance was ampicillin (83–87%). High-grade resistance was also found in ceftriaxone (40–62%), cotrimoxazole (40–93%) and amoxicillin with clavulanic acid (30–83%) [E. coli to gentamicin (97.7%) or amikacin (96.0%) and high resistance to ampicillin (70%) [E. coli was resistant to amoxicillin with clavulanic acid and cotrimoxazole in about 20–30% of samples (depend on age group). These results showed similarity with our outcomes.In recent years, the variability of microorganisms detected in urine cultures has increased. Considering the prior studies, the most dominant bacterial strain is still  and 87% ,43,44,45(30–83%) ,43,44,45in (70%) . Anotherin (70%) , found tE. coli, the highest resistance was found against ampicillin (47.2%) and amoxicillin with clavulanic acid (24.8%). Moreover, our results were interesting with regard to obtained statistical significance in increasing antibiotics resistance to amoxicillin with clavulanic acid (p < 0.01), gentamicin (p < 0.05) and ceftazidime (p < 0.01). Interestingly, the increasing sensitivity to nitrofurantoin was observed (p < 0.05). Prior studies and our results confirmed an unwanted trend in increasing antibiotic resistance. In addition, this phenomenon is observed in relation to drugs used in severe infections, such as meningitis, which makes it even more alarming. On the other hand, an increasing sensitivity to nitrofurantoin may indicate more frequent use of antibiotics instead of chemotherapeutics in mild infections. Furthermore, the decreasing susceptibility to commonly used antibiotics, such as amoxicillin with clavulanic acid, is worth mentioning due to its misuse .In our research, the percentage of resistance to commonly used antibiotics was lower than in prior studies, although we observed significantly decreasing susceptibility of bacteria. In the case of Finally, we tried to assess whether the inflammatory markers are associated with susceptibility of microbes to used antibiotics. In the available literature, we did not find any information about research studies related to this topic. Unfortunately, we were unabl to estimate precise values of CRP, PCT or WBC at which the antibiotic resistance can be ascertained. However, by using the CART trees method, we were able to slightly determine inflammatory markers’ values to which we can suspect that bacteria are predisposed to be resistant to antibacterial drugs.E. coli isolated from children with WBC above 7.80 K/µL and PCT value > 0.49 ng/mL were sensitive. In case of nitrofurantoin, we found that values of CRP above 0.11 mg/L and WBC above 12.18 K/µL were associated with susceptibility to this drug (100% of cases). Results of our study seem to be useful due to the fact that urine culture is a time consuming method. There is a chance to initially assess whether the bacterium will be sensitive to used antibiotics and predict empiric antimicrobial treatment if we know the values of inflammatory markers, until urine cultures become available.In summary, we made an attempt to evaluate cut-off points of inflammatory markers’ values in case of amoxicillin with clavulanic acid, ampicillin, cefuroxime, gentamicin and nitrofurantoin . Considering amoxicillin with clavulanic acid, this point was determined at the value of CRP of 97.91 mg/L, above which there were observed higher percentages of sensitive cases. The high risk of resistance to ampicillin was found in children with WBC below or equal 14.45 K/µL and PCT ≤ 0.08 ng/mL. In the case of WBC > 14.45 K/µL, the resistance’s risk was greater if CRP was in the range of 43.91–123.47 mg/L and PCT was ≤0.28 ng/mL. The most important results concerning cefuroxime revealed that all patients with values of CRP > 0.42 mg/L and PCT ≤ 6.92 ng/mL had confirmed susceptibility. Moreover, our results were interesting with regard to estimate the cut-off point for gentamicin—100% of There were some limitations to this study, including that it was small, single–center and contained regional data. We have also focused on the one specific infection that could have had an impact on the calculated sensitivity of the inflammatory markers, which should therefore be interpreted with caution. Furthermore, there could have been clinical signs of severity in some patients that were not captured in our study and that would justify the use of antibiotics. Finally, we described the added value of markers of inflammation testing to guide antibiotic prescription without considering patient–related factors, such as the uptake of prescribed antibiotics and acceptance of a non–antibiotic management strategy by the patient. Not all clinical variables that may affect inflammatory markers, such as anaemia, were included in the evaluation.Reached results indicate that increasing antibiotic resistance is a significant ongoing problem. Due to high percentage of resistance to amoxicillin with clavulanic acid, it is reasonable not to use this antibiotic empirically in our region. However, cefuroxime seems to be a promising choice as a first-line treatment. Our initial study results show that there are potential factors such as specific CRP and WBC levels, which can help in making decisions of first-line empiric antibiotic therapy. However, more studies on a larger group of patients are needed do confirm these data.