function [k, CCNspec, d] = kappa_fun(dist,Dpbins,CCNspec,Dp)

%% linear bins
avgSSbins=[0.1:0.05:0.85];
%% total UHSAS
for i = 1:length(Dpbins)-1
    dlogDp(i) = log10(Dpbins(i+1)/Dpbins(i));
end
dlogDp(length(Dpbins))=dlogDp(length(Dpbins)-1);
dlogDp=dlogDp';

dist_conc = dist;
tot_conc = sum(dist_conc);

for i = 1:length(dist_conc)
    sumdist_conc(i)=sum(dist_conc(end-i+1:end));
end
sumdist_conc=fliplr(sumdist_conc);
%% find Dcrit with CCN spec and SMPS cumulative dist
for i = 1:length(CCNspec(:,1))
    [A IndDcrit] = min(abs(1*sumdist_conc-1*CCNspec(i,1)));
    Dcrit(i) = Dpbins(IndDcrit)/1e6;
    if isnan(CCNspec(i,1))
        Dcrit(i) = nan;
    end
end

% constants
T = 273.15; % K
Tc = T - 273.15;% C
Mw = 18.016/1000; % kg/mol
Rv = 461; %J/kg K
R = 8.314; % J/(K mol)
rol = 1000;% kg/m^3 (density of water)
sigmalv = 0.0761-Tc*1.55e-4; %N/m p132 Curry & webster surface tension
%% find kappa 
A = 4*sigmalv*Mw/(R*T*rol);
k(:)=(4*A^3)./(27.*(Dcrit.^3).*log(avgSSbins(1:end)/100+1).^2);
d = Dcrit(1:9); %critical diameter at an SS of 0.2% (SS(3) = 0.2)
%% determine which kappa to display (depends on particle size choosen)
[~, ind]= min(abs(Dcrit-Dp)); %subtract diameter of interest
k = max(k(ind));% kappa
if isempty(k) || (Dp-.1)>nanmax(Dcrit)
    k=nan;
end